| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet which is excellent in elongation flange formability and also impact resistance, and has a TS of≥780 MPa, and to provide a method for producing the high strength hot rolled steel sheet. SOLUTION: The high strength hot rolled steel sheet has a composition containing, by mass, 0.06 to 0.15% C,≤1.2% Si, 0.5 to 1.6% Mn,≤0.04% P,≤0.005% S,≤0.05% Al and 0.05 to 0.16% Ti, and the balance Fe with inevitable impurities, and has a microstructure made of a ferrite (F) phase and a bainite (B) phase, and in which precipitates with a size of <20 nm including 650 to 1,100 ppm Ti are precipitated in the F phase, and theΔHv of the B phase is≤150; wherein, the Hv of the B phase denotes a difference between the maximum value and the minimum value in the Vickers hardness of the B phase at 30 parts measured at the position of the 1/4 of the sheet thickness in the cross-section of the sheet thickness along the rolling direction. COPYRIGHT: (C)2011,JPO&INPIT |
