Study of Hot Deformation Behavior of EN25 Steel in the Presence of Non-metallic Inclusions

The Gleeble® simulator 3800 has been used to study the hot deformation behavior of EN25B steel in the presence of inclusions. The experimental flow stress values are analyzed to generate the processing map, which identified the safe deformation zone at two true strain levels with maximum of 50% deformation. At a comparatively lower true strain of 0.4, the safe zone locates in the high-temperature (1050 to 1150 °C) and high-strain-rate regime (2.5 to10 s⁻¹). At higher strain (0.69), the safe zone moves to further right to a higher-temperature zone (1070-1150 °C) but extends further to lower strain rates (1.25 to 10 s⁻¹). The amount of dynamically recrystallized grains was estimated under various deformation conditions, and it decreased with a decrease in temperature, irrespective of strain rates. The investigation of non-metallic inclusions (NMIs) was conducted via electrolytic extraction, followed by SEM and XCT examination. Inclusion size estimated by XCT analysis of electrolytically extracted inclusions on paper was found to be more accurate and ~ 50% higher than SEM analysis on the surface of the sample. At high strain rates and temperatures, the outcomes demonstrated the existence of harmless finer inclusions, validating the location of the safe zone. Additionally, a constitutive model for flow stress in steel of grade EN25 has been created.