[Technical Field]
5 [0001]
The present invention relates to a hot stamping member. Priority is claimed on
Japanese Patent Application No. 2020-084583, filed May 13, 2020, the content of which
is incorporated herein by reference.
[Background Art]
10 [0002]
In recent years, there has been a demand for the weight reduction of automotive
vehicle bodies from the viewpoint of environmental protection and resource saving, and
the application of high strength steel sheets to automotive members has been
accelerating. Automotive members are manufactured by press forming, and an increase
15 in the strength of steel sheets does not only increase forming loads but also degrades
formability, which creates a problem with the formability of high strength steel sheets
into members with a complicated shape. In order to solve such a problem, the
application of hot stamping techniques, in which a steel sheet is heated to a high
temperature in an austenite region where the steel sheet softens and then formed by
20 pressing, is underway. Hot stamping is drawing attention as a technique in which a
quenching treatment is carried out in a die at the same time as pressing, thereby
satisfying both formability into automotive members and the securement of the strength
of automotive members.
[0003]
25 In a case where hot stamping is carried out on a steel sheet that is a bare material
1
on which plating or the like has not been carried out, there is a need to carry out hot
stamping in a non-oxidative atmosphere in order to suppress the formation of scale
during heating and the decarburization of the surface layer. However, even when hot
stamping is carried out in a non-oxidative atmosphere, the steel sheet is in the
5 atmospheric atmosphere when the steel sheet is conveyed from a heating furnace to a
pressing machine, thus, a scale is formed on the surface of the hot-stamped steel sheet.
The scale on the surface of the steel sheet is poorly adhesive and easily exfoliates, which
creates a concern of an adverse influence on other steps. Therefore, there is a need to
remove the scale by shot blasting or the like. Shot blasting has a problem of affecting
10 the shapes of steel sheets. In addition, there is a problem in that the productivity of a
hot stamping step deteriorates due to a scale removal step.
[0004]
In order to improve the adhesion of scale on the surface of a steel sheet, there is
a method in which Al plating or Zn plating is formed on the surface of the steel sheet.
15 When Al plating or Zn plating is formed, since scale that is formed on the surface of a
steel by hot stamping has favorable adhesion, a step of removing scale becomes
unnecessary. Therefore, the productivity of the hot stamping step is improved.
[0005]
In a case where Al plating is provided on a steel sheet, a reaction is caused
20 between Aland water on the surface of the Al plating during hot stamping, and hydrogen
is generated. Therefore, there is a problem in that the amount of intruding hydrogen
into the steel sheet is large. When the amount of hydrogen intruding into the steel sheet
is large, stress that is loaded after hot stamping leads to cracking of the steel sheet
(hydrogen embrittlement).
25 [0006]
2
5
In order to reduce the amount of intruding hydrogen in a steel sheet provided
with Al plating, for example, Patent Document 1 discloses a technique for enriching the
surface region of a steel sheet with nickel.
[0007]
In addition, Patent Document 2 discloses a technique for coating a steel sheet
with a barrier pre-coat containing nickel and chromium and having a weight ratio Ni/Cr
of 1.5 to 9.
[Citation List]
[Patent Document]
10 [0008]
[Patent Document 1]
PCT International Publication No. WO 2016/016707
[Patent Document 2]
PCT International Publication No. WO 20171187255
15 [Patent Document 3]
Japanese Unexamined Patent Application, First Publication No. H11-269664
[Patent Document 4]
Japanese Unexamined Patent Application, First Publication No. H4-246182
[Summary of the Invention]
20 [Problems to be Solved by the Invention]
[0009]
However, in a case where a hot stamping member is produced by the hot
stamping of the steel sheet described in Patent Document 1 or Patent Document 2, since
there is a potential difference between Al and Ni on the surface of the hot stamping
25 member, there is a problem in that corrosion of the hot stamping member proceeds.
3
[0010]
The present invention has been made in consideration of the above-described
problem, and an objective of the present invention is to provide a hot stamping member
having excellent corrosion resistance even when having a plating layer containing Ni and
5 Al on the surface of the hot stamping member.
[Means for Solving the Problem]
[0011]
As a result of intensive studies, the present inventors found that, when a Ni layer
is provided on the surface of an Al plating layer, and a heat treatment during hot
10 stamping is controlled, it is possible to suppress the diffusion of Fe into the outermost
surface of a hot stamping member and to suppress the corrosion of the hot stamping
member. In addition, similarly, it was found that, when the heat treatment during hot
stamping is controlled to appropriate! y alloy Al and Ni, it is possible to suppress
corrosion attributed to the potential difference between Al and Ni.
15 [0012]
The present invention has been made by further progressing studies based on the
above-described finding, and the gist thereof is as described below.
(1) A hot stamping member according to one aspect of the present invention is
a hot stamping member including a base material and a plating layer provided on
20 the base material, in which the plating layer has
aNi-rich region where aNi content is 50 mass% or more,
anAl-rich region where aNi content is less than 50 mass%, anAl content is 10
mass% or more and an Fe content is 50 mass% or less, and
an Fe-rich region where anAl content is 10 mass% or more and an Fe content is
25 more than 50 mass% in this order from a surface of the plating layer,
4
5
10
15
20
25
in a region from the surface of the plating layer to a 100 nm position in a
thickness direction from the surface of the plating layer,
a maximum value of a Ni content is 50 mass% or more, and
an Fe content is 10 mass% or less,
in a region from the 100 nm position in the thickness direction from the surface
of the plating layer to a 500 nm position in the thickness direction from the surface of the
plating layer,
a maximum value of a Ni content is 5 mass% or more, and
an Fe content is 25 mass% or less, and
in a region from the 500 nm position in the thickness direction from the surface
of the plating layer to a 1000 nm position in the thickness direction from the surface of
the plating layer,
a maximum value of a Ni content is 1 mass% or more, and
an Fe content is 30 mass% or less.
(2) The hot stamping member according to (1 ),
in which, in a region from the surface of the plating layer to a 20 nm position in
the thickness direction from the surface of the plating layer,
at least one of a Ni oxide and a Ni hydroxide may be present, and
aNi content may be 30 mass% or more.
(3) The hot stamping member according to (1) or (2),
in which the chemical composition of the base material may be, by mass%,
C: 0.01% or more and less than 0.70%,
Si: 0.005% to 1.000%,
Mn: 0.15% to 3.00%,
sol. Al: 0.00020% to 0.50000%,
5
5
10
15
20
25
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%,
Nb: 0% to 0.150%,
V: 0% to 1.000%,
Ti: 0% to 0.150%,
Mo: 0% to 1.000%,
Cr: 0% to 1.000%,
B: 0% to 0.0100%,
Ca: 0% to 0.010%,
REM: 0% to 0.300%, and
a remainder: Fe and an impurity,
( 4) The hot stamping member according to (3 ),
in which the chemical composition of the base material may contain, by mass%,
one or two or more selected from the group consisting of:
Cu: 0.005% to 1.00%,
Ni: 0.005% to 1.00%,
Nb: 0.010% to 0.150%,
V: 0.005% to 1.000%,
Ti: 0.010% to 0.150%,
Mo: 0.005% to 1.000%,
Cr: 0.050% to 1.000%,
B: 0.0005% to 0.0100%,
6
5
10
Ca: 0.001% to 0.010%, and
REM: 0.001% to 0.300% or less.
[Effects of the Invention]
[0013]
According to the above-described aspect of the present invention, it is possible
to provide a hot stamping member having excellent corrosion resistance even when
having a plating layer containing Ni and Al on the surface of the hot stamping member.
[Brief Description of Drawings]
[0014]
Fig. 1 is a profile in a depth direction of a plating layer according to an
embodiment of the present invention.
Fig. 2 is a profile from a surface of the plating layer according to the
embodiment of the present invention to a 1000 nm position of the plating layer.
[Embodiment(s) for implementing the Invention]
15 [0015]

As a result of intensive studies, the present inventors found that, in order to
obtain excellent corrosion resistance, it is important to control the distributions of Al, Ni
and Fe in the depth direction in a plating layer of a hot stamping member by producing
20 anAl-plated steel sheet including aNi plating layer on the surface of anAl plating layer
and, furthermore, appropriately carrying out a heat treatment during hot stamping.
25
[0016]
As a result of additional intensive studies, the present inventors obtained the
following findings.
(A) When a hot stamping member includes a plating layer, and the plating layer
7
includes aNi-rich region where the Ni content is 50 mass% or more, anAl-rich region
where the Ni content is less than 50 mass%, the Al content is 10 mass% or more and the
Fe content is 50 mass% or less and an Fe-rich region where the Al content is 10 mass%
or more and the Fe content is more than 50 mass%, it is possible to suppress the
5 corrosion of the hot stamping member.
10
15
(B) When the maximum value of the Ni content is set to 50 mass% or more and
the Fe content is set to 10 mass% or less in a region from the surface of the plating layer
to a 100 nm position in the thickness direction from the surface of the plating layer, it is
possible to suppress the corrosion of the hot stamping member.
(C) When the maximum value of the Ni content is set to 5 mass% or more and
the Fe content is set to 25 mass% or less in a region from the 100 nm position in the
thickness direction from the surface of the plating layer to a 500 nm position in the
thickness direction from the surface of the plating layer, it is possible to suppress the
corrosion of the hot stamping member.
(D) When the maximum value of the Ni content is set to 1 mass% or more and
the Fe content is set to 30 mass% or less in a region from the 500 nm position in the
thickness direction from the surface of the plating layer to a 1000 nm position in the
thickness direction from the surface of the plating layer, it is possible to suppress the
corrosion of the hot stamping member.
20 [0017]
In a hot stamping member according to the present embodiment, the
configuration of the hot stamping member was determined based on the above-described
findings. In the hot stamping member according to the present embodiment, an
intended effect of the present invention can be obtained due to the synergistic effects of
25 the above-mentioned configurations. The hot stamping member according to the
8
present embodiment includes a base material and a plating layer provided on the base
material. As techniques for providing Ni plating on Al plating, there was a technique by
which Ni plating is provided on Al plating in order to suppress the wear of an electrode at
the time of resistance welding as in Patent Documents 3 and 4. However, in a hot
5 stamping member obtained by hot -stamping a steel sheet provided with Al plating, an Al
oxide coating is formed on the surface of the Al plating on the surface. Therefore, when
anAl-plated steel sheet is hot-stamped, Al erodes (diffuses) toward a welding electrode
(usually, a Cu-Cr alloy is used), and there is no case where a Cu-Al-Fe-based
intermetallic compound is formed at the tip end portion of the welding electrode. Even
10 when resistance welding is carried out on a hot stamping member obtained by hotstamping
anAl-plated steel sheet, the welding electrode is hardly consumed. Therefore,
there has been no motivation for using an expensive steel sheet having Ni plating
provided on Al plating in hot stamping using Patent Documents 3 and 4. Therefore,
there have been no hot stamping members that can be manufactured by hot-stamping a
15 steel sheet having Ni plating provided on Al plating. In the present specification,
numerical ranges expressed using "to" include numerical values before and after "to" as
the lower limit value and the upper limit value. Numerical values expressed with "more
than" and "less than" are not included in numerical ranges. Regarding chemical
compositions, "%" indicates "mass%" in all cases.
20 [0018]
(Plating layer)
The structure of the plating layer of the hot stamping member according to the
present embodiment will be described using Fig. 1. Fig. 1 is a depth profile of the
plating layer of the hot stamping member. The vertical axis of Fig. 1 indicates the
25 content (mass%) of each element, and the horizontal axis indicates the depth from the
9
outermost surface of the hot stamping member (outermost surface: 0 ~m). In the depth
profile, Fe contents where contents of 5% or more are detected, Al contents, Ni contents,
Si contents and 0 contents are shown in Fig. 1. In this example, the Ni content
decreases up to approximately 10 mass% at a depth of near 0.1 ~m, and furthermore, the
5 Ni content increases as the depth increases. The reason therefor is not clear, but the
following reasons are conceivable. Since a dense Ni oxide coating is formed near the
surface of the hot stamping member, and Al is not diffused into the Ni oxide coating, the
surface becomes a high-concentration Ni region. Incidentally, anAl oxide is formed in
the following region of the Ni oxide coating, and oxygen increases, whereby a decrease
10 in the Ni content is noticeable when detected elements are expressed as percentages.
15
Since Al reacts with oxygen more easily than Ni, it is considered that Al diffuses into the
surface, consequently, the Ni content decreases up to approximately 10 mass% at a depth
of near 0.1 ~m, and furthermore, the Ni content increases as the depth increases.
[0019]
The Ni-rich region where the Ni content of the plating layer of the hot stamping
member reaches 50 mass% or more is a region A in Fig. 1. The Al-rich region where
the Ni content is less than 50 mass%, the Al content is 10 mass% or more and the Fe
content is 50 mass% or less is a region B in Fig. 1. The Fe-rich region where the Al
content is 10 mass% or more and the Fe content is more than 50 mass% is a region C in
20 Fig. 1. When the Ni-rich region where the Ni content reaches 50 mass% or more is
present on the outermost surface of the hot stamping member, and the Ni-rich region, the
Al-rich region and the Fe-rich region are present in the plating layer in this order, it is
possible to suppress the corrosion of the hot stamping member. The thickness of the
plating layer of the hot stamping member is calculated from the total of the thicknesses of
25 individual regions of the Ni-rich region, the Al-rich region and the Fe-rich region.
10
[0020]
Next, the structure of the hot stamping member according to the present
embodiment from the surface of the plating layer to a 1000 nm position in the thickness
direction from the surface of the plating layer will be described using Fig. 2. The
5 vertical axis of Fig. 2 indicates the content (mass%) of each element, and the horizontal
axis indicates the depth from the outermost surface of the hot stamping member
(outermost surface: 0 ~m). In the depth profile, Fe contents, Al contents, Ni contents, Si
contents and 0 contents where contents of 5% or more are detected are shown in Fig. 2.
10
[0021]
A region from the surface of the plating layer to the 100 nm position in the
thickness direction from the surface of the plating layer of the hot stamping member
according to the present embodiment is a region D in Fig. 2. A region from the 100 nm
position in the thickness direction from the surface of the plating layer to a 500 nm
position in the thickness direction from the surface of the plating layer of the hot
15 stamping member is a region E in Fig. 2. A region from the 500 nm position in the
20
thickness direction from the surface of the plating layer to a 1000 nm position in the
thickness direction from the surface of the plating layer is a region Fin Fig. 2.
Hereinafter, each region will be described.
[0022]
"Region from surface of plating layer to 100 nm position in thickness direction
from surface of plating layer"
In the region from the surface of the plating layer of the hot stamping member to
the 100 nm position in the thickness direction from the surface of the plating layer of the
hot stamping member, the maximum value of the Ni content is 50 mass% or more and
25 the Fe content is 10 mass% or less. In the region from the surface of the plating layer to
11
the 100 nm position in the thickness direction from the surface of the plating layer, the Al
content may be set to 1 mass% or more.
[0023]
In a case where the maximum value of the Ni content is less than 50 mass% in
5 the region from the surface of the plating layer of the hot stamping member to the 100
nm position in the thickness direction from the surface of the plating layer of the hot
stamping member, the Al content or the Fe content in the outermost surface of the hot
stamping member becomes excessively large, and the corrosion resistance of the hot
stamping member deteriorates. Therefore, the maximum value of the Ni content is 50
10 mass% or more. A more preferable maximum value of the Ni content is 70 mass% or
more. The Ni content may be set to 90 mass% or less.
[0024]
In a case where the Fe content is more than 10 mass% in the region from the
surface of the plating layer of the hot stamping member to the 100 nm position in the
15 thickness direction from the surface of the plating layer of the hot stamping member, Fe
that causes the corrosion of the hot stamping member is excessively present on the
outermost surface of the hot stamping member, and the red rust resistance of the hot
stamping member deteriorates. Therefore, the Fe content is 10 mass% or less. A more
preferable Fe content is 5 mass% or less.
20 [0025]
In a case where the maximum value of the Al content is less than 1 mass% in the
region from the surface of the plating layer of the hot stamping member to the 100 nm
position in the thickness direction from the surface of the plating layer of the hot
stamping member, there is a case where an intermetallic compound of Ni and Al, which
25 improves the white rust resistance of the hot stamping member, is not formed.
12
Therefore, the maximum value of the Al content is preferably set to 1 mass% or more.
A more preferable maximum value of the Al content is 5 mass% or more. The Al
content may be 80 mass% or less. In the region from the surface of the plating layer to
the 100 nm position in the thickness direction from the surface of the plating layer, the Cr
5 content may be set to 6 mass% or less, 4 mass% or less, 2 mass% or less or 1 mass% or
less, and the ratio (Ni/Cr) of the Ni content (mass%) to the Cr content (mass%) may be
10 or more, 15 or more, 30 or more or 50 or more.

[CLAIMS]
1. A hot stamping member comprising:
a base material; and
a plating layer provided on the base material,
wherein the plating layer has
aNi-rich region where aNi content is 50 mass% or more,
anAl-rich region where aNi content is less than 50 mass%, anAl content is 10
mass% or more and an Fe content is 50 mass% or less, and
an Fe-rich region where anAl content is 10 mass% or more and an Fe content is
10 more than 50 mass% in this order from a surface of the plating layer,
15
20
25
in a region from the surface of the plating layer to a 100 nm position in a
thickness direction from the surface of the plating layer,
a maximum value of aNi content is 50 mass% or more, and
an Fe content is 10 mass% or less,
in a region from the 100 nm position in the thickness direction from the surface
of the plating layer to a 500 nm position in the thickness direction from the surface of the
plating layer,
a maximum value of aNi content is 5 mass% or more, and
an Fe content is 25 mass% or less, and
in a region from the 500 nm position in the thickness direction from the surface
of the plating layer to a 1000 nm position in the thickness direction from the surface of
the plating layer,
a maximum value of aNi content is 1 mass% or more, and
an Fe content is 30 mass% or less.
71
2. The hot stamping member according to claim 1,
wherein, in a region from the surface of the plating layer to a 20 nm position in
the thickness direction from the surface of the plating layer,
at least one of a Ni oxide and a Ni hydroxide is present, and a Ni content is 30
5 mass% or more.
10
15
20
25
3. The hot stamping member according to claim 1 or 2,
wherein the chemical composition of the base material is, by mass%,
C: 0.01% or more and less than 0.70%;
Si: 0.005% to 1.000%;
Mn: 0.15% to 3.00%;
sol. Al: 0.00020% to 0.50000%;
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%;
Nb: 0% to 0.150%;
V: 0% to 1.000%;
Ti: 0% to 0.150%;
Mo: 0% to 1.000%;
Cr: 0% to 1.000%;
B: 0% to 0.0100%;
Ca: 0% to 0.010%;
REM: 0% to 0.300%; and
72
a remainder: Fe and an impurity.
4. The hot stamping member according to claim 3,
wherein the chemical composition of the base material contains, by mass%, one
5 or two or more selected from the group consisting of:
10
15
Cu: 0.005% to 1.00%;
Ni: 0.005% to 1.00%;
Nb: 0.010% to 0.150%;
V: 0.005% to 1.000%;
Ti: 0.010% to 0.150%;
Mo: 0.005% to 1.000%;
Cr: 0.050% to 1.000%;
B: 0.0005% to 0.0100%;
Ca: 0.001% to 0.010%; and
REM: 0.001% to 0.300% or less.
73
[Abstract]
This hot stamping member is a hot stamping member including a base material
and a plating layer provided on the base material, in which the plating layer has aNi-rich
region, anAl-rich region and an Fe-rich region in this order from a surface of the plating
5 layer, in a region from the surface of the plating layer to a 100 nm position in the
thickness direction from the surface of the plating layer, Ni and Fe satisfy predetermined
contents, in a region from the 100 nm position in the thickness direction from the surface
of the plating layer to a 500 nm position in the thickness direction from the surface of the
plating layer, Ni and Fe satisfy predetermined contents, and, in a region from the 500 nm
10 position in the thickness direction from the surface of the plating layer to a 1000 nm
position in the thickness direction from the surface of the plating layer, Ni and Fe satisfy
predetermined contents.