"I was once a Porsche" - researchers at TU Dresden give metal components a second life

Metals are the building blocks of the global economy. According to the World Steel Industry Association, around 1.9 billion tons of crude steel were produced in 2022. Added to this are millions of tons of other metals such as aluminium and copper. These unimaginable quantities are cast, rolled, forged, milled and welded. This results in a wide variety of metal qualities and components that are suitable for the manufacture of vehicles, machines, bridges, pipes, tools and household appliances.

A large proportion of these valuable materials are melted down at the end of their service life and processed into new components. This saves resources and energy compared to the extraction of raw materials and new production. But it remains an enormously energy-intensive process. "Around 90 percent of the energy required to manufacture a metal component is needed for melting and rolling," says Alexander Brosius, Professor of Forming Manufacturing Processes at the Dresden University of Technology (TU Dresden).

• Making melting unnecessary

Together with Andrés Fabián Lasagni, Professor of Laser-based Manufacturing at TU Dresden, Brosius wants to make the reuse and recycling of metal components more sustainable. With a new project called "2nd Life Metal Components", they want to bypass the melting process - instead, metal parts are cut up directly, pressed into a flat sheet, welded back together and formed into new shapes. The Werner Siemens Foundation (WSS) is supporting the innovative project with a total of 13 million euros over the next eight years.

The novel approach is based on joining several different steel or aluminum components into a new one. A challenge, as Andrés Fabián Lasagni says: "The old pieces of metal that we want to use come in very different shapes, thicknesses, strengths and qualities." In today's processes, melting ensures that a uniform starting product is always produced for subsequent sheet metal processing.

• Scrap metal puzzle

The researchers have designed completely new process chains for the planned upcycling without melting: First, the delivered and available components are sorted, cleaned or stripped if necessary and the geometry, sheet thickness and chemical composition are recorded. Then the actual processing begins: curved, three-dimensional components - for example a car door or a dishwasher tub - are cut open using laser cutting technology and pressed flat. "Cuts need to be made in the right places so that no creases or cracks form when the flat sheet is pressed," explains Alexander Brosius.

The mechanical properties of the resulting flat, two-dimensional sheet metal parts are now characterized more precisely - without destroying them in the process: The strength, the microstructure and the surface structure are decisive for how and for what purpose a sheet metal part can be further processed. The research and development of methods to determine such properties quickly, accurately and reliably throughout the entire process are important parts of the project.

This is followed by a step that is reminiscent of putting together a jigsaw puzzle: the appropriate parts for a planned workpiece are selected, joined together and re-welded. This is followed by the technique that makes the entire project possible: so-called "macrostructured deep drawing". Deep drawing is one of the most important forming processes in forming technology. The sheet metal blank is clamped between a holder, known as a blank holder, and a die and then transformed into a hollow body - for example a tub, a sleeve or a pot - by stretching and compressing it.

• "I was once a Porsche"

Thanks to an innovative finishing technique, the Dresden research team's project goes far beyond pure metal recycling. "We will produce metal components that have different, better functionalities than the original products," says Lasagni. Using laser technology, it is also possible to label or mark the components. A micrometer-sized groove protects this information from mechanical abrasion - and it can only be read out again using special software. Important information could include the composition, properties or origin of a component. More playful applications would also be possible: one idea is to point out the previous life of the piece of metal: "I was once a garbage can." Or: "I used to be a Porsche."