AUSTENIC STAINLESS STEEL, METAL BASED, FORGED STEEL AND CAST STEEL UNDERSTANDING THE SAME AND PREPAR

专利摘要:
Patent Summary: "Austenitic Stainless Steel". The present invention relates to an austenitic stainless steel which is described herein. in the described embodiments, austenitic stainless steel comprises 16.00 wt% chromium to 30.00 wt% chromium; 8.00 wt% nickel to 27.00 wt% nickel; not more than 7,00% by weight molybdenum; 0.40 wt% nitrogen to 0.70 wt% nitrogen, 1.0 wt% manganese to 4.00 wt% manganese, and less than 0.10 wt% carbon in that the ratio of manganese to nitrogen is controlled to less than or equal to 10.0. Austenitic stainless steel based on specified minimum pren (equivalent corrosion resistance) values is also described. (1) pre = wt% cr + 3.3x- wt% (mo) + 16 wt%> 0.40 to 0.70 with w present. 19846807v1
公开号:BR112013030258B1
申请号:R112013030258-5
申请日:2012-05-24
公开日:2019-10-08
发明作者:Cecil Vernon Roscoe
申请人:Upl, L.L.C. D/B/A United Pipelines Of America Llc；
IPC主号:

专利说明:

Descriptive Report of the Invention Patent for AUSTENITIC STAINLESS STEEL OF METALLIC BASE, FORGED STEEL AND CAST STEEL UNDERSTANDING THE SAME AND METHOD OF PREPARATION OF THE REFERRED STAINLESS STEEL.
BACKGROUND AND FIELD OF THE INVENTION [001] This invention relates to Austenitic Stainless Steel.
[002] Traditionally, 300 series of austenitic stainless steels such as UNS S30403 (304L) and UNS S30453 (304LN) have chemical compositions specified in percentage by weight as illustrated in Table 1 here:
TABLE 1
No. ofUNS TypeÇ Mn P s Si Cr Ni Mo N S 30403 304L min17.50 8.00 max 0.030 2.00 0.045 0.030 0.75 19.50 12.000.10 No. ofUNS TypeÇ Mn P s Si Cr Ni Mo N S 30453 304LN min18.00 8.000.10 max 0.030 2.00 0.045 0.030 0.75 20.00 12.000.16
[003] There are several shortcomings with the aforementioned conventional austenitic stainless steels associated with their particular specification ranges. This can potentially result in a lack of adequate control of the chemical analysis in the melting stage, which is necessary to optimize the properties of the Alloys to produce an excellent combination of mechanical strength and good corrosion resistance properties.
[004] The mechanical properties that are obtained with alloys such as UNS S30403 and UNS S30453 are not optimized and are relatively low compared to other generic stainless steel groups such as 22Cr Duplex and 25Cr Duplex stainless steels and 25Cr Super Duplex stainless steels . This is shown in Table 2 which compares the properties of these conventional austenitic stainless steels with typical grades of 22Cr Duplex stainless steels,
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25Cr Duplex and 25Cr Super Duplex.
TABLE 2
Mechanical Properties of Austenitic Stainless Steels
No. of Type Resistance to Choice limit Stretched Toughness UNStraction forgive 2in mentNote 2 or 50mmMax MinMin Min Brinell Rockwell B Ksi Mpa Ksi Mpa % S30403 304L 70 485 25 170 40 201 92 S30453 304LN 75 515 30 205 40 217 95
Mechanical Properties of 22Cr Duplex Stainless Steels
No. of Type Resistance to Choice limit Stretched Toughness UNStraction forgive 2in mentNote 2 or 50mmMax MinMin Min Brinell Rockwell B Ksi Mpa Ksi Mpa % S31803 2205 90 620 65 450 25 293 31 S32205 2205 95 655 65 450 25 293 31 S32304 2304 87 600 58 400 25 290 32
Mechanical Properties of 25Cr Duplex and 25Cr Super Duplex Stainless Steels
No. of Type Resistance to Choice limit StretchedToughness UNStraction forgive 2in mentNote 2 or 50mmMax Min Min Min Brinell Rockwell B Ksi Mpa Ksi Mpa % S32760108 750 80 550 25 270S32750 2507 116 795 80 550 15 310 32 S39274116 800 80 550 15 310 32 S32520112 770 80 550 25 310
Note 2: The hardness figures cited apply to the solution ringed condition.
[005] It is an objective of this to provide an austenitic stainless steel that alleviates at least one of the disadvantages of the prior art and / or provide the public with a useful choice.
SUMMARY OF THE INVENTION
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3/166 [006] According to a first aspect of the invention, in that sense austenitic stainless steel according to claim 1 is provided.
[007] Other preferred features can be found in the dependent claims.
[008] As can be appreciated from the described modalities, the austenitic stainless steel alloy (Cr-Ni-Mo-N) comprises a high level of nitrogen that has a unique combination of properties of high mechanical resistance with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. Specifically, the described modalities also talk about the problem of relatively low mechanical strength properties in conventional 300 series austenitic stainless steels such as UNS S30403 and UNS S30453 when compared to 22Cr Duplex Stainless Steels and 25Cr Super Duplex Stainless Steels. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 304LM4N [009] For ease of explanation, a first embodiment of the invention is referred to as 304LM4N. Generally speaking, 304LM4N is a high-strength austenitic stainless steel (Cr-Ni-Mo-N) alloy that comprises a high level of nitrogen and is formulated to obtain a minimum specified Corrosion Resistance Equivalent of PREn 25, and preferably PREn 30. PREn is calculated according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[0010] 304LM4N high strength austenitic stainless steel has a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion.
[0011] The chemical composition of high austenitic stainless steel
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4/166 resistance 304LM4N is selective and characterized by an alloy of chemical elements in percentage by weight (p) as follows, maximum 0.030% by weight of C (Carbon), maximum 2.00% by weight of Mn (Manganese) , maximum 0.030% by weight of P (Phosphorus), maximum 0.010% by weight of S (Sulfur), maximum 0.75% by weight of Si (Silicon), 17.50% by weight of Cr (Chromium) to 20.00% by weight of Cr, 8.00% by weight of Ni (Nickel) to 12.00% by weight of Ni, 2.00 maximum of% by weight of Mo (Molybdenum), and 0.40% by weight of N (Nitrogen) to 0.70% by weight of N.
[0012] 304LM4N stainless steel also mainly comprises Fe (Iron) as the remainder and may also contain many small amounts of other elements such as a maximum of 0.010% by weight of B (Boron), a maximum of 0.10% by weight of Ce (Cerium), maximum 0.050% by weight of Al (Aluminum), maximum 0.01% by weight of Ca (Calcium) and / or maximum 0.01% by weight Mg (Magnesium) and other impurities that are not normally present at residual levels.
[0013] The chemical composition of 304LM4N stainless steel is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. As a result, 304LM4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time achieving excellent hardness at ambient temperatures and temperatures
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5/166 cryogenic. In view of the fact that the chemical composition of 304LM4N high strength austenitic stainless steel is adjusted to obtain a PREn> 25, but preferably PREn> 30, this ensures that the material also has good resistance to general corrosion and localized corrosion ( Pitting and Crack Corrosion) in a wide range of process environments. 304LM4N stainless steel also improved resistance to stress corrosion cracking in chloride-containing environments when compared to conventional Austenitic Stainless Steels such as UNS S30403 and UNS S30453.
[0014] It has been determined that the ideal chemical composition range of 304LM4N stainless steel is carefully selected to understand the following chemical elements in percentage by weight as follows based on the first modality,
Carbon (C) [0015] Carbon content of 304LM4N stainless steel is <0.030% by weight of C (ie, maximum 0.030% by weight of C). Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C. Manganese (Mn) [0016] Stainless steel 304LM4N of the first embodiment can come in two variations: low manganese or high manganese.
[0017] For low manganese alloys, the manganese content of 304LM4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[0018] For high manganese alloys, the manganese content of
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6/166 stainless steel 304LM4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn, and more preferably the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25.
Phosphorus (P) [0019] Phosphorus content of 304LM4N stainless steel is controlled to be <0.030% by weight of P. Preferably, alloy 304LM4N has <0.025% by weight of P and more preferably <0.020% by weight of P Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P. Sulfur (S) [0020] Sulfur content of 304LM4N stainless steel of the first embodiment is <0.010% in weight of S. Preferably, 304LM4N has <0.005% by weight of S and more preferably <0.003% by weight of S, and even more preferably <0.001% by weight of S.
Oxygen (O) [0021] Oxygen content of 304LM4N stainless steel is controlled to be as low as possible and in the first embodiment, 304LM4N has <0.070% by weight of O. Preferably, 304LM4N alloy has <0.050% by weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [0022] Silicon content of 304LM4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <
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0.75 wt% Si. More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content can be> 0.75% Si weight and <2.00% Si weight.
Chromium (Cr) [0023] Chromium content of 304LM4N stainless steel of the first modality is> 17.50% by weight of Cr and <20.00% by weight of Cr. Preferably, the alloy has> 18.25% by weight of Cr.
Nickel (Ni) [0024] Nickel content of 304LM4N stainless steel is> 8.00% by weight of Ni and <12.00% by weight of Ni. Preferably, the upper Ni limit of the alloy is <11% by weight of Ni and more preferably <10% by weight of Ni.
Molybdenum (Mo) [0025] Molybdenum content of 304LM4N stainless steel alloy is <
2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.00% by weight of Mo. More preferably, the lower limit of Mo is> 1.0% by weight of Mo.
Nitrogen (N) [0026] Nitrogen content of 304LM4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably , the 304LM4N alloy has> 0.4-0% by weight of N and <0.60% by weight of N, and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [0027] THE CORROSION RESISTANCE EQUIVALENT (PREn) is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[0028] 304LM4N stainless steel is specifically formulated
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8/166 to have the following composition:
(i) chromium content of> 17.50% by weight of Cr and <20.00% by weight of Cr, but preferably> 18.25% by weight of Cr;
(ii) molybdenum content <2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.00% by weight of Mo and more preferably> 1.0% by weight of Mo ;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. [0029] With a high nitrogen level, 304LM4N stainless steel obtains PREn of> 25, and preferably PREn> 30. This ensures that the alloy has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in a wide range of process environments. 304LM4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S30403 and UNS S30453. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[0030] The chemical composition of 304LM4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent [Cr] divided by the equivalent [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1 , 05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C - 1,250 degrees C followed by tempering with Water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the zone affected by heat from welding, is controlled by optimization of the
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9/166 balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[0031] Stainless steel 304LM4N also has mainly
Iron (Fe) like the rest and can also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent as follows,
Boron (B) [0032] Stainless steel 304LM4N may not have boron intentionally added to the alloy and as a result the level of boron is typically> 0.0001% by weight of B and <0.0006% by weight of B for mills who prefer not to intentionally add boron to heating. Alternatively, 304LM4N stainless steel can be produced to specifically include <0.010% by weight of B. Preferably, the boron range is> 0.001% by weight of B and <0.010% by weight of B and more preferably> 0.0015 % by weight of B and <0.0035% by weight of B. In other words, boron is specifically added during the production of stainless steel but controlled to obtain such levels.
Cerium (Ce) [0033] The 304LM4N stainless steel of the first embodiment may also include <0.10% by weight of Ce, but preferably> 0.01% by weight of Ce and <0.10% by weight of Ce. More preferably, the amount of cerium is> 0.03% by weight of Ce and <0.08% by weight of Ce. If stainless steel contains cerium, it may also possibly contain other Rare Earth Metals (REM) such as Lanthanum since REMs are very often supplied to stainless steel producers as a mixed metal. It should be noted that Rare Earth Metals can be used individually or together as
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10/166 mixed metal providing the total number of REMs according to the Ce levels specified here.
Aluminum (Al) [0034] Stainless steel 304LM4N of the first embodiment may also comprise <0.050% by weight of Al, but preferably> 0.005% by weight of Al and <0.050% by weight of Al and more preferably> 0.010% in Al weight and <0.030% Al weight.
Calcium (Ca) / Magnesium (Mg) [0035] Stainless steel 304LM4N can also include <0.010% by weight of Ca and / or Mg. Preferably, stainless steel may have> 0.001% by weight of Ca and / or Mg and <0.010% by weight of Ca and / or Mg and more preferably> 0.001% by weight of Ca and / or Mg and <0.005% in weight of Ca and / or Mg and other impurities that are normally present at residual levels.
[0036] Based on the above characteristics, stainless steel
304LM4N has a minimum flow limit of 55 ksi or 380 MPa for the forged version. More preferably, a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. Most preferably a minimum yield limit of 48 ksi or 330 MPa can be obtained for the cast version. Based on the preferred strength values, comparisons of the forged mechanical strength properties of 304LM4N stainless steel, with those of UNS S30403 in Table 2, suggest that the minimum yield strength of 304LM4N stainless steel should be 2.5 times greater than that specified for UNS S30403. Similarly, a comparison of the forged mechanical strength properties of the new and innovative 304LM4N stainless steel, with those of UNS S30453 in Table 2, suggests that the minimum yield strength of 304LM4N stainless steel should be 2.1 times greater than that specified for UNS
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S30453.
[0037] The 304LM4N stainless steel of the first modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of the new and innovative 304LM4N stainless steel, with those of UNS S30403 in Table 2, may suggest that the minimum tensile strength of 304LM4N stainless steel is more than 1.5 times greater than that specified for UNS S30403. Similarly, a comparison of the forged mechanical strength properties of the new and innovative 304LM4N austenitic stainless steel, with those of UNS S30453 in Table 2, suggests that the minimum tensile strength of 304LM4N stainless steel should be 1.45 times greater than that specified for UNS S30453. In fact, if the forged mechanical strength properties of the new and innovative 304LM4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel in Table 2, then it should be demonstrated that the minimum tensile strength of 304LM4N stainless steel is in the region of 1.2 times greater than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of 304LM4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S30403 and UNS S30453 and the tensile strength properties are better than those specified for 22 Cr Duplex and Stainless Steel similar to those specified for 25 Cr Super Duplex Stainless Steel.
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12/166 [0038] This means that applications using stainless steel
Forged 304LM4N can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 304LM4N stainless steel compared to conventional austenitic stainless steels such as UNS S30403 and S30453 because the minimum allowable design stresses can be significantly high. In fact, the minimum allowable design stresses for forged 304LM4N stainless steel may be greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel.
[0039] For certain applications, other stainless steel variants
304LM4N was intentionally formulated to be produced containing specific levels of other ligament elements such as copper, tungsten and vanadium. It was determined that the ideal chemical composition range of the other 304LM4N stainless steel variants is selective and characterized by alloys of chemical compositions in percentage by weight as follows,
Copper (Cu) [0040] The copper content of 304LM4N stainless steel is <1.5 0% by weight of Cu, but preferably> 0.50% by weight of Cu and <1.50% by weight of Cu and more preferably <1.00% by weight of Cu for the lower copper strip alloys. For high copper band alloys, the copper content may include <3.50% by weight, but preferably> 1.50% by weight of Cu and <3.50% by weight of Cu and more preferably <2, 50% by weight of Cu.
[0041] Copper can be added individually or in conjunction with tungsten, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Copper is expensive and for that reason is being intentionally limited to optimize the eco
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13/166 alloy name, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
T ungsteno (W) [0042] The tungsten content of 304LM4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W. For stainless steel 304LM4N variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N).
[0043] This tungsten-containing variant of stainless steel
304LM4N is specifically formulated to have the following composition:
(i) chromium content> 17.50% by weight of Cr and <20.00% by weight of Cr, but preferably> 18.25% by weight of Cr;
(ii) molybdenum content <2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.00% by weight of Mo and more preferably> 1.0% by weight of Mo ;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[0044] The tungsten-containing variant of 304LM4N stainless steel has a high specified level of nitrogen and a PREnw> 27, but preferably PREnw> 32. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by corrosion by Pits or crack. Tungsten can be added
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14/166 swimming individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the total corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Vanadium (V) [0045] The vanadium content of 304LM4N stainless steel has <
0.50% by weight of V, but preferably> 0.10% by weight of V and <0.50% by weight of V and more preferably <0.30% by weight of V. Vanadium can be added individually or in conjunction with copper, tungsten, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements to also improve the overall corrosion performance of the alloy. Vanadium is expensive and for that reason is intentionally being limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [0046] For certain applications, other variants of 304LM4N high strength austenitic stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 304LM4N stainless steel can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C. These specific variants of high strength austenitic stainless steel 304LM4N can be considered as versions 304HM4N or 304M4N respectively.
Titanium (Ti) / Niobium (Nb) / Niobium (Nb) plus tantalum (Ta)
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15/166 [0047] In addition, for certain applications, other stabilized variants of 304HM4N or 304M4N stainless steels are desirable, which have been specifically formulated to be produced containing high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight C, but preferably <0.050% by weight of C, or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the Titanium stabilized versions which are referred to as 304HM4NTi or 304M4NTi to contrast with the generic 304LM4N stainless steel versions.
[0048] The titanium content is controlled according to the following formulas:
[0049] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 304HM4NNb or 304M4NNb where the content of niobium is controlled according to the following formulas:
[0050] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min,
1.0% by weight of Nb max, respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions of 304HM4NNbTa or 304M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[0051] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[0052] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum from the alloy can be treated
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16/166 thermal stabilization at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[0053] The forged and cast versions of 304LM4N stainless steel along with the other variants and modalities discussed here are generally supplied in the solution-annealed condition. However, welds for fabricated components, modules and fabrications are generally supplied in the welded condition, with the proviso that suitable Welding Procedure Qualifications are pre-qualified according to the respective standards and specifications. For specific applications, forged versions can also be supplied in cold working condition.
EFFECT OF THE PROPOSED CONNECTION ELEMENTS AND THEIR COMPOSITIONS [0054] One of the most important properties of stainless steels is normally their resistance to corrosion, without which, they would find few industrial applications, since in many instances their mechanical properties can be matched by less expensive materials.
[0055] Changes in the content of the bonding element that are desirable to establish attractive corrosion-resistant characteristics can have a marked effect on stainless steel metallurgy. Consequently, this can affect the physical and
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17/166 mechanics that can be used practically. The establishment of certain desirable properties such as high strength, ductility and hardness are dependent on the control of the microstructure and this can limit the attainable corrosion resistance. Binding elements in the solid solution, manganese sulfide inclusions and various phases that can precipitate producing depleted chromium and molybdenum zones around the precipitates, can all have a profound influence on the microstructure, the mechanical properties of the alloy and the maintenance or breakage of passivity.
[0056] Thus, it is extremely challenging to derive an ideal composition of the alloy elements in order for the alloy to have good mechanical resistance properties, excellent ductility and hardness and even good weldability and resistance to general and localized corrosion. This is especially true in view of the complex range of metallurgical variables that produce the alloy composition and how each variable affects passivity, microstructure and mechanical properties. It is also necessary to incorporate this knowledge into new alloy development, manufacturing and heat treatment programs. In the following passages, it is discussed how each of the alloy elements is optimized to obtain the properties mentioned above. Chromium effect [0057] Stainless steels derive their passive bonding characteristics with chromium. Iron bonding with chromium changes the primary passivation potential in the active direction. This in turn expands the passive potential range and reduces the current passive density of the ipass. In chloride solutions, an increase in the chromium content of stainless steels increases the potential of Pites E _P thereby expanding the passive potential range. Chromium, for this reason, increases resistance to localized corrosion (Pitting and Slit Corrosion) as well as general corrosion. An increase in chromium, which is a ferrite-forming element, can
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18/166 be balanced by an increase in nickel and other austenite-forming elements such as nitrogen, carbon and manganese in order to primarily maintain an austenitic microstructure. However, it was found that chromium in conjunction with molybdenum and silicon may increase the tendency for intermetallic phases to precipitate and deleterious precipitates. For this reason, there is practically a maximum limit on the level of chromium that can be increased without enhancing the rate of intermetallic phase formation in thick sections which, in turn, can result in a reduction in ductility, hardness and corrosion performance of the turns on. This 304LM4N stainless steel was specifically formulated to have a chromium content> 17.50 wt% Cr and <20.00 wt% Cr for optimal results. Preferably, the chromium content is> 18.25% by weight
Nickel effect [0058] It has been found that nickel changes the potential of EP Pites in the prime direction, thereby extending the passive potential range, and also reduces the current passive density i pass. Nickel therefore increases resistance to localized corrosion and general corrosion in austenitic stainless steels. Nickel is an Austenite-forming element and the level of nickel, manganese, carbon and nitrogen is optimized in the first modality to balance ferrite-forming elements such as chromium, molybdenum and silicon to maintain primarily an austenitic microstructure. Nickel is extremely expensive and for that reason is being intentionally limited to optimize the alloy's economy, while at the same time optimizing the alloy's ductility, hardness and corrosion performance. This 304LM4N stainless steel was specifically formulated to have a nickel content> 8.0 0% by weight of Ni and <12.00% by weight of Ni, but preferably <11.00% by weight of Ni and more preferably < 10.00% by weight of Ni.
Molybdenum effect
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19/166 [0059] At particular levels of chromium content, it was found that molybdenum has a strong beneficial influence on the passivity of austenitic stainless steels. The addition of molybdenum changes the potential of Pites in the noblest direction in this way extending the passive potential range. Increasing the molybdenum content also reduces i max and in this way molybdenum improves resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in chloride environments. Molybdenum also improves resistance to chloride stress corrosion breakage in chloride containing environments. Molybdenum is a ferrite-forming element and the level of molybdenum together with chromium and silicon is optimized to balance austenite-forming elements such as nickel, manganese, carbon and nitrogen to primarily maintain an austenitic microstructure. However, molybdenum in conjunction with chromium and silicon can increase the tendency for intermetallic phases to precipitate and deleterious precipitates. At high levels of molybdenum, it is possible to experience macrosegregation, particularly in foundries and primary products, which can also increase the kinetics of such intermetallic phases and deleterious precipitates. Sometimes other elements such as tungsten can be introduced into the heat in order to decrease the relative amount of molybdenum required in the alloy. For this reason, there is practically a maximum limit on the level of molybdenum that can be increased without enhancing the rate of intermetallic phase formation in thick sections which, in turn, can result in a reduction in ductility, hardness and corrosion performance of turns on. This 304LM4N stainless steel was specifically formulated to have a molybdenum content of <2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.0% by weight of Mo and more preferably> 1 , 0% by weight of Mo.
Nitrogen effect
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20/166 [0060] In the first modality (and in the subsequent modalities), one of the most significant improvements in the performance of localized corrosion of austenitic stainless steels is obtained by increasing nitrogen levels. Nitrogen raises the potential of Ep Pites in this way by expanding the passive potential range. Nitrogen modifies the passive protective film to improve protection for breaking passivity. It has been reported ¹ that high concentrations of nitrogen have been observed on the metal side of the passive metal-to-metal interface using Auger electron spectroscopy. Nitrogen is an extremely strong austenite-forming element along with carbon. Similarly, manganese and nickel are also austenite-forming elements although to a lesser extent. The levels of austenite-forming elements such as nitrogen and carbon, as well as manganese and nickel are optimized in these modalities to balance ferrite-forming elements such as chromium, molybdenum and silicon to maintain primarily an austenitic microstructure. As a result, nitrogen indirectly limits the propensity to form intermetallic phases since diffusion rates are much slower in Austenite. In this way, the kinetics of intermetallic phase formation are reduced. Likewise, in view of the fact that austenite has a good solubility for nitrogen, this means that the potential to form harmful precipitates such as M2X (carbonitrites, nitrites, borides, boron-nitrites or boron-carbides) as well as M23C6 carbides, in the weld metal and heat-affected zone of welding, during welding cycles, is reduced. Nitrogen in the solid solution is primarily responsible for increasing the mechanical strength properties of 304LM4N stainless steel while ensuring that an austenitic microstructure optimizes the ductility, hardness and corrosion performance of the alloy. Nitrogen, however, has limited solubility both in the melting stage and in a soluble solution.
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21/166 da. This 304LM4N stainless steel was specifically formulated to have a nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0 , 40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. Manganese effect [0061] Manganese is a austenite-forming element and the level of manganese, nickel, carbon and nitrogen is optimized in modalities to balance ferrite-forming elements such as chromium, molybdenum and silicon to maintain primarily an austenitic microstructure. For this reason, a high level of manganese indirectly allows a high solubility of carbon and nitrogen both in the melting stage and in a solid solution in order to minimize the risk of harmful precipitates such as M2X (carbo-nitrites, nitrites, borides, borons). nitrites or boron carbides) as well as M23C6 carbides. For this reason, increasing the concentration of manganese to specific levels to improve solubility in solid nitrogen would result in an improvement in the local corrosion performance of austenitic stainless steel. Manganese is also a more profitable element than nickel and can be used to some degree to limit the amount of nickel being used in the alloy. However, there is a limit on the manganese level that can be used successfully since this can result in the formation of manganese sulphide inclusions which are favorable sites for pit initiation, thus adversely affecting the corrosion performance of Steel austenitic stainless steel. Manganese also increases the tendency for precipitation of intermetallic phases as well as deleterious precipitates. For this reason, there is practically an upper limit on the manganese level that can be increased without enhancing the intermetallic phase formation rate in thick sections which, in turn, can result in a
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22/166 reduction in ductility, hardness and corrosion performance of the alloy. This 304LM4N stainless steel was specifically formulated to have a manganese content> 1.00% by weight of Mn and <2.00% by weight of Mn, but preferably with a manganese content> 1.20% by weight of Mn and <1.50% by weight of Mn. The manganese content can be controlled to ensure the manganese to nitrogen ratio is <5.0, and preferably> 1.42 and <5.0. More preferably, the ratio is> 1.42 and <3.75 for the lower manganese alloys. The manganese content can be characterized by an alloy containing> 2.0% by weight of Mn and <4.0% by weight of Mn, but preferably <3.0% by weight of Mn and more preferably <2, 50% by weight of Mn, with an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably the ratio is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25 for high manganese alloys. Sulfur, Oxygen and Phosphorus Effect [0062] Impurities such as Sulfur, Oxygen and Phosphorus can have a negative influence on the mechanical properties and resistance to localized corrosion (Pitting and Slit Corrosion) and general corrosion on austenitic stainless steel. This is because Sulfur, in conjunction with manganese at specific levels, promotes the formation of manganese sulphide inclusions. In addition, Oxygen in conjunction with aluminum or silicon at specific levels, promotes the formation of oxide inclusions such as Al2O3 or SiO2. These inclusions are favorable sites for initiation of Pitess in this way adversely affecting the performance of localized corrosion, ductility and steel hardness. austenitic stainless steel. Likewise, Phosphorus promotes the formation of harmful precipitates that are favorable sites for Pitess initiation that adversely affect the resistance to corrosion by Pites and cracking of the alloy as well as reducing its ductility and hardness. In addition, Sulfur, Oxygen and Phosphorus have an adverse effect on the
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23/166 hot ticability of forged austenitic stainless steels and sensitivity to hot break and cold break, particularly in foundries and weld metal from austenitic stainless steel welds. Oxygen at specific levels can also result in porosity in austenitic stainless steel castings. This can generate potential break initiation sites within the molten components that experience high cyclical loads. For this reason, modern fusion techniques such as electric arc fusion, vacuum induction and oxygen decarbonation fusion, or argon oxygen decarbonation in conjunction with other secondary remelting techniques such as Electro-Spill Remelting or Vacuum Remelting as well as other refinement techniques are used to ensure that extremely low Sulfur, Oxygen and Phosphorus contents are obtained to improve the hot feasibility of forged stainless steel and to reduce the sensitivity to hot breaking and cold breaking and porosity particularly in foundries and in the weld weld metal. Modern fusion techniques also result in a reduction in the level of inclusions. This improves the cleanliness of austenitic stainless steel and therefore the ductility and hardness as well as the total corrosion performance. This 304LM4N stainless steel has been specifically formulated to have a sulfur content of <0.010% by weight of S, but preferably with a sulfur content of <0.005% by weight of S and more preferably <0.003% by weight of S and even more preferably <0.001% by weight of S. The oxygen content is as low as possible and controlled to <0.070% by weight of O, but preferably <0.050% by weight of O and more preferably <0.030% by weight of O and even more preferably <0.010% by weight of O and even more preferably <0.005% by weight of O. The phosphorus content is controlled to <0.030% by weight of P, but preferably <0.025% by weight of P, and more preferably <0.020% by weight of
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P, and even more preferably <0.015% by weight of P, and even more preferably <0.010% by weight of P.
Silicon Effect [0063] Silicon changes the potential of Pites in the prime direction thereby extending the passive potential range. silicon also enhances the fluidity of the melt during the production of stainless steels. Likewise, silicon improves the fluidity of the hot-weld metal during welding cycles. silicon is a ferrite forming element and the silicon level together with chromium and molybdenum is optimized to balance austenite forming elements such as nickel, manganese, carbon and nitrogen to primarily maintain an austenitic microstructure. silicon content in the range of 0.75 wt% Si and 2.00 wt% Si can improve oxidation resistance for high temperature applications. However, excess silicon content of approximately 1.0% by weight of Si, in conjunction with chromium and molybdenum, may increase the tendency for intermetallic phases to precipitate and deleterious precipitates. For this reason, there is practically a maximum limit on the level of silicon that can be increased without enhancing the rate of intermetallic phase formation in thick sections which, in turn, can result in a reduction in ductility, hardness and corrosion performance of the turns on. This 304LM4N stainless steel was specifically formulated to have a silicon content of <0.75% by weight of Si, but preferably> 0.25% by weight of Si and <0.75% by weight of Si and more preferably> 0 , 40 wt% Si and <0.60 wt% Si. The silicon content can be characterized by an alloy containing> 0.75 wt% Si and <2.00 wt% Si for specific high temperature applications where improved oxidation resistance is required.
Carbon effect [0064] Carbon is an extreme Austenite-forming element
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25/166 strong together with nitrogen. Similarly, manganese and nickel are also austenite-forming elements, albeit to a lesser degree. The levels of austenite-forming elements such as carbon and nitrogen, as well as manganese and nickel are optimized to balance ferrite-forming elements such as chromium, molybdenum and silicon to primarily maintain an austenitic microstructure. As a result, carbon is indirectly limited to the propensity to form intermetallic phases since diffusion rates are much slower in Austenite. In this way, the kinetics of intermetallic phase formation are reduced. Likewise, in view of the fact that Austenite has a good solubility for carbon, this means that the potential to form harmful precipitates such as M2X (carbo-nitrites, nitrites, borides, boron-nitrites or borocarbons) as well as M23C6 carbides, in the weld metal and heat-affected zone of welding, during welding cycles, is reduced. Carbon and nitrogen in the solid solution are primarily responsible for increasing the mechanical strength properties of 304LM4N stainless steel while ensuring that an austenitic microstructure optimizes the ductility, hardness and corrosion performance of the alloy. The carbon content is normally restricted to a maximum of 0.030% by weight of C to optimize properties and also to ensure good hot feasibility of forged austenitic stainless steels. This 304LM4N stainless steel was specifically formulated to have a carbon content of <maximum 0.030% by weight of C, but preferably> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C C. For certain applications, where a high carbon content is> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C is desirable, specific variants of stainless steel
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26/166 dable 304LM4N, that is, 304HM4N or 304M4N respectively, were also intentionally formulated.
Boron, cerium, aluminum, calcium and magnesium effect [0065] The hot feasibility of stainless steels is improved by introducing discrete amounts of other elements such as boron or cerium. If stainless steel contains cerium, it may also possibly contain other rare earth metals (REM) such as lanthanum since REMs are very often supplied to stainless steel producers as a mixed metal. In general, the typical residual level of boron present in stainless steels is> 0.0001% by weight of B and <0.0006% by weight of B for plants that prefer not to intentionally add boron to heating. 304LM4N stainless steel can be produced without the addition of boron. Alternatively, 304LM4N stainless steel can be produced to have specifically a boron content> 0.001% by weight B and <0.010% by weight of B, but preferably> 0.0015% by weight of B and <0.0035% by weight. B. weight The beneficial effect of boron in hot feasibility results from ensuring that boron is retained in a solid solution. It is therefore necessary to ensure that deleterious precipitates such as M2X (borides, boron-nitrites or boron-carbides) do not precipitate on the microstructure at the grain boundaries of the base material during production and heat treatment cycles or on the welded weld metal and zone affected by heat from welding during welding cycles.
[0066] 304LM4N stainless steel can be produced to specifically have a cerium content of <0.10% by weight of Ce, but preferably> 0.01% by weight of Ce and <0.10% by weight of Ce and more preferably> 0.03% by weight of Ce and <0.08% by weight of Ce. Cerium forms cerium oxysulfides in stainless steel to work with hot feasibility but, at specific levels, these do not adversely affect the corrosion resistance of the material. For certain
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27/166 tions, where a high carbon content of> 0.04% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C is desirable, stainless steel 304LM4N variants can also be produced to have specifically a boron content <0.010% by weight of B, but of preferably> 0.001% by weight of B and <0.010% by weight of B and more preferably> 0.0015% by weight of B and <0.0035% by weight of B or a cerium content <0.10% by weight of Ce, but preferably> 0.01% by weight of Ce and <0.10% by weight of Ce and more preferably> 0.03% by weight of Ce and <0.08% by weight of Ce. It should be noted that Rare Earth Metals can be used individually or together as a mixed metal providing the total amount of REMs according to the Ce levels specified here. 304LM4N stainless steel can be produced to specifically contain aluminum, calcium and / or magnesium. These elements can be added to deoxidize and / or desulfurize stainless steel in order to improve its cleanliness as well as the material's hot practicality. Where relevant, the aluminum content is typically controlled to have an aluminum content <0.05 0% by weight of Al, but preferably> 0.005% by weight of Al and <0.050% by weight of Al and more preferably> 0.010 % by weight of Al and <0.030% by weight of Al in order to inhibit nitrite precipitation. Similarly, the calcium and / or magnesium content is typically controlled to have a Ca and / or Mg content of <0.010% by weight of Ca and / or Mg, but preferably> 0.001% by weight of Ca and / or Mg and <0.010% by weight of Ca and / or Mg and more preferably> 0.001% by weight of Ca and / or Mg and <0.005% by weight of Ca and / or Mg to restrict the amount of spout formation on melting.
Other variants [0067] For certain applications, other variants of stainless steel
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304LM4N can be formulated to be produced containing specific levels of other binding elements such as copper, tungsten and vanadium. Similarly, for certain applications, where a high carbon content> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C is desirable, specific variants of stainless steel 304LM4N, i.e. 304HM4N or 304M4N respectively, have been intentionally formulated. In addition, for certain applications, where a high carbon content> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C but preferably <0.040% by weight of C is desirable, specific variants of 304HM4N or 304M4N stainless steel alloys, ie stabilized titanium, 304HM4NTi or 304M4NTi, stabilized niobium, 304HM4NNb or 304M4NNb and niobium plus stabilized tantalum, 304HM4NNbTa or 304M4NNbTa were also intentionally formulated. The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum from the alloys can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
Copper effect [0068] The beneficial effect of copper additions on color resistance
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29/166 stainless steel rosin in non-oxidizing media is well known. If approximately 0.50% by weight of copper is added, the active dissolution rate in boiling hydrochloric acid and the loss of crack corrosion in Chloride solutions are both decreased. It was found that the general corrosion resistance in sulfuric acid also improves with the addition of copper up to 1.50% by weight of Cu. ² copper is a forming element of Austenite along with nickel, manganese, carbon and nitrogen. For this reason, copper can improve the performance of localized and general corrosion of stainless steels. The levels of copper and other austenite-forming elements are optimized to balance ferrite-forming elements such as chromium, molybdenum and silicon to primarily maintain an austenitic microstructure. For this reason, a variant of 304LM4N stainless steel was specifically selected to have a copper content <1.50% by weight of Cu, but preferably> 0.50% by weight of Cu and <1.50% by weight of Cu Cu and more preferably <1.00% by weight of Cu for the lower copper strip alloys. The copper content of 304LM4N can be characterized by an alloy comprising <3.50% by weight of Cu, but preferably> 1.50% by weight Cu and <3.50% by weight of Cu and more preferably <2 , 50% by weight of Cu for high copper band alloys.
[0069] Copper can be added individually or in conjunction with tungsten, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Copper is expensive and for that reason is being intentionally limited to optimize the alloy's economy, while at the same time optimizing the alloy's ductility, hardness and corrosion performance.
Tungsten effect [0070] Tungsten and molybdenum occupy a similar position in the
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30/166 periodic table and have a similar power and influence on resistance to localized corrosion (Pitting and Crevice Corrosion). At particular levels of chromium and molybdenum content, tungsten has a strong beneficial influence on the passivity of austenitic stainless steels. Addition of tungsten changes the potential of Pites in the noblest direction, thereby extending the passive potential range. Increasing the tungsten content also reduces the current passive i pass density. Tungsten is present in the passive layer and is adsorbed without changing the oxide state ³ . In acidic chloride solutions, tungsten probably passes directly from the metal in the passive film, by interacting with water and forming an insoluble WO3 rather than by dissolving it after the adsorption process. In neutral Chloride solutions, the beneficial effect of tungsten is interpreted by the interaction of WO3 with other oxides, resulting in enhanced stability and enhanced bonding of the oxide layer to the base metal. Tungsten improves resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in chloride environments. Tungsten also improves resistance to chloride stress corrosion cracking in chloride containing environments. Tungsten is a ferrite forming element and the tungsten level together with chromium, molybdenum and silicon is optimized to balance austenite forming elements such as nickel, manganese, carbon and nitrogen to maintain primarily an austenitic microstructure. However, tungsten in conjunction with chromium, molybdenum and silicon can increase the tendency for intermetallic phases to precipitate and deleterious precipitates. For this reason, there is practically an upper limit on the level of tungsten that can be increased without enhancing the rate of intermetallic phase formation in thick sections which, in turn, can result in a reduction in ductility, hardness and corrosion performance of the turns on. For this reason, a variant of this stainless steel
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31/166 stainless steel 304LM4N was specifically formulated to have a tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the total corrosion performance of turns on. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Vanadium effect [0071] At particular levels of chromium and molybdenum content, vanadium has a strong beneficial influence on the passivity of austenitic stainless steels. Addition of vanadium changes Pites' potential in the noblest direction in this way by extending the passive potential range. Increasing the vanadium content also reduces imax and thus vanadium, in conjunction with molybdenum improves resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in chloride environments. Vanadium in conjunction with molybdenum can also improve resistance to chloride stress corrosion breakdown in chloride containing environments. However, vanadium in conjunction with chromium, molybdenum and silicon may increase the tendency for intermetallic phases to precipitate and deleterious precipitates. Vanadium has a strong tendency to form harmful precipitates such as M2X (carbo-nitrites, nitrites, borides, boronitrites or boron carbides) as well as M23C6 carbides. For this reason, there is practically a maximum limit on the level of vanadium that can be increased without enhancing the rate of intermetallic phase formation in thick sections. Vanadium also increases the propensity to form such deleterious precipitates in the weld metal and affected zone
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32/166 welding heat during welding cycles. These intermetallic phases and deleterious phases can, in turn, result in a reduction in ductility, hardness and corrosion performance of the alloy. For this reason, a variant of this 304LM4N stainless steel was specifically formulated to have a vanadium content <0.5 0% by weight of V, but preferably> 0.10% by weight of V and <0.50% by weight of V and more preferably <0.30% by weight of V. Vanadium can be added individually or in conjunction with copper, tungsten, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements to also improve the total corrosion performance of the alloy. Vanadium is expensive and for that reason is intentionally being limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Titanium, niobium and niobium plus tantalum effect [0072] For certain applications, where a high carbon content>
0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably < 0.040% by weight of C is desirable, specific variants of stainless steel 304HM4N or 304M4N, ie 304HM4NTi or 304M4NTi, were intentionally formulated to have a titanium content according to the following formulas: Ti 4 x C min, 0.70 % by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy. The titanium-stabilized variants of the alloys can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium can be added individually or in conjunction with copper, tungsten, vanadium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements to optimize ductility, duPetition 870190038552, from 24/04/2019, p. 57/204
33/166 alloy corrosion performance and corrosion performance.
[0073] Likewise, for certain applications, where a high carbon content> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C is desirable, specific variants of stainless steel 304HM4N or 304M4N, ie 304HM4NNb or 304M4NNb, were intentionally formulated to have a content of niobium according to the following formulas: Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the league. In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions of 304HM4NNbTa or 304M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas: Nb + Ta 8 x C min, 1.0 % by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max. Variants stabilized by niobium and stabilized by niobium plus tantalum from the alloys can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten, vanadium and / or titanium in all the various combinations of these elements to optimize the ductility, hardness and corrosion performance of the alloy.
Corrosion Resistance Equivalent [0074] It is evident from the above that several bonding elements in stainless steels change the potential of Pites in the prime direction. These beneficial effects are complex and interactive and efforts have been made to use empirical relationships of composition derived for Pites resistance indices. The most commonly used formulas
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34/166 accepted used for calculating CORROSION RESISTANCE EQUIVALENT:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[0075] It is generally recognized that such Alloys as described here with PREN values less than 40, can be classified as Austenitic Stainless Steels. While such alloys as described here with PREN values greater than or equal to 40, they can be classified as Super Austenitic Stainless Steels reflecting their resistance to general and superior localized corrosion. This 304LM4N stainless steel was specifically formulated to have the following composition:
(i) chromium content> 17.50% by weight of Cr and <20.00% by weight of Cr, but preferably> 18.25% by weight of Cr, (ii) molybdenum content <2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.0% by weight of Mo and more preferably> 1.0% by weight of Mo (iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
[0076] 304LM4N stainless steel has a high specified level of nitrogen and a PREn> 25, but preferably PRE n> 30. As a result, 304LM4N stainless steel has a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. There are reservations about the use of such formulas in total isolation. The formulas do not take into account the beneficial effects of other elements such as tungsten which improves Pites performance. For 304LM4N stainless steel variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT
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35/166 is calculated using the formulas: PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N). It is generally recognized that such alloys as described here with PREnw values less than 40 can be classified as Austenitic Stainless Steels. While such alloys as described here with PREnw values of greater than or equal to 40, they can be classified as Super Austenitic Stainless Steels reflecting their superior and general corrosion resistance. This variant containing tungsten of stainless steel 304LM4N was specifically formulated to have the following composition:
(i) chromium content> 17.50% by weight of Cr and <20.00% by weight of Cr, but preferably> 18.25% by weight of Cr, (ii) molybdenum content <2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.0% by weight of Mo and more preferably> 1.0% by weight of Mo, (iii) nitrogen content <0.70 % by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W is <1.00% by weight of W and more preferably> 0.75% by weight of W.
[0077] The tungsten-containing variant of 304LM4N stainless steel has a specified high level of nitrogen and a PREnw> 27, but preferably PREnw> 32. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by corrosion by Pits or crack.
Austenitic microstructure [0078] The chemical composition of 304LM4N stainless steel of the first modality is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material afterwards
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36/166 solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching.
[0079] The microstructure of the base material of 304LM4N in the heat treated condition by solubilization, together with welded weld metal and the zone affected by welding heat, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements, such as as discussed above, to primarily ensure that the alloy is austenitic.
[0080] The relative effectiveness of elements that stabilize the phases of ferrite and austenite can be expressed in terms of their [Cr] and [Ni] equivalents. The combined effect of using [Cr] and [Ni] equivalents was demonstrated using the method proposed by Schaeffler4 to predict the weld metal structures. The Schaeffler ⁴ diagram is strictly only applicable to rapidly melted and cooled alloys such as welding or cold casting. However, the Schaeffler ⁴ diagram can also produce an indication of the 'source' material phase balance. Schaeffler ⁴ predicted stainless steel weld metal structures formed in rapid cooling according to their chemical composition expressed in terms of their [Cr] and [Ni] equivalents. The Schaeffler ⁴ diagram used equivalents of [Cr] and [Ni] according to the following formulas:
Equivalent of [Cr] =% by weight of Cr +% by weight of Mo + 1.5 x% by weight of Si + 0.5 x% by weight of Nb (1)
Equivalent of [Ni] =% by weight of Ni + 30 x% by weight of C + 0.5 x% by weight of Mn (2) [0081] However, the Schaeffler diagram ⁴ does not take into account the significant influence of nitrogen in Austenite stabilization. For this reason, the Schaeffler ⁴ diagram was modified by DeLong ⁵ to incorporate the important influence of nitrogen as an element
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37/166 to Austenite trainer. The diagram of DeLong ⁵ used the same formulas of equivalent of [Cr] as used by Schaeffler ⁴ in equation (1). However, the [Ni] equivalent has been modified according to the following formulas:
Equivalent of [Ni] =% by weight of Ni + 30 x% by weight (C + N) + 0.5 x% by weight of M n (3) [0082] This diagram by DeLong ⁵ shows the ferrite content in terms of magnetically determined ferrite content and the number of Welding Research Council (WRC) Ferrite. The difference in the number of ferrite and the ferrite in percentage (that is, in values> 6% of Ferrite) is related to the calibration procedures of the WRC and the calibration curves used with the magnetic measurements. A comparison of the Schaeffler diagram ⁴ and the Schaeffler diagram ^fourth modified DeLong5 reveals that for an equivalent data [Cr] is equivalent to [Ni], the DeLong5 diagram predicts a higher ferrite content (i.e., roughly 5 % bigger).
[0083] Both the Schaeffler4 diagram and the DeLong5 diagram were mainly developed for welding and are, therefore, not strictly applicable to 'relative' material. However, they provide a good indication of the phases likely to be present and produce valuable information on the relative influence of the different ligament elements.
[0084] Schoefer6 demonstrated that a modified version of the Schaeffler4 diagram can be used to describe the number of ferrite in foundries. This was achieved by transforming the coordinates of the Schaeffler diagram 4 a or a number of ferrite or ferrite in percent of volume on the horizontal axis as adopted by ASTM in A800 / A800M - 10 ⁷ . The vertical axis is expressed as a ratio of the equivalent of [Cr] divided by the equivalent of [Ni]. Schoefer ⁶ also modified the factors of [Cr] equivalent and equivalent
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38/166 of [Ni] according to the following formulas:
Equivalent of [Cr] =% by weight of Cr + 1.5 x% by weight of Si + 1.4 x% by weight of Mo +% by weight of Nb - 4.99 (4)
Equivalent of [Ni] =% by weight of Ni + 30 x% by weight of C + 0.5 x% by weight of Mn + 26 x% by weight (N - 0.02) + 2.77 (5) [ 0085] It is also suggested that other elements that are Ferrite stabilizers are also likely to influence the [Cr] equivalent factors to produce a variation in such equations adopted by Schoefer ⁶ . This includes the following elements that have been designated with the respective [Cr] equivalent factors that may be relevant to the alloy variants contained here:
Element Equivalent factor of [Cr] T ungsteneVanadium 0.722.27 Titanium 2.20 T tantalum 0.21 Aluminum 2.48
[0086] Likewise, it is also suggested that other elements that are austenite stabilizers are also likely to influence the [Ni] equivalent factors to produce a variation in such equations adopted by Schoefer ⁶ . This includes the following element that has been designated with the respective [Ni] equivalent factor that may be relevant to the alloy variants contained here:
[Ni] equivalent factor element
Copper 0,44 [0087] However, ASTM A800 / A800M - 10 ⁷ establishes that the Schoefer diagram ⁶ is only applicable to Stainless Steel Alloys containing weighting percentage elements according to the following specification range:
C Mn Si Cr Ni Mo Nb N
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MIN 17.00 4.00
MAX 0.20 2.00 2.00 28.00 13.00 4.00 1.00 0.20 [0088] From the above, it can be deduced that the nitrogen content in 304LM4N stainless steel is <0.70 % by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. This exceeds the maximum limitations of Schoefer's diagram ⁶ as adopted by ASTM A800 / A800M - 10 ⁷ . Notwithstanding this, where appropriate, the Schoefer diagram ^{6 will} produce a relative comparison of the number of Ferrite or Ferrite in Percentage of Volume present in austenitic stainless steels containing High nitrogen.
[0089] Nitrogen is an extremely strong Austenite-forming element along with carbon. Similarly, manganese and nickel are also austenite-forming elements albeit to a lesser degree. The levels of austenite forming elements such as nitrogen and carbon, as well as manganese and nickel are optimized to balance ferrite forming elements such as chromium, molybdenum and silicon to primarily maintain an austenitic microstructure. As a result, nitrogen is indirectly limited to the propensity to form intermetallic phases since diffusion rates are much slower in austenite. In this way, the kinetics of intermetallic phase formation are reduced. Likewise, in view of the fact that austenite has a good solubility for nitrogen, this means that the potential to form harmful precipitates such as M2X (carbo-nitrites, nitrites, borides, boron-nitrites or boron-carbides) as well as M23C6 carbides, in the weld metal and zone affected by heat from welding, during welding cycles, is reduced. As already discussed, other variants of stainless steels can also include elements such as tungsten, vanadium, titanium, tantalum, aluminum
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40/166 and copper.
[0090] For this reason, 304LM4N stainless steel was specifically developed to primarily ensure that the microstructure of the base material in the heat treated condition by solubilization together with welded weld metal and the heat affected zone of welds is Austenitic. This is controlled by optimizing the balance between austenite forming elements and ferrite forming elements. For this reason, the chemical analysis of 304LM4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95.
[0091] As a result, 304LM4N stainless steel exhibits a unique combination of High strength and Ductility at ambient temperatures while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In addition, the alloy can be produced and supplied in a non-magnetic condition. Ideal Chemical Composition [0092] As a result of the above, it has been determined that the ideal chemical composition range for 304LM4N stainless steel is selective and includes a percentage by weight as follows:
(i) <maximum 0.030% by weight of C, but preferably> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C;
(ii) <2.0% by weight of Mn, but preferably> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and < 1.50% by weight of Mn, with an Mn to N ratio of <5.0 and preferably> 1.42 and <5.0 but more preferably,> 1.42 and <3.75, for lower manganese band alloys;
(iii) <0.030% by weight of P, but preferably <0.025% by weight of P and more preferably <0.020% by weight of P and up to
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41/166 more preferably <0.015% by weight of P and even more preferably <0.010% by weight of P;
(iv) <0.010% by weight of S, but preferably <0.005% by weight of S and more preferably <0.003% by weight of S, and even more preferably <0.001% by weight of S;
(v) <0.070% by weight of O, but preferably <0.050% by weight of O, and more preferably <0.030% by weight of O, and even more preferably <0.010% by weight of O, and even more preferably <0.005% by weight of O;
(vi) <0.75 wt% Si, but preferably> 0.25 wt% Si and <0.75 wt% Si and more preferably> 0.40 wt% Si and <0 , 60% by weight of Si;
(vii)> 17.50% by weight of Cr and <20.00% by weight of Cr, but preferably> 18.25% by weight of Cr;
(viii)> 8.00% by weight of Ni and <12.00% by weight of Ni, but preferably <11% by weight of Ni and more preferably <10% by weight of Ni;
(ix) <2.00% by weight of Mo, but preferably> 0.50% by weight of Mo and <2.00% by weight of Mo and more preferably> 1.0% by weight of Mo;
(x) <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0 , 60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
[0093] 304LM4N stainless steel has a high specified level of nitrogen and a PREn> 25, but preferably PREn> 30. The chemical composition of 304LM4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr ] divided by the equivalent of [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95.
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42/166 [0094] Stainless steel 304LM4N also contains mainly
Fe like the rest and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium as well as other impurities that may be present at residual levels. 304LM4N stainless steel can be produced without the addition of boron and the residual level of boron is typically> 0.0001% by weight of B and <0.0006% by weight of B for plants that prefer not to intentionally add boron to heating. Alternatively, 304LM4N stainless steel can be produced to have specifically a boron content> 0.001% by weight B and <0.010% by weight of B, but preferably> 0.0015% by weight of B and <0.0035% by weight. weight of B. cerium can be added with a content of cerium <0.10% by weight of Ce, but preferably> 0.01% by weight of Ce and <0.10% by weight of Ce and more preferably> 0 , 03% by weight of Ce and <0.08% by weight of Ce. If stainless steel contains cerium, it may also possibly contain other Rare Earth Metals (REM) such as Lanthanum since REMs are very often supplied to stainless steel producers as a mixed metal. It should be noted that Rare Earth Metals can be used individually or together as a mixed metal providing the total amount of REMs according to the Ce levels specified here. aluminum can be added with an aluminum content of <0.050% by weight of Al, but preferably> 0.005% by weight of Al and <0.050% by weight of Al and more preferably> 0.010% by weight of Al and <0.030% by weight weight of Al. calcium and / or magnesium can be added with a Ca and / or Mg content of> 0.001 and <0.01% by weight of Ca and / or Mg but preferably <0.005% by weight of Ca and / or Mg.
[0095] From the above, applications using forged 304LM4N stainless steel can often be designed with reduced wall thicknesses, thereby resulting in significant weight savings
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43/166 when specifying 304LM4N stainless steel compared to conventional austenitic stainless steels such as UNS S30403 and S30453 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 304LM4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel.
[0096] It should also be appreciated that if stainless steel
Forged 304LM4N is specified and used, this can result in total savings in manufacturing and construction costs because thinner wall components can be designed which are easier to handle and require less manufacturing time. For this reason, 304LM4N stainless steel can be used in a wide range of industrial applications where structural integrity and corrosion resistance is required and is particularly suitable for offshore and offshore oil and gas applications.
[0097] Forged 304LM4N stainless steel is ideal for use in a wide range of Applications in various Markets and Industrial Sectors such as top piping systems and manufactured modules used for floating Liquefied Natural Gas (FLNG) ships in the deep sea because of the savings of significant weight and manufacturing time savings that can be achieved, which in turn results in significant cost savings. 304LM4N stainless steel can also be specified and can be used for plumbing systems used for both offshore and onshore applications, such as plumbing systems used for offshore FLNG ships and onshore LNG plants, in view of its properties of high mechanical resistance and ductility, as well as having excellent hardness at ambient and cryogenic temperatures.
[0098] In addition to austenitic stainless steel 304LM4N, there are also
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44/166 a second modality is appropriately referred to as 316LM4N in this description.
316LM4N [0099] 316LM4N high strength austenitic stainless steel comprises a high level of nitrogen and a Corrosion Resistance Equivalent specified in PREn 30, but preferably PREn 35. The Corrosion Resistance Equivalent as designated by PREn is calculated from according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00100] 316LM4N stainless steel was formulated to have a unique combination of high mechanical resistance properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 316LM4N stainless steel is selective and characterized by an alloy of chemical elements in percentage by weight as follows, 0.030% by weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 16.00% by weight of Cr to 18.00% by weight of Cr, 10.00% by weight of Ni to 14.00% in Ni weight, 2.00 wt% Mo to 4.00 wt% Mo, 0.40 wt% N to 0.70 wt% N.
[00101] 316LM4N stainless steel also mainly comprises Fe as the remainder and may also contain very small amounts of other elements such as 0.010% by weight of B max, 0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels. The chemical composition of 316LM4N stainless steel is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by
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45/166 quenching with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is Austenitic. As a result, 316LM4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical analysis of 316LM4N stainless steel is adjusted to guarantee a PREn> 30, but preferably PRE n> 35, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 316LM4N stainless steel also improved resistance to stress corrosion breaking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31603 and UNS S31653.
[00102] It has been determined that the optimal chemical composition range of 316LM4N stainless steel is carefully selective to understand the following chemical elements in weight percent as follows based on a second modality, Carbon (C) [00103] Carbon content of steel 316LM4N stainless steel is <maximum 0.030% by weight of C, but preferably> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C.
Manganese (Mn) [00104] The 316LM4N stainless steel of the second modality can come in two variations: Low manganese or high manganese.
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46/166 [00105] For low manganese alloys, the manganese content of 316LM4N stainless steel is <2.0% by weight of Mn, but preferably> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such a composition, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the ratio is> 1.42 and <3.75.
[00106] For high manganese alloys, the manganese content of 316MN4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn, and more preferably the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With these selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25.
Phosphorus (P) [00107] The phosphorus content of 316LM4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the alloy 316LM4N has <0.025% by weight of P and more preferably <0.020% by weight of P P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P. Sulfur (S) [00108] The sulfur content of 316LM4N stainless steel is <0.010% by weight Preferably, 316LM4N has <0.005% by weight of S and more preferably <0.003% by weight of S, and even more preferably <0.001% by weight of S.
Oxygen (O) [00109] The oxygen content of 316LM4N stainless steel is controlled to be as low as possible and in the second mode, the
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316LM4N has <0.070% by weight of O. Preferably, 316LM4N has <0.050% by weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and up to also more preferably <0.005% by weight of O. Silicon (Si) [00110] The silicon content of 316LM4N stainless steel has <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight Si weight and <0.75% Si weight. More preferably, the range is> 0.40% Si weight and <0.60% Si weight. However, for high temperature applications, in whereas improved oxidation resistance is required, the silicon content can be> 0.75% by weight of Si and <2.00% by weight of Si.
Chromium (Cr) [00111] The chromium content of 316LM4N stainless steel is> 16.00% by weight of Cr and <18.00% by weight of Cr. Preferably, the alloy has> 17.25% by weight of Cr.
Nickel (Ni) [00112] The nickel content of 316LM4N stainless steel is> 10.00% by weight of Ni and <14.00% by weight of Ni. Preferably, the upper Ni limit of the alloy is <13.00% by weight of Ni and more preferably <12.00% by weight of Ni.
Molybdenum (Mo) [00113] The molybdenum content of 316LM4N stainless steel is> 2.00% by weight of Mo and <4.00% by weight of Mo. Preferably, the lower limit is> 3.0% by weight of Mo.
Nitrogen (N) [00114] The nitrogen content of 316LM4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, the 316LM4N has> 0.40% by weight of N and <0.60% by weight of N, and even more preferably>
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0.45% by weight of N and <0.55% by weight of N.
PREn [00115] The corrosion resistance equivalent (PREn) is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00116] 316LM4N stainless steel was specifically formulated to have the following composition:
(i) chromium content> 16.00% by weight of Cr and <18.00% by weight of Cr, but preferably> 17.25% by weight of Cr, (ii) molybdenum content> 2.00% by weight of Mo and <4.00% by weight of Mo, but preferably> 3.0% by weight of Mo, (iii) nitrogen content <0.70% by weight of N, but preferably> 0, 40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. [00117] With a high nitrogen level, 316LM4N stainless steel obtains a PREn> 30, but preferably PREn> 35. This ensures that the alloy also has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in a wide range of process environments. 316LM4N stainless steel also improved resistance to stress corrosion breaking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31603 and UNS S31653. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00118] The chemical composition of 316LM4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95, in order
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49/166 of primarily obtaining an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00119] 316LM4N stainless steel also has mainly Fe as the remainder and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent and the compositions of these elements are the same as those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00120] Stainless steel 316LM4N according to the second modality has a minimum flow limit of 55 ksi or 380 MPa for the forged version. More preferably, a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum yield limit of 48 ksi or 330 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 316LM4N stainless steel with those of UNS S31603 suggests that the minimum yield strength of 316LM4N stainless steel should be 2.5 times greater than that specified for UNS S31603 . Similarly, a comparison of the forged mechanical strength properties of the new and innovative stainless steel
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316LM4N, with those of UNS S31653, may suggest that the minimum yield limit of 316LM4N stainless steel is 2.1 times greater than that specified for UNS S31653.
[00121] 316LM4N stainless steel according to the second modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained and for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 316LM4N stainless steel, with those of UNS S31603, may suggest that the minimum tensile strength of 316LM4N stainless steel is more than 1.5 times greater than that specified for UNS S31603. Similarly, a comparison of the forged mechanical strength properties of 316LM4N stainless steel, with those of UNS S31653, may suggest that the minimum tensile strength of 316LM4N stainless steel should be 1.45 times greater than that specified for UNS S31653. In fact, if the forged mechanical strength properties of the new and innovative 316LM4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel, then it should be demonstrated that the minimum tensile strength of 316LM4N stainless steel should be in the region of 1, 2 times greater than that specified for S31803 and similar to that specified for Stainless Steel 25 Cr Super Duplex. For this reason, the minimum mechanical strength properties of 316LM4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31603 and UNS S31653 and the tensile strength properties are better than those specified for 22 Cr Du Stainless Steel
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51/166 plex and similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00122] This means that applications using forged 316LM4N stainless steel can often be designed with reduced wall thicknesses, thereby resulting in significant weight savings when specifying 316LM4N stainless steel compared to conventional austenitic stainless steels such as UNS S31603 and S31653 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 316LM4N stainless steel may be greater than for 22 Cr Duplex Stainless Steels and similar to 25 Cr Super Duplex Stainless Steels.
[00123] For certain applications, other variants of 316LM4N stainless steel were intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It has been determined that the optimal chemical composition range of the other 316LM4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 316LM4N.
T ungsteno (W [00124] The tungsten content of 316LM4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W. For 316LM4N stainless steel variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N). [00125] This variant containing tungsten from stainless steel
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316LM4N was specifically formulated to have the following composition:
(i) chromium content> 16.00% by weight of Cr and <18.00% by weight of Cr, but preferably> 17.25% by weight of Cr;
(ii) molybdenum content> 2.00% by weight of Mo and <4.00% by weight of Mo, but preferably> 3.0% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[00126] The tungsten-containing variant of 316LM4N stainless steel has a high specified level of nitrogen and a PREnw> 32, but preferably PRENW> 37. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by corrosion by Pits or crack. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [00127] For certain applications, other variants of 316LM4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 316LM4N stainless steel can
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53/166 is> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C , but preferably <0.040% by weight of C. These specific variants of 316LM4N stainless steel can be considered as versions 316HM4N or 316M4N respectively.
titanium o (Ti) / Niobium (Nb) / Niobium (Nb) plus tantalum (Ta) [00128] In addition, for certain applications, other stabilized variants of 316HM4N or 316M4N stainless steel are desirable, which have been specifically formulated to be produced containing high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
[00129] (i) This includes stabilized versions of titanium which are referred to as 316HM4NTi or 316M4NTi to contrast with the generic 316LM4N stainless steel versions. The titanium content is controlled according to the following formulas:
[00130] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 316HM4NNb or 316M4NNb where the content of niobium is controlled according to the following formulas:
[00131] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 316HM4NNbTa or 316M4NNbTa where the content of niobium plus tantalum is
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54/166 controlled according to the following formulas:
[00132] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00133] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of the elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00134] The forged and cast versions of 316LM4N stainless steel along with the other variants and modalities discussed here are generally supplied in the solution-annealed condition. However, welds for prepared Components, modules and fabrications are generally supplied in the welded condition, providing that appropriate Welding Procedure Qualifications are pre-qualified according to the respective standards and specifications. For specific applications, forged versions can also be supplied in cold working condition.
[00135] It should be appreciated that the effect of the various elements and their compositions as discussed in relation to 304LM4N are also applicable to 316LM4N (and the modalities discussed below) to appreciate how the ideal chemical composition is obtained for 316LM4N stainless steel (and the rest of the modalities).
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55/166 [00136] In addition to 304LM4N and 316LM4N austenitic stainless steels, an additional variation appropriately referred to as 317L57M4N is also proposed in this sense and this forms a third embodiment of this invention.
[317L57M4N] [00137] 317L57M4N high strength austenitic stainless steel has a high level of nitrogen and a Corrosion Resistance Equivalent specified by PREn 40, but preferably PREn 45. The Corrosion Resistance Equivalent as designated by PREn is calculated according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00138] 317L57M4N stainless steel was formulated to have a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 317L57M4N stainless steel is selective and characterized by an alloy of chemical elements in percentage by weight as follows, 0.030% by weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 18.00% by weight of Cr to 20.00% by weight of Cr, 11.00% by weight of Ni to 15.00% in Ni weight, 5.00 wt% Mo to 7.00 wt% Mo, 0.40 wt% N to 0.70 wt% N.
[00139] 317L57M4N stainless steel also mainly comprises Fe as the remainder and may also contain very small amounts of other elements such as 0.010% by weight of B max, 0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels.
[00140] The chemical composition of 317L57M4N stainless steel is optimized in the melting stage to primarily ensure a miPetition 870190038552, from 04/24/2019, pg. 80/204
56/166 austenitic croestructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. As a result, 317L57M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time achieving excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical analysis of 317L57M4N stainless steel is adjusted to obtain a PREn> 40, but preferably PREn> 45, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 317L57M4N stainless steel also improved resistance to stress corrosion cracking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753.
[00141] It has been determined that the ideal chemical composition range of 317L57M4N stainless steel is carefully selected to understand the following chemical elements in percentage by weight as follows based on the third modality,
Carbon (C) [00142] The carbon content of 317L57M4N stainless steel is <maximum 0.030% by weight of C. Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C.
Manganese (Mn)
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57/166 [00143] 317LM57M4N stainless steel of the third modality can come in two variations: low manganese or high manganese.
[00144] For low manganese alloys, the manganese content of 317L57M4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[00145] For high manganese alloys, the manganese content of 317L57M4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn, and more preferably, the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25.
Phosphorus (P) [00146] The phosphorus content of 317L57M4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the alloy
317L57M4N has <0.025% by weight of P and more preferably <0.020% by weight of P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P.
Sulfur (S) [00147] The sulfur content of 317L57M4N stainless steel of the third embodiment includes <0.010% by weight of S. Preferably, the
317L57M4N has <0.005% by weight of S and more preferably <0.003% by weight of S, and even more preferably <0.001% by weight
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58/166 S.
Oxygen (O) [00148] The oxygen content of 317L57M4N stainless steel is controlled to be as low as possible and in the third embodiment, 317L57M4N also has <0.070% by weight of O. Preferably, the 317L57M4N alloy has <0.050% by weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [00149] The silicon content of 317L57M4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <0.75% by weight Si. More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content it can be> 0.75% Si weight and <2.00% Si weight.
Chromium (Cr) [00150] The chromium content of 317L57M4N stainless steel is> 18.00% by weight of Cr and <20.00% by weight of Cr. Preferably, the alloy has> 19.00% by weight of Cr.
Nickel (Ni) [00151] The nickel content of 317L57M4N stainless steel is> 11.00% by weight of Ni and <15.00% by weight of Ni. Preferably, the upper Ni limit of the alloy is <14.00% by weight of Ni and more preferably <13.00% by weight of Ni for the lower nickel band alloys.
[00152] For high nickel band alloys, the nickel content of 317L57M4N stainless steel can have> 13.50% by weight of Ni and <17.50% by weight of Ni. Preferably, the upper limit of Ni is <16.50% by weight of Ni and more preferably <15.50% by weight of Ni
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59/166
Ni for high nickel band alloys.
Molybdenum (Mo) [00153] The molybdenum content of 317L57M4N stainless steel alloy is> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 6.00% by weight of Mo . In other words, molybdenum has a maximum of 7.00% by weight of Mo.
Nitrogen (N) [00154] The nitrogen content of 317L57M4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, the 317L57M4N can be> 0.40% by weight of N and <0.60% by weight of N, and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [00155] THE CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00156] 317L57M4N stainless steel was specifically formulated to have the following composition:
(i) chromium content> 18.00% by weight of Cr and <20.00% by weight of Cr, but preferably> 19.00% by weight of Cr;
(ii) molybdenum content> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 6.00% by weight of Mo (iii) nitrogen content <0.70% in weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and up to more preferably> 0.45% by weight of N and <0.55% by weight of N. [00157] With a high nitrogen level, 317L57M4N stainless steel obtains a PREn of> 40, and preferably PREn> 45. This ensures that the alloy has a good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in a
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60/166 wide range of process environments. 317L57M4N stainless steel also improved resistance to stress corrosion cracking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00158] The chemical composition of 317L57M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by temper with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00159] 317L57M4N stainless steel also has mainly Fe as the rest and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same like those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00160] Stainless steel 317L57M4N according to the third modality has a minimum flow limit of 55 ksi or 380 MPa
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61/166 for the forged version. More preferably, a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum yield limit of 48 ksi or 330 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of the new and innovative 317L57M4N stainless steel with those of UNS S31703 suggests that the minimum yield strength of 317L57M4N stainless steel should be 2.1 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of 317L57M4N stainless steel with those of UNS S31753 suggests that the minimum yield strength of 317L57M4N stainless steel should be 1.79 times greater than that specified for UNS S31753.
[00161] 317L57M4N stainless steel according to the third modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 317L57M4N stainless steel with those of UNS S31703 suggests that the minimum tensile strength of 317L57M4N stainless steel should be more than 1.45 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of the new and innovative 317L57M4N stainless steel with those of UNS S31753 suggests that the minimum tensile strength of 317L57M4N stainless steel should be 1.36 times greater than that specified
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62/166 for UNS S31753. In fact, if the forged mechanical strength properties of 317L57M4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel in Table 2, then it can be shown that the minimum tensile strength of 317L57M4N stainless steel is in the region of 1.2 times greater than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of 317L57M4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753 and the tensile strength properties are better than those specified for 22 Cr Duplex and Stainless Steel similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00162] This means that applications using forged 317L57M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 317L57M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703 and S31753 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 317L57M4N stainless steel are greater than for 22 Cr Duplex Stainless Steels and similar to 25 Cr Super Duplex Stainless Steels.
[00163] For certain applications, other variants of 317L57M4N stainless steel were intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It was determined that the ideal chemical composition range of the other 317L57M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, pass them on
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63/166 genes related to these elements for 304LM4N are also applicable here for 317L57M4N.
T ungsteno (W) [00164] The tungsten content of 317L57M4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W. For 317L57M4N stainless steel variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N).
[00165] This variant containing tungsten of stainless steel 317L57M4N was specifically formulated to have the following composition:
(i) chromium content> 18.00% by weight of Cr and <20.00% by weight of Cr, but preferably> 19.00% by weight of Cr;
(ii) molybdenum content> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 6.00% by weight of Mo, (iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[00166] The tungsten-containing variant of 317L57M4N stainless steel has a high specified level of nitrogen and a PREnw> 42, but preferably PREnw> 47. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by corrosion by Pits or crack. Tungsten can be added individually or in conjunction with copper, va
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64/166 nadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [00167] For certain applications, other variants of 317L57M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 317L57M4N stainless steel can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C. These specific variants of 317L57M4N stainless steel are versions 317H57M4N or 31757M4N respectively.
Titanium (Ti) / Niobium (Nb) / Niobium (Nb) plus tantalum (Ta) [00168] Furthermore, for certain applications, other stabilized variants of 317H57M4N or 31757M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon may be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 317H57M4NTi or 31757M4NTi to contrast with the generic 317L574N steel versions. The titanium content is controlled according to the following formulas:
[00169] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilizing derivatives 870190038552, of 24/04/2019, p. . 89/204
65/166 titanium alloy wheels.
(ii) There is also stabilized niobium, versions 317H57M4NNb or 31757M4NNb where the niobium content is controlled according to the following formulas:
[00170] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 317H57M4NNbTa or 31757M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00171] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00172] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00173] Forged and cast versions of 317L57M4N stainless steel along with the other variants are generally supplied in the same way as the initial modes.
[00174] Also, in this sense an additional variation is proposed
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66/166 appropriately referred to as high strength austenitic stainless steel 317L35M4N, which is a fourth embodiment of the invention. 317L35M4N stainless steel has virtually the same chemical compositions as 317L57M4N stainless steel with the exception of the molybdenum content. In this way, instead of repeating the various chemical compositions, only the difference is described.
[317L35M4N] [00175] As mentioned above, 317L35M4N has exactly the same content of carbon, manganese, phosphorus, sulfur, oxygen, silicon, chromium, nickel and nitrogen in weight by weight as the third modality, 317L57M4N stainless steel, except the molybdenum content. In 317L57M4N stainless steel, the molybdenum level is between 5.00% by weight and 7.00% by weight of Mo. In contrast, the molybdenum content of 317L35M4N stainless steel is between 3.00% by weight and 5.00% Mo. In other words, the 317L35M4N can be considered as a lower molybdenum version of 317L57M4N stainless steel.
[00176] It should be appreciated that the passages related to 317L57M4N are also applicable here, except for the molybdenum content. Molybdenum (Mo) [00177] The molybdenum content of 317L35M4N stainless steel can be> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo. In other words, the molybdenum content of 317L35M4N has a maximum of 5.00% by weight of Mo. PREn [00178] THE CORROSION RESISTANCE EQUIVALENT for 317L35M4N is calculated using the same formulas as 317L57M4N, but because of the different molybdenum content, PREN is> 35, but preferably PREn> 40. This ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range
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67/166 of process environments. 317L35M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00179] The chemical composition of 317L35M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by temper with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. As a result, 317L35M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00180] Like the 317L57M4N modality, 317L35M4N stainless steel also contains mainly Fe as the remainder and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same as those of 317L57M4N and therefore, those of 304LM4N.
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68/166 [00181] The 317L35M4N stainless steel of the fourth modality has a minimum yield limit and a minimum tensile strength comparable or similar to those of 317L57M4N stainless steel. Likewise, the strength properties of the forged and cast versions of the 317L35M4N are also comparable to those of the 317L57M4N. In this way, the specific resistance values are not repeated here and reference is made to the initial passages of 317L57M4N. A comparison of the properties of forged mechanical strength between 317L35M4N and those of conventional austenitic stainless steel UNS S31703, and between 317L35M4N and those of UNS S31753, suggests higher tensile strengths and yields of magnitude similar to those found for 317L57M4N. Similarly, a comparison of the tensile properties of 317L35M4N demonstrates that they are better than those specified for 22 Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel, just like the 317L57M4N.
[00182] This means that applications using forged 317L35M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 317L35M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703 and S31753 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 317L35M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel.
[00183] For certain applications, other variants of 317L35M4N stainless steel were intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It was determined that the
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69/166 Ideal chemical composition of the other 317L35M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 317L57M4N and those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 317L35M4N.
T ungstene (W) [00184] The tungsten content of 317L35M4N stainless steel is similar to that of 317L57M4N and the CORROSION RESISTANCE EQUIVALENT, PRENW, of 317L35M4N calculated using the same formulas as mentioned above for 317L57M4N is> 37, and from preferably PRENW> 42, due to the different molybdenum content. It should be evident that the passage related to the use and effects of tungsten for 317L57M4N is also applicable for 317L35M4N.
[00185] Also, the 317L35M4N may have high levels of carbon referred to as 317H35M4N and 31735M4N which correspond respectively to 317H57M4N and 31757M4N discussed earlier and the carbon weight% ranges discussed above are also applicable for 317H35M4N and 31735M4N.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00186] In addition, for certain applications, other stabilized variants of 317H35M4N or 31735M4N stainless steel are desirable, which have been specifically formulated to be produced containing high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 317H35M4NTi or 31735M4NTi to contrast with the generic 317L35M4N. The titanium content is controlled according to the
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70/166 following formulas:
[00187] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, 317H35M4NNb or 31735M4NNb, versions where the niobium content is controlled according to the following formulas:
[00188] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 317H35M4NNbTa or 31735M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00189] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00190] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00191] Forged and cast versions of stainless steel
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317L35M4N together with the other variants are generally provided in the same way as the initial modalities.
[00192] Also, in this sense, an additional variation appropriately referred to as 312L35M4N is proposed in this description, which is a fifth embodiment of the invention.
[312L35M4N] [00193] The high strength austenitic stainless steel 312L35M4N has a high level of nitrogen and a Corrosion Resistance Equivalent specified in PREn 37, but preferably PREn 42. The Corrosion Resistance Equivalent as designated by PREN is calculated according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00194] 312L35M4N stainless steel was formulated to have a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 312L35M4N stainless steel is selective and characterized by a chemical analysis alloy in percentage by weight as follows, 0.030% by weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 20.00% by weight of Cr to 22.00% by weight of Cr, 15.00% by weight of Ni at 19.00% in Ni weight, 3.00 wt% Mo to 5.00 wt% Mo, 0.40 wt% N to 0.70 wt% N.
[00195] 312L35M4N stainless steel also contains mainly Fe as the rest and may also contain very small amounts of other elements such as 0.010% by weight of B max, 0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels.
[00196] The chemical composition of 312L35M4N stainless steel is
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72/166 optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. As a result, 312L35M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical composition of 312L35M4N stainless steel is adjusted to obtain a PREn> 37, but preferably PREn> 42, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting corrosion and Crack Corrosion) in a wide range of process environments. 312L35M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753.
[00197] It has been determined that the ideal chemical composition range of 312L35M4N stainless steel is carefully selected to understand the following chemical elements in percentage by weight as follows based on the fifth modality,
Carbon (C) [00198] The carbon content of 312L35M4N stainless steel is <maximum 0.030% by weight of C. Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C.
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Manganese (Mn) [00199] Stainless steel 312L35M4N of the fifth modality can come in two variations: low manganese or high manganese.
[00200] For low manganese alloys, the manganese content of 312L35M4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[00201] For high manganese alloys, the manganese content of 312L35M4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn and more preferably, the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25.
Phosphorus (P) [00202] The phosphorus content of 312L35M4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the alloy
317L57M4N has <0.025% by weight of P and more preferably <0.020% by weight of P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P.
Sulfur (S) [00203] The sulfur content of 312L35M4N stainless steel of the fifth modality includes <0.010% by weight of S. Preferably, the
312L35M4N has <0.005% by weight of S and more preferably <
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0.003% by weight of S, and even more preferably <0.001% by weight of S.
Oxygen (O) [00204] The oxygen content of 312L35M4N stainless steel is controlled to be as low as possible and in the fifth embodiment, 312L35M4N has <0.070% by weight of O. Preferably, the
312L35M4N has <0.050% by weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [00205] The silicon content of 312L35M4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <0.75% by weight Si. More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content it can be> 0.75% Si weight and <2.00% Si weight.
Chromium (Cr) [00206] The chromium content of 312L35M4N stainless steel is> 20.00% by weight of Cr and <22.00% by weight of Cr. Preferably, the alloy has> 21.00% by weight of Cr.
Nickel (Ni) [00207] The nickel content of 312L35M4N stainless steel is> 15.00% by weight of Ni and <19.00% by weight of Ni. Preferably, the upper limit of Ni of the alloy is <18.00% by weight of Ni and more preferably <17.00% by weight of Ni.
Molybdenum (Mo) [00208] The molybdenum content of the 312L35M4N stainless steel alloy is> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably
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75/166 yield> 4.00% by weight of Mo. In other words, the molybdenum of this modality has a maximum of 5.00% by weight of Mo.
Nitrogen (N) [00209] The nitrogen content of 312L35M4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, 312L35M4N has> 0.40% by weight of N and <0.60% by weight of N, and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [00210] THE CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00211] Stainless steel 312L35M4N was specifically formulated to have the following composition:
(i) chromium content> 20.00% by weight of Cr and <22.00% by weight of Cr, but preferably> 21.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. [00212] With a high nitrogen level, stainless steel 312L35M4N obtains a PREn of> 37, and preferably PREn> 42. This ensures that the alloy has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in a wide range of process environments. 312L35M4N stainless steel also improved resistance to stress corrosion cracking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS
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S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00213] The chemical composition of 312L35M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer ⁶ , is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by temper with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00214] Stainless steel 312L35M4N also has mainly Fe as the rest and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same like those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00215] Stainless steel 312L35M4N according to the fifth modality has a minimum flow limit of 55 ksi or 380 MPa for the forged version. More preferably, a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum flow limit of 48 ksi or
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330 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of the new and innovative 312L35M4N stainless steel with those of UNS S31703 suggests that the minimum yield strength of 312L35M4N stainless steel should be 2.1 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of 312L35M4N stainless steel, with those of UNS S31753, suggests that the minimum yield strength of 312L35M4N stainless steel should be 1.79 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 312L35M4N stainless steel with those of UNS S31254 suggests that the minimum yield strength of 312L35M4N stainless steel should be 1.38 times greater than that specified for UNS S31254.
[00216] Stainless steel 312L35M4N according to the fifth modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 312L35M4N stainless steel with those of UNS S31703 suggests that the minimum tensile strength of 312L35M4N stainless steel should be more than 1.45 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of 312L35M4N stainless steel with those of UNS S31753 suggests that the minimum tensile strength of 312L35M4N stainless steel should
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78/166 is 1.36 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 312L35M4N stainless steel with those of UNS S31254 suggests that the minimum tensile strength of 312L35M4N stainless steel should be 1.14 times greater than that specified for UNS S31254. In fact, if the forged mechanical strength properties of 312L35M4N stainless steel are compared to those of 22 Cr Duplex Stainless steel, then it can be demonstrated that the minimum tensile strength of 312L35M4N stainless steel is in the region of 1.2 times greater than than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of 312L35M4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31703, UNS S31753 and UNS S31254 and the tensile strength properties are better than those specified for Stainless Steel 22 Cr Duplex and similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00217] This means that applications using forged 312L35M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 312L35M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S31254 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 312L35M4N stainless steel are greater than for 22 Cr Duplex Stainless Steels and similar to 25 Cr Super Duplex Stainless Steels. [00218] For certain applications, other variants of stainless steel 312L35M4N were intentionally formulated to be produced.
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79/166 of those containing specific levels of other binding elements such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 312L35M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, passages related to these elements for 304LM4N are also applicable for 312L35M4N.
T ungsteno (W) [00219] The tungsten content of 312L35M4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W, and more preferably> 0.75% by weight of W. For stainless steel 312L35M4N variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N).
[00220] This variant containing tungsten from stainless steel 312L35M4N was specifically formulated to have the following composition:
(i) chromium content> 20.00% by weight of Cr and <22.00% by weight of Cr, but preferably> 21.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[00221] The tungsten-containing variant of stainless steel
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312L35M4N has a high specified level of nitrogen and a PREnw> 39, but preferably PREnw> 44. It should be emphasized that these equations ignore the effects of microstructural factors in the breakdown of pitting or crack corrosion. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon [00222] For certain applications, other variants of stainless steel 312L35M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 312L35M4N stainless steel can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C. These specific variants of stainless steel 312L35M4N are versions 312H35M4N or 31235M4N respectively.
Titanium (Ti) / Niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00223] Furthermore, for certain applications, other stabilized variants of stainless steel 312H35M4N or 31235M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon may be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes stabilized versions of titanium that are re
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81/166 wounds such as 312H35M4NTÍ or 31235M4NTÍ to contrast with the generic 312L35M4N steel versions. The titanium content is controlled according to the following formulas:
[00224] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions of 312H35M4NNb or 31235M4NNb where the content of niobium is controlled according to the following formulas:
[00225] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions of 312H35M4NNbTa or 31235M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00226] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00227] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve color performance. Petition 870190038552, from 24/04/2019, p. 106/204
82/166 total roson of the alloy.
[00228] The forged and cast versions of 312L35M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00229] Also, in this sense an additional variation is proposed, appropriately referred to as high strength austenitic stainless steel 3112L57M4N, which is a sixth embodiment of the invention. Stainless 312L57M4N has virtually the same chemical composition as stainless steel 312L35M4N with the exception of the molybdenum content. In this way, instead of repeating the various chemical compositions, only the difference is described.
[312L57M4N] [00230] As mentioned above, 312L57M4N has exactly the same content of carbon, manganese, phosphorus, sulfur, oxygen, silicon, chromium, nickel and nitrogen in% by weight as the fifth modality, stainless steel 312L35M4N, except the molybdenum content. In the 312L35M4N, the molybdenum content is between 3.00% by weight and 5.00% by weight. In contrast, the molybdenum content of 312L57M4N stainless steel is between 5.00% by weight and 7.00% by weight. In other words, 312L57M4N can be considered as a high molybdenum version of 312L35M4N stainless steel.
[00231] It should be appreciated that the passages related to 312L35M4N are also applicable here, except for the molybdenum content. Molybdenum (Mo) [00232] The molybdenum content of 312L57M4N stainless steel can be> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 6.00% by weight of Mo. In other words, the molybdenum content of 312L57M4N has a maximum of 7.00% by weight of Mo. PREn [00233] THE CORROSION RESISTANCE EQUIVALENT for
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83/166 the 312L57M4N is calculated using the same formulas as 312L35M4N but because of the molybdenum content, PREN is> 43, but preferably PREN> 48. This ensures that the material also has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 312L57M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00234] The chemical composition of 312L57M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00235] Like the 312L35M4N modality, 312L57M4N stainless steel also contains mainly Fe as the remainder and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same as
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84/166 those of 312L35M4N and thus, those of 304LM4N.
[00236] The stainless steel 312L57M4N of the sixth modality has a minimum yield limit and a minimum tensile strength comparable or similar to those of stainless steel 312L35M4N. Likewise, the strength properties of the forged and cast versions of the 312L57M4N are also comparable to those of the 312L35M4N. In this way, the specific resistance values are not repeated here and reference is made to the initial passages of 312L35M4N. A comparison of the properties of forged mechanical strength between 312L57M4N and those of conventional austenitic stainless steel UNS S31703, and between 312L57M4N and those of UNS S31753 / UNS S31254, suggests stronger tensile strengths and yields of similar magnitude to those found for 312L35M4N. Similarly, a comparison of the tensile properties of 312L57M4N demonstrates that they are better than those specified for 22Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel, just like the 312L35M4N.
[00237] This means that applications using forged 312L57M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 312L57M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S31254 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 312L57M4N stainless steel are greater than for 22 Cr Duplex Stainless Steels and similar to 25 Cr Super Duplex Stainless Steels.
[00238] For certain applications, other variants of stainless steel 312L57M4N were intentionally formulated to be produced
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85/166 of those containing specific levels of other binding elements such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 312L57M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 312L35M4N and those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 312L57M4N.
T ungstene (W) [00239] The tungsten content of 312L57M4N stainless steel is similar to that of 312L35M4N and the CORROSION RESISTANCE EQUIVALENT, PRENW, of 312L57M4N calculated using the same formulas as mentioned above for 312L35M4N is PRENW> 45, and preferably PRENW> 50, due to the different molybdenum content. It should be evident that the passage related to the use and effects of tungsten for 312L35M4N is also applicable for 312L57M4N.
[00240] Also, 312L57M4N may have high levels of carbon referred to as 312H57M4N or 31257M4N which correspond to 312H35M4N and 31235M4N respectively discussed above and the weight% carbon ranges discussed above are also applicable for 312H57M4N and 31257M4N.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00241] In addition, for certain applications, other stabilized variants of stainless steel 312H57M4N or 31257M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon may be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 312H57M4NTi or 31257M4NTi to contrast with the
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86/166 stainless steel versions 312L57M4N generic. The titanium content is controlled according to the following formulas:
[00242] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions of 312H57M4NNb or 31257M4NNb where the content of niobium is controlled according to the following formulas:
[00243] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 312H57M4NNbTa or 31257M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00244] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00245] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
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87/166 [00246] Forged and cast versions of 312L57M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00247] Also, in this sense, an additional variation appropriately referred to as 320L35M4N is proposed in this description, which is a seventh embodiment of the invention.
[320L35M4N] [00248] 320L35M4N high strength austenitic stainless steel has a high nitrogen level and a Corrosion Resistance Equivalent specified in PREn 39, but preferably PREn 44. The Corrosion Resistance Equivalent as designated by PREn is calculated according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00249] Stainless steel 320L35M4N was formulated to have a unique combination of properties of high mechanical resistance with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 320L35M4N stainless steel is selective and characterized by a chemical analysis alloy in percentage by weight as follows, 0.030% by weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 22.00% by weight of Cr to 24.00% by weight of Cr, 17.00% by weight of Ni to 21.00% in Ni weight, 3.00 wt% Mo to 5.00 wt% Mo, 0.40 wt% N to 0.70 wt% N.
[00250] Stainless steel 320L35M4N also contains mainly Fe as the remainder and may also contain very small amounts of other elements such as 0.010% by weight of B max, 0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels.
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88/166 [00251] The chemical composition of 320L35M4N stainless steel is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by quenching with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. As a result, 320L35M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical composition of 320L35M4N stainless steel is adjusted to obtain a PREN> 39, but preferably PREN> 44, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting corrosion and Crack Corrosion) in a wide range of process environments. 320L35M4N stainless steel also improved resistance to stress corrosion breaking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753.
[00252] It has been determined that the ideal chemical composition range of 320L35M4N stainless steel is carefully selected to understand the following chemical elements in weight percent as follows, based on the seventh modality,
Carbon (C) [00253] The carbon content of 320L35M4N stainless steel is <maximum 0.030% by weight of C. Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and
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89/166 more preferably <0.025% by weight of C.
Manganese (Mn) [00254] Stainless steel 320L35M4N of the seventh modality can come in two variations: low manganese or high manganese.
[00255] For low manganese alloys, the manganese content of 320L35M4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[00256] For high manganese alloys, the manganese content of 320L35M4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn and more preferably, the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25.
Phosphorus (P) [00257] The phosphorus content of 320L35M4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the alloy
320L35M4N has <0.025% by weight of P and more preferably <0.020% by weight of P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P.
Sulfur (S) [00258] The sulfur content of 320L35M4N stainless steel of the seventh modality includes <0.010% by weight of S. Preferably, the
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320L35M4N has <0.005% by weight of S and more preferably <0.003% by weight of S, and even more preferably <0.001% by weight of S.
Oxygen (O) [00259] The oxygen content of 320L35M4N stainless steel is controlled to be as low as possible and in the seventh mode, 320L35M4N has <0.070% by weight of O. Preferably, 320L35M4N has <0.050% by weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [00260] The silicon content of 320L35M4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <0.75% by weight Si. More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content it can be> 0.75% Si weight and <2.00% Si weight.
Chromium (Cr) [00261] The chromium content of 320L35M4N stainless steel is> 22.00% by weight of Cr and <24.00% by weight of Cr. Preferably, the alloy has> 23.00% by weight of Cr.
Nickel (Ni) [00262] The nickel content of 320L35M4N stainless steel is> 17.00% by weight of Ni and <21.00% by weight of Ni. Preferably, the upper limit of Ni of the alloy is <20.00% by weight of Ni and more preferably <19.00% by weight of Ni.
Molybdenum (Mo) [00263] The molybdenum content of 320L35M4N stainless steel alloy is>
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3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo.
Nitrogen (N) [00264] The nitrogen content of 320L35M4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, 320L35M4N has> 0.40% by weight of N and <0.60% by weight of N, and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [00265] THE CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00266] Stainless steel 320L35M4N was specifically formulated to have the following composition:
(i) chromium content> 22.00% by weight of Cr and <24.00% by weight of Cr, but preferably> 23.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo, (iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. [00267] With a high nitrogen level, 320L35M4N stainless steel obtains a PREN of> 39, and preferably PREN> 44 This ensures that the alloy has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 320L35M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS
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S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00268] The chemical composition of 320L35M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00269] Stainless steel 320L35M4N also has mainly Fe as the rest and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same like those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00270] The 320L35M4N stainless steel according to the seventh modality has a minimum flow limit of 55 ksi or 380 MPa for the forged version. More preferably, a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum flow limit of 48 ksi or
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330 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 320L35M4N stainless steel with those of UNS S31703 suggests that the minimum yield strength of 320L35M4N stainless steel should be 2.1 times greater than that specified for UNS S31703 . Similarly, a comparison of the forged mechanical strength properties of 320L35M4N stainless steel with those of UNS S31753 suggests that the minimum yield strength of 320L35M4N stainless steel should be 1.79 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 320L35M4N stainless steel with those of UNS S32053 suggests that the minimum yield strength of 320L35M4N stainless steel should be 1.45 times greater than that specified for UNS S32053.
[00271] The 320L35M4N stainless steel according to the seventh modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on preferred values, a comparison of the forged mechanical strength properties of 320L35M4N stainless steel with those of UNS S31703 suggests that the minimum tensile strength of 320L35M4N stainless steel should be more than 1.45 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of 320L35M4N stainless steel with those of UNS S31753 suggests that the minimum tensile strength of 320L35M4N stainless steel should be 1.36 times greater than that specified for UNS S31753.
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Likewise, a comparison of the forged mechanical strength properties of 320L35M4N stainless steel with those of UNS S32053 suggests that the minimum tensile strength of 320L35M4N stainless steel should be 1.17 times greater than that specified for UNS S32053. In fact, if the forged mechanical strength properties of 320L35M4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel, then it can be demonstrated that the minimum tensile strength of 320L35M4N stainless steel is in the region of 1.2 times greater than than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of the new and innovative 320L35M4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31703, UNS S31753 and UNS S32053 and the tensile strength properties are better than those specified for 22 Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00272] This means that applications using forged 320L35M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 320L35M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S32053 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 320L35M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel. [00273] For certain applications, other variants of 320L35M4N stainless steel were intentionally formulated to be produced containing specific levels of other bonding elements such as
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95/166 such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 320L35M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, passages related to these elements for 304LM4N are also applicable for 320L35M4N.
T ungstene (W) [00274] The tungsten content of 320L35M4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W, and more preferably> 0.75% by weight of W. For 320L35M4N stainless steel variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N).
[00275] This tungsten-containing variant of 320L35M4N stainless steel was specifically formulated to have the following composition:
(i) chromium content> 22.00% by weight of Cr and <24.00% by weight of Cr, but preferably> 23.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[00276] The tungsten-containing variant of 320L35M4N stainless steel has a high specified level of nitrogen and a
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PREnw> 41, but preferably PREnw> 46. It should be emphasized that these equations ignore the effects of microstructural factors in the breakdown of pitting or crack corrosion passivity. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [00277] For certain applications, other variants of 320L35M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 320L35M4N stainless steel can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C. These specific variants of 320L35M4N stainless steel are versions 320H35M4N or 32035M4N respectively.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00278] In addition, for certain applications, other stabilized variants of stainless steel 320H35M4N or 32035M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes stabilized versions of titanium that are re
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97/166 wounds such as 320H35M4NTÍ or 32035M4NTÍ to contrast with the generic 320L35M4N versions. The titanium content is controlled according to the following formulas:
[00279] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 320H35M4NNb or 32035M4NNb where the content of niobium is controlled according to the following formulas:
[00280] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 320H35M4NNbTa or 32035M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00281] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00282] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum from the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve color performance Petition 870190038552, from 24/04/2019, p. 122/204
98/166 total roson of the alloy.
[00283] Forged and cast versions of 320L35M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00284] Also, in this sense, an additional variation appropriately referred to as 320L57M4N high strength austenitic stainless steel is proposed, which is an eighth modality of the invention. 320L57M4N stainless steel has virtually the same chemical composition as 320L35M4N with the exception of the molybdenum content. In this way, instead of repeating the various chemical compositions, only the difference is described.
[320L57M4N] [00285] As mentioned above, 320L57M4N has exactly the same content of carbon, manganese, Phosphorus, Sulfur, Oxygen, silicon, chromium, nickel and nitrogen in weight by weight as the seventh modality, 320L35M4N stainless steel, except the molybdenum content. In 320L35M4N, the molybdenum content is between 3.00% by weight and 5.00% by weight of Mo. In contrast, the 320L57M4N stainless steel molybdenum content is between 5.00% by weight and 7.00% by weight of Mo. In other words, the 320L57M4N can be considered as a high molybdenum version of 320L35M4N stainless steel.
[00286] It should be appreciated that the passages related to 320L35M4N are also applicable here, except for the molybdenum content. Molybdenum (Mo) [00287] The molybdenum content of 320L57M4N stainless steel can be> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 6.00% by weight of Mo. In other words, the molybdenum content of 320L57M4N has a maximum of 7.00% by weight of Mo. PREn [00288] THE CORROSION RESISTANCE EQUIVALENT for
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99/166 the 320L57M4N is calculated using the same formulas as a 320L35M4N but because of the molybdenum content, PREn is> 45, but preferably PREn> 50. This ensures that the material also has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 320L57M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00289] The chemical composition of 320L57M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00290] Like the 320L35M4N modality, 320L57M4N stainless steel also contains mainly Fe as the remainder and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent and the compositions of these elements are the same as
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100/166 those of 320L35M4N and thus, those of 304LM4N.
[00291] Stainless steel 320L57M4N of the eighth modality has a minimum yield limit and a minimum tensile strength comparable or similar to those of stainless steel 320L35M4N. Likewise, the strength properties of the forged and cast versions of the 320L57M4N are also comparable to those of the 320L35M4N. In this way, the specific resistance values are not repeated here and reference is made to the initial passes of 320L35M4N. A comparison of the properties of forged mechanical strength between 320L57M4N and those of conventional austenitic stainless steel UNS S31703, and between 320L57M4N and those of UNS S31753 / UNS S32053, suggests stronger tensile strengths and yields of the magnitude similar to those found for 320L35M4N. Similarly, a comparison of the 320L57M4N tensile properties demonstrates that they are better than those specified for 22 Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel, just like the 320L35M4N.
[00292] This means that applications using forged 320L57M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 320L57M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S32053 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 320L57M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel.
[00293] For certain applications, other variants of 320L57M4N stainless steel have been intentionally formulated to be produced
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101/166 of those containing specific levels of other binding elements such as copper, tungsten and vanadium. It was determined that the ideal chemical composition range of the other 320L57M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 320L35M4N and those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 320L57M4N.
T ungstene (W) [00294] The tungsten content of 320L57M4N stainless steel is similar to that of 320L35M4N and the CORROSION RESISTANCE EQUIVALENT, PRENW, of 320L57M4N calculated using the same formulas as mentioned above for 320L35M4N is PRENW> 47, and preferably PRENW> 52, due to the different molybdenum content. It should be evident that the passage related to the use and effects of tungsten for 320L35M4N is also applicable for 320L57M4N.
[00295] In addition, the 320L57M4N may have high levels of carbon referred to as 320H57M4N or 32057M4N which correspond respectively to 320H35M4N and 32035M4N previously discussed and the weight% carbon ranges discussed above are also applicable for 320H57M4N and 32057M4N.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00296] Furthermore, for certain applications, other stabilized variants of 320H57M4N or 32057M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon may be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 320H57M4NTi or 32057M4NTi to contrast with the
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Generic 320L57M4N. The titanium content is controlled according to the following formulas:
[00297] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 320H57M4NNb or 32057M4NNb where the niobium content is controlled according to the following formulas:
[00298] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 320H57M4NNbTa or 32057M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00299] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00300] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
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103/166 [00301] The forged and cast versions of 320L57M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00302] Also, in this sense, an additional variation appropriately referred to as 326L35M4N is proposed in this description, which is a ninth embodiment of the invention.
[326L35M4N] [00303] The high strength austenitic stainless steel 326L35M4N has a high level of nitrogen and a Corrosion Resistance Equivalent specified in PREn 42, but preferably PREn 47. The Corrosion Resistance Equivalent as designated by PREN is calculated according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00304] Stainless steel 326L35M4N was formulated to have a unique combination of properties of high mechanical resistance with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 326L35M4N stainless steel is selective and characterized by a chemical analysis alloy in percentage by weight as follows, 0.030% by weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 24.00% by weight of Cr to 26.00% by weight of Cr, 19.00% by weight of Ni to 23.00% in Ni weight, 3.00 wt% Mo to 5.00 wt% Mo, 0.40 wt% N to 0.70 wt% N.
[00305] Stainless steel 326L35M4N also contains mainly Fe as the remainder and may also contain very small amounts of other elements such as 0.010% by weight of B max, 0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels.
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104/166 [00306] The chemical composition of 326L35M4N stainless steel is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by quenching with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. As a result, 326L35M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical composition of 326L35M4N stainless steel is adjusted to obtain a PREN> 42, but preferably PREN> 47, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting corrosion and Crack Corrosion) in a wide range of process environments. 326L35M4N stainless steel also improved resistance to stress corrosion breaking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753.
[00307] It has been determined that the optimal chemical composition range of 326L35M4N stainless steel is carefully selected to understand the following chemical elements in weight percent as follows, based on the ninth modality.
Carbon (C) [00308] The carbon content of 326L35M4N stainless steel is <maximum 0.030% by weight of C. Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and
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105/166 more preferably <0.025% by weight of C.
Manganese (Mn) [00309] Stainless steel 326L35M4N of the ninth modality can come in two variations: low manganese or high manganese.
[00310] For low manganese alloys, the manganese content of 326L35M4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[00311] For high manganese alloys, the manganese content of 326L35M4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn and more preferably, the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25 for high manganese alloys. Phosphorus (P) [00312] The phosphorus content of 326L35M4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the alloy
326L35M4N has <0.025% by weight of P and more preferably <0.020% by weight of P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P.
Sulfur (S) [00313] The sulfur content of 326L35M4N stainless steel of the ninth modality includes <0.010% by weight of S. Preferably, the
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326L35M4N has <0.005% by weight of S and more preferably <0.003% by weight of S, and even more preferably <0.001% by weight of S.
Oxygen (O) [00314] The oxygen content of the 326L35M4N stainless steel is controlled to be as low as possible and in the ninth modality, the 326L35M4N has <0.070% by weight of O. Preferably, the
326L35M4N has <0.050% by weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [00315] The silicon content of 326L35M4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <0.75% by weight Si. More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content it can be> 0.75% Si weight and <2.00% Si weight.
Chromium (Cr) [00316] The chromium content of 326L35M4N stainless steel is> 24.00% by weight of Cr and <26.00% by weight of Cr. Preferably, the alloy has> 25.00% by weight of Cr.
Nickel (Ni) [00317] The nickel content of 326L35M4N stainless steel is> 19.00% by weight of Ni and <23.00% by weight of Ni. Preferably, the upper limit of Ni of the alloy is <22.00% by weight of Ni and more preferably <21.00% by weight of Ni.
Molybdenum (Mo) [00318] The molybdenum content of the stainless steel alloy 326L35M4N
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107/166 is> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo.
Nitrogen (N) [00319] The nitrogen content of 326L35M4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, 326L35M4N has> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [00320] THE CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00321] Stainless steel 326L35M4N was specifically formulated to have the following composition:
i) chromium content> 24.00% by weight of Cr and <26.00% by weight of Cr, but preferably> 25.00% by weight of Cr;
ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. [00322] With a high nitrogen level, 326L35M4N stainless steel obtains a PREN > 42, but preferably PREN> 47. This ensures that the alloy has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crevice Corrosion) in a wide range of process environments. 326L35M4N stainless steel also improved resistance to stress corrosion cracking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS
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S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00323] The chemical composition of 326L35M4N stainless steel is optimized in the melting stage to ensure that the ratio of the [Cr] equivalent divided by the [Ni] equivalent, according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00324] Stainless steel 326L35M4N also has mainly Fe as the rest and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same like those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00325] Stainless steel 326L35M4N according to the ninth modality has a minimum flow limit of 55 ksi or 380 MPa for the forged version. More preferably, a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum flow limit of 48 ksi or 330
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MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 326L35M4N stainless steel with those of UNS S31703 suggests that the minimum yield limit of 326L35M4N stainless steel should be 2.1 times greater than that specified for UNS S31703 . Similarly, a comparison of the forged mechanical strength properties of 326L35M4N stainless steel with those of UNS S31753 suggests that the minimum yield strength of 326L35M4N stainless steel should be 1.79 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 326L35M4N stainless steel with those of UNS S32615 suggests that the minimum yield strength of 326L35M4N stainless steel should be 1.95 times greater than that specified for UNS S32615.
[00326] Stainless steel 326L35M4N according to the ninth modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. Most preferably a minimum tensile strength of 109 ksi or 750 MPa can be obtained for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on preferred values, a comparison of the forged mechanical strength properties of 326L35M4N stainless steel with those of UNS S31703 suggests that the minimum tensile strength of 326L35M4N stainless steel should be more than 1.45 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of 326L35M4N stainless steel with those of UNS S31753 suggests that the minimum tensile strength of 326L35M4N stainless steel should be 1.36 times greater than that specified for UNS S31753. Of
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110/166 likewise, a comparison of the forged mechanical strength properties of 326L35M4N stainless steel with those of UNS S32615 suggests that the minimum tensile strength of 326L35M4N stainless steel should be 1.36 times greater than that specified for UNS S32615 . In fact, if the forged mechanical strength properties of 326L35M4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel, then it can be shown that the minimum tensile strength of 326L35M4N stainless steel is in the region of 1.2 times greater than than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of 326L35M4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31703, UNS S31753 and UNS S32615 and the tensile strength properties are better than those specified for Stainless Steel 22 Cr Duplex and similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00327] This means that applications using forged 326L35M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 326L35M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S32615 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 326L35M4N stainless steel are greater than for 22 Cr Duplex Stainless Steels and similar to 25 Cr Super Duplex Stainless Steels.
[00328] For certain applications, other variants of stainless steel 326L35M4N were intentionally formulated to be produced containing specific levels of other bonding elements such
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111/166 such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 326L35M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, passages related to these elements for 304LM4N are also applicable for 320L35M4N.
T ungsteno (W) [00329] The tungsten content of 326L35M4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W, and more preferably> 0.75% by weight of W. For 326L35M4N stainless steel variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N).
[00330] This variant containing tungsten of stainless steel 326L35M4N was specifically formulated to have the following composition:
(i) chromium content> 24.00% by weight of Cr and <26.00% by weight of Cr, but preferably> 25.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W, more preferably> 0.75% by weight of W .
[00331] The tungsten-containing variant of stainless steel 326L35M4N has a high specified level of nitrogen and a
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PREnw> 44, but preferably PREnw> 49. It should be emphasized that these equations ignore the effects of microstructural factors in the breakdown of pitting or crack corrosion passivity. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [00332] For certain applications, other variants of stainless steel 326L35M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 320L35M4N stainless steel can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C. These specific variants of stainless steel 326L35M4N are versions 326H35M4N or 32635M4N respectively.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00333] In addition, for certain applications, other stabilized variants of 326H35M4N or 32635M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon may be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 326H35M4NTi or 32635M4NTi to contrast with the
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113/166 versions of generic 326L35M4N. The titanium content is controlled according to the following formulas:
[00334] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions of 326H35M4NNb or 32635M4NNb where the niobium content is controlled according to the following formulas:
[00335] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 326H35M4NNbTa or 32635M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00336] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00337] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
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114/166 [00338] Forged and cast versions of 326L35M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00339] Also, in this sense, an additional variation appropriately referred to as high-strength austenitic stainless steel326L57M4N is proposed, which is a tenth modality of the invention. 326L57M4N stainless steel has virtually the same chemical composition as 326L35M4N stainless steel with the exception of the molybdenum content. In this way, instead of repeating the various chemical compositions, only the difference is described.
[326L57M4N] [00340] As mentioned above, 326L57M4N has exactly the same content of carbon, manganese, Phosphorus, Sulfur, Oxygen, silicon, chromium, nickel and nitrogen in weight% as the ninth modality, stainless steel 326L35M4N, except the molybdenum content. In 326L35M4N, the molybdenum content is between 3.00% by weight and 5.00% by weight of Mo. In contrast, the molybdenum content of 326L57M4N stainless steel is between 5.00% by weight and 7.00% by weight of Mo. In other words, the 326L57M4N can be considered as a high molybdenum version of the 326L35M4N stainless steel.
[00341] It should be appreciated that the passages related to 326L35M4N are also applicable here, except for the molybdenum content. Molybdenum (Mo) [00342] The molybdenum content of 326L57M4N stainless steel can be> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 6.00% by weight of Mo and <7.00% by weight of Mo, and more preferably> 6.50% by weight of Mo. In other words, the molybdenum content of 326L57M4N has a maximum of 7.00% by weight of Mo.
PREn
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115/166 [00343] THE CORROSION RESISTANCE EQUIVALENT for 326L57M4N is calculated using the same formulas as 326L35M4N but because of the molybdenum content, PREn is> 48.5, but preferably PREn> 53.5. This ensures that the material also has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 326L57M4N stainless steel also improved resistance to stress corrosion breaking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00344] The chemical composition of 326L57M4N stainless steel is optimized in the melting stage to ensure that the ratio of the [Cr] equivalent divided by the [Ni] equivalent, according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00345] Like the 326L35M4N mode, the 326L57M4N stainless steel also contains mainly Fe as the rest and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in percentage
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116/166 by weight and the compositions of these elements are the same as those of 326L35M4N, and therefore, those of 304LM4N.
[00346] Stainless steel 326L57M4N of the tenth modality has a minimum yield limit and a minimum tensile strength comparable or similar to those of stainless steel 326L35M4N. Likewise, the strength properties of the forged and cast versions of the 326L57M4N are also comparable to those of the 326L35M4N. In this way, the specific resistance values are not repeated here and reference is made to the initial passages of 326L35M4N. A comparison of the properties of forged mechanical strength between 326L57M4N and those of conventional austenitic stainless steel UNS S31703, and between 326L57M4N and those of UNS S31753 / UNS S32615, suggests stronger tensile strengths and yields of similar magnitude to those found for 326L35M4N. Similarly, a comparison of the 326L57M4N tensile strength properties demonstrates that they are better than those specified for 22Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel, just like the 326L35M4N.
[00347] This means that applications using forged 326L57M4N stainless steel can often be designed with reduced wall thicknesses, thereby resulting in significant weight savings when specifying 326L57M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S32615 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 326L57M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel.
[00348] For certain applications, other stainless steel variants
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326L57M4N, were intentionally formulated to be produced containing specific levels of other binding elements such as copper, tungsten and vanadium. It has been determined that the optimal chemical composition range of the other 326L57M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 326L35M4N and those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 326L57M4N.
T ungstene (W) [00349] The tungsten content of the 326L57M4N stainless steel is similar to that of the 326L35M4N and the CORROSION RESISTANCE EQUIVALENT, PRENW, of 326L57M4N calculated using the same formulas as mentioned above for 326L35M4N is PRENW>
50.5, and preferably PRENW> 55.5, due to the different molybdenum content. It should be evident that the passage related to the use and effects of tungsten for 326L35M4N is also applicable for 326L57M4N.
[00350] Also, the 326L57M4N may have high levels of carbon referred to as 326H57M4N or 32657M4N which correspond respectively to 326H35M4N and 32635M4N discussed earlier and the weight% carbon ranges discussed above are also applicable for 326H57M4N and 32657M4N.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00351] In addition, for certain applications, other stabilized variants of 326H57M4N or 32657M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight
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(i) This includes the stabilized versions of titanium which are referred to as 326H57M4NTi or 32657M4NTi to contrast with the generic 326L57M4N. The titanium content is controlled according to the following formulas:
[00352] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions of 326H57M4NNb or 32657M4NNb where the niobium content is controlled according to the following formulas:
[00353] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 326H57M4NNbTa or 32657M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00354] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00355] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These linking elements can be used individually or in all
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119/166 various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00356] Forged and cast versions of 326L57M4N stainless steel, along with the other variants, are generally supplied in the same way as the initial modes.
[00357] Also, in this sense an additional variation is appropriately referred to as 351L35M4N in this description, which is an eleventh embodiment of the invention.
[351L35M4N] [00358] Stainless steel 351L35M4N has a high nitrogen level and a Corrosion Resistance Equivalent specified in PREn 44, but preferably PRE n 49. The Corrosion Resistance Equivalent as designated by PREn is calculated according to with the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00359] 351L35M4N stainless steel was formulated to have a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 351L35M4N stainless steel is selective and characterized by a chemical analysis alloy in percentage by weight as follows, 0.030% by weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 26.00% by weight of Cr to 28.00% by weight of Cr, 21.00% by weight of Ni to 25.00% in Ni weight, 3.00 wt% Mo to 5.00 wt% Mo, 0.40 wt% N to 0.70 wt% N.
[00360] Stainless steel 351L35M4N also contains mainly Fe like the rest and can also contain very small amounts of other elements such as 0.010% by weight of B max,
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0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels.
[00361] The chemical composition of 351L35M4N stainless steel is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is Austenitic. As a result, 351L35M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical analysis of 351L35M4N stainless steel is adjusted to obtain a PREN> 44, but preferably PREN> 49, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting corrosion and Crack Corrosion) in a wide range of process environments. 351L35M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753.
[00362] It has been determined that the ideal chemical composition range of 351L35M4N stainless steel is carefully selected to understand the following chemical elements in weight percent as follows, based on the eleventh modality.
Carbon (C)
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121/166 [00363] The carbon content of 351L35M4N stainless steel is <maximum 0.030% by weight of C. Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C.
Manganese (Mn) [00364] Stainless steel 351L35M4N of the eleventh modality can come in two variations: low manganese or high manganese.
[00365] For low manganese alloys, the manganese content of 351L35M4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[00366] For high manganese alloys, the manganese content of 351L35M4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn and more preferably, the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio for high manganese alloys is> 2.85 and <7.50 and even more preferably> 2.85 and <6.25.
Phosphorus (P) [00367] The phosphorus content of 351L35M4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the alloy
351L35M4N has <0.025% by weight of P and more preferably <0.020% by weight of P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P.
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Sulfur (S) [00368] The sulfur content of eleventh modality 351L35M4N stainless steel includes <0.010% by weight of S. Preferably, 351L35M4N has <0.005% by weight of S and more preferably <0.003% by weight of S S, and even more preferably <0.001% by weight of S.
Oxygen (O) [00369] The oxygen content of 351L35M4N stainless steel is controlled to be as low as possible and in the eleventh mode, the 351L35M4N has <0.070% by weight of O. Preferably, the 351L35M4N has <0.050% in weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [00370] The silicon content of 351L35M4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <0.75% by weight Si. More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content it can be> 0.75% Si weight and <2.00% Si weight.
Chromium (Cr) [00371] The chromium content of 351L35M4N stainless steel is> 26.00% by weight of Cr and <28.00% by weight of Cr. Preferably, the alloy has> 27.00% by weight of Cr.
Nickel (Ni) [00372] The nickel content of 351L35M4N stainless steel is> 21.00% by weight of Ni and <25.00% by weight of Ni. Preferably, the upper limit of Ni in the alloy is <24.00% by weight of Ni and more preferably
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123/166 <23.00% by weight of Ni.
Molybdenum (Mo) [00373] The molybdenum content of 351L35M4N stainless steel is> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo.
Nitrogen (N) [00374] The nitrogen content of 351L35M4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, the 351L35M4N has> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [00375] THE CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00376] The 351L35M4N stainless steel was specifically formulated to have the following composition:
(i) chromium content> 26.00% by weight of Cr and <28.00% by weight of Cr, but preferably> 27.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo, [00377] (iii) nitrogen content <0 , 70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N. [00378] With a high nitrogen level, 351L35M4N stainless steel obtains a PREN> 44, but preferably PREN > 49. This ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. Stainless steel
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124/166 xível 351L35M4N also improved resistance to stress corrosion breakage in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00379] The chemical composition of 351L35M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00380] The 351L35M4N stainless steel also has mainly Fe as the rest and can also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent, and the compositions of these elements are the same like those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00381] The stainless steel 351L35M4N according to the eleventh modality has a minimum flow limit of 55 ksi or 380 MPa for the forged version. More preferably, the flow limit
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125/166 minimum 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum yield limit of 48 ksi or 330 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 351L35M4N stainless steel with those of UNS S31703 suggests that the minimum yield strength of 351L35M4N stainless steel should be 2.1 times greater than that specified for UNS S31703 . Similarly, a comparison of the forged mechanical strength properties of 351L35M4N stainless steel, with those of UNS S31753, suggests that the minimum yield strength of 351L35M4N stainless steel should be 1.79 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 351L35M4N stainless steel with those of UNS S35115 suggests that the minimum yield strength of 351L35M4N stainless steel should be 1.56 times greater than that specified for UNS S35115.
[00382] The stainless steel 351L35M4N according to the eleventh modality has a minimum tensile strength of 102 ksi or 700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained for the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 351L35M4N stainless steel with those of UNS S31703 suggests that the minimum tensile strength of 351L35M4N stainless steel should be more than 1.45 times greater than that specified for UNS S31703.
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Similarly, a comparison of the forged mechanical strength properties of 351L35M4N stainless steel with those of UNS S31753 suggests that the minimum tensile strength of 351L35M4N stainless steel should be 1.36 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 351L35M4N stainless steel, with those of UNS S35115, suggests that the minimum tensile strength of 351L35M4N stainless steel should be 1.28 times greater than that specified for UNS S35115. In fact, if the forged mechanical strength properties of 351L35M4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel, then it can be demonstrated that the minimum tensile strength of 351L35M4N stainless steel is in the region of 1.2 times greater than than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of 351L35M4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31703, UNS S31753 and UNS S35115 and the tensile strength properties are better than those specified for Stainless Steel 22 Cr Duplex and similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00383] This means that applications using forged 351L35M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 351L35M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S35115 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 351L35M4N stainless steel are greater than for Stainless Steel
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127/166 ve 22 Cr Duplex and similar to Stainless Steel 25 Cr Super Duplex. [00384] For certain applications, other variants of 351L35M4N stainless steel were intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 351L35M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, passages related to these elements for 304LM4N are also applicable for 351L35M4N.
T ungstene (W) [00385] The tungsten content of 351L35M4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W, and more preferably> 0.75% by weight of W. For 351L35M4N stainless steel variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N). [00386] This variant containing tungsten of stainless steel 351L35M4N was specifically formulated to have the following composition:
(i) chromium content> 26.00% by weight of Cr and <28.00% by weight of Cr, but preferably> 27.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo, (iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but
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128/166 ference> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[00387] The tungsten-containing variant of stainless steel 351L35M4N has a high specified level of nitrogen and a PREnw> 46, but preferably PREnw> 51. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by corrosion by Pits or crack. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [00388] For certain applications, other variants of 351L35M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 351L35M4N stainless steel can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C. These specific variants of 351L35M4N stainless steel are versions 351H35M4N or 35135M4N respectively.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00389] In addition, for certain applications, other stabilized variants of stainless steel 351H35M4N or 35135M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight
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129/166 are C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 351H35M4NTi or 35135M4NTi to contrast with the generic 351L35M4N.
[00390] The titanium content is controlled according to the following formulas:
[00391] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 351H35M4NNb or 35135M4NNb where the content of niobium is controlled according to the following formulas:
[00392] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other variants of the alloy can also be produced to contain niobium plus stabilized tantalum,
351H35M4NNbTa or 35135M4NNbTa versions where the content of niobium plus tantalum is controlled according to the following formulas: [00393] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00394] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all various combinations
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130/166 nations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00395] The forged and cast versions of 351L35M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00396] Also, in this sense, an additional variation appropriately referred to as high-strength austenitic stainless steel351L57M4N is proposed, which is a twelfth embodiment of the invention. 351L57M4N stainless steel has virtually the same chemical composition as 351L35M4N with the exception of the molybdenum content. In this way, instead of repeating the various chemical compositions, only the difference is described.
[351L57M4N] [00397] As mentioned above, the 351L57M4N has exactly the same content of carbon, manganese, phosphorus, sulfur, oxygen, silicon, chromium, nickel and nitrogen in weight by weight as the eleventh modality, stainless steel 351L35M4N, except the molybdenum content. In the 351L35M4N, the molybdenum content is between 3.00% by weight and 5.00% by weight of Mo. In contrast, the 351L57M4N stainless steel molybdenum content is between 5.00% by weight and 7.00% by weight of Mo. In other words, the 351L57M4N can be considered as a high molybdenum version of the 351L35M4N stainless steel.
[00398] It should be appreciated that the passages related to 351L35M4N are also applicable here, except for the molybdenum content. Molybdenum (Mo)
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131/166 [00399] The molybdenum content of 351L57M4N stainless steel can be> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 5.50% by weight of Mo and < 6.50 wt% Mo and more preferably> 6.00 wt% Mo. In other words, the molybdenum content of 351L57M4N has a maximum of 7.00% by weight of Mo.
PREn [00400] THE CORROSION RESISTANCE EQUIVALENT for the 351L57M4N is calculated using the same formulas as 351L35M4N but because of the molybdenum content, PREN is> 50.5, but preferably PREN> 55.5. This ensures that the material also has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 351L57M4N stainless steel also improved resistance to stress corrosion cracking in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00401] The chemical composition of 351L57M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the zone affected by heat from welds, is controlled by optimizing the balance between Austenite forming elements and Elemen
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132/166 ferrite former to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00402] Like the 351L35M4N modality, 351L57M4N stainless steel also mainly comprises Fe as the remainder and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent and the compositions of these elements are the same as those of 351L35M4N, and therefore, those of 304LM4N.
[00403] The twelfth modality 351L57M4N stainless steel has a minimum yield limit and a minimum tensile strength comparable or similar to those of 351L35M4N stainless steel. Likewise, the strength properties of the forged and cast versions of the 351L57M4N are also comparable to those of the 351L35M4N. In this way, the specific resistance values are not repeated here and reference is made to the initial passages of 351L35M4N. A comparison of the properties of forged mechanical strength between 351L57M4N and those of conventional austenitic stainless steel UNS S31703, and between 351L57M4N and those of UNS S31753 / UNS S35115, suggests stronger tensile strengths and yields of magnitude similar to those found for 351L35M4N. Similarly, a comparison of the tensile properties of 351L57M4N demonstrates that they are better than those specified for 22 Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel, just like the 351L35M4N.
[00404] This means that applications using forged 351L57M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying stainless steel
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351L57M4N compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S35115 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 351L57M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel. [00405] For certain applications, other variants of stainless steel 351L57M4N, were intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 351L57M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 351L35M4N and those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 351L57M4N.
T ungstenium (W) [00406] The tungsten content of 351L57M4N stainless steel is similar to that of 351L35M4N and the CORROSION RESISTANCE EQUIVALENT, PRENW, of 351L57M4N calculated using the same formulas as mentioned above for 351L35M4N is PRENW>
52.5, and preferably PRENW> 57.5, due to the different molybdenum content. It should be evident that the passage related to the use and effects of tungsten for 351L35M4N is also applicable for 351L57M4N.
[00407] Also, the 351L57M4N may have high levels of carbon referred to as 351H57M4N or 35157M4N which correspond to 351H35M4N and 35135M4N respectively discussed above and the weight% carbon ranges discussed above are also applicable for 351H57M4N and 35157M4N.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta)
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134/166 [00408] In addition, for certain applications, other stabilized variants of stainless steel 351H57M4N or 35157M4N are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 351H57M4NTi or 35157M4NTi to contrast with the generic 351L57M4N.
[00409] The titanium content is controlled according to the following formulas:
[00410] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 351 H57M4NNb or 35157M4NNb where the content of niobium is controlled according to the following formulas:
[00411] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other variants of the alloy can also be produced to contain niobium plus stabilized tantalum,
351H57M4NNbTa or 35157M4NNbTa versions where the content of niobium plus tantalum is controlled according to the following formulas: [00412] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00413] To variants of stabilized titanium, stabilized niobium and
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135/166 niobium plus stabilized tantalum from the alloy can be given a stabilization heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00414] The forged and cast versions of the 351L57M4N stainless steel, along with the other variants, are generally supplied in the same way as the initial modes.
[00415] Also, in this sense, an additional variation appropriately referred to as 353L35M4N is proposed in this description, which is a thirteenth modality of the invention.
[353L35M4N] [00416] Stainless steel 353L35M4N has a high nitrogen level and a Corrosion Resistance Equivalent specified in PREn 46, but preferably PRE n 51. The Corrosion Resistance Equivalent as designated by PREN is calculated according to with the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00417] Stainless steel 353L35M4N was formulated to have a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. The chemical composition of 353L35M4N stainless steel is selective and characterized by a chemical analysis alloy in weight percentage as follows, 0.030% in
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136/166 weight of C max, 2.00% by weight of Mn max, 0.030% by weight of P max, 0.010% by weight of S max, 0.75% by weight of Si max, 28.00% by weight from Cr to 30.00% by weight of Cr, 23.00% by weight of Ni to 27.00% by weight of Ni, 3.00% by weight of Mo to 5.00% by weight of Mo, 0, 40% by weight of N to 0.70% by weight of N.
[00418] 353L35M4N stainless steel also contains mainly Fe as the remainder and may also contain very small amounts of other elements such as 0.010% by weight of B max, 0.10% by weight of Ce max, 0.050% by weight of Al max, 0.01% by weight of Ca max and / or 0.01% by weight Mg max and other impurities that are normally present at residual levels.
[00419] The chemical composition of 353L35M4N stainless steel is optimized in the melting stage to primarily ensure an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is Austenitic. As a result, 353L35M4N stainless steel exhibits a unique combination of high strength and ductility at ambient temperatures, while at the same time ensuring excellent hardness at ambient temperatures and cryogenic temperatures. In view of the fact that the chemical analysis of 353L35M4N stainless steel is adjusted to obtain a PREN> 46, but preferably PREN> 51, this ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting corrosion and Crack Corrosion) in a wide range of process environments. 353L35M4N stainless steel also improved strength
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137/166 to the breakdown of stress corrosion in chloride-containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753.
[00420] It has been determined that the ideal chemical composition range of 353L35M4N stainless steel is carefully selected to understand the following chemical elements in weight percentage as follows, based on the thirteenth modality,
Carbon (C) [00421] The carbon content of 353L35M4N stainless steel is <maximum 0.030% by weight of C. Preferably, the amount of carbon should be> 0.020% by weight of C and <0.030% by weight of C and more preferably <0.025% by weight of C.
Manganese (Mn) [00422] Stainless steel 353L35M4N of the thirteenth modality can come in two variations: low manganese or high manganese.
[00423] For low manganese alloys, the manganese content of 353L35M4N stainless steel is <2.0% by weight of Mn. Preferably, the range is> 1.0% by weight of Mn and <2.0% by weight of Mn and more preferably> 1.20% by weight of Mn and <1.50% by weight of Mn. With such compositions, this obtains an ideal Mn to N ratio of <5.0, and preferably> 1.42 and <5.0. More preferably, the relationship is>
1.42 and <3.75.
[00424] For high manganese alloys, the manganese content of 353L35M4N is <4.0% by weight of Mn. Preferably, the manganese content is> 2.0% by weight of Mn and <4.0% by weight of Mn and more preferably, the upper limit is <3.0% by weight of Mn. Even more preferably, the upper limit is <2.50% by weight of Mn. With such selective ranges, this obtains an Mn to N ratio of <10.0, and preferably> 2.85 and <10.0. More preferably, the Mn to N ratio of high manganese alloys is> 2.85 and <7.50 and even more preferably
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138/166> 2.85 and <6.25.
Phosphorus (P) [00425] The phosphorus content of 353L35M4N stainless steel is controlled to be <0.030% by weight of P. Preferably, the 353L35M4N alloy has <0.025% by weight of P and more preferably <0.020% by weight of P P. Even more preferably, the alloy has <0.015% by weight of P and even more preferably <0.010% by weight of P.
Sulfur (S) [00426] The sulfur content of the thirteenth modality 353L35M4N stainless steel includes <0.010% by weight of S. Preferably, 353L35M4N has <0.005% by weight of S and more preferably <0.003% by weight of S S, and even more preferably <0.001% by weight of S.
Oxygen (O) [00427] The oxygen content of 353L35M4N stainless steel is controlled to be as low as possible and in the thirteenth modality, the 353L35M4N has <0.070% by weight of O. Preferably, the 353L35M4N has <0.050% in weight of O and more preferably <0.030% by weight of O. Even more preferably, the alloy has <0.010% by weight of O and even more preferably <0.005% by weight of O.
Silicon (Si) [00428] The silicon content of 353L35M4N stainless steel is <0.75% by weight of Si. Preferably, the alloy has> 0.25% by weight of Si and <0.75% by weight of Si More preferably, the range is> 0.40 wt% Si and <0.60 wt% Si. However, for specific high temperature applications where improved oxidation resistance is required, the silicon content may be> 0.75% by weight of Si and <2.00% by weight of Si.
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Chromium (Cr) [00429] The chromium content of 353L35M4N stainless steel is> 28.00% by weight of Cr and <30.00% by weight of Cr. Preferably, the alloy has> 29.00% by weight of Cr.
Nickel (Ni) [00430] The nickel content of 353L35M4N stainless steel is> 23.00% by weight of Ni and <27.00% by weight of Ni. Preferably, the upper limit of Ni in the alloy is <26.00% by weight of Ni and more preferably <25.00% by weight of Ni.
Molybdenum (Mo) [00431] The molybdenum content of 353L35M4N stainless steel is> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo.
Nitrogen (N) [00432] The nitrogen content of 353L35M4N stainless steel is <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N. More preferably, the 353L35M4N has> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
PREn [00433] CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N).
[00434] 353L35M4N stainless steel was specifically formulated to have (i) chromium content> 28.00% by weight of Cr and <30.00% by weight of Cr, but preferably> 29.00% by weight of Cr ;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably
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140/166 ratio> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N.
[00435] With a high nitrogen level, 353L35M4N stainless steel obtains a PREN> 46, but preferably PREN> 51. This ensures that the material also has a good resistance to general corrosion and localized corrosion (Pitting Corrosion and Corrosion of Slit) in a wide range of process environments. 353L35M4N stainless steel also improved resistance to stress corrosion breaking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00436] The chemical composition of 353L35M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and < 1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by tempering with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00437] 353L35M4N stainless steel also has mainly Fe as the rest and can also contain very small amounts
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141/166 quenas of other elements such as boron, cerium, aluminum, calcium and / or magnesium in percentage by weight, and the compositions of these elements are the same as those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here.
[00438] Stainless steel 353L35M4N according to the thirteenth modality has a minimum flow limit of 55 ksi or 380 MPa for the forged version. Most preferably a minimum yield limit of 62 ksi or 430 MPa can be obtained for the forged version. The cast version has a minimum flow limit of 41 ksi or 280 MPa. More preferably, a minimum yield limit of 48 ksi or 330 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 353L35M4N stainless steel with those of UNS S31703 suggests that the minimum yield strength of 353L35M4N stainless steel should be 2.1 times greater than that specified for UNS S31703 . Similarly, a comparison of the forged mechanical strength properties of 353L35M4N stainless steel, with those of UNS S31753, suggests that the minimum yield strength of 353L35M4N stainless steel should be 1.79 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 353L35M4N stainless steel, with those of UNS S35315, suggests that the minimum yield strength of 353L35M4N stainless steel should be 1.59 times greater than that specified for UNS S35315.
[00439] Stainless steel 353L35M4N according to the thirteenth modality has a minimum tensile strength of 102 ksi or700 MPa for the forged version. More preferably, a minimum tensile strength of 109 ksi or 750 MPa can be obtained for
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142/166 the forged version. The cast version has a minimum tensile strength of 95 ksi or 650 MPa. More preferably, a minimum tensile strength of 102 ksi or 700 MPa can be obtained for the cast version. Based on the preferred values, a comparison of the forged mechanical strength properties of 353L35M4N stainless steel with those of UNS S31703 suggests that the minimum tensile strength of 353L35M4N stainless steel should be more than 1.45 times greater than that specified for UNS S31703. Similarly, a comparison of the forged mechanical strength properties of 353L35M4N stainless steel with those of UNS S31753 suggests that the minimum tensile strength of 353L35M4N stainless steel should be 1.36 times greater than that specified for UNS S31753. Likewise, a comparison of the forged mechanical strength properties of 353L35M4N stainless steel with those of UNS S35315 suggests that the minimum tensile strength of 353L35M4N stainless steel should be 1.15 times greater than that specified for UNS S35315. In fact, if the forged mechanical strength properties of 353L35M4N stainless steel are compared to those of 22 Cr Duplex Stainless Steel, then it can be shown that the minimum tensile strength of 353L35M4N stainless steel is in the region of 1.2 times greater than than that specified for S31803 and similar to that specified for 25 Cr Super Duplex Stainless Steel. For this reason, the minimum mechanical strength properties of 353L35M4N stainless steel have been significantly improved compared to conventional austenitic stainless steels such as UNS S31703, UNS S31753 and UNS S35315 and the tensile strength properties are better than those specified for Stainless Steel 22 Cr Duplex and similar to those specified for 25 Cr Super Duplex Stainless Steel.
[00440] This means that applications using stainless steel
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Forged 353L35M4N can often be formulated with reduced wall thicknesses, thus resulting in significant weight savings when specifying 353L35M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S35315 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 353L35M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel. [00441] For certain applications, other variants of 353L35M4N stainless steel were intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It was determined that the ideal chemical composition range of the other 353L35M4N stainless steel variants according to claim 1, is selective and the copper and vanadium compositions are the same as those of 304LM4N. In other words, passages related to these elements for 304LM4N are also applicable for 353L35M4N.
T ungstene (W) [00442] The tungsten content of 353L35M4N stainless steel is <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W, and more preferably> 0.75% by weight of W. For stainless steel 353L35M4N variants containing tungsten, the CORROSION RESISTANCE EQUIVALENT is calculated using the formulas:
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N).
[00443] This variant containing tungsten of stainless steel 353L35M4N was specifically formulated to have the following composition:
(i) chromium content> 28.00% by weight of Cr and <30.00% by weight
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144/166 weight of Cr, but preferably> 29.00% by weight of Cr;
(ii) molybdenum content> 3.00% by weight of Mo and <5.00% by weight of Mo, but preferably> 4.00% by weight of Mo;
(iii) nitrogen content <0.70% by weight of N, but preferably> 0.40% by weight of N and <0.70% by weight of N and more preferably> 0.40% by weight of N and <0.60% by weight of N and even more preferably> 0.45% by weight of N and <0.55% by weight of N; and (iv) tungsten content <2.00% by weight of W, but preferably> 0.50% by weight of W and <1.00% by weight of W and more preferably> 0.75% by weight of W.
[00444] The tungsten-containing variant of 353L35M4N stainless steel has a specified high level of nitrogen and a PREnw> 48, but preferably PREnw> 53. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by corrosion by Pits or crack. Tungsten can be added individually or in conjunction with copper, vanadium, titanium and / or niobium and / or niobium plus tantalum in all the various combinations of these elements, to also improve the overall corrosion performance of the alloy. Tungsten is extremely expensive and for that reason is being intentionally limited to optimize the economy of the alloy, while at the same time optimizing the ductility, hardness and corrosion performance of the alloy.
Carbon (C) [00445] For certain applications, other variants of 353L35M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon content of 353L35M4N can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0, 08% by weight of C, but preferably <0.040% by weight of C. These variants are
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145/166 specific features of 353L35M4N stainless steel are versions 353H35M4N or 35335M4N respectively.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00446] In addition, for certain applications, other stabilized variants of 353H35M4N or 35335M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon Specifically, the amount of carbon can be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and < 0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 353H35M4NTi or 35335M4NTi to contrast with the generic 353L35M4N.
[00447] The titanium content is controlled according to the following formulas:
[00448] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 353H35M4NNb or 35335M4NNb where the content of niobium is controlled according to the following formulas:
[00449] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions 353H35M4NNbTa or 35335M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00450] fNb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10%
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146/166 by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00451] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00452] Forged and cast versions of 353L35M4N stainless steel together with the other variants are generally supplied in the same way as the initial modes.
[00453] Also, in this sense, an additional variation appropriately referred to as high strength austenitic stainless steel353L57M4N is proposed, which is a fourteenth modality of the invention. 353L57M4N stainless steel has virtually the same chemical composition as 353L35M4N with the exception of the molybdenum content. In this way, instead of repeating the various chemical compositions, only the difference is described.
[353L57M4N] [00454] As mentioned above, the 353L57M4N has exactly the same content of carbon, manganese, phosphorus, sulfur, oxygen, silicon, chromium, nickel and nitrogen in weight by weight as the thirteenth modality, 353L35M4N stainless steel, except the molybdenum content. In the 353L35M4N, the molybdenum content is between 3.00% in
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147/166 weight and 5.00% Mo weight. In contrast, 353L57M4N's molybdenum content is between 5.00% by weight and 7.00% by weight of Mo. In other words, the 353L57M4N can be considered as a high molybdenum version of the 353L35M4N stainless steel.
[00455] It should be appreciated that the passages related to 353L35M4N are also applicable here, except for the molybdenum content. Molybdenum (Mo) [00456] The molybdenum content of 353L57M4N stainless steel can be> 5.00% by weight of Mo and <7.00% by weight of Mo, but preferably> 5.50% by weight of Mo and <6.50 wt% Mo, and more preferably> 6.00 wt% Mo. In other words, the molybdenum content of 353L57M4N has a maximum of 7.00% by weight of Mo.
PREn [00457] THE CORROSION RESISTANCE EQUIVALENT for the 353L57M4N is calculated using the same formulas as a 353L35M4N but because of the molybdenum content, the PREN is> 52.5, but preferably PREN> 57.5. This ensures that the material also has good resistance to general corrosion and localized corrosion (Pitting Corrosion and Crack Corrosion) in a wide range of process environments. 353L57M4N stainless steel also improved resistance to stress corrosion cracking in chloride containing environments when compared to conventional austenitic stainless steels such as UNS S31703 and UNS S31753. It should be emphasized that these equations ignore the effects of microstructural factors in breaking passivity by pitting or crack corrosion.
[00458] The chemical composition of 353L57M4N stainless steel is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoe
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148/166 fer6, is in the range of> 0.40 and <1.05, but preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment typically performed in the range of 1,100 degrees C to 1,250 degrees C followed by water quenching. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is austenitic. The alloy can therefore be produced and supplied in a non-magnetic condition.
[00459] Like 353L35M4N, stainless steel 353L57M4N also mainly comprises Fe as the remainder and may also contain very small amounts of other elements such as boron, cerium, aluminum, calcium and / or magnesium in weight percent and the compositions of these elements they are the same as those of 353L35M4N and therefore, those of 304LM4N.
[00460] The 14th modality 353L57M4N stainless steel has a minimum yield limit and a minimum tensile strength comparable or similar to those of 353L35M4N stainless steel. Likewise, the strength properties of the forged and cast versions of the 353L57M4N are also comparable to those of the 353L35M4N. In this way, the specific resistance values are not repeated here and reference is made to the initial passages of 353L35M4N. A comparison of the properties of forged mechanical strength between 353L57M4N and those of conventional austenitic stainless steel UNS S31703, and between 353L57M4N and those of UNS S31753 / UNS S35315, suggests stronger tensile strengths and yields of magnitude similar to those found for 353L35M4N. Similarly, a comparison of the tensile properties of
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353L57M4N demonstrates that they are better than those specified for 22 Cr Duplex Stainless Steel and similar to those specified for 25 Cr Super Duplex Stainless Steel, just like the 353L35M4N.
[00461] This means that applications using forged 353L57M4N stainless steel can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying 353L57M4N stainless steel compared to conventional austenitic stainless steels such as UNS S31703, S31753 and S35315 because the minimum allowable design stresses are significantly high. In fact, the minimum allowable design stresses for forged 353L57M4N stainless steel are greater than for 22 Cr Duplex Stainless Steel and similar to 25 Cr Super Duplex Stainless Steel.
[00462] For certain applications, other variants of 353L57M4N stainless steel have been intentionally formulated to be produced containing specific levels of other bonding elements such as copper, tungsten and vanadium. It has been determined that the ideal chemical composition range of the other 353L57M4N stainless steel variants is selective and the copper and vanadium compositions are the same as those of 353L35M4N and those of 304LM4N. In other words, the passages related to these elements for 304LM4N are also applicable here for 353L57M4N.
T ungstene (W) [00463] The tungsten content of stainless steel 353L57M4N is similar to that of 353L35M4N and the CORROSION RESISTANCE EQUIVALENT, PRENW, of 353L57M4N calculated using the same formulas as mentioned above for 353L35M4N is PRENW>
54.5, and preferably PRENW> 59.5, due to the different molybdenum content. It must be evident that the passage related to the use and
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150/166 tungsten effects for 353L35M4N are also applicable for 353L57M4N.
[00464] Also, the 353L57M4N may have high levels of carbon referred to as 353H57M4N or 35357M4N which correspond to 353H35M4N and 35335M4N respectively discussed above and the weight% carbon ranges discussed above are also applicable for 353H57M4N and 35357M4N.
Titanium (Ti) / niobium (Nb) / niobium (Nb) plus tantalum (Ta) [00465] In addition, for certain applications, other stabilized variants of 353H57M4N or 35357M4N stainless steel are desirable, which have been specifically formulated to be produced comprising high levels of carbon. Specifically, the carbon may be> 0.040% by weight of C and <0.10% by weight of C, but preferably <0.050% by weight of C or> 0.030% by weight of C and <0.08% by weight of C, but preferably <0.040% by weight of C.
(i) This includes the stabilized versions of titanium which are referred to as 353H57M4NTi or 35357M4NTi to contrast with the generic 353L57M4N. The titanium content is controlled according to the following formulas:
[00466] Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy.
(ii) There is also stabilized niobium, versions 353H57M4NNb or 35357M4NNb where the content of niobium is controlled according to the following formulas:
[00467] Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0% by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy.
(iii) In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, versions
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353H57M4NNbTa or 35357M4NNbTa where the content of niobium plus tantalum is controlled according to the following formulas:
[00468] Nb + Ta 8 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + T at max, 0.10% by weight of Ta max.
[00469] The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum of the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can be added individually or in conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of elements to adjust stainless steel for specific applications and also to improve the overall corrosion performance of the alloy.
[00470] Forged and cast versions of 353L57M4N stainless steel along with the other variants are generally supplied in the same way as the initial modes.
[00471] The described modalities should not be interpreted as limiting and others can be formulated in addition to those described here. For example, the aforementioned modalities or series of austenitic stainless steels for all different types of alloy compositions and their variants can be produced with chemical compositions tailored to specific applications. Such an example is the use of a high manganese content of> 2.00% by weight of Mn and <4.00% by weight of Mn, in order to reduce the level of nickel content by an amount proportionally according to the equations proposed by Schoefer.6 This would reduce the total spending of the alloys
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152/166 since nickel is extremely expensive. For this reason, the nickel content may be intentionally limited to optimize the economy of the alloys.
[00472] The described modalities can also be controlled to satisfy other criteria to those already defined here. For example, in addition to the manganese to nitrogen ratios, the modalities are also controlled to have specific manganese to carbon + nitrogen ratios.
[00473] For LM4N, types of low manganese band alloys that obtain an ideal M + to C + N ratio of <4.76, and preferably> 1.37 and <4.76. More preferably, the ratio of Mn to C + N is> 1.37 and <3.57. For LM4N, types of high manganese strip alloys that obtain an ideal Mn to C + N ratio of <9.52, and preferably> 2.74 and <9.52. More preferably, the ratio of Mn to C + N for these LM4N, types of high manganese alloys is> 2.74 and <7.14 and even more preferably the ratio of Mn to C + N is> 2.74 to < 5.95. The current modalities include the following: the types
304LM4N, 316LM4N, 317L35M4N, 317L57M4N, 312L35M4N,
312L57M4N, 320L35M4N, 320L57M4N, 326L35M4N and 326L57M4N, 351L35M4N, 351L57M4N, 353L35M4N, 353L57M4N of alloy and its variants that can comprise up to 0.030% by weight of maximum carbon, [00474] for the LMs of Higas, obtains an ideal M + to C + N ratio of <4.55, and preferably> 1.25 and <4.55. More preferably, the ratio of Mn to C + N is> 1.25 and <3.41. For HM4N, types of high manganese alloys that obtain an ideal M + to C + N ratio of <9.10, and preferably> 2.50 and <9.10. More preferably, the Mn to C + N ratio for these HM4N, high manganese alloy types is> 2.50 and <6.82 and even more preferably the Mn to C + N ratio is
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153/166> 2.50 to <5.68. The current modalities include the following: types 304HM4N, 316HM4N 317H57M4N, 317H35M4N, 312H35M4N,
312H57M4N, 320H35M4N, 320H57M4N, 326H35M4N, 326H57M4N, 351H35M4N, 351H57M4N, 353H35M4N and 353H57M4N of alloy and its variants that can comprise from 0.040% by weight of carbon to 0.10% by weight of carbon, and [004] types of low manganese alloys that obtain an ideal M + to C + N ratio of <4.64, and preferably> 1.28 and <4.64. More preferably, the ratio of Mn to C + N is> 1.28 and <3.48. For M4N, types of high manganese alloys that obtain an ideal Mn to C + N ratio of <9.28, and preferably> 2.56 and <9.28. More preferably, the Mn to C + N ratio for these M4N, high manganese alloy types is> 2.56 and <6.96 and even more preferably the Mn to C + N ratio is> 2.56 to < 5.80. The current modalities include the following: types 304M4N, 316M4N 31757M4N, 31735M4N, 31235M4N, 31257M4N, 32035M4N, 32057M4N, 32635M4N, 32657M4N, 35135M4N, 35157M4N,
35335M4N and 35357M4N of alloy and its variants which may comprise from more than 0.030% by weight of carbon to 0.080% by weight of carbon.
[00476] NOENIUSTM high strength austenitic and super austenitic stainless steel series including types LM4N, HM4N and M4N of alloy, as well as the other variants discussed here, can be specified and used as a range of Products and Product Packages for systems complete.
[00477] It should be evident that ranges of chemical composition specified for an element (eg, chromium, nickel, molybdenum, carbon and nitrogen, etc.) for specific types of alloy composition and their variants may also be applicable to elements in other types of alloy composition and its variants.
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Products, Markets, Industrial Sectors and Applications [00478] The proposed series of high strength austenitic and super austenitic stainless steels N'GENIUS ^TM can be specified to international standards and specifications and used for a range of products used for both high and sea and on land in view of its properties of high mechanical resistance, excellent ductility and hardness at ambient and cryogenic temperatures, together with good weldability and good resistance to general and localized corrosion.
Products [00479] Products include, but are not limited to, Primary and Secondary Products such as Ingots, Continuous Cast Plates, Laminated Plates, Blocks, Palanquilha, Bar, Flat Bar, Frames, Rod, Wire, Welding Wire, Welding Consumables, Plate, Laminated Sheet, Strip and Rolled Strip, Forgings, Static Castings, Die Castings, Centrifugal Castings, Powder Metallurgical Products, Hot Isoestatic Presses, Seamless Plumbing, Seamless Pipe and Tube, Drill Pipe, Tubular Products from Campo do Campo Oil, Frames, Condenser Tubes and Heat Exchangers, Welded Plumbing, Welded Pipe and Tube, Tubular Products, Induction Coils, Top Welded Frames, Seamless Frames, Fasteners, Nuts, Screws and Legs, Bar, Rod and Stretched Wire Cold and Cold Reduced, Cold Stretched and Cold Reduced Pipe and Tube, Flanges, Compact Flanges, Clamp Connectors, Forged Frames, Pumps, Valves ulas, separators, ships and auxiliary products. The Primary and Secondary Products above are also relevant to Metallurgically Coated Products (for example, ThermoMechanically Bonded, Hot Cylinder Bonded, Explosively Bonded etc.), Welded Overlapping Coated Products, Products
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Mechanically Coated or Hydraulically Coated Products or CRA Coated Products.
[00480] As can be seen from the number of alternative alloy compositions discussed above, the proposed NOENIUSTM high strength austenitic and super austenitic stainless steels can be specified and used in various markets and industrial sectors in a wide range of applications. Significant weight savings and manufacturing time savings can be achieved when using these Alloys which in turn result in significant expense savings in total construction costs.
Markets, Industrial Sectors and Applications [00481] Production and Distribution Oil and Gas Industries (Onshore and Offshore Including Surface Water, Deep Water and Ultra Deep Water Technology) [00482] Finished Product Applications may include, however, they are not limited to the following:
[00483] Onshore and Offshore Pipelines including Interfield Field Pipelines and Drains, Arable Land Pipelines and Drains, Structural Reinforcers, High Pressure and High Temperature Pipelines (HPHT) for multiphase fluids such as Oil, Gas and Condensate containing Chlorides, CO2 and H2S, and other constituents, Seawater Injection Pipelines and Formation Water Injection, Subsea Production System Equipment, Distribution Pipes, Mining Drills, Connections, Coils, Nut Hooks, Tubular, OCTG and Frames, Steel Catenary Rising Pipes, Rising Pipes, Structural Spray Zone Rising Pipes, River and Canal Crossings, Valves, Pumps, Separators, Ships, Filtration Systems, Forgings, Fasteners and all Products Associated Aids and Equipment.
[00484] Plumbing Package Systems: such as Plumbing Systems
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156/166 Process and Utility Systems, Seawater Cooling Systems and Brandy Systems that can be used in all types of applications Onshore and Offshore. Offshore applications include, but are not limited to, Fixed Platform, Floating Platform, SPA's and Hulls such as Process Platform, Utility Platform, Wellhead Platform, Rising Tube Platform, Compression Platform, FPSO's Infrastructure, FSO's , SPA and Hull, Manufactures, Modules manufactured and all Associated Auxiliary Products and Equipment.
[00485] Piping Package Systems: such as Umbilicals, Condensers, Heat Exchangers, Desalination, Desulfide and all Associated Auxiliary Products and Equipment. LNG Industries [00486] Finished Product Applications may include, but are not limited to, the following: Pipeline Infrastructure and Plumbing Package Systems, Fabrications, Fabricated Modules, Valves, Ships, Pumps, Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used for the Manufacture of Floating Liquefied Natural Gas (FLNG) vessels on the high seas, Liquefied Natural Gas (LNG) Plants on land or FSRU, Vessels and Ships as well as Terminals for processing, storage and transport of Liquefied Natural Gas (LNG) at cryogenic temperatures.
[00487] Chemical Process, Petrochemical, GTL and Refining Industries [00488] Finished Product Applications may include, but are not limited to, the following:
[00489] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Products
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Associated Aids and Equipment, including Railway and Road Chemical Tankers used for the processing and transportation of corrosive aggressive fluids from the Chemical Process, Petrochemical, Liquid Gas and Refining Industries as well as acids, alkalis and other corrosive fluids including chemicals typically found in Torres Vacuum, Atmospheric Towers and Hydro Treaters.
Environmental Protection Industries [00490] Finished Product Applications may include, but are not limited to, the following:
[00491] Pipelines and Plumbing Package Systems, Infrastructure, Fabrications, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used for waste products and wet toxic gases from Industries Chemical Process and Refinement, Pollution Control, for example, vapor recovery systems, CO2 containment and Flue Gas Desulfurization. Iron and Steel Industries [00492] Finished Product Applications may include, but are not limited to, the following:
[00493] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forging, Fasteners and all Associated Auxiliary Products and Equipment used for the production and processing of Iron and Steel.
Mining and Minerals Industries [00494] Finished Product Applications may include, but are not limited to, the following:
[00495] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships,
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Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used for Mining and Minerals extraction and for the transportation of erosive-corrosive sludge as well as mine dewatering.
Energy Industries [00496] Finished Product Applications may include, but are not limited to, the following:
[00497] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forging, Fasteners and all Associated Auxiliary Products and Equipment used for the generation of Energy and for the transportation of corrosive media associated with energy generation ie fossil fuel, flammable gas, nuclear fuel, geothermal energy, hydroelectric energy and all other forms of energy generation.
Pulp and Paper Industries [00498] Finished Product Applications may include, but are not limited to, the following:
[00499] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used in the Pulp and Paper Industries and for transportation of aggressive fluids in pulp whitening plants.
Desalination Industries [00500] Finished Product Applications may include, but are not limited to, the following:
[00501] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Products
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Associated Aids and Equipment used in the Desalination Industries and for the transport of seawater and brines used in desalination plants.
Marine, Naval and Defense Industries [00502] Finished Product Applications may include, but are not limited to, the following:
[00503] Pipelines and Plumbing Package Systems, Fabrications, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used for the Marine, Naval and Defense Industries and the transportation of aggressive media and plumbing utility systems for chemical tankers, construction vessel and submarines.
Water and Wastewater Industries [00504] Finished Product Applications may include, but are not limited to, the following:
[00505] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used in the Water and Wastewater Industries including Water Pipe Frame used for water wells, utility distribution networks, sewage networks and irrigation systems.
Architecture, Engineering and Construction Industries [00506] Finished Product Applications may include, but are not limited to, the following:
[00507] Pipe, Plumbing, Infrastructure, Fabrications, Forgings and Fasteners and all Associated Auxiliary Products and equipment used for Structural, Integrity and Decorative applications in Architecture, Civil and Mechanical Engineering and the ConsPetition industries 870190038552, of 24/04 / 2019, p. 184/204
160/166 truction.
Food and Fermentation Industries [00508] Finished Product Applications may include, but are not limited to, the following:
[00509] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forging, Fasteners and all Associated Auxiliary Products and Equipment used in Food and Beverage Industries as well as related Consumer Products. Pharmaceutical, Biochemical, Health and Medical Industries [00510] Finished Product Applications may include, but are not limited to, the following:
[00511] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forging, Fasteners and all Associated Auxiliary Products and Equipment used in the Pharmaceutical, Biochemical, Health and Medical Industries as well as related Consumer Products.
Automotive Industries [00512] Finished Product Applications may include, but are not limited to, the following:
[00513] Pipelines and Plumbing Package Systems, Infrastructure, Manufacturing, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forging, Fasteners, Components and all Associated Auxiliary Products and Equipment used in the Automotive Industries including vehicle production for Road and Railway applications as well as Surface and Underground Mass Transit Systems.
Specialist Research and Development Industries [00514] Finished Product Applications may include, but are not limited to,
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161/166 are limited to the following:
[00515] Pipelines and Plumbing Package Systems, Infrastructure, Fabrications, Manufactured Modules, Valves, Pumps, Ships, Filtration Systems, Forgings, Fasteners and all Associated Auxiliary Products and Equipment used in the Specialist Research and Development Industries.
[00516] This invention relates to austenitic stainless steels, comprising a high level of nitrogen and a minimum specified Corrosion Resistance Equivalent for each type of designated alloy. The Corrosion Resistance Equivalent as designated by PREN is calculated according to the formulas:
PREn =% Cr + (3.3 x% Mo) + (16 x% N); and / or
PREnw =% of Cr + [3.3 x% of (Mo + W)] + (16 x% of N), [00517] where applicable, as discussed above, for each type of alloy designated.
[00518] The range of carbon low alloy for different modes or types of austenitic stainless steel and / or stainless steels super austenitic were referred to as 304LM4N, 316LM4N, 317L35M4N, 317L57M4N, 312L35M4N, 312L57M4N, 320L35M4N, 320L57M4N, 326L35M4N, 326L57M4N , 351L35M4N, 351L57M4N, 353L35M4N and 353L57M4N and these among other variants have been described. In the described modalities, austenitic stainless steels and / or super austenitic stainless steels, comprise 16.00% by weight of chromium to 30.00% by weight of chromium; 8.00% nickel by weight to 27.00% nickel by weight; not more than 7.00% by weight of molybdenum and not more than 0.70% by weight of nitrogen, but preferably 0.40% by weight of nitrogen to 0.70% by weight of nitrogen. For lower carbon band alloys these comprise no more than 0.030% carbon weight. For lower manganese alloys these comprise no more than 2.00% in terms of
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162/166 weight of manganese with the controlled manganese to nitrogen ratio less than or equal to 5.0 and preferably a minimum of
1.42 and less than or equal to 5.0, or more preferably a minimum of 1.42 and less than or equal to 3.75. For high manganese alloys these comprise no more than 4.00% by weight of manganese with the ratio of manganese to nitrogen controlled to less than or equal to 10.0 and preferably a minimum of 2.85 and less than or equal to 10.0, or more preferably to a minimum of 2.85 and less than or equal to 7.50, or even more preferably to a minimum of 2.85 and less than or equal to 6 , 25, or even more preferably at a minimum of 2.85 and less than or equal to 5.0, or even more more preferably at a minimum of 2.85 and less than or equal to 3.75. The level of Phosphorus is not more than 0.030% by weight of Phosphorus and is controlled as low as possible so that it can be less than or equal to 0.010% by weight of Phosphorus. The level of Sulfur is no more than 0.010% by weight of Sulfur and is controlled as low as possible so that it can be less than or equal to 0.001% by weight of Sulfur. The level of Oxygen in the Alloys is no more than 0.070% by weight of Oxygen and is crucially controlled as low as possible so that it can be less than or equal to 0.005% by weight of Oxygen. The level of silicon in the alloys is no more than 0.75% by weight of silicon, except for specific high temperature applications where improved oxidation resistance is required, where the silicon content can be 0.75% by weight 2.00% silicon by weight of silicon. For certain applications, other variants of stainless steel and super austenitic stainless steels have been intentionally formulated to be produced containing specific levels of other bonding elements such as copper of not more than 1.50% by weight of copper for strip alloys lower copper and non-copper
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163/166 more than 3.50% by weight of copper for high copper band alloys, tungsten of not more than 2.00% by weight of tungsten and vanadium of not more than 0.50% by weight vanadium. austenitic stainless steels and super austenitic stainless steels, also contain mainly Fe as the remainder and may also contain very small amounts of other elements such as boron of not more than 0.010% by weight of boron, cerium of not more than 0, 10% by weight of cerium, aluminum of not more than 0.050% by weight of aluminum and calcium and / or magnesium of not more than 0.010% by weight of calcium and / or magnesium. Austenitic stainless steels and Super austenitic stainless steels were formulated to have a unique combination of high mechanical strength properties with excellent ductility and hardness, together with good weldability and good resistance to general and localized corrosion. Chemical analysis of stainless steels and Super austenitic stainless steels is characterized in that it is optimized in the melting stage to ensure that the ratio of the equivalent of [Cr] divided by the equivalent of [Ni], according to Schoefer6, is in the range of> 0.40 and <1.05, or preferably> 0.45 and <0.95, in order to primarily obtain an austenitic microstructure in the base material after solubilization heat treatment, typically performed in the range of 1,100 degrees C 1,250 degrees C followed by quenching with water. The microstructure of the base material in the heat treated condition by solubilization, together with welded weld metal and the heat affected zone of welds, is controlled by optimizing the balance between austenite forming elements and ferrite forming elements to primarily ensure that the alloy is Austenitic. Alloys can therefore be produced and supplied in a non-magnetic condition. The minimum specified mechanical strength properties of the new and innovative Stainless steels and Super austenitic stainless steels,
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164/166 have been significantly improved compared to their respective counterparts, including austenitic stainless steels such as, UNS S30403, UNS S30453, UNS S31603, UNS S31703, UNS S31753, UNS S31254, UNS S32053, UNS S32615, UNS S35315 and UNS S35315 and UNS S35315 and UNS S35315 and UNS S35315. In addition, the minimum specified Tensile Strength properties may be better than that specified for 22 Cr Duplex Stainless Steel (UNS S31803) and similar to those specified for 25 Cr Super Duplex Stainless Steel (UNS S32760). This means that System components for different applications using forged stainless steels are characterized in that the alloys can often be designed with reduced wall thicknesses, thus resulting in significant weight savings when specifying stainless steels compared to austenitic stainless steels. conventional methods such as those detailed here because the minimum allowable design stresses can be significantly high. In fact, the minimum allowable design stresses for forged austenitic stainless steel may be greater than those specified for 22 Cr Duplex Stainless Steel and similar to that specified for 25 Cr Super Duplex Stainless Steel.
[00519] For certain applications, other variants of austenitic stainless steel and super austenitic stainless steels were specifically formulated to be produced containing higher levels of carbon than that previously defined here above. The high carbon range of alloys for the different types of austenitic stainless steels and super austenitic stainless steels, have been referred to as 304HM4N, 316HM4N, 317H35M4N, 317H57M4N, 312H35M4N, 312H57M4N, 320H35M4N, 320H57M4N, 320H57M4N, 320H57M4N, 320H57M4N, 353H57M4N and these types of alloy comprise from 0.040% by weight of carbon to less than
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165/166 than 0.10% by weight of carbon. While 304M4N, 316M4N, 31735M4N, 31757M4N, 31235M4N, 31257M4N, 32035M4N,
32057M4N, 32635M4N, 32657M4N, 35135M4N, 35157M4N,
35335M4N and 35357M4N alloy types comprise from more than 0.030% by weight of carbon to 0.080% by weight of carbon.
[00520] In addition, for certain applications, other variants of the high carbon range of alloys for austenitic stainless steel and super austenitic stainless steels are desirable, which have been specifically formulated to be produced as stabilized versions. These specific variants of austenitic stainless steel and super austenitic stainless steels are stabilized titanium, HM4NTi or M4NTi types of alloy where the titanium content is controlled according to the following formulas: Ti 4 x C min, 0.70% by weight Ti max or Ti 5 x C min, 0.70% by weight Ti max respectively, in order to have stabilized titanium derivatives of the alloy. Similarly, there are stabilized niobium, HM4NNb or M4NNb alloy types where the niobium content is controlled according to the following formulas: Nb 8 x C min, 1.0% by weight of Nb max or Nb 10 x C min, 1.0 % by weight of Nb max respectively, in order to have stabilized niobium derivatives of the alloy. In addition, other alloy variants can also be produced to contain niobium plus stabilized tantalum, HM4NNbTa or M4NNbTa types of alloy where the content of niobium plus tantalum is controlled according to the following formulas: Nb + Ta 8 x C min, 1, 0% by weight of Nb + Ta max, 0.10% by weight of Ta max, or Nb + Ta 10 x C min, 1.0% by weight of Nb + Ta max, 0.10% by weight of Ta max . The variants of stabilized titanium, stabilized niobium and niobium plus stabilized tantalum from the alloy can be given a stabilizing heat treatment at a temperature lower than the initial solubilization heat treatment temperature. Titanium and / or niobium and / or niobium plus tantalum can also be added individually or in
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166/166 conjunction with copper, tungsten and vanadium in all the various combinations of these elements to optimize the alloy for certain applications where high carbon content is desirable. These bonding elements can be used individually or in all various combinations of the elements to adjust austenitic stainless steels for specific applications and to also optimize the total corrosion performance of the alloys.
REFERENCES
1. A. J. Sedriks, Stainless Steels '84, Proceedings of Goteborg Conference, Book No 320. The Institute of Metals, 1 Carlton House Terrace, London SW1Y 5DB, p. 125, 1985.
2. P. Guha and C. A.Clark, Duplex Stainless Steel Conference Proceedings, ASM Metals / Materials Technology Series, Paper (8201 018) p. 355, 1982.
3. N. Bui, A.Irhzo, F. Dabosi and Y. Limouzin-Maire, Corrosion NACE, Vol. 39, p. 491, 1983.
4. A.L. Schaeffler, Metal Progress, Vol. 56, p. 680, 1949.
5. C. L. Long and W. T. DeLong, Welding Journal, Vol. 52, p. 281s, 1973.
6. E. A.Schoefer, Welding Journal, Vol. 53, p. 10s, 1974.
7. ASTM A800 / A800M - 10

权利要求:
Claims (35)
[1]
1. Austenitic stainless steel with a metallic base having a non-magnetic austenitic microstructure with a metallic base, characterized by the fact that it comprises 16.00% by weight of Chromium to 30.00% (Cr) by weight of Chromium; 8.00% by weight of Nickel to 27.00% (Ni) by weight of Nickel; not more than 7.00% by weight of Molybdenum (Mo); 0.40 wt% Nitrogen to 0.70 wt% Nitrogen (N), 1.0 wt% Manganese less than 4.00 wt% Manganese (Mn), and no more than 1 , 0% by weight of Niobium (Nb), less than 0.10% by weight of Carbon (C), <0.070% by weight of Oxygen, not more than 2.00% by weight of Silicon,> 0, 03% by weight of Cerium and <0.08% by weight of Cerium, and optionally additionally comprising at least one element selected from boron, Rare Earth Metals (REM), Aluminum, Calcium, Magnesium, Copper, Tungsten, Vanadium, Titanium , and / or Niobium plus Tantalum;
the rest of the microstructure of the matelica base being iron and unavoidable impurities, in which the ratio of Manganese (Mn) to Nitrogen (N) is controlled to> 2.85 and <7.50; and wherein the ratio of Chromium Equivalent [Cr] to Nickel Equivalent is determined and controlled to more than 0.40 and less than 1.05; and where the Chromium Equivalent ratio is determined and controlled according to the first formula:
[Cr] = (Cr in% of weight) + (1.5 x Si in% of weight) + (1.4 x Mo in% of weight) + (Nb in% of weight) - 4.99; and where the Nickel Equivalent is determined and controlled according to the second formula:
[Ni] = (Ni in% of weight) + (30 x C in% of weight) + (0.5 x Mn in% of weight) + ((26 x% in weight) ((N - 0.02) ) + 2.77;
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[2]
2/8 and in which the ratio of Chromium Equivalent [Cr] divided by the Nickel Equivalent is optimized in the molten stage in order to first obtain a non-magnetic austenitic metallic microstructure after thermal treatment of solubilization in the range of 1100 ° C at 1250 ° C followed by water quenching.
2. Austenitic stainless steel with a metallic base according to claim 1, characterized by the fact that it also comprises <0.030% by weight of Carbon, or 0.020% to 0.030% Carbon.
[3]
Metal-based austenitic stainless steel according to any one of claims 1 and 2, characterized in that it also comprises no more than 2.0% by weight of Mn.
[4]
Metal-based austenitic stainless steel according to any one of claims 1 to 3, characterized in that it also comprises from 1.0% by weight Manganese to 2.0% by weight of Manganese, or Manganese is> 1 , 20% by weight and <1.50% by weight of Manganese.
[5]
Metal-based austenitic stainless steel according to any one of claims 1 to 4, characterized by the fact that it also comprises the ratio of Manganese to Nitrogen is controlled to less than or equal to 3.75.
[6]
Metal-based austenitic stainless steel according to any one of claims 1 to 5, characterized in that it also comprises <0.030% by weight of Phosphorus.
[7]
Metal-based austenitic stainless steel according to any one of claims 1 to 6, characterized by the fact that it also comprises <0.010% by weight of sulfur; or less than 0.001% by weight of Sulfur.
[8]
8. Metal-based austenitic stainless steel according to any of claims 1 to 7, characterized by the fact that it also comprises Oxygen is <0.050% by weight of Oxygen.
[9]
9. Metal-based austenitic stainless steel according to
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Any of claims 1 to 8, characterized by the fact that it also comprises no more than 0.75% by weight of silicon; or Silicon is> 0.25% by weight and <0.75% by weight of Silicon.
[10]
Metal-based austenitic stainless steel according to any one of claims 1 to 9, characterized in that it also comprises <0.010% by weight of boron or> 0.001% by weight of boron and <0.010% by weight of boron.
[11]
11. Metal-based austenitic stainless steel according to any one of claims 1 to 10, characterized by the fact that it also comprises <0.050% by weight of aluminum; or> 0.005% by weight of Aluminum and <0.050% by weight of Aluminum.
[12]
Metal-based austenitic stainless steel according to any one of claims 1 to 11, characterized in that it also comprises <0.010% by weight of Calcium; or> 0.001% by weight of Calcium and <0.010% by weight of Calcium.
[13]
Metal-based austenitic stainless steel according to any one of claims 1 to 12, characterized in that it also comprises <0.010% by weight of magnesium; or> 0.001% by weight of Magnesium and <0.010% by weight of Magnesium.
[14]
Metal-based austenitic stainless steel according to any one of claims 1 to 13, characterized by the fact that it also comprises <1.50% by weight of Copper; or> 0.50% by weight of Copper and <3.50% by weight of Copper.
[15]
15. Austenitic stainless steel with a metallic base according to any one of claims 1 to 14, characterized by the fact that it also comprises <2.00% by weight Tungsten; or> 0.50% by weight of ungene and <1.00% by weight of ungene.
[16]
16. Metal-based austenitic stainless steel according to any one of claims 1 to 15, characterized by the fact that it also comprises <0.50% by weight of Vanadium; or> 0.10% by weight of Vanadium and <0.50% by weight of Vanadium.
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[17]
17. Metal-based austenitic stainless steel according to any one of claims 1 to 16, characterized in that it also comprises from 0.040% by weight of carbon to less than 0.10% by weight of carbon.
[18]
18. Metal-based austenitic stainless steel according to claim 17, characterized by the fact that Carbon is> 0.030% by weight of Carbon and <0.08% by weight of Carbon.
[19]
19. Austenitic stainless steel with a metal base according to claim 17 or 18, characterized by the fact that it also comprises no more than 0.70% by weight Titanium.
[20]
20. Austenitic stainless steel with a metallic base according to claim 19, when dependent on claim 17, characterized by the fact that Titanium is more than Ti (min); on what
Ti (min) is calculated from 4xC (min); and where
C (min) is the minimum amount of carbon.
[21]
21. Austenitic stainless steel with a metallic base according to claim 19, when dependent on claim 18, characterized by the fact that Titanium is more than Ti (min); on what
Ti (min) is calculated from 5xC (min); and where
C (min) is the minimum amount of carbon.
[22]
22. Metal-based austenitic stainless steel according to any one of claims 1 to 21, when dependent on claim 17, characterized by the fact that Niobium is more than Nb (min); on what
Nb (min) is calculated from 8xC (min), where
C (min) is the minimum amount of carbon.
[23]
23. Metal-based austenitic stainless steel according to any one of claims 1 to 22, when dependent on claim 18, characterized by the fact that Niobium is more than Nb (min); on what
Nb (min) is calculated from 10xC (min), where
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C (min) is the minimum amount of carbon.
[24]
24. Metallic-based austenitic stainless steel according to claim 22 or 23, characterized by the fact that it also comprises no more than 1.0% by weight of Niobium plus Tantalum and a maximum of 0.10% by weight of Tantalum .
[25]
25. Metal-based austenitic stainless steel according to claim 24, when dependent on claim 17, characterized by the fact that Niobium and Tantalum is more than Nb + Ta (min); on what
Nb + Ta (min) is calculated from 8xC (min), where
C (min) is the minimum amount of carbon, (with 0.10% by weight of Ta max).
[26]
26. Metal-based austenitic stainless steel according to claim 24, when dependent on claim 18, characterized by the fact that Niobium and Tantalum is more than Nb + Ta (min); on what
Nb + Ta (min) is calculated from 10xC (min), where
C (min) is the minimum amount of carbon, (with 0.10% by weight of Ta max).
[27]
27. Metal-based austenitic stainless steel according to any one of claims 1 to 16, characterized by the fact that it has a Corrosion Resistance Equivalent (PREn) of> 25; on what
PREn =% by weight of Chromium + (3.3 x% by weight of Molybdenum) + (16 x% by weight of Nitrogen).
[28]
28. Metal-based austenitic stainless steel according to any of claims 1 to 26, characterized by the fact that Nitrogen is 0.40 to 0.60% by weight and the metal base has a specified Pitting Resistance Equivalent ( PREn) of> 25, where
PREn =% by weight of Chromium + (3.3 x% by weight of MolibPetition 870190038552, of 24/04/2019, page 196/204
6/8 diene) + (16 x% by weight of Nitrogen).
[29]
29. Metallic-based austenitic stainless steel according to any one of claims 1 to 26, characterized by the fact that it comprises 0.50 to 1.00% by weight of Tungsten and has a Corrosion Resistance Equivalent (PREnw) 27 ; on what
PREnw =% by weight of Chromium + [(3.3 x% by weight (Molybdenum + T ungstene)) + (16 x% by weight of Nitrogen).
[30]
30. Metal-based austenitic stainless steel according to any one of claims 1 to 26, characterized by the fact that it comprises 0.40 to 0.60% by weight of Nitrogen, 0.50% by weight to 1.00% in Tungsten weight and has a specified Pite Resistance Equivalent (PREnw) 27; on what
PREnw =% by weight of Chromium + [(3.3 x% by weight (Molybdenum + T ungstene)) + (16 x% by weight of Nitrogen).
[31]
31. Metal-based austenitic stainless steel according to any one of claims 1 to 30, characterized in that the ratio of Chromium Equivalents to Nickel Equivalents is more than 0.45 and less than 0.95.
[32]
32. Forged steel, characterized by the fact that it comprises metal-based austenitic stainless steel as defined in any one of claims 1 to 31.
[33]
33. Cast steel, characterized by the fact that it comprises austenitic stainless steel as defined in any one of claims 1 to 31.
[34]
34. Austenitic stainless steel according to any one of claims 1 to 35, characterized by the fact that [Cr] and [Ni] are also defined by:
Chromium equivalent, [Cr] = (Cr in% of weight) + (1.5 x Si in% of weight) + (1.4 x Mo in% of weight) + (Nb in% of weight) + (0 , 72 x W in% of weight) + (2.27 x V in% of weight) + (2.20 x Ti in% of weight) + (0.21 x Ta in% of weight) + 0.28 x Al in weight%) - 4.99; and
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Nickel equivalent, [Ni] = (Ni in% of weight) + (30 x C in% of weight) + (0.5 x Mn in% of weight) + ((26 x% in weight) ((N - 0.02)) + (0.44% x Cu in% by weight) + 2.77, where the% by weight of Nb, W, V, Ti, Ta, Al and Cu are non-zero; and where
Nb = Niobium
W = Tungsten;
V = Vanadium;
Ti = Titanium;
Ta = Tantalum;
Al = Aluminum; and
Cu = Copper.
[35]
35. Method of preparation of austenitic stainless steel with a metallic base having a non-magnetic austenitic microstructure with a metallic base, characterized by the fact that it comprises 16.00% by weight of Chromium to 30.00% by weight of Chromium (Cr); 8.00% by weight of Nickel to 27.00% by weight of Nickel (Ni); not more than 7.00% by weight of Molybdenum (Mo); 0.40% by weight of Nitrogen to 0.70% by weight of Nitrogen (N), 1.0% by weight of Manganese less than 4.00% by weight of Manganese (Mn), not more than 1, 0% by weight of Niobium (Nb), less than 0.10% by weight of Carbon (C), <0.070% by weight of Oxygen, not more than 2.00% by weight of Silicon,> 0.03 % by weight of Cerium and <0.08% by weight of Cerium; the metal-based non-magnetic austenitic microstructure optionally additionally comprising at least one element selected from boron, Rare Earth Metals (REM), Aluminum, Calcium, Magnesium, Copper, Tungsten, Vanadium, Titanium, and / or Niobium plus Tantalum;
the rest of the microstructure of the matelica base being iron and unavoidable impurities, the method comprising:
Petition 870190038552, of 04/24/2019, p. 198/204
8/8 (i) perform a solution heat treatment of the metal alloy composition at a temperature between 1100 ° C and 1250 ° C, in which the ratio of Chromium Equivalent divided by the Nickel Equivalent is optimized in the molten step of in order to obtain a non-magnetic austenitic metal-based microstructure first after heat treatment of solubilization in the range of 1100 ° C to 1250 ° C followed by water quenching;
where the ratio of Manganese (Mn) to Nitrogen (N) is controlled to> 2.85 and <7.50; and the ratio of Chromium Equivalent [Cr] to Nickel Equivalent is determined and controlled to more than 0.40 and less than 1.05; and where the Chromium Equivalent ratio is determined and controlled according to the first formula:
[Cr] = (Cr in% of weight) + (1.5 x Si in% of weight) + (1.4 x Mo in% of weight) + (Nb in% of weight) - 4.99; and where the Nickel Equivalent is determined and controlled according to the second formula:
[Ni] = (Ni in% of weight) + (30 x C in% of weight) + (0.5 x Mn in% of weight) + ((26 x% in weight) ((N - 0.02) ) + 2.77.

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法律状态:
2018-01-16| B25A| Requested transfer of rights approved|Owner name: UPL, L.L.C. D/B/A UNITED PIPELINES OF AMERICA LLC |

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2019-01-29| B07A| Application suspended after technical examination (opinion) [chapter 7.1 patent gazette]|

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2019-08-27| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2019-10-08| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 24/05/2012, OBSERVADAS AS CONDICOES LEGAIS. (CO) 20 (VINTE) ANOS CONTADOS A PARTIR DE 24/05/2012, OBSERVADAS AS CONDICOES LEGAIS |

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SG2011038874|2011-05-26|

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SG201103887-4|2011-05-26|

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