PURPOSE: To manufacture ferromagnetic metal powder for magnetic recording by a method wherein a water-soluble salt of metal is reacted with alkali peroxoborate to deposit peroxoborate of the metal on the surface of an oxide or hydrated oxide of metal solely or mainly consisting of iron, which is then reduced in reducing gas such as hydrogen gas.
CONSTITUTION: Powder of iron oxide, hydrated iron oxide or either one of them additionally containing other metals such as Ni and Co is dispersed in a solution containing ammonium peroxoborate. Then, a solution of water-soluble salt of Mg, Ca, Sr, BA, Co, Ni, Zn, Zr or Al is added thereto under churning to deposit an insoluble salt or less-soluble salt of the element on the powder surface, thereby producing an uniform coating of that salt. After filtration and drying, the powder is reduced in reducing gas under heating to obtain metal powder. During reduction under heating, sintering between grains of the iron oxide or hydrated iron oxide is effectively prevented so as to provide granular metal powder with high articular powder ratio. Further, due to the stable coating resulted from peroxoborate, it becomes possible to obtain the metal iron powder highly resistant against corrosion.
KIMURA KAZUO
ARAI TADASHI
IGARASHI KEIKO
DAINIPPON INK RIKAGAKU KENKUYS