ULTRA-HIGH MAGNETIC FLUX DENSITY UNIDIRECTIONAL ELECTRICAL SHEET EXCELLENT IN HIGH MAGNETIC FIELD IRON LOSS AND COATING CHARACTERISTICS AND PRODUCTION METHOD THEREFOR

摘要

Unidirectional electrical sheet comprises ferrite and at least 0.01 ppm and less than 1000 ppm of bismuth in terms of mass% present on a primary coating interface. The sheet is produced by subjecting it to preliminary annealing at at least 700[deg]C for 1-20 sec before decarburization annealing and controlling an atmosphere in this temperature region, or controlling a maximum reaching temperature B (degrees C) before a final cold rolling to within a range represented by an expression, -10xIn(A)+1100 = B = 10 x ln(A)+1220, according to bismuth (Bi) content A (ppm) and heating the steel sheet cold-rolled to a final sheet thickness, before being decarburization annealed, to at least 700[deg]C within 10 sec or at a heating rate of at least 100[deg]C/sec, or immediately subjecting it to preliminary annealing at at least 700[deg]C for 1-20 sec before decarburization annealing, or controlling titania (TiO 2) amount B against 100 pts.wt. of magnesia (MgO) and MgO coating amount C (g/m 2>) that are used when applying and drying an anneal separating agent mainly containing MgO to within a range A 0>.>8>less than or equal to B x C less than or equal to 400, according to Bi content A (ppm).