A wear-resistant and drag-reducing stirring head based on a bionic structure for friction stir welding

Abstract

The application discloses a wear-resistant and drag-reducing stirring head for friction stir welding based on a bionic structure, which is a single structure and comprises a stirring needle, a shaft shoulder, a heat dissipation section and a clamping section, wherein the stirring needle is located at the front end of the shaft shoulder, and the rear end of the shaft shoulder is sequentially connected with the heat dissipation section and the clamping section. The stirring needle is in a conical frustum shape, and cutting flow guide grooves and bionic micro grooves are formed on the side surface of the stirring needle; the bionic micro grooves are in a spiral shape and surround the part of the side surface of the stirring needle without the cutting flow guide grooves in a clockwise direction. The bionic micro groove structure mainly plays a flow guiding role on the plastic metal, can make the plastic metal flow and mix rapidly and sufficiently, reduces the advancing resistance and friction of the stirring head, and prolongs the service life of the stirring needle. The bionic ball pit-shaped non-smooth surface structure on the shaft shoulder reduces the adhesion with the base material, improves the wear resistance and service life.

Description

TECHNICAL FIELD

[0001] The application relates to a friction stir welding tool, in particular to a wear-resistant and drag-reducing friction stir welding tool based on a bionic structure. BACKGROUND

[0002] Friction stir welding is a new solid-phase welding technology, which uses the high temperature generated by the stirring and friction between a high-speed rotating stirring tool and base material to make the metal reach a thermoplastic state, so that the welding connection between metals is realized. Friction stir welding can effectively avoid the welding metallurgical problems such as pores and cracks that occur when aluminum alloy and other metals are welded by melting, has high welding efficiency, is environmentally friendly and non-polluting, and is therefore popularized and applied in the fields of aerospace, new energy vehicles, rail transit and the like. The stirring tool is the key to friction stir welding and is the prerequisite for obtaining a high-quality joint. A conventional stirring tool mainly consists of a shoulder and a stirring pin, and the geometric shape and size of the stirring tool determine the heat input mode and heat generation of the welding process, and also play a role in fully stirring the welded metal and maintaining the welding formation. Restricted by factors such as stirring tool structure design, raw materials and processing technology, the conventional stirring tool has the problems of rapid wear, aluminum adhesion and insufficient stirring of the base material during use, which leads to mismatching of the welding process and defects, and thus affects the welding efficiency and production cost. The special structure of the stirring tool shoulder and stirring pin has high cutting and stirring capacity for plastic metals, but at the same time generates a large friction force and forward resistance, so that the main shaft of the friction stir welding equipment must have a very high rotating torque and forward driving force, and the equipment hardware has high requirements and high investment cost. In view of the above, there is an urgent need for a new friction stir welding tool that can improve the interface characteristics between the stirring tool and the base material and has the characteristics of wear resistance and drag reduction. SUMMARY

[0003] The application aims to solve the above-mentioned problems in the process of friction stir welding, and provides a wear-resistant and drag-reducing friction stir welding tool based on a bionic structure.

[0004] The wear-resistant and drag-reducing friction stir welding tool based on a bionic structure provided by the application is a single structure, and the stirring tool comprises a stirring pin, a shoulder, a heat dissipation section and a clamping section. The stirring pin is located at the front end of the shoulder, and the rear end of the shoulder is sequentially connected with the heat dissipation section and the clamping section.

[0005] The stirring pin is a conical frustum, the diameter of the rear end of the stirring pin is 7mm, the diameter of the front end of the stirring pin is 5mm, and the total length of the stirring pin is in the range of 3-6mm according to the thickness of the welding plate.

[0006] The cutting flow guide grooves are helical and circumferentially arranged on the side of the stirring needle in a clockwise direction, the design pitch of the cutting flow guide grooves is twice the length of the axis of the stirring needle, the length of the cutting flow guide grooves is 0.8 times the length of the axis of the stirring needle, the cross section of the cutting flow guide grooves is semicircular, the diameter of the cross section of the cutting flow guide grooves is 1 mm, the depth of the cutting flow guide grooves is 0.5 mm, three cutting flow guide grooves are arranged on the outer side of the stirring needle at an angle of 120°, and the biomimetic micro groove is helical and circumferentially arranged on the side of the stirring needle without the cutting flow guide grooves in a clockwise direction, the pitch of the biomimetic micro groove is 0.4-0.5 mm, the length of the biomimetic micro groove is 0.9 times the length of the axis of the stirring needle, the structure of the biomimetic micro groove is set by imitating the structure of the micro groove of the scale on the body surface of a shark, the depth of the biomimetic micro groove is 0.2-0.25 mm, the structure of the biomimetic micro groove can effectively reduce the friction and resistance between the stirring needle and the plastic metal, promote the flow of the plastic metal, and improve the welding quality.

[0007] The outer diameter of the shaft shoulder is 16 mm, the outer edge of the shaft shoulder is processed with a 0.5 mm x 45° chamfer, the shaft shoulder is set as a flat surface or an inner concave surface with an angle of not more than 5°, and a involute flow guide groove is further arranged on the shaft shoulder, the involute flow guide groove is arranged in two groups, the two groups of involute flow guide grooves are symmetrically distributed on the shaft shoulder, the cross section of the involute flow guide groove is semicircular with a radius of 0.375-0.5 mm, the depth of the involute flow guide groove is 0.375-0.5 mm, the starting radius of the involute flow guide groove is 4 mm, the turning angle of the involute flow guide groove is from 0° to 360°, the radius increment of the involute flow guide groove is 4 mm, two involute biomimetic strips are arranged between the two groups of involute flow guide grooves along the linear shape of the involute flow guide grooves, a plurality of biomimetic ball pits are uniformly arranged on each involute biomimetic strip, the radius of the biomimetic ball pit is 0.25-0.375 mm, the starting radius of the involute biomimetic strip is 4 mm, the turning angle of the involute biomimetic strip is from 0° to 360°, the radius increment of the involute biomimetic strip is 4 mm, the distance between adjacent biomimetic ball pits on the involute biomimetic strip is 0.25-0.375 mm, the biomimetic ball pit is set by imitating the pit-shaped non-smooth surface on the outer shell of a dung beetle, and the structure of the biomimetic ball pit can significantly improve the interface relationship between the shaft shoulder of the stirring head and the base material, reduce the adhesion between the shaft shoulder and the plastic metal, reduce the friction, and improve the wear resistance and use performance of the stirring head.

[0008] The diameter of the heat dissipation section is 28 mm, the front end of the heat dissipation section is smoothly connected with the shaft shoulder, and a heat dissipation groove is arranged on the outer circular surface of the heat dissipation section, each heat dissipation groove is a trapezoidal groove, the depth of the trapezoidal groove is 0.8-1 mm, the upper width of the trapezoidal groove is 2 mm, the lower width of the trapezoidal groove is 1 mm, four trapezoidal grooves are arranged on the outer circular surface of the heat dissipation section, and the distance between adjacent trapezoidal grooves is 2 mm.

[0009] The clamping section has a diameter of 20mm, and a fastening plane is formed on one side surface of the clamping section, so that the stirring head can be installed on a tool holder of a commonly used friction stir welding device through the fastening plane.

[0010] The stirring head is made of 4Cr5MoSiV1 material, and is subjected to quenching and high-temperature tempering heat treatment, and the overall hardness of the stirring head is HRC 47-50.

[0011] The working principle of the present application is as follows:

[0012] The stirring head for friction stir welding based on the bionic structure is fixed on a 20mm general side top type tool holder of a friction stir welding device or a special mechanical processing device, and is tightly pressed by bolts through the fastening plane during use. During welding, the stirring head rotates at a high speed counterclockwise, and the stirring pin and the shoulder produce intense stirring and friction with the welding material. The cutting guide groove on the side surface of the stirring pin cuts the plastic metal during rotation, and at the same time, drives the plastic metal to transfer from top to bottom along the cutting guide groove; the bionic micro groove on the stirring pin is inspired by the micro groove structure of the shark skin scale, which can improve the fluid structure and flow state of the boundary layer flowing through the surface, reduce the effective friction area and friction strength of the surface and the fluid, significantly reduce the shear pressure on the inner wall of the bionic micro groove, and at the same time, the protrusions between the bionic micro grooves also play a role in inhibiting the lateral flow of the fluid, so that the structure has better drag reduction effect than the smooth surface, and can also play a role in guiding the flow of the plastic metal, so that the plastic metal fully flows and mixes, the resistance to forward movement of the stirring head is reduced, the friction is reduced, and the service life of the stirring pin is improved.

[0013] The shoulder produces a large amount of friction heat by friction with the welding metal, and the involute guide groove on the shoulder can realize the transfer of the plastic metal from outside to inside, so as to ensure that the plastic metal is kept inside the shoulder; the bionic ball pit on the shoulder is inspired by the pit-shaped non-smooth surface feature existing on the surface of the beetle shell, and the introduction of the bionic ball pit can change the flow state of the plastic metal on the surface of the shoulder, reduce the turbulence intensity of the near-surface fluid, and form vortexes at the bottom of the bionic ball pit. These small eddies can act as "rolling bearings" for the plastic metal, so that the plastic metal flowing on the top of the bionic ball pit is subjected to rolling friction, which greatly reduces the friction resistance. Therefore, the structure can effectively reduce the friction and resistance, reduce the torque, reduce the adhesion, improve the wear resistance, improve the service life and the performance of the joint during work.

[0014] The heat dissipation grooves on the heat dissipation section improve the heat dissipation capacity of the device during welding, and also improve the service life and strength of the device to a certain extent. The stirring head provided by this invention is made of 4Cr5MoSiV1 material and, with the help of quenching and high-temperature tempering heat treatment process, has high high-temperature strength, hot hardness and high wear resistance. At the same time, this type of biomimetic stirring head can be processed into different sizes according to the plate thickness, and is suitable for welding non-ferrous metals such as aluminum and magnesium alloys.

[0015] The beneficial effects of this invention are:

[0016] The biomimetic microgroove structure of the stirring pin in the wear-resistant, drag-reducing friction stir welding head provided by this invention primarily guides the flow of ductile metal, enabling rapid and thorough flow and mixing. This reduces the forward resistance and friction of the stirring head, thus extending the service life of the stirring pin. The biomimetic spherical, pitted, non-smooth surface structure on the shoulder continuously generates heat through friction with the welding metal during operation. This unique structure reduces friction and resistance while maintaining the weld shape, lowering torque, reducing adhesion to the base material, and improving wear resistance and service life. The biomimetic stirring head possesses wear-resistant and drag-reducing properties, improving its service life, reducing the hardware requirements of welding equipment, and enhancing the quality of the weld joint. Attached Figure Description

[0017] Figure 1 This is an isometric view of the stirring head described in this invention.

[0018] Figure 2 This is a front view of the stirring head described in this invention.

[0019] Figure 3 This is a front view of the stirring needle described in this invention.

[0020] Figure 4 This is a cross-sectional view of the guide groove cut on the outer side of the stirring pin described in this invention.

[0021] Figure 5 This is a cross-sectional view of the biomimetic microgroove on the outer side of the stirring pin described in this invention.

[0022] Figure 6 This is the front view of the shoulder described in this invention.

[0023] Figure 7 This is a cross-sectional view of the involute flow guide groove and biomimetic spherical pit of the shoulder described in this invention.

[0024] Figure 8 This is a schematic diagram of the heat dissipation section and clamping section of the stirring head described in this invention.

[0025] Figure 9This is a schematic diagram illustrating the use and installation of the stirring head described in this invention.

[0026] The annotations in the image above are as follows:

[0027] 1. Stirring needle 2. Shaft shoulder 3. Heat dissipation section 4. Clamping section 5. Cutting guide groove

[0028] 6. Bionic microgrooves 7. Involute flow guide grooves 8. Involute bionic belts

[0029] 9. Bionic sphere recess; 10. Heat dissipation groove; 11. Fastening surface; 12. Knife handle.

[0030] 13. Bolts. Detailed Implementation

[0031] Please see Figures 1 to 9 As shown:

[0032] The wear-resistant and drag-reducing stirring head for friction stir welding based on a biomimetic structure provided by the present invention is a single structure. The stirring head includes a stirring pin 1, a shoulder 2, a heat dissipation section 3, and a clamping section 4. The stirring pin 1 is located at the front end of the shoulder 2, and the rear end of the shoulder 2 is connected to the heat dissipation section 3 and the clamping section 4 in sequence.

[0033] The stirring pin 1 is truncated cone-shaped, with a rear end diameter of 7mm and a front end diameter of 5mm. The total length of the stirring pin 1 is 3-6mm depending on the thickness of the welding plate.

[0034] The stirring pin 1 has cutting guide grooves 5 and biomimetic microgrooves 6 machined around its side perimeter. The cutting guide grooves 5 are spirally arranged clockwise around the side of the stirring pin 1. The designed pitch of the cutting guide grooves 5 is twice the length of the axis of the stirring pin 1. The length of the cutting guide grooves 5 is 0.8 times the length of the axis of the stirring pin 1. The cross-section of the cutting guide grooves 5 is semi-circular with a diameter of 1 mm and a depth of 0.5 mm. There are three cutting guide grooves 5, which are evenly distributed on the outside of the stirring pin 1 at a 120° angle. Around the perimeter, the biomimetic microgroove 6 is spirally arranged clockwise around the part of the stirring pin 1 where the flow guide groove 5 is not cut. The pitch of the biomimetic microgroove 6 is 0.4-0.5mm, and the machining length of the biomimetic microgroove 6 is 0.9 times the axial length of the stirring pin 1. The structure and shape of the biomimetic microgroove 6 are designed to mimic the microgroove structure of the dermal scutes on the surface of a shark. The depth of the biomimetic microgroove 6 is 0.2-0.25mm. The structure of the biomimetic microgroove 6 can effectively reduce the friction and resistance between the stirring pin 1 and the plastic metal, promote the flow of the plastic metal, and improve the welding quality.

[0035] The outer diameter of shoulder 2 is 16mm. The outer edge of shoulder 2 is machined with a 0.5mm × 45° chamfer. Shoulder 2 is either flat or concave with an inward angle of no more than 5°. Shoulder 2 also has two sets of involute guide grooves 7, symmetrically distributed on shoulder 2. The cross-section of each involute guide groove 7 is a semicircle with a radius of 0.375-0.5mm. The depth of each involute guide groove 7 is 0.375-0.5mm. The initial radius of each involute guide groove 7 is 4mm. The rotation angle of each involute guide groove 7 ranges from 0° to 360°, with a radius increment of 4mm. Along the shoulder between the two sets of involute guide grooves 7, the involute guide grooves extend along the curve of the grooves. The device is equipped with two involute bionic bands 8, each with several bionic spherical pits 9 evenly distributed on it. The radius of the bionic spherical pits 9 is 0.25-0.375mm. The initial radius of the involute bionic band 8 is 4mm. The rotation angle of the involute bionic band 8 ranges from 0° to 360°. The radius increment of the involute bionic band 8 is 4mm. The spacing between adjacent bionic spherical pits 9 on the involute bionic band 8 is 0.25-0.375mm. The bionic spherical pits 9 are designed to mimic the pitted, non-smooth surface of a dung beetle's shell. The structure of the bionic spherical pits 9 can significantly improve the interface relationship between the stirring head shoulder 2 and the base material, reduce the adhesion between the shoulder 2 and the plastic metal, reduce friction, and improve the wear resistance and performance of the stirring head.

[0036] The diameter of heat dissipation section 3 is 28mm. The front end of heat dissipation section 3 smoothly transitions to the shoulder 2. Heat dissipation grooves 10 are machined around the outer circular surface of heat dissipation section 3. Each heat dissipation groove 10 is a trapezoidal groove with a depth of 0.8-1mm, a width of 2mm at the top and 1mm at the bottom. A total of four trapezoidal grooves are machined on the outer circular surface of heat dissipation section 3, with a spacing of 2mm between adjacent trapezoidal grooves.

[0037] The diameter of the clamping section 4 is 20mm. One side of the clamping section 4 is machined with a fastening plane 11, which allows the stirring head to be mounted on the handle of a commonly used friction stir welding equipment.

[0038] The stirring head is made of 4Cr5MoSiV1 material and undergoes quenching and high-temperature tempering heat treatment. The overall hardness of the stirring head is HRC47-50.

[0039] Working principle of the invention:

[0040] The present invention provides a wear-resistant and drag-reducing stirring head for friction stir welding based on a biomimetic structure. During use, it is fixed to a 20mm universal side-mounted tool holder 12 on a friction stir welding device or a specialized machining equipment, and tightened by bolts 13 through a fastening plane 11. During welding, the stirring head rotates counterclockwise at high speed, and the stirring pin 1 and shoulder 2 generate intense stirring and friction with the welding material. The cutting and guiding grooves 5 on the side of the stirring pin 1 cut and stir the plastic metal during rotation, while simultaneously driving the plastic metal to transfer from top to bottom along the cutting and guiding grooves 5. The biomimetic microgrooves 6 on the stirring pin 1 are inspired by the microgroove structure of shark dermal scutes. This structure can improve the fluid structure and flow state flowing through its surface boundary layer, reduce the effective friction area and friction intensity between the surface and the fluid, and significantly reduce the shear pressure on the inner wall of the biomimetic microgrooves 6. At the same time, the protrusions between the biomimetic microgrooves 6 also play a role in inhibiting the lateral flow of the fluid. Therefore, this structure has a better drag reduction effect than a smooth surface, and can also guide the flow of plastic metal, allowing the plastic metal to flow and mix fully, reducing the forward resistance of the stirring head, reducing friction, and improving the service life of the stirring pin 1.

[0041] The shoulder 2 generates significant frictional heat due to friction with the welded metal. The involute guide groove 7 on the shoulder 2 facilitates the transfer of ductile metal from the outside in, ensuring that the ductile metal is retained within the shoulder 2. The biomimetic spherical recesses 9 on the shoulder 2 mimic the pitted, non-smooth surface features of a dung beetle's shell. The introduction of these recesses alters the flow state of the ductile metal on the shoulder 2 surface, reduces the turbulence intensity of the near-surface fluid, and creates vortices at the bottom of the recesses. These small vortices act as "rolling bearings" for the ductile metal, subjecting the ductile metal flowing over the top of the recesses to rolling friction, significantly reducing frictional resistance. Therefore, this structure effectively reduces friction and resistance, lowers torque, reduces adhesion, improves wear resistance, extends service life, and enhances joint performance during operation.

[0042] The heat dissipation grooves 10 on the heat dissipation section 3 improve the heat dissipation capacity of the device during welding, and also improve the service life and intensity of the device to a certain extent. The stirring head provided by this invention is made of 4Cr5MoSiV1 material and, with the help of quenching and high-temperature tempering heat treatment process, has high high-temperature strength, hot hardness and high wear resistance. At the same time, this type of biomimetic stirring head can be processed into different sizes according to the plate thickness, and is suitable for welding non-ferrous metals such as aluminum and magnesium alloys.

Claims

1. A wear-resistant and drag-reducing stirring head for friction stir welding based on a biomimetic structure, the stirring head being a single-unit structure, comprising a stirring pin, a shoulder, a heat dissipation section, and a clamping section, wherein the stirring pin is located at the front end of the shoulder, and the rear end of the shoulder is sequentially connected to the heat dissipation section and the clamping section, characterized in that: The stirring pin is truncated cone-shaped, with a rear end diameter of 7mm and a front end diameter of 5mm. The total length of the stirring pin ranges from 3-6mm depending on the thickness of the welding plate. The stirring pin has circumferentially machined cutting guide grooves and biomimetic microgrooves. The cutting guide grooves are spiral-shaped, winding clockwise around the side of the stirring pin. The designed pitch of the cutting guide grooves is twice the length of the stirring pin's axis, and the machined length of the cutting guide grooves is 0.8 times the length of the stirring pin's axis. The cross-section of the cutting guide grooves is semi-circular, with a diameter of 1mm and a depth of 0.5mm. Three cutting guide grooves are provided. The biomimetic microgrooves are evenly distributed around the outer surface of the stirring pin at a 120° angle. They spiral clockwise around the uncut sections of the stirring pin. The pitch of the microgrooves is 0.4-0.5 mm, and their machining length is 0.9 times the length of the stirring pin's axis. The shape of the microgrooves mimics the microgrooves on the dermal scutes of a shark. The depth of the microgrooves is 0.2-0.25 mm. The outer diameter of the shoulder is 16 mm, and the outer edge of the shoulder is chamfered at 0.5 mm × 45°. The shoulder is either flat or concave with an involute flow-guiding groove. Two sets of involute flow guide grooves are symmetrically distributed on the shoulder. The cross-section of each involute flow guide groove is a semi-circle with a radius of 0.375-0.5 mm, a depth of 0.375-0.5 mm, and an initial radius of 4 mm. The rotation angle of the involute flow guide grooves ranges from 0° to 360°, with a radius increment of 4 mm. On the shoulder between the two sets of involute flow guide grooves, two involute biomimetic bands are arranged in line with the shape of the involute flow guide grooves. Each involute biomimetic band has several biomimetic spherical pits evenly distributed on it, with a radius of 0.25-0.375 mm. The initial radius of each involute biomimetic band is 4 mm. The diameter is 4mm, the involute bionic belt has a rotation angle from 0° to 360°, the radius increment of the involute bionic belt is 4mm, the spacing between adjacent bionic sphere pits on the involute bionic belt is 0.25-0.375mm, and the bionic sphere pits are designed to mimic the pitted, non-smooth surface of the dung beetle shell; the diameter of the heat dissipation section is 28mm, the front end of the heat dissipation section smoothly transitions to the shoulder, the outer circular surface of the heat dissipation section is machined with heat dissipation grooves, each heat dissipation groove is a trapezoidal groove with a depth of 0.8-1mm, a width of 2mm at the top of the trapezoidal groove, and a width of 1mm at the bottom of the trapezoidal groove. A total of four trapezoidal grooves are machined on the outer circular surface of the heat dissipation section, and the spacing between adjacent trapezoidal grooves is 2mm.

2. The wear-resistant and drag-reducing stirring head for friction stir welding based on a biomimetic structure according to claim 1, characterized in that: The clamping section has a diameter of 20mm, and one side of the clamping section is machined with a fastening plane, which allows the stirring head to be mounted on the handle of a commonly used friction stir welding device.

3. The wear-resistant and drag-reducing stirring head for friction stir welding based on a biomimetic structure according to claim 1, characterized in that: The stirring head is made of 4Cr5MoSiV1 material and undergoes quenching and high-temperature tempering heat treatment. The overall hardness of the stirring head is HRC47-50.

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