CN116685422A - Steel sheet for hot stamping and hot stamping member - Google Patents

Abstract

The steel sheet for hot stamping is characterized in that it comprises, in order: a base steel sheet; an Al-Si alloy coating, wherein the Al content is 75% by mass or more, the Si content is 3% by mass or more, and the total of the Al content and the Si content is 95% by mass or more; an Al oxide film with a thickness of 0 to 20 nm; and a surface coating, wherein the total of the Sn content, Ni content, and Zn content exceeds 90% by mass, the Sn content is 10% by mass or more, and the Ni content is less than 90% by mass. % by mass, and the Zn content is less than 50% by mass, the thickness of the above-mentioned Al-Si alloy coating is 5-50 μm, and the thickness of the above-mentioned surface coating is more than 300nm and not more than 2500nm.

Description

Steel sheets for hot stamping and hot stamping components

technical field

The present invention relates to a steel plate for hot stamping and a hot stamping member. this application claims priority based on Japanese Patent Application No. 2021-064884 for which it applied in Japan on April 6, 2021, and uses the content here.

Background technique

In recent years, from the viewpoint of environmental protection and resource saving, the weight reduction of automobile bodies has been demanded, and the application of high-strength steel sheets to automotive components has been accelerated. Automobile components are produced by press forming, but as the strength of steel sheets increases, not only does the forming load increase, but also the formability decreases. Therefore, for high-strength steel sheets, the formability of components with complex shapes is a problem. In order to solve such problems, the application of hot stamping technology in which the steel sheet is heated to a high temperature in the softened austenite region and then press-formed is advanced. Hot stamping is attracting attention as a technology that achieves both formability to automotive components and strength assurance of automotive components by performing quenching treatment in a die simultaneously with press working.

When hot stamping is performed on a bare steel sheet that has not been plated, it is necessary to perform hot stamping in a non-oxidizing atmosphere in order to suppress the formation of scale and decarburization of the surface layer during heating. However, even if hot stamping is performed in a non-oxidizing atmosphere, scale is formed on the surface of the hot-stamped steel sheet because the atmosphere from the heating furnace to the press is atmospheric. Since the scale on the surface of the steel sheet has poor adhesion and easily peels off, there is concern about adverse effects on other processes. Therefore, it is necessary to remove it using shot blasting or the like. Shot peening has a problem of affecting the shape of the steel sheet. In addition, there is a problem that the productivity of the hot stamping process decreases due to the descaling process.

As a method for improving the adhesion of scale on the surface of the steel sheet, there is a method of forming a plated layer on the surface of the steel sheet. By forming a plated layer, even if hot stamping is performed, since a scale with good adhesion is formed on the surface of the steel sheet, the process of removing the scale becomes unnecessary. Therefore, by forming the plated layer, the productivity of the hot stamping process is improved.

As a method of forming a plating layer on the steel sheet surface, a method of forming a Zn plating layer or an Al plating layer is conceivable, but when a Zn plating layer is used, there is a problem of liquid metal embrittlement (Liquid Metal Embrittlement, hereinafter referred to as LME). LME refers to a phenomenon in which, when a tensile stress is applied in a state in which liquid metal is in contact with the surface of a solid metal, the solid metal originally exhibiting ductility becomes embrittled. The melting point of Zn is low, and during hot stamping, molten Zn enters along the prior austenite grain boundaries of Fe, causing microcracks in the steel plate.

When Al plating is applied to a steel sheet, the above-mentioned LME problem does not occur, but a reaction between Al and water occurs on the surface of the Al plating during hot stamping to generate hydrogen. Therefore, there is a problem that the amount of hydrogen penetrating into the steel sheet is large. If the amount of hydrogen intruded into the steel sheet is large, the steel sheet will be cracked (hydrogen embrittlement) when stress is applied after hot stamping.

Patent Document 1 discloses a technique for suppressing the intrusion of hydrogen into a steel material at high temperature by enriching nickel in the surface region of the steel plate.

Patent Document 2 discloses a technique for suppressing the intrusion of hydrogen into steel by coating a steel sheet with a barrier precoat layer containing nickel and chromium and having a weight ratio of Ni/Cr of 1.5 to 9. .

However, the method of Patent Document 1 may not be able to sufficiently suppress the intrusion of hydrogen generated when Al plating is performed. In addition, the method of Patent Document 2 may not be able to sufficiently suppress the intrusion of hydrogen into the steel sheet in an environment where the dew point is not controlled (for example, in a high dew point environment such as 30° C.). In addition, it is considered that if the Al-plated steel sheet is used in an environment where the steel sheet is corroded after hot stamping, a large amount of hydrogen may be accumulated in the steel sheet, which may cause delayed fracture.

prior art literature

patent documents

Patent Document 1: Japanese PCT Publication No. 2017-525849

Patent Document 2: Japanese National Publication No. 2019-518136

Contents of the invention

The problem to be solved by the invention

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a steel sheet that can suppress the intrusion of hydrogen even in a high dew point environment even in the case of hot stamping an Al-plated steel sheet, and provide a steel sheet after hot stamping. A hot stamped member excellent in suppression of hydrogen intrusion in the steel sheet, and a steel sheet for hot stamping capable of producing the hot stamped member.

means to solve the problem

The inventors of the present invention have conducted intensive studies, and as a result, found that by providing a steel sheet for hot stamping with an Al-Si alloy coating with a surface coating having a desired chemical composition and thickness, even in an environment where the dew point is not controlled Even when hot stamping is performed, the intrusion amount of hydrogen into the steel sheet for hot stamping can be sufficiently suppressed, and it becomes easy to suppress the amount of hydrogen intrusion into the steel sheet after hot stamping.

The present invention was obtained by further research based on the above knowledge, and its gist is as follows.

(1) A steel sheet for hot stamping according to an aspect of the present invention is characterized in that it comprises, in order: a base steel sheet; The total of the Al content and the aforementioned Si content is 95% by mass or more;

Al oxide film with a thickness of 0-20nm; and

A surface coating wherein the total of the Sn content, the Ni content, and the Zn content exceeds 90% by mass, the Sn content is 10% by mass or more, the Ni content is less than 90% by mass, and the Zn content is less than 50% by mass,

The thickness of the Al-Si alloy coating is 5-50 μm,

The thickness of the surface plating layer is more than 300 nm and not more than 2500 nm.

(2) The steel sheet for hot stamping according to the above (1), wherein the surface plating layer may be provided as an upper layer of the Al-Si alloy plating layer in direct contact with the Al-Si alloy plating layer.

(3) The steel sheet for hot stamping according to the above (1), wherein the Al oxide film may have a thickness of 2 to 20 nm.

(4) The steel sheet for hot stamping according to any one of (1) to (3) above, wherein the chemical composition of the base steel sheet may be calculated as:

C: 0.25～0.70%,

Si: 0.005～1.000%,

Mn: 0.30～3.00%,

P: 0.100% or less,

S: 0.1000% or less,

N: 0.0100% or less,

Cu: 0～1.00%,

Ni: 0 to 1.00%,

Cr: 0～1.000%,

Mo: 0 to 1.000%,

Nb: 0 to 0.200%,

V: 0～1.000%,

Ti: 0 to 0.150%,

B: 0～0.0100%,

Co: 0 to 1.00%,

W: 0～1.00%,

Sn: 0～1.00%,

Sb: 0 to 1.00%,

Zr: 0 to 1.00%,

Mg: 0～0.150%,

Al: 0～1.0000%,

Ca: 0～0.010%,

REM: 0%～0.300%, and

The remainder: Fe and impurities.

(5) The steel sheet for hot stamping according to the above (4), wherein the chemical composition of the base steel sheet may contain, in mass %, one or more elements selected from the following elements:

Cu: 0.01 to 1.00%,

Ni: 0.01 to 1.00%,

Cr: 0.001～1.000%,

Mo: 0.001 to 1.000%,

Nb: 0.001 to 0.200%,

V: 0.01～1.00%,

Ti: 0.001 to 0.150%,

B: 0.001～0.0100%,

Co: 0.01 to 1.00%,

W: 0.01～1.00%,

Sn: 0.01 to 1.00%,

Sb: 0.01 to 1.00%,

Zr: 0.01 to 1.00%,

Mg: 0.001 to 0.150%,

Al: 0.0010～1.0000%,

Ca: 0.001 to 0.010%, and

REM: 0.001 to 0.300%.

(6) A hot stamped member according to an aspect of the present invention includes a base steel material and a coating layer provided on the base steel material, and the coating layer has, in order from the surface of the coating layer:

A surface-rich region in which the sum of the Sn content, the Ni content, and the Zn content is 50% by mass or more, the Sn content is 7% by mass or more, the Ni content is less than 72% by mass, and the Zn content is less than 40% by mass;

An Al-rich region in which the sum of the Sn content, the Ni content, and the Zn content is less than 50% by mass, the Al content is 10% by mass or more, and the Fe content is 50% by mass or less; and

Fe-enriched region, wherein the Al content is 10% by mass or more and the Fe content exceeds 50% by mass,

The maximum value of the sum of the Sn content, the Ni content, and the Zn content is 50% by mass or more, and the Fe content is 10% by mass in the region from the above-mentioned surface of the above-mentioned plating layer to a position 100 nm in the thickness direction from the above-mentioned surface of the above-mentioned plating layer. the following,

The maximum value of the sum of the Sn content, the Ni content, and the Zn content is 5 mass in the region from the position of 100 nm in the thickness direction to the position of 500 nm in the thickness direction from the above-mentioned surface of the coating layer. % or more, Fe content is 40% by mass or less,

The maximum value of the sum of the Sn content, the Ni content, and the Zn content is 1 mass in the region from a position 500 nm in the thickness direction from the above-mentioned surface of the plating layer to a position 1000 nm in the thickness direction from the above-mentioned surface of the plating layer % or more, and the Fe content is 50% by mass or less.

(7) The hot stamped member according to (6) above, wherein the Ni content in the surface-layer-rich region may be less than 50% by mass.

(8) The hot stamped member according to the above (6) or (7), wherein, in the region from the surface of the plating layer to the position 20 nm from the surface of the plating layer in the thickness direction, there may be At least one of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide, and the total of Sn content, Ni content, and Zn content is 30% by mass or more.

(9) The hot stamped member according to any one of the above (6) to (8), wherein the chemical composition of the base steel material may be calculated as:

C: 0.25～0.70%,

Si: 0.005～1.000%,

Mn: 0.30～3.00%,

P: 0.100% or less,

S: 0.1000% or less,

N: 0.0100% or less,

Cu: 0～1.00%,

Ni: 0 to 1.00%,

Cr: 0～1.000%,

Mo: 0 to 1.000%,

Nb: 0 to 0.200%,

V: 0～1.00%,

Ti: 0 to 0.150%,

B: 0～0.0100%,

Co: 0 to 1.00%,

W: 0～1.00%,

Sn: 0～1.00%,

Sb: 0 to 1.00%,

Zr: 0 to 1.00%,

Mg: 0～0.150%,

Al: 0～1.0000%,

Ca: 0～0.010%,

REM: 0%～0.300%, and

The remainder: Fe and impurities.

(10) The hot stamped member according to the above (9), wherein the chemical composition of the base steel material may contain, in mass %, one or more elements selected from the following elements:

Cu: 0.01 to 1.00%,

Ni: 0.01 to 1.00%,

Cr: 0.001～1.000%,

Mo: 0.001 to 1.000%,

Nb: 0.001 to 0.200%,

V: 0.01～1.00%,

Ti: 0.001 to 0.150%,

B: 0.0010～0.0100%,

Co: 0.01 to 1.00%,

W: 0.01～1.00%,

Sn: 0.01 to 1.00%,

Sb: 0.01 to 1.00%,

Zr: 0.01 to 1.00%,

Mg: 0.001 to 0.150%,

Al: 0.0010～1.0000%,

Ca: 0.001 to 0.010%, and

REM: 0.001 to 0.300%.

Invention effect

According to the above aspect of the present invention, it is possible to provide a solution that can suppress the intrusion of hydrogen even in a high dew point environment even when hot stamping the steel plate that has been subjected to Al plating, and that the intrusion of hydrogen into the steel plate after hot stamping can be prevented. A hot-stamped member with excellent suppression properties, and a steel sheet for hot-stamping capable of producing the hot-stamped member.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a steel sheet for hot stamping according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a steel sheet for hot stamping according to another embodiment of the present invention.

Fig. 3 is an example of measurement results of glow discharge emission analysis of hot stamped members.

FIG. 4 is an example of measurement results of glow discharge emission analysis of a hot stamped member.

Detailed ways

<Steel Sheet for Hot Stamping>

The inventors of the present invention have conducted intensive research, and as a result, it has been found that if the steel plate on which the Al coating is formed is hot stamped in an environment where the dew point is not controlled, there is a possibility that Al on the surface of the Al coating reacts with water in the atmosphere. As a result, a large amount of hydrogen is generated, and a large amount of hydrogen penetrates into the steel plate.

The inventors of the present invention have conducted further intensive studies and obtained the following findings as a result.

(A) If the total of Sn content, Ni content, and Zn content exceeds 90% by mass, the Sn content is 10% by mass or more, the Ni content is less than 90% by mass, and the Zn content is less than 50% by mass as the surface coating. If the coating is applied, the intrusion of hydrogen into the steel sheet during hot stamping at a high dew point can be suppressed.

(B) If the thickness of the surface plating layer is more than 300 nm and 2500 nm or less, the reaction with water in the atmosphere can be sufficiently suppressed, and the amount of hydrogen penetrating into the steel sheet can be reduced.

Regarding the steel sheet for hot stamping according to the present embodiment, the configuration of the steel sheet for hot stamping was determined based on the above knowledge. The steel sheet for hot stamping according to the present embodiment can obtain the effect targeted by the present invention due to the synergistic effect of each plating. The steel sheet 10 for hot stamping includes a base steel sheet 1 , an Al-Si alloy plating layer 2 , and a surface layer plating layer 4 in this order as shown in FIG. 1 . In the case of having an Al oxide film, the hot stamped steel sheet 10A includes a base steel sheet 1 , an Al—Si alloy plating layer 2 , an Al oxide film 3 , and a surface plating layer 4 in this order as shown in FIG. 2 . Each configuration will be described below. In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit. Values expressed as "below", "over" are not included in the numerical range. All "%" about the chemical composition means "mass %".

(mother plate)

The steel sheet (base steel sheet) 1 of the steel sheet for hot stamping 10 according to the present embodiment may have a chemical composition of a known steel sheet for hot stamping. For example, the chemical composition in mass % is C: 0.25% to 0.70%, Si: 0.005% to 1.000%, Mn: 0.30% to 3.00%, P: 0.100% or less, S: 0.1000% or less, N: 0.0100% or less , Cu: 0% to 1.00%, Ni: 0% to 1.00%, Cr: 0% to 1.000%, Mo: 0% to 1.000%, Nb: 0% to 0.200%, V: 0% to 1.00%, Ti : 0% to 0.150%, B: 0% to 0.0100%, Co: 0% to 1.00%, W: 0% to 1.00%, Sn: 0% to 1.00%, Sb: 0% to 1.00%, Zr: 0 % to 1.00%, Mg: 0% to 0.150%, Al: 0% to 1.0000%, Ca: 0% to 0.010%, REM: 0% to 0.300%, and the rest are Fe and impurities.

"C: 0.25% to 0.70%"

C is an important element for ensuring hardenability. When the C content is less than 0.25%, sufficient hardenability cannot be obtained, so it becomes difficult to secure a tensile strength of 1600 MPa or more. Therefore, the C content is preferably set to 0.25% or more. The C content is preferably 0.28% or more. The tensile strength of the hot stamped member of this embodiment is not necessarily limited to 1600 MPa or more, and the C content may be set to less than 0.25%. In this case, you may set the lower limit of C content to 0.20%, 0.22%, or 0.24%. On the other hand, when the C content exceeds 0.70%, the strength of the hot stamped member becomes too high, and the limit hydrogen amount decreases significantly. Therefore, the C content is preferably set to 0.70% or less. The C content is preferably 0.55% or less, 0.50% or less, 0.45% or less, 0.40% or less, 0.36% or less, or 0.32% or less.

"Si: 0.005% to 1.000%"

Si is an element contained in order to ensure hardenability. When the Si content is less than 0.005%, it becomes difficult to secure a tensile strength of 1600 MPa or more. Therefore, the Si content is preferably set to 0.005% or more. A more preferable Si content is 0.100% or more or 0.150% or more. Even if Si is contained in excess of 1.000%, the above effect is saturated, so the Si content is made 1.000% or less. The Si content is preferably 0.500% or less. The tensile strength of the hot stamped member of this embodiment is not necessarily limited to 1600 MPa or more, and the Si content may be set to less than 0.005%. In this case, the lower limit of the Si content may be set to 0.002% or 0.004%.

"Mn: 0.30% to 3.00%"

Mn is an element that contributes to the improvement of the strength of a hot stamped member by solid solution strengthening. When the Mn content is less than 0.30%, the solid solution strengthening ability is insufficient, the martensite becomes soft, and the tensile strength decreases. Therefore, in order to set the tensile strength at 1600 MPa or more, the Mn content is preferably set at 0.30% or more. It is not necessary to limit the tensile strength of the hot stamped member of this embodiment to 1600 MPa or more, and the Mn content may be set to less than 0.30%. In this case, the lower limit of the Mn content may be set to 0.20%, 0.24%, or 0.27%. The Mn content is more preferably 0.40% or more, 0.50% or more, 0.60% or more, or 0.80% or more. On the other hand, if the Mn content is set to exceed 3.00%, not only coarse inclusions are formed in the steel and fractures are likely to occur, but also the hydrogen embrittlement resistance of the hot stamped member is also reduced, so the Mn content is set to 3.00% or less. The Mn content is preferably 2.50% or less or 2.00% or less. A more preferable Mn content is 1.80% or less, 1.60% or less, 1.40% or less, 1.20% or less, or 1.00% or less.

"P: 0.100% or less"

P is an impurity element that segregates at grain boundaries and lowers the strength of grain boundaries. If the P content exceeds 0.100%, the strength of the grain boundaries will decrease significantly, and the hydrogen embrittlement resistance of the hot stamped member will decrease. Therefore, the P content is preferably set to 0.100% or less. The P content is more preferably 0.050% or less, 0.030% or less, or 0.015% or less. A still more preferable P content is 0.010% or less or 0.005% or less. The lower limit of the P content is not particularly limited. Therefore, the lower limit of the P content is 0%. If it is attempted to reduce the P content to less than 0.0005%, the cost of removing P will increase significantly, which is not economically preferable, so 0.0005% or 0.001% can also be set as the lower limit in practice.

"S: 0.1000% or less"

S is an impurity element that forms inclusions in steel. If the S content exceeds 0.1000%, a large number of inclusions are formed in the steel, and the hydrogen embrittlement resistance of the hot stamped member decreases. Therefore, the S content is preferably set to 0.1000% or less. The S content is more preferably 0.0300% or less, 0.0100% or less, 0.0070% or less, or 0.0050% or less. The lower limit of the S content is not particularly limited. Therefore, the lower limit of the S content is 0%. If it is attempted to reduce the S content to less than 0.00015%, the cost of desulphurization will increase significantly, which is not economically preferable, so 0.00015% or 0.0005% may be set as the lower limit in practice. The S content may be 0.0010% or more or 0.0050% or more.

"N: 0.0100% or less"

N is an impurity element, and is an element that forms nitrides in steel to degrade the toughness and hydrogen embrittlement resistance of the hot stamped member. If the N content exceeds 0.0100%, coarse nitrides will be formed in the steel, and the hydrogen embrittlement resistance of the hot stamped member will be significantly reduced. Therefore, the N content is set to 0.0100% or less. The N content is preferably 0.0050% or less. The lower limit of the N content is not particularly limited. Therefore, the lower limit of the N content is 0%. If an attempt is made to reduce the N content to less than 0.0015%, the cost of deN will greatly increase, which is not economically preferable, so 0.0015% or 0.0020% may be set as the lower limit in practice.

The base steel sheet constituting the steel sheet 10 for hot stamping according to the present embodiment may contain Cu: 0.01 to 1.00%, Ni: 0.01 to 1.00%, Cr: 0.001 to 1.000%, Mo: 0.001 to 1.000%, and Nb: 0.001 to 1.000%. 0.200%, V: 0.01-1.00%, Ti: 0.001-0.150%, B: 0.001-0.0100%, Co: 0.01-1.00%, W: 0.01-1.00%, Sn: 0.01-1.00%, Sb: 0.01-1.00 %, Zr: 0.01 to 1.00%, Mg: 0.001 to 0.150%, Al: 0.0010 to 1.0000%, Ca: 0.001 to 0.010%, and REM: 0.001 to 0.300%, can be replaced by one or more of them as optional elements Part of Fe. The content when the following optional elements are not contained is 0%.

"Cu: 0% to 1.00%"

Cu diffuses into the plated layer of the hot stamped member during hot stamping, and has the effect of reducing the intrusion of hydrogen during heating in the manufacture of the hot stamped member, so Cu may be contained as needed. In addition, Cu is an element effective for improving the hardenability of steel and stably ensuring the strength of a hardened coated steel member. When Cu is contained, the Cu content is preferably set to 0.01% or more in order to reliably exert the above-mentioned effects. The Cu content is more preferably 0.10% or more. The Cu content is more preferably 0.15% or more. On the other hand, even if it contains more than 1.00%, the above-mentioned effects are saturated, so the Cu content is preferably set to 1.00% or less. The Cu content is more preferably 0.350% or less.

"Ni: 0% to 1.00%"

Ni is an important element for suppressing hot embrittlement caused by Cu at the time of production of the base steel sheet and ensuring stable production, and therefore Ni may be contained. When the Ni content is less than 0.01%, the above-mentioned effects may not be sufficiently obtained. Therefore, the Ni content is preferably set to 0.01% or more. The Ni content is preferably 0.05% or more. More preferably, the Ni content is 0.10% or more.

On the other hand, if the Ni content exceeds 1.00%, the limiting hydrogen content of the coated steel member decreases. Therefore, the Ni content is preferably set to 1.00% or less. The Ni content is preferably 0.50% or less or 0.25% or less. More preferably, the Ni content is 0.20% or less.

"Cr: 0% to 1.000%"

Cr is an element that contributes to the improvement of the strength of the hot stamped member through solid solution strengthening, and therefore may be contained as necessary. When Cr is contained, the Cr content is preferably set to 0.001% or more in order to reliably exert the above-mentioned effect. The Cr content is more preferably 0.050% or more. The Cr content is more preferably 0.100% or more. On the other hand, even if the content exceeds 1.000%, the above-mentioned effects are saturated, so the Cr content is preferably set to 1.000% or less. The Cr content is more preferably 0.800% or less, 0.500% or less, or 0.250% or less.

"Mo: 0% to 1.000%"

Mo is an element that contributes to the improvement of the strength of a hot stamped member through solid solution strengthening, and therefore may be contained as necessary. When Mo is contained, the Mo content is preferably set to 0.001% or more in order to reliably exert the above-mentioned effects. The Mo content is more preferably set to 0.005% or more. The Mo content is more preferably 0.010% or more. It is particularly preferable that the Mo content is 0.100% or more. On the other hand, even if it contains more than 1.000%, the above-mentioned effects are saturated, so the Mo content is preferably set to 1.000% or less. The Mo content is more preferably 0.800% or less, 0.500% or less, or 0.250% or less.

"Nb: 0% to 0.200%"

Nb is an element that contributes to the improvement of the strength of the hot stamped member through solid solution strengthening, and therefore may be contained as necessary. In the case where Nb is contained, the Nb content is preferably set to 0.001% or more in order to reliably exhibit the above effects. The Nb content is more preferably set to 0.010% or more. The Nb content is more preferably 0.030% or more. On the other hand, even if more than 0.200% of Nb is contained, the above effects are saturated, so the Nb content is preferably set to 0.200% or less. The Nb content is more preferably 0.100% or less.

"V: 0~1.00%"

V is an element that forms fine carbides and increases the limit hydrogen content of hot stamped parts through its fine-graining effect and hydrogen capture effect. Therefore, V may also be contained. In order to obtain the above-mentioned effect, V is preferably contained in an amount of 0.01% or more, more preferably in an amount of 0.10% or more.

However, when the V content exceeds 1.00%, the above-mentioned effects are saturated and the economic efficiency is reduced. Therefore, when V is contained, the V content is preferably set to 1.00% or less. The V content is more preferably 0.700% or less, 0.400% or less, or 0.250% or less.

"Ti: 0% to 0.150%"

Ti is an element that contributes to the improvement of the strength of a hot stamped member through solid solution strengthening, and therefore may be contained as necessary. When Ti is contained, the Ti content is preferably set to 0.001% or more in order to reliably exert the above-mentioned effects. The Ti content is more preferably set to 0.010% or more. The Ti content is preferably 0.020% or more. On the other hand, even if it contains more than 0.150%, the above-mentioned effects are saturated, so the Ti content is preferably set to 0.150% or less. The Ti content is more preferably 0.100% or less, 0.060% or less, or 0.040% or less.

"B: 0% to 0.0100%"

B is an element that segregates at grain boundaries to increase the grain boundary strength, and therefore may be contained as necessary. When B is contained, the B content is preferably set to 0.0005% or more in order to reliably exert the above-mentioned effects. The B content is more preferably set to 0.0005% or more. The B content is more preferably 0.0010% or more. On the other hand, even if it is contained in excess of 0.0100%, the above effects are saturated, so the B content is preferably set to 0.0100% or less. The B content is more preferably 0.0075% or less, 0.0040% or less, or 0.0025% or less.

"Co: 0% to 1.00%"

Co is an element that has the effect of raising the martensite start temperature (Ms point), and since it improves the toughness of a hot stamped member, it may be contained as necessary. When Co is contained, the Co content is preferably set to 0.01% or more in order to reliably exert the above-mentioned effects. A more preferable Co content is 0.08% or more. On the other hand, if the Co content exceeds 1.00%, the hardenability of steel decreases. Therefore, the Co content is preferably set to 1.00% or less. The Co content is more preferably 0.90% or less, 0.50% or less, or 0.10% or less.

"W: 0% to 1.00%"

W is an element capable of improving the hardenability of steel and stably securing the strength of a quenched hot stamped member. Therefore, W may also be contained. In addition, W is an element that improves corrosion resistance in a corrosive environment. In order to obtain the above effects, it is preferable to contain 0.01% or more of W.

However, when the W content exceeds 1.00%, the above-mentioned effects are saturated and the economic efficiency is reduced. Therefore, when W is contained, the W content is preferably set to 1.00% or less. The W content is more preferably 0.75% or less, 0.40% or less, or 0.10% or less.

"Sn: 0% to 1.00%"

Sn is an element that improves corrosion resistance in a corrosive environment. Therefore, Sn may also be contained. In order to obtain the above effects, it is preferable to contain 0.01% or more of Sn.

However, if the Sn content exceeds 1.00%, the grain boundary strength will decrease, and the limit hydrogen amount of the coated steel member after quenching will decrease. Therefore, when Sn is contained, the Sn content is preferably set to 1.00% or less. The Sn content is more preferably 0.60% or less, 0.10% or less, or 0.05% or less.

"Sb: 0% to 1.00%"

Sb is an element that improves corrosion resistance in a corrosive environment. Therefore, Sb may also be contained. In order to obtain the above effects, it is preferable to set the Sb content to 0.01% or more.

However, if the Sb content exceeds 1.00%, the grain boundary strength decreases, and the limiting hydrogen content of the quenched hot stamped member decreases. Therefore, when Sb is contained, the Sb content is preferably set to 1.00% or less. The Sb content is more preferably 0.60% or less, 0.10% or less, or 0.05% or less.

"Zr: 0% to 1.00%"

Zr is an element that improves corrosion resistance in a corrosive environment. Therefore, it may also be contained. In order to obtain the above effects, it is preferable to set the Zr content to 0.01% or more.

However, if the Zr content exceeds 1.00%, the grain boundary strength decreases, and the limiting hydrogen content of the quenched hot stamped member decreases. Therefore, when Zr is contained, the Zr content is preferably set to 1.00% or less. The Zr content is more preferably 0.60% or less, 0.20% or less, or 0.05% or less.

"Mg: 0% to 0.150%"

Mg is an element that deoxidizes the molten steel to strengthen the steel, and improves the toughness of the hot stamped member. Therefore, Mg may also be contained as needed. In order to securely obtain the above effects, the Mg content is preferably set to 0.001% or more. More preferably, it is 0.008% or more. On the other hand, when the Mg content exceeds 0.150%, the above-mentioned effects are saturated and the cost increases. Therefore, the Mg content is preferably set to 0.150% or less. More preferably, it is 0.100% or less, 0.050% or less, or 0.010% or less.

"Al: 0% to 1.0000%"

Al is an element generally used as a deoxidizer for steel. Therefore, Al may also be contained. In order to obtain the above effects, it is preferable to contain 0.0010% or more of Al. The Al content is more preferably 0.0100% or more.

However, if the Al content exceeds 1.0000%, the above-mentioned effects are saturated and the economic efficiency is reduced. Therefore, the Al content in the case of containing Al is set to 1.0000% or less. A preferable Al content is 0.5000% or less, 0.1000% or less, 0.0500% or less, or 0.0300% or less.

"Ca: 0% to 0.010%"

Ca is an element that deoxidizes the molten steel to make the steel sound. In order to reliably exert this function, it is preferable to set the Ca content to 0.001% or more. On the other hand, even if it contains more than 0.010%, the above-mentioned effects are saturated, so the Ca content is preferably set to 0.010% or less. The Ca content is more preferably set to 0.007% or less, 0.005% or less, or 0.003% or less.

"REM: 0% to 0.300%"

Like Ca, REM is an element that has the effect of reducing the size of inclusions in steel and increasing the limiting hydrogen content of the coated steel member after quenching. In order to reliably exert this effect, it is preferable to set the REM content to 0.001% or more. On the other hand, even if it contains more than 0.300%, the above-mentioned effects are saturated, so the REM content is preferably set to 0.300% or less. The REM content is more preferably set to 0.100% or less, 0.050% or less, 0.010% or less, or 0.005% or less.

In this embodiment, REM refers to a total of 17 elements including Sc, Y, and lanthanide elements, and the content of REM refers to the total content of these elements.

"Remainder: Fe and Impurities"

The remainder of the chemical composition of the base steel sheet 1 constituting the steel sheet for hot stamping 10 of the present embodiment is Fe and impurities. Impurities are components that are inevitably mixed or intentionally added from steel raw materials or scrap and/or in the steelmaking process, and do not hinder the properties of the hot stamped member after hot stamping the steel sheet 10 for hot stamping according to this embodiment. allowed within the range.

The above-mentioned chemical composition of the base steel sheet 1 may be measured by a general analytical method. For example, it may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry; Inductively Coupled Plasma-Atomic Emission Spectrometry). It should be noted that C and S may be measured by combustion-infrared absorption method, and N may be measured by inert gas melting-thermal conductivity method. The coating on the surface can be removed by mechanical grinding and then the chemical composition can be analyzed.

"Metal Organization"

Next, the metal structure of the base steel sheet 1 constituting the steel sheet for hot stamping 10 of the present embodiment will be described. The metal structure of the base steel sheet 1 of the steel sheet 10 for hot stamping is not limited, but may be ferrite: 20 to 80%, pearlite: 20 to 80%, and the remainder bainite, in terms of cross-sectional area ratio. One or more of martensite or retained austenite. The area ratio of the remainder may also be less than 5%.

(Measurement method of area ratio of ferrite and pearlite)

The measurement of the area ratios of ferrite and pearlite was performed by the following method. The cross-section parallel to the rolling direction at the central position in the width direction of the sheet was finished to a mirror surface, and polished using colloidal silica not containing an alkaline solution for 8 minutes at room temperature to remove strain introduced into the surface layer of the sample. At any position in the longitudinal direction of the sample section, in such a way that the depth from the surface is 1/4 of the plate thickness can be analyzed, for a length of 50 μm, a depth of 1/8 from the surface to a depth of 3 The /8 depth region was measured by the electron backscatter diffraction method at a measurement interval of 0.1 μm to obtain crystal orientation information. For the measurement, an apparatus composed of a thermal field emission scanning electron microscope (JSM-7001F manufactured by JEOL) and an EBSP detector (DVC5 detector manufactured by TSL) was used. At this time, the vacuum degree in the apparatus was set at 9.6×10 ⁻⁵ Pa or less, the accelerating voltage was set at 15 kV, the irradiation current level was set at 13, and the electron beam irradiation level was set at 62. Furthermore, a reflected electron image is taken in the same field of view.

First, crystal grains in which ferrite and cementite precipitated in layers were identified from reflection electron images, and the area ratio of the crystal grains was calculated to obtain the area ratio of pearlite. Afterwards, for crystal grains other than the crystal grains discriminated as pearlite, the obtained crystal orientation information was obtained using the "Grain Average Misorientation (Grain Average Misorientation)" carried in the software "OIM Analysis (registered trademark)" attached to the EBSP analyzer. Average misorientation)" function, the area with Grain Average Misorientation value below 1.0° is judged as ferrite. The area ratio of ferrite is obtained by calculating the area ratio of the region judged to be ferrite.

(Measurement method of area ratio of bainite, martensite and retained austenite)

The total of the area ratios of bainite, martensite, and retained austenite in this embodiment is set to a value obtained by subtracting the area ratios of ferrite and pearlite from 100%.

The thickness of the base steel sheet 1 of the steel sheet for hot stamping 10 of the present embodiment is not particularly limited, but is preferably set to 0.5 to 3.5 mm from the viewpoint of weight reduction of the vehicle body. The thickness of the base steel plate 1 is preferably 0.8 mm or more, 1.0 mm or more, or 1.2 mm or more. The thickness of the base steel plate 1 is preferably 3.2 mm or less, 2.8 mm or less, or 2.4 mm or less.

(Al-Si alloy coating)

The Al—Si alloy plating layer 2 of the steel sheet 10 for hot stamping according to the present embodiment is provided as an upper layer of the base steel sheet 1 . The Al—Si alloy plating layer 2 is a plating layer mainly composed of Al and Si. Here, having Al and Si as main components means that at least 3 mass % or more of Si is contained, and the total of the Al content and the Si content is 95 mass % or more. That is, in the Al-Si alloy plating layer 2, the Al content is 75 mass % or more, the Si content is 3 mass % or more, and the sum total of the said Al content and the said Si content is 95 mass % or more. The Al content in the Al-Si alloy coating layer 2 is 75 to 97% by mass. When the Al content in the Al-Si alloy coating layer 2 is in this range, an oxide scale with good adhesion is formed on the surface of the base steel sheet during hot stamping. . The Al content in the Al-Si alloy plating layer 2 is preferably 95% by mass or less or 93% by mass or less. The Al content in the Al-Si alloy plating layer 2 may be 91% by mass or less or 88% or less, and may be 78% or more, 81% or more, or 85% or more.

The Si content in the Al-Si alloy plating layer 2 is preferably 3% by mass or more or 5% by mass or more. More preferably, the Si content in the Al-Si alloy plating layer 2 is 7% by mass or more or 9% by mass or more. The Si content in the Al-Si alloy plating layer 2 is preferably 20% by mass or less. More preferably, the Si content is 15% by mass or less or 12% by mass or less. If the Si content in the Al—Si alloy plating layer 2 is 3% by mass or more, alloying of Fe—Al can be suppressed. In addition, if the Si content in the Al-Si alloy plating layer 2 is 20% by mass or less, the rise of the melting point of the Al-Si alloy plating layer 2 can be suppressed, and the temperature of the hot-dip coating bath can be lowered. Therefore, if the Si content in the Al-Si alloy plating layer 2 is 20% by mass or less, the production cost can be reduced. The remainder in the Al-Si alloy plating layer 2 is Fe and impurities. Examples of impurities include components inevitably mixed in the production of the Al—Si alloy coating 2 , components in the base steel sheet 1 , and the like.

The thickness (average layer thickness) of the Al-Si alloy plating layer 2 of the steel sheet 10 for hot stamping of this embodiment is 5 micrometers or more. A more preferable thickness of the Al-Si alloy plating layer 2 is 8 μm or more, 12 μm or more, or 15 μm or more. If the thickness of the Al-Si alloy plating layer 2 is less than 5 μm, a scale with good adhesion cannot be formed during hot stamping. The thickness of the Al-Si alloy plating layer 2 is 50 μm or less. A more preferable thickness of the Al-Si alloy plating layer 2 is 45 μm or less, 40 μm or less, or 35 μm or less. If the thickness of the Al-Si alloy plating layer 2 exceeds 50 μm, not only the above-mentioned effects are saturated, but also the cost becomes high.

The thickness of the Al-Si alloy plating layer 2 was measured as follows. After cutting in the thickness direction of the steel sheet 10 for hot stamping, the cross section of the steel sheet 10 for hot stamping is ground. For the cross-section of the hot stamping steel sheet 10 after grinding, the ZAF method is used for line analysis from the surface of the hot stamping steel sheet 10 to the base steel sheet 1 by an electron probe microanalyzer (Electron Probe Micro Analyzer: FE-EPMA), The Al concentration and the Si concentration in the detected components were measured. The measurement conditions may be set such that the acceleration voltage is 15 kV, the beam diameter is about 100 nm, the irradiation time per point is 1000 ms, and the measurement pitch is 60 nm. A region where the Si concentration is 3% by mass or more and the sum of the Al concentration and the Si concentration is 95% by mass or more is determined as the Al—Si alloy plating layer 2 . The thickness of the Al—Si alloy plating layer 2 is set to be the length of the above-mentioned region in the plate thickness direction. The thickness of the Al—Si alloy plating layer 2 was measured at five positions at intervals of 5 μm, and the arithmetic mean of the obtained values was taken as the thickness of the Al—Si alloy plating layer 2 .

Al content and Si content in the Al-Si alloy coating 2 are according to the test method recorded in JIS K 0150 (2009), collect test pieces, by measuring the Al content and the 1/2 position of the total thickness of the Al-Si alloy coating 2 Si content, the Al content and Si content in the Al—Si alloy coating 2 in the steel sheet 10 for hot stamping were obtained.

(Al oxide film)

The Al oxide film 3 of the steel sheet 10 for hot stamping according to the present embodiment is provided as an upper layer of the Al—Si alloy plating layer 2 in contact with the Al—Si alloy plating layer 2 . The Al oxide film is set to a region where the O content is 20 atomic % or more. The Al oxide film may not be present. The thickness of the Al oxide film is 0 to 20 nm.

The thickness (average film thickness) of the Al oxide film 3 of the steel sheet 10 for hot stamping of this embodiment is 20 nm or less. The thickness of the Al oxide film 3 is preferably 10 nm or less. When the thickness of the Al oxide film 3 of the steel sheet 10 for hot stamping exceeds 20 nm, the coating rate of the surface plating layer 4 provided as the upper layer of the Al oxide film 3 becomes less than 90%, and the hydrogen embrittlement resistance may be reduced. Since the Al oxide film 3 may not be present, the lower limit of the Al oxide film 3 is 0 nm. In this case, the surface plating layer 4 is formed so as to be in contact with the Al—Si alloy plating layer 2 . The thickness of the Al oxide film 3 may be 2 nm or more.

The thickness of the Al oxide film 3 was evaluated by alternately repeating Ar sputtering and X-ray photoelectron spectroscopy (XPS) measurement. Specifically, the XPS measurement was performed after sputtering the steel sheet 10 for hot stamping by Ar sputtering (acceleration voltage: 20 kV, sputtering rate: 1.0 nm/min). This Ar sputtering and XPS measurement were alternately performed, and these measurements were repeated from the peak of the bonding energy of 73.8 eV to 74.5 eV of the 2p orbital of Al after oxidation appeared until it disappeared in the XPS measurement. The average film thickness of the Al oxide film 3 is calculated from the following sputtering time and sputtering rate: from the position where the O content becomes 20 atomic % or more for the first time after the start of sputtering to the position where the O content becomes less than 20 atomic % Sputtering time until The sputtering rate was performed in terms of SiO ₂ . The thickness of the Al oxide film 3 is set as an arithmetic mean value measured at two places.

(surface coating)

The surface plating layer 4 of the steel sheet 10 for hot stamping according to the present embodiment is provided as an upper layer of the Al oxide film 3 in contact with the Al oxide film 3 . In the absence of the Al oxide film 3 , the surface plating layer 4 is provided as an upper layer of the Al—Si alloy plating layer 2 and is provided in direct contact with the Al—Si alloy plating layer 2 . The surface plating layer 4 is an alloy plating layer or a Sn plating layer containing two or more of Zn, Sn, and Ni. In the surface plating layer 4, the total of the Sn content, the Ni content, and the Zn content exceeds 90% by mass, the Sn content is 10% by mass or more, the Ni content is less than 90% by mass, and the Zn content is less than 50% by mass. When the chemical composition of the surface coating layer 4 is within the above-mentioned range, the elements and oxides constituting the surface coating layer are less likely to cause a reduction reaction of hydrogen, and even if hydrogen atoms are generated and adsorbed on the surface, the hydrogen atoms are promoted to be bonded to each other. The Tafel (Tafel) reaction in which hydrogen gas desorbs has an effect of making it difficult for hydrogen to penetrate into the base steel plate. Therefore, by forming the surface plating layer 4 , it is possible to suppress the intrusion amount of hydrogen into the steel sheet 10 for hot stamping during hot stamping. Therefore, the surface plating layer 4 can also be called a hydrogen intrusion preventing layer.

In order to reduce the amount of hydrogen intrusion into the hot stamped member, the total of the Sn content, Ni content, and Zn content of the surface plating layer 4 exceeds 90% by mass. The total of the Sn content, Ni content and Zn content of the surface plating layer 4 may be 92 mass % or more, 94 mass % or more, 96 mass % or more, or 98 mass % or more, or may be 100 mass %. On the other hand, the total of the Sn content, the Ni content, and the Zn content of the surface plating layer 4 may be 98 mass % or less, 96 mass % or less, or 94 mass % or less.

In order to suppress the intrusion of hydrogen into the hot stamped member, the Sn content of the surface plating layer 4 is 10% by mass or more. The Sn content of the surface plating layer 4 may be 12% by mass or more, 14% by mass or more, 16% by mass or more, 18% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 60% by mass or more, 80% by mass or more. Mass % or more, 90 mass % or more, 94 mass % or more, 96 mass % or more, or 98 mass % or more. In particular, the Sn content of the surface plating layer 4 may be 100% by mass. That is, the surface plating layer 4 may be a 100% Sn plating layer. On the other hand, the Sn content of the surface plating layer 4 may be 98% by mass or less, 96% by mass or less, 94% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 60% by mass or less, or 50% by mass or less. % or less, 30 mass % or less, or 20 mass % or less.

In order to reduce the amount of hydrogen intrusion into the hot stamped member, the Ni content of the surface plating layer 4 is less than 90% by mass. The Ni content of the surface plating layer 4 may be 85 mass % or less, 80 mass % or less, 60 mass % or less, 40 mass % or less, 20 mass % or less, 10 mass % or more, 8 mass % or less, 6 mass % or less, 4 Mass % or less, 2 mass % or less, 0 mass %. On the other hand, the Ni content of the surface plating layer 4 may be 2% by mass or more, 4% by mass or more, 6% by mass or more, 8% by mass or more, 10% by mass or more, 20% by mass or more, 40% by mass or more, 60% by mass or more. % or more, 80% by mass or more, or 85% by mass or more.

In order to reduce the amount of hydrogen intrusion into the hot stamped member, the Zn content of the surface plating layer 4 is less than 50% by mass. The Zn content of the surface plating layer 4 may be 48 mass % or less, 46 mass % or less, 44 mass % or less, 40 mass % or less, 30 mass % or less, 20 mass % or less, 10 mass % or more, 8 mass % or less, 6 Mass % or less, 4 mass % or less, 2 mass % or less, or 0 mass %. On the other hand, the Zn content of the surface plating layer 4 may be 1% by mass or more, 2% by mass or more, 4% by mass or more, 6% by mass or more, 8% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more. % or more or 30% by mass or more.

If the total content of Sn, Ni, and Zn in the surface plating layer 4 exceeds 90% by mass, the surface plating layer 4 may contain elements (including impurities, etc.) other than Sn, Zn, and Ni. The total content of elements other than Sn, Zn, and Ni is 10% or less. The total content of elements other than Sn, Ni, and Zn may be 5% by mass or less, 3% by mass or less, or 1% by mass or less.

The surface plating layer 4 in this embodiment has a thickness exceeding 300 nm. This is because if the thickness of the surface plating layer 4 is 300 nm or less, the penetration of hydrogen into the base steel sheet 1 during hot stamping cannot be sufficiently suppressed. A more preferable thickness of the surface plating layer 4 is 400 nm or more or 500 nm or more. In addition, when the thickness of the surface plating layer 4 exceeds 2500 nm, the effect of suppressing the intrusion of hydrogen into the base steel sheet 1 is saturated, and the cost becomes high. Therefore, the thickness of the surface plating layer 4 is 2500 nm or less. The thickness of the surface coating layer 4 is preferably 2000 nm or less, 1500 nm or less or 1000 nm or less, more preferably 730 nm or less.

The coverage of the surface plating layer 4 with respect to the Al oxide film 3 (in the absence of the Al oxide film 3, the coverage rate of the surface plating layer 4 with respect to the Al-Si alloy plating layer 2) is preferably 90% or more. More preferably, the coverage of the surface plating layer 4 is 95% or more. If the coverage rate of the surface plating layer 4 is less than 90%, there is a possibility that the reaction between water vapor and Al cannot be sufficiently suppressed on the surface of the Al—Si alloy plating layer 2 during hot stamping. The coverage of the surface plating layer 4 may be 100% or less, and may be 99% or less.

The coverage of the surface plating layer 4 was evaluated by XPS measurement. Specifically, the Quantum 2000 manufactured by ULVAC-PHI was used for the XPS measurement, Al Kα rays were used as the radiation source, and the output power was 15kV, 25W, the spot size was 100μm, and the number of scans was 10 times on the steel sheet 10 for hot stamping. It was measured by scanning in the energy range, analyzed using the analysis software MultiPak V.8.0 manufactured by ULVAC-PHI, and obtained the content of Sn (atomic %), the content of Zn (atomic %), and the content of Ni in the detected metal components. content (atomic %), Al content (atomic %), and content of other components (atomic %). By converting the obtained content (atom %) into content (mass %), Sn content (mass %), Zn content (mass %), Ni content (mass %), and Al content (mass %) can be obtained. Calculate the total content of Sn content (mass %), Zn content (mass %), and Ni content (mass %) relative to the Sn content (mass %), Zn content (mass %), Ni content (mass %), and Al content The ratio (%) of the total of (mass %), let the obtained ratio be a coverage rate.

The thickness of the surface coating layer 4 can be measured by glow discharge luminescence analysis (GDS). The discharge conditions can be measured at 35W (constant power mode), the Ar pressure at the time of measurement is 600Pa, and the discharge range is 4mmφ. The distance between the electrodes can also be set to 0.15 mm to 0.25 mm, and the measurement can be performed by selectively applying high-frequency, direct glow, high-frequency glow, etc. from the back of the sample. The discharge voltage may be measured at 30W to 50W (constant power mode), and the Ar pressure at the time of measurement may be measured at 500Pa to 700Pa. The discharge range can also be measured from 2mmφ to 6mmφ. As for the measurement time at one point, it is also possible to measure the time until 90% or more of Fe is detected (set as α), and further measure about 20% of this time (α×0.2) (total α+0.2α). The thickness of the surface plating layer 4 can be obtained by measuring from the outermost surface of the steel sheet 10 for hot stamping to a region where Al is detected and the total of the plating components (Sn, Zn, Ni) as the surface plating layer becomes 50%. . The thickness (nm) of the surface plating layer 4 was obtained as follows. First, from the depth and measurement time from the start to the end of the measurement (when Al is detected and the total of the plating components (Sn, Zn, Ni) as the surface plating layer becomes 50%), the measured value per unit time is calculated. Depth of chipping. Next, the thickness of the surface plating layer 4 of the steel sheet 10 for hot stamping is calculated by multiplying the measured time by the obtained depth of chipping per unit time.

Regarding the respective contents of Zn, Sn, and Ni in the surface plating layer 4, the concentration of each element at the center position in the plate thickness direction of the surface plating layer 4 obtained in the measurement of the thickness of the surface plating layer 4 described above is taken as the content of each element.

<Hot stamping components>

Next, the hot stamped member of the present embodiment is obtained by hot stamping the steel sheet 10 for hot stamping. When the steel sheet 10 for hot stamping contains Cu in the base steel material, Cu may diffuse to the surface of the hot stamping member. The constituent components (Sn, Zn, Ni) of the surface plating layer and their oxides (hydroxides) may remain on the surface of the hot stamped member of this embodiment. Hereinafter, a hot stamped member obtained by hot stamping the steel sheet 10 for hot stamping according to this embodiment will be described. The hot stamped member of the present embodiment includes a base steel material and a plating layer provided on the base steel material.

(parent steel)

The base material (base steel material) has the same chemical composition as the base steel plate 1 of the steel plate 10 for hot stamping. The chemical composition of the base steel material can be measured by the method described above.

(plating)

The plating layer of the hot stamped member has, in order from the surface of the plating layer: a surface-rich region in which the total of the Sn content, Zn content, and Ni content is 50% by mass or more, the Sn content is 7% by mass or more, and the Ni content is less than 72% by mass %, and the Zn content is less than 40% by mass; the Al-rich region, wherein the total of the Sn content, Zn content and Ni content is less than 50% by mass, the Al content is 10% by mass or more, and the Fe content is 50% by mass or less and an Fe-rich region in which the Al content is 10% by mass or more and the Fe content exceeds 50% by mass. In addition, the Ni content in the surface layer-rich region may be less than 50% by mass.

Hereinafter, the coating will be described by taking, as an example, the case of a hot stamping member obtained by hot stamping a hot stamping steel sheet 10 in which the surface coating 4 is a 100% Sn coating. The structure of the plating layer of the hot stamped member of this embodiment is demonstrated using FIG. 3. FIG. Fig. 3 is a depth curve of a coating of a hot stamped component. 3 , the vertical axis represents the content of each element, and the horizontal axis represents the depth from the outermost surface of the hot stamped member (the outermost surface: 0 μm). A thin solid line indicates the content of Fe, a dashed-dotted line indicates the content of Al, and a thick solid line indicates the content of Sn. Here, for the sake of convenience, the description will be given based on Fig. 3 in which the surface coating layer is 100% Sn coating layer, but in the case where the surface layer coating layer 4 is not 100% Sn coating layer, in the following description, as long as the "Sn content" is replaced with " The sum of Sn content, Ni content and Zn content" becomes easy to understand. Therefore, "(Note 1)" is added to "Sn content" which can be replaced with "total of Sn content, Ni content, and Zn content".

When the steel sheet 10 for hot stamping is coated with a Sn content of 100%, the Sn content (Note 1) of the coating layer of the hot stamping member is 50% by mass or more, and the Sn content is 7% by mass or more (Note 2: due to The Sn content is 50% by mass or more, so of course the Sn content is 5% by mass or more, but in order to make it easy to understand the case other than surface plating with a Sn content of 100%, this requirement is also described for the sake of caution), Ni The Sn-enriched region where the content is less than 90% by mass and the Zn content is less than 40% by mass (Note 3: When the steel sheet 10 for hot stamping is not surface-coated with a Sn content of 100%, it becomes Sn , Ni and Zn-enriched region) the surface enriched region becomes region A in FIG. 3 .

The Al-rich region where the Sn content (Note 1) is less than 50% by mass, the Al content is 10% by mass or more, and the Fe content is 50% by mass or less is the region B in FIG. 3 . The Fe-rich region where the Al content is 10% by mass or more and the Fe content exceeds 50% by mass is a region C in FIG. 3 .

Corrosion of the hot stamped member can be suppressed by the presence of a plating layer having a surface layer-rich region, an Al-rich region, and an Fe-rich region in this order from the outermost surface of the hot stamped member. Including the case where the surface coating of the steel sheet 10 for hot stamping is 100% Sn coating, the position that becomes the boundary between the surface enriched region and the Al enriched layer of the hot stamping member is substantially the Sn content, the Ni content, and the Zn content. The sum of them becomes the position of 50% by mass. That is, regarding the requirements of "the Sn content is 7% by mass or more, the Ni content is less than 72% by mass, and the Zn content is less than 40% by mass" in the surface-rich layer, the lower limit of the Sn content can also be increased or lowered. The upper limit of the Ni content, lower the upper limit of the Zn content. For example, the lower limit of the Sn content in the surface layer-rich region may be set to 8 mass%, 9 mass%, or 10 mass%. The upper limit of the Ni content in the surface layer-rich region may be set to 70% by mass, 65% by mass, 60% by mass, 50% by mass, 40% by mass, 20% by mass, or 10% by mass. The upper limit of the Zn content in the surface layer-rich region may be set to 45% by mass, 42% by mass, 40% by mass, 35% by mass, 30% by mass, 20% by mass, or 10% by mass.

The thickness of the plated layer of the hot stamped member is calculated from the sum of the thicknesses of the surface-layer-enriched region, the Al-enriched region, and the Fe-enriched region. In addition, in the following description, the content of each element which is not described as a maximum value and an average value is the content of each element in each depth position.

In the hot stamped member of this embodiment, the maximum value of the sum of the Sn content, Ni content, and Zn content is 50% by mass or more in the region from the surface of the plating layer to a position 100 nm in the thickness direction from the surface of the plating layer, Fe content is 10% by mass or less.

In the hot stamped member of this embodiment, the total of the Sn content, Ni content, and Zn content in the region from the position of 100 nm in the thickness direction from the surface of the plating layer to the position of 500 nm in the thickness direction from the surface of the plating layer The maximum value is 5% by mass or more, and the Fe content is 40% by mass or less.

In the hot stamped member according to the present embodiment, the total of the Sn content, Ni content, and Zn content in the region from the position of 500 nm in the thickness direction from the surface of the plating layer to the position of 1000 nm in the thickness direction from the surface of the plating layer is the maximum The value is 1% by mass or more, and the Fe content is 50% by mass or less.

Hereinafter, the case of a hot stamped member obtained by hot stamping a steel sheet 10 for hot stamping having a surface layer 4 formed by Sn plating (that is, the sum of the Ni content and the Zn content is 0% by mass) is taken as an example. illustrate. The structure of the hot stamped member according to the present embodiment from the surface of the plating layer to a position 1000 nm in the thickness direction from the surface of the plating layer will be described with reference to FIG. 4 . 4 , the vertical axis represents the content of each element, and the horizontal axis represents the depth from the outermost surface of the hot stamped member (the outermost surface: 0 μm). A thin solid line indicates the content of Fe, a dashed-dotted line indicates the content of Al, and a thick solid line indicates the content of Sn. Here, for the sake of convenience, the description will be given based on FIG. 4 in which the surface coating is 100% Sn coating, but in the case where the surface coating 4 is not 100% Sn coating, in the following description, just replace "Sn content" with " The sum of Sn content, Ni content and Zn content" becomes easy to understand. Therefore, "(Note 1)" is added to "Sn content" which can be replaced with "total of Sn content, Ni content, and Zn content".

In the hot stamped member according to the present embodiment, the region from the surface of the plating layer to a position 100 nm in the thickness direction from the surface of the plating layer is a region D in FIG. 4 . The region of the hot stamped member from the position of 100 nm to the position of 500 nm in the thickness direction from the surface of the plating layer in the thickness direction is the region E in FIG. 4 . The region from the position of 500 nm to the position of 1000 nm in the thickness direction from the surface of the plating layer in the thickness direction is the region F in FIG. 4 . Each area will be described below.

"Area from the surface of the plating layer to a position 100 nm in the thickness direction from the surface of the plating layer"

In the region from the surface of the plated layer of the hot stamped member to a position 100 nm in the thickness direction from the plated surface of the hot stamped member, the maximum value of the Sn content (Note 1) is 50% by mass or more, and the Fe content is 10% by mass the following. In the region from the surface of the plating layer to a position 100 nm in the thickness direction from the surface of the plating layer, the Al content may be set to 1% by mass or more.

When the maximum value of the Sn content (Note 1) is less than 50% by mass in the region from the surface of the plated layer of the hot stamped member to the position 100 nm in the thickness direction from the surface of the plated layer of the hot stamped member When the Al content or Fe content in the outermost surface of the member is excessively increased, the amount of hydrogen intrusion during hot stamping of the hot stamped member decreases. Therefore, the maximum value of the Sn content (Note 1) is 50% by mass or more. A more preferable maximum value of the Sn content (Note 1) is 70% by mass or more. The Sn content (Note 1) can also be set to 90% by mass or less.

When the Fe content exceeds 10% by mass in the region from the surface of the coating of the hot stamping member to the position 100 nm in the thickness direction from the surface of the coating of the hot stamping member, Fe that becomes the cause of corrosion of the hot stamping member is in The number of places on the outermost surface of the hot stamped member (the surface of the plated layer of the hot stamped member) increases excessively, and the red rust resistance of the hot stamped member decreases. Therefore, the Fe content is 10% by mass or less. More preferable Fe content is 5 mass % or less.

When the maximum value of the Al content is less than 1% by mass in the region from the surface of the plated layer of the hot stamped member to a position 100 nm in the thickness direction from the surface of the plated layer of the hot stamped member, (including the surface layer plated component (Sn oxides, etc.) adhesion decreases, and the Sn oxide on the surface layer becomes easy to peel off, which may cause pressure scars caused by the peeled objects. Therefore, the maximum value of the Al content is preferably set to 1% by mass or more. A more preferable maximum value of the Al content is 5% by mass or more. The Al content may be 50% by mass or less.

"The area from the position of 100nm in the thickness direction from the surface of the plating layer to the position of 500nm in the thickness direction from the surface of the plating layer"

The maximum value of the Sn content (Note 1) is 5% by mass in the region from the position of 100 nm in the thickness direction to the position of 500 nm in the thickness direction from the plated surface of the hot stamped member Above, the Fe content is 40% by mass or less. It should be noted that, also including the case where the surface coating layer 4 of the steel sheet 10 for hot stamping is a 100% Sn coating layer, except that the maximum value of the total of the Sn content, the Ni content, and the Zn content is 5% by mass or more, it may be The maximum value of the Sn content is set to be 0.5% by mass or more or 1% by mass or more.

When the maximum value of the Sn content (Note 1) is less than 5 in the region from the position of 100 nm in the thickness direction to the position of 500 nm in the thickness direction from the surface of the plated layer of the hot stamped member In the case of mass %, the adhesion (including the oxide of the surface layer plating component, etc.) decreases, and the Sn oxide on the surface layer tends to peel off, which may cause pressure damage due to the peeled matter. Therefore, the maximum value of the Sn content (Note 1) is 5% by mass or more. A more preferable maximum value of the Sn content (Note 1) is 10% by mass or more.

When the Fe content exceeds 40% by mass in the region from the position of 100 nm in the thickness direction to the position of 500 nm in the thickness direction from the coating surface of the hot stamping member in the thickness direction, the hot stamping The Fe content in the outermost surface of the member increases excessively. Therefore, the Fe content is 40% by mass or less. More preferable Fe content is 25 mass % or less.

In the region from 100 nm to 500 nm in the thickness direction from the surface of the plated layer of the hot stamped member in the thickness direction, the remainder is Al, Si and impurities. Impurities are components mixed or intentionally added from steel raw materials or scrap and/or in the process of manufacturing the hot stamped member of this embodiment, and elements that are allowed within a range that does not inhibit the properties of the hot stamped member can be exemplified.

"The area from the position of 500nm in the thickness direction from the surface of the plating layer to the position of 1000nm in the thickness direction from the surface of the plating layer"

The maximum value of the Sn content (Note 1) is 1% by mass in the region from the position 500 nm in the thickness direction from the surface of the plated layer of the hot stamped member to the position 1000 nm in the thickness direction from the plated layer surface of the hot stamped member Above, Fe content is 50 mass % or less.

When the maximum value of Sn content (Note 1) is less than 1 in the region from the position of 500nm in the thickness direction to the position of 1000nm in the thickness direction from the surface of the plated layer of the hot stamped member When the mass % is less than 100%, the alloying may not be sufficiently advanced during the heat treatment, and the adhesion of the plating of the surface layer may become insufficient. Therefore, the maximum value of the Sn content (Note 1) is 1% by mass or more. A more preferable maximum value of the Sn content (Note 1) is 5% by mass or more. The maximum value of the Sn content (Note 1) may be 30% by mass or less.

When the Fe content exceeds 50 mass % in the region from the position of 500 nm in the thickness direction to the position of 1000 nm in the thickness direction from the coating surface of the hot stamping member in the thickness direction, hot stamping The Fe content in the outermost surface of the member is excessively increased. Therefore, the Fe content is 50% by mass or less. More preferable Fe content is 40 mass % or less.

In the region from 500nm to 1000nm in thickness direction from the surface of the plated layer of the hot stamped member in the thickness direction, the remainder is Al, Si and impurities. Impurities are components mixed or intentionally added from steel raw materials or scrap and/or in the process of manufacturing the hot stamped member of this embodiment, and elements that are allowed within a range that does not inhibit the properties of the hot stamped member can be exemplified.

The depth profile of each element of the plating layer of the hot stamped member can be measured by glow discharge luminescence analysis (GDS). The distance between the electrodes can also be set to 0.15 mm to 0.25 mm, and the measurement can be performed by selectively applying high-frequency, direct glow, high-frequency glow, etc. from the back of the sample. The discharge voltage may be measured at 30W to 50W (constant power mode), and the Ar pressure at the time of measurement may be measured at 500Pa to 700Pa. The discharge range can also be measured from 2mmφ to 6mmφ. As for the measurement time at one point, it is also possible to measure the time until 90% or more of Fe is detected (set as α), and further measure about 20% of this time (α×0.2) (total α+0.2α). The depth profile of each element can be obtained by measuring from the outermost surface of the hot stamped member to the region where the Fe element of the base steel material is stable. The depth (nm) from the surface of the plating layer was obtained as follows. First, the chipped depth per unit time is calculated from the chipped depth from the start to the end of the measurement and the measurement time. Next, the measured time was multiplied by the obtained depth of chipping per unit time to calculate the depth from the surface of the plated layer of the hot stamped member. When the unevenness of the surface of the hot stamping member is severe and vacuum cannot be evacuated, the measurement is performed by pressing an indium wire with a diameter of several hundred μm onto the hot stamping member to form a sealing material. A circle of the same extent as the evacuated portion of the measured portion was surrounded with indium wire, and the indium wire was placed on the hot stamped member to fill the surface irregularities, and then GDS measurement was performed.

"At least one of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide on the surface of the plating layer"

Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide or At least one of Zn hydroxides. This is because at least one of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide or Zn hydroxide exists on the surface of the coating, so that chemical conversion and electrodeposition coating Sex becomes good. Examples of the Sn oxide include SnO, SnO ₂ , and SnO ₃ . As the Sn hydroxide, Sn(OH) ₂ is exemplified. As a Zn oxide, Zn(OH) ₂ is mentioned. ZnO is mentioned as a Zn hydroxide. Examples of Ni oxides include NiO and Ni ₂ O ₃ . Examples of Ni hydroxides include NiOH and Ni(OH) ₂ .

"The sum of the Sn content, Zn content, and Ni content is 30% by mass or more in the region from the surface of the plating layer to a position 20 nm in the thickness direction from the surface of the plating layer"

The total of the Sn content, Zn content, and Ni content in the region from the plated surface of the hot stamped member to a position 20 nm in the thickness direction from the plated surface of the hot stamped member is preferably 30% by mass or more. When the total of the Sn content, the Zn content, and the Ni content is 30% by mass or more, the amount of hydrogen penetration after hot stamping can be further suppressed. A more preferable total of the Sn content, the Zn content, and the Ni content is 40% by mass or more.

Confirmation of the presence of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide can be performed by X-ray photoelectron spectroscopy (XPS measurement). Specifically, XPS measurement was performed after performing sputter etching of the hot stamped member by Ar sputtering (acceleration voltage: 20 kV, sputtering rate: 1.0 nm/min). Quantum 2000 manufactured by ULVAC-PHI was used for XPS measurement, using a ray source Al Kα ray, with an output power of 15kV, 25W, a spot size of 100μm, and a scan frequency of 10 times on the outermost surface of the hot stamping component in the entire energy range. Scan to measure. This Ar sputter etching and XPS measurement were performed alternately, and these measurements were repeated from the plated layer to a position of 20 nm in the thickness direction. The depth from the surface of the plating layer was calculated from the sputter etching time and the sputtering rate. The sputter etching rate was performed in terms of SiO ₂ . In the region from the surface of the plating layer of the hot stamping member to the position 20 nm in the thickness direction from the surface of the plating layer, the 486.0 eV to 486.8 eV originating from the 2p orbital of Sn oxide or Sn hydroxide, and the 486.8 eV originating from Zn When a peak is detected at 1021.7eV to 1022.5eV of the 2p orbital of the oxide or Zn hydroxide, and 854eV to 857eV of the 2p orbital of the Ni oxide or Ni hydroxide, it is determined that it is on the surface of the plated layer of the hot stamping member At least one of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide exists in the region up to 20 nm in the thickness direction from the surface of the plating layer. More specifically, regarding the presence or absence of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide, the XPS measurement of the sample was performed by the above-mentioned method, and the sample was removed. sample, and then measure the background. Thereafter, the background is removed from the measurement data of the sample. After background removal, when a peak of 1000 c/s or more is detected in the portion corresponding to the peak of each oxide and each hydroxide, it is judged that there are Sn oxides, Sn hydroxides, Ni oxides, and Ni hydroxides. compound, Zn oxide or Zn hydroxide at least one. The total of the Sn content, Zn content, and Ni content in the area from the surface of the coating layer of the hot stamping member to the position 20 nm in the thickness direction from the surface of the coating layer is calculated from all the elements detected by the above-mentioned XPS measurement. out.

"Thickness of coating"

The thickness of the plated layer of the hot stamped member is set to the sum of the thicknesses of the surface-layer-rich region, the Al-rich region, and the Fe-rich region. When the thickness of the plated layer of the hot stamped member is less than 5 μm, sufficient corrosion resistance may not be obtained. Therefore, the thickness of the plating layer is preferably 5 μm or more. The thickness of the plating layer is more preferably 10 μm or more, 20 μm or more, or 30 μm or more. When the thickness of the plating layer exceeds 200 μm, the effect of improving the corrosion resistance is saturated. Therefore, the thickness of the plating layer is preferably set to 200 μm or less. The thickness of the plating layer may also be set to 180 μm or less, 150 μm or less, 120 μm or less, or 100 μm or less.

In the above, the case of the hot stamping member obtained by hot stamping the steel sheet 10 for hot stamping in which the surface plating layer 4 is a Sn plating layer was demonstrated.

The plate thickness of the hot stamped member of the present embodiment is not particularly limited, but is preferably set to 0.5 to 3.5 mm from the viewpoint of weight reduction of the vehicle body. The plate thickness of the hot stamped member is preferably 0.8 mm or more, 1.0 mm or more, or 1.2 mm or more. The plate thickness of the hot stamped member is preferably 3.2 mm or less, 2.8 mm or less, or 2.4 mm or less.

The tensile strength of the hot stamped member of this embodiment is not particularly limited, but may be set to 1150 MPa or more, 1300 MPa or more, 1500 MPa, or 1600 MPa or more from the viewpoint of vehicle body weight reduction. The tensile strength of the hot stamped member may also be set to 2500 MPa or less, 2200 MPa or less, 2000 MPa or less, or 1800 MPa or less.

<Manufacturing method of steel sheet for hot stamping>

Next, a preferred method of manufacturing the steel sheet 10 for hot stamping will be described. The slab (steel material) to be subjected to hot rolling may be any slab produced by a conventional method, for example, any slab produced by a general method such as a continuous casting slab or a thin slab continuous caster. Hot rolling may also be performed by a general method, and is not particularly limited. After hot rolling, it is coiled to obtain a base steel plate.

After coiling, cold rolling may be further performed if necessary. The cumulative rolling reduction in cold rolling is not particularly limited, but is preferably set to 40 to 60% from the viewpoint of shape stability of the base steel sheet.

"Al-Si Alloy Plating"

Al-Si alloy plating is directly applied to the above-mentioned hot-rolled steel sheet, or Al-Si alloy plating is applied after cold rolling. The method of the Al-Si alloy plating layer 2 is not particularly limited, and a hot-dipping method, an electroplating method, a vacuum evaporation method, a coating method, a spraying method, and the like can be used. Particularly preferred is the hot-dipping method.

In the case of forming the Al-Si alloy plating layer 2 by the hot-dipping method, the composition is adjusted so that at least the Si content becomes 3% by mass or more, and the total of the Al content and the Si content becomes 95% by mass or more. The above-mentioned base steel sheet 1 was dipped in a coating bath to obtain an Al-Si alloy-coated steel sheet. The temperature of the coating bath is preferably in the temperature range of 660°C to 690°C. Before the Al-Si alloy plating layer 2 is applied, the hot-rolled steel sheet may be plated after the temperature of the hot-rolled steel sheet is raised to around 650° C. to 780° C. of the plating bath temperature.

In addition, in the case of performing hot-dip plating, there is a possibility that Fe may be mixed in the plating bath as an impurity in addition to Al or Si. In addition, Ni, Mg, Ti, Zn, Sb, Sn, Cu may be further contained in the plating bath as long as the Si content is 3% by mass or more and the total of the Al content and the Si content is 95% by mass or more. , Co, In, Bi, Ca, mixed rare earth alloys, etc.

"Al Oxide Film Removal"

Before forming the surface plating layer 4 , the Al oxide film of the steel sheet on which the Al-Si alloy plating layer 2 is formed (hereinafter referred to as Al-coated steel sheet) may be removed to obtain a steel sheet from which the Al oxide film has been removed. The removal of the Al oxide film 3 is performed by immersing the Al-plated steel sheet in an acidic or alkaline removing solution. Diluted hydrochloric acid (0.1 mol/L of HCl) etc. are mentioned as an acidic removal liquid. As the alkaline removing liquid, an aqueous sodium hydroxide solution (NaOH is 0.1 mol/L) and the like may be mentioned. The immersion time is adjusted so that the Al oxide film 3 after the surface plating layer 4 is formed becomes 20 nm or less. For example, when the bath temperature is 40° C., the Al oxide film is removed by immersion for 1 minute.

"Surface Plating"

The steel sheet for hot stamping is preferably obtained by removing the Al oxide film 3 after the Al-Si alloy plating layer is formed, or after the surface plating layer 4 is formed so that the average film thickness of the Al oxide film 3 becomes 20 nm or less, The surface plating layer 4 is formed by performing Sn plating, Sn—Ni plating, Sn—Zn plating, Sn—Ni—Zn plating, or the like on the steel sheet from which the Al oxide film has been removed within 1 minute. The surface plating layer 4 may also be formed by electroplating, vacuum deposition, or the like.

In the case where the surface coating 4 is a Sn coating, for example, it contains 0.3-0.5 mol/L of stannous sulfate, 0.5-0.8 mol/L of sulfuric acid, 0.15-0.3 mol/L of cresol sulfonic acid, and 0.003-0.007 mol/L of β-naphthol. mol/L, gelatin 1-3g/L Sn plating bath, the steel plate after forming the Al-Si alloy plating layer or after removing the Al oxide film is used as a cathode for immersion. After dipping, the Sn plating layer can be formed by controlling the energization time at a current density of 0.5 to 5 A/dm ² so that the thickness exceeds 300 nm. For the anode, tin plates are preferably used. Preferably, the pH of the Sn plating bath is set to 1.2 to 3.0, and the temperature of the Sn plating bath is set to 15 to 30°C.

When the surface coating layer 4 is formed of a coating layer mainly composed of a plurality of elements such as Sn-Ni coating layer, Sn-Zn coating layer, and Sn-Ni-Zn coating layer, it is preferable to heat the metal with electron beams by a vapor deposition device. for alloy plating. The vapor deposition amount is determined by the vapor pressure at the heating temperature. Therefore, in order to obtain an alloy plating layer exceeding 300 nm, it is preferable to adjust the heating temperature of each metal.

<Hot stamping process>

A hot stamped member can be obtained by hot stamping the steel sheet for hot stamping produced above. Hereinafter, an example of the conditions of hot stamping will be described, but the conditions of hot stamping are not limited to these conditions.

The above-mentioned steel sheet for hot stamping is placed in a heating furnace, and heated to a temperature above the Ac ₃ point (attainment temperature) at a heating rate of 1.5°C/sec to 10.0°C/sec. If the heating temperature is 1.5°C/sec to 10.0°C/sec, surface diffusion of Fe can be prevented. If the reaching temperature is Ac ₃ points or higher, springback can be suppressed, which is preferable. In addition, Ac ₃ point (degreeC) is represented by following (1) formula.

Ac ₃ =912-230.5×C+31.6×Si-20.4×Mn-14.8×Cr-18.1×Ni+16.8×Mo-39.8×C

u(1)

In addition, the symbol of the element in the said formula is content by mass % of the said element, and 0 is substituted when it does not contain.

The holding time after reaching the attained temperature is preferably set to 5 seconds to 300 seconds. When the holding time is 5 seconds to 300 seconds, since the diffusion of Fe to the hot stamping surface can be suppressed, it is preferable.

The retained steel plate was hot stamped and cooled to room temperature to obtain a hot stamped member. The cooling rate from hot stamping to room temperature is preferably 5°C/sec or more. If the cooling rate is 5°C/sec or more, diffusion of Fe to the outermost surface of the hot stamped member can be suppressed.

In addition, if necessary, tempering may be performed after hot stamping. For example, you may hold|maintain at 250 degreeC for 30 minutes.

Example

Next, examples of the present invention will be described, but the conditions in the examples are examples of conditions employed to confirm the practicability and effects of the present invention, and the present invention is not limited to this example of conditions. Various conditions can be employed in the present invention as long as the object of the present invention is achieved without departing from the gist of the present invention.

(manufacturing of mother steel plate)

Steel slabs produced by casting molten steels with the chemical compositions shown in Tables 1A, 1B, 2A, and 2B were heated to a temperature of Ac ₃ to 1400° C. and hot-rolled to obtain hot-rolled steel sheets (base steel sheets). The steel sheets of No. 16 and No. 36 were cold rolled at a cumulative reduction ratio of 50% after hot rolling, and rolled from 3.2 mm to a thickness of 1.6 mm. In addition, in the case of only hot rolling, it was rolled to a thickness of 1.6 mm by hot rolling. Empty columns in Tables 1A, 1B, 2A, 2B indicate no intentional addition.

[Table 1A]

[Table 1B]

[Table 2A]

[Form 2B]

[Table 3A]

Underlined indicates outside the scope of the present invention

[Table 3B]

Underlined indicates outside the scope of the present invention

[Table 3C]

Underlined indicates outside the scope of the present invention

[Table 3D]

Underlined are outside the scope of the invention [Table 4A]

[Form 4B]

[Form 4C]

[Table 4D]

[Table 5A]

[Form 5B]

[Table 5C]

[Form 5D]

[Table 6A]

[Form 6B]

[Form 6C]

[Table 6D]

(Al-Si plating)

Al—Si alloy plating was applied to the base steel sheet produced above. The coating bath of Al—Si alloy adjusted the composition of the coating bath so that it may become the Al content and Si content described in Table 3A, 3B, 3C, and 3D. The base steel sheets produced by the above method were immersed in a coating bath with adjusted components to obtain Al—Si alloy plated steel sheets described in Tables 3A, 3B, 3C, and 3D.

(removal of Al oxide film)

The Al oxide film on the surface of the Al—Si alloy plated steel sheet was removed by the methods described in Tables 3A, 3B, 3C, and 3D. In the case of an alkali described in Tables 3A, 3B, 3C, and 3D, a 0.1 mol/L sodium hydroxide aqueous solution was used as a removal liquid. In the case of an acid described in Tables 3A, 3B, 3C, and 3D, 0.1 mol/L dilute hydrochloric acid was used as a removal solution. The Al-Si plated steel sheet obtained above was immersed in a removal solution to obtain a steel sheet from which the Al oxide film was removed. When "-" appears in the table, it means that the Al oxide film was not removed.

(surface coating)

Next, for steel sheets Nos. 35 and 52 to 58, a treatment of forming a surface plating layer by electroplating was performed on the Al-Si alloy-plated steel sheet or the Al-Si alloy-plated steel sheet from which the Al oxide film was removed. In the case that the surface coating is a Sn coating, it contains 0.3-0.5 mol/L of stannous sulfate, 0.5-0.8 mol/L of sulfuric acid, 0.15-0.3 mol/L of cresol sulfonic acid, and 0.003-0.007 mol/L of β-naphthol. L. Dip an Al-Si alloy plated steel sheet in a Sn plating bath with 1-3 g/L of gelatin. After immersion, a tin plate was used as the anode, and the current density was 0.5 to 5 A/dm ² , and the energization time was controlled so that the thickness exceeded 300 nm to form a Sn plating layer. The pH of the Sn plating bath is set to 1.2 to 3.0, and the temperature of the Sn plating bath is set to 15 to 30°C.

In addition, in the steel sheets Nos. 1 to 34, 36 to 50, and 59 to 112, the Al—Si alloy plated steel sheets or the Al oxide film-removed steel sheets were treated to form surface plating layers by vapor deposition. Specifically, it is formed by vapor deposition under the following conditions: device capacity (chamber interior capacity): 0.6 m ³ , distance from the vapor deposition metal source to the steel plate (substrate): 0.6 m, and vacuum during vapor deposition. Density: 5.0×10 ^-3 to 2.0×10 ^-5 Pa, capacity of crucible for vapor deposition metal source: 40ml, inner diameter: 30φ, vapor deposition method: electron beam, electron beam irradiation conditions: voltage 10V (fixed), current 0.7-1.5A, steel plate temperature: 50-600°C, steel plate rotation speed: 15rpm. For the vapor-deposited metal, a metal having a purity of 99.9% by mass or higher was used. The microstructures of the steel sheet, which is the base material of the obtained steel sheet for hot stamping, were confirmed by the above method. As a result, in terms of the area ratio of the cross section, ferrite: 20 to 80%, pearlite: 20 to 80%, Remainder: Less than 5%.

(hot stamping)

Next, the steel sheets for hot stamping were hot stamped under the conditions described in Tables 5A, 5B, 5C, and 5D in a high dew point environment (30° C.) to obtain hot stamped members.

(Thickness of Al-Si alloy coating)

The thickness of the Al-Si alloy plating layer was measured as follows. The steel sheet for hot stamping obtained by the above-mentioned manufacturing method is cut in the thickness direction of the sheet. Afterwards, the cross section of the steel sheet for hot stamping is ground, and the cross section of the steel sheet for hot stamping after grinding is subjected to line analysis by FE-EPMA from the surface of the steel sheet for hot stamping to the steel plate using the ZAF method, and the detected components are measured. Al concentration and Si concentration. The measurement conditions were set at an acceleration voltage of 15 kV, a beam diameter of approximately 100 nm, an irradiation time per point of 1000 ms, and a measurement pitch of 60 nm. The measurement was performed in the range including the surface coating, the Al-Si alloy coating, and the steel sheet. The area where the Si concentration is 3% by mass or more and the sum of the Al concentration and the Si concentration is 95% by mass or more is determined to be the Al-Si alloy coating, and the thickness of the Al-Si alloy coating is set to be 100% in the thickness direction of the above-mentioned area. length. The thickness of the Al—Si alloy plating layer was measured at five positions at intervals of 5 μm, and the arithmetic mean of the obtained values was taken as the thickness of the Al—Si alloy plating layer. The evaluation results are shown in Tables 3A, 3B, 3C, and 3D.

(Determination of Al content and Si content in Al-Si alloy coating)

The Al content and the Si content in the Al-Si alloy coating were obtained in the following manner: the Al content and the Si content in the Al-Si alloy coating in the steel sheet 10 for hot stamping: According to the test method described in JIS K 0150 (2005), The test piece was collected, and the Al content and the Si content at the 1/2 position of the entire thickness of the Al-Si alloy plating layer were measured. The obtained results are shown in Tables 3A, 3B, 3C, and 3D.

(thickness of Al oxide film)

The thickness of the Al oxide film was evaluated by alternately repeating Ar sputtering and X-ray photoelectron spectroscopy (XPS) measurement. Specifically, XPS measurement was performed after sputtering the steel sheet for hot stamping by Ar sputtering (acceleration voltage: 0.5 kV, sputtering rate based on SiO ₂ : 0.5 nm/min). The XPS measurement was performed using a radiation source Al Kα ray, with an output power of 15 kV, 25 W, a spot size of 100 μm, a scan count of 10 times, and an entire energy range of 0 to 1300 eV. Ar sputtering and XPS measurement were performed alternately, and these measurements were repeated from the peak of Al's 2p orbital bonding energy of 73.8 eV to 74.5 eV in the XPS measurement until it disappeared. The thickness of the Al oxide film was calculated from the following sputtering time and sputtering rate: from the position where the O content becomes 20 atomic % or more for the first time after the start of sputtering to the position where the O content becomes lower than 20 atomic % shooting time. The sputtering rate was performed in terms of SiO ₂ . The thickness of the Al oxide film was set as the arithmetic mean value measured at two places. The obtained results are shown in Tables 3A, 3B, 3C, and 3D.

(thickness of surface coating)

The average layer thickness (thickness) of the surface plating layer 4 can be measured by glow discharge luminescence analysis (GDS). The measurement was performed in such a manner that the discharge condition was 35 W (constant power mode), the Ar pressure during measurement was 600 Pa, and the discharge range was 4 mmφ. The distance between electrodes was set at 0.18 mm. As for the measurement time at one point, the time until 90% or more of Fe was detected was measured (set as α), and about 20% of this time was further measured (α×0.2) (total α+0.2α). Measurement was performed from the outermost surface of the steel sheet 10 for hot stamping to a region where Al was detected and the total of plating components (Sn, Zn, Ni) as the surface plating layer reached 50%. The thickness (nm) of the surface plating layer was obtained as follows. First, the chipped depth per unit time is calculated from the chipped depth from the start to the end of the measurement and the measurement time. Next, the thickness of the surface plating layer of the steel sheet 10 for hot stamping was calculated by multiplying the measured time by the obtained depth of chipping per unit time. The obtained results are shown in Tables 4A, 4B, 4C, and 4D.

(Sn content, Zn content, Ni content of surface coating)

Regarding the content of main elements in the surface coating (the content of any one of Sn content, Zn content, and Ni content), the Sn concentration at the center position in the thickness direction of the surface coating obtained in the measurement of the thickness of the surface coating The concentration of the element having the largest numerical value among , Zn concentration, and Ni concentration was set as the content of the main element. Specifically, for the arithmetic mean (N=2) of the values measured at the center of the surface coating in the thickness direction, the numerical value of the largest element among the Sn content, Zn content, and Ni content is set as the main element content. The obtained results are shown in Tables 4A, 4B, 4C, and 4D.

(Coverage rate of surface coating)

The coverage rate of the surface plating layer was evaluated by XPS measurement. The XPS measurement uses a radiation source Al Kα ray, and scans the steel sheet 10 for hot stamping in the entire energy range of 0 to 1300 eV at an output of 15 kV, 25 W, a spot size of 100 μm, and 10 scans. In the case of Sn plating, the Sn content (atomic %) and the Al content (atomic %) were calculated. Next, the ratio (mass %) of the Ni content to the total of the Sn content (mass %) and the Al content (mass %) was calculated, and the obtained ratio was defined as the coverage rate (%) of the Sn plating. In the case of alloy plating, the Sn content (atomic %), the Zn content (atomic %), the Ni content (atomic %), and the Al content (atomic %) were calculated. Next, the ratio (%) of the Zn content to the total of the Zn content and the Al content was calculated, and the obtained ratio was defined as the coverage rate (%) of the alloy plating. The obtained results are shown in Tables 4A, 4B, 4C, and 4D.

(depth curve of coating)

The depth profile of each element of the plated layer of the hot stamped member is obtained by measuring with GDS. The conditions are that the distance between the electrodes is set to 0.19 mm, and the high frequency is applied from the back of the sample. The measurement was performed in such a manner that the discharge voltage was 35 W (constant power mode), the Ar pressure during measurement was 600 Pa, and the discharge range was 4 mmφ. The measurement time for one location was about 12 minutes, and about 50 μm was etched. The depth of the plating layer was calculated by the method described above. The depth profile of each element is obtained by measuring from the surface of the hot stamped member to the region where the Fe element of the base material is stable.

In the region from the surface of the plated layer of the hot stamped member to the position 100 nm in the thickness direction from the surface of the plated layer of the hot stamped member, the case where the Fe content is 5% by mass or less is set as I, and the case where the content of Fe is 5% by mass or less is set as I, and when it exceeds 5% by mass and When it is 10 mass % or less, it is set as II, and when it exceeds 10 mass %, it is set as III. In addition, the case where the total maximum value of the Sn content, Ni content, and Zn content is 70 mass % or more is set as I, the case of 50 mass % or more and less than 70 mass % is set as II, and the case of less than 50 mass % is set as I. The case of mass % is set to III, the case of the maximum Al content of 5 mass % or more is set to I, the case of 1 mass % to less than 5 mass % is set to II, and the case of less than 1 mass % % of cases set to III.

In the region from the position of 100 nm in the thickness direction to the position of 500 nm in the thickness direction from the surface of the plated layer of the hot stamped member in the thickness direction, the case where the Fe content is 15% by mass or less is set as In I, the case where it exceeds 15% by mass and 40% by mass or less is referred to as II, and the case where it exceeds 40% by mass is referred to as III. In addition, the case where the total maximum value of the Sn content, Ni content, and Zn content is 10 mass % or more is set as I, the case of 5 mass % or more and less than 10 mass % is set as II, and the case of less than 5 mass % is set as I. The case of mass % was set to III.

In the region from the position of 500 nm in the thickness direction to the position of 1000 nm in the thickness direction from the surface of the plated layer of the hot stamped member in the thickness direction, the case where the Fe content is 20% by mass or less is set as In I, the case of 20 mass % to 50 mass % is set as II, and the case of exceeding 50 mass % is set as III. In addition, the case where the total maximum value of the Sn content, the Zn content, and the Ni content is 5% by mass or more is defined as I, the case of 1% by mass or more and less than 5% by mass is defined as II, and the case of less than 1% by mass is defined as II. The case of mass % was set to III.

In Tables 6A, 6B, 6C, and 6D, the determination of the regions from the surface to 1000 nm was performed by setting all the regions as I or II to G as pass. In the judgment of each area, even one of them was classified as III, and it was set as B as a failure. Sn+Ni+Zn in the table means the total (% by mass) of the Sn content, the Ni content, and the Zn content.

It should be noted that the regions (0-100nm) in Tables 6A, 6B, 6C, and 6D refer to the region from the surface of the plating layer to the position 100 nm in the thickness direction from the surface of the plating layer. The area (100-500nm) in the table 6A, 6B, 6C, 6D refers to the area from the surface of the coating to the 500nm position in the thickness direction from the surface of the coating in the thickness direction. The area (500-1000nm) in table 6A, 6B, 6C, 6D refers to the area from the surface of the coating to the 1000nm position in the thickness direction from the surface of the coating to the 1000nm position in the thickness direction.

(At least one of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide in the region from the surface of the plating layer to a position 20 nm in the thickness direction from the surface of the plating layer 1 type)

At least 1 of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide in the region from the surface of the plating layer to a position 20 nm in the thickness direction from the surface of the plating layer The presence of species was confirmed by X-ray photoelectron spectroscopy (XPS measurement). Specifically, XPS measurement was performed after performing sputter etching of the hot stamped member by Ar sputtering (acceleration voltage: 20 kV, sputtering rate: 1.0 nm/min). Quantum 2000 manufactured by ULVAC-PHI was used for XPS measurement, using a ray source Al Kα ray, with an output power of 15kV, 25W, a spot size of 100μm, and a scan frequency of 10 times on the outermost surface of the hot stamping component in the entire energy range. Scanned to measure. This Ar sputter etching and XPS measurement were performed alternately, and these measurements were repeated from the plated layer to a position of 20 nm in the thickness direction. The depth from the surface of the plating layer was calculated from the sputter etching time and the sputtering rate. In the area from the surface of the coating layer of the hot stamping member to the position 20 nm in the thickness direction from the surface of the coating layer, the Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, When a peak is detected within any range of Zn oxide or Zn hydroxide, it is determined that Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydrogen exists on the surface of the coating. at least one of oxides. The sputter etching rate was performed in terms of SiO ₂ . In addition, the total of the Sn content, Ni content and Zn content in the area from the surface of the coating layer of the hot stamping member to the position 20 nm in the thickness direction from the surface of the coating layer is calculated from all elements detected by XPS measurement. out.

(Determination of the area from the surface to the 20nm position)

Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide or Zn hydroxide will exist in the area from the surface of the coating to the position 20 nm in the thickness direction from the surface of the coating. The case where at least one of the above and the total of the Sn content, Ni content, and Zn content is 30% by mass or more is set to G, and the other cases are set to B. The results are shown in Tables 6A, 6B, 6C, 6D.

(Determination of each enrichment area)

According to the GDS measurement results of the depth curve of each element of the coating of the hot stamping member, the surface enriched region of the coating (the sum of Sn content, Ni content and Zn content: 50% by mass or more, Sn content : 7% by mass or more, Ni content: less than 72% by mass, and Zn content: less than 40% by mass), Al-rich region (Al content: 10% by mass or more, Fe content: 50% by mass or less), Fe-rich In the case of each area of the concentrated area (Al content: 10% by mass or more, Fe content: more than 50% by mass) (judgment of each enriched area) is set to G, and when these areas are not provided, set to b. The obtained results are shown in Tables 6A, 6B, 6C, and 6D.

(tensile strength)

The tensile strength of the hot stamped member was obtained by preparing the No. 5 test piece described in JIS Z 2241:2011 from an arbitrary position of the hot stamped member, and obtained it according to the test method described in JIS Z 2241:2011. In addition, the test No. 49 in which the scale state was bad was not evaluated. The measurement results are shown in Tables 5A, 5B, 5C, and 5D.

(Amount of hydrogen intruded into the furnace)

For hot stamping components, hydrogen analysis is carried out at elevated temperature to determine the amount of hydrogen in the hot stamping components. After hot stamping, after the temperature drops to about 100°C, it is immersed in liquid nitrogen, cooled to below -10°C and frozen, and the amount of diffusible hydrogen released up to 300°C is used in the temperature-rising hydrogen analysis. The intrusion hydrogen amount (mass ppm) of the hot stamped member was evaluated. Set the amount of intruded hydrogen below 0.2wt.ppm as E, set 0.20wt.ppm ~ 0.35wt.ppm as Gr, set 0.35wt.ppm ~ 0.6wt.ppm as G, and exceed 0.6wt.ppm ppm is set to B. Those evaluated as E, Gr, and G were judged to be able to suppress the amount of intrusive hydrogen even in a high dew point environment, and were set as acceptable. The case of B was regarded as unqualified. The measurement results are shown in Tables 5A, 5B, 5C, and 5D. In addition, evaluation of the amount of intruded hydrogen was not performed for steel sheets with early fractures and steel sheets with a tensile strength lower than 1600 MPa.

(Hydrogen intrusion into hot stamped parts (exposure test))

A part of the hot stamped member was kept at 60° C. for 3 days to remove hydrogen, and then exposed to an environment within 0.5 km from the coast of Okinawa for 6 months, and the amount of hydrogen intrusion into the hot stamped member after that was investigated. The temperature-rising detachment method is implemented with a sample size of 10x40 mm, a temperature-rising range: room temperature to 200°C, and a temperature-rising rate: 100°C/hour, and is obtained from the cumulative amount up to 200°C.

When the accumulated amount of hydrogen at this time was 0.7 wt.ppm or more, it was evaluated as poor (B), and when it was less than 0.7 wt.ppm, it was evaluated as good (G). The obtained results are shown in Tables 5A, 5B, 5C, and 5D.

As shown in Tables 5A, 5B, 5C, and 5D, steel plate Nos. 21, 22, 25, 26, 32, 42, 57, 58, 63-66, 71-109, 111, The amount of intruded hydrogen in the heating furnace of 112 and the amount of intruded hydrogen after hot stamping are also small. In Comparative Example 20 and the like, since the Zn concentration is 50% by mass or more, the amount of intruded hydrogen after hot stamping is high.

Industrial availability

According to the present invention, even a steel sheet for hot stamping coated with Al has excellent resistance to hydrogen embrittlement by reducing the amount of intruded hydrogen even in hot stamping under a high dew point environment, so it is industrially applicable. high sex.

Explanation of symbols

1 steel plate

2Al-Si alloy coating

3 Al oxide film

4 surface coating

10 steel plate for hot stamping

Claims (10)

1. A steel plate for hot stamping, characterized in that it possesses successively: Mother steel plate; Al-Si alloy coating, wherein the Al content is 75% by mass or more, the Si content is 3% by mass or more, and the total of the Al content and the Si content is 95% by mass or more; Al oxide film with a thickness of 0-20nm; and A surface coating wherein the total of the Sn content, the Ni content, and the Zn content exceeds 90% by mass, the Sn content is 10% by mass or more, the Ni content is less than 90% by mass, and the Zn content is less than 50% by mass, The thickness of the Al-Si alloy coating is 5-50 μm, The thickness of the surface coating is more than 300nm and less than 2500nm. 2. The steel sheet for hot stamping according to claim 1, wherein the surface plating layer is provided as an upper layer of the Al-Si alloy plating layer in direct contact with the Al-Si alloy plating layer. 3. The steel sheet for hot stamping according to claim 1, wherein the Al oxide film has a thickness of 2 to 20 nm. 4. The steel sheet for hot stamping according to any one of claims 1 to 3, wherein the chemical composition of the base steel sheet is: C: 0.25～0.70%, Si: 0.005～1.000%, Mn: 0.30～3.00%, P: 0.100% or less, S: 0.1000% or less, N: 0.0100% or less, Cu: 0～1.00%, Ni: 0 to 1.00%, Cr: 0～1.000%, Mo: 0 to 1.000%, Nb: 0 to 0.200%, V: 0～1.000%, Ti: 0 to 0.150%, B: 0～0.0100%, Co: 0 to 1.00%, W: 0～1.00%, Sn: 0～1.00%, Sb: 0 to 1.00%, Zr: 0 to 1.00%, Mg: 0～0.150%, Al: 0～1.0000%, Ca: 0～0.010%, REM: 0%～0.300%, and The remainder: Fe and impurities. 5. The steel sheet for hot stamping according to claim 4, wherein the chemical composition of the base steel sheet contains one or more elements selected from the following elements in mass %: Cu: 0.01 to 1.00%, Ni: 0.01 to 1.00%, Cr: 0.001～1.000%, Mo: 0.001 to 1.000%, Nb: 0.001 to 0.200%, V: 0.01～1.00%, Ti: 0.001 to 0.150%, B: 0.001～0.0100%, Co: 0.01 to 1.00%, W: 0.01～1.00%, Sn: 0.01 to 1.00%, Sb: 0.01 to 1.00%, Zr: 0.01 to 1.00%, Mg: 0.001 to 0.150%, Al: 0.0010～1.0000%, Ca: 0.001 to 0.010%, and REM: 0.001 to 0.300%. 6. A hot stamping member, characterized in that it comprises a base steel material and a coating layer provided on the base steel material, and the coating layer has in order from the surface of the coating layer: A surface-rich region in which the sum of the Sn content, the Ni content, and the Zn content is 50% by mass or more, the Sn content is 7% by mass or more, the Ni content is less than 72% by mass, and the Zn content is less than 40% by mass; An Al-rich region in which the sum of the Sn content, the Ni content, and the Zn content is less than 50% by mass, the Al content is 10% by mass or more, and the Fe content is 50% by mass or less; and Fe-enriched region, wherein the Al content is 10% by mass or more and the Fe content exceeds 50% by mass, In the region from the surface of the plating layer to a position 100 nm in the thickness direction from the surface of the plating layer, the maximum value of the sum of the Sn content, Ni content, and Zn content is 50% by mass or more, and the Fe content 10% by mass or less, The sum of the Sn content, Ni content and Zn content in the region from the position of 100 nm in the thickness direction to the position of 500 nm in the thickness direction from the surface of the coating layer The maximum value is 5% by mass or more, the Fe content is 40% by mass or less, The sum of the Sn content, Ni content and Zn content in the region from the position of 500 nm in the thickness direction to the position of 1000 nm in the thickness direction from the surface of the coating layer The maximum value is 1% by mass or more, and the Fe content is 50% by mass or less. 7. The hot stamped component according to claim 6, characterized in that the Ni content of the surface enriched region is less than 50% by mass. 8. The hot stamping member according to claim 6 or 7, wherein, in the region from the surface of the plating layer to a position 20 nm from the surface of the plating layer in the thickness direction, At least one of Sn oxide, Sn hydroxide, Ni oxide, Ni hydroxide, Zn oxide, or Zn hydroxide is present, and the total of Sn content, Ni content, and Zn content is 30% by mass or more. 9. The hot stamping member according to any one of claims 6-8, characterized in that, the chemical composition of the parent steel is calculated in mass %: C: 0.25～0.70%, Si: 0.005～1.000%, Mn: 0.30～3.00%, P: 0.100% or less, S: 0.1000% or less, N: 0.0100% or less, Cu: 0～1.00%, Ni: 0 to 1.00%, Cr: 0～1.000%, Mo: 0 to 1.000%, Nb: 0 to 0.200%, V: 0～1.00%, Ti: 0 to 0.150%, B: 0～0.0100%, Co: 0 to 1.00%, W: 0～1.00%, Sn: 0～1.00%, Sb: 0 to 1.00%, Zr: 0 to 1.00%, Mg: 0～0.150%, Al: 0～1.0000%, Ca: 0～0.010%, REM: 0%～0.300%, and The remainder: Fe and impurities. 10. The hot stamping member according to claim 9, characterized in that the chemical composition of the base steel material contains one or more elements selected from the following elements in mass %: Cu: 0.01 to 1.00%, Ni: 0.01 to 1.00%, Cr: 0.001～1.000%, Mo: 0.001 to 1.000%, Nb: 0.001 to 0.200%, V: 0.01～1.00%, Ti: 0.001 to 0.150%, B: 0.0010～0.0100%, Co: 0.01 to 1.00%, W: 0.01～1.00%, Sn: 0.01 to 1.00%, Sb: 0.01 to 1.00%, Zr: 0.01 to 1.00%, Mg: 0.001 to 0.150%, Al: 0.0010～1.0000%, Ca: 0.001 to 0.010%, and REM: 0.001 to 0.300%.