Excellent welding steel pipe in and sour resistance and acid gas corrosion

摘要

PROBLEM TO BE SOLVED: To provide an API standard X80 class high strength steel tube. ;SOLUTION: This welded steel tube is composed of a base material, having a chemical composition consisting of, by weight, 0.02-0.15% C, 0.01-0.5% Si, 0.1-2% Mn, 0.2-1% Cr, 0.005-0.1% Al, 0.0005-0.005% Ca, ≤0.015% P, ≤0.002% S, ≤0.5% Cu, ≤0.7% Ni, ≤0.3% Mo, ≤0.1% Nb, ≤0.1% V, ≤0.05% Ti, and the balance Fe with inevitable impurities, and a weld metal. At this time, Cr content in the weld metal satisfies, in relation with Cr content in the base material, either of the following (a) and (b): (a) in the case where Cr⁰ is 0.4 to 1, CrW(%)≤(1/2)×Cr⁰(%); (b) in the case where Cr⁰ is 0.2 to 0.4%, CrW (%)(1/2)×Cr⁰ (%)-0.2, where Cr⁰ and CrW represent Cr content in the base material and Cr content in the weld metal, respectively.;COPYRIGHT: (C)1997,JPO