Abstract
M.Tech. (Metallurgy)
In the last decade, the growing demand for ecological and economical casting processes has led to the promotion and continuous interest in the non-toxic and cheap, inorganic binders in foundry core making and moulding processes. The new generation inorganic binders usually come in two parts, part one is the binder and part two is a breakdown agent. There is a knowledge gap on the strength development and residual strength of the one component new generation inorganic binders in South Africa. The relationship of performance and residual strength is also unknown with local silica sands from different geological origins in South Africa. The foundrymen have limited knowledge on the strength development and residual strength that can be obtained from new generation single component inorganic binders. This study provides information to foundries and binder manufacturers on strength development and residual strength of single component inorganic binder systems with different local sands. The methodology of the study was achieved through experimental work in the laboratory and a casting trial in a local foundry. The laboratory experiments involved characterisation of the silica sands, strength development and residual strength testing of the binder with different sands and curing processes. The findings of the study did show that the different sand sources show different strength development and residual strength. The new generation single component inorganic binders can achieve good strength development when using a sand with good physical and chemical characteristics. The no bake ester cured achieved a highest strength of 280 N/cm2 after 24 hours. The carbon dioxide cured achieved a highest strength of 164 N/cm2 after 24 hours with minimal gassing time. The heat cured achieved a highest strength of 419N/cm2. The results indicate good strength development. High temperature residual strength of these binders is relatively low ranging from 0-31 N/cm2 depending on the curing method and silica sand source. The information from this study will be important for foundries to make informative core making and moulding decisions.