Patent ID: 7857917
Filing Date: 2010-12-28
Classification: B22D,C21D,C22C

Abstract:
1. A method of production of steel for welded structures excellent in low temperature toughness of the weld heat affected zone (HAZ), characterized by preparing a molten steel comprised of, by mass %, C: 0.03 to 0.12%, Si: 0.05 to 0.30%, Mn: 1.6 to 3.0%, P: 0.015% or less, S: 0.002 to 0.015%, Cu+Ni: 0.10% or less, Al: 0.001 to 0.050%, Ti: 0.005 to 0.030%, Nb: 0.005 to 0.10%, N: 0.0025 to 0.0060%, and a balance of iron and unavoidable impurities, and casting the molten steel by a continuous casting method to obtain a slab, cooling the slab at a cooling rate from near the solidification point to 800° C. of 0.1 to 0.6° C./s, followed by reheating the slab to a temperature between 1100° C. and 1200° C., hot rolling the slab to obtain a steel plate in a pre-recrystallization temperature range by a cumulative reduction rate of 40% or more, finishing the hot rolling at 850° C. or more, followed by cooling the steel plate from 800° C. or more at a cooling rate of 5° C./s or more to 400° C. or less.