阅读说明：本技术 一种超细芯丝多芯MgB2超导线带材的制备方法 (Superfine cored wire multicore MgB2Method for preparing superconducting wire strip ) 是由 王庆阳 熊晓梅 杨芳 闫果 冯勇 于 2021-08-05 设计创作，主要内容包括：本发明公开了一种超细芯丝多芯MgB-(2)超导线带材的制备方法,该方法包括：一、将装管前驱粉末混合后研磨得混合粉末,对包套材料进行表面清洗；二、将混合粉末填装到一次包套中拉拔加工,得到单芯线材；三、将多根单芯线材与中心插棒、边缘插棒集束组装到二次包套中行真空封焊；四、依次进行热挤压、孔型轧制和拉拔并配合中间热处理工艺；五、经成相热处理得到超细芯丝多芯MgB-(2)超导线带材。本发明通过对多根单芯线材集束组装后的结构设计并采用热挤压,提高了各亚组元之间的结合强度,保证了各亚组元之间的协同变形能力,增加了超导芯丝的数量并减小了超导芯丝的直径,降低多芯MgB-(2)超导线带材的交流损耗性能,满足交流传输应用的需求。(The invention discloses a multi-core MgB of superfine core wire 2 A method for producing a superconducting wire tape, comprising: firstly, mixing and grinding pipe-loading precursor powder to obtain mixed powder, and cleaning the surface of a sheath material; secondly, filling the mixed powder into a primary sheath for drawing processing to obtain a single-core wire; thirdly, assembling a plurality of single-core wires, a central plunger and an edge plunger in a bundling manner into the secondary sheath for vacuum seal welding; fourthly, carrying out hot extrusion, hole-pattern rolling and drawing in sequence and matching with an intermediate heat treatment process; fifthly, obtaining the superfine cored wire multi-core MgB through phase-forming heat treatment 2 Superconducting wire tape. The invention improves the bonding strength among the sub-components and ensures the cooperative deformability among the sub-components by the structural design of bundling and assembling a plurality of single-core wires and adopting hot extrusion,the number of the superconducting core wires is increased, the diameter of the superconducting core wires is reduced, and the multi-core MgB is reduced 2 The alternating current loss performance of the superconducting wire strip meets the requirement of alternating current transmission application.)

1. Superfine cored wire multicore MgB₂A method for producing a superconducting wire tape, characterized in that the method comprises the steps of:

step one, mixing and grinding the pipe loading precursor powder to obtain mixed powder, and carrying out surface cleaning on a sheath material comprising a primary sheath and a secondary sheath; the tube-filling precursor powder comprises amorphous B powder and Mg powder, wherein the granularity of the amorphous B powder is 200-400 nm, and the granularity of the Mg powder is 1-5 mu m;

step two, filling the mixed powder obtained in the step one into a primary sheath after surface cleaning, and then performing drawing processing to obtain a single-core wire;

step three, bundling and assembling a plurality of single-core wires obtained in the step two, the central plunger and the edge plunger sub-component into the secondary sheath subjected to surface cleaning in the step one to obtain a multi-core complex, and then performing vacuum sealing and welding;

step four, carrying out hot extrusion, hole-pattern rolling and drawing on the multi-core composite body subjected to vacuum sealing welding in the step three in sequence and matching with an intermediate heat treatment process to obtain the multi-core MgB of the superfine core wire₂A wire tape;

step five, obtaining the superfine core wire multicore MgB in the step four₂The wire and the strip are subjected to phase forming heat treatment to obtain the superfine cored wire multi-core MgB₂A superconducting wire tape; the superfine cored wire multi-core MgB₂The equivalent diameter of the single superconducting core filament in the superconducting wire tape is not more than 10 μm.

2. The multi-core MgB of claim 1₂The preparation method of the superconducting wire strip is characterized in that the mass purity of the amorphous B powder in the step one is not less than 99 percent; the mass purity of the Mg powder is not less than 99.5%.

3. The multi-core MgB of claim 1₂The preparation method of the superconducting wire strip is characterized in that the filling process of the mixed powder in the step two is completed under the protection of high-purity argon, and the mass purity of the high-purity argon is 99.999%.

4. The multi-core MgB of claim 1₂The preparation method of the superconducting wire strip is characterized in that the cross section of the single-core wire in the step two is hexagonal, the secondary sheath adopted for bundling assembly is a B30 alloy sheath, the vacuum seal welding is electron beam welding under the vacuum condition, and the vacuum degree under the vacuum condition is less than 1 x 10^-3Pa。

5. The multi-core MgB of claim 1₂The preparation method of the superconducting wire strip is characterized in that the hot extrusion system in the fourth step is as follows: the temperature is 400-450 ℃, the extrusion speed is 10-20 mm/s, and the system of the intermediate heat treatment process is as follows: keeping the temperature at 450 ℃ for 1-2 h.

6. The multi-core MgB of claim 1₂The preparation method of the superconducting wire strip is characterized in that the system of the phase-forming heat treatment in the step five is as follows: keeping the temperature of 600-680 ℃ for 1-2 h.

Technical Field

The invention belongs to the technical field of superconducting wire strip processing, and particularly relates to a multi-core MgB of superfine core wires₂A method for preparing superconducting wire tape.

Background

Magnesium diboride (MgB)₂) Is a metal compound with a simple binary structure, which has been successfully synthesized in the fifties of the last century, but the superconductivity of the metal compound is not discovered for the first time by Japanese scientists until 2001. MgB₂The material has the advantages of large coherence length, no grain boundary weak connection phenomenon, simple crystal structure, low cost of raw materials and the like, and can be applied in liquid hydrogen, namely in a 20K temperature region. Currently international MgB₂The application research of magnets, cables and the like has been greatly advanced, and the research also aims at MgB₂Materials, particularly wire, have placed more and higher demands. For example, MgB is required₂The wire has lower alternating current loss, higher transmission performance, electromagnetic stability and the like. And MgB is currently commercialized internationally₂The wire rod is generally manufactured by a powder tube filling Process (PIT), such as ex-situ powder tube filling (ex-situ PIT) by ASG company of italy, Hitachi company of japan and Sam Dong company of korea, and so-called continuous powder filling molding (CTFF) by Hyper Tech company of usa, which is essentially a powder tube filling process. Because the flowability of the Mg-B system tubulation precursor powder in the subsequent plastic deformation process is poor, the multicore MgB is usually caused₂The phenomena of sheath group interlayer fracture, superconducting core wire fracture and the like occur in the wire processing process, so the company MgB₂The number of the superconducting core filaments of the commercial wire rod is generally between 12 and 37 cores, and the diameter of the superconducting core filament is generally between 50 and 100 mu m. Multi-core MgB of over 100 cores₂The superconducting wire/strip is generally assembled and processed for more than three times, the process flow is long, and only short samples are reported. For practical multi-core long wires with length of more than one hundred meters, the phenomena of fracture and discontinuity of the superconducting core wire are particularly obvious, and the practical process of the material is restricted. To reduce MgB₂The most direct process for the AC loss performance of wire isThe diameter of the superconducting core wire is reduced, the superconducting wire with the smaller diameter can be obtained by processing the wire to a smaller size, but the process cost is greatly increased, the process popularization is not facilitated, the number of the core wires is increased in another feasible scheme, and higher requirements are provided for subsequent processing processes.

In view of the above-mentioned deficiencies of the prior art, the present group has proposed an extrusion process for preparing multicore MgB₂Method for superconducting wires (ZL201410363120.8), but it is not possible to achieve finer superconducting core filaments, i.e. multicore MgBs with a diameter of less than 10 μm₂And (4) preparing the superconducting wire.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a multi-core MgB of superfine core wire aiming at the defects of the prior art₂A method for preparing superconducting wire tape. The method improves the bonding strength among the sub-components, ensures the cooperative deformability among the sub-components and avoids the problems of the rupture of a jacket material barrier layer and the rupture of a core wire in the subsequent processing process by optimally designing the structure after the bundling and the assembly of a plurality of single-core wires and adopting hot extrusion, thereby increasing the number of the superconducting core wires, reducing the diameter of the superconducting core wires, and effectively reducing the diameter of the multi-core MgB₂The alternating current loss performance of the superconducting wire strip meets the requirement of alternating current transmission application.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: superfine cored wire multicore MgB₂A method for producing a superconducting wire tape, characterized in that the method comprises the steps of:

step one, mixing and grinding the pipe loading precursor powder to obtain mixed powder, and carrying out surface cleaning on a sheath material comprising a primary sheath and a secondary sheath; the tube-filling precursor powder comprises amorphous B powder and Mg powder, wherein the granularity of the amorphous B powder is 200-400 nm, and the granularity of the Mg powder is 1-5 mu m;

step two, filling the mixed powder obtained in the step one into a primary sheath after surface cleaning, and then performing drawing processing to obtain a single-core wire;

step three, bundling and assembling a plurality of single-core wires obtained in the step two, the central plunger and the edge plunger sub-component into the secondary sheath subjected to surface cleaning in the step one to obtain a multi-core complex, and then performing vacuum sealing and welding;

step four, carrying out hot extrusion, hole-pattern rolling and drawing on the multi-core composite body subjected to vacuum sealing welding in the step three in sequence and matching with an intermediate heat treatment process to obtain the multi-core MgB of the superfine core wire₂A wire tape;

step five, obtaining the superfine core wire multicore MgB in the step four₂The wire and the strip are subjected to phase forming heat treatment to obtain the superfine cored wire multi-core MgB₂A superconducting wire tape; the superfine cored wire multi-core MgB₂The equivalent diameter of the single superconducting core filament in the superconducting wire tape is not more than 10 μm.

The method mixes and grinds the tube-loading precursor powder to ensure that the amorphous B powder with micro-nano particle size and the Mg powder with micro-nano particle size are fully and uniformly mixed in the tube-loading precursor powder, avoids the generation of large pores after phase formation and is the multi-core MgB of the superfine core wire₂A foundation is laid for the preparation of superconducting wire strips; because the chemical activity of Mg is higher, the mixing and grinding process of the tube-loading precursor powder is usually finished in a vacuum glove box under the inert atmosphere environment to avoid introducing impurity phases and ensure the multi-core MgB of the superfine core wire₂Purity of superconducting phase in superconducting wire tape. Then, the mixed powder is filled into a tube and drawn to obtain single-core wires, a plurality of single-core wires are assembled in a line bundle to form a multi-core complex, hot extrusion, hole-pattern rolling and drawing are carried out, and phase heat treatment is combined to obtain the multi-core MgB of the superfine core wire₂The invention relates to a superconducting wire strip, which improves the bonding strength between a single-core wire and sub-components of a central plunger and an edge plunger in a multi-core complex through a hot extrusion process, ensures the cooperative deformation capability among the sub-components, and avoids the problems of the fracture of a jacket material barrier layer and the fracture of a core wire in the subsequent processing process, thereby increasing the number of superconducting core wires, reducing the diameter of the superconducting core wires, and realizing the superfine core wire multi-core MgB with the equivalent diameter of not more than 10 mu m of a single superconducting core wire₂The preparation of superconducting wire and strip material, and the number of the superfine core wires can reach more than 100 cores, thereby effectively reducing the multi-core MgB₂Of superconducting tapesThe alternating current loss performance meets the requirement of alternating current transmission application, and the method is simple in process, low in cost and beneficial to popularization.

In the first step of the invention, the surface cleaning of the sheath material comprises two steps of deoiling treatment and oxide removal treatment: usually, the deoiling treatment process is completed in ultrasonic cleaning equipment, the cleaning solution is a metal cleaning agent aqueous solution with the mass concentration of 1 per mill, the ultrasonic cleaning time is 15 min-30 min, and in order to ensure the deoiling effect and the operability, the temperature of the cleaning solution is kept at 30-60 ℃; whereas the oxide removal treatment is typically accomplished in aqueous nitric acid.

After the mixed powder in the second step of the invention is filled into the sheath material, the single-core wire rod is obtained by drawing processing with the pass processing rate of 10 percent, and the central plunger rod and the edge plunger rod are obtained by processing simultaneously as the sub-components, and the cross section shape of the central plunger rod is completely the same as that of the single-core wire rod. Because the stress at the central position of the cross section of the multi-core composite body is concentrated in the plastic processing processes of hot extrusion, hole-pattern rolling, drawing and the like of the subsequent multi-core composite body, the Nb/Cu composite rod is usually arranged at the position as a central inserted rod, and the core breaking phenomenon is avoided by utilizing the good plastic processing performance of the Nb/Cu composite rod; meanwhile, an oxygen-free copper rod is usually adopted as an edge insert rod to improve the filling ratio during cluster assembly, avoid the folding phenomenon of the sub-component single-core wire during the initial upsetting process during hot extrusion, have good heat conduction and electric conductivity, improve the percentage of Cu in the multi-core wire strip, and be beneficial to improving the multi-core MgB of the superfine core wire₂Electromagnetic and thermal stability of superconducting wire tape.

In the third step of cluster assembly, central plug rods are arranged at the core part of a secondary sheath used for cluster assembly, the number of the central plug rods is usually 7 or 17, single-core wires are arranged around the central plug rods, the number of the single-core wires is usually 100 or 300, and gaps between the secondary sheath and the single-core wires are sequentially filled with edge plug rods and oxygen-free copper, so that the cluster assembly density is improved, the gaps between the single-core wires and the secondary sheath are reduced, and the multi-core MgB of the superfine core wires is further reduced₂The porosity between the superfine core filaments in the superconducting wire strip is beneficial to reducing the alternating current loss performance.

The superfine cored wire multi-core MgB₂The preparation method of the superconducting wire strip is characterized in that the mass purity of the amorphous B powder in the step one is not less than 99 percent; the mass purity of the Mg powder is not less than 99.5%. The quality purity of the optimized amorphous B powder and Mg powder is beneficial to improving the quality purity of the superconducting phase and ensuring the multi-core MgB of the superfine core wire₂The superconducting performance of the superconducting wire strip; typically, the amorphous B powder and Mg powder in the tubulation precursor powder are mixed according to the Mg: b was calculated and weighed at a molar ratio of 1: 2.

The superfine cored wire multi-core MgB₂The preparation method of the superconducting wire strip is characterized in that the filling process of the mixed powder in the step two is completed under the protection of high-purity argon, and the mass purity of the high-purity argon is 99.999%. By adopting high-purity argon protection, the reaction of high-activity active powder and water vapor or oxygen elements in the air is effectively avoided.

The superfine cored wire multi-core MgB₂The preparation method of the superconducting wire strip is characterized in that the cross section of the single-core wire in the step two is hexagonal, the secondary sheath adopted for bundling assembly is a B30 alloy sheath, the vacuum seal welding is electron beam welding under the vacuum condition, and the vacuum degree under the vacuum condition is less than 1 x 10^-3Pa. The cross section of the single-core wire rod is designed into a hexagon shape, so that the close adhesion between the adjacent single-core wire rods after bundling and assembling is facilitated, a stable structure is formed, the smooth proceeding of the subsequent hot extrusion, hole pattern rolling and drawing processes is facilitated, the loading quantity of the single-core wire rods in bundling and assembling is increased, and the multi-core MgB of the superfine core wire is further increased₂The number of core wires in the superconducting wire strip is reduced, and the multi-core MgB of the superfine core wires is reduced₂The porosity between the superfine core filaments in the superconducting wire strip is beneficial to reducing the alternating current loss performance. Meanwhile, the non-magnetic B30 alloy with higher strength and good plastic processing performance is used as the secondary sheath, so that the smooth deformation of the multi-core complex in the subsequent hot extrusion process is facilitated, the number of single-core wires loaded in one bundling assembly is increased, and the superconducting core wire with more (more than 100 cores) number is obtainedMgB₂The superconducting wire strip has thinner superconducting core wires (the equivalent diameter is not more than 10 mu m), thereby solving the problem of preparing multi-core MgB by the traditional powder tube-filling process₂Core breaking and wire breaking during wire material.

The superfine cored wire multi-core MgB₂The preparation method of the superconducting wire strip is characterized in that the hot extrusion system in the fourth step is as follows: the temperature is 400-450 ℃, the extrusion speed is 10-20 mm/s, and the system of the intermediate heat treatment process is as follows: keeping the temperature at 450 ℃ for 1-2 h. The multi-core compound body after vacuum sealing and welding is preheated to 400-450 ℃ to reduce the deformation resistance in the extrusion process, then a single-pass hot extrusion process with large processing rate is adopted, the extrusion speed is 10-20 mm/s, the preferred extrusion ratio is 10 generally, and good bonding performance between a single-core wire in the multi-core compound body and a central plunger and an edge plunger is ensured; and removing an oxide layer formed on the surface of the hot extrusion piece in the hot processing process by adopting an acid etching or peeling process after the hot extrusion, and then further reducing and elongating the hot extrusion piece by adopting hole-pattern rolling and drawing and matching with an intermediate heat treatment process to form the superfine core wire.

The superfine cored wire multi-core MgB₂The preparation method of the superconducting wire strip is characterized in that the system of the phase-forming heat treatment in the step five is as follows: keeping the temperature of 600-680 ℃ for 1-2 h. According to the invention, the precursor powder for loading the tube is made into MgB through the phase-forming heat treatment₂The superconducting phase ensures the superconducting performance of the product.

Compared with the prior art, the invention has the following advantages:

1. according to the invention, through carrying out optimized design on the structure after bundling and assembling a plurality of single-core wires, the hot extrusion process is adopted to improve the bonding strength between the single-core wires and the sub-components of the central plunger and the edge plunger in the multi-core complex, and the subsequent pass rolling and drawing are combined, so that the cooperative deformability among the sub-components is ensured, and the problems of cracking of the barrier layer of the sheath material and even the core wire in the subsequent processing process are avoided, thereby increasing the number of the superconducting core wires, reducing the diameter of the superconducting core wire, realizing that the equivalent diameter of the superconducting core wire is not more than 10 mu m, and the number of the superconducting core wires reaches the number of the superconducting core wiresMulti-core MgB of ultra-fine core wire above 100 cores₂Preparation of superconducting wire and strip material for effectively reducing multi-core MgB₂The alternating current loss performance of the superconducting wire strip meets the requirement of alternating current transmission application.

2. The invention adopts the non-magnetic B30 alloy with higher strength and good plastic processing performance as the secondary sheath, which is beneficial to the smooth deformation of the multi-core complex in the subsequent hot extrusion process, thereby improving the quantity of single-core wires loaded in one-time bundling assembly and further obtaining MgB with more superconducting core wires (which can exceed 100 cores)₂The superconducting wire strip has thinner superconducting core wires (the equivalent diameter is not more than 10 mu m), thereby solving the problem of preparing multi-core MgB by the traditional powder tube-filling process₂Core breaking and wire breaking during wire material.

3. The invention adopts a single-pass large-processing-rate hot extrusion process after cluster assembly to ensure that mixed powder, primary sheath, secondary sheath, central plunger, edge plunger and other multi-component complex system multi-core structure MgB in a single-core wire rod₂The cooperative deformation of each component in the wire further improves the binding force between the sub-components, and solves the problem of poor binding force between core wires in the traditional drawing process.

Drawings

FIG. 1 is a cross-sectional view showing the structure of a multicore composite of the present invention.

FIG. 2 shows the multi-core MgB of the ultra-fine core wire prepared in example 1 of the present invention₂A cross-sectional microscopic view of the superconducting wire.

Description of reference numerals:

1-loading tube precursor powder; 2, primary covering; 3-a central plunger;

4-edge plunger. And 3, secondary sheathing.

Detailed Description

Example 1

The embodiment comprises the following steps:

step one, amorphous B powder with the granularity of 300nm and the mass purity of 99 percent and Mg powder with the granularity of 5 mu m and the mass purity of 99.5 percent are mixed according to the proportion of Mg: calculating and weighing the molar ratio of B to 1:2, grinding the mixture to obtain mixed powder, and simultaneously carrying out surface cleaning on the sheath materials including a primary sheath Nb/Cu composite pipe and a secondary sheath B30 alloy sheath, wherein the surface cleaning comprises two steps of deoiling treatment and oxide removing treatment: firstly, ultrasonically cleaning a metal cleaner aqueous solution with the mass concentration of 1 per mill in ultrasonic cleaning equipment at 50 ℃ for 20min to finish deoiling treatment, and then removing surface oxides by using a nitric acid aqueous solution;

step two, in a vacuum glove box with the quality purity of 99.999% under the protection of argon, filling the mixed powder obtained in the step one into an Nb/Cu composite tube with the surface cleaned and dried, then drawing at a pass processing rate of 10% to obtain a single-core wire, wherein the cross section of the single-core wire is in a regular hexagon, the opposite side distance of the regular hexagon is 3.1mm, simultaneously processing to obtain an Nb/Cu central inserted rod with a cross section in a regular hexagon and an opposite side distance of the regular hexagon of 3.1mm, and an oxygen-free copper edge inserted rod with diameters of 2.0mm, 1.5mm and 1.0mm as subcomponents, and then cleaning the single-core wire, the Nb/Cu central inserted rod and the oxygen-free copper edge inserted rod, cutting and straightening according to the length of 150 mm;

thirdly, placing 19 straightened Nb/Cu central insertion rods in the second step into a core part of a B30 alloy sheath, orderly surrounding 180 straightened single-core wires in the second step around the 19 Nb/Cu central insertion rods, filling gaps between the B30 alloy sheath and the single-core wires with the straightened oxygen-free copper edge insertion rods and the oxygen-free copper in the second step to obtain a multi-core composite body, wherein the cross section of the multi-core composite body is shown in figure 1, and then performing electron beam sealing welding under the vacuum condition, wherein the vacuum degree under the vacuum condition is less than 1 multiplied by 10^-3Pa; the outer diameter of the B30 alloy sheath is 64mm, and the inner diameter is 48 mm;

step four, heating the multi-core complex subjected to vacuum sealing welding in the step three to 430 ℃, preserving heat for 1.5 hours, carrying out single-pass extrusion at the extrusion speed of 15mm/s, removing an oxide layer on the surface of an extrusion piece through peeling, and then processing to obtain the fine-core-wire multi-core MgB with the diameter of 0.812mm by adopting a pass rolling and drawing process with the pass processing rate of 12 percent and matching with an intermediate heat treatment process with the temperature preservation of 450 ℃ for 1.5 hours₂A wire rod;

step five, obtaining the superfine core wire multicore MgB in the step four₂The wire is subjected to phase-forming heat treatment at 650 ℃ for 1.5h under the protection of flowing argon to obtain the multi-core MgB of the superfine core wire₂A superconducting wire; the superfine cored wire multi-core MgB₂The equivalent diameter of the single superconducting core filament in the superconducting wire rod is 9.5 μm.

FIG. 2 shows the multi-core MgB of the ultra-fine core wire prepared in this example₂The cross-sectional microstructure of the superconducting wire is shown in FIG. 2, and the multi-core MgB of the ultra-fine core wire₂The outer sheath of the superconducting wire is B30 cupronickel alloy, the central part is 19 Nb/Cu central inserted rods, and 180 MgBs are distributed between the outer sheath and the Nb/Cu central inserted rods₂The black part of the/NbCu single-core superconducting core wire is MgB₂Superconducting core wires, wherein oxygen-free copper stabilizer material MgB is filled between the single-core superconducting core wires₂A Nb/Cu barrier layer is arranged between the superconducting core wire and the oxygen-free copper stabilizer material, which shows that the superfine core wire multi-core MgB with the diameter of 0.812mm is obtained by combining cluster assembly with composite processing technologies such as hot extrusion, drawing, rolling and the like₂The equivalent diameter of the single superconducting core wire is 9.5 mu m, and the barrier layer has no crack phenomenon.

Example 2

The embodiment comprises the following steps:

step one, amorphous B powder with the granularity of 200nm and the mass purity of 99 percent and Mg powder with the granularity of 1 mu m and the mass purity of 99.5 percent are mixed according to the proportion of Mg: calculating and weighing the molar ratio of B to 1:2, grinding the mixture to obtain mixed powder, and simultaneously carrying out surface cleaning on the sheath materials including a primary sheath Nb/Cu composite pipe and a secondary sheath B30 alloy sheath, wherein the surface cleaning comprises two steps of deoiling treatment and oxide removing treatment: firstly, carrying out ultrasonic cleaning for 15min at 60 ℃ in ultrasonic cleaning equipment by adopting a metal cleaner aqueous solution with the mass concentration of 1 per mill, so as to finish deoiling treatment, and then removing surface oxides by adopting a nitric acid aqueous solution;

step two, in a vacuum glove box with the quality purity of 99.999% under the protection of argon, filling the mixed powder obtained in the step one into an Nb/Cu composite tube with the surface cleaned and dried, then drawing at a pass processing rate of 10% to obtain a single-core wire, wherein the cross section of the single-core wire is in a regular hexagon, the opposite side distance of the regular hexagon is 3.1mm, simultaneously processing to obtain an Nb/Cu central inserted rod with a cross section in a regular hexagon and an opposite side distance of the regular hexagon of 3.1mm, and an oxygen-free copper edge inserted rod with diameters of 2.0mm, 1.5mm and 1.0mm as subcomponents, and then cleaning the single-core wire, the Nb/Cu central inserted rod and the oxygen-free copper edge inserted rod, cutting and straightening according to the length of 180 mm;

thirdly, placing 19 straightened Nb/Cu central insertion rods in the second step into a core part of a B30 alloy sheath, orderly surrounding 222 straightened single-core wires in the second step around the 19 Nb/Cu central insertion rods, filling gaps between the B30 alloy sheath and the single-core wires with the straightened oxygen-free copper edge insertion rods and the oxygen-free copper to obtain a multi-core composite, and performing electron beam sealing welding under a vacuum condition, wherein the vacuum degree of the vacuum condition is less than 1 x 10^-3Pa; the outer diameter of the B30 alloy sheath is 64mm, and the inner diameter is 53.5 mm;

step four, heating the multi-core complex subjected to vacuum sealing welding in the step three to 400 ℃, preserving heat for 1.5 hours, carrying out single-pass extrusion at the extrusion speed of 20mm/s, removing an oxide layer on the surface of an extrusion piece through peeling, and then processing to obtain the fine-core-wire multi-core MgB with the diameter of 0.8mm by adopting a pass rolling and drawing process with the pass processing rate of 15% and an intermediate heat treatment process with the temperature preservation of 450 ℃ for 1 hour₂A wire rod;

step five, obtaining the superfine core wire multicore MgB in the step four₂The wire is subjected to phase forming heat treatment in the protection of flowing argon and heat preservation at 680 ℃ for 1h to obtain the multi-core MgB of the superfine core wire₂A superconducting wire; the superfine cored wire multi-core MgB₂The equivalent diameter of a single superconducting core filament in the superconducting wire rod is 9 μm.

Example 3

The embodiment comprises the following steps:

step one, amorphous B powder with the granularity of 400nm and the mass purity of 99 percent and Mg powder with the granularity of 10 mu m and the mass purity of 99.5 percent are mixed according to the proportion of Mg: calculating and weighing the molar ratio of B to 1:2, grinding the mixture to obtain mixed powder, and simultaneously carrying out surface cleaning on the sheath materials including a primary sheath Nb/Cu composite pipe and a secondary sheath B30 alloy sheath, wherein the surface cleaning comprises two steps of deoiling treatment and oxide removing treatment: firstly, carrying out ultrasonic cleaning for 30min at 30 ℃ in ultrasonic cleaning equipment by adopting a metal cleaning agent aqueous solution with the mass concentration of 1 per mill to finish deoiling treatment, and then removing surface oxides by adopting a nitric acid aqueous solution;

step two, in a vacuum glove box with the quality purity of 99.999% under the protection of argon, filling the mixed powder obtained in the step one into a Nb/Cu composite tube with the surface cleaned and dried, then drawing at a pass processing rate of 10% to obtain a single-core wire, wherein the cross section of the single-core wire is in a regular hexagon, the opposite side distance of the regular hexagon is 4.0mm, and meanwhile, the Nb/Cu central inserted rod with the cross section in the regular hexagon and the opposite side distance of the regular hexagon of 3.1mm and the oxygen-free copper edge inserted rod with the diameters of 2.0mm, 1.5mm and 1.0mm are obtained as subcomponents, and then the single-core wire, the Nb/Cu central inserted rod and the oxygen-free copper edge inserted rod are cut off and straightened according to the length of 165mm after being cleaned;

step three, placing 7 straightened Nb/Cu central insertion rods in the step two into a core part of a B30 alloy sheath, orderly surrounding 102 straightened single-core wires in the step two around the 7 Nb/Cu central insertion rods, filling gaps between the B30 alloy sheath and the single-core wires with the straightened oxygen-free copper edge insertion rods and the oxygen-free copper in the step two to obtain a multi-core composite body, and performing electron beam sealing welding under a vacuum condition, wherein the vacuum degree of the vacuum condition is less than 1 x 10^-3Pa; the outer diameter of the B30 alloy sheath is 64mm, and the inner diameter is 43.5 mm;

step four, heating the multi-core complex subjected to vacuum sealing welding in the step three to 450 ℃, preserving heat for 1 hour, carrying out single-pass extrusion at the extrusion speed of 10mm/s, removing an oxide layer on the surface of an extrusion piece through peeling, and then processing to obtain the fine-core-wire multi-core MgB with the diameter of 0.85mm by adopting a pass rolling and drawing process with the pass processing rate of 10 percent and an intermediate heat treatment process with the heat preservation at 450 ℃ for 2 hours₂A strip of material;

step five, obtaining the product in the step fourThe superfine core wire multi-core MgB₂The strip is subjected to phase forming heat treatment in the flowing argon protection at the temperature of 600 ℃ for 2 hours to obtain the superfine cored wire multi-core MgB₂A superconducting tape; the superfine cored wire multi-core MgB₂The equivalent diameter of the individual superconducting core filaments in the superconducting tape is 10 μm.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.