Study On Microstructure And Mechanism Of Free Fluorine Mold Flux

Fluoride can reduce the viscosity of the slag and promote the crystallization of the crystal.At the same time,it also brings about a series of problems such as damage to human health and pollution.There are generally Li₂O,Na₂O,MgO,B₂O₃,BaO and TiO₂ in the substitute of fluorine free continuous casting slag.The first three kinds of fluorine substitutes are generally recognized as the solvent of the slag.The physical and chemical properties of these components have been more studied.Based on this,three kinds of fluorine substitutes for B₂O₃,BaO and TiO₂ are mainly studied.The relationship between the metallurgical properties of the fluorine and the microstructure of the slag are studied by the Scigress molecular dynamics software and the experimental method.The fluorine free slag phase diagram is drawn by Factsage,and the influence of the fluorine substitute on the slag is established on the macro.The metallurgical properties of mold fluxes are tested by viscosity crystallization equipment.The relationship between microstructure and metallurgical properties of mold fluxes is analyzed by factsage thermodynamic software and Scigress molecular dynamics software.The main conclusions are as follows:1)With the increase of CaF₂ content,the viscosity of the slag is reduced,and the crystallization of the protective slag becomes more and more easy.The polymerization degree of the slag network body is reduced by CaF₂.2)The viscosity of TiO₂ decreased in 3%⁹%,and the viscosity of 9%¹1%increased.The crystallization properties are enhanced with the increase of TiO₂ content.The content of TiO₂ is in3%⁷%,and TiO₂ is alkaline.When the content of TiO₂ is more than 7%,it is acidity.According to the kinetic calculation,the degree of polymerization of the dregs increases with the increase of the content of TiO₂.3)B₂O₃ can reduce the viscosity of mold fluxes.When the B₂O₃ content is greater than 5%,the viscosity decreasing rate becomes slower.B₂O₃ inhibits the precipitation of crystals,and the content is more than 9%.According to the kinetics calculation,the degree of polymerization of slag increases with the increase of B₂O₃ content.The increase of polymerization degree leads to the difficulty of particle moving.Therefore,the crystallization performance is getting worse.4)With the increase of BaO content,the viscosity of the slag decreased.According to the kinetic simulation,BaO easily lost O atoms,which can decrease of the degree of dissolution and the decrease of the viscosity of the slag.The radius of the Ba ion is larger,and the resistance to movement in the melt is large.The movement of ions in the slag is difficult,which leads to the poor crystallization of BaO-containing slag.