EP0181696A1 - Production of metallic material - Google Patents

Production of metallic material Download PDF

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Publication number
EP0181696A1
EP0181696A1 EP85307093A EP85307093A EP0181696A1 EP 0181696 A1 EP0181696 A1 EP 0181696A1 EP 85307093 A EP85307093 A EP 85307093A EP 85307093 A EP85307093 A EP 85307093A EP 0181696 A1 EP0181696 A1 EP 0181696A1
Authority
EP
European Patent Office
Prior art keywords
fibres
extrusion
microns
diameter
metallic material
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.)
Withdrawn
Application number
EP85307093A
Other languages
German (de)
English (en)
French (fr)
Inventor
Charles Edmund King
Thomas Edmund Pignon
Alan Arthur Bourne
Simon Neville Balderson
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.)
Johnson Matthey PLC
Original Assignee
Johnson Matthey PLC
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 Johnson Matthey PLC filed Critical Johnson Matthey PLC
Publication of EP0181696A1 publication Critical patent/EP0181696A1/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00—Extruding metal; Impact extrusion
    • B21C23/02—Making uncoated products
    • B21C23/04—Making uncoated products by direct extrusion
    • B21C23/08—Making wire, bars, tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/005—Continuous casting of metals, i.e. casting in indefinite lengths of wire

Definitions

  • This invention relates to the production of metallic material and in particular to the production of metallic fibres having a cross-sectional diameter less than about 50 microns.
  • Metallic fibres having a cross-sectional diameter of less than about 50 microns, preferably less than about 25 microns, are particularly useful for the shielding of electronic components from electromagnetic radiation, particularly in the frequency range 100kHz to 1GHz.
  • Electronic components by which is meant microcomputers and the like, are being used in ever increasing numbers in the control systems of for example aircraft, missiles and land transport vehicles, both civil and military, and in hospital equipment and other areas, and failure of such components due to interference by ambient electromagnetic radiation is recognised as being a potentially catastrophic hazard.
  • Shielding involves either protection of a component from external radiation or prevention of emission of radiation generated by the shielded component from contributing to the ambient radiation.
  • metallic materials may be processed direct from the molten state to form filaments, fibres or particulates, and that such products may have a diameter or minimum dimension of 50 microns or less by a process which involves extrusion of the melt to form a transiently unstable state which is subsequently stabilised by solidification.
  • a process for the production of metallic material comprises extrusion of molten metallic material through an orifice to forma transiently unstable state, and stabilisation of the unstable state by solidification.
  • the direct product of the process is preferably in the form of fibres, although filamentary material or particulates may be produced by varying the conditions.
  • the rate of solidification can be influenced inter alia by the temperature of the ambient atmosphere and of the melt and may determine the structural nature, that is the degree and type of crystallinity, as well as the physical form of the product.
  • the structural nature in turn influences the electrical conductivity and other properties of the product.
  • molten we mean to include slurries of solid material in a molten continuous phase, as well as materials in the 100X molten condition.
  • Metals when in the molten state have very low viscosities, typically substantially less than 10 poise, for example 1.5 poise. At these low viscosities, the dominant intrinsic force acting on an extruded quantity of molten metal is surface tension. Surface tension tends to form the extrudate into a sphere and this form, in the absence of other forces, is regarded as the natural stable state. According to the invention, this state is transiently de-stabilised to form an unstable, preferably fibrous, state which is then stabilised by solidification.
  • De-stabilisation is achieved by applying a pulling force to the extrudate in addition to the pushing force exerted on the molten material to cause extrusion, and maintaining said pulling force until stabilisation by solidification is effected.
  • both the pushing extrusion force and the pulling de-stabilisation force comprise centrifugal force.
  • the molten metallic material may be contained in a rotatable reservoir equipped at the periphery thereof with one or more extrusion orifices. Rotation of the reservoir sets up a centrifugal force in the melt which at a certain angular velocity, depending on the quantity of material in the reservoir, is sufficient to overcome surface tension forces across the mouth of the orifice to initiate extrusion; maintenance of this force causes continued extrusion.
  • the extrudate issues from the orifices initially radially and is subject to a marginally higher centrifugal force compared with that acting within the orifice because of the higher velocity; this constitutes the pulling force which destabilises the extrudate and forms an unstable, preferably fibrous, state.
  • the velocity and hence the centrifugal pulling force increase with increasing fibre length thus continuing the destabilising force on the molten extrudate until stabilisation takes place by solidification.
  • metal in this specification we mean to include metals and alloys and other materials whose viscosity behaviour in the colten state is similar to that of molten metals and which are therefore susceptible of being processed according to the invention. We believe that any metallic material is susceptible of being so processed provided that, in the case of the higher-melting materials, a sufficiently high temperature can be sustained under extrusion conditions.
  • the process according to the invention is distinguished from melt spinning of high-viscosity materials, for example oxide glasses, in that, for the spinning of high-viscosity materials, the orifices are relatively large and surface tension acts to reduce the diameter of the molten fibre. This is a process known as "necking down” but, in contradistinction to the case with low viscosity materials, there is no tendency towards the formation of spheres.
  • the molten high-viscosity material although filamentary, is at all times in a stable state, the stability arising from the combination of surface tension and viscosity forces.
  • the maximum size of the extrusion orifice in the process according to the present invention is dictated mainly by the surface tension of the molten material, in that surface tension forces should act to prevent issue of the material except under extrusion conditions.
  • the preferred maximum orifice size to produce fibres or other products in a fine state is 150 microns, with sizes of 50 microns or below or even 10 microns or below being particularly preferred for the production of very fine products.
  • Fibres formed according to the process of the invention are preferably formed as an integral part of the extrusion process, that is, by the extrudate breaking by being subjected to shear or bending forces or by the applied pulling force exceeding the tensile strength of the extrudate, or by a combination of both. Fibres may be formed for example either by the pulling force -exceeding the tensile strength of the extrudate,and/or by air resistance or an applied draught creating shear forces.
  • the invention is particularly suitable for the production of metallic fibres, filaments or particulates having a diameter of about 50 microns or less, preferably 25 microns or even 10 microns or less.
  • a diameter of about 50 microns or less preferably 25 microns or even 10 microns or less.
  • the temperature of the ambient atmosphere may be controlled in order to influence the rate of solidification.
  • the invention may be used to produce particulates, for example spheroids or ellipsoids, which are the result of the process operating at or near limiting parameters such that surface tension forces are dominant.
  • extruded material is emitted from the extrusion orifices as droplets which may approach or attain the natural stable state in flight before stabilisation by solidification.
  • the invention may be used to produce filaments, that is, fibres of long and indefinite length.
  • the aspect ratio (length/diameter) of fibre is of importance because, for a given conductivity level, the metal loading required may be reduced with fibres of high aspect ratio.
  • the diameter of fibres produced according to the process of the invention is readily controllable by selecting the appropriate extrusion orifice diameter.
  • the length of the fibres is controllable, within limits set by air resistance and other external influences, by the angular velocity, in that for a given extrusion temperature and for all angular velocities greater than the minimum velocity required for extrusion to take place (called the "critical" angular velocity), the fibre length decreases with increasing velocity.
  • the aspect ratio may readily be controlled.
  • the aspect ratio should be greater than 10:1, preferably greater than 50:1.
  • the desirable maximum fibre length is determined by the processing conditions of incorporating the material into a polymer matrix, since these conditions may cause breakage of long fibres, depending on their ductility. It is considered that for fibres of normal ductility the longest practicable fibre length is approximately 1 cm in the matrix, although fibres of exceptionally high ductility may undergo elongation during polymer processing. For an aspect ratio of 100:1, the diameter required for a 1 cm fibre would be 100 microns and this is readily achievable by the process according to the invention.
  • the fibre length may be reduced to 2.5 mm or less while still retaining an aspect ratio of 100:1, or alternatively the fibre length may be held at 1 cm to provide an aspect ratio of 400:1.
  • Aspect ratios in the range 50 to 500:1 are preferred, although aspect ratios up to about 3,000:1 may be realisable using the process according to the invention.
  • this aspect ratio we regard the product as being filamentary, that is to say, in the form of continuous fibres or strands of indefinite length.
  • the present invention also provides filaments fibres and particulates of metallic material when produced by the process according to the invention, in particular particulates and filaments having a diameter of 50 microns or less, preferably 25 microns or less, and fibres having an aspect ratio ip the range 10:1 to 3,000:1, preferably 50:1 to 500:1.
  • Fibres according to the invention may optionally be coated or treated before being incorporated into plastics or other materials to provide a material suitable for electromagnetic shielding.
  • Thermoplastic plastics materials are preferred.
  • the fibres may be incorporated into other binders or matrices for electromagnetic shielding or other purposes, particularly where it is desired to provide a continuous electrically conductive path therethrough.
  • Plastics or other materials containing fibre according to the invention may be pigmented or otherwise coloured without the presence of the fibre creating undue influence on the pigmentation or colouration.
  • Fibre produced according to the invention is ductile, that is,not embrittled or work hardened, and is thus eminently suitable for satisfactory incorporation into plastics or other materials without breakage of the fibre.
  • ductile fibre causes less damage to equipment, for example moulds, used to process the material.
  • segregated network is meant a semi-ordered arrangement of fibres, being neither randomly orientated nor highly aligned, and in this condition the metal loading may be reduced to a minimum.
  • Metal loadings of or below about 1% by volume are adequate with fibre having a diameter below about 25 microns, for example 15 microns, in a segregated network within a plastics or other material, and lower levels are adequate with smaller diameter or higher aspect ratio fibre.
  • the invention also provides a composite material suitable for electromagnetic shielding and comprising fibre according to the invention incorporated in a binder or matrix, especially a plastics material.
  • a composite material suitable for electromagnetic shielding and comprising fibre according to the invention incorporated in a binder or matrix, especially a plastics material.
  • Such composite materials are preferably for structural use although may be for coating use.
  • the fibres form a segregated network within the binder or matrix.
  • the invention provides apparatus for the production of metallic material; the apparatus comprising means for extrusion of molten metallic material through an orifice, whereby the extrudate is formed into a transiently unstable state which is subsequently stabilised by solidification.
  • the material so produced is in the form of fibre, although it may be filamentary or particulate.
  • the extrusion means preferably comprises a rotatable reservoir for holding a quantity of molten metallic material and equipped at the periphery thereof with one or more extrusion orifices, which may be of 150 microns or less diameter, more preferably 50 microns or less or even 10 microns or less.
  • extrusion proceeds under centrifugal force set up in the molten metallic material by rotation of the reservoir and the unstable state is formed by a pulling force inherent in the extrudate and also derived from centrifugal force.
  • heater elements, thermocouples or other temperature measuring devices and the like may be carried by the reservoir.
  • the apparatus or parts thereof are preferably insulated or otherwise adapted to minimise heat losses.
  • a receptacle preferably surrounds the apparatus to receive solidified product.
  • apparatus is shown generally at 10 and consists of a circular reservoir 11 for holding molten metallic material and defined by upper and lower plates 12 and 13 respectively, each having a central aperture and bolted together by bolts 14 carried in holes 15 which are tapped in plate 13.
  • the aperture in plate 12 constitutes the mouth of the reservoir.
  • Notches 16 are provided in lip 17 of plate 12; these notches form in conjunction with corresponding lip 18 of plate 13 extrusion orifices at the periphery of the reservoir.
  • the notches and orifices (the latter shown at 19 in Fig. 2) are shown, oversize in the drawings for the sake of clarity.
  • upper and lower plates 12 and 13 is secured by means of bolts (not shown) through holes 20 formed in lower plate 13 to rotatable shaft 21 via suitable bushing means to close the aperture in lower plate 13.
  • the shaft is driven by a suitable motor (not shown).
  • the apparatus as shown in Fig. 1 is contained in a drum to allow a free flight path for the extruded material of approximately 10 cm.
  • metallic material is introduced into the mouth of the reservoir.
  • the material is either in the molten state or is heated to above its melting temperature by heating elements associated with the reservoir.
  • the reservoir is rotated and the molten material, because of its low viscosity, automatically distributes itself under the influence of centrifugal force evenly around the interior periphery of the reservoir.
  • the critical angular velocity is reached, extrusion of molten material through the orifices begins. (The critical angular velocity is a function of the surface tension of the molten material, the amount of molten material in the reservoir, the diameter of the orifice and the radius of the reservoir).
  • the extrudate emerging from the orifices is subject to a pulling force also derived from centrifugal force which overcomes the tendency to form a sphere and produces instead an unstable state which is ultimately stabilised by solidification.
  • the unstable state preferably comprises fibres which are cropped from the extrudate under the influence of bending due to atmospheric drag.
  • top plates 12 may be held in stock, each containing notches of a different size from the other plates, to allow for the use of different sizes of extrusion orifice.
  • the reservoir may be equipped with thermocouples and so or., electrically connected via slip rings mounted around the shaft 21.
  • extrusion orifices of diameter down to about 5 microns may be provided by drilling in stainless steel foil, for example, or by utilising electron microscopy apertures.
  • material is produced having a diameter approximately 0.25 to 0.9 times that of the extrusion orifice from which it issues, depending on conditions.
  • the physical form of the material is generally smooth although nodes or other undulations may occur at intervals. These appear to be influenced by the extrusion conditions and are therefore controllable.
  • a rotation speed of 1160 r.p.m. (equivalent to a periphery speed of 800 cm/sec) produced fibres of length 4 to 9 mm and a diameter of 73 microns
  • a rotation speed of 2180 r.p.m. (equivalent to a periphery speed of 1500 cm/sec) produced fibres of length 2 to 6 mm and a diameter of 66 microns.
  • the temperature as well as the speed influence the length of the fibres and, while we have not measured precise extrusion temperatures, the initial temperature of the melt was 400°C at 1160 r.p.m. and 380°C at 218°C.
  • fibres of lead/tin eutectic i.e. 62% Sn, 38% Pb
  • initial temperature 460°C.
  • rotation speed 1660 r.p.m. equivalent to a periphery speed of 1100 cm/sec.
  • fibres were formed having a length of 1 to 15 mm and a diameter of 18 microns.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Fibers (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Powder Metallurgy (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Non-Insulated Conductors (AREA)
EP85307093A 1984-10-08 1985-10-03 Production of metallic material Withdrawn EP0181696A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8425384 1984-10-08
GB8425384 1984-10-08

Publications (1)

Publication Number Publication Date
EP0181696A1 true EP0181696A1 (en) 1986-05-21

Family

ID=10567863

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85307093A Withdrawn EP0181696A1 (en) 1984-10-08 1985-10-03 Production of metallic material

Country Status (9)

Country Link
EP (1) EP0181696A1 (fi)
JP (1) JPS61123448A (fi)
KR (1) KR860003063A (fi)
AU (1) AU4820585A (fi)
DK (1) DK444985A (fi)
FI (1) FI853823L (fi)
IL (1) IL76549A0 (fi)
NO (1) NO853965L (fi)
ZA (1) ZA857588B (fi)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0736942B2 (ja) * 1987-12-08 1995-04-26 東洋紡績株式会社 一方向樹枝状組織を有する高靭性及び高柔軟性の金属繊維

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1592140A (en) * 1924-08-22 1926-07-13 Peake Wire-spinning machine
US2825108A (en) * 1953-10-20 1958-03-04 Marvaland Inc Metallic filaments and method of making same
US3466352A (en) * 1967-12-18 1969-09-09 Corbett Ass Inc Process for producing fibers
US3543831A (en) * 1967-01-09 1970-12-01 United Aircraft Corp Electrostatic coatings
US3658979A (en) * 1965-03-30 1972-04-25 Monsanto Co Method for forming fibers and filaments directly from melts of low viscosities
US3861452A (en) * 1971-05-10 1975-01-21 Establissements Michelin Raiso Manufacture of thin, continuous steel wires
US3960200A (en) * 1972-11-14 1976-06-01 Allied Chemical Corporation Apparatus for liquid quenching of free jet spun metal
JPS59107752A (ja) * 1982-12-10 1984-06-22 Kubota Ltd 金属細線製造装置
EP0117884A1 (en) * 1983-03-04 1984-09-12 Toray Industries, Inc. Lead fibers, a method of producing same and radiation shielding materials comprising same

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1592140A (en) * 1924-08-22 1926-07-13 Peake Wire-spinning machine
US2825108A (en) * 1953-10-20 1958-03-04 Marvaland Inc Metallic filaments and method of making same
US3658979A (en) * 1965-03-30 1972-04-25 Monsanto Co Method for forming fibers and filaments directly from melts of low viscosities
US3543831A (en) * 1967-01-09 1970-12-01 United Aircraft Corp Electrostatic coatings
US3466352A (en) * 1967-12-18 1969-09-09 Corbett Ass Inc Process for producing fibers
US3861452A (en) * 1971-05-10 1975-01-21 Establissements Michelin Raiso Manufacture of thin, continuous steel wires
US3960200A (en) * 1972-11-14 1976-06-01 Allied Chemical Corporation Apparatus for liquid quenching of free jet spun metal
JPS59107752A (ja) * 1982-12-10 1984-06-22 Kubota Ltd 金属細線製造装置
EP0117884A1 (en) * 1983-03-04 1984-09-12 Toray Industries, Inc. Lead fibers, a method of producing same and radiation shielding materials comprising same

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENTS ABSTRACTS OF JAPAN, vol. 8, no. 227 (M-332) [1664], 18th October 1984; & JP - A - 59 107 752 (KUBOTA TEKKO K.K.) 22-06-1984 *

Also Published As

Publication number Publication date
KR860003063A (ko) 1986-05-19
JPS61123448A (ja) 1986-06-11
FI853823L (fi) 1986-04-09
NO853965L (no) 1986-04-09
AU4820585A (en) 1986-04-17
DK444985D0 (da) 1985-10-01
FI853823A0 (fi) 1985-10-02
IL76549A0 (en) 1986-02-28
DK444985A (da) 1986-04-09
ZA857588B (en) 1986-08-27

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Inventor name: BOURNE, ALAN ARTHUR

Inventor name: BALDERSON, SIMON NEVILLE

Inventor name: PIGNON, THOMAS EDMUND

Inventor name: KING, CHARLES EDMUND