Method for manufacturing continuous wire

Abstract

There is provided a method of manufacturing a continuous wire comprising forming a strip formed from at least one metallic material into a channel, placing at least one powder into the channel and sealing edges of the channel together to produce a wire, wherein the method further comprises mixing the powder with a carrier liquid to create a slurry and placing the slurry into the channel. The carrier liquid is chemically inert with respect to the at least one powder.

Claims

1. A method of manufacturing wires comprising a strip formed from at least one metallic material into a channel, placing at least two different powders into the channel and sealing edges of the channel together to produce a wire, wherein the method further comprises mixing the at least two different powders with a carrier liquid chemically inert with respect to the at least two different powders to create a slurry, placing the slurry into the channel and heating after the slurry has been placed in the channel so as to leave a solid residue within the channel before laser-seam welding.

2. The method of manufacturing wires according to claim 1, comprising mixing a plurality of powders individually with the carrier liquid to create a plurality of slurries and then combining the plurality of slurries to create one combined slurry.

3. The method of manufacturing wires according to claim 1, wherein the liquid carrier is one of a liquid hydrocarbon or one of ethyl alcohol, acetone, methyl acetate, or ethyl-acetate.

4. The method of manufacturing wires according to claim 1, wherein the at least two different powders are capable of forming a superconductive material.

5. The method of manufacturing wires according to claim 1, wherein the at least one metallic material is one of Ni, or Co, or Nb, or Ti, or Fe, or alloys of these materials, or stainless steels, or Mg, or Cu bronze or Monel.

6. The method of manufacturing wires according to claim 1, wherein the strip is formed from at least two metallic materials having different electrical conductivities.

7. The method of manufacturing wires according to claim 1, wherein the strip is formed from multilayers of metallic materials.

8. The method of manufacturing wires according to claim 1, wherein the wire is a superconductive wire.

9. The method of manufacturing wires according to claim 1, wherein the at least two different powders comprise one or more of B, Mg, MgB2, NbTi, NbSn, NbZr, NbAl, Nd, Fe, As(OF), Mg with B, or Nb with Ti or Nb with Zr, Nb with Al or Nb with Sn.

10. The method of manufacturing wires according to claim 1, wherein a first powder is MgB2 and a second powder is a mixture of Mg and B.

11. The method of manufacturing wires according to claim 1, wherein the powders contain doping additions such as nitrides, borides, silicides, carbon or carbon inorganics, metal oxides, metallic elements or organic compounds.

12. The method of manufacturing wires according to claim 1, wherein the channel is formed into a U-shaped profile.

13. The method of manufacturing wires according to claim 1, wherein the edges of the channel are sealed by welding in an inert atmosphere to create a sealed wire.

14. The method of manufacturing wires according to claim 13, wherein the sealed wire is further processed by rolling to smaller diameters.

15. The method of manufacturing wires according to claim 13 wherein the sealed wire is heat treated.

16. The method of manufacturing wires according to claim 1, wherein the method is a continuous process.

17. The method of manufacturing wires according to claim 1, wherein the wire is drawn, extruded, swaged, rolled or deformed to smaller size by mechanical deformation to produce smaller diameter wire.

18. The method of manufacturing wires according to claim 1, wherein the wire is thermomechanically treated to react the powder or powders.

Description

(1) The invention will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 shows a schematic representation of a wire production line;

(3) FIG. 2 shows a schematic representation of a filling stage forming part of the production line.

DESCRIPTION

(4) It should be noted that the present invention is not limited to the examples and sketches described herein, and various combinations and modifications can be implemented without changing the purpose of the invention.

(5) FIG. 1 is a schematic illustration of a continuous seamless superconductive wire production line 10 in accordance with the invention. Bimetallic strip 10 formed from a sheet of Copper conjoined with a sheet of Steel is fed continuously from strip dispenser 12 to edge profiling unit 14 where strip 10 is formed into a U-shaped profile. At stage 16, a U-shaped channel 21 formed by the cavity of the U profile is filled with particles of amorphous powder contained in a liquid slurry and the slurry dried, as will be described in more detail with reference to FIG. 2.

(6) The U-shaped channel is then closed by closing rollers 18 and seam welded along its length in an inert argon atmosphere using in-line welding equipment 20 to form a perfectly closed seam. The sealed and filled strip is then rolled to smaller diameters using rollers 22 to create wire 28, typically to produce wire between 10 to 5 mm wide and 0.8 to 2.5 mm thick. Wire 28 then undergoes in-line heat treatment 24 in a protective atmosphere to make sure that the fusion and chemical reactions of all constituents are complete or to soften the metallic material allowing further size reduction to take place. Optionally eddy current measurements 29 can be undertaken to quantify the wire characteristics and ensure quality control. The superconductive wire 28 is then stored on a cable assembly 30.

(7) FIG. 2 shows the steps within filling stage 16. The constituents required for superconductive wire 28 are typically Mg 32, B 34 and MgB.sub.2 36 together with optional dopants so as to create a superconductive MgB.sub.2 wire. Other powder constituents can be used depending on the type of wire required so as to produce, for example, low temperature superconductors such as Nb-based intermetallics, NbTi, high-temperature perovskite superconductors, iron based superconductors such as NdFeAs(OF), and other superconducting materials which can be manufactured by Powder-in-tube technique. Doping compounds can be nitrides, borides, silicides, carbon or carbon inorganics, metal oxides, metallic elements or organic compounds. Boron and magnesium powders have particle sizes of below 10 microns (most of the powder is below 1 microns) and 150 microns, respectively. Particle size distribution of superconductive powders could vary from few nanometres to tens of microns.

(8) The process starts with transforming continuously fed flat bimetallic strip to a U profile followed by an unique powder feeding technology allowing micron sized Mg and Cu powders, typically 300-50 microns in diameter, as well as nano sized B and dopant powders to be fed continuously to a U shaped material. Laser seam welding technology is applied to seal the conductor seam allowing continuous wire production.

(9) Powders with different particle size distribution, different particle shape and densities are difficult to mix homogenously. In addition, flowability of fine powders become very poor as their particle size gets smaller and they can easily get clogged.

(10) It is important to ensure continuity of the same quality of MgB.sub.2 powder (purity, crystallinity, density, thickness) inside the wire.

(11) In FIG. 2, the constituent powders 32, 34, 36 required to form wire 28 are mixed in a low temperature boiling point liquid in containers 40, with the liquid not oxidizing to any of the powders. The liquid can be, but not limited to, methyl, ethyl of isopropyl alcohol. Other suitable liquids include acetone, methyl acetate, ethyl-acetate and other hydrocarbons. The constituent powders can be mixed together in one container or in separate containers so that they are only combined once suspended within the liquid.

(12) The fine powders such as Mg, B, MgB.sub.2, doping additives as well as other metallic and non-metallic constituents are transferred to containers 40 either in a mixed state or individually. Powders are mixed in a liquid medium 41 such as ethyl alcohol, which is chemically inert to all of the powder constituents even at its boiling point. Depending on the powder composition, acetone, methyl acetate, ethyl-acetate, alcohols or other liquid hydrocarbons can be used to prepare the slurry mix.

(13) The powders are mixed until they are homogeneously distributed in an ethyl alcohol flowing one phase slurry. Powder mixture can be fed into ethyl alcohol up to 58% solid content ratio. After this ratio it gets harder to mix the powders as one phase.

(14) By mixing the powders into an inert carrier liquid, problems with oxidation, moisture absorption and so on are avoided and the powders are mixed to a better homogeneity level. Oxidation, moisture, electrostatic charge and compression of the powders are not a problem.

(15) The slurry mixing containers 40 are designed to continuously mix the slurry in a manner that fine powders are uniformly dispersed within the slurry mix without creating any segregation or preferential separation. This ensures consistent, segregation free at a high precision rate to relatively small U shaped profiles. Feeding tubes 39 are connected to slurry pumps or feeders such as peristaltic, progressive cavity and rotary pumps to pump mixed slurry through feeding tubes 39 into the U shaped profile 21 through feed nozzles.

(16) Using a standard pump 42, the slurry is then fed into the moving U-shaped strip. Strip feeder can easily communicate with the pump and adjust the system speed. The solvent within the U profile 21 needs to be removed prior to laser seam-welding and so the filled strip is dried down to any moisture level using in-line heaters 44 which can be tube furnaces, ceramic heaters, infra-red heaters, or induction heaters. The evaporated solvent is removed either by blowing hot air or hot gas or extracted using a vacuum pump.

(17) The mix remaining within the profile then becomes ready for seam-welding.

(18) The powder after drying is denser than the prior art powder mixture prepared and fed with standard mixing and feeding techniques. The denser mixture not only improves the conductivity properties but also prevents any powder movement caused by air flow created due to temperature dependent air expansion during laser welding. This invention can be used for any type of fine powders or fine powder mixtures fed into a wire.

(19) The method of using an inert slurry can be used in the production of any powder-containing wire, such as used in welding, arc spraying and bimetal-sheathed insulated wires.

(20) Thus superconductive wires using the powder-in-tube process can be manufactured using a continuous automated seam welding process based on the use of bimetallic clad strip and a slurry feeding system.