Influence of basicity on physical properties of slags of the СаО – SiO₂ – 18 % Cr₂O₃ – 6 % B₂O₃ – 3 % Аl₂O₃ – 8 % МgO system

Abstract

Influence of basicity on viscosity, crystallization onset temperature, phase composition, and structure of slags of the СаО – SiO2 – 18 % Cr2O3 – 6 % B2O3 – 3 % Аl2O3 – 8 % МgO system in the basicity range (B = CaO/SiO2 ) from 1.0 up to 2.5 was studied using vibrational viscometry, thermodynamic modeling, and Raman spectroscopy. It was established that the physical properties of slags depend on the balance of polymerization degree and phase composition. Acid slags with a basicity of 1.0 belong to the category of “long” slags and are characterized by an increased proportion of high-temperature phases up to 34.1 %. However, despite the fact that the proportion of high-temperature phases is 1.6 times higher compared to the proportion of low-temperature ones, they are characterized by a simpler silicate structure, providing a viscosity of no more than 0.25 Pa·s at a crystallization onset temperature of 1530 °C. An increase in basicity of slags of the studied oxide system (up to 2.5), along with an increase in the proportion of high-temperature phases (by almost 5.9 times), is accompanied by formation of a more complex silicate structure. The resulting four-coordination structural elements [CrO4] and [AlO4] are embedded in the silicate structure and complicate it, which increases the polymerization degree. Thus, at basicity of 2.5, due to a high proportion of high-temperature phases in the slag and development of polymerization process, slag crystallization onset temperature increases to 1700 °C and its viscosity reaches 1.0 Pa·s at a temperature of 1670 °C.