| 摘要 |
<p>A steel plate having high tensile strength and excellent low temperature toughness manufactured although Mn is not used in a large content is provided, and a manufacturing method of the steel plate is provided. A manufacturing method of a steel plate for a linepipe having ultra-high strength and excellent low temperature toughness comprises the steps of: heating a steel slab comprising, by weight percent, 0.03 to 0.10% of C, 0 to 0.6% of Si, 1.6 to 2.1% of Mn, 0 to 1.0% of Cu, 0 to 1.0% of Ni, 0.02 to 0.06% of Nb, 0.1% or less of V, 0.1 to 0.5% of Mo, 1.0% or less of Cr, 0.005 to 0.03% of Ti, 0.01 to 0.06% of Al, 0.0005 to 0.0025% of B, 0.001 to 0.006% of N, 0 to 0.006% of Ca, 0.02% or less of P, 0.005% or less of S, and the balance of Fe and other unavoidable impurities to a temperature of 1050 to 1150 deg.C; subjecting the heated slab to a single rolling operation or a multistage rolling operation of two or more rolling operations to a reduction ratio of 20 to 80% in a temperature range of an austenite recrystallization temperature or higher; subjecting the rolled slab to a single rolling operation or a multistage rolling operation of two or more rolling operations to a reduction ratio of 40 to 80% in a temperature range of the Ar3 temperature to the austenite recrystallization temperature to manufacture a steel plate; cooling the rolled steel plate at a cooling rate of 20 to 50 deg.C/sec; and stopping cooling of the steel plate at a temperature of 200 to 400 deg.C.</p> |
