Hot Deformation Behavior of EN30B Forged Steels in the Presence of Non-metallic Inclusions

The hot deformation behavior of EN30B steel in the presence of inclusion has been studied using the Gleeble (R) simulator 3800. The processing maps are developed to identify the range of parameters (temperature, strain, and strain rate) for a safe deformation zone. Safe deformation zones are identified at various strain levels. The safe zone is found to lie in the high temperatures (1110 to 1150 ?) and high strain rates (6 to 10 s(-1)) at lower deformation (true strain = 0.4), which subsequently moves to low strain rates (0.1 to 0.8/s) and wide temperature regime (1000 to 1150 ?) at higher strain labels (0.6 to 1.2). With the shear band generation, there is a competition between favorable and unfavorable microstructural evolution, which shifts the safe zone at various strain levels. The evolution of inclusions and cracks at different strain rates and temperatures is examined using SEM and correlated with the processing maps. Cracks were initiated at compound inclusions and propagated in the lower temperatures and higher strain rate regimes, identified as the unstable plastic deformation zone in the processing map. An estimated higher volume fraction of the dynamically recrystallized grains in the safe deformation zone attributed to arresting the cracks.