Features of kinetics of destroying austenite and the regularities of formation of the C82DCRV steel structure during continuous cooling

Formulation of the problem. Since the cooling of rolled metal under deformation-thermal treatment in a real production process occurs not in isothermal conditions, but with a continuous temperature decrease, the study of the decay of austenite under continuous cooling is of great practical importance. Purpose. Investigation of the kinetics of the decay of austenite, as well as the regularities in the formation of the structure of C82DCrV steel during continuous cooling with different rates from an elevated heating temperature. Results. The kinetics of the transformations was studied and a continuous cooling transformation diagram (CCTD) of the decomposition of supercooled austenite of C82DCrV steel (EN ISO 16120-2:2011) alloyed chromium and vanadium from the heating temperature 1040 °C was constructed. When constructing the TCD, the differential thermal analysis method was used, using a reference sample. The most effective intervals of air cooling rates have been established, which make it possible to form at least 90 % of sorbit in the rolled product structure, exclude the release of the excess phase (cementite secondary), and the appearance of structures formed by intermediate and shear mechanisms. The results of the research have been industrialized when developing the cooling mode for wire rod with a diameter of 8.0...12.0 mm from steel C82DCrV on the Stelmor line in the flow of a continuous fine-wire mill 320/150: the temperature of the rolling formation on the Stelmor line must be at least 1040 °C, further accelerated air cooling of the metal turns on the conveyor should be carried out at a rate of not less than 13 °C/sec and not more than 20 °C/sec to a temperature range of 570...540 °C followed by quasi-isothermal exposure under heat-insulating covers.