Browsing by Author "Kononenko, Ganna"

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    Development of a Model for Calculating Changes in K76f Rail Steel Temperature to Determine the Heat Treatment Parameters
    (National Academy of Sciences of Ukraine, 2021) Babachenko, Oleksandr; Kononenko, Ganna; Podolskyi, Rostyslav
    ENG: Introduction. The conditions of operation of the railways of Ukraine and the prospects for their entry into the international system of transport corridors require the development and modernization of railway tracks, including rails. Problem Statement. Given the necessity to ensure the main operational parameter of the rails (wear resistance), regulatory and technical documents standardize hardness. The most progressive European standard EN 13674-1-2011 establishes that the hardness of the rail head at a depth of 20 mm shall be, at least, 321 HB, while STU 4344:2004 requires, at least, 321 HB at a depth of 11 mm. At the same time, according to EN 13674-12011, the rail surface hardness without the formation of needle structures shall be, at least, 405 HB. Purpose. To determine the possibility of achieving hardness without needle structures for rail head made of steel 0,80% C, 0,25% Si, 0,97% Mn, 0,055% V (hereinafter referred to as K76F), which complies with the world requirements, based on the calcination experiment and calculations with the use of the model; to determine the rational cooling rate for K76F steel during heat treatment. Materials and Мethods. K76F rail steel with 0.80% C, 0.25% Si, 0.97% Mn, 0.055% V. Techniques: metallographic studies, hardness measurements, determination of calcination by end quenching, modeling by means of mathematical calculation with the use of QForm heat treatment software package. Results. The change in temperature, the formation of structure and hardness across the section of a K76F steel sample for calcination tests according to GOST5657 has been modeled. The changes in the hardness and microstructure has been experimentally established, depending on the distance to the heat sink surface; the cooling rate in the points where the hardness meets the requirements of EN 13674-1-2011 for rails has been determined. Conclusions. The analysis of the model has shown a high accuracy of the model and the convergence of the experimental results with the calculated ones. It has been established that the requirements of EN 13674-1-2011 can be achieved up to a hardness of 405 HB without the formation of needle structures on steel that meets the chemical composition of K76F according to DSTU 4344: 2004.
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    Physical Modelling of Additives Dissolution Features in the Bath of an Induction Furnace Crucible
    (Associazione Italiana di Metallurgia, Milano, Italia, 2024) Molchanov, Lavr; Golub, Tetiana; Kononenko, Ganna; Koveria, Andrii; Kimstach, Tetiana V.
    ENG: The technology of melting metals in an induction furnace allows the production of a wide range of alloyed steels to meet the different needs of society and is more environmentally friendly as it produces fewer emissions. A special interest for modern metallurgy are the processes of alloying and deoxidizing, which occur directly in the induction furnace by introducing lump additives. In this work, the investigation of the process of melting of additives during induction melting has been studied in order to determine the optimal modes of introduction of deoxidizing and alloying additives into the melt, providing their maximum assimilation by the liquid metal. The study was carried out on the physical model simulating the crucible of a laboratory induction furnace equipped with a closed system of hydrodynamic circulation of liquid. The results demonstrate that the most rational place for the introduction of ferroalloys into the induction furnace crucible is the area of the melt located at a distance of 1/2 radius from the center of the crucible. There is also a tendency for the dissolution time to decrease as the depth of introduction into the melt increases. Considering that in practical industrial conditions, it is extremely difficult to organize the introduction of deoxidizing and alloying agents into the volume of metal melt, the necessity of holding the melt when introducing ferroalloy is reasonable.