Classifications

• • B22F1/0014—
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
  • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/12—Metallic powder containing non-metallic particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/10—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of articles with cavities or holes, not otherwise provided for in the preceding subgroups
  • B22F5/106—Tube or ring forms
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/10—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/35—Iron
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2302/00—Metal Compound, non-Metallic compound or non-metal composition of the powder or its coating
  • B22F2302/25—Oxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2302/00—Metal Compound, non-Metallic compound or non-metal composition of the powder or its coating
  • B22F2302/45—Others, including non-metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2303/00—Functional details of metal or compound in the powder or product
  • B22F2303/01—Main component
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2304/00—Physical aspects of the powder
  • B22F2304/10—Micron size particles, i.e. above 1 micrometer up to 500 micrometer

Definitions

• the present invention relates to a mixed powder for powder metallurgy.
• a sintered body with a complex shape such as a net shape or the like can be formed by sintering an iron-based powder.
• a sintered body is used, for example, as a structural component such as an automobile component or the like. With an increasing demand for higher dimensional accuracy of such a component, the dimensional accuracy needs to be improved by further cutting the sintered body.
• cost reduction in a cutting process is also deemed to be important.
• cost can be lessened by extending the lifetime of a cutting tool; however, a sintered body like that described above tends to have low machinability and shorten the lifetime of the cutting tool.
• a mixed powder for powder metallurgy in which an additive that improves machinability and extends the lifetime of the cutting tool is mixed into an iron-based powder.
• an additive that improves machinability for example, a powder of manganese sulfide (MnS), sulfur (S), or the like is used.
• MnS manganese sulfide
• S sulfur
• Such a machinability improving material serves as a lubricant that reduces resistance in cutting or as a starting point for dividing chips, thereby extending the lifetime of the cutting tool.
• the machinability improving material in the mixed powder for powder metallurgy is increased, the machinability of the sintered body to be formed is improved, and thereby the lifetime of the cutting tool is extended.
• the content of the machinability improving material is increased, a problem arises in which a mechanical property such as crushing strength or the like of a sintered material is degraded or a dimensional change rate is changed by sintering, requiring an additional die. Consequently, in general, the content of the machinability improving material in the mixed powder for powder metallurgy is approximately 0.3% by mass to 0.5% by mass.
• Japanese Unexamined Patent Application Publication No. 1997-279204 proposes an iron-based mixed powder for powder metallurgy containing a powder of a CaO-Al 2 O 3 -SiO 2 -based composite oxide at 0.02% by weight to 0.3% by weight.
• use of a composite oxide containing Ca as a main component can reduce degradation of mechanical properties of a sintered body, prevent staining of the sintered body and damage on a sintering furnace, and reduce abrasion of a cutting tool in high-speed cutting.
• an object of the present invention is to provide a mixed powder for powder metallurgy which can form a sintered material having excellent machinability.
• a mixed powder for powder metallurgy contains an iron-based powder as a main component and further contains a powder of at least one sulfide selected from CaS, MnS, and MoS 2 ; and a powder wherein a percentage content of magnesium oxide is greater than or equal to 0.005% by mass and less than or equal to 0.025% by mass, wherein the magnesium oxide has an average particle size D50 of greater than or equal to 0.5 ⁇ m and less than or equal to 5.0 ⁇ m.
• the sulfide serves as a lubricant and generates an oxide which causes a magnesium oxide particle having a relatively small particle size to attach to a surface of a cutting tool, thereby reducing wear of the cutting tool by a hard oxide or the like in a sintered body. Accordingly, a sintered material formed by sintering the mixed powder for powder metallurgy has excellent machinability and enables the cutting tool to have a relatively long lifetime.
• a total content of the sulfide is preferably greater than or equal to 0.04% by mass and less than or equal to 0.20% by mass. This configuration can reduce degradation of mechanical properties and the like of the sintered material formed by sintering the mixed powder for powder metallurgy.
• “Iron-based powder” as referred to herein means a pure iron powder, an iron alloy powder, or a mixed powder thereof, “to contain as a main component” as referred to herein means that a content is greater than or equal to 90% by mass.
• “Average particle size D50” as referred to herein means a particle size at which an accumulated volume in a particle size distribution measured by a laser diffraction scattering method reaches 50%.
• the mixed powder for powder metallurgy of the present invention can form a sintered material having excellent machinability.
• a mixed powder for powder metallurgy contains an iron-based powder as a main component and further contains a powder of a sulfide and a powder of magnesium oxide (MgO). Furthermore, the mixed powder for powder metallurgy may further contain, for example, a copper powder, a graphite powder, a powder lubricant, or the like.
• the iron-based powder which is the main component of the mixed powder for powder metallurgy, is not particularly limited; for example, a reduced iron-based powder, an atomized iron-based powder, an electrolytic iron-based powder, or the like can be used.
• the iron-based powder is not limited to a pure iron powder; for example, a steel powder obtained by pre-alloying alloy elements (a pre-alloyed steel powder), a steel powder obtained by partially alloying alloy elements (a partially alloyed steel powder), or the like can be used, or a mixture of a plurality of kinds thereof may also be used.
• the alloy elements for example, known elements that improve properties of a sintered body, such as copper, nickel, chromium, molybdenum, sulfur, and the like, can be contained.
• the iron-based powder only needs to be of such a size as to be used as a main raw material powder for powder metallurgy, and the average particle size D50 of the iron-based powder is not particularly limited; for example, the average particle size D50 can be greater than or equal to 40 ⁇ m and less than or equal to 120 ⁇ m.
• the sulfide In the sintered body obtained by sintering the mixed powder for powder metallurgy, the sulfide remains in a form of original particles. Since the sulfide is softer than an iron base, which is a main component of the sintered body, machinability of the sintered body is improved; in addition, the sulfide has lubricity and reduces abrasion in cutting, thereby extending the lifetime of a cutting tool.
• the sulfide in the sintered body is desulfurized by heat generated in the cutting, generating an oxide. It is conceivable that the oxide attaches to a surface of the cutting tool and forms a film that protects the cutting tool, and in addition, the oxide serves as a binder that causes the magnesium oxide, which is very hard, to attach to the surface of the cutting tool.
• At least one of CaS, MnS, and MoS 2 is used.
• the lower limit of a total content of the sulfide is preferably 0.04% by mass, and more preferably 0.06% by mass.
• the upper limit of the total content of the sulfide is preferably 0.20% by mass, and more preferably 0.18% by mass. In a case in which the total content of the sulfide is less than the lower limit, machinability may fail to be sufficiently improved. Conversely, in a case in which the total content of the sulfide is greater than the upper limit, mechanical properties of the sintered body obtained by sintering the mixed powder for powder metallurgy may be degraded.
• the lower limit of an average particle size D50 of the sulfide such as CaS, MnS, or the like is preferably 1.0 ⁇ m, and more preferably 1.5 ⁇ m.
• the upper limit of the average particle size D50 of the sulfide is preferably 10 ⁇ m, and more preferably 8 ⁇ m.
• the average particle size D50 of the sulfide is less than the lower limit, it may be difficult to uniformly disperse the sulfide in the mixed powder for powder metallurgy, and/or the mixed powder for powder metallurgy may become unduly expensive.
• the average particle size D50 of the sulfide is greater than the upper limit, machinability of the sintered body obtained by sintering the mixed powder for powder metallurgy may fail to be sufficiently improved.
• Magnesium oxide is a chemically stable, hard material. For this reason, a powder of the magnesium oxide exists as micro particles even in the sintered body obtained by sintering the mixed powder for powder metallurgy. The micro particles of the magnesium oxide are attached to the surface of the cutting tool by the oxide attributed to the sulfide, thereby protecting the cutting tool and improving machinability of the sintered body.
• the lower limit of a content of the magnesium oxide is 0.005% by mass, and preferably 0.010% by mass.
• the upper limit of the content of the magnesium oxide is 0.025% by mass, and preferably 0.020% by mass.
• wear of the cutting tool may fail to be reduced.
• the dimensional change rate in sintering may increase, or mechanical properties such as crushing strength and the like of the sintered body may be insufficient.
• the lower limit of an average particle size D50 of the magnesium oxide is 0.5 ⁇ m, and preferably 0.7 ⁇ m.
• the upper limit of the average particle size D50 of the magnesium oxide is 5.0 ⁇ m, and preferably 3.0 ⁇ m.
• the average particle size D50 of the magnesium oxide is less than the lower limit, an aggregate of the MgO is formed, and it may become more difficult to uniformly disperse the magnesium oxide in the mixed powder for powder metallurgy.
• a weight ratio is constant, the number of MgO particles becomes large, and the MgO existing at a boundary between iron powder particles increases, thereby inhibiting sintering.
• the dimensional change rate may increase or mechanical properties such as crushing strength and the like may be insufficient.
• the average particle size D50 of the magnesium oxide is greater than the upper limit, sintering may be inhibited, causing a decrease in strength, the cutting tool may be chipped and wear thereof may be accelerated, the magnesium oxide particles may fail to be attached to the cutting tool, shortening the lifetime of the cutting tool, and/or processing accuracy may be decreased.
• the magnesium oxide having a sufficiently small particle size can attach to the surface of the cutting tool, extending the lifetime thereof, without causing damage that accelerates wear of the cutting tool.
• the copper powder serves as a binder that bonds particles of the iron-based powder to one another, thereby improving the strength of the sintered body obtained by sintering the mixed powder for powder metallurgy.
• the copper powder can be selected from a wide range of copper powders that are used for powder metallurgy; for example, an electrolytic copper powder, an atomized copper powder, or the like can be used.
• the copper powder may be simply mixed into the iron-based powder, may be attached to a surface of the iron-based powder by use of a binder, or may be mixed into the iron-based powder and subjected to heat treatment to be attached to the surface of the iron-based powder in a dispersed manner.
• the lower limit of a content of the copper powder depends on strength and hardness required for the sintered body, and is preferably 0.8% by mass, and more preferably 1.0% by mass.
• the upper limit of the content of the copper powder is preferably 5.0% by mass, more preferably 3.0% by mass, and particularly preferably 2.0% by mass. In a case in which the content of the copper powder is less than the lower limit, an effect of improving the strength of the sintered body may be insufficient. Conversely, in a case in which the content of the copper powder is greater than the upper limit, carbon diffusion may be inhibited and the strength of the sintered body may be insufficient.
• the lower limit of an average particle size D50 of the copper powder is preferably 5 ⁇ m, and more preferably 10 ⁇ m.
• the upper limit of the average particle size D50 of the copper powder is preferably 50 ⁇ m, and more preferably 40 ⁇ m.
• the average particle size D50 of the copper powder is less than the lower limit, it may be difficult to uniformly disperse the copper powder in the mixed powder for powder metallurgy, and/or the mixed powder for powder metallurgy may become unduly expensive.
• the average particle size D50 of the copper powder is greater than the upper limit, the strength of the sintered body obtained by sintering the mixed powder for powder metallurgy may fail to be sufficiently improved.
• the graphite powder forms a hard pearlite phase by reacting with iron in sintering of the mixed powder for powder metallurgy, thereby increasing the strength of the sintered body to be obtained.
• the graphite powder for example, a natural graphite powder, an artificial graphite powder, or the like can be used.
• the graphite powder may be simply mixed into the iron-based powder or may be attached to the surface of the iron-based powder by use of a binder.
• the lower limit of a content of the graphite powder is preferably 0.2% by mass, and more preferably 0.5% by mass.
• the upper limit of the content of the graphite powder is preferably 1.5% by mass, and more preferably 1.0% by mass. In a case in which the content of the graphite powder is less than the lower limit, the effect of improving the strength of the sintered body may be insufficient. Conversely, in a case in which the content of the graphite powder is greater than the upper limit, toughness of the sintered body may be insufficient.
• the lower limit of an average particle size D50 of the graphite powder is preferably 1 ⁇ m, and more preferably 3 ⁇ m.
• the upper limit of the average particle size D50 of the graphite powder is preferably 30 ⁇ m, and more preferably 20 ⁇ m. In a case in which the average particle size D50 of the graphite powder is less than the lower limit, it may be difficult to uniformly disperse the graphite powder in the mixed powder for powder metallurgy, or the mixed powder for powder metallurgy may become unduly expensive.
• the average particle size D50 of the graphite powder is greater than the upper limit, segregation may occur in the sintered body obtained by sintering the mixed powder for powder metallurgy, and the strength of the sintered body may fail to be sufficiently improved.
• the powder lubricant reduces friction between particles when the mixed powder for powder metallurgy is compacted, thereby improving formability thereof and extending die lifetime. In sintering, the powder lubricant is eliminated through evaporation or thermal decomposition.
• the powder lubricant for example, a powder of a metal soap such as zinc stearate, of a non-metallic soap such as ethylene bis-amide, or of the like is used.
• the lower limit of a content of the powder lubricant is preferably 0.2% by mass, and more preferably 0.5% by mass.
• the upper limit of the content of the powder lubricant is preferably 1.5% by mass, and more preferably 1.0% by mass.
• the content of the powder lubricant is less than the lower limit, formability of a compact of the mixed powder for powder metallurgy may be insufficient.
• density of the sintered body obtained by sintering the mixed powder for powder metallurgy, which has been compacted may be decreased and the strength of the sintered body may be insufficient.
• the lower limit of an average particle size D50 of the powder lubricant is preferably 3 ⁇ m, and more preferably 5 ⁇ m.
• the upper limit of the average particle size D50 of the powder lubricant is preferably 50 ⁇ m, and more preferably 30 ⁇ m.
• the average particle size D50 of the powder lubricant is less than the lower limit, it may be difficult to uniformly disperse the powder lubricant in the mixed powder for powder metallurgy, and/or the mixed powder for powder metallurgy may become unduly expensive.
• the average particle size D50 of the powder lubricant is greater than the upper limit, the strength of the sintered body obtained by sintering the mixed powder for powder metallurgy may fail to be sufficiently improved.
• the sulfide serves as a lubricant and generates an oxide which makes a magnesium oxide particle having a small particle size attach to the surface of the cutting tool, thereby reducing wear of the cutting tool by a hard oxide or the like in the sintered body. Consequently, the sintered material formed by sintering the mixed powder for powder metallurgy has excellent machinability and enables the cutting tool to have a relatively lifetime.
• CaS or MnS calcium sulfide (“CaS” in the table) having an average particle size D50 of 4.9 ⁇ m, which was obtained by reducing calcium sulfate (CaSO 4 ) having an average particle size D50 of 2.4 ⁇ m in an atmosphere of a reducing gas such as hydrogen or the like, or manganese sulfide (“MnS” in the table) having an average particle size D50 of 4.9 ⁇ m was used.
• magnesium oxide magnesium oxide having an average particle size D50 of 0.7 ⁇ m, magnesium oxide having an average particle size D50 of 2.5 ⁇ m, or magnesium oxide having an average particle size D50 with 3.2 ⁇ m was used.
• the powder lubricant an ethylene bis-amide-based wax having an average particle size D50 of 27 ⁇ m was used.
• the mixed powders for powder metallurgy Nos. 1 to 15 were each compacted in a die, whereby ring-shaped compacts each having an outer diameter of 64 mm, an inner diameter of 24 mm, and a height of 20 mm were formed. It is to be noted that conditions for compacting were set so that each compact had a density of 7.00 g/cm 3 .
• the compacts obtained were sintered in a nitrogen gas atmosphere containing a hydrogen gas at 10% by volume at a temperature of 1,120° C. for 60 minutes, whereby sintered bodies were obtained.
• flank wear width Vb flank face of the cutting tool after the turning test was measured.
• a drilling test was performed on the sintered bodies formed from the mixed powders for powder metallurgy Nos. 1, 5, 8, 13, 14, and 15.
• a drill “AD-4D,” a coated carbide drill (available from OSG Corporation) having a diameter of 3.8 mm, was used. Processing conditions were as follows: a peripheral velocity of the drill was 2 m/min (4,358 rpm), a feed rate was 450 mm/min (0.103 mm/rev), and “Yushiroken EC50,” a water-soluble fluid (available from YUSHIRO CHEMICAL INDUSTRY CO.,LTD.), was poured as a cutting oil onto the sintered bodies during cutting. To ensure a cutting distance, 180 non-through holes were formed with depths of 10 mm.
• the iron-based powder, the copper powder, the graphite powder, the magnesium oxide, and the powder lubricant were of the same types and proportions those used for the mixed powders for powder metallurgy Nos. 1 to 15.
• the machinability improving material manganese sulfide of the same type and proportion to that in the mixed powders for powder metallurgy Nos. 1 to 15, sulfur (“S” in the table) having an average particle size D50 of 46.1 ⁇ m, and iron sulfide (“FeS” in the table) having an average particle size D50 of 13.5 ⁇ m, the sulfur and the iron sulfide having passed a 100-mesh wire screen, were used.
• the mixed powders for powder metallurgy Nos. 16 to 32 were each compacted in a die in a manner similar to that of the mixed powders for powder metallurgy Nos. 1 to 15, whereby ring-shaped compacts were formed; the compacts obtained were sintered in a nitrogen gas atmosphere containing a hydrogen gas at 10% by volume at a temperature of 1,130° C. for 60 minutes, whereby sintered bodies were obtained.
• flank wear width Vb flank face of the cutting tool after the turning test was measured.
• the iron-based powder, the copper powder, the graphite powder, the magnesium oxide, and the powder lubricant were of the same types and proportions to those used for the mixed powders for powder metallurgy Nos. 1 to 15.
• the machinability improving material manganese sulfide of the same type and proportion to that in the mixed powders for powder metallurgy Nos. 1 to 15 and molybdenum disulfide (“MoS 2 ” in the table) having an average particle size D50 of 5.0 ⁇ m were used.
• the mixed powders for powder metallurgy Nos. 33 to 39 were each compacted in a die in a manner similar to that of the mixed powders for powder metallurgy Nos. 16 to 32, whereby ring-shaped compacts were formed; the compacts obtained were sintered under conditions similar to those of Nos. 16 to 32, whereby sintered bodies were obtained.
• the mixed powder for powder metallurgy according to the present invention is suitably used for producing a high-precision component which requires cutting after sintering.

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• 2018
  • 2018-10-30 JP JP2018203514A patent/JP6929259B2/ja active Active
  • 2018-12-17 BR BR112020014533A patent/BR112020014533B8/pt active IP Right Grant
  • 2018-12-17 EP EP18902349.2A patent/EP3744441A4/en active Pending
  • 2018-12-17 US US16/963,652 patent/US20210060640A1/en not_active Abandoned
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