RECRYSTALLIZATION AND MAGNETIC-PROPERTIES OF PURIFIED 3-PERCENT SILICON STEELS

The effect of impurities on the tertiary recrystallization and magnetic properties of the thin (10 to 100-mu-m) silicon steels was investigated. For purification, the conventional grain oriented silicon steels, which were used as starting materials with a thickness of 0.30 mm were pre-annealed at 1200-degrees-C in a vacuum of 1 x 10(-3) Pa before cold rolling. In sheets without pre-annealing, the tertiary recrystallization was observed after annealing for at least 3 h over 1200-degrees-C in a vacuum. On the other hand, in pre-annealed sheets, the tertiary recrystallization was completed within 10 min at an annealing temperature of 1150-degrees-C in a vacuum. Through recrystallization, B8 increased to 1.95 T. Even in sheets annealed at 1050-degrees-C, the B8 increased with increasing the annealing time, and became 1.95 T after anneals of 2 h. The pre-annealed sheets were also annealed in hydrogen atmosphere. In this case, at annealing temperatures over 1100-degrees-C, the tertiary recrystallization was completed in less than 1 h. Using the purified sheets, silicon steels with B8 over 1.9 T can be obtained by short time and low temperature annealing in either a vacuum or a hydrogen atmosphere.