GB871965A - Thermosetting refractory materials - Google Patents

Abstract

In bonding granular non-acid refractory material, which is non-reactive with calcium orthosilicate and contains only small amounts of lime, e.g. less than 3%, by the process of heating it with a small amount of, e.g. 5 to 25%, by weight, of a low-melting siliceous substance sufficient lime-bearing material, e.g. 5 to 30% by weight, is added to the mixture to ensure the presence of at least 6% lime in excess of that necessary to form calcium orthosilicate with all the silica in the granular refractory, and an overall lime/silica ratio of at least 1,87. The amount of low-melting siliceous substance should be such as to provide at least 5% by weight of siliceous liquid when the mixture is heated to 1500 DEG C. which liquid cools and then bonds the refractory grains by reacting on further heating of the mixture with the lime present to form a calcium silicate at least as basic as the orthosilicate. Suitable granular refractories are dead-burned magnesite and chrome ore, both 50% coarser than 20 mesh, and iron low-melting siliceous substance may be copper blast-furnace slag, phosphorus slag, calcium or calcium-magnesium silicate, which should be readily fusible, should contain alumina and iron oxide, and should be relatively coarse, e.g. pass a 6 mesh screen but be 50% retained on a 20 mesh screen; alternatively it may be fine, e.g. pass a 100 mesh screen, in which case both the refractory material and the lime bearing grains should be coarser than 20 mesh. The presence of both siliceous fines and limebearing fines is to be avoided. Specification 697,653 is referred to.