High-Frequency Resistance Welding
An industrial tube welding process utilizing high-frequency alternating current to edge-heat preformed strip material immediately prior to upset forging.
HF resistance welding is a process for longitudinal seam welding of pipes. High-frequency current is introduced into the sheet edges via contact rolls or an induction coil. The current flows along the edges and heats them locally to welding temperature before they are pressed together under pressure. It is important that the edges are clean and parallel and the contact pressure is correct. If the current is too high, the material burns out; if it is too low, the seam does not weld properly. You have to adjust the power so that the edges glow evenly and match the pipe travel speed to it. When the seam is cleanly pressed and the flash emerges evenly inside and out, the setting is right.