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Effect of variation of different additives on some selected properties of silica sand mould for aluminium castings

Sani A. Salihu    

 The quality of castings in a green sand mould is influenced significantly by its properties, such as green compressive strength, shear strength, shatter index, compatibility, moisture content, permeability and others which depend on input parameters. Usually, the aforementioned properties of a particular casting differ due to variation in composition of the moulding sand mixtures, sand grain shape and size, bonding capacity of the binder, type and quantity of additives used, etc. The present work focuses on the effect of various additives namely, marula shell powder (MSP), silica flour (SF), corn flour (CF) and shea butter (Vitellaria paradoxa) shell powder (SBSP) at different proportions. The quantity of the aforementioned additives for experimentation was varied from 1.0 to 6.0 wt.%. The specimens were tested for moisture contents, green compressive strength, permeability number, shatter index, green shear strength and compatibility. From the obtained test results, all the experimental additives were found to improve the selected moulding properties of the Dukku silica sand. However, moulding sand sample with shea butter shell power 6.0 wt.% (SBSP) and silica flour 3.0 wt.% revealed a better compaction as compared to corn flour and MSP. The presence of silica flour and SBSP in the moulding sand was found to improve sand strength and permeability. Green compression strength, shatter index, and shear strength were found to be highest for the SBSP and SF.