Steels for rails

Transport by rail is an efficient way of moving goods and people while managing problems such as congestion and the consequences on the environment. The relatively low energy consumption and CO₂ emissions are attributed to the low rolling-resistance due to the stiffness of the wheel and rail, leading to small contact area [1]. Investments in rail transportation has boomed in recent years. London, with the oldest underground rail system in the world, has added the Elisabeth Line at a cost of some £14 billion; China now has the largest high-speed rail system in the world. All these developments rely on the safe performance of steel rails, which suffer from two primary damage mechanisms, rolling-contact fatigue caused essentially by repeated contact stresses with the wheel, and a variety of wear mechanisms. Factors such as weldability are important, given that all modern rails are continuous. This review deals with the detailed physical-metallurgy of rail steels, including alloy design, microstructure, variety and choice, and damage mechanisms.