Magnetic Anisotropic Behaviour of CRGO Steels for Quality Assessment

Abstract

An investigation on quality assessment of cold rolled grain oriented (CRGO) steels is carried out in this research with the supports of microstructure, texture and magnetic property evaluation in one virgin and three service exposed CRGO sheets. The microstructure evolution reveals oxidation, precipitation and widening at grain boundary of service exposed samples, justifying structural deterioration with service exposure. Additionally, the misorientation of Goss grains is found with higher angle range for service exposed (7°–31°) than virgin (6°–17°) CRGO. The service exposed CRGO sheets are also examined with poor magnetic properties of high core loss compared to virgin one. The non-destructive evaluation explains the deterioration of magnetic anisotropy in service exposed CRGO sheets, which would be beneficial for the rapid inspection of CRGO quality. The quality degradation of CRGO sheet is justified through the lowering of magnetic anisotropy factor and Steinmetz exponent. This research outcome would be the baseline to transformer manufacturer for the separation of inferior quality CRGO sheets amongst good one.