| 摘要 |
PURPOSE:To obtain a cold rolled steel strip having excellent deep drawability without any development of rough surface by controlling the cooling velocity in the specific temp. range after solidifying in a continuous casting process under a specific steel composition, to omit the hot rolling process. CONSTITUTION:Molten steel composing of wt% of 0.0010-0.080% C, 0.05-1.0% Mn, 0.005-0.30% Si, 0.003-0.10% P, <=0.020% S, 0.005-0.070% sol.Al, 0.0010-0.0070% N, 0.0003-0.0030% B, <=0.080% Ti under satisfying Ti >=3.42N+1.5S+4C and further containing 0.003-0.050% Nb and the balance of Fe and inevitable impurities, is continuously cast. The obtd. cast strip having <=10mm thickness is cooled at >=V( deg.C/s) cooling velocity for 950-750 deg.C after solidification. Next, after winding it is cold-rolled and annealed. Herein, V( deg.C /s)=5.0X10<-4>/(Nb%XB%).
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