PURPOSE: To prepare the titled powder having a small carbide particle size and proper oxygen content, by applying annealing reduction treatment to a high carbon alloyed steel powder formed by a water spray method under a specific condition in a vacuum, an inert gas or a reductive gas atmosphere.
CONSTITUTION: Annealing reduction treatment is applied to a high carbon alloied steel powder formed by a water spray method under a condition for holding said powder under heating at a predetermined temp. within a temp. range of 650W 850°C for a predetermined time in a vacuum, an inert gas or a reductive gas atmosphere. By this treatment, because the average particle size of precipitated carbide becomes 0.3μm or less, contents of carbon and alloyed components in the substrate are held under a high state and, as the result, an over-saturated austenite state prior to annealing reduction is held. In addition, reductive reaction is not perfectly advanced because of low temp. annealing reduction while oxygen content is held to 0.1W0.5wt% and excellent sintering property is shown.
NOUDA FUMIO
SATOU ROKUROU
