High-frequency welding is a solid-state resistance welding method that utilizes a 10–500 kHz high-frequency current to generate resistance heat at the joint surface of the workpiece, achieving interatomic bonding with or without pressure. Its core physical effects are the skin effect and proximity effect.
Based on the method of introducing the high-frequency current into the workpiece, high-frequency welding is mainly divided into contact high-frequency welding and induction high-frequency welding. In contact high-frequency welding, the high-frequency current is transferred to the workpiece through mechanical contact; in induction high-frequency welding, the high-frequency current induces a current within the workpiece through the coupling effect of an external induction coil.
The advantages of contact high-frequency welding are low ineffective current shunting, high efficiency, small heat-affected zone, the ability to weld pipes with diameters of approximately 8–1270 mm, and welding speeds up to 100–120 m/min. The advantages of induction welding are no electrode pressure or consumption, easy welding adjustment, stable process and good quality, and low requirements for strip material.
However, induction welding requires 40-50% more power than contact welding, and its speed is about 1/2 to 2/3 that of contact welding under the same power and pipe gauge. In production practice, induction welding is usually chosen.