Homopolar Pulse Welding of Rail

The homopolar pulse welding process uses a single unidirectional, high current electrical pulse from a homopolar generator to heat the interface between two workpieces in solid contact. When the interface reaches an optimum temperature, forging pressure is applied, and the workpieces coalesce without melting and without use of either a flux or a filler. The weld is completed in from 1 to 2 s. Because current distribution and heat generation can be made uniform throughout the workpiece section, irregular sections such as rails can be welded. Ninety lbm/yd rail has been welded with the process using a 10 MJ homopolar generator. The welds were excellent metallurgically, but there were fixturing problems with mechanical clamping, alignment, and current delivery. A through-feeding fixture for welding pipe has been designed and built that successfully addresses these fixturing problems, and electrical contacts and clamps for welding rails are presently being designed. A compact system that could serve as the power supply for an in-track rail welding system has recently become commercially available.