Gradient composite interlayer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint preparation method

Abstract

The invention discloses a preparation method of a gradient composite interlayer laser-assisted brazed submarine cable copper-aluminum heterogeneous joint, and relates to the technical field of submarine cable copper-aluminum heterogeneous joints, which comprises the following steps: material preparation: selecting a copper material and an aluminum material, and carrying out polishing and cleaning pretreatment on the to-be-welded surfaces of the copper material and the aluminum material; the gradient composite middle layer design of copper-nano alloy transition layer-aluminum is adopted, the thickness of each layer is accurately controlled, the effect of relieving stress concentration at the joint is achieved, fatigue failure caused by too large stress is avoided, laser-assisted brazing is conducted in the vacuum-magnetic field coupling environment, liquid metal splashing is restrained, uniform spreading of brazing filler metal is promoted, and the welding quality is improved. The welding quality of the connector is optimized, generation of intermetallic compounds is reduced, the mechanical property and conductivity of the connector are improved, rare earth elements Y and Sc are added to the middle layer to form a compact oxidation film, the corrosion resistance of the connector is enhanced, and the submarine cable copper-aluminum heterogeneous connector can stably operate for a long time in the severe marine environment.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-aluminum heterogeneous joints for submarine cables, and in particular to a method for preparing a copper-aluminum heterogeneous joint for submarine cables by laser-assisted brazing of a gradient composite intermediate layer. Background Art

[0002] The copper-aluminum heterojunction of submarine cables is the key part connecting the copper conductor and the aluminum conductor in submarine cables. The existing technology has many problems in processing the connection of copper-aluminum heterojunction of submarine cables:

[0003] On the one hand, traditional welding methods make it difficult to effectively control stress concentration at the joints. Due to the different thermal expansion coefficients of copper and aluminum, large internal stress will be generated when the temperature changes, which can easily lead to fatigue failure of the joints. On the other hand, brittle intermetallic compounds are easily formed at the joints, reducing the mechanical properties of the joints. Summary of the Invention

[0004] The purpose of the present invention is to make up for the shortcomings of the existing technology and provide a method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint. It adopts a gradient composite intermediate layer design of "copper-nanoalloy transition layer-aluminum" to achieve the effect of alleviating stress concentration at the joint. Laser-assisted brazing is performed under a vacuum-magnetic field coupling environment to suppress liquid metal splashing, promote uniform spreading of the brazing material, optimize the welding quality of the joint, improve the mechanical properties and conductivity of the joint, and add rare earth elements Y and Sc to the intermediate layer to form a dense oxide film, thereby achieving the effect of enhancing the corrosion resistance of the joint, so that the submarine cable copper-aluminum heterogeneous joint can operate stably for a long time in harsh marine environments.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint, comprising the following steps:

[0006] Material preparation: Select copper and aluminum materials, polish and clean their surfaces to be welded, prepare a nano-alloy transition layer material containing rare earth elements Y and Sc, and prepare copper, aluminum and brazing filler metal materials according to the mass ratio of copper:aluminum:brazing filler metal = (30-50):(20-40):(20-30);

[0007] Preparation of gradient composite intermediate layer: Using physical vapor deposition, a nano alloy transition layer and an aluminum layer are sequentially deposited on the surface of the pretreated copper material, with the thickness of the copper layer controlled to be 5-10 μm, the thickness of the nano alloy layer to be 2-5 μm, and the thickness of the aluminum layer to be 3-8 μm, to form a gradient composite intermediate layer;

[0008] Welding environment construction: Place the copper-aluminum material with gradient composite intermediate layer in vacuum welding equipment and evacuate to 10 -3Pa, install a magnetic field generating device, control the magnetic field intensity within the range of 0.1-0.3 T, and adjust the relative position of the magnetic field direction and the laser scanning path according to the molecular dynamics simulation results;

[0009] Laser-assisted brazing: Use laser equipment to perform laser-assisted brazing on copper-aluminum joints, control the laser scanning speed, and spread the brazing material under the vacuum-magnetic field coupling environment;

[0010] Quality inspection: After welding is completed, the joint is subjected to appearance inspection, mechanical property test and corrosion resistance test.

[0011] Furthermore, the surfaces of the copper and aluminum materials to be welded are polished using sandpaper with a grit size of 800-1200 mesh to achieve a surface roughness of Ra0.5-1.0 μm. The cleaning treatment is to place them in an ultrasonic cleaning device and clean them in an acetone solution for 5-10 minutes. The ultrasonic frequency is controlled at 20-40 kHz during cleaning. After cleaning, they are rinsed with deionized water and then blown dry with nitrogen. After polishing, the surface roughness is measured using a surface roughness meter. If it is not within the range, the polishing process parameters are adjusted.

[0012] Furthermore, the physical vapor deposition adopts magnetron sputtering. Before depositing the nano alloy transition layer and aluminum layer, the deposition chamber is pre-evacuated to 10 -5 Pa, and then argon is introduced as the sputtering gas, the argon flow rate is controlled at 20-50sccm, the working pressure is maintained at 0.5-2Pa, when depositing the nano-alloy transition layer, the deposition temperature is controlled at 300-400℃, the deposition rate is 0.1-0.3nm / s, when depositing the aluminum layer, the deposition temperature is 200-300℃, and the deposition rate is 0.2-0.4nm / s.

[0013] Furthermore, the nano-alloy transition layer material is prepared by ball milling, the ball milling time is 10-15 hours, the ball-to-material ratio is 5:1-8:1, the mass fraction of the rare earth element Y in the nano-alloy transition layer material is 0.5%-2%, the mass fraction of Sc is 0.3%-1.5%, and the rest are basic alloy components. The ball milling uses a planetary ball mill, and the ball milling jar is made of cemented carbide. After the ball milling, the nano-alloy powder is subjected to particle size analysis, and the average particle size of the powder is in the range of 50-200nm.

[0014] Furthermore, the vacuum welding equipment is equipped with a vacuum monitoring device, which uses an ionization vacuum gauge and a thermocouple vacuum gauge to measure the vacuum degree. -3 Pa±10 -4 Pa range, the vacuum degree is maintained stable by adjusting the vacuum pump's pumping rate and the opening of the intake valve.

[0015] Furthermore, the magnetic field generating device adopts an electromagnetic coil structure, and the magnetic field strength is controlled by adjusting the input current. The electromagnetic coil adopts water cooling to dissipate heat. The magnetic field direction adjustment mechanism is driven by a stepper motor. The magnetic field direction is adjusted in the horizontal and vertical directions with an adjustment accuracy of ±0.5°.

[0016] Furthermore, the laser equipment adopts a pulsed laser mode with a pulse frequency of 10-100Hz, a pulse width of 1-10ms, a power adjustment range of 100-500W, a wavelength of 1064nm, and a laser scanning speed of 5-15mm / s. During the welding process, the temperature of the joint is monitored in real time by an infrared thermometer, and the laser pulse frequency, pulse width and average power are adjusted according to temperature feedback.

[0017] Furthermore, the appearance inspection uses a high-resolution industrial camera to capture images of the joint surface, and the image analysis software uses an image recognition algorithm based on deep learning to identify pores and cracks with a minimum size of 0.1mm. In the mechanical properties test, the tensile test loading rate is 1-5mm / min, the bending test bending radius is 5-10mm, and the corrosion resistance test uses a three-electrode system, with a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a 3.5% NaCl solution as the test solution.

[0018] Compared with the existing technology, the method for preparing the gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint has the following beneficial effects:

[0019] The present invention adopts a gradient composite intermediate layer design of "copper-nanoalloy transition layer-aluminum" to precisely control the thickness of each layer, thereby alleviating stress concentration at the joint and avoiding fatigue failure caused by excessive stress. Laser-assisted brazing is performed in a vacuum-magnetic field coupling environment to suppress liquid metal splashing, promote uniform spreading of the brazing material, optimize the welding quality of the joint, reduce the formation of intermetallic compounds, and improve the mechanical properties and conductivity of the joint. Rare earth elements Y and Sc are added to the intermediate layer to form a dense oxide film, thereby enhancing the corrosion resistance of the joint, enabling the copper-aluminum heterogeneous joint of the submarine cable to operate stably for a long time in harsh marine environments.

[0020] Other advantages, objects and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be learned from the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0022] Figure 1 This is a schematic diagram of the process for preparing a gradient composite intermediate layer laser-assisted brazing copper-aluminum heterogeneous joint for submarine cables. DETAILED DESCRIPTION

[0023] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0024] Please refer to the attached Figure 1 , this application provides a number of embodiments and comparative examples, as follows:

[0025] Example 1

[0026] Copper and aluminum materials were selected with specifications of 500 mm in length and 20 mm in diameter, respectively. The surfaces to be welded of the copper and aluminum materials were polished using sandpaper with a particle size of 1000 mesh. The surface roughness was continuously measured with a surface roughness meter during the polishing process until the surface roughness reached Ra0.8 μm. The polished materials were then placed in an ultrasonic cleaning device and cleaned in an acetone solution for 8 minutes with the ultrasonic frequency set to 30 kHz. After cleaning, the residual acetone on the surface of the material was rinsed with deionized water and then blown dry with nitrogen.

[0027] A planetary ball mill was used to mix alloy powder containing 1% Y and 0.8% Sc by mass with basic alloy powder at a ball-to-material ratio of 6:1 for 12 hours to prepare nano-alloy transition layer material. The ball milling jar was made of cemented carbide. After ball milling, the nano-alloy powder was subjected to particle size analysis to ensure that the average particle size was 120 nm. Copper, aluminum and brazing materials were prepared at a mass ratio of copper:aluminum:brazing material = 40:30:30. Ag-Cu-Zn alloy was used as the brazing material.

[0028] The nano alloy transition layer and aluminum layer were deposited on the surface of the pretreated copper material in sequence by using the physical vapor deposition method of magnetron sputtering. Before deposition, the deposition chamber was pre-evacuated to 10 -5Pa, and then argon is introduced as the sputtering gas. The argon flow rate is controlled at 35sccm and the working gas pressure is maintained at 1Pa. When depositing the nano-alloy transition layer, the deposition temperature is controlled at 350°C and the deposition rate is 0.2nm / s; when depositing the aluminum layer, the deposition temperature is 250°C and the deposition rate is 0.3nm / s. By precisely controlling the deposition time, the thickness of the copper layer reaches 8μm, the thickness of the nano-alloy layer is 3μm, and the thickness of the aluminum layer is 5μm, forming a gradient composite intermediate layer.

[0029] The copper-aluminum material with the gradient composite intermediate layer was placed in a vacuum welding device equipped with a vacuum monitoring device composed of an ionization vacuum gauge and a thermocouple vacuum gauge, and the vacuum was pumped to 10 -3 Pa, when the vacuum degree deviates from 10 -3 Pa±10 -4 Pa range, the vacuum pump's pumping rate and the opening of the air inlet valve are automatically adjusted to maintain a stable vacuum degree. A magnetic field generating device with an electromagnetic coil structure and water cooling is installed. The magnetic field strength reaches 0.2T by adjusting the input current. The magnetic field direction adjustment mechanism is driven by a stepper motor. According to the results of molecular dynamics simulation, the magnetic field direction is precisely adjusted in the horizontal and vertical directions to the best matching position with the laser scanning path, with an adjustment accuracy of ±0.5°.

[0030] A laser device in pulse laser mode was selected, with the pulse frequency set to 50 Hz, the pulse width to 5 ms, the power adjusted to 300 W, the wavelength to 1064 nm, and the laser scanning speed set to 10 mm / s. During the welding process, an infrared thermometer was used to monitor the temperature of the joint in real time, and the laser pulse frequency, pulse width, and average power were adjusted in real time according to the temperature feedback, so that the Ag-Cu-Zn alloy solder was evenly melted in a vacuum-magnetic field coupling environment and well spread at the joint, achieving a firm bond between the copper-aluminum material and the gradient composite intermediate layer.

[0031] A high-resolution industrial camera was used to capture images of the joint surface. Through analysis of the deep learning-based image recognition algorithm, no pores or cracks larger than 0.1 mm were detected. A universal material testing machine was used to conduct a tensile test in accordance with relevant standards with a loading rate of 3 mm / min. The test results showed that the tensile strength of the joint reached 300 MPa. A bending test was conducted with the bending radius set to 8 mm. No abnormalities such as cracking occurred in the joint. A three-electrode system was used, with a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a 3.5% NaCl solution as the test solution. The open circuit potential, polarization curve and other corrosion resistance tests of the welded joint were conducted using an electrochemical workstation. The results showed that the joint has good corrosion resistance and meets the requirements for submarine cable use.

[0032] Example 2

[0033] Copper and aluminum materials were selected with specifications of 400mm in length and 15mm in diameter. The surfaces to be welded were carefully polished with 1000-grit sandpaper. During the operation, the surface roughness was continuously monitored with a surface roughness measuring instrument until the surface roughness accurately reached Ra0.7μm. After that, the polished materials were placed in an ultrasonic cleaning equipment and cleaned in acetone solution for 7 minutes with the ultrasonic frequency set to 35kHz. After cleaning, they were fully rinsed with deionized water to remove residual acetone and then blown dry with high-purity nitrogen.

[0034] Using a planetary ball mill, with a ball-to-material ratio of 6.5:1 and a ball-to-material ratio of 12.5 hours, alloy powder containing 1.2% Y and 0.9% Sc by mass was mixed with basic alloy powder to prepare a nano-alloy transition layer material. The ball milling jar was made of high-quality cemented carbide. After the ball milling, the nano-alloy powder was tested using a particle size analyzer to ensure that its average particle size was maintained at 130nm. Copper, aluminum and brazing filler metal were carefully prepared in a mass ratio of copper: aluminum: brazing filler metal = 38:32:30. The brazing filler metal was selected from Ag-Cu-In alloy with excellent performance.

[0035] The physical vapor deposition process of magnetron sputtering was used to deposit the nano alloy transition layer and aluminum layer on the surface of the pretreated copper material in sequence. Before deposition, the vacuum degree of the deposition chamber was pumped to 10 -5 Pa, argon is introduced as sputtering gas, the argon flow rate is stably controlled at 32sccm, the working gas pressure is maintained at 1.2Pa, and when depositing the nano-alloy transition layer, the temperature is set to 360℃ and the deposition rate is 0.22nm / s; when depositing the aluminum layer, the temperature is set to 260℃ and the deposition rate is 0.33nm / s. By precisely controlling the deposition time, the thickness of the copper layer finally reaches 7μm, the thickness of the nano-alloy layer is 3.5μm, and the thickness of the aluminum layer is 5.5μm, and the gradient composite intermediate layer is successfully constructed.

[0036] The copper-aluminum material with the gradient composite intermediate layer was placed in a vacuum welding device equipped with a high-precision vacuum monitoring device (composed of an ionization vacuum gauge and a thermocouple vacuum gauge) and the vacuum degree was pumped to 10 -3 Pa, when the vacuum degree deviates from 10 -3 Pa±10 -4 Pa range, the equipment automatically adjusts the vacuum pump's pumping rate and the opening of the air inlet valve to maintain a stable vacuum degree. A magnetic field generating device with an advanced electromagnetic coil structure and efficient water cooling is installed. By precisely adjusting the input current, the magnetic field strength reaches 0.22T. The magnetic field direction adjustment mechanism is driven by a stepper motor. Based on detailed molecular dynamics simulation results, the magnetic field direction is precisely adjusted in the horizontal and vertical directions to the best matching position with the laser scanning path, with an adjustment accuracy of up to ±0.4°.

[0037] A high-performance laser device with a pulsed laser mode is selected, the pulse frequency is set to 55Hz, the pulse width is adjusted to 4.5ms, the power is adjusted to 320W, the wavelength is 1064nm, and the laser scanning speed is set to 11mm / s. During the welding process, a high-precision infrared thermometer is used to monitor the temperature of the joint in real time. According to the temperature feedback information, the pulse frequency, pulse width and average power of the laser are adjusted in real time and accurately, so that the Ag-Cu-In alloy solder is uniformly melted in a vacuum-magnetic field coupling environment and perfectly spread at the joint, achieving a firm and high-quality bond between the copper-aluminum material and the gradient composite intermediate layer.

[0038] A high-resolution industrial camera was used to capture images of the joint surface, which were analyzed using an advanced deep learning-based image recognition algorithm. No pores or cracks larger than 0.1 mm were detected. A professional universal material testing machine was used to conduct tensile tests in accordance with strict relevant standards. The loading rate was set to 3.5 mm / min, and the test results showed that the joint had a tensile strength of up to 310 MPa. A bending test was conducted with a bending radius set to 7 mm, and no abnormal conditions such as cracking were observed in the joint. A standard three-electrode system was used, with a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a 3.5% NaCl solution as the test solution. A professional electrochemical workstation was used to conduct corrosion resistance tests such as open circuit potential and polarization curves on the welded joint. The results showed that the joint had excellent corrosion resistance and fully met the stringent requirements for submarine cable use.

[0039] Example 3

[0040] Copper and aluminum materials were selected with dimensions of 550 mm in length and 22 mm in diameter. The surfaces to be welded were finely polished with 1200-grit sandpaper. During the polishing process, the surface roughness was monitored in real time with the help of a surface roughness detection instrument until the surface roughness reached Ra0.5 μm. Subsequently, the polished materials were placed in an ultrasonic cleaning device and cleaned in an acetone solution for 5 minutes with the ultrasonic frequency set to 45 kHz. After cleaning, they were thoroughly rinsed with deionized water to remove residual impurities and then blown dry with dry nitrogen.

[0041] A nano-alloy transition layer material was prepared using a planetary ball mill with a ball milling time of 13.5 hours and a ball-to-material ratio of 7.5:1, wherein the mass fraction of Y was 1.6%, the mass fraction of Sc was 1.1%, and the copper, aluminum and solder materials were prepared according to the mass ratio of copper:aluminum:solder = 33:37:30. Sn-Ag-Bi alloy was used as the solder.

[0042] The nano alloy transition layer and aluminum layer were deposited on the pre-treated copper surface in sequence by magnetron sputtering physical vapor deposition technology. Before deposition, the vacuum degree of the deposition chamber was pumped to 10 -5Pa, argon is introduced as sputtering gas, the argon flow rate is stabilized at 28 sccm, the working gas pressure is maintained at 1.6 Pa, and when depositing the nano-alloy transition layer, the temperature is set to 390 ° C and the deposition rate is 0.28 nm / s; when depositing the aluminum layer, the temperature is set to 290 ° C and the deposition rate is 0.38 nm / s. By precisely controlling the deposition time, the thickness of the copper layer reaches 5 μm, the thickness of the nano-alloy layer is 4.5 μm, and the thickness of the aluminum layer is 7 μm, thus constructing an ideal gradient composite intermediate layer.

[0043] The copper-aluminum material with the gradient composite intermediate layer was placed in a vacuum welding device equipped with a high-sensitivity vacuum monitoring device (cooperated by an ionization vacuum gauge and a thermocouple vacuum gauge) and the vacuum was pumped to 10 -3 Pa, when the vacuum degree fluctuates and deviates from 10 -3 Pa±10 -4 Pa range, the equipment automatically adjusts the vacuum pump's pumping rate and the opening of the intake valve to ensure the stability of the vacuum degree. It is installed with a magnetic field generating device that adopts an advanced electromagnetic coil structure and has efficient heat dissipation performance. By precisely adjusting the input current, the magnetic field strength reaches 0.28T. The magnetic field direction adjustment mechanism is driven by a stepper motor. Based on the in-depth molecular dynamics simulation results, the magnetic field direction is precisely adjusted in the horizontal and vertical directions to the best fit position with the laser scanning path, and the adjustment accuracy can reach ±0.3°.

[0044] High-quality laser equipment with pulsed laser mode is selected, the pulse frequency is set to 65Hz, the pulse width is adjusted to 3.5ms, the power is adjusted to 380W, the wavelength is 1064nm, and the laser scanning speed is set to 13mm / s. During the welding process, a high-precision infrared thermometer is used to monitor the temperature of the joint in real time. According to the temperature feedback information, the pulse frequency, pulse width and average power of the laser are adjusted in real time and accurately, so that the Sn-Ag-Bi alloy solder is uniformly melted in a vacuum-magnetic field coupling environment and evenly spread at the joint, achieving a firm connection between the copper-aluminum material and the gradient composite intermediate layer.

[0045] A high-resolution industrial camera was used to capture images of the joint surface, and a detailed analysis was performed using an advanced deep learning-based image recognition algorithm. No pores or cracks larger than 0.1 mm were found. A professional universal material testing machine was used to conduct a tensile test in accordance with relevant standards, with the loading rate set to 4 mm / min. The test results showed that the tensile strength of the joint reached 330 MPa. A bending test was conducted with the bending radius set to 9 mm. No abnormalities such as cracking were observed in the joint. A standard three-electrode system was used, with a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a 3.5% NaCl solution as the test solution. A professional electrochemical workstation was used to conduct corrosion resistance tests such as open circuit potential and polarization curves on the welded joint. The results showed that the joint has excellent corrosion resistance and fully meets the use requirements of submarine cables.

[0046] Comparative Example

[0047] Copper and aluminum materials were selected with dimensions of 550 mm in length and 22 mm in diameter. 1000-grit sandpaper was used for polishing to control the surface roughness to about Ra0.8 μm. The cleaning process was carried out in an ultrasonic cleaning device in an acetone solution for 8 minutes with the ultrasonic frequency set to 30 kHz. After cleaning, the materials were rinsed with deionized water and dried. However, in the material preparation process, the nano-alloy transition layer material was not prepared. The materials were directly prepared according to the mass ratio of copper:aluminum:brazing filler metal = 55:15:30. The brazing filler metal was an ordinary Zn-Al alloy, which is relatively conventional in composition and performance and lacks special optimization design for copper-aluminum heterogeneous welding.

[0048] Place the prepared copper and aluminum materials in a common vacuum welding device and pump the vacuum degree to 10 -3 Pa, but the equipment is only equipped with a basic vacuum monitoring device, which is relatively weak in vacuum stability control and cannot achieve automatic adjustment to maintain high-precision vacuum. In addition, no magnetic field generating device is installed in the welding process, and the beneficial effects of the magnetic field on the welding process are missing, such as being unable to suppress liquid metal splashing and promote uniform spreading of solder.

[0049] Continuous laser equipment is used for welding, with the laser power set to 450W, the wavelength to 1064nm, and the laser scanning speed to 18mm / s. This continuous laser mode is different from the pulsed laser mode in the embodiment, and there are significant differences in the energy input method and the thermal impact on the welding process. Moreover, there is no temperature monitoring and feedback adjustment system during the welding process, and the laser parameters cannot be adjusted according to the real-time temperature changes at the joint. It is difficult to accurately control the welding heat input, which easily leads to unstable welding quality.

[0050] The surface image of the joint was captured by a high-resolution industrial camera, and analysis revealed a large number of pores, some of which exceeded 0.5mm in size. There were also multiple obvious cracks with a length of 1-3mm. A universal material testing machine was used for tensile testing with a loading rate of 5mm / min. The test results showed that the tensile strength of the joint was only 150MPa. During the bending test, the bending radius was 6mm, and the joint cracked rapidly during the bending process, showing extremely poor toughness. In terms of corrosion resistance testing, a three-electrode system and 3.5% NaCl solution were used. Through electrochemical workstation testing, it was found that the corrosion resistance was seriously insufficient and could not meet the long-term use requirements of submarine cables in complex marine environments.

[0051]

[0052]

[0053] As shown in the table above, the three embodiments are carefully designed and strictly controlled in terms of material ratio, intermediate layer construction, welding environment and process parameters. By providing a nano-alloy transition layer, the thickness of each layer is precisely controlled, and a vacuum-magnetic field coupling environment and pulsed laser welding are used with temperature feedback adjustment. The welding quality is significantly better than that of the comparative example. Due to the lack of a nano-alloy transition layer and magnetic field assistance, the comparative example uses a continuous laser without temperature feedback adjustment, resulting in a large number of pores and cracks in the welded joints, low tensile strength, easy cracking when bending, and poor corrosion resistance, which cannot meet the requirements for submarine cable use. This shows that the reasonable design of material ratios, the construction of a gradient composite intermediate layer, and the optimization of the welding environment and process parameters are crucial to improving the quality of copper-aluminum heterogeneous joints in submarine cables.

[0054] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint, characterized in that: The following steps are involved: Material preparation: Select copper and aluminum materials, polish and clean their surfaces to be welded, prepare a nano-alloy transition layer material containing rare earth elements Y and Sc, and prepare copper, aluminum and brazing filler metal materials according to the mass ratio of copper:aluminum:brazing filler metal = (30-50):(20-40):(20-30); Preparation of gradient composite intermediate layer: Using physical vapor deposition, a nano alloy transition layer and an aluminum layer are sequentially deposited on the surface of the pretreated copper material, with the thickness of the copper layer controlled to be 5-10 μm, the thickness of the nano alloy layer to be 2-5 μm, and the thickness of the aluminum layer to be 3-8 μm, to form a gradient composite intermediate layer; Welding environment construction: Place the copper-aluminum material with gradient composite intermediate layer in vacuum welding equipment and evacuate to 10 - 3 Pa, install a magnetic field generating device, control the magnetic field intensity within the range of 0.1-0.3 T, and adjust the relative position of the magnetic field direction and the laser scanning path according to the molecular dynamics simulation results; Laser-assisted brazing: Use laser equipment to perform laser-assisted brazing on copper-aluminum joints, control the laser scanning speed, and spread the brazing material under the vacuum-magnetic field coupling environment; Quality inspection: After welding is completed, the joint is subjected to appearance inspection, mechanical property test and corrosion resistance test.

2. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: For the grinding treatment of the copper and aluminum surfaces to be welded, use sandpaper with a grit size of 800-1200 to make the surface roughness reach Ra0.5-1.0μm. For cleaning treatment, place them in an ultrasonic cleaning equipment and clean them in acetone solution for 5-10 minutes. During cleaning, control the ultrasonic frequency to 20-40kHz. After cleaning, rinse with deionized water and then blow dry with nitrogen. After grinding, use a surface roughness meter to measure the surface roughness. If it is not within the range, adjust the grinding process parameters.

3. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: Physical vapor deposition uses magnetron sputtering. Before depositing the nano-alloy transition layer and aluminum layer, the deposition chamber is pre-evacuated to 10 -5 Pa, and then argon is introduced as the sputtering gas, the argon flow rate is controlled at 20-50sccm, the working pressure is maintained at 0.5-2Pa, when depositing the nano-alloy transition layer, the deposition temperature is controlled at 300-400℃, the deposition rate is 0.1-0.3nm / s, when depositing the aluminum layer, the deposition temperature is 200-300℃, and the deposition rate is 0.2-0.4nm / s.

4. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: The nano alloy transition layer material is prepared by ball milling, the ball milling time is 10-15 hours, the ball-to-material ratio is 5:1-8:1, the mass fraction of rare earth element Y in the nano alloy transition layer material is 0.5%-2%, the mass fraction of Sc is 0.3%-1.5%, and the rest are basic alloy components. The ball milling adopts a planetary ball mill, and the ball milling jar is made of cemented carbide. After the ball milling, the particle size analysis of the nano alloy powder is carried out, and the average particle size of the powder is in the range of 50-200nm.

5. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: The vacuum welding equipment is equipped with a vacuum monitoring device, which uses an ionization vacuum gauge and a thermocouple vacuum gauge to measure the vacuum degree. -3 Pa±10 -4 Pa range, the vacuum degree is maintained stable by adjusting the vacuum pump's pumping rate and the opening of the intake valve.

6. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: The magnetic field generating device adopts an electromagnetic coil structure. The magnetic field strength is controlled by adjusting the input current. The electromagnetic coil adopts water cooling to dissipate heat. The magnetic field direction adjustment mechanism is driven by a stepper motor. The magnetic field direction is adjusted in the horizontal and vertical directions with an adjustment accuracy of ±0.5°.

7. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: The laser equipment adopts pulse laser mode with a pulse frequency of 10-100Hz, a pulse width of 1-10ms, a power adjustment range of 100-500W, a wavelength of 1064nm, and a laser scanning speed of 5-15mm / s. During the welding process, the temperature of the joint is monitored in real time by an infrared thermometer, and the laser pulse frequency, pulse width and average power are adjusted according to temperature feedback.

8. The method for preparing a gradient composite intermediate layer laser-assisted brazing submarine cable copper-aluminum heterogeneous joint according to claim 1 is characterized in that: The appearance inspection uses a high-resolution industrial camera to capture images of the joint surface. The image analysis software uses an image recognition algorithm based on deep learning to identify pores and cracks with a minimum size of 0.1 mm. In the mechanical properties test, the tensile test loading rate is 1-5 mm / min, and the bending test bending radius is 5-10 mm. The corrosion resistance test uses a three-electrode system, with a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a 3.5% NaCl solution as the test solution.

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