Steel sheet
Abstract
What is claimed is a steel sheet having a predetermined chemical composition, in which a microstructure includes, by area ratio, ferrite: 5.0% or less, martensite and tempered martensite: more than 90.0% in total, and a remainder: one or two or more of bainite, pearlite, and residual austenite, when an interface where an orientation difference between adjacent martensite and tempered martensite is 15 degrees or more is defined as a prior austenite grain boundary, grain boundary binding energy E GB determined by a concentration of each alloying element on the prior austenite grain boundary is 0.50 or more, and a tensile strength is 1,500 MPa or more.
Claims
exact text as granted — not AI-modified1 . A steel sheet comprising, as a chemical composition, by mass %:
C: 0.150% to 0.400%; Si: 0.01% to 2.00%; Mn: 0.80% to 2.00%; P: 0.0001% to 0.0200%; S: 0.0001% to 0.0200%; Al: 0.001% to 1.000%; N: 0.0001% to 0.0200%; O: 0.0001% to 0.0200%; Co: 0% to 0.500%; Ni: 0% to 1.000%; Mo: 0% to 1.000%; Cr: 0% to 2.000%; Ti: 0% to 0.500%; B: 0% to 0.0100%; Nb: 0% to 0.500%; V: 0% to 0.500%; Cu: 0% to 0.500%; W: 0% to 0.100%; Ta: 0% to 0.100%; Mg: 0% to 0.050%; Ca: 0% to 0.050%; Y: 0% to 0.050%; Zr: 0% to 0.050%; La: 0% to 0.050%; Ce: 0% to 0.050%; Sn: 0% to 0.050%; Sb: 0% to 0.050%; As: 0% to 0.050%; and a remainder: Fe and impurities, wherein a microstructure includes, by area ratio,
ferrite: 5.0% or less,
martensite and tempered martensite: more than 90.0% in total, and
a remainder: one or two or more of bainite, pearlite, and residual austenite,
when an interface where an orientation difference between adjacent martensite and tempered martensite is 15 degrees or more is defined as a prior austenite grain boundary, grain boundary binding energy E GB determined by a concentration of each alloying element on the prior austenite grain boundary satisfies Expression (1), and a tensile strength is 1,500 MPa or more,
E
G
B
=
1
+
(
3
×
[
Co
]
+
0
.7
×
[
Ni
]
+
5
.5
×
[
Mo
]
+
0
.7
×
[
Cr
]
+
2.9
×
[
Ti
]
+
4
7
×
[
B
]
+
4.3
×
[
Nb
]
+
4
.
5
×
[
V
]
+
5
.
2
×
[
W
]
+
3.1
×
[
Ta
]
+
4
.3
×
[
Zr
]
-
0
.
2
5
×
[
Mn
]
-
0
.
1
×
[
P
]
-
[
Cu
]
-
1
.1
×
[
Sn
]
-
0.6
×
[
Sb
]
-
0
.9
×
[
As
]
)
≥
0
.50
,
(
1
)
here, [chemical symbol] in the expression represents the concentration of each alloying element by mass % on the prior austenite grain boundary.
2 . The steel sheet according to claim 1 ,
wherein the chemical composition comprises one or more of Co: 0.01% to 0.500%, Ni: 0.01% to 1.000%, Mo: 0.01% to 1.000%, Cr: 0.001% to 2.000%, Ti: 0.001% to 0.500%, B: 0.0001% to 0.0100%, Nb: 0.001% to 0.500%, V: 0.001% to 0.500%, Cu: 0.001% to 0.500%, W: 0.001% to 0.100%, Ta: 0.001% to 0.100%, Mg: 0.001% to 0.050%, Ca: 0.001% to 0.050%, Y: 0.001% to 0.050%, Zr: 0.001% to 0.050%, La: 0.001% to 0.050%, Ce: 0.001% to 0.050%, Sn: 0.001% to 0.050%, Sb: 0.001% to 0.050%, and As: 0.001% to 0.050%.
3 . The steel sheet according to claim 1 ,
wherein a coating layer containing zinc, aluminum, magnesium, or an alloy of these metals is provided on a surface.
4 . The steel sheet according to claim 2 ,
wherein a coating layer containing zinc, aluminum, magnesium, or an alloy of these metals is provided on a surface.Join the waitlist — get patent alerts
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