Towards a Better Understanding of the Chemical Reactions Between Iron Carbide and Silicon Carbide

This article contains the research results of the equilibrium interaction of iron carbide (Fe3C) with silicon carbide (SiC) in a temperature interval of 700-2000 K with the formation of iron silicides (Fe3Si, Fe5Si3, FeSi, FeSi2 ), by using the program of the Finnish metallurgical company Outokumpy HSC Chemistryj-5.1 for  Windows with regard to the electrothermal production of ferrosilicium from siliceous and carboncontaining raw materials. On the basis of the received regression equations connecting the Gibbs energy change with the temperature and the silicon content in a ferroalloy, the response surfaces (change of the Gibbs free energy - ∆GT0) and their horizontal sections for three groups of ferroalloys were constructed with the program Mathcad. The silicon content in the first group of alloys is 14.3-23%, in the second group of alloys – 23-33.3% and in the third group of alloys – 33.3-42.8%. It was established, that the reactions between Fe3C and SiC with the formation of iron silicides in the range of temperatures 700-2000 K are possible, and the probability of these reactions increases with increasing the mole ratio Fe3C/SiC from 0.166 to 1.0. As a result of the reactions the low-silicon ferrosilicium can be obtained, answering to a grade FS20 with Si content from 19 to 27% and consisting of a mixture of Fe3Si and Fe5Si3, and also the ferrosilicium corresponding to a grade FS25 with a Si content from 23 to 29% and consisting of a mixture of Fe5Si3 and FeSi. It was found, that at the technological temperature of 1900-2000 K the maximum Si content in the received ferrosilicium can’t be more than 37.7-38.8%. Production of the medium-silicon and the high-silicon ferrosilicium answering to grades FS45- FS90 from the Fe3C-SiC mixture is impossible from a thermodynamic point of view. The received information extends our knowledge about the iron silicides formation during the electrothermal production of ferrosilicium with a silicon content in the alloy from 19 to 90%

Study of the Chemical Interactions Between Iron Phosphides and Iron Silicides

This article contains the research results of the thermodynamic modeling of interaction of iron phosphides Fe2P and FeP with FeSi2, obtained by a method of the total thermodynamic analysis on the basis of the program HSC-5.1 of the Finnish metallurgical company Outokumpu, developed on both a principle of the Gibbs energy minimization, and also kinetics of the phosphorus release by ferrosilicon from the electrothermal ferrophosphorus – a by-product of the yellow phosphorus production. It was found, that temperature of the beginning of the phosphorus formation in systems iron phosphides – FeSi2 depends on a mole ratio of phosphorus in the phosphides. At the increasing this ratio from 33.3 to 50%, the temperature of the beginning of the phosphorus formation decreases from 1362 K to 1290 K. At lower temperature (773 K) there is the formation of intermediate FeP2 and FeP in a system Fe2P-FeSi2 and intermediate FeP2 in a system FeP-FeSi2, which react with FeSi2 with temperature increasing and form a gaseous phosphorus. The process proceeds in kinetic mode and is characterized by apparent activation energy of 281-389 kJ/mol