Rails for Low Operating Temperature and High Speed

The operation of railways in cold regions places high demands on rails. This paper summarizes the Russian Railways experience and studies of the probability of rail breaks at low temperature. Test methods and standards for rails designed for low-temperature operation have been developed. These include rail toughness, low-temperature drop tests, fracture toughness under static (К_IC) and cyclic loading of full-profile rail samples (К_fc). A production technology and technical conditions for thermally hardened rails have been developed, which can ensure their reliable operation at low temperatures and high speeds. Values of impact toughness at low temperature (КCU at −60 °C > 25 J/cm²) and low-temperature drop strength (the work of destruction more than 90,000 Nm of full-profile rail samples at a temperature of −60 °C) is provided by the fine-grained structure of rail steel. It is achieved by obtaining vanadium carbonatites due to the increased content of vanadium (0.05–0.15%) and nitrogen (0.008–0.020%), as well as thermal treatment. To prevent the occurrence of rail breaks rail flaw detection is of great importance. High-speed train operation in cold regions is disadvantaged by increased crashing of rails in welds heat-affected zones which cannot be eliminated by local heat treatment. Only fundamental changes in the production technology of welded 800 m rail strings, when induction heat treatment is performed after welding, allows reducing the softened zone length to 4–6 mm and solving the problem of rail straightness during the entire period of its operation.