	US 12,435,401 B2
	Steel material
Keiichi Kondo, Tokyo (JP); Yuji Arai, Tokyo (JP); Keiichi Nakamura, Tokyo (JP); Taro Oe, Tokyo (JP); Takenori Kuramoto, Tokyo (JP); Yosuke Takeda, Tokyo (JP); and Hiroki Kamitani, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/995,368
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Apr. 15, 2021, PCT No. PCT/JP2021/015628 § 371(c)(1), (2) Date Oct. 3, 2022, PCT Pub. No. WO2021/210655, PCT Pub. Date Oct. 21, 2021.
Claims priority of application No. 2020-073017 (JP), filed on Apr. 15, 2020.
Prior Publication US 2023/0203631 A1, Jun. 29, 2023
Int. Cl. C22C 38/54 (2006.01); C21D 9/08 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01)

CPC C22C 38/54 (2013.01) [C21D 9/08 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C21D 2211/001 (2013.01)]

8 Claims

1. A steel material consisting of, in mass %,

C: 0.15 to 0.45%,

Si: 0.05 to 1.00%,

Mn: 0.05 to less than 0.80%,

P: 0.030% or less,

S: 0.0100% or less,

Al: 0.100% or less,

Cr: 0.30 to 1.50%,

Mo: 0.25 to 2.00%,

Ti: 0.001 to 0.015%,

N: 0.0100% or less,

O: 0.0050% or less,

V: 0 to 0.05%,

Nb: 0 to 0.010%,

B: 0 to less than 0.0005%,

Ca: 0 to 0.0100%,

Mg: 0 to 0.0100%,

rare earth metal: 0 to 0.0100%,

Ni: 0 to 0.50%, and

Cu: 0 to 0.50%,

with the balance being Fe and impurities,

wherein:

a grain size number of prior-austenite grains is less than 7.0;

on a precondition that a content of each element is within a range described above, Formula (1) to Formula (4) are satisfied;

a yield strength is 896 MPa or more; and

an absorbed energy at −10° C. is 95 J or more:

{C+Mn/5+(Cu+Ni)/15+(Cr+Mo+V)/5+10×B}×(7.0/GN)^0.45≥0.678 (1)

{Mn/5.5+10×Ti+1.2×V+15×Nb+200×B}×(7.0/GN)^0.45≤0.240 (2)

10×Ti+V+10×Nb≥0.015 (3)

(10×Ti+1.2×V+30×Nb)/Mo≤0.205 (4)

where, a content in mass % of a corresponding element is substituted for each symbol of an element, and the grain size number is substituted for “GN”.