Transient influence of cerium on inclusions in an Al-killed non-oriented electrical steel

Industrial trials and thermodynamic analysis were performed to investigate the transient influence of cerium on inclusions in an Al-killed non-oriented electrical steel. Inclusions were statistically analyzed using an automatic scanning electron microscope. Without cerium addition, inclusions in the molten steel were predominately MgO center dot Al2O3 ones as well as a small number of Al2O3-MgO-CaO ones, and precipitates of AlN and MgS formed in the continuous casting slab. In the steel with approximately 10 ppm total oxygen and 10 ppm total sulphur, inclusions of MgO center dot Al2O3 were modified into homogeneous Ce2O2S ones and Ce-Al-Mg-Ca-S-O dual-phase ones by 35 ppm cerium. With increasing time, the content of cerium decreased to 23 ppm in the tundish and dual-phase inclusions of Ce-Al-Mg-Ca-S-O transformed into CeAlO3 ones. During cooling, inclusions of CeAlO3 transformed into dual-phase MgO-CexS ones in the steel with approximately 14 ppm total magnesium. Thermodynamic analysis was in good agreement with observed results.