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WO2006072162A1 - Méthode d'élaboration de composants métalliques en poudre présentant une surface densifiée - Google Patents

Méthode d'élaboration de composants métalliques en poudre présentant une surface densifiée Download PDF

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Publication number
WO2006072162A1
WO2006072162A1 PCT/CA2005/001970 CA2005001970W WO2006072162A1 WO 2006072162 A1 WO2006072162 A1 WO 2006072162A1 CA 2005001970 W CA2005001970 W CA 2005001970W WO 2006072162 A1 WO2006072162 A1 WO 2006072162A1
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WIPO (PCT)
Prior art keywords
article
density
powder
surface region
blend
Prior art date
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Ceased
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PCT/CA2005/001970
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English (en)
Inventor
Huw David
Peter K. Jones
Roger Lawcock
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Stackpole Ltd
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Stackpole Ltd
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Filing date
Publication date
Application filed by Stackpole Ltd filed Critical Stackpole Ltd
Priority to US11/813,400 priority Critical patent/US20090129964A1/en
Priority to MX2007008208A priority patent/MX2007008208A/es
Priority to EP05823969A priority patent/EP1850989A4/fr
Priority to JP2007549770A priority patent/JP2008527166A/ja
Priority to CA002594364A priority patent/CA2594364A1/fr
Publication of WO2006072162A1 publication Critical patent/WO2006072162A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps
    • B22F3/164—Partial deformation or calibration
    • B22F3/168—Local deformation
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/11—Making amorphous alloys
    • 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
    • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
    • 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
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps
    • B22F3/164—Partial deformation or calibration
    • B22F2003/166—Surface calibration, blasting, burnishing, sizing, coining
    • 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
    • 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

Definitions

  • the present invention relates to methods of manufacturing powder metal components. More specifically, the invention provides a method of densifying the core and surface of a powder metal component to achieve a product having an evenly densified surface.
  • Powder metal (PM) technology is a lower cost alternative for producing components that could be made from wrought metal.
  • the use of PM components is precluded in many applications because of inferior mechanical strength caused by residual porosity. Therefore, in the manufacture of PM articles, the achievement of high density, close to that of wrought steel (generally assumed to be approximately 7.86 g/cc), is of significant importance since the strength and durability of a PM article is directly related to its density.
  • the basic steps involved in the manufacture of a powder metal component are: a) blending the desired metal powders; b) compacting the powder to the desired shape; c) sintering the compact; and d) forming the sintered compact to the desired final shape.
  • the final step is used to impart the required dimensional features of the article. Following the forming step, it is also common to perform a heat treatment on the finished article to impart, where desired, certain mechanical properties as known in the art.
  • the final density of a PM article is dependent on the characteristics of the powders in the blend, sintering conditions, and the compressive forces applied to the article primarily during the compaction and forming steps. It is common in known methods to compact a powder blend to a moderate initial density, approximately 7.0 g/cc, and further densifying the compact during subsequent forming steps. Various compositions of metal powder blends are known in the art as are methods of compaction and sintering. Examples of known blends and methods are taught in U.S. Patent number 5,476,632 (incorporated herein by reference). [0004] For manufacturing articles having a bearing surface and the like, it is known to increase the surface density at the desired locations to provide a densified region that is capable of withstanding the bearing forces.
  • U.S. Patent number 5,540,883 (incorporated herein by reference), teaches a method of densifying a selected surface portion of a sintered article by applying rolling cylinders or the like to create a bearing surface on an article.
  • the bearing surface by virtue of having an increased density is better suited to withstand the physical stresses (i.e. rolling or sliding stresses) applied on that portion of the article.
  • a specific section of the article can be provided with a density that approximates the theoretical maximum value while the rest of the article has a density of approximately 90% to 98% of the theoretical maximum value.
  • the reference is directed to providing bearing surfaces or bushings, which are inherently cylindrical and do not have a complex shape. Moreover, the reference does not teach any alteration of the core density during the cylindrical surface densification step.
  • U.S. patent number 5,884,527 teaches a method of roll forming a sintered gear comprising meshing a sintered pre-form in interference with a rotating roll forming gear die.
  • This method is mainly suited for surface densifying pre-forms of specific geometries, such as gear teeth, that permit the design of a rolling die to impart the necessary combination of line contact and relative motion between the die and pre-form.
  • U.S. Patent number 6,168,754 teaches a method of densifying the contoured surface of a sintered pre-form comprising forcing said article at ambient temperatures through a series of dies having successively more interference contact with the surfaces to be densified.
  • a disadvantage of this method is the need for multiple dies and the inherent complexity and cost.
  • U.S. Patent number 6,013,225 teaches a method of surface densifying a pre-form utilizing a method of selectively heating the surface of said article and forcing it through a die.
  • Inherent disadvantages of this method are the requirement of a separate surface heating step, decreased tool life due to elevated die temperatures and the corresponding detrimental effect on dimensional accuracy.
  • the densification step is typically conducted after the forming step, when the formed article has its final shape and is close to final core density.
  • the known methods are generally incapable of surface densifying contoured surfaces, require unduly complex dies, and/or involve high process costs.
  • published U.S. applicationl 0/767,014 published under number 2004/0177719
  • This reference teaches a process wherein a powder metal is compacted to the final form, sintered and then surface densified prior to sizing or forging.
  • This reference stipulates that for any final surface having a complex or irregular shape, special densification processes are required (such as peening).
  • peening special densification processes
  • the present invention seeks to mitigate at least some of the deficiencies in the prior art powder metal manufacturing methods.
  • the present invention provides a method of producing powder metal components with high core and surface densities and with high precision on contoured forms.
  • the invention provides a method of densifying a sintered powder metal article by first surface densifying a cylindrical surface on a sintered perform and subsequently forming the article to final core density and final shape in a closed die cavity, wherein the formed article has a compressed length of 5 to 30% less than the original sintered length.
  • the invention provides a method of making a sintered metal article comprising: blending one or more lubricants, carbon, alloys, and iron; pressing the blend to form a compact; sintering the compact to produce a sintered powder metal article; densifying the surface of the article at ambient temperature by relative motion between the article and a densification tool; and, forming the article in a closed die cavity having a clearance for movement of said article so as to allow the article to assume a final shape and final density.
  • the invention provides a method of densifying a sintered metal article comprising: blending one or more lubricants, graphite, iron and one or more of ferromanganese, ferromolybedenum and ferrochromium; pressing the blend to form a compact; sintering the compact at a temperature of at least 125O 0 C; surface densifying at least one cylindrical surface of the sintered article by roller burnishing; forming said article at between 600 and 1300 MPa in a closed cavity so as to produce a final part with core a density of 90 to 98% of the theoretical density, a compressed length of 5 to 30% less than the sintered length and contoured densified surfaces.
  • the invention provides a method of making a sintered metal article by blending one or more lubricants, carbon, and iron powder pre-alloyed with Mn, Mo, Cr, Ni, etc; pressing the mixture, or blend, to produce a compact; sintering the compact at a temperature of at least 1100 0 C; surface densifying at least one cylindrical surface of the sintered article by roller burnishing; forming the article to a final core density and shape in a closed die cavity; wherein the formed article has a compressed length of 5 to 30% less than the original sintered length.
  • the invention provides a method of making a sintered metal article by: blending one or more lubricants, carbon, and elemental or substantially pure iron and one or more of Mn, Mo, Ni, Cu, etc in elemental form; pressing the mixture, or blend, to produce a compact; sintering the compact at a temperature of at least 1100 0 C; surface ' densifying at least one cylindrical surface of the sintered article by roller burnishing; and subsequently forming the article to a final core density and shape in a closed die cavity, wherein the formed article has a compressed length of 5 to 30% less than the original sintered length.
  • the invention provides a method of producing overrunning clutches or the like with high core density and densified contact surfaces.
  • the present invention provides a method for producing a powder metal article having a three dimensional shape and having at least one densified surface region, the method comprising: a) providing a blend of powdered metals; b) compacting the blend to form a pre-form having a general shape of the article, the preform being generally cylindrically shaped at a region corresponding to the at least one densified surface region; c) sintering the pre-form; d) densifying the at least one surface region of the pre-form; and, e) forming the pre-form to a desired final density and into a desired three dimensional shape of the article.
  • the present invention provides a method for producing a powder metal article having a three dimensional shape and having at least one densified surface region, the method comprising: a) providing a blend of powdered metals; b) compacting the blend to form a pre-form having a general shape of the article, the pre-form having a density of between 70% to 90% of the theoretical maximum density and being generally cylindrically shaped at a region corresponding to the at least one densified surface region; c) sintering the pre-form; d) densifying the at least one surface region of the pre-form to at least 90% of the theoretical maximum density; and, e) forming the pre-form to a desired final density and into a desired three dimensional shape of the article.
  • the invention provides a powder metal pre-form having a general shape of a desired article, the pre-form having a density of between 70% to 90% of the theoretical maximum density and being generally cylindrically shaped at at least one surface region.
  • Figure 1 is a top view of a die, in an open position, with the top punch removed, loaded with a pre-form.
  • Figure 2 is a cross sectional view of the die of Figure 1.
  • Figure 3 is a top view of a die, in a closed position, with the top punch removed, loaded with a pre-form.
  • Figure 4 is a cross sectional view of the die of Figure 3.
  • Figure 5 is a graph comparing the sub-surface density gradients of a surface densified pre-form and the final C-Mn-Mo one-way clutch outer race formed at 985 MPa.
  • Figure 6 is a graph of the formed core density of a C-Mn-Mo one-way clutch outer race.
  • Figure 7 is a graph of the formed closure of a C-Mn-Mo one-way clutch outer race.
  • Figure 8 is a graph of the formed radial movement of a C-Mn-Mo one-way clutch outer race.
  • Figure 9 is a graph comparing the sub-surface density gradients of a surface densified pre-form and the final formed shape for a C-Mo one-way clutch inner race formed at 925 MPa.
  • Figure 10 is a graph of the formed core density of a C- Mo one-way clutch inner race.
  • Figure 11 is a graph of the formed closure of a C-Mo one-way clutch inner race.
  • Figure 12 is a graph of the formed radial movement of a C-Mo one-way clutch inner race. DETAILED DESCRIPTION OF THE INVENTION
  • Metal powder a metal that is in a fine powder form.
  • the metal may be pure (i.e. iron), pre-alloyed iron (i.e. iron alloyed with other metals such as, but not limited to, one or more of molybdenum, chromium or nickel), or an alloy of one or more metals (i.e. ferro manganese, ferro molydenum or ferro chromium).
  • Powder metal article an article formed from a metal powder.
  • the metal powder is compressed under high pressures in a die or mould having a desired shape.
  • the compressed article may be subjected to other processes such as sintering etc. to achieve desired physical properties.
  • Binder metal blend a blend of one or more metal powders and other additives such as lubricants, carbon (e.g. graphite) etc.
  • Sintering a process wherein a compact is subjected to high temperatures and selected atmospheres (e.g. a reducing atmosphere) to cause the compact to become a coherent mass by heating without melting. Sintering is normally performed on a powder metal compact to impart desired physical properties.
  • selected atmospheres e.g. a reducing atmosphere
  • "Surface densification” or “Selective densification” the step of densifying a select portion of a sintered compact, usually the outer surface or a portion thereof.
  • the densification is preferably conducted by means of rollers and the like as known in the art.
  • various apparatus for densifying surfaces will be apparent to persons skilled in the art after reviewing the following description.
  • the densification step can be conducted on the entire surface of the compact or on one or more cylindrical portions thereof.
  • the term "region” or “densified surface region” will be understood to mean the entire surface or a portion thereof.
  • the densified surface region will typically be densified to a density of between 80% and 100%, and preferably at least 98%, of the theoretical maximum density. Further, the depth of the densified region would be at least 0.025mm (or 0.001 inches) from the surface. In one embodiment, the densified region would extend to a thickness of about lmm ( or 0.04 inches) from the surface.
  • Theoretical maximum density refers to the density of the powder metal compact when processed until no pores exist. In the general case, the theoretical maximum density would be the density of wrought steel, i.e. 7.86 g/cc.
  • Forming a process of providing a sintered compact with its final shape. This step is normally performed in a closed die or mould, wherein the sintered compact is subjected to pressure to result in the final dimensions and density of the final article.
  • the forming step is known by various terms including: sizing, coining, repressing, re-striking and powder forging.
  • the sintered compact may also be heated prior to the forming step in order to improve the malleabilty of the material.
  • Heat treatment a process of treating a formed sintered article wherein the article is subjected to high temperatures, select atmospheres (e.g. protective atmosphere, vacuum, carburizing, etc.), and rapid cooling to obtain desired mechanical properties.
  • Heat treatment methods include, but are not limited to, through-hardening, carburizing and induction hardening which are typically followed with a tempering treatment for optimum properties.
  • the present invention provides a method of surface densifying the contoured surfaces of a sintered powder metal article, such as, for example, the cam forms of a one-way clutch, by first surface densifying a cylindrical surface of a lower density preform and forming the article to final desired shape and density in a closed die cavity.
  • the surface densification step is performed prior to the forming step.
  • the steps of the invention are as follows: a) mixing one or more powder metals to form the desired blend; b) compacting the powder to create a pre-form; c) sintering the pre-form; d) performing a surface densification step on the pre-form; and e) forming the article to the desired shape and core density.
  • the formed article may be further shaped and heat treated.
  • > invention utilizes low alloy steel compositions, where the carbon content is less than 0.7% and preferably below 0.3% by weight of the final sintered article.
  • the powder compositions may comprise low cost iron powders, which are blended with calculated amounts of ferro alloys, graphite and lubricant such that the final desired composition is achieved following sintering and the ⁇ powder blend is suited to compaction in rigid compaction dies.
  • these powder i blends are provided in U.S. Patent No. 5,476,632 (incorporated herein by reference).
  • the use r of substantially pure iron powder admixed with ferro alloys may be preferred as such ! powders are relatively highly compressible and are relatively inexpensive as compared to pre- » alloyed powders.
  • the powder blend of the invention may comprise elemental or substantially I pure iron powder blends, fully pre-alloyed powder blends and partially pre-alloyed powder blends. It will be appreciated that any composition of powder metal blend may be used in the ; present invention.
  • alloys of iron such as ferro i manganese, ferro molydenum and ferro chromium may be used individually, or in ⁇ combination, as required to achieve desired performance requirements of the final article.
  • one, two, or three ferro alloys may be blended with the base iron powder.
  • alloy elements can be used in the process described herein, depending on the P final product performance requirements, including: carbon, chromium, copper, manganese,
  • the base iron powder will generally have a particle size distribution in the range of 10 to 350 ⁇ m. This range includes the base iron powder particle sizes of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, or 350 ⁇ m and any size there-between.
  • the alloying additions typically will have a particle size distribution in the range of 2 to 20 ⁇ m. This range includes the particle size of alloying additions of 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20 ⁇ m and any size there-between.
  • Commercially available lubricant powder is added to the blend to facilitate compaction. Typical lubricants include zinc stearate, stearic acid or ethylene bistearamide. Various particle sizes, lubricants and other additives will be apparent to persons skilled in the art.
  • the present invention may be used with pre-alloyed powder metals, some examples being molybdenum or chromium-molybdenum pre-alloys having between 0 to 1.5% of each alloy with the remainder being unavoidable impurities.
  • sintering can be conducted at temperatures of 1100 0 C to 115O 0 C, or alternatively at higher temperatures greater than 125O 0 C.
  • Typical commercial examples of prealloyed molybdenum powders are Quebec Metal Powder sold under the trademarks QMP AtometTM 4401, and Hoeganaes AncorsteelTM 85HP, both of which have approximately 0.85% by weight molybdenum.
  • the particle size of the pre-alloyed molybdenum powder metal is typically within the range of 45 to 250 ⁇ m. Between 0 to 0.7% carbon by weight may be added. Compacting is facilitated by the addition of the lubricants discussed previously.
  • the compaction step is performed in the known manner using powder formulated as discussed above, whereby the blended powder is pressed in a rigid die at approximately 400 MPa to between 70 and 90% of the theoretical maximum density.
  • Various other pressures and end product densities will be apparent to persons skilled in the art.
  • the shape and dimensions of the resulting compact, or pre-form are substantially similar to the final article with the exception of allowances for size change due subsequent operations.
  • one or more surface regions to be densified are maintained in a cylindrical form. These areas may, in the final article, be later formed into complex, non-cylindrical shapes, as will be discussed further below. As will be made clear in the following description, by maintaining the surface regions to be densified in a cylindrical form, the surface densification of the compact is facilitated.
  • the compacted article, or pre-form is then sintered using methods commonly known in the art.
  • the sintering process may be conducted in a reducing atmosphere or vacuum at a temperature in excess of 125O 0 C such that oxides from both the iron and alloy additions contained in the compact are reduced and metallurgical bonds are formed between contacting particles to impart strength and ductility to the sintered article.
  • the chemical reduction process also allows for uniform diffusion of alloying elements throughout the iron particles resulting in a homogeneous microstructure.
  • an isothermal hold or slow cooling treatment may also be utilised to maximize the ferrite content of said article as described, for example, in U.S. Patent No.
  • the isothermal treatment step serves to improve the malleability of the sintered article.
  • the isothermal treatment step can be included within the cooling phase of the sintering step (i.e. it can form a part of the sintering step) or can be included as a separate step following sintering.
  • sintering may take place at conventional sintering temperatures of 1100° to 115O 0 C or at a higher temperature up to 135O 0 C.
  • no significant densification occurs during the sintering process. As such, the density of the sintered compact will remain substantially the same as that of the compacted pre-form.
  • Densification of the surface is generally performed using a plurality of small diameter rollers in a roller burnishing tool to cold roll the one or more cylindrical surfaces of the sintered compact.
  • a roller burnishing tool for example, to a cylindrical surface, compresses the surface, collapsing the pores contained therein so that the surface of the article has a density approaching the theoretical maximum density.
  • the surface densification step of the present invention is conducted on one or more generally cylindrical surfaces (or surface regions) of the pre-form.
  • the invention allows the use of less expensive (and easier to use) roller apparatus to achieve the desired densification.
  • the invention makes it possible to achieve a uniform densification over the entire area being densified.
  • the use of a roller densification apparatus, in accordance with a preferred embodiment of the invention results in an optimum surface finish and dimensional control, which is not possible with known shot peening methods. This, therefore, offers an important advantage over other processes known in the art.
  • the surface regions being densified are provided with densities of at least 80% and up to 100% of the theoretical maximum density.
  • the densified surface region has an approximate thickness of between 0.025mm to lmm (i.e. 0.001 to 0.04 inches) below the surface.
  • the core density of the preform is not significantly altered during the surface densification step and, therefore, the core of the pre-form remains the same as that resulting from the compaction step.
  • the article may subsequently be annealed, at temperatures between 800° and HOO 0 C in a protective atmosphere or vacuum, for the purpose of developing proper metallurgical bonding, re-crystallizing the densified surface material and obtaining an advantageous micro structure for forming or contact fatigue durability.
  • the surface region being densified by this step may comprise either or both of the inner and outer regions of the pre-formed article. This aspect is described, for example, in U.S. Patent numbers 5,540,883 and 5,972,132 (the entire contents of which are incorporated herein by reference)
  • the selectively densified article is then subjected to a forming operation to achieve the desired final density, shape and dimensional requirements.
  • the forming step is preferably carried out in a closed die and at ambient temperatures, although, if required, elevated temperatures may also be used.
  • the final density is obtained and closely controlled by the movement of the sintered material during forming and the dimensions are controlled by the rigid die set. Such dies are commonly known in the art. Where the final dimensions are not critical to component functionality, complete filling of the die cavity may not be required.
  • the forming operation is alternatively referred to in the art as, inter alia, sizing, coining, repressing, forging or re-striking. These processes will be known to persons skilled in the art.
  • All of the above mentioned processes involve the application of pressure to a sintered compact enclosed within a rigid die cavity.
  • Conventional rigid dies as used in regular sizing/coining/repressing/restriking presses may be used in the present invention to achieve the final surface configuration and higher density of the final article with precise control.
  • Forming is accomplished by the selection of the composition of the sintered article, by the selection of appropriate sintering temperature and furnace profile, by the selection of pressure used in the forming operation, and the selection of the forming tool to provide the necessary clearance between the tools and the sintered article for movement of the sintered compact to the final shape. The required choice of these parameters will be known to persons skilled in the art.
  • the article After forming, the article will have a final core density of between 90% and 98% of the theoretical maximum, and the densified surfaces will have assumed the final configuration with overall radial dimensions of the contoured form, differing by 0.1 to 10% as compared to the diameter of the surface densified region of the pre-form. Further, the final article will normally have a length dimension that is approximately between 5 to 30% less .than the same dimension measured on the sintered and surface densified pre-form.
  • FIG. 1 to 4 illustrate a die having a punch or ram with walls 12 and 14 and an outer die wall 16.
  • the outer wall 16 is stationary while the punch walls 12 and 14 are designed to move towards and away from each other. It will be understood that, in some systems, one of punch walls 12 or 14 may also remain stationary.
  • the combination of these elements (12, 14, and 16) form a die cavity 20 into which a sintered pre-form 22 is inserted.
  • the surface of the pre-form will have a densified layer 23, having a generally cylindrical geometry are described above.
  • the die cavity is of the shape of the desired final product.
  • the pre-form is dimensioned to be smaller than the die cavity, thereby leaving a clearance 24 between the pre-form 22 and the outer walls 16 and 18.
  • the pre-form is compressed and radially expanded until is fills, and assumes the shape of, the die cavity 20.
  • the final punch position is illustrated in Figures 3 and 4, which also show the final formed article 26 with the densified surface 28 after having assumed the shape of the die walls 16 and 18.
  • Figures 1 to 4 only illustrate a die for the forming operation. It will be understood by persons skilled in the art that the actual shape and configuration of the die will depend upon the specific article being formed.
  • the die can include core rods, moveable outer walls or other configurations necessary to achieve the final article shape.
  • Figures 1 to 4 serve to illustrate a forming operation conducted on the outer surface of a sintered pre-form.
  • the forming die can be used to provide the article with a desired outer and/or inner shape also as known in the art.
  • the forming operation can be used to form multilevel parts, such as an over-running clutch or other such articles as known in the art.
  • the article may optionally be annealed, at temperatures between 800 and 1300°C in a protective atmosphere or vacuum and with suitable cooling in order to obtain proper metallurgical bonding and to fully develop the desired mechanical properties.
  • the final article is usually required to have high wear and fatigue resistance.
  • heat treatment such as carburizing, quenching and tempering, etc.
  • a prior through hardening treatment either applied as a forced cooling, or quenching following annealing or as a separate heat treatment operation may be applied to increase the core yield strength. Both methods produce an article with a hardened surface case and a hard core that is resistant to wear and exhibits superior fatigue performance.
  • Various other heat treatment methods will be known to persons skilled in the art.
  • the invention described herein relates to the surface densification of a PM article while it still has a simple cylindrical geometry (i.e. prior to final forming of the article) and utilizes the ductility of the pre-formed material to impart the final contoured shape to the densified surface.
  • the invention provides an improvement over previously known methods, which require surface densification of the final formed article.
  • one of the key advantages of the present invention lies in its ability to provide an improved, efficient process for producing a PM article having a complex shape and with specific surface densification.
  • Example 1 Carbon Manganese Molybdenum Outer Race
  • Iron powder, lubricant, graphite, ferromanganese and ferromolybdenum were blended to achieve a sintered composition of approximately 0.2% carbon, 0.9% manganese and 0.5% molybdenum.
  • the powder was formed into rings, which were compacted to a density of 6.5g/cc (approximately 83% of the theoretical maximum) with a pressure of about 350 MPa.
  • the compacted rings were sintered at 128O 0 C for 20 minutes. A nitrogen/hydrogen atmosphere was maintained throughout the cycle.
  • each sintered ring was surface densified by the method described in U.S. Patent No. 6,110,419 (incorporated herein by reference) thereby achieving a local surface density in excess of 99% of the theoretical maximum density, while the core density remained at 6.5g/cc.
  • This density profile is illustrated in Figure 5.
  • the bore surface densif ⁇ ed rings were formed in a closed die with a core rod having the geometry of the final cam form. The material exhibited remarkable ductility and densification. At forming pressures of 700 to 1050 MPa, core densities of 7.30 To 7.55g/cc were obtained as illustrated in Figure 6.
  • Example 2 Carbon Molybdenum Inner Race
  • a blend with a sintered composition of 0.6% carbon and 0.9% molybdenum was prepared by combining iron powder, ferromolybdenum, graphite, and lubricant. Rings of the powder blend were compacted to 85% of theoretical maximum density with pressure of approximately 520 MPa. The rings were sintered in a nitrogen/hydrogen atmosphere for 20 minutes at 128O 0 C followed by an isothermal hold (as described in U.S. Patent No. 5,997,805, incorporated herein by reference) resulting in a malleable sintered article. The cylindrical outer surface of the sintered rings was selectively densified using the roller burnishing method (as described in U.S. Patent No.
  • Example 1 the material exhibited remarkable ductility and through-densification. Core densities of 7.20 to 7.45g/cc were achieved at forming pressures of 750 to 1050 MPa (as illustrated in Figure 10) resulting in axial closures of 12 to 16% of the sintered length (as illustrated in Figure 11). Radial movement of up to 4% of the sintered inner radius was obtained as shown in Figure 12. As in Example 1, after the forming step, the densified bore layer was intact ( Figure 9), the core density was increased as said, the surface had substantially assumed the final cam shape and the active cam form exhibited both excellent surface finish and dimensional stability.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)

Abstract

La présente invention décrit une méthode d'élaboration d'un article métallique en poudre en trois dimensions et présentant au moins une surface densifiée. Ladite méthode comprend les étapes suivantes : a) obtention d'un mélange de métaux pulvérulents ; b) compactage dudit mélange afin d'obtenir une ébauche de la forme générale dudit article ; c) frittage de ladite ébauche ; d) densification d'au moins une zone de surface cylindrique de ladite ébauche ; et e) mise en forme de ladite ébauche, au cours de laquelle cette dernière acquiert sa densité définitive ainsi que la forme en trois dimensions dudit article.
PCT/CA2005/001970 2005-01-05 2005-12-23 Méthode d'élaboration de composants métalliques en poudre présentant une surface densifiée Ceased WO2006072162A1 (fr)

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US11/813,400 US20090129964A1 (en) 2005-01-05 2005-12-23 Method of forming powder metal components having surface densification
MX2007008208A MX2007008208A (es) 2005-01-05 2005-12-23 Metodo de formacion de componentes de polvo de metal con densificacion de superficie.
EP05823969A EP1850989A4 (fr) 2005-01-05 2005-12-23 Méthode d'élaboration de composants métalliques en poudre présentant une surface densifiée
JP2007549770A JP2008527166A (ja) 2005-01-05 2005-12-23 表面緻密化粉末金属部品を製造する方法
CA002594364A CA2594364A1 (fr) 2005-01-05 2005-12-23 Methode d'elaboration de composants metalliques en poudre presentant une surface densifiee

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WO2016172032A1 (fr) * 2015-04-23 2016-10-27 The Timken Company Procédé de mise en forme d'un élément de palier
WO2022036157A1 (fr) * 2020-08-12 2022-02-17 Montana Technological University Compositions d'alliage de métal sec et procédés associés

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US20100178194A1 (en) * 2009-01-12 2010-07-15 Accellent, Inc. Powder extrusion of shaped sections
CN101879598B (zh) * 2010-06-28 2011-09-28 莱芜钢铁股份有限公司 连铸结晶器用粉末合金自润滑轴承的制造方法
JP5936954B2 (ja) * 2012-08-23 2016-06-22 Ntn株式会社 機械部品の製造方法
US10480619B2 (en) * 2016-08-22 2019-11-19 Johnson Electric International AG Ring gear, gear device and mold for manufacturing the ring gear
CN107763171A (zh) * 2016-08-22 2018-03-06 德昌电机(深圳)有限公司 一种齿圈体、包含该齿圈体的齿轮减速装置及生产该齿圈体的模具
DE102018105782A1 (de) * 2018-03-13 2019-09-19 Schunk Sintermetalltechnik Gmbh Verfahren und Behandlungsvorrichtung zur Herstellung von pulvermetallurgischen Sinterformteilen

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CA2268649A1 (fr) * 1996-10-15 1998-04-23 Zenith Sintered Products, Inc. Densification d'une surface de composants de machine realisee par metallurgie des poudres
CA2294066A1 (fr) * 1997-06-19 1998-12-30 Stackpole Limited Formage d'articles a haute teneur en carbone et haute densite
US6143240A (en) * 1997-11-14 2000-11-07 Stackpole Limited High density forming process with powder blends
US20040177719A1 (en) * 2003-10-03 2004-09-16 Kosco John C. Powder metal materials and parts and methods of making the same
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WO2016172032A1 (fr) * 2015-04-23 2016-10-27 The Timken Company Procédé de mise en forme d'un élément de palier
US9810264B2 (en) 2015-04-23 2017-11-07 The Timken Company Method of forming a bearing component
WO2022036157A1 (fr) * 2020-08-12 2022-02-17 Montana Technological University Compositions d'alliage de métal sec et procédés associés
US11794242B2 (en) 2020-08-12 2023-10-24 Montana Technological University Dry metal alloying compositions and related methods

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Publication number Publication date
CA2594364A1 (fr) 2006-07-13
US20090129964A1 (en) 2009-05-21
MX2007008208A (es) 2007-11-07
EP1850989A1 (fr) 2007-11-07
EP1850989A4 (fr) 2011-06-29
JP2008527166A (ja) 2008-07-24

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