An electrode extension model for gas metal arc welding

The electrode extension during gas metal arc welding is predicted using a one-dimensional model of the melting electrode. Joule heating in the electrode, heat directly applied to the end of the electrode from the condensing electrons, and heat transferred from the droplet, together with conduction along the electrode are considered. The thermal conductivity, the thermal diffusivity, and the electrical resistivity of the electrode material are allowed to vary with temperature. The steady-state electrode extension is predicted to an accuracy of 1.9 mm. The onset of short-circuiting as the current is decreased for a given electrode feed speed is predicted within 9%. Dynamic analysis shows that the gas metal arc welding process acts as a low-pass filter for electrode extension with respect to the square of the current and with respect to electrode feed speed. As the mean welding current is increased, the electrode extension (or arc length is the contact-tube-to-work distance is constant) has a smaller response to perturbations in the current or electrode feed speed. The quasi-linear transfer functions between electrode extension and current squared and between electrode extension and electrode feed speed can be described by one zero, two pole parametric fits. The transfer functions are linear inmore » the amplitude of the excitation up to 10% of the mean excitation. The model transfer functions were verified with experiments.« less