WRIST will develop and demonstrate flexible and cost effective joining processes for rail products, and in particular for the more recently introduced bainitic rail steel grades, for which currently available conventional welding techniques have been shown to be inadequate. The project will offer a step change in the joint performance and reliability, providing an extended in-service life for a range of rail materials, which are facing increasing demands due to the increasing speed and growth of railway’s load. This will be delivered by the combined development of the joining processes itself, computational modelling, material and joint characterisation and testing, both on small-scale laboratory tests and full scale trials in test or industrial tracks.
WRIST will :
1. Develop two innovative methods (automatic forged aluminothermic welding and orbital friction welding) for joining rails which will both reduce the width of the HAZ and minimise the loss of mechanical properties in the weld zone. These innovations will also deliver increased reliability, a longer lifetime of the rails and welds, combined with a reduction of the maintenance cost.
•A revolutionary methodology for hot forged aluminothermic welding will be developed, which enhances the internal integrity by modifying the cast structure. At the same time, the total delivery time is reduced by ensuring process control and positive verification of the quality immediately after welding, rather than the current practice of a follow-up inspection visit. The process will be automated and will include inprocess quality monitoring systems coupled to remote data management and diagnostic tools to maximise reliability and operational performance
•To enable rails to be welded using orbital friction welding and to be able to exploit the benefits of this welding process, a new variant of the orbital friction welding process will be developed. It will be demonstrated that this process is a valuable alternative for realising high-performance rail joints.
2. Facilitate an increased use of bainitic rail steel grades that possess greater resistance to the key degradation mechanism of rolling contact fatigue. Full commercial exploitation of low carbon carbide-free bainitic rail steels has been prevented due to the difficulty of welding these steels using conventional rail welding processes. Since the proposed welding techniques in WRIST have the capability to minimize the HAZ at either side of the joint, it is also expected to limit the damage to the original bainitic microstructure through tempering. The use of bainitic rails will become easier and more cost effective for rail operators.
3. Permit the achievement of lower life cycle costs for track maintenance and renewal by eliminating the source of higher dynamic forces at “cupped” or irregular geometry welds that are responsible for the more rapid loss of track geometry and necessitate expensive maintenance tamping intervention.
4. Enable an increased use of more environmental friendly joining processes, such as friction welding. This process does not require fluxes or shielding gases, produces no harmful smoke, fumes or slag, which will reduce the overall environmental impact of track construction and maintenance. The much reduced rate of degradation due to the small HAZ and the resultant longer life span of the track will also be a key contributor to lowering the carbon footprint of railway transportation.
5. Deliver environmental benefits by reducing the use of carbon fuels and gas, reduction of exposure to noise, dust and vibrations by automating and incorporating in-process monitoring of the aluminothermic process, more efficient preheating and reduction in remedial grinding to achieve the required straightness.