HIGH STRENGTH STEEL PLATE FOR WELDING STRUCTURE WITH SUPERIOR HAZ TOUGHNESS FOR HIGH HEAT INPUT WELDING AND METHOD FOR MANUFACTURING THE SAME

摘要

According to an aspect of the present invention, a manufacturing method of steel for a welding structure with excellent heat-affected zone toughness for high heat input welding comprises: a step of heating a steel slab comprising 0.04-0.07 wt% of carbon (C), 0-0.2 wt% (excluding 0 wt%) of silicon (Si), 1.4-1.6 wt% of manganese (Mn), 0-0.01 wt% (excluding 0 wt%) of phosphorus (P), 0-0.001 wt% (excluding 0 wt%) of sulfur (S), 0.03-0.07 wt% of aluminum (S_Al), 0-0.3 wt% (excluding 0 wt%) of copper (Cu), 0.01-0.04 wt% of niobium (Nb), 0.3-0.9 wt% of nickel (Ni), 0.01-0.02 wt% of titanium (Ti), 5-15 ppm% of boron (B), 7-140 ppm of nitrogen (N), and the remainder consisting of iron (Fe) and inevitable impurities at a temperature of 900-1,150°C; a step of primarily rolling the heated slab at a temperature of an austenite recrystallization region or higher; a step of secondly rolling the primarily rolled plate in an austenite non-recrystallization region; and a step of cooling the hot-rolled plate to 200-400°C at a cooling rate of 4°C/second or higher.