Influence of Punching and Tool Wear on the Magnetic Properties of Nonoriented Electrical Steel

Because electric cars are manufactured in high quantities, the influence of punching of nonoriented electrical steel with respect to tool wear becomes an important topic for the automotive industry. With regard to quality assurance, it is necessary to investigate the local degradation of the magnetic properties due to the plastic deformation caused by the cutting process. In this contribution, both the local changes of the microstructure of the material and the magnetic properties will be considered. Different methods for analyzing the manufactured electrical steel laminations were applied. Cutting edges generated under different states of tool wear were examined by means of optical microscopy and electron backscatter diffraction to visualize the influence of plastic deformations. The magnetic properties of punched electrical steel laminations as a function of increasing tool wear have been determined by hysteresis measurements of stacked ring cores. With respect to quality assurance purposes spatially resolved measurements have been carried out to determine local magnetic properties and find a suitable correlation to application-relevant quantities.