Effects of Heat Treatment Under Strong Magnetic Field of 1 T or More on Magnetic Properties of Non-Oriented Electrical Steel Sheet

The effects of applying an external dc magnetic field during heat treatment were studied with the objective of improving the magnetic properties of non-oriented electrical steel sheets. In this paper, we report on the effects of the magnitude and direction of the magnetic field applied during heat treatment by comparing the magnetic properties of samples in which the longitudinal direction is parallel to either the rolling direction (RD) or the rolling transverse direction (TD). The heat treatment temperature was controlled to be 1123 and 1273 K. During the heat treatment, the magnetic field was applied parallel to the longitudinal direction of sheet samples, and the magnetic field strength was 10 T at maximum. The magnetic properties of a sample heat-treated under the magnetic field vary with the direction of the materials because of their magnetic anisotropy. The magnetic anisotropy could be reduced by controlling the magnetic characteristics by applying a certain external magnetic field during cooling. Application of the strong magnetic field of 10 T throughout the heat treatment, i.e., during both heating and cooling, remarkably caused the iron loss to increase and the magnetic permeability to decrease in the RD of the material. However, in the TD, since the magnetic properties of the measured sample only changed slightly, the resulting iron loss was lower than that in the RD.