P 1294 – Novel joining technology for production of hybrid component structures with short flange made of ultra high strength steel and aluminum
In lightweight vehicle construction, ultra-high strength steels are increasingly being used and are combined with components made of aluminum alloys. For this combination of materials, mechanical joining processes have been further developed, however, have basic technological limits and are not applied as widely as resistance welding technology, particularly in the small and medium-sized enterprises (SMEs). Especially during joining hot-stamped components with thin Al-sheets, high joining forces and small tolerance fields are required for a stable joining process. The rivet geometry during the self-piercing riveting must be adapted exactly to the application and the required flange length is large.
For the realization of a cost – effective lightweight construction, a novel method for dissimilar joints made of ultra-high strength steels with aluminum sheets was developed. Where by using simple cost-effective joining elements the short flanges < 10 mm can be realized. The technology is intended to enable SMEs to use their know-how in resistance welding technology and thus to produce steel-aluminum joints without having to switch to riveting or screw technology, which involves considerable investments in systems and continuing education of employees. The joining elements can be easily manufactured by cutting welding wire. The intermetallic phases in the joint plane can be avoid or reduce, so the drop off in joint strength can be avoid.
The sheets should be joint by a very short welding time – less than 30 ms, due to the lower heat input and to provide the possibility of additional adhesive bonding. The properties of joints were determined on suitable test specimens, whereby a special multispot-welded specimen simulated the complex stresses during the production process as well as during industrial manufacturing. In addition to users from the field of component and supplier industries, manufacturers of welding systems, which are mainly small and medium-sized enterprises, can also profit from the results.
Prof. Dr.-Ing. S. Jüttner