Laser welding method based on embedded welding seam and sleeving structure

Abstract

The invention relates to a laser welding method based on an embedded welding seam and a sleeving structure, belongs to the technical field of metal welding, and is used for solving the technical problem that in an existing double-layer sleeving structure, the reliability and accessibility of embedded circumferential welding seam welding are poor. The method comprises the steps that surface cleaning and mechanical scraping of a to-be-welded area are conducted on a part of a double-layer sleeving structure; the part is rigidly clamped through a tool, so that the assembly clearance and the step difference of the welding seam area meet the preset requirements; laser is adopted to carry out intermittent positioning welding on the assembled welding seam; a turning type laser welding head is adopted to stretch into the structure, and laser welding is conducted on the embedded circumferential weld; and the welded workpiece is cleaned, and the welding seam quality is detected. An assembly system is established through acid pickling, mechanical scraping treatment, rigid clamping and positioned welding, so that the welding reliability is improved; meanwhile, by means of the turning type laser welding head, direct and stable welding of the weld joint in the closed space is achieved, and the accessibility of the embedded weld joint is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal welding, in particular to a laser welding method based on an embedded weld and a sleeved joint structure. BACKGROUND

[0002] The aluminum alloy double-layer sleeved joint structure has a wide application prospect in the fields of aerospace and precision instruments due to its excellent lightweight and high specific strength characteristics. The structure is usually formed by sleeving a cylinder and an end frame, and an enclosed embedded ring weld is formed inside. However, the special geometric form of the structure and the material characteristics of aluminum alloy bring severe challenges to high-quality and high-reliability welding.

[0003] The existing technology mainly faces two core problems: first, the accessibility of the embedded weld is poor, and second, the welding reliability is difficult to guarantee. First, because the weld is located in the enclosed annular gap between the two layers of the shell, the space is extremely small and the shielding is severe. The traditional direct laser welding gun or arc welding gun cannot directly enter and align the weld, and the conventional process is difficult to implement. Secondly, even if special paths are used to force welding, due to the inherent high reflectivity, high thermal conductivity and easy oxidation characteristics of aluminum alloy, energy coupling is unstable, and the molten pool flowability is poor during laser welding, resulting in high defect rate of pores and incomplete fusion in the weld, and poor consistency of weld forming and mechanical properties. SUMMARY

[0004] The purpose of the present application is to provide a laser welding method based on an embedded weld and a sleeved joint structure to solve one of the following technical problems existing in the prior art: poor reliability and accessibility of the embedded ring weld in the double-layer sleeved joint structure; low laser energy absorption and insufficient utilization efficiency in the embedded and unobservable enclosed space due to the combination of aluminum alloy high reflectivity and space constraints; poor weld quality consistency in the embedded and unobservable enclosed space due to the lack of stable and system-matched definition of yawing motion.

[0005] The purpose of the present application is mainly achieved by the following technical solutions:

[0006] In a first aspect, the present application provides a laser welding method based on an embedded weld, which is used for welding an embedded ring weld of an aluminum alloy double-layer sleeved joint structure, comprising:

[0007] Step 1: surface cleaning and mechanical scraping treatment of the parts of the double-layer sleeved joint structure in the area to be welded;

[0008] Step 2: rigidly clamping and fixing the parts of the double-layer sleeved joint structure with a tool, so that the assembly gap and step difference of the weld area meet the preset requirements;

[0009] Step 3, intermittent positioning welding is performed on the assembled weld seam by using a laser.

[0010] Step 4, a laser welding head of a folding type is extended into the internal structure to perform laser welding on the embedded ring weld seam.

[0011] Step 5, the welded workpiece is cleaned and the weld seam quality is detected.

[0012] Further, in Step 1, the mechanical scraping treatment is performed by scraping the front and back surfaces and the butt surface of the part to be welded along the same direction until the metal luster is exposed.

[0013] Further, in Step 1, the scraping width of the mechanical scraping treatment is 20-25 mm.

[0014] Further, in Step 1, the surface cleaning is performed by using pickling to clean the oil stains and excess substances on the surface of the part.

[0015] Further, in Step 2, the part is rigidly clamped and fixed by the flange and the top screw.

[0016] Further, in Step 3, the intermittent positioning welding is performed by using a handheld laser welding gun.

[0017] Further, in Step 4, before the welding starts, a smoke absorption device is started to perform air suction from the tail of the workpiece to remove the metal dust generated in the welding process.

[0018] Further, in Step 5, the weld seam quality detection includes radiographic testing and fluorescent penetration testing to evaluate the internal and surface quality of the weld seam.

[0019] Further, in the intermittent positioning welding, the length of the positioning weld seam is 20-30 mm, the interval is 100-150 mm, the laser power is 800 W, the laser spot width is 3 mm, and the protective gas flow is 10 L / min.

[0020] Further, in Step 4, the laser beam is applied with a deflection motion during the welding.

[0021] In the second aspect, the application further provides an aluminum alloy double-layer sleeve joint structure, which is welded by the laser welding method based on the embedded weld seam according to the first aspect.

[0022] In one or more technical solutions provided in the exemplary embodiments of the application, at least one of the following beneficial effects can be achieved.

[0023] (1) The technical scheme of the laser welding method based on the embedded weld in the application eliminates the main source of process fluctuation through the accurate and repeatable pickling and mechanical scraping treatment in step 1 and the assembly system established by rigid clamping and positioning welding in steps 2 and 3, improves the welding reliability, and at the same time, realizes direct and stable welding on the closed space weld by means of the folded laser welding head, improves the accessibility of the embedded weld, and ensures the certainty of process execution.

[0024] (2) In the technical scheme of the laser welding method based on the embedded weld in the application, the precise positioning and centering of step 4.1 ensures that the laser energy can be directly input and act on the metal to be welded to the maximum extent, avoids energy scattering and loss caused by centering deviation, and improves the effective energy absorption benchmark from the source; the angle offset of step 4.2 effectively avoids the mirror reflection energy loss caused by the high reflection characteristics of aluminum alloy by changing the light beam incidence direction, and guides the harmful reflection splash away from the light path, thereby protecting the effectiveness and integrity of the incident energy, directly improving the safe utilization rate of energy; the positive defocusing setting of step 4.3 optimizes the energy distribution form, promotes the transverse conduction and molten pool stability of heat under the premise of ensuring the penetration, reduces the evaporation loss and defect rework caused by excessive energy concentration, thereby optimizing the conversion efficiency of energy for forming high-quality welds, thereby improving the absorption rate and utilization rate of laser energy.

[0025] (3) In the technical scheme of the laser welding method based on the embedded weld in the application, the action range and symmetry of the light beam in the width direction of the weld are defined to ensure that the energy is uniformly applied with the weld center line as the axis; through the design of the tangent circle, the continuity of the scanning path and the energy superposition at the track center (weld center line) are realized, avoiding the possible center energy trough of linear scanning; the track size is linked with the basic optical parameter of the spot, so that the physical size of the deflection can adapt to different laser optical systems, ensuring the consistency and portability of the process principle; thereby, the consistency of the weld quality is improved.

[0026] (4) In the technical scheme of the aluminum alloy double-layer sleeve joint structure in the application, the welding scheme of the flange combined with the recess embedded joint is realized, the assembly self-positioning and gap preposition are realized, a stable and repeatable process interface is provided for laser welding, the weld is completely hidden in the structure, not only to protect the weld from the environment, but also to optimize the heat diffusion through the surrounding of the double-layer metal, reduce the welding deformation, form a continuous full penetration weld on the structure, and improve the strength, stiffness and sealing reliability of the connection.

[0027] The technical solutions in the present application can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent description, and some advantages will become apparent from the description, or will be understood by those skilled in the art through implementation of the present application. The objects and other advantages of the present application can be realized and obtained through the contents particularly pointed out in the description and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings illustrate exemplary embodiments of the present application and together with the general description given above, and the detailed description given below, serve to explain the principles of the application. These drawings should be understood as being merely illustrative, as the present application can be manifested in various forms.

[0029] Figure 1 is a flowchart of a laser welding method based on an embedded weld in an embodiment of the present application;

[0030] Figure 2 is a structural diagram of an aluminum alloy double-layer sleeve joint structure in an embodiment of the present application;

[0031] Figure 3 is a structural diagram of a welding flange and a welding groove in an embodiment of the present application;

[0032] Figure 4 is a flowchart of debugging of a laser welding joint in an embodiment of the present application.

[0033] REFERENCE NUMERALS:

[0034] 1 - cylinder, 11 - welding flange, 12 - annular boss, 2 - end frame, 21 - welding groove. DETAILED DESCRIPTION

[0035] In order to make the technical problems to be solved by the present application, the technical solutions and the beneficial effects more clearly understood, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0036] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific embodiments.

[0037] Embodiment 1

[0038] As shown in Figure 1 and Figure 2 , embodiment 1 of the present application provides a laser welding method based on an embedded weld, aiming to solve the problems of poor reliability and accessibility of embedded ring weld welding.

[0039] The method is used for welding the embedded ring weld of the aluminum alloy double-layer sleeve joint structure, comprising:

[0040] Step 1, surface cleaning and mechanical scraping treatment of the parts of the double-layer sleeve joint structure;

[0041] Step 2, rigidly clamping and fixing the parts of the double-layer sleeve joint structure by using a tool, so that the assembly gap and the step difference of the weld area meet the preset requirements;

[0042] Step 3, intermittent positioning welding of the welded joint after assembly by using laser;

[0043] Step 4, laser welding of the embedded ring weld by using a folded laser welding head to extend into the internal structure;

[0044] Step 5, cleaning and weld quality detection of the welded workpiece.

[0045] In step 1, the surface cleaning removes the oxide film and oil stains on the surface of the aluminum alloy, avoiding welding pores and inclusions; the mechanical scraping further removes the stubborn oxide layer in the welding area and forms a rough surface conducive to laser absorption, which improves the laser absorption rate of the aluminum alloy and reduces welding defects.

[0046] In step 2, the rigid clamping and fixing of the sleeve joint parts by using a tool is to accurately control and minimize the assembly gap and the step difference (misalignment) of the weld area, which is crucial for laser welding because the laser spot is small and the energy is concentrated. Excessive gap or step difference can easily lead to welding through, incomplete fusion or poor weld formation, thereby ensuring the stability of the welding process and the consistency of the joint. For example, the assembly gap and the step difference meeting the preset requirements can be that the gap and the step difference are not greater than 0.2 mm; the rigid clamping can be achieved by clamping the parts onto the tool, and using the front and rear flanges and the top wire to tightly clamp the parts, so that the fixed abutment position of the parts does not move.

[0047] In step 3, before formal welding, intermittent positioning welding (spot welding) is performed by using laser, which serves to preliminarily fix the parts at multiple evenly distributed positions, compensate for possible minor deficiencies of the tool, prevent changes in the assembly position due to stress or vibration during subsequent formal welding or movement, and ensure that the ring weld maintains the preset assembly accuracy throughout the welding cycle.

[0048] In step 4, by using the folded laser welding head, the laser beam can be accurately guided and focused on the embedded ring weld position that cannot be directly reached by conventional welding guns, realizing direct laser welding of the internal closed space weld, and improving the accessibility of the structure.

[0049] In step 5, cleaning is performed after the welding is completed, mainly to remove welding spatters, dust and other residues, and then the weld quality is detected (usually including visual inspection, non-destructive testing such as X-ray or penetration testing, etc.), the purpose is to find and evaluate whether there are pores, cracks, incomplete penetration and other defects in time.

[0050] In this way, a complete process chain from pretreatment, assembly, welding to detection is formed, through the accurate repeatable pickling and mechanical scraping treatment in step 1, and the assembly system established by rigid clamping and positioning welding in steps 2 and 3, the main source of process fluctuation is eliminated, and the reliability of welding is improved; at the same time, the direct and stable welding of the closed space weld is realized by means of the folding laser welding head, the accessibility of the embedded weld is improved, and the certainty of process execution is ensured.

[0051] Further, in step 1, the mechanical scraping treatment is to scrape the front and back surfaces and the butt surface of the part to be welded along the same direction until the metal luster is exposed.

[0052] Through directional mechanical scraping, the aim is to remove the oxidation layer and the pollution layer of the welding area, expose the clean base material surface, and form a directional microtexture to facilitate laser absorption. This improves the surface absorption rate of the laser, ensures the stable arc striking and molten pool, and at the same time reduces the defects such as pores and incomplete fusion caused by the inclusion of oxidation film and impurities.

[0053] Further, in step 1, the scraping width of the mechanical scraping treatment is 20-25 mm.

[0054] The scraping width of 20-25 mm ensures that the welding area is completely covered and extends outward to a sufficient clean area, which provides a stable base environment without oxidation layer and pollution for the molten pool formed by the laser and its surrounding high-temperature heat-affected zone, not only ensuring the purity of the weld, but also preventing the inclusion of unscraped oxidation film at the edge of the molten pool, thereby reducing the formation tendency of weld defects such as pores and inclusions, and ensuring the stability of the welding metallurgical quality.

[0055] Further, in step 1, the surface cleaning uses pickling to clean the oil stains and excess materials on the surface of the part.

[0056] Pickling can dissolve the natural aluminum oxide layer on the surface of the aluminum alloy and the attached oil stains, deeply clean the base material, and provide a uniform initial surface for subsequent mechanical treatment. In this way, the oxidation film affecting welding is removed, the sensitivity of welding pores is reduced, and the burden of mechanical scraping is reduced, laying a key metallurgical foundation for obtaining a dense and defect-free weld.

[0057] Further, in step 2, the parts are rigidly clamped and fixed by flanges and jacks.

[0058] By using flange to provide large area reference surface and axial constraint, and cooperating with top screw to exert radial locking force, the relative position between parts is forced to be kept during the whole welding process, so that the butt joint interface meets the requirements of laser welding on gap and misalignment, and the micro displacement caused by clamping stress, thermal expansion or welding process itself is effectively inhibited by rigid clamping, thereby ensuring the stability of welding assembly precision in thermal cycle.

[0059] Further, step 2 further comprises the step of leveling the parts of the double-layer sleeve joint structure, specifically, placing the parts after assembly and positioning on the platform, leveling the parts by using the supporting blocks, and measuring the weld to be in a horizontal state by using the angle level.

[0060] The leveling step ensures that the annular weld to be welded on the assembly is in a horizontal plane by setting adjustable supporting blocks between the platform and the parts and accurately measuring by using the angle level, which can provide a stable and unified reference space posture for subsequent 360° annular welding; thus, the asymmetry of molten pool flow caused by gravity is reduced, the consistency of welding parameters (such as defocusing amount and shielding gas coverage) in the whole annular welding is ensured, thereby obtaining a high-quality annular weld with uniform penetration and symmetrical shape, and improving the stability of the welding process and the predictability of the results.

[0061] Further, in step 3, the intermittent positioning welding is implemented by using a handheld laser welding gun.

[0062] This can realize rapid and local metallurgical connection at multiple key points of the annular weld in the final assembly posture, and the positioning weld formed by auxiliary fixation of the tool clamping can be used as a stress support point in subsequent formal welding, effectively compensating for possible micro-relaxation of the tool, preventing the structure from rotating or shifting during welding, and ensuring the assembly consistency during all-position welding.

[0063] On this basis, during the intermittent positioning welding, the positioning weld length is 20-30 mm, the spacing is 100-150 mm, the laser power is 800 W, the laser spot width is 3 mm, and the shielding gas flow is 10 L / min.

[0064] Further, step 4 further comprises: starting the smoke absorption equipment before welding starts, and performing air extraction from the tail of the workpiece to remove metal dust generated during welding.

[0065] Starting the smoke absorption equipment and performing air extraction from the tail of the workpiece aims to establish a directional airflow before welding, timely and controllably discharge metal vapor and plasma / dust generated in the welding area from the closed welding cavity, reduce the scattering and attenuation of laser beam by smoke, protect the folded optical lens from pollution, and reduce the redeposition of smoke particles in the molten pool and heat affected zone, thereby ensuring the stability of the welding process and improving the internal and surface quality of the weld.

[0066] Further, in step 5, the weld quality detection includes radiographic testing and fluorescent penetrant testing to evaluate the internal and surface quality of the weld.

[0067] The combined method of radiographic testing and fluorescent penetrant testing aims to respectively perform non-destructive testing on the deep internal and near-surface area of the weld, realize stereoscopic and full-coverage screening of welding defects, effectively identify internal volumetric defects such as pores and incomplete fusion through radiographic testing, and be sensitive to surface open micro-cracks and pores through fluorescent penetrant testing. The combination of the two ensures the integrity and accuracy of defect detection and provides an objective basis for evaluating the mechanical properties, sealing performance and structural reliability of the weld.

[0068] Further, in step 4, the laser beam is applied with a deflection motion during welding.

[0069] The laser beam is applied with a deflection motion during welding, which aims to dynamically stir the molten pool and expand the heat-affected zone through the periodic lateral swinging of the spot in the weld area. The deflection motion helps to break the wrapping of the oxide film in the molten pool, promotes gas escape, and reduces the pore defects unique to aluminum alloy welding. At the same time, it can improve the interface wetting, fill in the small assembly gap, and obtain a wider, flatter and better metallurgical bonding weld appearance.

[0070] Further, in step 4, before laser welding of the embedded girth weld, the step of setting welding parameters is further included, which includes setting welding power, beam deflection parameters, welding speed, defocusing amount and protective gas flow.

[0071] By setting the core process parameters such as welding power, speed and deflection, a stable and repeatable energy input and heat action mode is established for embedded laser welding, ensuring that the welding process is controlled within the preset process window. Thus, it ensures consistent weld penetration and uniform forming, suppresses common defects such as pores and cracks in aluminum alloy welding, and improves the mechanical properties and sealing reliability of the joint. For example, for an embedded weld of aluminum alloy with a diameter of 300 mm and a welding depth of 4 mm, the welding power is set to 2120 W, the deflection is 0.6, the welding speed is 0.009 m / s, the frequency is 200, and the argon flow is 10 L / min.

[0072] Further, in step 4, the laser welding of the embedded girth weld is implemented in a segmented welding manner, including: driving the workpiece to rotate around its axis, dividing the whole girth weld into multiple welding segments; in each welding segment, the rotation of the workpiece is controlled so that the moving direction of the welding pool is within the circumferential range from the 5 o'clock position to the 2 o'clock position; after completing the welding of one welding segment, the workpiece is driven to rotate, so that the starting point of the next welding segment overlaps with the ending point of the previous segment in the circumferential direction, and the length of the overlap area is a predetermined length.

[0073] By segmented welding, the spatial distribution of welding heat input and the stress state of the molten pool can be actively controlled, and the forming quality of the girth weld in the closed space is optimized. The whole girth weld is divided into multiple short arc segments, which effectively disperses and reduces the cumulative thermal stress and deformation risk caused by continuous welding. The welding direction of each segment is limited to the gravity-assisted interval of 5 o'clock to 2 o'clock, so that the molten pool metal remains stable under the synergistic action of surface tension and gravity component, which is beneficial to gas escape and forming control. The setting of the length-controllable overlap area provides sufficient metallurgical transition and heat treatment space for the connection between segments, ensuring that the joint performance is consistent with the main weld. Therefore, the overall quality and consistency of the embedded girth weld are improved. By limiting each segment welding in the best gravity position, a high-quality weld surface with uniform forming, stable reinforcement, and no undercut and sagging defects is obtained. The setting of the overlap area completely eliminates the linear defects such as crater cracks and incomplete fusion at the segmented joint, ensuring the continuity and sealing reliability of the weld. At the same time, the dispersed heat input effectively inhibits the overall distortion of the thin-walled structure, making this method particularly suitable for the manufacturing of precision components with strict size accuracy and appearance requirements.

[0074] For example, the predetermined length is 15mm to 25mm.

[0075] Embodiment 1 of the present application further provides an aluminum alloy double-layer sleeve joint structure, which is welded by the laser welding method based on the embedded girth weld.

[0076] The structure made by this method has an embedded girth weld with low porosity, high density and excellent mechanical properties, ensuring the reliable sealing and structural integrity of the double-layer sleeve joint interface under harsh working conditions, and realizing the integrated manufacturing of lightweight, high precision and high strength which is difficult to achieve by traditional methods.

[0077] Further, as shown in Figure 2 and Figure 3 , the aluminum alloy double-layer sleeve joint structure includes a cylinder 1 and an end frame 2, the cylinder 1 is provided with a welding flange 11, and the end frame 2 is provided with a welding groove 21, the welding flange 11 can extend into the welding groove 21 to form a weld area, wherein the welding flange 11 and the welding groove 21 are in clearance fit.

[0078] The cylinder 1 as the main load-bearing structure, the welding flange 11 at the end thereof is matched with the welding groove 21 in clearance, which realizes quick and accurate self-guiding positioning during assembly, and the clearance between the two actively builds a size-controlled annular cavity, which provides the necessary physical space for laser beam energy deposition, molten pool formation and keyhole stability, and directly converts the structure assembly behavior into predictable welding process conditions.

[0079] The end frame 2 as the connecting or closing member, the welding groove 21 inside thereof is matched with the welding flange 11, and the welding groove 21 is matched with the welding flange 11 in clearance, which completes the axial positioning and structural closure, and the side wall thereof and the side wall of the welding flange 11 together form an annular welding interface with high geometric precision and good consistency, which protects the welding seam completely inside the structure, reduces external damage, and also creates a protected and accessible stable working environment for the folded laser welding joint.

[0080] Through the welding scheme of the flange combined with the groove embedded joint, the assembly self-positioning and clearance prepositioning are realized, a stable and repeatable process interface is provided for laser welding, the welding seam is completely hidden inside the structure, which not only protects the welding seam from the environment, but also optimizes heat diffusion through the surrounding of double-layer metal, reduces welding deformation, forms a continuous full penetration weld on the structure, and improves the strength, stiffness and sealing reliability of the connection, which integrates the connection function, process accessibility and quality control into one, and is especially suitable for the manufacturing of aluminum alloy thin-walled structures in the fields of aviation, aerospace and the like which have strict requirements on weight, precision and reliability.

[0081] Further, as shown in Figure 3 The annular boss 12 is arranged at the root of the welding flange 11, and a containing groove is arranged between the annular boss 12 and the extending end of the welding groove 21.

[0082] The annular boss 12 is located at the root of the flange, which acts as an axial stop structure, contacts or keeps a gap with the end face of the welding groove 21 during assembly, thereby limiting the insertion depth of the welding flange 11 and ensuring the consistency of the axial position of the welding area, and this helps to guide part of the heat from the welding seam and reduce the thermal deformation of the cylinder 1. The containing groove is an annular gap reserved between the annular boss 12 and the end face of the welding groove 21, which provides a space for welding thermal expansion to avoid internal extrusion stress due to thermal expansion of the structure, and can also accommodate a small amount of molten metal or shielding gas that may overflow, ensuring that the root of the welding seam is controllable.

[0083] The annular boss 12 can guide the accumulated heat in the weld area radially out during the high heat input of laser welding by its significantly increased cross-sectional area, which reduces the peak temperature and shortens the high temperature residence time. This active heat management mechanism narrows the welding heat affected zone and makes the gradient steeper, reducing the risk of uneven thermal deformation and microstructure coarsening of the cylinder body. At the same time, the accommodating groove between the boss and the groove end face provides axial allowance space for welding thermal expansion, avoiding abnormal internal stress caused by limited thermal expansion, thereby maintaining the stability and predictability of the thermal-mechanical coupling field during welding.

[0084] In addition, as a pre-set buffer space, the accommodating groove enhances the adaptability of the welding process to variable conditions. It can effectively absorb size fluctuations caused by assembly micro-deviation or thermal cycle, prevent micro-cracks caused by extrusion stress in the root area, and accommodate a small amount of molten metal or protective gas products that may overflow during welding, avoiding the inclusion of metal liquid in the root, ensuring the complete formation of the weld root. The rigid axial stop provided by the annular boss 12 eliminates assembly depth deviation, ensuring that the arc striking and arc collecting positions of each welding are consistent. The synergistic effect of the two improves the tolerance of the welding process to common interference factors such as assembly errors and heat input fluctuations, thereby improving the consistency and reliability of the weld quality.

[0085] Embodiment 2

[0086] Embodiment 2 of the present application is a further improvement based on embodiment 1, aiming to solve the technical problem of low laser energy absorption and insufficient utilization efficiency caused by the combination of high reflectivity of aluminum alloy and space constraints in the embedded and unobservable closed space.

[0087] As Figure 4 shown, in step 4, before welding with the folding laser welding head, a step of debugging the laser welding head is further included, which comprises:

[0088] Step 4.1, laser head positioning and centering, operating the instructor to control the folding laser welding head to extend into the double-layer sleeve joint structure until the light-emitting end reaches the embedded girth weld area, adjust the spatial position of the welding head to align the laser spot with the center position of the weld, and make the spot center line coincide with the theoretical weld center line;

[0089] Step 4.2, laser head angle bias setting, deflect the laser beam axis from the original state perpendicular to the weld axis by 5° along the circumferential tangent direction of the weld towards the welding direction. This angle bias can make the reflected spatter deviate from the incident light path;

[0090] Step 4.3, defocus amount setting, using distance sensor to measure and calibrate the reference distance between the laser head light exit end and the workpiece weld surface, set the process defocus amount of the laser to +3mm (positive defocus), that is, the laser focal plane is located 3mm above the workpiece surface. This positive defocus amount helps to obtain wider weld width and gentler penetration gradient.

[0091] In step 4.1, the folding laser welding head is precisely sent into the structure by operating the teach pendant, and its spatial six degrees of freedom are finely adjusted to ensure accurate centering of the laser spot with the invisible weld, which establishes a unique and accurate path for laser energy input and ensures the symmetry of energy distribution in subsequent welding, which is the basis for avoiding defects such as welding deviation and incomplete fusion. Invisible internal operations are converted into repeatable precise mechanical positioning.

[0092] In step 4.2, the laser beam axis is deflected 5° from the vertical state to the welding forward direction, which is used to break the mirror reflection path between the laser beam and the reflector (molten pool, spatter). Most of the high-energy reflected light and metal spatter will be deflected away from the sensitive lens and optical window, effectively avoiding lens contamination, coating burnout or sensor failure. This setting ensures the continuous and stable progress of the process while reducing equipment maintenance costs and failure risks.

[0093] In step 4.3, by setting a positive defocus amount of +3mm, the laser focal point plane is essentially lifted above the workpiece surface, thereby expanding the spot area on the workpiece surface and reducing the energy density. This energy distribution pattern can produce a wider and gentler molten pool, which enhances the bridging ability to small assembly gap fluctuations; and makes the molten pool edge transition smoother, reducing the tendency of undercut; also improves the consistency of the ring seam penetration through more uniform heat input, especially suitable for continuous rotation welding process in enclosed space.

[0094] Through the above debugging steps, the absorption rate and comprehensive utilization rate of laser energy are improved. Specifically, the precise positioning and centering of step 4.1 ensures that the laser energy can be directly input and act on the metal to be welded to the maximum extent, avoiding energy scattering and loss caused by deviation of centering, and improving the benchmark of effective energy absorption from the source; the angle offset of step 4.2 effectively avoids the loss of mirror reflection energy caused by the high reflection characteristics of aluminum alloy by changing the direction of beam incidence, and guides harmful reflected splashes away from the light path, thereby protecting the effectiveness and integrity of the incident energy, directly improving the safe utilization rate of energy; the positive defocusing setting of step 4.3 optimizes the energy distribution form, promotes the more sufficient transverse conduction of heat and the stability of the molten pool under the premise of ensuring the penetration, reduces the evaporation loss and defect rework caused by excessive concentration of energy, thereby optimizing the conversion efficiency of energy for forming high-quality welds, and the above-mentioned synergistic mechanism of precise input to reduce waste, change incidence to suppress reflection, and optimize distribution to improve conversion, together realizes the efficient, stable and controllable utilization of laser energy under restricted conditions, and solves the problem of energy utilization caused by space constraints and material characteristics.

[0095] Embodiment 3

[0096] Embodiment 3 of the present application is a further improvement based on embodiment 1 or embodiment 2, aiming to solve the technical problem of poor weld quality consistency in an embedded and non-directly observable closed space due to the lack of stable and system-matched definition of the yawing motion.

[0097] In step 4, the yawing motion of the laser beam adopts an "∞" shaped trajectory, which is composed of two adjacent circular trajectories tangent to the weld center line, and the diameter D of the circular trajectory is equal to 2 to 4 times the theoretical spot diameter d of the laser beam on the workpiece surface.

[0098] The above steps are used to establish a precise, quantifiable and reproducible geometric and energy distribution model for the "∞" shaped spatial scanning motion of the laser beam. By clearly defining the "∞" shaped trajectory as two circular trajectories tangent to each other on the weld center line, and by stipulating that the diameter D and the base spot diameter d maintain a fixed proportional relationship of 2 to 4 times, three key controls are achieved: first, the range and symmetry of the beam in the weld width direction are defined, ensuring that the energy is uniformly applied with the weld center line as the axis; second, through the design of the tangent circles, the continuity and energy superposition of the scanning path at the trajectory center (weld center line) are achieved, avoiding the possible center energy trough of linear scanning; third, the trajectory size is linked to the spot, a basic optical parameter, so that the physical scale of the deflection can adapt to different laser optical systems, ensuring the consistency and portability of the process principle; as a result, the consistency of the weld quality is improved, and by accurately quantifying the "∞" shaped trajectory as two tangent circles with a fixed proportional relationship with the spot diameter, the design first ensures the symmetry and repeatability of the laser energy distribution in the weld width direction, so that the bidirectional vortex stirring pattern in the molten pool is consistent every time the welding is performed, thereby stably controlling the formation probability of defects such as pores and inclusions within a very low and predictable range (such as a pore rate of less than 0.1%); second, this deterministic heat input mode forms a stable and uniform temperature field on the weld cross section, making the penetration and width of the molten pool insensitive to small assembly fluctuations (such as ±0.2mm), thereby ensuring the high uniformity of the geometry of different workpieces and different positions in the same weld; finally, the model establishes the calculation of the core process parameters (amplitude, frequency) on the basis of clear optical geometric relationships, eliminating the variables introduced by human experience, significantly widening the process window and enabling accurate reproduction, providing a quantifiable, programmable and reliable foundation for achieving high consistency of weld quality.

[0099] Further, the amplitude A (unit: mm) of the deflection motion and the wall thickness t (unit: mm) of the cylindrical part in the aluminum alloy double-layer sleeve joint structure satisfy the relationship:

[0100] A=k*t,

[0101] wherein the value range of the coefficient k is 0.15 to 0.35, and the coefficient k is obtained by experience;

[0102] At the same time, the frequency f (unit: Hz) of the deflection motion and the welding speed v (unit: m / s) satisfy the relationship:

[0103] f≥v / (0.03*A),

[0104] 0.03 is an empirical coefficient.

[0105] This establishes a deterministic mathematical relationship between the deflection parameter and the workpiece core attribute (wall thickness t), process parameters (welding speed v), formula A=k*t converts the originally selected amplitude A based on experience into a scientific calculation value based on the structure wall thickness, ensuring that the stirring intensity matches the material heat capacity; formula f≥v / (0.03*A) quantifies the process requirement of "ensuring welding continuity" as the lower limit constraint of the beam scanning frequency f, preventing incomplete fusion caused by discontinuous scanning; the above parameter system eliminates the randomness introduced by artificial experience, improves the repeatability and adaptability of the process, and calculates the amplitude based on the wall thickness, so that workpieces of different thicknesses can obtain appropriate molten pool stirring effect, ensuring the consistency and stability of the internal quality of the weld; at the same time, the constraint relationship between the frequency and the speed, amplitude ensures that the beam trajectory can fully overlap under all working conditions, reduces linear defects caused by intermittent scanning, and finally realizes high-quality and high-reliability welding results.

[0106] Further, the parameters of the deflection motion are dynamically adjusted based on multi-signal fusion: the oscillation main frequency F_p of the molten pool is extracted through the coaxial vision system, and the cooling rate R_c near the solidification line behind the molten pool is obtained through the infrared temperature measurement unit; the deflection frequency f is corrected according to the deviation of F_p from the preset reference frequency band (200-350Hz), and the combination of laser power P and deflection amplitude A is corrected according to the deviation of R_c from the preset ideal rate interval, wherein P and A are simultaneously reduced slightly when the cooling rate R_c is low.

[0107] Through the dual-sensing fusion of coaxial vision and infrared temperature measurement, real-time perception capability of key physical quantities (molten pool dynamics, thermal cycle) of the welding process is constructed, the deflection frequency f is dynamically adjusted based on the characterization of the oscillation main frequency F_p of the molten pool to maintain the molten pool in an ideal fluid state; the laser power P and the deflection amplitude A are adjusted in coordination based on the reflection of the cooling rate R_c on heat input and microstructure evolution, to realize accurate control of heat input, and the two together form a real-time closed loop of perception-decision-execution, enabling the process parameters to adapt to changes in the welding process; thereby, the self-adaptability of the welding process and the consistency of the results are improved, the forming defects such as spatter and undercut are effectively suppressed by stabilizing the molten pool oscillation; the microstructure and mechanical properties of the weld are improved by optimizing the cooling process, reducing deformation and softening of the heat affected zone, which can automatically compensate for disturbances such as assembly fluctuations and heat accumulation, so that the weld quality of different positions and different workpieces remains highly uniform, especially suitable for batch manufacturing of precision components with strict reliability requirements.

[0108] Those skilled in the art should understand that the above embodiments are only for clearly illustrating the present application, and are not intended to limit the scope of the present application. Based on the above disclosure, other changes or modifications can also be made by those skilled in the art, and these changes or modifications are still within the scope of the present application.

Claims

1. A laser welding method based on embedded weld seams, used for welding embedded circumferential weld seams in aluminum alloy double-layer sleeve structures, characterized in that, include: Step 1: Clean the surface of the double-layered sleeve structure parts and mechanically scrape the areas to be welded. Step 2: Use tooling to rigidly clamp and fix the double-layer sleeve structure parts so that the assembly gap and step difference in the weld area meet the preset requirements. Step 3: Use laser to perform intermittent positioning welding on the assembled weld seam; Step 4: Insert a folding laser welding head into the structure to perform laser welding on the embedded circumferential weld. Step 5: Clean the welded workpiece and inspect the weld quality.

2. The laser welding method based on embedded weld seam according to claim 1, characterized in that, In step 1, mechanical scraping involves using a scraper to scrape the front and back sides of the part to be welded and the mating surfaces in the same direction until the metal luster is exposed.

3. The laser welding method based on embedded weld seam according to claim 1, characterized in that, In step 1, the scraping width of the mechanical scraping process is 20mm-25mm.

4. The laser welding method based on embedded weld seam according to claim 1, characterized in that, In step 1, surface cleaning uses acid pickling to remove oil and excess material from the surface of the parts.

5. The laser welding method based on embedded weld seam according to claim 1, characterized in that, In step 2, the parts are rigidly clamped and fixed by the flange and set screws.

6. The laser welding method based on embedded weld seam according to claim 1, characterized in that, In step 3, intermittent positioning welding is performed using a handheld laser welding gun.

7. The laser welding method based on embedded weld seam according to claim 1, characterized in that, Step S4 also includes: before welding begins, starting the fume absorption equipment to extract air from the tail of the workpiece to remove metal dust generated during the welding process.

8. The laser welding method based on embedded weld seam according to claim 1, characterized in that, In step 5, weld quality inspection includes radiographic testing and fluorescent penetrant testing to assess the internal and surface quality of the weld.

9. The laser welding method based on embedded weld seam according to claim 1, characterized in that, When performing intermittent positioning welding, the length of the positioning weld is 20-30mm, the spacing is 100-150mm, the laser power is 800W, the laser spot width is 3mm, and the shielding gas flow rate is 10L / min.

10. A double-layer aluminum alloy sleeve structure, characterized in that, The structure is manufactured by laser welding based on embedded welds as described in any one of claims 1-9.

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