Hot stamping part and manufacturing method therefor
Abstract
A hot stamping part includes: a base material; a decarburization layer located on the base material; and an inner oxide layer located on the decarburization layer, wherein the hot stamping part has a tensile strength (TS) of 1680 MPa to 2000 MPa, and a hardness of the hot stamping part within a depth of 50 μm from a surface of the hot stamping part in a plate thickness direction of the hot stamping part and an average hardness of the hot stamping part satisfy Relational Expression 1. ( A / B ) ≤ 0 . 7 < Relational Expression 1 > (In Relational Expression 1, A denotes the hardness (Hv(≤50 μm)) within the depth of 50 μm in the plate thickness direction of the hot stamping part, and B denotes the average hardness (Hv(avg.)) of the hot stamping part.)
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A hot stamping part comprising:
a base material; a decarburization layer located on the base material; and an inner oxide layer located on the decarburization layer, wherein the hot stamping part has a tensile strength (TS) of about 1680 MPa to 2000 MPa, and a hardness of the hot stamping part within a depth of about 50 μm from a surface of the hot stamping part in a plate thickness direction of the hot stamping part and an average hardness of the hot stamping part satisfy Relational Expression 1.
(
A
/
B
)
≤
0
.
7
<
Relational
Expression
1
>
(In Relational Expression 1, A denotes the hardness (Hv(≤50 μm)) within the depth of 50 μm in the plate thickness direction of the hot stamping part, and B denotes the average hardness (Hv(avg.)) of the hot stamping part.)
2 . The hot stamping part of claim 1 , wherein a depth of the inner oxide layer satisfies Relational Expression 2.
C
≤
5
μ
m
<
Relational
Expression
2
>
(In Relational Expression 2, C denotes the depth of the inner oxide layer in the plate thickness direction of the hot stamping part.)
3 . The hot stamping part of claim 1 , wherein the hot stamping part has a VDA bending angle of about 60° or more.
4 . The hot stamping part of claim 1 , wherein the hot stamping part has a yield strength (YP) of about 1150 MPa to 1500 MPa and an elongation (EL) of about 4% to 10%.
5 . The hot stamping part of claim 1 , wherein the hot stamping part has a microstructure with a martensite fraction of about 90% or more.
6 . The hot stamping part of claim 1 , further comprising a plating layer located on the inner oxide layer.
7 . The hot stamping part of claim 6 , wherein a thickness of the plating layer is about 10 μm to 30 μm.
8 . A method of manufacturing a hot stamping part, comprising:
forming a blank by cutting a plated steel sheet having a plating layer formed on at least one surface of a base material; and heating the blank in a heating furnace having a plurality of sections with different temperature ranges, wherein the heating of the blank comprises:
a multi-stage heating step of heating the blank stepwise; and
a soaking step of heating the stepwise heated blank to a temperature of Ac3 to about 910° C.,
wherein a hardness of the hot stamping part within a depth of about 50 μm from a surface of the hot stamping part in a plate thickness direction of the hot stamping part and an average hardness of the hot stamping part satisfy Relational Expression 3.
(
A
/
B
)
≤
0
.
7
<
Relational
Expression
3
>
(In Relational Expression 3, A denotes the hardness (Hv(≤50 μm)) within the depth of 50 μm in the plate thickness direction of the hot stamping part, and B denotes the average hardness (Hv(avg.)) of the hot stamping part.)
9 . The method of manufacturing a hot stamping part of claim 8 , wherein a dew point of an annealing furnace of the base material is about −15° C. to +15° C.
10 . The method of manufacturing a hot stamping part of claim 8 , wherein an annealing temperature of the base material is about 750° C. to 900° C.
11 . The method of manufacturing a hot stamping part of claim 8 , further comprising:
after the heating of the blank, transferring the heated blank; forming a molded body by pressing the transferred blank with a mold; and cooling the formed molded body.
12 . The method of manufacturing a hot stamping part of claim 11 , wherein the hot stamping part further comprises:
a decarburization layer formed on the base material; and an inner oxide layer formed on the decarburization layer.
13 . The method of manufacturing a hot stamping part of claim 12 , wherein a depth of the inner oxide layer satisfies Relational Expression 4.
C
≤
5
μ
m
<
Relational
Expression
4
>
(In Relational Expression 4, C denotes the depth of the inner oxide layer in the plate thickness direction of the hot stamping part.)
14 . A hot stamping part comprising:
a base material; a decarburization layer located on a surface of the base material; an inner oxide layer located on the decarburization layer; and a plating layer located on the inner oxide layer,
wherein the base material comprises a microstructure with a martensite fraction of 90% or more;
wherein the hot stamping part has:
a tensile strength (TS) of 1680 MPa to 2000 MPa,
a yield strength (YP) of 1150 MPa to 1500 MPa,
an elongation (EL) of 4% to 10%, and
a VDA bending angle of 60° or more;
wherein a hardness of the hot stamping part within a depth of 50 μm from the surface of the hot stamping part and an average hardness of the hot stamping part satisfy Relational Expression 1:
(
A
/
B
)
≤
0.7
,
<
Relational
Expression
1
>
where A denotes the hardness (Hv(≤50 μm)) within the depth of 50 μm in the plate thickness direction, and B denotes the average hardness (Hv(avg.)) of the hot stamping part; and
wherein a depth of the inner oxide layer satisfies Relational Expression 2:
C
≤
5
μ
m
,
<
Relational
Expression
2
>
where C denotes the depth of the inner oxide layer in the plate thickness direction.
15 . The hot stamping part of claim 14 , wherein the decarburization layer has a hardness that is 70% or less of the average hardness of the base material measured at ¼ thickness from the surface of the base material.
16 . The hot stamping part of claim 14 , wherein the plating layer is a zinc (Zn)-based plating layer comprising zinc (Zn), iron (Fe), aluminum (Al), manganese (Mn), silicon (Si), and unavoidable impurities, and has a thickness of 10 μm to 30 μm.
17 . The hot stamping part of claim 14 , wherein the base material comprises:
0.25 wt % to 0.5 wt % carbon (C), 0.1 wt % to 0.8 wt % silicon (Si), 0.3 wt % to 3.0 wt % manganese (Mn), 0.01 wt % to 0.1 wt % of at least one of titanium (Ti), niobium (Nb), and vanadium (V), 0.01 wt % to 1.0 wt % chromium (Cr), and the remainder being iron (Fe) and unavoidable impurities.
18 . The hot stamping part of claim 14 , wherein the inner oxide layer comprises silicon (Si), manganese (Mn), and chromium (Cr) and has a depth of 5 μm or less.
19 . The hot stamping part of claim 14 , wherein the hot stamping part exhibits a crack depth of 10 μm or less when subjected to a VDA bending test in accordance with VDA238-100.
20 . The hot stamping part of claim 14 , wherein the decarburization layer and the inner oxide layer are formed by annealing the base material at a temperature of 750° C. to 900° C. in an annealing furnace with a dew point of −15° C. to +15° C.Join the waitlist — get patent alerts
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