AWS WHC-3.05:2008

High Frequency Welding
Scope : High-frequency resistance welding (HFRW) includes a group of resistance welding process variations that use high-frequency welding current to concentrate the welding heat at the desired location.1, 2 The heat generated by the electrical resistance of the workpiece to highfrequency currents produces the coalescence of metals, and an upsetting force usually is applied to produce a forged weld. High-frequency resistance welding is an automatedprocess and is not adaptable to manual welding. The two high-frequency resistance welding process variations discussed in this chapter are contact resistance welding and induction welding. Both variations use high-frequency current to produce the heat for welding. The current for contact high-frequency resistance welding is conducted into the workpiece through electrical contacts that physically touch the workpiece. For induction welding, the current is induced in the workpiece by magnetic coupling with an external induction coil. There is no physical contact with the workpiece. High-frequency resistance welding was developed during the late 1940s and early 1950s to fill the need for high-integrity butt joints and seam welds in pipe and tubing. The progressive development of this technology, detailed in Figure 5.1, served as the basis for the modern high-speed pipe and tube welding systems in current use. The principal application of high-frequency welding continues to be in the manufacture of seam-welded pipe and tube. The processes also are used in the manufacture of products such as spiral-fin boiler tubes, closed roll form shapes, and welded structural beams. Other examples of manufacturing applications are the welding of the metal shielding layer that surrounds high-frequency coaxial cable, the manufacture of butt joints in strip material and for solar panels, and for the butt joints in pipe and tubing. Topics covered in this chapter include the fundamentals of high-frequency welding, equipment and controls, process variations, economics of the process and safe practices. Additional sources of information are listed in the Supplementary Reading List at the end of the chapter