Experimental and Theoretical Analysis of Deep Penetration Welding Processes with Low-Power Laser-Assisted Plasma Arcs

本研究项目旨在进一步提高我们目前对激光辅助等离子弧焊工艺的认识，特别是考虑到实验验证的低激光束强度和低电弧电流下的深熔效应。首先，通过对不同类型的金属，如铁、铝、镁、钛或其合金进行珠对板焊接试验，确定加工条件。其次，旨在通过特定的实验和理论方法揭示负责过渡到深熔焊接状态的最相关的相互作用机制。首次验证了激光辅助等离子弧焊过程中能量传递效率和热-流-力相互作用可能发生的变化。这包括在深熔焊接条件下的光束吸收、电弧根形成和预热效应的研究。此外，还研究了电弧流与激光诱导蒸发过程相互作用所引起的环境压力分布和局部流场的变化对深穿透效果的影响。在激光辅助等离子弧焊试验中，将采用自主研发的激光束与等离子弧同轴排列方式，引导激光束穿过空心钨阴极。此外，还设计了不同的实验装置，以详细研究可能的相互作用现象。适应的数值模拟模式支持对不能通过实验方法直接观察到的效应进行评估。因此，将确定激光辅助等离子弧焊中最重要的相互作用机制。随着对工艺理解的提高，根据被焊材料的特殊性能，可以推导出激光辅助等离子弧焊的最佳参数设置指南。

This research project aims at the further improvement of our current knowledge about laser-assisted plasma arc welding processes with particular consideration of the experimentally verified deep penetration effect at low laser beam intensities and low arc currents. Firstly, the processing conditions are to be identified by means of bead-on-plate welding trials for different types of metals such as iron, aluminum, magnesium, titanium or their alloys. Secondly, it is intended to reveal the most relevant interaction mechanisms being responsible for the transfer into the deep penetration welding regime by particular experimental and theoretical approaches. For the first time, new research hypotheses, concerning possible changes of the energy transfer efficiency and of thermal and fluid-mechanical interactions during laser-assisted plasma arc welding, will be verified. This involves investigations of beam absorption, arc root formation and preheating effects under conditions of deep penetration welding. Furthermore, the impact of changes in ambient pressure distribution and local flow fields, induced by the arc flow in interaction with laser-induced evaporation processes, on the deep penetration effect are to be characterized. A self-developed coaxial arrangement of the laser beam and the plasma arc, which directs the laser beam through a thin hollow tungsten cathode, will be applied for the laser-assisted plasma arc welding trials. In addition, different experimental setups are designed for detailed investigations of possible interaction phenomena. Adapted numerical simulation models support the evaluation of effects that cannot be directly observed by experimental methods. As a result, the most important interaction mechanisms in laser-assisted plasma arc welding will be identified. With the improved process understanding, guidelines for optimal parameter settings for laser-assisted plasma arc welding can be derived, depending on the particular properties of the material being welded.