| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for stably manufacturing a high-strength hot-rolled steel sheet which has≥980 MPa TS (tensile strength) and is excellent in elongation property and stretch flanging property, at low cost. SOLUTION: The method for manufacturing the high-strength hot-rolled steel sheet excellent in the elongation property and the stretch flanging property includes the steps of: heating a steel slab which has the componential composition containing, by mass, 0.06-0.10% C, 0.3-1.0% Si, 0.5-1.5% Mn,≤0.03% P,≤0.005% S,≤0.05% Al, 0.05-0.20% Ti, >0.28% to≤0.40% V, and the balance Fe with inevitable impurities, to the temperature of 1,200-1,300°C; hot-rolling the heated steel slab at the finish temperature of 900-1,000°C; applying first forced cooling to the hot-rolled steel sheet to the cooling stop temperature of 700-800°C at an average cooling rate of≥50°C/s; air-cooling the firstly-cooled steel sheet for 3-10 seconds; applying second forced cooling to the air-cooled steel sheet at an average cooling rate≥50°C/s; and winding the secondly-cooled steel sheet at the winding temperature of 600-650°C. COPYRIGHT: (C)2011,JPO&INPIT
|
