Effect of microstructure modification on magnetic and mechanical properties of high-grade non-oriented silicon steel during annealing treatment

Abstract

The optimization of magnetic and mechanical properties by microstructure modification is tremendously challenging for high-grade non-oriented silicon steel. In the current study, the microstructure of cold-rolled high-grade non-oriented silicon steel was modified by recrystallization annealing to achieve high strength and good magnetic properties. The results indicate that recrystallization annealing significantly improved the magnetic properties, while negatively impacting its mechanical properties. At the early stage of annealing (<2 min), recrystallization nucleation occurred in the deformation matrix, leading to a significant decrease in dislocation density. This decrease in dislocation density resulted in a notable reduction in coercivity and hence enhancement in magnetic properties. However, the mechanical properties deteriorated due to the elimination of dislocations. With further increasing the annealing time (>2 min), the recrystallization grains grew within the fully recrystallized matrix. There was a slight decrease in both dislocation density and grain boundary density, leading to a slight decrease in iron loss and yield strength. The magnetic induction intensity of the fully recrystallized annealed sheets was primarily influenced by the recrystallization texture. Thus, the critical annealing time was 2 min to meet the demands of both magnetic and mechanical properties for the studied high-grade non-oriented silicon steel.