Refractory fireclay brick is unfired refractory bond clay, fireclays or grog materials developed with alumina (Al2O3) up to 40% and Silica up to 80 % . It is widely used due to the presence of mineral mullite that is reckoned for low thermal expansion and high refractoriness. This heat-resistant brick is used to line the interiors of bake ovens, furnaces and pits as it can easily withstand high temperatures and intense heat without breaking.
Manufacturing Process of Refractory Fireclay Brick
Combination of two or more clays is used for manufacturing this brick. Flint clay and kaolin ensures to impart high refractoriness. On the other hand, calcined clays are used for controlling the drying and firing shrinkages and plastic clays impart bonding strength. For the development of this brick, ground clay particles should be taken in proper proportion. These clays are efficiently grounded in a dry pan with a slotted opening in the bottom. Then, they are screened to the preferred sizes, mixed with a small amount of water and fed to an operated press. The extrusion process is also utilized for giving special shapes to the brick.
Bricks formed are dried in tunnel to attain several necessary ends. The temperature of firing is based on the maturing temperatures of the clays. Varied changes can be seen after this process such as driving off the free water, transformation of the minerals, oxidizing of iron compounds and organic matters, etc. Finally the clay particles are bonded together into a strong brick.
Types of Refractory Fireclay Brick
There are five standard classes of this brick that include:
1) Super Duty Fireclay Brick: This comes with excellent strength and refractoriness along with high volume stability at high temperatures. It comes with alumina content of 40 % to 44 %. In addition, it is resistant to cracking or spalling even after subjected to rapidly changing temperatures.
2) High Duty Fireclay Brick: Its excellent resistance to thermal shock makes it ideal to be used for lining of furnaces. The PCE value of this brick varies from 31.5 to 33.
3) Medium Duty Fireclay Brick: It is used in the applications, where moderate severity conditions are expected. It can easily withstand abrasion with PCE values ranging from 29 to 31.
4) Low Duty Fireclay Brick: This is used as back up brick with higher refractoriness. Its PCE values range from 15 to 27-29.
5) Semi Silica Fireclay Brick: It comes with excellent resistance to shrinkage, high load bearing strength and outstanding volume stability at relatively high temperatures.
Applications of Refractory Fireclay Brick
This brick is a versatile product used in different sectors due to high refractoriness, crushing strength, porosity, and dimensional accuracy. It is used in steel and aluminum plants, ceramics & glass production, petrochemical, blast furnace, hot blast stoves and furnaces. This is also an essential product to be used for creating thermal shields on space shuttles. In addition to this, it is also used in building cooking chamber in wood fired ovens, pizza ovens, etc. for creating fireplaces and wood heaters’ lining.