How to indicate the grade of welding steel: Welding steel includes carbon steel for welding, alloy steel for welding, stainless steel for welding, etc. The way to indicate the grade is to add the symbol “H” to the head of each type of welding steel grade. For example H08, H08Mn2Si, H1Cr18Ni9. For high-grade high-quality welded steel, add the symbol “A” at the end of the grade. For example H08A, H08Mn2SiA.

Commonly used welded steel pipes are divided into the following three types according to the welding processes used in their production.
① Continuous furnace welding (forge welding) steel pipe: It is characterized by high production efficiency and low production cost, but the metallurgical combination of the welded joint is incomplete, the weld quality is poor, and the comprehensive mechanical properties are poor.

② Resistance welded steel pipe: It is characterized by high production efficiency, high degree of automation, no need for welding rods and flux during welding, little damage to the base metal, and small deformation and residual stress after welding. However, its production equipment is complex, equipment investment is high, and the surface quality requirements of welded joints are also relatively high.

③Arc welded steel pipe: Its characteristic is that the welded joint achieves complete metallurgical bonding, and the mechanical properties of the joint can fully reach or be close to the mechanical properties of the base material. According to the shape of the weld, arc welded steel pipes can be divided into straight seam pipes and spiral welded pipes; according to the different protection methods used during welding, arc welded steel pipes can be divided into submerged arc welded steel pipes and melting arc welded steel pipes. There are two types of welded steel pipes.