Metallurgist最新文献

The selection of optimal processing modes in the technological process enables the achievement of desired properties in titanium alloy products. Their structural and phase state significantly determines the mechanical and operational properties of the final product. This paper analyzes the influence of temperature deformation modes during radial-shear rolling of VT3‑1 titanium alloy rods. Billets with a diameter of 95 mm were rolled in 1, 3 and 5 passes at temperatures of 1060, 980 and 900 °C, respectively. The temperature of radial shear rolling, as well as the macrostructure and microstructure of the obtained rods were analyzed. Differences in the formation of macrostructure and microstructure across the cross section, as well as at the front and rare ends of the rods are shown. Analysis of the temperature changes showed that the surface temperature of the rods reached the polymorphic transformation temperature only when heated in the β‑region. It remains lower during rolling in three and five passes. The axial zone has the highest temperature, which increases during deformation and leads to the formation of a macrostructure with a grain-size number from 4 to 6. The obtained results demonstrate the possibility of controlling the structure formation in the rods by varying the technological parameters, as well as the potential of using these findings to develop digital models with further accumulation of direct experimental data.

The study focuses on the development of a functional model describing cross-zone interactions within a reheating furnace used prior to rolling. Various methods for the identification of cross-zone interaction model, ranging from regression analysis to neural networks were described. A neural network model that reflects the state of the furnace zones while accounting for their mutual interactions was obtained. The overall regression coefficient (across all zones) was approximately 0.82, with individual zone coefficients ranging from 0.65 to 0.85. Cross-zone interactions were modeled, and the results were validated by expert evaluation.

This article presents the investigation of drawing parameters of wire products made of NiTiNOL alloy, followed by the pilot scale testing of the developed technology. The method of calculation of drawing parameters is based on experimental hardening curves of NiTiNOL alloy, presented in the form of graphs and formulas depending on the deformation temperature. Using the safety factor of the front end of the wire, the design routes for drawing the wire from a diameter of 7.0 to 0.12 mm were analyzed within the studied range of deformation temperatures. It is shown that the most rational for guaranteed fulfilment of non-breakage conditions during drawing of NiTiNOL alloy is a wire gauge of 7.0–4.0 mm at a deformation temperature of 650 °C. The experimental industrial drawing was carried out on a 7.0 mm diameter bar produced under industrial conditions using the hot pressing → hot rolling → machining technology. The hot drawing process was tested on a specially designed stand consisting of an induction heating unit, a stand with a four-roll cassette and a drawing drum, as well as a cutting machine, and an electric contact heating device to prepare the front end of the wire for drawing. The wire was drawn to a diameter of 4.0 mm under different temperature deformation conditions. On the basis of the obtained results, the dependence of the inductor power on the reduction of the cross-sectional area of the deformable wire from NiTiNOL alloy was determined. Technological directions for improving the technology were identified.

We present the results of quantitative evaluation of the resistance to hydrogen embrittlement of a domestic K52 low-alloy pipe steel with dispersed ferrite–bainite structure. As a result of tensile tests carried out at a low strain rate (slow strain-rate tests (SSRT)) in hydrogen-containing media with the use of smooth cylindrical samples (in a high-pressure chamber), we determine the coefficients of hydrogen embrittlement for the relative elongation and contraction (δ and ψ). Plasticity indices exhibit a trend to decrease as the concentration of hydrogen in the gas mixture increases (from 15 up to 100%) under a total pressure of 10 MPa but the relative lowering of the values of properties does not exceed 6%. The variations of the ductility of steel in terms of the relative contraction, which differs from the level of statistical error, were recorded in an atmosphere of pure gaseous hydrogen as the pressure increased up to 14 MPa and their level remained as high as 10%. The coefficient of hydrogen embrittlement of the studied steel obeys the regularity established in analyzing the literature data accumulated for pipe steels (of K52 strength level). The results of investigations enable us to conclude that K52 steel with dispersed ferrite-bainite structure is characterized by a high resistance to hydrogen embrittlement in pure hydrogen under a pressure of up to 14 MPa.

To identify potential improvements to the design of a composite metal-polymer barrier, simulation modeling of its interaction with a rigid impactor was carried out. The barrier design was optimized using a neural network-based approach. The optimization parameters included and the ultimate strength, thickness, and initial relative density of the porous interlayer and impact energy. The objective functions were the final density of the porous layer, the displacement of the impactor, and the transmitted force.

Continuous casting machine rolls and hot rolling mill work rolls are susceptible to surface cracking under dynamic loading. The fracture resistance of homogeneous metal compositions used for their manufacture and hardfacing is determined by the work of crack initiation. This is evaluated by separating the work of crack initiation from the work of crack propagation. Research on the dynamic fracture process of heterogeneous multilayer composites hardfaced on hot rolling mill work rolls confirmed that crack arrest at the interface between strong and ductile layers occurs by a delamination mechanism, ensuring high impact toughness. Furthermore, it was found that homogeneous steel compositions with cast and plastically deformed structures used for the manufacture and hardfacing of continuous casting machine rollers and work rolls exhibit a linear relationship between fatigue crack growth rate and stress intensity factor range. This linear relationship deviates in heterogeneous hardfaced metal structures, where the fatigue crack propagation rate varies and exhibits regions of abrupt deceleration. Similar behavior is observed in welded joints of steels with different compositions and mechanical properties. The study also revealed that in cases where there are significant differences in the structure and thermophysical properties between the hardfacing layer and the base material of continuous casting machine rollers, a sharp drop in the level of axial tensile stresses at the fusion boundary leads to the arrest of surface fatigue cracks. In the absence of such a drop in stress, the crack changes direction and slows down, but does not stop. In addition, the application of variable composition hardfacing technology to hot rolling mill work rolls not only reduces uneven wear along the roll barrel, but also increases resistance to surface cracking.

Extensive studies were conducted on two 18th century Persian Damascus blades. The morphology of the carbide banding was studied in relation to the shape of the end profiles. Specifically, the dagger blade (khanjar) has a cruciform cross section, while the saber blade (shamshir) has a lenticular end profile. Based on theoretical and experimental research, it was demonstrated that the morphology of carbide banding can vary significantly depending on the chemical and phase composition when evaluated in three dimensions. It has been shown that the quality of ancient Damascus blades depends on the distribution of non-metallic inclusions, such as oxides and sulfides, within the carbide layers. The mechanisms of blade failure at the cutting edge were identified. A comparative analysis of the relief changes in the cutting edge depending on the presence or absence of non-metallic inclusions in the carbide layers was performed using fractograms of fractures and scanning microstructures.

The paper reports on the crystalline structure of a new metastable compound (Bi₂Ge₂O₇) found in the Bi₂O₃–GeO₂ system. This new phase was synthesized from powders by slow cooling of the melt in a platinum container from 1125 °C. The X‑ray diffraction analysis was used to determine the monoclinic lattice parameters of the crystalline structure (a = 14.81691(4) Å, b = 5.28586(1) Å, c = 9.45669(4) Å, β = 124.4766(2) deg., V = 610.560(3) ų) and space group C2/c. The sample also contains a small admixture of α‑quartz-type GeO₂ (up to 2 wt. %), which could not be removed at this stage of research. Scanning electron microscopy and energy dispersive analysis revealed that the synthesized samples consist of Bi₂Ge₂O₇ plates and Bi₂Ge₂O₇+GeO₂ mixture, which is formed along the plate boundaries. The ratio of the initial components (32:68 mol. %) is the most optimal, as it allows obtaining the minimum content of impurity phase (GeO₂).

A typical challenge associated with pipe-rolling machinery comprising an automatic mill or a tandem mill is the occurrence of defects on the inner pipe surface, such as roll marks (depressions). The presence of such defects prevents the application of high-quality insulation coating to the inner pipe surface. A significant number of studies have been devoted to solving the issue of roll mark occurrence, however, the proposed solutions do not fully account for the specifics of pipe production using individual machinery units. Therefore, solving the problem requires either adapting the existing methods to a specific unit, or searching for new, more universal methods. The article provides a summary of the available information concerning the problem of roll mark formation on the inner pipe surface, and describes studies conducted by the authors in an attempt to refine the defect occurrence mechanisms using computer simulation. Based on the computer models and combined statistical analysis of the pipe quality, the factors contributing to the occurrence of defects have been identified.

The main reasons for implementing energy storage systems (ESS) are the excessive consumption of fossil fuels by gas piston or diesel generator sets and the poor quality of the electrical grid at the plant. These issues can even cause emergency shutdowns due to the weak dynamic response to sudden load changes of the generator. In such systems, ESS can take the backup generator unit out of service, reduce fuel consumption and mechanical loads on the generator equipment, and improve the reliability of the generator units, thereby reducing maintenance and repair costs. A lithium-ion battery-based energy storage system model has been developed for closed electrical systems, such as drilling sites. The study presents an example of modeling a real industrial process, specifically a drilling rig. The data is collected continuously over a 5-day period. The developed model is based on the principle of encapsulation (modularity), which allows it to be adapted to the needs of different metallurgical facilities involved in raw material extraction and processing or other metallurgical operations. The model enables preliminary calculations of power supply for metallurgical facilities, which increases their operational efficiency and facilitates the selection of necessary equipment.