Ultrasonic-assisted double-shaft-shoulder friction stir welding device and method with magnetic field

Abstract

An ultrasonic-assisted double-shaft-shoulder friction stir welding method and device with a magnetic field. Ultrasonic vibration generated by an ultrasonic transducer (12) acts on weld metal via transmission by means of a lower shaft shoulder (2), a lower magnet placement hole (10) is provided in the top of the ultrasonic transducer (12), and a magnetic-field generation apparatus is formed by a powerful magnet (11) installed in the lower magnet placement hole (10) and a powerful magnet (11) arranged in an upper magnet placement hole (4) in an upper shaft shoulder (1) to generate a magnetic field, thereby achieving magnetic field and ultrasonic-assisted friction stir welding. The magnetic field and an ultrasonic field are jointly applied, such that the plasticization resistance of materials during a welding process is reduced, plastic deformation and plastic flow of the weld metal are promoted, the residual stress is reduced, recrystallization nucleation of a weld nugget area is promoted, grains are refined, the macroscopic and microscopic segregation effect of the metal is improved, and the comprehensive mechanical property of a joint is enhanced.

Description

Ultrasonic-assisted dual-shoulder friction stir welding equipment and method with magnetic field Technical Field

[0001] The invention belongs to the technical field of friction stir welding, and in particular relates to an ultrasonic-assisted double-shoulder friction stir welding method and equipment with a magnetic field. Background Art

[0002] Friction stir welding is an environmentally friendly solid-phase joining technology. The high-speed rotating stirring head generates frictional heat at the contact point with the workpiece, causing the surrounding metal to form a plastic softening layer. The softened layer metal fills the cavity formed behind the stirring needle under the action of the rotating stirring head, and the material connection is achieved under the stirring and extrusion action of the stirring head shoulder and the stirring needle. It has broad application prospects in industrial manufacturing fields such as aviation, aerospace, shipbuilding, nuclear industry, and transportation. However, during the friction stir welding process, the shoulder needs to apply high pressure, which generates a large amount of frictional heat and plastic deformation. The stirring needle is easy to wear, and the frictional heat can easily cause the fine grains after plastic deformation to grow into coarse grains, resulting in uneven structure and reducing the strength and plasticity of the weld joint.

[0003] To improve weld quality and enhance joint mechanical properties, patent CN114083107A discloses a magnetic surround-type dual-shoulder friction stir welding tool and its installation method. These tools enhance the fluidity of the metal at the bottom of the weld, refine the weld grain, and improve welding efficiency. Patent CN116021141A discloses an ultrasonic composite friction stir welding device and method. These tools reduce the material's plasticization resistance during welding, promote plastic deformation and plastic flow of the weld metal, refine the grain, and improve joint performance.

[0004] Existing technologies for improving joint weld performance mostly rely on single magnetic field or ultrasonic assistance, which are inefficient, ineffective, and complex to install. Therefore, a new composite-assisted friction stir welding method is urgently needed to address the shortcomings of existing technologies and achieve high-performance welded joints.

[0005] Summary of the Invention

[0006] The present invention addresses the shortcomings of existing technologies by providing a magnetic field-assisted, ultrasonically assisted dual-shoulder friction stir welding device and method. This solution addresses existing challenges such as low efficiency, limited improvement in joint performance, and complex equipment installation.

[0007] The present invention is achieved through the following technical implementations.

[0008] The present invention provides an ultrasonic-assisted double-shoulder friction stir welding device with a magnetic field, comprising a double-shoulder device, a detachable stirring needle, a magnetic field generating device, and an ultrasonic generating device. The double-shoulder device comprises an upper shoulder and a lower shoulder, wherein the upper shoulder is connected to the main shaft of the friction stir welding machine to obtain rotational kinetic energy, the lower end of the upper shoulder is provided with an upper shoulder internal thread connected to the upper external thread of the detachable stirring needle, and the upper shoulder is built-in with an upper magnet placement hole for placing a powerful magnet. The detachable stirring needle is connected to the upper shoulder internal thread and the lower shoulder internal thread respectively through an external thread, with the stirring needle thread area in the middle. The lower shoulder is divided into an inner part and an outer part, wherein a ball is installed in the inner part, and the outer part of the lower shoulder wraps the inner part, with a gap of 1 mm in the middle. The lower shoulder is provided with a lower shoulder internal thread inside, which is connected to the lower external thread of the detachable stirring needle. The ball ensures that the inner part of the lower shoulder rotates with the stirring needle, while the outer part of the lower shoulder remains stationary. The lower shoulder is provided with a magnetic device, and the upper end of the ultrasonic generating device is provided with a magnetic device. The lower shoulder and the ultrasonic generating device are connected via the magnetic device at the upper end of the ultrasonic generating device and the magnetic device at the lower end of the lower shoulder. The ultrasonic generating device includes an ultrasonic transducer, an ultrasonic transmission cable, and an ultrasonic power supply. The ultrasonic transmission cable connects the ultrasonic power supply and the ultrasonic transducer, and the ultrasonic vibration generated by the ultrasonic transducer is transmitted through the lower shoulder to act on the weld metal. The ultrasonic transducer has a lower magnet mounting hole. A magnetic field generating device is formed by a strong magnet installed in the lower magnet mounting hole and a strong magnet built into the upper magnet mounting hole of the upper shoulder to generate a magnetic field, thereby achieving magnetic field and ultrasonic assisted friction stir welding.

[0009] Preferably, the detachable stirring needle is made of wear-resistant and high-temperature resistant tungsten alloy.

[0010] Preferably, the powerful magnets are all neodymium iron boron magnets, the powerful magnets are all cylindrical, and the powerful magnets are all axially magnetized structures.

[0011] Preferably, the strong magnet N-pole is placed in the upper magnet placement hole facing downward, and the strong magnet S-pole is placed in the lower magnet placement hole facing upward, forming a phenomenon in which opposite magnetic poles attract each other, which can enhance the magnetic field strength.

[0012] The present invention also provides an ultrasonic-assisted dual-shaft shoulder friction stir welding method with a magnetic field, the steps of which are as follows:

[0013] S1. Select a detachable stirring needle of appropriate length according to the thickness of the welded part. The thickness of the welded part should be equal to the length of the stirring needle thread.

[0014] S2. Assemble the double-shoulder device, the detachable stirring needle, the magnetic field generating device, and the ultrasonic generating device into the ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field.

[0015] S3. Clamp the workpiece on the clamping table, align the detachable stirring needle with the weld position, and tightly fit the upper shoulder 1 and the lower shoulder 2 with the upper and lower surfaces of the workpiece respectively.

[0016] S4. Set the welding parameters, mainly including the stirring head speed and welding speed. According to the requirements of the welding material, select a strong magnet with a strength in the range of 0.5T-1.6T, set the ultrasonic frequency to 5-15kW and the power to 15-30kHz, and start the welding equipment.

[0017] S5. The upper shoulder, the detachable stirring needle and the inner part of the lower shoulder are driven to rotate by the main shaft of the friction stir welding machine. The outer part of the lower shoulder is tightly fitted with the lower surface of the weldment and keeps sliding along the welding direction.

[0018] S6. Complete welding along the weld trajectory and realize magnetic field and ultrasonic composite assisted friction stir welding.

[0019] The beneficial effects brought about by the technical solution of the present invention are:

[0020] 1. This invention utilizes a dual external field, magnetic and ultrasonic, to assist friction stir welding. These dual fields act on the same axis, promoting plastic flow of metal in the weld, reducing defects, and improving weld microstructure. This addresses the issues of low efficiency and limited microstructure improvement associated with single external field assistance. The magnetic and ultrasonic fields are independently controlled and do not interfere with each other, allowing for different field combinations to be configured according to process requirements.

[0021] 2. The device of the present invention exists independently and does not affect the setting of welding speed and stirring head speed.

[0022] 3. The stirring needle of the present invention is detachable, and stirring needles of different sizes can be selected according to the thickness of the plate. The stirring needle is made of high-temperature resistant tungsten alloy. The stirring needle is easy to replace when it is worn, and the stirring needle can be quickly and low-cost replaced.

[0023] 4. This invention utilizes a dual-shoulder design, with the upper shoulder rotating and the lower shoulder stationary. This eliminates the need for complex welding fixtures and enables friction stir welding of pipes. The upper and lower shoulders maintain stable pressure on the base metal, ensuring consistent welding heat input and improving weld joint quality.

[0024] 5. The equipment of the present invention has a simple structure, is easy to install, easy to promote, and has good welding joint performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic diagram of the three-dimensional structure of the device of the present invention;

[0026] FIG2 is a schematic structural diagram of the device of the present invention;

[0027] FIG3 is a cross-sectional view of a shaft shoulder on the device of the present invention;

[0028] FIG4 is a cross-sectional view of a stirring needle of the device of the present invention;

[0029] FIG5 is a schematic diagram of the three-dimensional structure of the lower shoulder of the device of the present invention;

[0030] FIG6 is a schematic diagram of the external three-dimensional structure of the lower shoulder of the device of the present invention;

[0031] FIG7 is a schematic diagram of the three-dimensional structure of the lower shoulder of the device of the present invention;

[0032] FIG8 is a schematic structural diagram of an ultrasonic generating device of the present invention;

[0033] FIG9 is a SEM image of the welded composite material of Example 1.

[0034] FIG10 is an SEM image of the welded composite material of Comparative Example 1.

[0035] In the figure: 1-upper shoulder, 2-lower shoulder, 3-upper shoulder internal thread, 4-upper magnet placement hole, 5-lower shoulder internal thread, 6-ball, 7-magnetic device, 8-external thread, 9-stirring needle thread, 10-lower magnet placement hole, 11-strong magnet, 12-ultrasonic transducer, 13-ultrasonic transmission cable, 14-ultrasonic power supply, 15-screw. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to specific embodiments and drawings, but is not limited thereto.

[0037] As shown in Figures 1 to 8, an ultrasonic-assisted double-shoulder friction stir welding device with a magnetic field includes a double-shoulder device, a detachable stirring needle, a magnetic field generating device, and an ultrasonic generating device. The double-shoulder device includes an upper shoulder 1 and a lower shoulder 2. The upper shoulder 1 is connected to the main shaft of the stir friction welding machine through an upper screw 15 to obtain rotational kinetic energy. The lower end of the upper shoulder 1 is provided with an upper shoulder internal thread 3 connected to the upper external thread 8 of the detachable stirring needle. The upper shoulder 1 has a built-in upper magnet placement hole 4, which can accommodate a strong magnet 11. The detachable stirring needle is connected to the upper shoulder internal thread 3 and the lower shoulder internal thread 5 respectively through the external thread 8, with the stirring needle thread 9 area in the middle. The lower shoulder 2 is divided into an inner part and an outer part, with a ball 6 installed inside. The outer part of the lower shoulder 2 wraps the inner part, and the gap in the middle is 1mm. The lower shoulder 2 is provided with a lower shoulder internal thread 5, which is connected to the lower external thread 8 of the detachable stirring needle. The ball 6 ensures that the inner part of the lower shoulder rotates with the stirring needle, and the outer part of the lower shoulder remains stationary. A magnetic attraction device 7 is provided at the bottom end of the lower shoulder 2, and a magnetic attraction device 7 is provided at the top end of the ultrasonic generating device. The lower shoulder and the ultrasonic generating device are connected via the magnetic attraction device 7 at the top end of the ultrasonic generating device and the magnetic attraction device 7 at the bottom end of the lower shoulder 2. The ultrasonic generating device includes an ultrasonic transducer 12, an ultrasonic transmission cable 13, and an ultrasonic power supply 14. The ultrasonic transmission cable 13 connects the ultrasonic power supply 14 and the ultrasonic transducer 12. The ultrasonic vibration generated by the ultrasonic transducer 12 is transmitted through the lower shoulder 2 to act on the weld metal. The ultrasonic transducer 12 has a lower magnet mounting hole 10. A magnetic field generating device is formed by a strong magnet 11 installed in the lower magnet mounting hole 10 and a strong magnet 11 built into the upper magnet mounting hole 4 of the upper shoulder 1 to generate a magnetic field, thereby achieving magnetic field and ultrasonic assisted friction stir welding.

[0038] The double-shoulder device provided by the present invention is suitable for plate welding and pipe welding without rigid pad support. The welding machine can drive the upper shoulder 1 to rotate and the lower shoulder 2 to slide along the welding direction. By selecting a detachable stirring needle suitable for the plate thickness, the upper and lower shoulders are connected to form a stirring head combination of different specifications. The magnetic field generating device and ultrasonic generating device provided by the present invention realize that during the stir friction welding process, the magnetic field and ultrasonic field move synchronously with the stirring head. Different from the existing single external field auxiliary welding device, the single external field is not enough to fully promote the plastic fluidity of the material during solid-state welding. The magnetic field and ultrasonic field are applied together to reduce the plasticization resistance of the material during welding, promote the plastic deformation and plastic flow of the weld metal, reduce residual stress, promote recrystallization nucleation in the weld core zone, refine the grains, improve the macro- and micro-segregation effects of the metal, and improve the comprehensive mechanical properties of the joint.

[0039] The detachable stirring needle is made of wear-resistant and high-temperature resistant tungsten alloy.

[0040] The powerful magnets 11 are all neodymium iron boron magnets, are all cylindrical, and have an axially magnetized structure.

[0041] The strong magnet N-level placed in the upper magnet placement hole 4 faces downward, and the strong magnet S-level placed in the lower magnet placement hole 10 faces upward, forming a magnetic field with opposite poles. The convergence of magnetic lines of force can enhance the magnetic field strength.

[0042] Example 1

[0043] The installation and welding method of the ultrasonic-assisted dual-shoulder friction stir welding equipment with a magnetic field is as follows:

[0044] S1. The welding plate is 3 vol.% (ZrB2+Al2O3) / 7085 aluminum-based composite material with a plate size of 120×45×4 mm and a plate thickness of 4 mm. A stirring needle with a thread area length of 4 mm is selected.

[0045] S2. Assemble the double-shoulder device, the detachable stirring needle, the magnetic field generating device, and the ultrasonic generating device into the ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field.

[0046] S3. Then the weldment is clamped on the clamping table, the detachable stirring needle is aligned with the weld position, and the upper shoulder 1 and the lower shoulder 2 are tightly fitted with the upper surface and the lower surface of the weldment in a clamped state.

[0047] S4. Set the welding parameters: stirring head speed to 1200 rpm, welding speed to 120 mm / min, magnetic field device to generate a constant magnetic field of 0.5 T, ultrasonic power to 10 kW, and ultrasonic frequency to 20 kHz. Start the welding equipment.

[0048] S5. The upper shoulder 1, the detachable stirring needle and the inner part of the lower shoulder are driven to rotate by the main shaft of the friction stir welding machine. The outer part of the lower shoulder is tightly fitted with the lower surface of the weldment and keeps sliding along the welding direction.

[0049] S6. Complete welding along the weld trajectory and realize magnetic field and ultrasonic composite assisted friction stir welding.

[0050] FIG9 is a SEM image of 3 vol.% (ZrB2+Al2O3) / 7085 aluminum-based composite material welded by the apparatus of the present invention. The nanoparticles are more dispersed in the welding area, the agglomeration phenomenon is reduced, and the welding defects are reduced.

[0051] Comparative Example 1

[0052] The welding plate is 3vol.% (ZrB2+Al2O3) / 7085 aluminum-based composite material with a plate size of 120×45×4mm and a plate thickness of 4mm. The stirring head speed is 1200r / min, the welding speed is 120mm / min, and the existing stir friction welding device is used for flat plate butt welding, which is different from welding without applying external field auxiliary.

[0053] FIG10 is a SEM image of 3 vol.% (ZrB2+Al2O3) / 7085 aluminum matrix composite material by friction stir welding without external field assistance.

Claims

1. An ultrasonic-assisted double-shoulder friction stir welding device with a magnetic field, characterized in that: The equipment includes a double-shoulder device, a detachable stirring needle, a magnetic field generating device, and an ultrasonic generating device; the double-shoulder device includes an upper shoulder and a lower shoulder, the upper shoulder is connected to the main shaft of the stir friction welding machine to obtain rotational kinetic energy, the lower end of the upper shoulder is provided with an upper shoulder internal thread connected to the upper external thread of the detachable stirring needle, the upper shoulder has a built-in upper magnet placement hole for placing a strong magnet; the detachable stirring needle is connected to the upper shoulder internal thread and the lower shoulder internal thread respectively through the external thread, and the middle is the stirring needle thread area; the lower shoulder is divided into an inner and an outer part, the inner part is installed with a ball, and the outer part of the lower shoulder wraps the inner part; the lower shoulder is provided with a lower shoulder internal thread, and the lower shoulder internal thread is connected to the lower external thread of the detachable stirring needle, and the ball ensures that the inner part of the lower shoulder As the stirring needle rotates, the outside of the lower shoulder remains stationary; a magnetic device is provided at the bottom end of the lower shoulder, and a magnetic device is provided at the upper end of the ultrasonic generating device, and the lower shoulder and the ultrasonic generating device are connected by the magnetic device at the upper end of the ultrasonic generating device and the magnetic device at the bottom end of the lower shoulder; the ultrasonic generating device includes an ultrasonic transducer, an ultrasonic transmission cable, and an ultrasonic power supply; the ultrasonic transmission cable connects the ultrasonic power supply and the ultrasonic transducer, and the ultrasonic vibration generated by the ultrasonic transducer acts on the weld metal through the transmission of the lower shoulder, the ultrasonic transducer has a lower end magnet placement hole, and a magnetic field generating device is formed by a strong magnet installed in the lower end magnet placement hole and a strong magnet built into the upper end magnet placement hole of the upper shoulder to generate a magnetic field, thereby realizing magnetic field and ultrasonic assisted friction stir welding.

2. The ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field according to claim 1, characterized in that: The gap between the outer side of the lower shoulder and the inner side of the lower shoulder is 1 mm.

3. The ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field according to claim 1, characterized in that: The detachable stirring needle is made of wear-resistant and high-temperature resistant tungsten alloy.

4. The ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field according to claim 1, characterized in that: The powerful magnets are all neodymium iron boron magnets, the powerful magnets are all cylindrical, and the powerful magnets are all axially magnetized structures.

5. The ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field according to claim 1, characterized in that: The strong magnet placed in the upper magnet placement hole has its N pole facing downward, and the strong magnet placed in the lower magnet placement hole has its S pole facing upward, forming a phenomenon in which opposite magnetic poles attract each other, which can enhance the magnetic field strength.

6. A method for implementing ultrasonic-assisted double-shoulder friction stir welding with a magnetic field using the apparatus according to claim 1, characterized in that: The specific steps are as follows: S1. Select a detachable stirring pin of appropriate length according to the thickness of the welded part. The thickness of the welded part should be equal to the thread length of the stirring pin. S2, assembling the double-shoulder device, the detachable stirring needle, the magnetic field generating device, and the ultrasonic generating device into the ultrasonic-assisted double-shoulder friction stir welding equipment with a magnetic field; S3. Clamp the workpiece on the clamping table, align the detachable stirring needle with the weld position, and tightly fit the upper shoulder 1 and the lower shoulder 2 with the upper and lower surfaces of the workpiece respectively; S4. Set the welding parameters, including the stirring head speed, welding speed, select a strong magnet according to the requirements of the welding material, set the ultrasonic frequency and power, and start the welding equipment; S5. The upper shoulder, the detachable stirring needle and the inner part of the lower shoulder are driven to rotate by the main shaft of the friction stir welding machine. The outer part of the lower shoulder is in close contact with the lower surface of the weldment and keeps sliding along the welding direction. S6. Complete welding along the weld trajectory and realize magnetic field and ultrasonic composite assisted friction stir welding.

7. The method according to claim 6, wherein In step S4, the strength of the strong magnet is in the range of 0.5T-1.6T; the ultrasonic frequency is 5-15kW, and the power is 15-30kHz.

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