Investigating of the influence of non-stationary processes in arc plasma on the depth penetration in high frequency TIG welding

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The advantage of high frequency TIG (HF-TIG) welding in comparison to conventional TIG welding is a significant concentration of energy density in arc either a higher welding depth or welding velocity. The underlying physical interactions of a conventional TIG arc welding with high frequency pulse current are not investigated sufficiently: in fact, the effect of frequency on the depth welding effect was mentioned [EWM-2002] but the effect of pulse current on the depth of penetration was not investigated.Increase of the weldings depth by HF-TIG-welding is not caused by increasing the power of energy source of welding, but it is derived from the combination of physical mechanisms (Arc contraction, behaviour of the current density in arc, fluid dynamics in weld pool etc.) These mechanisms are associated with the direct interaction of HF-pulse currents with the plasma and the metal (as well as its evaporation) and with the changes of characteristics of Anode processes. This should be considered for development of self-consistent model.The aim of this project is the development of a self-consistent model, which describes the physical phenomena in HF-TIG-welding and provides the characterization of mechanisms to increase the depth of welding using these processes. This leads to a considerable knowledge of the effect of increasing welding depth by HF-TIG-welding which is basically well-known, the expression of the dependency of the effects on the concerning complex physical mechanisms are not described sufficiently. The project provides the essential insight of the interactions between a TIG-arc welding and a superimposed high frequency pulse current.The self-consistent model will be developed on the basis of coupled component models which consider the present knowledge about essential physical parameters and interactions mechanisms between the arc, the pulse high frequency current and the metallic base material respectively weld pool. Based on this model, the mechanisms for increasing the welding depth by HF-TIG-welding dependent on the technical parameters will be determined. Furthermore, evaluating and quantifying the influencing variables of this mechanism in interaction with the welding parameters such as pulse shape, frequency and current will be considered. For this purpose, theoretical and experimental methods will be used.The gained knowledge particularly discloses the potential of technology possibilities of HF-TIG welding in the whole and the usage of the high frequency-pulse to increase the welding depth. With that technology, the advantage of a high work piece will be useful with simultaneously more efficient heat input and better energy usage as an alternative for the conventional TIG welding.