A welding method for medium-thickness 7A52 high-strength aluminum alloy

Abstract

This invention relates to a welding method for medium-thickness 7A52 high-strength aluminum alloy, comprising the following steps: First, the welding bevel of the workpiece is machined using a milling process; oil stains on the workpiece surface are removed by acid and alkali washing, and then the workpiece is dried; then, the workpiece is preheated before welding; finally, the workpiece is assembled, and the PMC (Pulse Multi Control) welding process is used to complete the welding. After welding, the weld is aesthetically pleasing and free from welding defects such as undercut, porosity, and slag inclusions. Compared with existing technologies, this invention for welding medium-thickness 7A52 high-strength aluminum alloy has advantages such as low welding heat input, narrow heat-affected zone, small post-weld deformation, low spatter, good welding quality, and high welding efficiency. Furthermore, this invention is simple to operate, has low equipment cost, and is easy to promote and apply.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a welding method for a medium-thickness 7A52 high-strength aluminum alloy. Background Technology

[0002] 7A52 high-strength aluminum alloy is a heat-treatable aluminum alloy. After rolling, solution treatment and aging, its strength can reach more than 500MPa. It has the characteristics of low density, high specific strength and easy processing and forming. It is widely used as an armor structure material in the field of weaponry and equipment.

[0003] Currently, welding of 7A52 high-strength aluminum alloys often employs traditional methods such as pulsed MIG welding, CMT welding, TIG welding, friction stir welding, laser welding, and laser-MIG hybrid welding. Traditional pulsed MIG welding suffers from high heat input during the welding process, resulting in significant post-weld deformation and a large heat-affected zone. Furthermore, the inability to precisely control droplet transfer during welding leads to excessive spatter, severely impacting joint quality. CMT welding, through a combination of mechanical wire retraction and short-circuit transfer, achieves spatter-free droplet transfer, significantly reducing heat input. However, the lower heat input also results in shallow weld penetration and low deposition efficiency, making CMT unsuitable for welding medium-thickness (5–25 mm) 7A52 high-strength aluminum alloys. While TIG welding offers relatively low heat input and good weld quality, its welding efficiency is low when welding medium-thickness 7A52 high-strength aluminum alloys. Although friction stir welding can achieve medium-thickness 7A52 high-strength aluminum alloy welding, it is difficult to apply to welding complex and irregular joint types. While laser welding and laser-MIG hybrid welding methods can be applied to welding medium-thickness 7A52 high-strength aluminum alloys, the equipment costs are relatively high.

[0004] Therefore, there is a current need for a welding method for medium-thickness 7A52 high-strength aluminum alloys that features low welding heat input, narrow heat-affected zone, small post-weld deformation, good welding quality, applicability to welding complex and irregular joint types, high welding efficiency, low equipment cost, simple operation, and easy promotion and application. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a welding method for medium-thickness 7A52 high-strength aluminum alloy that has low welding heat input, high welding efficiency, good welding quality and low equipment cost, in light of the current state of the technology.

[0006] The solution adopted by this invention to solve the above-mentioned technical problem is: a welding method for medium-thickness 7A52 high-strength aluminum alloy, characterized by comprising the following steps:

[0007] 1) The welding bevel of the workpiece is machined using milling technology;

[0008] 2) Remove oil stains from the workpiece surface using acid and alkali washing, and then air dry;

[0009] 3) Preheat the workpiece before welding;

[0010] 4) Assemble the workpiece;

[0011] 5) The PMC welding process is used to complete the welding of the workpiece.

[0012] Preferably, in step 1), when the thickness of the 7A52 high-strength aluminum alloy is 5 to 15 mm, the welding bevel adopts a single V bevel form with a bevel angle of 70 ± 5° and a blunt edge of 0 mm.

[0013] Preferably, in step 1), when the thickness of the 7A52 high-strength aluminum alloy is 15-25mm, the welding bevel adopts a double V bevel form, the two bevels are oriented opposite to each other, the bevel angle is 70±5°, and the blunt edge is 0-1mm.

[0014] Preferably, step 2) acid-base washing involves first washing with a 20% NaOH solution, followed by rinsing with clean water; then washing with a 5% HNO3 solution, followed by rinsing with clean water; and finally, air-drying after rinsing.

[0015] Preferably, the preheating temperature in step 3) is 80-90°C, and the temperature is maintained for 2 hours. The preheated workpiece is then welded within 3 hours.

[0016] Preferably, in step 4), before assembly, the area within 30mm on both sides of the bevel should be polished with a stainless steel wire brush until a bright metal body is exposed, and then cleaned with acetone. Preferably, for workpieces welded with a single V-groove, the joint assembly gap is 0.5-1mm; for workpieces welded with a double V-groove, the joint assembly gap is 1-2mm.

[0017] Preferably, the welding wire used in step 5) has the following chemical composition by weight percentage: Mg: 5.0–5.5%, Si: ≤0.15%, Fe: ≤0.3%, Cu: ≤0.005%, Mn: 0.05–0.2%, Cr: 0.05–0.15%, Zn: ≤0.2%, Ti: 0.06–0.10%, Zr: 0.01–0.10%, B: 0.0002–0.05%, with the remainder being Al and unavoidable impurity elements. The welding wire diameter is Ф1.2 mm.

[0018] The reasons for using the above-mentioned components and mass percentages in the welding wire are as follows: Mg (Mg) dissolves in the Al matrix to form an α-solid solution, increasing the strength of the weld joint. The Mg content in the welding wire is 5.0–5.5%, higher than that of the 7A52 high-strength aluminum alloy base material, which can compensate for Mg loss during base material welding. Combined with the PMC welding process, this further reduces Mg loss in both the base material and the weld metal. When Si content exceeds 0.15%, it easily forms the Mg2Si impurity phase, reducing the joint's plasticity; therefore, a Si content ≤0.15% is selected for the welding wire. Fe, Mn, and other elements easily form the brittle phase (FeMn)Al6, decreasing the weld metal's plasticity; therefore, an Fe content ≤0.3% is selected for the welding wire. Ti, Zr, B, and other elements form phases such as Al3Ti, Al3Zr, and TiB2, which act as nucleation points during weld solidification, refining the grains and reducing the weld's cracking tendency. PMC welding process has low heat input and high undercooling during weld metal solidification. Combined with elements such as Ti, Zr, and B in the welding wire, it can further refine the grains and reduce the tendency of weld cracking.

[0019] Preferably, the protective gas in step 5) is argon with a purity of ≥99.99%, and the welding torch angle is 70-75°.

[0020] Step 5) When performing the root pass welding, use a copper or stainless steel process backing on the back of the bevel to prevent the molten pool from collapsing and the base material from burning through. For workpieces welded using a double V-groove, an alternating welding method on both sides should be adopted to avoid large welding deformation. At the same time, when performing the root pass welding on the back side, mechanical methods should be used to clean the weld root to avoid defects such as incomplete fusion during the back pass welding.

[0021] Considering that in step 5), excessive welding current during the root pass welding can easily lead to burn-through of the base material, while insufficient welding current can easily lead to incomplete penetration, a welding current of 160–180 A is preferred for the root pass welding. To improve the penetration depth and avoid incomplete penetration defects, a shorter arc length should be used. Preferably, the arc length correction for the root pass welding is -5 to 0. To reduce the difficulty of arc initiation during the arc-starting stage, a larger arc-starting current and arc-starting current time should be set. Preferably, the arc-starting current for the root pass welding is 240–270 A, and the arc-starting current time is 0.1–0.2 s. To avoid crater cracks during the arc-ending stage, a lower welding current and current dwell time should be set during the arc-ending stage. Preferably, the arc-ending current for the root pass welding is 80–90 A, and the arc-ending current time is 0.5–0.6 s.

[0022] Preferably, the welding process parameters adopted in step 5) for the root pass welding are as follows: arc starting current 240-270A, arc starting time 0.1-0.2s, welding current 160-180A, voltage 20-22V, welding speed 0.5-0.6m / min, shielding gas flow rate 15-20L / min, arc extension 15-20mm, arc length correction -5-0, arc ending current 80-90A, and arc ending time 0.5-0.6s.

[0023] Considering that during filler welding, a welding current greater than 220A can easily lead to coarse grains inside the weld, a wider heat-affected zone, and affect the mechanical properties of the weld joint; while a welding current less than 200A can easily lead to difficulty in escaping porosity from the weld, resulting in porosity defects inside the weld, it is preferable to use a welding current of 200–220A for filler welding. Simultaneously, to avoid undercut defects during filler welding, a longer arc length should be used; preferably, an arc length correction of 0–5 is used. To reduce the difficulty of arc initiation during the arc-starting stage, a larger arc-starting current and arc-starting current time should be set; preferably, a 300–330A arc-starting current and an arc-starting current time of 0.1–0.2s are used for filler welding. To avoid crater cracks during the arc-ending stage, a lower welding current and current dwell time should be set during the arc-ending stage; preferably, a 100–110A arc-ending current and an arc-ending current time of 0.5–0.6s are used for filler welding.

[0024] Preferably, the welding process parameters adopted in step 5) for filler welding are as follows: arc starting current 300-330A, arc starting time 0.1-0.2s, welding current 200-220A, voltage 22-24V, welding speed 0.3-0.5m / min, shielding gas flow rate 15-20L / min, arc extension 15-20mm, arc length correction 0-5, arc ending current 100-110A, and arc ending time 0.5-0.6s.

[0025] Preferably, in step 5) during the root pass and fill pass welding, the pre-gas supply time is 5-6 seconds. This removes air from the gas pipe and establishes an inert gas protective environment before arc ignition. This is to prevent porosity and weld metal oxidation caused by air mixing into the protective gas pipe during the arc ignition stage.

[0026] Preferably, in step 5), during the root pass and fill pass welding, the delayed gas supply time is 4–6 seconds to avoid weld oxidation during the arc termination stage.

[0027] Preferably, during step 5), the interpass temperature is controlled to be below 80°C to avoid coarse grains in the weld and heat-affected zone, suppress welding cracks, and control welding deformation.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] 1. PMC welding process falls under the category of pulsed welding processes, which incorporates a controllable short-circuit transition process during the pulse transition. By autonomously reducing the welding current of the welding machine, low spatter droplet separation is achieved, significantly reducing the welding heat input.

[0030] 2. When encountering changes in welding position and weld geometry, constant penetration depth and equal arc length can be achieved through penetration depth and arc length stabilizers, thus enabling this process to be applied to welding complex and irregular joint forms.

[0031] 3. Compared with the traditional pulsed arc welding process, the PMC welding process increases the welding speed by 15%, reduces the welding heat input by 15%, increases the penetration depth by 60%, and can increase productivity by up to 65%. The tensile strength and elongation after fracture of the 7A52 high-strength aluminum alloy welded joint obtained by the present invention are higher than those of the traditional pulsed MIG welding process.

[0032] 4. Compared with laser and laser-MIG hybrid welding, the equipment cost is lower and it is easier to promote and apply. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described in detail below with reference to examples. In the various embodiments of the present invention, the equipment used in the PMC welding process is a TPS 600i welding machine manufactured by Fronius GmbH, Austria, with a maximum welding current of 600A, including a controllable short-circuit transfer process, penetration depth and arc length stabilizers. This application applies the PMC welding process to medium-thickness 7A52 high-strength aluminum alloy, optimizes the selection of suitable welding wire based on the characteristics of medium-thickness 7A52 high-strength aluminum alloy, and improves related steps and welding process parameters.

[0034] Example 1

[0035] The following steps are taken when welding 10mm thick 7A52 high-strength aluminum alloy using the PMC welding process:

[0036] 1) The welding bevel is machined by milling. The bevel is a single V bevel with a bevel angle of 70° and a blunt edge of 0mm.

[0037] 2) First, clean the test plate with a 20% NaOH solution by mass, and then rinse it with clean water. Then clean it with a 5% HNO3 solution by volume, and then rinse it with clean water. After rinsing, dry it immediately.

[0038] 3) Preheat the test plate to 80℃ before welding and keep it at that temperature for 2 hours.

[0039] 4) First, use a stainless steel wire brush to grind the area within 30mm on both sides of the bevel until the bright metal body is exposed. Then clean it with acetone. Finally, assemble the workpiece, with a joint assembly gap of 0.7mm.

[0040] 5) PMC welding was performed on 10mm thick high-strength 7A52 aluminum alloy. The chemical composition (by weight percentage) of the welding wire used was as follows: Mg: 5.0%, Si: 0.058%, Fe: 0.158%, Cu: 0.0002%, Mn: 0.118%, Cr: 0.085%, Zn: 0.0067%, Ti: 0.085%, Zr: 0.012%, B: 0.019%, with the remainder being Al and unavoidable impurities. The welding wire diameter was Ф1.2mm, the shielding gas was argon with a purity ≥99.99%, and the welding torch angle was 73°.

[0041] When performing the root pass welding, a stainless steel process backing is used on the back of the bevel to prevent the molten pool from collapsing and the base material from burning through.

[0042] The welding process parameters used are as follows:

[0043] Root pass welding: arc starting current 255A, arc starting time 0.1s, pre-gas supply time 6s, welding current 170A, voltage 21.3V, welding speed 0.5m / min, shielding gas flow rate 17L / min, dry extension 15mm, arc length correction -3, arc ending current 85A, arc ending time 0.5s, delayed gas supply time 5s.

[0044] Filler welding: arc starting current 300A, arc starting time 0.1s, pre-gas supply time 5s, welding current 200A, voltage 22.3V, welding speed 0.4~0.5m / min, shielding gas flow rate 15L / min, dry extension 16mm, arc length correction 0~2, arc ending current 100A, arc ending time 0.5s, delayed gas supply time 4s.

[0045] After welding, the weld seam is aesthetically pleasing, free from welding defects such as undercut, porosity, and slag inclusions. The heat-affected zone of the weld seam is narrow, and welding deformation is minimal. The tensile properties of the 10mm thick 7A52 high-strength aluminum alloy welded joint are shown below:

[0046]

[0047] As can be seen from Example 1, the tensile strength and elongation after fracture of the 10mm thick 7A52 high-strength aluminum alloy welded joint obtained by the present invention are higher than those of the traditional pulsed MIG welding process.

[0048] Example 2

[0049] The following steps are taken when welding 20mm thick 7A52 high-strength aluminum alloy using the PMC welding process:

[0050] 1) The welding bevel is machined by milling. The bevel adopts a double V bevel form, with the two bevels facing away from each other. The bevel angle is 70° and the blunt edge is 1mm.

[0051] 2) First, clean the test plate with a 20% NaOH solution by mass, and then rinse it with clean water. Then clean it with a 5% HNO3 solution by volume, and then rinse it with clean water. After rinsing, dry it immediately.

[0052] 3) Preheat the test plate to 85℃ before welding and keep it at that temperature for 2 hours.

[0053] 4) First, use a stainless steel wire brush to grind the area within 30mm on both sides of the bevel until the bright metal body is exposed. Then clean it with acetone. Finally, assemble the joint, with a joint assembly gap of 1.5mm.

[0054] 5) PMC welding of 20mm thick 7A52 high-strength aluminum alloy was performed. The chemical composition (by weight percentage) of the welding wire used was: Mg: 5.1%, Si: 0.052%, Fe: 0.154%, Cu: 0.0002%, Mn: 0.123%, Cr: 0.1%, Zn: 0.0036%, Ti: 0.075%, Zr: 0.011%, B: 0.0078%, with the remainder being Al and unavoidable impurities. The welding wire diameter was Ф1.2mm, the shielding gas was argon with a purity ≥99.99%, and the welding torch angle was 70°. To avoid significant welding deformation, a double-sided alternating welding method was used. To prevent coarse grains in the weld and heat-affected zone, suppress welding deformation, and avoid welding cracks, the interpass temperature should be controlled below 80℃ during welding. For the root pass, a stainless steel process backing was required on the back of the bevel. To avoid defects such as incomplete fusion during back-side root pass welding, the weld seam is cleaned with an angle grinder before the back-side root pass welding is performed.

[0055] The welding process parameters used are as follows:

[0056] Root pass welding: arc starting current 260A, arc starting time 0.2s, pre-gas supply time 6s, welding current 170A, voltage 21.3V, welding speed 0.55m / min, shielding gas flow rate 18L / min, dry extension 17mm, arc length correction -3, arc ending current 85A, arc ending time 0.6s, delayed gas supply time 5s.

[0057] Filler welding: arc starting current 310A, arc starting time 0.2s, pre-gas supply time 6s, welding current 200A, voltage 22.3V, welding speed 0.3~0.5m / min, shielding gas flow rate 17L / min, dry extension 18mm, arc length correction 0~5, arc ending current 104A, arc ending time 0.6s, delayed gas supply time 5s.

[0058] After welding, the weld seam is aesthetically pleasing, free from welding defects such as undercut, porosity, and slag inclusions. The heat-affected zone of the weld seam is narrow, and welding deformation is minimal. The tensile properties of the 20mm thick 7A52 high-strength aluminum alloy welded joint are shown below:

[0059]

[0060] As can be seen from Example 2, the tensile strength and elongation after fracture of the 20mm thick 7A52 high-strength aluminum alloy welded joint obtained by the present invention are higher than those of the traditional pulsed MIG welding process.

[0061] Example 3:

[0062] The steps are the same as in Example 1, except for the welding bevel angle, preheating temperature, assembly gap, welding wire chemical composition, and welding process parameters. In this example, in step 1), when the thickness of the 7A52 high-strength aluminum alloy is 5mm, the bevel is a single V bevel with a bevel angle of 65° and a blunt edge of 0mm. In step 3), the preheating temperature is 80°C and held for 2 hours. In step 4), the joint assembly gap is 0.5mm. In step 5), the weight percentage of the chemical composition of the welding wire used for welding is: Mg: 5.3%, Si: 0.131%, Fe: 0.211%, Cu: 0.005%, Mn: 0.09%, Cr: 0.142%, Zn: 0.167%, Ti: 0.069%, Zr: 0.09%, B: 0.032%, with the remainder being Al and unavoidable impurity elements. The welding torch angle is 70°. During the root pass welding, a copper process backing is used on the back of the bevel. The rest is the same as in Example 1.

[0063] The PMC welding process parameters used are as follows:

[0064] Root pass welding: arc starting current 240A, arc starting time 0.1s, pre-gas supply time 5s, welding current 160A, voltage 20.6V, welding speed 0.6m / min, shielding gas flow rate 15L / min, dry extension 20mm, arc length correction -1, arc ending current 80A, arc ending time 0.5s, delayed gas supply time 4s.

[0065] After welding, the weld seam is aesthetically pleasing, free from welding defects such as undercut, porosity, and slag inclusions. The heat-affected zone of the weld seam is narrow, and welding deformation is minimal. The tensile properties of the 5mm thick 7A52 high-strength aluminum alloy welded joint are shown below:

[0066]

[0067] As can be seen from Example 3, the tensile strength and elongation after fracture of the 5mm thick 7A52 high-strength aluminum alloy welded joint obtained by the present invention are higher than those of the traditional pulsed MIG welding process.

[0068] Example 4:

[0069] The steps are the same as in Examples 1 and 2, the difference being the welding bevel angle, preheating temperature, assembly gap, welding wire chemical composition, and welding process parameters. In this example, in step 1), when the thickness of the 7A52 high-strength aluminum alloy is 15mm, a single V bevel or a double V bevel can be used. When using a single V bevel, the bevel angle is 75° and the blunt edge is 0mm. When using a double V bevel, the bevel angle is 65° and the blunt edge is 0.5mm. In step 3), the preheating temperature is 85℃, and the holding time is 2 hours. In step 4), the joint assembly gap is 1mm for both single V and double V bevel types. Step 5) The welding wire used for welding has the following chemical composition by weight percentage: Mg: 5.25%, Si: 0.14%, Fe: 0.149%, Cu: 0.0002%, Mn: 0.187%, Cr: 0.119%, Zn: 0.0045%, Ti: 0.085%, Zr: 0.082%, B: 0.02%, with the remainder being Al and unavoidable impurity elements. The welding torch angle is 75°. For the root pass, a copper backing is used on the back of the bevel. The rest is the same as in Examples 1 and 2.

[0070] For the single V-groove type, the PMC welding process parameters used are as follows:

[0071] Root pass welding: arc starting current 270A, arc starting time 0.2s, pre-gas supply time 6s, welding current 180A, voltage 21.6V, welding speed 0.5m / min, shielding gas flow rate 20L / min, dry extension 17mm, arc length correction -5, arc ending current 90A, arc ending time 0.6s, delayed gas supply time 6s.

[0072] Filler welding: arc starting current 320A, arc starting time 0.1s, pre-gas supply time 5s, welding current 210A, voltage 22.7V, welding speed 0.4~0.5m / min, shielding gas flow rate 17L / min, dry extension 16mm, arc length correction 0~3, arc ending current 105A, arc ending time 0.5s, delayed gas supply time 5s.

[0073] For the double V-groove design, the PMC welding process parameters used are as follows:

[0074] Root pass welding: arc starting current 240A, arc starting time 0.1s, pre-gas supply time 5s, welding current 160A, voltage 20.6V, welding speed 0.6m / min, shielding gas flow rate 15L / min, dry extension 20mm, arc length correction -2, arc ending current 80A, arc ending time 0.5s, delayed gas supply time 4s.

[0075] Filler welding: arc starting current 300A, arc starting time 0.1s, pre-gas supply time 5s, welding current 210A, voltage 22.7V, welding speed 0.3~0.5m / min, shielding gas flow rate 15L / min, dry extension 15mm, arc length correction 0~3, arc ending current 100A, arc ending time 0.5s, delayed gas supply time 4s.

[0076] After welding, the weld seam is aesthetically pleasing, free from welding defects such as undercut, porosity, and slag inclusions. The heat-affected zone of the weld seam is narrow, and welding deformation is minimal. The tensile properties of the 15mm thick 7A52 high-strength aluminum alloy welded joint are shown below:

[0077]

[0078] As can be seen from Example 4, the tensile strength and elongation after fracture of the 15mm thick 7A52 high-strength aluminum alloy welded joint obtained by the present invention are higher than those of the traditional pulsed MIG welding process.

[0079] Example 5:

[0080] The steps are the same as in Example 2, except for the welding bevel angle, preheating temperature, assembly gap, welding wire chemical composition, and welding process parameters. In this example, step 1) when the thickness of the 7A52 high-strength aluminum alloy is 25mm, the bevel adopts a double V bevel form with a bevel angle of 75° and a blunt edge of 0mm. Step 3) the preheating temperature is 90℃, and the holding time is 2h. Step 4) the joint assembly gap is 2mm. Step 5) the weight percentage of the chemical composition of the welding wire used for welding is: Mg: 5.5%, Si: 0.11%, Fe: 0.28%, Cu: 0.004%, Mn: 0.19%, Cr: 0.06%, Zn: 0.18%, Ti: 0.09%, Zr: 0.017%, B: 0.048%, with the remainder being Al and unavoidable impurity elements. The welding torch angle is 72°. The rest is the same as in Example 2.

[0081] The PMC welding process parameters used are as follows:

[0082] Root pass welding: arc starting current 270A, arc starting time 0.2s, pre-gas supply time 6s, welding current 180A, voltage 21.6V, welding speed 0.5m / min, shielding gas flow rate 20L / min, dry extension 15mm, arc length correction -5, arc ending current 90A, arc ending time 0.6s, delayed gas supply time 6s.

[0083] Filler welding: arc starting current 330A, arc starting time 0.2s, pre-gas supply time 6s, welding current 220A, voltage 23.8V, welding speed 0.3~0.5m / min, shielding gas flow rate 20L / min, dry extension 19mm, arc length correction 0~5, arc ending current 110A, arc ending time 0.6s, delayed gas supply time 6s.

[0084] After welding, the weld seam is aesthetically pleasing, free from welding defects such as undercut, porosity, and slag inclusions. The heat-affected zone of the weld seam is narrow, and welding deformation is minimal. The tensile properties of the 25mm thick 7A52 high-strength aluminum alloy welded joint are shown below:

[0085]

[0086] As can be seen from Example 5, the tensile strength and elongation after fracture of the 25mm thick 7A52 high-strength aluminum alloy welded joint obtained by the present invention are higher than those of the traditional pulsed MIG welding process.

Claims

1. A welding method for medium-thickness 7A52 high-strength aluminum alloy, characterized in that, Includes the following steps: 1) The welding bevel of the workpiece is machined using a milling process; 2) Remove oil stains from the workpiece surface using acid and alkali washing, and then air dry; 3) Preheat the workpiece before welding; 4) Assemble the workpiece; 5) The PMC welding process is used to complete the welding of the workpiece; In step 5), the welding process parameters adopted for the root pass welding are as follows: arc starting current 240-270A, arc starting time 0.1-0.2s, pre-gas supply time 5-6s, welding current 160-180A, voltage 20-22V, welding speed 0.5-0.6m / min, shielding gas flow rate 15-20L / min, arc extension 15-20mm, arc length correction -5 to 0, arc ending current 80-90A, arc ending time 0.5-0.6s, and delayed gas supply time 4-6s. Step 5) When performing the root pass welding, use a process backing made of copper or stainless steel on the back of the bevel. In step 5), the welding process parameters adopted for filler welding are as follows: arc starting current 300-330A, arc starting time 0.1-0.2s, pre-gas supply time 5-6s, welding current 200-220A, voltage 22-24V, welding speed 0.3-0.5m / min, shielding gas flow rate 15-20L / min, arc extension 15-20mm, arc length correction 0-5, arc ending current 100-110A, arc ending time 0.5-0.6s, and delayed gas supply time 4-6s. In step 5), the welding wire diameter is Ф1.2mm, the shielding gas is argon with a purity ≥99.99%, the welding torch angle is 70~75º, and the interpass temperature is controlled below 80℃ during welding.

2. The welding method according to claim 1, characterized in that, In step 1), when the thickness of the 7A52 high-strength aluminum alloy is 5 to 15 mm, the welding bevel adopts a single V bevel form with a bevel angle of 70 ± 5 º and a blunt edge of 0 mm.

3. The welding method according to claim 1, characterized in that, In step 1), when the thickness of the 7A52 high-strength aluminum alloy is 15-25mm, the welding bevel adopts a double V bevel form, with the two bevels facing away from each other, the bevel angle being 70±5º, and the blunt edge being 0-1mm.

4. The welding method of claim 1, wherein, Step 2) acid-base washing involves first cleaning with a 20% NaOH solution, followed by rinsing with clean water; then cleaning with a 5% HNO3 solution, followed by rinsing with clean water; and finally, air drying after rinsing.

5. The welding method of claim 1, wherein, The chemical composition (by weight percentage) of the welding wire used in step 5) is as follows: Mg: 5.0–5.5%, Si: ≤0.15%, Fe: ≤0.3%, Cu: ≤0.005%, Mn: 0.05–0.2%, Cr: 0.05–0.15%, Zn: ≤0.2%, Ti: 0.06–0.10%, Zr: 0.01–0.10%, B: 0.0002–0.05%, the remainder being Al and unavoidable impurity elements.

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