Effect of carbon content on hot deformation behaviors of vanadium microalloyed steels

The compressive deformation behaviors of a low carbon vanadium microalloyed steel and a medium carbon vanadium microalloyed steel were investigated at the temperatures from 900 degrees C to 1100 degrees C and strain rates from 0.005 s(-1) to 10 s(-1) on Gleeble-1500 thermo-mechanical simulator. It was found that increasing the carbon content of vanadium microalloyed steels decreased the flow stress at lower strain rates, whilst at higher strain rates carbon addition led to higher flow stress, especially at the initial stage of deformation. The flow stress constitutive equations of hot deformation were developed for the experimental steels; results showed that carbon addition has the trend to reduce the hot deformation activation energy. The dependence of the characteristic points under different deformation conditions on the Zener-Hollomon parameter and the relationship between critical strain (critical stress) and peak strain (peak stress) of the experimental steels were analyzed, and the results were in reasonable agreement with those reported before. The work hardening behavior of both steels was investigated and it was found that carbon addition can decrease the work hardening rate when strained at lower strain rates. Dynamic recrystallization analysis showed that carbon addition can accelerate the occurrence and the rate of dynamic reaystallization. (C) 2013 Elsevier B.V. All rights reserved.