期刊名称：Advances in Science and Technology Research Journal
印刷版ISSN：2080-4075
电子版ISSN：2299-8624
出版年度：2021
卷号：15
期号：4
页码：72-80
DOI：10.12913/22998624/142473
语种：English
出版社：Society of Polish Mechanical Engineers and Technicians
摘要：The paper presents the results of research on the infl uence of plastic deformation and cooling conditions on microstructure, hardness and a shape of CCT-diagram (Continuous Cooling Transformations) of newly developed multi-phase steel assigned for die forgings, combining high strength, crack resistance and fatigue strength. The diagrams of undeformed and plastically deformed supercooled austenite transformations of steel containing 0.175% C, 1.87% Mn, 1.0% Si, 0.22% Mo as well as Ti and V microadditions were determined. Dilatometric tests were performed using a Bahr 805 A/D dilatometer. Specimens were austenitized at the temperature of 1000 °C for 300 s and successively cooled to ambient temperature at selected rates ranging from 60 °C/s to 0.1 °C/s. In order to determine the infl uence of plastic deformation on the shape of CCT-diagram, samples were deformed at the temperature of 1000 °C using a 50% degree of deformation, and then cooled in the same rate range (as the undeformed samples). The tests showed the following temperature results: Ac3 = 960 °C, Ac1 = 832 °C and a relatively low MS temperature equal to 330 °C. Plastic deformation of steel at the temperature of 1000 °C, prior to the beginning of phase transformations, leads to signifi cant increase in the ferritic transformation range, shifting the temperature of its beginning higher temperatures in the whole range of cooling rates. It was also revealed that the specimens plastically deformed at the austenitizing temperature, exhibit higher hardness compared to the undeformed specimens. The elaborated CCT-diagrams of supercooled austenite transformations constitute the basis for correct development of the conditions of thermo-mechanical treatment of forgings from the tested steel.
