Effect of Ce-La on inclusion evolution in Al-killed high strength steel
Ruming Geng, Jing Li, Chengbin Shi, Jianguo Zhi, Bin Lü
Abstract
The mechanism of inclusion evolution after rare earth addition based on oxide metallurgy was investigated experimentally and using thermodynamic calculations, where Ce-La was added to Al-killed high strength steel during Ruhrstahl-Heraeus refining to modify the oxide inclusions within the steel. The typical inclusions observed before Ce-La addition were spherical magnesium aluminate spinel inclusions. And fewer individual Al 2 O 3 inclusions and Al 2 O 3 –TiO x inclusions were also observed. The addition of Ce-La led to transformation of MgO · Al 2 O 3 spinel inclusions to (Ce,La) 2 O 3 , (Ce,La) 2 O 2 S and (Ce,La) 2 O 2 S + MgO · Al 2 O 3 inclusions. Thermodynamic calculations indicated that Ce-La combined with dissolved oxygen and sulfur in molten steel to form rare earth inclusions, while the remainder of the Ce and La modified MgO · Al 2 O 3 to (Ce,La) 2 O 3 and (Ce,La) 2 O 2 S.