Aluminum-steel structure transition joint, butt joint and welding method thereof

Abstract

The application provides an aluminum-steel structure transition joint, a butt joint and a welding method thereof. The welding method of the aluminum-steel structure transition joint comprises the following steps: polishing and polishing the to-be-welded surfaces of a complex layer, an intermediate layer and a base layer to be welded respectively; the complex layer is an aluminum alloy plate, the intermediate layer is an aluminum-manganese aluminum alloy plate, and the base layer is a steel plate; the treated base layer and intermediate layer are subjected to first explosive welding to obtain an aluminum alloy-steel composite plate; the aluminum alloy-steel composite plate is subjected to leveling and surface polishing treatment; the aluminum alloy surface of the obtained aluminum alloy-steel composite plate and the complex layer are subjected to second explosive welding, and the welded composite plate is processed into a transition joint. The aluminum-manganese aluminum alloy plate is used as the intermediate layer, the composite plate is obtained through layered two-time explosive welding, the transition joint is prepared through cold working, the joint butt joint is realized through electromagnetic pulse welding, and the transition connection between the dissimilar metals of the aluminum alloy and the steel is realized.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to an aluminum-steel structural transition joint, a butt joint, and a welding method thereof. Background Technology

[0002] In the field of shipbuilding and marine engineering, to achieve lightweight hulls and lower the center of gravity to improve navigation stability and speed, a composite structure design using steel as the main hull and aluminum alloy as the superstructure is widely adopted both domestically and internationally. Key components such as the helipad, passageways, and command center require high-strength dissimilar metal connections between the aluminum alloy structure and the steel deck. Traditional mechanical riveting processes suffer from drawbacks such as complex assembly and low construction efficiency, making them unsuitable for modern construction requirements.

[0003] Against this backdrop, aluminum-steel composite transition joints, produced through explosive welding, are gradually replacing mechanical riveting as the mainstream solution due to their ability to simplify construction processes and improve connection efficiency. This type of joint combines steel, an intermediate layer, and aluminum alloy through explosive welding to form a layered metallic composite material. After leveling, polishing, and cold working, it is used for transition connections between aluminum alloy and steel structures.

[0004] Patent application number 201610803070.X discloses a method for preparing an aluminum alloy-pure aluminum-steel composite plate, in which pure aluminum is used as the intermediate layer, which can alleviate the interfacial stress generated during explosive welding. However, the mechanical properties of pure aluminum itself are relatively low, which means that the overall tensile strength of the joint is limited by the upper limit of the strength of the pure aluminum intermediate layer, making it difficult to meet the high bonding strength requirements of shipbuilding and marine engineering. In addition, patent application number CN201910631072.9 discloses a welding method for 917 steel plate + aluminum-titanium steel composite material, which solves the problems of welding deformation and weld quality. However, for the butt joint connection between aluminum-steel composite transition joints, the gap is still generally filled by injection. Under this connection method, the overall connection strength of the joint is negligible. Under the influence of relative movement of steel and aluminum buildings and the multi-field coupling effect of high temperature, high humidity, high salt and strong radiation marine environment, factors such as thermal expansion and contraction, corrosion and aging will cause the gap filling adhesive to fail quickly. At the same time, seawater will provide sufficient electrolyte after entering the joint gap, which will inevitably cause galvanic corrosion between steel and aluminum, thus seriously affecting the bonding strength of steel-aluminum interface. In extreme cases, it will cause steel-aluminum delamination cracking failure. Summary of the Invention

[0005] In view of this, the present invention aims to provide an aluminum-steel structural transition joint, a butt joint, and a welding method thereof, in order to solve the problems of low interfacial bonding strength of aluminum alloy-aluminum alloy-steel joints in the prior art, and the further reduction of interfacial bonding strength caused by the joint butt welding process.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides a welding method for an aluminum-steel structural transition joint, comprising the following steps:

[0008] S1: Pretreatment of materials

[0009] The surfaces to be welded, including the cladding layer, intermediate layer, and base layer, are ground and polished respectively; the cladding layer is an aluminum alloy plate, the intermediate layer is an aluminum-manganese alloy plate, and the base layer is a steel plate.

[0010] S2: Perform the first explosive welding.

[0011] The base layer and intermediate layer after the pretreatment in step S1 are subjected to the first explosive welding to obtain an aluminum alloy-steel composite plate; the aluminum alloy-steel composite plate is then leveled and surface polished.

[0012] S3: Perform the second explosive welding.

[0013] The aluminum alloy surface and the cladding layer in the aluminum alloy-steel composite plate obtained in step S2 are subjected to a second explosive welding to obtain an aluminum alloy-aluminum alloy-steel composite plate.

[0014] S4: Processing and shaping

[0015] The aluminum alloy-aluminum alloy-steel composite plate obtained in step S3 is cold-worked to obtain the aluminum-steel structural transition joint.

[0016] This invention avoids multi-layer interface instability that occurs during single-explosive welding by using two explosive welding processes. At the same time, the intermediate layer uses an aluminum-manganese alloy instead of traditional pure aluminum, which significantly improves the metallurgical bonding strength of each interface of the composite plate and solves the problem of limited overall strength caused by insufficient mechanical properties of the intermediate layer in traditional transition joints. Furthermore, both explosive welding processes can form a strong metallurgical bond, ensuring uniform and stable overall mechanical properties of the transition joint.

[0017] In this invention, the intermediate layer is preferably an aluminum-manganese wrought aluminum alloy plate, more preferably a 3103 aluminum alloy plate or a 3004 aluminum alloy plate, the cladding layer is preferably a 5083 aluminum alloy plate, and the base layer is preferably a CCSB steel plate.

[0018] Furthermore, step S2 includes:

[0019] Inside the explosion-proof container, the base layer is placed on a leveled foundation, and the intermediate layer is placed on the base layer; a support is installed between the base layer and the intermediate layer to form an assembly gap, the height of which is 8~15mm;

[0020] The explosive is evenly spread on the middle layer, and the ratio of the amount of explosive to the area of ​​the middle layer is 15~20 kg / m². A detonator is placed in the explosive frame to detonate the explosive for the first explosion welding, thus obtaining the aluminum alloy-steel composite plate.

[0021] The invention uses an explosion-proof container to achieve the effects of vibration reduction and noise reduction, smoke and dust removal, weakening shock waves and controlling flying debris, which is more conducive to environmental protection. At the same time, the assembly gap of 8~15mm and the explosive dosage of 15~20kg / m² can ensure that the base layer and the intermediate layer form a tight metallurgical bond by high-speed impact, avoiding defects such as incomplete penetration and inclusions, and improving the bonding quality of the steel-aluminum interface.

[0022] Furthermore, step S3 includes:

[0023] Inside the explosion-proof container, the aluminum alloy-steel composite plate is placed on a leveled foundation, and the cladding layer is placed on the aluminum alloy-steel composite plate with the cladding layer close to the aluminum alloy side of the aluminum alloy-steel composite plate; a support is installed between the cladding layer and the aluminum alloy-steel composite plate to form an assembly gap, the height of which is 8~15mm.

[0024] Explosives are evenly spread on the composite layer, with the ratio of explosives to the area of ​​the composite layer being 10~15 kg / m². A detonator is placed inside the explosive frame to detonate the explosives for a second explosive welding, thus obtaining the aluminum alloy-aluminum alloy-steel composite plate.

[0025] This invention uses an explosion-proof container to achieve the effects of vibration reduction and noise reduction, smoke and dust removal, weakening of shock waves and control of flying debris, which is more conducive to environmental protection. At the same time, the assembly gap of 8~15mm and the explosive dosage of 10~15kg / m² can ensure that the high-speed impact between the cladding layer and the intermediate layer forms a tight metallurgical bond, avoiding the defect of non-composite, and forming a metallurgically bonded three-layer composite plate.

[0026] In this invention, the apparatus used for explosive welding is existing technology, and will not be described in detail here.

[0027] Furthermore, the thickness of the base layer is 5-25mm, the thickness of the intermediate layer is 2-8mm, and the thickness of the overlay layer is 4-15mm.

[0028] The thickness of the base layer of this invention is set to 5~25mm, which can meet the load-bearing strength requirements of steel hulls. The thickness of the intermediate layer is set to 2~8mm, which can ensure the metallurgical bonding of the steel-aluminum interface during explosive welding and provide sufficient mechanical transmission path. The thickness of the cladding layer is set to 4~15mm, which is suitable for the use of aluminum superstructures. At the same time, the overall thickness combination facilitates subsequent cold working and butt welding operations.

[0029] In this invention, the dimensions of the base layer are preferably 10-20mm thick × 800-1200mm wide × 3500-4500mm long; the dimensions of the intermediate layer are preferably 3-6mm thick × 800-1200mm wide × 3500-4500mm long; and the dimensions of the overlay layer are preferably 8-10mm thick × 800-1200mm wide × 3500-4500mm long.

[0030] Furthermore, in step S4, the cold processing includes one or more of sawing, water cutting, and wire cutting.

[0031] This invention employs a cold working process, which avoids damage to the original metallurgical interface of the composite plate caused by hot working, and ensures the dimensional accuracy and interface integrity of the transition joint.

[0032] The present invention also provides an aluminum-steel structural transition joint, which is obtained by welding using the welding method described in the above technical solution.

[0033] The aluminum-steel structural transition joint of the present invention is a three-layer metallurgical bonding structure consisting of a cladding layer (aluminum alloy), an intermediate layer (aluminum-manganese aluminum alloy), and a base layer (steel). Its interface shear strength and tensile strength are significantly higher than those of traditional pure aluminum intermediate layer composite plates, which can meet the requirements of higher strength steel-aluminum connection and is suitable for the harsh use scenarios of ships and marine engineering.

[0034] This invention provides a welding method for butt joints, comprising the following steps:

[0035] Step (1): Processing the bevel

[0036] The aluminum-steel structure transition joint described in the above technical solution is processed flat and arranged in opposite directions to form a butt joint to be welded; a V-shaped bevel is processed at the connection of the butt joint to be welded, wherein the bottom of the V-shaped bevel is on the base layer and the top is on the cladding layer; the surface of the V-shaped bevel is polished until the metal luster is exposed.

[0037] Step (2): Perform base layer welding

[0038] The base layer of the butt joint to be welded is overlaid with weld until it reaches the interface between the base layer and the intermediate layer, and a base layer weld bead is formed within the V-groove.

[0039] Step (3): Perform intermediate layer welding

[0040] After the overlay welding is completed, an aluminum alloy transition plate is assembled at the V-groove, and an electromagnetic pulse welding machine is used to weld the aluminum alloy transition plate to the base weld bead.

[0041] Step (4): Perform cladding welding

[0042] After welding is completed, the cladding layer is overlaid to form a cladding weld bead within the V-groove, thus obtaining the butt joint.

[0043] This invention replaces the traditional glue injection connection method with conventional overlay welding for the base layer and cladding layer of the transition joint described in the above technical solution, and electromagnetic pulse welding for the intermediate layer. This completely solves the problems of low glue injection connection strength, easy failure of glue layer, galvanic corrosion and delamination cracking caused by seawater intrusion.

[0044] Furthermore, in step (1), the angle of the V-shaped bevel is 30°~45°.

[0045] Furthermore, in step (2), MAG welding is preferably used to butt weld the base layer of the transition joint; in step (4), MIG welding is preferably used to butt weld the cladding layer of the transition joint.

[0046] In this invention, the angle of the V-groove is 30°~45°. This setting provides sufficient operating space for base layer welding, aluminum alloy transition plate assembly, and cladding welding, ensuring uniform weld filling without dead corners and avoiding incomplete penetration defects. At the same time, this angle can reduce welding stress concentration, reduce the risk of welding deformation of butt joints, and improve the mechanical properties of joints.

[0047] Furthermore, step (3) includes:

[0048] A support is placed on the surface of the base weld bead, and the aluminum alloy transition plate is placed on the support, with a gap of 0.5~3.5mm between the base weld bead and the aluminum alloy transition plate; the input current of the electromagnetic pulse welding machine is set to 550~850kA, the discharge voltage to 15~35kV, and the frequency to 10~20kHz. The electromagnetic pulse welding machine is started, and the aluminum alloy transition plate is driven to impact the base weld bead at high speed by the Lorentz force generated by the induction coil, so as to realize the welding connection between the aluminum alloy transition plate and the base weld bead.

[0049] The invention sets a gap of 0.5~3.5mm to ensure that the aluminum alloy transition plate has sufficient acceleration space under the action of Lorentz force, so as to achieve metallurgical bonding after high-speed impact; the input current of 550~850kA, the discharge voltage of 15~35kV and the frequency of 10~20kHz can not only ensure the firm bonding between the transition plate and the base weld, but also avoid the formation of brittle intermetallic compounds, thereby improving the reliability and stability of the intermediate layer welding.

[0050] In this invention, the aluminum alloy transition plate is preferably an aluminum-manganese alloy plate, and more preferably the same material as the intermediate layer; the thickness of the aluminum alloy transition plate is 0.8~6mm; the thickness of the aluminum alloy transition plate is preferably not less than the thickness of the intermediate layer.

[0051] The present invention also provides a butt joint, which is obtained by welding using the welding method described in the above technical solution.

[0052] In this invention, it is preferable to weld the base layer of the butt joint described in the above technical solution to the steel structure, and to weld the cladding layer to the aluminum structure.

[0053] It should be noted that the main structure of large structural components such as ships is usually based on steel. Aluminum alloys, due to their lightweight, excellent corrosion resistance and easy processing and forming characteristics, are often used in the superstructure of large structural components. The aluminum alloy-aluminum alloy-steel composite plate and its butt joint described in this invention can serve as a transitional connection component between the aluminum alloy superstructure and the steel main structure, effectively improving the connection strength of this dissimilar metal connection.

[0054] Compared with existing technologies, the aluminum-steel structural transition joint, butt joint, and welding method described in this invention have the following advantages:

[0055] (1) The present invention uses an aluminum-manganese alloy as an intermediate layer, which improves the interfacial bonding strength and better meets the requirements for reliable connection between the aluminum superstructure and the steel main body. At the same time, the welding method of two explosions layer by layer is adopted to avoid instability during the single explosion welding process of multi-layer plates.

[0056] (2) The butt joint connection between the joints of the present invention is carried out by a combination of electromagnetic pulse welding and conventional welding to form an integral metallurgical bond structure without gaps and adhesive layer, which completely blocks the seawater intrusion path and solves the problem of galvanic corrosion from the root. Moreover, electromagnetic pulse welding is a solid phase welding, which avoids the generation of brittle intermetallic compounds. The connection strength and fatigue resistance of the butt joint are far superior to those of the glued joint, which is suitable for long-term reliable service requirements. Attached Figure Description

[0057] The accompanying drawings, which form part of this invention, 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:

[0058] Figure 1 This is a schematic diagram illustrating the explosive welding principle of the present invention;

[0059] Figure 2 This is a schematic diagram illustrating the electromagnetic pulse welding principle of the present invention;

[0060] Figure 3 A schematic diagram of the glue injection connection for existing technology mating joints;

[0061] Figure 4 This is a schematic diagram of the bevel angle of the present invention;

[0062] Figure 5This is a schematic diagram of electromagnetic pulse welding of the intermediate layer of the present invention;

[0063] Figure 6 This is a schematic diagram of the welding structure of the butt joint described in this invention;

[0064] Figure 7 This is a schematic diagram showing the connection between the butt joint described in this invention and the steel substrate and aluminum alloy structural components. Detailed Implementation

[0065] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following experimental examples were obtained by the inventors through numerous experiments. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0066] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0067] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0068] like Figure 1 As shown, the substrate is horizontally fixed on a flat foundation, the support is laid on the upper surface of the substrate, and the cover plate is laid parallel on the support to form an assembly gap between the substrate and the cover plate, reserving acceleration space for the high-speed movement of the cover plate.

[0069] During operation, the detonator is activated first to detonate the detonator, which in turn detonates the explosive and generates a vertically downward explosive force. This force drives the cover plate to move at high speed towards the base plate along the assembly gap. The two collide violently, and the interface metal undergoes instantaneous plastic deformation, ultimately forming a continuous and tight metallurgical bond.

[0070] It should be noted that, in this embodiment, the substrate is a base layer to be welded or an aluminum alloy-steel composite plate formed by a first explosive welding process; the cover plate is an intermediate layer or a cladding layer.

[0071] like Figure 2 As shown, the support is arranged on the upper surface of the substrate to support the cover plate and form a working gap; at the same time, the capacitor, resistor, high voltage switch and induction coil are connected in series to form a closed loop, and the induction coil is set above the cover plate and maintains a preset distance from the cover plate.

[0072] During operation, the capacitor is first charged to a preset voltage using an external power supply. After charging is complete, the high-voltage switch is closed, and the capacitor rapidly discharges through the induction coil, generating a strong instantaneous current. Simultaneously, a strong pulsed magnetic field is generated around the induction coil. This magnetic field acts on the cladding plate, inducing reverse eddy currents on its surface. The interaction between the eddy currents and the pulsed magnetic field creates a downward-vertically-directed Lorentz force. Driven instantaneously by the Lorentz force, the cladding plate impacts the substrate at high speed along the working gap. The interface metal achieves metallurgical bonding in the solid state, avoiding the formation of brittle Al-Fe intermetallic compounds and ensuring the mechanical properties and corrosion resistance of the welded joint.

[0073] Figure 3 This diagram illustrates the adhesive injection connection of existing butt joints. The adhesive bonding layer fills the entire butt gap to fill the gap and connect the two transition joints, forming only a physical bond without metallurgical bonding.

[0074] In the high-temperature, high-humidity, and high-salt marine environment, as well as under the effects of thermal expansion and contraction and vibration, the adhesive bonding layer of this structure is prone to aging and cracking, leading to failure. This causes seawater to intrude into the joint gap, forming an electrolyte environment, which triggers galvanic corrosion of the base layer and the cladding layer, ultimately resulting in delamination cracking and connection failure of the joint.

[0075] Example 1: A welding method for an aluminum-steel structural transition joint

[0076] S1: Pretreatment of materials

[0077] The base layer is selected as CCSB steel plate (15mm thick, 4000mm long, 1000mm wide), the middle layer is 3103 aluminum alloy plate (3mm thick, 4100mm long, 1050mm wide), and the cladding layer is 5083 aluminum alloy plate (10mm thick, 4100mm long, 1050mm wide). An angle grinder is used to grind and polish the surfaces of the three layers of plates to be welded to remove the surface oxide film, oil and impurities, revealing the metallic luster.

[0078] S2: Perform the first explosive welding.

[0079] After leveling the foundation inside the explosion-proof container, the base CCSB steel plate is laid horizontally on the foundation. Supports are evenly distributed on the upper surface of the base layer, and the intermediate 3103 aluminum alloy plate is laid parallel on the supports, forming an assembly gap of 10±1mm between the base layer and the intermediate layer. Explosives are laid on the upper surface of the intermediate layer, with the explosive amount to the area ratio of the intermediate layer being 17.5±0.5kg / m². Detonators are embedded in the preset position in the middle of the explosives, and the detonators are electrically connected to the external detonator through wires. The detonator is activated, and the explosive detonation velocity is 2500±50 m / s, which detonates the explosives to generate a vertically downward explosive force, driving the intermediate layer to impact the base layer at high speed, forming an aluminum alloy-steel composite plate. After the composite plate is removed, it is leveled using a leveling machine and then polished.

[0080] S3: Perform the second explosive welding.

[0081] On a flat foundation inside the explosion-proof container, the leveled and polished aluminum alloy-steel composite plate is placed horizontally with the 3103 aluminum alloy middle layer facing upwards. Supports are placed on the aluminum alloy surface, and the 5083 aluminum alloy cladding plate is laid parallel on the supports, forming an assembly gap of 12±1mm. Explosives are laid on the cladding, with the explosive amount to the area of ​​the cladding being 14.5±0.5kg / m². Detonators and initiators are placed in the same manner as the first explosive welding, and the explosives are detonated to drive the cladding to impact the aluminum alloy surface of the aluminum alloy-steel composite plate at high speed, forming an aluminum alloy-aluminum alloy-steel composite plate.

[0082] The obtained aluminum alloy-aluminum alloy-steel composite plate is subjected to non-destructive testing and finishing: After the composite plate is leveled, it is fully inspected using ultrasonic flaw detection equipment. If no defects such as non-bonding are found, it can directly proceed to subsequent processing; if defects are detected, the defective area is marked and removed.

[0083] S4: Processing and shaping

[0084] The aluminum alloy-aluminum alloy-steel composite plate obtained in step S3 is cold-worked using wire cutting technology to obtain an aluminum-steel structural transition joint of (15+3+10)mm×30mm×3800mm.

[0085] Example 2: A welding method for butt joints

[0086] Step (1): Processing the bevel

[0087] like Figure 4 As shown, the two transition joints obtained in Example 1 are processed flat and then placed opposite each other to form a butt joint to be welded. A 35° V-shaped bevel is processed at the connection of the butt joint using a mechanical processing method. The bottom of the bevel is located in the base layer and the top is located in the superimposed layer. The surface of the bevel is ground with an angle grinder until the metal luster is exposed.

[0088] Step (2): Perform base layer welding

[0089] Select the appropriate MAG welding parameters for CCSB steel plates and perform butt welding on the base layer of the two transition joints. Control the heat input during the welding process to avoid high temperature conduction to the intermediate layer. Weld to the interface between the base layer and the intermediate layer to form a smooth base layer weld bead. After welding, grind the weld bead surface to make it smooth and expose the metallic luster.

[0090] Step (3): Perform intermediate layer welding

[0091] like Figure 5 As shown, a 3103 aluminum alloy transition plate (3mm×38mm×35mm) of the same grade as the intermediate layer is selected. A support is placed on the surface of the base weld bead, and the transition plate is placed on the support to form a gap of 2±1mm between the transition plate and the base weld bead. The parameters of the electromagnetic pulse welding machine are adjusted, with the input current set to 600kA, the discharge voltage to 20kV, and the frequency to 12kHz. The induction coil is set parallel to the transition plate at a preset distance above it. The high-voltage switch is closed, and the capacitor discharges rapidly through the induction coil to generate a strong pulsed magnetic field, which induces eddy currents on the surface of the transition plate. The interaction between the eddy currents and the magnetic field generates a Lorentz force, which drives the transition plate to impact the base weld bead at high speed, thus achieving the welding connection between the two.

[0092] Step (4): Perform cladding welding

[0093] Using MIG welding parameters suitable for 5083 aluminum alloy, the cladding layers of the two transition joints and the aluminum alloy transition plate were overlaid to fill the bevel and form a complete butt joint.

[0094] Example 3: A welding method for an aluminum-steel structural transition joint

[0095] S1: Pretreatment of materials

[0096] The base layer is selected as CCSB steel plate (20mm thick, 4000mm long, 1000mm wide), the middle layer is 3004 aluminum alloy plate (6mm thick, 4100mm long, 1050mm wide), and the cladding layer is 5083 aluminum alloy plate (8mm thick, 4100mm long, 1050mm wide). An angle grinder is used to grind and polish the surfaces of the three layers of plates to be welded to remove the surface oxide film, oil and impurities, revealing the metallic luster.

[0097] S2: Perform the first explosive welding.

[0098] After leveling the foundation inside the explosion-proof container, the base CCSB steel plate is laid horizontally on the foundation. Supports are evenly distributed on the upper surface of the base layer, and the intermediate 3004 aluminum alloy plate is laid parallel on the supports, forming an assembly gap of 12±1mm between the base layer and the intermediate layer. Explosives are laid on the upper surface of the intermediate layer, with the explosive amount to the area ratio of the intermediate layer being 18.5±0.5kg / m². Detonators are embedded in the preset position in the middle of the explosives, and the detonators are electrically connected to the external detonator through wires. The detonator is activated, and the explosive detonation velocity is 2500±50 m / s, which detonates the explosives to generate a vertically downward explosive force, driving the intermediate layer to impact the base layer at high speed, forming an aluminum alloy-steel composite plate. After the composite plate is removed, it is leveled using a leveling machine and then polished.

[0099] S3: Perform the second explosive welding.

[0100] On a flat foundation inside the explosion-proof container, the leveled and polished aluminum alloy-steel composite plate is placed horizontally with the 3004 aluminum alloy middle layer facing upwards. Supports are placed on the aluminum alloy surface, and the 5083 aluminum alloy cladding plate is laid parallel on the supports, forming an assembly gap of 10±0.5mm. Explosives are laid on the cladding, with the explosive amount to the area of ​​the cladding being 12.5±0.5kg / m². Detonators and initiators are placed in the same manner as the first explosive welding, and the explosives are detonated to drive the cladding to impact the aluminum alloy surface of the aluminum alloy-steel composite plate at high speed, forming an aluminum alloy-aluminum alloy-steel composite plate.

[0101] The obtained aluminum alloy-aluminum alloy-steel composite plate is subjected to non-destructive testing and finishing: After the composite plate is leveled, it is fully inspected using ultrasonic flaw detection equipment. If no defects such as non-bonding are found, it can directly proceed to subsequent processing; if defects are detected, the defective area is marked and removed.

[0102] S4: Processing and shaping

[0103] The aluminum alloy-aluminum alloy-steel composite plate obtained in step S3 is cold-worked using wire cutting technology to obtain an aluminum-steel structural transition joint of (20+6+8)mm×30mm×3800mm.

[0104] Example 4: A welding method for butt joints

[0105] Step (1): Processing the bevel

[0106] like Figure 4 As shown, the two transition joints obtained in Example 3 are processed flat and then placed opposite each other to form a butt joint to be welded. A 45° V-shaped bevel is processed at the connection of the butt joint using a mechanical processing method. The bottom of the bevel is located in the base layer and the top is located in the superimposed layer. The surface of the bevel is ground with an angle grinder until the metal luster is exposed.

[0107] Step (2): Perform base layer welding

[0108] Select the appropriate MAG welding parameters for CCSB steel plates and perform butt welding on the base layer of the two transition joints. Control the heat input during the welding process to avoid high temperature conduction to the intermediate layer. Weld to the interface between the base layer and the intermediate layer to form a smooth base layer weld bead. After welding, grind the weld bead surface to make it smooth and expose the metallic luster.

[0109] Step (3): Perform intermediate layer welding

[0110] like Figure 5 As shown, a 3004 aluminum alloy transition plate (6mm×32mm×35mm) of the same grade as the intermediate layer is selected. A support is placed on the surface of the base weld bead, and the transition plate is placed on the support to form a gap of 2±1mm between the transition plate and the base weld bead. The parameters of the electromagnetic pulse welding machine are adjusted, with the input current set to 850kA, the discharge voltage to 35kV, and the frequency to 17kHz. The induction coil is set parallel to the transition plate at a preset distance above it. The high-voltage switch is closed, and the capacitor discharges rapidly through the induction coil to generate a strong pulsed magnetic field, which induces eddy currents on the surface of the transition plate. The interaction between the eddy currents and the magnetic field generates a Lorentz force, which drives the transition plate to impact the base weld bead at high speed, thus achieving the welding connection between the two.

[0111] Step (4): Perform cladding welding

[0112] Select the MIG welding parameters suitable for 5083 aluminum alloy, weld the cladding of the two transition joints to the aluminum alloy transition plate, fill the bevel, and form a complete butt joint.

[0113] Figure 6 This is a schematic diagram of the welding structure of the butt joint described in this invention. It adopts a process that combines overlay welding and electromagnetic pulse welding to form a metallurgical bond, which can significantly improve the joint bonding strength.

[0114] Comparative Example 1: A welding method for an aluminum alloy-aluminum-steel transition joint

[0115] The difference from Example 1 is that pure aluminum is used as the intermediate layer, and the welding method is the same as in Example 1.

[0116] Application examples

[0117] Figure 7This is a schematic diagram illustrating the connection between the butt joint described in this invention and the steel substrate and aluminum alloy structural component. One end of the base layer (steel plate) of the butt joint is fixedly connected to the steel substrate by welding, and one end of the cladding layer (aluminum alloy plate) of the butt joint is correspondingly connected to the aluminum alloy structural component. The transitional function of the intermediate layer (aluminum-manganese alloy plate) of the butt joint is fully realized, effectively mitigating stress concentration caused by the difference in thermal expansion coefficients between steel and aluminum, preventing loosening, breakage, and other failures at the butt joint during use, and ensuring the stability and service life of the entire connection structure.

[0118] Test example:

[0119] The aluminum-steel structural transition joints obtained in Examples 1 and 3 and the joint obtained in Comparative Example 1 were subjected to main performance tests in accordance with CB20091 "Specification for Aluminum Alloy-Aluminum-Steel (Stainless Steel) Composite Transition Joints", China Classification Society "Materials and Welding Specifications", and MIL-J-24445A (SH) "Aluminum-Steel Bimetallic Joints". The results are shown in Table 1 below.

[0120]

[0121] It can be seen that the aluminum-steel structure transition joint obtained by the present invention has an interface shear strength and tensile strength that are more than 40% higher than those of the existing pure aluminum intermediate layer composite plate because the intermediate layer is made of 3-series aluminum-manganese aluminum alloy and combined with the layered explosive welding process. The joint is connected by a combination of MAG overlay welding, electromagnetic pulse welding and MIG welding, which is more airtight and firm than the glue injection connection.

[0122] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A welding method for butt joints, characterized in that, Includes the following steps: Step (1): Processing the bevel The aluminum-steel structure transition joint is processed flat and oriented to form a butt joint to be welded. A V-shaped bevel is machined at the joint to be welded, wherein the bottom of the V-shaped bevel is on the base layer and the top is on the cladding layer; the surface of the V-shaped bevel is polished until a metallic luster is exposed. The aluminum-steel structural transition joint is obtained by welding using the following steps: S1: Pretreatment of materials The surfaces to be welded, including the cladding layer, intermediate layer, and base layer, are ground and polished respectively; the cladding layer is an aluminum alloy plate, the intermediate layer is an aluminum-manganese alloy plate, and the base layer is a steel plate. S2: Perform the first explosive welding. The base layer and intermediate layer after the pretreatment in step S1 are subjected to the first explosive welding to obtain an aluminum alloy-steel composite plate; the aluminum alloy-steel composite plate is then leveled and surface polished. S3: Perform the second explosive welding. The aluminum alloy surface and the cladding layer in the aluminum alloy-steel composite plate obtained in step S2 are subjected to a second explosive welding to obtain an aluminum alloy-aluminum alloy-steel composite plate. S4: Processing and shaping The aluminum alloy-aluminum alloy-steel composite plate obtained in step S3 is cold-worked to obtain the aluminum-steel structure transition joint. Step (2): Perform base layer welding The base layer of the butt joint to be welded is overlaid with weld until it reaches the interface between the base layer and the intermediate layer, and a base layer weld bead is formed within the V-groove. Step (3): Perform intermediate layer welding After the overlay welding is completed, an aluminum alloy transition plate is assembled at the V-groove, and an electromagnetic pulse welding machine is used to weld the aluminum alloy transition plate to the base weld bead. Step (4): Perform cladding welding After welding is completed, the cladding layer is overlaid to form a cladding weld bead within the V-groove, thus obtaining the butt joint.

2. The welding method according to claim 1, characterized in that, Step S2 includes: Inside the explosion-proof container, the base layer is placed on a leveled foundation, and the intermediate layer is placed on the base layer; a support is installed between the base layer and the intermediate layer to form an assembly gap, the height of which is 8~15mm; The explosive is evenly spread on the middle layer, and the ratio of the amount of explosive to the area of ​​the middle layer is 15~20 kg / m². A detonator is placed in the explosive frame to detonate the explosive for the first explosion welding, thus obtaining the aluminum alloy-steel composite plate.

3. The welding method according to claim 2, characterized in that, Step S3 includes: Inside the explosion-proof container, the aluminum alloy-steel composite plate is placed on a leveled foundation, and the cladding layer is placed on the aluminum alloy-steel composite plate with the cladding layer close to the aluminum alloy side of the aluminum alloy-steel composite plate; a support is installed between the cladding layer and the aluminum alloy-steel composite plate to form an assembly gap, the height of which is 8~15mm. Explosives are evenly spread on the composite layer, with the ratio of explosives to the area of ​​the composite layer being 10~15 kg / m². A detonator is placed inside the explosive frame to detonate the explosives for a second explosive welding, thus obtaining the aluminum alloy-aluminum alloy-steel composite plate.

4. The welding method according to claim 1, characterized in that, The thickness of the base layer is 5~25mm, the thickness of the intermediate layer is 2~8mm, and the thickness of the overlay layer is 4~15mm.

5. The welding method according to claim 1, characterized in that, In step S4, the cold processing includes one or more of sawing, water cutting, and wire cutting.

6. The welding method according to claim 1, characterized in that, In step (1), the opening angle of the V-shaped bevel is 30°~45°.

7. The welding method according to claim 1, characterized in that, Step (3) includes: A support is placed on the surface of the base weld bead, and the aluminum alloy transition plate is placed on the support, with a gap of 0.5~3.5mm between the base weld bead and the aluminum alloy transition plate; the input current of the electromagnetic pulse welding machine is set to 550~850kA, the discharge voltage to 15~35kV, and the frequency to 10~20kHz. The electromagnetic pulse welding machine is started, and the aluminum alloy transition plate is driven to impact the base weld bead at high speed by the Lorentz force generated by the induction coil, so as to realize the welding connection between the aluminum alloy transition plate and the base weld bead.

8. A mating joint, characterized in that, It is obtained by welding according to any one of claims 1 to 7.

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