EP0103056B1 - Pièce métallique frittée et son procédé de fabrication - Google Patents

Pièce métallique frittée et son procédé de fabrication Download PDF

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Publication number
EP0103056B1
EP0103056B1 EP82304852A EP82304852A EP0103056B1 EP 0103056 B1 EP0103056 B1 EP 0103056B1 EP 82304852 A EP82304852 A EP 82304852A EP 82304852 A EP82304852 A EP 82304852A EP 0103056 B1 EP0103056 B1 EP 0103056B1
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EP
European Patent Office
Prior art keywords
seat
annular
polymeric material
matrix
metal matrix
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.)
Expired
Application number
EP82304852A
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German (de)
English (en)
Other versions
EP0103056A1 (fr
Inventor
Ricardo Gonzalez
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.)
Worcester Controls Corp
Original Assignee
Worcester Controls Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Worcester Controls Corp filed Critical Worcester Controls Corp
Priority to DE8282304852T priority Critical patent/DE3273359D1/de
Priority to EP82304852A priority patent/EP0103056B1/fr
Priority to AT82304852T priority patent/ATE22242T1/de
Publication of EP0103056A1 publication Critical patent/EP0103056A1/fr
Application granted granted Critical
Publication of EP0103056B1 publication Critical patent/EP0103056B1/fr
Expired 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
    • B22F3/24—After-treatment of workpieces or articles
    • B22F3/26—Impregnating
    • 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

Definitions

  • This invention relates to sintered metal bodies, and in particular but not exclusively, to such bodies of annular configuration suitable for use as the seat of a plug valve of the ball valve kind. It is desirable to use metal seats in such ball valves under certain conditions since the resultant valve structure can resist higher temperatures and pressures than valves which use other types of seat materials such as plastics materials, for example polytetrafluoroethylene (PTFE).
  • PTFE polytetrafluoroethylene
  • the McFarland patent discloses a metal seat for use in a floating type ball valve, the seat being formed of sintered metal of which the exterior surfaces are coated with a layer of cured polymeric material which extends to some extent into the interior pores or interstices of the sintered metal body.
  • valve seat of the McFarland patent is a porous structure which relies upon a continuous surface coating of polymeric material to provide the desired seal, or upon a caulking action of the polymeric material within the seat to effect a desired seal in the event that the polymer coating is destroyed by any means such as fire or abrasion.
  • valve seat of the McFarland patent being essentially porous throughout, tends to leak fluid through the seat when the seat is subjected to pressure if the integrity of the surface coating is impaired and the above-mentioned caulking effect is imperfect.
  • An object of the present invention is to provide a method of fabricating a leak-proof seat for use in a ball valve, together with a non-porous leak-free valve seat or seal for use in a ball valve offering improvements in relation to one or more of the shortcomings of the prior art as identified above.
  • the foregoing disadvantages of the structure disclosed in the McFarland patent are largely mitigated by providing a seat for a floating ball valve consisting of a sintered metal matrix of which the interparticulate spaces are completely filled with cured polymeric material, whereby the seat structure, in addition to being of metal construction and therefore adapted for use in those applications where metal seats are desirable, is nonporous throughout without regard to the presence or absence of a surface coating of polymeric material.
  • a surface coating can be provided to achieve additional initial lubricity
  • the provision of such a surface coating is optional only since the cured polymeric material which fills the interstices of the sintered metal matrix and in particular the portion thereof which is adjacent the surface of the seat, provides the desired lubricity. Any increase in temperature of the seat with a resultant expansion of the polymeric material within the seat, causes an extrusion or migration of said polymeric material from the interior of the seat through the surface of the seat to provide additional lubricity.
  • the expanded interior polymeric material is obliged to migrate through the matrix of sintered material towards the exterior surface of the seat and to exude from the matrix onto the seat surface thereby increasing the lubricity of the seat at the seat/ball interface of the valve.
  • a sintered metal body such as a valve member or valve seat according to the present invention can be prepared by a series of steps, and by using metal and polymeric materials in accordance with the disclosure of the above-mentioned United States patent to McFarland.
  • a sintered metal "green compact" structure is initially fabricated in the form and shape conventionally employed for ball valve seats and members, and then the green compact is sintered to fuse adjacent metal particles to each other. Then the resultant valve member or seat is impregnated with an emulsion of uncured polymeric material having lubricity, the impregnation being effected by means of a vacuum and/or positive pressure step. The liquid vehicle employed in the emulsion is then dried, and then the residual polymeric material is cured by heating.
  • a valve seat prepared by a series of steps as described above is considered to be completely fabricated except for a final surface finishing step such as grinding, to provide the seat with a desired surface accuracy, and the final seat is porous throughout except for a layer of polymeric material which covers the exterior surfaces of the seat.
  • the product of the above steps constitutes only the starting point for a further portion of the manufacturing process and, following the above-mentioned curing step, the valve seat or member is placed in a die and subjected to extremely high pressures which operate to collapse substantially all of the interparticulate cavities and voids throughout the seat onto the portions of the cured polymeric material within the sintered metal matrix.
  • the cured polymeric material within the sintered metal seat or member completely fills all of the collapsed interparticulate spaces within the seat and the seat is rendered nonporous throughout.
  • the seat can then be surface-finished, if necessary, or the seat can optionally be coated with a further layer of polymeric material which is thereafter surface-finished if necessary.
  • the sintered metal elements are proposed to be associated with a lubricant or polymeric material, see for example the United States patents: in addition to the above-discussed US patent 3,592,440 (McFarland).
  • prior workers in the field have proposed the use of a "coining" or compression of a sintered metal body-see for example the above-mentioned Chmura and Harris patents, but these proposals have been such that the resultant structure exhibits a high density or nonporous portion adjacent the surface of the body only, and a lower density porous structure underlies the surface of the body.
  • the pressure-applying step of the present invention is such that the valve seat or body so produced exhibits substantially uniform density throughout and is nonporous throughout.
  • a quantity of powdered metal e.g. stainless steel or bronze
  • a die whose interior configuration corresponds to the configuration desired of the final structure (e.g., an annular configuration when the object being prepared is a seat for use in a ball valve)
  • the powdered metal is subjected to pressures of the order of 30 tons per square inch to form a unitary metal body having the desired configuration.
  • the individual metal particles are held together simply by interparticle friction and the structure is termed a "green compact" in the parlance of the trade.
  • the green compact is then placed in a furnace and subjected to a high temperature which is less than the melting point of the metal material in the seat but which is sufficiently high to cause a coalescing of the interfaces between the various particles in the green compact to unify the structure into a sintered metal matrix.
  • the resultant structure is porous.
  • a PTFE emulsion is formed by mixing a quantity of submicron PTFE particles in an appropriate vehicle such as water, along with some wetting agents; it must be understood, however, as discussed in the afore-mentioned US patent 3,592,440 (McFarland), that other uncured polymeric materials can be employed and entrained or suspended in other liquid vehicles.
  • the emulsion produced in step 12, and the sintered metal seat produced by step 11 are then, in a step 13, placed in a vacuum chamber, initially in spaced relation to one another, and a vacuum is applied to the chamber to remove all air from the voids or pores in the sintered metal seat.
  • the sintered metal seat is then immersed in the emulsion, and the vacuum is broken (if desired, a positive pressure may also be introduced into the chamber) to drive the emulsion into the pores of the sintered metal seat.
  • the resultant polymer impregnated seat is then removed from the chamber and permitted to dry, in a step 14, e.g., at a temperature which is below the boiling point of water or which is otherwise suitable to remove the water or other liquid vehicle constituents from the emulsion, leaving a residue of PTFE (and/or of whatever other polymer is employed) in the pores of the sintered metal seat.
  • the impregnated seat is again placed in a furnace in a step 15, and is heated to sinter and cure the PTFE at an appropriate "Teflon-sintering" temperature, i.e. one which is considerably lower than the sintering temperature previously employed for the metal seat alone.
  • step 10 By way of example, if the green compact prepared in step 10 constitutes stainless steel particles, it would be sintered at approximately 1371°C (2500°F) whereas Teflon is sintered (in step 15) at around 371°C (700°F). Sintering step 15 is needed to coalesce the Teflon particles, previously in the emulsion, with one another since, otherwise, the Teflon particles would be driven out of the pores in the sintered metal seat when the seat is later subjected to fluid pressure.
  • Step 16 the structure is then subjected, in a step 16, to extremely high pressures which collapse substantially all of the interparticulate cavities and voids throughout the seat onto the enclosed PTFE or other cured polymer within the seat, to eliminate all interparticulate voids in the sintered metal seat to the extent possible, and to render the complete seat impervious to fluid flow, i.e., to make the final product "leak free” throughout.
  • Step 16 can be effected in the manner shown in Fig.
  • annular, polymer impregnated, sintered metal seat 20, produced by method steps 10­15 described above, is placed in a die 21 which has a cooperating plunger 22 that, together, define exterior surfaces which closely conform to all of the exterior surfaces of seat 20, whereafter extremely high pressures, in the order of 40 tons per square inch (6.3 tonnes per square centimetre), are applied to the seat to collapse all voids within the seat material and to render it nonporous and of substantially uniform density throughout.
  • the seat 20 following completion of step 16, is of sintered metal construction wherein cured PTFE (or whatever other polymer having desired lubricity is employed) fills the interparticulate spaces or collapsed voids of the sintered metal matrix throughout the body of the seat.
  • the seat is, accordingly, nonporous throughout. Indeed, seats constructed in accordance with the present invention have been found to hold bubble tight on helium, which is a most stringent leakage test. Those incremental portions of the polymer material which are adjacent the surface of the seat act as a lubricant at said surface.
  • step 16 since all interparticulate voids have been collapsed by step 16, when the seat is used in an application where the temperature is higher than room temperature, the cured polymer within the seat expands but has no place to go; and the resultant expansion is therefore manifested as an increase in the internal pressure of the seat through the matrix of sintered metal material, which experiences a migration of the cured polymer toward the surface of the seat and causes some extrusion of the polymer from the seat surface to increase the lubricity of the seat at the seat/ball interface.
  • the seat may, in a step 17, be dipped in a PTFE emulsion which is much more viscous in consistency than the emulsion in steps 12 and 13, to coat the seat with a layer of Teflon® or other polymer having desired lubricity, whereafter the coating layer is again sintered and cured to provide the seat with an outer envelope which gives the seat additional initial lubricity.
  • this final step is optional.
  • the outer polymer layer if provided, may be characteristically coloured to clearly identify the type of seat which has been produced.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Powder Metallurgy (AREA)
  • Adornments (AREA)

Claims (7)

1. Procédé de fabrication d'un siège étanche utilisable dans une vanne à boule, comprenant les opérations de compactage d'une masse de particules de métal, cette masse étant de configuration annulaire et présentant une face en forme d'anneau prévue pour être placée adjacente à une boule tournante dans une vanne à boule, de frittage de cette masse annulaire de manière à lier par fusion des particules adjacentes desdites particules de métal les unes aux autres, afin d'agglomérer ces particules en une matrice métallique poreuse de forme annulaire, d'imprégnation de cette matrice métallique annulaire avec une émulsion composée de particules non durcies d'un polymère dans un véhicule liquide, ladite opération d'imprégnation étant effectuée dans des conditions de pression positive pour repousser l'émulsion dans les espaces entre particules de la matrice métallique et pour remplir complètement avec ladite émulsion lesdits espaces entre particules dans toute la matrice métallique annulaire de séchage de cette matrice métallique annulaire imprégnée d'émulsion pour en éliminer ledit véhicule liquide, de façon à laisser un résidu de particules de polymère non durci dans les espaces entre particules, puis de chauffage de ladite matrice métallique annulaire pour fritter et durcir les particules de polymère qui restent dans les espaces entre particules, ledit procédé étant caractérisé en ce qu'il comprend la mise en place de ladite matrice métallique dans un moule comportant une cavité annulaire dont la configuration intérieure se conforme étroitement à la configuration annulaire extérieure de la matrice métallique annulaire imprégnée de polymère durci, et ensuite, au moyen dudit moule, l'appliquer d'une pression aux surfaces extérieures de la matrice métallique annulaire, d'une valeur de l'ordre de 463 à 618 MPa, de manière à écraser l'intérieur de la matrice sur le polymère durci à l'intérieur de la matrice, ce qui supprime tous les vides à l'intérieur de la matrice annulaire qui subsistaient dans la matrice après les opérations de séchage et de frittage/ durcissement, de sorte que ladite matrice annulaire devient entièrement non poreuse, l'opération d'appliçation de pression étant exécutée de manière à produire une pièce annulaire dont la forme et les dimensions sont adaptées à l'utilisation comme siège de boule dans une vanne à boule tournante, cette pièce annulaire ayant une densité sensiblement uniforme dans tout l'intérieur de ladite pièce et aux surfaces extérieures de ladite pièce après achèvement de ladite opération d'application de pression.
2. Procédé suivant la revendication 1, caractérisé en ce qu'il comprend en outre les opérations, effectuées après ladite opération d'application de pression, de revêtement des surfaces extérieures de la pièce annulaire avec une autre émulsion de particules de polymère, ladite autre émulsion étant plus visqueuse que l'émulsion employée dans l'opération d'imprégnation, et ensuite de séchage dudit revêtement et de frittage et durcissement des particules de polymère dans ledit revêtement, de manière à enfermer ladite pièce annulaire dans une enveloppe extérieure de polymère.
3. Procédé suivant la revendication 1 ou la revendication 2, caractérisé en ce que le polymère comprend du polytétrafluoroéthylène.
4. Siège, ou garniture de vanne, étanche et non poreux comprenant une pièce annulaire en particules métalliques frittées, constituant une matrice métallique qui présente une configuration extérieure adaptée à l'utilisation dans une vanne à boule comme un siège qui est en contact avec une boule tournante dans une telle vanne, et un polymère durci ayant des propriétés lubrifiantes déposé dans la matrice métallique, caractérisé en ce que tous les espaces entre particules de la matrice métallique constituant l'intérieure de la pièce annulaire sont complètement remplis avec ledit polymère durci à propriétés lubrifiantes, de sorte que ledit polymère rend ladite matrice métallique non poreuse dans tout l'intérieur de ladite pièce et de sorte que des augmentations de température de ladite pièce, qui engendrent une dilatation du polymère à l'intérieur de ladite matrice, provoquent une extrusion de portions dudit polymère durci, de l'intérieure de la pièce aux surfaces extérieures de ladite pièce qui sont prévues pour venir en contact avec la boule tournante d'une vanne à boule, afin de lubrifier lesdites surfaces extérieures tandis que les espaces entre particules à l'intérieur de ladite pièce restent complètement remplis par les portions non extrudées dudit polymère durci, les parties de surface extérieure de la pièce ayant sensiblement la même densité que l'intérieur de la pièce.
5. Siège ou garniture d'étanchéité de vanne suivant la revendication 4, caractérisé en ce que ledit polymère comprend du polytétrafluoroéthylène.
6. Siège ou garniture d'étanchéité de vanne suivant la revendication 4 ou la revendication 5, caractérisé en ce que l'extérieur dudit siège ou garniture est complètement recouvert d'une couche dudit polymère durci.
7. Siège ou garniture d'étanchéité de vanne, fabriqué par un procédé suivant l'une quelconque des revendications 1 à 3.
EP82304852A 1982-09-14 1982-09-14 Pièce métallique frittée et son procédé de fabrication Expired EP0103056B1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE8282304852T DE3273359D1 (en) 1982-09-14 1982-09-14 Sintered metal body and method of making same
EP82304852A EP0103056B1 (fr) 1982-09-14 1982-09-14 Pièce métallique frittée et son procédé de fabrication
AT82304852T ATE22242T1 (de) 1982-09-14 1982-09-14 Metallischer sinterkoerper und verfahren zu seiner herstellung.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP82304852A EP0103056B1 (fr) 1982-09-14 1982-09-14 Pièce métallique frittée et son procédé de fabrication

Publications (2)

Publication Number Publication Date
EP0103056A1 EP0103056A1 (fr) 1984-03-21
EP0103056B1 true EP0103056B1 (fr) 1986-09-17

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ID=8189770

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82304852A Expired EP0103056B1 (fr) 1982-09-14 1982-09-14 Pièce métallique frittée et son procédé de fabrication

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EP (1) EP0103056B1 (fr)
AT (1) ATE22242T1 (fr)
DE (1) DE3273359D1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109676141A (zh) * 2017-12-06 2019-04-26 全亿大科技（佛山）有限公司 异形复杂金属制品的制造方法及异形复杂金属制品

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB674056A (en) * 1948-11-16 1952-06-18 Edras Soc Manufacture of self-lubricating metallic bodies by sintering metallic powders
US2838829A (en) * 1956-09-05 1958-06-17 Toefco Engineering Company Method of making bearings
US3592440A (en) * 1969-10-16 1971-07-13 Hills Mccanna Co Ball valve

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109676141A (zh) * 2017-12-06 2019-04-26 全亿大科技（佛山）有限公司 异形复杂金属制品的制造方法及异形复杂金属制品

Also Published As

Publication number Publication date
DE3273359D1 (en) 1986-10-23
EP0103056A1 (fr) 1984-03-21
ATE22242T1 (de) 1986-10-15

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