Forming Of Laser-soldered Hybrid Tubes Made Of Aluminum And Steel

For the first time, the researchers combined two high-pressure approaches with the internal high-pressure forming of hybrid tubes - so-called tailored hybrid tubes: firstly, the weight saved through the geometry of the components, and secondly through the material. Pipes are generally well suited for lightweight construction because they are extremely stiff and stable in relation to their weight. If you also manufacture them from a combination of steel and aluminum, additional weight can be saved. Only those sections that are exposed to high loads are then made from heavy but strong steel - the rest of the component can be made of light aluminum. However, the production of such hybrid components is a challenge because steel is much more difficult to form than aluminum.In addition, the pipe sections must be connected to each other before forming so that the joining zone does not tear later. Welding is out of the question: a brittle seam would form here that cannot be formed.

The problems were solved by internal high pressure forming and laser soldering. The aluminum-silicon solder is locally heated and melted with the laser beam. Because the heat input is very low, there are no brittle components that impair the mechanical properties of the seam during forming. The soldered joint zone can withstand a pressure of up to 900 bar without tearing. 900 bar is more than sufficient in internal high pressure forming to deform both aluminum and steel. In order to achieve the most uniform possible deformation, the researchers experimented with different material grades. The result: Forming works best when the steel (E235 + C) is combined with a higher-strength aluminum alloy (EN AW-6082).

In hydroforming, a tube is placed in a mold and filled with water. If the pressure is now increased, the pipe slowly adapts to the shape - almost any geometry can be created. In the forming tests, the researchers concentrated primarily on the joining zone and reshaped this area in order to investigate the loads that this weakest zone of the component can withstand and where the limits of the process lie. In practice, the pipe sections away from the joining zone would rather be formed. This could be used, for example, to produce particularly light body components: critical areas that have to absorb large forces in the event of an accident - for example, the connection points to the B-pillar - would be formed from steel, while less stressed areas would be made from aluminum. (qui)

Reshaping

Hot forming of stainless steel in just one process step

Steel profiles

Thickness variable hollow profiles