Failure modes in aluminothermic rail welds under high axle load conditions

Aluminothermic welding of rails is widely used within the railway industry for in-track welding during re-rail and defect replacement. The process provides flexibility and low capital cost, but suffers from variable quality in finished welds, due to the inherent limitations of the processes used, and their operator dependency. The service performance of such welds can be considered in terms of the integrity of the joint, i.e. its ability to support the service loads without fatigue damage or fracture, and the batter behaviour of the running surface, which in turn influences the extent of impact loading. Under high axle load conditions, these performance requirements are unforgiving in terms of weld quality and material characteristics. In response to recent failures in aluminothermic welds, and in recognition that such welds represent one of the main risks for a catastrophic derailment, and a major limitation to further increases in axle loads, a program was undertaken to both remedy the current problem with premature failures, and to develop improved rail welding and track maintenance practices which would meet the performance demands of higher axle loads. (C) 2003 Elsevier Ltd. All rights reserved.