It is recommended that clay graphite crucibles be used for the induction melting of pure copper for rotor applications. These ceramic bonded crucibles are ideal for use with medium frequency induction melting, providing clean melting, good thermal conductivity and excellent resistance to chemical corrosion.
Figure 9.6.1: Clay graphite crucibles available from Morgan Molten Metal SystemsClay graphite crucibles perform better than graphite crucibles for melting copper, due to their lower cost, better oxidation resistance and lower electrical conductivity. The lower conductivity of the clay graphite material reduces the absorption of the induction field by the crucible, allowing more of the current be induced directly into the copper, thereby speeding the melting of the copper.