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Machine upgrades bring thinner-walled aluminium products to rail industry

Sapa is investing in new production lines at sites in Belgium and Sweden to meet the surging demand for larger and thinner-walled aluminium products in the rail industry.

Sapa is increasing from 6,500 to 8,200 tonnes the force of the large aluminium extrusion press at its plant in Lichtervelde, Belgium. The added power will enable the company to extrude 6xxx-series profiles that are up to 620 mm wide and up to 26 meters long, with an extremely thin wall thickness down to 1.6 mm. This reduces the amount of aluminium used in the section and lightens an already weight-saving solution, without sacrificing strength.

The upgraded press will begin series production in January 2017.

The company also has invested in a new large-scale friction stir welding machine at its Finspång plant in Sweden, offering single-sided and double-sided welding of extruded aluminium profiles, produced as 18 x 3.5-meter panels. The panels can be curved as well as flat.

“The combination of friction stir welding and the fact that we deliver a finished component with all the necessary fabrication and processing completed, makes it simpler and quicker to construct the entire car body,” says Bruno D’hondt, who is managing director of Sapa’s extrusion activities in the Benelux region.

Friction stir welding is a refined joining process in the production of aluminium car bodies for trains. It is an advanced technique that results in a stronger product.

Next-generation aluminium solutions

Steel and aluminium are the dominant materials used in the construction of train bodies. Applications include train sideboards, roof and floor panels, and cant rails, which connect the floor of the train to the side wall.

Aluminium’s benefits in high-speed train car bodies are its light weight, and its uniform and smooth surface – there are no “waves” in the metal, as with steel, meaning less finishing work after assembly. Furthermore, assembly in a modular fashion is more cost effective, compared with many smaller and heavier components. In this respect, the train industry is following the automotive industry.

Sven Lundin, market sector director for Sapa, points out that a train comprised of lightweight aluminium cars uses less energy to operate – to move – than a heavier train, and it is easier to start and stop, helping total journey time. Aluminium is also 100 percent recyclable, with low energy input and no loss in its material properties.

“With our metallurgical expertise and knowledge, we helped the industry begin substituting with aluminium and we keep our customers ahead, for example, with local application engineers involved in the early design phases of customer projects,” says Lundin. “With this kind of participation, we can help reduce customer costs by 10-to-15 percent, partly by optimizing the weight of designs.”

About friction stir welding

The friction stir welding (FSW) machine that Sapa has installed at its plant in Finspång is the largest in Europe and one of the largest in the world. It will become fully operational next month.

FSW joins metal surfaces through the effects of a rotary tool, pressure and heat. No filling material is needed, and FSW provides better mechanical properties and less heat deformation than other forms of welding. Double-sided welding is faster and generally produces higher quality results than single-sided welding.

As the first company in the world, Sapa introduced friction stir welding in 1996 to enable a process of solid-state joining as a production method. The method drastically advanced Sapa’s production and has brought to life new applications for customers the world over.