Smooth seam surfaces in laser deep penetration welding by producing a weld pool cavity

• Applicant: Professor Dr.-Ing. Peer Woizeschke
• Subject Area: Joining and Separation Technology
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 290705638

In car manufacturing, visible seams are commonly produced by laser beam brazing in order to ensure the fulfilment of the high requirements in terms of seam regularity and surface smoothness. Although deep penetration laser beam welding provides a higher energy efficiency and joint strength compared to brazing processes, up to now this process is unsuitable to create smooth seams due to its process related melt pool dynamics and thus inhomogeneous seam formation and pronounced weld ripples. Recent investigations at BIAS regarding a higher gap bridging ability showed that a phenomenon during laser deep penetration welding with transverse beam oscillation and wire feeding correlates with smooth seam surfaces. The observed phenomenon is a parameter related cavity directly moving behind the keyhole. Therefore, the objective of this project is to create optically smooth seams with higher process efficiency by using the cavity phenomenon during laser deep penetration welding. For this purpose, experimental testing along with numerical CFD calculations (Computational Fluid Dynamics) shall be carried out in order to investigate, on the one hand, the mechanisms of cavity formation, stabilization and closing as well as the damping effect of the cavity. On the other hand, the scalability of the cavity phenomenon and the welding process with regard to the sheet thickness as well as the transferability to other alloys and realistic weld seam courses will be tested and analysed. Finally, the process is compared with conventional laser joining processes for aluminum alloys to demonstrate its potential.

• DFG Programme: Research Grants