Magnetic Properties of Melt-Spun Didymium-Fe-Co-Nb-B System Ribbons and Their Bonded Magnets, and a Trial Manufacture of Vibration Brushless Motors Using These Bonded Magnet Rotor

The melt-spun ribbons of Didymium-Fe-Co-Nb-B system alloys were prepared by single roller liquid rapid-quenching method. The effects of composition, wheel velocity and heat treatment on the magnetic properties were investigated. As the result, Didymium12.5Fe70.5 Co10Nb1B6 ribbons prepared at a wheel velocity of 20.0 m/s were crystallized by heat treatment, and the optimum heat treatment condition was found to be at 625 °C for 5 min, and then the values of (BH)max and HcJ were 126.1 kJ/mc, 1048.8 kA/m, respectively. The value of (BH)max for the isotropic compression molding Didymium12.5Fe70.5CoNb1B6 bonded magnet prepared by using the ribbons annealed at 625 °C for 5 min was 91.0 kJ/mc and the density was 6.3 Mg/mc. Irreversible loss of the bonded magnet was −2.34%(at 125 °C). It was found that the vibration brushless motor using Didymium12.5Fe70.5Co10Nb1B6 bonded magnet rotor was better than that of using MQP-O bonded magnet rotor in the rotating speed stability for low-voltage area and the vibration force.