| 摘要 |
PURPOSE:To manufacture a cold rolled steel sheet having superior deep drawability by hot rolling and cold rolling an Al killed steel contg. specified amts. of C and Mn, repeatedly heating and cooling the cold rolled steel sheet under specified conditions in a continuous annealing furnace, cooling the steel sheet to a specified temp. and overaging it. CONSTITUTION:An Al killed steel contg., by weight, 0.007-0.1% C, 0.1-0.5% Mn, about 0.010-0.030% sol. Al, <=about 0.007% N, <=about 0.020% each of P and N is hot rolled and cold rolled. The cold rolled steel sheet is uniformly heated to a temp. at which gamma-iron accounts for 30-90vol% in the alpha+gamma range and it is cooled to a temp. in the alpha range. After the heating and cooling are repeated twice or more in a continuous annealing furnace, the steel sheet is cooled to 300-500 deg.C and overaged. Thus, a cold rolled low-C Al killed steel sheet having superior deep drawability is manufactured at a low cost.
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