Easily through 520 ° C: Heat treatment of aluminum

McKinsey estimates that the auto industry will triple its aluminum consumption to 16.9 million tonnes by 2030. The great advantage of the material in lightweight construction is that its properties can be specifically influenced.

Even as a basic raw material, aluminum has many advantages over other materials: its low density, lightness and durability. Perhaps the most important benefit: most of its properties can be specifically influenced. That's what a medium-sized German company has been using for 20 years – with heat treatment.

In the multi-shift system, Newalu processes approximately three million components per year at three locations in North Rhine-Westphalia and Bavaria – such as body parts and engines for automakers such as Audi, BMW, Mercedes- Benz and VW. The weight of a vehicle can be reduced by more than 60 kg thanks to lightweight aluminum construction. Small engines provide higher power with lower fuel consumption and lower emissions. Lightweight construction is not the only advantage of this material: aluminum can be cast in almost any imaginable form. This allows complex multifunctional components that it was expensive to bademble from separate components. However, it is only through the heat treatment that a molded component acquires the necessary strength and reduction of internal stresses. Aluminum can even be used as a substitute for steel. For this, aluminum components must withstand extreme temperatures.

Stability at extreme temperatures above 520 ° C

The heat treatment process includes solution heat treatment, quenching and subsequent aging. The exact nature of the procedure is customized for each order. "At the beginning of the heat treatment, the appropriate parameters, such as the temperature, the holding time of the molded parts in the furnace and the nature of the quenching process, should be defined and developed in close cooperation with the heating department. development of the car manufacturer, "says Martin Volpers, General Manager of Operations at Newalu GmbH. At extreme temperatures of over 520 ° C and subsequent quenching, it is up to you to decide how to store the components throughout the process. Before putting the aluminum components in the oven, custom frames are developed. Potential strain is detected and badyzed by 3D measurements. The racks are constructed in such a way that the components do not deform during the entire heat treatment process.

Quenching of components is just as essential to the success of heat treatment as heating. Newalu has developed a quenching technology in the polymer bath, which is particularly suitable for parts with different wall thicknesses. In a conventional water bath, the thin-walled areas cool much faster of a thick wall, which has an adverse effect on the residual stress of the component. In the case of the polymer bath, on the contrary, the polymer is deposited as a gel on the already cooled regions of the component and thus prevents rapid cooling. On thick and still hot areas, the polymer can not be deposited. As a result, the cooling process continues here until these zones have reached the desired target temperature. The high-speed air-quenching ready for production (HISAQ) was also developed in-house and patented in 2003. This leads to uniform cooling of the components, without deforming them. This makes it possible to thicken the walls with increased stability, which is particularly interesting for the body parts of the car. After cooling, the components can be further processed or badembled directly. On the way to the badembly line, some of the desired benefits of lightweight construction are already evident: weight, CO₂ and the costs are already recorded during transport.

The transition to electronic mobility is a market of the future

With electric mobility, the German car industry is facing one of the biggest structural changes in its history. "When it comes to lightweight aluminum construction, the move to electronic mobility is an absolute future market," said Stefan Matthaei, chief strategy officer at Newalu. The volume of the engine blocks to be treated will increase even initially because the combustion engines are connected by hybrid generators equipped with both engine blocks and electrical components. For purely electric powertrain components, an integrated control and cooling electric motor has about the same volume and weight of aluminum as a modern engine block. "For our business model, it does not matter whether we are heating an integrated engine block or a four-cylinder engine block," Matthaei said. The key words here are battery troughs or drum containers. Almost exclusively in die-cast aluminum, they are used for their complex structures that require high performance in case of impact. "These parts are really exciting because they are in no way inferior to the strength and rigidity requirements of the structural components of the bodywork, they are very large pieces, from about 1.20 m long, to the top of the body. 80 cm wide and 20 cm deep, where heat treatment know-how is important, "says Matthaei.