Dross formation and heat transfer during plasma arc cutting

Plasma arc cutting can be characterized in terms of two distinct speeds. At cutting speeds above , the plasma jet does not cut through metal plate. At speeds below , the molten metal from the kerf sticks to the bottom of the plate, forming the so-called dross. In the first part of this work, both speeds, and , have been measured in a wide range of cutting parameters (currents, metal thicknesses and nozzle orifice diameters) for oxygen plasma arc cutting of steel. In the second part of the work, models by which to calculate and are presented. Comparison of calculated and measured values of allowed us to obtain the efficiency with which the arc power is consumed by the cutting process. It is shown that the efficiency rises as the cutting speed increases. It is suggested that the speed separating dross-producing and dross-free modes of cutting corresponds to a specific value of the Weber number. Calculations performed according to this hypothesis agree well with our measurements of .