Research on the effects of high-speed annealing on the microstructure and properties of non-oriented electrical steel

This study used on-site produced non-oriented silicon steel cold-rolled sheets as experimental materials. Firstly, the Thermo-Cal software was used to conduct thermodynamic calculations in the composition system, studying the phase composition at different temperatures and determining the continuous annealing simulation process. Next, the CAS-300Ⅲ strip steel continuous annealing simulator was used to perform annealing experiments under a 75% H₂ + 25% N₂ atmosphere for six different process routes under rapid heating conditions (heating rates of 100 °C/s and 400 °C/s). Analytical and testing methods such as metallographic microscope, EBSD, and NIM-2000E silicon steel magnetic property tester were used to analyze the microstructure, texture percentage and distribution, and magnetic properties in the rolling direction (RD) and transverse direction (TD) for these six annealing processes. The study found that under the heating rate of 100 °C/s, insufficient annealing time would result in insufficient grain growth in the recrystallization process, leading to overly fine grains in the final sheet, which affected the magnetic properties and deteriorated iron losses. However, higher annealing temperatures could compensate for the inadequate grain growth caused by short annealing times. Under the ultra-high heating rate of 400 °C/s, shorter annealing times would reduce iron losses, while longer annealing times would increase iron losses, but this had little impact on the magnetic induction intensity.