US3577635A - Method for isostatic compression, such as the manufacture of powder bodies - Google Patents

Method for isostatic compression, such as the manufacture of powder bodies Download PDF

Info

Publication number
US3577635A
US3577635A US771966A US3577635DA US3577635A US 3577635 A US3577635 A US 3577635A US 771966 A US771966 A US 771966A US 3577635D A US3577635D A US 3577635DA US 3577635 A US3577635 A US 3577635A
Authority
US
United States
Prior art keywords
container
pressure
powder
chamber
bodies
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 - Lifetime
Application number
US771966A
Other languages
English (en)
Inventor
Carl Bergman
Harry Claesson
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.)
ABB Norden Holding AB
Original Assignee
ASEA AB
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 ASEA AB filed Critical ASEA AB
Application granted granted Critical
Publication of US3577635A publication Critical patent/US3577635A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/06—Electrodes
    • H05B7/08—Electrodes non-consumable
    • 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
    • B22F3/04—Compacting only by applying fluid pressure, e.g. by cold isostatic pressing [CIP]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H05B3/48—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material
    • H05B3/52—Apparatus or processes for filling or compressing insulating material in tubes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49082—Resistor making
    • Y10T29/49087—Resistor making with envelope or housing
    • Y10T29/49089—Filling with powdered insulation
    • Y10T29/49091—Filling with powdered insulation with direct compression of powdered insulation

Definitions

  • a body to be compressed is inserted within a flexible container containing a compression medium compatible with the body and the container is then placed within an outer compression chamber containing another compression medium compatible with the container and chamber.
  • the present invention relates, among other things, to a method of subjecting bodies or liquid to high pressure, such as in the manufacture of powder bodies, for example hard metal products, electrical heating elements comprising an electrical conductor surrounded by a body of compressed powder material and possibly a surrounding, tubular casing, welding or furnace electrodes, etc.
  • a central conductor is packed into a surrounding powder, in this case of insulating and heat-conducting type, possibly surrounded by a tube or other casing and the body is pressed in a suitably shaped tool or between rollers having a certain groove shape so that the powder (and casing) is compressed around the central conductor.
  • This method has certain disadvantages. A tool of a certain shape is required and it is difficult to avoid cracks, irregularities and air pockets in the finished product especially if it is afterwards bent or shaped to a nonlinear shape such as zigzag or spiral which is usual for heating elements.
  • hard metal bodies usually powder of hard material particles such as tungsten carbide and a binding metal such as nickel or cobalt, welding electrodes, etc. and the possibility has therefore been considered of manufacturing such bodies by other methods.
  • One such known method consists of placing one or more powder bodies, for example, of the above mentioned type, in a high pressure chamber for gaseous or hydraulic pressure medium and producing a high pressure in the chamber so that the bodies are compressed on all sides and the powder becomes even and relatively free from pockets of air, etc.
  • a high pressure chamber for gaseous or hydraulic pressure medium
  • the curing is preferably carried out before compacting. Sintering may take place either before and/or afterwards.
  • a pressure medium suitable for the compressed body may be unsuitable for the pressure container.
  • hydraulic oil in a finished hard metal body may decrease its usefulness. Hydraulic oil in a heating element, due to the nonconducting characteristic of the oil, makes the element difficult to test for insulation and remaining oil may cause an unpleasant odor when the heating element is used, and the oil may be difficult to remove. Disadvantages with similarly manufactured electrodes could also be shown.
  • a pressure medium of water-soluble type such as glycerine and ethylene glycol
  • Such pressure media may cause corrosion and the like in the walls of a pressure chamber which in turn may cause rupture or other damages in the high pressure apparatus. It can thus be said that it is often difficult to find a pressure medium which is suitable both for the high pressure container and for the compressed object.
  • the invention provides a solution of these and other similar problems and is characterized in that objects to be compressed are placed in a container having at least one elastomeric or displaceable wall or bottom, which container is also filled with pressure medium, sealed and placed in a pres sure chamber for hydraulic or pneumatic pressure medium, after which the pressure in the chamber is increased and the container compressed so that the object within is also compressed.
  • the advantages of isostatic compression are thus utilized to the full and at the same time large scale production is effected.
  • the pressure medium operating on the object can be selected taking the object into consideration and that in the out pressure chamber can be selected with a view to the technical conditions required in the chamber. Thus, expensive molding tools are avoided and the shape or length of the object is irrelevant.
  • the invention also relates to a means for performing this method.
  • the means is characterized in that it comprises a container having at least one elastomeric or displaceable wall or bottom for powder bodies or the like and for pressure medium, which container can be sealed and immersed in a pressure chamber to compress the container and bodies placed in this, by means of a pressure medium in the chamber.
  • a means operates effectively as an inner pressure vessel.
  • the elastic wall, etc. rapidly alters shape when pressure is effected in the outer chamber and the inner container is compressed until pressure equality is reached in container and chamber.
  • the bodies in the container will be isostatically compressed with the same pressure as occurs in the chamber without coming into contact with the outer pressure medium.
  • the container is provided with a bottom in the form of a perforated wall, a grid or net which is surrounded by the elastic wall.
  • a perforated wall a grid or net which is surrounded by the elastic wall.
  • the wall may be displaceable in the form of a piston, movable in a cylindrical space.
  • FIG. I shows a container in a high pressure chamber, which container is provided with a wall (bottom) in the form of an elastomeric membrane.
  • FIGS. 2 and 3 show alternative embodiments.
  • FIG. 1 shows a container I2, which by means of a cross member or other lifting device, can be lowered into a pressure chamber 11, said container having thin metal walls, such as thin steel.
  • the container I2 may of course be placed in the chamber before being filled. In certain cases several containers may be placed in the same pressure chamber.
  • a powder body, or several powder bodies, here for example a spiral heating element billet 13 is placed in the container 12 and then the container filled with suitable pressure medium, such as water and closed with the lid 14.
  • the powder body or bodies may consist of hard metal bodies, consisting of hard material grains (tungsten carbide, etc.) and binder (Co or Ni), possibly enclosed in a thin casing of plastic or the like which is removed after compression and before subsequent treatment such as turning.
  • the powder in the hard metal bodies must be compressed to become sufficiently dense and strong so that it can be subsequently machined, for example in a lathe, before being sintered after which further machining is extremely difficult. It is desirable to prevent substances penetrating into the powder which might deteriorate the quality of the bodies, and this is done by using a pressure medium which is harmless when in direct contact with the body and by enclosing the body in a casing during the compression. There is a risk, however, that a small amount of pressure medium will penetrate into the powder body when the casing is removed and for this reason the composition of the pressure medium is also important.
  • a suitable pressure medium is glycerine, possibly with the addition of ethylene glycol.
  • the powder body 13 may also comprise heating elements or thermoelements having straight or curved shape, consisting of one or more central electrical conductors surrounded by a powder of electrically insulating, but heat-conducting type, such as aluminum oxide or quartz.
  • a thin plastic casing, later removable, or a sheathing tube to hold the powder together, sealed at the ends before the compression, may be placed around the body.
  • the powder in these bodies must be strongly compressed and this should be done after the body has been bent to its final shape.
  • the heating element 13 in the case shown is meander formed before the compression.
  • the method can also be used for welding and furnace electrodes, machine components in powder form. hotplates, powder bodies consisting of several layers, etc.
  • a suitable pressure medium of the manufacture of heating elements is water which is electrically conducting and thus permits the usual insulation test in the finished product, but which evaporates and disappears when the element is used.
  • a perforated plate 15 is arranged to permit the passage of pressure medium and below this an elastomeric or flexible membrane or sack 16 is sealingly arranged.
  • the membrane encloses a compression space which must be at least as large as the decrease in total space which takes place in the container 12 when full pressure has been reached in the outer chamber, that is the space at to (sack space) must at least correspond to the compression of the total space in the container 12.
  • the wall may consist of a relatively thin-walled, cylindrical tube.
  • a supporting space l7 axially limited by a wall or support to carry the container and protect the sack 16.
  • the support space 17 may be open at the bottom or limited by a perforated plate 18, net or grid to permit the passage of pressure medium from the outer pressure chamber 19 to the supporting space H7.
  • the container 12 with supporting space l7 and sack 16 is lowered into an outer pressure chamber for gaseous or hydraulic pressure medium, such as hydraulic oil which is water repellent and noncorrosive.
  • gaseous or hydraulic pressure medium such as hydraulic oil which is water repellent and noncorrosive.
  • the container l2 may be positioned or suspended in the chamber H and the latter pressurized to SOD-40,000 atm., for example, 6000 atm. by means of a conventional pump and/or press means 20.
  • the container 12 When the container 12 has been filled with the object and pressure medium, in this case heating element billet and water, and sealed at M after air has been removed, it is lowered into the pressure chamber 11 after which the pressure in the outer chamber is raised to, for example, 6000 atm., and thispressure also operates on the container 12 and its sack 16.
  • the container 12 is compressed and the sack space decreases so that pressure equilibrium is achieved between the outer and inner pressure spaces.
  • the container may possibly also be heated to a certain extent.
  • the bodies 13 are compressed isostatically by the inner-pressure and when the pressure ceases in the chamber 11 the sack space expands again.
  • the degree of compression it may be mentioned that at a pressure of 6000 atm. the container (space and sack space) is compressed to 84 percent of its original volume.
  • the sack space must therefore be at least 16 percent of the inner total volume.
  • the total volume assumes its greatest value and during the isostatic compressure it assumes its minimum volume.
  • the object in'the container is isostatically compressed and becomes uniformly and homo eneously com ressed.
  • Fl 3 shows a container l with a comp etely closed bottom 22 through which at least one tube 23 communicates with the sack space and the container space.
  • the sack 16 may also be attached to sorne other part of the support space 17, for example, around the perforated plate 18.
  • bottom 22 may also be provided with channels at its periphery.
  • the method according to the above may also be used for the manufacture of plastic bodies in which case a billet of base material and curing agent is subjected to isostatic compression, possibly also heat and is thus cured, Liquids may also be subjected to isostatic pressure in order to undergo certain alterations.
  • the above method relates to the separation of two different pressure media for the reasons given above.
  • Method of subjecting bodies to high pressure preferably the manufacture of powder bodies, such as hard metal products, electrical heating elements comprising an electric conductor surrounded by a body of compressed power material and possibly a surrounding, tubular casing, and welding and furnace electrodes, said method comprising isostatic compression, characterized in that objects to be compressed are placed in a hollow container with at least one elastomeric or displaceable wall or bottom, which container is also filled with liquid pressure medium and is sealed and placed in a pressure chamber for hydraulic or pneumatic pressure medium, after which the pressure in the chamber is increased and the container compressed so that the container including liquid pressure medium and objects is also compressed and thus the objects are isostatically compressed.
  • Method of manufacturing powder bodies according to claim 1 characterized in that before compression the powder body is placed in a thin casing of plastic, metal foil or the like, substantially only to keep the powder material together before the compression.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Fluid Mechanics (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Press Drives And Press Lines (AREA)
  • Powder Metallurgy (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)
US771966A 1967-11-08 1968-10-30 Method for isostatic compression, such as the manufacture of powder bodies Expired - Lifetime US3577635A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE15322/67A SE323179B (fr) 1967-11-08 1967-11-08

Publications (1)

Publication Number Publication Date
US3577635A true US3577635A (en) 1971-05-04

Family

ID=20300490

Family Applications (1)

Application Number Title Priority Date Filing Date
US771966A Expired - Lifetime US3577635A (en) 1967-11-08 1968-10-30 Method for isostatic compression, such as the manufacture of powder bodies

Country Status (5)

Country Link
US (1) US3577635A (fr)
AT (1) AT289521B (fr)
DE (1) DE1806608A1 (fr)
GB (1) GB1237779A (fr)
SE (1) SE323179B (fr)

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4094672A (en) * 1975-12-22 1978-06-13 Crucible Inc. Method and container for hot isostatic compacting
US4117367A (en) * 1974-05-13 1978-09-26 U.S. Philips Corporation High-pressure discharge lamp
US4210621A (en) * 1978-03-23 1980-07-01 The Dow Chemical Company Method of applying vermicular expanded graphite composite material
US4212621A (en) * 1979-06-21 1980-07-15 Michelotti Paul E Bladder molding
US4217318A (en) * 1975-02-28 1980-08-12 Honeywell Inc. Formation of halide optical elements by hydrostatic press forging
US4409174A (en) * 1981-12-24 1983-10-11 The United States Of America As Represented By The Secretary Of The Army Method for batch production of isostatically pressed calcium powder discs
US4582682A (en) * 1983-08-11 1986-04-15 Mtu Motoren-Und Turbinen-Union Munchen Gmbh Method of producing molded parts by cold isostatic compression
US4599215A (en) * 1983-11-30 1986-07-08 Luft & Raumfahrt Deutsche Process and device for producing compressed mouldings from loose or sintered metal powder
US4612163A (en) * 1984-09-04 1986-09-16 Nippon Kokan Kabushiki Kaisha Method of molding powders of metal, ceramic and the like
US4744943A (en) * 1986-12-08 1988-05-17 The Dow Chemical Company Process for the densification of material preforms
US4761264A (en) * 1986-06-17 1988-08-02 Nippon Kokan Kabushiki Kaisha Method for molding powders
US4776995A (en) * 1985-03-22 1988-10-11 Fiber Materials, Inc. Method of making a structure
US4810456A (en) * 1986-12-24 1989-03-07 Hewlett-Packard Company Method of preventing shrinkage defects in electrophoretic gel columns
US4836849A (en) * 1987-04-30 1989-06-06 Westinghouse Electric Corp. Oxidation resistant niobium alloy
US4931241A (en) * 1987-08-06 1990-06-05 Ltv Aerospace And Defense Company Method for producing structures by isostatic compression
US5147086A (en) * 1990-08-08 1992-09-15 Kabushiki Kaisha Kobe Seiko Sho Preparation of capsule for use in isostatic pressing treatment
US5227576A (en) * 1991-03-14 1993-07-13 Industrial Materials Technology Method for forming complex patterns in the interior of a pressed part formed of compacted particulate material, and apparatus
EP0603462A2 (fr) * 1992-12-21 1994-06-29 Metal Casting Technology, Inc. Procédé et appareil pour le serrage d'un objet
US5490969A (en) * 1994-06-30 1996-02-13 General Electric Company Mould for isostatic pressing
US5561834A (en) * 1995-05-02 1996-10-01 General Motors Corporation Pneumatic isostatic compaction of sintered compacts
US5816090A (en) * 1995-12-11 1998-10-06 Ametek Specialty Metal Products Division Method for pneumatic isostatic processing of a workpiece
US7967605B2 (en) 2004-03-16 2011-06-28 Guidance Endodontics, Llc Endodontic files and obturator devices and methods of manufacturing same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1081618A (en) * 1912-03-28 1913-12-16 Westinghouse Lamp Co Process of preparing billets of refractory materials.
US3054147A (en) * 1960-12-30 1962-09-18 Paul B Archibald Method for solvent-isostatic pressing
US3313871A (en) * 1964-12-29 1967-04-11 Gen Motors Corp Method and apparatus for hydrostatically compacting metal powders
US3462797A (en) * 1966-11-09 1969-08-26 Atomic Energy Commission Fabrication of elongated products
US3477096A (en) * 1967-07-20 1969-11-11 Nat Forge Co Self-closing vacuum port for dry bag isostatic moulding press

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1081618A (en) * 1912-03-28 1913-12-16 Westinghouse Lamp Co Process of preparing billets of refractory materials.
US3054147A (en) * 1960-12-30 1962-09-18 Paul B Archibald Method for solvent-isostatic pressing
US3313871A (en) * 1964-12-29 1967-04-11 Gen Motors Corp Method and apparatus for hydrostatically compacting metal powders
US3462797A (en) * 1966-11-09 1969-08-26 Atomic Energy Commission Fabrication of elongated products
US3477096A (en) * 1967-07-20 1969-11-11 Nat Forge Co Self-closing vacuum port for dry bag isostatic moulding press

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4117367A (en) * 1974-05-13 1978-09-26 U.S. Philips Corporation High-pressure discharge lamp
US4217318A (en) * 1975-02-28 1980-08-12 Honeywell Inc. Formation of halide optical elements by hydrostatic press forging
US4094672A (en) * 1975-12-22 1978-06-13 Crucible Inc. Method and container for hot isostatic compacting
US4210621A (en) * 1978-03-23 1980-07-01 The Dow Chemical Company Method of applying vermicular expanded graphite composite material
US4212621A (en) * 1979-06-21 1980-07-15 Michelotti Paul E Bladder molding
US4409174A (en) * 1981-12-24 1983-10-11 The United States Of America As Represented By The Secretary Of The Army Method for batch production of isostatically pressed calcium powder discs
US4582682A (en) * 1983-08-11 1986-04-15 Mtu Motoren-Und Turbinen-Union Munchen Gmbh Method of producing molded parts by cold isostatic compression
US4599215A (en) * 1983-11-30 1986-07-08 Luft & Raumfahrt Deutsche Process and device for producing compressed mouldings from loose or sintered metal powder
US4612163A (en) * 1984-09-04 1986-09-16 Nippon Kokan Kabushiki Kaisha Method of molding powders of metal, ceramic and the like
US4776995A (en) * 1985-03-22 1988-10-11 Fiber Materials, Inc. Method of making a structure
US4761264A (en) * 1986-06-17 1988-08-02 Nippon Kokan Kabushiki Kaisha Method for molding powders
WO1988004396A1 (fr) * 1986-12-08 1988-06-16 The Dow Chemical Company Procede de densification d'ebauches de materiaux
US4744943A (en) * 1986-12-08 1988-05-17 The Dow Chemical Company Process for the densification of material preforms
US4810456A (en) * 1986-12-24 1989-03-07 Hewlett-Packard Company Method of preventing shrinkage defects in electrophoretic gel columns
US4836849A (en) * 1987-04-30 1989-06-06 Westinghouse Electric Corp. Oxidation resistant niobium alloy
US4931241A (en) * 1987-08-06 1990-06-05 Ltv Aerospace And Defense Company Method for producing structures by isostatic compression
US5147086A (en) * 1990-08-08 1992-09-15 Kabushiki Kaisha Kobe Seiko Sho Preparation of capsule for use in isostatic pressing treatment
US5227576A (en) * 1991-03-14 1993-07-13 Industrial Materials Technology Method for forming complex patterns in the interior of a pressed part formed of compacted particulate material, and apparatus
EP0603462A2 (fr) * 1992-12-21 1994-06-29 Metal Casting Technology, Inc. Procédé et appareil pour le serrage d'un objet
US5340419A (en) * 1992-12-21 1994-08-23 Metal Casting Technology, Inc. Method and apparatus for densifying an article
EP0603462A3 (fr) * 1992-12-21 1995-02-22 Metal Casting Tech Procédé et appareil pour le serrage d'un objet.
US5490969A (en) * 1994-06-30 1996-02-13 General Electric Company Mould for isostatic pressing
US5561834A (en) * 1995-05-02 1996-10-01 General Motors Corporation Pneumatic isostatic compaction of sintered compacts
US5816090A (en) * 1995-12-11 1998-10-06 Ametek Specialty Metal Products Division Method for pneumatic isostatic processing of a workpiece
US7967605B2 (en) 2004-03-16 2011-06-28 Guidance Endodontics, Llc Endodontic files and obturator devices and methods of manufacturing same
US10052173B2 (en) 2004-03-16 2018-08-21 Guidance Endodontics, Llc Endodontic files and obturator devices and methods of manufacturing same

Also Published As

Publication number Publication date
GB1237779A (en) 1971-06-30
DE1806608A1 (de) 1969-06-26
SE323179B (fr) 1970-04-27
AT289521B (de) 1971-04-26

Similar Documents

Publication Publication Date Title
US3577635A (en) Method for isostatic compression, such as the manufacture of powder bodies
US3015855A (en) Method of and device for making hollow bodies
US1226470A (en) Refractory-metal tube.
US4264556A (en) Thermal isostatic densifying method and apparatus
US4216017A (en) Method and equipment for sintering under pressure
WO1999019101A1 (fr) Systeme et un procede de solidification de poudres
US3363037A (en) High-temperature isostatic pressing of articles
US3061877A (en) High-pressure die
US3613157A (en) Pressure chamber for treating material with high pressure,such as isostatic compression of powder bodies
US3246056A (en) Production of low-permeability, highdensity, carbon and graphite bodies
US3255490A (en) Pressure device
US1286089A (en) Method of producing hollow objects of compressed metallic powder.
US3462797A (en) Fabrication of elongated products
US3567903A (en) Method of bonding particles into unitary bodies
US3365751A (en) High temperature high pressure apparatus
US4999145A (en) Method of forming hybrid arc tubes
JP2986480B2 (ja) 放電焼結装置及びその装置を用いて放電焼結を行う方法
US4440706A (en) Isostatic molding of two-terminal ceramic insulator
US2123778A (en) Electric wire
RU181811U1 (ru) Устройство для электроимпульсного прессования неэлектропроводных порошковых материалов
US3213164A (en) Process for compaction of zeolite powders
US3478423A (en) Pressing and compressing tubular heaters
SU1139564A1 (ru) Способ изготовлени изделий из электропроводных нетермостойких порошковых материалов
US2475321A (en) Molded core
US3873308A (en) Method for the elimination of erosion failures on the surfaces of high pressure-high temperature devices