Classification and Performance of Four Kinds of Fused Corundum

Fused corundum is calcined alumina or bauxite as the material, the electric arc furnace in the recovery atmosphere and melting and metal and other impurities separated, and then obtained by condensation. According to the use of materials and melting process different common types are: fused white corundum, fused corundum, fine fused corundum, bauxite-based fused corundum (commonly known as high alumina corundum, sub-white corundum) and zirconia corundum and so on.

To bauxite as the material melting brown corundum, the general only to restore the smelting. The carbonaceous material for the recovery agent is generally coke or anthracite. The requirements for anthracite are: fixed C ≥ 80%, ash ≤ 10%, volatile <7%, water <3%. The participation of coke or anthracite is based on the demand for the recovery of SiO2, Fe2O3 and TiO2. Participation in the material necessary to fully boring and roasting dehydration, the size of the furnace is generally 10 to 40 mm, not too fine, coke or anthracite particle size of 1 to 5 mm.

  The melting process is carried out in a three-phase arc furnace with a gap type (furnace cooling method) and tilting type (pouring into other ladle cooling methods).

 Fused white corundum

 Now generally referred to as "fused alumina" generally refers to "fused white corundum". It is made of industrial alumina as the material, melted in the arc furnace at high temperature, its A12O3 content of not less than 99%, white, block material, significant porosity of 6% to 10%, the main crystal phase is a-A12O3, crystal Long and rhombic, and often bony-like crystals. Because the material is very pure, in the electric furnace operation does not occur chemical reaction, but the molten liquid temperature, cooling rate and so on the block structure has a great impact. In terms of homogeneity, it is important to achieve as fine as possible. It is necessary to pay attention to the content of Na2O in the speckle, and it is necessary to pay attention to the content of Na2O in the center of the block. In addition, the block guess there are a small amount of nepheline, glass flat.

  Fine fused corundum

  Fine fused corundum is based on industrial alumina as a material, to participate in admixture, melting in the electric furnace. Melting should be carried out in strict operation to control the excess generation of carbides. Fine cast corundum appearance is gray, gray black or gray, A12O3 greater than 98%, significantly higher porosity than fused white corundum, generally less than 4%, bulk density greater than 3.8g · cm-3, the main crystal phase is a-A12O3 , Sub-crystal phase FeTiO3, CaA112O9, Ca3Si8O9, TiN, Ti4O7, etc., there are a small amount of glass phase. Fine corundum C content should be ≤ 0.14%, and should try to reduce the formation of β-A12O3 to improve corundum particle strength and corrosion resistance. When the carbides contained in the fused corundum (A14C3, A14O4C, A12C), the carbides can react with water at room temperature:

(A14C3 + 12H2O → 4A1 (OH) 3 + 3CH4 ↑

Resulting in fused corundum particles pulverized. Manufacture of unshaped refractory materials can cause the construction of loose, bulging, and even severe cracking. Fine fused corundum in the refractory products to do more aggregate, in the use of unshaped refractory guess is constantly expanding.

 Fused corundum

Corundum is a natural bauxite as a material to carbon (mainly coke) as a recovery agent, together with iron as a sediment agent (clarifier) ​​to form a ferrosilicon in the furnace bottom.

Corundum is brown, generally A12O3 ≥ 94.5%, SiO2 ≤ 3.5%, TiO2 ≤ 3.5%, Fe2O3 ≤ 1%. The composition of the mineral deposits is dominated by a-A12O3. The central part of the crystal shape is diamond-shaped, thick-shaped and cracked. There are more silicon oxide and calcium oxide in the periphery, and the most coarse grains are Skeleton-like crystal. Because the impurities have not been completely removed, so the corundum also contains rutile and other sub-crystal phase and glass phase, ferroalloy and solid solution. The corners of the corundum are largely dependent on the titanium oxide remaining in the product.

The corundum is mainly used as abrasive. In recent years has been used for large and medium-sized blast furnace out of iron ditch castables and iron-free water gun mud aggregate and the manufacture of general corundum brick (including high alumina silicon carbide brick) material.

  Alumina-based fused corundum

 Also known as sub-white corundum or high alumina corundum, in fact, bauxite-based fine fused corundum. It is in the recovery of the atmosphere and handling conditions under the conditions of fused or primary bauxite and made, when the melt involved in the recovery agent (carbon), sediment agent (iron) and decarburizing agent (scale). In the exercise, early with excessive recovery agent to restore the TiO2 removed in the late exercise and then participate in decarburization or oxygen to remove excess carbon, and then get whitening corundum. Its physical and chemical goals and fine fused corundum close to the color also close to the general A12O3 content of more than 97%, significant porosity of less than 4%; corundum crystal is generally granular, scale 1 ~ 15 mm; primary impurity mineral hexaaluminate ), Rutile, aluminum titanate and its solid solution. But in the mineral composition contains a high titanium dioxide, thermal expansion coefficient is more fine fused corundum high. Used in unshaped refractory materials, hot air furnace brick and A12O3-SiC-C brick.