Lightweight Mullite Bricks

Lightweight mullite bricks (also called mullite bricks) are made of synthetic fused mullite or sintered mullite, pressed by selected shaping processes and fired in high-temperature furnaces. Lightweight mullite bricks offer high density, low porosity, good hot strength, and good slag resistance. Mullite bricks are preferred for high temperature, high load applications, such as at the hot end of regenerative chambers of glass melters, the superstructure of the furnace, and the arch of glass fiber melters, due to their excellent thermal properties, excellent strength at high temperature, great resistance to thermal shock, etc.

The mullite brick comprises the following chemical components in percentage by weight: 35 to 72 percent of Al₂O₃, 27 to 64 percent of SiO₂, and 1 to 1.2 percent of Fe₂O₃. Mullite bricks are high-alumina refractories with mullite (3Al₂O₃·2SiO₂) as the main crystal phase. Generally, the alumina content is between 70% and 80%. Lightweight mullite bricks have high refractoriness, which can reach above 1790℃. The starting temperature of load softening is 1600～1700℃. It has good thermal shock resistance with a cold crushing strength of 70～260MPa. There are two types of mullite refractories: sintered mullite bricks and fused mullite bricks. If the Al₂O₃ content in refractory brick is more than 80%, we call it corundum mullite brick. If there is ZrO₂ in the brick, we call it zircon mullite brick.

Lightweight mullite bricks are widely used in glass furnaces, hot blast stoves, etc.