| 摘要 |
PURPOSE: A high yield strength ratio type super high strength cold rolled steel sheet and a manufacturing method thereof are provided to have the high strength more than 980 MPa of tensile strength, to have a very low yield strength difference, and to have excellent the weldability and the bending workability. CONSTITUTION: A high yield strength ratio type super high strength cold rolled steel sheet with excellent weldability and bending workability are excellent includes 0.070-0.095 wt% of C, 0.05-0.50 wt% of Si, 2.0-2.4 wt% of Mn, 0.001-0.100 wt% of P, 0.01 wt% or less of S, 0.01-0.10 wt% of Sol.Al, 0.01 wt% or less of N, 0.5-1.0 wt% of Cr, 0.03-0.15 wt% of Mo, 0.001-0.006 wt% of B, 0.001-0.100 wt% of Sb, one or more kinds among 0.003-0.080 wt% of Ti and 0.003-0.080 wt% of Nb, and the rest of Fe and other unavoidable impurities. If the cold-rolled steel sheet satisfies Ceq less than 0.24, the weldability and the bending workability are excellent. Formula 1 : Ceq=C+Mn/20+Si/30+2P+4S. |
