Tertiary recrystallization and iron loss of ultra thin silicon steels

Tertiary recrystallized grain-oriented silicon steel sheets with thicknesses from 80 μm to 20 μm were developed. Such ultrathin sheets were produced with appropriate cold rolling and annealing. The magnetic induction B₈ of the sheet was above 1.95 T and the coercive force H_c was below 7 A/m. The AC iron loss of the sheet depended on the sheet thickness and was minimized for a 30-μm-thick sheet having W13/50=0.33 W/kg. This value is about 3/5 of that of the best-grade conventional silicon steel sheet. The loss was reduced further by W13/50=0.17 W/kg when a tensile stress of 4 kg/mm ² was applied to the sheet. This loss is comparable to that of a Fe-Si-B amorphous sheet. Moreover, 5 μm thick grain-oriented sheets can be obtained by applying cold rolling to the tertiary recrystallized sheets with a thickness of 20 μm and then annealing them