Corus supplies rails for world speed record

The world train speed record of 515kph was broken on Tuesday 3rd April, when a TGV travelling on rails supplied by Corus reached a speed of 574.8kph between Paris and Strasbourg.

Corus Rail has supplied all of the rails for TGV tracks right from its inception; this has involved developing specific manufacturing processes and controls to provide the unrivalled levels of straightness, running surface quality and material homogeneity required to operate trains at over 300 kph.

The rails for the TGV high-speed train tracks are made in the Corus factory in Hayange, France, an industrial site that started making rails in 1897. For the new TGV East line, Corus supplied 300 km of high-speed line, plus 44km of tracks to link the new line to the existing network. In all, 1300 km of UIC60 rails (60kg per metre) were supplied, in unit lengths of 80m. These unit lengths were welded together in the SNCF workshops at Saulon (Côte d'Or) to make long welded rails of 400m in length, and then taken to the laying location on special trains. The total weight of this order amounts to 78,000 tonnes of steel, which is eight times the weight of the Eiffel Tower.

At more than 300 kph in commercial operation, and over 550 kph for the speed record, rail straightness has to meet very stringent requirements. It reduces the vibrations and dynamic overloads that lead to rolling stock and track damage and are detrimental to passenger comfort. The vertical deviations authorized, for example, are set at 0.3 mm over a distance of 3 m, i.e. four times less than on a conventional track! It was necessary to rethink and redesign the full rail production chain and the means of control, to ensure perfect geometry, eliminate all impurities from the steel, or guarantee the chemical and mechanical homogeneity of all the rails made for high-speed tracks.

Steel for high-speed rails is made solely from cast iron. Just making the blooms, i.e. the bars of raw steel that are then rolled to shape, involves five stages: blast furnace, oxygen converter, refining station, vacuum degassing station, and continuous casting. At each stage, the objective is to remove all the inclusions that reduce metal strength and can lead to fatigue, while ensuring perfect chemical and mechanical homogeneity throughout each bloom. The blooms are then reheated and descaled using high-pressure water jets (200 bars). The universal rolling process developed by Corus is then used to directly forge the full rail cross-section. To preserve the rail surface quality throughout all these processes, all the movements are made friction-free by using motorized rollers or pilgrim’s step mobile table systems. It is also necessary to anticipate the final geometry of the rails, to overcome the deformations resulting from the variations in steel temperature during production. Specific prior bending and straightening systems have been developed for the purpose.