| abstract |
PROBLEM TO BE SOLVED: To provide a high burring hot rolled steel sheet having bake hardenability with a strength exceeding 490 MPa class and a method for producing the same. SOLUTION: In mass%, C: 0.01 to 0.1%, Si: 0.005 to 2%, Mn: 0.1 to 3%, P ≦ 0.1%, S ≦ 0.03%, Al: 0.001 to 0.1%, N ≦ 0.005% Ti: 0.05-0.2%, Ti (*) = Ti- (48/14) N- (48/32) S ≧ 0% and C- (12/48) Ti (*) ≦ 0.05% C, S, N, and Ti in the range that satisfies the requirements, the balance consists of Fe and inevitable impurities, the microstructure is mainly bainitic ferrite, and the average grain size of the prior austenite grains is more than 8μm ~ 80μm A high burring hot-rolled steel sheet having bake hardenability. And, after finishing rolling of the steel slab of this component at a final step reduction ratio of 1 to 15% at Ar3 + 50 ° C. or more, 0.5 to 5 seconds later, Ar3 to Bf is cooled at a cooling rate of 80 to 500 ° C./s. And a method for producing the steel sheet, wherein the steel sheet is cooled to a temperature of 500 ° C. or lower at a cooling rate of 20 ° C./s or higher. [Selection] Figure 1 |