During welding, straight seam welding shall be carried out for the bent pipe seam. Since the welding is automatic ambush welding, the main reason is that the welder should be more responsible. During welding, the welding position should be adjusted to ensure the straightness of the weld. The end trimming process is to flatten the two ends of the bent tube blank to ensure that the nozzle is perpendicular to the centerline and there is no angle or height unevenness. At the same time, after flattening, the end surface is polished.