Connecting structure and method for dissimilar materials

Abstract

The invention provides a dissimilar material connecting structure and method, and relates to the technical field of material processing. The dissimilar material connecting structure comprises a casting and a connecting piece, wherein a plurality of pre-casting holes are formed in the casting; each pre-casting hole is internally provided with one insert, each insert comprises a connecting section, and each connecting section has a pre-assembling state in the corresponding pre-casting hole and a separating state far away from the corresponding pre-casting hole; the connecting piece is attached to one side of the casting; when the connecting sections are in the preassembled state, part of the connecting sections are connected with the connecting pieces in a welded mode. By means of the scheme, high-strength and high-reliability connection of the casting and the connecting piece can be achieved, special equipment is not needed, the overall production cost can be reduced, the production process is simplified, the connecting efficiency of the connecting piece and the casting is greatly improved, and the production period is shortened.

Description

Technical Field

[0001] This invention relates to the field of materials processing technology, and more specifically, to a structure and method for joining dissimilar materials. Background Technology

[0002] With the automotive industry's increasing emphasis on lightweighting, magnesium alloys, due to their low density and high specific strength, are finding ever-expanding applications in automobile manufacturing. Their use in castings has gradually extended from interior body parts to structural components. However, because magnesium alloys have a close-packed hexagonal crystal structure, they have fewer slip systems that can be activated at room temperature, limiting their plastic deformation capabilities. This characteristic is particularly pronounced in the joining of dissimilar materials like steel and magnesium, making them highly susceptible to cracking at the joint.

[0003] Currently, a mature and reliable steel-magnesium joining process has not yet been developed, which has become a key bottleneck restricting the large-scale application of magnesium alloys in automotive structural components.

[0004] There is currently no effective solution to the aforementioned technical problems. Summary of the Invention

[0005] The main objective of this invention is to provide a dissimilar material connection structure and method to solve the problem of poor steel-magnesium connection performance in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a dissimilar material connection structure is provided, comprising: a casting having a plurality of pre-cast holes; an insert having one insert disposed in each pre-cast hole, the insert including a connecting segment having a pre-installed state located within the pre-cast hole and a separated state away from the pre-cast hole; and a connector having abutted against one side of the casting; wherein, when the connecting segment is in the pre-installed state, a portion of the connecting segment is connected to the connector by welding.

[0007] Furthermore, the connectors and inserts are made of the same material, while the castings and inserts are made of different materials.

[0008] Furthermore, the casting is made of magnesium alloy.

[0009] Furthermore, the connector is made of low-carbon steel.

[0010] Furthermore, the connecting section is a barrel-shaped structure with an opening on one side, and the insert also includes a connecting flange. The connecting flange extends outward in the circumferential direction along the opening side of the connecting section. The bottom of the connecting section is welded to the connector, and the connecting flange overlaps the surface of the casting.

[0011] Furthermore, the outer wall of the connecting section is connected to the wall of the pre-cast hole, and the hollow area enclosed between the inner walls of the connecting section forms an operating space, which is used for connecting the connecting section and the connector.

[0012] Furthermore, the insert is connected to the pre-cast hole on the casting by an interference fit.

[0013] Furthermore, the connector is spot-welded to the bottom of the connecting section.

[0014] According to another aspect of the present invention, a method for joining dissimilar materials is provided, the method comprising: opening a plurality of pre-cast holes in a casting, wherein the material of the casting is a magnesium alloy; selecting inserts that match the depth of the pre-cast holes; aligning the inserts with the pre-cast holes, applying pressure to the inserts with a pressure head to press the inserts into each pre-cast hole, so that the casting and the inserts form an integral structure; and welding the inserts to a connector, wherein the materials of the connector and the inserts are low-carbon steel.

[0015] Optionally, the insert and the connector are welded together by: contacting the connector with the end of one electrode cap and the insert with the end of another electrode cap; spot welding the connector and the insert together using the two electrode caps, wherein the welding current is I, the welding time is t, the welding pressure is F, 6.5KA≤I≤7.5KA, 240ms≤t≤260ms, and 2400N≤F≤2600N.

[0016] Optionally, the method further includes: after the insert and connector are spot welded, detecting the welding parameter information at the connection between the insert and connector, wherein the welding parameter information includes at least shear force, tensile force, and weld nugget diameter; if the shear force is confirmed to be ≥7KN, the tensile force is confirmed to be ≥2.1KN, and the weld nugget diameter is confirmed to be ≥4.3mm, the welding is confirmed to be complete.

[0017] By applying the technical solution of this invention, regular pre-cast holes are opened on the casting, and the insert is set to a structure that matches the pre-cast holes. The connecting section of the insert is extended into the pre-cast holes until it contacts and connects with the connector that fits against the other end of the casting. The connecting section is in a pre-installed state. At this time, the insert and the casting form an integral structure. Then, by welding the insert and the connector together, a high-strength and high-reliability connection between the casting and the connector can be achieved. No special equipment is required, which can reduce the overall production cost, simplify the production process, greatly improve the connection efficiency between the connector and the casting, and shorten the production cycle. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A schematic diagram of a first embodiment of the dissimilar material connection structure according to the present invention is shown;

[0020] Figure 2 A schematic diagram of a second embodiment of the dissimilar material connection structure according to the present invention is shown;

[0021] Figure 3 It shows Figure 2 Enlarged view of point A in the middle;

[0022] Figure 4 A schematic diagram of a third embodiment of the dissimilar material connection structure according to the present invention is shown;

[0023] Figure 5 A schematic diagram of a fourth embodiment of the dissimilar material connection structure according to the present invention is shown;

[0024] Figure 6 A flowchart illustrating an embodiment of the dissimilar material joining method according to the present invention is shown.

[0025] The above figures include the following reference numerals:

[0026] 10. Castings; 101. Precast holes;

[0027] 20. Insert; 200. Operating space; 21. Connecting section; 22. Connecting flange;

[0028] 30. Connectors;

[0029] 40. Electrode cap. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art. In the drawings, for clarity, the thickness of layers and regions may be exaggerated, and the same reference numerals are used to denote the same devices, and therefore their description will be omitted.

[0034] Combination Figures 1 to 5 As shown, according to a specific embodiment of this application, a dissimilar material connection structure is provided.

[0035] Specifically, such as Figures 1 to 3 , Figure 5 As shown, the dissimilar material connection structure includes a casting 10, an insert 20, and a connector 30. The casting 10 has multiple pre-cast holes 101. Each pre-cast hole 101 contains an insert 20, which includes a connecting section 21. The connecting section 21 has a pre-installed state located within the pre-cast hole 101, and also has a separated state away from the pre-cast hole 101. The connector 30 is fitted to one side of the casting 10. When the connecting section 21 is in the pre-installed state, a portion of the connecting section 21 is connected to the connector 30 by welding.

[0036] By applying the technical solution of this embodiment, regular pre-cast holes 101 are opened on the casting 10, and the insert 20 is set to a structure that matches the pre-cast holes 101. By extending the connecting section 21 of the insert 20 into the pre-cast holes 101 until it contacts and connects with the connector 30 that fits against the other end of the casting 10, the connecting section 21 is in a pre-installed state. At this time, the insert 20 and the casting 10 form an integral structure. Then, by welding the insert 20 and the connector 30 together, a high-strength and high-reliability connection between the casting 10 and the connector 30 can be achieved. No special equipment is required, which can reduce the overall production cost, simplify the production process, greatly improve the connection efficiency between the connector 30 and the casting 10, and shorten the production cycle.

[0037] It should be noted that the location and number of pre-cast holes 101 can be determined according to the installation environment of casting 10 and connector 30. The pre-cast holes 101 are set through casting 10 along the thickness direction of casting 10. When the connecting section 21 of insert 20 extends into the pre-cast hole 101 and passes through the pre-cast hole 101 to contact connector 30, the connecting section 21 is in a pre-installed state. At this time, since the connecting section 21 is in contact with connector 30, the connecting section 21 and connector 30 can be welded together to form an integral structure, so that casting 10 and connector 30 are tightly connected together.

[0038] Specifically, the connector 30 and the insert 20 are made of the same material, while the casting 10 and the insert 20 are made of different materials. By making the connector 30 and the insert 20 the same material, the matching coefficients of thermal expansion during the welding process can be ensured, welding stress can be reduced, connection stability can be improved, thermal stress concentration at the connection point can be reduced, and the service life of the connection structure can be extended. On the other hand, by making the casting 10 and the insert 20 different materials, a high-strength connection between the two materials can be achieved, thereby utilizing the advantages of different materials in terms of specific strength, weight, hardness, etc., to improve the reliability and stability of the connection.

[0039] It should be noted that, since the connection between the connector 30 and the casting 10 is made of dissimilar materials, the melting point, coefficient of thermal expansion, and electrical conductivity of the different materials are very different, making direct welding impossible. Therefore, by introducing the insert 20 and selecting the same material as the connector 30, the adverse effects caused by these factors can be effectively avoided, such as cracks caused by thermal stress and welding problems caused by excessive contact resistance. Furthermore, by connecting the insert 20 and the casting 10 through a mating connection, a stable and high-strength connection between the connector 30 and the casting 10 can be achieved.

[0040] In a preferred embodiment of this application, the casting 10 is made of magnesium alloy, and the connector 30 is made of low-carbon steel. Magnesium alloys are widely used in the automotive manufacturing field due to their lightweight and high specific strength, especially in applications pursuing lightweight design. Low-carbon steel, as a common engineering material, has good weldability, plasticity, and toughness. Therefore, low-carbon steel can provide a stable connection foundation for the magnesium alloy casting, and through the connection structure in the above embodiment, the magnesium alloy and low-carbon steel can be firmly connected together.

[0041] In this embodiment, low-carbon steel is relatively inexpensive, easy to process and obtain. Using it as a connector not only reduces overall manufacturing costs but also avoids the use of more expensive and potentially environmentally harmful materials. The strength and reliability of low-carbon steel effectively compensate for the potential weaknesses of magnesium alloy at the connection, especially considering the limitations of magnesium alloy in plastic deformation. By embedding the low-carbon steel connector 30 into the magnesium alloy casting 10, the mechanical properties of the connection area can be significantly enhanced, making it more robust under load or stress. Through the material combination of the magnesium alloy casting and the low-carbon steel connector, the requirements for automotive lightweighting are met while ensuring the performance and cost of the connection.

[0042] The connection structure in this embodiment can be mainly applied to vehicle structures, such as vehicle frames, body panels, car chassis, door hinges, integrated rear floor, integrated front engine compartment, and other structural components that need to be connected with steel materials. Magnesium alloys can effectively reduce the vehicle's weight and improve its power and handling, while low-carbon steel as the material of the connector 30 can ensure the safety and reliability of the connection.

[0043] Furthermore, such as Figure 3As shown, the connecting section 21 is a barrel-shaped structure with an opening on one side. The insert 20 also includes a connecting flange 22, which extends outward in the circumferential direction along the opening side of the connecting section 21. The bottom of the connecting section 21 is welded to the connector 30, and the connecting flange 22 overlaps the surface of the casting 10. The connecting section 21 is designed as a barrel-shaped structure with an opening on one side, forming a closed space around the connector 30. This provides additional support and protection for the connector 30 during welding, increases the contact area of ​​the connection point, and allows the welding operation to distribute heat evenly over a wider range, which helps to form a stronger weld nugget. At the same time, the bottom of the connecting section 21 is directly welded to the connector 30, ensuring a tight bond between the two and forming a solid connection base. The connecting flange 22 extends outward from the opening side of the connecting section 21 along the circumference, expanding outward along the edge of the opening of the connecting section 21. This increases the contact area between the insert 20 and the surface of the casting 10, providing a better mechanical interlocking effect between the two. The connecting flange 22 overlaps the surface of the casting 10, forming a physical anchor, which can maintain the stability of the connection even under the action of external forces. In addition, this design can also cover up any uneven areas that may exist between the connecting section 21 and the casting 10, improving the aesthetics and sealing of the connection.

[0044] In this embodiment, the overlapping effect of the connecting flange 22 and the surface of the casting 10 is used to form a composite connection structure, which increases the connection area and improves the connection strength between the casting 10 and the insert 20. This significantly enhances the shear force and tensile force at the connection point, thereby improving the overall load-bearing capacity of the connection structure. Even when subjected to complex conditions such as vibration and impact during vehicle operation, the connection point can remain stable, effectively avoiding safety hazards caused by connection failure.

[0045] Furthermore, such as Figure 4 As shown, the outer wall of the connecting section 21 is connected to the wall of the pre-cast hole 101, and the hollow area enclosed between the inner walls of the connecting section 21 forms an operating space 200. The operating space 200 is used for connecting the connecting section 21 and the connector 30. The operating space 200 provides sufficient space for the welding process, facilitating the operation of the welding equipment, and also allows for the adjustment of welding parameters, thereby enhancing the flexibility and controllability of the welding process and improving welding quality and production efficiency.

[0046] In one embodiment of this application, such as Figure 1 As shown, the welding equipment includes at least an electrode cap 40, which is a pointed electrode cap. The end of the electrode cap can extend into the operating space 200 to perform welding operations on the bottom end of the connecting section 21.

[0047] Preferably, the insert 20 is connected to the pre-cast hole 101 on the casting 10 via an interference fit. The size of the insert 20 is set to be slightly larger than the outer diameter of the pre-cast hole 101. Pressure is applied to the insert 20 by an external instrument or pressure head. When the insert 20 is pressed into the pre-cast hole 101, extrusion occurs between the insert 20 and the hole wall of the pre-cast hole 101, forming a mechanical locking effect. The interference fit utilizes the elastic deformation characteristics of the material to make the insert 20 fit tightly against the casting 10, thereby achieving a high-strength and high-stability connection effect.

[0048] It should be noted that the insert 20 and the pre-cast hole 101 are interference-fitted, which increases the frictional resistance of the connecting surface through the physical locking effect, significantly improving the bonding strength between the connecting section 21 and the casting 10. At the same time, compared with other methods such as bolt connection, interference fit can reduce the time and cost required for assembly, while avoiding the use of additional fasteners, reducing material costs and overall weight.

[0049] In one embodiment of this application, the bottom of the connector 30 and the connecting segment 21 are connected by spot welding. The diameter of the pre-cast hole 101 is φ12-14mm. For a small-sized round hole, the end size of the pointed electrode cap also needs to be small to extend into the operating space 200 for welding. Therefore, pressure spot welding is applied to both ends of the connector 30 and the connecting segment 21 to bond the metal between the connector 30 and the connecting segment 21. The metal is melted by instantaneous high temperature to form a weld nugget, thereby achieving a solid connection between the metals. The connection speed is fast, the welding strength is high, and it is suitable for automated mass production.

[0050] It should be noted that spot welding is superior to traditional mechanical connections such as screwing or rivet welding. Traditional rivet or screw connections require interlocking between materials, and the use of rivets or screws cannot achieve product weight reduction. In contrast, the solution in this embodiment, which uses spot welding of inserts and connectors, can achieve a connection between steel and magnesium or magnesium and steel without the need for additional connecting elements. This ensures connection quality and reduces costs.

[0051] According to another specific embodiment of this application, a method for joining dissimilar materials is also provided, such as... Figure 6 As shown, the method includes the following steps:

[0052] Step S1: Multiple pre-cast holes are opened on the casting, wherein the material of the casting is magnesium alloy;

[0053] Specifically, pre-cast holes in magnesium alloy castings facilitate the subsequent installation of inserts, thereby achieving a stable connection between the casting and another component. The presence of pre-cast holes provides anchor points for the connection structure, ensuring that the connector can be accurately positioned and form a high-strength connection with the casting through subsequent spot welding and other connection processes.

[0054] It should be noted that the number and location of pre-cast holes can be set or adjusted according to connection requirements and structural characteristics of the casting. When setting multiple pre-cast holes, it is necessary to ensure sufficient safety distance between holes based on the mechanical properties of the casting to prevent crack propagation caused by stress concentration at the hole edges. At the same time, it is also necessary to consider the overall structural strength and rigidity of the casting to avoid weakening the load-bearing capacity of the casting due to excessive distribution of holes.

[0055] Step S2: Select an insert that matches the depth of the pre-cast hole;

[0056] Specifically, the depth of the insert should match the depth of the pre-cast hole to ensure that the insert can be fully pressed into the pre-cast hole so that the insert, passing through the pre-cast hole, contacts and connects with the connector at the other end of the casting. By pre-manufacturing and selecting inserts that match the size and number of pre-cast holes, adjustment and preparation work can be reduced, thereby improving the efficiency of the entire production process.

[0057] Step S3: Align the insert with the pre-cast hole, apply pressure to the insert through the pressure head, and press the insert into each pre-cast hole so that the casting and the insert form an integral structure.

[0058] Specifically, by using a pressure head or other pressing tools, uniform pressure is applied to the insert to avoid skewing of the insert during the pressing process and to prevent insert deformation or casting damage caused by uneven local stress.

[0059] It should be noted that the size of the insert can be set slightly larger than the size of the pre-cast hole. When the insert is pressed in using a pressure head or other pressing tools, the insert and the pre-cast hole can be connected by an interference fit. The casting material undergoes slight deformation around the insert, so that the insert and the casting are tightly combined to form an integral structure. The integral structure can not only significantly improve the physical strength of the connection, but also enhance the tensile and shear properties of the connection, and can withstand larger loads, avoiding loosening between the two during subsequent use.

[0060] Step S4: Weld the insert and the connector together, wherein the material of the connector and the insert is low carbon steel.

[0061] Specifically, the connector and insert are made of the same material, namely low-carbon steel. Welding is used to connect the connector and insert. Welding is fast, low-cost, and easy to automate. The weld nugget formed by welding can provide a high-strength connection effect. At the same time, by adjusting the welding parameters, it can be adapted to different connector thicknesses and connection requirements, showing good process adaptability and flexibility.

[0062] Through the above steps, multiple pre-cast holes are made in the casting, where the casting material is magnesium alloy. Inserts matching the depth of the pre-cast holes are selected. The inserts are aligned with the pre-cast holes, and pressure is applied to them using a pressure head to press them into each pre-cast hole, forming an integral structure between the casting and the inserts. The inserts are then welded to the connectors, where both the connectors and inserts are made of low-carbon steel. By combining pre-cast holes, interference fits, and welding technology, an efficient connection between the magnesium alloy casting and the low-carbon steel connector is achieved. The connection process is simple and quick, with high connection strength and reliability, making it suitable for mass production.

[0063] Optionally, the insert is welded to the connector, the method including:

[0064] Step S41: The connector is brought into contact with the end of one electrode cap, and the insert is brought into contact with the end of the other electrode cap;

[0065] Specifically, pointed electrode caps can be used, and spot welding is performed on both ends of the connector and insert at their contact points. A closed circuit is formed between the two electrode caps. The welding machine applies current pulses, and the current generates high temperatures at the contact points, causing a weld nugget to form at the contact points between the connector and insert. This dual-electrode contact method accelerates the welding process, reduces welding time, and the weld nugget formed during the welding process significantly enhances the bonding force between the connector and insert, improving the stability and reliability of the connection.

[0066] Step S42: Spot welding is performed on the connector and the insert using two electrode caps. The welding current is I, the welding time is t, and the welding pressure is F. The values ​​are: 6.5KA≤I≤7.5KA, 240ms≤t≤260ms, and 2400N≤F≤2600N.

[0067] Specifically, a higher current is beneficial for rapidly heating the material to a molten state, thereby forming a weld nugget between the connector and the insert. The selection of the current must take into account the conductivity and thickness of the material to ensure the formation of a weld nugget with sufficient strength. The selection of the welding time must ensure that the current has enough time to act on the material to reach a molten state, while avoiding overheating due to excessive time, which could lead to changes in material properties or welding defects such as cracks or uneven weld points. Applying appropriate pressure helps maintain stable contact between the connector and the insert during the welding process, and also helps in the formation of the weld nugget and the shaping during the post-weld cooling process, ensuring the strength and stability of the connection.

[0068] Preferably, the welding current I is 7kA, the welding time is 250ms, and the welding pressure is 2500N. By setting the welding current, time, and pressure to the above parameters, the heat and pressure generated during the welding process can be precisely controlled to ensure the quality of the weld nugget formation. At the same time, the fast welding time and stable welding current can significantly improve welding efficiency and reduce production costs.

[0069] By adjusting the current, time, and pressure through steps S41-S42, the optimal welding conditions are found to achieve high-quality welding results, ensuring stable weld quality and connection strength that meets design requirements.

[0070] Optionally, the method further includes:

[0071] Step S5: After the insert and connector are spot welded, the welding parameter information at the connection between the insert and connector is detected. The welding parameter information includes at least shear force, tensile force, and weld nugget diameter.

[0072] Specifically, shear force tests are performed on weld joints using standard shear force testing equipment to evaluate their performance under shear loads. Shear force testing verifies the weld joint's ability to resist external forces parallel to the weld nugget surface, ensuring the reliability of the connection under lateral loads. Tensile force tests are then performed on the weld joints using a tensile testing machine to evaluate their ability to withstand tensile forces along the weld nugget axis. Tensile force testing checks the stability of the weld joint under longitudinal loads, ensuring the connector will not detach from the casting or break under tensile stress. The weld nugget diameter is typically measured visually or using measuring tools to ensure it is within the expected range. A weld nugget diameter that is too small may indicate incomplete welding and insufficient connection strength; while a weld nugget diameter that is too large may cause excessive melting or deformation of the material around the weld, affecting the aesthetics and functionality of the connection.

[0073] It should be noted that non-destructive testing methods such as ultrasonic testing, magnetic particle testing, or eddy current testing can be used to conduct preliminary inspections of weld joints and assess their surface quality and internal defects. For critical components or situations where weld strength needs to be verified, destructive testing methods such as pull-out tests and shear tests can be selected to directly apply force to the weld joints and obtain data such as shear force and tensile force through testing.

[0074] Step S6: If the shear force is ≥7KN, the tensile force is ≥2.1KN, and the weld nugget diameter is ≥4.3mm, the welding is confirmed to be complete.

[0075] Specifically, the weld joint must be able to withstand at least 7 kN of lateral force without failure and at least 2.1 kN of longitudinal tensile force to ensure the connection strength and stability of the connector under axial load. A larger weld nugget diameter means that the weld joint has a larger contact area, which can provide stronger connection force and better durability.

[0076] Through steps S5-S6, by setting test standards for shear force, tensile force, and weld nugget diameter and strictly following these standards, it is ensured that a high-quality weld is formed between the connector and the insert, and the connection strength reaches the predetermined standard. This verifies the performance of the connection structure, ensures the reliability and safety of the connection, and thus meets the high requirements for connection strength and stability in industrial fields such as automobile manufacturing.

[0077] This application also provides a preferred embodiment of a method for joining dissimilar materials. In this embodiment, a 4.4mm thick high-pressure magnesium alloy casting and a 1.5mm thick ST280 steel plate are joined. First, the casting holes are pre-cast to lay the foundation for subsequent joining. Then, inserts are designed and manufactured to ensure they meet the joining requirements. Subsequently, the inserts are pressed into the pre-cast holes to achieve initial fixation. Finally, spot welding is used to complete the stable connection between the magnesium alloy casting and the steel. The specific steps are as follows:

[0078] Step 1: First, pre-drill φ12 pre-cast holes in the casting, with a hole spacing of 40mm, for a total of 24 holes;

[0079] Step 2: Insert the designed insert with an inner diameter of φ10, a wall thickness of 1mm, an outer diameter of φ16, and a depth of 4.4mm into the pre-cast hole. The insert is made of low carbon steel.

[0080] Step 3: Weld the casting with the insert inlaid to the 1.5mm ST280 steel plate. Select a pointed electrode cap with a diameter of φ6 and a diameter of φ13*20mm. Spot weld the insert to the steel plate. The welding pressure is 2500N, the welding time is 252ms, and the welding current is 7KA.

[0081] Step 4: After welding, the weld joint is cut and its performance is tested. The joint obtained in this embodiment is tested and the shear force is 7.97KN, the tensile force is 2.31KN, and the weld nugget diameter is 6.04mm.

[0082] Step 5: Repeat the welding process according to the welding parameters until the welding is completed.

[0083] As can be seen from the above description, the dissimilar material joining method in this embodiment has the following beneficial effects: This method breaks through the limitations of traditional joining technology, designs special processes for the characteristics of the two materials, and achieves high-strength and high-reliability connections. Using this technology, vehicle manufacturers do not need to purchase expensive special equipment, effectively reducing equipment investment costs; at the same time, it simplifies the production process, greatly improves the joining efficiency, and shortens the production cycle; by optimizing process parameters, it reduces material waste and energy consumption, significantly reducing production costs, and providing an economical and efficient solution for lightweight automotive manufacturing.

[0084] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0085] In addition to the above, it should be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this specification refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0086] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dissimilar material connection structure, characterized in that, include: A casting (10) having a plurality of pre-cast holes (101) provided thereon; Insert (20), each of the pre-cast holes (101) is provided with one insert (20), the insert (20) includes a connecting section (21), the connecting section (21) has a pre-installed state located in the pre-cast hole (101), and the connecting section (21) has a separated state away from the pre-cast hole (101); A connector (30) is fitted to one side of the casting (10); When the connecting segment (21) is in the pre-installed state, part of the connecting segment (21) is connected to the connector (30) by welding.

2. The dissimilar material connection structure according to claim 1, characterized in that, The connector (30) is made of the same material as the insert (20), while the casting (10) is made of a different material than the insert (20).

3. The dissimilar material connection structure according to claim 2, characterized in that, The casting (10) is made of magnesium alloy.

4. The dissimilar material connection structure according to claim 2, characterized in that, The material of the connector (30) is low carbon steel.

5. The dissimilar material connection structure according to any one of claims 1-4, characterized in that, The connecting section (21) is a barrel-shaped structure with an opening on one side. The insert (20) also includes a connecting flange (22). The connecting flange (22) extends outward in the circumferential direction along the opening side of the connecting section (21). The bottom of the connecting section (21) is welded to the connector (30), and the connecting flange (22) overlaps the surface of the casting (10).

6. The dissimilar material connection structure according to any one of claims 1-4, characterized in that, The outer wall of the connecting section (21) is connected to the wall of the pre-cast hole (101), and the hollow area formed between the inner walls of the connecting section (21) forms an operating space (200). The operating space (200) is used to connect the connecting section (21) and the connector (30).

7. The dissimilar material connection structure according to claim 6, characterized in that, The insert (20) is connected to the pre-cast hole (101) on the casting (10) by an interference fit.

8. The dissimilar material connection structure according to claim 6, characterized in that, The connector (30) is connected to the bottom of the connecting section (21) by spot welding.

9. A method for joining dissimilar materials, characterized in that, The method includes: Multiple pre-cast holes are opened on the casting, wherein the material of the casting is a magnesium alloy; Select an insert that matches the depth of the pre-cast hole; Align the insert with the pre-cast hole, apply pressure to the insert with a pressure head, and press the insert into each of the pre-cast holes so that the casting and the insert form an integral structure; The insert and the connector are welded together, wherein the materials of the connector and the insert are low-carbon steel.

10. The method for joining dissimilar materials according to claim 9, characterized in that, The method of welding the insert to the connector includes: The connector is brought into contact with the end of one electrode cap, and the insert is brought into contact with the end of the other electrode cap; The connector and the insert are spot welded using two electrode caps, wherein the welding current is I, the welding time is t, the welding pressure is F, 6.5KA≤I≤7.5KA, 240ms≤t≤260ms, and 2400N≤F≤2600N.

11. The method for joining dissimilar materials according to claim 9, characterized in that, The method further includes: After the insert and the connector are spot welded, the welding parameter information at the connection between the insert and the connector is detected. The welding parameter information includes at least shear force, tensile force, and weld nugget diameter. Welding is confirmed to be complete when the shear force is ≥7KN, the tensile force is ≥2.1KN, and the weld nugget diameter is ≥4.3mm.

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