Russian Metallurgy (Metally)最新文献

The possibility of producing track links from low-alloy steel 30GSL with local hardening using surface alloying technology in a casting mold is shown. An alloyed layer is formed in the pin holes of the part by alloying with a high-carbon FMn78 ferromanganese powder, which increases the wear resistance of the track links and eliminates burnt-on sand. This method of manufacturing track links makes it possible to replace expensive 110G13L steel, which is used for producing track links, with cheaper low-alloy 30GSL steel without deteriorating the mechanical properties and the operational characteristics.

The study presents results on processing ammonium-sulfate solutions obtained after leaching reduced ferruginous laterite ores from the Buruktal deposit in the presence of (NH₄)₂SO₄. We identified conditions for selective hydrolytic precipitation of Fe(III), Ni, and Co hydroxides, considering (NH₄)₂CO₃, NaOH, and Na₂CO₃ as reagents. The study determined that preliminary iron removal with ammonium carbonate at pH 4.0 enables nearly complete precipitation of mixed Ni/Co hydroxides from ammonium-sulfate solutions at pH 9.3 when using NaOH as the neutralizing precipitant. Under these conditions, the residual Ni concentration in solution remains below 4 mg/L.

When metals and alloys are used to manufacture equipment, questions often arise as to the extent to which the materials employed for these purposes affect the characteristics of the base process as a whole and its progress at individual stages: where and what can be neglected as minor and insignificant factors, and where such simplifications are unacceptable due to loss of interpretive accuracy, as well as what must be strictly avoided or circumvented by other means. Experience shows that such issues are always easier to resolve when using pure metals than with their mixtures, and even more so with alloys. However, abandoning the use of alloys is often not an option. Therefore, it is necessary to explore comparative evaluation approaches for the stated influence when moving from pure metals to mechanical mixtures and further to alloys, taking into account the characteristics of the selected process setup and the importance of specific control factors. It is reasonable to begin with alloys containing a minimal number of metals. It turned out that, under all conditions, oxidation of metals to significant levels of consumption in mixtures based on organic solvents, including mixed types, is possible even at room temperature and near-room temperatures. The oxidation of pure metals proceeds the slowest, while lead in the alloy oxidizes the fastest. In the latter case, the entire supply of lead is consumed first, after which the consumption of tin noticeably accelerates (essentially begins).

The technique for constructing stress–strain diagrams for structural metal materials in the “true stress–true residual strain” coordinates has been developed up to fracture of samples from parameters of instrumented indentation and scratching. It is proposed that the plastic segment of the tensile test diagram in the region of uniform straining be obtained from the kinetic diagram of indentation by a spherical indenter. The segment of the tensile test diagram in the strain concentration region can be obtained from the scratching diagram. The methodology developed in this study has been approved with positive result for several structural materials (steels of various structural classes and titanium alloys).

The essence of the method of high-speed flame spraying is revealed, and its main advantages over subsonic flame spraying are shown. The theoretical and practical aspects of the application of high-speed flame spraying for creating wear-resistant coatings on machine parts for various functional purposes are analyzed. It has been established that the high-speed method is mainly used for agglomerated sintered metal–carbide powders, where an alloy of nickel or cobalt can serve as the metal, and chromium or tungsten carbide can be the carbide. These powder materials are used in engineering as an alternative to electroplated chromium coatings and allow for the formation of dense wear-resistant coatings with a hardness of 800–1400 HV. This method can also be recommended for spraying purely metal powders. The feasibility of using supersonic spraying for restoring the geometric dimensions of worn-out machine parts of various types has been substantiated.

The effect of technological parameters on the chemical refining of gold is studied using an artificial neural network (ANN) in the Python programming language with the Keras library. The key factors affecting the technological process “Chemical Gold Refining” from the personnel side are determined. Data verification is performed using mathematical methods, and graphs illustrating neural network training results are constructed. The investigation results can be applied to automate the control of operational risks during the refining production process.

A technology of producing carbon structural steels by remelting scrap with oxygen blowing in a 30‑t electric arc furnace is considered. To improve the furnace performance, a series of pilot-industrial heats are conducted when oxygen is injected below the bath surface using one window and three wall-mounted multifunctional tuyeres. This technology of an oxidation period decreases the heat time, the metal loss, and the specific oxygen flow rate.

The article describes the results of tool wear tests of a tool for deformational cutting in external finning of copper heat-exchange tubes. The test method and equipment are presented. The tool wear topography is analyzed, the tool wear criterion is determined, and graphs of changes in linear and mass wear parameters are constructed. The tool wear life was 90 min at a cutting path of 13.3 km. A three-tool copper tube finning machine with the given tool life provides finning of 368 linear meters of tubes.

Theoretical investigation demonstrates that the effect observed during crystallization under isostatic pressure is determined by how the atoms involved interact with each other and how they form particular compounds. We formulate concepts that are used as a basis for a model of a crystal lattice in an equilibrium state without any external influences. A system of equations is derived which allows one to find the key parameters characterizing the configuration of the outer electron shell of an atom under isostatic pressure. The main parameters describing the electron density distribution of the native shells of an atom are determined.

The structure of modified layers in carbon steels after thermodiffusion zinc coating in an ammonia atmosphere was studied. Theoretical analysis of phase diagrams identified the possible phases in the Fe–Zn–N system, including solid solutions, intermetallics, and nitrides. Metallographic, electron microscopic, and Auger electron spectroscopic analyses showed that diffusion zinc coating in ammonia produces modified layers consisting of an outer coating based on chemical compounds and a diffusion layer of solid solutions with a transition zone. Parallel nitriding of steel and an increase in layer microhardness due to solid-solution strengthening were observed.