| 摘要 |
A hot rolled steel sheet that is excellent in all properties required in press working, specifically shape freezing ability, hole-expandability, and bendability, although the hot rolled steel sheet has a high tensile strength of 980 MPa or more is provided, and a method for manufacturing the hot rolled steel sheet is provided. A hot rolled steel sheet comprises: 0.010 to 0.05% by mass of C; 0.5 to 2.5% by mass of Si; 2.5 to 3.5% by mass of Mn; 0.01 to 0.1% by mass of Al; 0.30% by mass or less of Ti; 0.008% by mass or less of N; and 0.005% by mass or less of S, wherein contents of C, Ti, N, and S satisfy the mathematical expression (1), [C]-{[Ti]-(48/14)x[N]-(48/32)x[S]}/4<=0.01, wherein contents of Si and Mn satisfy the mathematical expression (2), 0.20<=([Si]/[Mn])<=0.85, wherein [] represents a content(percent by mass) of each element, and wherein structure of the hot rolled steel has 90 percent by area or more of bainitic ferrite, 5 percent by area or less of martensite, and 5 percent by area or less of bainite based on the observation field area.
|
