Analysis of the advantages and disadvantages of clay bricks

Clay refractory bricks refer to clay products with Al2O3 content of 30% to 40% aluminum silicate materials. The clay refractory bricks of Sunrise Refractory Group are cheap, durable, and have the advantages of fire resistance, heat insulation, sound insulation, and moisture absorption. They are widely used in the field of high temperature furnaces.

 

The mineral composition of clay bricks is mainly kaolinite (Al2O3 · 2SiO2 · 2H2O) and 6% ~ 7% impurities (oxides of potassium, sodium, calcium, titanium, and iron). The firing process of clay bricks is mainly a process in which kaolinite is continuously dehydrated and decomposed to form mullite (3Al2O3 · 2SiO2) crystals. SiO2 and Al2O3 in clay bricks form eutectic low melting point silicates with impurities during firing, and are surrounded by mullite crystals.

 

Clay brick is a weakly acidic refractory product, which can resist the erosion of acidic slag and acidic gases, and has a slightly lower resistance to alkaline substances. Clay bricks have good thermal properties and are resistant to rapid cold and heat.

The fire resistance of clay bricks is comparable to that of silicon bricks, up to 1690 ~ 1730 ℃, but the softening temperature under load is more than 200 ℃ lower than that of silicon bricks. Because in addition to the high refractory mullite crystals, clay bricks also contain nearly half of the low-melting amorphous glass phase.

 

In the temperature range of 0 ~ 1000 ℃, the volume of clay bricks expands uniformly as the temperature rises. The linear expansion curve approximates a straight line with a linear expansion rate of 0.6% ~ 0.7%, which is only about half that of silicon bricks. When the temperature reaches 1200 ° C and then continues to heat up, its volume will begin to shrink from the maximum expansion. Residual shrinkage of clay bricks causes loosening of gray joints in masonry, which is a major disadvantage of clay bricks. When the temperature exceeds 1200 ° C, the low-melting matter in the clay brick gradually melts, and the particles are tightly held by each other due to the surface tension, thereby causing volume shrinkage.