US 2026/0218356 A1Published application

Steel material suitable for use in sour environment

AssigneeNippon Steel Corporation

InventorsShinji YOSHIDA, Yuji ARAI, Kuniaki ITOH, Takuya OKAMURA

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Abstract

The steel material according to the present disclosure has the chemical composition described in the description, and a yield strength of 862 MPa or more, and satisfies Formulae (1) to (4). In the steel material, a number density NDF of precipitates having an equivalent circular diameter of 20 to 150 nm is 0.650/μm2 or more, and a number density NDC of precipitates having an equivalent circular diameter of 250 nm or more is 0.290/μm2 or less. ( 0.157 × C - 0.0006 × Cr - 0.0098 × Mo - 0.0482 × V + 0.0006 ) / θ Cr ≤ 0.3 ( 1 ) ( 1 + 263 × C - Cr - 16 × Mo - 80 × V ) / ( 98 - 358 × C + 159 × Cr + 15 × Mo + 96 × V ) ≤ 0.355 ( 2 ) - 9.7 × Mn - 104 × S + 0.8 × Mo + 0.08 × Ni 2 - 4.1 × Ni - 5.1 × Ti ≥ - 9. ( 3 ) 15.8 × Si - 33.8 × Mn - 28.8 × Ni ≥ - 51. ( 4 )

A steel material consisting of, in mass %,

C:
more than 0.20 to 0.35%,
Si:
0.05 to 1.50%,
Mn:
0.02 to 1.00%,
P:
0.025% or less,
S:
0.0100% or less,
Al:
0.005 to 0.100%,
Ni:
more than 0.10 to 2.50%,
Cr:
0.40 to 1.50%,
Mo:
0.30 to 1.50%,
Ti:
0.002 to 0.050%,
B:
0.0001 to 0.0050%,
N:
0.0100% or less,
O:
0.0100% or less,
V:
0 to 0.60%,
Nb:
0 to 0.030%,
Ca:
0 to 0.0100%,
Mg:
0 to 0.0100%,
Zr:
0 to 0.0100%,
rare earth metal:
0 to 0.0100%,
Co:
0 to 0.50%,
W:
0 to 0.50%,
Cu:
0 to 0.50%, and
the balance being Fe and impurities,
wherein:
a yield strength is 862 MPa or more,
a Cr concentration in precipitates having an equivalent circular diameter of 20 nm or more is defined as “θCr”,
within ranges of contents of elements of the steel material, the contents of elements of the steel material and a Cr concentration θCr in precipitates having an equivalent circular diameter of 20 nm or more satisfy Formulae (1) to (4), and
in the steel material:
a number density NDF of precipitates having an equivalent circular diameter of 20 to 150 nm is 0.650/μm2 or more, and
a number density NDC of precipitates having an equivalent circular diameter of 250 nm or more is 0.290/μm2 or less:
(
0.157
×
C
-
0.0006
×
Cr
-
0.0098
×
Mo
-
0.0482
×
V
+
0.0006
)
/
θ
Cr
≤
0.3
(
1
)
(
1
+
2
⁢
6
⁢
3
×
C
-
Cr
-
1
⁢
6
×
Mo
-
80
×
V
)
/
⁢
(
98
-
358
×
C
+
1
⁢
5
⁢
9
×
Cr
+
15
×
Mo
+
9
⁢
6
×
V
)
≤
0
.
3
⁢
55
(
2
)
-
9.7
×
Mn
-
104
×
S
+
0.8
×
Mo
+
0.08
×
Ni
2
-
4.1
×
Ni
-
5.1
×
Ti
≥
-
9.
(
3
)
15.8
×
Si
-
33.8
×
Mn
-
28.8
×
Ni
≥
-
51.
(
4
)
where, a content in units of percent by mass of a corresponding element is substituted for each symbol of an element in Formulae (1) to (4), and if a corresponding element is not contained, “0” is substituted for the symbol of the relevant element, and a Cr concentration in units of mass fraction in precipitates having an equivalent circular diameter of 20 nm or more is substituted for θCr in Formula (1).

184 more elements

Abstract

Claims8