The motion behavior of nonmetallic inclusions at the interface of molten steel and slag fundamentally affects the removal of inclusions. Therefore, from an analysis of forces, this study constructed a mathematical model of inclusion movement. Compared with other models that only consider the forces acting on nonmetallic inclusions at the interface, the proposed model considers not only cases in the inclusions which enter the slag interior and rebound into the molten steel, but also the effect of fluid flow containing the inclusions with different Re numbers on the drag force. The application of this established model has not taken Reynolds number of fluid flow into consideration. The model can predict the motion of inclusions at the interface and in nearby areas and provide a curve of inclusion displacement vs time. The mathematical model was verified with a physical model, with the curve of displacement vs time obtained from physical experiment being consistent with the calculated curve. The preliminary calculation results show that inclusions having liquid film at their surfaces are rebounded into the steel when they have size within a certain range but enter the slag phase directly when they are beyond that size range.

Effects of the evolution of inclusions on the pitting corrosion resistance of 304 stainless steel with different contents of the rare-earth element yttrium (Y) were studied using thermodynamic calculations, accelerated immersion tests, and electrochemical measurements. The experimental results showed that regular Y₂O₃ inclusions demonstrated the best pitting resistance, followed in sequence by (Al,Mn)O inclusions, the composite inclusions, and irregular Y₂O₃ inclusions. The pitting resistance first decreased, then increased, and then decreased again with increasing Y content, because sulfide inclusions were easily generated when the Y content was low and YN inclusions were easily generated at higher Y contents. The best pitting corrosion resistance was obtained for 304 stainless steel with addition of 0.019% Y.

Te is a seldom-used alloying element, which is mainly used in free-machining steel. The Te content in this kind of steel is relatively low, and only a small amount of MnTe is generated. In previous studies, the effect of Te on the formation of inclusions was not fully studied. In order to clarify the mechanism, different amounts of tellurium were added into 38MnVS6 steel to form a certain amount of MnTe. The MnTe wrapped the MnS, forming a composite inclusion. With the increase of Te content in the steel, the diameter of inclusion increased, while the aspect ratio of inclusion varied little. The aspect ratio of most inclusions was in the range of 1~3. Besides, the MnS in the MnTe-MnS composite inclusions gradually changed from one big particle to several small particles. The solidification of the steel, as well as the precipitation of MnS and MnTe, was the main factor that affecting the formation of the composite inclusion. The mechanism of the process was systematically expressed in the current study.