Refractory metal high-wall-thickness tantalum tube intelligent temperature and speed control electron beam welding method

Abstract

The application provides a refractory metal high-wall-thickness tantalum tube intelligent temperature and speed control electron beam welding method, relates to the refractory metal welding technical field, and aims at the thick-wall tantalum tube with a wall thickness of greater than or equal to 5 mm. When electron beam welding is performed, the molten pool temperature is monitored in real time through infrared temperature measurement, the welding process parameters are adjusted through temperature feedback, and the welding power is controlled. After the welding is completed, the electron beam welding equipment is not immediately turned off, the molten pool is gradiently slowly cooled through infrared temperature measurement, and the electron beam power gradually decreases. The specific attenuation process is as follows: 100% (welding power) to 80% to 60% to 40% to 20% to 0. Each power level is maintained for 5 to 10 seconds, sudden temperature drop and huge thermal stress are avoided, and post-welding delayed deformation is inhibited from the source.

Description

Technical Field

[0001] This invention relates to the field of refractory metal welding technology, and in particular to an intelligent temperature and speed controlled electron beam welding method for high-wall-thickness tantalum tubes made of refractory metals. Background Technology

[0002] Thick-walled tantalum tubes are widely used in high-end fields such as aerospace and nuclear industry as conveying pipelines, structural conduits, and sealing fittings under extreme working conditions due to their excellent corrosion resistance and high-temperature stability. However, tantalum readily absorbs hydrogen and oxygen at high temperatures, leading to porosity, grain boundary embrittlement, and oxide inclusions, which severely affect joint performance. Furthermore, due to its excessive wall thickness, traditional electron beam welding typically uses fixed process parameters, neglecting the accumulation of thermal stress during welding, making it difficult to achieve uniform penetration across the entire thickness. Additionally, stress release during post-weld cooling affects coaxiality.

[0003] Existing patent CN104801844B provides an electron beam welding method for thin-walled circumferential welds of tantalum and tungsten metals, which solves the defects such as incomplete penetration or weld depressions that occur locally during the welding of tantalum and tungsten. The method fixes the base material to be welded on the tooling, and uniform penetration is achieved by adjusting the rotation angle during welding, thus avoiding defects such as weld depressions. However, this method is only applicable to electron beam welding of thin-walled refractory metals, and it only sets the welding parameters before welding. The welding parameters are fixed in segments and cannot achieve intelligent temperature control or real-time changes in electron beam current and welding speed.

[0004] Patent CN119741364B provides an electron beam welding device and its control method, proposing an electron beam welding scheme of "three-dimensional model driving + path optimization + motion synchronous control". This scheme focuses on three-dimensional static modeling and path optimization of the material to be welded before welding, but does not consider the temperature change of the molten pool during the welding process. It cannot adjust the core parameters such as electron beam power and welding speed in real time, which can easily lead to excessive heat input, stress accumulation, and defects such as porosity and cracks.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes. For thick-walled tantalum tubes with a wall thickness ≥ 5 mm, the method involves real-time monitoring of the molten pool temperature using infrared thermography during electron beam welding. Welding process parameters are adjusted and welding power controlled based on temperature feedback. Furthermore, after welding, the electron beam welding equipment is not immediately shut down. Instead, the molten pool is gradually cooled using infrared thermography, causing the electron beam power to decrease gradually. The specific attenuation process is: 100% (welding power) → 80% → 60% → 40% → 20% → 0, with each power level maintained for 5-10 seconds. This avoids the sudden temperature drop that could generate significant thermal stress, thus suppressing delayed post-weld deformation at its source.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes, comprising the following steps: S1: Pretreatment of thick-walled tantalum tubes; S2: Position the pre-treated thick-walled tantalum tube using a tooling fixture, and then load the assembled tooling fixture and tantalum tube together into the electron beam welding vacuum chamber. S3: In a vacuum environment, electron beam welding begins. The PLC intelligent controller automatically adjusts the electron beam current and / or tooling rotation speed according to the tantalum tube wall thickness, real-time molten pool temperature and molten depth fluctuations to ensure that the molten pool temperature remains stable throughout the process and achieve constant heat input control. S4: After electron beam welding is completed, the power decay and slow cooling stage begins. The electron beam power is controlled to gradually decrease according to the preset step decay mode for slow cooling. S5: After the tantalum tube cools to room temperature, remove the tantalum tube from the tooling, clean it, and then perform vacuum stress-relief annealing to complete the tantalum tube welding.

[0008] Furthermore, based on the above technical solution, the thick-walled tantalum tube is a tantalum tube with a wall thickness ≥ 5 mm and a purity ≥ 99.95%; And / or, in step S1, the preprocessing includes: The circumferential weld end face of the tantalum tube is machined and mirror-polished to ensure a smooth, burr-free, and tilt-free surface with a surface roughness Ra ≤ 0.6 μm after polishing. The tantalum tube is then immersed in an acid pickling solution for 5-8 minutes to remove surface oxide scale. After acid pickling, it is ultrasonically cleaned in anhydrous ethanol for 20-30 minutes to remove residual acid and impurities. Finally, the tantalum tube is placed in a vacuum drying oven at 120-150℃ and a vacuum degree ≤ 1×10⁻⁶. -2 Dry under Pa conditions for 40-60 minutes.

[0009] Furthermore, based on the above technical solution, in step S2, the tooling includes a base, a centering shaft, a bidirectional clamping mechanism, and a rotary drive mechanism. The centering shaft is horizontally fixed above the base by a bracket. The axis of the centering shaft coincides with the axis of the tantalum tube to be welded. The outer diameter of the centering shaft is adapted to the inner diameter of the tantalum tube. The tantalum tube is sleeved on the centering shaft and can rotate relative to the centering shaft. The part of the centering shaft that contacts the inner wall of the tantalum tube is made of pure molybdenum material. The bidirectional clamping mechanism includes two clamping components, which are respectively disposed at both ends of the centering shaft and fixedly installed on the base. The two clamping components have opposing clamping ends for applying clamping force from both ends of the tantalum tube to clamp and fix the tantalum tube and ensure that the welded circumferential seam is aligned. The clamping end surfaces of the two clamping components that contact the end face of the tantalum tube are provided with an anti-stick coating to prevent the tooling from sticking and contaminating the tantalum tube at high temperature. The rotary drive mechanism is located on the radial side of the centering shaft and along the axial direction of the centering shaft, between the two clamping members; the output end of the rotary drive mechanism is connected to the centering shaft or directly to the tantalum tube; the rotary drive mechanism is used to drive the tantalum tube to rotate at a constant speed around the axis of the centering shaft during the welding process, so as to realize the continuous welding of the circumferential seam.

[0010] Furthermore, based on the above technical solution, in step S3, the vacuum environment is achieved by evacuating the vacuum level in the electron beam welding vacuum chamber to ≤5×10⁻⁶. -4 Pa, maintain for 10-15 minutes; A coaxial infrared pyrometer is installed in the vacuum chamber corresponding to the circumferential weld area, at a distance of 280-310mm from the weld, and the angle between the infrared pyrometer and the electron beam gun is 28-35°, to monitor the temperature of the molten pool in real time during the welding process and to feed the temperature data back to the PLC intelligent controller. The infrared pyrometer has a sampling frequency of ≥100kHz, a temperature measurement range of 600℃~2200℃, and a temperature measurement accuracy of ±1%.

[0011] Furthermore, based on the above technical solution, in step S3, before starting electron beam welding, the tooling rotation drive mechanism is first activated to drive the tantalum tube to rotate at a constant speed of 145-155 mm / min.

[0012] Furthermore, based on the above technical solution, in step S3, during the welding process, in order to ensure that the thick-walled tantalum tube achieves good penetration and does not overheat, the target molten pool temperature, electron beam current, and tooling rotation speed are pre-set in the PLC intelligent controller according to the wall thickness of the thick-walled tantalum tube. Specifically: When the tantalum tube wall thickness is greater than or equal to 5 mm and less than or equal to 8 mm, the target welding pool temperature is set to 1800~1950℃, the electron beam current is 65mA~75mA, and the tooling rotation speed is 160~200mm / min in advance in the PLC intelligent controller. When the tantalum tube wall thickness is greater than 8mm and less than or equal to 12mm, the target welding pool temperature is set to 1950~2100℃, the electron beam current is 75mA~85mA, and the tooling rotation speed is 125-170mm / min in advance in the PLC intelligent controller. When the tantalum tube wall thickness is greater than 12mm, the target welding pool temperature is set to 2100℃~2200℃, the electron beam current is 85mA~100mA, and the tooling rotation speed is 80~125mm / min in advance in the PLC intelligent controller.

[0013] Furthermore, based on the above technical solution, the PLC intelligent controller first adjusts the process parameters in real time by controlling the melt depth. When the melt depth fluctuation value is ≤0.6mm, the PLC intelligent controller does not adjust the process parameters; when the melt depth fluctuation value is >0.6mm, the PLC intelligent controller controls the electron beam current to increase or decrease by 3-5mA based on the preset electron beam current. If, after adjusting the electron beam current by increasing or decreasing it, the melt depth fluctuation remains >0.6mm and the melt depth deviation fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: When the wall thickness of the tantalum tube is greater than or equal to 5 mm and less than or equal to 8 mm, if the temperature of the target molten pool is higher than the preset temperature, the electron beam current should be reduced by 3-5 mA and the tooling rotation speed should be increased by 2-4 mm / min; if the temperature of the target molten pool is lower than the preset temperature, the electron beam current should be increased by 3-5 mA and the tooling rotation speed should be reduced by 2-4 mm / min. When the tantalum tube wall thickness is greater than 8 mm and less than or equal to 12 mm, if the target molten pool temperature is higher than the preset temperature, the electron beam current should be reduced by 3~5 mA and the tooling rotation speed should be increased by 2~4 mm / min; if the target molten pool temperature is lower than the preset temperature, the electron beam current should be increased by 3~5 mA and the tooling rotation speed should be reduced by 2~4 mm / min. When the tantalum tube wall thickness is greater than 12mm, if the target molten pool temperature is higher than the preset temperature, the electron beam current is reduced by 3~5mA and the tooling rotation speed is increased by 2~4mm / min based on the adjusted electron beam current; if the target molten pool temperature is lower than the preset temperature, the electron beam current is increased by 3~5mA and the tooling rotation speed is reduced by 2~4mm / min based on the adjusted electron beam current.

[0014] Furthermore, based on the above technical solution, in step S4, the stepped attenuation mode specifically refers to: Using the stable welding power during the main welding as the reference power, the electron beam power is gradually reduced in a gradient of 100%→80%→60%→40%→20%→0, where 100% is the reference power value for the main welding stage, and the electron beam is completely cut off when it finally decays to 0; the duration of each power level is controlled to be 5s~10s.

[0015] Furthermore, based on the above technical solution, step S5 specifically includes the following steps: S51: After the slow cooling stage, keep the tooling and tantalum tube intact, place the tantalum tube together with the tooling in the electron beam welding vacuum chamber, and use the residual vacuum environment and natural cooling conditions of the vacuum chamber to allow the tantalum tube to cool slowly to room temperature with the furnace. S52: After the tantalum tube cools to room temperature with the furnace, remove the tantalum tube and tooling from the vacuum chamber, and clean the surface of the weld joint area of ​​the tantalum tube to remove the surface oxide layer, spatter and residual impurities formed during welding and slow cooling, so as to obtain a clean weld surface. S53: The cleaned tantalum tube is placed into a vacuum annealing furnace for vacuum stress-relief annealing.

[0016] Furthermore, based on the above technical solution, vacuum stress-relief annealing includes the following conditions: annealing temperature of 1050℃~1150℃, and vacuum degree ≤1×10⁻⁶. -3 Pa, heat preservation time is 60min~90min.

[0017] The present invention provides an intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes, the beneficial effects of which include the following: 1. The welding method provided by this invention can achieve uniform and stable penetration of the entire thickness of the tantalum tube cross section, eliminating harmful defects such as incomplete penetration and overheating from the root. Combined with X-ray non-destructive testing for post-weld re-inspection, it can ensure that the weld density reaches the stringent index of ≥99.9%, significantly improving the tightness and cross-sectional mechanical uniformity of the tantalum tube joint, thereby effectively ensuring the sealing integrity of the pipeline system and the safety of media transportation under long-term service conditions.

[0018] 2. Thick-walled tantalum tubes welded using the welding method provided by this invention exhibit weld joints free of porosity, cracks, and oxide inclusions, with a purity ≥99.99%, meeting the requirements for high-purity tantalum tubes. The joint tensile strength is ≥90% of the base material, elongation ≥15%, and airtightness ≤1×10⁻⁶. -9 Pa·m 3 / s, suitable for high-voltage operating conditions; 3. The welding method provided by this invention can effectively control welding deformation. The deformation of the tantalum tube after welding is ≤0.1mm / m, the coaxiality error is ≤0.05mm, and there is basically no warping, elliptical deformation, or delayed deformation, thus ensuring the dimensional accuracy of the pipe. 4. The welding method provided by this invention improves the stability and repeatability of the welding process through intelligent closed-loop control. The pass rate of welding deformation, weld penetration and weld density is increased by more than 30% compared with the traditional method, making it suitable for industrial mass production. 5. The welding method provided by this invention is a fully vacuum, oxidation-free welding process that preserves the corrosion resistance and high purity of tantalum tubes, making it suitable for the stringent requirements of high-end fields such as aerospace, nuclear industry, and semiconductors. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the tooling structure provided by the present invention; legend: 1. Base; 2. Centering shaft; 3. Bidirectional clamping mechanism; 31. Clamping component; 4. Tantalum tube; 5. Rotary drive mechanism. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0022] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected," "linked," and "set up" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; a wired connection, a radio connection, or a wireless communication signal connection. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0023] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0024] According to a first aspect of the present invention, a method for intelligent temperature and speed controlled electron beam welding of refractory metal high-wall-thickness tantalum tubes is provided, comprising the following steps: S1: Pretreatment of thick-walled tantalum tubes; S2: Position the pre-treated thick-walled tantalum tube using a tooling fixture, and then load the assembled tooling fixture and tantalum tube together into the electron beam welding vacuum chamber. S3: In a vacuum environment, electron beam welding begins. The PLC intelligent controller automatically adjusts the electron beam current and / or tooling rotation speed according to the tantalum tube wall thickness, real-time molten pool temperature and molten depth fluctuations to ensure that the molten pool temperature remains stable throughout the process and achieve constant heat input control. S4: After electron beam welding is completed, the power decay and slow cooling stage begins. The electron beam power is controlled to gradually decrease according to the preset step decay mode for slow cooling. S5: After the tantalum tube cools to room temperature, remove the tantalum tube from the tooling, clean it, and then perform vacuum stress-relief annealing to complete the tantalum tube welding.

[0025] As an optional embodiment of the present invention, the thick-walled tantalum tube is a tantalum tube with a wall thickness ≥ 5 mm and a purity ≥ 99.95%.

[0026] In an optional embodiment of the present invention, step S1 includes the following preprocessing: The circumferential weld end face of the tantalum tube is machined and mirror-polished to ensure a smooth, burr-free, and tilt-free surface with a surface roughness Ra ≤ 0.6 μm after polishing. The tantalum tube is then immersed in a pickling solution (hydrofluoric acid: hydrogen peroxide: sulfuric acid: water = 1:1:1:2) for 5-8 minutes to remove surface oxide scale. After pickling, it is ultrasonically cleaned in anhydrous ethanol for 20-30 minutes to remove residual acid and impurities. Finally, the tantalum tube is placed in a vacuum drying oven at 120-150℃ and a vacuum degree ≤ 1×10⁻⁶. -2 Dry under Pa conditions for 40-60 minutes to thoroughly remove moisture and gas adsorbed on the surface and inner wall of the tantalum tube. Finally, place it in a vacuum bag and evacuate to prevent oxidation of the weld joint, which would affect the performance of the weld joint.

[0027] As an optional embodiment of the present invention, in step S2, as follows: Figure 1 As shown, the tooling includes a base 1, a centering shaft 2, a bidirectional clamping mechanism 3, and a rotary drive mechanism 5; The base 1 of the tooling is covered with a high-purity molybdenum pad to support the tantalum tube 4 during the welding process and to prevent the base material from contaminating the tantalum tube. The centering shaft 2 is horizontally fixed above the base 1 by a bracket. The axis of the centering shaft 2 coincides with the axis of the tantalum tube 4 to be welded. The outer diameter of the centering shaft 2 is matched with the inner diameter of the tantalum tube 4. The tantalum tube 4 is sleeved on the centering shaft 2 and can rotate relative to the centering shaft 2. The part of the centering shaft 2 that contacts the inner wall of the tantalum tube 4 is made of pure molybdenum material.

[0028] The bidirectional clamping mechanism 3 includes two clamping components 31, which are respectively disposed at both ends of the centering shaft 2 in the axial direction and fixedly installed on the base 1. The two clamping components 31 have opposing clamping ends, which are used to apply clamping force from both ends of the tantalum tube 4 to clamp and fix the tantalum tube 4 and ensure that the welded circumferential seam is aligned. The clamping end surfaces of the two clamping components 31 that contact the end face of the tantalum tube 4 are provided with an anti-stick coating to prevent the tooling from sticking and contaminating the tantalum tube 4 at high temperature. The rotary drive mechanism 5 is located on the radial side of the centering shaft 2 and is positioned between the two clamping members 31 along the axial direction of the centering shaft 2. The output end of the rotary drive mechanism 5 is connected to the centering shaft 2 or directly to the tantalum tube 4. The rotary drive mechanism 5 is used to drive the tantalum tube 4 to rotate at a constant speed around the axis of the centering shaft 2 during the welding process to achieve continuous welding of the circumferential seam.

[0029] In an optional embodiment of the present invention, in step S3, the vacuum environment is achieved by evacuating the vacuum level in the electron beam welding vacuum chamber to ≤5×10⁻⁶. -4 Maintain the pressure at 10-15 Pa for 10-15 minutes to ensure no air remains in the vacuum chamber and prevent the tantalum tube from oxidizing, absorbing hydrogen, or absorbing nitrogen during the welding process.

[0030] As an optional embodiment of the present invention, a coaxial infrared pyrometer (model KLEIBER KMGA740) is set in the vacuum chamber corresponding to the circumferential weld area, at a distance of 280-310mm from the weld, preferably 300mm, and the angle between the infrared pyrometer and the electron beam gun is 28-35°, preferably 30°, to monitor the temperature of the molten pool in real time during the welding process and to feed the temperature data back to the PLC intelligent controller. Furthermore, the infrared pyrometer has a sampling frequency of ≥100kHz (at least 100,000 times per second), a temperature measurement range of 600℃~2200℃, a temperature measurement accuracy of ±1%, and the temperature measurement data is transmitted to the PLC intelligent controller (model Siemens S7-1214C DC / DC / DC) in real time.

[0031] In an optional embodiment of the present invention, in step S3, the tantalum tube wall thickness is measured online using a PRIMO SC multi-channel EMAT main unit. Its low-frequency magnetic field design does not interfere with the electron beam, and the wall thickness measurement accuracy is ±3μm. The thickness measurement data is uploaded to the PLC controller in real time. The PLC dynamically adjusts the fixture rotation speed and electron beam current accordingly, maintaining a constant heat input throughout the welding process and ensuring a stable molten pool temperature. The PRIMO SC multi-channel EMAT main unit is an existing device, an industrial-grade ultrasonic testing instrument launched by the American company Innerspec.

[0032] As an optional embodiment of the present invention, in step S3, before starting electron beam welding, the tooling rotation drive mechanism is activated to drive the tantalum tube to rotate at a constant speed of 145-155 mm / min (e.g., 146 mm / min, 148 mm / min, 150 mm / min, 152 mm / min, 154 mm / min, etc.).

[0033] As an optional embodiment of the present invention, in step S3, during the welding process, in order to ensure that the thick-walled tantalum tube achieves good penetration and does not overheat, the target molten pool temperature, electron beam current, and tooling rotation speed are preset in the PLC intelligent controller according to the wall thickness of the thick-walled tantalum tube. Specifically: When the tantalum tube wall thickness is greater than or equal to 5mm and less than or equal to 8mm, the target molten pool temperature for welding should be preset in the PLC intelligent controller to be 1800~1950℃, the electron beam current to be 65mA~75mA, and the tooling rotation speed (i.e., welding speed) to be 160~200mm / min. Specifically: When the tantalum tube wall thickness is greater than or equal to 5 mm and less than or equal to 6 mm (e.g., 5.2 mm, 5.5 mm, 5.7 mm, etc.), the target molten pool temperature for welding is set to greater than or equal to 1800℃ and less than or equal to 1850℃ (e.g., 1810℃, 1820℃, 1830℃, 1840℃, etc.), the electron beam current is greater than or equal to 65 mA and less than or equal to 68 mA (e.g., 66 mA, 67 mA, etc.), and the welding speed is greater than 190 mm / min and less than or equal to 200 mm / min (e.g., 192 mm / min, 194 mm / min, 195 mm / min, 196 mm / min, 198 mm / min, etc.). When the tantalum tube wall thickness is greater than 6 mm and less than or equal to 7 mm (e.g., 6.2 mm, 6.5 mm, 6.7 mm, etc.), the target molten pool temperature for welding is set to be greater than 1850℃ and less than or equal to 1900℃ (e.g., 1860℃, 1870℃, 1880℃, 1890℃, etc.), the electron beam current is greater than 68 mA and less than or equal to 72 mA (e.g., 69 mA, 70 mA, 71 mA, etc.), and the welding speed is greater than 180 mm / min and less than or equal to 190 mm / min (e.g., 182 mm / min, 184 mm / min, 185 mm / min, 186 mm / min, 188 mm / min, etc.). When the tantalum tube wall thickness is greater than 7 mm and less than or equal to 8 mm (e.g., 7.2 mm, 7.5 mm, 7.7 mm, etc.), the target molten pool temperature for welding is set to be greater than 1900℃ and less than or equal to 1950℃ (e.g., 1910℃, 1920℃, 1930℃, 1940℃, etc.), the electron beam current is greater than 72 mA and less than or equal to 75 mA (e.g., 73 mA, 74 mA, etc.), and the welding speed is greater than 160 mm / min and less than or equal to 180 mm / min (e.g., 165 mm / min, 170 mm / min, 175 mm / min, etc.).

[0034] When the tantalum tube wall thickness is greater than 8mm and less than or equal to 12mm, the target welding pool temperature should be pre-set in the PLC intelligent controller to be greater than 1950℃-2100℃, the electron beam current to be greater than 75mA-85mA, and the tooling rotation speed to be greater than 125-170mm / min. Specifically: When the tantalum tube wall thickness is greater than 8mm and less than or equal to 9mm (e.g., 8.2mm, 8.5mm, 8.7mm, etc.), the target molten pool temperature for welding is set to be greater than 1950℃ and less than or equal to 2000℃ (e.g., 1960℃, 1970℃, 1980℃, 1990℃, etc.), the electron beam current is greater than 75mA and less than or equal to 78mA (e.g., 76mA, 77mA, etc.), and the welding speed is greater than 155mm / min and less than or equal to 170mm / min (e.g., 157mm / min, 160mm / min, 165mm / min, 167mm / min, etc.). When the tantalum tube wall thickness is greater than 9mm and less than or equal to 10mm (e.g., 9.2mm, 9.5mm, 9.7mm, etc.), the target molten pool temperature for welding is set to be greater than 2000℃ and less than or equal to 2050℃ (e.g., 2010℃, 2020℃, 2030℃, 2040℃, etc.), the electron beam current is greater than 78mA and less than or equal to 82mA (e.g., 79mA, 80mA, 81mA, etc.), and the welding speed is greater than 140mm / min and less than or equal to 155mm / min (e.g., 142mm / min, 145mm / min, 150mm / min, 153mm / min, etc.). When the tantalum tube wall thickness is greater than 10 mm and less than or equal to 12 mm (e.g., 10.5 mm, 11 mm, 11.5 mm, etc.), the target molten pool temperature for welding is set to be greater than 2050℃ and less than or equal to 2100℃ (e.g., 2060℃, 2070℃, 2080℃, 2090℃, etc.), the electron beam current is greater than 82 mA and less than or equal to 85 mA (e.g., 83 mA, 84 mA, etc.), and the welding speed is greater than 125 mm / min and less than or equal to 140 mm / min (e.g., 127 mm / min, 130 mm / min, 135 mm / min, 137 mm / min, etc.).

[0035] When the tantalum tube wall thickness is greater than 12mm (e.g., 13mm), the target molten pool temperature for welding is set in advance in the PLC intelligent controller to be greater than 2100℃ and less than or equal to 2200℃ (above 2200℃ exceeds the upper limit of the temperature measuring equipment, and too low a temperature will not penetrate and cannot form an effective weld), the electron beam current is greater than 85mA and less than or equal to 100mA (e.g., 90mA, 95mA, 97mA, etc.), and the tooling rotation speed is greater than 80mm / min and less than or equal to 125mm / min (e.g., 85mm / min, 90mm / min, 195mm / min, 100mm / min, 110mm / min, 120mm / min, etc.).

[0036] Specifically, in the electron beam welding of thick-walled tantalum tubes, the three parameters—target molten pool temperature, electron beam current, and tooling rotation speed—must be matched. Any deviation from the reasonable range will damage the weld formation quality. If the target molten pool reference temperature is too high, the actual heat input will be too large, leading to excessive fluidity of the molten pool metal, which can easily cause burn-through, weld surface depressions, or weld beads. At the same time, the grains in the high-temperature zone will coarsen rapidly, reducing the joint plasticity. If the temperature is too low, the heat input will be insufficient, making it impossible to stably penetrate the workpiece, easily resulting in incomplete root penetration or incomplete welding. Furthermore, the molten pool fluidity will be poor, increasing the tendency for porosity and slag inclusions. If the electron beam current is too high, the energy density will surge, causing the tantalum material at the center of the beam spot to vaporize instantaneously, producing a cutting effect and severe spatter, and even penetrating the tooling backing plate, resulting in a serrated weld. If the beam current is too low, the effective penetration depth will be insufficient. The shortcomings are that even with speed adjustments, full penetration is difficult to achieve, and the weld cross-section often exhibits root incomplete fusion defects, severely weakening the load-bearing capacity. Excessive tooling rotation speed means insufficient heating time per unit arc length, leading to a sharp increase in the molten pool cooling rate. The liquid metal does not have enough time to spread and vent, easily resulting in longitudinal cracks, undercut, and poor fusion, and the weld width is too narrow with an unreasonable forming coefficient. Conversely, excessively low speed results in excessively long beam current action time, excessive heat accumulation, leading to overheating burn-through, a significantly widened heat-affected zone, and coarsening of the microstructure. Simultaneously, the tantalum tube experiences increased thermal deformation, affecting the alignment accuracy of the circumferential weld. Therefore, these three parameters must be controlled synergistically; excessively high or low speeds will disrupt the heat input balance, resulting in substandard weld quality.

[0037] As an optional embodiment of the present invention, the real-time weld depth fluctuation is detected in real time using a water-cooled miniature ultrasonic probe (model ZK-WS5-φ4). Both the ultrasonic probe and the electron beam gun are located 3mm behind the circumference of the circumferential weld and 2mm away from the pipe wall.

[0038] Furthermore, the PLC intelligent controller first adjusts the process parameters in real time through the melt depth. When the melt depth fluctuation is ≤0.6mm, the PLC intelligent controller does not adjust the process parameters; when the melt depth fluctuation is >0.6mm, the PLC intelligent controller controls the electron beam current to rapidly increase or decrease by 3-5mA (e.g., 3.5mA, 4mA, 4.5mA, etc.) based on the preset electron beam current. The electron beam current is the first priority adjustment method of the PLC because it responds quickly and can change the heat input density in milliseconds.

[0039] Specifically, after welding begins, when the positive deviation of the actual penetration depth from the preset penetration depth value (i.e., wall thickness) exceeds 0.6 mm (actual penetration depth is higher than the preset value), the PLC intelligent controller will rapidly reduce the electron beam current from the current preset value by 3 to 5 mA; when the negative deviation of the actual penetration depth from the preset penetration depth value (actual penetration depth is lower than the preset value) exceeds 0.6 mm, the PLC intelligent controller will rapidly increase the electron beam current from the current preset value by 3 to 5 mA.

[0040] As an optional embodiment of the present invention, when the electron beam current has been adjusted by increasing or decreasing, but the melt depth fluctuation value remains >0.6mm and the melt depth deviation has not been effectively converged, a control program is input according to the preset technical parameters of the PLC intelligent controller, including: When the tantalum tube wall thickness is greater than or equal to 5 mm and less than or equal to 8 mm, if the target molten pool temperature is higher than the preset temperature, reduce the electron beam current by 3-5 mA (e.g., 3.5 mA, 4 mA, 4.5 mA, etc.) and increase the tooling rotation speed (i.e., welding speed) by 2-4 mm / min (e.g., 2.5 mm / min, 3 mm / min, 3.5 mm / min, etc.); if the target molten pool temperature is lower than the preset temperature, increase the electron beam current by 3-5 mA (e.g., 3.5 mA, 4 mA, 4.5 mA, etc.) and decrease the tooling rotation speed (i.e., welding speed) by 2-4 mm / min (e.g., 2.5 mm / min, 3 mm / min, 3.5 mm / min, etc.). When the tantalum tube wall thickness is greater than 8 mm and less than or equal to 12 mm, if the target molten pool temperature is higher than the preset temperature, reduce the electron beam current by 3-5 mA (e.g., 3.5 mA, 4 mA, 4.5 mA, etc.) and increase the tooling rotation speed (i.e., welding speed) by 2-4 mm / min (e.g., 2.5 mm / min, 3 mm / min, 3.5 mm / min, etc.); if the target molten pool temperature is lower than the preset temperature, increase the electron beam current by 3-5 mA (e.g., 3.5 mA, 4 mA, 4.5 mA, etc.) and decrease the tooling rotation speed (i.e., welding speed) by 2-4 mm / min (e.g., 2.5 mm / min, 3 mm / min, 3.5 mm / min, etc.). When the tantalum tube wall thickness is greater than 12mm, if the target molten pool temperature is higher than the preset temperature, reduce the electron beam current by 3~5mA (e.g., 3.5mA, 4mA, 4.5mA, etc.) and increase the tooling rotation speed (i.e., welding speed) by 2~4mm / min (e.g., 2.5mm / min, 3mm / min, 3.5mm / min, etc.); if the target molten pool temperature is lower than the preset temperature, increase the electron beam current by 3~5mA (e.g., 3.5mA, 4mA, 4.5mA, etc.) and decrease the tooling rotation speed (i.e., welding speed) by 2~4mm / min (e.g., 2.5mm / min, 3mm / min, 3.5mm / min, etc.).

[0041] As an optional embodiment of the present invention, in step S4, the stepped attenuation mode specifically refers to: Using the stable welding power during the main welding as the reference power, the electron beam power is gradually reduced in a gradient of 100%→80%→60%→40%→20%→0, where 100% is the reference power value for the main welding stage, and the electron beam is completely cut off when it finally decays to 0. Under the power holding state at each level, the duration is controlled to be 5s to 10s, so that the temperature of the molten pool decreases slowly in a gradient as the electron beam power decreases step by step, thereby achieving gradient slow cooling of the molten pool.

[0042] Specifically, in the power decay and slow cooling stage of step S4, the electron beam power is gradually reduced from 100% to 0 in a gradient manner. The decay rate of each stage is set at 20%, which is an optimized threshold determined based on the thermophysical properties of tantalum and the metallurgical quality requirements of the weld. If the decay gradient exceeds 20%, such as decreasing by 30% in each stage, it means that the power decrease rate is too fast, the heat supply to the weld area per unit time is reduced sharply, the solidification time of the molten pool is shortened drastically, and the liquid metal does not have enough time to flow and compensate during the cooling and shrinkage process. This leads to the formation of continuous and loose micropores between dendrites. At the same time, the gas dissolved inside the molten pool cannot float to the surface and escape due to the excessively fast cooling rate. A large amount of it is trapped in the solidified structure and generates dense pores. In addition, the excessively fast cooling rate causes the weld metal to nucleate and grow rapidly at a high degree of undercooling, resulting in significant grain coarsening, deterioration of the uniformity of the joint structure, and obstruction of dislocation movement. Ultimately, this leads to a significant decrease in the plasticity of the welded joint, an increase in brittleness, and the overall mechanical properties failing to meet engineering requirements.

[0043] Furthermore, during the gradual reduction of power, the residual electron beam heat input is used to perform gradient cooling of the weld pool, avoiding the sudden cooling phenomenon caused by the direct cutting off of the heat source after welding. This eliminates the huge thermal stress caused by the rapid temperature change and controls the delayed deformation of the weld joint from the root. Furthermore, throughout the entire slow cooling phase, the vacuum chamber maintains the vacuum state set during the main welding process, continuously pumping vacuum and keeping the vacuum level constant until the molten pool is completely solidified. This is to prevent the high-temperature molten pool from coming into contact with the atmosphere during the cooling process and being oxidized or contaminated, while ensuring that the slow cooling effect is not affected by the external atmosphere.

[0044] As an optional embodiment of the present invention, step S5 specifically includes the following steps: S51: After the slow cooling stage, keep the tooling and tantalum tube together without disassembling them. Place the tantalum tube together with the tooling in the electron beam welding vacuum chamber. Utilize the residual vacuum environment and natural cooling conditions of the vacuum chamber to allow the tantalum tube to cool slowly to room temperature with the furnace. This step avoids additional thermal stress caused by a sudden drop in local temperature of the tantalum tube due to disassembling the tooling at high temperature. It also prevents uneven elastic recovery caused by the release of clamping force, thereby effectively ensuring the coaxiality accuracy of the tantalum tube. S52: After the tantalum tube cools to room temperature with the furnace, remove the tantalum tube and tooling from the vacuum chamber and clean the surface of the weld joint area of ​​the tantalum tube (for example, use a micro straight grinder to grind local protrusions and thick oxide blocks, grind at a uniform speed in one direction, and use sandpaper to grind the weld until smooth) to remove the surface oxide layer, spatter and residual impurities formed during welding and slow cooling, and obtain a clean weld surface. S53: The cleaned tantalum tube is placed into a vacuum annealing furnace for vacuum stress-relief annealing; Vacuum stress-relief annealing includes the following conditions: annealing temperature of 1050℃~1150℃, and vacuum degree ≤1×10 -3 Pa, heat preservation time is 60min~90min.

[0045] Specifically, vacuum stress-relief annealing fully releases and homogenizes residual welding stress in the weld and heat-affected zone, while refining the grain structure, improving the uniformity of the structure, and enhancing the plasticity and toughness of the welded joint. Furthermore, during the annealing process, the microstructure recovery and stress relaxation effect of the material at high temperatures are utilized to further correct the coaxiality deviation that may occur during the welding process of the tantalum tube, ensuring that the dimensional accuracy and mechanical properties of the final product meet the requirements for use.

[0046] The present invention will now be described in further detail with reference to specific embodiments and comparative examples. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.

[0047] Example 1 This embodiment provides an intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes, including the following steps: S1: Pretreatment of thick-walled tantalum tubes; Among them, the thick-walled tantalum tube has a purity of 99.95%, and its dimensions are 8mm thickness, 50mm outer diameter, and 100mm length, making it suitable for industrial exchange pipelines. Preprocessing includes: The circumferential weld end face of the tantalum tube was machined and mirror-polished, resulting in a surface roughness Ra of 0.6 μm. The tantalum tube was then immersed in a pickling solution (hydrofluoric acid: hydrogen peroxide: sulfuric acid: water = 1:1:1:2) for 7 minutes. After pickling, it was ultrasonically cleaned with anhydrous ethanol for 20 minutes. Finally, the tantalum tube was placed in a vacuum drying oven at 120℃ and a vacuum of 5×10⁻⁶. -3 Dry under Pa conditions for 60 minutes; finally, place in a vacuum bag and remove the vacuum to prevent oxidation.

[0048] S2: Place the pre-treated thick-walled tantalum tube onto the high-purity molybdenum centering shaft of the tooling, adjust the circumferential gap to 0.02mm, and the positioning error to 0.02mm; then put the assembled tooling and tantalum tube into the electron beam welding vacuum chamber, debug and start the rotary drive mechanism, at which time the tantalum tube rotation speed is 150mm / min.

[0049] Among them, such as Figure 1 As shown, the tooling includes a base 1, a centering shaft 2, a bidirectional clamping mechanism 3, and a rotary drive mechanism 5; The base 1 of the tooling is covered with a high-purity molybdenum pad to support the tantalum tube 4 during the welding process and to prevent the base material from contaminating the tantalum tube. The centering shaft 2 is horizontally fixed above the base 1 by a bracket. Its axis coincides with the axis of the tantalum tube 4 to be welded. The outer diameter of the centering shaft 2 is matched with the inner diameter of the tantalum tube 4. The tantalum tube 4 is sleeved on the centering shaft 2 and can rotate relative to the centering shaft 2. The part of the centering shaft 2 that contacts the inner wall of the tantalum tube 4 is made of pure molybdenum material.

[0050] The bidirectional clamping mechanism 3 includes two clamping components 31, which are respectively disposed at both ends of the centering shaft 2 in the axial direction and fixedly installed on the base 1. The two clamping components 31 have opposing clamping ends, which are used to apply clamping force from both ends of the tantalum tube 4 to clamp and fix the tantalum tube 4 and ensure that the welded circumferential seam is aligned. The clamping end surfaces of the two clamping components 31 that contact the end face of the tantalum tube 4 are provided with an anti-stick coating to prevent the tooling from sticking and contaminating the tantalum tube 4 at high temperature. The rotary drive mechanism 5 is located on the radial side of the centering shaft 2. Along the axial direction of the centering shaft 2, the rotary drive mechanism 5 is located between the two clamping members 31. The output end of the rotary drive mechanism 5 is connected to the centering shaft 2 or directly to the tantalum tube 4. The rotary drive mechanism 5 is used to drive the tantalum tube 4 to rotate at a constant speed around the axis of the centering shaft 2 during the welding process, so as to realize the continuous welding of the circumferential seam.

[0051] S3: Evacuate to 4×10 -4 Pa, hold for 10 minutes, and start electron beam welding in a vacuum environment; the PLC intelligent controller automatically adjusts the electron beam current and / or tooling rotation speed according to the tantalum tube wall thickness, real-time molten pool temperature and molten depth fluctuations to ensure that the molten pool temperature remains stable throughout the process and achieve constant heat input control. The tantalum tube has a wall thickness of 8mm. The target molten pool temperature for welding is set to be greater than 1900℃ and less than or equal to 1950℃ in the PLC intelligent controller. The electron beam current is 74mA and the tooling rotation speed is greater than or equal to 167 and less than or equal to 173mm / min. Real-time weld depth fluctuations are detected using a water-cooled miniature ultrasonic probe (model ZK-WS5-φ4). Both the ultrasonic probe and the electron beam gun are located 3mm behind the circumference of the circumferential weld and 2mm away from the pipe wall.

[0052] The wall thickness of tantalum tubes is measured online using the PRIMO SC multi-channel EMAT main unit. Its low-frequency magnetic field design does not interfere with the electron beam, and the wall thickness measurement accuracy is ±3μm. The thickness measurement data is uploaded to the PLC controller in real time.

[0053] A coaxial infrared pyrometer (model KLEIBER KMGA740) was installed in the vacuum chamber corresponding to the circumferential weld area, 300 mm away from the weld, with the angle between the infrared pyrometer and the electron beam gun being 30 degrees. o It is used to monitor the temperature of the molten pool in real time during the welding process and feed the temperature data back to the PLC intelligent controller; The infrared pyrometer has a sampling frequency of ≥100kHz (at least 100,000 times per second), a temperature measurement range of 600℃~2200℃, a temperature measurement accuracy of ±1%, and the temperature measurement data is transmitted to the PLC intelligent controller (model Siemens S7-1214C DC / DC / DC) in real time.

[0054] As welding progresses, the PLC intelligent controller first adjusts the process parameters in real time based on the penetration depth. When the penetration depth fluctuation is ≤0.6mm (the preset penetration depth is 8mm), the PLC intelligent controller does not adjust the process parameters. When the penetration depth fluctuation is >0.6mm (the preset penetration depth is 8mm), the PLC intelligent controller controls the electron beam current to rapidly increase or decrease by 3mA based on the preset electron beam current. If the change in melt depth is still greater than 0.6 mm after the electron beam current has been increased or decreased, and the melt depth deviation still fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: when the temperature is higher than 1950℃, reduce the electron beam current by 3mA and increase the rotation speed to 173mm / min. When the temperature is below 1900℃, the electron beam current is increased by 3mA and the rotation speed is reduced to 167mm / min to maintain temperature stability.

[0055] S4: After electron beam welding is completed, the power decay and slow cooling stage begins. The electron beam power is controlled to gradually decrease according to the preset step decay mode for slow cooling. The stepped attenuation mode is specifically as follows: Using the stable welding power during the main welding as the reference power (the stable power is 4.5kW at this time), the electron beam power is gradually reduced in the gradient of 100%→80%→60%→40%→20%→0, where 100% is the reference power value of the main welding stage, and the electron beam is completely cut off when it finally decays to 0. In each power holding state, the duration is controlled to be 5s to 10s, so that the temperature of the molten pool decreases slowly in a gradient manner as the electron beam power decreases step by step, thereby realizing the gradient vacuum slow cooling of the molten pool. S5: After the slow cooling stage, keep the tooling and tantalum tube intact. Place the tantalum tube and tooling together in the electron beam welding vacuum chamber. Utilize the residual vacuum environment and natural cooling conditions of the vacuum chamber to allow the tantalum tube to slowly cool to room temperature with the furnace. After the tantalum tube has cooled to room temperature with the furnace, remove the tantalum tube and tooling from the vacuum chamber and perform surface cleaning on the weld joint area of ​​the tantalum tube (use a micro direct grinder to grind local protrusions and thick oxide deposits, unidirectional uniform speed grinding, and use sandpaper to grind the weld seam until smooth) to remove the surface oxide layer, spatter, and residual impurities formed during welding and slow cooling, obtaining a clean weld seam surface. Place the cleaned tantalum tube into a vacuum annealing furnace for vacuum stress-relief annealing (annealing temperature 1150℃, vacuum degree 4×10). -4 (Pa, heat preservation time is 90min), to complete the tantalum tube welding.

[0056] Example 2 This embodiment provides an intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes, including the following steps: S1: Pretreatment of thick-walled tantalum tubes; Among them, the thick-walled tantalum tube has a purity of 99.95%, and its dimensions are 5mm thickness, 50mm outer diameter, and 100mm length, making it suitable for industrial tantalum tube products. The pretreatment is the same as in Example 1.

[0057] S2: Place the pretreated thick-walled tantalum tube onto the high-purity molybdenum centering shaft of the tooling (the tooling structure is the same as in Example 1), adjust the circumferential gap to 0.02mm, and the positioning error to 0.02mm; then put the assembled tooling and tantalum tube into the electron beam welding vacuum chamber, debug and start the rotary drive mechanism, at which time the tantalum tube rotation speed is 150mm / min.

[0058] S3: Evacuate to 4×10 -4 Pa, maintain for 10 minutes, and start electron beam welding in a vacuum environment; the PLC intelligent controller automatically adjusts the tooling rotation speed and electron beam current according to the tantalum tube wall thickness, real-time molten pool temperature and molten depth fluctuations to ensure that the molten pool temperature remains stable throughout the process and achieve constant heat input control. The tantalum tube has a wall thickness of 5mm. The target molten pool temperature for welding is set to be greater than or equal to 1800℃ and less than or equal to 1850℃ in the PLC intelligent controller. The electron beam current is 65mA and the tooling rotation speed is greater than or equal to 198mm / min and less than or equal to 200mm / min. Real-time weld depth fluctuations are detected using a water-cooled miniature ultrasonic probe (model ZK-WS5-φ4). Both the ultrasonic probe and the electron beam gun are located 3mm behind the circumference of the circumferential weld and 2mm away from the pipe wall.

[0059] The wall thickness of tantalum tubes is measured online using the PRIMO SC multi-channel EMAT main unit. Its low-frequency magnetic field design does not interfere with the electron beam, and the wall thickness measurement accuracy is ±3μm. The thickness measurement data is uploaded to the PLC controller in real time.

[0060] A coaxial infrared pyrometer (model KLEIBER KMGA740) was installed in the vacuum chamber corresponding to the circumferential weld area, 300 mm away from the weld, with the angle between the infrared pyrometer and the electron beam gun being 30 degrees. o It is used to monitor the temperature of the molten pool in real time during the welding process and feed the temperature data back to the PLC intelligent controller; The infrared pyrometer has a sampling frequency of ≥100kHz (at least 100,000 times per second), a temperature measurement range of 600℃~2200℃, a temperature measurement accuracy of ±1%, and the temperature measurement data is transmitted to the PLC intelligent controller (model Siemens S7-1214C DC / DC / DC) in real time.

[0061] As welding progresses, the PLC intelligent controller first adjusts the process parameters in real time based on the penetration depth. When the penetration depth fluctuation is ≤0.6mm (the preset penetration depth is 5mm), the PLC intelligent controller does not adjust the process parameters. When the penetration depth fluctuation is >0.6mm (the preset penetration depth is 5mm), the PLC intelligent controller controls the electron beam current to rapidly increase or decrease by 3mA based on the preset electron beam current. If the change in melt depth is still greater than 0.6 mm after the electron beam current has been increased or decreased, and the melt depth deviation still fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: when the temperature is higher than 1850℃, reduce the electron beam current by 3mA and increase the rotation speed to 200mm / min. When the temperature is below 1800℃, increase the electron beam current by 3mA and reduce the rotation speed to 198mm / min to maintain temperature stability.

[0062] S4: After electron beam welding is completed, the power decay and slow cooling stage begins. The electron beam power is controlled to gradually decrease according to the preset step decay mode for slow cooling. The stepped attenuation mode is specifically as follows: Using the stable welding power during the main welding as the reference power (the stable power is 4.2kW ​​at this time), the electron beam power is gradually reduced in the gradient of 100%→80%→60%→40%→20%→0, where 100% is the reference power value of the main welding stage, and the electron beam is completely cut off when it finally decays to 0. In each power holding state, the duration is controlled to be 5s to 10s, so that the temperature of the molten pool decreases slowly in a gradient manner as the electron beam power decreases step by step, thereby realizing the gradient vacuum slow cooling of the molten pool. S5: After the slow cooling stage, keep the tooling and tantalum tube intact. Place the tantalum tube and tooling together in the electron beam welding vacuum chamber. Utilize the residual vacuum environment and natural cooling conditions of the vacuum chamber to allow the tantalum tube to slowly cool to room temperature with the furnace. After the tantalum tube has cooled to room temperature with the furnace, remove the tantalum tube and tooling from the vacuum chamber and perform surface cleaning on the weld joint area of ​​the tantalum tube (use a micro direct grinder to grind local protrusions and thick oxide deposits, unidirectional uniform speed grinding, and use sandpaper to grind the weld seam until smooth) to remove the surface oxide layer, spatter, and residual impurities formed during welding and slow cooling, obtaining a clean weld seam surface. Place the cleaned tantalum tube into a vacuum annealing furnace for vacuum stress-relief annealing (annealing temperature 1050℃, vacuum degree 4×10). -4 (Pa, heat preservation time is 90min), to complete the tantalum tube welding.

[0063] Example 3 This embodiment provides an intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes, including the following steps: S1: Pretreatment of thick-walled tantalum tubes; Among them, the thick-walled tantalum tube has a purity of 99.95%, and its dimensions are 6.5mm thickness, 60mm outer diameter, and 100mm length, making it suitable for industrial exchange pipelines. The pretreatment is the same as in Example 1.

[0064] S2: Place the pretreated thick-walled tantalum tube onto the high-purity molybdenum centering shaft of the tooling (structure same as in Example 1), adjust the circumferential gap to 0.02mm, and the positioning error to 0.02mm; then put the assembled tooling and tantalum tube into the electron beam welding vacuum chamber, debug and start the rotary drive mechanism, at which time the tantalum tube rotation speed is 155mm / min.

[0065] S3: Evacuate to 4×10 -4 Pa, maintain for 10 minutes, and start electron beam welding in a vacuum environment; the PLC intelligent controller automatically adjusts the electron beam current and / or the rotation speed of the tooling according to the tantalum tube wall thickness, real-time molten pool temperature and molten depth fluctuations to ensure that the molten pool temperature remains stable throughout the process and achieve constant heat input control. The tantalum tube has a wall thickness of 6.5 mm. The target molten pool temperature for welding is set in the PLC intelligent controller to be greater than 1850℃ and less than or equal to 1900℃, the electron beam current is 72mA, and the tooling rotation speed is greater than or equal to 182mm / min and less than or equal to 187mm / min. Real-time weld depth fluctuations are detected using a water-cooled miniature ultrasonic probe (model ZK-WS5-φ4). Both the ultrasonic probe and the electron beam gun are located 3mm behind the circumference of the circumferential weld and 2mm away from the pipe wall.

[0066] The wall thickness of tantalum tubes is measured online using the PRIMO SC multi-channel EMAT main unit. Its low-frequency magnetic field design does not interfere with the electron beam, and the wall thickness measurement accuracy is ±3μm. The thickness measurement data is uploaded to the PLC controller in real time.

[0067] A coaxial infrared pyrometer (model KLEIBER KMGA740) was installed in the vacuum chamber corresponding to the circumferential weld area, 300 mm away from the weld, with the angle between the infrared pyrometer and the electron beam gun being 30 degrees. o It is used to monitor the temperature of the molten pool in real time during the welding process and feed the temperature data back to the PLC intelligent controller; The infrared pyrometer has a sampling frequency of ≥100kHz (at least 100,000 times per second), a temperature measurement range of 600℃~2200℃, a temperature measurement accuracy of ±1%, and the temperature measurement data is transmitted to the PLC intelligent controller (model Siemens S7-1214C DC / DC / DC) in real time.

[0068] As welding progresses, the PLC intelligent controller first adjusts the process parameters in real time based on the penetration depth. When the penetration depth fluctuation is ≤0.6mm (the preset penetration depth is 6.5mm), the PLC intelligent controller does not adjust the process parameters. When the penetration depth fluctuation is >0.6mm (the preset penetration depth is 6.5mm), the PLC intelligent controller controls the electron beam current to rapidly increase or decrease by 3mA based on the preset electron beam current. If the change in melt depth is still greater than 0.6 mm after the electron beam current has been increased or decreased, and the melt depth deviation still fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: when the temperature is higher than 1900℃, reduce the electron beam current by 3mA and increase the rotation speed to 187mm / min. When the temperature is below 1850℃, increase the electron beam current by 3mA and reduce the rotation speed to 182mm / min to maintain temperature stability.

[0069] S4: After electron beam welding is completed, the power decay and slow cooling stage begins. The electron beam power is controlled to gradually decrease according to the preset step decay mode for slow cooling. The stepped attenuation mode is specifically as follows: Using the stable welding power during the main welding as the reference power (the stable power is 4.32kW at this time), the electron beam power is gradually reduced in the gradient of 100%→80%→60%→40%→20%→0, where 100% is the reference power value of the main welding stage, and the electron beam is completely cut off when it finally decays to 0. In each power holding state, the duration is controlled to be 5s to 10s, so that the temperature of the molten pool decreases slowly in a gradient manner as the electron beam power decreases step by step, thereby realizing the gradient vacuum slow cooling of the molten pool. S5: After the slow cooling stage, keep the tooling and tantalum tube intact. Place the tantalum tube, along with the tooling, into the electron beam welding vacuum chamber. Utilize the residual vacuum environment and natural cooling conditions of the chamber to allow the tantalum tube to slowly cool to room temperature with the furnace. Once the tantalum tube has cooled to room temperature, remove the tantalum tube and tooling from the vacuum chamber. Clean the weld joint area of ​​the tantalum tube to remove the surface oxide layer, spatter, and residual impurities formed during welding and slow cooling, obtaining a clean weld surface. Place the cleaned tantalum tube into a vacuum annealing furnace for vacuum stress-relief annealing (annealing temperature 1100℃, vacuum degree 4×10⁻⁶). -4 (Pa, heat preservation time is 90min), to complete the tantalum tube welding.

[0070] Comparative Example 1 The main difference between this comparative example and Example 1 is that in step S4, the stepped attenuation mode decreases in increments of 30%, specifically as follows: Using the stable welding power during the main welding as the reference power, the electron beam power is gradually reduced in a gradient of 100%→70%→40%→10%→0, where 100% is the reference power value for the main welding stage, and the electron beam is completely cut off when it finally decays to 0. The remaining steps and technical parameters are the same as in Example 1.

[0071] Comparative Example 2 The main difference between this comparative example and Example 1 is that in step S3, the target molten pool temperature for welding is set to be greater than 1900 and less than or equal to 1950°C, the electron beam current is 74mA, and the tooling rotation speed is 155~159mm / min. As welding progresses, the PLC intelligent controller first adjusts the process parameters in real time based on the penetration depth. When the penetration depth fluctuation is ≤0.6mm, the PLC intelligent controller does not adjust the process parameters; when the penetration depth fluctuation is >0.6mm, the PLC intelligent controller controls the electron beam current to rapidly increase or decrease by 3mA based on the preset electron beam current. If the change in melt depth is still greater than 0.6 mm after the electron beam current has been increased or decreased, and the melt depth deviation still fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: when the temperature is higher than 1950℃, reduce the electron beam current by 3mA and increase the rotation speed to 159mm / min. When the temperature is below 1900℃, increase the electron beam current by 3mA and reduce the rotation speed to 155mm / min to maintain temperature stability.

[0072] The remaining steps and technical parameters are the same as in Example 1.

[0073] Comparative Example 3 The main difference between this comparative example and Example 1 is that in step S3, the target molten pool temperature for welding is set to be greater than 1900 and less than or equal to 1950°C, the electron beam current is 74mA, and the tooling rotation speed is 205~210mm / min. As welding progresses, the PLC intelligent controller first adjusts the process parameters in real time based on the penetration depth. When the penetration depth fluctuation is ≤0.6mm, the PLC intelligent controller does not adjust the process parameters; when the penetration depth fluctuation is >0.6mm, the PLC intelligent controller controls the electron beam current to rapidly increase or decrease by 3mA based on the preset electron beam current. If the change in melting depth is still greater than 0.6 mm after the electron beam current has been increased or decreased, and the melting depth deviation still fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: when the temperature is higher than 1950℃, reduce the electron beam current by 3mA and increase the rotation speed to 210mm / min. When the temperature is below 1900℃, increase the electron beam current by 3mA and reduce the rotation speed to 205mm / min to maintain temperature stability.

[0074] The remaining steps and technical parameters are the same as in Example 1.

[0075] Comparative Example 4 The main difference between this comparative example and Example 1 is that in step S3, the target molten pool temperature for welding is set to be greater than 1900 and less than or equal to 1950°C, the electron beam current is 60mA, and the tooling rotation speed is greater than or equal to 167mm / min and less than or equal to 173mm / min in advance in the PLC intelligent controller; the remaining steps and technical parameters are the same as in Example 1.

[0076] Comparative Example 5 The main difference between this comparative example and Example 1 is that in step S3, the target molten pool temperature for welding is set to be greater than 1900 and less than or equal to 1950°C, the electron beam current is 80mA, and the tooling rotation speed is greater than or equal to 167mm / min and less than or equal to 173mm / min in advance in the PLC intelligent controller; the remaining steps and technical parameters are the same as in Example 1.

[0077] Performance testing The tensile strength and elongation of the welded joint were tested using a WDW-100 tensile testing machine according to GB / T 228.1-2021 Metallic materials, tensile testing - Part 1: Test method at room temperature.

[0078] The airtightness was tested using a helium mass spectrometer leak detector. An internal vacuum was created, and the interfaces were sealed with vacuum sealant. The internal vacuum was then reduced to 1×10⁻⁶. -9 Pa·m 3 For speeds below a certain value, use helium gas to inspect the weld. If the leak detector does not alarm or the vacuum level does not change, it indicates that the weld meets the requirements.

[0079] Deformation: The dimensions of the sample were collected by a coordinate measuring machine (CMM), and the deformation and coaxiality error were automatically calculated using a Zeiss DuraMax 555 CMM. Density was determined using a Waygate Phoenix v|tome|x L300 non-destructive X-ray inspection system. Results data Table 1 As shown in Table 1, compared to Example 1, Comparative Example 1 changed the slow cooling power gradient from 20% to 30%, resulting in a sharp drop in power and a dramatic increase in the cooling rate of the molten pool. Under conditions of extreme supercooling, liquid tantalum rapidly nucleates, and the interdendritic micropores cannot be filled in time, preventing gases such as hydrogen and oxygen from escaping, ultimately leading to dense micropores and porosity. Although there are no visible cracks, the internal microscopic defects reduce the effective load-bearing area, drastically decrease plasticity, and consequently reduce strength.

[0080] As shown in Table 1, compared with Example 1, Comparative Example 2 has a lower welding speed than the lower limit set by this invention. This results in excessive heat accumulation due to the electron beam dwell time per unit area, leading to severe overheating of the molten pool and excessive fluidity of the liquid metal. Consequently, the weld surface is rough, and the weld slag fails to penetrate (actually, the molten pool collapses). Furthermore, the high-temperature dwell time causes a rapid coarsening of the β-phase grains, thus increasing the macroscopic deformation (0.12 mm / m). 2 The tensile strength dropped to 191 MPa, and the elongation (19.7%) was also low.

[0081] As shown in Table 1, compared with Example 1, Comparative Example 3 has a welding speed higher than the upper limit set by this invention, resulting in a shorter heating time per unit arc length. This significantly reduces the electron beam penetration capability, preventing the formation of an effective molten pool at the weld root, despite a small external deformation (0.08 mm / m). 2 However, since the actual weld penetration depth is less than the wall thickness, the effective load-bearing thickness of the joint is greatly reduced, the tensile strength is only 213 MPa, and the root is not fused, which can easily become a crack source during tension. The elongation (23.2%) is also lower than that of Example 1.

[0082] According to Table 1, compared with Example 1, Comparative Example 4 has a smaller electron beam current, so the weldment only melts on the surface and does not fuse at the bottom. The actual weld penetration is only a fraction of the wall thickness. The section reduction rate is limited during stretching, and the tensile strength (208 MPa) is significantly lower than that of Example 1.

[0083] As shown in Table 1, compared with Example 1, Comparative Example 5 had an excessively high electron beam current and extremely high beam spot energy, causing instantaneous vaporization of the tantalum material, resulting in weld burn-through, front-side depression, and severe spatter (leaking). A large amount of liquid metal was blown away, causing severe discontinuity in the weld cross-section and inducing a large number of oxide inclusions. Consequently, the three core indicators—density (99.5%), tensile strength (186 MPa), and elongation (18.9%)—were the worst among all samples.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for intelligent temperature and speed controlled electron beam welding of refractory metal high-wall-thickness tantalum tubes, characterized in that, include: Includes the following steps: S1: Pretreatment of thick-walled tantalum tubes; S2: Position the pre-treated thick-walled tantalum tube using a tooling fixture, and then load the assembled tooling fixture and tantalum tube together into the electron beam welding vacuum chamber. S3: In a vacuum environment, electron beam welding begins. The PLC intelligent controller automatically adjusts the electron beam current and / or tooling rotation speed according to the tantalum tube wall thickness, real-time molten pool temperature and molten depth fluctuations to ensure that the molten pool temperature remains stable throughout the process and achieve constant heat input control. S4: After electron beam welding is completed, the power decay and slow cooling stage begins. The electron beam power is controlled to gradually decrease according to the preset step decay mode for slow cooling. S5: After the tantalum tube cools to room temperature, remove the tantalum tube from the tooling, clean it, and then perform vacuum stress-relief annealing to complete the tantalum tube welding.

2. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, The thick-walled tantalum tube is a tantalum tube with a wall thickness ≥ 5 mm and a purity ≥ 99.95%; And / or, in step S1, the preprocessing includes: The circumferential weld end face of the tantalum tube is machined and mirror-polished to ensure a smooth, burr-free, and tilt-free surface with a surface roughness Ra ≤ 0.6 μm after polishing. The tantalum tube is then immersed in an acid pickling solution for 5-8 minutes to remove surface oxide scale. After acid pickling, it is ultrasonically cleaned in anhydrous ethanol for 20-30 minutes to remove residual acid and impurities. Finally, the tantalum tube is placed in a vacuum drying oven at 120-150℃ and a vacuum degree ≤ 1×10⁻⁶. -2 Dry under Pa conditions for 40-60 minutes.

3. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, In step S2, the tooling includes a base (1), a centering shaft (2), a bidirectional clamping mechanism (3), and a rotary drive mechanism (5). The centering shaft (2) is horizontally fixed above the base (1) by a bracket. The axis of the centering shaft (2) coincides with the axis of the tantalum tube (4) to be welded. The outer diameter of the centering shaft (2) is adapted to the inner diameter of the tantalum tube (4). The tantalum tube (4) is sleeved on the centering shaft (2) and can rotate relative to the centering shaft (2). The part of the centering shaft (2) that contacts the inner wall of the tantalum tube (4) is made of pure molybdenum material. The bidirectional clamping mechanism (3) includes two clamping components (31), which are respectively disposed at both ends of the centering shaft (2) in the axial direction and fixedly installed on the base (1); the two clamping components (31) have opposing clamping ends, which are used to apply clamping force from both ends of the tantalum tube (4) to clamp and fix the tantalum tube (4) and ensure that the welded circumferential seam is aligned. The clamping end surfaces of the two clamping components (31) that contact the end face of the tantalum tube (4) are provided with an anti-stick coating to prevent the tooling from sticking and contaminating the tantalum tube (4) at high temperature; The rotary drive mechanism (5) is located on the radial side of the centering shaft (2) along the axial direction of the centering shaft (2), and the rotary drive mechanism (5) is located between two clamping members (31); the output end of the rotary drive mechanism (5) is connected to the centering shaft (2) or directly to the tantalum tube (4) for transmission; the rotary drive mechanism (5) is used to drive the tantalum tube (4) to rotate at a constant speed around the axis of the centering shaft (2) during the welding process, so as to realize the continuous welding of the circumferential seam.

4. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, In step S3, the vacuum environment is achieved by evacuating the electron beam welding vacuum chamber to a vacuum level ≤5×10⁻⁶. -4 Pa, maintain for 10-15 minutes; A coaxial infrared pyrometer is installed in the vacuum chamber corresponding to the circumferential weld area, at a distance of 280-310mm from the weld, and the angle between the infrared pyrometer and the electron beam gun is 28-35°, to monitor the temperature of the molten pool in real time during the welding process and to feed the temperature data back to the PLC intelligent controller. The infrared pyrometer has a sampling frequency of ≥100kHz, a temperature measurement range of 600℃~2200℃, and a temperature measurement accuracy of ±1%.

5. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, In step S3, before starting electron beam welding, the tooling rotation drive mechanism is activated to drive the tantalum tube to rotate at a constant speed of 145-155 mm / min.

6. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, In step S3, during the welding process, to ensure good penetration of the thick-walled tantalum tube without overheating, the target molten pool temperature, electron beam current, and tooling rotation speed are pre-set in the PLC intelligent controller according to the wall thickness of the tantalum tube. Specifically: When the tantalum tube wall thickness is greater than or equal to 5 mm and less than or equal to 8 mm, the target welding pool temperature is set to 1800~1950℃, the electron beam current is 65mA~75mA, and the tooling rotation speed is 160~200mm / min in advance in the PLC intelligent controller. When the tantalum tube wall thickness is greater than 8mm and less than or equal to 12mm, the target welding pool temperature is set to 1950~2100℃, the electron beam current is 75mA~85mA, and the tooling rotation speed is 125-170mm / min in advance in the PLC intelligent controller. When the tantalum tube wall thickness is greater than 12mm, the target welding pool temperature is set to 2100℃~2200℃, the electron beam current is 85mA~100mA, and the tooling rotation speed is 80~125mm / min in advance in the PLC intelligent controller.

7. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, The PLC intelligent controller first adjusts the process parameters in real time by controlling the melt depth. When the melt depth fluctuation is ≤0.6mm, the PLC intelligent controller does not adjust the process parameters; when the melt depth fluctuation is >0.6mm, the PLC intelligent controller controls the electron beam current to increase or decrease by 3-5mA based on the preset electron beam current. If, after adjusting the electron beam current by increasing or decreasing it, the melt depth fluctuation remains >0.6mm and the melt depth deviation fails to converge effectively, then the control program is input according to the preset technical parameters of the PLC intelligent controller, including: When the wall thickness of the tantalum tube is greater than or equal to 5 mm and less than or equal to 8 mm, if the temperature of the target molten pool is higher than the preset temperature, the electron beam current should be reduced by 3-5 mA and the tooling rotation speed should be increased by 2-4 mm / min; if the temperature of the target molten pool is lower than the preset temperature, the electron beam current should be increased by 3-5 mA and the tooling rotation speed should be reduced by 2-4 mm / min. When the tantalum tube wall thickness is greater than 8 mm and less than or equal to 12 mm, if the target molten pool temperature is higher than the preset temperature, the electron beam current should be reduced by 3~5 mA and the tooling rotation speed should be increased by 2~4 mm / min; if the target molten pool temperature is lower than the preset temperature, the electron beam current should be increased by 3~5 mA and the tooling rotation speed should be reduced by 2~4 mm / min. When the tantalum tube wall thickness is greater than 12mm, if the target molten pool temperature is higher than the preset temperature, the electron beam current is reduced by 3~5mA and the tooling rotation speed is increased by 2~4mm / min based on the adjusted electron beam current; if the target molten pool temperature is lower than the preset temperature, the electron beam current is increased by 3~5mA and the tooling rotation speed is reduced by 2~4mm / min based on the adjusted electron beam current.

8. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, In step S4, the step-attenuation mode specifically refers to: Using the stable welding power during the main welding as the reference power, the electron beam power is gradually reduced in a gradient of 100%→80%→60%→40%→20%→0, where 100% is the reference power value for the main welding stage, and the electron beam is completely cut off when it finally decays to 0; the duration of each power level is controlled to be 5s~10s.

9. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 1, characterized in that, Step S5 specifically includes the following steps: S51: After the slow cooling stage, keep the tooling and tantalum tube intact, place the tantalum tube together with the tooling in the electron beam welding vacuum chamber, and use the residual vacuum environment and natural cooling conditions of the vacuum chamber to allow the tantalum tube to cool slowly to room temperature with the furnace. S52: After the tantalum tube cools to room temperature with the furnace, remove the tantalum tube and tooling from the vacuum chamber, and clean the surface of the weld joint area of ​​the tantalum tube to remove the surface oxide layer, spatter and residual impurities formed during welding and slow cooling, so as to obtain a clean weld surface. S53: The cleaned tantalum tube is placed into a vacuum annealing furnace for vacuum stress-relief annealing.

10. The intelligent temperature and speed controlled electron beam welding method for refractory metal high-wall-thickness tantalum tubes according to claim 9, characterized in that, Vacuum stress-relief annealing includes the following conditions: annealing temperature of 1050℃~1150℃, and vacuum degree ≤1×10 -3 Pa, heat preservation time is 60min~90min.

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