GB811985A - Improvements in or relating to refractory material - Google Patents

Abstract

A non-fused crystalline refractory material consists essentially of agglomerated intergrown crystals of periclase and magnesia spinels of iron oxide and alumina, in amounts calculated as 10 to 90 per cent. of periclase, 5 to 85 per cent. of magnesioferrite and 5 to 85 per cent. of magnesium aluminate and containing not more than 2,0 per cent. of lime; the material preferably contains not more than 5 per cent. silica, 1 per cent. boron calculated as B2O3, and 1 per cent. of alkali calculated as the oxide; a minor amount of the magnesium, iron and aluminium oxides in the spinels may be replaced by other spinel-forming metal oxides. Finely divided mill scale and bauxite, or alternatively laterite alone, in amounts calculated as 5 to 85 per cent. of magnesioferrite and of magnesium aluminate are intimately admitted with precipitated magnesium hydroxide in an amount sufficient to react with all of the iron oxide and alumina to form magnesia spinels and to provide from 10 to 90 per cent. of excess periclase and the admixture is fired at 1600 DEG to 1800 DEG C. for at least one-half hour. In an alternative procedure, the iron oxide material and the alumina material are first admixed in amounts to provide 94 to 40 per cent. calculated as FeO, of the iron oxide-providing material and 6 to 60 per cent., calculated as Al2O3, of the alumina-providing material; the admixture so heated to cause at least partial reaction to form a product containing iron aluminate which is then admixed with the periclase material and fired. According to an example, 16,7 lb. Bayer process aluminium hydroxide and 10,9 lb. of a technical grade powdered ferric oxide were intimately blended with 736 lb. of a slurry of magnesium hydroxide containing 33 per cent. MgO. The resultant slurry was dried, briquetted and fired to 1700 DEG C. for one-half hour. Reference is made to the related matter of Specifications 811,986 and 811,987.