About 70% of the cast metal objects around us, from bathroom taps to automobile gearboxes, are manufactured in foundries using a method called sand casting. Molten metal is poured into moulds made from green sand — a mixture of sand (about 80%) and clay (about 10%). At high temperatures of about 1500 degrees Celsius required for casting, clay forms a coating on the sand particles, and the sand becomes unusable for further casting. The disposal of such sand has severe environmental and cost implications, particularly for small foundries.
In a new study, researchers from the Indian Institute of Technology Bombay have demonstrated a practical and economical way to reuse this green sand. In this study, researchers led by Prof Sanjay Mahajani have proposed mechanical methods to reclaim the sand as opposed to the expensive heat treatment method. The team has developed an efficient way to remove the clay using an abrasion and sieving unit. This is a two-stage method where the sand particles are rubbed against pebbles in the first stage and sieved in the second stage to separate the clay particles.
The study, published in the Journal of Materials Processing Technology, brings in an invention that caters to the needs of small and medium scale foundry owners.