Effect of Additions on Properties of the Mullite-Based Investment Materials

Abstract

Additives will affect directly the clinic operational properties of investment materials, and finally affect the quality of castings. The relationship between additions and properties of the mullite-based investments has been studied. This paper describes effect of HBO3, Na5P3O10 and (NaPO3)6 on properties (including fluidity, initial setting time and compressive strength) of the mullite-based investment materials.It is found that with addition of HBO3, the fluidity of the mullite-based investment materials improves greatly, the initial setting time prolongs, and the compressive strength of investment materials changes little；with addition of Na5P3O10, the fluidity of mullite-based investments improves greatly, the compression strength increases, and the amount of silica gel decreases clearly；with addition of (NaPO3)5, the fluidity of mullite-based investments increases, the initial setting time prolongs, the compression strength decreases, and the amount of silica gel decreases clearly.