Effect of Annealing Temperature and Time on the Magnetic Properties and Magnetic Anisotropy of a Temper-Rolled, Semi-processed Non-oriented Electrical Steel

The effect of final annealing temperature and time on the core loss, magnetic permeability, and magnetic anisotropy of a temper-rolled, semi-processed 0.5 wt.% Si non-oriented electrical steel was investigated. The magnetic properties of the steel sheets at 50-400 Hz and 0.5-1.50 T were measured by the Epstein frame method on strips cut along both the rolling (RD) and transverse directions (TD). Optimal magnetic properties were obtained when the annealing temperature was at 800-825 degrees C, and the annealing time was 2-4 h. Relatively large magnetic anisotropy between the RD and TD was observed in samples after recrystallization (similar to 10% in core loss and similar to 70% in relative permeability), while deformed and non-recrystallized samples showed small anisotropy in magnetic properties. Regardless of the processing state of the steel, i.e., temper-rolled, recovered, or recrystallized, the core loss followed quadratic polynomial functions with respect to both the frequency and magnetic flux density, while the relative magnetic permeability followed cubic polynomial functions with respect to both the frequency and magnetic flux density. The microstructure and texture of selected samples were characterized by electron backscatter diffraction, which revealed the correlations between the magnetic properties of the steel and the microstructure and texture.