Self-punching friction rivet and friction welding system

Abstract

The utility model relates to a self-punching friction rivet and a friction welding system, the self-punching friction rivet comprises a rivet cover and a rivet body, the rivet cover comprises a connecting part suitable for being connected with a driving device and an abutting part suitable for abutting against a piece to be connected, and the abutting part is provided with a first containing cavity suitable for containing the piece to be connected. The nail body is connected with the nail cover, the nail body and the nail cover jointly define a second containing cavity, first threads are arranged on the outer side face of the nail body, and second threads are arranged on the inner wall of the second containing cavity. The self-punching friction rivet is driven by external equipment to abut against a to-be-connected piece and rotate, friction heat is generated to soften the to-be-connected piece, the rivet body penetrates through the upper-layer to-be-connected piece under the action of axial pressure, part of redundant materials of the upper-layer to-be-connected piece are extruded out and flow into the first containing cavity, meanwhile, the contact area between the rivet body and the upper-layer to-be-connected piece is increased, and the service life of the rivet body is prolonged. The flowing direction and position of redundant materials are effectively controlled, and the connection reliability is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of automobile manufacturing, in particular to a self-piercing friction rivet and a friction welding system. Background Art

[0002] With the continuous development of intelligent and electrified passenger cars and the increasing demand of users for new functions and requirements of cars, the equipment weight of new energy vehicles is also increasing. In addition, affected by the new energy three-electric system, the equipment weight of new energy vehicles is 15% to 30% heavier than that of fuel vehicles of the same level. The increase in the equipment weight of the whole vehicle is bound to increase the driving energy consumption and reduce the cruising range, so lightweighting is an inevitable trend in the development of new energy vehicles.

[0003] At present, a hot technology in the industry to achieve lightweight new energy vehicles is to use integrated die-cast aluminum alloy structural parts to replace the original body steel plate stamping and welding parts. However, due to the mechanical properties of die-cast aluminum alloys compared with high-strength steel and ultra-high-strength steel, there is still a gap. Considering the maintenance convenience and maintenance cost of die-cast aluminum alloy parts after collision, steel parts will continue to be used in the body for a long time. Moreover, according to the current development trend of the industry, the current development trend of the body "lower aluminum and upper steel" is relatively obvious. Therefore, the application of large die-cast aluminum alloy structural parts needs to consider the difficulty of steel-aluminum connection, and needs to be matched with matching connection technology. At present, SPR and FDS are the most widely used connection technologies for die-cast aluminum structural parts. These two technologies have certain advantages, but they also have certain limitations: First, for SPR, different types of rivets and rivet molds need to be matched according to the strength and thickness of the connected steel plates, which increases the cost of procurement and on-site production, consumes more manpower and material resources, and there are still certain difficulties in connecting with ultra-high-strength steel or hot-formed steel. At the same time, for large or larger-sized ultra-large die-cast structural parts such as integrated die-cast rear floors and integrated die-cast front cabins, due to the current pressure The limitations of casting process, etc., can easily cause difficulty in filling the edge of the die-casting mold and uneven composition of the die-cast parts during the die-casting process, resulting in large fluctuations in the material properties of the structural parts connection area, especially the elongation. The elongation at some locations is poor, only 3%~5%, which cannot meet the elongation requirements of SPR self-piercing riveting, and easily lead to serious riveting cracks on one side of the cast aluminum. For FDS connection technology, it can achieve connection between cast aluminum and ultra-high-strength steel or hot-formed steel, but it will leave higher convex points on one side, affecting the appearance. At the same time, the sealing is not as good as SPR, and it cannot be used in areas on the chassis with high sealing requirements. Utility Model Content

[0004] Based on this, it is necessary to provide a self-piercing friction rivet and a friction welding system to address the above problems.

[0005] The present application provides a self-piercing friction rivet, comprising a nail cover and a nail body, wherein the nail cover comprises a connecting portion suitable for connecting a driving device, and an abutting portion suitable for abutting a to-be-connected piece, wherein the abutting portion has a first accommodating cavity suitable for accommodating a piece to be connected. The nail body is connected to the nail cover, and the nail body and the nail cover together enclose a second accommodating cavity, a first thread is provided on the outer surface of the nail body, and a second thread is provided on the inner wall of the second accommodating cavity. The self-piercing friction rivet abuts against the to-be-connected piece and rotates under the drive of an external device, generating friction heat to soften the to-be-connected piece, and the nail body penetrates the upper layer of the to-be-connected piece under the action of axial pressure, and part of the excess material of the upper layer of the to-be-connected piece is squeezed out and flows into the first accommodating cavity.

[0006] In one of the embodiments, an abutment structure for increasing the contact area with the piece to be connected is provided on the end of the nail body that contacts the piece to be connected.

[0007] In one of the embodiments, the abutment structure penetrates the upper part to be connected and contacts the upper surface of the lower part to be connected before stopping pressing down, and continues to rotate under the drive of an external device to generate friction heat and melt the lower part to be connected. The abutment structure is upset and plastically deformed under the action of axial pressure and welded to the lower part to be connected to form a solid phase connection.

[0008] In one embodiment, the first thread and / or the second thread is a self-locking thread.

[0009] In one embodiment, the nail body is a hollow structure.

[0010] In one embodiment, the nail cover is integrally connected to the nail body.

[0011] In one embodiment, the types of the first thread and the second thread are adapted to the thickness of the upper and lower parts to be connected, and to the mechanical properties of the connection between the parts to be connected.

[0012] In one of the embodiments, a fixing structure is provided on the connecting portion of the nail cover, and the fixing structure is suitable for fixedly connecting to a driving device.

[0013] In one embodiment, the nail cover is coaxially arranged with the nail body.

[0014] The present application also provides a friction welding system, comprising the above-mentioned self-piercing friction rivet, a driving device, an upper layer of parts to be connected and a lower layer of parts to be connected, wherein the upper layer of parts to be connected is an aluminum plate, and the lower layer of parts to be connected is a steel plate.

[0015] The design of the nail cover of the self-piercing friction rivet takes into account the connection with the driving device, and the design of the abutment portion can effectively abut against the part to be connected, and provide sufficient support force to ensure stability during the connection process. The nail body is connected to the nail cover to form a second accommodating chamber together. The outer surface of the nail body is provided with a first thread, and the inner wall of the second accommodating chamber is provided with a second thread. The nail body is mainly subjected to axial pressure and rotational friction during the connection process, and the first thread and the second thread ensure the firmness and stability of the connection. The first accommodating chamber is mainly used to store the excess material squeezed out by the nail body during the connection process, while increasing the contact area with the upper layer of the part to be connected, effectively controlling the flow direction and position of the excess material, and improving the reliability of the connection. During the connection process, the self-piercing friction rivet is driven by an external device to abut against the part to be connected with a certain axial pressure and rotation speed. In this process, friction heat is generated, softening the material of the part to be connected. As the nail body penetrates the upper layer of the part to be connected, part of the excess material is squeezed out and flows into the first accommodating chamber, ensuring the firmness and stability of the connection. The rivet does not require prefabricated holes, can realize the connection of aluminum plates with ultra-high-strength steel or hot-formed steel, and has a wider range of applications. This means that it is suitable for the connection needs of a variety of different materials and structures, providing more options for various engineering applications. The riveted joint is a non-through joint, which has better sealing than FDS and can achieve connection with a closed cavity. This design makes the rivet suitable for application scenarios where sealing needs to be maintained, such as automotive body structure or aerospace. The rivet uses friction heat to soften the upper cast aluminum material during the connection process, effectively solving the problem of easy cracking of the riveted joint due to the low edge elongation of large die-cast aluminum structural parts. This design makes the riveting process more stable and reliable, and improves the quality and durability of the connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a structural diagram of a self-piercing friction rivet provided in one embodiment of the present application;

[0017] FIG2 is a cross-sectional view of a self-piercing friction rivet provided in one embodiment of the present application;

[0018] FIG. 3 is a cross-sectional schematic diagram of a friction welding system provided in an embodiment of the present application.

[0019] Description of reference numerals:

[0020] 100-nail cover; 110-first accommodating cavity;

[0021] 200-nail body; 210-second accommodating cavity; 220-first thread; 230-second thread;

[0022] 300- upper layer to be connected;

[0023] 400-Lower layer parts to be connected. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the utility model. However, the utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the utility model, so the utility model is not limited by the specific embodiments disclosed below.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0029] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0030] Referring to Fig. 1 and Fig. 2, an embodiment of the utility model provides a self-piercing friction rivet, comprising a nail cover 100 and a nail body 200, wherein the nail cover 100 comprises a connecting portion suitable for connecting a driving device, and an abutting portion suitable for abutting a to-be-connected member, wherein the abutting portion has a first accommodating cavity 110 suitable for accommodating a member to be connected. The nail body 200 is connected to the nail cover 100, and the nail body 200 and the nail cover 100 jointly enclose a second accommodating cavity 210, wherein a first thread 220 is arranged on the outer surface of the nail body 200, and a second thread 230 is arranged on the inner wall of the second accommodating cavity 210. The self-piercing friction rivet abuts against the to-be-connected member and rotates under the drive of an external device, thereby generating friction heat to soften the to-be-connected member, and the nail body 200 penetrates the upper layer to-be-connected member 300 under the action of axial pressure, and part of the excess material of the upper layer to-be-connected member 300 is squeezed out and flows into the first accommodating cavity 110.

[0031] In this embodiment, the design of the nail cover 100 takes into account the connection with the driving device, and the design of the abutment portion can effectively abut against the to-be-connected member and provide sufficient support force to ensure stability during the connection process. The nail body 200 is connected to the nail cover 100 to form a second accommodating chamber 210 together. A first thread 220 is provided on the outer surface of the nail body 200, and a second thread 230 is provided on the inner wall of the second accommodating chamber 210. The nail body 200 mainly bears axial pressure and rotational friction during the connection process, and the first thread 220 and the second thread 230 ensure the firmness and stability of the connection. The first accommodating chamber 110 is mainly used to store the excess material squeezed out by the nail body 200 during the connection process, while increasing the contact area with the upper layer to-be-connected member 300, effectively controlling the flow direction and position of the excess material, and improving the reliability of the connection. During the connection process, the self-piercing friction rivet is driven by an external device to abut against the to-be-connected member with a certain axial pressure and rotational speed. In this process, friction heat is generated to soften the material of the to-be-connected member. As the nail body 200 penetrates the upper layer of the member to be connected 300 , part of the excess material is squeezed out and flows into the first accommodating cavity 110 , thereby ensuring the firmness and stability of the connection.

[0032] The rivet does not require prefabricated holes and can achieve the connection between aluminum plates and ultra-high-strength steel or hot-formed steel, with a wider range of applications. This means that it is suitable for the connection needs of a variety of different materials and structures, providing more options for various engineering applications. The riveted joint is a non-through joint, which has better sealing than FDS and can achieve connection with a closed cavity. This design makes the rivet suitable for application scenarios where sealing needs to be maintained, such as automotive body structures or aerospace fields. The rivet uses friction heat to soften the upper cast aluminum material during the connection process, effectively solving the problem of easy cracking of the riveted joint due to the low edge elongation of large die-cast aluminum structural parts. This design makes the riveting process more stable and reliable, and improves the quality and durability of the connection.

[0033] In one embodiment, an abutment structure for increasing the contact area with the part to be connected is provided on the end of the nail body 200 that contacts the part to be connected.

[0034] In this embodiment, the design of the abutment structure increases the contact area between the nail body 200 and the parts to be connected, making the connection more firm and stable. The increased contact area can effectively disperse the pressure and stress during the connection process, reduce the stress concentration at the connection site, and improve the reliability and durability of the connection. Specifically in this embodiment, the abutment structure is an arc-shaped rivet leg. The arc-shaped rivet leg increases the welding area with the underlying steel plate, which is beneficial to heat conduction and material flow during the welding process, thereby improving the welding quality and connection strength, and can effectively improve the stability and reliability of the connection, and reduce the risk of connection failure. During the connection process, the increased contact area and welding area can effectively disperse and withstand the effects of external forces, reduce the stress concentration and fracture risk at the connection site, and extend the service life of the connection.

[0035] In one embodiment, the abutment structure penetrates the upper part to be connected 300 and contacts the upper surface of the lower part to be connected 400, then stops pressing down, and continues to rotate under the drive of an external device to generate friction heat and melt the lower part to be connected 400. Under the action of axial pressure, the abutment structure is upset and plastically deformed and welded to the lower part to be connected 400 to form a solid phase connection.

[0036] In this embodiment, the abutment structure is welded with the lower layer of the connected part 400 under the action of the friction heat and axial pressure generated by the rotation. Through the solid phase connection form of welding, the strength and stability of the connection part are enhanced, making the connection more durable. In addition, the abutment structure also produces upsetting and plastic deformation under the action of axial pressure. Upsetting refers to the change in the shape of the connection part during the connection process, usually by compression or stretching, so that the diameter or cross-sectional area of ​​the connection part increases, thereby increasing the firmness and stability of the connection. Plastic deformation refers to the plastic deformation of the material of the connection part, forming a new structure, making the connection more stable and durable. Through the form of solid phase connection, the strength of the connection part is enhanced, and it can withstand greater tensile, shear and torsion forces, thereby increasing the durability and reliability of the connection, and can withstand long-term use and external forces. This connection method simplifies the connection process, does not require additional welding materials or melting processes, and can complete the connection process only through the rotation and axial pressure of the external device. Such simplification makes the connection process more efficient and faster, and is not limited by the elongation of large die-cast aluminum alloy structural parts, which improves the part yield rate. At the same time, it can reduce the types of body connection rivets, improve current production efficiency and the reliability of body steel-aluminum connections, and reduce costs at the same time.

[0037] In one embodiment, the first thread 220 and / or the second thread 230 are self-locking threads. Specifically in this embodiment, the first thread 220 and the second thread 230 are both self-locking threads. This design can provide a more secure connection during the connection process and prevent the connection parts from loosening or falling off due to external vibration or load. The design of the self-locking thread can enhance the friction between the connection parts and ensure the tight fit between the connection parts during the connection process, thereby improving the stability and reliability of the connection and extending the service life of the connection parts.

[0038] In one embodiment, the nail body 200 is a hollow structure. The hollow structure makes the nail body 200 more flexible and elastic, and is more adaptable to connecting irregular surfaces or when a certain deformation is required. The design of the hollow structure can provide more surface area for welding, thereby increasing the contact area with the parts to be connected, improving the welding effect and the stability of the connection. In addition, the design of the hollow structure can also reduce the stress concentration of the material, making the connecting parts more fatigue-resistant and extending the service life.

[0039] In one embodiment, the nail cover 100 is integrally connected to the nail body 200. The integral connection of the nail cover 100 and the nail body 200 can reduce the number of parts and simplify the structure, thereby reducing the complexity and process of assembly. The integral connection design can improve the stability and rigidity between the connected parts and reduce the problems caused by looseness or friction between the connected parts. The integral connection design can reduce the processing and assembly costs of parts, thereby reducing the overall production cost and improving production efficiency. The integral connection design can also reduce the gap and looseness between the connected parts, ensure the reliability and stability of the connection, and reduce the risk of connection failure.

[0040] In one embodiment, the model of the first thread 220 and the second thread 230 is adapted to the thickness of the upper layer to be connected 300 and the lower layer to be connected 400, as well as the mechanical properties of the connection between the parts to be connected. In this embodiment, the model of the first thread 220 and the second thread 230 is adapted according to the thickness of the upper layer to be connected 300 and the lower layer to be connected 400 and the mechanical properties of the connection. Proper selection of the thread model can ensure the firmness, stability and reliability of the connection. The specification, pitch and other parameters of the thread should match the thickness of the parts to be connected to ensure that the thread can fully penetrate and provide sufficient fixing force during the connection process. The model of the thread should also consider the mechanical properties of the connecting parts, including tensile strength, shear strength, etc. Selecting a suitable thread model can ensure that the mechanical properties of the connecting parts meet the requirements during the connection process, while avoiding the situation where the thread is loose or damaged. The larger the model of the thread, the better the mechanical properties of the connection joint. By selecting a thread model that matches the thickness of the parts to be connected, it can be ensured that the thread can fully penetrate and provide sufficient fixing force, thereby ensuring the firmness and stability of the connection. Selecting the appropriate thread type can ensure a close fit between the connected parts, improve the effect and quality of the connection, and reduce the stress concentration and fracture risk between the connected parts. Since the thread type can be selected according to the thickness and mechanical properties of the different parts to be connected, it can meet the needs of different application scenarios and has a wider range of applicability and flexibility.

[0041] Specifically in this embodiment, the first thread 220 is an external thread, and the second thread 230 is an internal thread. When the internal thread is M4 and the external thread is M6, the 3.0mm thick THAS cast aluminum plate and the 1.2mm thick DP590 steel plate are connected by the rivet, and the mechanical properties of the connection joint are tested to reach 2.7kN; when the internal thread is M6 and the external thread is M8, the 3.0mm thick THAS cast aluminum plate and the 1.2mm thick DP590 steel plate are connected by the rivet, and the mechanical properties of the connection joint are tested to reach 3.2kN; when the internal thread is M4 and the external thread is M6, the 1.4mm thick 6082 aluminum plate and the 1.2mm thick DP590 steel plate are connected by the rivet, and the mechanical properties of the connection joint are tested to reach 2.2kN. It should be noted that this application does not limit the specific models of the first thread 220 and the second thread 230, and the mechanical properties of the connection calibration shall prevail.

[0042] In one embodiment, a fixing structure is provided on the connecting portion of the nail cover 100, and the fixing structure is suitable for fixing and connecting the driving device.

[0043] The fixing structure is designed on the connection part of the nail cover 100 to ensure that the connection drive device can be firmly connected to the nail cover 100, thereby improving the stability and reliability of the connection. Specifically in this embodiment, the fixing structure is a groove adapted to the drive device. This connection method can reduce the risk of connection failure caused by loosening or falling off of the drive device. The design of the fixing structure simplifies the connection process, reduces the operating steps and tool use of the operator, and improves the convenience and efficiency of the operation. This helps to reduce production costs and improve production efficiency.

[0044] In one embodiment, the nail cover 100 is coaxially arranged with the nail body 200. The coaxial arrangement of the nail cover 100 and the nail body 200 can simplify the structural design and reduce the number and complexity of parts. Because their central axes are coincident, no additional alignment or adjustment steps are required, saving time and cost for manufacturing and assembly. The coaxial arrangement can ensure the alignment accuracy between the nail cover 100 and the nail body 200, making the connection more accurate and stable, helping to reduce errors and deviations during the connection process, and improving the quality and reliability of the connection. The coaxial arrangement simplifies the connection structure and reduces the adjustment and alignment steps during the assembly process, thereby improving production efficiency, reducing production costs, and making the connection more secure and able to withstand greater external forces and vibrations.

[0045] Referring to FIG3 , an embodiment of the present invention further provides a friction welding system, comprising the above-mentioned self-piercing friction rivet, a driving device, an upper layer to be connected part 300 and a lower layer to be connected part 400 , wherein the upper layer to be connected part 300 is an aluminum plate and the lower layer to be connected part 400 is a steel plate.

[0046] The working process of the above-mentioned friction welding system is as follows: first, the rivet is screwed into one side of the aluminum plate. The rivet rotates at high speed under the action of the driving device, and the heat generated by the rotating friction acts on the upper aluminum plate to control the heating of the aluminum plate but not to reach the melting temperature. The friction heat generated in this process softens the cast aluminum plate and improves its fluidity. The rivet penetrates the upper aluminum plate under the pressure, and some excess cast aluminum material is squeezed out and flows into the first accommodating cavity under the rivet cover; after penetrating the aluminum plate and contacting the upper surface of the lower steel plate, the rivet stops pressing down and continues to rotate to generate friction heat and melt the lower steel plate. Under the action of axial pressure, the abutment structure of the rivet body is upset and plastically deformed and welded to the lower steel plate. After reaching the preset feed depth and energy input, the rivet stops rotating, and the driving device maintains pressure. After the joint is cooled, a solid phase connection is formed between the rivet and the lower steel plate, locking the cast aluminum plate between the rivet head and the steel plate, thereby forming a reliable connection.

[0047] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A self-piercing friction rivet, characterized in that: include: A nail cover (100), the nail cover (100) comprising a connecting portion suitable for connecting to a driving device, and an abutting portion suitable for abutting against a to-be-connected member, the abutting portion having a first accommodating cavity (110) suitable for accommodating the to-be-connected member; A nail body (200), the nail body (200) being connected to the nail cover (100), the nail body (200) and the nail cover (100) jointly enclosing a second accommodating cavity (210), a first thread (220) being arranged on the outer surface of the nail body (200), and a second thread (230) being arranged on the inner wall of the second accommodating cavity (210); The self-piercing friction rivet abuts against the to-be-connected part and rotates under the drive of an external device, thereby generating friction heat to soften the to-be-connected part, and the rivet body (200) penetrates the upper to-be-connected part (300) under the action of axial pressure, and part of the excess material of the upper to-be-connected part (300) is squeezed out and flows into the first accommodating cavity (110).

2. The self-piercing friction rivet according to claim 1, characterized in that: An abutment structure for increasing the contact area with the piece to be connected is provided on one end of the nail body (200) that contacts the piece to be connected.

3. The self-piercing friction rivet according to claim 2, characterized in that: After the abutment structure penetrates the upper part to be connected (300) and contacts the upper surface of the lower part to be connected (400), it stops pressing down and continues to rotate under the drive of an external device to generate friction heat and melt the lower part to be connected (400). Under the action of axial pressure, the abutment structure is upset and plastically deformed and welded to the lower part to be connected (400) to form a solid phase connection.

4. The self-piercing friction rivet according to claim 1, characterized in that: The first thread (220) and / or the second thread (230) are self-locking threads.

5. The self-piercing friction rivet according to claim 1, characterized in that: The nail body (200) is a hollow structure.

6. The self-piercing friction rivet according to claim 1, characterized in that: The nail cover (100) is integrally connected to the nail body (200).

7. The self-piercing friction rivet according to claim 1, characterized in that: The types of the first thread (220) and the second thread (230) are adapted to the thickness of the upper layer of the connected component (300) and the lower layer of the connected component (400), as well as the connection mechanical properties between the connected components.

8. The self-piercing friction rivet according to claim 1, characterized in that: A fixing structure is provided on the connecting portion of the nail cover (100), and the fixing structure is suitable for fixing and connecting with a driving device.

9. The self-piercing friction rivet according to claim 1, characterized in that: The nail cover (100) is coaxially arranged with the nail body (200).

10. A friction welding system, comprising the self-piercing friction rivet according to any one of claims 1 to 9, a driving device, an upper layer of a part to be connected (300) and a lower layer of a part to be connected (400), characterized in that: The upper layer of the member to be connected (300) is an aluminum plate, and the lower layer of the member to be connected (400) is a steel plate.

Images