PRODUCTION OF EXTRA THIN COLD-ROLLED SOFT STEEL PLATE HAVING EXCELLENT DUCTILITY AND DEEP DRAWABILITY BY LOW TEMPERATURE BOX ANNEALING

摘要

PURPOSE:To obtain an extra thin cold-rolled soft steel plate having excellent ductility and deep drawability by containing the specific quantities of C, Mn, S, Al, N, and O in a steel slab, hot-rolling this steel slab, cold-rolling primarily it at the specific cold-rolling rate, cold-rolling secondarily it at the specific cold-rolling rate and next executing control-annealing to it. CONSTITUTION:The composition of steel slab is wt% of 0.001-0.006% C, 0.03-0.25% Mn, 0.001-0.015% S, 0.002-0.015% Al, 0.002-0.007% N, 0.001-0.005% O and remaining part of Fe with inevitable impurities. This steel slab is finished under hot- rolling at Ar3 point or more for the finishing temp. and wound at 650-750 deg.C winding temp. and acid pickling is executed to the hot-rolled coil obtd. Next, the primary cold-rolling is executed at 30-85% the cold-rolling rate and the primary annealing is executed by open coil annealing. In succession, the secondary cold-rolling is executed at 60-95% the cold-rolling rate and the secondary annealing is executed at 550-650 deg.C by tight coil annealing (the low temp. box annealing). By this method, the extra thin (=0.5mm) cold-rolled steel plate having high ductility and deep drawability is obtd.