| 简介 |
PROBLEM TO BE SOLVED : To increase the density of a sintered body at a low temp. by controlling its thickness to a specified range, allowing it to contain chill crystals of specified grain size in a specified volume ratio in the vicinity of the cooling face, furthermore controlling the volume ratio of the part in which α-Fe of specified grain size to the specified one and composing the balance of granular crystals of specified grain size and columnar crystals of specified size. SOLUTION : By a roll rapid cooling method, an alloy thin strip for the raw material of a permanent magnet having 30 to 1000 μm thickness, contg. chill crystals of <=3 μm grain size by 1 to 30% volume ratio in the vicinity of the cooling face, and in which the volume ratio of the part in which α-Fe of <=3 μm average grain size is precipitated is 1 to 10%, and the balance is composed of granular crystals of 3 to 50 μm grain size and columnar crystals of 3 to 100 μm minor axis and 20 to 600 μm major axis can be obtd. By pulverizing this thin strip, fine powder having a grain size distribution in which the ones of <=3 μm average grain size are contained by 1 to 30 vol.%, and the grain size of the balance is 3 to 10 μm and large in an R rich phase and a B rich phase of the low m.p. can easily be obtd. |
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