Fundamental Research On Deposition And Peeling Of Inclusions In Aluminum Deoxidized Steel On The Submerged Entry Nozzle

Aluminum is widely used in steelmaking due to its high efficiency and low cost.However,inclusions were formed during aluminum add into molten steel;these inclusions will be attached to the nozzle wall that caused nozzle clogging.Nozzle clogging has affected the casting process for a long time.The nozzle needs to be replaced frequently when the nozzle is blocked by the nozzle clogs,which increases the intermittent operation of continuous casting that affects slab quality.The molten stream in the mold will be biased when the nozzle clogging exists,affecting the transport of inclusions.The casting will stop when the nozzle clog blocks the nozzle severely,which results in economic loss.The peeled nozzle clogs will be captured by the solidified shell that forms rolling defects and reduced steel quality.The key to solving nozzle clogging is to analyze the influence factors and simulate the formation process.The mechanism of inclusion transport in the boundary layer was investigated.The mechanism of deposition and peeling of the inclusion on the nozzle wall were studied.The multi-scale model was established to simulate the nozzle clogging formation and peeling.The effect of nozzle clog on the molten steel flow,inclusion transport,and the distribution of peeled nozzle clog in the solidified shell was studied.The scope of the paper has a significant meaning in reducing nozzle clogging,stabilizing production,and improving the cleanliness of steel.The boundary layer of the hydraulic submerged entry nozzle was measured by particle image velocity technology;the sweep and ejection events were extracted by the quadrant analysis method;the inclusion transport was calculated by the inclusion transport model.The mechanism of inclusion transport was studied:the inclusion transport to the nozzle wall when the sweep events occurred;the inclusion leaves the nozzle wall when the ejection events occurred.The distribution of sweep events was increased when the morphology of the nozzle wall changed from a smooth wall to a clogged wall,which accelerated the formation of the nozzle clogs.The results provide a theoretical basis for inhibiting the transport of inclusions to the wall,reducing the nozzle clogging,and providing academic support for the mechanism model of the inclusion deposition and peeling on the nozzle wall.The mechanism model of inclusion deposition and peeling was established by applying the mechanism of inclusion transport in the boundary layer and the force analysis of the inclusion on the nozzle wall.Under the condition of the current study,the nozzle clogging will be reduced when the count of inclusion in molten steel decreases;the molten steel viscosity,molten steel density,and surface tension of the molten steel increase.The study has provided a theoretical basis for controlling nozzle clogging.The deposition and peeling of inclusion on the nozzle wall were observed in situ.The effect of the content of inclusion in molten steel on inclusion deposit on the refractory wall was studied;results show that the deposition rate will increase when the content of inclusion is higher in the molten steel;results were consistent with the simulation results of inclusion deposition and peeling model.The multi-scale model of inclusion deposition and peeling on the nozzle wall was established based on the mechanism model of inclusion deposition and peeling.The formation process of nozzle clogs in the bilateral-port nozzle was simulated,and the simulation results of nozzle clogs were verified by industrial experiments.The molten steel flow was biased,the floatation rate of the inclusion in molten steel was decreased,and the count of peeled nozzle clogs was increased when the nozzle clog grew.In the straight submerged entry nozzle,the molten steel flow was diverse,the count of peeled nozzle clogs was increased,the size of the peeled nozzle clog decreased,and the floatation rate was decreased when the nozzle clog grew.The model is provided a theoretical method for predicting and modifying nozzle clogging and improving the cleanliness of steel.