Effect of Ce2O3 content on structure, viscosity, and melting properties of CaO-Al2O3-MgO-SiO2-Ce2O3 slag

Abstract

To ensure the reliable operation of high aluminum steel smelting, it is common practice to employ low-reactivity CaO-Al2O3-based slag. Various analytical methods, including scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, and so on, are employed to investigate the impact of Ce2O3 content on the crystalline phase and structure within the CaO-Al2O3-MgO-SiO2 slag. Concurrently, the slag properties of viscosity and melting temperature are assessed. The findings reveal that the principal crystalline phases in the CaO-Al2O3-MgO-SiO2 slag include Ca3Al4MgO10, Ca3Al2O6, and MgO. Additionally, the introduction of Ce2O3 leads to the formation of the high melting temperature CaCeAlO4 phase, whose abundance correlates positively with the Ce2O3 content. Ce2O3 demonstrates efficient bridging oxygen bond disruption, causing the transformation of network former [AlO4]-tetrahedron into network modifier [AlO6]-octahedron. Simultaneously, Q4Al shifts to Q2Al and Q3Al in [AlO4]-tetrahedron, resulting in a marked reduction in degree of polymerization of slag. This reduction is evident in decreased viscosity and melting temperature, reaching the minimum value of 0.153 Pa·s and 1331 °C, respectively. However, the Ce2O3 content is beyond 15 wt%, Q2Al and Q3Al transform into Q4Al, which lead to an upward trend in high-temperature viscosity. Furthermore, as the temperature decreases, the precipitation of the CaCeAlO4 phase from the slag occurs. The content and precipitation temperature of CaCeAlO4 increase with rising Ce2O3 content, representing the primary factor behind the elevation of low-temperature viscosity and melting temperature.