Research progress on volatilization characteristics of electroslag metallurgical slag system
Electroslag remelting is a method to purify molten steel,using the resistance heat generated by the current passing through the slag as a heat source for smelting.The products prepared by electroslag remelting have the advantages of high purity,dense structure,uniform composition,and smooth surface,so electroslag remelting is widely used in the preparation of high-end metal materials.To ensure the conductivity of the slag,the electric slag system contains a certain amount of CaF2,which causes severe volatilization during the smelting process and pollutes the environment.The volatilization of fluoride causes significant fluctuations in slag composition,which affects the smelting process and product quality.From the aspects of slag composition,smelting environment,thermodynamics and kinetics,the factors affecting the volatilization of fluoride and the effective methods to reduce the volatilization of fluoride in the slag system are discussed.The effects of CaF2,w((CaO))/w((SiO2))and w((CaO))/w((Al2O3))on the volatilization of slag system are introduced.Reducing the content of CaF2,increasing the w((CaO))/w((SiO2))and decreasing the w((CaO))/w((Al2O3))in the slag would effectively reduce the volatilization of fluoride in the slag.And the possibility of using alkali metal oxides(Li2O,Na2O,K2O),TiO2 and B2O3 instead of CaF2 to develop low fluorine slag is discussed.One of the important directions for future development of low fluorine/non fluorine slag is to replace CaF2 with Na2O,TiO2,B2O3,etc.The effects of smelting temperature and environmental humid-ity on the volatilization of fluorine-containing slag are reviewed.Reducing the smelting temperature,increasing the heating rate,premelting the slag system and maintaining dryness could effectively inhibit the volatilization of fluo-ride.On the basis of investigating the current research status of volatilization thermodynamics and kinetics of electric slag system,the applicability of the slag molecular ion coexistence theory to calculate the activity of slag system compo-nents is introduced,the kinetic mechanism of slag system volatilization is summarized,and the kinetic limiting links of fluo-rine containing slag volatilization in electric slag remelting process are summarized.The molecular ion model has high accu-racy in calculating the activity of common slag system components,and its applicability to other special slag systems still needs further verification.Future research on volatilization kinetics of slag systems should focus on the mass transfer pro-cess of anions and cations participating in volatilization reactions from the main body to the reaction interface,as well as the nucleation,growth,and bubbling processes of reaction products,in order to reduce fluoride volatilization.
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