Technical requirements and application of clay-bonded refractory castables
Clay-bonded refractory castables are castable refractory materials made of soft clay as a binder, refractory aggregates such as alumina-silica or corundum-mullite, powder and admixtures.
Clay-bonded refractory castables are divided into clay, high-alumina, corundum-mullite and high-alumina lightweight according to the type of refractory aggregate. According to their performance characteristics, they are divided into ordinary and high-strength clay-bonded refractory castables.
Clay-bonded refractory castables are mainly composed of binders, refractory aggregates, powders and admixtures. The chemical composition, physical and refractory properties of the selected bonded clays vary depending on their origin. The technical requirements for clay binders used as refractory castables are: Al2O3 29%~35%, Fe2O3＜1.8%, R2O<1.1%, loss on ignition 10%~14%, refractoriness greater than 1670℃, and a wide sintering temperature range. In the mineral composition, it should contain a small amount of substances such as montmorillonite and mica to give it better bonding properties and plasticity. Clay powder with a fineness of less than 0.088mm should account for more than 60%, and its dosage is 7%~13%.
Compared with cement-bonded refractory castables, clay-bonded refractory castables have the characteristics of high medium-temperature strength, high hot strength, good volume stability at high temperature and strong spalling resistance.
According to the operating temperature and other conditions of thermal equipment such as furnaces, different types of clay-bonded refractory castables can be reasonably selected, and they can also be used together with metal or non-metallic anchors. Ordinary clay-bonded refractory castables can be used as furnace linings for thermal equipment such as steel rolling heating furnaces, soaking furnaces and sintering machine ignition furnaces. High-strength clay-bonded refractory castables are used for key parts such as burner bricks, water-cooling pipe wrapping, soaking furnace mouth and protruding belts, desulfurization spray guns of mixing iron cars and certain parts of rotary kilns.