scope:

The high-frequency resistance-welding process is an important but not widely known commercial process. Many thousands of tons of steel pipe alone are produced by the process every year. The process offers unique characteristics, such as high welding speed, which produce substantial economic advantages for its users. High-frequency currents (10,000 to 500,000 cycle) have been used for several years to make welds in a variety of materials and shapes. In some cases, the high-frequency current is used to melt metal which then forms the weld. However, in most high-frequency welds the welding current is used to prepare the faying surfaces of the parts being welded so that a good solid state weld can be produced. If molten metal is produced, it does not remain in the joint and does not contribute directly to the coalescence which is the weld. This makes most of the high-frequency welding which is done upset butt welding. This report will consider only upset butt welding.