Complete Firing Temperature Guide for Sintered Bricks: Avoid Defects and Improve Brick Quality
Firing temperature is the most critical control index in the entire sintered brick manufacturing process, which directly determines the yield, appearance, structural strength and long-term durability of brick products. The most suitable firing temperature for sintered brick mixtures and green bricks is controlled between 900℃ and 1100℃. In this standard temperature range, the brick green body can achieve partial melting and complete sintering, forming a stable and qualified brick structure that meets industrial production regulations.
Unreasonable temperature control will directly lead to unqualified products. If the firing temperature is too high or the high-temperature sintering time is too long, overfired bricks will be produced. Typical features of overfired bricks include dark color, crisp knocking sound and obvious body deformation, which seriously affects the overall qualification rate of finished products. On the contrary, if the firing temperature is too low or the sintering time is insufficient, underfired bricks are easy to form. Underfired bricks are light in color, dull in knocking sound, low in mechanical strength, high in water absorption, and poor in alkali resistance and durability, which cannot meet standard engineering usage requirements.
On the basis of standard temperature control, different kiln atmospheres will produce two common types of sintered bricks: red bricks and blue bricks. When sintered at 900–1100℃ under a continuous oxidizing atmosphere, the iron elements in the raw materials form ferric oxide (Fe₂O₃), turning the bricks red, which are known as red bricks. If red bricks are further smoldered in a reducing atmosphere after oxidation sintering, ferric oxide (Fe₂O₃) will be reduced to grayish-green ferrous oxide (FeO), forming blue bricks. Blue bricks have denser texture, better alkali resistance and higher durability than red bricks, yet higher production costs limit their wide application in the market.
In modern energy-saving production, industrial wastes such as coal slag and high-carbon fly ash can be mixed into raw materials to produce internal combustion bricks. During the 900–1100℃ sintering process, the carbon contained in the waste materials burns inside the green brick, assisting uniform sintering. This technology saves a large amount of external fuel, reduces clay raw material consumption by 5%–10%, and increases the brick strength by about 20%. Meanwhile, internal combustion bricks have lower bulk density and thermal conductivity, with more stable overall performance.
