Processing method for different intermetallic welding surfaces of special-shaped structure and welded joint

Abstract

This invention relates to the field of precision welding and special processing technology, specifically to a method for processing the weldable surfaces of different metals with irregular structures and a welded joint. The method includes the following steps: 1) Scanning the contour of the irregular inner cavity of the casting base material, designing the shape of the electrode for electrical discharge machining based on this contour, designing the working end of the electrode as a large trapezoidal structure combining a mountain peak shape and small trapezoids, and using this large trapezoidal electrode to perform electrical discharge machining on the inner cavity boss of the base material to form a sloping small step; 2) Prefabricating a deformable alloy plate according to the electrode contour and assembling it at the inner cavity step of the base material; 3) Removing the small trapezoidal electrode, using the mountain peak-shaped electrode to form a uniform V-shaped welding bevel at the joint between the small step of the base material and the deformable alloy plate, and precisely controlling the assembly gap between the two; 4) Polishing and cleaning the joint bevel in preparation for filler wire welding. This invention solves the problems of low assembly accuracy, poor bevel quality, and numerous welding defects in welding different metals with irregular structures.

Description

Technical Field

[0001] This invention relates to the field of precision welding and special processing technology, and more specifically, to a method for processing the surfaces to be welded between different metals with irregular structures and a welding joint. Background Technology

[0002] In the manufacturing and remanufacturing of high-end equipment such as modern aero-engines and gas turbines, there is a frequent need to join dissimilar metals, such as high-performance cast superalloys (e.g., IN738, Rene'108) components with high-ductility superalloys (e.g., Hastelloy X, Haynes 230) sheets. These joins are often used for the repair of high-temperature components, welding of wear-resistant liners, or assembly of complex components. Because the areas to be joined are often located in enclosed or semi-enclosed cavities with complex curved contours, such as blade crowns and combustion chamber walls, traditional processes face significant challenges. 1) Assembly matching accuracy is difficult to guarantee: The inner cavity of the casting is mostly an irregular curved surface. It is difficult to achieve a precise fit between the mating surface prepared by machining or manual methods and the plate. The assembly gap is uneven and difficult to control. Excessive local gap can easily lead to burn-through or lack of fusion during welding, while too small a gap may cause a sharp increase in welding stress due to the difference in thermal expansion.

[0003] 2) Poor mechanical properties of the joint structure: Due to space and accessibility limitations, such joints are usually designed as corner joints or lap joints. These joints have inherent stress concentration problems, and under the influence of differences in the thermophysical properties of dissimilar materials (such as coefficient of thermal expansion and thermal conductivity), cracks are prone to initiation at the weld root and heat-affected zone, which seriously affects the reliability of the joint under high temperature and alternating loads.

[0004] 3) The contradiction between machinability and precision: For irregularly shaped areas such as deep cavities and narrow slits, subtractive machining methods such as CNC milling are limited by tool length, diameter and interference, making it difficult to achieve precise forming; while manual repair is inefficient, inconsistent and the quality depends too much on the operator's experience.

[0005] 4) Poor adaptability to welding processes: Fillet welds or lap welds require the welding torch to be adjusted at multiple angles, making operation extremely difficult in space-constrained areas. Furthermore, to penetrate the root, a large welding heat input is often required, which can easily lead to overheating of the cast base material, grain coarsening, or precipitation of harmful phases, while also exacerbating welding deformation.

[0006] In the existing technology, although precision machining and manual lamination are commonly used to address the above problems, they have limitations: long processing cycle, high cost, easy to introduce deformation for complex curved surfaces and thin-walled parts, and unstable final assembly quality, which affects the performance and quality of welded joints.

[0007] Therefore, there is an urgent need to develop an integrated processing method and specialized tools that can systematically solve the challenges of "high-precision matching of irregular internal cavities", "optimization of joint mechanical configuration" and "adaptation to efficient and precise welding processes". Summary of the Invention

[0008] To overcome the problems of long processing cycles, high costs, easy deformation of complex curved surfaces and thin-walled parts, unstable assembly quality, and impact on the performance and quality of welded joints in existing technologies, this invention aims to provide a method for processing the welding surfaces of different metals in irregular structures and a welded joint. This method, through an innovative combined electrode design and step-by-step EDM process, fundamentally transforms traditionally difficult-to-weld corner / lap joints into easily controllable and high-performance V-type butt joints, thereby achieving high-precision and highly reliable connections between different metals in irregular internal cavity structures.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for processing weldable surfaces between dissimilar metals with irregular shapes includes the following steps: S1: Electrode design and machining: Scan the irregular inner cavity contour of the casting base material, and offset the inner cavity contour by 0.1~0.3mm at equal intervals according to the scanning data to form the electrode outer surface; Based on the electrode outer surface, design and machine a large trapezoidal combined electrode with a small trapezoid-peak structure, wherein the peak structure includes a top surface for controlling the welding assembly gap, a peak slope surface for forming the welding bevel, and an edge platform that forms a uniform height small step on the upper surface of the boss; S2: Base material pre-processing: Using a combined large trapezoidal electrode, the base material to be welded area is subjected to one electrical discharge machining to form a small step with a slope on the inner cavity boss of the base material. S3: Plate prefabrication and assembly: Based on the electrode outline, process the deformable alloy plate and assemble it onto the stepped sidewall formed in S2, ensuring that the plate end face fits the stepped sidewall. S4: Bevel EDM and Gap Control: Remove the small trapezoidal electrode, keep the mountain peak structure electrode posture unchanged, and use the mountain peak structure electrode to perform secondary EDM on the edge of the assembled deformable alloy plate and the side wall of the base material step. Use the mountain peak slope to form a uniform V-shaped welding bevel in one step. The assembly gap between the deformable alloy plate and the side wall of the base material step is 0.1~0.5mm. S5: Welding preparation: Polish and clean the V-shaped bevel processed in S4 to prepare for filler wire welding.

[0010] A further improvement of the present invention is that the combined large trapezoidal electrode is made of copper material, and its working end includes a small trapezoidal structure segment and a mountain peak structure segment; the outer surface of the combined large trapezoidal electrode is a contoured surface formed by offsetting the irregular inner cavity contour of the parent material by 0.1~0.3mm at equal intervals.

[0011] A further improvement of the present invention is that the small trapezoidal structural segment is detachable, its top surface is flush with the top surface of the mountain peak structural segment electrode, its height matches the thickness of the deformable alloy plate to be assembled, and the electrode outline matches the width of the deformable alloy plate to be assembled.

[0012] A further improvement of the present invention is that the mountain peak structure segment is located outside the small trapezoidal structure segment and includes: a top surface with a width a1 of 0.1~0.5mm and a peak height b1 of 1~3mm. This electrode is used for positioning and tool setting, and for controlling the final assembly gap between the plate and the inner wall of the base material to be 0.1~0.5mm during secondary electrical discharge machining; the mountain peak slope is a symmetrical plane, used for electro-erosion to create a V-shaped welding groove, with an included angle θ of 40~80°; an edge platform located at the bottom of the mountain peak slope with a width a2 of 1~5mm, and a chamfer with a radius r of 0.5~3mm at its corner, used to smooth the upper surface of the boss and form a small step of uniform height during primary electrical discharge machining; the electrode mountain peak structure is double-peaked or multi-peaked, and the peak spacing a3 is determined according to the inner cavity size of the component.

[0013] A further improvement of the present invention is that the mass percentage of Al and Ti in the casting base material is 3% to 8%; and / or, the mass percentage of Al and Ti in the deformation alloy plate is 0% to 1%, and its thickness b2 is 1 to 3 mm.

[0014] A further improvement of the present invention is that, in S3, the edges of the plate are ground before assembly; during assembly, the plate is pressed tightly against and fixed to the bearing surface and side wall of the small step.

[0015] A further improvement of the present invention is that, in S2 and S4, during electrical discharge machining, the discharge gap between the outer surface of the electrode and the inner wall of the base material is 0.1~0.3mm.

[0016] A further improvement of the present invention is that, in S5, the filler wire welding is performed using argon arc welding or plasma welding, and the composition of the welding wire used is the same as that of the deformable alloy plate.

[0017] A welded joint between different metals with an irregular structure, which is processed according to the method described above, wherein the different metals include an irregular casting base material and a deformation alloy plate. The base material is provided with an assembly positioning step processed by a trapezoidal electrode structure. The plate is assembled on the bearing surface and side wall of the step. The plate and the base material are welded together by a V-groove welded by a mountain peak electrode structure. The assembly gap between the two is 0.1~0.5mm.

[0018] A further improvement of the present invention is that the angle of the V-shaped bevel is 40~80°.

[0019] Compared with the prior art, the present invention has at least the following beneficial technical effects: This invention creatively designs a combined electrode that integrates multiple functions, including a "contour reference," a "prefabricated step forming device," a "gap controller," and a "one-time beveling forming device." Through two precise electrical discharge machining processes, the originally separate assembly surface preparation and beveling processes are seamlessly integrated, realizing the direct transformation from irregular internal cavities to high-quality mating joints.

[0020] This invention achieves sub-millimeter precision assembly control: through precise scaling design of electrode outer surface (offset discharge gap) and precise dimensional control of mountain peak structure top surface, a uniform assembly gap of 0.1~0.5mm can be stably achieved on complex curved surfaces, laying a solid foundation for subsequent low heat input and high-quality welding.

[0021] This invention transforms corner / lap joints, which are prone to stress concentration, into V-shaped butt joints with a more reasonable stress distribution. This structure not only facilitates vertical welding with a welding torch and simplifies the process, but also allows for a smaller welding heat input, significantly reducing the tendency for hot cracking, deformation, and thermal damage to the base material during welding of dissimilar materials, and greatly improving the high-temperature strength and fatigue performance of the joint.

[0022] This invention leverages the non-contact nature and absence of macroscopic cutting forces inherent in electrical discharge machining (EDM), making it unrestricted by tool rigidity and accessibility limitations. This makes it particularly suitable for machining complex internal cavities such as engine blades. The process is digitally controlled, ensuring high repeatability and overcoming the instability of manual operation, significantly improving yield and the consistency of repair quality. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the combined electrode structure in this invention.

[0025] Figure 2 for Figure 1 Enlarged view of point A in the middle.

[0026] Figure 3 for Figure 2 Enlarged view of point B in the middle.

[0027] Figure 4 This is a schematic diagram of the prefabricated sheet material in Example 1.

[0028] Figure 5Here is a schematic diagram of electrical discharge machining in Example 1: (a) A large trapezoidal combined electrode is used to machine the inner cavity boss of the base material to form a small step with a slope; (b) The small trapezoidal electrode is removed and a mountain peak structure electrode is used to machine the butt joint bevel.

[0029] Figure 6 In the middle (a) and (b), respectively, welding schematic diagrams of Example 1 and Comparative Example 1 are shown.

[0030] Figure 7 In the middle (a)-(c), the macroscopic morphology of the welded joints of Examples 1, 2 and Comparative Example 1 are respectively.

[0031] Explanation of reference numerals in the attached figures: 1-Mountain peak top surface; 2-Mountain peak slope surface; 3-Edge platform; 4-Outer surface; 10-Casting base material; 20-Deformation alloy plate; 30-Mountain peak-shaped electrode; 40-Small trapezoidal electrode; 50-V-type welding groove. Detailed Implementation

[0032] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0033] In the description of this invention, it should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0034] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0036] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0037] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0038] In a first aspect, the present invention provides a method for processing weldable surfaces between different metals with irregular structures and a welded joint, comprising the following steps: S1: Three-dimensional data acquisition and electrode design and fabrication The contour data of the irregular inner cavity of the casting base material is obtained using a 3D scanning device; the contour is offset inward by a discharge gap value (preferably 0.1~0.3mm) to form the design reference for the electrode outer surface; based on this reference, a special electrode with a combined large trapezoidal structure at the working end is designed and processed. The electrode consists of a detachable small trapezoidal structure segment and an outer mountain peak structure segment; the mountain peak structure segment includes at least a top surface for positioning, a symmetrical slope surface for forming a V-shaped bevel, and an edge platform for forming a flat bearing step in one processing step; S2: Pre-processing of base material and positioning step forming Using the combined large trapezoidal electrode, the first electrical discharge machining is performed on the welding area of ​​the base material (usually the inner cavity boss). By utilizing the outer surface and edge platform of the electrode, a small inclined step with a flat bearing surface and sidewall that matches the electrode contour is machined on the boss. S3: Panel Prefabrication and Assembly Based on the electrode surface data, prefabricate the deformable alloy plate and assemble it onto the small step sidewall described in S2 to ensure that the end face of the plate is initially attached to the step sidewall. S4: Precision machining of beveling and final clearance control Remove the small trapezoidal structure segment, keep the electrode posture of the mountain peak structure segment unchanged, and use its mountain peak slope to perform a second electrical discharge machining on the edge of the assembled plate and the side wall of the base material step, so as to simultaneously process a uniform V-shaped welding groove in one go, and precisely control the final assembly gap between the plate and the side wall of the base material within the range of 0.1~0.5mm. S5: Welding Preparation The V-groove after processing is polished and cleaned, and then welded using filler wire welding (such as argon arc welding or plasma welding). During welding, the axis of the welding torch can be basically perpendicular to the groove surface, making the operation simple.

[0039] In a second aspect, the present invention provides a combined large trapezoidal electrode for implementing the above method, wherein the working end is composed of a detachable small trapezoidal structural segment and a mountain peak structural segment fixed on the periphery.

[0040] The outer surface of the electrode is designed with equidistant offset based on the inner cavity contour of the base material to ensure the discharge spark machining gap.

[0041] The top surface of the small trapezoidal structure segment is flush with the top surface of the mountain peak structure segment. Its height matches the thickness of the plate to be assembled, and its outline width matches the assembly width of the plate, so as to reserve assembly space for the plate in the first processing.

[0042] The mountain peak structure segment includes: 1) Top surface: 0.1~0.5mm wide, used for positioning and tool setting reference in electrical discharge machining.

[0043] 2) Mountain slope surface: symmetrically arranged with an included angle of 40~80°, used for electro-erosion forming of V-shaped welding grooves.

[0044] 3) Edge platform: Located at the bottom of the slope, with a width of 1~5mm and a chamfer of 0.5~3mm at the corner, used to flatten the upper surface of the boss and form a positioning step of uniform height in one processing.

[0045] 4) The electrode peaks can be double-peak or multi-peak structures, and the peak spacing a3 is determined according to the internal cavity size of the component.

[0046] Preferably, the electrode is made of copper.

[0047] Preferably, the mass percentage of Al and Ti in the casting base material is 3% to 8%; and / or, the mass percentage of Al and Ti in the deformation alloy plate is 0% to 1%, and its thickness b2 is 1 to 3 mm.

[0048] Preferably, the edges of the plate are polished before assembly; during assembly, the plate is pressed tightly against and fixed to the bearing surface and side wall of the small step.

[0049] Preferably, the discharge gap between the outer surface of the electrode and the inner wall of the base material is 0.1~0.3mm.

[0050] Preferably, the plate and the base material are connected by a V-groove weld formed by the mountain peak electrode structure, and the assembly gap between the two is 0.1~0.5mm.

[0051] Preferably, the filler wire welding is performed using argon arc welding or plasma welding, and the composition of the welding wire used is the same as that of the deformable alloy plate.

[0052] Preferably, the angle of the V-shaped bevel is 40~80°.

[0053] Example 1 The base material of the casting to be welded is an IN738 cast high-temperature alloy blade, with an Al and Ti mass percentage of approximately 5.5%, which falls within the range of 3% to 8% as described in claim 3. The area to be repaired is the side of the irregularly shaped boss within the inner cavity of the blade crown.

[0054] Deformation alloy sheet: Hastelloy X deformation alloy sheet, wherein the mass percentage of Al and Ti is <0.5%, which is within the range of 0% to 1% in claim 3; the sheet thickness b2 is 1.5 mm, which is within the range of 1 to 3 mm in claims 2 and 3.

[0055] Processing steps: S1: Electrode Design and Fabrication The three-dimensional data of the irregular inner cavity contour of the blade crown was accurately obtained using a blue light 3D scanner. Based on the scan data, the inner cavity contour surface was offset inward by 0.2 mm at equal intervals to generate the design reference for the electrode outer surface (4).

[0056] Based on this benchmark, a large trapezoidal composite electrode with a small trapezoid-peak structure was designed and fabricated (see...). Figure 1 The specific parameters of the electrode are as follows: 1) Mountain peak structure segment (30): Top surface width a1 = 0.2mm Peak height b1 = 1.5mm The angle θ between the slopes of the mountain peak is 60°. Edge platform width a2 = 1.5mm Platform corner chamfer radius r = 1mm 2) Small trapezoidal structure segment (40): Its top surface is flush with the top surface of the mountain peak structure segment, its height matches the thickness of the deformable alloy plate (1.5mm), its outer contour matches the width of the plate to be assembled, and it is designed to be detachable.

[0057] 3) Electrodes are made of copper.

[0058] S2: Pre-processing of base material The assembled trapezoidal electrode is installed on an electrical discharge machining (EDM) machine. The electrode posture is adjusted so that its outer surface (4) and the area to be machined in the inner cavity of the base material (10) maintain a discharge gap of approximately 0.2 mm. An EDM process is performed. After machining, a small step with a beveled surface corresponding to the electrode contour is formed on the inner cavity boss of the base material (see [link to EDM machine]). Figure 5 The edge platform (3) of the bearing surface electrode of the step is formed by electro-erosion, and the sidewall is formed by the sloping surface (2) of the electrode.

[0059] S3: Panel Prefabrication and Assembly Based on the electrode outline (4) contour data generated in S1, Hastelloy X-deformed alloy sheet (20) is precisely prefabricated by five-axis milling, and its thickness is consistent with the height of the trapezoidal electrode (see Figure 4 Before assembly, the edges of the plate to be welded are manually ground. Then, the plate (20) is assembled onto the small step processed by S2, lightly pressed and ensured that its end face fits against the side wall of the step, and pressed and fixed to the bearing surface and side wall of the step.

[0060] S4: Beveling Electrical Discharge Machining and Clearance Control Remove the small trapezoidal structure segment from the electrode, leaving only the mountain peak structure segment. Keep the electrode's posture and position on the machine tool unchanged. Using this mountain peak structure electrode, perform a second electrical discharge machining (EDM) on the edge of the assembled plate (20) and the step sidewall of the base material (10). During machining, the mountain peak slope surface (2) of the electrode is used to simultaneously erode the plate and the base material, forming a uniform V-shaped welding groove (50). At the same time, by controlling the feed of the top surface (1) of the electrode, the final assembly gap between the plate and the step sidewall of the base material is precisely controlled to be 0.2 mm, and the V-shaped groove angle after machining is 60° (see Figure 5 ).

[0061] S5: Welding Polish and clean the V-groove machined by S4. Use pulsed TIG welding with filler wire of the same composition as the Hastelloy X-shaped alloy sheet. During welding, keep the welding torch axis basically perpendicular to the groove surface, and use a welding current of 85A (see...). Figure 6 ).

[0062] Example 2 The base material of the casting to be welded is the installation edge (irregular curved surface) of the transition section of the combustion chamber of Rene108 cast high-temperature alloy, and its Al+Ti content meets the requirements of claim 3.

[0063] Deformation alloy sheet: Haynes 230 deformation alloy sheet, 2.0 mm thick, with Al+Ti content meeting the requirements of claim 3.

[0064] Processing steps: S1: Scan the irregular mounting edge contour of the Rene108 base material, offset by 0.15mm to form the electrode outer surface. Design and fabricate a combined large trapezoidal electrode, with the peak structure segment parameters set as follows: a1=0.3mm, b1=2.0mm, θ=50°, a2=2.0mm, r=1.5mm. The height of the small trapezoidal structure segment matches the plate thickness (2.0mm).

[0065] S2: Use a complete electrode to perform an electrical discharge machining on the mounting edge of the base material to form a prefabricated step.

[0066] S3: Prefabricate Haynes 230 deformable alloy plates according to the electrode outline data, grind the edges, assemble them onto the steps, and fix them in place.

[0067] S4: Remove the small trapezoidal structure segment and perform secondary EDM using a mountain-shaped electrode. The final assembly clearance is controlled at 0.25mm, and a 50° V-shaped bevel is machined.

[0068] S5: After polishing and cleaning the bevel, plasma filler wire welding is used to complete the welding. The composition of the welding wire is consistent with that of the deformation alloy plate.

[0069] (Optional extension): For longer welds, the electrode peak structure can be designed as a double-peak or multi-peak continuous structure to form a longer continuous V-groove in one processing stroke, further improving efficiency.

[0070] Comparative Example 1 (Traditional Method): Using traditional manual methods: relying on experience, the inner cavity bosses of the blades are manually ground and the deformable alloy plates are fitted to form corner joints, followed by conventional corner welding (see...). Figure 6 ).

[0071] Effect comparison: like Figure 7 As shown, the welds obtained in Examples 1 and 2 are uniform and continuous, with no defects such as lack of fusion or porosity inside, and the good microstructure endows them with excellent mechanical properties. Compared with Example 1, the weld obtained in Example 2 has a larger depth-to-width ratio, which is attributed to the higher energy density of plasma welding, which can greatly reduce heat input, thus improving welding performance. The weld in Comparative Example 1 has an irregular appearance and contains local lack of fusion and cracks, which seriously affects the performance of the welded joint and may even lead to the scrapping of the welded part.

[0072] In summary, this invention, through its innovative combined large trapezoidal electrode design and step-by-step processing technology, deeply integrates electrical discharge machining (EDM) precision forming with optimized weld joints, systematically solving problems such as low assembly accuracy, poor bevel quality, and weak joint performance in welding dissimilar metals with irregular structures. This method is particularly suitable for the precision repair and manufacturing of high-temperature components in high-end equipment such as aerospace engines and gas turbines, possessing extremely high practical value and promising prospects for widespread application.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0074] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for processing weldable surfaces between dissimilar metals with irregular shapes, characterized in that, Includes the following steps: S1: Electrode design and machining: Scan the irregular inner cavity contour of the casting base material, and offset the inner cavity contour by 0.1~0.3mm at equal intervals according to the scanning data to form the electrode outer surface; Based on the electrode outer surface, design and machine a large trapezoidal combined electrode with a small trapezoid-peak structure, wherein the peak structure includes a top surface for controlling the welding assembly gap, a peak slope surface for forming the welding bevel, and an edge platform that forms a uniform height small step on the upper surface of the boss; S2: Base material pre-processing: Using a combined large trapezoidal electrode, the base material to be welded area is subjected to one electrical discharge machining to form a small step with a slope on the inner cavity boss of the base material. S3: Plate prefabrication and assembly: Based on the electrode outline, process the deformable alloy plate and assemble it onto the stepped sidewall formed in S2, ensuring that the plate end face fits the stepped sidewall. S4: Bevel EDM and Gap Control: Remove the small trapezoidal electrode, keep the mountain peak structure electrode posture unchanged, and use the mountain peak structure electrode to perform secondary EDM on the edge of the assembled deformable alloy plate and the side wall of the base material step. Use the mountain peak slope to form a uniform V-shaped welding bevel in one step. The assembly gap between the deformable alloy plate and the side wall of the base material step is 0.1~0.5mm. S5: Welding preparation: Polish and clean the V-shaped bevel processed in S4 to prepare for filler wire welding.

2. The method for processing the welding surfaces between different metals in an irregular structure according to claim 1, characterized in that, The combined large trapezoidal electrode is made of copper, and its working end includes a small trapezoidal structure segment and a mountain peak structure segment. The outer surface of the combined large trapezoidal electrode is a contoured surface formed by offsetting the irregular inner cavity contour of the base material by 0.1~0.3mm.

3. The method for processing the welding surfaces between different metals in an irregular structure according to claim 2, characterized in that, The small trapezoidal structure segment is detachable, its top surface is flush with the top surface of the mountain peak structure segment electrode, its height matches the thickness of the deformable alloy plate to be assembled, and the electrode outline matches the width of the deformable alloy plate to be assembled.

4. The method for processing the welding surfaces between different metals in an irregular structure according to claim 2, characterized in that, The mountain-shaped structural section is located outside the small trapezoidal structural section and includes: a top surface with a width a1 of 0.1~0.5mm and a peak height b1 of 1~3mm. This electrode is used for positioning and tool setting, and to control the final assembly gap between the plate and the inner wall of the base material to 0.1~0.5mm during secondary EDM; the mountain-shaped slope is a symmetrical plane used for electro-erosion to create a V-shaped welding groove, with an included angle θ of 40~80°; an edge platform located at the bottom of the mountain-shaped slope with a width a2 of 1~5mm, and a chamfer with a radius r of 0.5~3mm at its corner, used to smooth the upper surface of the boss and form a small step of uniform height during primary EDM; the electrode mountain-shaped structure is double-peaked or multi-peaked, and the peak spacing a3 is determined according to the inner cavity size of the component.

5. The method for processing the welding surfaces between different metals with irregular structures according to claim 1, characterized in that, The mass percentage of Al and Ti in the casting base material is 3% to 8%; and / or, the mass percentage of Al and Ti in the deformation alloy plate is 0% to 1%, and its thickness b2 is 1 to 3 mm.

6. The method for processing weldable surfaces between different metals in an irregular structure according to claim 1, characterized in that, In S3, the edges of the plate need to be polished before assembly; during assembly, the plate is pressed tightly against and fixed to the bearing surface and side wall of the small step.

7. The method for processing the welding surfaces between different metals in an irregular structure according to claim 1, characterized in that, In S2 and S4, during electrical discharge machining, the discharge gap between the outer surface of the electrode and the inner wall of the base material is 0.1~0.3mm.

8. The method for processing the welding surfaces between different metals in an irregular structure according to claim 1, characterized in that, In S5, the filler wire welding is performed using argon arc welding or plasma welding, and the composition of the welding wire used is the same as that of the deformable alloy plate.

9. A welded joint between dissimilar metals of an irregular shape, formed by the method according to any one of claims 1-8, characterized in that, Different metals include shaped casting base material and deformation alloy plate. The base material is provided with assembly positioning steps processed by trapezoidal electrode structure. The plate is assembled on the bearing surface and side wall of the step. The plate and the base material are connected by V-shaped groove welding processed by mountain peak electrode structure. The assembly gap between the two is 0.1~0.5mm.

10. The welded joint between dissimilar metals with an irregular structure according to claim 9, characterized in that, The angle of the V-shaped bevel is 40~80°.

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