Fabrication of Fe-based ribbon with controlled permeability by Joule heating under tensile stress

We prepared an Fe-based ribbon with controlled permeability and low magnetic loss by Continuous Stress-Annealing by Joule Heating (CSA-JH) method. The shortest annealing time necessary for the obtaining of the ribbons with completely developed anisotropy was 1 sec, but in order to obtain the sufficiently crystallized ribbons with small saturation magnetostriction it is required to perform annealing longer than 2 sec. A toroidal core was prepared from a long ribbon with controlled permeability and small saturation magnetostriction, and the magnetic loss and relative permeability of the core were evaluated in the frequency range of 0.1 - 3 MHz. The permeability was kept constant up to 2 MHz, and the magnetic loss is lower than that for other types of core with a similar permeability value. These results suggest that the CSA-JH method is a promising method for realizing an Fe-based core with excellent magnetic properties.Proceedings of the 18th International Symposium on Soft Magnetic Material

High Temperature Magnetic Properties of Fe–Cu–Nb–Si–B Cores With Creep-Induced Anisotropy

Fe-Cu-Nb-Si-B ribbons with creep-induced anisotropy fabricated by continuous stress-annealing were formed into toroidal cores. The temperature dependence of their magnetic loss and relative permeability at Bm = 0.1 T was evaluated in the frequency range of 0.5-1 MHz and temperature range from room temperature to 523 K. We found that the cores can be used up to 523 K without magnetic property deterioration. This suggests that the proposed cores have superior high temperature properties compared with conventional gapped-ferrite cores allowing use at high temperature

Magnetic properties of Fe-based toroidal cores prepared by continuous Joule heating under tensile stress.

Fe-based toroidal cores with a permeability value of several hundreds were prepared by the continuous Joule heating method under tensile stress at a high moving velocity of 120 cm/min, corresponding to an effective annealing time of approximately 1.8 s, and their magnetic properties were evaluated. The prepared core showed a constant permeability value up to 2 MHz and a low magnetic loss compared with those for conventional cores with controlled permeability. An investigation of dc-bias properties of the core suggested that the core has constant and good magnetic properties below the dc-bias field of 1 kA/m which is approximately 50% of the anisotropy field. Consequently, the continuous Joule heating under a tensile stress method at high moving velocity enables us to prepare a long annealed ribbon in a short time with simple equipment and improves productivity for the fabrication process of high performance Fe-based toroidal cores with controlled permeability. c2007 American Institute of Physic

Direct evidence for structural origin of stress-induced magnetic anisotropy in Fe?Si?B?Nb?Cu nanocrystalline alloys

The structural origin of magnetic anisotropy in Fe?Si?B?Nb?Cu alloys annealed under a tensile stress of 200 MPa is studied by transmission x-ray diffraction. The diffraction peak of the (310) plane, whose normal vector is parallel to the tensile direction (ribbon direction), appears at a lower angle than the one perpendicular to it by about 0.1°. This indicates that the spacing of the (310) plane normal to the tensile direction is about 0.2% larger than the one parallel to it. This is direct evidence for the structural origin of the stress-induced magnetic anisotropy of nanocrystalline soft magnetic alloys

Origin of the magnetic anisotropy induced by stress annealing in Fe-based nanocrystalline alloy

The dependence of the structural anisotropy of Fe-Si-B-Nb-Cu alloy on the applied stress during annealing has been studied by transmission x-ray diffraction. After crystallizing under stress, the Fe-Si nanocrystals show anisotropy in the lattice spacing of the (620) planes. Their elongations are proportional to the applied stress and show a linear correlation with the magnetic anisotropy energy, Ku. These results indicate that Ku originates from a magnetoelastic effect due to an elastic elongation of the Fe-Si phase constrained by the surrounding amorphous phase

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

Nanocrystallized Fe73.5Cu1Nb3Si15.5B7 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

Magnetic properties of Fe-based ribbons and toroidal cores prepared by continuous stress-annealing by joule heating

INTERMAG 2006 - IEEE International Magnetics Conference; San Diego, CA; 8 May 2006 through 12 May 200

Stress-induced magnetic and structural anisotropy of nanocrystalline Fe-based alloys

The structural anisotropy of Fe-Si-B-Nb-Cu nanocrystalline alloys annealed under tensile stress was studied by x-ray diffraction techniques with transmission geometry. A clear difference was observed in the peak positions of the Fe-Si crystals under two different conditions: with the diffraction vector parallel or perpendicular to the applied stress. The strains calculated from the anisotropy of the peak positions show a linear response to the applied stress, independent of Si content, indicating that the observed structural anisotropy is due to a quenching of the elastic strain, not in the directional ordering of the Fe-Si pair. The induced magnetic anisotropy energy is well explained by the residual strains and their magnetostrictions