Wire rod structure capable of remarkably improving mechanical property of Bi-2212 wire rod and preparation method of wire rod structure

Abstract

The invention discloses a wire rod structure capable of remarkably improving the mechanical property of a Bi-2212 wire rod, the wire rod structure is characterized in that a copper core with a silver sheath is introduced into the Bi-2212 wire rod to obtain the Bi-2212 wire rod with a copper core composite structure with the silver sheath, and in addition, the invention further discloses a preparation method of the wire rod structure. Comprising the following steps: 1, putting a copper core with a silver sheath and Bi-2212 powder into a silver tube to obtain an initial wire; and 2, drawing the initial wire rod to obtain the Bi-2212 wire rod of the copper core composite structure with the silver sheath. According to the invention, by introducing the copper core with the silver sheath, an original cylindrical core wire is changed into an annular core wire structure in which the copper core with the silver sheath is inserted, so that the mechanical property of the wire is improved from the inherent structure of the core wire, the operation is simple, the controllability and operability are high, and the quick application in Bi-2212 wires is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature superconducting material preparation, and in particular relates to a wire structure capable of significantly improving the mechanical properties of a Bi-2212 wire and a preparation method thereof. Background Art

[0002] Bi-2212 wire is the only high-temperature superconducting wire that exhibits isotropic properties and excellent current-carrying performance at low temperatures and high fields. It holds broad application prospects in future applications such as high-field magnets and fusion reactors. However, the intrinsic mechanical properties of Bi-2212 wire remain relatively low. In practical applications, it faces extremely complex electromagnetic, magnetic, and thermal stress fields, requiring excellent mechanical properties to ensure practical engineering applications. Currently, there are three main methods for improving the mechanical properties of Bi-2212 wire: one is to fine-tune the silver sheath or silver matrix assembly method within the wire, achieving a slight improvement in mechanical properties while minimizing cross-sectional area loss in the superconducting core; another is to use high-voltage equipment to increase the density of the superconducting core, thereby improving the mechanical properties of the wire; and the third is to enhance the prepared wire through complex subsequent reinforcement processes (such as adding an outer sheath). The first method is ineffective, while the second and third methods are costly, seriously hindering the application of Bi-2212 wire in future large-scale high-field magnets. At present, the methods for improving the intrinsic mechanical properties of Bi-2212 wire have low cost-effectiveness, which further hinders the commercial application of the wire.

[0003] Therefore, it is necessary to propose a cost-effective wire structure and a preparation method thereof that can significantly improve the mechanical properties of Bi-2212 wire. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing technologies and provide a wire structure that significantly improves the mechanical properties of Bi-2212 wire. This structure introduces a silver-sheathed copper core to produce a Bi-2212 wire with a silver-sheathed copper core composite structure. This transforms the original cylindrical core wire into a circular core wire structure with an internal silver-sheathed copper core composite structure, significantly improving the wire's mechanical properties.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a wire structure that significantly improves the mechanical properties of Bi-2212 wire, characterized in that the wire structure is: a copper core with a silver sheath is introduced into the Bi-2212 wire to obtain a Bi-2212 wire with a silver sheathed copper core composite structure.

[0006] The present invention is different from the current idea of improving the mechanical properties of Bi-2212 wire by fine-tuning the assembly mode of the silver matrix and the superconducting core wire or using high voltage to increase the density of the core wire. Instead, it starts from the perspective of changing the initial structure of the Bi-2212 wire, introducing a copper core with a silver sheath into the Bi-2212 wire, so that the copper core composite structure with a silver sheath in the Bi-2212 wire serves as a reinforced core, and the original cylindrical core wire is transformed into a circular core wire structure with a copper core composite structure with an inserted silver sheath. The silver sheath can physically isolate the copper core from the superconducting powder, preventing the reinforced copper core from direct contact with the superconducting material and affecting subsequent phase formation, while the inserted copper core can significantly improve the mechanical properties of the wire.

[0007] In addition, the present invention also provides a method for preparing a wire structure that significantly improves the mechanical properties of Bi-2212 wire, characterized in that the method comprises the following steps:

[0008] Step 1: Place a silver-sheathed copper core and Bi-2212 powder into a silver tube to obtain an initial wire;

[0009] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire having a copper core composite structure with a silver sheath.

[0010] The present invention inserts a silver-sheathed copper core into a silver tube in a powder-sheathing process and performs Bi-2212 powder-sheathing to obtain an initial wire, and then draws the wire according to a conventional processing technology to obtain a Bi-2212 wire with a silver-sheathed copper core composite structure. The mechanical properties of the Bi-2212 wire are improved by inserting the silver-sheathed copper core.

[0011] The above method is characterized in that the outer diameter of the silver sheath in step 1 is 30% to 60% of the inner diameter of the silver tube, the outer diameter of the silver sheath fluctuates by no more than 10%, the diameter of the copper core is 30% to 65% of the outer diameter of the silver sheath, the diameter of the copper core fluctuates by no more than 10%, and the copper core and the silver sheath are tightly matched. In the present invention, by controlling the outer diameter of the silver sheath, maximum performance improvement is ensured, preventing the problem that the effect of improving the texture of the core filament by thinning the core filament is less than the reduction of the superconducting area due to the outer diameter of the silver sheath being too large, and also preventing the problem that the copper core and silver sheath composite structure is easily broken due to the outer diameter of the silver sheath being too small. Copper has better intrinsic mechanical properties than silver. By controlling the diameter of the copper core and placing it in the center, the mechanical properties are significantly improved while maximizing the effective area of the superconducting core filament. In addition, the copper core and the silver sheath are tightly matched, ensuring that the copper core and silver sheath composite structure has the maximum performance improvement effect, preventing the problem that the embedded silver sheath is easily broken due to the copper core diameter being too large, and preventing the problem that the copper core diameter is too small to achieve the reinforcement effect.

[0012] The above method is characterized in that the silver-sheathed copper core in step 1 is positioned on the axis of the silver tube, and the Bi-2212 powder is placed in the silver tube after the silver-sheathed copper core. By controlling the position of the silver-sheathed copper core on the axis of the silver tube and placing the silver-sheathed copper core before the Bi-2212 powder, the present invention ensures uniformity in the structure and performance of the Bi-2212 wire with a silver-sheathed copper core composite structure, thereby maximizing the advantages of the Bi-2212 wire with a silver-sheathed copper core composite structure in improving mechanical properties.

[0013] The above method is characterized in that the copper core in step 1 is a solid structure. In the present invention, the copper is a solid structure, which significantly improves the mechanical properties while maximizing the effective area of the superconducting core wire.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The present invention starts from the perspective of changing the initial structure of Bi-2212 wire and introduces a silver-sheathed copper core into the Bi-2212 wire by changing the idea of refining the core wire. The silver-sheathed copper core composite structure in the Bi-2212 wire serves as a reinforcing core, significantly improving the mechanical properties of the wire.

[0016] 2. The present invention inserts a silver-sheathed copper core into a silver tube in a powder-sheathing process and performs Bi-2212 powder-sheathing to obtain an initial wire, which is then drawn according to a conventional processing technique to obtain a Bi-2212 wire having a silver-sheathed copper core composite structure. By inserting the silver-sheathed copper core, the mechanical properties of the Bi-2212 wire are increased. The process has simple operation, low cost, strong controllability and operability, and a high output-input ratio. The Bi-2212 wire with enhanced mechanical properties can be directly prepared without the need for additional special equipment or technology, which is conducive to its rapid application in the preparation of the Bi-2212 wire and further promotes the engineering application of the Bi-2212 wire in high-field magnets.

[0017] 3. The present invention inserts a copper core and a silver sheath simultaneously into the center of the silver tube during the powder filling stage, and the copper core is just embedded in the silver sheath. Then, a conventional processing technology is used to prepare a Bi-2212 wire with a copper core composite structure having a silver sheath, thereby significantly improving the mechanical properties of the Bi-2212 wire. Compared with Bi-2212 wires of the same diameter but without a silver sheath but with a copper core, the mechanical properties are improved by 13% to 67%.

[0018] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0019] Example 1

[0020] This embodiment includes the following steps:

[0021] Step 1: Assemble a silver sheath with an outer diameter of 6 mm and a wall thickness of 1.35 mm and a copper core with a diameter of 3.08 mm, then place it in the axis position of a silver tube with an outer diameter of 12 mm and a wall thickness of 1 mm, and then place Bi-2212 powder in the silver tube to obtain an initial wire; the outer diameter of the silver sheath fluctuates by no more than 10%, and the diameter of the copper core fluctuates by no more than 10%, and the copper core and the silver sheath fit tightly together;

[0022] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire with an outer diameter of 1.0 mm and a copper core composite structure having a silver sheath.

[0023] Comparative Example 1

[0024] This comparative example comprises the following steps:

[0025] Step 1: Place Bi-2212 powder in a silver tube with an outer diameter of 12 mm and a wall thickness of 1 mm to obtain an initial wire;

[0026] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire with an outer diameter of 1.0 mm.

[0027] The tensile strength of the Bi-2212 wire with a silver-sheathed copper core composite structure prepared in Example 1 and the Bi-2212 wire prepared in Comparative Example 1 were tested. The tensile strength of the Bi-2212 wire with a silver-sheathed copper core composite structure prepared in Example 1 was 59% higher than that of the Bi2212 wire prepared in Comparative Example 1.

[0028] By comparing Example 1 with Comparative Example 1, it can be seen that the tensile strength of the Bi-2212 wire with the silver-sheathed copper core composite structure is improved by introducing the silver-sheathed copper core composite structure in Example 1.

[0029] Example 2

[0030] This embodiment includes the following steps:

[0031] Step 1: Assemble a silver sheath with an outer diameter of 3.08 mm and a wall thickness of 1.00 mm and a copper core with a diameter of 0.96 mm, then place the silver sheath on the axis of a silver tube with an outer diameter of 12 mm and a wall thickness of 1.00 mm, and then place Bi-2212 powder in the silver tube to obtain an initial wire; the outer diameter of the silver sheath fluctuates by no more than 10%, and the diameter of the copper core fluctuates by no more than 10%, and the copper core and the silver sheath fit tightly together;

[0032] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire with an outer diameter of 1.0 mm and a copper core composite structure having a silver sheath.

[0033] The tensile strength of the Bi-2212 wire with a silver-sheathed copper core composite structure prepared in Example 2 and the Bi2212 wire prepared in Comparative Example 1 were tested. The tensile strength of the Bi-2212 wire with a silver-sheathed copper core composite structure prepared in Example 2 was 13% higher than that of the Bi2212 wire prepared in Comparative Example 1.

[0034] Example 3

[0035] This embodiment includes the following steps:

[0036] Step 1: Assemble a silver sheath with an outer diameter of 5.64 mm and a wall thickness of 0.85 mm and a copper core with a diameter of 3.64 mm, then place the silver tube with an outer diameter of 12.00 mm and a wall thickness of 1.20 mm at the axial position, and then place Bi-2212 powder in the silver tube to obtain an initial wire; the outer diameter of the silver sheath fluctuates by no more than 10%, and the diameter of the copper core fluctuates by no more than 10%, and the copper core and the silver sheath fit tightly together;

[0037] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire with an outer diameter of 1.0 mm and a copper core composite structure having a silver sheath.

[0038] The tensile strength of the Bi-2212 wire with a silver-sheathed copper core composite structure prepared in Example 3 and the Bi2212 wire prepared in Comparative Example 1 were tested. The tensile strength of the Bi-2212 wire with a silver-sheathed copper core composite structure prepared in Example 3 was 67% higher than that of the Bi2212 wire prepared in Comparative Example 1.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A wire structure that significantly improves the mechanical properties of Bi-2212 wire, characterized in that: The wire structure is as follows: a copper core with a silver sheath is introduced into a Bi-2212 wire to obtain a Bi-2212 wire with a copper core composite structure with a silver sheath.

2. A method for preparing a wire structure having significantly improved mechanical properties of Bi-2212 wire as claimed in claim 1, characterized in that: The method comprises the following steps: Step 1: Place a silver-sheathed copper core and Bi-2212 powder into a silver tube to obtain an initial wire; Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire having a copper core composite structure with a silver sheath.

3. The method according to claim 2, characterized in that In step 1, the outer diameter of the silver sleeve is 30% to 60% of the inner diameter of the silver tube, and the fluctuation of the outer diameter of the silver sleeve does not exceed 10%. The diameter of the copper core is 30% to 65% of the outer diameter of the silver sleeve, and the fluctuation of the diameter of the copper core does not exceed 10%. The copper core and the silver sleeve are tightly matched.

4. The method according to claim 2, characterized in that The copper core with the silver sheath in step 1 is located on the axis of the silver tube. The silver tube is placed with the copper core with the silver sheath and then Bi-2212 powder is placed.

5. The method according to claim 2, characterized in that The copper core described in step 1 is a solid structure.