| 摘要 |
PURPOSE:To considerably increase the press formability of a cold rolled steel plate, at the time of continuously annealing said steel plate, by heating the steel plate to above its recrystallization temperature and holding the same at this temperature, then subjecting the same to cooling and overaging treatment under the specific conditions. CONSTITUTION:A cold rolled steel plate is put into a continuous annealing furnace, where it is quickly heated up to a temperature above its recrystallization temperature and below its A1 transformation point, after which it is slowly heated at a rate of <=20 deg.C/sec. from the A1 transformation point up to 850 deg.C. Or it is quickly heated up to the recrystallization temperature-850 deg.C and is held at these temperatures for a fixed time. Next, at the time of cooling, it is slowly cooled at cooling rates of 5- 40 deg.C/sec. down to 650 deg.C-A1 transformation point, after which it is quenched by contact cooling with water-cooled rolls, water spray cooling or cooling with boiling water, at cooling rates of 50-500 deg.C/sec. down to overaging initiation tempratures of 500-600 deg.C. Following to this, it is continuously or stepwise cooled down to 250-400 deg.C at cooling rates of 10-100 deg.C/min. and is thereby overaged. |
