Welding High Performance Bridge Steel with a Pulsed Energy Source

This proposal is in response to announcement DTRT57-13-R-SBIR2 in the area 13.2-FH1, Development of Innovative Welding for High Performance Bridge Steel. It is proposed to use Homopolar Generator (HPG) Welding to join the high performance bridge steel in the 3” by 30” cross sections mentioned in the announcement in under 1 second. All of the energy required to perform the weld is stored in the spinning rotor of the pulsed power supply. Through electromechanical conversion the rotational energy is converted to a high discharge current that passes directly through the weld interface. Electrodes are clamped to the workpiece either side of the weldment and high current is passed through the plates to bring them to forge temperature. At this time, an upset pressure is applied and the weld is created by resistance-forge welding process. This process has been used to weld High Performance Steel pipe, 12” in diameter, with a 9/16” wall thickness. The pipes show good strength and toughness in the in both the weld metal and the heat –affected zone. These welds were accomplished with 3, 10 Megajoule, generators operating in parallel and the larger cross sections can be welded by adding generator units in parallel.