The high-frequency welding process of
straight seam steel pipe is completed in the high-frequency welded pipe unit. The high-frequency welded pipe unit is usually composed of rolling forming, high-frequency welding, extrusion, cooling, sizing, flying saw cutting, and other components. The front end of the unit is equipped with a material storage looper, and the rear end of the unit is equipped with a steel pipe turning frame; The electrical part is mainly composed of a high-frequency generator, DC excitation generator, and instrument automatic control device. Thermally expanded straight seam steel pipe refers to the expansion of straight seam steel pipes through diameter expansion technology to meet the needs of customers. There are two processes for straight seam steel pipes: double-sided submerged arc welding and high-frequency welding. Double-sided submerged arc welding can produce straight seam steel pipes with a diameter of about 1500. The expansion we are talking about now mainly refers to high-frequency welded pipes. There are two points The reason is that the production caliber of the high-frequency welded pipe itself is relatively small, so it needs to be enlarged.
1. Reasonable material selection. For precision and messy molds, micro-deformation mold steels with good quality should be selected. For mold steels with serious carbide segregation, reasonable casting and quenching and tempering heat treatment should be carried out. For larger mold steels that cannot be cast, solid solution double refinement heat treatment can be carried out. Reasonably select the heating temperature and control the heating speed. For precision and messy molds, slow heating, preheating and other balanced heating methods can be used to reduce the heat treatment deformation of the mold.
2. Correct heat treatment process operation and reasonable tempering heat treatment process are also useful methods to reduce the deformation of precision and messy molds. The reasons for the deformation of precision and messy molds are often messy, but we only need to grasp the rules of deformation, analyze the causes of its occurrence, and use special methods to prevent the deformation of the mold, which can be reduced and controlled.
3. Pre-heat treatment is required for precision and messy molds to eliminate the remaining stress generated during machining. For precision and messy molds, if conditions permit, try to use vacuum heating and quenching and cryogenic treatment after quenching. Under the premise of ensuring the hardness of the mold, try to use pre-cooling, graded cooling quenching, or a warm quenching process.
4. The design and description of the mold should be reasonable, the thickness should not be too disparate, and the shape should be symmetrical. For molds with large deformation, the deformation rules should be mastered, and machining allowances should be reserved. For large, precise, and messy molds, a combined design can be used. For some precision and messy molds, pre-heat treatment, aging heat treatment, quenching, and tempering nitriding heat treatment can be used to control the precision of the mold. When repairing defects such as mold trachoma, air hole 5, wear, etc., use equipment with small thermal influence such as a cold welding machine to avoid deformation during the repair process.
