ERW pipe processing principle

Posted by zora li on November 16th, 2022

ERW pipe processing principle

At present, ordinary fluids and ordinary straight seam welded pipes on the market are generally used for high-frequency resistance welding production. They are characterized by high production efficiency, small heat-affected zone of the weld, and low requirements for the quality of the joint surface. Any change in the shape of the opening can lead to quality problems in the weld.

Roll grooving is the process of using grooved joints as pipe fittings in pipe pretreatment. Its working principle is to use the groove rolling mill to drive the pipe to rotate, the pipe radially presses radially with the moving pressure roller, and the seamless pipe adopts the pressure roller structure to cool out the specified groove at a fixed position.

A "rolling groove cracking" is the root cause of insufficient weld strength, coupled with severe deformation of the rolling groove processing, resulting in weld stress concentration and tearing. Raw materials are the source of product quality, and production must master its characteristics. From the welding point of view, the influence of raw materials on the quality of the weld is mainly reflected in the welding and organization of the material. The elements of the alloying elements and the morphology of the weld quality also have an effect. The high content of sulfur and phosphorus in the material is easy to cause crystal segregation; the high carbon content will promote the formation of martensite and embrittle the weld metal; if the grain size of the metal structure is too large, the crystallographic direction of the weld will be strengthened; it is easy to promote the formation of impurities. segregation. Inclusions, delamination, width and thickness fluctuations in non-metallic materials, and various factors may cause weld cracks and reduce weld strength.

The main welding process parameters of ERW steel pipe include input power, raw material production speed, opening angle, welding pressure, induction coil (induction contact) and impedance position. The unreasonable setting of welding parameters is an important cause of rolling groove cracking. If the input power is not enough, the speed is too fast, the input heat is not enough, the edge of the steel strip is not completely melted, and the solid oxide at the end cannot be extruded to form low-temperature welding defects; on the contrary, the input heat is too large, metal splash and return inclusions and other defects. Second, welding pressure is also important. If the welding pressure is not enough, the fusion line on both sides of the metal microscopic streamline is not obvious, and the welding strength cannot meet the requirements; on the other hand, if the welding pressure is too large, the weld seam is irregular, and the rising angle of the metal streamline is too large. It should be reduced when appropriate, the fusion line will not be deformed, and the metal streamline angle is an ideal state of 45°~60° to ensure the strength of the weld.

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