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Session Chair: Sarah Nothdurft, Laser Zentrum Hannover e.V., Germany
Location:Room 1 ICM
1:30pm - 1:45pm
Influence of beam parameters on the capillary formation and the depth progress in laser spot welding of copper
Frauke Faure, Rudolf Weber, Thomas Graf
Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany
Laser spot welding of copper with a welding depth in the range of several millimeters has gained increasing attention due to the growing field of electromobility. Deep spot welds require the formation of a capillary and this again defines the process time for each weld which is of particular interest for achieving high productivity. The capillary formation and the depth progress are influenced by the laser beam parameters. Spot welding with a laser power of up to 16 kW, a wavelength of 1030 nm and beam diameters of 200 µm and 600 µm were investigated. High-speed X-Ray imaging with a temporal resolution of 0.5 ms during the welding process was used to analyze the depth progress. With the maximum power of 16 kW, a welding depth of 4 mm was achieved in copper within 5 ms. In this talk, the critical beam parameters influencing the depth progress will be discussed.
1:45pm - 2:00pm
Influence of defocusing in deep penetration welding of copper by using visible wavelengths
Florian Kaufmann1, Jakob Ermer1,2, Andreas Maier1, Markus Müller1, Stephan Roth1,2, Michael Schmidt1,2,3
1Bayerisches Laserzentrum GmbH (blz), Germany; 2Erlangen Graduate School in Advances Optical Technologies (SAOT); 3Institute of Photonic Technologies (LPT)
High-quality joining of copper materials has become a key factor in any electric application like electric engines, batteries or power electronics. By now high-power laser beam sources emitting visible laser radiation are available to promote the already well-suited joining method of laser beam welding. Consequently, this process can now face the challenges of welding highly reflective materials, such as copper, which originate mainly in the low absorption of conventionally used infrared wavelengths at room temperature and the rapid jump of the absorption at the transition from solid to liquid state. However, up to now mostly the heat conduction welding process has been examined and the effects of shorter wavelengths on deep welding have been neglected. Thus, for this work the scope lies on the wavelength dependent intensity needed to overcome the deep penetration welding threshold and the alteration of energy incoupling into the vapour capillary.
2:00pm - 2:15pm
Process control of aluminum-copper mixed joints during laser beam welding in vacuum
Uwe Reisgen, Simon Olschok, Niklas Holtum, Christian Frey
RWTH Aachen University - Welding and Joining Institute ISF, Aachen, 52062, GERMANY
The creation of aluminum-copper mixed joints are difficult to produce in all welding processes. This is due to the unavoidable formation of intermetallic phases (IMP), which reduce the mechanical technological properties of the weld and to the different melting points of pure aluminum and copper.
Laser beam welding in vacuum with a single-mode fiber laser ensures precise temporal and local energy input, allowing a controlled degree of melting copper and homogeneous mixing of both materials. The aim is to record the radiation characteristics of the mixed joint in vacuum to determine the degree of copper and consequently the IMP.
It is shown that the currently used 4-wire method does not allow inference of IMP. A more promising method, which was successfully tested on laser beam in vacuum welds, is detection of the characteristic copper wavelength 521.8 nm, which allows conclusions to be drawn about the copper content in the weld.
2:15pm - 2:30pm
Remote laser beam welding of copper to aluminum using a frequency-doubled disk laser
Lazar Tomcic, Christoph Neumeier, Michael F. Zaeh
Technical University of Munich, Institute for Machine Tools and Industrial Management, Germany
When joining copper and aluminum, intermetallic compounds with complex properties can form and negatively affect the mechanical and electrical properties of the weld seam. Laser beam sources with emission in the visible wavelength range enable welding of copper with high process efficiency since its absorptivity is significantly higher there than for the near-infrared wavelength range. In this study, copper was welded to aluminum in an overlap configuration, using a continuous wave laser beam source emitting at 515 nm. Preliminary experiments were carried out to identify a suitable process window for further experiments. Subsequently, the electrical resistance and the tensile joint strength in dependence of the feed rate were determined. Through metallographic cross-sections, the weld seam and the formation of intermetallic compounds were investigated. The results show that dissimilar joints with good physical properties can be obtained using green laser radiation, enabling new possibilities for joining copper and aluminum.