1993 Volume 33 Issue 5 Pages 605-614
By using torsional test, microstructural changes in commercially available C-Mn and vanadium microalloyed steel were studied and changes in austenite on rolling through roughing and finishing mills were estimated on the basis of preliminary static recrystallization determinations. A method for determining the temperature at which recrystallization starts to be inhibited in microalloyed steel involving experimental measurements of the activation energy was developed. The influence of the activation energy on changes in austenite brought about by rolling at an ordinary hot strip mill was established by torsional simulation of various thermal cycles, both at a roughing and at a finishing mill. Austenite in C-Mn steel was found to be impossible to harden under these conditions–not even on rolling at a finishing mill at temperatures close to Ar3–as a result of its activation energy being constant at all temperatures. On the other hand, hardening of austenite in microalloyed steel was readily accomplished at a finishing mill at temperatures below the critical recrystallization temperature (915°C) as the activation energy increases sharply below such a temperature.