Abstract
Ultra-Rapid Annealing (URA) is an effective means of producing Fe-rich nanocrystalline soft magnetic materials with desirable soft magnetic properties. However, compared to existing annealing techniques, URA presents many unique processing challenges that have so far limited its scalability. In this study, a novel Continuous Ultra-Rapid Annealing (CURA) technique is introduced. This technique is based on a reel-to-reel process and is considered suitable for industrial-scale production. The effectiveness of CURA is evaluated by comparing the microstructural and magnetic properties of a heating-rate-sensitive nanocrystalline (Fe0.8Co0.2)86B14 alloy produced by URA and CURA. It is seen that both techniques produce comparable soft magnetic properties and that the continuous annealing process is stable after a short settling time. A proof-of-concept electric motor containing a CURA prepared nanocrystalline stator core is also demonstrated and compared to an equivalent motor with a Fe-Si steel stator core. It is shown that the CURA production process can be used to produce magnetically soft nanocrystalline materials with complex geometries and that they can deliver increased performance in existing commercial applications.
Highlights
IntroductionIn the three decades since their discovery nanocrystalline soft magnetic materials have become commercially available for use in applications such as current sensing, power filtering and highfrequency transformers. More recently, electric motors using nanocrystalline stator cores have been demonstrated to have a higher efficiency than equivalent motors produced using amorphous or FeSi steel stator cores. if nanocrystalline cored electric motors and other devices are to have both high efficiency and high specific power density there is a need for nanocrystalline materials with a saturation magnetic polarization (Js) equal to, or greater than, that of Fe-Si steels.Ultra-Rapid Annealing (URA) has been demonstrated as a viable means of producing nanocrystalline soft magnetic materials with a Js comparable to that of Fe-Si steels (1.85 to 2.02 T) while maintaining a low coercivity (2.5 to 9.3 A/m). the high heating rates (>104 K/s) and short annealing times (
For the Ultra-Rapid Annealing (URA) and Continuous Ultra-Rapid Annealing (CURA) prepared samples only bcc crystallisation reflection peaks are observed with grain sizes (D) of 22.2 nm and 21.6 nm, respectively
As all other aspects of the motor and its controller were left unchanged this improvement is attributed to the reduced core loss of nanocrystalline (Fe0.8Co0.2)86B14 compared to Fe-Si steel. This simplistic proof of concept electric motor demonstrates that the CURA process can be used for the production of Fe-rich nanocrystalline soft magnetic materials with sufficient quantity and quality that they can be machined into complex geometries and used with existing commercial applications
Summary
In the three decades since their discovery nanocrystalline soft magnetic materials have become commercially available for use in applications such as current sensing, power filtering and highfrequency transformers. More recently, electric motors using nanocrystalline stator cores have been demonstrated to have a higher efficiency than equivalent motors produced using amorphous or FeSi steel stator cores. if nanocrystalline cored electric motors and other devices are to have both high efficiency and high specific power density there is a need for nanocrystalline materials with a saturation magnetic polarization (Js) equal to, or greater than, that of Fe-Si steels.Ultra-Rapid Annealing (URA) has been demonstrated as a viable means of producing nanocrystalline soft magnetic materials with a Js comparable to that of Fe-Si steels (1.85 to 2.02 T) while maintaining a low coercivity (2.5 to 9.3 A/m). the high heating rates (>104 K/s) and short annealing times (
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