Effect of Ce on inclusion, microstructure and mechanical properties of Al-killed high-strength steel

ABSTRACT The effect of Ce on inclusion evolution in the Al-killed high-strength steel is investigated through experimental observations and thermodynamic calculations. The microstructures are analysed by scanning electron microscope (SEM), optical microscope (OM) and electron backscattered diffraction (EBSD) analysis. Mechanical properties tests are carried out to study the effect of Ce on the tensile and impact properties. The results show that after Ce treatment, the typical inclusions are modified from Al2O3 inclusions and Al2O3+MnS complex inclusions to Ce-O-S inclusions, and the inclusions are refined. The area fraction, size and length/width ratio of martensite-austenite (M-A) constituents decrease with the addition of Ce. In the Ce-containing steel, the grains are finer, and the proportion of high angle grain boundaries and low-Σ coincidence site lattice boundaries is higher. Ce can improve the plasticity and impact toughness of the steel while maintaining high strength.