Kobe Steel, Ltd.

Sae Hamamoto

Tatsuya Asai

Yukihiro Utsumi

Yuichi Futamura

Tetsuji Hoshika

Atsuhiro Shiraki

Haruka Araki

Kenji Saito

Keisuke Nakata

A cold-rolled steel sheet has a chemical composition of C: 0.12% to 0.3%, Si: 0.5% or less, Mn: less than 1.5%, Al: 0.15% or less, N: 0.01% or less, P: 0.02% or less, and S: 0.01% or less, with the remainder including iron and inevitable impurities and has a martensite single-phase structure as its steel microstructure. In a surface region of the steel sheet from the surface to a depth one-tenth the gauge, the number density of n-ary groups of inclusions determined by specific n-th determinations is 120 or less per 100 cmof a rolling plane, where the distance in steel sheet rolling direction between outermost surfaces of two outermost particles of the group of inclusions is 100 &#x3bc;m or more. The steel sheet is a high-strength cold-rolled steel sheet which has a sufficiently minimized rate of bending fracture starting from inclusions and thereby has excellent bending workability.

High-strength cold-rolled steel sheet excellent in bending workability

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Kakogawa, Japan

Sae Hamamoto