Vacuum electron beam welding method for beryllium aluminum alloys

Abstract

The application discloses a kind of vacuum electron beam welding methods of beryllium aluminum alloy, belong to metal material welding technical field, comprising the following steps: A, beryllium aluminum alloy plate is polished and cleaned and is handled;B, beryllium aluminum alloy plate is clamped with welding fixture, and the position to be welded is placed in the welding work area of electron beam welding system workstation;C, electron beam welding system is pumped to welding work vacuum degree, sets welding process parameter;D, preheating treatment is carried out to workpiece before welding, starts electron beam welding system, and beryllium aluminum alloy plate is welded;E, after welding, carries out postwelding slow cooling treatment.The application is designed by electron beam welding process and tooling fixture, optimizes electron beam welding heat input, controls cooling rate and the like mode, improves the uniformity of weld molten metal composition and organization, and the beryllium aluminum alloy weld obtained is not only free from crack, pore and other welding defects, simultaneously, but also makes the mechanical property of welded joint better than base material.

Description

Technical Field

[0001] This invention relates to the field of metal material welding technology, and in particular to a vacuum electron beam welding method for beryllium aluminum alloy. Background Technology

[0002] Beryllium aluminum alloys are lightweight alloys with excellent mechanical, thermal, optical, and machining properties, and have important applications in aerospace, high-end civilian technologies, and other fields. Currently, beryllium aluminum alloys are prepared using two methods: powder metallurgy and investment casting. Powder metallurgy produces beryllium aluminum alloys with smaller grain sizes, higher alloy strength, and better uniformity; however, it is difficult to achieve clean-cut shapes for complex structures, resulting in large machining allowances and high manufacturing costs. Investment casting is a simple process with a short cycle time and low cost, but it is prone to defects such as segregation, shrinkage porosity, and voids in large-sized structural parts, leading to lower alloy strength. Therefore, for complex-shaped and large-sized beryllium aluminum alloy structural parts, simple preparation methods such as casting and powder metallurgy are no longer sufficient to meet their high engineering requirements. Welding technology for beryllium aluminum alloys is of great practical significance for expanding their engineering applications.

[0003] Literature review reveals that current research on beryllium-aluminum alloy welding primarily focuses on three areas: laser welding, friction stir welding, and helium arc welding. For laser welding, a method for laser welding of cast beryllium-aluminum alloys (CN113210857A) can be referenced, but the mechanical properties of the welded material are only 0.6-0.9 times that of the base material, indicating low weld quality. For friction stir welding, a method for friction stir welding of beryllium-aluminum alloy plates (CN112935521A) can be referenced, but the welding process involves many controllable factors, resulting in poor controllability and limited industrial applicability. For helium arc welding, a method for helium arc welding of cast beryllium-aluminum alloys (CN113664329A) can be referenced, but the addition of beryllium-aluminum welding wire further reduces controllability. Therefore, a new welding process needs to be developed to replace existing methods.

[0004] Electron beam welding technology possesses unique and excellent characteristics, including small spot size, large aspect ratio, low welding heat input, low joint stress, small workpiece deformation, and high controllability. It can significantly refine the weld microstructure, reduce residual thermal stress, and prevent crack formation. Currently, this technology has been increasingly and successfully applied to the manufacture of industrial-scale alloy products. Domestic and international research institutions and scholars have conducted extensive research on the equipment, processes, microstructure, and properties of electron beam welding of Ti, Ni, Mg, and Al alloys. The mechanical properties of beryllium-aluminum alloy welded joints are crucial to the service life of beryllium-aluminum alloys in engineering applications. Therefore, researching electron beam welding processes for beryllium-aluminum alloys to improve the microstructure and mechanical properties of welded joints is essential. However, existing literature has not conducted relevant research on electron beam welding of beryllium-aluminum alloys, and whether electron beam welding is suitable for beryllium-aluminum alloy welding requires further experimental verification. Summary of the Invention

[0005] The purpose of this invention is to provide a vacuum electron beam welding method for beryllium-aluminum alloys, addressing the aforementioned problems. The inventors have conducted in-depth research on the electron beam welding process of beryllium-aluminum alloys. Through extensive experimental trial and error and continuous optimization of the welding process, they have overcome the technical defects in electron beam welding of beryllium-aluminum alloys, resulting in an electron beam welding method for beryllium-aluminum alloys with excellent welding quality, thus providing a new welding approach for beryllium-aluminum alloy welding.

[0006] The technical solution adopted in this invention is as follows: A vacuum electron beam welding method for beryllium aluminum alloy, comprising the following steps:

[0007] A. Grind and clean the beryllium aluminum alloy plate that needs to be welded to remove oxides, oil stains and debris from the surface of the beryllium aluminum alloy plate.

[0008] B. Clamp the above-treated beryllium aluminum alloy plate with a welding fixture and place the position to be welded in the welding work area of ​​the electron beam welding system workbench;

[0009] C. Evacuate the electron beam welding system to the working vacuum level and set the welding process parameters;

[0010] D. Preheat the workpiece before welding, then start the electron beam welding system to weld the beryllium aluminum alloy plate. The welding process parameters are: accelerating voltage 50kV-200kV, electron beam current 1mA-10mA, focusing current 2000mA-2800mA, welding speed 1mm / s-50mm / s, and working chamber vacuum degree less than 9×10⁻⁶. -3 Pa;

[0011] E. After welding is completed, slow cooling treatment can be performed.

[0012] In this invention, the electron beam welding process parameters are the core influencing factors. The inventors have concluded through experiments that, while ensuring welding efficiency, the electron beam current should not exceed 10mA. If it exceeds this, the beryllium aluminum alloy welding sample is prone to spatter on the surface of the weld due to overcurrent, and shrinkage porosity will occur inside the weld of the welding sample. The focusing current should not exceed 2800mA. If it exceeds this, the welding sample is also prone to oxidation, resulting in defects such as shrinkage porosity.

[0013] Furthermore, in step A, the beryllium aluminum alloy workpiece is polished with SiC sandpaper, then ultrasonically cleaned with acetone, and finally dried.

[0014] Furthermore, the welding fixture includes a base, a welding platform is provided at the center of the end face of the base, and a first fixed support and a second fixed support are symmetrically arranged on both sides of the welding platform. The first fixed support and the second fixed support are respectively connected to a first clamping plate and a second clamping plate to clamp the beryllium aluminum alloy plate. The main function of the welding fixture is to eliminate the deformation of the beryllium aluminum alloy plate caused by internal stress, allowing the internal stress to be released through the weld penetration zone. This avoids welding deformation, improves welding quality, and helps eliminate welding defects such as shrinkage porosity and voids in the weld area.

[0015] Furthermore, both the first and second clamping plates are provided with symmetrically arranged U-shaped through holes for adjusting the fixed position of the first and second clamping plates, thereby facilitating the welding of beryllium aluminum alloy plates of different sizes and specifications.

[0016] Furthermore, in step D, the beryllium-aluminum alloy plate is preheated using an electron beam welding system. The electron beam current during preheating is 0.5mA-1.5mA, the focusing current is 1500mA-1600mA, the preheating time is 0.2min-0.5min per cycle, and the number of preheating cycles is 1-3. Preheating is primarily to reduce the formation of hot cracks. Unlike traditional direct heating preheating, this invention utilizes electron beam preheating. Experiments have shown that, while ensuring preheating efficiency, the electron beam current and focusing current should be as low as possible. Excessive electron beam current can cause spatter on the weld surface of the beryllium-aluminum alloy weld sample due to overcurrent, and shrinkage porosity can occur inside the weld. Excessive focusing current can cause oxidation of the weld sample, resulting in shrinkage porosity and other defects. Therefore, electron beam current and focusing current within the aforementioned ranges are suitable for electron beam preheating.

[0017] Preferably, in step D, the accelerating voltage is 70kV-200kV, the electron beam current is 2mA-40mA, the focusing current is 2100mA-2600mA, the welding speed is 2mm / s-40mm / s, and the working chamber vacuum degree is less than 8×10⁻⁶. -3More preferably, the accelerating voltage is 120kV-170kV, the electron beam current is 2mA-20mA, the focusing current is 2200mA-2500mA, the welding speed is 3mm / s-30mm / s, and the working chamber vacuum degree is less than 5×10 Pa. -3 Pa. More preferably, the accelerating voltage is 130kV-160kV, the electron beam current is 3mA-10mA, the focusing current is 2200mA-2400mA, the welding speed is 2mm / s-10mm / s, and the working chamber vacuum degree is 2.5×10⁻⁶ Pa. -3 Pa -4.5×10 -3 Pa.

[0018] Furthermore, in step D, the thickness of the weld is 1mm-6mm, preferably 3mm-5mm.

[0019] Furthermore, the present invention is applicable to the welding of beryllium aluminum alloys with the following alloy composition (in mass percentage): Al content 35%-39%, Si content 0.001%-0.005%, Fe content 0.01%-0.03%, Mn content 0.002%-0.009%, Cu content 0.001%-0.002%, O content 0.002%-0.005%, with the balance being Be and unavoidable impurities.

[0020] Furthermore, through experimental analysis, it was found that in step E, the cooling rate after welding should be controlled to be below 8000 K / s. If the cooling rate is higher than this, shrinkage defects are likely to occur, reducing the welding quality of beryllium aluminum alloy.

[0021] As described above, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. This invention avoids welding defects and hot cracks at the weld joint by designing electron beam welding processes and tooling fixtures, optimizing the heat input of electron beam welding, and effectively controlling the cooling rate. It improves the uniformity of the composition and structure of the molten metal in the weld, refines the structure of the weld joint, and the resulting beryllium-aluminum alloy weld joint is free from welding defects such as cracks and porosity. At the same time, the mechanical properties of the beryllium-aluminum alloy plate weld joint are superior to those of the base material. Through testing, the microhardness of the beryllium-aluminum alloy base material is 115HV-125HV, while the microhardness of the weld joint is 165HV-175HV. The mechanical properties of the weld joint are significantly higher than those of the base material.

[0023] 2. This invention, through in-depth research on the electron beam welding process of beryllium-aluminum alloys, and through extensive experimental trial and error and continuous optimization of the welding process, has obtained an electron beam welding method for beryllium-aluminum alloys with excellent welding quality. This welding method improves the welding quality of beryllium-aluminum alloys, the welding process is simple and uncomplicated, and it has strong operability and stability, providing a new welding approach for beryllium-aluminum alloy welding. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the welding fixture structure of the present invention;

[0025] Figure 2 The image shows the metallographic structure of the beryllium-aluminum alloy weld obtained in Example 1 of this invention.

[0026] Figure 3 This is a metallographic photograph of the beryllium-aluminum alloy weld obtained by welding in Comparative Example 1 of this invention;

[0027] Figure 4 This is a metallographic photograph of the beryllium-aluminum alloy weld obtained by welding in Comparative Example 2 of this invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings.

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] Example 1

[0031] A vacuum electron beam welding method for beryllium-aluminum alloys includes the following steps:

[0032] S1. Two identical beryllium aluminum alloy plates are used as the first and second workpieces. The first and second workpieces are ground and cleaned. The workpiece surfaces are ground with SiC sandpaper, and then ultrasonically cleaned with acetone or ethanol to remove oxides and machining oil. The beryllium aluminum alloy plate is composed of the following elements by mass percentage: Al content 37%, Si content 0.002%, Fe content 0.03%, Mn content 0.009%, Cu content 0.001%, O content 0.003%, and the balance is Be and unavoidable impurities.

[0033] S2. Clamp the first and second workpieces, which have been processed as described above, with welding fixtures, and place the position to be welded in the center of the electron beam welding system's worktable, as shown below. Figure 1 As shown;

[0034] S3. Evacuate the electron beam welding system to the welding working vacuum level and set the welding process parameters;

[0035] S4. Before welding, the workpiece is preheated. The electron beam current during preheating is 1mA, the focusing current is 1500mA, the single preheating time is 0.3min, and the number of preheating cycles is 2.

[0036] S5. Start the electron beam welding system and perform electron beam welding on the area to be welded; the electron beam welding process parameters are as follows:

[0037] Weld thickness: 2mm;

[0038] Accelerating voltage: 150kV;

[0039] Electron beam current: 4mA;

[0040] Focusing current: 2500mA;

[0041] Welding speed: 8mm / s;

[0042] Vacuum level in the work chamber: less than 3×10 -3 Pa;

[0043] S6. After welding is completed, the welded joint is slowly cooled at a rate of 7000 K / s.

[0044] In the above embodiments, the welding fixture is as follows: Figure 1 As shown, it includes a base 1, and a welding platform 2 is provided in the middle of the end face of the base 1. The platform 2 has a groove structure. A first fixed support 3 and a second fixed support 4 are symmetrically arranged on both sides of the welding platform 2. The first fixed support 3 and the second fixed support 4 are respectively connected to a first clamping plate 5 and a second clamping plate 6 by bolts 11. There are clamping openings (not marked) between the first fixed support 3 and the first clamping plate 5, and between the second fixed support 4 and the second clamping plate 6, so as to clamp the first workpiece 7 by the cooperation between the first fixed support 3 and the first clamping plate 5, and to clamp the second workpiece 8 by the cooperation between the second fixed support 4 and the second clamping plate 6. Meanwhile, to facilitate adjustment of the relative position between the first workpiece 7 and the second workpiece 8, the first clamping plate 5 is provided with a first U-shaped through hole 9, and the first fixed support 3 is provided with a threaded groove corresponding to the first U-shaped through hole 9, so that the first clamping plate 5 can slide and adjust along the end face of the first fixed support 3, thereby adjusting the position of the first workpiece 7 relative to the second workpiece 8. To ensure that the first clamping plate 5 can slide and adjust parallel to the first fixed support 3, the first U-shaped through hole 9 and the corresponding threaded groove are symmetrically provided in twos. Correspondingly, the second clamping plate 6 is also provided with a second U-shaped through hole 10 identical to the first U-shaped through hole 9, to facilitate adjustment of the relative position of the second workpiece 8.

[0045] In this invention, a welding fixture is used to fix the first workpiece 7 and the second workpiece 8 during the welding process. For convenient vacuum electron beam welding, the welding fixture applies horizontal and vertical constraint forces to the weld penetration zone, preventing the welding pressure generated in the weld penetration zone from being released through the workpiece and thus preventing deformation of the workpiece, i.e., reducing deformation caused by internal stress. Simultaneously, the welding pressure can only be released along the weld direction in the weld penetration zone. Combined with the designed welding process parameters and post-weld cooling rate, welding quality is ensured while releasing welding pressure, improving the mechanical properties of the weld.

[0046] The beryllium-aluminum alloy welded specimens obtained in Example 1 were subjected to mechanical property testing and metallographic observation. The mechanical property test results of the welded specimens are shown in Table 1, and the metallographic structure is as follows: Figure 2 As shown, in Figure 2 In the weld, the interfaces of the beryllium aluminum alloy plates on both sides of the weld are almost parallel, with no misalignment or deformation. The microstructure inside the weld is evenly distributed, with no obvious welding defects such as porosity or shrinkage, which indicates that the welding quality is excellent.

[0047] Example 2

[0048] Example 2 is the same as Example 1, except that the alloy composition of the beryllium aluminum alloy is (in mass percentage): Al content is 37%, Si content is 0.003%, Fe content is 0.02%, Mn content is 0.007%, Cu content is 0.002%, O content is 0.004%, and the balance is Be and unavoidable impurities.

[0049] The mechanical properties of the beryllium-aluminum alloy welded specimens obtained in Example 2 are shown in Table 1.

[0050] Example 3

[0051] Example 3 is the same as Example 1, except that the electron beam welding process parameters are as follows:

[0052] Weld thickness: 2mm;

[0053] Accelerating voltage: 150kV;

[0054] Electron beam current: 3mA;

[0055] Focusing current: 2400mA;

[0056] Welding speed: 7mm / s;

[0057] Vacuum level in the work chamber: less than 3×10 -3 Pa.

[0058] The mechanical properties of the beryllium-aluminum alloy welded specimens obtained in Example 3 are shown in Table 1.

[0059] Comparative Example 1

[0060] Comparative Example 1 is the same as Example 1, except that the welding fixture of the present invention was not used for welding, but the tooling fixture provided with the electron beam welding system was used to fix and weld the beryllium aluminum alloy.

[0061] The mechanical properties of the beryllium-aluminum alloy welded specimens obtained in Comparative Example 1 are shown in Table 1, and their metallographic structures are as follows: Figure 3 As shown. By Figure 3 It can be seen that the beryllium aluminum alloy plate on one side of the weld was obviously warped, indicating that the beryllium aluminum alloy plate on that side underwent significant deformation during welding. As can be seen from the metallographic image, its welding quality is not as good as that of Example 1.

[0062] Comparative Example 2

[0063] Comparative Example 2 is the same as Example 1, except that the slow cooling rate is 9000 K / s.

[0064] The mechanical properties of the beryllium-aluminum alloy welded specimens obtained in Comparative Example 2 are shown in Table 1, and their metallographic structures are as follows: Figure 4 As shown. By Figure 4 It can be seen that the beryllium-aluminum alloy plates on both sides of the weld did not warp, but there was obvious shrinkage porosity defect deep in the weld. This indicates that when the slow cooling rate is higher than 8000 K / s, the cooling rate is too fast, causing the beryllium phase in the weld area to solidify first, while the aluminum phase does not have enough time to shrink, thus producing shrinkage porosity defect.

[0065] Comparative Example 3

[0066] Comparative Example 3 is the same as Example 1, except that the electron beam current is adjusted to 15mA and the focusing current is adjusted to 3000mA during electron beam welding.

[0067] The mechanical properties of the beryllium-aluminum alloy welded specimens obtained by welding in Comparative Example 3 are shown in Table 1.

[0068] Table 1. Results of mechanical property testing of welded specimens from Examples 1-3 and Comparative Examples 1-3

[0069]

[0070] As shown in Table 1, the welded specimens in Examples 1-3 all fractured in the base material after tensile testing; while the welded specimens in Comparative Examples 1-3 all fractured at the weld after tensile testing, and their tensile strength was about 44-48% of that of the beryllium aluminum base alloy.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A vacuum electron beam welding method for beryllium aluminum alloy, characterized in that, Includes the following steps: A. The beryllium aluminum alloy plate to be welded is ground and cleaned; the beryllium aluminum alloy plate is composed of the following elements by mass percentage: Al content 35%-39%, Si content 0.001%-0.005%, Fe content 0.01%-0.03%, Mn content 0.002%-0.009%, Cu content 0.001%-0.002%, O content 0.002%-0.005%, with the balance being Be and unavoidable impurities; B. Clamp the above-treated beryllium aluminum alloy plate with a welding fixture and place the position to be welded in the welding work area of ​​the electron beam welding system workbench; C. Evacuate the electron beam welding system to the working vacuum level and set the welding process parameters; D. Preheat the workpiece before welding, then start the electron beam welding system to weld the beryllium aluminum alloy plate. The welding process parameters are: accelerating voltage 50kV-200kV, electron beam current 1mA-10mA, focusing current 2000mA-2800mA, welding speed 1mm / s-50mm / s, and working chamber vacuum degree less than 9×10⁻⁶. -3 Pa; E. After welding is completed, slow cooling treatment can be performed.

2. The welding method as described in claim 1, characterized in that, In step A, the beryllium aluminum alloy workpiece is polished with SiC sandpaper, then ultrasonically cleaned with acetone, and finally dried.

3. The welding method as described in claim 1, characterized in that, The welding fixture includes a base, a welding platform is provided in the middle of the end face of the base, and a first fixed support and a second fixed support are symmetrically arranged on both sides of the welding platform. The first fixed support and the second fixed support are respectively connected to a first clamping plate and a second clamping plate to clamp the beryllium aluminum alloy plate.

4. The welding method as described in claim 3, characterized in that, Both the first and second clamping plates are provided with symmetrically arranged U-shaped through holes for adjusting the fixed position of the first and second clamping plates.

5. The welding method according to any one of claims 1-4, characterized in that, In step D, the beryllium aluminum alloy plate is preheated using an electron beam welding system. The electron beam current during preheating is 0.5mA-1.5mA, the focusing current is 1500mA-1600mA, the preheating time is 0.2min-0.5min, and the number of preheating cycles is 1-3.

6. The welding method as described in claim 5, characterized in that, In step D, the accelerating voltage is 130kV-160kV, the electron beam current is 3mA-10mA, the focusing current is 2200mA-2400mA, the welding speed is 2mm / s-10mm / s, and the working chamber vacuum degree is 2.5×10⁻⁶. -3 Pa -4.5×10 -3 Pa.

7. The welding method as described in claim 5, characterized in that, In step D, the thickness of the weld is 1mm-6mm.

8. The welding method as described in claim 5, characterized in that, In step E, the cooling rate after welding is controlled to be below 8000 K / s.

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