| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength hot-rolled steel sheet combining the corrosion resistance of a weld, and to provide a method for production thereof. <P>SOLUTION: The high-strength hot-rolled steel sheet contains, by mass, >0.035% to ≤0.055% C, ≤0.2% Si, ≤0.7% Mn, ≤0.03% P, ≤0.03% S, ≤0.1% Al, ≤0.01% N, 0.08-0.25% Ti, 0.0005-0.0040% B, 0.0005% solid-solved B, and the balance Fe with inevitable impurities. The steel sheet has a matrix including a ferrite phase having an area ratio of >95%, and a composition such that a Ti carbide having an average grain size of <10 nm finely precipitates in the ferrite crystal grain of the ferrite phase and the volume ratio of the Ti carbide is ≥0.0015 to ≤0.007. Further, the steel sheet has a tensile strength of 780 MPa and is excellent in corrosion resistance of the weld. <P>COPYRIGHT: (C)2013,JPO&INPIT |
