Resulting from almost 30 years of heat-treated rail manufacture and research, the future of rail has been defined with Stress-Free heat-treated rails from Tata Steel. Rail produced using the company’s unique heat treatment process means track operators can enjoy up to five times longer life than is achievable using standard, non-heat-treated rail. What’s more, the opening of a new Tata Steel plant able to produce Stress-Free heat-treated rail in lengths of up to 108m, means greater productivity and reliability for customers. Standard rail is produced by furnace heating and rolling at red hot temperatures. Several stages of rolling are required before the rails are finally cooled and straightened to provide the accuracy required for modern track. The result of the cooling and straightening processes is rail containing high residual stresses. The patented Tata Steel heat treatment process sees the rail move through a set of induction furnaces where an alternating electromagnetic field heats the steel very quickly to approximately 950°C. Using compressed air, the rail is then cooled rapidly, which results in high hardness with a very fine-grained microstructure that delivers an exceptionally high elongation value. Tata Steel Stress-Free rails contain foot residual stress of less than 50 MPa – indeed, they are often compressive, which are in fact beneficial to performance as they help close (or squeeze together) any potential cracks, preventing them from growing further.
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