| 摘要 |
PURPOSE:To manufacture a high-tensile hot-rolled steel plate excellent in deep drawability, by subjecting a steel having a specific composition consisting of C, Mn, S, Si, P, Ti, Nb, and Fe to soaking, rolling and precipitation treatment of TiC or NbC under specific conditions. CONSTITUTION:A steel having a composition which consists of, by weight, <=0.015% C, 0.3-1.5% Mn, <=0.02% S, 0.2-1.5% Si, 0.02-0.15% P, and the balance Fe with inevitable impurities and further contains, if necessary, 0.0005-0.005% B and to which <=0.2% Ti and/or <=0.3% Nb is added so that C/12<(Ti*/48+Nb/93)<3XC/12 (where Ti*=Ti-48/14.N-48/32.S) is satisfied is soaked to 950-1,250 deg.C and roughed. Subsequently, the roughed steel plate is subjected to precipitation treatment of TiC or NbC so as to reduce the quan tity of solid-solution C. Then, while applying lubrication at 500-800 deg.C, warm rolling is applied at 60-95% total draft to control crystal orientation, followed by winding, pickling, and annealing treatment. In this way, superior deep drawability and high tensile strength can be obtained.
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