High-formability and super-strength cold-rolled steel sheet

Abstract

A high-formability and super-strength cold-rolled steel sheet and a manufacturing method thereof. The weight percentage of its components is: C 0.15-0.25%, Si 1.00-2.00%, Mn 1.50-3.00%, P≤0.015%, S≤0.012%, Al 0.03-0.06%, N≤0.008%, and the rest are Fe and inevitable impurities. The manufacturing method comprises the following steps: 1) smelting and casting; 2) heating to 1170˜1230° C. and performing thermal insulation; 3) performing hot rolling, the finish rolling temperature being 880±30° C., and coiling at 550˜650° C.; and 4) performing acid washing, cold rolling, and annealing, the cold rolling reduction being 40-60%, annealing at 860-920° C., and performing slow cooling to 690-750° C. with the cooling rate of 3˜10° C./s; performing rapid cooling at 240˜320° C., with the cooling speed ≥50° C./s, then heating to 360˜460° C., and performing thermal insulation for 100˜500 s to cool to the room temperature at last. Finally, a high-formability, low-rebound property and super-strength cold-rolled steel sheet with the yield strength of 600˜900 MPa, the tensile strength of 980˜1150 MPa, the elongation of 17˜25% is obtained.