Graphite metallization method

Abstract

The invention discloses a graphite metallization method which comprises the following steps: S1, pretreating the surface of graphite to remove grease or impurities on the surface; s2, an equal-height tool is wound on the surface of the graphite from bottom to top, the graphite is placed in a tray, and a cushion block is arranged between the graphite and the tray; s3, the surface of the graphite is coated with the brazing paste through a brushing tool, and the surface of the graphite is evenly coated with the brazing paste with the same thickness through an equal-height tool; s4, the graphite assembly part with the surface coated with the brazing paste is placed in vacuum brazing equipment, vacuum heating is carried out, then cooling is carried out, the brazing paste is clad on the surface of graphite, and therefore graphite metallization is completed, namely, a brazing layer is formed on the surface of the graphite; the uniform adhesion of the brazing paste on the surface of the graphite is controlled through an equal-height tool, and the thickness of a brazing layer is moderate.

Description

Technical Field

[0001] This invention relates to the field of graphite brazing technology, and more particularly to a method for graphite metallization. Background Technology

[0002] Graphite possesses excellent thermal conductivity and exhibits a significant temperature gradient. Simultaneously, graphite boasts a high melting point, low density, and strong high-temperature stability, making it a highly stable material at high temperatures. Due to graphite's high-temperature resistance, a layer of material with a melting point lower than its own can be deposited on its surface, thus achieving bonding between the graphite and the welding layer. This application enables the welding of specialized materials and plays a crucial role in graphite brazing. Graphite brazing typically includes methods such as sintered metal powder bonding, thermal spraying, and physical / chemical vapor deposition.

[0003] Sintered metal powder method: Mo-Mn powder slurry is coated on the graphite surface and sintered at high temperature (1300-1500°C) in a reducing atmosphere (H2 / N2 mixture). Mn acts as an activator, while Mo serves as the main metal layer. Ni is usually electroplated onto the Mo layer to improve solderability and oxidation resistance. This process is complex and costly, but the coating has a strong bond, making it suitable for large parts or special shapes. Thermal spraying method: Such as plasma spraying of Mo or Ni-based alloys. The coating is porous and has relatively low bonding strength, usually requiring post-treatment (such as remelting, impregnation) or for thick-layer applications. Physical / chemical vapor deposition method: A layer of metal (such as Ti, Cr, Mo, Ni, Cu, or a combination thereof) is directly deposited on the graphite surface. Ti / Cr acts as an active layer, reacting and adhering with carbon, and Cu / Ni is then deposited on top as a solderable layer. This process is relatively clean and controllable, suitable for precision components. However, the above methods involve many steps, are costly, and the metallization layer may introduce thermal expansion mismatch problems.

[0004] Meanwhile, silver-based active solder AgCuTi is also a commonly used solder for graphite brazing, and it has good wettability. A layer of silver-based solder is coated on the graphite surface, and at high temperatures, the active elements of the solder react with the graphite to form a dense metal layer. However, the technical difficulties of graphite brazing are as follows: First, the graphite surface has a certain microscopic porosity, making it difficult for the solder to adhere to its surface; second, impurities will precipitate on the graphite surface at high temperatures, thus affecting the adhesion of the solder.

[0005] Therefore, it is hoped that a new method for metallizing graphite can be proposed to overcome the above-mentioned defects. Summary of the Invention

[0006] The purpose of this invention is to provide a graphite metallization method that uses economical brazing filler metal with strong overall performance, and the brazing process of the brazing method is simple and practical.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a graphite metallization method, comprising the following steps: S1. Pre-treating the surface of graphite to remove surface grease or impurities; S2. Wrapping a height-equalizing tool around the surface of the graphite from bottom to top, and placing the graphite with the height-equalizing tool wrapped around it in a tray, with a pad between the graphite and the tray; S3. Applying brazing paste to the surface of the graphite using a brush, and using the height-equalizing tool to easily control the application of the brazing paste to the same thickness, thereby making the brazing paste uniformly and consistently applied to the surface of the graphite; S4. Placing the graphite assembly with the brazing paste applied to its surface in a vacuum brazing device, heating it under vacuum and then cooling it to melt the brazing paste onto the surface of the graphite, thereby completing the graphite metallization and facilitating bonding with other metals.

[0008] In a preferred embodiment, a brazing layer is formed on the surface of the metallized graphite. The brazing filler metal of the brazing layer is AgCuTi active brazing filler metal, and the mass percentage of element Ag in the AgCuTi active brazing filler metal is 68.7%-70.7%, the mass percentage of element Ti is 2%-5%, and the remaining balance is element Cu.

[0009] In a preferred embodiment, the thickness of the brazing layer is 0.1 mm.

[0010] In a preferred embodiment, step S3 is the solder coating stage, and in the solder coating stage, the solder paste is in the form of a paste.

[0011] In a preferred embodiment, step S1 includes a pre-welding preparation stage, in which the surface of the graphite is first pre-cleaned with anhydrous ethanol solution, then ultrasonically cleaned, and finally dried.

[0012] In a preferred embodiment, step S1 includes a surface treatment stage following the pre-welding preparation stage, in which the surface of the graphite is polished using W300 and W800 grit sandpaper to remove surface impurities from the graphite.

[0013] In a preferred embodiment, the thickness of the equal-height tooling is 0.1 mm.

[0014] In a preferred embodiment, the tray is a stainless steel tray, and the inner surface of the tray is coated with a layer of solder resist.

[0015] In a preferred embodiment, the pad is a stainless steel pad that has been wiped clean with anhydrous ethanol.

[0016] In a preferred embodiment, the graphite has a thermocouple hole at the top to monitor the thermocouple temperature at all times during the brazing process.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the brazing method of the present invention uses a specially made AgCuTi active brazing filler metal, which makes a dense metal layer formed on the surface of graphite after brazing, and there are no pores; in addition, the uniform adhesion of the brazing paste on the surface of graphite is controlled by equal height tooling, and the thickness of the brazed layer is moderate; thus, the surface of the brazed layer is uniform and dense in the metallographic display of large volume graphite metallized parts. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the graphite metallized part in a preferred embodiment of the present invention.

[0019] Figure 2 yes Figure 1 The diagram shows a cross-sectional view of a graphite metallized component placed on a tray. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the embodiments of the present invention, and should not be construed as limiting the present invention.

[0021] Please see Figures 1 to 2 As shown, a preferred embodiment of the present invention discloses a graphite metallization method, which uses a more economical brazing filler metal with strong comprehensive performance, and the brazing process of the brazing method is simple and practical; while solving the welding problems of special materials, the technical difficulties encountered in the brazing process are solved through process control.

[0022] The graphite metallization method includes the following steps: Pre-welding preparation stage: First, use anhydrous ethanol solution to pre-clean the surface of graphite 10, then perform ultrasonic cleaning, and finally vacuum drying. Surface treatment stage: The surface of graphite 10 is polished with W300 and W800 grit sandpaper to remove surface impurities, specifically to remove impurities from the white marks on the surface; after polishing with low grit sandpaper, it is then finished with high grit sandpaper. Assembly stage: A special height-equalizing tool 30 is wound around the surface of graphite 10 from bottom to top, and the graphite 10 with the height-equalizing tool 30 wound around it is placed in a tray 40, the tray 40 having a pad 41 located between the inner surface of the tray 40 and the bottom surface of the graphite 10. Solder application stage: Use a special brush to apply solder paste to the surface of graphite 10. By using the equal height tool 30, the application of solder paste can be easily controlled to the same thickness, that is, the thickness of the solder paste does not exceed the thickness of the equal height tool 30, so that the solder paste is applied evenly and with a consistent thickness to the surface of graphite 10. Vacuum brazing stage: The graphite assembly with the brazing paste applied to its surface is placed in a vacuum brazing equipment. The surface of the graphite 10 is melted and coated with brazing paste by vacuum heating and then cooling. The thermocouple temperature is monitored at all times during the brazing process to ensure that it meets the process parameters, thereby completing the metallization of the graphite, that is, forming a brazing layer 20 on the surface of the graphite 10 to facilitate bonding with other metals.

[0023] The final graphite metallized part 100 is obtained through the above brazing method. Metallographic analysis of the graphite metallized part 100 shows that the surface of the brazing layer 20 is uniform and dense. In this embodiment, the graphite metallized part 100 includes a cylindrical graphite 10 and a brazing layer 20 located on the outer surface of the graphite 10. The brazing filler metal of the brazing layer 20 is AgCuTi active brazing filler metal, and the mass percentage of element Ag in the AgCuTi active brazing filler metal is 68.7%-70.7%, the mass percentage of element Ti is 2%-5%, and the remaining balance is element Cu.

[0024] Furthermore, the pre-welding preparation stage and surface treatment stage are used to pre-treat the surface of the graphite 10 to remove surface grease or impurities. In the brazing filler metal application stage, the brazing paste is in paste form. The equal-height fixture 30 has a thickness of 0.1 mm and is used to control the thickness of the brazing paste during application; that is, the equal-height fixture 30 controls the uniform adhesion of the brazing paste to the surface of the graphite 10, ensuring that the final brazed layer 20 has a suitable thickness. Therefore, the thickness of the brazed layer 20 is 0.1 mm.

[0025] Meanwhile, the tray 40 is a stainless steel tray, and its inner surface is coated with a layer of solder resist to prevent solder from dripping and sticking. Furthermore, the pad 41 is a stainless steel pad wiped clean with anhydrous ethanol, also to prevent solder from dripping. Figure 2 As shown, the graphite 10 is provided with a thermocouple hole 11 at the top, which is used to monitor the thermocouple temperature of the graphite 10 at all times during the welding stage of the vacuum equipment.

[0026] In this invention, the brazing method uses a specially formulated AgCuTi active brazing filler metal, which forms a dense metal layer on the surface of the graphite 10 after brazing, and is free of pores. Furthermore, the uniform adhesion of the brazing paste to the surface of the graphite 10 is controlled by the equal-height tooling 30, and the thickness of the brazing layer 20 is moderate. As a result, the surface of the brazing layer 20 is uniform and dense in the metallographic display of the graphite metallized part 100.

[0027] In summary, the above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention should still fall within the scope of the present invention.

Claims

1. A method of metalizing graphite, characterized by: It comprises the following steps: S1. Pre-treating the surface of graphite to remove surface grease or impurities; S2. Wrapping the surface of the graphite with an isometric tool from bottom to top, and placing the graphite wrapped with the isometric tool in a tray, and providing a spacer between the graphite and the tray; S3. Using a brush coating tool to apply the brazing paste on the surface of the graphite, and using the isometric tool to control the application of the brazing paste to the same thickness, so that the brazing paste is uniformly and uniformly applied on the surface of the graphite; S4. Placing the graphite assembly with the above surface coated with brazing paste in a vacuum brazing device, and heating and then cooling by vacuum to melt the brazing paste on the surface of the graphite, thereby completing the metallization of the graphite to facilitate the combination with other metals.

2. The method of graphitizing according to claim 1, wherein: The surface of the metallized graphite forms a brazing layer, the filler metal of the brazing layer is AgCuTi active filler metal, and the mass percentage of element Ag in the AgCuTi active filler metal is 68.7%-70.7%, the mass percentage of element Ti is 2%-5%, and the remaining amount is element Cu.

3. The method of graphitizing as defined in claim 2, wherein: The thickness of the brazing layer is 0.1mm.

4. The method of graphitizing as defined in claim 2, wherein: The step S3 is a filler metal application stage, and in the filler metal application stage, the brazing paste is in a paste form.

5. The method of graphitizing according to claim 1, wherein: The step S1 includes a pre-welding preparation stage, in which the surface of the graphite is first pre-cleaned with anhydrous ethanol solution, then ultrasonic cleaned, and then dried after cleaning.

6. The method of graphitizing as defined in claim 5, wherein: The step S1 includes a surface treatment stage after the pre-welding preparation stage, in which the surface of the graphite is polished with W300 and W800 abrasive paper to remove surface impurities of the graphite.

7. The method of graphitization of claim 1, wherein: The thickness of the isometric tool is 0.1mm.

8. The method of graphitization of claim 1, wherein: The tray is a stainless steel tray, and the inner surface of the tray is coated with a layer of solder resist.

9. The method of graphitizing as defined in claim 8 wherein: The spacer is a stainless steel spacer wiped clean with anhydrous ethanol.

10. The method of graphitization of claim 1, wherein: The graphite is provided with a thermocouple hole at the top to monitor the thermocouple temperature at all times during brazing. The graphite is provided with a thermocouple hole at the top to monitor the thermocouple temperature at all times during brazing.

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