Titanium alloy cabin penetrating part high-efficiency precise low-stress welding manufacturing method

Abstract

This invention relates to the field of metal welding technology, specifically to a high-efficiency, precision, and low-stress welding manufacturing method for titanium alloy through-hole components. Addressing the problems of low efficiency, large deformation, and prominent residual stress in traditional fillet welds, this invention modifies the fillet joint between the through-hole component and the pressure-resistant structural shell into a zero-gap butt joint between a conformal skirt and the shell opening. A narrow-gap bevel with a large blunt edge is set on the assembly mating surface, and a high-energy beam single-pass self-fusion root pass weld penetrates the blunt edge in one go. Subsequently, laser-arc hybrid welding is used for filling, and a symmetrical alternating welding sequence is implemented to balance heat accumulation. After welding, the weld is subjected to conformal local stress-relief annealing, while key parts of the through-hole component are forcibly cooled using copper cold sleeves and copper cold jackets. This invention significantly improves the welding efficiency of through-hole components, effectively controls welding deformation, precisely reduces residual stress, and significantly improves the structural reliability after welding.

Description

Technical Field

[0001] This invention relates to the field of metal material welding technology, and more specifically, to a method for manufacturing titanium alloy through-hole components with high efficiency, precision, and low stress welding. Background Technology

[0002] In modern ships and marine engineering equipment, deep-sea submersibles, and high-end pressure vessels, pressure-resistant cylindrical shells are core load-bearing components that withstand extremely high external hydrostatic pressure or internal pressure. Through-hull joints, serving as functional interfaces connecting the inside and outside of the hull for laying pipelines, cables, drive shafts, and other critical systems, are crucial for ensuring the overall structural integrity, structural strength, and long-term service reliability through the quality of their welded joints. These joints typically use circumferential fillet welds to connect the through-hull joints to the hull. Titanium alloys, with their excellent corrosion resistance, high strength-to-weight ratio, and good mechanical properties, have become the preferred material for through-hull joints and pressure hulls. However, their inherent high chemical reactivity, narrow welding process window, and extreme sensitivity to heat input expose systemic technical challenges in traditional manufacturing methods for these complex joints, including extremely low welding efficiency, passive and uncontrolled deformation control, and the significant harm caused by residual welding stress.

[0003] First, from a structural geometry and accessibility perspective, the through-hull component is typically a thick-walled member with a central through-hole, while the connected pressure shell may be a thicker or thinner cylinder. This "thick-thin" heterogeneous connection results in a highly unbalanced heat input transfer between the two: the shell dissipates heat quickly with a narrow heat-affected zone, while the through-hull component dissipates heat slowly with a wide heat-affected zone. This leads to severe uneven thermal expansion and contraction, generating complex welding stresses and deformations in the highly constrained joint. Typical manifestations include localized shell indentations, through-hull component axis misalignment, shell roundness distortion (ellipticization), and weld angular deformation. These deformation modes are intertwined and extremely difficult to correct, directly causing assembly accuracy deviations and affecting subsequent system assembly and even equipment performance. Second, the through-hull component is located on top of the shell, and its welding joint is in three-dimensional space. The welding operation space is usually limited, and welding can mostly only be performed from one side of the shell, with poor or complete accessibility to the inside. This obstructs the welder's line of sight, requiring non-standard operating postures, which not only reduces welding speed but also affects the stability of process parameters and the consistency of weld formation. Furthermore, traditional through-hull components are often made from integral forgings through extensive machining, resulting in low material utilization and long manufacturing cycles. Finally, titanium alloys are highly chemically reactive and extremely sensitive to welding heat input. Overheating leads to coarse grains, decreased plasticity, and embrittlement due to the absorption of oxygen, nitrogen, and hydrogen from the air. Therefore, strict control of heat input is essential in the process, which in turn limits the improvement of welding efficiency.

[0004] Traditional solutions primarily rely on multi-pass, low-parameter tungsten inert gas welding (GTAW / TIG). However, this welding method is extremely inefficient. To control heat input and ensure quality, a slow, controlled approach is necessary. A medium-sized through-hull weld often requires 10-20 passes, taking tens of hours, becoming a major bottleneck on the production line's critical path. Furthermore, deformation and stress control are somewhat arbitrary. Welding deformation heavily relies on the welder's experience for pre-deformation or post-weld correction, while residual stress is largely left to its own devices, lacking proactive and precise control methods. In addition, weld quality consistency is poor. Due to its high dependence on individual welder skills, quality fluctuates greatly when working in confined spaces, and the geometry of fillet welds severely interferes with ultrasonic and radiographic non-destructive testing signals, making defect detection and evaluation difficult.

[0005] To improve the welding efficiency and quality of titanium alloy structures, various advanced processes have been developed and applied in the welding field in recent years. Existing patent CN116174858A discloses a narrow-gap welding method for thick titanium alloy plates. Its core technology lies in using a U-shaped narrow-gap bevel with a large blunt edge, and employing keyhole tungsten inert gas (K-TIG) welding for the entire root pass, fill pass, and cap pass. This method provides initial rigidity through the large blunt edge, effectively resisting deformation during the root pass welding; the high-current deep penetration characteristic of K-TIG welding enables single-pass self-fusion root pass with the blunt edge, improving root pass efficiency; its dual-TIG K-TIG fill pass welding design further enhances fill pass efficiency and quality. However, it is mainly designed for two-dimensional planar welds such as butt joints of flat plates or longitudinal and circumferential seams of cylindrical bodies. The connection between through-hull components and the shell is essentially a three-dimensional corner joint, with joint form, stress state, and thermal conduction boundary conditions that are drastically different from butt joints. Directly applying this technology to corner welds cannot solve the fundamental problems inherent in corner joints, such as poor accessibility, asymmetrical thermal field, and high restraint stress. Its tooling and process parameter system is not applicable to the special geometry of the through-cabin component.

[0006] Existing patent CN113927192A discloses a welding method for large-diameter titanium alloy pipes. This method proposes a process route of "K-TIG welding without filler wire for the root pass + MIG welding for the fill pass." A narrow-gap welding bevel is designed based on the workpiece thickness; for plates thicker than 12mm, a U-shaped bevel is used, with a bevel blunt edge height of 8-10mm. High-current K-TIG welding achieves single-pass self-fusion root pass for the blunt edge of the thick plate, followed by efficient fill pass using MIG welding. A water-cooling device for the welding torch solves the engineering challenge of wire feeding blockage in titanium alloy MIG welding. This method is the first to apply K-TIG welding to titanium alloy pipe welding. Compared to the traditional TIG welding root pass + fill pass process, the overall welding efficiency is increased by more than 2 times, while significantly improving the weld's tolerance for assembly gaps and misalignment, providing a new technical approach for efficient welding of thick titanium alloy plates. However, this solution is designed for coaxial circumferential butt welding of titanium alloy pipes with equal wall thickness. Its process design revolves around the uniform heat conduction characteristics of symmetrical structures. However, the welding of the through-hole component and the pressure shell involves asymmetrical structures with two different wall thicknesses. The heat capacity and heat dissipation conditions of the two structures differ greatly, and this solution cannot solve the complex deformation problem caused by asymmetrical heat input. Secondly, the bevel blunt edge height of this solution is only 8~10mm. For welding pressure shells with a thickness of 20~60mm to through-hole components, it cannot meet the single-pass full penetration root pass requirement for thick structures. Moreover, this solution only focuses on welding efficiency and weld tolerance, without addressing the control technology of welding residual stress or the precision protection of the sealing surface of the through-hole component. These two aspects are precisely the core technical indicators for welding through-hole components. Summary of the Invention

[0007] In view of this, the present invention aims to propose a high-efficiency, precision, and low-stress welding manufacturing method for titanium alloy through-hull components, so as to solve the problems of low efficiency, uncontrollable deformation, and prominent residual stress hazards in the fillet welds of through-hull components in the prior art.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0009] This invention discloses a high-efficiency, precision, and low-stress welding manufacturing method for titanium alloy through-hole components. The welding manufacturing method includes:

[0010] Joint design: A conformal skirt is machined at the welding end of the through-hole component, and a shell opening is machined at the welding end of the pressure-resistant structure shell. The conformal skirt can be assembled with the shell opening to form a butt joint. After the conformal skirt is butt-jointed with the shell opening, a narrow gap bevel is formed. The root of the narrow gap bevel is provided with a blunt edge, and the blunt edge is formed by assembling the conformal skirt with the shell opening.

[0011] Root pass welding: Between the mating surfaces with blunt edges, a single pass autofusion root pass welding method is used to completely melt through the blunt edges in one go, forming a root pass weld.

[0012] Filling weld: A composite welding method is used to fill the narrow gap groove to form a filling weld. The filling process follows a symmetrical and alternating welding sequence.

[0013] Post-weld treatment: After welding, the root pass weld and filler weld form a butt weld. The butt weld area is subjected to conformal local heat treatment, while the non-heat-treated areas of the through-hole parts are cooled and protected.

[0014] Furthermore, the conformal skirt protrudes along the central axis of the through-hull component toward the end of the pressure-resistant structural shell to be welded, and it is coaxially arranged with the through-hull component.

[0015] Furthermore, the conformal skirt has a skirt bevel on its end face facing the pressure-resistant structural shell, and a skirt blunt edge is provided at the bottom of the skirt bevel.

[0016] Furthermore, the shell opening has a mating bevel on its end face facing the through-hole component, and the bottom of the mating bevel has a mating blunt edge; the mating bevel and the skirt bevel are arranged opposite to each other to form a narrow gap bevel; the mating blunt edge and the skirt blunt edge are arranged opposite to each other, and the two can be joined together to form a blunt edge.

[0017] Furthermore, the narrow gap bevel is a U-shaped bevel with a bevel angle of 3° to 8°; and the thickness of the blunt edge is 15 to 20 mm.

[0018] Furthermore, the welding methods used for the root pass welding include high-power laser welding or keyhole tungsten inert gas welding.

[0019] Furthermore, the composite welding method is laser-arc composite welding, in which the laser beam and the electric arc are arranged one in front of the other, with the laser in front and the electric arc behind.

[0020] Furthermore, the symmetrical alternating welding sequence includes: when the narrow gap bevel is a single-sided bevel, alternating symmetrical welding is performed along the circumference of the narrow gap bevel; or, when the narrow gap bevel is a double-sided bevel, layered alternating symmetrical welding is performed on the upper and lower double narrow gap bevels.

[0021] Furthermore, conformal local heat treatment is carried out by conformal local heating strips attached to the butt weld, with a heating temperature of not less than 500°C; and the outer side of the conformal local heating strips is covered with an insulation layer.

[0022] Furthermore, cooling protection includes: covering the outer surface of the penetration component with a copper cold sleeve having cooling channels and / or inserting a copper cold sleeve having cooling channels into the core of the penetration component.

[0023] Compared with existing technologies, the efficient, precision, and low-stress welding manufacturing method for titanium alloy through-hole components described in this invention has the following advantages:

[0024] (1) Leapfrog improvement in welding efficiency: This invention fundamentally improves welding accessibility by innovatively transforming the traditional corner joint into a conformal skirt butt joint structure, converting the three-dimensional corner weld into a two-dimensional planar weld. The combination of large blunt edge and narrow gap bevel design and high-energy beam root pass welding with composite welding filler significantly reduces the number of welding passes and filler volume, greatly shortening the total welding time and realizing a leap from inefficient manual operation to efficient automated manufacturing of titanium alloy through-hull welding.

[0025] (2) Effective control of welding deformation: The large blunt edge structure adopted in this invention provides sufficient rigid support for the root pass welding, and the welding method that can completely penetrate the blunt edge in one go has the characteristics of deep penetration with low heat input, thus suppressing the total amount of welding heat input from the source. Combined with the double-sided alternating symmetrical filling process, the heat accumulation process on both sides of the weld is effectively balanced, realizing the active control of the welding thermal field. Through the synergistic effect of the above processes, welding deformation is effectively controlled, and the dimensional and positional deviations such as the axial deviation of the through-hull parts and the local concavity of the shell are significantly reduced, and the assembly accuracy is greatly improved.

[0026] (3) Precise Residual Stress Reduction: This invention reduces the initial residual stress level of the weld by optimizing welding process parameters, and combined with conformal local heat treatment technology, achieves precise and proactive reduction of residual stress in the weld area. Simultaneously, by designing a dedicated cooling protection device to force-cool the critical sealing parts of the through-hull components, the adverse effects of the heat treatment process on the dimensional accuracy and surface condition of functional parts are effectively avoided. The resulting low-stress weld condition significantly enhances the structure's ability to resist fatigue loads, greatly improving the long-term service reliability of the equipment.

[0027] (4) Improved process stability and quality reliability: After transforming the corner weld structure into a butt weld structure, the geometric shape of the weld is more regular, providing good testing conditions for subsequent non-destructive testing. This effectively avoids interference from the geometric shape of the corner weld on the testing signal, improving the defect detection rate and the reliability of the testing results. At the same time, the process method of this invention has a high degree of standardization, reduces the dependence on the welding operator's skills, and is easy to automate production, ensuring the consistency and stability of welding quality in the mass production process. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a front view of the corner joint between the through-cabin component and the pressure-resistant hull in Comparative Example 1;

[0030] Figure 2This is a front view of the single-sided narrow gap bevel as described in Embodiment 1 of the present invention;

[0031] Figure 3 This is a front view of the double-sided narrow gap bevel as described in Embodiment 2 of the present invention;

[0032] Figure 4 This is a top view of the local heating stress relief and protection device of the present invention;

[0033] Figure 5 This is a schematic diagram of the local heating stress relief and protection device of the present invention.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1. Through-hull component; 11. Conformal skirt; 111. Skirt bevel; 112. Skirt blunt edge; 2. Pressure-resistant structural shell; 21. Shell opening; 211. Butt joint bevel; 212. Butt joint blunt edge; 3. Narrow gap bevel; 4. Blunt edge; 5. Conformal local heating band; 6. Butt weld; 7. Copper cold sleeve; 8. Copper cold sleeve. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] This invention provides a high-efficiency, precision, and low-stress welding manufacturing method for titanium alloy through-hole components. The welding manufacturing method includes:

[0038] Joint design: A conformal skirt 11 is machined at the welding end of the through-hole component 1, and a shell opening 21 is machined at the welding end of the pressure-resistant structure shell 2. The conformal skirt 11 can be assembled with the shell opening 21 to form a butt joint; after the conformal skirt 11 is butt-jointed with the shell opening 21, a narrow gap bevel 3 is formed. The root of the narrow gap bevel 3 is provided with a blunt edge 4, and the blunt edge 4 is formed by assembling the conformal skirt 11 with the shell opening 21.

[0039] Root pass welding: Between the mating surfaces of the blunt edge 4, a single pass self-fusion root pass welding is performed using a welding method that can completely melt through the blunt edge 4 in one go, forming a root pass weld.

[0040] Filling weld: A composite welding method is used to fill the narrow gap groove 3 to form a filling weld. The filling process follows a symmetrical and alternating welding sequence.

[0041] Post-weld treatment: After welding is completed, the root pass weld and the filler weld form the butt weld 6. The area of ​​the butt weld 6 is subjected to conformal local heat treatment, while the non-heat-treated area of ​​the through-hole component 1 is cooled and protected.

[0042] This invention will transform the traditional three-dimensional corner joint ( Figure 1The joint was modified into a coaxial mating joint between the conformal skirt 11 and the shell opening 21. Figure 2 This invention transforms fillet welds into welds between two-dimensional planes, improving weld accessibility, adapting to automated welding for increased efficiency, and eliminating asymmetric heat conduction in thick-thin structures, thus suppressing welding deformation at its source. Furthermore, the butt joint formed by this invention features a narrow-gap groove 3 with a blunt edge 4, significantly reducing weld filler volume and welding passes, while the blunt edge 4 provides high rigidity support to resist welding shrinkage deformation, laying the structural foundation for single-pass full penetration root pass welding. In terms of welding process, this invention employs a welding method that can penetrate the blunt edge 4 in one pass to complete the root pass, replacing traditional multi-layer, multi-pass welding, significantly reducing time and total heat input. The use of composite welding for symmetrical alternating filling of the narrow-gap groove 3 balances heat accumulation in the butt weld 6, further controlling deformation, improving efficiency, and ensuring the quality of the butt weld 6. Furthermore, this invention precisely reduces the residual stress in the butt weld 6 area through conformal local heat treatment, and simultaneously uses copper cold tooling to force cooling the non-heat-treated area of ​​the through-hole component 1, which not only achieves low-stress manufacturing, but also protects the accuracy of key sealing surfaces, thus helping to achieve the goal of efficient, precise and highly reliable welding.

[0043] It should be noted that the manufacturing method of the conformal skirt 11 is flexible and can be achieved using a variety of advanced forming processes. Specifically:

[0044] Traditional forging and rolling billet processing: Titanium alloy forgings or thick plates can be used as billets, and the geometric structure of the conformal skirt 11 can be directly formed through machining (such as turning and milling). This method is mature and reliable, and is suitable for mass production of parts with relatively standard structures.

[0045] 3D Printing Near-Net-Shape Forming: To adapt to complex structures, optimize materials, or improve material utilization, 3D printing technology can be used to directly form a near-net-shape blank of the through-hull part 1 with conformal skirt 11. For example, "multi-array laser powder feeding additive manufacturing" technology can be used, through the synergy of multiple laser beams and powder feeding nozzles, to efficiently and precisely clad titanium alloy powder layer by layer, directly manufacturing a blank of the through-hull part 1 with complex shape and dense structure and conformal skirt 11. Alternatively, "cold metal transfer (CMT) wire feeding additive manufacturing" technology can be used, utilizing the stable and spatter-free characteristics of CMT welding arc, to precisely control the droplet transfer and deposit titanium alloy wire layer by layer, forming a blank of the through-hull part 1 with conformal skirt 11 with minimal deformation and high dimensional accuracy. Regardless of the additive manufacturing process used, the formed skirt blank only requires a small amount of subsequent finishing to achieve the precision requirements for "zero-gap" assembly with the shell opening 21. This method is particularly suitable for manufacturing small-batch, customized, or internally functional components (such as cooling channels).

[0046] Regardless of the manufacturing process used, the resulting conformal skirt 11 must be precisely aligned with the shell opening 21 through coaxial positioning, and the two must achieve zero-gap transition assembly through tight contact of the assembly mating surfaces, transforming the traditional three-dimensional corner weld into a two-dimensional planar weld.

[0047] Specifically, the conformal skirt 11 protrudes along the central axis of the through-hole component 1 toward the end of the pressure-resistant structural shell 2 to be welded, and it is coaxially arranged with the through-hole component 1.

[0048] More specifically, the conformal skirt 11 has a skirt bevel 111 on its end face facing the pressure-resistant shell 2, and a skirt blunt edge 112 at the bottom of the skirt bevel 111. The shell opening 21 has a mating bevel 211 on its end face facing the through-cabin 1, and a mating blunt edge 212 at the bottom of the mating bevel 211; the mating bevel 211 and the skirt bevel 111 are arranged opposite to each other to form a narrow gap bevel 3; the mating blunt edge 212 and the skirt blunt edge 112 are arranged opposite to each other, and the two can be joined together to form a blunt edge 4.

[0049] Through the above structure, the traditional three-dimensional corner joint is transformed into a two-dimensional planar weld joint, which significantly improves the weld accessibility. The skirt bevel 111 and the butt joint bevel 211 together form a narrow gap bevel 3, which greatly reduces the amount of filler metal. The skirt blunt edge 112 and the butt joint blunt edge 212 fit together to form a thick blunt edge 4, which provides rigid support for high-energy beam root pass welding and suppresses welding deformation from the source. At the same time, the zero gap fit significantly reduces the tensile stress caused by welding shrinkage and effectively prevents root cracks.

[0050] It should be noted that the fitting surfaces of the skirt blunt edge 112 and the mating blunt edge 212 must achieve an extremely high degree of fit. This is crucial for achieving "zero gap" and ensuring the quality of the root of the root weld. The fitting surfaces refer to the two surfaces on the skirt blunt edge 112 and the mating blunt edge 212 that come into contact and fit together. In actual manufacturing, precision machining is required to ensure the flatness and parallelism of the fitting surfaces, and special positioning fixtures are needed to ensure that the fitting surfaces of the skirt blunt edge 112 and the mating blunt edge 212 fit tightly and do not misalign during assembly. This invention, by adding a structurally and functionally integrated "conformable skirt 11" transition piece, actively shifts the connection interface from the complex and inconvenient junction of the "curved surface of the pressure-resistant shell 2 and the side of the through-cabin part 1" to the "end face of the conformal skirt 11 and the end face of the shell opening 21," which is easier to process, assemble, weld, and inspect. This is the primary design for achieving the goals of high efficiency, precision, and low stress in the entire method.

[0051] Specifically, the narrow gap bevel 3 is a U-shaped bevel with a bevel angle of 3° to 8°; and the thickness of the blunt edge 4 is 15 to 20 mm.

[0052] The retention of a thick 15-20mm blunt edge 4 provides a solid material foundation for high-energy beam single-pass root pass welding under zero-gap assembly. This structure effectively resists the shrinkage stress caused by local melting during root pass welding, establishing a low-deformation tone from the very first weld and avoiding the risk of welding cracks due to root gap shrinkage. The smaller bevel angle further limits the volume of the welding area, and combined with the large blunt edge 4 structure, allows for precise control of the total heat input throughout the welding process. This not only helps reduce welding deformation and residual stress but also limits the width of the heat-affected zone of the titanium alloy, thus helping to maintain the mechanical properties of the base material.

[0053] It should be noted that the sidewall of the U-shaped narrow gap groove 3 extends outward gently from the surface of the blunt edge 4 at a small angle of 3° to 8°. This design minimizes the cross-sectional area of ​​the groove while ensuring the accessibility of the welding torch and the fusion of the sidewall of the butt weld 6. Furthermore, this design of a large blunt edge 4 and a small-angle narrow gap groove 3 is specifically designed to match the subsequent "high-energy beam root pass welding" and "composite filler welding" processes. If a traditional low-heat-input welding method is used, single-pass penetration of the blunt edge 4 may not be achieved, or the filler efficiency may be low, failing to leverage the advantages of this structure. Therefore, the groove design and welding process are inseparable. Moreover, the configuration of the narrow gap groove 3 is selected based on the wall thickness of the through-hole component 1.

[0054] Preferably, when the wall thickness is less than or equal to 30 mm, a single-sided narrow-gap bevel 3 is used, that is, the bevel is processed only on a single side of the conformal skirt 11 and the shell opening 21, such as... Figure 2 As shown, this facilitates single-pass filler welding from the outside. When the wall thickness is greater than 30mm, a double-sided narrow-gap bevel 3 is used, that is, the bevel is machined at two opposite positions above and below the conformal skirt 11 and the shell opening 21, as shown. Figure 3 As shown, two welding channels are formed, one above the other in a symmetrical manner.

[0055] Specifically, the welding methods used for the root pass welding include high-power laser welding or keyhole tungsten inert gas welding.

[0056] The welding method used for the root pass welding has the characteristics of large penetration depth, low heat input and fast welding speed. It can completely melt through the 15~20mm thick blunt edge 4 in one pass, realizing single-pass self-fusion root pass welding. Compared with traditional TIG welding, it significantly reduces the number of welding passes and total heat input, suppresses welding deformation from the source, and avoids the heat accumulation and residual stress problems caused by multi-layer and multi-pass welding.

[0057] Preferably, the high-power laser welding uses fiber laser welding, and the keyhole tungsten inert gas welding uses high-current K-TIG welding. Both adopt a self-fusion root pass process and do not require filler wire. The welding process uses pure argon gas protection to avoid oxidation and embrittlement of the titanium alloy weld.

[0058] It should be noted that when using the above welding method, the assembly gap must be controlled within 0~0.1mm to ensure uniform penetration and the absence of incomplete fusion defects. Simultaneously, due to the extremely low heat input, the interpass temperature must be strictly controlled to not fall below 150℃ during welding to prevent martensitic phase transformation or cold cracking caused by excessively rapid cooling. For high-power laser welding, care must also be taken to prevent laser reflection damage to the equipment, and the workpiece surface should be clean and free of oil.

[0059] Specifically, the composite welding method is laser-arc composite welding, in which the laser beam and the electric arc are arranged one in front and the other behind.

[0060] More specifically: the symmetrical alternating welding sequence includes: when the narrow gap groove 3 is a single-sided groove, alternating symmetrical welding is performed along the circumference of the narrow gap groove 3; or, when the narrow gap groove 3 is a double-sided groove, layered alternating symmetrical welding is performed on the upper and lower double narrow gap grooves 3.

[0061] The laser preheats the molten pool and creates a small hole, reducing the material's resistance to the arc and improving arc stability. The subsequent arc fills the weld wire and increases deposition efficiency. Together, they create a deep-penetrating, wide weld bead, maintaining the high aspect ratio advantage of laser deep-penetration welding while improving weld formation and bridging capabilities. It also significantly reduces porosity sensitivity, making it particularly suitable for rapid filling of narrow-gap grooves in titanium alloys. The symmetrical, alternating welding sequence, by planning the spatial and temporal distribution of heat input, forces a balance in heat accumulation on both sides of the weld, effectively counteracting asymmetric shrinkage caused by localized concentrated heating.

[0062] Preferably, when the narrow gap bevel 3 is a single-sided bevel, the bevel can be divided into several arc segments along the circumference and numbered according to the principle of symmetry. The welding sequence is as follows: first weld the first segment, then jump to the arc segment symmetrical to the first segment, then weld the second segment, and then weld the second symmetrical arc segment until welding is completed. When there are two symmetrical narrow gap bevels 3, the filling is carried out in a cyclical sequence of "upper side first arc segment - lower side first arc segment - upper side second arc segment - lower side second arc segment" to ensure that the heat input on the upper and lower sides always maintains a dynamic balance in the thickness direction.

[0063] Specifically, conformal local heat treatment is carried out by conformal local heating strip 5 attached to the butt weld 6, with a heating temperature of not less than 500℃; and the outer side of conformal local heating strip 5 is covered with a heat insulation layer.

[0064] More specifically, the cooling protection includes: covering the outer surface of the penetration component 1 with a copper cold sleeve 7 having cooling channels and / or inserting a copper cold sleeve 8 having cooling channels into the core of the penetration component 1.

[0065] The conformal local heating band 5 fits the geometry of the butt weld 6, and together with the insulation layer, it achieves precise and uniform heating of the weld area, effectively eliminating residual welding stress and avoiding deformation or performance degradation of large structures caused by overall heat treatment. At the same time, the copper cold sleeve 7 and / or copper cold sleeve 8 force cooling of key parts such as the sealing surface of the through-hole component 1 keeps the temperature below 150°C, ensuring that its dimensional accuracy and surface condition are not affected by heat treatment, thus achieving the dual goals of stress relief and precision protection.

[0066] It should be noted that the conformal local heating strip 5 preferably uses flexible ceramic heating elements, which can be bent and fitted according to the shape of the butt weld 6; its heat preservation time is directly proportional to the butt weld 6, and is usually more than twice the total thickness of the butt weld 6, measured in minutes. The copper cold sleeve 7 and copper cold jacket 8 have internal cooling channels, such as spiral water channels or axial channels, and efficiently remove heat through continuous flow of cooling water or other media. Their installation must ensure good contact with the surface of the through-body 1 to achieve optimal thermal conductivity.

[0067] Example 1

[0068] This embodiment discloses a high-efficiency and precision welding method for titanium alloy through-hole components, used for Figure 2 The specific steps for welding the through-cabin component 1 (with a wall thickness of less than 30mm) to the pressure-resistant shell 2 are as follows:

[0069] First, the joint structure was modified. A TC4 titanium alloy forging was selected and machined to form the through-hull part 1, with an outer diameter of φ400mm and a thickness of 25mm, and a precision-machined sealing surface at the end. A TC4 titanium alloy cylindrical shell with a thickness of 60mm was selected as the pressure-resistant structural shell 2. A conformal skirt 11 with a height of 50mm was machined at the end of the through-hull part 1 facing the pressure-resistant structural shell 2, with the central axis of the conformal skirt 11 coinciding with the central axis of the through-hull part 1. A shell opening 21 was machined on the pressure-resistant structural shell 2, perfectly matching the geometry of the conformal skirt 11. The conformal skirt 11 and the shell opening 21 can form an end-to-end zero-clearance butt joint, transforming the traditional three-dimensional spatial fillet weld into a two-dimensional planar weld, fundamentally improving welding accessibility.

[0070] Specifically, the conformal skirt 11 protrudes towards the pressure-resistant shell 2 and is cylindrical with a height of 50mm. A skirt bevel 111 is machined on the outer edge of the end face of the conformal skirt 11 facing the pressure-resistant shell 2, and an unmachined blunt edge 112 is retained at the root of the skirt bevel 111. Correspondingly, a mating bevel 211 is machined on the shell opening 21 of the pressure-resistant shell 2, and an unmachined blunt edge 212 is retained at the root of the mating bevel 211. When the through-hull component 1 is assembled with the pressure-resistant shell 2, the skirt bevel 111 and the mating bevel 211 together form a narrow gap bevel 3 with one side open. The opening of this narrow gap bevel 3 faces the external welding space of the through-hull component 1, facilitating the entry of welding tools for welding from the outside. Meanwhile, the blunt edge 112 of the skirt and the blunt edge 212 of the butt joint fit together to form a blunt edge 4 with a larger thickness. This blunt edge 4 provides rigid support and penetration reference for high-energy beam root pass welding, and can achieve single-pass full penetration welding under zero-gap assembly conditions, thus suppressing welding heat input and welding deformation from the source.

[0071] Preferably, the narrow gap bevel 3 is U-shaped with a bevel angle of 3°, and the bevel opens gently outward from the root, meaning that the angle formed by a single sidewall of the U-shaped bevel and the end face of the blunt edge 4 is 3°. Furthermore, the thickness of the blunt edge 4 is 15 mm.

[0072] Secondly, a high-energy beam root pass was performed based on the blunt edge 4. A 20kW fiber laser was used for single-pass self-fusion root pass welding. The laser beam was focused on the surface of the blunt edge 4, and the welding parameters were: laser power 18kW, welding speed 1.2m / min, and pure argon gas as the shielding gas. The laser deep penetration effect formed a keyhole, completely melting through the 15mm thick blunt edge 4 in one pass, forming the root pass weld. After the root pass weld, the back of the weld was uniformly formed, without defects such as incomplete penetration or undercut.

[0073] Next, composite welding and symmetrical alternating filler welding were performed. After the root pass welding was completed, the narrow gap groove 3 was filled using a laser-arc composite welding method. The welding system consisted of a 20kW fiber laser and a MIG welding machine, with the laser beam and arc arranged in a front-to-back configuration, the laser in front and the arc behind. The filler welding was completed in two passes, employing a "segmented symmetrical alternating" strategy: the U-shaped groove was divided into four equal segments along its length, numbered A, B, C, and D according to the principle of symmetry, where A and D are symmetrical, and B and C are symmetrical. The welding sequence was: first weld segment A, then segment D, then segment B, and finally segment C. This segmented symmetrical heat input method balanced the heat accumulation in different areas of the U-shaped groove, actively controlled the welding heat cycle, and effectively suppressed shell indentation and skew deformation of the through-hole component 1 caused by uneven local heating. The filler welding parameters were: laser power 10kW, MIG welding current 220A, voltage 24V, and welding speed 0.8m / min. The interpass temperature is controlled above 150℃ to prevent cold cracking. After filling, a filler weld is formed, which together with the root pass weld constitutes the butt weld 6.

[0074] Finally, conformal local heat treatment and protection of critical areas are implemented. Immediately after welding, [further treatment is required]. Figure 4 and Figure 5 The localized heating stress relief and protection device shown performs localized stress-relieving annealing, i.e., heat treatment, on the butt weld 6 area. This device includes a conformal localized heating band 5, an insulation layer, a temperature controller, a copper cold sleeve 7, and a copper cold jacket 8. The conformal localized heating band 5 perfectly conforms to the shape of the butt weld 6, tightly covering its upper and lower surfaces. An insulation layer is wrapped around the outside of the conformal localized heating band 5. The heating temperature and heating rate of the conformal localized heating band 5 are monitored and controlled in real time by the temperature controller to reduce heat loss.

[0075] The heat treatment process parameters are as follows: heating temperature 580±10℃, heating rate ≤100℃ / h, holding time 2h, cooling rate ≤150℃ / h, and after cooling to below 200℃, the conformal local heating belt 5 and the insulation layer are removed.

[0076] Simultaneously, the non-heat-treated areas of the through-cabin component 1 are cooled and protected. For example... Figure 4 and Figure 5 As shown, to protect the sealing surface at the end of the through-hole component 1, a copper cold sleeve 7 is wrapped around the outer surface of the through-hole component 1 near the sealing surface. The copper cold sleeve 7 has a spiral-shaped first cooling water channel inside, through which circulating cooling water is continuously supplied. A copper cold sleeve 8 is coaxially inserted into the inner hole of the through-hole component core, with its outer wall tightly fitted to the inner hole wall of the through-hole component core. A second cooling water channel with an axial through-hole is formed inside the wall of the copper cold sleeve 8, through which circulating cooling water is continuously supplied. The cooling water flow rate is controlled at 10 L / min to ensure that the temperature of the sealing surface area remains below 150℃ during heat treatment.

[0077] Upon completion, various performance tests were conducted according to current national standards: a laser tracker was used to systematically test the shape and position accuracy of the welded structure in accordance with GB / T1958-2017 "Geometrical Specifications (GPS) for Product"; X-ray diffraction was used to quantitatively test the residual stress in the weld and heat-affected zone in accordance with GB / T7704-2017 "Non-destructive Testing: X-ray Stress Measurement Method"; and ultrasonic testing was used to detect internal defects in butt weld 6 in accordance with GB / T37557-2019 "Non-destructive Testing: Ultrasonic Testing Method for Titanium Alloy Welds".

[0078] The total welding time in this embodiment was approximately 5.5 hours, representing a 77.1% increase in efficiency compared to the 24 hours in Comparative Example 1. After welding, the axial deviation of the through-hull component 1 was ≤0.4mm; there were no obvious dents around the opening of the pressure-resistant shell 2, with local dents ≤1.2mm; the overall roundness error of the pressure-resistant shell 2 was ≤1.5mm, meeting the design accuracy requirements. After heat treatment, the maximum residual tensile stress in the butt weld 6 area was ≤160MPa, compared to 680MPa in Comparative Example 1, representing a stress reduction rate of 76.5%. The butt weld 6 was geometrically regular, exhibited no interference echoes during ultrasonic testing, and had uniform radiographic film density, resulting in a 100% defect detection rate and a 99.0% first-pass yield.

[0079] Example 2

[0080] This embodiment discloses a high-efficiency and precision welding method for titanium alloy through-hole components, used for Figure 3 The welding and manufacturing of the through-hole component 1 with a wall thickness of 30mm or more and the pressure-resistant structural shell 2. In this embodiment, the material and performance testing standards of the through-hole component 1 and the pressure-resistant structural shell 2, as well as the joint structure formed by the two, are the same as in embodiment 1, with the following differences:

[0081] First, this embodiment employs a double-sided narrow-gap bevel design for the 60mm through-hull component 1. Specifically, the conformal skirt 11 protrudes towards the pressure-resistant structural shell 2 and has a cylindrical structure. Two symmetrically distributed skirt bevels 111 are machined on the outer edge of the end face of the conformal skirt 11 facing the pressure-resistant structural shell 2. Unprocessed skirt blunt edges 112 are retained at the root of these two skirt bevels 111. Correspondingly, two symmetrically distributed mating bevels 211 are machined on the shell opening 21 of the pressure-resistant structural shell 2, with unprocessed mating blunt edges 212 retained at the root of the mating bevels 211. When the through-hull component 1 is assembled with the pressure-resistant structural shell 2, the two skirt bevels 111 and their corresponding mating bevels 211 together form two symmetrical narrow-gap bevels 3. The openings of these two narrow-gap bevels 3 are opposite and both face the direction of the external welding space of the through-hull component 1, facilitating the entry of welding tools for welding from the outside. Meanwhile, the blunt edge 112 of the skirt and the blunt edge 212 of the butt joint fit together to form a blunt edge 4 with a larger thickness. This blunt edge 4 provides rigid support and penetration reference for high-energy beam root pass welding, and can achieve single-pass full penetration welding under zero-gap assembly conditions, thus suppressing welding heat input and welding deformation from the source.

[0082] Preferably, the narrow gap bevel 3 is U-shaped with a bevel angle of 5°, and the bevel opens gently outward from the root, meaning that the angle formed by a single sidewall of the U-shaped bevel and the end face of the blunt edge 4 is 5°. Furthermore, the thickness of the blunt edge 4 is 20 mm.

[0083] When performing composite welding and symmetrical alternating filling, the filling process adopts a "double-sided alternating symmetrical" strategy: after the root pass is completed, the inner and outer narrow gap bevels 3 are filled in layers, following the welding sequence of "upper side-lower side-segmental alternation" to balance the heat accumulation on the upper and lower sides of the blunt edge 4, effectively eliminating the angular deformation and shell depression problems caused by thick-thickness welding. Specifically, the upper and lower bevels are equally divided into 4 segments and numbered, where A and D are symmetrical, B and C are symmetrical; the arc segment A1 of the upper bevel and the arc segment A2 of the lower bevel are symmetrical. During filling, the filling is carried out in a cyclical sequence of upper arc segment A1-lower arc segment A2-upper arc segment D1-lower arc segment D2.

[0084] Immediately after welding, use the following method: Figure 4 and Figure 5 The localized heating stress relief and protection device shown performs heat treatment on the butt weld 6 area and provides cooling protection for the non-heat-treated area of ​​the through-hole component 1. Subsequently, various performance tests are carried out on the welded structure using the same testing methods as in Example 1.

[0085] The total welding time in this embodiment is approximately 6 hours, representing a 75% increase in efficiency compared to the 24 hours in Comparative Example 1. After welding, the axial deviation of the through-hull component 1 is ≤0.5mm; there are no obvious depressions around the opening of the pressure-resistant shell 2, with local depressions ≤1.2mm; the overall roundness error of the pressure-resistant shell 2 is ≤1.5mm, meeting the design accuracy requirements. After heat treatment, the maximum residual tensile stress in the butt weld 6 area is ≤180MPa, compared to 680MPa in Comparative Example 1, representing a stress reduction rate of 73.5%. The butt weld 6 is geometrically regular, exhibits no interference echoes during ultrasonic testing, and has uniform radiographic film density, resulting in a 100% defect detection rate and a 98.5% first-pass yield.

[0086] Comparative Example 1

[0087] like Figure 1 As shown, this comparative example provides a conventional corner joint welding method for the titanium alloy through-hole component 1 and the pressure-resistant structural shell 2. In this comparative example, the material, size specifications, and performance testing standards of the through-hole component 1 and the pressure-resistant structural shell 2 are the same as those in Example 1, except that:

[0088] In this comparative example, the through-hole component 1 is inserted into the opening of the pressure-resistant structural shell 2, forming a T-shaped corner joint between the two, with the angle of the welding area being α.

[0089] Next, assembly and fixing are carried out. The through-hull component 1 and the pressure-resistant shell 2 are positioned and fastened using tooling fixtures to ensure that the assembly gap between the two is controlled within 0~0.5mm. Due to the corner joint, the welding operation space is limited, and the welding torch can usually only approach the weld from one side of the shell.

[0090] Next, welding is performed. The entire welding process uses manual or semi-automatic TIG welding in multiple passes, with eight locating welds evenly spaced circumferentially, each weld being 15-20mm long. For the root pass, the welding current is 110A, voltage 12V, welding speed 60mm / min, and argon gas flow rate 15L / min. After the root pass, filler and capping welds are performed, requiring a total of 15-20 passes. For the filler pass, the welding current is 130-150A, voltage 12-14V, and welding speed 50-80mm / min. The interpass temperature is strictly controlled below 150℃, and the oxide layer on the weld surface must be cleaned with a stainless steel wire brush after each pass. Because the through-hull component 1 is located on one side of the pressure-resistant shell 2, the operating space is narrow, requiring the welder to kneel and weld from the outside. The inside is inaccessible, making back gas protection impossible; only a simple back argon purging device provides basic protection.

[0091] Finally, after welding, the weld surface is ground to remove oxide scale and spatter. The entire weld is then subjected to stress-relieving annealing in a furnace at a temperature of 580℃ for 2 hours. After cooling to room temperature in the furnace, the weld is removed from the furnace.

[0092] After welding is completed, the welded structure is subjected to various performance tests using the same testing methods as in Example 1.

[0093] In this comparative example, the fillet welds of the through-hull component 1 and the pressure-resistant shell 2 took approximately 24 hours to complete, with 4 hours for the root pass and 20 hours for the fillet weld, severely hindering production progress. Geometric accuracy testing revealed that the axis of the through-hull component 1 was misaligned relative to the reference plane of the pressure-resistant shell 2, with a maximum deviation of 2.5 mm; significant depressions appeared around the opening of the pressure-resistant shell 2, with local depressions reaching 3.8 mm; and the overall roundness error of the pressure-resistant shell 2 reached 3.2 mm, indicating severe welding deformation. Residual stress testing showed that the maximum residual stress in the weld area reached 680 MPa, approaching 90% of the yield strength of TC4 titanium alloy, posing a risk of stress corrosion cracking. Ultrasonic non-destructive testing revealed two non-fusion defects at the weld root, and the geometry of the fillet weld significantly interfered with the detection signal, resulting in insufficient reliability in defect detection.

[0094] In summary, this invention transforms the traditional corner joint between the through-hull component 1 and the pressure-resistant structural shell 2 into a conformal skirt 11 butt joint. Combined with a narrow gap bevel 3 with a large blunt edge 4, high-energy beam single-pass root pass welding, symmetrical alternating laser-arc composite welding, conformal local heat treatment, and forced cooling of key parts, it achieves high-efficiency, high-precision, and low-stress manufacturing of titanium alloy through-hull components.

[0095] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for high-efficiency, precision, and low-stress welding of titanium alloy through-cabin components, characterized in that, The welding manufacturing method includes: Joint design: A conformal skirt (11) is machined at the welding end of the through-hole component (1), and a shell opening (21) is machined at the welding end of the pressure-resistant structural shell (2). The conformal skirt (11) can be assembled with the shell opening (21) to form a butt joint. After the conformal skirt (11) is butt-jointed with the shell opening (21), a narrow gap bevel (3) is formed. The root of the narrow gap bevel (3) is provided with a blunt edge (4), and the blunt edge (4) is formed by assembling the conformal skirt (11) with the shell opening (21). Root pass welding: Between the mating surfaces of the blunt edge (4), a single pass self-fusion root pass welding is performed using a welding method that can completely melt through the blunt edge (4) in one pass, and a root pass weld is formed. Fill welding: The narrow gap groove (3) is filled by a composite welding method to form a fill weld, and the filling follows a symmetrical alternating welding sequence; Post-weld treatment: After welding is completed, the root weld and the filler weld constitute a butt weld (6). The area of ​​the butt weld (6) is subjected to conformal local heat treatment, and the non-heat-treated area of ​​the through-hole component (1) is cooled and protected.

2. The welding manufacturing method according to claim 1, characterized in that, The conformal skirt (11) protrudes along the central axis of the through-hole component (1) toward the end of the pressure-resistant structural shell (2) to be welded, and is coaxial with the through-hole component (1).

3. The welding manufacturing method according to claim 2, characterized in that, The conformal skirt (11) has a skirt bevel (111) on its end face facing the pressure-resistant structural housing (2), and a skirt blunt edge (112) is provided at the bottom of the skirt bevel (111).

4. The welding manufacturing method according to claim 3, characterized in that, The shell opening (21) has a mating bevel (211) on its end face facing the through-hole component (1), and the bottom of the mating bevel (211) has a mating blunt edge (212); the mating bevel (211) and the skirt bevel (111) are arranged opposite to each other to form the narrow gap bevel (3); the mating blunt edge (212) and the skirt blunt edge (112) are arranged opposite to each other, and the two can be joined together to form the blunt edge (4).

5. The welding manufacturing method according to claim 4, characterized in that, The narrow gap bevel (3) is a U-shaped bevel with a bevel angle of 3°~8°; and the thickness of the blunt edge (4) is 15~20mm.

6. The welding manufacturing method according to claim 1, characterized in that, The welding methods used for the root pass welding include high-power laser welding or keyhole tungsten inert gas welding.

7. The welding manufacturing method according to claim 1, characterized in that, The composite welding method is laser-arc composite welding, in which the laser beam and the electric arc are arranged one in front of the other, with the laser in front and the electric arc behind.

8. The welding manufacturing method according to claim 1, characterized in that, The symmetrical alternating welding sequence includes: when the narrow gap groove (3) is a single-sided groove, alternating symmetrical welding is performed along the circumference of the narrow gap groove (3); or, when the narrow gap groove (3) is a double-sided groove, layered alternating symmetrical welding is performed on the upper and lower double narrow gap grooves (3).

9. The welding manufacturing method according to claim 1, characterized in that, The conformal local heat treatment is carried out by conformal local heating strip (5) attached to the butt weld (6), and the heating temperature is not lower than 500°C; and the outer side of the conformal local heating strip (5) is covered with a heat insulation layer.

10. The welding manufacturing method according to claim 1, characterized in that, The cooling protection includes: covering the outer surface of the transom (1) with a copper cold sleeve (7) having cooling channels and / or inserting a copper cold sleeve (8) having cooling channels into the core of the transom (1).

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