Low Temperature Treatment of N. K .S. Permanent Magnet of Al-Ni-Co Type

概要

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To obtain the best characteristics of an Al-Ni-Co type permanent magnet, it has hitherto been heated above 1250℃, which is in the range of the solid solution of the alloy, but recently, the same or even better properties of the alloy have been obtained by heating below 1000℃, that is, by the low temperature treatment. In 1953, the authors have found the following conditions of low temperature treatment with Al-Ni-Co type N.K.S. F-1 permanent magnet : the heating temperature is 875℃, the holding time at 875℃ is 1 hr, the cooling velocity from 875°to 750℃ is about 1℃/sec and the temperature range effective to magnetic cooling is 875°〜800℃. The variations in the optimum temperature in the low temperature treatment were measured with a series of magnet alloys containing various amounts of alloying elements such as Al, Ni, Co, Cu and Ti, and at the same time the Curie points of these magnets were measured. The experiments show that the optimum temperature in the low heat treatment coincides with the Curie point at the standard composition at which the magnet properties are the best. It is assumed that the effect of the low temperature treatment is most conspicuous when the difference between Curie point and the optimum temperature of the low temperature treatment is the smallest.
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