Abstract
High-permeability grain-oriented (HGO) electrical steel constitutes the best option for transformer cores because the magnetic flux can be aligned to the easy magnetizing axis of the material, therefore reducing the transformer energy loss. In this type of steel, magnetic Barkhausen noise (MBN) evaluation serves as a quality indicator for magnetic properties because it probes the loss process along the hysteresis loop. It is shown that MBN characterization can also be used as an indicator of grain size and distribution, but the strategy to correlate MBN with the polycrystalline structure differs from that of other studies, which sometimes present contradictory results restricted to the tested materials. By evaluating the MBN in HGO steel samples as a function of surface position, it is possible to show that the local intensity of the phenomenon forms contour lines that follow the grain distribution. This finding can be further used to indirectly estimate the grain size of a sample without the need of surface treatment. A specific MBN sensor was developed to obtain detailed measurements with reliable results.
Published Version
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