The alloy for the rare earth magnet thin the band and alloy fines and cooling suddenly those

摘要

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.