Patent ID: 8221564
Filing Date: 2012-07-17
Classification: C21D,C22C

Abstract:
1. A method for manufacturing a steel sheet having high strength and formability and being suitable for hot dip galvanizing, comprising: performing a homogenization treatment on an aluminum killed steel slab at a temperature of 1050° C. to 1300° C., the aluminum killed steel slab comprising, by weight %: C: 0.05% to 0.25%; Si: 0.1% to 1.5%; S: 0.02% or less; N: 0.01% or less; Al: 0.455% to 2.0%; Mn: 1.0% to 2.5%; P: 0.001% to 0.1%; Sb: 0.005% to 0.10%; the balance of Fe and other unavoidable impurities; hot rolling the aluminum killed steel slab under a finishing hot rolling temperature of 850° C. to 950° C. and a coiling temperature of 400° C. to 700° C., to form a hot rolled steel sheet; cold rolling the hot rolled steel sheet under a cold rolling reduction ratio of 30% to 80% and annealing the cold rolled steel sheet at a temperature of 700° C. to 870° C., and then cooling the annealed steel sheet to a temperature range of 620° C. to 700° C. at a cooling rate of 1 to 7° C./sec, the steel sheet having a microstructure consisting of ferrite and austenite.