Hot deformation and recrystallization of 3% silicon steel part 2: Effect of microstructural variables on static recrystallization

Abstract

The recrystallization kinetics and the recrystallized grain size of 3 % Si steel after hot rolling at temperatures of 900 to 1 100°C and annealing at the rolling temperature have been investigated for a range of initial grain sizes from 140 to 850 μm and initial austenite contents from 0 to 16%. It is shown that, in single phase ferrite, nucleation of recrystallization takes place only at grain boundaries, whereas some intragranular nucleation also occurs when austenite is present during rolling. Finer initial grain size and the presence of austenite therefore lead to faster recrystallization and to finer recrystallized grain size. Recovery during annealing causes a rapid decrease in stored energy, and therefore a decrease in the growth rate of recrystallizing regions with annealing time. This results in plateaux in the fraction recrystallized, which decrease in level with increase in initial grain size and with decrease in initial austenite content. Recrystallization kinetics approximate closely to site saturated nucleation and to negligible coarsening of recrystallized grains, leading to simple relationships between the time for 0.3 fraction of recrystallization and the fully recrystallized grain size. © 2005 ISIJ.