Specification
Title of the Invention : Coated Steel Member, Coated Steel Plate and Method for Manufacturing Them
Technical field
[0001]
The present invention relates to coated steel members, coated steel sheets, and methods of manufacturing them.
This application claims priority based on Japanese Patent Application No. 2019-211299 filed in Japan on November 22, 2019, the content of which is incorporated herein.
Background technology
[0002]
In the automotive field, the application of steel sheets with high tensile strength (high-strength steel sheets) is expanding in order to improve both fuel efficiency and collision safety against the backdrop of recent stricter environmental regulations and crash safety standards. there is However, as the strength increases, the press formability of the steel sheet deteriorates, making it difficult to manufacture products with complicated shapes.
[0003]
Specifically, the ductility of steel sheets decreases as strength increases, and when processed into complex shapes, there is a problem of fractures at highly processed parts. In addition, as the strength of the steel sheet increases, springback and wall warping occur due to residual stress after processing, and the problem of deterioration in dimensional accuracy also arises. Therefore, it is not easy to press-form a steel sheet having high strength, particularly a tensile strength of 780 MPa or more, into a product having a complicated shape. Roll forming rather than press forming facilitates the processing of high-strength steel sheets, but its application is limited to parts with a uniform longitudinal cross-section.
[0004]
Therefore, in recent years, for example, as disclosed in Patent Documents 1 to 3, hot stamping technology has been adopted as a technology for press forming materials that are difficult to shape, such as high-strength steel plates. Hot stamping technology is a hot molding technology in which a material to be molded is heated and then molded.
[0005]
With this technology, the material is heated and then molded. Therefore, the steel material is soft at the time of forming and has good formability. As a result, even a high-strength steel sheet can be accurately formed into a complicated shape. Moreover, in the hot stamping technique, quenching is performed at the same time as forming with a press die, so the steel member after forming has sufficient strength.
[0006]
For example, Patent Document 1 discloses that a steel member having a tensile strength of 1400 MPa or more after forming can be obtained by hot stamping technology.
[0007]
　In recent years, countries around the world have set even higher CO2 reduction targets, and automobile companies are promoting fuel efficiency reductions in consideration of crash safety. Not only gasoline-powered vehicles, but also rapidly-moving electric-powered vehicles are in need of higher-strength materials in order to protect not only passengers but also batteries from collisions and offset the increase in weight. For steel members, for example, there is a need for hot-stamped members having a strength exceeding 1.5 GPa, which is generally used as steel members formed by hot stamping.
[0008]
However, many metal materials deteriorate in various properties as their strength increases, and their susceptibility to hydrogen embrittlement in particular increases. It is known that the susceptibility to hydrogen embrittlement increases in steel members when the tensile strength is 1.2 GPa or more, and there are cases of hydrogen embrittlement cracking in bolt steel, where high strength has been promoted ahead of the automotive field. do. It is feared that the hot stamped member having a tensile strength exceeding 1.5 GPa will further increase the susceptibility to hydrogen embrittlement.
[0009]
The most popular steel sheets for hot stamping are coated steel sheets with aluminum plating on the surface (aluminized steel sheets). However, since aluminized steel sheets absorb hydrogen during hot stamping heating, there is a risk that hydrogen embrittlement cracking will occur after the body is assembled after hot stamping in the region where the strength exceeds 1.5 GPa where the susceptibility to hydrogen embrittlement increases. . Therefore, in order to apply a hot-stamped member having a tensile strength exceeding 1.5 GPa to a vehicle body in order to further reduce the weight of the vehicle body, it is necessary to sufficiently reduce the risk of hydrogen embrittlement cracking.
[0010]
Regarding high-strength steel materials with a tensile strength exceeding 1.5 GPa, for example, Patent Document 2 discloses hot press-formed products having excellent toughness and a tensile strength of 1.8 GPa or more. Patent Document 3 discloses a steel material having an extremely high tensile strength of 2.0 GPa or more, and further having good toughness and ductility. Patent Document 4 discloses a steel material having a high tensile strength of 1.8 GPa or more and further having good toughness. Patent Document 5 discloses a steel material having an extremely high tensile strength of 2.0 GPa or more and good toughness.
However, Patent Documents 2 to 5 disclose that hydrogen embrittlement resistance, especially when using an aluminum-plated steel sheet, is not sufficient to prevent hydrogen absorption. Higher demands on safety may not be met satisfactorily.
[0011]
In addition, regarding high-strength steel materials excellent in hydrogen embrittlement resistance using aluminized steel sheets, for example, Patent Document 6 discloses that the heating atmosphere of steel sheets is set to an atmosphere with a dew point of 30 ° C. or less to limit the amount of hydrogen that penetrates into steel materials. In addition, a method for suppressing hydrogen embrittlement after hot stamping by reducing residual stress after post-processing is disclosed.
However, in Patent Document 6, measures against hydrogen embrittlement of high-strength steel materials exceeding 1.5 GPa are not sufficient, and in applying high-strength steel materials having a tensile strength exceeding 1.5 GPa to automobile members, higher requirements for safety may not be able to fully respond to
prior art documents
patent literature
[0012]
Patent Document 1: Japanese Patent Application Laid-Open No. 2002-102980
Patent Document 2: Japanese Patent Application Laid-Open No. 2012-180594
Patent Document 3: Japanese Patent Application Laid-Open No. 2012-1802
Patent Document 4: International Publication No. 2015/182596
Patent Document 5: International Publication No. 2015/182591
Patent Document 6: Japanese Patent Application Laid-Open No. 2008-266721
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0013]
The present invention has been made to solve the above problems, and has a coated steel member having high tensile strength and excellent hydrogen embrittlement resistance, a coated steel plate suitable as a material for the steel member, and It aims at providing the manufacturing method of.
Means to solve problems
[0014]
The gist of the present invention is the following coated steel member, coated steel plate and manufacturing method thereof. Hereinafter, a steel sheet whose surface is not coated, which is a raw material for the coated steel sheet, is simply referred to as "steel sheet".
(1) In mass %, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo: 0 .10-1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0.010%, Al: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Sb: 0-1.00%, Zr: 0-1.00 %, and REM: 0 to 0.30%, the balance being Fe and impurities, a steel plate substrate having a chemical composition, a coating formed on the surface of the steel plate substrate and containing Al and Fe, and wherein the maximum Cu content in the range from the surface to a depth of 5.0 μm is 150% or more with respect to the Cu content of the steel plate base material.
(2) In mass %, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo: 0 .10-1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0.010%, Al: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Sb: 0-1.00%, Zr: 0-1.00 %, and REM: 0 to 0.30%, the balance being Fe and impurities, a steel sheet having a chemical composition, a coating containing Al on the surface of the steel sheet, and the steel sheet and the coating and a boundary formed therebetween, wherein the maximum Cu content at said boundary is 80% or more of the average Cu content of said steel plate.
(3) In mass %, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo: 0 .10-1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0.010%, Al: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Sb: 0-1.00%, Zr: 0-1.00 %, and REM: 0 to 0.30%, the balance being Fe and impurities. A hot-rolling step of subjecting the hot-rolled steel sheet to a hot-rolled steel sheet, a winding step of winding the hot-rolled steel sheet, and optionally a hot-rolled sheet annealing step of annealing the hot-rolled steel sheet. Depending on the above, the hot-rolled steel sheet is descaled and cold-rolled to form a cold-rolled steel sheet, and if necessary, the hot-rolled steel sheet or the cold-rolled steel sheet is annealed. An annealing step of forming an annealed steel sheet, and an Al-based coating is formed by immersing the hot-rolled steel sheet, the cold-rolled steel sheet, or the annealed steel sheet in an Al-based plating bath having a bath temperature of 600 ° C. or higher, and then a coating step of cooling to 200° C. or lower at an average cooling rate of less than 30° C./sec.
(4) The method for producing a coated steel sheet according to (3) above may further include a post heat treatment step of annealing the coated steel sheet obtained by the coating step in a temperature range of 450 to 800°C.
(5) In mass %, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo: 0 .10-1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0.010%, Al: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Sb: 0-1.00%, Zr: 0-1.00 %, and REM: 0 to 0.30%, the balance being Fe and impurities. A hot-rolling step of subjecting the hot-rolled steel sheet to a hot-rolled steel sheet, a winding step of winding the hot-rolled steel sheet, and optionally a hot-rolled sheet annealing step of annealing the hot-rolled steel sheet. Depending on the above, the hot-rolled steel sheet is descaled and cold-rolled to form a cold-rolled steel sheet, and if necessary, the hot-rolled steel sheet or the cold-rolled steel sheet is annealed. An annealing step of forming an annealed steel sheet, and an Al-based coating is formed by immersing the hot-rolled steel sheet, the cold-rolled steel sheet, or the annealed steel sheet in an Al-based plating bath having a bath temperature of 600 ° C. or higher, and then A coating step of cooling to 200 ° C. or less at an average cooling rate of less than 30 ° C./sec to form a coated steel plate, and the coated steel plate is heated at a rate of 1.0 to 100 ° C./sec in an atmosphere with a dew point of 30 ° C. or less. a heat treatment step of heating to Ac3 point to (Ac3 point + 300) ° C. at a high speed, and then cooling to Ms point or lower at an upper critical cooling rate or higher.
(6) The method for manufacturing a coated steel member according to (5) above may further include a post-heat treatment step of annealing the coated steel sheet in a temperature range of 450 to 800° C. after the coating step.
Effect of the invention
[0015]
According to the above aspect of the present invention, a coated steel member and a coated steel sheet having high tensile strength and excellent resistance to hydrogen embrittlement, and methods for producing them are provided.be able to.
The coated steel member of the present invention has high strength and excellent resistance to hydrogen embrittlement, so when applied to automobile parts, it contributes to improving fuel efficiency and collision safety.
Brief description of the drawing
[0016]
[Fig. 1] Fig. 1 is a schematic diagram showing an example of a coated steel member according to the present embodiment.
[Fig. 2] Fig. 2 is a schematic diagram showing an example of a coated steel sheet according to the present embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0017]
In order to obtain a coated steel member having high tensile strength and excellent resistance to hydrogen embrittlement, the present inventors investigated the effects of the surface layer structure, the chemical composition of the steel material (steel plate base material), and the internal structure on these properties. did. As a result, the following findings were obtained.
[0018]
　Many of the materials used in hot stamped parts that are generally manufactured are coated steel sheets with aluminum plating, which has excellent corrosion resistance, applied to the surface of the steel sheets. When this coated steel sheet is subjected to hot stamping, an alloying reaction between Al on the surface and Fe in the steel sheet progresses during heating, and a coated steel member having an Al—Fe-based coating is obtained. Most of the commonly used steel sheets that exhibit a tensile strength of 1.5 GPa after hot stamping have a similar chemical composition and contain about 0.20% by mass of C, and this C increases the strength after hot stamping. I have secured. In addition, in order to ensure hardenability during hot stamping manufacturing, it often contains about 1.3% by mass of Mn and about 0.002% by mass of B.
[0019]
(a) In order to further reduce the weight of the vehicle body, the present inventors conducted a detailed study to obtain a high-strength member exceeding 1.5 GPa after hot stamping by increasing the C content. As a result, it was found that by setting the C content to 0.25% by mass or more, an ultra-high tensile strength of 1.5 GPa or more can be obtained after hot stamping. On the other hand, the susceptibility to hydrogen embrittlement increased with the ultra-high tensile strength of 1.5 GPa or more, and there was concern about the risk of hydrogen embrittlement cracking due to hydrogen entering in the heating furnace during the production of hot stamped members. .
[0020]
(b) The present inventors first investigated the relationship between hydrogen and surface reaction in a coated steel member having a high-strength Al—Fe-based coating with a tensile strength exceeding 1.5 GPa, and reduced the amount of intruding hydrogen. We worked to improve hydrogen embrittlement resistance. As a result, it was found that by distributing Cu, which has a low hydrogen solid solubility, in the outermost layer of the steel material, hydrogen penetration into the steel material can be suppressed due to its barrier effect. The reasons for this are as follows. That is, during hot stamping heating, H 2 O in the air reacts with the aluminum plating on the surface, and after diverging to 2H due to the catalytic effect, some H penetrates into the steel material. Cu suppresses the divergence from H 2 to 2H, that is, suppresses the generation of hydrogen atoms, thereby reducing the amount of intruding hydrogen.
[0021]
(c) The present inventors further investigated the relationship between the chemical composition, structure, and hydrogen embrittlement susceptibility of steel materials having a tensile strength exceeding 1.5 GPa, and found that hydrogen embrittlement resistance due to the improvement of the critical hydrogen content (Hc) worked to improve As a result, it was found that the hydrogen embrittlement susceptibility of the steel material is reduced by reducing the Mn content, that is, the limit hydrogen content at which hydrogen embrittlement does not occur is increased. On the other hand, in order to compensate for the decrease in hardenability due to the reduction in the Mn content, and to suppress hot brittleness during steel sheet production when the above-described Cu is contained, when Ni is contained, Ni is hydrogen It was also found to promote embrittlement. As a result of studies by the present inventors, Si is also effective in suppressing hot shortness due to Cu. , it was found that stable steel plate production is possible. In addition, Si is an element that has the effect of improving hardenability by suppressing pearlite precipitation, and Mo is also an element that enhances hardenability. Therefore, it was found that the lack of hardenability can be compensated for by reducing Mn by including Si and Mo.
In addition, when Nb is contained, the internal structure of the steel material becomes finer (grain refinement). Therefore, it was found that the inclusion of Nb suppresses fracture of the grain boundary, which is often the starting point of hydrogen embrittlement, and improves the critical hydrogen content.
[0022]
Based on the above knowledge, the present inventors have greatly improved hydrogen embrittlement resistance by reducing the amount of penetrating hydrogen and improving the limit hydrogen amount of steel materials, and have achieved a high-strength hot stamping member exceeding 1.5 GPa. We also developed a coated steel sheet suitable for the material. Such a steel member can be safely applied to a vehicle body while sufficiently reducing the risk of hydrogen embrittlement.
[0023]
Each requirement of the coated steel member according to one embodiment of the present invention (coated steel member according to this embodiment), coated steel plate (coated steel plate according to this embodiment), and their manufacturing methods will be described below in detail.
[0024]
(A) Coated steel member
As shown in FIG. 1, the coated steel member according to the present embodiment includes a steel plate substrate 1 having a predetermined chemical composition and a coating 2 containing Al and Fe (hereinafter referred to as Al - Fe-based coating).
In addition, a Cu-enriched region 3 having a Cu content equal to or higher than the Cu content of the steel plate base material is formed in the surface layer of the coating 2. As a result, a range from the surface of the coated steel member to a depth of 5.0 μm is formed. is 150% or more of the Cu content of the steel plate base material.
[0025]
(A1) Chemical composition of steel plate base material
The steel plate base material of the coated steel member according to this embodiment has a predetermined chemical composition. Specifically, in mass %, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo : 0.10-1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0.010%, Al: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Sb: 0-1.00%, Zr: 0-1 .00%, and REM: 0-0.30%, with the balance being Fe and impurities.
The reasons for limiting each element are as follows. Here, the chemical composition of the steel plate substrate refers to the portion of the coated steel member excluding the surface Al-Fe-based coating and the Cu-enriched region (for example, 1/4 of the thickness of the steel plate substrate from the surface of the steel plate substrate) position) shall refer to the chemical composition. Hereinafter, % regarding content is % by mass unless otherwise specified. In addition, the range shown between "-" includes the values ​​at both ends as the lower limit and the upper limit.
[0026]
C: 0.25-0.65%
C is an element that enhances the hardenability of steel and improves the strength of coated steel members after hardening such as hot stamping. However, if the C content is less than 0.25%, it becomes difficult to ensure sufficient strength (more than 1.5 GPa) in the coated steel member after quenching. Therefore, the C content should be 0.25% or more. The C content is preferably 0.28% or more.
On the other hand, if the C content exceeds 0.65%, the strength of the coated steel member after quenching becomes too high, and the limit hydrogen content drops significantly. Therefore, the C content should be 0.65% or less. The C content is preferably 0.60% or less.
[0027]
　Si: 0.10 to 1.00%
Si is an element that is effective in enhancing the hardenability of steel and stably ensuring the strength after hardening. In addition, Si is an element that has the effect of suppressing hot shortness due to Cu during steel sheet production and ensuring stable productivity. In order to obtain this effect, it is necessary to contain 0.10% or more of Si. The Si content is preferably 0.35% or more.
On the other hand, when the Si content in the steel exceeds 1.00%, the heating temperature required for austenite transformation during heat treatment becomes significantly high. As a result, the cost required for heat treatment may increase, and ferrite may remain at the time of hot stamping heating to reduce the strength of the coated steel member. Therefore, the Si content should be 1.00% or less. The Si content is preferably 0.60% or less.
[0028]
　Mn: 0.30 to 1.00%
　Mn is an element that lowers the limit hydrogen content of the coated steel member after quenching. In particular, when the Mn content exceeds 1.00%, the reduction in the limit amount of hydrogen becomes significant. Therefore, the Mn content is limited to 1.00% or less. It is preferable to limit the Mn content to 0.80% or less.
On the other hand, Mn is an element that is extremely effective in improving the hardenability of steel and stably ensuring the strength after hardening. Mn is also an element that lowers the Ac3 point and promotes lowering of the quenching treatment temperature. If the Mn content is less than 0.30%, these effects are not sufficient, so the Mn content is made 0.30% or more. The Mn content is preferably 0.40% or more.
[0029]
P: 0.050% or less
　P is an element that lowers the limit hydrogen content of the coated steel member after quenching. In particular, when the P content exceeds 0.050%, the reduction in the critical hydrogen content becomes significant. Therefore, the P content is limited to 0.050% or less. The P content is preferably limited to 0.005% or less. Since P is preferably as small as possible, it may be 0%, but from the viewpoint of cost, it may be 0.001% or more.
[0030]
S: 0.0100% or less
　S is an element that lowers the limit hydrogen content of the coated steel member after quenching. In particular, when the S content exceeds 0.0100%, the reduction in the limit amount of hydrogen becomes significant. Therefore, the S content is limited to 0.0100% or less. The S content is preferably limited to 0.0050% or less. Since the S content is preferably as small as possible, it may be 0%, but from the viewpoint of cost, it may be 0.0001% or more.
[0031]
N: 0.010% or less
　N is an element that lowers the limit hydrogen content of the coated steel member after quenching. In particular, when the N content exceeds 0.010%, coarse nitrides are formed in the steel and the limit hydrogen content is significantly lowered. Therefore, the N content should be 0.010% or less. The lower limit of the N content is not particularly limited and may be 0%. However, if the N content is less than 0.0002%, the steelmaking cost will increase, which is economically undesirable. Therefore, the N content may be 0.0002% or more, or 0.0008% or more.
[0032]
Ti: 0.010-0.100%
Ti suppresses recrystallization and forms fine carbides to suppress grain growth when the steel sheet is heated to a temperature of Ac 3 or higher and subjected to heat treatment, thereby making the austenite grains finer. It is an element that has Therefore, the inclusion of Ti has the effect of improving the limit amount of hydrogen in the coated steel member. In addition, Ti is an element that preferentially combines with N in steel to suppress the consumption of B due to the precipitation of BN, and promotes the effect of improving the hardenability due to B, which will be described later. If the Ti content is less than 0.010%, the above effects cannot be sufficiently obtained. Therefore, the Ti content should be 0.010% or more. Ti content is preferably 0.015% or more.
On the other hand, if the Ti content exceeds 0.100%, the amount of TiC precipitated increases and C is consumed, so the strength of the coated steel member after quenching decreases. Therefore, the Ti content should be 0.100% or less. Ti content is preferably 0.080% or less.
[0033]
B: 0.0005-0.0100%
B is an important element because even a very small amount has the effect of dramatically increasing the hardenability of steel. Further, B is an element that strengthens the grain boundary and improves the limit hydrogen amount by segregating at the grain boundary, and is an element that suppresses grain growth of austenite when the steel sheet is heated. If the B content is less than 0.0005%, the above effects may not be sufficiently obtained. Therefore, the B content should be 0.0005% or more. B content is preferably 0.0010% or more.
On the other hand, when the B content exceeds 0.0100%, a large amount of coarse compounds are precipitated and the limit hydrogen amount of the coated steel member is lowered. Therefore, the B content should be 0.0100% or less. B content is preferably 0.0080% or less.
[0034]
Nb: 0.02-0.10%
　Nb is fine coalIt is an important element because it forms carbides and has the effect of increasing the limit hydrogen content of steel due to its grain refining effect. If the Nb content is less than 0.02%, the above effects may not be sufficiently obtained. Therefore, the Nb content should be 0.02% or more. The Nb content is preferably 0.03% or more.
On the other hand, if the Nb content exceeds 0.10%, the carbides become coarse and the critical hydrogen content of the coated steel member decreases. Therefore, the Nb content should be 0.10% or less. The Nb content is preferably 0.08% or less.

The scope of the claims
[Claim 1]
in % by mass,
　　C: 0.25 to 0.65%,
　　Si: 0.10 to 1.00%,
　Mn: 0.30 to 1.00%,
P: 0.050% or less,
S: 0.0100% or less,
　　N: 0.010% or less,
　Ti: 0.010 to 0.100%,
B: 0.0005 to 0.0100%,
Nb: 0.02 to 0.10%,
Mo: 0.10-1.00%,
　Cu: 0.15 to 1.00%,
Ni: 0.05 to 0.25%,
Cr: 0 to 1.00%,
　　V: 0 to 1.00%,
　　Ca: 0 to 0.010%,
Al: 0 to 1.00%,
Sn: 0 to 1.00%,
W: 0-1.00%,
Sb: 0 to 1.00%,
　　Zr: 0 to 1.00%, and
REM: 0-0.30%
A steel plate base material having a chemical composition containing and the balance being Fe and impurities;
a coating formed on the surface of the steel plate base material and containing Al and Fe;
has
　The maximum Cu content in the range from the surface to a depth of 5.0 μm is 150% or more with respect to the Cu content of the steel plate base material
A coated steel member characterized by:
[Claim 2]
in % by mass,
　　C: 0.25 to 0.65%,
　　Si: 0.10 to 1.00%,
　Mn: 0.30 to 1.00%,
P: 0.050% or less,
S: 0.0100% or less,
　　N: 0.010% or less,
　Ti: 0.010 to 0.100%,
B: 0.0005 to 0.0100%,
Nb: 0.02 to 0.10%,
Mo: 0.10-1.00%,
　Cu: 0.15 to 1.00%,
Ni: 0.05 to 0.25%,
Cr: 0 to 1.00%,
　　V: 0 to 1.00%,
　　Ca: 0 to 0.010%,
Al: 0 to 1.00%,
Sn: 0 to 1.00%,
W: 0-1.00%,
Sb: 0 to 1.00%,
　　Zr: 0 to 1.00%, and
REM: 0-0.30%
and a steel sheet having a chemical composition in which the balance is Fe and impurities;
A coating containing Al on the surface of the steel plate,
a boundary formed between the steel plate and the coating;
has
　The maximum Cu content at the boundary is 80% or more of the average Cu content of the steel sheet
A coated steel plate characterized by:
[Claim 3]
% by mass, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100 % or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo: 0.10- 1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0 .010%, Al: 0 to 1.00%, Sn: 0 to 1.00%, W: 0 to 1.00%, Sb: 0 to 1.00%, Zr: 0 to 1.00%, and A slab preparation step of melting a steel having a chemical composition containing REM: 0 to 0.30% and the balance being Fe and impurities, and casting the steel to obtain a slab;
A hot-rolling process in which the slab is hot-rolled into a hot-rolled steel sheet,
A winding process for winding the hot-rolled steel sheet,
A hot-rolled sheet annealing step of annealing the hot-rolled steel sheet as necessary,
If necessary, the hot-rolled steel sheet is subjected to descaling and cold-rolled into a cold-rolled steel sheet;
An annealing step in which the hot-rolled steel sheet or the cold-rolled steel sheet is annealed to obtain an annealed steel sheet as necessary,
The hot-rolled steel sheet, the cold-rolled steel sheet, or the annealed steel sheet is immersed in an Al-based plating bath having a bath temperature of 600 ° C. or higher to form an Al-based coating, and then to 200 ° C. or lower at a rate of less than 30 ° C./sec. A coating step of cooling at an average cooling rate;
A method for producing a coated steel sheet, comprising:
[Claim 4]
Furthermore, a post heat treatment step of annealing the coated steel plate obtained by the coating step in a temperature range of 450 to 800 ° C,
The method for producing a coated steel sheet according to claim 3, characterized in that:
[Claim 5]
% by mass, C: 0.25 to 0.65%, Si: 0.10 to 1.00%, Mn: 0.30 to 1.00%, P: 0.050% or less, S: 0.0100 % or less, N: 0.010% or less, Ti: 0.010-0.100%, B: 0.0005-0.0100%, Nb: 0.02-0.10%, Mo: 0.10- 1.00%, Cu: 0.15-1.00%, Ni: 0.05-0.25%, Cr: 0-1.00%, V: 0-1.00%, Ca: 0-0 .010%, Al: 0 to 1.00%, Sn: 0 to 1.00%, W: 0 to 1.00%, Sb: 0 to 1.00%, Zr: 0 to 1.00%, and A slab preparation step of melting a steel having a chemical composition containing REM: 0 to 0.30% and the balance being Fe and impurities, and casting the steel to obtain a slab;
A hot-rolling process in which the slab is hot-rolled into a hot-rolled steel sheet,
A winding process for winding the hot-rolled steel sheet,
A hot-rolled sheet annealing step of annealing the hot-rolled steel sheet as necessary,
If necessary, the hot-rolled steel sheet is subjected to descaling and cold-rolled into a cold-rolled steel sheet;
An annealing step in which the hot-rolled steel sheet or the cold-rolled steel sheet is annealed to obtain an annealed steel sheet as necessary,
The hot-rolled steel sheet, the cold-rolled steel sheet, or the annealed steel sheet is immersed in an Al-based plating bath having a bath temperature of 600 ° C. or higher to form an Al-based coating, and then to 200 ° C. or lower at a rate of less than 30 ° C./sec. A coating step of cooling at an average cooling rate to form a coated steel sheet;
The coated steel sheet is heated from Ac3 point to (Ac3 point + 300) ° C. at a temperature increase rate of 1.0 to 100 ° C./sec in an atmosphere with a dew point of 30 ° C. or less, and then upper critical cooling to Ms point or less. a heat treatment step of cooling at a speed or higher;
A method for manufacturing a coated steel member, comprising:
[Claim 6]
After the coating step, a post heat treatment step of annealing the coated steel plate in a temperature range of 450 to 800 ° C is further provided,
The manufacturing method of the coated steel member according to claim 5, characterized by: