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

Amorphous Fe_73.5Cu₁Nb₃Si_15.5B₇ ribbons that are 2 mm wide and 20 mum thick were prepared by the continuous stress annealing-Joule heating (CSA-JH) method in air under tensile stresses of 50 to 175 MPa. Processing parameters such as the supplied current density and the moving velocity were varied. The ribbons were annealed at various conditions, and the relationship between the developed anisotropy and moving velocity was evaluated. Then, toroidal cores with 20 mm diameters were prepared from 50 cm-long ribbons, and the ac-magnetic properties were confirmed. The core exhibited ultimate low magnetic loss and constant permeability values. These results show that the joint procedure of continuous stress annealing with a furnace and Joule heating is an effective technique for producing high performance toroidal cores with controlled permeability.