Effects of Rolling Passes and Annealing Methods on the Magnetic Properties of Ultrathin Grain‐Oriented Silicon Steel

ABSTRACTThis study investigates the influence of rolling passes and annealing methods on the microstructure and texture of ultrathin grain‐oriented silicon steel, aiming to improve its magnetic properties by optimising processing parameters. The results show that under identical total rolling reductions and annealing conditions, more rolling passes weaken η‐fibre recrystallisation texture, thus reducing magnetic induction (B8). Meanwhile, more rolling passes lead to coarser microstructure after short annealing, whereas non‐η‐fibre oriented grains exhibit more pronounced growth advantage with prolonged annealing. Consequently, the sheets rolled by 4–5 passes show an initially decreasing and then increasing trend in iron loss. When the rolling method is same, higher annealing temperatures accelerate non‐η‐fibre oriented grain growth. This not only drives grain sizes into a critical range that raises iron loss but also exacerbates the weakening of η‐fibre texture, collectively deteriorating magnetic properties. To sum up, the magnetic properties of ultrathin grain‐oriented silicon steel are predominantly determined by the extent to which η‐fibre oriented grains are consumed by other growing grains during annealing. In this study, optimal magnetic properties, specifically B8 > 1.8 T and P1.5/400 < 12 W/kg, can be achieved through four‐pass rolling combined with annealing at 820°C or 850°C by adjusting the annealing time.