Effects of surface treatments on the hysteresis losses of GO iron silicon steel

Surface defects were produced onto commercial grain oriented iron silicon steel coated with forsterite by laser scribing and by chemical etching. Laser intensity was varied from 1 to 10 kW/cm2 and also the defect raster was varied. Dynamic hysteresis loops of unscribed and scribed electrical steel sheets have been measured in the range of 0.05-500 Hz using Epstein frames and a computer-controlled hysteresis recorder. From dynamic hysteresis loops the dynamic and static power losses were separated. In addition to the well-known reduction of dynamical losses also a reduction of the static hysteresis losses up to 5% due to the surface treatment was found when low laser intensities were used. It is assumed that this is due to a higher mobility of new 180° domain walls created by the surface treatment. The higher number of mobile Bloch walls in the electrical steel sheets lead to the reduction of static losses, too.