Metal / frp butt welding connection method using a transition joint

Abstract

The application provides a metal / FRP butt welding connection method using a transition joint, which solves the technical problems of low interface connection strength and limited joint bearing capacity when metal plates and FRP thick plates are butt welded. The application introduces a transition joint, which is provided with a joint main body, a metal connecting part and an FRP connecting part connected with the joint main body. The metal connecting part is in a mortise and tenon structure or a groove structure and is connected with the corresponding metal plate. The FRP connecting part is composed of multiple layers of parallel and equidistant metal sheets. The FRP matrix is heated, flows and is gradiently cooled and solidified in a mold cavity to obtain an integrated structure of the FRP-transition joint, thereby realizing the metal / FRP butt welding connection method. The application can be widely applied to the field of welding technology.

Description

Technical Field

[0001] This application belongs to the field of welding method technology, and more specifically, relates to a metal / FRP butt welding connection method using a transition joint. Background Technology

[0002] With societal development, energy conservation and emission reduction have become widely recognized topics. The concept of "lightweighting," originating in the racing industry, is a crucial way to achieve energy conservation, emission reduction, and lower vehicle energy consumption. With the emergence of new materials, replacing or partially replacing traditional aluminum, steel, and other metal materials with higher strength and lighter weight has become a trend. Fiber-reinforced resin (FRP) composites, as an important component of new materials, possess advantages such as high specific strength, good corrosion resistance, and low density, showing broad application prospects in vehicle, high-speed rail, and aircraft structures. However, due to the significant differences in physicochemical properties between metal materials and FRP materials, the most widely used joining methods in industry are currently adhesive bonding and mechanical bonding. Adhesive bonding methods suffer from long curing times and the tendency for the adhesive layer to age, fail, and detach. Mechanical bonding methods, due to the introduction of other structural components, increase the overall weight of the structure, and stress concentration at the connection points can easily occur, posing certain potential failure risks. Scholars have already explored the feasibility of welding methods for metal / FRP structure connections. The principle is that the high thermal conductivity of the metal material allows welding heat to be transferred to the metal / FRP interface, causing the FRP material to flow under heat and adhere to the metal material.

[0003] In practical engineering, butt welding of thick plates is a crucial step in achieving lightweight metal / FRP composite structures. Currently, research on thin plate lap joints is more extensive, but research on thick metal / FRP plate butt welding is limited. Furthermore, after welding, tensile forces act perpendicularly on the butt joint interface. Compared to lap joints, thick metal / FRP plate butt joints have lower load-bearing capacity, and their tensile and fatigue properties are insufficient to meet the actual service requirements of the components.

[0004] Patent CN106271029A discloses a method for joining metal materials and resin-based composite materials using friction stir welding. It utilizes an integrated friction stir welding tool with a shoulder / stirring pin, and welds the metal plate on top and the resin-based composite material below. The stirring pin penetrates the metal plate without entering the FRP material, thus initially achieving a connection between the metal and FRP. However, its joint type is lap joint, and it causes significant wear on the stirring head for materials such as high-strength steel, which is not conducive to practical industrial applications.

[0005] Therefore, how to achieve butt welding connection between thick plates of metal materials and FRP materials, improve the interface connection strength to meet the service requirements of metal / FRP structural components under different working conditions, and be compatible with multiple welding methods to meet the welding requirements of various metal materials and FRP materials in different positions has become the technical bottleneck that this invention aims to overcome. Summary of the Invention

[0006] To address the shortcomings of the aforementioned background technology, this invention provides a metal / FRP butt welding connection method utilizing a transition joint. By introducing a transition joint, which comprises a joint body, an FRP connecting part connected to the joint body, and a metal connecting part, the FRP connecting part is cured and bonded to a hybrid material composed of an FRP matrix and reinforcing fibers, achieving a multi-layer metal / FRP lap joint connection process and improving the bonding strength between the transition joint and the FRP matrix. The metal connecting part is connected to the metal sheet via a tenon or mortise structure or a bevel structure, and is compatible with welding methods such as friction stir welding, laser welding, and arc welding, thus realizing a metal / FRP butt welding connection method.

[0007] Therefore, the present invention provides a method for metal / FRP butt welding connection using a transition joint, specifically comprising the following steps:

[0008] (1) Prepare a transition joint. The transition joint has a joint body. One end of the joint body is connected to the FRP connection part. The FRP connection part is composed of multiple layers of parallel and equally spaced metal sheets. The FRP connection part of the transition joint is surface treated. The upper and lower surfaces of each layer of metal sheet are covered with a surface treatment layer. The other end of the joint body is connected to the metal connection part.

[0009] (2) The transition joint is clamped and fixed at the end of the mold cavity, the FRP matrix is ​​heated to a viscous state, and mixed with the reinforcing fiber to form a mixed material. The mixed material is poured into the mold cavity, the mixed material is immersed in the FRP connection part of the transition joint, the temperature is gradually reduced, the mixed material is cured, and an integrated structural component of "FRP-transition joint" is obtained.

[0010] (3) Connect the metal sheet and the metal connection of the transition joint and weld them to obtain a metal / FRP composite component.

[0011] Preferably, the metal connection is a mortise and tenon structure or a bevel structure.

[0012] Preferably, in step (1), before surface treatment of the FRP connection part of the transition joint, the transition joint needs to be cleaned with an organic solvent or cleaning agent to remove surface oxides and oil stains. The organic solvent is alcohol or acetone.

[0013] Preferably, in step (2), the FRP connection part of the transition joint is placed inside the mold cavity, and the joint body and metal connection part are placed outside the mold cavity.

[0014] Preferably, in step (2), the heating temperature is 260-290℃ and the cooling gradient is 10℃ / min.

[0015] Preferably, in step (2), the FRP matrix is ​​a thermoplastic resin-based composite matrix.

[0016] Preferably, the thermoplastic resin-based composite matrix is ​​one of PPS, PEEK, and PA66.

[0017] Preferably, in step (2), the reinforcing fiber is chopped carbon fiber or chopped glass fiber.

[0018] Preferably, the metal / FRP composite component needs to be placed in air to cool to room temperature.

[0019] Preferably, the air humidity is 20-30%.

[0020] Preferably, the transition joint is made of one of the following materials: aluminum alloy, magnesium alloy, titanium alloy, low carbon steel, or stainless steel.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) In the metal / FRP butt welding connection method using a transition joint of the present invention, by introducing a transition joint, the metal / FRP butt connection form is transformed into an lap joint form between multiple layers of metal sheets and the FRP substrate, which effectively increases the bonding area between the metal / FRP sheets and simplifies the metal / FRP butt welding connection process. In addition, the metal connection part of the transition joint adopts a tenon and mortise structure or a bevel structure. This structural design is conducive to the mating connection between the transition joint and the metal sheet, and is compatible with welding methods such as friction stir welding, laser welding, and arc welding, thereby improving the stability and adaptability of the metal sheet welding process.

[0023] (2) In the metal / FRP butt welding connection method of the present invention using a transition joint, the FRP connection part of the transition joint is surface treated so that the upper and lower surfaces of each metal sheet are covered with a surface treatment layer, thereby achieving the purpose of forming an effective connection between each metal sheet and the mixed material, effectively improving the bonding strength between the transition joint and the FRP matrix, and the resulting metal / FRP composite component has better mechanical properties and can be applied to more complex working conditions.

[0024] (3) In the metal / FRP butt welding connection method using a transition joint of the present invention, the transition joint is fixed at the end of the mold cavity, and the plasticized FRP matrix and reinforcing fibers are flow-injected and solidified with the transition joint to form an integrated "FRP-transition joint" structure. This process can be incorporated into the actual production process of FRP sheets, thereby improving the overall production efficiency and making it suitable for industrial production. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the transition joint structure of the mortise and tenon joint in this invention;

[0027] Figure 2 This is a schematic diagram of the transition joint structure of the bevel structure in this invention;

[0028] Figure 3 This is a schematic diagram of the molding process of the integrated FRP-transition joint structure in Embodiment 2 of the present invention;

[0029] Figure 4 This is a schematic diagram of the welding process between the aluminum alloy transition joint and the aluminum alloy plate in Embodiment 2 of the present invention;

[0030] Explanation of symbols in the diagram:

[0031] 1. Transition joint; 2. Metal connection part; 3. FRP connection part; 4. Mold cavity; 5. Feed port; 6. Mixed material; 7. Aluminum alloy sheet; 8. Joint body; 9. Friction stir welding device; 10. Mortise and tenon structure; 11. Bevel structure; 12. Metal sheet. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0033] Example 1

[0034] This invention provides a transition joint, wherein the transition joint 1 can be made of one of the following materials: aluminum alloy, magnesium alloy, titanium alloy, low carbon steel, or stainless steel. For example... Figure 1 and Figure 2As shown, the transition joint 1 is provided with a joint body 8. One end of the joint body 8 is connected to the metal connecting part 2, and the other end is connected to the FRP connecting part 3. The FRP connecting part 3 is composed of multiple layers of parallel and equally spaced metal sheets 12. This structural design can effectively increase the bonding area between the metal sheet 12 and the FRP material and simplify the metal / FRP butt welding connection process.

[0035] The metal connection part 2 is either a mortise and tenon structure 10 or a bevel structure 11. If the metal connection part 2 is a mortise and tenon structure 10, it is connected to the metal sheet using the mortise and tenon joint, and the transition joint 1 is welded to the metal sheet using friction stir welding. If the metal connection part 2 is a bevel structure 11, it is connected to the metal sheet, and the transition joint 1 is welded to the metal sheet using welding methods such as arc welding or laser welding. Both structural designs improve the stability of the metal sheet welding process and facilitate rapid and efficient welding.

[0036] A method for metal / FRP butt welding connection using transition joint 1, the specific steps of which are as follows:

[0037] (1) Clean the transition joint 1 with an organic solvent or cleaning agent to remove surface oxides and oil stains. The organic solvent here is alcohol or acetone. Then, perform surface treatment on the FRP connection part of the transition joint so that the upper and lower surfaces of each metal sheet 12 are covered with a surface treatment layer. Surface treatment methods include, but are not limited to, anodizing, micro-arc oxidation, silane coupling agent treatment, etc.

[0038] (2) Figure 3 As shown, the transition joint 1 is clamped and fixed at the end of the mold cavity 4. The FRP connecting part 3 of the transition joint 1 is fully inserted into the mold cavity 4. The main body and metal connecting part 2 of the transition joint 1 are placed outside the mold cavity 4. The width and height of the joint body 8 of the transition joint 1 are the same as the width and height of the mold cavity 4.

[0039] (3) The FRP matrix is ​​heated to 260-290℃ to reach a viscous flow state, and then mixed with reinforcing fibers to form a composite material 6. The composite material 6 is poured into the mold cavity 4 through the inlet 5, immersing the FRP connecting part 3 of the transition joint 1. After maintaining this state for 3-5 minutes, a gradient cooling process is performed at a gradient of 10℃ / min, allowing the FRP matrix to fully solidify. The solidified composite material 6 completely encapsulates the FRP connecting part 3 of the transition joint 1, forming an integrated "FRP-transition joint" structure. The FRP matrix is ​​a thermoplastic resin-based composite material matrix. Preferably, the thermoplastic resin-based composite material matrix is ​​one of PPS, PEEK, or PA66. The reinforcing fibers are chopped carbon fibers or chopped glass fibers.

[0040] (4) Connect the metal plate and the metal connection part 2 of the transition joint 1, and select the corresponding welding method according to the structure of the metal connection part to perform welding. The welding method includes, but is not limited to, friction stir welding, arc welding, laser welding and other methods to obtain metal / FRP composite components.

[0041] (5) Place the welded metal / FRP composite component in an air humidity of 20-30% to cool it to room temperature.

[0042] Example 2

[0043] A method for metal / FRP butt welding connection using transition joint 1, the specific steps of which are as follows:

[0044] In this embodiment, the transition joint 1 is an aluminum alloy transition joint, its FRP connecting part 3 is composed of multiple layers of parallel and equally spaced aluminum alloy sheets, its metal connecting part 2 is a tenon and mortise structure 10, the FRP matrix is ​​PA66, the chopped fiber is chopped carbon fiber, the metal plate is aluminum alloy plate 7, and the welding method is friction stir welding.

[0045] (1) Immerse the aluminum alloy transition joint in 5% sodium hydroxide and 5% hydrochloric acid solutions in sequence to remove oxides on the surface of the aluminum alloy transition joint, and then clean and wipe the aluminum alloy transition joint with acetone.

[0046] (2) Clean the FRP connection part 3 of the aluminum alloy transition joint with 5% sodium hydroxide solution, prepare silane coupling treatment solution, immerse the FRP connection part 3 of the aluminum alloy transition joint in the silane treatment solution and keep it for 60s. After the surface of the FRP connection part 3 of the aluminum alloy transition joint is covered with silane film, place the transition joint 1 at 120℃ to dry for 40min. The silane film layer is cured on the surface of the aluminum alloy sheet.

[0047] (3) The surface-treated aluminum alloy transition joint is installed at the end of the mold cavity 4. The aluminum alloy transition joint is clamped and fixed using a clamp. The FRP connection part 3 of the aluminum alloy transition joint is fully inserted into the mold cavity 4, and the joint body 8 and the aluminum alloy connection end are placed outside the mold cavity 4.

[0048] (4) Figure 3 As shown in the diagram, the arrows indicate the flow direction of the mixed material. The PA66 resin matrix is ​​heated to 275℃, reaching a viscous flow state, and then mixed with chopped carbon fibers to form mixed material 6. This mixed material 6 is poured into the mold cavity 4 through the inlet 5, allowing it to fully impregnate the FRP connection part 3 of the aluminum alloy transition joint. After maintaining this temperature for 3-5 minutes, a cooling process is initiated at a rate of 10℃ / min, cooling to 20℃ to allow the mixed material 6 to fully solidify. The solidified mixed material 6 completely encapsulates the FRP connection part 3 of the aluminum alloy transition joint, forming an integrated "FRP-transition joint" structural component.

[0049] (5) Figure 4 As shown in the figure, the arrow indicates the welding direction. The friction stir welding device 9 is used to weld the transition joint of the integrated structure of "FRP-transition joint" in step (4) to the aluminum alloy plate 7.

[0050] First, the aluminum alloy transition joint and the aluminum alloy plate 7 are combined and connected by the mortise and tenon structure 10 of the aluminum alloy connection end of the aluminum alloy transition joint through the step structure of the edge of the aluminum alloy plate 7.

[0051] Next, set the welding starting position by aligning the edge of the stirring pin with the front end of the metal connection part of the aluminum alloy transition joint. Then, move the stirring pin a distance r towards the center of the aluminum alloy plate 7, where r is the actual radius of the stirring head shoulder. Set this position as the X-axis origin. On the Y-axis of the weld, select a position that will not touch the clamp as the Y-axis origin. Slowly lower the stirring pin to about 2-3mm. Place a 0.15mm feeler gauge under the stirring pin and continue to lower the stirring pin until it presses down on the feeler gauge. Pull the feeler gauge and adjust the Z-axis orientation of the stirring pin until the feeler gauge feels blocked when pulled out. Select three points on the tenon structure 10 connection surface of the aluminum alloy connection end of the aluminum alloy transition joint and take the average value. Set the average value as the welding Z-axis origin. At this time, the stirring pin is 0.15mm away from the surface of the tenon structure 10 connection of the aluminum alloy connection end.

[0052] The welding speed is set to 500-300 mm / min, the stirring needle speed is 1000-500 rpm, the shoulder pressing amount is 0.2 mm, the welding tilt angle is 1°, the pressing speed is 4 mm / min, the initial dwell time is 5 s, welding begins, and the composite component is cooled to room temperature using a compressed air cooler until welding is completed.

[0053] (6) Place the composite component in an air humidity of 25% to cool to room temperature.

[0054] Example 3

[0055] Unlike Example 2, in step (4), the PA66 resin matrix is ​​heated to 260°C, the PA66 resin matrix reaches a viscous flow state, and is mixed with short-cut carbon fibers to form a composite material 6. The composite component is obtained by the same stir friction welding method as in Example 2, and the composite component is placed in an air humidity of 20% to cool to room temperature.

[0056] Example 4

[0057] Unlike Example 2, in step (4), the PA66 resin matrix is ​​heated to 290°C, the PA66 resin matrix reaches a viscous flow state, and is mixed with short-cut carbon fibers to form a composite material 6. The composite component is obtained by the same stir friction welding method as in Example 2, and the composite component is placed in an air humidity of 30% to cool to room temperature.

[0058] In summary, the metal / FRP butt welding connection method of the present invention, by introducing a transition joint 1, transforms the metal / FRP butt connection into an lap joint between multiple metal sheets and the FRP substrate, effectively increasing the bonding area between the metal sheets and the FRP material, simplifying the metal / FRP butt welding connection process, and being applicable to various welding methods, thereby improving the applicability of welding methods in the metal / FRP structure welding process.

[0059] In summary, firstly, in the metal / FRP butt welding connection method using a transition joint of the present invention, by introducing a transition joint 1, the metal / FRP butt connection form is transformed into an lap joint form between multiple layers of metal sheets and the FRP substrate, effectively increasing the bonding area between the metal / FRP sheets and simplifying the metal / FRP butt welding connection process. Secondly, the metal connection portion of the transition joint 1 adopts a tenon and mortise structure 10 or a bevel structure 11. This structural design facilitates the mating connection between the transition joint 1 and the metal sheet, and is compatible with welding methods such as friction stir welding, laser welding, and arc welding, improving the stability and adaptability of the metal sheet welding process.

[0060] Secondly, in the metal / FRP butt welding connection method using transition joints of the present invention, the FRP connection part 3 of the transition joint 1 is surface treated so that the upper and lower surfaces of each metal sheet 12 are covered with a surface treatment layer, thereby achieving the purpose of forming an effective connection between each metal sheet 12 and the hybrid material, effectively improving the bonding strength between the transition joint 1 and the FRP matrix, and the resulting metal / FRP composite component has better mechanical properties and can be applied to more complex working conditions.

[0061] Finally, in the metal FRP thick plate butt welding connection method using a transition joint of the present invention, the transition joint 1 is fixed at the end of the mold cavity 4, and the plasticized FRP matrix and reinforcing fibers are flow-injected and cured with the transition joint 1 to form an integrated "FRP-transition joint" structure. This process can be incorporated into the actual production process of FRP sheets, thereby improving the overall production efficiency and making it suitable for industrial production.

[0062] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for metal / FRP butt welding connection using a transition joint, characterized in that, Includes the following steps: (1) Prepare a transition joint. The transition joint is provided with a joint body. One end of the joint body is connected to an FRP connecting part. The FRP connecting part is composed of multiple layers of parallel and equally spaced metal sheets. The FRP connecting part of the transition joint is surface treated. The upper and lower surfaces of each layer of metal sheet are covered with a surface treatment layer. The other end of the joint body is connected to the metal connecting part. (2) The transition joint is clamped and fixed at the end of the mold cavity, the FRP matrix is ​​heated to a viscous state, and mixed with the reinforcing fiber to form a mixed material. The mixed material is poured into the mold cavity, the mixed material is immersed in the FRP connection part of the transition joint, the temperature is gradually reduced, the mixed material is cured, and an integrated structural component of "FRP-transition joint" is obtained. (3) Connect and weld the metal connection parts of the metal sheet and the transition joint to obtain a metal / FRP composite component; In step (2), the FRP connection part of the transition joint is placed inside the mold cavity, and the joint body and the metal connection part are placed outside the mold cavity.

2. The metal / FRP butt welding connection method using a transition joint according to claim 1, characterized in that, The metal connection part is a mortise and tenon structure or a bevel structure.

3. The metal / FRP butt welding connection method using a transition joint according to claim 1, characterized in that, In step (1), before surface treatment of the FRP connection part of the transition joint, it is necessary to clean the transition joint with an organic solvent or cleaning agent to remove surface oxides and oil stains. The organic solvent is alcohol or acetone.

4. The metal / FRP butt welding connection method using a transition joint according to claim 1, characterized in that, In step (2), the heating temperature is 260-290℃ and the cooling gradient is 10℃ / min.

5. The method for metal / FRP butt welding connection using a transition joint according to claim 1, characterized in that, In step (2), the FRP matrix is ​​a thermoplastic resin-based composite matrix.

6. The method for metal / FRP butt welding connection using a transition joint according to claim 5, characterized in that, The thermoplastic resin-based composite matrix is ​​one of PPS, PEEK, and PA66.

7. The method for metal / FRP butt welding connection using a transition joint according to claim 1, characterized in that, In step (2), the reinforcing fiber is chopped carbon fiber or chopped glass fiber.

8. The method for metal / FRP butt welding connection using a transition joint according to claim 1, characterized in that, The metal / FRP composite component needs to be placed in air to cool to room temperature.

9. The method for metal / FRP butt welding connection using a transition joint according to claim 8, characterized in that, The air humidity is 20-30%.

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