| 摘要 |
PURPOSE:To manufacture the titled thin steel sheet having excellent cold workability, by hot rolling steel contg. C, Si, Mn Cr, which are in a specific relation of composition, by finishing the steel sheet at a specific temp., by cooling the steel sheet under specific conditions, and by winding it at a specific temp. CONSTITUTION:A steel material consisting in wt% of 0.06-0.1 C, 0.8-.2 Si, 0.7-1.2 Mn, 0.8-1.2 Cr, <=0.03 P, <=0.01 S, 0.03-0.09 sol. Al, the balance being Fe and inevitable impurities, the composition satisfying the following relations: Mn/ Si<=1.05, 2.5-3.9XC%-1.3XMn%<=CR%<=3-3.9XC%-1.3XMn%, is hot rolled and finished at 780-860 deg.C temp. The cooling is performed at 15-25 deg.C/sec mean cooling rate from finish roll to winding, and at 25-45 deg.C/sec. cooling rate in temp. range <=750 deg.C. The winding is performed at 550-630 deg.C temp. |
