Study On The Influence Of Yttrium Oxide On The Properties Of Mold Flux For Low Alloy Steel Continuous Casting

Low alloy steel is a type of high-performance steel with a wide range of applications and many types.Adding rare-earth to the steel during the production of low alloy steel can effectively improve the performance of the steel.Continuous casting is an important stage to determine the quality of steel.It is found that the rare earth steel mold flux will be agglomerated in actual production,indicating that some of the rare earth oxides have been dissolved in the mold flux to change its performance.Take the raw slag that has not been added to the crystallizer on site and the final slag that has completely participated in the cooling process of the slab.The physical and chemical properties of these two slag samples were detected.It was found that yttrium oxide（Y₂O₃）had a greater impact on the physical and chemical properties of the mold flux.In this study,by adding a certain percentage of Y₂O₃ to the low alloy steel E36 steel continuous casting mold flux,hemisphere point method,rotating inner body method,synchronous thermal analysis and other methods were used to explore the protection of low alloy steel continuous casting by Y₂O₃ content.The influence of slag melting temperature,viscosity,crystallization temperature and other physical and chemical properties,phase composition and element migration.This study provides a theoretical basis for the optimal design and development of low alloy steel continuous casting mold flux.The study found that with the increase of the content of Y₂O₃ in the flux,the melting temperature gradually increased,and the turning temperature in the viscosity-temperature curve of the flux also increased significantly.At the same temperature,the mold flux with 6%Y₂O₃content has the highest viscosity,and the mold flux with 4%Y₂O₃ content has the lowest viscosity among the mold flux containing Y₂O₃.Under the cooling condition of 5°C/min,the crystallization temperature of the mold flux will increase with the increase of Y₂O₃ content in the slag.Among them,the maximum is 1209°C when the content of Y₂O₃ is 6%,and it is slightly lower than the former at 1198°C when the content of Y₂O₃ is 8%.Through the use of X-ray diffraction analysis（XRD）and electron scanning microscope（SEM-EDS）to analyze the mold flux after the viscosity test,it was found that the crystalline phase both had gunite（Ca₄Si₂O₇F）and calcium aluminium yellow feldspar（Ca₂Al₂SiO₇）,When the content of Y₂O₃ is 2%,Al₂Y₄O₉ will also be precipitated in the mold flux.When the content of Y₂O₃ is 4%,a small amount of CaYAl₃O₇ crystal characteristic peaks appear in the X-ray diffraction pattern of the mold flux,and the protection when the content of Y₂O₃ is 6%and 8%The characteristic peaks of Al₂Y₄O₉ and Y₂O₃ will appear simultaneously in the slag.Observing the phase morphology through scanning electron microscope,it was found that with the increase of Y₂O₃ content,the irregular rectangular crystalline phase in the mold flux gradually increased.Through energy spectrum analysis,it was found that Ca,F,and Y elements clustered in a brighter backscattered area,and Na,Al,and O elements were clustered in a darker backscattered area.It was also found that the distribution of Y and Al elements in the mold flux has a strong complementarity.Fourier transform infrared spectroscopy and Raman spectroscopy analysis of the high-temperature premelted water-quenched slag found that the regularity of the number of Si-O bonds can explain the change in the viscosity of the slag of different components.Through the peak fitting analysis of the Raman spectrum of each component,the proportions of Q₀,Q₁,Q₂,Q₃ in the protective flux of each component are obtained,and then the types and types of different silica tetrahedrons in the protective flux of each component are inferred In terms of quantity,it was found that the proportions of the mold fluxs Q₀,Q₁,Q₂,and Q₃ of each component are consistent with the laws of viscosity,transition temperature,and crystallization temperature,which can explain the changes in physical and chemical properties from a structural perspective.Through the above research,it was found that the influence of Y₂O₃ on the physical and chemical properties of the mold flux,and the theoretical support was found from the perspective of melt structure,which provided a theoretical basis for the optimal design of the low alloy steel continuous casting mold flux.