THE ROLE OF DEFORMABILITY INDEX IN THE EVALUATION AND CONTROL OF PROPERTIES OF CLAY - BONDED MOULDING SANDS

Abstract

Investigations have been carried out to study the role of deformability index in the evaluation and control of the properties of clay-bonded moulding sands. It has been frltablished that deformability index along with green compressive strength, both measured simultaneously on a single apparatus, can be used as a criterion for the eva-luation and control of the clay-bonded system sands under some specific conditions. In the sand mixes containing F-32 silica sand having AFS grain fineness number 56 (0.23 mm average grain size) and sodium bentonite (Geko type having 80% montmoril-lonite), the temper water level state as determined by the 'hand-feel' technique has been observed to correspond to an average value of deformability index of 17.0. It has been shown that a sand sample showing a deformability index of 17.0 possesses reasonably high values of green compressive strength, green tensile strength, permeability and shatter index. The assessment of the correct temper water level state of a moulding sand is more easily and reproducibly possible by deformability index measurements than by earlier techniques such as mouldability index and compactability