Research On The Phase Equilibrium Of MIVM Between Slag, Molten Iron And Furnace Gas

In the process of steel smelting,thermodynamic data of all components is indispensable to confirm the extent of reaction.Unfortunately,the experiments of measuring activity do not have sufficient accuracy and stability to ensure the reliability of experimental data in the process of measurement.Hence,there is no doubt that great convenience can be achieved in the actual production process if we can predict the activity of related components with models.In this paper,the thermodynamic properties of all component in Mn-Fe-C,Mn-Si-C,Fe-C-Cr,Fe-Cr-P,Fe-Mn-P and Mn-Fe-Si-C alloys are calculated by the molecular interaction volume model?MIVM?.The predicted results are compared with Wagner interaction parameter formula?WIPF?and Uniform Interaction Parameter Formula?UIPF?both have been widely applied in iron and steel smelting and literature data.The result show that the predicted values of MIVM are in good agreement with the experimental data and meanwhile the predictive effect of MIVM is superior to that of WIPF and UIPF.For example,the average relative error between predicted values of MIVM and experimental data is 5%for Fe in Fe-Cr-P system,while that of WIPF and UIPF are 53%and 51%,respectively.Therefore,according to the better effectiveness and reliability of the MIVM are verified by comparing the predicted component activities with their experimental data.We have reasons to believe that replacing WIPF and UIPF by MIVM in prediction of the thermodynamic properties of multicomponent liquid alloys is feasible theoretically.Based on the above conclusion,all component activities in Fe-Si-P and Fe-C-P liquid alloys are predicted,and its thermodynamic behavioral tendency can be exhibited intuitively from the predicted iso-activity curves.This could provide some reference values in the steelmaking process.Moreover,the author research on the relationship between various calculating coordination number of component and correspongding predicted results of MIVM.The results show that there is a one-to-one correspondence between the different values of the coordination number and binary parameters B_ij and B_ji.That is to say,the binary parameters,B_ij and B_ji,will change along with the different coordination numbers obtained by simplify model parameter or different coordination number formulas.But interestingly,this one-to-one changing parameters and coordination numbers will not influence the fitting result and predictive effect of MIVM seriously if they are used in pair.That means that each coordination number has a value of B_ij that corresponds to that coordination number.The prediction effect of MIVM is determined ultimately by the fitting effect of its sub-binary system.For the slag system,an activity calculation model for calculating activity of each component is established and their results are compared with experimental data calculated by the MIVM pseudo-multicomponent approach.The predicted results have good agreement with the experimental data within a reasonable range.For example,the average relative error between predicted values of MIVM and experimental data are 45%,34%,82%for CaO,FeO and SiO₂ in CaO-FeO-SiO₂ system,respectively.It shows that the MIVM pseudo-multicomponent approach has technical feasibility in thermodynamic properties predicting of slag components.Finally,a preliminary study on the equilibrium distribution of chromium between slag and metal has been done during the reversion process by the formula combination of MIVM and its pseudo-multicomponent approach,through its influencing factors can be predicted.The result indicted that increasing the temperature and the basicity of slag,reducing the partial pressure of CO can reduce the values of Cr₂O₃ in slag.Among them,the partial pressure of CO is the most decisive factor.This work provides certain reference values for steel smelting theory in blast furnace and may offer help to blast furnace operating practices.