An electrical feedthrough and a preparation method thereof

Abstract

The present application discloses an electrical feedthrough, comprising: a housing having a through hole passing therethrough; an insulator disposed in the through hole of the housing; a cylinder passing through the insulator; and a guide pin disposed in the cylinder. A first longitudinal portion of the guide pin is fixedly connected to the cylinder, and there is a gap between a second longitudinal portion of the guide pin and the cylinder. The insulator is located around the second portion of the guide pin, and a portion of the cylinder corresponding to the insulator is radially contracted. By adopting the present application, the possibility of cracks caused by stress concentration during the cooling process of the insulator is effectively reduced, the sealing performance of the product is improved, and the stability of the electrical feedthrough during service is also improved.

Description

Technical Field

[0001] This application relates to the technical field of nuclear reactors, and particularly to an electrical penetration and a preparation method thereof. Background Art

[0002] An electrical penetration is a special electrical device installed on a reactor containment or pressure vessel for signal transmission and power delivery. The electrical penetration needs to achieve the sealing of radioactive substances inside the reactor while ensuring electrical continuity. However, in the actual production, processing, and use of electrical penetrations, due to the differences in the thermal expansion coefficients of different materials, stresses will be generated between the materials during temperature changes. In order to improve the irradiation stability of electrical penetrations, it has become the latest trend to use inorganic glass sealing materials to replace the original organic sealing materials. However, inorganic glass is a material that is extremely prone to cracking, and excessive stress will cause cracks in it, seriously affecting the service safety of electrical penetrations. Summary of the Invention

[0003] Based on the problems in the above background art, this application aims to provide an electrical penetration and a preparation method thereof, which can improve the service safety of electrical penetrations.

[0004] In a first aspect, this application provides an electrical penetration, including:

[0005] An outer housing having a through hole passing through it;

[0006] An insulator disposed in the through hole of the outer housing;

[0007] A cylinder passing through the insulator; and

[0008] A guide pin penetrating through the cylinder, a first longitudinal part of the guide pin being fixedly connected to the cylinder, a second longitudinal part of the guide pin having a gap with the cylinder, the insulator being located around the second part of the guide pin, and a part of the cylinder corresponding to the insulator being radially contracted.

[0009] Optionally, a stepped hole is provided in the cylinder, an inner diameter of a first section of the cylinder is smaller than an inner diameter of a second section of the cylinder, the first part of the guide pin is received in the first section of the cylinder, and the second part of the guide pin is received in the second section of the cylinder.

[0010] Optionally, the first part and the second part of the guide pin have the same diameter, a positioning portion is provided on the guide pin, the positioning portion separates the first part and the second part of the guide pin, and abuts against a shoulder of the stepped hole of the cylinder.

[0011] Optionally, the wall thickness of the second section of the cylinder is 1.0 - 4.0 mm, and the difference between the wall thicknesses of the first and second sections of the cylinder is 0.2 - 2.0 mm.

[0012] Optionally, the diameter of the first part of the guide pin is greater than that of the second part, and the cylinder has a uniform inner diameter.

[0013] Optionally, the insulator is an insulator, the material of the cylinder is 4J42 alloy, and the material of the guide pin is metal copper or copper alloy.

[0014] Optionally, the diameter of the guide pin is 20 - 70 mm.

[0015] In a second aspect, the present application provides a method for manufacturing an electrical feedthrough, comprising the following steps:

[0016] S101: Provide or prepare a housing, an insulator, a cylinder, and a guide pin. The diameter of the first part of the guide pin in the longitudinal direction is substantially the same as the inner diameter of the first section of the cylinder, and the diameter of the second part of the guide pin in the longitudinal direction is smaller than the inner diameter of the second section of the cylinder;

[0017] S102: Insert the guide pin into the cylinder so that the first part of the guide pin is fixedly connected to the first section of the cylinder, and there is a gap between the second part of the guide pin and the second section of the cylinder;

[0018] S103: Assemble the guide pin, the cylinder, the insulator, and the housing on a sintering fixture, where the insulator is located around the cylinder, the insulator is embedded in the through hole of the housing, and is located around the second part of the guide pin; and

[0019] S104: Perform hermetic sealing so that the insulator shrinks and squeezes the cylinder to deform.

[0020] Optionally, step S102 further includes: fixedly connecting the first part of the guide pin to the first section of the cylinder by brazing.

[0021] Optionally, the sintering fixture is made of graphite material.

[0022] Optionally, the insulator is made of glass material.

[0023] Optionally, the electrical feedthrough is the electrical feedthrough according to any one of the first aspect.

[0024] As described above, the present application adds a component of the cylinder body, and the cylinder body and the guide pin are of an integral structure. When preparing the electrical penetration member described in the present application, during the process of putting the outer casing, the insulator, the cylinder body and the guide pin into a vacuum furnace for hermetic sealing, each component expands due to heat and then cools. During the cooling process, the outer casing and the insulator contract inward and squeeze the cylinder body, and the corresponding part of the cylinder body and the insulator generates a radial contraction deformation. During this process, the contraction deformation of the cylinder body is used to absorb part of the stress generated during the cooling of the insulator, playing a buffering role, so as to optimize the stress distribution in the insulator, reduce the possibility of cracks caused by stress concentration during the cooling of the insulator, and improve the sealing performance of the product.

[0025] In addition, due to the large temperature change during the operation of the nuclear reactor, during the service process of the electrical penetration member of the present application, it will naturally be affected by the surrounding environmental temperature. The cylinder body can contract or expand according to the stress change condition inside the electrical penetration member, absorb the abnormal stress generated by the temperature change, and ensure the insulation and sealing performance of the electrical penetration member. Therefore, the setting of the cylinder body also improves the stability of the electrical penetration member to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without exceeding the scope of protection required by the present application.

[0027] Figure 1 is a schematic diagram of the un-sealed state of the electrical penetration member given in the embodiment of the present application;

[0028] Figure 2 is Figure 1 a schematic diagram of the electrical penetration member after hermetic sealing and forming in

[0029] Figure 3 is another schematic diagram of the un-sealed state of the electrical penetration member given in the embodiment of the present application;

[0030] Figure 4 is Figure 3 a schematic diagram of the electrical penetration member after hermetic sealing and forming in

[0031] Figure 5 is a flowchart of a method for preparing the electrical penetration member given in the embodiment of the present application;

[0032] Figure 6 is a von Mises stress distribution diagram of different positions of the insulators of the electrical penetration members of the present application and the traditional method;

[0033] Figure 7 It is the tangential stress distribution diagram at different positions of the insulators of the electrical feedthrough of the present application and the traditional method;

[0034] Figure 8 It is the axial stress distribution diagram at different positions of the insulators of the electrical feedthrough of the present application and the traditional method;

[0035] Figure 9 It is the radial stress distribution diagram at different positions of the insulators of the electrical feedthrough of the present application and the traditional method;

[0036] Figure 10 It is the relationship diagram between the displacement and the applied load of the guide pin of the electrical feedthrough of the present application and the traditional method under mechanical load;

[0037] Figure 11 It is the schematic diagram of the morphological comparison of the electrical feedthrough of the present application and the traditional method under thermal shock test.

[0038] In the figure, 1 is the outer shell; 11 is the through hole; 2 is the insulator; 3 is the cylinder; 4 is the guide pin; 41 is the first part; 42 is the second part; 43 is the positioning part. Detailed implementation manners

[0039] Next, in combination with the accompanying drawings in the embodiments of the present application, the technical solutions of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0040] For the convenience of understanding the technical solutions of the present application and more clearly reflecting the inventive concept of the present application, first, the existing electrical feedthrough and its preparation process will be briefly introduced.

[0041] The existing electrical feedthrough (traditional method) is usually composed of a metal shell, a glass insulator, and a metal guide pin. The metal shell serves as an external support structure, the glass insulator realizes the sealing and insulation effects, and the metal guide pin realizes the transmission of signals or electrical energy.

[0042] During the preparation process of the electrical feedthrough, the pressed glass insulator, the metal shell, and the metal guide pin are put into a vacuum furnace for fusion sealing, that is, the glass insulator is first heated to a molten state and then cooled. During the cooling process, the glass insulator solidifies and is bonded to the metal guide pin as a whole. During the cooling process, compressive stresses that contract inwardly will be generated inside each component. Therefore, when the glass insulator is subjected to excessive compressive stress, cracks may occur, resulting in the loss of the sealing effect of the entire electrical feedthrough.

[0043] Refer to Figure 1 andFigure 2 , an electrical feedthrough disclosed in an embodiment of the present application, includes a housing 1, an insulator 2, a cylinder 3, and a guide pin 4. Among them Figure 1 shows the electrical feedthrough in an unsealed state, Figure 2 shows the electrical feedthrough after being sealed.

[0044] The housing 1 is of a cylindrical structure, and a through hole 11 penetrating therethrough is axially provided on the housing 1. The housing 1 is made of a metal material, such as 304 stainless steel, etc.

[0045] The insulator 2 is arranged in the through hole 11 of the housing 1 and is fixedly connected to the inner wall of the housing 1 as a whole.

[0046] Both ends of the cylinder 3 are open. As Figure 1 shown, the cylinder 3 has a through hole along its longitudinal direction, with openings at both the upper and lower ends in the figure, and the cylinder 3 passes through the insulator 2. Optionally, the cylinder 3 is made of a metal material and has a certain toughness, and can deform when subjected to an external force.

[0047] The guide pin 4 can have a longitudinally extended structure, is inserted into the cylinder 3, and both ends of the guide pin 4 extend out of the cylinder 3. One end of the guide pin 4 along the longitudinal direction is called the first part 41, and the other end is called the second part 42. Then the first part 41 of the guide pin 4 is fixedly connected to the inner wall of the cylinder 3, and there is a gap between the second part 42 of the guide pin 4 and the inner wall of the cylinder 3. The insulator 2 is located around the second part 42 of the guide pin 4, and this gap is used to absorb the deformation of the cylinder 3.

[0048] Referring to Figure 1 and Figure 2 , in a possible implementation form of an embodiment of the present application, a stepped hole is provided inside the cylinder 3. The end of the cylinder 3 with a smaller inner diameter is called the first section, and the other end is called the second section. Then the first part 41 of the guide pin 4 is accommodated in the first section of the cylinder 3, and the second part 42 of the guide pin 4 is accommodated in the second section of the cylinder 3. The part of the cylinder 3 corresponding to the insulator 2 is fixedly connected to the insulator 2 and contracts radially, as Figure 2 shown.

[0049] It should be understood that the number of the cylinders 3 and the guide pins 4 should be determined according to the requirements in actual production operations, and can be one or more. When there are multiple cylinders 3 and guide pins 4, they can be evenly distributed on the insulator 2 to reduce the possibility of stress concentration in the insulator 2.

[0050] Compared with the electrical feedthrough in the prior art, the present application adds the component of the cylinder body 3, and the cylinder body 3 and the guide pin 4 are of an integral structure. When preparing the electrical feedthrough in the present application, during the process of putting the outer shell 1, the insulator 2, the cylinder body 3 and the guide pin 4 into a vacuum furnace for hermetic sealing, each component expands due to heat and then cools. During the cooling process, the outer shell 1 and the insulator 2 contract inward and squeeze the cylinder body 3, and the part of the cylinder body 3 corresponding to the insulator 2 undergoes a radial contraction deformation. In this process, the contraction deformation of the cylinder body 3 is utilized to absorb part of the stress generated during the cooling of the insulator 2, playing a buffering role, thereby being able to optimize the stress distribution condition inside the insulator 2 and reduce the possibility of cracks caused by stress concentration during the cooling of the insulator 2, and improving the sealing performance of the product.

[0051] In addition, due to the large temperature change during the operation of the nuclear reactor, during the service process of the electrical feedthrough of the present application, it will naturally be affected by the surrounding environment temperature. The cylinder body 3 can contract or expand according to the stress change condition inside the electrical feedthrough, absorb the abnormal stress generated by the temperature change, and ensure the insulation and sealing performance of the electrical feedthrough. Therefore, the setting of the cylinder body 3 also improves the stability of the electrical feedthrough to a certain extent.

[0052] It should be noted that when the cylinder body 3 contracts radially to the final form, according to the actual deformation amount, the inner wall of the cylinder body 3 may not contact the guide pin 4.

[0053] Refer to Figure 1 and Figure 2 , as an optional technical solution of an embodiment of the present application, the diameters of the first part 41 and the second part 42 of the guide pin 4 are the same. A positioning portion 43 is provided on the guide pin 4, and the positioning portion 43 separates the first part 41 and the second part 42 of the guide pin 4. Optionally, the positioning portion 43 is an annular structure (such as a protruding annular portion) fixedly provided along the circumferential direction of the guide pin 4, and the positioning portion 43 abuts against the shoulder of the stepped hole in the cylinder body 3.

[0054] Through the setting of the positioning portion 41, during the process of fixing the cylinder body 3 and the guide pin 4, it is convenient to quickly determine the position of the guide pin 4 inside the cylinder body 3, improve the processing efficiency, and at the same time can more accurately determine the relative position between the guide pin 4 and the cylinder body 3, improving the precision of the product.

[0055] As an optional technical solution of an embodiment of the present application, the insulator 2 adopts a glass insulator, the cylinder body 3 is made of 4J42 alloy, and the guide pin 4 is made of metal copper. The thermal expansion coefficient of the 4J42 alloy is similar to that of the insulator 2, and the bonding stability with the insulator 2 is better after forming.

[0056] It should be noted that when the electrical feedthrough in the prior art is processed, since its guide pin is in direct contact with the insulator, considering that the thermal expansion coefficients of the 4J42 alloy material and the insulator are similar and the bonding is more stable, the guide pin is generally made of 4J42 alloy. However, the electrical conductivity of the 4J42 alloy is inferior to that of copper, and its cost is higher than that of copper. In this application, since the cylinder body 3 is provided and the cylinder body 3 is directly bonded and fixed to the insulator 2 as a whole, the material of the guide pin 4 can be copper. Therefore, compared with the prior art method, the electrical conductivity of the guide pin 4 is improved and the production cost is reduced.

[0057] As an optional technical solution of the embodiment of the present application, the wall thickness of the second section of the cylinder body 3 is 1.0 - 4.0 mm, and the difference between the wall thicknesses of the first section and the second section of the cylinder body 3 is 0.2 - 2.0 mm. Optionally, in an embodiment of the present application, the wall thickness of the second section of the cylinder body 3 is set to 2.3 mm, and the wall thickness of the first section is set to 3.5 mm. In this case, before the electrical feedthrough is formed, that is, before the part of the cylinder body 3 corresponding to the insulator 2 undergoes shrinkage deformation, the gap between the inner wall of the second section of the cylinder body 3 and the guide pin 4 is 1.2 mm.

[0058] Controlling the wall thicknesses of the two sections of the cylinder body 3 within a certain range ensures that the cylinder body 3 itself will not be damaged during the deformation process. At the same time, by controlling the wall thickness values of the two sections of the cylinder body 3, the gap between the second section of the cylinder body 3 and the guide pin 4 is controlled within a certain range, so as to achieve the purpose of absorbing stress while ensuring that the insulator 2 can be firmly bonded to the outer wall of the cylinder body 3.

[0059] As an optional technical solution of the embodiment of the present application, the diameter of the guide pin 4 is 20 - 70 mm. Optionally, in an embodiment of the present application, the diameter of the guide pin 4 is set to 25 mm.

[0060] Refer to Figure 3 and Figure 4 , in another possible implementation form of the embodiment of the present application, the diameter of the first part 41 of the guide pin 4 is greater than the diameter of the second part 42, and the cylinder body 3 has a uniform inner diameter, that is, the inner diameters of the two sections of the cylinder body 3 are the same. In the above form, there is also a gap between the second part 42 of the guide pin 4 and the cylinder body 3. During the forming process of the electrical feedthrough, the part of the cylinder body 3 corresponding to the insulator 2 can also shrink radially to achieve the effects of absorbing stress and deformation and improving the product sealing performance.

[0061] Refer to Figure 5 , the embodiment of the present application also discloses a preparation method of an electrical feedthrough, including the following steps:

[0062] S101: Provide or prepare a housing, an insulator, a cylinder, and a guide pin. Among them, the diameter of the first part of the guide pin along the longitudinal direction is basically the same as the inner diameter of the first section of the cylinder. At the same time, the diameter of the second part of the guide pin along the longitudinal direction must be smaller than the inner diameter of the second section of the cylinder.

[0063] S102: Insert the guide pin into the cylinder so that the first part of the guide pin along the longitudinal direction is fixedly connected to the first section of the cylinder. After the fixation is completed, there is a gap between the second part of the guide pin along the longitudinal direction and the inside of the second section of the cylinder.

[0064] S103: Assemble the guide pin, the cylinder, the insulator, and the housing on a sintering fixture, so that the insulator is embedded in the through hole of the housing, and the insulator should be located around the cylinder.

[0065] S104: Put the guide pin, the cylinder, the insulator, and the housing into a vacuum furnace for fusion sealing. During the cooling process of the fusion sealing, the insulator shrinks and squeezes the cylinder to deform radially.

[0066] It should be understood that the fusion sealing process specifically includes two stages: heating and cooling. After each component is placed in the vacuum furnace, high-purity nitrogen is introduced and gradually heated up. It is kept warm for 20 minutes in the temperature range of 920°C - 980°C for the sealing process. Then it is cooled down to 500°C and kept warm for a period of time to eliminate part of the stress, and finally slowly cooled to room temperature. During the cooling process, the housing and the insulator shrink and squeeze the corresponding part of the cylinder to deform, completing the preparation of the electrical penetrator.

[0067] As an optional technical solution in the embodiment of the present application, in step S102, the first part of the guide pin is connected to the first section of the cylinder by brazing. Apply brazing filler metal at the connection between the guide pin and the cylinder, and then under high-temperature conditions, perform high-temperature brazing on the guide pin and the cylinder to fix the guide pin and the cylinder as a whole.

[0068] As an optional technical solution in the embodiment of the present application, in step S103, the sintering fixture is made of graphite material. The graphite material not only has sufficient mechanical strength and is easy to machine, but also has the characteristic of high temperature resistance. During the fusion sealing process, it will not infiltrate and mix with the glass at high temperature, which can ensure the cleanliness of the glass, ensure the forming quality of the product, and the expansion coefficient of graphite is small, and the volume change is small during the temperature change process, and it is not easy to generate stress with other structures.

[0069] Optionally, in the embodiment of the present application, the insulator is made of glass material. In step S101, when preparing the insulator, mix glass powder and a certain amount of paraffin and add them into a pressing mold, fully stir and mix under heating conditions, and press into shape. Finally, obtain the insulator through debinding and vitrification. Optionally, the mass ratio of the glass powder to the paraffin is 20:1, and the heating condition is 90°C - 110°C.

[0070] Optionally, the electrical feedthrough described in any of the above embodiments is prepared by this preparation method.

[0071] Referring to Figures 6 - 9 , the stress inside the electrical feedthroughs of the present application and the traditional method is detected by numerical simulation. It should be noted that the horizontal axis "distance" refers to the vertical distance between each part of the insulator and its top surface in the longitudinal direction. "Inner" refers to the part of the insulator close to the guide pin, "outer" refers to the part of the insulator close to the outer casing, and "middle" refers to the part of the insulator located between the guide pin and the outer casing.

[0072] As can be seen from the figure, the von Mises stress in the glass and the tangential stress at the "inner" position are significantly optimized. These optimizations can improve the stability of the electrical feedthrough during service and reduce crack initiation. (The von Mises stress has no negative value. The larger the value, the greater the possibility of cracking. The positive values of the remaining radial, axial, and tangential stresses represent tensile forces, and the negative values represent compressive forces.)

[0073] Referring to Figure 10 , a mechanical property test is carried out on the electrical feedthroughs of the present application and the traditional method. The specific operation includes: fixing the outer casing and applying an axial load to the guide pin. It can be seen that the maximum load that the guide pins of the electrical feedthroughs of the present application and the traditional ones can withstand is not much different (the present application is slightly higher than the traditional method), but the displacement before failure of the present application is twice that of the traditional method. Thanks to the elastic deformation of the cylinder in the present application, the addition of the cylinder can enable the electrical feedthrough to obtain higher compressive strength, toughness, and the ability to resist harsh environmental conditions.

[0074] Referring to Figure 11 , a thermal shock test is carried out on the electrical feedthroughs with the same characteristic dimensions of the present application and the traditional method. The test piece is heated to 500 °C and kept warm for 30 minutes, and then quickly cooled in the air. In the figure, (a) is a schematic diagram of the test process of the electrical feedthrough of the present application, and (b) is a schematic diagram of the test process of the electrical feedthrough of the traditional method. In the test piece of the traditional method, during the cooling process, radial cracks initiate from the position close to the guide pin and expand towards the outer casing, and the cracks disappear after a few minutes. This is because the tangential tensile stress during the cooling process causes the radial cracks to appear. As the temperature decreases, the pressure of the outer casing on the insulator continues to increase, resulting in the "healing" of the cracks in a physical sense. In the structure of the present application, due to the buffering effect of the cylinder, no cracks appear in the insulator during the entire cooling process. Therefore, the structure of the present application can improve the mechanical properties and accident tolerance ability of the electrical feedthrough.

[0075] The above has introduced the embodiments of the present application in detail. Specific examples are used herein to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only for helping to understand the technical solution and its core idea of the present application. Therefore, any changes or deformations made by those skilled in the art based on the idea of the present application, within the specific implementation manners and application scope of the present application, fall within the protection scope of the present application. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. An electrical feedthrough, characterized in that, Comprising: An outer housing having a through hole therethrough; An insulator disposed within the through hole of the outer housing; A cylinder body passing through the insulator; And A guide pin inserted into the cylinder body. A first longitudinally extending portion of the guide pin is fixedly connected to the cylinder body, and there is a gap between a second longitudinally extending portion of the guide pin and the cylinder body. The insulator is located around the second portion of the guide pin, and a portion of the cylinder body corresponding to the insulator is radially contracted; Wherein, a stepped hole is provided in the cylinder body, the inner diameter of the first section of the cylinder body is smaller than that of the second section, the first portion of the guide pin is received within the first section of the cylinder body, and the second portion of the guide pin is received within the second section of the cylinder body; alternatively, the cylinder body has a uniform inner diameter, and the diameter of the first portion of the guide pin is larger than that of the second portion.

2. The electrical feedthrough according to claim 1, characterized in that, When a stepped hole is provided in the cylinder body, the diameters of the first and second portions of the guide pin are the same, a positioning portion is provided on the guide pin, the positioning portion separates the first and second portions of the guide pin and abuts against the shoulder of the stepped hole of the cylinder body.

3. The electrical feedthrough according to claim 1, characterized in that, When a stepped hole is provided in the cylinder body, the wall thickness of the second section of the cylinder body is 1.0 - 4.0 mm, and the difference between the wall thicknesses of the first and second sections of the cylinder body is 0.2 - 2.0 mm.

4. The electrical feedthrough according to any one of claims 1-3, characterized in that, The insulator is made of a glass sealing material, the cylinder body is made of 4J42 alloy, and the guide pin is made of metal copper or copper alloy.

5. The electrical feedthrough according to any one of claims 1-3, characterized in that, The diameter of the guide pin is 20 - 70 mm.

6. A method for preparing an electrical feedthrough as described in any one of claims 1-5, characterized in that, Comprising the following steps: S101: Providing or preparing an outer housing, an insulator, a cylinder body, and a guide pin. The diameter of the first longitudinally extending portion of the guide pin is substantially the same as the inner diameter of the first section of the cylinder body, and the diameter of the second longitudinally extending portion of the guide pin is smaller than the inner diameter of the second section of the cylinder body; S102: Inserting the guide pin into the cylinder body such that the first portion of the guide pin is fixedly connected to the first section of the cylinder body, and there is a gap between the second portion of the guide pin and the second section of the cylinder body; S103: Assembling the guide pin, the cylinder body, the insulator, and the outer housing onto a sintering fixture, wherein the insulator is located around the cylinder body, the insulator is inserted into the through hole of the outer housing and is located around the second portion of the guide pin; And S104: Performing a hermetic seal such that the insulator shrinks and squeezes the cylinder body to deform.

7. The preparation method according to claim 6, characterized in that, Step S102 further includes: fixedly connecting the first portion of the guide pin to the first section of the cylinder body by means of brazing.

8. The preparation method according to claim 6, characterized in that, The sintering fixture is made of graphite material.

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