Submerged arc welding is a welding method in which an arc burns under a layer of flux. Submerged arc welded pipe mainly includes straight seam submerged arc welded pipe (LSAW) and spiral submerged arc welded pipe (SSAW)

Polyurethane insulation pipe has excellent characteristics such as light bulk density, high strength, heat insulation, sound insulation, flame retardant, cold resistance, anti-corrosion, non-absorbent, simple and quick construction, etc.

Galvanized pipe, also known as galvanized steel pipe, is divided into two types: hot-dip galvanized and cold-dip galvanized pipe. Hot-dip galvanized galvanized layer is thick, and has the advantages of uniform coating, strong adhesion and long service life. The cost of cold-dip galvanized pipe is low, the surface is not very smooth, and its corrosion resistance is much worse than that of hot-dip galvanized pipe.

Pores in welded seam of welded steel pipe not only affect the tightness of pipe weld and cause pipe leakage, but also become the induction point of corrosion, which seriously reduces the strength and toughness of weld.

The so-called bright heat treatment includes bright annealing, bright normalizing, bright quenching and bright tempering. In order to prevent oxidation and decarburization of the surface of the stainless steel seamless pipe so that it does not lose its metallic luster, heat treatment should be carried out in a protective atmosphere or vacuum as mentioned above.

The size defects of seamless pipes include uneven wall thickness, excessive wall thickness, excessive outer diameter, bending