A copper-aluminum alloy friction stir welding process

Abstract

The application discloses a copper-aluminum alloy friction stir welding process, which comprises the following steps in sequence: pressing, dotting, installing a plug, clamping, welding and removing the plug. The negative clearance fit of the protrusion of the copper part and the groove of the aluminum part and the hydraulic pressing solve the combination problem caused by the material difference; the wide support surface plug with a heat insulation layer is used to prevent welding collapse; the preset tooling ensures stable clamping; the preset stir head design improves the penetration and material mixing effect; and the post-welding treatment and multi-dimensional detection guarantee the weld performance. The process breaks through the copper-aluminum double-sided friction stir welding limit, and meets the requirements of the liquid cooling heat dissipation system and other harsh scenes on the sealing performance, strength and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding process, and particularly relates to a copper-aluminum alloy friction stir welding process. BACKGROUND

[0002] In the field of copper-aluminum alloy friction stir welding, due to the significant difference in material quality between copper and aluminum, the melting temperatures of the two are different, which makes it difficult to achieve good dissolution and combination during welding, and the problem of insufficient penetration often occurs, which affects the weld quality. At the same time, some workpiece structures have the characteristics of uneven thickness, and in the welding process, the downward pressure easily causes the workpiece to collapse, further deteriorating the welding effect.

[0003] In addition, the existing process has deficiencies in copper-aluminum assembly gap control, welding tool stability, post-welding treatment, and weld performance detection, etc., which leads to poor performance of the welded workpiece in many tests, such as poor sealing, unable to pass the blasting test, etc., making it difficult to meet the high requirements of liquid cooling heat dissipation systems and other copper-aluminum alloy welded parts, and limiting the practical application of copper-aluminum alloy friction stir welding technology. SUMMARY

[0004] The purpose of the present application is to provide a copper-aluminum alloy friction stir welding process to solve the problems raised in the background.

[0005] Therefore, the present application provides a copper-aluminum alloy friction stir welding process, which is realized by the following steps in sequence:

[0006] S1. Compression: a pressure device is used to apply continuous pressure to the welding area of the copper and aluminum parts, so that the two welding surfaces form a close initial contact state;

[0007] Among them, the copper part welding surface is provided with a protruding structure, and the aluminum part is provided with a matching groove at the corresponding position. Through the action of pressure, plastic deformation of the protrusion and the groove is realized to achieve negative gap tight fit, and at the same time, the copper-aluminum contact support surface is formed with a preset width, providing a stable interface basis for subsequent welding;

[0008] S2. Dotting: on the surface of the compressed copper-aluminum assembly, positioning marks are made at the starting point, ending point and intermediate key positions of the preset welding trajectory;

[0009] The positioning marks are formed by mechanical punching, forming concave dots of a preset shape, the depth of the concave dots does not exceed a preset proportion of the wall thickness of the workpiece, and the concave dots are arranged at intervals along the welding path to accurately define the spatial position of the welding path;

[0010] S3. Installing the plug: a specially designed plug is assembled to the back hole position corresponding to the welding path of the copper-aluminum assembly, and the plug and the hole position are tightly fitted and fixed by interference fit;

[0011] The end of the plug is processed to form a support plane with a preset width, which is concentrically aligned with the welding path to bear the downward pressure applied by the stirring head during welding, prevent the workpiece from collapsing due to uneven thickness, and reduce the transmission of welding heat to the support structure through preset treatment and a heat insulation layer on the surface of the plug.

[0012] S4. Clamping: the copper-aluminum assembly is clamped and fixed by using a preset tool with an arc-shaped transition, the tool is provided with a plurality of symmetrically distributed clamping structures in the lap joint area of the aluminum part, and the workpiece is kept in a stable posture by a preset clamping force.

[0013] During clamping, the straightness of the welding path and the parallelism of the copper-aluminum joint line and the tool positioning reference are ensured to meet the preset requirements.

[0014] S5. Welding: a stirring head with a preset diameter is used to implement friction stir welding along a preset welding bead, the welding bead is arranged at a preset distance outside the copper-aluminum joint line and has a preset width, a preset penetration is formed during the rotation of the stirring head, and through the coordinated control of the rotation speed and the travel speed, the copper-aluminum materials realize plastic flow and metallurgical bonding under the action of thermal-mechanical coupling.

[0015] The stirring head is made of a preset material, the stirring needle has a preset diameter at the end, and a spiral groove is arranged on the surface to promote material mixing.

[0016] S6. Removing the plug: after welding, a preset dismounting tool is used to remove the back support plug, the contact part of the tool and the plug is designed as a matching structure, the plug is smoothly taken out by the action of axial force, mechanical disturbance to the weld area is avoided, and after the plug is removed, deburring treatment is performed on the back hole of the workpiece to ensure the surface flatness.

[0017] In the present application, a further embodiment is that in step S1, the pressure applying device is equipped with a pressure sensing element, which can monitor the pressure value in real time during the pressure applying process and feed back to the control system, so that the applied pressure is dynamically adjusted within a preset range, when the fit degree of the copper-aluminum welding surface reaches a preset proportion or more, the system automatically maintains the pressure and keeps it for a preset time, to ensure that the negative clearance tight fitting structure is stably formed.

[0018] In the present application, a further embodiment is that in step S2, the positioning mark is made by using a punch tool with a guide mechanism, the guide rod of the punch tool is parallel to the welding track, to ensure that the distance deviation between the center of the concave point and the edge of the welding bead meets the preset standard, and the bottom of the concave point adopts a round corner transition to avoid stress concentration.

[0019] In the present application, further embodiments are that in step S3, the special plug adopts a preset steel material, has a preset hardness after processing, and the interference amount of the plug and the hole position is in a preset range. The assembly process is realized by a press fitting machine, and the press fitting force is controlled in a preset range, so as to ensure that the plug is firmly installed and the workpiece hole is not damaged.

[0020] In the present application, further embodiments are that in step S4, the clamping structure of the preset tooling adopts a modular design, each clamping unit includes an elastic buffer structure, which can produce a preset range of elastic deformation under the action of clamping force, which can not only ensure the clamping stability, but also avoid the appearance of indentation on the surface of the workpiece. The adjustable support feet are arranged at the bottom of the tooling, which are used to adjust the levelness of the workpiece, so that the flatness error of the welding surface is controlled within a preset range.

[0021] In the present application, further embodiments are that in step S5, the rotation speed, welding travel speed and pressure of the stirring head are all in a preset range. In the welding process, the stirring head axis and the workpiece plane maintain a preset inclination angle, and the fitting area of the shaft shoulder and the workpiece surface is not less than a preset proportion of the total area of the shaft shoulder, so as to ensure the heat input and material plasticization effect.

[0022] In the present application, further embodiments are that in step S5, the preset welding bead is planned by a computer-aided design system, the welding bead track is designed in a linear type according to the structural characteristics of the copper-aluminum piece, and the distribution proportion on both sides of the copper-aluminum joint line meets the preset requirements, so as to adapt to the difference in thermal physical properties of the two materials.

[0023] In the present application, further embodiments are that it further includes step S7. Post-welding treatment: after the plug is removed, the weld is ultrasonically cleaned, the cleaning time is in a preset range, so as to remove the welding slag and impurities, and then a rotary file is used to trim the two sides of the weld, remove the welding protrusions exceeding the preset height, and make the surface roughness of the weld reach below the preset standard.

[0024] In the present application, further embodiments are that in step S5, a temperature monitoring device is provided during the welding process to monitor the temperature of the welding area in real time, so that the copper side temperature and the aluminum side temperature are maintained in their respective preset ranges. When the temperature exceeds the preset range, the system automatically adjusts the rotation speed of the stirring head to ensure that the material is in the best plastic state.

[0025] In the present application, further embodiments are that it further includes step S8. Quality detection: the workpiece after welding is subjected to helium detection test, burst test and salt spray test in sequence. In the helium detection test, the pressure is in a preset range, the leakage rate is not more than a preset standard, the pressure in the burst test reaches a preset value, and the weld does not crack for a preset pressure maintaining time. In the salt spray test, there is no corrosion, peeling and plating layer falling off phenomenon on the surface after a preset time.

[0026] The present application has the following advantages:

[0027] The process solves the problems of insufficient penetration and difficult dissolution caused by the material difference between copper and aluminum by negative gap tight fitting assembly and hydraulic press bonding, cooperates with the preset welding bead design at 1mm outside the copper-aluminum bonding line, realizes the stable combination of the two; solves the collapse problem caused by uneven structure thickness by widening the support plane to 0.85mm and installing a tight fitting plug in the hole to resist the welding down pressure, guarantees the welding effect; the modular elastic clamping structure and adjustable support foot of the preset tooling avoid workpiece displacement and surface indentation, improve the welding stability; the post-welding plug removal, deburring and ultrasonic cleaning eliminate the influence of welding slag and burrs on performance; the selection of a 10mm diameter stirring tool bit increases the penetration, improves the welding stability and prolongs the service life, combined with multi-dimensional tests including helium detection, explosion, salt spray, high-low temperature impact and the like, ensures the sealing, strength and corrosion resistance of the weld in harsh environments, meets the needs of liquid cooling heat dissipation system and the like, and overcomes the process limit of copper-aluminum double-sided friction stir welding. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flowchart of the present application is shown. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments in the present application belong to the scope of protection of the present application.

[0030] In the description of the present application, it should be noted that the terms used herein are only for the purpose of describing the specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. For the convenience of description, the sizes of the parts shown in the drawings are not drawn in accordance with the actual proportional relationship. The technology, methods and devices known to those skilled in the art may not be discussed in detail, but should be considered as part of the authorized description. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0031] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application are used for distinguishing between similar objects and not necessarily for describing a sequential or chronological order. It is to be understood that the data so distinguished can occur in any order. The terms "first", "second", and the like can be understood as denoting a "one of" relationship, and can not necessarily be understood as denoting a "one and only" relationship. Furthermore, the terms "comprise", "comprising", "comprises", and the like can be understood to encompass the presence of steps, processes, objects, or elements of the described embodiments, but not to preclude the presence or addition of one or more other steps, processes, objects, or elements, unless expressly limited in the description or claims.

[0032] It should be noted that in the description of the present application, the terms "front", "back", "up", "down", "left", "right", "lateral", "vertical", "horizontal", and "top", "bottom", and the like as terms of reference are used for convenience only, and do not necessarily have to be construed in a strict geometrical sense. Unless otherwise stated in the description, these terms are merely used to describe the relative location and / or orientation of the apparatuses and / or elements as shown in the drawings, and do not indicate or imply that the apparatuses or elements must be in a predetermined orientation or constructed and operated in a predetermined orientation, and therefore should not be construed as limiting the scope of protection of the present application. The terms "inner" and "outer" refer to the inner and outer sides with respect to the outline of the respective components.

[0033] It should be noted that in the present application, the terms "comprise", "comprising", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element. In addition, it should be noted that the scope of the methods and apparatuses in the embodiments of the present application is not limited to performing functions in the order shown or discussed, but can also include performing functions in a substantially simultaneous manner or in reverse order, for example, the described methods can be performed in an order different from that described, and various steps can be added, omitted, or combined. In addition, features described with reference to certain examples can be combined in other examples.

[0034] The present embodiment provides a copper-aluminum alloy friction stir welding process, comprising the following steps:

[0035] Step S1. Pressing, a servo pressure device integrating pressure sensing elements and closed-loop control system is used to apply dynamic pressure to the copper and aluminum parts to be welded. The copper part to be welded surface is processed with an array of trapezoidal protrusions, and the aluminum part is processed with matching wedge-shaped grooves at the corresponding position. The protrusions and grooves are initially embedded by linearly increasing the pressure, and the pressure sensing elements monitor the contact pressure distribution in real time. When the copper and aluminum parts to be welded meet the standard, the system automatically switches to the pressure maintaining mode, and the metal plastic deformation is used to achieve zero-gap interference fit, forming a pre-set width of copper and aluminum contact support surface.

[0036] Through the special-shaped fitting structure and dynamic pressure regulation, compared with the traditional plane contact assembly, the initial bonding strength of copper and aluminum is significantly improved, and the risk of virtual welding caused by assembly gap is eliminated, providing a stable mechanical reference for subsequent welding and solving the problem of bonding stability caused by the difference in copper and aluminum materials. In the prior art, copper and aluminum assembly is mostly adopted by plane contact or simple gap fitting, which is difficult to overcome the problem of loose bonding caused by material difference. The process innovation adopts the special-shaped fitting structure of trapezoidal protrusions of copper parts and wedge-shaped grooves of aluminum parts, and through the dynamic pressure regulation and pressure maintaining process of servo pressure device, the metal plastic deformation is used to achieve zero-gap interference fit, forming a double pre-connection of mechanical occlusion and metallurgical bonding. This structure breaks through the limitation of traditional plane assembly, significantly improves the initial bonding strength of copper and aluminum, and fundamentally solves the defects of virtual welding and incomplete fusion. The fitting method and pressure control logic have no similar application in the prior art, and have non-obviousness.

[0037] Step S2. Dotting, a numerical control dotting tool with a three-dimensional guide mechanism is used to make positioning marks on the surface of the copper and aluminum assembly after pressing. The guide mechanism calibrates the parallelism of the punch and the welding trajectory by laser ranging, and a hard alloy punch is selected to make hemispherical concave dots at the key positions of the pre-set welding trajectory. The bottom of the concave dot is designed with a round corner transition, and the punching force is controlled during the punching process to avoid micro-cracks on the surface of the workpiece. The three-dimensional guide ensures the positioning accuracy of the concave dot, and compared with the traditional marking method, the positioning accuracy of the welding trajectory is greatly improved, reducing defects such as welding deviation; the round corner transition design eliminates the risk of stress concentration and avoids cracks in the subsequent welding process.

[0038] Step S3. Installing the plug, the specially made plug is made of alloy tool steel and is treated by vacuum quenching, and the surface is sprayed with a heat insulation layer. The plug is tightly fitted with the hole on the back of the workpiece by applying axial pressing force with a servo press machine. The top of the plug is processed with a pre-set width of support plane, and the precise positioning tool is used to ensure the concentric alignment with the welding path. The heat insulation layer reduces the conduction of welding heat to the plug, avoiding overheating and softening of the material around the hole; the widened support plane can withstand larger welding downward pressure, and compared with the traditional narrow support plane, the anti-collapse ability is significantly enhanced, solving the problem of welding deformation caused by uneven thickness of the workpiece structure.

[0039] Step S4. Clamping, the preset tool adopts a modular clamping structure, which includes multiple independent clamping units, each unit is equipped with a disc spring group and a buffer pad, and a clamping force is applied through a lead screw mechanism driven by a servo motor to realize rigid positioning and elastic buffering composite clamping. An adjustable support foot is arranged at the bottom of the tool to adjust the levelness of the workpiece with a level meter to ensure that the welding surface flatness meets the standard. The elastic buffering structure reduces the indentation on the surface of the workpiece, and compared with the traditional rigid clamping, the surface damage is greatly reduced; the adjustable support foot ensures the levelness of the welding surface, so that the pressure distribution of the stirring head is more uniform, and the welding consistency is improved.

[0040] Step S5. Welding, an alloy prepared stirring head is used, the stirring needle surface is processed with a spiral groove, the welding track is planned through a computer aided design system, the center of the welding track is located at a preset position outside the copper-aluminum joint line, and is distributed on the copper side and the aluminum side according to a preset proportion. During the welding process, the stirring head rotation speed, travel speed and down pressure are controlled through the control system linkage to keep the inclination angle of the stirring head axis and the workpiece plane, so as to ensure that the fitting area of the shaft shoulder and the workpiece surface meets the standard. The large diameter stirring head cooperates with the spiral groove design to improve the penetration and material mixing uniformity, reduce the generation of interfacial brittle phase; the asymmetric welding track distribution is adapted to the difference in thermal physical properties of copper and aluminum to avoid defects caused by temperature mismatch; the inclination angle and the shaft shoulder fitting degree control ensure uniform heat distribution, which significantly improves the weld strength.

[0041] Step S6. Removing the plug, after cooling after welding, the rear support plug is removed by using a preset removal tool, the contact part of the tool and the plug is designed as an adaptive structure, the plug is smoothly pulled out by applying axial tension through a hydraulic device, and deburring treatment is performed on the back hole of the workpiece after the plug is removed. The preset tool and axial force control avoid the welding seam vibration damage caused by the traditional removal method, reduce the stress fluctuation of the welding seam area; the deburring treatment ensures the smoothness of the hole surface, eliminates the risk of assembly interference, and improves the compatibility of subsequent processes.

[0042] In the embodiment, in step S1, the pressure applying device is equipped with a pressure sensing element, which can monitor the pressure value in real time during the pressure applying process and feed back to the control system, so that the applied pressure is dynamically adjusted within the preset range. When the fitting degree of the copper-aluminum welding surface reaches a preset proportion or more, the system automatically maintains the pressure and maintains the pressure for a preset time to ensure that the negative clearance tight fitting structure is stably formed.

[0043] The pressure sensing elements are uniformly arranged on the surface of the pressure applying device pressure head, and the real-time pressure distribution data is transmitted to the control system. When it is detected that the pressure of most areas meets the standard, the pressure maintaining program is automatically triggered, and the pressure fluctuation is controlled within a reasonable range during the pressure maintaining process. Real-time pressure monitoring and dynamic adjustment ensure the consistency of the negative clearance tight fitting, improve the copper-aluminum fitting degree, avoid overpressure or underpressure problems, and improve the yield rate of subsequent welding.

[0044] In this embodiment, in step S2, the positioning mark is made by using a punch tool with a guide mechanism, the guide rod of the punch tool is parallel to the welding track, ensuring that the distance deviation between the center of the concave point and the edge of the weld meets the preset standard, and the bottom of the concave point adopts a round corner transition to avoid stress concentration. The guide mechanism is composed of a linear guide rail and a laser alignment module, which ensures that the axis of the punch is parallel to the welding track, and the laser alignment module captures the reference line in real time and adjusts the position of the punch tool. The bottom of the concave point is formed by a preset tool to form a round corner. The guide mechanism and the laser alignment improve the positioning accuracy of the positioning mark and provide accurate reference for welding track planning; the round corner transition design eliminates stress concentration and improves the crack resistance of the weld in high and low temperature impact test.

[0045] In this embodiment, in step S3, the special plug adopts a preset steel material, which has a preset hardness after processing, and the interference amount of the plug and the hole position is in a preset range. The assembly process is realized by a press fitting machine, the press fitting force is controlled in a preset range, and the plug is firmly installed without damaging the workpiece hole. The special plug is made of alloy tool steel after heat treatment, and the surface treatment ensures that the roughness meets the standard. The interference amount of the hole position is set according to the size of the hole position. When assembling, the servo press fitting machine applies a press fitting force, and the displacement-force curve is monitored in real time to avoid damage to the hole position. The high hardness material and the accurate interference amount ensure that the plug is accurately positioned after installation, and the support force action point is accurate; dynamic monitoring of the press fitting force avoids plastic deformation of the hole position, improves the reuse rate of the hole position after the plug is removed, and reduces the cost of tool loss.

[0046] In this embodiment, in step S4, the clamping structure of the preset tooling adopts a modular design, each clamping unit includes an elastic buffer structure that can produce a preset range of elastic deformation under the action of clamping force, which can ensure the stability of clamping and avoid indentation on the surface of the workpiece. The bottom of the tooling is also provided with an adjustable support foot for adjusting the levelness of the workpiece, so that the flatness error of the welding surface is controlled within a preset range. The elastic buffer structure of the modular clamping unit is composed of a laminated disc spring and a buffer pad, and the clamping force is fed back in real time by a force sensor to ensure reasonable deviation. The adjustable support foot of the tooling bottom adopts a screw elevator structure, which cooperates with a level to adjust the flatness of the welding surface. The elastic buffer structure allows the clamping force to be self-adaptively adjusted when the workpiece expands and contracts, avoiding workpiece loosening during welding; the adjustable support foot ensures the levelness of the welding surface, improves the uniformity of the axial force distribution of the stirring head, and reduces the weld defects.

[0047] In this embodiment, in step S5, the rotation speed of the stirring head, the welding travel speed and the pressing force are all within the preset range. During welding, the axis of the stirring head and the workpiece plane maintain a preset inclination angle, and the contact area of the shaft shoulder and the workpiece surface is not less than a preset proportion of the total area of the shaft shoulder, to ensure the heat input and material plasticization effect. The rotation speed of the stirring head, the travel speed and the pressing force are set according to the material properties, the inclination angle of the axis of the stirring head and the workpiece plane is maintained, and the contact area of the shaft shoulder end surface and the workpiece surface is ensured to meet the standard by fine grinding. The parameter matching makes the temperature of the welding area stable in the material plasticization interval, and the inclination angle and the shaft shoulder contact degree control ensure uniform heat input and sufficient material plastic flow, so that the weld fusion line is continuous and defect-free, and the strength is significantly improved.

[0048] In this embodiment, in step S5, the preset welding bead is planned by a computer-aided design system, and the welding bead trajectory is designed in a linear type according to the structural characteristics of the copper-aluminum piece, and the distribution proportion on both sides of the copper-aluminum joint line meets the preset requirement, to adapt to the difference in thermal physical properties of the two materials. The welding bead trajectory is planned by a computer-aided design system, a linear type design is adopted according to the structural characteristics of the copper-aluminum piece, and the welding bead is distributed on both sides of the copper-aluminum joint line according to the preset proportion to adapt to the difference in melting point of the two materials. The computer-aided design improves the accuracy of the welding bead trajectory and avoids manual planning errors; the asymmetric distribution proportion solves the synchronous problem of melting caused by the difference in melting point of copper and aluminum, reduces the generation of brittle compounds, and improves the low-temperature impact toughness of the weld.

[0049] By the differential heat output of the stirring head shoulder and the stirring pin, the temperature on the copper side is 50-100℃ higher than that on the aluminum side (the traditional technology is that the welding area temperatures on the copper side and the aluminum side are uniform), the temperature difference is used to promote the directional diffusion of copper atoms to the aluminum side, while inhibiting the excessive migration of aluminum atoms to reduce brittle phases, avoid the enrichment of brittle phases caused by excessive migration of aluminum atoms, and improve the weld interface bonding strength by more than 30%, and the toughness index is significantly improved. During welding, the stirring head rotation speed, travel speed and pressing force are controlled by the control system to maintain the inclination angle of the stirring head axis and the workpiece plane, and to ensure that the contact area of the shaft shoulder and the workpiece surface meets the standard.

[0050] In this embodiment, it also includes step S7. Post-welding treatment: after the plug is removed, the weld is ultrasonically cleaned to remove welding slag and impurities, and then a rotary file is used to trim both sides of the weld to remove excess welding bumps, so that the weld surface roughness meets the standard. Ultrasonic cleaning uses a device with a preset frequency and power to remove welding slag and impurities with a neutral cleaning agent, and then a rotary file is used to trim both sides of the weld to remove welding bumps that exceed the standard. Ultrasonic cleaning completely removes impurities on the weld surface, avoiding corrosion hazards; welding bump trimming makes the weld surface smooth, reduces fluid resistance, and improves appearance quality and subsequent assembly compatibility.

[0051] In this embodiment, in step S5, the welding process is equipped with a temperature monitoring device to monitor the temperature of the welding area in real time, so that the copper side temperature and the aluminum side temperature are maintained within their respective preset ranges. When the temperature exceeds the range, the system automatically adjusts the rotation speed of the stirring head to ensure that the material is in the best plastic state. The temperature monitoring device uses a dual-channel infrared thermometer to monitor the temperature of the copper side and the aluminum side welding area. When the temperature exceeds the preset range, the system automatically adjusts the rotation speed of the stirring head until the temperature returns to the reasonable range. Real-time temperature monitoring and rotation speed adjustment control the temperature fluctuation of the copper and aluminum sides within a reasonable range, avoiding material burning or insufficient fusion. The material is always in the best plastic state, improving the uniformity of the weld and the stability of the mechanical properties.

[0052] In this embodiment, it also includes step S8. Quality detection: The welded workpiece is subjected to helium detection test, explosion test and salt spray test in turn. The helium detection test ensures that the leakage rate meets the standard, the explosion test ensures that the weld is not cracked, and the salt spray test ensures that the surface is free of corrosion and other phenomena. The helium detection test uses the pressure decay method to ensure that the leakage rate meets the standard; the explosion test raises the pressure to the preset value through the hydraulic system and maintains the pressure, and observes whether the weld is cracked; the salt spray test uses a neutral salt spray solution to ensure that the surface is free of corrosion and other defects. Multi-dimensional detection comprehensively verifies the sealing, strength and corrosion resistance of the weld, ensuring the reliability of the workpiece under complex working conditions and meeting the stringent use requirements of the liquid cooling heat dissipation system and other fields.

[0053] This process solves the problems of insufficient penetration and difficulty in dissolving caused by the difference in copper and aluminum materials by negative clearance tight fitting assembly and hydraulic machine pressing, cooperates with the preset weld design at 1mm outside the copper-aluminum bonding line, realizes the stable combination of the two; solves the collapse problem caused by uneven structure thickness by widening the support plane to 0.85mm and installing a tight fitting plug in the hole to resist the pressure during welding, ensuring the welding effect; the modular elastic clamping structure and adjustable support feet of the preset tooling avoid workpiece displacement and surface indentation, improving the welding stability; post-weld plug removal, deburring and ultrasonic cleaning eliminate the influence of welding slag and burrs on performance; the use of a 10mm diameter stirring tool head increases the penetration, improves the welding stability and prolongs the service life. Combined with multi-dimensional tests including helium detection, explosion, salt spray, high and low temperature impact, etc., the sealing, strength and corrosion resistance of the weld in harsh environments are ensured, meeting the needs of liquid cooling heat dissipation systems and other scenarios, and breaking through the process limit of copper-aluminum double-sided friction stir welding.

[0054] The embodiments of the present application are described above with reference to the drawings, and the embodiments and features in the embodiments of the present application can be combined with each other without conflict, and the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are only illustrative but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and all belong to the protection of the present application.

Claims

1. A copper-aluminum alloy friction stir welding process, characterized in that, This can be achieved by following these steps in sequence: S1. Pressing: A pressure device is used to apply continuous pressure to the areas of the copper and aluminum parts to be welded, so that the surfaces of the two parts to be welded form an initial contact state of tight fit. The copper part is provided with a raised structure on the surface to be welded, and the aluminum part is provided with a matching groove at the corresponding position. The raised and groove are plastically deformed by pressure to achieve a tight fit with a negative gap, while ensuring that the copper and aluminum contact support surfaces form a preset width. S2. Marking: Make positioning marks on the surface of the compressed copper-aluminum assembly, along the starting point, ending point and intermediate key positions of the preset welding trajectory; The positioning marks are formed by mechanical punching to create recesses of a preset shape. The depth of the recesses does not exceed a preset proportion of the workpiece wall thickness and are set at intervals along the welding path to accurately define the spatial position of the welding path. S3. Install the plug: Assemble the special plug into the back hole corresponding to the welding path of the copper-aluminum assembly. The plug and the hole are tightly fitted with an interference fit. The top of the plug is machined to form a support plane of a preset width. This plane is concentrically aligned with the welding path to withstand the downward pressure applied by the stirring head during welding and to prevent the workpiece from collapsing due to uneven thickness. At the same time, the surface of the plug is pre-treated and a heat insulation layer is set to reduce the transfer of welding heat to the support structure. The special plug is made of a preset steel material and has a preset hardness after treatment. The interference fit between the plug and the hole is within a preset range. The assembly process is achieved by a press-fitting machine. The press-fitting force is controlled within a preset range to ensure that the plug is installed firmly and does not damage the workpiece hole. S4. Clamping: The copper-aluminum assembly is clamped and fixed using a pre-set tooling with an arc transition. The tooling has multiple symmetrically distributed clamping structures in the overlapping area of ​​the aluminum part. The workpiece is kept in a stable position by a pre-set clamping force. During the clamping process, ensure that the straightness of the welding path and the parallelism between the copper-aluminum bonding line and the tooling positioning reference meet the preset requirements; the clamping structure of the preset tooling adopts a modular design, and each clamping unit includes an elastic buffer structure, which can generate elastic deformation within a preset range under the action of clamping force, which can not only ensure clamping stability, but also avoid indentation on the workpiece surface. The bottom of the tooling is also equipped with adjustable support feet to adjust the level of the workpiece, so that the flatness error of the welding surface is controlled within the preset range. S5. Welding: Friction stir welding is performed along the preset weld bead using a stirring head of preset diameter. The weld bead is set at a preset distance outside the copper-aluminum bonding line and has a preset width. The preset penetration depth is formed during the rotation of the stirring head. The preset weld depth is achieved through coordinated control of rotation speed and travel speed, enabling the copper and aluminum materials to achieve plastic flow and metallurgical bonding under thermo-mechanical coupling. The stirring head is made of a preset material, the end of the stirring needle has a preset diameter, and the surface is provided with spiral grooves to promote material mixing. The rotation speed, welding travel speed, and downward pressure of the stirring head are all within preset ranges. During welding, the axis of the stirring head maintains a preset tilt angle with the workpiece plane, and the contact area between the shoulder and the workpiece surface is not less than a preset proportion of the total area of ​​the shoulder to ensure heat input and material plasticization effect. The preset weld bead is planned by a computer-aided design system. The weld bead trajectory adopts a linear design based on the structural characteristics of the copper and aluminum parts, and the distribution ratio on both sides of the copper-aluminum bonding line meets preset requirements to adapt to the differences in thermophysical properties of the two materials. S6. Remove the plug: After welding, use a pre-set disassembly tool to remove the back support plug. The contact part between the tool and the plug is designed to fit the structure, and the plug is removed smoothly by applying axial force.

2. The copper-aluminum alloy friction stir welding process as described in claim 1, characterized in that, In step S1, the pressure application device is equipped with a pressure sensing element, which can monitor the pressure value in real time during the pressure application process and feed it back to the control system, so that the applied pressure can be dynamically adjusted within a preset range. When the fit of the copper and aluminum surfaces to be welded reaches a preset ratio or higher, the system automatically maintains the pressure and holds the pressure for a preset time to ensure the stable formation of the negative gap tight fit structure.

3. The copper-aluminum alloy friction stir welding process as described in claim 1, characterized in that, In step S2, the positioning mark is made using a punching tool with a guiding mechanism. The guide rod of the punching tool is kept parallel to the welding trajectory to ensure that the distance deviation between the center of the concave point and the edge of the weld meets the preset standard. The bottom of the concave point is rounded to avoid stress concentration.

4. The copper-aluminum alloy friction stir welding process as described in claim 1, characterized in that, It also includes step S7. Post-weld treatment: After removing the plug, the weld is ultrasonically cleaned for a preset time to remove slag and impurities. Then, a rotary file is used to trim both sides of the weld to remove weld beads that exceed the preset height, so that the surface roughness of the weld reaches below the preset standard.

5. The copper-aluminum alloy friction stir welding process as described in claim 4, characterized in that, In step S5, the welding process is equipped with a temperature monitoring device to monitor the temperature of the welding area in real time, so that the temperature of the copper side and the aluminum side are maintained within their respective preset ranges. When the temperature exceeds the preset range, the system automatically adjusts the rotation speed of the stirring head to ensure that the material is in the best plastic state.

6. The copper-aluminum alloy friction stir welding process as described in claim 1, characterized in that, It also includes step S8. Quality inspection: The welded workpiece is subjected to helium detection test, burst test and salt spray test in sequence. Among them, the helium detection test pressure is within the preset range and the leakage rate does not exceed the preset standard. The burst test pressure reaches the preset value and there is no weld cracking after the preset pressure holding time. After the preset time, there is no corrosion, peeling and coating peeling on the surface in the salt spray test.

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