Abstract: During railway track changs, frequent impact and contact occur, which imposes strict requirements on the mechanical properties of steel. Therefore, high manganese steel is often used. A study was conducted on the evolution of steel and slag composition, as well as the composition, quantity, morphology, and size of non-metallic inclusions during the LF refining process of high manganese steel for special tracks produced  by a domestic steel plant.The results indicated that the main inclusions in the high manganese steel were MnO-Al₂O₃-MgO-CaO-SiO₂-MnS inclusions. The inclusions entering the LF station were mainly MnO-SiO₂-CaO-Al₂O₃-MgO composite inclusions, with sizes ranging from 1.01  μm to 43.98 μm, and presented as a three-layer structure with a regular spherical shape.After deoxidation and alloying at the LF exit, the size and quantity of the formed inclusions decreased significantly. The large-sized inclusions were mainly those of the CaO-Al₂O₃-MgO-MnO system, with irregular shapes. These inclusions no longer contained  SiO₂, and the Mn content in the inclusions was also greatly reduced.After LF refining, the average diameter, maximum diameter, number density, and area fraction of inclusions all showed an decreasing trend overall, while the basicity of the slag showed an increasing trend overall. The mass fraction of T.O in steel decreases from 16.90×10^-6 to 6.65×10^-6, indicated a good deoxidation effect.Thermodynamic calculations were performed using FactSage. The results showed that with the increasing of T.Al content in steel, Al₂O₃ and CaS gradually increased in inclusions; with the increasing of T.Ca content in steel， CaS and CaO gradually increased in inclusions, while Al₂O₃ gradually decreased. The calculated results have a good correspondence with the actual results.

Key words: high manganese steel rails, evolution of slag composition, evolution of steel composition, evolution of inclusions, thermodynamic calculation