| The 2:17 type sintered SmCo permanent magnetic powders with high properties were prepared by adjusting the parameters of ball milling. The processing and the main properties of the sintered Sm2Co17 hard magnets made by powder injection molding were first studied systematically. A large amount of experimental and theoretical analyses were conducted by optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), X-ray diffraction analysis (XRD), thermo gravimetric analysis (TGA) and differential thermal analysis (DTA).The effects of the milling time, the charge ratio, the arrangement of balls with different diameters and the liquid medium on the properties of ultima powders had been investigated. The results of experiments showed that the powders with lower oxygen can be obtained in shorter milling time by increasing the charge ratio properly, using balls with different diameters and adding proper liquid medium. When the bulk of balls was about 45% of the whole and the charge ratio was 30:1, in which φ 10: φ 8: φ6:4φ4=0.175:0.35:0.3:0.175(wt), the powders with best properties were obtained by the protection of gasoline after 3h milling. The average granularity was 4.25 m, and the content of oxygen was 0.27wt%. At the same time, the Br was 0.696T, iHc was 136.29IkA/m and (BH)m was 24.292kJ/m3.The injection molding and debinding processing of two kinds of wax-based mult-polymeric system feeding were studied. The optimum powder loading capacity of feedstock Sm2Coi7 was 50~55Vol%. The debinding effect of 79%PW+20%HDPE +1%SA binder system was better. The process of solvent + thermal debinding was studied in order to decrease the content of carbon and lessen contamination, and the route was: firstly debinded in 60℃ for 8h, subsequently heated at the rate of 8℃/min to300℃, and then heated at the rate of 4℃/min to 500℃ and keep for 90mins, in the end heated at rate of 8℃/minto 700℃ and keep for 60mins.The influence of sintered temperature and the initial density on the densification was also investigated. The result showed that the density increased rapidly with rising temperature from 1200-1280℃. On the other hand, the ultimate density increased with the initial density at the same sintered temperature and keeping time. The properties of sintered Sm2Con magnets made by injection molding was the Br of 0.714T, iHcof 1083.0kA/m and (BH)mof 76.5kJ/m3, lower than dry compaction due toAbstractthe lower density and higher content of oxygen. The effect of the content of oxygen and the density of magnets was analysed. On the basis of it, the conclusions were pointed out that in order to get high performance magnets by PIM, it is necessary to increase the powder loading of feeding to obtain the pre-sintering body with higher initial density, at the same time, it is an effective way to enhance the (BH)m of magnets by decrease the oxygen content in magnets by means of choosing the binder components and relevant debinding process properly to reduce the temperature of mixing, shorten the debinding period and decrease oxidation. |
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