Vol 58, No 5 (2017)

To organize in-furnace dust settling in the Vanyukov furnace at OAO SUMZ (Revda, Russia), acoustic emitter technology is used. The emitter design includes a nozzle tube, an air nozzle, a resonator, and a focusing surface. Starting from the surface area of the furnace melt bath and recommended specific acoustic power for in-furnace dust settling, the summary acoustic field sound power is calculated and the optimal amount and arrangement places of acoustic emitters are determined. To form the acoustic field in the Vanyukov furnace for melting copper sulfide zinc-containing feedstock and deplete liquid converter slags, four acoustic emitters are mounted in the end wall through an inspection window, two on the apothecary side and two on the loading side of charge materials. In general, six pilot modes of testing the in-furnace dust settling system with various operational settings of acoustic emitters and one base mode for comparing performance characteristics are implemented. The duration of pilot periods varies from 5 to 18 days, and the total aggregate service time is 68 days. The presence of the acoustic field in the working furnace space at any emitter operation settings promote a decrease in the concentration of dust particles after the chain of gas purifiers (in the commodity point). It is revealed by the experimental data that the minimal summary acoustic field sound power, which decreases the dust concentration due to the coagulation of dust particles inside the furnace space, is 800 W.

The possibility of the additional purification of ammonia rhenium desorbates with respect to molybdenum in the course of the sorption recovery of rhenium from Mo-containing solutions with the help of Purolite A170 and Purolite A172 weak base anion-exchange resins is considered. The pH-dependence of sorption of Re(VII) and Mo(VI) on these anion-exchange resins is investigated in static conditions with the 1 M (NH₄)₂SO₄ background in the solution. It is shown that the range of pH, in which anion-exchange resins retain the ability to sorb Re(VII), is also spread to a weakly basic region. A substantial decrease in the adsorption of Re(VII) starts already with an increase in pH above 7.5. The capacity of anion-exchange resins with respect to Mo(VI) starts to decrease noticeably with an increase in pH of solutions above 5.0, and molybdenum almost ceases to sorb by both anion-exchange resins upon reaching pH ~ 7.0. In order to decrease the Mo(VI) content in rhenium desorbates with the sorption recovery of Re(VII) from Mo-containing solutions on weak base anion-exchange resins, the following flowsheet is suggested. Initially, the main amount of sorbed Mo(VI) is desorbed by contacting the saturated anion-exchange resin with the ammonium sulfate solution upon mixture stirring and holding constant pH of the solution in limits of 7.0–7.5 due to the addition of dosed amounts of ammonia solution. Then anion-exchange resin is separated from the ammonium sulfate solution containing Mo(VI), washed with water, and Re(VII) is desorbed by ammonium solution in dynamic conditions. The verification of the proposed method for the resins saturated by sorption from the model solution of the composition, g/L, 98 H₂SO₄, 4 Mo(VI), and 0.5 Re(VII) showed the occurrence of desorption of no less than 90% sorbed molybdenum during the treatment of anion-exchange resins with ammonium sulfate solution. Herewith, concentration ratio Re(VII) : Mo(VI) in ammoniacal rhenium desorbates when using A170 anion-exchange resin increases 11-fold and when using A172 anion-exchange resin, it increases 20-fold compared with that attained without the additional washing of Mo(VI). Losses of Re(VII) with the Mo-containing desorbate (reversible) do not exceed 5.2% of the amount of sorbed Re(VII).

The development of modern foundry production is characterized by a constant increase in requirements for the quality of fabricated casting and rational use of material resources, which determines the search for new technical and process solutions, making it possible to acquire the required properties of cast wares along with resource saving. Herewith, the question of revelation and investigation into the regularities of the influence of thermal-temporal parameters of smelting and pouring of aluminum alloys into the casting mold during the lost foam casting on tightness and mechanical and qualitative characteristics of thin-wall castings remain poorly known and complex for implementation, especially allowing for the performance of resourcesaving measures. In this publication, the influence of process parameters of smelting on the strength, tightness, and content of nonmetallic inclusions in castings of the gas-analyzer case made of AK7 alloy during the lost foam casting is considered. The data set acquired based on the experimental investigations has been subjected to statistical processing. The use of statistic models makes it possible to acquire the results of the influence of the holding time and content of secondary materials in the charge on strength and tightness of mentioned castings. The results of an investigation into the influence of holding the AK7 melt at the overheating temperature of 880–890°С on the content of nonmetallic inclusions in castings show that it can be regulated varying the holding time. This procedure decreases the melt microinhomogeneity and provides the acquisition of numerous castings with a minimal content of nonmetallic inclusions.

In order to determine the temperature gradients in ingots fabricated by the directional solidification (DS) using an UVNS-6 installation produced by VIAM (Moscow), single-crystalline ingots made of VZhM3 nickel superalloy have been prepared. Herewith, DS technologies with liquid-metal cooling (LMC) and without it are used (the Bridgman–Stockbarger method). A tin melt is used as the LMC. Readings of thermocouples installed on the surface of a ceramic mold are recorded during ingot DS. The DS of ingots made of VZhM3 nickel superalloy using the UVNS-6 installation is simulated in the ProCast program using thermal properties of the alloy, ceramic mold, and parts of the DS installation found in articles, as well as boundary conditions between them (interface heat-transfer coefficients). The good coincidence of the calculated and experimental temperature distributions in the mold during solidification using the Bridgman–Stockbarger and the LMC technique is shown, which makes it possible to use simulation of the ingot fabrication in the ProCast program to predict the temperature gradient at the solidification front, the solidification front profile, and the size of the mushy zone (where the dendritic alloy structure is formed). The temperature gradient attained in the ingot in the case of using the Bridgman–Stockbarger method by the results of simulation was 36°C/cm. The temperature gradient in the case of applying the LMC technique is 204°C/cm; i.e., it turned out sixfold higher than that attained when using the Bridgman–Stockbarger technique. Thermal properties and boundary conditions can be demanded when performing computer simulating of nickel superalloys blade casting process.

The method of forming parts of a half-sphere type in a stamp, where a die is the generatrix of the part, is presented. This is attained due to the use of an elastic steel element arranged along the puncheon contour in the stamp design. This process scheme makes it possible to combine drawing out and calibration in one stamp. Calibration when drawing out spherelike parts is necessary because of the fact that a large segment free of contact with the puncheon and a die, on which the billet losses stability and starts to corrugate, is formed in a billet. An elastic element made of spring steel and arranged along the contour of a rigid puncheon calibrates the part at the final drawing-out stage. The schematic of stamping for a half-spherical part with relative thickness S' = S/D₀ × 100% = 1.5–0.15 is presented in the article. In that work calculations of elastic element’s geometrical parameters were made. To develop semi sphere part from aluminum alloy 5056 with thickness elastic element made of steel 1060 was designed. Dimension of gap between punch and elastic element was determined as well. Maximum values of strengths happened in elastic element during stamping were calculated. It was investigated that elastic element do not have plastic flow deformation. Use of elastic element helps to produce parts with accurate geometrical dimensions and compensate elastic restitution. Also due to increase of friction elastic element allows block weakest section.

In this paper, the mechanical behaviors of the spot welding aluminum alloy in both baked and unbaked conditions are investigated. The spot welded specimens with two different base aluminum alloy sheets are studied by tensile and fatigue tests. The test results of unbaked specimens are compared with the baked which are baked at 185°C for 20 min. The stress distribution of the specimens and the fatigue life under different stress is simulated by finite element method (FEM). The paint bake treatment can increase the ductility of both base materials and spot joints. The fatigue life is increased with high loading stress due to the pinning effect; while with low fatigue load, it has the opposite rule because the compressive residual stress is released during the bake hardening process, which can restrain the fatigue crack growth rate in low stress. The simulated results of FEM model can well verify the experiment data.

In this work, we have studied the effects of solution heat treatment followed by ageing on the corrosion behavior of AA2014 aluminum alloy welded by AA5554 aluminum alloy. Two samples are then analyzed, in the first case the solution heat treatment is followed by quenching and natural ageing of 90 days (sample 1), and in the second one, the solution heat treatment is followed by quenching and artificial ageing of twelve hours at 190°C (sample 2). The principal observations can be summarized as: evaporation of magnesium in fusion zone, and diffusion of magnesium and copper from the heat affected zone to the fusion zone were identified. Solution heat treatment, quenching and 90 days of natural ageing leads to a uniform corrosion in the heat affected zone and in the fusion one, when the material is immersed for ten seconds in Keller reagent solution. After immersion in 0.3% NaCl chloride solution, and after solution treatment and quenching, we observed that applied artificial ageing at 190°C causes localized corrosion surrounding precipitates and then develops uniform corrosion in all zones, particularly in the fusion one. Finally, it is noted that the surface of different zones became nobler after applying solution heat treatment followed by natural ageing.

Nanopowders of ZrO₂–Y₂O₃–CeO₂ and ZrO₂–Y₂O₃–CeO₂–Al₂O₃ systems are investigated with the purpose of studying the influence of pH of the dispersed medium on the solubility of nanopowder particles of a complex composition in an aqueous medium after membrane filtration and centrifugation to further prepare the stable dispersions necessary for toxicological investigations of nanoparticles. Concentrations of elements remaining in a supernatant after the sample preparation, which includes membrane filtration and centrifugation, are measured by inductively coupled plasma optical emission spectroscopy. It is established that that the largest aggregative stability of the nanopowder dispersion without the Al₂O₃ additive corresponds to the optimal range of pH 5.5–9.5, while with the Al₂O₃ additive, it is region pH 7.0. The results evidence that, when dispersing these powders, the hydrosol of yttrium oxyhydroxide, which is dissolved at pH < 6.0, is formed. When dissolving in water of the powder with the Al₂O₃ additive in the neutral medium, aluminum hydroxide is formed; in the acidic medium (pH < 6), it is replaced by main soluble aluminum salts; and in the alkali medium (pH > 7), amphoteric aluminum hydroxide is dissolved because of the formation of aluminates.

A review of results of applying the powder technology of self-propagating high-temperature synthesis (SHS) for obtaining various nanomaterials that can be used according to the tribotechnical indentation is given. First, these are low-cost nanopowders of sulfides, oxides, nitrides, carbides, borides, and metals which are suitable as solid lubricants and friction modifiers for liquid and plastic lubricating materials. Second, these are solid compact nanostructured ceramic and composite materials for the fabrication of tribotechnical construction. This type of nanomaterial can be fabricated both ex situ from SHS nanopowders by sintering or introduction into the melt both in situ in one stage from initial powders reagents by gasostatic SHS technology, forced SHS compaction, SHS casting, and SHS in the melt, which considerably simplifies and cheapens the production of such materials. Third, these are SHS materials for the deposition of nanostructured coatings of various thicknesses with a high wear resistance and low friction coefficients, such as nanostructured materials for surfacing and spraying, electrospark alloying electrodes, multicomponent targets for magnetron sputtering, cathodes for vacuum-arc evaporation, and nanodispersed fillers of electrochemical and chemical coatings.

The liquidus surface in SiC–B₄C–Me^dB₂ quasi-ternary eutectic systems (where Me^dB₂ is CrB₂, VB₂, NbB₂, TaB₂, ZrB₂, HfB₂, and W₂B₅) is modeled in the approximation of the regular solution model based on the experimental data on bordering systems and individual compounds. The calculated and experimental data are compared. Regularities of the structure of phase diagrams of SiC–B₄C–Me^dB₂ systems are analyzed. It is noted that the diboride concentration appropriately decreases in the triple eutectic with an increase in its melting point. Correlation dependences between the eutectic temperature and melting point \({t_{eut}} = f\left( {t_m^{M{e^d}{B_2}}} \right)\) and formation enthalpy of diboride \({t_{eut}} = f\left( {\vartriangle H_f^{M{e^d}{B_2}}} \right)\) are constructed. The character of dependences is close to previously observed similar dependences in SiC–Me^dB₂ and B₄C–Me^dB₂ bordering quasi-binary systems. It is concluded based on the analysis of the structure and parameters of analyzed systems that it is promising to develop a broad series of construction and functional ceramic materials and coatings fabricated by “free” sintering and by pulsed methods of heating and consolidation based on the considered systems.