Browsing by Author "Kamkina, Liudmyla V."

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Determining Physical-Chemical Patterns during the Formation of Brazed Joints between Tungsten and Carbon-Carbon Composite Material
(TECHNOLOGY CENTER PC, Kharkiv, 2026) Huba, Roman M.; Kamkina, Liudmyla V.; Bushtruk, Serhii I.; Troian, Andrii O.; Asmolovskyi, Serhii Yu.; Oslavskyi, Serhii Yu.
ENG: This study investigates experimentally produced brazed joints between carbon-carbon composite material (CCCM) and tungsten in a vacuum. The task addressed is to obtain high-temperature brazed joints capable of operating at temperatures of 1400–1600°C in a vacuum under conditions of high thermal cycling loads. Existing methods for joining CCCM with tungsten testify for a virtual lack of experience in brazing such materials, especially for structures of thermal emission equipment. In this work, a method was used to produce a metallized layer zone with partial melting using a mixture of Ti-Nb-Zr powders on the inner surface of an CCCM sample. Subsequently, the CCCM and tungsten samples were brazed with a Ti-Nb filler metal at a temperature of 1840°C in a vacuum. The results of microstructural analysis revealed that the brazed joint exhibits a zonal structure. Zone I – a reaction carbide layer (width 10–12 μm), zone II – diffusion layer (width up to 70 μm), zone III – reaction layer adjacent to tungsten (width up to 30 μm). The results of phase formation modeling conducted at a temperature of 1840°C indicate the predominant formation of TiC, NbC, Nb6C5, and Nb2C. Additionally, the distribution of C, Ti, Nb, and W in the brazed joint was determined. The results of the microhardness study confirmed the accuracy of the simulation and showed that microhardness values decrease from Zone I (2300 HV) to Zone III (500–600 HV). The proposed solutions demonstrate that the metallized layer helps retain solder in the joint gap; reduces thermomechanical stresses; and promotes the formation of a gradual hardness gradient. Together, these characteristics improve the ductile properties of the brazed joint. The results of this study could be applied in the field of instrument engineering, specifically in the manufacture of cathode components whose emitters are made from ultrafine powders of rare-earth borides or their alloys.
High-Entropy Alloys. A New Concept for the Design of Innovative Structural Materials
(Ukrainian State University of Science and Technologies, Dnipro, 2026) Kamkina, Liudmyla V.; Proidak, Yurii S.; Mianovska, Yana V.; Guba, Roman M.; Bezshkurenko, Oleksii G.
ENG: Modern technologies require state-of-the-art materials that meet their conditions, regardless of operating conditions. Alloys with high entropy can replace traditional materials, work under impacts, dynamic loads, elevated temperatures, etc. These alloys are used for the manufacture of tools, molds, dies, mold casting in parts that require high strength, resistance to oxidation and wear, can also be used in environments with high corrosion resistance parameters (plumbing, marine conditions), in aggressive conditions and in the chemical industry. High entropy alloys are quite easy to investigate and control, and can be obtained by the same methods as traditional alloys, such as: casting, rapid melt quenching, film sputtering, electrolysis, and mechanical alloying. Electroslag remelting (ESD) can greatly improve the purity, hardening structure, and transverse mechanical properties of steel. However, the increasing demands on the mechanical properties of steel are prompting metallurgists to make more efforts to eliminate defects in steel microstructures such as shrinkage and segregation. The combination of directional crystallization technology with electroslag melting technology effectively eliminates macrosegregation in the cast ingot through a shallow molten metal bath controlled by directional crystallization. Increasing the strength of alloys can be achieved either by alloying a solid solution (elements in the internodes) or by isolating the solidification phases or artificially introducing microparticles. Curing phases (carbides, nitrides, carbonitrides, intermetals) can be endogenous (formed from elements introduced into the melt in a liquid state or during its solidification and subsequent cooling) or exogenous (usually introduced into the melt just before crystallization begins, and there is also an increase in size and deterioration in the distribution of solidification phases.
Investigation of Physico-Chemical Characteristics of Iron-Containing Technogenic Raw Materials in the Conditions of JSC “AMT”
(Croatian Metallurgical Society (CMS), Zagreb, Croatia, 2023) Mukhametkhan, M.; Mukhametkhan, M.; Zhabalova, G.; Kamkina, Liudmyla V.
ENG: The results of experiments conducted to determine the efficiency of the use of man-made waste, including largescale in volume among the waste of metallurgical production, melted films and sludge of the oxygen converter shop are presented. During the study of the sludge of the converter shop, the chemical, phase, granulometric composition and density of rolling scale and sludge of the oxygen converter shop were revealed.
Physical and Chemical Audits and Comparative Analyses of Scrap Remelting Technology Indicators for High-Alloyed Steel with Special Purposes Using the Duplex-Slag Process and the Resource-Saving Mono-Slag Process
(Ukrainian State University of Science and Technologies, Dnipro, 2025) Projdak, Yurii S.; Gorobets, Anton P.; Zhadanos, Oleksandr V.; Kamkina, Liudmyla V.; Yaroshenko, Y. O.
ENG: The goal. The research purpose is a physicochemical audit and comparative analysis of the indicators of the technologies for remelting scrap of high-alloy special-purpose steels using a two-slag process and a resource-efficient single-slag process to create an innovative technology for the electric steelmaking process. Methodology. The research used miscellaneous methods and modern equipment for studying the physical chemistry of metallurgical processes, including optical metallography methods on the “Neophot-24” installation, to assess the microstructure of the metal and the mineralogical composition of the slags. Experimental and industrial smelting was carried out to determine the balance of alloying elements by certified chemical and spectral analysis of the metal and slag. Results and scientific novelty. To ensure the rational composition of the slag of reduced basicity during melting, a mixture with the following composition was synthesized from oxides classified as "chemically pure": 50%СаО-35%SiO2-5%Al2O3-5%MgO-5%FeO. This allows for the reduction of the loss of alloying elements and increases the efficiency of remelting. According to the results of the analysis conducted by the requirements of DSTU 8966:2019 regarding the contamination of the metal with non-metallic inclusions and their crystalline and chemical composition, it was found that the vast majority of inclusions are represented by silicates with a size of 7-10 μm. These indicators depend on the size and conditions of crystallization of the ingot. Changes in the content of alloying elements due to the remelting process were analyzed. It was confirmed that the losses of expensive alloying elements (Cr, Mo, W, V) depend not only on their chemical affinity for oxygen but also on the formation of compounds of the type СаО*МеО in the slag, where МеО oxide has an acidic nature of interaction. New knowledge has been obtained regarding the physical properties and phase composition of lime-iron slag of the CrO-FeO-SiO2-(Ме)O system where Me-Mn, Cr, V, Mo. The obtained scientific results significantly complement the research of domestic and foreign scientists due to the novelty of the approach and practical orientation to the needs of specific industries. Practical value. The developed technological solutions for predicting the optimal composition of the metal dump for metal scraps of alloyed special-purpose steels will increase the technical and economic performance of steelmaking in electric furnaces and promote the reuse of valuable materials. This is important in the context of the constant increase in the cost of raw materials and efforts aimed at reducing the impact on the environment, as well as on the sustainable development of Ukraine (solving environmental problems, reducing greenhouse gas emissions, reducing the consumption of ferroalloys, etc.).
Physico-Chemical Justification and Experimental Verification of a Waste-Free Method of Oxidative Dephosphorization of a High-Phosphorus Manganese Alloy
(National Metallurgical Academy of Ukraine, Ukrainian State University of Science and Technologies, Dnipro, 2024) Kamkina, Liudmyla V.; Velychko, K. A.; Velychko, A. G.; Jiang, Zhouhua
ENG: The purpose of the study: physicochemical justification of the process conditions and development of a rational algorithm for a single-stage waste-free method of oxidative dephosphorization of a high-phosphorus manganese alloy. Methods: thermodynamic analysis of the main reactions during oxidative refining of manganese alloys with a high phosphorus content. Experimental verification of the main stages of refining. Results: The physicochemical essence of the refining process of a high-phosphorus manganese alloy, which consists in creating conditions for oxidation in the alloy of manganese, carbon and silicon, is considered. The thermodynamic forecast of the course of reactions under the given conditions of oxidative refining of the associated metal confirms the possibility of obtaining three products: low-phosphorus manganese slag, ferric melt and phosphorus-containing slag with a phosphorus oxide content of 18-20% (phosphorus fertilizer). Scientific novelty: Based on the results of high-temperature mathematical modeling, it was established that the most rational oxygen consumption, which ensures the achievement of the tasks, is ~ 13 m3. As an oxidant, it is advisable to use oxygen blown by air, which is introduced into the converter bath using an inflatable nozzle from above. In this case, the total air consumption per 100 kg of alloy should be about 50 m3. Practical value: In the work, based on the thermodynamic forecast of the behavior of the elements of the accompanying alloy in oxidizing conditions, assessment of the thermal side of the process and further experimental verification, results were obtained that confirm the possibility of creating a waste-free technological scheme for refining a high-phosphorus alloy. In this case, it is advisable to carry out the refining of the alloy in conditions close to the conditions of modern production of low-phosphorus manganese slag, in which the temperature of the accompanying alloy is 1320...1350°C.
Regulation of Carbon and Phosphorus Content in Manganese Alloys when Processed in an Oxidizing Gas Environment or Oxide System
(Ukrainian State University of Science and Technologies, Dnipro, 2024) Velychko, K. A.; Mianovska, Yana V.; Kamkina, Liudmyla V.
ENG: Purpose: Determination of rational methods for reducing the carbon and phosphorus content in manganese alloys. Research methodology: thermodynamic calculations and experimental studies of decarburization and dephosphorization of a high-phosphorus manganese alloy. Research materials: As a high-carbon ferromanganese with a high phosphorus content, an associated metal (manganese alloy) obtained during the production of low-phosphorus slag at the Nikopol Ferroalloy Plant was used. Rolling scale was used as an oxidant (composition, wt. %: FeO – 59.5; Fe3O4 – 38.9). Research results: The features of dephosphorization of manganese alloys were considered. According to the adopted “classical” technology, a useful product of dephosphorization of manganese concentrates is manganese slag with a low phosphorus content. Oxidation of phosphorus dissolved in the metal can occur as a result of its interaction with oxygen in the gas phase, while the oxidation of this slag, the higher its basicity, the greater the probability of phosphorus oxidation. Considering the basicity of the slag, the higher the FeO content in it, the better the conditions for removing phosphorus from the metal. The process of dephosphorization of the associated metal includes the oxidation of phosphorus, the binding of phosphorus oxide into strong compounds (phosphates) and their transition to the slag phase. Scientific novelty: The composition of the associated metal includes silicon, which has a much higher affinity for oxygen than phosphorus; Then, naturally, it will first be oxidized with the formation of silicon oxide with a melting point much higher than the temperature of experimental studies. Practical significance: The results obtained show that when oxidizing the associated metal with iron scale at a specific consumption of 114 kg/t of metal, the total degree of extraction: silicon 88.16%, phosphorus 71.03%. At the same time, the manganese content in the metal decreased by 6.48% due to the reduction of rolling scale.