Electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy material

Abstract

This invention relates to an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials, belonging to the field of electron beam welding technology. It addresses one of the problems encountered in existing electron beam welding methods for ZL114A / ZL270, namely, the presence of obvious cracks, incomplete fusion, and excessive internal porosity within the weld seam. The electron beam welding method of this invention includes: tack welding of assembled ZL114A and ZL270 alloy test plates; welding using a dual electron beam synchronous welding method with one electron beam preheating the weld seam first, followed by the other electron beam for the final welding; during the final welding process, the center of the electron beam spot is shifted from the butt joint of the test plates towards the ZL270 alloy plate side.

Description

Technical Field

[0001] This invention belongs to the field of electron beam welding technology, and particularly relates to an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. Background Technology

[0002] ZL114A cast aluminum alloy is an Al-Si-Mg ternary alloy. Due to its light weight, excellent mechanical properties, and good weldability, its welded parts have been widely used in aerospace and other fields in recent years. ZL270 aluminum alloy is a new type of aluminum alloy developed in recent years. It has excellent tensile strength, good mechanical properties, corrosion resistance, and good weldability, and its application in the aerospace field is gradually increasing.

[0003] In the actual production of aerospace products, due to the differences in service environment, temperature, and required mechanical properties of different parts of the same component, there is an increasing need to weld ZL114A and ZL270 aluminum alloys together. This involves welding dissimilar aluminum alloy materials. Because ZL114A and ZL270 alloys have different compositions and contents, their corresponding physical property parameters differ. Furthermore, the elongation of the two materials is around 5%, making them prone to defects such as porosity and cracks during welding, thus posing a significant welding challenge.

[0004] Currently, the main welding methods for dissimilar aluminum alloys include argon arc welding, laser welding, and friction stir welding. Each of these methods has certain limitations. Argon arc welding has a large heat input, resulting in significant component deformation during the welding process and a high likelihood of forming numerous cracks in the weld. Simultaneously, the weld and heat-affected zone are severely heated during welding, leading to significant grain coarsening and reduction in the mechanical properties of the weld. While friction stir welding avoids the porosity, cracking, and deformation problems associated with fusion welding of aluminum alloys, its weld structure is relatively simple, and its welding efficiency is lower than that of fusion welding, hindering its widespread application. Laser welding offers advantages such as controllable heat input, a small heat-affected zone, high welding speed, high welding efficiency, and minimal welding deformation. However, due to severe laser reflection from the molten pool during aluminum alloy welding, the weld penetration depth is limited, making it difficult to achieve high-performance welding of thick aluminum alloys. Electron beam welding, with its high power density, large welding depth, and high welding quality, has become one of the preferred solutions for welding dissimilar aluminum alloys. During the research process, the applicant discovered that when using electron beam welding of ZL114A / ZL270, if the process parameters are not properly controlled, obvious cracks may easily appear inside the weld, or problems such as incomplete fusion and excessive internal porosity may occur. Therefore, there is an urgent need to develop an efficient and high-quality electron beam welding method for welding dissimilar materials such as ZL114A / ZL270. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials to solve one of the following technical problems: When electron beam welding ZL114A / ZL270 is performed, obvious cracks, lack of fusion, and excessive internal porosity are easily present in the weld.

[0006] This invention provides an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials, comprising:

[0007] The assembled ZL114A and ZL270 alloy test plates were tack welded. Welding was carried out using a dual electron beam synchronous welding method with one electron beam preheating the weld first, and the other electron beam performing the formal welding. During the formal welding process, the center of the electron beam spot was shifted from the test plate joint to the ZL270 alloy plate side.

[0008] Furthermore, the following steps are included:

[0009] Step 1: Welding joint design. The welding joint is a lock-bottom butt joint type.

[0010] Step 2, Assembly: Secure the ZL114A and ZL270 aluminum alloy plates firmly using the test plate clamps;

[0011] Step 3: Place the assembled ZL114A and ZL270 alloy test plates into the vacuum chamber and evacuate the vacuum chamber;

[0012] Step 4: Teach the weld trajectory;

[0013] Step 5: Perform tack welding on the ZL114A and ZL270 alloy test plates;

[0014] Step 6: Welding is carried out using a dual electron beam synchronous welding method with one electron beam arranged in front and behind. One electron beam is used to preheat the weld first, and the other electron beam is used to perform the formal welding. During the formal welding process, the center of the electron beam spot is shifted from the test plate joint to the ZL270 alloy plate side.

[0015] Step 7: Repair and weld the weld seam;

[0016] Step 8: Grinding after welding.

[0017] Furthermore, in step 2, the maximum butt gap of the weld is controlled to be less than 0.2 mm, and the step difference is not greater than 10% of the base metal thickness.

[0018] Furthermore, in step 4, the electron beam current used is controlled to be 3-5 mA.

[0019] Furthermore, in step 3, the vacuum level of the vacuum chamber is controlled at 2×10⁻⁶. -2 Pa ~ 7×10-2 Pa.

[0020] Furthermore, in step 5, the process parameters for tack welding are: working distance 295-305mm, accelerating voltage 55-60kV, focusing current surface coke + (0.01-0.04)A, electron beam current 15-22mA, and welding speed 980-1010mm / min.

[0021] Furthermore, in step 6, the preheated electron beam current is 8–10 mA.

[0022] Furthermore, in step 6, the line energy density E during the formal welding is between 115.5 J / mm and 225 J / mm.

[0023] Furthermore, in step 6, the center of the electron beam spot is controlled to be offset by 0.15 to 0.2 mm from the joint of the test plate towards the ZL270 alloy plate.

[0024] Furthermore, in step 6, during the actual electron beam welding, the scanning waveform adopts an "O"-shaped scanning method.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] (1) The electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials of the present invention adopts a synchronous welding method with dual electron beams arranged in front and behind, which can realize simultaneous preheating and welding, effectively reducing the formation of internal cracks in the dissimilar joint during the welding process; the electron beam spot center is used to weld from the test plate joint to the ZL270 alloy plate side, which can solve the problem of incomplete fusion caused by irregular molten pool shape.

[0027] (2) The method of the present invention uses vacuum electronic welding of aluminum alloys, which concentrates energy, has low heat input, small heat-affected zone, and small welding deformation. At the same time, the vacuum environment can effectively prevent the oxidation of the weld and the loss of elements.

[0028] (3) The method of the present invention uses an “O”-shaped scanning method to agitate the molten pool with an electron beam during the welding process, which causes the pores inside the molten pool to escape rapidly before the molten pool solidifies, thereby reducing internal pore defects.

[0029] (4) The weld surface obtained by the method of the present invention is smooth and beautiful, free from defects such as inclusions, cracks, and depressions. The weld interior is free from defects such as cracks, incomplete penetration, and incomplete fusion. The weld quality meets the requirements of Class I weld in GJB1718A-2005 standard. The tensile strength of the joint reaches 245-255 MPa, exceeding 80% of the ZL114A base metal strength of 300 MPa, and the elongation after fracture is 3%-4%.

[0030] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0031] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0032] Figure 1 This is a schematic diagram of the structure of the ZL114A / ZL270 dissimilar aluminum alloy welded joint of the present invention;

[0033] Figure 2 This is a schematic diagram of the dual electron beam welding of the present invention;

[0034] Figure 3 This is a surface morphology diagram of the ZL114A / ZL270 dissimilar aluminum alloy weld in Embodiment 1 of the present invention;

[0035] Figure 4 This is a surface morphology diagram of the ZL114A / ZL270 dissimilar aluminum alloy weld in Embodiment 2 of the present invention;

[0036] Figure 5 This is a surface morphology diagram of the ZL114A / ZL270 dissimilar aluminum alloy weld in Embodiment 3 of the present invention.

[0037] Figure label:

[0038] 1-Electron beam, 2-Deflection coil, 3-Preheating electron beam, 4-Welding electron beam, 5-Workpiece weld, 6-“O”-shaped scanning mode, 7-Welding direction, 8-ZL114A alloy connector, 9-ZL270 alloy connector. Detailed Implementation

[0039] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and are used to illustrate the principles of the present invention.

[0040] This invention provides an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. The method includes: tack welding of assembled ZL114A and ZL270 alloy test plates; welding using a dual electron beam synchronous welding method with front and rear arrangement, wherein one electron beam preheats the weld first, and the other electron beam performs the formal welding; during the formal welding process, the center of the electron beam spot is shifted from the test plate joint to the ZL270 alloy plate side.

[0041] Compared with the prior art, the electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials of the present invention adopts a synchronous welding method with dual electron beams arranged in front and behind, which can realize simultaneous preheating and welding, effectively reducing the formation of internal cracks in the dissimilar joint during the welding process; the electron beam spot center is used to weld from the test plate joint to the ZL270 alloy plate side, which can solve the problem of incomplete fusion caused by irregular molten pool shape; the weld surface obtained by the method of the present invention is flat and beautiful, without inclusions, cracks, depressions and other defects, and the weld interior is free from cracks, incomplete penetration and incomplete fusion, and the weld quality meets the requirements of Class I weld in GJB1718A-2005 standard.

[0042] Specifically, the electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials of the present invention includes the following steps:

[0043] Step 1: Welding joint design. The welding joint is a lock-bottom butt joint type.

[0044] Step 2, Assembly: Secure the ZL114A and ZL270 aluminum alloy plates firmly using the test plate clamps;

[0045] Step 3: Place the assembled ZL114A and ZL270 alloy test plates into the vacuum chamber and evacuate the vacuum chamber;

[0046] Step 4: Teach the weld trajectory using a smaller electron beam;

[0047] Step 5: Perform tack welding on the ZL114A and ZL270 alloy test plates;

[0048] Step 6: Welding is carried out using a dual electron beam synchronous welding method with one electron beam arranged in front and behind. One electron beam preheats the weld first, and the other electron beam performs the formal welding within 0.1 to 1 second. During the formal welding process, the center of the electron beam spot is shifted from the test plate joint to the ZL270 alloy plate side.

[0049] Step 7: Repair and weld the weld seam;

[0050] Step 8, Post-weld grinding: After welding, grind and clean the weld surface to remove the volatile metal layer on the surface.

[0051] Specifically, the chemical composition of the above-mentioned ZL114A by weight percentage is as follows: Si 6.5%~7.5%, Fe≤0.2%, Cu≤0.1%, Mn≤0.1%, Mg 0.45%~0.75%, Zn≤0.1%, Ti≤0.1%, with the balance being Al.

[0052] Specifically, the chemical composition of the aforementioned ZL270, by weight percentage, is as follows: Cu 4.3%–5.8%, Mg 0.25%–0.5%, Ti 0.15%–0.35%, Mn 0.7%–1.5%, with the balance being Al.

[0053] Specifically, in step 1 above, such as Figure 1 As shown, in order to ensure assembly quality, the welding joint is a lock-bottom butt joint; the ZL114A alloy joint 8 is equipped with a lock bottom, and the ZL270 alloy joint 9 is located on the upper side of the lock bottom.

[0054] Specifically, step 2 above also includes a pre-welding cleaning process before assembly, which involves grinding and scraping the ZL114A and ZL270 aluminum alloy plates.

[0055] Specifically, in step 2 above, the ZL114A and ZL270 aluminum alloy plates are firmly fixed using a test plate fixture to ensure that the weld gap and step difference meet the pre-welding requirements.

[0056] Specifically, in step 2 above, considering that an excessively large maximum butt gap in the weld can cause the weld surface to collapse during electron beam welding, resulting in surface depression and insufficient weld strength, and that an excessively large step difference reduces the effective butt thickness of the weld, lowering its load-bearing capacity and causing the overall strength to fail to meet requirements, the maximum butt gap in the weld should be controlled to be below 0.2 mm, and the step difference should not exceed 10% of the base metal thickness.

[0057] Specifically, in step 3 above, in order to effectively prevent oxidation and element loss in the weld, the vacuum level of the vacuum chamber is controlled at 2×10⁻⁶. -2 Pa ~ 7×10 -2 Pa.

[0058] Specifically, in step 4 above, the electron beam spot is kept in the center of the weld during the teaching process. Considering that both excessively large and small electron beam currents during the teaching process will affect the accuracy of electron beam positioning of the weld center, the electron beam current used is controlled to be 3-5 mA.

[0059] Specifically, in step 5 above, tack welds are uniformly applied along the weld seam, with each segment of the tack weld being 20-30mm long and the tack weld spacing being 50-80mm.

[0060] Specifically, in step 5 above, the process parameters for controlling the tack welding are: working distance 295-305mm, accelerating voltage 55-60kV, focusing current surface coke + (0.01-0.04)A, electron beam current 15-22mA, and welding speed 980-1010mm / min.

[0061] Specifically, in step 6 above, along the welding direction 7, a synchronous welding method with dual electron beams arranged in front and behind is adopted. After the preheating electron beam 3 preheats the weld seam 5 of the workpiece, the welding electron beam 4 immediately follows to perform the formal welding. The preheating and formal welding are closely connected, and the alloy test plate can still maintain a relatively high temperature during the formal welding, thereby reducing the temperature gradient and internal thermal stress in the welding process, thus preventing the generation of internal cracks in the weld seam.

[0062] Specifically, such as Figure 2 The diagram shows a schematic of dual electron beam welding according to the present invention. Electron beam 1 passes through deflection coil 2. A pre-set current is applied inside the deflection coil to form an electromagnetic field, which generates a Lorentz force on the passing electron beam. Under the action of the Lorentz force, the electron beam is deflected. Dual electron beam welding can be achieved by changing the current value inside the deflection coil.

[0063] Specifically, in step 6 above, considering that excessive preheating electron beam current would lead to excessively high temperatures in the ZL114A and ZL270 alloy test plates, causing coarsening of the internal structure and affecting joint performance, while insufficient preheating would result in low temperatures in the alloy test plates and limited crack suppression, the preheating electron beam current is controlled at 8–10 mA.

[0064] Specifically, in step 6 above, considering that if the line energy density E during the formal welding is too small, it is easy to cause incomplete welding, and if the line energy density E is too large, it is easy to cause burn-through; therefore, the line energy density E during the formal welding is controlled between 115.5 J / mm and 225 J / mm.

[0065] Specifically, in step 6 above, the linear energy density E is related to the thickness of the welded joint. After in-depth research, this invention controls E = 18.25x + 79, where x is the thickness of the welded joint, and the range of x is 2 to 8 mm.

[0066] Specifically, in step 6 above, E = UI / v, where U is the accelerating voltage, I is the electron beam current, and v is the welding speed; during implementation, a deviation of 3 J / mm is allowed in E. Preferably, in step 6 above, the welding parameters for the formal welding are controlled as follows: working distance 295–305 mm, accelerating voltage 55–60 kV, focusing current surface focal current (0.01–0.04) A, electron beam current 35–50 mA, and welding speed 800–1000 mm / min.

[0067] Specifically, in step 6 above, considering that ZL270 has a higher melting point and specific heat capacity than ZL114A, the electron beam spot center is biased towards the ZL270 side. This allows more energy to be applied to the ZL270 alloy and less energy to be applied to the ZL114A, resulting in a relatively consistent amount of metal melting on both sides of the joint, thus obtaining a regularly shaped molten pool and solving the problem of incomplete penetration.

[0068] After in-depth research, the inventors considered that if the electron beam spot center is too large or too small from the test plate joint to the ZL270 alloy plate side, it will lead to irregular molten pool shape, thus affecting the joint performance. Therefore, the electron beam spot center is controlled to be 0.15-0.2 mm from the test plate joint to the ZL270 alloy plate side.

[0069] Specifically, in step 6 above, during the actual electron beam welding, the scanning waveform adopts an "O"-shaped scanning mode 6, with a scanning amplitude of 1mm and a scanning frequency of 300Hz. By adopting the "O"-shaped scanning mode 6, the electron beam agitates the molten pool during the welding process, causing the pores inside the molten pool to escape rapidly before the molten pool solidifies, thereby reducing internal porosity defects.

[0070] Specifically, in step 7 above, considering that an excessively large working distance leads to a reduced weld depth and poor weld surface formation, while an excessively small working distance allows metal vapors to enter the electron gun's working chamber during welding, causing discharge problems, excessively large accelerating voltage results in strong beam penetration, easily leading to burn-through; excessively small voltage reduces weld depth, preventing internal pores from escaping effectively, thus highlighting porosity issues. Excessively large focusing current easily leads to joint burn-through; excessively small focusing current reduces weld depth, highlighting porosity issues. Excessively large electron beam current leads to excessive penetration, causing burn-through; excessively small current reduces weld depth, highlighting porosity issues. Excessively large welding speed reduces weld depth and highlights porosity issues; excessively small welding speed increases weld width, easily exceeding standard requirements, resulting in large heat input and significant component deformation. Therefore, the process parameters for controlling the modification welding are: working distance 295~305mm, accelerating voltage 55~60kV, focusing current surface coke + (0.08~0.12)A, electron beam current 20~30mA, and welding speed 1150~1200mm / min.

[0071] Specifically, the electron beam welding method of this invention produces welds with smooth and aesthetically pleasing surfaces, free from inclusions, cracks, depressions, and other defects. The weld interior is free from cracks, incomplete penetration, and lack of fusion. The weld quality meets the requirements for Class I welds in GJB1718A-2005 standard. The tensile strength of the joint reaches 245–255 MPa, exceeding 80% of the ZL114A base material strength of 300 MPa, and the elongation after fracture is 3%–4%.

[0072] Compared with the prior art, the electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials of the present invention adopts a synchronous welding method with dual electron beams arranged in front and behind, which can realize simultaneous preheating and welding, effectively reducing the formation of internal cracks in the dissimilar joint during the welding process; the electron beam spot center is used to weld from the test plate joint to the ZL270 alloy plate side, which can solve the problem of incomplete fusion caused by irregular molten pool shape; the weld surface obtained by the method of the present invention is flat and beautiful, without inclusions, cracks, depressions and other defects, and the weld interior is free from cracks, incomplete penetration and incomplete fusion, and the weld quality meets the requirements of Class I weld in GJB1718A-2005 standard.

[0073] The method of the present invention uses vacuum electronic welding of aluminum alloys, which concentrates energy, reduces heat input, minimizes heat-affected zone, and minimizes welding deformation. At the same time, the vacuum environment can effectively prevent oxidation and element loss in the weld.

[0074] The method of the present invention employs an "O"-shaped scanning method, in which the electron beam agitates the molten pool during the welding process, causing the pores inside the molten pool to escape rapidly before the molten pool solidifies, thereby reducing internal porosity defects.

[0075] Example 1

[0076] A specific embodiment of the present invention discloses an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials, wherein the welding object is a 4mm thick ZL114A / ZL270 dissimilar aluminum alloy flat butt joint. (See attached...) Figure 1 As shown, the joint structure is a lock-bottom butt joint, with a 3mm lock-bottom section left on one side of the ZL114A alloy. The electron beam welding method in this embodiment includes:

[0077] Step 1: Welding joint design. The welding joint is a lock-bottom butt joint type.

[0078] Step 2, Assembly: Secure the ZL114A and ZL270 aluminum alloy plates firmly using test plate clamps; the maximum butt joint gap of the weld is 0.15mm, and the step difference is 0.2mm;

[0079] Step 3: Place the assembled ZL114A and ZL270 alloy test plates into the vacuum chamber and evacuate the vacuum chamber; the vacuum level of the vacuum chamber is 3×10⁻⁶. -2 Pa;

[0080] Step 4: Teach the weld trajectory using a smaller electron beam current; the electron beam current used is 3mA.

[0081] Step 5: Perform tack welding on ZL114A and ZL270 alloy test plates; the length of each tack weld is 20mm, and the tack weld spacing is 50mm; tack weld parameters: working distance 300mm, accelerating voltage 60kV, focusing current surface coke +0.02A, electron beam current 18mA, welding speed 1000mm / min;

[0082] Step 6: Welding is performed using a dual electron beam synchronous welding method with one electron beam preheating the weld seam first, followed by the other electron beam for formal welding within 0.5 seconds after preheating. During formal welding, the center of the electron beam spot is shifted from the test plate joint towards the ZL270 alloy plate. The preheating electron beam current is 8mA. The linear energy density E during formal welding is 152J / mm. The welding parameters for formal welding are: working distance 300mm, accelerating voltage 60kV, focusing current surface coke -0.02A, electron beam current 42.2mA, welding speed 1000mm / min. During welding, the center of the electron beam spot is shifted 0.15mm towards the ZL270 alloy plate. The electron beam uses an "O"-shaped scanning method with a scanning amplitude of 1mm and a scanning frequency of 300Hz.

[0083] Step 7: Perform finishing welding on the weld; the process parameters for finishing welding are: working distance 300mm, accelerating voltage 60kV, focusing current surface coke +0.1A, electron beam current 22mA, welding speed 1200mm / min;

[0084] Step 8, Post-weld grinding: After welding, grind and clean the weld surface to remove the volatile metal layer on the surface.

[0085] like Figure 3 As shown, the weld surface obtained by the method in this embodiment is smooth and aesthetically pleasing, free from defects such as oxidation and cracks. The weld interior is free from defects such as cracks, incomplete penetration, and lack of fusion, and contains no visible inclusions, meeting the requirements for Class I welds in GJB1718A-2005 standard. The joint's ultimate tensile strength reaches 255 MPa, exceeding 80% of the ZL114A base metal strength of 300 MPa, with an elongation of 4%.

[0086] Example 2

[0087] A specific embodiment of the present invention discloses an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. The welding object is a 6mm thick ZL114A / ZL270 dissimilar aluminum alloy flat butt joint. The joint structure is a lock-bottom butt joint, with a 3mm lock-bottom remaining on the ZL114A alloy side. The electron beam welding method of this embodiment includes:

[0088] Step 1: Welding joint design. The welding joint is a lock-bottom butt joint type.

[0089] Step 2, Assembly: Secure the ZL114A and ZL270 aluminum alloy plates firmly using test plate clamps; the maximum butt joint gap of the weld is 0.18mm, and the step difference is 0.4mm;

[0090] Step 3: Place the assembled ZL114A and ZL270 alloy test plates into the vacuum chamber and evacuate the vacuum chamber; the vacuum level of the vacuum chamber is 4×10⁻⁶. -2 Pa;

[0091] Step 4: Teach the weld trajectory using a smaller electron beam current; the electron beam current used is 3.5mA.

[0092] Step 5: Perform tack welding on ZL114A and ZL270 alloy test plates; the length of each tack weld segment is 25mm, and the tack weld spacing is 55mm; tack weld parameters: working distance 300mm, accelerating voltage 60kV, focusing current surface coke +0.01A, electron beam current 20mA, welding speed 1000mm / min;

[0093] Step 6: Welding is performed using a dual electron beam synchronous welding method with one electron beam preheating the weld seam first, and the other electron beam performing the formal welding within 0.8 seconds after preheating. During the formal welding process, the center of the electron beam spot is shifted from the test plate joint to the ZL270 alloy plate side. The preheating electron beam current is 9mA. The linear energy density E during formal welding is 188.5J / mm. The welding parameters for formal welding are: working distance 300mm, accelerating voltage 60kV, focusing current surface coke -0.03A, electron beam current 52.4mA, welding speed 1000mm / min. During welding, the center of the electron beam spot is shifted 0.18mm to the ZL270 alloy plate side. The electron beam uses an "O"-shaped scanning method with a scanning amplitude of 1mm and a scanning frequency of 300Hz.

[0094] Step 7: Perform finishing welding on the weld; the process parameters for finishing welding are: working distance 300mm, accelerating voltage 60kV, focusing current surface coke +0.11A, electron beam current 25mA, welding speed 1200mm / min;

[0095] Step 8, Post-weld grinding: After welding, grind and clean the weld surface to remove the volatile metal layer on the surface.

[0096] like Figure 4As shown, the weld surface obtained by the method in this embodiment is smooth and aesthetically pleasing, free from defects such as oxidation and cracks. The weld interior is free from defects such as cracks, incomplete penetration, and lack of fusion, and contains no visible inclusions, meeting the requirements for Class I welds in GJB1718A-2005 standard. The joint's ultimate tensile strength reaches 250 MPa, exceeding 80% of the ZL114A base metal strength of 300 MPa, with an elongation of 3.6%.

[0097] Example 3

[0098] A specific embodiment of the present invention discloses an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. The welding object is an 8mm thick ZL114A / ZL270 dissimilar aluminum alloy flat butt joint. The joint structure is a lock-bottom butt joint, with a 3mm lock-bottom remaining on the ZL114A alloy side. The electron beam welding method of this embodiment includes:

[0099] Step 1: Welding joint design. The welding joint is a lock-bottom butt joint type.

[0100] Step 2, Assembly: Secure the ZL114A and ZL270 aluminum alloy plates firmly using test plate clamps; the maximum butt joint gap of the weld is 0.2mm, and the step difference is 0.5mm;

[0101] Step 3: Place the assembled ZL114A and ZL270 alloy test plates into the vacuum chamber and evacuate the vacuum chamber; the vacuum level of the vacuum chamber is 4.5 × 10⁻⁶. -2 Pa;

[0102] Step 4: Teach the weld trajectory using a smaller electron beam current; the electron beam current used is 4mA.

[0103] Step 5: Perform tack welding on ZL114A and ZL270 alloy test plates; the length of each tack weld segment is 30mm, and the tack weld spacing is 70mm; tack weld parameters: working distance 300mm, accelerating voltage 60kV, focusing current surface coke +0.02A, electron beam current 22mA, welding speed 1000mm / min;

[0104] Step 6: Welding is performed using a dual electron beam synchronous welding method with one electron beam preheating the weld seam first, and the other electron beam performing the formal welding within 1 second after preheating. During the formal welding process, the center of the electron beam spot is shifted from the test plate joint to the ZL270 alloy plate side. The preheating electron beam current is 10mA. The linear energy density E during formal welding is 225J / mm. The welding parameters for formal welding are: working distance 300mm, accelerating voltage 60kV, focusing current surface coke -0.04A, electron beam current 50mA, welding speed 800mm / min. During welding, the center of the electron beam spot is shifted 0.2mm to the ZL270 alloy plate side. The electron beam uses an "O"-shaped scanning method with a scanning amplitude of 1mm and a scanning frequency of 300Hz.

[0105] Step 7: Perform finishing welding on the weld; the process parameters for finishing welding are: working distance 300mm, accelerating voltage 60kV, focusing current surface coke +0.12A, electron beam current 28mA, welding speed 1200mm / min;

[0106] Step 8, Post-weld grinding: After welding, grind and clean the weld surface to remove the volatile metal layer on the surface.

[0107] like Figure 5 As shown, the weld surface obtained by the method in this embodiment is smooth and aesthetically pleasing, free from defects such as oxidation and cracks. The weld interior is free from defects such as cracks, incomplete penetration, and lack of fusion, and contains no visible inclusions, meeting the requirements for Class I welds in GJB1718A-2005 standard. The joint's ultimate tensile strength reaches 245 MPa, exceeding 80% of the ZL114A base metal strength of 300 MPa, with an elongation of 3%.

[0108] The inventors conducted extensive research during the research process, and some unsuccessful solutions are now presented as comparative examples.

[0109] Comparative Example 1

[0110] This comparative example provides an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. The welding object is the same as in Example 1, and the method includes the following steps:

[0111] Steps 1-4 are the same as in Example 1, and will not be repeated here;

[0112] Step 5: Uniformly preheat the ZL114A and ZL270 alloy test plates along the weld seam. The preheating parameters are: accelerating voltage 50kV, surface focusing current +0.03A, electron beam current 3mA, and welding speed 1000mm / min;

[0113] Step 6: Perform uniform tack welding on the workpiece along the weld seam. The parameters for tack welding are: accelerating voltage 50kV, surface focusing current +0.03A, electron beam current 12mA, welding speed 1000mm / min; the length of each weld segment is 23mm.

[0114] Step 7, Formal Welding. The parameters for formal welding are: accelerating voltage 50kV, surface focusing current, electron beam current 18mA, and welding speed 1000mm / min.

[0115] Step 8: Perform surface finishing welding on the weld. The parameters for surface finishing welding are: accelerating voltage 50kV, surface focusing current +0.1A, electron beam current 10mA, and welding speed 1000mm / min.

[0116] Step 9: Grinding after welding.

[0117] In this case, since aluminum alloys conduct heat relatively quickly, electron beam preheating and electron beam welding were carried out in steps. After preheating, the specimen dissipated heat quickly, and the temperature of the specimen had dropped significantly when welding was performed. After welding, there were obvious cracks inside the weld.

[0118] Comparative Example 2

[0119] This comparative example provides an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. The welding object is the same as in Example 1, and the method is roughly the same as in Example 1. The difference is that in step 6, the center of the electron beam spot is directly opposite the weld joint.

[0120] In this example, due to the differences in physical properties between ZL114A and ZL270 aluminum alloys, the difference in melting point and specific heat capacity when the electron beam spot is aligned with the weld joint results in an irregular molten pool shape and incomplete fusion defects.

[0121] Comparative Example 3

[0122] This comparative example provides an electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials. The welding object is the same as in Example 1, and the method is roughly the same as in Example 1. The difference is that in step 7, the accelerating voltage is 50kV and the welding speed is 1500mm / min.

[0123] In this example, the porosity inside the weld exceeded the standard.

[0124] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. An electron beam welding method for ZL114A / ZL270 dissimilar aluminum alloy materials, characterized in that, The chemical composition of ZL270, by weight percentage, is: Cu 4.3%~5.8%, Mg 0.25%~0.5%, Ti 0.15%~0.35%, Mn 0.7%~1.5%, with the balance being Al; The electron beam welding method includes the following steps: Step 1: Welding joint design. The welding joint is a lock-bottom butt joint type. Step 2, Assembly: Secure the ZL114A and ZL270 aluminum alloy plates firmly using the test plate clamps; Step 3: Place the assembled ZL114A and ZL270 alloy test plates into the vacuum chamber and evacuate the vacuum chamber; Step 4: Teach the weld trajectory; Step 5: Perform tack welding on the ZL114A and ZL270 alloy test plates; Step 6: Welding is carried out using a dual electron beam synchronous welding method with one electron beam arranged in front and behind. One electron beam preheats the weld first, and the other electron beam performs the formal welding within 0.1~1s. During the formal welding process, the center of the electron beam spot is shifted from the test plate joint to the ZL270 alloy plate side. Step 7: Repair and weld the weld seam; Step 8: Post-weld grinding; In step 5, the process parameters for tack welding are: working distance 295~305mm, accelerating voltage 55~60kV, focusing current surface coke + (0.01-0.04)A, electron beam current 15~22mA, and welding speed 980~1010mm / min; In step 6, the preheating electron beam current is 8~10mA; In step 6, the line energy density E during formal welding is related to the thickness of the weld joint, E = 18.25x + 79, where x is the thickness of the weld joint, and the range of x is 2~8mm; the welding parameters for formal welding are controlled as follows: working distance 295~305mm, accelerating voltage 55~60kV; In step 6, during the electron beam welding process, the scanning waveform adopts an "O" shaped scanning method; the scanning amplitude is 1mm and the scanning frequency is 300Hz. In step 7, the process parameters for modification welding are: working distance 295~305mm, accelerating voltage 55~60kV, focusing current surface coke + (0.08~0.12)A, electron beam current 20~30mA, and welding speed 1150~1200mm / min; The joint has a tensile strength of 245~255MPa and an elongation after fracture of 3%~4%.

2. The electron beam welding method according to claim 1, characterized in that, In step 2, the maximum butt gap of the weld is controlled to be less than 0.2 mm, and the step difference is not greater than 10% of the base material thickness.

3. The electron beam welding method according to claim 1, characterized in that, In step 4, the electron beam current used is controlled to be 3~5mA.

4. The electron beam welding method according to claim 1, characterized in that, In step 3, the vacuum level of the vacuum chamber is controlled between 2×10⁻² Pa and 7×10⁻² Pa.

5. The electron beam welding method according to claim 1, characterized in that, In step 5, the process parameters for tack welding are: working distance 300~305mm, accelerating voltage 55~60kV, focusing current surface coke + (0.01-0.04)A, electron beam current 15~22mA, and welding speed 980~1010mm / min.

6. The electron beam welding method according to claim 1, characterized in that, In step 6, the preheated electron beam current is 8~9mA.

7. The electron beam welding method according to claim 1, characterized in that, In step 6, the line energy density E during the formal welding is between 115.5 J / mm and 225 J / mm.

8. The electron beam welding method according to claim 1, characterized in that, In step 6, the center of the electron beam spot is controlled to be offset from the test plate joint to the ZL270 alloy plate by 0.15~0.2mm.

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