Abstract
As used chrome-based refractories may contain toxic Cr6+, the chrome-free Mg2TiO4 phase is being considered which is known to improve hot strength and resistance to thermal shock and slag corrosion. As in situ Mg2TiO4 formation generates porosity, preformed aggregates are desirable. Dilatometric studies revealed that when dead burned magnesia is combined with industrial anatase instead of rutile, it expanded less (1 % versus 7.2 %) and the reaction occurred earlier (965 ℃ compared to 1120 ℃). After sintering at 1,600 ℃, rutile produced an aggregate with 3.8 % open porosity, whereas anatase led to 0 % porosity and a bulk density of 3.24 g/cm3 with a thermal expansion coefficient (70–1,600 ℃) of 13.5 × 10−6 K−1. Moreover, replacing rutile by anatase eliminates the undesirable MgTiO3 phase. The anatase-based aggregate consisted of a Mg2TiO4 matrix with residual unreacted MgO and an intergranular, refractory CaTiO3 phase. The rutile-based aggregate was deemed unsuitable due to a low-melting microstructure of forsterite contiguous with CaTiO3.
