Characterization and evolution of non-metallic inclusions in GCr15 bearing steel during refining process

The evolution of the inclusion characteristics of GCr15 bearing steel in industrial high basicity refining slag was studied. The number of inclusions with the size larger than 13 mu m (Ds inclusions) at the end of ladle furnace refining is 0.3 N/mm2, and the type of inclusions are MgO-Al2O3 and a small amount of CaO-Al2O3-MgO complex inclusions. At the end of RH refining, the number of Ds inclusions is 0.1 N/mm2, and the type of inclusions is CaO-Al2O3 with a high melting point. The inclusions in tundish stage are mainly high melting point CaO-Al2O3 inclusions, in which Ds inclusions disappear and 97% of the inclusions are less than 6 mu m. The transition mechanism of inclusions with different [Ca] and [Mg] contents was calculated by thermodynamic FactSage software. The results show that the basicity of refining slag has a great influence on the [Al] content and a little influence on the [Ca] content in molten steel. The [Al] content in molten steel can be increased by increasing the basicity and Al2O3 content of refining slag. This method can inhibit the formation of low melting point CaO-Al2O3 inclusions and reduce the size of inclusions.