The inner and outer surfaces of large-diameter spiral seam submerged arc welded pipes should be bright, without residual acid and oxide scale, and defects such as cracks, inclusions, scars, delamination, weld concave, and incomplete penetration. Surface defects should be polished and removed, the polished area should have a smooth transition with the base material, and the wall thickness after polishing should be no less than the minimum wall thickness specified in 3.0.6. If the depth of the defect exceeds the minimum wall thickness mentioned above, welding repair can be carried out after obtaining the consent of the purchaser. The welding materials and welding processes used for welding repair must also comply with the provisions of 4.0.2. After welding repair, the weld area should be filmed and re-examined according to the requirements of 4.0.9.

The inner and outer welds of large-diameter welded pipes should be flush with the surface of the welded pipe or evenly convex. The weld excess height should meet the following requirements:
1. The outer side is not greater than 50% of the wall thickness, but the maximum is 3mm; take the smaller value.
2. The inner side is not greater than 25% of the wall thickness, but the maximum is 3mm, whichever is smaller.
The inner and outer weld surfaces should be relatively smooth, without unevenness, and the weld and the base material should have a smooth transition, and no concave phenomenon is allowed. According to various equipment, pipelines, structural parts and use environments, the welding technology requirements are different for different media and pressure levels.

First) Purpose and requirements of steel pipe welding technology:
1. Master the definition, classification, and advantages and disadvantages of steel pipe welding.
2. Master the safety and technical measures to prevent electric shock and fire, explosion, poisoning, radiation, and special environment welding.
3. Understand the importance of welding safety production and welding labor protection measures.
4. Understand the development and application of welding technology at home and abroad.

Second) Contents of steel pipe welding technology
1) Welding methods: A) Protected state; B) Unprotected state; C) Vacuum state; D) Underwater state, etc.;
2) Welding equipment: A) Arc welding machine; B) Resistance welding machine; C) Spot welding machine; D) Black welding machine; E) Explosion welding machine; F) Bimetallic composite diffusion (metallurgical) welding machine, etc.;
3) Welding control: A) Automatic welding control; B) Computer welding control; C) Profiling welding control, etc.