A superconducting contact and a method for preparing the same

Abstract

The present invention discloses a superconducting contact and a preparation method thereof, and belongs to the technical field of superconducting contact processing. The raw materials of the superconducting contact of the present invention are composed of Nb powder, Ti powder and TiB2 powder, and the mass ratio of Nb powder, Ti powder and TiB2 powder in the raw materials is 50~55:40~45:4~5. The addition of TiB2 powder to the raw materials of the present invention can enhance the anti-melting welding ability of NbTi alloy. After testing, the superconducting contact prepared by the present invention did not undergo melting welding in 20,000 electrical contact tests. The present invention provides an electric contact material for the superconducting field, and the electric contact material has a higher critical current value and better anti-melting welding performance.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting contact processing, and relates to a superconducting contact and a preparation method thereof. Background Art

[0002] Electrical contacts are important components of high-voltage circuit breakers, switch cabinets, disconnectors, and grounding switches. They have the functions of breaking and conducting. When they are in contact, the circuit is connected, and their relative movement can open or close the circuit. The performance of electrical contacts directly affects the quality and service life of high-voltage electrical appliances. Currently, commonly used electrical contact materials include silver cadmium oxide materials, etc.

[0003] At present, superconducting materials have been widely used in nuclear fusion, superconducting magnetic resonance imaging, large particle colliders, quantum computing, superconducting motors and other fields, but superconducting contacts in superconducting circuits and systems are still blank. Although commonly used electrical contact materials have their own advantages, there are still defects in applying them to the superconducting field.

[0004] For example, silver cadmium oxide material has high electrical conductivity, thermal conductivity, low and stable contact resistance, excellent resistance to electrical wear, resistance to welding and thermal stability. When working under an electric arc, the large amount of cadmium vapor produced by the violent decomposition of cadmium oxide has an effective arc extinguishing effect. However, cadmium vapor is a toxic substance that is harmful to the human body and the environment, and corresponding protective measures need to be taken during use.

[0005] Therefore, it is of great significance to provide a superconducting conductive contact material that is safe for human body and environment and has good arc extinguishing effect and anti-welding performance. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a superconducting contact and a preparation method thereof. The raw materials of the superconducting contact are composed of Nb powder, Ti powder and TiB2 powder, and the mass ratio of Nb powder, Ti powder and TiB2 powder in the raw materials is 50~55:40~45:4~5. The present invention can enhance the anti-fusion welding ability of NbTi alloy by adding TiB2 powder to the raw materials. After testing, the superconducting contact prepared by the present invention did not undergo fusion welding in 20,000 electrical contact tests. The present invention provides an electric contact material for the superconducting field, and the electric contact material has a higher critical current value and better anti-fusion welding performance.

[0007] To achieve the technical purpose of the present invention, on the one hand, the present invention provides a superconducting contact, wherein the raw materials of the superconducting contact are composed of Nb powder, Ti powder and TiB2 powder, and the mass ratio of Nb powder, Ti powder and TiB2 powder in the raw materials is 51:45:4. The raw materials of the superconducting contact are all spherical powders, the particle size of Nb powder and Ti powder is not higher than 50μm, and the particle size of TiB2 powder is not higher than 50nm.

[0008] On the other hand, the present invention claims protection for a method for preparing the above-mentioned superconducting contact, which specifically comprises the following steps:

[0009] S1: Weigh Nb powder, Ti powder and TiB2 powder in a weight ratio of 50-55:40-45:4-5 to obtain raw materials, refine the raw material size by ball milling, and then fully mix them by three-dimensional mixing.

[0010] Furthermore, the above-mentioned Nb powder, Ti powder and TiB2 powder are all spherical powders, the particle size of Nb powder and Ti powder is not higher than 50μm, and the particle size of TiB2 powder is not higher than 50nm. The rotation speed of ball milling powder mixing is 500-800 rpm, the time of ball milling powder mixing is 2-4h, the vibration frequency of three-dimensional powder mixing is 700-800 times / min, and the time of three-dimensional powder mixing is 2-4h.

[0011] S2: The raw materials after S1 is fully mixed are loaded into a mold, first pressed, and then sintered by spark plasma sintering process to obtain NbTi-TiB2 alloy.

[0012] Furthermore, the pressing mold used in the pressing is a graphite mold, the inner wall diameter of the mold is 30 mm, and a Ta sheet is used as a barrier to prevent graphite from entering the alloy and causing pollution. The pressure is 100-800 MPa, and the holding time is 30-60 seconds. The temperature of the spark plasma sintering is 1200-1600°C, the sintering time is 1-2 hours, and the vacuum degree is not less than 5.0×10 -3 Pa.

[0013] S3: The surface of the NbTi-TiB2 alloy is wrapped with copper foil and then cold rolled to obtain a NbTi-TiB2 / Cu rod, which is then heated and drawn, and annealed during the heating and drawing process. The heating and drawing and aging heat treatment are performed alternately to obtain a small-sized NbTi-TiB2 / Cu rod.

[0014] Furthermore, the copper foil is used to prevent NbTi from sticking to the mold during the stretching process, and its thickness is 0.2~0.6mm. The purpose of the cold rolling is to make the copper foil better adhere to the surface of the NbTi-TiB2 alloy. The number of cold rolling is 1~2 times, and the processing rate is 3~5%. In order to reduce the work hardening during the heating and drawing process, annealing is performed during the heating and drawing process, and the annealing temperature is 150~250℃, and the annealing time is 1~2h. During the heating and drawing process, the heating temperature is 100~200℃, the drawing speed is 50~70m / min, and the processing rate between passes is 10~20%. The aging heat treatment is carried out alternately with the heating and drawing, and the purpose is to realize the "precipitation-crushing-growth-crushing" of the α-Ti flux pinning phase to improve the critical current density of the superconducting contact, improve its current carrying capacity and reliability, the aging heat treatment temperature is 300~600℃, the aging heat treatment time is 20~30h, and the above-mentioned small specification is a diameter of 3~5mm.

[0015] S4: The Cu on the surface of the NbTi-TiB2 / Cu rod is peeled off by a peeling process, and then the rod is sawed according to the required size to obtain a NbTi-TiB2 electrical contact.

[0016] Preferably, the stripping die used in the stripping process in S4 has a die angle of 1-3°, a stripping speed of 5-10 m / min, a sawing length of 10-20 mm, and a sawing diameter of 2-4 mm.

[0017] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0018] (1) The present invention refines the size of Nb powder, Ti powder and TiB2 powder by ball milling and three-dimensional powder mixing, and mixes them evenly, thereby alleviating the problem of non-melting blocks easily appearing during smelting due to the large difference in melting points of Nb and Ti. TiB2 powder containing B is further added to promote the uniform melting and mixing of Nb and Ti. The present invention also adopts a spark plasma sintering process to provide a stable high-temperature environment and precise smelting parameters, thereby reducing the risk of non-melting blocks.

[0019] (2) The present invention adds TiB2 powder to the raw materials to enhance the arc extinguishing effect and anti-welding ability of the NbTi alloy, and the present invention screens out the optimal addition amount of TiB2 powder through experiments. The superconducting contact obtained by using Nb powder, Ti powder and TiB2 powder in a weight ratio of 51:45:4 has excellent anti-welding performance, and no welding occurred in 20,000 electrical contact tests.

[0020] (3) The present invention wraps copper foil on the surface of the NbTi-TiB2 alloy, thereby solving the problem of easy mold sticking and difficulty in plastic deformation after adding TiB2 raw material to the NbTi alloy.

[0021] (4) The critical current of the electrical contact material provided by the present invention at 5 T is 869~1160A, indicating that the material can withstand a higher current density without losing superconducting properties. It can be seen that the electrical contact material of the present invention is preferably applied in the superconducting field. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0023] Figure 1 This is a metallographic microscope image of a superconducting contact.

[0024] Figure 2 This is a diagram showing the anti-welding test results of superconducting contacts. DETAILED DESCRIPTION

[0025] 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.

[0026] In the embodiment of the present invention, Nb powder, Ti powder and TiB2 powder are all spherical powders, the particle size of Nb powder and Ti powder is 50 μm, and the particle size of TiB2 powder is 50 nm.

[0027] Example 1

[0028] This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps:

[0029] S1: Weigh Nb powder, Ti powder and TiB2 powder in a weight ratio of 51:45:4 to obtain raw materials, refine the raw material size by ball milling, the rotation speed of the ball milling is 500 rpm, the ball milling time is 2 h, and then fully mix by three-dimensional mixing, the vibration frequency of the three-dimensional mixing is 700 times / min, and the three-dimensional mixing time is 2 h.

[0030] S2: The fully mixed raw materials of S1 were loaded into a graphite mold with an inner wall diameter of 30 mm and a Ta sheet as a barrier. The mold was first pressed at a pressure of 100 MPa and a holding time of 60 s. Then, the spark plasma sintering (SPS) process was used for sintering at a temperature of 1600 °C, a sintering time of 1 h, and a vacuum degree of 5.0 × 10 -3 Pa, and obtain NbTi-TiB2 alloy.

[0031] S3: The surface of the NbTi-TiB2 alloy was wrapped with 0.2 mm copper foil and then cold rolled. The number of cold rolling was 1 time and the processing rate was 3% to obtain a NbTi-TiB2 / Cu rod. Then it was heated and drawn. The heating temperature was 100°C, the drawing speed was 50 m / min, the processing rate between passes was 10%, and annealing was performed during the heating and drawing process. The annealing temperature was 150°C and the annealing time was 2 h. Aging heat treatment was performed alternately with heating and drawing. The aging heat treatment temperature was 300°C and the aging heat treatment time was 20 h. A NbTi-TiB2 / Cu rod with a diameter of 3 mm was obtained.

[0032] S4: The Cu on the surface of the NbTi-TiB2 / Cu rod is stripped off by a stripping process. The die angle of the stripping die is 1° and the stripping speed is 5 m / min. Then the rod is sawed according to the required size (sawing length is 10 mm and sawing diameter is 2 mm) to obtain a NbTi-TiB2 electrical contact.

[0033] The metallographic microscope image of the superconducting contact prepared in this embodiment is as follows: Figure 1 As shown, the critical current of the superconducting contact at 5T is 1036A. The superconducting contact prepared in this embodiment was subjected to an anti-welding test, and it was found that no welding occurred in the 20,000 electrical contact tests ( Figure 2 ).

[0034] Example 2

[0035] This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps:

[0036] S1: Weigh Nb powder, Ti powder and TiB2 powder in a weight ratio of 51:45:4 to obtain raw materials, refine the raw material size by ball milling, the rotation speed of the ball milling is 600 rpm, the ball milling time is 2 h, and then fully mix the raw materials by three-dimensional mixing, the vibration frequency of the three-dimensional mixing is 750 times / min, and the three-dimensional mixing time is 2 h.

[0037] S2: The fully mixed raw materials of S1 were loaded into a graphite mold with an inner wall diameter of 30 mm and a Ta sheet as a barrier. The mold was first pressed at a pressure of 400 MPa and a holding time of 50 s. Then, the spark plasma sintering (SPS) process was used for sintering at a temperature of 1400 °C, a sintering time of 1 h, and a vacuum degree of 5.0 × 10 -3 Pa, and obtain NbTi-TiB2 alloy.

[0038] S3: The surface of the NbTi-TiB2 alloy was wrapped with 0.3mm copper foil and then cold rolled. The number of cold rolling was 1 time and the processing rate was 3% to obtain a NbTi-TiB2 / Cu rod. Then it was heated and drawn. The heating temperature was 150℃, the drawing speed was 60m / min, the processing rate between passes was 15%, and annealing was performed during the heating and drawing process. The annealing temperature was 200℃ and the annealing time was 2h. Aging heat treatment was performed alternately with heating and drawing. The aging heat treatment temperature was 350℃ and the aging heat treatment time was 25h. A NbTi-TiB2 / Cu rod with a diameter of 4mm was obtained.

[0039] S4: The Cu on the surface of the NbTi-TiB2 / Cu rod is stripped off by a stripping process. The die angle of the stripping die is 2° and the stripping speed is 7 m / min. Then the rod is sawed according to the required size (sawing length is 15 mm and sawing diameter is 3 mm) to obtain a NbTi-TiB2 electrical contact.

[0040] The critical current of the superconducting contact prepared in this embodiment at 5 T is 960 A. The superconducting contact prepared in this embodiment was subjected to an anti-welding test, and it was found that no welding occurred in 20,000 electrical contact tests.

[0041] Example 3

[0042] This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps:

[0043] S1: Weigh Nb powder, Ti powder and TiB2 powder in a weight ratio of 51:45:4 to obtain raw materials, refine the raw material size by ball milling, the rotation speed of the ball milling is 700 rpm, the ball milling time is 3 h, and then fully mix by three-dimensional mixing, the vibration frequency of the three-dimensional mixing is 800 times / min, and the three-dimensional mixing time is 3 h.

[0044] S2: The fully mixed raw materials of S1 were loaded into a graphite mold with an inner wall diameter of 30 mm and a Ta sheet as a barrier. The mold was first pressed at a pressure of 600 MPa and a holding time of 50 s. Then, the spark plasma sintering (SPS) process was used for sintering at a temperature of 1500 °C, a sintering time of 2 h, and a vacuum degree of 5.0 × 10 -3 Pa, and obtain NbTi-TiB2 alloy.

[0045] S3: The surface of the NbTi-TiB2 alloy was wrapped with 0.4 mm copper foil and then cold rolled. The number of cold rolling was 2 times and the processing rate was 4% to obtain a NbTi-TiB2 / Cu rod. Then it was heated and drawn. The heating temperature was 150°C, the drawing speed was 60 m / min, the processing rate between passes was 20%, and annealing was performed during the heating and drawing process. The annealing temperature was 200°C and the annealing time was 2h. Aging heat treatment was performed alternately with heating and drawing. The aging heat treatment temperature was 500°C and the aging heat treatment time was 30h. A NbTi-TiB2 / Cu rod with a diameter of 5 mm was obtained.

[0046] S4: The Cu on the surface of the NbTi-TiB2 / Cu rod is stripped off by a stripping process. The stripping die angle is 3° and the stripping speed is 5 m / min. Then the rod is sawed according to the required size (sawing length is 20 mm and sawing diameter is 4 mm) to obtain a NbTi-TiB2 electrical contact.

[0047] The critical current of the superconducting contact prepared in this embodiment at 5 T is 869 A. The superconducting contact prepared in this embodiment was subjected to an anti-welding test, and it was found that no welding occurred in 20,000 electrical contact tests.

[0048] Example 4

[0049] This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps:

[0050] S1: Weigh Nb powder, Ti powder and TiB2 powder in a weight ratio of 51:45:4 to obtain raw materials, refine the raw material size by ball milling, the rotation speed of the ball milling is 800 rpm, and the ball milling time is 4 h. Then, fully mix the raw materials by three-dimensional mixing, the vibration frequency of the three-dimensional mixing is 800 times / min, and the three-dimensional mixing time is 4 h.

[0051] S2: The fully mixed raw materials of S1 were loaded into a graphite mold with an inner wall diameter of 30 mm and a Ta sheet as a barrier. The mold was first pressed at a pressure of 800 MPa and a holding time of 30 s. Then, the spark plasma sintering (SPS) process was used for sintering at a temperature of 1200 °C, a sintering time of 2 h, and a vacuum degree of 5.0 × 10 -3 Pa, and obtain NbTi-TiB2 alloy.

[0052] S3: The surface of the NbTi-TiB2 alloy was wrapped with 0.6mm copper foil and then cold rolled. The number of cold rolling was 2 times and the processing rate was 5% to obtain a NbTi-TiB2 / Cu rod. Then it was heated and drawn. The heating temperature was 200℃, the drawing speed was 70m / min, the processing rate between passes was 20%, and annealing was performed during the heating and drawing process. The annealing temperature was 250℃ and the annealing time was 1h. Aging heat treatment was performed alternately with heating and drawing. The aging heat treatment temperature was 600℃ and the aging heat treatment time was 30h. A NbTi-TiB2 / Cu rod with a diameter of 5mm was obtained.

[0053] S4: The Cu on the surface of the NbTi-TiB2 / Cu rod is stripped off by a stripping process. The die angle of the stripping die is 3° and the stripping speed is 10 m / min. Then the rod is sawed according to the required size (sawing length is 20 mm and sawing diameter is 4 mm) to obtain a NbTi-TiB2 electrical contact.

[0054] The critical current of the superconducting contact prepared in this embodiment at 5 T is 1160 A. The superconducting contact prepared in this embodiment was subjected to an anti-welding test, and it was found that no welding occurred in 20,000 electrical contact tests.

[0055] The embodiments described above are part of the embodiments of the present invention, but not all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.

Claims

1. A method for preparing a superconducting contact, characterized in that: include: Weighing raw materials, the raw materials consisting of Nb powder, Ti powder and TiB2 powder; The raw materials are mixed evenly, loaded into a mold, pressed, and sintered to obtain a NbTi-TiB2 alloy; Wrapping copper foil on the surface of the NbTi-TiB2 alloy, cold rolling, and heating and drawing to obtain a NbTi-TiB2 / Cu rod; The NbTi-TiB2 / Cu rod is subjected to a peeling process to remove the surface Cu, and the superconducting contact is obtained after sawing; The mass ratio of Nb powder, Ti powder and TiB2 powder in the raw material is 50-55:40-45:4-5; The thickness of the copper foil is 0.2-0.6 mm; Annealing is performed during the heating and drawing process, and the heating and drawing is performed alternately with aging heat treatment; The sawing length is 10-20 mm, and the sawing diameter is 2-4 mm.

2. The preparation method according to claim 1, characterized in that: The uniform mixing is achieved by ball milling and three-dimensional mixing; The speed of the ball milling powder mixing is 500-800 rpm, and the time of the ball milling powder mixing is 2-4 hours; The vibration frequency of the three-dimensional powder mixing is 700-800 times / minute, and the three-dimensional powder mixing time is 2-4 hours.

3. The preparation method according to claim 1, characterized in that: The mold contains a barrier material; The pressing pressure is 100-800 MPa, and the pressing holding time is 30-60 s.

4. The preparation method according to claim 1, characterized in that: The sintering is spark plasma sintering; The sintering temperature is 1200-1600°C, the sintering time is 1-2 hours, and the vacuum degree during the sintering process is not less than 5.0×10 -3 Pa.

5. The preparation method according to claim 1, characterized in that: The number of cold rolling is 1 to 2 times, and the processing rate of cold rolling is 3 to 5%.

6. The preparation method according to claim 1, characterized in that: The heating temperature of the heating drawing is 100-200° C., the drawing speed of the heating drawing is 50-70 m / min, and the processing rate between passes is 10-20%.

7. The preparation method according to claim 1, characterized in that: The annealing temperature is 150-250°C and the annealing time is 1-2h; The temperature of the aging heat treatment is 300-600°C, and the time of the aging heat treatment is 20-30h; The diameter of the NbTi-TiB2 / Cu rod is 3-5 mm.

8. The preparation method according to claim 1, characterized in that: In the peeling process, the die angle of the peeling die is 1-3°, and the peeling speed is 5-10 m / min.

9. The superconducting contact prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The raw materials of the superconducting contact are composed of Nb powder, Ti powder and TiB2 powder; The mass ratio of Nb powder, Ti powder and TiB2 powder in the raw materials of the superconducting contact is 50-55:40-45:4-5.

10. The superconducting conductive contact according to claim 9, characterized in that: The raw materials of the superconducting contacts are all spherical powders; The particle sizes of the Nb powder and the Ti powder are not higher than 50 μm, and the particle size of the TiB2 powder is not higher than 50 nm.

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