A method for testing the internal surface insulation strength of a ceramic

Abstract

This invention discloses a method for testing the insulation strength of the inner surface of ceramics, belonging to the field of ceramic materials technology. The sealing component consists of a ceramic part and metal cover plates. An inner platform is provided on the inner wall of the ceramic part, and two metal cover plates are sealed to the inner platform with solder. An intermediate cavity is left between the ceramic part and the metal cover plates. During testing, measuring electrodes are first connected to the metal cover plates, and then the sealing component is placed in an insulating medium for power frequency withstand voltage testing. The initial test voltage starts from 30-90 kV, with a stabilization time of 1-2 minutes. The voltage is increased by 1-10 kV each time until the ceramic part breaks down at the surface. The ratio of the breakdown voltage to the height of the inner platform is used to obtain the insulation strength of the inner surface of the ceramic part. Because the distance between the inner and outer surfaces of the ceramic part is much smaller than that between the outer and outer surfaces, and the outer surface is immersed in the insulating medium, the inner surface breaks down preferentially during measurement, thus effectively measuring the insulation strength of the inner surface of the ceramic part.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and specifically relates to a method for testing the insulation strength of the inner surface of ceramics. Background Technology

[0002] Vacuum interrupters are core components of medium- and high-voltage power switches. Their main function is to rapidly extinguish the arc and suppress current after the power supply to the medium- and high-voltage circuit is cut off, utilizing the excellent insulation of the vacuum inside the tube, thus preventing accidents and unforeseen events. They are primarily used in power transmission and distribution control systems, and also in power distribution systems in metallurgy, mining, petroleum, chemical, railway, broadcasting, communications, and industrial high-frequency heating. They feature energy saving, material saving, fire resistance, explosion protection, small size, long service life, low maintenance costs, reliable operation, and no pollution.

[0003] The ceramic shell is one of the components of a vacuum interrupter, playing a role in insulation, support, and sealing. In medium-voltage applications, due to the relatively large design margin, the insulation strength of the ceramic inner surface has almost no impact on the internal insulation of the interrupter. However, in high-voltage applications, the insulation strength of the ceramic inner surface plays a crucial role in the insulation of the vacuum interrupter, directly affecting its withstand voltage level. Different manufacturing methods and processes result in different inner surface insulation strengths for the ceramic interrupter. However, for a long time, due to the influence of the interrupter's structure and measurement methods, the insulation strength of the ceramic outer surface has been lower than that of the inner surface. During measurement, the outer surface breaks down preferentially, making it impossible to measure the true insulation strength of the inner surface. Therefore, it is impossible to determine which process produces ceramics with better inner surface insulation strength. Because of this inability to assess, it is impossible to improve the inner surface insulation strength through process optimization.

[0004] In current ceramic insulation strength measurement processes, the outer surface is the first to break down, making it impossible to measure the true insulation strength of the inner surface, determine which process produces better inner surface insulation strength, or improve the inner surface insulation strength through process optimization. Therefore, it is necessary to design a method for measuring the inner surface insulation strength of ceramics. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for testing the insulation strength of the inner surface of ceramics, so as to solve the technical problem that existing ceramic insulation strength measurement methods cannot measure the true insulation strength of the inner surface of ceramics.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for testing the insulation strength of the inner surface of ceramics, comprising:

[0008] First, the measuring electrode is connected to the sealing component, which consists of a ceramic component and a metal cover plate. The inner wall of the ceramic component has an inner platform, and the metal cover plate is sealed on the inner platform. The measuring electrode is connected to the metal cover plate. Then, the sealing component is placed in an insulating medium and a power frequency withstand voltage test is performed. The voltage is gradually increased until the inner surface of the ceramic component breaks down. The insulation strength of the inner surface of the ceramic component is obtained based on the ratio of the breakdown voltage to the height of the inner platform.

[0009] Preferably, when performing power frequency withstand voltage testing, the initial test voltage starts from 30 to 90 kV, the voltage stabilization time is 1 to 2 minutes, and the voltage is increased by 1 to 10 kV each time until the voltage increases to the point where the inner surface of the ceramic breaks down.

[0010] Preferably, there are two metal cover plates, including a first metal cover plate and a second metal cover plate placed symmetrically.

[0011] Preferably, the metal cover is sealed to the inner platform by solder.

[0012] Preferably, the solder is silver-copper 28 solder.

[0013] Preferably, an intermediate cavity is provided between the ceramic component and the metal cover plate; the vacuum degree of the intermediate cavity is ≤1×10⁻⁶. - 5 Pa / m 3 .

[0014] Preferably, the diameter of the metal cover is larger than the diameter of the inner platform.

[0015] Preferably, the metal cover is made of 316 stainless steel, oxygen-free copper TU1 or 4J33 Kovar.

[0016] Preferably, the height of the ceramic component is greater than three times the height of the inner platform.

[0017] Preferably, the ceramic part is alumina ceramic, and the mass percentage of alumina in the ceramic part is greater than 92%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention discloses a method for testing the insulation strength of the inner surface of a ceramic component. First, a measuring electrode is connected to the metal cover plate of a sealing component, ensuring effective connection between the measuring electrode and the metal cover plate. The measuring voltage is effectively applied to the metal cover plate and both sides of the inner surface of the ceramic component's inner platform. Then, the sealing component is placed in an insulating medium to improve the outer surface insulation strength and prevent preferential breakdown of the outer surface. Next, a power frequency withstand voltage test is performed, gradually increasing the voltage until the inner surface of the ceramic component breaks down. Based on the ratio of the breakdown voltage to the height of the inner platform, the insulation strength of the inner surface of the ceramic component is finally measured. The sealing component consists of a ceramic component and a metal cover plate. An inner platform is provided on the inner wall of the ceramic component, and the metal cover plate is sealed onto the inner platform, forming a vacuum cavity between the upper and lower metal cover plates and the ceramic component. Furthermore, the insulation distance between the inner surface and the outer surface within the cavity is less than the insulation distance between the inner and outer surfaces. Conventional testing directly utilizes the ceramic components used in vacuum interrupters. These components are metallized at both ends, and then sealed with metal covers. This ensures the distance between the inner and outer surfaces is roughly the same, while the interior is evacuated, providing good insulation. During testing, the ceramic components are placed in an insulating medium, but the insulation of this medium is less than that of a vacuum. Therefore, surface breakdown occurs on the outer surface of the ceramic, meaning only the outer surface can be tested, not the inner surface. This invention adds an inner platform to the ceramic component used in the vacuum interrupter. This inner platform is metallized, and a metal cover is sealed to it. The two ends of the ceramic shell are not metallized, resulting in a smaller inner insulation distance than the outer insulation distance. The height of the inner platform is then rationally designed based on the height and wall thickness of the ceramic shell to ensure that breakdown occurs on the inner wall, not the outer wall or the ceramic body itself.

[0020] Furthermore, during the power frequency withstand voltage test, the voltage starts from a low voltage, is stabilized for 1 to 2 minutes, and is increased by 1 to 10 kV each time until the ceramic component breaks down. The inner surface insulation strength of the ceramic component is obtained based on the ratio of the breakdown voltage to the height of the inner platform.

[0021] Furthermore, metallization is performed at both ends of the inner platform of the ceramic component to achieve a seal between the metal cover and the ceramic component.

[0022] Furthermore, there are two metal cover plates, including a first metal cover plate and a second metal cover plate placed symmetrically. The inner surfaces of the two cover plates are smooth and burr-free and have good electrical conductivity. The thickness of the part where the cover plate is sealed to the ceramic part is less than 1mm to prevent excessive stress from causing the ceramic shell to crack.

[0023] Furthermore, the metal cover plate is sealed to both ends of the inner platform of the ceramic component in a vacuum furnace using solder, specifically silver-copper 28 solder. The vacuum level in the vacuum furnace is better than 1×10⁻⁶ when the solder melts. -5 Pa / m 3 To ensure the vacuum level of the internal cavity after sealing; an intermediate cavity is left between the ceramic component and the metal cover plate, and the vacuum level of the intermediate cavity at room temperature is ≤1×10 -5 Pa / m 3It is comparable to the vacuum level inside the vacuum interrupter. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the sealing component for measuring the insulation strength of the inner surface of the ceramic in an arc-extinguishing chamber, as disclosed in this invention.

[0025] Figure 2 This is a schematic diagram of a ceramic component for measuring the insulation strength of the inner surface of an arc-extinguishing chamber, as disclosed in this invention.

[0026] Figure 3 This is a schematic diagram of the metal cover plate for measuring the insulation strength of the inner surface of the ceramic in an arc-extinguishing chamber, as disclosed in this invention.

[0027] Figure 4 This is a schematic diagram of an existing ceramic component used to measure the insulation strength of the inner surface of an arc-extinguishing chamber.

[0028] Wherein: 1-Ceramic part; 2-First metal cover plate; 3-Second metal cover plate; 4-Intermediate cavity; 5-Inner platform; 6-Inner surface of ceramic part; 7-Outer surface of ceramic part. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings:

[0032] This invention discloses a method for testing the insulation strength of the inner surface of ceramics, comprising:

[0033] First, the measuring electrodes are connected to the metal cover plate of the sealing component. Then, the sealing component is placed in an insulating medium for power frequency withstand voltage testing. Finally, the insulation strength of the inner surface of the ceramic component 1 is measured. During the power frequency withstand voltage test, the voltage starts from 30-90kV, with a stabilization time of 1-2 minutes, increasing by 1-10kV each time until the ceramic component 1 breaks down. The inner surface insulation strength of the ceramic component 1 is obtained based on the ratio of the breakdown voltage to the height of the inner platform. The sealing component consists of a ceramic component 1 and a metal cover plate. An inner platform 5 is provided on the inner wall of the ceramic component 1, and the metal cover plate is sealed onto the inner platform 5. There are two metal cover plates, including a first metal cover plate 2 and a second metal cover plate 3 placed symmetrically. The metal cover plates are sealed onto the inner platform 5 using silver-copper solder. An intermediate cavity 4 is left between the ceramic component 1 and the metal cover plate. The vacuum degree of the intermediate cavity 4 is ≤1×10⁻⁶. -5 Pa / m 3 The metal cover is made of 316L stainless steel and oxygen-free copper TU1 or 4J33 Kovar; the height of ceramic part 1 is more than three times the height of the inner platform 5; ceramic part 1 is alumina ceramic, and the mass percentage of alumina is greater than 92%.

[0034] See Figure 1 This is a schematic diagram of a sealing component for measuring the insulation strength of the inner surface of an arc-extinguishing chamber ceramic, as disclosed in this invention. Figure 1 As can be seen, the sealing component for measuring the insulation strength of the ceramic inner surface of the arc-extinguishing chamber consists of a ceramic component 1 and two metal cover plates, including a first metal cover plate 2 and a second metal cover plate 3. The vacuum degree in the intermediate cavity 4 formed by the ceramic component 1 and the two metal cover plates is ≤1×10⁻⁶. -5 Pa / m 3 It is comparable to a vacuum interrupter.

[0035] See Figure 2 This is a schematic diagram of a ceramic component for measuring the insulation strength of the inner surface of an arc-extinguishing chamber, as disclosed in this invention. As can be seen from the diagram, an inner platform 5 is provided on the inner wall of the ceramic component 1, and the two ends of the inner platform 5 are metallized to facilitate the sealing of the metal cover plate to the metallized ends of the inner platform 5 in a vacuum furnace using silver-copper solder.

[0036] See Figure 3 This is a schematic diagram of a metal cover plate for measuring the insulation strength of the inner surface of the ceramic in an arc-extinguishing chamber, as disclosed in this invention. As can be seen from the diagram, the thickness of the metal cover plate at the sealing position with the ceramic component 1 is less than 1 mm to reduce stress during the sealing process and prevent the ceramic component from cracking.

[0037] See Figure 4This is a schematic diagram of an existing ceramic component used to measure the insulation strength of the inner surface of an arc-extinguishing chamber ceramic. As can be seen from the diagram, the ceramic component is metallized on both end faces, and then a metal cover plate is sealed on the two end faces of the ceramic. In this way, the distance between the inner and outer surfaces is basically the same, and the interior is evacuated, resulting in good insulation. When testing, the ceramic component is placed in an insulating medium. The insulation of the insulating medium is not as good as that of a vacuum, so surface breakdown occurs on the outer surface of the ceramic. Only the outer surface can be measured, and the inner surface cannot be measured.

[0038] Example 1

[0039] A method for testing the insulation strength of the inner surface of a ceramic, comprising:

[0040] When measuring the inner surface insulation strength of ceramic component 1, the measuring electrodes were connected to the first metal cover plate 2 and the second metal cover plate 3. The sealing component was then placed in the insulating medium, and a power frequency withstand voltage test was performed using a power frequency test bench to measure the inner surface insulation strength of ceramic component 1 between the first metal cover plate 2 and the second metal cover plate 3. Since the distance between the inner and outer surfaces of ceramic component 1 is much smaller than the distance between the outer and outer surfaces, and the outer surface is still immersed in the insulating medium, the inner surface breaks down preferentially during measurement. Therefore, the inner surface insulation strength of the arc-extinguishing chamber ceramic can be effectively measured. In the actual measurement, the height of ceramic component 1 was 167 mm, the height of the inner platform 5 was 50 mm, the voltage started at 60 kV, the voltage stabilization time was 1 minute, and the voltage was increased by 5 kV each time until the voltage reached 95 kV, at which point the inner surface of the sample broke down. Based on the ratio of the breakdown voltage to the height of the inner platform, the final inner surface insulation strength of this sample was 1.9 kV / mm.

[0041] The selected sealing component consists of a ceramic part 1, a first metal cover plate 2, and a second metal cover plate 3. An inner platform 5 is provided on the inner wall of the ceramic part 1. The metal cover plate is sealed to the inner platform 5 using silver-copper 28 solder. The metal cover plate is made of 316 stainless steel. The vacuum degree of the intermediate cavity between the ceramic part 1 and the metal cover plate is 0.5 × 10⁻⁶. -5 Pa / m 3 The height of ceramic component 1 is 3.34 times the height of the inner platform; ceramic component 1 is alumina ceramic, and the mass percentage of alumina is 96.7%.

[0042] Example 2

[0043] A method for testing the insulation strength of the inner surface of a ceramic, comprising:

[0044] When measuring the inner surface insulation strength of ceramic component 1, the measuring electrodes were connected to the first metal cover plate 2 and the second metal cover plate 3. The sealing component was then placed in the insulating medium, and a power frequency withstand voltage test was performed using a power frequency test bench to measure the inner surface insulation strength of ceramic component 1 between the first metal cover plate 2 and the second metal cover plate 3. Since the distance between the inner and outer surfaces of ceramic component 1 is much smaller than the distance between the outer and outer surfaces, and the outer surface is still immersed in the insulating medium, the inner surface breaks down preferentially during measurement. Therefore, the inner surface insulation strength of the arc-extinguishing chamber ceramic can be effectively measured. In the actual measurement, the height of ceramic component 1 was 120 mm, the height of the inner platform 5 was 35 mm, the voltage started at 30 kV, the stabilization time was 1.2 min, and the voltage was increased by 4 kV each time. When the voltage reached 66 kV, the inner surface of the sample broke down. Based on the ratio of the breakdown voltage to the height of the inner platform, the final inner surface insulation strength of this sample was 1.88 kV / mm.

[0045] The selected sealing component consists of a ceramic component 1, a first metal cover plate 2, and a second metal cover plate 3. An inner platform 5 is provided on the inner wall of the ceramic component 1. The metal cover plate is sealed to the inner platform 5 using silver-copper 28 solder. The metal cover plate is made of oxygen-free copper TU1. The vacuum degree of the intermediate cavity between the ceramic component 1 and the metal cover plate is 1×10⁻⁶. -5 Pa / m 3 The height of ceramic part 1 is 3.42 times the height of the inner platform; ceramic part 1 is alumina ceramic with a high-temperature glaze on the outer surface, and the mass percentage of alumina is 92.5%.

[0046] Example 3

[0047] A method for testing the insulation strength of the inner surface of a ceramic, comprising:

[0048] When measuring the inner surface insulation strength of ceramic component 1, the measuring electrodes are connected to the first metal cover plate 2 and the second metal cover plate 3. The sealing component is then placed in the insulating medium, and a power frequency withstand voltage test is performed using a power frequency test bench to measure the inner surface insulation strength of ceramic component 1 between the first metal cover plate 2 and the second metal cover plate 3. Since the distance between the inner and outer surfaces of ceramic component 1 is much smaller than the distance between the outer and outer surfaces, and the outer surface is still immersed in the insulating medium, the inner surface breaks down preferentially during measurement. Therefore, the inner surface insulation strength of the arc-extinguishing chamber ceramic can be effectively measured. In the actual measurement, the height of ceramic component 1 is 180 mm, the height of the inner platform 5 is 55 mm, the voltage starts from 70 kV, the voltage stabilization time is 1.5 min, and the voltage is increased by 5 kV each time. When the voltage reaches 100 kV, the inner surface of the sample breaks down. Based on the ratio of the breakdown voltage to the height of the inner platform, the final inner surface insulation strength of this sample is 1.82 kV / mm.

[0049] The selected sealing component consists of a ceramic part 1, a first metal cover plate 2, and a second metal cover plate 3. An inner platform 5 is provided on the inner wall of the ceramic part 1. The metal cover plate is sealed to the inner platform 5 using silver-copper 28 solder. The metal cover plate is made of 4J33 Kovar. The vacuum degree of the intermediate cavity between the ceramic part 1 and the metal cover plate is 0.8 × 10⁻⁶. -5 Pa / m 3 The height of ceramic component 1 is 3.27 times the height of the inner platform; ceramic component 1 is alumina ceramic, and the mass percentage of alumina is 92.5%.

[0050] Example 4

[0051] A method for testing the insulation strength of the inner surface of a ceramic, comprising:

[0052] When measuring the inner surface insulation strength of ceramic component 1, the measuring electrodes were connected to the first metal cover plate 2 and the second metal cover plate 3. The sealing component was then placed in the insulating medium, and a power frequency withstand voltage test was performed using a power frequency test bench to measure the inner surface insulation strength of ceramic component 1 between the first metal cover plate 2 and the second metal cover plate 3. Since the distance between the inner and outer surfaces of ceramic component 1 is much smaller than the distance between the outer and outer surfaces, and the outer surface is still immersed in the insulating medium, the inner surface breaks down preferentially during measurement. Therefore, the inner surface insulation strength of the arc-extinguishing chamber ceramic can be effectively measured. In the actual measurement, the height of ceramic component 1 was 90 mm, the height of the inner platform 5 was 25 mm, the voltage started at 30 kV, the voltage stabilization time was 1 minute, and the voltage was increased by 4 kV each time. When the voltage reached 46 kV, the inner surface of the sample broke down. Based on the ratio of the breakdown voltage to the height of the inner platform, the final inner surface insulation strength of this sample was 1.84 kV / mm.

[0053] The selected sealing component consists of a ceramic component 1, a first metal cover plate 2, and a second metal cover plate 3. An inner platform 5 is provided on the inner wall of the ceramic component 1, and the metal cover plate is sealed to the inner platform 5 using silver-copper solder. The metal cover plate is made of oxygen-free copper TU1. The vacuum degree of the intermediate cavity between the ceramic component 1 and the metal cover plate is 1×10⁻⁶. -5 Pa / m 3 The height of ceramic part 1 is 3.6 times the height of the inner platform; ceramic part 1 is alumina ceramic with a high-temperature glaze on the outer surface, and the mass percentage of alumina is 92.5%.

[0054] Example 5

[0055] When measuring the inner surface insulation strength of ceramic component 1, the measuring electrodes are connected to the first metal cover plate 2 and the second metal cover plate 3. The sealing component is then placed in the insulating medium, and a power frequency withstand voltage test is performed using a power frequency test bench to measure the inner surface insulation strength of ceramic component 1 between the first metal cover plate 2 and the second metal cover plate 3. Since the distance between the inner and outer surfaces of ceramic component 1 is much smaller than the distance between the outer and outer surfaces, and the outer surface is still immersed in the insulating medium, the inner surface breaks down preferentially during measurement. Therefore, the inner surface insulation strength of the arc-extinguishing chamber ceramic can be effectively measured. In the actual measurement, the height of ceramic component 1 is 225 mm, the height of the inner platform 5 is 70 mm, the voltage starts from 90 kV, the voltage stabilization time is 2 minutes, and the voltage is increased by 5 kV each time. When the voltage reaches 140 kV, the inner surface of the sample breaks down. Based on the ratio of the breakdown voltage to the height of the inner platform, the final inner surface insulation strength of this sample is 2 kV / mm.

[0056] The selected sealing component consists of a ceramic part 1, a first metal cover plate 2, and a second metal cover plate 3. An inner platform 5 is provided on the inner wall of the ceramic part 1, and the metal cover plate is sealed to the inner platform 5 using silver-copper solder. The metal cover plate is made of 316L stainless steel. The vacuum degree of the intermediate cavity between the ceramic part 1 and the metal cover plate is 0.5 × 10⁻⁶. -5 Pa / m 3 The height of ceramic component 1 is 3.21 times the height of the inner platform; ceramic component 1 is alumina ceramic, and the mass percentage of alumina is 96.7%.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method of testing the internal surface insulation strength of a ceramic, characterized in that The application relates to a method for measuring the inner surface insulation strength of a ceramic sealing element. The measuring electrode is connected to the sealing element which is composed of a ceramic part (1) and a metal cover plate, the inner wall of the ceramic part (1) is provided with an inner platform (5), the metal cover plate is sealed to the inner platform (5), and the measuring electrode is connected to the metal cover plate; then the sealing element is placed in an insulating medium, power frequency voltage resistance detection is carried out, the voltage is gradually increased to the inner surface of the ceramic part (1) to be broken down, and the inner surface insulation strength of the ceramic part (1) is obtained according to the ratio of the breakdown voltage to the height of the inner platform (5); The metal cover plate comprises a first metal cover plate (2) and a second metal cover plate (3) which are symmetrically arranged. The ceramic piece (1) and the metal cover plate leave an intermediate cavity (4) between them; the vacuum degree of the intermediate cavity (4) is ≤1×10 -5 Pa / m 3 ; The height of the ceramic part (1) is greater than three times the height of the inner platform.

2. The test method for ceramic internal surface insulation strength according to claim 1, characterized by, When the power frequency voltage resistance detection is carried out, the initial detection voltage is 30-90 kV, the voltage stabilization time is 1-2 min, the voltage is increased by 1-10 kV each time, and the voltage is increased to the inner surface of the ceramic part to be broken down.

3. The method of testing the inner surface insulation strength of a ceramic according to claim 1, wherein The metal cover plate is sealed to the inner platform (5) through solder.

4. The method of testing the inner surface insulation strength of a ceramic according to claim 3, wherein The solder is silver copper 28 solder.

5. The method of testing the inner surface insulation strength of a ceramic according to claim 1, wherein The diameter of the metal cover plate is greater than the diameter of the inner platform (5).

6. The method of testing the inner surface insulation strength of a ceramic according to claim 1, wherein The metal cover plate is made of 316 stainless steel, oxygen-free copper TU1 or 4J33 Kovar.

7. The method of testing the inner surface insulation strength of a ceramic according to claim 1, wherein The ceramic part (1) is alumina ceramic, and the mass percentage of alumina in the ceramic part (1) is greater than 92%.

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