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

Spiral steel pipe (SSAW steel pipe) is a welded steel pipe made by rolling low-carbon carbon structural steel or low-alloy structural steel strip into a tube blank at a certain helical angle (called forming angle), and then welding the pipe seams.

Large-diameter welded pipes generally use double-sided submerged arc welding welded steel pipes, which can be divided into large-diameter straight seam welded pipes and large-diameter spiral welded pipes according to their weld seams.

Because seamless steel pipes work under high temperature and high pressure conditions for a long time, the material will undergo stress relaxation, plastic deformation and ductility reduction, initial structure changes, and corrosion.

After the two edges of the large-diameter welded pipe billet are heated to the welding temperature, under the extrusion of the extrusion roller, the single metal grains formed are infiltrated and crystallized with each other to form a strong weld.