Tertiary recrystallization was observed after cold-rolling and annealing conventional silicon steels. The magnetic induction Ba at 800A/m of tertiary recrystallized sheets about 75pm thick is as high as 1.97T. Magnetic domain width in these sheets is wider than 1mm, hence the domain refining techniques such as mechanical scratching and chemical etching are employed in order to reduce the iron loss. The iron loss of the sheet mechanically scratched under the application of a tensile stress of 4kg/mm are as follows: W17/S0=0.42W/kg and W13/S0=0.19W/kg. However, this domain refining effect disappears after anneal ing for 30 minutes at 800oe. On the other hand, the domain refining by the chemical etching is ef fecti ve for the iron loss of the sheets even if they are annealed, and the iron loss of the sheet 71pm thick under the application of a tensile stress of 4kg/mm is as follows: W17/50=0.35W/kg and W13/50=0.17W/kg. The iron loss of a chemically etched sheet with thickness of 31pm is as follows: W17/50=0.21W/kg and W13/50=0.13W/kg.
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