| 摘要 |
PURPOSE:To prepare a highly compressible alloyed steel powder, by heating an alloyed steel powder in a reductive atmosphere containing hydrogen to perform decarburization reduction thereof while gradually cooling the treated powder through a temp. range in the vicinity of a transformation point. CONSTITUTION:An alloyed steel powder containing one or more of alloying elements is subjected to decarburization reduction by heating the same at 900 deg.C or more for 10min or more in a reductive atmosphere containing hydrogen to adjust its C-content to 0.03wt% or less and its O-content to 0.15wt% or less. Subsequently, the treated alloy is gradually cooled to 600 deg.C at a cooling speed of 30 deg.C/min or less or, after the aforementioned decarburization reduction, if necessary, said treated powder may be cooled to a room temp. at once and subsequently heated to about 800-600 deg.C to be held for about 10min or more in a hydrogen-containing atmosphere. By this method, an alloyed steel powder of which the green compact density is approx, 6.9g/cm<2> under molding pressure of about 5T/cm<2> can be prepared.
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