Metallurgist最新文献

The results of comprehensive studies on the physicomechanical and tribological properties of VT6 titanium alloy with an applied Cu-Mo antifriction coating are presented. The authors have established the formation patterns of the physicomechanical and tribological properties of the VT6 alloy with a Cu-Mo composite coating obtained by low-temperature plasma-assisted magnetron sputtering. A significant improvement in the properties of VT6 titanium alloy with these coatings has been demonstrated. Increased coating hardness was established while maintaining high adhesion values (bond strength) to the titanium substrate. Comparative tribological tests under dry friction conditions showed that the average friction coefficient decreases by 9.5–9.8 times, while the wear intensity of the surface layer is reduced by two orders of magnitude.

Processing of carbonaceous gold ores with high preg-robbing activity (PRA) remains one of the most complicated challenges in hydrometallurgy. These ores may actively adsorb dissolved gold, which significantly reduces the efficiency of conventional cyanidation procedures. We focus our attention on the ore taken from a deposit in the Russian Far East, containing 1.2–1.6 g/ton gold and characterized by a high PRA of 87–98% (according to the Irgiredmet method). We performed a series of comprehensive tests, including laboratory, pilot, and semi-commercial tests, carried out with an aim to develop a flexible combined process flowsheet. These studies included the gravity and flotation enrichment with the use of special carbon-suppressing reagents, gravity-flotation recleaning of concentrates, carbon-in-leach (CIL) cyanidation with an addition of diesel fuel, and high-temperature treatment of CIL tailings. The applied set of analytic methods is quite large and includes fire assay, atomic absorption spectroscopy (AAS), phase and X-ray fluorescence (XRF) analyses, infrared (IR) and X-ray diffraction (XRD) analyses, as well as PRA testing. The developed two-stage gravity enrichment made it possible to get 63.76% gold recovery. The application of additional procedures of flash and conventional flotation increased the level of recovery up to 87.99%; while the procedure of flotation concentrate cleaning reduced PRA from 88.2% down to 62.6–70.6%. In the CIL process, 0.3 kg/ton of diesel fuel additionally suppressed PRA, achieving the level of ∼80% for the operational gold recovery and 82.06% for the total recovery. The procedure of high-temperature treatment of tailings recovered an extra amount of gold (0.7 g/ton), thus raising the overall recovery to 83.17%. The developed flowsheet demonstrates the efficiency of the integrated approach to processing unyielding low-grade preg-robbing ores and gives relatively high levels of gold recovery for low consumption of reagents. Process design criteria were developed for the design of gold-ore-processing plants.

This study is devoted to the production of ceramic matrix composite materials based on borides with a binder made of a high-entropy alloy CoCrCuFeNi using powder metallurgy methods. The composite materials were synthesized by hot pressing of powder mixtures after high-energy ball milling in planetary centrifugal mills. The ceramic matrix of the composites was based on borides (Cr₄B, Cr₂B, CrB, and Ni₃B), while the metallic binder consisted of a solid solution of all metallic components, with a face-centered cubic crystal lattice. The resulting boride-based cermets are characterized by a combination of high hardness, strength, and ductility. With a boron content of up to 20 wt. %, the cermets were comparable in strength to the high-entropy alloy CoCrCuFeNi (1600 MPa) with a hardness of up to 8.34 GPa. The wear resistance of the developed cermets correlates with the boron content and the proportion of boride phases. Samples with a boron content of 40–50 wt. % demonstrate extremely high wear resistance, with a friction coefficient of approximately 0.5 when paired with Al₂O₃.

In metallurgical processes, especially in pyrometallurgy (production of copper, zinc, lead, and other metals from sulfide ores), large amounts of sulfur dioxide are released in the processes of roasting and smelting. The problem of neutralization of sulfur dioxide released in the course of processing of sulfide ores and in some other metallurgical processes is an important ecological and commercial task. As a result of efficient removal of SO₂ from metallurgical exhaust gases not only decreases harmful emissions, but also allows one to obtain various valuable products, such as free sulfur and sulfur-containing compounds. For the implementation of processes of this kind, it is necessary to have new (more efficient) catalysts obtained on the basis of available local raw materials.

In the present work, we synthesize various nickel-containing catalysts by the impregnation method based on local clinoptilolite samples and study their catalytic activity in the process of hydrogen reduction of sulfur dioxide to elemental sulfur. The experimental conditions were as follows: the rate of volume flow of the gas mixture W = 500–1500 h⁻¹, the H₂:SO₂ ratio = 2.0–2.2, the catalyst particle size = 0.5–3 mm, and the volume fraction of SiO₂ in the gas mixture = 10–30%.

It is established that nickel-containing catalysts based on clinoptilolite exhibit high catalytic activity under the conditions typical of metallurgical exhaust gases. The optimal parameters of the process of hydrogen reduction of SO₂ sulfur in the presence of catalysts with a nickel content of 10 wt.% are as follows: W = 1000 h⁻¹, H₂:SO₂ = 2.1, and T = 773 °K. Based on the accumulated experimental data, we perform mathematical modeling, which makes it possible to predict the behavior of the system in various modes and under different conditions.

Computer modeling of three-roll screw rolling processes for steel billets was performed using the QForm finite element analysis environment at roll feed angles of 12° and 20°. The QForm point tracing function was employed to construct the helical surfaces described by points on the billet diameter during rolling. The coordinate data of the traced points defining these helical surfaces were divided into four groups based on the dimensions of the actual deformation zone. A statistical and geometric assessment of the helicity of the resulting helical surfaces was conducted for each group. It was established that helicity can occur only when the traced points are located on the entry side, outside the boundaries of the actual deformation zone.

The paper presents the initial characteristics of the metal-powder compositions (MPC) of alloy VZhL718 (IN718) used in this study, obtained by the plasma rotating electrode process (PREP) and vacuum induction gas atomization (VIGA), including chemical composition, processing properties, MPC particle size distribution parameters, and morphology.

The contents of gaseous impurities were determined for the MPCs in the initial state and after a single selective laser melting (SLM) cycle, as well as for the SLM-synthesized samples. Explanations of the resulting differences were provided.

The porosity of the VZhL718-PS samples (PS = powder-based, synthesized) synthesized from PREP-derived powders was evaluated and compared with the existing porosity data for the VZhL718-PS material synthesized from VIGA-derived powders. Assumptions were made regarding the impact of the MPC production method on the observed differences.

The surface roughness of the VZhL718-PS samples synthesized from PREP- and VIGA-derived MPCs was measured. Differences in roughness levels of the samples were determined, and roughness variation patterns were established for the upper and lower sides of the samples at different inclination angles. Explanations for the observed differences were provided.

Mechanical properties were determined for the VZhL718-PS samples synthesized from PREP-derived MPC in the XY direction after complete heat treatment. The obtained results were compared with the available data for the VZhL718-PS material synthesized from VIGA-derived MPC.

A technological process and design concept for a profiling mill to roll round tubes into hexagonal tubes made of boron-alloyed steels have been developed. Key relationships for calculating the rolling parameters are presented, and prototype tube samples have been rolled. Profiling (drawing) of round tubes into hexagonal form is shown to achieve high geometric accuracy and good surface quality.

Using the QForm software package to model the combined casting, rolling, and extrusion (CCRE) process, the temperatures, strain rates, and energy-force parameters were determined for the specified deformation and geometric conditions of the existing SP-200 and SP-400 combined processing units. The forces acting on the rolls and the die, the torques on the rolls, and the power required from the drive motors for these units were calculated. A comparison of these values with the permissible limits of the existing equipment demonstrated that the CCRE process can be implemented without overloading the machinery. Furthermore, the modeling data obtained can be used to design and assemble the deformation units for the existing equipment. Using these units, experimental studies were conducted on the production of 9 mm diameter rods from 1580 and 01570 alloys, and pilot batches were produced. The structure and mechanical properties of the resulting rods were investigated. Subsequently, these rods were drawn into welding wire up to 3 mm in diameter, suitable for welding structures in the rocket and space technology industry.

This paper describes the development and implementation of a process for producing wire rod from 38Si7 spring steel in accordance with DIN EN 10089. The wire rod is intended for manufacturing rail clips used in rail fastenings. The process was tailored to customer specifications to achieve the required product quality and properties. The study established the reheating schedule and the rolling and cooling conditions for 38Si7 wire-rod production. The reported results provide process-level novelty for producing spring-steel wire rod and include efficient conditions for reheating, rolling, two-stage cooling, as well as measures for transportation and storage.

The article explores the possibility of improving the surface quality of workpieces produced by additive manufacturing using consumable electrode arc surfacing (wire-arc additive manufacturing, WAAM). A method of additional surface treatment of the obtained workpiece in the form of plasma-arc remelting is proposed. It was established that the process of smoothing the side surface of an additively manufactured sample by remelting using a straight-polarity plasma arc immediately after surfacing allows for a smoother, more even surface without significant protrusions. It was found that remelting results in the formation of zones across the sample cross-section with slightly different α‑phase morphology, while no defects such as pores or cracks were detected. It was shown that the level of microhardness across the entire wall cross-section does not correspond to a single specific value, but rather ranges from 300 to 470 HV, depending on the microstructure dispersion and phase ratio.