High alumina fire bricks
are refractories with more than 48% AL2O3 content in aluminosilicate refractories. According to the composition of main minerals in the products, high alumina fire materials
are classified into four types: mullite-corundum, corundum-mullite, mullite and corundum. According to the content of AL2O3, high-alumina bricks for general use can be divided into three grades: first grade AL2O3 > 65%; second grade AL2O3 55% - 65%; third grade AL2O3 48% - 55%.
(1) The refractoriness of high alumina fire bricks
is relatively high in aluminosilicate refractories. With the increase of the content of AL2O3 in products, the refractoriness of high alumina refractory bricks increases, generally not less than 1750-1790 C. If the content of AL2O3 is more than 95%, the refractoriness of corundum products can be as high as 1900-2000 C.
(2) The load softening temperature of high-alumina fire bricks
decreases with the increase of SiO 2 and metal oxide content in products. The load softening temperature of high-alumina bricks is 1420-1530 C. The load softening temperature of corundum products containing more than 95% AL2O3 is over 1600 C.
(3) The slag resistance of high alumina fire bricks
has strong corrosion resistance to acidic or alkaline slag because of the high and neutral content of AL2O3 in the products.
(4) The thermal shock resistance of high alumina fire bricks
is that corundum and mullite coexist in their products, and the linear expansion coefficient of corundum is larger than that of mullite. Therefore, the thermal shock resistance of high alumina fire bricks
is poor due to the difference of expansion in products when the temperature changes. Generally, the number of water cooling is only 3-5 times.
(5) The change of reheating line of high alumina fire bricks
depends on the degree of firing of products. If the firing temperature is enough and Yan is sufficient, the volume is stable and the reburning line changes little. On the contrary, due to recrystallization within the product, residual shrinkage will occur. In view of the above characteristics of high alumina fire bricks
, it is mainly used to build coke oven combustion chamber furnace head and carbonization chamber bottom furnace head and other parts, but it is not suitable for carbonization chamber wall brick, because at high temperature it will produce curling, warping angle and so on.