PROBLEM TO BE SOLVED: To provide a hot rolled steel sheet having high strength (TS: ≥1,180 MPa) and also having excellent workability.;SOLUTION: The hot rolled steel sheet has a composition composed of, by mass, 0.10 to 0.16% C, ≤0.5% Si, 0.5 to 1.8% Mn, ≤0.5% Al and 0.001 to 0.005% N, and further composed of at least one kind selected from 0.14 to 0.2% Ti and 0.25 to 0.40% Nb, and the balance Fe with inevitable impurities, and has a dual phase structure composed of, by volume fraction, 30 to 45% of a tempered bainite phase and a ferrite phase, in which the ferrite phase and tempered bainite phase both contain MX precipitates with an external diameter of 10 nm (wherein: M denotes a metallic element(s); and X denotes carbon or nitrogen).;COPYRIGHT: (C)2010,JPO&INPIT
展开▼
