Stress relief annealing is a process of heating steel pipes (seamless pipes, welded steel pipes) to an appropriate temperature, and gradually cooling down after holding for a certain period of time. Its purpose is to remove the residual stress of the steel pipe due to machining, deformation processing, casting, forging, heat treatment and welding.

Among the standards for seamless steel pipes and welded steel pipes, Brinell hardness is the most widely used, and the indentation diameter is often used to express the hardness of the material, which is intuitive and convenient. But it is not suitable for steel pipes of harder or thinner steel.

Both stainless steel seamless pipes and stainless steel welded pipes can be cold processed --- cold rolling and cold drawing to meet higher requirements for cold processed products.

The main production process layout and equipment composition of row-roll forming The row-roll forming machine is a major component of the welded pipe production line. It is the core of production and the key equipment on the production line, which is responsible for bending flat steel strips into round tube billets.

ASTM A519 Grade 4130 is a carbon and aluminum alloy steel seamless tube for mechanical engineering manufactured in accordance with American Society for Testing and Materials

The production process of galvanized straight seam welded pipe is relatively simple. The main production processes are electric resistance welded straight seam steel pipe (ERW pipe) and submerged arc welded straight seam steel pipe (LSAW pipe). Straight seam pipe has high production efficiency, low cost and rapid development.