Effect of test variables on apparent activation energy for hot working and critical recrystallization temperatures of V-microalloyed steel

The effect of test variables on the apparent activation energy for hot working of a medium carbon V-microalloyed steel, Q(HW), and the critical recrystallization temperature, T-nr, have been studied by means of isothermal continuous and anisothermal multipass torsion test. The Q(HW) is found to be temperature dependent. Above the T-nr, the Q(HW)(U) is close to that of austenite self diffusion, Q(SD), irrespective of the type of test or test variables. Below the T-nr, the Q(HW)(L) is not only considerably higher, but that based on multipass flow curve exibits a strong interpass time dependence. With increasing interpass time from 1.8 to 10 s the Q(HW)(L) and the T-nr increase and decrease respectively. The former is assumed to be controlled by solute drag, while the latter both by solute drag and precipitation pinning. Beyond 10 s, the two parameters exhibit the same trend, and the precipitation pinning is assumed to be the only recrystallization inhibiting mechanism.