The production process of high-frequency spiral welded steel pipes (ERW steel pipes) mainly depends on the type of product. From raw materials to finished products, a series of processes is required. The completion of these processes requires various corresponding mechanical equipment, welding, electrical control, and testing equipment. So, in the production of high-frequency welded steel pipes, what are the effects of the operation on welding quality?
1. High-frequency spiral welded steel pipes in welding pressure
Welding pressure is one of the main parameters of the welding process. After both sides of the tube blank are heated to the welding temperature, ordinary metal grains are formed under the action of extrusion pressure, that is, mutual crystallization produces welding. Welding pressure affects the strength and toughness of the weld. When the applied welding pressure is small, the weld of the metal cannot be completely suppressed, and the non-metallic inclusions and metal oxides remaining in the weld are not easy to be discharged due to low pressure, the weld strength is reduced, and the weld strength is easy to crack; when the pressure is too high, most of the metal that reaches the welding temperature is squeezed, which not only reduces the strength of the weld, but also produces excessive internal and external burrs or surfacing and other defects. Therefore, in practical applications, the optimal welding pressure should be obtained according to different specifications. Due to the possible tolerances of the width and thickness of the tube blank, as well as the fluctuations in welding temperature and welding speed, changes in welding extrusion pressure may be involved. The amount of welding extrusion is generally controlled by adjusting the spacing between the extrusion rollers, and can also be controlled by the diameter of the tube before and after the extrusion rollers.
2. High-frequency spiral welded steel pipe at welding speed
Welding speed is also one of the main parameters in the welding process, which is related to the heating system, weld deformation speed, and mutual crystallization speed. In high-frequency welding, the welding quality improves with the increase of welding speed. This is because the heating time shortens the width of the edge heating zone and shortens the time for the formation of metal oxides. When the welding speed decreases, not only the heating zone becomes wider, but also the width of the melting zone changes with the change of input heat, resulting in larger internal burrs. When welding at low speed, the input heat is small and welding is difficult. If the specified value is not followed, welding is prone to defects. Therefore, in high-frequency welded steel pipes, the appropriate welding speed should be selected according to different specifications, and the maximum welding speed allowed by the mechanical equipment and welding equipment of equipment is limited.
3. High-frequency spiral welded steel pipe at the opening angle
The opening angle refers to the angle between the two sides of the blank tube at the front end of the extrusion roller. The opening angle is related to the stability of the firing process and has a great influence on the quality of the weld. When the opening angle is reduced, the distance between the edges is also reduced, which enhances the proximity effect. Under the same conditions, the edge heating temperature can be increased, thereby increasing the welding speed. In the case of too small an opening angle, the distance between the confluence point of the squeeze rollers and the center line will be extended, resulting in the edge not being squeezed at the highest temperature, which will reduce the quality of the weld and increase the power consumption. Tip: In case of ASTM A53 B grade in ERW (electric resistance welded) tubes, the weld should be heat-treated at a minimum of 1000°F [540°C]. In this way, the untempered martensite is retained. In case of ASTM A53 B cold expanded tubes, the expansion should not exceed 1.5% of the required outside diameter.
Post time: Jul-04-2025