Method of making iron base magnetic material alloy powder

A method of preparing an iron based nanocrystalline alloy powder for a nanocrystalline permanent magnet, comprising the steps of:

• cooling a melt of an Fe—B—R alloy by a quenching process to obtain a solidified alloy having an R2Fe14B crystalline phase wherein R is at least one rare earth element with a thickness of 80 μm through 300 μm;
• annealing and crystallizing the rapidly solidified alloy to impart permanent magnet properties to the alloy, said annealed alloy comprising, as constituent phases, Fe, and Fe—B alloy, and a compound with an R2Fe14B crystal structure, wherein the mean crystal grain size of the constituent phases is 100 nm or less;
• and
• pulverizing the alloy using a pin mill to obtain a powder of a mean particle size of 10 μm through 100 μm, wherein the portion of the pin mill that contacts the alloy comprises cemented carbide material,
• wherein the pulverizing step is conducted without causing substantial change between a first particle size distribution for 10 kg of the alloy pulverized and a second particle size distribution for 50 kg of the alloy pulverized.