Rails for transport are a long-established product of the global steel industry, but the demands of modern railway networks have become ever more sophisticated. Richard Barrett profiles ArcelorMittals rail production capabilities and summarises the advantages gained by recent investments made at the steelmakers Spanish rail mill
Whether it is a high-speed inter-city express, a heavy-duty freight train or a tram trundling through city streets, the rails on which they run are crucial parts of their performance and efficiency.
While few train passengers give rails a second thought beyond perhaps noticing the classic rhythmic beat of wheels passing over joints in older tracks or over the points at intersections the technology for producing them has advanced substantially over the years.
For high-speed lines, long gone are the old-fashioned short lengths of track with gaps and fishplates at rail joints to allow for expansion. Much longer lengths of rail with strict flatness tolerances have replaced them, laid under tension and welded together at site to create continuous and seamless stretches of smooth and quiet transit.
The area of contact between a wheel of an express train and the rails that it rides on is remarkably small sometimes compared to the surface area of a coin, or the total surface area of a CD for the wheel-to-rail contact for a complete train. Consequently a train places large loads on a steel rail as it passes and braking creates friction on a rails surface.
Much research has gone into optimising steel grades, heat treating and hardening rails, as well as ensuring adequate fatigue resistance. The consequences of rail failure can, of course, be catastrophic.
A number of steelmakers in Europe have invested in the special capabilities needed to make modern rails. Key producers include Austrias Voestalpine (Schienen), the UKs British Steel, and the worlds largest steelmaker, ArcelorMittal.
The last of these producers has two rail mills in Poland at Dabrowa Górnicza and Chorzów another at Rodange in Luxembourg, and a fourth at Gijón in Spain. Together with ArcelorMittals US rail mill in Steelton, the companys rail production capacity exceeds 1 million tonnes per year.
High-speed, heavy-haul, underground and tram rails of many gauges, cross-sections and geometries form ArcelorMittals range, including crane and contact rails. Grooved rails for tramways are produced for rails installed flush with city road surfaces.
ArcelorMittal reports that it has supplied more than 1.5 million tonnes of rails for high-speed networks in Europe. The steelmaker has supplied rail to Turkey and has been selected for the first lines in the Middle East (Saudi Arabia), Africa (Morocco) and South America (Mexico). Its rails for underground systems and inter-city railways have also been installed in Europe and in Latin America (including Argentina, Brazil, Colombia and Venezuela). The steelmakers tram rails have also been deployed worldwide, including America, Europe, Africa and Asia.
ArcelorMittals recent rail investments have been driven by the types and locations of its markets. For example, it makes 120-metre-long rails in Poland one of just three mills with that capability in Europe, the steelmaker notes.
Facilities for head-hardened line for transport rails have been developed at its Spanish works, while grooved rail capabilities have advanced in Luxembourg and Poland, with low-carbon vanadium grades (LCV). ArcelorMittal LCV rails are particularly well suited to embedded tram tracks due to their low carbon content. This allows the best deposit and welding techniques to be utilised, which extends the life of the rail.
The companys Spanish mill recently completed extending its plant to enable production of rails 108 metres long, with its first rail of that length shipped in October last year. The investment entailed changing from duo to universal rolling technology, extending the length of the cooling bed, finishing line and transfer equipment to accommodate longer rails, and installing state-of-the-art ultrasonic rail inspection equipment to increase the speed of testing and to optimise the quality of the rail produced.
The upgrade was achieved in a three-step process to minimise disruption to mill operation. Routine maintenance closures were used to achieve the revamp. Supplied by SMS group, the universal stands were installed in September 2016, using existing stand motors to drive them, and the modifications needed to the run-out area and cooling beds to accommodate longer rails were made during summer last year, together with instrumentation and control upgrades.
Javier Álvarez-Linera, CEO of ArcelorMittal Europe Long Products-Asturias (Spain), explains that the rolling mill in Gijón increased its maximum length of rail rolled from 90 metres to 108 metres to enable production of the standard 108 metre length of rail needed for high-speed lines in Western Europe. The Spanish mill has capacity to produce 400,000 tpy of rail. Álvarez-Linera also explained that the main advantages of the universal rolling technology installed are a higher rail surface quality and optimised internal stresses. Greater control on mill parameters, which utilises both horizontal and vertical rolls, also improves productivity and provides better yield, he noted.
Following the upgrade to universal rolling, the mill has redeveloped its roll pass designs to satisfy applicable standards. Rail weights produced in Gijón range between 45 and 65 kg per metre. A typical rolling campaign might require 4,000 tonnes of rail or more, but minimum order sizes obviously depend on market conditions. At the lower end of that weight range, a 4,000 tonne rolling campaign would yield over 85 km of rails.
With its ability to make long rails in Poland and Spain, ArcelorMittal says that it can serve all EU railway networks. Longer rails require fewer welds. They also reduce maintenance costs, according to ArcelorMittal. Better rail surface quality and improved dimensional tolerances also result in a more comfortable ride for passengers.
ArcelorMittals R&D activities for rail have focused on process development, control and inspection, advanced testing and in-use properties all as aids to product development.
For example, computer-aided hot-rolling simulations have helped to determine the thermomechanical profiles of rails as they exit the mill, the optimal layout for cooling rails in air, the degree of deformation between rail supports on cooling beds to determine the best distance between them, and the most appropriate distribution of cooling water and straightening technology to relieve residual stresses. Advanced mechanical testing and equipment to measure properties in-use includes a rolling contact fatigue bench using full-size wheels and loads.
The steelmakers support for the rail market extends beyond the mill to installation processes, such as aluminothermic and flash-butt welding, life-cycle cost prediction, and repair welding of rails by using conventional arc welding, surface hardening and laser cladding.
As populations grow, cities expand and nations with insufficient rail production of their own look to expand their railway infrastructure networks, existing rail producers have cause for optimism. Replacement rails for aging transport systems in the developed world generate further demand. Nevertheless, railway line demand is cyclical in nature because it often depends on public funds for infrastructure development.
Amit Sengupta, chief marketing officer, ArcelorMittal Europe Long Products, notes that there was a slowdown in European demand for rail a couple of years ago, but that it has improved recently and is favourable on a 4-5 year horizon. He adds that there was a recovery in the market last year, particularly in Spain and Poland, while demand in Germany has been stable and the UK market is picking up.
The organisations and railway authorities buying rail usually do so through a competitive open tender process, which typically results in 1-2 year supply contracts. There are also prequalification requirements and, depending on contract size, rail purchasers may choose several suppliers for a large project. While some want a fixed price, others might include an annual price escalator.
How does ArcelorMittal distinguish itself from competitors? Sengupta says that this is possible through the breadth of the steelmakers product range, in terms of the number of different types of rails that it can produce across its different mills, including some unique products. Also with innovative tools to support customers, such as the new App Rail tool that provides interactive information regarding standards and profiles. He adds that ArcelorMittal has a Rail Excellence centre for R & D and A welding pilot plant in Spain, which includes the development of new qualities for high-strength, heavy-haul railways.
Service levels, in terms of getting rail to the job site, are another distinguishing factor, Sengupta notes. In Germany, for example, ArcelorMittal sometimes works with independent welding shops to join rails and create even longer lengths for shipping to site. Some railway administrations prefer to do all the welding on job site. Developing solutions to enhance the logistics side of the business is another aspect of ArcelorMittals vision for its rail business.
Javier Álvarez-Linera said that ArcelorMittal is aiming to extend its offer to customers by satisfying more bespoke requirements for non-standard lengths and profiles when required, by providing welded rails if requested and by responding to customer demands for harder material particularly head-hardened rail and new hardened qualities to improve the track performance.
By: Richard Barrett