Numerical Simulation of Laser-Hollow TIG Coaxial Hybrid Arc Characteristics

Literature Overview

This 2021 study by Lei Zheng, Zhu Zongtao, Li Yuanxing, Liu Yan, and Chen Hui from Southwest Jiaotong University investigates the characteristics of a coaxial hybrid welding process combining continuous fiber laser with a hollow TIG arc. Published in Chinese Journal of Lasers, the research employs numerical simulation using FLUENT with user-defined functions (UDF) to model the temperature field, velocity field, pressure distribution, and electromagnetic field of the hybrid arc under steady-state conditions.

Core Technical Findings

The researchers established a mathematical model of the coaxial hybrid arc system using GAMBIT for mesh generation with a minimum element size of 0.1 mm, then solved the governing equations using FLUENT with UDFs for laser heat source, momentum source terms, energy source terms, and material property settings. The simulation was conducted at 150 W laser power and 118 A current, with results compared against a standalone hollow TIG arc under identical conditions.

The key finding is that the laser-hollow TIG coaxial hybrid arc exhibits significantly elevated temperature fields, with both maximum temperature and high-temperature zone area substantially increased compared to the standalone hollow TIG arc. This leads to markedly enhanced energy density and penetration capability. Additionally, the increased temperature and elevated pressure within the tungsten electrode cavity accelerate plasma flow velocity in the upper-middle region of the arc.

Simulation Parameters and Results

The reduction in arc pressure and electromagnetic field strength is an interesting and somewhat counterintuitive result. The increased temperature leads to gas expansion and reduced density, which in turn decreases the electromagnetic forces acting on the plasma. This suggests that the laser component fundamentally alters the arc physics beyond simply adding heat.

Engineering Practice Implications

For welding engineers in the pipe and fitting fabrication industry, this hybrid process represents a promising approach to achieving deeper penetration with potentially reduced total energy input compared to standalone processes. The enhanced penetration capability is particularly valuable for welding thick-walled pipes and heavy section fittings where deep penetration is required.

The accelerated plasma flow velocity in the upper arc region may influence weld pool dynamics, potentially affecting bead geometry and porosity formation. Engineers should consider the implications of altered arc pressure and electromagnetic forces on weld pool stability and spatter generation when adopting this hybrid process.

Key Reflections

The most significant contribution of this study is the quantitative demonstration that laser-hollow TIG coaxial hybrid welding is not merely a superposition of two independent heat sources but rather a fundamentally altered arc phenomenon. The laser component modifies the arc temperature field, which in turn affects plasma flow, pressure distribution, and electromagnetic forces. This understanding is critical for process optimization, as simply scaling laser power and current independently may not yield the expected results.

The experimental validation of simulation results adds credibility to the numerical predictions, though further investigation into transient behavior and dynamic effects during actual welding would strengthen the findings. For engineers evaluating hybrid welding processes for critical applications, this study provides a solid foundation for understanding the fundamental physics that govern process performance.