High alumina bricks are mainly divided into ordinary high alumina bricks and modified high alumina fire bricks. Ordinary high aluminum bricks refer to commonly used standard fired bricks, while modified high alumina refractory bricks mainly refer to: high-load soft high alumina firebricks, micro-expansion high alumina fire bricks, low creep high alumina bricks and phosphate bonded high alumina refractory bricks. Kind.
1. Ordinary high alumina bricks.
Its main mineral composition is mullite, corundum and glass phase.
Mainly used for lining of blast furnaces, hot blast furnaces, electric furnace tops, blast furnaces, reverberatory furnaces, and rotary kilns. In addition, it is also widely used in open hearth regenerative checker bricks, plugs for pouring systems, nozzle bricks, etc.
2. High-load soft high-alumina bricks.
Compared with ordinary high alumina bricks, the difference is the matrix part and the binder part.
(1) In addition to the addition of three-stone concentrate, high alumina materials (finely ground high alumina bauxite, industrial alumina or a-Al2O3 powder, corundum powder) are reasonably introduced according to the theoretical composition of the chemical composition after firing close to mullite. , High-aluminum corundum powder).
(2) Choose high-quality ball clay as the bonding agent, and use clay composite bonding agent or mullite bonding agent depending on the variety.
By adopting the above method, the softening temperature under load is increased by 50-70°C.
3. Micro-expansion high alumina brick
It is made with high alumina bauxite as the main raw material, added with three stone concentrates, and made in accordance with the production process of high alumina bricks. In order to make it expand appropriately during use, the key is to select the three-stone mineral and its particle size, and control the firing temperature, so that part of the selected stone mineral is mullite, and part of the three-stone mineral remains. The remaining three-stone minerals are further mulliteized (primary or secondary mulliteized) during use, accompanied by swelling reaction. The selected three-stone minerals are preferably composite materials. Because the decomposition temperature of the three stone minerals is different. The swelling produced by mullite petrochemicals is also different. Using this feature, there is a corresponding expansion effect due to different working temperatures, compacting the brick joints, improving the overall compactness of the bricks, and improving the resistance of the bricks to slag penetration.
Four, low creep high alumina brick
With the development of large-volume, high-air temperature technology and longevity of iron-making blast furnaces, higher requirements have been put forward for refractory materials for hot blast furnaces, requiring materials to withstand long-term thermal stress and high air temperature without being easily damaged. Therefore, high alumina bricks for hot blast stoves are required to have a low creep rate. This plays an important role in the longevity of the hot blast stove. The physical and chemical indicators are as follows:
In order to solve its creep resistance, the method of adding beneficial minerals is adopted, and the so-called unbalanced reaction is used to solve the problem. When the creep temperature is 1550℃, 1500℃, the additives are quartz and three stone minerals; the creep temperature is 1450℃, At 1400°C and 1350°C, the additives are three-stone minerals, and corundum, a-Al2O3, etc. are introduced accordingly; when the creep temperature is 1300°C, 1270°C, and 1250°C, the additives are three-stone minerals. Among them, three stone minerals, activated alumina, etc. are mainly added in the form of a matrix, and the complete or nearly complete mulliteization of the matrix is the key. Because of the mulliteization of the matrix, the mullite content of the material will be increased and the glass phase content will be reduced. The excellent mechanical and thermal properties of mullite are conducive to the improvement or enhancement of the high-temperature performance of the material.
Studies have shown that adding 15%-35% sillimanite concentrate in its production can produce high-load soft, low-creep high alumina bricks for blast furnace hot blast stoves with a creep temperature of 1400-1450°C. For low-creep high-alumina bricks with a creep temperature of 1500~-1550℃, in addition to adding an appropriate amount of sillimanite, a certain amount of mullite must be added; or some raw materials of fused corundum and silica are used.
5. Phosphate bonded high alumina bricks
It is a chemically bonded refractory product made of dense special-grade or first-grade high-alumina bauxite clinker as the main raw material, phosphoric acid solution or aluminum phosphate solution as the binder, and after being shaped by a semi-dry machine and heat-treated at 400-600℃ . It is a non-burning brick. In order to avoid the large shrinkage of the product during high-temperature use, it is necessary to introduce heat-expandable raw materials such as kyanite, sillimanite, pyrophyllite, silica, etc. into the ingredients. Compared with ceramic-bonded fired high alumina, it has better peel resistance, but its load softening temperature is lower, and its corrosion resistance is poor. Therefore, a small amount of fused corundum mullite, etc. needs to be added to strengthen the matrix. Suitable for cement kilns, electric furnace tops and ladle etc.
