The difference between silica brick and semi-silica brick

Silica bricks have more crystal shape changes below 600 °C, and larger volume changes. Above 600°C, there is no change in crystal form, the coefficient of thermal expansion is small, and the change in volume is small. Therefore, it is necessary to pay attention to the slow heating of the furnace body built with silica bricks in the initial stage of the oven.

Semi-silica brick is a kind of quartz clay brick, which is formed and fired from quartzite with clay as a binder. The semi-silica brick contains not less than 20% Al2O3, not less than 65% SiO2, its refractoriness is 1670℃, and its softening point under load is not less than 1250℃. The resistance to rapid cooling and rapid heating of semi-silica bricks is better than that of silica bricks, and the volume stability is better than that of clay bricks and silica bricks. When heated, the clay in the brick shortens and the quartz expands, so that excellent volume stability can be obtained, which is the primary benefit of semi-silica bricks.

Semi-silica bricks can be used for the furnace body, preheater and flue of pit heating furnace.