WATER-COOLED-TYPE TMCP STEEL STOCK AND LARGE-DIAMETER STEEL PIPE AND WELDING EXECUTING METHOD THEREFOR

摘要

PURPOSE:To manufacture a water-cooled-type TMCP steel stock suitable for large-diameter steel pipe for line pipe by incorporating specific percentages of C, Si, Mn, P, S, Nb, Ti, Al, N, and O to Fe. CONSTITUTION:A steel stock having a composition which consists of, by weight, 0.04-0.21% C, =0.25% Si, 0.4-2.0% Mn, =0.025% P, =0.015% S, 0.005-0.1% Nb, 0.005-0.1% Ti, =0.025% Al, =0.008% N, =0.005% O, and the balance essentially Fe and further contains, if necessary, one or =2 kinds among =1.0% Cu, =1.0% Ni, =1.0% Cr, =0.5% Mo, =0.1% V, 0.0005-0.005% B, and =0.005% Ca and in which Mn%-48XAl%=0.4% is satisfied is prepared. By this method, the water-cooled-type TMCP steel stock securing sufficient strength and toughness even if subjected to flash butt welding can be obtained.