Different types and appearance requirements of straight seam steel pipes

Different types and appearance requirements of straight seam steel pipes The high-frequency welding process of straight seam steel pipes is completed in high-frequency welded pipe units. High-frequency welded pipe units are 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 flip rack; the electrical part mainly consists of a high-frequency generator, a DC excitation generator, and an instrument automatic control device. Hot expansion of straight seam steel pipes refers to the expansion of straight seam steel pipes through diameter expansion technology to achieve the purpose required by 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. What we are talking about now is pipe expansion. It mainly refers to high-frequency welded pipes. There are two reasons. The production caliber of high-frequency welded pipes themselves is relatively small, so they need to be expanded. There are many types of straight seam steel pipes, according to the purpose: general welded pipes, oxygen-blown welded pipes, galvanized welded pipes, wire casings, roller pipes, metric welded pipes, automobile pipes, deep well pump pipes, transformer pipes, electric welded special-shaped pipes, and electric welded thin-walled pipes. General welded pipes: General welded pipes are used to transport low-pressure fluids. Made of Q235, L245, and Q235B steel. Galvanized steel pipes: It is to coat the surface of the black pipe with zinc. It is divided into hot and cold. The hot zinc layer is thick, and the cold price is cheap. Oxygen-blown welded pipes: Generally, they are small-diameter welded steel pipes, which are often used for steelmaking oxygen blowing. Wire casings: They are pipes for distribution structures, which are ordinary electric welded carbon steel pipes. Electric welded thin-walled pipes: They are small-diameter pipes used for furniture and lamps. Roller pipes: The electric welded steel pipes on the belt conveyor have required ovality. Transformer pipes: They are ordinary carbon steel pipes. Used to manufacture transformer heat dissipation pipes and other heat exchangers. Requirements for the appearance of straight seam steel pipes: 1. Cracks, unfused, pores, slag inclusions, and spatter are not allowed. 2. The weld surface of pipes with a design temperature below -29 degrees, stainless steel, and alloy steel pipes with a greater tendency to harden shall not have undercutting. The undercut depth of other material pipe welds should be greater than 0.5mm, the continuous undercut length should not be greater than 100mm, and the total length of undercuts on both sides of the weld should not be greater than 10% of the total length of the weld. 3. The weld surface shall not be lower than the pipe surface. The weld excess height shall not be greater than 3mm (the maximum width of the rear groove of the weld joint assembly). 4. The misalignment of the weld joint shall not be greater than 10% of the wall thickness and not greater than 2mm. Methods for preheating and deformation of straight seam steel pipes: 1. Reasonable material selection. For precision and messy molds, micro-deformation mold steel with good material should be selected. For mold steel with serious carbide segregation, reasonable casting and tempering heat treatment should be carried out. For larger and uncastable mold steels, solid solution double refinement heat treatment can be carried out. Reasonably select the heating temperature and control the heating speed. For precision messy molds, slow heating, preheating, and other balanced heating methods can be used to reduce mold heat treatment deformation. 2. Correct heat treatment process operation and reasonable tempering heat treatment process are also effective methods to reduce the deformation of precision messy molds. The deformation causes of precision messy molds are often messy, but we only need to master its deformation rules, analyze the causes of its occurrence, and use special methods to avoid mold deformation. It can be reduced and controlled. 3. Precision messy molds should be pre-heat-treated to eliminate the residual stress generated during machining. For precision messy molds, if conditions permit, vacuum heating quenching and deep cold treatment after quenching should be used as much as possible. Under the premise of ensuring the hardness of the mold, try to use pre-cooling, graded cooling quenching, or warm quenching process. 4. The mold design should be reasonable, the thickness should not be too different, the shape should be symmetrical, and the deformation rules should be mastered for molds with large deformation, and processing allowances should be reserved. For large and precision messy molds, a combined design can be used. For some precise and messy molds, pre-heat treatment, aging heat treatment, quenching, and nitriding heat treatment can be used to control the accuracy of the mold. When repairing defects such as mold sand holes, pores, wear, etc., use equipment with low heat impact such as cold welding machines to avoid deformation during the repair process. Post time: Dec-30-2024