Abstract: A thermodynamics model for deoxidation in industrial pure iron system with Al， CaSi， CaSiBa as deoxidizers was developed by calculating the equilibrium mass fractions of Si， Al in steel based on the thermodynamics equilibrium and mass conservation. The results from the thermodynamics model can be in a good agreement with the experimental results. The deoxidizers of Al， CaSi and CaSiBa can make the FeO content in slag decrease to 0.04%， 0.08% and 0.08%， respectively. Meanwhile， not only can Al make the oxygen potential of slag decrease to the lowest value， but also its deoxidizing product of Al₂O₃ change little， which shows the excellent performance of stabilizing slag composition.

Key words: slag ion and molecule coexistence theory, electroslag remelting, deoxidation, thermodynamic model