Abstract: In a preliminary molding step 1, a metallic powder mixture 7 obtained by blending an iron-based metal powder 7a with graphite 7b such that the graphite is present in an amount of preferably not less than 0.1% by weight, more preferably not less than 0.3% by weight, is compacted into a preform 8 having a density of not less than 7.3 g/cm3. In a provisional sintering step 2, the preform 8 is provisionally sintered at a predetermined temperature to form a metallic powder-molded body 9 having a structure in which the graphite remains along a grain boundary of the metal powder. In a re-compaction step 3, the metallic powder-molded body 9 is re-compacted into a re-compacted body 10. In a re-sintering step 4, the re-compacted body 10 is re-sintered to obtain a sintered body 11. In a heat treatment step 5, the sintered body 11 is heat-treated to obtain a heat-treated sintered body 11.

Abstract: A high density iron based forged part such as a mechanical part is produced by a method comprising the following steps in the sequence set forth: (a) preparing iron based powder mixture containing iron based metal powder and graphite powder; (b) preliminarily compacting the iron based powder mixture to form a preliminary compact; (c) sintering the preliminary compact in a non-oxidizing atmosphere whose nitrogen partial pressure is 30 kPa or less, at a temperature of 950° C. or more and of 1300° C. or less to form a forming material; and (d) forging the forming material by closed die forging or enclosed die forging to produce a high density forged part.

Abstract: In a preliminary molding step 1, a metallic powder mixture 7 obtained by blending an iron-based metal powder 7a with graphite 7b such that the graphite is present in an amount of preferably not less than 0.1% by weight, more preferably not less than 0.3% by weight, is compacted into a preform 8 having a density of not less than 7.3 g/cm3. In a provisional sintering step 2, the preform 8 is provisionally sintered at a predetermined temperature to form a metallic powder-molded body 9 having a structure in which the graphite remains along a grain boundary of the metal powder. In a re-compaction step 3, the metallic powder-molded body 9 is re-compacted into a re-compacted body 10. In a re-sintering step 4, the re-compacted body 10 is re-sintered to obtain a sintered body 11. In a heat treatment step 5, the sintered body 11 is heat-treated to obtain a heat-treated sintered body 11.

Abstract: In a preliminary molding step 1, a metallic powder mixture 7 obtained by blending an iron-based metal powder 7a with graphite 7b such that the graphite is present in an amount of preferably not less than 0.1% by weight, more preferably not less than 0.3% by weight, is compacted into a preform 8 having a density of not less than 7.3 g/cm3. In a provisional sintering step 2, the preform 8 is provisionally sintered at a predetermined temperature to form a metallic powder-molded body 9 having a structure in which the graphite remains along a grain boundary of the metal powder. In a re-compaction step 3, the metallic powder-molded body 9 is re-compacted into a re-compacted body 10. In a re-sintering step 4, the re-compacted body 10 is re-sintered to obtain a sintered body 11. In a heat treatment step 5, the sintered body 11 is heat-treated to obtain a heat-treated sintered body 11.

Abstract: A process for producing a sintered powder metal body is disclosed. A powdery mixture is prepared by blending a graphite powder in amount of not less than 0.3% by weight with an iron based metal powder. The powdery mixture is compacted into a preform having a density of not less than 7.3 g/cm.sup.3. The preform is sintered at a temperature of 800-1000.degree. C. to form the sintered powder metal body having a predetermined structure. The predetermined structure of the sintered powder metal body includes iron based metal particles and graphite particles retained between the iron based metal particles.