Method of manufacturing large-diameter steel pipe having excellent resistance to sour gas resistant

摘要

PURPOSE:To obtain the large diameter steel pipe excellent in sour gas resistance by subjecting base metals having specified chemical composition to one-pass submerged arc welding on the inside and outside by using low oxygen-base flux and an extra low carbon-base high Mn-low N-Ti-base welding wire to obtain weld metal having specified composition. CONSTITUTION:In the UOE steel pipe, the chemical composition of the base metals contains, by weight %, 0.02-0.05% C, 0.01-0. 05% Nb, 0.01-0.025% Ti, 0.002-0.005% Ca, 0.05-0.3% Mo and 0.01-0.08% V and ESSP of the expression I satisfies 1.5-6.0. These base metals are subjected to one-pass submerged arc welding on the inside and outside by using the low oxygen-base flux end the extra low carbon-base high Mn-low N-Ti-base welding wire. The weld metal contains 0.02-0.06% C, Ti, Al, Mo, B, etc., and PWM of the expression II is regulated to 0.13-0.16 and alpha of the expression III is regulated to (-10)-(+10). Consequently, the maximum hardness of a weld zone is suppressed and high toughness thereof is attained.