Effects of magnetically supported laser beam welding of aluminium alloys

Systematic investigations of the influence of an external magnetic field on the seam cross-section in CO2 laser beam welding of aluminium alloys will be presented in this paper. It will be shown that, in dependence of the orientation of the magnetic field, the shape of the cross-section is changed and an increase of the cross-sectional area of up to 50 % can be reached. In addition, the melt flow is stabilized in presence of the magnetic field, which results in less fluctuations of the cross-sectional area. Further systematic welding experiments with filler wire were performed within a magnetic field and, to intensify the magneto-fluid-dynamic forces, an external electric current was applied. During these experiments new effects were found, not noticed before. The most important one is the fact that melt can be pushed down or lifted up in dependence on the particular parameters. Whereas in magnetically supported welding with Nd:YAG lasers no significant effect could be observed in first experiments, it turned out that effects can be achieved similar to the results obtained with a CO2 laser when an external electric current is utilized. In order to visualize the weld-pool dynamics, thermo-graphic pictures and high-speed video observations were taken.