Evolution Of Viscosity And Structure Of Slag During The Ladle Furnace Refining Process

The analysis on the relationship between the physical properties of metallurgical slag and its melt structure is helpful to understand the micro essence of metallurgical function of molten slag,which can provide the guidance for designing the metallurgical slag and improving the smelting effect.Focusing on the composition of ladle furnace refining slag,the melt structure and viscosity of experimental slag were measured.And then based on the flow theory of silicate network,the viscosity prediction model for CaO-SiO2-Al2O3-FexO slag was established,which realized the accurate prediction of slag viscosity.The melt structure of molten slag was measured by Raman spectroscopy.The result shows that Fe3+ exists in the forms of[FeO4]-tetrahedron and[FeO6]-octahedron.With increasing w(CaO)/w(SiO2),Fe3+ is inclined to form[FeO6]-octahedral unit,and Al3+ exists as the coordination cation(Al3+)and the tetrahedral units of Q2Al,Q3Al,and Q4Al.As the value of Al/(Al+Si)increases from 0.41 to 0.85,Q2Al unit transforms into Q3Al or Q4Al units,and Si4+exists as Q0Si,Q1Si and Q2Si tetrahedral units.With the further increase in Al/(Al+Si),Al3+coordinated with the Si-O non-bridging oxygen bond gradually increases in molten slag.In general,during the upgrading process of ladle refining slag,the NBO/T of molten slag decreases and the degree of polymerization of melt slag increases.The viscosity of molten slag was measured by the rotating cylinder method.The result shows that during the upgrading process of ladle refining slag,the viscosity of molten slag decreases with the increasing w(CaO)/w(SiO2)(R=4.00?11.00),and the viscosity is more significant when the temperature of molten slag is 1823K and the basicity of molten slag is 11.00.Meanwhile,the viscosity of molten slag increases with the increasing mass fraction of Al2O3(30%?50%),but viscosity is affected weakly by the Al2O3 content on the condition of higher temperature.Based on the analysis results of the melt structure,the viscosity prediction model of CaO-SiO2-Al2O3-FexO quaternary slags was established referring to the flow mechanism of the silicate network.The comparison between the prediction data and the experimental data shows that the average uncertainty for the prediction model by the model evaluation parameter is 13.34%,which is higher than the prediction accuracy of other models such as QVC.The model could establish the quantitative relationship between the macro viscosity and micro structure of molten slag,which is propitious to deeply understanding the mechanism of the viscosity transition of metallurgical slag.