THE availability of rail networks depends heavily on the reliability and durability of turnouts, especially their crossings and points. To increase the robustness and the operational lifespan of crossings and their points in various applications, Vossloh joined forces with ArcelorMittal Industeel and developed a brand new steel grade for the railway industry.
Named CogX, this heat-treated laminated steel has a minimum initial hardness of 450HB. After in-service work hardening, the hardness on the running surface is above 550HB while the the material offers a minimum tensile strength of 1400N/mm2.
Decades of know-how in crossing design and manufacturing as well as extensive knowledge from countless international reference projects have gone into this development.
Typically, the material is supplied in heavy plates of dimensions up to 6000mm x 2000mm and a thickness of 60-200mm. This size allows the cutting of all geometries and a highly accurate milling of the switch blades and crossings.
Since CogX is much harder than Cogidur steel, which displays a hardness of between 370-400HB and is currently used for light rail turnouts, the application range is much wider. Additionally, the material characteristics allow a higher tonnage and speed.
CogX also supports more effective prototype development since the designs are milled out of the steel plate. As a result, a number of new designs and new track types can be realised:
- crossings or points of crossings for conventional railways
- crossings for heavy-haul lines
- crossings for metro applications, and
- crossings, half switches and switches for tramway applications.
In spite of the steel grade’s characteristics, welding is still possible. Direct flash butt welding with rails and arc welding have been qualified according to applicable European standards. The arc welding process requires lower preheating temperatures (between 150 and 250oC) than for rails.
All simulations as well as internal and external tests have shown that a crossing made of CogX has a lower wear rate than a crossing made of Cogidur and explosion depth hardened manganese. The comparison between profile measurements of a CogX and Cogidur crossing are shown in Figure 1. Here wear tests on the same crossing geometry with an axleload of 36 tonnes also demonstrated that there is no material flow and deformation on the running surface. Since the new steel is superior in maintaining the profile and resisting creep, Vossloh expects a 30% longer operational lifespan of the components and a 40% higher reliability in comparison with Cogidur.
As a consequence of the positive test results, a first pilot project is now running in Sweden on a conventional line as part of the European project C4R. Vossloh sees more opportunities to test this material on conventional railways, but also on heavy haul, metro and light rail lines.