The Fabrcation Of Economical Mould Pressing Bonded NdFeB Permanent Magnets

This paper presents comparative systematic research of problems in the preparation of economical mould pressing bonded NdFeB permanent magnets, which include the fabricating of economical rapidly-quenching NdFeB magnetic powder and mould pressing bonded NdFeB permanent magnets; the effect of the NdFeB magnetic powder on the magnetic properties of the magnets and the effect of the cathode electrophoretic coating on the corrosion resistance of the NdFeB magnets.The results shows that the optimum course to produce low cobalt content Nd11(FeCoZr)83B6 powder is: 28m/s quenching, 660℃×40Min crystallization The magnetic properties of the magnets fabricated by the powder are: Br=667.4mT, Hcj=755kA/m, Hcb=443kA/m, (BH)m=75kJ/m3. The ratio of properties to price of the Nd11(FeCoZr)83B6 powder is much higher than that of MQP-B powder.By the compare of seven kinds of hot-curing epoxide resin, we found a kind of mixture cohesion which give attention to both'magnetic properties and compress stress. When compressing, the proper pressure is between 7-11 t/cm2, the keeping time is 60S or so. Mend the method of the compress can improve the density and the magnetic properties of the magnets. The curing of the magnets always in the vacuum circumstance. As far as the mixture cohesion is concerned, the optimized curing temperature and time are 120× and 120Min.Add proper amount of KH550 silane coupling agents and lubricant to the powder can improve the density and the properties of the magnets, the appropriate amount is 1‰-2‰ of the powder, respectively. The granularity arrange can also improve the density and the properties of the magnets. Magnetic select can great improve the properties. Combining press mending with granular arrange and magnetic select, the density and the properties can be improved remarkably.Bonded NdFeB magnets need the protection of the cathode electrophoreticcoating. In order to get proper thickness of the coating, the temperature of the electrophoresis should be controlled between 28℃-30℃; the voltage of the initial stage is 90V, the sediment voltage is between 180-190V; the time of electrophoresis is between 90S-1508. After the electrophoresis, the magnets should be solidified on the low temperature firstly, then solidified in the high temperature. The proper solidified temperature is 170℃, and the time is 20Min. By this course, the magnets will have a coat which thickness is 30um. The magnets will have little increasing weight in the corrosive environment after 96 hours.