KINETICS OF OXIDATION OF Ca–Ge SYSTEM MELTS BY AIR OXYGEN

Abstract

With the introduction of complex alloys and metals – reoxidizers into liquid steel, their waste is observed, or more precisely, oxidation by the gas phase of the furnace. To select the optimal composition of complex deoxidizers, it is necessary to know the physicochemical laws of this process, which are little studied. To study the kinetics of oxidation of metal melts, the method of continuous sample weighing is used, which is usually used in the study of high-temperature corrosion of solid metals. The mechanism of interaction of liquid metals with oxygen is similar in nature to high-temperature gas corrosion of solid metals. In both cases, adsorption of gas molecules on the metal surface, nucleation, and then growth of an oxide film take place. In this work, the kinetics of oxidation of Ca-Ge melts with atmospheric oxygen was studied using thermogravimetry, IR spectroscopy, and X-ray phase analysis. It is shown that germanium additions up to 33.3 at % increase the resistance of melts to oxidation. An increase in temperature contributes to an increase in the rate of oxidation of melts of the Ca–Ge system. The process of oxidation of the investigated melts obeys the parabolic law. The true rate of oxidation is on the order of 10–4 kg · m–2 · s–1. The apparent activation energy of oxidation, depending on the composition of the alloys, is 39.8–526.7 kJ/mol. The products of melt oxidation are СaGe4О9 and GeО2. The mechanism of the influence of germanium on the kinetics of oxidation of Ca-Ge melts has been established. The CaGe4O9 oxide plays a dominant role in the formation of a protective oxide film.