Abstract: Slag-metal equilibrium experiments and a thermodynamic model of the action concentration based on the ion and molecule coexistence theory (IMCT) were used to study in controlling Al and Ti elements during the electroslag remelting (ESR) process of Inconel 625 alloy. The influencing mechanisms of slag components on burning loss of Al and Ti were investigated and the relationship of the activity and its ratio for each slag component with chemical composition in the system was provided， respectively. The results indicate that the slag system with the TiO₂ of 3% has a good effect on the Al and Ti preservation. The CaO in the slag will cause different degrees of burning loss of Al and Ti， in which the excess CaO can lead to the phenomenon of burning the Ti and increasing the Al content. The Al oxidation is restrained with the temperature， in contrast to the Ti oxidation. Eventually， at the 1823K， the composition of the slag system is selected as w(CaF₂)=50%~60%， w(Al₂O₃)=15%~20%， w(CaO)=14%~20%， w(MgO)=3% and w(TiO₂)=2.5%~3.5%， respectively， so as to reduce the Al and Ti burnout effectively during the ESR process of Inconel 625.

Key words: Inconel 625 alloy; electroslag remelting; ion and molecule coexistence theory; thermodynamics; oxidation of Al and Ti