Welding wire and method for welding forming of thin-wall complex high-pressure die-casting runner plate

Abstract

The invention discloses a welding wire and method for welding forming of a thin-wall complex high-pressure die-casting runner plate, and belongs to the technical field of welding. The welding wire for welding forming of the thin-wall complex high-pressure die-casting runner plate comprises the following component elements of 5.0 wt%-5.5 wt% of Mg, 1.7 wt%-2.5 wt% of Si, 0.5 wt%-0.65 wt% of Mn, 0.1 wt%-0.3 wt% of Sc, 1.3 wt%-2.6 wt% of La + Ce, 0.02 wt%-0.1 wt% of Zr, 0.05 wt%-0.2 wt% of Ti, smaller than or equal to 0.15 wt% of Fe, smaller than or equal to 0.03 wt% of Cu and the balance Al and inevitable impurity elements, and the total amount of the impurity elements is smaller than or equal to 0.15 wt%. Generation of weld defects can be reduced, and the strength and toughness of the weld are improved.

Description

Technical Field

[0001] The invention relates to a welding wire and a method for welding and forming a thin-walled complex high-pressure die-casting flow channel plate, belonging to the technical field of welding. Background Art

[0002] Compared with traditional fuel vehicles, the thermal management system of new energy vehicles is more complex, and its modularization and integration have become an important development trend. At present, the preparation of refrigerant flow plate generally adopts a process route combining forging and vacuum brazing. The specific process is: use 6000 series aluminum alloy materials, forge and machine, and then vacuum braze with 3000 series or 6000 series plates to complete the assembly. However, the forging process is long, the machining amount is large, it is difficult to prepare complex components, and the effective yield rate is low, resulting in high product costs.

[0003] The current new energy vehicle market is highly competitive, and major OEMs are demanding cost reduction and efficiency improvement. The use of high-pressure die-casting to produce refrigerant flow plates can improve production efficiency and significantly reduce costs. However, the die-casting materials (melting point higher than 640°C) on the market that can meet the requirements of high-temperature vacuum brazing (brazing temperature>610°C) have poor die-casting performance, and the products are prone to defects such as shrinkage holes and cracks, which significantly reduce the pressure resistance of the products. If the flow plate is prepared using materials with excellent die-casting performance, it is necessary to rely on traditional welding methods (such as argon arc welding), but argon arc welding has a large amount of heat input during the welding process, which can easily cause deformation of thin-walled structures, seriously affecting the dimensional accuracy of the liquid cooling structure and the patency of the internal flow channel. In addition, for the welding of complex flow channels, due to the complexity of the structure, traditional welding methods are difficult to achieve uniform and high-quality welding, and defects such as pores and unfused are prone to occur, resulting in reduced sealing of the liquid cooling structure and leakage of coolant, which in turn affects the heat dissipation effect of the system.

[0004] As an advanced welding technology, laser wire welding has the advantages of concentrated energy, small heat-affected zone, and high weld strength. In theory, it is suitable for welding and forming of thin-walled structures. However, the structure of thin-walled complex high-pressure die-casting manifold plates has its own particularity, especially the complex shape of the flow channel leads to poor welding accessibility. If the aluminum-silicon welding wire commonly used in laser wire welding is used for welding, the weld toughness is poor and crack defects are more likely to occur; and due to the high silicon content (the silicon content in ER4043 aluminum-silicon welding wire is 5%), the product has poor corrosion resistance in corrosive environments (corrosive media such as coolant and cooling oil), which in turn affects the product's pressure resistance; therefore, aluminum-silicon welding wires and supporting welding operations are difficult to meet the welding quality requirements of thin-walled complex high-pressure die-casting manifold plates. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a welding wire and method for the welding and forming of a thin-walled and complex high-pressure die-casting runner plate, which can reduce the generation of weld defects and improve the strength and toughness of the weld; the performance of the product after welding is comparable to that of a forged product, meeting the requirements of helium detection tests and burst pressure tests.

[0006] In a first aspect, the present invention relates to a welding wire for the welding and forming of a thin-walled and complex high-pressure die-casting runner plate, comprising elements of the following components:

[0007] Mg: 5.0 - 5.5 wt%, Si: 1.7 - 2.5 wt%, Mn: 0.5 - 0.65 wt%, Sc: 0.1 - 0.3 wt%, La + Ce: 1.3 - 2.6 wt%, Zr: 0.02 - 0.1 wt%, Ti: 0.05 - 0.2 wt%, Fe: ≤0.15 wt%, Cu: ≤0.03 wt%, with the balance being Al and inevitable impurity elements, wherein the total impurity elements ≤0.15 wt%;

[0008] The weight ratio of the Mg / Si elements is 2 - 3:1.

[0009] For example, the content of the Mg element can be 5.0 wt%, 5.1 wt%, 5.2 wt%, 5.3 wt%, 5.4 wt%, 5.5 wt%, etc.

[0010] For example, the content of the Si element can be 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, etc.

[0011] For example, the weight ratio of the Mg / Si elements can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, etc.

[0012] For example, the content of the Mn element can be 0.50 wt%, 0.53 wt%, 0.57 wt%, 0.59 wt%, 0.60 wt%, 0.62 wt%, 0.65 wt%, etc.

[0013] For example, the content of the Sc element can be 0.10 wt%, 0.15 wt%, 0.20 wt%, 0.25 wt%, 0.30 wt%, etc.

[0014] For example, the total content of rare earth elements La and Ce can be 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, etc.; the contents of the rare earth elements La and Ce are both greater than 0.5 wt%.

[0015] For example, the content of Zr element can be 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, etc.

[0016] For example, the content of Ti element can be 0.05 wt%, 0.10 wt%, 0.15 wt%, 0.20 wt%, etc.

[0017] For example, the content of Fe element can be 0.15 wt%, 0.10 wt%, 0.05 wt%, etc.

[0018] For example, the content of Cu element can be 0.03 wt%, 0.02 wt%, 0.01 wt%, etc.

[0019] The second aspect of the present invention relates to a method for welding and forming a thin-walled complex high-pressure die-casting runner plate. A pulsed laser welding device is used to weld the runner plate body and the cover plate to form a thin-walled complex high-pressure die-casting runner plate, including the following processes:

[0020] Control the laser power to be 4 - 5 kW and the laser frequency to be 150 - 250 Hz for welding;

[0021] During welding, the focus is aligned with the surface of the runner plate body for zero defocus welding.

[0022] For some specific embodiments, the runner plate body is made of AlSi10MnMg material, and the cover plate is made of 6-series aluminum alloy material;

[0023] The corresponding welding wire includes elements of the following components:

[0024] Mg: 5.0 - 5.5 wt%, Si: 1.7 - 2.5 wt%, Mn: 0.5 - 0.65 wt%, Sc: 0.1 - 0.3 wt%, La + Ce: 1.3 - 2.6 wt%, Zr: 0.02 - 0.1 wt%, Ti: 0.05 - 0.2 wt%, Fe: ≤0.15 wt%, Cu: ≤0.03 wt%, the balance is Al and unavoidable impurity elements, wherein the total impurity elements ≤0.15 wt%;

[0025] The weight ratio of the Mg / Si elements is 2 - 3:1;

[0026] Preferably, the contents of La and Ce are both greater than 0.5 wt%.

[0027] For some specific embodiments, the laser swing amplitude is also controlled within the range of 0.2 - 0.5 mm to control the weld width.

[0028] For some specific embodiments, the laser power can be set to 4.0 kw, 4.1 kw, 4.2 kw, 4.3 kw, 4.4 kw, 4.5 kw, 4.6 kw, 4.7 kw, 4.8 kw, 4.9 kw, 5.0 kw, etc., and the laser frequency can be set to 150 Hz, 160 Hz, 170 Hz, 180 Hz, 190 Hz, 200 Hz, 210 Hz, 220 Hz, 230 Hz, 240 Hz, 250 Hz, etc.

[0029] For some specific embodiments, the wire filling speed matches the laser welding speed, and the wire filling speed is controlled between 3.0 - 4.5 m / min; preferably, a monitoring device and an automatic welding control device are provided. The monitoring device is electrically connected to the automatic welding control device and transmits the weld image signal, and the automatic welding control device is electrically connected to the pulsed laser welding device and transmits the wire filling speed control signal; during the welding process, the forming condition of the weld is monitored in real time by the monitoring device, and the automatic welding control device receives the weld image signal and generates a wire filling speed control signal to finely adjust the wire filling speed of the pulsed laser welding device; preferably, the monitoring device adopts a machine vision solution. Specifically, a CMOS or CCD camera can be used to obtain the weld image signal. For example, when it is found that the weld has a depression, the wire filling speed is appropriately increased within the above speed range; when the weld has an excessive reinforcement, the wire filling speed is appropriately decreased within the above speed range.

[0030] For some specific embodiments, during the laser wire filling welding process, a laser tracking heating method is adopted to synchronously perform weld heat treatment to inhibit the generation and propagation of weld cracks; preferably, the laser tracking heating is specifically: along the welding path, an auxiliary laser heat source is arranged behind the pulsed laser welding device, and the power of the auxiliary laser heat source is controlled between 200 - 300 W, and the heating time is 0.5 - 2.0 s, and it quickly heats following the weld formed by the pulsed laser welding first. For example, the laser power is 200 W, 210 W, 220 W, 230 W, 240 W, 250 W, 260 W, 270 W, 280 W, 290 W, 300 W, etc., and the heating time is 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1.0 s, 1.1 s, 1.2 s, 1.3 s, 1.4 s, 1.5 s, 1.6 s, 1.7 s, 1.8 s, 1.9 s, 2.0 s, etc.

[0031] For some specific embodiments, it further includes pre-welding treatment, and the pre-welding treatment is to control the surface roughness of the workpiece within the range of Ra3.2 to Ra6.3; for example, the surface roughness is controlled to be Ra3.2, Ra3.5, Ra3.6, Ra3.8, Ra4.0, Ra4.3, Ra4.7, Ra4.9, Ra5.0, Ra5.5, Ra6.0, Ra6.1, Ra6.3, etc.;

[0032] To achieve this roughness range, it is generally necessary to perform pre-treatment on the surface of the workpiece before welding; the pre-treatment of the workpiece surface includes cleaning, mechanical grinding, and / or surface chemical corrosion. Before welding, the workpiece to be welded is thoroughly cleaned to remove impurities such as oil stains and oxide scales on the surface. Preferably, ultrasonic cleaning is combined with a special cleaning agent to ensure the cleaning effect; mechanical grinding or chemical corrosion treatment is performed on the welding part, which can significantly increase the surface roughness and enhance the wettability during welding.

[0033] Compared with the prior art, the present invention has the following technical effects:

[0034] 1) The melting point of the welding wire is higher than that of the traditional aluminum-silicon welding wire. The composition has good fluidity in the aluminum-magnesium eutectic range, and has small shrinkage during the solidification process, which can reduce the generation of weld defects; the content of silicon element is reduced, and the toughness of the alloy is improved. The content of magnesium element is greatly increased, and it is excessive relative to the silicon element. It can not only form a strengthening phase with the silicon element to enhance the weld strength, further improve the strength and toughness of the weld, but also increase the weldability and corrosion resistance; Sc and rare earth elements are also added to the welding wire, which can refine the weld grains during the welding process, is beneficial to the formation of strengthening phases, and thus plays a role in improving the strength and toughness of the weld;

[0035] 3) In the case of 0 defocus, controlling the laser power, frequency, and welding speed within the above parameter ranges can not only ensure the penetration of the weld, control the weld quality, but also effectively control the heat input and reduce the deformation of the workpiece;

[0036] 4) Through laser tracking heating, the newly formed weld undergoes a short annealing process at high temperature, which promotes the uniform and dispersed precipitation of strengthening phases, inhibits the generation and expansion of weld cracks, and further improves the strength and toughness of the weld;

[0037] 5) After welding, the product undergoes helium detection test and burst pressure test, showing good welding quality and pressure resistance performance. Description of the Drawings

[0038] Figure 1 It is the TEM photo of the weld in Example 1;

[0039] Figure 2 It is the TEM photo of the weld in Comparative Example 1;

[0040] Figure 3 It is the TEM photo of the weld in Comparative Example 2. Specific embodiments

[0041] The present invention will be described in detail below in conjunction with specific embodiments. For experimental methods where specific conditions are not indicated in the examples, they are carried out according to conventional methods and conditions.

[0042] In the examples and comparative examples of the present invention, welding wires were designed according to the element compositions in Table 1 below. A pulsed laser welding device was used to weld the runner plate body (made of AlSi10MnMg material) and the cover plate (grade 6063, cover plate thickness 3 mm) to obtain a thin-walled complex high-pressure die-cast runner plate. After welding, the welding quality was evaluated by helium leak testing and burst pressure testing.

[0043] The specific operation and requirements of helium leak testing are as follows: The test is carried out on a helium leak testing bench at 23 ± 5 °C, the test pressure is 20 bar gauge pressure (helium concentration > 70%), and the leakage value should not exceed 10 g / y.

[0044] The specific operation and requirements of burst pressure testing are as follows: Hydraulic oil is filled in the valve body at 23 ± 5 °C. After completely exhausting the air, the pressure is increased to 5 MPa at a rate of 1 MPa / s, and then increased to 10 MPa at a rate of 0.1 MPa / s. It is held at 10 ± 0.5 MPa for 5 min, and then the pressure is continuously increased until the product ruptures, and the burst pressure is recorded; if the burst pressure is greater than 10 MPa, the product performance requirements are met.

[0045] Table 1 Element composition table

[0046] Example 1

[0047] The welding and forming of the thin-walled complex high-pressure die-cast runner plate in this example includes the following processes:

[0048] S1, workpiece pretreatment; The two workpieces of the runner plate body and the cover plate to be welded are comprehensively cleaned by ultrasonic cleaning in combination with an alkaline solution (such as NaOH solution) to remove impurities on the workpiece surface; then the welding part is mechanically polished with sandpaper to make the surface roughness reach Ra4.0;

[0049] S2, laser welding; During welding, the focus is aligned with the surface of the runner plate body, and it is welded with 0 defocus. The laser power is controlled at 4300 W, the laser frequency is 200 Hz, and the laser swing amplitude is 0.3 mm; The composition of the welding wire is shown in Table 1, the diameter of the welding wire is 1.2 mm, and the wire filling speed is controlled at 3.0 - 4.5 m / min;

[0050] S3, Post-weld heat treatment; Along the welding path, an auxiliary laser heat source is set behind the pulsed laser welding device. The power of the auxiliary laser heat source is 250 W, the heating time is 1.5 s, and it follows the weld formed by the pulsed laser in front at a speed of 3 m / min for rapid heating.

[0051] After helium leak detection, the measured leakage rate is 7.6 g / y; After burst pressure testing, the measured burst pressure of the product is 12.8 MPa, which is comparable to that of forged products; It can meet the quality and usage requirements.

[0052] Figure 1 This is the TEM scanning electron micrograph of the welded structure in this embodiment. It can be found that dark and strong and tough phases with a diameter of several nanometers precipitate in the weld. These dot-like strong and tough phases are dispersed, significantly improving the mechanical properties of the product.

[0053] Example 2

[0054] The welding and forming of the thin-walled and complex high-pressure die-casting runner plate in this embodiment includes the following processes:

[0055] S1, Workpiece pretreatment; The two workpieces of the runner plate main body and the cover plate to be welded are thoroughly cleaned by using ultrasonic cleaning in combination with an alkaline solution to remove impurities on the workpiece surface; Then, the welding part is mechanically polished with sandpaper to make the surface roughness reach Ra4.5;

[0056] S2, Laser welding; During welding, the focus is aligned with the surface of the runner plate main body, and 0 defocus welding is performed; The laser power is controlled at 4500 W, the laser frequency is 180 Hz, and the laser swing amplitude is 0.3 mm; The wire rod composition is shown in Table 1, the wire rod diameter is 1.2 mm, and the wire filling speed is controlled at 3.0 - 4.5 m / min;

[0057] S3, Post-weld heat treatment; Along the welding path, an auxiliary laser heat source is set behind the pulsed laser welding device. The power of the auxiliary laser heat source is 300 W, the heating time is 0.8 s, and it follows the weld formed by the pulsed laser in front at a speed of 3 m / min for rapid heating.

[0058] After helium leak detection, the measured leakage rate is 7.5 g / y; After burst pressure testing, the measured burst pressure of the product reaches 13.4 MPa; It can meet the quality and usage requirements.

[0059] Example 3

[0060] The welding and forming of the thin-walled and complex high-pressure die-casting runner plate in this embodiment includes the following processes:

[0061] S1, Workpiece pretreatment: The main body of the runner plate and the cover plate to be welded are thoroughly cleaned by ultrasonic cleaning combined with an alkaline solution to remove impurities on the workpiece surface. Then, the welding area is mechanically polished with sandpaper to achieve a surface roughness of Ra6.1.

[0062] S2, Laser welding: During welding, the focus is aligned with the surface of the runner plate main body, and 0 defocus welding is performed. The laser power is controlled at 5000W, the laser frequency is 250Hz, and the laser swing amplitude is 0.2mm. The wire filler composition is shown in Table 1, the wire diameter is 1.2mm, and the wire filling speed is controlled at 3.0 - 4.5m / min.

[0063] S3, Post-weld heat treatment: Along the welding path, an auxiliary laser heat source is set behind the pulsed laser welding device. The power of the auxiliary laser heat source is 220W, the heating time is 1.4s, and it rapidly heats the weld formed by the pulsed laser in advance at a speed of 3m / min.

[0064] After helium leak detection, the measured leakage rate is 8.9g / y; after burst pressure testing, the measured burst pressure of the product reaches 11.6MPa, which can meet the quality and usage requirements.

[0065] Example 4

[0066] The welding and forming of the thin-walled complex high-pressure die-casting runner plate in this example includes the following processes:

[0067] S1, Workpiece pretreatment: The main body of the runner plate and the cover plate to be welded are thoroughly cleaned by ultrasonic cleaning combined with an alkaline solution to remove impurities on the workpiece surface. Then, the welding area is mechanically polished with sandpaper to achieve a surface roughness of Ra5.8.

[0068] S2, Laser welding: During welding, the focus is aligned with the surface of the runner plate main body, and 0 defocus welding is performed. The laser power is controlled at 4700W, the laser frequency is 220Hz, and the laser swing amplitude is 0.18mm. The wire filler composition is shown in Table 1, the wire diameter is 1.2mm, and the wire filling speed is controlled at 3.0 - 4.5m / min.

[0069] S3, Post-weld heat treatment: Along the welding path, an auxiliary laser heat source is set behind the pulsed laser welding device. The power of the auxiliary laser heat source is 240W, the heating time is 1.0s, and it rapidly heats the weld formed by the pulsed laser in advance at a speed of 3.5m / min.

[0070] After helium leak detection, the measured leakage rate is 7.3g / y; after burst pressure testing, the measured burst pressure of the product reaches 14.2MPa, and the quality and usage requirements can be met.

[0071] Comparative Example 1

[0072] This comparative example for the welding and forming of a thin-walled complex high-pressure die-casting runner plate includes the following processes:

[0073] S1, workpiece pretreatment; The two workpieces of the runner plate main body and the cover plate to be welded are comprehensively cleaned by ultrasonic cleaning in combination with an alkaline solution to remove impurities on the workpiece surface; Then, the welding part is mechanically polished with sandpaper to make the surface roughness reach Ra4.7;

[0074] S2, laser welding; During welding, the focus is aligned with the surface of the runner plate main body, and 0 defocus welding is performed; Control the laser power at 4300W, the laser frequency at 200Hz, and the laser swing at 0.3mm; The wire rod grade is 4043, and the composition is shown in Table 1. The wire diameter is 1.2mm, and the wire filling speed is controlled at 3.0 - 4.5m / min;

[0075] S3, post-weld heat treatment; Along the welding path, an auxiliary laser heat source is set behind the pulsed laser welding device. The power of the auxiliary laser heat source is 250W, the heating time is 1.5s, and it follows the weld formed by the pulsed laser at a speed of 3m / min for rapid heating.

[0076] After helium leak detection, the measured leakage rate is 11.8g / y, and the helium leak detection is not passed; During the burst pressure test, it ruptured when the pressure was increased to 7.5MPa, and the burst pressure test was not passed; The product does not meet the welding quality requirements.

[0077] As Figure 2 shown, it can be found that the AlFeSi phase is formed in the weld, and the presence of dispersion-strengthened precipitated phases during the heat treatment is not found. The lack of strengthening phases may be the main reason for the unqualified welding quality.

[0078] Comparative Example 2

[0079] This comparative example for the welding and forming of a thin-walled complex high-pressure die-casting runner plate includes the following processes:

[0080] S1, workpiece pretreatment; The two workpieces of the runner plate main body and the cover plate to be welded are comprehensively cleaned by ultrasonic cleaning in combination with an alkaline solution to remove impurities on the workpiece surface; Then, the welding part is mechanically polished with sandpaper to make the surface roughness reach Ra5.0;

[0081] S2, laser welding; During welding, the focus is aligned with the surface of the runner plate main body, and -1 defocus welding is performed; Control the laser power at 4300W, the laser frequency at 200Hz, and the laser swing at 0.3mm; The wire is the same as in Example 1, and the composition is shown in Table 1. The wire diameter is 1.2mm, and the wire filling speed is controlled at 3.0 - 4.5m / min;

[0082] After helium leak detection test, the measured leakage rate is 9.1 g / y; after burst pressure test, the measured burst pressure of the product reaches 10.4 MPa; basically meeting the product quality and usage requirements.

[0083] As Figure 3 shown, it can be found that strengthening phases with relatively large sizes (hundreds of nanometers) are formed in the weld. These strengthening phases precipitate during the solidification process and have relatively large sizes. Although the weld is strengthened, the strengthening effect is slightly worse than that of Example 1.

[0084] It should be emphasized that the above are only the preferred embodiments of the present invention, and it does not impose any form of limitation on the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A welding wire for the welding and forming of a thin-walled complex high-pressure die-casting runner plate, characterized in that, Elements comprising the following components: Mg: 5.0 - 5.5 wt%, Si: 1.7 - 2.5 wt%, Mn: 0.5 - 0.65 wt%, Sc: 0.1 - 0.3 wt%, La + Ce: 1.3 - 2.6 wt%, Zr: 0.02 - 0.1 wt%, Ti: 0.05 - 0.2 wt%, Fe: ≤0.15 wt%, Cu: ≤0.03 wt%, the balance being Al and unavoidable impurity elements, wherein the total impurity elements ≤0.15 wt%; The weight ratio of the Mg / Si elements is 2 - 3:

1.

2. The welding wire according to claim 1, wherein, The contents of La and Ce are both greater than 0.5 wt%.

3. A method for welding and forming a thin-wall complex high-pressure die-casting runner plate, characterized in that, Using a pulsed laser welding device to weld the runner plate body and the cover plate, and forming a thin-walled complex high-pressure die-cast runner plate, including the following processes: Controlling the laser power to be 4 - 5 kW and the laser frequency to be 150 - 250 Hz for welding; During welding, the focus is aligned with the surface of the runner plate body, and zero defocus welding is performed.

4. The method according to claim 3, characterized in that, The runner plate body is made of AlSi10MnMg material, and the cover plate is made of 6-series aluminum alloy material; the corresponding welding wire comprises elements of the following components: Mg: 5.0 - 5.5 wt%, Si: 1.7 - 2.5 wt%, Mn: 0.5 - 0.65 wt%, Sc: 0.1 - 0.3 wt%, La + Ce: 1.3 - 2.6 wt%, Zr: 0.02 - 0.1 wt%, Ti: 0.05 - 0.2 wt%, Fe: ≤0.15 wt%, Cu: ≤0.03 wt%, the balance being Al and unavoidable impurity elements, wherein the total impurity elements ≤0.15 wt%; The weight ratio of the Mg / Si elements is 2 - 3:

1.

5. The method according to claim 4, characterized in that, The contents of La and Ce are both greater than 0.5 wt%.

6. The method according to claim 3, wherein The laser swing is also controlled within the range of 0.2 - 0.5 mm.

7. The method according to claim 3, characterized in that During the laser wire filling welding process, weld seam heat treatment is synchronously performed by using a laser tracking heating method. The laser tracking heating is specifically: along the welding path, an auxiliary laser heat source is arranged behind the pulsed laser welding device, the power of the auxiliary laser heat source is controlled between 200 - 300 W, the heating time is 0.5 - 2.0 s, and rapid heating is carried out following the weld seam formed by the pulsed laser in advance.

8. The method according to claim 3 or 7, characterized in that, A monitoring device and an automatic welding control device are also provided. The monitoring device is electrically connected to the automatic welding control device and transmits weld seam image signals, and the automatic welding control device is electrically connected to the pulsed laser welding device and transmits wire filling speed control signals; during the welding process, the forming situation of the weld seam is monitored in real time by the monitoring device, and the wire filling speed is adjusted in real time by using the automatic welding control device; the wire filling speed is matched with the laser welding speed, and the wire filling speed is controlled between 3.0 - 4.5 m / min.

9. The method according to claim 3, characterized in that, It also includes pre-welding treatment; the pre-welding treatment is to control the surface roughness of the workpiece within the range of Ra3.2 - Ra6.

3.

10. The method according to claim 9, characterized in that The pre-welding treatment includes cleaning, mechanical grinding and / or surface chemical corrosion.

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