One of the main applications of welding is to produce tubes and other closed profiles made of steel, aluminium or copper. Flat strips are formed by rollers until the desired shape is reached. The tube blank is conveyed through a ring-shaped inductor and the induced currents generate flow through the edges of the tube until they reach the point of contact provided by the rollers.
Fives Celes installations are generally equipped with high-frequency generators with a rating of several hundred kW and use either M.O.S. transistor technology for frequencies up to 400 kHz for high power and up to 2MHz for low power (CELES MP product range). Power transmission is obtained without contact. High-frequency welding makes it possible to avoid the wear and tube marking caused by sliding contacts. Some other advantages of this process are the high production rate attainable (transfer speeds of 100 to 150 m/min are common), the quality and regularity of the weld, the possibility of welding strips without first pickling, and the low power consumption.
Induction welding is also used to product finned tubes for heat exchangers. Attaching the fins requires the continuous welding of spiral fins on a carbon steel tube at high speed. Unlike traditional tube welding, the HF power is applied via sliding contacts on the tube and on the fin. In comparison with flame welding, this process doubles the productivity of a welding installation.