Preparation Of Bonded Ndfeb Magnets, Injection Molding

Powder injection molding technique may not only manufacture the final shape magnet directly but also resolve the processing problem of Nd-Fe-B magnetic materials perfectly. At present, this technique has caught many advanced nation's eyes around the world, so its development and industrialization are very quickly . This paper studies the technology of preparing isotropical Nd-Fe-B magnetic through powder injection molding process. At the same time ,the eventual magnet quality of Nd-Fe-B bonded magnet affected by magnetic powder by milling , filler surface treatment, binder, magnetic powder loading was discussed .Form several groups of experiments ,we get some conclusions .The results show that the particle size of rapidly quenching Nd-Fe-B permanent magnet must been treated to make bonded magnet. Different ball milling craft have significant effects on the particle size and the oxygen content of the powder,and the magnetic properties of polymer-bonded is inflenced directly. The magnetic powder is milled in petroleum aether.ball to powder ratio is 4:1,the time of milling is 2 hours.by this means ,the powder whose average particle size is over 200 um can be milled to powder whose particle size is less than 20 um ,and the oxygen content of powder can be controlled to 0.3%. Bonded magnets are prepared by using commercial EVA , PP ,HDPE, PA 12 . The order of eventual magnet quality of magnets with different bonders is as follows: EVA>HDPE>PP> PA 12 , and the order of mechanic properties of bonded magnet is as follows : PA12>PP>HDPE>EVA, Fuller surface treatments have great influence on the (BH)max of bonded magnet.Magnetic powder treated by silicane can be made to magnet with highest magnetic properties ,the research can show that the best addictive quantity of silicane is 1 % of the weight of powder . SA can improve the mobility of the feedstock,and the best addictive quantity of it is 10% of the weight of binder.the suitable time of mixing is 45 minutes.The paper also studies the effect of powder loading on the properties of magnet .the study shows that the powder loading can improve the magnetic properties of bonded magnet greatly.and the maximum of powder loading is 65%,and with the powder loading ,the bonded magnet can beobtained,whose (BH)max=62kJ/m3, sc=73.5MPa.