Composition and Process Optimization of Modified Heat-Hardened Sodium Silicate Bonded-Ceramic Sand

Ceramic sand with high heat resistance is used as foundry sand, because of the direct contact with molten metal during pouring. However, the sodium silicate bonded ceramic sand (SSBCS) prepared with sodium silicate as a binder still has the problems of short storage time and poor collapsibility. Therefore, it is necessary to modify SSBCS with the modifier. In this paper, the composition and process parameters of the complex modifier (TiO2, ZnO and SiC) of modified heat-hardened SSBCS were optimized, and the modification mechanism was analyzed. The results revealed that the heat-hardened SSBCS had the best comprehensive properties when the composition of the complex modifier was 0.4% TiO2, 0.3% ZnO and 1% SiC, the heating temperature was 150℃ and the heating time was 120 s. Compared with unmodified SSBCS, the instant tensile strength (σ0), 4 h tensile strength (σ4h) and 24 h tensile strength (σ24h) of the modified sand core increased by 31%, 26% and 28%, and the residual tensile strength (σ800°C) decreased by 30%. In addition, this modified SSBCS could be applied to actual production.