The difference between ERW (straight seam resistance welding) and HFW (high frequency welding) is mainly the principle.

Resistance welding, as the name implies, is a method of applying pressure through the electrode after the weldment is assembled, and using the resistance heat generated by the current through the contact surface of the joint and the adjacent area to perform welding. High-frequency welding: When high-frequency current passes through a metal conductor, there will be two peculiar effects: skin effect and proximity effect. High-frequency welding uses these two effects to weld steel pipes. These two effects are the basis of achieve high-frequency welding.

High-frequency welding uses the skin effect to concentrate the energy of high-frequency current on the surface of the work-piece; and uses the proximity effect to control the position and range of the high-frequency current flow path. The speed of the current is very fast, it can heat the adjacent steel plate edges in a short time, melt, and realize the butt joint by extrusion. Each has its own strengths and its own shortcomings. Generally, specific choices should be analyzed according to specific situations.