STEEL PLATE FOR HOT PRINTING AS WELL AS METHOD FOR PRODUCTION AND USE

专利摘要:
Steel Sheet for Hot Stamping as well as Method for Production and Use thereof The present invention relates to a steel sheet for hot stamping which is excellent in the strength of the part after hot stamping. and in the delayed fracture strength comprising a high strength high strength steel plate in which effective hydrogen scavengers are formed in the steel material. The steel plate of the present invention solves this problem by forming fe-mn-based composite oxides in the steel plate and capturing hydrogen at the interfaces of the composite oxides and matrix steel and in the voids around the compound oxides. specifically, it provides a hot-rolled steel plate comprising chemical ingredients containing by weight% c: 0.05 to 0.40%, si: 0.02% or less, mn: 0 , 1 to 3%, s: 0.02% or less, p: 0.03% or less, al: 0.005% or less, ti: 0.01% or less, n: 0.01% or less, a or both have a total of 0.005 to 1%, and o: 0.003 to 0.03%, which has an unavoidable remainder of faith and impurities, and which contains fe-mn-based composite oxide particles with an average diameter 0.1 to 15 µm dispersed in the steel plate or have crushed voids around the composite oxide particles, a method of producing it, and a method of producing a hot-stamped high strength workpiece.
公开号:BR112013022953B1
申请号:R112013022953-5
申请日:2011-03-09
公开日:2019-03-19
发明作者:Kazuhisa Kusumi；Yuji Ogawa；Masayuki Abe；Hidekuni Murakami；Kengo Takeda；Jun Maki
申请人:Nippon Steel & Sumitomo Metal Corporation；
IPC主号:

专利说明:

DESCRIPTION REPORT OF THE PATENT OF STEEL FOR STEEL PLATE FOR USE IN HOT STAMPING, AS WELL AS A METHOD FOR PRODUCTION AND USE OF THE SAME.
DESCRIPTION Technical Field [001] The present invention relates to a steel plate for use in hot stamping that is excellent in resistance to delayed fracture, to a method of producing it, and to a high-strength part that is formed by hot stamping when using this steel sheet. In particular, it refers to a method of producing a high-strength part that is used for a structural part of an automobile.
Background to the Invention [002] In recent years, reducing the weight of automobiles has been strongly demanded from the point of view of the global environment. In automobile bodies, for example, columns, door impact sleepers, bumper sleepers, and other structural parts for automobiles, high strength steel sheet is being used to reduce the thickness of the steel sheet to try to reduce the weight. For this reason, the strength of the steel plate is being increased. In particular, high strength steel sheet with a tensile strength (TS) of more than 1,000 MPa is being developed, but a higher strength of the steel sheet leads to a drop in workability and formability of the press at the time of production of a piece. In particular, it is more difficult to ensure product accuracy due to elastic recovery, etc.
[003] To solve these problems, in recent years, as a technique to simultaneously satisfy a greater resistance and workability of the precision of the steel sheet and the product, the method of hot stamping (method of tempering with pressing) pasPetição 870180028007, de 04/06/2018, p. 6/64
2/50 I am to be used as a practical method. For example, this is disclosed in PLT 1. This heats the steel sheet up to about 900Ό or something in the austenite region, and then forms it by hot pressing and, when forming with pressing, puts it on contact with a common temperature matrix to abruptly cool it and thus obtain a high resistance material. Due to this method of hot stamping, the residual stress that is introduced at the time of forming by pressing is also reduced, so that the inconveniences of fracture, weak freezing of the form, etc., which become problems in sheet metal. high-strength steel with a TS of around 1,180 MPa, are suppressed and the production of parts with good relative accuracy of the product becomes possible.
[004] In the high-strength steel plate that is used for automobiles, etc., the problems mentioned above become more serious the higher the resistance. In addition, in particular in high-strength materials of more than 1,000 MPa, as was known in the past, there is the inherent problem of hydrogen embrittlement (also called seasonal cracking or delayed fracture). In the case of steel plate for use in hot compression, when the residual stress due to pressing at a high temperature is small, hydrogen penetrates the steel at the time of pressing and the susceptibility to hydrogen embrittlement is increased due to residual stress after pressing.
[005] As a method to prevent cracking due to delayed fracture, there is the method of controlling the heating atmosphere at the time of hot stamping. For example, PLT 2 proposes the method of making the hydrogen concentration in the hot stamping heating atmosphere 6% by volume or less and making the dew point 10 * Ό. This is related to a method of control
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3/50 of the hot stamping heating atmosphere. That is, by controlling the hydrogen concentration and the dew point, the penetration of external hydrogen into the steel sheet during heating is suppressed. Therefore, this does not improve the steel sheet itself. It can only be applied to hot stamping that has a system to control the atmosphere.
[006] In addition, as a steel sheet for use in hot stamping, there is the well-known steel sheet that traps the hydrogen that penetrates the steel sheet and thus prevents delayed fracture. For example, PLT 3 proposes a steel plate for use in hot stamping that improves resistance to delayed fracture. This technique encompasses the average particle size range of 0.01 to 5.0 pg of Mg oxides, sulfides, composite crystals, and composite precipitates, for example, one or more composite oxides between them, in steel in an amount of 1 x 10 ² to 1 x 10 ⁷ per square mm. These composite and precipitated composite oxides and crystals that have these as nuclei act as hydrogen capture sites to thereby improve the resistance to delayed fracture.
[007] In addition, as a similar technique, PLT 4 presents the technique of producing high strength thin gauge steel sheet which is excellent in resistance to hydrogen embrittlement characterized by making bainite or martensite the largest phases in terms of the area rate, causing one or more oxides of Nb, V, Cr, Ti and Mo, sulfides, nitrides, composite crystals and precipitates composites in the particles to satisfy an average particle size d: 0.001 to 5.0 pm, a density p: 100 to 1 x 10 ¹³ / mm ² , and a standard deviation ratio σ between the average particle size and the average particle size d: σ / d <1.0, and with a tensile strength 980 MPa or more.
[008] In addition, on the steel plate for use in enamelling,
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4/50 to improve the susceptibility to scaly appearance, it is known that the conformation of voids in the steel sheet is effective to trap hydrogen. PLT 5 proposes the conformation of compound oxides based on Fe-Nb-Mn in the steel plate and the increased segregation of Nb and Mn in the oxides in order to increase the capacity to trap hydrogen. However, the technique that is described in PLT 5 is the technique that assumes a steel plate for use in enamelling that has a low C (carbon) content (usually 0.01% by weight or less). In high-strength steel sheet with high C content (0.05% by weight or more than C) as in steel sheet for use in automobiles, the action of C oxidation cannot be ignored. Therefore, this cannot simply be applied.
[009] Furthermore, the problematic amount of hydrogen in the steel sheet for use in enamelling is a high concentration of 10 to 100 ppm, whereas with the high strength steel sheet an amount of hydrogen of a very low concentration 1 to 3 ppm is considered a problem. Therefore, the art that is described in PLT 5 cannot be applied, since it is a high-strength steel sheet with an excessively large C content. [0010] To apply these techniques to high-strength steel materials with a high C (carbon) content, the appropriate control of the size (average particle size) and the presence (density) of oxides, etc., present in the plate steel is an important requirement. However, strict control to obtain a particle size and density that are effective as hydrogen capture sites and that do not form starting points for large cracks is not technically easy.
List of Citations
Patent Literature
PLT 1: Japanese Patent Publication No. 10-96031A
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5/50
PLT 2: Japanese Patent Publication No. 2006-51543A PLT 3: Japanese Patent Publication No. 2006-9116A PLT 4: Japanese Patent Publication No. 2005-68548A PLT 5: W02008 / 038474A
Brief Description of the Invention
Technical Problem [0011] The state of the art was explained above with regard to measures against delayed fracture due to the hydrogen embrittlement of the hot stamped steel sheet. The problem is that at the present point in time there is no technique that suppresses the delayed fracture due to hydrogen embrittlement when a high-strength steel plate with a high C content is hot-stamped.
[0012] Therefore, an objective of the present invention is to provide a steel sheet for use in hot stamping which is excellent in the strength of parts after hot stamping and in the resistance to delayed fracture comprising high strength steel sheet with high C content where resistance is ensured while effective hydrogen captors are formed in the steel material, a method of producing it, and a method of producing a high-strength hot-stamped part.
Problem Solution [0013] The inventors of the present invention took note of the fact that, to improve the steel sheet for use in hot stamping for delayed fracture resistance, the capture of hydrogen that penetrates the steel sheet is effective and engaged in intensive research based on this fact. As a result of this, they discovered that it is possible to cause the formation of FeMn-based compound oxides in the steel plate and trap hydrogen at the interfaces of the compound oxides and the matrix steel and thereby complete the present
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6/50 invention.
[0014] In high-strength steel plate with a high C content, the inclusions of metal oxides normally become defects. For this reason, as much as possible, the oxygen in the steel is removed and the metal oxide conformation is suppressed. Therefore, in addition to adding Al and other deoxidizing elements, the oxygen concentration is reduced in the melting steel stage.
However, to cause the formation of Fe-Mn-based compound oxides in steel as in the present invention, it is necessary to leave oxygen in the steel to a certain extent. In addition, C itself has a deoxidizing action, so that in general, with the steel sheet with a high C content, the oxygen in the steel ends up becoming small in quantity.
[0016] Therefore, the inventors of the present invention found that by reducing the concentration of Al in the steel plate, weakening the deoxidizing effect, and by ensuring an oxygen concentration in the steel, it is possible to cause the formation of compound oxides even in the plate steel with high C content.
[0017] In addition, they found that, to increase the hydrogen capture effect of compound oxides, it is effective to crush the compound oxides and increase their surface area. They found that by crushing and making compound oxides thinner, their effect as defects falls and this leads to an improvement in the performance of the steel sheet. In addition, they learned that if there are gaps around the compound oxides, the effect of hydrogen capture is further enhanced.
[0018] The inventors of the present invention engaged in intensive studies on the production method for the above. They learned that molten steel with a high C content has a high viscosity, so that Fe-Mn-based compound oxides
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7/50 have difficulty increasing and Fe-Mn-based oxides of steel can be easily formed in steel.
[0019] In addition, it has been learned that the lamination (hot or cold lamination) of a plate comprising steel on which Fe-Mn compound oxides are formed, compound oxides can be stretched and crushed. In this way, they discovered that it is possible to efficiently form hydrogen capture sites on the steel plate that do not become the starting points of cracks. In addition, they found that it is possible to form effective voids in a similar process. The present invention has been completed on the basis of these findings. The object of the present invention is as follows:
(1) steel plate for use in hot stamping which comprises the chemical ingredients that contain, in% by mass,
C: 0.05 to 0.40%,
Si: 0.001 to 0.02%,
Mn: 0.1 to 3%,
Al: 0.0002 to 0.005%,
Ti: 0.0005 to 0.01%,
O: 0.003 to 0.03%, one or more of Cr and Mo in a total of 0.005 to 2%, and a remainder of Fe and unavoidable impurities, in which the steel plate contains Fe-based composite oxide particles. Mn with an average diameter of 0.1 to 15 pm dispersed on the steel plate.
[0020] It should be noted that S, P and N are unavoidable impurities, but they are restricted to the following levels:
S: 0.02% or less,
P: 0.03% or less,
N: 0.01% or less,
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8/50 (2) The steel plate for use in hot stamping as indicated in (1) which also contains, in mass%, the ingredients that are included in one or more groups among the three groups (a) a (c):
(a) B: 0.0005 to 0.01%;
(b) one or more of Nb, V, W and Co in a total of 0.005 to 1%; and (c) one or more Ni and Cu in a total of 0.005 to 2%.
(3) The steel sheet for use in hot stamping as indicated in (1) or (2), where there are voids around the composite oxide particles.
(4) The steel sheet for use in hot stamping as indicated in (1) or (2), where the voids around the composite oxide particles have average sizes of 10 to 100% of the average particle size of composite oxide.
(5) The steel sheet for use in hot stamping as indicated in (1) or (2), where the steel sheet is coated by any of the aluminum cladding, the zinc-aluminum cladding and the zinc coating.
(6) A method of producing the steel plate for use in hot stamping, which comprises the hot rolling of a plate of chemical ingredients indicated in (1) or (2) in which the raw rolling of the plate occurs. of a lamination rate of 70% or more and the final crude lamination of the plate by a lamination rate of 70% or more.
(7) The method of producing the steel sheet for use in hot stamping as indicated in (6), which further comprises stripping the hot-rolled steel sheet that was obtained by hot rolling and hot rolling. cold-rolled steel sheet at a rolling rate of 30% or more.
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9/50 (8) The method of producing the steel sheet for use in hot stamping as indicated in (7), which further comprises the annealing of the cold rolled steel sheet that was obtained by cold rolling.
(9) A method of producing a high-strength part when using the steel sheet for use in hot stamping, which comprises heating the steel sheet as indicated in (1) or (2) to a temperature from the austenite region of Ac ₃ or more, and then the forming of the steel sheet by a die begins, and the cooling of the steel sheet in the die after forming until quenching.
Advantageous Effects of the Invention [0021] The high strength steel sheet for use in hot stamping of the present invention stretches and crushes the compound oxides to thereby form the composite oxide particle and its surrounding voids that are effective as capture sites. hydrogen. Because of this, there is no need to strictly control the size (average particle size) and the presence status (density) of the oxides, etc., as in the past and it is possible to obtain a steel sheet that is excellent in characteristics. delayed fracture. If a member is used which is produced from the steel sheet of the present invention, it is considered that it is possible that it contributes significantly to a lower weight and greater safety of automobiles. The contribution to the industry is great.
Brief Description of the Drawings [0022] FIG. 1 is a schematic view showing the state in which common compound oxides are stretched and crushed and many crushed voids (hydrogen trapping capacity) are formed on the steel plate.
[0023] FIG. 2 is a schematic view showing the state in
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10/50 that common oxides are stretched and crushed and few crushed voids (hydrogen capture capacity) are formed on the steel plate.
[0024] FIG. 3 is a schematic view showing that the crushed voids are not formed when fine oxides are present.
[0025] FIG. 4 is a cross-sectional view of the shape of a matrix set that is used in the examples.
[0026] FIG. 5 is a view showing the shape of a punch that is used in the examples as seen from above.
[0027] FIG. 6 is a view showing the shape of a matrix that is used in the examples as seen from below.
[0028] FIG. 7 is a schematic view of a hot stamped part.
[0029] FIG. 8 is a view showing the shape of a test piece for assessing delayed fracture strength as seen from above.
Description of Modalities [0030] In the following, the present invention will be explained in detail.
[0031] The fact that the delayed fracture occurs due to the diffusible hydrogen coming from the external environment that penetrates the steel sheet and diffuses into the steel sheet at room temperature is already known. Therefore, if it could trap hydrogen from the outside environment that penetrates somewhere inside the steel sheet, it might be possible to render the hydrogen harmless and the delayed fracture would be suppressed.
[0032] The inventors of the present invention have found that the casting of a plate comprising steel in which Fe-Mn-based compound oxides are formed in the steelmaking process and by hot rolling and cold rolling of the plate to stretch and crushing the compound oxides, it is possible to form fine voids between the
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11/50 Fe-Mn-based composite oxide particles finely crushed, where the voids are effective as hydrogen capture sites, since diffusible hydrogen, believed to be the cause of the delayed fracture, is trapped in these parts , and the susceptibility to delayed fracture decreases. In addition, the inventors of the present invention discovered that these voids were of sizes and shapes whereby they did not easily become the starting points of cracks and sought to apply steel to a hot stamping material where strength is required.
[0033] Firstly, the reasons for limiting the strength of a part after the hot stamping of the present invention and of the steel sheet ingredients for use in hot stamping which is excellent in delayed fracture resistance for the strips will be explained predetermined. Here, for the ingredients,% means% by mass.
C: 0.05 to 0.40% [0034] C is an element that is added to form the structure after having cooled the martensite and ensuring the quality of the material. To improve strength, 0.05% or more of C is needed, but if the C content exceeds 0.40% the strength at the time of deconformation with impact and weldability deteriorates, so it was applied 0.05 at 0.40% C. In terms of strength, moreover, the C content is preferably 0.15% or more, and more preferably 0.2% or more.
[0035] In addition, from the point of view of deterioration of resistance at the time of deconformation with impact or weldability and the effect of C deoxidation, the C content is preferably 0.35% or less, and more preferably 0.3% or less.
Si: 0.001 to 0.02% [0036] Si acts as a deoxidizing element. The present
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12/50 prevention requires that a certain amount or more of oxides be ensured, so that Si, which reduces the oxygen content, is limited to 0.02% or less. To obtain the effective amount of oxides, the Si content is 0.015% or less, and more preferably 0.01% or less. The lower limit of Si content is not particularly a problem, but due to the time and expense involved in removing Si, the lower limit is 0.001%.
Mn: 0.1 to 3% [0037] Mn is an element that affects hot stamping capacity and hardenability and is effective in increasing the strength of the steel sheet. In addition, Mn, by addition, forms oxides composed of Fe-Mn, so that it is an important ingredient in the present invention. These compound oxides form trap locations for the hydrogen that causes the delayed fracture. For this reason, the addition of Mn is effective for improving the resistance to delayed fracture.
[0038] In addition, the compound oxides formed are thin in size, so they are effective in suppressing the formation of large cracks in the perforated surfaces. To form oxides and use Mn to the maximum extent as hydrogen capture locations, it is sufficient to proactively add Mn since the addition facilitates the control of the oxide composition. If the Mn is less than 0.1%, this effect cannot be achieved. For this reason, the Mn content can be 0.1% or more. To obtain this effect reliably, the Mn content is preferably 0.5% or more. In addition, 1.30% or more is more preferable.
[0039] In addition, if the Mn content exceeds 3.0%, Mn helps with cosegregation with P and S, causes a drop in toughness, and lowers the resistance to delayed fracture. For this reason, the Mn content should be 3% or less. More preferably, the Mn content can be
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13/50
2.0% or less, and more preferably 1.50% or less.
S: 0.02% or less [0040] S is contained as an unavoidable impurity. If it is contained in excess, it degrades workability, becomes a cause of deterioration in toughness, and reduces resistance to delayed fracture. For this reason, the less S, the better. As the allowable range, the content is defined as 0.02% or less. Preferably, the index should be made 0.01% or less. In addition, by limiting the S content to 0.005% or less, the impact characteristics are markedly improved.
P: 0.03% or less [0041] P is an element that is contained as an unavoidable impurity and has a harmful effect on toughness when added in excess. It reduces resistance to delayed fracture. For that reason, the less P, the better. As the allowable range, the content is limited to 0.03% or less. In addition, 0.025% or less is preferable. In addition, if it is 0.02% or less, the effect of improving the resistance to delayed fracture is great.
Al: 0.0002 to 0.005% [0042] Al is an element that is required for use as a deoxidizing material for molten steel. The present invention requires that a certain amount or more of oxides be ensured, so that if Al, which has a deoxidizing effect, is present at more than 0.005%, the amount of oxides to improve the resistance to delayed fracture cannot be increased. assured. For this reason, the upper limit is 0.005%. If a safety margin is considered, the Al content is preferably 0.004% or less, and more preferably 0.003% or less. In addition, the lower limit is not particularly adjusted, but removing Al involves time and expense, so 0.0002% or more is practical.
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Ti: 0.0005 to 0.01% or less [0043] Ti is also a deoxidizing element. The lower limit is not particularly adjusted, but the removal of Ti involves time and expense, so the content is sufficiently 0.0005% or more, and preferably 0.001% or more. On the other hand, the addition of a large amount reduces the oxides, which improves the resistance to delayed fracture, so that the upper limit is 0.01%. In addition, 0.008% or less is preferable. In addition, if it is 0.006% or less, the effect of improving the resistance to delayed fracture is great.
N: 0.01% or less [0044] If the N is greater than 0.01%, the nitrides increase and the dissolved N causes hardening with aging, whereby a tendency is seen for the tenacity to deteriorate . P, the lower the N, the better. As the allowable range of N, the content is limited to 0.01% or less in the range. Preferably, it is 0.008% or less. If it is 0.006% or less, it is possible to suppress the deterioration of toughness, so this is preferable.
One or both Cr and Mo in a total of 0.005 to 2% [0045] Cr and Mo are both elements that improve hardenability. In addition, they have the effect of causing the precipitation of M23C6-type carbides in the matrix and have the effect of increasing the strength and refining the carbides. For this reason, one or both Cr and Mo are added in a total of 0.005 to 2%. If it is less than 0.005%, these effects cannot be expected sufficiently. Most preferably, the content should be 0.01% or more. In addition, if it is 0.05% or more, the effect is marked. In addition, if it exceeds 2% in total, the conventional yield strength increases excessively, toughness is degraded, and resistance to delayed fracture is reduced. If possible, from the point of view of delayed fracture resistance, the content is more preferably 1.5% or less.
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15/50 (Ο: 0.003 to 0.03%) [0046] Ο Ο is an element that is required for the conformation of oxides composed of Fe-Mn in the present invention. The inclusion of 0.003 to 0.03% is necessary. If it is less than 0.003%, a sufficient amount of Fe-Mn compound oxides cannot be formed. From the point of view of the conformation of oxides composed of Fe-Mn, 0.005% or more is preferable. On the other hand, if it includes more than 0.03%, the molten plate ends up with gas bubbles and other internal defects, so the upper limit is 0.03%. From the point of view of internal defects, less is better. An O content of 0.02% or less is preferable. If possible, if it is 0.015% or less, the defects markedly decrease.
B: 0.0005 to 0.01% [0047] B is an element that is effective in improving hardenability. To make this effect more effective, adding 0.0005% or more is necessary. To make this effect more reliable, 0.001% or more is preferable. In addition, 0.0015% or more is more preferable. On the other hand, even if it is added in excess, the effect is saturated, so that 0.01% became the upper limit. Viewed from a cost versus effect standpoint, 0.008% or less is preferable. If possible, 0.005% or less is more preferable.
One or more of Nb, V, W and Co in a total of 0.005 to 1% [0048] Nb, ο V, W and Co are carbide forming elements. They form precipitates to ensure the resistance of the hot-stamped and abruptly cooled member. In addition, these are the necessary elements that are contained in Fe-Mn-based compound oxides, act as hydrogen capture sites that are effective for improving delayed fracture resistance, and improve delayed fracture resistance. One or more of these elements can be added. If the addition quantities
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16/50 exceed a total of more than 1%, the increase in the conventional limit of elasticity increases excessively. For that reason, 0.7% or less is more preferable. If possible, 0.5% or less is even more preferable. On the other hand, if it is less than 0.005%, the improvement in strength and the effect as a hydrogen capture site is difficult to obtain. From the point of view of obtaining this effect reliably, 0.01% or more is preferable.
One or both of Ni and Cu in a total of 0.005 to 2% [0049] Ni and Cu are elements that improve strength and toughness, but if they are added in a total of more than 2%, the melting capacity decreases , so the upper limit is 2%. From the point of view of castability, the content can be reduced. 1% or less is more preferable. 0.5% or less is more preferable. On the other hand, if it is less than 0.005% in total, the effect of improving strength and toughness is difficult to obtain, so that one or both Ni and Cu can be added in a total of 0.005% or more . From the point of view of strength and toughness, 0.01% or more is preferable. In addition, 0.02% or more is more preferable.
[0050] Next, the method of producing the steel sheet for use in hot stamping, which is excellent in the delayed fracture resistance of the present invention, will be explained.
[0051] In the present invention, it is possible to reduce the steel adjusted in the composition of ingredients of the present invention by the usual reduction, by continuous casting, and by the steel plate production process. In particular, in order to form the Fe-Mn-based compound oxides that characterize the present invention, it is preferable to add the elements of low deoxidizing capacity first in the steel melting and reduction processes. For example, by adding Mn, Si, Al, etc., in that order, the effect of the present invention can be achieved more strikingly.
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17/50 [0052] The mechanism by which these steelmaking conditions affect the properties of the steels of the invention is believed to be as follows: Fluctuations in the composition of the compound oxides of the steels of the invention are mainly due to fluctuations in the composition of thermodynamic oxides when casting and solidifying steel. Basically, this is accomplished by using the state of imbalance in the oxide composition process that approaches the state of equilibrium due to the change in concentration and the change in the temperature of the system. With the addition of a weak oxidizing element A first, the oxygen in the molten steel forms common oxides of A, but the addition of an element B with an intense bonding force with oxygen thereafter, the element A in the oxides of A is exchanged for element B. In the process, common compound oxides of A and B (compound oxides of AB) are formed. If you finish with the addition of the strong deoxidizing element first, forming a compound after that becomes difficult. Not only that, a large amount of oxides is formed together with the addition, and deoxidation occurs. The large amount of oxides that floats in the molten steel makes dispersing the oxides in the steel difficult. As a result, the effect of improving the delayed fracture resistance of the product is reduced.
[0053] Due to such a mechanism, time is required for the formation of common compound oxides after the addition of a weak oxidizing element. On the other hand, if an excessively long time ends after the addition of an element, the composition of the compound oxides of A-B is too close to that of the oxides of B in steady state. Not only does the effect of the compound oxides become smaller, but the oxides also float again and end up leaving the melting steel so that the improvement effect
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18/50 of the characteristics is inhibited.
[0054] The voids that function as hydrogen capture sites are formed mainly in the cold rolling process after hot rolling. That is, the compound oxides based on FeMn are crushed by lamination, whereby crushed voids are formed around the composite oxide particles. For this reason, it is important to control the shape of the compound oxides in the hot rolling process.
[0055] In the present invention, the composite oxide parts that are dispersed in the steel were originally an integrated composite oxide. That is, at the time of casting when the final melting steel is adjusted in the ingredients, there was a large mass of simple oxide, but it is believed that it is stretched, crushed and dispersed finely in the rolling process. Such stretching and crushing occur mainly in the rolling process. When the temperature of the steel plate is high (1,000Ό or more), the oxides are mainly stretched.
[0056] On the other hand, when the temperature of the steel plate is low (1,000X3 or less), the oxides are mainly crushed. In such a process, if there is a segregation in the composition in the oxides, the extent of the stretch will differ depending on the portion of the oxides, and the shape of the oxides will become complicated. In addition, thin (thin) portions are preferably crushed, whereas portions with large fluctuations in shape are expected to be preferably crushed due to the concentration of the deconformation stress. As a result, portions that differ in composition are efficiently crushed and dispersed. At the time of this crushing, voids are sometimes formed around the composite oxide particles. These become hydrogen capture sites in steel and are also believed to improve
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19/50 remarkable resistance to the delayed fracture of hot stamped products.
[0057] The above will be explained with reference to the figures.
[0058] FIG. 1 is a schematic view showing the state in which the common compound oxides are stretched and crushed and a large number of crushed voids (hydrogen capture capacity) are formed in the steel plate. In FIG. 1, the common compound oxides 1 are formed by two different types of oxides 1-1 and 1-2 as composites. Compound oxides 1 and 2 are hot rolled crude (shown by arrows in FIG. 1) in stretched compound oxides 3 and oxides 3-1 and 3-2 are also stretched. Then, they are finally hot rolled 4 (shown by arrows in FIG. 1) and further stretched and crushed. At that time, oxides of different hardness are crushed, so that numerous crushed voids 5 are formed around particles 5-1 and 5-2 of crushed compound oxides. These crushed voids 5 also become hydrogen trap locations whereby resistance to delayed fracture is improved.
[0059] In opposition to this, the case where, as in the past, only the common oxides that are contained are shown in FIG. 2. Common oxides 6 are 2 hot rolled crude (shown by arrows in FIG. 2) to become stretched oxides 7. Then, they are finally hot rolled 4 (shown by arrows in FIG. 1) to be stretched and crushed. However, since these are masses of oxides, the crushed oxides 8 also do not disperse as fine composite oxide particles as in the present invention. Therefore, it is not possible to obtain the crushed voids 5 that are sufficient as hydrogen capture sites.
[0060] FIG. 3 is a schematic view showing that crushed voids are not formed before hot rolling, that is, there are
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20/50 fine oxides in the plate stage. If the thin compound oxides 6 'at the plate stage as in FIG. 3, the fine oxides 6 'are hard to draw by crude lamination 2 (shown by arrows in FIG. 3). As a result, even with the final lamination 4 (shown by arrows in FIG. 3), the oxides are not crushed in this way, so that the voids 5 that form hydrogen capture sites are difficult to form.
[0061] It should be noted that, although not shown, cold rolling, in the same way as final hot rolling 4 (shown by arrows in FIGURES 1 to 3), has the effect of more finely crushing the oxides.
[0062] In order to capture hydrogen efficiently, it is desirable that the composite oxide particles disperse uniformly in the steel plate. In addition, the interfaces between the composite oxide particles and the matrix steel become hydrogen capture sites, so the composite oxide particles must have large specific surface areas (surface areas per unit weight). For this reason, compound oxides are desirably thin. In addition, also from the point of view of eliminating defects, compound oxides are desirably thin.
[0063] In addition, the voids that are formed around the composite oxide particles also become smaller if the composite oxide particles are small. Therefore, also from the point of view of reducing the volume of voids in the steel plate, the compound oxides are preferably thinner. In addition, the fact that lamination allows compound oxides to be stretched, crushed and thinned is convenient, as this is possible with current processes as they are presented.
[0064] The Fe-Mn-based compound oxides that are covered by the present invention are Fe-Mn-based compound oxides that
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21/50 comprise oxides of Fe, Mn, Si, Al, etc., joined together as compounds. Compound oxides are preferably thin in size, but if they are too thin in size the effect of hydrogen capture is reduced. Therefore, the diameter of the compound oxides is preferably 0.10 pm or more. This is because in oxides that are smaller than this range the great peculiarity in the characteristics of the steel sheet of the present invention, that is, the effect as hydrogen capture sites becomes extremely small. Preferably, it is 0.50 pm or more, more preferably 1.0 pm or more, and even more preferably 2.0 pm or more. [0065] The upper limit of the diameter does not have to be particularly limited if the effect of the present invention is considered. However, although it is dependent on the oxygen contained, if the common compound oxides become larger, the density of the number of compound oxides will decrease and the effect of hydrogen capture will be lessened. In addition, excessively coarse oxides, as is generally known, become the starting points for cracking the steel sheet when the product sheet is worked and thus impair workability. If these factors are considered, the average diameter of the compound oxides is preferably maintained at 15 pm or less, preferably at 10 pm or less, and more preferably at 5 pm or less.
[0066] The average diameter of the oxides and the voids near the oxides are preferably observed by an optical microscope or a scanning electron microscope after polishing a cross section of the steel plate. In addition, for detailed observation, the steel plate is preferably used in the preparation of a thin-film sample, and is then observed by a transmission-type electron microscope. The measurement of voids is described, for example, in the JIS standard (Japanese Industrial Standard) G0555
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22/50
Microscopic Testing Methods for Non-Metallic Inclusions of Steel.
[0067] Similarly, when crushed voids are formed, their sizes are not particularly limited. The size of an empty space is a long axis of 0.1 to 5 pm for an aspect ratio of 2 to 10. However, if the crushed voids are too large, defects in the voids arise and the characteristics of the steel materials are degraded. Typically, size is the size of the crushed compound oxides. Therefore, the average size of the crushed voids is 100% or less than the average size of the compound oxides (particles). From the point of view of defects, the voids must also be small. Preferably, they should be 80% or less. The lower limit of the average void size is not particularly stipulated. Even if the average size is 0, that is, there is no empty space, the hydrogen capture sites are formed by the interfaces of composite oxides and steel. The average gap size in the present invention is defined as the average value of the long axes and the short axes of five voids.
[0068] Hot lamination, in particular raw lamination, is at a high temperature, so that the compound oxides also soften and the difference in the hardness of the matrix iron is also small. That is, in the region of the rough rolling temperature, that is, the temperature region of about 1,000X3 or more, there is almost no fracture of the compound oxides due to the lamination and the compound oxides are stretched.
[0069] In addition, if it is lower than 1,000Ό, preferably 900Ό or less, the compound oxides are difficult to stretch. In the previous stage of the final hot lamination, the fracture of the extension where fine cracks are formed occurs in part of the compound oxides. In addition, in the final hot rolling or
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23/50 cold rolling, compound oxides are crushed from the fine cracks that have been formed. In order to obtain the compound oxides which are properly stretched and have fine cracks at the same time and are crushed in this way, temperature control at the time of hot rolling and control of the tension and the stress rate in different regions of the temperature become necessary.
[0070] If the region of the hot working temperature is too high, it is not possible to apply enough tension to form cracks in the compound oxides. In addition, if it is too low, the compound oxides are not stretched in the state, but are close to the spherical shapes, so the cracks are difficult to form. Proper stretching and thickness reduction are necessary for the formation of cracks. For this reason, it is necessary to control and provide the stretching of the compound oxides by appropriate deconformation at a higher temperature in the hot rolling and in the formation of cracks in the low temperature region. In addition, the shape of the compound oxides that form such cracks, as explained above, becomes more complex when there is a difference in concentration within the compound oxides and a difference in the shaping ability. The efficient shaping of effective voids becomes possible.
[0071] The heating temperature of the hot rolling mill and the winding temperature, etc., of the conditions of the hot rolling mill can be adjusted as usually in the usual operating region. In order to sufficiently obtain the stretching effect of the compound oxides in the hot rolling, the heating temperature of the hot rolling should be from 1,000 to 1,400 * C. Preferably, it should be 1,050Ό or more. Due to this, the lamination of the crude hot can be carried out at I.OOOO or more and, after that, the lamination at
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Final hot 24/50 can run at 1,000Ό or less. The final temperature of the final lamination should be 800Ό or less. Preferably, it should be 750Ό or less. Because of this, oxides and strained compounds are crushed more and more. Maintaining the winding temperature at 700Ό or less is economically advantageous.
[0072] In addition, to control the shape of the compound oxides, the plate is preferably cold rolled at a rolling rate of 70% or more and finally rolled at a rolling rate of 70% or more. The higher the lamination rate, the more effective in crushing and stretching the compound oxides, so that the sheet is more preferably rolled in bulk at a lamination rate of 75% or more. 80% or more is more preferable. In addition, it is even more preferable if the lamination rate in the final lamination is 80% or more. 90% or more is more preferable. That is, with this lamination rate, the compound oxides are stretched and crushed and become hydrogen capture sites that are effective in improving the resistance to delayed fracture.
[0073] Also in hot rolling, the composite oxide particles that become hydrogen capture sites are obtained, but an additional cold lamination allows the compound oxides to become thinner and the effect of the hydrogen capture to be thereby improved. For cold rolling to sufficiently crush compound oxides, the rolling rate for cold rolling should be 30% or more. This is because with a rate of 30% or more of cold rolling, the compound oxides are stretched and crushed to form hydrogen capture sites that are effective in improving resistance to delayed fracture and resistance to delayed fracture is further improved. . In addition, 40% or more is more preferable, and when it is 50% or more the improvement in resistance to delayed fracture becomes marked. In particular, when
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25/50 deep drawing becomes necessary, it is preferable that the lamination rate in cold rolling is 60% or more.
[0074] In the case of annealing, both the continuous annealing method and the box annealing method that is performed on a common cold-rolled steel sheet can be used.
[0075] When the steel sheet for use in hot stamping is used as a structural part for an automobile, it is mainly used treated on its surface. In particular, it is mainly used as a coated steel sheet. As a coated steel sheet, an aluminum-coated, zinc-aluminum and zinc-coated sheet is normally used. The steel sheet for use in hot stamping of the present invention can also be coated by common methods. For example, when applying the aluminum coating by hot dip, the surface of the steel sheet must be coated by 30 to 100 g / m ² or something on one side.
[0076] In addition, to produce a high-strength part by means of hot stamping in the present invention, the steel sheet is first heated in the austenite region, that is, up to the point of transformation of Ac ₃ or region higher austenite. In this case, it is sufficient that the austenite region is reached. If it is too high, particle thickening or oxidation will be marked, so this is not preferred. Then, the plate begins to be formed by the set of matrices. By restricting the part after having been worked on by the die set while it is cooling quickly and by causing the martensite to be hardened, it is possible to produce a high-strength part.
[0077] If the cooling rate becomes slow, the quench is no longer provided and the target resistance can no longer be obtained, so
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26/50 that the speed of rapid cooling in the austenite region remains the critical cooling rate that is affected by the ingredients or the structure of the steel or something else. The temperature of completion of the cooling is preferably the temperature of completion of the transformation of martensite or lower.
[0078] It should be noted that tempering does not need to be performed particularly, but can be performed according to the need to correct the resistance too large or improve the toughness.
Examples [0079] In the following, examples will be used to explain the present invention.
Example 1 [0080] The steels of the chemical ingredients that are shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3 have been melted to produce plates. It should be noted that Tables 2-1 to 2-3 show types of steel that have Type A, X and AC steels that are described in Table 1-1 and Table 1-2 as base steels and have different ingredient elements which are described in Tables 2-1 to 2-3 mixed with them.
[0081] These plates were heated up to 1,050 to 1,350Ό and hot rolled to a finishing temperature of 800 to 900Ό and a winding temperature of 450 to 680Ό to obtain hot-rolled steel sheets 4 mm thick. Then the sheets were stripped, and then cold rolled to obtain a thickness of 1.6 mm cold rolled steel sheet. Then, they were annealed continuously (annealing temperature from 720 to 830Ό). In addition, parts of cold rolled steel sheets were hot dip galvanized (base weight: one side, 30 to 90 g / m ² ), annealed galvanized (base weight: one side, 30 to 90
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27/50 g / m ² ), and coated with hot-dip aluminum (base weight: one side, 30 to 100 g / m ² ) in a continuous hot-dip line. Steel plate types are shown in Tables 1-1 to 3 and 2-1 to 3. Steel plate types are shown below:
[0082] HR: hot-rolled steel sheet, CR: cold-rolled steel sheet (annealed material), AL: steel sheet coated with hot-dip aluminum, Gl: hot-dip galvanized steel sheet, and GA: hot-dip galvanized steel sheet.
[0083] The average particle size (arithmetic mean) of the oxides composed of Fe-Mn in a produced steel plate and the presence of crushed voids were determined by polishing a cross section of the steel plate, and then it was observed by an optical microscope or a scanning electron microscope or a transmission type electron microscope after the sample has been prepared in a thin film. The results are shown together in Tables 1-1 to 3 and Tables 2-1 to 3. The criteria for the judgment are shown below:
Average particle size of compound oxides:
Good: average diameter from 0.1 to 15 pm,
Poor: average diameter of less than 0.1 pm or more than 15 pm.
[0084] An average diameter of the compound oxides, as explained above, from 0.1 to 15 pm was considered to be adequate.
Crushed voids around compound oxides: Good: average void size of 0.1 pm or more, Poor: average void size of less than 0.1 pm.
[0085] The average size of the voids crushed around the compound oxides, as explained above, is preferably 0.1 pm or more.
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28/50 [0086] Then, these cold-rolled steel sheets were heated by a heating furnace to above the point of Ac3, that is, the austenite region from 880 to 950Ό, and then they were worked on hot. For the atmosphere of the heating furnace, the combustion exhaust gas was used. The concentration of hydrogen in the atmosphere was 2%, while the dew point was 20Ό.
[0087] A cross section of the matrix array format is shown in FIG. 4. FIG. 4 shows the shapes of a die 9 and the punch 10. The shape of the punch when viewed from above is shown in FIG. 5. TO FIG. 5 shows the punch 10. The shape of the matrix when viewed from below is shown in FIG. 6. FIG. 6 shows the matrix 9. In the matrix set, the matrix shape is determined based on the punch with a 1.6 mm gap in the plate thickness. The blank size was 1.6 mm thick x 300 mm x 500 mm. The conformation conditions were taken as a punch speed of 10 mm / s, a compression force of 200 tons, and a containment time in the lower dead center of 5 seconds. A schematic view of the hot stamped part 11 is shown in FIG. 7.
[0088] The tempering characteristic of the hot stamped part was evaluated by polishing the cross section, by corroding it by Nital, then the microstructure was observed by an optical microscope and the rate of the martensite area was determined. The results of the judgment are shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3. The judgment criteria are shown below:
Good: rate of 90% or more of the martensite area, Regular: rate of 80% or more of the martensite area, and Poor: rate of less than 80% of the martensite area.
[0089] A martensite area rate of 80% or more was considered the preferable range.
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29/50 [0090] Resistance to delayed fracture was assessed by applying tension through drilling. The position of the drilling hole 13 in the center of the test piece 12 which is shown in FIG. 8 was drilled when using a 10 mm diameter of punch and when using a 10.5 mm diameter of the die. FIG. 8 shows the shape of the piece seen from above. FIG. 8 shows part 12 and the entire center of the punch 13. The drilling was carried out within 30 minutes after the hot forming. The number of pieces observed was 10. For the assessment of resistance to hydrogen embrittlement, the entire circumference of the hole was observed one week after drilling to judge the presence of any cracks. The state was observed by a magnifying glass or an electron microscope. The results of the trial are shown in Table 3. The criteria for the trial are shown below:
Total number of pieces with fine cracks in 10 pieces:
Very good: 0,
Good: 1,
Regular: less than 5,
Poor: 5 or more.
[0091] A number of pieces with fine cracks of less than five were judged to be adequate, but naturally the lower the number, the better.
[0092] As shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3, if within the scope of the present invention it is learned that it is possible to obtain a steel sheet that is sufficiently reinforced by tempering in hot stamping die and is excellent at delayed fracture resistance.
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30/50
Table 1-1% by weight
Class Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. > c.3 Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Comp. Crushed voids 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0Average oxide particle size 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0. Characteristic of delayed fracture VG VG VG 0 VG VG VG 0 0> VG VG 0 VG VG VG 0 VG VG VG 0 CL Area feemartensite 0 0 X 0 0 0 X 0 0 0 X 0 0 0 cl 0 0 0 CL 0 0 COO 0.015 0.0162 0.0245 0.0104 0.015 0.0162 0.0245 st othe o inthe o 0.0162 0.0245 0.0104 0.015 0.0162 0.0245 Othe o 0.015 0.0162 0.0245 0.0104 0.0025 Cr + Mo CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN CN Mo 0.2 0.2 0.2 0.2 0.2 0.2 CNO CN o CN o CNO 0.2 0.2 0.2 CN o CN o CN o CN o CNO CNO 0.2 CN o Oz 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 CO o oO 0.003 0.003 0.003 0.003 0.003 eoo‘o 0.003 0.003 0.003 0.003 0.003 0.0030.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 sT O O o 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 < 0.003 0.003 0.003 0.003 0.003 eoo‘o 0.003 0.003 CO o o o ’ 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 CO 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 CN O O o ’ 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 CL 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 the o 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mn CN LO CN LD CN in CN LD 1 ^CN IO 0.8 CO 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 m o o θ ' 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 O 0.22 0.05 0.03 0.40 0.22 0.05 0.03 0.40 CN CN θ ' 0.05 0.03 0.40 0.22 0.05 0.03 0.40 0.22 0.05 0.03 0.40 0.55 Type of steel sheet HR HR HR HR CR CR CR CR _ |< AL AL AL 0 0 0 0 GA GA GA GA GA Q. °.- Φ t> 1— Ό CO < m 0 Q < 00 0 Q <0 Q < CD O Q < CD 0 Q LU Exp. No. 7 2-1 3-1 4-1CN COLD CO00 03 O V CN CO sT LO CO 1 ^
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31/50 ο 1 (0
Ο (0 Ζ3 C

Φ JD (0
Class Ex. Comp. Ex. Inv. Ex. Comp. Ex. Comp. Q. And the O.3 Ex. Comp. > c Ex. Comp. Ex. Inv. Ex. Comp. Crushed voids00 10 0 0Average oxide particle size 0. 00 CL 0. 0 0 0 CL Characteristic of delayed fracture CL VG O. CL 0. CL 0 LL · VG CL Martensite area rate 0 0 0. 0 0 0 0 0 0 0 m O 0.0023 0.0149 0.0153 0.0151 COo o o 0.0013 ΙΌO o 0.015 0.0161 0.0022 Cr + Mo CM O 0.01 0.01 CM_ CM CM CM ~ CM ~ CM Mo CMO C l o CM θ ' CM θ ' CM θ ' 0.2 0.2 O1 0.01 0.01 z 0.003 0.003 0.003 εοο'ο CO o o θ ' 0.003 CO o o θ ' 0.003 0.003 0.003 i— 0.004 0.004 0.004 0.004 sh o o o 0.004 ’Μ o o o 0.004 0.004 0.004 < 0.003 0.003 eoo‘o 0.003 CO o o o 0.003 CO o o o ’ 0.003 0.001 0.04 CO 0.002 0.002 0.002 0.002 LO o o 0.024 CM o o o ’ 0.002 0.002 0.002 CL 0.01 0.01 0.01 0.01 o o “ 0.01 LD CM O o 0.035 0.01 0.01 Mn OM 3.0 0.05 3.6 CM CM CM CM CM CM in 0.05 0.005 0.005 0.005 in o o o “ 0.005 IO O O θ ' 0.005 0.005 0.005 O 0.22 0.22 0.22 0.22 CM CM θ ' 0.22 CM CMO 0.22 0.22 0.22 Type of steel sheet CR CR CR CR DC o CR Say the CR CR CR ° o.- ω o l— o ro LL 0 T"3 z O Exp. No. 00 05 20 CM CM CM 23 slCM 25 26 27
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32/50
Table 1-2
Class Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Crushed voids 00 0 0 0 0 0 0 0 0 0 0 0 Average oxide particle size 0 0. 0 0 0 0 0 0 0 0 0 0 0 0 Characteristic of delayed fracture VG CL VG VG VG VG 0. CL VG VG VG VG VG VG Area feemartensite 0 0 LL LL · LL · LL · 0 0 0 0 0 0. 0 0 m 0.0048 0.0052 00 ^ r o o o 0.0048 0.0045 0.0054 O 0.03 0.0013 0.0149 0.0153 00O o 0.0145 0.0154 0.015 0.0163 0.0183 0.0193 0.0233 0.0134 0.0121 Cr + Mo CM CN 0.005 0.08 O 00 o CO 2.5 0.2 0.2 0.2 CM o 0.2 CM o Mo 0.2 0.2 0.005 80’0 O O CO O L— O O" 8’0 O 2.5 0.2 0.2 0.2 0.2 0.2 CM o z 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.0030.001 0.04 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 < 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 <Z) 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 CL 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mn CN OJ CM 00CO 0.2 CM CO IO00- 04 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 O 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.15 0.10 0.03 0.25 0.30 | t · 8.1— u ο ό ra CR CR CR CR CR CR CR CR CR CR CR CR CR CR . | ra &1— ro 0. σ The. ω I- D > § X > N AA AB B.C > <o 'LLI Z 00 CM 03 CM CO σϊ CM CO POO s | co LO CO POO r ^ · CO 00 CO 0 CO The Μ ^-
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33/50
Table 1-2 (continued)
Class Ex. Comp. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Crushed voids0 0 0 0 00 0 0 0 00 0 Average oxide particle size CL 0 0 0 0 0 0. 0 0 0 0 0 CL 0 0 Characteristic of delayed fracture CL VG VG VG VG VG □. VG VG VG VG VG O. VG VG Area feemartensite 0 0 0 0. 0 0 0 0 0 O. 0 0 0 0 0 m 0.0043 0.0052 00 Mo o o 0.0048 0.0045 0.0054 0.0043 0.0052 0.0048 0.0048 0.0045 0.0054 0.0043 0.0052 CO o o o ’ O 0.0025 0.0183 0.0193 0.0233 0.0134 0.0121 0.0025 0.0183 0.0193 0.0233 0.0134 0.0121 0.0025 0.0183 0.0193 Cr + Mo CM o 0.2 CM o 0.2 CM o CM o CMO 0.2 0.2 0.2 0.2 CM o 0.2 CM o CM o O2 L— O 0.2 CM cf 0.2 0.2 CM o ” CM cT 0.2 0.2 0.2 0.2 0.2 0.2 0.2 CM o CM o “ z 0.003 εοοΌ 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.0030.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 < 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 <Z) 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 CL 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ç 0.4 inω CM0.4 IO° o CM0.4 10<z> 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 O 0.55 0.15 0.10 0.03 0.25 0.30 0.55 0.15 0.10 0.03 0.25 0.30 0.55 0.15 0.10 1 t · 8.1— u ο ό ra CR _l< _l< _l< _l< _l< _l< 0 0 0 0 0 0 GA GA 1 · 8.1— ro αν > N AA AB B.C αν > - NAB B.C AD > - N > <o 'LLI Z CM M ^- WITH- MM- 10 m- CO r ^ · si ^- 00 Μ ^- Hi Μ ^- O10CM10 CO10 Μ ^- 1010 CO10
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34/50
Table 1-3
Class Ex. Comp. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Comp. Ex. Inv. Ex. Comp. Ex. Inv. Crushed voids 0 0 00 0 0 0 0 0 0 Average particle size ofoxide 0 0 0 CL 0 0 0 0 0.0 0 0 Characteristic of delayed fracture VG VG VG 0. VG 0 LL · LL · CL CL LL · CL VG Martensite area rate0 0 0 0 0 0 0 0 CL 0 0 0 m 0.0048 0.0045 0.0054 0.0043 0.0044 0.0048 O)O o o 0.0049 0.0049 0.0053 0.0053 0.0048 0.0053 O 0.0233 0.0134 0.0121 0.0025 0.0173 0.0103 CO o o o εοοΌ 0.0013 0.0144 0.0144 0.0155 0.0157 Cr + Mo CN o CN o CN o 0.2 0.2 0.2 CN o 0.2 0.2 0.2 0.2 0.2 0.2 MoCr 0.2 0.2 CN o CNCD CN o 0.2 CN θ ' 0.2 CNO 0.2 CN o 0.2 CN θ ' z 0.003 0.003 0.003 0.003 0.003 0.003 CO O OO 0.003 0.003 0.003 0.003 0.003 0.0030.004 0.004 0.004 0.004 0.004 0.004 o o o 0.004 0.004 0.004 0.004 0.004 0.004 < 0.003 0.003 εοοΌ 0.003 0.003 0.003 CO o o o ’ CO o o * 0.003 0.003 0.003 0.003 0.0030.002 0.002 0.002 0.002 0.002 0.002 CN O o o ‘ 0.002 0.002 0.002 0.002 0.002 0.002 CL 0.01 0.01 0.01 0.01 0.01 0.01 o o ‘ 0.01 0.01 0.01 0.01 0.01 0.01 Mn 00 CN0.4 CO CO co_ co_ CO 0.03 O' 3.3 CO ώ 0.005 0.005 0.005 0.005 0.001 0.007 the θ ' 0.02 0.023 0.005 0.005 0.005 0.005 O 0.03 0.25 0.30 0.55 0.22 0.22 CN CNO 0.22 0.22 0.22 0.22 0.22 0.22 S ra o.y- Φ JZ (ü (D O1— Ό THE CL Ό ra GA GA GA GA CR CR DC o CR CR CR CR CR CR 1 Φ 8.I— the ra AA AB B.C αν UJ < LL<AG2 AH < AI2 rv AK > <O LU C 57 58 59 60 s 62 POO 63-1 64 65 65-1 66 67
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35/50
Table 1-3 (continued)
Ex. Inv. Ex. Comp. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. 0 0 0 0 0 0 00 0 00 0 0 0 0 0 0 0 0 0 0 O 0 0 0 0 0 0 CL 0 0 0 0. 0 0 0 0 0 0 0 0 0 0 0 000 0 00 0 00 0 0 0 0 0 0 0LL LL · > CL > > 0. > > > > 0. LL · > > > > LL · 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 LO00 00 CO Μ ^- CO r ^. LO LOLO 00 O) CO LO00 LOsj- COLO LO sj- sj- LO LO LO m · Μ ^- LO LO LO Μ ^- LO LO LO Μ ^- OCM B* CO O O O O O O O O O O O O O O O O O O O O O OO O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O CO CO CO COCO CM 00 CO CO K- 00 LO COCO CO CO LO LO COCOLO CO CO sj- 00 O t—CO O OLO CO Μ ^- LO LO LO LOCO sj- CM O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 00 CM CM CXI CM CM CM CM CM CM CM CM CM CM CM O t— CMCMCM CM τ— CM CM O O O O O O O O O O O O O O T- T- CM CM T- T- T- O O O r—CO CM CO CM O OO CM O O O O 00 CO CM CM CM CM CM CM CM CM CM CM CM CM CM CM O O CMO00 00 CD CM CM O O O O O O O O O O O O O O T- O O T- O O O O O CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO O r> co O O CO O O CO co co co CO CO CO CO CO CO CO CO CO CO CO O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O in si ^- ^ i- O T—CO O co O O O O O O O OCM CO CO CO CO CO CO CO CO CO CO CO O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O CM CMCO CO CO CO OLO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO O O O O O O O r ^. O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O CO CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CMCO O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O LO LOCM CO O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O CO CO CO CO CO CO CO CO CO CO CO CO CO CO LO CO LO LO CO CO CO CO CO T- T- T- T- T- T- T- T- T- T- T- T- T- T- O O O O T- T- T- T- T- LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO LO m O O O O O O O O O O O O CO CO CO CO CO CO CO CO CO CO CO O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM O O O O O O O O O O O O O O O O O O O O O O O OC Dí Dí Dí 0i 0Í 0i 0Í (Z tt Dí Dí Dí 0i 0iyouocQi Dí 0Í O O O O O O O O O O O O O O O O O O O O O O O _ |z O 0. σ tx1- Ξ) > § X > N < CO 0 Q LU LL · 0 I < < < < < < < < < < < < <c < < m QC 00 QC QC QC QC QC 00 CD OCM CO Μ ^- LO CO r ^ · 00 σ> OCM CO Μ ^- LO CO r ^ · 00 CD O CO CO r ^. r ^ · r ^ · r ^ · r ^ · r ^ · r ^. r ^ · r ^ · r ^ · 00 00 00 00 00 00 00 00 00 00 CD
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Table 2-1 (% by mass)
F tfí tfí(0 O > cώ > c.2 >C ώ > cώ >C ώ Q. What about O ώ Q_ And O ώ > C.3 > c.3 > C.3 > c.3 > c.3 > c.3 > cώ > c.3 > cώ > cώ > c.5 > ci5 Q. And the O.3 > cώ > C.3 > C.3 > c.3 > C.3 J. ® o® tn tn S ra> the E o »0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 manho> oxide dio dio, (D (D Φ1- And Ο.Ό O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Φ COώ -σ75 ra E -σffl O T * -= s 4- ra ra m ra 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 The ‘i = 4 = Ϊ > > > > > LL LL > > > > > > > > > > > > LL > > > > > ro (D _TD TD ™ωçS ro t!ra E «l— 'W E 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O O OCO s | - O O Μ ^- O O CO O O O ± 3 O O in O in CM inO O 00 00 O z o O O OO CM CMO CM 00 O O O O O O CO O CO CO CO O O O O O O + + O CO 00 uo O O CO CM CO uo00 00 O X3 o O O O O uo 00 O O CM CO O CMCO CO COm z o O O O O O O O O O O O OO O O O O C |CO CO CO 3 O O O 00 IOO O LO LOO O O O O O O O O OCMO O LOm OCO CO CO z O O OO O CO COCO CO CM CO5O' O O' O* CM O O O O O O O LOO LO 00 CM CO LO CO CO CO CO CO > O O O O O O O O O O O 00O CO 00CO LC M- 00 00_Q O O OO O O O O O O O Oz O O OO O O O O O O O O O ® 8. o S ^- Qi Qi Qi Qi Qi Qi 0Í Hi Hi Hi Hi Hi 0Í Hi Qi 0i Qi Hi 0Í Hi Hi Hi Hi Hi Qi Η Ό ü Ό O O O O O O O O O O O O 0 O O O O O O O O O O O 0 ο Φο. ο ωcd o ra Η ό ra ό < < < < < < < < < < < < < < < < < < < < < < < < < A <D 3"J x _1z O 0. Cí Hi 0Ξ) > £ X > N < ASS O Q LU LL · 0 1— T3 ra ASS ASS CO CO CO CO CO ASS ASS ASS CO ASS ASS ASS ASS ASS CO CO O 0 0 0 0 0 0 OçCOCM CO sl- LO CO00 03 OCM CO M ^- LO CM CO Μ ^- LD CO N. 00 CD O O O O O O O O O O LU CD CD CD CD CD CD CD CD CD
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Table 2-1 (continued)
Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 VG VG VG VG VG VG CL 0 0 0 0 0 0 0 O o ° 0 0.03 0.04 0.50 1.00 0.54 2.20 o the CD LO o 0.01 0.032 0.04 00 o CO 0.02 0.01 IO θ 'LO θ ' st 0.05 O CO θ ' 0.55 CR CR CR CR CR CR CR < X X X X X X I o O "3O X o _ | O CM z o CO00 03 120 CM 122
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Table 2-2 (mass%)
Φ tfí tfí (0 O Q. What about O ώ > c.2 > cώ > cώ > cώ > cώ > cώ > c.3 > c.3 > c.3 > c.3 > c.3 > c.3 Q. What about O ώ > c.3 > cώ > cώ > ci5 > C.5 > C.3 >C ώ > c.3 > c.3 > Ci3 J. ® o® tn tn S ra> the E o » 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 manho> titanium oxide dio , (D (D Φ1- E Q.-O O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Φ CO ώ -σS ra S tj ffl O T * - = s 4- ra ra m ra0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 0 0 0 0 0 Q = 4 = E LL > > > > > > > > > > > > LL > > > > > > > > > > «Φ - TD TD ™ CO ç S ro t! ra E «l— 'W E 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0O O O n O OOΜ ^- CO O O O Oco O O . + 3 inO O 00 00 O 00 O O 00 00 z o CM ^_ O' cm ' * - Oin CMCO O O O O O 00 O O O O O O O O O O O O O + +O CO 00 LG 00 03 CO CM CO 00 03 10 10 lg lg LG O IO LG in LG 42 OO O O O sj-O O CM CO O CMCO CO CO si- LG O co 00 coz oO O O O O O O O O O O OO O O O OO O O O CO CO co 00 3 LGO O lg lgLG O O LG LG O OO O O O O O O O O O OCO CO co CO OCO CO z OO CO CO LG oo O CM 00r> 5 O O O" OO*CXI O O O O O O O O OCO LG 00 03 O M ^- r ^ · CXI CO LG CO CO CO co 00 CO co co 00 00 > O O O O O O O O O O O O O O O O LG CM 00 O CO 00CO 00 03 LG LG LG LG LG LG LG LO in LG _QO O OO O O O O O O O OLG O O O O zO O OO O O O O O O O O O O O O O O ® 8. o S ^- 0Í tt 0Í 0Í oc 0Í Qi A.D A.D DT cr cr cr cr cr cr cr cr cr cr _l _l _l _l 1- Ό ü 73 O O O O O O 0 Q O O O O O O O O O O O O < < < < ο Φo_ o toΦ O (0 Η ό ra ό X X X X X X X X X X X X X X X X X X X X X X X X_Action O CL σ A.D « 1- Ξ) > § X > N < m O Q LU LL · 0 I O Q LU LL · 1— u ra O O O O O O 0 O O O O O Q Q Q Q Q Q Q Q Q Q Q Q O ç COlg CO00 03 COCM COLG CO00 05 OCM CO mr LG COCM CM CM CM CM CM CXI CO CO CO CO CO CO CO CO CO CO Mst s | - sT sf M- LLI
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Table 2-2
> > > > > > > > > ç ç ç ç ç Ç ç ç ç Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > > > > > > > > 0 0 0 0 0 0 0 0 0 O O O O O OO OCO O O O O M ^- O CO O O 00 00 O 00 O CXIO OJO O O O O O O O O O m O in in in in ΙΌ O in LO O CO CO COin O 00 OO O O O O - = - O CO CO 00LO O O LO LO O O O O O O O O O OCO CO OCO CO CO CO O OO OLT>in OO OO O O O O OCO CO CO CO CO CO CO CO 00 O O O O O O O O O LO LD LD in LO LO LC LO LOLD O O O OLO O O O O O O O O O O -1 1 < < < 0 0 0 0 0 0 0 X X X X X X X X X 0 I O Q LU LL 0 I O Q Q Q Q Q Q Q Q Q00 Hi OC l COit s | - s | - sT LO LO LO ΙΌ IO it
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Table 2-3 (% by mass)
F tfí tfí(0 O > cώ > c.2 > cώ > cώ >C ώ > cώ > cώ > c.3 > c.3 > c.3 Q. And the O.3 Q. And the O.3 > c.3 > cώ > c.3 > cώ > cώ > cώ > cώ > cώ > c ώ J. ® o® tn tn S ra> the E o » 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Average oxide particle size O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Characteristic of delayed fracture 0> 0> 0> 0> 0> 0> 0> 0> 0> 0> LL LL 0> 0> 0> 0> 0> 0> 0> 0> 0> Martensite area rate 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ± 3 z O CO o O o ° o O o ° 0 O o oCM O o ω CO o o sjO o LO o The CD LO o o CXI cxí the LO CXjNb + V +Co + W O10 CO o the mCO o the mO IO in o o the CD LO o o o CXJ CO o o dog o CO LOO o The 00 slθ ' The 03O CO o o CXI o o CO CXI θ ' 3O CO o o LO o LO o O it the the o CXI CO o o the o 00 o LOzCO co ~ co ~ co CXI o θ ' the o LO θ 'LO θ ' st 5 LO o oCO o o OO O O O CXI o o> CO o ’ CO o ’ CO o CO o CO o CO LO O o 00 o * 03 1 ^. O CXI o _Q z io o o ’ lo o o ’ lo o o ’ LO o ’ LO LO o ’ LO O o o ‘ CM COO o ‘ c o ‘CO o θ ' £ ra tra &1— Τ3 Ο ra <0 <0 <0 <0 <0 X o X O X o X o X o X o x o there the X o X 0 IX 0 x0 X 0 X 0 X 0 X 0 ο ^ω S ο ω ra o ra Η ό ra ό X X X X X <: <: <: <: <: <: <: <:<: <: <: <: <: Steel type Q Q LU Q LL Q 0 Q I Q Q "3 Q X Q _1 Q Q z Q The Q X Q σ Q IX Q tn Q Q Ξ) Q Q 1 X Q > <o LU c CO lo it CO LO 03 LO CO CO CXI CO POO sr CO LO CO POO CO 00 CO 03 CO o r ^ · 1 ^ · CXI r ^ · CO r ^ · sr r ^ - LO r ^. CO r ^.
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Table 2-3
> > > Q_ And the > > > > > > _ç _ç _ç O _ç _ç _ç _ç _ç _ç Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 0 > > > Ll_ > > > > > > 0 0 0 0 0 0 0 0 0 0 O O O O sl ^- CO O O O O O O 00 00 O 00 O CXICO O O O O O O O O O 00 0) in in ΙΌ in in O CO O CXICO CO CO sl ^- in O O O OO O O O OCO CO O O LO mm O O O O O O OCO CO CO CO O CO LOO CXI 00OO O OOO O O O CO LC CO CO CO CO CO CO O O O O O O O O 00 00 0> in in in LO LO LO O O O O O O O OLO O O O O O O O O O O OC oc there there OC A.D A.D OC 0C OC O O O O O O O O O O O O O O O O O O O O < < < < < < < < < < > - N < CO O Q LL · 0 IQ Q uJ UJ UI UI UI UI UI UI00 Hi nCXI COit CO r ^ · r ^. r ^. 00 00 00 00 00 00 00
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Example 2 [0093] Steel types A, X and AC that are shown in Tables
1-1 and 1-2 were used to study rolling conditions. These plates were heated to 1,050 to 1,350X3 and then hot rolled by a finishing temperature of 800 to 900X3 and by a winding temperature of 450 to 680X3 to obtain hot-rolled steel sheets. Plates, crude laminated sheets, the thickness and crude lamination rate of hot-rolled sheets and the final lamination rate are shown in Tables 3-1 and 3-2. Then, a portion of the hot-rolled steel sheets was stripped, and then cold-rolled. The thickness of the cold rolled sheet and the cold rolling rate are shown in Tables 3-1 and 3-
2. Then, part of the steel sheets were annealed continuously (annealing temperature from 720 to 830X3). In addition, parts of the steel sheets were hot dip galvanized (base weight: one side, 30 to 90 g / m ² ), hot dip galvanized (base weight: one side, 30 to 90 g / m ² ), and coated with hot-dip aluminum (base weight: one side, 30 to 100 g / m ² ) in a continuous hot-dip line. The types of the steel sheet are shown in tables 3. The types of the steel sheets are shown below:
[0094] HR: hot-rolled steel sheet, CR: cold-rolled steel sheet (annealed material), AL: steel sheet coated with hot-dip aluminum, Gl: hot-dip galvanized steel sheet, and GA: hot-dip galvanized steel sheet.
[0095] The average particle size of the Fe-Mn compound oxides in a produced steel plate and the presence of crushed voids were determined by polishing a cross section of the steel plate, and then it was observed by an optical microscope or a mi
Petition 870180028007, of 04/06/2018, p. 47/64
43/50 scanning type electroscope or a transmission type electron microscope after the sample has been prepared as a thin film. The results are shown in Tables 3-1 to 3-2. The judgment criteria are shown below:
Average particle size of compound oxides:
Good: average diameter from 0.1 to 15 pm,
Poor: average diameter less than 0.1 pm or greater than 15 pm.
Crushed voids around compound oxides: Good: average void size 0.1 pm or more, Poor: average void size less than 0.1 pm.
[0096] Then, these cold-rolled steel sheets were heated by a heating oven to more than the point of Ac3, that is, the austenite region from 880 to 950X3, and thereafter they were worked on hot. For the atmosphere of the heating furnace, the flue exhaust gas was used. The hydrogen concentration in the atmosphere was 2%, while the dew point was 20Ό.
[0097] The cross section of the matrix set format that is used in the examples is shown in FIG. 4. FIG. 4 shows the shapes of the die 9 and the punch 10. The shape of the punch as seen from above is shown in FIG. 5. FIG. 5 shows the punch 10. The shape of the die as seen from below is shown in FIG. 6. FIG. 6 shows the matrix 9. In the matrix set, the matrix shape is determined based on the punch with a 1.6 mm gap in the plate thickness. The blank size was 1.6 mm thick x 300 mm x 500 mm. The conformation conditions were taken as a punch speed of 10 mm / s, a compression force of 200 tons, and a retention time in the lower dead center of 5 seconds. A schematic view of the hot pressed part is shown in FIG. 7.
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44/50 [0098] The tempering characteristic of the steel plate was evaluated by polishing the cross section, by corroding it by Nital, and then the microstructure was observed by an optical microscope and the rate of the martensite area was determined. The results of the judgment are shown in Tables 3-1 and 3-2. The judgment criteria are shown below:
Good: martensite area rate of 90% or more,
Regular: martensite area rate of 80% or more, and Poor: less martensite area rate less than 80%.
[0099] Resistance to delayed fracture was assessed by applying tension by means of drilling. The position of the drilling hole 13 in the center of the test piece 12 which is shown in FIG. 8 was perforated when using a 10 mm diameter punch and when using a die with a diameter that provides a 15% ± 2 spacing. FIG. 8 shows the shape of the piece seen from above. FIG. 8 shows part 12 and the center of drilling hole 13. Drilling was performed within 30 minutes after hot forming. The number of pieces observed was 10. For the assessment of resistance to hydrogen embrittlement, the entire circumference of the hole was observed one week after drilling to judge the presence of any cracks. The state was observed by a magnifying glass or an electron microscope. The results of the judgment are shown in Tables 3-1 and 3-2. The judgment criteria are shown below:
Total number of parts with fine cracks in 10 parts:
Very good: 0,
Good: 1,
Regular: less than 5, and
Poor: 5 or more.
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45/50 [00100] As shown in Tables 3-1 and 3-2, it is learned that if it falls within the scope of the production method that is recommended by the present invention, the steel sheet can be obtained, which is sufficiently reinforced by die stamping by hot stamping and which is more excellent in delayed fracture resistance.
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Table 3-1
Class Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. s& | (B O S. h r 0. 0 0 0 0. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 £ D (Π o c _Λ 3 · σ to .2 ο χΕ E t * °η 2 íc φΗ E CL Ό 0. 0 0 0 0. 0 0 0 0 0 0 0. 0 0 0 0 0 0 0 (D - ¹³ Ό ra o; (Π = Έ000 0 0 0 0 0 0 <0 1— li 2 0. LL 0. LL · LL · LL · LL · 0. LL · > (0 Φ _ T5 O Jg tfí AND Mars area fee O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ® os £ (0 Cold lamination rate O 00 O O O O O O O co cxí cxí cxí cxí cxí O CXI 00 LO LO LO LO LO co from ão) O sP ffl O * · Final laminated rate ( io O CO 00 LO LO LO LO LO LO LO 00 00 00 00 00 00 00 LOO 00 co CXI CXI CXI CXI CXI CXI CXI co LO 00 00 00 00 00 CXI CO 00 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 φ _Λ oCO co 00 00 ξξ E - «Ε E 1— ^m <D -co CO co 00 CXI CN 00Γ3 poo 3.3 3.3 Poo Γ3 Xt Xt Xt 03 03 00 00 CO 1 ^ 1 ^ 00 00 00 00 oo 00 00 00 00 00 cold rolling thicknessmm) CXI CXI CXI CXI CXI CXI CXI CXI LU T5 O * T— T— τ— T— lamination thickness auentenm) LOLO LO LO_ 03 LO LO LO LO LOLU Ό THE CT Ό co CO co co CO co co 00 co co co r— T— cxí cxí cxí cxí cxí co essura lamina o (mm) CL Ο Έw <o ira> z O O O O O O O O O O O O O O O O O O O ui o n o CXJ CXI COS | - s | - s | · S | - s | - φ <0 -OO. E 2 Em 3 σ ° F O O O O O O O O O O O O O O O O O O O io io LO LO O LO LO LO LO O LO LO LO LO LO LO LO LO LO LU tn ό ο. Ά- CN CXI CXI OJ τ—CN CN CXI CN OJ CXJ CXI CXI CXI CN φ Φ Ό Ό (Ü o ° Q_ (Ü O. ç- CVi _l< _l<1— O (0 z z z z z z < 0 0 z z z z z < < 0 0 z (B _and Ε o Hi Hi oc 0Í Hi Hi Hi Hi Hi Hi Hi Hi Hi A.D A.DHi Hi Hi —1 S- T T T T T T. T T T T T. O O O O O O 0 O Â _φ & l— u ra < < < < < < < < < < < < < < < < < < < T- r ^ · r- 00 03 OCXI 00LO co r ^ · 00 03 OCXI 00 M ^- ,> <O CO 00 00 00 03 03 03 03 03 03 03 03 03 03 O O O α O LU E CXI CXI CXI CXI CXI
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Table 3-1 (continued)
Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Ex. Inv. Ex. Inv. > C.3 Ex. Inv. > C.3 O 0 0. 0 0 0 CL 0 0 0 0 0 0 0 0. 0 0 0 CL 0 0 0 0 0 0 0 > > □. 0 LL 0 D. LL · 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O O O CO 1 ^ 1 ^ O it 10 O CO 00 LO LO LO LO LO LO co1 ^ O CO CO CM CM CM CM CXI CXI o> CO CO 1 ^oo 03 03 03 03 03 03 00 00 00 st st CXI CM 00 st O 00 Γ3 st St St CO CO 03 03 00 00 CO00 00 00 00 CXI CXI T— T— LOLO LO LO CO CO CO CO 00 00 00 CO CO 00 O O O O O O O O O O O O st st CXI CM CO s | - s | - s | -st stO O O O O O O O O O O O LO LO LO IO LO LO O LO O LO LO LO CXI CXI CXI CXI CXI CM CM CXI CM CM _lz z z z z z z z z z < 0 A.D A.D A.D A.D The. A.D A.D A.D The. A.D A.D (£. O O I I T I I I T I I T < < X X X X X X X X X X T- LO CO r ^.00 03 OCM CO st LO O O O O O O CXI CM CM CM CM CM CM CXI CM CM CM CM
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Table 3-2
Φ tfí tfí (0 U > c.3 Q. And the O.3 > cώ > cώ >C ώ > cώ > cώ > cώ > cώ > cώ > cώ Q. What about O ώ > cώ > c.3 Q. What about O ώ > c.3 > C.3 > cThe > ci5 > ci5 > c.3 Q. And the O.3 Crushed empty space 0 0 0 0 0 0 0 0 0 0 0 CL 0 0 tx 0 0 0 0 0 0 0 Average oxide particle size O CL 0 0 0 0 0 0 0 0 0 CL 0 0 0. 0 0 0 0 0 0 CL Delayed fracture rate 0 Q. LL 0 0> 0> 0 0 0 0 0> CL LL · 0 0. LL · 0 0 0 0 0 CL Area feemartensite 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Cold rolling rate (%)O oCXJ 00 CO CO The CXj 10 O o CO O o O o r *. O o r *. O o O o 1 ^ The co 1 ^ The o CXl Final lamination rate(%) 10 box 03 Poo CO 10 03 oo_ co ’03 m oj 03 o o 03 o o 03 o o 03 o o 03 o o 03 LON. 00 LON. CO poo1 ^ 00 co 00 LO cxí 03 LO CXl 03 LO cxj 03 LO cxj 03 LO cxj 03 LO cxj 03 LO CXÍ 03 co co 03 Crude rolling rate (%) CO CO 00 00 00 00 00 00 oo oo 00 CXl03 0000 00 CO Coco Coco1 ^ O00 O00 O00 O00 Si OO oo Cold rolling thickness(mm)CXl CXl 04 OJ OJ Hi CXl CXl CXl CXl CX ( Hot rolling thickness (mm) CO LOJ oj CO sl- LO LO co ’ LO co ’ LO co ’ CO CO co co CO co CO LO_ Lamination thickness ingross (mm) O O O O o s | - O S | - O O O O O The CXl the co O O o s | - o s | - o s | - O O O O Plate thickness (mm) o i © CXl O10 CXl O10 CM O10 OJ O10 OJ O10OJ the L0 CXl O10 CXl o in CXl the LO CXl the LOCXl O10 CXl o l © CXl o l © CXl the o the LO o o CXl o o CXl O The CXl o o CXl O10 CXl O10 CXl Type of steel sheet <0 z z z z z < _l< 0 <0 z z z z z z z _l< 0 <0 z z Lamination tX o tX o tX o IX o tx o tx o IX o tx o tx o tx o tx o tx T tx T tx T tx T tx T tx T tx T tx T tx T tx T tx o Steel type X X X X X X X X X X X <: <: <: < <: <: <: <: <: dç> <LU COCM 1 ^CM 00CM 03CM the OJ OJ CM OJ CXl CXl CXl CO OJ OJ s | CXl CXl i © CXlCXl co CXl CXl r ^ · CXl CXl 00 CXlCXl 03 CXl CXl the CM co CM CXJ with CXJ CO co CXl Μ ^- CO CXl LO CO CXl CO co CXl r ^. coCXl
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49/50
Table 3-2 (continued)
Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 LL LL · LL · LL · LL · 0 VG VG VG 0 0 0 0 0 0 0 0 0 CO 00 00 00 00 O O O OCO CO CO CO CO CXI O O CO CO 00 CO 00 00 LO CO CO 00 CO 00 00 00 LO O LOLO LO LO LO LO 00 CM Oo> 03 03 03 03 03 03 03 0000 00 00 00 00 00 00 00 00 CXI CXI CXI CM CM CM CXI CXI CM t— t— t— t— t— T— t— T- T- O O)_ O3 ~ 2.5 CO si- LO O O O O O O O O O s | - s | - O O O O O O O O O LO LO LO LO LO LO LO 10 in CXI CXI CXI CXI CXI CM CXI CXI CXI z < AL 0 GA z z z z tx tx tx tX IX IX tx tx tx O O O O O O O O O O O O 0 0 O O O O < < < < < < < < < 00 03 OCM 00LO CO CO CO s | - sTM ^- Tj-Μ ^- CXI CM CM CM CM CM CM CXI CM
Petition 870180028007, of 04/06/2018, p. 54/64
50/50
Industrial Applicability [00101] The present invention can be used as a steel material for use in hot stamping. With regard to its field of use, this can be used in a wide range of industrial fields such as auto parts, household appliances, machinery, etc.
List of Common Compound Oxides Reference Signs
1-1, 1-2 hot rolling oxides crude drawn compound oxides
3-1, 3-2 drawn oxides hot rolling end crushed empty space (hydrogen capture capacity)
5-1 and 5-2 crushed oxides common oxides
6 'fine oxides drawn oxides crushed oxides die puncture die hot stamped test piece perforated hole position

权利要求:
Claims (6)
[1]
1. Steel plate for use in hot stamping, characterized by the fact that it consists of the following chemical ingredients, in% by mass,
C: 0.05 to 0.40%,
Si: 0.001 to 0.02%,
Mn: 0.1 to 3%,
Al: 0.0002 to 0.005%,
Ti: 0.0005 to 0.01%,
O: 0.003 to 0.03%,
N: 0.01% or less,
S: 0.02% or less,
P: 0.03% or less, one or more of Cr and Mo in a total of 0.005 to 2%, and optionally one or more groups between the three groups (a) to (c):
(a) B: 0.0005 to 0.01%;
(b) one or more of Nb, V, W and Co in a total of 0.005 to 1%; and (c) one or more Ni and Cu in a total of 0.005 to 2%; and a remainder of Fe and unavoidable impurities, in which the steel plate contains Fe-Mn-based composite oxide particles with an average diameter of 0.1 to 15 pm dispersed in the steel plate, and where there are voids around of said composite oxide particles and said voids have an average size of 0.1 pm or more.
[2]
2. Steel plate for use in hot stamping, according to claim 1, characterized by the fact that the steel plate is coated by any one of the aluminum coating,
Petition 870180028007, of 04/06/2018, p. 56/64
2/2 the zinc-aluminum coating and the zinc coating.
[3]
3. Steel plate production method for use in hot stamping, as defined in claim 1, characterized by the fact that it comprises the hot rolling of a plate of chemical ingredients as defined in claim 1 at a temperature of 1000 to 1400 Ό, in which the slab is subjected to rough lamination at a temperature of 1000 “C or more at a lamination rate of 70% or more and the slab is subjected to final lamination at a lamination rate of 70% or more, wherein the method optionally comprises coating the steel sheet.
[4]
4. Steel plate production method for use in hot stamping, according to claim 3, characterized by the fact that it also comprises the stripping of hot rolled steel sheet that was obtained by hot rolling and rolling cold-rolled steel sheet at a rolling rate of 30% or more.
[5]
5. Steel sheet production method for use in hot stamping, according to claim 4, characterized by the fact that it also comprises the annealing of the cold rolled steel sheet that was obtained by cold rolling.
[6]
6. Use of the steel sheet as defined in claim 1, characterized by the fact that it is for the production of a hot-rolled piece of high strength.

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法律状态:
2018-01-09| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|

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2019-02-12| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2019-03-19| 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 09/03/2011, OBSERVADAS AS CONDICOES LEGAIS. |

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2019-11-19| B25D| Requested change of name of applicant approved|Owner name: NIPPON STEEL CORPORATION (JP) |

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2022-01-04| B21F| Lapse acc. art. 78, item iv - on non-payment of the annual fees in time|Free format text: REFERENTE A 11A ANUIDADE. |

优先权:

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申请号 | 申请日 | 专利标题

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PCT/JP2011/056124|WO2012120692A1|2011-03-09|2011-03-09|Steel sheets for hot stamping, method for manufacturing same, and method for manufacturing high-strength parts|

---