Grain oriented silicon steel sheet with new ceramic films characterized by ultra-low iron loss

Abstract

An improvement in the iron loss in grain oriented silicon steel sheet was investigated for ceramic coatings of TiN, CrN and TiC produced by ion plating on polished silicon steel sheets. The experimental results obtained are summarized as follows. (1) The magnetic flux density B8 (T) of silicon steel sheets with the ceramic films was moderately increased by 0.004–0.015 T, while the iron loss W17/50 (W/kg) was dramatically improved by 0.12–0.20 W/kg. This improvement in the iron loss was most marked in silicon steel sheets with a higher magnetic flux density. For example, silicon steel sheet with B8=1.93 T and W17/50=0.88 W/kg resulted in magnetic domain refinement for a very low iron loss of 0.55 W/kg, which corresponds to an improvement in iron loss of about 40%. (2) Silicon steel sheets with TiN or CrN films showed dramatically improved magnetic properties, while samples with TiC, SiC, SiO2, or Al2O3 films showed slightly less improvement than those with TiN or CrN films. (3) The ceramic film-coated silicon steel sheets showed no deterioration in magnetic properties after strain-relief annealing, superior compressive stress dependence on magnetostriction, and good lamination performance. (4) The attainment of ultra-low iron loss was due to an improvement in the hysteresis loss by using a polished steel surface that was clean and free from impurities, and to the reduced eddy current loss arising from the strong surface tension of the ceramic films. (5) It is considered that ceramic coating of a polished silicon steel sheet by such physical techniques as PVD and CVD is suitable for improving the iron loss in silicon steel sheet. © 1992, The Japan Institute of Metals. All rights reserved.