Nonferrous ore concentration
Ignatkina V.A. Option of selective collectors during flotation of minerals possessing similar flotation properties
A computational method of choosing collecting agents is presented for investigation of foam mineral separation with application of the "hard/soft acids and bases" principle (Pearson principle) by the example of sulfide and calcium-containing minerals. Computation data concerning absolute hardness and electronegativity of cations of heavy metals (copper, iron, zinc, lead) and calcium, hard acids, ionized and nonionized collectors as well as of charge transfer in "acid"–"base" mating couple are given. Nonionized low-polar compounds are potentially capable of increasing additionally the differences in the adsorbed bed structure of collecting agents on the minerals to be separated. With regard to the degree of charge transfer in "acid" (metal cation) – "base" (collecting agent), the computational results match up with the experimental ones (nonfrothing flotation, adsorption, IR-spectroscopy).
Key words: flotation, collecting agent, absolute hardness, mating couple, ionization potential, electron affinity, degree of charge transfer, structure, adsorption.
Extractive metallurgy of nonferrous metals
Melnikov Y.T., Krinitsyn D.O., Zhukova N.N. Dissolution rate of sulfur at tetrachlorethylene
The kinetic regularities of sulfur dissolving in tetrachloroethylene has been established depending on temperature, hydrodynamic conditions, and tetrachloroethylene concentration. Using the rotating disc method, it is found that the process takes place in the combined mode. Its diffusion and kinetic constituents are found. The reaction order of the kinetic constituent for tetrachloroethylene is 1,5 and the experimental process activation energy is 39,2±2,0 kJ/mol. Activation energy of diffusion constituent of convective mass-process transfer in dissolving sulfur in tetrachloroethylene is 28,0±2 kJ/mol.
Key words: sulfur, tetrachloroethylene, nonaqueous solution, dissolution rate, rotating disc method, activation energy.
Belousova N.V., Arkhipova E.O., Parfenov V.A. Oxidation of molten alloys of the Bi–Pb system
Using the high-temperature gravimetric analysis, oxidation of the Bi–Pb system melts has been investigated at isothermal and non-isothermal conditions. The effect of temperature conditions on the composition of scale formed is found. The possibility is shown to produce single-phase scale consisting of lead bismuthate in direct oxidation of the melt by oxygen from the air.
Key words: oxidation, melts, bismuth, lead.
Nozhko S.I. Method to determine electrolytic bath efficiency for aluminum production
The existing methods of determination of the electrolytic bath capacity for aluminum production are systematized. The most applicable method under the industrial conditions is shown to be metal-indicated one with the use of copper as a metal-indicator. Investigations of the kinetics of copper dissolving have been carried out at the industrial aluminum electrolytic baths and a formula for calculation of their capacity is derived. Optimal weight of a metal-indicator charge (copper) and a sample volume (number of electrolytic baths) are found.
Key words: aluminum electrolytic bath, copper, electrolytic bath capacity, current yield.
Extractive metallurgy of less-common and precious metals
Tsygankova M.V., Bukin V.I., Lysakova E.I., Smirnova A.G., Reznik A.M. Vanadium recovery from ash produced in oil burning at thermal power stations
Vanadium recovery conditions from vanadium-containing ashes of foreign thermal power stations: "Fiomo Santo" (Italy) – sample 1, Leina city (Germany) – 2, Caliari (Italy) – 3 have been established. It is shown that there is no united approach for direct recovery of vanadium from different ashes. Each ash requires its own leaching conditions depending on its chemical and phase compositions: for samples 1 and 2 – leaching respectively with water and 9 % sulfuric acid at S : L = 1 : 4 and t = 60¸80 °C for 30 min; for sample 3 – leaching with 5 % sulfuric acid over hydrogen peroxide at S : L = 1 : 4 and t = 20 °C for 30 min and then at 60 °C for 60 min. The conditions of hydrolytic deposition of vanadium from produced leaching solutions have been selected. It is shown that for the purpose of its most complete precipitation from the solutions at the stage of hydrolytic deposition, vanadium shall be transferred to oxidation degree of +5 by means of hydrogen peroxide at t = 20 °C for 30 min and then vanadium pentoxide shall be deposited at pH = 1,8¸2,0 и t = 95 °C for 2 h.
Key words: vanadium, ash from thermal power station, leaching, nickel, recovery, hydrolytic deposition, vanadium pentoxide.
Casting production
Drokina V.V., Belov V.D., Chekhonin S.N. Casting production from aluminum alloys by foundry into temporary molds manufactured in three-dimensional print plants
At present the enterprises of Russia use the 3D print method for manufacture of molds and casting forms in preparing the production of cast parts. For producing forms by this method in production of "pilot" casts from aluminum and magnesium alloys, MISiS Institute uses "ZPrinter 310 Plus" plant and ZCast molding sand. Because lacking the data for strength and thermophysical properties of the molding sand, it is difficult to optimize the mold wall thickness in designing. In this connection, physical and processing characteristics of ZCast mixture have been determined as applied to different conditions of the mold wall "forming" before its pouring with aluminum alloy. The results obtained showed the method of fast prototype-making of molds, and casting forms can be effectively used in the foundry production to manufacture casts from aluminum alloys, especially at the of cast parts production preparation stage.
Key words: prototype-making, 3D print, aluminum alloys, ZCast, casting form, cast part, strength and thermophysical properties.
Metal forming
Maksimov E.A. Investigation of additional mechanism to reduce pressure and rise drafting during asymmetric rolling of aluminum alloy strips
Change of longitudinal deformation of strips from aluminum alloys has been experimentally investigated in the course of symmetric and asymmetrical rolling. The results obtained allow revealing an additional mechanism of rolling pressure decrease and single drafting increase in the course of asymmetrical rolling.
Key words: experimental researches, aluminum alloys, asymmetrical rolling, pressure decrease, single drafting increase.
Lopatin N.V., Maradudina O.N., Diakonov G.S. Analysis of structure formation and properties of VT6 alloy in upsetting blanks of symmetrical-truncated cone form
Based on the results of experimental and theoretical investigations, strain and high-speed hardening parameters have been established for VT6 alloy at deformation temperature of 780–940 °C and strain rates from 5·10–3 to 1 s–1. Using "Deform3D" software, a mathematical model of upsetting VT6 alloy blanks that have symmetrical-truncated cone form has been constructed. The features of stress-strain state on the lateral surface in upsetting are determined and a mathematical model of structure formation is constructed.
Key words: mathematical model, upsetting, VT6 alloy, rheological model, structure.
Zagirov T.M., Zherebtsov Yu.V., Kadirov E.M., Yenikeev F.U. Method to take into account the influence of grain growth in finite element modeling of the superplastic metal working of advanced materials
The effect of grain growth is taken into consideration when setting the boundary problem in the deformable solid mechanics with respect to the technological processes of superplastic metal working of microcrystalline and ultrafine-grained materials. The specific example of computational solution of the boundary value problem in the creep theory is given in the ANSYS software for the experimental data known from the literature. Finite element modeling is effected by using educational version of the commercial ANSYS-code. A good agreement of the finite element solutions is obtained with corresponding experimental data. An analysis of the finite element solution has been carried out and some distinctive features of stress and strain state in the deformation site are found. Among other things, it is established that in the vicinity of the fastening contour there is a complex nonproportional stressing when the stress trajectories in the Ilushion space have large curvature regardless of the corresponding deformation trajectories are of negligible curvature.
Key words: superplasticity, strain strengthening, model-based analysis, boundary value problem, ANSYS.
Materials science and heat treatment
Solonin A.N., Churyumov A.Yu., Mikhailovskaya A.V., Ryazantseva M.A. Modeling of the structure evolution of Al–Cu–Mg alloys during natural aging
Investigation and modeling of natural aging in alloys in the Al-Cu and Al-Cu-Mg systems have been carried out. The electrical resistance measurement was the main method for determination of the kinetic aging parameters. Using the Avrami equation in differential form, a model of the structure evolution (changes in the volume fraction of the Guinier-Preston zones and depletion of solid solution) and changes in the yield strength of alloys during natural aging is constructed. There are two types of zones (Guinier-Preston and Guinier-Preston-Bagariatsky zones) in the ternary Al-Cu-Mg system, that’s why the system of differential equations is used for describing the breakdown of supersaturated solid solution at the room temperature. The accuracy of the model of composition and aging time dependence of yield strength is 6 %, which does not exceed the error of experimental determination of the property.
Key words: aluminum alloys, natural aging, modeling, yield strength, evolution of the structure.
Zolotorevsky V.S., Pozdnyakov A.V., Khvan A.V. Thermodynamic calculations of the effective crystallization range and its relationship to hot tearing index of binary and ternary-component alloys based on aluminum
By the example of the Al–Cu, Al–Mg and Al–Si binary systems, a correlation between experimentally determined hot tearing index (HTI) and calculated value of the effective interval of crystallization (EIC) obtained as the difference between the temperature of formation of a certain number of solid phases (65–90 wt.%) and the temperature of the nonequilibrium solidus has been studied. It is shown that the position of the HTI maximum practically coincides with the calculated EIC maximum. A good convergence between the calculated and experimentally determined EIC values is found. In the studied Al–Cu–Mg, Al–Cu–Si and Al–Si–Mg ternary systems, the correlation of calculated EIC and HTI is significantly worse. It is shown that the same correlation of HTI and calculated EIC can be obtained in the radial cross sections of the ternary systems in the case when all the alloys compared by HTI crystallize according to the same reactions involving the same phases.
Keywords: state diagrams, hot tearing, effective interval of crystallization.
Powder materials and coatings
Nikolenko S.V., Pyachin S.A., Burkov A.A. The formation of еlectrospark coatings of the hard alloy WC–8%Co with an additive of Al2O3
This paper contains the results the formation of coatings by the electrospark alloying using WC–8%Co alloy based electrode material with additive of aluminum oxide nanopowder. Adding Al2O3 in the hard alloy is shown to increase the mass transfer coefficient, microhardness, and wear resistance of the coatings to be formed. The duration of electric discharge considerably affects the phase composition of the alloyed layer.
Key words: electrospark alloying, electrode material, hardsurfacing coating, mass transfer, phase composition, microhardness, wear resistance.
Chronicle
Vladimir Sergeevich Panov is 75 years old
