METHOD OF MAKING COLD-REDUCED AL-KILLED STEEL STRIP FOR PRESS- FORMING BY CONTINUOUS CASTING AND CONTINUOUS ANNEALING PROCESS

摘要

1464232 Annealing steel sheet NIPPON KOKAN KK 13 Jan 1975 1420/75 Heading C7A Cold reduced steel strip suitable for pressforming operations contains in percentage by wt:- with a sol. Al:N ratio of 8:1 to 25:1 and is processed by continuous casting, hot-rolling, coiling at 680‹C, cold-rolling and continuous annealing with shelf treatment. Preferably the steel is subjected to decarburization by vacuum degassing and is coiled at 700-780‹C. A typical composition is:- while a preferred annealing cycle comprises heating to below 800‹C for 30-90 seconds, cooled to 550-650‹C at less than 30‹C/sec, quenched to ambient at more than 200‹C/sec, reheated to 300- 500‹C, slowly cooled within that range for 30- 180 seconds and then cooled. Alternatively the steel may be cooled directly to the intermediate treatment temperature.