Failure investigation of lime coated grey cast iron moulds at TEMCO ferroalloy smelter

Abstract

Abstract This case study outlines an investigation to identify the root cause for the failure of casting machine moulds, manufactured from grey cast iron, at the TEMCO Ferroalloy smelter in Bell Bay, Tasmania. A preliminary stress analysis shows that the thermal stresses developed in the moulds during operation are insufficient to cause failure in a non-defective mould. The failure can instead be attributed to high temperature oxidation that results from a combination of high mould surface temperature, decomposition of the hydrated lime release coating and the grey cast iron structure. Preventing the oxidation reaction would eliminate this material damage and increase the service life of the moulds. The formation of the high temperature oxide can be prevented by reducing the maximum surface temperature of the mould, using a coating that does not release water at operating temperatures or using moulds manufactured from a different type of cast iron.