CORPO CONFORMADO POR ESTAMPAGEM A QUENTE

Abstract

This hot-stamped object has a predetermined chemical composition, and when a region ranging, in the thickness direction from the surface, from a position corresponding to 1 / 8 the thickness to a position corresponding to 3 / 8 the thickness is defined as a 1 / 4 depth position, the microstructure at the 1 / 4 depth position comprises, in areal proportion, 80.0% or more of martensite and 0.0-5.0%, excluding 5.0%, of retained austenite. In the microstructure at the 1 / 4 depth position, the number density of iron-based carbide grains present in the martensite and have a circle-equivalent diameter exceeding 0.5 μm is less than 0.050 grains / μm2 and the average distance between any of the iron-based carbide grains and another iron-based carbide grain closest thereto is 3.0 μm or greater. In the microstructure at the 1 / 4 depth position, the prior austenite grain size is 20.0 μm or less.

Description

1 / 128 BODY FORMED BY HOT STAMPING TECHNICAL FIELD

[001] The present invention relates to a body formed by hot stamping.

[002] Priority is claimed to Japanese Patent Application No. 2023-065610, filed on April 13, 2023, the content of which is incorporated herein by reference. PREVIOUS TECHNIQUE

[003] In the steel sheet sector for vehicles, aiming to improve both fuel consumption and collision safety, considering the recent and stringent environmental regulations and collision safety standards, the application of a steel sheet that has a high tensile strength (high-strength steel sheet) has expanded. However, the formability through pressing of a steel sheet decreases with increasing strength, which makes it difficult to produce a product with a complex shape.

[004] Specifically, the ductility of steel sheet decreases with high strength, and there is a problem since the steel sheet fractures in a highly processed portion in a case where the steel sheet is processed into a complex shape. Furthermore, with the high strength of the steel sheet, residual stress after processing causes springback and wall curvature, which also causes a problem since dimensional accuracy is deteriorated. Therefore, it is not easy to form a steel sheet with high strength, particularly a tensile strength of 780 MPa or more, into a product with a complex shape by pressing. Rolling, instead of pressing, facilitates the processing of high-strength steel sheet; however, its application is limited to components that have a uniform cross-section in the direction. Petition 870250084126, dated 09 / 18 / 2025, page 7 / 147 2 / 128 of the same length.

[005] Therefore, in recent years, for example, as described in Patent Documents 1 to 3, hot stamping has been adopted as a forming technology by pressing a material that is difficult to form, such as high-strength steel sheets. Hot stamping is a hot forming technology that consists of heating a material to be formed and then forming the material.

[006] In this technology, the material is shaped after being heated. Therefore, the steel is soft during forming and has good formability. Consequently, even a high-strength steel sheet can be precisely formed into a complex shape. Furthermore, in hot stamping, since tempering is carried out simultaneously with forming by a pressing die, the steel (steel element, body formed by hot stamping) after forming exhibits sufficient strength.

[007] For example, Patent Document 1 describes that it is possible to impart a tensile strength of 1,400 MPa or more to a steel element obtained by forming a steel sheet by means of hot stamping.

[008] In recent years, countries around the world have set higher CO2 reduction targets, and every vehicle manufacturer has made progress in reducing fuel consumption while considering crash safety. Not only gasoline vehicles, but also electric vehicles, which have been developing rapidly, require, as their materials, higher strength materials to protect not only passengers but also batteries from collisions and to compensate for the increased weight. For example, for a steel element used in vehicles and similar applications, it is necessary to use steel with excellent crash resistance characteristics and Petition 870250084126, dated 09 / 18 / 2025, page 8 / 147 3 / 128 greater strength, exceeding the strength generally used in Patent Document 1 described above or for a steel element (body formed by hot stamping) currently formed by hot stamping.

[009] With respect to a high-strength steel with a tensile strength of 1.5 GPa or more, for example, Patent Document 2 describes a press-formed article that exhibits excellent toughness and a tensile strength of 1.8 GPa or more, subjected to hot press forming. Patent Document 3 describes a steel that has an extremely high tensile strength of 2.0 GPa or more, and also good toughness and good ductility. Patent Document 4 describes a steel that has an extremely high tensile strength of 1.8 GPa or more, and also good toughness. Patent Document 5 describes a steel that has an extremely high tensile strength of 2.0 GPa or more, and also good toughness.

[0010] However, as a result of the present inventors' studies, it has been discovered that, in Patent Documents 2 to 5, sufficient collision resistance characteristics (resistance to bending crack formation and resistance to crack propagation during collision deformation) may not be obtained to meet the growing demands of recent years. LIST OF QUOTES Patent Documents

[0011] Patent Document 1: Unexamined Japanese Patent Application, First Publication No. 2002-102980

[0012] Patent Document 2: Unexamined Japanese Patent Application, First Publication No. 2012-180594

[0013] Patent Document 3: Unexamined Japanese Patent Application, First Publication No. 2012-1802 Petition 870250084126, dated 09 / 18 / 2025, page 9 / 147 4 / 128

[0014] Patent Document 4: International Publication PCT No. WO2015 / 182596

[0015] Patent Document 5: International Publication PCT No. WO2015 / 182591 SUMMARY OF THE INVENTION Technical Problem

[0016] As described above, hot-stamped formed bodies having a tensile strength of 1.5 GPa (1,500 MPa) or more have been described. However, in any case, there is room for improvement in impact resistance characteristics.

[0017] Therefore, an objective of the present invention is to provide a hot-stamped formed body that has high strength and excellent impact resistance characteristics. Solution to the Problem

[0018] The present inventors conducted studies on improving collision resistance characteristics based on the premise of a hot-stamped body in which the C content is increased to obtain high resistance.

[0019] As a result, they obtained the following findings. (i) In a case where a high-strength hot-stamped body (e.g., a tensile strength of 1.5 GPa or more) is obtained, a large amount of carbon (C) is contained to ensure high strength, as described in Patent Documents 2 and 3. In this case, it is likely that an undissolved carbide will remain in the hot-stamped body. In a case where a coarse carbide (iron-based carbide) having a circular equivalent diameter greater than 0.5 μm is present in large quantities in the microstructure of the hot-stamped body, it serves as Petition 870250084126, dated 09 / 18 / 2025, page 10 / 147 5 / 128 mo origin of cracks during bending or as an origin of crack propagation. (ii) The smaller the amount of coarse carbide, the greater the impact resistance characteristics (bending capacity and crack propagation resistance characteristics). Furthermore, even in a case where coarse carbide is present, the crack propagation resistance characteristics are enhanced in a case where the average distance between the carbides ensures at least a certain amount. (iii) In a case where ferrite and pearlite are present in large quantities in the microstructure of the body formed by hot stamping, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease, and in a case where retained austenite is present in large quantities, the crack propagation resistance characteristics decrease. Furthermore, in a case where the grain size of the previous austenite is coarse, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease.

[0020] The present invention was conceived in view of the above discoveries. The essence of the present invention is as follows.

[0021] [1] A body formed by hot stamping according to an aspect of the present invention includes, as a chemical composition, in % by mass: C: 0.20% to 0.70%; Si: 0.010% to 2.000%; Mn: 0% to 2.00%; P: 0.100% or less; S: 0.0100% or less; N: 0.0100% or less; O: 0.0200% or less; Al: 0.0010% to 0.5000%; Mo: 0.0010% to 1.0000%; B: 0.0005% to 0.0100%; Ti: 0.010% to 0.100%; Nb: 0% to 0.100%; Cr: 0% to 1.00%; Co: 0% to 3.00%; Ni: 0% to 3.00%; Cu: 0% to 1.00%; V: 0% to 1,000%; W: 0% to 1.00%; Ca: 0% to 1.0000%; Mg: 0% to 1.0000%; REM: 0% to 1.0000%; Sb: 0% to 1,000%; Petition 870250084126, dated 09 / 18 / 2025, p. 11 / 147 6 / 128 Zr: 0% to 1.000%; As: 0% to 1.000%; one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi, and Sn: 0% to 1.000% in total;and a remainder: Fe and impurities where, in a case where the range from a position at 1 / 8 of a thickness to a position at 3 / 8 of the thickness in a thickness direction of a surface is defined as the 1 / 4 depth position, a microstructure at the 1 / 4 depth position includes, by area proportion, martensite: 80.0% or more and retained austenite: 0.0% or more and less than 5.0%, in the microstructure at the 1 / 4 depth position, the number density of an iron-based carbide present in the martensite and having a circular equivalent diameter of more than 0.5 μm is less than 0.050 particles^m2, and the average distance between the iron-based carbide and another iron-based carbide closest to the iron-based carbide is 3.0 μm or more, and in the microstructure at the 1 / 4 depth position, the grain size of the preceding austenite is 20.0 μm or less.

[0022] [2] In the body formed by hot stamping according to [1], the decarburization index Dc may be 0.085 or more.

[0023] [3] In the body formed by hot stamping according to [1] or [2], when a surface strip at 50 μm is defined as a portion of the surface layer, the microstructure of the surface layer portion may include, by area proportion, ferrite: more than 5.0%.

[0024] [4] In the body formed by hot stamping according to any one of [1] to [3], the chemical composition may include, in % by mass, C: more than 0.40% and 0.70% or less, Si: 0.010% to 2.000%, Mn: 0% to 1.00%, P: 0.100% or less, S: 0.0100% or less, N: 0.0100% or less, O: 0.0200% or less, Al: 0.0010% to 0.5000%, Mo: 0.0010% to 1.0000%, B: 0.0005% to 0.0100%, Ti: Petition 870250084126, dated 09 / 18 / 2025, page 12 / 147 7 / 128 0.010% to 0.100%, Nb: 0% to 0.100%, Cr: 0% to 1.00%, Co: 0% to 3.00%, Ni: 0% to 3.00%, Cu: 0% to 1.00%, V: 0% to 1.000%, W: 0% to 1.00%, Ca: 0% to 1.0000%, Mg: 0% to 1.0000%, REM: 0% to 1.0000%, Sb: 0% to 1.000%, Zr: 0% to 1.000%, As: 0% to 1.000%, one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi and Sn: 0% to 1.000% in total and a remainder: Fe and impurities.

[0025] [5] In the body formed by hot stamping according to any one of [1] to [4], a coating may be provided on the surface.

[0026] [6] In the body formed by hot stamping according to [5], the coating may contain mainly an Fe-Al based alloy.

[0027] [7] In the body formed by hot stamping according to [5], the coating may contain mainly an Fe-Zn based alloy. Advantageous Effects of the Invention

[0028] According to the above aspect of the present invention, it is possible to provide a hot-stamped formed body that has high strength and excellent impact resistance characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1. A diagram showing an example of an impact force-displacement curve obtained in an instrumented impact test. DESCRIPTION OF THE MODALITIES Body formed by hot stamping

[0030] A body formed by hot stamping according to an embodiment of the present invention (body formed by hot stamping according to the present embodiment) will be described. Petition 870250084126, dated 09 / 18 / 2025, p. 13 / 147 8 / 128

[0031] Next, a strip from a position at 1 / 8 of a thickness to a position at 3 / 8 of the thickness in a thickness direction of a surface will be described as a 1 / 4 depth position and a strip from the surface to 50 μm will be described as a surface layer portion.

[0032] The surface that serves as a reference for the surface layer portion and the 1 / 4 depth position is a surface of the hot-stamped body. In a case where the hot-stamped body has a coating (has a base metal portion and a coating), the surface means a surface of the base metal portion, excluding the coating.

[0033] The body formed by hot stamping according to the present embodiment has a predetermined chemical composition and, when a range from a position at 1 / 8 of a thickness to a position at 3 / 8 of the thickness in a thickness direction of a surface is defined as the 1 / 4 depth position, a microstructure at the 1 / 4 depth position includes, by area proportion, martensite: 80.0% or more and retained austenite: 0.0% or more and less than 5.0%, in the microstructure at the 1 / 4 depth position, the number density of an iron-based carbide present in the martensite and having a circular equivalent diameter of more than 0.5 μm is less than 0.050 particle^m2 and the average distance between the iron-based carbide and another nearest iron-based carbide is 3.0 μm or more and, in the microstructure at the 1 / 4 depth position, the grain size of Previous austenite thickness is 20.0 μm or less.

[0034] The hot-stamped body formed according to the present embodiment may have a coating on its surface. In this case, the hot-stamped body has a base metal portion made of steel and a coating formed Petition 870250084126, dated 09 / 18 / 2025, page 14 / 147 9 / 128 of the surface of the base metal portion. Furthermore, in this case, the chemical composition and microstructure described above are the chemical composition and microstructure of the base metal portion.

[0035] They will be described below. Chemical Composition

[0036] The body formed by hot stamping according to the present embodiment has a chemical composition that includes, in % by mass, C: 0.20% to 0.70%, Si: 0.010% to 2.000%, Mn: 0% to 2.00%, P: 0.100% or less, S: 0.0100% or less, N: 0.0100% or less, O: 0.0200% or less, Al: 0.0010% to 0.5000%, Mo: 0.0010% to 1.0000%, B: 0.0005% to 0.0100%, Ti: 0.010% to 0.100%, Nb: 0% to 0.100%, Cr: 0% to 1.00%, Co: 0% to 3.00%, Ni: 0% to 3.00%, Cu: 0% to 1.00%, V: 0% to 1.000%, W: 0% to 1.00%, Ca: 0% to 1.0000%, Mg: 0% to 1.0000%, REM: 0% to 1.0000%, Sb: 0% to 1.000%, Zr: 0% to 1.000%, As: 0% to 1.000%, one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi and Sn: 0% to 1.000% in total and a remainder: Fe and impurities.

[0037] The reasons for limiting the quantity of each element are as follows.

[0038] From now on, a range indicated by A to B indicates a range where A is a minimum limit and B is a maximum limit (A or more and B or less). However, a value represented by greater than or less than is not included as a minimum or maximum limit. For example, greater than A to B indicates that the value is greater than A and B or less. C: 0.20% to 0.70%

[0039] OC is an element that increases the hardenability of steel and increases the strength of a hot-stamped body obtained after a steel sheet has undergone a heat treatment, such as hot stamping. In a case where the content of Petition 870250084126, dated 09 / 18 / 2025, p. 15 / 147 10 / 128 If the carbon content (C) is less than 0.20%, it becomes difficult to ensure sufficient strength in the body formed by hot stamping. Therefore, the C content is defined as 0.20% or more. The C content is preferably defined as 0.30% or more, and in a case where greater tensile strength is obtained, the C content is more preferably 0.33% or more, or greater than 0.40%. The C content is even more preferably greater than 0.44%.

[0040] In a case where the C content is greater than 0.70%, the number density and mean distance of a coarse iron carbide fall outside the specified ranges and therefore the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease. Therefore, the C content is defined as 0.70% or less. The C content is preferably defined as 0.60% or less and, more preferably, as 0.55% or less.

[0041] That is, the C content is 0.20% to 0.70% and may be, for example, preferably 0.30% to 0.70%, more preferably greater than 0.40% to 0.70% and, even more preferably, greater than 0.44% to 0.70%, 0.30% to 0.60%, 0.33% to 0.60%, greater than 0.40% to 0.60%, greater than 0.44% to 0.60% or greater than 0.44% to 0.55%. Yes: 0.010% to 2.000%

[0042] Silicon (Si) is an effective element for ensuring the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) of the body formed by hot stamping, increasing the hardenability of the steel, suppressing the increase in the amount of coarse iron-based carbide, and ensuring the numerical density and average distance of coarse iron carbide. To obtain the above effect, the Si content is defined as 0.010% or more. The Si content is preferably defined as Petition 870250084126, dated 09 / 18 / 2025, p. 16 / 147 11 / 128 mo 0.100% or more, and more preferably 0.200% or more.

[0043] In a case where the Si content in the steel is greater than 2.000%, the amount of retained austenite increases and the crack propagation resistance characteristics decrease. Therefore, the Si content is defined as 2.000% or less. The Si content is preferably 1.500% or less and, more preferably, 1.000% or less.

[0044] That is, the Si content is from 0.010% to 2.000%, for example, preferably from 0.100% to 1.500% and, more preferably, from 0.200% to 1.000%. Mn: 0% to 2.00%

[0045] Mn may not be contained (it may be 0%), however, it is a very effective element for increasing the hardenability of steel and ensuring strength after quenching. In addition, Mn is an element that reduces Ac3 (transformation point) and promotes a reduction in the quenching treatment temperature. Therefore, Mn may be contained. In a case where the above effect is obtained, the Mn content is preferably 0.05% or more, more preferably 0.15% or more, and even more preferably 0.17% or more or 0.20% or more.

[0046] In a case where the Mn content is greater than 2.00%, the amount of coarse iron carbide increases, the number density and average distance of the coarse iron carbide cannot be satisfied, and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) after quenching decrease. Therefore, the Mn content is defined as 2.00% or less. The Mn content is preferably 1.50% or less, more preferably 1.00% or less, and even more preferably 0.80% or less or 0.60% or less.

[0047] That is, the Mn content is 0% to 2.00%, for example, preferably 0.05% to 1.50% or 0% to 1.00%, more preferably 0.15% to 1.00%, and even more preferably 0.17% to 0.80%. Petition 870250084126, dated 09 / 18 / 2025, p. 17 / 147 12 / 128 or 0.20% to 0.60%. P: 0.100% or less

[0048] OP is an impurity element. In a case where P segregates at grain boundaries, the strength of the grain boundaries decreases and the crack propagation resistance characteristics decrease. Therefore, the P content is defined as 0.100% or less. The P content is preferably 0.050% or less, 0.030% or less, or 0.020% or less.

[0049] The minimum limit for P content does not need to be particularly specified and is 0%. However, in a case where the P content is reduced to less than 0.0001%, the cost of dephosphorization increases significantly, which is not economically advantageous. Therefore, the P content can be defined as 0.0001% or more, 0.001% or more, 0.003% or more, or 0.005% or more.

[0050] That is, the P content is from 0% to 0.100% and, for example, preferably from 0.0001% to 0.100%. S: 0.0100% or less

[0051] OS is an impurity element and is an element that forms an inclusion in steel. Since the inclusion serves as the origin of cracks or a path for crack propagation, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease in a case where the S content is high. Therefore, the S content is defined as 0.0100% or less. The S content is preferably 0.0080% or less, 0.0050% or less, 0.0030% or less, 0.0020% or less, or 0.0010% or less.

[0052] The minimum limit for sulfur content does not need to be specifically defined and is 0%. However, in a case where the sulfur content is reduced to less than 0.0001%, the cost of desulfurization increases significantly, which is not economically advantageous. Therefore, Petition 870250084126, dated 09 / 18 / 2025, p. 18 / 147 13 / 128 the content of S can be defined as 0.0001% or more, 0.0002% or more, or 0.0003% or more.

[0053] That is, the S content is from 0% to 0.0100% and, for example, preferably from 0.0001% to 0.0100%. N: 0.0100% or less

[0054] NO is an impurity element and is a nitride-forming element in steel. Since nitride serves as a crack origin or a path for crack propagation, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease in a case where the N content is high. Therefore, the N content is defined as 0.0100% or less. The N content is preferably 0.0080% or less or 0.0050% or less.

[0055] The minimum limit for N content does not need to be particularly specified and is 0%. However, in a case where the N content is reduced to less than 0.0001%, the cost of denitrification increases significantly, which is not economically advantageous. Therefore, the N content can be defined as 0.0001% or more, 0.0004% or more, or 0.0010% or more.

[0056] That is, the N content is from 0% to 0.0100% and, for example, preferably from 0.0001% to 0.0100%. O: 0.0200% or less

[0057] OO is an impurity element and is an element that forms a coarse oxide of Al, Ti, Mg or similar, which serves as a source of cracking. In a case where the O content is high, the amount of coarse oxide of Al, Ti, Mg or similar increases and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) of the hot-stamped body decrease. Therefore, the O content is defined as 0.0200% or less. The O content is preferably 0.0100% or less. Petition 870250084126, dated 09 / 18 / 2025, p. 19 / 147 14 / 128 nos, more preferably 0.0050% or less and, even more preferably, 0.0040% or less, 0.0030% or less or 0.0020% or less.

[0058] The minimum limit for O content does not need to be particularly specified and is 0%. However, in a case where the O content is less than 0.0001%, the cost of deoxidation increases significantly, which is not economically advantageous. Therefore, the O content can be defined as 0.0001% or more, 0.0005% or more, or 0.0010% or more.

[0059] That is, the O content is from 0% to 0.0200% and, for example, preferably from 0.0001% to 0.0200%. Al: 0.0010% to 0.5000%

[0060] Aluminum (Al) is an element that acts to deoxidize molten steel and impart strength to the steel (suppressing the occurrence of defects, such as air bubbles, in the steel). In a case where the Al content is less than 0.0010%, deoxidation is not carried out adequately, the number of air bubbles and the amount of coarse oxide increase, and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease. Therefore, the Al content is defined as 0.0010% or more. The Al content is preferably 0.0050% or more, 0.0100% or more, 0.0150% or more, 0.0200% or more, or 0.0250% or more.

[0061] In a case where the Al content is greater than 0.5000%, the amount of coarse oxide increases in the steel and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) of the hot-stamped body decrease. Therefore, the Al content is defined as 0.5000% or less. The Al content is preferably 0.4000% or less, 0.3000% or less, 0.2000% or less, 0.1500% or less, 0.1000% or less, or 0.0750% or less. Petition 870250084126, dated 09 / 18 / 2025, p. 20 / 147 15 / 128

[0062] That is, the Al content is from 0.0010% to 0.5000%, for example, preferably from 0.0050% to 0.4000%, more preferably from 0.0100% to 0.3500% or 0.0150% to 0.3000% and, even more preferably, from 0.0200% to 0.2000%, 0.0250% to 0.1500%, 0.0200% to 0.1000% or 0.0200% to 0.0750%.

[0063] In this embodiment, the Al content refers to a total Al content (total Al content). Mo: 0.0010% to 1.0000%

[0064] Mo is an element that dissolves in the grains of pre-existing austenite during heating before hot stamping, increasing the strength of the body formed by hot stamping. To reliably obtain this effect, the Mo content is defined as 0.0010% or more. The Mo content is preferably 0.0100% or more.

[0065] In a case where the Mo content is greater than 1.0000%, the amount of an inclusion based on Mo increases. Since the inclusion serves as a crack origin or path for crack propagation, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) of the hot-stamped body decrease in a case where the Mo content is high. Therefore, the Mo content is defined as 1.0000% or less. The Mo content is preferably 0.8000% or less or 0.6000% or less.

[0066] That is, the Mo content is from 0.0010% to 1.0000% and, for example, preferably from 0.0100% to 0.8000% or 0.0100% to 0.6000%. B: 0.0005% to 0.0100%

[0067] OB is an element that improves the hardenability of steel. In a case where the B content is less than 0.0005%, hardenability decreases and the amount of martensite decreases. Therefore, the desired strength cannot be obtained and the strength characteristics are affected. Petition 870250084126, dated 09 / 18 / 2025, page 21 / 147 16 / 128 impact resistance (folding capacity and crack propagation resistance characteristics) decreases. Therefore, the B content is defined as 0.0005% or more. The B content is preferably 0.0010% or more and, more preferably, 0.0015% or more.

[0068] In a case where the B content is greater than 0.0100%, the amount of a coarse nitride, such as BN, increases and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) of the hot-stamped body decrease. Therefore, the B content is defined as 0.0100% or less. The B content is preferably 0.0080% or less, 0.0060% or less, 0.0040% or less, or 0.0030% or less.

[0069] That is, the B content is from 0.0005% to 0.0100%, for example, preferably from 0.0010% to 0.0080% and, more preferably, from 0.0015% to 0.0060%, from 0.0015% to 0.0040% or from 0.0015% to 0.0030%. Ti: 0.010% to 0.100%

[0070] Ti is a nitrogen-fixing element that, as TiN, achieves a hardenability-enhancing effect due to the solid solution B and increases the strength of the body formed by hot stamping through precipitation hardening due to the formation of a fine carbide or carbonitride. In a case where the Ti content is less than 0.010%, these actions cannot be obtained. Therefore, the Ti content is defined as 0.010% or more. The Ti content is preferably 0.020% or more or 0.030% or more.

[0071] In a case where the Ti content is greater than 0.100%, the amount of coarse nitride or carbonitride, such as TiN or (Ti, Nb)(C, N), increases in the steel and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) of the hot-stamped body decreases. Petition 870250084126, dated 09 / 18 / 2025, p. 22 / 147 17 / 128 nuem. Therefore, the Ti content is defined as 0.100% or less. The Ti content is preferably 0.080% or less, 0.060% or less, 0.050% or less, or 0.040% or less.

[0072] That is, the Ti content is from 0.010% to 0.100% and may be, for example, preferably from 0.020% to 0.080%, more preferably from 0.030% to 0.060%, from 0.030% to 0.050%, from 0.010% to 0.040% or from 0.020% to 0.040%.

[0073] The chemical composition of the body formed by hot stamping according to the present embodiment may contain the elements described above (basic elements) and a remainder of Fe and impurities. One or two or more of the following elements (optional elements) may be additionally contained instead of a portion of Fe. Nb: 0% to 0.100%

[0074] Nb is an element that forms a carbide or carbonitride in steel and increases the strength of the body formed by hot stamping through precipitation hardening. Therefore, Nb may be contained. In a case where the above effect is obtained, the Nb content is preferably defined as 0.001% or more. The Nb content is more preferably 0.005% or more, 0.009% or more, or 0.015% or more.

[0075] In a case where the Nb content is greater than 0.100%, the amount of a carbide or carbonitride, such as NbC or (Nb,Ti)(C,N), increases in the steel and the toughness of the body formed by hot stamping decreases. Therefore, the Nb content is defined as 0.100% or less. The Nb content is preferably 0.080% or less, 0.060% or less, or 0.050% or less.

[0076] That is, the Nb content is from 0% to 0.100%, preferably from 0.001% to 0.100%, more preferably from 0.005% to 0.080% and, even more preferably, from 0.009% to 0.060% or 0.015% to 0.050%. Petition 870250084126, dated 09 / 18 / 2025, p. 23 / 147 18 / 128 Cr: 0% to 1.00%

[0077] Cr is an element that dissolves in the grains of the preceding austenite during heating before hot stamping and increases the strength of the body formed by hot stamping. Therefore, Cr may be present. In a case where the above effect is obtained, the Cr content is preferably defined as 0.01% or more. The Cr content is more preferably 0.10% or more or 0.20% or more.

[0078] In a case where the Cr content is greater than 1.00%, the hydrogen embrittlement resistance (hydrogen embrittlement resistance characteristics) of the hot-stamped body decreases. Therefore, the Cr content is defined as 1.00% or less. The Cr content is preferably 0.70% or less, 0.65% or less, 0.60% or less, or 0.55% or less.

[0079] That is, the Cr content is from 0% to 1.00%, for example, preferably from 0.01% to 1.00%, more preferably from 0.10% to 0.70% and, even more preferably, from 0.20% to 0.65%, 0.20% to 0.60% or 0.20% to 0.55%. Co: 0% to 3.00%

[0080] Cobalt is an element that increases the strength of the body formed by hot stamping through solid solution strengthening. Therefore, Cobalt may be included. In a case where the above effect is obtained, the Cobalt content is preferably defined as 0.01% or more. The Cobalt content is more preferably 0.10% or more and, even more preferably, 0.20% or more.

[0081] The above effect is saturated even in a case where a large amount of Co is contained. Therefore, the Co content is defined as 3.00% or less. The Co content is preferably 2.50% or less. The Co content is more preferably 2.20% or less, 2.00% or less, 1.00% or less, 0.70% or less, 0.65% or less, Petition 870250084126, dated 09 / 18 / 2025, p. 24 / 147 19 / 128 0.60% or less or 0.55% or less.

[0082] That is, the Co content is from 0% to 3.00%, for example, preferably from 0.01% to 2.50%, more preferably from 0.01% to 2.20%, from 0.01% to 2.00%, from 0.10% to 2.20%, from 0.10% to 2.00% or from 0.20% to 2.00% and, even more preferably, from 0.20% to 1.00%, from 0.20% to 0.70%, from 0.20% to 0.65%, from 0.20% to 0.60% or from 0.20% to 0.55%. Ni: 0% to 3.00%

[0083] Ni is an element that dissolves in austenite and is useful for increasing the hardenability of steel and tensile strength. Therefore, Ni may be contained. In a case where the above effect is obtained, the Ni content is preferably defined as 0.001% or more. The Ni content is more preferably 0.01% or more or 0.10% or more.

[0084] In a case where the Ni content is greater than 3.00%, the above effect is saturated and the cost of the alloy increases. Therefore, the Ni content is defined as 3.00% or less. The Ni content is preferably 2.50% or less or 2.00% or less and, more preferably, 1.00% or less, 0.70% or less, 0.65% or less, 0.60% or less or 0.55% or less.

[0085] That is, the Ni content is 0% to 3.00%, for example, preferably 0.001% to 2.50% or 0.01% to 2.00%, more preferably 0.10% to 1.00% and, even more preferably, 0.10% to 0.70%, 0.10% to 0.65%, 0.10% to 0.60% or 0.10% to 0.55%. Cu: 0% to 1.00%

[0086] Copper (Cu) is an element that dissolves into the austenite grains during preheating before hot stamping, increasing the strength of the body formed by hot stamping. Therefore, Cu may be present. In cases where the above effect is achieved, the Cu content is preferably set at 0.01% or more. More preferably, the Cu content is 0.10%. Petition 870250084126, dated 09 / 18 / 2025, p. 25 / 147 20 / 128 or more.

[0087] The above effect is saturated even in a case where a large amount of Cu is contained. Therefore, the Cu content is defined as 1.00% or less. The Cu content is preferably 0.80% or less, 0.60% or less, or 0.30% or less.

[0088] That is, the Cu content is 0% to 1.00%, for example, preferably 0.01% to 0.80% or 0.01% to 0.60%, more preferably 0.10% to 0.80% and, even more preferably, 0.10% to 0.60% or 0.10% to 0.30%. V: 0% to 1,000%

[0089] V is an element that forms a carbonitride in steel to impart a strength-enhancing effect to the body formed by hot stamping through precipitation hardening. Therefore, V may be present. In a case where the above effect is obtained, the V content is preferably defined as 0.010% or more.

[0090] In a case where the V content is defined as greater than 1.000%, a large amount of carbonitride is generated in the steel, and the hydrogen embrittlement resistance of the hot-stamped body thus decreases. Therefore, the V content is defined as 1.000% or less. The V content is preferably 0.800% or less, 0.600% or less, or 0.300% or less.

[0091] That is, the V content is from 0% to 1.000%, for example, preferably from 0.010% to 0.800%, more preferably from 0.010% to 0.600% and, even more preferably, from 0.010% to 0.300%. W: 0% to 1.00%

[0092] W is an element that confers the effect of increasing the strength of the body formed by hot stamping. Therefore, W may be included. In a case where the above effect is obtained, the W content is preferably set at 0.01% or more and, more preferably, at 0.10% or more. Petition 870250084126, dated 09 / 18 / 2025, page 26 / 147 21 / 128

[0093] The above effect is saturated even in a case where a large amount of W is contained. Therefore, the W content is defined as 1.00% or less. The W content is preferably 0.80% or less, 0.60% or less, or 0.30% or less.

[0094] That is, the W content is from 0% to 1.00%, for example, preferably from 0.01% to 0.80%, more preferably from 0.01% to 0.60% and, even more preferably, from 0.01% to 0.30% or 0.10% to 0.30%. Ca: 0% to 1.0000%

[0095] Calcium is an element that suppresses the generation of a coarse oxide that serves as the origin of cracks. Therefore, calcium may be included. In a case where the above effect is obtained, the calcium content is preferably set at 0.0001% or more and, more preferably, at 0.0010% or more.

[0096] The above effect is saturated even in a case where a large amount of Ca is contained. Therefore, the Ca content is defined as 1.0000% or less. The Ca content is preferably 0.4000% or less, 0.1000% or less, 0.0700% or less, 0.0200% or less, or 0.0100% or less.

[0097] That is, the Ca content is from 0% to 1.0000% and, for example, preferably from 0.0001% to 0.4000%, 0.0001% to 0.1000% or 0.0001% to 0.0700%, more preferably from 0.0010% to 0.1000% and, even more preferably, from 0.0010% to 0.0700%, 0.0010% to 0.0200% or 0.0010% to 0.0100%. Mg: 0% to 1.0000%

[0098] Mg is an element that forms a fine oxide or sulfide in molten steel and suppresses the formation of coarse MnS. Furthermore, Mg is an element that disperses a series of fine oxides, conferring a refining effect on the microstructure. Therefore, Mg may be present. In a case where the above effect is obtained, the Mg content is preferably... Petition 870250084126, dated 09 / 18 / 2025, page 27 / 147 22 / 128 cia, defined as 0.0001% or more.

[0099] In a case where the Mg content is greater than 1.0000%, the amount of oxide in the steel increases, which negatively affects the toughness of the body formed by hot stamping. Therefore, the Mg content is defined as 1.0000% or less. The Mg content is preferably 0.4000% or less, 0.1000% or less, 0.0700% or less, 0.0200% or less, or 0.0100% or less.

[00100] That is, the Mg content is from 0% to 1.0000%, for example, preferably from 0.0001% to 0.4000%, more preferably from 0.0001% to 0.1000% and, even more preferably, from 0.0001% to 0.0700%, 0.0001% to 0.0200%, 0.0001% to 0.0100%, 0.0010% to 0.1000%, 0.0010% to 0.0700%, 0.0010% to 0.0200% or 0.0010% to 0.0100%. REM: 0% to 1.0000%

[00101] REM is an element that suppresses the generation of a coarse oxide that serves as the origin of cracks. Therefore, REM may be contained. In a case where the above effect is obtained, the REM content is preferably set at 0.0001% or more and, more preferably, at 0.0010% or more.

[00102] The above effect is saturated even in a case where a large amount of REM is contained. Therefore, the REM content is defined as 1.0000% or less. The REM content is preferably 0.4000% or less, 0.1000% or less, 0.0700% or less, 0.0200% or less, or 0.0100% or less.

[00103] That is, the REM content is 0% to 1.0000%, for example, preferably 0.0001% to 1.0000%, 0.0001% to 0.4000% or 0.0001% to 0.1000%, more preferably 0.0010% to 0.1000% and, even more preferably, 0.0010% to 0.0700%, 0.0010% to 0.0200% or 0.0010% to 0.0100%.

[00104] In this embodiment, REM refers to a total of 17 elements, including Sc, Y and lanthanide, and the content of REM refers to Petition 870250084126, dated 09 / 18 / 2025, p. 28 / 147 23 / 128 total content of these elements. Sb: 0% to 1,000%

[00105] Sb is an element that suppresses the generation of an oxide that serves as a source of cracks to improve the deformability of the body formed by hot stamping. Therefore, Sb may be contained. In a case where the above effect is obtained, the Sb content is defined as preferably 0.001% or more, more preferably 0.002% or more, and even more preferably 0.010% or more.

[00106] The above effect is saturated even in a case where a large amount of Sb is contained. Therefore, the Sb content is defined as 1.000% or less. The Sb content is preferably 0.400% or less, 0.100% or less, 0.050% or less, or 0.020% or less.

[00107] That is, the Sb content is from 0% to 1.000%, for example, preferably from 0.001% to 1.000%, 0.001% to 0.400%, 0.001% to 0.100%, 0.001% to 0.050% or 0.001% to 0.020%, more preferably from 0.002% to 0.400%, 0.002% to 0.100% or 0.010% to 0.050% and, even more preferably, from 0.001% to 0.020%, 0.002% to 0.020% or 0.010% to 0.020%. Zr: 0% to 1,000%

[00108] Zr is an element that contributes to inclusion control, particularly to the fine dispersion of inclusions, and increases the toughness of the body formed by hot stamping. Therefore, Zr may be included. In a case where the above effect is obtained, the Zr content is preferably set at 0.001% or more and, more preferably, at 0.010% or more.

[00109] In a case where a large amount of Zr is contained, the surface properties may deteriorate. Therefore, the Zr content is defined as 1.000% or less. The Zr content is preferably 0.400% or less, 0.200% or less, or 0.100% or less.

[00110] In other words, the Zr content is from 0% to 1,000%, for example, of Petition 870250084126, dated 09 / 18 / 2025, p. 29 / 147 24 / 128 preference of 0.001% to 1.000%, of 0.001% to 0.400%, of 0.001% to 0.200% or of 0.001% to 0.100%, more preferably of 0.010% to 0.200% and, even more preferably, of 0.010% to 0.100%. As: 0% to 1,000%

[00111] As is an element that reduces the austenitizing temperature and refines the grains of the previous austenite, thus contributing to improved resistance to hydrogen embrittlement. Therefore, As may be included. In a case where the above effect is obtained, the As content is preferably set at 0.001% or more and, more preferably, at 0.005% or more.

[00112] The above effect is saturated even in a case where a large amount of As is contained. Therefore, the As content is defined as 1.000% or less. The As content is preferably 0.400% or less, 0.200% or less, or 0.100% or less.

[00113] That is, the As content is from 0% to 1.000%, for example, preferably from 0.001% to 1.000%, from 0.001% to 0.400% or from 0.005% to 0.400%, more preferably from 0.001% to 0.200% or from 0.005% to 0.400% and, even more preferably, from 0.001% to 0.100% or from 0.005% to 0.100%. One or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi, and Sn: 0% to 1.000% of the total.

[00114] Ta, Re, Os, Ir, Tc, Pb, Se, Bi, and Sn are elements that improve resistance to hydrogen embrittlement. Therefore, they may be included. In a case where the above effect is obtained, the total content is preferably defined as 0.010% or more.

[00115] In a case where the total quantity of these elements is greater than 1.000%, the effect is saturated and the cost increases. Therefore, in a case where they are contained, the total content is defined as 1.000% or less. The total content is preferably 0.800% or less and, more preferably, 0.500% or less, 0.400% or less, 0.200%. Petition 870250084126, dated 09 / 18 / 2025, p. 30 / 147 25 / 128 or less or 0.100% or less.

[00116] That is, the total quantity of one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi and Sn is from 0% to 1.000%, for example, preferably from 0.010% to 0.800%, more preferably from 0.010% to 0.500% and, even more preferably, from 0.010% to 0.400%, 0.010% to 0.200% or 0.010% to 0.100%.

[00117] As described above, the chemical composition of the hot-stamped body according to this embodiment contains basic elements and a remainder of Fe and impurities or contains basic elements, one or two or more optional elements and a remainder of Fe and impurities.

[00118] Examples of impurities include elements that are mixed in from a steel feedstock or scrap and / or during steelmaking and are permitted within a range where the characteristics of the hot-stamped body formed according to the present embodiment do not deteriorate.

[00119] The chemical composition of the hot-stamped body described above can be measured by a general analytical method after cutting the decarburized layer, described later, through mechanical grinding or similar. For example, the chemical composition can be measured by inductively coupled plasma atomic emission spectrometry (ICPAES). Elements that are difficult to measure with ICP-AES are measured by other methods. For example, C and S can be measured using a combustion infrared absorption method, N can be measured using an inert gas fusion thermal conductivity method, and O can be measured using a non-dispersive inert gas fusion infrared absorption method. Tc can be measured by inductively coupled plasma mass spectrometry (ICP-MS). Petition 870250084126, dated 09 / 18 / 2025, page 31 / 147 26 / 128

[00120] In a case where the body formed by hot stamping has a coating on a surface, the chemical composition of the base metal portion can be analyzed after the coating and the decarburized layer are removed by mechanical grinding. Microstructure Microstructure at the 1 / 4 depth position includes, by area proportion, martensite: 80.0% or more and retained austenite: 0.0% or more and less than 5.0%.

[00121] In a case where the area ratio of martensite is less than a predetermined amount and a large amount of ferrite, pearlite, or bainite is present, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease. Furthermore, the tensile strength also decreases. Therefore, the area ratio of martensite is defined as 80.0% or more (including 100.0%). In the present embodiment, martensite includes so-called fresh martensite and tempered martensite (including self-tempered martensite). To further improve the impact resistance characteristics (bending capacity and crack propagation resistance characteristics), the area ratio of martensite is preferably 85.0% or more, more preferably 90.0% or more, and even more preferably 95.0% or more.

[00122] That is, the martensite area is 80.0% or more (up to 100.0%), for example, preferably 85.0% to 100.0%, more preferably 90.0% to 100.0%, and even more preferably 95.0% to 100.0%.

[00123] Furthermore, retained austenite is transformed into hard martensite through strain-induced transformation during collision deformation. Therefore, in a case where the ratio of Petition 870250084126, dated 09 / 18 / 2025, p. 32 / 147 27 / 128 The larger the retained austenite area, the lower the crack propagation resistance characteristics. In the hot-stamped body according to the present embodiment, the proportion of retained austenite area is defined as less than 5.0% (including 0.0%). To further improve the crack propagation resistance characteristics, the proportion of retained austenite area is preferably less than 4.0% and, more preferably, less than 2.0%. That is, the proportion of retained austenite area is 0.0% or more and less than 5.0%, preferably 0.0% or more and less than 4.0%, and, more preferably, 0.0% or more and less than 2.0%.

[00124] The remainder of the microstructure, in addition to martensite and retained austenite, includes ferrite, pearlite and / or bainite.

[00125] The area proportion thereof may be 20.0% or less (including 0.0%) in total to ensure 80.0% or more of martensite. The area proportion of martensite is preferably less than 20.0%, more preferably 15.0% or less, and even more preferably 10.0% or less or 5.0% or less.

[00126] In microstructure, the area ratio of each microstructure (each phase) can be obtained using the following method.

[00127] From any position 50 mm or more away from an end portion of the hot-stamped body (in a case where a sample is not collected from this position, from a position that avoids the end portion), a sample is cut in a cross-section parallel to the rolling direction and the thickness direction (thickness direction of the base steel sheet) so that a microstructure at a position 1 / 4 depth (a range from a position at 1 / 8 of the surface thickness to a position at 3 / 8 of the surface thickness in the thickness direction) can be observed. The sample size depends on Petition 870250084126, dated 09 / 18 / 2025, page 33 / 147 The 28 / 128 measuring device, however, is adjusted to a size that can be observed at approximately 10 mm in the rolling direction.

[00128] The microstructure identification is performed using the following method with the sample described above.

[00129] The cross-section (observation surface) parallel to the lamination direction and the thickness direction is polished with silicon carbide sandpaper No. 600 to No. 1500 and then receives a mirror finish using a liquid obtained by dispersing diamond powder with a particle size of 1 to 6 μm in a dilute solution of alcohol or similar or pure water. The cross-section is then polished for 8 minutes using colloidal silica with a particle size of 0.25 μm and without alkaline solution at room temperature to remove the deformation introduced in a surface layer of the sample.At any position in the longitudinal direction of the sample cross-section, a 200 μm long strip in the lamination direction, from a position at 1 / 8 of the surface thickness to a position at 3 / 8 of the surface thickness, with a position at 1 / 4 of the surface thickness as a center, is measured at 0.1 μm measurement intervals using a backscattered electron diffraction method to obtain information about the crystal orientation. For the measurement, an EBSD analysis device consisting of a thermal field emission scanning electron microscope (JSM-7001F, manufactured by JEOL Ltd.) and an EBSD detector (Hikari detector, manufactured by AMETEK, Inc.) is used. In this case, the vacuum level inside the EBSD analysis device is set to 9.6 χ 105Pa or less, the acceleration voltage is set to 20 kV, the operating distance (WD) is set to 15 mm, and the radiation current level is set to 18.When collecting a pattern using EBSD, in the OIM Data Collection software function coupled with the EBSD analysis device, the camera settings are adjusted so that... Petition 870250084126, dated 09 / 18 / 2025, page 34 / 147 29 / 128 exposure time is 3.65 and the gain is 0.39. Furthermore, when detecting a band of a pattern by EBSD, the maximum peak count of the Hough transform is set to 9 and the minimum peak count is set to 5. For the analysis, a database of a bcc crystal structure, Iron (Alpha), and a database of an fcc structure, Iron (Gamma), are selected. In a case where the structure to be analyzed has a bct crystal structure, it is analyzed as a bcc structure.

[00130] For the crystal orientation information obtained, a region with an fcc crystal structure is determined as retained austenite using the Phase Map function provided by the OIM Analysis software (registered trademark) coupled to the EBSD analysis device. The area ratio of retained austenite is calculated to obtain the area ratio of retained austenite. Then, regions with a bcc crystal structure are determined as bainite, ferrite, pearlite, and martensite (fresh martensite and tempered martensite). For these regions, using the Grain Orientation Spread Map function provided by OIM Analysis (registered trademark) described above, a region with a Grain Orientation Spread of 1° or less is extracted as ferrite under the condition that a grain boundary with an erroneous crystal orientation of 15° or more is considered a crystalline grain boundary (15° grain boundary).The area ratio of extracted ferrite is calculated to obtain the ferrite area ratio.

[00131] Next, using the Highlight function provided in the OIM Analysis (registered trademark) described above, the ferrite region (region with Grain Orientation Spread of 1° or less) and the remaining region (region with Grain Orientation Spread greater than 1°) are separated. Then, in the ferrite region (region with Grain Orientation Spread of 1° or less), the maximum value of the Grain Average IQ of the ferrite region is obtained using the Grain Average IQ MAP function. Petition 870250084126, dated 09 / 18 / 2025, page 35 / 147 30 / 128 provided in the OIM Analysis (registered trademark) described above, under the condition that a 15° grain boundary is considered a crystalline grain boundary. Then, in the remaining region (region with Grain Orientation Spread greater than 1°), a region with more than ^ / 2 is extracted as bainite and pearlite and a region with ^ / 2 or less is extracted as martensite (fresh martensite and tempered martensite) using the Grain Average IQ MAP function provided in the OIM Analysis (registered trademark) described above, under the condition that a 15° grain boundary is considered a crystalline grain boundary. The area ratio of extracted bainite and pearlite and the area ratio of extracted martensite (fresh martensite and tempered martensite) are calculated to obtain the area ratio of bainite and pearlite and the area ratio of martensite (fresh martensite and tempered martensite).

[00132] The area ratio of each microstructure can be obtained using the Phase MAP, Grain Orientation Spread MAP, and Grain Average IQ MAP functions provided in the OIM Analysis (registered trademark) described above.

[00133] In this document, in a case where the ferrite area ratio is 0%, a separate sample is collected from the hot-stamped body to be measured, heated to an Ac3 temperature of 70°C, held for 10 minutes in the above temperature range, and then subjected to a quenching heat treatment at an average cooling rate of 100°C / s or more from the above temperature range to room temperature to generate ferrite. The ferrite area ratio is obtained for the sample using the above procedure. Using the obtained ferrite area ratio, the area ratios of bainite, pearlite, and martensite in the hot-stamped body to be measured are obtained using the above procedure.

[00134] To observe the same region as the measurement region in Petition 870250084126, dated 09 / 18 / 2025, page 36 / 147 31 / 128 EBSD by SEM, a Vickers indentation is imprinted near an observation position. Then, the same region, including the Vickers indentation, is polished to remove surface layer contamination, and chemical etching with Nital is performed on it. Next, the same field of view of the EBSD observation surface is observed at 3,000x magnification in a secondary electron image with an accelerating voltage set to 15 kV using a thermal field emission scanning electron microscope (FE-SEM: JSM-7001F, manufactured by JEOL Ltd.). Through observation, the position of a microstructure that corresponds to the position determined as martensite in the EBSD microstructure identification described above is specified.

[00135] In the present document, in a case where the rolling direction of the body formed by hot stamping is not clear, the rolling direction is first determined by means of the following method before the sample is cut, so that a cross-section parallel to the rolling direction and the thickness direction can be observed.

[00136] A test specimen is collected from any position 50 mm or more from the distance of an end portion of the hot-stamped formed body, so that a cross-section parallel to the thickness direction can be observed. The cross-section of the collected sample is finished by mirror polishing and then observed at each of the magnifications of 100x, 200x, 500x, and 1000x using an optical microscope. An observation result at an appropriate magnification at which the dimensions of the inclusion can be measured is selected according to the dimensions of the inclusion. As an observation range, a strip with a width of 500 μm or more in the total thickness of the sheet is defined, and a region with low luminance is determined. Petition 870250084126, dated 09 / 18 / 2025, page 37 / 147 32 / 128 as inclusion. During observation, observation can be performed within a plurality of visual fields, so that at least two inclusions can be observed. Then, a surface parallel to a surface rotated in 5° increments in a range of 0° to 180° around the direction of the sheet thickness as an axis is observed using the method described above with reference to the cross-section initially observed using the method described. With respect to each of the inclusions in the obtained cross-sections, a maximum length is defined as the inclusion length, and the inclusion length in a direction perpendicular to the direction of the maximum length is defined as the inclusion thickness. The average value of the axis ratios (length / thickness) of the plurality of inclusions is calculated for each cross-section, and the cross-section in which the average value of the axis ratios of the inclusions is the largest is specified.A direction parallel to the longitudinal direction of the inclusion in the cross-section is defined as the rolling direction. In the microstructure at the 1 / 4 depth position, the number density of the iron-based carbide present in martensite and having a circular equivalent diameter greater than 0.5 µm is less than 0.050 particles / µm².

[00137] In a case where a coarse carbide (iron-based carbide) present in martensite and having a circular equivalent diameter greater than 0.5 µm is present in large quantities, it serves as a source of crack formation during bending or as a source of crack propagation. Therefore, in the body formed by hot stamping according to the present embodiment, the numerical density of this coarse iron-based carbide is reduced. Specifically, in a case where the numerical density of the iron-based carbide (iron-based carbide that Petition 870250084126, dated 09 / 18 / 2025, page 38 / 147 33 / 128 has a circular equivalent diameter greater than 0.5 μm) present in martensite and which has a circular equivalent diameter greater than 0.5 μm is 0.050 particles^m2 or more, the collision resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease significantly. Therefore, the number density of the iron-based carbide present in martensite and which has a circular equivalent diameter greater than 0.5 μm is defined as less than 0.050 particles^m2. From the point of view of further improving the collision resistance characteristics (bending capacity and crack propagation resistance characteristics), the number density is preferably less than 0.030 particles^m2, more preferably less than 0.020 particles^m2 and, even more preferably, less than 0.010 particles^m2.

[00138] The more coarse iron-based carbides are reduced, the greater the collision resistance characteristics (bending capacity and crack propagation resistance characteristics) and therefore the minimum numerical density limit will not be limited. However, since it is not easy to define the numerical density for 0 particles^m2, the minimum limit can be defined for 0.0001 particles^m2. The numerical density is, more preferably, 0.001 particles^m2 or more and, even more preferably, 0.002 particles^m2 or more, 0.003 particles^m2 or more or 0.005 particles^m2 or more. That is, the numerical density of the iron-based carbide present in martensite, which has a circular equivalent diameter greater than 0.5 μm, can be, for example, 0.0001 particles^m2 or more and less than 0.050 particles^m2, 0.001 particles la^m2 or more and less than la^m2 or more and less than la^m2 or more and less than 0.050 particle^m2, 0.001 particle0.030 particle^m2, 0.002 particle0.030 particle^m2, 0.003 particlePetition 870250084126, of 09 / 18 / 2025, p. 39 / 147 34 / 128 la / pm2 or more and less than 0.020 particles / pm2 or 0.005 particles / pm2 or more and less than 0.010 particles / pm2. In the microstructure at the 1 / 4 depth position, the average distance between the iron-based carbide present in martensite with an equivalent circular diameter greater than 0.15 μm and the nearest iron-based carbide present in martensite with an equivalent circular diameter greater than 0.5 μm is 3.0 μm or more.

[00139] Even in a case where the coarse iron-based carbide described above is present, the crack propagation resistance characteristics are improved in a case where the average intercarbide distance between coarse iron-based carbides ensures at least a certain amount.

[00140] Therefore, in the hot-stamped body according to the present embodiment, the average distance between an iron-based carbide present in martensite and having a circular equivalent diameter greater than 0.5 μm and another nearby iron-based carbide present in martensite and having a circular equivalent diameter greater than 0.5 μm is defined as 3.0 μm or more. That is, in the hot-stamped body according to the present embodiment, the crack propagation resistance characteristics are improved by reducing the presence of adjacent coarse iron-based carbides. The average distance is preferably 5.0 μm or more and more preferably 8.0 μm or more. The maximum limit of the average distance is not limited and the average distance can be 30.0 μm or less. The average distance is preferably 20.0 μm or less or 15.0 μm or less.That is, the average distance is 3.0 μm or more and can be, for example, from 3.0 to 30.0 pm, from 5.0 to 30.0 pm, from 5.0 to 20.0 pm, from 5.0 to 15.0 μm, or from 8.0 to 30.0 pm. Petition 870250084126, dated 09 / 18 / 2025, page 40 / 147 35 / 128

[00141] The identification of iron-based carbide and the measurement of the equivalent circle diameter of iron-based carbide, the number density of iron-based carbide that has an equivalent circle diameter greater than 0.5 μm, and the average distance between an iron-based carbide that has an equivalent circle diameter greater than 0.5 μm and another nearest iron-based carbide that has an equivalent circle diameter greater than 0.5 μm can be performed using the following methods.

[00142] For the identification of iron-based carbide, the microstructure is identified by the FE-SEM described above, and the same sample with an indentation is used and observed with a transmission scanning electron microscope (STEM: JEM-2100 manufactured by JEOL Ltd.). Within a visual field in which the microstructure is observed, in a 200 μm long strip in the lamination direction, from a position at 1 / 8 of the surface thickness to a position at 3 / 8 of the thickness, with a position at 1 / 4 of the surface thickness in the thickness direction as the center, the precipitates are extracted using a replica extraction method. For the extraction of the precipitates, the observation surface on which the microstructure is observed by FE-SEM, as described above, is subjected to carbon deposition and immersed in a scaling liquid to elute only the base metal. The floating replica film is washed and collected on a grid.In the band (excluding the grid portion) identified as martensite in the microstructure, the extracted precipitates are observed at 5,000x magnification using a scanning transmission electron microscope (STEM), and point analysis is performed using energy-dispersive X-ray spectroscopy (EDX: JED-2300T manufactured by JEOL Ltd.) coupled to the microscope. Point analysis is performed in a position... [Petition 870250084126, dated 09 / 18 / 2025, page 41 / 147.] 36 / 128 centroid (centroid obtained from the observed image (planar shape)) of the observed precipitates. Quantitative analysis of the precipitates by EDX is performed for Fe and all other alloying elements described above, excluding C, N, B, O, P, and S, and precipitates containing 70% or more by mass of iron (Fe) are determined to be an iron-based carbide. Observation of the precipitates by STEM is performed with an accelerating voltage of 200 kV, and point analysis of the precipitates by EDX is performed with an irradiation current of 2.56 nA and a measurement time of 60 seconds at each point. Observation is performed in 5 or more visual fields at 200 μm² or more / visual field.

[00143] The circular equivalent diameter of the precipitates, determined as iron-based carbide, is obtained. In this case, the maximum length of the iron-based carbide is considered the major axis, the minimum length is considered the minor axis, and the value calculated as (major axis χ minor axis)0'5 from the major axis and the minor axis of the iron-based carbide is defined as the circular equivalent diameter.

[00144] In this document, the maximum length is the maximum length of a gap between two parallel lines that are in contact with the outer periphery of the iron-based carbide interposed between the parallel lines. The minimum length is the minimum length of the gap between the two parallel lines described above that are in contact with the outer periphery of the iron-based carbide interposed between the parallel lines. In carbides, carbide having a circular equivalent diameter greater than 0.5 μm is extracted, and the number density in each visual field is calculated by dividing the quantity by the area in each visual field. The average value of the number densities is defined as the number density of the iron-based carbide having a diameter Petition 870250084126, dated 09 / 18 / 2025, page 42 / 147 37 / 128 circular equivalent larger than 0.5 μm in the body formed by hot stamping according to the present embodiment.

[00145] In addition, a distance between iron-based carbides that have a circular equivalent diameter greater than 0.5 μm is measured, and a distance between the nearest carbides is determined in each visual field. Specifically, iron-based carbides that have a diameter greater than 0.5 μm are extracted, and their centroid coordinates are calculated. Then, an iron-based carbide is optionally selected, and particles are searched radially from the centroid coordinates of the iron-based carbide. In this case, a step angle for the radial search is set to 1 degree or less. With respect to all carbides detected from the step angle, the smallest distance between the outer peripheries (edges) of the carbides is obtained, which is provided as a measurement value. This process is performed on all detected carbides to obtain the distance between the nearest carbides.In the method described above, the average value of the distances between the nearest carbides, measured in the visual fields, is defined as the average distance between the nearest iron-based carbides. In the microstructure at the 1 / 4 depth position, the grain size of the previous austenite is 20.0 μm or less.

[00146] In a case where the grains of pre-existing austenite are coarse, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease. Therefore, in the body formed by hot stamping according to the present embodiment, the grain size of the pre-existing austenite is defined as 20.0 μm or less. From the point of view of further improving the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) Petition 870250084126, dated 09 / 18 / 2025, page 43 / 147 38 / 128 crack), the grain size of the prior austenite is preferably 15.0 μm or less and, more preferably, 13.0 μm or less, 12.0 μm or less, 11.0 μm or less or 10.0 μm or less. The minimum limit of the grain size of the prior austenite is not particularly restricted, however, to improve the hardenability of the body formed by hot stamping in a hot stamping step and to obtain a predetermined martensite fraction, the grain size of the prior austenite is preferably 2.0 μm or more and, more preferably, 3.0 μm or more.

[00147] That is, the grain size of the previous austenite is 20.0 μm or less and can be, for example, 2.0 to 20.0 μm, 2.0 to 15.0 μm, 3.0 to 15.0 μm, 3.0 to 13.0 μm, 3.0 to 12.0 μm, 3.0 to 11.0 μm or 3.0 to 10.0 μm.

[00148] The grain size of the previous austenite (previous grain size γ) can be obtained using the following method.

[00149] From any position 50 mm or more away from an end portion of the hot-stamped body (in a case where a sample is not collected from this position, from a position that avoids the end portion), a sample is cut so that a cross-section parallel to the rolling direction and the thickness direction can be observed. The sample size depends on the measuring device, however, it is adjusted to a size that can be observed at approximately 10 mm in the rolling direction.

[00150] A cross-section of the sample serving as an observation surface is polished using silicon carbide sandpaper No. 600 to No. 1500 and then mirror-finished using a liquid obtained by dispersing diamond powder with a particle size of 1 μm to 6 μm in a dilute solution of alcohol or similar or pure water. Electrolytic polishing is then performed to Petition 870250084126, dated 09 / 18 / 2025, p. 44 / 147 39 / 128 to finish the observation surface. At any position in the longitudinal direction of the sample cross-section, a 200 μm long strip, from a position at 1 / 8 of the surface thickness to a position at 3 / 8 of the thickness, with a position at 1 / 4 of the surface thickness as the center, is measured at 0.1 μm measurement intervals by means of a backscattered electron diffraction method to obtain information about the crystal orientation. For the measurement, an EBSD analysis device consisting of a thermal field emission scanning electron microscope and an EBSD detector can be used, and, as a device, an EBSD analysis device consisting of a JSM-7001F manufactured by JEOL Ltd. and a Hikari detector manufactured by AMETEK, Inc. can be used.In this case, the vacuum level inside the EBSD analysis device is set to 9.6 χ 10⁻⁵ Pa or less, the acceleration voltage is set to 20 kV, the operating distance (WD) is set to 15 mm, and the irradiation current level is set to 18. When collecting a pattern using EBSD, in the OIM Data Collection software function attached to the EBSD analysis device, the camera settings are set so that the exposure time is 3.65 and the gain is 0.39. Furthermore, when detecting a band of a pattern using EBSD, the maximum peak count of the Hough transform is set to 9 and the minimum peak count is set to 5. For the analysis, a database of a bcc, Iron (Alpha) crystal structure and a database of an fcc, Iron (Gamma) structure are selected. In a case where the structure to be analyzed has a bct crystal structure, it is analyzed as a bcc structure.

[00151] Using the crystal orientation information obtained, the crystal orientation of the previous austenite grains is calculated from the crystal orientation ratio between the previous austenite grains and the crystal grains that have a bcc structure after the transformation and Petition 870250084126, dated 09 / 18 / 2025, page 45 / 147 40 / 128 The average grain size of the previous austenite grains is calculated using the calculated crystal orientation.

[00152] The crystal orientation of the previously created austenite grains is calculated using the following method. First, a crystal orientation map of the previously created austenite grains is created using the method described on pages 24 to 30 of SHINNITTETSU SUMIKIN GIHO No. 404 (2016). The analysis is performed under conditions where the orientation relationship between ferrite (bcc structure) and austenite (fcc structure) is given such that an admissible angle is 3 degrees or less from the KS relationship and an admissible error of the orientation difference between the austenite crystals determined as ordinary austenite is 5 degrees or less in the reconstruction of the austenite microstructure and the austenite microstructure before the phase transformation is reconstructed. The grain boundaries of the reconstructed austenite are determined to have an orientation difference of 15 degrees or more between adjacent crystal grains.Furthermore, except for the grains of previous austenite, where not all crystal grains are included in the visual field of the photograph, such as an edge portion of the visual field of the photograph, the analysis is performed using the Area Fraction of the Grain Size (diameter) chart in OIM Analysis (registered trademark) described above to obtain the average grain size of the grains of previous austenite. The decarbonization index Dc is preferably 0.085 or higher.

[00153] In addition to the microstructure control described above, a decarburized layer that is present in a certain area of ​​the surface of the hot-stamped body makes it possible to further improve the impact resistance characteristics (bending capacity and crack propagation resistance characteristics).

[00154] In the related technique, the items evaluated in the layer des Petition 870250084126, dated 09 / 18 / 2025, pp. 46 / 147 41 / 128 Carbided features include the thickness of the decarburized layer, the hardness distribution in the decarburized layer, and similar factors. However, according to the present inventors' studies, it has been found that these items are correlated with the impact resistance characteristics (bending capacity and crack propagation resistance characteristics), but the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) may not necessarily be improved solely by controlling these items.For example, as a result of the present inventors' studies, it was discovered that, even in a case where the thickness (decarburization depth) of the decarburized layer is the same, in a case where a region of the surface layer has a pronounced hardness distribution (the degree of change in hardness is large), the improvement in bending capacity is less than in a case where the hardness distribution is gradual and the correlation with the thickness (decarburization depth) of the decarburized layer is weak.

[00155] Therefore, in the body formed by hot stamping according to the present embodiment, the decarburization index is used as a new index and the impact resistance characteristics are further improved than in the related technique by controlling the new index. Since this index takes into account information about the hardness of the surface layer region, in addition to the thickness (decarburization depth) of the decarburized layer, it exhibits a high correlation with impact resistance performance.

[00156] Specifically, a decarburization index Dc is defined as 0.085 or higher. This decarburization index is an index to quantify the amount of carbon loss from the surface of the hot-stamped body to a position at 200 Petition 870250084126, dated 09 / 18 / 2025, pp. 47 / 147 42 / 128 μm distance. From the point of view of ensuring folding capability, the decarburization index Dc is preferably 0.100 or more and, more preferably, 0.120 or more, 0.130 or more, 0.140 or more or 0.150 or more.

[00157] Due to the method of calculating the decarburization index Dc, the maximum limit is 1.000. The decarburization index Dc is preferably 0.800 or less from the point of view of ensuring tensile strength. The decarburization index Dc is more preferably 0.500 or less and, even more preferably, 0.200 or less.

[00158] That is, Dc is 0.085 or more and can be 0.085 or more and 0.800 or less, 0.085 or more and 0.800 or less, 0.100 or more and 0.800 or less, 0.085 or more, and 0.500 or less, 0.085 or more. 0.200 or less, 0.100 or more, and 0.500 or less, 0.120 or more 0.500 or less, 0.130 or more, and 0.500 or less, 0.140 or more. 0.200 or less, 0.150 or more, and 0.500 or less, or 0.150 or more and 0.200 or less.

[00159] The decarbonization index Dc can be obtained using the following method.

[00160] A distribution of element concentration along the thickness of the sheet metal in a hot-stamped body is measured using a glow discharge emission analyzer (glow discharge optical emission spectrometry, GD-OES). In this document, a measurement range is defined from the surface of the hot-stamped body to a position 200 μm from the surface (200 μm depth position), and the measurement interval is set to 0.02 μm or less. The measurement is performed on all elements included in the hot-stamped body.

[00161] In a case where the body is shaped by stamping a Petition 870250084126, dated 09 / 18 / 2025, pp. 48 / 147 43 / 128 hot stamped parts have a coating on the surface; the surface mentioned in this document is an interface between the coating and the base metal portion. In a case where the hot stamped body has a coating on the surface, all or part of the coating is removed by mechanical or chemical polishing so that it is possible to perform the measurement to a depth of 200 μm from the surface of the base metal portion (interface between the base metal portion and the coating) and the GD-OES measurement is performed. In the GD-OES measurement, a region with an Fe concentration (Fe content) of 90% by mass or more is considered the base metal portion, and a measurement point where the Fe concentration reaches 90% by mass or more of the surface is considered the surface of the base metal portion.

[00162] Next, with respect to the measurement values ​​of C concentration (C content) (1,000 points or more) from a position 180 μm away from the surface of the hot-stamped body (180 μm depth position) to a depth position of 200 μm, the average value is calculated and considered as the C concentration of a part where the influence of decarburization is not exerted.

[00163] However, in a case where the measurement can be performed at a depth where the C content can be determined to reach the same level as the average C content of the base metal (a part that is not affected by decarburization), the measurement range can be defined to one side of the surface from a depth position of 200 μm (however, the measurement is performed at 50 μm or more from the surface). In this case, regarding the measurement value of the C concentration in a region up to 20 μm from a deeper portion analyzed towards one side of the surface layer, in a case where the absolute value of the difference between the value Petition 870250084126, dated 09 / 18 / 2025, pp. 49 / 147 44 / 128 The average of the C concentrations in the region up to 20 μm from the deepest portion towards the surface layer side, and the maximum value of the C concentration measurement values ​​in the 20 μm region from the deepest portion towards the surface layer side, is 0.05% by mass or less, and the absolute value of the difference between the average value of the C concentrations in the 20 μm region from the deepest portion towards the surface layer side and the minimum value of the C concentration measurement values ​​in the 20 μm region from the deepest portion towards the surface layer side is 0.05% by mass or less, the average value of the C concentrations in the 20 μm region from the deepest portion towards the surface layer side can be defined as the C concentration of the part that is not affected by decarburization.In a case where the deepest portion is 120 μm deep, the phrase "measurement value of C concentration in the region up to 20 μm from the deepest portion towards the surface layer" means the concentration of C contained from the position at 100 μm depth to the position at 120 μm depth.

[00164] In a region of the surface of a body formed by hot stamping up to a position where the C concentration is the C concentration at a position where decarburization does not occur, the amount of decrease in C concentration per unit depth (a value obtained by subtracting the C concentration at each measurement point from the C concentration at the position where decarburization does not occur) is calculated, and an integrated value of the product of the unit depth and the amount of decrease in C concentration is obtained and defined as the area of ​​the C-deficient region (area A). In this document, unit depth means a GD-OES measurement interval. Then, the product of the C concentration at the position where decarburization does not occur and 200 ^m) is Petition 870250084126, dated 09 / 18 / 2025, page 50 / 147 45 / 128 defined as a reference area (area B) and a value (area A / area B) obtained by dividing the deficient area in C (area A) by the reference area (area B) is defined as a decarbonization index Dc.

[00165] Furthermore, in the present embodiment, as a result of the GDS analysis, a distance from the surface to the position where the C content is initially determined to be the same level as the average C content of the base metal (C concentration at the position which is determined to be a part that is not affected by decarburization) is defined as the decarburization depth (a range of 50 μm or more from the surface is analyzed).

[00166] In the hot-stamped body formed according to the present embodiment, the decarburization depth is preferably 180 μm or less, from the point of view of productivity. The decarburization depth is more preferably 150 μm or less. Otherwise, the decarburization depth can be adjusted to a thickness less than 1 / 8 of the thickness of a flat portion of the molded body. The decarburization depth is preferably 10 μm or more. The microstructure of the surface layer portion preferably includes, by area proportion, ferrite: more than 5.0%.

[00167] In a case where the surface layer portion of the molded body includes a softer microstructure than the inner layer by a certain amount or more, and the microstructure of the surface layer portion is adequately controlled, it is possible to further improve the impact resistance characteristics (bending capacity and crack propagation resistance characteristics). Therefore, the proportion of ferrite area in the microstructure of the surface layer portion is preferably defined as greater than 5.0%.

[00168] The ferrite area ratio is preferably 10.0% Petition 870250084126, dated 09 / 18 / 2025, page 51 / 147 46 / 128 or more, and more preferably 20.0% or more.

[00169] In the microstructure of the surface layer portion, the remainder, in addition to ferrite, includes more than 5.0% martensite (fresh martensite and tempered martensite) and / or bainite and less than 5.0% retained austenite and pearlite in total.

[00170] The microstructure of the surface layer portion can be observed in the same way as at the 1 / 4 depth position, and each area proportion can be measured. With respect to a measurement position, a range from the surface up to 50 μm in the thickness direction is defined, instead of the 1 / 4 depth position. Coating

[00171] All or part of the surface of the body formed by hot stamping according to the present embodiment may have a coating.

[00172] The coating can be a coating (Fe-Al based coating) that mainly contains an Fe-Al based alloy or a coating (Fe-Zn based coating) that mainly contains an Fe-Zn based alloy. The coating is also referred to as a membrane, alloy coating layer, or intermetallic compound layer.

[00173] A coating containing primarily an Fe-Al-based alloy is a coating containing 70% or more by mass of Fe and Al in total, and a coating containing primarily an Fe-Zn-based alloy is a coating containing 70% or more by mass of Fe and Zn in total. A coating containing primarily an Fe-Al-based alloy may also contain, in addition to Fe and Al, Si, Mg, Ca, Sr, Ni, Cu, Mo, Mn, Cr, C, Nb, Ti, B, V, Sn, W, Sb, Zn, Co, In, Bi, Zr, Se, As, REM and a remainder of impurities. A coating containing primarily an Fe-Zn-based alloy may also contain, in addition to Fe and Zn, Si, Mg, Ca, Sr, Ni, Cu, Mo, Mn, Cr, C, Nb, Petition 870250084126, dated 09 / 18 / 2025, p. 52 / 147 47 / 128 Ti, B, V, Sn, W, Sb, Al, Co, In, Bi, Zr, Se, As, REM and the rest of impurities.

[00174] By providing the coating, corrosion resistance is obtained, so that an effect of improving resistance to hydrogen embrittlement when used in a vehicle can be achieved.

[00175] The coating thickness is preferably 10 to 100 μm.

[00176] Such a coating, for example, a coating containing primarily an Fe-Al alloy, is formed by performing a heat treatment, such as hot stamping, on a steel sheet that includes a coating (Al-based coating) containing primarily Al. Furthermore, a coating containing primarily an Fe-Zn alloy is formed by performing a heat treatment, such as hot stamping, on a steel sheet that includes a coating (Zn-based coating) containing primarily Zn. The coating containing primarily Al is a coating containing 70% or more by mass of Al, and the coating containing primarily Zn is a coating containing 70% or more by mass of Zn. The coating, which mainly contains Al, may also contain, in addition to Al, Si, Mg, Ca, Sr, Ni, Cu, Mo, Mn, Cr, C, Nb, Ti, B, V, Sn, W, Sb, Zn, Co, In, Bi, Zr, Se, As, REM and a remainder of impurities.The coating, which mainly contains Zn, may also contain, in addition to Zn, Si, Mg, Ca, Sr, Ni, Cu, Mo, Mn, Cr, C, Nb, Ti, B, V, Sn, W, Sb, Al, Co, In, Bi, Zr, Se, As, REM and a remainder of impurities.

[00177] The chemical composition and coating thickness can be obtained by performing a linear analysis (qualitative analysis and quantitative analysis described below) on a cross-section using a field emission electron beam microanalyzer (FE-EPMA). Petition 870250084126, dated 09 / 18 / 2025, page 53 / 147 48 / 128

[00178] Specifically, from any position 50 mm or more away from an end portion of the hot-stamped body (in a case where a sample cannot be collected from this position, from a position avoiding the end portion), a sample is cut so that a cross-section parallel to the rolling direction and the thickness direction can be observed. The sample size depends on the measuring device, however, it is adjusted to a size that can be observed for about 10 mm in the rolling direction. Then, the cross-section (observation surface) parallel to the rolling direction and the thickness direction is polished with a silicon carbide sandpaper No. 600 to No. 1500 and then a mirror finish is applied using a liquid obtained by dispersing a diamond powder with a particle size of 1 to 6 μm in a dilute solution of an alcohol or similar or pure water. The sample is subjected to linear analysis using FE-EPMA.In an observation interval using FE-EPMA (JXA8530F manufactured by JEOL Ltd.), the quantities of the elements are quantitatively analyzed through line analysis with a magnification of 500 times.

[00179] In FE-EPMA, the accelerating voltage is defined as 15 kV, the beam diameter is defined as 100 nm, and the entire wavelength region is subjected to line analysis (qualitative analysis) using a fast scanning method to detect the contained elements. Then, the same conditions are defined for the accelerating voltage and beam diameter, the irradiation time per point is defined as 1000 ms, and the measurement step is defined as 60 nm. Then, considering a length of 200 μm in the direction of the depth of the sheet thickness from the coating surface, line analysis (quantitative analysis) is performed using a ZAF method on the elements Fe, Al, Zn, and Si. Petition 870250084126, dated 09 / 18 / 2025, page 54 / 147 49 / 128 other elements detected by the qualitative analysis described above and the quantitative values ​​of the elements are obtained. A region where the Fe concentration is 90% by mass or more is determined as the base metal and a region where the Fe concentration is less than 90% by mass is determined as the coating. A distance in the direction of the depth of the coating surface to the position where the Fe concentration becomes 90% by mass or more is measured and defined as a coating thickness.

[00180] The coating thickness described above is measured five times at positions where the distance between measurement points is 10 μm or more in a visual field. The measurement is performed in any 10 visual fields. The average value of the coating thicknesses obtained from the total of 50 measurements described above is determined as the coating thickness.

[00181] The chemical composition of the coating is obtained during the coating thickness measurement described above. Specifically, in the quantitative analysis to measure the coating thickness described above, in the range from the coating surface to the position where the Fe concentration initially becomes less than 90% by mass, the average value of each element is calculated in relation to the Fe, Al, Zn, and Si elements analyzed and other elements detected by the qualitative analysis described above, and the chemical composition of the coating is obtained. The measurement is performed five times at positions where the distance between the measurement points is 10 μm or more in a visual field. The measurement is performed in any 10 visual fields. The chemical composition of the coating obtained for each measurement is averaged over a total of 50 measurements, and this is defined as the chemical composition of the coating. Features Tensile Strength Petition 870250084126, dated 09 / 18 / 2025, page 55 / 147 50 / 128

[00182] In the hot-stamped body according to the present embodiment, the tensile strength is preferably 1,500 MPa or more, considering the contribution to the weight reduction of a vehicle body. The tensile strength is preferably 1,800 MPa or more, more preferably 2,000 MPa or more, and even more preferably 2,200 MPa or more.

[00183] Tensile strength may be 3,000 MPa or less from the point of view of ensuring resistance to hydrogen embrittlement.

[00184] To obtain the tensile strength of a flat part of the body formed by hot stamping (for example, in the case of a hat-shaped element, a part of the top sheet or a flat part other than the top sheet), a sheet-shaped test specimen of smaller size (length of the parallel part: 32 mm, width of the parallel part: 6.25 mm) according to ASTM A370: 2022 is collected, maintaining the material thickness (in a case where a coating is provided, without excluding the coating) so that the tensile direction is parallel to the rolling direction and a tensile test according to JIS Z 2241: 2022 is carried out with a calibration length of 25 mm and a crosshead separation rate of 1.0 mm / min at 20°C.Tensile strength is calculated as the value obtained by dividing the maximum test force by the cross-sectional area obtained by multiplying the material thickness (in a case where a coating is provided, the material thickness is a thickness that excludes the measured coating thickness) by the width of the parallel portion of 6.25 mm. Collision Resistance Characteristics

[00185] In the body formed by hot stamping according to the present embodiment, as described above, excellent impact resistance characteristics (bending capacity and crack propagation resistance characteristics) are obtained by Petition 870250084126, dated 09 / 18 / 2025, page 56 / 147 51 / 128 control the chemical composition and microstructure.

[00186] Regarding bending capacity, as described below, for a bending test, a sample with a width of 30 mm in a direction orthogonal to the rolling and a length of 60 mm in a rolling direction is collected from a flat part of the hot-stamped formed body (for example, in the case of a hat-shaped element, a part of the top sheet or a flat part other than the top sheet), maintaining the thickness of the hot-stamped formed body material (in a case where a coating is provided, without excluding the coating) and the bending test is carried out in accordance with VDA standard VDA238-100:2017 so that the direction of a bending edge is in the direction orthogonal to the rolling.

[00187] The product of a maximum bending angle obtained by the bending test and the tensile strength is preferably 80,000 (MPa^degrees) or more. The product is more preferably 90,000 (MPa^degrees) or more. The product is even more preferably 100,000 (MPa^degrees) or more.

[00188] Crack propagation resistance characteristics are obtained through a test in accordance with JIS Z 2242: 2018 and JIS B 7755: 2011 standards. From a flat part of the hot-stamped body (e.g., in the case of a hat-shaped element, a part of the top sheet, or a flat part other than the top sheet), a test specimen (a test specimen with a shape in accordance with JIS Z 2242: 2018, except for thickness, including a notch shape described later) with a size of 10 mm wide and 55 mm long is collected while maintaining the thickness of the hot-stamped body material (in the case where a coating is provided, without excluding the coating) so as Petition 870250084126, dated 09 / 18 / 2025, page 57 / 147 52 / 128 where the rolling direction is in the direction of the specimen length and a V-notch (notch angle: 45°, notch root radius: 0.25 mm, notch root width: 8 mm, notch position (center): a position 27.5 mm away from an end portion in the direction of the specimen length (with a depth of 2 mm)) is provided in the specimen. Then, three specimens are superimposed, fixed with a screw and subjected to an instrumented impact test. In a case where the sheet thickness is 2.00 mm or less, three specimens are superimposed to perform the test and in a case where the sheet thickness is greater than 2.00 mm, one specimen is used without overlapping to perform the test.

[00189] The instrumented impact test is performed at 20°C, and the impact time and force from the beginning to the end of the test are measured. Then, the displacement is calculated from the product of the instrumented impact test speed and the measured time. Since the crack surface length of the Charpy specimen is 8 mm, the average value of the impact forces measured in the region where the displacement is 8 mm or more is defined as the baseline parameter. After subtracting the baseline parameter from the impact forces at all measurement points, an impact force-displacement curve is created. Figure 1 is a diagram showing an example of the impact force-displacement curve obtained in the instrumented impact test. Since the impact force obtained in the instrumented Charpy test includes noise due to inherent vibration, smoothing processing is performed using 30-point moving average processing.

[00190] In the impact force-displacement curve obtained, an area under the curve from a displacement of 0 mm to a displacement of 8 mm was calculated and the value obtained is determined as total energy. Petition 870250084126, dated 09 / 18 / 2025, page 58 / 147 53 / 128 of impact. Next, the impact force (at the instant the cracks are initiated in Figure 1) is sought, at which a rapid decrease in the impact force-displacement curve begins, and a corresponding displacement (displacement at the instant the cracks are initiated) is obtained. An area under the displacement curve from 0 mm to the displacement at the instant the cracks are initiated is calculated and defined as the crack initiation energy. A value obtained by subtracting the crack initiation energy from the total impact energy is defined as the crack propagation energy. The ratio between the crack propagation energy and the total impact energy (crack propagation energy / (crack initiation energy + crack propagation energy)) is defined as an index of the crack propagation resistance characteristics.A rapid decrease in the impact-displacement force curve refers to a case where the amount of decrease in impact force per unit of displacement is 50% or more of the maximum measured impact force.

[00191] Regarding crack propagation resistance characteristics, the crack propagation energy / (crack initiation energy + crack propagation energy) is preferably 0.10 or more. The crack propagation energy / (crack initiation energy + crack propagation energy) is, more preferably, 0.20 or more and, even more preferably, 0.30 or more. Thickness

[00192] In the body formed by hot stamping, the thickness of the flat portion (thickness of the steel sheet as material (excluding the coating)) is preferably from 0.8 to 3.0 mm, from the point of view of hardenability. The thickness can be 1.2 to 3.0 mm, 1.4 to 3.0 mm or 1.5 to 3.0 mm. Manufacturing Method

[00193] The body formed by hot stamping according to Petition 870250084126, dated 09 / 18 / 2025, page 59 / 147 54 / 128 with the present embodiment can be manufactured by means of a manufacturing method that includes the following steps: (I) a preliminary heat treatment step to heat a steel sheet having a predetermined chemical composition to a temperature range greater than 950°C and 1200°C or less, such that the average heating rate is 2°C / s or more, holding the steel sheet for 1 second or more and 1200 seconds or less in the temperature range and cooling the steel sheet after holding, such that the average cooling rate from the temperature range to a cooling stop temperature of 100°C or less is less than 15°C / s and the average cooling rate between 700°C and 500°C is less than 10°C / s; and (II) a hot stamping step to perform hot stamping (cooling with a die and a punch at the same time) such that the steel sheet, after the preliminary heat treatment step, is heated to a temperature range Ac3 to 1.At 100°C, with an average heating rate of 2°C / s or more and less than 50°C / s, the steel sheet is held in this temperature range for 10 seconds or more and 600 seconds or less. Forming is initiated at a temperature range of 650°C or more after holding, and cooling is carried out so that the average cooling rate to 250°C is 10°C / s or more.

[00194] Furthermore, in a case where a coating is formed on the surface of the body formed by hot stamping, a coating step to form the coating may be included between the preliminary heat treatment step and the hot stamping step.

[00195] Next, the preferred conditions for each step will be described. Known conditions can be applied to conditions that are not described. Petition 870250084126, dated 09 / 18 / 2025, page 60 / 147 55 / 128

[00196] In this document, Ac3 can be calculated using the following expression based on the quantity of each element. Ac3 (°C) = 910 - 203 χ C0·5+ 66 χ Si - 25 χ Mn + 700 χ P - 11 χ Cr + 109 χ Al + 400 χ Ti - 15.2 χ Ni + 104 χ V + 31.5 χ Mo...(1)

[00197] In Expression (1), the element symbol indicates the quantity of each element in % by mass and 0 is substituted in a case where the element is not contained. Preliminary Heat Treatment Stage

[00198] In the preliminary heat treatment stage, a steel plate (including a case where a coating is applied to a surface) having a predetermined chemical composition is heated to a preliminary heat treatment temperature in a temperature range greater than 950°C and less than or equal to 1200°C, such that the average heating rate is 2°C / s or more and the steel plate is held in this temperature range for 1 second or more and 1200 seconds or less. After maintenance, the steel plate is cooled so that the average cooling rate from the temperature range (specifically, the temperature when maintenance is completed) to a cooling stop temperature less than or equal to 100°C is less than 15°C / s and the average cooling rate between 700°C and 500°C is less than 10°C / s.

[00199] In this step, the iron-based carbide that was dissolved is precipitated again during cooling and grown by Ostwald ripening to increase the distance between the iron carbides.

[00200] Some of the iron-based carbides generated in the preliminary heat treatment step may not be completely dissolved and may remain in the hot stamping stage for later processing. However, once it is possible to ensure Petition 870250084126, dated 09 / 18 / 2025, page 61 / 147 56 / 128 a predetermined average distance or greater between the carbides, the crack propagation resistance characteristics can be improved.

[00201] Preliminary heat treatment is performed before the hot stamping stage, however, it differs from annealing performed on a cold-rolled steel sheet in the following respects.

[00202] The normal annealing performed on a cold-rolled steel sheet is based on the idea that the microstructure of a base metal is homogenized and, by performing low-temperature heating without making the grain size of the previous austenite coarse and by suppressing the thickening of the iron-based carbide and dispersing it finely, stretch flangability, elongation, and the like are ensured. In contrast, the preliminary heat treatment in the present embodiment is different, since it is based on the idea that the iron-based carbide formed in the cold-rolling annealing step is redissolved by high-temperature heating and thickened during Ostwald maturation cooling to control the carbide spacing and the crack propagation resistance characteristics after hot stamping.

[00203] In a case where the average heating rate to the preliminary heat treatment temperature is less than 2°C / s, the pre-existing austenite grains become coarser and the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease. The maximum limit of the average heating rate is not specified. However, since productivity is reduced in terms of unit fuel consumption, the average heating rate is preferably 50°C / s or less and, more preferably, 10°C / s or less.

[00204] Furthermore, in a case where the treatment temperature Petition 870250084126, dated 09 / 18 / 2025, p. 62 / 147 57 / 128 preliminary thermal (holding temperature range) is 950°C or lower, the iron-based carbide in the steel sheet is not dissolved, and the number density of the iron-based carbide having a circular equivalent diameter greater than 0.5 μm and the average distance between the iron carbides after the hot stamping step do not fall within the desired ranges. In this case, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease.

[00205] In a case where the temperature of the preliminary heat treatment is greater than 1,200°C, the grains of pre-existing austenite become coarser. In this case, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease.

[00206] In a case where the holding time in the temperature range described above is less than 1 second, the iron-based carbide in the steel sheet is not dissolved, and the number density of the iron-based carbide that has a circular equivalent diameter greater than 0.5 μm and the average distance between the iron carbides after the hot stamping step do not fall within the desired ranges. In a case where the holding time is greater than 1200 seconds, the pre-existing austenite grains become coarser. In this case, the impact resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease.

[00207] In a case where the average cooling rate from the holding temperature to the cooling stop temperature of 100°C or less is 15°C / s or more, the Ostwald ripening of the iron-based carbide generated during cooling is insufficient and the average distance between iron carbides that have a circular equivalent diameter greater than 0.5 μm after the Petition 870250084126, dated 09 / 18 / 2025, p. 63 / 147 The 58 / 128 hot stamping stage does not fall within the desired range. The minimum limit for the average cooling rate from the holding temperature to the cooling stop temperature of 100°C or less is not specifically mentioned. However, from a productivity standpoint, the average cooling rate to 100°C or less is preferably 2°C / s or more, and more preferably 5°C / s or more.

[00208] Ostwald ripening is particularly affected by a temperature range of 700°C to 500°C. Therefore, even in a case where the average cooling rate from the holding temperature to the cooling stop temperature of 100°C or less is less than 15°C / s, in a case where the average cooling rate between 700°C and 500°C is 10°C / s or more, the Ostwald ripening of the iron-based carbide generated during cooling is insufficient, and the average distance between iron carbides that have a circular equivalent diameter greater than 0.5 μm after the hot stamping step does not fall within the desired range. Therefore, it is necessary to meet both cooling rates. The minimum limit of the average cooling rate between 700°C and 500°C is not particularly specified.However, from a productivity standpoint, the average cooling rate between 700°C and 500°C is preferably 1°C / s or more, and more preferably 4°C / s or more.

[00209] Furthermore, in a case where hot stamping is performed without cooling to 100°C or less, untransformed austenite, in which carbon is concentrated, may remain and, therefore, during heating for hot stamping, the untransformed austenite may be decomposed into an iron-based carbide during heating in the hot stamping step and the number density of the iron-based carbide that Petition 870250084126, dated 09 / 18 / 2025, pp. 64 / 147 59 / 128 has an equivalent circular diameter greater than 0.5 μm, which can increase excessively. Therefore, cooling is carried out at 100°C or less under the conditions described above.

[00210] Since the chemical composition does not change in the preliminary heat treatment stage and in the subsequent hot stamping stage, the chemical composition of the steel sheet to be subjected to the preliminary heat treatment stage can be the same as that of the steel sheet formed by hot stamping to be finally obtained. Furthermore, the steel sheet can be any hot-rolled steel sheet, cold-rolled steel sheet, or similar, and there are no limitations. In addition, the method of manufacturing the steel sheet is not limited; however, the steel sheet is manufactured under the conditions described below, for example.

[00211] The microstructure of the steel sheet to be subjected to the preliminary heat treatment stage is not limited, preferably being a microstructure that includes ferrite and pearlite from the point of view of workability. Bainite and retained austenite may be included as remnants in the microstructure. Coating Stage

[00212] In a case where a coating is formed on the surface, the coating step can be performed after the preliminary heat treatment step and before the hot stamping step. In the coating step, a coating is formed on the surface of the steel sheet to provide a coated steel sheet. The coating method is not particularly limited; a hot-dip coating method, an electroplating method, a vacuum vapor deposition method, a coating method, a thermal spraying method, and similar methods can be used. A hot-dip coating method is the most popular in the industry. Petition 870250084126, dated 09 / 18 / 2025, page 65 / 147 60 / 128

[00213] Examples of the coating may include an Al-based coating containing Al and a Zn-based coating containing Zn.

[00214] In a case where an Al-based coating is applied, the coating becomes an Fe-Al-based coating in the subsequent hot stamping step. Furthermore, in a case where a Zn-based coating is applied, the coating becomes an Fe-Zn-based coating in the subsequent hot stamping step.

[00215] In a case where an Al-based coating is formed by hot-dip plating, in addition to Al, Fe is mixed into the hot-dip plating bath as an impurity in many cases. Besides the elements described above, Si, Mg, Ca, Sr, Ni, Cu, Mo, Mn, Cr, C, Nb, Ti, B, V, Sn, W, Sb, Zn, Co, In, Bi, Zr, Se, As and other various metals may be contained in the hot-dip plating bath, provided that 70% or more by mass of Al is contained.

[00216] In a case where hot-dip coating is performed, the steel sheet, after the preliminary heat treatment step, can be heated and the hot-dip coating can be performed at a temperature close to the temperature of the hot-dip coating bath (e.g., 650°C to 750°C in a hot-dip coating case based on Al and 400°C to 500°C in a hot-dip coating case based on Zn).

[00217] Coating pre-treatments and post-treatments are not particularly limited, and pre-coating, solvent coating, alloy treatment or similar may be performed. As an alloy treatment, for example, a heat treatment may be performed at 450°C to 600°C in the case of a Zn-based coating and at 650°C to 750°C in the case of an Al-based coating. Petition 870250084126, dated 09 / 18 / 2025, page 66 / 147 61 / 128 Hot Stamping Stage

[00218] In the hot stamping stage, the steel sheet, after the preliminary heat treatment or coating stage, is heated to a hot stamping heating temperature in a temperature range of Ac3 (°C) or higher and 1,100°C or lower at an average heating rate of 2°C / s or higher and lower than 50°C / s held in this temperature range for 10 seconds or more and 600 seconds or less. After holding, forming is initiated at a temperature range of 650°C or higher and hot stamping (cooling with die and punch simultaneously) is performed so that the average cooling rate to 250°C is 10°C / s or higher.

[00219] In this step, the grain size of the previous austenite and the area proportions of the phases in the microstructure are controlled.

[00220] In a case where the average heating rate to the heating temperature by hot stamping is less than 2°C / s, the grains of pre-existing austenite become coarser. In a case where the average heating rate is equal to or greater than 50°C / s, the amount of undissolved iron-based carbide having a circular equivalent diameter greater than 0.5 μm increases, and the number density of iron-based carbide having a circular equivalent diameter greater than 0.5 μm and the average distance between iron carbides cannot be adjusted within predetermined ranges.

[00221] Furthermore, in a case where the heating temperature via hot stamping (and the subsequent holding temperature range) is lower than Ac3 (°C), the ferrite area ratio increases in the microstructure at the 1 / 4 depth position of the hot-stamped body, and the predetermined martensite area ratio cannot be achieved. In addition Petition 870250084126, dated 09 / 18 / 2025, page 67 / 147 62 / 128 of this, the amount of undissolved iron-based carbide increases, and the number density of iron-based carbide having a circular equivalent diameter greater than 0.5 μm and the average distance between iron carbides having a circular equivalent diameter greater than 0.5 μm do not fall within the desired ranges. In a case where the heating temperature is greater than 1100°C, the pre-existing austenite grains become coarser, and the collision resistance characteristics (bending capacity and crack propagation resistance characteristics) decrease. Furthermore, from the point of view of suppressing a decrease in collision resistance characteristics (bending capacity and crack propagation resistance characteristics), the heating temperature is preferably 1000°C or lower. The heating temperature is more preferably 950°C or lower.

[00222] Furthermore, in a case where the holding time is less than 10 seconds, the amount of undissolved iron-based carbide having a circular equivalent diameter greater than 0.5 μm increases excessively, and the number density of iron-based carbide having a circular equivalent diameter greater than 0.5 μm and the average distance between the iron carbides cannot be adjusted within the predetermined ranges. In a case where the holding time is greater than 600 seconds, the grains of previous austenite become coarser.

[00223] In a case where the initial forming temperature of the hot stamping is less than 650°C, the amount of ferrite increases and a predetermined martensite area ratio cannot be satisfied in the hot stamped body.

[00224] In a case where the average cooling rate at 250°C is less than 10°C / s, the amount of at least one of ferrite, pearlite, and bainite increases during cooling and a proportion of Petition 870250084126, dated 09 / 18 / 2025, page 68 / 147 The predetermined martensite area of ​​63 / 128 cannot be satisfied in the body formed by hot stamping. Preferred Manufacturing Method for Steel Sheet to be Subjected to Preliminary Heat Treatment

[00225] The steel sheet to be subjected to the preliminary heat treatment step is obtained under manufacturing conditions that include, for example, the heating step, hot rolling step and coiling step, and subsequently, also including a cold rolling step and / or an annealing step, as necessary. Furthermore, in a case where a hot-stamped body with a coating is obtained, a coating forming step may be performed to form a coating on the steel sheet to be subjected to the preliminary heat treatment step. Heating Stage

[00226] In the heating stage, the steel, as a plate with a predetermined chemical composition, is heated before being subjected to hot rolling. The heating temperature is preferably set to 1,100°C or higher, and the holding time in this temperature range is preferably set to 20 minutes or more. After holding, hot rolling is carried out.

[00227] The heating temperature is preferably set to 1,100°C or higher and the holding time is preferably set to 20 minutes or more from the point of view of the rolling load in the hot rolling stage. More preferably, the heating temperature is 1,200°C or higher and the holding time is 25 minutes or more. The heating temperature is preferably 1,350°C or lower and the holding time is preferably 120 minutes or less. Hot Rolling Stage Petition 870250084126, dated 09 / 18 / 2025, page 69 / 147 64 / 128

[00228] The hot rolling stage generally includes rough rolling, finishing rolling and coiling.

[00229] Among these, the finishing lamination is preferably carried out in a temperature range in which the finishing lamination temperature (finishing temperature) is 800°C or higher, considering the sheet shape. The finishing lamination temperature is more preferably 830°C or higher. The finishing lamination temperature is preferably 1,050°C or lower.

[00230] After final rolling, the steel sheet is wound onto a coil. Thus, a hot-rolled steel sheet is obtained. The winding temperature is preferably set to 750°C or less to promote scale removal in the subsequent pickling stage. Furthermore, considering the rolling force in the cold rolling stage, the coiling temperature is preferably 600°C or more. Cold Rolling Stage

[00231] The steel sheet to be subjected to the preliminary heat treatment stage may be a hot-rolled steel sheet after the hot rolling stage or it may be a cold-rolled steel sheet obtained by cold rolling the hot-rolled steel sheet.

[00232] In a case where the steel sheet is a cold-rolled steel sheet, the cold rolling can be carried out with a cumulative reduction by normal rolling, for example, a cumulative reduction by rolling of 30% to 90%.

[00233] In a case where cold rolling is performed, prior to cold rolling, a reheating treatment (hot-rolled sheet annealing) may be performed to soften the hot-rolled steel sheet. Petition 870250084126, dated 09 / 18 / 2025, pp. 70 / 147 65 / 128 Annealing Stage

[00234] Cold-rolled steel sheet after cold rolling can be annealed to homogenize the microstructure of the steel.

[00235] Examples of annealing conditions include conditions in which the steel sheet is heated to a temperature range of 750°C to 900°C (annealing temperature), held in this temperature range for 10 to 600 seconds, and then cooled to 500°C or less at an average cooling rate of 5°C / s or more. From the point of view of promoting recrystallization of the steel microstructure, homogenizing it, the annealing temperature is preferably 750°C or more and the holding time in this temperature range is preferably 10 seconds or more. Furthermore, from the point of view of productivity, the annealing temperature is preferably 900°C or less and the holding time in this temperature range is preferably 600 seconds or less.

[00236] In a case where a decarburization index Dc of the hot-stamped body is defined as 0.085 or more, a region of the surface layer (at a given distance from the surface) of the steel sheet is preferably decarburized by controlling the annealing atmosphere in the annealing step. Preferably, the annealing atmosphere contains 2 to 20% by volume of hydrogen and a remainder of impurities, such as nitrogen and oxygen, and is an atmosphere containing H2O with a dew point of -10°C or higher and 20°C or lower. To promote decarbonization by increasing the oxygen potential in the atmosphere and thus increasing the decarbonization index, the hydrogen concentration can be adjusted to 2% by volume or more and the dew point can be adjusted to -10°C or more; preferably, the hydrogen concentration is 3% by volume or more and the dew point is 0°C or more; and most preferably, the hydrogen concentration is... Petition 870250084126, dated 09 / 18 / 2025, p. 71 / 147 66 / 128 of 4% by volume or more and the dew point is 5°C or more. From the point of view of suppressing condensation in the equipment and not compromising productivity, the hydrogen concentration can be adjusted to 20% by volume or less and the dew point can be adjusted to 20°C or less; preferably, the hydrogen concentration is 15% by volume or less and the dew point is 15°C or less, and more preferably, the hydrogen concentration is 10% by volume or less and the dew point is 10°C or less. Furthermore, to promote the decarburization reaction and increase the decarburization index, the annealing temperature is preferably 780°C or higher. The annealing temperature is preferably 790°C or higher. Furthermore, the annealing temperature is preferably 890°C or lower, and more preferably 880°C or lower from a productivity standpoint.The holding time in this temperature range is preferably 20 seconds or more, and more preferably 60 seconds or more, in order to promote the decarburization reaction and increase the decarburization index. From a productivity standpoint, the holding time in this temperature range is preferably 590 seconds or less. Furthermore, in a case where the proportion of ferrite area in the surface layer of the hot-stamped body is set to more than 5.0%, in addition to the annealing conditions described above, it is preferable to control the annealing temperature to 820°C or higher and the holding time in this temperature range to 90 seconds or more. EXAMPLES

[00237] Plates (steel types 1 to 61) with the chemical compositions shown in Tables 1-1 to 1-4 were prepared (the column for total Ta and similar in the tables indicates the total amount of one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi and Sn). Petition 870250084126, dated 09 / 18 / 2025, page 72 / 147 67 / 128

[00238] The plates were subjected to a heating stage, a hot rolling stage, a cold rolling stage, and an annealing stage under the conditions shown in Tables 2-1 to 2-4, and steel plates from Tests Nos. 1 to 1-3 were obtained. In the tables, - indicates that the corresponding stage was not performed. Furthermore, the average cooling rate in the annealing stage in Tables 2-1 to 2-4 is the average cooling rate to the cooling stop temperature of 500°C or lower after holding.

[00239] The steel sheets obtained were subjected to a preliminary heat treatment step and a hot stamping step, under the conditions shown in Tables 2-5 to 2-12, to obtain hot-stamped shaped bodies. In the hot stamping step, the steel sheet was shaped into a hat shape using a die and punch.

[00240] In addition, in some examples, the steel sheets underwent a coating step prior to the hot stamping step. In the coating step, a hot-dip Zn coating or a hot-dip Al coating was applied to form a coating layer on a surface. Petition 870250084126, dated 09 / 18 / 2025, page 73 / 147 Table 1-1 Steel Type Chemical Composition (% by mass) * Remaining Fe and Impurities C Si Mn PsN₂ Al Mo B Ti Nb Cr Co Ni 1 0.20 0.200 1.20 0.010 0.0030 0.0022 0.0018 0.0360 0.0200 0.0018 0.023 2 0.45 0.300 0.40 0.010 0.0003 0.0024 0.0020 0.0360 0.2800 0.0022 0.017 3 0.68 0.300 0.40 0.012 0.0002 0.0026 0.0014 0.0300 0.1500 0.0019 0.025 4 0.18 0.200 1.00 0.010 0.0020 0.0030 0.0019 0.0300 0.0100 0.0020 0.020 5 0.79 0.360 0.42 0.015 0.0003 0.0027 0.0016 0.0410 0.2200 0.0021 0.020 6 0.46 0.010 0.50 0.011 0.0003 0.0024 0.0017 0.0300 0.2000 0.0030 0.023 7 0.46 1.000 0.50 0.011 0.0008 0.0027 0.0019 0.0400 0.1000 0.0025 0.021 8 0.45 2.000 0.44 0.011 0.0004 0.0024 0.0015 0.0420 0.3000 0.0018 0.025 9 0.45 0.005 0.40 0.011 0.0003 0.0026 0.0017 0.0330 0.2800 0.0020 0.020 10 0.45 2.100 1.00 0.012 0.0005 0.0028 0.0016 0.0300 0.3100 0.0022 0.022 11 0.46 0.500 0.05 0.010 0.0007 0.0030 0.0015 0.0350 0.6000 0.0025 0.021 12 0.45 0.300 1.00 0.010 0.0004 0.0024 0.0018 0.0360 0.0500 0.0020 0.023 13 0.44 0.200 1.96 0.010 0.0005 0.0036 0.0017 0.0320 0.0100 0.0019 0.020 14 0.45 0.200 2.10 0.010 0.0004 0.0025 0.0017 0.0360 0.1000 0.0023 0.021 15 0.45 0.300 0.40 0.095 0.0003 0.0030 0.0017 0.0310 0.3000 0.0017 0.019 16 0.45 0.300 0.45 0.110 0.0005 0.0031 0.0020 0.0320 0.3100 0.0020 0.022 68 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 74 / 147 Steel type Chemical composition (% by mass) * Remaining iron and impurities C Si Mn PSNO Al Mo B Ti Nb Cr Co Ni 17 0.35 0.300 1.30 0.010 0.0100 0.0025 0.0014 0.0310 0.0300 0.0018 0.019 18 0.35 0.310 1.32 0.010 0.0150 0.0027 0.0016 0.0320 0.0300 0.0020 0.018 19 0.45 0.200 0.40 0.010 0.0003 0.0090 0.0018 0.0400 0.3000 0.0022 0.035 20 0.45 0.230 0.42 0.011 0.0007 0.0160 0.0015 0.0340 0.2900 0.0025 0.020 21 0.47 0.320 0.48 0.011 0.0003 0.0028 0.0017 0.0010 0.2800 0.0021 0.021 22 0.46 0.310 0.45 0.010 0.0004 0.0035 0.0020 0.2500 0.2900 0.0020 0.022 23 0.46 0.300 0.46 0.010 0.0005 0.0030 0.0016 0.5000 0.2900 0.0021 0.023 24 0.47 0.320 0.48 0.011 0.0003 0.0028 0.0017 0.0009 0.2900 0.0025 0.022 25 0.47 0.300 0.50 0.010 0.0007 0.0030 0.0015 0.5100 0.3000 0.0021 0.022 26 0.45 0.400 0.90 0.010 0.0003 0.0024 0.0014 0.0360 0.0010 0.0025 0.024 27 0.45 0.300 0.40 0.010 0.0005 0.0027 0.0020 0.0350 0.5100 0.0024 0.020 28 0.46 0.320 0.20 0.011 0.0005 0.0030 0.0018 0.0360 0.9500 0.0022 0.021 29 0.21 0.200 1.10 0.010 0.0020 0.0035 0.0014 0.0360 0.0005 0.0020 0.021 30 0.45 0,320 0.30 0.011 0.0005 0.0030 0.0019 0.0360 1.1000 0.0023 0.021 69 / 128 Petition 870250084126, dated 09 / 18 / 2025, page 75 / 147 Table 1-2 Steel type Chemical composition (% by mass) * Remaining iron and impurities C Si Mn PSNO Al Mo B Ti Nb Cr Co Ni 31 0.21 0.200 1.20 0.010 0.0019 0.0038 0.0015 0.0310 0.1000 0.0006 0.025 32 0.45 0.300 0.40 0.010 0.0004 0.0024 0.0016 0.0360 0.2900 0.0050 0.020 33 0.45 0.300 0.40 0.010 0.0003 0.0025 0.0016 0.0360 0.3000 0.0095 0.021 34 0.21 0.200 1.20 0.010 0.0019 0.0045 0.0015 0.0200 0.0300 0.0002 0.015 35 0.46 0.300 0.40 0.010 0.0006 0.0030 0.0017 0.0240 0.3000 0.0110 0.019 36 0.46 0.300 0.40 0.011 0.0004 0.0025 0.0016 0.0370 0.3000 0.0025 0.010 37 0.46 0.300 0.40 0.011 0.0005 0.0026 0.0016 0.0350 0.3000 0.0024 0.051 38 0.46 0.300 0.40 0.010 0.0003 0.0026 0.0015 0.0320 0.3000 0.0026 0.095 39 0.20 0.200 1.20 0.010 0.0020 0.0047 0.0017 0.0300 0.0100 0.0017 0.005 40 0.47 0.320 0.40 0.010 0.0007 0.0030 0.0016 0.0320 0.3000 0.0025 0.110 41 0.46 0.430 0.41 0.007 0.0004 0.0025 0.0017 0.0380 0.2500 0.0022 0.030 0.018 42 0.46 0.430 0.40 0.011 0.0004 0.0026 0.0017 0.0370 0.2000 0.0023 0.027 0.27 43 0.46 0.420 0.40 0.010 0.0005 0.0025 0.0017 0.0400 0.2000 0.0025 0.025 1,00 44 0.45 0.300 0.40 0.010 0.0003 0.0030 0.0020 0.0350 0.1900 0.0022 0.019 0.50 45 0.46 0.300 0.40 0.011 0.0004 0.0028 0.0015 0.0370 0.2000 0.0023 0.020 46 0.46 0.300 0.40 0.010 0.0005 0.0030 0.0020 0.0350 0.2000 0.0025 0.020 70 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 76 / 147 Steel Type Chemical Composition (% by mass) * Remaining Fe and Impurities C Si Mn PsN0 Al Mo B Ti Nb Cr Co Ni 47 0.46 0.300 0.40 0.012 0.0004 0.0036 0.0015 0.0360 0.2000 0.0024 0.021 48 0.46 0.290 0.40 0.011 0.0005 0.0040 0.0150 0.0380 0.2000 0.0025 0.022 49 0.46 0.300 0.40 0.010 0.0004 0.0038 0.0014 0.0360 0.2000 0.0023 0.021 50 0.46 0.300 0.40 0.012 0.0006 0.0039 0.0019 0.0390 0.2000 0.0025 0.021 51 0.46 0.300 0.40 0.011 0.0006 0.0037 0.0018 0.0360 0.2000 0.0024 0.022 52 0.46 0.300 0.40 0.010 0.0005 0.0031 0.0018 0.0340 0.2000 0.0026 0.020 53 0.46 0.300 0.41 0.010 0.0003 0.0025 0.0015 0.0360 0.2100 0.0021 0.019 54 0.46 0.300 0.40 0.010 0.0004 0.0034 0.0016 0.0340 0.2000 0.0025 0.022 55 0.46 0.300 0.40 0.011 0.0003 0.0036 0.0019 0.0330 0.2000 0.0024 0.021 56 0.46 0.300 0.40 0.012 0.0005 0.0033 0.0016 0.0380 0.2000 0.0020 0.022 57 0.46 0.290 0.40 0.011 0.0007 0.0041 0.0220 0.0410 0.2000 0.0024 0.023 58 0.46 0.440 0.40 0.008 0.0003 0.0027 0.0018 0.0390 0.6000 0.0022 0.030 0.050 59 0,30 0.230 1.66 0.010 0.0006 0.0025 0.0017 0.0300 0.0100 0.0017 0.020 0.080 0.18 60 0.34 0.220 1.30 0.007 0.0004 0.0023 0.0019 0.0430 0.0100 0.0018 0.028 0.049 0.20 61 0.46 0.400 0.39 0.012 0.0005 0.0026 0.0017 0.0370 0.2000 0.0023 0.029 0.030 0.50 71 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 77 / 147 Table 1-3 Steel Type Chemical Composition (% by mass) * Remaining Fe and impurities Ac3 Cu VW Ca Mg REM Sb Zr As Total Ta and similar (°C) 1 823 2 810 3 779 4 831 5 773 6 787 7 849 8 927 9 792 10 918 11 842 12 790 13 758 14 757 15 871 16 881 72 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 78 / 147 Steel Type Chemical Composition (% by mass) * Remaining Fe and impurities Ac3 Cu VW Ca Mg REM Sb Zr As Total Ta and similar (°C) 17 796 18 796 19 812 20 807 21 805 22 834 23 860 24 806 25 859 26 798 27 819 28 838 29 822 30 842 73 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 79 / 147 Table 1-4 Steel Type Chemical Composition (% by mass) * Remaining Fe and impurities Ac3 Cu VW Ca Mg REM Sb Zr As Total Ta and similar (°C) 31 824 32 812 33 812 34 816 35 809 36 807 37 823 38 840 39 815 40 846 41 819 42 817 43 818 44 800 45 0.20 808 46 0.300 838 74 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 80 / 147 Steel Type Chemical Composition (% by mass) * Remaining Fe and impurities Ac3 Cu VW Ca Mg REM Sb Zr As Total Ta and similar (°C) 47 0.30 809 48 808 49 0.0020 808 50 0.0090 809 51 0.0090 809 52 0.020 807 53 0.010 807 54 0.010 808 55 0.010 808 56 0.100 810 57 809 58 0.050 837 59 789 60 793 61 814 75 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 81 / 147 Table 2-1 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% by vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 1 1 1200 60 900 640 47 2 -20 780 90 10 2 2 1230 62 910 635 47 4 0 810 90 7 3 3 1290 70 895 656 47 6 10 830 240 7 4 4 1200 60 905 620 47 2 -20 770 95 7 5 5 1280 70 899 660 47 6 10 800 90 8 6 6 1240 65 900 640 47 3 -15 780 60 7 7 7 1250 70 950 610 47 6 10 860 60 7 8 8 1250 70 960 620 47 6 10 860 60 7 9 9 1200 60 900 630 47 3 -15 780 60 7 10 10 1200 60 900 630 47 6 10 855 60 7 11 11 1250 60 950 640 47 4 0 780 100 7 12 12 1250 65 900 645 47 2 -25 770 90 7 13 13 1250 60 900 634 47 2 -20 780 90 7 14 14 1250 60 910 636 47 2 -20 780 90 7 76 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 82 / 147 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% by vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 15 15 1250 60 903 640 47 5 5 800 90 7 16 16 1250 50 912 645 47 5 5 800 90 7 17 17 1240 60 910 643 47 - - - - - 18 18 1240 60 915 637 47 - - - - - 19 19 1250 50 900 632 47 - - - - - 20 20 1250 60 905 641 47 - - - - - 21 21 1250 60 900 639 47 4 0 800 60 7 22 22 1250 60 905 640 47 4 0 800 60 7 23 23 1250 60 904 641 47 4 0 800 60 7 24 24 1250 60 903 644 47 4 0 800 60 8 25 25 1250 60 920 650 47 4 0 800 60 7 26 26 1240 60 900 630 47 - - - - - 27 27 1250 60 930 632 47 4 0 800 60 7 28 28 1240 60 980 653 47 4 0 800 60 7 77 / 128 Petition 870250084126, dated 09 / 18 / 2025, page 83 / 147 Table 2-2 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% by vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 29 29 1250 60 930 634 47 2 -20 780 90 9 30 30 1250 60 980 652 47 - - - - - 31 31 1200 60 900 640 47 - - - - - 32 32 1200 60 900 640 47 4 0 800 90 7 33 33 1200 60 900 640 47 4 0 800 90 7 34 34 1200 60 900 640 47 - - - - - 35 35 1200 60 900 640 47 6 10 800 60 7 36 36 1250 60 920 638 47 5 5 800 90 10 37 37 1250 60 920 632 47 5 5 800 90 10 38 38 1250 60 920 640 47 5 5 800 90 10 39 39 1200 60 900 640 47 - - - - - 40 40 1250 60 920 645 47 - - - - - 41 41 1250 60 920 630 47 5 5 800 90 7 42 42 1250 60 910 635 47 5 6 800 90 7 78 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 84 / 147 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% by vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 43 43 1250 60 920 635 47 5 6 800 90 7 44 44 1250 60 910 634 47 5 7 800 90 7 45 45 1250 60 915 631 47 5 6 800 90 7 46 46 1250 60 917 630 47 5 6 800 90 7 47 47 1250 60 918 637 47 5 6 800 90 7 48 48 1250 60 920 633 47 5 5 800 90 7 49 49 1250 60 920 633 47 5 6 800 90 7 50 50 1250 60 920 633 47 5 5 800 90 7 51 51 1250 60 918 640 47 5 6 800 90 7 52 52 1250 60 920 635 47 5 6 800 90 7 53 53 1250 60 919 637 47 5 6 800 90 7 54 54 1250 60 920 632 47 5 6 800 90 7 55 55 1250 60 918 635 47 5 5 800 90 7 56 56 1250 60 920 639 47 5 5 800 90 7 79 / 128 Petition 870250084126, dated 09 / 18 / 2025, page 85 / 147 Table 2-3 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% by vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 57 41 1100 60 918 629 47 5 5 800 90 6 58 41 1350 60 920 640 47 5 5 800 90 6 59 41 1250 20 917 643 47 5 6 800 90 6 60 41 1250 120 923 643 47 5 6 800 90 6 61 41 1200 60 895 645 47 5 6 800 90 6 62 41 1249 60 1045 623 47 5 5 800 90 6 63 41 1255 60 918 600 47 5 6 800 90 6 64 41 1249 60 918 749 47 5 6 800 90 6 65 41 1254 60 925 650 - - - - - - 66 41 1255 60 926 640 30 5 7 800 90 6 67 41 1247 60 917 667 50 5 7 800 90 6 68 41 1251 60 918 625 47 5 5 750 90 7 69 41 1249 60 925 627 47 5 6 880 90 6 70 41 1249 60 921 625 47 5 7 800 20 7 80 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 86 / 147 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% by vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 71 41 1252 60 921 635 47 5 7 820 590 6 72 41 1250 60 920 631 47 2 -10 780 90 7 73 41 1251 60 921 634 47 10 20 800 90 6 74 41 1250 60 924 622 47 5 7 800 90 7 75 41 1248 60 920 646 47 5 7 800 90 7 76 41 1246 60 916 620 47 5 6 800 90 7 77 41 1247 60 921 637 47 5 5 800 90 7 78 41 1255 60 919 647 47 5 6 800 90 6 79 41 1246 60 925 637 47 5 5 800 90 6 80 41 1250 60 919 646 47 5 6 800 90 6 81 41 1252 60 924 624 47 5 6 800 90 7 82 41 1255 60 918 636 47 5 6 800 90 7 83 41 1251 60 916 648 47 5 6 800 90 6 84 41 1253 60 923 629 47 5 7 800 90 6 81 / 128 Petition 870250084126, dated 09 / 18 / 2025, page 87 / 147 Table 2-4 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 85 41 1253 60 920 634 47 5 6 800 90 6 86 41 1248 60 920 650 47 5 7 800 90 6 87 41 1245 60 917 640 47 5 7 800 90 6 88 41 1253 60 918 646 47 5 7 800 90 6 89 41 1255 60 921 643 47 5 7 800 90 6 90 41 1245 60 915 639 47 5 6 800 90 7 91 41 1251 60 924 638 47 5 7 800 90 7 92 41 1248 60 916 631 47 5 5 800 90 7 93 41 1245 60 920 639 47 5 5 800 90 6 94 41 1246 60 922 625 47 5 7 800 90 6 95 41 1246 60 919 642 47 5 6 800 90 6 96 41 1252 60 925 632 47 5 7 800 90 6 97 41 1250 60 925 644 47 5 7 800 90 6 98 41 1251 60 923 626 47 5 7 800 90 6 82 / 128 Petition 870250084126, dated 09 / 18 / 2025, p. 88 / 147 Test No. Manufacturing Method Steel Type Heating Step Hot Rolling Step Cold Rolling Step Annealing Step Heating Temperature (°C) Holding Time (min) Finishing Rolling Temperature (°C) Coiling Temperature (°C) Cumulative Reduction by Rolling (%) Hydrogen Concentration (% vol) Dew Point (°C) Annealing Temperature (°C) Holding Time (s) Average Cooling Rate (°C / s) 99 41 1246 60 923 647 47 5 7 800 90 7 100 41 1255 60 915 649 47 5 7 800 90 7 101 41 1250 60 916 628 47 5 6 800 90 7 102 41 1249 60 916 626 47 5 5 800 90 6 103 41 1251 60 920 650 47 5 5 820 90 6 104 57 1250 60 920 635 47 5 5 800 90 7 105 58 1250 60 920 631 47 5 5 800 90 7 106 58 1250 60 920 630 47 5 5 800 90 7 107 58 1250 60 920 630 47 5 5 780 160 7 108 41 1250 60 920 629 47 5 5 800 90 7 109 1 1200 60 900 640 47 8 20 830 300 10 110 41 1250 60 920 634 47 2 -35 760 30 7 111 59 1250 60 915 620 47 - - - - - 112 60 1248 60 910 624 47 - - - -- 113 61 1248 60 920 603 47 5 6 800 90 7 83 / 128 Petition 870250084126, dated 09 / 18 / 2025, page 89 / 147 Table 2-5 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 1 5 980 95 10 5 Hot-dip coating based on Zn 2 4 1000 90 10 4 3 4 1000 100 8 5 4 4 1000 90 9 5 5 4 1000 100 12 8 6 4 1005 91 10 5 7 5 1000 95 8 5 8 5 1000 94 7 4 9 5 980 100 10 5 10 5 1000 90 7 5 11 4 1000 90 8 4 Hot-dip coating based on Al 84 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 90 / 147 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 12 5 1000 60 9 6 13 4 1000 200 8 6 14 5 1000 200 10 8 15 5 990 60 8 4 16 5 990 65 8 4 17 5 1000 60 10 5 18 5 1000 60 10 5 19 5 1000 60 10 5 20 5 1000 60 10 5 21 5 1000 60 8 4 22 5 1000 60 8 4 Hot-dip coating based on Zn 23 5 1000 60 8 4 24 5 1000 60 8 4 85 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 91 / 147 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 25 5 1000 60 8 4 26 5 1000 60 8 5 27 5 1000 60 8 5 28 5 1000 60 8 5 86 / 128 Petition 870250084126, dated 09 / 18 / 2025, page 92 / 147 Table 2-6 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 29 5 980 96 10 5 30 5 1000 60 8 5 31 5 970 90 10 5 32 5 1000 60 8 5 33 5 1000 60 8 5 Hot-dip coating based on Al 34 5 970 90 10 5 35 5 1000 60 8 5 36 5 1000 60 10 5 37 5 1000 60 10 5 38 5 1000 60 9 4 39 5 1000 60 10 5 40 5 1000 60 10 5 41 5 1000 60 10 6 42 5 1000 60 10 5 87 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 93 / 147 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 43 5 1000 60 9 7 44 5 1000 60 9 7 45 5 1000 60 9 4 46 5 1000 60 9 6 47 5 1000 60 9 7 48 5 1000 60 8 7 49 5 1000 60 10 5 50 5 1000 60 8 4 51 5 1000 60 9 4 52 5 1000 60 10 4 53 5 1000 60 10 5 54 5 1000 60 9 6 55 5 1000 60 9 5 56 5 1000 60 10 6 88 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 94 / 147 Table 2-7 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 57 5 1000 60 10 6 58 5 1000 60 10 6 59 5 1000 60 9 5 60 5 1000 60 8 5 61 5 1000 60 8 6 62 5 1000 60 10 6 63 5 1000 60 9 5 64 5 1000 60 9 6 65 5 1000 60 8 5 66 5 1000 60 10 6 67 5 1000 60 10 6 68 5 1000 60 8 5 69 5 1000 60 10 5 70 5 1000 60 9 5 89 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 95 / 147 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 71 5 1000 60 9 5 72 5 1000 60 10 6 73 5 1000 60 10 6 74 2 1000 60 9 6 75 1 1000 60 10 6 76 5 952 60 10 5 77 5 1190 60 9 6 78 5 940 60 10 6 79 5 1230 60 10 6 80 5 1000 1 8 6 81 5 1000 1200 9 6 82 5 1000 0 10 6 83 5 1000 1250 8 5 84 5 1000 15 14 5 90 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 96 / 147 Table 2-8 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 85 5 1000 60 20 5 86 5 1000 60 10 9 87 5 1000 60 10 12 88 5 1000 60 9 6 89 5 1000 60 9 5 90 5 1000 60 8 6 91 5 1000 60 9 5 92 5 1000 60 9 6 93 5 1000 60 9 5 94 5 1000 60 8 6 95 5 1000 60 9 6 96 5 1000 60 9 6 97 5 1000 60 10 6 91 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 97 / 147 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 98 5 1000 60 10 5 99 5 1000 60 9 5 100 5 1000 60 9 5 101 5 1000 60 9 5 102 5 1000 60 8 5 103 5 1000 60 8 6 104 5 1000 60 8 7 105 5 1000 60 9 5 106 5 1000 60 9 5 107 5 1000 60 9 5 108 45 1000 60 10 6 109 5 980 95 10 5 92 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 98 / 147 Test No. Manufacturing Method Preliminary Heat Treatment Step Coating Step Average Heating Rate (°C / s) Preliminary Heat Treatment Temperature (°C) Holding Time (s) Average Cooling Rate from Preliminary Heat Treatment Temperature to 100°C or Lower (°C / s) Average Cooling Rate between 700°C and 500°C (°C / s) Coating Type 110 5 1000 60 9 5 Hot-dip coating based on Zn 111 5 1000 60 10 5 112 5 1000 60 10 5 113 5 1000 60 10 5 93 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 99 / 147 Table 2-9 Experiment No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 1 5 900 60 700 90 2 5 920 60 715 115 3 5 900 60 705 120 4 5 900 60 703 110 5 5 900 60 707 125 6 5 918 59 720 116 7 6 900 58 725 120 8 8 960 55 780 95 9 5 920 60 750 120 10 7 950 60 790 90 11 5 900 60 720 120 12 5 900 60 725 105 13 6 920 60 790 120 14 6 920 60 795 125 94 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 100 / 147 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 15 5 900 30 700 100 16 5 900 30 700 100 17 5 900 60 740 110 18 5 900 60 745 110 19 5 900 60 750 100 20 5 900 60 753 105 21 5 900 60 754 110 22 5 900 60 755 111 23 5 900 60 755 112 24 5 900 60 746 110 25 5 900 60 750 113 26 5 900 60 742 110 27 5 900 60 743 105 28 5 900 60 744 111 95 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 101 / 147 Table 2-10 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 29 5 900 60 700 90 30 5 900 60 740 107 31 5 890 60 751 120 32 5 900 60 740 106 33 5 900 60 740 105 34 5 890 60 750 105 35 5 900 60 740 108 36 5 900 60 742 105 37 5 900 60 743 104 38 5 900 60 745 105 39 5 900 60 740 108 40 5 900 60 740 110 41 5 900 60 760 100 42 5 900 60 755 100 96 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 102 / 147 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 43 5 900 60 754 109 44 5 900 60 755 103 45 5 900 60 765 109 46 6 920 60 761 109 47 5 900 60 755 108 48 5 900 60 754 101 49 5 900 60 768 102 50 5 900 60 757 109 51 5 900 60 766 105 52 5 900 60 762 106 53 5 900 60 757 104 54 5 900 60 759 107 55 5 900 60 753 107 56 5 900 60 757 108 97 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 103 / 147 Table 2-11 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 57 5 900 60 759 101 58 5 900 60 754 100 59 5 900 60 751 100 60 5 900 60 763 103 61 5 900 60 752 105 62 5 900 60 764 104 63 5 900 60 750 102 64 5 900 60 756 105 65 5 900 60 751 102 66 5 900 60 764 100 67 5 900 60 752 101 68 5 900 60 762 102 69 5 900 60 754 101 70 5 900 60 756 101 98 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 104 / 147 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 71 5 900 60 752 105 72 5 900 60 770 100 73 5 900 60 768 100 74 5 900 60 756 104 75 5 900 60 752 105 76 5 900 60 753 100 77 5 900 60 762 102 78 5 900 60 755 101 79 5 900 60 752 102 80 5 900 60 762 103 81 5 900 60 757 104 82 5 900 60 759 103 83 5 900 60 758 101 84 5 900 60 753 103 99 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 105 / 147 Table 2-12 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 85 5 900 60 759 102 86 5 900 60 751 102 87 5 900 60 757 101 88 2 900 60 756 102 89 49 900 60 750 105 90 0.5 900 60 753 103 91 60 900 60 765 103 92 5 840 60 760 103 93 5 1090 60 759 101 94 5 800 60 753 100 95 5 1150 60 751 101 96 5 900 10 765 104 97 5 900 600 764 100 98 5 900 5 764 100 100 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 106 / 147 Test No. Manufacturing Method Hot Stamping Step Average Heating Rate (°C / s) Heating Temperature in Hot Stamping (°C) Holding Time (s) Initial Forming Temperature (°C) Average Cooling Rate to 250°C (°C / s) 99 5 900 650 756 100 100 5 900 60 660 102 101 5 900 60 600 105 102 5 900 60 759 20 103 5 900 60 759 5 104 5 900 60 750 100 105 40 860 20 750 100 106 20 860 20 750 100 107 5 900 60 760 105 108 5 900 60 758 100 109 5 900 60 700 90 110 5 900 60 755 102 111 5 900 60 750 115 112 5 900 60 756 116 113 5 900 60 755 100 101 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 107 / 147 102 / 128

[00241] Regarding the body formed by hot stamping obtained, the microstructure at the 1 / 4 depth position and the microstructure of a portion of the surface layer were observed as described above, and the area proportions of the microstructures were obtained. Although not shown in the tables, with the exception of ferrite in the portion of the surface layer, more than 5.0% martensite and / or bainite and less than 5.0% retained austenite and / or pearlite were included in the total.

[00242] Furthermore, in the microstructure at the 1 / 4 depth position, the number density of an iron-based carbide present in martensite that has a circular equivalent diameter greater than 0.5 μm and the average distance between the iron-based carbide and another iron-based carbide closest to it that has a circular equivalent diameter greater than 0.5 μm were obtained.

[00243] In addition, the decarbonization index and decarbonization depth were obtained.

[00244] The results are shown in Tables 3-1 to 3-4. In the examples where hot-dip coating based on Zn or hot-dip coating based on Al was performed, a coating containing primarily an Fe-Zn based alloy or a coating containing primarily an Fe-Al based alloy was formed with a thickness of 30 μm. Petition 870250084126, dated 09 / 18 / 2025, pp. 108 / 147 Table 3-1 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 1 1.60 0.5 99.0 0.3 0.7 0.008 9.0 10.5 0.050 15 Fe-Zn 30 2 1.60 0.8 98.0 0.6 1.4 0.012 7.0 12.6 0.139 107 3 1.60 6.0 97.0 0.8 2.2 0.025 4.5 9.8 0.200 140 4 1.60 0.6 89.0 0.5 10.5 0.006 10.0 10.9 0.050 20 5 1.60 0.3 99.0 0.3 0.7 0.060 2.8 10.0 0.160 125 6 1.60 0.1 98.0 0.3 1,7 0.016 6.8 11.3 0.070 20 7 1.60 1.5 98.0 1.0 1.0 0.011 8.4 10.6 0.171 130 8 1.60 2.0 95.0 3.5 1.5 0.007 12.0 13.0 0.170 130 9 1.60 0.1 97.5 0.1 2.4 0.060 2.9 11.5 0.060 18 10 1.60 2.3 94.0 6.0 0.0 0.006 16.0 12.6 0.168 128 11 1.60 2.5 97.5 0.3 2.2 0.005 15.0 12.4 0.140 110 Fe-AI 30 12 1.60 0.0 100.0 0.0 0.0 0.043 3.7 9.6 0.040 12, 103 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 109 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 13 1.60 0.0 100.0 0.0 0.0 0.044 3.2 9.4 0.049 15 14 1.60 0.0 100.0 0.0 0.0 0.068 2.4 9.0 0.049 15 15 1.60 1.9 90.0 0.3 9.7 0.018 6.7 10.8 0.150 120 16 1.60 1.8 90.0 0.3 9.7 0.019 6.6 10.5 0.150 119 17 1.60 2.0 99.0 0.1 0.9 0.014 8.2 11.5 0.020 10 18 1.60 2.0 98.0 0.0 2.0 0.012 8.0 11.1 0.020 10 19 1.60 1.0 99.0 0.1 0.9 0.016 6.5 10.1 0.020 10 20 1.60 1.0 99.0 0.1 0.9 0.016 6.7 9.9 0.020 10 21 1.60 0.0 100.0 0.0 0.0 0.012 8.1 10.0 0.140 110 22 1.60 0.5 98.0 0.2 1.8 0.014 8.3 9.8 0.139 108 Fe-Zn 30 23 1.60 0.9 96.0 1.0 3.0 0.015 7.8 10.3 0.149 119 24 1.60 0.0 100.0 0.0 0.0 0.014 8.0 10.2 0.140 109 25 1.60 1.0 93.0 0.8 6.2 0.016 6.8 10.4 0.150 120 104 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 110 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 26 1.60 2.0 88.0 0.2 11.8 0.031 4.1 10.3 0.030 12 27 1.60 0.0 99.0 0.1 0.9 0.012 8.5 9.8 0.138 103 28 1.60 0.2 100.0 0.0 0.0 0.012 6.8 11.6 0.138 102 105 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 111 / 147 Table 3-2 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 29 1.60 1.0 90.0 0.1 9.9 0.010 9.0 10.6 0.050 15 30 1.60 o,o 100.0 o,o 0.0 0.019 5.5 8.1 0.030 12 31 1.60 0.0 97.0 0.1 2.9 0.006 11.0 12.1 0.010 5 32 1.60 0.2 100.0 0.0 0.0 0.012 8.3 11.8 0.140 110 33 1.60 0.0 100.0 0.0 0.0 0.014 8.3 12.0 0.140 112 Fe-AI 30 34 1.60 0.3 78.0 0,1 21.9 0.008 12.3 12.1 0.010 5 35 1.60 0.0 98.0 0.3 1.7 0.019 5.3 11.7 0.170 130 36 1.60 0.3 97.0 0.0 3.0 0.014 8.4 12.6 0.151 120 37 1.60 0.2 99.0 0.1 0.9 0.018 6.0 10.3 0.157 123 38 1.60 0.3 99.0 0.2 0.8 0.017 8.2 9.5 0.148 118 39 1.60 1.0 89.0 0.1 10.9 0.014 8.1 11.0 0.030 12 40 1.60 1.0 100.0 0.0 0.0 0.016 7.1 9.3 0.030 12 106 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 112 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 41 1.60 0.6 100.0 0.0 0.0 0.008 9.8 6.4 0.150 120 42 1.60 0.8 99.0 0.1 0.9 0.028 4.3 10.8 0.156 122 43 1.60 0.5 97.0 0.2 2.8 0.018 7.0 9.8 0.157 123 44 1.60 0.0 95.3 4.7 0.0 0.020 5.4 10.2 0.160 127 45 1.60 0.2 98.0 0.1 1.9 0.024 5.1 10.2 0.155 119 46 1.60 0.3 98.0 0.3 1.7 0.015 7.9 10.1 0.155 120 47 1.60 0.1 100.0 0.0 0.0 0.019 5.6 10.2 0.156 122 48 1.60 0.2 99.0 0.3 0.7 0.015 7.8 10.1 0.150 120 49 1.60 0.2 99.0 0.1 0.9 0.026 4.7 9.8 0.155 120 50 1.60 0.2 99.0 0.3 0.7 0.016 7.6 10.0 0.150 120 51 1.60 0.3 100.0 0.0 0.0 0.026 4.9 9.9 0.155 121 52 1.60 0.2 98.0 0.3 1.7 0.020 5.4 9.8 0.156 122 53 1.60 0.2 97.0 0.3 2.7 0.023 5.3 9.9 0.154 119 107 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 113 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 54 1.60 0.1 100.0 0.0 0.0 0.028 4.4 10.1 0.153 121 55 1.60 o.1 99.0 o.1 0.9 0.027 4.5 10.2 0.150 120 56 1.60 0.2 98.0 0.1 1.9 0.025 4.9 9.8 0.151 120 108 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 114 / 147 Table 3-3 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 57 1.60 0.6 99.0 0.1 0.9 0.010 9.5 7.8 0.150 120 58 1.60 0.6 100.0 o,o 0.0 0.007 11.3 8.1 0.150 120 59 1.60 1.0 100.0 0.0 0.0 0.011 9.3 7.4 0.155 121 60 1.60 1.0 100.0 0.0 0.0 0.009 8.3 7.8 0.155 121 61 1.60 0.9 100.0 0.0 0.0 0.010 9.9 6.8 0.154 121 62 1.60 0.6 100.0 0.0 0,0 0.009 10.0 6.2 0.150 120 63 1.60 0.9 100.0 0.0 0.0 0.002 16.8 6.2 0.155 121 64 1.60 0.9 99.0 0.1 0.9 0.032 3.9 6.5 0.156 121 65 3.00 0.0 100.0 0.0 0.0 0.016 7.7 11.5 0.030 13 66 1.60 1.2 100.0 0.0 0.0 0.010 8.1 6.8 0.164 127 67 0.80 1.2 100.0 0.0 0.0 0.007 11.5 6.2 0.163 126 68 1.60 0.4 100.0 0.0 0.0 0.014 7.2 6.5 0.140 111. 109 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 115 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 69 1.60 5.2 100.0 0.0 0.0 0.006 13.4 6.6 0.170 130 70 1.60 0.1 100.0 0.0 0.0 0.012 8.8 6.5 0.162 125 71 1.60 15.0 100.0 0.0 0.0 0.008 11.2 6.7 0.180 135 72 1.60 0.0 100.0 0.0 0.0 0.009 9.6 6.3 0.090 40 73 1.60 4.0 100.0 0.0 0.0 0.007 9.9 6.4 0.200 145 74 1.60 1.2 100.0 0.0 0.0 0.003 15.8 14.7 0.163 126 75 1.60 1.0 100.0 0.0 0.0 0.003 16.4 20.5 0.166 127 76 1.60 1.0 99.0 0.2 0.8 0.032 3.8 6.1 0.155 120 77 1.60 0.5 100.0 0.0 0.0 0.002 19.7 16.8 0.150 119 78 1.60 0.9 99.0 0.1 0.9 0.064. 2.7 6.1 0.154 120 79 1.60 2.0 100.0 0.0 0.0 0.002 22.3 20.8 0.150 119 80 1.60 0.9 99.0 0.1 0.9 0.046 3.1 6.2 0.154 119 81 1.60 0.9 100.0 0.0 0.0 0.004 15.1 15.4 0.155 120 110 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 116 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 pm (particles / pm2) Average distance between the iron-based carbide and the nearest other iron-based carbide (pm) Grain size of previous austenite (pm) Type Thickness (pm) 82 1.60 07 99.0 0.2 0.8 0.056 2.9 6.2 0.154 120 83 1.60 0.8 100.0 0.0 0.0 0.003 19.9 20.2 0.154 120 84 1.60 0.9 100.0 0.0 0.0 0.014 5.9 6.3 0.154 120 111 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 117 / 147 Table 3-4 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 μm (particles^m2) Average distance between the iron-based carbide and the nearest other iron-based carbide (^m) Grain size of previous austenite (^m) Type Thickness (^m) 85 1.60 0.9 99.0 0.1 0.9 0.016 2.9 6.4 0.154 120 86 1.60 1.0 100.0 0.0 0.0 0.015 5.2 6.2 0.155 121 87 1.60 0.9 99.0 0.2 0.8 0.018 1.4 6.4 0.154 120 88 1.60 1.0 100.0 0.0 0.0 0.007 9.4 13.7 0.155 121 89 1.60 1.0 99.0 0.3 0.7 0.043 3.3 5.9 0.155 121 90 1.60 0.8 100.0 0.0 0.0 0.006 10.7 20.4 0.153 119 91 1.60 1.2 98.0 0.2 1.8 0.059 2.9 5.4 0.156 123 92 1.60 0.7 96.0 0.2 3.8 0.018 5.4 5.5 0.152 118 93 1.60 0.7 100.0 0.0 0.0 0.006 11.1 14.6 0.152 118 94 1.60 4.5 78.0 0.5 21.5 0.058 2.9 5.6 0.153 119 95 1.60 0.0 100.0 0.0 0.0 0.003 18.0 26.5 0.140 108 96 1.60 0.9 99.0 0.3 0.7 0.030 4.2 6.1 0.154 119 112 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 118 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 μm (particles^m2) Average distance between the iron-based carbide and the nearest other iron-based carbide (^m) Grain size of previous austenite (^m) Type Thickness (^m) 97 1.60 1.1 100.0 0.0 0.0 0.007 10.8 13.8 0.156 123 98 1.60 0.8 96.0 0.2 3.8 0.055 2.9 6.1 0.153 118 99 1.60 1.3 100.0 0.0 0.0 0.006 17.2 20.5 0.156 122 100 1.60 0.9 85.0 0.4 14.6 0.009 10.4 6.4 0.154 119 101 1.60 0.7 75.0 0.2 24.8 0.010 10.1 6.5 0.154 119 102 1.60 0.6 83.0 0.3 16.7 0.012 6.3 6.4 0.150 118 103 1.60 50.0 21.0 0.2 78.8 0.014 6.0 6.4 0.155 121 104 1.60 0.2 98.7 0.3 1.0 0.016 7.6 10.0 0.140 108 105 1.60 0.0 82.0 0.0 18.0 0.030 4.0 1.2 0.153 118 106 1.60 0.0 90.0 0.0 10.0 0.025 4.5 3.0 0.154 120 107 1.60 3.6 100.0 0.0 0.0 0.010 9.4 5.2 0.155 120 108 1.60 0.4 100.0 0.0 0.0 0.038 3.8 6.1 0.152 117 109 1.60 9.0 97.0 0.0 3.0 0.007 11.0 10.7 0.230 170 113 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 119 / 147 Test No. Body formed by hot stamping Sheet thickness (Thickness of the flat portion) (mm) Microstructure Decarburization index Decarburization depth (pm) Coating Surface layer portion at 1 / 4 depth Ferrite area ratio (%) Martensite area ratio (%) Retained austenite area ratio (%) Remaining area ratio (%) Number density of iron-based carbide present in martensite and having a circular equivalent diameter of more than 0.5 μm (particles^m2) Average distance between the iron-based carbide and the nearest other iron-based carbide (^m) Grain size of previous austenite (^m) Type Thickness (^m) 110 1.60 0.0 100.0 0.0 0.0 0.007 9.9 6.3 0.000 0 111 1.60 1.0 99.4 0.1 0.5 0.026 6.5 8.3 0.020 10 112 1.60 1.2 99.2 0.3 0.5 0.023 6.9 8.6 0.020 10 113 1.60 0.7 99.2 0.1 0.7 0.030 3.9 6.2 0.155 120 114 / 128 Petition 870250084126, dated 09 / 18 / 2025, pp. 120 / 147 115 / 128

[00245] A sample was collected from a portion of the top plate of the body formed by hot stamping into a hat shape and the tensile strength was measured as follows.

[00246] In addition, bending capacity and crack propagation resistance characteristics were evaluated as impact resistance characteristics.

[00247] The results are shown in Tables 3-5 to 3-8. Tensile Strength

[00248] From a top portion of the hot-stamped sheet metal, a reduced-size sheet-shaped test specimen (parallel portion length: 32 mm, parallel portion width: 6.25 mm) according to ASTM A370: 2022 was collected, maintaining the material thickness (in a case where a coating was provided, without excluding the coating) so that the tensile direction was parallel to the rolling direction, and a tensile test according to JIS Z 2241: 2022 was performed, with a calibration length of 25.0 mm and a crosshead separation rate of 1.0 mm / min at 20°C to obtain a tensile strength.Tensile strength was calculated as a value obtained by dividing the maximum test force by the cross-sectional area obtained by multiplying the material thickness (in a case where a coating was provided, the material thickness was a measured thickness excluding the coating thickness) by the width of the parallel portion of 6.25 mm.

[00249] In a case where the tensile strength was 1,500 MPa or more, it was determined that the steel plate had high strength. Folding Capability

[00250] From a top sheet of the body formed by hot stamping, a sample 30 mm wide Petition 870250084126, dated 09 / 18 / 2025, pp. 121 / 147 A 116 / 128 mm (direction orthogonal to the rolling) and 60 mm long (direction of the rolling) sample was collected, maintaining the thickness of the hot-stamped body material (in a case where a coating was provided, without excluding the coating), and with this sample, a bending test was performed so that the direction of a bending edge was orthogonal to the rolling. The bending test was performed according to the VDA238100:2017 standard and the maximum bending angle was obtained.

[00251] In a case where the product of tensile strength and maximum bending angle was 80,000 (MPa^degree) or more, the bending capacity was determined to be excellent. In a case where the product of tensile strength and maximum bending angle was 90,000 (MPa^degree) or more, the bending capacity was determined to be excellent, and in a case where the product was 100,000 (MPa^degree) or more, the bending capacity was determined to be even better. Crack propagation resistance characteristics

[00252] Crack propagation resistance characteristics were obtained by a test in accordance with JIS Z 2242: 2018 and JIS B 7755: 2011 standards. Specifically, from a portion of the top plate of the hot-stamped formed body, a test specimen with a size of 10 mm wide and 55 mm long was collected while maintaining the thickness of the hot-stamped formed body material (in a case where a coating was provided, without excluding the coating) so that the rolling direction was in a direction along the length of the test specimen and a V-notch (notch angle: 45°, notch root radius: 0.25 mm, notch root width: 8 mm, notch position (center): a position 27.5 mm away from an end portion in the direction along the length of the test specimen) with a Petition 870250084126, dated 09 / 18 / 2025, pp. 122 / 147 117 / 128 a depth of 2 mm was formed in the specimen. Then, three specimens were stacked, fixed with a screw and subjected to an instrumented impact test. In the present document, in a case where the plate thickness was 2.00 mm or less, three specimens were stacked to perform the test and, in a case where the plate thickness was greater than 2.00 mm, one specimen was used without stacking to perform the test.

[00253] The instrumented impact test was performed at 20°C and an impact moment and force from the beginning to the end of the test were measured. A displacement was calculated from the product of a test speed of the instrumented impact test and the measured time. Since the length of the fracture surface of the Charpy specimen was 8 mm, the average value of the impact forces measured in the region where the displacement was 8 mm or more was defined as the baseline.After subtracting the base from the impact forces at all measurement points, an impact-displacement force curve was created. Since the impact force obtained in the instrumented Charpy test included noise due to inherent vibration, smoothing processing was performed by executing 30-point moving average processing.

[00254] Figure 1 shows an example (schematic diagram) of the impact force-displacement curve. In the obtained impact force-displacement curve, an area under the curve from a displacement of 0 mm to a displacement of 8 mm was calculated, and the value obtained was defined as the total impact energy. Next, the impact force at which a rapid decrease in the impact force-displacement curve began was sought using the procedure described above, and a corresponding displacement (displacement at the moment the cracks were initiated) was obtained. An area under the curve from the displacement of 0 mm to the displacement at the moment the cracks began was then calculated. Petition 870250084126, dated 09 / 18 / 2025, pp. 123 / 147 The number of cracks initiated, 118 / 128, was calculated and defined as the crack initiation energy. A value obtained by subtracting the crack initiation energy from the total impact energy was defined as the crack propagation energy. The ratio between the crack propagation energy and the total impact energy was defined as an index of the crack propagation resistance characteristics. In a case where the ratio between the crack propagation energy and the total impact energy (crack propagation energy / total impact energy) was 0.10 or more, the crack propagation resistance characteristics were determined to be excellent.In a case where the ratio between crack propagation energy and total impact energy was 0.20 or more, the crack propagation resistance characteristics were determined to be even more refined, and in a case where the ratio was 0.30 or more, the crack propagation resistance characteristics were determined to be even more refined. Table 3-5. Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 1 1541 53 81673 0.30 Example of the Invention 2 2313 57 131841 0.28 Example of the Invention 3 2658 41 108978 0.19 Example of the Invention 4 1472 60 88320 0.30 Comparative Example 5 2704 28 75712 0.07 Comparative Example Petition 870250084126, dated 09 / 18 / 2025, pp. 124 / 147 119 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 6 2365 40 94600 0.25 Example of the Invention 7 2324 57 132468 0.30 Example of the Invention 8 2307 65 149955 0.30 Example of the Invention 9 2360 33 77880 0.08 Comparative Example 10 2340 59 138060 0.09 Comparative Example 11 2305 55 Example of Invention 12: 2351 38, 89338 0.16. Example of Invention 13: 2378 35, 83230 0.14. Example of Invention 14: 2444 30, 73320 0.06. Comparative Example 15: 2300 55, 126500 0.12. Example of Invention 16: 2310 56, 129360 0.09. Comparative Example 17: 2070 40, 82800 0.15. Example of Invention 18: 2046 37, 75702 0.08. Comparative Example 19: 2345 35, 82075 0.14 Example of the Invention 20 2347 32 75104 0.09 Comparative Example 21 2335 51 119085 0.23 Example of the Invention 22 2314 51 118014 0.22 Example of the Invention, Petition 870250084126, dated 09 / 18 / 2025, pages 125 / 147 120 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 23 2293 50 114650 0.20 Example of the Invention 24 2324 34 79016 0.09 Comparative Example 25 2289 33 75537 0.09 Comparative Example 26 2278 39 88842 0.14 Example of the Invention 27 2355 55 129525 0.27 Example of the Invention 28 2322 52 120744 0.24 Example of the Invention Table 3-6 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 29 1468 58 85144 0.32 Comparative Example 30 2342 32 74944 0.09 Comparative Example Petition 870250084126, dated 09 / 18 / 2025, pp. 126 / 147 121 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 31 1533 55 84315 0.31 Example of the Invention 32 2330 52 121160 0.25 Example of the Invention 33 2345 49 114905 0.20 Example of the Invention 34 1386 55 76230 0.09 Comparative Example 35 2350 34 79900 0.09 Comparative Example 36 2285 60 Example of the Invention 37 2334 55 128370 0.22 Example of the Invention 38 2355 46 108330 0.16 Example of the Invention 39 1455 55 80025 0.30 Comparative Example 40 2374 33 78342 0.09 Comparative Example 41 2437 54 131598 0.35 Example of the Invention 42 2399 50 119950 0.16 Example of the Invention 43 2405 53 127465 0.21 Example of the Invention Petition 870250084126, dated 09 / 18 / 2025, pp. 127 / 147 122 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 44 2350 50 117500 0.15 Example of the Invention 45 2416 48 115968 0.24 Example of the Invention 46 2442 53 129426 0.25 Example of the Invention 47 2427 52 126204 0.24 Example of the Invention 48 2417 46 111182 0.20 Example of the Invention 49 2414 48 115872 0.22 Example of the Invention 50 2392 50 119600 0.28 Example of the Invention 51 2377 49 116473 0.23 Example of the Invention 52 2410 51 122910 0.24 Example of the Invention 53 2370 50 118500 0.20 Example of the Invention 54 2440 50 122000 0.21 Example of the Invention 55 2391 45 107595 0.19 Example of the Invention 56 2389 46 109894 0.20 Example of the Invention Petition 870250084126, dated 09 / 18 / 2025, pp. 128 / 147 123 / 128 Table 3-7 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 57 2410 49 118090 0.29 Example of the Invention 58 2405 55 132275 0.35 Example of the Invention 59 2417 52 125684 0.31 Example of the Invention 60 2422 56 135632 0.32 Example of the Invention 61 2440 55 134200 0.32 Example of the Invention 62 2444 54 131976 0.36 Example of the Invention 63 2448 62 151776 0.41 Example of the Invention 64 2411 48 115728 0.24 Example of the Invention 65 2410 37 89170 0.30 Example of the Invention 66 2427 56 135912 0.35 Example of the Invention 67 2389 60 143340 0.37 Example of the Invention 68 2444 50 122200 0.28 Example of the Invention 69 2401 65 156065 0.37 Example of the Invention Petition 870250084126, dated 09 / 18 / 2025, pp. 129 / 147 124 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 70 2425 55 133375 0.35 Example of the Invention 71 2378 65 154570 0.34 Example of the Invention 72 2451 44 107844 0.32 Example of the Invention 73 2388 64 152832 0.34 Example of the Invention 74 2399 54 129546 0.38 Example of the Invention 75 2268 35 79380 0.09 Comparative Example 76 2449 47 115103 0.20 Example of the Invention 77 2351 45 105795 0.15 Example of the Invention 78 2408 33 79464 0.08 Comparative Example 79 2277 35 79695 0.08 Comparative Example 80 2378 39 92742 0.13 Example of the Invention 81 2360 47 110920 0.17 Example of the Invention 82 2371 33 78243 0.07 Comparative Example Petition 870250084126, dated 09 / 18 / 2025, pp. 130 / 147 125 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 83 2277 35 79695 0.08 Comparative Example 84 2431 55 133705 0.25 Example of the Invention Table 3-8 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 85 2436 50 121800 0.09 Comparative Example 86 2445 53 129585 0.24 Example of the Invention 87 2439 52 126828 0.05 Comparative Example 88 2297 46 105662 0.20 Example of the Invention 89 2391 43 102813 0.12 Example of the Invention Petition 870250084126, dated 09 / 18 / 2025, pp. 131 / 147 126 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 90 2260 35 79100 0.08 Comparative Example 91 2414 33 79662 0.08 Comparative Example 92 2378 50 118900 0.21 Example of the Invention 93 2286 50 114300 0.23 Example of the Invention 94 2201 35 77035 0.07 Comparative Example 95 2230 35 78050 0.07 Comparative Example 96 2390 45 107550 0.21 Example of the Invention 97 2297 45 103365 0.21 Example of the Invention 98 2341 34 79594 0.09 Comparative Example 99 2267 35 79345 0.09 Comparative Example 100 2250 48 108000 0.26 Example of the Invention 101 2189 36 78804 0.08 Comparative Example 102 2357 51 120207 0.21 Example of the Invention Petition 870250084126, dated 09 / 18 / 2025, pp. 132 / 147 127 / 128 Test No. Body formed by hot stamping Observations Characteristics Resistance Bending capacity Bending capacity Crack propagation resistance characteristics Tensile strength (MPa) Maximum bending angle (degrees) Tensile strength χ Maximum bending angle (MPa^degree) Crack propagation energy / (Crack initiation energy + Crack propagation energy) 103 1296 59 76464 0.09 Comparative Example 104 2400 33 79200 0.08 Comparative Example 105 2380 53 126140 0.22 Example of the Invention 106 2367 55 130185 0.23 Example of the Invention 107 2453 58 142274 0.38 Example of the Invention 108 2397 47 112659 0.16 Example of the Invention 109 1503 105 157815 0.40 Example of the Invention 110 2502 33 82566 0.12 Example of the Invention 111 1834 44 80696 0.18 Example of the Invention 112 2047 43 88021 0.20 Example of the Invention 113 2406 49 117894 0.15 Example of the Invention

[00255] As can be seen from the results in Tables 1-1 to 3-8, in the examples (Examples of the Invention) in which, in bodies formed by hot stamping having a tensile strength of 1,500 MPa or more, the chemical composition, the area proportions Petition 870250084126, dated 09 / 18 / 2025, pp. 133 / 147 128 / 128 in the microstructure at the 1 / 4 depth position, the number density of the iron-based carbide present in the martensite, which has a circular equivalent diameter greater than 0.5 μm, the average distance and grain size of the previous austenite were within the ranges of the present invention, and excellent collision resistance characteristics were obtained.

[00256] In the Comparative Examples, even in a case where the tensile strength was less than 1,500 MPa or 1,500 MPa or greater, one or more of the following chemical composition, the area proportions in the microstructure at the 1 / 4 depth position, the number density of the iron-based carbide present in the martensite and having a circular equivalent diameter greater than 0.5 μm, the average distance of the iron-based carbide present in the martensite and having a circular equivalent diameter greater than 0.5 μm, and the grain size of the previous austenite were outside the range of the present invention. As a result, it was not possible to obtain sufficient impact resistance characteristics. INDUSTRIAL APPLICABILITY

[00257] According to the present invention, it is possible to provide a hot-stamped shaped body that has high strength and excellent impact resistance characteristics. Therefore, the present invention has high industrial applicability. Petition 870250084126, dated 09 / 18 / 2025, pp. 134 / 147

Claims

1 / 4 CLAIMS 1. Body formed by hot stamping, characterized in that it comprises, as a chemical composition, in % by mass: C: 0.20% to 0.70%; Si: 0.010% to 2.000%; Mn: 0% to 2.00%; P: 0.100% or less; S: 0.0100% or less; N: 0.0100% or less; O: 0.0200% or less; Al: 0.0010% to 0.5000%; Mo: 0.0010% to 1.0000%; B: 0.0005% to 0.0100%; Ti: 0.010% to 0.100%; Nb: 0% to 0.100%; Cr: 0% to 1.00%; Co: 0% to 3.00%; Ni: 0% to 3.00%; Cu: 0% to 1.00%; V: 0% to 1.000%; W: 0% to 1.00%; Ca: 0% to 1.0000%; Mg: 0% to 1.0000%; REM: 0% to 1.0000%; Sb: 0% to 1.000%; Zr: 0% to 1.000%; Co: 0% to 1.000%; one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi and Sn: 0% to 1.000% in total; and Petition 870250084126, dated 09 / 18 / 2025, p.135 / 147 2 / 4 remaining: Fe and impurities, wherein, in a case where a strip from a position at 1 / 8 of the thickness to a position at 3 / 8 of the thickness in a thickness direction of a surface is defined as a 1 / 4 depth position, a microstructure at the 1 / 4 depth position includes, by area proportion: martensite: 80.0% or more, and retained austenite: 0.0% or more and less than 5.0%, in the microstructure, at the 1 / 4 depth position, a number density of an iron-based carbide present in the martensite and having a circular equivalent diameter greater than 0.5 μm is less than 0.050 particles^m2 and an average distance between the iron-based carbide and another iron-based carbide closest to the iron-based carbide is 3.0 μm or more, and in the microstructure, at the 1 / 4 depth position At depth, the grain size of the previous austenite is 20.0 μm or less.

2. Body formed by hot stamping, according to claim 1, characterized in that the decarburization index Dc is 0.085 or more.

3. Body formed by hot stamping, according to claim 1 or 2, characterized in that, when a strip from the surface to 50 μm is defined as a portion of the surface layer, a microstructure of the surface layer portion includes, by area proportion: ferrite: more than 5.0%.

4. Body formed by hot stamping, according to claim 1 or 2, characterized in that the chemical composition includes, in % by mass: Petition 870250084126, dated 09 / 18 / 2025, p. 136 / 147 3 / 4 C: more than 0.40% and 0.70% or less, Si: 0.010% to 2.000%, Mn: 0% to 1.00%, P: 0.100% or less, S: 0.0100% or less, N: 0.0100% or less, O: 0.0200% or less, Al: 0.0010% to 0.5000%, Mo: 0.0010% to 1.0000%, B: 0.0005% to 0.0100%, Ti: 0.010% to 0.100%, Nb: 0% to 0.100%, Cr: 0% to 1.00%, Co: 0% to 3.00%, Ni: 0% to 3.00%, Cu: 0% to 1.00%, V: 0% to 1.000%, W: 0% to 1.00%, Ca: 0% to 1.0000%, Mg: 0% to 1.0000%, REM: 0% to 1.0000%, Sb: 0% to 1.000%, Zr: 0% to 1.000%, As: 0% to 1.000%, one or more selected from Ta, Re, Os, Ir, Tc, Pb, Se, Bi and Sn: 0% to 1.000% in total, and a remainder: Fe and impurities.

5. Body formed by hot stamping, according to claim 1 or 2, characterized in that a coating is provided on the surface. Petition 870250084126, dated 09 / 18 / 2025, pp. 137 / 147 4 / 4 6. Body formed by hot stamping, according to claim 5, characterized in that the coating mainly contains an Fe-Al based alloy.

7. Body formed by hot stamping, according to claim 5, characterized in that the coating mainly contains an Fe-Zn based alloy. Petition 870250084126, dated 09 / 18 / 2025, pp. 138 / 147

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