Aluminate magnesia spinels
Scope and purpose
Aluminum magnesia spinel made from quality raw materials is of particular interest to the refractory industry. The development of spinel production technology was carried out in two different directions: spinel with an excess of MgO for magnesian refractories and spinel with an excess of Al2O3 for spinel corundum concrete and masses.
The brand of spinel MR 66 with an excess of MgO is widely used as a substitute for lame ore in the production of basic products. Heat resistance is caused by a microcracked structure and voids formed due to the difference in the values of thermal expansion coefficients. The reversible thermal expansion of MR 66 is about 2 times lower than that of MgO. Periclase-spinel products have established themselves as an effective material for lining rotary kilns in the cement industry, where periclase-chromite refractories were previously used. A higher durability is explained by the property of periclase-spinel products to hold the coating without excessive impregnation and chipping. A small amount of free magnesium oxide, which is part of this material, also plays a positive role, forming spinel at the contact with alumina. An empirically determined increase in volume during sintering of one mole of MgO and a mole of Al2O3 is 5%. Thus, in refractories based on high alumina raw materials, the addition of MR 66 will facilitate expansion. In masses and mortars on phosphate binders, free MgO MR 66 can serve as a setting accelerator. But since it interacts very actively with water, this brand of spinel is inappropriate to use in concrete. Spinels AR 78 and AR 90 with an excess of Al2O3 are an indispensable component of concrete used in steel-pouring ladles. In spinel-containing refractories, AR 78 is preferably used in the form of fine and medium fractions, whereas AR 90 in the coarse-grained part.
Material manufactured by ALMATIS (Germany)
|The chemical composition of spinels,%||MR 66||AR 78 (with an excess of Al2O3)||AR 90 (with an excess of Al2O3)|
|Al2O3 by difference||(min. 63.0)||(min. 74.0)||(min. 87.0)|
|Physical properties of||MR 66||AR 78 (with an excess of Al2O3)||AR 90 (with an excess of Al2O3)|
|Apparent density, g / cm2||3.3||3.3||3.4|
Advantages of MR 66 spinel with excess MgO:
- gives products improved heat resistance, which is traditionally associated with chromium ore additives;
- does not create difficulties with the disposal of hazardous waste;
- can be used to replace chromium-containing raw materials in refractories for limestone kilns and nozzles of regenerators of glass melting furnaces.
Advantages of spinel AR 78 and AR 90 with excess Al2O3:
- the addition of alumina composition to molded and unformed refractories significantly improves slag resistance and heat resistance;
- the introduction of the mixture improves the tensile strength during bending in the hot state and thermomechanical properties in General.
Concerning the acquisition aluminate magnesia spinels and receipt of detailed advice on product properties, delivery conditions and the conclusion of the contract, please contact the managers: