Effects of Cerium Addition on Solidification Structure and Mechanical Properties of Cr30Mo2 Super Ferritic Stainless Steel

The effect of different Ce contents on the microstructure and mechanical properties of Cr30Mo2 super ferrite stainless steel was studied. The results show that the types of inclusion in the Cr30Mo2 super ferrite stainless steel are mainly Cr-rich oxides and Al-Si composite oxides with irregular shapes, which are converted into Ce2O3 after Ce addition and spherical composite inclusions rich in Al and Si in the core and Al and Ce in the outer layer, with small size, round shape and the significantly reduced inclusion content. Ce2O3 can be used as heterogeneous nucleation core, which can increase casting nucleation rate and reduce grain size. However, excessive Ce content results in abnormal increase of grain size. Trace Ce can significantly improve the plasticity of Cr30Mo2 stainless steel at room temperature. Adding 0.07wt% Ce can increase the elongation after fracture of Cr30Mo2 super ferritic stainless steel castings from 1.5% to about 20%.