Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N60/00—Superconducting devices
  • H10N60/01—Manufacture or treatment
  • H10N60/0184—Manufacture or treatment of devices comprising intermetallic compounds of type A-15, e.g. Nb3Sn
• • 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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S505/00—Superconductor technology: apparatus, material, process
  • Y10S505/80—Material per se process of making same
  • Y10S505/812—Stock
  • Y10S505/814—Treated metal
• • 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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S505/00—Superconductor technology: apparatus, material, process
  • Y10S505/80—Material per se process of making same
  • Y10S505/815—Process of making per se
  • Y10S505/822—Shaping
• • 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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S505/00—Superconductor technology: apparatus, material, process
  • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
  • Y10S505/884—Conductor
  • Y10S505/887—Conductor structure
• • 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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S505/00—Superconductor technology: apparatus, material, process
  • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
  • Y10S505/917—Mechanically manufacturing superconductor
  • Y10S505/918—Mechanically manufacturing superconductor with metallurgical heat treating
  • Y10S505/919—Reactive formation of superconducting intermetallic compound
• • 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
  • Y10T29/49014—Superconductor

Definitions

• ABSTRACT A method for producing a composite superconducting wire including one or more strands of high-field Type 11 superconductor embedded in a conductive matrix of normal material and the product of the said method.
• a composite body is prepared which includes a matrix in which are embedded one or more rods of a metal which is capable of forming a high-field Type II superconductor upon high temperature extruded to an intermediate diameter. and then is hot drawn to a final diameter at temperatures exceeding about 100C. by multiple passes through drawing dies. the composite being reduced in crosssectional area approximately 15 to 2092 per draw. in a preferred mode of practicing the invention.
• the rods comprise vanadium or niobium. with the matrix being respeo tively gallium-bronze or tin-bronze. and the supercoir ductive strands being formed by high temperature diffusion of the gallium or tin into the rods subsequent to drawing.
• Composite superconducting wire characterized by multiple longitudinally extending strands of high-field superconducting alloy in a surrounding matrix of copper or similar good thermal conductor, has found increasing application for use in the coils of superconducting magnets capable of producing extremely high magnetic fields.
• Composite superconducting wire of the foregoing type is typically produced by initial preparation of a billet comprised of a copper extrusion can which contains a plurality of close-packed hexagonally-formed rod inserts.
• Each such rod insert may typically consist of a central round rod of a Type ll superconductor, such as a niobium-titanium alloy, surrounded by one or more concentric tubes of high purity OFHC copper, the unit being drawn to a cohesive hexagonal bar before insertion into the extrusion can.
• the can containing the packed rods is suitably sealed at its ends and thereupon subjected to extrusion or swaging and drawing opera tions, which gradually reduce the diameter of the billet 1 and of the contained inserts.
• the final very small diameter fine wire achieved by this technique contains the individual strands of the superconductor alloy in the surrounding copper matrix.
• the drawing operations cited are, for reasons to be set forth below, conducted at room temperature, and during the course of such mechanical working of the said billet, annealing may be required between draws, in order to remove the effects of cold work and maintain the required ductility for additional reduction in area.
• the billet is appropriately reduced, in a manner similar to that indicated for the Nb-Ti composite wire, and after the desired fine diameter composite wire is achieved, the resultant product is subjected to a prolonged heating schedule which serves to diffuse the gallium or tin into the central conductor to form the desired superconducting alloy thereat.
• the Lorentz force acting on a flux line is such that if such line is not pinned to the wire, it will start to move, generating localized heating which may initiate transition to the normal state.
• lattice imperfections introduced by plastic deformation, and inhomogeneities in alloy composition are capable of providing pinning sites that restrain movement of the flux lines.
• Cold-working techniques utilized in accordance with the foregoing processes serve to generate the desired lattice imperfections thereby providing pinning sites.
• the rods of the composite body are an alloy-type material, such as Nb-Zr or Nb-Ti, encased in a pure copper matrix
• the requirements for annealing are not too stringent.
• intermetallic compounds such as V Ga or Nb sn
• the Ga-bronze or Snbronze matrices present in the composites being drawn work-harden very rapidly. Therefore, the composite being worked will typically require intermediate an nealing after each two or three draws or every 40% reduction in cross-sectional area where cold-drawing is indeed utilized.
• the complex process of producing small diameter multifllament superconducting wire of which the annealing is but a part includes the steps of wire-drawing, placing the wire in an annealing furnace, annealing the wire in an inert atmosphere for a period of time, cooling the wire in a manner to prevent surface oxidation, stringing the annealed wire through a wire-drawing machine, drawing the wire, and then repeating the entire operation after the material has work hardened. Accordingly, it will be appreciated that the time required where annealing must be effected every two or three draws, together with the attendant expense, renders a process such as this completely economically prohibitive for practical production operations.
• a composite billet is initially formed, consisting of a conductive matrix of normal material in which are embedded one or more rods of a metal which is capable of forming a high-field Type II superconductor upon high temperature reac tion with a component of said matrix.
• the metallic rods are embedded in a matrix of copper, or other good thermal conductor such as silver or gold, containing in alloy the second element of the superconducting strands to be formed.
• the composite billet is extruded to an intermediate diameter, and thereafter drawn at temperatures over about lC and typically in the ap proximate range of l00 to 300C, to a final diameter, by reducing the cross-sectional area approximately -20% per draw.
• the upper temperature limit is controlled by the stability of the wire drawing lubricant and ultimately by oxidation of the surface of the wire.
• high temperature lubricants such as molybdenum disulfide or graphite, and an inert gas shield
• the high-field superconductors such as the in termetallic compounds V Ga and Nb Sn, are formed after drawing by high temperature reaction and diffusion.
• the drawing process may be effectively carried out without frequent intermediate annealing: in general such an anneal is required not more frequently than every 10 to 12 draws.
• a pro-annealed ll0-strand vanadium in Ga-bronze matrix wire (l4.85% Ga overall) can be hot-drawn from 57 to 13 mils at 218C with only one additional intermediate anneal.
• the resultant product is found to be essentially equivalent to wire formed from the same billet where such billet is cold-drawn.
• the initial stages of the method in accordance with the present invention may be substantially identical with methodology utilized in the prior art for preparation of composite superconducting wire.
• the primary requirement for the billet is that it include a conductive matrix of normal material which encases or surrounds longitudinally extending rods of a material which is capable of forming the desired high-field Type I] superconductor upon high temperature reaction with a component of the matrix.
• the billet can be assembled in any practical manner, which will yield the aforementioned construction.
• a body of the desired matrix alloy may be initially cast and longitudinal passages then formed therein by boring or drilling, with the rods thereupon being inserted within the passages to provide the desired billet construction.
• Bronze alloys constitute the matrix material employed in this preferred embodiment.
• a bronze matrix is defined as a copper based alloy containing the material which forms the desired high-field Type [I superconductor as the principal added element.
• a billet is initially prepared including a plurality of close-packed rods mounted within a bronze extrusion can, which billet is evacuated and sealed at both ends prior to extrusion and drawing.
• Methodology of this general type is disclosed at various places in the art, including, for example, in U.S. Pat. No. 3,618,205.
• the composite wire to be formed is of the preferred type, including multiple strands of a Type II high-field intermetallic compound superconductor in a bronze matrix
• hexagonally-shaped metallic rods are initially prepared including one element of the superconductor material to be formed.
• the rods in particular, comprise a central core of the metallic element contained within a surrounding tubular cladding of a bronze alloy, e.g., copper and the other element of the superconductor.
• the rods will consist of a core of vanadium surrounded by a tubular cladding of Ga bronze, i.e., copper containing about l570 gallium.
• Ga bronze i.e., copper containing about l570 gallium.
• a plurality of such rods are thus close-packed (the rods are initially worked to a hexagonal cross-section) within the surrounding extrusion can, so that the resulting billet consists in the aggregate of, for example, vanadium rod cores surrounded by a matrix of Ga bronze.
• the initial billet will essentially comprise longitudinally extending elements of niobium encased within a matrix of Sn-bronze.
• Billets of the type described above may be initially extruded at relatively elevated temperatures, e.g., on the order of 500C, and may then be cold-drawn at room temperature to an intermediate diameter, from which point hot-drawing to a final desired diameter is accomplished.
• relatively elevated temperatures e.g., on the order of 500C
• cold-drawn at room temperature to an intermediate diameter, from which point hot-drawing to a final desired diameter is accomplished.
• EXAMPLE I A 1.050 inch diameter extruded billet containing 1 l0 strands of vanadium in a gallium-bronze (about 15% Ga by weight) matrix was cold drawn to 0.205 inch diameter using a reduction in area of about 13-20% per draw. Work-hardening of the matrix required annealing in an argon atmosphere for one hour at 500C after every 2 or 3 draws.
• the 0.205 inch wire was then drawn down to 8 mils in accordance with the method of this invention by the following schedule:
• V Ga reaction zone area was derived from planimeter measurements made on photomicrographs of the center and the edge of a cross-section of this 8 mil diameter wire.
• the V Ga reaction zone area was calculated as the difference be tween the total strand area and the unreacted strand area.
• the total V Ga reaction zone area is ascertained.
• In order to determine critical current density for a specific magnetic field level divide the critical current at that level by the total V Ga reaction zone area.
• Samples of this wire were annealed, mounted on graphite spools to be used for testing, and heated in vacuum for 120 hours at 600C in order to form the in termetallic compound V Ga on the periphery of each strand. After this high temperature reaction, testing at the boiling point of helium was conducted.
• a single strand niobium in 10% Sn, 90% copper, matrix billet was made by induction melting pure tin and OFHC copper in a graphite tube in an argon atmosphere, lowering a niobium rod into the center of the tube and cooling. After zone remelting the solidified bronze billet to eliminate bubbles and cavities, a billet 8.7 inches long and 0.558 inch diameter was obtained. The billet was homogenized at 500C for two hours in argon and water quenched. It was then hot-drawn at 100 to 110C from 0.558 inch to 0.140 inch diameter, with anneals (and quench) at 0.273 inch and 0.140 inch diameters.
• drawing temperatures exceed about 100C.
• drawing temperature being formed is V Ga
• a preferable operating range for drawing is from about 200 to 300C although higher temperatures may indeed be utilized.
• the composite product being formed is to be Nb Sn
• a drawing temperature of about "C was proven to be satisfactory.
• the wire Prior to drawing, the wire is typically preheated to a temperature close to that at which it will be drawn, This can be effected in any convenient manner, e.g., through use of inductive heating via an induction coil, by passage of the wire through a radiant tube, or so forth.
• a factor governing the upper temperature limit for this invention is the stability of the wire drawing lubricant employed during warm drawing.
• a low temperature lubricant such as one with a petroleum base
• these lubricants are stable up to about 300C. Therefore, for obvious safety reasons the hot drawing temperature should be maintained well below this temperature.
• high temperature lubricants such as graphite or molybdenum disulfide
• hot drawing temperatures up to approximately 600C can be practiced. Therefore, the se lection of a drawing lubricant is a controlling factor for determining the temperature at which hot drawing is conducted.
• a commercial fatty acid base wire drawing lubricant was modified by adding 5% M08 This modification permitted satisfactory hot drawing temperatures up to 350C. When hot drawing was conducted above this temperature, the wire surface oxidized and the lubricant appeared to decompose. It is quite probable that by increasing the amount of M05 a higher drawing temperature could be employed.
• pinning sites are formed as the result of lattice imperfections created by cold work. Since the niobium and vanadium rod inserts have substantially higher tensile strength levels than the matrix material, what might be considered hot working for the matrix is still cold working for the inserts. Therefore, pinning sites are still induced into the inserts. Once induced, these sites remain as lattice imperfections after subsequent processing, such as hot drawing and high temperature diffusion.
• a method for producing a composite superconducting wire including a high-field Type ll superconducting strand embedded in a conductive metallic ma trix of normal material comprising the steps of:
• assembling a composite body including a rod surrounded by said matrix, said rod comprising a metal which forms an intermetallic compound characterized as a high-field Type II superconductor upon high temperature diffusion reaction with an alloying element of said matrix;
• said rod comprises a metal selected from the group consisting of niobium and vanadium.
• rods comprise vanadium and wherein said matrix consists essentially of a bronze containing gallium as the principal alloying element.
• rods comprise niobium and wherein said matrix consists essentially of a bronze containing tin as the principal alloying element.
• thermoforming step is conducted at temperatures in the range of about C to about 600C and the range within which substantial diffusion takes place is at least about 600C.
• PRODUCTS should be -PRODUCT- 2.
• line 8 after "temperature” insert --reaction with a component of said matrix.
• the body is-- Signed and Scaled this thirtieth D f March 1976 [SEAL] Arrest.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Superconductor Devices And Manufacturing Methods Thereof (AREA)

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Cited By (17)

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Citations (4)

• 1973
  • 1973-03-19 US US342895A patent/US3918998A/en not_active Expired - Lifetime
• 1974
  • 1974-03-15 DE DE19742412573 patent/DE2412573B2/de not_active Ceased
  • 1974-03-18 FR FR7409137A patent/FR2222776B1/fr not_active Expired
  • 1974-03-19 GB GB1209574A patent/GB1451168A/en not_active Expired
  • 1974-03-19 JP JP49031391A patent/JPS5026076A/ja active Pending

Patent Citations (4)

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