Experience in maintaining railtrack in Japan

This paper describes the state of the art concerning the welding processes for continuous welded rail (CWR) in maintaining rail track in Japan and the reliability of rail welds. In order to extend the service life of CWR,it is important to perform reliable welding for joints by utilizing appropriate welding processes, inspection methods and well-trained welding personnel. It is well known that flash welding (FW) and aluminothermic welding (TW) are commonly used in the world. On the other hand, gas pressure welding (GP) and enclosed arc welding (EA) have progressively been expanded in Japan. Both welding processes have been contributing much to the high-speed tracks of SHINKANSEN (bullet trains in Japan) since 1964. Features of GP and EA, originally developed in Japan, are introduced including characteristics of equipment, productivity of process, mechanical properties of weld and welding procedure for head hardened rails. Recent topics of process developments are also introduced, such as the semiautomatic process in enclosed arc welding. Moreover, the importance of the application of appropriate inspection to rail welds is emphasized in order to secure the reliability of rail welds.