Influence of Refractory-Steel Interfacial Reaction on the Formation Behavior of Inclusions in Ce-containing Stainless Steel

Abstract

Effect of Ce addition on the interfacial reaction between alumina refractory and 25wt%Cr-20wt%Ni-4wt%Si-0.5wt%Mn stainless steel deoxidized by Al at 1 873 K was investigated to understand the contribution of the refractory-steel reaction to the inclusion evolution processes. The oxygen content markedly decreased by Al deoxidation, followed by a sluggish decrease by Ce addition greater than 0.5 wt%. The Ce content continuously decreased, but the higher the initial Ce content, the lower the Ce-decreasing rate was obtained. The content of Al initially decreased due to the formation of Al-rich inclusions, followed by an abrupt increase mainly due to a reduction of alumina refractory by Ce at the steel-refractory interface. The content of Al decreased again because of the formation of CeAlO3 compound not only as inclusions but also as refractory-steel reaction products. The CeAl11O18 and CeAlO3 were formed at the refractory side, while the Ce2O3 and CeAlO3 were formed at the steel side in the 0.5 wt% and 1.0 wt% Ce added systems. From the refractory-steel reaction mechanism, the process of inclusion evolution was proposed to three steps as follows. The initial SiO2-rich oxides are reduced by Al, resulting in the formation of aluminosilicates inclusions (Step 1). The Al2O3 in the inclusions are reduced by cerium, resulting in the formation of Ce-rich oxides (Step 2). Because the Ce content continuously decreased due to the refractory-steel reaction, the inclusions transform from Ce-Al complex oxides to Al-rich aluminosilicates and from Ce2O3 to Ce-Al complex oxides in the 0.1 wt% and 0.5 wt% Ce added systems (Step 3).