Patent ID: 11946112
Assignee: JFE STEEL CORPORATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B | IPC C

Claim 5:
6. A method for producing a high-strength steel sheet, the high-strength steel sheet being the high-strength steel sheet according to claim 2, the method comprising:
a casting step in which, after completion of refining, which is carried out in an RH vacuum degasser with a circulation time of 500 seconds or more, continuous casting is performed in a manner such that a difference between a casting temperature and a solidification temperature is 10° C. or greater and 35° C. or less, a flow rate of molten steel at a solidification interface near a mold meniscus is 0.5 to 1.5 m/min, and the steel is passed through a bending section and a straightening section at a temperature of 550° C. or higher and 1050° C. or lower;
a hot rolling step in which a steel starting material obtained in the casting step is heated directly after the casting step or after cooling to a temperature of 1220 to 1300° C. and held for 80 minutes or more; and hot rolling is performed in a manner such that an amount of reduction for a first pass of rough rolling is 10% or greater, and an amount of reduction for a first pass of finish rolling is 20% or greater;
a cold rolling step in which, after a hot-rolled steel sheet obtained in the hot rolling step is pickled, the hot-rolled steel sheet is subjected to cold rolling; and
an annealing step in which a cold-rolled steel sheet obtained in the cold rolling step is annealed.