Electro slag crucible melting for recycling of low oxygen high conductivity copper scrap

Abstract

Recycling of oxygen free high conductivity (OFHC) copper scrap was carried out through a modified electro slag melting technique using a graphite electrode and graphite crucible. Of the three slags used, a cryolite based slag was found to yield copper ingots with low (2 to 40 ppm) oxygen content and high (up to 98% IACS) conductivity. A slag as well as graphite of high purity are essential since the impurities present in the slag and graphite may contaminate the copper during melting. Possible mechanisms of impurity (Fe, Si, Mg, Ca and S) pick-up by copper are discussed. Identical results were obtained using cathode copper instead of OFHC copper scrap indicating that the process may be used to produce low oxygen high conductivity copper ingots directly from cathode copper.