A manufacturing process for an integral impeller for a liquid metal pump

Abstract

The application discloses a manufacturing process of an integral impeller for a liquid metal pump. The application adopts the technical concept of the dissection method, separates a blade part from a cover plate, and processes the blade part and the cover plate separately, then through a precise assembly welding process and a special heat treatment process, the integral manufacturing of the impeller is completed. The application makes the manufacturing of the impeller with an internal flow channel structure convenient and feasible, greatly reduces the manufacturing cost, has good economy, and is convenient for mass production. The application separately processes the blade and the cover plate through numerical control processing, the roughness of the processed blade type flow channel can easily meet the requirements, and the blade and the cover plate are assembled and then subjected to high-temperature heat treatment, so that the high-temperature performance of the impeller can be ensured.

Description

Technical Field

[0001] This invention relates to the field of liquid metal pumps, and more specifically, to a manufacturing process for an integral impeller for liquid metal pumps. Background Technology

[0002] The impellers of liquid metal pumps operate in high-temperature environments, reaching up to 550℃, requiring sufficient service life and stable, reliable operation. Therefore, the impellers face high demands, needing not only matching hydrodynamic properties but also high-temperature material properties, including mechanical properties and corrosion resistance. The impeller has a closed, elongated structure with internal flow channels. Currently, cutting tools cannot fully reach these flow channels, making it virtually impossible to directly manufacture the blade flow channels using CNC machining. Precision casting can, to some extent, solve the machining challenges of small, integral impellers with a nominal diameter not exceeding φ300 and a weight generally not exceeding 50kg. However, the high cost of precision casting molds makes it economically unfeasible and difficult to mass-produce. Furthermore, the surface roughness of the blade flow channels in cast impellers rarely meets the design requirement of Ra1.6 or less. The utility model patent with announcement number CN203009383U discloses a small-flow closed-type fully milled three-dimensional impeller. Although this utility model can be manufactured by CNC machining, an annular groove needs to be machined on the impeller hub so that the CNC milling cutter can complete the machining of the entire flow channel of the impeller from three positions and directions: the air inlet, the air outlet, and the annular groove. This not only destroys the integrity of the impeller hub, but also increases the machining difficulty and process complexity. Moreover, the machining method applicable to this utility model is still difficult to apply to the manufacturing of impellers with complex flow channels. Summary of the Invention

[0003] In existing manufacturing processes for integral impellers for liquid metal pumps, it is difficult to achieve product processing or meet mass production requirements using CNC machining and precision casting methods. To overcome these shortcomings, this invention provides a manufacturing process for integral impellers for liquid metal pumps that can meet precision requirements and is also economical.

[0004] The technical solution of this invention is: a manufacturing process for an integral impeller for a liquid metal pump, comprising the following steps:

[0005] A manufacturing process for an integral impeller for a liquid metal pump includes the following steps:

[0006] Step 1. Design the impeller as a separate structure consisting of blades and a cover plate, with the blades and cover plate being precision CNC machined separately;

[0007] Step 2. Prepare the assembly tooling for welding, preventing deformation, and vacuuming;

[0008] Step 3. Place the blades and cover plates together on the welding anti-deformation and vacuum assembly fixture for plug welding;

[0009] Step 4. Grind the weld seam smooth;

[0010] Step 5. Evacuate to below 50Pa, while heating the entire system above 80℃, repeating at least twice, and immediately assemble and weld the vacuum device to achieve overall sealing;

[0011] Step 7. The workpiece is subjected to high-temperature heat treatment at 960-980℃ for 2 hours;

[0012] Step 6. Remove all tooling, take off the welded impeller semi-finished product, and take a sample from it as a welding witness piece. Perform macroscopic metallographic examination, room temperature and high temperature mechanical property tests, impact test, and intergranular corrosion test on the weld dissection of the welding witness piece.

[0013] This invention employs a dissection-based technical concept, separating and separately processing the blades and cover plate. Then, through precision welding and special heat treatment processes, the impeller is manufactured as a whole. The impeller's dynamic balancing quality and impeller simulation tests are then conducted to ensure it meets design requirements. This invention makes the manufacture of impellers with internal flow channels convenient and feasible, meeting precision requirements while significantly reducing manufacturing costs, resulting in good economic efficiency and facilitating mass production.

[0014] Preferably, the welding anti-deformation and vacuum assembly fixture includes an anti-deformation fixture and a vacuum fixture. In step four, after the blade and cover plate are stacked, they are positioned on the anti-deformation fixture, and the vacuum fixture presses on the stacked blade and cover plate. During welding, the blade and cover plate will deform due to heat. If not controlled, this will affect the assembly accuracy of the blade and cover plate. Using the anti-deformation fixture can position and effectively constrain the blade and cover plate, keeping the deformation within the allowable range. After the blade and cover plate are stacked and positioned on the anti-deformation fixture, the flow channel between the blade and cover plate forms a closed cavity. The vacuum fixture draws the cavity into a negative pressure state, and the pressure difference between the inside and outside generates a clamping force to keep the blade and cover plate relatively fixed, further improving the anti-deformation ability and ensuring the assembly accuracy of the blade and cover plate.

[0015] Preferably, the anti-deformation fixture includes an anti-deformation fixture base plate and a sealing ring. The sealing ring is fixed to the anti-deformation fixture base plate, and the outer circumferential surface of the blade and cover plate assembly fits into the inner circumferential surface of the sealing ring. After the outer circumferential surface of the blade and cover plate assembly fits into the inner circumferential surface of the sealing ring, the blade and cover plate assembly is radially positioned by the sealing ring, and the internal flow channel opening of the impeller located on the impeller rim is closed by the sealing ring.

[0016] Preferably, the vacuuming fixture includes a vacuuming fixture base and a gas path assembly. The gas path assembly is fixed on the vacuuming fixture base, and the vacuuming fixture base and the gas path assembly are connected by a gas path. The vacuuming fixture base presses against the stacked assembly of the blades and the cover plate, and is connected to the flow channel between the blades and the cover plate by a gas path. The vacuuming fixture base serves both to press the blades and the cover plate together and to connect the flow channel with the gas path assembly.

[0017] As a preferred option, a PT (Pressure Testing) inspection of the weld position is performed before welding the blades and cover plates to meet the Class I requirements of NB / T47013.5. The PT inspection of the weld position can promptly detect defects such as openings and cracks on the surface of the parts, ensuring that the weld position meets the required strength after welding.

[0018] Preferably, in step two, cleanliness is checked using anti-pilling gloves, ensuring that the surfaces of the blades and cover plates are free of foreign matter. The welding area must maintain the necessary cleanliness to avoid introducing impurities during welding, which could affect the weld strength.

[0019] As a preferred option, in step four, the welding is performed by argon arc welding for the root pass and manual electric arc welding for the cover pass, while the remaining tooling is welded by argon arc welding.

[0020] As a preferred option, a PT inspection is also performed on the plug weld after grinding in step five to meet the Class I requirements of NB / T47013.5. Performing a PT inspection on the plug weld after welding can promptly detect defects such as incomplete welds and weld detachment.

[0021] The beneficial effects of this invention are:

[0022] This invention addresses the challenge of machining integral impellers with internal flow channels. It employs a dissection-based design, separating and machining the blades and cover plate separately. Then, through precision welding and specialized heat treatment, the entire impeller is manufactured.

[0023] It offers good economic efficiency and is easy to mass-produce. This invention makes the manufacture of impellers with internal flow channel structures convenient and feasible, greatly reducing manufacturing costs, thus offering good economic efficiency and facilitating mass production.

[0024] This invention ensures the impeller's machining accuracy and high-temperature material properties. The blades and cover plates are individually CNC machined, resulting in a blade profile flow channel surface roughness that easily meets requirements. Furthermore, the assembled blades and cover plates undergo high-temperature heat treatment to guarantee the impeller's high-temperature performance. Attached Figure Description

[0025] Figure 1 This is a sectional view of the impeller's shaft section;

[0026] Figure 2 This is a schematic diagram of the disassembled structure of an impeller manufactured using the present invention;

[0027] Figure 3This is a schematic diagram of a process state for manufacturing an impeller using the present invention;

[0028] Figure 4 This is a schematic diagram of another process state for manufacturing an impeller using the present invention.

[0029] In the diagram, 1-blade, 101-chassis, 102-flow channel wall, 103-flow channel, 104-fitting rib, 2-cover plate, 201-fitting groove, 3-assembly welding anti-deformation and vacuuming assembly tooling, 301-anti-deformation tooling, 3011-anti-deformation tooling base plate, 3012-sealing ring, 302-vacuuming tooling, 3021-vacuuming tooling base, 3022-air circuit assembly, 4-tensioning sleeve tooling. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1:

[0032] like Figures 1 to 4 As shown, a manufacturing process for an integral impeller for a liquid metal pump includes the following steps:

[0033] Step 1. The impeller is designed as a split structure consisting of blade 1 and cover plate 2. Blade 1 includes a chassis 101, a flow channel wall 102 on the chassis 101, a flow channel 103 formed between the flow channel walls 102, a mating rib 104 on the top of the flow channel wall 102, and a mating groove 201 on the cover plate 2 that corresponds to the position and size of the rib 104. A sleeve is provided at the center of blade 1, and a central hole coaxial with the sleeve is provided at the center of cover plate 2. Blade 1 and cover plate 2 are respectively precision CNC machined.

[0034] Step 2. Clean the surfaces of blade 1 and cover plate 2 with alcohol. The cleanliness requirement is to check with anti-pilling gloves and ensure that there are no foreign objects on the surfaces of blade 1 and cover plate 2.

[0035] Step 3. Prepare and clean the welding anti-deformation and vacuum assembly fixture 3;

[0036] Step 4. Perform a PT inspection on the weld positions of the blades and cover plates. The inspection results must meet the requirements of NB / T47013.5 Class I. Then, stack the blades 1 and cover plates 2 coaxially on the welding anti-deformation and vacuum assembly fixture 3. The ribs 104 and the mating grooves 201 are aligned and fitted one-to-one for plug welding. The welding anti-deformation and vacuum assembly fixture 3 includes an anti-deformation fixture 301 and a vacuum assembly fixture 302. The anti-deformation fixture 301 includes an anti-deformation fixture base plate 3011 and a sealing ring 3012. The sealing ring 3012 is fixed on the anti-deformation fixture base plate 3011 and is coaxial with the anti-deformation fixture base plate 3011. The outer circumferential surface of the stacked assembly of blades 1 and cover plates 2 is adapted and fitted to the inner circumferential surface of the sealing ring 3012. The vacuum assembly fixture 302 includes a vacuum... The vacuum fixture base 3021 and the gas path assembly 3022 are fixed on the vacuum fixture base 3021. The vacuum fixture base 3021 and the gas path assembly 3022 are connected by a gas path. The vacuum fixture base 3021 presses on the stacked assembly of blade 1 and cover plate 2 and is connected to the flow channel between blade 1 and cover plate 2 by a gas path. After the blade 1 and cover plate 2 are stacked, they are positioned on the anti-deformation fixture 301 and welded to the sealing ring 3012 to ensure a seal. The vacuum fixture 302 presses on the stacked assembly of blade 1 and cover plate 2. The plug weld assembly adopts argon arc welding for the root pass and manual electric arc welding for the cover pass. The remaining fixtures are welded by argon arc welding.

[0037] Step 5. Grind the plug weld formed in the previous step until smooth, and prepare for PT (Potential Test). The PT should meet the requirements of NB / T47013.5 Class I.

[0038] Step 6. Vacuuming is performed to prevent oxidation of the metal surface and maintain material properties. The vacuum level is controlled at 50Pa. At the same time, the entire system is heated and the temperature is controlled at 80℃. This is repeated twice. Immediately afterward, the vacuuming fixture 302 is assembled and welded together, that is, the cover plate 2 is welded to the vacuuming fixture base 3021 to achieve overall sealing.

[0039] Step 7. The workpiece, namely blade 1, cover plate 2 and the assembly of the anti-deformation and vacuuming fixture 3, is subjected to high-temperature heat treatment at 960℃ for 2 hours.

[0040] Step 8. Remove all tooling, take off the welded impeller semi-finished product, and use the first piece as the welding witness piece. Perform macroscopic metallographic inspection on the weld dissection of the welding witness piece, and conduct room temperature and high temperature mechanical property tests, impact tests, and intergranular corrosion tests on the material. All test results must meet the requirements of the base material austenitic stainless steel 316. After the welding witness piece passes the test, proceed with the formal plug weld assembly of the product.

[0041] Step 9. Use tensioning sleeve tool 4 to perform a one-time precision machining on the impeller semi-finished product to ensure machining accuracy;

[0042] Step 10. Dynamic balance inspection;

[0043] Step 11. Performance testing of the high-temperature test bench.

[0044] Example 2:

[0045] In step six, the vacuum level is controlled at 45 Pa, and the entire workpiece is heated at 82°C, repeated three times. In step seven, the workpiece undergoes high-temperature heat treatment at 980°C for 2 hours. The rest is the same as in Example 1.

Claims

1. A manufacturing process for an integral impeller for a liquid metal pump, characterized in that, Includes the following steps: Step 1. Design the impeller as a separate structure consisting of blades and a cover plate, with the blades and cover plate being precision CNC machined separately; Step 2. Prepare the assembly tooling for welding, preventing deformation, and vacuuming; Step 3. Place the blade and cover plate together on the assembly welding anti-deformation and vacuuming fixture for plug welding; the assembly welding anti-deformation and vacuuming fixture includes an anti-deformation fixture and a vacuuming fixture. The anti-deformation fixture includes an anti-deformation fixture base plate and a sealing ring. The sealing ring is fixed on the anti-deformation fixture base plate and is coaxial with the anti-deformation fixture base plate. The outer peripheral surface of the stacked assembly of the blade and cover plate is adapted and fitted to the inner peripheral surface of the sealing ring. After the blade and cover plate are stacked, they are positioned on the anti-deformation fixture and welded to the sealing ring to ensure a seal. The vacuuming fixture is pressed on the stacked assembly of the blade and cover plate. Step 4. Grind the weld seam smooth; Step 5. Evacuate to below 50Pa, while heating the entire system above 80℃, repeating at least twice, and immediately assemble and weld the vacuum device to achieve overall sealing; Step 7. The workpiece is subjected to high-temperature heat treatment at 960-980℃ for 2 hours; Step 6. Remove all tooling, take off the welded impeller semi-finished product, and take a sample from it as a welding witness piece. Perform macroscopic metallographic examination, room temperature and high temperature mechanical property tests, impact test, and intergranular corrosion test on the weld dissection of the welding witness piece.

2. The manufacturing process for an integral impeller for a liquid metal pump according to claim 1, characterized in that, The vacuuming fixture includes a vacuuming fixture base and an air passage assembly. The air passage assembly is fixed on the vacuuming fixture base and the vacuuming fixture base and the air passage assembly are connected by an air passage. The vacuuming fixture base presses on the stacked assembly of the blade and the cover plate and is connected to the flow channel between the blade and the cover plate by an air passage.

3. The manufacturing process for an integral impeller for a liquid metal pump according to claim 2, characterized in that, Before welding the blades and cover plates, a PT inspection of the weld position is performed to ensure that it meets the requirements of NB / T47013.5 Class I.

4. The manufacturing process for an integral impeller for a liquid metal pump according to claim 1, characterized in that, In step two, the cleanliness requirement is to use anti-pilling gloves to check for foreign objects on the blade and cover plate surfaces.

5. The manufacturing process for an integral impeller for a liquid metal pump according to claim 1, characterized in that, In step four, the welding process uses argon arc welding for the root pass followed by manual electric arc welding for the cover pass, while the remaining tooling is welded using argon arc welding.

6. The manufacturing process for an integral impeller for a liquid metal pump according to claim 1, characterized in that, In step five, a PT test is also performed after the weld seam is ground to ensure it meets NB / T47013.5 Class I.

7. The manufacturing process for an integral impeller for a liquid metal pump according to any one of claims 1 to 6, characterized in that, It also includes a dynamic balancing test procedure.

8. The manufacturing process for an integral impeller for a liquid metal pump according to any one of claims 1 to 6, characterized in that, It also includes high-temperature test bench performance testing procedures.

Images