BARKHAUSEN NOISE IN GRAIN-ORIENTED 3% Si-Fe AT 50 HZ

Nkwachukwu Chukwuchekwa – Anthony Moses – Phil Anderson

   Barkhausen noise (BN) measurements were performed on samples of high permeability and conventional grain-oriented steels at both high and low flux densities in order to investigate the characteristics in each magnetization regimes. Previous works deal with measurements of Barkhausen noise carried out at high flux densities (0.2 T and above) but this work demonstrates that Barkhausen noise has different characteristics at low flux densities (8 mT to 0.2 T). The results show that the amplitude sum and the RMS Barkhausen signals are higher for High Permeability Grain-Oriented (HGO) steel than Conventional Grain-Oriented (CGO) steel at high flux densities because the grain size of HGO is higher than that of CGO. Domain wall spacing increases with increasing grain size. Hence increased grain size means domain walls move further between pinning sites resulting in larger BN signal. Below 0.2 T, the BN signal becomes higher for CGO steel. HGO samples were mechanically scribed on one surface transverse to the rolling direction. It was observed that scribing reduced the BN amplitude at high flux densities. This is due to the decrease of domain width by scribing. Then the trend reverses again at low flux density.

Keywords: Barkhausen noise, grain-oriented steel, amplitude sum analysis, RMS analysis, grain size

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