	US 12,221,666 B2
	Steel sheet and method for producing same
Kengo Takeda, Tokyo (JP); Yuya Suzuki, Tokyo (JP); Toyomitsu Nakamura, Tokyo (JP); and Seiji Furusako, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/599,443
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Nov. 15, 2019, PCT No. PCT/JP2019/044956 § 371(c)(1), (2) Date Sep. 28, 2021, PCT Pub. No. WO2020/225936, PCT Pub. Date Nov. 12, 2020.
Claims priority of application No. 2019-088962 (JP), filed on May 9, 2019.
Prior Publication US 2022/0177994 A1, Jun. 9, 2022
Int. Cl. C21D 9/46 (2006.01); B22D 11/11 (2006.01); B32B 15/01 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/44 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/52 (2006.01); C22C 38/54 (2006.01); C22C 38/58 (2006.01); C23C 2/26 (2006.01)

CPC C21D 9/46 (2013.01) [B22D 11/11 (2013.01); B32B 15/013 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/007 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/021 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C21D 8/0273 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/44 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/52 (2013.01); C22C 38/54 (2013.01); C22C 38/58 (2013.01); C23C 2/26 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/004 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)]

7 Claims

1. A steel sheet having a chemical composition comprising, by mass %,

C: 0.050 to 0.300%,

Si: 0.01 to 2.00%,

Mn: 0.10 to 4.00%,

P: 0.0001 to 0.0200%,

S: 0.0001 to 0.0200%,

N: 0.0001 to 0.0200%,

Al: 0.001 to 1.000%,

Ti: 0.001 to 0.500%,

B: 0.0007 to 0.0100%,

Co: 0 to 0.50%,

Ni: 0 to 1.00%,

Mo: 0 to 1.00%,

Cr: 0 to 2.000%,

Nb: 0 to 0.500%,

V: 0 to 0.500%,

Cu: 0 to 0.500%,

W: 0 to 0.100%,

Ta: 0 to 0.100%,

Sn: 0 to 0.050%,

Sb: 0 to 0.050%,

As: 0 to 0.050%,

Mg: 0 to 0.0500%,

Ca: 0 to 0.050%,

Y: 0 to 0.050%,

Zr: 0 to 0.050%,

La: 0 to 0.050%,

Ce: 0 to 0.050%, and

a balance of Fe and impurities, wherein

the steel sheet comprises, by area ratio,

ferrite: 5.0 to 40.0%,

total of martensite and tempered martensite: 10.0 to 60.0%,

bainite: 5.0 to 40.0%, and

retained austenite: 5.0 to 25.0%,

the remaining structures comprise 10.0% or less of pearlite,

in a surface layer region down to a depth of 100 μm from the surface in the sheet thickness direction, (Fe, Mn)₂B precipitates having a circle equivalent diameter of 50 to 300 nm are present in a number density of 1/500 μm²or more.