Improving magnetic properties of non-oriented electrical steels by controlling grain size prior to cold rolling

Abstract

Abstract The 0.5 mm-thick Fe-0.9 wt%Si-0.3 wt%Al non-oriented electrical steel sheets were successfully produced with one-stage and two-stage cold rolling methods. The comparative investigations were conducted on the relationships between the processing routes, microstructures, textures and magnetic properties. This study mainly focused on how to increase the grain sizes prior to cold rolling and its influences on subsequent microstructure and texture evolution. The results showed that the fine microstructure prior to final cold rolling led to the pronounced γ-fiber texture, fine recrystallized grains and deteriorated magnetic properties after final annealing. Nevertheless, by introducing a low-reduction cold rolling and intermediate annealing, coarse grains could be generated prior to the final cold rolling. When the cold rolling reduction was 11%, a relatively homogeneous microstructure composed of fully coarse grains was produced. The increased grain sizes promoted the generation of dense shear bands during final cold rolling, which served as the nucleation sites for λ-grains and Goss grains. This resulted in the improved magnetic properties due to the weakened γ-fiber texture, strengthened λ-fiber texture and Goss texture and increased grain sizes in the final annealed sheets. This work provided a new way to improve the magnetic properties of non-oriented electrical steels by controlling the grain sizes prior to final cold rolling.