High-frequency welded pipe is a steel pipe that uses the skin effect and adjacent effect generated by high-frequency current to connect steel plates. The emergence and maturity of high-frequency welding technology is a key process in the production of ERW pipe. The quality of high-frequency welding directly affects the overall strength, quality level and production speed of welded pipe products.

Submerged arc welding (including submerged arc surfacing and electroslag surfacing, etc.) is a method in which the arc burns under the flux layer for welding. Its inherent advantages such as stable welding quality, high welding productivity, no arc light and little smoke make it the main welding method in the manufacture of important steel structures such as pressure vessels, pipe section manufacturing (mainly SSAW pipes and LSAW pipes), and box-shaped beams and columns.

The flaring test is a method to test the deformation performance of the steel pipe end flaring process. When performing the flaring test, press the top core with a certain taper into one end of the metal tube sample to make it evenly expand to the flaring rate (%) specified in the relevant technical conditions, and then check whether there are cracks and other defects at the flaring , to determine whether it is qualified or not.

During the processing of steel pipes (seamless pipes or welded steel pipes), residual stress is generated, and the higher ones are near the yield limit. Most of the residual stress in the steel pipe shows a great harmful effect. For example, the strength of the steel pipe is reduced, the fatigue limit of the workpiece is reduced, stress corrosion and brittle fracture are caused, and the component is deformed due to the relaxation of the residual stress, which affects the dimensional accuracy of the component. Therefore, it is very necessary to reduce and eliminate the residual stress of components.

Square pipe is a name for square pipes, that is, steel pipes with equal side lengths. Square tubes can be divided into seamless square tubes and welded square tubes according to the presence or absence of welds. Seamless square pipe is a square steel pipe with four corners. It is a square steel pipe formed by cold drawing and extrusion of seamless steel pipe. There is an essential difference between seamless square pipe and welded square pipe. Steel pipes have a hollow section and are used in large quantities as pipes for transporting fluids. Welded square tube is a square tube made of steel plate or strip steel after crimping and welding.

Stainless steel seamless pipe is a hollow long cylindrical steel, and its scope of application is used as a pipe for conveying fluid. Mainly widely used in petroleum, chemical, medical, food, light industry, mechanical instruments and other industrial pipelines and mechanical structural components. The stainless steel pipe is made of acid-resistant and heat-resistant steel billets, which are heated, pierced, sized, hot-rolled, and cut.