Recrystallization Behavior of Non-oriented Electrical Steel Sheets after Skew Cold Rolling

Stress-relief annealing is an indispensable processing step for non-oriented electrical steel (NOES) sheets to achieve optimal magnetic properties. The annealing microstructure and texture are not only dependent on the annealing conditions, but also on the prior thermomechanical processing history. To investigate the effect of deformation mode on the recrystallization behavior, a NOES containing 0.9 wt% Si was cold rolled by skew rolling in which the hot-rolled-and-annealed plate was fed at 45° into the rolls to change both the initial texture and the deformation mode. The skew-cold-rolled sheets and those rolled by conventional and cross rolling were then annealed at different temperatures (650 to 1050 °C) for different times (0.5 to 30 min). The recrystallization behavior was characterized using electron backscatter diffraction (EBSD) techniques. It was found that the cold rolling deformation mode and the initial texture have a significant effect on the recrystallization behavior. The recrystallization rates of the skew- and cross- rolled sheets are higher than that of conventionally rolled steel if the annealing temperature is low (650 °C) or the annealing time is short (0.5 min). When the annealing temperature is relatively high (850 °C) and the annealing time is relatively long (2 min), the difference in recrystallization rate is small. In all the cases, skew rolling promotes the formation of the desired <001>//ND (normal direction) texture, and the unfavorable <111>//ND texture is essentially eliminated.