CA1330401C - Method and apparatus for making a forged metal article - Google Patents

Abstract

APPARATUS FOR MAKING A FORGED METAL ARTICLE
ABSTRACT OF THE DISCLOSURE
A method and apparatus for making forged, fully dense metal articles having contoured surfaces, for example, gears is provided.

Description

,j - --` 1330~Dl ., i METHOD AND APPARATUS FOR MAKING A FORGED METAL ARTICLE
Back~round of_the Invention ¦ a) Field of_the Invention This invention relates to a method and apparatus for making a metal article and more particular-ly, an apparatus for making a fully dense forged metal article having an intricate contoured surface.
b) Description of the Prior Art Metal parts having contoured surfaces, for example, gears having a plurality of teeth have been pro-duced by machining a ~lock of metal with the desired contoured surface, or by powder metallurgy techniques in which metal particles are compacted into the desired contoured surface and the compact is sintered. If a powdered metal technique is used a complex tooling appa-ratus is often required and tool wear has been typically excessive. Additionally, the resulting metal article has had relatively lower physical properties due to having a density less than fully dense material. In cases in ~ 20 which good physical properties are required, such as many ; gear applications, the articles have to be produced by machining a block of solid metal. This process, however, ~t results in an article which is expensive to produce.
Lastly, there are many advantages associated - 25 wlth the use of metal articles produced by powder metal-lurgy techniques, for example, the ability to readily vary the powder metal composition to provide particular characteristics, and the ability to form intricate con-tours while minimizing or avoiding machining operations.
; It would be advantageous if metal articles having intricate contoured surfaces and good physical properties could be produced using an apparatus which is -~;
;, ~ $ ~ reliable and economical in operation. ~-ÇA i ;~ SummarY of the Invention ~ ~ 35 It is an object of this invention to provide an ~, ~
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apparatus for producing a forged, metal article with a contoured surface.
It is a further object of this invention to provide an apparatus for producing a forged fully dense metal article with an intricate contoured surface in a single stroke operation in which the article is made from a powdered metal.
It is still a further object of this invention to provide an apparatus for produclnq a forged fully dense metal article with a helical contoured surface in a single stroke operation.
It is yet another object of this invention to provide a method of producing a fully dense forged metal article with a helical contoured surface in a single 15 forging operation.
~ In accordance with the invention there is ¦-~ provided an apparatus for producing in a single stroke a .
~; forged metal article with a contoured surface comprising:
a die assembly having a die passage therethrough and a i 20 die having a profi.led surface in said assembly; upper and -;~ :
3~ lower punch assemblies, said die assembly being disposed . ~ between said punch assemblies, said upper punch assembly , ~ comprising an upper punch housi.ng, a first forging punch mounted in said housing and a tubular punch sleeve sur-n~ 25 rounding said first punch, means for axially reciprocat-; ing said upper housing relative to said die assembly to . ~ reciprocate said first punch and sleeve w.ith respect to . ~ said die assembly, said sleeve being slidably mounted in . ~ said upper housing for axial telescopic retraction into 30 said~upper housing relative to said first p~unch, said I ~ :
lower punch assembly including a second forging punch extending into said die passage in opposed relationship wi.th said fi.rst punch, said second punch being adapted to support an article to be forged in said die assembly, and . ~ :
35 means for axislly rsis~ng ssid second punch in ssid die . 2 ~ , , ~ , ~ ,:

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passage to eject a forged article from said die assembly.
In accordance wi.th another aspect of the invention there is provided an apparatus for producing a fully dense forged, metal article with a heli.cal con-~` 5 toured surface comprising: a die assembly having a die passage therethrouqh, a die having a profiled surface seated in said passage, anA first and second forging punches mounted for opposed axial ~ovement in said die I passage, said punches having no helical form incorporated i,: 10 therein.
~ In accordance with still another aspect of the ~ i.nventi.on, there is provided a method of producing a .~ ~
, fully dense forged metal article with a contoured surface :. :I comprising providing a metal preform having a continuous 15 ~houlder defined between a body portion of a fi.rst peri- :
~ pheral dimension and a head portion of a second peripher- ~-¦~ al dimension less than ~aid first dimension, heating said metal preform, supporting said preform i.n a die cavity about an impacting axis with said body portion circum-scri.bed by a di.e having a profiled surface, and circum-: scribing cavity between said profiled surface and said :.
~:~ body portion, forgi.ngly impacting said head portion along ~. said axis to effect flow of the metal laterally outwardly ;;~ ; of said body porti.on through said circumscribing cavity 25 to mate with said profiied surface and produce a forged :
metal article with a contoured surface matching the profiled surface of the die, and ejecting the forged :
. ~ article from the die. :.
In this specification the expressions "contoured sura~e"l and "~profiled surface" particularly contemplate surfaces havi.ng a plurality of ridges and . ~ furrows or ~ome simi.lar pattern of ribs and grooves, ~ .;
;~ whether straight or not; by way of example there may be mentioned the surface of a gear, sprocket or spline. .~-~ 35 In this specification the expression "contoured 3~

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surface" is employed to define the surface of a forged metal article of the invent;on, for example, a gear; and the expression "profiled surface" is employed to define the surface of a die which is to form the "contoured 5 surface". Thus the "contoured surface" of the article and the "profiled surface" of the die are complementary or mating surfaces.
srief Description of the Drawinqs The invention is illustrated in a particular 10 and preferred embodiment by reference to the accompanying drawings in which:
FIGS. 1, 2 and 3 illustrate schematically an apparatus of the invention at different stages of the method of the invention for producing a forged metal 15 article, particularly a helical gear of the invention;
FIG. 4 shows schematically the preform for the helical gear employed in FIG. 1, and FIG. 5 shows the forged article produced in the stage illustrated in FIG. 3.
20 Description of Preferred Embodiments with Reference to - the Drawings With further reference to the drawings, FIGS. 1 to 3 show an apparatus 10 for producing a forged metal ;~ article 18 in accordance with the invention. FIGS. 1, 2 25 and 3 show the apparatus in sequential stages of the method of the invention. FIG. 1 illustrates a loading step, FIG. 2 illustrates a forging step and FIG. 3 illus-trates an ejection step.
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With further reference to FIGS. 1 to 3, 30 apparatus 10 includes an upper punch assembly 12, a lower punch assembly 14 ahd a die assembly 16 thérebetween.
With particular reference to FIG. 1, a sintered powder metal preform 20 is shown supported in die assem-~; bly 16 and with reference to FIG. 3, a forged article 18 35 is shown being ejected. It is to be understood that ;; ~ ;;` ' ,~ ~

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~330~1 metal preform 20 may also be made of solid metal materi-al.
Upper punch assembly 12 i.ncludes a punch housing 22, a forqing punch 24 and a punch sleeve 26. :~
5 Housing 22 and forging punch 24 are fixedly mounted to a base 23.
Sprin~ means 28 are disposed in housing 22 between base 23 and an inner end 44 of punch sleeve 26.
This spring means will typically take the form of actual 10 spring or hydraulically loaded biasing means.
Forging punch 24 includes a generally flat forging surface 30 and a smooth cylindrical surface 31.
Sleeve 26 includes a shoulder 32, an outer slide surface 34 and an inner tubular wall 35. :` -Housing 22 i.nc].udes a flange 36 and a cylindrical quide surface 38. ..
Sleeve 26 further includes an outer locating : -end 40 having a flat annular surface 42.
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. Die assembly 16 includes a die casing 46, a die 20 clamping ring 48 and a die plate 50. :
Die passage 52 extends through assembly 16.
~- ~ Die casing 46 includes an annular seat 54 on which die plate 50 is mounted by means of clamping ring ~: 48. Any convenient means, for example, screws, may be .
25 employed to lock die plate 50 in annular seat 54 with clamping ring 48.
Die plate 50 has an inwardly facing profiled ~:~
surface porti.on 58 which circumscribes preform 20 and a ~; vertical impact axis 59. An annular cavity or space 56 -30 is defined between~profiled surface 58 and preform 20.
Profiled surface 58 particularly comprises a plurality of extending ridges and furrows. If the final ;~
forged article 18 is to be a helical article these ridges - and furrows will be inclined at an angle rPlative to axi.s ::-35 59. ~ -'~
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Lower punch assembly 14 includes a forging punch 60-mounted by punch clamp ring 62 including a punch adaptor 64.
Punch adaptor 64 has a cylindrical passage h5 '5 therethrough which receives a cylindrical rod 68 having a :!cylindrical flange base 69 of lower base plate of appara-tus 10. Flange 69 and punch 60 support the load during the forging operation. A shim plate 66 is located on flange base 69.
A pair of ejection rods 70 is disposed to slide through ejector passages 71 in shim plate 66 to enqage f the underside of adaptor 64.
daptor 64 preferably has an annular groove 72 circumscribing cylindrical passage 65, containing ball 15 bearings 74 or the like which support forging punch 60 during ejection for free rotation relative to clamp ring f 62 and adaptor 64.
Forging punch 60 has a generally flat support surface 76 and a smooth cylindrical surface 78.
With further reference to FIG. 4, preform 20 has a cylindrical body 82, a cylindrical head 84 and a shoulder 86. Cylindrical body 82 has a height h. It is to be understood that shape of preform 20 may take other forms.
With further reference to FIG. 5, a forged, ,i~ powder metal article 18 has a generally cylindrical body ,~ 88 with a plurality of inclined ridges 90 separated by furrows 92 on its circumferential surface. Forged arti-cle 18 includes a generally flat surface 96.
~ Body 8,8 has a height h which is ,substantially the same as the height h of body 82 of preform 20 in FIG.

In the method of the invention, a metal part ~`~ which typically will be cylindrical to provide a preform 0 ~- III~J~ rlO ~ 5~ b~

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preform 20 are selected having regard to the dimensions of the forged article 18 desired. Thus the body 82 of preform 20 typically has a height h correspondinq gener-ally to the height h of the forged article 18 desired.
The dimensions of cylindrical head 84, and of the shoul-der 86 are selected so that cylindrical head 84 will be matingly received within tubular ~all 35 adjacent locat--ing end 40 of sleeve 26, an~ annul~r surface 42 of locat-ing end 40 will engage the shoulder 86 to locate preform 20 securely in position in preparation for impact by forging punch 24.
In the operation of the apparatus 10, forging punch 60 extends vertically upward in die passage 52 and preform 20 is supported on flat supporting surface 76 so that the cylindrlcal body 82 of preform 20 is surrounded by and spaced inwardly of profiled surface 58 of die plate 50.
The profiled surface 58 of die plate 50 has generally a height h corresponding to the height h of cylindrical body 82. An annular cavity or space 56 is preferably provided between profiled surface 58 and cylindrical body 82.
Upper punch assembly 12 is supported above die ;~
assembly 16 with punch 24 in opposed relationship with ;~ 25 punch 60.
Punch sleeve 26 is urged downwardly of housing 22 by spring means 28, with slide surface 34 of sleeve 26 in sliding engagement with guide surface 38 of housing 22, until shoulder 32 of sleeve 26 engages flange 36 of housingj22. In!this configuration illustrated in FIG. l,;
forging surface 30 of punch 24 is spaced inwardly of annular surface 42 of sleeve 26, and vertically above ~ head 84 (see FIG. 4) of preform 20; and annular surface "~ 42 is vertically above shoulder 86 (see FIG. 4).
` ~ 35 In the forging step particularly illustrated by .~
~ 7 ` ~!330~01 reference to FIGS. 1 and 2, upper punch assembly 12 includin~ housing 22, sleeve 26 an~ forging punch 24 is moved vertically downwardly until cylindrical head 84 is contained within locatinq end 40 of sleeve 26, and the annular surface 42 of locating end 40 engages shoulder 86. Wi.th continued travel of punch assembly 12 downwa.rd-ly, sleeve 26 is retracted within housing 22, while -maintaining engagement between annular surface 42 and shoul~er 86. Duri.ng such retraction sli,de surface 34 of ,. , sleeve 26 slides against guide surface 38 of housing 22.
It is to be understood that other means could be used to close off profiled surface 58 as punch 24 engages preform 20.
With the retraction of tubular guide 26 into housing 22, tubular wall 35 of sleeve 26 slides against cylindrical surface 31 of punch 24. Forging surface 30 of punch 24 impacts cylindri.cal head 84 to effect forging lateral flow of metal of preform 20 lnto the only space ~, available, namely, annular cavity or space 56, and die space so that the metal flows laterally to engage the ~: profiled surface 58 of ~he die. There is thus formed in ?`:~ the cylindrical body 82 a contoured surface which matches the profiled surface 58 of die plate 50. ~:
~: As the metal flows laterally into contact with ' the profiled surface 58, the metal is cooled by contact with the die plate 50. ' .
~,~ On completion of the impacting or forging step ~ :
',`"~, the punch assembly 12 is raised as shown in FIG. 3 where~
-~ after sleeve 26 is telescoped out of housing 22 under the ~:
~action af sprin~s 28. ,, ! ' In order to eject the forged article 18, ejec-tor rods 70 are slid upwardly through ejector passages 71 of shim plate 66, to engage the underside of adaptor 64, whereby adaptor 64 is elevated with forging punch 60.
With its elevation, punch 60 rotates, if needed, on d~ 8 ;j , ~ 3 3 ~

bearings 74 as the ridges and furrows 90 and 92 of the forged article 18 slide vertically with respect to the corresponding furrows and ridges of the profiled surface 5~.
The forged article 18 more particularly shown in FIG. 5 may thereafter be machined as desired.
The invention is further illustrated by reference to the followlng Description of the Preferred Embodiments and Example.
Description of the Preferred Embodiments 1 The invention has particular application in the production of ferrous metal gears, especially helical gears in which the contoured surface is relatively com-plex, and the invention is further described by reference to such application. It is to be understood, however, that it would work equally well for nonferrous metal - articles such as copper and brass metals.
In carrying out the method of the invention to produce a gear of powder metal, a ferrous metal powder is blended to a homogeneous mix with any desired additives, for example, alloying metals in powder form, graphite and lubricants as is known in the art.
~ The blended powder is compacted to form a `~ cylindrical compact in conventional manner and then typically sintered to form a preform.
The sintered preform is heated to an elavated temperature suitable for the forging operation, by way -of example a temperature of 950 to 1250 C. The die preferably is likewise heated but to a lower temperature 30 ~by way of example 275 to 355 C., such that the sintered metal flowing under the forging impact pressure and cools on contact with the die. -~
The appropriate temperatures will depend in ~ part on the composition of the sintered metal.
i ~ The heated preform is supported in a die cavity ~ ;`~

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such that a body portion is spaced radially inwardly of an annular die having a profiled inner surface, the body portion and the profiled surface being in opposed rela-tionship; suitably the body portion and annular die have their centers coincident on the same vertical axis.
The heated preform is forgingly impacted by driving a forging punch under high pressure, by way of example 25 to 75 tsi, into contact with the cylindrical head of the preform, in particular by driving the punch along the vertical axis.
As part of the forging step the head is snu~ly received in a retractable punch sleeve which isolates the head for impact by the forging punch and prevents lateral flow of the metal in the head. The sintered metal in the head flows downwardly under the forging impact into the body and then laterally outwardly from the body into the space between the body and the die and then to mate with the profiled surface.
The laterally flowed metal cools on contact -~
;~20 with the die and is ejected easily from the die.
The punch surf-aces are smooth, non-profiled surfaces and the die has the sole profiled surface. This feature provides for longer tool life and greatly simpli-fied tool design. ~
A forged powder ferrous metal article produced ~ ;
in accordance with the invention will typically have a strength of at least on the order of 150,000 to 200,000 psi, and a yield of the order of 135,000 to 155,000 psi.
In the case of the production of a helical gear ;; 30 in which the prQjfiled surface of the die and the result-ing contoured surface of the gear both comprise helically -inclined ridges and furrows, ejection of the forged article requires relative rotation of the forged article and the die. This is achieved by supporting the preform 3~ and subsequently formed forged article in the die cavity ,,~ ~ .

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on a vertically upstanding forge punch mounted for free rotation about its axis. Ejection of the forged article is carried out by elevating the upstanding forge punch and allowing it to rotate relative to the die.
i 5 Example ,i A ferrous powder was blended with 0.5% by weight of graphite and 0.75% by weight of a lubricant to ' form a ho.nogeneous mix.
~, The ferrous powder mix was compacted in a die to a density of 6.4 g/cc to form a solid cylindrical , preform.
;J The preform was sintered in a sintering belt ;~i furnace at a temperature of 1121 C. for 10 minutes in an atmosphere of rich endothermic gas.
j~yi 15 The thus sintered preform was machined to a ;~ stepped diameter preform 20 as shown in FIG. 4, so that, by reference to FIGS. 1 to 4, the head 84 (FIG. 4) had a slightly smaller diamet~r than the diameter of the tubu-;~ lar wall 35 and the forging punch 24; and the cylindrical ~- 20 body 82 had a diameter corresponding to the diameter of the forging punch 60. The cylindrical body 82 had a ~- height h generally corresponding to the height of the profiled surface 58 of die plate 50. The profiled sur-face had a helix angle of 22 .
Die plate 50 was heated to a temperature of 315 C. and sprayed with a lubricating mixture of water and graphite.
The preform 20 was similarly lubricated with a mixture of water and graphite, and heated to a tempera-ture of,1065 C.~inia tu~e furnace having an atmosphere of rich endothermic gas.
The preform 20 was supported on punch 60 in the die assembly 16 as shown in FIG. 1, and was forged under impact of forging punch 24 at a pressure of 40 tsi as illustrated in FIG. 2.

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It was found that the resulting forged article cooled quickly as a result of the contact with the die plate 50. Forging punch 60 was elevated by means of the ejecti.on rods 70, and rotated during elevation on bear-5 ings 74 to elevate the forged article 18 out of the dieassembly 16.
The floor 96 was partially machined out of article 18 to produce a helical gear with a contoured surface of teeth and channels having a helix angle of lO 22.
While there have been descri.bed what are at present considered to be the preferred embodiments of this inven-tion, it will be obvious to those skilled in the art that , various changes and modifications may be made therein ~ -s~ 15 without departing from the invention, and it is aimed, therefore, in the appended claims to cover all such ~:
changes and modi.fications as fall within the true spirit and scope of the invention.

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Claims (12)

1. An apparatus for producing in a single stroke a forged metal article with a contoured surface comprising:
a die assembly having a die passage therethrough and a die having a profiled surface in said assembly, upper and lower punch assemblies, said die assembly being disposed between said punch assemblies, said upper punch assembly comprising an upper punch housing, a first forging punch mounted in said housing and a punch sleeve surrounding said first punch, means for axially reciprocating said upper housing relative to said die assembly to reciprocate said first punch and sleeve with respect to said die assembly, said sleeve being slidably mounted in said upper housing for axial telescopic retraction into said upper housing relative to said first punch, said lower punch assembly including a second forging punch extending into said die passage in opposed relationship with said first punch, said second punch being adapted to support an article to be forged in said die assembly, said second punch having mounting means allowing for free rotation relative to said axis, and means for axially raising said second punch in said die passage to eject a forged article from said die assembly.

2. An apparatus according to claim 1, wherein said die comprises an annular die member, and said profiled surface is an inner circumferential surface of said die member.

3. An apparatus according to claim 2, wherein said profiled surface comprises a plurality of ridges and furrows.

4. An apparatus according to claim 3, wherein said ridges and furrows are helically inclined relative to the axis of the annular die member.

5. An apparatus according to claim 4, wherein said forged metal article is made from a powdered metal.

6. An apparatus according to claim 1, 2, 3 or 4, wherein said punches have no profiled surface corresponding to the profiled surface of said die.

7. An apparatus according to claim 1, wherein only said die has a profiled surface in said die assembly.

8. An apparatus according to claim 2, 3 or 4, wherein only said die has a profiled surface in said die assembly.

9. An apparatus for producing in a single stroke a forged metal article with a helical contoured surface comprising:
a die assembly having a die passage therethrough and a die having a helical profiled surface in said assembly, upper and lower punch assemblies, said die assembly being disposed between said punch assemblies, said upper punch assembly comprising an upper punch housing, a first forging punch mounted in said housing and a punch sleeve surrounding said first punch, means for axially reciprocating said upper housing relative to said die assembly to reciprocate said first punch and sleeve with respect to said die assembly, said sleeve being slidably mounted in said upper housing for axial telescopic retraction into said upper housing relative to said first punch, said lower punch assembly including a second forging punch extending into said die passage in opposed relationship with said first punch, said second punch being adapted to support an article to be forged in said die assembly and having mounting means allowing for free rotation with respect to the axle of the die assembly, said upper and lower punches having no helical form incorporated therein, and means for axially raising said second punch in said die passage to eject a forged article from said die assembly.

10. A method of producing a forged, metal article with a contoured surface comprising:
providing a metal preform having a continuous shoulder defined between a body portion of a first peripheral dimension and a head portion of a second peripheral dimension less than said first dimension;
heating said metal preform;
supporting said heated preform in a die cavity about an impacting axis with said body portion circumscribed by a die having a profiled surface, and a circumscribing cavity between said profiled surface and said body portion;
heating said die;
forgingly impacting said head portion of said heated preform along said axis to effect flow of the sintered metal laterally outwardly of said body portion through said circumscribing cavity to mate with said profiled surface and produce a forged metal article with a contoured surface matching the profiled surface of the die, wherein said preform is supported on a lower forging punch and impacted with an upper reciprocating punch, said lower punch being mounted for free rotation about said impacting axis, and said step of ejecting comprises rotating and elevating said lower punch to elevate said article out of said profiled surface of said die.

11. The method of Claim 10 wherein said contoured surface is a helical contoured surface.

12. The method of Claim 11 wherein said preform is made from a powder metal.