Refractory properties
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Author:haoyangnaihuo
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Published time: 2018-03-27
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Larger amounts of silica bricks and clay bricks. Silica bricks are siliceous products containing more than 93% of SiO2. The raw materials used are silica and waste silica bricks. Silica bricks have strong resistance to acidic slag, but they are vulnerable to alkaline slag. Its softening temperature is very high, and its refractoriness is close to that. After re-calcination, the volume does not shrink or even slightly expand, but the thermal shock resistance is poor. Silicon bricks are mainly used in coke ovens, glass melting furnaces, acid steelmaking furnaces and other thermal equipment. Clay brick contains 30%～46% alumina. It is mainly made of fire-resistant clay, and its refractoriness is 1580～1770°C. It has good thermal shock resistance and belongs to weak acid refractory material. It has corrosion resistance to acid slag and is widely used. Is the largest production of a type of refractories.
In common and special refractories, the following are commonly used varieties:
Acidic
Larger amounts of silica bricks and clay bricks. Silica bricks are siliceous products containing more than 93% of SiO2. The raw materials used are silica, waste silica bricks and so on. Silica bricks have strong resistance to acidic slag, but they are vulnerable to alkaline slag. Its softening temperature is very high and it is close to its refractoriness. After re-calcination, the volume does not shrink and even slightly expands, but its thermal shock resistance is poor. Silicon bricks are mainly used in coke ovens, glass melting furnaces, acid steelmaking furnaces and other thermal equipment. The clay brick contains 30%～46% alumina, which is mainly made of fire-resistant clay, and its refractoriness is 1580～1770°C. It has good thermal shock resistance and belongs to weak acid refractory material. It has corrosion resistance to acid slag and is widely used. Is the largest production of a type of refractories.
Neutral
The main crystal phases in high-aluminum products are mullite and corundum, and the content of corundum increases with the increase of alumina content. Corundum products containing more than 95% aluminum oxide are a kind of high-quality refractory materials with wide application. The chrome brick is mainly made of chrome ore, and the main crystal phase is chromite. Its corrosion resistance to steel slag is good, but its thermal shock resistance is poor, and its high temperature load deformation temperature is low. Chromium-magnesia bricks made with different proportions of chrome ore and magnesia have good thermal shock resistance and are mainly used as alkaline open hearth top bricks.
Carbonaceous products are another type of neutral refractories. According to the composition of carbonaceous raw materials and the mineral composition of products, they are divided into three categories: carbon bricks, graphite products, and silicon carbide products. Carbon bricks are made from high-quality petroleum coke, tar, and bitumen as binders, and fired at 1300°C in air-isolated conditions. Graphite products (except natural graphite) are obtained by graphitizing carbonaceous materials in an electric furnace at 2500 to 2800°C. Silicon carbide products are based on silicon carbide as raw materials, and clay, silica and other binders are fired at 1350-1400°C. Silicon carbide-silicon carbide products can also be produced by adding silicon carbide and silicon powder in an electric furnace under a nitrogen atmosphere.
Carbonaceous products have a low coefficient of thermal expansion, high thermal conductivity, good thermal shock resistance, and high high temperature strength. It does not soften under long-term use at high temperature, it is not attacked by any acid and alkali, it has good salt resistance, it is not wetted by metal and slag, light weight, it is a high-quality high-temperature material. The disadvantage is that it is easily oxidized at high temperatures and should not be used in an oxidizing atmosphere. Carbonaceous products are widely used in high-temperature furnace linings (bottoms, hearths, lower parts of the furnace body, etc.), linings for smelting non-ferrous metal furnaces. Graphite products can be used as reaction tanks and petrochemical autoclave linings. Silicon carbide and graphite products can also be made from smelting copper with gold and light alloys.
Alkaline
Magnesium products represented. It contains more than 80% to 85% of magnesium oxide, with periclase as the main crystalline phase. The main raw materials for the production of magnesia bricks are magnesite, seawater magnesia, magnesium hydroxide extracted from seawater, calcined at high temperature, etc.). Good resistance to alkaline slag and iron slag. The melting point of pure magnesium oxide is as high as 2800°C. Therefore, the refractoriness of magnesium brick is higher than that of clay brick and silicon brick. Since the mid-50s of the 20th century, due to the adoption of oxygen-blown converters and the use of alkaline hearth furnace tops, the production of basic refractories has gradually increased, and the production of clay bricks and silica bricks has decreased. Basic refractories are mainly used for open hearth furnaces, oxygen furnaces, electric furnaces, non-ferrous metal smelting, and some high-temperature thermal equipment.
