A brazed aluminum joint strengthening apparatus and method

Abstract

The application relates to the technical field of post-processing of metal welded joints, and discloses a strengthening treatment device for brazed aluminum joints, which comprises a rack and a control system, the rack is fixedly provided with a high-frequency induction welding module, a temperature real-time monitoring module, a pulse ultrasonic generating module and a three-dimensional positioning module; and the high-frequency induction welding module, the temperature real-time monitoring module, the pulse ultrasonic generating module and the three-dimensional positioning module are electrically connected with the control system. The strengthening treatment device and method for the brazed aluminum joints can precisely control the pulse ultrasonic action of the semi-solid temperature window, the brittle phase size of the interface of the brazed aluminum joint is refined from 50-100 mu m in the traditional process to 5-10 mu m, the brittle phases are uniformly distributed, and there is no obvious stress concentration point; the impact toughness of the joint after the strengthening treatment is greater than or equal to 12 J / cm2, which is more than 80% higher than that of the untreated joint; the fatigue life is improved by more than 50%, and no cracks are generated after one million alternating loads.

Description

Technical Field

[0001] This invention relates to the field of post-treatment technology for metal welded joints, specifically to a strengthening treatment device and method for brazed aluminum joints. Background Technology

[0002] Welded joints of aluminum and aluminum alloys with brazing filler metals are widely used in automotive piping, industrial vibration damping connectors, electronic instrument housings and other fields because they combine the advantages of aluminum's lightweight and high strength with the low-temperature bonding of brazing filler metals.

[0003] However, brazed aluminum joints have a core technical challenge: during the welding process, the aluminum matrix and the brazing filler metal are prone to interfacial reactions, generating coarse and brittle intermetallic compound phases. These brittle phases have high hardness and poor plasticity, making them weak points for stress concentration in the joint area. Under dynamic loads, thermal cycling, and other service conditions, these brittle phases can easily become the source of crack initiation, and crack propagation can directly lead to joint failure. At the same time, conventional heat treatment strengthening methods (such as annealing and tempering) are difficult to effectively refine or eliminate these brittle phases. Instead, excessively high heating temperatures can cause the brazing filler metal to soften, reducing the load-bearing capacity of the joint.

[0004] In existing technologies, methods for improving the brittle phase of welded joints mostly focus on optimizing the solder composition, such as adding rare earth elements and metal powders. However, these methods can only suppress the formation of brittle phases to a certain extent and cannot effectively refine the coarse brittle phases in the formed joint. Another technology uses ultrasonic vibration to assist welding, but the ultrasonic waves acting on the welding process can easily interfere with the solder spreading and metallurgical bonding, leading to new defects such as porosity and inclusions in the joint. Therefore, a strengthening treatment device and method for brazed aluminum joints is proposed. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a strengthening treatment device and method for brazed aluminum joints. It has the advantages of accurately refining the brittle phase of the formed brazed aluminum joint without damaging the solder performance. It solves the problems of existing methods for improving the brittle phase of welded joints, which cannot effectively refine the coarse brittle phase of the formed joint. Furthermore, ultrasonic vibration-assisted welding can easily interfere with the solder spreading and metallurgical bonding, leading to new defects such as porosity and inclusions in the joint.

[0007] (II) Technical Solution

[0008] To achieve the aforementioned goal of precisely refining the brittle phase of a pre-formed brazed aluminum joint without damaging the solder performance, the present invention provides the following technical solution: a strengthening treatment device for brazed aluminum joints, comprising a frame and a control system, wherein a high-frequency induction welding module, a real-time temperature monitoring module, a pulsed ultrasonic generator module, and a three-dimensional positioning module are fixedly installed on the frame; the high-frequency induction welding module, the real-time temperature monitoring module, the pulsed ultrasonic generator module, and the three-dimensional positioning module are all electrically connected to the control system.

[0009] Preferably, the high-frequency induction welding module includes a high-frequency induction coil and a power adjustment unit.

[0010] Preferably, the real-time temperature monitoring module is a non-contact infrared thermometer, with its temperature probe facing the welding area on the top of the frame, collecting welding temperature data in real time and feeding it back to the control system.

[0011] Preferably, the pulsed ultrasound generating module includes an ultrasound generator and an amplitude transformer, the end of which is made of silicon nitride ceramic material.

[0012] Preferably, the three-dimensional positioning module includes an X / Y / Z three-axis servo displacement platform, and the pulse ultrasound generating module is fixed on the three-axis displacement platform.

[0013] Preferably, the control system adopts a PLC controller with a built-in process parameter preset module and linkage control program; it can preset the joint temperature threshold, ultrasonic action parameters, and cooling rate parameters.

[0014] A method for strengthening brazed aluminum joints, based on a strengthening device for brazed aluminum joints, comprises the following steps:

[0015] Step 1: Forming the brazed aluminum joint:

[0016] Fix the aluminum part to be welded on the tooling table of the high-frequency induction welding module and lay the brazing base solder; set the high-frequency induction welding parameters through the control system, heat up to 600-620℃ above the melting point of the solder, and hold for 10-15 seconds; complete the basic welding of the brazed aluminum joint.

[0017] Step 2: Temperature Monitoring and Ultrasonic Trigger Preparation

[0018] After the welding insulation is completed, the high-frequency induction heating is turned off, and the real-time temperature monitoring module tracks the joint temperature change in real time; the ultrasonic trigger temperature threshold is preset to 570-580℃ by the control system.

[0019] Step 3: Pulsed ultrasound enhancement treatment:

[0020] When the joint temperature drops to the preset threshold, the control system automatically starts the three-dimensional positioning module, drives the amplitude rod of the pulse ultrasound generator module to move to the center position of the joint, and applies contact pressure; then the pulse ultrasound generator module is started, and the ultrasound action time is 2-5 minutes.

[0021] Step 4: Gradient cooling and shaping:

[0022] After the ultrasonic enhancement effect ends, the control system automatically shuts down the pulse ultrasound generation module, drives the three-dimensional positioning module to remove the amplitude transformer from the joint, and starts the cooling unit to control the joint to cool to room temperature at a rate of 3-5℃ / s.

[0023] Preferably, the aluminum parts to be welded in step one are preferably 1060 pure aluminum or 6061 aluminum alloy with a thickness of 0.5-5mm; the brazing base solder is a highly compatible brazing base solder or a traditional brazing solder.

[0024] (III) Beneficial Effects

[0025] Compared with the prior art, the present invention provides a strengthening treatment device and method for brazed aluminum joints, which has the following beneficial effects:

[0026] 1. The strengthening treatment device and method for the brazed aluminum joint, through precise control of the pulsed ultrasonic action within the semi-solid temperature window, refines the brittle phase size of the brazed aluminum joint interface from 50-100μm in the traditional process to 5-10μm, with the brittle phase uniformly distributed and no obvious stress concentration points; the impact toughness of the joint after strengthening treatment is ≥12J / cm², which is more than 80% higher than that of the untreated joint; the fatigue life is increased by more than 50%, and no cracks are generated after one million cycles of alternating load.

[0027] 2. The device and method for strengthening the brazed aluminum joint integrate welding, temperature measurement, ultrasonic strengthening and cooling functions. The device achieves full-process automated linkage through PLC control system without manual intervention. The high-precision positioning and pressure control of the three-dimensional positioning module ensure that the ultrasonic energy is applied evenly to the joint, and the product qualification rate is increased to more than 99.5%, which is suitable for industrial mass production.

[0028] 3. The strengthening treatment device and method for the brazed aluminum joint uses ultrasonic action on the semi-solid stage of the solder, avoiding the problem of ultrasonic interference with solder spreading during the welding process, and eliminating the need for additional chemical reagents; the treatment process has a low temperature, which will not cause the brazing solder to soften; it is compatible with a variety of brazing base solders and aluminum parts of different thicknesses, and is suitable for components that bear dynamic loads, such as automotive aluminum pipe joints and industrial equipment vibration damping connectors. Attached Figure Description

[0029] Figure 1 This is a structural diagram of the strengthening treatment device for brazed aluminum joints of the present invention;

[0030] Figure 2 This is a flowchart of the strengthening treatment method for brazed aluminum joints according to the present invention.

[0031] In the diagram: 1. Frame; 2. Control system; 3. High-frequency induction welding module; 4. Real-time temperature monitoring module; 5. Pulse ultrasound generator module; 6. Three-dimensional positioning module. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figure 1-2 A strengthening treatment device for brazed aluminum joints includes a frame 1 and a control system 2. A high-frequency induction welding module 3, a real-time temperature monitoring module 4, a pulsed ultrasonic generator module 5, and a three-dimensional positioning module 6 are fixedly installed on the frame 1. The high-frequency induction welding module 3, the real-time temperature monitoring module 4, the pulsed ultrasonic generator module 5, and the three-dimensional positioning module 6 are all electrically connected to the control system 2.

[0034] The high-frequency induction welding module 3 includes a high-frequency induction coil and a power adjustment unit. The frequency of the high-frequency induction coil is adjustable from 200 to 400 kHz, and the power is adjustable from 500 to 2000 W. It can be adapted to the brazing of aluminum parts of different thicknesses, ensuring that the solder melts fully and the aluminum substrate is not damaged by overheating.

[0035] The real-time temperature monitoring module 4 uses a non-contact infrared thermometer with a temperature measurement accuracy of ±1℃ and a response time of ≤100ms. The temperature probe is directly facing the welding joint area at the top of the frame 1, and can collect joint temperature data in real time and feed it back to the control system 2.

[0036] The pulsed ultrasound generation module 5 includes an ultrasound generator and an amplitude transformer. The ultrasound generator has an adjustable frequency range of 20-40kHz, an adjustable amplitude range of 5-15μm, and an adjustable pulse duty cycle range of 50%-70%. The end of the amplitude transformer is made of wear-resistant ceramic material, preferably silicon nitride ceramic, with a hardness ≥HV1200, which can prevent adhesion to high-temperature joints and ensure efficient transmission of ultrasonic vibration.

[0037] The three-dimensional positioning module 6 includes an X / Y / Z three-axis servo displacement platform with a positioning accuracy of ±0.01mm and a load capacity of ≥500N. The pulse ultrasound generation module 5 is fixed on the three-axis displacement platform and can precisely adjust the contact position and contact pressure between the amplitude transformer and the connector to ensure that the ultrasonic energy is uniformly applied to the connector area.

[0038] The control system 2 adopts a PLC controller with a built-in process parameter preset module and linkage control program; it can preset the joint temperature threshold, ultrasonic action parameters, and cooling rate parameters, where the joint temperature threshold is 570-580℃; when the joint temperature fed back by the real-time temperature monitoring module 4 reaches the preset threshold, the three-dimensional positioning module 6 is automatically started to drive the amplitude rod to crimp the joint, and then the pulse ultrasonic generation module 5 is triggered; after the ultrasonic action time ends, the ultrasonic module is automatically turned off and the cooling unit is started to control the joint cooling rate; the whole process does not require manual intervention, ensuring process consistency.

[0039] A method for strengthening brazed aluminum joints, based on a strengthening device for brazed aluminum joints, comprises the following steps:

[0040] Step 1: Forming the brazed aluminum joint:

[0041] The aluminum parts to be welded are fixed on the tooling table of the high-frequency induction welding module 3. The brazing base solder is laid. The aluminum parts to be welded are preferably 1060 pure aluminum or 6061 aluminum alloy with a thickness of 0.5-5mm. The brazing base solder is a highly compatible brazing base solder or traditional brazing solder. The high-frequency induction welding parameters are set through the control system 2: frequency 200-400kHz, power 500-2000W, heating rate 5-8℃ / s, heating to 600-620℃ above the melting point of the solder, the melting point of the solder is 600-620℃, and holding at the temperature for 10-15s. The basic welding of the brazed aluminum joint is completed.

[0042] Step 2: Temperature Monitoring and Ultrasonic Trigger Preparation

[0043] After the welding heat preservation is completed, the high-frequency induction heating is turned off, and the temperature real-time monitoring module 4 tracks the joint temperature change in real time. The control system 2 presets the ultrasonic trigger temperature threshold to 570-580℃. This temperature range is the semi-solid temperature window of the brazing filler metal. At this time, the filler metal is in a solid-liquid coexistence state, the brittle phase has not been completely precipitated and the plasticity is good, which is convenient for ultrasonic vibration to break it.

[0044] Step 3: Pulsed ultrasound enhancement treatment:

[0045] When the joint temperature drops to the preset 570-580℃, the control system 2 automatically starts the three-dimensional positioning module 6, drives the amplitude rod of the pulse ultrasonic generator module 5 to move to the center position of the joint, and applies a contact pressure of 50-100N; then the pulse ultrasonic generator module 5 is started, and the process parameters are set: ultrasonic frequency 20-40kHz, amplitude 5-15μm, pulse duty cycle 50%-70%, and ultrasonic action time 2-5min.

[0046] Under the action of ultrasonic vibration, the semi-solid solder undergoes violent plastic flow and shear deformation, breaking the coarse and brittle phases that are about to precipitate or have already formed into fine particles; at the same time, the ultrasonic cavitation effect can eliminate defects such as micropores and cracks inside the joint and refine the solder grains.

[0047] Step 4: Gradient cooling and shaping:

[0048] After the ultrasonic strengthening effect is completed, the control system 2 automatically shuts down the pulse ultrasonic generator module 5 and drives the three-dimensional positioning module 6 to remove the amplitude rod from the joint; the cooling unit is started to control the joint to cool to room temperature at a rate of 3-5℃ / s. Rapid cooling can inhibit the brittle phase particles after breakage from growing again and ensure that the brittle phase is distributed in the solder matrix in a fine and uniform state; after cooling is completed, the strengthened brazed aluminum joint is obtained.

[0049] Example 1:

[0050] This embodiment is applied to a 2mm thick 6061 aluminum alloy pipe joint with a welding gap of 0.1mm. A highly compatible brazing filler metal is used, consisting of 1.5% lanthanum and cerium (by mass ratio 2:1), 1.5% silicon powder, 0.3% copper powder, and the balance being aluminum. The specific processing procedure is as follows: Figure 2 As shown, the steps are as follows:

[0051] Step 1. Brazing aluminum joint forming: Fix the 6061 aluminum alloy part to be welded on the tooling table of the high-frequency induction welding module 3, and evenly spread the above-mentioned brazing base solder; set the high-frequency induction welding parameters through the control system 2: frequency 300kHz, power 1200W, heating rate 6℃ / s, heat up to the temperature above the melting point of the solder, i.e. 610℃, hold for 12s, and complete the basic welding forming.

[0052] Step 2. Temperature monitoring and ultrasonic trigger preparation: After the welding heat preservation is completed, the control system 2 automatically turns off the heating function of the high-frequency induction welding module 3, and the real-time temperature monitoring module 4 starts and tracks the joint temperature change in real time; the control system 2 presets the ultrasonic trigger temperature threshold to 570℃, which is within the semi-solid temperature window of the brazing filler metal, providing the best working conditions for brittle phase breakage.

[0053] Step 3. Pulse ultrasonic strengthening treatment: When the joint temperature fed back by the real-time temperature monitoring module 4 drops to 570℃, the control system 2 automatically starts the three-dimensional positioning module 6, drives the amplitude rod of the pulse ultrasonic generator module 5 to move to the center position of the joint, and applies a contact pressure of 80N; then the pulse ultrasonic generator module 5 is started, and the process parameters are set as follows: ultrasonic frequency 30kHz, amplitude 10μm, pulse duty cycle 60%, ultrasonic action time 3min; during this process, the semi-solid solder undergoes violent plastic flow and shear deformation, breaking the coarse brittle phase that is about to precipitate or has initially formed into fine particles, while the ultrasonic cavitation effect eliminates defects such as micropores and cracks inside the joint;

[0054] Step 4. Gradient cooling and shaping: After the ultrasonic strengthening effect is completed, the control system 2 automatically shuts down the pulse ultrasonic generator module 5 and drives the three-dimensional positioning module 6 to remove the amplitude rod from the joint; then the cooling unit is started, and the joint is controlled to cool to room temperature at a rate of 4℃ / s. The rapid cooling effectively inhibits the brittle phase particles after breakage from growing again, ensuring that the brittle phase is distributed in the solder matrix in a fine and uniform state.

[0055] Testing revealed that the brittle phase size at the interface of the reinforced 6061 aluminum alloy pipe joint was 8μm, the impact toughness reached 14J / cm², no cracks were generated after one million alternating load tests, and the tensile strength of the joint was 98MPa, which is a significant improvement compared to the traditional process.

[0056] Example 2:

[0057] This embodiment is applied to a 0.8mm thick 1060 pure aluminum vibration damping connector with a welding gap of 0.08mm. Traditional solder is used, consisting of 90% aluminum and 10% tin. The specific processing steps are as follows:

[0058] Step 1. Forming the brazed aluminum joint: Fix the 1060 pure aluminum part to be welded on the tooling table of the high-frequency induction welding module 3, and lay traditional brazing solder; set the high-frequency induction welding parameters through the control system 2: frequency 250kHz, power 800W, heating rate 5℃ / s, heat up to 610℃, which is above the melting point of the solder, hold for 10s, and complete the basic welding.

[0059] Step 2. Temperature monitoring and ultrasonic trigger preparation: After turning off the heating function of the high-frequency induction welding module 3, the real-time temperature monitoring module 4 monitors the joint temperature in real time, and the ultrasonic trigger temperature threshold is preset to 575℃ by the control system 2.

[0060] Step 3. Pulse ultrasound enhancement treatment: When the joint temperature drops to 575℃, the three-dimensional positioning module 6 drives the amplitude rod of the pulse ultrasound generator module 5 to move to the center of the joint and apply a contact pressure of 60N. The pulse ultrasound generator module 5 is started and the parameters are set as follows: ultrasonic frequency 25kHz, amplitude 8μm, pulse duty cycle 55%, and action time 2.5min.

[0061] Step 4. Gradient cooling and shaping: After the ultrasonic treatment is completed, the amplitude rod is removed under the drive of the three-dimensional positioning module 6, and the cooling unit cools the joint to room temperature at a rate of 3℃ / s.

[0062] Testing revealed that the brittle phase size at the joint interface of the reinforced 1060 pure aluminum shock absorber connector in this embodiment is 6μm, the impact toughness is 12.5J / cm², no cracks were observed after one million cycles of alternating load, and the tensile strength of the joint is 85MPa, meeting the service requirements for the shock absorber connector to withstand dynamic loads.

[0063] Example 3:

[0064] This embodiment is applied to a 5mm thick 1060 pure aluminum heavy equipment connector with a welding gap of 0.18mm. A highly compatible brazing filler metal is used, with a composition of 1.2% lanthanum and cerium (by mass ratio 3:1), 2.5% silicon powder, 0.4% copper powder, and the balance being aluminum. The specific processing steps are as follows:

[0065] Step 1. Forming of brazed aluminum joint: The parameters of the high-frequency induction welding module 3 are set to 400kHz frequency, 2000W power, and 8℃ / s heating rate through the control system 2. The temperature is raised to 600℃, which is above the melting point of the solder, and held for 15s to complete the basic welding formation.

[0066] Step 2. Temperature monitoring and ultrasonic trigger preparation: The ultrasonic trigger temperature threshold is preset to 590℃ by the control system 2, and the real-time temperature monitoring module 4 continuously tracks the temperature change of the connector.

[0067] Step 3. Pulse ultrasound enhancement treatment: When the temperature reaches 590℃, the three-dimensional positioning module 6 drives the amplitude rod of the pulse ultrasound generator module 5 to apply a 100N contact pressure to the joint. Then the pulse ultrasound generator module 5 starts according to the set parameters: frequency 40kHz, amplitude 15μm, pulse duty cycle 70%, and action time 5min.

[0068] Step 4. Gradient cooling and shaping: The cooling unit cools the joint to room temperature at a rate of 5℃ / s to complete the strengthening treatment.

[0069] Testing revealed that the brittle phase size at the joint interface of the 1060 pure aluminum heavy equipment connector after the reinforcement treatment in this embodiment is 10μm, the impact toughness is 15.2J / cm², no cracks were found after one million cycles of alternating load, and the tensile strength of the joint is 108MPa, making it suitable for the high-strength connection requirements of heavy equipment.

[0070] Example 4:

[0071] This embodiment is applied to a 0.5mm thick 6061 aluminum alloy precision sensor connector, with a welding gap of 0.05mm. Traditional solder is used, consisting of 95% aluminum and 5% tin. The specific processing steps are as follows:

[0072] Step 1. Forming of brazed aluminum joint: The parameters of the high-frequency induction welding module 3 are set to frequency 200kHz, power 500W, heating rate 5℃ / s, temperature rise to 620℃, and hold for 10s through the control system 2 to complete the basic welding.

[0073] Step 2. Temperature monitoring and ultrasonic trigger preparation: The ultrasonic trigger temperature threshold is preset to 590℃ by the control system 2, and the real-time temperature monitoring module 4 provides real-time feedback of the connector temperature data;

[0074] Step 3. Pulse ultrasound enhancement treatment: When the temperature reaches 590℃, the three-dimensional positioning module 6 drives the amplitude rod of the pulse ultrasound generator module 5 to apply a contact pressure of 50N. The pulse ultrasound generator module 5 is set with the following parameters: frequency 20kHz, amplitude 5μm, pulse duty cycle 50%, and action time 2min.

[0075] Step 4. Gradient cooling and shaping: Cool to room temperature at a rate of 3℃ / s to obtain the reinforced precision sensor connector.

[0076] Tests showed that the brittle phase size at the joint interface of the 6061 aluminum alloy precision sensor connector after the reinforcement treatment in this embodiment is 5μm, the impact toughness is 12.1J / cm², no cracks were found after one million cycles of alternating load, and the tensile strength of the connector is 82MPa, which meets the high precision and high reliability requirements of precision sensor connectors.

[0077] To further verify the superiority of the technical solution of the present invention, the following comparative examples were set up for comparative testing. Except for the specified variables, the devices used in each comparative example are the same as those in the above embodiments of the present invention, as detailed below:

[0078] Comparative Example 1:

[0079] Based on the conventional cooling process without ultrasonic strengthening, the same 6061 aluminum alloy pipe joint, brazing base solder and high-frequency induction welding module 3 as in Example 1 were used. Only the pulse ultrasonic strengthening process was omitted. After welding, the material was allowed to cool naturally to room temperature. The ultrasonic-related actions of the pulse ultrasonic generator module 5 and the three-dimensional positioning module 6 were not activated.

[0080] Test results: The brittle phase size at the joint interface was 75 μm, the impact toughness was only 6.5 J / cm², and obvious cracks appeared after 500,000 alternating loads. The tensile strength of the joint was 72 MPa, which was far lower than the performance index of Example 1. This indicates that pulsed ultrasonic strengthening treatment plays a key role in refining the brittle phase and improving its performance.

[0081] Comparative Example 2:

[0082] The process of applying ultrasound to the welding melting stage is used to process 6061 aluminum alloy pipe joints of the same specifications as in Example 1. The same frame 1, control system 2, high-frequency induction welding module 3, real-time temperature monitoring module 4, pulse ultrasound generation module 5, three-dimensional positioning module 6 and material parameters are used as in Example 1. The only difference is that the timing of the ultrasound application is adjusted to the welding melting stage, i.e., the temperature is 610℃, while the other parameters remain unchanged.

[0083] Test results: The solder spread was uneven, and pore defects appeared inside the joint. The brittle phase size was 45μm, the impact toughness was 9J / cm², and cracks appeared after 800,000 cycles of alternating load. The tensile strength of the joint was 80MPa. Because the ultrasonic action on the melting stage interfered with the metallurgical bonding process, the performance improvement was limited and there were forming defects. This proves the rationality of the present invention in applying ultrasonic at the semi-solid temperature window.

[0084] Comparative Example 3:

[0085] Using a process where the ultrasonic action temperature deviates from the semi-solid window, the same 6061 aluminum alloy pipe joint as in Example 1 was processed. The ultrasonic trigger temperature was set to 600℃ through the control system 2, i.e. the solder was in a fully liquid state, while the other parameters remained unchanged.

[0086] Test results: The solder was splashed and lost due to ultrasonic vibration. The brittle phase size at the joint interface was 48μm, the impact toughness was 8.2J / cm², and cracks appeared after 600,000 cycles of alternating load. The tensile strength of the joint was 75MPa. The deviation from the semi-solid temperature window resulted in poor refinement of the brittle phase and incomplete joint formation, further verifying the optimization value of the 570-590℃ temperature window.

[0087] Comparative Example 4:

[0088] Using a constant ultrasound process instead of pulsed ultrasound, the same 1060 pure aluminum vibration damping connector as in Example 2 was processed. The only difference was that the ultrasound mode of the pulsed ultrasound generator module 5 was changed to continuous ultrasound with a duty cycle of 100%, while the other parameters remained unchanged.

[0089] Test results: Local overheating of the joint caused the solder to soften, the brittle phase size at the interface was 32μm, the impact toughness was 9.5J / cm², and cracks appeared after 700,000 cycles of alternating load. The tensile strength of the joint was 78MPa. Constant ultrasound can easily cause local thermal damage, affecting the load-bearing capacity of the joint, which shows the advanced nature of the pulsed ultrasound parameter design.

[0090] As can be seen from the performance test results of Examples 1 to 4 and Comparative Examples 1 to 4 above, the strengthening treatment device and method for brazed aluminum joints of the present invention have significant technical advantages and performance improvement effects compared with the process without ultrasonic strengthening, the process of mismatch during ultrasonic action, and the process of ultrasonic parameters deviating from the optimized range:

[0091] From the perspective of brittle phase refinement, Examples 1 to 4, through precise control of pulsed ultrasound within the 570-590℃ semi-solid temperature window, stably controlled the brittle phase size at the brazed aluminum joint interface to 5-10 μm, with uniform distribution and no agglomeration. Comparative Example 1, without ultrasonic strengthening treatment, had a coarsened brittle phase size to 75 μm, becoming the core weak point of stress concentration in the joint. Comparative Example 2 applied ultrasound to the solder melting stage, interfering with the metallurgical bonding process, yet the brittle phase size still reached 45 μm. Comparative Example 3 deviated from the semi-solid temperature window, applying ultrasound at the 150℃ full liquid stage, resulting in solder splashing and loss, with a brittle phase size of 48 μm. Comparative Example 4 used constant ultrasound instead of pulsed ultrasound, leading to localized overheating of the joint, with a brittle phase size of 32 μm, all significantly larger than the brittle phase size of the embodiments of this invention.

[0092] Analysis of the joint's mechanical properties and fatigue resistance shows that the joints in Examples 1 to 4 all have an impact toughness ≥12.1 J / cm², with a maximum of 15.2 J / cm², and a tensile strength ≥82 MPa, with a maximum of 108 MPa. Moreover, no cracks were generated after one million cycles of alternating load, demonstrating excellent fatigue resistance. In contrast, Comparative Example 1, without ultrasonic strengthening, has an impact toughness of only 6.5 J / cm² and a tensile strength of 72 MPa, and cracks appeared after 500,000 cycles of alternating load. Due to mismatch in ultrasonic process parameters, Comparative Examples 2-4 have an impact toughness of only 8.2-9.5 J / cm², a tensile strength of 75-80 MPa, and a fatigue life of only 600,000 to 800,000 cycles of alternating load, which is far lower than the performance indicators of the embodiments of this invention.

[0093] Judging from the quality of the joint formation, the solder in Examples 1 to 4 was evenly spread, and there were no defects such as pores or inclusions inside the joint. The product qualification rate was consistently above 99.5%. In Comparative Example 2, the ultrasonic action during the melting stage caused uneven solder spreading and pores. In Comparative Example 3, the ultrasonic action during the full liquid stage caused solder to splash and be lost, resulting in incomplete joint formation. In Comparative Example 4, constant ultrasonic action caused the solder to soften, affecting the joint's load-bearing capacity. All of these examples showed obvious forming defects.

[0094] In summary, this invention achieves efficient refinement and performance improvement of the brittle phase in brazed aluminum joints through precise control of the semi-solid temperature window, optimization of pulsed ultrasonic parameters, and integrated automated control of the device. This is significantly superior to existing processes and demonstrates outstanding creativity and practicality.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A strengthening treatment device for brazed aluminum joints, comprising a frame (1) and a control system (2), characterized in that: The frame (1) is fixedly installed with a high-frequency induction welding module (3), a real-time temperature monitoring module (4), a pulse ultrasound generating module (5), and a three-dimensional positioning module (6); the high-frequency induction welding module (3), the real-time temperature monitoring module (4), the pulse ultrasound generating module (5), and the three-dimensional positioning module (6) are all electrically connected to the control system (2).

2. The strengthening treatment device for brazed aluminum joints according to claim 1, characterized in that: The high-frequency induction welding module (3) includes a high-frequency induction coil and a power adjustment unit.

3. The strengthening treatment device for brazed aluminum joints according to claim 1, characterized in that: The real-time temperature monitoring module (4) is a non-contact infrared thermometer. Its temperature probe is facing the welding area at the top of the frame (1) to collect welding temperature data in real time and feed it back to the control system (2).

4. The strengthening treatment device for brazed aluminum joints according to claim 1, characterized in that: The pulsed ultrasound generating module (5) includes an ultrasound generator and an amplitude transformer, the end of which is made of silicon nitride ceramic material.

5. The strengthening treatment device for brazed aluminum joints according to claim 1, characterized in that: The three-dimensional positioning module (6) includes an X / Y / Z three-axis servo displacement platform, and the pulse ultrasound generating module (5) is fixed on the three-axis displacement platform.

6. The strengthening treatment device for brazed aluminum joints according to claim 4, characterized in that: The control system (2) adopts a PLC controller with a built-in process parameter preset module and linkage control program; it can preset the joint temperature threshold, ultrasonic action parameters, and cooling rate parameters.

7. A method for strengthening brazed aluminum joints, characterized in that, The strengthening treatment apparatus for brazed aluminum joints according to claims 1-6 comprises the following steps: Step 1: Forming the brazed aluminum joint: Fix the aluminum part to be welded on the tooling table of the high frequency induction welding module (3) and lay the brazing base solder; set the high frequency induction welding parameters through the control system (2), heat up to 600-620℃ above the melting point of the solder, and keep it at that temperature for 10-15 seconds; complete the basic welding of the brazed aluminum joint. Step 2: Temperature Monitoring and Ultrasonic Trigger Preparation After the welding and heat preservation are completed, the high-frequency induction heating is turned off, and the temperature real-time monitoring module (4) tracks the joint temperature change in real time; the ultrasonic triggering temperature threshold is preset to 570-580℃ through the control system (2); Step 3: Pulsed ultrasound enhancement treatment: When the joint temperature drops to the preset threshold, the control system (2) automatically starts the three-dimensional positioning module (6), drives the amplitude rod of the pulse ultrasonic generator module (5) to move to the center position of the joint, and applies contact pressure; then the pulse ultrasonic generator module (5) is started, and the ultrasonic action time is 2-5 minutes. Step 4: Gradient cooling and shaping: After the ultrasonic enhancement effect ends, the control system (2) automatically shuts down the pulse ultrasonic generator module (5), drives the three-dimensional positioning module (6) to remove the amplitude rod from the joint; starts the cooling unit, and controls the joint to cool to room temperature at a rate of 3-5℃ / s.

8. The method for strengthening a brazed aluminum joint according to claim 7, characterized in that: The aluminum parts to be welded in step one are preferably 1060 pure aluminum or 6061 aluminum alloy with a thickness of 0.5-5mm; the brazing base solder is a highly compatible brazing base solder or a traditional brazing solder.

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