Study On Non-Newtonian Fluid Characteristics Of Aluminate-Based Mold Flux

For continuous casting of high aluminum steel,aluminate-based mold flux has become one of the new type of mold flux with great potential.However,due to the influence of the basic composition,its viscosity is relatively high,and the function of mold flux lubrication the slab is not good.In order to solve the above problems,this paper proposes that the new aluminate mold flux has relatively high viscosity in the low shear rate region above the meniscus by virtue of the shear rate difference in different regions of the mold and the non-Newtonian fluid characteristics of the metallurgical slag,so as to prevent slag entrapment.In the high shear rate region below the meniscus,non-Newtonian fluid with shear thinning can solve the problem of insufficient lubrication.However,there are few reports on the non-Newtonian fluid characteristics of aluminate-based mold flux,which need to be improved.In this paper,a new type of aluminate-based CaO-Al₂O₃-Li₂O-B₂O₃ mold flux is used as the research object.Based on the principle of rheology,the influence of temperature change and composition change of mold flux on shear thinning non-Newtonian fluid characteristics of aluminate-based mold flux is studied by quasi-Newtonian fluid method.With the help of Raman spectroscopy,the microstructure of the slag was analyzed,and the internal relationship between shear thinning characteristics and melt structure is clarified.Under the condition of this paper,the following conclusions are obtained:（1）With the decrease of temperature,the shear thinning properties of mold flux increase gradually.When the mass fraction of B₂O₃ is increased to 8%or the mass fraction of Li₂O is 6%or 14%,the flow state of mold flux varies slightly with temperature change.With the decrease of temperature,the mold flux undergoes three flow states:Newtonian fluid,shear thinning and sharp increase of shear thinning,and exists an obvious critical temperature of non-Newtonian fluid transition.（2）With the increase of w（CaO）/w（Al₂O₃）,the shear thinning properties of mold flux increase at 1300℃.With the increase of B₂O₃ mass fraction and Li₂O mass fraction,the shear thinning properties of mold flux decrease gradually at 1300℃.When B₂O₃ mass fraction increases to 8%or Li₂O mass fraction increases to 14%,the shear thinning properties of mold flux disappear and mold flux changes from pseudoplastic fluid to Newtonian fluid.（3）The shear thinning properties of mold flux are mainly affected by melt structure.Above the break temperature,due to the decrease of temperature,the increase of w（CaO）/w（Al₂O₃）and the decrease of flux mass fraction,the degree of polymerization of mold flux melt increases and the temporary viscosity loss under shear increases,then the shear thinning characteristics are strengthened.