Calcined refractory brick for industrial furnaces - made from mixt. of periclase, chromite, and chromic oxide

摘要

Calcined, directly-bonded, basic refractory magnesite-chromite moulded brick, in which the matrix contains chromium-enriched spinel structures which bond the individual periclase crystals together. The novelty is that the brick is made using a mixt. by wt of (1) 40-75% periclase contg. min. 94% MgO, (2) 25-60% chromite, and (3) 0.5-10% Cr2O3 powder. The periclase pref. contains 96-99% MgO and the mixt. has an esp. pref. ratio CaO/SiO2 of 0.5: 1 with total SiO2 below 2%. The mixt. is pressed into a brick and calcined at min. 1700 degrees C esp. 1760 degrees C. The mixt. pref. has CaO/SiO ratio max. 1:1, with total SiO2 below 3%, and the pref. mixt. contains (1) 55-65% periclase, (2) 35-45% chromite, (3) 2-7%, Cr2O3, esp. 4% Cr2O3 with size below 0.044 mm, and partic. a max. average size of 10 mu m. Calcining at 1760 degrees C is pref. for min. 4 hrs. Used for linings in industrial furnaces exposed to heavy wear. As compared with conventional bricks, the invention provides, a brick with a significant improvement is working life, better resistance to thermal shock and splitting and better resistance to slag penetration.