巴西专利BR112014015190B1 SEWLESS STEEL PIPE FOR USE IN OIL WELL AND METHOD FOR PRODUCING IT.

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Patent Summary: "High strength continuous steel pipe for use in oil well that has excellent resistance to cracking under sulfide stress". it is a continuous steel tube having a composition containing by weight% c: 0.15 to 0.50%, si: 0.1 to 1.00%, mn: 0.3 to 1.0 %, p: 0.015% or less, s: 0.005% or less, al: 0.01 to 0.1%, n: 0.01% or less, cr: 0.1 to 1.7%, mo: 0 40 to 1.1%, v: 0.01 to 0.12%, nb: 0.01 to 0.08%, ti: 0.03% or less and b: 0.0005 to 0.0030, and a structure composed of a tempered martensite phase as a main phase with a subsequent austenite grain size number of 8.5 or more and has a hardness distribution whereby in four portions 90 ° apart from each other in the circumferential direction, hardness is 295 hv10 or less at any of an inner surface lateral region of 2.54 to 3.81 mm from the inner surface of the pipe, an outer surface lateral region at the same distance from the outer surface of the pipe and one center of thickness. therefore, the continuous steel pipe has high grade strength of 758.42 mpa (110 ksi) (conventional yield strength: 758 mpa or more) and excellent ssc resistance. the composition may additionally contain cu and / or w and / or ni and / or ca.
公开号:BR112014015190B1
申请号:R112014015190-3
申请日:2012-12-18
公开日:2019-04-16
发明作者:Kenichiro Eguchi；Yasuhide Ishiguro；Yukio Miyata
申请人:Jfe Steel Corporation；
IPC主号:

专利说明:

[001] The present invention relates to a seamless steel tube of high strength suitable for use in an oil well and particularly for the improvement of resistance to cracking under sulfide stress (resistance to SSC) in acidic environments that contain hydrogen sulfide. The term high force represents a grade strength of 758.42 MPa (110 ksi), that is, it represents the case of a yield limit of 758 MPa or more and 862 MPa or less.
BACKGROUND TECHNIQUE [002] In recent years, from the point of view of fluctuating oil prices and depletion of estimated oil sources in the near future, unseen deep oil wells, oil wells and gas wells in harsh corrosive environments under the so-called acidic environments that have been actively developed. The use of tubular products in oil fields in such environments requires including materials that have both high strength and excellent corrosion resistance (acid resistance).
[003] For this requirement, for example, Patent Literature 1 describes steel for tubular products for the oil industry that have excellent resistance to cracking under sulfide stress (SSC resistance), the steel that contains C: 0.15 to 0.35%, Si: 0.1 to 1.5%, Mn: 0.1 to 2.5%, P: 0.025% or less, S: 0.004% or less, sol. Al: 0.001 to 0.1%, Ca: 0.0005 to 0.005% and a non-metallic inclusion based on Ca that has a composition containing CaS and CaO in a total of 50% by weight or more and an oxide composed of Ca-AI less than 50% by weight and steel that has a hardness in the range of 21 to 30 HRC and a specified relationship between hardness and total amount X (% in
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2/34 mass) of CaO and CaS. One technique described in Patent Literature 1 includes accelerating a reaction with harmless CaS and CaO by decreasing the amount of the Ca-AI compound oxide adverse to SSC resistance, producing steel for use in an oil well that is resistant to Enhanced SSC.
[004] Patent Literature 2 describes a method for producing a seamless steel tube that has little variation in strength and a microstructure with austenite grain size No. 6 or more according to ASTM standards, the method which includes the drilling and hot rolling of a billet, which forms a tube under the condition of a finishing rolling temperature of 900Ό to 1100Ό to produce a seamless steel pipe and quench the steel pipe while holding the same in a region of temperature equal to or greater than an Ar3 point and temper, the billet that has a composition that contains C: 0.15 to 0.35%, Si: 0.1 to 1.5%, Mn: 0 , 1 to 2.5%, P: 0.03% or less, S: 0.005% or less, sun. Al: 0.001 to 0.1% or less, Cr: 0.1 to 1.5%, Mo: 0 to 1.0%, N: 0.0070% or less, V: 0 to 0.15%, B : 0 to 0.0030%, Ti: 0 to A% where A = 3.4 x N (%) and Nb: 0.005 to 0.012%. One technique described in Patent Literature 2 includes the formation of a microstructure by adjusting the steel composition and the finishing rolling temperature · thus, in order to decrease the variation in strength [005] Additionally, Patent Literature 3 describes a method for producing a seamless steel pipe that has high strength and high resistance to corrosion. One technique described in Patent Literature 3 relates to a method for producing a seamless steel tube by tempering and tempering a steel tube and then applying a plastic deformation with a sectional plasticity rate. 10 to 90% in the steel tube in a hot manner at 400Ό to 750Ό, the steel tube containing C: 0.30% or less, Si: 0.05 a
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1.00%, Μη: 0.30 to 1.20%, S: 0.03% or less, Cr: 0.50 to 1.50%, Mo: 0.10 to 2.00%, Ni: 0 , 50% or less and Cu: 0.10% or less. The technique described in Patent Literature 3 decreases the hardness of the inner and outer surface layers of the steel tube, which comes into contact with a corrosive atmosphere, which produces a seamless steel tube that satisfies both high strength and high strength corrosion.
[006] Patent Literature 4 describes steel that has excellent resistance to sulfide cracking. The technique described in Patent Literature 4 includes controlling a composition so that it contains C: 0.01 to 0.10%, Si: 0.05 to 0.60%, Mn: 0.50 to 2.50 %, P: 0.010% or less, S: less than 0.002%, Al: 0.005 to 0.100%, Ti: 0.005 to 0.020% and Ca: 0.0005 to 0.0050% and the microVickers hardness control at 250 .or less and a deviation in hardness in the thickness direction at 60 or less, so as to improve the crack resistance of steel sulfide cracking.
[007] Patent Literature 5 describes a method for producing a high strength corrosion resistant steel tube A technique described in Patent Literature 5 includes quenching and tempering a steel tube twice, the steel tube containing C: 0.30% or less, Si: 0.05 to 1.00%, Mn: 0.30 to 1.00%, P: 0.03% or less, S: 0.03% or less , Cr: 0.30 to 1.50%, Mo: 0.10 to 2.00%, Al: 0.01 to 0.05% and N: 0.015% or less, and which additionally contains at least one among Nb : 0.01 to 0.04%, V: 0.03 to 0.10%, Ti: 0.01 to 0.05%, B: 0.0010 to 0.0050% and Ca: 0.0010 to 0 , 0050%, where a complete curve removal is performed in a cold or hot manner after a first temper and temper, and a slight or no curve removal is performed after a second temper and temper, thereby producing a tube of high-strength corrosion-resistant steel that has a small curve and a uniform hardness distribution of 758.42 MPa (110 ksi) or more in the right direction thickness
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4/34 wall.
Citation List
Patent Literature [PTL 1] Publication of Unexamined Japanese Patent Application No. 2002-60893 [PTL 2] Publication of Unexamined Japanese Patent Application No. 2000-219914 [PTL 3] Publication of Unexamined Japanese Patent Application No. 05-287380 [PTL 4] Publication of Unexamined Japanese Patent Application No. 07-166293 [PTL 5] Japanese Unexamined Patent Application Publication No. 05-287381
SUMMARY OF THE INVENTION
Technical Problem [008] However, several factors that affect SSC resistance are very complicated and in the present situation, the conditions to ensure stable resistance to SSC in 758.42 MPa high strength steel tubes (110 ksi) are not clear. For example, in the technique described in Patent Literature 1, the specific conditions of maximum hardness and inclusions in formation useful for the improvement of SSC resistance are not specified. Additionally, in the technique described in Patent Literature 2, only one difference between the maximum hardness and minimum hardness are described, an absolute value for maximum hardness is not described and specific conditions to ensure resistance to SSC are not mentioned. In the technique described in Patent Literature 3, the SSC resistance of a portion of the surface layer is improved, however, the SSC resistance of the steel tube as a whole cannot be considered satisfactory. The technique described in Patent Literature 4 is capable of producing a steel tube that has YS of up to
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5/34 about 500 MPa degree, however, has the problem of difficulty in producing a steel tube that has a strength greater than that order. The technique described in Patent Literature 5 requires repetition of quenching and tempering twice and includes straightening the removal of the curve between the quenching and tempering times, thus, in such a way as to cause the possibility of complicating the process and decrease productivity.
[009] An objective of the present invention is to solve the problems mentioned above of the related technique and to provide a high strength seamless steel tube that has excellent resistance to cracking under sulfide stress (SSC resistance), which is suitable for use in an oil well. The term excellent resistance to cracking under sulfide stress (SSC resistance) refers to a case in which no cracking occurs with an applied stress of 85% yield strength for a duration of more than 720 hours in a constant charge in a saturated aqueous solution of H2S containing 0.5% acetic acid and 5.0% sodium chloride (liquid temperature: 24Ό) according to NACE TMO177 Method A standards.
Solution to the Problem [0010] To obtain the objective, the inventors of the present invention have intensively studied several factors that affect the strength and resistance to sulfide cracking of a seamless steel pipe. As a result, it has been found that to satisfy both the high strength and excellent resistance to cracking under sulfide stress in a seamless steel pipe for use in an oil well, the seamless steel pipe is required to contain Mo in an amount decreased to about 1.1% or less and necessarily contain Cr, V, Nb and B in adequate quantities and have a hardness distribution where the hardness of Vickers HV10 measured in a
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6/34 lateral region of internal surface of 2.54 to 3.81 mm of the internal surface of the tube in the direction of thickness, a lateral region of external surface of 2.54 to 3.81 mm of the external surface of the tube in the direction of thickness and at a center of thickness in each of the four portions separated at 90 ° from each other in the circumferential direction of the steel pipe is 295 HV10 or less at maximum (maximum hardness) in various positions in the circumferential direction of the steel pipe. Additionally, it was found that uniformity in the structure is important for this requirement.
[0011] Based on the findings, the present invention was obtained through additional investigations. That is, the essence of the present invention is as follows.
[0012] (1) A seamless steel tube for use in an oil well that has excellent resistance to cracking under sulfide stress, the steel tube that has the composition that contains, in mass%, C: 0.15 at 0.50%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.0%, P: 0.015% or less, S: 0.005% or less, Al: 0.01 to 0, 1%, N: 0.01% or less, Cr: 0.1 to 1.7%, Mo: 0.40 to 1.1%, V: 0.01 to 0.12%, Nb: 0.01 at 0.08%, Ti: 0.03% or less, B: 0.0005 at 0.003% and the balance composed of Fe and unavoidable impurities, in which in four portions separated at 90 ° from each other in the circumferential direction · the hardness of Vickers HV10 measured with a load of 10 kgf (test force: 98 MPa) is 295 HV10 or less in all three positions in each of a lateral region of internal surface from 2.54 to 3.81 mm from the inner surface of the tube in the direction of thickness, a lateral region of outer surface of 2.54 to 3.81 mm from the outer surface of the tube in the direction of thickness · and a center of the thickness.
[0013] (2) The seamless steel tube for use in an oil well described in (1), in which the composition additionally contains, in mass%, one or two selected from Cu: 1.0% or less and Ni:
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1.0% or less.
[0014] (3) The seamless steel tube for use in an oil well described in (1) or (2), in which the composition additionally contains, in mass%, W: 2.0% or less.
[0015] (4) The seamless steel tube for use in an oil well described in any one of (1) to (3), in which the composition additionally contains, in mass%, Ca: 0.001 to 0.005%.
[0016] (5) The seamless steel tube for use in an oil well described in any one of (1) to (4), where a deviation in wall thickness is 8% or less.
[0017] (6) A method for producing a seamless steel tube for use in an oil well that has excellent resistance to cracking under sulfide stress, the method which includes producing a seamless steel tube with a shape predetermined by means of hot work of a raw material of steel tube that has a composition that contains, in mass%, C: 0.15 to 0.50%, Si: 0.1 to 1.0%, Mn : 0.3 to 1.0%, P: 0.015% or less, S: 0.005% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Cr: 0.1 to 1.7%, Mo: 0.40 to 1.1%, V: 0.01 to 0.12%, Nb: 0.01 to 0.08%, Ti: 0.03% or less, B: 0 .0005 to 0.003% and the balance of Fe and unavoidable impurities, cooling the seamless steel tube at room temperature at a cooling rate equal to or greater than that of air cooling, additional tempering and tempering of the seamless steel tube by reheating medium and then performing hot straightening within a temperature range of 580Ό or more and a tempering temperature or less to produce a seamless steel tube that has a hardness distribution in which in four portions separated at 90 ° from one another in the circumferential direction, the Vickers HV10 hardness measured with a load of 10 kgf (test force: 98 MPa) is 295 HV10 or less in all three positions in each of one
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8/34 lateral region of internal surface of 2.54 to 3.81 mm of the internal surface of the tube in the direction of thickness, a lateral region of external surface of 2.54 to 3.81 mm of the external surface of the tube in the direction of thickness and a center of thickness.
[0018] (7) The method for producing a seamless steel pipe for use in an oil well described in (6), in which the raw material of the steel pipe is a steel plate formed by means of hot rolling of a casting plate.
[0019] (8) The method for producing a seamless steel pipe for use in an oil well described in (6) or (7), in which the temperature of the crude steel pipe material in a heating furnace for Hot work deviates by ± 20O over the entire circumference and the entire length of the raw material of steel pipe.
[0020] (9) The method for producing a seamless steel tube for use in an oil well described in (6) or (7), in which the temperature of a material to be laminated during hot work deviates within ± 50O over the entire circumference and the entire length of the material to be laminated.
[0021] (10) The method for producing a seamless steel tube for use in an oil well described in any one of (6) to (9), in which the quenching and tempering are repeated twice or more. [0022] (11) The method for producing a seamless steel tube for use in an oil well described in any one of (6) to (9), where, instead of tempering and tempering, tempering is repeated twice and then the temper is played.
[0023] (12) The method for producing a seamless steel tube for use in an oil well described in any one of (6) to (11), where tempering includes reheating to a tempering temperature within a range from an AC3 transformation point to 1050Ό,
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9/34 hold for 5 minutes or more and then cool quickly and tempering includes holding at a tempering temperature within a range of 630Ό to 730Ό for 10 minutes or more and then cooling. [0024] (13) The method for producing a seamless steel tube for use in an oil well described in any one of (6) to (12), wherein the composition additionally contains, in mass%, one or two selected from Cu: 1.0% or less and Ni: 1.0% or less, [0025] (14) The method for producing a seamless steel tube for use in an oil well described in any of ( 6) to (13), where the composition additionally contains, in mass%, W: 2.0% or less.
[0026] (15) The method for producing a seamless steel tube for use in an oil well described in any one of (6) to (14), where the composition additionally contains, in mass%, Ca: 0.001 to 0.005%.
Advantageous Effects of the Invention [0027] According to the present invention, it is possible to easily produce, at low cost, a high strength seamless steel tube that has a high strength of 758.42 MPa (110 ksi) and excellent strength the cracking under sulfide stress in a rigorous corrosive environment containing hydrogen sulfide, thus, in a way that demonstrates significant industrial advantages.
BRIEF DESCRIPTION OF THE DRAWINGS [0028] Figure 1 is an exemplary schematic view showing cross-section hardness measurement positions.
DESCRIPTION OF MODALITIES [0029] First, the reasons for limiting a steel tube composition of the present invention are described. Later in this document, Bulk% will be shown simply by means of% unless otherwise specified.
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C: 0.15 to 0.50% [0030] C has the function of increasing the steel strength and is an important element to guarantee the desired high strength. In addition, C is an element to improve hardening and contributes to the formation of a structure composed of a tempered martensite phase as a main phase. To achieve this effect, a content of 0.15% or more is required. On the other hand, with a content that exceeds 0.50%, a large amount of carbides that function according to hydrogen trapping sites is precipitated during tempering and, thus, it is impossible to delay the diffusible hydrogen from entering the steel excessively and suppress cracking during tempering. Therefore, the C content is limited to 0.15 to 0.50%. The C content is preferably 0.20 to 0.30%.
Si: 0.1 to 1.0% [0031] Si is an element that works as a deoxidizer and that has the function of increasing the steel strength by dissolving in steel and that suppresses the quick softening during tempering. To achieve this effect, a content of 0.1% or more is required. On the other hand, with a content that exceeds 1.0%, an inclusion based on thick oxide is conformed and, thus, works according to a strong hydrogen trap site and induces a decrease in the amount of effective elements dissolved. Therefore, the Si content is limited to a range of 0.1 to 1.0%. The Si content is preferably 0.20 to 0.30%.
Mn: 0.3 to 1.0% [0032] Mn is an element that has the function of increasing the steel strength by improving the hardening and preventing the weakening of the grain contour due to the S connecting to the S and setting S according to MnS. In the present invention, a content of 0.3% or more is required. On the other hand, with a content that exceeds 1.0%, the cementite precipitated in grain outlines is thickened, so as to decrease the
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11/34 resistance to cracking under sulfide stress. Therefore, the Mn content is limited to a range of 0.3 to 1.0%. The Mn content is most preferably 0.4 to 0.8%.
P: 0.015% or less [0033] OP shows the tendency to segregate in grain boundaries in a state of solid solution and to cause cracking of grain boundary embrittlement or similar, and is therefore preferably decreased by quantity as much as possible. However, a content of up to 0.015% is permissible. Therefore, the P content is limited to 0.015% or less. The P content is more preferably 0.013% or less.
S: 0.005% or less [0034] S is present mainly according to steel-based sulfide inclusions and decreases ductility, stiffness and corrosion, resistance such as crack resistance under sulfide stress and the like. Although the S may be partially present in a solid solution state, however, in this case, the S shows the tendency to segregate in grain boundaries and to cause cracking of grain boundary embrittlement or similar, and is thus preferably decreased in quantity as much as possible. However, an excessive decrease in quantity quickly increases the cost of reducing ores. Therefore, in the present invention, the S content is limited to 0.005% or less, which has permissible adverse effects.
Al: 0.01 to 0.1% [0035] Al works as a deoxidizer and contributes to the refining of austenite crystal grains by binding to N to conform AIN. To achieve this effect, an Al content of 0.01% or more is required. On the other hand, with an Al content that exceeds 0.1%, large amounts of oxide-based inclusions are thus increased, so that the stiffness is reduced. Therefore, the Al content is limited to a range of 0.01 to 0.1%. The Al content is preferably 0.02 to 0.07%.
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Ν: 0.01% or less [0036] ON binds to elements that form nitride, such as Mo, Ti, Nb, Al and the like to form precipitates of the MN type. However, these precipitates decrease resistance to SSC and decrease amounts of precipitate of MC and M ₂ C during tempering, thus making it impossible to expect the desired upper strength. In this way, N is preferably reduced in quantity as much as possible and the N content is limited to 0.01% or less. Due to the fact that MN type precipitates have the effect of suppressing the thickening of crystal grains during the heating of a crude steel and similar material, the N content is preferably about 0.003% or more.
Cr: 0.1 to 1.7% [0037] Cr is an element that contributes to an increase in steel strength through an increase in hardening and improves resistance to corrosion. In addition, Cr binds to C to form carbides based on M3C, M7C3 and M ^ Ce and the like during tempering. In particular, M3C-based carbides improve resistance to softening by tempering, decreasing a change in strength due to tempering and facilitating force adjustment. To achieve this effect, a Cr content of 0.1% or more is required. On the other hand, with a Cr content that exceeds 1.7%, large amounts of carbides based on M7C3 and carbides based on M ^ Ce are shaped and function according to hydrogen trap sites, thus, in such a way that it decreases resistance to cracking under sulfide stress. Therefore, the Cr content is limited to a range of 0.1 to 1.7%. The Cr content is preferably 0.5 to 1.5% and more preferably 0.9 to 1.5%.
Mo: 0.40 to 1.1% [0038] Mo forms carbides and contributes to an increase in strength through precipitation hardening and to an additional improvement in crack resistance under sulfide stress through
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13/34 segregation in previous austenite grain contours. In addition, Mo has the function of densifying corrosion products and suppressing the formation and growth of pits that serve as initiation of cracking. To achieve this effect, a Mo content of 0.40% or more is required. On the other hand, with a Mo content that exceeds 1.1%, precipitates of type M2C in the form of a needle and, in some cases, Laves phase (Fe2Mo) are shaped, so that the resistance to cracking under the sulfide stress. Therefore, the Mo content is limited to a range of 0.40 to 1.1%. The Mo content is preferably 0.6 to 1.1%.
V: 0.01 to 0.12% [0039] Ο V is an element that forms a carbide or nitride and contributes to the steel straightening. To achieve this effect, a V content of 0.01% or more is required. On the other hand, with a V content that exceeds 0.12%, the effect is saturated and an effect that corresponds to the content cannot be expected, which causes an economic disadvantage. Therefore, the V content is limited to a range of 0.01 to 0.12%. The V content is preferably 0.02 to 0.08%.
Nb: 0.01 to 0.08% [0040] Nb delays recrystallization in a region of austenite temperature (γ) to contribute to γ grain refinement, works significantly in the refinement of a martensite substructure (for example example, a package, a block, or a clapboard) and has the function of steel straightening forming a carbide. To achieve this effect, an Nb content of 0.01% or more is required. On the other hand, with an Nb content that exceeds 0.08%, the precipitation of coarse precipitates (NbC and NbN) is accelerated, so that it results in a decrease in crack resistance under sulfide stress. Therefore, the Nb content is limited to a range of 0.01 to 0.08%. The Nb content is more preferably 0.02 to 0.06%. The package is defined as a region made up of a group of strips arranged in parallel and which have 0
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14/34 usual twinning plan and the block consists of a group of parallel slats that have the same orientation.
Ti: 0.03% or less [0041] Ti is an element that forms a carbide or nitride and contributes to the steel straightening. To achieve this effect, a Ti content of 0.01% or more is preferred. On the other hand, with a Ti content that exceeds 0.03%, the formation of coarse TiN is accelerated during casting and the TiN is not dissolved even by means of subsequent heating, which results in a decrease in stiffness and strength cracking under sulfide stress. Therefore, the Ti content is limited to a range of 0.03% or less. The Ti content is more preferably 0.01 to 0.02%.
B: 0.0005 to 0.003% [0042] B is an element that contributes to the improvement of hardening to a light content, and in the present invention, a content of 0.0005% or more is required. On the other hand, even with a high content that exceeds 0.003%, the effect is saturated, or conversely, a desired effect cannot be expected due to the formation of Fe-B boride, which causes an economic disadvantage. In addition, with a content that exceeds 0.003%, the formation of coarse borides, such as M02B, Fe2B and the like, is accelerated and, thus, cracking occurs easily during hot rolling. Therefore, the B content is limited to a range of 0.0005 to 0.003%. The B content is preferably 0.001 to 0.003%.
[0043] The components described above are basic, however, if necessary, the basic composition may additionally contain at least one selected from Cu: 1.0% or less, Ni: 1.0% or less, W: 2.0 % or less and Ca: 0.001 to 0.005%.
Cu: 1.0% or less [0044] Cu is an element that has the function of increasing the strength
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15/34 steel and improve rigidity and corrosion resistance and can be added according to demand. In particular, when strict resistance to cracking under sulfide stress is required, Cu is a very important element. When added, Cu forms a dense corrosion product that suppresses the formation and growth of pits that serve as crack initiation and thus significantly improves crack resistance under sulfide stress. Therefore, in the present invention, a content of 0.03% or more is preferred. On the other hand, even a content that exceeds 1.0% leads to saturation of the effect and an increase in cost. Therefore, the Cu content is preferably limited to 1.0% or less. The Cu content is most preferably 0.03 to 0.10%. Ni: 1.0% or less [0045] Ni is an element that has the function of increasing steel strength and improving rigidity and resistance to corrosion and can be added according to demand. To obtain the effect, a Ni content of 0.03% or more is preferred. However, even a content that exceeds 1.0% leads to saturation of the effect and an increase in cost. Therefore, the Ni content is preferably limited to 1.0% or less.
W: 2.0% or less [0046] W forms carbides to contribute to steel straightening and can be added according to demand.
[0047] Like Mo, W forms carbides to contribute to an increase in strength due to precipitation hardening and segregates, in a solid solution, in previous austenite grain contours to contribute to the improvement in resistance to cracking under tension sulfide. To obtain the effect, a content of 0.03% or more is preferred, although with a content that exceeds 2.0%, the crack resistance under sulfide stress is degraded. Therefore, the W content is preferably limited to 2.0% or less. The W content is most preferably 0.05 to 0.50%.
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Ca: 0.001 to 0.005% [0048] Ca is an element that has the function of converting elongated sulfide-based inclusions to granular inclusions, that is, the function of controlling the shape of inclusions and having the effect of improving ductility, rigidity and resistance to cracking under sulfide stress by controlling the shape of inclusions. Ca can be added according to demand. This effect becomes significant at a content of 0.001% or more, although with a content that exceeds 0.005%, the amounts of non-metallic inclusions are increased and the ductility, stiffness and crack resistance under sulfide stress are, to a certain extent. mode, decreased. Therefore, the Ca content is preferably limited to a range of 0.001 to 0.005%.
[0049] The balance excluding the components described above is composed of Fe and unavoidable impurities.
[0050] Next, the steel tube of the present invention has the composition described above and also has a structure that contains a tempered martensite phase as a main phase and previous austenite grains with grain size No. 8.5 or more.
[0051] To guarantee the high grade strength of 758.42 MPa (110 ksi) at relatively low levels of alloy elements without containing large amounts of alloy elements, the steel tube of the present invention has a martensite phase structure however, from the point of view of guaranteeing desired stiffness, ductility, and resistance to cracking under sulfide stress, the structure is composed of a tempered martensite phase as a main phase formed by tempering the martensite phase. The main phase refers to a structure that includes a single phase of tempered martensite or that contains the phase of tempered martensite and a second phase of less than 5%, by volume within a range that has no influence on characteristic 870180146205, of 10/30/2018, p. 19/46
17/34 cas. When the content of the second phase is 5% or more, additional strength and stiffness, ductility, and the like are degraded. Examples of the second phase include bainite, perlite, ferrite, a mixed phase thereof and the like. Therefore, the structure composed of a tempered martensite as a main phase represents a structure that contains 95% by volume or more of tempered martensite phase.
[0052] In addition, the steel tube of the present invention has the structure containing grains (γ) of previous austenite with a grain size number of 8.5 or more. A value measured according to JIS G 0551 standards is used as the previous austenite grain size number. With the prior austenite grain size No. of grains less than 8.5, a martensite phase substructure produced by transforming a thickened y phase and the desired crack resistance under sulfide stress cannot be guaranteed.
[0053] In addition, the steel tube of the present invention is characterized in that, as shown in Figure 1, in four portions separated at 90 ° from one another in the circumferential direction, the hardness of Vickers HV10 measured with a load of 10 kgf (test force: 98 MPa) is 295 HV10 or less in all three positions in each of a side region of inner surface 2.54 to 3.81 mm from the inner surface of the tube in the thickness direction, a side region of external surface of 2.54 to 3.81 mm of the external surface of the tube in the thickness direction, and a center of the thickness. That is, the steel tube of the present invention has a hardness of 295 HV10 at a maximum, at least, in the three positions in each of the inner surface side, the outer surface side and the thickness center. When the hardness exceeds 295 HV10 in any of the measurement positions in each of the three regions in the thickness direction, the crack resistance under sulfide stress is degraded. To uniformly produce the steel tube that has excellent resistance to cracking under tension
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18/34 of sulfide, it is an essential requirement that the hardness be 295 HV10 or less in all measurement positions in each of the three regions in the thickness direction [0054] The following is a preferred method for producing a steel of the present invention is described.
[0055] A raw steel pipe material having the composition described above is used as a starting material and the raw steel pipe material is heated to a predetermined temperature range and then hot worked to form a pipe seamless steel with predetermined dimensions.
[0056] In the present invention, a method for producing the crude steel tube material that has the composition described above does not need to be particularly limited, however, it is preferable that a liquid steel having the composition described above is refined by means of a common known refinement method with the use of a converter, an electric oven, a vacuum melting furnace, or the like and shaped into a casting plate, such as a billet by means of a common known continuous casting method. The casting plate is preferably subjected to additional hot work, such as laminating by heating to form a steel plate. This is effective for smoothing the structure of the resulting crude steel pipe material and for adjusting the hardness of a steel pipe to 295 HV10 or less. Furthermore, instead of the continuous casting method, a rough ingot making method for the production of raw steel pipe material is not a problem.
[0057] The raw material of steel pipe is preferably heated to a temperature in the range of 1000Ό to 1350Ό. With a heating temperature of less than 1000Ό, the carbides are not melted enough. On the other hand, with a heating temperature that exceeds 1350Ό, the excessive grain thickening
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19/34 crystal causes thickening of cementite in previous austenite grain (γ) contours and significant concentration (segregation) of impurity elements, such as P, S and similar in the grain contours, thus, so as to weaken the contours of grain and easily produce grain boundary fracture. In view of productivity, the temperature retention time is preferably 4 hours or less.
[0058] In addition, the raw material of the steel tube is preferably retained under heating in the heating furnace for hot work such that it has a temperature distribution within ± 20 ° over the entire circumference and throughout the length. When the temperature distribution of the raw steel pipe material during heating is out of range, variation occurs in the steel pipe structure after hot work and a desired uniform hardness distribution cannot be guaranteed after tempering and tempering. [0059] The raw material from the heated steel tube is then formed into a tube by means of hot work using a common manufacturing process of a laminator with a Mannesmann type chuck or a laminator on a Mannesmann type chuck, so that produces the seamless steel tube with predetermined dimensions. The seamless steel tube can be produced by means of hot extrusion of the press type. After tube making, the seamless steel tube is cooled to room temperature at a cooling rate equal to or greater than that of air cooling. During hot work, the temperature of the material to be laminated (raw steel pipe material) preferably deviates within ± 50 ° along the entire circumference and the entire length of the material to be laminated. When the temperature of the material to be laminated during rolling is out of range, variation occurs in the structure of the steel tube after hot working and a desired uniform hardness distribution cannot be guaranteed after tempering and tempering.
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20/34 [0060] By controlling the temperature of the raw steel tube material or the material to be laminated as described above, the resulting wall thickness derivation of the steel tube can be adjusted to 8% or less. The deviation in wall thickness is calculated using the following expression.
[0061] The deviation of wall thickness = (maximum wall thickness - minimum wall thickness) / (average wall thickness) [0062] To stabilize the material and make the structure uniform, the seamless steel tube, after hot work, it is subjected to tempering by means of reheating and rapid cooling (water cooling) and is also tempered. Tempering and tempering are preferably repeated twice or more. Tempering can be repeated twice or more and then tempering can be carried out. By repeating the quench and tempering twice or more or by repeating the quench twice or more, the structure becomes more uniform, thus reducing the maximum hardness and significantly increasing the crack resistance under sulfide stress .
[0063] In the present invention, quenching is a process that includes reheating to a quenching temperature of a transformation point Αθ3 or more and 1050Ό or less, preferably 830Ό to 940Ό and then rapid cooling (water cooling) from the quench temperature to a temperature range of a transformation point of Ms or less, preferably 100Ό or less. This can result in a structure composed of a martensite phase as a main phase that has a thin substructure transformed from a γfine phase. Heating to a tempering temperature below the transformation point Ac3 cannot produce a single austenite phase and therefore cannot sufficiently produce the martensite structure by subsequent cooling, and thus the desired strength cannot be guaranteed. Therefore, the
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21/34 heating for tempering is preferably limited to the transformation point AC3 or more. On the other hand, tempering at a high temperature that exceeds 1050Ό causes the structure to thicken and reduces the stiffness and resistance to cracking under sulfide stress.
[0064] In addition, cooling from the quench heating temperature is preferably water cooling at 2 O / s or more and is performed in a temperature region of the transformation point of Ms or less, preferably , 100Ό or less. As a result, a satisfactory hardened structure (95% by volume or more of martensite structure) can be formed. In addition, the retention time at the quench temperature is 5 minutes or more and, preferably, 10 minutes or less. As a result, the structure becomes more uniform and the maximum hardness in a section of the steel pipe can be adjusted stably to 295 HV10 or less. [0065] The seamless steel tube subjected to tempering is then tempered.
[0066] In the present invention, tempering is performed to try to stabilize the structure by reducing excessive disagreement and to provide both the high strength and excellent resistance to cracking under desired sulfide stress.
[0067] The tempering temperature is preferably a temperature within a temperature range of 630 ° C to 730Ό. With the tempering temperature deviating to the bottom side of the strip, the number of hydrogen trapping sites, such as discrepancies, is increased and the crack resistance under sulfide stress is degraded. Although with the tempering temperature deviating to the upper side of the strip, the structure is significantly softened and, therefore, the desired high strength cannot be guaranteed. In addition, quantities of needle-like precipitates M2C are increased, so that the resistance
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22/34 to cracking under sulfide stress. Tempering is preferably a process that includes holding at a temperature within the range described above for 10 minutes or more and then cooling to room temperature at a cooling rate, preferably equal to or greater than that of air cooling . When the retention time at the tempering temperature is less than 10 minutes, a desired uniform structure cannot be achieved. The retention time is preferably 80 minutes or less. With an excessively long temper retention time, a Laves phase (Fe2Mo) is precipitated.
[0068] After hardening and tempering, straightening is performed for straightening failures in the shape of the steel tube and for decreasing hardness variation. Straightening is a hot straightening performed in a temperature range of 580Ό or more and the tempering temperature or less. Cold straightening performed at room temperature increases the density of disagreement and therefore cannot improve crack resistance under sulfide stress corrosion. This applies to straightening performed within a low temperature region of less than 580Ό. In addition, straightening within a high temperature region beyond the tempering temperature decreases strength. The straightening is preferably performed in such a way that a rate of sectional plasticity is 1% or more and less than 10%. With a sectional plasticity rate of less than 1%, the straightening effect is unsatisfactory. On the other hand, with a sectional plasticity rate of 10% or more, plastic deformation is applied, thus increasing the density of discrepancies that serve as sources of hydrogen trapping and decreasing SSC resistance.
[0069] The present invention is described in further detail below based on examples.
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EXAMPLES [0070] The molten steel that has each of the compositions shown in Table 1 was refined with a converter and formed into a casting plate using a continuous casting method. The casting plate was used as a raw steel tube material and hot worked using a Mannesmann type mandrel laminator manufacturing process to produce a tube according to a seamless steel tube with dimensions shown in Table 2 and then the tube was cooled in air at room temperature. Then, the hot-worked seamless steel tube was tempered by reheating to the tempering temperature shown in Table 2 and cooling by water and then tempered under the conditions shown in Table 2. Then, the straightening was performed at a temperature shown in Table 2.
[0071] A sample was taken from each of the resulting steel tubes and a structural observation test, a tensile test, a cross section hardness test and a corrosion test were performed. The test methods were as follows.
(1) Structure observation test [0072] A sample for structure observation was taken from each of the steel tubes and a section (section C) perpendicular to the longitudinal direction of the tube was polished and then corroded (solution of metallographic attack: nital liquid), and the structure was observed with an optical microscope (magnification: 1000 times) and a scanning electron microscope (magnification: 2000 times) and imaged to measure the type and fraction of the structure with an image analyzer .
[0073] Additionally, previous austenite grain contours were exposed by means of corrosion with a picral attack solution and the resulting structure was observed in three fields of vision with an optical microscope (magnification: 1000 times) to determine the number of
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24/34 previous austenite grain size using a cutting method according to JIS G 0551 standards.
(2) Cross section hardness test [0074] As shown in Figure 1, in four portions separated at 90 ° from one another in the circumferential direction at a position of 400 mm from one end of each of the resulting steel tubes, the hardness of Vickers HV10 was measured with a load of 10 kgf (test force: 98 MPa) in three positions in each of the lateral regions of the inner surface 2.54 to 3.81 mm from the inner surface of the tube in the direction thick, a lateral region of external surface of 2.54 to 3.81 mm of the external surface of the tube in the thickness direction and a center of the thickness. The measurement positions were three positions in each of the regions. The measured values were averaged to determine an arithmetic mean as an average HV10 hardness and the maximum HV10 hardness for each of the steel tubes was determined.
(3) Corrosion test [0075] Ten corrosion test samples were taken from each of the steel tubes and a constant load test was conducted in a saturated aqueous solution of H2S that contains 0.5% acetic acid and 5.0% sodium chloride (liquid temperature: 24Ό) according to NACE TMO177 Method A standards. After loading with a loading stress of 85% yield strength for 720 hours, the presence of cracking in the samples was observed to assess crack resistance under sulfide stress. Cracking was observed with the use of a projector with a magnification of 10 times. The crack resistance under sulfide stress was assessed from the crack incidence (= (number of samples cracked) / (total number of samples) x 100 (%)).
[0076] The results obtained are shown in Table 3.
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Table 1
comments Examplecomparative Example ofadaptation Example ofadaptation Example ofadaptation Examplecomparative Example ofadaptation Example ofadaptation Example ofadaptation Chemical composition (% by mass) Here 1 0.002 0.002 0.002 0.002 1 COOOthe ~ 0.002 Ti, W OOH Ti: 0.02 Ti: 0.02 cT co o3 < OOH Ti: 0.02 Ti: 0.02 Ti: 0.02 Cu, Ni 1 1 Cu; 0.10,Ni: 0.05 1 1 1 Cu: 0.05 Cu: 0.05 ω 0.0025 0.0020 0.0021 0.0021 0.0021 0.0025 0.0017 0.0020 Nb 1 1 0.03 0.05 0.05 0.03 0.03 0.05 0.05 > 1 1 0.03 0.03 0.03 1 1 0.03 0.07 0.03 Mo 0.01 0.99 O00the ~ OCOthe ~ 0.27 0.95 0.79 0.81 O 0.50 O co O O in CO CO 0.0028 OOOthe ~ 0.0027 OCOOOthe ~ OCOOOthe ~ 0.0050 0.0033 dogOOthe ~ < OOthe ~ 0.025 0.028 0.027 0.034 OOthe ~ 0.029 0.027 ω 0.0020 0.0007 0.0007 0.0007 OOthe ~ 0.0020 0.0007 0.0007 CL 0.015 OOthe ~ OOthe ~ 0.011 00OOthe ~ 0.015 OOthe ~ OOthe ~ Mn O 0.6 0.6 0.6 0.5 O 0.6 0.6 ώ 0.25 0.25 0.27 0.26 0.26 0.25 0.26 0.25 O 0.25 0.25 0.25 0.25 0.24 0.25 0.26 0.25 No. insteel <l ω O O LUI Ll_ O ΞΕ
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Examplecomparative Examplecomparative Examplecomparative Example ofadaptation Example ofadaptation Example ofadaptation 0.002 0.002 0.002 1 1 1 Ti: 0.02 Ti: 0.02 Ti: 0.02 Ti: 0.02 Ti: 0.02 Ti: 0.02 1 1 1 1 1 1 0.0020 0.0020 0.0023 0.0021 0.0021 0.0021 0.03 0.05 1 1 0.05 0.05 0.05 0.02 1 1 0.05 0.03 0.03 0.03 0.37 0.81 0.70 O00the ~ 0.97 0.97 - CO 0.7 CO CO O dogOOthe ~ 0.0039 0.0035 0.0027 0.0027 0.0027 0.033 0.027 0.072 0.028 0.028 0.028 COOOthe ~ 0.0007 COOOthe ~ 0.0007 0.0007 0.0007 COOOthe ~ OOthe ~ 0.006 OOthe ~ OOthe ~ OOthe ~ 0.5 0.6 0.4 0.6 0.6 0.6 0.26 0.25 0.27 0.27 0.27 0.27 0.24 0.26 0.27 0.25 0.25 0.25 -) l *1 _l 2
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Table 2
Commentrivers ExampleComparedtivo Exampleof thatvention Exampleof thatvention Exampleof thatvention ExampleComparedtivo ExampleComparedtivo Straightenment Rateinplastici-dadesection-final (%) LO - LO σ> LO - Temp, (° C) 585 610 620 610 595 530 Hot treatment conditions Repeat-tition QT QT QT QT QT QT Temper T c <> = O c E -ο ω = £ oo »£ 1— s— ^s - 1 1 1 1 1 1 Temp. hardening (° C) 1 1 1 1 1 Quenching Q Retention time (min) 1 1 1 1 Temp. hardening (° C) 1 1 1 1 1 Temper T Retention time (min) 20 30 30 30 20 80 Temp. hardening (° C) 675 700 720 700 069 625 Quenching Q Retention time (min) it LO LO LO LO LO Temp. hardening (° C) 920 920 920 920 920 890 Hot working conditions Temperature difference during lamination(Ό) (maximum-minimum) 48 33 36 σ> 30 39 R, ώ E o, cfe -o θ 'Ω. φ T3 θ O £ (FROM 03 OOC q - fc o - c P Sc, <L> 3 fc ΓΤ _c 'TO 2 = ee CO CO u- u- CO u- Steel tube dimensions Hi θ Φ '7 ^W Λ 73 Ό ω $ π £ £ ω ω o. co Q ⁷³ £ Q. u- LO co co (Outside diameter in mmip x wall thickness in mm)) 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 ° (D Ç 7 -A θ ^'73 TO <l CO O O LLII O No. of steel tube - OJ CO LO CO
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Commentrivers ExampleComparedtivo Exampleof thatvention Exampleof thatvention Exampleof thatvention Exampleof thatvention ExampleComparedtivo ExampleComparedtivo Straightenment Rateinplastici-dadesection-final (%) LO σ> - LO σ> LO LO Temp, (° C) 590 615 605 590 585 585 585 Hot treatment conditions Repeat-tition QT QT QT QT QT QT QT Temper T c <> = O c E -ο ω = £ oo »£ 1— s— ^s - 1 1 1 1 1 1 1 Temp. hardening (° C) 1 1 1 1 1 1 Quenching Q Retention time (min) 1 1 1 1 1 1 1 Temp. hardening (° C) 1 1 1 1 1 1 1 Temper T Retention time (min) 09 80 30 80 80 09 80 Temp. hardening (° C) 685 710 700 685 685 675 675 Quenching Q Retention time (min) O it LO LO LO LO LO Temp. hardening (° C) 1100 890 920 910 890 920 890 Hot working conditions Temperature difference during lamination(Ό) (maximum-minimum) 48 42 30 22 27 42 42 R, ώ E o, cfe -oθ 'Ω. φ T3 θ O £<L> E ro o £ o '57 -4 - 3 t π- r '4, = CO r ^ - r ^ - r ^ - CO CO OO Steel tube dimensions Hi <L>(L>'7 ^W Λ ¹³ Ό ω $ π £ £ ω ω o. Co Q 73 á CL CO r ^ - CO LO (Outside diameter in mmip x wall thickness in mm)) 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 178φχ22.2 ° (D Ç 7 -SO ^'73 TO O O LL 0 I —Ι -> i No. of steel tube r ^ - OO σ> O - OJ CO
Petition 870180146205, of 10/30/2018, p. 31/46
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Commentrivers ExampleComparedtivo ExampleComparedtivo Exampleof thatvention ExampleComparedtivo Exampleof thatvention Exampleof thatvention ExampleComparedtivo Straightenment Rateinplastici-dadesection-final (%) LO it it LO LO LO LO Temp, (° C) 590 550 585 560 595 605 565 Hot treatment conditions Repeat-tition QT QT QT QT QTQT QT QT Temper T c <> = O c Ε -ο ω = £ oo »£ 1— s— ^s - 1 1 1 1 30 1 Temp. hardening (° C) 1 1 1 1 700 1 1 Quenching Q Retention time (min) 1 1 1 1 LO 1 1 Temp. hardening (° C) 1 1 1 870 1 1 Temper T Retention time (min) 30 30 80 80 30 30 30 Temp. hardening (° C) 069 675 099 099 695 685 685 Quenching Q Retention time (min) it it it LO LO LO LO Temp. hardening (° C) 920 870 870 870 870 870 870 Hot working conditions Temperature difference during lamination(Ό) (maximum-minimum) 27 27 39 24 29 43 R, ώ E o, cfe -oθ 'Ω. φ T3 θ O £<L> E ro o £ o '57 -, <L> - 3 t π- r 'te, = r ^ - r ^ - r ^ - r ^ - LO Steel tube dimensions Hi <L> (L>(Λ ι T3 Ό, —χ.ω $ π £ £ ω ω o. coQ £ Q. r ^ - it CO LO CO CO (Outside diameter in mmip x wall thickness in mm)) 178φχ22.2 215.9φ x 31.8 215.9φ x 31.8 215.9φ x 31.8 244.5φ x 15.5 244.5φ x 15.5 244.5φ x 15.5 ° (D Ç 7 -S O '‘-I _l _l _l _l _l No. of steel tube it CO r ^ - CO σ> 20
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Commentrivers Exampleof thatvention Exampleof thatvention ExampleComparedtivo ExampleComparedtivo ExampleComparedtivo Exampleof thatvention Straightenment Rateinplastici-dadesection-final (%) Temp, (° C) 585 585 585 585 585 595 Hot treatment conditions Repeat-tition QT QT QT QT QT QQT Temper T c ^ω tz oc E -ο ω = tu ο φ ojÊ. 1— s— ^s - 1 1 1 1 1 30 Temp. hardening (° C) 1 1 1 1 1 700 Quenching Q Retention time (min) 1 1 1 1 1 Temp. hardening (° C) 1 1 1 1 1 870 Temper T Retention time (min) 30 80 80 80 80 1 Temp. hardening (° C) 099 099 099 099 099 1 Quenching Q Retention time (min) Temp. hardening (° C) 870 870 870 870 870 870 Hot working conditions Temperature difference during lamination(Ό) (maximum-minimum) 32 37 37 37 mlml 26 R, ώ E o, θ 'Ω. φ õ ° £ tU E ro TD £ o '57 - Jr tD 1- C tD SP a <-, <U - 3 t -T _c -ro .i: O CO CO mlcmI CO CO Steel tube dimensions Hi you (Dt / 5 1 Ό Ό χ«® $ 2 £ £ ω ω o. coQ τ3 £ Q. CO r ^ - £ 1 r ^ - r ^ - CO (Outside diameter in mmip x wall thickness in mm)) 215.9φ x 31.8 215.9φ x 31.8 215.9φ x 31.8 215.9φ x 31.8 215.9φ x 31.8 244.5φ x 15.5 ° (D Ç 7 4; O '“t- ⁷³ TO z z z z No. of steel tube oj 22 23 24 25 26
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Table 3
1 ro ro ro 1 1 1 ro ro ro (Z) AND (Z) (Z) (Z) AND AND Ε (Z) (Z) (Z) Oro 5 Φ The Φ The Φ The 5 Sg Sg Φ The Φ The Φ Theσ ç 4 fo the c the c the c 4 fo 4 fo 4 fo the c the c The c ω Q_ s- CL Φ cl ω cl ω Q_ s- Q_ s- Ω_ s- cl ω cl ω cl ω AND c ω £ Q- And £ And £ And £ c ω £ Q- c ω £ Q- c ω £ Q- Ε Ϊ Ε Ϊ Ε Ϊ O Φ Φ - Φ - Φ - Φ Φ φ Φ - Φ - Φ - ω X X X X X X X X X X LU LU LU LU LU LU LU LU LU LU 3Π-scφ J_ Cp 'U S t f— O O O Ο (Z)CZ) Π3 <φ ._ o O O O O O O Ο O O O O -1— »f— T ^-T ^- T ^- τ ^-ω ro Ο φ Φ QT 6th -Ξ the E ro ro j; c í (Z) CL— Φ O σ> CN r ~ σ> σ> σ> O CO 00 Φ> 4 P Φ C CO r ~ 00 LO τ— CO 00 00 CO CN CN CN CN CN CO CN CN CN CN (Z) ç Ό ASS ro the 2 s— (Z) - c Φ (Z) O y— O σ> 00 00 00 CN CO O Ό LO 00 00 00 LO T— r ~ r ~ 00 00 Φ Φ W CN CN CN CN CN CO CN CN CN CN Φ(Z) 2 Ο -σ ω ω φ φ * Ό õ * _ro ro gt Ε4 8.4 00 CO CO 00 00 ο LO r ~ CO N 00 r ~ 00 LO T ^- r ~ CO 00 r ~ Φi_ CN CN CN CN CN CO CN CN CN CN D ro = s> < Ό _l W Φ ω Ό ro O AND CO 00 CN LO CO CO X CO σ> 00 σ> r ~ cçd 00 00 σ> σ> > -ro CN CN CN CN CN col CN CN CN CN X Φ Ό ω 2 LO CO 00 LO O LO 00 LO (Z) CO O CO O r ~ CO O 00 ageration r ~ σ> 00 σ> 00 00 00 σ> 00 'ÜZ + - · YSMPa 00 r ~ r ~ r ~ LO O CO Q. LO r ~ CO O σ> r ~ r ~ O σ> O CO 00 r ~ 00 r ~ σ> r ~ r ~ 00 r ~ CL ω „E σ -g ω o The C £ O O O O O ο O O O O > ro = 3 A, § T ^- T ^- T ^- T ^- T ^- τ ^- T ^- T ^- T ^- T ^-Qo rn - 2 g ω> ll ^w ro ώ ώ ώ ώ ώ ώ ώ m m m ro M— D * ω ω ω ω ω ω ω m m m -t— » O + + + + + + + + + + Q_ Esl i— H H H H H Η H H H H , φ φ ro 4 «>φ The ZJ 4 O O O O O Ο O O O O D -F ^ro O. oo ' T— T— T— T— τ— oo ' T— T— T— Z ™ 'ro s ^c O) ^cω XO_ steel <1 ω O O LUI ο O O LL O No. of steel tube - CN CO LO CO r ~ 00 σ> O
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ro 1 1 1 1 ro 1 ro ro 1 ro w w AND AND AND AND w AND w w AND w O'03-t— »ç ro o'& o c Io Coiactive ôg° ro Sg° ro Sg° ro ro o'& o c Sg° ro ro o'& o c ro o'& o c og ° ro ro othe c ω O. ro The. ç: Q_ s- Q_ s- Q_ s- O. ro Q_ s- cl ro cl ro Q. s- cl ro AND And £ c £ 3 Q- c £ 3 Q- c £ 3 Q- c £ 3 Q- And £ c £ 3 Q- And £ And £ c ω S Q- AND O Φ - Φ Φ Φ Φ Φ - Φ Φ - Φ - Φ Φ - O X X X X X X X X X X X LLI LLI LLI LLI LLI LLI LLI LLI ILI LLI LU 3Π-sc 03o o U · w <φ .Ξ ol_ -I- »M- »(- O 100 100 100 20 O 30 O O 50 O ro ro the ro ro QT 6th -And the E ro ro ro c í ω Jr Q-— _ro 00 CO O T ^- CM 00 O U3 03 Φ> 4 3 ro c r- CO 03 03 r- r- 00 CO 00 03 CO ^ ro £ 4 CM CM CM CM CM CM CM CM CM CM CM ω ç 73 ASS ro the 2 O s— (Λ —5 c Φ w CM U3 CM U3 T— CM U3 CM 103O 73 00 CO O O 00 00 00 r- 00 03 00 -ro ro ω w CM CM CO CO CM CM CM CM CM CM CM Φ(/) 2 Ο -σ ro ω ro ro * Ό õ * _roro ro t E4 8.4 T— O CO CO U3 O r- U3 CO 00 03 N 00 CO 03 03 r- 00 CO r- r- 00 r- Φi_ CM CM CM CM CM CM CM CM CM CM CM D ro = 3> < Ό _i «ro ω Ό ro O AND CO U3 CO | HI M O col 00 y— Q> l 03 X 03 r- ÇN T— OM 03 OM r- 03 OM 00 > > ro CM CM col col cmI CM cmI CM CM cmI CM ΞΕ Φ Ό ω g_ r- CO 03 00 r- CO CM CM r- 03 w ç- CO CM O O O U3 CM CM ç- ageration 03 00 03 03 03 03 03 00 03 03 03 '5— YSMPa CM 03 CO r- 00 03 U3 y— r- Q_ CO CM 00 O 03 03 O CO CO O O00 r- 00 00 00 r- r- 00 00 00 00 CL ω „E σ -g ω a The C £ O O O O O O O O O O O > ro = 3 § T ^- T ^- T ^- T ^- T ^- T ^- T ^- T ^- T ^-2 g ω> u ^w ro ώ ώ ώ ώ ώ ώ ώ ώ m m m ro M— D * ω ω ω ω ω ω ω ω m m m -t— » O + + + + + + + + + + + Q_ Esl i— H H H H H H H H H H H , ro ro ro S w> sl «fc. O O O Oco ~ 0.5 0.5 0.5 2.0 O O 0.5 ro, g ro ² E - c ω XO_ steel ΞΕ - ¹ -3l * l _l _l _l _l _l _l 2 in bosteel CM CO U3 CO r- 00 03 O O Z3 λ v ^- v ^- v ^- v ^- v ^- v ^- v ^- v ^- v ^- CM CM 4Z
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CO 1 1 1 CO w w AND AND AND w O'03-t— »ç Φ Theσthe c Io Coiactive ôg4 to og 4 to Φ Theσthe c ω CL Φ CL V Q. s- Q. s- ο. ω AND And £ c 03 S Q- c 03 S Q- c 03 S Q- AND O Φ - Φ Φ Φ Φ - O X X X X X LU LU LU LU LU c ^υ <φ ω yokehere-(%) ω ^w<φ. ^c o O O O w -O -b £ CN CD CO ω co ο φ ω QC 6th -And ό E d. ,. co co j; c í ω CL - co O CN 00 O 00 Φ> 4 -5 Φ c r- r- CO r- CO CN CN CN CN CN ω ç T0 ASS co ° i 2 s— (Λ —5 c Φ w CO co CO io y— l (5J T5 00 00 00 00 r- O ‘Φ Φ Φ W CN CN CN CN CN Φ(/) 2 Ο -σ ω ω φ φ * T0 õ * _roco co t E4 8.4 LO co LO N r- r- r- r- co Φi_ CN CN CN CN CN D CO = 3> < T0 _l W Φ ω T0 CO O AND O ^ laughs Ql CO | CO T " X σ> r- > ‘CO CN col col col CN X Φ T0 ω g_ CN O co O O w LO ageration σ> σ> σ> σ> 00 'ÜZ + - · YSMPa CN co co y— co Q. O O O O O 00 00 00 00 00 CL ω „E σ -g ω a o c E O O O O co > co = 3 S_, 5 T ^- T ^- T ^- T ^- O O rn - 2 g ω> LL ^w co m m m m m CO M— D * m m m m m -t— » O + + + + + Q_ Esl i— H H H H H , φ φ CO S C! W> ω | 0.5 0.5 0.5 0.5 2.0 ^{Z E} ω χ i o O X X X X _l O co in bosteel CN co IO co O Z3 / ή CN CN CN CN CN X φT0
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Petition 870180146205, of 10/30/2018, p. 36/46
34/34 [0077] In any of the examples of the present invention, the steel pipe has high strength (yield strength: 758 MPa or more) and excellent resistance to cracking under desired sulfide stress and a desired hardness distribution with a Maximum hardness of 295 HV10 or less can be guaranteed on the steel pipe. On the other hand, in the comparative examples of the scope of the present invention, a desired structure, high desired strength and a desired hardness distribution with a maximum hardness of 295 HV10 or less and / or a desired hardness distribution with a maximum hardness of 295 HV10 or less cannot be guaranteed and the crack resistance under sulfide stress is degraded.

权利要求:
Claims (9)
[1]
1. Seamless steel tube for use in an oil well, the steel tube having a composition containing,% by mass:
C: 0.15 to 0.50%, Si: 0.1 to 1.0%,
Mn: 0.3 to 1.0%, P: 0.015% or less,
S: 0.005% or less, Al: 0.01 to 0.1%,
N: 0.01% or less, Cr: 0.1 to 1.7%,
Mo: 0.40 to 1.1%, V: 0.01 to 0.12%,
Nb: 0.01 to 0.08%, Ti: 0.03% or less,
B: 0.0005 to 0.003%, and said tube is characterized by the fact that the balance composed of Fe and unavoidable impurities and that it has a structure composed of a tempered martensite phase as a main phase and previous austenite grains with a number grain size of 8.5 or more, measured according to JIS G 0551 standards, in which in four portions separated at 90 ° one from the other in the circumferential direction, the hardness of Vickers HV10 measured with a load of 10 kgf (test force: 98 MPa) is 295 HV10 or less in all three positions in each of a side region of inner surface 2.54 to 3.81 mm from the inner surface of the tube in the thickness direction, a region lateral of external surface of 2.54 to 3.81 mm of the external surface of the tube in the thickness direction and a center of the thickness;
where a deviation in wall thickness of the seamless steel tube is 8% or less.
[2]
2. Seamless steel tube for use in an oil well, according to claim 1, characterized by the fact that the composition additionally contains, in% by weight, one or two selected from Cu: 1.0% or less and Ni: 1.0% or less.
Petition 870180146205, of 10/30/2018, p. 38/46
2/4
[3]
3. Seamless steel tube for use in an oil well, according to claim 1 or 2, characterized by the fact that the composition additionally contains, in mass%, W: 2.0% or less.
[4]
4. Seamless steel pipe for use in an oil well, according to any one of claims 1 to 3, characterized by the fact that the composition additionally contains, in mass%, Ca: 0.001 to 0.005%.
[5]
5. Method for producing a seamless steel tube for use in an oil well, the method being characterized by the fact that it comprises forming a seamless steel tube with a predetermined shape by submitting to hot work a raw material of steel tube that has a composition that contains, in% by mass,
C: 0.15 to 0.50%, Si: 0.1 to 1.0%
Mn: 0.3 to 1.0%, P: 0.015% or less,
S: 0.005% or less, Al 0.01 to 0.1%,
N: 0.01% or less, Cr 0.1 to 1.7%,
Mo: 0.40 to 1.1%, V: 0.01 to 0.12%,
Nb: 0.01 to 0.08%, Ti: 0.03% or less,
B: 0.0005 to 0.003%, and the balance composed of Fe and unavoidable impurities; heating the raw steel tube material within a range of 1000 de to 1350Ό, cooling the seamless steel tube to room temperature at a cooling rate equal to or greater than that of air cooling; additionally subject to quenching, where quenching includes reheating to a quenching temperature within a range of an Ac3 transformation point at 1050Ό, holding for 5 minutes or more, and then cooling in water at 2O / s or more, then temper the seamless steel pipe at a tempering temperature within a range of 630Ό to
Petition 870180146205, of 10/30/2018, p. 39/46
3/4
730Ό, hold for 10 minutes or more and then cool down; and then perform hot straightening within a temperature range of 580Ό or more and at a tempering temperature or less to obtain a sectional plasticity rate of 1% or more and less than 10% to produce a steel tube seamless that has a hardness distribution in which in four portions separated 90 ° from each other in the circumferential direction, the Vickers HV10 hardness measured with a load of 10 kgf (test force: 98 MPa) is 295 HV10 or less in all three positions in each of a lateral region of internal surface of 2.54 to 3.81 mm from the internal surface of the tube in the direction of thickness, a lateral region of external surface of 2.54 to 3.81 mm of the surface outer tube in the thickness direction and a center of the thickness;
wherein the temperature of the steel pipe crude material in a hot-work heating furnace deviates within ± 20 ° over the entire circumference and the entire length of the steel pipe crude material; and wherein the temperature of a material to be laminated during hot work deviates within ± 50 ° over the entire circumference and the entire length of the material to be laminated.
[6]
6. Method for producing a seamless steel tube for use in an oil well, according to claim 5, characterized by the fact that the raw material of the steel tube is a shaped steel plate hot-rolled one casting plate.
[7]
7. Method for producing a seamless steel tube for use in an oil well, according to claim 5 or 6, characterized by the fact that tempering and tempering are carried out twice or more.
[8]
8. Method for producing a seamless steel tube for use in an oil well, according to claim 5 or 6,
Petition 870180146205, of 10/30/2018, p. 40/46
4/4 characterized by the fact that, instead of tempering and tempering after reheating, tempering after reheating is carried out twice or more and then tempering is performed.
[9]
9. Method for producing a seamless steel tube for use in an oil well, according to any one of claims 5 to 8, characterized in that the composition additionally contains, in mass%, at least one selected group from Groups A to C consisting of:
Group A: one or two selected from Cu: 1.0% or less and Ni: 1.0% or less;
Group B: W: 2.0% or less; and
Group C: Ca: 0.001 to 0.005%.

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同族专利:

公开号 | 公开日

RU2014130096A|2016-02-20|

EP2796587A4|2015-01-07|

RU2607503C2|2017-01-10|

JP2013129879A|2013-07-04|

CN104011251A|2014-08-27|

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CN104011251B|2016-06-08|

US20140352836A1|2014-12-04|

EP2796587A1|2014-10-29|

MX2014007572A|2014-08-27|

BR112014015190A8|2017-06-13|

BR112014015190A2|2017-06-13|

WO2013094179A1|2013-06-27|

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法律状态:
2018-03-13| B06T| Formal requirements before examination|

2018-08-07| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application according art. 36 industrial patent law|

2019-02-12| B09A| Decision: intention to grant|

2019-04-16| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 18/12/2012, OBSERVADAS AS CONDICOES LEGAIS. (CO) 20 (VINTE) ANOS CONTADOS A PARTIR DE 18/12/2012, OBSERVADAS AS CONDICOES LEGAIS |

优先权:

申请号 | 申请日 | 专利标题

JP2011280675A|JP2013129879A|2011-12-22|2011-12-22|High-strength seamless steel tube for oil well with superior sulfide stress cracking resistance, and method for producing the same|

JP2011-280675|2011-12-22|

PCT/JP2012/008073|WO2013094179A1|2011-12-22|2012-12-18|High-strength seamless steel pipe with excellent resistance to sulfide stress cracking for oil well, and process for producing same|

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