3. Modern rails

The rails move in three main directions:

• in order to reduce the number of welds (and also increase rolling mill productivity), rails, long delivered to European customers in 36 m train lengths, are now delivered in 100 to 110 m lengths, eliminating 2 out of 4 electrical welds. This represents an advantage for welding workshops, and guarantees better track straightness, particularly for TGV tracks, where speeds reach 300 km/h and more. For reasons specific to ships, overseas export rails are limited to 25 m in the hold or 50 m on deck;

• heavy trains (35 to 40 tonnes/axle) produce spalling on the surface of pearlitic rails. The idea therefore arose to increase hardness to 400 HB by reducing the proportion of ferrite and increasing carbon content up to (or even beyond) the hypoeutectoid threshold. However, results at the TTCI...