Composition Design And Performance Study Of Mold Fluxes For Rare Earth Treated Steels

During continuous casting rare earth treated steels,the performance of mold fluxes was deteriorated due to the reactions between mold fluxes and rare earth and the flotation of rare earth inclusions,as a result,the continuous casting process was disturbed and surface defect of billet was induced by the deteriorated properties of the mold flux.Hence,study and developing mold fluxes with appropriate properties for rare earth treated steels hold great significance for promoting the development of technologies of rare earth application in steels.Based on the previous research,phase diagrams and thermodynamic data,mold fluxes of CaO-Al2O3-SiO₂-Li2O-B2O3 systerm for rare earth treated steels was devised,and then,compositions of the new mold flux were adjusted and its properties were optimizated.Under this experimental condition,the main conclusions were summarized as follows:?1?The new mold flux with w?CaO?/w?Al2O3?of 1.50,Li2O content of 10%,B2O3 content of 5%,CeO₂ content of 5%showed similar properties with the traditional mold fluxes,and its performance was stable during continuous casting of rare earth treated steels.?2?The melting temperature and viscosity of traditional mold fluxes had a substantial increase after adding CeO₂,the breaking temperature of viscosity rised significantly and the crystallizability increased due to the precipitation of CaO·2CeO₂·2SiO₂.?3?The melting temperature and viscosity of the new mold flux was stable after adding CeO₂,the main crystal phase shifted from Li2O·Al2O3 to 2CaO-2CeO₂·Al2O3 which precipitated at a low temperature,thus the significant increase of breaking temperature could be avoided and the crystallizability could remain stable.