| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-tensile strength cold-rolled steel sheet superior in elongation and formability for extension flange, particularly, having a TS of 980 MPa or higher, an elongation of 16% or higher, and a hole expansion rate of 50% or more, which is an evaluation index for formability for extension flange, and further having the small dispersion of elongation characteristics in a sheet width direction. SOLUTION: This cold-rolled steel sheet has a composition comprising 0.08-0.15 mass% C, 1.6-3.0 mass% Si, 2.0-3.5 mass% Mn, 0.015 mass% or less P, 0.005 mass% or less S, 0.05 mass% or less Al and the balance Fe with unavoidable impurities; and has a structure comprising a ferrite of 65%-85% by an area rate and the balance a tempered martensite. COPYRIGHT: (C)2004,JPO&NCIPI
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