Physical Simulation Research On Molten Steel Flow Field And Mass Transfer In Bloom Mould

With the continuous development of steel industry,the performance of steel products put forward higher demand.Adding aluminum as an alloy element into the steel can obviously improve the oxidation resistance,electrical and magnetic properties of the steel.However,the[Al]in molten steel is easy to react with the mould during the continuous casting process,which leads to the increasing of alkalinity,viscosity and poor lubrication of mould fluxes,affects the surface quality of bloom cast.Quantitative control of the composition of mould fluxes during continuous casting process is the key to control the quality of high aluminum steel,and the composition change of mould fluxes during continuous casting process is determined by the mass transfer of Al in molten steel,the factors affecting the mass transfer in molten steel are determined by the flow field in the mould.Therefore,it is of great significance to establish the relationship between the parameters which affecting the flow field and the mass transfer coefficient of[Al]in molten steel for improving the quality of high aluminum steel.In this paper,a physical simulation model of 1:0.6 was established based on bloom mould by using the similarity principle.Firstly,the structure size of SEN and operation parameters which affect the flow field of the molten steel were optimized.Based on the theory of boundary layer,a physical simulation method for measuring the mass transfer coefficient of[Al]in molten steel is developed.The relationship between the concentration of Al₂O₃ in the mould fluxes and the capacity mass transfer coefficient is established by using the double film theory,and the effect of casting speed,immersion depth of SEN and electromagnetic stirring parameters on mass transfer coefficient of[Al]in molten steel and concentration of Al₂O₃ in the mould fluxes was studied.The experimental results of flow field in the mould showed that the liquid level fluctuation was small and the slag layer was not active,so the melting uniformity of the mould fluxes cannot be guaranteed.In view of the problem of the original SEN,,selected the 1#and"2#nozzles through the experiment,which are suitable for the present technological conditions.Through industrial application,the field sampling and analysis of the bloom cast showed that compared with the original SEN,the quantity of oxide inclusions greater than 5μm in the bloom cast is reduced by 24%,and the amount of inclusions in each position is more uniform.It showed that the optimizing nozzle was beneficial to improve the flow field of molten steel and the quality of bloom cast.The results of mass transfer simulation in the mould showed that the capacity mass transfer coefficient of[Al]in molten steel increases with the increase of casting speed and decreases with the increase of the immersion depth of the SEN under the reasonable conditions of flow field,and with the increase of the casting speed,the capacity mass transfer coefficient of[Al]in the molten steel increases with the increase of the casting speed.The equilibrium concentration of Al₂O₃ in the mould fluxes increased with the increase of the casting speed,which was independent of the immersion depth and the electromagnetic stirring intensity.The equilibrium time of Al₂O₃ in the mould fluxes increased with the increase of the casting speed and the immersion depth of the SEN,decreased with the increase of electromagnetic stirring intensity.