基于等离子弧和熔池的数值模拟，研究了热导型等离子弧焊的电弧物理特性和熔池动态行为，并使用光谱诊断、熔池红外热成像和示踪粒子检测对数值模拟结果进行了实验验证。结果表明，在热导型等离子弧焊中，等离子体向下冲击熔池表面后，向熔池边缘流动。在熔池内部存在2个相反的涡流，熔池中心的逆时针涡流由电弧压力、Marangoni力和Lorentz力驱动，而熔池尾部的顺时针涡流则由电弧剪切力、Marangoni力和浮力驱动。此外，热导型等离子弧焊中的熔池温度高于小孔型等离子弧焊，这是由热导型等离子弧焊中等离子弧能量密度相对较高，熔池内部对流相对较弱导致的。

Conduction plasma arc welding is widely used to weld thin stainless-steel plates in a liquefied natural gas carrier, in which high arc energy density can be achieved through the constraint effects of the constricting nozzle. However, the welding current is relatively low, such that a keyhole is not formed inside the molten pool in conduction plasma arc welding, causing significantly different arc physical characteristics and molten pool dynamic behaviors from those of keyhole plasma arc welding. In this study, a one-way coupled electrode-arc-molten pool model was developed, and spectral analysis, infrared thermography, and particle tracing methods were used to investigate the arc physical characteristics and molten pool dynamic behaviors in conduction plasma arc welding. In conduction plasma arc welding, numerical and experimental results show that plasma impinges on the surface and flows toward the edge of the molten pool. Two contrary convective eddies were found inside the molten pool. The counterclockwise eddy at the center of the molten pool is driven by arc pressure, Marangoni forces, and Lorentz forces, and the clockwise eddy at the rear part of the molten pool is driven by plasma shear stress, Marangoni forces, and buoyancy forces. Additionally, the maximum temperature of the molten pool in conduction plasma arc welding is higher than that in keyhole plasma arc welding due to higher arc energy density and weaker convection.