PIPELINE HAVING EXCELLENT CARBON DIOXIDE CORROSION RESISTANCE AND STEEL PIPE FOR THIS PIPELINE AND CIRCUMFERENTIAL WELDING METHOD FOR THIS PIPE

摘要

PURPOSE:To improve the carbon dioxide corrosion resistance of the pipeline by incorporating a weld metal contg. Cr in a specific range into a base material contg. alloy elements of specific ratios. CONSTITUTION:The base material contg. =0.25% C, 0.01 to 0.50% Si, 0.1 to 2.0% Mn, =0.03% P, =0.01% S, 0.25 to 1.0% Cr, and 0.01 to 0.10% Al, and consisting of the balance Fe and unavoidable impurities is so constituted that the content of the Cr in the weld metal is in the range from the region lower by 0.2% than the base material to the region higher by 1.0%. The pipeline to be used for environment contg. CO2 is decreased in the corrosion over the entire surface thereof and the local corrosion in the weld zone and is improved in the carbon dioxide corrosion resistance in this way.