Manual helium arc welding method for niobium-zirconium alloy welding seam

Abstract

The invention provides a manual helium arc welding method for a niobium-zirconium alloy welding seam. The manual helium arc welding method comprises the following steps that S1, a to-be-welded area and the periphery of a to-be-welded niobium-zirconium alloy workpiece are polished and cleaned; s2, the workpiece treated in the step S1 is placed in a sealed welding cabin, the welding cabin is vacuumized till the preset vacuum degree is achieved, then inert gas is filled, and after the oxygen content and the water content in the cabin are both smaller than or equal to 1 ppm, welding is prepared to be started; s3, a manual helium arc welding process is adopted for welding, and helium serves as protective gas in the welding process; s4, segmented welding is adopted during welding, and after one segment of welding is completed and the temperature of a weld joint is reduced to a preset cooling temperature, welding of a lower segment of a weld bead is conducted; and S5, after welding is completed, after the workpiece is cooled to the preset taking-out temperature, the workpiece is taken out of the welding cabin. According to the Nb-1Zr alloy thin-walled tube welding method, the Nb-1Zr alloy thin-walled tube is welded, oxidation in the Nb-1Zr alloy welding process is effectively avoided by adopting a manual helium arc welding process and setting of a special welding environment, and the problems of oxidation and air holes in niobium-zirconium alloy welding are solved.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a manual helium arc welding method for niobium-zirconium alloy welds. More particularly, it relates to a manual helium arc welding method for achieving oxidation-free, full-penetration, and porosity-free niobium-zirconium alloy welds. Background Technology

[0002] Niobium-zirconium alloy (Nb-1Zr) is a high-temperature resistant and corrosion-resistant material with niobium (Nb) as the matrix and zirconium (Zr) as the main alloying element. Niobium, as a refractory metal, possesses a high melting point, high strength, and excellent corrosion resistance. The addition of zirconium further refines the grain size, improving the material's machinability and fatigue strength. Through a special alloying process and precise heat treatment technology, Nb-1Zr alloy achieves a balance between strength and toughness, maintaining stable mechanical properties over a wide temperature range of -253℃ to 2000℃. Therefore, it has broad application prospects in the aerospace and nuclear industries. In aerospace, it can be used to manufacture high-temperature components such as rocket engine nozzles and satellite structural parts to withstand extreme temperatures and severe thermal shocks. In the nuclear industry, due to its extremely low neutron absorption cross-section, it is an ideal choice for manufacturing key devices such as nuclear fuel cladding and pressure vessels, effectively reducing neutron loss and improving nuclear reaction efficiency. As a "safety barrier" for the reactor core of nuclear power plants, it can operate stably for long periods in environments with strong radiation and high-pressure water.

[0003] However, welding Nb-1Zr alloy has the following problems: First, Nb-1Zr alloy is easily oxidized at high temperatures to form zirconium oxide (ZrO2). Zirconia has a high oxygen ion diffusion rate, which will form oxygen diffusion channels, accelerate the diffusion of oxygen into the material, and thus intensify the oxidation process, resulting in easy oxidation of Nb-1Zr alloy during welding and easy porosity in the weld. Second, current research on Nb-1Zr alloy is mainly focused on the field of material preparation, and there are few relevant literature and patents on its welding. Moreover, existing welding research focuses on the vacuum electron beam welding of Nb-1Zr alloy with other dissimilar metals, and no relevant literature and patents on manual helium arc welding of Nb-1Zr alloy have been found.

[0004] Patent document CN119035683A discloses a method and joint for joining molybdenum-rhenium alloy and niobium-zirconium alloy. The method includes the following steps: grinding the niobium-zirconium alloy and molybdenum-rhenium alloy to be welded; cleaning the PdNi foil and the ground niobium-zirconium alloy and the molybdenum-rhenium alloy; placing the molybdenum-rhenium alloy, the PdNi foil and the niobium-zirconium alloy in order from top to bottom to obtain the workpiece to be welded, and applying a preset pressure to the side of the molybdenum-rhenium alloy away from the PdNi foil; placing the workpiece to be welded in a vacuum brazing furnace, wherein the vacuum degree in the vacuum brazing furnace reaches 2 to 5 × 10⁻⁶. ～3When Pa is reached, heating is turned on, and the temperature is maintained at 1200℃~1300℃ for 1~30 minutes to obtain a joint. This patent document's technical solution addresses the welding of niobium-zirconium alloys and dissimilar alloys using a vacuum brazing furnace, but it does not solve the problems in the prior art addressed by this invention. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a manual helium arc welding method for niobium-zirconium alloy welds.

[0006] A manual helium arc welding method for niobium-zirconium alloy welds provided by the present invention includes the following steps: S1: Grind and clean the area to be welded and the surrounding area of ​​the niobium-zirconium alloy workpiece to be welded; S2: Place the workpiece treated in S1 into a sealed welding chamber, evacuate the welding chamber to the preset vacuum level, then fill it with inert gas and start the gas purification system until the oxygen content and water content in the chamber are ≤1ppm and then prepare to start welding. S3: Welding is performed using manual helium arc welding, with helium as the protective gas during the welding process; S4: Welding is carried out in segments. After completing one segment of welding, wait for the weld temperature to drop to the preset cooling temperature before welding the next segment. S5: After welding is completed, wait for the workpiece to cool to the preset removal temperature before removing the workpiece from the welding chamber.

[0007] Preferably, in step S1, the grinding and cleaning process specifically involves grinding the area to be welded and its surroundings until a metallic luster is exposed, and then cleaning the ground area with a volatile cleaning agent.

[0008] Preferably, the volatile cleaning agent is alcohol.

[0009] Preferably, in S2, the preset vacuum level is below 5 Pa; the inert gas is argon.

[0010] Preferably, in S3, the purity of the helium gas is ≥99.999%; spot welding is performed before welding, and the weld points are evenly distributed along the circumference of the workpiece to be welded during spot welding.

[0011] Preferably, the process parameters for spot welding are as follows: the welding current is pulsed current, the peak pulse current is 40-80A, the base current is 10-30A, the welding voltage is 10-15V, and the shielding gas flow rate is 10-20L / min.

[0012] Preferably, in S3, after the manual helium arc welding is started, it is held for 1 to 2 seconds until the molten pool is completely melted, and then the welding torch is moved and filler wire welding is performed. The filler wire is made of the same material as the niobium-zirconium alloy workpiece.

[0013] Preferably, the welding process parameters for manual helium arc welding are as follows: the welding current is pulsed current, the peak pulse current is 60-100A, the base current is 20-40A, the welding voltage is 10-18V, the welding speed is 70-150mm / min, and the shielding gas flow rate is 10-20L / min.

[0014] Preferably, in S4, the single-segment welding length of the segmented welding is 30-50mm, and the preset cooling temperature is below 150℃.

[0015] Preferably, in step S5, the preset extraction temperature is below 60°C, and after welding is completed, a weld inspection step is also included, which includes liquid penetration detection, gas pressure test and helium leak detection.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention addresses the welding of thin-walled Nb-1Zr alloy tubes. By employing a manual tungsten inert gas (TIG) welding process, combined with specific pre-welding treatment, welding environment control, segmented welding, and cooling control measures, oxidation during the Nb-1Zr alloy welding process can be effectively avoided, thus solving the oxidation and porosity problems in niobium-zirconium alloy welding.

[0017] 2. This invention fills a technological gap in the field by proposing a manual helium arc welding process for Nb-1Zr alloys. Compared with existing vacuum electron beam welding processes for dissimilar metals, manual helium arc welding is more flexible, has lower equipment requirements, and is more accessible, making it easier to promote and apply in actual production. Attached Figure Description

[0018] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This invention mainly embodies the flowchart of a manual helium arc welding method for niobium-zirconium alloy welds. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0020] Example 1 The process flow of the manual helium arc welding method for niobium-zirconium alloy welds of the present invention is as follows: Figure 1 As shown.

[0021] The first step is to grind and clean the area to be welded and the surrounding area of ​​the Nb-1Zr alloy tube (niobium-zirconium alloy workpiece). Specifically, the area to be welded and the surrounding area are ground until the metal luster is exposed, and then the ground area is cleaned with a volatile cleaning agent. In this embodiment, alcohol is used to remove the surface oxide layer and impurities to ensure the cleanliness of the welding interface.

[0022] The composition of Nb-1Zr alloy tubes is shown in Table 1: Table 1 Chemical composition of Nb-1Zr alloy

[0023] The second step involves placing the Nb-1Zr alloy tube, treated in the first step, into a sealed welding chamber. A vacuum pump is then activated to evacuate the working chamber to a preset vacuum level. In this embodiment, a welding glove box is used as the sealed welding chamber, with a preset vacuum level below 5 Pa. Specifically, the vacuum level is evacuated to 2.6 Pa. Subsequently, an inert gas (argon is used in this embodiment) is introduced, and the gas purification system is activated to purify the gas inside the chamber. The oxygen and water content inside the chamber are monitored in real time. Welding is prepared to begin when the oxygen content is ≤1 ppm and the water content is ≤1 ppm. In this embodiment, after the final argon filling, the oxygen content inside the chamber is 0.1 ppm and the water content is 1 ppm, meeting the welding preparation conditions.

[0024] The third step involves manual helium arc welding, with helium as the shielding gas during the welding process. The purity of the helium is ≥99.999%. In this embodiment, helium with a purity of 99.999% is selected to increase the thermal conductivity of the arc and increase the weld penetration.

[0025] The fourth step involves spot welding for positioning before actual welding. During spot welding, weld points are evenly distributed along the circumference of the Nb-1Zr alloy tube to be welded. Specifically, in this embodiment, one weld point is spot welded every 90° within the circumference, for a total of four weld points, achieving uniform positioning. Spot welding uses pulsed current, with the following process parameters: peak pulse current 40–80A, base current 10–30A, welding voltage 10–15V, and shielding gas flow rate 10–20L / min. In this embodiment, the specific spot welding process parameters are: peak pulse current 70A, base current 25A, welding voltage 12V, and shielding gas flow rate 16L / min, ensuring the positioning welds are firm and defect-free.

[0026] Step 5: After spot welding, proceed with the formal welding. After manually igniting the helium arc, hold the arc for 1-2 seconds until the molten pool is completely penetrated. In this embodiment, the tungsten electrode is held at the arc ignition point for 1 second to ensure complete penetration and avoid incomplete penetration defects. Then, move the welding torch for filler wire welding. The welding wire is made of the same material as the Nb-1Zr alloy tube; specifically, wire drawn from Nb-1Zr alloy material with a specification of φ1.2mm can be used to ensure material consistency and bonding strength between the weld and the base material. The process parameters for the formal welding are as follows: pulsed current, peak pulse current 60-100A, base current 20-40A, welding voltage 10-18V, welding speed 70-150mm / min, and shielding gas flow rate 10-20L / min. In this embodiment, the specific process parameters selected are: peak pulse current 90A, base current 30A, welding voltage 15V, welding speed 150mm / min, and shielding gas flow rate 16L / min to achieve stable welding.

[0027] The sixth step involves segmented welding, with each segment having a preset length of 30-50mm. After each segment is completed, the weld temperature is allowed to drop to a preset cooling temperature before proceeding with the next segment. This prevents the accumulation of high temperatures from continuous welding, which could lead to weld oxidation or deformation. In this embodiment, each segment is 40mm long, and the preset cooling temperature is below 150℃; specifically, it is reduced to 140℃ in this embodiment.

[0028] Step 7: After welding is completed, wait for the Nb-1Zr alloy tube (the workpiece to be welded) to cool to below the preset removal temperature before removing it from the sealed welding chamber. After removal, observe the appearance of the weld; it should be silvery-white, well-protected, unoxidized, and free of porosity. The weld should be fully penetrated, and both the front and back sides should be well-formed. The preset removal temperature is below 60°C; in this embodiment, it is specifically cooled to 55°C.

[0029] Step 8, after welding is completed, includes weld inspection. In this embodiment, weld inspection covers three methods: liquid penetration testing, gas pressure testing, and helium leak detection. In this embodiment, all three methods are used: (1) liquid penetration testing of the weld, the results of which meet the requirements; (2) gas pressure testing of the weld, maintaining a test pressure of 0.26 MPa, and no pressure drop for 30 minutes, the results of which meet the requirements; (3) helium leak detection of the weld, the leakage rate of which is 4.2 × 10⁻⁶. -7 Pa·m 3 / s, the result meets the requirements.

[0030] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0031] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A manual helium arc welding method for niobium-zirconium alloy welds, characterized in that, Includes the following steps: S1: Grind and clean the area to be welded and the surrounding area of ​​the niobium-zirconium alloy workpiece to be welded; S2: Place the workpiece treated in S1 into a sealed welding chamber, evacuate the welding chamber to the preset vacuum level, then fill it with inert gas and start the gas purification system until the oxygen content and water content in the chamber are ≤1ppm and then prepare to start welding. S3: Welding is performed using manual helium arc welding, with helium as the protective gas during the welding process; S4: Welding is carried out in segments. After completing one segment of welding, wait for the weld temperature to drop to the preset cooling temperature before welding the next segment. S5: After welding is completed, wait for the workpiece to cool to the preset removal temperature before removing the workpiece from the welding chamber.

2. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 1, characterized in that, In step S1, the grinding and cleaning process specifically involves grinding the area to be welded and its surroundings until a metallic luster is exposed, and then cleaning the ground area with a volatile cleaning agent.

3. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 2, characterized in that, The volatile cleaning agent is alcohol.

4. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 1, characterized in that, In S2, the preset vacuum level is below 5 Pa; the inert gas is argon.

5. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 1, characterized in that, In S3, the purity of the helium gas is ≥99.999%; spot welding is performed before welding, and the weld points are evenly distributed along the circumference of the workpiece to be welded during spot welding.

6. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 5, characterized in that, The process parameters for spot welding are as follows: the welding current is pulsed current, with a peak pulse current of 40-80A and a base current of 10-30A; the welding voltage is 10-15V; and the shielding gas flow rate is 10-20L / min.

7. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 1, characterized in that, In S3, after the manual helium arc welding is started, it is held for 1 to 2 seconds until the molten pool is completely melted. Then the welding torch is moved and filler wire welding is performed. The filler wire is made of the same material as the niobium-zirconium alloy workpiece.

8. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 7, characterized in that, The welding process parameters for manual helium arc welding are as follows: the welding current is pulsed current, with a peak pulse current of 60-100A and a base current of 20-40A; the welding voltage is 10-18V; the welding speed is 70-150mm / min; and the shielding gas flow rate is 10-20L / min.

9. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 1, characterized in that, In S4, the single-segment welding length of the segmented welding is 30-50mm, and the preset cooling temperature is below 150℃.

10. The manual helium arc welding method for niobium-zirconium alloy welds as described in claim 1, characterized in that, In S5, the preset extraction temperature is below 60°C. After welding is completed, a weld inspection step is also included, which includes liquid penetration detection, gas pressure test and helium leak detection.

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