Abstract: In order to study the thermodynamics on deoxidization and the inclusion control of heavy rail steel,FactSage thermodynamic software was used,combining with the actual production,to analyze the complex deoxidization of U75V heavy rail steel and the formation of inclusions under corresponding conditions.The results show that in the production process of heavy rail steel,the dissolved oxygen content in steel decreased continuously with the deoxidization reaction and the movement of deoxidization equilibrium,and the composition of inclusions transformed from SiO₂-MnO to SiO₂-MnO-Al₂O₃ and CaO-SiO₂-Al₂O₃-MgO constantly,the final inclusion was composed of CaO-SiO₂-Al₂O₃-MgO.It was unreasonable to guide the actual production using the thermodynamics of pure iron since there was a large deviation between pure iron and commercial steel on the deoxidization thermodynamics,moreover,the deoxidization thermodynamics for actual molten steel was not yet systematic,and further research was needed.Inclusion controlling should also be considered during the deoxidization process,and it was necessary to ensure the deoxidization effect without affecting the removal efficiency of inclusions and preventing the formation of large size inclusions.

Key words: heavy rail steel, deoxidization, inclusions, thermodynamics