Patent ID: 6652670
Filing Date: 2003-11-25
Classification: C21D,C22C

Abstract:
A method for manufacturing a steel sheet comprising the steps of:(a) rough-rolling a continuously cast slab containing C in an amount consisting essentially of 0.8% or less by weight to form a sheet bar; (b) finish-rolling the sheet bar from step (a) at a finishing temperature of (Ar3 transformation pointâ€”20Â° C.) or more to form a steel strip; (c) rapidly cooling the steel strip from step (b) in a primary cooling step after completion of the finish-rolling at a cooling speed of 200Â° C./sec or more to a temperature of from 500 to 800Â° C.; (d) cooling the cooled steel strip from the primary cooling step (c) in a secondary cooling step at a cooling speed of less than 60Â° C./sec; and (e) coiling the cooled steel strip from the secondary cooling step (d) at a coiling temperature of from 400 to 750Â° C. to form a coiled steel sheet.