| 摘要 |
PURPOSE:To obtain a high-strength sintered steel excellent in dimensional accuracy in the as-sintered state, by adding a graphite powder and an Ni powder to an alloy-steel powder containing Mn, Cr, and Mo, by compacting the resulting powder mixture, by sintering the resulting green compact in a nonoxidizing atmosphere, and by subjecting the sintered compact to furnace cooling and then to tempering treatment. CONSTITUTION:A graphite powder (0.4-1.0%, by weight) and 2.0-8.0% Ni powder are added to an alloy-steel powder containing 0.5-1.5% Mn, 0.5-1.5% Cr, and 0.1-0.5% Mo. Subsequently, the above alloy-steel powder to which the powders of graphite and Ni are added is compacted to >=7.0g/cm<3> green density, and the resulting green compact is sintered in an N2-gas, NH3 decomposed-gas, or H2-gas atmosphere or under vacuum under the conditions of 1,100-1,300 deg.C and 20-60min. Then, the sintered compact is subjected to furnace cooling at 10-30 deg.C/min cooling rate and to tempering treatment under the conditions, preferably, of 120-150 deg.C and 5-120min so as to be formed into the desired high-purity sintered steel.
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