Patent ID: 6692584
Filing Date: 2004-02-17
Classification: C21D,C22C

Abstract:
A high tensile cold-rolled steel sheet which has superior ductility and strain age-hardening characteristics having a &Dgr;TS of 50 MPa or more, having a composition comprising, on a mass % basis,0.05% to 0.30% of C, 0.4% to 2.0% of Si, 0.7% to 3.0% of Mn, 0.08% or less of P, 0.02% or less of Al, and 0.0050% to 0.0250% of N, wherein N/Al is 0.3 or more, 0.0010% or more of N in a solid-solution state is contained, and the balance is Fe and unavoidable impurities, and the high tensile cold-rolled steel sheet has a composite structure comprising 20% to 80% of a ferrite phase, 10% to 60% of a bainite phase, and 3.0% or more of a residual austenite phase.