- The Clay Science Society of Japan
- 粘土科学 (ISSN:04706455)
- vol.18, no.3, pp.105-115, 1978-09-25 (Released:2011-09-20)
Clay has played an important role in the refractories industry because of its special properties such as favorable plasticity, good sinterability and low cost. An outline of fire clay refractories and the features of clays are mentioned in this paper.The principal chemical composition of clays is silica, alumina and water, and these consist mineralogically of kaoline mineral and quartz. Clays also contain impurities, for example iron oxide, potassium oxide, and sodium oxide, and therefore also contain feldspar, sericite and pyrophyllite.In industrial ceramics, clays are used two ways. One way is the dead burning of clays which is used for large grog or refractory grain particles in fire clay refractories. The process requires special properties such as high density and high temperature stability. In the second way, clays are used for binder for which it is necessary to have favorable plasticity.Fire clay refractories are composed of refractory grain particles of burned clay and binder clay, their properties are decided by the raw materials and heat treatment used.The chemical composition of fire clay refractories are silica, alumina and accessary components which are the same as clays, and these mineralogically consist of mullite, cristobalite and a glass phase.This fact suggests that the kinds and quantity of impurity contained in the formation of cristobalite give a marked effect on the shrinkage, tightening and the spalling of a ceramic body.Damage in fire clay refractories can be observed during service in the following cases; 1) presence of impurities which cause the formation of glass, 2) thermal expansion spalling due to the presence of cristobalite, 3) alkali attack in the blast furnace, 4) bloating phenomena in the ladle.