Increasing the Properties of Copper Alloys by Refining–Modifying Treatment with Melt Carbonates of Alkaline Earth Metals

Abstract

The main tasks of treating a melt of brass are analyzed. A comparison of traditional treatment methods with the proposed method of improving the quality of the alloy is presented. The equilibrium conditions for the decomposition reactions of carbonates are considered when treating the melt in an open and closed ladle. The conditions for the reaction of carbonate decomposition are formulated. The possibility of the simultaneous flotation of the resulting gaseous product of the decomposition of carbonates in the process of refining the brass melt from dissolved gases and nonmetallic inclusions is considered. An analysis of the thermodynamic conditions of slagging impurities by introducing carbonates of alkali and alkaline earth metals through the interaction of their oxides with oxides of silicon and aluminum in the melts is presented. The possibilities of enhancing the physicomechanical properties of brass castings due to the modifying effect provided by the formation of oxides of calcium, strontium, barium, and sodium as a result of the dissociation of their carbonates are investigated. The applied technology of treating the melt of brass with alkaline earth metal carbonates in a pouring ladle and methods for studying the results from the point of view of microstructural analysis and values ​​of mechanical tests are described. The use of carbonates in the treatment of a brass melt created a more favorable microstructure, contributed to a decrease in the average nominal grain size, increased its uniformity, and reduce the likelihood of formation of an enlarged α phase. Extensive studies of the microstructure of samples with various treatment options for melts with carbonates are carried out. A study of the mechanical properties of brass samples before and after melt treatment with various combinations of alkaline earth metal carbonates is conducted. Compositions of carbonate mixtures that have the most favorable complex effect on the strength of brass with a simultaneous increase in the plasticity indices are determined. The optimum composition of the carbonate mixture is chosen experimentally. Efficiency of treatment is confirmed by industrial tests. The simplicity and other positive features of the proposed technology of refining–modifying treatment of a brass melt with mixtures of alkaline earth metal carbonates are noted.