EP3441161A1 - Verfahren zur herstellung eines sinterkörpers und sinterkörper - Google Patents

Verfahren zur herstellung eines sinterkörpers und sinterkörper Download PDF

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Publication number
EP3441161A1
EP3441161A1 EP17779150.6A EP17779150A EP3441161A1 EP 3441161 A1 EP3441161 A1 EP 3441161A1 EP 17779150 A EP17779150 A EP 17779150A EP 3441161 A1 EP3441161 A1 EP 3441161A1
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EP
European Patent Office
Prior art keywords
sintered body
green compact
machining
machined
compact
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP17779150.6A
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English (en)
French (fr)
Other versions
EP3441161A4 (de
EP3441161B1 (de
Inventor
Tomoyuki Ishimine
Tetsuya Hayashi
Terukazu Tokuoka
Toshihiko Kaji
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sumitomo Electric Sintered Alloy Ltd
Sumitomo Electric Industries Ltd
Original Assignee
Sumitomo Electric Sintered Alloy Ltd
Sumitomo Electric Industries Ltd
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Publication of EP3441161A1 publication Critical patent/EP3441161A1/de
Publication of EP3441161A4 publication Critical patent/EP3441161A4/de
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • 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
    • B22F1/06—Metallic powder characterised by the shape of the 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
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • 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
    • B22F5/008—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of engine cylinder parts or of piston parts other than piston rings
    • 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
    • B22F5/06—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of threaded articles, e.g. nuts
    • 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
    • B22F5/08—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs
    • 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
    • B22F5/08—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs
    • B22F5/085—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs with helical contours
    • 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
    • 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
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • B22F2003/026—Mold wall lubrication or article surface lubrication
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/247—Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
    • 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
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • B22F2009/0824—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid with a specific atomising fluid
    • B22F2009/0828—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid with a specific atomising fluid with water
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • B22F3/03—Press-moulding apparatus therefor

Definitions

  • the present invention relates to a method for manufacturing a sintered body and to a sintered body.
  • PTL 1 discloses a metallic member manufacturing method (a sintered body manufacturing method) comprising: calcining a compact prepared by pressure molding of a metal powder; machining the calcined compact; and then subjecting the machined compact to main firing.
  • the calcined compact prepared by calcining the compact has higher mechanical strength than the uncalcined compact, is less likely to chip during machining, and is therefore easily machined.
  • the calcined compact has a lower hardness than the sintered body subjected to the main firing and is therefore easily machined.
  • the green compact is calcined to increase its mechanical strength, and then the calcined compact is machined, so that chipping and cracking are less likely to occur during the machining.
  • the sintered body manufacturing method of the present disclosure comprises:
  • the sintered body of the present disclosure is an iron-based sintered body having an overall average relative density of 93% or more.
  • the green compact is calcined, particles of the metal powder are sintered to some extent.
  • the hardness of the calcined compact is lower than the hardness of the sintered body subjected to the main firing, the calcined compact has a certain hardness. Therefore, the technique in PTL 1 is susceptible to improvement in machinability.
  • the particles of the metal powder are sintered during the calcination, machining chips must be melted in order to reuse the machining chips.
  • One object of the present disclosure is to provide a high-productivity sintered body manufacturing method in which an unsintered green compact can be easily machined.
  • the unsintered green compact can be easily machined, and therefore the sintered body of the present disclosure can be manufactured with high productivity.
  • the green compact is produced by uniaxial pressing using the die.
  • the raw material powder can be molded under application of very high contact pressure. Therefore, a green compact having a high and uniform relative density with no brittle portions present locally can be easily obtained.
  • the green compact obtained by uniaxial pressing is excellent in mechanical strength, and chipping and cracking are less likely to occur during machining. Specifically, since the green compact obtained by uniaxial pressing can be subjected to the machining step without calcination, the sintered body manufacturing method can produce the sintered body with high productivity.
  • the green compact produced has a uniform relative density of 93% or more. Therefore, when the machined compact prepared by machining the green compact is sintered, the change in the dimensions of the machined compact is stabilized. Specifically, the degree of contraction of the machined compact does not vary locally, and the entire machined compact contracts substantially uniformly. This can prevent the actual dimensions of the sintered body from deviating largely from the design dimensions.
  • the relative density is 95% or more.
  • the green compact since the green compact is subjected to the machining step without sintering, machining resistance during the machining step is low. Therefore, the speed of machining can be about 5 to about 10 times faster than that when a solidified metal body is machined, and the life of tools used for the machining can be about 10 to about 100 times longer. Since the machining resistance of the green compact is low, the stiffness of cutting tools and shanks can be low, and long or small-diameter cutting tools and shanks can be used for machining. Since flexibility in selection of cutting tools and shanks is high as described above, fewer constraints are imposed on the design of the shape of the sintered body, i.e., its design flexibility is high. For example, a finely machined sintered body such as a hollowed sintered body can be produced.
  • the machining chips generated during the machining can be reused without melting the chips. This is because, since the green compact is produced by cold pressure molding and is not sintered before machining, the metal powder contained in the machining chips is not altered.
  • the green compact since the green compact is machined before it is sintered, the green compact can be easily machined into a complex helical gear shape.
  • the green compact obtained can have a high density and excellent machinability.
  • the cutting may be performed using at least one working tool such as a milling cutter, a hob, a broach, or a pinion cutter. Since the green compact is excellent in machinability, the cutting can be easily performed with high precision using any of the above working tools.
  • a working tool such as a milling cutter, a hob, a broach, or a pinion cutter. Since the green compact is excellent in machinability, the cutting can be easily performed with high precision using any of the above working tools.
  • the sintered body in this embodiment has an average relative density of 93% or more and is a novel innovative sintered body. Since the average relative density of the sintered body in the embodiment is 93% or more, its mechanical strength compares favorably with that of a machined product prepared from a solidified metal body.
  • the sintered body in this embodiment is manufactured by the sintered body manufacturing method in the preceding embodiment. Therefore, the sintered body can be manufactured with higher productivity than a machined product prepared from a solidified metal body.
  • the average relative density is 95% or more.
  • the sintered helical gear can be used as, for example, a component of a transmission of an automobile.
  • the sintered body according to the embodiment has a mechanical strength that compares favorably with that of a machined product prepared from a solidified metal body. Therefore, the sintered body sufficiently functions as a component of an automobile to which a high load is applied.
  • the teeth of the helical gear are less likely to be damaged during use even when the teeth are inclined 30° or more with respect to the axial line.
  • the angle of the teeth with respect to the axial line increases, the noise generated when the helical gear is engaged with another gear is further reduced.
  • the angle of the teeth with respect to the axial line is 50° or more.
  • the sintered body manufacturing method according to the embodiment comprises the following steps.
  • the metal powder is a main material forming the sintered body, and examples of the metal powder include an iron powder and an iron alloy powder composed mainly of iron.
  • the metal powder used is a pure iron powder or an iron alloy powder.
  • the "iron powder composed mainly of iron” means that the iron alloy contains, as its component, elemental iron in an amount of more than 50% by mass, preferably 80% by mass or more, and more preferably 90% by mass or more.
  • the iron alloy include an alloy containing at least one alloying element selected from Cu, Ni, Sn, Cr, Mo, Mn, and C. The above alloying elements contribute to improvement in the mechanical properties of the iron-based sintered body.
  • the metal powder used may be an iron powder, and a powder of any of the above alloying elements (an alloying powder) may be added to the iron powder.
  • the component of the metal powder in the raw material powder is iron.
  • the iron reacts with the alloying element during sintering in the subsequent sintering step and is thereby alloyed.
  • the content of the metal powder is, for example, 90% by mass or more and is 95% by mass or more.
  • the metal powder used may be produced by, for example, a water atomization method, a gas atomization method, a carbonyl method, or a reduction method.
  • the average particle diameter of the metal powder is, for example, from 20 ⁇ m to 200 ⁇ m inclusive and from 50 ⁇ m to 150 ⁇ m inclusive.
  • the metal powder is easy to handle and is easily pressure-molded in the subsequent molding step (S2).
  • the average particle diameter of the metal powder is 20 ⁇ m or more, the flowability of the raw material powder can be easily ensured.
  • the average particle diameter of the metal powder is 200 ⁇ m or less, a sintered body with a dense structure can be easily obtained.
  • the average particle diameter of the metal powder is the average particle diameter of the particles included in the metal powder and is a particle diameter (D50) at which a cumulative volume in a volumetric particle size distribution measured by a laser diffraction particle size distribution measurement apparatus is 50%.
  • D50 particle diameter
  • the use of the fine-grain metal powder allows the surface roughness of the sintered body to be reduced and its corner edges to be sharpened.
  • a raw material powder prepared by mixing a metal powder and an internal lubricant is generally used to prevent the metal powder from sticking to the die.
  • the raw material powder contains no internal lubricant.
  • the content of the internal lubricant is 0.2% by mass or less based on the total mass of the raw material powder. This is because a reduction in the ratio of the metal powder in the raw material powder is prevented to obtain a green compact with a relative density or 93% or more in the molding step described later.
  • the raw material powder is allowed to contain a small amount of an internal lubricant so long as a green compact with a relative density or 93% or more can be produced in the subsequent molding step.
  • the internal lubricant used can be a metallic soap such as lithium stearate or zinc stearate.
  • an organic binder may be added to the raw material powder.
  • the organic binder include polyethylene, polypropylene, polyolefin, polymethyl methacrylate, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyether, polyvinyl alcohol, vinyl acetate, paraffin, and various waxes.
  • the organic binder may be added as needed or may not be added. When the organic binder is added, the amount of the organic binder added is such that a green compact with a relative density or 93% or more can be produced in the subsequent molding step.
  • a die is used to uniaxial press the raw material powder to thereby produce a green compact.
  • the die used for the uniaxial pressing includes a die block and a pair of punches to be fitted into upper and lower openings of the die block.
  • the raw material powder filled into a cavity of the die block is compressed by the upper and lower punches to thereby produce a green compact.
  • the green compact that can be formed using this die has a simple shape. Examples of the simple shape include a circular columnar shape, a circular tubular shape, a prismatic columnar shape, and a prismatic tubular shape.
  • a punch having a projection or recess on its punching surface may be used. In this case, a recess or projection corresponding to the projection or recess of the punch is formed in the green compact having the simple shape.
  • the green compact having the simple shape is intended to include such a green compact having a recess or projection.
  • the pressure (contact pressure) during the uniaxial pressing may be 600 MPa or higher. By increasing the contact pressure, the relative density of the green compact can be increased.
  • the contact pressure is preferably 1,000 MPa or higher.
  • the contact pressure is more preferably 1,500 MPa or higher.
  • the upper limit of the contact pressure is not particularly specified.
  • an external lubricant used may be a metallic soap such as lithium stearate or zinc stearate.
  • the external lubricant used may be a fatty acid amide such as lauric acid amide, stearic acid amide, or palmitic acid amide or a higher fatty acid amide such as ethylene bis-stearic acid amide.
  • the overall average relative density of the green compact obtained by uniaxial pressing is 93% or more.
  • the overall average relative density of the green compact is preferably 95% or more, more preferably 96% or more, and still more preferably 97% or more.
  • the overall average relative density of the green compact can be determined as follows. Cross sections of the green compact that intersect the direction of a pressing axis (preferably cross sections perpendicular to the pressing axis direction) are taken at a position near the center in the pressing axis direction, a position near one end, and a position near the other end. Then the cross sections are subjected to image analysis. More specifically, first, images of a plurality of viewing fields are captured in each cross section.
  • the images of the viewing fields are captured in each cross section from positions distributed uniformly as much as possible.
  • the captured image of each viewing field is subjected to binarization processing to determine the ratio of the area of the metal particles in the viewing field, and the ratio of the area is regarded as the relative density in the viewing field.
  • the relative densities determined in the viewing fields are averaged to compute the overall average relative density of the green compact.
  • the position near one end (the other end) is, for example, a position within 3 mm from a surface of the green compact.
  • the green compact is machined without sintering.
  • the machining is typically cutting, and a cutting tool is used to machine the green compact into a prescribed shape.
  • Examples of the cutting include milling and lathe turning.
  • Examples of the milling include drilling.
  • Examples of the cutting tool used for drilling include a drill and a reamer, and examples of the cutting tool used for milling include a milling cutter and an end mill.
  • Examples of the cutting tool used for lathe turning include a turning tool and an indexable cutting insert.
  • the cutting may be performed using a hob, a broach, a pinion cutter, etc.
  • a machining center that can automatically perform a plurality of types of processing may be used for machining.
  • FIG. 1 An upper illustration in Fig. 1 schematically shows how a green compact 200 is machined with a cutting tool 100, and a lower illustration schematically shows how a solidified metal body 300 is machined with the cutting tool 100.
  • the green compact 200 formed by packing metal particles 202 under pressure, the green compact 200 is machined such that the metal particles 202 are torn off the surface of the green compact 200 by the cutting tool 100. Therefore, machining chips 201 generated as a result of machining are composed of metal powder of metal particles 202 separated from the green compact 200.
  • the powdery machining chips 201 can be reused without melting.
  • the clusters may be pulverized as needed.
  • the solidified metal body 300 is machined such that the surface of the solidified metal body 300 is shaved off by the cutting tool 100. Machining chips 301 generated by machining are composed of elongated structures and must be melted for reuse.
  • the surface of the green compact Before the machining, the surface of the green compact may be coated or impregnated with a volatile or plastic solution containing an organic binder dissolved therein in order to prevent chipping and cracking from occurring in the surface layer of the green compact during machining.
  • the green compact may be machined while compressive stress is applied to the green compact in such a direction that the tensile stress acting on the green compact is counteracted to thereby prevent chipping and cracking from occurring in the green compact.
  • compressive stress is applied to the green compact in such a direction that the tensile stress acting on the green compact is counteracted to thereby prevent chipping and cracking from occurring in the green compact.
  • strong tensile stress acts on a portion near an opening of the machined hole from which the broach protrudes when it pierces the green compact.
  • One method for applying the compressive stress that counteracts the tensile stress to a green compact is to stack a plurality of green compacts one on top of another. It is preferable to dispose a dummy green compact, a plate material, etc. below the lowermost green compact.
  • the machined compact obtained by machining the green compact is sintered.
  • a sintered body in which the particles of the metal powder are in contact with each other and bonded together is obtained.
  • well-known conditions suitable for the composition of the metal powder can be used.
  • the sintering temperature is, for example, from 1,100°C to 1,400°C and from 1,200°C to 1,300°C inclusive.
  • the sintering time is, for example, from 15 minutes to 150 minutes inclusive and from 20 to 60 minutes inclusive.
  • the degree of machining in the machining step may be adjusted according to the difference between the actual dimensions of the sintered body and its design dimensions.
  • the machined compact prepared by machining the high-density green compact with a relative density or 93% or more contracts substantially uniformly during sintering. Therefore, by adjusting the degree of machining in the machining step according to the difference between the actual dimensions after sintering and the design dimensions, the actual dimensions of the sintered body can be very close to the design dimensions. This allows time and effort in the subsequent finish machining to be reduced. When a machining center is used for the machining, the degree of machining can be easily adjusted.
  • the surface of the sintered body is, for example, polished.
  • the surface roughness of the sintered body is thereby reduced, and the dimensions of the sintered body are adjusted to the design dimensions.
  • the overall average relative density of the sintered body is approximately the same as the overall average relative density of the unsintered green compact.
  • the overall average relative density of the sintered body is preferably 95% or more, more preferably 96% or more, and still more preferably 97% or more. The larger the average relative density, the higher the strength of the sintered body.
  • the captured image of each viewing field is subjected to binarization processing to determine the ratio of the area of the metal particles in the viewing field, and the ratio of the area is regarded as the relative density in the viewing field. Then the relative densities determined in the viewing fields are averaged to compute the overall average relative density of the green compact.
  • the pressing axis direction of the sintered body can be easily found by observing the deformation state of the metal powder in the cross sections of the sintered body because the sintered body has been uniaxially pressed in its production process.
  • the position near one end (the other end) is, for example, a position within 3 mm from a surface of the green compact.
  • the sintered body manufacturing method in the embodiment and a conventional sintered body manufacturing method were used to produce assemblies 1 shown in Fig. 2 and each including planetary gears 2 and a planetary carrier 3.
  • Each planetary gear 2 is a helical gear having teeth 20 extending obliquely to an axial line as shown in Fig. 3 (see a dash-dot line).
  • the planetary carrier 3 includes a disk-shaped first member 31 and a second member 32 having three bridge portions 32b formed in its disk portion 32s.
  • a raw material powder was prepared by mixing an Fe-2 mass % Ni-0.5 mass % Mo alloy powder with 0.3% by mass of C (graphite) powder.
  • the true density of the raw material powder was about 7.8 g/cm 3 .
  • the raw material powder was pressure-molded by uniaxial pressing to produce the following three types of green compacts.
  • the molding pressure was 1,200 MPa for each of these cases.
  • the overall average relative densities of these three types of green compacts were determined and found to be 93% or more.
  • the green compacts for the planetary gears 2 were machined to form teeth 20 inclined 50° with respect to their axial line.
  • the green compact for the first member 31 was machined to form a boss portion 31b by shaving as shown in Fig. 1 .
  • a hole was formed at the center of the boss portion 31b, and teeth of an internal gear were formed inside the hole.
  • the green compact for the second member 32 was machined to form the bridge portions 32b by shaving. Then, as shown in the lower illustration in Fig.
  • an inner circumferential surface portion (a portion indicated by a black arrow) included in a base portion of each bridge portion 32b and connected to the disk portion 32s was formed into an R shape.
  • the strength of the bridge portions 32b can be improved.
  • the machined compacts were sintered to produce the planetary gears 2 and planetary carrier 3 composed of the sintered bodies. During the sintering, no chipping and cracking occurred in the sintered bodies. Finally, the planetary gears 2 and the planetary carrier 3 were, for example, polished so that their dimensions were closer to the design dimensions and their surface roughness was reduced.
  • the average relative densities of the planetary gears 2 and the planetary carrier 3 in sample A were determined and found to be about 93% or more.
  • the average relative density was converted to an average bulk density, and the average bulk density of each of the planetary gears 2 and the planetary carrier 3 was 7.5 g/cm 3 .
  • the viewing fields captured in the cross sections include portions of the teeth 20 of the planetary gears 2. The relative density of only these portions was determined and found to be 96.2%.
  • the planetary gears 2 and the planetary carrier 3 in sample A had mechanical strength comparable to that of planetary gears and a planetary carrier formed from solidified metal bodies produced by a melting method. It was therefore found that the planetary gears 2 and the planetary carrier 3 in sample A can be sufficiently used for components of automobiles.
  • the same raw material powder as sample A was prepared and subjected to near net shape molding to produce green compacts having a shape close to the shape of the planetary gears 2 and a green compact having a shape close to the shape of the planetary carrier 3. Since the planetary gears 2 are helical gears, a rotary press was used for near net shape molding of the planetary gears 2. With the rotary press, the inclination of the teeth 20 with respect to the axial line cannot be 45° or more. With the rotary press, the available molding pressure was much lower than 600 MPa.
  • the near-net shaped green compacts were sintered and subjected to finish machining to thereby produce planetary gears 2 and a planetary carrier 3 in sample B.
  • the relative densities of viewing fields in cross sections were determined by the same method as that for sample A. The relative densities were different for different viewing fields. Specifically, in the teeth 20 of the planetary gear 2, the average relative density was about 88.5% (average bulk density: 6.9 g/cm 3 ). In portions other than the teeth 20, the average relative density was about 89.7% (average bulk density: 7.0 g/cm 3 ). The overall average relative density of sample B was about 89%.
  • the mechanical strength of the planetary gears 2 and the planetary carrier 3 in sample B was much worse than that of a planetary gear and a planetary carrier formed from solidified metal bodies produced by a melting method.
  • the planetary gears 2 and the planetary carrier 3 in sample B may be unsuitable for components of automobiles.
  • the sintered body manufacturing method in the embodiment can be preferably used to produce a sintered member having a complicated shape that is difficult to produce only by pressure molding using a die.
  • the sintered body manufacturing method in the embodiment can be used to produce, for example, sprockets, rotors, gears, rings, flanges, pulleys, vanes, bearings, etc. used for machines such as automobiles.

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EP17779150.6A 2016-04-07 2017-04-04 Verfahren zur herstellung eines sinterkörpers und sinterkörper Active EP3441161B1 (de)

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JP2016077069A JP6509771B2 (ja) 2016-04-07 2016-04-07 焼結体の製造方法
PCT/JP2017/014145 WO2017175772A1 (ja) 2016-04-07 2017-04-04 焼結体の製造方法、および焼結体

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CN107921535A (zh) 2018-04-17
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US20180236548A1 (en) 2018-08-23
WO2017175772A1 (ja) 2017-10-12
EP3441161A4 (de) 2019-02-13
CN107921535B (zh) 2020-06-30
EP3441161B1 (de) 2024-07-17

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