PURPOSE: To improve magnetic properties, such as iron loss and magnetic flux density, by performing purification annealing after secondary recrystallization annealing in a dry hydrogen atmosphere and then performing holding in an atmosphere with specific dew point.
CONSTITUTION: A slab of silicon-containing steel is rolled and subjected to decarburizing annealing. A separation agent at annealing is applied to the surface of the resulting steel sheet to perform secondary recrystallization annealing. Successively purification annealing is done in a dry hydrogen atmosphere of 1150-1250°C for 30min-20hr, followed by cooling down to 600-900°C. Then holding in this temp. region is done in an atmosphere of 5-50°C dew point for 30min-5hr. After a course of these treatments, insulating tension coating is applied and flattening annealing is done, by which the steel sheet is finished into a product. By this method, the grain-oriented silicon steel sheet excellent in magnetic properties can be obtained.
IWAMOTO KATSUO
NISHIIKE UJIHIRO
