Effect of Nb Content on Hot Flow Stress, Dynamic Recrystallization and Strain Accumulation Behaviors in Low Carbon Bainitic Steel

Compressive deformation behaviors of low carbon steels with different Nb contents were investigated in the temperature range 900oC to 1100oC and strain rates from 0.05s-1 to 2s-1 by single pass deformation. Multi-pass compressive deformation processes were also carried out to examine strain accumulation under different Nb contents. In single pass deformations, dynamic recrystallization (DRX) can be observed in the case of low strain rate and high temperature, and the higher Nb steel exhibits higher deformation activation energy (Qdef) and critical strain value (εc) for the onset of DRX. However during multi-pass compression process (interval time of 3-4s), the higher Nb steel has larger strain accumulation between passes, so it is easier for high Nb steel that DRX happens during hot strip rolling process, which starts at relative high rolling temperature.