Ceramic Coating for Cast House Application

Abstract

The coatings for moulds and cores represent an integral part of castings production. Basic role of ceramic coatings is to form an efficient refractory barrier between the sand substrate and liquid metal flow during the phase of casting, solidification and forming of the castings. This provides a smooth and clean surface of castings, with no adhered sand or defects due to metal penetration into the mould (lumps, dents, rough surface and alike). Dimension accuracy and surface appearance of castings depend both on metal and mould. In casting practice, sand casting technology is widely applied for castings production. Quartz sand mostly used in the composition of mould and core blends has a number of faults – low refractoriness, high heat expand coefficient, causing casting surface faults, especially when metals and alloys with high melting temperatures are concerned. Higher quality mould blends based on zircon, olivine, chromite, sinter magnesite containing much better thermalphysical properties than quartz sand are relatively less applied for their high pricing. Various additions to mould blend are used more frequently, as well application of ceramic coatings on moulds and cores. Application of higher quality ceramic coatings significantly influences either reduction or elimination of expensive cast house cleaning and machining operations for the castings, thus directly reducing production costs of a foundry.