Preparation method of Ni3Sn wire by internal tin method

Abstract

The invention relates to the technical field of superconducting materials, in particular to a method for preparing a Ni3Sn wire through an internal tin method. The method comprises the following steps: by taking inner tin method Nb3Sn wire sub-components in different shapes as initial raw materials, densely arranging and filling the initial raw materials into Ta tubes with corresponding sizes, then filling the Ta tubes filled with the sub-components into oxygen-free copper tubes to form an inner tin method Nb3Sn composite wire, processing the inner tin method Nb3Sn composite wire to a fixed size, wrapping two ends of the composite wire with polytetrafluoroethylene to prevent an acid solution from entering the composite wire, and finally obtaining the inner tin method Nb3Sn composite wire. And after acid pickling, the composite wire is loaded into the oxygen-free copper pipe again, and the steps are repeated to obtain the internal tin method Nb3Sn wire rods with different copper ratios. According to the large-copper-ratio wire prepared through the method, the defect that an Nb3Sn wire prepared through an existing preparation method is prone to breakage and unstable in the large-size stage stretching process is overcome, the mold universality is improved, and stretching of the Nb3Sn wire prepared through the internal tin method with different copper ratios can be completed through a fixed mold.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting materials, in particular to a method for preparing niobium-tin wire by internal tin method. Background Art

[0002] Nb3Sn superconducting wire has a high critical current density and is an important raw material for manufacturing high-field magnets. The internal tin method is one of the main methods for preparing Nb3Sn superconducting wire. At present, the Nb3Sn superconducting wire with the highest performance and the widest application in the world is prepared by the internal tin method. Its composite wire usually adopts a single composite method, that is, the subcomponents are assembled into oxygen-free copper tubes for multiple drawing to obtain Nb3Sn composite wire. In order to improve the machinability, thermal stability at low temperatures, and thermal conductivity of the composite wire, non-superconducting materials (such as Cu) are often added to the superconducting wire. The copper ratio refers to the volume ratio of copper to non-copper. The copper to non-copper volume ratio of Nb3Sn wire is defined as the volume ratio of the copper area of ​​the wire stabilizing material to the non-copper area of ​​the wire, which is a key parameter of superconducting wire. The internal tin method Nb3Sn wire needs to undergo a heat treatment process to form the Nb3Sn superconducting phase. During the heat treatment process, the Sn in the subcomponent inside the Ta tube will first undergo an interdiffusion reaction with Cu, and then react with Nb to form Nb3Sn. Therefore, after the heat treatment process, there will be no oxygen-free copper inside the Ta tube. The copper ratio of the internal tin method Nb3Sn wire refers to the volume ratio of the copper outside the Ta tube to the non-copper inside the Ta tube. The copper ratio of the internal tin method Nb3Sn wire is only related to the outer oxygen-free copper tube; the traditional internal tin method Nb3Sn wire copper ratio is about 0.92~1.08, and the oxygen-free copper tube used is 65mm in outer diameter and 46.3mm in inner diameter (i.e. φ65 / φ46.3). In order to further improve the thermal conductivity, flexibility and durability of the wire, it is necessary to prepare Nb3Sn wire with a large copper ratio.

[0003] At present, Nb3Sn superconducting wires with large copper ratios are mostly produced by increasing the wall thickness of oxygen-free copper tubes. After a single assembly, they are processed by cold drawing. Nb3Sn superconducting wires with too high copper ratios will increase the wall thickness of the oxygen-free copper tubes. The internal core wires will deform unevenly during the large-size stretching stage, causing breakage, which increases the difficulty of cold drawing during the large-size stretching stage. In addition, Nb3Sn superconducting wires prepared by increasing the wall thickness of oxygen-free copper tubes have an outer diameter of 80mm when the copper ratio is 2. When the copper ratio of the superconducting wire is greater than 2, the outer diameter of the copper tube also increases, which cannot meet the requirements of conventional superconducting wire processing molds that the copper outer diameter of the superconducting wire is not more than 75mm. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing niobium wire by internal tin method, which increases the copper ratio in superconducting wire by repeating the composite wire assembly-stretching process, while improving the copper ratio of Nb3Sn wire and overcoming the technical problem of difficulty in cold drawing of large-size wire in the stretching stage caused by the existing internal tin method for preparing Nb3Sn wire and single use of thick oxygen-free copper tube for assembly.

[0005] In one aspect, the present invention provides a method for preparing a niobium-tin wire by an internal tin method, the method comprising the following steps:

[0006] Step 1: densely arranging the subcomponents, placing them in the barrier layer in sequence, and then placing them in the first oxygen-free copper tube, and after multiple stretching, obtaining the first Nb3Sn superconducting wire precursor;

[0007] Step 2: placing the first Nb3Sn superconducting wire precursor in a second oxygen-free copper tube and stretching it multiple times to obtain a second Nb3Sn superconducting wire precursor;

[0008] Step 3: Repeat step 2 until the final Nb3Sn billet is obtained, and after multiple stretching, the Nb3Sn superconducting wire is obtained.

[0009] Furthermore, in the method for preparing the Nb3Sn wire, the specifications of the first oxygen-free copper tube or the second oxygen-free copper tube are independently selected from an outer diameter of 20 to 75 mm, an inner diameter of 15 to 60 mm, and a length of 600 to 10000 mm.

[0010] Furthermore, in the method for preparing the Nb3Sn wire, in any step of the multiple stretching, the pass processing rate is 2 to 30%, and the stretching speed is 1 to 100 m / min.

[0011] Furthermore, in the method for preparing the Nb3Sn wire, the material of the barrier layer is Ta and the diameter is 20 to 60 mm.

[0012] Furthermore, in the preparation method of the Nb3Sn wire, the subcomponents are densely arranged in the form of hexagonal subcomponents, semicircular subcomponents, and fan-shaped subcomponents; and the length of a single subcomponent is 600 to 4000 mm.

[0013] Furthermore, in the method for preparing the Nb3Sn wire, the size of the first Nb3Sn superconducting wire precursor is 10 to 50 mm.

[0014] Furthermore, in the method for preparing the Nb3Sn wire, the two ends of the first Nb3Sn superconducting wire precursor are wrapped during the processing in step 2.

[0015] On the other hand, the present invention provides a Nb3Sn wire prepared by the above-mentioned method for preparing the Nb3Sn wire.

[0016] Furthermore, the outer diameter of the Nb3Sn wire is 20-75 mm, and the copper ratio is not less than 2.

[0017] Furthermore, the copper ratio of the Nb3Sn wire is not less than 8.

[0018] It is particularly noted that, generally, the preparation method of the Nb3Sn wire provided by the present invention is not only suitable for the preparation of low copper ratio Nb3Sn wire (copper ratio less than 2), but also suitable for the preparation of high copper ratio Nb3Sn wire (copper ratio not less than 2), and is most suitable for the preparation of high copper ratio Nb3Sn wire (copper ratio not less than 8).

[0019] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0020] The present invention provides a method for preparing niobium-tin wire by internal tin method, wherein subcomponents of Nb3Sn wires of different shapes are used as initial raw materials, which are densely packed into Ta tubes of corresponding sizes, and then the Ta tubes with subcomponents are packed into oxygen-free copper tubes to form Nb3Sn precursors of internal tin method, and the Nb3Sn precursors are assembled into oxygen-free copper tubes for multiple times to obtain Nb3Sn wires of internal tin method with required copper ratio. In particular, the method can be used to prepare Nb3Sn wires with an outer diameter of copper tubes not greater than 75 mm when the copper ratio is greater than 2, which cannot be achieved by the prior art.

[0021] The present invention changes the single use of thick oxygen-free copper tubes to assemble the large copper ratio internal tin method Nb3Sn composite wire by repeating the composite wire assembly-stretching process into multiple assemblies using thinner-walled oxygen-free copper tubes, so that the core wire of the wire is uniformly deformed in the large-size stretching stage, thereby ensuring the stability of the large copper ratio wire in the large-size stretching stage, and ensuring the subsequent long-line processing capacity and the stability of the wire performance; in addition, the use of thin-walled oxygen-free copper tubes increases the versatility of molds, and the stretching of Nb3Sn wires with different copper ratios and internal tin methods can be completed using a fixed mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The cross-sectional structure diagram of a Nb3Sn wire prepared by a method for preparing a niobium-tin wire by an internal tin process of the present invention; in the figure: 1-subcomponent, 2-Ta tube, 3-oxygen-free copper tube, 4-oxygen-free copper tube, 5-oxygen-free copper tube. DETAILED DESCRIPTION

[0023] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0024] Example 1

[0025] This embodiment is for preparing a Nb3Sn superconducting wire with a designed copper ratio of 9.61.

[0026] Select the barrier layer Ta tube with a diameter of 40mm and a length of 2.5m, H8mm, semicircular 8mm, fan-shaped 6mm sub-component, length of 2.5m, and the selected oxygen-free copper tube 3 specifications are After cleaning the Ta tube and the subcomponents, the subcomponents are first densely packed and bundled into the Ta tube, and then loaded into the cleaned oxygen-free copper tube 3 to obtain the final Nb3Sn billet, which is then stretched multiple times at a processing rate of 2% to 15% to obtain a 40mm first Nb3Sn superconducting wire precursor.

[0027] The first Nb3Sn superconducting wire precursor is wrapped with polytetrafluoroethylene at both ends and then cleaned to prevent acid from entering the wire during the cleaning process; the cleaning process first uses an emulsifier to ultrasonically clean the surface oil stains, then cleans with a nitric acid solution, then cleans the surface with a chromic acid solution, rinses the surface acid stains with water, and finally dehydrates with alcohol to complete the cleaning; the specifications are selected as The oxygen-free copper tube 4 is prepared by placing the first Nb3Sn superconducting wire precursor after cleaning into the oxygen-free copper tube after cleaning, and then the second Nb3Sn superconducting wire precursor with a diameter of 39 mm is obtained by multiple stretching at a processing rate of 2% to 30% and a stretching speed of 1 to 100 m / min. The first Nb3Sn superconducting wire precursor and the second Nb3Sn superconducting wire precursor preparation steps are repeated once to obtain the internal tin method Nb3Sn final billet with a designed copper ratio of 9.6, and then the second Nb3Sn superconducting wire precursor is obtained by multiple stretching at a processing rate of 2% to 30% and a stretching speed of 1 to 100 m / min. The cross-sectional structure diagram of Nb3Sn superconducting wire is shown in FIG. Figure 1 shown.

[0028] The copper mass method is used to measure the copper to non-copper volume ratio of the prepared superconducting wire. This method is limited to externally stable circular cross-section Cu / Nb3Sn wires. The measurement is carried out according to the following steps:

[0029] a) Take a sample with a length between 300mm and 500mm, and determine its mass (M1), length (L) and wire diameter (D). The wire diameter should be measured at 5 different equally divided points on the line, and the average value should be taken. From this, the volume (V1) of the sample can be calculated according to the formula.

[0030] V1=π(D / 2) 2 L

[0031] b) Place the sample in nitric acid until all the copper of the stabilizing material is corroded away, then quickly remove it and rinse it with clean water to minimize the corrosion of the bronze in the non-copper part.

[0032] c) The sample should be completely dry after cleaning.

[0033] d) Measure the mass of the non-copper part (M2).

[0034] e) The density of copper is 8.93g / cm 3 Calculate the volume of the non-copper part (V2) according to the formula.

[0035] (V2) = (M1-M2) / 8.93

[0036] f) Calculate the copper to non-copper volume ratio (R) of the copper mass method based on the sample volume (V1) and the copper part volume (V2). Cu，C ).

[0037] (R Cu，C )=V2 / (V1-V2)

[0038] A sample with a length of 500 mm was taken from the Nb3Sn superconducting wire prepared in Example 1, and its mass was tested to be 10.81 g. The wire diameters at 5 different points were taken, and the average value was calculated to be 0.818 mm. The sample was placed in nitric acid until all the copper of the stabilizing material was corroded away, and the sample was quickly removed and washed with water. After washing, the sample was completely dried, and the mass of the non-copper part was measured to be 8.68 g. The copper ratio can be calculated by the formula to be 9.61, which is consistent with the designed copper ratio.

[0039] The patented method is used to prepare wire with a copper ratio of 9.61, using only the specification of The oxygen-free copper tube is suitable for conventional superconducting wire processing molds, and no breakage occurs during the processing of diameters above φ14.07mm. When stretched to the final size, the wire is only broken once, and the cumulative stretching length reaches 51,800m. If the thick-walled copper tube is used in a single composite method, The outer diameter is far beyond the conventional superconducting wire processing mold, which greatly increases the processing difficulty;

[0040] Example 2

[0041] This embodiment is for preparing a Nb3Sn superconducting wire with a designed copper ratio of 10.1.

[0042] Select the barrier layer Ta tube with a diameter of 45mm and a length of 3m, H9.5mm, semicircular 9.5mm, fan-shaped 7.5mm sub-component, and a length of 3m. The selected oxygen-free copper tube 3 specifications are After cleaning the Ta tube and the subcomponents, the subcomponents are first densely packed and bundled into the Ta tube, and then loaded into the cleaned oxygen-free copper tube 3 to obtain the final Nb3Sn billet, which is then stretched multiple times at a processing rate of 2% to 15% to obtain a 35mm first Nb3Sn superconducting wire precursor.

[0043] The first Nb3Sn superconducting wire precursor is wrapped with polytetrafluoroethylene at both ends and then cleaned to prevent acid from entering the wire during the cleaning process; the cleaning process first uses an emulsifier to ultrasonically clean the surface oil stains, then cleans with a nitric acid solution, then cleans the surface with a chromic acid solution, rinses the surface acid stains with water, and finally dehydrates with alcohol to complete the cleaning; the specifications are selected as The oxygen-free copper tube 4 is prepared by placing the cleaned intermediate-size Nb3Sn superconducting wire into the cleaned oxygen-free copper tube, and then the second Nb3Sn superconducting wire precursor with a diameter of 34 mm is obtained by multiple stretching at a processing rate of 2% to 30% and a stretching speed of 1 to 100 m / min. The first Nb3Sn superconducting wire precursor and the second Nb3Sn superconducting wire precursor preparation steps are repeated three times to obtain the internal tin method Nb3Sn final billet with a designed copper ratio of 10, and then the Nb3Sn superconducting wire is obtained by multiple stretching at a processing rate of 2% to 30% and a stretching speed of 1 to 100 m / min. Nb3Sn superconducting wire.

[0044] Referring to the wire copper ratio measurement method of Example 1, the copper ratio of the Nb3Sn superconducting wire produced in this example was measured.

[0045] A sample of 500 mm in length of the Nb3Sn superconducting wire prepared in Example 2 was taken and its mass was tested to be 15.53 g and the average wire diameter was 0.818 mm. The sample was placed in nitric acid until all the copper of the stabilizing material was corroded away, and the sample was quickly removed and washed with water. After washing, the sample was completely dried and the mass of the non-copper part was measured to be 13.39 g. The copper ratio can be calculated by the formula to be 10.1, which is consistent with the designed copper ratio.

[0046] The patented method is used to prepare wire with a copper ratio of 10.1, using only the specification of The oxygen-free copper tube is suitable for conventional superconducting wire processing molds, and no breakage occurs during the processing of diameters above φ14.07mm. When stretched to the final size, the wire only breaks 3 times, and the cumulative stretching length reaches 30150m. If the thick-walled copper tube is used in a single composite method, The outer diameter is far beyond the conventional superconducting wire processing mold, which greatly increases the processing difficulty;

[0047] Example 3

[0048] This example is to prepare a Nb3Sn superconducting wire with a designed copper ratio of 8.85

[0049] Select the barrier layer Ta tube with a diameter of 50mm and a length of 5m, H10mm, semicircular 10mm, fan-shaped 8mm sub-component, and a length of 5m. The selected oxygen-free copper tube 3 specifications are After cleaning the Ta tube and the subcomponents, the subcomponents are first densely packed and bundled into the Ta tube, and then loaded into the cleaned oxygen-free copper tube 3 to obtain the final Nb3Sn billet, which is then stretched multiple times at a processing rate of 2% to 15% to obtain the first Nb3Sn superconducting wire precursor with a size of 32 mm.

[0050] The first Nb3Sn superconducting wire precursor is wrapped with polytetrafluoroethylene at both ends and then cleaned to prevent acid from entering the wire during the cleaning process; the cleaning process first uses an emulsifier to ultrasonically clean the surface oil stains, then cleans with a nitric acid solution, then cleans the surface with a chromic acid solution, rinses the surface acid stains with water, and finally dehydrates with alcohol to complete the cleaning; the specifications are selected as The oxygen-free copper tube 4 is prepared by placing the first Nb3Sn superconducting wire precursor after cleaning into the oxygen-free copper tube after cleaning, and then the second Nb3Sn superconducting wire precursor with a diameter of 30 mm is obtained by multiple stretching at a processing rate of 2% to 30% and a stretching speed of 1 to 100 m / min. The first Nb3Sn superconducting wire precursor and the second Nb3Sn superconducting wire precursor preparation steps are repeated twice to obtain the internal tin method Nb3Sn final billet with a designed copper ratio of 8.8, and then the second Nb3Sn superconducting wire precursor is obtained by multiple stretching at a processing rate of 2% to 30% and a stretching speed of 1 to 100 m / min. Nb3Sn superconducting wire.

[0051] Referring to the wire copper ratio measurement method of Example 1, the copper ratio of the Nb3Sn superconducting wire produced in this example was measured.

[0052] A sample of 500 mm in length of the Nb3Sn superconducting wire prepared in Example 3 was taken and its mass was tested to be 22.61 g and the average wire diameter was 0.818 mm. The sample was placed in nitric acid until all the copper of the stabilizing material was corroded away, and the sample was quickly removed and washed with water. After washing, the sample was completely dried and the mass of the non-copper part was measured to be 20.50 g. The copper ratio can be calculated by the formula to be 8.85, which is consistent with the designed copper ratio.

[0053] The patented method is used to prepare wire with a copper ratio of 8.85, using only the specification of The oxygen-free copper tube is suitable for conventional superconducting wire processing molds, and no breakage occurs during the processing of diameters above φ14.07mm. When stretched to the final size, no wire breakage occurs, and the cumulative stretching length reaches 35360m. If the thick-walled copper tube is used in a single composite method, The outer diameter is far beyond the conventional superconducting wire processing mold, which greatly increases the processing difficulty.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a Nb3Sn wire, characterized in that: include: Step 1: densely arranging the subcomponents, placing them in the barrier layer in sequence, and then placing them in the first oxygen-free copper tube, and after multiple stretching, obtaining the first Nb3Sn superconducting wire precursor; Step 2: placing the first Nb3Sn superconducting wire precursor in a second oxygen-free copper tube and stretching it multiple times to obtain a second Nb3Sn superconducting wire precursor; Step 3: Repeat step 2 until the final Nb3Sn billet is obtained, and after multiple stretching, the Nb3Sn superconducting wire is obtained.

2. The method for preparing Nb3Sn wire according to claim 1, characterized in that: The specifications of the first oxygen-free copper tube or the second oxygen-free copper tube are independently selected from an outer diameter of 20 to 75 mm, an inner diameter of 15 to 60 mm, and a length of 600 to 10000 mm.

3. The method for preparing Nb3Sn wire according to claim 1, characterized in that: In any step of multiple stretching, the pass processing rate is 2-30%, and the stretching speed is 1-100 m / min.

4. The method for preparing Nb3Sn wire according to claim 1, characterized in that: The material of the barrier layer is Ta, and the diameter is 20-60 mm.

5. The method for preparing Nb3Sn wire according to claim 1, characterized in that: The subcomponents are densely arranged in the form of hexagonal subcomponents, semicircular subcomponents, and fan-shaped subcomponents; the length of a single subcomponent is 600 to 4000 mm.

6. The method for preparing Nb3Sn wire according to claim 1, characterized in that: The size of the first Nb3Sn superconducting wire precursor is 10 to 50 mm.

7. The method for preparing Nb3Sn wire according to claim 1, characterized in that: During the processing of step 2, both ends of the first Nb3Sn superconducting wire precursor are wrapped.

8. A Nb3Sn wire, characterized in that: The method is prepared by the method according to any one of claims 1 to 7.

9. The Nb3Sn wire according to claim 8, characterized in that The outer diameter of the Nb3Sn wire is 20-75 mm, and the copper ratio is not less than 2.

10. The Nb3Sn wire according to claim 9, characterized in that: The copper ratio of the Nb3Sn wire is not less than 8.

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