Magnetic Properties of Fe-Based Ribbons and Toroidal Cores Prepared by Continuous Joule Heating Under Tensile Stress

Nanocrystallized Fe_73.5Cu₁Nb₃Si _15.5B₇ ribbons with controlled permeability were prepared by using continuous stress-annealing by Joule heating (CSA-JH) method. An optimization of the annealing conditions revealed that a completely developed anisotropy perpendicular to the ribbon axis can be obtained stably in the moving velocity range from 1 to 200 cm/min at the current density of 37.5 A/mm². In particular, the highest velocity of 200 cm/min achieved the significant reduction in effective annealing time. The core made from the above-mentioned ribbon had good ac-magnetic properties such as constant permeability up to 2 MHz and low magnetic loss compared with those for different types of cores with controlled permeability. Consequently, it was clarified that the CSA-JH method is one of effective techniques for production of high performance toroidal cores with controlled permeability