Static recrystallization behaviour of a wide range of austenite grain sizes in microalloyed steels

The static recrystallization kinetics of four steels microalloyed with Nb, Ti and Nb-Ti have been investigated, covering conventional and hot direct r oiling conditions. The influence of the grain size on the recrystallization time has been studied for a wide range of grain sizes (20-1000 mu m). For the same deformation conditions it has been observed that the quadratic dep endence on grain size works well in the range of finer grain sizes (<160 mu m). In contrast, the recrystallization times measured at coarse grain size s are significant ly lower than those predicted by this dependence. However , when the whole grain size range analysed is considered, a linear dependen ce on grain size gives the best fit to experimental data. The effect of str ain on the recrystallization kinetics has been also analysed for different initial grain sizes. It has been observed that the time to reach a 50 % rec rystallized fraction (t(0.5)) shows a dependence on strain of the type t(0. 5)proportional to epsilon(-rho), the exponent being influenced by the initi al grain size. A unique equation has been proposed to describe the static r ecrystallization kinetics of Nb, Ti and Nb-Ti microalloyed steels. The pred ictions of the equations have been compared to previously published data on similar steels.