ERW Pipe Production Process and Rolling Groove Processing Principle

At present, ordinary fluids on the market of general straight seam welded pipes are generally used in high frequency resistance welding production. They are characterized by high production efficiency, small welding heat affected zone, and low requirements on the quality of bonding surfaces, but the molding quality requirements and molding process Any change in the shape of the V-shaped opening in the hole may cause welding quality problems.


Roll groove machining is the process of pipe pretreatment using groove joints as pipe fittings. The working principle is that the rolling groove type rolling mill is used to drive the rotating tube and the radial pressure is applied to the subsequent radial pressure roll of the tube. The structure is used to weld the pressure roll in a fixed position in the welded tube and cool out the specified groove.


“Rolling groove cracking” is the root cause of insufficient welding strength. In addition to the severe deformation of the groove milling, stress concentration and tearing of the weld seam are caused. Raw materials are the source of product quality, and production must master its characteristics. From the welding point of view, the impact of raw materials on the quality of welds is mainly reflected in the welding and organization of materials. The composition of the alloy elements and the shape of the weld quality also affect. The high content of sulfur and phosphorus in the material can easily cause segregation of crystals. The high carbon content will promote the formation of martensite and the embrittlement of the weld metal. If the grain size of the metal structure is too large, the crystallographic direction of the weld will be strengthened. Easily promote the segregation of impurities. In non-metallic materials such as inclusions, lamellae, width and thickness fluctuations, various factors may cause welding cracks and reduce welding strength.


The main welding process parameters of the ERW steel pipe are the input power, the production speed of the raw material, the opening angle, the welding pressure, the position of the induction coil (inductive contact) and the impedance, and the like. The irrational welding process parameters are an important reason for the cracking phenomenon in rolling. If the input power is not enough, the speed is too fast, the input heat is insufficient, the edge of the strip cannot be completely melted, and the solid oxide at the end can not be extruded to form a low-temperature welding defect; otherwise, the input heat is too large, the metal splashes and returns to the package and other defects. Second, welding pressure is also very important. If the welding pressure is not enough, the weld lines on the two sides of the streamline of the metal structure are not obvious, and the welding strength does not meet the requirements; on the other hand, the welding pressure is too large, the irregular weld seam, the metal streamline rising angle is too large, only when the The welding pressure is appropriate, the fusion line should not be deformed, and the angle of the ideal flow of the metal flow line 45° to 60° ensures the weld strength.