Hot-stamping formed body

Abstract

This hot-stamping formed body has a predetermined chemical composition, in an interior region, a standard deviation of grain sizes of prior austenite grains of 5.0 μm or less, in a surface layer region, an area ratio of bainite of more than 10%, a maximum value of pole density of a texture of 4.0 or less, and a deboronization index of 0.05 or more.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a hot-stamping formed body.

[0002] Priority is claimed on Japanese Patent Application No. 2022-067020, filed Apr. 14, 2022, the content of which is incorporated herein by reference.BACKGROUND ART

[0003] In recent years, there has been a demand for a reduction in a weight of a vehicle body for a vehicle in terms of environmental protection and resource saving, and a high-strength steel sheet has been applied to vehicle members. Vehicle members are manufactured by press forming, but not only a forming load is increased but also the formability deteriorates as the strength of a steel sheet is increased. For this reason, the formability of a high-strength steel sheet into a member having a complicated shape becomes an issue.

[0004] In order to solve this issue, the application of a hot stamping technique in which press forming is performed after a steel sheet is heated up to a high temperature of an austenite range where the steel sheet softens is in progress. Hot stamping is attracting attention as a technique that achieves both the formability of a steel sheet into a vehicle member and strength of a vehicle member by performing hardening of the steel sheet in a die at the same time as press working.

[0005] For example, Patent Document 1 discloses an electrolytic zinc-based plated steel sheet having a high yield ratio and excellent bendability, in which the critical hydrogen amount in the steel is 0.20 mass ppm or less.PRIOR ART DOCUMENTPatent Document

[0006] [Patent Document 1] PCT International Publication No. WO2020 / 079925Non-Patent Document

[0007] Non-Patent Document 1: Acta Materialia, 58 (2010), 6393-6403DISCLOSURE OF THE INVENTIONProblems to be Solved by the Invention

[0008] In order to make vehicle members lighter, it is effective to increase the strength of steel sheets. In order to increase the strength of the steel sheets, there is a method of increasing the Mn content in order to improve hardenability of the steel sheet. However, increasing the Mn content poses problems such as hydrogen embrittlement cracking and early fracture.

[0009] Hydrogen embrittlement cracking is a phenomenon in which a steel member, to which high stress is applied in use, suddenly fractures due to hydrogen which is irrupted into the steel from an external environment. This phenomenon is also called delayed fracture due to the mode of the occurrence of fracture. It is generally known that hydrogen embrittlement cracking is more likely to occur in the steel sheet as tensile strength of the steel sheet increases. It is considered that this is because the higher tensile strength of the steel sheet, the greater residual stress in the steel sheet after a component is formed. This susceptibility to hydrogen embrittlement cracking (delayed fracture) is called hydrogen embrittlement resistance.

[0010] Early fracture is a phenomenon in which fracture occurs at a stress lower than tensile strength estimated from the hardness of the steel member. This susceptibility to early fracture is called early fracture resistance:

[0011] In Patent Document 1, bendability is considered, but hydrogen embrittlement resistance and early fracture resistance are not considered.

[0012] The present invention has been made in view of the above-mentioned problem. An object of the present invention is to provide a hot-stamping formed body having high strength, and excellent hydrogen embrittlement resistance and early fracture resistance.Means for Solving the Problem

[0013] The gist of the present invention is as follows.

[0014] [1] A hot-stamping formed body according to an aspect of the present invention comprising, as a chemical composition, by mass %;

[0015] C: more than 0.40% and 0.70% or less;

[0016] Si: 0.010% to 3.00%;

[0017] Mn: 0.60% to 3.00%;

[0018] P: 0.100% or less;

[0019] S: 0.0100% or less;

[0020] N: 0.0200% or less;

[0021] O: 0.0200% or less;

[0022] Al: 0.0010% to 0.5000%;

[0023] Nb: 0.0010% to 0.100%;

[0024] Ti: 0.010% to 0.200%;

[0025] Cr: 0.01% to 0.80%;

[0026] Mo: 0.0010% to 1.000%;

[0027] B: 0.0005% to 0.0200%;

[0028] Co: 0% to 4.00%;

[0029] Ni: 0% to 3.00%;

[0030] Cu: 0% to 3.00%;

[0031] V: 0% to 3.00%;

[0032] W: 0% to 3.00%;

[0033] Ca: 0% to 1.000%;

[0034] Mg: 0% to 1.000%;

[0035] REM: 0% to: 1.000%;

[0036] Sb: 0% to 1.000%;

[0037] Sn: 0% to 1.000%;

[0038] Zr: 0% to 1.000%;

[0039] As: 0% to 0.100%; and

[0040] a remainder: Fe and impurities, in an interior region, which is a region between 4 / 16 depth of a sheet thickness from a surface of the hot-stamping formed body and 5 / 16 depth of the sheet thickness from the surface,

[0041] a standard deviation of grain sizes of prior austenite grains is 5.0 μm or less,

[0042] in a surface layer region, which is a region between the surface and 1 / 25 depth of the sheet thickness from the surface,

[0043] an area ratio of bainite is more than 10%,

[0044] a maximum value of pole density of a texture is 4.0 or less, and

[0045] a deboronization index is 0.05 or more.

[0046] [2] The hot-stamping formed body according to [1] may comprise, as the chemical composition, by mass %, one or more selected from the group consisting of:

[0047] Co: 0.01% to 4.00%;

[0048] Ni: 0.01% to 3.00%;

[0049] Cu: 0.01% to 3.00%;

[0050] V: 0.01% to 3.00%;

[0051] W: 0.01% to 3.00%;

[0052] Ca: 0.001% to 1.000%;

[0053] Mg: 0.001% to 1.000%;

[0054] REM: 0.001% to 1.000%;

[0055] Sb: 0.001% to 1.000%;

[0056] Sn: 0.001% to 1.000%;

[0057] Zr: 0.001% to 1.000%; and

[0058] As: 0.001% to 0.100%.Effects of the Invention

[0059] According to the above-described aspects of the present invention, it is possible to provide a hot-stamping formed body having high strength, excellent hydrogen embrittlement resistance and early fracture resistance.BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1 A FIGURE explaining the method to obtain a deboronization index.EMBODIMENTS OF THE INVENTION

[0061] The present inventors found that by reducing the standard deviation of grain sizes of prior austenite grains in the interior region, hydrogen embrittlement resistance and early fracture resistance of the hot-stamping formed body can be improved. In addition, the present inventors found that in the surface layer region, by generating a desired amount of bainite, by creating the texture with a desired crystal orientation, and by achieving a desired deboronization index, hydrogen embrittlement resistance can be further improved.

[0062] The present inventors found that in order to obtain a hot-stamping formed body having the above features, it is particularly effective to perform finish rolling and annealing under desired conditions during manufacturing of a steel sheet for hot stamping.

[0063] Hereinafter, the hot-stamping formed body according to the present embodiment will be described in detail. First, the reason the chemical composition of the hot-stamping formed body according to the present embodiment is limited will be described.

[0064] A limited numerical range described using “to” described below includes a lower limit and an upper limit. Numerical values represented using “less than” or “more than” are not included in a numerical range. All percentages (%) related to the chemical composition mean mass %.

[0065] The hot-stamped formed body according to the present embodiment comprises, as a chemical composition, by mass %, C: more than 0.40% and 0.70% or less, Si: 0.010% to 3.00%, Mn: 0.60% to 3.00%, P: 0.100% or less, S: 0.0100% or less, N: 0.0200% or less, O: 0.0200% or less, Al: 0.0010% to 0.5000%, Nb: 0.0010% to 0.100%, Ti: 0.010% to 0.200%, Cr: 0.01% to 0.80%, Mo: 0.0010% to 1.000%, B: 0.0005% to 0.0200%, and a remainder: Fe and impurities. Each element will be described below.C: More than 0.40% and 0.70% or Less

[0066] C is an element that improves the strength of the hot-stamping formed body. When the C content is 0.40% or less, a desired strength of the hot-stamping formed body cannot be obtained. For this reason, the C content is set to more than 0.40%. The C content is preferably 0.42% or more or 0.44% or more.

[0067] Meanwhile, when the C content is more than 0.70%, toughness of martensite deteriorates and excellent hydrogen embrittlement resistance cannot be obtained. For this reason, the C content is set to 0.70% or less. The C content is preferably 0.65% or less or 0.60% or less.Si: 0.010% to 3.00%

[0068] Si is an element that improves strength of the hot-stamping formed body by solid-solution strengthening. When the Si content is less than 0.010%, a desired strength cannot be obtained. For this reason, the Si content is set to 0.010% or more. The Si content is preferably 0.05% or more, 0.10% or more or 0.15% or more.

[0069] Meanwhile, when the Si content is more than 3.00%, the amount of ferrite increases and a desired microstructure cannot be obtained. For this reason, the Si content is set to 3.00% or less. The Si content is preferably 2.00% or less, 1.00% or less or 0.70% or less.Mn: 0.60% to 3.00%

[0070] Mn promotes the transformation from prior austenite to pearlite in a hot-rolled steel sheet having the chemical composition of the present embodiment, and contributes to control of grain size distribution of prior austenite of the hot-stamping formed body. In order to set the standard deviation of grain sizes of prior austenite grains, the Mn content is set to 0.60% or more. The Mn content is preferably 0.70% or more or 1.00% or more.

[0071] Meanwhile, when the Mn content is more than 3.00%, transformation from prior austenite to pearlite in a hot-rolled steel sheet having the chemical composition of the present embodiment is excessively promoted, and the standard deviation of grain sizes of prior austenite grains in the hot-stamping formed body cannot be set to a desired range. For this reason, the Mn content is set to 3.00% or less. The Mn content is preferably 2.50% or less or 2.30% or less.P: 0.100% or Less.

[0072] P is an impurity element, and by segregating in the grain boundaries, it becomes a starting point for fracture and deteriorates early fracture resistance. For this reason, the P content is set to 0.100% or less. The P content is preferably 0.050% or less or 0.010% or less.

[0073] The lower limit of the P content is not particularly limited, but may be 0%. However, when the P content is reduced to less than 0.0001%, the dephosphorization cost increases significantly, which is not preferable economically. For this reason, the P content may be set to 0.0001% or more, 0.001% or more or 0.005% or more.S: 0.0100% or Less

[0074] S is an impurity element, and forms inclusions in steel. The inclusions become starting points for fracture and deteriorate early fracture resistance. For this reason, the S content is set to 0.0100% or less. The S content is preferably 0.0080% or less, 0.0050% or less or 0.0030% or less.

[0075] The lower limit of the S content is not particularly limited, but may be 0%. However, when the S content is reduced to less than 0.0001%, the desulfurization cost increases significantly, which is not preferable economically. For this reason, the S content may be set to 0.0001% or more, 0.0002% or more, 0.0003% or more or 0.0010% or more.N: 0.0200% or Less

[0076] N is an impurity element, and forms nitrides in steel. The nitrides become starting points for fracture and deteriorate early fracture resistance. For this reason, the N content is set to 0.0200% or less. The N content is preferably 0.0150% or less, 0.0100% or less, 0.0060% or less or 0.0040% or less.

[0077] The lower limit of the N content is not particularly limited, but may be 0%. However, when the N content is reduced to less than 0.0001%, the denitrification cost increases significantly, which is not preferable economically. For this reason, the N content may be set to 0.0001% or more or 0.0010% or more.O: 0.0200% or Less

[0078] O forms a coarse oxide that becomes a starting point for fracture in steel when a large amount of O is comprised, and deteriorates early fracture resistance of the hot-stamping formed body. For this reason, the O content is set to 0.0200% or less. The O content is preferably 0.0100% or less, 0.0070% or less or 0.0040% or less.

[0079] The O content may be 0%, in order to disperse many oxides during deoxidizing of molten steel, the O content may be set to 0.0005% or more or 0.0010% or more.Al: 0.0010% to 0.5000%

[0080] Al is an element having an effect of deoxidizing molten steel and achieving soundness of the steel. When the Al content is less than 0.0010%, deoxidation is not sufficiently performed, and coarse oxides are generated and early fracture resistance deteriorates. For these reasons, the Al content is set to 0.0010% or more. The Al content is preferably 0.0050% or more, 0.0100% or more or 0.0300% or more.

[0081] Meanwhile, when the Al content is more than 0.5000%, coarse oxides are generated in steel, and early fracture resistance of the hot-stamping formed body deteriorates. For this reason, the Al content is set to 0.5000% or less. The Al content is preferably 0.4000% or less, 0.3000% or less, or 0.2000% or less or 0.1000% or less.Nb: 0.0010% to 0.100%

[0082] Nb is an element that forms carbonitride in steel and improves strength of the hot-stamping formed body by precipitation strengthening. When the Nb content is less than 0.0010%, a desired strength cannot be obtained. For this reason, the Nb content is set to 0.0010% or more. The Nb content is preferably 0.005% or more, 0.009% or more or 0.015% or more.

[0083] Meanwhile, when the Nb content is more than 0.100%, many carbonitrides are generated in steel, and early fracture resistance of the hot-stamping formed body deteriorates. For this reason, the Nb content is set to 0.100% or less. The Nb content is preferably 0.080% or less or 0.060% or less.Ti: 0.010% to 0.200%

[0084] Ti is an element that forms carbonitride in steel and improves strength of the hot-stamping formed body by precipitation strengthening. When the Ti content is less than 0.010%, a desired strength cannot be obtained. For this reason, the Ti content is set to 0.010% or more. The Ti content is preferably 0.020% or more or 0.025% or more.

[0085] Meanwhile, when the Ti content is more than 0.200%, many carbonitrides are generated in steel, and early fracture resistance of the hot-stamping formed body deteriorates. For this reason, the Ti content is set to 0.200% or less. The Ti content is preferably 0.150% or less, 0.100% or less, 0.080% or less, 0.060% or less or 0.050% or less.Cr: 0.01% to 0.80%

[0086] Cr is an element that increases strength of the hot-stamping formed body by dissolving in prior austenite grains during heating before hot stamping. When the Cr content is less than 0.01%, a desired strength cannot be obtained. For this reason, the Cr content is set to 0.01% or more. The Cr content is preferably 0.10% or more, 0.15% or more or 0.20% or more.

[0087] Meanwhile, when the Cr content is more than 0.80%, coarse intermetallic compounds are formed in the hot-stamping formed body and early fracture resistance deteriorates. For this reason, the Cr content is set to 0.80% or less. The Cr content is preferably 0.70% or less, 0.50% or less or 0.40% or less.Mo: 0.0010% to 1.000%

[0088] Mo is an element that increases strength of the hot-stamping formed body by dissolving in prior austenite grains during heating before hot stamping. When the Mo content is less than 0.0010%, a desired strength cannot be obtained. For this reason, the Mo content is set to 0.0010% or more. The Mo content is preferably 0.010% or more, 0.050% or more or 0.100% or more.

[0089] Meanwhile, when the Mo content is more than 1.000%, coarse intermetallic compounds are formed in the hot-stamping formed body and early fracture resistance deteriorates. For this reason, the Mo content is set to 1.000% or less. The Mo content is preferably 0.800% or less, 0.600% or less or 0.400% or less.B: 0.0005% to 0.0200%

[0090] B is an element that improves the hardenability of steel. When the B content is less than 0.0005%, a desired strength cannot be obtained. For this reason, the B content is set to 0.0005% or more. The B content is preferably 0.0010% or more or 0.0015% or more.

[0091] Meanwhile, when the B content is more than 0.0200%, coarse intermetallic compounds are formed in the hot-stamping formed body and early fracture resistance deteriorates. For this reason, the B content is set to 0.0200% or less. The B content is preferably 0.0150% or less, 0.0100% or less, 0.0080% or less, 0.0040% or less or 0.0030% or less.

[0092] The remainder of the chemical composition of the hot-stamping formed body may be Fe and impurities. Elements which are unavoidably mixed from a steel raw material or scrap and / or during the manufacture of steel and are allowed in a range where the properties of the hot-stamping formed body according to the present embodiment do not deteriorate are exemplary examples of the impurities.

[0093] The hot-stamping formed body may comprise the following elements as: optional elements. The content of the following optional elements obtained in a case where the following optional elements are not contained is 0%.Co: 0% to 4.00%

[0094] Co is an element that improves strength of the hot-stamping formed body by solid-solution strengthening. In order to reliably obtain the effect, it is preferable that the Co content be set to 0.01% or more. The Co content is more preferably set to 0.05% or more.

[0095] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Co content is set to 4.00% or less. If necessary, the upper limit of Co content may be set to 1.00%, 0.50%, 0.10%, 0.05% or 0.02%.

[0096] Ni: 0% to 3.00%

[0097] Ni has an effect of increasing strength of the hot-stamping formed body by dissolving in prior austenite grains during heating before hot stamping. In order to reliably obtain the effect, the Ni content is preferably set to 0.01% or more.

[0098] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Ni content is preferably set to 3.00% or less. If necessary, the upper limit of Ni content may be set to 1.50%, 1.00%, 0.50%, 0.10%, 0.05% or 0.02%.Cu: 0% to 3.00%

[0099] Cu has an effect of increasing strength of the hot-stamping formed body by dissolving in prior austenite grains during heating before hot stamping. In order to reliably obtain the effect, the Cu content is preferably set to 0.01% or more. The Cu content is more preferably set to 0.05% or more.

[0100] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Cu content is preferably set to 3.00% or less. If necessary, the upper limit of Cu content may be set to 1.50%, 1.00%, 0.50%, 0.10%, 0.05% or 0.02%.V: 0% to 3.00%

[0101] V has an effect of forming carbonitride in steel and improves strength of the hot-stamping formed body by precipitation strengthening. In order to reliably obtain the effect, the V content is preferably set to 0.01% or more. The V content is more preferably set to 0.05% or more.

[0102] Meanwhile, when the V content is more than 3.00%, many carbonitrides are generated in steel, and early fracture resistance of the hot-stamping formed body deteriorates. For this reason, the V content is set to 3.00% or less. If necessary, the upper limit of V content may be set to 1.50%, 1.00%, 0.50%, 0.10%, 0.05% or 0.02%.W: 0% to 3.00%

[0103] W has an effect of improving strength of the hot-stamping formed body. In order to reliably obtain the effects, the W content is preferably set to 0.01% or more. The W content is preferably set to 0.05% or more.

[0104] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the W content is preferably set to 3.00% or less. If necessary, the upper limit of W content may be set to 1.50%, 1.00%, 0.50%, 0.10%, 0.05% or 0.02%.Ca: 0% to 1.000%

[0105] Ca is an element that suppresses generation of carbides that become starting points for fracture, and contributes to improvement of early fracture resistance. In order to reliably obtain the effect, the Ca content is preferably set to 0.001% or more.

[0106] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Ca content is set to 1.000% or less. If necessary, the upper limit of Ca content may be set to 0.100%, 0.010%, 0.005%, 0.001%, 0.0005% or 0.0002%.Mg: 0% to 1.000%

[0107] Mg forms oxides and sulfides in molten steel, suppresses formation of a coarse MnS, disperses a lot of fine oxides, miniaturizes the microstructure, and contributes to improvement of early fracture resistance. In order to reliably obtain these effects, the Mg content is preferably set to 0.001% or more.

[0108] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Mg content is set to 1.000% or less. If necessary, the upper limit of Mg content may be set to 0.100%, 0.010%, 0.005%, 0.001%, 0.0005% or 0.0002%.REM: 0% to 1.000%

[0109] REM suppresses generation of oxides that become starting points of fracture and contributes to improvement of early fracture resistance. In order to reliably obtain the effect, the REM content is preferably set to 0.001% or more.

[0110] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the REM content is set to 1.000% or less. If necessary, the upper limit of REM content may be set to 0.100%, 0.010%, 0.005%, 0.001%, 0.0005% or 0.0002%.

[0111] In the present embodiment, REM refers to a total of 17 elements that are composed of Sc, Y and lanthanoid, and the REM content refers to the total content of these elements,Sb: 0% to 1.000%

[0112] Sb suppresses generation of oxides that become starting points of fracture and contributes to improvement of early fracture resistance. In order to reliably obtain the effect, the Sb content is preferably set to 0.001% or more.

[0113] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Sb content is set to 1.000% or less. If necessary, the upper limit of Sb content may be set to 0.100%, 0.050%, 0.020%, 0,010%, 0.005% or 0.002%,Sn: 0% to 1.000%

[0114] Sn suppresses generation of oxides that become starting points of fracture and contributes to improvement of early fracture resistance. In order to reliably obtain the effect, the Sn content is preferably set to 0.001% or more.

[0115] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Sn content is set to 1.000% or less. If necessary, the upper limit of Sn content may be set to 0.100%, 0.050%, 0.020%, 0.010%, 0.005% or 0.002%.Zr: 0% to 1.000%

[0116] Zr suppresses generation of oxides that become starting points of fracture and contributes to improvement of early fracture resistance. In order to reliably obtain the effect, the Zr content is preferably set to 0.001% or more.

[0117] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the Zr content is set to 1.000% or less. If necessary, the upper limit of Zr content may be set to 0.100%, 0.050%, 0.020%, 0.010%, 0.005% or 0.002%.As: 0% to 0.100%

[0118] As refines the prior austenite grains by lowering an austenite single-phase transformation temperature, and contributes to improvement of early fracture resistance. In order to reliably obtain the effect, the As content is preferably set to 0.001% or more.

[0119] Meanwhile, since the above effect will be saturated even if a large amount is comprised, the As content is set to 0.100% or less. If necessary, the upper limit of As content may be set to 0.100%, 0.050%, 0.020%, 0,010%, 0.005% or 0.002%.

[0120] The above-mentioned chemical composition of the hot-stamping formed body may be measured by a standard analysis method. For example, the chemical composition may be measured using inductively coupled plasma-atomic emission spectrometry (ICP-AES). C and S may be measured using a combustion-infrared absorption method, N may be measured using an inert gas fusion-thermal conductivity method, and O may be measured using an inert gas fusion-nondispersive infrared absorption method.

[0121] When a plating layer or a coating film is provided on the surface of the hot-stamping formed body, the chemical composition is analyzed after the plating layer or the coating film is removed by mechanical grinding.

[0122] Next, the microstructure of the hot-stamping formed body according to the present embodiment will be described.

[0123] In the hot-stamping formed body according to the present embodiment, in the interior region, which is a region between 4 / 16 depth of the sheet thickness (thickness of the hot-stamping formed body) from the surface of the hot-stamping formed body and 5 / 16 depth of the sheet thickness from the surface, the standard deviation of grain sizes of prior austenite grains is 5.0 μm or less; in the surface layer region, which is a region between the surface and 1 / 25 depth of the sheet thickness from the surface, the area ratio of bainite is more than 10%, the maximum value of pole density of the texture is 4.0 or less, and the deboronization index is 0.05 or more.

[0124] The interior region in the present embodiment refers to a region between 4 / 16 depth of the sheet thickness from the surface of the hot-stamping formed body and 5 / 16 depth of the sheet thickness from the surface.

[0125] In addition, the surface layer region refers to a region between the surface of the hot-stamping formed body and 1 / 25 depth of the sheet thickness from the surface.

[0126] When the hot-stamping formed body has the plating layer or the coating film on the surface thereof, the “surface” refers to the interface of the plating layer or the coating film and the base steel sheet, and for convenience, the plating layer or the coating film is excluded from the hot-stamping formed body. Specifically, when the hot-stamping formed body has the plating layer or the coating film on the surface thereof, as described below, for convenience, a region where the Fe concentration is less than 90% by mass in GD-OES measurement, that is, the plating layer or the coating film is excluded from the hot-stamping formed body, the measuring point where the Fe concentration is 90% by mass (the interface of the base steel sheet and the plating layer) is regarded as the surface of the hot-stamping formed body. As described above, the plating layer or the coating film is excluded from the hot-stamping formed body, when the thickness of the plating layer or the coating film is very small compared to the sheet thickness (thickness) of the hot-stamping formed body and can be ignored (however, when only the plating layer is formed, the thickness of the plating layer is often very small and can be ignored in most cases), when measuring the sheet thickness (thickness) of the hot-stamping formed body, the sheet thickness (thickness) of the hot-stamping formed body may be regarded as the sheet thickness (thickness) including the plating layer or the coating film.“Interior Region”Standard Deviation of Grain Sizes of Prior Austenite Grains: 5.0 μm or Less

[0127] By reducing the dispersion of grain sizes of prior austenite grains in the interior region, that is, by reducing the standard deviation, an increase of local residual stress can be suppressed. As a result, hydrogen embrittlement resistance and early fracture resistance of the hot-stamping formed body can be improved. When the standard deviation of grain sizes of prior austenite grains is more than 5.0 μm, hydrogen embrittlement resistance and early fracture resistance deteriorate. For this reason, the standard deviation of grain sizes of prior austenite grains is set to 5.0 μm or less, preferably 4.0 μm or less, 3.0 μm or less or 2.5 μm or less.

[0128] The lower limit of the standard deviation of grain sizes of prior austenite grains is not particularly limited, but may be set to 0.1 μm. 0.5 μm, 1.0 μm or 1.5 μm.

[0129] The standard deviation of grain sizes of prior austenite grains is obtained by the following method.

[0130] A sample is cut out from an arbitrary position away from an end surface of the hot-stamping formed body by a distance of 50 mm or more (a position that avoids an end portion in a case where the sample cannot be collected at this position) so that a sheet thickness cross section parallel to a rolling direction can be observed. The size of the sample depends on a measurement device, but is set to a size that can be observed by about 10 mm in the rolling direction.

[0131] After polishing the cross section of the sample using silicon carbide paper of #600 to #1500, the cross section of the sample is mirror-finished using liquid in which diamond powder having a grain size in the range of 1 μm to 6 μm is dispersed in a diluted solution of alcohol or the like or pure water. Next, the observation surface is finished by electrolytic polishing. At an arbitrary position on the cross section of the sample in a longitudinal direction, a region which has a length of 50 μm and is present between 4 / 16 depth of the sheet thickness from the surface and 5 / 16 depth of the sheet thickness from the surface is measured at a measurement interval of 0.1 μm by an electron backscatter diffraction method, and thus, crystal orientation information is obtained. An EBSD analyzer composed of a Schottky emission scanning electron microscope and an EBSD detector may be used for measurement, for example, an EBSD analyzer composed of JSM-7001F manufactured by JEOL Ltd. and DVC 5-type detector manufactured by TSL Solutions may be used for measurement. In this case, the degree of vacuum in the EBSD analyzer may be set to 9.6×10−5 Pa or less, an accelerating voltage may be set to 15 kV, and an irradiation current level may be set to 13.

[0132] By using the obtained crystal orientation information, the crystal orientation of prior austenite grains is calculated from the crystal orientation relationship between general prior austenite grains and grains having a body-centered structure after transformation, and after calculating the average grain size of prior austenite grains using the crystal orientation, the standard deviation is calculated.

[0133] The method for calculating the crystal orientation of prior austenite grains is the following method. First, the crystal orientation map of the prior austenite grains is created by the method described in Non-Patent Document 1. For one of prior austenite grain included in the observed visual field, an average value of a shortest diameter and a longest diameter is calculated, and the average value is regarded as the grain size of the prior austenite grain. The above operation is performed on all prior austenite grains except for the prior austenite grains which are not entirely included in the photographed visual fields, such as grains in an end portion of the photographed visual field, and the grain sizes of all the prior austenite grains in the photographed visual fields are obtained. By calculating the standard deviation from the obtained grain sizes of all austenite grains, the standard deviation of grain sizes of austenite grains is obtained.

[0134] In addition, in the present embodiment, the rolling direction of the hot-stamping formed body is determined by the following method.

[0135] First, a sample is cut out from an arbitrary position away from an end surface of the hot-stamping formed body by a distance of 50 mm or more so that a sheet thickness cross section parallel to a rolling direction can be observed. After finishing the cross section of the collected sample by mirror polishing, observations with an optical microscope at 100, 200, 500, and 1000 magnifications are performed respectively. Depending on the size of the inclusion, an observation result with an appropriate magnification that the size of the inclusion can be measured is selected. The observation area is width of 500 μm or more and full of the sheet thickness, and the areas with low brightness are determined to be inclusions. The observation may be performed at multiple fields when observing. Next, using the sheet thickness cross section initially observed by the above method as a reference, in the range of 0° to 180° with the sheet thickness direction as the axis, the cross-sectional observation of the plane parallel to the plane rotated in 5° increments is performed in the same way as the above method. The average values of the lengths of the long axes of the plurality of inclusions in each cross section are calculated respectively. The cross section in which the obtained average value of the length of the long axes of the inclusions is maximum is specified. A direction parallel to the longitudinal direction of the inclusion in the cross section is determined as the rolling direction.

[0136] The microstructure of the interior region is not particularly limited as long as the desired strength, hydrogen embrittlement resistance and early fracture resistance can be obtained, for example, in area %, the microstructure may consist of martensite and bainite of 90% to 100% (90% or more and 100% or less) in total, and ferrite and residual austenite of 0% to 10% (0% or more and 10% or less) in total. Martensite in the present embodiment includes untempered martensite (fresh martensite) and tempered martensite.

[0137] The microstructure of the hot-stamping formed body is measured by the following method.

[0138] A sample is cut out from an arbitrary position away from an end surface of the hot-stamping formed body by a distance of 50 mm or more (a position that avoids an end portion in a case where the sample cannot be collected at this position) so that a sheet thickness cross section parallel to the rolling direction can be observed. The size of the sample depends on a measurement device, but is set to a size that can be observed by about 10 mm in the rolling direction.

[0139] After polishing the cross section of the sample using silicon carbide paper of #600 to #1500, the cross section is mirror-finished using liquid in which diamond powder having a grain size in the range of 1 μm to 6 μm is dispersed in a diluted solution of alcohol or the like or pure water. Next, the observation surface is finished by electrolytic polishing. At an arbitrary position on the cross section of the sample in a longitudinal direction, a region which has a length of 50 μm and is present between 4 / 16 depth of the sheet thickness from the surface and 5 / 16 depth of the sheet thickness from the surface is measured at a measurement interval of 0.1 μm by an electron backscatter diffraction method, and thus, crystal orientation information is obtained. An EBSD analyzer composed of a Schottky emission scanning electron microscope and an EBSD detector may be used for measurement, for example, an EBSD analyzer composed of JSM-7001F manufactured by JEOL Ltd. and DVC 5-type detector manufactured by TSL Solutions may be used for measurement. In this case, the degree of vacuum in the EBSD analyzer may be set to 9.6×10:5 Pa or less, an accelerating voltage may be set to 15 kV, and an irradiation current level may be set to 13.

[0140] In the obtained crystal structure information, using “Phase Map” function installed in the software “OIM Analysis (registered trademark)” attached to the EBSD analyzer, a region where a crystal structure is fec is determined as residual austenite. The area ratio of the residual austenite is calculated, thereby the area ratio of the residual austenite is obtained. Next, regions where the crystal structure is bcc is determined as bainite, martensite, and ferrite. In these regions, under the condition that boundary with 5° is regarded as the grain boundary, using “Grain Average Misorientation” function installed in the software “OIM Analysis (registered trademark)” attached to the EBSD analyzer, regions where a grain average misorientation is 0.5° or lower are extracted as ferrite. By calculating the area ratio of the extracted ferrite, the area ratio of ferrite is obtained.

[0141] Subsequently, the area ratio of the remaining region (the region where “Grain Average Misorientation” is more than 0.5°) is calculated, and this area ratio is determined as the total area ratio of martensite and bainite.“Surface Layer Region”Area Ratio of Bainite: More than 10%

[0142] By generating bainite in the surface layer region, dislocation density of the surface layer region can be decreased. As a result, irruption of hydrogen from the external environment can be suppressed, and hydrogen embrittlement resistance of the hot-stamping formed body can be improved. Furthermore, by generating bainite in the surface layer region, since excessive softening of the surface layer can be suppressed, hydrogen embrittlement resistance can be improved while maintaining a load bearing of the member. When the area ratio of bainite in the surface layer region is 10% or less, hydrogen embrittlement resistance deteriorates. For this reason, the area ratio of bainite is set to more than 10%, preferably 20% or more, 40% or more or 60% or more. The upper limit of the area ratio of bainite is not particularly limited, but may be set to 100%, 90% or 80%.

[0143] In the microstructure of the surface layer region, except for bainite, martensite of 0% to 90% (0% or more and 90% or less), ferrite and residual austenite of 0% to 65% (0% or more and 65% or less) may be included.

[0144] The area ratio of the microstructure is calculated for the surface layer region (the region between the surface and 1 / 25 depth of the sheet thickness from the surface) by the following method.

[0145] A sample is cut out from an arbitrary position away from an end surface of the hot-stamping formed body by a distance of 50 mm or more (a position that avoids an end portion in a case where a sample cannot be collected at this position) so that a sheet thickness cross section parallel to the rolling direction can be observed. The size of the sample depends on a measurement device, but is set to a size that can be observed by about 10 mm in the rolling direction.

[0146] After polishing the cross section of the sample using silicon carbide paper of #600 to #1500, the cross section is mirror-finished using liquid in which diamond powder having a grain size in the range of 1 μm to 6 μm is dispersed in a diluted solution of alcohol or the like or pure water, Next, the observation surface is finished by electrolytic polishing. At an arbitrary position on the cross section of the sample in a longitudinal direction, a region which has a length of 50 μm and is present between the surface of the hot-stamping formed body and 1 / 25 depth of the sheet thickness from the surface is measured at a measurement interval of 0.1 μm by an electron backscatter diffraction method, and thus, crystal orientation information is obtained. An EBSD analyzer composed of a Schottky emission scanning electron microscope and an EBSD detector may be used for measurement, for example, an EBSD analyzer composed of JSM-7001F manufactured by JEOL Ltd. and DVC 5-type detector manufactured by TSL Solutions may be used for measurement. In this case, the degree of vacuum in the EBSD analyzer may be set to 9.6×10−5 Pa or less, an accelerating voltage may be set to 15 kV, and an irradiation current level may be set to 13.

[0147] In the obtained crystal structure information, using the “Phase Map” function installed in the software “OIM Analysis (registered trademark)” attached to the EBSD analyzer, a region where a crystal structure is fcc is determined as residual austenite. The ratio of the residual austenite is calculated, thereby the area ratio of the residual austenite is obtained. Next, in the regions where the crystal structure is bcc, under the condition that boundary with 5° is regarded as the grain boundary, using the “Grain Average Misorientation” function installed in the software “OIM Analysis (registered trademark)” attached to the EBSD analyzer, regions where a grain average misorientation is more than 0.50° and 0.75° or lower are extracted as bainite. By calculating the area ratio of the extracted bainite, the area ratio of bainite is obtained.

[0148] Subsequently, the region where “Grain Average Misorientation” is 0.5° or lower is extracted as ferrite. By calculating the area ratio of the extracted ferrite, the area ratio of ferrite is obtained. The remaining region (the region where “Grain Average Misorientation” is more than) 0.75° is extracted as martensite, and the area ratio thereof is calculated, thereby the area ratio of martensite is obtained.“Surface Layer Region”Crystal Orientation in Surface Layer Region: Maximum Value of Pole Density of Texture is 4.0 or Less

[0149] By controlling the texture in the surface layer region, irruption of hydrogen from the external environment can be suppressed, and hydrogen embrittlement resistance of the hot-stamping formed body can be improved. When the maximum value of pole density of the texture in the surface layer region is more than 4.0, hydrogen embrittlement resistance of the hot-stamping formed body deteriorates. For this reason, the maximum value of pole density of the texture in the surface layer region is set to 4.0 or less, preferably 3.5 or less, 3.0 or less or 2.5 or less.

[0150] The lower limit of the pole density of the texture in the surface layer region is not particularly limited, but may be set to 1.0 or 1.2.

[0151] In the surface layer region (the region between the surface and 1 / 25 depth of the sheet thickness from the surface), the texture in the surface layer region is obtained by the following method.

[0152] A sample is cut out from an arbitrary position away from an end surface of the hot-stamping formed body by a distance of 50 mm or more (a position that avoids an end portion in a case where the sample cannot be collected at this position) so that a sheet thickness cross section parallel to a rolling direction can be observed. The size of the sample depends on a measurement device, but is set to a size that can be observed by about 10 mm in the rolling direction.

[0153] After polishing the cross section of the sample using silicon carbide paper of #600 to #1500, the cross section of the sample is mirror-finished using liquid in which diamond powder having a grain size in the range of 1 μm to 6 μm is dispersed in a diluted solution of alcohol or the like or pure water. Next, the observation surface is finished by electrolytic polishing. At an arbitrary position on the cross section of the sample in a longitudinal direction, a region which has a length of 1000 μm and is present between the surface and 1 / 25 depth of the sheet thickness from the surface is measured at a measurement interval of 5.0 μm by an electron backscatter diffraction method, and thus, crystal orientation information is obtained. An EBSD analyzer composed of a Schottky emission scanning electron microscope and an EBSD detector may be used for measurement, for example, an EBSD analyzer composed of JSM-7001F manufactured by JEOL Ltd. and DVC 5-type detector manufactured by TSL. Solutions may be used for measurement. In this case, the degree of vacuum in the EBSD analyzer may be set to 9.6×10−5 Pa or less, an accelerating voltage may be set to 15 kV, and an irradiation current level may be set to 13.

[0154] By using the obtained crystal orientation information, using the “Texture” function installed in the software “OIM Analysis (registered trademark)” which is attached to the EBSD analyzer, intensity calculation is performed using a Harmonic Series Expansion for grains whose crystal structure is bcc. At this time, the expansion order is set to 16, and a half width when applied to a Gaussian distribution is set to 5°. Next, the “Texture Plot” function is used for the output file after the intensity calculation to output a φ2=45° cross section in the orientation distribution function (ODF). The maximum value of the pole density in the @2=45° cross section is regarded as the maximum value of pole density of the texture in the surface layer region.“Surface Layer Region”Deboronization Index: 0.05 or More

[0155] The deboronization index is an index that quantitatively represents the amount of decrease of the B concentration in the surface layer region. By decreasing the B concentration in the surface layer region, deformability of prior austenite grain is improved by reducing strength of prior austenite before transformation, and the generation of grains having random orientation is facilitated in the surface layer region. When the deboronization index in the surface layer region is less than 0.05, grains having a desired texture cannot be obtained in the surface layer region. For this reason, the deboronization index is set to 0.05 or more, preferably 0.20 or more, 0.30 or more or 0.35 or more.

[0156] The upper limit of the deboronization index is not particularly limited, but may be set to 1.00, 0.80 or 0.60.

[0157] The deboronization index in the surface layer region is obtained by the following method.

[0158] An element concentration distribution in the sheet thickness direction in the hot-stamping formed body is measured using glow discharge optical emission spectrometry (GD-OES: Manufactured by Horiba, Ltd., Marcus type high-frequency glow discharge optical emission spectrometer, GD-PROFILER-HR). The measurement conditions are an analysis diameter of 4 mm, a sputtering rate of 4 μm / min, an argon pressure of 600 Pa, an RF output of 35 W, and a measurement interval of 0.02 μm or less. All elements that are comprised in the hot-stamping formed body are measured.

[0159] In a case where the hot-stamping formed body has the plating layer on the surface, the “surface” refers to the interface of the plating layer and the base steel sheet. In a case where the hot-stamping formed body has the plating layer or the coating film on the surface, GD-OES measurement is performed after removing a part or all of the plating layer or the coating film by mechanical polishing or chemical polishing such that measurement to 200 μm depth from the surface of the base steel sheet (the interface of the plating layer and the base steel sheet) can be performed. In the GD-OES measurement, a measuring point where the Fe concentration becomes 90 mass % is regarded as the surface of the hot-stamping formed body. In addition, in the following description, for ease of explanation, the hot-stamping formed body may be referred to as a base steel sheet.

[0160] Next, B concentrations from the surface of the hot-stamping formed body to at least 100 μm depth from the surface are measured. After measuring the B concentration at a position of 100 μm depth from the surface, in a case where the absolute value of the difference between the average value of the B concentration in a region from 80 μm to 100 μm and the maximum value of the measured value of the B concentration in the region from 80 μm to 100 μm is 0.0006% by mass or less, and, in a case where the absolute value of the difference between the average value of the B concentration in the region from 80 μm to 100 μm and the minimum value of the measured value of the B concentration in the region from 80 μm to 100 μm is 0.0006% by mass or less, the measurement in the depth direction of the B concentration is finished at the position of 100 μm depth from the surface.

[0161] In a case where the requirements for ending the measurement are not satisfied, the measurement of the B concentration in the depth direction is continued. Then, each time a new B concentration measurement value is obtained in the depth direction, the average value of the B concentration in the region between the deepest part and 20 μm from the deepest part to the surface side is calculated. In a case where the absolute value of the difference between the average value of the B concentration in the region between the deepest part and 20 μm from the deepest part to the surface side and the maximum value of the measured value of the B concentration in the region between the deepest part and 20 μm from the deepest part to the surface side is 0.0006 mass % or less, and, in a case where the absolute value of the difference between the average value of the B concentration in the region between the deepest part and 20 μm from the deepest part to the surface side and the minimum value of the measured value of the B concentration in the region between the deepest part and 20 μm from the deepest part to the surface side is 0.0006 mass % or less, the measurement of the B concentration in the depth direction is finished at the position. For example, when the measured value of the B concentration at 150 μm depth from the surface is obtained, in a case where the absolute value of the difference between the average value of the B concentration in the region between 130 μm depth from the surface and 150 μm depth from the surface and the maximum value of the measured value of the B concentration in the region between 130 μm depth from the surface and 150 μm depth from the surface is 0.0006 mass % or less, and, in a case where the absolute value of the difference between the average value of the B concentration in the region between 130 μm depth from the surface and 150 μm depth from the surface and the minimum value of the measured value of the B concentration in the region between 130 μm depth from the surface and 150 μm depth from the surface is 0.0006 mass % or less, the measurement of the B concentration in the depth direction is finished at the position of 150 μm depth from the surface.

[0162] Even if the requirements for ending the measurement described above are not satisfied and the measurement of the B concentration in the depth direction cannot be finished, the measurement of the B concentration in the depth direction is finished when the measurement of the B concentration at the position of 200 μm depth from the surface is completed. Then, at the time when the measurement of the B concentration in the depth direction is finished, the average value of the B concentration in the region between the deepest part (the deepest position where the B concentration used for calculating the deboronization index was obtained) and the position of 20 μm from the deepest part to the surface side is used for the below calculation of the deboronization index (hereinafter, the average value of the B concentration in the region will be referred to as the average B concentration at the deepest part of 20 μm).

[0163] For convenience of measurement, for example, after measuring the B concentration to 200 μm depth from the surface, in a region between 100 μm and 200 μm from the surface, the shallowest depth position that satisfies the ending condition for the B concentration measurement in the depth direction is searched for, and in a case where the depth position is found, the deboronization index may be calculated without using the measurement results of the B concentration at the position deeper than the shallowest depth position. For example, the B concentration may be measured from the surface to 200 μm depth from the surface, in this case, in a case where a shallowest depth position that satisfies the ending condition for B concentration measurement in the depth direction exists in a region of 100 μm or more depth from the surface, the measurement is regarded as ending at the depth position, and the deboronization index is calculated.

[0164] In the region between the deepest part and 20 μm from the deepest part to the surface side of the hot-stamping formed body, the amount of decrease in the B concentration per unit depth (the value obtained by subtracting the B concentration at each measurement point from the average B concentration at the deepest part of 20 μm) is calculated, the integrated value of the product of the unit depth and the amount of decrease in the B concentration is calculated and determined as the area of the B-depletion region (area of region A in FIG. 1). However, when the value obtained by subtracting the B concentration at each measurement point from the average B concentration at the deepest part of 20 μm is negative, it is integrated as 0 (due to the B removal phenomenon near the surface, the B concentration at each measurement point is in most cases lower than the average B concentration at the deepest part of 20 μm, and the integrated value becomes positive). Next, the product of the average B concentration at the deepest part of 20 μm and the length of 200 μm is calculated as a reference area (area of rectangular region B in FIG. 1). The value obtained by dividing a B-depletion area (area of region A) by the reference area (area of region B) is defined as the deboronization index (area of region A / area of region B). Even in a case where the above-mentioned requirement for ending the measurement is satisfied in a region from the surface to 200 μm, the reference area (area of region B) is calculated by assuming that the length by which the average B concentration at the deepest part of 20 μm is multiplied is 200 μm.

[0165] The hot-stamping formed body may have a plating layer on the surface. By having the plating layer on the surface, corrosion resistance can be improved after hot stamping. Examples of the plating layer include an aluminum plating layer, aluminum-galvanized layer, aluminum-silicon plating layer, hot-dip galvanized layer, electrogalvanized layer, galvannealed layer, zinc-nickel plating layer, aluminum-magnesium-zinc-based plating layer.

[0166] Next, a steel sheet for hot stamping for obtaining the hot-stamping formed body according to the present embodiment will be described.

[0167] The steel sheet for hot stamping has the above-described chemical composition. The microstructure of the steel sheet for hot stamping is not particularly limited as long as a desired strength, hydrogen embrittlement resistance and early fracture resistance are obtained after hot stamping, for example, in area %, the microstructure may consist of ferrite: 5% to 90%, bainite and martensite: 0% to 100%, pearlite: 10% to 95%, and residual austenite: 0% to 5%. In addition to these, iron carbides, alloy carbides, intermetallic compounds, and inclusions may be included.

[0168] Further, the steel sheet for hot stamping may have a plating layer on the surface. By having the plating layer on the surface, corrosion resistance can be improved after hot stamping. Examples of the plating layer include an aluminum plating layer, aluminum-galvanized layer, aluminum-silicon plating layer, hot-dip galvanized layer, electrogalvanized layer, galvannealed layer, zinc-nickel plating layer, aluminum-magnesium-zinc-based plating layer.Manufacturing Method of Steel Sheet for Hot Stamping

[0169] A manufacturing method to obtain the steel sheet for hot stamping for obtaining the hot-stamping formed body according to the present embodiment will be described. In order to obtain the above-described hot-stamping formed body, it is particularly effective to control the finish rolling condition and the annealing condition in the manufacturing method of the steel sheet for hot stamping.Finish Rolling

[0170] In finish rolling, it is preferable to set the rolling reduction of the final pass (final rolling reduction) to 20% or more. The final rolling reduction can be expressed as {(t0−t1) / t0}×100(%), where to is the sheet thickness before rolling of the final pass, and t1 is the sheet thickness after rolling of the final pass. By increasing the final rolling reduction, pearlite is uniformly dispersed in the hot-rolled steel sheet after rolling. This pearlite becomes a reverse transformation site of prior austenite during heating of hot stamping. For this reason, when pearlite is uniformly dispersed, the standard deviation of grain sizes of prior austenite grains in the hot-stamping formed body becomes small. As a result, the early fracture resistance of the hot-stamping formed body can be improved. More preferably, the final rolling reduction is 30% or more, 40% or more or 45% or more.

[0171] In the chemical composition of the hot-stamping formed body according to the present embodiment, when the Mn content is 0.60% or more, in order to preferably control the texture of the surface layer region of the hot-stamping formed body, it is important to increase the final rolling reduction of final rolling as described above.

[0172] The casting method of molten steel, the conditions of heating before hot rolling, rough rolling, coiling, and cold rolling are not particularly limited, and may be standard conditions. The coiling temperature may be set to 750° C. or lower. By setting the coiling temperature to 750° C. or lower, it is possible to suppress ferrite from being connected and arranged in the hot-rolled steel sheet after rolling, and pearlite is uniformly dispersed. This pearlite becomes a reverse transformation site of prior austenite during heating of hot stamping. For this reason, when pearlite is uniformly dispersed, the standard deviation of the grain sizes of prior austenite grains in the hot-stamping formed body becomes small. As a result, early fracture resistance of the hot-stamping formed body can be improved.

[0173] Furthermore, for the purpose of softening the hot-rolled steel sheet, a softening heat treatment may be performed on the coil after coiling. The softening heat treatment method is not particularly limited, and standard conditions may be adopted.Annealing

[0174] After cold rolling, it is preferable to perform annealing to heat for 15 seconds or more in an oxidizing atmosphere. Generally, it is preferable to perform annealing in a reducing atmosphere in order to suppress formation of scale. However, in the present embodiment, formation of scale on the steel sheet surface is promoted by performing annealing in the oxidizing atmosphere. During heating of hot stamping, the scale formed on the steel sheet surface becomes an oxidation source, and C and B in the surface layer region are oxidized. Since oxidized C and B leave the surface layer of the steel sheet, the amounts of C and B are reduced in the surface layer region. As a result, the strength of the prior austenite grains decreases and they become easily deformed, and grains having random orientation are likely to be generated. Thereby, grains having a desired texture can be generated in the surface layer region.

[0175] The heating temperature during annealing may be set to a temperature range of 730° C. to 900° C., and by staying in this heating temperature range for 15 seconds or more, formation of scale can be promoted while suppressing peeling of scale. The time for annealing is preferably 100 seconds or more, more preferably 200 seconds or more, and even more preferably 300 seconds or more. On the other hand, annealing for more than 3600 seconds is not preferable since the prior austenite grain sizes become coarser, the grain boundary diffusion rate of B decreases, removal of B does not proceed, and the deboronization index cannot be 0.05 or more. For this reason, the annealing time is preferably 3600 seconds or less.

[0176] After annealing in the oxidizing atmosphere, the annealing step may be performed again in an oxidizing atmosphere or a non-oxidizing atmosphere unless a treatment for removing oxide scale (for example, pickling) is performed.

[0177] In the present embodiment, the oxidizing atmosphere may be any heating atmosphere that generates oxide scale on the surface layer of the steel sheet, and may be a standard condition. For example, in a gas combustion atmosphere, it is preferable to create an atmosphere in which the mixture ratio of air and fuel (air-fuel ratio) is controlled to 0.80 or more, and more preferably controlled to exceed 1.00. It is preferable to generate an oxide scale of 15 μm or more on the steel sheet surface by annealing in the oxidizing atmosphere.

[0178] It is preferable that the oxide scale on the steel sheet surface remain in subsequent processes. That is, it is preferable to perform hot stamping, which will be described later, with the oxide scale remaining. Oxide scale is removed by shot blasting after hot stamping.

[0179] Furthermore, even when the plating layer is formed on the surface of the steel sheet for hot stamping, oxide scale remains at the interface between the base steel sheet and the plating layer. When the plating layer is formed, the oxide scale disappears after hot stamping due to an alloying reaction during heating before hot stamping.

[0180] A hot-stamping formed body according to the present embodiment is obtained by hot stamping the steel sheet for hot stamping manufactured by the above-described method. The hot stamping conditions are not particularly limited. However, for example, it is preferable to heat the steel sheet for hot stamping to a temperature range of 800° C. to 1000° C. and hold in this temperature range for 60 to 600 seconds. When the heating temperature is lower than 800° C., austenitization becomes insufficient, a desired distribution of prior austenite grain sizes cannot be obtained, and early fracture resistance may deteriorate. On the other hand, when the heating temperature is higher than 1000° C., the grains of prior austenite grow excessively, a desired distribution of prior austenite grain sizes cannot be obtained, and early fracture resistance may deteriorate. When the holding time is shorter than 60 seconds, austenitization becomes insufficient, a desired distribution of prior austenite grain sizes cannot be obtained, and early fracture resistance may deteriorate. When the holding time is longer than 600 seconds, grains of prior austenite grow excessively, a desired distribution of prior austenite grain sizes cannot be obtained, and early fracture resistance may deteriorate.

[0181] A heating atmosphere is not particularly limited, and may be standard conditions, for example, such as the atmosphere, a gas combustion atmosphere with a controlled ratio of air and fuel, or a nitrogen atmosphere, and the dew point of these gases may be controlled.

[0182] After holding in the temperature range, hot stamping is performed. After hot stamping, cooling may be performed to a temperature range of 250° C. or lower at an average cooling rate of 20° C. / s or faster.

[0183] Examples of heating methods before hot stamping include heating using an electric furnace and gas furnace, flame heating, electrical heating, high-frequency heating, and induction heating.

[0184] By the above methods, the hot-stamping formed body according to the present embodiment is obtained. A tempering treatment at 130° C. to 600° C. may be performed after hot stamping, or a baking hardening treatment after painting may be performed. In addition, a portion of the hot-stamping formed body may be tempered by laser irradiation or the like to provide a partially softened region.Example

[0185] Next, examples of the present invention will be described. Conditions in the examples are one example of conditions employed to confirm the feasibility and effects of the present invention, but the present invention is not limited to these examples. The present invention may employ various conditions to achieve the object of the present invention without departing from the scope of the present invention.

[0186] Slabs manufactured by casting molten steel having a chemical composition shown in Tables 1A to IT were heated, held in a temperature range of 1200° C. or higher for 20 minutes or longer, and then subjected to finish rolling, coiling, and annealing under conditions shown in Tables 2A to 2H. Except for some examples, annealing was performed in an oxidizing atmosphere. For examples not specifically described in the notes in the tables, in annealing in the oxidizing atmosphere, the mixture ratio of air and fuel (air-fuel ratio) was controlled to 1.05 in the gas combustion atmosphere. For some examples, as described in the tables, annealing was performed in the reducing atmosphere, and the coils after coiling were subjected to softening heat treatment.

[0187] The obtained steel sheets for hot stamping were heated to a temperature range of higher than 800° C. in a furnace continuously supplied with nitrogen gas (hot stamp heating), held in the temperature range, subjected to hot stamping, and then cooled to 250° C. or lower at an average cooling rate of 20° C. / s or faster. As a result, the hot-stamping formed bodies shown in Tables 3A to 3H were obtained. In addition, for the examples not specifically described in the notes in the tables, a gas combustion atmosphere was used in which the mixture ratio of air and fuel (air-fuel ratio) was controlled to 0.85.

[0188] However, for some examples, as described in the tables, heating in a furnace adjusted to a different atmosphere, re-annealing, plating, tempering, heating of hot stamping, or the like were performed.

[0189] The underlines in the tables indicate that it is outside the scope of the present invention, falls outside the preferable manufacturing conditions, or the characteristic value is not preferable.

[0190] Measurements of the microstructure (including the standard deviation of the grain sizes of austenite grains), deboronization index, and pole density of the texture of the hot-stamping formed body were performed by the above-described methods. In addition, the mechanical properties of the hot-stamping formed body were evaluated by the following methods.Tensile Strength

[0191] The tensile (maximum) strength TS of the hot-stamping formed body was obtained, in accordance with JIS Z 2241:2011, by preparing a No. 5 test piece from an arbitrary position of the hot-stamping formed body and conducting a tensile test. The crosshead speed was set to 1 mm / min. When the tensile strength TS was 2200 MPa or more, it was determined as having high strength and successful, and when the tensile strength TS was less than 2200 MPa, it was determined as not having high strength and not successful.

[0192] In addition, for examples in which early fracture resistance described below was determined as not successful, the value obtained by multiplying the Vickers hardness, which is measured by the method for early fracture resistance evaluation described below, by 3.3 (=Vickers hardness×3.3) was regarded as the tensile strength.Hydrogen Embrittlement Resistance

[0193] Hydrogen embrittlement resistance of the hot-stamping formed body was evaluated by the following method, A test piece with a length of 68 mm and a width of 6 mm was taken from an arbitrary position of the hot-stamping formed body, and the edges of the test piece were polished using silicon carbide paper of #200 to #1500, and then mirror finishing was performed using a liquid in which diamond powder with a particle size of 1 μm to 6 μm was dispersed in a diluent such as alcohol and pure water. Furthermore, the corners of the test piece were chamfered using silicon carbide paper of #200 to #1500. A stress of 800 MPa or more was applied to the test piece, the test piece was immersed in a liter of hydrochloric acid adjusted to pH 4 at room temperature for 48 hours, and the presence or absence of cracks was determined. When no crack occurred under the load stress of 800 MPa or more, it was determined as successful. When no crack occurred at 800 MPa, an evaluation of “Fair” was used in the tables, when no crack occurred at 900 MPa, an evaluation of “Good” was used in the tables, when no crack occurred at 1000 MPa, an evaluation of “Very Good” was used in the tables, and when no crack occurred at 1100 MPa or higher, an evaluation of “Excellent” was used in the tables. On the other hand, when a crack occurred at a load stress of 800 MPa, it was determined as not successful and “Bad” was described in the tables.Early Fracture Resistance

[0194] The early fracture resistance was evaluated by the value calculated by dividing the tensile strength of the hot-stamping formed body, which was obtained by the above method, by the value obtained by multiplying the Vickers hardness, which was obtained by the following method, by 3.3 (tensile strength / (Vickers hardness×3.3)). When the value was 0.60 or more, it was determined as having excellent early fracture resistance and successful, and when the value was less than 0.60, it was determined as not successful. The value obtained by multiplying the Vickers hardness by 3.3 is the tensile strength estimated from the hardness, and when the measured value of the tensile strength is 0.60 times or more of the estimated tensile strength, then it can be determined as having excellent early fracture resistance.

[0195] The Vickers hardness used for evaluation of early fracture resistance was obtained by the following method. First, from an arbitrary position 50 mm or more away from the end surface of the hot-stamping formed body, a sample was cut out so that a cross section perpendicular to the surface (sheet thickness cross section) could be observed. The size of the sample depended on the measuring device, but was set to a size that could be observed by 10 mm in the rolling direction. A cross section of the sample was polished using silicon carbide paper of #600 to #1500, and then mirror finishing was performed using a liquid in which diamond powder with a particle size of 1 μm to 6 μm was dispersed in a diluent such as alcohol and pure water. For a mirror-finished cross section, using a micro Vickers hardness tester at any position in the area between a position of 4 / 16 depth of the sheet thickness from the surface and a position of 5 / 16 depth of the sheet thickness from the surface, hardness was measured in a direction parallel to the sheet surface (rolling direction) under a load of 1 kgf at intervals of three times or more the indentations. The Vickers hardness was obtained by measuring a total of 20 points and calculating the average value.TABLE 1AChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBA10.360.391.340.0040.00200.00280.00190.05800.0280.0430.240.2020.0033A20.410.451.330.0050.00190.00310.00190.04500.0210.0450.250.1900.0018A30.430.431.220.0050.00050.00280.00250.04300.0380.0400.340.1340.0028A40.440.391.330.0060.00130.00220.00170.05400.0230.0280.260.1790.0018A50.450.391.340.0070.00180.00280.00290.04500.0380.0390.260.2170.0029A60.460.441.330.0070.00070.00250.00290.04400.0340.0270.250.1530.0027A70.470.451.250.0070.00060.00320.00310.06100.0350.0360.310.1650.0033A80.490.391.280.0090.00050.00250.00330.05200.0300.0460.240.1810.0025A90.520.411.270.0040.00160.00240.00150.06100.0370.0370.320.1590.0021A100.550.421.350.0050.00060.00230.00160.05100.0250.0380.240.2190.0033A110.580.411.310.0080.00060.00320.00260.04700.0340.0350.280.2190.0029A120.630.431.230.0040.00090.00210.00250.05300.0280.0270.310.1760.0021A130.680.421.210.0060.00220.00240.00220.05400.0320.0310.290.1340.0021A140.720.401.220.0050.00160.00190.00230.05700.0220.0390.250.1570.0026B10.47 0.0051.260.0090.00210.00300.00240.05200.0300.0380.300.2180.0033B20.47 0.0131.260.0060.00200.00260.00180.04500.0250.0400.330.1660.0027B30.460.031.320.0090.00050.00220.00300.04600.0420.0380.320.2130.0026B40.470.071.230.0090.00060.00200.00230.06000.0410.0320.240.1910.0028B50.470.131.350.0060.00040.00310.00170.04000.0380.0440.260.1400.0021B60.470.211.320.0090.00130.00250.00240.05600.0210.0330.340.1760.0031B70.450.271.330.0060.00070.00300.00190.05500.0300.0420.270.2150.0021B80.450.351.260.0070.00220.00320.00320.04300.0250.0300.240.2100.0020B90.450.431.270.0070.00170.00290.00240.04800.0280.0370.280.1520.0023B100.460.621.230.0050.00150.00310.00280.05100.0380.0270.260.1300.0031B110.450.851.210.0090.00180.00210.00240.05900.0260.0310.270.2210.0027B120.451.611.340.0050.00140.00300.00290.04600.0210.0430.240.2160.0022B130.472.411.340.0050.00100.00310.00260.05800.0200.0260.270.1540.0029B140.472.891.350.0050.00060.00220.00350.05200.0350.0380.250.1570.0028B150.453.101.350.0060.00060.00310.00240.04800.0260.0460.290.1470.0026The underline indicates that it is outside the scope of the present invention.TABLE 1BChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesA1Comparative steelA2Steel of present inventionA3Steel of present inventionA4Steel of present inventionA5Steel of present inventionA6Steel of present inventionA7Steel of present inventionA8Steel of present inventionA9Steel of present inventionA10Steel of present inventionA11Steel of present inventionA12Steel of present inventionA13Steel of present inventionA14Comparative steelB1Comparative steelB2Steel of present inventionB3Steel of present inventionB4Steel of present inventionB5Steel of present inventionB6Steel of present inventionB7Steel of present inventionB8Steel of present inventionB9Steel of present inventionB10Steel of present inventionB11Steel of present inventionB12Steel of present inventionB13Steel of present inventionB14Steel of present inventionB15Comparative steelTABLE 1CChemical composition (mass %) remainder being Fe and impurities.SteelCSiMnPSNOAlNbTiCrMoBC10.470.410.560.0080.00120.00300.00200.03900.0250.0450.340.1630.0025C20.470.390.620.0080.00110.00230.00290.04800.0390.0350.260.1700.0025C30.470.450.720.0070.00070.00280.00340.04400.0300.0360.260.1960.0031C40.450.400.910.0070.00160.00260.00200.05400.0260.0350.230.1930.0022C50.470.411.210.0060.00040.00300.00140.05000.0330.0300.290.2120.0022C60.460.441.320.0060.00170.00190.00310.05300.0270.0290.330.2180.0022C70.450.431.590.0050.00090.00330.00180.04100.0220.0350.260.1930.0018C80.450.431.820.0080.00040.00250.00320.05800.0380.0380.340.1710.0024C90.450.432.100.0090.00160.00250.00240.05700.0360.0310.290.1340.0020C100.470.402.290.0060.00170.00320.00210.05300.0300.0410.280.2260.0019C110.460.402.420.0040.00110.00300.00300.03900.0190.0450.250.1330.0026C120.470.442.670.0040.00150.00260.00160.05500.0230.0330.300.1740.0033C130.470.422.910.0050.00110.00320.00210.04100.0270.0330.230.2110.0033C140.460.453.120.0050.00120.00200.00230.05900.0350.0350.250.1820.0029D10.460.391.22 0.00070.00210.00240.00190.05000.0390.0290.320.1330.0028D20.450.451.330.0040.00140.00300.00170.04200.0400.0250.270.1440.0032D30.450.451.320.0070.00060.00250.00280.04000.0260.0390.330.1750.0025D40.470.431.270.0090.00200.00230.00200.05200.0340.0420.320.2170.0027D50.470.451.290.0130.00170.00330.00350.05100.0300.0370.330.1420.0027D60.460.401.330.0410.00210.00300.00190.05000.0250.0420.330.2110.0027D70.470.451.240.0680.00100.00340.00310.04100.0200.0370.240.1610.0033D80.470.391.350.0890.00110.00330.00150.05300.0400.0320.270.2290.0032D90.450.421.240.1300.00130.00330.00270.05000.0330.0290.270.1590.0020EL0.460.431.270.0080.00010.00300.00270.04500.0390.0350.300.2080.0020E20.460.411.350.0090.00030.00320.00240.05400.0200.0370.280.1420.0030E30.470.431.240.0090.00080.00290.00170.05700.0390.0310.300.2140.0030E40.460.451.340.0040.00110.00270.00240.05600.0350.0410.260.1480.0029E50.450.401.270.0070.00220.00320.00190.06100.0230.0270.260.1950.0022E60.460.421.210.0050.00420.00260.00250.04700.0390.0320.240.2150.0033E70.470.411.310.0080.00680.00220.00270.05700.0360.0310.310.2240.0020E80.460.391.260.0050.00940.00230.00170.04100.0380.0450.320.2170.0027E90.470.451.320.0040.01700.00290.00240.05500.0370.0400.250.1440.0018The underline indicates that it is outside the scope of the present invention.TABLE 1DChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesC1Comparative steelC2Steel of present inventionC3Steel of present inventionC4Steel of present inventionC5Steel of present inventionC6Steel of present inventionC7Steel of present inventionC8Steel of present inventionC9Steel of present inventionC10Steel of present inventionC11Steel of present inventionC12Steel of present inventionC13Steel of present inventionC14Comparative steelD1Steel of present inventionD2Steel of present inventionD3Steel of present inventionD4Steel of present inventionD5Steel of present inventionD6Steel of present inventionD7Steel of present inventionD8Steel of present inventionD9Comparative steelE1Steel of present inventionE2Steel of present inventionE3Steel of present inventionE4Steel of present inventionE5Steel of present inventionE6Steel of present inventionE7Steel of present inventionE8Steel of present inventionE9Comparative steelTABLE 1EChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBF10.470.391.250.0060.00040.00020.00310.04500.0350.0420.310.1300.0032F20.470.391.210.0040.00130.00080.00350.04300.0240.0420.340.1880.0025F30.450.441.210.0040.00100.00190.00290.04200.0390.0310.270.2090.0026F40.470.391.310.0060.00180.00310.00320.05600.0320.0330.260.1570.0023F50.450.411.270.0090.00110.00490.00290.05400.0400.0340.300.1610.0022F60.460.451.340.0060.00180.00660.00180.05400.0330.0290.280.1610.0030F70.460.441.260.0040.00120.01060.00230.06000.0260.0390.260.1740.0019F80.450.451.310.0060.00180.01850.00320.05400.0330.0340.280.1610.0030F90.450.391.300.0070.00170.02400.00270.05600.0320.0350.260.2280.0028G10.470.451.320.0090.00090.00300.00070.04100.0390.0360.250.1790.0028G20.460.411.280.0040.00060.00260.00140.05100.0270.0260.340.2290.0028G30.470.451.230.0040.00120.00280.00210.04700.0310.0340.270.1540.0032G40.470.421.320.0060.00150.00210.00350.05200.0330.0330.250.1390.0023G50.450.431.240.0080.00200.00230.00520.05900.0290.0280.300.1870.0019G60.450.441.280.0040.00080.00310.00810.04100.0410.0260.280.2280.0027G70.460.401.220.0090.00150.00240.01910.06100.0230.0300.330.1600.0023G80.460.431.280.0040.00160.00270.02410.05900.0370.0350.300.2010.0033H10.470.441.310.0060.00130.00340.00250.00080.0280.0340.260.1570.0019H20.470.451.270.0090.00180.00280.00170.00140.0250.0400.320.1810.0018H30.470.401.340.0060.00040.00290.00150.00520.0270.0450.230.2000.0021H40.460.431.350.0060.00200.00330.00150.01610.0250.0340.320.2280.0018H50.470.411.290.0060.00090.00200.00250.02520.0290.0300.260.2060.0028H60.460.391.240.0040.00190.00340.00320.03920.0330.0270.230.1650.0032H70.460.431.350.0050.00110.00340.00350.04910.0290.0450.290.2120.0021H80.460.421.340.0080.00110.00340.00210.06890.0320.0350.340.1960.0030H90.460.421.330.0090.00140.00290.00180.08120.0320.0360.230.1710.0020H100.470.451.260.0050.00190.00240.00220.12770.0370.0410.290.1360.0029H110.460.391.340.0060.00030.00320.00340.26550.0400.0390.290.2210.0032H120.450.401.230.0080.00100.00340.00140.36910.0360.0280.290.1960.0019H130.460.401.230.0080.00170.00190.00340.49150.0200.0320.240.1670.0029H140.460.441.320.0040.00200.00220.00270.52140.0380.0420.300.1460.0021The underline indicates that it is outside the scope of the present invention.TABLE 1FChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesF1Steel of present inventionF2Steel of present inventionF3Steel of present inventionF4Steel of present inventionF5Steel of present inventionF6Steel of present inventionF7Steel of present inventionF8Steel of present inventionF9Comparative steelG1Steel of present inventionG2Steel of present inventionG3Steel of present inventionG4Steel of present inventionG5Steel of present inventionG6Steel of present inventionG7Steel of present inventionG8Comparative steelH1Comparative steelH2Steel of present inventionH3Steel of present inventionH4Steel of present inventionH5Steel of present inventionH6Steel of present inventionH7Steel of present inventionH8Steel of present inventionH9Steel of present inventionH10Steel of present inventionH11Steel of present inventionH12Steel of present inventionH13Steel of present inventionH14Comparative steelTABLE 1GChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBI10.470.401.230.0070.00100.00260.00350.04900.00070.0350.280.1770.0023I20.450.401.220.0040.00220.00290.00340.04100.00130.0280.310.1350.0033I30.450.451.280.0070.00060.00270.00200.04100.0030.0340.230.1950.0031I40.470.441.280.0070.00170.00220.00250.05600.0070.0320.280.1630.0029I50.450.401.240.0090.00100.00200.00210.05200.0110.0360.250.1810.0031I60.460.391.300.0090.00050.00280.00150.04100.0190.0350.240.1850.0025I70.460.391.350.0090.00120.00320.00290.03900.0240.0440.270.1700.0023I80.470.451.350.0080.00170.00330.00300.05900.0360.0400.320.1580.0026I90.460.391.250.0070.00160.00260.00310.04500.0420.0250.330.1600.0023I100.460.441.290.0090.00030.00220.00350.04800.0540.0450.310.1480.0021I110.450.411.250.0070.00220.00300.00250.03900.0680.0430.280.1530.0030I120.470.391.250.0050.00190.00340.00260.05300.0830.0400.250.1720.0021I130.460.391.250.0080.00070.00220.00190.04200.0920.0410.310.1610.0030I140.450.451.280.0060.00150.00230.00170.04600.1210.0430.300.2000.0029J10.450.411.250.0080.00130.00200.00350.05800.0370.0080.250.1490.0021J20.450.441.270.0090.00100.00270.00150.04600.0340.0120.280.1410.0031J30.460.451.270.0050.00110.00270.00240.04300.0280.0180.300.1720.0028J40.460.451.350.0050.00210.00230.00260.04000.0300.0220.330.1710.0029J50.460.451.310.0090.00040.00260.00160.05200.0340.0280.320.2200.0028J60.470.401.280.0090.00170.00260.00300.05500.0400.0340.280.1620.0028J70.470.441.280.0040.00160.00230.00340.05300.0260.0460.280.1990.0030J80.470.431.230.0070.00100.00250.00170.06100.0340.0580.330.2290.0022J90.470.441.240.0050.00120.00210.00190.05900.0220.0760.250.1680.0028J100.460.451.320.0040.00150.00270.00260.04100.0300.1120.320.1580.0028J110.470.441.240.0070.00120.00250.00190.05300.0340.1870.250.2290.0028J120.460.391.280.0040.00030.00240.00350.05200.0190.2090.300.2040.0030The underline indicates that it is outside the scope of the present inventionTABLE 1HChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesI1Comparative steelI2Steel of present inventionI3Steel of present inventionI4Steel of present inventionI5Steel of present inventionI6Steel of present inventionI7Steel of present inventionI8Steel of present inventionI9Steel of present inventionI10Steel of present inventionI11Steel of present inventionI12Steel of present inventionI13Steel of present inventionI14Comparative steelJ1Comparative steelJ2Steel of present inventionJ3Steel of present inventionJ4Steel of present inventionJ5Steel of present inventionJ6Steel of present inventionJ7Steel of present inventionJ8Steel of present invention19Steel of present inventionJ10Steel of present inventionJ11Steel of present inventionJ12Comparative steelTABLE 1IChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBK10.450.431.290.0080.00220.00280.00330.04800.0310.0310.0090.1390.0021K20.470.411.270.0050.00060.00260.00300.04800.0210.0430.0130.1930.0026K30.470.411.250.0060.00090.00310.00340.06100.0210.0370.0510.1500.0032K40.450.391.310.0070.00160.00230.00320.05100.0250.0260.0870.1960.0032K50.470.451.250.0050.00130.00250.00180.04600.0370.0270.120.2050.0031K60.450.411.350.0050.00210.00270.00350.04200.0290.0360.180.2190.0030K70.450.431.300.0070.00150.00240.00310.05400.0250.0250.230.2150.0028K80.470.421.220.0080.00050.00280.00260.04400.0290.0320.270.2110.0025K90.460.451.220.0060.00040.00330.00140.05800.0210.0460.340.1940.0019K100.470.431.280.0040.00200.00200.00190.04400.0180.0270.430.1730.0019K110.460.411.350.0050.00200.00270.00300.05000.0310.0260.610.1780.0021K120.470.441.260.0080.00200.00280.00260.05300.0200.0340.770.1590.0032K130.470.411.310.0040.00060.00230.00340.04000.0320.0340.840.2140.0027L10.450.441.290.0040.00040.00320.00280.05000.0270.0450.270.00080.0028L20.470.451.280.0050.00180.00240.00260.05100.0200.0430.320.00130.0024L30.470.431.350.0040.00090.00280.00160.03900.0180.0460.290.00530.0024L40.460.451.230.0040.00130.00290.00290.05700.0260.0350.240.0220.0018L50.460.451.330.0070.00210.00260.00240.05800.0300.0440.330.0750.0033L60.460.391.300.0050.00150.00320.00260.04900.0270.0280.260.1320.0031L70.470.401.260.0060.00100.00320.00280.04500.0390.0270.280.1910.0025L80.460.421.240.0080.00150.00230.00230.05000.0200.0430.230.2370.0019L90.470.391.330.0050.00170.00330.00190.05600.0330.0350.300.3540.0018L100.460.451.250.0080.00110.00300.00320.04400.0380.0460.300.4940.0022L110.470.391.320.0070.00100.00300.00300.03900.0330.0420.230.6710.0021L120.450.431.240.0090.00150.00300.00250.06000.0200.0350.260.8890.0022L130.470.411.240.0080.00170.00190.00160.04700.0280.0400.241.2410.0033The underline indicates that it is outside the scope of the present inventionTABLE 1JChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesK1Comparative steelK2Steel of present inventionK3Steel of present inventionK4Steel of present inventionK5Steel of present inventionK6Steel of present inventionK7Steel of present inventionK8Steel of present inventionK9Steel of present inventionK10Steel of present inventionK11Steel of present inventionK12Steel of present inventionK13Comparative steelL1Comparative steelL2Steel of present inventionL3Steel of present inventionL4Steel of present inventionL5Steel of present inventionL6Steel of present inventionL7Steel of present inventionL8Steel of present inventionL9Steel of present inventionL10Steel of present inventionL11Steel of present inventionL12Steel of present inventionL13Comparative steelTABLE 1KChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBM10.460.391.310.0060.00160.00210.00330.05300.0370.0260.290.1360.0002M20.450.431.350.0040.00180.00300.00330.04000.0400.0330.260.2090.0007M30.450.441.350.0090.00050.00200.00250.06100.0410.0430.340.1880.0012M40.450.401.270.0060.00180.00330.00250.05800.0320.0430.340.1920.0018M50.460.451.270.0050.00070.00340.00160.04900.0210.0460.330.1980.0021M60.460.431.240.0040.00180.00220.00260.04700.0190.0290.340.1480.0033M70.460.411.280.0050.00160.00240.00190.04400.0380.0410.230.1890.0047M80.470.431.340.0040.00170.00220.00220.05800.0420.0430.250.1460.0071M90.470.451.340.0070.00030.00340.00330.04500.0200.0330.240.1400.0122M100.470.431.280.0040.00170.00220.00190.05800.0420.0410.250.1890.0182M110.450.391.320.0070.00120.00320.00330.06100.0320.0270.280.1840.0216N10.450.441.310.0050.00130.00270.00180.05600.0270.0380.270.1480.0022N20.470.401.210.0070.00140.00200.00260.06000.0350.0300.340.2070.0031N30.460.401.260.0090.00130.00250.00230.05000.0400.0280.230.1870.0024N40.470.431.300.0070.00110.00230.00170.04600.0330.0290.340.1710.0019N50.470.431.260.0050.00160.00190.00290.05000.0420.0330.310.2280.0031N60.450.441.280.0070.00130.00210.00210.04200.0360.0290.270.1560.0024N70.470.431.230.0070.00210.00320.00310.04900.0290.0310.320.2090.0023N80.450.391.280.0060.00200.00340.00350.04900.0260.0340.250.1480.0022N90.470.451.320.0070.00070.00200.00200.05200.0390.0300.230.1680.0024N100.450.411.290.0070.00030.00260.00170.04700.0210.0330.280.1910.0023N110.450.411.220.0050.00220.00190.00270.05200.0240.0430.270.1920.0027N120.470.431.290.0050.00050.00220.00170.04800.0190.0320.310.2290.0026N130.450.431.340.0060.00090.00200.00310.06000.0230.0280.260.1470.0033The underline indicates that it is outside the scope of the present inventionTABLE 1LChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesM1Comparative steelM2Steel of present inventionM3Steel of present inventionM4Steel of present inventionM5Steel of present inventionM6Steel of present inventionM7Steel of present inventionM8Steel of present inventionM9Steel of present inventionM10Steel of present inventionM11Comparative steelN10.06Steel of present inventionN20.11Steel of present inventionN30.24Steel of present inventionN40.41Steel of present inventionN50.62Steel of present inventionN60.87Steel of present inventionN71.12Steel of present inventionN81.34Steel of present inventionN91.59Steel of present inventionN101.71Steel of present inventionN111.92Steel of present inventionN122.51Steel of present inventionN133.67Steel of present inventionTABLE 1MChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBO10.470.421.280.0040.00180.00290.00190.05600.0400.0430.330.1760.0020O20.460.411.260.0090.00090.00230.00150.05300.0300.0270.300.2170.0023O30.470.441.250.0040.00110.00340.00170.03900.0180.0380.290.1850.0024O40.470.391.330.0050.00110.00270.00180.05600.0290.0290.290.2040.0029O50.460.431.310.0040.00220.00340.00210.04500.0250.0270.260.1770.0027O60.470.391.310.0040.00040.00340.00150.04500.0190.0290.330.1530.0026O70.470.451.270.0080.00160.00300.00270.05400.0250.0250.250.1950.0024O80.460.411.280.0040.00190.00260.00160.04200.0220.0320.340.1440.0022O90.460.411.330.0060.00060.00210.00180.03900.0250.0280.330.1810.0028O100.470.421.320.0060.00120.00290.00150.04900.0200.0260.300.1840.0031O110.470.421.320.0070.00100.00330.00330.05500.0390.0290.250.2080.0021O120.460.441.240.0060.00150.00220.00270.05600.0380.0350.240.2130.0022P10.470.421.230.0070.00130.00210.00320.04200.0210.0280.260.1320.0027P20.470.421.290.0080.00160.00240.00140.04500.0310.0300.280.1940.0020P30.460.451.240.0050.00070.00300.00150.05900.0420.0410.260.1990.0021P40.460.441.330.0080.00120.00330.00300.05700.0400.0460.280.1820.0019P50.450.391.350.0050.00130.00270.00160.04900.0290.0300.310.1630.0031P60.450.391.260.0060.00190.00320.00180.04400.0230.0460.300.2230.0025P70.470.391.210.0070.00050.00270.00150.03900.0230.0320.290.2260.0024P80.470.391.300.0080.00210.00200.00150.06100.0240.0260.270.1980.0019P90.450.451.330.0090.00140.00190.00210.06000.0310.0280.260.1430.0022P100.450.421.290.0090.00080.00200.00210.06000.0260.0350.250.2190.0032P110.470.421.230.0070.00070.00210.00190.04500.0190.0250.320.2220.0020P120.450.441.240.0060.00030.00300.00180.05700.0190.0400.290.1710.0028TABLE 1NChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesO10.03Steel of present inventionO20.11Steel of present inventionO30.26Steel of present inventionO40.42Steel of present inventionO50.87Steel of present inventionO61.23Steel of present inventionO71.65Steel of present inventionO81.91Steel of present inventionO92.14Steel of present inventionO102.55Steel of present inventionO112.77Steel of present inventionO122.96Steel of present inventionP10.06Steel of present inventionP20.13Steel of present inventionP30.25Steel of present inventionP40.41Steel of present inventionP50.85Steel of present inventionP61.31Steel of present inventionP71.61Steel of present inventionP81.89Steel of present inventionP92.22Steel of present inventionP102.49Steel of present inventionP112.71Steel of present inventionP122.92Steel of present inventionTABLE 1OChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBQ10.460.431.350.0050.00080.00300.00200.04700.0360.0260.280.1640.0031Q20.470.391.300.0080.00190.00300.00350.05700.0250.0290.250.1410.0032Q30.460.391.330.0040.00080.00190.00220.03900.0370.0360.260.2010.0032Q40.460.391.330.0060.00100.00310.00280.04900.0240.0450.300.1820.0024Q10.450.411.280.0070.00210.00250.00340.05400.0390.0460.290.2200.0028Q20.470.401.300.0070.00130.00190.00150.04200.0210.0420.290.1740.0032Q30.460.421.340.0080.00060.00210.00290.04300.0350.0430.340.1700.0020Q40.470.431.240.0080.00210.00290.00290.05400.0420.0250.240.2030.0033Q10.460.451.330.0040.00180.00220.00300.04100.0320.0360.250.2270.0018Q20.460.441.270.0070.00060.00310.00230.04400.0320.0270.280.1960.0019Q30.470.441.290.0090.00080.00250.00260.04500.0340.0250.300.1710.0019Q40.460.451.270.0050.00140.00210.00330.05400.0280.0400.230.2210.0019R10.460.411.340.0070.00180.00300.00330.05700.0230.0280.230.2250.0032R20.450.391.290.0050.00190.00210.00330.04700.0230.0320.320.1880.0021R30.460.441.220.0070.00200.00280.00280.05800.0360.0430.290.2050.0020R40.470.441.270.0070.00200.00240.00340.04000.0390.0460.240.1620.0024R50.450.401.290.0050.00040.00230.00190.04200.0350.0300.320.1980.0029R60.460.451.220.0070.00180.00290.00210.04800.0290.0320.240.1980.0032R70.470.451.280.0090.00150.00220.00240.04000.0250.0250.300.1430.0027R80.460.401.220.0040.00130.00260.00330.04200.0360.0440.260.2220.0022R90.450.441.300.0090.00030.00280.00240.05100.0230.0330.250.1320.0022R100.460.401.320.0080.00120.00230.00180.05000.0180.0390.290.1930.0022R110.470.401.350.0080.00200.00200.00180.05100.0320.0350.340.1480.0027R120.460.411.310.0040.00090.00220.00200.04300.0360.0290.330.1550.0028TABLE 1PChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesQ10.06Steel of present inventionQ20.12Steel of present inventionQ30.23Steel of present inventionQ40.42Steel of present inventionQ10.81Steel of present inventionQ21.34Steel of present inventionQ31.63Steel of present inventionQ41.86Steel of present inventionQ12.20Steel of present inventionQ22.51Steel of present inventionQ32.68Steel of present inventionQ42.90Steel of present inventionR10.07Steel of present inventionR20.14Steel of present inventionR30.25Steel of present inventionR40.46Steel of present inventionR50.84Steel of present inventionR61.37Steel of present inventionR71.59Steel of present inventionR81.81Steel of present inventionR92.23Steel of present inventionR102.52Steel of present inventionR112.67Steel of present inventionR122.91Steel of present inventionTABLE 1QChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBS10.470.401.260.0070.00210.00290.00160.05100.0230.0440.260.1640.0033S20.460.411.250.0080.00170.00240.00320.04700.0410.0330.260.2060.0027S30.460.391.250.0050.00080.00290.00320.04600.0280.0450.320.1560.0025S40.470.401.300.0040.00050.00220.00350.06000.0190.0430.230.1950.0033S50.470.431.230.0060.00030.00250.00200.04500.0330.0360.270.1540.0023S60.460.411.300.0080.00120.00240.00310.05700.0220.0380.330.1650.0026S70.450.411.340.0090.00040.00190.00260.04400.0230.0390.290.2130.0021S80.460.421.340.0060.00200.00250.00290.04700.0250.0330.330.1350.0029T10.460.401.290.0050.00050.00300.00140.04200.0260.0290.270.1860.0024T20.460.451.270.0080.00220.00250.00280.05900.0370.0390.340.2050.0028T30.450.441.320.0080.00060.00320.00330.04600.0330.0260.250.1400.0021T40.460.451.320.0060.00030.00290.00300.04300.0190.0400.270.1930.0020T50.470.391.270.0080.00050.00270.00210.04000.0290.0370.320.2200.0032T60.470.441.310.0040.00040.00200.00180.04700.0410.0320.290.1680.0026T70.470.411.220.0040.00130.00260.00350.05800.0280.0310.260.2120.0020T80.450.411.340.0040.00030.00250.00350.05500.0250.0350.230.1870.0023U10.470.431.340.0080.00150.00300.00180.05600.0400.0320.260.1600.0031U20.470.441.230.0080.00140.00270.00200.04500.0220.0290.310.1350.0020U30.450.411.280.0050.00200.00320.00260.05800.0250.0370.340.1460.0019U40.450.451.270.0080.00220.00200.00160.04300.0290.0450.230.1540.0025U50.450.411.270.0070.00090.00210.00280.04400.0240.0460.260.1410.0028U60.460.411.220.0040.00100.00220.00180.05400.0270.0250.260.1940.0022U70.460.441.230.0070.00070.00300.00250.05500.0210.0300.300.1720.0033U80.460.391.290.0050.00190.00290.00150.05600.0300.0250.330.2150.0028V10.470.401.240.0080.00180.00220.00170.05200.0180.0250.330.2210.0028V20.460.401.310.0080.00150.00260.00320.04300.0400.0460.260.1410.0028V30.450.391.220.0050.00090.00250.00340.03900.0380.0350.260.1310.0025V40.460.391.260.0060.00110.00340.00250.04700.0200.0260.240.2170.0018V50.460.421.230.0070.00130.00250.00210.06100.0210.0340.340.1310.0022V60.470.441.240.0070.00100.00230.00300.05800.0410.0300.310.1560.0031V70.450.431.310.0070.00090.00200.00230.05700.0330.0330.250.1470.0031V80.450.411.330.0060.00050.00240.00230.05900.0340.0450.300.1340.0030TABLE 1RChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesS10.002Steel of present inventionS20.010Steel of present inventionS30.120Steel of present inventionS40.290Steel of present inventionS50.440Steel of present inventionS60.620Steel of present inventionS70.770Steel of present inventionS80.920Steel of present inventionT10.002Steel of present inventionT20.020Steel of present inventionT30.110Steel of present inventionT40.280Steel of present inventionT50.430Steel of present inventionT60.610Steel of present inventionT70.790Steel of present inventionT80.930Steel of present inventionU10.002Steel of present inventionU20.030Steel of present inventionU30.100Steel of present inventionU40.270Steel of present inventionU50.410Steel of present inventionU60.620Steel of present inventionU70.780Steel of present inventionU80.920Steel of present inventionV10.002Steel of present inventionV20.020Steel of present inventionV30.110Steel of present inventionV40.290Steel of present inventionV50.430Steel of present inventionV60.600Steel of present inventionV70.750Steel of present inventionV80.910Steel of present inventionTABLE 1SChemical composition (mass %) remainder being Fe and impuritiesSteelCSiMnPSNOAlNbTiCrMoBW10.460.391.250.0040.00070.00220.00150.05500.0210.0370.310.1680.0024W20.470.391.210.0050.00210.00210.00310.04400.0320.0250.260.2260.0018W30.460.441.250.0070.00200.00340.00280.04800.0210.0320.230.1490.0029W40.470.441.210.0080.00170.00230.00260.06000.0420.0290.310.2230.0018W50.470.451.210.0070.00170.00220.00150.03900.0190.0320.260.1670.0019W60.460.421.220.0090.00180.00330.00260.05400.0340.0320.310.1400.0018W70.470.431.280.0090.00040.00210.00280.05700.0320.0370.280.2190.0024W80.470.401.230.0040.00160.00310.00240.05200.0330.0290.300.1830.0026X10.460.421.240.0050.00160.00340.00210.06100.0290.0310.300.2190.0027X20.470.431.310.0090.00140.00280.00330.03900.0240.0370.230.1670.0026X30.450.431.330.0070.00070.00200.00200.06000.0290.0250.280.1580.0026X40.470.421.240.0040.00090.00310.00220.04600.0220.0380.320.1990.0027X50.450.401.300.0080.00060.00230.00210.05300.0410.0260.250.2180.0033X60.470.411.210.0050.00110.00240.00310.05000.0250.0300.280.2210.0027X70.470.421.340.0050.00060.00290.00250.04600.0280.0420.250.1660.0033X80.470.451.340.0080.00090.00200.00290.03900.0370.0440.330.1450.0027AA10.450.431.310.0090.00070.00310.00210.06000.0290.0370.230.2190.0026AA20.450.401.240.0070.00110.00240.00220.05000.0410.0380.250.1990.0033AA30.470.421.300.0050.00060.00290.00310.04600.0280.0300.250.2210.0033Y10.450.391.210.0060.00210.00300.00280.05600.0230.0380.320.1590.0029Y20.470.411.210.0040.00220.00190.00240.04600.0310.0450.340.1350.0024Y30.470.391.280.0040.00090.00310.00180.05800.0350.0430.310.2230.0020Y40.460.441.310.0090.00200.00240.00180.05100.0320.0340.340.2040.0033Z10.470.430.810.0070.00100.00190.00190.04300.0300.0440.250.2140.0033Z20.460.431.310.0070.00030.00310.00140.04900.0190.0280.270.1900.0021Z30.450.432.040.0050.00130.00200.00290.04600.0400.0290.290.1610.0029Z40.460.432.230.0040.00040.00310.00330.04000.0210.0310.330.2100.0024TABLE 1TChemical composition (mass %) remainder being Fe and impuritiesSteelCoNiCuVWCaMgREMSbSnZrAsNotesW10.002Steel of present inventionW20.030Steel of present inventionW30.130Steel of present inventionW40.260Steel of present inventionW50.410Steel of present inventionW60.590Steel of present inventionW70.730Steel of present inventionW80.920Steel of present inventionX10.002Steel of present inventionX20.020Steel of present inventionX30.110Steel of present inventionX40.260Steel of present inventionX50.420Steel of present inventionX60.620Steel of present inventionX70.760Steel of present inventionX80.910Steel of present inventionAA10.002Steel of present inventionAA20.025Steel of present inventionAA30.081Steel of present inventionY10.070.25Steel of present inventionY20.10Steel of present inventionY31.00Steel of present inventionY40.050.260.120Steel of present inventionZ1Steel of present inventionZ2Steel of present inventionZ3Steel of present inventionZ4Steel of present inventionTABLE 2AFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes1A156554786120895368Comparative example2A252554755127897358Present invention example3A354549783118896360Present invention example4A456552762119909353Present invention example5A556551780106903354Present invention example6A652546764105896365Present invention example7A753553764110915365Present invention example8A854556787123896360Present invention example9A956544766122901375Present invention example10A1054544782105915365Present invention example11A1155545769114895348Present invention example12A1253551758116898368Present invention example13A1352550790102908357Present invention example14A1451543792127903364Comparative example15B151541784107909345Comparative example16B254559793112902345Present invention example17B353544762128924352Present invention example18B456554757100923367Present invention example19B554542773108912353Present invention example20B655560772115911353Present invention example21B755544792115923364Present invention example22B851552759101905351Present invention example23B956560794117924362Present invention example24B1055548774101924369Present invention example25B1155550775124914367Present invention example26B1251547778111918359Present invention example27B1356548771123923355Present invention example28B1454545792102910364Present invention example29B1552556776118908362Comparative example30C153545765104896372Comparative example31C255546761114925365Present invention example32C352551771123900362Present invention example33C453557785106895371Present invention example34C551556771116895354Present invention example35C654556787120902366Present invention example36C753554768122902363Present invention example37C851555778119905358Present invention example38C952551786127900367Present invention example39C1056552781108919365Present invention example40C1156549761109898346Present invention example41C1253558756117908359Present invention example42C1352552773113905364Present invention example43C1454553788120898368Comparative example44D156557761129920367Present invention example45D256555769105920362Present invention example46D356555784107907355Present invention example47D452554780121910345Present invention exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 2BFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes48D556540776127910355Present invention example49D652541782101896352Present invention example50D753558760106911353Present invention example51D853550759124895359Present invention example52D952555758100915370Comparative example53E153540787101904353Present invention example54E253552779106917345Present invention example55E356549793120917364Present invention example56E454548758109904373Present invention example57E551551779118895345Present invention example58E651550755109905362Present invention example59E756559773126909362Present invention example60E851559791100908345Present invention example61E953540783108904350Comparative example62F156550768106914371Present invention example63F254549780112919374Present invention example64F356540756116914362Present invention example65F453542787127907370Present invention example66F551555778107915375Present invention example67F656555790127900371Present invention example68F751543760100922372Present invention example69F851542778116900370Present invention example70F956548763104913365Comparative example71G154555786123897357Present invention example72G253558795129909373Present invention example73G353557789125914359Present invention example74G452540755112924365Present invention example75G554555790101896357Present invention example76G656557794123908350Present invention example77G754558788115910372Present invention example78G855550789102915354Comparative example79H152549779121910369Comparative example80H256543771104923369Present invention example81H355558788113911348Present invention example82H454551768100904347Present invention example83H551548755119902363Present invention example84H652546766111916362Present invention example85H755549760112903355Present invention example86H853554766115912347Present invention example87H955555773119914370Present invention example88H1051544775111914355Present invention example89H1151554791128911369Present invention example90H1252543782124899353Present invention example91H1353556787111924362Present invention example92H1453544775125905348Comparative example93I155555763119916375Comparative example94I251552760128900365Present invention exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 2CFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes95I356542787114896362Present invention example96I456542755129915363Present invention example97I556560768124905354Present invention example98I651550757100900370Present invention example99I753541763102912354Present invention example100I852551778120914360Present invention example101I951551781111918359Present invention example102I1056549771124907368Present invention example103I1154557785119920355Present invention example104I1254548781108922351Present invention example105I1351545764108922348Present invention example106I1455548769114899360Comparative example107J156552774107919367Comparative example108J251552792111914357Present invention example109J353550789127899369Present invention example110J455559784111910348Present invention example111J556559759109898366Present invention example112J654545783112903374Present invention example113J753558781119899347Present invention example114J852540791112900368Present invention example115J953540771117907374Present invention example116J1053546776121923373Present invention example117J1153540771119900374Present invention example118J1254556790124911351Comparative example119K154557792130901369Comparative example120K251546791117908371Present invention example121K352540772116917349Present invention example122K453544785119907375Present invention example123K552547766116909362Present invention example124K653545794111910364Present invention example125K755556771106903369Present invention example126K856558765107900373Present invention example127K955542774117912358Present invention example128K1056542776125914373Present invention example129K1156554767123899346Present invention example130K1254556774101907372Present invention example131K1352553776117920353Comparative example132L154555757130897368Comparative example133L256545779129898361Present invention example134L354555775100915372Present invention example135L452547776120898354Present invention example136L552545768127914357Present invention example137L655545763119925365Present invention example138L753540792103911358Present invention example139L856541793100909350Present invention example140L956541779125917375Present invention example141L1052558776121920366Present invention exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 2DFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes142L1153547767117917349Present invention example143L1253547783102908368Present invention example144L1356559786112917346Present invention example145M154550793118914351Comparative example146M256550784126907360Comparative example147M351552785124922375Present invention example148M453559773129919357Present invention example149M552559768111897361Present invention example150M656551778124924346Present invention example151M755556788121924368Present invention example152M851554755106914361Present invention example153M954551787120902364Present invention example154M1051556755129924346Present invention example155M1156559772115921353Comparative example156N151549777129917352Present invention example157N251544758128914364Present invention example158N356542765113907373Present invention example159N451544761112911365Present invention example160N552557785112899350Present invention example161N653543784123903353Present invention example162N754560767103899366Present invention example163N853544785100896366Present invention example164N953544757114922367Present invention example165N1051557770106916355Present invention example166N1155553764101906358Present invention example167N1252549785126904356Present invention example168N1353555779101910361Present invention example169O154550793111921370Present invention example170O251557787105907348Present invention example171O352548783104925353Present invention example172O452552761130920360Present invention example173O553554775130914353Present invention example174O653546779108908356Present invention example175O751558782128897365Present invention example176O856560780121900354Present invention example177O956545787109918372Present invention example178O1053548770110905346Present invention example179O1153551766109907375Present invention example180O1251559767108902355Present invention example181P153546769125924366Present invention example182P251542766112919363Present invention example183P352560764103915357Present invention example184P456560785121902347Present invention example185P552545773104910367Present invention example186P653552775122910352Present invention example187P752549780112897355Present invention example188P851553783119911366Present invention exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 2EFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes189P955549770110900368Present invention example190P1052548788108900356Present invention example191P1154560792113924351Present invention example192P1253552775113910345Present invention example193Q151553787126910359Present invention example194Q254547795115904357Present invention example195Q356560795106897360Present invention example196Q454553766103917358Present invention example197Q152545794107919359Present invention example198Q255540763110917370Present invention example199Q354541759119923352Present invention example200Q453554774106910347Present invention example201Q153551776128925347Present invention example202Q254548773130905354Present invention example203Q353555761109925355Present invention example204Q453558759122913348Present invention example205R154552765125915369Present invention example206R254555758114896354Present invention example207R353560767100905349Present invention example208R453542775129917364Present invention example209RS51542779108909371Present invention example210R654545755100901356Present invention example211R751555772104914359Present invention example212R856559758102897350Present invention example213R955546787121901355Present invention example214R1053547756121903347Present invention example215R1151551786105916355Present invention example216R1253555765100924347Present invention example217S152544770104923363Present invention example218S253551755101908375Present invention example219S355544769109919351Present invention example220S454545793116907354Present invention example221S556550795118912359Present invention example222S652549756102905363Present invention example223S754554795102909352Present invention example224S853541791111912357Present invention example225T154558765130914361Present invention example226T251552764112897371Present invention example227T351558791106915373Present invention example228T456543775122909352Present invention example229T554547757103916358Present invention example230T655543755107921372Present invention example231T751542784124923346Present invention example232T851541790105898348Present invention example233U154548795122904368Present invention example234U252546369128915357Present invention example235U356554783118911359Present invention exampleTABLE 2FFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes236U456558769114919346Present invention example237U555545769101923358Present invention example238U656550774114917361Present invention example239U754543789115923360Present invention example240U851552760121905367Present invention example241V152556790128908374Present invention example242V255552763124909358Present invention example243V354548771128903368Present invention example244V455552773109901361Present invention example245V553553776105904349Present invention example246V652541768114897360Present invention example247V754542757100906371Present invention example248V855542766125900354Present invention example249W151544764101920370Present invention example250W256545758110895361Present invention example251W356560771117912359Present invention example252W454546765129902374Present invention example253W553542793128896360Present invention example254W655556785112898368Present invention example255W751542767128900350Present invention example256W856556763100916352Present invention example257X156553771104919353Present invention example258X251556765104922374Present invention example259X351550770128919345Present invention example260X451551791119907353Present invention example261X553550765108906349Present invention example262X652556788118896356Present invention example263X756557779111917345Present invention example264X856543764127896347Present invention example265AA156556770104907349Present invention example266AA251550779118896356Present invention example267AA351556771115903364Present invention example268Y151556794111900358Present invention example269Y252560770124920373Present invention example270Y356555777110903364Present invention example271Y456548770104919374Present invention example272Z154554788115896356Present invention example273Z254553771102912354Present invention example274Z356548765127918371Present invention example275Z455557779124899365Present invention example276Z215554761117896350Comparative example277Z222560766127921348Present invention example278Z233551776102897359Present invention example279Z242547765117896360Present invention example280Z250552755119908350Present invention example281Z252552778101909363Present invention example282Z251604778101911362Present invention exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 2GFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes283Z256655781115903368Present invention example284Z256708783115905362Present invention example285Z253721793124919357Present invention example286Z255774777106907362Softening heatComparative exampletreatment on coilafter coiling287Z256 25761120896351Softening heatPresent invention exampletreatment on coilafter coiling288Z252252772106902360Softening heatPresent invention exampletreatment on coilafter coiling289Z253405780109918374Softening heatPresent invention exampletreatment on coilafter coiling290Z255553765 11920357Comparative example291Z252557777 16898349Present invention example292Z251543783 24895347Present invention example293Z253542763 41909370Present invention example294Z252550782 60899354Present invention example295Z251540761107899369Present invention example296Z251558779170920366Present invention example297Z256543772232925357Present invention example298Z256558772367904346Present invention example299Z251548788480905366Present invention example300Z256543771603903365Present invention example301Z2555417801213 902349Present invention example302Z2555607601809 913375Present invention example303Z252552720106903345Comparative example304Z252542739112900355Present invention example305Z251540750127895347Present invention example306Z252555765106916355Present invention example307Z254546772124905347Present invention example308Z255541781128904353Present invention example309Z255540799111897371Present invention example310Z255547820100898348Present invention example311Z255556842116895355Present invention example312Z256555861117895351Present invention example313Z251552885111896355Present invention example314Z254543919121909361Comparative example315Z254558764117898353Annealing in reducingComparative exampleatmosphere316Z252559767108905375Annealing in reducingComparative exampleatmosphere317Z252547775118906372Re-annealing afterPresent invention exampleannealing inoxidizing atmosphere318Z255558778114920347Aluminum platingPresent invention example319Z254545757130915364Aluminum galvanizedPresent invention exampleplating320Z252540787115896368Aluminum-siliconPresent invention exampleplating321Z254559771123907357Hot-dip galvanizedPresent invention exampleplating322Z256555783102897362ElectrogalvanizedPresent invention exampleplating323Z256554781126923354Galvannealed platingPresent invention example324Z253552756120899357Zinc-nickel platingPresent invention example325Z255544765108915358Aluminum-Present invention examplemagnesium-zincplating326Z251560784127772366Comparative example327Z256557766130804364Present invention example328Z256550787120821361Present invention exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 2HFinalrollingCoilingAnnealingAnnealingHeatingHoldingExaminationreductiontemperaturetemperaturetimetemperaturetimeNo.Steel%° C.° C.s° C.sNotesNotes329Z255552784111843357Present invention example330Z255547790112858359Present invention example331Z256558762101870364Present invention example332Z252540761123870369Present invention example333Z253541760120887366Present invention example334Z251560765115903363Present invention example335Z253556792121920346Present invention example336Z256542769106937354Present invention example337Z256541771115951366Present invention example338Z255546761127972368Present invention example339Z256558781129988346Present invention example340Z2515567891061021 364Comparative example341Z255559767104906 53Comparative example342Z252543760117901 64Present invention example343Z255555789123908 81Present invention example344Z255548765102916106Present invention example345Z251543758100908126Present invention example346Z256547767128895187Present invention example347Z255558780129898245Present invention example348Z256540774108919293Present invention example349Z256556773110919332Present invention example350Z254544760119903368Present invention example351Z251552766114924398Present invention example352Z253543773111913436Present invention example353Z253542770107895499Present invention example354Z251552781100910524Present invention example355Z251558787123899568Present invention example356Z253541780125909588Present invention example357Z256553792125905623Comparative example358Z254552781100897353Annealing inPresent invention examplegas combustionatmosphere (air-fuel ratio: 0.80)359Z255549757113914363Annealing inPresent invention examplegas combustionatmosphere (air-fuel ratio: 0.85)360Z256555761112909369Annealing inPresent invention examplegas combustionatmosphere (air-fuel ratio: 1.10)361Z255560778129925375Hot-stampingPresent invention exampleheating: atmosphere(furnace heating)362Z254549758103918359Hot-stamping heating:Present invention examplenitrogen gas (dewpoint of −30° C.)363Z254545758118905361Hot-stamping heating:Present invention examplenitrogen gas (dewpoint of 0° C.)364Z256552769104899353Hot-stamping heating:Present invention examplenitrogen gas (dewpoint of +10° C.)365Z251559786116906354Hot-stamping heating:Present invention exampleelectrical heating366Z255556769105905368TemperingPresent invention exampletemperature: 150° C.367Z251550764117896359TemperingPresent invention exampletemperature: 170° C.368Z256552783125917355TemperingPresent invention exampletemperature: 200° C.369Z251543787111897352TemperingPresent invention exampletemperature: 310° C.370Z255547771109900348TemperingPresent invention exampletemperature: 429° C.371Z254547761100911345TemperingPresent invention exampletemperature: 513° C.372Z256559782121901357TemperingPresent invention exampletemperature: 588° C.373Z252554782125903348Partial softeningPresent invention exampletreatment wasperformed374Z251585785100900325Hot-stampingPresent invention exampleheating atmosphere(furnace heating)375Z252548790110897340Annealing inComparative examplereducing atmosphere,Hot-stampingheating atmosphere(furnace heating)376Z2535578403700 900330Comparative exampleThe underline indicates that it falls outside the preferable manufacturing conditions.TABLE 3AInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes 1A12.4971.50.4121710.98ExcellentComparative example 2A22.4641.80.3722530.98ExcellentPresent invention example 3A32.1781.70.4423520.94ExcellentPresent invention example 4A42.4861.50.4324260.97ExcellentPresent invention example 5A51.9791.50.3724750.97ExcellentPresent invention example 6A62.5602.10.4725040.97ExcellentPresent invention example 7A72.0691.60.4825250.95ExcellentPresent invention example 8A82.5842.50.4526010.81Very GoodPresent invention example 9A92.1962.10.4427020.84Very GoodPresent invention example10A102.2712.20.3728060.85Very GoodPresent invention example11A112.0632.10.4630010.84Very GoodPresent invention example12A122.0641.70.4531020.64FairPresent invention example13A132.0902.10.3832060.66FairPresent invention example14A142.1942.00.4825260.47FairComparative example15B11.9631.80.4921730.91ExcellentComparative example16B22.5701.70.3822550.99ExcellentPresent invention example17B32.1722.20.5022920.90ExcellentPresent invention example18B42.3812.10.4623540.94ExcellentPresent invention example19B52.4602.10.3723950.98ExcellentPresent invention example20B62.4771.50.4324210.96ExcellentPresent invention example21B72.2662.20.4424760.94ExcellentPresent invention example22B82.5772.40.5025060.96ExcellentPresent invention example23B92.4642.10.3825250.94ExcellentPresent invention example24B102.1742.30.4525440.93ExcellentPresent invention example25B112.4531.70.4325440.93Very GoodPresent invention example26B122.0522.00.3625460.99Very GoodPresent invention example27B132.2252.30.3725410.98GoodPresent invention example28B142.4122.20.3625460.96FairPresent invention example29B152.4 51.60.5025440.98BadComparative example30C15.8782.20.5024510.46FairComparative example31C24.9621.90.4825500.66ExcellentPresent invention example32C33.5902.40.4924980.73ExcellentPresent invention example33C42.9622.20.4824230.82ExcellentPresent invention example34C52.5742.00.3924820.92ExcellentPresent invention example35C61.9812.10.4824310.92ExcellentPresent invention example36C72.1732.50.4624580.94ExcellentPresent invention example37C82.5882.20.4524240.99ExcellentPresent invention example38C92.2862.50.4724430.94ExcellentPresent invention example39C102.1862.30.4324670.97ExcellentPresent invention example40C112.8772.50.4124300.84ExcellentPresent invention example41C123.7931.70.4424250.72ExcellentPresent invention example42C134.9742.10.4324840.62ExcellentPresent invention example43C145.6941.50.3524580.56FairComparative example44D12.5991.60.3925260.93ExcellentPresent invention example45D21.9821.80.4224910.99ExcellentPresent invention example46D32.0992.50.5024160.91ExcellentPresent invention example47D42.0612.40.4024190.93ExcellentPresent invention exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.TABLE 3BInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes48D52.0682.40.4424150.88ExcellentPresent invention example49D62.1991.80.4425010.76ExcellentPresent invention example50D72.4612.20.4624880.73ExcellentPresent invention example51D82.5861.70.4324270.65ExcellentPresent invention example52D92.5822.40.4724070.39FairComparative example53E12.3751.80.4624580.95ExcellentPresent invention example54E22.2852.00.4424520.98ExcellentPresent invention example55E32.2792.50.3724820.97ExcellentPresent invention example56E41.9921.60.4725370.91ExcellentPresent invention example57E52.3612.40.3524240.96ExcellentPresent invention example58E62.4652.50.5025100.80ExcellentPresent invention example59E72.4762.20.4624630.74ExcellentPresent invention example60E82.0942.30.5024330.65ExcellentPresent invention example61E92.3621.80.4324350.32FairComparative example62F12.3912.30.4424040.92ExcellentPresent invention example63F22.5661.70.4024920.90ExcellentPresent invention example64F32.0712.20.3825460.94ExcellentPresent invention example65F42.3891.50.3625440.94ExcellentPresent invention example66F52.2622.50.3724130.84ExcellentPresent invention example67F62.2882.40.3724370.71ExcellentPresent invention example68F72.4692.50.3825040.61ExcellentPresent invention example69F82.2892.40.3724170.62ExcellentPresent invention example70F91.9602.30.4425320.31FairComparative example71G12.2801.60.4824590.98ExcellentPresent invention example72G22.5942.40.5024730.97ExcellentPresent invention example73G32.4652.30.4724490.97ExcellentPresent invention example74G42.1901.70.3525280.96ExcellentPresent invention example75G52.1812.10.4424430.86ExcellentPresent invention example76G62.4642.40.4424140.72ExcellentPresent invention example77G72.3912.40.4525210.67ExcellentPresent invention example78G82.4602.30.4824280.34FairComparative example79H11.9881.80.3524760.31FairComparative example80H22.4951.80.4024310.67ExcellentPresent invention example81H32.4911.50.3824710.70ExcellentPresent invention example82H42.3682.10.4624490.86ExcellentPresent invention example83H52.2782.30.4824010.81ExcellentPresent invention example84H62.4831.70.4425160.94ExcellentPresent invention example85H72.5852.20.4024160.90ExcellentPresent invention example86H82.1812.10.3724740.91ExcellentPresent invention example87H92.5831.60.4824500.92ExcellentPresent invention example88H101.9922.40.3725320.86ExcellentPresent invention example89H111.9731.80.4324350.81ExcellentPresent invention example90H122.5951.80.4825500.65ExcellentPresent invention example91H132.2871.50.4924610.68ExcellentPresent invention example92H142.0671.60.4024760.37FairComparative example93I12.4711.50.4020300.97ExcellentComparative example94I22.4931.80.4922740.97ExcellentPresent invention exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.TABLE 3CInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes 95I32.3762.00.4423680.97ExcellentPresent invention example 96I42.2961.70.5023300.99ExcellentPresent invention example 97I52.0762.10.4523540.92ExcellentPresent invention example 98I62.3812.40.4424880.97ExcellentPresent invention example 99I72.5772.30.4924740.91ExcellentPresent invention example100I82.0932.50.4724660.98ExcellentPresent invention example101I92.5612.30.3924310.95ExcellentPresent invention example102I102.1761.90.4124350.95ExcellentPresent invention example103I111.9801.60.4824450.84ExcellentPresent invention example104I122.1922.30.4825460.76ExcellentPresent invention example105I132.5641.80.4124410.69ExcellentPresent invention example106I142.5931.60.4525210.38FairComparative example107J12.5781.80.3919510.91ExcellentComparative example108J22.1611.50.4722830.99ExcellentPresent invention example109J31.9912.40.4723900.93ExcellentPresent invention example110J42.3612.00.4823810.91ExcellentPresent invention example111J52.2941.80.4024470.97ExcellentPresent invention example112J62.2762.00.3724410.92ExcellentPresent invention example113J72.5921.70.4524750.97ExcellentPresent invention example114J82.3761.50.4024780.88ExcellentPresent invention example115J92.3711.80.4925460.77ExcellentPresent invention example116J102.0852.50.4424350.63ExcellentPresent invention example117J112.3761.70.4024250.62ExcellentPresent invention example118J122.0951.90.4025280.53FairComparative example119K12.3911.70.5020340.95ExcellentComparative example120K22.5902.20.4523000.91ExcellentPresent invention example121K31.9791.70.3523210.94ExcellentPresent invention example122K42.5672.50.4023860.98ExcellentPresent invention example123K52.3721.50.3823560.91ExcellentPresent invention example124K62.2772.50.4923720.93ExcellentPresent invention example125K72.4682.00.3924170.92ExcellentPresent invention example126K82.1642.30.4524940.98ExcellentPresent invention example127K92.3972.20.3725180.93ExcellentPresent invention example128K102.0972.20.4924370.85ExcellentPresent invention example129K112.4852.20.3724140.77ExcellentPresent invention example130K122.3622.10.3924760.65ExcellentPresent invention example131K132.3782.10.3725290.39FairComparative example132L12.3682.40.4220090.97ExcellentComparative example133L22.2752.50.4822920.98ExcellentPresent invention example134L32.0701.80.4623460.99ExcellentPresent invention example135L42.2732.30.4123210.94ExcellentPresent invention example136L52.5941.70.4923560.94ExcellentPresent invention example137L62.1971.70.3724610.92ExcellentPresent invention example138L72.3741.80.4324880.92ExcellentPresent invention example139L82.3672.20.4324530.96ExcellentPresent invention example140L92.3661.80.4324860.99ExcellentPresent invention example141L102.5942.30.3924920.88ExcellentPresent invention exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.TABLE 3DInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes142L111.9982.30.4024350.74ExcellentPresent invention example143L122.5881.50.3825450.67ExcellentPresent invention example144L132.0931.70.3525230.36FairComparative example145M12.0961.90.4020950.91ExcellentComparative example146M22.1812.00.4722280.90ExcellentPresent invention example147M32.5771.90.4923350.92ExcellentPresent invention example148M41.9932.30.4125470.92ExcellentPresent invention example149M52.3732.40.4725470.95ExcellentPresent invention example150M62.3842.40.4625480.94ExcellentPresent invention example151M72.0962.20.3825040.82ExcellentPresent invention example152M82.1941.60.4125470.74ExcellentPresent invention example153M92.2981.70.4924610.64ExcellentPresent invention example154M102.1981.60.4524550.62ExcellentPresent invention example155M111.9642.20.5025280.35FairComparative example156N12.3802.50.4126230.91ExcellentPresent invention example157N22.4971.70.4327040.95ExcellentPresent invention example158N32.3671.60.4826540.99ExcellentPresent invention example159N42.5772.10.3626010.91ExcellentPresent invention example;160N52.1752.10.4526760.95ExcellentPresent invention example161N62.5952.50.3927270.90ExcellentPresent invention example162N72.2892.10.3726910.92ExcellentPresent invention example163N82.0971.60.4427460.98ExcellentPresent invention example164N92.0792.10.4128530.91ExcellentPresent invention example165N102.0851.50.4027460.91ExcellentPresent invention example166N112.1701.80.4628960.98ExcellentPresent invention example167N122.4861.50.5026750.97ExcellentPresent invention example168N132.5942.10.3626460.97ExcellentPresent invention example169O11.9692.20.3625950.95ExcellentPresent invention example170O22.3752.20.4429320.91ExcellentPresent invention example171O32.0632.30.4427330.92ExcellentPresent invention example172O42.3771.90.3725520.92ExcellentPresent invention example173O52.3611.60.3928020.99ExcellentPresent invention example174O61.9732.50.3926580.93ExcellentPresent invention example175O72.3712.50.4929530.95ExcellentPresent invention example176O82.3961.90.4429480.98ExcellentPresent invention example177O92.2702.10.3626550.96ExcellentPresent invention example178O102.1942.30.3726400.97ExcellentPresent invention example179O112.2772.20.4227970.96ExcellentPresent invention example180O122.5881.80.4526920.97ExcellentPresent invention example181P12.0691.60.4829930.97ExcellentPresent invention example182P22.2911.70.4329470.91ExcellentPresent invention example183P32.1981.90.3625910.94ExcellentPresent invention example184P42.0852.00.4927680.96ExcellentPresent invention example185P52.0842.10.4729840.91ExcellentPresent invention example186P62.2761.50.4528660.90ExcellentPresent invention example187P72.3622.00.5028960.92ExcellentPresent invention example188P82.3661.80.4229220.98ExcellentPresent invention exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.TABLE 3EInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes189P91.9952.50.3725810.99ExcellentPresent invention example190P102.2641.90.4525920.93ExcellentPresent invention example191P112.0862.40.4725780.91ExcellentPresent invention example192P122.4991.50.4427300.98ExcellentPresent invention example193Q11.9962.10.4928630.94ExcellentPresent invention example194Q22.5812.20.3528600.96ExcellentPresent invention example195Q31.9781.70.4728000.95ExcellentPresent invention example196Q42.2641.90.4529150.96ExcellentPresent invention example197Q11.9641.50.4325980.99ExcellentPresent invention example198Q22.1912.30.4925580.97ExcellentPresent invention example199Q32.0622.00.4728530.94ExcellentPresent invention example200Q42.4821.60.3529580.93ExcellentPresent invention example201Q11.9901.90.4229710.91ExcellentPresent invention example202Q22.0851.80.3726590.94ExcellentPresent invention example203Q32.5831.60.3725690.99ExcellentPresent invention example204Q42.1642.20.3727200.95ExcellentPresent invention example205R12.1921.60.3528040.93ExcellentPresent invention example206R21.9802.50.4129850.99ExcellentPresent invention example207R31.9671.50.4127080.92ExcellentPresent invention example208R42.2762.20.3629050.99ExcellentPresent invention example209R52.1851.80.4527990.90ExcellentPresent invention example210R62.2982.00.3629620.92ExcellentPresent invention example211R72.4732.20.3827870.92ExcellentPresent invention example212R82.0731.90.4127340.94ExcellentPresent invention example213R92.5881.60.3728870.94ExcellentPresent invention example214R102.0712.50.4929360.90ExcellentPresent invention example215R112.2871.50.4029200.95ExcellentPresent invention example216R122.0801.80.4727090.95ExcellentPresent invention example217S12.3672.50.3624690.94ExcellentPresent invention example218S22.0682.20.4825420.90ExcellentPresent invention example219S32.3722.40.3925280.90ExcellentPresent invention example220S42.4941.90.4125290.95ExcellentPresent invention example221S51.9601.90.4224690.98ExcellentPresent invention example222S61.9772.30.5025130.97ExcellentPresent invention example223S72.2921.60.4524070.99ExcellentPresent invention example224S82.5752.20.4025500.99ExcellentPresent invention example225T12.3772.10.3925020.95ExcellentPresent invention example226T22.5701.90.3924470.93ExcellentPresent invention example227T32.3752.00.4124810.98ExcellentPresent invention example228T42.4881.50.4425230.91ExcellentPresent invention example229T51.9971.80.4224330.98ExcellentPresent invention example230T61.9631.90.3824750.96ExcellentPresent invention example231T72.2801.70.3824100.93ExcellentPresent invention example232T82.2792.50.3925310.93ExcellentPresent invention example233U12.5682.30.4124120.94ExcellentPresent invention example234U22.3671.50.4024650.98ExcellentPresent invention example235U32.5932.40.4525360.96ExcellentPresent invention exampleTABLE 3FInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes236U42.5832.40.4124240.98ExcellentPresent invention example237U52.4881.70.3624990.95ExcellentPresent invention example238U62.5692.30.3825030.99ExcellentPresent invention example239U72.4782.40.4224150.97ExcellentPresent invention example240U81.9602.00.4324540.92ExcellentPresent invention example241V12.0841.80.4725150.97ExcellentPresent invention example242V22.4781.60.4024780.93ExcellentPresent invention example243V32.0642.40.4125210.96ExcellentPresent invention example244V42.4732.40.4725480.96ExcellentPresent invention example245V52.4782.50.4724230.93ExcellentPresent invention example246V62.3872.20.4425200.98ExcellentPresent invention example247V72.2941.50.4225310.93ExcellentPresent invention example248V82.3802.50.3925140.99ExcellentPresent invention example249W12.0732.40.3924440.99ExcellentPresent invention example250W22.3831.60.4424030.92ExcellentPresent invention example251W32.1721.80.4725140.91ExcellentPresent invention example252W42.5891.60.3924960.99ExcellentPresent invention example253W51.9871.30.3724980.95ExcellentPresent invention example254W62.5642.20.3724370.94ExcellentPresent invention example255W72.0851.60.4824120.96ExcellentPresent invention example256W82.4691.80.3924530.92ExcellentPresent invention example257X12.0932.10.5024600.95ExcellentPresent invention example258X22.1691.80.3825430.93ExcellentPresent invention example259X32.4961.90.3825310.90ExcellentPresent invention example260X42.5691.60.4825240.93ExcellentPresent invention example261X51.9802.50.4724640.97ExcellentPresent invention example262X62.0922.00.4324800.90ExcellentPresent invention example263X72.1711.70.4325000.93ExcellentPresent invention example264X82.3791.80.3524440.90ExcellentPresent invention example265AA12.1722.10.4424890.90ExcellentPresent invention example266AA22.2791.80.4325020.90ExcellentPresent invention example267AA32.3791.80.3824480.93ExcellentPresent invention example268Y11.9701.60.3924360.97ExcellentPresent invention example269Y22.2822.00.4824460.97ExcellentPresent invention example270Y32.4641.90.4724360.99ExcellentPresent invention example271Y42.4782.20.4725360.94ExcellentPresent invention example272Z12.3782.50.3725400.99ExcellentPresent invention example273Z22.1741.60.3724230.93ExcellentPresent invention example274Z32.5972.10.4025440.97ExcellentPresent invention example275Z42.0772.00.4324490.96ExcellentPresent invention example276Z25.6904.20.3525240.40BadComparative example277Z22.3692.00.4624270.61ExcellentPresent invention example278Z22.3782.20.4324180.70ExcellentPresent invention example279Z22.4742.10.4225260.87ExcellentPresent invention example280Z22.4861.60.4024340.90ExcellentPresent invention example281Z22.5651.70.3524960.96ExcellentPresent invention example282Z22.0931.70.3624440.91ExcellentPresent invention exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.TABLE 3GInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes283Z22.5682.50.4224790.84ExcellentPresent invention example284Z22.5662.40.4124530.75ExcellentPresent invention example285Z22.1732.10.4524380.67ExcellentPresent invention example286Z25.5732.20.4724630.33FairComparative example287Z22.4911.90.3524840.91ExcellentPresent invention example288Z22.0801.70.3924680.97ExcellentPresent invention example289Z22.1672.50.4825250.93ExcellentPresent invention example290Z22.0 34.90.0325320.97BadComparative example291Z22.2153.70.1224400.99FairPresent invention example292Z22.2283.20.2325450.98GoodPresent invention example293Z22.5462.70.3424630.99Very GoodPresent invention example294Z22.0942.50.5025290.94ExcellentPresent invention example295Z22.3861.60.4224500.93ExcellentPresent invention example296Z22.4971.60.4224130.93ExcellentPresent invention example297Z22.4742.30.4124470.96ExcellentPresent invention example298Z22.4792.20.4024300.96ExcellentPresent invention example299Z22.0902.00.3624150.96ExcellentPresent invention example300Z22.5922.50.4225430.92ExcellentPresent invention example301Z22.4982.50.4524040.91ExcellentPresent invention example302Z22.3982.40.4425020.99ExcellentPresent invention example303Z22.1 75.10.0225210.92BadComparative example304Z22.4113.30.0725040.90FairPresent invention example305Z22.0303.40.2224630.96GoodPresent invention example306Z22.0532.70.3024380.92Very GoodPresent invention example307Z22.1941.70.4725190.97ExcellentPresent invention example308Z22.3932.40.4225350.93ExcellentPresent invention example309Z22.2602.20.4324710.97ExcellentPresent invention example310Z22.3621.70.4524310.99ExcellentPresent invention example311Z21.9532.90.3224410.97Very GoodPresent invention example312Z22.1223.50.2424340.91GoodPresent invention example313Z22.0113.60.0925270.99FairPresent invention example314Z22.4 34.60.0124280.92BadComparative example315Z22.4 55.10.0224480.91BadComparative example316Z22.3 34.40.0224460.99BadComparative example317Z21.9641.90.4225440.99ExcellentPresent invention example318Z22.2811.90.4424980.95ExcellentPresent invention example319Z22.0971.70.4425050.96ExcellentPresent invention example320Z22.0782.50.3824780.94ExcellentPresent invention example321Z22.2751.90.4325350.94ExcellentPresent invention example322Z22.1762.50.4625070.98ExcellentPresent invention example323Z22.0881.70.3925340.94ExcellentPresent invention example324Z22.4901.50.5025370.90ExcellentPresent invention example325Z22.5692.20.3524730.99ExcellentPresent invention example326Z25.4822.10.4324220.36FairComparative example327Z21.9672.10.3624810.94ExcellentPresent invention example328Z22.0791.50.4125220.90ExcellentPresent invention example329Z22.5892.20.3824960.95ExcellentPresent invention exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.TABLE 3HInterior regionStandardSurface layer regiondeviation ofMaximum valueEvaluationEvaluationgrain sizes ofof pole densityDeboronizationTensileof earlyof hydrogenExaminationprior γ grainsBainiteof textureindexstrengthfractureembrittlementNo.Steelμmarea %——MParesistanceresistanceNotes330Z22.3892.30.4124860.92ExcellentPresent invention example331Z22.4842.30.4825230.98ExcellentPresent invention example332Z22.3991.60.4725450.90ExcellentPresent invention example333Z22.5641.70.4924390.99ExcellentPresent invention example334Z22.1951.70.4124530.94ExcellentPresent invention example335Z22.2712.20.3925150.92ExcellentPresent invention example336Z23.0652.00.4624210.83ExcellentPresent invention example337Z22.7672.10.3724600.80ExcellentPresent invention example338Z23.9612.00.4824050.79ExcellentPresent invention example339Z24.6861.50.3725180.69ExcellentPresent invention example340Z25.6691.60.4224930.39FairComparative example341Z25.8912.40.4224840.58FairComparative example342Z24.8742.20.4425300.63ExcellentPresent invention example343Z23.7891.80.4224420.73ExcellentPresent invention example344Z23.0792.20.5024370.88ExcellentPresent invention example345Z22.1661.50.5024450.99ExcellentPresent invention example346Z22.0771.70.3724620.92ExcellentPresent invention example347Z21.9881.80.3624220.92ExcellentPresent invention example348Z22.0611.90.4925490.92ExcellentPresent invention example349Z22.4732.30.4825070.94ExcellentPresent invention example350Z21.9992.00.4025170.92ExcellentPresent invention example351Z21.9732.50.3824370.96ExcellentPresent invention example352Z22.2771.70.4324490.98ExcellentPresent invention example353Z21.9802.20.4924890.95ExcellentPresent invention example354Z23.0992.50.5024300.86ExcellentPresent invention example355Z23.2671.80.5024760.71ExcellentPresent invention example356Z24.4682.30.4324620.61ExcellentPresent invention example357Z25.3741.70.3524510.39FairComparative example358Z22.1971.80.3724690.95ExcellentPresent invention example359Z22.1761.80.3824370.95ExcellentPresent invention example360Z22.2661.90.4624110.99ExcellentPresent invention example361Z22.1821.90.3824330.99ExcellentPresent invention example362Z22.3882.30.3524510.92ExcellentPresent invention example363Z22.3821.50.3924240.92ExcellentPresent invention example364Z22.2661.80.4624030.97ExcellentPresent invention example365Z22.5742.50.4125180.97ExcellentPresent invention example366Z22.1942.10.3724250.98ExcellentPresent invention example367Z22.3741.80.4824230.96ExcellentPresent invention example368Z22.4751.80.4423980.98ExcellentPresent invention example369Z22.3651.80.4323190.93ExcellentPresent invention example370Z22.5691.80.3922070.96ExcellentPresent invention example371Z22.1741.70.4122740.95ExcellentPresent invention example;372Z22.2732.50.3622330.99ExcellentPresent invention example373Z22.5932.50.4524240.93ExcellentPresent invention example374Z22.4781.50.4323980.91ExcellentPresent invention example375Z22.3764.20.0224810.90BadComparative example376Z22.6742.80.0324670.92BadComparative exampleThe underline indicates that it is outside the scope of the present invention, or the characteristic value is not preferable.From Tables 3A to 3H, it can be seen that the hot-stamping formed bodies according to the present invention examples had high strength and excellent hydrogen embrittlement resistance and early fracture resistance. On the other hand, it can be seen that in the hot-stamping formed bodies according to comparative examples, one of the properties deteriorated.INDUSTRIAL APPLICABILITYAccording to the above-described aspects of the present invention, it is possible to provide a hot-stamping formed body having high strength and excellent hydrogen embrittlement resistance and early fracture resistance.

Claims

1. A hot-stamping formed body comprising, as a chemical composition, by mass %:C: more than 0.40% and 0.70% or less;Si: 0.010% to 3.00%;Mn: 0.60% to 3.00%;P: 0.100% or less;S: 0.0100% or less;N: 0.0200% or less;O: 0.0200% or less;Al: 0.0010% to 0.5000%;Nb: 0.0010% to 0.100%;Ti: 0.010% to 0.200%;Cr: 0.01% to 0.80%;Mo: 0.0010% to 1.000%;B: 0.0005% to 0.0200%;Co: 0% to 4.00%;Ni: 0% to 3.00%;Cu: 0% to 3.00%;V: 0% to 3.00%;W: 0% to 3.00%;Ca: 0% to 1.000%;Mg: 0% to 1.000%;REM: 0% to 1.000%;Sb: 0% to 1.000%;Sn: 0% to 1.000%;Zr: 0% to 1.000%;As: 0% to 0.100%; anda remainder: Fe and impurities,in an interior region, which is a region between 4 / 16 depth of a sheet thickness from a surface of the hot-stamping formed body and 5 / 16 depth of the sheet thickness from the surface,a standard deviation of grain sizes of prior austenite grains is 5.0 μm or less,in a surface layer region, which is a region between the surface and 1 / 25 depth of the sheet thickness from the surface,an area ratio of bainite is more than 10%,a maximum value of pole density of a texture is 4.0 or less, anda deboronization index is 0.05 or more.

2. The hot-stamping formed body according to claim 1 comprising, as the chemical composition, by mass %, one or more of:Co: 0.01% to 4.00%;Ni: 0.01% to 3.00%;Cu: 0.01% to 3.00%;V: 0.01% to 3.00%;W: 0.01% to 3.00%;Ca: 0.001% to 1.000%;Mg: 0.001% to 1.000%;REM: 0.001% to 1.000%;Sb: 0.001% to 1.000%;Sn: 0.001% to 1.000%;Zr: 0.001% to 1.000%; andAs: 0.001% to 0.100%.

Images