The inner and outer surfaces of the large-diameter welded pipe of the spiral seam submerged arc welded pipe should be bright, and there should be no residual acid and oxide scale. Surface defects should be removed by grinding, the grinding place should have a smooth transition with the base material, and the wall thickness after grinding should be ensured not less than the Z minimum wall thickness specified in 3.0.6. If the depth of the defect exceeds the minimum wall thickness Z mentioned in the second description, it can be repaired by welding after obtaining the consent of the purchaser. Welding materials and welding procedures used for welding repairs must also comply with the provisions of 4.0.2. After the weld area is repaired by welding, it shall be re-examined by filming according to the requirements of 4.0.9. The inner and outer weld beads of the large-diameter welded pipe should be flush with the surface of the welded pipe or have a uniform protrusion.
The weld height shall meet the following requirements:
a. The outer side is not more than 50% of the wall thickness, but the Z maximum is 3mm; take the smaller value.
b. The inner side is not more than 25% of the wall thickness, but the Z maximum is 3mm, whichever is smaller.
c. The surface of the inner and outer weld bead should be smooth, without unevenness, and the weld and base metal should have a smooth transition, and no concave phenomenon is allowed.
According to various equipment, pipelines, structural parts, and use environments, the medium and pressure levels required for the packaging are different, and the welding technical requirements are different.
First) Welding technical purpose and requirements:
a. Master the definition, classification, and advantages and disadvantages of welding.
b. Master the safety technical measures to prevent electric shock and prevent fire, explosion, poisoning, radiation, and welding in a special environment.
c. Understand the importance of welding safety production and welding labor protection measures.
d. Understand the development and application of welding technology at home and abroad.
Second) the content of welding technology
1) Welding method: A) protected state; B) unprotected state; C) vacuum state; D) water state, etc.;
2) Welding equipment: A) arc welding machine; B) resistance welding machine; C) spot welding machine; D) black welding machine; E) explosive welding machine; F) bimetal composite diffusion (metallurgical) welding machine, etc.;
3) Welding control: A) automatic welding control; B) computer welding control; C) profiling welding control, etc.