Hot deformation characteristics of non-oriented electrical steels with and without phase transformation during thermomechanical processing

Hot rolling plays a critical role in determining the final microstructure, texture, and magnetic properties of non-oriented electrical steels (NOES). Especially, NOES with and without phase transformation not only show different flow behaviors during hot rolling but also result in different final microstructures and textures. However, detailed investigations on such different behaviors of NOES have rarely been seen in the literature. In this study, the hot deformation characteristics of two non-oriented electrical steels containing (weight percentage) 1.3 % Si (with phase transformation) and 3.2 % Si (without phase transformation) were investigated by uniaxial compression in a temperature range of 850–1050 °C and a strain rate range of 0.01–1.0 s −1 , to evaluate the differences in deformation behavior and microstructure. The stress-strain curves were modeled using Zener-Hollomon constitutive equations and the material parameters were obtained. It is demonstrated that the difference in deformation behavior between the two steels is due to the presence/absence of austenite-ferrite phase transformations, and to the difference in activation energy and the amount of precipitate-forming elements, which influence the work hardening and softening mechanisms.