Gas Metal Arc Root Welding of Pearlitic Rails Using Magnetic Arc Deflection

Abstract

Magnetic arc deflection was applied to improve gas metal arc root welds on R260 pearlitic rail steel foot samples. During laboratory welding trials parameter optimization was carried out which comprised the welding current, voltage and speed, layer sequence, filler wire diameter, and the external magnetic field. Results were evaluated by visual inspection, and the lateral and diagonal penetration in cross-sections, as well as the microstructure and the hardness in the HAZ. Additionally, the influence of the external magnetic field on the process was studied using a high-speed camera. Overall best results were finally obtained in high welding current spray arc mode (380-400A) with the 1,6mm solid wire and at high welding speed (65cm/min) and two pass per layer sequence, in combination with maximum 30mT magnetic flux density and increased welding voltage (30-31V) for longer arc. A continuously well-formed root with sufficient lateral penetration was achieved and a smooth transition from base metal to weld metal at the lower edges could be achieved. Inside base metal HAZ the microstructure was fully pearlitic and no soft zone occurred. Furthermore, the size of the HAZ was in comparison to aluminothermic weld reduced by more than 75% in comparison to an AT rail weld.