Effect of Cerium on the Microstructure and Inclusion Evolution of C-Mn Cryogenic Vessel Steels

The effects of Cerium (Ce) were studied on the casting slab quality, microstructure, and inclusion evolution of cryogenic vessel steel. An optical metallographic microscope, scanning electron microscope, energy dispersive spectrometer, and Thermo-calc thermodynamic software were used for characterization and analysis. The results indicated that the central segregation was significantly improved after adding Ce and reached the lowest level when the content of Ce was 0.0009 wt.%. Meanwhile, the presence of Ce reduces the size of ferrite and improves pearlite morphology. Ce also enables the modification of Al₂O₃ and MnS + Ti₄C₂S₂ inclusions into ellipsoid CeAlO₃ and spherical Ce₂O₂S + Ti₄C₂S₂ composite inclusions, respectively, which are easier to remove. The formed Ce₂O₂S inclusions are fine and can work as heterogeneous nucleation points to refine the microstructure of steel.