	US 12,392,020 B2
	Hot-rolled steel sheet
Kazumasa Tsutsui, Tokyo (JP); Hiroshi Shuto, Tokyo (JP); and Koutarou Hayashi, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/790,645
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Dec. 11, 2020, PCT No. PCT/JP2020/046322 § 371(c)(1), (2) Date Jul. 1, 2022, PCT Pub. No. WO2021/153036, PCT Pub. Date Aug. 5, 2021.
Claims priority of application No. 2020-010945 (JP), filed on Jan. 27, 2020.
Prior Publication US 2023/0047602 A1, Feb. 16, 2023
Int. Cl. C22C 38/50 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/08 (2006.01); C22C 38/10 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01); C22C 38/16 (2006.01); C22C 38/44 (2006.01); C23C 2/06 (2006.01); C23C 2/28 (2006.01); C23C 2/40 (2006.01)

CPC C22C 38/50 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/008 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/08 (2013.01); C22C 38/10 (2013.01); C22C 38/12 (2013.01); C22C 38/14 (2013.01); C22C 38/16 (2013.01); C22C 38/44 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C23C 2/06 (2013.01); C23C 2/28 (2013.01); C23C 2/40 (2013.01)]

4 Claims

1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %:

C: 0.040% to 0.250%;

Si: 0.05% to 3.00%;

Mn: 0.50% to 4.00%;

sol. Al: 0.001% to 2.000%;

P: 0.100% or less;

S: 0.0300% or less;

N: 0.1000% or less;

O: 0.0100% or less;

Ti: 0% to 0.300%;

Nb: 0% to 0.100%;

V: 0% to 0.500%;

Cu: 0% to 2.00%;

Cr: 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 0.020%;

one or two or more of Zr, Co, Zn, or W: 0% to 1.00% in total;

Sn: 0% to 0.050%; and

a remainder comprising of Fe and impurities, wherein a metallographic structure contains, by area %, more than 92.0% and 100.0% or less of martensite and tempered martensite in total, less than 3.0% of residual austenite, and less than 5.0% of ferrite,

has a ratio S₆₀/S₇, which is a ratio of a density S₆₀of a length of a grain boundary having a crystal misorientation of 60° to a density S₇of a length of a grain boundary having a crystal misorientation of 7° about a <110> direction, of more than 0.34 and less than 0.60,

has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 980 MPa or more.