METHOD FOR WELDING LARGE DIAMETER STRAIGHT-SEAM PIPES Russian patent published in 2021 - IPC B23K31/02 B23K9/16 B21C37/08 B23K33/00 

FIELD: pipe production.

SUBSTANCE: invention relates to pipe production, in particular to a method for welding a longitudinal seam of welded straight-seam pipes of large diameter. A longitudinal joint of a pipe is assembled in an assembly mill, welding of a connecting technological seam with a melting electrode in a protective gas medium, and subsequent welding of working outer and inner seams are carried out. First, the connecting technological seam is welded with a technological burner with the melting electrode in the protective gas medium. Then, after the crystallization of the technological seam, the first layer of an outer seam is welded directly on the assembly mill with the melting electrode in a mixture of argon-based protective gases by a burner, which is installed with an offset from the technological burner welding the connecting technological seam at a distance of 400÷1000 mm. Then, multi-arc submerged welding is carried out, first for an inner seam and then for the remaining part of the outer seam.

EFFECT: optimizing cooling rates to obtain the required phase composition of metal in the zone of thermal influence of the welded joint, which leads to an increase in the quality of resulting welded pipes.

1 cl, 2 dwg, 2 tbl