A diffusion bonding apparatus and method for synchronously coupling pulsed current with oscillating pressure

Abstract

This invention relates to the technical field of diffusion welding, specifically to a diffusion bonding device and method that synchronously couples pulsed current and oscillating pressure. It includes a furnace chamber, a pressure head assembly, a pulsed current system, a servo hydraulic system, an ultrasonic system, a flaw detector, and a controller. The workpiece to be welded is positioned between an upper pressure head and a lower pressure head; the pulsed current system applies pulsed current to the workpiece through the pressure head assembly; the servo hydraulic system applies pulsed welding pressure to the workpiece; the ultrasonic system applies ultrasonic vibration to the workpiece; the flaw detector performs ultrasonic scanning of the weld and generates a detection signal; the controller receives the detection signal generated by the flaw detector and controls the execution of an in-situ secondary welding operation; wherein the pulsed current and the pulsed welding pressure have the same operating frequency and synchronized pulse phase. This invention solves the problems of long welding time and low efficiency in diffusion bonding processes.

Description

Technical Field

[0001] This invention relates to the technical field of diffusion welding, and more specifically, to a diffusion connection device and method that synchronously couples pulsed current and oscillating pressure. Background Technology

[0002] Diffusion welding refers to a method of metallurgical bonding achieved through interfacial atomic diffusion by bringing the surfaces of the workpieces into contact and causing localized plastic deformation under high temperature and pressure. With the increasing demands for precision and performance in aerospace, precision instruments, and other fields, reducing welding temperature, shortening welding time, and controlling welding deformation while ensuring joint quality has become a key direction for the development of diffusion welding technology. Among related technologies, pulsed current-assisted diffusion welding technology has attracted widespread attention due to its advantages such as rapid heating rate and concentrated heat source at the weld interface. The workpieces are heated by pulsed current, and ultrasonic vibration is applied during the welding process to promote atomic diffusion and break down the surface oxide film. Simultaneously, low-frequency pulsed pressure is applied to the workpiece after ultrasonic-assisted welding to further break down intermetallic compounds and refine grains. After welding, the workpiece is cooled in the furnace and removed.

[0003] However, the applied pulse pressure frequency is low, which differs from the high-frequency characteristics of the pulse current by hundreds of times in time scale, making it impossible to form synchronous coupling. As a result, the millisecond-level thermal softening window generated by the pulse current cannot be utilized in time, limiting welding efficiency and energy utilization, and making it difficult to accurately control welding deformation. At the same time, during online inspection after welding, the workpiece needs to be cooled and the furnace opened for sampling for offline inspection. If defects are found and re-welding is required, the sample must be re-loaded, heated, and vacuumed, resulting in a long overall process time and low efficiency. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a diffusion connection device and method that synchronously couples pulse current and oscillating pressure, thereby solving the problems of long welding time and low efficiency in the diffusion connection process.

[0005] This invention provides a diffusion connection device for synchronous coupling of pulse current and oscillating pressure, comprising: The furnace cavity is used to provide a vacuum welding environment; A pressure head assembly is disposed within the furnace cavity, comprising an upper pressure head and a lower pressure head, with the workpiece to be welded disposed between the upper pressure head and the lower pressure head; A pulsed current system is used to apply a pulsed current to the workpiece to be welded through the pressure head assembly to generate Joule heat at the weld seam of the workpiece as a welding heat source. A servo hydraulic system is used to drive a pressure-applying component located outside the pressure head assembly to apply pulsed welding pressure to the workpiece to be welded via the pressure head assembly; An ultrasonic system for applying ultrasonic vibrations to the workpiece to be welded via the pressure head assembly during the welding process; A flaw detector, which is used to perform ultrasonic scanning on the weld and generate a detection signal through the pressure head assembly after welding is completed; The controller is communicatively connected to the pulse current system, the servo hydraulic system, the ultrasonic system, and the flaw detector. The controller is used to: regulate the timing of the pulse current system, the servo hydraulic system, and the ultrasonic system; and receive the detection signal generated by the flaw detector. When it is determined that there is a defect in the weld, the controller controls the pulse current system and the servo hydraulic system to perform an in-situ secondary welding operation while maintaining the vacuum environment of the furnace cavity. The pulsed current and the pulsed welding pressure have the same operating frequency and are synchronized in phase.

[0006] Preferably, both the upper pressure head and the lower pressure head include a connecting plate and a pressure tool head, a vibration tool head, and a detection tool head that are vertically disposed on the side of the connecting plate facing the workpiece to be welded, and the pressure tool head, the vibration tool head, and the detection tool head are all cylindrical and arranged in parallel.

[0007] Preferably, the pressure-applying component includes an upper graphite pressure head and a lower graphite pressure head, wherein the upper graphite pressure head is disposed above the upper pressure head and the lower graphite pressure head is disposed below the lower pressure head; The servo hydraulic system is used to drive the upper graphite head and the lower graphite head to move toward each other, so as to apply the pulsed welding pressure to the workpiece to be welded via the upper and lower heads.

[0008] Preferably, it further includes a positive electrode and a negative electrode, the positive electrode being connected between the upper graphite indenter and the pressure tool head of the upper indenter, and the negative electrode being connected between the lower graphite indenter and the pressure tool head of the lower indenter; The pulsed current system is powered by the positive electrode and the negative electrode, so that the pulsed current forms a current loop through the pressure tool head of the upper pressure head, the weld seam, and the pressure tool head of the lower pressure head.

[0009] Preferably, the ultrasonic system includes an amplitude transformer and an ultrasonic generator; the upper end of the vibrating tool head passes through the connecting plate and is connected to the amplitude transformer, and the ultrasonic generator supplies power to the vibrating tool head through the amplitude transformer. Preferably, a flexible sealing element is provided between the vibrating tool head and the connecting plate to allow the vibrating tool head to be flexibly connected to the connecting plate; the lower end of the vibrating tool head is used to attach to the workpiece to be welded.

[0010] Preferably, the probe head is mounted on the connecting plate via a telescopic mechanism. The telescopic mechanism includes a mounting cavity and a driving element. The mounting cavity is located within the connecting plate, and the driving element is located within the mounting cavity and connected to the probe head. After welding is completed, the driving element drives the probe head to move to be attached to the workpiece to be welded.

[0011] The present invention also includes a diffusion connection method for synchronous coupling and online detection of pulse current and oscillating pressure, using the above-mentioned diffusion connection device, comprising the following steps: The workpiece to be welded is assembled between the pressure head assemblies, the furnace cavity is evacuated and a pre-pressure is applied to the workpiece to be welded; A pulsed current is applied to the workpiece to be welded through a pulsed current system to generate Joule heat at the weld as a welding heat source; at the same time, a pulsed welding pressure is applied to the workpiece to be welded through a servo hydraulic system, and ultrasonic vibration is applied to the workpiece to be welded through an ultrasonic system to perform diffusion welding. The pulsed current and the pulsed welding pressure have the same operating frequency and are synchronized in pulse phase. After welding is completed, the pulsed current and the pulsed welding pressure are turned off, the flaw detector is started, and the weld is ultrasonically scanned while maintaining the vacuum state of the furnace cavity to generate a detection signal; The detection signal is used to determine whether there is a defect in the weld. If a defect is found, an in-situ secondary welding operation is performed.

[0012] Preferably, the frequency of the pulsed current is 20-40kHz, and the duty cycle is 50%-83.33%; the frequency of the pulsed welding pressure is the same as the frequency of the pulsed current, and the duty cycle is the same as the duty cycle of the pulsed current; the frequency of the ultrasonic vibration during the welding process is 20-30kHz, and the amplitude is 1-7μm.

[0013] Preferably, determining whether there is a defect in the weld based on the detection signal includes: calculating the weld bonding rate; when the weld bonding rate is lower than a preset threshold, triggering the in-situ secondary welding operation; the process parameters of the in-situ secondary welding operation are the same as those of the primary welding, or at least one welding parameter is adjusted according to the type and degree of the detected defect.

[0014] The beneficial technical effects of this invention are as follows: This invention discloses a diffusion connection device that synchronously couples pulsed current and oscillating pressure. The pulsed current system, servo hydraulic system, and ultrasonic system are all coordinated by a controller, achieving the synergistic application of thermodynamic and acoustic fields. The pulsed current and pulsed welding pressure have the same operating frequency and are phase-synchronized, ensuring that within each pulse cycle, while the current heats the weld interface to a softened state, the pressure simultaneously applies to the softened interface, achieving precise densification while the weld is still hot. Ultrasonic vibration is continuously applied during the welding process, utilizing cavitation and acoustoplastic effects to break down the interface oxide film and promote atomic diffusion. A flaw detector operates independently after welding, performing online scanning of the weld and generating detection signals. The controller determines the presence of defects based on these signals and, if defects are found, controls each system to perform in-situ secondary welding operations. This closed-loop process allows the entire welding, inspection, and repair welding process to be completed continuously without opening the furnace, effectively solving the problems of long overall process time and low efficiency caused by the separation of welding and inspection processes in the prior art. It achieves the technical effects of reducing welding temperature, shortening welding time, controlling welding deformation, and improving joint quality.

[0015] The diffusion connection method of the present invention, which synchronously couples and detects pulse current and oscillating pressure, has the same beneficial technical effects as the above-mentioned diffusion connection device compared with the prior art, and will not be described again here. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a diffusion connection device for synchronous coupling of pulse current and oscillating pressure in one embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the upper or lower pressure head in one embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the synergistic effect of pulsed current, pulsed pressure, and ultrasonic assistance on the workpiece during the welding process in one embodiment of the present invention. Figure 4 for Figure 3 The waveform diagrams of pulsed current, pulsed welding pressure, and ultrasound are shown.

[0017] Figure 5 This is a scanning electron microscope image of a welded joint obtained by a diffusion connection method for synchronous coupling and online detection of pulse current and oscillating pressure in one embodiment of the present invention. Figure 6 This is a scanning electron microscope image of a welded joint obtained by a hot pressing method in the prior art.

[0018] Explanation of reference numerals in the attached figures: 1-Furnace cavity; 01-Workpiece to be welded; 3-Pulse current system; 4-Servo hydraulic system; 5-Ultrasonic system; 6-Flaw detector; 21-Upper pressure head; 22-Lower pressure head; 201-Pressure tool head; 202-Vibration tool head; 203-Detection tool head; 204-Connecting plate; 301-Positive electrode; 302-Negative electrode; 401-Upper graphite pressure head; 402-Lower graphite pressure head; 51-Amplitude rod; 52-Ultrasonic generator. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0020] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0021] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0022] See Figure 1As shown, a specific embodiment of the present invention provides a diffusion connection device for synchronous coupling of pulsed current and oscillating pressure, including a furnace chamber 1, a pressure head assembly, a pulsed current system 3, a servo hydraulic system 4, an ultrasonic system 5, a flaw detector 6, and a controller. The furnace chamber 1 provides a vacuum welding environment; the pressure head assembly is disposed within the furnace chamber 1, including an upper pressure head 21 and a lower pressure head 22, with the workpiece 01 to be welded positioned between the upper pressure head 21 and the lower pressure head 22; the pulsed current system 3 applies a pulsed current to the workpiece 01 through the pressure head assembly to generate Joule heat at the weld seam of the workpiece 01 as a welding heat source; the servo hydraulic system 4 drives a pressure-applying component located outside the pressure head assembly to apply pulsed welding pressure to the workpiece 01 via the pressure head assembly; the ultrasonic system 5 applies ultrasonic vibration to the workpiece 01 through the pressure head assembly during the welding process; and the flaw detector 6 is used for... After welding, the weld is ultrasonically scanned by the pressure head assembly and a detection signal is generated. The controller is communicatively connected to the pulse current system 3, the servo hydraulic system 4, the ultrasonic system 5, and the flaw detector 6. The controller is used to: regulate the timing of the pulse current system 3, the servo hydraulic system 4, and the ultrasonic system 5; and receive the detection signal generated by the flaw detector 6. When a defect is found in the weld, the controller controls the pulse current system 3 and the servo hydraulic system 4 to perform an in-situ secondary welding operation while maintaining the vacuum environment of the furnace cavity. The pulse current and the pulse welding pressure have the same working frequency and the pulse phase is synchronized.

[0023] Specifically, the pressure head assembly is used to transmit pressure, current, and ultrasonic vibration to the workpiece 01 to be welded. The upper pressure head 21 and lower pressure head 22 are arranged opposite each other, with the workpiece 01 clamped between them. The servo hydraulic system 4 serves as the power source, driving the pressure-applying component located outside the pressure head assembly. The pressure-applying component then transmits the pressure to the upper pressure head 21 and lower pressure head 22, ultimately acting on the workpiece 01. The pulsed current system 3 introduces pulsed current into the pressure head assembly through wires and electrodes. The current flows through the pressure head assembly across the weld interface of the workpiece 01, generating Joule heat using the high contact resistance at the weld interface. The ultrasonic system 5 transmits high-frequency mechanical vibration to the pressure head assembly through a transducer and amplitude transformer, and then from the pressure head assembly to the weld interface. The flaw detector 6 is set independently of the ultrasonic system 5 and is specifically used for post-weld inspection. It is connected to the detection component in the pressure head assembly via a signal cable. The controller, as the control core of the entire device, coordinates the operation of each system according to a preset timing sequence and receives the detection signals from the flaw detector 6 to determine defects and make repair welding decisions. Flaw detector 6 is an ultrasonic flaw detector.

[0024] It should be noted that this embodiment achieves the coordinated application of the thermodynamic and acoustic fields by unifying the timing of the pulsed current system 3, the servo hydraulic system 4, and the ultrasonic system 5 under the coordination of the controller. The pulsed current and the pulsed welding pressure have the same operating frequency and are phase-synchronized, so that in each pulse cycle, while the current heats the weld interface to a softened state, the pressure is applied to the softened interface, achieving precise densification while the weld is still hot. Ultrasonic vibration is continuously applied during the welding process, utilizing cavitation and acoustoplastic effects to break the oxide film at the interface and promote atomic diffusion. The flaw detector 6 works independently after welding, scanning the weld online and generating detection signals. The controller determines whether defects exist based on the detection signals, and if defects are found, controls each system to perform in-situ secondary welding operations. This closed-loop process allows the entire welding, inspection, and repair welding process to be completed continuously without opening the furnace, effectively solving the problem of long overall process time and low efficiency caused by the separation of welding and inspection processes in the background technology, and achieving the technical effects of reducing welding temperature, shortening welding time, controlling welding deformation, and improving joint quality.

[0025] See Figure 2 As shown, in one embodiment of the present invention, both the upper pressure head 21 and the lower pressure head 22 include a connecting plate 204 and a pressure tool head 201, a vibration tool head 202 and a detection tool head 203 vertically disposed on the side of the connecting plate 204 facing the workpiece 01 to be welded. The pressure tool head 201, the vibration tool head 202 and the detection tool head 203 are all cylindrical and arranged in parallel.

[0026] Specifically, the connecting plate 204 is a circular or square metal disc, serving as the mounting base for the three tool heads. The pressure tool head 201, vibration tool head 202, and detection tool head 203 are evenly spaced on the surface of the connecting plate 204, with their axes parallel to each other and perpendicular to the surface of the connecting plate 204. The vibration tool head 202 can be flexibly connected to the connecting plate 204, the detection tool head 203 can be telescopically connected to the connecting plate 204, and multiple pressure tool heads 201 can be provided and fixedly connected to the connecting plate 204.

[0027] Furthermore, the pressure tool head 201 may include two or more, and the vibration tool head 202 may include one or more. The pressure tool head 201 and the vibration tool head 202 are arranged at intervals along the same circumference, and the probe tool head 203 may be located at the center of the connecting plate 204. The pressure tool head 201 is made of an alloy (titanium-zirconium-molybdenum).

[0028] It should be noted that this embodiment achieves functional decoupling by assigning the three functions of pressurization, vibration, and detection to independent tool heads. This ensures that when the pressure head assembly is closed, the pulsed welding pressure applied by the servo hydraulic system 4 is primarily borne by the pressurization tool head 201, while the vibration tool head 202 and detection tool head 203 do not bear the main welding pressure. Simultaneously, the vibration tool head 202 is flexibly connected to the connecting plate 204, ensuring that ultrasonic vibration can be effectively transmitted to the workpiece 01 while preventing vibration energy from being transferred to the connecting plate 204 and interfering with the normal operation of the pressurization tool head 201 and detection tool head 203. The three tool heads are arranged side-by-side in space, functionally independent, and decoupled in terms of force, allowing the three physical processes of vertical pressurization, ultrasonic vibration, and ultrasonic detection to proceed in a coordinated manner without interference. This effectively solves the problem of interference between welding pressure and ultrasonic vibration in traditional diffusion welding devices, providing a structural basis for direct post-weld online inspection at the welding station.

[0029] In one embodiment of the present invention, the pressure-applying component includes an upper graphite pressure head 401 and a lower graphite pressure head 402. The upper graphite pressure head 401 is disposed above the upper pressure head 21, and the lower graphite pressure head 402 is disposed below the lower pressure head 22. The servo hydraulic system 4 is used to drive the upper graphite pressure head 401 and the lower graphite pressure head 402 to move toward each other, so as to apply pulsed welding pressure to the workpiece 01 to be welded via the upper pressure head 21 and the lower pressure head 22.

[0030] Specifically, the upper graphite pressure head 401 is located above the upper pressure head 21, and its lower end face contacts the upper end face of the connecting plate 204 of the upper pressure head 21 or indirectly contacts it through a conductive component. The lower graphite pressure head 402 is located below the lower pressure head 22, and its upper end face contacts the lower end face of the connecting plate 204 of the lower pressure head 22 or indirectly contacts it through a conductive component. The servo hydraulic system 4 includes a servo controller, a servo motor, a hydraulic pump, a high-response servo valve or proportional valve, and a pressure sensor. The pressure sensor is used to detect the actual pressure applied to the workpiece 01 in real time and feed it back to the controller. The controller adjusts the hydraulic oil flow through the high-response servo valve or proportional valve to form a closed-loop control, so that the peak value and phase of the pulse welding pressure can be synchronized with the peak value and phase of the pulse current. The upper graphite pressure head 401 and the lower graphite pressure head 402 are made of high-purity isostatic graphite, which has the characteristics of high temperature resistance, high conductivity, and self-lubrication.

[0031] It should be noted that the use of graphite as the material for the pressure-applying component in this embodiment is a preferred solution after comprehensively considering conductivity, high temperature resistance, and self-lubrication. The servo hydraulic system 4 achieves millisecond-level precise adjustment of the pulsed welding pressure through closed-loop control, enabling the pressure to maintain the same frequency and phase synchronization with the pulsed current. Pressure is applied to the interface at the same instant as the current heats the weld interface to a softened state, achieving the maximum densification effect with minimal pressure. At the same time, pressure is released and stress is relieved during the current cut-off interval, avoiding the accumulation of macroscopic plastic deformation in the base material of the workpiece 01 to be welded. This effectively solves the contradiction between welding pressure and deformation control in traditional diffusion welding.

[0032] In one embodiment of the present invention, a positive electrode 301 and a negative electrode 302 are further included. The positive electrode 301 is connected between the upper graphite pressure head 401 and the pressure tool head 201 of the upper pressure head 21, and the negative electrode 302 is connected between the lower graphite pressure head 402 and the pressure tool head 201 of the lower pressure head 22. The pulse current system 3 is powered by the positive electrode 301 and the negative electrode 302, so that the pulse current forms a current loop through the pressure tool head 201 of the upper pressure head 21, the weld seam, and the pressure tool head 201 of the lower pressure head 22.

[0033] Specifically, the positive electrode 301 is a conductive copper busbar or copper pillar, with its upper end in contact with the lower end face of the upper graphite indenter 401 and its lower end in contact with the upper end of the pressure tool head 201 of the upper indenter 21. Similarly, the negative electrode 302 is a conductive copper busbar or copper pillar, with its upper end in contact with the lower end of the pressure tool head 201 of the lower indenter 22 and its lower end in contact with the upper end face of the lower graphite indenter 402. The pulse current system 3 includes a pulse power supply. The positive output terminal of the pulse power supply is connected to the positive electrode 301 via a wire, and the negative output terminal is connected to the negative electrode 302 via a wire. When the pulse power supply outputs a pulse current, the current flows sequentially through the positive electrode 301, the pressure tool head 201 of the upper indenter 21, the weld interface of the workpiece 01, the pressure tool head 201 of the lower indenter 22, and the negative electrode 302, forming a complete current loop. Due to the microscopic contact resistance at the weld interface, according to Joule's law, the Joule heat generated at this point is much greater than that at other parts of the circuit, making it the main welding heat source.

[0034] It should be noted that in this embodiment, the positive electrode 301 and the negative electrode 302 are respectively disposed between the pressure application component and the pressure tool head 201, so that the current path and the pressure path are highly integrated in space. The pressure tool head 201 not only undertakes the task of transmitting pulsed welding pressure, but also serves as a conductive channel for the pulsed current to flow into the workpiece 01 to be welded. The current is focused on the weld interface to generate Joule heating, realizing differential heating. The weld rapidly heats up to the welding temperature, while the base material only endures a lower temperature. This effectively avoids the grain coarsening and performance deterioration caused by the base material being exposed to high temperatures for a long time in traditional diffusion welding, and solves the problems of high welding temperature and large base material deformation.

[0035] In one embodiment of the present invention, the ultrasonic system 5 includes an amplitude transformer 51 and an ultrasonic generator 52; the upper end of the vibrating tool head 202 passes through the connecting plate 204 and is connected to the amplitude transformer 51, and the ultrasonic generator 52 supplies power to the vibrating tool head 202 through the amplitude transformer 51. A flexible sealing element is provided between the vibrating tool head 202 and the connecting plate 204 to flexibly connect the vibrating tool head 202 and the connecting plate 204; the lower end of the vibrating tool head 202 is used to attach to the workpiece 01 to be welded.

[0036] Specifically, the amplitude transformer 51 is made of titanium alloy and is in the shape of a stepped shaft. A drive rod extends from its lower end, passing through a through hole in the connecting plate 204 and rigidly connected to the upper end of the vibrating tool head 202 via a thread. An annular gap exists between the outer circumferential surface of the drive rod and the inner wall of the through hole. The ultrasonic generator 52 converts the industrial frequency AC power into a high-frequency electrical signal of 20-30kHz. This electrical signal is converted into mechanical vibration by a piezoelectric ceramic transducer and input to the thicker end of the amplitude transformer 51. The amplitude transformer 51 amplifies the amplitude using its variable cross-section characteristics, and the amplified vibration is directly transmitted to the vibrating tool head 202 via the drive rod. A flexible sealing element is disposed between the vibrating tool head 202 and the connecting plate 204. Specifically, it can be a high-temperature resistant fluororubber O-ring or a metal bellows sleeved on the outer circumference of the vibrating tool head 202. The outer edge of the flexible sealing element is sealed to the inner wall of the through hole, and the inner edge is sealed to the outer wall of the vibrating tool head 202.

[0037] It should be noted that in this embodiment, the through-hole connection structure, through which the drive rod passes through the through hole of the connecting plate 204 and is rigidly connected to the vibration tool head 202, allows the ultrasonic vibration amplified by the amplitude transformer 51 to be directly transmitted to the vibration tool head 202 without passing through the connecting plate 204. The annular gap between the outer circumferential surface of the drive rod and the inner wall of the through hole structurally eliminates the possibility of vibration being transmitted through the contact surface to the connecting plate 204. At the same time, the flexible sealing element maintains the vacuum seal of the furnace cavity 1, and due to its low rigidity, it cannot transmit high-frequency vibrations, thus forming a second isolation barrier for vibration. The lower end of the vibration tool head 202 is attached to the surface of the workpiece 01 with a pressure much lower than that of pulse welding, solely to ensure stable acoustic contact and effectively transmit ultrasonic vibrations to the weld interface. This structure achieves a precise transmission path for ultrasonic vibration, namely, the amplitude transformer 51, the drive rod, the vibration tool head 202, and the weld interface. The connecting plate 204 and the pressure tool head 201 and the probe tool head 203 installed on it are not on this vibration transmission chain, thus ensuring that the vibration-assisted welding function does not interfere with other functions.

[0038] In one embodiment of the present invention, the probe tool head 203 is mounted on the connecting plate 204 via a telescopic mechanism. The telescopic mechanism includes a mounting cavity and a driving element. The mounting cavity is opened in the connecting plate 204, and the driving element is located in the mounting cavity and connected to the probe tool head 203. After welding is completed, the driving element drives the probe tool head 203 to move to be attached to the workpiece 01 to be welded.

[0039] Specifically, the mounting cavity is a cylindrical blind hole opened within the connecting plate 204, with its opening facing the side of the workpiece 01 to be welded. The driving element is any one of a miniature cylinder, an electromagnetic push rod, or a piezoelectric actuator, with its fixed end installed at the bottom of the mounting cavity and its movable end connected to the tail end of the probe head 203. During welding, the driving element keeps the probe head 203 in a retracted, hidden position, so that the end face of the probe head 203 is retracted into the mounting cavity and does not contact the workpiece 01 to avoid interference from the high welding temperature and strong pulse current. After the welding heat preservation is completed, the workpiece 01 is cooled to the preset detection temperature with the furnace, and the controller controls the driving element to push the probe head 203 to the contact position, so that its end face is pressed against the surface of the workpiece 01. The flaw detector 6 is electrically connected to the probe head 203 through a signal cable and sends high-frequency electrical pulses to the probe head 203. The piezoelectric crystal inside the probe head 203 converts the electrical signal into ultrasonic waves and emits them to the weld, and converts the ultrasonic waves reflected back from the weld into electrical signals and transmits them back to the flaw detector 6. After the test is completed, the driving element retracts the probe head 203 to a hidden position.

[0040] It should be noted that in this embodiment, the probe head 203 is designed as a retractable, concealed structure, allowing it to completely avoid the high-temperature and high-pulse current environment during welding. It only extends briefly to scan the workpiece 01 during inspection. The retractable design effectively protects the precision piezoelectric elements inside the probe head 203 from prolonged exposure to the high welding temperature, while also avoiding electromagnetic interference to the detection signal caused by the high-pulse current during welding. Post-weld online inspection does not require opening the furnace door or disrupting the vacuum environment of the furnace cavity. The closed-loop process of defect judgment and in-situ secondary welding formed in conjunction with the controller effectively solves the problems of lengthy and inefficient processes caused by offline post-weld inspection in the prior art, reducing the overall process time by at least half.

[0041] See Figure 3 and Figure 4 As shown, the present invention also provides a diffusion connection method for synchronous coupling and online detection of pulse current and oscillating pressure, using the above-mentioned diffusion connection device, comprising the following steps: S1: Assemble the workpiece 01 to be welded between the pressure head assemblies, evacuate the furnace chamber 1 and apply pre-pressure to the workpiece 01 to be welded; S2: A pulsed current is applied to the workpiece 01 to be welded through the pulsed current system 3 to generate Joule heat at the weld as a welding heat source; at the same time, a pulsed welding pressure is applied to the workpiece 01 to be welded through the servo hydraulic system 4, and ultrasonic vibration is applied to the workpiece 01 to be welded through the ultrasonic system 5 to perform diffusion welding. Among them, the pulse current and the pulse welding pressure have the same operating frequency and the pulse phase is synchronized; S3: After welding is completed, turn off the pulse current and pulse welding pressure, start the flaw detector 6, and perform ultrasonic scanning on the weld while maintaining the vacuum state of the furnace chamber 1 to generate a detection signal; determine whether there is a defect in the weld based on the detection signal, and perform in-situ secondary welding operation when a defect is found.

[0042] Specifically, the pre-pressure is applied by the servo hydraulic system 4 before the pulsed welding pressure is applied. This pre-pressure is used to eliminate the assembly gap between the pressure head assembly and the workpiece 01 to be welded, establishing a stable initial physical contact. The pre-pressure value is typically around 2 MPa, much smaller than the peak value of the pulsed welding pressure. The frequency of the pulsed current is 30 kHz with a duty cycle of 60%; the frequency of the pulsed welding pressure is also 30 kHz with a duty cycle of 60%, and the peak pressure is 5 tons; the frequency of the ultrasonic vibration is 25 kHz with an amplitude of 5 μm and a power of 1.5 kW. The controller triggers the pulsed current system and the servo hydraulic system with the same clock signal, ensuring that the pulse outputs of both are strictly synchronized. The welding holding time is typically 1-5 minutes. After welding, the workpiece 01 is cooled with the furnace to approximately 150°C, and the controller activates the flaw detector 6 and scans the weld seam through the detection tool head 203.

[0043] It should be noted that the diffusion bonding method provided in this embodiment achieves precise coupling of the thermal field within a millisecond-level time window by setting the pulsed current and pulsed welding pressure to be of the same frequency and phase. The pressure is simultaneously applied to the weld interface the instant the current heats the interface to a softened state. This synchronous coupling method ensures that the heating and pressurization within each pulse cycle are completely sequential, maximizing energy utilization efficiency and avoiding energy waste and deformation accumulation caused by asynchronous heating and pressurization. Simultaneously, ultrasonic vibration is continuously applied throughout the welding heat preservation process. This utilizes the ultrasonic cavitation effect to break up the interface oxide film, the acoustic plasticity effect to reduce the material's deformation resistance, and the acoustic flow effect to promote interface atomic diffusion. These effects are simultaneously superimposed with the electroplasticity and electrodiffusion effects of the pulsed current, further reducing the welding temperature and required pressure. The continuous online post-weld inspection and in-situ secondary welding create a closed loop for the entire diffusion bonding process without opening the furnace, effectively solving the problem of long overall process time and low efficiency caused by the separation of welding and inspection processes in the prior art. Actual measurements show that, compared to traditional hot-press diffusion welding, this method can reduce the welding temperature by more than 500℃, shorten the welding time from 15-180 minutes to 1-5 minutes, increase the strength of the welded joint by more than 30%, and reduce the overall process time by at least half.

[0044] In one embodiment of the present invention, the frequency of the pulse current is 20-40kHz and the duty cycle is 50%-83.33%; the frequency of the pulse welding pressure is the same as the frequency of the pulse current and the duty cycle is the same as the duty cycle of the pulse current; the frequency of the ultrasonic vibration during the welding process is 20-30kHz and the amplitude is 1-7μm.

[0045] Specifically, the frequency of the pulsed current, the frequency of the pulsed welding pressure, and the frequency of the ultrasonic vibration can be selected according to the type and thickness of the material to be welded. For aluminum alloys with low melting points, a lower pulsed current frequency and duty cycle can be selected to reduce the energy input density; for titanium alloys or high-temperature alloys with high melting points, a higher frequency and duty cycle can be selected. The amplitude of the ultrasonic vibration can be adjusted according to the thickness and toughness of the oxide film on the surface of the workpiece to be welded. When the oxide film is thicker, a larger amplitude is selected to enhance the cavitation film removal effect.

[0046] It should be noted that the parameter range given in this embodiment is an optimized range verified through extensive experiments. Within this parameter range, the pulsed current can generate sufficient Joule heat to rapidly raise the weld interface to the welding temperature. The frequency of the pulsed welding pressure is strictly consistent with and phase-synchronized with the frequency of the pulsed current, ensuring that each thermal softening window can be utilized in a timely manner. The frequency of ultrasonic vibration is on the same order of magnitude as the frequency of the pulsed current. The three energy fields can work synergistically on the same time scale, producing a superposition effect of electroplasticity, acoustic plasticity, and pulsed pressure densification, achieving a low-temperature, rapid, high-quality welding effect that cannot be achieved by a single field.

[0047] In one embodiment of the present invention, determining whether there is a defect in the weld seam based on the detection signal includes: calculating the weld seam fusion rate; when the fusion rate is lower than a preset threshold, triggering an in-situ secondary welding operation; the process parameters of the in-situ secondary welding operation are the same as those of the primary welding operation, or at least one welding parameter is adjusted according to the type and degree of the detected defect.

[0048] Specifically, the weld ratio is calculated by the image processing module built into the controller. The ultrasonic C-scan image generated by the flaw detector 6 is transmitted to the controller. The controller uses image processing algorithms to identify welded and unwelded areas and calculates the weld ratio as the percentage of the welded area to the total weld area. The preset threshold is set according to the workpiece's usage requirements, typically between 95% and 99%. When the weld ratio is lower than the preset threshold, the controller automatically selects a repair welding scheme based on the type (e.g., hole, crack, or lack of weld) and severity (e.g., defect area and distribution density) of the defect. For example, for localized unwelded defects, only that area can be repaired, and the repair welding parameters can be the same as the first weld; for large-area unwelded or severe defects, the welding temperature can be increased, the holding time extended, or the welding pressure increased.

[0049] It should be noted that this embodiment uses the weld bonding rate as a quantitative indicator to objectively evaluate welding quality, ensuring that the need for re-welding is based on accurate data rather than the subjective experience of the operator. Simultaneously, adjusting the re-welding parameters allows the system to adopt differentiated re-welding strategies for different types and degrees of defects, avoiding unnecessary energy waste or the introduction of new welding problems caused by simplistic re-welding. The closed-loop process of detection-judgment-re-welding effectively solves the problems of low efficiency and poor process continuity caused by the separation of welding and detection in traditional diffusion welding, ensuring that the weld quality of the products meets the preset standards.

[0050] In summary, the diffusion connection method for synchronous coupling and online detection of pulse current and oscillating pressure of this invention includes the following steps: S1: Assembly and vacuum preloading of component 01 to be welded S11: After pre-treatment such as grinding and cleaning of the surfaces to be welded of the two parts 01, they are assembled between the upper pressure head 21 and the lower pressure head 22 of the pressure head assembly in a butt or lap joint manner.

[0051] S12: Close the furnace door of furnace chamber 1 and start the vacuum system to evacuate furnace chamber 1 to a vacuum welding environment.

[0052] S13: After reaching the preset vacuum level, the controller instructs the servo hydraulic system 4 to drive the pressure application component to apply a pre-pressure of approximately 2 MPa to the pressure head assembly. This pre-pressure is much lower than the subsequent peak pulse welding pressure, which can reach 5 tons. Its purpose is to eliminate gaps between the contact interfaces and establish stable physical contact.

[0053] During the pre-pressure phase, the pulse current system 3 and the ultrasonic system 5 remain off. The probe head 203 is held in a concealed position by a telescopic mechanism, retracting into the connecting disc 204 above it.

[0054] S2: Multi-field synchronously coupled diffusion welding. See also Figure 3 and Figure 4 As shown.

[0055] The controller uses the same clock signal as a reference to synchronously issue commands: Activate pulsed current: Start the pulsed current system 3, and apply a pulsed current with a frequency of 30kHz and a duty cycle of 60% to the workpiece 01 to be welded through the positive electrode 301, the negative electrode 302, and the pressure tool head 201 of the upper and lower pressure heads. The current generates Joule heat at the weld interface with the highest resistance, which serves as the main welding heat source.

[0056] Activate pulse pressure: Synchronously activate the high-frequency mode of the servo hydraulic system 4, and apply pulsed welding pressure to the workpiece 01 to be welded through the upper graphite pressure head 401, lower graphite pressure head 402, and pressure tool head 201. The pulsed welding pressure has the same frequency (30kHz), duty cycle (60%), and phase synchronization as the pulse current. The peak pressure can reach 5 tons.

[0057] Start ultrasonic vibration: The ultrasonic system 5 is started synchronously. The ultrasonic generator 52 transmits a high-frequency electrical signal to the transducer, which is amplified by the amplitude transformer 51 and directly drives the vibration tool head 202. The vibration tool head 202 is lightly placed on the surface of the workpiece 01 to be welded, and ultrasonic vibration with a frequency of 25kHz, an amplitude of 5μm, and a power of 1.5kW is applied to the weld.

[0058] In the aforementioned synchronous coupling process, it proceeds continuously within a millisecond-level time window: whenever the pulsed current heats the weld interface to a softened state, the synchronous pulsed pressure peak immediately compacts it. At the moment of pressure unloading, the continuously operating ultrasonic vibration plays a major role, driving the interface to generate high-frequency horizontal tangential friction, breaking the oxide film and promoting atomic diffusion.

[0059] The welding process lasts 1-5 minutes.

[0060] S3: Post-weld online inspection and in-situ repair welding S31: After the welding heat preservation time ends, the controller simultaneously shuts off the pulse current and pulse welding pressure, and the ultrasonic system 5 also stops vibrating.

[0061] The workpiece 01 to be welded is cooled in the vacuum furnace chamber 1. When the infrared thermometer detects that the weld temperature has dropped to about 150°C, the inspection procedure is initiated.

[0062] S32: The controller controls the telescopic mechanism to extend the probe head 203 from its concealed position, allowing it to lightly contact the surface of the workpiece 01 to be welded. Then, the flaw detector 6 is activated, and the probe head 203 performs an ultrasonic C-scan on the weld, generating a detection signal.

[0063] S33: The controller's image processing module calculates the weld bonding rate based on the detection signal. If the bonding rate is ≥ 99%, the welding quality is qualified, the vacuum system is shut off, the furnace is opened and the workpiece is removed, and the process ends.

[0064] If the weld success rate is less than 99%, the controller determines that a defect exists and, after automatic or prompting operator confirmation, directly performs a second in-situ welding operation while maintaining a vacuum environment in furnace chamber 1 and ensuring the pressure head assembly still presses the workpiece firmly. The parameters of the repair welding procedure (such as pulse current, pressure, ultrasonic vibration, and holding time) can be the same as the first welding, or adjusted according to the type and extent of the defect (such as hole size and unwelded area).

[0065] S34: After the repair welding is completed, the inspection procedure, i.e., S33, can be executed again until the welding rate meets the requirements, thus forming a closed-loop quality control process of welding, inspection, and repair welding.

[0066] See Figure 5 As shown, in the diffusion bonding method of the present invention, the workpiece 01 to be welded is made of aluminum alloy. The welded joint obtained under the welding parameters of 460 degrees Celsius, 120 min, and 5 MPa has a strength greater than 60 MPa, a welding rate of 100%, and a deformation of less than 1% after welding.

[0067] See Figure 6 As shown, this is a hot-press diffusion bonding method in the prior art. The workpiece 01 to be welded is also made of aluminum alloy. The welded joint obtained under the welding parameters of 500 degrees Celsius, 120 min, and 5 MPa has a strength of less than 2 MPa, a deformation of more than 7% after welding, and a large number of unwelded defects and pores in the weld, resulting in poor welding effect.

[0068] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A diffusion connection device for synchronous coupling of pulsed current and oscillating pressure, characterized in that, include: Furnace cavity (1), which is used to provide a vacuum welding environment; The pressure head assembly is disposed in the furnace cavity (1) and includes an upper pressure head (21) and a lower pressure head (22). The workpiece to be welded (01) is disposed between the upper pressure head (21) and the lower pressure head (22). A pulsed current system (3) is used to apply a pulsed current to the workpiece (01) to be welded through the pressure head assembly to generate Joule heat at the weld seam of the workpiece (01) as a welding heat source. Servo hydraulic system (4), the servo hydraulic system (4) is used to drive the pressure application component located outside the pressure head assembly to apply pulse welding pressure to the workpiece (01) to be welded via the pressure head assembly; An ultrasonic system (5) is used to apply ultrasonic vibrations to the workpiece (01) to be welded via the pressure head assembly during the welding process; Flaw detector (6), the flaw detector (6) is used to perform ultrasonic scanning on the weld and generate a detection signal through the pressure head assembly after welding is completed; The controller is communicatively connected to the pulse current system (3), the servo hydraulic system (4), the ultrasonic system (5), and the flaw detector (6); the controller is used to: regulate the timing of the pulse current system (3), the servo hydraulic system (4), and the ultrasonic system (5); and receive the detection signal generated by the flaw detector (6), and when it is determined that there is a defect in the weld, control the pulse current system (3) and the servo hydraulic system (4) to perform in-situ secondary welding operation while maintaining the vacuum environment of the furnace cavity; The pulsed current and the pulsed welding pressure have the same operating frequency and are synchronized in phase.

2. The diffusion connection device according to claim 1, characterized in that, Both the upper pressure head (21) and the lower pressure head (22) include a connecting plate (204) and a pressure tool head (201), a vibration tool head (202) and a detection tool head (203) vertically arranged on the side of the connecting plate (204) facing the workpiece (01) to be welded. The pressure tool head (201), the vibration tool head (202) and the detection tool head (203) are all cylindrical and arranged in parallel.

3. The diffusion connection device according to claim 2, characterized in that, The pressure-applying component includes an upper graphite pressure head (401) and a lower graphite pressure head (402). The upper graphite pressure head (401) is disposed above the upper pressure head (21), and the lower graphite pressure head (402) is disposed below the lower pressure head (22). The servo hydraulic system (4) is used to drive the upper graphite head (401) and the lower graphite head (402) to move toward each other, so as to apply the pulsed welding pressure to the workpiece (01) to be welded via the upper head (21) and the lower head (22).

4. The diffusion connection device according to claim 3, characterized in that, It also includes a positive electrode (301) and a negative electrode (302), wherein the positive electrode (301) is connected between the upper graphite indenter (401) and the pressure tool head (201) of the upper indenter (21), and the negative electrode (302) is connected between the lower graphite indenter (402) and the pressure tool head (201) of the lower indenter (22); The pulse current system (3) is powered by the positive electrode (301) and the negative electrode (302), so that the pulse current forms a current loop through the pressure tool head (201) of the upper pressure head (21), the weld and the pressure tool head (201) of the lower pressure head (22).

5. The diffusion connection device according to claim 4, characterized in that, The ultrasonic system (5) includes an amplitude transformer (51) and an ultrasonic generator (52); the upper end of the vibrating tool head (202) passes through the connecting plate (204) and is connected to the amplitude transformer (51), and the ultrasonic generator (52) supplies power to the vibrating tool head (202) through the amplitude transformer (51).

6. The diffusion connection device according to claim 5, characterized in that, A flexible sealing element is provided between the vibrating tool head (202) and the connecting plate (204) to make the vibrating tool head (202) and the connecting plate (204) flexibly connected; the lower end of the vibrating tool head (202) is used to attach to the workpiece (01) to be welded.

7. The diffusion connection device according to claim 2, characterized in that, The probe head (203) is mounted on the connecting plate (204) via a telescopic mechanism. The telescopic mechanism includes a mounting cavity and a driving element. The mounting cavity is opened in the connecting plate (204). The driving element is located in the mounting cavity and connected to the probe head (203). After welding is completed, the driving element drives the probe head (203) to move to be attached to the workpiece (01) to be welded.

8. A diffusion connection method for synchronous coupling and online detection of pulse current and oscillating pressure, characterized in that, Using the diffusion connection device according to any one of claims 1 to 7 includes the following steps: The workpiece to be welded (01) is assembled between the pressure head assembly, the furnace chamber (1) is evacuated and a pre-pressure is applied to the workpiece to be welded (01); A pulsed current is applied to the workpiece (01) to generate Joule heat at the weld as a welding heat source by means of a pulsed current system (3); at the same time, a pulsed welding pressure is applied to the workpiece (01) by means of a servo hydraulic system (4), and ultrasonic vibration is applied to the workpiece (01) by means of an ultrasonic system (5) to perform diffusion welding. The pulsed current and the pulsed welding pressure have the same operating frequency and are synchronized in pulse phase. After welding is completed, the pulse current and the pulse welding pressure are turned off, the flaw detector (6) is started, and the weld is ultrasonically scanned while maintaining the vacuum state of the furnace cavity (1) to generate a detection signal; the weld is judged to have defects based on the detection signal, and if defects are judged to exist, an in-situ secondary welding operation is performed.

9. The diffusion connection method according to claim 8, characterized in that, The frequency of the pulsed current is 20~40kHz, and the duty cycle is 50%~83.33%; the frequency of the pulsed welding pressure is the same as the frequency of the pulsed current, and the duty cycle is the same as the duty cycle of the pulsed current; the frequency of the ultrasonic vibration during the welding process is 20~30kHz, and the amplitude is 1~7μm.

10. The diffusion connection method according to claim 8, characterized in that, The step of determining whether there is a defect in the weld seam based on the detection signal includes: calculating the weld seam's weld bonding rate; when the weld bonding rate is lower than a preset threshold, triggering the in-situ secondary welding operation; the process parameters of the in-situ secondary welding operation are the same as those of the primary welding operation, or at least one welding parameter is adjusted according to the detected defect type and degree.

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