US 11,913,087 B2
High-strength steel sheet and method for producing same
Fusae Shiimori, Tokyo (JP); Hayato Saito, Tokyo (JP); Nobusuke Kariya, Tokyo (JP); and Katsumi Kojima, Tokyo (JP)
Assigned to JFE STEEL CORPORATION, Tokyo (JP)
Appl. No. 16/754,138
Filed by JFE STEEL CORPORATION, Tokyo (JP)
PCT Filed Oct. 29, 2018, PCT No. PCT/JP2018/040182
§ 371(c)(1), (2) Date Apr. 7, 2020,
PCT Pub. No. WO2019/088044, PCT Pub. Date May 9, 2019.
Claims priority of application No. 2017-211181 (JP), filed on Oct. 31, 2017.
Prior Publication US 2020/0332383 A1, Oct. 22, 2020
Int. Cl. C21D 9/46 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01); C22C 38/26 (2006.01); C22C 38/28 (2006.01); C22C 38/32 (2006.01)
CPC C21D 9/46 (2013.01) [C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/12 (2013.01); C22C 38/14 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C22C 38/32 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)] 5 Claims
 
1. A high-strength steel sheet comprising a chemical composition containing, in mass %,
C: 0.03% or more and 0.15% or less,
Si: 0.01% or more and 0.05% or less,
Mn: more than 0.6% and 1.5% or less,
P: 0.025% or less,
S: 0.02% or less,
Al: 0.01% or more and 0.088% or less,
N: 0.0005% or more and 0.0100% or less,
Ti: 0.005% or more and 0.020% or less,
B: 0.0005% or more and 0.0100% or less,
Nb: 0.005% or more and 0.020% or less, and
optionally at least one selected from the group consisting of
Cr: 0.005% or more and 0.100% or less,
Ni: 0.005% or more and 0.150% or less, and
Mo: 0.005% or more and 0.050% or less,
with the balance being Fe and inevitable impurities, wherein
the high-strength steel sheet has a metallic structure consisting of, in area ratio, 90% or more and 99% or less of ferrite and 1% or more and 10% or less of martensite, the martensite has a maximum grain size of 5 μm or less, and a ratio of martensite having a grain size of 2 μm or less is 80% or more,
the high-strength steel sheet has a tensile strength of 512 MPa or more, and
the high-strength steel sheet has a sheet thickness of 0.1 to 0.8 mm.