Low rare-earth Nd–Fe–B bonded magnets with improved irreversible flux loss

Abstract

The effects of Nb addition on magnetic properties and irreversible flux loss were studied on bonded magnets with compositions of Nd8Fe86−xB6Nbx, where x=0–3. An irreversible flux loss was measured at Pc=2 after exposure at 393 K for 3.6 ks in air. It was found that the Nb addition of 2 at. % or more decreased the irreversible flux loss. The value was less than 5%, similar to that obtained with MQP-B magnets. Br decreased with the increase in Nb content. The effect of Nd content on the magnetic properties and irreversible flux loss was also studied on the bonded magnets with compositions of NdxFe92−xB6Nb2, where x=6–8. The bonded magnet with the optimum composition of Nd6.5Fe85.5B6Nb2 had Br similar to that of MQP-Q magnets that did not contain Nb, and the value of irreversible flux loss was comparable to that of MQP-B magnets. A multipole magnetizability test on the bonded magnets with the above optimum composition was carried out, and the total flux of the bonded magnets was about 10% higher than that of MQP-B magnets for the 23 mm outside diameter magnet with 48 poles.