| 摘要 |
<p>A high-strength hot-rolled steel sheet that has a composition which contains, in terms of mass%, 0.035-0.07%, excluding 0.035%, C, up to 0.3% Si, 0.35-0.7%, excluding 0.35%, Mn, up to 0.03% P, up to 0.03% S, up to 0.1% Al, up to 0.01% N, and 0.135-0.235% Ti so that the contents of C, S, N, and Ti satisfy the relationship ((Ti-(48/14)N-(48/32)S)/48)/(C/12)<1.0 (C, S, N, and Ti are the contents of the respective elements (mass%)), with the remainder comprising Fe and incidental impurities, and that has a structure comprising both a matrix which comprises a ferrite phase in an areal proportion higher than 95% and titanium carbide which has an average grain diameter less than 10 nm and has finely precipitated in the crystal grains of the ferrite phase. This steel sheet hence has a tensile strength of 780 MPa or higher.</p> |
