Low and medium pressure boiler tubes are made of steel ingots or solid tube billets through perforation into capillary tubes, which are then hot-rolled, cold-rolled or cold-drawn.It is suitable for the manufacture of high-quality carbon structural steel hot-rolled, hot-extruded, hot-expanded and cold-drawn, cold-rolled seamless steel pipes for various low and medium pressure boilers.

Galvanized steel is widely used in all walks of life. The advantage of using galvanized steel is to protect the internal steel structure with metallic zinc that can form a dense oxide protective layer in the air. In the case of being welded or scratched, due to the existence of Zn-Fe primary battery, the relatively active galvanized part can be used as a sacrificial anode, delaying the corrosion of steel and having good corrosion resistance. However, due to the existence of the galvanized layer, cracks, pores, and slag inclusions are easily generated during welding, and it is difficult to obtain good welding quality.

ERW steel pipes may have various defects, and the names of defects are not completely uniform. Combined with the production characteristics of ERW welded pipes, it is concluded that there are the following defects.

Rolling seamless steel pipes should focus on operating in strict accordance with the construction specifications and technical requirements related to indirect technology, rather than processing and repairing after cracks.For metals of special materials and new steel grades, tests should be carried out before rolling to find a more practical probe technology for review to ensure the welding quality.

DIN 2391 standard specifies the Seamless steel tubes used for Mechanical and Automobile.The main products of steel / steel grade: DIN2391-1(ST35, ST45, ST52).

Trimming is concentrated before the pipeline leaves the factory. In order to ensure the welding quality, a comprehensive inspection and correction are carried out before welding, so that the end face, bevel angle, blunt edge and roundness of the pipe meet the requirements of the size of the butt joint.When individual steel pipes need to be beveled on site, gas welding is used to cut, remove the slag, and then use a grinding wheel to smooth it.The corresponding operation procedure is: check the size of the interface joint → clear the cavity → determine and adjust the staggered position of the longitudinal weld of the steel pipe → find the straight line for the first time → adjust the gap size of the counterpart → level the pipe line → find the straight line of the pipeline → spot welding.