inFluence of ultrA-high Speed on The laser weLding process efficiency And Stability

• Applicant: Professor Dr. Thomas Graf
• Subject Area: Production Automation and Assembly Technology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431336540

The application of deep penetration laser welding of copper materials is limited by instabilities occurring at the vapour capillary and within the melt pool. Up to now, complex countermeasures, such as oscillation of the laser power or spatial beam oscillation, are applied to prevent the resulting formation of defects. The project FASTLAS investigates laser welding at high feed rates and laser powers as a strategy to increase the seam quality and the process efficiency in laser welding of copper. In a cooperative approach, the diagnostics and the experimental resources of the IFSW will be combined with the competencies of the PIMM in the field of modelling and simulation of laser material processing.The IFSW will apply the online X-ray videography to quantify the geometry of the capillary and the fluid dynamics in the melt pool. The distribution of the absorbed laser power and the local temperatures will be determined. This will be done with temporal resolutions of 2 kHz and spatial resolutions of about 20 µm due to the highly dynamic interactions in the copper laser welding process. Based on these measurements, the PIMM will develop a comprehensive model of the welding process. In particular, the geometry dependent incoupling of the laser power and the gas phase will be included in the model, since these are crucial for the understanding of the physical processes that lead to the creation of welding defects and to the stabilization of the process when welding at high feed rates. Based on this comprehensive, multiphysical model, a tool for the prediction and optimization of the welding process will be developed.The strategy of stabilizing the capillary by welding at high feed rates and laser power and thereby increasing the quality of the resulting weld seams is based on preliminary investigations by the project partners. With increasing feed rate, a stabilization of the capillary geometry was found experimentally and theoretically, which resulted in an increase of the seam quality. However, the interaction of incoupling, thermodynamics and fluiddynamics in the melt pool and gas phase are not yet known. This applies in particular to the processing of copper with laser powers of more than 10 kW at feed rates of more than 10 m/min. Given the steady progress in laser technology, it is expected that in the near future a multiple of the today established laser powers will be available at reasonable costs. Laser welding of copper with seam depths of a few millimetres at very high feed rates will then be applicable in industrial environment.The project will contribute to the promotion of production technology for power electronics, most prominently in the field of e-mobility. If successful, incentives will be created to develop high-performance lasers and associated systems technology. The cooperation is intended to facilitate the exchange of knowledge and the joint use of the respective resources. A long-term cooperation is targeted.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Morgan Dal