Steel-magnesium alloy self-piercing riveting composite plate and process
By using a self-piercing riveting process to form an interlocking structure between steel plates and magnesium alloy plates, the problem of joining dissimilar materials such as steel and magnesium alloys is solved, achieving lightweight body and high-strength connection, and supporting automated production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG GEELY HLDG GRP CO LTD
- Filing Date
- 2026-01-08
- Publication Date
- 2026-06-16
AI Technical Summary
Existing technologies are insufficient to effectively solve the problem of efficient connection between dissimilar materials such as steel and magnesium alloys, especially in vehicle body structures. Existing connection methods such as adhesive bonding, screwing, and riveting suffer from poor peel resistance, significant weight increase, low connection efficiency, or complex processes.
The self-piercing riveting process is used to insert and compress the deformed and interlocked steel plate and magnesium alloy plate into the self-piercing riveting die through self-piercing rivets to form an interlocking structure, which includes a combination of a top magnesium alloy plate, a middle steel plate and a bottom steel plate. Self-piercing rivets and self-piercing riveting dies with specific parameters are used to achieve a high-strength connection.
It achieves lightweight body, high connection strength and is not easy to crack, avoids pre-drilling, supports automated production, and is suitable for connecting body structural components.
Smart Images
Figure CN122209931A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of self-piercing riveting technology for dissimilar materials, and particularly to a steel-magnesium alloy self-piercing riveting composite plate and its process. Background Technology
[0002] Lightweighting the vehicle body can effectively improve energy consumption, increase driving range, and enhance vehicle handling performance. Magnesium alloy has a density of approximately 1.75 g / cm³. 3 Magnesium alloys possess superior specific strength compared to aluminum alloys. Applying them to vehicle body structural components can effectively reduce vehicle weight, achieving lightweighting. Integrated cast magnesium alloy structural components can also improve body rigidity and simplify the vehicle body manufacturing process, thus reducing weight while increasing efficiency and reducing costs. Currently, most body-in-whites are primarily constructed with steel structural components; therefore, the issue of efficient and high-quality connections between magnesium alloy structural components and steel structural components urgently needs to be addressed.
[0003] To address this issue, the significant difference in melting points between magnesium alloys and steel, coupled with the difficulty in achieving a large-scale solid solution between them, makes direct welding a challenging method for joining dissimilar materials. Currently, the main welding techniques available for joining dissimilar materials include adhesive bonding, screwing, and riveting. Adhesive bonding exhibits poor peel resistance and energy absorption, screwing adds significant weight and has low connection efficiency, while riveting requires pre-drilling holes in the plates to be joined, placing higher demands on workpiece dimensions and positioning accuracy, hindering automation, and also resulting in low connection efficiency. Summary of the Invention
[0004] This invention provides a steel-magnesium alloy self-piercing riveting composite plate, comprising a deformable interlocking steel plate and a magnesium alloy plate. One of the steel plate and the magnesium alloy plate is pierced from above by a self-piercing rivet. The pierced portion, together with the self-piercing rivet, compresses the other of the steel plate and the magnesium alloy plate. The other of the steel plate and the magnesium alloy plate flows into a self-piercing riveting die below and deforms, forming an interlocking structure between the steel plate, the magnesium alloy plate, and the self-piercing rivet. The steel-magnesium alloy self-piercing riveting composite plate comprises a top layer, a middle layer, and a bottom layer, which are stacked sequentially from top to bottom. The top layer is a magnesium alloy plate, and the middle and bottom layers are steel plates. The thickness T1 of the top layer is less than 4 mm, the thickness T3 of the bottom layer is greater than 1.2 mm, and the elongation at break of the bottom layer material is greater than 20%.
[0005] Furthermore, the Vickers hardness value of the self-piercing rivet is not less than 510 HV, and the length L of the self-piercing rivet is 4.5~5mm higher than the total thickness of the top layer and the middle layer.
[0006] Furthermore, the present invention also includes a steel-magnesium alloy self-piercing riveting process for manufacturing the aforementioned steel-magnesium alloy self-piercing riveting composite plate, which includes the following steps: The steel plate and the magnesium alloy plate are stacked sequentially according to a preset layer order; The self-piercing rivet is inserted into the steel plate and the magnesium alloy plate from above. The self-piercing rivet expands and deforms within the steel plate and the magnesium alloy plate, causing the steel plate, the magnesium alloy plate, and the self-piercing rivet to interlock.
[0007] Furthermore, the self-piercing riveting components required for the steel-magnesium alloy self-piercing riveting process include at least: Self-piercing riveting guns are used to drive self-piercing rivets into sheet metal. A clamp is used to hold the sheet metal to be riveted. Self-piercing rivets are used to insert into sheet metal from above, and pull the sheet metal above into the sheet metal below, so that the two are deformed and interlocked. Self-piercing rivet dies are used to contact and support the sheet metal located below from below, and also to guide and shape the material flow as the sheet metal expands and deforms downward.
[0008] Furthermore, the self-piercing riveting die includes a flat-bottomed die, which is a reverse frustum structure recessed at the top of the self-piercing riveting die. The flat-bottomed die is used to guide the material flow of the bottom layer and shape it.
[0009] Furthermore, the self-piercing riveting die includes a concave bottom die, which includes a first groove and a second groove. The first groove is recessed at the top of the self-piercing riveting die, and the second groove is recessed at the top of the first groove. The concave bottom die is used to guide the material flow of the bottom layer and shape it.
[0010] Furthermore, the depth H1 of the flat-bottomed die ranges from 0.3 to 0.8 mm, the opening diameter D1 of the flat-bottomed die ranges from 9 to 13 mm, and the draft angle α1 of the sidewall of the flat-bottomed die ranges from 10 to 45°.
[0011] Furthermore, the depth H2 of the first groove ranges from 0.3 to 0.8 mm, the opening diameter D2 of the first groove ranges from 10 to 13 mm, the sidewall draft angle α2 of the first groove ranges from 10 to 45°, the depth H3 of the second groove ranges from 0.5 to 1.8 mm, and the opening diameter D3 of the second groove is 0.5 to 0.7 times the opening diameter D2 of the first groove.
[0012] Furthermore, the depth H1 of the flat-bottomed die ranges from 1.8 to 2.4 mm, the opening diameter D1 of the flat-bottomed die ranges from 9 to 13 mm, and the draft angle α1 of the sidewall of the flat-bottomed die ranges from 6 to 10°.
[0013] Furthermore, the first groove is a reverse frustum structure recessed on the top of the self-piercing riveting die, and the first groove is used to guide the material flow of the bottom layer and shape it.
[0014] Furthermore, the second groove is a reverse frustum structure recessed at the top of the first groove, with a draft angle α3 ranging from 10 to 45°, or the second groove is a reverse hemispherical structure recessed at the top of the first groove.
[0015] The steel-magnesium alloy self-piercing riveting composite plate provided by this invention rivets steel plates and magnesium alloy plates into one piece through a self-piercing riveting process. It can combine multiple steel plates and magnesium alloy plates in a lapped configuration. By selecting self-piercing rivets and self-piercing dies of different sizes and structures according to the combination form and parameters of the steel plates and magnesium alloy plates, good joint forming can be achieved. This enables vehicle body lightweighting, high connection strength and resistance to cracking, avoids pre-drilling, and is conducive to automated production. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the steel-magnesium alloy self-piercing riveting composite plate provided by the present invention.
[0017] Figure 2 This is a schematic diagram of the self-piercing riveting die and the flat-bottomed die in this invention.
[0018] Figure 3 This is a riveting diagram of the first, second, and third embodiments of the present invention.
[0019] Figure 4 This is a schematic diagram of the concave bottom mold and the reverse frustum structure in this invention.
[0020] Figure 5 This is a schematic diagram of the concave bottom mold and the inverted hemispherical structure in this invention.
[0021] Figure 6 This is a riveting schematic diagram of the fourth embodiment of the present invention.
[0022] Figure 7 This is a schematic diagram comparing the shallow (0.5mm) and deep (0.8mm) flat-bottomed dies.
[0023] Figure 8 Comparison of equivalent strain contour maps for flat-bottomed die depths of 0.5mm, 0.8mm, and 1.2mm.
[0024] Figure 9 This is a schematic diagram of the plastic flow displacement distribution of cast magnesium under the flat-bottomed die.
[0025] Figure 10 This is a schematic diagram of a flat-bottomed die applied to thick top and middle layers of steel plates.
[0026] Figure 11 This is a schematic diagram of a concave bottom die applied to thick top and middle layers of steel plates.
[0027] Figure 12 This is a schematic diagram of a flat-bottomed die applied to a thick bottom steel plate.
[0028] Figure 13 This diagram illustrates the change in riveting force during the self-piercing riveting process for a flat-bottomed die 31 with a depth of 0.6 mm, a flat-bottomed die 31 with a depth of 0.8 mm, and a concave-bottomed die 32.
[0029] In the diagram: 11. Steel plate; 12. Magnesium alloy plate; 1a. Top layer; 1b. Middle layer; 1c. Bottom layer; 2. Self-piercing rivets; 21. Rivet feet; 3. Self-piercing riveting die; 31. Flat-bottomed die; 32. Concave-bottomed die; 321. First groove; 322. Second groove. Detailed Implementation
[0030] To further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.
[0031] It should be noted that the terms "first," "second," "third," and "fourth," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. Furthermore, the terms "above" and "below" in the process-related parts of this invention refer to "above" and "below" from a process and production perspective, not the actual orientation or posture of the product after assembly and application. For example, in the production of the steel-magnesium alloy self-piercing riveting composite plate of this invention, the self-piercing riveting direction is from top to bottom, but the completed steel-magnesium alloy self-piercing riveting composite plate can be applied to vehicle body structural parts in any orientation for further processing.
[0032] Self-piercing riveting (SPR) is a riveting process that eliminates the need for pre-drilling holes in the top material. Instead, a rivet penetrates the top material under external force, allowing it to flow through the bottom material and create a permanent, interlocking deformation. It is suitable for high-strength connections between dissimilar materials and is easily automated due to the lack of pre-drilling. However, magnesium alloys have a close-packed hexagonal crystal structure with a relatively low number of slip systems. Furthermore, casting defects in cast magnesium alloys result in poor ductility. Therefore, the self-piercing riveting process can easily cause cracking in the magnesium alloy sheet, leading to failure.
[0033] Please see Figure 1 and Figure 2The steel-magnesium alloy self-piercing riveting composite plate provided by the present invention includes a steel plate 11 and a magnesium alloy plate 12 with deformation interlocking. One of the steel plate 11 and the magnesium alloy plate 12 is pierced from above by a self-piercing rivet 2. The part of the steel plate 11 and the magnesium alloy plate 12 pierced by the self-piercing rivet 2 together compresses the other of the steel plate 11 and the magnesium alloy plate 12. The other of the steel plate 11 and the magnesium alloy plate 12 flows into the self-piercing riveting die 3 below and deforms, so that the steel plate 11, the magnesium alloy plate 12 and the self-piercing rivet 2 form an interlock. Specifically, the self-piercing riveting components required for producing the steel-magnesium alloy self-piercing riveting composite plate of the present invention include at least a self-piercing riveting gun, a clamp, a self-piercing rivet 2, and a self-piercing riveting die 3. The self-piercing riveting gun is used to insert the self-piercing rivet 2 into the plate; the clamp is used to fix the plate to be riveted; the self-piercing rivet 2 includes two rivet legs 21 located below it, with a certain width between the rivet legs 21. When the self-piercing rivet 21 is inserted into the plate from above, the rivet legs 21 will move downward and slightly open within the plate above, and then insert into the plate below, opening slightly outward in a figure-eight shape. The self-piercing riveting die 3 is used to contact and support the bottom plate from below, and also to guide the material flow and shape it as the bottom plate expands and deforms downwards. When the self-piercing rivet 21 penetrates the plate, the material of the plate is naturally squeezed and flows into the self-piercing riveting die 3 and abuts against it. The self-piercing riveting die 3 can lift this part of the material to form a downward protruding bump at the bottom of the steel-magnesium alloy self-piercing riveting composite plate, ensuring the correct overall posture of the self-piercing rivet 2 and the correct shape of the rivet foot 21 within the plate. In one embodiment of the present invention, the steel-magnesium alloy self-piercing riveting composite plate is a combination of steel-magnesium alloy with magnesium alloy plate 12 on the upper layer and steel plate 11 on the lower layer. The steel plate 11 and magnesium alloy plate 12 are respectively made and used as body structural parts, and the steel-magnesium alloy self-piercing riveting composite plate is made and used as part of the rear body. In some embodiments of the present invention, the steel plate 11 may be made of one or more of mild steel, high-strength steel, and hot-formed steel, and the magnesium alloy plate 12 may be made of one or more of high-pressure die-casting magnesium alloy and semi-solid injection casting magnesium alloy. The present invention uses a self-piercing riveting process to rivet the steel plate 11 and the magnesium alloy plate 12 together, achieving lightweight vehicle body, high connection strength, and resistance to cracking, avoiding pre-drilling, and facilitating automated production.
[0034] Furthermore, such as Figure 3As shown, the steel-magnesium alloy self-piercing riveting composite plate of the present invention includes a top layer 1a, a middle layer 1b, and a bottom layer 1c. The top layer 1a, middle layer 1b, and bottom layer 1c are stacked sequentially from top to bottom. The top layer 1a is either a steel plate 11 or a magnesium alloy plate 12, the bottom layer 1c is the other of the steel plate 11 and magnesium alloy plate 12, and the middle layer 1b is a steel plate 11. In a preferred embodiment of the present invention, the steel-magnesium alloy self-piercing riveting composite plate can be a combination of three layers of steel-steel-magnesium alloy from top to bottom, or a combination of three layers of magnesium alloy-steel-steel from top to bottom. That is, magnesium alloy plate 12 cannot be used as the middle layer 1b. This is because the thickness of magnesium alloy plate 12 is relatively large. If a combination of steel-magnesium alloy-magnesium alloy or magnesium alloy-magnesium alloy-steel is used, the overall thickness of the material will be too large, which will greatly increase the difficulty of piercing the self-piercing riveting and may even make it impossible to pierce. The whole structure is not easy to pierce and form, and it does not meet the size requirements of the rear vehicle body.
[0035] Please refer to the following: Figure 3 In the first embodiment of the present invention, the top layer 1a and the middle layer 1b are steel plates 11, and the bottom layer 1c is a magnesium alloy plate 12, and the overall maximum tensile strength of the top layer 1a and the middle layer 1b is less than 600 MPa. The parameters of the steel plates 11 of the top layer 1a and the middle layer 1b are set in this way because: when selecting parameters, priority should be given to whether the plate can be successfully pierced by the self-piercing rivet 2, so it cannot have too high a tensile strength. The self-piercing rivet 2 selected in the present invention is made of steel. If the tensile strength of the steel plates 11 of the top layer 1a and the middle layer 1b is too high, it will cause the self-piercing rivet 2 to fail to pierce the steel plates 11, thus causing the self-piercing riveting to fail.
[0036] In the second embodiment of the present invention, the top layer 1a and the middle layer 1b are steel plates 11, the bottom layer 1c is a magnesium alloy plate 12, the total thickness T2 of the top layer 1a and the middle layer 1b is less than 1 mm, and the overall maximum tensile strength of the top layer 1a and the middle layer 1b is greater than 600 MPa. Additionally, as... Figure 2 As shown, the self-piercing riveting die 3 has a flat-bottomed die 31 at its top. The flat-bottomed die 31 is a reverse frustum structure recessed at the top of the self-piercing riveting die 3. The depth H1 of the flat-bottomed die 31 ranges from 0.3 to 0.8 mm, the opening diameter D1 of the flat-bottomed die 31 ranges from 9 to 13 mm, and the draft angle α1 of the sidewall of the flat-bottomed die 31 ranges from 10 to 45°. Please refer to the following: Figure 7 Taking magnesium alloy plate 12 made of cast magnesium as an example, during self-piercing riveting, in order to avoid cracking of the cast magnesium, the parameters of the flat-bottom die 31 need to be selected according to the thickness of the plate. Generally speaking, the shallower the flat-bottom die 31, the smaller the deformable space of the bottom layer 1c during self-piercing riveting, but the higher the piercing difficulty of the top layer 1a and the middle layer 1b. Figure 7The upper half of the image shows the situation when puncture is successful; the deeper the flat-bottomed die 31, the easier it is to puncture the top layer 1a and the middle layer 1b, but the higher the possibility of cracking. Figure 7 The lower half of the image shows the cracking situation when the depth of the flat-bottomed die 31 is large; the circled part represents the crack. Please refer to the attached image as well. Figure 8 and Figure 9 ,from Figure 8 Finite element simulations show that as the depth H1 of the flat-bottomed die 31 increases, the magnesium alloy plate 12 located in the bottom layer 1c will exhibit an increased difference in equivalent strain between its central and peripheral portions in the area below the nail holes after self-piercing riveting. Please refer to the following for details. Figure 9 , Figure 9 The longer the arrow shown, the greater the plastic flow displacement, thus increasing the strain difference between the central and peripheral parts of the bottom layer 1c. This is actually an increase in the relative plastic flow displacement between the two material parts, ultimately leading to shear cracking. Therefore, in the second embodiment, since the total thickness T2 of the top layer 1a and the middle layer 1b is set to be relatively small, the depth H1 and the opening diameter D1 of the flat-bottomed die 31 can also be set to be relatively small. The self-piercing die 3, thus configured, can match the relatively small total thickness of the top layer 1a and the middle layer 1b, avoiding cracking of the magnesium alloy plate 12 of the bottom layer 1c due to insufficient tensile strength of the steel plate 11 of the top layer 1a and the middle layer 1b.
[0037] Please refer to the following: Figure 5 and Figure 6 In the third embodiment of the present invention, the top layer 1a and the middle layer 1b are steel plates 11, the bottom layer 1c is a magnesium alloy plate 12, the total thickness T2 of the top layer 1a and the middle layer 1b is greater than 1 mm, and the overall maximum tensile strength of the top layer 1a and the middle layer 1b is greater than 600 MPa. Please refer to the following: Figure 10 and Figure 11 For high-strength, thick, multi-layered steel plates 11, using a flat-bottomed die 31 can easily lead to the collapse or excessive bending of the nail feet 21, preventing the formation of an interlocking structure and causing self-piercing riveting failure. However, when a concave-bottomed die 32 is used, the joint forming and interlocking are good, and there are no through-cracks inside the joint. Although there are cracks on the joint surface, they do not penetrate deep into the joint, which is permissible to a certain extent. Figure 10 As shown, during the riveting process of the flat-bottomed die 31, the magnesium alloy plate 12 below the self-piercing rivet 2 is confined inside the flat-bottomed die 31 and cannot flow. The material of the magnesium alloy plate 12 is subjected to hydrostatic pressure in the X / Y / Z directions. Since the metal cannot deform or shrink in volume under hydrostatic pressure, it can only undergo rapid work hardening, thereby increasing the resistance encountered by the self-piercing rivet 2 during the riveting process, causing the rivet foot 21 to collapse or bend excessively. Figure 11As shown, the concave bottom die 32 provides a flow space for the material in the area below the self-piercing rivet 2 during the riveting process, avoiding or alleviating the situation where the material of the magnesium alloy plate 12 is subjected to hydrostatic pressure in three directions. Therefore, compared with the flat bottom die 31, the concave bottom die 32 can reduce the resistance of the rivet foot 21 during the riveting process, avoid excessive bending or collapse of the rivet foot 21, and achieve good joint forming. The concave bottom die 32 includes a first groove 321 and a second groove 322. The first groove 321 is a reverse frustum structure recessed at the top of the self-piercing die 3. The second groove 322 is a reverse frustum structure or a reverse hemispherical structure recessed at the top of the first groove 321. The depth H2 of the first groove 321 ranges from 0.3 to 0.8 mm, the diameter D2 of the opening of the first groove 321 ranges from 10 to 13 mm, and the draft angle α2 of the sidewall of the first groove 321 ranges from 10 to 45°. The depth H3 of the second groove 322 ranges from 0.5 to 1.8 mm, and the diameter D3 of the opening of the second groove 322 is 0.5 to 0.7 times the diameter D2 of the opening of the first groove 321. When the second groove 322 is a reverse frustum structure, its draft angle α3 ranges from 10 to 45°. As mentioned above, during self-piercing riveting, to avoid cracking, the parameters of the concave bottom die 32 need to be selected according to the thickness of the sheet metal. In the third embodiment, since the total thickness T2 of the top layer 1a and the middle layer 1b is set to be relatively large, higher requirements are placed on the top die of the self-piercing riveting die 3. Therefore, it is chosen to be a concave bottom die 32 with "two layers". Its depth (H2+H3) parameter and opening diameter D3 parameter are both greater than those of the flat bottom die 31 in the second embodiment. The top layer 1a, the middle layer 1b and the concave bottom die 32 configured in this way can reduce the riveting resistance during the self-piercing riveting process while preventing cracking of the magnesium alloy sheet, and avoid the nail feet 21 of the self-piercing rivet 2 (see Figure 1 It collapses under pressure.
[0038] Furthermore, in the first, second, and third embodiments of the present invention, the self-piercing rivet 2 is countersunk, and for the steel-steel-magnesium alloy combination, the average Vickers hardness value of the self-piercing rivet 2 is greater than 490 HV, and the length L of the self-piercing rivet 2 is 2.8~3.8mm higher than the total thickness (T1+T2) of the top layer 1a, the middle layer 1b, and the bottom layer 1c.
[0039] Please refer to this carefully. Figure 4 In the fourth embodiment of the present invention, the top layer 1a is a magnesium alloy plate 12, the middle layer 1b and the bottom layer 1c are steel plates 11, the thickness T1 of the top layer 1a is less than 4 mm, the thickness T3 of the bottom layer 1c is greater than 1.2 mm, and the elongation at break of the material of the bottom layer 1c is greater than 20%. Please refer to the following: Figure 12When the thickness of the bottom steel plate 11 exceeds 1.2 mm and its ductility is greater than 20%, a deep flat-bottomed die 31 can form a good joint structure and interlocking, and neither the magnesium alloy plate 12 nor the steel plate 11 cracked. The depth H1 of the flat-bottomed die 31 ranges from 1.8 to 2.4 mm, the opening diameter D1 of the flat-bottomed die 31 ranges from 9 to 13 mm, and the draft angle α1 of the sidewall of the flat-bottomed die 31 ranges from 6 to 10°. Compared with the steel-steel-magnesium alloy combination, the magnesium alloy-steel-steel combination in the fourth embodiment has a larger total thickness and higher strength. If the same self-piercing rivet 2 and self-piercing die 3 as in the second or third embodiment are used, it is easy for the self-piercing rivet 2 to fail to pierce the steel plate 11. Please refer to [further details needed]. Figure 13 ,Depend on Figure 13 As shown in the chart, the riveting force experienced by the self-piercing rivet 2 during the self-piercing riveting process, i.e., the resistance it encounters when penetrating the sheet metal, varies with its stroke. It is evident that when using the flat-bottom die 31, the shallower the depth of the die 31, the greater the resistance experienced by the self-piercing rivet 2 when penetrating the sheet metal. Furthermore, this resistance acts on the rivet foot 21, making it prone to excessive bending or collapse. Conversely, when using the concave-bottom die 32, the resistance experienced by the self-piercing rivet 2 decreases significantly, which helps prevent excessive bending or collapse of the rivet foot 21, achieving good forming. Therefore, the steel-steel-magnesium alloy combination in the fourth embodiment requires higher hardness from the self-piercing rivet 2. The Vickers hardness value of the self-piercing rivet 2 is not less than 510 HV, and the length L of the self-piercing rivet 2 is 4.5~5mm greater than the total thickness (T1+T2-T3) of the top layer 1a and the middle layer 1b. To address this, corresponding adjustments need to be made to the self-piercing riveting die 3, such as setting a deeper flat-bottomed die 31. This configuration of the top layer 1a, bottom layer 1c parameters, and the flat-bottomed die 31 helps reduce the riveting force during the self-piercing riveting process, preventing the rivet feet 21 of the self-piercing rivet 2 from bulging or collapsing, and ensuring a good interlocking structure between the materials.
[0040] Furthermore, the present invention also includes a steel-magnesium alloy self-piercing riveting process for manufacturing the aforementioned steel-magnesium alloy self-piercing riveting composite plate, which includes the following steps: The steel plate 11 and the magnesium alloy plate 12 are stacked in sequence according to the preset layer order; The self-piercing rivet 2 is inserted into the steel plate 11 and the magnesium alloy plate 12 from above. The self-piercing rivet 2 expands and deforms within the steel plate 11 and the magnesium alloy plate 12, so that the steel plate 11, the magnesium alloy plate 12 and the self-piercing rivet 2 form an interlock.
[0041] In summary, the steel-magnesium alloy self-piercing riveting composite plate provided by this invention rivets steel plate 11 and magnesium alloy plate 12 into one piece through a self-piercing riveting process. It can combine multiple layers of steel plate 11 and magnesium alloy plate 12. By selecting self-piercing rivets 2 and self-piercing rivet dies 3 of different sizes and structures according to the combination form and parameters of steel plate 11 and magnesium alloy plate 12, good joint forming can be achieved, which can realize vehicle body lightweighting, high connection strength and not easy to crack, avoid pre-drilling, and facilitate automated production.
[0042] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A steel-magnesium alloy self-piercing riveting composite plate, characterized in that: The device includes a deformable interlocking steel plate (11) and a magnesium alloy plate (12). One of the steel plate (11) and the magnesium alloy plate (12) is pierced from above by a self-piercing rivet (2). The pierced portion, together with the self-piercing rivet (2), compresses the other of the steel plate (11) and the magnesium alloy plate (12). The other of the steel plate (11) and the magnesium alloy plate (12) flows into the self-piercing riveting die (3) below and deforms, thereby forming an interlock between the steel plate (11), the magnesium alloy plate (12), and the self-piercing rivet (2). The structure of the steel-magnesium alloy self-piercing riveting composite plate includes a top layer (1a), a middle layer (1b), and a bottom layer (1c). The top layer (1a), the middle layer (1b), and the bottom layer (1c) are stacked sequentially from top to bottom. The top layer (1a) is a magnesium alloy plate (12), and the middle layer (1b) and the bottom layer (1c) are steel plates (11). The thickness T1 of the top layer (1a) is less than 4 mm, the thickness T3 of the bottom layer (1c) is greater than 1.2 mm, and the elongation at break of the material of the bottom layer (1c) is greater than 20%.
2. The steel-magnesium alloy self-piercing riveting composite plate as described in claim 1, characterized in that: The self-piercing rivet (2) has a Vickers hardness value of not less than 510 HV, and the length L of the self-piercing rivet (2) is 4.5~5mm higher than the total thickness of the top layer (1a) and the middle layer (1b).
3. A steel-magnesium alloy self-piercing riveting process, characterized in that: It is used to manufacture the steel-magnesium alloy self-piercing riveting composite plate as described in any one of claims 1 to 2, and includes the following steps: The steel plate (11) and the magnesium alloy plate (12) are stacked sequentially according to a preset layer order; The self-piercing rivet (2) is inserted into the steel plate (11) and the magnesium alloy plate (12) from above. The self-piercing rivet (2) expands and deforms within the steel plate (11) and the magnesium alloy plate (12), thereby interlocking the steel plate (11), the magnesium alloy plate (12) and the self-piercing rivet (2).
4. The steel-magnesium alloy self-piercing riveting process as described in claim 3, characterized in that: The self-piercing riveting components required for the steel-magnesium alloy self-piercing riveting process include at least the following: A self-piercing riveting gun is used to insert self-piercing rivets (2) into sheet metal. A clamp used to hold the sheet metal to be riveted; Self-piercing rivets (2) are used to pierce into the plate from above and drive the plate above into the plate below, so that the two are deformed and interlocked. The self-piercing riveting die (3) is used to contact and provide support to the sheet metal located below from below, and also to guide the material flow and shape it as the sheet metal below expands and deforms downward.
5. The steel-magnesium alloy self-piercing riveting process as described in claim 4, characterized in that: The self-piercing riveting die (3) includes a flat-bottomed die (31), which is a reverse frustum structure recessed on the top of the self-piercing riveting die (3). The flat-bottomed die (31) is used to guide the material flow of the bottom layer (1c) and shape it.
6. The steel-magnesium alloy self-piercing riveting process as described in claim 4, characterized in that: The self-piercing riveting die (3) includes a concave bottom die (32), which includes a first groove (321) and a second groove (322). The first groove (321) is recessed at the top of the self-piercing riveting die (3), and the second groove (322) is recessed at the top of the first groove (321). The concave bottom die (32) is used to guide the material flow of the bottom layer (1c) and shape it.
7. The steel-magnesium alloy self-piercing riveting process as described in claim 5, characterized in that: The depth H1 of the flat-bottomed die (31) ranges from 0.3 to 0.8 mm, the diameter D1 of the opening of the flat-bottomed die (31) ranges from 9 to 13 mm, and the draft angle α1 of the sidewall of the flat-bottomed die (31) ranges from 10 to 45°.
8. The steel-magnesium alloy self-piercing riveting process as described in claim 6, characterized in that: The depth H2 of the first groove (321) ranges from 0.3 to 0.8 mm, the opening diameter D2 of the first groove (321) ranges from 10 to 13 mm, the sidewall draft angle α2 of the first groove (321) ranges from 10 to 45°, the depth H3 of the second groove (322) ranges from 0.5 to 1.8 mm, and the opening diameter D3 of the second groove (322) is 0.5 to 0.7 times the opening diameter D2 of the first groove (321).
9. The steel-magnesium alloy self-piercing riveting process as described in claim 5, characterized in that: The depth H1 of the flat-bottomed die (31) ranges from 1.8 to 2.4 mm, the diameter D1 of the opening of the flat-bottomed die (31) ranges from 9 to 13 mm, and the draft angle α1 of the sidewall of the flat-bottomed die (31) ranges from 6 to 10°.
10. The steel-magnesium alloy self-piercing riveting process as described in claim 6, characterized in that: The first groove (321) is a reverse frustum structure recessed on the top of the self-piercing riveting die (3). The first groove (321) is used to guide the material flow of the bottom layer (1c) and shape it.
11. The steel-magnesium alloy self-piercing riveting process as described in claim 10, characterized in that: The second groove (322) is a reverse frustum structure recessed at the top of the first groove (321), and its draft angle α3 ranges from 10 to 45°, or the second groove (322) is a reverse hemispherical structure recessed at the top of the first groove (321).