Effects of adding SiO₂ or Al₂O₃ on the wetting and penetration characteristics of calcium ferrite melts, CaO·Fe₂O₃ (CF) and CaO·2Fe₂O₃(CF₂), to sintered hematite substrate have been examined. And the wetting and penetration characteristics were discussed from the viewpoints of the relation to the viscosity and surface tension of calcium ferrite melts. The effects of the addition of calcium ferrite slag with SiO₂ or Al₂O₃ on the strength of sintered hematite pellets were also examined.
The slag tablets of CF₂-based slag neither melt completely nor spread uniformly on the hematite substrate at the experimental temperature at 1300°C in this study. The wettability of CF-based slag melts on sintered hematite substrate was improved by the addition of SiO₂ or Al₂O₃, and the spreading rate was increased with increasing the value of η/γ (viscosity/surface tension of slag melts). The penetration of CF-based slag melts into sintered hematite substrate was depressed by the addition of SiO₂ or Al₂O₃, and the penetration depth was increased with increasing the value of η/γ surface tension/ viscosity of slag melts). The sintered hematite pellet with CF-5 mass%Al₂O₃ slag sintered at 1200°C had the highest compressive strength in this study. Because the liquidus temperature of CF slag is decreased to about 1200 °C by adding 5 mass% Al₂O₃, and the sufficient amount of liquid phase, which has the appropriate wetting and penetrating characteristics controlled by the surface tension and the viscosity, as a binder was formed.