Bonding element for diffusion bonding comprising heating element and bonding structure having outer metal surface
By integrating the bonding structure and heating elements in the bonding element and achieving diffused bonding using local heating, the problem of handling large components and high energy consumption in the prior art is solved, and effective bonding and energy saving to larger components is achieved.
Patent Information
- Application Number
- CN202380068616.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-09-26
- Filing Date
- 2023-09-25
- Publication Date
- 2025-05-02
AI Technical Summary
Existing diffusion bonding techniques have limitations in handling large components or consuming high energy, and require the components to be placed in a furnace for extended periods of heating.
The need to place the components in the furnace is avoided by integrating the bonding structure and heating elements in the bonding element and positioning them between the two parts, diffused bonding is achieved using local heating.
Adhesion to larger components is achieved and the heating energy consumed is reduced, suitable for forming a permanent seal between vacuum chambers or large pipe sections.
Smart Images
Figure CN119923303A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a bonding element and a bonding method for bonding parts. Background Art
[0002] In many industries, reliable sealing between components (e.g., between flanges of pipe sections being joined) is important. In some cases, gaskets or spring-loaded metal seals may be sufficient to provide a gas-tight seal between components when compressed. For high temperature and pressure applications or where sufficient compression cannot be maintained, it may be necessary to permanently join the components by, for example, welding or brazing. This is not always possible and may damage the components to be joined.
[0003] Diffusion bonding is a solid-state technique for permanently joining parts. It operates on the principle of solid-state diffusion, in which atoms of two solid surfaces (e.g., metal surfaces) spread between themselves over time. It can be used to join similar or dissimilar materials, including a wide range of metals, alloys, and ceramic materials, including aluminum alloys, titanium alloys, steels, copper alloys, silicon carbide (SiC), silicon nitride (Si3N4), and metal matrix composites. Diffusion bonding is usually performed by applying high pressure and high temperature (but below the lowest melting point of the respective parts or any interlayers) to the parts to be joined in a vacuum or inert gas environment.
[0004] Figure 1 A schematic diagram of a system 1 for diffusion bonding is shown. Two parts 2 are pressed together by a hydraulic press 3 and heated by a heater 4 in an evacuated furnace 5 to induce bonding between the parts 2. Diffusion bonding is used in a wide range of industries, but due to the need to place the parts in a suitable furnace 5 and heat them for a long period of time, diffusion bonding is generally only used to manufacture relatively small component assemblies. Summary of the invention
[0005] In one aspect, the present invention provides a method of bonding two components, the method comprising: positioning a bonding element including a bonding structure and a heating element between the two components; compressing the bonding element between the two components; and heating the bonding structure using the heating element so that the bonding structure is diffusion bonded to each of the two components and provides a bond between the two components. Advantageously, by positioning the bonding structure and the heating element between the two components, diffusion bonding can be achieved by simply providing localized heating to the bonding structure, rather than placing the assembly in a furnace. This enables diffusion bonding to be used for larger assemblies and / or consume less heating energy than previously possible. For example, diffusion bonding can be used to form permanent seals between parts of a vacuum chamber or large pipe sections.
[0006] At least an outer surface of the bonding structure comprises a material suitable for diffusion bonding to each of the two components, such as a metal, or in some embodiments, aluminum.
[0007] In another aspect, the present invention provides a bonding element for bonding (e.g., suitable for diffusion bonding) two components, the bonding element comprising: a bonding structure having an outer metal surface; and a heating element (e.g., a resistive heating element) adjacent to the bonding structure (e.g., such that the heating element provides localized heating to the bonding structure during use); wherein the bonding element is configured to be positioned between the two components, and the heating element is configured to sufficiently heat the bonding structure during use so that the outer metal surface of the bonding structure bonds to each of the two components.
[0008] The bonding element may include a spring-energised metal seal, the heating element includes a coil spring of the spring-energised metal seal, and the bonding element includes a sealing sheath at least partially surrounding the coil spring. In this embodiment, positioning the bonding element between the two components can form a seal between the components, and then making the seal permanent by heating the bonding element from the inside to bond the bonding element to each of the components. In a typical spring-energised metal seal, both the spring and the outer sheath form a closed loop. In this embodiment, the spring does not form a closed loop (e.g., the spring has at least one separation) so that a voltage can be applied across the spring.
[0009] In another aspect, the present invention provides a bonding element for bonding two parts, the bonding element comprising: a bonding structure for positioning between the two parts; and a heating element, the heating element being connected to the bonding structure and being configured to sufficiently heat the bonding structure so that the bonding structure is bonded to each of the two parts. Thus, the bonding structure bonds the two parts together. The bonding structure can be a sealing structure (e.g., comprising a closed ring) that also provides a seal between the two parts when used for bonding. The bonding or sealing structure can include a metal (e.g., aluminum) surface (e.g., a shell, a sheath, or a foil) that at least partially encapsulates the heating element. Thus, the bonding or sealing structure can be configured to diffusely bond its metal surface to the corresponding surfaces of the two parts in use (e.g., aluminum diffusion bonding).
[0010] In another aspect, the present invention provides a method of bonding two components, the method comprising: providing a bonding element comprising a bonding structure and a heating element, wherein the heating element is connected to the bonding structure; positioning the bonding element between the two components; applying pressure to the bonding element via the two components; and heating the bonding structure using the heating element to bond the bonding structure to each of the two components. The bonding structure can be a sealing structure (e.g., comprising a closed loop), whereby bonding the bonding structure to each of the two components also includes providing a seal between the two components. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:
[0012] Figure 1 A schematic diagram showing a system for diffusion bonding;
[0013] Figure 2 A schematic diagram showing a bonding element;
[0014] Figure 3 A schematic diagram showing two components being bonded by a bonding element;
[0015] Figure 4 showing a schematic cross section of a bonding element; and
[0016] Figure 5 A flow chart showing a bonding method. DETAILED DESCRIPTION
[0017] Embodiments described herein provide a bonding element for bonding two components. The bonding element includes a bonding structure and a heating element, the bonding structure is used to be positioned between the two components, the heating element is adjacent to the bonding structure, and is configured to provide local sufficient heating to the bonding structure to cause the bonding structure to diffusely bond to each of the two components, thereby bridging the two components and bonding them together. Conveniently, when the bonding structure is formed as, for example, a closed ring, the bonding structure can also be used as a sealing structure that provides a seal between the two components when used for bonding. The following description focuses on embodiments of the present invention, wherein the bonding element includes a sealing structure, but it will be appreciated that providing a local heating element is advantageous for bonding structures that are generally suitable for diffusion bonding.
[0018] The sealing structure can include metal or any other suitable material that can form diffusion bonding with the parts to be joined. For example, aluminum can form diffusion bonding with a wide range of metals, ceramics, glasses and crystalline solids. Therefore, the sealing structure can be configured for aluminum diffusion bonding and form a bonding interlayer or structure between the two parts. The selection of the material for the sealing structure can depend on the material of the facing surfaces of the parts to be joined. These surfaces can include any suitable material, including metal (e.g., copper), ceramics, glass or crystalline solids. The parts (and / or their facing surfaces) can include the same or different materials. For example, the bonding element can be arranged to provide a seal between a metal part and a ceramic part.
[0019] The sealing structure may include a metal sheath, foil or shell at least partially enclosing the heating element, i.e. the heating element is an internal heating element for the sealing structure. The sealing structure may include a metal tube. For example, the sealing structure may be an aluminum tube, wherein the heating element is positioned inside the tube.
[0020] The heating element is typically a resistive heating element. An electric current may be passed through the resistive element to generate heat and thereby heat the sealing structure. The resistive heating element may comprise any material having sufficient power density to provide the desired heating. For example, the resistive heating element may comprise one or more of nickel, chromium, iron, or aluminum. For example, the resistive heating element may comprise a nickel-chromium alloy or a Kanthal RTM The resistive material of the electrical heating element will be insulated from the sealing structure (and the components to be joined). For example, the heating element may comprise a mineral insulated heater, such as a magnesium oxide (MgO) coated metal element.
[0021] The sealing structure comprises an opening configured to provide access to the heating element.For example, in the case of a tube, the tube may comprise one or more openings for electrical connection to the heating element.
[0022] Each component may include flanges, wherein the bonding element is configured to be positioned between the flanges when bonding. For example, the sealing structure may form a ring. The sealing structure may be substantially circular. For example, the sealing structure may include a circular aluminum tube.
[0023] The bonding element may be configured to provide a permanent hermetic seal between the two components for use in ultra-high vacuum (UHV) environments. For example, a bonding element configured to provide an interlayer aluminum diffusion bond between two components may provide a permanent hermetic seal for use in UHV.
[0024] Embodiments described herein also provide a method for bonding two components. The method includes: providing a bonding element including a sealing structure and a heating element, wherein the heating element is connected to the sealing structure; positioning the bonding element between the two components; applying pressure to the bonding element via the two components; and heating the sealing structure using the heating element so that the sealing structure is bonded to each of the two components and provides a seal between them. The bonding element can be a bonding element as described above. Typically, the method includes aluminum interlayer diffusion bonding. For example, the sealing structure can include aluminum, and heating the sealing structure under pressure causes aluminum diffusion bonding between the sealing structure and each of the two components.
[0025] The two components may comprise a flange. The heating step may comprise applying a voltage across a heating element. Typically, the heating element is a resistive heating element.
[0026] The sealing structure may be heated to a temperature in the range of 400°C to 600°C for a time in the range of 0.5h to 12h and with a linear load (pressure) in the range of 80 N / mm to 120 N / mm. For example, the sealing structure may be heated to a temperature of 500°C with a heating element for a time in the range of 0.5h to 1h while applying a linear load of 100 N / mm. In other embodiments, lower pressures (<100 N / mm) may be used for longer times (>1h) to form an adequate seal.
[0027] Diffusion bonding, especially with aluminum, typically requires a furnace enclosure that is ideally evacuated to less than 1x10 -4 The invention relates to a furnace which is used for bonding elements having a development length of up to about 600 mm. The furnace can have a pressure of 1000 mbar and can exert an axial force on the items being bonded, typically in the order of 60 kN, for bonding elements having a development length of up to about 600 mm. Such furnaces can be expensive and consume a lot of energy. In addition, there are severe restrictions on the size of the workpieces that can be accommodated in such a facility.
[0028] Embodiments of the present invention may at least partially overcome these problems by directly heating the material forming the bond. By providing localized heating, less energy may be consumed and the same size constraints may not apply. Thus, the bonding elements and methods may be suitable for sealing between parts of fusion reactors or other large structures where seal integrity is important in potentially harsh environments.
[0029] Figure 2is a schematic diagram of an embodiment of a bonding element 6 including a sealing structure and a heating element, the sealing structure being an aluminum tube 7 formed into a circular shape, but a closed ring of any shape may also be used as the sealing structure, the heating element being a resistive heating element 8 that can be connected to a power source via an output terminal 9. The heating element is enclosed by the sealing structure. The resistive heating element 8 includes an insulator 10 for electrically insulating the heating element from the sealing structure. The heating element may be a mineral insulated (MI) heating element, and the insulator 10 may include a magnesium oxide (MgO) coating. In use, the bonding element is disposed between two parts to be bonded and heated under pressure to cause diffusion bonding between the aluminum tube 7 and the parts. These parts may include, for example, metal, ceramic or glass.
[0030] The resistance heating element 8 may include one or more of nickel, chromium, iron, and aluminum. For example, the resistance heating element 8 may include nickel-chromium alloy (Nichrome) or Kanthal RTM Nichrome is a family of alloys containing nickel and chromium that can be used as resistance wire in heating elements. Kanthal RTM Kanthal is a trademark for a family of iron-chromium-aluminium (FeCrAl) alloys used in a range of electrical resistance and high temperature applications. Kanthal FeCrAl alloys consist primarily of iron, chromium (20% to 30%) and aluminium (4% to 7.5%). These materials may be particularly suitable for providing sufficient power density for the required heating. The heating element may be formed as a spring with interruptions so that a voltage is applied across the spring to cause heating.
[0031] In other embodiments, the sealing structure includes an aluminum coating on another material (e.g., a metal alloy). For example, the sealing structure may include Inconel with an aluminum coating for diffusion bonding. RTM or steel (e.g., stainless steel, austenitic stainless steel, iron alloyed with chromium and nickel). Inconel RTM Inconel is a trademark for a family of austenitic nickel-chromium-based alloys. Inconel alloys are resistant to oxidation and corrosion and are suitable for service in extreme environments subject to high pressure and heat.
[0032] In one embodiment, a mineral insulated (MI) heating element (i.e., a resistance wire coated with MgO) is surrounded by an aluminum tube, which may have been welded in the form of a closed ring. In this embodiment, the aluminum tube may be cut on the outer equatorial region so that in cross section the tube has the form of a C. The heating element may then be introduced radially to be located inside the aluminum tube, with the cold end and the terminal end protruding from the cutout. Alternatively, if a single-ended terminal MI heater is used, the tube may have a single tangential bore / hole through which the closed end of the element passes, enabling the heated section to have a closed path around the inside of the aluminum tubular ring.
[0033] Figure 3 1 is a schematic cross-section of two metal parts including flanges 11, 12 in the process of being bonded by bonding element 6. Bonding element 6 includes an outer metal shell 13 (e.g., comprising aluminum), which is a tube with an opening (i.e., a split tube with a C-shaped cross-section) that partially encloses heating element 14. Heating element 14 can be a resistive heating element. The opening in metal shell 13 allows external connection to heating element 14. Flanges 11, 12 are joined by bolts 15, which apply pressure to bonding element 6 between flanges 11, 12. Other devices such as hydraulic presses can be used to squeeze metal parts together during bonding. The bonding process may require several hours for forming a sufficiently strong seal, and the time required may depend on the amount of heat and pressure applied and the specific metal used for bonding.
[0034] Figure 4 1 shows a schematic cross-section of a portion of a bonding element according to an embodiment. The bonding element includes an inner heating element 16, a sheath or tube 17 at least partially encapsulating the heating element 16, and an outer bonding layer 18 on the sheath 17. The heating element 16 may include a metal coil or spring with an outer electrical insulation layer. The sheath 17 may be made of, for example, Inconel RTM The outer layer 18 is formed of a metal such as stainless steel or another suitable thermally conductive material, which can provide structural stability and a desired shape for the bonding element. The outer layer 18 provides suitable bonding properties for forming a diffusion bond and can include a metal such as aluminum. In use, heat is transferred from the heating element 16 to the outer layer 18 via the metal sheath 17 to promote diffusion bonding of the outer layer 18 to the adjacent components under compressive pressure and other suitable environmental conditions (such as vacuum or inert gas environment).
[0035] For some applications, forming a seal between metal parts requires operating in an ultra-high vacuum (UHV) environment. UHV is a vacuum of less than about 100 nanometers (7.5×10-10 A vacuum state characterized by a pressure of 1000 psi (2000 psi) torr. UHV conditions are created by pumping gas out of the UHV chamber. Embodiments of the bonding element disclosed herein may be suitable for sealing a UHV chamber.
[0036] Figure 5 is a flow chart showing the steps of a method for bonding two components. The method comprises: S1, providing a bonding element comprising a sealing structure and a heating element; and S2, positioning the bonding element between the components. The bonding element can be a bonding element as described herein, for example comprising an aluminum tube or sheath and a resistive heating element such as an insulated coil. The method also comprises: S3, applying pressure to the bonding element via the two components; and S4, heating the sealing structure to bond to each of the two components. For example, the extrusion components can be separated so that a linear load of about 100 N / mm is applied to the bonding element, while the heating element heats the sealing structure to a temperature of about 500°C. At this temperature and pressure, a sufficient seal can be formed within about 0.5h to 1h.
[0037] Although specific embodiments have been described, it should be appreciated that those skilled in the art may implement other embodiments that fall within the scope of the claims.Any feature of one embodiment may be appropriately combined with features of other embodiments.
Claims
1. A method for bonding two parts, the method comprising: positioning a bonding element including a bonding structure and a heating element between the two components; compressing the bonding element between the two components; as well as The bonding structure is heated using the heating element to diffusion bond the bonding structure to each of the two components, thereby bonding the two components together.
2. The method according to claim 1, wherein: The bonding structure includes a sealing structure that forms a seal between the two components.
3. The method according to claim 2, wherein: The two components comprise a flange of the vacuum chamber.
4. A method according to any one of the preceding claims, wherein: The heating element is positioned within the bonding structure.
5. A method according to any one of the preceding claims, wherein: The step of heating includes passing an electric current through the heating element.
6. A method according to any one of the preceding claims, wherein: An exterior surface of the bond structure comprises a material suitable for diffusion bonding to each of the two components.
7. The method according to claim 6, wherein: The material includes metal.
8. The method according to claim 6 or 7, wherein: The material includes aluminum.
9. A method according to any one of the preceding claims, wherein: The bonded structure is heated to a temperature of 500° C. for a time in the range of 0.5 hours to 1 hour using the heating element, and wherein the step of compressing comprises applying a linear load of approximately 100 N / mm.
10. A bonding element for bonding two components, the bonding element comprising: Bonded structures with external metal surfaces; as well as a heating element adjacent to the bonding structure; Wherein the bonding element is configured for positioning between the two components and the heating element is configured to heat the bonding structure in use to cause the outer metal surface of the bonding structure to bond to each of the two components.
11. The bonding element according to claim 10, wherein The heating element is located within the bonding structure.
12. The bonding element according to claim 10 or 11, wherein: The bonding structure includes a sheath at least partially surrounding the heating element.
13. The bonding element according to claim 12, wherein: The outer metal surface of the bonding structure includes a metal coating on the jacket.
14. The bonding element according to any one of claims 10 to 13, wherein The exterior metal surface comprises aluminum.
15. The bonding element according to any one of claims 10 to 14, wherein The heating element comprises a mineral insulated heating element.
16. The bonding element according to any one of claims 10 to 15, wherein The bonding structure includes a closed loop.
17. The bonding element according to claim 16, wherein The bonding structure includes a metal tube.
18. The bonding element according to claim 16, wherein The bonding structure has a C-shaped cross-section.
19. The bonding element according to any one of claims 10 to 18, wherein The bonding element includes a spring-loaded metal seal, the heating element includes a coil spring of the spring-loaded metal seal, and the bonding element includes a sheath at least partially surrounding the coil spring.
20. A bonding element for bonding two parts, the bonding element comprising: a bonding structure for positioning between the two components; as well as a heating element connected to the bonding structure and configured to heat the bonding structure sufficiently to cause the bonding structure to bond to each of the two components; Wherein, the bonding structure comprises a metal surface at least partially encapsulating the heating element, and the bonding structure is configured for diffusion bonding to the two components.
21. The bonding element according to claim 20, wherein The metal surface comprises a shell or a foil.
22. The bonding element according to claim 20 or 21, wherein: The bonding structure includes a sealing structure that provides a seal between the two components when used for bonding.
23. A bonding element according to any one of claims 20 to 22, wherein The metal includes aluminum, and the bonding structure is configured for diffusion bonding of the aluminum to the two components.