A NUMERICAL PREDICTION OF THE TEMPERATURE DISTRIBUTION IN THE THERMIONIC CATHODE OF A WELDING ARC

The thermal phenomena at the surface of the thermionic cathode of a welding arc are influenced strongly by the mutual interactions of several physical processes. A steady-state axisymmetric finite-element model, incorporating the effects due to the main physical processes in the cathode of normal GTA operations, has been used to determine the spatial variations of the thermal fields. The model differs from previous models in that it considers cathode cooling due to the presence of flowing shielding gas. The calculated temperature distributions are compared with existing experimental data for a typical tip geometry, the numerical results agreeing well around the tip region, whilst the agreement is relatively poor in the regions away from the tip. Finally, the analyses are extended to certain common geometries to examine the consequences of changing the tip profile on the thermal behaviour.