PURPOSE: To form a uniform oxide film without deteriorating the magnetic characteristic and to stabilize the powder by granulating a magnetic metal powder consisting essentially of iron, allowing the granulated material to stand at the reaction temp. and oxidizing the material with an oxygen-contg. gas at a specified flow rate in the vapor phase.
CONSTITUTION: An unstable magnetic metal powder consisting essentially of iron obtained by reducing an iron compd. with hydrogen, etc., is oxidized with an oxygen-contg. gas in the vapor phase and stabilized. In this case, the granulated material to be stabilized is allowed to stand at an almost constant reaction temp. of 50-130°C, and a gas contg. 100-2500ppm, preferably 150-2000ppm, of oxygen is supplied at the rate of ≥30Nm3/hr, preferably 40-200Nm3/hr, per kg of the material to oxidize the material in the vapor phase. Consequently, the deterioration in the magnetic characteristic and generation of fine powder are prevented, a uniform oxide film is formed on the grain surface, and a magnetic metal powder which is never ignited and without any variance in the magnetic characteristic, especially saturation magnetization, is obtained.
NAKAMURA HIROYUKI
TAKATANI HITOSHI
