| 摘要 |
Provided is a hot-rolled steel sheet suitable for use as a cold-rolled steel sheet or a hot-dip galvanized steel sheet, with excellent material uniformity and cold rollability and having a tensile strength of 590 MPa or higher. The chemical composition of the steel sheet comprises, in mass%, 0.060-0.120% of C, 0.10-0.70% of Si, 1.00-1.80% of Mn, 0.10% or less of P, 0.010% or less of S, 0.01-0.10% of Al, 0.010% or less of N, and 0.010-0.100% of Nb in a range where the amount of Nb in solid solution is 5% or more of the total amount of Nb, with the remainder comprising Fe and inevitable impurities. The microstructure of the steel sheet comprises 75% or more, by volume fraction, of ferrite having an average crystal grain size of 15 µm or smaller, with the remainder comprising a phase formed at low temperatures. |
