Dynamic Recrystallization Behavior of Vanadium Microalloyed Cryogenic Fine Grain Structural Steel Pipe at High Strain Rate

Dynamic recrystallization (DRX) behavior of a vanadium microalloyed steel pipe was systematically investigated at temperatures range of 850-1,200 °C and a strain rate of 5 s^-1 on a Gleeble-3800 thermo-simulation machine. Constitutive equation was obtained by characteristic points of DRX which derived from the strain hardening rate and stress curves. DRX kinetics model was established for determining the recrystallization volume fraction (X). Effect of dynamic precipitation of V(C, N) imposed on DRX at temperatures from 850-1,000 °C was analyzed. Results show that true stress-strain curves exhibited no clearly defined stress peaks with typical dynamic recovery behavior. X increased from 43.9 % to 100 % with increasing deformation temperature, which was in reasonable agreement with the observation of microstructure. Moreover, the calculation pinning force of V(C, N) precipitates was weaker than the recrystallization driving force, revealing that V(C, N) precipitates could effectively retard rather than prevent the progress of DRX.