Spectroscopic investigations for spatial influence from a TIG electrical arc by laser radiation

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The purpose of the project is the fundamental understanding of the interaction between a TIG electrical arc and low power laser radiation. Empirical preliminary investigations have shown the possibility of substantially improving the welding speed in TIG welding if the laser wavelength is in the range of the used shield gas absorption line, and a spatial overlap of the electrical arc and the low power laser radiation can be realized. Following these investigations, the underlying mechanisms of the plasma excitation and the guiding of the electrical arc avoided by the laser will be systematically explained. A further purpose will be to understand and to qualify the relevant variables like wavelength, spot size, intensity and the spatial overlap of the laser radiation in interaction with the welding parameters. On the one hand it will be determined to what extent the laser radiation will be absorbed from the plasma depending on the mentioned variables. On the other hand it will be clarified how the stimulation of the volume of the electrical arc will affect the plasma properties. This includes the spatial and temporal reaction of the electrical arc to the laser effect. With low absorption of the laser radiation in the arc and a focusing close to the work piece surface, effects in the melt pool and in the base of the arc are expected, like an increase of metal evaporation. The latter can also be caused by the increased contraction of the electrical arc because of the laser effect. Therefore, the basic influence of the metal evaporation on the stimulation of the volume of the electrical arc will be analysed. In this content the influence of the laser radiation with wavelength in accordance to the absorption lines of the metal vapour will be evaluated too.The above mentioned results will be brought together to point out the possibilities of the concentration, stabilisation and guidance of the electrical arc initiated by the laser, in particular the hit point on the work piece. As an example a selected TIG-process will be used to demonstrate the potential of raising welding speed and/or welding depth and optimal parameters for the laser influence will be investigated.