APU compressor casing conical support welding repair method and repair device

Abstract

The application relates to the technical field of aero-engine maintenance, and discloses an APU compressor shell conical support welding repair method and a repair device, the method comprising the following steps: detecting and positioning a crack, cutting and separating an inner shell from an outer shell of the shell, and cleaning and washing the exposed crack; placing the separated parts on a tool for vacuum electron beam welding, sequentially performing three stages of positioning welding, penetration welding and modification welding, and slowly cooling under vacuum; after detection, re-welding, three-stage welding and slow cooling treatment are performed again; the device comprises a vacuum welding cavity, an electron beam emission system, a workpiece attitude adjusting platform, a weld visual tracking system and a special welding tool. The application can effectively reduce a heat affected zone and shell deformation, ensure complete fusion of a crack root, and improve the mechanical properties and sealing reliability of a repaired joint.

Description

Technical Field

[0001] This invention relates to the field of aircraft engine maintenance technology, and in particular to a welding repair method and device for the conical support of the APU compressor housing. Background Technology

[0002] The auxiliary power unit (APU) is a crucial component of aircraft. Under prolonged exposure to high-temperature, high-pressure airflow and complex alternating loads, the compressor casing's conical support joints are highly susceptible to stress concentration, leading to cracks, porosity, and other defects. This can result in gas leakage, severely impacting flight safety. Currently, the industry commonly employs TIG welding, laser cladding, or adhesive repair techniques to repair damage to such high-temperature alloy thin-walled casings. TIG welding involves filling with high-temperature alloy welding wire followed by stress-relief annealing. Laser cladding utilizes a high-energy-density beam to melt metal powder, achieving surface modification or weld overlay repair. Adhesive repair primarily relies on high-temperature resistant epoxy resins and other materials to seal micro-cracks. These existing technologies can restore some of the casing's functionality to a certain extent and can be applied under specific operating conditions.

[0003] However, in existing technologies, due to the complex structure and thin wall of the APU compressor casing, traditional welding methods involve a large heat input, which can easily lead to severe thermal deformation of the casing. This makes it difficult to meet assembly requirements in terms of dimensional accuracy, coaxiality, and flatness after repair. At the same time, existing processes often have insufficient fusion at the root of deep cracks, which can easily lead to secondary leaks. Furthermore, the mechanical properties of the repaired area usually fail to meet the original design specifications. The lack of dedicated precision clamping and alignment tooling also results in a high risk of weld misalignment during the welding process, making it difficult to achieve high-quality and high-reliability repairs. Summary of the Invention

[0004] This application provides a welding repair method and apparatus for the conical support of an APU compressor housing, which can solve the technical problems of stress concentration causing cracks in the conical support of the APU compressor housing, large heat input, severe deformation, unreliable repair, and lack of dedicated high-precision clamping tooling in traditional repair methods.

[0005] To solve the above problems, the present invention adopts the following technical solution: This application provides a welding repair method for the conical support of an APU compressor housing. The APU compressor housing includes an inner shell and an outer shell, and the connection between the inner shell and the outer shell is a conical support. The method includes the following steps: S1. Locate the crack location through air tightness testing or PT penetration testing, cut the inner and outer shells of the APU compressor housing to expose the cracks on the inner and outer shells, grind and clean the cracks to be repaired until the component substrate is exposed, and then perform ultrasonic cleaning and drying. S2, the separated inner shell and outer shell are placed on the welding fixture in sequence, and the cracks on the separated inner shell and outer shell are repaired by vacuum electron beam welding. The repair of each crack includes three welding stages in sequence: tack welding, penetration welding and finishing welding. S3, After the inner shell and outer shell are welded separately, they are subjected to slow cooling under vacuum conditions; S4. After the inner and outer shells are taken out of the furnace, the welds are polished and ground, and PT penetration testing is performed. S5, if both the inner shell and the outer shell pass the inspection, the inner shell and the outer shell are re-welded along the conical support. The re-welding includes three stages: tack welding, penetration welding and finishing welding. If a part fails the inspection, the crack is repositioned and steps S2-S4 are repeated. S6, after the welding is completed, it is slowly cooled under vacuum conditions, and the weld is polished after it is taken out of the furnace.

[0006] Preferably, in step S2 and / or step S5, without disrupting the vacuum conditions after the modification welding is completed, the electron beam is switched to defocusing mode to scan and heat the weld area, thereby achieving in-situ local heat treatment.

[0007] Preferably, in the in-situ local heat treatment, the electron beam current is 5mA-8mA, a large-range circular scan is used, the scan amplitude is 2mm-5mm, the frequency is 50Hz-80Hz, the heating temperature of the weld area is controlled to 500℃-650℃, and the vacuum slow cooling time is 10min.

[0008] Preferably, in steps S2 and / or S5, different scanning waveforms are used depending on the welding stage: During the tack welding stage: a small-amplitude circular scan is used, with a scan amplitude of X=Y=0.2-0.3mm and a frequency of 100-120Hz; Penetration welding stage: Use transverse elliptical scanning with scanning amplitude X=0.3-0.5mm, Y=0.1-0.2mm, and frequency 80-100Hz; Repair welding stage: Use longitudinal elliptical scanning with scanning amplitude X=0.1-0.2mm, Y=0.3-0.5mm, and frequency 120Hz-150Hz.

[0009] Preferably, the welding current in the tack welding stage is 8-10mA and the focusing current is 520-540mA; the welding current in the penetration welding stage is 14.5-16mA and the focusing current is 520-540mA; and the welding current in the finishing welding stage is 10-12mA and the focusing current is 550-570mA.

[0010] Preferably, in step S2 and / or step S5, the process parameters for vacuum electron beam welding are: welding vacuum degree ≤ 5 × 10⁻⁶. -2 Pa, chamber vacuum degree ≤3×10 -3 Pa, accelerating voltage of 60kV, welding speed of 500-650mm / min, working distance of 325mm.

[0011] Preferably, in step S1, grinding and cleaning the crack to be repaired includes grinding and cleaning within a 20mm range on both sides of the crack to be repaired; in step S3 and / or step S6, slow cooling treatment includes slow cooling in a vacuum chamber for at least 30 minutes before filling with gas and removing from the furnace.

[0012] Preferably, in step S5, before re-welding the inner shell and outer shell along the tapered support, a heat-conducting liner is placed on the back of the weld seam to accelerate heat dissipation.

[0013] To address the aforementioned technical problems, this application also provides a welding repair device for the conical support of an APU compressor housing used to implement the above method, comprising: A vacuum welding chamber, externally connected to a vacuum acquisition device; An electron beam emission system includes a generating device and an emission gun connected to the generating device, the emission gun being directed toward the interior of the vacuum welding chamber; A workpiece posture adjustment platform is fixedly installed inside the vacuum welding chamber; The weld seam visual tracking system includes a camera installed inside the vacuum welding chamber and aligned with the area to be welded. The weld seam visual tracking system is signal-connected to the electron beam emission system and the workpiece attitude adjustment platform, and is used to automatically correct deviations based on the identified weld seam center position to ensure weld alignment. And a welding fixture, which is detachably mounted on the workpiece attitude adjustment platform; The welding fixture mentioned above includes: A positioning chassis is fixed to the workpiece posture adjustment platform; An intermediate support assembly is disposed above the positioning chassis and includes a top plate and a bottom plate that are disposed opposite to each other and are detachable, and a support rod connecting the top plate and the bottom plate. The support rod is provided with a plurality of pre-tightening units evenly distributed along its circumference, and each pre-tightening unit is used to apply a pre-tightening force to the tapered support end face. A centering chuck is installed on the side of the top plate away from the bottom plate.

[0014] Preferably, the top plate and bottom plate are provided with positioning pin holes corresponding to the pin holes of the inner shell or outer shell flange. The centering chuck is provided with a plurality of limiting blocks evenly spaced along its axis. The outer diameter of the plurality of limiting blocks corresponds to the inner diameter of the APU compressor housing. After clamping, the radial runout of the housing is ≤0.05mm. The preload unit includes a screw adjustment mechanism and an elastic element sleeved on the screw adjustment mechanism. The preload force of a single preload unit is in the range of 10N-20N.

[0015] The technical solution adopted in this invention can achieve the following beneficial effects: This application provides a method and apparatus for welding repair of the conical support of an APU compressor housing. The method involves cutting and separating the inner and outer shells of the APU compressor housing to thoroughly expose the cracks. The exposed cracks are then ground, ultrasonically cleaned, and dried to remove all potential defect sources and ensure the cleanliness of the welding interface. Based on this, vacuum electron beam welding technology is used to sequentially perform three refined stages—positioning welding, penetration welding, and finishing welding—in a low-oxygen environment. By matching specific scanning waveforms and energy parameters for each stage, positioning welding stabilizes the initial position and prevents misalignment; penetration welding achieves deep and complete fusion; and finishing welding optimizes surface shaping and reduces stress concentration. Subsequently, under vacuum conditions… The process involves slow cooling, which effectively suppresses martensitic phase transformation and releases residual welding stress. After the split repair inspection is passed, the inner and outer shells are re-welded and undergo a three-stage welding and vacuum slow cooling process again, thereby restoring the overall structural integrity of the shell. This series of steps works synergistically to significantly reduce the width of the heat-affected zone and strictly control the deformation of the shell within a very small range. At the same time, it ensures that the joint is free of oxidation and porosity and has mechanical properties close to those of the base material. This effectively solves the problems of dimensional deviations, incomplete repair of crack roots, and insufficient performance after repair caused by excessive heat input in traditional welding methods, and greatly improves the reliability, consistency, and service life of the repair of key components of aero-engines.

[0016] In summary, this application constructs a complete closed loop from defect removal to high-performance restoration through a systematic technical approach of separate exposure, three-stage fine repair, vacuum temperature control, and overall restoration. This not only optimizes the microstructure properties but also ensures the achievement of precision assembly indicators at the macroscopic level, demonstrating significant engineering application value. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a welding repair method for the conical support of an APU compressor housing disclosed in some embodiments of this application; Figure 2 This is a schematic diagram of the APU compressor housing; Figure 3 yes Figure 2 Partial structural cross-sectional view of the APU compressor housing; Figure 4 This is a schematic diagram of a welding repair device for the conical support of an APU compressor housing disclosed in some embodiments of this application; Figure 5 This is a schematic diagram of a welding fixture for a welding repair device for the conical support of an APU compressor housing, as disclosed in some embodiments of this application.

[0019] In the picture: 1. Welding repair device for the conical support of the APU compressor housing; 20. Outer shell; 21. Inner shell; 22. Conical support; 10. Vacuum welding chamber; 11. Electron beam emission system; 12. Workpiece attitude adjustment platform; 13. Weld seam vision tracking system; 14. Welding fixtures; 100. Vacuum acquisition device; 140. Positioning chassis; 141. Intermediate support assembly; 142. Centering chuck; 143. Pre-tightening unit; 1410. Top plate; 1411. Bottom plate; 1412. Support rod; 1413. Locating pin hole; 1420. Limiting block. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0022] During the long-term operation of the APU (Auxiliary Power Unit) compressor casing, the conical support area is prone to stress concentration and cracking due to the impact of high-temperature and high-pressure airflow and alternating loads, leading to gas leakage. Existing maintenance techniques, such as replacing the entire casing, are not only costly but also time-consuming. Traditional argon arc welding repair processes, due to their large heat input, can cause severe thermal deformation of the thin-walled casing, making it difficult to meet assembly requirements in terms of dimensional accuracy, coaxiality, and flatness after repair. In addition, the heat-affected zone is wide, which can easily lead to a decrease in the hardness of the substrate. Laser cladding and other processes, when dealing with conical supports in confined spaces, suffer from poor equipment accessibility and insufficient penetration at the crack root, making it difficult to guarantee the quality and reliability of deep penetration welding.

[0023] The following is in conjunction with the appendix Figures 1 to 5 This application provides a detailed description of a welding repair method and device for the conical support of an APU compressor housing, through specific embodiments and application scenarios.

[0024] Please refer to Figure 1 The first embodiment of the present invention provides a welding repair method for the conical support of an APU compressor housing, the method comprising the following steps: Step S1: Locate the crack location through air tightness testing or PT penetration testing, cut the inner and outer shells of the APU compressor housing to expose the cracks on the inner and outer shells, grind and clean the cracks to be repaired until the component substrate is exposed, and then perform ultrasonic cleaning and drying. Specifically, airtightness testing involves filling the casing with compressed air and immersing it in water or applying a foaming agent, then observing the location of air bubbles to initially pinpoint the leak point. PT penetrant testing utilizes the principle of capillary action, applying a penetrant containing fluorescent or colored dyes to the surface of the part, penetrating into surface opening defects. After cleaning to remove excess penetrant, a developer is applied to absorb the penetrant from the defects back to the surface, thus clearly displaying the precise direction and length of the crack under ultraviolet or white light.

[0025] Please refer to Figure 2 and Figure 3 The APU compressor housing to be repaired includes an inner shell 21 and an outer shell 20, which are connected at a conical support 22. Cracks usually originate in the stress concentration area at this conical support. The inner shell 21 and the outer shell 20 are mechanically cut and separated along the conical support 22 to thoroughly expose cracks that were originally hidden or located deep in the joint surface, so as to ensure that subsequent repairs can reach the root of the crack.

[0026] Grinding and cleaning of cracks to be repaired can refer to using pneumatic grinding tools or hand files to remove oxide scale, oil, and altered metal layers from the crack and its surrounding area of ​​at least 20mm until a bright, fresh metal substrate is exposed. This eliminates stress concentration sources at the crack tip and prevents slag inclusions or incomplete fusion defects during welding. Ultrasonic cleaning involves placing the ground parts in an ultrasonic cleaner containing anhydrous ethanol or a special cleaning agent. The cavitation effect generated by high-frequency vibration removes tiny particles and residual grease adhering to the micropores of the parts. Drying involves placing the cleaned parts in an oven and heating them at a set temperature to remove residual moisture from the surface and interior, preventing the dissolution of hydrogen during welding, which could lead to porosity or hydrogen embrittlement.

[0027] In one specific embodiment, for a surface crack with a length of 15mm, the two ends of the crack are first marked by PT detection. Then, the inner shell and outer shell are separated using a wire EDM machine. Next, a V-shaped bevel is made along the crack direction using a 3mm diameter rotary file and ground down to the substrate. Finally, the crack is cleaned in an ultrasonic cleaner with a frequency of 40kHz for 10 minutes and dried in an oven at 120℃ for 30 minutes. This thorough defect cleaning and drying process provides a clean metallurgical bonding foundation for subsequent high-quality vacuum electron beam welding, effectively avoiding welding defects caused by contaminants.

[0028] Step S2: Place the separated inner shell and outer shell onto the welding fixture in sequence, and repair the cracks on the separated inner shell and outer shell by vacuum electron beam welding. The repair of each crack includes three welding stages in sequence: tack welding, penetration welding and finishing welding. Specifically, welding fixtures are used to precisely position and clamp thin-walled shells in a vacuum environment, limiting their radial runout and preventing welding thermal deformation; vacuum electron beam welding is a method that uses a high-speed electron beam that is accelerated and focused to bombard the joint of a workpiece in a high vacuum environment, converting kinetic energy into heat energy to achieve melting and connection. It has the characteristics of high energy density, low heat input, and large depth-to-width ratio.

[0029] It should be noted that the tack welding stage uses a smaller electron beam current and a higher scanning frequency to perform intermittent or continuous shallow fusion along the weld trajectory. Its function is to initially fix the two sides of the separated crack to prevent misalignment or gap changes during subsequent high-current welding. The penetration welding stage is the core welding process. By increasing the beam current and adjusting the focusing current, the electron beam penetrates the entire wall thickness to achieve complete fusion at the root of the weld, ensuring no incomplete penetration defects. At the same time, the vacuum environment is used to isolate oxygen and prevent oxidation of the high-temperature alloy. The finishing welding stage is performed after the penetration welding is completed. A specific scanning waveform is used to remelt the weld surface to fill undercut, refine the grains, smooth the weld transition zone, and reduce the stress concentration factor.

[0030] Step S3: After the inner shell and outer shell are welded separately, they are subjected to slow cooling under vacuum conditions; Specifically, vacuum slow cooling refers to maintaining a vacuum state inside the vacuum welding chamber after the three-stage welding is completed, turning off the electron beam emission system, and allowing the workpiece to cool naturally with the furnace or cool at a controlled cooling rate.

[0031] Understandably, this step utilizes the excellent thermal insulation properties and controllable cooling atmosphere of the vacuum environment to reduce the cooling rate of the weld and heat-affected zone, avoiding hardened structures (such as martensite) and huge thermal stress caused by rapid cooling, thereby preventing the generation of cold cracks and improving the toughness of the joint.

[0032] Step S4: After the inner and outer shells are taken out of the oven, the welds are polished and ground, and PT penetration testing is performed. Specifically, polishing involves using fine sandpaper or a polishing wheel to mechanically process the weld surface after welding, removing spatter, oxidation, and surface unevenness that may have occurred during the welding process, ensuring the weld surface finish meets inspection requirements. PT penetrant testing serves as an intermediate quality inspection method to verify the integrity of crack repairs on individual components (inner or outer shell). In practice, the inner and outer shells, after slow cooling, are polished separately, followed by the application of penetrant, cleaning agent, and developer. The components are then observed under ultraviolet light for crack detection. If cracks, porosity, or lack of fusion are detected, the component is deemed unqualified and the defect must be relocated and the process repeated. If no defects are found, the component passes inspection and is ready for welding.

[0033] Step S5: If both the inner shell and the outer shell pass the inspection, re-weld the inner shell and the outer shell along the conical support. The welding process includes three stages: tack welding, penetration welding, and finishing welding. If any part fails the inspection, the crack is repositioned and steps S2-S4 are repeated. Specifically, the inner and outer shells, after being individually repaired and tested, are butt-welded at the conical supports according to their original assembly relationship to restore the overall structural integrity of the shell.

[0034] It should be noted that the welding process also follows a three-stage welding strategy: first, tack welding is performed to ensure that the gap between the inner and outer shells is uniform and without misalignment; second, penetration welding is performed to achieve full penetration connection of the conical support joint surface and ensure structural strength; and finally, finishing welding is performed to optimize the appearance and mechanical properties of the weld.

[0035] Understandably, this step forms a closed-loop quality control logic with the aforementioned single-piece repair: the welding operation is only performed when both the inner and outer shells pass the aforementioned PT test; if any part fails the test, the system immediately triggers the rework process, that is, the crack location of that part is repositioned, and the complete sub-cycle from vacuum electron beam welding repair (S2) to slow cooling (S3) and then to testing (S4) is executed again until both parts pass; this step-by-step verification and conditional execution mechanism minimizes the risk of scrapping the final product and ensures the overall sealing and structural reliability of the shell after repair.

[0036] Step S6: After the welding is completed, the weld is slowly cooled under vacuum conditions, and then polished after being taken out of the furnace.

[0037] It should be noted that this step is the final heat treatment and surface treatment of the welded assembly. Slow cooling under vacuum conditions aims to eliminate the overall thermal stress generated during the welding process, preventing deformation or cracking due to differences in stiffness between the inner and outer shells. The process principle is the same as described above, but the target is the assembled shell. Polishing after removal from the furnace is to remove excess weld seam material and heat discoloration, ensuring a smooth transition between the repaired area and the base material, and restoring the aerodynamic shape and dimensional accuracy of the part.

[0038] Specifically, after the welding is completed, the component is slowly cooled to near room temperature in a vacuum chamber, then removed from the vacuum. A polishing tool is used to finely grind the circumferential weld seam until the surface is smooth and flat. If necessary, a brief PT test or airtightness retest can be performed to confirm the final quality. Through this series of final processing steps, the repaired APU compressor housing is restored to near-new condition in terms of geometry, surface quality, and internal microstructure, meeting the stringent usage requirements of aero-engine components.

[0039] Understandably, the aforementioned cutting, separation, and deep cleaning solve the problem that traditional integral welding cannot completely remove deep cracks and oxide impurities, laying a clean substrate foundation for high-quality welding. The three-stage vacuum electron beam welding process of positioning, penetration, and finishing adopted by the above method utilizes the high energy density and low heat input characteristics of electron beams, combined with parameter optimization at different stages, to ensure the penetration and forming of thin-walled parts, effectively control the width of the heat-affected zone, and suppress welding deformation. The subsequent vacuum slow cooling treatment utilizes the heat insulation and oxygen-free characteristics of the vacuum environment to achieve a slow transformation of the weld structure, significantly reducing residual stress and cold cracking tendency. The aforementioned intermediate inspection and rework mechanism, combined with the aforementioned conditional welding logic, constructs a multi-level quality defense line, ensuring that only defect-free parts can enter the next process, thereby fundamentally improving the success rate and reliability of APU compressor housing crack repair, and achieving the maintenance goals of low cost, short cycle, and high performance.

[0040] Furthermore, in step S2 and / or step S5, without disrupting the vacuum conditions after the modification welding is completed, the electron beam is switched to defocusing mode to scan and heat the weld area, thereby achieving in-situ local heat treatment.

[0041] Specifically, maintaining the vacuum condition without disrupting it means keeping the vacuum level inside the vacuum welding chamber ≤5×10 after completing the finishing weld stage. -2 Under the condition of Pa, no gas charging and unloading operation is performed; the existing electron beam emission system is used directly for subsequent heat treatment processes.

[0042] Understandably, this continuous operation method avoids surface oxidation, hydrogen embrittlement, and thermal shock deformation caused by drastic temperature changes that may occur during the process of transferring the workpiece from a vacuum environment to an atmospheric environment and then re-entering the furnace.

[0043] Specifically, the defocusing mode refers to adjusting the focusing current in the electron beam emission system to significantly increase the diameter of the electron beam spot and reduce the energy density, thereby converting the high-energy concentrated heat source originally used for deep penetration welding into a large-area low-energy heat source suitable for surface heating.

[0044] Simultaneously, through scanning, heat is uniformly applied over a wider area, avoiding localized overheating and burning through the thin-walled shell, while ensuring the uniformity of the temperature field throughout the weld area. This scanning heating process aims to heat the weld area to the temperature range required for stress-relief annealing (e.g., 500℃-650℃), promoting the recovery and recrystallization of the metal lattice and releasing the tensile residual stress generated during welding. This process utilizes secondary precise temperature control based on the residual heat of welding, achieving a seamless connection between welding and heat treatment.

[0045] The following specific example illustrates this step: After the inner shell crack repair welding is completed, the control system immediately instructs the electron gun to adjust the focusing current, so that the beam spot diameter is expanded to 5-10mm, and activates the deflection coil to make the electron beam perform a circular scan within a range of 2-3mm on both sides of the weld at a frequency of 50Hz. At this time, the electron beam current is maintained at a low level of 5-8mA, and heating is continued for about 10 minutes to stabilize the temperature of the weld area at about 600℃, and then it is naturally cooled slowly in a vacuum environment.

[0046] Understandably, this step aims to address the issues of secondary oxidation, dimensional deformation, and cumbersome procedures in traditional welding repair caused by separate post-weld heat treatment. The execution is carried out by the control unit and electron beam emitter of the vacuum electron beam welding system. Based on the modified weld completed in the previous steps, it directly performs mode switching and parameter adjustments. Through dynamic conversion of electron beam modes and precise control of the scanning trajectory, the function of deep penetration welding to large-area annealing is reused, resulting in repair welds with low residual stress and high structural stability. This significantly improves the fatigue life and dimensional accuracy of the APU compressor housing after repair, effectively avoiding the accumulation of positioning errors caused by repeated furnace entry and exit. Combined with the aforementioned vacuum environment maintenance measures, it ensures oxidation-free protection of the workpiece throughout the entire process from high-temperature welding to heat treatment and then to cooling, completely eliminating the risk of surface contamination caused by re-entry into the furnace in traditional processes. Simultaneously, the in-situ localized heat treatment utilizes the precise positioning and clamping stability of the welding fixture, avoiding distortion and deformation caused by uneven stress release during workpiece transfer.

[0047] Furthermore, in the in-situ local heat treatment, the electron beam current is 5mA-8mA; Specifically, the beam current can be fine-tuned based on real-time temperature feedback from the weld area to ensure accurate heat input. For example, when processing thinner shell areas, the beam current can be set to 5mA to prevent overheating; while for areas with greater thickness or higher heat capacity, the beam current can be adjusted to 8mA to ensure heating efficiency. By controlling the beam current within the low current range of 5mA-8mA, it complements the aforementioned finishing welding stage, providing sufficient heat for stress-relief annealing while avoiding grain coarsening or matrix softening caused by excessive heat input.

[0048] It employs a large-area circular scan with a scan amplitude of 2mm-5mm and a frequency of 50Hz-80Hz. Specifically, in in-situ local heat treatment, the electron beam deflects along a circular trajectory on the weld surface, transforming the concentrated point heat source into a surface heat source, thereby expanding the heating area and making the temperature distribution more uniform. This large-scale circular scanning method, combined with low beam current, can effectively eliminate local hot spots, prevent new thermal stress caused by uneven heating, and ensure that the weld and surrounding area as a whole enter the stress-relief temperature field.

[0049] Control the heating temperature of the weld area to 500℃-650℃, and the vacuum slow cooling time is 10 minutes; Specifically, for the high-temperature alloy used in the APU compressor housing, controlling the temperature at around 580℃ effectively eliminates stress without causing a decline in material properties. The determination of the vacuum slow cooling time depends on the workpiece's heat capacity; for example, setting it to 10 minutes allows the workpiece to slowly dissipate heat in a vacuum, avoiding rapid cooling caused by air convection. By controlling the heating temperature to 500℃-650℃ and combining it with 10 minutes of vacuum slow cooling, the relaxation process of the microstructure can be smoothly completed, significantly reducing residual stress and improving the fatigue life of the repaired area.

[0050] Understandably, this parameter combination for in-situ local heat treatment not only adapts to the material properties of the high-temperature alloy of the APU compressor housing, but also utilizes the same set of electron beam welding equipment to complete the dual processes of welding and heat treatment without breaking the vacuum, significantly shortening the maintenance cycle and reducing residual stress by more than 30%, effectively solving the technical problems of large heat-affected zone, difficult deformation control, and insufficient stress relief in traditional methods.

[0051] Furthermore, in steps S2 and / or S5, different scanning waveforms are used depending on the welding stage: During the tack welding stage: a small-amplitude circular scan is used, with a scan amplitude of X=Y=0.2-0.3mm and a frequency of 100-120Hz; Specifically, the tack welding stage refers to the initial stage of the welding process. Its function is to initially fix the crack edges on the separated inner and outer shells, preventing misalignment or positional movement during subsequent welding. The small-amplitude circular scanning used in this stage refers to the electron beam spot making a circular motion with a very small radius around the center of the weld. This scanning method ensures that the heat is evenly distributed in a small area, forming a stable molten pool nucleus. This parameter setting ensures the stability of arc initiation and avoids the risk of burn-through due to excessive energy concentration. Through this small-amplitude, high-frequency circular scanning, the relative position of the workpiece can be effectively locked, providing a precise reference for subsequent deep penetration welding.

[0052] Penetration welding stage: Use transverse elliptical scanning with scanning amplitude X=0.3-0.5mm, Y=0.1-0.2mm, and frequency 80-100Hz; Specifically, the penetration welding stage is the core stage for achieving full penetration of the weld. Its function is to ensure complete fusion at the root of the crack and eliminate incomplete penetration defects. The transverse elliptical scanning used in this stage can refer to the movement trajectory of the electron beam spot being a flat ellipse, with its major axis extending along the weld width direction (X direction) and its minor axis compressed along the weld depth direction (Y direction).

[0053] The scanning amplitude X=0.3-0.5mm and Y=0.1-0.2mm means that the oscillation range of the electron beam in the lateral direction is significantly larger than that in the longitudinal direction, thus distributing more energy on the base material on both sides of the weld and promoting sidewall fusion. The frequency of 80-100Hz controls the rhythm of heat input and prevents local overheating. The wide and shallow heat source distribution formed by the electron beam can fully heat the thick-walled areas on both sides of the crack, and use the laterally extended energy field to drive the molten metal to flow towards the root, achieving a deep penetration effect. At the same time, by using lateral elliptical scanning in conjunction with circular scanning in the tack welding stage, the former greatly expands the width of the molten pool on the stable reference established by the latter, thereby achieving high-quality root fusion while ensuring alignment accuracy.

[0054] Repair welding stage: Use longitudinal elliptical scanning with scanning amplitude X=0.1-0.2mm, Y=0.3-0.5mm, and frequency 120Hz-150Hz.

[0055] Specifically, the finishing stage of the welding process is the final stage of the welding process. Its function is to improve the surface formation of the weld, reduce undercut, and lower the stress concentration factor.

[0056] The scanning amplitude X=0.1-0.2mm and Y=0.3-0.5mm indicate that the electron beam has a large oscillation range in the longitudinal direction, which helps to lengthen the tail of the molten pool, allowing the molten metal enough time to backfill and smoothly transition; the high-frequency scanning of 120Hz-150Hz further refines the grains and improves the surface finish.

[0057] The electron beam under these parameters forms a thin heating band on the weld surface, effectively eliminating the problem of excessive weld reinforcement or uneven surface that may be left by the previous penetration welding. Through the synergy of longitudinal elliptical scanning and the previous transverse elliptical scanning, the former uses longitudinal heat accumulation to optimize surface wettability, while the latter uses transverse energy distribution to ensure internal penetration. The combination of the two achieves high-quality repair from the inside out.

[0058] Understandably, this application achieves precise matching of energy distribution with the functional requirements of each stage by dynamically switching scanning waveforms at different welding stages. Specifically, the small-amplitude circular scan in the locating welding stage utilizes its energy concentration characteristics to quickly establish a stable molten pool core, preventing workpiece misalignment and laying the geometric foundation for subsequent processes. On this basis, the penetration welding stage switches to a transverse elliptical scan, using its large value in the X direction to expand the energy coverage range, enhancing the heating capacity of the base material on both sides of the crack, ensuring deep penetration and defect-free root bonding. Subsequently, the finishing welding stage adopts a longitudinal elliptical scan, using its large value in the Y direction to lengthen the tail of the molten pool, promoting a smooth transition of molten metal and surface shaping, effectively reducing stress concentration. These three scanning waveforms do not exist in isolation but are sequentially connected according to the physical laws of the welding thermal process. Through this phased differentiated control, not only is the contradiction of a single waveform being unable to simultaneously address positioning accuracy, penetration depth, and surface quality overcome, but the overall mechanical properties and dimensional accuracy of the weld repair at the conical support of the APU compressor housing are also significantly improved.

[0059] Furthermore, the welding current during the tack welding stage is 8-10mA, and the focusing current is 520-540mA; Specifically, setting the welding beam current to a low energy range of 8-10mA is to minimize heat input while ensuring the formation of an effective weld nugget for positioning, thus preventing initial deformation of the thin-walled shell due to localized overheating. Simultaneously, controlling the focusing current within the range of 520-540mA ensures the electron beam spot remains moderately focused, guaranteeing sufficient penetration depth at the point of contact to resist assembly stress while preventing excessive penetration that could lead to burn-through on the back side. This combination of low beam current and moderate focusing current enables precise workpiece positioning while minimizing the heat-affected zone, providing a stable geometric basis for subsequent penetration welding.

[0060] The welding current during the penetration welding stage is 14.5-16mA, and the focusing current is 520-540mA. Specifically, at this stage, the welding beam current needs to be significantly increased to the high-energy range, i.e., 14.5-16mA, to provide sufficient energy density to overcome the high melting point characteristics of high-temperature alloys and ensure that the molten pool can penetrate deep into the crack root to achieve metallurgical bonding. The focusing current continues to be maintained in the range of 520-540mA, consistent with or slightly adjusted from the tack welding stage. The purpose is to maintain the penetration capability of the electron beam, so that the beam spot energy is concentrated on the central axis of the weld, forming a nail-shaped molten pool with an ideal depth-to-width ratio. The strong vapor pressure generated by the high beam current helps to expel the gas in the molten metal and reduce porosity, while the stable focusing current ensures the uniformity of the molten pool depth. Using this range of beam current in combination with a specific range of focusing current, and combined with the transverse elliptical scanning method of the above embodiment, the molten pool can be effectively stirred, promoting gas escape and refining the grains.

[0061] During the finishing welding stage, the welding current is 10-12mA and the focusing current is 550-570mA. Specifically, at this stage, the welding beam current is reduced compared to the penetration welding stage, adjusted to 10-12 mA to reduce thermal disturbance to the solidified weld and prevent grain coarsening. Crucially, the focusing current is increased to a higher level of 550-570 mA. This adjustment alters the focusing state of the electron beam, further reducing the beam diameter and concentrating the energy density more effectively on the surface with a narrower distribution. Specifically, the higher focusing current makes the electron beam sharper, enabling precise melting of minute protrusions or depressions on the weld surface without causing extensive remelting of the deeper base material. By reducing the beam current to control overall heat input and simultaneously increasing the focusing current to optimize the beam morphology, the two work synergistically to refine the weld microstructure and precisely refine the surface morphology, effectively reducing post-weld residual stress and improving fatigue life.

[0062] Understandably, the tack welding stage utilizes a combination of low beam current and moderate focusing current to achieve stable workpiece positioning while minimizing thermal damage. Building upon this, the penetration welding stage significantly increases the beam current to 14.5-16 mA while maintaining a stable focusing current, providing sufficient penetration energy to ensure complete fusion and density at the crack root. Furthermore, the finishing welding stage moderately reduces the beam current to 10-12 mA and significantly increases the focusing current to 550-570 mA, using a high-energy-density fine beam spot to precisely remelt the weld surface. This phased, dynamic parameter adjustment strategy not only solves the problems of excessively large heat-affected zone, severe deformation, or poor surface finish caused by traditional single-parameter welding, but also achieves comprehensive control from internal fusion quality to external aesthetic finish through synergistic cooperation with different scanning waveforms in the above embodiments. Ultimately, this results in the repaired APU compressor housing maintaining dimensional accuracy while possessing excellent mechanical properties and sealing reliability.

[0063] Furthermore, in step S2 and / or step S5, the process parameters for vacuum electron beam welding are: welding vacuum degree ≤ 5 × 10⁻⁶. -2 Pa, chamber vacuum degree ≤3×10 -3 Pa, accelerating voltage of 60kV, welding speed of 500-650mm / min, working distance of 325mm.

[0064] Specifically, a high vacuum environment is maintained by continuously pumping air through a vacuum acquisition device. Its function is to minimize the probability of collisions between gas molecules and high-speed electrons, prevent electron beam scattering or energy loss, and avoid oxidation reactions between the high-temperature molten pool and residual gas, thereby ensuring the purity of the weld metal.

[0065] For high-temperature alloy components with a certain thickness, such as the APU compressor housing, an accelerating voltage of 60kV can ensure that the electron beam penetrates the root of the crack and eliminates incomplete fusion defects.

[0066] Welding speed is determined based on the balance between heat input and molten pool solidification rate. Its function is to control the width of the heat-affected zone and prevent the thin-walled shell from deforming due to overheating, while ensuring complete weld penetration.

[0067] The working distance is achieved by adjusting the height of the workpiece posture adjustment platform. Its function is to ensure that the electron beam is in the optimal focusing state on the workpiece surface, so as to obtain the smallest spot diameter and the highest power density.

[0068] Furthermore, in step S1, grinding and cleaning the crack to be repaired includes grinding and cleaning within a 20mm range on both sides of the crack to be repaired; in step S3 and / or step S6, slow cooling treatment includes slow cooling in a vacuum chamber for at least 30 minutes before filling with gas and removing from the furnace.

[0069] Specifically, when exposing cracks, the process involves not only removing the crack itself but also mechanically grinding an area extending at least 20mm to both sides of the crack's direction. This step aims to thoroughly remove any oxide film, oil, microcrack tips, and work-hardened layers that may be present in the heat-affected zone around the crack. This prevents these contaminants from being drawn into the molten pool during subsequent vacuum electron beam welding, thus preventing them from forming porosity or inclusions. This expanded cleaning method significantly increases the cleanliness of the weld interface, ensuring that the electron beam energy effectively targets the base material rather than surface contaminants, thereby reducing weld porosity and improving fusion quality from the source.

[0070] After the inner and outer shells are welded separately and after the fusion welding is completed, because high-temperature alloy materials are prone to martensitic transformation and huge thermal stress during rapid cooling, the workpiece is not immediately removed from the vacuum environment or cooled by cooling gas. Instead, it is kept in a vacuum state for natural or controlled cooling, and the duration of this heat preservation and slow cooling process is not less than 30 minutes. By extending the high-temperature residence time and slowing down the cooling rate, the smooth transformation of the weld metal structure is promoted, the residual stress is fully relaxed, cold cracks are avoided, the precipitation of brittle phases is effectively suppressed, the toughness and crack resistance of the joint are significantly improved, and the service life of the repaired shell under alternating loads is ensured.

[0071] Furthermore, in step S5, before re-welding the inner shell and outer shell along the tapered support, a heat-conducting liner is placed on the back of the weld seam to accelerate heat dissipation.

[0072] Specifically, the thermally conductive liner refers to a high thermal conductivity metal block that is closely attached to the back of the area to be welded. The preferred material is oxygen-free copper or pure copper. It utilizes its excellent thermal conductivity as a heat sink medium. The shape of the thermally conductive liner is adapted to the curvature of the conical support of the APU compressor housing to ensure surface contact or tight fit with the back of the weld.

[0073] In practice, the thermally conductive liner is fixed to the corresponding weld position inside the shell using tooling fixtures or directly pressed against it, and its coverage area at least covers the entire circumferential weld path and heat-affected zone. The function of the thermally conductive liner is to act as an artificial heat dissipation channel. When the high-temperature heat generated by electron beam welding is conducted deep into the base material, it quickly absorbs and dissipates the heat, thereby reducing the peak temperature at the weld root and shortening the residence time of the material in the high-temperature zone.

[0074] Understandably, when welding a thin-walled shell with a thickness of only 1mm, without using a heat-conducting backing plate, local heat accumulation can easily lead to the collapse of the molten pool or even burn-through. However, by using a copper heat-conducting backing plate with a thickness of 5mm-10mm, the heat is rapidly diffused laterally, effectively preventing burn-through defects. This forced heat dissipation method at the back can significantly reduce the width of the welding heat-affected zone, suppress shell deformation caused by uneven thermal gradients, and ensure dimensional accuracy after welding.

[0075] It should be noted that the welding process includes three stages: tack welding, penetration welding, and finishing welding. Throughout the entire welding process, the thermally conductive backing plate remains on the back of the weld to dissipate heat. In the tack welding stage, the thermally conductive backing plate prevents micro-cracks from forming at the tack weld due to instantaneous high heat. In the penetration welding stage, the high-energy-density electron beam penetrates the weld, and the thermally conductive backing plate promptly removes excess heat, ensuring that the penetration depth is controlled within the predetermined range without damaging the substrate. In the finishing welding stage, the thermally conductive backing plate assists in the rapid solidification of the weld surface and refines the grain structure.

[0076] Please refer to Figure 4 and Figure 5 To achieve the above method, another embodiment of the present invention provides a welding repair device 1 for the conical support of an APU compressor housing, comprising: A vacuum welding cavity 10 is externally connected to a vacuum acquisition device 100; The electron beam emission system 11 includes a generating device and an emission gun connected to the generating device, with the emission gun facing the interior of the vacuum welding chamber 10. The workpiece posture adjustment platform 12 is fixedly installed inside the vacuum welding chamber 10; The weld seam visual tracking system 13 includes a camera installed inside the vacuum welding chamber 10 and aligned with the area to be welded. The weld seam visual tracking system 13 is signal-connected to the electron beam emission system 11 and the workpiece posture adjustment platform 12, and is used to automatically correct deviation according to the identified weld seam center position to ensure weld alignment. And a welding fixture 14, which is detachably mounted on the workpiece posture adjustment platform 12; The welding fixture 14 includes: The positioning chassis 140 is fixed on the workpiece posture adjustment platform 12; The intermediate support assembly 141 is disposed above the positioning chassis 140, including a top plate 1410 and a bottom plate 1411 disposed opposite to each other, and a support rod 1412 connecting the top plate 1410 and the bottom plate 1411. The support rod 1412 is provided with a plurality of pre-tightening units 143 evenly distributed along its circumference, and each pre-tightening unit 143 is used to apply pre-tightening force to the tapered support end face. The centering chuck 142 is installed on the side of the top plate 1410 away from the bottom plate 1411.

[0077] Specifically, the vacuum welding chamber 10 is a vertical quick-opening door structure or a horizontal structure, forming a sealed space inside to accommodate the APU compressor housing to be repaired and provide an oxygen-free welding environment. The outer wall of the vacuum welding chamber 10 is usually equipped with an observation window to monitor the internal condition, and has reserved maintenance ports and pipeline interfaces. The vacuum acquisition device 100 is a vacuum pump group or vacuum generation system, which is connected to the vacuum welding chamber 10 through pipelines to extract air from the chamber, so that the vacuum degree of the welding chamber reaches ≤5×10-2Pa and the vacuum degree of the gun chamber reaches ≤3×10-3Pa, thereby preventing the high-temperature alloy from absorbing oxygen and hydrogen during the welding process, resulting in embrittlement or porosity.

[0078] The workpiece posture adjustment platform 12 is a mechanical platform with multi-degree-of-freedom motion capability. In this embodiment, it is specifically a multi-axis rotary table, which is fixedly installed at the bottom inside the vacuum welding chamber 10. The workpiece posture adjustment platform 12 carries and adjusts the spatial posture of the welding fixture 14 so that the conical support to be welded is always at the optimal working distance and angle of the firing gun. When the weld direction changes, the platform can drive the workpiece to move or rotate, and in conjunction with the deflection scanning of the electron beam, complete the welding of complex trajectories.

[0079] The weld seam visual tracking system 13 is a detection module that integrates optical imaging and image processing functions. It includes a camera, which is installed inside the vacuum welding chamber 10 and aligned with the area to be welded. The camera is a high-temperature resistant and radiation-resistant industrial camera used to collect image information of the weld seam area in real time. The weld seam visual tracking system 13 is connected to the electron beam emission system 11 and the workpiece posture adjustment platform 12 to form a closed-loop control loop.

[0080] Its working principle is that the camera identifies the actual position of the weld center and transmits the deviation signal to the control system. The control system then drives the deflection coil in the electron beam emission system 11 to adjust the beam direction, or drives the workpiece posture adjustment platform 12 to fine-tune the workpiece position, thereby achieving automatic correction and ensuring that the weld is strictly aligned. This linkage mechanism effectively solves the problem that manual operation is difficult to correct weld offset in real time.

[0081] Please refer to Figure 5 The welding fixture 14 is a clamping auxiliary device designed specifically for APU compressor housings. It is detachably mounted on the workpiece posture adjustment platform 12, making it easy to replace according to different housing models. The main function of the welding fixture 14 is to provide a high-precision positioning reference and uniform clamping force to prevent the thin-walled housing from deforming under the action of welding thermal stress.

[0082] The positioning chassis 140 serves as the base for the welding fixture 14 and is fixed in conjunction with the workpiece posture adjustment platform 12. Each pre-tightening unit 143 is used to apply pre-tightening force to the tapered support end face. Its function is to eliminate the assembly gap between the inner shell and the outer shell before welding, and to prevent incomplete welding or burn-through caused by the existence of gaps. The intermediate support assembly 141, through the combination of the top plate 1410, the bottom plate 1411 and the pre-tightening unit 143, achieves adaptive fitting and uniform pressing of the part to be repaired.

[0083] The outer diameter of the centering chuck 142 is set to correspond to the inner diameter of the APU compressor housing, which is used to limit the radial runout of the housing.

[0084] Understandably, by setting up a weld seam visual tracking system 13 and linking it with the electron beam emission system 11, automatic centering of the weld seam is achieved, significantly improving the consistency and pass rate of welding. Since the pre-tightening unit 143 on the intermediate support assembly 141 can apply a uniform and adjustable pre-tightening force, the assembly gap between the tapered support end faces is effectively eliminated, avoiding welding incomplete fusion defects. Furthermore, the cooperation between the centering chuck 142 and the positioning base 140 limits the radial runout of the housing, thereby ensuring the welding coaxiality and meeting the high-precision assembly requirements of the APU compressor housing. The entire welding process is completed within the vacuum welding chamber 10, isolating air pollution and thus improving the mechanical properties and corrosion resistance of the weld seam.

[0085] Furthermore, the top plate 1410 and the bottom plate 1411 are provided with positioning pin holes 1413 corresponding to the pin holes of the inner shell or outer shell flange. The centering chuck 142 is provided with a plurality of limiting blocks 1420 evenly spaced along its axis. The outer diameter of the plurality of limiting blocks 1420 corresponds to the inner diameter of the APU compressor housing. After clamping, the radial runout of the housing is ≤0.05mm. The preload unit 143 includes a screw adjustment mechanism and an elastic element sleeved on the screw adjustment mechanism. The preload force of a single preload unit 143 is in the range of 10N-20N.

[0086] Specifically, the location of the positioning pin holes 1413 strictly corresponds to the original process pin hole positions on the inner and outer flanges of the APU compressor housing to be repaired, so as to achieve precise angular positioning of the housing on the tooling and prevent the housing from rotating or misaligning during the welding process.

[0087] The centering chuck 142 refers to the clamping device installed on the side of the top plate 1410 of the intermediate support assembly 141 away from the bottom plate 1411. It is used to clamp the inner or outer diameter of the housing to achieve radial centering. The limiting block 1420 is an independent component that constitutes the clamping claw of the centering chuck 142. Multiple limiting blocks 1420 are evenly spaced along the axis of the centering chuck 142, and the outer diameter formed by their outer contours corresponds to the inner diameter of the APU compressor housing. The number of limiting blocks 1420 can be adjusted according to the diameter of the housing. For example, it can be a three-jaw, four-jaw, or multi-jaw structure. This application embodiment does not make any special limitation in this regard.

[0088] The function of the elastic element is to provide buffering and constant preload compensation after the screw is locked, to avoid preload fluctuations caused by thermal expansion or vibration, and to prevent rigid contact damage to the housing surface. The preload of a single preload unit 143 is 10N-20N. This value is set according to the load-bearing capacity of the thin-walled structure of the APU compressor housing. It can ensure a tight fit at the tapered support to eliminate assembly gaps, and avoid excessive clamping force that could cause local deformation of the housing. The number of preload units 143 can be set according to the circumferential distribution of the support rods 1412, for example, four, six or eight evenly distributed along the circumference. This application embodiment does not make any special limitation on this.

[0089] It should be noted that, in order to better penetrate the electron beam into the inner shell and outer shell during welding, the top plate 1410 or the bottom plate 1411 needs to be disassembled accordingly, and the inner shell or outer shell needs to be installed on another plate to facilitate welding.

[0090] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0091] Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0092] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for welding repair of a conical support at an APU compressor housing, wherein the APU compressor housing includes an inner shell and an outer shell, and the connection between the inner shell and the outer shell is a conical support, characterized in that... Includes the following steps: S1. Locate the crack location through air tightness testing or PT penetration testing, cut the inner and outer shells of the APU compressor housing to expose the cracks on the inner and outer shells, grind and clean the cracks to be repaired until the component substrate is exposed, and then perform ultrasonic cleaning and drying. S2, the separated inner shell and outer shell are placed on the welding fixture in sequence, and the cracks on the separated inner shell and outer shell are repaired by vacuum electron beam welding. The repair of each crack includes three welding stages in sequence: tack welding, penetration welding and finishing welding. S3, After the inner shell and outer shell are welded separately, they are subjected to slow cooling under vacuum conditions; S4. After the inner and outer shells are taken out of the furnace, the welds are polished and ground, and PT penetration testing is performed. S5, if both the inner shell and the outer shell pass the inspection, the inner shell and the outer shell are re-welded along the conical support. The re-welding includes three stages: tack welding, penetration welding and finishing welding. If a part fails the inspection, the crack is repositioned and steps S2-S4 are repeated. S6, after the welding is completed, it is slowly cooled under vacuum conditions, and the weld is polished after it is taken out of the furnace. In step S2 and / or step S5, without breaking the vacuum conditions after the modification welding is completed, the electron beam is switched to defocusing mode to scan and heat the weld area to achieve in-situ local heat treatment. In the in-situ local heat treatment, the electron beam current is 5mA-8mA, a large-range circular scan is used, the scan amplitude is 2mm-5mm, the frequency is 50Hz-80Hz, the heating temperature of the weld area is controlled to 500℃-650℃, and the vacuum slow cooling time is 10min. In steps S2 and / or S5, different scanning waveforms are used depending on the welding stage: During the tack welding stage: a small-amplitude circular scan is used, with a scan amplitude of X=Y=0.2-0.3mm and a frequency of 100-120Hz; Penetration welding stage: Use transverse elliptical scanning with scanning amplitude X=0.3-0.5mm, Y=0.1-0.2mm, and frequency 80-100Hz; Repair welding stage: Use longitudinal elliptical scanning with scanning amplitude X=0.1-0.2mm, Y=0.3-0.5mm, and frequency 120Hz-150Hz; The welding current during the tack welding stage is 8-10 mA, and the focusing current is 520-540 mA; the welding current during the penetration welding stage is 14.5-16 mA, and the focusing current is 520-540 mA; the welding current during the finishing welding stage is 10-12 mA, and the focusing current is 550-570 mA. In step S2 and / or step S5, the process parameters for vacuum electron beam welding are: welding vacuum degree ≤ 5 × 10⁻⁶. -2 Pa, chamber vacuum degree ≤3×10 -3 Pa, accelerating voltage of 60kV, welding speed of 500-650mm / min, working distance of 325mm.

2. The welding repair method for the conical support of the APU compressor housing according to claim 1, characterized in that, In step S1, grinding and cleaning the crack to be repaired includes grinding and cleaning within a 20mm range on both sides of the crack to be repaired; in step S3 and / or step S6, slow cooling treatment includes slow cooling in a vacuum chamber for at least 30 minutes before filling with gas and removing from the furnace.

3. The welding repair method for the conical support of the APU compressor housing according to claim 1, characterized in that, In step S5, before re-welding the inner shell and outer shell along the tapered support, a heat-conducting liner is placed on the back of the weld seam to accelerate heat dissipation.

4. The welding repair method for the conical support of the APU compressor housing according to any one of claims 1-3, characterized in that, This method is applied to a welding repair device for the conical support of an APU compressor housing, comprising: A vacuum welding chamber, externally connected to a vacuum acquisition device; An electron beam emission system includes a generating device and an emission gun connected to the generating device, the emission gun being directed toward the interior of the vacuum welding chamber; A workpiece posture adjustment platform is fixedly installed inside the vacuum welding chamber; The weld seam visual tracking system includes a camera installed inside the vacuum welding chamber and aligned with the area to be welded. The weld seam visual tracking system is signal-connected to the electron beam emission system and the workpiece attitude adjustment platform, and is used to automatically correct deviations based on the identified weld seam center position to ensure weld alignment. And a welding fixture, which is detachably mounted on the workpiece attitude adjustment platform; The welding fixture mentioned above includes: A positioning chassis is fixed to the workpiece posture adjustment platform; An intermediate support assembly is disposed above the positioning chassis and includes a top plate and a bottom plate that are disposed opposite to each other and are detachable, and a support rod connecting the top plate and the bottom plate. The support rod is provided with a plurality of pre-tightening units evenly distributed along its circumference, and each pre-tightening unit is used to apply a pre-tightening force to the tapered support end face. A centering chuck is installed on the side of the top plate away from the bottom plate.

5. The welding repair method for the conical support of the APU compressor housing according to claim 4, characterized in that, The top and bottom plates are provided with positioning pin holes corresponding to the pin holes of the inner or outer shell flange. The centering chuck is provided with multiple limiting blocks evenly spaced along its axis. The outer diameter of the multiple limiting blocks corresponds to the inner diameter of the APU compressor housing. After clamping, the radial runout of the housing is ≤0.05mm. The preload unit includes a screw adjustment mechanism and an elastic element sleeved on the screw adjustment mechanism. The preload force of a single preload unit is 10N-20N.

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