Numerical simulation of end face heating in alternating current flash butt welding based on electrical–thermal bidirectional coupling

An appropriate temperature field before the upsetting process plays a key role in the quality of joints, and the temperature of rail flash butt welding (FBW) is mainly formed by the Joule heat generated by the current passing through the end face contact resistance; therefore, it is necessary to study the current distribution and end face heating during rail welding. In this study, through a combination of finite element simulation and experiment, an electric–thermal bidirectional coupling model of alternating current rail FBW is established, and the distribution of alternating current (AC) inside the rail and influence of the electrode feeding mode on the heating uniformity of the end face are investigated. The results demonstrate that the skin effect at the bottom of the rail is the most significant when the AC passes through the low-temperature variation area of the rail. The AC flowed along the surface of the rail, and the current near the end face flowed from the surface to the inside of the rail. The current distribution on the end face is almost uniform. In addition, the temperature distribution of the hybrid-type feeding method is the most uniform on the end face under AC power, and the fixed type has poor uniformity. The maximum difference between the simulated value and the measured value of the temperature interval width is 2.9 mm, and the error is controlled within 8.3%. The calculated results are in line with the measured results, indicating that the model established in this study is reasonable and feasible.