METHOD FOR MANUFACTURING HIGH STRENGTH STEEL STRIPS WITH SUPERIOR FORMABILITY AND EXCELLENT COATABILITY

摘要

A method for manufacturing a steel sheet used for structural members, elements, etc. of au¬ tomobiles, such as a variety of members of automobiles including a front side member, pillar, and the like, and more particularly, a method for manufacturing a steel sheet having a high strength and formability as well as hot-dip galvanizing properties is disclosed. In the method, after an aluminum killed steel slab, which comprises, 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; 0.02% 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, is subjected to a homogenization treatment at a temperature range of 10500C to 13000C, the aluminum killed steel slab is subjected to a hot rolling under a finishing hot rolling temperature of 85O0C to 95O0C and a coiling temperature of 4000C to 7000C, followed by a cold rolling under a cold rolling reduction ratio of 30% to 80%, and annealing the cold rolled steel sheet.