The inner surface welding method of welding torch and multi-electrode submerged arc inner surface welding machine as well as the large-diameter welded steel pipe

摘要

PROBLEM TO BE SOLVED: To provide a welding torch and a multi-electrode submerged arc inner surface welder of using the same, suitable for being applied to inner surface seam welding of a large diameter welding steel pipe such as a UOE steel pipe.SOLUTION: The welding torch comprises a bending part for bending a fed welding wire in an axial direction of a tip, and the welding torch comprises a feed roll row for guiding the welding wire to the tip on the inside of it, and the feed roll row is constituted of a feed roll row arranged along the inside of a passage in the bending part of the welding wire and a feed roll row arranged along the outside of the passage, and each of the feed roll row arranged along the inside of the passage and feed roll row arranged along the outside of the passage, is constituted of a flat roll and a grooved roll, and the number and arrangement of the flat roll in each of the feed roll rows are determined without varying the projection length from the tip of the welding wire in welding, and without impairing wire communicability of the welding wire.