High alumina refractory brick is also known as high alumina brick, its production and viscose brick production process is similar, the difference is with powder mixed with high alumina clinker more, higher fire resistance than clay brick, acid and alkali resistance candle better performance, suitable for a variety of kiln firing belt, etc.
Al2O3 containing more than 48% aluminum silicate refractory bricks are collectively referred to as high aluminum refractory bricks.According to the content of Al2O3, it is divided into three levels: I grade (Al2O3>75%);II grade (Al2O3:60%~75%);Ⅲ (Al2O3 48% ~ 60%), etc.According to the mineral composition, it can be divided into: low mullite (including siliconite) and mullite (Al2O3 is 48%~71.8%), mullite-corundum and corundum -mullite (Al2O3 is 71.8%~95%), diamond (Al2O3 is 95%~100%) and other refractory bricks.
With the increase of Al2O3 content in high-alumina refractory brick, the amount of mullite and corundum components also increases, while the amount of glass decreases correspondingly, and the fire-resistance and density of high-alumina refractory brick also increase accordingly.When Al2O3 content in high-alumina brick is less than 71.8%, the high-temperature stable crystal phase in high-alumina refractory brick is mullite, which increases with the content of Al2O3.For Al2O3 containing more than 71.8% of high-alumina refractory brick, the high-temperature stable crystal phase is mullite and corundum. With the increase of 71.8% of Al2O3 content, the quantity of corundum increases and the quantity of mullite decreases, and the high-temperature performance of high-alumina refractory brick is improved correspondingly.
The firing temperature of high alumina refractory bricks depends on the sintering properties of bauxite raw materials.When using super and I grade bauxite clinker (volume density 2.80g/cm3), the structure of the raw material is uniform, the impurity content is high, which makes the body easy to sintering, but the firing temperature range is narrow, easy to cause over or under burning.When grade II bauxite clinker (volume density 2.55g/cm3) is used, the expansion and loose effect caused by secondary mullite makes the body not easy to be sintered, so the sintering temperature is slightly higher.The level III bauxite clinker (bulk density 2.45 g/cm3) or higher, compact structure, low content of Al2O3, firing temperature is low, usually slightly higher than the firing temperature of the clinker clay brick of 30 ~ 50 ℃.High alumina refractory bricks are fired in an oxidizing flame.
The softening temperature of high alumina refractory bricks under load is an important property.The experimental results show that it varies with the content of Al2O3 in high-alumina refractory bricks: when the content of Al2O3 is lower than the theoretical composition of mullite, the equilibrium phase of high-alumina refractory bricks is mullite-glass phase.The content of mullite increased with the content of Al2O3, and the softening temperature under load increased accordingly.
High aluminum refractory clay brick worse than thermal shock resistance, 850 ℃ water cycle 3 ~ 5 times.The main reason is that the thermal expansion of corundum is higher than mullite.And Ⅰ, Ⅱ high alumina brick thermal shock resistance than Ⅲ high aluminum refractory brick.
In production, the composition of clay particles is usually adjusted to improve the particle structure characteristics of high alumina refractory brick, so as to improve its heat shock resistance.In recent years, a certain amount of synthetic cordierite was added into the ingredients of high-alumina refractory bricks to produce high-alumina refractory bricks with high heat shock resistance, and obvious results were obtained.
The slag resistance of high alumina refractory brick also increases with the increase of Al2O3 content.Reducing the impurity content is beneficial to improve the corrosion resistance.
The difference between high alumina refractory brick and clay brick is that high alumina refractory brick has good service performance, so it has a longer service life than clay brick.