Zirconium alloy welding method

Abstract

The invention discloses a zirconium alloy welding method. The zirconium alloy welding method comprises the following steps that firstly, a V-shaped welding groove is formed in a to-be-welded part of a zirconium alloy plate; secondly, the zirconium alloy plates provided with the V-shaped welding grooves in the first step are assembled to form welding seams, and welding rods are placed at the welding seams; and thirdly, plasma welding is adopted for welding the welding seam after the welding rod is placed in the second step. According to the welding method, the V-shaped welding groove is formed in the to-be-welded part, and the zirconium alloy plate is welded through plasma welding, so that welding stress generated due to temperature gradient in the welding process can be reduced, metal materials on the two sides of the groove can be heated and cooled more uniformly during welding, generation of the welding stress is reduced, and the welding quality is improved. And the welding joint with excellent mechanical property and corrosion resistance is obtained, and the method is suitable for the technical field of zirconium alloy welding.

Description

Technical Field

[0001] The invention belongs to the technical field of zirconium alloy welding, and in particular relates to a zirconium alloy welding method. Background Art

[0002] The use of zirconium alloys is mainly concentrated in spent fuel reprocessing dissolvers. These devices operate in high temperature, strong acid, and high radiation environments, which have high requirements for the corrosion resistance of the materials. Compared with materials such as stainless steel, zirconium alloys have excellent corrosion resistance under these extreme conditions.

[0003] However, when zirconium alloy is welded, welding stress is easily induced by large temperature changes, which causes fracture and deformation at the weld due to welding stress, and sharply reduces the mechanical properties and corrosion resistance of the zirconium alloy weld, thus failing to meet the high performance requirements of key equipment for spent fuel reprocessing. Therefore, it is urgent to develop a welding method that can maintain high strength and corrosion resistance of zirconium alloy welded joints. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a method for welding zirconium alloys. The welding method can reduce the welding stress generated by the temperature gradient during the welding process by opening a V-shaped welding groove at the part to be welded and using plasma welding to weld the zirconium alloy plate. During welding, the metal materials on both sides of the groove can be heated and cooled more evenly, reducing the generation of welding stress and preventing the welded joint from deforming or cracking, thereby solving the problem of low mechanical properties and corrosion resistance of the welded joint of zirconium alloy in the prior art.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a zirconium alloy welding method, characterized in that the welding method comprises the following steps:

[0006] Step 1: Open a V-shaped welding groove at the part to be welded of the zirconium alloy plate;

[0007] Step 2: Assemble the zirconium alloy plates with the V-shaped welding grooves in step 1 to form a weld, and place welding rods at the weld;

[0008] Step 3: Use plasma welding to weld the weld after the welding rod is placed in step 2.

[0009] The above-mentioned zirconium alloy welding method is characterized in that the groove angle of the V-shaped welding groove in step 1 is 17° to 23°, and the blunt edge thickness of the V-shaped welding groove is 0.5mm to 1mm.

[0010] The above-mentioned zirconium alloy welding method is characterized in that the assembly gap in step 2 is 0.5 mm to 1 mm.

[0011] The above-mentioned zirconium alloy welding method is characterized in that the welding process described in step three is: an argon protection device is installed at the weld, a welding gun passes through the welding gun inlet of the argon protection device close to the weld, a sealing ring is used to seal the welding gun and the welding gun inlet, and then argon gas is introduced, and welding is carried out after turning on the welding gun power for 5 minutes to 6 minutes.

[0012] The present invention performs welding 5 to 6 minutes after the welding gun is turned on, so that a stable plasma environment can be formed during welding and the heat source energy can be evenly distributed, which helps to achieve uniform heating and melting of the weld. At the same time, it can reduce spatter and oxidation during welding, reduce defects such as inclusions and pores in the weld, and make the weld joint more dense and uniform.

[0013] The above-mentioned zirconium alloy welding method is characterized in that the flow rate of the argon gas is 12L / min to 25L / min.

[0014] The above-mentioned zirconium alloy welding method is characterized in that the welding process parameters in step three are: welding current 40A~50A, welding voltage 10V~20V, welding speed 5cm / min~15cm / min, plasma gas flow rate 15L / min~30L / min.

[0015] The present invention can generate enough heat by controlling the welding current within the range of 40A-50A, so that the energy density of the plasma arc is high and the arc column temperature is high, thereby enhancing the penetration ability and improving the welding efficiency; by controlling the welding voltage within the range of 10V-20V, in combination with the welding current, it is helpful to form a stable arc and a uniform molten pool, and a weld with a large aspect ratio, a small heat-affected zone and small deformation can be obtained, thereby improving the welding quality; by controlling the plasma gas flow rate within the range of 15L / min-30L / min, the stability and protection effect of the plasma arc can be ensured, and a sufficient plasma gas flow rate can cooperate with the argon atmosphere to prevent harmful gases in the air from invading the molten pool, reduce the oxidation and nitridation of the weld metal, and improve the weld quality.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention uses plasma welding to weld zirconium alloy plates, which is faster than other welding methods and can obtain dense, beautifully shaped welds that meet 100% radiographic inspection requirements; by opening a V-shaped welding groove at the part to be welded, the fusion area of ​​the weld can be increased, so that the metal materials on both sides of the groove can be melted more quickly during the welding process, further improving the welding efficiency; at the same time, the V-shaped welding groove helps to reduce the welding stress generated by the temperature gradient during the welding process, and the metal materials on both sides of the groove can be heated and cooled more evenly during welding, thereby reducing the generation of welding stress, preventing the weld joint from deformation or cracking, and effectively improving the quality of the weld joint.

[0018] 2. The present invention adopts plasma welding to weld zirconium alloy plates, so that the heat affected zone of the weld is reduced and has a lower oxidation rate. At the same time, an argon protection device is adopted, the welding gun and the welding gun inlet of the argon protection device are sealed, and a stable plasma environment is provided to further reduce the probability of the weld contacting with air, avoid reaction with elements such as hydrogen, oxygen, and nitrogen to form brittle compounds during welding, and thus prevent the mechanical properties and corrosion resistance of the weld from being sharply reduced.

[0019] 3. The present invention is used to improve the welding efficiency and welding quality of the welding joint by controlling the welding environment and welding process parameters.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the microstructure diagram of the welded joint of Example 1 of the present invention.

[0022] Figure 2 This is a graph showing the uniform corrosion rate results of the welding joints of Example 1 of the present invention and Comparative Example 1.

[0023] Figure 3 Graph showing the tensile test results of the welded joints of Example 1 of the present invention and Comparative Example 1.

[0024] Figure 4 This is a graph showing the uniform corrosion rate results of the welding joints of Example 1 of the present invention and Comparative Example 2.

[0025] Figure 5 Graph showing the tensile test results of the welded joints of Example 1 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0026] Example 1

[0027] The welding method of this embodiment comprises the following steps:

[0028] Step 1: Open a V-shaped welding groove with a groove angle of 17° and a blunt edge thickness of 0.5 mm at the part to be welded of the zirconium alloy plate;

[0029] Step 2: Assemble the zirconium alloy plates with the V-shaped welding grooves in step 1 to form a weld, and place welding rods at the weld; the assembly gap is 0.5 mm;

[0030] Step 3: Install the argon protection device at the weld, pass the welding gun through the welding gun inlet of the argon protection device close to the weld, use a sealing ring to seal the welding gun and the welding gun inlet, pass argon gas with a flow rate of 25L / min, turn on the welding gun power supply for 5 minutes before welding; the welding process parameters are: welding current 40A, welding voltage 20V, welding speed 5cm / min, plasma gas flow rate 30L / min.

[0031] The microstructure of the welded joint of this embodiment is analyzed. Figure 1 As shown in the figure, there are no pores, cracks or inclusions inside the weld joint, indicating that the weld joint has good welding quality.

[0032] Comparative Example 1

[0033] The difference between this comparative example and Example 1 is that welding is performed immediately after the welding gun power is turned on in step 3.

[0034] The welded joints of this comparative example and Example 1 were subjected to uniform corrosion tests in a boiling nitric acid solution with a concentration of 8 mol / L, wherein the nitric acid solution contained ruthenium ions, cerium ions, vanadium ions and chromium ions. The results are as follows: Figure 2 As shown, the corrosion rate of the welded joint in this comparative example is higher than that in Example 1, indicating that the welded joint in Example 1 has more excellent corrosion resistance.

[0035] The welded joints of this comparative example and Example 1 were subjected to room temperature tensile tests. The results are as follows: Figure 3 As shown, the tensile strength of the comparative weld joint is 610 MPa and the yield strength is 552 MPa, while the tensile strength of the weld joint in Example 1 is 707 MPa and the yield strength is 629 MPa. The tensile strength and yield strength of the comparative weld joint are lower than those in Example 1, indicating that the weld joint in Example 1 has more excellent mechanical properties.

[0036] Comparative Example 2

[0037] The difference between this comparative example and Example 1 is that in step 1, no V-shaped welding groove is provided at the part to be welded of the zirconium alloy plate.

[0038] The welded joints of this comparative example and Example 1 were subjected to uniform corrosion tests in a boiling nitric acid solution with a concentration of 8 mol / L, wherein the nitric acid solution contained ruthenium ions, cerium ions, vanadium ions and chromium ions. The results are as follows: Figure 4 As shown, the corrosion rate of the welded joint in this comparative example is higher than that in Example 1, indicating that the opening of a V-shaped welding groove can improve the corrosion resistance of the welded joint.

[0039] The welded joints of this comparative example and Example 1 were subjected to room temperature tensile tests. The results are as follows: Figure 5 As shown, the tensile strength of the comparative weld joint is 650 MPa and the yield strength is 582 MPa. The tensile strength and yield strength of the comparative weld joint are lower than those of Example 1, indicating that the opening of a V-shaped welding groove can improve the mechanical properties of the weld joint.

[0040] Example 2

[0041] The welding method of this embodiment comprises the following steps:

[0042] Step 1: Open a V-shaped welding groove with a groove angle of 20° and a blunt edge thickness of 0.8 mm at the part to be welded of the zirconium alloy plate;

[0043] Step 2: Assemble the zirconium alloy plates with the V-shaped welding grooves in step 1 to form a weld, and place welding rods at the weld; the assembly gap is 0.6 mm;

[0044] Step 3: Install the argon protection device at the weld, pass the welding gun through the welding gun inlet of the argon protection device close to the weld, use a sealing ring to seal the welding gun and the welding gun inlet, and then introduce argon gas with a flow rate of 18L / min, turn on the welding gun power supply for 6 minutes before welding; the welding process parameters are: welding current 45A, welding voltage 15V, welding speed 10cm / min, plasma gas flow rate 22L / min.

[0045] The welded joint of this embodiment was subjected to a uniform corrosion test in a boiling nitric acid solution with a concentration of 8 mol / L. The nitric acid solution contained ruthenium ions, cerium ions, vanadium ions and chromium ions, and the corrosion rate was not higher than 0.008 mm / a. The welded joint of this embodiment was subjected to a room temperature tensile test. The tensile strength of the welded joint was 712 MPa and the yield strength was 633 MPa. In summary, the welded joint of this embodiment has excellent corrosion resistance and mechanical properties.

[0046] Example 3

[0047] The welding method of this embodiment comprises the following steps:

[0048] Step 1: Open a V-shaped welding groove with a groove angle of 23° and a blunt edge thickness of 1.0 mm at the part to be welded of the zirconium alloy plate;

[0049] Step 2: Assemble the zirconium alloy plates with the V-shaped welding grooves in step 1 to form a weld, and place welding rods at the weld; the assembly gap is 1.0 mm;

[0050] Step 3: Install the argon protection device at the weld, pass the welding gun through the welding gun inlet of the argon protection device close to the weld, use a sealing ring to seal the welding gun and the welding gun inlet, and then introduce argon gas with a flow rate of 25L / min, turn on the welding gun power supply for 6 minutes before welding; the welding process parameters are: welding current 50A, welding voltage 20V, welding speed 15cm / min, plasma gas flow rate 30L / min.

[0051] The welded joint of this embodiment was subjected to a uniform corrosion test in a boiling nitric acid solution with a concentration of 8 mol / L. The nitric acid solution contained ruthenium ions, cerium ions, vanadium ions and chromium ions, and the corrosion rate was not higher than 0.008 mm / a. The welded joint of this embodiment was subjected to a room temperature tensile test. The tensile strength of the welded joint was 715 MPa and the yield strength was 636 MPa. This indicates that the welded joint of this embodiment has excellent corrosion resistance and mechanical properties.

[0052] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for welding a zirconium alloy, characterized in that: The welding method comprises the following steps: Step 1: Open a V-shaped welding groove at the part to be welded of the zirconium alloy plate; Step 2: Assemble the zirconium alloy plates with the V-shaped welding grooves in step 1 to form a weld, and place welding rods at the weld; Step 3: Use plasma welding to weld the weld after the welding rod is placed in step 2.

2. A zirconium alloy welding method according to claim 1, characterized in that: The groove angle of the V-shaped welding groove in step 1 is 17° to 23°, and the blunt edge thickness of the V-shaped welding groove is 0.5mm to 1mm.

3. The method for welding zirconium alloy according to claim 1, characterized in that: The assembly gap in step 2 is 0.5 mm to 1 mm.

4. The method for welding zirconium alloy according to claim 1, characterized in that: The welding process described in step three is: install the argon protection device at the weld, pass the welding gun through the welding gun inlet of the argon protection device close to the weld, use a sealing ring to seal the welding gun and the welding gun inlet, then pass argon gas, turn on the welding gun power supply for 5 minutes to 6 minutes before welding.

5. The method for welding zirconium alloy according to claim 3, characterized in that: The flow rate of the argon gas is 12 L / min to 25 L / min.

6. The method for welding zirconium alloy according to claim 1, characterized in that: The welding process parameters in step three are: welding current 40A-50A, welding voltage 10V-20V, welding speed 5cm / min-15cm / min, plasma gas flow rate 15L / min-30L / min.

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