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完善我们目前对激光辅助等离子弧焊工艺的认识，特别是考虑到在低激光强度和小电流下的实验验证的深熔效应。首先，通过对不同类型的金属，如铁、铝、镁、钛或其合金进行堆焊试验，确定加工条件。其次，通过具体的实验和理论分析，揭示了影响深熔焊区过渡的最重要的相互作用机制。首次验证了激光辅助等离子弧焊过程中能量传递效率以及热和流体-机械相互作用的可能变化的新的研究假设。这涉及到对深熔焊条件下的束流吸收、弧根形成和预热效应的研究。此外，还研究了弧流与激光蒸发过程相互作用引起的环境压力分布和局部流场的变化对深熔透效应的影响。在激光辅助等离子弧焊试验中，将采用自行研制的激光束与等离子弧同轴布置，将激光束引导通过薄的中空钨阴极。此外，还设计了不同的实验装置来详细研究可能的相互作用现象。经过调整的数值模拟模型支持对实验方法无法直接观察到的影响的评估。因此，激光辅助等离子弧焊中最重要的相互作用机制将被识别出来。随着工艺理解的改进，可以根据被焊接材料的特殊性能，得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.