Abstract
The spinel hercynite (FeAl2O4) occurs as a reaction product with the deoxidation by aluminium of liquid steel, or when iron oxides come into contact with alumina refractories. The behaviors of hercynite in liquid iron and steel are of great interest, but until recently, few investigations of the rate of formation and reduction of hercynite have been carried out.
In this work, the rate of formation of hercynite from mixture of ferrous oxide and alumina at temperatures from 850°C to 1200°C was measured. The rate of reduction by hydrogen stream at 700°C to 900°C was measured by the thermo-balance method. As the supplementary work, the products of reduction by hydrogen, solid carbon and soluble carbon in liquid iron were examined by X-ray diffraction.
The results obtained are as follows:
1) The rate of formation agrees with Jander's equation and the value of activation energy is 60kcal/mol, approximately. The relation between rate constant (k) and temperature (T°K) is represented by the equation:
logk=-14410/T+7.69
2) The rate of reduction agrees with McKewan's equation and the relation between log k and T can be expressed by the following equation:
logk=-8390/T+2.42
From this equation, the activation energy is found to be approximately 39kcal/mol.
3) It is found that FeAl2O4 is decomposed into Fe and materials of spinel type with H2 or carbon, in the first stage of reduction, and at high temperature the spinel materials finally become α-Al2O3.
