Patent ID: 11965225
Assignee: ARCELORMITTAL
Field: Materials, metallurgy (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. A cold-rolled and heat treated steel sheet, made of a steel having a composition comprising, by weight percent:
0.1%≤C≤0.4%
3.5%≤Mn≤8.0%
0.1%≤Si≤1.5%
Al≤3%
Mo≤0.5%
Cr≤1%
Nb≤0.1%
Ti≤0.1%
V≤0.2%
B≤0.004%
0.002%≤N≤0.013%
S≤0.003%
P≤0.015%,
a remainder being iron and unavoidable impurities,
the cold-rolled and heat-treated steel sheet having a structure consisting of, in surface fraction:
between 8 and 50% of retained austenite;
at most 80% of intercritical ferrite, ferrite grains of the intercritical ferrite having an average size of at most 1.5 μm;
at most 1% of cementite, wherein particles of the cementite have an average size lower than 50 nm; and
martensite and/or bainite.