| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high-strength cold-rolled steel sheet in which fracture starting from inclusions is suppressed in bending, and which has excellent bending workability. <P>SOLUTION: In the high-strength cold-rolled steel sheet excellent in bending workability, a steel sheet has a composition satisfying 0.05-0.3% C, 3.0% or less Si (excluding 0%), 1.5-3.5% Mn, 0.1% or less P (excluding 0%), 0.05% or less S (excluding 0%), and 0.15% or less Al (excluding 0%), with the remainder including iron and inevitable impurities, the steel structure is a composite structure including a ferrite structure and a martensite-containing second phase, and, in a surface region from a surface to a depth one-tenth the gage of the steel sheet, the number density of n-ary groups of inclusions is 120 or less per 100 cm<SP>2</SP>of a rolling plane, in which each of the n-ary groups of inclusions is determined by an n-th determination as specified, and, in each of the n-ary groups of inclusions, the distance in a steel sheet rolling direction between outermost surfaces of two outermost particles of the n-ary group of inclusions is 80μm or more. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
