Characteristics of the high-current argon arc with various electrode materials

A study was made of the fundamental properties of the high-current d-c arc in argon at atmospheric pressure, at currents of 25 to 100 amperes and for various electrode materials. Spectroscopic observations were made on the arc, and data for the voltage-current and voltage-arc length characteristics were taken for all materials tested. Anode melting rates were determined for copper, iron, and titanium. In addition, some information on minimum starting currents was obtained. These arc studies made it possible to develop a new empirical equation which depicts the electrical characteristics of the arcs investigated over a wide range of currents, including the positive slope region of the V-I curves. With this equation as a basis, reasonable energy and voltage balance relationships were developed and the relative values of the equation constants for the different materials were used for a comparison of their effects on the arc characteristics. In general, the arc is affected more by changes in gas composition than by changes in electrode materials. The melting rate data seemed to support a conclusion that in arcs of this type, over the current range studied, the anode drop is zero or extremely small.