US3679807A - Die-furnace, especially for the fabrication of sintered products - Google Patents

Die-furnace, especially for the fabrication of sintered products Download PDF

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Publication number
US3679807A
US3679807A US141800A US3679807DA US3679807A US 3679807 A US3679807 A US 3679807A US 141800 A US141800 A US 141800A US 3679807D A US3679807D A US 3679807DA US 3679807 A US3679807 A US 3679807A
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US
United States
Prior art keywords
die
furnace
packing material
assembly
product
Prior art date
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Expired - Lifetime
Application number
US141800A
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English (en)
Inventor
Jacques Carcey
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.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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Publication of US3679807A publication Critical patent/US3679807A/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/06—Induction heating, i.e. in which the material being heated, or its container or elements embodied therein, form the secondary of a transformer
    • 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
    • B22F3/003—Apparatus, e.g. furnaces
    • 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
    • B22F3/14—Both compacting and sintering simultaneously
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/18—Charging particulate material using a fluid carrier

Definitions

  • This invention relates to an apparatus comprising a pressure die which is primarily intended to permit the compression of a powder to be sintered and a furnace which is combined with the die and serves to heat said powder to a high temperature, all the conditions which are necessary for the sintering process being consequently brought together within a Single apparatus.
  • the chief aim of the invention is to increase the performances of conventional dies, to permit at the same time the possibility of a larger geometry for the parts employed and, while improving the uniformity of temperatures through the sintered product, to limit the thermal gradients between the heating source and the product through the die itself, thereby reducing the differences in thermal expansion during operation as a result of temperature variations.
  • a further object of the invention is to provide a simple and relatively inexpensive assembly comprising a die of refractory material which is capable of being employed a large number of times without any danger of seizure, in particular at the time of displacement of plungers which carry out within the die the compression of the product to be sintered.
  • a further object of the invention is to permit immediate application of the die-furnace under consideration to all the usual sintering processes and especially to those in which the compression of the product to be sintered is an isostatic compression obtained by means of a fusible metal or pressure-transmitting agent as well as to the processes in which said isostatic compression is accompanied by mechanical creep or plastic flow as a result of deformation and reduction in volume of an intermediate casing.
  • a die-furnace as constructed in accordance with the invention also has a number of other related features which are preferably to be considered in combination but could also be considered separately and are primarily concerned with the following aspects:
  • the banding assembly is constituted by a series of superposed open loops insulated from each other and associated with mechanical means for positional locking of each loop with respect to the next in order to form a rigid non-deformable block
  • the primary winding of the heating device is constituted by a tubular inductor which is cooled in particular by water, the primary circuit being passed through the banding assembly by means of a coaxial passage, the external portion of said passage being connected to ground in order to prevent induction phenomena within the banding assembly
  • the secondary circuit comprises at least two concentric loops in closed relation the metallic sleeve of the secondary circuit is provided with cut-out portions in order that the compression forces applied by the banding assembly should be transmitted to the die by means of the packing material
  • the packing material is constituted by a refractory substance and especially by concrete made from an insulating cement mixed with grains of high-density alumina.
  • the concrete which is employed has a variable particle-size distribution within its mass between the banding assembly and the die the die-furnace is rigidly fixed to the cooled internal wall of a leak-tight outer enclosure for creating a vacuum, said enclosure being provided with an opening for establishing a communication with a pump set and dynamic seals providing a leak-tight passage through the enclosure wall for plungers which serve to compress the product to be sintered and penetrate axially into the die the product to be sintered can be surrounded if necessary by a deformable casing which is placed directly within the die.
  • the reference numeral 1 designates the apparatus or die-furnace as a whole comprising a die 2 of a type which is known per se and designed in the form of a heat-resisting circular cylinder which is open at both ends and formed of sintered alumina or any other material which is capable of carrying out this function.
  • a product 3 to be sintered at a suitable temperature and pressure is placed within said cylinder and is either a ceramic or metallic refractory powder which has been pre-densified in the cold state in the most suitable manner or a powder of the same type which is placed within a sealed staticvacuum enclosure.
  • the diefumace under consideration is provided at its periphery with a banding assembly 4 which will be described in greater constructional detail with reference to FIG. 2, said assembly being so arranged that a system of forces directed towards the axis of the die 2 is continuously applied to this latter.
  • the region which is located between the die 2 and the banding assembly 4 is filled with packing material 5 preferably consisting of refractory concrete which, in the exemplified embodiment herein described, is formed of insulating cement and grains of high-density alumina.
  • the die-furnace l is associated with an induction heating device constituted by a primary winding 6 and a completely closed secondary circuit which is formed in the embodiment illustrated in FIG. 1 by means of two coaxial sleeves 7 and 8 which surround the die 2 and are joined together by means of radial portions 9 and 10.
  • the primary winding 6 is preferably of the cooled inductor type consisting of a tubular conductor 12, a cooling fluid 11 which is preferably water being circulated within said conductor.
  • the primary winding 6 is passed through the banding assembly 4 by means of a coaxial device 14 which is also cooled the highfrequency current is admitted at the center the return to the exterior which is insulated from the admission by means of a suitable insulator 13 is preferably the high-frequency ground. This penetration device prevents any stray induction within the banding assembly 4.
  • the external banding assembly 4 is constituted by means of a series of open and superposed loops 15 which are metallic, for example, and insulated from each other, said loops being disposed in an irregular manner and associated with interlocking means constituted by the packing material and/or parts of high-density alumina which serve to secure the abovementioned loops with respect to each other in order to constitute a rigid non-deformable block at the periphery of the die-furnace.
  • the sleeves 7 and 8 which constitute the secondary circuit of the heating device are provided with a series of openings such as 17 and 18 which are suitably distributed across the surface of said sleeves.
  • the die-furnace can also be arranged so that the external surface of the banding assembly 4 should be coupled to the wall 19 of a sealed enclosure 20 which completely surrounds said assembly and is connected by means of a duct 21 to a pump set (not illustrated) which serves to create a vacuum within the enclosure and especially around the product 3 to be sintered which is placed within the die 2.
  • the enclosure 20 is associated with two plungers which are designated respectively by the reference numerals 22 and 23 and pass through the end-walls 24 and 25 of said enclosure with interposition of dynamic seals 26 and 27, said plungers 22 and 23 being adapted to engage axially within the die 2.
  • temperature-measuring instruments and especially thermocouples 28 are placed at different points of the die-furnace l and especially within blind-end bores 29 which are formed within the die 2 itself.
  • the practical construction of the equipment makes it necessary to ensure that the winding 6 should pass through the enclosure wall by means of a vacuum-tight coaxial passage 30.
  • the sealed enclosure 20 could be dispensed with and the product 3 to be sintered could be simply placed within a closed vacuum-type casing 31 which maintains a static vacuum within the product, in which case the die-furnace is placed in the surrounding atmosphere.
  • the compression of the product 3 is naturally carried out in a static vacuum.
  • the axial thrust of the plungers which penetrate into the die is converted by means of a metal which is capable of melting at the operating temperature into an isostatic pressure on the product which is accordingly subjected to simple compression, thereby resulting in rearrangement of the product by plastic flow.
  • the axial thrust is converted by means of a pressure-transmitting agent which can be either a fusible metal or a refractory powder at the operating temperature into isostatic compression on the product together with a plastic flow action produced by means of a deformation and reduction in volume of a deformable casing which surrounds the product to be sintered.
  • the above mentioned operations can be carried out according to requirements either in a dynamic vacuum or in a static vacuum
  • the last-mentioned solution has the advantage of simplification of the apparatus as a whole and especially of removing the problems involved in degassing of the packing material of the die-furnace itself.
  • the product to be sintered under pressure is advantageously pre-densified in the cold state and in a vacuum, then placed within a compression casing which is deformable at operating temperatures, said casing being surrounded by suitable envelopes or shells which contain a pressure-transmitting agent and prevent any diffusion of this latter into the product itself
  • this second method can be carried out either in a static or dynamic vacuum.
  • the action of the plungers 22 and 23 on the product 3 within the die 2 produces high radial thrust forces on the internal surface of said die.
  • this latter usually has low tensile strength and consequently high mechanical fragility.
  • This disadvantage is completely removed by virtue of the external banding assembly 4 and by reason of the fact that this latter produces action on the die 2 through the intermediary of the packing material 5 while applying radial forces which are readily transmitted through the openings 17 and 18 formed in the sleeves 7 and 8 of the secondary heating circuit.
  • the die-furnace under consideration has another significant advantage which arises from the particular design concept of the heating device itself and makes it possible especially to limit the value of the thermal gradient within the die 2 proper.
  • the heat build-up in the charging loop of the secondary circuit as a result of a resistive effect and the simultaneous heat build-up in the assembly consisting of product and casing under the induction heating effect makes it possible to maintain the die in a uniform temperature zone.
  • the product itself may be heated by induction by means of the secondary circuit on condition that said product has the property of conductivity at the operating frequency, in which case the heat buildup takes place within the product itself.
  • the die-furnace under consideration makes it possible under the conditions described in the foregoing to contemplate either continuous or non-continuous sintering of any ceramic, refractory or metallic material at high temperatures which can attain 1500" C or more under pressures ranging from a few Kg/cm" to 2 T/cm or more.
  • the design concept of the apparatus as a whole is such that hot delivery of the sintered product from the mold can readily be carried out while retaining said product in a zone which is not subjected to mechanical stresses during cooling.
  • the furnace makes it possible to form on the product a uniform-temperature zone which may be localized within the product itself if necessary.
  • the structural design of the primary winding and of its grounded coaxial passage within the banding assembly prevents stray-induction effects, in particular within the loops of the banding assembly.
  • the packing material can be chosen so as to have a different particle-size distribution according to the zones which are occupied and to constitute in particular an insulating material which plays a contributory role in improving the interlocking of the loops of said assembly.
  • the design concept of the heating device permits efficient banding by virtue of its transformer and cut-out portions while at the same time carrying out either direct sintering of metallic materials under pressure or alternatively sintering of refractory or ceramic substances if use is made of a sealed vacuum enclosure or an unsealed enclosure of metallic type.
  • the die-furnace also has greater potentialities on the one hand as a result of banding by consolidation through the heating device and on the other hand by virtue of the uniformity of temperatures in the die and in the product as achieved by simultaneous heat build-up in the charging loop of the secondary circuit and in the assembly consisting of product and casing. Hot take-out, continuous pressing, incorporation with a pressing and evacuating system or incorporation with a standardized modular assembly for hot-pressing can be contemplated.
  • a die-furnace especially for the fabrication of sintered products comprising a die of a type known per se of a cylindrical element of refractory material, a banding assembly surrounding said die externally, packing material between said die and said banding assembly transmitting to said die the radial force produced by said assembly, an induction heating device within said packing material a primary winding for said device having circular turns connected externally of the die-furnace to a high-frequency electric power supply and a completely closed secondary circuit for said device in which a current is induced by said primary winding and surrounding and heating the external surface of said die and coaxial with said primary winding.
  • banding assembly comprises a plurality of superposed open loops insulated from each other and interlocked by said packing material to form a rigid non-deformable block.
  • loops are a metallic sleeve having cut-out portions whereby the compressive forces produced by said banding assembly are transmitted to said die by said packing material.
  • a die-furnace according to claim 1 said die-furnace being rigidly fixed to the cooled internal wall of a leak-tight outer enclosure supporting a vacuum, an opening in said enclosure communicating with a pump set and a leak-tight passage through said enclosure for plungers compressing the product to be sintered and axially entering said die.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Furnace Details (AREA)
  • Press-Shaping Or Shaping Using Conveyers (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
US141800A 1970-05-12 1971-05-10 Die-furnace, especially for the fabrication of sintered products Expired - Lifetime US3679807A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7017174A FR2087235A5 (xx) 1970-05-12 1970-05-12

Publications (1)

Publication Number Publication Date
US3679807A true US3679807A (en) 1972-07-25

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Family Applications (1)

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US141800A Expired - Lifetime US3679807A (en) 1970-05-12 1971-05-10 Die-furnace, especially for the fabrication of sintered products

Country Status (7)

Country Link
US (1) US3679807A (xx)
BE (1) BE766576A (xx)
CH (1) CH532440A (xx)
DE (1) DE2123105A1 (xx)
FR (1) FR2087235A5 (xx)
GB (1) GB1313462A (xx)
NL (1) NL7106443A (xx)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5134260A (en) * 1990-06-27 1992-07-28 Carnegie-Mellon University Method and apparatus for inductively heating powders or powder compacts for consolidation
US5987054A (en) * 1997-02-10 1999-11-16 Inductotherm Corp. Induction coil and coreless induction furnace employing same
US20050123430A1 (en) * 2003-12-09 2005-06-09 Xian Yao Method for forming ultra hard sintered compacts using metallic peripheral structures in the sintering cell
US8479552B1 (en) * 2007-05-22 2013-07-09 Temper Ip, Llc Method and die for forming a tubular blank into a structural component
US9174263B2 (en) 2012-05-23 2015-11-03 Temper Ip, Llc Tool and shell using induction heating
US9656317B1 (en) 2014-02-03 2017-05-23 Temper Ip, Llc Stamp, mold, quench of aluminum and magnesium sheet

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2437127A (en) * 1945-10-01 1948-03-02 Hpm Dev Corp Apparatus for powder metallurgy
US2908739A (en) * 1956-06-14 1959-10-13 Siemens Ag Water cooled crucible for high frequency heating
US3303258A (en) * 1963-06-20 1967-02-07 Junker Otto Vacuum induction furnace
US3311695A (en) * 1964-10-09 1967-03-28 Ohio Crankshaft Co Coil assembly for an induction melting furnace and method of making same
FR1548603A (xx) * 1967-10-25 1968-12-06

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2437127A (en) * 1945-10-01 1948-03-02 Hpm Dev Corp Apparatus for powder metallurgy
US2908739A (en) * 1956-06-14 1959-10-13 Siemens Ag Water cooled crucible for high frequency heating
US3303258A (en) * 1963-06-20 1967-02-07 Junker Otto Vacuum induction furnace
US3311695A (en) * 1964-10-09 1967-03-28 Ohio Crankshaft Co Coil assembly for an induction melting furnace and method of making same
FR1548603A (xx) * 1967-10-25 1968-12-06

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5134260A (en) * 1990-06-27 1992-07-28 Carnegie-Mellon University Method and apparatus for inductively heating powders or powder compacts for consolidation
US5987054A (en) * 1997-02-10 1999-11-16 Inductotherm Corp. Induction coil and coreless induction furnace employing same
US20050123430A1 (en) * 2003-12-09 2005-06-09 Xian Yao Method for forming ultra hard sintered compacts using metallic peripheral structures in the sintering cell
US7368079B2 (en) * 2003-12-09 2008-05-06 Smith International, Inc. Method for forming ultra hard sintered compacts using metallic peripheral structures in the sintering cell
US8479552B1 (en) * 2007-05-22 2013-07-09 Temper Ip, Llc Method and die for forming a tubular blank into a structural component
US9032772B2 (en) 2007-05-22 2015-05-19 Temper Ip, Llc Method and process for forming a product
US9174263B2 (en) 2012-05-23 2015-11-03 Temper Ip, Llc Tool and shell using induction heating
US10307810B1 (en) 2012-05-23 2019-06-04 Temper Ip, Llc Tool and shell using induction heating
US11338344B1 (en) 2012-05-23 2022-05-24 Temper Ip, Llc Tool and shell using induction heating
US9656317B1 (en) 2014-02-03 2017-05-23 Temper Ip, Llc Stamp, mold, quench of aluminum and magnesium sheet

Also Published As

Publication number Publication date
GB1313462A (en) 1973-04-11
FR2087235A5 (xx) 1971-12-31
NL7106443A (xx) 1971-11-16
BE766576A (xx) 1971-09-16
DE2123105A1 (de) 1971-11-25
CH532440A (fr) 1973-01-15

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