Empress Catherine II St. Petersburg Mining University, St. Petersburg, Russia:

R. Yu. Feshchenko, Cand. Eng., Associate Prof., Dept. of Metallurgy, e-mail: Feschenko_RYu@pers.spmi.ru
O. O. Erokhina, Postgraduate Student
I. O. Litavrin, Student

Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia:
S. V. Ryaboshuk, Senior Lecturer, Higher School of Physics and Technology of Materials

Graphite products, including arc furnace electrodes, are characterized by mass loss during operation in high-temperature conditions. The consumption of electrodes depends on many factors: the pressure of the gas phase (in particular, the oxidizing agent), the average temperature over the electrode surface, and the quality of the product itself. The maximum oxidation rate is reached in the part closest to the metal, which is determined by the temperature gradient over the electrode surface from the area of the holders to the end of the electrode. At the same time, as the operation progresses, the electrode changes its shape from cylindrical to conical. Depending on the temperatures, three modes of oxidation can be distinguished, depending on the limiting factor. At the same time, the third mode is typical for arc furnaces – it is limited by mass transfer, which is caused by elevated temperatures over the electrode surface. This explains the low applicability of standard solutions used to improve the oxidative resistance of graphite products (including magnesium electrolysis anodes) operated under different temperature conditions and, accordingly, under a different oxidation regime – the formation of protective glassy coatings using borate or phosphate solutions. In order to improve the oxidation resistance of arc furnace electrodes, it is possible to adjust the technological modes of their manufacture or additional technical solutions in the field of operating electrodes directly in arc furnaces (for example, cooling by spraying water in the area of electrode holders). The mechanisms of siliconization of graphite, as well as the oxidation of the formed silicon carbide, are considered. It is proposed to use the carbothermal reduction of silicon oxide in order to obtain a protective coating on the surface of electrodes containing silicon carbide, as an alternative to expensive siliconizing processes. A variant of increasing the oxidative resistance of samples during the formation of a coating containing chromium carbide is also considered. The proposed solutions have the potential to be implemented on the basis of target enterprises, which is due to the possibility of reducing the rate of electrode oxidation by half – which can reduce the cost of metal production by approximately 8,5%.

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