Metallurgist最新文献

In this study, magnetite (Fe₃O₄) nanoparticles were prepared by the chemical-metallurgy method using such surfactants as sodium dodecyl sulfate (SDS) and disodium salt of ethylenediaminetetraacetic acid (Trilon B). The dispersity, particle size, and magnetic parameters of the resulting powders were studied. The magnetization of Fe₃O₄ nanoparticles obtained with the addition of SDS and Trilon B was shown to be greater than that of Fe₃O₄ nanoparticles without the addition of surfactants. The coercivity values were approximately the same for the three cases under study. The use of surfactants has made it possible to obtain magnetite nanoparticles with high magnetization values, which makes them suitable for various applications in biomedicine.

The Novotroitsk Plant of Chromium Compounds specializes in the processing of chromite and dolomite ores, which are delivered to the first workshop of the grinding department, where they are crushed and ground in a ball mill. Operational experience has shown that the failure of the ball mill installed in this workshop leads to unplanned downtime due to failure of drive components, which accounts for 11.3% of the nominal operating time of the workshop. In order to increase the reliability of the technological equipment, it is proposed to replace the existing electric drive, which includes an obsolete 4A series electric motor and a special reducer, with a modern R167DV280V4/BVG122 motor-reducer, which transmits the rotation to the mill drum through a gear coupling. The development of the new drive has simplified its design and reduced the labor intensity of maintenance and repair. This technical solution increases the operating time between repairs, thus reducing operating costs. Calculations show that the implementation of the project solutions will lead to a 0.02% reduction in the cost of processing 1 ton of ore, a 1.37% increase in production profitability, and a 1.29% increase in sales profit. The additional investment does not exceed 3.4 million rubles and will be recovered in less than 3 months.

The present paper contains the results of investigations of the applications of jet electrolytic-plasma polishing for processing coronary stents. Significant improvements of the visual quality and surface roughness of the stents are demonstrated. The efficiency and possibility of using the method for finishing processing of these products is shown.

The structure and phase composition of coatings formed on the surface of the CrNi50WMoTiAlNb alloy by hot dip aluminizing with subsequent heat treatment were studied. Aluminizing of the CrNi50WMoTiAlNb alloy allows forming a continuous coating with a clearly distinguishable layered structure, in which the upper layer is represented by Al with eutectic inclusions, the middle layer consists of a mixture of Al and intermetallics (CrAl₇ and k-Al76Cr18Ni6), and a thin boundary layer has the following structure: φ‑Al77.5Cr12.5Ni10 + k-Al76Cr18Ni6/φ-Al77.5Cr12.5Ni10/Ni₂Al₃(Cr). Heat treatment of the aluminized CrNi50WMoTiAlNb alloy at 1100 °C leads to the formation of an intermetallic coating due to the diffusion-driven redistribution of chemical elements.

The composition of corrosion products and solid deposits in the form of conical protrusions in the vicinity of a through-hole discovered during the repair of a gas condensate well after 256 days of operation in the Dengizkul field (Uzbekistan) was investigated. The area of corrosive destruction was located 5–8 cm from the perimeter of the through hole and extended in the direction of gas condensate flow. The quantitative distribution of nine chemical elements in corrosion products and solid deposits was determined. These deposits contain all the alloying and impurity elements of the pipe steel, as well as chlorine originating from gas condensate, hydrochloric acid used for well treatment, and water. In addition to iron, the highest concentration of sulfur in the corrosion products is observed, ranging from 19.29 to 33.85 wt %, indicating that iron is predominantly present in the form of sulfides. The concentration of the remaining alloying and impurity elements is generally less than 1%, but in samples from certain areas it reaches up to 2.23 wt %. The concentrations of chlorine, calcium, and silicon in solid deposits from gas condensate-containing fluids exceed their levels in corrosion products. These elements are present in concentrations greater than 1%. The research findings may prove useful in understanding the mechanism of pipe steel degradation and in optimizing acid treatment processes during well operations.

The authors investigate the patterns of martensitic transformation during quenching of sintered steels containing ultrafine particles. The presence of porosity in sintered steels was found to accelerate the process of martensitic transformation due to the facilitated nucleation of martensite on the pore surfaces and the lower resistance of porous austenite to transformation deformations. As a result, an increase in porosity leads to an increase in the martensite start temperature. At the same time, the introduction of ultrafine particles does not affect the martensite start temperature.

A technological method for producing tubes from PtRh7 platinum-rhodium alloy by hot extrusion has been examined. Finite element analysis was used to perform process calculations. Two technological variants were simulated—with extrusion speeds of 27 mm/s and 3 mm/s. It was found that extrusion at a low speed may lead to metal cooling, resulting in an unacceptable increase in axial stresses and forces. Graphical data on strain and temperature distribution are presented. The extrusion process was implemented using a rational variant of parameters.

Or aim is to study the processes of changes in the microstructure and fine structure of pipe steel in he course of long-term holding at elevated temperatures (400 °C). By the method of transmission-electron microscopy, we investigated samples 1420 × 25.8 mm in size of the base metal of a pipe of strength class K60 in the initial state and after holding for up to 200 h at a temperature of 400 °C. It is shown that, in the course of long-term holding at 400 °C, we do not observe any noticeable changes in the structure of the ferrite matrix of samples of the base metal of the pipes made of specially developed steel, including the dislocation and subgrain structures of ferrite, as compared with samples without tempering. We recorded the changes observed in the course of tempering at 400 °C in the high-carbon phase of the samples as compared to an initial sample. Indeed, we detect tempering of martensite “islands,” precipitation of cementite particles, and decomposition of austenite into a ferrite–cementite mixture. Carbonitride phases do not undergo any visible changes in the course of tempering and are identical for all investigated samples. The obtained results serve as a microstructural justification of stability of the level of the mechanical properties of the investigated steel as a result of long-term holding at 400 °C.

The article presents the results of developing a model that employs artificial neural networks (ANNs) to predict the structural-phase composition of the weld-affected zone (WAZ) metal in high-strength steels used to produce pipes of K60–K70 strength classes. The model consists of four sub-blocks that sequentially predict parameters determining the final structural-phase composition of the WAZ metal, such as average austenite grain diameter, critical temperatures of austenite decomposition, and both qualitative and quantitative structural-phase compositions. Each sub-block utilizes ANNs that have been developed, trained, and stored as functions in the MATLAB software environment.

At the NRC “Kurchatov Institute”—VIAM, metal powder compositions (MPC) of domestic heat-resistant titanium aluminide alloys were fabricated using electrode induction melting gas atomization. They included Ti–44.5AI–2V–1Nb–2Cr–0.1Gd (at %) γ‑TiAl alloy (grade VIT7L) and Ti–22Al–23Nb–0.5Mo–0.8Zr–1.4 V–0.4Si–0.2C (at. %) orthorhombic Ti₂AlNb alloy (grade VTI‑4). Elemental analysis of the metal powders demonstrated a close match to the initial cast electrodes. The powders consist of rapidly solidified in-situ particles with dendritic structure and metastable phase compositions of (γ+α(α₂)+β) and (β+α₂+O), typical for the quenched state of the VIT7L and VTI‑4 alloys, respectively. The MPCs of the target fraction (40–100 µm) displayed high quality indices of flowability and sphericity, making them suitable for additive manufacturing by selective electron beam melting (SEBM) technology.