| 摘要 |
PURPOSE:To manufacture a hot-rolled high-tension steel sheet having superior workability by adding a very small amount of Nb to a steel similar in composition to a C-Si-Mn steel for popular use. CONSTITUTION:The composition of a steel billet is composed of, by weight, 0.02-0.2% C, 0.3-1.5% Mn, <=1.5% Si, <=0.02% P, <=0.01% S, 0.008-0.025% Nb and the balance Fe with inevitable impurities. The billet is heated and subjected to continuous hot finish rolling at >=80% total draft and (Ar3+50 deg.C) final rolling pass temp. The resulting steel sheet is coiled at 300-550 deg.C. A hot-rolled high- tension steel sheet having superior workability is obtd. The steel sheet has a fine bainite-base composite structure consisting of bainite and ferrite. |
