Research On Thermodynamics And Kinetics Of Desulphurization In The Electroslag Remelting Process Of Inconel 718 Superalloy

Inconel 718 superalloy is widely used in extreme harsh environments such as aviation,aerospace,petroleum,electric power,chemical industry and energy because of its unique characteristics of high temperature resistance,corrosion resistance,oxidation resistance and high strength.However,sulfur as an impurity element in Inconel 718 superalloy,sulfur will reduce the creep resistance of Inconel 718 alloy,sulfur is easily segregated at the grain boundary and surface of nickel-base superalloy,resulting in long-lasting life and work of the alloy at high temperatures.The stability is reduced,and how to accurately control the sulfur content in the Inconel 718superalloy is essential for improving the high temperature stability of the material and the long-lasting life of the high temperature.Therefore,based on the thermodynamics and kinetics of desulfurization in the electroslag remelting process of Inconel 718superalloy,the favorable conditions for reducing the sulfur content in the superalloy are clarified,and the influence of slag component on desulfurization during electroslag remelting is clarified.And the mass transfer coefficient and interfacial desulfurization rate of interface desulfurization and mass transfer,and explore the factors limiting the desulfurization during electroslag remelting.In this paper,the mass-concentration control equation of CaF₂-CaO-Al₂O₃-SiO₂-TiO₂-MgO-FeO slag component is established by using the molecular and ion coexistence theory,mass conservation law and mass action law of slag structure,and then the electroslag weight is constructed.The thermodynamic model of desulfurization in the melting process was studied to study the distribution ratio of slag-gold sulphur under different slag conditions.Secondly,the kinetic model of interfacial desulfurization was established by using Fick’s second law,permeability theory and membrane theory to study the interface at different temperatures.The mass transfer coefficient of sulfur and the interfacial desulfurization mass transfer rate are defined as a function of temperature and interfacial desulfurization mass transfer rate.The results show that the mass concentration control equation of the seven-membered slag CaF₂-CaO-Al₂O₃-SiO₂-TiO₂-MgO-FeO is established by using[Fe]-[O]equilibrium and[Fe]-[Al]-[O]equilibrium.A thermodynamic model for slag desulfurization was constructed.The model is verified by experiments,which shows that the desulfurization thermodynamic model based on[Fe]-[Al]-[O]equilibrium is better than the desulfurization thermodynamic model based on[Fe]-[O]equilibrium.The model can be more accurate.Reflect the desulfurization capacity of the slag.The CaO,CaF₂,and MgO in the CaF₂-CaO-Al₂O₃-SiO₂-TiO₂-MgO-FeO seven-component slag can increase the sulfur distribution ratio and enhance the desulfurization ability of the slag.The components Al₂O₃,SiO₂,TiO₂,FeO can be reduced.The sulfur distribution ratio suppresses the desulfurization of the slag.When the FeO content is between 0.4%and 1%,part of FeO in the slag will combine with Al₂O₃,SiO₂ and CaO in the slag to form complex molecules such as FeO·Al₂O₃,2FeO·SiO₂,CaO·FeO·SiO₂,and reduce The activity of FeO reduces the influence of FeO content on the sulfur partition ratio.According to the study of interface desulfurization and mass transfer kinetics,with the increase of temperature from 1833K to 1873K,the desulfurization and mass transfer rate of the interface between metal phase and slag increased from 3.48×10^-7mol/cm³·s to 3.69×10^-7mol/cm³·s,the function of the interface desulfurization mass transfer rate as a function of temperature is:C=0.0055T-6.56.