Influence of phase composition of aluminous porcelain on its mechanical strength

A change in the phase composition caused by variations in the properties of the raw materials and batch composition affects the physical properties of fired porcelain. Variations in oxide content are shown for an aluminous porcelain used for producing high-voltage insulators. 69 phase compositions were calculated for porcelain in which the concentrations were: mullite, 14.47-19-57%; residual quartz, 6.83-15.29%; and glass phase, 43.66-51.80%, and the data were processed by computer using the least-squares method. Mathematical models were obtained for the relationship between strength and phase composition in which there are only two variables, namely the concentration of mullite and residual quartz. It is concluded that the flexural strength of aluminous porcelain increases with an increase in the proportion of one of the crystalline phases. The maximum increase in strength can be attained by increasing the content of mullite in the fired porcelain, at the same time reducing the amount of residual quartz and glass phase. The tensile strength increases with an increase in the mullite proportion.