Non-oriented electrical steel with core losses comparable to grain-oriented electrical steel

A 3.2 wt% Si non-oriented electrical steel (NOES) was processed using conventional rolling and annealing routes, i.e. hot rolling, hot band annealing, cold rolling, and final annealing. The evolution of texture during all the thermomechanical processing stages was investigated using electron backscatter diffraction (EBSD) techniques. It was found that the final annealing temperature and holding time had a profound effect on the texture. At higher temperatures and shorter holding times, the desired 1 0 0//ND (normal direction) texture was promoted, while the magnetically unfavorable 1 1 1//ND texture was weakened. The magnetic properties of the steel sheets were measured by Epstein frame method and magnetic Barkhausen noise (MBN) analysis, and it was found that the AC (alternating current) core losses of the NOES annealed at 850 °C for 60 min were comparable to grain-oriented electrical steel (GOES) with the same silicon content and the same sheet thickness, even in the rolling direction (RD). The DC (direct current) core losses and the MBN decreased with increasing grain size, due to the decrease of the pinning sites (grain boundaries). The good magnetic properties of the processed NOES were attributed to a combination of an optimized texture and an appropriate grain size, which was, in turn, the result of proper hot band annealing, fast heating during annealing and a good selection of the annealing temperature and holding time.