Patent ID: 11732321

Abstract:
Provided are: a steel sheet having a high strength and excellent stretch formability; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which the integration degree of the (111)<112> orientation of ferrite is 3.0 or higher, and the integration degree of the (252)<2-11> orientation of martensite and tempered martensite is 5.0 or lower. The method of producing the steel sheet includes: the step of continuously casting a molten steel having the prescribed chemical composition, and performing 5 to 40% rolling reduction at a temperature of 800° C. to lower than 1,200° C. in a period after the continuous casting until cooling to room temperature; the hot rolling step of performing hot rolling with a finishing temperature of 650 to 950° C.; the step of coiling the resulting hot-rolled steel sheet at a coiling temperature of 400 to 700° C.; the step of retaining the hot-rolled steel sheet at (coiling start temperature+20° C. to 100° C.) for 5 to 300 minutes; the step of cold rolling the hot-rolled steel sheet at a rolling reduction ratio of 10.0 to 90.0%; and the step of annealing the resulting cold-rolled steel sheet at 700 to 900° C.