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

该项目的目的是对TIG电弧与低功率激光辐射之间相互作用的基本理解。初步的实证研究表明，如果激光波长在所用的保护气体吸收线范围内，可以大幅度提高TIG焊接的焊接速度，并且可以实现电弧与低功率激光辐射的空间重叠。在这些研究之后，将系统地解释等离子体激发和激光避免电弧引导的潜在机制。进一步的目的将是了解和限定相关变量，如波长、光斑大小、强度和激光辐射的空间重叠与焊接参数的相互作用。一方面，激光辐射被等离子体吸收的程度取决于上述变量。另一方面，将阐明电弧体积的刺激将如何影响等离子体的性质。这包括电弧对激光效应的空间和时间反应。由于电弧对激光辐射的吸收较低，且聚焦位置靠近工件表面，因此预计熔池和电弧底部的影响会增加金属的蒸发。后者也可由激光效应引起的电弧收缩增大引起。因此，本文将分析金属蒸发对电弧体积刺激的基本影响。本文还对波长与金属蒸气吸收谱线一致的激光辐射的影响进行了评价。上述结果将结合在一起，指出由激光引起的电弧集中、稳定和引导的可能性，特别是工件上的命中点。作为一个例子，将使用选定的tig工艺来演示提高焊接速度和/或焊接深度的潜力，并将研究激光影响的最佳参数。

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.