High-temperature Interactions of Alumina–Carbon Refractories with Molten Iron

Abstract

The interfacial behaviour of alumina/carbon refractories with liquid iron was investigated at 1550°C, with emphasis on the chemical interactions occurring both in the interfacial region as well as in the bulk of the refractory. The sessile drop technique was used to determine the interfacial wetting behaviour and the phase transformations during the chemical reactions were determined using SEM and EDS. Alumina–carbon refractories were prepared using two types of carbonaceous materials–synthetic graphite and natural graphite. From the experimental results, it was clearly observed that molten iron had penetrated to varying extents into all refractory substrates. The highest penetration was observed for alumina–carbon refractory substrates containing 10% synthetic graphite, while all alumina–natural graphite substrates showed much lower levels of metal penetration. Contact angles for synthetic graphite and natural graphite containing refractories showed an initial drop in the first 5 min of the experiment before increasing and stabilising at different values depending on the composition of the refractories. The initial drop in the contact angles was in direct correspondence with increasing carbon pickup values for these samples. Natural graphite samples generally showed lower carbon pickup as compared to synthetic graphite samples of similar carbon content. The differences in metal penetration and interfacial wetting behaviour were found to depend on the carbon pickup and the ash content of the refractory substrates, with the ash helping in the formation of an interfacial layer which limited reactions with the metal, and in filling the pores within the refractory.