Effects of Mould Additives on Hardness Property of Grey Cast Iron

Abstract

This study investigates effects of mould additives on the hardness property of grey cast iron using silica sand in Kebbi State. Five moulds with 25% iron dust, 25% coal dust, 25% saw dust and 25% iron dust, coal dust and saw dust additives were prepared respectively with silica sand using bentonite as a binder in wooden mould boxes. The melt was prepared with selected scraps which after superheated to 1555? were tapped while 0.2% inoculant (Fe-Si) was added to the stream to allow uniform dissolution of the inoculant in the melt. Thereafter, the melt was quickly poured into the prepared moulds to avoid gasification of the inoculants where cooling and solidification occurred. Hardness measurement was made using standard approach with Rockwell hardness (HRc). Specimens for microscopy studies were prepared from the samples by machining to appropriate dimensions. Etching for eutectic cells photography and microstructure were done by using Stead’s reagent and nital respectively. The microstructures were examined. Results obtained revealed microstructures with varied amount of eutectic cells and different graphite morphologies. Also, highest hardness value of 61.10 HRC was revealed by mould with saw dust additive and lowest with coal dust additive with 42.10HRC.