A zirconium-nickel dissimilar metal welding method based on active temperature field regulation

Abstract

The present invention discloses a zirconium-nickel dissimilar metal welding method based on active temperature field regulation, comprising the following steps: S1: cleaning the parent metal; grinding and cleaning the butt end faces and welding surfaces of the zirconium and nickel alloy tubes to obtain clean zirconium and nickel parent metals; S2: assembling the parts to be welded; assembling the end faces of the clean parent metals to be welded in a protective air cavity of a rotating clamping device; S3: welding; welding at a predetermined welding point using a laser scanner, controlling the heat source gradient distribution of the parent metals at both ends of the weld by regulating the laser power, establishing weld temperature field feedback through an infrared temperature sensor, and performing real-time monitoring and regulation of the laser power; S4: post-weld heat treatment; adjusting the laser power in real time based on the weld temperature field feedback to regulate the cooling process of the weld. The present invention achieves effective connection of zirconium and nickel refractory metals by controlling the regional welding temperature field, avoiding the temperature range of forming brittle compounds, ensuring the uniformity of the molten pool between the Zr and Ni materials, and reducing welding defects such as thermal cracks and pores.

Description

Technical Field

[0001] The present invention relates to the technical field of dissimilar metal welding, and in particular to a zirconium-nickel dissimilar metal welding method based on active temperature field regulation. Background Art

[0002] As global climate change becomes increasingly serious, controlling carbon emissions has become a critical global issue. Currently, the primary approach to controlling carbon emissions is to promote the use of clean energy, reduce carbon emissions at the source, improve energy efficiency, and promote the development of a circular economy. Nuclear power, a recognized clean energy source, is an inevitable trend in future clean energy development.

[0003] Zirconium has an extremely low thermal neutron absorption cross-section, low radiation brittleness within the reactor, and excellent corrosion resistance in high-temperature, high-pressure steam. Pure zirconium also offers moderate mechanical properties, good processability, and excellent compatibility with uranium fuel, which can improve uranium fuel utilization efficiency. Therefore, it is widely used in components such as fuel cladding tubes, positioning spacers, and component boxes. Nickel, with its excellent corrosion resistance, is often used as a structural material in the nuclear industry. Therefore, the use of pure zirconium and pure nickel welded joints in reactor components requires research on the performance of zirconium / nickel joints.

[0004] After pure zirconium is melted, the liquid metal has good fluidity and low crack sensitivity, but its chemical properties are active. At high temperatures, it will react with O, N, and H elements in the air. The melting point of pure zirconium is higher than that of pure nickel, but its thermal expansion coefficient is only 1 / 2 of that of pure nickel. At the same time, it has disadvantages such as low thermal conductivity, poor thermal conductivity, and low specific heat capacity. A small energy change will cause a sharp change in temperature, resulting in high residual stress and thermal stress. Pure nickel has good weldability, but poor thermal conductivity. The welding heat is not easy to dissipate, and it is easy to overheat, resulting in coarse grains. Pure nickel and pure zirconium have poor metallurgical compatibility and extremely low solubility in each other. The maximum solubility of Ni in α-Zr is less than 0.8%, and the solubility of Zr in γ-Ni is only 0.6%. Only intermetallic compounds such as NiZr, NiZr2, and Ni5Zr can be generated. In addition, there are many eutectic reactions that may occur between pure nickel and pure zirconium. For example, at 1170℃, γ-Ni+Ni5Zr will be generated, and at 1070℃, Ni 21 Zr8+Ni 10 Zr7 will generate NiZr+NiZr2 at 1010℃, and NiZr2+β-Zr at 960℃. The coarse grains in the heat-affected zone (HAZ) are also prone to thermal cracking. Therefore, while ensuring full penetration, the welding line energy should be minimized. Scanning should be added to promote molten pool flow, increase weld width, and ensure joint airtightness. Before welding, the weld surface should be cleaned to avoid moisture, oxides, and other factors that may affect weld quality.

[0005] At present, brazing, electron beam welding and arc welding are mainly used for the application of nickel and zirconium in nuclear industry materials. The applicable welding conditions and quality control are as follows: (1) Brazing needs to be carried out in a vacuum or argon environment to avoid metal oxidation. At the same time, brazing also faces challenges such as difficulty in ensuring critical dimensions and low strength and corrosion resistance of the brazed joint due to the formation of intermetallic compounds in the transition zone. In addition, brazing also has the problem of many cold welds and difficulty in detection during large-scale welding; (2) Electron beam welding also needs to be carried out in a vacuum environment to prevent the electron beam from scattering and chemically reacting in the welding area. Therefore, electron beam welding has problems such as complex welding parameters, many process influencing factors, and difficult equipment maintenance, making welding quality control difficult; (3) Arc welding has a large heat input during welding, which is easy to cause pores and residual stress, and is more likely to cause this problem for thin plate materials.

[0006] Laser welding is a welding method with high energy density and adjustable regional heat input. It can weld not only thin plates but also thick plates. It has the advantages of stable welding quality, beautiful welds, fast welding speed, small weld spots, low welding heat and small thermal deformation. However, due to the fast cooling speed of passive heat dissipation during welding, zirconium and nickel easily form hard and brittle amorphous alloys and intermetallic compounds, which makes the weld extremely prone to brittle fracture during the subsequent cooling process.

[0007] Therefore, how to achieve one-time forming during welding, and at the same time control the microstructure through the temperature field, narrow the range of the heat-affected zone, reduce the formation of brittle phases, realize the effective connection of refractory dissimilar metals, and obtain low-stress welds, has become a difficult problem that needs to be solved urgently. Summary of the Invention

[0008] The present invention provides a zirconium-nickel dissimilar metal welding method based on active temperature field regulation, aiming to achieve one-time forming of zirconium-nickel refractory metal welds while reducing welding difficulty and environmental requirements, and improving the overall performance of the welds by simplifying the welding and heat treatment systems.

[0009] To achieve its purpose, the present invention adopts the following technical solutions:

[0010] A zirconium-nickel dissimilar metal welding method based on active temperature field regulation comprises the following steps:

[0011] S1: Cleaning the base metal; grinding and ultrasonic cleaning the butt end faces and welding surfaces of the zirconium and nickel alloy tubes to remove the surface oxide film and oil stains to obtain clean zirconium and nickel base metals;

[0012] S2: Assembling the parts to be welded; aligning the cleaned zirconium and nickel base metals to be welded in step S1 and assembling them in the protective air cavity of the rotating clamping device of the metal welding system;

[0013] S3: Welding: A laser scanner is used to reciprocate at the predetermined welding point for welding. During the welding process, shielding gas is introduced into the shielding gas cavity through the vent holes located on the side of the rotating clamping device. The heat source gradient distribution of the parent material at both ends of the weld is controlled by adjusting the laser power to adapt to the melting points of different parent materials. At the same time, the weld temperature field feedback is established through the infrared temperature sensor to monitor and adjust the laser power in real time.

[0014] S4: Post-weld heat treatment; according to the weld temperature field feedback established in step S3, the laser power is adjusted in real time to control the cooling process of the weld.

[0015] Furthermore, in step S1, the thickness of the zirconium-nickel alloy tube is 0.57±0.03 mm, and the diameter is 8.36±0.05 mm.

[0016] Furthermore, in step S3, the laser spot diameter of the laser scanner is 30-40 μm.

[0017] Furthermore, in step S3, the laser movement path of the laser scanner is an "S" shape connected end to end, the laser movement path overlap rate is 20%, and the overall direction of the path is perpendicular to the weld.

[0018] Furthermore, in step S3, the temperature field is perpendicular to the weld as a whole and is composed of a series of Gaussian curves with gradually decreasing peak values. Within a range of ≤1 mm at the joint of the zirconium and nickel base materials, the temperature decreases from 1700°C to 1400°C from the zirconium side to the nickel side, with a temperature decrease of 20 to 22°C per 100 μm.

[0019] Furthermore, in step S3, a laser scanner is used to preheat the weld with a 200-300W laser before welding. The laser power during welding is 540-650W, the welding speed is 30-50 rad / min, and the defocus is -2-+2mm. After welding is completed, the laser power is reduced within 2-6 minutes to gradually cool the weld, and the laser power is reduced from 400W to 100W. During the welding process, the shielding gas is Ar, and the gas flow rate is 10-20L / min.

[0020] Furthermore, in step S3, the stress distribution of the weld is controlled by regulating the temperature field, and the area formed by the self-melting of zirconium accounts for ≥80% of the total area of the weld.

[0021] Furthermore, in step S4, when the infrared temperature sensor detects that the temperature of the base material is 940-960°C and the temperature of the weld is 1170-1200°C, the temperature starts to drop. During cooling, the temperature field at the weld extending toward the base on both sides decreases by 10-20°C every 100 μm.

[0022] Furthermore, the protective air cavity of the rotating clamping device in step S2 is detachable.

[0023] Furthermore, in step S3, the temperature field is controlled by a metal welding system, which includes a laser welding module, a welding protection module, and a post-processing module; the infrared temperature sensor is electrically connected to a signal input terminal of a PLC programmable controller, and a signal output terminal of the PLC programmable controller is electrically connected to the laser welding module, the welding protection module, and the post-processing module respectively; the post-processing module is also electrically connected to the signal input terminal of the PLC programmable controller;

[0024] The laser welding module feeds back information on the weld temperature field established by the infrared temperature sensor to ensure that the temperature distribution in the welding area meets the predetermined requirements and serves as a post-processing heat source;

[0025] The shielding gas of the welding protection module is used to protect the weld. During welding, the laser of the laser welding module penetrates the shielding gas cavity of the welding protection module from the top of the rotating clamping device to weld the internal parts to be welded.

[0026] The post-processing module receives the signal about the welding area temperature transmitted by the infrared temperature sensor to the PLC programmable controller to detect the weld temperature and regulate the weld temperature field established by the infrared temperature sensor; when the post-processing heat source does not meet the requirements, the post-processing module feeds back the signal to the PLC programmable controller, and the PLC programmable controller controls the laser welding module to dynamically adjust the laser power and scanning speed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention achieves effective connection of zirconium and nickel refractory metals by controlling the regional welding temperature field. The high energy density and dynamic scanning capability formed by the regional welding temperature field control can accurately control the heat input, keep the overall temperature of the weld below 960°C, avoid the temperature range where brittle compounds are easily formed, ensure the uniformity of the molten pool between the Zr and Ni materials, and significantly reduce welding defects such as thermal cracks and pores. Compared with traditional welding methods, the flexible trajectory adjustment and rapid cooling characteristics of the laser help to improve metallurgical bonding and inhibit the formation of brittle phases. At the same time, it can significantly reduce the heat-affected zone and residual stress, and reduce welding deformation. In addition, its non-contact processing method and adaptability to complex workpiece shapes make the weld surface quality higher and the subsequent processing requirements lower. It provides a reliable technical guarantee for the high-quality connection of Zr-Ni dissimilar alloys, effectively overcomes the problems of brittle fracture, pores and cold welds caused by traditional welding, significantly improves the manufacturing level of nuclear fuel components, and solves the problem of the difficulty of welding Zr-Ni dissimilar alloys.

[0029] 2. The present invention uses an active temperature field control method for welding, which improves production efficiency, reduces energy consumption and environmental pollution, enhances the adaptability and automation level of the welding process, and provides important support for the development of modern welding technology, enabling this type of new material to be more widely used in fields such as nuclear reactor components, high-performance electromagnetic shielding equipment, and cutting-edge weapon systems. Compared with passive heat dissipation during welding, active control significantly improves weld quality, reduces the heat-affected zone, and can adapt to complex welding needs through real-time, precise, and flexible laser power adjustment. In addition, active control reduces dependence on the environment and materials, provides greater flexibility and controllability, and can respond to changes in the welding process in real time, ensuring that the temperature field is always in the optimal state, avoiding defects caused by temperature fluctuations, and thus ensuring the stability and consistency of the welding process.

[0030] 3. The present invention adopts a metal welding system, which realizes precise control of the weld temperature field during welding and slow cooling treatment of the weld by gradually reducing the laser power or dynamically adjusting the heat input, thereby reducing welding residual stress, optimizing the weld microstructure, and effectively reducing the tendency of thermal cracking. At the same time, it eliminates the limitation of traditional post-weld heat treatment that requires additional heating equipment, is more energy-saving and efficient, and is suitable for engineering needs of complex geometric welding and dissimilar material connection.

[0031] 4. The zirconium-nickel dissimilar metal welding method based on active temperature field control provided by this invention converts a single-peaked Gaussian heat source into an overall controllable temperature field through partial path overlap. This ensures a more uniform temperature distribution, effectively reduces thermal stress concentration caused by excessive temperature gradients due to path spacing, and reduces the risk of thermal cracking and deformation of the material. Furthermore, a 20% overlap rate of welding paths helps maintain the stability of the molten pool, improves the fluidity of the molten material, promotes the escape of gases within the molten pool, reduces the formation of pores and inclusions, and further improves the quality and performance of the weld.

[0032] 5. Because zirconium alloys produce different microstructures at different cooling rates, a martensite phase forms when cooled at a relatively fast rate, and no significant segregation of alloying elements occurs. Rapid heating and cooling also reduce the amount of dissolved nitrogen in the metal, resulting in good corrosion resistance for the weld. Under slow cooling conditions, a Widmanstätten microstructure forms, adversely affecting weld performance. Furthermore, the zirconium-nickel compounds formed within the molten pool easily form brittle phases at high cooling rates, reducing weld strength. Therefore, controlling the cooling rate of different areas after welding is particularly important. Therefore, the present invention utilizes temperature field control and heat source monitoring technology, with a laser scanner controlling the cooling rate of different areas of the weld and part of the substrate based on feedback from an infrared temperature sensor, thereby achieving high-quality and high-strength welds and substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the zirconium-nickel dissimilar metal welding method of the present invention;

[0034] Figure 2 It is a schematic structural diagram of the metal welding system of the present invention;

[0035] Figure 3 A schematic diagram of the laser path overlap and welding direction of the present invention;

[0036] Figure 4 It is a planar projection diagram of the weld of the present invention;

[0037] Figure 5 Schematic diagram of temperature field distribution within one scanning cycle of the present invention;

[0038] Figure 6 for Figure 5 Schematic diagram of temperature field distribution after superposition of the next scanning cycle;

[0039] Figure 7 Overlay cross-sectional views of the temperature field after multiple scans;

[0040] Figure 8 This is a physical picture of the welding sample obtained in Example 1 of the present invention;

[0041] Figure 9 This is a microstructure diagram of the weld seam of the welding sample of Example 1 of the present invention;

[0042] Figure 10 This is a comparison chart of the tensile strength of the samples obtained in Examples 1-3 of the present invention and the samples without temperature field control.

[0043] In the figure: 1 - rotating clamping device; 2 - laser scanner; 3 - welding seam; 4 - infrared temperature sensor; 5 - ventilation hole. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] Industrial application: Welding of Zr-Ni dissimilar metal positioning grids in nuclear power plants.

[0046] Example 1

[0047] This time, N36 and GH4169 dissimilar metal laser welding was carried out. According to the zirconium-nickel dissimilar metal welding method based on active temperature field control provided by the present invention, Figure 1 As shown, the following steps are included:

[0048] S1: Cleaning the parent material; grinding and ultrasonically cleaning the butt end faces and welding surfaces of the N36 and GH4169 alloy tubes to remove the surface oxide film and oil stains, thereby obtaining clean N36 and GH4169 parent materials; wherein, the thickness of the N36 alloy tube is 0.57 mm, the diameter is 8.36 mm, and by mass percentage, the Zr content of the N36 alloy tube is 97 wt%, the Sn content is 0.9 wt%, the Nb content is 0.9 wt%, the Fe content is 0.2 wt%, and the rest are impurities; the thickness of the GH4169 alloy tube is 0.57 mm, the diameter is 8.36 mm, and by mass percentage, the Ni content of the GH4169 alloy tube is 50 wt%, the Cr content is 17 wt%, the Mo content is 2.8 wt%, the Nb content is 4.75 wt%, and the rest are impurities;

[0049] S2: Assemble the parts to be welded; assemble the cleaned N36 and GH4169 base materials to be welded in step S1 at the end faces of the parts to be welded. Figure 2 In the metal welding system shown, the protective gas cavity of the rotary clamping device 1 is detachable, and the assembly gap between the end faces to be welded is 0.2 mm;

[0050] S3: Welding; Before welding, the weld 3 is preheated using a 200W laser from a laser scanner 2. This preheating method uses existing low-power laser heating to reduce residual stress and weld cracks. During welding, a 540W laser from a laser scanner 2 is moved back and forth at the predetermined weld point. The welding speed is 40 rad / min, the defocus is 1mm, and the laser spot diameter of the laser scanner 2 is 30μm. The laser path overlap and welding direction are as follows: Figure 3 As shown, the laser movement path of laser scanner 2 is an "S"-shaped path connected end to end, with a 20% overlap ratio. The overall direction of the path is perpendicular to the weld seam. During welding, shielding gas Ar is introduced into the shielding gas chamber through vents 5 located on the side of the rotating clamping device 1. The shielding gas is turned on 1 minute before welding to fill the shielding gas chamber with Ar gas at a gas flow rate of 20L / min. The heat source gradient distribution of the base material at both ends of the weld seam 3 is controlled by adjusting the laser power to adapt to the melting points of different base materials. At the same time, the weld temperature field feedback is established through infrared temperature sensor 4, which monitors and adjusts the laser power in real time. Figure 4 This is the weld plane projection diagram of the present invention, Figure 5 This is a schematic diagram of the temperature field distribution within a scanning cycle of the present invention. Figure 6 for Figure 5 Schematic diagram of temperature field distribution after superposition of the next scanning cycle. Figure 7 It is a superimposed cross-sectional view of the temperature field after multiple scans. Among them, one scanning cycle is the arc process of the laser spot from one side of the base material to the other side of the base material. The whole welding process consists of multiple scanning cycles. Figure 4-7As can be seen, the overall temperature field is perpendicular to weld 3 and consists of a series of Gaussian curves with gradually decreasing peak values. To achieve a smaller heat-affected zone (HAZ), effectively reduce the area of material change caused by high temperature, and minimize thermal stress and shrinkage deformation after cooling, the temperature is reduced from 1700°C to 1400°C within a range of ≤1mm at the zirconium-nickel base metal joint, from the zirconium side to the nickel side, with a temperature reduction of 22°C per 100μm. After laser scanner 2 stops, the shielding gas is stopped for 2 minutes to prevent weld oxidation.

[0051] S4: Post-weld heat treatment: After completing a single-pass weld, a post-processing step is performed. Based on the weld temperature field feedback established in step S3, the laser power is adjusted in real time to control the weld cooling process. Specifically, after welding, the laser power is reduced from 400W to 100W within 4 minutes, gradually cooling the weld to avoid the formation of hard and brittle phases caused by excessive cooling rates and improve weld strength. When infrared temperature sensor 4 detects a base metal temperature of 940°C and a weld temperature of 1170°C, cooling begins. During slow cooling, the temperature field at the weld extending toward the substrate on both sides decreases by 10°C for every 100μm.

[0052] The temperature field control method of the present invention is used to control the stress distribution of the weld seam. Figure 8 The N36 and GH4169 dissimilar metal weld specimens shown in the figure show that the area formed by the self-melting of GH4169 accounts for 83% of the total weld area. The resulting weld is well-formed, with no defects such as cracks or lack of fusion. The weld structure of the weld specimens was observed using an EDAX Hikari Plus EBSD instrument. The EDAX Hikari Plus has an angular resolution of 0.1° and a spatial resolution of 50 nm. The results are shown in Figure 2. Figure 9 As shown in the EBSD IPF image, the weld pool grains are broken and refined. The high energy density and rapid cooling rate of the laser, as well as the movement of the heat source, promote the distribution of the NiZr phase in a fine, dispersed form. This microstructural change effectively hinders dislocation movement and enhances the mechanical properties of the weld. At the same time, the refined NiZr phase improves the toughness and corrosion resistance of the weld, making the weld more stable under stress, significantly enhancing the overall strength and reliability of the weld and optimizing the weld microstructure.

[0053] Example 2

[0054] This time, Zr-4 and GH4169 dissimilar metal laser welding was carried out. According to the zirconium-nickel dissimilar metal welding method based on active temperature field control provided by the present invention, Figure 1 As shown, the following steps are included:

[0055] S1: Cleaning the parent material; grinding and ultrasonically cleaning the butt end faces and welding surfaces of the Zr-4 and GH4169 alloy tubes to remove the surface oxide film and oil stains, thereby obtaining clean Zr-4 and GH4169 parent materials; wherein, the thickness of the Zr-4 alloy tube is 0.60 mm, the diameter is 8.41 mm, and by mass percentage, the Zr content of the Zr-4 alloy tube is 97.5 wt%, the Sn content is 1.4 wt%, the Fe content is 0.2 wt%, the Cr content is 0.1 wt%, and the remainder is impurities; the thickness of the GH4169 alloy tube is 0.60 mm, the diameter is 8.41 mm, and by mass percentage, the Ni content of the GH4169 alloy tube is 50 wt%, the Cr content is 17 wt%, the Mo content is 2.8 wt%, the Nb content is 4.75 wt%, and the remainder is impurities;

[0056] S2: Assemble the parts to be welded; assemble the cleaned Zr-4 and GH4169 base materials to be welded in step S1 at the ends thereof. Figure 2 In the metal welding system shown, the protective gas cavity of the rotary clamping device 1 is detachable, and the assembly gap between the end faces to be welded is 0.2 mm;

[0057] S3: Welding; Before welding, the weld 3 is preheated using a 250W laser from a laser scanner 2. This preheating method uses existing low-power laser heating to reduce residual stress and weld cracks. During welding, a 600W laser from a laser scanner 2 is moved back and forth at the predetermined weld point. The welding speed is 30 rad / min, the defocus is 2 mm, and the laser spot diameter of the laser scanner 2 is 35 μm. The laser path overlap and welding direction are as follows: Figure 3 As shown, the laser movement path of the laser scanner 2 is an "S" shape, with an overlap rate of 20%, and the overall direction of the path is perpendicular to the weld seam 3. During welding, shielding gas Ar is introduced into the shielding gas cavity through the vent 5 provided on the side of the rotating clamping device 1. The shielding gas is turned on 1 minute before welding to fill the shielding gas cavity with Ar gas atmosphere. The gas flow rate is 20L / min. The heat source gradient distribution of the parent material at both ends of the weld seam 3 is controlled by adjusting the laser power to adapt to the melting points of different parent materials. At the same time, the weld temperature field feedback is established through the infrared temperature sensor 4 for real-time monitoring and regulation of the laser power. Figure 4 This is the weld plane projection diagram of the present invention, Figure 5 This is a schematic diagram of the temperature field distribution within a scanning cycle of the present invention. Figure 6 for Figure 5 Schematic diagram of temperature field distribution after superposition of the next scanning cycle. Figure 7 It is a superimposed cross-sectional view of the temperature field after multiple scans. Among them, one scanning cycle is the arc process of the laser spot from one side of the base material to the other side of the base material. The whole welding process consists of multiple scanning cycles. Figure 4-7As can be seen, the overall temperature field is perpendicular to weld 3 and consists of a series of Gaussian curves with gradually decreasing peak values. To achieve a smaller heat-affected zone (HAZ), effectively reduce the area of material change caused by high temperature, and minimize thermal stress and shrinkage deformation after cooling, the temperature is reduced from 1700°C to 1400°C within a range of ≤1mm from the zirconium side to the nickel side, with a temperature reduction of 20°C per 100μm. After laser scanner 2 stops, the shielding gas is stopped for 2 minutes to prevent weld oxidation.

[0058] S4: Post-weld heat treatment: After completing a single-pass weld, a post-processing step is performed. Based on the weld temperature field feedback established in step S3, the laser power is adjusted in real time to control the weld cooling process. Specifically, after welding, the laser power is reduced from 400W to 100W within 6 minutes, gradually cooling the weld to avoid the formation of hard and brittle phases caused by excessive cooling rates and improve weld strength. When the infrared temperature sensor 4 detects a base metal temperature of 950°C and a weld temperature of 1190°C, cooling begins. During the slow cooling process, the temperature field at the weld extending toward the substrate on both sides decreases by 15°C for every 100μm.

[0059] By controlling the stress distribution of the weld using the temperature field control method of the present invention, a Zr-4 and GH4169 dissimilar metal weld specimen was obtained, in which the area formed by the self-melting of GH4169 accounted for 80% of the total weld area. The weld was well-formed, with no defects such as cracks or lack of fusion.

[0060] Example 3

[0061] This time, R60702 and N6 dissimilar metal laser welding was carried out. According to the zirconium-nickel dissimilar metal welding method based on active temperature field control provided by the present invention, Figure 1 As shown, the following steps are included:

[0062] S1: Cleaning the parent material; grinding and ultrasonically cleaning the butt end faces and welding surfaces of the R60702 and N6 alloy tubes to remove the surface oxide film and oil stains, thereby obtaining clean R60702 and N6 parent materials; wherein, the thickness of the R60702 alloy tube is 0.54 mm, the diameter is 8.31 mm, and by mass percentage, the Zr content of the R60702 alloy tube is 97.5 wt%, the Hf content is 2.24 wt%, the Fe content is 0.06 wt%, the Cr content is 0.01 wt%, and the rest are impurities; the thickness of the N6 alloy tube is 0.54 mm, the diameter is 8.31 mm, and by mass percentage, the Ni content of the N6 alloy tube is 99.6 wt%, the Mg content is 0.08 wt%, the Mn content is 0.05 wt%, the Fe content is 0.07 wt%, and the rest are impurities;

[0063] S2: Assemble the parts to be welded; assemble the cleaned R60702 and N6 base materials to be welded in step S1 at the ends thereof. Figure 2 In the metal welding system shown, the protective gas cavity of the rotary clamping device 1 is detachable, and the assembly gap between the end faces to be welded is 0.2 mm;

[0064] S3: Welding; Before welding, the weld 3 is preheated using a 300W laser from a laser scanner 2. This preheating method uses existing low-power laser heating to reduce residual stress and weld cracks. During welding, a 650W laser from a laser scanner 2 is moved back and forth at the predetermined weld point. The welding speed is 50 rad / min, the defocus is -2 mm, and the laser spot diameter of the laser scanner 2 is 40 μm. The laser path overlap and welding direction are as follows: Figure 3 As shown, the laser movement path of the laser scanner 2 is an "S" shape, with an overlap rate of 20%, and the overall direction of the path is perpendicular to the weld seam 3. During welding, shielding gas Ar is introduced into the shielding gas cavity through the vent 5 provided on the side of the rotating clamping device 1. The shielding gas is turned on 1 minute before welding to fill the shielding gas cavity with Ar gas atmosphere. The gas flow rate is 20L / min. The heat source gradient distribution of the parent material at both ends of the weld seam 3 is controlled by adjusting the laser power to adapt to the melting points of different parent materials. At the same time, the weld temperature field feedback is established through the infrared temperature sensor 4 for real-time monitoring and regulation of the laser power. Figure 4 This is the weld plane projection diagram of the present invention, Figure 5 This is a schematic diagram of the temperature field distribution within a scanning cycle of the present invention. Figure 6 for Figure 5 Schematic diagram of temperature field distribution after superposition of the next scanning cycle. Figure 7 It is a superimposed cross-sectional view of the temperature field after multiple scans. Among them, one scanning cycle is the arc process of the laser spot from one side of the base material to the other side of the base material. The whole welding process consists of multiple scanning cycles. Figure 4-7 As can be seen, the overall temperature field is perpendicular to weld 3 and consists of a series of Gaussian curves with gradually decreasing peak values. To achieve a smaller heat-affected zone (HAZ), effectively reduce the area of material change caused by high temperature, and minimize thermal stress and shrinkage deformation after cooling, the temperature is reduced from 1700°C to 1400°C within a range of ≤1mm from the zirconium side to the nickel side, with a temperature reduction of 20°C per 100μm. After laser scanner 2 stops, the shielding gas is stopped for 2 minutes to prevent weld oxidation.

[0065] S4: Post-weld heat treatment: After completing a single-pass weld, a post-processing step is performed. Based on the weld temperature field feedback established in step S3, the laser power is adjusted in real time to control the weld cooling process. Specifically, after welding is completed, the laser power is reduced from 400W to 100W within 2 minutes, gradually cooling the weld to avoid the formation of hard and brittle phases caused by excessive cooling rates and improve weld strength. When the infrared temperature sensor 4 detects a base metal temperature of 960°C and a weld temperature of 1200°C, cooling begins. During the slow cooling process, the temperature field at the weld extending toward the substrate on both sides decreases by 20°C for every 100μm.

[0066] By controlling the weld stress distribution using the temperature field control method of the present invention, a dissimilar metal welding specimen of R60702 and N6 was obtained, in which the area formed by N6 self-melting accounted for 84% of the total weld area. The weld was well-formed, with no defects such as cracks or lack of fusion.

[0067] In the above embodiments of the present invention, the temperature field is controlled by a metal welding system, which uses an LD150HS1206 laser scanner 2 and an XIR-1800 Thermal Camera System infrared temperature sensor 4 from Shanghai GEZE Laser Technology Co., Ltd. The metal welding system includes a laser welding module, a welding protection module, and a post-processing module. The infrared temperature sensor is electrically connected to a signal input terminal of a programmable logic controller (PLC), and a signal output terminal of the PLC is electrically connected to the laser welding module, the welding protection module, and the post-processing module, respectively. The post-processing module is also electrically connected to a signal input terminal of the PLC.

[0068] The laser welding module feeds back information on the weld temperature field established by the infrared temperature sensor to ensure that the temperature distribution in the welding area meets the predetermined requirements and serves as a post-processing heat source;

[0069] The shielding gas of the welding protection module is used to protect the weld. During welding, the laser of the laser welding module penetrates the shielding gas cavity of the welding protection module from the top of the rotating clamping device to weld the internal parts to be welded.

[0070] The post-processing module is responsible for performing slow cooling treatment on the temperature after welding to reduce welding stress and optimize the weld microstructure; the post-processing module receives the signal about the temperature of the welding area transmitted by the infrared temperature sensor to the PLC programmable controller to detect the weld temperature and regulate the weld temperature field established by the infrared temperature sensor; when the post-processing heat source does not meet the requirements, the post-processing module feeds back the signal to the PLC programmable controller, and the PLC programmable controller receives the signal to control the laser welding module to dynamically adjust the laser power and scanning speed to achieve the purpose of automatically adjusting the slow cooling temperature, ensuring that the welding area obtains the optimal temperature gradient, and further improving the welding quality.

[0071] This metal welding system monitors the weld temperature in real time and dynamically adjusts parameters such as laser power and scanning speed to ensure that the weld zone temperature remains within a predetermined range, thereby preventing the formation of intermetallic compounds and thermal cracks and ensuring weld quality. A high-precision infrared temperature sensor provides real-time temperature data feedback, and the PLC programmable controller automatically adjusts laser parameters based on temperature changes, using an adaptive control algorithm to precisely regulate the temperature. High-precision temperature sampling and rapid response ensure stable temperature control during the welding process and post-processing, preventing temperature fluctuations and improving the mechanical properties and reliability of the weld.

[0072] The tensile strength of the samples obtained in Examples 1-3 of the invention was compared with that of the samples without temperature field control. The results are as follows: Figure 10 As shown in the figure, analysis shows that after actively controlling the temperature field using the present invention, the area of zirconium self-melting accounts for ≥80% of the total weld area, significantly improving the joint strength of the zirconium-nickel dissimilar alloy. The weld is well-formed, with no defects such as cracks or lack of fusion, and the weld microstructure is optimized. By improving the process parameters, process flow, and welding process, this method effectively overcomes the brittle fracture, porosity, and cold weld problems caused by traditional welding, simplifies the pre- and post-weld processing, and improves welding efficiency.

Claims

1. A zirconium-nickel dissimilar metal welding method based on active temperature field control, characterized in that: The following steps are involved: S1: Cleaning the base metal; grinding and ultrasonic cleaning the butt end faces and welding surfaces of the zirconium and nickel alloy tubes to remove the surface oxide film and oil stains to obtain clean zirconium and nickel base metals; S2: Assembling the parts to be welded; aligning the end faces of the zirconium and nickel base materials to be welded, which were cleaned in step S1, and assembling them in the protective air cavity of the rotating clamping device (1) of the metal welding system; S3: welding; a laser scanner (2) with a laser spot diameter of 30 to 40 μm is used to move back and forth at a predetermined welding point for welding. The laser movement path of the laser scanner is an "S" shape connected end to end, the laser movement path overlap rate is 20%, and the overall direction of the path is perpendicular to the weld; during the welding process, a protective gas is introduced into the protective gas cavity through a vent (5) provided on the side of the rotating clamping device (1), and the heat source gradient distribution of the base material at both ends of the weld (3) is controlled by adjusting the laser power to adapt to the melting point of different base materials. At the same time, a weld temperature field feedback is established through an infrared temperature sensor (4) to monitor and adjust the laser power in real time. The temperature field is perpendicular to the weld as a whole and consists of a series of Gaussian curves with gradually decreasing peak values. Within the range of ≤1 mm at the joint of the zirconium and nickel base materials, the temperature decreases from 1700°C to 1400°C from the zirconium side to the nickel side, and the temperature decreases by 20 to 22°C per 100 μm; The temperature field is controlled by a metal welding system, which includes a laser welding module, a welding protection module, and a post-processing module; the infrared temperature sensor is electrically connected to the signal input terminal of a PLC programmable controller, and the signal output terminal of the PLC programmable controller is electrically connected to the laser welding module, the welding protection module, and the post-processing module respectively; the post-processing module is also electrically connected to the signal input terminal of the PLC programmable controller; The laser welding module feeds back information on the weld temperature field established by the infrared temperature sensor to ensure that the temperature distribution in the welding area meets the predetermined requirements and serves as a post-processing heat source; The shielding gas of the welding protection module is used to protect the weld. During welding, the laser of the laser welding module penetrates the shielding gas cavity of the welding protection module from the top of the rotating clamping device to weld the internal parts to be welded. The post-processing module receives the signal about the temperature of the welding area transmitted by the infrared temperature sensor to the PLC programmable controller to detect the weld temperature and regulate the weld temperature field established by the infrared temperature sensor; when the post-processing heat source does not meet the requirements, the post-processing module feeds back the signal to the PLC programmable controller, and the PLC programmable controller controls the laser welding module to dynamically adjust the laser power and scanning speed; S4: Post-weld heat treatment; according to the weld temperature field feedback established in step S3, the laser power is adjusted in real time to control the cooling process of the weld.

2. The zirconium-nickel dissimilar metal welding method based on active temperature field control according to claim 1, characterized in that: In step S1, the thickness of the zirconium-nickel alloy tube is 0.57±0.03 mm, and the diameter is 8.36±0.05 mm.

3. The zirconium-nickel dissimilar metal welding method based on active temperature field control according to claim 2, characterized in that: In step S3, a laser scanner is used to preheat the weld with a 200-300W laser before welding. The laser power during welding is 540-650W, the welding speed is 30-50 rad / min, and the defocus is -2-+2mm. After welding is completed, the laser power is reduced from 400W to 100W within 2-6 minutes to gradually cool the weld. The shielding gas during welding is Ar, and the gas flow rate is 10-20L / min.

4. The zirconium-nickel dissimilar metal welding method based on active temperature field control according to claim 3, characterized in that: In step S3, the stress distribution of the weld is controlled by regulating the temperature field, and the area formed by the self-melting of zirconium accounts for ≥80% of the total area of the weld.

5. The zirconium-nickel dissimilar metal welding method based on active temperature field control according to claim 4, characterized in that: In step S4, when the infrared temperature sensor (4) detects that the temperature of the base material is 940-960°C and the temperature of the weld is 1170-1200°C, the temperature starts to drop. During the cooling process, the temperature of the weld extending toward the base material on both sides decreases by 10-20°C every 100 μm.

6. A zirconium-nickel dissimilar metal welding method based on active temperature field control according to any one of claims 1 to 5, characterized in that: The protective air cavity of the rotating clamping device in step S2 is detachable.

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