| 摘要 |
Provided is a high-strength hot-rolled steel sheet having excellent mass-production punchability and tensile strength (TS) of at least 900 Mpa, and a method for manufacturing same. A steel slab having a composition containing, by mass%, more than 0.07% and no more than 0.2% C, at least 2.0% Si, 1.0-3.0% Mn, no more than 0.1% Al, 0.05-0.3% Ti, and 0.05-0.3% V, is heated to at least 1100°C, the total rolling reduction of the rough rolling and the final two passes is at least 30%, and finish rolling is performed with the rolling ending temperature being within a range of (Ar3 transformation point)-(Ar3 transformation point + 120°C), and after finish rolling is completed, cooling is started within 2 seconds, and winding is performed at a winding temperature of 300-500°C at an average cooling speed of at least 40°C/s. Using this method, a high-strength hot-rolled steel sheet having a tensile strength of at least 900 Mpa and significantly improved mass-production punchability is achieved, the steel sheet having a composition with a bainite phase of more than 90% by volume, the average bainite lath interval being no more than 0.45 µm, and the proportion of Fe-type carbides precipitated on the bainite laths among all Fe-type carbides being at least 10%. |
