| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To highly efficiently produce a cold-rolled steel sheet excellent in deep drawability. <P>SOLUTION: A steel ingot or a steel billet is prepared, which contains, by mass%, less than 0.010% of C, 1.5% or less of Si, 2.0% or less of Mn, 0.10% or less of P, 0.010% or less of S, 0.0005-0.10% of Al, 0.0060% or less of N, 0.001-0.10% of Ti, and 0.001-0.10% of Nb, while satisfying the relation: (C/12+N/14+S/32)/(Ti/48+Nb/93)≤1.4, and the balance comprising Fe and impurities. The steel ingot or steel billet is subjected to: hot-rolling to be completed at a temperature of (Ar<SB POS="POST">3</SB>point-30°C) or higher; cooling to 750°C at an average cooling rate of 400°C/sec or more within a period of 0.5 second after completion of the hot-rolling; pickling after coiling at a temperature of 400°C or higher and lower than 640°C; cold-rolling with a rolling reduction of 60-95%; and annealing at a temperature of 750-880°C. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
