Effect Of Fluxing Agents On Melt Structure And Viscosity Of Mold Fluxes

With the development of efficient continuous casting technology,the influence of mold fluxes on the quality of slab becomes more and more prominent.The workers of continuous casting at home and abroad are devoted to the optimum design of slag components and the development of new slag system.In this paper,fluoride-free mold fluxes based on CaO-SiO2 system were studied,the melt structure of the mold fluxes were determined by Raman spectrometer,and the viscosity of the fluxes were determined by melt physical comprehensive tester.The influences of fluxing agents such as B2O3,Na2O and Li2O on the melt structure and viscous properties of mold flux were analyzed,and the mechanism of different fluxes in silicate fluxes was discussed.The research work will provide an important theoretical basis for the performance optimization of the existing mold fluxes and the design and development of new type of mold fluxes.Li2O or Na2O in the CaO-SiO2-B2O3 slag system can effectively reduce the slag polymerization degree,viscosity and breaking temperature,their mechanisms were slightly different.Under the same amount of addition,Li2O had stronger effect on the polymerization degree,viscosity and the breaking temperature than that of Na2O.In the conditions of the slag system of this paper,when the additions of Na2O were less than 15%or the additions of Li2O were less than 10%,the decrease of the degree of polymerization was mainly affected by the decrease of the network former units,the increase of network modifier structural units and the increase of the low-polymerized network former units in the CaO-SiO2-B2O3 slag system.When the Li2O additions were more than 10%,the relative proportion of the low-polymerized network former units Q0 and Q1 in the slag still played a dominant role,and the degree of polymerization of the flux decreased.The influence of B2O3 on the degree of polymerization of CaO-SiO2-Na2O slag system and CaO-SiO2-Li2O slag system was different.In the CaO-SiO2-Na2O slag system,when the additions of B2O3 were less than 10%,moderately increasing the content can effectively increase the relative proportion of the network modifier and the network former structural units of the low degree of polymerization,thereby reducing the degree of slag polymerization.When the additions were more than 10%,the formation of[BO4]5-tetrahedron can be promoted,thereby increasing the degree of polymerization of the mold fluxes.In the CaO-SiO2-Li2O slag system,increasing the additions of B2O3 can effectively promote the formation of highpolymerized network former units Q2 and Q3,thus increasing the degree of polymerization.Appropriately adding B2O3 in CaO-SiO2-Na2O slag system can play a significant role in reducing the viscosity and the breaking temperature.In the slag system of this paper,with the increase of B2O3 additions,the viscosity of the mold fluxes gradually decreased firstly and then increased slightly,and the breaking temperature show a gradual decreasing trend.The role of B2O3 in CaO-SiO2-Li2O slag system was different.With the increase of B2O3 additions,the breaking temperature of mold fluxes decreased gradually and the viscosity increased.