Vacuum arc-extinguishing chamber monitoring window brazing process based on transparent ceramic YAG and vacuum arc-extinguishing chamber monitoring window

Abstract

The invention discloses a vacuum arc-extinguishing chamber monitoring window brazing process based on transparent ceramic YAG and a vacuum arc-extinguishing chamber monitoring window, and the vacuum arc-extinguishing chamber monitoring window brazing process comprises the following steps: arranging a circular groove on the outer surface of aluminum oxide ceramic as a connecting surface of a monitoring hole and YAG, designing the connecting surface into a step-shaped structure, and cleaning the surface of the monitoring hole of an aluminum oxide ceramic shell and the brazing surface of the YAG; uniformly stirring molybdenum, manganese and titanium metal powder and the mixed solution, coating the surface of the monitoring hole and the brazing surface of the YAG with the mixed solution, and then performing sintering treatment to form a transition layer; and after a layer of nickel is electroplated on the transition layer, the Kovar ring is used as an intermediate metal piece, and the surface of the monitoring hole, the Kovar ring and the brazing surface of the YAG are sequentially brazed together, so that the monitoring window of the vacuum arc-extinguishing chamber is obtained. According to the method, materials and structures used in the brazing process are comprehensively optimized, so that generated thermal stress is low, the risk of brazing failure is greatly reduced, the rate of finished products is increased, and meanwhile the process complexity and cost are reduced.

Description

Technical Field

[0001] This invention belongs to the field of high voltage switch technology, specifically relating to a brazing process for a vacuum interrupter monitoring window based on transparent ceramic YAG and the vacuum interrupter monitoring window itself. Background Technology

[0002] Maintaining a high internal vacuum level in a vacuum interrupter is crucial for ensuring reliable circuit breaking performance and preventing re-breakdown. Traditional methods struggle to directly monitor the vacuum level online. However, the alumina ceramic-sealed transparent monitoring window technology is a key technology developed for vacuum interrupters to meet the needs of online vacuum monitoring and intelligent diagnostics. It aims to create an optical observation channel without compromising the original high airtightness, high insulation, and mechanical strength of the vacuum interrupter. This technology allows for real-time monitoring of the vacuum state within the interrupter using laser spectroscopy and other methods, enabling early warning of insulation capacity—crucial for ensuring the safety and reliability of power systems.

[0003] The alumina ceramic-sealed transparent monitoring window technology involves creating an opening in the alumina ceramic shell of a vacuum interrupter and sealing it with a transparent ceramic window possessing excellent optical properties. Alumina ceramic is widely used as the shell of vacuum interrupters due to its excellent electrical insulation, mechanical strength, and good sealing performance with metal components. However, it is inherently opaque, necessitating the introduction of a transparent window material. It is crucial to ensure a strong and absolutely airtight seal between the transparent ceramic window and the alumina ceramic shell to maintain the vacuum integrity of the interrupter. The coefficients of thermal expansion of the materials involved in the sealing process must be matched as closely as possible to the alumina ceramic and transparent window materials to avoid excessive thermal stress during the sealing process and subsequent temperature changes, which could lead to cracking or leakage. The entire sealing process, including sealing temperature and atmosphere control, must be precise to ensure that it does not negatively impact the optical transmittance of the transparent window or contaminate the interior of the interrupter.

[0004] The most common processing technique currently used is to create a monitoring hole by opening the ceramic shell of the vacuum interrupter, and then sealing the monitoring hole with MgAlON transparent ceramic using an inorganic sealing agent, resulting in a vacuum interrupter with a transparent monitoring window. The ceramic shell used is alumina ceramic, and the inorganic sealing agent consists of a solvent and inorganic sealing powder, which is glass powder or glaze powder with a melting temperature of 800–1000℃. However, in existing technologies using MgAlON transparent ceramic as the monitoring window material, uneven shrinkage during cooling after brazing with the alumina ceramic shell can generate greater residual thermal stress, reducing the reliability of the sealing structure and increasing the risk of cracking in the window or brazing area. To alleviate the aforementioned sealing stress, a specially formulated brazing filler metal is required for the MgAlON transparent ceramic, and extremely precise control of the brazing temperature profile and holding time is necessary. This increases the complexity and cost of the process, and the strength of MgAlON ceramic decreases significantly at high temperatures, while the high temperature of brazing may have an even greater impact on its mechanical properties.

[0005] Therefore, there is an urgent need to develop an efficient brazing process for the monitoring window of the vacuum interrupter to reduce process complexity and cost. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a brazing process for a vacuum interrupter monitoring window based on transparent ceramic YAG.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0010] A circular groove is set on the outer surface of the alumina ceramic as a monitoring hole, and the surface of the monitoring hole and the brazing surface of YAG are cleaned.

[0011] Molybdenum, manganese, and titanium metal powders are mixed with a solution and coated onto the surface of the monitoring hole and the brazing surface of YAG. Then, a sintering treatment is performed to form a transition layer. The mixed solution is composed of ethyl cellulose, terpineol, dibutyl phthalate, and oleic acid.

[0012] After electroplating a layer of nickel on the transition layer, the monitoring hole surface, the Kovar ring, and the brazing surface of the YAG are sequentially brazed together using the Kovar ring as an intermediate metal component to obtain the vacuum interrupter monitoring window of this embodiment.

[0013] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, wherein: the sintering treatment to form a transition layer is performed at a temperature of 1500–1600°C.

[0014] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, the sintering atmosphere is a wet hydrogen protective atmosphere.

[0015] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, the mixed solution is composed of ethyl cellulose, terpineol, dibutyl phthalate, and oleic acid, wherein the mass ratio of ethyl cellulose, terpineol, dibutyl phthalate, and oleic acid is 70-80:12-20:5:3-5.

[0016] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, the Kovar ring is of model 4J42.

[0017] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, the monitoring hole surface, Kovar ring, and YAG brazing surface are sequentially brazed together, wherein the brazing filler metal is an AgCu28 brazing filler ring.

[0018] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, the brazing temperature is 800–850°C.

[0019] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter described in this invention, the thickness of the AgCu28 brazing ring is 0.1 to 0.15 mm.

[0020] As a preferred embodiment of the brazing process for the monitoring window of the vacuum interrupter chamber described in this invention, the YAG has a thermal expansion coefficient of 8×10⁻⁶. -6 / K, the coefficient of thermal expansion of the alumina ceramic is 9.042×10. -6 / K, the coefficient of thermal expansion of the Kovar ring is 1×10⁻⁶. -5 / K.

[0021] Another objective of this invention is to overcome the shortcomings of the prior art and provide a vacuum interrupter monitoring window obtained by brazing a transparent ceramic YAG-based brazing process.

[0022] Beneficial effects of this invention:

[0023] (1) The present invention comprehensively optimizes the materials and structure used in the brazing process, resulting in lower thermal stress, greatly reducing the risk of brazing failure, improving the yield, and reducing process complexity and cost.

[0024] (2) The monitoring window of this invention can withstand the high-pressure environment inside the GIS tank for a long time, with a leakage rate as low as 2.36×10 -11 Pa·m 3 These characteristics make YAG ceramics more promising and advantageous in applications such as transparent monitoring windows for vacuum interrupters that require long life and high reliability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0026] Figure 1 This is a schematic diagram of the airtightness test of the monitoring window of the vacuum interrupter prepared in Embodiment 1 and Comparative Examples 1 to 13 of the present invention.

[0027] Figure 2 The diagram shows the structure of the hydraulic test mold in the airtightness testing device for the monitoring window of the vacuum interrupter obtained in Embodiment 1 and Comparative Examples 1-13 of the present invention.

[0028] Figure 3 This is a structural diagram of the monitoring window of the vacuum interrupter chamber obtained in Embodiment 1 of the present invention.

[0029] Figure 4 This is a physical image of the vacuum interrupter and monitoring window prepared in Embodiment 1 of the present invention.

[0030] Figure 5 This is a physical image of the vacuum interrupter monitoring window prepared in Comparative Example 1 of the present invention.

[0031] Figure 6 This is a thermal stress distribution diagram of the monitoring window of the vacuum interrupter obtained in Embodiment 1 of the present invention.

[0032] Figure 7 This is a physical image of the vacuum interrupter monitoring window prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0036] The transparent ceramic yttrium aluminum garnet (YAG) used in this invention has a Mohs hardness of approximately 8.5, exhibiting outstanding resistance to brittle fracture. Its flexural strength typically reaches 200–300 MPa, far exceeding that of ordinary glass. It can withstand greater mechanical stress and thermal shock. The average linear coefficient of thermal expansion (CTE) of YAG is extremely low, approximately 7–8 × 10⁻⁶, within the range from room temperature to high temperatures (above 1000°C). -6 / K.

[0037] The method for verifying the airtightness of the vacuum interrupter after brazing according to this invention is as follows: the testing device includes a water pressure testing pump, a water pressure testing mold, and a sealed window structure, such as... Figure 1 As shown. The hydrostatic test mold includes a front seat 1, a rear seat 2, a connector 3, a sealing ring 4, and screws 5, as shown. Figure 2 As shown. The front and rear seats, equipped with corresponding sealing rings, are fixed to the side of the alumina ceramic shell 6 of the vacuum interrupter by screws 5. Water from the water pressure pumping device enters the cavity formed by the front seat 1, sealing ring 4, alumina ceramic shell 6 of the vacuum interrupter, and monitoring window 7 of the vacuum interrupter through the connector. Eight standard air pressures are simulated by water pressure to verify the pressure-bearing capacity of the window components.

[0038] Example 1

[0039] The vacuum interrupter based on transparent YAG ceramic in this embodiment includes an alumina ceramic shell 6, a monitoring window 7 opened on the outside of the alumina ceramic shell, and a Kovar ring 8 disposed between the alumina ceramic shell 6 and the monitoring window 7. Figure 3 As shown.

[0040] This embodiment is based on the brazing process of the monitoring window of the vacuum interrupter chamber made of transparent ceramic YAG, specifically as follows:

[0041] (1) A circular groove is set on the outer surface of an alumina ceramic shell with a diameter of 150 mm and a thickness of 10 mm as a monitoring hole. The groove has a depth of 6 mm, an inner diameter of 22 mm at the opening, an inner diameter of 13 mm at the bottom, and a verticality of 0.01 on the sidewall. The transparent ceramic YAG has an outer diameter of 20 mm near the opening, an outer diameter of 12 mm near the bottom, and an overall height of 4.5 mm. The surface of the monitoring hole and the brazing surface of the transparent ceramic YAG are cleaned to remove oil and impurities. The coefficient of thermal expansion of YAG is 8 × 10⁻⁶. -6 / K, the coefficient of thermal expansion of alumina ceramic is 9.042×10. -6 / K.

[0042] (2) The three metal powders of molybdenum, manganese and titanium are stirred evenly with the mixed solution, wherein the mass ratio of molybdenum, manganese and titanium is 80:15:5, and the ratio of the total mass of the three metal powders to the total mass of the mixed solution is 4:1. The above mixture is coated on the surface of the monitoring hole and the brazing surface of YAG and then sintered at 1500℃ in a wet hydrogen protective atmosphere, so that the activating elements react with the surface of the monitoring hole and the brazing surface of YAG to form a transition layer;

[0043] The mixed solution consists of ethyl cellulose (binder), terpineol (solvent), dibutyl phthalate (plasticizer), and oleic acid (dispersant) in a mass ratio of 80:12:5:3.

[0044] (3) After electroplating a layer of nickel on the transition layer, a Kovar ring of model 4J42 is used as the intermediate metal part. The Kovar ring has an outer diameter of 21.5 mm, an inner diameter of 20.5 mm, a height of 5 mm, a wall thickness of 0.5 mm, and an annular step width of 4.5 mm. The monitoring hole surface, the Kovar ring, and the brazing surface of YAG are sequentially brazed together with a 0.1 mm thick AgCu28 brazing filler ring at 800 °C to obtain the vacuum interrupter monitoring window of this embodiment. Figure 4 As shown; where the coefficient of thermal expansion of the Kovar ring is 1×10⁻⁶. -5 / K,YAG's shape adapts to the integrated structure consisting of the monitoring port and Kovar ring.

[0045] After brazing, it was found that no parts were deformed by compression or damaged. This is because the expansion of the alumina ceramic shell, brazing metal, and YAG is small at the brazing temperature.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that YAG is replaced with MgAlON material, which has a coefficient of thermal expansion of 5.8 × 10⁻⁶. -6 / K, the rest of the preparation process is the same as in Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 1 is that the sintering temperature of the transition layer in step (2) is adjusted to 1600℃, while the rest of the preparation process is the same as in Example 1, thus obtaining the monitoring window of this comparative example.

[0050] The leakage rate of the monitoring window of Example 1 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0051] Table 1. Effects of different window materials and sintering temperatures on the leakage rate of the monitoring window.

[0052]

[0053] Comparing the leakage rates of monitoring windows made of different window materials in Table 1, it can be seen that the monitoring window prepared in Example 1 is not easily broken and has a leakage rate as low as 2.36 × 10⁻⁶. -11 Pa·m 3 This is because the present invention matches the thermal expansion coefficients of YAG and alumina ceramics, and simultaneously uses Kovar materials with similar thermal expansion coefficients for high-temperature brazing. This method results in low sealing stress, making the final window less prone to breakage and exhibiting an extremely low leakage rate after sealing. In contrast, Comparative Example 1 used MgAlON as the window material, resulting in high stress and window breakage during sealing. Figure 5 As shown.

[0054] Figure 6 The thermal stress of the monitoring window after sealing in Example 1 is further demonstrated. It can be clearly seen from the figure that the stress is mainly concentrated on the sealing surface, with a stress value of 600-800 MPa, which is within the tensile strength of YAG transparent ceramic. At the same time, the use of Kovar material with a similar coefficient of thermal expansion for high-temperature brazing further reduces the amount of deformation at high temperature and prevents product damage or even leakage.

[0055] Furthermore, comparing the leakage rates of the monitoring windows obtained at different sintering temperatures in Table 1, it can be seen that when the sintering temperature of the ceramic was only increased by 100°C compared to Example 1, the glass phase in the transition layer excessively flowed or even volatilized, causing excessive glass phase to penetrate into the ceramic substrate. This ultimately led to the formation of a "glass phase depletion layer" near the interface of the metallization layer and the ceramic. This depletion layer is very brittle and easily becomes a crack initiation point. The surface cracking of the transition layer after high-temperature sintering in Comparative Example 2 is shown below. Figure 7 As shown.

[0056] Comparative Example 3

[0057] The difference between this comparative example and Example 1 is that only the molybdenum in step (2) of the three metals molybdenum, manganese and titanium is changed to aluminum. The rest of the preparation process is the same as that of Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0058] Comparative Example 4

[0059] The difference between this comparative example and Example 1 is that only molybdenum in step (2) is changed to chromium among the three metals: molybdenum, manganese, and titanium. The rest of the preparation process is the same as in Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0060] Comparative Example 5

[0061] The difference between this comparative example and Example 1 is that only the manganese in the three metals of molybdenum, manganese and titanium in step (2) is changed to iron. The rest of the preparation process is the same as that in Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0062] Comparative Example 6

[0063] The difference between this comparative example and Example 1 is that only the titanium in the three metals of molybdenum, manganese and titanium in step (2) is changed to copper. The rest of the preparation process is the same as that in Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0064] The leak rates of the test comparison samples 3 to 6 monitoring windows are shown in Table 2.

[0065] Table 2. Effects of transition layer metal elements on leakage rate of monitoring window.

[0066]

[0067] As shown in Table 2, the monitoring window with the lowest leakage rate was obtained by sintering a mixture of molybdenum, manganese, and titanium metal powders with a mixed solution. This is because molybdenum's coefficient of thermal expansion is well-matched with alumina ceramics, and it is very stable in a high-temperature hydrogen atmosphere, preventing reduction or oxidation. Manganese, as an activator, reacts with alumina and the glassy phase in the ceramic during sintering to form a transition layer such as manganese aluminum spinel (MnAl2O4), greatly enhancing the chemical bonding between the metal layer and the ceramic. Adding titanium allows for even stronger reduction and reaction with the ceramic, forming a titanium compound transition layer. Only by using all three simultaneously can the optimal monitoring window performance be obtained. If chromium, manganese, and titanium metal powders are used, although chromium's coefficient of thermal expansion is similar to that of alumina ceramics, its instability in subsequent high-temperature sintering and a hydrogen atmosphere ultimately leads to a significantly higher leakage rate in the monitoring window, failing to meet the airtightness requirements of the vacuum interrupter.

[0068] Comparative Example 7

[0069] The difference between this comparative example and Example 1 is that only the binder ethyl cellulose in the mixed solution of step (2) is changed to acrylic resin, while the rest of the preparation process is the same as that of Example 1, so as to obtain the vacuum interrupter monitoring window of this comparative example.

[0070] Comparative Example 8

[0071] The difference between this comparative example and Example 1 is that only the solvent terpineol in the mixed solution of step (2) is changed to castor oil, while the rest of the preparation process is the same as that of Example 1, so as to obtain the vacuum interrupter monitoring window of this comparative example.

[0072] Comparative Example 9

[0073] The difference between this comparative example and Example 1 is that only the plasticizer dibutyl phthalate in the mixed solution of step (2) is changed to dioctyl phthalate, and the rest of the preparation process is the same as that of Example 1, so as to obtain the vacuum interrupter monitoring window of this comparative example.

[0074] Comparative Example 10

[0075] The difference between this comparative example and Example 1 is that only the dispersant oleic acid in the mixed solution of step (2) is changed to lecithin, while the rest of the preparation process is the same as that of Example 1, so as to obtain the vacuum interrupter monitoring window of this comparative example.

[0076] Comparative Example 11

[0077] The difference between this comparative example and Example 1 is that only the mass ratio of the mixed solution in step (2) is adjusted from 80:12:5:3 to 70:20:5:5. The rest of the preparation process is the same as in Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0078] The leak rates of the test comparison samples 7 to 11 monitoring windows are shown in Table 3.

[0079] Table 3. Effects of Mixed Solution Components and Proportions on Leakage Rate in Monitoring Window

[0080]

[0081] As shown in Table 2, the composition and ratio of the mixed solution have a significant impact on the brazing effect. In Example 1, under the conditions of molybdenum, manganese, and titanium metal powders, and then mixed with the corresponding mixed solution, the leakage rate of the monitoring window after brazing was the lowest. Ethyl cellulose was chosen as the binder to provide the film-forming properties and strength of the paste, allowing the dried coating to adhere completely to the ceramic until sintering is complete. Terpineol, the solvent, evaporates slowly, preventing the paste from drying too quickly and causing cracks. Dibutyl phthalate, the plasticizer, increases the flexibility of the coating and prevents brittleness after drying. Oleic acid, the dispersant, prevents the sedimentation and agglomeration of solid particles, keeping the paste uniform and stable. Conversely, in Comparative Examples 7-11, the use of other binders, solvents, plasticizers, and dispersants all led to a decrease in the airtightness of the vacuum interrupter.

[0082] Comparative Example 12

[0083] The difference between this comparative example and Example 1 is that only the Kovar material in step (3) is changed to stainless steel material, while the rest of the preparation process is the same as in Example 1, so as to obtain the vacuum interrupter monitoring window of this comparative example.

[0084] Comparative Example 13

[0085] The difference between this comparative example and Example 1 is that only the electroplating of a layer of nickel on the transition layer in step (3) is changed to electroplating a layer of silver. The rest of the preparation process is the same as in Example 1, and the vacuum interrupter monitoring window of this comparative example is obtained.

[0086] The leak rate of the test comparison sample 12-13 monitoring window is shown in Table 4.

[0087] Table 4. Influence of intermediate metal components and electroplating materials on the leakage rate of the monitoring window.

[0088]

[0089] As shown in Table 4, electroplating a layer of nickel on the sintered molybdenum-manganese layer primarily serves to prevent the molybdenum layer from oxidizing during subsequent high-temperature brazing and significantly improves the wettability of the silver-copper alloy brazing filler metal to the metallized layer, thereby forming a dense, strong, and vacuum-tight brazed joint. Using silver instead fails to achieve this effect, thus significantly reducing the leakage rate. This invention selects the 4J42 Kovar ring as the metal for brazing transparent YAG ceramic and alumina ceramic. The Kovar ring includes both sides and a bottom surface, both capable of high-temperature brazing of stepped brazing surfaces. At a brazing temperature of approximately 800°C, the coefficient of thermal expansion of 4J42 Kovar material is only about 1 × 10⁻⁶. -5 / K is similar to YAG and ceramic materials. The expansion of the three at the brazing temperature is not much different. Therefore, it can be ensured that the parts will not be squeezed and deformed or even broken after brazing.

[0090] In summary, this invention provides a novel brazing process for monitoring windows in vacuum interrupters based on transparent YAG ceramic. By comprehensively optimizing the materials and structure used in the brazing process, the resulting thermal stress is lower, significantly reducing the risk of brazing failure and improving the yield rate. Simultaneously, it reduces process complexity and cost, enabling the monitoring window to withstand the high-pressure environment inside the GIS tank for extended periods. These characteristics make YAG ceramics more promising and advantageous in applications requiring long lifespan and high reliability for transparent monitoring windows in vacuum interrupters.

[0091] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A brazing process for a monitoring window of a vacuum interrupter based on transparent ceramic YAG, characterized in that: include, A circular groove is set on the outer surface of the alumina ceramic as a monitoring hole, and the surface of the monitoring hole and the brazing surface of YAG are cleaned. Molybdenum, manganese, and titanium metal powders are mixed with a solution and coated onto the surface of the monitoring hole and the brazing surface of YAG. Then, a sintering treatment is performed to form a transition layer. The mixed solution is composed of ethyl cellulose, terpineol, dibutyl phthalate, and oleic acid. After electroplating a layer of nickel on the transition layer, the monitoring hole surface, the Kovar ring, and the brazing surface of the YAG are sequentially brazed together using the Kovar ring as the intermediate metal component to obtain the monitoring window of the vacuum interrupter.

2. The brazing process for the monitoring window of the vacuum interrupter as described in claim 1, characterized in that: The transition layer is formed by sintering, wherein the sintering temperature is 1500-1600℃.

3. The brazing process for the monitoring window of the vacuum interrupter as described in claim 2, characterized in that: The sintering atmosphere is a wet hydrogen protective atmosphere.

4. The brazing process for the monitoring window of the vacuum interrupter as described in claim 1, characterized in that: The mixed solution is composed of ethyl cellulose, terpineol, dibutyl phthalate, and oleic acid, wherein the mass ratio of ethyl cellulose, terpineol, dibutyl phthalate, and oleic acid is 70-80:12-20:5:3-5.

5. The brazing process for the monitoring window of the vacuum interrupter as described in claim 1, characterized in that: The Kovar ring is model 4J42.

6. The brazing process for the monitoring window of the vacuum interrupter as described in claim 1, characterized in that: The monitoring hole surface, Kovar ring, and YAG brazing surface are sequentially brazed together, wherein the brazing filler metal is AgCu28 brazing filler ring.

7. The brazing process for the monitoring window of the vacuum interrupter as described in claim 6, characterized in that: The brazing temperature is 800–850°C.

8. The brazing process for the monitoring window of the vacuum interrupter as described in claim 6, characterized in that: The thickness of the AgCu28 solder ring is 0.1–0.15 mm.

9. The brazing process for the monitoring window of the vacuum interrupter as described in claim 1, characterized in that: The coefficient of thermal expansion of the YAG is 8×10. -6 / K, the coefficient of thermal expansion of the alumina ceramic is 9.042×10. -6 / K, the coefficient of thermal expansion of the Kovar ring is 1×10⁻⁶. -5 / K.

10. The monitoring window of the vacuum interrupter obtained by brazing according to any one of claims 1 to 9.

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