Manufacture and Properties of Sintered Permanent Magnetic Nd-Fe-B

　　Manufacture and Properties of Sintered Permanent Magnetic Nd-Fe-B
　　The key techniques for manufacturing high performance sintered Nd-Fe-B permanent magnet have been studied in the aspects of process, magnetic aligning and microstructure, in order to improve the magnet quality for its competitive ability in international market and technological added value,and develop the application of the rich resource, rear earth, in our country.A nominal Nd29.51Tb0.4Nb0.06FebalB0.98wt% alloy was prepared by strip casting, breaking, pressing and sintering process. The microstructures of rapid casting strips in different neodymium standard state cooling speed or flake thickness were compared and analyzed. The effects of different breaking process on the magnetic particle size were investigated. The orientations of the magnet pressed in both rubber die and steel die were tested. Further more, the effect of sintering temperature on microstructure and magnetic performance was studied.The results show that (1) the grain of strap sample, with average size 3.428μm, obtained in cooling speed of 2.6m/s was more uniform than that in other speeds, based on the experiment conditions. The flake with thickness of 0.35mm～0.40mm has ideal microstructure, that is, the dominant plate crystal was fine and uniform, and the Nd rich phase was distributed evenly between the plate crystals, andα-Fe dendritic precipitation was inhibited. (2) the particle sizes http://www.999magnet.com/products/112-neodymium-standard-state of the magnet milling by hydrogen breaking process is finer than that of milling by mechanical breaking (3) The orientations of the magnet pressed in rubber die is better than in steel die. (4) the grain size of the magnet sintered in 1055℃was uniform and fine, and the average grain size was about 10μm and Nd rich phase was distributed uniformly, which was the proper sintering temperature to manufacture magnet with less rare-earth element content.The permanent magnet prepared by strip casting, hydrogen breaking, rubber die forming and lower temperature sintering has achieved good magnetic properties: Br=1.463T(14.63kGs), Hcj = 997kA/m(12.54kOe), (BH)max = 419kJ/m3(52.6MGsOe), Hk/Hcj=0.956, and the better stability and square degree. The Nd-Fe-B magnet can provide the market requirement, such as the application of nuclear magnetic resonance.