Aue customer order 2*40GP alumina carbon bricks.
There are different types of blast furnace alumina carbon bricks, and the raw materials used are also different. Refractory aggregates and powders are mainly made of super-grade and first-class bauxite clinker, and materials such as white corundum and brown corundum can also be used; carbon materials are mainly flake graphite, and medium-temperature pitch, etc.; silicon carbide is made of super-grade or first-class products. Phenolic resin for dense SiC binder can also be used, its solid content ≥ 75%, free phenol ≤ 6%, residual carbon content ≥ 43%, moisture content ≤ 2%, density about 1.1g/cm3. The critical particle size of the refractory aggregate used in this brick is 8mm, and its general mix ratio: coarse aggregate 40% ~ 60%, fine aggregate 5% ~ 20%, flake graphite 8% ~ 15%, SiC 4% ~ 10%, Refractory powder 15%~25% and binder 4%~6%. In addition, superfine powder, anti-alkali agent and expansion agent are added as needed.
The production process of alumina carbon bricks, its technical measures are multi-level gradation of refractory aggregates, additives or solid binders and refractory powders are made into premixed powder, and appropriate amount of additives are added at the same time. When mixing materials, first add granules and binder, after the granules are completely wrapped by the binder, add various powders, and knead for 15-20 minutes; the crushed materials are formed on a 300t brick press, and the number of times of pressing is quite large. in 10 times. The larger the tonnage of the brick press, the less the pressurization times, but not less than 5 times. At the same time, the operation should be light before heavy, so as to facilitate exhaust and reduce cracks.
After forming the semi-finished product, inspect the appearance, size and quality, etc. The semi-finished products that pass the inspection are put into the downdraft kiln to be roasted and solidified, and can be heated directly or indirectly. The roasting and curing temperature depends on the type of binder, generally 200~250°C, and the roasting time is generally 20~50h. Among them, the resin begins to soften at 50~60°C, and the solvent in the resin is removed at 100~110°C, so it should be properly kept warm. When the curing temperature is reached, in order to complete the reaction and form a carbon bond, it should also be properly kept warm. Of course, the final formation of carbon bonds is carried out at higher temperatures. The products after leaving the kiln should be stacked in the warehouse, or temporarily stored in the open air.
The performance of alumina carbon bricks after heat treatment is better, and the compressive strength is generally 35 ~ 45MPa; when the hot surface temperature is 900°C, the thermal conductivity is generally about 10W/(m K); the compressive strength of the bricks after the alkali resistance test The strength is 25~50MPa, and the air permeability is also very small. The air permeability of No. 4 and No. 5 is zero, so they are called dense aluminum carbon bricks.
The dense type has excellent alkali resistance. After the alkali resistance test, the strength not only does not decrease, but increases; when the slag resistance test is carried out, when the weight loss is 21%, it still shows excellent performance. The corrosion index of molten iron, aluminum carbon is ≥2.852, and carbon block is generally about 25%. Compared with silicon nitride-bonded SiC bricks, under the same slag resistance test conditions, the dense type has a weight loss rate of about 0.7%, complete edges and corners with oblique cracks, and the latter has a weight loss rate of about 0.9%, and edges and corners have complete oblique cracks.
The residual brick after use generally loses its strength due to the loss of binder, and is in the form of powder. If it is fired after buried charcoal, there is no such phenomenon, so fired aluminum-carbon bricks came into being, but some properties are slightly inferior to unfired aluminum-carbon bricks.