Effect of Refining Slag Composition on the Cleanliness of 25Cr2Ni4MoV Rotor Steel

The effect of different refining slag components on the cleanliness of 25Cr2Ni4MoV turbine rotor steel was studied through four industrial experiments. It is found that less total oxygen, dissolved oxygen, inclusion quantity and smaller inclusion size could be obtained with a basicity of the refining slag between 3 and 4 and a C/A ratio between 7 and 10. FactSage7.0 was used to study the influence of slag composition on dissolved oxygen in molten steel and Al2O3 inclusion adsorption. The results reveal that high basicity is beneficial to reduce dissolved oxygen in molten steel, and less Al2O3 inclusions exist with high basicity and high C/A. Then, the evolution of typical inclusions in the refining process was discussed. Next, the physicochemical parameters of refining slag were analyzed, the viscosity and melting point of the four groups of refining slag showed that the addition of SiO2 and Al2O3 in the slag can reduce the amount of CaF2. Finally, the influence of the composition of refining slag on the lining erosion was investigated.