Patent ID: 11926881
Assignee: JFE STEEL CORPORATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B  Y | IPC B  C

Claim 0:
1. A high-strength cold-rolled steel sheet having a chemical composition comprising, by mass %:
C: 0.10 to 0.30%;
Si: 0.50 to 2.00%;
Mn: 2.5 to 4.0%;
P: 0.050% or less;
S: 0.020% or less;
Al: 0.10% or less;
N: 0.01% or less;
Ti: 0.100% or less;
B: 0.0003 to 0.0030%; and
the balance being Fe and incidental impurities,
wherein N and Ti satisfy formula (1):

([N]/14)/([Ti]/47.9)<1  (1)

where [N] and [Ti] are contents, by mass %, of N and Ti, respectively,

a total area fraction of martensite and bainite is 95% or more,
a number density of bainite grains having an area of 3 μm2 or more and a carbon concentration of less than 0.7[C] is 1200 grains/mm2 or less, where [C] is a content, by mass %, of C, and
the steel sheet has a hole expansion ratio of 30% or more.