| abstract |
A high strength hot-rolled steel sheet having small fluctuation of mechanical properties in a coil and excellent in stretch flangeability. Wherein the steel sheet contains at least one selected from the group consisting of C: not more than 0.06%, not more than 0.06%, Si: not more than 0.3%, Mn: not more than 0.8%, P: not more than 0.03%, S: not more than 0.02%, Al: not more than 0.1% : 0.05 to 0.10%, and the balance Fe and unavoidable impurities. Si and Mn are reduced as much as possible to reduce segregation and the like, and the fluctuation of the strength due to the difference in position in the coil is reduced. Also, the steel sheet structure is a structure in which the ferrite phase occupies 95% or more of the area ratio, the average grain size of the ferrite grain is 1 占 퐉 or more, and the TiC having the average grain size of 7 nm or less is dispersed in the ferrite grain. As a result, a high-strength hot-rolled steel sheet with a yield strength of 530 MPa or more is obtained. |