DEVELOPMENT OF AUSTENITE MICROSTRUCTURE OF HSLA-TYPE STEEL DURING HOT-WORKING

The paper investigates the influence of hot-working parameters on the course of thermally activated dynamic and static processes in HSLA (High Strength Low Alloy) constructional steel, containing 0.17 % C, 1.37 % Mn and microadditions of Nb, Ti, V in the amounts of 0.025 %, 0.004 % and 0.019 %, respectively. In order to determine the stess - strain curves and the kinetics of recrystallization of plastically deformed austenite, the Gleeble 3800 thermomechanical simulator was used. Specimens were tested in the temperature range from 900 to 1000 degrees C, at the deformation rate of 3 s(-1). Microstructure of primary austenite was revealed after two-stage compression of samples with given strain, with isothermal holding for the period from 0.2 s to 120 s; the activation energy of plastic deformation process of examined steel was determined. Obtained research results will allow to develop the technology of HSLA type microalloyed steel metal plates with the method of thermomechanical treatment - recrystallization controlled rolling.