环氧树脂粘度和充磁次数对两步室温压各向异性粘结Nd-Fe-B磁体性能的影响

Effects of Epoxy Resin Viscosity and Magnetizing Frequencyon Properties of Anisotropic Bonded Nd-Fe-B Magnets

采用两步室温压工艺即室温预成型+高温取向成型制备各向异性粘结Nd-Fe-B磁体,研究了环氧树脂粘度和交变磁场充磁次数对磁体性能的影响。环氧树脂在140℃时粘度较小(约150 Pa·s)且具有一个较长的低粘度平台(约200 s),预成型坯体在140℃保温1 min时预热效果最好,制备的粘结磁体具有最高的最大磁能积((BH)_(max))、取向度(DOA)和密度(127 kJ·m^(-3),0.55,5.91 g·cm^(-3))。140℃保温1 min时,粘结磁体(BH)_(max),DOA在交变磁场充磁2次时达到最大值(133 kJ·m^(-3)、0.59);140℃保温6 min时,粘结磁体(BH)_(max),DOA在交变磁场充磁4次时达到最大值(108 kJ·m^(-3)、0.52);密度则随着交变磁场充磁次数的增加逐渐降低。随着保温时间的延长,环氧树脂粘度增大,流动性降低,导致粘结磁体(BH)_(max),DOA和密度降低,可以通过增加交变磁场充磁次数使粉末颗粒向磁场方向转动来提高磁体DOA,进而提高(BH)_(max)。

Anisotropic bonded Nd-Fe-B magnets were prepared by two step compression process,called a cold preforming step and next a warm alignment and densifification step,and the epoxy resin viscosity and magnetizing frequency were investigated to improve the properties of bonded magnets.The epoxy resin exhibits low viscosity (about 150 Pa·s) at 140℃ for 200 s.As the preformed body presents best preheating effect at 140℃ for1 min,the Nd-Fe-B bonded magnet gets the maximum (BH)_(max),DOA and density (127 k J·m^(-3),0.55,5.91g·cm^(-3)).When heated at 140℃ for 1 and 6 min,the maximum (BH)_(max) and DOA of bonded magnets (133k J·cm^(-3),0.59 for 1 min and 108 k J·cm^(-3),0.52 for 6 min) are obtained by applying twice and 4 times alternating magnetic field,respectively,while the density of bonded magnets decreases with the number of times of alternating magnetic field.The increase of epoxy resin viscosity,extension of heating time,reduces the lubricity and fluidity of epoxy resin,which results in the decrease of (BH)_(max),DOA and density in bonded magnets.Therefore,the DOA and (BH)_(max) can be improved by increasing the number of times y of alternating magnetic field to rotate particles in the direction of magnetic field.