Rail Welding Technology & Research On Improving The Rails Thermit Welding Process

With the rapid development of CWR, the amounts of rail steel joints welded by Flash Welding or Thermite Welding process are increasing more and more. Track Maintenance departments have paid more and more attention to the essential quality of the rail welds. If premature failure fracture arises, the broken rail welded joint will endanger traffic safety.Currently, many experts and scholars have done a lot of work to enhance the quality of thermite welded rail steel joint, and they focused on how to prevent welding defects by operating the welding process, but ignored improving the process itself. There are still fewer theoretical guidance and practical application cases about improved the process.So, if we learn from Flash Welding and Pressure Welding, increase postweld heat-treated for the thermite welded rail steel joint, the quality may be enhanced, and early failure will be avoided likely. Like that, it has more practical significance and the traffic safety is ensured.The main work of this paper is as followed. Firstly, expounding and analysising the principle of rail welding and heat-treatment. Secondly, comparing mechnical properties and welding defects of three different welding processes, and taking the rail welded joints broken cases occurred in Guangzhou Railway Group Corporation for example, to explain the reasons of failure fracture, to suggest the ways of improve the quality of the thermite welded rail steel joint. Lastly, comparing mechnical properties of two different Thermit Welded joints, the first one is experimented postweld heat-treated, and another is not. Except for this distinguish, the welding process and material is the same. The compared mechnical properties include microstructure, strength, toughness and hardness. Based on this, the aim of the present work was to analyze the effect of heat treatment on the properties of thermite welded rails.It has been found that postweld heat-treatment can enhance the tensile properties of the thermite welded rail steel joint, and improve the elongation greatly, however, weaken the hardness distribution in the vertical section.