Study On Non-Newtonian Fluid Properties Of Mold Fluxes For High Manganese And High Aluminum Steel

Mold flux is a key material to enhance continuous casting efficiency and improve slab quality.Its main functions are controlling heat transfer,lubrication slab,absorbing inclusion of molten steel,avoiding second oxidization of molten steel and heat preservation.The lubrication of mold flux is achieved through mold flux film between slab and mold.The viscosity of mold flux is an important parameter to measure the lubrication of mold flux.The past researches on mold flux are all based on that mold flux is Newtonian fluid whose viscosity tends to be a constant value.Since many researchers focused on non-Newtonian behavior of mold flux to design new mold flux to meet the different demands in recent years,It is of great practical significance to study the change of fluid properties of mold flux in complex conditions of temperature and shearing force.In this paper,the non-Newtonian fluid properties of traditional CaO-SiO2 based mold flux and the new type of mold flux based on CaO and Al2O3 for high manganese and high aluminum steel are compared and studied and the lubrication of non-Newtonian fluid mold flux are evaluated by numerical simulation to provide some suggestions to the development of mold flux for high manganese and high aluminum steel.Firstly,an new method for measuring non-Newtonian fluid properties of mold flux is proposed though theoretical analysis and experimental verification,defining fluid type of mold flux by results of different sizes of probes and then coming to accurate constitutive equations,which is more accurate and convenient than the former methods.On this basis,the non-Newtonian fluid properties of three kinds of mold flux are compared and studied.It was found that traditional mold flux with weak capability of crystallization shows weak non-Newtonian fluid properties in high temperature and stronger shear thinning properties after the break temperature.Mold flux with strong capability of crystallization shows strong shear thinning properties during the entire cooling process and this kind of shear thinning gets stronger after the break temperature.The new type of mold flux for high manganese and high aluminum steel shows stronger non-Newtonian fluid properties than traditional mold flux.Also,the non-Newtonian fluid properties are relative to the capability of crystallization.Mold flux with strong capability of crystallization shows stronger non-Newtonian fluid properties than those with weak capability of crystallization.Based on this,numerical simulations were performed to evaluate the lubrication of non-Newtonian fluid mold flux.The results showed that there is no difference in the inflow of liquid slag into the mold-strand gap on meniscus between the Newtonian fluid mold flux and non-Newtonian fluid mold flux.But the slag consumption and the thickness of slag film of non-Newtonian fluid mold flux are much higher than Newtonian fluid mold flux,which leading to better lubrication.