Metallurgist最新文献

This study examined the impact of homogenizing annealing on the degree of carbide inhomogeneity in hot-rolled bars made from 1.5Cr bearing steel. Qualitative microstructure assessments were conducted and analyzed. It was determined that the required quality of the final product is achieved by homogenizing the continuously cast billets through annealing. During this process, diffusion mechanisms promote a uniform chemical composition throughout the billets and resulting hot-rolled bars. Homogenizing annealing was performed at 1200 °C for six hours, followed by slow cooling under a thermal insulating cover, hot rolling, and a two-stage controlled cooling process using an improved regimen on the 370/150 wire rod mill and the Stelmor cooling line. As a result, the microstructure of 1.5Cr bearing steel exhibited a significant reduction in carbide inhomogeneity. This reduction was evaluated according to the GOST 801 and SEP 1520 standards. Homogenizing annealing of the continuously cast billet, followed by hot rolling, resulted in a more uniform microstructure with reduced carbide liquation, as well as decreased chemical and structural heterogeneity. These improvements were observed across the entire size range, with wire rod diameters from 5.5 to 18.5 mm.

The physical properties of barite-borate slags have been studied to assess the possibility of using them in the processes of cleaning metals from harmful impurities, and in means of protection from penetrating radiation. It is recommended to prepare them from natural barite and borate ores by remelting in ore-thermal furnaces. It is proposed to form a smelting charge from 80% barite and 20% borate ores (colemanite) to achieve high basicity and mobility of the resulting melt. The Terra software package was used to establish the conditions for its production and phase composition. It is recommended to perform remelting at 1800–2000 K to form the final composition of the slag. To assess the possibility of practical production and use of barite-borate slags, their viscosity and crystallization temperature were studied. The viscosity of melts containing 80, 70, and 60% barite ore, as well as colemanite, did not exceed 0.2–0.5 Pa∙s at the furnace remelting and tapping temperatures (1800–1900 K), which characterizes them as fluid. A melt with 80% barite ore has approximately the same viscosity at high temperatures as melts with 70 and 60% barite ore. This means that higher amounts of barite ore can be used, which introduces a strong basic oxide, such as BaO. The crystallization temperature of the melts was determined from the logarithmic relationship between viscosity and reciprocal absolute temperature. For the studied melts, such temperature ranges from 1675 to 1745 K, which is quite achievable in ore-thermal furnaces. By remelting a charge with 80% barite ore and 20% colemanite in an ore-thermal furnace, the following slag composition was obtained (wt. %): BaO—62.5, B₂O₃—10.5, CaO—10.3, SiO₂—13.7, MgO—1.1, and Al₂O₃—1.9. Boron losses amounted to 7.2%. The ratio of all basic to all acidic oxides, including Al₂O₃, was 2.83. In terms of its composition and physical properties, the obtained slag can be tested as a refining flux to remove harmful impurities from metals, as well as a means for protection against penetrating radiation.

A detailed study of the effect of cooling rate and impurities (iron and silicon) on the microstructure and phase composition of new casting alloys, such as Al–3.5Zn–3.5Mg–3.5Cu–1Y(1.6Er)–0.2Zr–0.2Cr–(0.15–0.5)Fe–(0.15–0.5)Si–0.1Ti, revealed a number of important features. In all four studied compositions, the iron impurity is almost completely (0.15–0.5%) dissolved in the crystallization phase—(Al, Zn, Fe)₈Cu₄Y(Er). Individual particles of the Al₃Fe phase were detected after homogenization of alloys that were crystallized at a minimum cooling rate (0.016 K/s). During crystallization of the Er-containing alloys, only one phase (Mg₂Si) is formed by the silicon impurity (0.15–0.5%). In the Y‑containing alloys, additional needle–shaped crystals of the (Al, Cu)₄YSi phase were identified. In general, it can be noted that the phase composition of the Er-containing alloys is not sensitive to the impurity content in the studied range, while in case of the Y‑containing alloys, only silicon impurity content should be limited to 0.15% to avoid a decrease in ductility due to coarse needle-shaped particles.

A surface modification technique of titanium with aluminides was experimentally tested. This method involves the explosion welding of a steel-aluminum-titanium composite, followed by pressure treatment to reduce the thickness of the aluminum layer. Subsequent annealing creates a diffusion zone of sufficient thickness at the steel-aluminum interface, enabling the spontaneous separation of the steel layer. A final heat treatment is then applied to induce liquid-phase interaction. The study demonstrates that the aluminide-based coating on the titanium surface forms due to the upward transport of detached TiAl₃ fragments from the reaction zone by circulating melt flows.

This study presents research findings on the sulfidization and flotation processes of oxidized copper ore containing 0.86% total copper, 78% of which is in the form of oxidized minerals represented by malachite, azurite, and chrysocolla. Using a probabilistic-deterministic experimental design method, the influence of sulfidizer and collector consumption, as well as the agitation time of the pulp with the sulfidizer, was investigated. A mathematical process model was developed, and the optimal sulfidization and flotation processes conditions were determined, under which copper recovery in the flotation concentrate reached 85.1%, which is 3.2% higher than without the reagent.

The development of technologies for the production of long-length deformed semi-finished jewelry products made from new precious metal alloys that meet European safety requirements is an urgent task given high competition and varying domestic and international market conditions. In this study, 585 (14 K) white gold and 925 (sterling) silver alloys were used. The author-developed software tools were used to design the reduction schedules for these alloys during shape rolling and drawing of long-sized semi-finished products. In addition, the DEFORM 3D software package was used to model the deformation treatment processes. By employing respective planning and regression analysis methods, formulas were obtained for calculating the strength properties of deformed semi-finished products obtained from the studied alloys, which were used to design and model their treatment processes. Experimental studies of the processes of shape rolling of rods and drawing wire made from the studied alloys were carried out in the laboratory. The obtained results confirmed the adequacy of the computer models. The developed technologies are recommended for implementation in production, as they can reduce the labor intensity of the production and improve the quality of finished products, as well as increase the yield and reduce the defect ratio when manufacturing jewelry products.

This study investigates the microstructures and properties of brazed joints between sheets of novel experimental Al–Ca–Ce (−Mn) system alloys using aluminum-, silicon-, copper-, and zinc-based braze filler metals (Al–6% Si–24% Cu and Zn–4% Al). The composition and microstructure of the base material, filler metal, and their interfaces, as well as the mutual diffusion of components, were analyzed using scanning electron microscopy, electron probe microanalysis, and X-ray diffraction analysis. The results reveal that the Al–Ca–Ce (−Mn) alloys exhibit a more refined microstructure in the base material compared to the filler metal. An intensive diffusion of calcium, cerium, and manganese from the base metal into the filler metal in the Al–Ca–Ce (−Mn) system alloys leads to the formation of both well-known intermetallic compounds, such as Al₄Ca and Al₁₁Ce₃, and intermetallic phases, including Al₈CaZn₃ and Al₂Cu. The Vickers hardness of the brazed seam was found to be about 2.5 times higher than that of the base metal. During tensile testing, samples with Al–6% Si–24% Cu filler metal fractured along the joint boundary, whereas samples with Zn–4% Al filler metal demonstrated higher strength within the joint zone, resulting in fracture occurring outside this region. The combination of the Al–3Ca–3Ce–1Mn base material1 and Zn–4% Al filler metal demonstrated the highest tensile strength. This work highlights the potential of Al–Ca–Ce system alloys as standalone filler metals for joining high-temperature aluminum alloys.

We describe the experience of improving the narrow wall of the copper crystallizer of a continuous casting machine based on the new design of angular coupling. We present the method aimed at the numerical analysis of the angular coupling and make conclusions obtained after the trial operation of the new structure.

This study focuses on computer-aided analysis of manufacturing processes for cold-deformed tubes. The detailed initial data and mathematical model ensure the production of finished products with specified mechanical properties.

The method for evaluating damascene structure quality, developed by Sukhanov and Khaidakov, enables a more precise attribution of antique Damascus artifacts. This approach assesses items based on their period of origin and the quality of their Damascus pattern. The study demonstrates that antique Damascus items are most effectively evaluated using an integral quality index (ΣQ). This metric represents the total score obtained by five chemical and structural analysis techniques, with each method rated on a five-point scale from the lowest to the highest quality of the damascene structure. The method was tested on Persian and Indian dagger, knife, and saber blades from the 17th to 19th centuries held in private collections. The findings indicate significant discrepancies in certain external attribution parameters of antique edged weapons. This comprehensive approach to quality assessment is proposed as a supplementary criterion for determining the cultural value of antique blades, aiding in the identification of forgeries and mass-produced imitations.