A method for connecting dissimilar metals

Abstract

The present application provides a method for connecting dissimilar metals, comprising the following process steps: designing a mortise and tenon structure for two metal sheets of different materials; splicing the metal mortise and tenon structures to reduce local stress concentration at the butt joint and increase fracture energy consumption; machining through holes in a direction perpendicular to the splicing direction of the mortise and tenon structures to further reduce stress concentration in the butt joint structure; reinforcing the spliced ​​mortise and tenon structure by passing screws or rivets through the through holes; pre-stirring friction processing the joint parts with high hardness in the two metal sheets to obtain a local fine-grained structure; and performing stir friction welding at the joints.

Description

Technical Field

[0001] The present application relates to the field of welding, and in particular to an efficient method for connecting dissimilar metals. Background Art

[0002] With the rapid development of science and technology, lightweighting has become one of the important goals in the manufacturing field. The extensive application of light metals such as titanium alloys, aluminum alloys, and magnesium alloys has led to the welding structure of dissimilar metals. However, the welding structure of dissimilar metals is connected by the metallurgical bonding formed by the intermetallic compound layer at the interface of the two. The thickness of the intermetallic compound layer is usually micron-level. When the compound layer reaches more than 10 microns, it will form agglomeration, which will deteriorate the performance of the joint. In addition, the elastic modulus and hardness of dissimilar metals are different, which is easy to form stress concentration at the interface, and the metallurgical bonding strength at the micron level cannot overcome the large stress. The bonding strength of dissimilar metals is usually very low, and it is difficult to reach 60% of that of relatively soft metals, which limits the application of dissimilar metals in dynamic working environments.

[0003] Domestic and foreign researchers have conducted a lot of research in the field of dissimilar metal welding. Common welding methods include: laser welding, TIG welding, MIG welding, brazing and stir friction welding; the main ways are to control heat input, add reinforcing particles or intermediate layers, add auxiliary ultrasonic devices or magnetic fields, suppress the thickness of the intermetallic compound layer of the joint and suppress the growth of grains in the stirring zone. The advantages of the welding method are low machining requirements and simple procedures, but the inherent connection characteristics of this technology are relying on the intermetallic compound layer, which does not have metallic properties, resulting in brittle fracture; therefore, the combination form is contradictory to the application purpose.

[0004] The above information disclosed in the background technology is only used to increase the understanding of the background technology of the present application, and therefore, it may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] This application adopts the mortise and tenon structure design to achieve mechanical bite, and uses bolt connection to disperse stress concentration and increase fracture energy consumption. This changes the dissimilar metal connection structure from brittle fracture to ductile fracture, and has the possibility of dynamic operation. At the same time, the joint is pre-stirred and friction processed locally; the crushing effect and friction heat generated by the high-speed rotation of the stirring needle can achieve local refinement of the joint structure of hard metals such as steel and titanium alloy, which not only avoids the coarsening of the entire plate structure and the reduction of mechanical properties, but also improves the fluidity of the joint, thereby improving the overall performance of the component.

[0006] This application is mainly implemented through the following technical solutions:

[0007] A method for connecting dissimilar metals, comprising the following process steps:

[0008] (1) Design the mortise and tenon structure of two metal plates of different materials;

[0009] (2) Insert the two metal sheets together, and the length of the insertion layer is L 拼插 ≥ Plate thickness D 板厚 , the thickness D1 of the relatively soft interlayer and the thickness D2 of the relatively hard interlayer are equal or different to reduce the local stress concentration at the butt joint;

[0010] (3) Through holes are processed in a direction perpendicular to the direction of insertion of the mortise and tenon structure to further reduce stress concentration in the butt joint structure;

[0011] (4) Use screw or rivet length L 钉 ≥ Plate thickness, pass through the through hole to reinforce the mortise and tenon structure after splicing;

[0012] (5) Pre-stirring friction processing is performed on the joint area with high hardness of the two metal plates to obtain a local fine-grained structure;

[0013] (6) Stir friction welding is performed at the joint.

[0014] In some embodiments of the present application, the two metal plates of different materials include n layers of relatively soft metal and n+1 layers of relatively hard metal mortise and tenon joints; the number of screws or rivets is n, n×π·R 2 ≤1 / 3 of the intercalation surface area, the intercalation surface area is the intercalation length L 拼插 × Insertion layer width W 拼插 , where R 钉 is the screw radius,

[0015] In some embodiments of the present application, there are multiple through holes, and the number of screws or rivets is the same as the number of through holes, forming a screw group or a rivet group, and the arrangement methods include neat arrangement, staggered arrangement, or topologically optimized arrangement.

[0016] In some embodiments of the present application, the shape of the mortise and tenon structure includes one or more of a cuboid, a step, and a triangle, and the height of the tenon along the thickness direction of the plate is W. 凸榫 , number m, m×W 凸榫 ≤1 / 2 plate thickness W 拼插 , L 延伸 ≥0, tenon extension length L 延伸 With tenon length L 凸榫 The sum shall not be less than the plate thickness.

[0017] In some embodiments of the present application, the tenon is the metal with higher hardness among the two metal plates or the metal with lower hardness among the two metal plates; the pre-friction stir processing parameter range in step (5) is a rotation speed of 150-450 rpm and a forward speed of 20-100 mm / min; the friction stir welding parameter range in step (6) is: a rotation speed of 500-1600 rpm and a forward speed of 50-120 mm / min.

[0018] In some embodiments of the present application, a method for connecting dissimilar metals includes the following process steps:

[0019] (1) Design the mortise and tenon structure of two metal plates of different materials;

[0020] (2) n layers of soft metal and n+1 layers of hard metal mortise and tenon structure are inserted, and the length of the inserted layer is L 拼插 ≥ Plate thickness D 板厚 , the thickness D1 of the relatively soft interlayer and the thickness D2 of the relatively hard interlayer are equal or different to reduce the local stress concentration at the butt joint;

[0021] (3) Through holes are processed in a direction perpendicular to the direction of insertion of the mortise and tenon structure to further reduce stress concentration in the butt joint structure;

[0022] (4) Use screw or rivet length L 钉 ≥ Plate thickness, number of screws or rivets through the through hole, n, n×π·R 2 ≤1 / 3 of the intercalation surface area, the intercalation surface area is the intercalation length L 拼插 × Insertion layer width W 拼插 , where R 钉 The radius of the screw is used to reinforce the mortise and tenon structure after insertion;

[0023] (5) Pre-stirring friction processing of the joint with high hardness in the two metal sheets, with the parameter range of rotation speed 150-450 rpm and forward speed 20-100 mm / min, to obtain a local fine-grained structure;

[0024] (6) Stir friction welding is performed at the joint, with parameter range: rotation speed 500-1600 rpm, forward speed 50-120 mm / min.

[0025] In some embodiments of the present application, there are multiple through holes, and the number of screws or rivets is the same as the number of through holes, forming a screw group or a rivet group, and the arrangement methods include neat arrangement, staggered arrangement, or topologically optimized arrangement.

[0026] In some embodiments of the present application, the shape of the mortise and tenon structure includes but is not limited to a cuboid, a step, a triangle, etc., and the height of the tenon along the thickness direction of the plate is W. 凸榫 , number m, m×W凸榫 ≤1 / 2 plate thickness W 拼插 , L 延伸 ≥0, the tenon extension part can be 0, the tenon extension length L 延伸 With tenon length L 凸榫 The sum shall not be less than the plate thickness.

[0027] In some embodiments of the present application, the tenon is a metal with a higher hardness among the two metal sheets or a metal with a lower hardness among the two metal sheets.

[0028] In some embodiments of the present application, the plate material connected by the mortise and tenon joint is a flat surface, a multi-deformed surface or a curved surface;

[0029] In some embodiments of the present application, the mortise and tenon layers may be reinforced by bolt connection, riveting, additive connection, welding, bonding, and the like.

[0030] In some embodiments of the present application, a reinforcement phase is added to the hard metal joint before pre-friction stir processing.

[0031] In some embodiments of the present application, the reinforcing phase is silicon, boron, Al2O3, or TiAl3 particles.

[0032] In some embodiments of the present application, a reinforcement phase is added to the joint portion with high hardness of two metal sheets by means of grooves, pre-made holes, foil layers or coatings.

[0033] In some embodiments of the present application, the plate material includes but is not limited to metal materials such as titanium, steel, aluminum, magnesium, and copper alloy.

[0034] In some embodiments of the present application, when the material to be welded is a titanium aluminum alloy, the generation of Ti-Al compounds Ti3Al, TiAl, and TiAl3 is suppressed by adding a silicon reinforcement phase.

[0035] In some embodiments of the present application, when the two plates are TC4 and 7A04 aluminum alloys, TC4 and 7A04 aluminum alloys are rolled structures before welding, the TC4 grain size is 42μm, and the aluminum alloy grain size ranges from 50 to 145μm; the titanium alloy is a long-axis structure, and the aluminum alloy is a lamellar structure; the TC4 after pre-stirring and the 7A04 after stir friction welding are both equiaxed fine-grained structures, the grains are refined, and the joint toe and void defects are significantly reduced.

[0036] The advantages of the present application are at least that the present application is to design a multi-layer mortise and tenon structure of a dissimilar metal joint, and to insert the multi-layer mortise and tenon structure to reduce the local stress concentration at the docking point and increase the fracture energy consumption; to add through holes, screws or rivets to fasten for topological optimization, and further reduce the stress concentration of the docking structure; to improve the plasticity of the hard metal sheet by the refinement and organization regulation of the local organization of the joint, and improve the fluidity of the relatively hard metal; the hard metal joint after pre-stirring has improved fluidity due to equiaxed and refined grains, and the defects such as the joint toe and voids are reduced, and the mechanical properties of the joint are improved; the plate after pre-stirring can continue to stir friction welding on the other side, which increases the fine grain area of ​​the joint and improves the toughness of the joint; and the intermetallic compounds of the joint are suppressed by adding elements or reinforcing particles in pre-stirring. Through the dissimilar metal connection method of the present application, the local stress concentration of the entire cross section can be reduced, the dissimilar metal connection strength can be improved, the crack propagation path and fracture energy consumption of the connection structure can be increased, and the structure can serve in a dynamic working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 This is a schematic diagram of dissimilar metal connection according to Example 1 of the present application;

[0039] Figure 2 Comparison diagram of conventional welding and mortise and tenon joints, where (a) welding; (b) mortise and tenon joints;

[0040] Figure 3 This is a comparison chart of impact toughness in Example 1 of the present application;

[0041] Figure 4 This is a connection diagram of Example 2 of the present application;

[0042] Figure 5 This is a connection diagram of Example 3 of the present application;

[0043] Figure 6 This is a connection diagram of Example 4 of the present application;

[0044] Figure numerals: 1-tenon, 2-mortise, 3-fastening structure, 4-structure obtained by pre-stirring friction processing on relatively hard metal, 5-structure obtained by pre-stirring friction processing on relatively soft metal. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to 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 application.

[0047] 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0048] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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, or it can be the internal communication of two components. For ordinary technicians in this field, the above terms in this application can be understood in specific circumstances.

[0049] Example 1

[0050] The method for connecting dissimilar metals in this embodiment is as follows:

[0051] 1. Two tenons 1 and three mortises 2 are processed for titanium alloy TC4 and aluminum alloy 7A01 respectively, and the height of the mortise and tenon structure along the thickness direction of the plate is mortise thickness D1 = 2 mm, and tenon thickness D2 = 2 mm;

[0052] 2. Butt and fix the titanium / aluminum metal plates;

[0053] 3. Process the threaded through hole with specification of M2 on the mortise and tenon joint part, and the through hole diameter is 2R 钉 2mm;

[0054] 4. L 钉The length is 10mm, the same as the plate thickness, and the bolt structure is screwed in to secure it.

[0055] This embodiment eliminates the metallurgical bonding layer in conventional dissimilar metal welding, that is, eliminates the intermetallic compound layer. The mortise and tenon structure design is adopted to achieve mechanical bite, and the bolt connection is used to disperse the stress concentration. This changes the dissimilar metal connection structure from brittle fracture to ductile fracture, and has the possibility of dynamic operation.

[0056] Compared with various welding methods, the dissimilar metals connected by the mortise and tenon structure have no metallurgical bonding layer. The metallurgical bonding layer is an intermetallic compound layer with ceramic properties. It cannot coordinate the plastic deformation of titanium / aluminum when subjected to stress, thus causing brittle fracture. The multi-layer mortise and tenon connection form weakens the local stress concentration and widens the stress-bearing area of ​​the connection.

[0057] The impact toughness of TC4, 7A01 and composite joints in this patent are 41.5, 12.5 and 28.0 J / cm respectively 2 It can be seen that the impact toughness of the composite joint of this patent invention is more than twice that of the aluminum alloy base material, while the impact toughness of conventional titanium / aluminum dissimilar metal welding is much lower than that of the base material.

[0058] Example 2

[0059] The method for connecting dissimilar metals in this embodiment is as follows:

[0060] 1. Process tenons 1 of relatively soft metal and mortises 2 of relatively hard metal respectively, the thickness of single-layer tenons and mortises is 4 mm, five layers in total, and the plate thickness is 20 mm;

[0061] 2. Fix the heterogeneous metal plates together;

[0062] 3. Process the M4 thread through holes on the mortise and tenon joints;

[0063] 4. Use M4 bolts and nuts to fasten the through hole structure 3. In this embodiment, rivets are used to fix the through hole structure 3.

[0064] 5. Pre-friction stir processing of relatively hard metals, with a rotation speed of 450 rpm and a forward speed of 40 mm / min, to obtain a fine-grained microstructure 4 structure;

[0065] 6. Stir friction welding was performed on relatively soft metal with parameters of rotation speed of 1000 rpm and forward speed of 80 mm / min to obtain weld position 5.

[0066] This embodiment improves the plasticity of hard metal plates and the fluidity of relatively hard metals by grain refinement and tissue regulation of the local structure of the joint; the fluidity of the hard metal joint after pre-stirring is improved due to the equiaxed and refined grains, defects such as joint toes and voids are reduced, and the mechanical properties of the joint are improved; the plate after pre-stirring can continue to be stir-friction welded on the other side, which increases the fine grain area of ​​the joint and improves the toughness of the joint.

[0067] Example 3

[0068] The method for connecting dissimilar metals in this embodiment is as follows:

[0069] 1. Processing polygonal tenon 1 of relatively soft metal and mortise 2 of relatively hard metal, respectively. The tenon includes an extension portion L. 延伸 =15mm and polygonal tenon L 凸榫 =15mm two parts, L 延伸 With L 凸榫 The sum of the lengths is not less than the plate thickness D 板厚 =40mm, the height of the tenon is D 凸榫 =10mm, number is 2;

[0070] 2. Fix the heterogeneous metal plates together;

[0071] 3. Process the φ7 through hole on the mortise and tenon joint;

[0072] 4. Use φ7 rivets to fasten the structure 3. This embodiment uses rivet structures to be driven in and fixed.

[0073] This embodiment combines tenons and mortises of different shapes, and the processing method is highly flexible and has high bonding strength.

[0074] Example 4

[0075] The method for connecting dissimilar metals in this embodiment is as follows:

[0076] 1. A polygonal tenon 1 is made of relatively soft metal and a mortise 2 is made of relatively hard metal. The mortise has three parts. The upper surface is represented by 2-1, the core is represented by 2-2, and the lower surface is represented by 2-3. The thickness of the upper, middle and lower surface is represented by D 2-1 , D 2-2 and D 2-3 To indicate that the length of the tenon and mortise should not be less than the thickness of the board D 板厚 =60mm, upper and lower surface thickness D 2-1 and D 2-3 15mm, core thickness D 2-2 The thickness of the interlayer D1 with dissimilar metals is 10mm;

[0077] 2. Butt-join and fix the relatively soft metal sheet and the relatively hard metal sheet among the two metal sheets;

[0078] 3. Process φ10 through holes on the mortise and tenon joints;

[0079] 4. Coaxial friction stir additive fastening is adopted, the diameter of the friction stir additive filler is 10 mm, the feeding parameters are the rotation speed of 300 rpm and the pressing speed of 30 mm / min.

[0080] Compared with direct mortise and tenon joints, the pre-mixed hard metal joints have improved fluidity due to equiaxed and refined grains, reduced defects such as joint toe and voids, and improved joint mechanical properties; the pre-mixed plates can continue to stir friction welding on the other side, which increases the fine grain area of ​​the joint and improves the toughness of the joint;

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for connecting dissimilar metals, characterized in that: The process steps include: (1) Design the mortise and tenon structure of two metal plates of different materials; (2) Insert the two metal sheets together, and the length of the insertion layer is L 拼插 ≥ Plate thickness D 板厚 , the thickness D1 of the relatively soft interlayer and the thickness D2 of the relatively hard interlayer are equal or different to reduce the local stress concentration at the butt joint; (3) Processing a through hole in a direction perpendicular to the direction of insertion of the mortise and tenon structure to further reduce stress concentration in the butt joint structure; (4) Use screw or rivet length L 钉 ≥ Plate thickness, pass through the through hole to reinforce the mortise and tenon structure after splicing; (5) Pre-stirring friction processing is performed on the joint area with high hardness of the two metal sheets to obtain a local fine-grained structure; (6) Perform friction stir welding at the joint.

2. A method for connecting dissimilar metals according to claim 1, characterized in that: The two metal plates of different materials include n layers of relatively soft metal and n+1 layers of relatively hard metal mortise and tenon joints; the number of screws or rivets is n, n×π·R 钉 2 ≤1 / 3 of the intercalation surface area, the intercalation surface area is the intercalation length L 拼插 × Insertion layer width W 拼插 , where R 钉 is the screw radius.

3. A method for connecting dissimilar metals according to claim 1, characterized in that: There are multiple through holes, and the number of screws or rivets is the same as the number of through holes, forming a screw group or a rivet group, and the arrangement method includes neat arrangement, staggered arrangement, or topological optimization arrangement.

4. A method for connecting dissimilar metals according to claim 1, characterized in that: The shape of the mortise and tenon structure includes one or more of a cuboid, a step, and a triangle. The height of the tenon along the thickness direction of the plate is W. 凸榫 , number m, m×W 凸榫 ≤1 / 2 plate thickness, L 延伸 ≥0, tenon extension length L 延伸 With tenon length L 凸榫 The sum shall not be less than the plate thickness.

5. The method for connecting dissimilar metals according to claim 1, characterized in that: The tenon is the metal with higher hardness among the two metal sheets or the metal with lower hardness among the two metal sheets; the pre-friction stir processing parameter range in step (5) is a rotation speed of 150-450 rpm and a forward speed of 20-100 mm / min; the friction stir welding parameter range in step (6) is a rotation speed of 500-1600 rpm and a forward speed of 50-120 mm / min.

6. A method for connecting dissimilar metals according to claim 1, characterized in that: The plate material connected by mortise and tenon joints is a flat surface, a multi-deformed surface or a curved surface.

7. The method for connecting dissimilar metals according to claim 1, characterized in that: Add reinforcement phase to hard metal joints before pre-friction stir processing.

8. A method for connecting dissimilar metals according to claim 7, characterized in that: The reinforcing phase is silicon, boron, Al2O3, and TiAl3 particles.

9. A method for connecting dissimilar metals according to claim 7 or 8, characterized in that: Reinforcement is added to the joint where the hardness of the two metal sheets is high by means of grooves, pre-formed holes, foil layers or coatings.

10. The method for connecting dissimilar metals according to claim 1, characterized in that: The plate material includes titanium, steel, aluminum, magnesium, and copper alloy.

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