	US 11,891,680 B2
	Steel material suitable for use in sour environment
Yohei Otome, Tokyo (JP); Hiroki Kamitani, Tokyo (JP); Atsushi Soma, Tokyo (JP); Taro Oe, Tokyo (JP); Nobuaki Komatsubara, Tokyo (JP); Yuji Arai, Tokyo (JP); and Hideki Takabe, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/414,727
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Feb. 13, 2020, PCT No. PCT/JP2020/005642 § 371(c)(1), (2) Date Jun. 16, 2021, PCT Pub. No. WO2020/166675, PCT Pub. Date Aug. 20, 2020.
Claims priority of application No. 2019-025200 (JP), filed on Feb. 15, 2019.
Prior Publication US 2022/0042148 A1, Feb. 10, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/32 (2006.01); C21D 8/10 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/20 (2006.01); C22C 38/22 (2006.01); C22C 38/24 (2006.01); C22C 38/26 (2006.01); C22C 38/28 (2006.01); C22C 38/30 (2006.01); C22C 38/40 (2006.01); C21D 1/25 (2006.01); C22C 38/44 (2006.01)

CPC C22C 38/32 (2013.01) [C21D 1/25 (2013.01); C21D 8/105 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/20 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C22C 38/30 (2013.01); C22C 38/40 (2013.01); C22C 38/44 (2013.01); C21D 2211/001 (2013.01)]

10 Claims

1. A steel material comprising:

a chemical composition consisting of, in mass %:

C: 0.15 to 0.45%,

Si: 0.05 to 1.00%,

Mn: 0.01 to 1.00%,

P: 0.030% or less,

S: 0.0050% or less,

Al: 0.005 to 0.100%,

Cr: 0.55 to 1.10%,

Mo: 0.70 to 1.00%,

Ti: 0.002 to 0.020%,

V: 0.05 to 0.30%,

Nb: 0.002 to 0.100%,

B: 0.0005 to 0.0040%,

N: 0.0100% or less,

O: less than 0.0020%,

Ca: 0 to 0.0100%,

Mg: 0 to 0.0100%,

Zr: 0 to 0.0100%,

rare earth metal: 0 to 0.0100%,

Cu: 0 to 0.50%,

Ni: 0 to 0.50%,

Co: 0 to 0.50%, and

W: 0 to 0.50%,

with the balance being Fe and impurities,

and satisfying Formula (1),

wherein

in the steel material, a grain diameter of a prior-austenite grain is 15.0 μm or less,

an average area of precipitate which is precipitated in a prior-austenite grain boundary is 12.5×10⁻³μm²or less, and

a yield strength is 758 to 862 MPa:

Mo/Cr≥1.90 (1)

where, content in mass % of a corresponding element is substituted for each symbol of an element in Formula (1).