High-frequency induction welding is used widely by the tube-producing industry. The process requires a high-frequency current to be induced in the open seam tube by an induction coil located ahead of the weld point. Tube edges are spaced apart when they move through the coil, forming an open V, which will have the apex slightly ahead of the weld point. The coil connected to the high-frequency power supply through a transformer has no contact with the pipes. The open seam acts as a single-turn secondary thus inducing a high current that flows through the edges. High-frequency current density is highest at the edges, of the open V and the apex itself. The tube is heated rapidly raising the edges to the welding temperature when they meet at the apex. Pressure rolls force the heated edges together completing the weld.