The heat treatment process of fused mullite brick is very important, which directly affects the product quality. This process is a process to obtain a large number of crystals and a small amount of glass phase, with sufficient strength without excessive internal stress. It is divided into two stages: crystallization and annealing
1. Crystallization stage
For fused mullite bricks, mullite crystals inside the products are expected to be fibrous or fine grains, which are evenly distributed. The main factor determining the grain size is the cooling rate. Mullite crystals began to precipitate stably at 1750-1800 degree . Therefore, the melt should be cooled rapidly within the temperature range from the beginning of crystallization to 1800 degree , so as to ensure a large mullite content in the product
2. Annealing stage
For the products after crystallization, due to the uneven heat dissipation of each part and the internal temperature difference, stress will be generated, which will cause the products to crack or lack corners and edges. Therefore, the products should be annealed. There are two annealing methods, self annealing and external heating annealing. Self annealing depends on the good thermal insulation layer outside the mold. The slow cooling temperature range is 1800-1100 degree , controlled at 60-70 degree / h. external heating annealing is commonly used in tunnel or annealing furnace, and the cooling temperature is controlled at 100-150 degree / h
The heat treatment process of electric fused mullite brick is improved, and the products with excellent quality can be obtained to a great extent
