High Frequency Welding

High frequency welding is the effect of skin effect and the adjacent high frequency current generated by the use of the butt plate and other metal materials up new welding process. Emergence of high frequency welding technology and mature, directly contributed to the development of the huge industry of Longitudinal welded pipe (ERW pipe) , it is a key step in the production of Longitudinal welded pipe production. The quality of high-frequency welded pipes directly affects the overall strength, quality level and productivity of pipe products. 

High-frequency welding equipment is used to achieve high-frequency welding electrical - mechanical systems, high-frequency welding equipment by high-frequency welding machines and pipe forming machine composed. Which generally consists of a high-frequency welding machine high frequency generator and feeding device composed of two parts, its role is to generate high-frequency current and control it; molding machine by the squeeze roller frame composition, its role is to be a high-frequency current extruding the molten portion to exclude the oxide layer and the steel sheet surface impurities, the steel plate is completely fused together. 

Many factors affect the quality of the high-frequency welding, and the interaction of these factors in the same system, a factor that has changed, other factors also as it is changed. Therefore, when high-frequency adjustment, frequency adjustment of the local light is noted that the current is insufficient or the amount of compression, etc., which must be adjusted according to the specific conditions of the molding system, from all aspects related to high-frequency welding adjustments. After the high-frequency welding necessarily exclude air, is: In real tool joints, expel excess air, full of welds purpose. 

There are two ways to get the high frequency welding: contact welding and induction welding. 
Resistance welding electrodes is a copper pipe welded on both sides of the contact portion is the induced current penetration is good, high-frequency current effects due to the two copper electrode in direct contact with the steel plate to obtain maximum use, the contact welding welding efficiency higher and lower power consumption, has been widely used in high-speed low precision pipe production, particularly in the production of thick steel pipe generally requires the use of contact welding. But there are two drawbacks to contact welding: First contact with the copper electrode and steel, wear out quickly; Second, due to the impact of the steel surface flatness and edge straightness, poor contact welding current stability, the higher internal and external weld burr when welding precision and thin-walled tube is generally not used. 

Induction welding is one or more turns of the induction trap outside the welded steel pipe, multi-turn better than a single turn, but more difficult to produce a multi-turn induction loop installation. Induction loop with a higher pitch pipe surface-hour efficiency, but is likely to cause the discharge pipe between the induction coil and the general induction loop to keep away from the pipe surface 5 ~ 8 mm gap is appropriate. When using induction welding, due to the induction loop is not in contact with the plate, so there is no wear and tear, the induced currents are more stable, to ensure the stability of the welding, good welding steel surface quality, weld formation, such as in the production of high API When precision tubes, basically in the form of induction welding.

Read more: ERW pipe vs. HFW pipe