Ruthenium-vanadium solder for brazing high-reliability electric vacuum cathode assembly as well as preparation method and application of ruthenium-vanadium solder

Abstract

The invention provides ruthenium-vanadium solder for high-temperature brazing of a cathode assembly of a high-reliability vacuum electronic device and a preparation method and application of the ruthenium-vanadium solder. The preparation method comprises the following steps that firstly, raw materials are subjected to high purification treatment; 2, component optimization and alloying sintering; and thirdly, ruthenium-vanadium alloy powder is prepared through the rotating electrode atomization technology, and the granularity is precisely regulated and controlled through airflow classification. According to the technology, the technologies of raw material high purification, alloying, rotating electrode atomization and the like are combined, and the characteristics of high purity, stable melting point, fine powder, narrow particle size distribution and the like of the ruthenium-vanadium solder are ensured. The brazing flux is suitable for high-reliability brazing of the tungsten porous body cathode assembly with the superfine aperture in the hydrogen atmosphere, the melting point of the brazing flux is 1750 + / -20 DEG C, and the wetting angle lt is achieved; the free-running property is good, and the cleanliness is high.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy solder, and in particular to a high-temperature solder for brazing an ultrafine-aperture tungsten porous body and a molybdenum support tube in a high-reliability electric vacuum cathode assembly and a preparation method thereof. Background Art

[0002] Microwave vacuum electronic devices have absolute advantages in high-power and high-frequency applications. Studies in recent years have shown that the use of ultrafine tungsten powder of 1 to 3 μm and lowering the sintering temperature of tungsten sponge can increase the pore density of tungsten sponge and optimize the pore distribution, which helps to improve the performance and reliability of the cathode in high-power and high-frequency applications. However, if the tungsten sponge prepared by ultrafine tungsten powder continues to be brazed at the original brazing temperature (i.e. 1920°C), it will be densified and sintered for the second time, resulting in changes in pore performance and size shrinkage, thereby destroying the cathode performance. Therefore, it is required to reduce the brazing temperature of high-reliability cathode components by 100°C to 120°C to ensure that the pore size and pore diameter of the tungsten sponge will not change and shrink during brazing.

[0003] Currently, there are few solders that can meet the brazing requirements of the above-mentioned high-reliability ultra-fine aperture cathode components. The melting point of the conventional eutectic ruthenium-vanadium alloy is about 1790°C, which is a certain distance from the high-reliability ultra-fine aperture cathode component requiring the solder melting point of 1750°C. Adjusting the melting point of the ruthenium-vanadium alloy, the wettability with the W / Mo matrix, and the ductility have a great influence on the welding quality. At the same time, the working environment of the high-reliability cathode is extremely sensitive to impurities, and the ruthenium-vanadium solder is required to have high purity to ensure a clean welding environment without spattering and the reliability of the cathode assembly at high temperature. However, ruthenium and vanadium are extremely easy to oxidize, and excessive oxygen content can easily cause solder spattering, which is not conducive to electric vacuum welding. Summary of the invention

[0004] The purpose of the present invention is to provide a high-temperature solder for brazing ultra-fine pore tungsten porous body and molybdenum support tube of cathode assembly of high-reliability vacuum electronic device and its preparation method. Through high purification of raw materials, alloying and rotary atomization powder making process, the prepared ruthenium-vanadium solder has a melting point of 1750±20℃, a purity of 99.95%, a fine particle size and a narrow distribution, a solder wetting angle of <6.8°, good fluidity and high cleanliness. It can reduce the brazing temperature by 100℃ to 120℃ while ensuring good pore performance of tungsten sponge.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A ruthenium-vanadium solder for high-temperature brazing of cathode components of vacuum electronic devices. The purity of the ruthenium-vanadium solder is not less than 99.95%, the oxygen content is less than 6ppm, D50 is less than or equal to 15μm, and the particle size distribution range is narrow.

[0007] In some preferred embodiments, the solder is Ru-V series eutectic alloy or hypereutectic alloy solder powder;

[0008] In some preferred embodiments, the melting point of the ruthenium vanadium solder is 1750°C±20°C; preferably, the wetting angle of the ruthenium vanadium solder is <6.8°, and the fluidity is good.

[0009] In some preferred embodiments, the mass fraction of ruthenium in the ruthenium-vanadium solder is 60% to 80%.

[0010] In some preferred embodiments, the ruthenium-vanadium solder further comprises a third element;

[0011] The third element is selected from any one of the following elements or a combination of at least two: Pt, Pd, Co, Ni;

[0012] Preferably, the added mass percentage of the third type element is 2% to 4%.

[0013] In a second aspect, the present invention further provides a method for preparing the ruthenium-vanadium solder for high-temperature brazing, comprising the following steps:

[0014] 1) High-purity processing of raw materials: electron beam melting combined with hydrogenation-dehydrogenation process is used to prepare high-purity vanadium powder, and hydrometallurgical process is used to prepare high-purity ruthenium powder;

[0015] 2) Composition optimization and alloy sintering: Ruthenium powder, vanadium powder and the third element are mixed uniformly according to the composition ratio, cold isostatically pressed and sintered to prepare vanadium-ruthenium alloy rods;

[0016] 3) The ruthenium-vanadium welding powder is prepared by the rotating electrode atomization process, and the air flow classification is used to accurately control the particle size and its distribution.

[0017] In some preferred embodiments, the hydrogen absorption and embrittlement property of vanadium is utilized to remove interstitial atomic impurities in the raw vanadium by a hydrogenation-dehydrogenation process; the interstitial atomic impurities include any one of the following elements or a combination of at least two of them: O, N, C.

[0018] In some preferred embodiments, in step 1), the purity of hydrogen is above 99.999%; and or

[0019] Hydrogenation temperature 300°C to 550°C; and or

[0020] Dehydrogenation temperature is 600℃~850℃.

[0021] In some preferred embodiments, in step 2), the alloy sintering temperature is 1500° C. to 1600° C.; and or

[0022] Sintering time is 3h~6h.

[0023] In some preferred embodiments, in step 2) and / or step 3), the alloy sintering and / or rotating electrode atomization process is carried out under a high-purity hydrogen protective atmosphere with a purity greater than 99.999%.

[0024] In a third aspect, the present invention also provides a use of the ruthenium-vanadium solder for high-temperature welding in a cathode assembly of a vacuum electronic device.

[0025] The method for preparing a ruthenium-vanadium solder for high-temperature welding of the present invention removes low vapor pressure metal impurities in the raw material vanadium through electron beam melting and purification.

[0026] The invention discloses a method for preparing a ruthenium-vanadium solder for high-temperature welding. The method utilizes the property of metal vanadium that it easily absorbs hydrogen and becomes brittle. The hydrogenation-dehydrogenation process is used to further remove interstitial atomic impurities such as O, N, and C in the vanadium. Hydrogen not only assists in crushing but also serves as a protective and purifying atmosphere, thereby controlling the contact between vanadium powder and impurity atoms such as O and N, thereby obtaining vanadium powder with higher purity.

[0027] The preparation method of a ruthenium vanadium solder for high temperature welding described in the present invention adjusts the solder composition and melting point by adding one or more of Pt, Pd, Co, and Ni, and simultaneously adopts hydrogen sintering alloying to obtain a stable hypoeutectic or hypereutectic phase structure, thereby ensuring that the solder structure is stable and the melting point fluctuation range is small.

[0028] The alloy powder is prepared by the rotary atomization electrode process. The entire atomization process is protected by a 99.999% high-purity hydrogen atmosphere, and further alloying is carried out without contact pollution to ensure high purity of the solder.

[0029] Compared with the prior art, the present invention has the following characteristics:

[0030] 1. The ruthenium-vanadium solder of the present invention has low vapor pressure and is suitable for hydrogen brazing of vacuum electronic devices. The brazing melting temperature range is 1750°C ± 20°C, the brazing temperature is 1800°C ± 20°C, and the welding temperature is stable.

[0031] 2. The ruthenium-vanadium solder of the present invention has high purity, fine particle size and narrow distribution, good wettability and flowability during brazing, a wetting angle of <6.8°, strong gap-filling ability, and good high-temperature strength of the weld.

[0032] 3. Use high-purity hydrogen atmosphere and utilize the metal's hydrogen absorption to increase its embrittlement to achieve assisted crushing, protection and purification of the atmosphere, ensuring that the oxygen content of the solder is less than 6ppm and that the solder does not splash, which is beneficial to the performance of high-reliability electric vacuum cathode components. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 to Figure 3 These are pictures of the wetting state of the ruthenium-vanadium alloy solder powders prepared in Examples 1 to 3 after melting on a Mo substrate. DETAILED DESCRIPTION

[0034] Example 1

[0035] The ruthenium-vanadium alloy solder composition of this embodiment is 70% Ru-28% V-2% Pd.

[0036] The preparation method of the ruthenium-vanadium alloy solder of this embodiment is as follows:

[0037] Electron beam melting and purification of vanadium: The raw vanadium block is ultrasonically cleaned and vacuum dried, electron beam melted into 10 mm round rods and then broken into vanadium blocks. -3 Pa, dry and degassing under 600℃ conditions.

[0038] Preparation of high-purity vanadium powder by hydrogenation-dehydrogenation: hydrogen is introduced at 380°C for 2-4 hours. The purity of the high-purity hydrogen used is greater than 99.999%. The prepared vanadium hydride particles are crushed and then ground. The ball-to-material ratio is 6:1, the ball mill speed is 220r / min, and the ball milling time is 4-6 hours. The above vanadium hydride powder is placed in a vacuum furnace and evacuated to 1×10 -3 Pa, dehydrogenation at 750℃ for 6-8h to obtain vanadium powder with a purity of ≥99.96%.

[0039] Activation and purification of ruthenium powder: The ruthenium powder was reduced at 350°C for 2 hours to reduce the content of surface adsorbed oxygen.

[0040] Preparation of ruthenium-vanadium alloy rods: ruthenium powder, vanadium powder and palladium powder were mixed at a mass fraction of 70:28:2 for 48 hours, cold isostatically pressed, and hydrogen sintered to form vanadium-ruthenium alloy rods with a diameter of Ф20 mm×600 mm.

[0041] Preparation of powder by rotating electrode atomization: Load the electrode rod of Ф20mm×600mm into the atomization chamber through the mechanical shaft, and extend the electrode rod into the atomization chamber, with a length of one-fourth of the entire electrode rod length. Then, evacuate the atomization chamber to a three-stage vacuum and fill it with high-purity hydrogen (99.999%) to ensure the positive pressure in the atomization chamber, and wash the furnace repeatedly for 3 times. Adjust the electrode rod speed to 15000r / min, start the plasma gun, load the electrode rod with a current of 1350A, and the atmosphere pressure is 2bar; as the front end of the electrode rod is heated, a micro-area liquid film is continuously formed, and the electrode rod maintains a high speed while also maintaining a step rate of 1.5mm / s.

[0042] Particle classification and post-processing: Powder particle classification is carried out by using a vibrating screen combined with airflow air separation equipment. The obtained ruthenium vanadium powder is reduced with hydrogen at 300°C for 2h to remove the oxygen adsorbed on the surface.

[0043] like Figure 1 As shown, the purity of the prepared ruthenium vanadium powder is ≥99.95%, and the particle size is D 50 It is 14.132μm, the melting point is 1770℃, and the wetting angle is 6.8°.

[0044] Example 2

[0045] The ruthenium-vanadium alloy solder composition of this embodiment is 75% Ru-22.6% V-2.4% Pt.

[0046] The preparation method of the ruthenium-vanadium alloy solder of this embodiment is as follows:

[0047] Electron beam melting and purification of vanadium: The raw vanadium block is ultrasonically cleaned and vacuum dried, electron beam melted into 10 mm round rods and then broken into vanadium blocks. -3 Pa, dry and degassing under 600℃ conditions.

[0048] Preparation of high-purity vanadium powder by hydrogenation-dehydrogenation: hydrogen is introduced at 380°C for 2-4 hours. The purity of the high-purity hydrogen used is greater than 99.999%. The prepared vanadium hydride particles are crushed and then ground. The ball-to-material ratio is 6:1, the ball mill speed is 220r / min, and the ball milling time is 4-6 hours. The above vanadium hydride powder is placed in a vacuum furnace and evacuated to 1×10 -3 Pa, dehydrogenation at 750℃ for 6-8h to obtain vanadium powder with a purity of ≥99.96%.

[0049] Activation and purification of ruthenium powder: The ruthenium powder was reduced at 350°C for 2 hours to reduce the content of surface adsorbed oxygen.

[0050] Preparation of ruthenium-vanadium alloy rods: ruthenium powder, vanadium powder and platinum powder are prepared in a mass fraction ratio of 75:22.6:2.4, mixed for 48 hours, cold isostatically pressed, and hydrogen sintered into alloy rods with a diameter of Ф20 mm×600 mm.

[0051] Preparation of powder by rotating electrode atomization: Load the electrode rod of Ф20mm×600mm into the atomization chamber through the mechanical shaft, and extend the electrode rod into the atomization chamber, with a length of one-fourth of the entire electrode rod length. Then, evacuate the atomization chamber to a three-stage vacuum and fill it with high-purity hydrogen (99.999%) to ensure the positive pressure in the atomization chamber, and wash the furnace repeatedly for 3 times. Adjust the electrode rod speed to 15000r / min, start the plasma gun, load the electrode rod with a current of 1350A, and the atmosphere pressure is 2bar; as the front end of the electrode rod is heated, a micro-area liquid film is continuously formed, and the electrode rod maintains a high speed while also maintaining a step rate of 1.5mm / s.

[0052] Particle classification and post-processing: Powder particle classification is carried out by using a vibrating screen combined with airflow air separation equipment. The obtained ruthenium vanadium powder is reduced with hydrogen at 300°C for 2h to remove the oxygen adsorbed on the surface.

[0053] like Figure 2 As shown, the purity of the prepared ruthenium vanadium powder is ≥99.95%, and the particle size is D 50 It is 12.337μm, the melting point is 1755℃, and the wetting angle is 6.2°.

[0054] Example 3

[0055] The ruthenium-vanadium alloy solder of this embodiment has a composition of 78% Ru-18.5% V-1% Pt-2.5% Ni.

[0056] The preparation method of the ruthenium-vanadium alloy solder of this embodiment is as follows:

[0057] Electron beam melting and purification of vanadium: The raw vanadium block is ultrasonically cleaned and vacuum dried, electron beam melted into 10 mm round rods and then broken into vanadium blocks. -3 Pa, dry and degassing under 600℃ conditions.

[0058] Preparation of high-purity vanadium powder by hydrogenation-dehydrogenation: hydrogen is introduced at 380°C for 2-4 hours. The purity of the high-purity hydrogen used is greater than 99.999%. The prepared vanadium hydride particles are crushed and then ground. The ball-to-material ratio is 6:1, the ball mill speed is 220r / min, and the ball milling time is 4-6 hours. The above vanadium hydride powder is placed in a vacuum furnace and evacuated to 1×10 -3 Pa, dehydrogenation at 750℃ for 6-8h to obtain vanadium powder with a purity of ≥99.96%.

[0059] Activation and purification of ruthenium powder: The ruthenium powder was reduced at 350°C for 2 hours to reduce the content of surface adsorbed oxygen.

[0060] Preparation of ruthenium-vanadium alloy rods: ruthenium powder, vanadium powder, platinum powder, and nickel powder are mixed in a mass fraction of 78:18.5:1:2.5 for 48 hours, cold isostatically pressed, and hydrogen sintered into alloy rods with a diameter of Ф20 mm×600 mm.

[0061] Preparation of powder by rotating electrode atomization: Load the electrode rod of Ф20mm×600mm into the atomization chamber through the mechanical shaft, and extend the electrode rod into the atomization chamber, with a length of one-fourth of the entire electrode rod length. Then, evacuate the atomization chamber to a three-stage vacuum and fill it with high-purity hydrogen (99.999%) to ensure the positive pressure in the atomization chamber, and wash the furnace repeatedly for 3 times. Adjust the electrode rod speed to 15000r / min, start the plasma gun, load the electrode rod with a current of 1350A, and the atmosphere pressure is 2bar; as the front end of the electrode rod is heated, a micro-area liquid film is continuously formed, and the electrode rod maintains a high speed while also maintaining a step rate of 1.5mm / s.

[0062] Particle classification and post-processing: Powder particle classification is carried out by using a vibrating screen combined with airflow air separation equipment. The obtained ruthenium vanadium powder is reduced with hydrogen at 300°C for 2h to remove the oxygen adsorbed on the surface.

[0063] like Figure 3 As shown, the purity of the prepared ruthenium vanadium powder is ≥99.95%, and the particle size is D 50 It is 12.716μm, the melting point is 1740℃, and the wetting angle is 5.8°.

[0064] All of the above are primary implementations of this intellectual property and do not set limitations on other forms of implementation of this new product and / or new method. Those skilled in the art will use this important information and modify the above content to achieve similar implementations. However, all modifications or transformations based on the new product of this invention belong to the reserved rights.

[0065] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A ruthenium-vanadium solder for high temperature brazing of cathode components of vacuum electronic devices, characterized in that: The purity of the ruthenium-vanadium solder is not less than 99.95%, the oxygen content is less than 6ppm, and D 50 ≤15μm.

2. The ruthenium-vanadium solder for high temperature brazing according to claim 1, characterized in that: The melting point of the ruthenium vanadium solder is 1750°C±20°C; preferably, the wetting angle of the ruthenium vanadium solder is <6.8°.

3. The ruthenium-vanadium solder for high temperature brazing according to claim 1, characterized in that: The mass fraction of ruthenium in the ruthenium-vanadium solder is 60% to 80%.

4. The ruthenium-vanadium solder for high temperature brazing according to claim 1, characterized in that: The ruthenium-vanadium solder also contains a third element; The third element is selected from any one of the following elements or a combination of at least two: Pt, Pd, Co, Ni; Preferably, the added mass percentage of the third type element is 2% to 4%.

5. A method for preparing the ruthenium-vanadium solder for high temperature brazing according to any one of claims 1 to 4, comprising the following steps: 1) High-purity processing of raw materials: electron beam melting combined with hydrogenation-dehydrogenation process is used to prepare high-purity vanadium powder, and hydrometallurgical process is used to prepare high-purity ruthenium powder; 2) Composition optimization and alloy sintering: ruthenium powder, vanadium powder and one or more of Pt, Pd, Co and Ni are mixed uniformly according to a certain composition ratio, cold isostatically pressed and sintered to prepare vanadium-ruthenium alloy rods; 3) The ruthenium-vanadium welding powder is prepared by the rotating electrode atomization process, and the air flow classification is used to accurately control the particle size and its distribution.

6. The method for preparing the ruthenium-vanadium solder for high temperature brazing according to claim 5, characterized in that: By utilizing the hydrogen absorption and embrittlement property of vanadium, a hydrogenation-dehydrogenation process is adopted to remove interstitial atomic impurities in the raw vanadium; the interstitial atomic impurities include any one of the following elements or a combination of at least two of them: O, N, and C.

7. The method for preparing the ruthenium-vanadium solder for high temperature welding according to claim 5, characterized in that In the step 1), the purity of hydrogen is above 99.999%; and or Hydrogenation temperature 300°C to 550°C; and or Dehydrogenation temperature is 600℃~850℃.

8. The method for preparing ruthenium-vanadium solder for high temperature welding according to claim 5, characterized in that: In the step 2), the alloy sintering temperature is 1500° C. to 1600° C.; and or Sintering time is 3h~6h.

9. The method for preparing the ruthenium-vanadium solder for high temperature welding according to claim 5, characterized in that: In step 2) and / or step 3), the alloy sintering and / or the rotating electrode atomization process is carried out under a high-purity hydrogen protective atmosphere with a purity greater than 99.999%.

10. Use of the ruthenium-vanadium solder for high temperature welding according to any one of claims 1 to 4 in a cathode assembly of a vacuum electronic device.

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