Effect of Nb on Hot Deformation Behavior and Microstructure of Fe-6.5 wt% Si High-Silicon Electrical Steel

Hot rolling is one of the key processes in the new casting-rolling forming process of high-silicon electrical steel. The hot deformation characteristics, microstructure, and defects after deformation strongly influence the formability in subsequent warm- and cold-rolling processes. This study investigates the hot compression behavior of Fe-6.5 wt% Si-0.15wt%Nb and Fe-6.5 wt% Si samples at 800-1100 degrees C as well as the effect of Nb on the flow stress, dynamic recrystallization, and ordered structure of high-silicon electrical steel. The results show that the grain size of the Nb-containing as-cast samples is small. The Nb-rich second-phase particles can inhibit the growth of dynamic recrystallization grains during hot compression and refine the dynamic recrystallization microstructure; consequently, the hot activation energy of Nb-containing samples is 11.8% higher than that of Nb-free samples. Microcracks appear in the Nb-free samples at temperatures of 800 and 1100 degrees C and strain rates of 1 and 10 s(-1); the addition of Nb can effectively inhibit the generation of microcracks during hot deformation. The addition of Nb reduces the ordered degree of high-silicon electrical steel after hot compression, which is beneficial to the subsequent warm- and cold-rolling processes.