A method and apparatus for fabricating complex hollow structures using pulsed DC and induced eddy current cyclic loading assisted diffusion bonding.

Abstract

This invention discloses a method and apparatus for fabricating complex hollow structures using pulsed DC and induction eddy current cyclic loading assisted diffusion bonding, relating to a method for assisted heating diffusion bonding. It achieves efficient and uniform heating of metallic materials. Step 1: Prepare a predetermined complex hollow metal structure to be diffuse bonded, polish and clean the surface of the complex hollow metal structure; Step 2: Place the complex hollow metal structure in a tooling mold for molding, and place the mold into a vacuum furnace; Step 3: Set up a dual-source control system; Step 4: Perform diffusion bonding under specified parameters, depressurize after the diffusion time is completed, and cool in the furnace until it reaches room temperature before removing the part. This invention combines pulsed DC heating and induction eddy current heating for diffusion bonding, improving diffusion efficiency while ensuring temperature uniformity, increasing the welding rate, and improving the quality of the diffusion joint.

Description

Technical Field

[0001] This invention relates to a method for assisted heating diffusion bonding. Specifically, this invention relates to a method and apparatus for fabricating complex hollow structures using pulsed DC and induced eddy current cyclic loading assisted diffusion bonding, for controlling and optimizing the diffusion bonding process between metals. Background Technology

[0002] In modern industrial manufacturing, especially in aerospace and high-end machinery manufacturing, diffusion bonding technology is a key material joining technology that achieves permanent bonding between metallic materials through interatomic diffusion. This technology is particularly suitable for applications with extremely high requirements for joint integrity, high temperature resistance, and mechanical properties, such as aircraft panel structural components and microchannel structural components for electronic components.

[0003] However, common diffusion bonding processes rely heavily on continuous furnace heating, which has several limitations and shortcomings. First, furnace heating typically requires prolonged heating and holding times, resulting in high energy consumption and low efficiency. Second, global heating struggles to achieve precise temperature control and localized heating, easily introducing uneven thermal stress during processing. This can lead to material deformation or even damage, affecting the quality and performance of the final product. Furthermore, while single-pulse electric heating can provide rapid localized heating, it also has significant limitations. Primarily, because pulse heating is usually intermittent, it can cause uneven heating, especially on large-area or complex-shaped workpieces, making it difficult to maintain temperature consistency. The high-intensity localized heating of pulsed electric heating can also cause rapid oxidation or other thermal damage to the material surface, further limiting its application in precision manufacturing.

[0004] Other auxiliary heating methods exist in the prior art. For example, Chinese invention patent application CN116689929A ​​discloses a method for electric field-assisted rapid bonding of alumina ceramics and titanium alloys. The alumina ceramics and titanium alloys to be welded are mechanically ground and polished, and an Nb layer is deposited on the alumina ceramic surface using magnetron sputtering. After assembly into the furnace, the temperature is raised to 700-900°C at a rate of 5-15°C / min, held for 1-2 hours, and then an electric field is applied, cooling to 400°C at a rate of 5-10°C / min. Finally, the alumina ceramics and titanium alloys are cooled in the furnace to complete the diffusion bonding. The advantage of this method is that it significantly reduces the bonding temperature and time required for welding, improves diffusion bonding efficiency, and reduces production costs. However, single electric auxiliary heating can lead to some areas of the material heating too quickly while others are underheated. In diffusion bonding, this uneven heating can result in inconsistent quality of the bonding interface, affecting the performance and reliability of the final product.

[0005] Therefore, how to ensure the continuity and uniformity of heating during diffusion bonding, and further guarantee the welding rate and diffusion bonding efficiency, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the above problems, this invention proposes a method and apparatus for preparing complex hollow structures using pulsed DC and induction eddy current cyclic loading assisted diffusion connection. By combining induction eddy current heating and electric pulse cyclic heating, and utilizing the uniformity and deep heating capability of induction eddy current heating, as well as the rapid response and high energy efficiency of electric pulse heating, efficient and uniform heating of metallic materials is achieved.

[0007] The technical solution of the present invention includes the following steps:

[0008] Step 1: Prepare the predetermined complex hollow metal structure to be diffused and bonded, and polish and clean the surface of the complex hollow metal structure.

[0009] Step 2: Place the complex hollow metal structure into tooling mold 3 for molding, and then place tooling mold 3 into a vacuum furnace;

[0010] Step 3: Build a dual-source control system;

[0011] Pressure heads for diffusion connection are arranged on the upper and lower sides of the tooling mold 3, and electrodes 1 are arranged on the pressure heads and clamped on the pressure heads. The electrodes 1 and the pulse power supply are connected through the pressure head protection circuit. Induction coils 2 are arranged around the tooling mold 3, and induction coils 2 and induced eddy current power supply are connected through the coil protection circuit.

[0012] Set the pulse frequency of the pulse power supply and the modulation frequency of the induced eddy current power supply to be the same, so that when the pulse power supply and the induced eddy current power supply are turned on, the induced eddy current power supply provides heat during the duty cycle of the pulse power supply.

[0013] Step 4: Set the diffusion connection process parameters, pulsed DC electrode power supply parameters, and induced eddy current parameters. The vacuum furnace applies pressure to the mold through the pressure head and performs diffusion connection under the specified parameters. After the diffusion time is over, the pressure is released and the part is cooled in the furnace. After cooling to room temperature, the part is removed.

[0014] The pretreatment of complex hollow metal structural components in step 1 specifically includes:

[0015] Apply a layer of boron nitride spray as a solder stop agent to the non-diffusion connection area of ​​the complex hollow metal structure. Dry with cold air, then progressively polish the diffusion connection area using 120#, 400#, 800#, and 1500# sandpaper. Next, polish the metal surface with mirror polishing compound and a soft cloth or polishing wheel, gradually increasing the polish until a mirror finish is achieved. Then, immerse the part in different cleaning solutions depending on the metal material to remove surface grease and residual polishing compound. Finally, ultrasonically clean in alcohol, dry with cold air, and seal the cleaned part for safekeeping.

[0016] In step 3, the pulse power supply parameters are set as follows: pulse frequency 5~100Hz; duty cycle 20%~80%; current density 0.1~100A / mm². 2 ;

[0017] The parameters of the induced eddy current power supply are set as follows: oscillation frequency of 1~500kHz; modulation frequency of 5~100Hz; induced current of 0~150A.

[0018] In step 4, before the diffusion connection heating and pressurization begins, a vacuum is evacuated using a vacuum valve to achieve a vacuum level of 10. - 3 Pa and below, then start increasing temperature and pressure;

[0019] For magnesium alloys, after vacuuming, 15 kPa argon gas needs to be introduced into the furnace through a gas cylinder and a gas pipe.

[0020] The combined heating rate of pulsed DC current heating and induction eddy current heating is 100°C / min~200°C / min, and heating is stopped after the temperature is raised to the specified temperature for diffusion connection.

[0021] For steel, the specified temperature range for diffusion bonding is 900°C to 1200°C;

[0022] For aluminum alloys, the specified temperature range for diffusion bonding is 400°C to 600°C.

[0023] For titanium alloys, the specified temperature range for diffusion bonding is 750°C to 1000°C;

[0024] For magnesium alloys, the specified temperature range for diffusion bonding is 400°C to 600°C.

[0025] After the temperature rises to the specified temperature for diffusion connection, the control electrode (1) applies pressure to the tooling mold (3), and stops the pressure rise after 1 minute when the pressure reaches 1~10MPa.

[0026] After reaching the required temperature and pressure, stabilize the dual-source control parameters and maintain the temperature for 1-4 hours. After the temperature and pressure maintenance is completed, allow the furnace to cool to room temperature before opening the furnace and removing the parts to obtain the finished product.

[0027] This invention combines pulsed DC heating and induction eddy current heating for diffusion joint heating, which improves diffusion efficiency while ensuring temperature uniformity, increases the welding rate, and enhances the quality of diffusion joints, thus providing the following beneficial effects:

[0028] I. This invention provides a method for assisted diffusion bonding combining pulsed DC heating and induction eddy current cyclic loading. The pulsed DC heating provides localized, high-energy heat input, which helps to rapidly raise the temperature of a specific region. High temperatures can increase the atomic movement rate in the material, promoting interatomic diffusion. In this way, pulsed DC heating can accelerate the redistribution and recrystallization of atoms in the material surrounding pores, thereby filling the pores and achieving a bonding rate of over 95% after pore removal.

[0029] II. This invention provides a method for assisted diffusion connection of pulsed DC and induction eddy current cyclic loading, wherein the effect of induction eddy current heating mainly affects the surface layer of the workpiece, especially the edge region of the material. During the heating process, the heat generated in the edge region propagates to the center region through thermal conduction, which helps to reduce the temperature difference between the center and the edge, further improving the temperature uniformity, and ensuring that the temperature difference between the lowest and highest temperatures of the entire complex hollow metal structure is less than 5°C.

[0030] Third, this invention effectively combines the two methods. Dual-source linkage can fill the duty cycle of single-pulse DC heating, significantly improving heating efficiency. Pulse DC heating can rapidly apply high energy to the material, causing rapid temperature rise. Induction eddy current heating generates eddy currents within the material through the generated electromagnetic field; these eddy currents rapidly generate heat through resistance. The combination of these two heating methods enables a very rapid temperature rise rate, thereby shortening the time the material needs to remain at high temperatures. Reducing residence time effectively reduces excessive grain growth, improving both diffusion bonding efficiency and diffusion bonding joint quality. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the diffusion connection method using pulsed DC and induced eddy current cyclic assistance in this invention;

[0032] Figure 2 This is a schematic diagram of a thin-walled hollow structure for a rare-earth magnesium alloy slotted waveguide antenna, fabricated using the pulsed DC and induced eddy current cyclic assisted diffusion connection method described in this invention.

[0033] Figure 3A schematic diagram of the cross-section of a thin-walled hollow structure of a rare-earth magnesium alloy slotted waveguide antenna; a combined support block for the diffusion connection region and auxiliary diffusion connection.

[0034] Figure 4 Schematic diagram of a stainless steel multilayer microchannel hollow structure;

[0035] Figure 5 The waveform is a composite loading waveform of pulsed DC and induced eddy current.

[0036] The reference numerals in the attached figures represent the following: 1. Indenter / electrode; 2. Induction coil; 3. Tooling mold; 4. Magnesium alloy slotted waveguide antenna thin-walled hollow structure; 5. Stainless steel multilayer microchannel hollow structure cover plate; 6. Stainless steel multilayer microchannel hollow structure substrate. Detailed Implementation

[0037] To clearly illustrate the technical features of this patent, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings. Example

[0038] This invention proposes an innovative solution where induction eddy current heating provides a stable and broad thermal field, suitable for large-area heating, while electric pulse heating can rapidly increase the temperature when needed, solving the problem that single heating technologies struggle to balance speed and uniformity. Through this combined technology, this invention not only significantly improves the heating efficiency of diffusion bonding but also enhances the heat treatment quality of the joint, reduces energy consumption, and optimizes the production process. The implementation of this heating method provides a more reliable, economical, and environmentally friendly auxiliary heating technology for diffusion bonding of high-performance metallic materials.

[0039] Specific embodiments of the present invention are as follows:

[0040] like Figures 2-3 As shown, in this example, the diffusion connection material is rare-earth magnesium alloy, and the processing target is a thin-walled hollow structure of a slotted waveguide antenna. The provided method for manufacturing a thin-walled hollow structure of a rare-earth magnesium alloy slotted waveguide antenna using pulsed DC and induced eddy current cyclic assisted diffusion connection includes the following steps:

[0041] Step 1: Fabricate the predetermined thin-walled hollow structure 4 of the magnesium alloy slotted waveguide antenna to be diffused and connected, and polish and clean the surface of the structure.

[0042] Apply a layer of boron nitride spray as a solder stop agent to the non-diffusion connection area of ​​the complex hollow metal structure. Dry with cold air, then progressively polish the diffusion connection area using 120#, 400#, 800#, and 1500# sandpaper. Next, polish the metal surface with mirror polishing compound and a soft cloth or polishing wheel, gradually increasing the polish until a mirror finish is achieved. Immerse in a phosphoric acid solution to remove surface grease and residual polishing compound. Finally, ultrasonically clean in alcohol, dry with cold air, and seal for storage.

[0043] Step 2: Place the thin-walled hollow structure 4 of the magnesium alloy slotted waveguide antenna into the tooling mold 3 for molding. Place a combined support block in the hollow part of this structure to prevent the structure from collapsing and failing due to diffusion connection pressure. Place the tooling mold 3 into the vacuum furnace.

[0044] Step 3: Build a dual-source control system;

[0045] Pressure heads for diffusion connection are arranged on the upper and lower sides of the tooling mold 3, and electrodes 1 are arranged on the pressure heads and clamped on the pressure heads. The electrodes 1 and the pulse power supply are connected through the pressure head protection circuit. Induction coils 2 are arranged around the tooling mold 3, and induction coils 2 and induced eddy current power supply are connected through the coil protection circuit.

[0046] like Figure 5 As shown, the pulse frequency of the pulse power supply and the modulation frequency of the induced eddy current power supply are set to be the same, so that when the pulse power supply and the induced eddy current power supply are turned on, the induced eddy current power supply provides heat during the duty cycle of the pulse power supply.

[0047] Set the pulse power supply parameters as follows:

[0048] The pulse frequency is 5~100Hz;

[0049] Duty cycle is 20%~80%;

[0050] Current density is 0.1~100A / mm 2 .

[0051] Set the parameters of the induced eddy current power supply as follows:

[0052] The oscillation frequency is 1~500kHz;

[0053] The modulation frequency is 5~100Hz;

[0054] Induced current 0~150A.

[0055] Step 4: Set the diffusion connection process parameters, pulsed DC electrode power supply parameters, and induced eddy current parameters. The vacuum furnace applies pressure to the mold through the pressure head and performs diffusion connection under the specified parameters. After the diffusion time is over, the pressure is released and the part is cooled in the furnace. After cooling to room temperature, the part is removed.

[0056] Before the diffusion connection temperature and pressure increase begins, a vacuum is evacuated using a vacuum valve to achieve a vacuum level of 10. -3 At Pa and below, 15 kPa argon gas is introduced into the furnace through a gas cylinder and a gas pipe, and then the temperature and pressure are increased.

[0057] The combined heating rate of pulsed DC current heating and induction eddy current heating is 100°C / min~200°C / min, and heating is stopped after reaching 400°C~600°C. After the temperature reaches the diffusion temperature, the pressure head electrode is controlled by the control console to increase the pressure to 1~10MPa over 1 minute and then stop. After reaching the desired temperature and pressure, the dual-source control parameters are stabilized, and the temperature is held for 1~4 hours. After the holding and pressure holding are completed, the furnace is cooled to room temperature before the parts are removed. Example

[0058] like Figure 4 As shown, in this example, the diffusion bonding material is stainless steel, and the processing target is a multi-layer microchannel hollow structure. The provided method for manufacturing a stainless steel multi-layer microchannel hollow structure using pulsed DC and induction eddy current cyclic assisted diffusion bonding includes the following steps:

[0059] Step 1: Prepare the predetermined stainless steel single-layer microchannel hollow structure 5 to be diffused and connected, and polish and clean the surface of the structure.

[0060] Apply a layer of boron nitride spray as a solder stop agent to the non-diffusion connection area of ​​the complex hollow metal structure. Dry with cold air, then progressively polish the diffusion connection area using 120#, 400#, 800#, and 1500# sandpaper. Next, polish the metal surface with mirror polishing compound and a soft cloth or polishing wheel, gradually increasing the polish until a mirror finish is achieved. Immerse in stainless steel pickling solution to remove surface grease and residual polishing compound. Finally, ultrasonically clean in alcohol, dry with cold air, and seal for storage.

[0061] Step 2: Stack the stainless steel microchannel hollow structure substrate 6 in the mold, place the stainless steel microchannel hollow structure substrate 5 on the top layer of the structure, and put the mold into the vacuum furnace.

[0062] Step 3: Build a dual-source control system;

[0063] Pressure heads for diffusion connection are arranged on the upper and lower sides of the tooling mold 3, and electrodes 1 are arranged on the pressure heads and clamped on the pressure heads. The electrodes 1 and the pulse power supply are connected through the pressure head protection circuit. Induction coils 2 are arranged around the tooling mold 3, and induction coils 2 and induced eddy current power supply are connected through the coil protection circuit.

[0064] like Figure 5 As shown, the pulse frequency of the pulse power supply and the modulation frequency of the induced eddy current power supply are set to be the same, so that when the pulse power supply and the induced eddy current power supply are turned on, the induced eddy current power supply provides heat during the duty cycle of the pulse power supply.

[0065] Set the pulse power supply parameters as follows:

[0066] The power-on frequency is 5~100Hz;

[0067] Duty cycle is 20%~80%;

[0068] Current density is 0.1~100A / mm 2 .

[0069] Set the parameters of the induced eddy current power supply as follows:

[0070] The oscillation frequency is 1~500kHz;

[0071] The modulation frequency is 5~100Hz;

[0072] The induced current is 0~150A.

[0073] Step 4: Set the diffusion connection process parameters, pulsed DC electrode power supply parameters, and induced eddy current parameters. The vacuum furnace applies pressure to the mold through the pressure head and performs diffusion connection under the specified parameters. After the diffusion time is over, the pressure is released and the part is cooled in the furnace. After cooling to room temperature, the part is removed.

[0074] Before the diffusion connection temperature and pressure increase begins, a vacuum is evacuated using a vacuum valve to achieve a vacuum level of 10. -3 Pa and below, then start increasing temperature and pressure.

[0075] The combined heating rate of pulsed DC current heating and induction eddy current heating is 100°C / min~200°C / min, and heating is stopped after reaching 900°C~1200°C. After the temperature reaches the diffusion temperature, the pressure head electrode is controlled by the control console to increase the pressure to 1~10MPa over 1 minute and then stop. After reaching the desired temperature and pressure, the dual-source control parameters are stabilized, and the temperature is held for 1~4 hours. After the holding and pressure holding are completed, the furnace is cooled to room temperature before the parts are removed.

[0076] There are many specific ways to implement this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for fabricating complex hollow structures using pulsed DC and induced eddy current cyclic loading assisted diffusion bonding, characterized in that, Includes the following steps: Step 1: Prepare the predetermined complex hollow metal structure to be diffused and bonded, and polish and clean the surface of the complex hollow metal structure. Step 2: Place the complex hollow metal structure into the tooling mold (3) for molding, and put the tooling mold (3) into the vacuum furnace; Step 3: Build a dual-source control system; A pressure head for diffusion connection is arranged on the upper and lower sides of the tooling mold (3), and an electrode (1) clamped on the pressure head is arranged on the pressure head. The electrode (1) and the pulse power supply are connected through the pressure head protection circuit. An induction coil (2) is arranged around the tooling mold (3), and the induction coil (2) and the eddy current power supply are connected through the coil protection circuit. Set the energizing frequencies of the pulse power supply and the induced eddy current power supply to be the same, so that when the pulse power supply and the induced eddy current power supply are turned on, the induced eddy current power supply powers and supplies heat during the duty cycle of the pulse power supply. Step 4: Set the diffusion connection process parameters, pulsed DC electrode power supply parameters, and induced eddy current parameters. The vacuum furnace applies pressure to the mold through the pressure head and performs diffusion connection under the specified parameters. After the diffusion time is over, the pressure is released and the part is cooled in the furnace. After cooling to room temperature, the part is removed.

2. The method for preparing complex hollow structures using pulsed DC and induced eddy current cyclic loading assisted diffusion connection according to claim 1, characterized in that, The pretreatment of complex hollow metal structural components in step 1 specifically includes: Apply a layer of boron nitride spray to the non-diffusion connection area of ​​the complex hollow metal structure as a solder stop agent, then dry it with cold air. Next, use 120#, 400#, 800#, and 1500# sandpaper to grind the diffusion connection area of ​​the complex hollow metal structure step by step. Then, use mirror polishing paste and a soft cloth or polishing wheel to polish the metal surface, gradually increasing the polishing degree until the surface achieves a mirror effect. Then, use different immersion solutions for different metal materials to wash away surface grease and residual polishing paste. Finally, ultrasonically clean it in alcohol, dry it with cold air, and seal and store the cleaned parts.

3. The method for preparing complex hollow structures using pulsed DC and induced eddy current cyclic loading assisted diffusion connection according to claim 1, characterized in that, In step 3, the pulse power supply parameters are set as follows: pulse frequency 5~100Hz; duty cycle 20%~80%; current density 0.1~100A / mm². 2 ; The parameters of the induced eddy current power supply are set as follows: oscillation frequency of 1~500kHz; modulation frequency of 5~100Hz; induced current of 0~150A.

4. The method for preparing complex hollow structures using pulsed DC and induced eddy current cyclic loading assisted diffusion connection according to claim 1, characterized in that, In step 4, before the diffusion connection heating and pressurization begins, a vacuum is evacuated using a vacuum valve to achieve a vacuum level of 10. -3 Pa and below, then start increasing temperature and pressure; For magnesium alloys, after vacuuming, 15 kPa argon gas is introduced into the furnace through a gas cylinder and a gas pipe. The combined heating rate of pulsed DC current heating and induction eddy current heating is 100°C / min~200°C / min, and heating is stopped after the temperature is raised to the specified temperature for diffusion connection. For steel, the specified temperature range for diffusion bonding is 900°C to 1200°C; For aluminum alloys, the specified temperature range for diffusion bonding is 400°C to 600°C. For titanium alloys, the specified temperature range for diffusion bonding is 750°C to 1000°C; For rare earth magnesium alloys, the specified temperature range for diffusion bonding is 400°C to 600°C. After the temperature rises to the specified temperature for diffusion connection, the control electrode (1) applies pressure to the tooling mold (3), and stops the pressure rise after 1 minute when the pressure reaches 1~10MPa. After reaching the required temperature and pressure, stabilize the dual-source control parameters and maintain the temperature for 1-4 hours. After the temperature and pressure maintenance is completed, allow the furnace to cool to room temperature before opening the furnace and removing the parts to obtain the finished product.

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