Laser Repairing of Damaged Steel Rail with Filler Wire

The surface of damaged steel rail not only affects the comfort of train, but also influences train´s safety. Traditional welding methods are limited to applications for their low automatic degree, and the quality can not be guaranteed as well. So the newly technology of laser welding with filler wire to repair the damaged steel rail was used in this study. In order to set a process of laser welding with filler wire and tempering treatment technology after laser overlaying welding applied to U71Mn rail, laser repairing experiments with front-feeding were performed on the rail firstly. Then after the molding process was optimized by microstructure and micro-hardness, the microstructure properties of overlaying welding of rail were tested. The results indicated that laser welding with filler wire welding has good property with the process parameters after optimized, and the structure properties of overlaying layer were improved by using tempering heat treatment between the laser welding repairs. Most of martensite in laser overlaying layer was eliminated and the micro-hardness of weld seam and the hardness of heat affected zone were decreased after medium tempering heat treatment at 400°C. The microstructure properties of the overlay layer met the Railways´ repair welding standard.