METHOD OF MANUFACTURING STEEL PLATE FOR ULTRA HIGH HEAT-INPUT WELDING AND STEEL PLATE FOR ULTRA HIGH HEAT-INPUT WELDING MANUFACTURED THEREOF

摘要

The present invention relates to a method of manufacturing a steel plate for ultra high heat-input welding, and a steel plate for ultra high heat-input welding manufactured thereof. The method comprises: a step of heating a slab including 0.04-0.07 wt% of C, 0.03-0.18 wt% of Si, 1.4-1.6 wt% of Mn, 0.009-0.034 wt% of Al, greater than 0 wt% and equal to or less than 0.01 wt% of P, greater than 0 wt% and equal to or less than 0.003 wt% of S, 0.10-0.16 wt% of Cu, 0.15-0.25 wt% of Ni, 0.10-0.20 wt% of Cr, 0.009-0.02 wt% of Nb, 0.010-0.025 wt% of Ti, 0.0008-0.0014 wt% of B, 0.0050-0.0080 wt% of B, 0.0005-0.0020 wt% of Ca, 0.0005-0.0020 wt% of Zr, and the remaining consisting of Fe and inevitable impurities at temperatures of 1120-1150C in a heating furnace; a step of roughly rolling the heated slab; a finish rolling step of rolling the roughly rolled slab at temperatures of 840-900C and rolling the slab at a temperature drop of 30C or less and reduction ratio per pass of 7-15% by 5-8 passes to manufacture the steel plate; and a cooling step of injecting cooling water on the steel plate, and terminating the injection of the cooling water at a cooling speed of 4-7 C/sec and a temperature of 550C30C and performing an air cooling process, thereby manufacturing a thick steel plate having Ti/N ratio of 2.5-2.9 while having a content of N of 65 ppm or greater.;COPYRIGHT KIPO 2016