ELECTROSEAMED STEEL PIPE AND PROCESS FOR PRODUCING SAME

摘要

A process for producing an electroseamed steel pipe having a low yield ratio and excellent anti-aging properties, characterized by comprising subjecting a steel piece to hot rolling, winding the hot-rolled product at 600°C or lower to produce a hot-rolled steel sheet, then molding the hot-rolled steel sheet into a tubular form, electroseaming/welding abutting faces of the tubular steel sheet to produce an electroseamed steel pipe, and heating the electroseamed steel pipe at a heating temperature of 400-720°C, wherein the steel piece contains 0.03 to 0.12% of C, 0.03 to 0.5% of Si, 0.5 to 2.0% of Mn, 0.03% or less of P, 0.003% or less of S, 0.10% or less of Al, 0.003% or more and less than 0.01% of Nb, 0.005 to 0.03% of Ti and 0.006% or less of N, the formula Ti > 3.4N and the formula (weld crack sensitivity composition) (Pcm) = 0.21% are fulfilled, and the remainder is made up by Fe and unavoidable impurities.