The production process for high-frequency welded steel pipes (ERW steel pipes) depends primarily on the product type. From raw materials to finished product, a series of processes is required. These processes require various mechanical equipment, welding, electrical control, and testing equipment. So, how does operation affect weld quality during high-frequency welded steel pipe production?
1. Welding Pressure for High-Frequency Welded Steel Pipes
Welding pressure is one of the key parameters in the welding process. After both sides of the tube are heated to welding temperature, the extrusion pressure creates common metal grains, which crystallize and weld together. Welding pressure affects the strength and toughness of the weld. Low welding pressure cannot completely suppress the metal weld. Residual non-metallic inclusions and metal oxides in the weld are difficult to expel due to the low pressure, resulting in reduced weld strength and increased risk of cracking. Excessive pressure squeezes out most of the metal that has reached the welding temperature, reducing weld strength and also causing defects such as excessive internal and external burrs or overlays. Therefore, in practical applications, the optimal welding pressure should be determined for each specification. Due to possible tolerances in tube width and thickness, as well as fluctuations in welding temperature and speed, the welding extrusion pressure may vary. The amount of extrusion is generally controlled by adjusting the gap between the extrusion rollers or by adjusting the tube diameter before and after the extrusion rollers.
2. Welding Speed for High-Frequency Welded Steel Pipes
Welding speed is also a key parameter in the welding process, affecting the heating system, weld deformation rate, and inter-crystallization rate. In high-frequency welding, weld quality improves with increasing welding speed. This is because the heating time shortens the width of the edge heating zone, reducing the time for metal oxide formation. When welding speed decreases, not only does the heating zone widen, but the width of the melting zone also varies with the heat input, leading to larger internal burrs. Low welding speeds result in low heat input and welding difficulties. Failure to adhere to specified values can easily lead to weld defects. Therefore, for high-frequency welded steel pipes, the appropriate welding speed should be selected based on the specific specifications, and the maximum welding speed allowed by the equipment’s mechanical and welding equipment is limited.
3. Opening Angle for High-Frequency Welded Steel Pipes
The opening angle refers to the angle between the two sides of the tube at the front end of the extrusion rollers. The opening angle affects the stability of the firing process and significantly impacts weld quality. As the opening angle decreases, the distance between the edges decreases, enhancing the proximity effect. All other conditions being equal, the edge heating temperature can be increased, thereby increasing welding speed. If the opening angle is too small, the distance between the converging point of the squeeze rollers and the centerline is increased, resulting in the edges not being squeezed at the highest temperature, which reduces weld quality and increases power consumption.
Tip: For ASTM A53 Grade B ERW (electric resistance welded) tubing, the weld should be heat-treated at a minimum of 1000°F (540°C). This preserves the untempered martensite. For ASTM A53 Grade B cold-expanded tubing, the expansion should not exceed 1.5% of the desired outside diameter.
Post time: Sep-09-2025