| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot-rolled steel sheet that is improved in extensibility while maintaining such a high strength as a tensile strength of 590 MPa or more.SOLUTION: A high-strength hot-rolled steel sheet includes, by mass, 0.03-0.15% C, 1.5% or less Si, 0.5-2.0% Mn, 0.04% or less P, 0.005% or less S, 0.005-0.10% Al, 0.007% or less N and the balance Fe and inevitable impurities. In the high-strength hot-rolled steel sheet, a difference in Vickers hardness between a surface layer part and a plate thickness central part of the steel sheet is 50 or less and a tensile strength is 590 MPa or more. |
