Method for producing steel sheet for cold rolling and method for producing cold-rolled steel sheet

Abstract

A method for manufacturing a steel sheet for cold rolling, including hot-rolling a slab so that an outlet temperature of a finishing rolling mill is 800° C. or higher and 940° C. or lower, cooling at least a portion of the hot-rolled steel sheet, at a water volume density of 100 L/min/m2 or more for 0.1 seconds or more, within 3.0 seconds after passing through a final stand of the finishing rolling mill and being sent out on a run-out table, and coiling, at a coiling temperature of 550° C. or higher, the cooled hot-rolled steel sheet.

1 . A method for manufacturing a steel sheet for cold rolling, the method comprising:
 hot-rolling a slab having a chemical composition containing:   C: 0.15% by mass or more and 0.25% by mass or less,   Si: 0.8% by mass or more and 3.0% by mass or less,   Mn: 1.8% by mass or more and 3.0% by mass or less,   Ni, Cu, Cr, and Mo: 1.0% by mass or less (including 0% by mass),   Ti, Nb, V: 1.0% by mass or less (including 0% by mass), and   B: 0.01% by mass or less (including 0% by mass),   so that an outlet temperature of a finishing rolling mill is 800° C. or higher and 940° C. or lower;   cooling at least a portion of the hot-rolled steel sheet, at a water volume density of 100 L/min/m 2  or more for 0.1 seconds or more, within 3.0 seconds after passing through a final stand of the finishing rolling mill and being sent out on a run-out table; and   coiling, at a coiling temperature of 550° C. or higher, the cooled hot-rolled steel sheet.   
     
     
         2 . The method for manufacturing a steel sheet for cold rolling according to  claim 1 , wherein the slab further contains:
 P: 0.1% by mass or less (including 0% by mass),   S: 0.01% by mass or less (including 0% by mass),   Al: 0.10% by mass or less (including 0% by mass), and   N: 0.01% by mass or less (including 0% by mass).   
     
     
         3 . A method for manufacturing a cold-rolled steel sheet, comprising cold-rolling a steel sheet manufactured by the method according to  claim 1  at a rolling rate of 30% to 80%.