FIELD
[0001]
The present invention relates to a hot stamped body.
10 BACKGROUND
[0002]
As a technique for press-forming a material which is difficult to shape, such as high
strength steel sheet, hot stamping (hot pressing) is known. Hot stamping is a hot shaping
technique which shapes a material supplied for shaping after heating it. In this technique, the
15 material is shaped after heating, therefore at the time of shaping, the steel material is soft and has
good shapeability. Therefore, even a high strength steel material can be precisely formed into a
complicated shape. Further, the press die simultaneously performs the shaping and hardening,
therefore it is known that after shaping, the steel material has sufficient strength.
[0003]
20 PTL 1 describes a plated steel sheet for hot pressing characterized by having an Al-Znbased
alloy plating layer containing Al: 20 to 95 mass%, Ca+Mg: 0.01 to 10 mass%, and Si on
the steel sheet surface. Further, PTL 1 describes that such a plated steel sheet can prevent the
plating from adhering to the die at the time of hot pressing, since oxides of Ca or Mg are formed
on the surface of the Al-Zn-based alloy plating layer.
25 [0004]
In relation to an Al-Zn-based alloy plating, PTL 2 describes an alloy plated steel material
characterized by containing, by mass%, Al: 2 to 75%, Fe: 2 to 75%, and a balance of 2% or more
of Zn and unavoidable impurities in the plating layer. Further, PTL 2 teaches that, from the
viewpoint of improvement of the corrosion resistance, it is effective to further include Mg: 0.02
30 to 10%, Ca: 0.01 to 2%, Si: 0.02 to 3%, etc., in the plating layer.
[0005]
Further, in relation to an Al-Zn-based alloy plating, PTL 3 describes a Zn-based plated steel
material for hot pressing having at a surface-most layer an oxide layer mainly comprising Zn and
containing Mn in 1% or more in mass%, having underneath that a plating layer comprising a Zn35
based alloy, and containing in the Zn-based plating layer one or more of Ni: 0.01 to 20%, Cr:
0.01 to 10%, Mn: 0.01 to 10%, Mo: 0.01 to 5%, Co: 0.01 to 5%, Al: 0.01 to 60%, Si: 0.01 to 5%,
2
Mg: 0.01 to 10%, Ca: 0.01 to 5%, and Sn: 0.01 to 10%.
[0006]
Further, PTL 4 describes a plated steel material comprising a steel material and a plating
layer arranged on the surface of the steel material and containing a Zn-Al-Mg alloy layer,
wherein the Zn-Al-Mg alloy layer has a Zn phase, the Zn phase 5 contains an Mg-Sn intermetallic
compound phase, and the plating layer contains, by mass%, Zn: more than 65.0%, Al: more than
5.0% to less than 25%, Mg: more than 3.0% to less than 12.5%, Ca: 0% to 3.00%, Si: 0% to less
than 2.5%, etc.
[0007]
10 Similarly, PTL 5 describes a plated steel material comprising a steel material and a plating
layer arranged on a surface of the steel material and containing a Zn-Al-Mg alloy layer, wherein,
in a cross-section of the Zn-Al-Mg alloy layer, an area ratio of an MgZn2 phase is 45 to 75%, an
area ratio of a total of the MgZn2 phase and Al phase is 70% or more, an area ratio of a Zn-Al-
MgZn2 ternary eutectic structure is 0 to 5%, and the plating layer contains, by mass%, Zn: more
15 than 44.90% to less than 79.90%, Al: more than 15% to less than 35%, Mg: more than 5% to less
than 20%, Ca: 0.1% to less than 3.0%, Si: 0% to 1.0%, etc.
[CITATIONS LIST]
[PATENT LITERATURE]
20 [0008]
[PTL 1] Japanese Unexamined Patent Publication No. 2012-112010
[PTL 2] Japanese Unexamined Patent Publication No. 2009-120948
[PTL 3] WO 2005-113233
[PTL 4] WO 2018/139619
25 [PTL 5] WO 2018/139620
SUMMARY
[TECHNICAL PROBLEM]
[0009]
30 If, for example, using a Zn-based plated steel material in hot stamping, the material is
worked in a state where the Zn is molten, therefore the molten Zn will sometimes penetrate into
the steel and cause cracking inside the steel material. Such a phenomenon is called “liquid metal
embrittlement (LME)”. It is known that the fatigue characteristics of a steel material fall due to
the LME.
35 [0010]
On the other hand, if using a plated steel material containing Al as a constituent of the
3
plating layer in hot stamping, it is known that, for example, the hydrogen generated at the time of
heating in the hot stamping will sometimes penetrate the steel material and cause hydrogen
embrittlement cracking.
[0011]
However, in conventional Al-Zn-based plated steel materials 5 used in hot stamping, there
has not necessarily been sufficient study from the viewpoint of suppressing LME and hydrogen
embrittlement cracking. As a result, in a hot stamped body obtained from such a plated steel
material, there was still room for improvement relating to the LME resistance and hydrogen
penetration resistance.
10 [0012]
Therefore, an object of the present invention is to provide a hot stamped body improved in
the LME resistance and hydrogen penetration resistance and, further, excellent in the corrosion
resistance.
15 [SOLUTION TO PROBLEM]
[0013]
The present invention to achieve the above object is as follows:
(1) A hot stamped body comprising a steel base material and a plating layer formed on a
surface of the steel base material, wherein the plating layer has a chemical composition
20 comprising, by mass%,
Al: 15.00 to 45.00%,
Mg: 5.50 to 12.00%,
Si: 0.05 to 3.00%,
Ca: 0.05 to 3.00%,
25 Fe: 20.00 to 50.00%,
Sb: 0 to 0.50%,
Pb: 0 to 0.50%,
Cu: 0 to 1.00%,
Sn: 0 to 1.00%,
30 Ti: 0 to 1.00%,
Sr: 0 to 0.50%,
Cr: 0 to 1.00%,
Ni: 0 to 1.00%,
Mn: 0 to 1.00%, and
35 balance: Zn and impurities,
the plating layer comprises an interfacial layer positioned at an interface with the steel base
4
material and containing Fe and Al and a main layer positioned on the interfacial layer,
the main layer comprises, by area ratio, 10.0 to 70.0% of an Mg-Zn containing phase and
30.0 to 90.0% of an Fe-Al containing phase,
the Mg-Zn containing phase comprises at least one selected from the group consisting of an
5 MgZn phase, Mg2 Zn3 phase, and MgZn2 phase, and
the Fe-Al containing phase comprises an FeAl phase and Fe-Al-Zn phase and an area ratio
of the Fe-Al-Zn phase in the main layer is more than 10.0 to 75.0%.
(2) The hot stamped body according to the above (1), wherein the chemical composition
of the plating layer comprises, by mass%,
10 Al: 25.00 to 35.00% and
Mg: 6.00 to 10.00%.
(3) The hot stamped body according to the above (1) or (2), wherein the Mg-Zn containing
phase comprises an MgZn phase, and an area ratio of the MgZn phase in the main layer is 5.0%
or more.
15 (4) The hot stamped body according to any one of the above (1) to (3), wherein the Mg-Zn
containing phase comprises an MgZn phase and Mg2 Zn3 phase, and an area ratio of a total of
the MgZn phase and Mg2 Zn3 phase in the main layer is 25.0 to 50.0%.
(5) The hot stamped body according to any one of the above (1) to (4), wherein an area
ratio of the FeAl phase in the main layer is 5.0 to 25.0%.
20
[ADVANTAGEOUS EFFECTS OF INVENTION]
[0014]
According to the present invention, it is possible to provide a hot stamped body improved in
the LME resistance and hydrogen penetration resistance and, further, excellent in the corrosion
25 resistance.
BRIEF DESCRIPTION OF DRAWINGS
[0015]
FIG. 1 shows a backscattered electron image (BSE image) of a scanning electron
30 microscope (SEM) of a plating layer cross-section in a conventional hot stamped body including
an Al-Zn-Mg-based plating layer.
FIG. 2 shows a backscattered electron image (BSE image) of a scanning electron
microscope (SEM) of a plating layer cross-section in a hot stamped body according to the
present invention (Example 13).
35 FIG. 3 shows a backscattered electron image (BSE image) of a scanning electron
microscope (SEM) of a plating layer surface before hot stamping in a hot stamped body
5
according to the present invention.
FIG. 4 is a graph showing a relationship between a point of change of a cooling speed when
cooling a plating layer and formation of an acicular Al-Zn-Si-Ca phase.
5 DESCRIPTION OF EMBODIMENTS
[0016]

The hot stamped body according to an embodiment of the present invention comprises a
steel base material and a plating layer formed on a surface of the steel base material, wherein the
10 plating layer has a chemical composition comprising, by mass%,
Al: 15.00 to 45.00%,
Mg: 5.50 to 12.00%,
Si: 0.05 to 3.00%,
Ca: 0.05 to 3.00%,
15 Fe: 20.00 to 50.00%,
Sb: 0 to 0.50%,
Pb: 0 to 0.50%,
Cu: 0 to 1.00%,
Sn: 0 to 1.00%,
20 Ti: 0 to 1.00%,
Sr: 0 to 0.50%,
Cr: 0 to 1.00%,
Ni: 0 to 1.00%,
Mn: 0 to 1.00%, and
25 balance: Zn and impurities,
the plating layer comprises an interfacial layer positioned at an interface with the steel base
material and containing Fe and Al and a main layer positioned on the interfacial layer,
the main layer comprises, by area ratio, 10.0 to 70.0% of an Mg-Zn containing phase and
30.0 to 90.0% of an Fe-Al containing phase,
30 the Mg-Zn containing phase comprises at least one selected from the group consisting of an
MgZn phase, Mg2 Zn3 phase, and MgZn2 phase, and
the Fe-Al containing phase comprises an FeAl phase and Fe-Al-Zn phase and an area ratio
of the Fe-Al-Zn phase in the main layer is more than 10.0 to 75.0%.
[0017]
35 For example, if using a conventional Zn-based plated steel material or an Al-Zn-based
plated steel material for hot stamping, in general the plated steel material will be heated in the
6
hot stamping to about 900°C or a higher temperature than that. Zn has a boiling point of about
907°C, which is relatively low, therefore at such a high temperature, the Zn in the plating layer
will evaporate or melt, resulting in the partial formation of a high concentration Zn liquid phase
in the plating layer and the penetration of the liquid Zn into the crystal grain boundaries in the
steel in some cases causing liquid meta 5 l embrittlement (LME) cracking.
[0018]
On the other hand, in a conventional Al plated steel material not containing Zn, LME
cracking due to Zn will not occur, but at the time of heating in the hot stamping, the water vapor
in the atmosphere will sometimes be reduced by the Al in the plating layer, resulting in the
10 generation of hydrogen. As a result, the generated hydrogen will sometimes penetrate the steel
material and cause hydrogen embrittlement cracking. Further, in an Al-Zn-based plated steel
material as well, since Zn has a relatively low boiling point as explained above, at the time of hot
stamping at a 900°C or higher temperature, a part of the Zn will evaporate and sometimes will
react with the water vapor in the atmosphere and cause the generation of hydrogen. In such a
15 case, hydrogen embrittlement cracking is liable to occur due to hydrogen penetrating the steel
material due to not only the Al, but also the Zn. In addition, from the viewpoint of improvement
of the corrosion resistance, regarding the Mg and other elements which are added to the Znbased
plated steel material or Al-Zn-based plated steel material, sometime parts thereof will
evaporate at the time of heating in hot stamping at a high temperature and, in the same way as
20 the case of Zn, cause production of hydrogen triggering hydrogen embrittlement cracking.
[0019]
Further, if the elements Zn and/or Mg having the effect of improving the corrosion
resistance evaporate at the time of hot stamping at a high temperature and parts of those elements
are lost, naturally a problem will arise in that it is not possible to maintain sufficient corrosion
25 resistance in the body after hot stamping. Furthermore, if the Zn and/or Mg in the plating layer
evaporate and are lost, in the plating layer after the hot stamping, relatively large amounts of Al-
Fe-based intermetallic compounds and/or Zn-Fe-based intermetallic compounds will be formed
between the Fe which had been diffused from the base iron and the Al and/or Zn in the plating
layer. These intermetallic compounds become causes of red rust in corrosive environments.
30 [0020]
Therefore, the inventors studied the corrosion resistance, LME resistance, and hydrogen
penetration resistance in hot stamped bodies which include Al-Zn-Mg-based plating layers. As a
result, the inventors discovered that in a hot stamped body comprising an Al-Zn-Mg-based
plating layer having a predetermined chemical composition and containing a predetermined
35 amount of an Mg-Zn containing phase in the plating layer after hot stamping, it is possible to
remarkably reduce or suppress LME and penetration of hydrogen into the steel material due to
7
the heating in the hot stamping and to achieve sufficient corrosion resistance. Below, this will be
explained more specifically while referring to the drawings.
[0021]
FIG. 1 shows a backscattered electron image (BSE image) of a scanning electron
microscope (SEM) of a plating layer cross-sect 5 ion in a conventional hot stamped body
containing an Al-Zn-Mg-based plating layer. Referring to FIG. 1, it will be understood that the
plating layer 1 contains a thick oxide layer 2 containing Zn and Mg. The oxide layer 2 is
believed to be the result of at least part of the Zn and Mg evaporating due to heating at about
900°C in the hot stamping or a higher temperature than that depositing on the surface of the
10 plating layer as oxides. On the other hand, a diffusion layer 3 is positioned below the plating
layer 1. The diffusion layer 3 forms part of the steel base material 4. The diffusion layer 3 results
from the Al constituent in the plating layer diffusing into the steel base material 4 and forming a
solid solution due to the heating in the hot stamping.
[0022]
15 In a conventional hot stamped body containing an Al-Zn-Mg-based plating layer such as
shown in FIG. 1, the Zn and Mg evaporate during the heating in the hot stamping, therefore
LME and hydrogen penetration into the steel material occur. Furthermore, the corrosion
resistance of the hot stamped body greatly falls due to the loss of at least part of the Zn and Mg
due to evaporation of these elements and the decrease in the Zn and Mg in the metal phase
20 accompanying formation of the oxides. In addition, for example, LME cracking is liable to be
caused even when the concentration of Zn in the plating layer 1 relatively rises due to
evaporation of Mg.
[0023]
FIG. 2 shows a backscattered electron image (BSE image) of a scanning electron
25 microscope (SEM) of a plating layer cross-section in a hot stamped body according to the
present invention (Example 13). Referring to FIG. 2, the plating layer 1 comprises an interfacial
layer 5 positioned at the interface with the steel base material 4, more specifically at the interface
with the diffusion layer 3 forming part of the steel base material 4, and containing Fe and Al and
a main layer 6 positioned on the interfacial layer 5. Further, it will be understood that the main
30 layer 6, in contrast to the case of FIG. 1, contains an Mg-Zn containing phase 7 containing at
least one selected from the group consisting of an MgZn phase, Mg2 Zn3 phase, and MgZn2
phase and an Fe-Al containing phase 8 comprised of an Fe-Al-Zn phase 8a (relatively darkly
colored islands of phase) and FeAl phase 8b (relatively lightly colored islands of phase). In
particular, it will be understood that the main layer 6 shown in FIG. 2 has a structure (island-in35
sea structure) of a matrix phase of an Mg-Zn containing phase 7 in which islands of the Fe-Al
containing phase 8 (islands of Fe-Al-Zn phase 8a and islands of FeAl phase 8b) are present, in
8
particular are present dispersed. In the hot stamped body according to the present invention, by
including an Mg-Zn containing phase 7 such as shown in FIG. 2 in the main layer 6 of the
plating layer 1 in a relatively large amount, it is possible to remarkably reduce or suppress
occurrence of LME and penetration of hydrogen into the steel material and to achieve sufficient
5 corrosion resistance.
[0024]
While not intending to be bound by any specific theory, in the hot stamped body according
to the present invention, as explained in detail later in relation to the method of production, at the
start of heating in the hot stamping, it is believed that the Ca leached out from the acicular Al-
10 Zn-Si-Ca phase present in the surface structure of the plating layer is preferentially oxidized by
the oxygen in the atmosphere and forms a dense Ca-based oxide film at the surface-most part of
the plating layer. In other words, it is believed that the acicular Al-Zn-Si-Ca phase present in the
surface structure of the plating layer before hot stamping functions as a supply source of Ca for
forming a Ca-based oxide film at the start of heating in hot stamping, then the Ca-based oxide
15 film obtained by the oxidation of Ca supplied, more specifically a Ca- and Mg-containing oxide
film, functions as a barrier layer.
[0025]
Due to the function of such a barrier layer, it is believed that evaporation of Zn and Mg in
the plating layer to the outside and the related occurrence of LME and the penetration of
20 hydrogen from the outside can be decreased or suppressed. As a result, it is believed that in the
body finally obtained after hot stamping, unlike the case of FIG. 1, Zn and Mg can be kept from
forming a thick oxide layer in the plating layer, can be made present as an Mg-Zn containing
phase 7 in a relatively large amount, i.e., in an amount of 10.0 to 70.0% by area ratio in the main
layer 6, and therefore the drop in corrosion resistance due to the evaporation of Zn and Mg to the
25 outside can be remarkably suppressed.
[0026]
Below, the hot stamped body according to an embodiment of the present invention will be
explained in detail. In the following explanation, the “%” relating to the contents of the
constituents means “mass%” unless otherwise indicated.
30 [0027]
[Steel Base Material]
The steel base material according to the embodiment of the present invention may be a
material having any thickness and composition. It is not particularly limited, but, for example, is
preferably a material having a thickness and composition suitable for application to hot
35 stamping. Such a steel base material is known, and may include, for example, a steel sheet
having a 0.3 to 2.3 mm thickness and comprising, by mass%, C: 0.05 to 0.40%, Si: 0.50% or
9
less, Mn: 0.50 to 2.50%, P: 0.03% or less, S: 0.010% or less, sol. Al: 0.10% or less, N: 0.010%
or less, and a balance: Fe and impurities (for example, a cold rolled steel sheet), etc. Below, the
constituents contained in the steel base material preferably applied in the present invention will
be explained in detail.
5 [0028]
[C: 0.05 to 0.40%]
Carbon (C) is an element effective for raising the strength of a hot stamped body. However,
if the C content is too great, the hot stamped body sometimes falls in toughness. Therefore, the C
content is 0.05 to 0.40%. The C content is preferably 0.10% or more, more preferably 0.13% or
10 more. The C content is preferably 0.35% or less.
[0029]
[Si: 0 to 0.50%]
Silicon (Si) is an element effective for deoxidizing steel. However, if the Si content is too
great, the Si in the steel diffuses at the time of heating in the hot stamping and forms oxides at
15 the steel material surface. As a result, the efficiency of phosphate treatment sometimes falls.
Further, Si is an element making the Ac3 point of the steel rise. For this reason, since the heating
temperature of the hot stamping has to be the Ac3 point or more, if the amount of Si becomes
excessive, the heating temperature of the hot stamping of the steel will inevitably become higher.
In other words, steel with a large amount of Si is heated to a higher temperature at the time of hot
20 stamping and, as a result, Zn, etc., in the plating layer will unavoidably evaporate. To avoid such
a situation, the Si content is 0.50% or less. The Si content is preferably 0.30% or less, more
preferably 0.20% or less. The Si content may also be 0%, but to obtain the effect of deoxidation,
etc., the lower limit value of the Si content, while changing depending on the desired deoxidation
level, is generally 0.05%.
25 [0030]
[Mn: 0.50 to 2.50%]
Manganese (Mn) raises the hardenability and raises the strength of the hot stamped body.
On the other hand, even if including Mn in excess, the effect become saturated. Therefore, the
Mn content is 0.50 to 2.50%. The Mn content is preferably 0.60% or more, more preferably
30 0.70% or more. The Mn content is preferably 2.40% or less, more preferably 2.30% or less.
[0031]
[P: 0.03% or Less]
Phosphorus (P) is an impurity contained in steel. P segregates at the crystal grain boundaries
to cause a drop in the toughness of the steel and causes a drop in the delayed fracture resistance.
35 Therefore, the P content is 0.03% or less. The P content is preferably as small as possible and is
preferably 0.02% or less. However, excessive reduction of the P content invites a rise in costs,
10
therefore the P content is preferably 0.0001% or more. The inclusion of P is not essential,
therefore the lower limit of the P content is 0%.
[0032]
[S: 0.010% or Less]
Sulfur (S) is an impurity contained in steel. S forms 5 sulfides to cause a drop in the
toughness of the steel and cause a drop in the delayed fracture resistance. Therefore, the S
content is 0.010% or less. The S content is preferably as small as possible and is preferably
0.005% or less. However, excessive reduction of the S content invites a rise in costs, therefore
the S content is preferably 0.0001% or more. The inclusion of S is not essential, therefore the
10 lower limit of the S content is 0%.
[0033]
[sol. Al: 0 to 0.10%]
Aluminum (Al) is effective for deoxidation of steel. However, excessive inclusion of Al
causes the Ac3 point of the steel material to rise and accordingly the heating temperature of the
15 hot stamping becomes higher and Zn, etc. in the plating layer unavoidably evaporate. Therefore,
the Al content is 0.10% or less, preferably 0.05% or less. The Al content may also be 0%, but to
obtain the effect of deoxidation, etc., the Al content may be 0.01% or more. In this Description,
the Al content means the content of so-called acid-soluble Al (sol. Al).
[0034]
20 [N: 0.010% or Less]
Nitrogen (N) is an impurity unavoidably contained in steel. N forms nitrides to cause a drop
in the toughness of the steel. If boron (B) is further contained, N bonds with B to cause a
reduction in the amount of B in solid solution and cause a drop in the hardenability. Therefore,
the N content is 0.010% or less. The N content is preferably as small as possible and is
25 preferably 0.005% or less. However, excessive reduction of the N content invites a rise in costs,
therefore the N content is preferably 0.0001% or more. The inclusion of N is not essential,
therefore the lower limit of the N content is 0%.
[0035]
The basic chemical composition of the steel base material suitable for use in the
30 embodiment according to the present invention is as explained above. Further, the above steel
base material may optionally contain one or more of B: 0 to 0.005%, Ti: 0 to 0.10%, Cr: 0 to
0.50%, Mo: 0 to 0.50%, Nb: 0 to 0.10%, and Ni: 0 to 1.00%. Below, these elements will be
explained in detail. The inclusion of these element is not essential, therefore the lower limits of
the contents of the elements are 0%.
35 [0036]
[B: 0 to 0.005%]
11
Boron (B) raises the hardenability of steel and raises the strength of the steel material after
hot stamping, therefore may be included in the steel base material. However, even if including B
in excess, the effect becomes saturated. Therefore, the B content is 0 to 0.005%. The B content
may also be 0.0001% or more.
5 [0037]
[Ti: 0 to 0.10%]
Titanium (Ti) can bond with nitrogen (N) to form nitrides and keep the hardenability from
dropping due to formation of BN. Further, due to the pinning effect, Ti can refine the austenite
grain size and raise the toughness, etc., of the steel material at the time of the heating in the hot
10 stamping. However, even if including Ti in excess, the effect becomes saturated. Further, if Ti
nitrides precipitate in excess, sometimes the toughness of the steel will fall. Therefore, the Ti
content is 0 to 0.10%. The Ti content may be 0.01% or more.
[0038]
[Cr: 0 to 0.50%]
15 Chromium (Cr) is effective for raising the hardenability of steel and raising the strength of
the hot stamped body. However, if the Cr content is excessive and a large amount of Cr carbides
which are difficult to melt at the time of heating in hot stamping are formed, it becomes difficult
for the steel to transform to austenite, and conversely the hardenability falls. Therefore, the Cr
content is 0 to 0.50%. The Cr content may also be 0.10% or more.
20 [0039]
[Mo: 0 to 0.50%]
Molybdenum (Mo) raises the hardenability of steel. However, even if including Mo in
excess, the above effect becomes saturated. Therefore, the Mo content is 0 to 0.50%. The Mo
content may also be 0.05% or more.
25 [0040]
[Nb: 0 to 0.10%]
Niobium (Nb) is an element which forms carbides to refine the crystal grains at the time of
hot stamping and raise the toughness of the steel. However, if including Nb in excess, the above
effect becomes saturated and further the hardenability falls. Therefore, the Nb content is 0 to
30 0.10%. The Nb content may also be 0.02% or more.
[0041]
[Ni: 0 to 1.00%]
Nickel (Ni) is an element able to suppress embrittlement caused by molten Zn at the time of
heating in hot stamping. However, even if including Ni in excess, the effect becomes saturated.
35 Therefore, the Ni content is 0 to 1.00%. The Ni content may also 0.10% or more.
[0042]
12
In the steel base material according to the embodiment of the present invention, the balance
other than the above constituents is comprised of Fe and impurities. The “impurities” in the steel
base material mean constituents entering due to various factors in the production process, first
and foremost the raw materials such as the ore and scrap, when industrially producing the hot
stamped body according to the embodiment of the present invention, 5 and not intentionally added
to the hot stamped body.
[0043]
[Plating Layer]
According to the embodiment of the present invention, a plating layer is formed on the
10 surface of the above steel base material. For example, if the steel base material is a steel sheet,
the plating layer is formed on at least one surface of the steel sheet, i.e., one surface or both
surfaces of the steel sheet. The plating layer comprises an interfacial layer positioned at the
interface with the steel base material and containing Fe and Al and a main layer positioned on
the interfacial layer. The plating layer has the following average composition.
15 [0044]
[Al: 15.00 to 45.00%]
Al is an element essential for suppressing the evaporation of the Zn and Mg at the time of
the heating in the hot stamping. As explained above, it is believed that due to the presence of the
acicular Al-Zn-Si-Ca phase in the surface structure of the plating layer before the hot stamping,
20 the Ca leaching out from the acicular Al-Zn-Si-Ca phase at the start of the heating in the hot
stamping is preferentially oxidized by the oxygen in the atmosphere and a dense Ca-based oxide
film, more specifically a Ca- and Mg-containing oxide film, is formed on the outermost surface
of the plating layer. Such a Ca-based oxide film is believed to function as a barrier layer for
suppressing evaporation of the Zn and Mg. To express the function of the barrier layer, the
25 content of Al in the plating layer after hot stamping has to be 15.00% or more, preferably is
20.00% or more or 25.00% or more. On the other hand, if the Al content is more than 45.00%,
Al4 Ca and other intermetallic compounds are preferentially formed at the plating layer before
the hot stamping and formation of the acicular Al-Zn-Si-Ca phase in a sufficient amount
becomes difficult. Therefore, the Al content is 45.00% or less, preferably 40.00% or less or
30 35.00% or less.
[0045]
[Mg: 5.50 to 12.00%]
Mg is an element effective for improving the corrosion resistance of the plating layer and
improving the coating blistering, etc. Further, Mg has the effect of forming liquid phase Zn-Mg
35 and suppressing LME cracking at the time of the heating in the hot stamping. If the Mg content
is low, the possibility of LME occurring increases. From the viewpoint of improvement of the
13
corrosion resistance and suppression of the LME, the Mg content is 5.50% or more, preferably
6.00% or more. On the other hand, if the Mg content is too high, an excessive sacrificial
corrosion action tends to cause coating blistering and flow rust to rapidly become larger.
Therefore, the Mg content is 12.00% or less, preferably 10.00% or less.
5 [0046]
[Si: 0.05 to 3.00%]
Si is an element essential for suppressing evaporation of Zn and Mg at the time of the
heating in the hot stamping. As explained above, due to the presence of the acicular Al-Zn-Si-Ca
phase in the surface structure of the plating layer before the hot stamping, it is possible to form a
10 barrier layer comprised of a Ca-based oxide film for suppressing evaporation of Zn and Mg at
the time of heating in the hot stamping. To express the function of the barrier layer, the Si
content in the plating layer after hot stamping has to be 0.05% or more, preferably is 0.10% or
more, more preferably 0.40% or more. On the other hand, if the Si content is excessive, an
Mg2 Si phase is formed at the interface of the steel base material and the plating layer at the
15 plating layer before hot stamping and the corrosion resistance greatly deteriorates. Further, if the
Si content is excessive, the Mg2 Si phase is preferentially formed at the plating layer before the
hot stamping and it becomes difficult to make the acicular Al-Zn-Si-Ca phase form in a
sufficient amount. Therefore, the Si content is 3.00% or less, preferably 1.60% or less, more
preferably 1.00% or less.
20 [0047]
[Ca: 0.05 to 3.00%]
Ca is an element essential for suppressing evaporation of Zn and Mg at the time of heating
in the hot stamping. As explained above, due to the presence of the acicular Al-Zn-Si-Ca phase
in the surface structure of the plating layer before the hot stamping, it is possible to form a
25 barrier layer comprised of a Ca-based oxide film for suppressing evaporation of Zn and Mg at
the time of heating in the hot stamping. To express the function of the barrier layer, the Ca
content in the plating layer after hot stamping has to be 0.05% or more, preferably is 0.40% or
more. On the other hand, if the Ca content is excessive, Al4 Ca and other intermetallic
compounds are preferentially formed at the plating layer before the hot stamping and it becomes
30 difficult to make the acicular Al-Zn-Si-Ca phase form in a sufficient amount. Therefore, the Ca
content is 3.00% or less, preferably 2.00% or less, more preferably 1.50% or less.
[0048]
[Fe: 20.00 to 50.00%]
If heating the plated steel material at the time of hot stamping, the Fe from the steel base
35 material diffuses in the plating layer, therefore the plating layer inevitably contains Fe. Fe bonds
with the Al in the plating layer to form at the interface with the steel base material an interfacial
14
layer mainly comprised of an intermetallic compound containing Fe and Al and further form an
Fe-Al containing phase in the main layer positioned on the interfacial layer. Therefore, the Fe
content becomes higher the greater the thickness of the interfacial layer and the greater the
amount of Fe-Al containing phase in the main layer. If the Fe content is low, the amount of the
Fe-Al containing phase decreases, therefore the st 5 ructure of the main layer easily collapses. More
specifically, if the Fe content is low, the Zn and Mg contents relatively increase, therefore at the
time of the heating in the hot stamping, these elements easily evaporate and as a result hydrogen
penetration easily occurs. Therefore, the Fe content is 20.00% or more, preferably 25.00% or
more. On the other hand, if the Fe content is too high, the amount of the Fe-Al containing phase
10 in the main layer becomes greater and the amount of the Mg-Zn containing phase in the main
layer relatively decreases, therefore the corrosion resistance falls. Therefore, the Fe content
becomes 50.00% or less, preferably 45.00% or less, more preferably 40.00% or less.
[0049]
The chemical composition of the plating layer is as explained above. Furthermore, the
15 plating layer may optionally contain one or more of Sb: 0 to 0.50%, Pb: 0 to 0.50%, Cu: 0 to
1.00%, Sn: 0 to 1.00%, Ti: 0 to 1.00%, Sr: 0 to 0.50%, Cr: 0 to 1.00%, Ni: 0 to 1.00%, and Mn: 0
to 1.00%. While not particularly limited to this, from the viewpoint of causing the actions and
functions of the above basic constituents forming the plating layer to be sufficiently manifested,
the total content of these elements is preferably 5.00% or less, more preferably 2.00% or less.
20 Below, these elements will be explained in detail.
[0050]
[Sb: 0 to 0.50%, Pb: 0 to 0.50%, Cu: 0 to 1.00%, Sn: 0 to 1.00%, and Ti: 0 to 1.00%]
Sb, Pb, Cu, Sn, and Ti can be contained in the MgZn2 phase present in the main layer, but
if within predetermined ranges of contents, do not detrimentally affect the performance of the hot
25 stamped body. However, if the contents of the elements are excessive, at the time of the heating
in the hot stamping, sometimes oxides of these elements will precipitate and cause deterioration
of the surface properties of the hot stamped body and the phosphate treatment will become poor
and the corrosion resistance after coating will deteriorate. Furthermore, if the Pb and Sn contents
become excessive, the LME resistance will tend to fall. Therefore, the contents of Sb and Pb are
30 0.50% or less, preferably 0.20% or less, while the contents of Cu, Sn, and Ti are 1.00% or less,
preferably 0.80% or less, more preferably 0.50% or less. On the other hand, the contents of
elements may also be 0.01% or more. These elements are not essential. The lower limits of the
contents of these elements are 0%.
[0051]
35 [Sr: 0 to 0.50%]
Sr can be included in the plating bath at the time of production of the plating layer so as to
15
suppress the formation of the top dross formed on the plating bath. Further, Sr tends to suppress
oxidation by air at the time of the heating in the hot stamping, therefore can suppress color
changes in the body after the hot stamping. These effects are exhibited even in small amounts,
therefore the Sr content may be 0.01% or more. On the other hand, if the Sr content is excessive,
the occurrence of coating blistering and flow ru 5 st becomes larger and the corrosion resistance
tends to deteriorate. Therefore, the Sr content is 0.50% or less, preferably 0.30% or less, more
preferably 0.10% or less.
[0052]
[Cr: 0 to 1.00%, Ni: 0 to 1.00%, and Mn: 0 to 1.00%]
10 Cr, Ni, and Mn concentrate near the interface of the plating layer and the steel base material
and have the effect of eliminating spangles of the plating layer surface, etc. To obtain such an
effect, the contents of Cr, Ni, and Mn are preferably respectively 0.01% or more. On the other
hand, these elements may be included in the interfacial layer or included in the Fe-Al containing
phase present in the main layer. However, if the contents of these elements are excessive, the
15 coating blistering and flow rust become greater and the corrosion resistance tends to deteriorate.
Therefore, the contents of Cr, Ni, and Mn are respectively 1.00% or less, preferably 0.50% or
less, more preferably 0.10% or less.
[0053]
[Balance: Zn and Impurities]
20 The balance in the plating layer aside from the above constituents is comprised of Zn and
impurities. Zn is an essential constituent in the plating layer from the viewpoint of preventing
corrosion. Zn is present mainly as the Mg-Zn containing phase in the main layer of the plating
layer and greatly contributes to improvement of the corrosion resistance. If the Zn content is less
than 3.00%, sometimes a sufficient corrosion resistance cannot be maintained. Therefore, the Zn
25 content is preferably 3.00% or more. The lower limit of the Zn content may be 10.00%, 15.00%,
or 20.00%. On the other hand, if the Zn content is too high, at the time of the heating in the hot
stamping, Zn easily evaporates and as a result LME and hydrogen penetration easily occur.
Therefore, the Zn content is preferably 50.00% or less. The upper limit of the Zn content may be
45.00%, 40.00%, or 35.00%. Further, Zn can be substituted by Al, therefore a small amount of
30 Zn can form a solid solution with the Fe in the Fe-Al containing phase. Further, the “impurities”
in the plating layer mean constituents entering due to various factors in the production process,
first and foremost the raw materials, when producing the plating layer, and not intentionally
added to the plating layer. In the plating layer, the impurities may contain elements other than
the elements explained above in trace amounts to an extent not detracting from the effect of the
35 present invention.
[0054]
16
The chemical composition of the plating layer is determined by dissolving the plating layer
in an acid solution to which an inhibitor is added for inhibiting corrosion of the steel base
material and measuring the obtained solution by the ICP (high frequency inductively coupled
plasma) emission spectrometry method. In this case, the measured chemical composition is the
average composition of the tot 5 al of the main layer and the interfacial layer.
[0055]
The thickness of the plating layer may be, for example, 3 to 50 mm. Further, if the steel base
material is a steel sheet, the plating layer may be provided at both surfaces of the steel sheet or
may be provided at only one surface. The amount of deposition of the plating layer is not
10 particularly limited, but for example may be 10 to 170 g/m2 per surface. The lower limit may be
20 or 30 g/m2 and the upper limit may be 150 or 130 g/m2 . In the present invention, the amount
of deposition of the plating layer is determined from the change in weight before and after acid
washing by dissolving the plating layer in an acidic solution to which an inhibitor for inhibiting
corrosion of the base iron has been added.
15 [0056]
[Interfacial Layer]
The interfacial layer is a layer containing Fe and Al, more specifically a layer at which, at
the time of the heating in the hot stamping, the Fe from the steel base material diffuses in the
plating layer and bonds with the Al in the plating layer and is mainly comprised of an
20 intermetallic compound containing Fe and Al (below, also simply referred to as an “Fe-Al
containing intermetallic compound”).
[0057]
An Fe-Al containing intermetallic compound is an intermetallic compound having a
predetermined mass ratio or atomic ratio and in general has a Fe: approximately 67% and Al:
25 approximately 33% stoichiometric composition (mass%). According to examination under a
transmission electron microscope (TEM), sometimes an FeAl3 phase with a high Al
concentration is formed as microprecipitates not forming layers at the surface layer of the
interfacial layer and an Fe3 Al phase, etc., with a high Fe concentration is formed as
microprecipitates not forming layers near the steel base material. If using scanning electron
30 microscope-energy dispersive X-ray spectrometry (SEM-EDX), etc., to quantitatively analyze
the interfacial layer by a power of about 5000X, the Al content fluctuates in the range of 30.0 to
36.0%. Further, the interfacial layer sometimes contains small amounts of Zn, Mn, Si, Ni, etc., in
accordance with the chemical compositions of the steel base material and the plating layer.
Therefore, the interfacial layer generally contains Al: 30.0 to 36.0% and has a balance of Fe and
35 less than 3.0% of other constituents (for example, Zn, Mn, Si, and Ni).
[0058]
17
The interfacial layer further forms a barrier layer of the steel base material and has a certain
corrosion resistance. Therefore, the interfacial layer prevents leaching of the steel base material
at the time of corrosion under the coating and can suppress the formation of flow rust generated
from a cut (specifically, red rust forming stripe patterns in a manner dripping from the cut). To
obtain such an effect, the thickness of the 5 interfacial layer is preferably 0.1 mm or more, more
preferably 0.5 mm or more. However, if the interfacial layer is too thick, due to the Fe-Al
containing intermetallic compound being brittle, sometimes the fatigue characteristics after hot
stamping fall. For this reason, the thickness of the interfacial layer is preferably 10.0 mm or less,
more preferably 7.0 mm or less, most preferably 5.0 mm or less.
10 [0059]
[Main Layer]
The main layer includes an area ratio of 10.0 to 70.0% of an Mg-Zn containing phase and
30.0 to 90.0% of an Fe-Al containing phase. The main layer has the effect of inhibiting the
formation of scale at the time of hot stamping and contributes to corrosion resistance of the hot
15 stamped body as well. The main layer has a mixed structure of an Mg-Zn containing phase and
Fe-Al containing phase and generally, as shown in FIG. 2, has the structure (island-in-sea
structure) of a matrix phase of an Mg-Zn containing phase 7 in which islands of Fe-Al
containing phase 8 are present, in particular are present dispersed. If referring to FIG. 2, the
islands of the Fe-Al containing phase 8 include not only the islands of the Fe-Al-Zn phase 8a and
20 islands of the FeAl phase 8b present respectively individually, but also groups of islands of the
Fe-Al-Zn phase 8a adjoining each other.
[0060]
[Mg-Zn Containing Phase]
In an embodiment according to the present invention, by configuring the plating layer after
25 hot stamping so that Zn and Mg having a corrosion resistance improving effect are present as an
Mg-Zn containing phase in the main layer in an area ratio of an amount of 10.0 to 70.0%,
occurrence of LME and hydrogen penetration to the steel material due to the heating at the time
of hot stamping can be remarkably reduced or suppressed and, even in the body after hot
stamping, sufficient corrosion resistance can be achieved. If the area ratio of the Mg-Zn
30 containing phase is less than 10.0%, it is not possible to sufficiently obtain such an effect.
Therefore, the area ratio of the Mg-Zn containing phase is 10.0% or more, preferably 15.0% or
more, more preferably 25.0% or more. On the other hand, the area ratio of the Mg-Zn containing
phase may be 70.0% or less, for example, may be 60.0% or less or 50.0% or less.
[0061]
35 The Mg-Zn containing phase includes at least one phase selected from the group consisting
of an MgZn phase, Mg2 Zn3 phase, and MgZn2 phase. Here, the MgZn phase, Mg2 Zn3 phase,
18
and MgZn2 phase are intermetallic compounds, therefore while the atomic ratios of Mg and Zn
of the phases may be considered to be substantially constant, in actuality they fluctuate
somewhat since sometimes Al, Fe, etc., dissolve partially. Therefore, in the present invention, in
phases having a chemical composition in which the total of the Mg and Zn contents is 90.0% or
more, a phase where the atomic ratio of Mg/5 Zn is 0.90 to 1.10 is defined as an MgZn phase, a
phase where an atomic ratio of Mg/Zn is 0.58 to 0.74 is defined as an Mg2 Zn3 phase, and a
phase where an atomic ratio of Mg/Zn is 0.43 to 0.57 is defined as an MgZn2 phase. By the Mg-
Zn containing phase including these phases, the corrosion resistance of the hot stamped body can
be remarkably improved. In particular, when the Mg-Zn containing phase includes an MgZn
10 phase and/or Mg2 Zn3 phase, it is possible to suppress LME at the time of hot stamping. To
reliably obtain such an effect, the Mg-Zn containing phase preferably includes an MgZn phase
with a large Mg content. The area ratio of the MgZn phase in the main layer is preferably 5.0%
or more and 10.0% or more is more preferable. Further, the Mg-Zn containing phase preferably
includes an MgZn phase and Mg2 Zn3 phase. The area ratio of the total of the MgZn phase and
15 Mg2 Zn3 phase in the main layer is preferably 10.0% or more or 25.0% or more. On the other
hand, it may be 60.0% or less or 50.0% or less. By controlling the Mg-Zn containing phase to
within such a range, it is possible to remarkably reduce or suppress the occurrence of LME and
hydrogen penetration to the steel material occurring due to the heating at the time of hot
stamping and possible, even in the body after hot stamping, to achieve sufficient corrosion
20 resistance.
[0062]
[Fe-Al Containing Phase]
As explained above, the main layer includes an area ratio of 30.0 to 90.0% of an Fe-Al
containing phase. If the area ratio of the Fe-Al containing phase is more than 90.0%, the amount
25 of the Mg-Zn containing phase contained in the main layer becomes smaller and the corrosion
resistance falls. On the other hand, the area ratio of the Fe-Al containing phase may be 30.0% or
more, for example, may be 40.0% or more. The Fe-Al containing phase becomes a barrier at the
time corrosion progresses in the Mg-Zn containing phase, therefore by establishing the presence
of the Fe-Al containing phase, the corrosion resistance can be improved. Explaining this in more
30 detail, the Fe-Al containing phase (Fe-Al-Zn phase and FeAl phase) is present in the main layer
not as a laminar structure, but as an island structure, therefore if corrosion progresses in the Mg-
Zn containing phase having the corrosion resistance improving effect, the corrosion will proceed
in a spotted state avoiding these islands of the Fe-Al containing phase. As a result, it is believed
possible to delay progress of corrosion of the Mg-Zn containing phase.
35 [0063]
The Fe-Al containing phase includes the Fe-Al-Zn phase and FeAl phase. The area ratio of
19
the Fe-Al-Zn phase in the main layer is more than 10.0 to 75.0%. In the present invention, the
Fe-Al containing phase means a phase having a chemical composition where the total of Fe, Al,
and Zn is 90.0% or more. In the Fe-Al containing phase having such a chemical composition, a
phase where the Zn content is 1.0% or more is defined as an Fe-Al-Zn phase and a phase where
the Zn content is less than 1.0% is defined as 5 an FeAl phase. While not intending to be bound by
any specific theory, it is believed that the Fe-Al-Zn phase and FeAl phase do not grow at the
interface of the plating layer and the steel base material from the steel base material to inside the
plating layer in a layer shape, but form nuclei of spherical shapes in the plating layer in the
molten state at the time of the heating in the hot stamping and then grow into island shapes.
10 [0064]
As explained in detail later, by suitably controlling the production conditions of the plated
steel material before hot stamping, it is possible to establish the presence of the acicular Al-Zn-
Si-Ca phase dispersed in the surface structure of the plating layer. As a result, it is possible to
suppress the evaporation of Zn and Mg at the time of the heating in the hot stamping. By
15 suppressing the evaporation of Zn and Mg, it is believed that nuclei are formed inside the main
layer in the molten state and the Fe-Al containing phase grows to island shapes. In an
embodiment according to the present invention, the area ratio of the Fe-Al-Zn phase in the main
layer may, for example, be 20.0% or more or 30.0% or more and may be 70.0% or less, 65.0% or
less, or 60.0% or less. Further, in an embodiment according to the present invention, the area
20 ratio of the FeAl phase in the main layer may be, for example, 3.0% or more or 5.0% or more
and may be 25.0% or less, 20.0% or less, or 17.0% or less. As explained above, the Fe-Al
containing phase, in particular the Fe-Al-Zn phase and FeAl phase, has island shapes. While not
particularly limited, the aspect ratio almost never is more than 5.0. In general, the Fe-Al
containing phase has island shapes of an aspect ratio of 5.0 or less, for example, 4.0 or less or 3.0
25 or less. The lower limit of the aspect ratio is not particularly prescribed, but, for example, may be
1.0 or more, 1.2 or more, or 1.5 or more. In the present invention, the “aspect ratio” means the
ratio of the longest axis of the Fe-Al containing phase (Fe-Al-Zn phase and FeAl phase) (long
axis) and the longest axis in the axes of the Fe-Al containing phase perpendicular to the same
(short axis).
30 [0065]
[Other Intermetallic Compounds]
The main layer may contain other intermetallic compounds besides those contained in the
Mg-Zn containing phase and Fe-Al containing phase. The other intermetallic compounds are not
particularly limited, but, for example, intermetallic compounds containing Si and Ca or other
35 elements contained in the plating layer, specifically Mg2 Si, Al4Ca, etc., may be mentioned.
However, if the area ratio of the other intermetallic compounds in the main layer becomes too
20
large, sometimes it is not possible to sufficiently secure the Mg-Zn containing phase and/or Fe-
Al containing phase. Therefore, the area ratio of the other intermetallic compounds, for example,
the area ratio of the Mg2 Si and Al4Ca, is preferably a total of 10.0% or less. 5.0% or less is
more preferable.
5 [0066]
[Oxide Layer]
The surface of the plating layer is sometimes formed with an oxide layer due to oxidation of
the plating constituents. Such an oxide layer is liable to cause a drop in the chemical
convertibility and electrodeposition coatability after hot stamping. Therefore, the thickness of the
10 oxide layer is preferably small. For example, it is preferably 1.0 mm or less. If the Zn and Mg
evaporate at the time of hot stamping, a thick Mg-Zn containing oxide layer of more than 1.0 mm
is formed.
[0067]
[Diffusion Layer]
15 In an embodiment according to the present invention, as shown in FIG. 2, sometimes a
diffusion layer 3 is formed below the plating layer 1. The diffusion layer forms part of the steel
base material. More specifically, due to the heating in the hot stamping, the Al constituent in the
plating layer diffuses in the steel base material and forms a solid solution. If there is a diffusion
layer, the thickness is generally 0.1 mm or more, for example, 0.5 mm or more or 1.0 mm or more.
20 However, if the diffusion layer becomes too thick, the Al constituent in the plating layer, in
particular the main layer, becomes too small, therefore this is not preferable. Therefore, the
thickness of the diffusion layer is generally 15.0 mm or less, preferably 10.0 mm or less, more
preferably 5.0 mm or less.
[0068]
25 The thicknesses of the main layer, the interfacial layer, the diffusion layer, and the oxide
layer are determined by cutting out a test piece from the hot stamped body, burying it in a resin
etc., then polishing the cross-section and measuring the image observed by an SEM. Further, if
examining these in a backscattered electron image of the SEM, the contrast at the time of
observation will differ depending on the metal constituents, therefore it is possible to identify the
30 layers and confirm the thicknesses of the layers. If the interface of the interfacial layer and the
main layer is hard to discern and the thickness of the interfacial layer cannot be specifically
determined, it is also possible to perform line analysis and identify the position where the Al
content becomes 30.0 to 36.0% as the interface of the interfacial layer and the main layer. The
thicknesses of the main layer, the interfacial layer, the diffusion layer, and the oxide layer are
35 determined by performing similar observation in three or more different fields and finding the
averages of these.
21
[0069]
In the present invention, the area ratios of the phases of the main layer are determined in the
following way. First, a prepared sample is cut into a 25 mm´15 mm size, and any cross-section
of the plating layer is photographed by a power of 1500X by a scanning electron microscope
(SEM). From the BSE image of the same 5 and an SEM-EDS mapping image, the area ratios of
the phases at the main layer were measured by computer image processing. The averages of the
measurement values at any five fields (however, the measured areas in the fields are 400 mm2 or
more) were determined as the area ratios of the MgZn phase, Mg2 Zn3 phase, MgZn2 phase,
FeAl phase, Fe-Al-Zn phase, and other intermetallic compounds. Further, the area ratio of the
10 Mg-Zn containing phase was determined as the area ratio of the total of the MgZn phase,
Mg2 Zn3 phase, and MgZn2 phase. Similarly, the area ratio of the Fe-Al containing phase was
determined as the area ratio of the total of the FeAl phase and Fe-Al-Zn phase.
[0070]

15 Next, a preferred method for producing the hot stamped body according to the embodiment
of the present invention will be explained. The following explanation is intended to illustrate a
characteristic method for producing a hot stamped body according to the embodiment of the
present invention and is not intended to limit the hot stamped body to one produced by a
production method as explained below.

CLAIMS
[Claim 1]
A hot stamped body comprising a steel base material and a plating layer formed on a
surface of the steel base material, wherein the plating layer has a chemical composition
5 comprising, by mass%,
Al: 15.00 to 45.00%,
Mg: 5.50 to 12.00%,
Si: 0.05 to 3.00%,
Ca: 0.05 to 3.00%,
10 Fe: 20.00 to 50.00%,
Sb: 0 to 0.50%,
Pb: 0 to 0.50%,
Cu: 0 to 1.00%,
Sn: 0 to 1.00%,
15 Ti: 0 to 1.00%,
Sr: 0 to 0.50%,
Cr: 0 to 1.00%,
Ni: 0 to 1.00%,
Mn: 0 to 1.00%, and
20 balance: Zn and impurities,
the plating layer comprises an interfacial layer positioned at an interface with the steel base
material and containing Fe and Al and a main layer positioned on the interfacial layer,
the main layer comprises, by area ratio, 10.0 to 70.0% of an Mg-Zn containing phase and
30.0 to 90.0% of an Fe-Al containing phase,
25 the Mg-Zn containing phase comprises at least one selected from the group consisting of an
MgZn phase, Mg2 Zn3 phase, and MgZn2 phase, and
the Fe-Al containing phase comprises an FeAl phase and Fe-Al-Zn phase and an area ratio
of the Fe-Al-Zn phase in the main layer is more than 10.0 to 75.0%.
30 [Claim 2]
The hot stamped body according to claim 1, wherein the chemical composition of the
plating layer comprises, by mass%,
Al: 25.00 to 35.00% and
Mg: 6.00 to 10.00%.
35
[Claim 3]
37
The hot stamped body according to claim 1 or 2, wherein the Mg-Zn containing phase
comprises an MgZn phase, and an area ratio of the MgZn phase in the main layer is 5.0% or
more.
5 [Claim 4]
The hot stamped body according to any one of claims 1 to 3, wherein the Mg-Zn containing
phase comprises an MgZn phase and Mg2 Zn3 phase, and an area ratio of a total of the MgZn
phase and Mg2 Zn3 phase in the main layer is 25.0 to 50.0%.
10 [Claim 5]
The hot stamped body according to any one of claims 1 to 4, wherein an area ratio of the
FeAl phase in the main layer is 5.0 to 25.0%.