US2026085392A1PendingUtilityA1
Hot-rolled steel sheet
Est. expiryOct 31, 2042(~16.3 yrs left)· nominal 20-yr term from priority
C22C 38/52C22C 38/50C22C 38/48C22C 38/46C22C 38/44C22C 38/42C22C 38/06C22C 38/04C22C 38/02C22C 38/008C22C 38/005C22C 38/002C22C 38/001C21D 2211/009C21D 2211/005C21D 2211/001C21D 9/46C21D 8/0226C21D 6/002C22C 38/54C22C 38/58C22C 38/00C22C 38/32C22C 38/38
64
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References
0
Claims
Abstract
This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a position of ¼ from a surface in a sheet thickness direction, in terms of area %, residual austenite is less than 3.0%, ferrite is 15.0% or more and less than 60.0%, and pearlite is less than 5.0%, an E value is 10.7 or more, an I value is 1.020 or more, a CS value is −8.0×105 to 8.0×105, a standard deviation of Mn concentrations is 0.60 mass % or less, at the surface, a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.500 μm or more is 2.0×103 pieces/cm2 or less, and a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.005 μm to 0.050 μm is 1.0×105 pieces/cm2 or more.
Claims
exact text as granted — not AI-modified1 . A hot-rolled steel sheet comprising, in terms of mass %, as a chemical composition:
C: 0.050% to 0.250%, Si: 0.40% to 1.00%, Mn: 1.00% to 1.50%, sol. Al: 0.100% to 0.500%, Cr: 0.50% to 2.00%, P: 0.100% or less, S: 0.0300% or less, N: 0.1000% or less, O: 0.0100% or less, Ti: 0% to 0.500%, Nb: 0% to 0.500%, V: 0% to 0.500%, Cu: 0% to 2.00%, Mo: 0% to 1.00%, Ni: 0% to 2.00%, B: 0% to 0.0100%; Ca: 0% to 0.0200%; Mg: 0% to 0.0200%; REM: 0% to 0.1000%; Bi: 0% to 0.0200%; As: 0% to 0.100%; Zr: 0% to 1.00%; Co: 0% to 1.00%; Zn: 0% to 1.00%; W: 0% to 1.00%; Sn: 0% to 0.05%; a remainder comprising Fe and impurities, and the following formulas (A) and (B) are satisfied, wherein, a microstructure at a position of ¼ from a surface in a sheet thickness direction having, in terms of area %,
residual austenite at less than 3.0%,
ferrite at 15.0% or more and less than 60.0%, and
pearlite at less than 5.0%,
an Entropy value indicated by the following formula (1) is 10.7 or more,
an Inverse difference normalized value indicated by the following formula (2) is 1.020 or more,
a Cluster Shade value indicated by the following formula (3) is −8.0×10 5 to 8.0×10 5 , which are obtained by analyzing SEM images of the microstructure with a gray level co-occurrence matrices method,
a standard deviation of Mn concentrations is 0.60 mass % or less,
at the surface, a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.500 μm or more is 2.0×10 3 pieces/cm 2 or less, and a number density of Si—Al—Cr oxides having a sphere equivalent radius of 0.005 μm to 0.050 μm is 1.0×10 5 pieces/cm 2 or more,
0.06
%
≤
Ti
+
Nb
+
V
≤
0.5
%
,
(
A
)
Zr
+
Co
+
Zn
+
W
≤
1.
%
,
(
B
)
here, each element symbol in the formulas (A) and (B) indicates the content of the element in terms of mass %, and 0% is substituted when the element is not contained,
P(i,j) in the following formulas (1) to (5) is a gray level co-occurrence matrix, L in the following formula (2) is possible Quantization levels of grayscale of the SEM images, i and j in the following formulas (2) and (3) are natural numbers from 1 to the L, μ x and μ y in the following formula (3) are indicated by the in the following formulas (4) and (5),
[
Formula
1
]
Entropy
=
-
∑
i
∑
j
P
(
i
,
j
)
log
(
P
(
i
,
j
)
)
(
1
)
[
Formula
2
]
Inverse
difference
normalized
=
∑
i
∑
j
P
(
i
,
j
)
1
+
❘
"\[LeftBracketingBar]"
i
-
j
❘
"\[RightBracketingBar]"
L
(
2
)
[
Formula
3
]
Cluster
Shade
=
∑
i
∑
j
(
i
+
j
-
μ
x
-
μ
y
)
3
P
(
i
,
j
)
(
3
)
[
Formula
4
]
μ
x
=
∑
i
∑
j
i
(
P
(
i
,
j
)
)
(
4
)
[
Formula
5
]
μ
y
=
∑
i
∑
j
j
(
P
(
i
,
j
)
)
.
(
5
)
2 . The hot-rolled steel sheet according to claim 1 , wherein the chemical composition comprises, in terms of mass %, one or more of:
Ti: 0.001% to 0.500%, Nb: 0.001% to 0.500%, V: 0.001% to 0.500%, Cu: 0.01% to 2.00%, Mo: 0.01% to 1.00%, Ni: 0.02% to 2.00%, B: 0.0001% to 0.0100%; Ca: 0.0005% to 0.0200%; Mg: 0.0005% to 0.0200%; REM: 0.0005% to 0.1000%; Bi: 0.0005% to 0.0200%; As: 0.001% to 0.100%; Zr: 0.01% to 1.00%; Co: 0.01% to 1.00%; Zn: 0.01% to 1.00%; W: 0.01% to 1.00%; and Sn: 0.01% to 0.05%.Cited by (0)
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