阅读说明：本技术 一种Bi-2212超导线封头制作方法 (Bi-2212 superconducting wire end socket manufacturing method ) 是由 杨东昇 秦经刚 李建刚 刘方 金环 毛哲华 周超 武玉 陈俊凌 于 2019-11-08 设计创作，主要内容包括：本发明公开了一种Bi?2212超导线封头制作方法，包括以下步骤：(1)、制备矩形银基合金薄片；(2)、银基合金薄片中开出一道缝隙；(3)、将Bi?2212超导线端头放置于银基合金薄片上；(4)、将银基合金薄片沿宽边方向卷起，使银基合金薄片完全包裹Bi?2212超导线端头；(5)、将包裹有银基合金薄片的Bi?2212超导线端头压紧；(6)、加热缝隙另一侧未包裹Bi?2212超导线端头的银基合金薄片，融化后形成封头；(7)、加热银基合金薄片与Bi?2212超导线端头结合位置。本发明解决了Bi?2212超导线端头无法密封的问题。(The invention discloses a method for manufacturing a Bi-2212 superconducting wire end socket, which comprises the following steps: (1) preparing a rectangular silver-based alloy sheet; (2) a gap is formed in the silver-based alloy sheet; (3) placing the end of the Bi-2212 superconducting wire on a silver-based alloy sheet; (4) rolling the silver-based alloy sheet along the broadside direction to enable the silver-based alloy sheet to completely wrap the end of the Bi-2212 superconducting wire; (5) compacting the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet; (6) heating the silver-based alloy sheet which is not wrapped by the end of the Bi-2212 superconducting wire on the other side of the gap, and melting to form an end socket; (7) and heating the combination position of the silver-based alloy sheet and the end of the Bi-2212 superconducting wire. The invention solves the problem that the end of the Bi-2212 superconducting wire cannot be sealed.)

1. A method for manufacturing a Bi-2212 superconducting wire end socket is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing a rectangular silver-based alloy sheet, keeping the silver-based alloy sheet flat, and removing stains on the surface of the silver-based alloy sheet;

(2) the two parallel long edges of the silver-based alloy sheet are respectively a long edge A and a long edge B, a gap is formed in the silver-based alloy sheet along the direction perpendicular to the long edge A by taking the middle position of one long edge A of the silver-based alloy sheet as a starting point, the gap is parallel to the wide edge of the silver-based alloy sheet, one end of the gap is positioned in the middle position of the long edge A of the silver-based alloy sheet as the starting point, and the other end of the gap is spaced from the other long edge B of the silver-based alloy sheet by a certain distance;

(3) placing the end of the Bi-2212 superconducting wire on the silver-based alloy sheet close to the long side B of the silver-based alloy sheet, wherein the end of the Bi-2212 superconducting wire is axially parallel to the two long sides of the silver-based alloy sheet, the end of the Bi-2212 superconducting wire is integrally positioned on one side of the gap, and the end of the Bi-2212 superconducting wire is spaced from the extension line of the gap by a certain distance;

(4) rolling the silver-based alloy sheet along the broadside direction to enable the silver-based alloy sheet to completely wrap the end of the Bi-2212 superconducting wire;

(5) pressing the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet to enable the silver-based alloy sheet to be in close contact with the end of the Bi-2212 superconducting wire;

(6) vertically placing the wrapped end of the superconducting wire, wherein the superconducting wire is positioned at the lower end, heating the silver-based alloy sheet which is not wrapped with the end of the Bi-2212 superconducting wire at the other side of the gap by using a fire gun to melt the silver-based alloy sheet which is not wrapped with the end of the Bi-2212 superconducting wire at a heating temperature of more than or equal to 1000 ℃, and stopping heating until the melting position is close to the gap, thereby forming an end socket at the end of the Bi-2212 superconducting wire;

(7) and removing residues on the surface of the seal head, and heating the joint position of the silver-based alloy sheet and the end of the Bi-2212 superconducting wire at the temperature of 800-900 ℃ for more than or equal to 5 seconds to ensure that the edge of the silver-based alloy sheet generates creep deformation and improve the sealing property of the seal head.

2. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: in the step (1), the length-width ratio of the rectangular silver-based alloy sheet is more than 3.

3. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: in the step (1), the surface of the silver-based alloy sheet is wiped with alcohol to remove stains.

4. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: in the step (2), the length of the gap is greater than 1/3 of the width of the silver-based alloy sheet.

5. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: and (5) adopting an upper pressing die and a lower pressing die, and placing the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet between the upper pressing die and the lower pressing die so that the upper pressing die and the lower pressing die are combined to tightly press the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet.

6. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: and (5) after the heating is stopped in the step (6), spraying alcohol on the surface of the end socket to quickly cool the end socket.

7. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: the end seal of the Bi-2212 superconducting wire adopts a superconducting wire sleeve made of Ag-based alloy, and the melting treatment is carried out at the high temperature of more than 1000 ℃.

8. The method for manufacturing the end socket of the Bi-2212 superconducting wire according to claim 1, characterized in that: the Bi-2212 superconducting wire is manufactured by adopting a powder tube filling method, and the outer layer of the superconducting wire is made of silver-based alloy.

Technical Field

The invention relates to the field of superconducting wire processing methods, in particular to a method for manufacturing a Bi-2212 superconducting wire end socket.

Background

At present, in the superconducting Tokamak existing internationally and under construction, the highest plasma central field strength is the ITER device, the plasma central field strength is 5.3T, the highest field of a longitudinal field coil is 11.8T, and the transient highest field in the operation of a central solenoid is more 13T, which is close to the performance limit of Nb3Sn with the highest critical field in the use of low-temperature superconducting materials.

In order to meet the requirement of high magnetic field intensity, a superconducting magnet which can meet the requirements of magnetic field >15T, current >45kA and stable performance after electromagnetic circulation is performed ten thousand times needs to be manufactured. However, it is difficult to prepare magnets exceeding 15T at present due to the limitation of critical magnetic field on low-temperature superconducting wire.

The high-temperature superconducting material has excellent upper critical field and large critical current density. In the copper oxide high-temperature superconducting material, the Bi-2212 wire has excellent high-field current carrying capacity and lower alternating current loss, shows isotropy to a magnetic field, can be prepared into a round wire, and is easier to stranding cables. The material can still bear engineering current density with practical application significance even if the external field is as high as 45T at 4.2K, so that the material is a high-temperature superconducting material with the highest application prospect under high field (>20T) at present. The Bi-2212 superconducting cable is different from Nb3Sn and NbTi superconducting cables in processing procedures. The heat treatment is needed in high temperature, high pressure and aerobic atmosphere to improve the density of the Bi-2212 superconducting wire, thereby improving the performance thereof.

At present, the existing Bi-2212 superconducting wire needs to be subjected to heat treatment at 890 ℃ under high temperature and high pressure, in order to ensure the compactness of the superconducting strand, the superconducting wire which is longer than the temperature area of heat treatment equipment is usually used for heat treatment, and the two ends of the superconducting wire are ensured to be in a low-temperature area (the internal superconducting wire does not react or melt), which is equivalent to the sealing heads of the superconducting wires at the two ends. The Bi-2212 superconducting wire is expensive, so the operation greatly increases the cost, and many experiments which need to use short samples cannot be carried out or can be carried out only under normal pressure, thereby greatly limiting the development and application of the Bi-2212 superconducting wire.

Disclosure of Invention

The invention aims to provide a method for manufacturing a head of a Bi-2212 superconducting wire, which is used for forming the head at the end head of the Bi-2212 superconducting wire and solving the problem that the end head needs to be in a low-temperature region when the Bi-2212 superconducting wire is subjected to heat treatment in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for manufacturing a Bi-2212 superconducting wire end socket is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing a rectangular silver-based alloy sheet, keeping the silver-based alloy sheet flat, and removing stains on the surface of the silver-based alloy sheet;

(2) the two parallel long edges of the silver-based alloy sheet are respectively a long edge A and a long edge B, a gap is formed in the silver-based alloy sheet along the direction perpendicular to the long edge A by taking the middle position of one long edge A of the silver-based alloy sheet as a starting point, the gap is parallel to the wide edge of the silver-based alloy sheet, one end of the gap is positioned in the middle position of the long edge A of the silver-based alloy sheet as the starting point, and the other end of the gap is spaced from the other long edge B of the silver-based alloy sheet by a certain distance;

(3) placing the end of the Bi-2212 superconducting wire on the silver-based alloy sheet close to the long side B of the silver-based alloy sheet, wherein the end of the Bi-2212 superconducting wire is axially parallel to the two long sides of the silver-based alloy sheet, the end of the Bi-2212 superconducting wire is integrally positioned on one side of the gap, and the end of the Bi-2212 superconducting wire is spaced from the extension line of the gap by a certain distance;

(4) rolling the silver-based alloy sheet along the broadside direction to enable the silver-based alloy sheet to completely wrap the end of the Bi-2212 superconducting wire;

(5) pressing the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet to enable the silver-based alloy sheet to be in close contact with the end of the Bi-2212 superconducting wire;

(6) vertically placing the wrapped end of the superconducting wire, wherein the superconducting wire is positioned at the lower end, heating the silver-based alloy sheet which is not wrapped with the end of the Bi-2212 superconducting wire at the other side of the gap by using a fire gun to melt the silver-based alloy sheet which is not wrapped with the end of the Bi-2212 superconducting wire at a heating temperature of more than or equal to 1000 ℃, and stopping heating until the melting position is close to the gap, thereby forming an end socket at the end of the Bi-2212 superconducting wire;

(7) and removing residues on the surface of the seal head, and heating the joint position of the silver-based alloy sheet and the end of the Bi-2212 superconducting wire at the temperature of 800-900 ℃ for more than or equal to 5 seconds to ensure that the edge of the silver-based alloy sheet generates creep deformation and improve the sealing property of the seal head.

The method for manufacturing the end socket of the Bi-2212 superconducting wire is characterized by comprising the following steps: in the step (1), the length-width ratio of the rectangular silver-based alloy sheet is more than 3.

The method for manufacturing the end socket of the Bi-2212 superconducting wire is characterized by comprising the following steps: in the step (1), the surface of the silver-based alloy sheet is wiped with alcohol to remove stains.

The method for manufacturing the end socket of the Bi-2212 superconducting wire is characterized by comprising the following steps: in the step (2), the length of the gap is greater than 1/3 of the width of the silver-based alloy sheet.

The method for manufacturing the end socket of the Bi-2212 superconducting wire is characterized by comprising the following steps: and (5) adopting an upper pressing die and a lower pressing die, and placing the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet between the upper pressing die and the lower pressing die so that the upper pressing die and the lower pressing die are combined to tightly press the end of the Bi-2212 superconducting wire wrapped with the silver-based alloy sheet.

The method for manufacturing the end socket of the Bi-2212 superconducting wire is characterized by comprising the following steps: and (5) after the heating is stopped in the step (6), spraying alcohol on the surface of the end socket to quickly cool the end socket.

Has the advantages that:

the method for manufacturing the end socket of the Bi-2212 superconducting wire solves the problem that the end socket of the Bi-2212 superconducting wire cannot be sealed, and after the end socket of the Bi-2212 superconducting wire is sealed by the end socket manufactured by the method, the Bi-2212 superconducting wire can be subjected to high-temperature heat treatment integrally, so that the high-temperature heat treatment can be applied to shorter Bi-2212 superconducting wires, and the wide application of Bi-2212 superconducting materials in future magnets is promoted, particularly large superconducting magnets for fusion reactors.

Drawings

FIG. 1 is a schematic view of a silver-based alloy flake prepared in an embodiment of the present invention;

FIG. 2 is a schematic diagram of the placement of the end of a Bi-2212 superconducting wire in an embodiment of the present invention;

FIG. 3 is a schematic view of a silver-based alloy sheet after rolling in an embodiment of the present invention;

FIG. 4 is a schematic view of a compacted silver-based alloy flake in an embodiment of the invention;

FIG. 5 is a schematic view of heating to melt a silver-based alloy flake in an embodiment of the present invention;

FIG. 6 is a schematic view of a head made in an embodiment of the present invention;

FIG. 7 is a schematic representation of creep of the edges of a silver-based alloy sheet caused by heating in accordance with an embodiment of the present invention.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

As shown in fig. 1, a method for manufacturing a head of a Bi-2212 superconducting wire comprises the following steps:

(1) as shown in fig. 1, a rectangular silver-based alloy sheet 1 is prepared, so that the silver-based alloy sheet 1 is kept flat, and the aspect ratio of the rectangular silver-based alloy sheet is greater than 3, specifically: a length >15 mm; the width is more than 5mm, the thickness is more than 0.2mm, and the surface of the silver-based alloy sheet 1 is wiped by alcohol to remove stains; the sheet may be silver of national standard No. one.

(2) As shown in fig. 1, two long sides of a silver-based alloy sheet 1 are respectively a long side a and a long side B, a gap 2 is opened into the silver-based alloy sheet 1 by taking the middle position of one long side a of the silver-based alloy sheet 1 as a starting point, the gap 2 is parallel to the wide side of the silver-based alloy sheet 1, one end of the gap 2 is positioned at the middle position of the long side a of the silver-based alloy sheet 1 as the starting point, and the other end of the gap 2 is spaced from the other long side B of the silver-based alloy sheet 1 by a certain distance; the length of the gap is greater than 1/3 of the width of the silver-based alloy sheet, and the width of the gap is less than 2 mm.

(3) As shown in fig. 2, the Bi-2212 superconducting wire tip 3 is placed on the silver-based alloy sheet 1 near the long side B of the silver-based alloy sheet 1, the Bi-2212 superconducting wire tip 3 is axially parallel to the two long sides of the silver-based alloy sheet 1, the Bi-2212 superconducting wire tip 3 is entirely located on the side of the gap 2, and the Bi-2212 superconducting wire tip 3 is spaced from the extension line of the gap 2 by 1 mm. .

(4) The silver-based alloy sheet 1 was rolled up in the broadside direction (2 mm from the sheet edge) in accordance with the dotted line shown in fig. 2, so that the silver-based alloy sheet 1 completely wrapped the end 3 of the Bi-2212 superconducting wire, as shown in fig. 3.

(5) As shown in fig. 4, an upper pressing die 4 and a lower pressing die 5 are adopted, the Bi-2212 superconducting wire end 3 wrapped with the silver-based alloy sheet 1 is arranged between the upper pressing die 4 and the lower pressing die 5, the upper pressing die 4 and the lower pressing die 5 are oppositely closed and tightly press the Bi-2212 superconducting wire end 3 wrapped with the silver-based alloy sheet 1, and the silver-based alloy sheet 1 is tightly contacted with the Bi-2212 superconducting wire end 3;

(6) and as shown in fig. 5, the silver-based alloy sheet which is not covered with the Bi-2212 superconducting wire end 3 on the other side of the gap needs to be vertically placed, a high-temperature flame gun 6 is used for heating the silver-based alloy sheet which is not covered with the Bi-2212 superconducting wire end 3, so that the silver-based alloy sheet which is not covered with the Bi-2212 superconducting wire end 3 is melted, the flame temperature is higher than 1000 ℃, the melt body vertically moves downwards at a constant speed along the arrow in fig. 5 during melting, the melting time is related to the silver-based alloy sheet and the length, but the heating needs to be stopped when the melt body approaches the position of the gap 2, so that a seal head 7 is formed. After the heating is stopped, the sprayed alcohol is rapidly cooled. Since the melted silver-based alloy fills the voids and cools rapidly, it does not cause the Bi-2212 superconducting phase in the superconducting wire to melt and flow out.

(7) Scrubbing the surface of the seal head by alcohol, removing surface residues, heating the contact part of the silver-based alloy and the Bi-2212 superconducting wire, namely the position in a dotted circle shown in figure 7, by a high-temperature fire gun, wherein the heating temperature is 800-900 ℃, and the heating time is more than 5 seconds, so that the silver-based alloy generates creep deformation, the possible gaps are further reduced, and the sealing success rate is improved.

The end seal of the Bi-2212 superconducting wire adopts a superconducting wire sleeve made of Ag-based alloy with high purity (the purity of silver of national standard I is 99.99 percent), and the melting treatment is carried out at the high temperature of more than 1000 ℃. The Bi-2212 superconducting wire is manufactured by a powder tube filling method, the outer layer of the superconducting wire is made of silver-based alloy, and the silver-based alloy is used for preventing the Bi-2212 superconducting phase from reacting with a seal head material to reduce the performance of the superconducting wire. Temperatures above 1000 c are above the melting point of silver and do not cause the superconducting phase and the silver-based alloy to melt together too quickly for heat conduction due to the temperature being too high. The gap has the effect of preventing heat transfer too fast.

After the end socket is manufactured, the end socket can be detected:

1. the surface observation shows that the end socket is in a sphere shape, and the surface is smooth without any holes or gaps; no black superconducting phase is precipitated.

2. And fixing the superconducting wire, pulling the end socket by a force larger than 50N, and not separating, so that the end socket is firmly manufactured.

3. And (3) firing the end socket by using a high-temperature fire gun, wherein the temperature is required to be more than 1500 ℃, and the time is less than 5 seconds. And observing whether the superconducting phase or the pore exists on the surface and the bottom of the end socket.

The embodiments of the present invention are described only for the preferred embodiments of the present invention, and not for the limitation of the concept and scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall into the protection scope of the present invention, and the technical content of the present invention which is claimed is fully set forth in the claims.