Preparation and properties of some alumina-chrome refractories

Preparative procedures, grain growth, densification and change in corundum lattice dimensions in sintered compacts made from chromium (III) oxide/aluminium (III) oxide mixtures were evaluated in a study of some alumina-chrome refractories. High-energy milling using "A17 reactive" alumina gave densification at low temperature and rapid grain growth, also a low variability in modulus of rupture. X-ray diffraction studies confirmed solid solution formation, the corundum lattice dimensions decreasing with 7 wt% chromium (III) oxide, other compositions giving lattice expansion. The modulus of rupture at 1150 °C for a series of ethyl silicate-bonded alumina-chrome refractories containing 5 to 12 wt% chromium (III) oxide was also minimal at 7 wt% chromium (III) oxide. The composition of this series is typical of ethyl silicate-bonded alumina-chrome refractories used in the steel industry.