The recrystallization behavior of Nb microalloyed steels was studied using
hot torsion testing with the aim of modeling the recrystallization processe
s taking place during hot rolling. Continuous and Interrupted torsion tests
were performed in the temperature range 850 to 1050 degreesC at strain rat
es of 0.05 to 5/s on selected low carbon steels containing Cr, Mo, Nb, Ni a
nd Ti. The kinetics of static and metadynamic recrystallization were charac
terized and appropriate expressions were formulated for the recrystallizati
on kinetics. These are shown to depend on steel composition and the process
ing conditions. The rate of metadynamic recrystallization increases with st
rain rate and temperature and is observed to be independent of strain, in c
ontrast to the observations for static recrystallization. By means of extra
polations to mill strain rates,it is shown that metadynamic recrystallizati
on will always be more rapid than static recrystallization, even at the lar
gest possible accumulated strains. These calculations support the view that
the unexpected load drops occasionally observed in industrial mills (parti
cularly in the final few passes) are probably due to strain accumulation le
ading to the initiation of dynamic recrystallization, followed by metadynam
ic recrystallization.