省Co型・焼結アルニコ磁石合金の研究

概要

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An investigation was made of cobalt-saving sintered Alnico magnets by using water-atomized Fe-Ni and Fe-Ni-Cu alloy powders instead of carbonyl Ni powder which was necessary to diffuse in iron powders with Fe-Al alloy powders.(1) Water-atomized Fe-47 Ni powder contained about 0.1% oxygen which was comparatively low. Magnetic properties, by using this alloy powder, became better in shorter sintering time compared with the carbonyl Ni powder.(2) Co addition to this sintered magnet made coercive force (Hc) increase and keep remanence (Br) and sintering density constant. As a result of 6% Co addition, maximum energy product [(BH)max.] was also improved about 20%.(3) An optimum chemical composition of sintered magnet was found to be 27Ni-12Al-4Cu-(3Co)-Fe, when water-atomized Fe-47Ni powder was used. The use of water-atomized Fe-36Ni-5Cu powder instead of it produced in the magnetic properties a little improvement.(4) An optimum sintering temperature and time were 1300°C and more than 3hr respectively in the use of Fe-Ni-(Cu) powder, where higher densification was due to the effect of liquid phase sintering by Fe-50Al (m.p. 1180°C). By applying these sintering conditions, standard magnetic properties were obtained as follows:27Ni-12Al-4Cu-FeBr: 5200G, Hc: 520Oe, (BH)max.: 1.05MGOe27Ni-12Al-4Cu-3Co-FeBr: 5300G, Hc: 600Oe, (BH)max.: 1.20MGOe