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

Abstract

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 °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 °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.