Predictions of weld formation using gas tungsten arcs for various arc lengths from unified arc-electrode model

Predictions have been made of weld formation for stationary gas tungsten arc welding by making two-dimensional (2D) calculations of temperature and fluid flow velocity of the arc and the electrodes. The whole region of the arc system is modelled, including the tungsten cathode, the arc plasma and the workpiece anode, and convection within the weld pool. Predicted properties of the weld shape for 150 A arcs in argon and helium, for various arc lengths, are compared with experimental results of cross-sectional area of weld. Although total power to the anode increases with increasing arc length, for argon arcs the heat flux density at the axis of the anode becomes lower, with the result that the cross-sectional area of the weld becomes smaller with increasing arc length. For helium arcs total power to the anode also increases with increasing arc length, but the distribution of heat flux density to the anode is approximately constant, with the result that the cross-sectional area of the weld increases. These predictions are in agreement with experimental results that we have obtained.