An experimental study of the electric arc during vacuum arc remelting

An industrial vacuum are remelting (VAR) furnace has been instrumented, ena bling the electric are to be observed for the first time during the remelti ng of a zirconium alloy. The system employed combined high speed video moni toring with synchronized high frequency recording of the are voltage and wa s used to study the are behavior and the mechanisms of liquid metal transfe r from the electrode to the ingot. For current densities of the order of 10 to 20 A/cm(2) and are lengths less than 6 cm, the are is of the diffuse mu lticathode spot type. The metal droplet transfer mechanisms depend mainly o n the are length. For small lengths, transfer is very often preceded by a d rip-short, causing transitory extinction of the are. For long arcs (> 3 cm) , transfer is mainly by gradual erosion of the liquid induced by the cathod e spots.