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LBW of steel-aluminum corner joints generated by selected laser material melting

: Jahn, Axel; Wagner, Markus; Bellmann, Jörg; Standfuß, Jens; Brenner, Berndt; Beyer, Eckhard

Laser Institute of America -LIA-:
ICALEO 2015, 34th International Congress on Applications of Lasers & Electro-Optics. Conference Proceedings : October 18-22, 2015. Atlanta, Ga., USA
Orlando, Fla.: LIA, 2015
ISBN: 978-1-940168-05-0 (online)
S.702-708, Paper 1502
International Congress on Applications of Lasers & Electro-Optics (ICALEO) <34, 2015, Atlanta/Ga>
Fraunhofer IWS ()

Continuously rising demands on automotive and railway structures require significant weight reductions. Therefore lightweight concepts using metallic hybrid constructions, like steel-aluminum structures, are becoming more and more interesting. The required efficient joining technologies, especially for deformable hybrid body structures are not sufficiently applicable up to now. Conventional heat based joining techniques, like welding or brazing, mainly fail because of pronounced intermetallic phase formations in conjunction with reduced ductility. Therefore Fraunhofer IWS developed a new laser based joining technology especially for high deformable hybrid car body applications. For the joining of hybrid T-joints a controlled laser remote process has been combined with a novel construction approach, the so-called “web-slot-design”. In essence, a special contour is laser-cut into two separate sheet metal components (aluminum web plate / steel cover sheet). The T-joint assembly is produced by placing the web components through the slots of the cover sheet (creating a form fit). Lastly, a one-sided laser beam welding process is realized. The formation of intermetallic phases can be avoided by a selective melting process (thin metallic bond). This includes a highly controlled laser remote process to perform a selective melting only of the low melting material, in this case aluminum. By optimizing the laser remote process different joint shapes can be realized, that generate a one- or both-sided form fit. The paper presents significant results of process research, mechanical property benefits and experimental crash test results of hybrid demonstrator parts. Hence, the characteristics of this technology might be the key in order to solve existing challenges in automotive but also railway lightweight construction.