| 摘要 |
PURPOSE:To manufacture an extra thin cold-rolled steel sheet causing no fracture, etc., in box annealing at low temp. and combining high ductility with high deep drawability, by subjecting a low-C low-alloy steel slab to hot rolling, winding, and pickling and then to primary cold rolling and recrystallization annealing under specific conditions and subsequently to secondary cold rolling and secondary annealing. CONSTITUTION:The steel slab consisting of, by weight, 0.001-0.006% C, 0.03-0.25% Mn, 0.001-0.015% S, 0.02-0.07% Al, 0.002-0.007% N, 0.0010-0.0050% O, and the balance Fe with inevitable impurities is subjected to hot finish rolling at a finishing temp. of Ar3 point or above. The above plate is wind up at ordinary temp. and pickled, which is subjected to primary cold rolling at 30-85% cold draft and then to recrystallization annealing in the successive primary annealing, followed by secondary cold rolling at 80-95% cold draft and secondary annealing at 550-650 deg.C. In this way, the cold-rolled steel sheet of <=about 0.5mm thickness having high work hardening index and excellent in ductility and deep drawability can be obtained.
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