the body and refractory materials development and process for manufacture

摘要

Refractory bodies particularly for use in the construction of glass tanks and consisting essentially of crystals of mullite in a glassy matrix are made by adding a not readily soluble fluorine-containing substance to a mixture consisting substantially of alumina and silica and/or compounds thereof, a portion of these being in plastic form, and firing a body formed of the mixture at 1500-1770 DEG C.; the alumina-silica ratio in the mixture having a value, depending on the nature and quantity of the fluorine-containing substance and the firing temperature, approximating to that at which with increasing ratio corundum crystals first appear. In general increasing the firing temperature and lowering the quantity of fluorine-containing substance tend to prevent formation of corundum. Fluorine-containing substances specified are fluorspar, lepidolite, fluoride opal glass, cryolite, sodium silicofluoride and magnesium, aluminium, zinc and lead fluorides. Numerous examples are given in the Specification. In one example, a body consisting entirely of mullite is obtained by firing at 1720 DEG C. a mixture in which the alumina-silica ratio is 2.5 and containing 5 per cent fluorspar, in another a body containing 80 per cent mullite is obtained by firing at 1600-1720 DEG C. a mixture in which the alumina-silica ratio is 1.6 and containing 20 per cent fluoride opal glass. The bodies may be made by first preparing a grog from the mixture according to the invention and then making the body from the grog bound with the same raw materials. Specification 463,321 is referred to. The Provisional Specification refers to the addition of titanium oxide to the mixture from which the bodies are made.