Thin-wall rotary component electron beam wire adding welding method based on high self-sustaining plasma

Abstract

The invention discloses a thin-wall rotary component electron beam wire adding welding method based on high self-sustaining plasma, and belongs to the technical field of welding. The realization process is realized by regulating and controlling the stability of the plasma and the flow characteristic of a molten pool, a metal wire is arranged at the front edge of a beam spot focus of an electron beam, beam spot power distribution is regulated and controlled to control the plasma to be stabilized in the molten pool, a high-speed camera is used for identifying the melting condition of a wire, the wire feeding rate is controlled in a closed-loop mode, and the long-time self-sustaining property of the plasma is maintained. And meanwhile, the molten wire flows to the bottom of the welding seam in the molten pool based on the Malangei effect of the molten pool, and the hole pattern defect is taken away from the solidification front edge. After the high self-sustaining plasma is used, the flowing stability of a high-temperature melt of a welding seam can be improved, the defects of internal air holes, surface undercut and fluctuation caused by abnormal plasma expansion are reduced, and the quality of the welding seam is improved. The method has the advantages of being high in single-time welding yield, good in forming quality, excellent in long-time welding stability, wide in adaptive working condition and the like, and can be widely applied to welding forming of planes, curved surfaces and dissimilar materials.

Description

Technical Field

[0001] The present invention relates to an electron beam wire - feeding welding method for thin - walled rotary components based on high - self - sustaining plasma, belonging to the field of welding technology. Background Art

[0002] Electron beam welding is an efficient welding method that uses a high - energy - density electron beam as a heat source and plays an important role in the welding and forming of metal plates. It has been successfully applied to the precision welding and forming of components in fields such as aerospace, marine vessels, and rail transit. During the electron beam welding process, when the power of the high - energy electron beam is relatively high, the surface of the base material is easily melted, vaporized, or even violently sputtered under the action of the electron beam. The generated vapor recoil pressure rapidly throws the molten material in the molten pool around, resulting in the formation of a keyhole with a concave molten pool. Further, the electron beam acts on the bottom of the keyhole, intensifying the vaporization of the molten metal, and the high - pressure steam erupts upward to deepen the keyhole. When the keyhole is formed and deepened, it will cause changes in the flow of the molten pool, and then induce the formation of unstable plasma within a certain range near the keyhole and at the top of the weld. When electron beam welding operates in the deep - penetration welding mode, the unstable plasma has an adverse effect on the weld quality. In addition, the stability of the molten pool at the bottom of the weld often deteriorates due to plasma agitation, causing the welding mode to change to an unstable welding mode, resulting in defects such as undercut and depression on the surface of the opposite - side weld. For electron beam welding of conventional flat mating surfaces or outer curved surfaces, defects such as undercut on the weld surface can be flattened by secondary machining. However, when welding and connecting thin - walled rotary narrow spaces or closed cavities, the internal weld side often becomes an inaccessible area after welding and cannot be processed again, leading to deterioration of the weld surface flatness. Based on this, there is an urgent need to develop a new electron beam welding method for closed cavities with high surface flatness and internal quality.

[0003] At present, internal keyholes, surface undercut, and depression defects in high - energy electron beam welding are caused by plasma induced by uneven distribution of the input energy of the high - energy beam during the electron beam welding process. The agitation of unstable plasma deteriorates the stability of the molten pool, and the change in local molten pool flow causes the corresponding position of the material to be unable to be replenished in time. Conventional optimization methods for undercut and defects mainly involve adjusting process parameters such as the power and welding speed of the welding electron beam, and cooperating with adjusting the mating distance of the plates and taking post - treatment such as grinding and polishing. The specific control methods mainly rely on the actual experience of the operator. Combining the thickness of the base material, material properties, and weld shape, appropriately reducing the electron beam power and adjusting the welding speed can slow down the solidification rate of the molten pool during electron beam welding forming, thereby improving the stability of plasma and molten pool flow, and can reduce weld surface and internal defects to a certain extent. Adjusting the welding surface spacing, that is, appropriately reducing the weld gap, aims to distribute more electron beam energy for melting the base material, thereby reducing the excessive heat flux density at the center of the beam spot to control the plasma, and can partially improve the weld forming quality.

[0004] However, the adjustment of existing electron beam welding process parameters mostly relies on pre-experiment trial and error or the experience of operators. Often, a large number of experiments need to be carried out around multiple process parameters to explore the welding process window. It has not started from the formation mechanism of internal keyholes and surface undercuts and depressions, resulting in the parameter combinations for specific weld structures being inapplicable to other welding scenarios. In addition, in industrial applications, the welding of long and narrow welds on closed surfaces is often encountered. During the long welding process, the electron beam welding mode changes due to the change in the stability of the molten pool. Relying solely on optimizing welding parameters cannot guarantee the long-term welding stability and weld quality. Moreover, after the electron beam welding of rotating bodies and closed surfaces is formed, the weld surface located in the narrow inner cavity becomes a difficult-to-reach part, and the surface quality cannot be further improved by subsequent grinding and polishing. Therefore, the existing methods cannot fundamentally eliminate the undercut and depression problems caused by the deterioration of the plasma-induced molten pool stability during the electron beam welding process. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides an electron beam wire-feeding welding method for thin-walled rotating components based on highly self-sustaining plasma. For the electron beam wire-feeding welding of thin-walled rotating body components and closed surfaces, metal wire is conveyed to the focus of the high-energy beam convergence point to consume the electron beam energy and regulate the power distribution, thereby alleviating the excessive electron beam power and improving the stability of the high-temperature plasma. Relying on the plasma with highly self-sustaining characteristics to promote the gentle flow of the molten pool, regulating the distribution of the high-temperature melt to eliminate internal weld defects and optimize weld undercuts and defects, improving the quality of the first-time welding forming of closed surfaces, reducing the secondary grinding and polishing processes after welding, and is particularly suitable for the welding forming of closed surface cavity structures. A high-speed camera is used to identify the melting and solidification situation of the wire in real time, and the wire-feeding rate is closed-loop controlled to maintain the long-term self-sustainability of the steady-state plasma.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An electron beam wire-feeding welding method for thin-walled rotating components based on highly self-sustaining plasma realizes the elimination of internal weld defects and surface flattening by regulating the high-temperature plasma and the flow stability of the molten pool. The improvement of the molten pool stability is achieved by externally adding metal wire to regulate the distribution of the central power of the electron beam spot, so as to continuously control the stability of the high-temperature plasma. The means of optimizing the undercut and depression of the weld in the welding forming of the plate is to regulate the distribution of the molten metal in the molten pool. The specific welding method is: adding wire to melt and supplement the molten pool - stabilizing the central power of the electron beam to control the plasma - improving the flow stability of the molten pool - monitoring the high-speed camera and closing the loop to control the wire-feeding rate - ensuring the weld forming, including the following steps:

[0008] Step 1: Select the metal wire used for electron beam wire-feeding welding according to the type of the component to be welded.

[0009] Step 2: Use a tooling fixture to fix the spatial position and alignment gap of the rotating component, ensuring that the gap is slightly larger than the beam diameter of the electron beam. Place the center of the weld seam at the focal position where the electron beam spot converges. Fix the metal wire in front of the moving path of the electron beam in the forward wire feeding mode, and set the position of the wire feeding end at a certain point above the electron beam focus according to the thickness of the sheet.

[0010] Step 3: Start electron beam welding. The electron beam moves along the weld seam according to the preset program. The wire is fed into the molten pool at a fixed speed to regulate the power distribution of the electron beam spot center. The excessive electron beam power in the central area of the beam spot is used to melt the metal wire, relieve the plasma splash caused by the high electron beam power, and thus control the high-temperature plasma. The molten metal wire fills the molten pool to timely supplement the evaporation and boiling loss of the weld metal. At the same time, when the electron beam moves along the preset trajectory, the molten metal liquid supplemented by the melting of the wire moves to the bottom and rear side of the weld seam under the drive of the Marangoni effect in the molten pool and gradually solidifies. While completing the formation of the weld on the opposite side by the electron beam, the pores and keyholes at the bottom of the weld seam are carried away from the solidification front to reduce defects.

[0011] Step 4: During electron beam wire feeding welding, use a high-speed camera equipped with a filter to monitor and analyze the molten pool in real time, identify the droplet transfer situation of the metal wire near the focus of the high-energy beam, and perform a criterion for the stability of the molten pool flow based on the droplet transfer stability and transfer rate. According to the wire melting rate, the wire feeding rate of the wire feeder is closed-loop controlled to regulate the long-term stability of electron beam welding.

[0012] Step 5: After completing the electron beam welding of the weld seam, moderately mechanically polish the initial welding start position.

[0013] Further, the types of base materials to be welded can be titanium plates, aluminum plates, stainless steel plates, and copper plates.

[0014] Further, when the beam diameter of the electron beam is D, the alignment gap D1 of the sheet to be welded should be between D and 1.5D. The metal wire and the sheet to be welded are of the same material, and the wire diameter is between 0.4D and 0.6D.

[0015] Further, the position of the wire feeding end of the metal wire should be above the electron beam focus. In the forward wire feeding mode, the end of the wire is at the front of the electron beam path and the distance from the focus is 5% - 10% of the electron beam convergence focal length, so as to promote the heating and melting of the metal wire by the central energy of the electron beam before the focus converges.

[0016] Furthermore, the distribution of the central power of the electron beam is adjusted by melting the metal wire. Besides energy dissipation such as conduction and radiation, the central power of the electron beam is mainly used to melt the base material and the metal wire. When the central power of the beam spot is too high, it will cause the instability of the plasma inside the molten pool, which will in turn induce droplet splashing and deteriorate the flow and forming quality of the molten pool. The adjustment of the central power of the beam spot is controlled by changing the wire feeding speed. After determining the initial wire feeding speed according to the plate thickness, electron beam power and moving speed, observe the stability of the molten pool during the initial welding stage. If splashing occurs, appropriately increase the wire feeding speed to consume the electron beam power; if the forming surface of the molten pool bulges slightly, appropriately reduce the wire feeding speed.

[0017] Furthermore, the regulation of the plasma stability is achieved by adjusting the distribution of the central power of the electron beam. Plasma stability is the key to determining the front and back stability of the weld quality during the single-pass welding process of the rotating component. Based on the wire feeding method above the focal position, the high-energy electron beam power is consumed in advance before reaching the convergence point, avoiding the non-steady-state plasma caused by too high heat flux density, and then promoting the stability of the plasma in the molten pool to be well maintained during the whole welding process.

[0018] Furthermore, the optimization of the forming defects such as undercut and depression on the surface of the weld on the opposite side of the electron beam is achieved by regulating the flow of the molten pool inside the molten pool and the distribution of the molten metal at the bottom of the weld based on the Marangoni effect. By using a wire feeding speed that matches the electron beam power and moving speed, consume the excessive power at the center of the electron beam, and then control the smooth flow of the molten pool. At the same time, the smooth melt flow timely takes the keyhole defect at the solidification front on the surface of the weld on the opposite side away, preventing the latter from being captured by the solidification front to form pore or depression defects.

[0019] Furthermore, the electron beam wire addition welding technology is equipped with a high-speed camera and a wire feeding closed-loop control system. The high-speed camera is fixed above the side of the area to be welded in a paraxial manner, and a filter is configured in front of the camera lens. During electron beam welding, the high-speed camera monitors the droplet transfer situation at the end of the molten wire in real time. When the droplets are almost continuously transferred, the edges of individual droplets are clear and connected to each other, it is considered that the wire feeding rate meets the requirements of self-sustaining plasma at this time; when the droplets are connected in a line and their edges are fused with each other, it is determined that the wire feeding rate is too high, and the system closes the loop to control the wire feeder to reduce the feeding rate; when the droplet transfer is discontinuous, it is determined that the wire feeding rate is too low, and the system closes the loop to control the wire feeding rate to increase. Relying on the closed-loop control system with the high-speed camera as the main body, the wire feeding rate of the metal wire is controlled in real time to ensure the stability of the long weld welding process.

[0020] Furthermore, the electron beam wire - feeding welding technology of the rotary member is suitable for welding and forming between heterogeneous plates, such as titanium alloy - aluminum alloy, titanium alloy - stainless steel, etc. At this time, in addition to ensuring the quality of the weld formation, the added metal wire can also inhibit the formation of brittle intermetallic compounds at the interface to ensure the mechanical properties of the interface.

[0021] Furthermore, for the electron beam wire - feeding welding technology of the rotary member, only the initial welding area needs to be ground and polished after welding, and it can be extended to the welding and forming of planar welds and complex curved surfaces. After adjusting the electron beam power, it can be further applied to the welding and forming of thick plates.

[0022] Furthermore, the technical solution of the present invention regarding the regulation of plasma stability and self - sustainability by wire - feeding has the advantage of universality and can be extended to arc welding, laser welding, etc. The heat - flow distribution characteristics of the latter two heat sources are similar to those of the electron beam. The series of methods for wire - feeding welding involved in the present invention, including wire - melting to supplement the molten pool - stabilizing the high - energy beam power to control the plasma - improving the stability of molten pool flow - monitoring the closed - loop control of the wire - feeding rate by a high - speed camera - ensuring the weld formation, are equally applicable.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention has the advantages of high single - pass welding yield, good forming quality, excellent long - time welding stability, and wide adaptability to working conditions, and can be widely used for the welding and forming of planes, curved surfaces, and between dissimilar materials. Specifically as follows:

[0025] 1) High single - pass welding yield, improving the yield of primary weld formation. Using the electron beam wire - feeding welding method involved in the present invention can simultaneously improve the internal and surface quality, and based on the closed - loop control of a high - speed camera, it reduces manual intervention during the forming process and improves the welding forming quality and consistency.

[0026] 2) Good forming quality, reducing the surface grinding and polishing process of the weld. Using the electron beam wire - feeding welding method involved in the present invention can avoid defects such as weld bead undercut and depression on the weld surface, and there is no need for secondary surface grinding and polishing, especially suitable for rotating bodies and closed curved surfaces with narrow internal spaces.

[0027] 3) Excellent long - time welding stability. Based on the wire - feeding welding method of regulating plasma stability and molten pool flow stability, combined with the closed - loop control of the melting rate of the wire material, it can continuously ensure the forming quality during the full - cycle forming process of long welds.

[0028] 4) Wide adaptability to working conditions. The electron beam wire - feeding welding technology involved in the present invention is suitable for both open scenarios such as planar and curved - surface welds, and for the welding and forming of closed cavities. At the same time, it can also be applied to the high - quality welding and forming between dissimilar material plates. Description of the Drawings

[0029] Figure 1 This invention relates to the implementation flow chart of electron beam wire - feeding welding technology;

[0030] Figure 2 It is a schematic diagram of the weld pool cross - section based on wire - feeding regulation of plasma stability and forming quality;

[0031] Figure 3 It is a schematic diagram of a rotary component formed based on this technology;

[0032] Figure 4 It is a schematic diagram of the molten pool flow in the weld cross - section without wire - feeding regulation.

[0033] In the figure: 1 wire material, 2 disk - type wire feeder, 3 high - energy electron beam, 4 end of the electron beam generating device, 5 weld, 6 high - speed camera, 7 filter, 8 Ti6Al4V wire material, 9 high - temperature plasma, 10 Marangoni effect, 11 pore - type defects such as pores and keyholes, 12 straight weld of the cylinder section, 13 sputtering particles, 14 non - steady plasma, 15 undercut and depression defects. Detailed implementation manners

[0034] The following further illustrates the present invention in combination with specific implementation cases.

[0035] Example 1

[0036] Figure 1 This invention relates to the implementation flow chart of electron beam wire - feeding welding technology, Figure 2 It is a schematic diagram of the weld pool cross - section based on wire - feeding regulation of plasma stability and forming quality, Figure 3 It is a structural diagram of a rotary component formed based on this technology, Figure 4 It is a schematic diagram of the molten pool flow in the weld cross - section without wire - feeding regulation.

[0037] This invention is based on high - self - sustaining plasma for high - quality electron beam wire - feeding welding forming of thin - walled rotary components, aiming to solve the problems of poor surface quality of the weld in the narrow and closed inner cavity after welding of rotary components and the inability to process them. The elimination of internal defects and surface flattening of the weld are achieved by regulating the high - temperature plasma and the stability of the molten pool flow. The improvement of the molten pool stability is realized by adding a wire material to regulate the distribution of the beam spot center power of the electron beam to continuously control the stability of the high - temperature plasma. The means to optimize the undercut and depression of the weld in plate welding forming is to regulate the distribution of molten metal in the molten pool, mainly including the following steps: adding wire to melt and supplement the molten pool - stabilizing the electron beam center power to control the plasma - improving the stability of the molten pool flow - monitoring the closed - loop control of the wire - feeding rate by a high - speed camera - ensuring the weld forming.

[0038] Adding wire to melt and supplement the molten pool, such as Figure 1As shown in Fig. a, select the wire material for electron beam wire feeding welding according to the type of the component to be welded. The way to select the wire material is as follows: referring to the spot diameter (D) of the electron beam, the butting gap D1 of the plates to be welded should be between D and 1.5D. The wire material and the plates to be welded are made of the same material, and the wire diameter is between 0.4D and 0.6D. The wire material (1) is sent out by a disc type wire feeder (2) Figure 1 a), and the feeding position of the wire end is set above the focusing point of the electron beam convergence. In the forward wire feeding mode, the wire end is at the front edge of the electron beam path and the distance from the focus is 5% - 10% of the electron beam convergence focal length, so as to make the central energy of the electron beam complete the heating and melting of the wire material before converging at the focus.

[0039] Stabilize the plasma by controlling the central power of the electron beam. Turn on the electron beam welding. As Figure 1 shown in Fig. a and Fig. 1b, the high-energy electron beam (3) is sent out from the end (4) of the generating device and moves along the weld seam (5) according to a preset program. The wire is fed into the molten pool at a fixed speed to regulate the power distribution of the spot center of the electron beam. The excessive electron beam power in the central area of the spot is used to melt the wire material, so that the high-energy electron beam power is consumed in advance before reaching the convergence point, avoiding the non-steady-state plasma caused by the excessive heat flux density, and then improving the stability of the plasma in the molten pool. At the same time, the molten wire material continuously fills the molten pool to timely supplement the evaporation and boiling loss of the weld metal. When the electron beam moves along the preset trajectory, the molten metal liquid supplemented by the melting of the wire moves to the bottom and rear side of the weld under the drive of the Marangoni effect in the molten pool and gradually solidifies. While completing the formation of the weld on the opposite side of the electron beam, the pores and keyholes at the bottom of the weld are carried away from the solidification front to reduce defects.

[0040] Improve the stability of the molten pool flow and the internal and surface forming quality. After the electron beam wire melting promotes a highly self-sustaining plasma, regulate the flow of the molten pool inside the molten pool and the distribution of the molten metal at the bottom of the weld based on the Marangoni effect. By using a wire feeding speed that matches the electron beam power and moving speed, consume the excessive power in the center of the electron beam, and then control the smooth flow of the molten pool. At the same time, the smooth melt flow timely carries away the keyhole defects at the solidification front on the surface of the weld on the opposite side, preventing the latter from being captured by the solidification front to form pore or depression defects.

[0041] The wire feeding rate is monitored by a high-speed camera in a closed-loop control. The high-speed camera (6) is fixed above the side of the area to be welded in a paraxial manner. The camera frame rate is not less than 5000 fps. A filter (7) is configured in front of the camera lens and can be selected according to the arc radiation intensity. During electron beam welding, the high-speed camera monitors the droplet transfer situation at the end of the molten wire in real time. When the droplets are nearly continuously transferred, the edges of individual droplets are clear and connected to each other, the control system believes that the wire feeding rate at this time meets the requirements for maintaining a steady state and self-sustaining plasma. When the droplets are connected into a line and their edges are fused with each other, the system determines that the wire feeding rate is too high at this time, and the wire feeding mechanism is controlled in a closed loop to reduce the feeding rate. When it is recognized that the droplet transfer is discontinuous, the system determines that the wire feeding rate is too low, and the system controls the wire feeding rate to increase in a closed loop. Relying on the closed-loop control system with the high-speed camera as the main body, the feeding rate of the metal wire is controlled in real time to ensure the stability of the full-cycle welding process of the long weld.

[0042] After the rotary component is welded and formed based on the above series of steps, as Figure 1 shown in c, only the starting and stopping welding parts need to be appropriately mechanically ground and polished to obtain a weld with high flatness.

[0043] In this embodiment, electron beam welding is performed on two semi-cylindrical components. The two welds are symmetrically distributed on both sides of the circumference. The inner cavity radius of the cylindrical structure formed after welding is 45 mm, and the length is 1200 mm. The cylindrical component is made of forged Ti6Al4V with a uniform thickness (6 mm). Correspondingly, Ti6Al4V metal wire is used as the externally fed metal wire with a diameter of 2.4 mm. The beam diameter of the electron beam of the electron beam welding equipment is 4.5 mm, and the focal length is 40 mm. Before welding, a special positioning fixture is used to pre-align the welding surfaces of the TA15 semi-cylindrical components. The alignment gap is 5.8 mm. The distance between the electron beam head and the weld is adjusted so that the center of the weld corresponds to the positive focal position of the electron beam. The position of the feeding end of the Ti6Al4V wire is set 2.2 - 2.6 mm above the focal position. After setting the electron beam power to 2000 W, the welding speed to 0.02 m / s, and the wire feeding speed to 0.015 m / s, the electron beam welding process is started.

[0044] The weld pool cross-section based on wire addition to regulate plasma stability and forming quality is as Figure 2As shown in Figure a, during the movement of the electron beam head along the weld seam, the Ti6Al4V wire (8) is fed into the weld pool in a forward wire feeding manner. Continuously regulate the power distribution in the central region of the electron beam to ensure the stability of the high-temperature plasma (9), and drive the pore-shaped defects such as pores and keyholes inside the weld pool to move backward and upward and to the surface of the weld pool through the Marangoni effect (10) inside the weld pool, so as to make the pore-shaped defects away from the solidification front at the rear of the weld pool, eliminate the internal defects of the weld seam, and improve the internal quality. At the same time when the electron beam welding starts, start the high-speed filter monitoring and closed-loop control system. The frame rate of the high-speed camera is 6000 fps, and a 3-level neutral density filter is used to filter out the excessive arc light radiation. Under the filtered view, the molten droplets at the end of Ti6Al4V stably and continuously transition into the weld pool. When the welding stability changes due to heat accumulation in the second half of the welding process, the monitoring system makes a decision based on the change in droplet transfer and reduces the feeding rate of the Ti6Al4V wire. As Figure 2 shown in Figure b, synchronously and correspondingly reduce the electron beam power.

[0045] After completing the butt welding of the Ti6Al4V cylindrical component, as Figure 3 shown, the flatness of the surface of the straight weld (12) of the cylinder section is relatively good, and only the initial starting and stopping positions need to be moderately ground and polished.

[0046] Comparative Example 1

[0047] In this comparative example, the structural characteristics of the welded parts and the parameters such as the electron beam power and scanning speed selected are the same as those in the embodiment. The difference is that in this example, no additional Ti6Al4V wire is used to regulate the electron beam power, plasma and weld pool stability. The specific implementation process is as follows:

[0048] Select two Ti6Al4V semi-cylindrical plates as the welding objects. The thickness of the plates is 6 mm, and the length of the two weld seams is 1200 mm. The spot diameter of the electron beam of the electron beam welding equipment is 4.5 mm, and the focal length is 40 mm.

[0049] Before welding, use a special positioning tooling fixture to align the Ti6Al4V plates with the welding surfaces facing each other. The alignment gap is 5.8 mm, and adjust the distance between the electron beam head and the weld seam so that the center of the weld seam corresponds to the positive focus position of the electron beam. After setting the electron beam power to 2000 W and the welding speed to 0.02 m / s, start the electron beam welding process. During the movement of the electron beam along the weld seam, no additional measures are taken to ensure the weld formation.

[0050] The partial cross-section of the weld pool is as Figure 4As shown in Fig. a, the center power of the electron beam is not regulated by using wire materials and high-speed cameras. The light intensity of the electron beam shows a Gaussian distribution. The extremely high power at the center of the beam spot makes the temperature of the molten metal inside the molten pool rise sharply. The high-temperature molten melt on the surface of the molten pool boils and splashes violently, forming sputtering particles (13). At the same time, an unsteady plasma (14) is formed inside the weld molten pool. After the plasma is formed, its volume expands, inducing the splashing of metal droplets. More seriously, the high-temperature plasma violently stirs the molten pool, destroying the flow stability of the molten pool, and causing some keyhole defects to be captured by the solidification front to form undercut and depression defects (15). After the overall welding is formed, the surface of the weld on the inner wall of the cylindrical structure is uneven and cannot be surface-treated by subsequent grinding and polishing.

[0051] In summary, the plasma is a high-temperature ionized aggregate formed in the center of the molten pool under the concentrated heating action of a high-energy electron beam. Its high self-sustaining characteristic is achieved by regulating the power distribution of the beam spot center of the electron beam. After using the high self-sustaining plasma of the present invention, the flow stability of the high-temperature molten melt in the weld can be improved, the internal pores and surface undercut and undulation defects caused by the abnormal plasma expansion can be reduced, and the weld quality can be improved. The specific implementation process is achieved by regulating the plasma stability and the flow characteristics of the molten pool. A wire is placed at the front of the beam spot focus of the electron beam, and the beam spot power distribution is regulated to control the plasma to be stable inside the molten pool, avoiding the splashing of the molten pool. A high-speed camera is used to identify the melting and solidification condition of the wire to close-loop control the wire feeding rate to maintain the long-term self-sustaining property of the plasma. At the same time, the wire melts and flows to the bottom of the weld in the molten pool based on the Marangoni effect of the molten pool, taking the hole-type defects away from the solidification front to eliminate the surface defects on the opposite side of the weld. Thus, the secondary surface grinding and polishing process after electron welding can be reduced, which is especially suitable for the welding formation of thin-walled rotating narrow spaces or closed cavities.

[0052] The above embodiments only represent the implementation modes of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. An electron beam wire-feeding welding method for thin-walled rotary components based on a highly self-sustaining plasma, characterized in that The specific welding method is wire - feeding melting to supplement the molten pool - stabilizing the central power of the electron beam to control the plasma - improving the flow stability of the molten pool - monitoring the wire - feeding rate in a closed - loop manner with a high - speed camera - ensuring the weld formation, and includes the following steps: Step 1: Select the wire material used for electron beam wire - feeding welding according to the type of the component to be welded; Step 2: Fix the spatial position and alignment gap of the rotating component, ensuring that the gap is larger than the spot diameter of the electron beam; make the weld center at the converging and in - focus position of the electron beam spot; fix the wire material in front of the moving path of the electron beam in the forward wire - feeding mode; Step 3: Start the electron beam welding. The electron beam moves along the weld according to a preset program. The wire material is fed into the molten pool at a fixed speed to regulate the power distribution of the electron beam spot center. The excessive electron beam power in the central area of the spot is used to melt the wire material, relieve the plasma splash caused by the high electron beam power, and then control the high - temperature plasma. The molten wire material fills the molten pool to timely supplement the evaporation and boiling loss of the weld metal. At the same time, when the electron beam moves along the preset trajectory, the metal liquid supplemented by the melting of the wire moves to the bottom and rear side of the weld and gradually solidifies. While completing the formation of the weld on the opposite side by the electron beam, the pores and keyholes at the bottom of the weld are carried away from the solidification front; Step 4: During the electron beam wire - feeding welding, use a high - speed camera to monitor and analyze the molten pool in real - time, identify the droplet transfer situation of the wire material near the focus of the high - energy beam, and establish a criterion for the flow stability of the molten pool based on the droplet transfer stability and transfer rate; close - loop control the wire - feeding rate of the wire - feeder according to the wire - melting rate to regulate the long - term stability of the electron beam welding; Step 5: After completing the electron beam welding of the weld, moderately mechanically polish the initial welding position.

2. The electron beam wire feeding welding method for thin-walled rotating components based on high self-sustaining plasma according to claim 1, characterized in that, In Step 1, the type of the component to be welded can be titanium plate, aluminum plate, stainless - steel plate or copper plate.

3. A wire-feeding electron beam welding method for thin-walled rotating components based on a highly self-sustaining plasma according to claim 1, characterized in that, In Step 2, when the spot diameter of the electron beam is D, the alignment gap D1 of the plates to be welded should be between D and 1.5D; the wire material and the component to be welded are of the same material, and the wire diameter is between 0.4D and 0.6D.

4. A wire-feeding electron beam welding method for thin-walled rotary components based on a highly self-sustaining plasma according to claim 1, characterized in that, In Step 2, the position of the feeding end of the wire material is set above the electron beam focus according to the plate thickness. In the forward wire - feeding mode, the end of the wire material is at the front of the electron beam path and the distance from the focus is 5% - 10% of the electron beam convergence focal length, so as to promote the heating and melting of the wire material by the central energy of the electron beam before the focus converges.

5. A wire-feeding electron beam welding method for thin-walled rotary components based on a highly self-sustaining plasma according to claim 1, characterized in that, In Step 3, the power distribution of the electron beam spot center is adjusted by melting the wire material. Specifically: the adjustment of the spot center power is controlled by changing the wire - feeding speed. After determining the initial wire - feeding speed according to the plate thickness, electron beam power and moving speed, observe the stability of the molten pool in the initial welding stage. If splashing occurs, increase the wire - feeding speed to consume the electron beam power; if the forming surface of the molten pool bulges slightly, reduce the wire - feeding speed.

6. A wire-feeding electron beam welding method for thin-walled rotary components based on a highly self-sustaining plasma according to claim 1, characterized in that, In Step 3, the regulation of the plasma stability is achieved by adjusting the power distribution of the electron beam center.

7. A wire-feeding electron beam welding method for thin-walled rotary components based on high self-sustaining plasma according to claim 1, characterized in that In the third step, the optimization of the undercut, depression or other forming defects on the surface of the opposite-side weld by the electron beam is achieved by regulating the molten pool flow inside the molten pool and the distribution of the molten metal at the bottom of the weld through the Marangoni effect; by using a wire feeding speed that matches the electron beam power and moving speed, the excessive power at the center of the electron beam is consumed, thereby controlling the gentle flow of the molten pool; at the same time, the smooth melt flow timely takes the keyhole defect at the solidification front on the surface of the opposite-side weld away, preventing the latter from being captured by the solidification front to form pore or depression defects.

8. A wire-fed electron beam welding method for thin-walled rotary components based on a highly self-sustaining plasma according to claim 1, characterized in that, In the fourth step, a high-speed camera and a wire feeding closed-loop control system are equipped; the high-speed camera is fixed above the side of the area to be welded in a paraxial manner, and a filter is configured in front of the lens of the high-speed camera; during electron beam welding, the high-speed camera monitors the droplet transfer situation at the end of the welding wire in real time. When the droplets are transferred almost continuously, the edges of individual droplets are clear and connected to each other, it is considered that the wire feeding rate meets the requirements of the self-sustaining plasma at this time; when the droplets are connected in a line and their edges are fused with each other, it is determined that the wire feeding rate is too high, and the system closes the loop to control the wire feeder to reduce the feeding rate; when the droplet transfer is discontinuous, it is determined that the wire feeding rate is too low, and the system closes the loop to control the wire feeding rate to increase; relying on the closed-loop control system with the high-speed camera as the main body, the feeding rate of the metal wire is controlled in real time to ensure the stability of the long weld welding process.

9. A wire-fed electron beam welding method for thin-walled rotary components based on a highly self-sustaining plasma according to claim 1, characterized in that The electron beam wire feeding welding method for the thin-walled rotary member is suitable for the welding formation between heterogeneous plates. After welding, only the initial welding area needs to be ground and polished, and it can be extended to the welding formation of planar welds and complex curved surfaces. After adjusting the electron beam power, it can be further applied to the welding formation of thick plates.

10. A method for electron beam wire - feeding welding of thin - walled rotary components based on a highly self - sustaining plasma according to claim 1, characterized in that, In the electron beam wire feeding welding method, the electron beam used can be replaced by arc welding or laser welding.

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