| 摘要 |
<p>PURPOSE: A high-strength steel sheet and a manufacturing method thereof are provided to prevent the weldability and productivity of the high-strength steel sheet from deteriorating due to a large amount of alloy elements added to the same, and to improve the tensile strength of the high-strength steel sheet over 1180 MPa. CONSTITUTION: A manufacturing method of a high-strength steel sheet includes: a step (S110) of reheating a slab sheet material; a step (S120) of hot-rolling the reheated sheet material at a finish rolling temperature of 750 to 950°C; and a step (S130) of cooling the hot-rolled sheet material to a martensitic temperature range at an average cooling rate of 200-500°C/sec, and then coiling the cooled sheet material. The sheet material includes 0.1 to 0.35 wt% of C, 0.01 to 0.5 wt% of Si, 0.3 to 2.0 wt% of Mn, 0.002 to 0.1 wt% of Al, 0.02 wt% or less of P, 0.005 wt% or less of S, and 0.01 wt% or less of N, and further includes at least one among 0.01 to 0.1 wt% of Cr and 0.0005 to 0.004 wt% of B, and the remaining amount of Fe and inevitable impurities. [Reference numerals] (AA) Start; (BB) End; (S110) Reheating of a slab (SRT: 1200±50°C); (S120) Hot-rolling (FDT: 850±100°C); (S130) Cooling/coiling (300-500°C/sec, CT: 50-200°C)</p> |
