Laser cladding method for sealing surface of flange of nuclear power stainless steel container

Abstract

The application belongs to the technical field of laser cladding and aims to solve the corrosion problem of the sealing surface of a stainless steel container flange, and discloses a laser cladding method for the sealing surface of a nuclear power stainless steel container flange, which processes and removes the sealing surface of the flange, processes and removes the defects on the original austenitic stainless steel sealing surface in a whole circle, performs laser cladding repair on the processed sealing surface, adopts a nickel-based alloy powder to perform annular cladding from the inner diameter area of the sealing surface to the outer side, forms a cladding layer, and performs size recovery processing on the cladded sealing surface. The application has the advantages of small heat input and deformation, the repair layer and the base body are metallurgically combined, the corrosion resistance of the sealing surface of the flange can be greatly improved, and the application can realize online repair and automatic repair of the sealing surface of the flange of the nuclear power stainless steel container.

Description

Technical Field

[0001] This application belongs to the field of laser cladding technology, and in particular relates to a laser cladding method for the sealing surface of a stainless steel container flange in nuclear power plants. Background Technology

[0002] Nuclear power plants have numerous stainless steel containers in their primary and secondary loops, primarily connected to pipelines and other components via flange sealing surfaces. These flange sealing surfaces, constantly exposed to the internal media and subjected to high temperatures and pressures, are highly susceptible to corrosion and cracking, compromising sealing performance. Traditional methods such as grinding, localized welding repairs, and replacing sealing rings are ineffective, leading to recurring leaks in the stainless steel containers. Furthermore, prolonged use of these methods continuously deteriorates the condition of the flange sealing surfaces, impacting the safe and stable operation of the nuclear power plant.

[0003] The stainless steel flange seals of nuclear power plant containers are made of austenitic stainless steel forgings. Nuclear power plant operation and maintenance experience shows that the sealing surfaces of stainless steel container flanges are at high risk of corrosion under conditions such as internal pipeline media and high temperatures. Furthermore, periodic opening and maintenance can lead to mechanical damage to the surface, thus affecting sealing performance. To ensure the safe and reliable operation of nuclear power plants, it is necessary to develop a repair method suitable for the sealing surfaces of stainless steel container flanges.

[0004] Laser cladding repair technology is an advanced process that uses high-energy beams to strengthen and repair material surfaces. It offers a wide range of repair materials, virtually unrestricted by the cladding material itself, and features high precision, high efficiency, low heat input, minimal substrate deformation, and excellent repair performance. It is widely used in the petroleum, chemical, power, aerospace, and nuclear energy industries. To improve the corrosion resistance of repaired stainless steel container flange sealing surfaces, it is necessary to consider the flange sealing surface material, structure, and service conditions to ensure repair quality while preventing significant deformation of the flange surface, thereby guaranteeing sealing performance. Summary of the Invention

[0005] The purpose of this application is to provide a laser cladding method for the sealing surface of stainless steel container flanges in nuclear power plants, thereby solving the corrosion problem of stainless steel container flange sealing surfaces.

[0006] To achieve the above objectives, this application provides the following technical solution: A laser cladding method for the sealing surface of a stainless steel flange of a nuclear power plant includes: Step 1: Perform machining and removal treatment on the flange sealing surface, and remove the defects on the original austenitic stainless steel sealing surface by machining the entire circumference. Step 2: Perform laser cladding repair on the processed sealing surface. Use nickel-based alloy powder to perform circumferential cladding from the inner diameter area of ​​the flange sealing surface outward to form a cladding layer; Step 3: Perform dimensional restoration processing on the cladding sealing surface.

[0007] As an feasible approach, in step 1, the defects on the original austenitic stainless steel sealing surface are removed by machining with minimal processing. After machining, the surface is subjected to penetrant testing, and there should be no linear or circular indications.

[0008] As an feasible approach, in step 2, the nickel-based alloy powder is Inconel 690 powder, which is dried before laser cladding.

[0009] As one feasible method, the drying process is carried out at a temperature of 120°C for 2 hours.

[0010] As an feasible approach, in step 2, the process parameters for laser cladding are: laser power 1800W, scanning speed 600mm / s, powder feeding rate 1.0r / min, and weld overlap rate 50%.

[0011] As an feasible approach, in step 2, both the protective gas and the powder feeding gas for laser cladding are argon, with a purity of ≥99.99%, a protective gas flow rate of 35 L / min, and a powder feeding gas flow rate of 7.5 L / min.

[0012] As an feasible approach, in step 2, the starting point of the annular cladding is 1 to 1.5 mm away from the inner diameter edge of the flange sealing surface, and the entire cladding layer is constructed layer by layer from the inside out.

[0013] As an feasible approach, in step 2, after the laser cladding is completed, the cladding layer should be visually inspected and should be free of cracks or defects.

[0014] As an feasible approach, in step 3, the dimensions of the cladding sealing surface are restored by machining; after machining, the inner / outer diameter, roughness, and flatness are inspected to ensure they meet the design requirements; the surface of the cladding layer after machining is subjected to a penetration test, and there should be no linear or circular indications.

[0015] As one feasible approach, the defects include cracks, pits, and pitting.

[0016] Compared with existing technologies, the laser cladding method for the sealing surface of stainless steel nuclear power vessel flanges provided in this application has the following advantages: In response to the common leakage problem caused by corrosion defects in the sealing surface of stainless steel vessel flanges in nuclear power plants and the need for flange sealing surface repair, this application provides a laser cladding method suitable for repairing the sealing surface of stainless steel vessel flanges in nuclear power plants. It has the advantages of low heat input and low deformation, and the repair layer is metallurgically bonded to the substrate, which can significantly improve the corrosion resistance of the flange sealing surface.

[0017] This application enables online and automatic repair of the sealing surfaces of stainless steel vessel flanges in nuclear power plants.

[0018] This application can be used for both corrective repair of defects in the sealing surface of container flanges and preventive welding of the entire sealing surface. Attached Figure Description

[0019] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the technical description will be briefly introduced below.

[0020] Figure 1 A flowchart of the laser cladding method for the sealing surface of a stainless steel nuclear power vessel flange provided in this application; Figure 2 This is a schematic diagram of laser cladding on the sealing surface of a stainless steel nuclear power vessel flange provided in this application; Figure 3 This is a schematic diagram of the sealing surface of the stainless steel nuclear power vessel flange after fusion processing, as provided in this application.

[0021] Explanation of reference numerals in the attached figures: 1-Flange sealing surface; 2-Welded layer. Detailed Implementation

[0022] The following detailed description provides further details on specific implementation methods.

[0023] like Figures 1 to 3 As shown, this application provides a laser cladding method for the sealing surface of a stainless steel flange of a nuclear power plant, comprising the following steps: Step 1: Removal of defects on the flange sealing surface.

[0024] Step 1.1: Using appropriate machining methods, remove defects such as cracks, pits, and pitting on the original austenitic stainless steel sealing surface by machining the entire circumference with minimal machining.

[0025] Step 1.2: Perform a penetrant test on the processed surface. There should be no linear or circular indications.

[0026] Step 2: Laser cladding repair of flange sealing surface.

[0027] Step 2.1: The repair is carried out using the laser cladding repair method of this invention. First, the cladding Inconel 690 powder is dried at 120°C for 2 hours.

[0028] Step 2.2: Repair using laser cladding equipment. Set the cladding process parameters as follows: laser power 1800W, scanning speed 600mm / s, powder feeding rate 1.0r / min, and weld overlap rate 50%. Both the shielding gas and the powder feeding gas are ≥99.99%Ar in purity, with a shielding gas flow rate of 35L / min and a powder feeding gas flow rate of 7.5L / min.

[0029] Step 2.3: Begin circumferential cladding from the inner diameter area of ​​the flange sealing surface outwards. The initial starting point should be 1-1.5mm from the inner diameter edge of the flange sealing surface to ensure the cladding layer does not damage the pipeline interior. Construct the entire Inconel 690 nickel-based alloy cladding layer layer by layer from the inside out, ensuring the cladding layer thickness can be subsequently machined to the original design dimensions of the flange sealing surface. Figure 1 As shown.

[0030] Step 2.4: After cladding, visually inspect the cladding layer; it should be free of cracks or defects.

[0031] Step 3: Restore the dimensions of the sealing surface.

[0032] Step 3.1: Using appropriate machining methods, the dimensions of the cladding sealing surface are restored, such as... Figure 2 As shown.

[0033] Step 3.2: Inspect the inner / outer diameter and roughness of the machined sealing surface to ensure that the inner / outer diameter, roughness, and flatness meet the design requirements.

[0034] Step 3.3: Perform a penetration test on the surface of the processed cladding layer. There should be no linear or circular indications.

[0035] Step 3.4: After the repair is completed, clean up the site.

[0036] In one embodiment, this method mainly includes defect removal of the flange sealing surface 1, laser cladding repair of the sealing surface, and restoration of the sealing surface dimensions, such as the following: (1) Cleaning the surface to be repaired: Remove the flange sealing surface 1, impurities and other things that affect the cladding quality.

[0037] (2) Repair materials: The base material is austenitic stainless steel. The cladding powder is Inconel 690 nickel-based alloy powder. Before laser cladding, the alloy powder needs to be placed in a vacuum drying oven, and the powder drying temperature is set to 120℃ for 2 hours.

[0038] (3) Repair of flange sealing surface 1: Take precautions against foreign objects, and perform cladding around the entire circumference starting from the inner diameter of flange sealing surface 1 (e.g. Figure 2As shown, the initial glazing point of the cladding layer (2) is 1-1.5 mm from the inner diameter edge of the flange sealing surface (1), ensuring that the cladding layer does not damage the inside of the pipeline. The entire 690 nickel-based alloy cladding layer is constructed layer by layer from the inside out. Figure 2 As shown.

[0039] (4) The process parameters used for the repair of flange sealing surface 1 are as follows: laser power 1800W, scanning speed 600mm / s, powder feeding rate 1.0r / min, and weld overlap rate 50%. The protective gas and the powder feeding gas are both ≥99.99%Ar with a purity of ≥99.99%, the protective gas flow rate is 35L / min, and the powder feeding gas flow rate is 7.5L / min.

[0040] (5) Post-repair machining: After the flange sealing surface 1 has cooled to room temperature, the surface of the finished cladding layer is machined by external milling to restore the original design dimensions of the flange sealing surface 1, such as... Figure 3 As shown.

[0041] (6) Post-processing inspection: The inner / outer diameter, roughness and flatness of the processed flange sealing surface 1 are inspected to ensure that the inner / outer diameter, roughness and flatness meet the design requirements. The cladding layer surface is subjected to a penetration test. After the test is qualified, the penetration area and adjacent areas are cleaned.

[0042] Therefore, this method can repair defects in the sealing surface of stainless steel container flanges in nuclear power plants, improve the corrosion resistance of the sealing surface of stainless steel container flanges in nuclear power plants, and solve the leakage problem caused by corrosion defects in the sealing surface of stainless steel container flanges in nuclear power plants.

[0043] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.

Claims

1. A laser cladding method for the sealing surface of a stainless steel flange of a nuclear power plant, characterized in that, include: Step 1: Perform machining and removal treatment on the flange sealing surface, and remove the defects on the original austenitic stainless steel sealing surface by machining the entire circumference. Step 2: Perform laser cladding repair on the processed sealing surface. Use nickel-based alloy powder to perform circumferential cladding from the inner diameter area of ​​the flange sealing surface outward to form a cladding layer; Step 3: Perform dimensional restoration processing on the cladding sealing surface.

2. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 1, mechanical processing is used to remove the defects on the original austenitic stainless steel sealing surface around the entire circumference with minimal machining.

3. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 2, the nickel-based alloy powder is Inconel 690 powder, which is dried before laser cladding.

4. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 3, characterized in that, The drying process is carried out at a temperature of 120°C for 2 hours.

5. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 2, the laser cladding process parameters are: laser power of 1800W, scanning speed of 600mm / s, powder feeding rate of 1.0r / min, and weld overlap rate of 50%.

6. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 2, both the protective gas and the powder feeding gas for laser cladding are argon, with a purity of ≥99.99%, a protective gas flow rate of 35 L / min, and a powder feeding gas flow rate of 7.5 L / min.

7. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 2, the starting point of the annular cladding is 1 to 1.5 mm away from the inner diameter edge of the flange sealing surface, and the entire cladding layer is constructed layer by layer from the inside out.

8. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 2, after the laser cladding is completed, the cladding layer is visually inspected and should be free of cracks or defects.

9. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, In step 3, the dimensions of the cladding sealing surface are restored by mechanical processing. After processing, the inner / outer diameter, roughness and flatness are inspected to ensure that they meet the design requirements. The surface of the cladding layer after processing is then subjected to a penetration test.

10. The laser cladding method for the sealing surface of a nuclear power plant stainless steel container flange according to claim 1, characterized in that, The defects include cracks, pits, and pitting.

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