Subelement for a semi-finished wire for the production of an nb3sn superconductor wire, having a moderation tube in the nb-containing reaction elements

Abstract

Disclosed is a subelement (1) for a semi-finished wire for producing an Nb3Sn superconductor wire, the subelement (1) comprising: - an Sn-containing core region (2); - a Cu-containing inner intermediate region (3) which surrounds the Sn-containing core region (2); - a ring region (4) that contains a multiplicity of Nb-containing reaction elements (5) and surrounds the inner intermediate region (3); - a Cu-containing peripheral region (7) that surrounds the ring region (4); wherein the Nb-containing reaction elements (5) at least include: - a tube structure which is at least partially made of an Nb alloy containing Nb and at least one other alloy component X; - a filling region which lies within the tube structure and in which a multiplicity of particles is disposed, wherein the particles contain at least one partner component Pk, wherein the at least one alloy component X and the at least one partner component Pk are selected such that they form precipitates XPk during reaction annealing of the subelement (1). The subelement is characterized in that a moderation tube, within which the filling region is located, is formed on an inner side of the tube structure.

Description

[0001] Subelement for a semi-finished wire for the production of an Nb3Sn superconducting wire, with moderation tube in the Nb-containing reaction elements

[0002] The invention relates to a sub-element for a semi-finished wire for the production of an NbsSn superconducting wire, wherein the sub-element comprises a Sn-containing core region, a Cu-containing inner intermediate region surrounding the Sn-containing core region, a ring region containing a plurality of Nb-containing reaction elements, wherein the ring region surrounds the inner intermediate region, and a Cu-containing surrounding region surrounding the ring region.wherein the Nb-containing reaction elements at least have a tube structure which is at least partially made of an Nb alloy containing Nb and at least one further alloying component X, a filling region which lies within the tube structure and in which a plurality of particles are arranged, wherein the particles contain at least one partner component Pk, wherein the at least one alloying component X and the at least one partner component Pk are selected such that they form precipitates XPk upon reaction annealing of the subelement.

[0003] One such sub-element has been made known, for example, by T. Bagni et al., “Report of the activities at UNIGE in 2021”, Swiss Accelerator Research and Technology (CHART) Scientific Reports 2021, WireChar and WireDev, 02 / 2022, available on the internet at https: / / chart.ch / wp-content / uploads / 2022 / 02 / Senatore_UNIGE_CHART_report_2021_rev.pdf.

[0004] Superconducting materials can transport electric current without significant ohmic losses. For example, superconducting wires are wound to create magnetic coils that can generate very high magnetic field strengths, as required in NMR spectroscopy or for the magnetic confinement of plasma in fusion power plants.

[0005] Despite significant advances in high-temperature superconductor materials, low-temperature superconductor materials (with a transition temperature of 40 K or less) remain highly important in practical applications. In particular, NbsSn-containing superconducting wires are used in the manufacture of magnetic coils for high magnetic field strengths. These superconducting wires must exhibit both high current-carrying capacity and mechanical robustness to withstand the stresses encountered during application.

[0006] The production of NbsSn superconducting wires involves manufacturing an unreacted semi-finished wire containing Nb and Sn. This wire is then formed into a desired shape, for example, wound into a coil, and subjected to a reaction annealing (also known as reaction heat treatment). During this process, the Nb and Sn contained in the wire react to form the superconducting NbsSn phase, thus transforming the wire into a superconducting wire.

[0007] An important variant of NbsSn superconducting wires are the IT wires (IT = Internal Tin). Here, a large number of Nb-containing rods are arranged around a Sn-containing core, for example as bundles of hexagonal rods with a surrounding diffusion barrier according to the RRP® type (RR.p® = rod restack process), or inserted into a Cu block, where several subelements share a common diffusion barrier, according to the Global Barrier type.

[0008] The superconducting current-carrying capacity of an NbsSn superconducting wire is significantly influenced by its microstructure. High current-carrying capacity can be achieved, in particular, by minimizing the mobility of superconducting flux tubes ("flux pinning"). Specifically, superconducting flux tubes can be bound at the grain boundaries of the NbsSn; consequently, a finer NbsSn microstructure can result in improved superconducting current-carrying capacity.

[0009] In WO 2015 / 175064 A2 by Xu et al., NbsSn superconducting wires are proposed in which the superconducting layer contains a multitude of small-grain-size NbsSn grains stabilized by metal oxide particles (e.g., ZrO₂). In one variant, a subelement is proposed comprising a Sn-based core, a Cu-based layer surrounding the core, a multitude of bundled Nb alloy rods (containing, for example, Zr), each with a copper sheath and surrounding the Cu-based layer, a barrier layer surrounding the bundled Nb alloy rods, and a metal matrix surrounding the barrier layer. Within the stack of copper-sheathed Nb alloy rods, metal oxide regions made of a metal oxide powder (e.g., SnO₂ powder) are established. In other words, within the stack of copper-sheathed Nb alloy rods, some rods are replaced by metal oxide regions. Xu et al.It states that fine ZrO2 particles precipitated in the NbsSn matrix reduce the NbsSn grain size, thereby increasing current-carrying capacity. The underlying approach to increasing superconducting current-carrying capacity has become known as "internal oxidation".

[0010] In X. Xu, "A review and prospects for NbsSn superconductor development", Superconductor Science and Technology, Vol. 30, No. 9, 093001, August 3, 2017, it is proposed to replace a Sn rod in the center of the subelement for an RRP® superconductor with a mixture of a Sn source powder and an oxide powder, or to use Nb-Zr tubes filled with oxide powder in the bundle region.

[0011] The aforementioned "Report of the activities at UNIGE in 2021" specifically proposes a subelement in which twelve Nb alloy filaments made of Nb-7.5Ta-2Hf are arranged in a ring around a tin core. Each Nb alloy filament has a hole drilled into it and filled with a tin-substance nanopowder. A significant grain refinement was observed compared to control samples without an oxygen source.

[0012] In G. Bovone et al., “Effects of the oxygen source configuration on the superconducting properties of internally-oxidized internal-Sn NbsSn wires”, Superconductor Science and Technology 36 (2023), 095018, NbsSn wires were also fabricated, with twelve Nb alloy filaments arranged around an Sn core, and the Nb alloy rods filled with an SnC powder. Hf or Zr oxide precipitates would inhibit NbsSn grain growth during heat treatment and would apparently also act as effective pinning centers.

[0013] From DE 10 2018 126 760 B4, a monofilament for an NbsSn superconducting wire is known, which is constructed according to the powder-in-tube principle. The monofilament comprises a powder core containing tin-containing powder, a surrounding reaction tube made of an alloy containing Nb and at least one alloy component X, at least one source for at least one partner component Pk, and a moderation tube. The powder core is arranged in the moderation tube, and the moderation tube is arranged inside the reaction tube. Precipitations XPk are formed from the alloy component X and the partner component Pk during reaction annealing. Various oxide and non-oxide precipitates XPk are proposed.

[0014] The object of the invention is to provide an NbsSn superconducting wire with which the superconducting current-carrying capacity can be further improved.

[0015] This problem is solved according to the invention by a sub-element of the type mentioned at the outset, which is characterized in that a moderation tube is formed on an inside of the tube structure, within which the filling area lies.

[0016] Within the scope of the invention, the superconducting current-carrying capacity of an NbsSn superconducting wire can be improved by incorporating the inventive sub-elements into the semi-finished wire for the NbsSn superconducting wire. The invention utilizes the principle of internal oxidation, whereby the formation of the XPk precipitates is improved.

[0017] The formation of XPk precipitates in an NbsSn superconducting wire manufactured with subelements according to the invention can, firstly, cause the direct binding of superconducting flux tubes (flux pinning) to the precipitates, and secondly, inhibit the grain growth of NbsSn grains. This latter effect can result in a finer microstructure of the NbsSn grains, and the numerous grain boundaries in this finer microstructure can, in turn, act as pinning centers. The inhibiting effect on NbsSn grain growth is greater the earlier the XPk precipitates are formed, particularly compared to the formation of NbsSn itself.

[0018] The arrangement of the particles according to the invention, which contain at least one partner component Pk (preferably with Pk=O), in the filling region of the Nb-containing reaction elements ensures a short diffusion path of the partner component Pk to the alloying component X (preferably with X=Zr or Hf), in particular shorter than when the partner component is arranged in the Sn-containing core region. This inherently promotes the early formation of XPk. Furthermore, the diffusion of the partner component Pk is generally spatially separated from the diffusion of the Sn, so that the two diffusions relative to each other can be more easily controlled by the structure of the sub-element, and in particular, better control over the size of the XPk precipitates is possible.

[0019] A problem in the formation of the XPk precipitates can arise because the partner component Pk is blocked on its way from the filling area into the tube structure, and then cannot distribute itself in the tube structure at all, or at least not as early as desired, in order to form the XPk precipitates.

[0020] If, as described in the prior art, the particles of the filling area are in direct contact with the pipe structure, very high local concentrations or partial pressures of the partner component Pk can be reached on the inside of the pipe structure from the start of its release. This is especially true if the filling area is filled exclusively with particles containing the partner component. In such cases, one or more phases can form locally on the inside of the pipe structure that would not have formed at a lower concentration of the partner component. These phases can block the further diffusion of the partner component Pk into the depths of the pipe structure. In particular, these phases can also form closed layers on the inside of the pipe structure, which can further impede the diffusion of the partner component into the pipe structure.If such a phase forms temporarily (i.e., dissolves again during the reaction annealing), the formation of the XPk precipitates can be delayed, and in particular, significantly delayed. If such a phase forms permanently (in the sense that it does not dissolve again during the - usual - reaction annealing), the formation of the precipitates can be completely prevented, or at least the quantity (and size) of the precipitates formed can be reduced, and in particular, significantly reduced. This leads to a deterioration in the current-carrying capacity of the finished superconducting wire in the prior art.

[0021] In many cases, oxygen (i.e., O) is used as the partner component Pk. If the particles (e.g., SnO₂ particles) of the filling region, as in the prior art, are directly adjacent to the tube structure (e.g., made of an NbZr alloy), an oxide boundary layer can form on the inside of the tube structure during reaction annealing due to the high partial pressure of O. In this example, this layer consists of NbO, and in the case of particularly high partial pressures, also of Nb₂Os. A superficial "external oxidation" then occurs on the radial inside of the tube structure, instead of the desired "internal oxidation" of the Zr, which is present throughout the tube structure as an alloying element X. While the NbO layer (or Nb₂Os layer) can regress during further reaction annealing, the oxygen only reaches the depth of the tube structure or the Zr in the NbZr alloy after a time delay.However, the growth of NbsSn grains can then no longer be inhibited as effectively. Consequently, the superconducting current-carrying capacity of the superconducting wire, which would have been possible without this time delay, is not achieved in the prior art.

[0022] Note that blocking phases can also occur with partner components other than oxygen. Likewise, the binding partner B, to which the partner component Pk is bound in the particles, can also be involved in the formation of a blocking phase; this binding partner B is also released at the beginning of the release of the partner component Pk (or the decomposition of the particles) and then appears in high concentration on the inside of the tube structure. Within the scope of the present invention, a moderation tube is provided on the radial inside of the tube structure. This moderation tube prevents the particles containing the partner component Pk from directly adjoining the tube structure in the subelement. This ensures that the local concentration is reduced.the partial pressure of the partner component Pk (and also of the bonding partner B) remains low after the decomposition of the particles on the inside of the tube structure begins.

[0023] Accordingly, the invention prevents the formation of phases that can only form on the inside of the tube structure at high concentrations of the partner component Pk (or the binding partner B). Since such phases can be prevented by the invention, they cannot (temporarily or permanently) impede the diffusion of the partner component from the filling region into the tube structure. In the subelement according to the invention, the partner component Pk can enter the tube structures of the Nb-containing reaction elements at an early stage and form XPk precipitates there at an early stage.

[0024] The partner component Pk (or the binding partner B), which wants to diffuse from the filling area to the tube structure, must first pass through the moderation tube. As it passes through the moderation tube, the partner component Pk (or the binding partner B) is distributed within the material of the moderation tube, particularly in a substantially uniform manner along its circumference. This prevents concentration peaks of the partner component Pk (or the binding partner B) on the inner surface of the tube structure adjacent to the moderation tube.

[0025] The material of the moderation tube is selected such that no diffusion-blocking phases can form on its inner surface during reaction annealing, even at high concentrations of Pk and / or B, together with the partner component Pk and / or its bonding partner B, if relevant. Generally, the moderation tube material should also be more noble than Nb so that the partner component Pk diffuses further into the Nb alloy of the tube structure. Furthermore, the moderation tube material is metallic and therefore electrically conductive. Suitable materials for a moderation tube are generally noble metals, with silver being preferred, particularly for cost reasons (but ruthenium, palladium, platinum, or gold, for example, can also be used). Many semi-precious metals (especially copper and nickel) can also be used as materials for the moderation tube.In general, the moderation tube should not contain tin (Sn) to avoid the undesired early formation of NbsSn during reaction annealing. The moderation tube should exhibit a certain permeability to the partner component Pk (e.g., oxygen) to allow diffusion of the partner component through it for the formation of the XPk precipitates. This can be ensured both by selecting the appropriate material and by using suitable dimensions / wall thicknesses for the moderation tube.

[0026] Within the scope of the invention, the formation of the XPk precipitates at the beginning of the reaction annealing process can be promoted and accelerated. In particular, the XPk precipitates can be formed before NbsSn forms, or at least in a relatively early stage of the NbsSn phase formation. As a result, the XPk precipitates can serve as nuclei for the formation of more NbsSn grains and very efficiently inhibit subsequent grain growth of NbsSn, resulting in a particularly fine microstructure of NbsSn grains. This leads to very good flux pinning of superconducting flux tubes, and a particularly high current-carrying capacity can be achieved in the superconducting wire.

[0027] The moderation tube can also contribute to maintaining good forming behavior (especially in cross-section-reducing forming processes such as extrusion or drawing) of the sub-element, particularly minimizing crack formation in the sub-element (or individual Nb-containing reaction elements). Preferably, the moderation tube contains Ag and / or Cu. Preferably, the alloying component X is selected as Zr or Hf. Metals are preferred as alloying components X, but non-metals are also possible. Preferably, the partner component Pk is selected to be 0, but other elements are also possible as partner component Pk. Alloying components X and partner components Pk that can be used within the scope of the invention can also be found in DE 10 2018 126 760 B4. The particles can, for example, contain a metal oxide, in particular Cu₂O and / or Ag₂Ü and / or SnÜ₂. Preferably, the entire filling area is free of Sn.If the filling region contains tin (e.g., in the particles), the total proportion of tin in the filling region should be low, for example, 25 at% as a proportion of the sum of all solid phases in the filling region, preferably 10 at% or less. The particles typically have a mean particle size (D50) of 100 nm or less, preferably 50 nm or less.

[0028] Note that the ring region may contain other elements besides the Nb-containing reaction elements described, such as additional elements for functional doping or mechanical stabilization / reinforcement, or simply Nb-containing elements of a different type (e.g., solid elements without tube structure and filling region).

[0029] The Nb-containing reaction elements and other elements in the ring region can each enclose a Cu-containing shell. The Nb-containing reaction elements and other elements in the ring region can have a hexagonal cross-section radially outward (especially when they are abutting each other in the ring region), or a circular cross-section (especially when they are inserted into recesses of a ring matrix).

[0030] Preferred embodiments of the invention

[0031] Embodiments relating to certain aspects of the moderation tube: A preferred embodiment of the sub-element according to the invention is one in which the moderation tube and at least an adjacent part of the tube structure are made of different materials. Accordingly, the material of the moderation tube can be selected such that it is less prone to forming a phase with the partner component Pk and / or its binding partner B from the particles, thus blocking the diffusion of the partner component Pk. Furthermore, the material of the moderation tube can be selected optimally for a uniform distribution of the diffusing partner component (or binding partner B).

[0032] An embodiment is also advantageous in which the moderation tube is free of the at least one partner component Pk contained in the particles in the filling region. This avoids local concentration peaks of the partner component Pk (or also of the associated binding partner B' in the moderation tube) in the moderation tube at the beginning of the release of the partner component Pk in the moderation tube.

[0033] In a preferred embodiment, the moderation tube is provided to be free of the at least one alloy component X contained in the Nb alloy from which the tube structure is at least partially manufactured. This avoids (even partial) consumption of the partner component Pk outside the tube structure, and the available amount of partner component Pk allows for the formation of a particularly large number of precipitates XPk within the region of the tube structure.

[0034] Embodiments relating to a filling area with powder

[0035] An advantageous embodiment involves filling the filling area with a powder containing the particles. This simplifies manufacturing. Furthermore, the powder can be pre-reduced in cross-section within the moderation tube to increase the packing density in the filling area. The reduced-cross-section, filled moderation tube is then inserted into the pipe structure. This improves the final current-carrying capacity.

[0036] In a preferred embodiment, the powder contains only the particles. In this case, a particularly large amount of partner component can be provided in a small space. Accordingly, high superconducting cross-sectional areas in the superconducting wire can be achieved. Furthermore, in this case, the advantage of the moderation tube in reducing the concentration of the partner component Pk (and / or the binding partner) is fully realized.

[0037] A further development is also advantageous in which the powder contains the particles as well as additional particles. These additional particles can provide desired functions in the manufacturing of the superconducting wire, particularly to influence its forming behavior or to control processes or chemical reactions during reaction annealing. Specifically, the additional particles can have a catalytic or supporting effect, for example, to accelerate the release of Pk from the particles, or the additional particles (or their components) can bind released substances, especially Sn from the particles (typically from SnO2 particles).

[0038] In one variant of this advanced development, at least some, and in particular all, of the additional particles are filler particles. These filler particles do not participate in the formation of XPk and NbsSn during reaction annealing. The filler particles typically remain completely unchanged during reaction annealing. They can consist of materials such as BN or SiC. Most often, the particles contain neither X, nor Pk, nor Nb, nor Sn. The filler particles dilute the particles in the filling region and can thus contribute to reducing the partial pressure of the partner component Pk on the inside of the moderation tube and within the moderation tube, and ultimately to reducing the partial pressure of the partner component on the inside of the tube structure. The same applies, where relevant, to the concentration of the binding partner B.Furthermore, the above also applies analogously to an additional moderation tube and to the outside of a core structure (see below).

[0039] Embodiments relating to a metallic matrix

[0040] In a particularly preferred embodiment, it is provided that a metallic matrix is ​​arranged in the filling area, and that the particles are distributed in the metallic matrix.

[0041] The metallic matrix can help establish a highly conductive electrical connection between the particles containing the partner component Pk in the filling region and the alloy component X in the tube structure. This allows a "local element" to be established between the particles (containing the bonding partner B and the partner component Pk) and the alloy component X. The partner component Pk preferentially binds to X rather than to B (generally, B is more noble than X), but the associated electrochemical reaction requires an electrical connection between the particles and the alloy component X in the Nb-containing alloy of the tube structure. If this electrical connection is ensured, early release of the partner component from the particles, and thus early diffusion of the partner component Pk to the alloy component X in the tube structure, can be achieved.Due to the metallic matrix in which the particles are distributed, a very large proportion of the particles, usually practically all of them, can participate in the electrochemical reaction from the very beginning of the reaction annealing. Accordingly, with the embodiment according to the invention, the precipitates can also be formed early during the reaction annealing. This allows for a particularly fine microstructure of the NbsSn and, consequently, a high superconducting current-carrying capacity of the superconducting wire. In this embodiment, the moderation tube is generally made of metal (preferably Ag or Cu) and is therefore electrically conductive. Preferably, the metallic matrix contains Ag and / or Cu.In the prior art, a simple bed of oxide, poorly conductive particles is arranged in the filling region, and consequently, a large proportion of the particles in the filling region are electrically insulated from the moderation tube and the tube structure, particularly by other particles. Therefore, in the prior art, at least initially, only a small proportion of the particles can be used as a source for the partner component Pk; consequently, the partner component is released only slowly, and the formation of the precipitates XPk is correspondingly delayed.

[0042] Typically, within the scope of the invention, at least 50%, preferably at least 90%, and particularly preferably 100% of the particles in the filling region have direct contact (and thus good electrical contact) with the metallic matrix. The metallic matrix forms a continuous, electrically conductive structure; in other words, the metallic matrix percolates (regardless of any division into subregions). The metallic matrix, together with the particles distributed therein, at least partially fills the filling region, typically to at least 50%, preferably to at least 70%, particularly preferably to at least 95%, and most preferably to 100% (in each case based on volume). Typically, there is (planar or quasi-planar) contact between the particles and the metallic matrix (on average) over at least 50% of the outer surface of the particles, and preferably over at least 90% of the outer surface of the particles.Preferably, the particles are individually distributed within the metallic matrix, corresponding to (planar or quasi-planar) contact between the particles and the metallic matrix (on average) over practically 100% of the particles' outer surface. The metallic matrix can also contribute to maintaining good forming behavior (especially in cross-sectional reduction processes such as extrusion or drawing) of the sub-element, particularly minimizing crack formation in the sub-element.

[0043] A preferred further development of this embodiment is characterized in that the metallic matrix is ​​at least partially formed by a metallic powder mixed with the particles. This allows a metallic matrix for the particles in the filling area to be established in a very simple manner. Note that cross-sectional reduction deformations typically achieve intimate contact between the particles of the metallic powder and the particles containing the at least one partner component Pk, particularly since the particles of the metallic powder can also be plastically deformed.

[0044] In another preferred embodiment, the metallic matrix is ​​at least partially formed by a metal body in which the particles are dispersed. This achieves particularly good contact between the particles and the metallic matrix, typically with contact over virtually 100% of the particles' outer surface. A high degree of filling of the matrix can also be achieved. In particular, the particles can be stirred into a liquid metallic melt, and the solidification of the melt forms the metal body in which the particles are dispersed (regardless of any forming processes). The metal body can, for example, be a wire, rod, or foil.

[0045] Embodiments relating to a core structure

[0046] A preferred embodiment provides that the Nb-containing reaction elements further have

[0047] - A core structure, wherein the filling region lies between the moderation tube and the core structure, the core structure being at least partially made of an Nb alloy containing Nb and at least one further alloying component X. Within the core structure, further Nb can be stored for the formation of NbsSn and further alloying component X for the formation of XPk precipitates, thereby shortening the average diffusion path of the partner component Pk. This can further accelerate the formation of the XPk precipitates. Furthermore, the cross-sectional area of ​​the sub-element in which superconducting NbsSn is formed can optionally be increased by the core element. Typically, the Nb alloys from which the tube structure and the core structure are each at least partially made are identical.

[0048] A particularly preferred embodiment includes an additional moderation tube on the outer surface of the core structure, outside of which the filling region lies, especially wherein the additional moderation tube and at least an adjacent part of the core structure are made of different materials. In other words, the filling region then lies radially between the moderation tube and the additional moderation tube. With the additional moderation tube, the local concentration of partner component Pk (released by the particles in the filling region) on the outer surface of the core structure can be kept low, analogous to the moderation tube with respect to the core structure. The same applies, and is relevant, to the concentration of the binding partner B.This prevents the formation of a phase or phases that would hinder the diffusion of the partner component Pk into the core structure. Accordingly, XPk precipitates can form early in the core structure during reaction annealing, and the grain growth of NbsSn can be effectively inhibited even in the core structure. Typically, the materials used for the moderation tube and the additional moderation tube are the same. Statements regarding the moderation tube also apply to the additional moderation tube.

[0049] Other embodiments

[0050] A preferred embodiment is one in which the moderation tube contains Cu and / or Ag. Typically, the moderation tube consists entirely of Cu or Ag. These materials are readily available at low cost and have proven effective in practice, particularly due to their low tendency to chemically react with oxygen and other common partner components. The same applies to any additional moderation tube that may be present. A further preferred embodiment is one in which the following applies to a minimum radial wall thickness WM of the moderation tube and a mean D50 particle size DP of the particles in the filling region:

[0051] WM>2*DP, preferably WM>3*DP, most preferably WM>5*DP. At these wall thicknesses, the function of the moderation tube, to avoid high concentrations or partial pressures of the partner component Pk (or, if relevant, of the binding partner B) on the inside of the tube structure, is effectively achieved. The particle size DP refers to the individual particle size ("crystallite size"); in particular, agglomerates or granules are not relevant. The same applies to any additional moderation tube that may be present.

[0052] A preferred embodiment also provides that at least some of the Nb-containing reaction elements are designed as doping reaction elements, wherein the doping reaction elements contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, and / or that additional doping elements are also arranged in the ring region, wherein the additional doping elements contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, in particular wherein the at least one element of the fourth subgroup of the periodic table comprises titanium, and / or that at least some of the Nb-containing reaction elements are designed as reinforcing reaction elements, wherein the reinforcing reaction elements contain at least one element of the fifth subgroup of the periodic table in at least one contained phase, and / or that additional reinforcing elements are also arranged in the ring region.wherein the reinforcing additive elements in at least one contained phase include at least one element of the fifth transition group of the periodic table, in particular wherein the at least one element of the fifth transition group of the periodic table comprises tantalum.

[0053] The formation of the NbsSn phase can be easily accelerated by doping with dopant elements and doping additives. The forming behavior, particularly the drawing behavior, of the subelement can be easily improved by reinforcement with reinforcing elements or reinforcing additives. Preferably, only a small fraction, e.g., 20% or less, of the Nb-containing reaction elements is configured as dopant elements and / or reinforcing elements, so that a further large fraction of the Nb-containing reaction elements, e.g., more than 80%, can be manufactured from a cost-effective standard alloy (e.g., NblZr).

[0054] A preferred embodiment is one in which the Nb-containing reaction elements are in contact with one another in the ring region, and in which the sub-element further comprises a diffusion barrier surrounding the ring region. Such sub-elements are inexpensive to produce and flexible in their design, particularly with regard to the size of the ring region. The Nb-containing reaction elements can have a hexagonal cross-section, which facilitates defined bundling. The diffusion barrier is typically arranged between the ring region and the surrounding area. The diffusion barrier ensures that the surrounding Cu retains high conductivity (and is not contaminated by Sn during reaction annealing and thus becomes less conductive), which electrically stabilizes the superconducting wire.Local diffusion barriers at each sub-element allow the pure, stabilizing copper in the superconducting wire to be positioned relatively close to the superconducting zones. Such sub-elements can be used for RRP®-type superconducting wires.

[0055] In another, equally preferred embodiment, the ring region comprises a copper-containing ring matrix forming a plurality of recesses into which the nitrogen-containing reaction elements are inserted. This approach is particularly simple. The ring matrix is ​​typically formed by a copper block or a copper-containing block with bores. The nitrogen-containing reaction elements (and optionally other elements) can be easily arranged in the ring region using the ring matrix. Corresponding sub-elements can be used for global barrier-type superconducting wires; in this case, several such sub-elements are surrounded by a common diffusion barrier in the semi-finished wire (after cross-sectional reduction).

[0056] Semi-finished wires according to the invention

[0057] The present invention also encompasses a semi-finished wire for the production of an NbsSn superconducting wire, comprising several bundled sub-elements according to the invention and described above. The number of bundled sub-elements can be selected according to the desired application. Typically, seven or more sub-elements are bundled to form a semi-finished wire.

[0058] In a preferred embodiment of the semi-finished wire according to the invention, the sub-elements are formed with a ring matrix as described above, into the recesses of which the Nb-containing reaction elements are inserted, and an overall diffusion barrier is present which surrounds all the bundled sub-elements on the outside. This overall diffusion barrier protects the surrounding pure Cu from the diffusion of Sn during the reaction annealing, thus ensuring high electrical conductivity of the surrounding Cu.

[0059] Inventive method for producing an NbsSn superconducting wire, associated superconducting wire and associated use

[0060] The present invention also encompasses a method for producing an NbsSn superconducting wire, characterized by the following steps:

[0061] Step a Manufacturing of a large number of products according to the invention, described above

[0062] Subelements, step b): Bundling of the subelements to form a semi-finished wire according to the invention, as described above,

[0063] Step c): Reaction annealing of the semi-finished wire to form NbsSn superconducting wire, whereby Sn and Nb react to form NbsSn. In step c), XPk precipitates are initially formed in the tube structures and / or the core structures, and only subsequently is at least the majority of the NbsSn formed. In this way, an NbsSn superconducting wire with particularly high current-carrying capacity can be obtained. The XPk precipitates are formed before at least the majority (more than 50%) of the total NbsSn formed (by volume), so that the grain growth of said majority can be inhibited by the precipitates. Accordingly, a particularly fine microstructure of the NbsSn in the superconducting wire can be obtained, and correspondingly strong flux pinning.Typically, at a point during the reaction annealing process when at least 50%, preferably at least 75%, of the total XPk precipitates formed have already been formed, only a maximum of 50%, preferably a maximum of 25%, of the total NbsSn formed has been formed (based on volume). The production of the sub-elements typically includes a cross-sectional reduction forming process (e.g., extrusion or drawing) at the end. The bundling in step b) can be carried out in a single stage or in multiple stages. The bundling in step b) typically includes a cross-sectional reduction forming process (e.g., extrusion or drawing) at the end. Typically, at the end of step b), the semi-finished wire is also deformed into a desired shape for the intended application, e.g., the winding of the semi-finished wire onto a spool holder.

[0064] The invention further comprises an NbsSn superconducting wire produced according to the inventive method described above. This NbsSn superconducting wire can achieve a particularly high superconducting current-carrying capacity.

[0065] Also within the scope of the present invention is the use of an NbsSn superconducting wire according to the invention, as described above, in a nuclear fusion device, particularly wherein the nuclear fusion device is a fusion power plant. Typically, the NbsSn superconducting wire is installed in one or more magnetic coils, which generate a magnetic field with which the fusion plasma is confined. The superconducting wire is typically arranged in a cable which, in addition to the superconducting wire, also includes copper and / or auxiliary wires (particularly as structures providing mechanical stability to the cable). Due to the high current-carrying capacity of the superconducting wire, the cable can be designed very freely and thus optimally adapted to the application.

[0066] The NbsSn superconducting wire according to the invention can alternatively also be used in NMR magnets, in particular to obtain a particularly compact NMR apparatus.

[0067] The NbsSn superconducting wire according to the invention can alternatively also be used in high-energy physics applications, particularly in particle accelerators, especially to generate a maximum magnetic field strength in the available installation space.

[0068] Further advantages of the invention will become apparent from the description and the drawing. Likewise, the features mentioned above and those described in more detail below can each be used individually or in any combination according to the invention. The embodiments shown and described are not to be understood as an exhaustive list, but rather serve as examples for illustrating the invention.

[0069] Detailed description of the invention and drawing

[0070] Fig. 1 shows a schematic cross-sectional view of an embodiment of a sub-element according to the invention;

[0071] Fig. 2 shows a schematic cross-sectional view of an Nb-containing reaction element for a sub-element according to the invention, wherein a moderation tube is located between the tube structure and the filling region; Fig. 3 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein the filling region is located radially between the moderation tube and a core structure, for the invention;

[0072] Fig. 4 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein the filling area lies radially between the moderation tube and an additional moderation tube, wherein the additional moderation tube surrounds a core structure, for the invention;

[0073] Fig. 5 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a powder containing the particles is arranged in the filling area, for the invention;

[0074] Fig. 6 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a metallic powder is arranged in the filling area in which the particles are mixed, for the invention;

[0075] Fig. 7 shows a schematic cross-sectional view of an Nb-containing reaction element, wherein a metal body with particles dispersed therein is arranged in the filling area, for the invention;

[0076] Fig. 8 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein some Nb-containing reaction elements are designed as doping reaction elements and strengthening reaction elements;

[0077] Fig. 9 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein Nb-containing reaction elements, doping additive elements and reinforcing additive elements are arranged mixed in the ring region; Fig. 10 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein Nb-containing reaction elements and additive elements from an Nb alloy containing Nb and at least one further alloying element X are arranged mixed in the ring region;

[0078] Fig. 11 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein the Nb-containing reaction elements in the ring region have a hexagonal outer cross-section and a diffusion barrier is present;

[0079] Fig. 12 shows a schematic cross-sectional view of a further embodiment of a sub-element according to the invention, wherein the ring region comprises a Cu-containing ring matrix with recesses into which the Nb-containing reaction elements are inserted;

[0080] Fig. 13 shows a schematic cross-sectional view of an embodiment of a semi-finished wire according to the invention, comprising bundled hexagonal sub-elements, each with its own diffusion barrier;

[0081] Fig. 14 shows a schematic cross-sectional view of a further embodiment of a semi-finished wire according to the invention, comprising bundled, round sub-elements and an overall diffusion barrier;

[0082] Fig. 15 shows a schematic flow chart for an exemplary variant of a method according to the invention for the production of an NbsSn superconductor wire.

[0083] Figure 1 schematically shows an exemplary embodiment of a sub-element 1 according to the invention in cross-section. The sub-element 1 comprises a tin-containing core region 2. Here, this is formed by a rod made of a tin-containing alloy. The core region 2 can, in particular, also contain a certain proportion of copper. A tubular, copper-containing inner intermediate region 3 is formed around the core region 2. Here, the inner intermediate region 3 is formed by a copper tube in which the rod made of the tin-containing alloy is arranged. Alternatively, the core region 2 can also be formed, for example, by a tin-containing powder or a tin-containing powder mixture arranged in the surrounding, tubular inner intermediate region (not shown in detail).

[0084] A ring-shaped region 4 is formed around the inner intermediate region 3, in which a plurality of Nb-containing reaction elements 5 are arranged; the Nb-containing reaction elements 5 are explained in more detail in Fig. 2. In the design shown in Fig. 1, only Nb-containing reaction elements 5 are arranged as elements in the ring-shaped region 4; however, alternatively, other types of elements can also be present (e.g., dopants, see below in Figs. 8, 9, and 10). The spaces 6 between the elements contained in the ring-shaped region 4 (here, the Nb-containing reaction elements 5) are preferably filled with solid material, e.g., elemental copper or a copper alloy.

[0085] A copper-containing surrounding area 7 is arranged around the ring area 4, which here is designed as a copper tube.

[0086] In Fig. 2, an exemplary Nb-containing reaction element 5 from Fig. 1 is explained in more detail in a schematic cross-section.

[0087] The Nb-containing reaction element 5 comprises a tube structure 8, which is at least partially, and in the illustrated configuration completely, made of an alloy containing Nb and at least one further alloying component X. The further alloying component is Zr (zirconium). The tube structure 8 is made of NblZr; thus, the alloy contains 1 wt% Zr, and the remainder consists of Nb. A moderation tube 20 is formed on an inner surface 50 of the tube structure 8. The moderation tube 20 is made of silver (Ag).

[0088] Within the moderation tube 20, a filling region 9 is formed. A multitude of particles (not shown in detail in Fig. 2, but see, for example, Fig. 5, Fig. 6, and Fig. 7 below) are arranged in the filling region 9, each containing at least one partner component Pk. Here, the partner component Pk is O (oxygen). The partner component Pk is bound to a bonding partner B. Here, the bonding partner B is Cu (copper). The particles consist of Cu₂O. In the example shown, the filling region 9 is filled with a powder consisting exclusively of Cu₂O particles.

[0089] During reaction annealing (also called reaction heat treatment), precipitates XPk can form early on from the partner component Pk from the filling region 9 and the alloying component X from the tube structure 8, typically in the region of the tube structure 8. The XPk precipitates here consist of ZrÜ2. These XPk precipitates can inhibit grain growth of NbsSn grains, which are formed from the Nb from the tube structure 8 and the Sn from the core region of the subelement (see Fig. 1).

[0090] The moderation tube 20 ensures that the Cu₂O particles in the filling area 9 do not directly border the inner surface 50 of the tube structure 8, but only the moderation tube 20. When the Cu₂O particles begin to decompose during the reaction annealing, the partner component Pk, in this case oxygen (O), is released. The silver of the moderation tube 20 does not chemically react with the oxygen, even at the comparatively high local partial pressure reached during the decomposition of immediately adjacent Cu₂O particles. The oxygen diffuses into the silver of the moderation tube 20, where it is distributed essentially uniformly across the cross-section of the moderation tube 20. Accordingly, only a moderate partial pressure of oxygen is reached on the outside of the moderation tube 20, i.e., on the inner surface 50 of the tube structure 8.This ensures that no NbO layer forms on the inner surface 50 of the tube structure 8 during reaction annealing, which would hinder the diffusion of oxygen into the NblZr alloy of the tube structure 8. Instead, the oxygen can distribute itself over the entire cross-sectional area of ​​the tube structure 8 and form local precipitates of ZrÜ₂ throughout its volume early in the reaction annealing process. These ZrÜ₂ precipitates then efficiently inhibit the grain growth of the NbsSn grains that subsequently form in the tube structures 8 of the Nb-containing reaction elements 5 (particularly due to the longer diffusion path of Sn from the core structure 2 to the ring structure 4, see Fig. 1). This results in a finer NbsSn microstructure and a higher superconducting current-carrying capacity in the finished superconducting wire.

[0091] Note that the Nb-containing reaction element 5 is typically first manufactured with a larger cross-section, then subjected to a cross-section-reducing deformation (e.g. drawing or extrusion), and then installed in a sub-element (assembly not shown in detail).

[0092] In the following, some further, different structural designs of Nb-containing reaction elements and sub-elements for the invention are presented as examples; only the respective special features and, if applicable, deviations from the structural designs of Fig. 1 and Fig. 2 are explained.

[0093] Fig. 3 shows an advantageous design of an Nb-containing reaction element 5 in a schematic cross-section.

[0094] The Nb-containing reaction element 5 comprises the tube structure 8, here made of the alloy Nb7.5Hf, a moderation tube 20 on the inner 50 of the tube structure 8, a core structure 17, also made of the alloy Nb7.5Hf, and a filling region 9. The alloy component X is therefore chosen to be X=Hf. The moderation tube 20 consists of Cu. The particles in the filling region 9 consist of SnU2. The filling region 9 is annular and lies radially between the moderation tube 8 and the core structure 17.

[0095] By arranging the core structure 17, which also contains the alloy component X, radially within the filling area 9, diffusion paths for the partner component Pk to the alloy component X can be shortened, and the formation of precipitates XPk can thereby be accelerated. In the case of a core structure 17 that is comparatively small (here with a radius RK of the core structure 17 and a wall thickness WR of the tube structure 8, with approximately RK = 0.15 * WR, and generally with RK < 0.2 * WR), sufficiently rapid penetration of the core structure 17 with the partner component 0 is usually achieved during reaction annealing, even if an NbO layer should temporarily form on the outside 51 of the core structure 17.

[0096] Fig. 4 shows another advantageous design of an Nb-containing reaction element 5 in a schematic cross-section.

[0097] The Nb-containing reaction element 5 comprises the tube structure 8, here made of the alloy Nb7.5Hf, a moderation tube 20 on the inside 50 of the tube structure 8, a core structure 17, also made of the alloy Nb7.5Hf, an additional moderation tube 52 on the outside 51 of the core structure 17, and a filling region 9. The alloy component X is therefore chosen to be X=Hf. The moderation tube 20 and the additional moderation tube 52 are made of Cu. The particles in the filling region 9 are made of SnÜ2.

[0098] The filling area 9 is ring-shaped and lies radially between the moderation tube 20 and the additional moderation tube 52.

[0099] The additional moderation tube 52 prevents the formation of an NbO layer during reaction annealing on the outer surface 51 of the core structure 17, similar to how the moderation tube 20 does this on the inner surface 50 of the tube structure 8. The additional moderation tube 52 is particularly advantageous for larger core structures (especially with RK > 0.2 * WR). In the illustrated design, RK is approximately 0.7 * WR.

[0100] Fig. 5 shows another advantageous design of an Nb-containing reaction element 5 in a schematic cross-section.

[0101] In this design, the filling area 9 inside the moderation tube 20 is filled with a powder 53. The powder 53 contains particles 13, which contain the partner component Pk. In the illustrated embodiment, the particles 13 are made of Cu₂O (the partner component Pk is therefore 0), the moderation tube 20 is made of silver, and the tube structure 8 consists of Nb₇₅Hf (the alloying component X is therefore Hf, and the precipitates XPk are formed from HfÜ₂).

[0102] The powder 53 also contains further particles 54, which are configured here as filler particles 55. The filler particles 55 are made of silicon carbide (SiC). The filler particles 55 do not participate in the formation of the precipitates from HfÜ2, nor in the formation of NbsSn. Because the powder 53 partially consists of the filler particles 55, the (local) partial pressure of the partner component Pk, here O, is reduced both on the inside of the moderation tube 20 and subsequently on the inside 50 of the tube structure 8.

[0103] Additional powder components can easily be mixed into the powder 53, for example for doping purposes. Furthermore, the proportion (or quantity and size) of particles 13 in the filling area 9 is easily adjustable.

[0104] Note that in the schematic representation of Fig. 5, only a few particles 13 and further particles 54 are shown as examples, and the particles 13 and further particles 54 are depicted as exaggeratedly large (this also applies to the following figures). In particular, the (minimum) wall thickness WM of the moderation tube 20 and a mean particle size DP (D50) of the particles 13 are typically WM > 2*DP, preferably WM > 3*DP, and often also WM > 5*DP. Fig. 6 illustrates in more detail, in schematic cross-section, a preferred design of an Nb-containing reaction element 5 for the invention.

[0105] The tube structure 8 consists of a drilled NbZr rod 10 (where X=Zr is chosen as the alloying element X), on the inside 50 of which a copper tube is inserted as a moderation tube 20. The filling area 9 inside the moderation tube 20 contains a metallic matrix 11, which in the illustrated configuration is formed by a metallic powder 12. The metallic powder 12 is an Ag powder. The metallic powder 12 is mixed with particles 13 containing the partner component Pk. The particles 13 are formed by SnÜ2 particles (i.e., partner component Pk=O and bonding partner B=Sn). Thus, in this configuration as well, a powder 53 is arranged in the filling area 9.

[0106] In the illustrated design, the metallic matrix 11 occupies approximately 60% of the surface area of ​​the filling region 9, i.e., 60% of the cross-sectional area of ​​the filling region 9 is occupied by the metallic matrix 11; generally preferred are FMM > 5%, or even FMM > 50% or more, or even FMM > 80%. The remaining 40% of the cross-sectional area is comprised of voids and the particles 13; the surface area of ​​the particles 13 in relation to the total cross-sectional area of ​​the filling region 9 is approximately 10%. The proportion of Sn (here due to the particles 13) in the filling region 9, measured in atomic percent (at%) and based on the sum of all phases in the filling region 9 (here metallic matrix 11 and particles 13), is less than 10%; generally preferred are 25 at% or less, or even 10 at% or less.

[0107] An electrically conductive current path is provided between the individual particles 13 containing the partner components Pk in the filling region 9 and the alloy component X in the tube structure 8 via the electrically conductive metallic matrix 11 in the filling region 9 and the moderation tube 20. The redox reaction, in which the partner component Pk is released from the binding partner B on the particle 13 (and furthermore diffuses to the alloy component X in the tube structure 8, ultimately forming the precipitate XPk), can begin early and involve a large proportion of the particles present, typically practically all of them. Accordingly, the XPk precipitates (or at least most of them) can be formed before the NbsSn (or at least most of it) is formed (in each case, based on volume).This results in a particularly fine structure of the NbsSn grains in the finished NbsSn superconducting wire, and the NbsSn superconducting wire achieves a particularly high superconducting current-carrying capacity.

[0108] Further powder components can easily be mixed into the metallic powder 12, for example for doping purposes. In addition, the proportion (or quantity and size) of particles 13 in the filling area 9 is easily adjustable.

[0109] Fig. 7 illustrates in schematic cross-section another preferred design of an Nb-containing reaction element 5 for the invention.

[0110] The tube structure 8 is formed here by a drilled NbZr rod 10, on the inside 50 of which a moderation tube 20, here made of copper, is arranged. In the filling area 9, a metal body 15 is arranged, which here is designed as a wire (metal wire) 16 and inserted into the moderation tube 20. Alternatively, the metal body 15 can also be designed as a rod (not shown in detail). The metal body 15 here forms the metallic matrix 11. The wire 16 is made of elemental silver. The particles 13, which contain the partner component Pk, are dispersed in the metal body 15 or in the wire 16. In the design shown, the particles 13 are made of SnÜ2.

[0111] With this design, the filling area 9 can be practically completely filled in a simple manner by selecting the (outer) diameter of the wire 16 according to the inner diameter of the moderation tube 20 (with sufficient clearance for insertion). In the design shown, the metallic matrix 11 occupies approximately 90% of the surface area of ​​the filling area 9, i.e., 90% of the cross-sectional area of ​​the filling area 9 is occupied by the metallic matrix 11. The remaining 10% of the cross-sectional area is comprised of the particles 13. Here too, the proportion of Sn (due to the particles 13) in the filling area 9, measured in atomic percent (at%) and relative to the sum of all phases in the filling area 9 (here, the metallic matrix 11 and the particles 13), is less than 10%.

[0112] Fig. 8 shows a schematic cross-section of another embodiment of a sub-element 1 according to the invention, similar to that shown in Fig. 1. In contrast, in the embodiment shown, different types 21, 22, 23 of Nb-containing reaction elements 5 are provided in the ring region 4.

[0113] A first, largest part of the Nb-containing reaction elements 5 in the ring region 4 is formed here as regular Nb-containing reaction elements 21, wherein in the described design the tube structure (shown with cross hatching) consists of an NblZr alloy, the moderation tube consists of silver and the filling region is filled with particles of CU2O.

[0114] A second, smaller portion of the Nb-containing reaction elements 5 in the ring region 4 is configured as doping reaction elements 22, where the tube structure (shown horizontally striped) consists of an Nb₄H₄TilZr alloy. The titanium contained within, from group 4 of the periodic table, catalyzes the formation of NbsSn during reaction annealing. The moderation tube is again made of silver, and the filling region is filled with Cu₂O particles.

[0115] A third, also smaller, portion of the Nb-containing reaction elements 5 in the ring region is configured as reinforcing reaction elements 23, where the tube structure (shown vertically striped) consists of an Nb7,5TalZr alloy. The tantalum contained within, from the fifth transition group of the periodic table, mechanically reinforces the subelement 1. The moderation tube is again made of silver, and the filling region is filled with Cu2O particles.

[0116] Note that in other embodiments, for example, only doping reaction elements 22 or only strengthening reaction elements 23 may be arranged distributed within the regular Nb-containing reaction elements 21 (not shown in detail).

[0117] Fig. 9 shows a schematic cross-section of another embodiment of a sub-element 1 according to the invention, similar to that shown in Fig. 1. In contrast, the embodiment shown provides different elements 24 in the ring region 4.

[0118] A first, largest part of the elements 24 in the ring region 4 is formed here as Nb-containing reaction elements 5, wherein the tube structure (shown with cross hatching) consists of an NblZr alloy, the moderation tube consists of silver and the filling region is filled with particles of CU2O.

[0119] A second, smaller portion of the elements 24 in ring region 4 is formed as dopant elements 25 (shown as horizontal stripes). These dopant elements 25 each consist entirely of an Nb₄H₄Ti alloy. The titanium contained within, from group 4 of the periodic table, catalyzes the formation of NbsSn during annealing. The dopant elements 25 have no filling region and no moderation tube.

[0120] A third, also smaller, portion of the elements 24 in the ring region 4 is configured as reinforcing additive elements 26 (shown as vertical stripes). Here, the reinforcing additive elements 26 consist entirely of pure tantalum. The tantalum contained within, from group 5 of the periodic table, mechanically reinforces the subelement 1. The reinforcing additive elements 26 have no filling region or moderation tube and do not form NbsSn during heat treatment. Note that in other embodiments, for example, only doping additive elements 25 or only reinforcing additive elements 26 may be arranged distributed within the Nb-containing reaction elements 5 (not shown in detail).

[0121] Fig. 10 shows a schematic cross-section of another embodiment of a sub-element 1 according to the invention, similar to that shown in Fig. 1. In contrast, the embodiment shown again provides different elements 24 in the ring region 4.

[0122] A first part of the elements 24 in the ring region 4 is formed here as Nb-containing reaction elements 5, wherein the tube structure (shown with cross hatching) consists of an NblZr alloy, the moderation tube consists of silver, and the filling region is filled with particles of CU2O.

[0123] A second part of the elements 24 in ring region 4 is configured as Nb-containing additive elements 27 (shown completely hatched). Here, the Nb-containing additive elements 27 each consist entirely of an alloy containing Nb and at least one further alloying element X. The alloy of the Nb-containing additive elements 27 is again NblZr. The alloy of the Nb-containing additive elements 27 is thus chosen according to the alloy of the tube structures of the Nb-containing reaction elements 5, which is a preferred case. The Nb-containing additive elements 27 have no filling region and no moderation tube.

[0124] The first part and the second part are approximately the same size here, i.e., they comprise approximately the same number of elements 24 in the ring region 4 of the subelement 1.

[0125] The quantity of particles containing the partner component Pk in the filling regions of the Nb-containing reaction elements 5 is dimensioned such that a sufficient amount of partner component Pk, here with Pk=O, is available for the amount of alloying component X, here with X=Zr, in the Nb-containing reaction elements 5 and the Nb-containing additive elements 27 to form all intended precipitates XPk in the ring region 4. The production of the Nb-containing additive elements 27 is significantly cheaper than the production of the Nb-containing reaction elements 5. Accordingly, sub-element 1 of Fig. 10 is particularly cost-effective to manufacture.

[0126] Fig. 11 shows a schematic cross-section of a particularly preferred embodiment of a sub-element 1 according to the invention. The sub-element 1 is provided for an NbsSn superconductor wire of the RRP® type.

[0127] Subelement 1 comprises a tin-containing core region 2, which is surrounded by the copper-containing inner intermediate region 3. The inner intermediate region 3 is profiled on its radial outer surface, corresponding to a profile of the adjacent hexagonal elements 24 in the ring region 4. The hexagonal elements 24 in the ring region 4 are all configured here as nitrate-containing reaction elements 5 (see also the enlargement on the right in Fig. 11).

[0128] Each Nb-containing reaction element 5 comprises here an outer Cu-containing shell 30 with a hexagonal outer cross-section, here made of elemental copper, furthermore a tube structure 8, a moderation tube 20 and a filling area 9.

[0129] The Nb-containing reaction elements 5 are abutting each other in the ring region 4. An outer intermediate region 28, which here contains Cu, for example elemental copper, is arranged around the Nb-containing reaction elements 5 of the ring region 4. The outer intermediate region 28 has a radially inward profile corresponding to a profile of the adjacent hexagonal elements 24 in the ring region 4.

[0130] A diffusion barrier 29, for example made of Nb, is arranged around the outer intermediate region 28 and is formed in an annular shape in the illustrated design. The diffusion barrier 29 prevents the diffusion of Sn from the Sn-containing core region 2 (or other Sn sources inside the diffusion barrier 29) into the Cu-containing surrounding region 7, which is arranged around the diffusion barrier 29. This allows the Cu-containing surrounding region 7 to retain high electrical conductivity after reaction annealing. The Cu-containing surrounding region 7 is typically made of elemental Cu and, in the illustrated design, has a circular outer surface.

[0131] Note that in one variant of sub-element 1 the Cu-containing surrounding area 7 may have a hexagonal outer cross-section, and the diffusion barrier 29 may also be hexagonal-ring-shaped (instead of circular-ring-shaped) (not shown in Fig. 11, but see Fig. 13, right-hand side).

[0132] Fig. 12 illustrates a further, particularly preferred embodiment of a sub-element 1 according to the invention in a schematic perspective view, at an intermediate stage of its manufacture. A corresponding schematic cross-sectional view of the finished sub-element 1 is shown in Fig. 14, right-hand side. The sub-element 1 is designed for an NbsSn superconducting wire of the global barrier type.

[0133] Subelement 1 is based here on a drilled Cu block 31, which is essentially cylindrical in shape.

[0134] In a central, large bore 32 of the Cu block 31, the Sn-containing core area 2 is formed, here by filling an Sn-containing powder (e.g. a mixture of Sn powder and NbSn2 powder) into the central bore 32.

[0135] A subsequent, radially inner part of the Cu block 31 forms the Cu-containing inner intermediate region 3. Radially outwards, the ring region 4 adjoins, in which the Cu block 31 forms a plurality of recesses 33 or small bores.

[0136] Nb-containing reaction elements 5 are inserted into these recesses 33, each of which is formed with a tube structure 8, a moderation tube 20 and a filling area 9, see also the enlargement on the right in Fig. 12.

[0137] As a result, the Cu block 31 forms a Cu-containing ring matrix 34 in the ring region 4 for the Nb-containing reaction elements 5.

[0138] A subsequent, radially outer part of the Cu block 31 finally forms the Cu-containing surrounding area 7.

[0139] The sub-elements 1 of the RRP® type can be used to manufacture a semi-finished wire 35 as shown in the schematic cross-sectional view of Fig. 13. Here, the sub-elements 1 are designed in the variant with a hexagonal outer cross-section and a hexagonal-ring-shaped diffusion barrier 29; see the enlargement in Fig. 13 on the right and also Fig. 11 for further details of the sub-element 1.

[0140] Several hexagonal sub-elements 1 are placed next to each other and bundled, and arranged in a copper-containing sheathing tube 36. The sheathing tube 36 is made of elemental copper.

[0141] The diffusion barriers 29 of the subelements 1 prevent the Cu-containing surrounding areas 7 of the subelements 1 and the Cu-containing casing tube 36 from being contaminated by Sn from the interior of the subelements 1 during reaction annealing.

[0142] The sub-elements 1 of the Global Barrier type can be used to manufacture a semi-finished wire 35 as shown in the schematic cross-sectional view of Fig. 14. The sub-elements 1 are formed with a round outer surface and a copper block 31; see the enlargement in Fig. 14 on the right and also Fig. 12 for further details of the sub-element 1.

[0143] Several round sub-elements 1 are arranged in corresponding bores of a copper-containing wire matrix 37. The wire matrix 37 can, for example, be made of copper. A total diffusion barrier (or global diffusion barrier) 38, which here has an annular cross-section, is arranged around the wire matrix 37. The total diffusion barrier 38 can, for example, be made of elemental niobium. A copper-containing sheathing tube 39 is formed around the total diffusion barrier 38. The copper-containing sheathing tube 39 is here made of elemental copper.

[0144] The overall diffusion barrier 38 prevents the Cu-containing jacket tube 39 from being contaminated by Sn from the interior of the sub-elements 1 during reaction annealing.

[0145] Figure 15 illustrates the sequence of steps in the manufacture of an NbsSn superconducting wire 40 within the scope of the invention. Schematic partial diagrams of the various manufacturing steps are shown in chronological order from 11 to 126.

[0146] In step tl, a large number of sub-elements 1 are manufactured; typical sub-elements 1 for the invention are explained in the preceding figures.

[0147] In step t2, the sub-elements 1 are then subjected to a cross-section-reducing forming process, for example a drawing process or an extrusion process. This results in a tapered sub-element 1'.

[0148] In step t3, several tapered sub-elements 1' are bundled and arranged in a sheathing tube 36. This yields a semi-finished wire 35.

[0149] In the subsequent step t4, the semi-finished wire 35 undergoes a cross-sectional reduction process, such as drawing or extrusion. This results in a tapered semi-finished wire 35'. If desired, the tapered semi-finished wire can undergo further bundling and tapering iteration (not shown in detail). At the end of step t4, the tapered semi-finished wire 35' has the diameter required for the application. In step t5, the tapered semi-finished wire 35' is then formed into the desired shape. In the example shown, the tapered semi-finished wire 35' is wound onto a spool 41 to form a coil. Note that the tapered semi-finished wire 35' is still highly elastic and plastically deformable before reaction annealing (the heat treatment).

[0150] In step t6, the tapered semi-finished wire is subjected to reaction annealing in a furnace 42. During this process, the contained Nb reacts with the contained Sn to form NbsSn, with XPk precipitates inhibiting the grain growth of NbsSn grains. The previously tapered semi-finished wire thus becomes the finished NbsSn superconducting wire 40. In the example shown, this completes a superconducting magnet coil 43. Note that the NbsSn in the finished semi-finished wire is relatively brittle and should therefore not be deformed. The finished superconducting magnet coil 43 can be used, for example, in a nuclear fusion device (e.g., a fusion power plant) to generate a magnetic field that confines the plasma (not shown in detail).

[0151]

[0152] 1 subelement

[0153] 1' tapered subelement

[0154] 2 Sn-containing core area

[0155] 3 inner intermediate area

[0156] 4 ring area

[0157] 5 Nb-containing reaction element

[0158] 6 spaces

[0159] 7 Cu-containing environment

[0160] 8-pipe structure

[0161] 9 Filling area

[0162] 10 NbZr rod

[0163] 11 metallic matrix

[0164] 12 metallic powder

[0165] 13 particles

[0166] 15 metal bodies

[0167] 16 wire (metal wire)

[0168] 17 Core Structure

[0169] 20 Moderation tube

[0170] 21 regular Nb-containing reaction element

[0171] 22 Doping reaction element

[0172] 23 Amplification reaction element

[0173] 24 elements (in the ring area in general)

[0174] 25 Doping additive element

[0175] 26 Reinforcement add-on element

[0176] 27 Nb-containing additive element

[0177] 28 outer intermediate area

[0178] 29 Diffusion barrier (of the subelement)

[0179] 30 Cu-containing shell (of the Nb-containing reaction element)

[0180] 31 Cu block

[0181] 32 central large bore

[0182] 33 cutouts (in the ring area) 34 ring matrix

[0183] 35 Semi-finished wire

[0184] 35' tapered semi-finished wire

[0185] 36 Cu-containing sheathing tube (of the semi-finished wire)

[0186] 37 wire matrix

[0187] 38 Total diffusion barrier (of the semi-finished wire)

[0188] 39 Cu-containing sheathing tube (of the semi-finished wire)

[0189] 40 NbsSn superconducting wire

[0190] 41 coil formers

[0191] 42 Oven

[0192] 43 superconducting magnetic coil

[0193] 50 Inside of the pipe structure

[0194] 51 Outer surface of the core structure

[0195] 52 Additional moderation tube

[0196] 53 powders

[0197] 54 more particles

[0198] 55 filler particles

[0199] DP mean diameter of the particles

[0200] RK radius of the core structure

[0201] WM minimum wall thickness of the moderation tube

[0202] WR wall thickness of the pipe structure

Claims

Patent claims 1. Sub-element (1) for a semi-finished wire (35) for the production of an NbsSn superconducting wire (40), wherein the sub-element (1) comprises - a tin-containing core area (2), - a Cu-containing, inner intermediate region (3) surrounding the Sn-containing core region (2), - a ring region (4) containing a plurality of Nb-containing reaction elements (5), wherein the ring region (4) surrounds the inner intermediate region (3), - a Cu-containing surrounding region (7) surrounding the ring region (4); wherein the Nb-containing reaction elements (5) have at least - a tube structure (8) which is at least partially made of an Nb alloy containing Nb and at least one further alloying component X, - a filling region (9) located within the tube structure (8) in which a plurality of particles (13) are arranged, wherein the particles (13) contain at least one partner component Pk, wherein the at least one alloy component X and the at least one partner component Pk are selected such that they form precipitates XPk upon reaction annealing of the sub-element (1), characterized in that a moderation tube (20) is formed on an inner side (50) of the tube structure (8), within which the filling region (9) is located.

2. Subelement (1) according to claim 1, characterized in that the moderation tube (20) and at least an adjacent part of the tube structure (8) are made of different materials.

3. Subelement (1) according to one of the preceding claims, characterized in that the moderation tube (20) is free of the at least one partner component Pk contained in the particles (13) in the filling area (9).

4. Subelement (1) according to one of the preceding claims, characterized in that the moderation tube (20) is free of the at least one alloy component X contained in the Nb alloy from which the tube structure (8) is at least partially manufactured.

5. Subelement (1) according to one of the preceding claims, characterized in that the filling area (9) is filled with a powder (53) which contains the particles (13).

6. Subelement (1) according to claim 5, characterized in that the powder (53) contains exclusively the particles (13).

7. Subelement (1) according to claim 5, characterized in that the powder (53) contains the particles (13) as well as further particles (54).

8. Subelement (1) according to claim 7, characterized in that at least some of the further particles (54), in particular all further particles (54), are filler particles (55), wherein the filler particles (55) do not participate in the formation of XPk and Nb3Sn during reaction annealing.

9. Subelement (1) according to one of the preceding claims, characterized in that a metallic matrix (11) is arranged in the filling area (9) and that the particles (13) are arranged distributed in the metallic matrix (11).

10. Subelement (1) according to claim 9, characterized in that the metallic matrix (11) is at least partially formed by a metallic powder (12) which is mixed with the particles (13).

11. Subelement (1) according to claim 9 or 10, characterized in that the metallic matrix (11) is at least partially formed by a metal body (15) in which the particles (13) are dispersed.

12. Subelement (1) according to one of the preceding claims, characterized in that the Nb-containing reaction elements (5) further comprise - a core structure (17) wherein the filling area (9) is located between the moderation tube (20) and the core structure (17), wherein the core structure (17) is at least partially made of an Nb alloy containing Nb and at least one further alloying component X.

13. Subelement (1) according to claim 12, characterized in that an additional moderation tube (52) is formed on an outer side (51) of the core structure (17), outside of which the filling area (9) is located, in particular wherein the additional moderation tube (52) and at least an adjacent part of the core structure (17) are made of different materials.

14. Subelement (1) according to one of the preceding claims, characterized in that the moderation tube (20) contains Cu and / or Ag.

15. Subelement (1) according to one of the preceding claims, characterized in that for a minimum radial wall thickness WM of the moderation tube (20) and a mean D50 particle size DP of the particles (13) in the filling area (9) the following applies: WM>2*DP, preferably WM>3*DP, especially preferred WM>5*DP.

16. Subelement (1) according to one of the preceding claims, characterized in that at least a part of the Nb-containing reaction elements (5) are configured as doping reaction elements (22), wherein the doping reaction elements (22) contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, and / or that doping additive elements (25) are also arranged in the ring region (4), wherein the doping additive elements (25) contain at least one element of the fourth subgroup of the periodic table in at least one contained phase, in particular wherein the at least one element of the fourth subgroup of the periodic table comprises titanium, and / or that at least a part of the Nb-containing reaction elements (5) are configured as reinforcing reaction elements (23), wherein the reinforcing reaction elements (23) contain at least one element of the fifth subgroup of the periodic table in at least one contained phase.and / or that reinforcing elements (26) are also arranged in the ring region (4), wherein the reinforcing elements (26) contain at least one element of the fifth subgroup of the periodic table in at least one contained phase, in particular wherein the at least one element of the fifth subgroup of the periodic table comprises tantalum.

17. Subelement (1) according to one of claims 1 to 16, characterized in that the Nb-containing reaction elements (5) are adjacent to each other in the ring region (4), and that the subelement (1) further comprises a diffusion barrier (29) which surrounds the ring region (4).

18. Subelement (1) according to one of claims 1 to 16, characterized in that the ring region (4) has a Cu-containing ring matrix (34) which forms a plurality of recesses (33) into which the Nb-containing reaction elements (5) are inserted.

19. Semi-finished wire (35) for the production of an NbsSn superconducting wire (40), comprising several bundled sub-elements (1) according to one of the preceding claims.

20. Semi-finished wire (35) according to claim 19, characterized in that the sub-elements (1) are formed according to claim 18, and that an overall diffusion barrier (38) is present which surrounds the entirety of the bundled sub-elements (1) on the outside.

21. Method for producing an NbsSn superconducting wire (40), characterized by the following steps: Step a): Manufacturing a plurality of sub-elements (1) according to any one of claims 1 to 15, Step b): Bundling of the sub-elements (1) to form a semi-finished wire (35) according to one of claims 16 or 17, Step c): Reaction annealing of the semi-finished wire (35) to the NbsSn superconducting wire (40), wherein Sn and Nb react to form NbsSn, wherein in step c) precipitates XPk are first formed in the tube structures (8) and / or the core structures (17), and only subsequently is at least the largest part of the NbsSn formed.

22. NbsSn superconducting wire (40), produced according to a method according to claim 21.

23. Use of an NbsSn superconducting wire (40) according to claim 22 in a nuclear fusion device, in particular wherein the nuclear fusion device is a fusion power plant.

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