The requirement of modification of copper is proved in the article. As a modifier for copper the misch metal is proposed. The misch metal contains rare earth elements having greatest modifying ability. The results of experiments of the influence of misch metal in an amount from 0.0025 to 0.0125 wt. % on the formation of crystal structure of cast copper with different impurity content are presented. The metallographic analysis of macrostructure of copper is made and the average area of cross section of grains in the structure of copper is determined. The average area of cross section of grains in the structure of copper of brand M00 decreases from 5 to 0.9 mm2 with addition of 0.005 wt. % of misch metal. The average area of cross section of grains in the structure of copper of brand M1 decreases from 6 to 0.45 mm2 with addition of 0.005 wt. % of misch metal. An increase of quantity of added misch metal more than 0.005 wt. % dose does not lead to significant decrease of average area of cross section of grain in the structure of copper. The investigation of microstructure of samples of cast copper of brands of M00 and M1 is made. It is established that the addition of misch metal in the copper dose does not lead to increase in the thickness of the grain boundaries. The results of experiments are shown that addition of misch metal in the copper leads to increase of stregth and plastic properties of copper. Based on the results of experiments the mechanism of modification of copper is proposed.
At present time complex alloyed brasses are widely used for manufacturing of parts worked in fray conditions. The mechanical and service properties of this alloys are provided by presence of different structural constituents in the structure of alloys. The wear resistance is a basic property of complex alloyed brasses. The information on actual problems in the industrial production of cast bars, semi-finished products and [ pfrts]-непонятно] of complex alloyed brasses is presented in the article. In accordance with the increasing requirements of consumers to reliability and service life of parts the complex alloyed brass Cu62Zn31.6Mn3Al2Si0.8Ni0.4Cr0.2 was proposed as a material for production of parts. The development of technology of melting and semi-continuous casting of complex alloyed brass is an important problem. Moreover, for estimation of thermal contition of ingot and simulation of the process of solidification of the ingot, it is necessary to know thermal physic and physical characteristics of an alloy. Therefore, the research on determination of heat conductivity, heat capacity and density of complex alloyed brass, depending on temperature, was carried out. The obtained experimental data can be used to thermos-technical calculation of thermal contition of ingot and simulation of the process of solidification of ingot during semi-continuous casting for the purpose of determination of technological parameters of casting.
This paper is devoted to the possibility of using tin as an alloying element in a copper alloy for the contact wire manufacture for high-speed electrified railways. To this end, laboratory experiments were carried out to determine the effect of tin on the structure, mechanical and electrical properties of samples, made of low-alloy system Cu-Sn alloys, under the cold deformation. Cast rods and rolled billets of CuSn0,2, CuSn0,4 and CuSn0,6 alloys are made. The cast rods macrostructure is studied. The analysis showed that with the introduction of tin into copper, there is no zone of columnar crystals in the macrostructure. Moreover, it was found that grains of α-solid solution of tin in copper have a shape close to equiaxial. A structure analysis of rolled billets showed that an increase in the deformation degree leads to grinding of crystalline grains. The mechanical properties of rolled billets were determined: ultimate tensile strength σU, offset yield strength σ0.2 and elongation δ50. The dependence of the electrical resistivity of rolled billets on the deformation degree and the tin content in the alloy is determined. Еhe higher the tin content in the alloy and the deformation degree is, the higher is the electrical resistivity. The electrical resistivity of samples, made of CuSn0.2 and CuSn0.4 alloys, coincides with the GOST R 55647-2018 requirements. The laboratory studies have shown that tin-containing copper alloys (Sn is up to 0.4 wt. %) can be recommended as a material for the manufacture of contact wire.
The results of the study of phase composition, structure, and properties of multi-component complex alloyed wear-resistant brass are presented. The material contains aluminium, manganese, silicon, nickel, and chromium besides copper and zinc. A review of the influence of these components on the formation of intermetallics with different chemical composition and morphology is made. Based on the analysis it is revealed that the wear resistance of brass is highly dependent on the ratio of α-and β-phases and the volume fraction of the intermetallic particles. Chemical X-ray fluorescence, scanning electron microscopy (SEM) and electron-probe microanalysis (EPMA) are used. Based on the experiments it is established that alloys without chromium contain rod-shaped intermetallics based on Mn-Si compound with a ratio of length to cross sectional dimension 2–4. These intermetallics create the effect of anisotropy in an alloy. The presence of chromium in an alloy leads to the formation of equiaxial intermetallics with the chromium silicide core and manganese silicide coat; in this case the alloy is isotropic. It is established with metallographic study that the density of intermetallic compounds distribution of 50–130 thousand particles per 1 mm3 is required to archive the 291–298 HB hardness of brass. Cast ingots are made following the semi-casting method and then pressed to tube bars; the finished products are made by stamping so, the production technology can improve the mechanical characteristics of alloy.
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