Superconducting electrical contact and preparation method thereof

Abstract

The invention discloses a superconductive contact and a preparation method thereof, and belongs to the technical field of superconductive contact processing. Raw materials of the superconducting electrical contact are composed of Nb powder, Ti powder and TiB2 powder, the mass ratio of the Nb powder to the Ti powder to the TiB2 powder in the raw materials is 50-55: 40-45: 4-5, the TiB2 powder is added into the raw materials, the fusion welding resistance of NbTi alloy can be enhanced, and it is tested that fusion welding does not happen to the superconducting electrical contact prepared through the method in 20000 electric contact tests. The invention provides an electrical contact material for the superconducting field. The electrical contact material has a high critical current value and excellent fusion welding resistance.

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 method for preparing the same. The raw materials of the superconducting contact are Nb powder, Ti powder and TiB 2 Powder composition, Nb powder, Ti powder and TiB in raw materials 2 The mass ratio of the powder is 50-55:40-45:4-5. In the present invention, TiB is added to the raw material. 2 The powder can enhance the anti-welding ability of NbTi alloy. After testing, the superconducting electrical contact prepared by the present invention did not undergo welding in 20,000 electrical contact tests. The present invention provides an electrical contact material for the superconducting field, which has a higher critical current value and better anti-welding performance. In order 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 Nb powder, Ti powder and TiB 2 Powder composition, Nb powder, Ti powder and TiB in raw materials 2The mass ratio of the powders is 51:45:4. The raw materials of the superconducting contact are all spherical powders, the particle sizes of Nb powder and Ti powder are not higher than 50 μm, and TiB 2 The particle size of the powder is not higher than 50 nm.

[0007] 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: S1: Weigh Nb powder, Ti powder and TiB in a weight ratio of 50~55:40~45:4~5. 2 The raw materials are obtained by powdering, ball milling is used to refine the raw material size, and then three-dimensional powder mixing is used to fully mix the raw materials.

[0008] Furthermore, the above-mentioned Nb powder, Ti powder and TiB 2 The powders are all spherical powders, the particle size of Nb powder and Ti powder is not higher than 50μm, and the particle size of TiB 2 The particle size of the powder is not higher than 50nm. The rotation speed of the ball milling powder mixing is 500-800 rpm, the time of the ball milling powder mixing is 2-4h, the vibration frequency of the three-dimensional powder mixing is 700-800 times / min, and the time of the three-dimensional powder mixing is 2-4h.

[0009] S2: The raw materials after S1 is fully mixed are put into the mold, first pressed, and then sintered by spark plasma sintering process to obtain NbTi-TiB 2 alloy.

[0010] 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.

[0011] S3: NbTi-TiB 2 The alloy surface is wrapped with copper foil and then cold rolled to obtain NbTi-TiB 2 / Cu rod. Then heat and draw, and anneal during the heating and drawing process, heating and drawing and aging heat treatment are carried out alternately to obtain small-sized NbTi-TiB 2 / Cu rod.

[0012] Furthermore, the copper foil is used to prevent NbTi from sticking to the mold during the stretching process, and its thickness is 0.2-0.6 mm. The purpose of the cold rolling is to make the copper foil better adhere to the NbTi-TiB 2The alloy surface is cold rolled 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. 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, with the aim of achieving the "precipitation-crushing-growth-crushing" of the α-Ti flux pinning phase to increase the critical current density of the superconducting contact and improve its current carrying capacity and reliability. The aging heat treatment temperature is 300~600℃, and the aging heat treatment time is 20~30h. The above-mentioned small specifications are 3~5mm in diameter.

[0013] S4: Use the peeling process to convert NbTi-TiB 2 / Cu rod surface is stripped off, and then sawed into the required size to obtain NbTi-TiB 2 Electrical contacts.

[0014] 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.

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: (1) The present invention refines Nb powder, Ti powder and TiB powder by ball milling and three-dimensional mixing. 2 The powder size is adjusted and mixed evenly to alleviate the problem of Nb and Ti not melting easily due to the large difference in melting points. Further addition of TiB containing B 2 The powder promotes 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 unmelted blocks.

[0016] (2) The present invention adds TiB to the raw materials 2 The powder can enhance the arc extinguishing effect and anti-welding ability of NbTi alloy, and the present invention screens out TiB 2 Optimal addition amount of powder, Nb powder, Ti powder and TiB 2 The superconducting conductive contact obtained under the condition of powder weight ratio of 51:45:4 has excellent anti-welding performance, and no welding occurred in 20,000 electrical contact tests.

[0017] (3) The present invention is in NbTi-TiB 2 The surface of the alloy is wrapped with copper foil, which solves the problem of adding TiB to NbTi alloy. 2The raw materials are prone to problems such as mold sticking and plastic deformation.

[0018] (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

[0019] 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.

[0020] Figure 1 This is a metallographic microscope image of a superconducting contact.

[0021] Figure 2 This is a diagram showing the anti-welding test results of superconducting contacts. DETAILED DESCRIPTION

[0022] 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.

[0023] In the embodiment of the present invention, Nb powder, Ti powder and TiB 2 The powders are all spherical powders, the particle size of Nb powder and Ti powder is 50μm, and the particle size of TiB 2 The particle size of the powder is 50 nm.

[0024] Example 1 This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps: S1: Weigh Nb powder, Ti powder and TiB in a weight ratio of 51:45:4. 2 The raw materials were obtained by ball milling to refine the size of the raw materials. The rotation speed of the ball milling was 500 rpm and the time of the ball milling was 2 h. The raw materials were then fully mixed by three-dimensional mixing. The vibration frequency of the three-dimensional mixing was 700 times / min and the time of the three-dimensional mixing was 2 h.

[0025] 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, to obtain NbTi-TiB 2 alloy.

[0026] S3: NbTi-TiB 2 The alloy surface was wrapped with 0.2 mm copper foil and then cold rolled. The number of cold rolling was 1 and the processing rate was 3%. NbTi-TiB 2 / Cu rod. Then heated and drawn, the heating temperature was 100℃, the drawing speed was 50m / min, the processing rate between passes was 10%, and annealing was carried out during the heating and drawing process, the annealing temperature was 150℃, the annealing time was 2h, and the aging heat treatment was carried out alternately with the heating and drawing, the aging heat treatment temperature was 300℃, and the aging heat treatment time was 20h, and the NbTi-TiB with a diameter of 3mm was obtained. 2 / Cu rod.

[0027] S4: Use the peeling process to convert NbTi-TiB 2 / Cu rod surface Cu stripped, the stripping die angle is 1°, the stripping speed is 5m / min, and then sawing is performed according to the required size (sawing length is 10mm, sawing diameter is 2mm) to obtain NbTi-TiB 2 Electrical contacts.

[0028] 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 ).

[0029] Example 2 This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps: S1: Weigh Nb powder, Ti powder and TiB in a weight ratio of 51:45:4. 2 The raw materials were obtained by ball milling to refine the size of the raw materials. The speed of the ball milling was 600 rpm and the time of the ball milling was 2 h. The raw materials were then fully mixed by three-dimensional mixing. The vibration frequency of the three-dimensional mixing was 750 times / min and the time of the three-dimensional mixing was 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 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, to obtain NbTi-TiB2 alloy.

[0031] S3: NbTi-TiB 2 The alloy surface was wrapped with 0.3 mm copper foil and then cold rolled. The number of cold rolling was 1 and the processing rate was 3%. NbTi-TiB 2 / Cu rod. Then heated and drawn, the heating temperature was 150℃, the drawing speed was 60m / min, the processing rate between passes was 15%, and annealing was carried out during the heating and drawing process, the annealing temperature was 200℃, the annealing time was 2h, and the aging heat treatment was carried out alternately with the heating and drawing, the aging heat treatment temperature was 350℃, and the aging heat treatment time was 25h, and the NbTi-TiB with a diameter of 4mm was obtained. 2 / Cu rod.

[0032] S4: Use the peeling process to convert NbTi-TiB 2 / Cu rod surface Cu stripped, the stripping die angle is 2 °, the stripping speed is 7m / min, and then sawing is performed according to the required size (sawing length is 15mm, sawing diameter is 3mm) to obtain NbTi-TiB 2 Electrical contacts.

[0033] 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.

[0034] Example 3 This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps: S1: Weigh Nb powder, Ti powder and TiB in a weight ratio of 51:45:4. 2 The raw materials were obtained by ball milling to refine the size of the raw materials. The rotation speed of the ball milling was 700 rpm and the time of the ball milling was 3 h. The raw materials were then fully mixed by three-dimensional mixing. The vibration frequency of the three-dimensional mixing was 800 times / min and the time of the three-dimensional mixing was 3 h.

[0035] 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, to obtain NbTi-TiB 2 alloy.

[0036] S3: NbTi-TiB 2The alloy surface 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%. NbTi-TiB 2 / Cu rod. Then heated and drawn, the heating temperature was 150℃, the drawing speed was 60m / min, the processing rate between passes was 20%, and annealing was carried out during the heating and drawing process, the annealing temperature was 200℃, the annealing time was 2h, the aging heat treatment was alternately carried out with the heating and drawing, the aging heat treatment temperature was 500℃, the aging heat treatment time was 30h, and the NbTi-TiB with a diameter of 5mm was obtained. 2 / Cu rod.

[0037] S4: Use the peeling process to convert NbTi-TiB 2 / Cu rod surface Cu stripped, the stripping die angle is 3 °, the stripping speed is 5m / min, and then sawing is performed according to the required size (sawing length is 20mm, sawing diameter is 4mm) to obtain NbTi-TiB 2 Electrical contacts.

[0038] 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.

[0039] Example 4 This embodiment provides a method for preparing a superconducting contact, which specifically includes the following steps: S1: Weigh Nb powder, Ti powder and TiB in a weight ratio of 51:45:4. 2 The raw materials were obtained by powdering, and the raw materials were refined by ball milling at a rotation speed of 800 rpm for 4 h. The raw materials were then fully mixed by three-dimensional mixing at a vibration frequency of 800 times / min for 4 h.

[0040] 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, to obtain NbTi-TiB 2 alloy.

[0041] S3: NbTi-TiB 2 The alloy surface was wrapped with 0.6 mm copper foil and then cold rolled. The number of cold rolling was 2 times, and the processing rate was 5%. NbTi-TiB 2 / Cu rod. Then heated and drawn, the heating temperature was 200℃, the drawing speed was 70m / min, the processing rate between passes was 20%, and annealing was carried out during the heating and drawing process, the annealing temperature was 250℃, the annealing time was 1h, and the aging heat treatment was carried out alternately with the heating and drawing, the aging heat treatment temperature was 600℃, and the aging heat treatment time was 30h, and the NbTi-TiB with a diameter of 5mm was obtained. 2 / Cu rod.

[0042] S4: Use the peeling process to convert NbTi-TiB 2 / Cu rod surface Cu stripped, the stripping die angle is 3 °, the stripping speed is 10m / min, and then sawing is performed according to the required size (sawing length is 20mm, sawing diameter is 4mm) to obtain NbTi-TiB 2 Electrical contacts.

[0043] 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.

[0044] 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 superconducting contact, 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.

2. The superconducting contact according to claim 1, 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.

3. The method for preparing a superconducting contact according to any one of claims 1 to 2, 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.

4. The preparation method according to claim 3, characterized in that: The mass ratio of Nb powder, Ti powder and TiB2 powder in the raw material is 50-55:40-45:4-5; 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.

5. The preparation method according to claim 4, 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.

6. The preparation method according to claim 3, 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.

7. The preparation method according to claim 3, characterized in that: The thickness of the copper foil is 0.2-0.6 mm; The number of cold rolling is 1 to 2 times, and the processing rate of cold rolling is 3 to 5%.

8. The preparation method according to claim 3, characterized in that: Aging heat treatment and annealing are performed during the heating and drawing process; 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%.

9. The preparation method according to claim 8, 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.

10. The preparation method according to claim 3, 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; The sawing length is 10-20 mm, and the sawing diameter is 2-4 mm.

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