ERW straight seam steel pipe is made by using the skin effect of high-frequency current to heat the edge of the formed pipe billet to the welding temperature quickly and then extrude and weld it. According to different feeding methods, ERW welded pipes can be divided into high-frequency contact welding and high-frequency induction welding. Both of them use the skin effect and proximity effect of high-frequency current, and at the same time, they are pressure-welded into steel pipes under the action of extrusion rollers.

ERW contact welding straight seam steel pipe uses two electrodes or welding feet to contact the two edges of the formed tube respectively. The skin effect and proximity effect generated by high-frequency current are used to concentrate the welding current on the V-shaped notch, and the V-shaped notch The metal at the place is instantly heated to the welding temperature, and at the same time, the steel pipe is welded by pressing the extrusion roller; ERW induction welding is to first form the hot-rolled coil through the forming machine into a tube, when the tube passes through the induction coil (high frequency The induction coil of the welding machine generates a high-frequency magnetic field through the high-frequency current), and the high-frequency induced eddy current will be generated in the tube, and then the skin effect and the proximity effect of the high-frequency eddy current will be used to make the eddy current dense at the edge of the tube The V-shaped notch, the formed tube blank is quickly heated to the welding temperature due to its own resistance, and at the same time, it is pressure-welded into a steel pipe under the extrusion of the extrusion roller.