Patent ID: 11965223
Assignee: JFE STEEL CORPORATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. A steel sheet comprising:
a component composition containing
C: 0.10% to 0.35%,
Si: 0.01% to 2.0%,
Mn: 0.8% to 2.35%,
P: 0.05% or less,
S: 0.005% or less,
Al: 0.005% to 0.10%, and
N: 0.0060% or less on a mass basis,
the balance being Fe and inevitable impurities; and
a steel structure which has a ferrite area fraction of 30% or less including 0%, a bainite area fraction of 5% or less including 0%, a martensite and tempered martensite area fraction of 70% or more including 100%, and a retained austenite area fraction of 2.0% or less including 0% and in which the ratio of the dislocation density in the range of 0 μm to 20 μm from a surface of the steel sheet to the dislocation density of a through-thickness central portion of the steel sheet is 90% to 110% and the average of the top 10% of the sizes of cementite grains located in a depth of up to 100 μm from a surface of the steel sheet is 300 nm or less,
wherein a maximum camber of the steel sheet sheared to a length of 1 m in a longitudinal direction of the steel sheet is 15 mm or less.