Browsing by Author "Stoianov, Oleksandr M."

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Determining Changes in the Temperature Field of a Graphitized Hollow Electrode During Metal Processing Periods in Ladle-Furnace
(РС Тесhnology Сеntеr, Kharkiv, Ukraine, 2021) Ruban, Volodymyr O.; Stoianov, Oleksandr M.; Niziaiev, Kostiantyn; Synehin, Yevhen V.
ENG: This paper reports an analysis of the process of heating a graphitized hollow electrode (GHE) during steel processing in ladle-furnace. The results of the numerical modeling of electrode operation are given. The data on the temperature field of the electrode were obtained when electricity was supplied and during periods without electrical loading. Values of the Joule heat released at electrode operation during the periods of metal heating in ladle-furnace were calculated; they amounted to 1.11–1.15 MW/m3. Coefficients of the heat transfer by convection have been calculated for the inner and outer GHE surface: 1.60 and 1.80, and 5–17 W/(m2∙°C), respectively. Values of the electrode temperature gradient in the high-temperature zone were obtained, which, for the first heating period, reached 8,286 °C/m, for the third ‒ to 6,571 °C/m. It was established that during the cooling periods of the electrode, the temperature gradient is significantly reduced and amounts to the inner surface of 379 °C/m; to the outer surface ‒ 3,613 °C/m; the vertical plane to the end of the electrode ‒ 1,469 °C/m. The directions to improve the installation’s thermal work and reduce its resource intensity during out-of-furnace processing of steel have been defined. It has been determined that during the periods of electrode operation with current supply, significant values of the temperature gradient are observed, which are concentrated in the end part. During the periods of operation without current supply, a locally overheated zone forms, taking the shape of a torus flattened along the axis, which is created as a result of the accumulation of heat from the preceding period. The data have been acquired on the effect exerted by the gas supply through a hollow electrode on the parameters of formation of the high-temperature GHE regions. It has been shown that the supply of neutral gas through a graphitized hollow electrode at a flow rate of 0.05 m3/min shifts the high-temperature zone to the periphery by 3.5–4.2 mm, as well as reduces its height by 1.0–1.2 mm. The study reported here could make it possible to calculate expedient gas and material consumption for controlling the oxidation of metal and slag, to reduce the consumption of graphitized electrodes, to bring down energy- and resource costs for metal production.
Determining the Heat and Mass Transfer Patterns in the Tundish of a Continuous Casting Machine
(TECHNOLOGY CENTER PC, Kharkiv, 2025) Terekhov, Dmytro A.; Ruban, Volodymyr O.; Stoianov, Oleksandr M.
ENG: This study’s object is the thermal state of the tundish ladle in a continuous billet casting machine, aimed at prolonging the duration of the series of melts. This paper reports the numerical modeling of the heat and mass transfer processes in the tundish ladle of a continuous billet casting machine (CCM). The model takes into account the hydrodynamics of liquid steel, as well as the temperature distribution in the multilayer lining and the ladle casing; it also makes it possible to predict local wear of the lining based on the analysis of the technological parameters of the process and the chemical composition of steel. Special attention is paid to the study of the temperature and turbulent characteristics of the flow, the residence time of the steel in the ladle, and the influence of its composition on the intensity of destruction of the lining layers. The results make it possible to localize critical areas of thermal and mechanical overload of the ladle lining, in particular the contact zones of the liquid steel jet and the wall areas near the turbos tops, where the following are recorded: shear stress up to 275 Pa; turbulent kinetic energy over 0.14 m2/s2; and metal temperature up to 1830 K. The local wear map built shows the distribution of the lining erosion rate within 2.4–4.3 mm/h depending on the hydrodynamic and chemical conditions. The predictive model combines CFD parameters, the chemical composition of steel, and the pouring speed, which showed high accuracy confirmed by the coefficient of determination R2 = 0.99937. A feature of the result is the comprehensive combination of local flow conditions and steel composition with the erosion model, which has made it possible to give engineering-based recommendations for optimizing the ladle operating modes. The developed predictive model of liner wear rate could be used to monitor its condition, improve ladle operating modes, and increase the reliability of the continuous casting process.
Energy and Technological Modelling of Metallurgical Processes from Out-of-Furnace Iron Processing to Continuous Casting
(Baltija Publishing, Riga, Latvia, 2023) Stoianov, Oleksandr M.; Petrenko, Vitalii O.; Niziaiev, Kostiantyn G.
ENG: Purpose. Conducted energy-technological modeling of steelmaking processes. It is shown that at different stages of steel production, the increase in energy intensity of steel differs significantly and depends on the chosen technology, equipment and materials used. It has been established that for modern methods of off-blast refining of cast iron, the least energy-consuming technology is the use of mixtures based on lime and magnesium. For the oxygen-converter process, liquid cast iron contributes the largest increase in energy consumption, and for conditions of non-furnace processing of steel, the consumption of electricity for heating the metal. An assessment of the impact of the speed of steel pouring on the MBLZ and the carbon content in the metal on the energy costs of the process is also given.
Investigating Cavity Formation in an Electric Arc Zone During Out-of-Furnace Processing of Steel
(PC TECHNOLOGY CENTER, Ukraine, 2023) Ruban, Volodymyr O.; Stoianov, Oleksandr M.; Niziaiev, Kostiantyn H.; Synehin, Yevhen V.; Zhuravlova, Svitlana V.; Malii, Khrystyna V.
ENG: The object of this study is the interaction zone between a graphitized hollow electrode (GHE) and a metal bath on the «ladle-furnace» installation. The regularities of the formation of the geometric parameters of the hole were established for the purpose of further evaluation of the heat exchange under the electrode in the arc combustion zone under different operating conditions of the «ladle-furnace» installation. An experimental methodology was devised, and a laboratory setup was built for physical simulation on a cold model. The values of the geometric parameters of the cavity formed by the electric arc discharge in the sub-electrode zone were calculated. In particular, the area of the curved surface of the cavity is about 0.2 m2 at a depth of 40 mm. The regularities of formation of the geometry of the cavity during gas injection through the GHE channel have been established, in particular with regard to the area and depth of the cavity. Thus, with a gas consumption of 3–20 m3/h and a slag cover height of 100 mm, the area reaches 0.28–0.5 m2, while the depth of the cavity ranged from 5 cm to 19 cm, respectively. Rational flow rates of gas supplied through the channel of the graphitized hollow electrode were established, which for a slag cover of 100 mm are 3–6 m3/h and for a slag cover of 200 mm – 6–10 m3/h. The peculiarities of the formation of a metal cavity in the sub-electrode zone under the conditions of gas supply through the channel of a graphitized hollow electrode during out-of-furnace processing of steel at the «ladle-furnace» installation were investigated. The patterns of the formation of the geometry of the cavity in the arc combustion zone, which were obtained using cold modeling, could subsequently make it possible to perform calculations of heat transfer from the electric arc discharge to the metal bath. That will also make it possible to determine the share of heat absorbed by slag and metal under the conditions of using a conventional electrode, and a hollow one with gas supply through its channel during out-of-furnace processing of steel at the «ladle-furnace» installation.
The Investigation of the Thermal Performance of the Graphitized Hollow Electrode in the "Ladle-Furnace" with the Supply of Neutral Gas
(Physical-Technological Institute of Metals and Alloys of the National Academy of Sciences of Ukraine, Kyiv, 2023) Ruban, Volodymyr O.; Stoianov, Oleksandr M.
ENG: The article presents an analysis of heat transfer efficiency from an electric arc discharge formed in the sub-electrode zone to a metal bath under different operating conditions of the “ladle-furnace” (LF). A numerical modeling methodology has been developed, and the obtained data have been analyzed to determine the heat transfer efficiency with the supply of neutral gas through a graphitized hollow electrode (GHE). The objective of this study is the numerical modeling of the influence of changing the geometric parameters of the metal bath cavity formed by gas injection through the channel of the graphitized hollow electrode on the heat transfer efficiency from the electric arc to the metal bath at different thickness of the slag cover in the “ladle-furnace”. Research methods. Numerical modeling of the heating of the metal bath was performed on a developed 3D model of a steel ladle with liquid metal and a cavity zone formed under the action of an electric arc and gas supplied through the channel of the graphitized hollow electrode. Heating was conducted under different geometric parameters of the cavity and varying heights of the slag cover. The obtained data were analyzed, indicating the advantage of using the graphitized hollow electrode with gas supply through its channel compared to a conventional electrode. Results obtained. The share of heat absorbed by the slag and metal under the conditions of using a conventional electrode and a hollow electrode with gas supply through its channel was determined. The influence of the parameters of the reaction zone formed under the GHE on the heat transfer from the electric arc to the metal bath was determined, with maximum temperature increase values of the metal amounting to 0.6 ºC/min. Scientific novelty. New data were obtained regarding the influence of neutral gas supply through GHE on the amount of heat transferred to the metal by convection, and indicators of the heat flux density from the electric arc to the metal cavity in the sub-electrode zone were determined. Practical significance. It was determined that increasing the area of the metal cavity by supplying gas through the GHE channel improves the heat transfer from the electric arc to the metal bath. Meanwhile, increasing the thickness of the slag cover reduces heat losses to the furnace atmosphere. The carried out research provided important data regarding the thermal performance of the "ladle-furnace" in the sub-electrode zone, which can be further utilized for process optimization.
Study of the Regularities of Centerline Porosity Formation in Continuously Cast Billets Depending on Casting Parameters
(TECHNOLOGY CENTER PC, Kharkiv, 2026) Synehin, Yevhen V.; Ruban, Volodymyr O.; Niziaiev, Kostiantyn H.; Stoianov, Oleksandr M.; Zhuravlova, Svitlana V.
ENG: This study investigates the process that forms centerline porosity in the axial zone of a continuously cast steel billet during its hardening. The task addressed relates to the need to establish rational parameters for the temperature-speed mode of casting to minimize axial porosity, which is critical for increasing the density of the metal and the quality of rolled products. A comprehensive methodology for physical modeling of the hardening process using stearin as a model substance has been devised. Based on the analysis of similarity numbers (Biot, Fourier, Kosovych), the exact scales of modeling were established: by time – 1.854, by linear dimensions – 0.1778, by heat transfer coefficient – 0.04639. It was determined that for an adequate simulation of the formation of the bloom blank, the closing angle of the liquid core varies within 2.3–6°. Quantitative parameters of the experiment on the model were established: overheating of the melt in the range of 1.8–4.2°C, which corresponds to 15–35°C for steel. The resulting data are explained by the laws of convection heat transfer and phase transition. The angle of inclination of the crystallization front and the intensity of heat removal determine the moment of formation of "bridges" and interceptions in the thermal center, which directly defines the morphology and volume of shrinkage pores. Unlike conventional mathematical modeling, the proposed approach provides high visual reliability of defect formation due to the use of the π-theorem for the selection of physical parameters. This makes it possible to investigate critical system states without the risk of emergencies in industrial settings. The research results could be used for implementation at metallurgical enterprises in the design and optimization of billet cooling modes on a continuous billet casting machine (CCM), which will ensure an increase in the yield of suitable metal.