Permanent Moulds:

Permanent moulds are utilized when large quantity of identical shape is the needs. Metallic moulds facilitate rapid cooling rates and therefore refine grain structure. The common materials for permanent moulds are copper, steel, graphite etc.

Steel moulds facilitate precise solidification condition and are sensitive to thermal shocks. In order to avoid thermal shocks these moulds are sprayed along aluminium or Zirconium based sprays.

Specifically Copper moulds are utilized because of their higher thermal conductivity. Utilization of copper must be restricted because of high expense and in arriving at correct dimension.

Increasingly graphite moulds are becoming famous because of their low expense, excellent thermal conductivity and resistance to thermal shocks. But, these might be maintained well below the ovulation temperature of graphite.