Arc welding of annular seams under flux in high-strength X80 steel pipe

The relation between the content of martensitic-austenitic phase and the final temperature in accelerated cooling is investigated, in terms of the attainment of high deformability without failure. The ratio of the yield point to the strength ( Y / T ) in the longitudinal direction ( L ) of X80 steel pipe produced by UOE technology is found to be between 0.74–0.79. This indicates good deformability of the pipe. A welding technology has been developed such that the metal in the seam matches the strength of the X80 steel pipe. In industrial flexure tests, when the internal pressure is 72% of the standard yield point (SMYS) of X80 steel, the failure of X80 steel pipe welded by the given technology occurs in the basic metal, far from the annular weld.