Fireclay Refractory Bricks...

Fireclay Refractory Bricks  Fireclay refractory bricks are manufactured from unfired refractory bond clay and fireclays (chamotte), fired refractory clay or similar grog materials . Fireclay refractory bricks have two main components namely 18 % to 44 % of alumina (Al2O3) and  50 % to 80 % of silica (SiO2). The variety of clays and manufacturing techniques allows the production of numerous brick types appropriate to particular applications. The usefulness of fireclay refractory bricks are largely due to the presence of mineral mullite, which forms during firing and is characterized by high refractoriness and low thermal expansion. Raw materials for fireclay refractory bricks Refractory fireclay essentially consists of hydrated aluminum silicates with minor proportion of other minerals. The general formula for these aluminum silicates is Al2O3.2SiO2.2H2O, corresponding to 39.5 % alumina, 46.5 % silica, and 14 % water (H2O). Kaolinite is the most common member of this group. At high temperature, the combined water is driven off, and the residue theoretically consists of 45.9 % alumina and 54.1 % silica. However even the purest clays contain small amounts of other constituents , such as compounds of iron, calcium, magnesium, titanium, sodium, potassium, lithium, and usually some free silica. The total quantity of these fluxing agents, which lower the melting point, should be at a level of 5 % to 6 % maximum. TiO2 is not regarded as fluxing agent and was previously counted together with alumina. The name fireclay is given to a group of refractory clays which can generally withstand temperatures above pyrometric cone equivalent (PCE) value of 19. Refractoriness and plasticity are the two main properties needed in fireclay for its suitability in the manufacture of refractory bricks. A good fireclay should have a high fusion point (greater than 1580 deg C) and...