Measurement and Analysis of Plasma Arc Components

To better understand keyhole plasma arc (PA) and help improve the process, the authors recently observed that the electron flow may deviate from its ionized arc plasma which is electrically neutral. This phenomenon has been referred to as the arc separability which provides a better way to understand the arc fundamentally. Hence, in this study the authors designed an innovative experimental system to measure/record the heat and pressure from the separated arc components—arc plasma and electron flow. An algorithm was proposed to calculate/derive the distribution of the pressure from its bulk measurements that are easy to obtain accurately. Experiments were conducted to study the effects of welding parameters on the heat and pressure in the arc components. It is found that for the constrained PA, the heat applied into the work-piece through the arc plasma exceeds that from the electron flow and this dominance increases as the current increases. However, for the heat from the electron flow, the constraint on the arc does not change it significantly as can be seen from the comparison with that in free gas tungsten arc (GTA). For the pressure in PA, the arc plasma plays the dominant role in determining its amplitude, while the electron flow only primarily contributes to the distribution.