Quantitative Relationship Between Microstructure, Grain Orientation, and Magnetic Properties for Grain-Oriented Electrical Steels

Based on the high-permeability grain-oriented (GO) electrical steels with a thickness of 0.18-0.27 mm, the relationship between microstructure, grain orientation, and applied magnetic properties were quantitatively researched. Optical microscope (OM) and electron back scatter diffraction (EBSD) techniques were used to analyse the grain size and orientation of the 100 x 300 mm samples. An MPG-200D arbitrary waveform magnetic-field excitation system was used to measure the magnetic properties of the samples under sinusoidal, harmonic, and DC bias excitations. The results showed that the microstructure significantly affected the magnetic induction when the deviation angle between the average grain orientation and the Goss orientation is 3.6-8.5 degrees. The magnetic induction (B800) of the columnar crystal samples was as high as 1.95 T. There was an approximately monotonic relationship between the average grain size and B 800 , which was affected by both the grain size and texture intensity. The influence of different microstructures, such as columnar grains, equiaxed grains, and a small number of island grains, on the core loss was relatively small under sinusoidal excitation. However, the core loss was strongly sensitive to the microstructure under DC bias condition. The losses of the columnar crystal samples were significantly higher than those of the equiaxed crystal samples. We put forward five microstructure models for GO steels, and discussed the reasons for the formation of various typical microstructures and grain orientations. The results are beneficial for the targeted control of the optimal microstructures of high-performance GO electrical steels used in low-frequency and converter transformers.