Effect of stress annealing on loss and magnetostriction in grain-oriented silicon-iron

The power loss and magnetostriction of grain-oriented silicon-iron have been measured before and after annealing under stress. During heat treatment coatings were applied to the samples which were cut at various angles to the rolling direction. Application of coatings in the presence of a tensile stress of about 4 MPa produced the best results, higher tensions tended to cause rapid increases in power loss. High permeability and conventional materials reacted in similar fashions when stress annealed along the rolling direction, but transverse cut samples showed different responses when coated under stress. Aluminium coated samples showed similar trends when stress annealed along the rolling direction In general the results can be explained by the presence of differential contraction tensile stress combined with a locked-in stress caused by the tension anneal. Marginal improvements over the commercial materials were noted.