| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high strength hot-rolled steel sheet, surely obtaining a hole-expanding ratio λ of ≥125% and having excellent workability of 490 to 590 MPa TS, and a manufacturing method therefor. <P>SOLUTION: The high strength hot-rolled steel sheet excellent in the workability, has the peculiarity, in which the steel is composed by mass% of 0.04-0.1% C, 0.3-1.3% Si, 0.8-1.8% Mn, ≤0.03% P, ≤0.005% S, ≤0.005% N, 0.005-0.1% Al and at least one kind selected among 0.002 to <0.03% Ti, 0.002 to <0.03% V and 0.002 to <0.02% Nb and the balance Fe with inevitable impurities, and has the micro-structure of ≥85% the area ratio of ferritic-phase possessed in the whole structure, ≤10% the area ratio of bainitic-phase and ≤5% the area ratio of the other phase except the above ferritic-phase and the bainitic-phase and further, 30% to <80% the area ratio of acicular ferritic-phase possessed in the whole ferritic-phase. <P>COPYRIGHT: (C)2012,JPO&INPIT |
