Optimizing Green Strength of Foundry Sand Using Natural Starch as Additive

Abstract

For any naturally bonded sand to be used for metal casting, it must
possess a minimum of certain physio-chemical and mechanical
properties such as green strength. It is possible to optimize some of
these properties, for example, green strength by using additives in
different forms and quantities. In this study, several properties of Bida
foundry sand were investigated and the values of the green
compressive strength (GCS) and green shear strength (GSS) were
optimized using Taguchi’s L9 orthogonal array with % additive and
% water content as input factors. Thereafter the responses obtained
from the designed experimental runs were evaluated using analysis of
variance (ANOVA). Many of the physio-chemical properties obtained
indicated that the sand studied is suitable for non-ferrous castings.
With the addition of a natural starch (Cassava, Manihot esculenta
Crantz) an increase in green strengths were obtained with a maximum
of up to 30% when the additive was in gelatinized form. Quantity of
additive was found to be the most significant factor with optimal
values of GCS and GSS being 30.36 kN/m2 and 19.8kN/m2
. To control
the effect of process variability, the range of input factors to achieve
optimal values was found to be 3 – 6% additive and 5.5 – 7% water
content. The results obtained indicate that the green strength of the
moulding sand increased with the addition of a natural starch in
powdery and gelatinized forms. This can increase the application
applications of sand in making foundry moulds for non-ferrous
castings.