Spot welding interlayer preparation method, welding method and aerospace vehicle suitable for diffusion welding

Abstract

The present application relates to the technical field of spacecraft welding, and particularly relates to a point-shaped welding interlayer preparation method suitable for diffusion welding, a welding method and a spacecraft. The point-shaped welding interlayer preparation method comprises the following steps: solder preparation; planning a printing path; inkjet printing a welding interlayer; setting inkjet printing parameters, depositing solder along the printing path to the surface of the solder point through inkjet printing to form a point-shaped welding interlayer precursor; point laser scanning solidification; setting laser scanning parameters, and heating the point-shaped welding interlayer precursor through point laser scanning, and obtaining a point-shaped welding interlayer after the solder solidifies. The present application realizes point-shaped welding of a curved surface structure of a precision structure and a large-area dense joint through inkjet printing technology, so as to solve the problems of insufficient precision, poor curved surface adaptability, low solidification efficiency, unstable joint quality and the like in the prior art.

Description

Technical Field

[0001] This invention relates to the field of spacecraft welding technology, specifically to a method for preparing a spot welding intermediate layer suitable for diffusion welding, a welding method, and a spacecraft. Background Technology

[0002] In the field of aerospace vehicles, most components are highly precise, irregular structures such as thin-walled fins, microchannels, and honeycomb structures, which are extremely prone to deformation, burn-through, and collapse. These irregular structures, due to their extremely thin walls and minute geometric features, are highly susceptible to deformation, burn-through, or collapse during manufacturing and use. Furthermore, the operation of spacecraft in extreme environments such as high temperature, high pressure, and vibration places stringent requirements on the airtightness, sealing performance, and dimensional accuracy of various components. Conventional welding techniques, due to concentrated heat input and excessive temperature gradients, are prone to structural damage and cannot meet the demands of practical applications.

[0003] To enable the manufacturing and use of this type of multi-layered, high-precision structural component, TLP diffusion welding (Transient Liquid Phase Bonding) is currently widely adopted. TLP diffusion welding is an important method for welding complex structural components of aerospace vehicles, especially structures with a large number of internal weld points. Its core is to place an intermediate layer containing a melting-reducing element between the base materials being welded. The intermediate layer is then heated to melt or form a liquid phase with the base materials. High-quality joint connection is then achieved through isothermal solidification and composition homogenization. The precise addition of solder (dimensional accuracy, positional accuracy, and amount added) is the prerequisite and key to achieving high-quality welding of the component.

[0004] Currently, TLP welding is mainly applied to planar structures and large-area, low-number joints. For large-area curved structures and high-precision, densely packed joints, the preparation of the intermediate layer presents significant challenges. Traditional methods for preparing intermediate layers on curved surfaces include intermediate layer cutting, electroplating, and screen printing. Cutting methods suffer from poor precision and low efficiency in creating complex patterns, and cannot replicate small-sized patterns. For discontinuous, densely packed point features, placement and positioning are difficult. While electroplating can produce thinner intermediate layers, it struggles with multi-component intermediate layers, has complex processes, high costs, difficulty in achieving localized pattern deposition, and significant material waste. Screen printing, while enabling simple patterning, suffers from low printing precision, poor control over intermediate layer thickness, and issues such as edge overflow and uneven thickness. Especially for multi-point discontinuous structures, it easily leads to missed spots, single-point detachment, and difficulty adapting to curved substrates. This results in uneven element diffusion during welding, causing cracks and porosity in the joint, failing to meet the stringent requirements of high-end manufacturing for welding precision and joint quality. Existing patent application US20250300127A1 discloses a method for forming diffusion soldering areas using inkjet metal printing and performing diffusion soldering. This method involves multiple inkjet printings of different metal inks followed by soldering, meeting the reliability and miniaturization requirements of high-end semiconductor packaging. However, this technology suffers from low curing efficiency and is difficult to adapt to micro-spot soldering of large-area, densely packed solder joints. These problems severely restrict the reliability and service life of aerospace vehicles. Therefore, a novel soldering method is urgently needed to meet the stringent requirements of curved structures for soldering precision and joint quality. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a spot-welded intermediate layer suitable for diffusion welding, a welding method, and a spacecraft. It utilizes inkjet printing technology to achieve spot welding of curved structures with precision features and large-area dense joints. This method is suitable for welding scenarios where the intermediate layer is made of dissimilar metals or difficult-to-weld metal joints, thereby solving problems such as insufficient precision, poor surface adaptability, low curing efficiency, and unstable joint quality in existing technologies.

[0006] The first part of this invention provides a method for preparing a dot-matrix intermediate layer suitable for diffusion soldering, comprising the following steps: Solder preparation: mixing an alloy material, dispersant, binder, and solvent to match the substrate to be soldered, to prepare an inkjet solder; the mass ratio of alloy material:dispersant:binder:solvent is (15-40):(1-3):(1-2):(55-80); Planning the printing path: matching the welding joint of the base material with the solder dots of the substrate to be soldered, and along the normal direction of the surface of the substrate to be soldered, performing thickness slicing according to the required inkjet printing layer thickness of the solder, the number of slices being designed according to the thickness of the welding joint, and the thickness of each slice being 10-20 μm; filling each solder dot of each layer using a following circular contour and a reciprocating method, and the inkjet printed line... Width is 50-100μm, overlap rate is 30-50%; Inkjet printing of welding intermediate layer: Set inkjet printing parameters, and deposit solder along the printing path onto the surface of solder points to form a dot-shaped welding intermediate layer precursor; Inkjet printing parameters are: printing speed is 10-30mm / s, nozzle diameter is 40-50μm, single layer printing thickness is 10-20μm; Dot laser scanning curing: Set laser scanning parameters, and use a dot laser to scan and heat the dot-shaped welding intermediate layer precursor point by point. After the solder cures, a dot-shaped welding intermediate layer is obtained; Dot laser scanning parameters are: continuous laser, power is 10W, scanning speed is 10-30mm / s, spot diameter is 40-50μm, scanning spacing is 30-50μm.

[0007] Furthermore, the welding base material is a single-curved double-layer plate structure or a rotating double-layer plate structure. The double-layer plate consists of a smooth single-curved base to be welded and a protruding plate containing a welding joint. The smooth single-curved surface is provided with solder points, which are circular, square or other geometric shapes.

[0008] Furthermore, the spacing between adjacent solder points is 1-4 times the single typical repeating size of the solder point, matching the cross-section of the weld joint along the normal direction of the curved surface.

[0009] Furthermore, the alloy material is an alloy powder containing welding powder that matches the weld joint and a melting point reducing element; wherein, the welding powder is one or a combination of nickel, titanium, copper, chromium, tungsten and zirconium, with a particle size of 0.3-30μm; the melting point reducing element is one of boron or silicon.

[0010] Furthermore, the solvent is one or a combination of water, ethanol, ethylene glycol, glycerol, ethylene glycol ether, and ethylene glycol butyl ether.

[0011] Furthermore, the dispersant is one or more of the following: high-boiling-point alcohol ethers, polyols, lipids, and water.

[0012] Furthermore, the binder is one or more of the following: rosin, polyamide, hydrogenated castor oil, and acrylic resin.

[0013] Furthermore, the thickness of the spot-welded intermediate layer is 10-50μm, with an error of ≤5μm.

[0014] The second part of this invention provides a welding method, which uses the above-mentioned spot welding intermediate layer preparation method to perform dense spot discontinuous diffusion welding. The welding method includes: butt welding a substrate with a spot welding intermediate layer to a protruding plate with a welding joint to complete the assembly of the welding fixture; placing the welding fixture in a vacuum furnace and performing diffusion welding by segmented heating, wherein the first stage heating temperature is 200-450°C and the second stage heating temperature is 800-1500°C.

[0015] The third part of this invention provides an aircraft in which the welding of curved structures is performed using the welding method described above.

[0016] Based on the above solution, it can be seen that the technical solution of the present invention has at least one of the following beneficial effects compared with the prior art: This invention employs inkjet printing combined with laser scanning for diffusion welding, enabling precise patterned deposition of the intermediate layer. This effectively reduces post-weld debris, lowers subsequent cleaning costs, and significantly improves the TLP welding adaptability for complex curved structures. It provides a uniform channel for the diffusion of melting-reducing elements and base material elements during welding. Point laser scanning heating concentrates heat and enables precise local heating. The heating speed is fast, and the curing time is shortened by more than 90% compared to traditional thermosetting. This allows for rapid curing of the intermediate layer material while avoiding substrate deformation and intermediate layer material oxidation caused by overall heating. The cured intermediate layer is tightly bonded to the substrate, has high density, and is free of defects such as pores and cracks. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly described 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. In the drawings, the same or similar reference numerals represent the same or similar elements, wherein: Figure 1 This is a flowchart of the method for preparing the spot welding intermediate layer in this embodiment; Figure 2 This is a structural diagram of the single-curved double-layer plate of the welding matrix in this embodiment; Figure 3 This is a structural diagram of the rotating double-layer plate of the welding matrix in this embodiment; Figure 4 This is a planar structural diagram of the welding matrix in this embodiment; in, Figure 1-4 The correspondence between the reference numerals and component names in the attached drawings is as follows: 1. Base to be welded; 2. Welding joint; 3. Protrusion plate. Detailed Implementation

[0018] To better understand the technical solutions of the embodiments of the present invention, the embodiments of the present invention will be described in detail below.

[0019] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] The first part of this invention provides a method for preparing a spot welding intermediate layer suitable for diffusion welding, such as... Figure 1 As shown, it includes the following steps: Preparation of S1 solder: The alloy material matching the substrate to be soldered is mixed with a solvent to prepare the solder for inkjet printing; specifically, the alloy material matching the substrate to be soldered, the dispersant, the binder and the solvent are mixed to prepare the solder for inkjet printing; the mass ratio of the alloy material: the dispersant: the binder: the solvent is (15-40): (1-3): (1-2): (55-80); S2 Printing Path Planning: The printing path is planned based on the welding joint of the base material and the solder points on the substrate to be welded, with a matching design between the welding joint and the solder points. Specifically, the welding joint of the base material is matched with the solder points on the substrate to be welded. Along the normal direction of the surface of the substrate to be welded, thickness slices are made according to the required inkjet printing layer thickness of the solder. The number of slices is designed according to the thickness of the welding joint, with each slice thickness being 10-20 μm. Each solder point in each layer is filled using a circular contour-following and reciprocating method. The inkjet printing linewidth is 50-100 μm, and the overlap rate is 30-50%. S3 Inkjet Printing of Solder Intermediate Layer: Set inkjet printing parameters, and deposit solder along the printing path onto the surface of solder dots to form a dot-shaped solder intermediate layer precursor; the inkjet printing parameters are: printing speed of 10-30mm / s, nozzle diameter of 40-50μm, and single-layer printing thickness of 10-20μm. S4 Point Laser Scanning and Curing: The laser scanning parameters are set, and the point-to-point welding intermediate layer precursor is scanned and heated by a point laser. After the solder is cured, the point-to-point welding intermediate layer is obtained. The point laser scanning parameters are: continuous laser, power of 10W, scanning speed of 10-30mm / s, spot diameter of 40-50μm, and scanning spacing of 30-50μm.

[0021] This invention is the first to apply a composite process of inkjet printing and spot laser scanning curing to the preparation of the intermediate layer for diffusion soldering. Unlike traditional methods such as cutting, electroplating, and screen printing, it achieves non-contact, precise deposition and rapid local curing of the intermediate layer. Inkjet printing enables precise positioning and quantitative deposition of solder dots, avoiding the problems of overflow and leakage in traditional methods from the source, and significantly improving the position and dimensional accuracy of the intermediate layer. The flexible deposition characteristics of inkjet printing can be adapted to both planar and curved substrates, breaking through the limitation of traditional methods that are only applicable to simple planar structures. Local spot laser heating is used instead of overall heating to avoid substrate deformation and material oxidation, and the curing speed is significantly faster than traditional thermosetting methods.

[0022] In the above embodiments, such as Figure 2 and Figure 3 As shown, the welding base material is a single-curved double-layer plate structure or a rotating double-layer plate structure. The double-layer plate consists of a smooth single-curved substrate 1 to be welded and a raised plate 3 containing a welding joint 2. The smooth single-curved surface has solder points, which are circular, square, or other geometric shapes. The spacing between adjacent solder points is 1-4 times the typical repeating size of a single solder point, matching the cross-section of the welding joint along the normal direction of the curved surface. This invention is specifically adapted to the precision structures of typical single-curved or rotating double-layer plates in the aerospace field, solving the problems of difficult intermediate layer mounting, poor adhesion, and low welding strength that occur when using traditional welding methods for such curved surface structures. The precise matching of the solder point shape and spacing with the welding joint cross-section ensures complete adhesion between the intermediate layer and the joint during welding, improving the joint's airtightness and strength. The 1-2 times size interval between adjacent solder points ensures welding connection strength while avoiding solder accumulation and uneven diffusion, reducing welding defects.

[0023] In the above embodiments, this method also uses a planar double-layer plate structure, such as... Figure 4 As shown, the double-layer plate consists of a smooth, single-curved substrate 1 to be welded and a raised plate 3 containing a weld joint 2. Adjusting the inkjet parameters in processes that meet curved surface requirements also applies to flat surface requirements.

[0024] In the above implementation method, a welding requirements analysis is required before implementation: clarifying the material of the base material, the shape of the weld joint (circular / square, etc.), the design feature dimensions of the joint, the target thickness of the intermediate layer, and the positional accuracy requirements. The alloy material is an alloy powder containing welding powder and a melting point reducing element that matches the welding joint; wherein, the welding powder is one or a combination of nickel, titanium, copper, chromium, tungsten, and zirconium, with a particle size of 0.3-30μm; the melting point reducing element is either boron or silicon. The alloy powder material is generally selected as Ni-Cr-B, Ni-Cr-W alloy powder, and TC4 titanium alloy. Matching the welding powder with the welding joint material ensures welding strength. Boron and silicon, as highly efficient melting point reducing elements, can precisely control the liquid phase generation temperature and time, adapting to the TLP diffusion welding process. Selecting a powder with a particle size of 0.3-30μm balances the smoothness of inkjet printing with the density of the intermediate layer after curing, avoiding the problem of large particles clogging the nozzles, while excessively small particles may cause dispersion difficulties in solder preparation. In practical applications, as long as the welding strength is guaranteed, the melting point reducing element may not need to be added as required.

[0025] In the above embodiments, the preparation of the solder includes: mixing the alloy material with a solvent, followed by high-speed stirring and ultrasonic dispersion to obtain the solder. The mass ratio of the alloy material to the solvent is 15-40:55-80; the solvent is one or more combinations of water, ethanol, ethylene glycol, glycerol, ethylene glycol ether, and ethylene glycol butyl ether. This preparation is based on a fundamental formulation, ensuring welding strength after the alloy solution is welded to the joint without adding other dispersants or binders. An environmentally friendly, volatile, and highly dispersible mixed solvent is selected, which is easy to remove and cure after printing, leaving no residual impurities that affect welding quality. The 15-40% alloy material content ensures welding strength, while the 55-80% solvent content ensures the required viscosity and flowability of the solder during inkjet printing.

[0026] In the above embodiments, the preparation of the solder also includes a dispersant and a binder. The preparation steps include: mixing the alloy material, dispersant, binder, and solvent, followed by high-speed stirring and ultrasonic dispersion to obtain the solder. The mass ratio of alloy material:dispersant:binder:solvent is 15-40:1-3:1-2:55-80. Since the solder solution cannot guarantee the welding strength after welding to the joint, a dispersant and binder need to be added. The dispersant improves the powder dispersibility and prevents agglomeration; the binder enhances the adhesion between the precursor and the substrate, preventing detachment after printing and increasing welding strength. Through precise control of the formula, the solder viscosity, surface tension, and other properties can be guaranteed to meet the requirements of high-precision inkjet printing.

[0027] In the above embodiments, the dispersant is one or more of high-boiling-point alcohol ethers, polyols, lipids, and water; the binder is one or more of rosin, polyamide, hydrogenated castor oil, and acrylic resin. The dispersant and alloy material are well-matched and have good dispersibility, and are not easily volatilized at high temperatures, ensuring stable dispersion during the printing process; the selection of the binder ensures enhanced bonding during curing and complete decomposition without residue during welding.

[0028] In the above implementation, S2 plans the printing path, including: S21: Design the solder joint according to the welding joint; ensure that the two are perfectly matched and improve the welding accuracy.

[0029] S22: Along the normal direction of the surface to be soldered, perform thickness slicing according to the inkjet printing layer thickness of the required solder. The number of slices is designed according to the thickness of the solder joint, and the thickness of each slice is 10-20μm. Slicing along the normal direction of the surface adapts to the changes in the curvature of the surface, ensuring that the surface substrate is printed evenly, without drips or leaks.

[0030] S23: Each solder point in each layer is filled by following the circular contour and reciprocating method. The line width of inkjet printing is 50-100μm and the overlap rate is 30-50%, which ensures that the solder points are dense and uniform and the edges are neat and burr-free.

[0031] In the above implementation, when planning the inkjet printing path, it is necessary to analyze the adverse factors of intermediate layer formation, including the coffee ring effect caused by the viscosity of the printed solder ink, and the matching of dot features with the machine tool movement speed. The actual printing compensation size is determined based on the solder joint characteristics (e.g., if the designed solder joint diameter D is considered, the actual printing diameter is 0.1~0.5 mm smaller than the solder joint diameter after diffusion). The single-layer printing thickness and number of prints are determined based on the target thickness (e.g., if the target thickness is 30μm, and a single-layer printing thickness of 10μm is selected, then 3 prints are required). The printing path filling method is adjusted according to the coffee ring effect to avoid solder joint edge overflow and center depression. Based on the solder joint shape characteristics and machine tool movement characteristics, each solder point is selected to be filled using either a periphery-following or reciprocating method, and the printing path and printing speed are set.

[0032] In the above embodiments, it is also necessary to perform pretreatment of the substrate to be welded. The specific process is as follows: cleaning the substrate to be welded includes grinding, washing and drying. Among them, 1000-2000 grit sandpaper is used for grinding, and anhydrous ethanol, deionized water, acetone or pickling solution are used for ultrasonic cleaning in sequence to remove the surface oxide layer and oil stains, etc., and then the substrate is dried and cooled to room temperature for later use.

[0033] In the above embodiments, when inkjet printing the intermediate welding layer, the inkjet printing parameters are set as follows, based on the preset weld joint shape, the size of the dot-matrix intermediate welding layer, and the solid content of the solder ink: printing speed 10-30 mm / s, nozzle diameter 40-50 μm, and single-layer printing thickness 10-20 μm. After each layer is printed, whether to use dot laser scanning for heating and curing can be selected according to the state of the solder ink. For multi-layer printing, if the ink has high fluidity, the cumulative stacking of multiple layers will affect the pattern accuracy; therefore, dot laser scanning for heating and curing is used after each layer is printed.

[0034] In the above embodiment, during point laser scanning curing, the point laser scanning parameters are set according to the solvent type and solid content of the solder ink: continuous laser, power 10W, scanning speed 10-30mm / s, spot diameter 40-50μm, and scanning spacing 30-50μm. The point laser is used to scan and heat the pattern of the intermediate solder layer point by point, with the scanning path consistent with the printing path. This allows the solvent in the intermediate solder layer to evaporate quickly, preventing excessively thick multi-layer printing that could lead to ink flow problems and low precision in the shape of the intermediate solder joint.

[0035] In the above embodiments, the thickness of the dot-matrix welding intermediate layer is 10-50 μm, with an error ≤5 μm. The thickness requirement must meet the welding strength requirements of aerospace devices, ensuring uniform diffusion and reducing problems such as overflow, joint voids, and cracks. This thickness error requirement is achievable with inkjet printing, far superior to traditional screen printing and cutting methods. Considering the special characteristics of curved surfaces, an inkjet printing loading process is adopted, combined with a high-precision motion stage and path planning based on the three-dimensional topography scanning of the substrate. This allows for precise control of the distance and movement speed between the inkjet nozzles and the substrate surface according to the curvature changes of the curved substrate, ensuring the uniformity of the solder thickness at each solder point on the curved surface. Since this application protects the fabrication scheme, only the operating parameters are protected; the specific structure and composition of the equipment are not described in detail. Furthermore, the inkjet equipment is implemented using existing technology; controlling the relevant parameters is sufficient to achieve the fabrication requirements of this application.

[0036] The second part of this invention provides a welding method for dense, discontinuous diffusion welding using the aforementioned method for preparing a spot-welded intermediate layer. The welding method includes: butt-jointing a substrate with a spot-welded intermediate layer to a raised plate with a weld joint, completing the assembly of the welding fixture; placing the welding fixture in a vacuum furnace for segmented heating to perform diffusion welding. The first stage heating temperature is the temperature for solvent removal, and the second stage heating temperature is the diffusion welding temperature. This diffusion welding method is specifically adapted for dense, discontinuous weld intermediate layers. Vacuum segmented heating achieves solvent removal and diffusion welding processes while avoiding impurity contamination. The dense, discontinuous welding balances connection strength and structural lightweighting, reduces heat input and deformation, and is suitable for mass production of high-end aerospace components.

[0037] In the above embodiment, the substrate to be welded with the dotted welding intermediate layer is precisely aligned with the protruding plate with the welding joint under the positioning of the tooling. The alignment is checked with a precision alignment device to ensure that the solder dots of the intermediate layer pattern are tightly attached to the welding joint. The tooling is used to fix and clamp the substrate, thus completing the welding tooling assembly process.

[0038] In the above embodiment, the segmented heating of the vacuum furnace specifically involves: placing the assembled butt joint structure into the vacuum furnace for segmented heating. The first stage of heating serves to remove the intermediate solvent layer. The first stage heating temperature is 10°C higher than the boiling point of the mixed solvent. For example, if the boiling point of the solvent diethylene glycol monobutyl ether is 230°C, the solvent removal temperature is set to 240°C. The second stage heating temperature is the diffusion welding temperature, referencing the optimal diffusion welding process specifications for different base materials. Generally, it is the same as the solution treatment temperature of the base material. Sometimes, a two-stage heating method is used, with heat treatment at two temperature points. For example, the diffusion welding temperature for GH3230 high-temperature alloy is 1200°C, held for 4 hours. For TC4 titanium alloy diffusion welding, the welding temperature is two-stage heating: the second stage temperature is 800°C, held for 10 minutes, and the third stage temperature is 940°C, held for 30 minutes. The vacuum degree of the vacuum furnace is 1×10⁻⁶. –3 ~3×10 –3 Pa.

[0039] The third part of this invention provides an aircraft in which the welding of curved structures is performed using the aforementioned welding method. This design is specifically tailored for the complex curved structures of spacecraft, meeting the requirements for high airtightness and high reliability under extreme environments.

[0040] The welding method of the present invention has the following significant beneficial effects.

[0041] 1. High precision and controllable patterning: Utilizing inkjet printing technology, precise patterning deposition of the intermediate layer can be achieved with a printing accuracy of ±2μm. The thickness of the intermediate layer is uniform and controllable, and can be precisely controlled between 10-50μm. It can perfectly match complex-shaped weld joints, especially weld surfaces with a large number of dense dot-like discontinuous features. It solves the problems of difficult patterning and low precision of traditional methods, effectively reduces post-weld waste, and lowers subsequent cleaning costs.

[0042] 2. Excellent adaptability to curved surfaces: For welding curved surfaces, an inkjet printing loading process is adopted, combined with a high-precision motion stage and path planning based on the three-dimensional topography scanning of the substrate. The distance between the inkjet nozzle and the substrate surface can be precisely controlled according to the curvature changes of the curved substrate, so as to achieve uniform, drip-free, and leak-free deposition of large-area dense dot-like discontinuous solder on the curved substrate, which greatly improves the TLP welding adaptability of complex curved surface structures.

[0043] 3. Facilitates element diffusion during welding: The uniform thickness and dense structure of the intermediate layer provide a uniform channel for the diffusion of demelting elements and base material elements during welding, avoiding the problem of uneven diffusion caused by the uneven thickness of traditional intermediate layers, reducing the generation of brittle phases in the joint, and significantly improving the strength and toughness of the welded joint.

[0044] 4. High curing efficiency and high quality: Point laser scanning heating is used, which concentrates heat and enables precise local heating. The heating speed is fast, and the curing time is shortened by more than 90% compared with traditional thermal curing. It can quickly cure the intermediate layer material, while avoiding substrate deformation and intermediate layer material oxidation caused by overall heating. The cured intermediate layer is tightly bonded to the substrate, with high density and no defects such as pores or cracks.

[0045] 5. High material utilization and low cost: Inkjet printing deposits intermediate layer material only in the preset pattern area, and the material utilization rate can reach more than 95%. Compared with methods such as mask electroplating and sputtering, it greatly reduces material waste. At the same time, the process steps are simple, without the need for complex molds or masks, resulting in high preparation efficiency and reduced production costs.

[0046] 6. Wide applicability: The composition and printing parameters of the intermediate layer ink can be flexibly adjusted according to different welding base materials, such as titanium alloys, aluminum alloys, nickel-based alloys, etc., to adapt to different TLP welding needs and is suitable for precision welding scenarios in a variety of high-end manufacturing fields.

[0047]

Example 1

[0048] (1) Welding requirements analysis: The base material for welding is a single-curved layered plate structure, such as Figure 2 As shown, the upper plate is a smooth, single-curved panel, and the lower plate is a raised plate containing circular welded joints. The welded joints are circular in cross-section along the normal direction of the curved surface, with a diameter of 1mm, a spacing of 2mm, and a quantity of 1000 joints. The welded joints are the weld points on the welding surface. Based on welding requirements, the thickness of the intermediate layer is determined to be 20µm. The intermediate layer is prepared using inkjet printing combined with laser curing, which meets the welding requirements.

[0049] (2) Pretreatment of the substrate to be welded: Clean the GH3230 nickel-based alloy substrate to be welded. Specifically, polish it with 1500 grit sandpaper until the surface is smooth. Then, use anhydrous ethanol and deionized water to ultrasonically clean for 15 minutes each to remove the surface oxide layer and oil stains. Then, put it in an 80℃ oven to dry for 15 minutes and take it out to cool to room temperature for later use.

[0050] (3) Preparation of solder for dot-matrix welding intermediate layer (i.e. preparation of ink for inkjet printing): The alloy material is Ni-Cr-B alloy powder with a particle size of 1-5µm; polyethylene glycol dimethyl ether is used as a dispersant; acrylic modified epoxy resin is used as a binder; ethanol and deionized water are mixed in a volume ratio of 1:1 as a solvent; the mixture is prepared by mixing 15% Ni-Cr-B powder, 3% polyethylene glycol dimethyl ether, 2% acrylic modified epoxy resin, 80% water and ethylene glycol mixed solvent (water / ethylene glycol: 3 / 7, v / v) by mass fraction, stirring and then ultrasonically dispersing to prepare a uniform and stable solder for inkjet printing with a viscosity of 10~30mPa·s.

[0051] (4) Planning the inkjet printing path: The solder dots are designed according to the size and layout of the welded joint. The typical shape of the dense, discontinuous, patterned solder dots is a circle with a diameter of 1 mm and a thickness of 20 μm. The spacing between the solder dots in the XY direction is 2 mm. The path planning first includes slicing the substrate surface in the normal direction according to the thickness of the inkjet printing layer, printing two layers. The thickness of a single layer is controlled to be 20 μm by the process (the thickness after laser heating and curing is about 10 μm). Each solder dot in each layer is filled twice by following the circular outline, and the inside is filled with straight lines back and forth. The printing line width is 100 μm and the overlap rate is 50%.

[0052] (5) Inkjet printing of welding intermediate layer and spot laser scanning curing: According to the preset welding joint pattern and solder points (circular, 1mm in diameter, 20μm in thickness), set to print 2 layers and perform spot laser scanning twice. Fix the pre-treated GH3230 substrate to be welded on the worktable of the inkjet printing equipment, set the printing parameters: printing speed 10mm / s, nozzle diameter 50μm, single layer printing thickness 20μm. After printing one layer, use the same equipment for laser scanning and heating, set the laser parameters: continuous laser, power 10W, scanning speed 10mm / s, spot diameter 50μm, scanning interval 40μm, and perform point-by-point scanning and heating along the printed pattern to quickly cure the precursor and obtain a patterned dot welding intermediate layer.

[0053] (6) Welding fixture assembly: The substrate to be welded with the dotted welding intermediate layer and the protruding plate with the welding joint are precisely aligned under the fixture positioning to ensure that the solder dots of the intermediate layer pattern are tightly fitted with the welding joint, and the fixture is used to fix and clamp them.

[0054] (7) Vacuum furnace segmented heating: The assembled butt joint structure is placed in a vacuum furnace for segmented heating. The first segment of segmented heating is for removing the intermediate layer solvent, and the heating temperature of the first segment is 200℃. The second segment of segmented heating is for diffusion welding, and the heating temperature is 1200℃. The temperature is maintained for 4 hours, and the vacuum degree is 1×10⁻⁶. –3 ~3×10 –3 Pa.

[0055] The patterned dot-matrix welding intermediate layer prepared in this embodiment has a printing accuracy of ±2μm, good thickness uniformity, and is dense and non-porous, forming a tight bond with the GH3230 substrate to be welded. When this intermediate layer is used for diffusion welding of GH3230 alloy, the elements diffuse uniformly during the welding process, there are no obvious foreign matter after welding, and the tensile strength of the welded joint reaches more than 92% of the strength of the base material.

[0056]

Example 2

[0057] (1) Welding requirements analysis: The base material for welding is a double-layer plate structure of revolution, such as Figure 3 As shown, the inner plate is a smooth, single-curved rotating plate, and the outer plate is a raised rotating plate with circular welded joints. The welded joints are circular in cross-section along the normal direction of the curved surface, with a diameter of 2mm, a spacing of 3mm, and a quantity of 3000 joints. The welded joints are the weld points on the welding surface. Based on welding requirements, the thickness of the intermediate layer is determined to be 30µm. The intermediate layer is prepared using inkjet printing combined with laser curing, which meets the welding requirements.

[0058] (2) Pretreatment of the substrate to be welded: The TC4 titanium alloy substrate to be welded is cleaned. Specifically, it is polished with 2000 grit sandpaper until the surface is smooth, and then ultrasonically cleaned with acetone and pickling solution for 10 minutes in sequence to remove surface oil and oxide film. After that, it is cleaned with ethanol and dried.

[0059] (3) Preparation of solder for dot-matrix welding intermediate layer (i.e. preparation of ink for inkjet printing): The alloy material is Ti-Zr-Cu-Ni alloy powder with a particle size of 0.3-2µm; polyester dispersant, hydrogenated castor oil as binder; diethylene glycol monobutyl ether as solvent; mix according to the mass fraction of 40% Ti-Zr-Cu-Ni powder, 1% polyester dispersant, 1% binder and 58% mixed solvent, stir at high speed for 40min, and ultrasonically disperse for 25min to prepare a uniform and stable solder for inkjet printing with a viscosity of about 10mPa·s.

[0060] (4) Planning the inkjet printing path: The solder dots are designed according to the size and layout of the welded joint. The typical shape of the dense, discontinuous, patterned solder dots is a circle with a diameter of 2 mm and a thickness of 30 μm. The spacing between the solder dots in the XY direction is 3 mm. The path planning first includes slicing the substrate surface in the normal direction according to the thickness of the inkjet printing layer, printing six layers, and controlling the thickness of each layer to 10 μm through the process (the thickness after laser heating and curing is about 5 μm). Each solder dot in each layer is filled twice following the circular outline, and then filled with straight lines back and forth inside. The printing line width is 50 μm and the overlap rate is 30%.

[0061] (5) Inkjet printing of welding intermediate layer and spot laser scanning curing: According to the preset welding joint pattern and solder points (circular, 2mm in diameter, 30μm in thickness), set 6 layers to be printed and 6 spot laser scans. Fix the pre-treated TC4 substrate to be welded on the worktable of the inkjet printing equipment, set the printing parameters: printing speed 20mm / s, nozzle diameter 50μm, single layer printing thickness 10μm. After printing one layer, use the same equipment for laser scanning and heating, set the laser parameters: continuous laser, power 10W, scanning speed 20mm / s, spot diameter 50μm, scanning interval 40μm, and scan and heat point by point along the printed pattern to make the precursor cure quickly and obtain a patterned dot welding intermediate layer.

[0062] (6) Welding fixture assembly: The substrate to be welded with the dotted welding intermediate layer and the protruding plate with the welding joint are precisely aligned under the fixture positioning to ensure that the solder dots of the intermediate layer pattern are tightly fitted with the welding joint, and the fixture is used to fix and clamp them.

[0063] (7) Vacuum furnace segmented heating: The assembled docking structure is placed in a vacuum furnace and segmented heating is carried out. The first segment of segmented heating is to remove the intermediate layer solvent. The heating temperature of the first segment is 240℃. The second and third segments of segmented heating are diffusion welding temperatures. The temperature of the second segment is 800℃ and held for 10 minutes. The temperature of the third segment is 940℃ and held for 30 minutes.

[0064] The patterned dot-matrix welding intermediate layer prepared in this embodiment has a printing accuracy of ±5μm, good thickness uniformity, and is dense and non-porous, bonding tightly with the TC4 substrate to be welded. When this intermediate layer is used for diffusion welding of TC4 alloy, the element diffusion is uniform during the welding process, the excess material after welding is reduced by more than 20%, and the tensile strength of the weld joint reaches more than 88% of the strength of the base material. The welding quality is significantly better than that of traditional methods.

[0065] In summary, the advantages of the embodiments of the present invention are as follows: 1. Scanning path planning for solder with a large number of dense, discontinuous, patterned features in the TLP welding process. The path planning includes layer thickness slices along the normal direction on the surface of the base material to be welded. The accuracy of each solder point in each layer is controlled by the reciprocating filling of the internal structure following the shape filling composite. The layer thickness accuracy is controlled by printing multiple times with small layer thicknesses.

[0066] 2. For the first time, inkjet printing and dot laser scanning were combined and applied to the preparation of the intermediate layer for TLP welding, achieving high-precision patterning and rapid uniform curing of the intermediate layer.

[0067] 3. The intermediate layer ink formula and process parameters have been optimized to ensure smooth inkjet printing and the quality of the cured intermediate layer, adapting to the welding requirements of different base materials.

[0068] 4. The combination of patterned design and precise thickness control reduces post-weld waste from the source, optimizes the welding diffusion process, and improves joint quality.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a spot welding intermediate layer suitable for diffusion welding, characterized in that, Includes the following steps: Solder preparation: The alloy material, dispersant, binder and solvent that are matched to the substrate to be soldered are mixed to prepare the solder for inkjet printing; the mass ratio of the alloy material: the dispersant: the binder: the solvent is (15-40): (1-3): (1-2): (55-80); Planning the printing path: Match the welding joint of the welding base material with the solder point of the substrate to be welded. Along the normal direction of the curved surface of the substrate to be welded, perform thickness slicing according to the inkjet printing layer thickness of the required solder. The number of slices is designed according to the thickness of the welding joint, and the thickness of each slice is 10-20μm. Each solder point in each layer is filled using a circular outline and a reciprocating motion, with an inkjet printing linewidth of 50-100μm and an overlap rate of 30-50%. Inkjet printing of intermediate solder layer: The inkjet printing parameters are set, and the solder is deposited on the surface of the solder dot along the printing path by inkjet printing to form a dot-shaped intermediate solder layer precursor; the inkjet printing parameters are: printing speed of 10-30mm / s, nozzle diameter of 40-50μm, and single-layer printing thickness of 10-20μm. Point laser scanning curing: The laser scanning parameters are set, and the point-by-point welding intermediate layer precursor is scanned and heated by a point laser. After the solder is cured, the point-by-point welding intermediate layer is obtained. The point laser scanning parameters are: continuous laser, power of 10W, scanning speed of 10-30mm / s, spot diameter of 40-50μm, and scanning spacing of 30-50μm.

2. The method for preparing a spot-welded intermediate layer according to claim 1, characterized in that, The base material for welding is a single-curved double-layer plate structure or a rotating double-layer plate structure. The double-layer plate consists of a smooth, single-curved substrate to be welded and a raised plate containing the weld joint; wherein, The smooth single-curved surface is provided with solder points, which are circular, square or other geometric shapes.

3. The method for preparing a spot-welded intermediate layer according to claim 2, characterized in that, The spacing between adjacent solder points is 1-4 times the single typical repeating size of the solder point, matching the cross section of the weld joint along the normal direction of the curved surface.

4. The method for preparing a spot-welded intermediate layer according to claim 1, characterized in that, The alloy material is an alloy powder containing welding powder that matches the weld joint and a melting point reducing element; wherein, The welding powder is one or a combination of nickel, titanium, copper, chromium, tungsten and zirconium, with a particle size of 0.3-30 μm; The melting point reducing element is either boron or silicon.

5. The method for preparing a spot-welded intermediate layer according to claim 1, characterized in that, The solvent is one or a combination of water, ethanol, ethylene glycol, glycerol, ethylene glycol ether, and ethylene glycol butyl ether.

6. The method for preparing a spot-welded intermediate layer according to claim 1, characterized in that, The dispersant is one or more of the following: high-boiling-point alcohol ethers, polyols, lipids, and water.

7. The method for preparing a spot-welded intermediate layer according to claim 1, characterized in that, The binder is one or more of the following: rosin, polyamide, hydrogenated castor oil, and acrylic resin.

8. The method for preparing a spot-welded intermediate layer according to claim 1, characterized in that, The thickness of the dot-welded intermediate layer is 10-50 μm, with an error of ≤5 μm.

9. A welding method, characterized in that, The method for preparing a spot-welded intermediate layer according to any one of claims 2-8 is used for dense spot-discontinuous diffusion welding, wherein the welding method includes: The substrate to be welded with the aforementioned dotted welding intermediate layer is joined with the protruding plate with the welding joint to complete the welding fixture assembly. The welding apparatus is placed in a vacuum furnace and subjected to segmented heating for diffusion welding. The first stage heating temperature is 200-450℃, and the second stage heating temperature is 800-1500℃.

10. An aircraft, characterized in that, The welding of the aircraft employs the welding method described in claim 9 for welding curved structures.

Images