Balancing magnetic and mechanical properties of non-oriented electrical steel: correlation between microstructure and properties

High performance e-motors require a continuous enhancement of physical and mechanical properties for non-oriented electrical steel (NOES). However, the optimization of mechanical and magnetic properties simultaneously during NOES processing is extremely challenging where both properties directly influenced by alloy grain size, crystallographic texture, and dislocation density. In the current investigation, recrystallization annealing cycles were employed to modify the microstructure with the aim of balance magnetic and mechanical properties of NOES concurrently. The results showed that with increasing annealing temperatures, the degree of recrystallization and grain size increased, while the dislocation density reduced considerably at the early stage of recrystallization. Meanwhile, the values of texture parameter Aoverall∗ (which is a function of overall individual grain orientations and their alignments with easy magnetization directions) were increased. It was evident that the magnetic properties were significantly improved, however the alloy strength was reduced with increasing annealing temperatures. Here, the correlation between magnetic properties as well as alloy strength on grain size, texture, and dislocation density were determined. From crystallographic texture intensity and measured properties quantitative analyses it was concluded that grain size was the predominant factor in balancing the mechanical and magnetic properties of the studied steel. Furthermore, the optimal comprehensive properties (both magnetic and mechanical) were achieved by annealing at 800 °C, which yielded a magnetic induction B₅₀₀₀ of 1.616 T, a high-frequency iron loss P_1.0/400 of 22.43 W/kg, and a yield strength of 527 MPa.