Refractory materials are fabricated in two forms: shaped and unshaped (monolithic) refractories. Shaped refractories include fired and unfired materials with predetermined shapes, precast shapes and fusion cast refractories. Monolithic materials include plastic mixes, castables, ramming materials, dry vibratable, gunning materials, fettling materials, coatings and mortars. Monolithic materials differ from refractory bricks in that they are not shaped and fired before use. These materials do not have high energy requirements, are more readily available, take shorter times to install, can be repaired locally and require less manpower.
Generally, refractories are classified as basic, high alumina/silica, fireclay and insulating. There are also classes of “special refractories” which include Silicon Carbide, Silicon Nitride, Graphite, Zircon, Zirconia, fused cast and several others. Most refractory materials are supplied as preformed shapes. However, they also are manufactured in the form of special purpose clays, bonding mortars and monolithic such as castable, plastic refractories, ramming mixes and gunning mixes. In fact, many refractories materials have been developed specifically to meet the service conditions of a particular process. The characteristic properties of each refractory class are a function of both their raw material base and the methods used to manufacture the refractory products.
Breakage and rejection are two of the most common problems in ceramic manufacturing processes and It can come from a wide range of issues. Most ceramic manufacturers try to reduce their breakage and rejection as low as possible because small defect in a ceramic product can devalue the product by more than 50% or even mean a loss for a premium grade producer.