Research On Reaction Kinetics Of ?Al₂O₃-C?/Fe System

Al₂O₃-C refractories have excellent thermal shock resistance and resistance to melt erosion,so they are widely used in steel flow control system of continuous casting in the steel mill.In recent years,it has been found that the carbothermal reduction reaction of alumina can occur at the steelmaking temperature,which not only increases the content of aluminum and carbon in the molten steel,but also accelerates the destruction of the refractory material.Therefore,studying the reaction kinetics of the?Al₂O₃-C?/Fe system and reducing its reaction rate are of great significance for prolonging the service life of refractories and improving the quality of molten steel.The thesis investigated the Al₂O₃-C and?Al₂O₃-C?/Fe systems combining the experimental research and thermodynamic analysis studying.Firstly,the effects of carbon and iron on the formation of CO in?Al₂O₃-C?/Fe system at low temperature and the reaction kinetics of?Al₂O₃-C?/Fe system at high temperature were investigated.It was to reveal the kinetic characteristics of carbothermal reduction of alumina in?Al₂O₃-C?/Fe system.At the same time,the influence of antioxidants on the reaction rate of different system samples was studied by means of thermal analyzer and high temperature thermogravimetric furnace.It was to investigate the possibility of reducing the rate of carbothermal reduction of alumina in the?Al₂O₃-C?/Fe system.The main conclusions are as follows:?1?Below 1200°C,the presence of Fe reduced the initial formation temperature of CO in the Al₂O₃-C system.However,in this temperature range,regardless of the presence or absence of Fe,not Al₂O₃ but the oxide impurities reacted with C to form CO in the Al₂O₃-C refractories.The change of initial temperature of CO was not affected by a single factor,but by the interaction of carbon material activity and oxide impurities in the raw materials in the Al₂O₃-C and?Al₂O₃-C?/Fe systems.?2?The reaction kinetics of?Al₂O₃-C?/Fe system at high temperature was studied by non-isothermal analysis method and the expressions of activation energy E_a,the pre-factor A and the reaction rate constant k were obtained.The results showed that the activation energy and reaction rate constant in the lower temperature stage were lower than the high temperature stage.Combining with the Arrhenius diagram via calculation,the reaction model of the?Al₂O₃-C?/Fe system at different temperature stages was proposed.?3?The reaction kinetics of?Al₂O₃-C?/Fe system with different carbon materials was studied,it was found that the activation energy and reaction rate constant of the?Al₂O₃-C?/Fe system containing microcrystalline graphite were lower than the?Al₂O₃-C?/Fe system containing flake graphite at low temperature stage and high temperature stage.?4?The introduction of Ti₃AlC₂,Si and Al would reduce the reaction rate of?Al₂O₃-C?/Fe system.Comparing the reaction rates of Al₂O₃-C and?Al₂O₃-C?/Fe systems and analyszing the maps of SEM and EDS of refractories crucible and iron samples after the experiment,it was found that Fe promoted the reaction of Al₂O₃-C system.In the?Al₂O₃-C?/Fe system,the reaction between substances affected the content of aluminum and carbon in the molten iron.