| 摘要 |
PURPOSE:To produce a cold rolled steel plate of beautiful surfaces for deep drawing through continuous annealing treatment of an extremely short time, at the time of continuously annealing a cold rolled steel plate, by performing the over-aging treatment during the process in a reducing atmosphere and at specific temperatures. CONSTITUTION:A cold rolled steel plate is fed into a continuous annealing furnace of a jet flow direct firing system, where it is quickly heated at heating rates of >= 40 deg.C/sec. Next, it is held for a short time of <=30sec in a reducing atmosphere at 700-800 deg.C temperatures to reduce the oxide film having been formed at the hating. Upon ending of the above-mentioned heating and soaking treatment, it is subjected to primary cooling from near 600 deg.C down to near over aging treatment temperature at cooling rates of <=50 deg.C/sec. Next, the over aging treatment is started from a 520-550 deg.C temperature region in a reducing atmosphere. Finally, it is water-cooled from the over aging treatment temperature down to <=300 deg.C, and further, if necessary, it is slowly cooled from <=90 deg.C down to <=40 deg.C. |
