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27METALLOTHERMIC PRODUCTION OF FeCo M. Bugdayci*" and A. Turan"
aChemical and Process Engineering Department, Faculty of Engineering, Yalova University,
Yalova, 77200 Turkey
*e-mail: mehmet.bugdayci@yalova.edu.tr
DOI: 10.24411/9999-0014A-2019-10024
In high power applications, engines and generators in aviation industry, the use of soft magnetic materials with high mechanical strength is a necessity. Research on these high strength soft magnetic materials has been intensified in recent years and consequently significant improvements have been achieved. In these studies, it is shown that Fe-Co alloy is candidate material due to high Curie temperature, low magneto-crystal anisotropic property, high strength, and excellent magnetic properties for the applications. FeCo alloy containing 50% Fe and 50% Co is very difficult to shape due to its very brittle nature. The positive effects of vanadium or chromium addition on the composition to remove the fragility of the alloy appear in the literature. FeCo alloys are produced with high energy melting systems, in this study, they will be produced by reducing the oxides of their components by aluminothermic and magnesiothermic methods, which producing their own energy without the need any external energy. Magnetite (Fe3O4) and mill scale as oxidic iron raw materials, Co2O3 as cobalt source will be used. In order to remove the fragility of the alloy, a stoichiometric 2% vanadium addition will be carried out and V2O5 will be used as a vanadium source. In experiments performed to synthesize FeCo, magnetite is as a source of iron, Co3O4 is as a cobalt source, and aluminum was used as the reductant, and the effects of the change in aluminum stoichiometry on FeCo recovery efficiencies were investigated. Permendur 24 production of the target set of samples in the 90-95-100-110-120% of the samples containing stoichiometric Al weighing, weighing 100 g, mixed, then kept at 105°C for 40 min at ETUV dehumidification. The dried mixture was charged to the copper crucible in which the metalothermic reduction was carried out, and the reaction was carried out by means of a variant. Metallic samples and slag obtained from the experiment were analyzed by XRF and AAS techniques and consistent results were observed. The results of chemical analysis of metal and slag are given in Table 1. The metal yields obtained from these results are as in Fig. 1. When Table 1 and Fig. 1 were examined, Fe and Co yield in the 90% stoichiometric composition was determined as 70.94 and 59.45%, respectively, while these values reached 92.89 and 77.50% when Al stoichiometry increased to 105%. After this value, it was determined that the added aluminum had a tendency to self-reduce by lowering the reaction temperature and reduced the yield of metal.
Table 1. Results of chemical analysis of the metal obtained as a result of the experiments performed for FeCo production._
Stochiometry Fe Co Al
%90 53.92 14.27 30.81
%95 57.28 15.09 27.37
%100 62.33 18.48 19.19
%105 70.6 18.6 10.4
%110 68.04 18.2 13.1
% 115 65.08 17.34 16.58
%120 64.95 16.25 18.2
ÏSHS2019
Moscow, Russia
Fig. 1. Metal yields obtained by changing Al stoichiometry in experiments for FeCo production.
Simultaneously with the experiments conducted for the production of Permendur 24 and Permendur 49, thermodynamic examination of the system was carried out with the help of FactSage 7.1 program. The adiabatic temperature is an important parameter for the reaction to start and self-progress and must be a minimum of 1527°C. Figure 2 shows an adiabatic temperature graph drawn for the production of Permendur 24. When the graph is examined, it is seen that the adiabatic temperature of the system increased up to a certain point with the addition of increasing Al (2910°C) and then fell. This temperature is higher than 1527°C and is sufficient to start the reaction. This explains the reduction of metal recovery efficiencies after adding 105% stoichiometric Al in the experiments.
After determining the adiabatic temperature of the system, with the aluminum stoichiometry, the possible phases to be formed in the alloy are modeled. At this stage, FactSage program, the Gibbs free energy minimizer working with the logic of the equlibrium mode was used. The program shows the stable phases that can occur at simulated pressure and temperature values. The results obtained from the FeCo system are given in Fig. 3.
Fig. 2. Adiabatic temperature values with Al stochiometry in FeCo production.
Fig. 3. Possible phases obtained by Al stoichiometry in FeCo production.
This work was supported by research grants from the Yalova University scientific research
project unit (BAP) (project no. 2018/AP/0002). The authors are deeply grateful to the Yalova
University BAP.
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