Effect of Tensile Stress Annealing on the Texture, Grain Size, and Magnetic Properties of Ultra-Thin Grain-Oriented Silicon Steel

This study systematically investigated the influence of annealing tension on the microstructure, texture, and magnetic properties of ultra-thin grain-oriented silicon steel, which is of great significance for achieving the preparation of high-quality ultra-thin grain-oriented silicon steel. The research indicates that tension primarily affects the magnetic properties by influencing the intensity of the η-fiber texture (<001>//RD) and the grain size during the annealing process, exhibiting a consistent trend across different annealing temperatures. That is, the proportion of η-oriented grains (or the intensity of the η-fiber texture) first decreased and then increased with increasing tension. Correspondingly, the magnetic induction (B800) decreased initially and then increased with the rise in annealing tension. Specifically, when annealed at 800 °C for 30 min, B800 decreased to 1.79 T under 24 MPa tension and then recovered to 1.86 T under 40 MPa tension. When annealed at 775 °C for 30 min, B800 decreased to 1.81 T under 24 MPa tension and subsequently recovered to 1.88 T under 40 MPa tension. In terms of grain size, the annealing tension promoted an increase in the average grain size. The synergistic effect of microstructure and texture led to a trend where the iron loss value (P1.5/400) of the ultra-thin strip under tension first increased and then decreased: when annealed at 800 °C for 30 min, the iron loss initially increased to 14.68 W/kg and then decreased with increasing tension; similarly, when annealed at 775 °C for 30 min, the iron loss first increased to 18.81 W/kg and then decreased with increasing tension. The evolution of the microstructure and texture is determined by the competition between the nucleation and growth of η-oriented grains and other grains during recrystallization: in the nucleation stage, the annealing tension reduced the strong advantage of η-oriented grains to some extent; however, it is speculated that η-oriented grains possess an advantage during the grain growth stage.