Welding method for nickel-based alloy micro conduit

Abstract

The invention provides a welding method for a nickel-based alloy miniature conduit, and relates to the technical field of welding, the welding method for the nickel-based alloy miniature conduit is used for a conduit with the diameter smaller than 10 mm or the wall thickness not larger than 1 mm, and comprises the following steps that a lantern ring with the inner diameter equal to the outer diameter of the conduit is prepared, the guide pipe is made of nickel-based alloy which is the same as the guide pipe in material or can be metallurgically compatible; sleeving and fixing the lantern ring at the butted joint of the guide pipe; in the inert gas environment, the pulse current micro-arc TIG is used for welding the guide pipe, the pulse current micro-arc welding gun rotates for 1-3 circles relative to the guide pipe in the pulse current micro-arc TIG welding process, and the welding current is gradually reduced from arc starting to arc stopping. In the welding process, the lantern ring and base metal of the guide pipe are synchronously melted and then fully fused, the lantern ring becomes a part of welding seam metal to be filled with metal to compensate a welding seam, and under the constraint of microminiaturization and integration, integrated manufacturing of structure positioning, metallurgical bonding and performance enhancement is achieved.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a welding method for nickel-based alloy microcatheters. Background Technology

[0002] In high-end manufacturing, micropipeline systems made of nickel-based superalloys (such as Inconel 625, Inconel 718, and Hastelloy C-276) are widely deployed for transporting high-temperature, high-pressure fuels, hydraulic oils, or corrosive cooling media. These conduits typically have extremely small geometric dimensions, with outer diameters often less than 10 mm and wall thicknesses not exceeding 1 mm, sometimes even as small as 3 mm in outer diameter and 0.3 to 0.5 mm in wall thickness, forming typical small-diameter, thin-walled structures. However, the welding process for these micropipes faces multiple technical bottlenecks. Weld depressions and poor weld formation are prominent issues. Conventional welding methods rely solely on the melting of the base material to form a molten pool; surface tension causes the weld metal to shrink inward, resulting in outer diameter depressions, severely affecting sealing performance and structural integrity. Heat input control is extremely difficult; excessive energy input can easily lead to burn-through or permanent deformation, while insufficient energy input results in incomplete fusion defects, making precise control at the microscale extremely challenging. Although conventional TIG welding is a commonly used arc welding process, its arc diameter usually exceeds 2 mm, which is much larger than the 3 mm pipe diameter. The base current is difficult to adjust precisely, which can easily cause overheating damage in thin-walled areas, excessive expansion of the heat-affected zone, and significant deterioration of joint performance. Summary of the Invention

[0003] The present invention aims to solve the problems of weld depression and poor forming when traditional welding techniques are used to process micro-sized conduits.

[0004] To address the above problems, this invention provides a welding method for nickel-based alloy microcatheters.

[0005] This invention provides a welding method for nickel-based alloy microcatheters, used for catheters with a diameter less than 10 mm or a wall thickness not greater than 1 mm, comprising the following steps: S1: Prepare a collar with an inner diameter the same as the outer diameter of the catheter, made of a nickel-based alloy that is the same material as the catheter or metallurgically compatible. S2: Fit and secure the collar to the joint where the conduits are joined; S3: In an inert gas environment, pulsed current micro-arc TIG welding of the conduit. During the pulsed current micro-arc TIG welding process, the pulsed current micro-arc welding torch rotates 1 to 3 times relative to the conduit, and the welding current decreases from the start of the arc to the end of the arc.

[0006] Optionally, the distance between the electrode and the electrode of the pulsed current micro-arc welding torch is 0.3 to 1.5 mm.

[0007] Optionally, the welding parameters for pulsed current micro-arc TIG welding include: a constant current or DC pulse mode for welding current, a peak current of 5 to 15A, a base current of 1 to 3A, a pulse frequency of 0 to 1000Hz, a peak-to-time ratio of 0 to 100%, an arc width of 1.5 to 2.0mm, and a welding speed of 50 to 150mm / min.

[0008] Optionally, the welding current decreases at a constant rate from the start of the arc to the end of the arc.

[0009] Optionally, the welding current is 6 to 12A when the arc is started and 5 to 11A when the arc is terminated.

[0010] Optionally, the cross-section of the collar perpendicular to the conduit is circular or C-shaped.

[0011] Optionally, the electrode is a cerium-tungsten electrode, a lanthanum-tungsten electrode, or a thorium-tungsten electrode.

[0012] Optionally, the tip cone angle of the electrode is 15° to 30°, and the diameter of the electrode is controlled between 0.6 and 1.2 mm.

[0013] Optionally, after pulsed current micro-arc TIG welding, the micro-conduit is cooled to below 400°C in an inert gas environment, and the inner diameter of the micro-conduit after welding is not less than 40% of the diameter of the conduit before welding.

[0014] Optionally, the length of the collar is 0.5 to 5 mm and the thickness is no more than 2 mm.

[0015] The beneficial effects of the welding method for a nickel-based alloy microcatheter of the present invention are as follows: A collar with an inner diameter identical to the outer diameter of the conduit is prepared, ensuring seamless nesting. This collar is precisely fitted and fixed at the joint where the two conduits meet. During welding, the collar melts synchronously with the base material of the conduit and fully fuses, becoming part of the weld metal as filler metal to compensate for the weld, forming a full and depression-free weld. Furthermore, the collar acts as a precision clamp to ensure coaxial alignment and end-face contact between the two conduit segments, and as a structural reinforcing ring to enhance joint strength. Under the constraints of miniaturization and integration, integrated manufacturing of structural positioning, metallurgical bonding, and performance enhancement is achieved. The low heat input characteristics of pulsed current micro-arc TIG welding effectively prevent burn-through and deformation of thin-walled conduits. The rotational motion of the pulsed current micro-arc welding torch relative to the conduit ensures the circumferential uniformity of the weld, reduces reliance on operator skill, and improves process stability. Meanwhile, the pulsed current micro-arc welding torch is set to rotate 1 to 3 revolutions relative to the guide tube. The first revolution completes the basic welding, and the additional revolutions beyond one revolution play a crucial role in effectively remelting and heat-treating the arc-starting area (which is usually relatively weak due to incomplete thermal circulation). This compensates for defects that may be caused by insufficient thermal circulation during arc start-up, ensuring the uniformity and consistency of the entire circumferential weld and ultimately guaranteeing the integrity of the collar positioning function. The welding current is controlled by a gradual decrease. The initial current ensures reliable establishment of the initial molten pool over a very short distance. Subsequently, the current decreases smoothly and continuously as the welding torch rotates. This gradual decrease design is to actively compensate for the heat accumulation effect caused by the overall temperature rise of the workpiece during welding, avoiding defects caused by overheating in the latter half of the weld. It further optimizes the weld cooling process, thereby ensuring excellent mechanical properties of the joint and avoiding the problem of rapid solidification and shrinkage of the molten pool due to a sudden cessation of heat input, which could lead to crater depressions, shrinkage cavities, or even micro-cracks at the arc termination point. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of the welding method for nickel-based alloy microcatheters according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the catheter and collar 2 according to an embodiment of the present invention; Explanation of reference numerals in the attached figures: 1. Catheter; 2. Loop 2. Detailed Implementation

[0017] 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. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention's description is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "comprising" and its variations as used herein are open-ended inclusion, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below.

[0019] like Figure 1 As shown in the figure, an embodiment of the present invention provides a welding method for a nickel-based alloy microcatheter, used for a catheter 1 with a diameter less than 10 mm or a wall thickness not greater than 1 mm, comprising the following steps: S1: Prepare a collar 2 with the same inner diameter as the outer diameter of the conduit 1. The collar 2 and the conduit 1 are made of the same material as the conduit 1 or a nickel-based alloy that is metallurgically compatible. S2: As Figure 2 As shown, the collar 2 is fitted and fixed to the joint where the conduit 1 is connected; S3: In an inert gas environment, pulsed current micro-arc TIG welding of conduit 1. During the pulsed current micro-arc TIG welding process, the pulsed current micro-arc welding torch of conduit 1 rotates 1 to 3 times relative to conduit 1, and the welding current decreases from the start of the arc to the end of the arc.

[0020] Specifically, nickel-based alloy microcatheters refer to tubular structures made of nickel-based alloy materials with a diameter less than 10 mm or a wall thickness not exceeding 1 mm. Due to their size characteristics, these catheters present technical challenges in terms of heat input control, weld formation, and maintenance of mechanical properties during the welding process.

[0021] The collar 2 refers to a ring-shaped structure whose inner diameter is the same as the outer diameter of the conduit 1. The collar 2 is used as a filler material during the welding process and assists in the alignment and fixation of the conduit 1. The material of the collar 2 is the same as or metallurgically compatible with that of the conduit 1 to ensure the material uniformity and performance of the welded joint.

[0022] An inert gas environment refers to a protective space filled with an inert gas (such as argon, helium, or a mixture thereof) within the welding area. The purpose of this environment is to isolate the welding area from reactive gases such as oxygen and nitrogen in the air, thereby preventing oxidation and nitriding of the weld metal and ensuring the purity and mechanical properties of the weld.

[0023] Pulsed current micro-arc TIG welding refers to a tungsten inert gas (TIG) welding technology that uses a pulsed current mode. This technology achieves precise control of the welding heat input by periodically switching between peak and base currents. The micro-arc characteristic concentrates the arc energy, making it suitable for precision welding of small workpieces. TIG welding, also known as GTAW (Gas Tungsten Arc Welding), utilizes the arc heat generated between the tungsten electrode (which does not melt but only emits electrons and maintains the arc) and the workpiece to melt the base metal and filler wire (or even without filler wire). Simultaneously, an inert gas (primarily argon, supplemented by helium or an argon-helium mixture) protects the arc and molten pool, preventing air from reacting with the high-temperature metal, thus obtaining a dense and pure weld.

[0024] A pulsed current micro-arc welding torch refers to a specialized device used for pulsed current micro-arc TIG welding. It contains a tungsten electrode, and by controlling the distance between the electrode and the workpiece, as well as the current parameters, a stable micro-arc is generated to complete the welding operation.

[0025] In this embodiment, a collar 2 with the same inner diameter as the outer diameter of the conduit 1 is prepared. The inner diameter of the collar 2 is the same as the outer diameter of the conduit, ensuring seamless nesting. The collar 2 is precisely fitted and fixed at the joint where the two conduits meet. During the welding process, the collar 2 melts synchronously with the base material of the conduit 1 and fully fuses, becoming part of the weld metal as filler metal to compensate for the weld, forming a full and depression-free weld. Furthermore, the collar 2 also acts as a precision clamp to ensure the coaxial alignment and end face fit of the two conduit sections 1 during welding, and as a structural reinforcing ring to enhance the joint strength. Under the constraints of miniaturization and integration, integrated manufacturing of structural positioning, metallurgical bonding, and performance enhancement is achieved. The low heat input characteristics of pulsed current micro-arc TIG welding effectively avoid burn-through and deformation of the thin-walled conduit 1. The rotational movement of the pulsed current micro-arc welding torch relative to the conduit 1 ensures the circumferential uniformity of the weld, reduces dependence on operator skill, and improves process stability. Meanwhile, the pulsed current micro-arc welding torch is set to rotate 1 to 3 times relative to the guide tube 1. The first rotation completes the basic welding, and the additional rotations after the first rotation play a key role in effectively remelting and heat-treating the arc-starting area (which is usually relatively weak in quality due to incomplete thermal circulation). This compensates for the defects that may be caused by insufficient thermal circulation during arc start-up, ensures the uniformity and consistency of the entire circumferential weld, and ultimately guarantees the integrity of the positioning function of the collar 2. The welding current is controlled by a gradual reduction. The initial current ensures that the initial molten pool can be reliably established over a very short distance. Subsequently, the current decreases smoothly and continuously as the welding torch rotates. This reduction design is intended to actively compensate for the heat accumulation effect caused by the overall temperature rise of the workpiece during welding, avoid defects caused by overheating in the latter half of the weld, and further optimize the cooling process of the weld. This ensures the excellent mechanical properties of the joint and avoids the problem of rapid solidification and shrinkage of the molten pool due to a sudden cessation of heat input, which could lead to crater depressions, shrinkage cavities, or even microcracks at the arc termination point. For the conduit 1 with a wall thickness of no more than 1 mm, any tiny crater defect could severely weaken the sealing and mechanical strength of the weld and may affect the inner diameter.

[0026] Compared to traditional TIG welding, this application effectively solves the common problems of weld depression and poor formation in welding small-diameter thin-walled conduits by introducing a collar 2 with the same inner diameter as the outer diameter of the conduit 1 as filler material. In traditional TIG welding, without filler material, the molten pool metal easily contracts inward due to surface tension, leading to weld depression on the outer diameter. The collar 2 design in this application provides sufficient filler metal, ensuring a full weld formation. Pulsed current micro-arc TIG welding technology is employed, combined with a control strategy of decreasing welding current from arc ignition to arc termination, achieving precise management of heat input. This contrasts with conventional TIG welding, where the large arc diameter and high base current easily lead to overheating damage to the thin-walled base material. The low heat input characteristics of pulsed current micro-arc TIG welding, combined with current reduction, effectively avoid burn-through and deformation, and reduce the heat-affected zone, thereby improving the mechanical properties of the joint. Sleeving and fixing the collar 2 to the joint of the conduit 1 simplifies the assembly process and reduces reliance on high-precision tooling. The overall solution of this application provides an efficient, stable and high-performance solution for the precision welding of nickel-based alloy microcatheters through the synergistic effect of various technical features.

[0027] In some specific embodiments, during pulsed current micro-arc TIG welding, the pulsed current micro-arc welding torch rotates relative to the guide tube 1. This can be achieved by rotating the workpiece while keeping the welding torch stationary, or by rotating the welding torch around the workpiece while keeping the workpiece stationary. As long as the accuracy requirements for the relative motion of the two components are met, it is considered an equivalent substitution.

[0028] In addition to the standard square wave pulse, the pulse waveform can also use a double pulse or a soft-start pulse waveform. A double pulse (a high-frequency pulse superimposed on a low-frequency pulse) can further stir the molten pool, which is beneficial for gas escape and grain refinement.

[0029] In some specific embodiments, the aforementioned collar 2 is fitted and fixed to the joint where the conduit 1 is connected. The collar 2 can be fixed using various methods, such as self-fixation through a slight interference fit, or by applying a small amount of temporary spot welding between the collar 2 and the conduit 1 to ensure its positional stability during welding. Alternatively, a special clamp can be used to position and clamp the collar 2 and the conduit 1 to ensure alignment accuracy at the joint.

[0030] Subsequently, pulsed current micro-arc TIG welding is performed on the aforementioned conduit 1 within an inert gas environment. The inert gas environment can be created by setting a local protective gas shield in the welding area or by filling a closed cavity with inert gas. The implementation of pulsed current micro-arc TIG welding requires a TIG welding machine with pulse functionality and capable of outputting a small current. During the welding process, the pulsed current micro-arc welding torch rotates relative to the conduit 1, with the number of rotations controlled between 1 and 3. This rotational motion can be achieved by mounting the welding torch on a programmable rotating fixture, ensuring that the welding torch applies heat uniformly in the circumferential direction of the conduit 1, thereby obtaining a circumferentially consistent weld.

[0031] In pulsed current micro-arc TIG welding, the welding current decreases from the start of the arc to its termination. This decrease in current can be controlled by the program within the welding machine.

[0032] Optionally, the distance between the electrode of the pulsed current micro-arc welding torch and the collar 2 is 0.3 to 1.5 mm.

[0033] Specifically, the distance between the electrode of the pulsed current micro-arc welding torch and the collar 2 refers to the spatial interval between the tip of the welding torch electrode and the surface of the collar 2 to be welded during the welding operation. This distance is a key parameter affecting arc characteristics, energy density, and heat input efficiency. Several methods can be used to achieve precise control of this distance. For example, one method is to use a high-precision mechanical positioning device to calibrate the welding torch before welding and ensure that it maintains a preset distance of 0.3 to 1.5 mm throughout the welding process. Another method is to integrate an automated feedback control system, which can be equipped with a vision sensor or laser ranging module to monitor the distance between the electrode and the collar 2 in real time and dynamically adjust the position of the welding torch based on the measurement results to ensure that the distance is always maintained within the optimized range of 0.3 to 1.5 mm.

[0034] In this optional embodiment, by precisely limiting the distance between the electrode of the pulsed current micro-arc welding torch and the collar 2 to 0.3 to 1.5 mm, combined with the aforementioned welding method for nickel-based alloy micro-conduits, the arc stability and heat input management during the welding process can be significantly optimized. When performing pulsed current micro-arc TIG welding in an inert gas environment, if the electrode distance is too large, it is difficult to stably ignite the arc at low current, resulting in a dispersed and unstable arc, insufficient heat input, and inadequate molten pool formation, leading to incomplete fusion or poor weld formation. Conversely, if the electrode distance is too small, the arc energy is too concentrated, resulting in excessively high instantaneous heat input, which can easily cause the thin-walled micro-conduit 1 to burn through or suffer severe structural deformation at the moment of arc ignition. Therefore, controlling the distance between the electrode and the collar 2 within the optimized range of 0.3 to 1.5 mm ensures a moderate arc length, concentrated and stable arc energy density, and limits the heating area to a very small range, allowing the heat generated by pulsed current micro-arc TIG welding to act precisely and uniformly on the joint of the conduit 1. This precise heat input control, combined with the rotation of the pulsed current micro-arc welding torch relative to the guide tube 1 and the control of the decreasing welding current from arc ignition to arc termination, ensures the stable formation, full fusion, and orderly solidification of the molten pool. Thus, when welding nickel-based alloy micro-guide tubes with a diameter of less than 10 mm or a wall thickness of no more than 1 mm, it effectively avoids common defects such as burn-through, deformation, and lack of fusion, thereby improving welding quality and process stability.

[0035] In some specific embodiments, an automated welding platform integrating a high-precision motion control system and vision sensors can be used when welding nickel-based alloy microconductors. This platform can precisely clamp and position the welding torch and control its rotation at a preset speed during welding. The pulsed current micro-arc welding torch is mounted on a multi-axis robotic arm. Before welding begins, the distance between the welding torch electrode tip and the outer surface of the collar 2 is precisely measured and calibrated using a laser ranging module mounted on the robotic arm. Throughout the welding process, the vision sensor continuously monitors the shape and position of the arc, and, combined with arc voltage feedback, adjusts the posture and height of the robotic arm in real time to ensure that the distance between the electrode and the collar 2 is always maintained within the set range of 0.3 to 1.5 mm. Precisely controlling the distance between the electrode and the collar 2 of the pulsed current micro-arc welding torch within 0.3 to 1.5 mm significantly improves the stability of the arc and the accuracy of heat input during welding. This effectively solves the problems of arc drift caused by improper electrode distance, incomplete fusion due to insufficient heat input, and burn-through or severe deformation of the conduit 1 caused by excessive heat input. By combining pulsed current micro-arc TIG welding in an inert gas environment with controlled torch rotation and decreasing welding current, precise distance control ensures stable molten pool formation and solidification, resulting in well-formed welds with no depressions or protrusions on either the inner or outer surfaces. Simultaneously, it minimizes the heat-affected zone, thereby guaranteeing excellent mechanical properties and fatigue strength in the welded joint. For nickel-based alloy micro-conduits with diameters less than 10 mm or wall thicknesses no greater than 1 mm, this precise heat input control is crucial for obtaining high-quality welds, significantly improving weld yield and reliability.

[0036] Optionally, the welding parameters for pulsed current micro-arc TIG welding include: a constant current or DC pulse mode for welding current, a peak current of 5 to 15A, a base current of 1 to 3A, a pulse frequency of 0 to 1000Hz, a peak-to-time ratio of 0 to 100%, an arc width of 1.5 to 2.0mm, and a welding speed of 50 to 150mm / min.

[0037] Specifically, the welding current can be in constant current mode, providing a continuous and stable heat input. This is relatively simple to operate and suitable for situations where heat input control requirements are not extreme but stable penetration depth is needed. Alternatively, the welding current can be in DC pulse mode, achieving precise control of heat input by periodically switching between peak and base currents. This helps refine grains, improve weld formation, and reduce deformation, and is particularly suitable for thin-walled materials. The peak current is the main energy source for melting the base material and forming the molten pool. Setting it in the range of 5 to 15 A ensures effective melting and good penetration depth for nickel-based alloy microconductors, while avoiding burn-through or overheating due to excessive current. The base current, in the range of 1 to 3 A, maintains stable arc combustion in pulse mode and provides lower heat input between peak currents, helping to control the molten pool temperature, prevent molten pool solidification, and provide stable arc ignition conditions for the next pulse. The pulse frequency determines the rate at which the current switches between peak and base values, ranging from 0 to 1000 Hz. Lower frequencies (e.g., 0Hz, i.e., constant current) provide continuous heat input; higher frequencies allow for finer control of heat input distribution, promoting molten pool stirring, improving weld microstructure, and helping to suppress grain growth. The peak-time ratio refers to the percentage of peak current duration within a pulse cycle, ranging from 0% to 100%. Adjusting this ratio allows for precise control of the effective heat input, thus affecting molten pool size, penetration depth, and weld formation. Arc width control between 1.5 and 2.0 mm directly affects heat concentration and the extent of the heat-affected zone. For conduit 1, this arc width range allows for precise heat concentration in the weld area, preventing overheating damage to other areas of the pipe wall and contributing to a narrow and deep weld. Welding speed settings between 50 and 150 mm / min affect the heat input per unit length of weld and the residence time of the molten pool. Within this speed range, sufficient melting time is ensured to form a continuous weld, while avoiding excessive residence time leading to heat accumulation and deformation, or excessive speed resulting in incomplete fusion.

[0038] In this optional embodiment, precise control of heat input and stable arc maintenance during the welding process are achieved by finely setting various parameters of pulsed current micro-arc TIG welding. When performing pulsed current micro-arc TIG welding on the conduit 1 in an inert gas environment, the energy input method can be flexibly adjusted according to specific material and wall thickness requirements by selecting either constant current or DC pulse mode. The synergistic effect of peak current, base current, pulse frequency, and peak-to-time ratio effectively manages the formation and solidification process of the molten pool, avoiding burn-through or an excessively large heat-affected zone due to heat overload, and also preventing incomplete fusion due to insufficient heat. Optimization of the arc width and welding speed further ensures that heat is concentrated in the weld area and that welding is advanced at an appropriate speed, thereby forming a uniform and high-quality weld during the rotation of the pulsed current micro-arc welding torch relative to the conduit 1 for 1 to 3 revolutions. This combination of parameters, along with the rotation of the welding torch and the overall process of decreasing welding current from arc initiation to arc termination, can effectively overcome the problems faced by traditional welding methods in welding small-diameter, thin-walled nickel-based alloy conduits, such as weld depression, heat input control difficulties, mechanical property degradation, and poor process stability.

[0039] Optionally, the welding current decreases at a constant rate from the start of the arc to the end of the arc.

[0040] In some specific embodiments, a DC pulse mode can be used when welding nickel-based alloy microcatheters with a diameter of 3 mm and a wall thickness of 0.5 mm. In this mode, the peak current can be set to 10 A, the base current to 2 A, the pulse frequency to 500 Hz, and the peak-to-time ratio to 50%. Simultaneously, the arc width can be controlled at 1.8 mm, and the welding speed can be set to 100 mm / min. Throughout the welding process, the pulsed current micro-arc welding torch rotates 1 to 3 revolutions relative to the conduit 1, and the welding current decreases uniformly from arc initiation to arc termination. This allows for precise control of heat input during welding, effectively preventing burn-through and deformation of the conduit 1 during welding, while ensuring arc stability and good weld formation. This significantly improves the mechanical properties and fatigue strength of the weld joint, reduces the risk of coarse grains in the heat-affected zone, and thus improves the yield and reliability of nickel-based alloy microcatheter welding.

[0041] Optionally, the welding current is 6 to 12A when the arc is started and 5 to 11A when the arc is terminated.

[0042] Specifically, the uniform decrease in welding current from arc ignition to arc termination refers to the linear decrease in welding current from the initial arc ignition current value to the final arc termination current value during pulsed current micro-arc TIG welding. This uniform decrease can be achieved through: pre-setting the arc ignition and arc termination currents via the welding power source's control system and setting a fixed current decrease rate to maintain a linear change in the current throughout the decrease; or, using a welding power source with programmable control capabilities, defining a linear function relationship between the current and time or welding progress in the welding program to achieve a uniform current decrease. The welding current at arc ignition is 6 to 12 A, a characteristic that defines the current range in the initial stage of the welding process. The arc ignition current is a key parameter for establishing a stable arc and forming the initial molten pool in the early stages of welding. For welding nickel-based alloy micro-conduits, their thin-walled characteristics require the arc ignition current to be sufficiently high to rapidly melt the base material and form a stable molten pool, while avoiding excessive current that could lead to instantaneous burn-through or overheating. Controlling the arc-starting current within a narrow range of 6 to 12 A aims to precisely balance energy input, ensuring rapid formation and good fusion of the molten pool in the initial welding stage, while effectively suppressing excessive heat concentration, laying a stable foundation for subsequent welding processes. The welding current at the arc-ending point is 5 to 11 A, a characteristic that defines the current range at the end of the welding process. Precise control of the arc-ending current is crucial for the final weld quality and mechanical properties. Gradually reducing the current towards the end of welding avoids stress concentration caused by sudden solidification of the molten pool, thereby reducing the risk of weld end depressions, cracks, or porosity. Controlling the arc-ending current within the range of 5 to 11 A aims to achieve a smooth decrease in heat input, ensuring a smooth transition at the weld end, effectively suppressing grain coarsening in the heat-affected zone, and reducing residual stress, thus improving the overall quality and reliability of the weld.

[0043] In this optional embodiment, by precisely defining the specific ranges of the arc-starting and arc-ending currents during the welding process of nickel-based alloy microconductors, the problem of inaccurate heat input control in traditional welding methods is solved. During pulsed current micro-arc TIG welding in an inert gas environment, the welding current is precisely set between 6 and 12 A during the arc-starting stage. This ensures a stable arc is quickly established and a sufficiently large molten pool is formed in the initial welding stage, thereby achieving full fusion of the base material and avoiding incomplete fusion defects due to insufficient current. Simultaneously, this optimized current range effectively prevents overheating damage or burn-through to microconductors 1 with a diameter less than 10 mm or a wall thickness no greater than 1 mm. As the pulsed current micro-arc welding torch rotates 1 to 3 revolutions relative to the conduit 1 to complete the welding, the welding current is precisely controlled within the range of 5 to 11 A during the arc-ending stage. This decreasing current control method allows the heat input to decrease smoothly at the end of the welding process, effectively suppressing overheating of the molten pool and excessive shrinkage of the metal, thereby ensuring a smooth transition at the weld end and avoiding dents, cracks, or deformation. By precisely controlling the arc initiation and termination currents, combined with a strategy of gradually decreasing the overall welding current from arc initiation to arc termination, this solution achieves refined management of the welding heat input of the micro-conduit 1, ensuring good weld formation and excellent joint performance.

[0044] In some specific embodiments, a digital pulsed TIG welding machine with high-precision current programming capabilities can be used. When setting the welding parameters, the arc-starting current is set to 8.5A and the arc-ending current is set to 7.0A. Simultaneously, based on the diameter and wall thickness of the micro-conduit 1 and the expected welding speed, the total welding time required to complete 1 to 3 revolutions is calculated, for example, set to 30 seconds. The microcontroller or digital signal processor inside the welding machine automatically generates a linear current-decreasing ramp based on the set arc-starting current, arc-ending current, and total welding time, and precisely controls the output current to uniformly decrease from 8.5A to 7.0A within 30 seconds. This control method ensures that the heat input changes smoothly and predictably throughout the welding process, thereby optimizing the molten pool behavior and weld formation. In the pulsed current micro-arc TIG welding of nickel-based alloy microconduits, the uniform decrease in welding current ensures that the heat input remains highly uniform and stable throughout the entire welding cycle. This effectively avoids heat input fluctuations caused by inconsistent current change rates, thereby significantly reducing defects such as weld depressions, burn-through, and lack of fusion, and maintaining the stability and consistency of the molten pool. Ultimately, this approach improves the forming quality, mechanical properties, and process stability of microcatheter welded joints, especially for small-diameter, thin-walled nickel-based alloy catheters, where welding quality and yield are significantly improved.

[0045] Optionally, the cross section of the collar 2 perpendicular to the conduit 1 is circular or C-shaped.

[0046] Specifically, the collar 2 ensures a uniform contact surface with the conduit 1. This uniform contact helps reduce local stress concentration during installation and ensures that heat is evenly transferred from the collar 2 to the conduit 1 during welding, avoiding deformation or defects caused by uneven heat distribution. Furthermore, the circular cross-section is easy to machine and exhibits good stability under stress.

[0047] The collar 2 may have an opening, allowing it to be fitted onto the conduit 1 via a snap-fit ​​or elastic fit. This design greatly simplifies the assembly process, improves efficiency, and allows the collar 2 to accommodate the dimensional tolerances of the microconduit 1 to some extent, thereby reducing assembly stress caused by dimensional mismatches. During welding, the C-shaped cross-section still provides the necessary filler material and helps control the shape of the molten pool.

[0048] After the collar 2 is prepared, fitted, and fixed to the joint of the conduit 1, pulsed current micro-arc TIG welding is performed. Based on this, by limiting the cross-section of the collar 2 perpendicular to the conduit 1 to either circular or C-shaped, the collar 2 plays a more superior role throughout the welding process. Specifically, when the collar 2 has a circular cross-section, its contact surface with the conduit 1 is uniform. This ensures that the collar 2 can be stably and stress-free fixed to the conduit 1 during the fitting and fixing step, avoiding assembly difficulties caused by poor local contact. In the subsequent pulsed current micro-arc TIG welding process, the uniform contact surface promotes uniform heat conduction, effectively reducing thermal stress concentration, thereby optimizing the stability and forming quality of the weld pool. When the collar 2 has a C-shaped cross-section, its open structure greatly simplifies the fitting and fixing operation, allowing the collar 2 to be quickly and easily snapped onto the conduit 1, significantly improving assembly efficiency. This design also allows the collar 2 to adapt to the dimensional tolerances of the conduit 1 within a certain range, reducing assembly difficulties and potential deformation risks caused by tolerance accumulation. During the welding process, the C-shaped cross-section serves as a filler material, and its structure helps control the flow behavior of the molten pool, avoiding problems such as uncontrolled molten pool or poor weld formation. Through the above-mentioned collar 2 designs with different cross-sectional shapes, the solution of this application significantly improves the assembly convenience, molten pool control capability, and weld formation quality during the welding process of the micro-conduit 1 based on the basic pulsed current micro-arc TIG welding method. It effectively solves the limitations of the traditional collar 2 in terms of assembly, stress concentration, and molten pool control, thereby ensuring the mechanical properties and reliability of the welded joint.

[0049] The cross-section of the collar 2 perpendicular to the conduit 1 can be circular. For example, a solid circular ring with an outer diameter matching the outer diameter and an inner diameter matching the inner diameter of the conduit 1 can be used as the collar 2, and its cross-section is circular. This circular collar 2 can achieve a tight and uniform fit with the conduit 1 when fitted. In another embodiment, the cross-section of the collar 2 perpendicular to the conduit 1 can be C-shaped. For example, an annular structure with an opening can be used as the collar 2, and its cross-sectional shape is similar to the letter "C". This C-shaped collar 2 can elastically engage with the docking point of the conduit 1 through its opening, achieving quick positioning and fixation.

[0050] In this optional embodiment, by optimizing the cross-sectional shape of the collar 2, the problems of assembly difficulties, stress concentration during welding, and poor molten pool control caused by improper shape of the collar 2 during the microcatheter welding process are effectively solved. Specifically, the circular cross-section collar 2 ensures uniform contact and heat distribution, significantly reducing the risk of welding stress concentration; the C-shaped cross-section collar 2 greatly simplifies the assembly process, improves efficiency, and reduces deformation caused by dimensional tolerances. Therefore, the solution of this application significantly improves the process stability, weld formation quality, and joint reliability of nickel-based alloy microcatheter welding, thereby meeting the high-precision and high-performance requirements of high-end equipment for micro-pipeline systems.

[0051] Optionally, the electrode is a cerium-tungsten electrode, a lanthanum-tungsten electrode, or a thorium-tungsten electrode.

[0052] Specifically, cerium-tungsten electrodes can be selected as the electrode. Cerium-tungsten electrodes have a low electron work function, providing good arc ignition performance and a stable arc, while also exhibiting a low burn-off rate, making them suitable for DC or AC welding. Lanthanum-tungsten electrodes can also be selected. Lanthanum-tungsten electrodes are non-radioactive materials with an electron work function similar to cerium-tungsten electrodes, exhibiting excellent arc ignition performance, arc stability, and a long service life, especially at low currents, and are less prone to weld contamination. Furthermore, thorium-tungsten electrodes can also be selected. Thorium-tungsten electrodes possess excellent arc ignition performance and current carrying capacity, with a low burn-off rate, effectively extending electrode life and maintaining arc stability. Although thorium has weak radioactivity, its performance advantages still make it a viable electrode material for certain demanding applications.

[0053] In this optional embodiment, by limiting the electrode material to cerium-tungsten, lanthanum-tungsten, or thorium-tungsten electrodes, the problems of arc instability and electrode burn-off are solved, ensuring the stability and quality of the welding process. Specifically, cerium-tungsten, lanthanum-tungsten, or thorium-tungsten electrodes are selected as electrode materials. These materials have high electron emission capability, low work function, and excellent thermal stability, which can maintain the continuity and uniformity of the arc in pulsed current micro-arc TIG welding, reduce electrode burn-off and deformation caused by high temperature, thereby avoiding welding defects caused by arc fluctuations, and improving process reliability and joint strength. In the pulsed current micro-arc TIG welding process of nickel-based alloy microconductors, the selection of electrode material is crucial to the stability of the arc. When the distance between the electrode and the collar 2 is precisely controlled within a narrow range of 0.3 to 1.5 mm, the electron emission capability and burn-off resistance of the electrode directly affect the arc ignition success rate, continuity, and focusing of the arc. The use of cerium-tungsten, lanthanum-tungsten, or thorium-tungsten electrodes can ensure that the arc can still burn stably in low current and pulsed mode, and is not prone to drift or extinction. The high melting point and low evaporation rate of these electrode materials effectively suppress burn-out and passivation of the electrode tips, thus ensuring the long-term stability of the electrode geometry and maintaining the consistency of arc length and heat input. This stable micro-arc combined with precise distance control allows heat to be highly concentrated and uniformly applied to the joint of conduit 1, avoiding problems such as overheating and burn-through or lack of fusion common in traditional welding, and providing a reliable guarantee for the precision welding of small-diameter, thin-walled nickel-based alloy microconduits.

[0054] In some specific embodiments, when welding nickel-based alloy microcatheters, the electrode of the pulsed current micro-arc welding torch can be a lanthanum tungsten electrode. Lanthanum tungsten electrodes are favored due to their excellent non-radioactivity, good arc-starting performance, and long service life. In actual operation, this lanthanum tungsten electrode can stably maintain the arc, ensuring its continuity and uniformity even in low-current pulse mode, thereby effectively avoiding electrode burn-out and weld contamination, and guaranteeing the welding quality of the microcatheter joint. During the pulsed current micro-arc TIG welding of nickel-based alloy microcatheters, using cerium tungsten, lanthanum tungsten, or thorium tungsten electrodes as electrode materials can significantly improve arc stability and reduce electrode burn-out rate. This allows the arc to act continuously and uniformly on the welding area under precisely controlled electrode-to-ring distance 2, avoiding welding defects caused by electrode instability or burn-out, such as poor weld formation, incomplete fusion, or burn-through. This ensures the reliability of the welding process, improves the mechanical properties and fatigue strength of the weld, and is especially suitable for the precision connection of small-diameter, thin-walled nickel-based alloy micro-conduits where extremely high welding quality is required.

[0055] Optionally, the tip cone angle of the electrode is 15° to 30°, and the diameter of the electrode is controlled between 0.6 and 1.2 mm.

[0056] Specifically, the tip taper angle of an electrode refers to the taper angle formed by grinding the working end of the electrode. This angle setting has a crucial impact on the focusing and stability of the arc, current density distribution, and heat input efficiency. For example, the electrode tip can be ground using precision grinding equipment, such as a dedicated electrode grinder, and calibrated using an angle measuring tool to ensure the taper angle is within the range of 15° to 30°. Alternatively, prefabricated electrodes can be used, where suppliers produce electrodes with precise taper angles according to specific requirements, and welding operators only need to select electrodes that conform to this angle range. The electrode diameter refers to the cross-sectional dimension of the electrode rod. This dimension affects the electrode's current-carrying capacity, heat dissipation performance, arc size and stability, and adaptability to small welds. For example, commercially available standardized electrode products conforming to this diameter range can be selected. Alternatively, the required diameter can be achieved by machining (e.g., turning or grinding) a larger diameter electrode, but machining accuracy and surface quality must be ensured to avoid affecting electrode performance.

[0057] In this optional embodiment, by limiting the range of electrode tip cone angle and diameter, the arc characteristics and heat input control are optimized, solving the problems of arc instability and uneven energy distribution during welding. In the pulsed current micro-arc TIG welding method for nickel-based alloy microconduits, the electrode tip cone angle is 15° to 30°. This angle range ensures focused arc, reduces energy loss, and thus precisely controls the size and depth of the molten pool, avoiding weld depressions or incomplete fusion defects. Simultaneously, the electrode diameter is controlled between 0.6 and 1.2 mm. This size matches the microstructure of the microconduit 1, providing a suitable current density to maintain stable arc combustion and prevent excessive heat input leading to burn-through or insufficient heat input leading to incomplete fusion. When using specific electrode materials such as cerium-tungsten, lanthanum-tungsten, or thorium-tungsten electrodes, and maintaining the distance between the electrode and the collar 2 at 0.3 to 1.5 mm, this precise electrode geometry control further enhances the stability and focus of the arc. The electrode material ensures good electron emission performance, while the electrode distance ensures a short and stable arc. Based on this, the optimized tip cone angle and diameter can highly concentrate the arc energy in the welding area, enabling precise management of the heat input for micro-conduit welding, thereby effectively avoiding common problems in traditional welding such as burn-through, lack of fusion, and poor weld formation.

[0058] In some specific embodiments, when welding nickel-based alloy microcatheters with a diameter less than 10 mm and a wall thickness no greater than 1 mm, a lanthanum-tungsten electrode with a tip cone angle of 20° can be selected. This electrode is formed through a high-precision grinding process, resulting in a smooth cone surface that ensures the arc can be stably drawn from the tip. Simultaneously, the electrode has a diameter of 1.0 mm, matching the welding requirements of the microcatheter 1, and can maintain arc stability and good focusing at lower welding currents. During welding, the distance between the electrode and the collar 2 is set to 0.5 mm, and a pulsed current micro-arc TIG welding method is used, rotating the pulsed current micro-arc welding torch relative to the catheter 1 1 to 3 times, with the welding current decreasing from arc initiation to arc termination. Precise control of the electrode's tip cone angle and diameter significantly improves the arc stability and focusing of the pulsed current micro-arc TIG welding. This optimization ensures that the arc energy is highly concentrated and uniformly applied to the welding area of ​​the microcatheter 1, effectively avoiding arc drift and uneven heat input distribution. Therefore, well-formed welds without depressions or burn-through defects can be obtained, while significantly reducing the heat-affected zone and suppressing grain coarsening, thereby improving the mechanical properties and fatigue strength of the welded joint. Furthermore, the optimized electrode parameters also improve the stability of the welding process and reduce sensitivity to operational precision, thus increasing the yield and reliability of microcatheter welding.

[0059] Optionally, after pulsed current micro-arc TIG welding, the micro-conduit 1 is cooled to below 400°C in an inert gas environment, and the inner diameter of the conduit 1 after welding is not less than 40% of the diameter of the conduit 1 before welding.

[0060] Specifically, "after pulsed current micro-arc TIG welding" refers to initiating the subsequent cooling process immediately after the welding operation of the micro-conduit is completed, i.e., the instant the welding torch stops supplying power or the workpiece is removed. The purpose of this step is to determine the starting timing of the cooling process, ensuring that cooling is initiated immediately while the workpiece is still at a high temperature, thereby effectively controlling the subsequent thermal effects and preventing excessively long high-temperature dwell time.

[0061] "Cooling the conduit in an inert gas environment" refers to placing the welded conduit in a space filled with an inert gas (such as high-purity argon, helium, or a mixture thereof) for cooling. An inert gas environment effectively isolates the conduit from oxygen and nitrogen in the air, preventing oxidation reactions when the nickel-based alloy microconduit comes into contact with air at high temperatures, thereby maintaining the surface finish and metallurgical purity of the weld and heat-affected zone. This inert gas environment can be achieved by setting up a local inert gas protective shield or shroud in the welding area to continuously provide inert gas protection behind the weld; alternatively, the welded microconduit can be rapidly transferred to a pre-filled, sealed cooling chamber for cooling.

[0062] "Cooling to below 400°C" refers to reducing the temperature of the microconductor to below 400 degrees Celsius. The purpose of setting this temperature threshold is to limit the high-temperature residence time, effectively suppress grain coarsening in nickel-based alloys at high temperatures, reduce thermal stress, and prevent slow oxidation or adverse phase transformations that may occur at higher temperatures. This cooling process can be achieved by controlling the flow rate, temperature, or cooling time of the inert gas, for example, by using forced inert gas purging cooling, or by natural convection cooling while ensuring sufficient cooling time.

[0063] The requirement that "the inner diameter of the conduit after welding is not less than 40% of the diameter before welding" is a consequential characteristic designed to ensure that the inner diameter of the conduit does not decrease excessively due to thermal shrinkage during cooling, thereby guaranteeing its flow capacity and functionality. Achieving this goal requires comprehensive consideration of welding parameters, cooling rate, and material properties to minimize the thermal shrinkage effect. During cooling, auxiliary tooling such as internal supports or mandrels can be used to limit the shrinkage of the inner diameter, or the cooling rate can be precisely controlled to keep the material within an acceptable dimensional range during shrinkage.

[0064] In this optional embodiment, by precisely controlling the cooling process after welding, the problems of oxidation, grain coarsening, and dimensional deformation that may occur in micro-conduits at high temperatures are effectively solved, thereby ensuring joint quality and inner diameter stability. Specifically, after pulsed current micro-arc TIG welding is completed, the micro-conduit is immediately cooled in an inert gas environment. This inert gas protection not only isolates air during the welding process but also extends the protection to the cooling stage, ensuring that the high-temperature metal does not come into contact with oxygen during the cooling process, thereby completely avoiding oxidation of the weld and heat-affected zone and maintaining its excellent surface quality and metallurgical purity. At the same time, precisely controlling the cooling temperature below 400°C significantly shortens the residence time of the nickel-based alloy in the high-temperature zone, effectively suppressing grain coarsening, thereby maintaining good mechanical properties of the joint area, such as fatigue strength and creep strength. Furthermore, through meticulous management of the cooling process, combined with the inherently low heat input of pulsed current micro-arc TIG welding, the thermal shrinkage effect is minimized. This ensures that the inner diameter of the conduit remains at least 40% of its pre-welding diameter after cooling, meaning the inner diameter remains at least 1.0 mm after cooling. This maintains its flow capacity and prevents dimensional deformation from affecting its application in fluid transport systems. Therefore, this solution provides a complete and optimized solution from welding to cooling, significantly improving the overall quality and reliability of nickel-based alloy micro-conduit welded joints.

[0065] In some specific embodiments, after the micro-current micro-arc TIG welding of the microcatheter is completed, the welding equipment can be equipped with an automatic control system that immediately triggers a cooling procedure the instant the welding torch is raised and the power supply stops. At this time, a local inert gas shield above the welding station continuously blows high-purity argon gas into the weld area, for example, at a flow rate of 8 L / min, to maintain the inert gas environment. Simultaneously, a non-contact infrared temperature sensor monitors the surface temperature of the microcatheter weld area in real time. The cooling process is complete when the temperature sensor detects that the microcatheter surface temperature has dropped to 380°C. To further ensure the stability of the inner diameter, a 1.18 mm diameter ceramic mandrel can be pre-inserted inside the microcatheter before welding. This mandrel acts as an inner diameter support during cooling, effectively limiting the reduction in inner diameter caused by thermal shrinkage. It is removed after cooling is complete. This effectively avoids oxidation of the microcatheter at high temperatures after welding, maintaining the surface quality and metallurgical purity of the weld and heat-affected zone. Simultaneously, it significantly suppresses grain coarsening and improves the mechanical properties of the joint. In addition, precise control of the cooling process effectively reduces the deformation of the inner diameter caused by thermal shrinkage, ensuring the flow capacity and functionality of the microcatheter.

[0066] Optionally, the length of the collar 2 is 0.5 to 5 mm, and the thickness is no more than 2 mm.

[0067] Specifically, this length defines the axial dimension of the collar 2 along the micro-conduit axis. Its function is to provide sufficient support and fixation while limiting the heat conduction along the collar 2 during welding, thereby controlling the size of the heat-affected zone. For example, the axial length of the collar 2 can be precisely controlled within the range of 0.5 to 5 mm through precision turning, wire cutting, or laser cutting. This thickness defines the radial dimension of the collar 2. Its function is to reduce the material volume of the collar 2 itself, lowering its heat capacity, thereby preventing it from absorbing excessive heat during welding or becoming an excessively large heat sink, which would affect weld formation and heat input control. For example, the wall thickness of the collar 2 can be ensured not to exceed 2 mm through sheet metal stamping, precision casting, or powder metallurgy forming.

[0068] In this optional embodiment, by precisely defining the length and thickness of the collar 2, in synergy with the pulsed current micro-arc TIG welding method for nickel-based alloy microcatheters, the thermal management and mechanical support of the entire welding process are optimized. Specifically, limiting the length of the collar 2 to the range of 0.5 to 5 mm ensures that the collar 2 provides sufficient mechanical support and alignment function while its axial dimension is not excessively large. This is crucial for microcatheters with a diameter less than 10 mm or a wall thickness not greater than 1 mm, as an excessively long collar 2 would significantly increase the heat input and heat-affected zone during the welding process, thereby exacerbating the risk of deformation and burn-through of the microcatheter. At the same time, this length range also ensures that the collar 2 can effectively cover the butt joint, preventing displacement or misalignment of the joint during welding. In addition, limiting the thickness of the collar 2 to no more than 2 mm further reduces the material volume and heat capacity of the collar 2 itself. During the pulsed current micro-arc TIG welding process, the thinner collar 2 can reduce the absorption and conduction of heat in the weld area, preventing it from becoming an excessively large heat sink, thereby helping to maintain the stability of the molten pool and the uniform formation of the weld. This lightweight design also facilitates precise assembly and reduces additional material buildup, further lowering the likelihood of burn-through and deformation. Through the synergistic limitation of length and thickness, this design allows the collar 2 to more precisely control heat distribution during pulsed current micro-arc TIG welding, reducing the heat-affected zone and providing stable mechanical support. Combined with the inherent fine heat input control capabilities of pulsed current micro-arc TIG welding, this enables the entire welding system to more effectively meet the stringent requirements of heat sensitivity and dimensional stability in micro-conduit welding. The rotation of the pulsed current micro-arc welding torch relative to the conduit 1 by 1 to 3 revolutions, along with the control of the welding current decreasing from arc initiation to arc termination, assisted by the optimized collar 2, achieves more uniform molten pool formation and solidification, resulting in high-quality welds.

[0069] In some specific embodiments, when welding nickel-based alloy microcatheters with an outer diameter of 3 mm and a wall thickness of 0.3 mm, a collar 2 can be fabricated. The inner diameter of the collar 2 is the same as the outer diameter of the microcatheter, its axial length can be precisely machined to 1.5 mm, and its radial thickness is controlled at 0.8 mm. This collar 2 is fitted and fixed at the joint of two microcatheters. Subsequently, welding is performed in an inert gas environment using a pulsed current micro-arc TIG welding method. During the welding process, the pulsed current micro-arc welding torch rotates relative to the conduit, and the welding current decreases from the start of the arc to the end of the arc. Because the length and thickness of the collar 2 are optimized, the problems of difficult heat input control, insufficient assembly accuracy, and unstable weld quality caused by improper dimensions of the traditional collar 2 are effectively solved. Specifically, limiting the length of the collar 2 to 0.5 to 5 mm avoids excessive heat accumulation and expansion of the heat-affected zone caused by an excessively long collar 2, thereby significantly reducing the risk of deformation and burn-through of the microcatheter during welding. Meanwhile, this length range ensures that the collar 2 provides sufficient mechanical support and centering, guaranteeing the stability of the welded joint. Limiting the thickness of the collar 2 to no more than 2mm reduces its own heat capacity, preventing it from absorbing excessive heat or becoming an excessively large heat sink during welding. This helps maintain the stability of the molten pool and the uniform formation of the weld, further reducing the possibility of burn-through and deformation. These optimized dimensional parameters enable more precise heat management and a more stable welding process in pulsed current micro-arc TIG welding of microconductors, resulting in high-quality welds.

[0070] The present invention will be further described below with reference to specific embodiments.

[0071] Example 1, a welding method for nickel-based alloy microcatheters, includes the following steps: 1. Take a microcatheter 1 with a diameter of 3 mm or a wall thickness of 0.3 mm, and prepare a collar 2 with an inner diameter of 3 mm, an axial length of 1 mm and a thickness of 1 mm. The collar 2 is made of the same nickel-based alloy as the catheter 1. 2. Fit and fix the collar 2 onto the connector of the microcatheter 1; 3. In an argon gas environment, pulsed current micro-arc TIG welding of micro-conduits is performed. The distance between the tungsten electrode and the collar 2 is precisely set to 0.8 mm. The current decreases from 8.5 A at the start of the arc to 7.0 A at the end of the arc. During the pulsed current micro-arc TIG welding process, the pulsed current micro-arc welding torch rotates 1.8 times relative to the conduit 1, and the welding current decreases from the start of the arc to the end of the arc.

[0072] The inner diameter of the nickel-based alloy microcatheter after welding is ≥1.5mm, with no external depressions and uniform weld seam.

[0073] Comparative Example 1: A welding method for nickel-based alloy microcatheters, comprising the following steps: 1. Take a microcatheter 1 with a diameter of 3 mm or a wall thickness of 0.3 mm, and prepare a collar 2 with an inner diameter of 3 mm, an axial length of 1 mm and a thickness of 1 mm. The collar 2 is made of the same nickel-based alloy as the catheter 1. 2. Fit and fix the collar 2 onto the connector of the microcatheter 1; 3. In an argon gas environment, pulsed current micro-arc TIG welding of micro-conduits is performed. The distance between the tungsten electrode and the collar 2 is precisely set to 0.8 mm. A constant current of 8.5 A is used. During the pulsed current micro-arc TIG welding process, the pulsed current micro-arc welding torch rotates 1.8 times relative to the conduit 1. The welding current decreases from the start of the arc to the end of the arc.

[0074] The inner diameter of the nickel-based alloy microcatheter after welding was less than 1.2 mm and internal collapse occurred.

[0075] Comparative Example 2, a welding method for nickel-based alloy microcatheters, comprising the following steps: 1. Take a microcatheter 1 with a diameter of 3 mm or a wall thickness of 0.3 mm, and prepare a collar 2 with an inner diameter of 3 mm, an axial length of 1 mm and a thickness of 1 mm. The collar 2 is made of the same nickel-based alloy as the catheter 1. 2. Fit and fix the collar 2 onto the connector of the microcatheter 1; 3. In an argon gas environment, pulsed current micro-arc TIG welding of micro-conduits is performed. The distance between the tungsten electrode and the collar 2 is precisely set to 0.8 mm. A constant current of 7.0 A is used. During the pulsed current micro-arc TIG welding process, the pulsed current micro-arc welding torch rotates 1.8 revolutions relative to the conduit 1. The welding current decreases from the start of the arc to the end of the arc.

[0076] The nickel-based alloy microcatheter exhibits a lack of fusion defect.

[0077] As can be seen in Example 1, the welding current reduction control ensures that the initial current reliably establishes the initial molten pool over a very short distance. Subsequently, the current smoothly and continuously decreases as the welding torch rotates. This reduction design is to actively compensate for the heat accumulation effect caused by the overall temperature rise of the workpiece during welding, avoiding defects caused by overheating in the latter half of the weld. It further optimizes the cooling process of the weld, thereby ensuring excellent mechanical properties of the joint and avoiding the problem of rapid solidification and shrinkage of the molten pool due to a sudden cessation of heat input, which could lead to crater depressions, shrinkage cavities, or even microcracks at the arc termination point. While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A welding method for nickel-based alloy microcatheters, characterized in that, For catheters with a diameter less than 10 mm or a wall thickness not greater than 1 mm (1), the following steps are included: S1: Prepare a collar (2) with an inner diameter that is the same as the outer diameter of the catheter (1). The collar (2) is made of the same material as the catheter (1) or a nickel-based alloy that is metallurgically compatible. S2: Fit the collar (2) onto and fix it to the joint where the conduit (1) is connected; S3: In an inert gas environment, pulsed current micro-arc TIG welding is performed on the conduit (1). During the pulsed current micro-arc TIG welding process, the pulsed current micro-arc welding torch rotates 1 to 3 times relative to the conduit, and the welding current decreases from the start of the arc to the end of the arc.

2. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, The distance between the electrode of the pulse current micro-arc welding torch and the collar (2) is 0.3 to 1.5 mm.

3. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, The welding parameters for pulsed current micro-arc TIG welding include: the welding current adopts constant current or DC pulse mode, the peak current is 5 to 15A, the base current is 1 to 3A, the pulse frequency is 0 to 1000Hz, the peak time ratio is 0 to 100%, the arc width is between 1.5 and 2.0mm, and the welding speed is 50 to 150mm / min.

4. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, The welding current decreases at a constant rate from the start of the arc to the end of the arc.

5. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, The welding current is 6 to 12A when the arc is started and 5 to 11A when the arc is terminated.

6. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, The cross section of the collar (2) perpendicular to the conduit (1) is circular or C-shaped.

7. The welding method for nickel-based alloy microcatheters according to claim 2, characterized in that, The electrode is a cerium-tungsten electrode, a lanthanum-tungsten electrode, or a thorium-tungsten electrode.

8. The welding method for nickel-based alloy microcatheters according to claim 7, characterized in that, The tip cone angle of the electrode is 15° to 30°, and the diameter of the electrode is controlled between 0.6 and 1.2 mm.

9. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, After the pulsed current micro-arc TIG welding, the conduit (1) is cooled to below 400°C in the inert gas environment. After welding, the inner diameter of the conduit (1) is not less than 40% of the diameter of the conduit before welding.

10. The welding method for nickel-based alloy microcatheters according to claim 1, characterized in that, The length of the collar (2) is 0.5 to 5 mm and the thickness is no more than 2 mm.

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