Features of transformation during cooling from the austenitisation temperature of structural steel for hot pressure treatment
DOI:
https://doi.org/10.37142/2076-2151/2025-1(54)225Keywords:
structural steel, hot pressure treatment, austenite, ferrite, pearlite transformation, annealing, heat treatment, struc-ture, cooling.Abstract
Diachenko Yu., Fedorov M., Liutyi R. Features of transformation during cooling from the austenitisation temperature of structural steel for hot pressure treatment
The article considers the features of transformation during cooling from the austenitisation temperature of samples (products) from structural steel 50 for hot pressure treatment in the GL-1 environment, which are necessary to know when choosing heat treatment modes. The method of cooling in the GL-1 environment was used to develop annealing modes for steel products with a carbon content of 0.4-0.5 %. The peculiarities of heat removal from heated samples during their immersion in the GL-1 environment are shown on the example of steel 50 of standard composition. It was found that the heating curve of the GL-1 medium shows four temperature intervals interconnected with the temperature change during the sample cooling. The first interval of heating of the medium from 20 to 100 °C is caused by immersion of a sample with a temperature of 900 °C and its cooling to a temperature of 740 °C. In this interval, the temperature of GL-1 rises slowly due to the need to warm up its initial volume. In the second interval, from 100 °C to 220 °C, a sharper heating of the medium is observed due to heat absorption during the release of ferrite from austenite. The third interval covers heating from 220 to 250 °C and is associated with the absorption of heat released during the transformation of austenite into pearlite. The fourth interval of cooling of the GL-1 medium from a temperature of 250 °C and below is associated with the cooling of the sample after the structural and phase transformations that have taken place in it. It is substantiated that with an increase in the weight of products, the temperature of the beginning of the release of excess ferrite from austenite increases, the temperature of pearlite transformation slightly increases, and the duration of this transformation increases. The data obtained are the basis for the development of heat treatment modes for structural steels, which will increase its strength and service life under conditions of variable and repeated heating and cooling of the working layer during hot working.
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