| 摘要 |
According to an embodiment of the present invention, a method for manufacturing a thin steel sheet having ultra-high strength comprises: a step for winding a hot-rolled steel sheet including, in wt%, 0.1-0.3% of C, 0.1-1.5% of Si, 2.0-3.0% of Mn, 0.001-0.10% of P, 0.010% or less of P, 0.01-0.1% of Al, 0.3-1.0% of Cr, 0.0010-0.0030% of B, 0.01-0.1% of Ti, 0.001-0.01% of N, 0.02-0.05% of Nb, and residues comprising Fe and other unavoidable impurities; and a step for cold rolling the wound steel sheet. In the winding step, a coiling temperature (CT) is satisfied with a relational expression 1: 141 - 90.2C + 6.27Si - 14.6Mn - 5.47Cr - 0.0826CT < 45, and a relational expression 2: 1030C + 35.9Si + 246Mn + 189Cr + 0.487CT-489 < 830. |
