Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia:

V. A. Korovin, Assistant Professor of a Chair “Metallurgical Technologies and Equipment”, e-mail: mto@nntu.nnov.ru
T. D. Kurilina, Senior Lecturer of a Chair “Metallurgical Technologies and Equipment”
O. V. Tokarnikova, Engineer of a Chair “Metallurgical Technologies and Equipment”

At present time, many plants producing castings of non-ferrous alloys meet the problem of manufacturing high-quality products, especially when using low-quality charge materials. Application of scrap and own wastes leads inevitably to contamination by various impurities and increase of gas saturation of alloys, i. e. to lowering of the quality of castings and fabrication of products that don't meet the requirements of customers. This problem can be solved by refining-modifying melt processing. The carbonates of calcium, barium, strontium and sulfate present the particular interest in this regard. They can be used to realize the classical adsorption-flotation mechanism for melt refining with simultaneous modifying effect. The article presents the thermodynamic calculations of probable chemical and thermal carbonate reactions in copper alloy melt (brass) at the temperatures of ladle treatment. The performed thermodynamic calculations characterize dissociation and slagging during usage of carbonates and allow to conclude that sodium carbonate dissociation is the most possible in the temperature range 1200–1500 K. Thermal dissociation of barium and strontium carbonates is also occurred at the melting temperature of copper alloy, while this process for calcium carbonate is complicated and takes place at higher temperatures. The article presents the results of pilot-industrial studies directed on determination of the effectiveness of brass melt ladle treatment by carbonates in the conditions of “Casting and Mechanical Plant” (Semenov town, Nizhny Novgorod region). The testing results for the mechanical properties of the samples after brass melt processing by carbonates are presented and testify on its positive influence. The results of these studies demonstrate possibility and efficiency of refining and modifying of brass melt by the carbonates mixture, which is accompanied by of increase of mechanical properties and improvement of microstructure of castings.

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