Method and system for improving arc suppression depression of electron beam welding seam on small-diameter thin-wall end face

Abstract

The invention discloses a small-diameter thin-wall end face electron beam welding seam arc suppression depression improving method and system, and belongs to the technical field of electron beam welding.The method comprises the steps that positioned welding is conducted on a workpiece in a vacuum environment, and a plurality of welding spots are arranged in the circumferential direction at intervals; formal welding is conducted on the workpiece subjected to positioned welding in the first welding direction; performing modification welding in a second welding direction opposite to the first welding direction; controlling the beam incremental attenuation angle, the welding current and the focusing current of the formal welding and the modification welding; and after welding, the vacuum environment is inflated after the preset time is delayed, and the welding operation of the workpiece is completed. According to the method, the problem that the arc suppression area of the welding seam is sunken is solved, the front face and the back face of the welding seam both meet the standard requirements, double-face forming of the small-diameter thin-wall end face circumferential welding seam is achieved, welding seam forming is full and complete, and the problem that the part size is out of tolerance due to the fact that the arc suppression area of the part is sunken and argon arc welding repair welding is adopted is solved; and the method has certain practicability and adaptability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electron beam welding, and particularly relates to a method and system for improving the crater depression at the end of an electron beam weld with a small diameter and thin wall. Background Art

[0002] Electron Beam Welding (EBW), as a high-energy density welding technology, has been widely used in the fields of aerospace, nuclear industry, precision machinery manufacturing, etc. since its development due to its unique process advantages. This technology bombards the surface of the workpiece with a high-speed electron beam, converts kinetic energy into heat energy, locally melts the material to form a molten pool, and finally realizes metal connection. Compared with traditional welding methods, electron beam welding has the characteristics of high energy density, narrow heat-affected zone, small welding deformation, and large depth-to-width ratio, and is particularly suitable for welding high-precision, complex geometric shapes, and refractory metals, such as thin-walled components of aeroengines, rocket fuel tanks, etc.

[0003] In the field of aviation manufacturing, an aeroengine cylinder assembly uses electron beam welding to connect an oil pipe seat assembly, a cylinder assembly, and a piston assembly. Among them, the N2 weld joint is an end face circumferential weld with a diameter of 12 mm and a thickness of 1 mm. As Figure 2 shown, it is required that the crater depth should not be greater than 0.1 mm and the length should not be greater than 15 mm. Welding tests were carried out on welding test plates according to the process parameters in Table 1. After the welds were dressed, local depressions appeared in the front crater regions. Currently, during welding, the depressions caused by the formal welding and the dressing welding in the attenuation region are superimposed on each other, increasing the crater depth on the front of the weld, which is extremely likely to exceed the standard requirements. When the weld diameter is small, during the formal welding and the dressing welding processes, if the conventional increasing attenuation of 90° is used, due to the too short attenuation length, obvious depressions can be seen on the weld surface. As Figure 3 shown, a is the front forming diagram of the weld, and b is the back forming diagram of the weld. The crater depths both exceed the standard requirements. Any minor defect may lead to component failure and even cause major safety accidents. Therefore, in summary, currently in the welding of aeroengine cylinder assemblies, the depressions caused by the formal welding and the dressing welding in the attenuation region are superimposed on each other, increasing the crater depth on the front of the weld. Combined with other process designs, it may cause the crater depth of the weld after welding to exceed the allowable range. In this way, not only will the strength of the weld be reduced, but it will also become a stress concentration point under alternating loads, shortening the service life of the workpiece. Summary of the Invention

[0004] The present invention provides a method and system for improving the crater depression at the end of a small-diameter thin-walled electron beam weld, aiming to solve the problem that in the welding of aero-engine cylinder components, the depression depth of the weld may exceed the allowable range, which not only reduces the strength of the weld but also becomes a stress concentration point under alternating loads, shortening the service life of the workpiece.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for improving the crater depression at the end of a small-diameter thin-walled electron beam weld, including the following steps: S1. In a vacuum environment, detect the focusing current on the surface of the workpiece, perform tack welding on the workpiece, and arrange a plurality of weld spots at intervals along the circumferential direction of the tack weld; S2. Perform formal welding on the workpiece after tack welding in a first welding direction; Among them, the beam current increasing and decreasing angle for formal welding is 180° - 360°; S3. Adopt a second welding direction opposite to the first welding direction to perform dressing welding on the weld after formal welding; Among them, the beam current increasing and decreasing angle for dressing welding is 180° - 360°, the dressing welding uses a defocused electron beam, and the defocus current for dressing welding is 30 - 50 mA less than the surface focusing current; S4. After the welding operation is completed, inflate the vacuum environment after a preset delay time to complete the welding operation of the workpiece.

[0006] In some embodiments, in S1, the number of weld spots for tack welding is set to four, and the four weld spots for tack welding are evenly distributed along the circumference.

[0007] In some embodiments, in S1, the vacuum degree of the vacuum environment is not higher than mbar.

[0008] In some embodiments, in S2, the accelerating voltage for formal welding and dressing welding is the same.

[0009] In some embodiments, in S2 and S3, the first welding direction is clockwise and the second welding direction is counterclockwise.

[0010] In some embodiments, in S2 and S3, the focusing current for formal welding is 2020 mA, and the focusing current for dressing welding is 1970 - 1990 mA.

[0011] In some embodiments, in S2 and S3, the welding speeds for formal welding and dressing welding are the same.

[0012] In some embodiments, in S4, the preset delay time is 3 - 5 minutes.

[0013] The present invention also provides an improvement system for the arc - ending depression of small - diameter thin - wall end - face electron beam welds. The system includes a vacuum chamber, an electron gun, a direction control module, and a beam current adjustment module. Vacuum chamber: It is used to provide a vacuum environment and control the inflation delay time. Electron gun: It is used to generate an electron beam and perform tack welding, formal welding, and finishing welding. Direction control module: During the execution of the electron gun, it is used to adjust the welding directions of the formal welding and the finishing welding so that the welding directions of the formal welding and the finishing welding are opposite. Beam current adjustment module: It is used to set the beam current increment - decay angle to 180° - 360°, control the finishing welding to use a defocused electron beam, and the defocused current of the finishing welding is reduced by 30 - 50 mA compared with the surface - focused current.

[0014] Compared with the prior art, the improvement method and system for the arc - ending depression of small - diameter thin - wall end - face electron beam welds of the present invention have the following beneficial effects: For the improvement method of the arc - ending depression of small - diameter thin - wall end - face electron beam welds of the present invention, the present invention avoids the contamination of the weld by gas impurities through the setting of the vacuum environment and tack welding. At the same time, the workpiece is fixed by evenly distributed welding points to reduce welding deformation. Compared with the previous 90°, the present invention significantly extends the energy change region through the attenuation range of 180° - 360°, making the solidification of the molten pool tail smoother and reducing the local depression caused by the sudden drop of energy. The present invention makes the molten pool of the finishing welding fill the depression area of the formal welding by reverse welding direction, and the current difference further increases the amount of molten pool metal to form a reinforcement compensation shrinkage. Reducing the focusing current of the finishing welding can expand the action area of the electron beam, avoid excessive strength of the finishing welding, and ensure a full surface forming. After welding, it also avoids the oxidation of the high - temperature weld caused by premature inflation by delaying inflation and maintains the mechanical properties of the weld. The present invention effectively improves the problem of depression in the arc - ending area of the weld, enables both the front and back of the weld to meet the standard requirements after welding, realizes the double - sided forming of the circumferential weld of the small - diameter thin - wall end - face, and the weld has a full forming. It avoids the problem of part size out - of - tolerance caused by argon arc repair welding due to the depression in the arc - ending area. The welding method of the present invention can improve the welding quality and the strength of the workpiece, and has a certain practicality. Description of the Drawings

[0015] The accompanying drawings in the specification are used to provide a further understanding of the present invention, form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0016] Figure 1 It is the improved schematic diagram of the N2 weld flat - plate test in the improvement method of the arc - ending depression of small - diameter thin - wall end - face electron beam welds of the present invention; a is the front - face forming diagram of the weld, and b is the back - face forming diagram of the weld. Figure 2 Partial enlarged schematic view of the N2 weld in the prior art of the method and system for improving the crater at the end of the electron beam weld with a small diameter and thin wall of the present invention; Figure 3 Schematic diagram before improvement of the N2 weld flat plate test in the prior art of the method and system for improving the crater at the end of the electron beam weld with a small diameter and thin wall of the present invention; a is the front forming diagram of the weld, and b is the back forming diagram of the weld. Detailed implementation manners

[0017] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0019] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0020] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be construed as indicating or implying relative importance.

[0021] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0022] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if the terms "set", "install", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0023] How to effectively improve the problem of depression in the arc extinguishing area of the weld, so that both the front and back of the weld after welding can meet the standard requirements, realizing the double-sided forming of the circumferential weld of the small-diameter thin-wall end face, and improving the quality and fullness of the weld.

[0024] Based on this, the present invention provides a method for improving the arc extinguishing depression of the electron beam weld of the small-diameter thin-wall end face, including the following steps: S1. In a vacuum environment, detect the surface focusing current of the workpiece, perform tack welding on the workpiece, and arrange a plurality of weld spots at intervals along the circumferential direction of the tack welding; S2. Perform formal welding on the workpiece after tack welding in the first welding direction; Among them, the beam current increasing and decreasing angle of the formal welding is 180°-360°; S3. Adopt a second welding direction opposite to the first welding direction to perform dressing welding on the weld after formal welding; Among them, the beam current increasing and decreasing angle of the dressing welding is 180°-360°, the dressing welding uses a defocused electron beam, and the defocus current of the dressing welding is 30-50 mA less than the surface focusing current; S4. After the welding operation is completed, inflate the vacuum environment after a preset delay time to complete the welding operation of the workpiece.

[0025] The method for improving the arc extinguishing depression of the electron beam weld of the small-diameter thin-wall end face of the present invention ensures no oxidation interference during the welding process and improves the purity of the molten pool by performing tack welding in a vacuum environment. The present invention controls the beam current increasing and decreasing angle of 180°-360°, which can extend the attenuation length and improve the depression; and offsets the depression superposition effect of the formal welding through reverse dressing welding. The present invention can prevent the weld from being oxidized due to high temperature after welding, ensure the welding quality, and improve the strength of the workpiece after welding by delaying inflation after welding. The present invention can effectively improve the problem of arc extinguishing depression, and avoid part out-of-tolerance caused by arc extinguishing depression and part size out-of-tolerance caused by argon arc welding repair welding.

[0026] In some embodiments, for the method of improving the crater at the end of the electron beam weld of a small-diameter thin-walled end face in the present invention, the number of tack welds can be selected to be four, and the four tack welds are evenly distributed along the circumference. The even distribution and positioning of the four tack welds can evenly fix the workpiece to be welded, preventing the workpiece from shifting or deforming due to forces such as thermal stress during the welding process; in actual working conditions, the number of tack welds can be adjusted as needed. By defining the number and distribution of the tack welds, the present invention simplifies the operation process and improves the process repeatability, especially suitable for mass production.

[0027] In the method of improving the crater at the end of the electron beam weld of a small-diameter thin-walled end face in the present invention, the vacuum degree of the vacuum environment is controlled not to be higher than mbar. In this way, oxidation and porosity can be inhibited. The high-vacuum environment completely removes air, avoiding the generation of pores or oxide inclusions due to gas reactions in electron beam welding; and it can stabilize the path of the electron beam. The high vacuum reduces electron scattering, ensuring that the energy of the electron beam acts precisely on the weld area and improving stability.

[0028] Furthermore, in the method of improving the crater at the end of the electron beam weld of a small-diameter thin-walled end face in the present invention, the accelerating voltages of the main weld and the finishing weld are kept the same. By unifying the accelerating voltage, the present invention avoids fluctuations in the electron beam penetration ability, ensuring consistent weld penetration depth; and simplifies parameter adjustment, only requiring the adjustment of current and focusing parameters, reducing the operation complexity. Even further, the welding speeds of the main weld and the finishing weld in the present invention are the same. At the same speed, the solidification rhythm of the molten pool is the same, avoiding uneven heat input caused by speed differences; simplifies parameter setting, reduces debugging time, and improves production efficiency.

[0029] In the method of improving the crater at the end of the electron beam weld of a small-diameter thin-walled end face in the present invention, the first welding direction is clockwise and the second welding direction is counterclockwise. Through the complementary nature of the first welding and the second welding directions, the reverse welding makes the molten pool of the finishing weld cover the crater area of the main weld, directly offsetting the crater; avoiding the overlap of the heat-affected zones, the reverse path disperses the heat input, reducing deformation or degradation of material properties caused by local overheating.

[0030] In some embodiments, in the method of improving the crater at the end of the electron beam weld of a small-diameter thin-walled end face in the present invention, the focusing current of the main weld is 2020 mA, and the focusing current of the finishing weld is 1970 mA - 1990 mA. The high focusing current of the main weld in the present invention can increase the energy density of the electron beam, ensuring the weld penetration depth and the fusion quality at the root of the weld; the low focusing current of the finishing weld can expand the beam diameter of the electron beam, reduce the energy density, and preferentially fill the surface crater rather than deepen the weld penetration.

[0031] In addition, for the method of improving the crater depression at the end of the electron beam weld with a small diameter and thin wall in the present invention, after the welding operation is completed, inflation is delayed for 3 - 5 minutes. In this way, it can be fully cooled, and the delayed inflation time allows the weld to cool naturally to a safe temperature in a vacuum environment, avoiding high-temperature oxidation; preventing thermal shock, reducing the sudden cooling effect of gas flow on the weld during inflation, and enhancing the strength of the workpiece.

[0032] The present invention also provides a system for improving the crater depression at the end of the electron beam weld with a small diameter and thin wall. The system includes a vacuum chamber, an electron gun, a direction control module, and a beam current adjustment module, where: Vacuum chamber: Used to provide a vacuum environment and control the inflation delay time; Electron gun: Used to generate an electron beam and perform tack welding, formal welding, and dressing welding; Direction control module: Used to adjust the welding direction of the formal welding and dressing welding during the execution of the electron gun, so that the welding directions of the formal welding and dressing welding are opposite; Beam current adjustment module: Used to set the beam current increasing and decreasing angle to 180° - 360°, control the dressing welding to use a defocused electron beam, and the defocus current of the dressing welding is reduced by 30 - 50 mA compared to the surface focusing current.

[0033] The system for improving the crater depression at the end of the electron beam weld with a small diameter and thin wall in the present invention systematically solves the problem of crater depression at the end of the weld with a small diameter and thin wall through multi-dimensional combination, and improves the welding quality.

[0034] Table 1 Process parameters of the N2 weld flat plate test - before improvement

[0035] The following further details the method and system for improving the crater depression at the end of the electron beam weld with a small diameter and thin wall in the present invention through specific embodiments.

[0036] The method for improving the crater depression at the end of the electron beam weld with a small diameter and thin wall in the present invention is achieved in the following way: 1) Adopt reverse dressing welding; When welding flat plates and parts, when the welding direction and beam current increasing and decreasing angle of the dressing welding are the same as those of the formal welding, the depressions caused by the formal welding and dressing welding in the attenuation area are superimposed on each other, increasing the depth of the crater on the front of the weld, which is very likely to exceed the standard requirements. When the welding direction of the dressing welding is opposite to that of the formal welding, the depression generated by the formal welding in the attenuation area cancels out the positive reinforcement generated by the dressing welding in the increasing area, significantly reducing the depth of the crater on the surface of the weld.

[0037] 2) Extend the beam current increasing and decreasing length; When the weld diameter is small, if the conventional 90° incremental attenuation is used for the formal welding and finishing welding, due to the too short attenuation length, obvious depressions can be seen on the weld surface. When the incremental attenuation angle increases to 180° - 360°, the depression can be effectively improved.

[0038] 3) Reduce the welding current of the formal welding; On the premise of meeting the process requirements, after extending the beam current incremental attenuation length, appropriately reduce the formal welding beam current by (0.5 - 1) mA, which can reduce the metal overflow on the back of the weld and lower the surface depression depth. Then, appropriately increase the finishing welding current by (0.5 - 1) mA, which can effectively improve the surface depression defect of the weld.

[0039] As Figure 1 shown, by adopting the above three methods, the process test is carried out according to Table 2 below. As Figure 1 shown in Figure 1 a and Figure 1 b, the surface depression defect of the weld disappears.

[0040] Table 2 Process parameters of the second test of the N2 weld flat plate - after improvement

[0041] As a specific embodiment, the method for improving the arc - extinguishing depression of the small - diameter thin - wall end - face electron beam weld of the present invention is as follows: (1) Clamp the part or test piece in the vacuum chamber, and the area to be welded is within the working distance of the electron gun.

[0042] (2) Evacuate the vacuum chamber.

[0043] (3) Wait until the vacuum degree reaches mbar, and use the observation system to find the area to be welded.

[0044] (4) Perform tack welding on the welding joint to be welded in the clockwise direction, and evenly distribute 4 tack - welding points.

[0045] (5) Perform seal welding and formal welding on the welding joint to be welded in the clockwise direction, with a beam current incremental attenuation of 180°. The main process parameters are as follows: Seal welding: acceleration voltage 150 kV, welding current 1.5 mA, focusing current 2020 mA, welding speed 20 mm / s; Formal welding: acceleration voltage 150 kV, welding current 2.3 mA, focusing current 2020 mA, welding speed 20 mm / s; (6) Perform finishing welding on the welding joint to be welded in the counter - clockwise direction, with the beam current incremental attenuation angle of 180°. Among them, the acceleration voltage is 150 kV, the welding current is 2.5 mA, the focusing current is 1980 mA, and the welding speed is 20 mm / s.

[0046] After the welding is completed, wait for 4 minutes before filling the vacuum chamber with gas to prevent the parts from oxidation.

[0047] In summary, for the method and system for improving the crater depression at the end of electron beam welds with small diameter and thin wall, through process optimization, the problem of crater depression at the end of electron beam welds with small diameter and thin wall is effectively solved. By the complementary directions of the reverse finishing weld and the formal weld, the superposition effect of the molten pool shrinkage is offset; combined with the increase of the beam current increasing and decreasing angle to 180° - 360°, the depth of the crater depression is significantly reduced. The finishing weld current of the present invention is higher than that of the formal weld to supplement the molten pool metal to fill the shrinkage gap; the focusing current is differentiated to ensure the fullness of the weld surface and achieve double-sided forming. The present invention suppresses oxidation and porosity in a vacuum environment, and delays gas filling to avoid high-temperature oxidation, ensuring the quality of the welded workpiece. The present invention can adopt an automated process to reduce human error; avoid part out-of-tolerance caused by crater depression and part size out-of-tolerance caused by argon arc repair welding. The quality of the weld formation and process control are excellent, and the cost control is good. It is applicable to the manufacturing scenarios of some parts of aero-engines and has certain industrial application value.

[0048] Finally, it should be noted that the above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention; any person skilled in the art can smoothly implement the present invention according to the instructions and the above description. Any equivalent changes made by slightly modifying and evolving using the technical content disclosed above are equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving arc concavity of electron beam weld of small diameter thin wall end face, characterized in that: The steps include: S1. In a vacuum environment, detect the surface focusing current of the workpiece, perform tack welding on the workpiece, and arrange a number of welding points at intervals along the circumferential direction of the tack welding; S2, performing formal welding on the workpiece after positioning welding in the first welding direction; Among them, the beam increasing and attenuation angle of formal welding is 180°-360°; S3, using a second welding direction opposite to the first welding direction to perform touch-up welding on the weld after formal welding; Among them, the beam increasing and attenuation angle of the modification welding is 180°-360°, and the modification welding adopts a defocused electron beam. The defocused current of the modification welding is 30-50mA less than the surface focusing current; S4. After the welding operation is completed, the vacuum environment is inflated after a preset time to complete the welding operation of the workpiece.

2. The method for improving arc-closing depression of electron beam weld of small diameter thin wall end face according to claim 1, characterized in that: In S1, the number of the tack welding spots is set to four, and the four tack welding spots are evenly distributed along the circumference.

3. The method for improving arc-closing depression of electron beam weld of small diameter thin wall end face according to claim 1, characterized in that: In S1, the vacuum degree of the vacuum environment is not higher than mbar.

4. The method for improving arc-closing depression of electron beam weld of small diameter thin wall end face according to claim 1, characterized in that: In S2, the acceleration voltage of the main welding and the touch-up welding is the same.

5. The method for improving arc-end depression of electron beam weld of small diameter thin wall end face according to claim 1, characterized in that: In S2 and S3, the first welding direction is a clockwise direction, and the second welding direction is a counterclockwise direction.

6. The method for improving arc-closing depression of electron beam weld of small diameter thin wall end face according to claim 1, characterized in that: In S2 and S3, the focusing current of the formal welding is 2020mA, and the focusing current of the modification welding is 1970mA-1990mA.

7. The method for improving arc-closing depression of electron beam weld of small diameter thin wall end surface according to claim 1, characterized in that: In S2 and S3, the welding speeds of the main welding and the touch-up welding are the same.

8. The method for improving arc-end depression of electron beam weld of small diameter thin wall end face according to claim 1, characterized in that: In the step S4, the preset delay time is 3 minutes to 5 minutes.

9. A system based on the method for improving arc-end depression of small-diameter thin-wall end electron beam weld as claimed in any one of claims 1 to 8, characterized in that: The system comprises a vacuum chamber, an electron gun, a direction control module and a beam adjustment module, wherein: Vacuum chamber: used to provide a vacuum environment and control the inflation delay time; Electron gun: used to generate electron beam and perform positioning welding, formal welding and touch-up welding; Direction control module: used to adjust the welding direction of the main welding and the decoration welding during the execution of the electron gun, so that the welding directions of the main welding and the decoration welding are opposite; Beam adjustment module: used to set the beam increasing and attenuation angle to 180°-360°, control the use of defocused electron beam for modification welding, and the defocused current of modification welding is 30-50mA less than the surface focusing current.

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