Yasuto Fukada

Improvement in Fatigue Strength of Thermite Welds on Rails.

Thermite welding is widely used in the world. In the Japan railway company group, the application ratio of this method is approximately 40 % every year. The reasons why the thermite welding method is widely used are that the equipment has good mobility and the total working time of that is shorter than that of the enclosed arc welding method on site. Moreover, the operating skill, which is required for thermite welding, is less than that for enclosed arc welding. This welding method used now was introduced into Japan from Germany in 1979. After that, the thermite welding technique has been improved and developed. A wide gap method is one of newly proposed thermite welding in Japan. The root gap of this method is three times for that of conventional method. Therefore, it is feared that welds produced by wide gap method have less fatigue strength than those by conventional method. Because a welding heat input of wide gap method is much larger than that of conventional method. In this investigation, a new process with rail head air cooling for wide gap thermite welding is proposed in order to improve fatigue strength of thermite welded joint on rails.