Browsing by Author "Manko, Tamara"

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    Development of Fast Spheroidizing Annealing Modes and Modeling of the Intensification Process of Cementite Spheroidization of Low-Carbon Steels
    (TECHNOLOGY CENTER PC, Kharkiv, 2026) Shvachych, Hennadii H.; Sobolenko, Mariia O.; Ivashchenko, Valerii P.; Manko, Tamara; Moroz, Borys; Meshcheriakov, Leonid
    ENG: The object of research is the process of cementite spheroidization of 20Г2Р low-carbon steel 2during heat treatment, in particular spheroidizing annealing. Special attention in conducting research is paid to the influence of the initial structural state of the steel, temperature regimes and heating methods on the formation of the microstructure of the workpiece. Traditional methods of spheroidizing annealing are characterized by a significant duration of the regime, which reaches more than 10 hours and, in connection with this, energy costs, which limits the efficiency of the technological process. This is especially true for low-carbon steels with a relatively weak thermodynamic stimulus for spheroidization. The research problem is the need to reduce the duration of spheroidizing annealing of steel and reduce energy costs while ensuring a uniform distribution of cementite globules in the ferrite matrix. The scientific novelty of the obtained results lies in the development of high-speed regimes of spheroidizing annealing of 20Г2Р steel using the initial ferritic-bainite structure and non-isothermal holding with increasing temperature, in contrast to known studies based on long isothermal holdings. It is shown that the total duration of spheroidizing annealing of low-carbon steels significantly depends on the initial structural state of the workpiece. It is established that the transition from ferritic-pearlitic to ferritic-bainite initial structural state provides a reduction in the duration of cementite spheroidization from 1500–1800 s to 200–450 s. The features of the intensification of spheroidizing annealing of low-carbon steels have been studied and the influence of changes in the values of thermodynamic and kinetic factors during structural transformation has been established. The effectiveness of using non-isothermal holding with increasing temperature in a certain temperature range and optimization of spheroidizing treatment parameters has been proven. The practical significance of the results obtained lies in the implementation of the developed high-speed modes of spheroidizing annealing of 20Г2Р low-carbon steel for the production of coiled strip and wire with a diameter of 6.0–20.0 mm. The obtained structural states of the blanks provide the necessary set of properties for the subsequent manufacture of metal products by cold drawing, in particular products of complex configuration. The proposed approaches are fully suitable and meet the requirements for technological and mechanical properties of blanks for the manufacture of metal products by cold drawing.