Performance of kaolin and cassava starch as replacements for bentonite in moulding sand used in thin wall ductile iron castings

Abstract

Thin Wall Ductile Iron (TWDI) casting presents macroscopic and microscopic challenges using bentonite bonded moulding sand. In this study, moulding properties of bentonite, cassava starch and kaolin bonded silica sand were evaluated using various binder/sand formulations (6%, 9%, and 12%). TWDI samples of 3 mm thickness were cast using dry compression strength as criteria for each binder type. Cast samples were subjected to macroscopic, microscopic and Vickers hardness analysis. Kaolin bonded sand gave superior dry strength property of 650 KN/m 2 at 6 % addition. Samples showed nodularity and nodule counts of 96.2%, 587 nodules/mm 2 , 76.2%, 61 nodules/mm 2 and 96.5%, 985 nodules/mm 2 using kaolin, cassava starch and bentonite bonded sand respectively. Thickness deviations were observed in all samples, bentonite bonded samples being most significant. This study has shown that adopting kaolin as alternative binder for production of TWDI casting should be encouraged as properties of cast TWDIs samples were greatly improved. Keywords:Thin wall ductile iron (TWDI), binder/sand formulations, moulding sand properties, macroscopic and microscopic properties.

Archives of Foundry Engineering

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