Zirconium-nickel dissimilar metal welding method based on active regulation and control of temperature field

Abstract

The invention discloses a zirconium-nickel dissimilar metal welding method based on active regulation and control of a temperature field. The zirconium-nickel dissimilar metal welding method comprises the following steps that S1, base metal is cleaned; the butt-joint end faces and the welding surfaces of the zirconium and nickel alloy pipes are polished and cleaned, and clean zirconium and nickel base materials are obtained; s2, a to-be-welded part is assembled; the to-be-welded end face of the clean base metal is assembled in a protective gas cavity of the rotary clamping device; s3, welding is conducted; a laser scanner is adopted for welding at a preset welding position, heat source gradient distribution of base metal at the two ends of a welding seam is controlled by regulating and controlling laser power, welding seam temperature field feedback is established through an infrared temperature sensor, and real-time monitoring and laser power regulating and controlling are conducted; s4, postweld heat treatment; and the laser power is adjusted in real time according to welding seam temperature field feedback so as to adjust and control the welding seam cooling process. According to the method, effective connection of zirconium-nickel indissolvable metal is achieved by controlling the regional welding temperature field, the temperature range for forming brittle compounds is avoided, the uniformity of a molten pool between Zr and Ni materials is ensured, and welding defects such as hot cracks and air holes are reduced.

Description

Technical Field

[0001] The 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 the global climate change problem becomes increasingly serious, controlling carbon emissions has become an important issue that the world faces together. At present, the main measure to control carbon emissions is to promote the use of clean energy, reduce carbon emissions from the source, improve energy efficiency, and promote the development of a circular economy. Nuclear power, as a recognized clean energy, is an inevitable trend in the development of clean energy in the future.

[0003] Zirconium has an extremely low thermal neutron absorption cross section, low irradiation brittleness in the reactor, and excellent corrosion resistance in high-temperature and high-pressure water vapor. At the same time, pure zirconium has moderate mechanical properties, good processing performance, and good compatibility with uranium fuel, which can improve the efficiency of uranium fuel use. Therefore, it is widely used in fuel cladding tubes, positioning spacers, component boxes and other components. Nickel has good corrosion resistance and is often used as a structural material in the nuclear industry. Therefore, the use of pure zirconium and pure nickel welded joint components in reactors 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. It will react with O, N, and H elements in the air at high temperatures. 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 the disadvantages of low thermal conductivity, poor thermal conductivity, and low specific heat capacity. A small energy change will cause a sharp change in temperature, resulting in higher 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. Moreover, there are many eutectic reactions that may occur between pure nickel and pure zirconium. For example, γ-Ni+Ni5Zr will be generated at 1170℃, and Ni+Ni5Zr will be generated at 1070℃. 21 Zr8+Ni 10 Zr7 will generate NiZr+NiZr2 at 1010℃ and NiZr2+β-Zr at 960℃, and thermal cracks are easily generated under the joint action of coarse grains in the heat-affected zone. Therefore, when welding, the welding line energy should be reduced as much as possible under the premise of ensuring full penetration, and the molten pool flow should be promoted by adding scanning to increase the weld width and ensure the air tightness of the joint. At the same time, the welding surface should be cleaned before welding to avoid moisture, oxides, etc. that affect the welding 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 brazing joint due to the formation of intermetallic compounds in the transition zone. In addition, brazing also has the problem of many false 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, which 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 are easy to form hard and brittle amorphous alloys and intermetallic compounds, which makes the weld very easy to fracture during the subsequent cooling process.

[0007] Therefore, how to achieve one-time forming during welding, and at the same time regulate the organizational morphology through the temperature field, reduce 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 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, which aims 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 weld by simplifying the welding and heat treatment systems.

[0009] To achieve its purpose, the present invention adopts the following technical solution: A zirconium-nickel dissimilar metal welding method based on active temperature field regulation comprises the following steps: S1: Cleaning the parent material; 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 parent materials; S2: Assembling the parts to be welded; assembling the cleaned zirconium and nickel base materials to be welded in step S1 into the protective air cavity of the rotating clamping device of the metal welding system; S3: Welding: A laser scanner is used to reciprocate at a predetermined welding point for welding. During the welding process, protective gas is introduced into the protective gas cavity through the vent holes provided on the side of the rotating clamping device. The heat source gradient distribution of the parent materials 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 an infrared temperature sensor to monitor and adjust the laser power in real time. 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.

[0010] 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.

[0011] Furthermore, in step S3, the laser spot diameter of the laser scanner is 30-40 μm.

[0012] Furthermore, in step S3, the laser moving path of the laser scanner is an "S" shape connected end to end, the laser moving path overlap rate is 20%, and the overall direction of the path is perpendicular to the weld.

[0013] 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 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 for every 100 μm.

[0014] 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, the laser power is reduced within 2-6min 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.

[0015] 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.

[0016] Further, 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 to both sides of the substrate decreases by 10-20°C every 100 μm.

[0017] Furthermore, the protective air cavity of the rotating clamping device in step S2 is detachable.

[0018] 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 a 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 protective gas of the welding protection module is used to protect the weld. During welding, the laser of the laser welding module penetrates the protective 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.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention realizes the 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, control 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 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 greatly 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, providing a reliable technical guarantee for the high-quality connection of Zr-Ni dissimilar alloys, effectively overcoming the problems of brittle fracture, pores and cold welding caused by traditional welding, significantly improving the manufacturing level of nuclear fuel components, and solving the problem of difficulty in welding Zr-Ni dissimilar alloys.

[0020] 2. The present invention uses an active temperature field control method to improve production efficiency, reduce energy consumption and environmental pollution, enhance the adaptability and automation level of the welding process, and provide important support for the development of modern welding technology, so that this type of new material can be more widely used in 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 heat-affected zones, and can adapt to complex welding requirements through real-time, precise and flexible laser power adjustment. In addition, active control reduces dependence on the environment and materials, provides higher 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.

[0021] 3. The present invention adopts a metal welding system, which gradually reduces the laser power or dynamically adjusts the heat input to achieve precise control of the weld temperature field during welding and slow cooling of the weld, thereby reducing welding residual stress, optimizing the weld microstructure, and effectively reducing the tendency of thermal cracks. 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 connection of dissimilar materials.

[0022] 4. The zirconium-nickel dissimilar metal welding method based on active temperature field control provided by the present invention converts the single-peak Gaussian heat source into an overall controllable temperature field through partial overlap of the paths, which can ensure a more uniform temperature distribution, effectively reduce the thermal stress concentration caused by excessive temperature gradients caused by path spacing, and reduce the risk of thermal cracks and deformation of the material. At the same time, the 20% overlap rate of the welding path helps maintain the stability of the molten pool, improves the fluidity of the molten material, promotes the escape of gas in the molten pool, reduces the formation of pores and inclusions, and further improves the quality and performance of the weld.

[0023] 5. Since the structures of zirconium alloys obtained at different cooling rates are different, martensite phase is formed when cooling at a faster speed, and no obvious segregation of alloy elements occurs. The process conditions of rapid heating and rapid cooling will also reduce the amount of metal dissolved nitrogen, so that the weldment has good corrosion resistance. Under slow cooling conditions, Widmanstätten structure will be formed, which will have an adverse effect on the performance of the weld. The zirconium-nickel compound formed inside the molten pool is very easy to form a brittle phase at a high cooling rate, reducing the strength of the weld. Therefore, it is particularly important to control the cooling rate of different areas after welding. Therefore, the present invention uses temperature field control and heat source monitoring technology, and the laser scanner controls the cooling rate of different areas of the weld and part of the matrix according to the feedback of the infrared temperature sensor, so as to obtain high-quality and high-strength welds and substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the zirconium-nickel dissimilar metal welding method of the present invention; Figure 2 It is a schematic diagram of the structure of the metal welding system of the present invention; Figure 3 A schematic diagram of the laser path overlap and welding direction of the present invention; Figure 4 It is a plane projection diagram of the weld of the present invention; Figure 5 It 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 Overlay cross-sectional views of the temperature field after multiple scans; Figure 8 This is a physical picture of the welding sample obtained in Example 1 of the present invention; Fig. 9 This is a microstructure diagram of the weld of the welding sample of Example 1 of the present invention; Fig.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 regulation.

[0025] In the figure: 1-rotating clamping device; 2-laser scanner; 3-welding seam; 4-infrared temperature sensor; 5-ventilation hole. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution 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 used to limit the present invention.

[0027] Industrial application: Welding of Zr-Ni dissimilar metal positioning grids in nuclear power plants.

[0028] Example 1 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: S1: Cleaning the parent material; grinding and ultrasonic cleaning the butt end faces and welding surfaces of N36 and GH4169 alloy tubes to remove the surface oxide film and oil stains, and then 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 content of Zr in the N36 alloy tube is 97 wt%, the content of Sn is 0.9 wt%, the content of Nb is 0.9 wt%, the content of Fe 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 content of Ni in the GH4169 alloy tube is 50 wt%, the content of Cr is 17 wt%, the content of Mo is 2.8 wt%, the content of Nb is 4.75 wt%, and the rest are impurities; S2: Assemble the parts to be welded; assemble the cleaned N36 and GH4169 parent materials to be welded in step S1 at the end faces thereof. Figure 2 In the protective gas cavity of the rotating clamping device 1 in the metal welding system shown, the protective gas cavity is detachable, and the assembly gap of the end faces to be welded is 0.2 mm; S3: welding; before welding, the laser scanner 2 is used to preheat the weld 3 with a 200W laser. The preheating method uses the existing low-power laser heating method to reduce residual stress and welding cracks. During welding, the laser scanner 2 is used to reciprocate at the predetermined welding point with a 540W laser. 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 moving path of the laser scanner 2 is an "S" shape connected end to end, the overlap rate of the laser moving path is 20%, and the overall direction of the path is perpendicular to the weld. During the welding process, the protective gas Ar is introduced into the protective gas cavity through the vent hole 5 provided on the side of the rotating clamping device 1. The protective gas is turned on 1 minute before welding to fill the protective gas cavity with Ar gas atmosphere, and the gas flow rate is 20L / min; the heat source gradient distribution of the parent material at both ends of the weld 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 to monitor and adjust the laser power in real time. Figure 4 is a plan projection diagram of the weld 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 matrix to the other side of the base material matrix. The whole welding process consists of multiple scanning cycles. Figure 4-7It can be seen that the temperature field is perpendicular to the weld 3 as a whole, and is composed of a series of Gaussian curves with gradually decreasing peak values. In order to obtain a smaller heat affected zone (HAZ), effectively reduce the area where the material changes due to high temperature, and reduce thermal stress and shrinkage deformation after cooling, the temperature is reduced from 1700°C to 1400°C in the range of ≤1mm from the zirconium side to the nickel side, and the temperature decreases by 22°C for every 100μm; after the laser scanner 2 stops, the shielding gas stops 2min later to prevent oxidation of the weld; S4: Post-weld heat treatment; after completing single-pass welding, perform post-processing steps, and adjust the laser power in real time according to the weld temperature field feedback established in step S3 to control the cooling process of the weld. Specifically, the laser power after welding is reduced from 400W to 100W within 4 minutes, and the weld is gradually cooled to avoid the hard and brittle phase formed by too fast cooling rate and improve the weld strength; when the infrared temperature sensor 4 detects that the temperature of the base material is 940℃ and the weld temperature is 1170℃, the temperature starts to drop. When slowly cooling, the temperature of the temperature field at the extension of the weld to the base on both sides is reduced by 10℃ every 100μm.

[0029] The temperature field control method of the present invention is used to control the stress distribution of the weld and obtain Figure 8 The N36 and GH4169 dissimilar metal welding samples shown in the figure show that the area formed by the self-melting of GH4169 accounts for 83% of the total weld area. The weld is well-formed and no defects such as cracks and lack of fusion are found. The weld structure of the weld sample was observed using the EDAX Hikari Plus EBSD equipment. The EDAX Hikari Plus has an angular resolution of 0.1° and a spatial resolution of 50 nm. The results are shown in Figure 1. Fig. 9 As shown in the figure, it can be seen from the IPF image of EBSD that the grains of the weld pool are broken and refined. The high energy density and rapid cooling rate of the laser and the movement of the heat source cause the NiZr phase to be distributed in a fine and dispersed form. This change in the microstructure effectively hinders the movement of dislocations 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 when subjected to stress, thereby significantly improving the overall strength and reliability of the weld and optimizing the weld microstructure.

[0030] Example 2 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: S1: Cleaning the parent material; grinding and ultrasonic cleaning the butt end faces and welding surfaces of Zr-4 and GH4169 alloy tubes to remove the surface oxide film and oil stains, and 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 in the Zr-4 alloy tube is 97.5 wt%, Sn is 1.4 wt%, Fe is 0.2 wt%, Cr is 0.1 wt%, and the rest are impurities; the thickness of the GH4169 alloy tube is 0.60 mm, the diameter is 8.41 mm, and by mass percentage, the Ni in the GH4169 alloy tube is 50 wt%, Cr is 17 wt%, Mo is 2.8 wt%, Nb is 4.75 wt%, and the rest are impurities; S2: Assemble the parts to be welded; assemble the cleaned Zr-4 and GH4169 parent materials to be welded in step S1 at the ends thereof. Figure 2 In the protective gas cavity of the rotating clamping device 1 in the metal welding system shown, the protective gas cavity is detachable, and the assembly gap of the end faces to be welded is 0.2 mm; S3: welding; before welding, the laser scanner 2 is used to preheat the weld 3 with a 250W laser. The preheating method uses the existing low-power laser heating method to reduce residual stress and welding cracks. During welding, the laser scanner 2 is used to reciprocate at the predetermined welding point with a 600W laser. The welding speed is 30rad / min, the defocus is 2mm, and the laser spot diameter of the laser scanner 2 is 35μm. The laser path overlap and welding direction are as follows Figure 3 As shown, the laser moving path of the laser scanner 2 is an "S" shape connected end to end, the overlap rate of the laser moving path is 20%, and the overall direction of the path is perpendicular to the weld 3. During the welding process, the protective gas Ar is introduced into the protective gas cavity through the vent 5 provided on the side of the rotating clamping device 1. The protective gas is turned on 1 minute before welding to fill the protective gas cavity with Ar gas atmosphere, and the gas flow rate is 20L / min; the heat source gradient distribution of the parent material at both ends of the weld 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 to monitor and adjust the laser power in real time. Figure 4 is a plan projection diagram of the weld 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 matrix to the other side of the base material matrix. The whole welding process consists of multiple scanning cycles. Figure 4-7It can be seen that the temperature field is perpendicular to the weld 3 as a whole, and is composed of a series of Gaussian curves with gradually decreasing peak values. In order to obtain a smaller heat affected zone (HAZ), effectively reduce the area where the material changes due to high temperature, and reduce thermal stress and shrinkage deformation after cooling, the temperature is reduced from 1700°C to 1400°C in the range of ≤1mm from the zirconium side to the nickel side, and the temperature is reduced by 20°C for every 100μm; after the laser scanner 2 stops, the shielding gas is stopped 2min later to prevent oxidation of the weld; S4: Post-weld heat treatment; after completing single-pass welding, perform post-processing steps, and adjust the laser power in real time according to the weld temperature field feedback established in step S3 to control the cooling process of the weld. Specifically, the laser power after welding is reduced from 400W to 100W within 6 minutes, and the weld is gradually cooled to avoid the hard and brittle phase formed by too fast cooling rate and improve the weld strength; when the infrared temperature sensor 4 detects that the temperature of the base material is 950℃ and the weld temperature is 1190℃, the temperature starts to drop. When slowly cooling, the temperature of the temperature field at the extension of the weld to the base on both sides is reduced by 15℃ every 100μm.

[0031] By controlling the stress distribution of the weld by the temperature field control method of the present invention, a Zr-4 and GH4169 dissimilar metal welding sample was obtained, wherein the area formed by the self-melting of GH4169 accounted for 80% of the total weld area. The weld was well formed, and no defects such as cracks and lack of fusion were found.

[0032] Example 3 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: S1: cleaning the parent material; grinding and ultrasonic cleaning the butt end faces and welding surfaces of R60702 and N6 alloy tubes to remove the surface oxide film and oil stains, and 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, Hf, Fe, Cr, and the rest are impurities in the R60702 alloy tube; the thickness of the N6 alloy tube is 0.54 mm, the diameter is 8.31 mm, and by mass percentage, the Ni, Mg, Mn, Fe, and Fe are 99.6 wt%, 0.08 wt%, 0.05 wt%, 0.07 wt%, and the rest are impurities in the N6 alloy tube; S2: Assemble the parts to be welded; assemble the cleaned R60702 and N6 parent materials to be welded in step S1 at the ends thereof. Figure 2In the protective gas cavity of the rotating clamping device 1 in the metal welding system shown, the protective gas cavity is detachable, and the assembly gap of the end faces to be welded is 0.2 mm; S3: welding; before welding, the laser scanner 2 is used to preheat the weld 3 with a 300W laser. The preheating method uses the existing low-power laser heating method to reduce residual stress and welding cracks. During welding, the laser scanner 2 is used to reciprocate at the predetermined welding point with a 650W laser. The welding speed is 50rad / min, the defocus is -2mm, and the laser spot diameter of the laser scanner 2 is 40μm. The laser path overlap and welding direction are as follows Figure 3 As shown, the laser moving path of the laser scanner 2 is an "S" shape connected end to end, the overlap rate of the laser moving path is 20%, and the overall direction of the path is perpendicular to the weld 3. During the welding process, the protective gas Ar is introduced into the protective gas cavity through the vent 5 provided on the side of the rotating clamping device 1. The protective gas is turned on 1 minute before welding to fill the protective gas cavity with Ar gas atmosphere, and the gas flow rate is 20L / min; the heat source gradient distribution of the parent material at both ends of the weld 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 to monitor and adjust the laser power in real time. Figure 4 is a plan projection diagram of the weld 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 matrix to the other side of the base material matrix. The whole welding process consists of multiple scanning cycles. Figure 4-7 It can be seen that the temperature field is perpendicular to the weld 3 as a whole, and is composed of a series of Gaussian curves with gradually decreasing peak values. In order to obtain a smaller heat affected zone (HAZ), effectively reduce the area where the material changes due to high temperature, and reduce thermal stress and shrinkage deformation after cooling, the temperature is reduced from 1700°C to 1400°C in the range of ≤1mm from the zirconium side to the nickel side, and the temperature is reduced by 20°C for every 100μm; after the laser scanner 2 stops, the shielding gas is stopped 2min later to prevent oxidation of the weld; S4: Post-weld heat treatment; after completing single-pass welding, perform post-processing steps, and adjust the laser power in real time according to the weld temperature field feedback established in step S3 to control the cooling process of the weld. Specifically, after welding, the laser power is reduced from 400W to 100W within 2 minutes, and the weld is gradually cooled to avoid the hard and brittle phase formed by too fast cooling rate and improve the weld strength; when the infrared temperature sensor 4 detects that the temperature of the base material is 960℃ and the weld temperature is 1200℃, the temperature starts to drop. When slowly cooling, the temperature of the temperature field at the extension of the weld to the base on both sides is reduced by 20℃ every 100μm.

[0033] By controlling the stress distribution of the weld by the temperature field control method of the present invention, a R60702 and N6 dissimilar metal welding sample was obtained, wherein the area formed by the self-melting of N6 accounted for 84% of the total weld area. The weld was well formed, and no defects such as cracks and lack of fusion were found.

[0034] In the above embodiments of the present invention, the temperature field is controlled by a metal welding system, and the metal welding system uses a LD150HS1206 laser scanner 2 and an XIR-1800 Thermal Camera System infrared temperature sensor 4 of 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 the signal input end of the PLC programmable controller, and the signal output end 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 end 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 protective gas of the welding protection module is used to protect the weld. During welding, the laser of the laser welding module penetrates the protective 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 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, so as 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.

[0035] The metal welding system monitors the temperature of the weld in real time and dynamically adjusts parameters such as laser power and scanning speed to ensure that the temperature of the welding area is always kept within the predetermined range, thereby preventing the formation of intermetallic compounds and thermal cracks and ensuring the quality of the weld. The high-precision infrared temperature sensor provides real-time feedback of temperature data, and the PLC programmable controller automatically adjusts the laser parameters according to temperature changes, and uses an adaptive control algorithm to accurately adjust the temperature. High-precision temperature sampling and rapid response capabilities stabilize temperature control during the welding process and post-processing, avoid temperature fluctuations, and improve the mechanical properties and reliability of the weld.

[0036] 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: Fig.10 As shown, analysis shows that after the temperature field of the present invention is actively regulated, the area formed by zirconium self-melting accounts for ≥80% of the total weld area, significantly improving the connection strength of zirconium-nickel dissimilar alloys, with excellent weld formation, no defects such as cracks and lack of fusion, and optimizing the weld microstructure. This method effectively overcomes the problems of brittle fracture, pores and cold welding caused by traditional welding by improving process parameters, process flow and welding process, simplifies the processing process before and after welding, 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 parent material; 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 parent materials; S2: Assembling the parts to be welded; assembling the end faces of the zirconium and nickel base materials to be welded, which were cleaned in step S1, into the protective air cavity of the rotating clamping device (1) of the metal welding system; S3: welding; a laser scanner (2) is used to reciprocate at a predetermined welding position for welding. During the welding process, a protective gas is introduced into the protective gas cavity through a vent hole (5) provided on the side of the rotating clamping device (1). The heat source gradient distribution of the parent material at both ends of the weld (3) is controlled by adjusting the laser power to adapt to the melting points of different parent 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. 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. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in 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. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in claim 2, characterized in that: In step S3, the laser spot diameter of the laser scanner is 30-40 μm.

4. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in claim 3, characterized in that: In step S3, the laser moving path of the laser scanner is an "S" shape connected end to end, the laser moving path overlap rate is 20%, and the overall direction of the path is perpendicular to the weld.

5. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in claim 4, characterized in that: 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 the range of ≤1 mm at the joint of 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 for every 100 μm.

6. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in claim 5, 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, the laser power is reduced within 2-6min to gradually cool the weld, and the laser power is reduced from 400W to 100W. The protective gas during welding is Ar, and the gas flow rate is 10-20L / min.

7. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in claim 6, 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.

8. The zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in claim 7, 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 temperature field at the point where the weld extends toward the base material on both sides decreases by 10-20°C every 100 μm.

9. A zirconium-nickel dissimilar metal welding method based on active temperature field control as claimed in any one of claims 1 to 8, characterized in that: The protective air cavity of the rotating clamping device in step S2 is detachable.

10. A zirconium-nickel dissimilar metal welding method based on active temperature field control according to any one of claims 1 to 8, characterized in that: 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 end of a PLC programmable controller, and a signal output end 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 a signal input end 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 protective gas of the welding protection module is used to protect the weld. During welding, the laser of the laser welding module penetrates the protective 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.

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