Degradation of low-carbon MgO-C refractory by high-alumina stainless steel slags in VOD ladle slagline

A new type of low-carbon magnesia carbon refractory (LCMCR) substituting for MgO-Cr2O3 refractory was successfully used in vacuum oxygen decarburization (VOD) ladle slagline, and the composition and microstructure of the used LCMCR were investigated. The results indicated that the decarburizing reaction (MgO-C reaction) in the LCMCR under the VOD refining condition (high temperature, low pressure) was inhibited due to the low carbon content in the MgO-C refractory and the dense layer formed between slag and original layer. The dense layer prevented the penetration of the external O-2 into the LCMCR inside because of the lower permeability of this layer, and thus, the direct burnout of the C in the LCMCR was substantially restrained. On the other hand, the large size crystal and the ultra-low inclusions (SiO2 and Fe2O3) content of the fused magnesia in the LCMCR made the magnesia more slag resistance, because the grain boundary in magnesia had higher slag penetration resistance and the contact area between the slag and the magnesia was reduced. The two aspects of the inhibited decarburizing reaction and the high quality magnesia synthetically contributed to the high slag resistance of the LCMCR.