Separation of losses in oriented silicon steels from 0.13 to 0.34 mm thick

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Regular grain oriented 3% silicon steels were produced by conventional techniques to final gages ranging from 0.13 to 0.34 mm thick. The steels were evaluated at frequencies from 20 to 60 Hz and at inductions from 1.0 to 1.7T. Core loss minima were observed at about 0.2 mm; scribing at 5 mm intervals transverse to the rolling direction removed the minima and resulted in monotonic reduction in loss to as low as 1.32 W/kg/60Hz/1.7T at 0.135 mm thickness. Hysteresis loss, coercive force and domain wall spacing increased as thickness was decreased below 0.20 mm, and overcame the reduction in classical eddy-current losses, resulting in the observed minima. Scribing reduced the domain wall spacing and consequently the synchronous and asynchronous eddy-current losses. Electropolished samples with no forsterite and very smooth surfaces had larger domain wall spacings than the above samples, but the hysteresis losses and the synchronous and asynchronous eddy-current losses were reduced so that core losses were as low as 1.1W/kg/60Hz/1.7T and, with the sample under 10.3 MPa uniaxial tension, were as low as 1.00 W/kg/60Hz/1.7T at 0.10 mm thickness. With improved texture (lower hysteresis loss) and domain refinement (lower eddy-current losses), at 0.10 mm thick, core losses below 0.76 W/kg/60Hz/1.7T (0.34 W/#/60Hz/1.7T) are achievable.