Role of clay (Bentonite) on mold making process in foundry metallurgy

Abstract

The foundry engineer is usually familiar with the fact that there are different types of clay,such as kaolinite and montmorillonite (bentonite). The bonding action of kaolinite in moulding sands results from the free ionic bonds at the edges of a crystal. These broken bonds are capable of adsorbing foreign ions such as Na+ ;H+ etc. A clay’s maximum capacity absorb ions is called its base exchange and is expressed in milliequivalents per100 grams of clay(A milliequivalen =atomic weight in grams/1000). Green sand mould and dry sand mould using clay as bonds are known as conventional moulding processes since long time ago then CO2 was introduced later.While the green sand is still dominant as the most orthodox type of moulding process and may not be able to lose its position for its economical advantage.