Effect of Sn on Normalized Texture and Precipitates in Non-Oriented Silicon Steel for New Energy Vehicles

In the manufacturing process of high-grade non-oriented electrical steel, cast billets are subjected to hot rolling and normalizing treatments. These processes are implemented to optimize the microstructure and texture of steel sheets during production, mitigate corrugated defects, and enhance the magnetic properties of the final finished sheets. In this study, two types of high-strength non-oriented silicon steel test specimens were prepared via the incorporation of the trace alloying element Sn, namely one without Sn addition and the other with 0.045 wt% Sn. The test specimens were first hot-rolled to a thickness of 2.0 mm, followed by normalization treatment in the laboratory to simulate the continuous normalizing process employed by a domestic steel mill. The effects of Sn on the normalized microstructure, texture, and precipitates of non-oriented silicon steel tailored for new energy vehicles were investigated. The findings reveal that the alloying element Sn can increase the thickness of the recrystallized layer on the surface of hot-rolled sheets and refine the grain size of non-oriented silicon steel. After continuous normalizing treatment, a comparison between the two test specimens shows that as the normalizing temperature rises, the reduction in average grain size of the 0.045 wt% Sn specimen relative to the Sn-free specimen increases from 1.4% to 15.96%. Additionally, the incorporation of Sn reduces the fraction of the {111} texture component (detrimental to magnetic properties) while increasing the fraction of the {100} texture component (beneficial to magnetic properties) in the non-oriented silicon steel. Precipitates exhibited significant coarsening and a reduction in number with increasing temperature, while the addition of Sn exerted a certain inhibitory effect on precipitate growth. Furthermore, the 0.045 wt% Sn-containing test specimen achieved an optimal balance between magnetic and mechanical properties when subjected to normalization at 980 °C and annealing at 920 °C. Under these processing conditions, the magnetic induction B50 reached 1.733 T, the iron loss P1.5/50 was 2.01 W/kg, the yield strength was 410 MPa, and the tensile strength was 529 MPa.