Wire structure for improving mechanical property and critical current density of Bi-2212 wire and preparation method

Abstract

The invention discloses a wire structure for improving the mechanical property and critical current density of a Bi-2212 wire, the wire structure is characterized in that a silver core is introduced into the Bi-2212 wire to obtain the Bi-2212 wire with the silver core, in addition, the invention also discloses a preparation method of the wire structure, and the preparation method comprises the following steps: 1, putting the silver core 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 with the silver core. By introducing the silver core, based on the change of the wire structure, the original cylindrical core wire is changed into the annular core wire structure in which the silver core is inserted, the core wire is directly refined from the inherent structure of the core wire, the mechanical property of the wire is improved, the core wire is refined, the texture is improved, then the critical current density is improved, operation is easy, cost is low, and the method is suitable for industrial production. And controllability and operability are high, and rapid application in Bi-2212 wire rods 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 and a preparation method for improving the mechanical properties and critical current density of Bi-2212 wire. Background Art

[0002] The key technologies reported internationally, such as the high-pressure heat treatment wire method and the preparation of Bi-2212 powder based on the spray chemical combustion method, have significantly improved the critical current density (J) of Bi-2212 superconducting materials. c ), but the price of Bi-2212 superconducting material remains high. Only by further increasing the critical current density of Bi-2212 superconducting material can the cost-effectiveness of Bi-2212 superconducting material be further improved, ultimately significantly promoting its application in future large-scale high-field magnets. Furthermore, the intrinsic mechanical properties of Bi-2212 wire remain relatively low, requiring the use of high-voltage equipment to enhance these properties, which is costly.

[0003] Previous studies have shown that the texture of Bi-2212 wires is a confined texture constrained by a silver layer, and have predicted that further reducing the core diameter could improve the Bi-2212 texture and, consequently, the wire's current-carrying performance. Reducing the core diameter requires further reducing the powder particle size, but even with the most advanced powder preparation processes, the reduction in core diameter is small but not significant. No effective method for further reducing the core diameter has yet been proposed. Furthermore, current methods for improving the intrinsic mechanical properties of Bi-2212 wires are too cost-effective, further hindering their commercial application.

[0004] Therefore, a wire structure and preparation method for improving the mechanical properties and critical current density of Bi-2212 wire are needed. Summary of the Invention

[0005] 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 improves the mechanical properties and critical current density of Bi-2212 wire. This structure introduces a silver core to produce a Bi-2212 wire with a silver core. The original cylindrical core wire is transformed into a circular core wire structure with an internal silver core, which directly refines the core wire. This not only improves the mechanical properties of the wire, but also improves the texture of the core wire, thereby increasing the critical current density.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a wire structure for improving the mechanical properties and critical current density of Bi-2212 wire, characterized in that the wire structure is: a silver core is introduced into the Bi-2212 wire to obtain a Bi-2212 wire with a silver core.

[0007] The present invention is different from the current single idea of improving a single performance by reducing the core wire diameter by reducing the particle size of Bi-2212 powder or optimizing the heat treatment process to improve the critical current density of Bi-2212 wire, or by using a high-pressure heat treatment process to improve the mechanical properties of the wire. Instead, from the perspective of enhancing the texture of Bi-2212 wire and thus improving the current-carrying performance, a silver core is introduced into the Bi-2212 wire, so that the Bi-2212 wire also has a silver core as a reinforcement core, and the original cylindrical core wire is transformed into a circular core wire structure with a silver core inserted therein. The core wire is directly refined based on its inherent structure, which on the one hand improves the mechanical properties of the wire, and on the other hand refines the core wire to improve the texture, thereby simultaneously improving the critical current density.

[0008] In addition, the present invention also provides a method for preparing a wire structure for improving the mechanical properties and critical current density of Bi-2212 wire, characterized in that the method comprises the following steps:

[0009] Step 1: Place a silver core and Bi-2212 powder in a silver tube to obtain an initial wire;

[0010] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire with a silver core.

[0011] The present invention inserts a silver core into a silver tube in a powder filling process and performs Bi-2212 powder filling 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 core. The insertion of the silver core increases the mechanical properties and critical current density of the Bi-2212 wire.

[0012] The above method is characterized in that, in step 1, the diameter of the silver core is 24% to 50% of the inner diameter of the silver tube, the radius of the silver core is 1.2 to 2.5 times the wall thickness of the silver tube, and the fluctuation of the silver core diameter does not exceed 10%. In the present invention, by controlling the diameter of the silver core, the maximum performance improvement is ensured, preventing the problem that the effect of the thinning core wire to improve the texture is less than the reduction of the superconducting area due to the excessively large diameter of the silver core, and also preventing the problem that the silver core is easily broken due to the excessively small diameter of the silver core. By controlling the fluctuation of the silver core diameter, the uniformity of the overall processed wire is ensured. By controlling the relationship between the radius of the silver core and the wall thickness of the silver tube, a suitable silver core radius can ensure the continuity of the intermediate silver core during the processing process, thereby ensuring the simultaneous and stable improvement of the current-carrying performance and mechanical properties of the final wire.

[0013] The above method is characterized in that in step 1, the silver core is positioned along the axis of the silver tube, and the Bi-2212 powder is placed in the silver tube after the silver core. By controlling the silver core's position along the axis of the silver tube and placing the silver core before the Bi-2212 powder, the present invention ensures uniformity in the structure and performance of the silver-core Bi-2212 wire, maximizing the advantages of the silver-core Bi-2212 wire in terms of improved mechanical properties and critical current density performance.

[0014] The above method is characterized in that the silver core in step 1 is a solid structure. In the present invention, the silver is a solid structure, which increases the mechanical properties while maximizing the effective area of the superconducting core wire.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The present invention aims to enhance the texture of Bi-2212 wires and thus improve their current-carrying performance. By changing the approach of thinning the core wire, a silver core is introduced into the Bi-2212 wire, so that the Bi-2212 wire also has a silver core as a reinforcing core. The original cylindrical core wire is transformed into a circular core wire structure with an inserted silver core. The core wire is directly thinned based on its inherent structure. On the one hand, the mechanical properties of the wire are improved. On the other hand, the core wire is thinned to improve the texture, thereby simultaneously increasing the critical current density.

[0017] 2. The present invention obtains an initial wire by inserting a silver core into a silver tube and performing Bi-2212 powder filling in a powder filling process, and then draws the wire according to a conventional processing technology to obtain a Bi-2212 wire with a silver core. The process is simple to operate, low in cost, highly controllable and operable, and has a high output-input ratio. Bi-2212 wires with enhanced mechanical properties and improved current-carrying performance can be directly prepared without the need for additional special equipment or technology, thereby achieving rapid application in the preparation of Bi-2212 superconducting wires and further promoting the engineering application of Bi-2212 superconducting wires in high-field magnets.

[0018] 3. The tensile strength of the silver-core Bi-2212 wire prepared by the present invention is increased by 7% to 28%. On the other hand, it is beneficial to the refinement of the core filament of the Bi-2212 wire, thereby improving the texture and further increasing the critical current density of the Bi-2212 superconducting material. Compared with the Bi-2212 wire of the same diameter without the silver core, the critical current density of the silver-core Bi-2212 wire prepared by the present invention is 1.5 to 2.7 times that of the wire without the silver core.

[0019] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0020] Example 1

[0021] This embodiment includes the following steps:

[0022] Step 1: Place a silver core with a diameter of 2.95 mm at the axis of a silver tube with an outer diameter of 12 mm and a wall thickness of 1 mm, and then add Bi-2212 powder into the silver tube to obtain an initial wire; the diameter of the silver core fluctuates within 10%;

[0023] 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 silver core.

[0024] Comparative Example 1

[0025] This comparative example comprises the following steps:

[0026] 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;

[0027] Step 2: Drawing the initial wire obtained in step 1 to obtain a Bi-2212 wire with an outer diameter of 1.0 mm.

[0028] The tensile strength and critical current density of the Bi-2212 wire with a silver core prepared in Example 1 and the Bi2212 wire prepared in Comparative Example 1 were tested. The tensile strength of the Bi-2212 wire with a silver core prepared in Example 1 was 11% higher than that of the Bi2212 wire prepared in Comparative Example 1. The critical current density of the Bi-2212 wire with a silver core prepared in Example 1 was twice that of the Bi-2212 wire prepared in Comparative Example 1.

[0029] By comparing Example 1 with Comparative Example 1, it can be seen that in Example 1, the tensile strength and critical current density of the Bi-2212 wire with a silver core are simultaneously improved by introducing the silver core.

[0030] Example 2

[0031] This embodiment includes the following steps:

[0032] Step 1: Place a 5.00 mm diameter silver core at the axis of a silver tube with an outer diameter of 12 mm and a wall thickness of 1 mm, and then add Bi-2212 powder into the silver tube to obtain an initial wire; the diameter of the silver core fluctuates within 10%;

[0033] 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 silver core.

[0034] The tensile strength and critical current density of the Bi-2212 wire with a silver core 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 core prepared in Example 2 was 28% higher than that of the Bi2212 wire prepared in Comparative Example 1. The critical current density of the Bi-2212 wire with a silver core prepared in Example 2 was 2.7 times that of the Bi-2212 wire prepared in Comparative Example 1.

[0035] By comparing Example 2 with Comparative Example 1, it can be seen that in Example 2, the tensile strength and critical current density of the Bi-2212 wire with a silver core are simultaneously improved by introducing the silver core.

[0036] Example 3

[0037] This embodiment includes the following steps:

[0038] Step 1: Place a silver core with a diameter of 2.4 mm at the axis of a silver tube with an outer diameter of 12 mm and a wall thickness of 1.0 mm, and then add Bi-2212 powder into the silver tube to obtain an initial wire; the diameter of the silver core fluctuates within 10%;

[0039] 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 silver core.

[0040] The tensile strength and critical current density of the Bi-2212 wire with a silver core 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 core prepared in Example 3 was 7% higher than that of the Bi2212 wire prepared in Comparative Example 1. The critical current density of the Bi-2212 wire with a silver core prepared in Example 3 was 1.5 times that of the Bi-2212 wire prepared in Comparative Example 1.

[0041] By comparing Example 3 with Comparative Example 1, it can be seen that in Example 3, the tensile strength and critical current density of the Bi-2212 wire with a silver core are simultaneously improved by introducing the silver core.

[0042] 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 for improving the mechanical properties and critical current density of Bi-2212 wire, characterized in that: The wire rod structure is as follows: a silver core is introduced into a Bi-2212 wire rod to obtain a Bi-2212 wire rod with a silver core.

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

3. The method according to claim 2, characterized in that In step 1, the diameter of the silver core is 24% to 50% of the inner diameter of the silver tube, the radius of the silver core is 1.2 to 2.5 times the wall thickness of the silver tube, and the fluctuation of the diameter of the silver core does not exceed 10%.

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

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