The effect of the guillotine clearance on the magnetic properties of electrical steels

Measurements of the bulk magnetic properties of four non-oriented electrical steels after guillotine cutting with varying clearances are reported. A heterogeneous state of deformation is observed at the sheared edge. The deformation-affected zone extends to several millimeters away from the cut edge and possibly occupies the entire sample volume. An obvious correlation was established between the clearance of the guillotine cut and the general deterioration of the magnetic properties such as the total core losses (at 50 Hz), the coercive field, the relative permeability and the remanent induction. The existence of a transition zone was demonstrated in the range of applied clearances for which the magnetic properties were severely deteriorated. This clearance transition zone corresponds with the drastic change of one shearing parameter: the knife displacement at fracture. The observed effects are discussed in terms of the strain heterogeneities that are introduced in the sample by the guillotine cutting process