Study On Volatilization Mechanism And Influence Of Continuous Casting Mold Flux

The physical and chemical properties of the continuous casting mold flux plays a key role in the smooth continuous casting process and high-quality slab production and are determined by the compositions.When measuring the physical properties,such as melting point and viscosity of the fluorine-containing mold flux,it is often accompanied by high temperature and high temperature keeping time,Which can make the composition keeping volatilizing and the final determination performance of the slag is not the same with the beginning one.Such problems are common in the measurement of volatile component slag properties.Up to now,there is no effective solution to this problem.It is of great theoretical significance and practical application value to explore the volatilization mechanism of volatile components,predict the variation of slag composition and finally to get the accurate slag physical and chemical properties.In this paper,continuous casting mold flux is taken as the research object.The property deviation generated in the determination of melting point and viscosity was studied.The orthogonal test is used to design the compositions of mold flux,and the range of the slag is chosen referd to the industrial high carbon steel mold flux composition.The basic physic-chemical properties of the mold flux which is including the melting point,viscosity and phase change of the heating process,were calculated by FactSage software.The Gibbs free energy of each volatile reaction was also calculated.The melting point and viscosity of the mold flux were determined by experiments.Combined with the thermogravimetry and high temperature sampling,the volatilization mechanism of the mold flux was studied,and the slag composition corresponding to the physic-chemical properties of the mold flux was corrected to make them accurate.The main findings obtained are as follows:?1?The ease of the volatiles in the continuous casting mold slag is NaF>NaAlF₄>CaF₂>MgF₂>SiF₄>AlF₃>AlOF.The main volatiles are alkali metal fluorides and a small amount of alkali metal oxyfluorides.The main volatiles in the whole volatilization stage are NaF and CaF₂.NaAlF₄,AlF₃,AlOF and SiF₄ are in the different volatilization conditions which are formed according to the difference of the components;?2?The regression equation of theoretical melting point and the viscosity at 1300°C with composition changing results were calculated by FactSage software.And the melting point and viscosity of the slag was measured.The comparison shows that the difference between the thermodynamic calculation result and the actual measurement result melting point value is-25.38°C⁷3.19°C,the measured viscosity value at 1300°C is-0.342².018Pa·s;?3?In the orthogonal test design of the slag composition group.The weight loss of melting point determination process can reach 3.32%-12.42%,and the slag weight loss during the viscosity measurement process is 12.76%-25.73%.The kinetic equation of volatilization and the limiting conditions of volatilization of alkali metal fluoride were obtained by the weight loss curve of the protective slag.?4?The mold fluxes through different forming methods are measuring with the melting point and the thermogravimetric determination.The results showed that the volatilization mechanism is influenced by the different forming methods of the mold flux.And the reason for the difference in melting point is considered to be caused by the difference in composition of the pre-melted slag during the pre-melting process resulting in the determination of physical properties in the slag.?5?Through the theoretical analysis and measured data,combined with the measured slag weight loss and the residual slag composition to correct the composition.The regression model is obtained,and the corresponding changed components can be linked to different physical properties.The research results can provide more accurate support for the physical properties of continuous casting mold flux,and can provide reference for the determination of volatile slag performance.