| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method of producing a high strength cold rolled steel sheet having more excellent ductility and formability than the conventional TRIP(TRransformation Induced Plasticity) steel. <P>SOLUTION: The method of producing the high strength cold rolled steel sheet, applies a hot rolling process, a cold rolling process, an annealing process and a tempering process to steel containing, by mass%, 0.05-0.40% C, 0.20-3.0% Si, 0.01-2.8% Al, 0.5-3.0% Si+Al, 1.0-5.0% Mn and the balance Fe with inevitable impurities, thereby producing the high strength cold rolled steel sheet. In the method, the annealing process includes: a process of heating the steel sheet to a temperature between Ac<SB POS="POST">1</SB>point or higher and 1,000°C or lower and holding it at the temperature for 10-300 sec; a process of cooling the steel sheet to a temperature of >500°C at an average cooling rate of 2°C/sec to <10°C/sec and successively, cooling the steel sheet to 200-500°C at an average cooling rate of≥20°C/sec; a process of holding the steel sheet at the temperature range of 200-600°C for≥10 sec; and a process of cooling the steel sheet to≤100°C at an average cooling rate of 2°C/sec, and the tempering process includes a process of heating the steel sheet to a temperature of 200-600°C and holding it at the temperature for a prescribed time. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
