HOT-ROLLED STEEL FOR HYDROFORMING WITH HIGH STRENGTH AND EXCELLENT WORKABILITY AND METHOD OF MANUFACTURING THE SAME

摘要

PURPOSE: A high strength hot-rolled steel sheet with high strength and formability for hydroforming and a manufacturing method thereof are provided to improve both the strength and elongation ratio of a hot-rolled steel sheet and reduce the yield strength as well. CONSTITUTION: A method for manufacturing a high strength hot-rolled steel sheet with high strength and formability for hydroforming comprises a step of hot rolling a slab to an FDT of 870-910°C(S110) and a step of cooling and coiling the hot rolled sheet at a CT(Coiling Temperature) of 620-660°C(S120). The slab comprises carbon of 0.08-0.10 weight%, silicon of 0.030 weight% or less, manganese of 0.40-0.60 weight%, aluminum of 0.020-0.050 weight%, nitrogen of 40ppm or less, and iron and inevitable impurities of the remaining amount.