ANALYSIS OF ARC PRESSURE EFFECT ON METAL TRANSFER IN GAS-METAL ARC-WELDING

Metal transfer has been analyzed using both the static force balance method and the pinch instability theory. The influences of arc pressure as well as electromagnetic pressure in the development of instability in the cylindrical molten metal were considered. Using perturbation theory, the dispersion equation was obtained in terms of the arc current density, and the drop diameters were then calculated. The drop diameters, which were determined by considering the arc effect, were found to be greater than those drop diameters that were obtained without the arc effect. The transition current was obtained on the assumption that necking starts when the arc covers an entire drop, at which point spray transfer occurs as the molten droplet becomes cylindrical in shape. This explains why spray transfer or transition does not appear with carbon dioxide or helium shielding gas since the arc then exists only at the lower half of the droplet.