Abstract
Nitrided primary specimens containing 0.07% Bi were coated with MgO and annealed in 5%H2–N2 (Box annealing). The magnetic induction (B8) after Box annealing increased with increasing primary recrystallized grain size and decreased with increasing initial nitrogen content. The same primary recrystallized specimens were intermittently annealed in 100% N2 without MgO coating (Model annealing). B8 was measured at each annealing. The onset temperature of the secondary recrystallization (Tcr) was detected by a steep raise of B8. The maximum B8 decreased with increasing Tcr from 1075 to 1100°C. The initial grain size and nitrogen content for the maximum B8 was different in both annealing methods. This difference was explained on the assumption that Tcr mainly determines B8 in both annealing methods.
The direct effect of Bi on the selective growth of sharp Goss orientation was small. Bi worked as an inhibitor for grain growth in the primary recrystallization annealing stage.
