Study On Moving Behavior Of Inclusion During Process Of Passing Steel-Slag Interface

Inclusion removal in molten steel is very significant to improving steel quality. As the last process to remove inclusion, that inclusion passes interface and enters slag not only affects inclusion removal efficiency but also could become the limit of inclusion removal in some cases.The study on the process mentioned above was carried out in this paper. Based on the movement and force analyses of inclusion in molten steel, at steel-slag interface and in slag, a new mathematic model to characterize inclusion movement at interface was built successfully. The rationality and validity of the mathematic model was also verified through physical simulation experiments. The mathematic model expanded the Reynolds application range from0<Re<1to Re>0. Meanwhile, the inclusion movement region was extended from the steel-slag interface to the region including molten steel, steel-slag interface and slag. Therefore, the new model replenished and perfected the interface-movement mathematic model for inclusion.Based on the mathematic model above, all the influence factors of inclusion movement at steel-slag interface, including inclusion properties, molten steel properties, slag properties and interface properties, were studied. It was found that the passing ability of inclusion was enhanced as inclusion size, inclusion density and inclusion wettability increased, and was weakened as slag viscosity and steel-slag interfacial tension decreased, and was changeless with molten steel density, molten steel viscosity and slag density. With the properties of molten steel, slag and inclusion in this paper, the critical diameter of inclusion to pass steel-slag interface and enter into slag was236microns. The inclusion of which diameter was smaller than critical diameter could not pass through the steel-slag interface, and stay at the position expressed as R(1+cosθ) near steel-slag interface mathematically.According to the mathematic model proposed in this paper, a numerical simulation model about inclusion moving at interface was built through compiling the solid phase and multiphase flow with FLUENT software. Inclusion trajectory and the fluctuation of steel-slag interface were observed and analyzed. It was found that inclusion movement had a non-ignorable influence on steel-slag fluctuation, which pointed out a research direction for improving the mathematic model.In order to test the influence of steel-slag interface on inclusion removal, the mathetical model of inclusion movement at interface and PBM module were combined to build a new numerical simulation model to simulate the processes including inclusion collision and growing up, floating, and passing through steel-slag interface in100t RH. The following conclusions were found by the simulation results:①Steel-slag interface made an significant influence on inclusion removal in RH. The difference of inclusion removal rate between with interface influence and without interface influence was2.56%when the smelting time was600s;②Comparing with the inclusion of larger size, the inclusion of small size was easier to be impeded by steel-slag interface.③The optimal driving gas flow rate was60Nm3/h, with which the inclusion number at steel-slag interface was least;④For the inclusions among16μmand161.27μm, the impediment of interface decreases as the gas flow rate increases. For the other inclusions, the gas flow rate has little impact on the impediment of interface.