Viscosity, Surface Tension, and Density of Blast Furnace Slag and Synthetic Slags at Manufacturing Condition of Hard Granulated Slag

Abstract

Viscosity, surface tension, and density of blast furnace slag and synthetic slags which had nearly the same composition as that of the blast furnace slag were measured below the smelting temperature. The following results were obtained:
(1) Viscosity of synthetic CaO-SiO₂-Al₂O₃-MgO slags increases with increasing SiO₂ and Al₂O₃ contents, and decreases with increasing CaO and MgO contents. Small amounts of another compounds contained in the blast furnace slag cause the decrease of vicosity, and the extent of effect of these compounds on viscosity is similar to that of MgO.
(2) Surface tension of quaternary CaO-SiO₂-Al₂O₃-MgO system is not influenced by the interchange of Al₂O₃ and MgO but increases markedly with increasing (CaO/SiO₂) mol. The surface tension of the blast furnace slag is 472 to 498 dyn/cm in the temperature range 1 380° to 1 500°C, and sulfur has a great influence on the decrease of surface tension. The surface tension of all the systems studied here decreases with increasing temperature.
(3) Great increase of viscosity of blast furnace slag occurs when cooled below 1 405°C to 1 375°C, and it is made clear that this temperature range corresponds to the upper limit of the operation temperature to produce hard granulated slag in the factory.