Effect of Shear Cutting on Microstructure and Magnetic Properties of Non-Oriented Electrical Steel

In manufacturing electrical machine cores, the electrical steel laminations are often mechanically cut, leading to residual stress and a deterioration in magnetic properties. Several cutting techniques are used in the industry, such as shear cutting, punching, and laser cutting. The influence of shear cutting on the steel microstructure and magnetic properties was investigated in this paper. A single sheet tester was used for the measurements of two different grades of non-oriented electrical steel at different induction levels (0.1-1.5 T) and a wide range frequency (3 Hz-1 kHz). A scanning electron microscope was used for the characterization of the microstructure (grain size) at the cutting edges. The mechanical properties near the edge of the lamination were measured using nanoindentation. An increase in magnetic loss due to cutting was observed to be ~20% for B35AV1900 and ~9% for 35WW300, corresponding to a damaged area extending up to a distance of ~170 and ~140 μm, from the cut edge, respectively.