Method and experimental device capable of inhibiting solidification cracks of high-strength aluminum alloy

Abstract

The invention belongs to the technical field of welding equipment, and discloses a method and an experimental device capable of inhibiting solidification cracks of a high-strength aluminum alloy, the experimental device comprises molten drops, a swing light beam, a laser swing welding head, a connecting mechanism, a welding wire, an interlocking structure, a hollow tungsten electrode, a protective gas hood, an electric arc and a workpiece; the problem that the electric arc stability is poor in the conventional heterogeneous stranded welding wire electric arc welding process is solved, the hollow tungsten electrode electric arc provides a stable heat source to melt the welding wire to achieve low-splashing molten drop transition, meanwhile, the swing laser stirs a molten pool, uniform distribution of alloy elements is promoted, and the segregation problem caused by rapid solidification of high-strength aluminum alloy is solved. The aluminum wire and zirconium / titanium wire compounded stranded welding wire structure is adopted, microalloying elements are accurately transited to a molten pool on the premise of ensuring equal-strength matching of a welding seam and a base material, the grain refining effect is remarkable, the welding seam solidification crack inhibiting effect is remarkable, and meanwhile the joint strength is improved.

Description

Technical Field

[0001] This invention belongs to the field of welding equipment technology, and in particular relates to a method and experimental apparatus for suppressing solidification cracks in high-strength aluminum alloys. Background Technology

[0002] High-strength aluminum alloys (such as 2-series and 7-series aluminum alloys) have advantages such as low density, high strength, and good machinability, and are widely used in the aerospace field. Welding is a crucial basic process for manufacturing high-strength aluminum alloy components. However, during the molten welding of high-strength aluminum alloys, the solidification of the molten pool usually produces coarse dendritic structures and severe solute segregation. Under the action of welding stress, the weld will crack along the grain boundaries, forming solidification cracks, which seriously impairs the mechanical properties of the welded joint.

[0003] Choosing the right filler material is crucial for welding high-strength aluminum alloys. In actual production, 4-series Al-Si welding wire is commonly used for welding high-strength aluminum alloys, mainly utilizing the "healing effect" of silicon to reduce the tendency for solidification cracking. Therefore, it is widely used in actual production. However, its strength is not high enough to meet the requirements of high-performance aerospace components. Patent CN202211105367.0 developed a stranded welding wire that can suppress solidification cracking in high-strength aluminum alloys. By selecting several heterogeneous welding wires and introducing microalloyed zirconium, the microstructure of the weld is refined to control the grain size, thereby suppressing solidification cracking. However, this composite welding wire is usually composed of several heterogeneous welding wires with large differences in melting point. When used with existing commercial welding machines in welding experiments, arc instability easily occurs, affecting welding quality. At the same time, the addition of flux increases the complexity of the welding wire preparation process, thus increasing cost and hindering the widespread use of the welding wire, affecting the high-quality and efficient welding of high-strength aluminum alloys.

[0004] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0005] Existing composite welding wires are usually composed of several heterogeneous welding wires with large differences in melting point. When used with existing commercial welding machines for welding experiments, arc instability is likely to occur, which affects the welding quality. At the same time, the addition of flux powder increases the complexity of the welding wire preparation process, thereby increasing the cost and hindering the promotion and use of welding wires, thus affecting the high-quality and high-efficiency welding of high-strength aluminum alloys. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method and experimental apparatus for suppressing solidification cracks in high-strength aluminum alloys.

[0007] This invention is achieved by providing an experimental apparatus capable of suppressing solidification cracks in high-strength aluminum alloys, comprising:

[0008] Oscillating beam, laser oscillating welding head, connecting mechanism, heterogeneous stranded welding wire, interlocking structure, hollow tungsten electrode, protective gas shield, electric arc, workpiece;

[0009] Furthermore, the hollow tungsten electrode is embedded in the front end of the welding head, forming an arc circuit with the workpiece. The arc burns stably in the gap between the tungsten electrode and the workpiece. The welding wire extends from the left-side feeding system, and the molten droplet at the end serves as a filler material to transition and connect to the workpiece.

[0010] The laser oscillating welding head is vertically fixed to the upper part of the device via a connecting mechanism. The oscillating beam emitted by the head follows a vertically downward path, precisely focusing on the molten droplet at the end of the welding wire and the molten pool area of ​​the weld seam on the workpiece below. This stirring of the molten pool area promotes the uniform distribution of alloying elements. At the same time, the oscillating beam and the electric arc form a combined heat source, improving the stability of the welding process.

[0011] Furthermore, the protective gas hood covers the welding area, forming an inert gas protective cavity to suppress oxidation reactions during the welding process.

[0012] Furthermore, the interlocking structure is mechanically coupled at the connection between the stranded welding wire and the tungsten electrode, ensuring the stability of the stranded welding wire feeding, while simplifying the welding mechanism and enhancing the flexibility of position adjustment during the welding process.

[0013] Another object of the present invention is to provide a method for suppressing solidification cracks in high-strength aluminum alloys, comprising:

[0014] Step 1: The laser oscillating welding head is vertically fixed to the upper part of the device through the connecting mechanism. The oscillating beam emitted by it is precisely focused on the molten pool area of ​​the welding workpiece. The oscillation trajectory can be circular, infinite, or figure-eight, etc., which can realize the control and homogenization of the microstructure of the molten pool.

[0015] Step 2: The welding wire extends from the left-side feeding system, and the molten droplet at the end serves as a filler material to transition and connect to the workpiece; the hollow tungsten electrode is embedded at the front end of the welding head, forming an arc circuit with the workpiece. The arc burns stably in the gap between the tungsten electrode and the workpiece, providing a heat source to ensure the stable combustion of the arc.

[0016] Step 3: The protective gas cover covers the welding area to form an inert gas protective cavity to suppress oxidation reaction; the interlocking structure is mechanically coupled at the connection between the heterogeneous stranded welding wire and the tungsten electrode to ensure the wire feeding stability of the stranded welding wire, while simplifying the welding mechanism and enhancing the flexibility of the welding process posture adjustment.

[0017] Step 4: The overall layout is a vertical-horizontal composite structure, which enables efficient and stable operation of laser-arc composite welding.

[0018] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0019] The invention overcomes the problem of poor arc stability in conventional heterogeneous stranded welding wire arc welding. The hollow tungsten inert gas arc provides a stable heat source to melt the welding wire and achieve low spatter droplet transfer. At the same time, the oscillating laser stirs the molten pool, promoting the uniform distribution of alloying elements and overcoming the segregation problem caused by the rapid solidification of high-strength aluminum alloys.

[0020] This invention employs a stranded welding wire structure composed of aluminum wire and zirconium / titanium wire. Under the premise of ensuring equal strength matching between the weld and the base material, it precisely transitions microalloying elements to the molten pool, resulting in significant grain refinement, significant suppression of weld solidification cracks, and improved joint strength.

[0021] The hollow tungsten inert gas (TIG) welding torch of this invention is coaxially configured with the stranded welding wire. Furthermore, the inner wall of the hollow tungsten electrode is machined with a mechanical interlocking structure that matches the stranded welding wire, greatly improving the stability of wire feeding. Simultaneously, the coaxial arrangement of the dissimilar stranded welding wire and the arc welding torch simplifies the wire feeding mechanism and significantly enhances the flexibility of position adjustment during the welding process.

[0022] Through the synergistic effect of the above core technologies, solidification crack suppression is achieved while ensuring the good mechanical properties of high-strength aluminum alloy welded joints, resulting in higher welding efficiency and wider process adaptability, thus meeting the needs of high-quality, high-efficiency, and automated welding. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the experimental device provided in this embodiment of the invention, which can suppress solidification cracks in high-strength aluminum alloys.

[0024] Figure 2 This is a flowchart of a method for suppressing solidification cracks in high-strength aluminum alloys provided in an embodiment of the present invention.

[0025] Figure 3 The following are examples of solidification crack sensitivity experiments of high-strength aluminum alloys conducted using this experimental apparatus, as provided in the embodiments of the present invention: (a) crack sensitivity experiment conducted using conventional laser welding; (b) crack sensitivity experiment conducted using this experimental apparatus.

[0026] Figure 4 These are microstructure images of welds provided in the embodiments of the present invention: (a) solidified weld structure obtained by conventional laser welding; (b) solidified weld structure obtained in this experiment.

[0027] Figure 1 In the middle: 1. Molten droplet; 2. Oscillating beam; 3. Laser oscillating welding head; 4. Connecting mechanism; 5. Welding wire; 6. Interlocking structure; 7. Hollow tungsten electrode; 8. Protective gas shield; 9. Electric arc; 10. Workpiece. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] like Figure 1 As shown, the experimental apparatus system for suppressing solidification cracks in high-strength aluminum alloys provided in this embodiment of the invention includes:

[0030] 1. Molten droplet; 2. Oscillating beam; 3. Laser oscillating welding head; 4. Connecting mechanism; 5. Dissimilar stranded welding wire; 6. Interlocking structure; 7. Hollow tungsten electrode; 8. Protective gas shield; 9. Electric arc; 10. Workpiece.

[0031] The laser oscillating welding head 3 is vertically fixed to the upper part of the device via a connecting mechanism 4. Its oscillating beam 2 is precisely focused onto the molten pool in the welding area of ​​the workpiece 10 below, forming the main energy input channel. The welding wire 5 extends from the left-side feeding system, with its molten droplet 1 serving as filler material as it transitions towards the workpiece 10. A hollow tungsten electrode 7 is embedded at the front end of the welding head, forming an arc 9 circuit with the workpiece 10. The arc 9 burns stably in the gap between the tungsten electrode and the workpiece 10, providing an auxiliary heat source. A protective gas shield 8 covers the welding area, forming an inert gas protective chamber to suppress oxidation reactions. An interlocking structure 6 is mechanically coupled at the connection between the welding wire and the tungsten electrode, ensuring the stability of the dissimilar stranded welding wire feeding and simplifying the welding mechanism while enhancing the flexibility of position adjustment during the welding process. The overall vertical-horizontal composite layout enables efficient and stable operation of laser-arc 9 composite welding.

[0032] The upper part of the device is equipped with a laser oscillating welding head 3, which is connected to the column through a connecting mechanism 4. The welding head 3 is vertically aligned with the device base. The heterogeneous stranded welding wire 5 is horizontally introduced to the front end of the welding head 3 by the wire feeding mechanism on the left. The molten droplet 1 at the end of the welding wire 5 hangs inside the protective gas cover 8, forming a natural transition with the workpiece 10 below. The hollow tungsten electrode 7 is embedded in the center front end of the welding head 3, maintaining a fixed gap with the surface of the workpiece 10, in order to construct the arc 9 circuit.

[0033] The oscillating beam 2 is output from the laser oscillating welding head 3 and focused by the optical system to the center of the molten pool on the surface of the workpiece 10, acting together with the molten droplet 1 on the welding area; the electric arc 9 is ignited between the hollow tungsten electrode 7 and the workpiece 10, providing a stable auxiliary heat source for the molten pool; the protective gas cover 8 is fixed to the lower end of the welding head 3, enclosing the welding area with an inert gas environment to ensure that the molten droplet 1 and the molten pool are protected from oxidation.

[0034] The interlocking structure 6 is mechanically coupled to the connection between the welding wire 5 and the hollow tungsten electrode 7. The concentric feeding and positioning of the welding wire 5 and the tungsten electrode 7 are achieved through the assembly relationship between the locking pin and the sliding groove. The connecting mechanism 4 has a built-in angle adjustment hinge and positioning pin, so that the laser oscillating welding head 3 can withstand axial tangential force after assembly, and can also be aligned with the welding path through the fine adjustment screw.

[0035] During the operation, the laser oscillating welding head 3 drives the oscillating beam 2 to scan along a preset trajectory, so that the molten pool is dynamically heated evenly; the molten droplets 1 are continuously supplied with filler metal by the welding wire 5, and the wire feeding consistency is maintained by the interlocking structure 6; the electric arc 9 synchronously provides compensating heat flow to the molten pool and reduces the temperature gradient; the inert gas in the protective gas shield 8 flows continuously to suppress the formation of oxidation cracks between the molten pool and the high-strength aluminum alloy.

[0036] like Figure 2 As shown, the method for suppressing solidification cracks in high-strength aluminum alloys provided in this embodiment of the invention includes the following steps:

[0037] S101, the laser oscillating welding head is vertically fixed to the upper part of the device through the connecting mechanism, and the oscillating beam emitted by it is precisely focused on the molten pool in the welding area of ​​the workpiece below, forming the main energy input channel;

[0038] S102, the welding wire extends from the left feeding system, and the molten droplet at the end transitions to the molten pool connecting the workpiece as filler material; the hollow tungsten electrode is embedded in the front end of the welding head, forming an arc circuit with the workpiece, and the arc burns stably in the gap between the tungsten electrode and the workpiece, providing an auxiliary heat source.

[0039] S103, the protective gas shield covers the welding area, forming an inert gas protective cavity to suppress oxidation reaction; the interlocking structure is mechanically coupled at the connection between the heterogeneous stranded welding wire and the tungsten electrode to ensure coordinated control of arc parameters and beam oscillation;

[0040] The S104 features a vertical-horizontal composite layout, enabling efficient and stable laser-arc composite welding operations.

[0041] This invention provides a method and experimental apparatus for suppressing solidification cracks in high-strength aluminum alloys. The experimental apparatus comprises a stranded welding wire composed of multiple welding wires, a hollow tungsten inert gas (TIG) welding torch, and an oscillating laser welding head. The stranded welding wire is composed of aluminum welding wire and zirconium or titanium welding wire. While ensuring equal strength matching with the base material, microalloying elements are introduced into the molten pool to refine the solidification structure of the weld, thereby suppressing solidification cracks. During welding, the welding wire passes through the interior of the hollow tungsten inert gas (TIG) and forms a mechanical interlocking structure with it. The coaxiality of the hollow TIG welding torch with the stranded welding wire reduces process complexity and allows for flexible welding posture adjustment. Simultaneously, due to the unique material structure of the stranded welding wire, the interior of the hollow TIG is machined into a mechanical interlocking structure that matches the stranded welding wire, ensuring stable wire feeding. The entire welding process uses a hollow tungsten electrode welding torch to provide an arc heat source to melt the welding wire, achieving a stable droplet transfer. The oscillating beam stirs the molten pool to promote the uniform distribution of alloying elements, ultimately achieving high-quality and efficient welding of high-strength aluminum alloys and obtaining a good weld joint.

[0042] The stranded welding wire of the present invention is composed of two types of welding wire, including a combination of aluminum welding wire and zirconium welding wire or a combination of aluminum welding wire and titanium welding wire. The welding wire structure can be 1×3, 1×7 or 1×19.

[0043] The stranded welding wire of this invention is fed through the internal channel of a hollow tungsten electrode welding torch. The internal channel of the hollow tungsten electrode has a specific geometric structure, and its inner wall is machined with grooves and threads.

[0044] The internal channel geometry of the hollow tungsten electrode described in this invention forms a mechanical interlock with the external structure of the stranded welding wire. The function of the mechanical interlock structure is to ensure the stability and guidance of the welding wire during the feeding process and to prevent slippage or deviation.

[0045] The welding heat source of this invention consists of an electric arc generated by a hollow tungsten electrode and an oscillating laser. The main function of the electric arc heat source is to melt the stranded welding wire and the base material, forming a molten pool and achieving a stable droplet transfer. The function of the oscillating laser welding head is to stir the molten pool to promote the uniform distribution of alloying elements.

[0046] The oscillation trajectory of the laser oscillating welding head described in this invention can be circular, infinite, rectangular, elliptical, linear, figure-eight, etc.

[0047] The commercial space market is experiencing rapid growth, and the demand for launch vehicles, as a crucial component of space infrastructure, is steadily increasing. The propellant tank is the largest and most critical component of the launch vehicle's structure, accounting for approximately two-thirds of its length and over 50% of its total mass. As a pressure vessel used to store propellant, the tank also serves as the main load-bearing structure of the launch vehicle, bearing internal pressure and axial loads. It is a key component affecting the safety and reliability of the launch vehicle, making its manufacturing particularly important. Welding is a critical process in propellant tank manufacturing; the quality of the weld joints directly determines the load-bearing capacity and service life of the tank structure. Currently, propellant tank welding primarily utilizes tungsten inert gas welding (TIG), plasma arc welding, and friction stir welding. Existing welding technologies in propellant tank manufacturing mainly face problems of low production efficiency and high cost, severely restricting the widespread application of propellant tank component manufacturing. Laser welding technology has high energy density (10⁻⁶ Ω·cm). 6 ~10 8 W / cm 2 The advantages of laser welding technology, including high efficiency (welding speed of 10-100 mm / s) and high degree of automation, provide great potential for the welding of tank components. This enables high-quality and efficient manufacturing of tank components using laser welding technology.

[0048] This invention provides a method and experimental apparatus for suppressing solidification cracks in high-strength aluminum alloys. While suppressing solidification crack defects, it ensures good mechanical properties of the welded joints of high-strength aluminum alloys, achieving higher welding efficiency and wider process adaptability, thus meeting the requirements of high-quality, high-efficiency, and automated welding.

[0049] Example 1

[0050] The base material used in this embodiment is 2024 high-strength aluminum alloy. To verify the solidification crack sensitivity of the weld under different welding processes, the 2024 aluminum alloy was first processed into a fishbone sample. Subsequently, the 2024 high-strength aluminum alloy was welded using conventional oscillating laser-arc hybrid welding and the experimental apparatus of this invention. The average length of the cracks after welding was statistically analyzed, and the crack rate (average total crack length / weld length × 100%) was calculated as an evaluation index for the solidification crack sensitivity of the weld. The main process parameters of the conventional oscillating laser-arc hybrid welding process are: laser power 5kW, welding speed 20mm / s, wire spacing 4mm, welding current 30A, defocusing amount 0mm, the trajectory used is a circular oscillating trajectory, the oscillation amplitude and oscillation frequency are 1.5mm and 250Hz respectively, the welding wire used is ER2319 welding wire with a diameter of 1.2mm, the welding current is 120A, and the wire feed speed is 0.5m / min. The parameters used in this process are as follows: laser power 5kW, welding speed 20mm / s, wire spacing 4mm, defocusing amount 0mm, and a circular oscillating trajectory with an oscillation amplitude and frequency of 1.5mm and 250Hz, respectively. The TIG arc welding method is pulsed arc welding, using 1×7 heterogeneous stranded welding wire, with 6 peripheral wires being ER2319 wire and the center wire being ERZr2 wire, with a wire diameter of 1.2mm, a welding current of 120A, and a wire feed speed of 0.5m / min. During welding, an arc-fronting method is used, followed by oscillating beam stirring of the molten pool to achieve uniform distribution of alloying elements. Figure 3 (a) is a weld obtained by conventional laser oscillation-arc hybrid welding, with a solidification crack length of 65 mm. Figure 3 (b) The weld obtained by this experimental method shows that no solidification cracks appeared in the weld, indicating that the solidification cracks in the weld were effectively suppressed by this process. Figure 4 (a) shows the solidification structure of the weld obtained by conventional laser oscillation-arc hybrid welding. It can be seen that the weld microstructure is coarse and solidification cracks are generated along the grain boundaries. Figure 4 (b) shows the solidification structure of the weld obtained under this experimental method, achieving a fine and uniform distribution of the weld microstructure without the generation of solidification cracks.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An experimental apparatus capable of suppressing solidification cracks in high-strength aluminum alloys, characterized in that, The experimental device comprises a droplet, a swing beam, a laser swing welding head, a connecting mechanism, a welding wire, an interlocking structure, a hollow tungsten electrode, a protective gas cover, an electric arc and a workpiece; the laser swing welding head is vertically fixed on the upper part of the device through the connecting mechanism, and the swing beam emitted vertically downward is accurately focused on the droplet at the end of the welding wire and the welding area of the workpiece below to form a main energy input channel; the welding wire extends from the left side of the feeding system, and the droplet at the end serves as a filler material to transitionally connect the workpiece.

2. The experimental apparatus of claim 1, wherein, The hollow tungsten electrode is embedded in the front end of the welding head and forms an electric arc loop with the workpiece below, and the electric arc stably burns between the tungsten electrode and the workpiece to provide an auxiliary heat source.

3. The experimental apparatus of claim 1, wherein, The protective gas cover surrounds the welding area to form an inert gas protection cavity to inhibit the oxidation of the surface of the workpiece.

4. The experimental apparatus of claim 1, wherein, The interlocking structure is mechanically coupled to the connection between the welding head and the hollow tungsten electrode to realize the coordinated control of the electric arc parameters and the laser swing.

5. A method of inhibiting solidification cracking of a high strength aluminum alloy characterized by, The method comprises the following steps: the laser swing welding head is vertically fixed on the upper part of the device through the connecting mechanism, and the swing beam emitted vertically downward is accurately focused on the droplet at the end of the welding wire and the welding area of the workpiece below to form a main energy input channel; the welding wire extends from the left side of the feeding system, and the droplet at the end serves as a filler material to transitionally connect the workpiece, the hollow tungsten electrode is embedded in the front end of the welding head and forms an electric arc loop with the workpiece, and the electric arc stably burns between the tungsten electrode and the workpiece; the protective gas cover surrounds the welding area to form an inert gas protection cavity; the interlocking structure is mechanically coupled to the connection between the welding head and the hollow tungsten electrode to ensure the coordinated control of the electric arc parameters and the laser swing; the whole adopts a vertical and horizontal composite layout to realize the efficient and stable operation of laser and electric arc composite welding.

6. The method of claim 5, wherein, The swing beam reciprocates periodically in the transverse and longitudinal directions to expand the width of the molten pool and promote the flow of alloy melt.

7. The method of claim 5, wherein, The electric arc current is between 60 amperes and 120 amperes to ensure the cooperation of heat input between the hollow tungsten electrode and the workpiece and inhibit the generation of cracks.

8. An experimental apparatus control system for suppressing solidification cracking of high-strength aluminum alloy, characterized by comprising: a solidification cracking suppression device; a control device; and a control program. The method comprises a laser swing control unit, a welding wire supply control unit, an electric arc control unit, a protective gas control unit and an interlocking coordination unit; the laser swing control unit is used to drive the laser swing welding head to reciprocate according to a preset trajectory; the welding wire supply control unit is used to control the extension rate of the welding wire; the electric arc control unit is used to control the electric arc current and voltage; the protective gas control unit is used to adjust the gas flow and pressure inside the protective gas cover; and the interlocking coordination unit is used to dynamically adjust the electric arc control parameters according to the laser swing parameters to realize the coordinated control of energy input.

9. The control system of claim 8, wherein, The interlocking coordination unit collects real-time signals of the laser swing amplitude and the electric arc current to realize closed-loop feedback control.

10. The control system of claim 8, wherein, The protective gas control unit further controls the flow pulse of inert gas to optimize the protection effect and reduce gas consumption.

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