Manufacturing method of impeller for high-cycle-fatigue-resistant lead-bismuth pump

Abstract

The invention discloses a manufacturing method of an impeller for a high-cycle-fatigue-resistant lead-bismuth pump, based on a multi-gradient fuse arc forming process, an impeller blade is formed by a middle layer and a hard layer which are sequentially connected from the root to the end, the middle layer is formed by surfacing 22Cr12NiWMoV, and the hard layer is formed by surfacing Fe310M; the middle layer is divided into a first surfacing layer and a second surfacing layer, the hard layer is divided into a third surfacing layer and a fourth surfacing layer, and a transition layer formed by surfacing austenitic stainless steel is arranged between every two adjacent surfacing layers; impeller blades are formed through various dissimilar alloys in a gradient mode, the hardness is gradually increased from inside to outside, the transition layers are used for connecting the dissimilar alloys of the two adjacent surfacing layers in a fusion welding mode, and the possibility that cracks appear in a dissimilar alloy molten pool is reduced; according to the impeller blade manufactured through the method, the high-strain part has good creep resistance and erosion resistance, the abrasion and degradation speed of the tip end of the impeller blade in a high-temperature and high-rotating-speed lead-bismuth medium can be reduced, and the service life of the impeller for the lead-bismuth pump is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of blade additive manufacturing, and specifically relates to a method for manufacturing an impeller for a high-cycle fatigue-resistant lead-bismuth pump. Background Art

[0002] The lead-bismuth cooled fast reactor is one of the most promising reactor types among the candidate reactors for the fourth generation nuclear energy system. It can be used in offshore oil production, island development, power supply for big data centers, energy supply in remote areas, and special nuclear power. The lead-bismuth pump is the "heart" of the lead-bismuth reactor and the only rotating equipment in the nuclear island of the reactor. The lead-bismuth medium it pumps is a high-temperature (above 360°C), high-density, and highly corrosive liquid metal. Its working conditions are extremely harsh, and the impeller of the lead-bismuth pump needs to withstand the test of high temperature, high turnover fatigue, and erosion.

[0003] Studies have shown that when the linear velocity of the impeller blade reaches 12m / s under high temperature conditions, the creep and erosion of the blades start from the tip, and the macroscopic manifestation is curling and dimensional degradation. Conventional impellers are mostly made of 304 or 316 stainless steel, and the degradation rate of the blade tip is shown in the attached figure. Figure 1 As shown in the table, the limit value of blade wear thickness is 5000μm. When a conventional impeller runs at a linear speed of 12m / s under high temperature conditions for 6 months, the wear thickness of its blades is 3435.3μm. Therefore, it is estimated that its maximum service life is only 0.7 years. The design life of the impeller for the lead-bismuth pump is 5 years, so the conventional impeller cannot reach this design life and it is difficult to meet the requirements of the lead-bismuth pump. Therefore, in order to ensure the service life of the impeller of the lead-bismuth pump in high temperature and high speed lead-bismuth media, it is necessary to optimize the material and manufacturing process of the impeller. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for manufacturing a high-cycle fatigue resistant lead-bismuth pump impeller, to solve the technical problem of excessively rapid blade degradation of the lead-bismuth pump impeller, and to achieve the effect of increasing the service life of the lead-bismuth pump impeller.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for manufacturing an impeller for a high-cycle fatigue-resistant lead-bismuth pump comprises the following steps: 1) obtaining an impeller hub; 2) fusing a plurality of dissimilar alloys on the impeller hub using a multi-gradient fuse arc forming process to obtain an impeller blade whose hardness increases from its root to its end.

[0006] Furthermore, the plurality of heterogeneous alloys include 22Cr12NiWMoV and Fe310M, and the impeller blades include a middle layer and a hard layer connected in sequence from their root to their end, the middle layer is formed by 22Cr12NiWMoV surfacing, and the hard layer is formed by Fe310M surfacing.

[0007] Further, in the direction from the root to the end thereof, the middle layer is divided into a first surfacing layer and a second surfacing layer, and the hard layer is divided into a third surfacing layer and a fourth surfacing layer.

[0008] Furthermore, the hardness increase of the third weld overlay layer and the fourth weld overlay layer is less than or equal to 20%.

[0009] Furthermore, a first transition layer is formed by overlay welding between the impeller hub and the first overlay welding layer, a second transition layer is formed by overlay welding between the first overlay welding layer and the second overlay welding layer, a third transition layer is formed by overlay welding between the second overlay welding layer and the third overlay welding layer, and a fourth transition layer is formed by overlay welding between the third overlay welding layer and the fourth overlay welding layer, and each transition layer is austenitic stainless steel.

[0010] Furthermore, each transition layer is formed by ER309 surfacing.

[0011] Furthermore, the size ranges of the first transition layer, the first weld overlay layer, the second transition layer, the second weld overlay layer, the third transition layer, the third weld overlay layer, the fourth transition layer and the fourth weld overlay layer from the root to the end of the impeller blade are 0%-10%, 10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80% and 80%-100% respectively.

[0012] Furthermore, step 1) includes the following sub-steps: 11) forging to obtain a hub blank; 12) performing a solid solution treatment on the hub blank; 13) performing surface processing on the hub blank and removing excess substrate to obtain an impeller hub.

[0013] Furthermore, the manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention also includes the steps of 3) detecting the hardness of various locations on the impeller blades, and 4) fine-machining the impeller blades and selecting a tool for fine-machining according to the hardness of the processed parts.

[0014] The present invention also includes an impeller for a high cycle fatigue resistant lead-bismuth pump, wherein the impeller is manufactured by the manufacturing method as described above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention is based on a multi-gradient fuse arc forming process, and adopts a variety of heterogeneous alloys to fuse and form the impeller blades on the impeller hub, so that the hardness of the impeller blades presents a gradient distribution in the width direction of the impeller blades, so that the high-strain parts have better creep resistance and erosion resistance, which is beneficial to reduce the wear and degradation rate of the impeller blade tip in high-temperature, high-speed lead-bismuth media, and improve the service life of the lead-bismuth pump impeller.

[0016] 2. The manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention adopts 22Cr12NiWMoV and Fe310M to form the middle layer and the hard layer respectively in the direction from the root to the end of the impeller blade; on the premise of ensuring that the hardness of the end meets the use requirements, the impeller blades are gradient-formed with a variety of heterogeneous alloys, and the hardness is gradient-distributed, which can reduce the possibility of blade breakage during processing or use.

[0017] 3. In the manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention, the middle layer is divided into a first surfacing layer and a second surfacing layer, the hard layer is divided into a third surfacing layer and a fourth surfacing layer, and a transition layer is arranged between two adjacent surfacing layers. The transition layer is austenitic stainless steel, which is used for fusion welding to connect the dissimilar alloys of the two adjacent surfacing layers and share the stress of the cemented carbide under high and low temperature and stress conditions, which can effectively reduce the possibility of cracks in the molten pool of dissimilar cemented carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A table showing the degradation rate of the conventional stainless steel impeller tip as described in the background art; Figure 2 A table showing the material and hardness of the high cycle fatigue resistant impeller blade fuse for the lead-bismuth pump described in the embodiment; Figure 3 This is a table showing the degradation rate of the tip of the high cycle fatigue resistant impeller of the lead-bismuth pump described in the embodiment. DETAILED DESCRIPTION

[0019] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0020] Embodiment: A method for manufacturing an impeller for a high-cycle fatigue-resistant lead-bismuth pump comprises the following steps: 1) obtaining an impeller hub; 2) fusing a plurality of dissimilar alloys on the impeller hub using a multi-gradient fuse arc forming process to obtain an impeller blade whose hardness increases from its root to its end.

[0021] The manufacturing method of the high-cycle fatigue resistant impeller for a lead-bismuth pump described in the present invention is based on a multi-gradient fuse arc forming process, and uses a variety of heterogeneous alloys to fuse and form impeller blades on the impeller hub, so that the hardness of the impeller blades presents a gradient distribution in the direction of their own width, so that the high-strain position has better creep resistance and erosion resistance, which is beneficial to reducing the wear and degradation rate of the impeller blade tip in high-temperature, high-speed lead-bismuth media, and improving the service life of the impeller for the lead-bismuth pump; therefore, the manufacturing method described in the present invention can effectively solve the problem of excessively fast blade degradation rate of the impeller for the lead-bismuth pump, and achieve the effect of improving the service life of the impeller for the lead-bismuth pump.

[0022] Specifically, step 1) includes the following sub-steps: 11) forging the shape to obtain a hub blank (determined according to the impeller size); 12) performing a solid solution treatment on the hub blank; 13) performing a surface rough machining on the hub blank to remove excess substrate (roughness and machining allowance are not limited) to obtain an impeller hub; In this way, the impeller hub is formed by forging, which is conducive to ensuring the long-term stable operation of the impeller in a high-temperature lead-bismuth environment and avoiding slag flipping, gas flipping and other phenomena during the multi-gradient fuse process; the surface of the hub blank is processed by CNC machining and strictly processed according to the three-dimensional dimensions to ensure high dimensional accuracy and good surface finish.

[0023] See also Figure 2 In step 2), the multiple dissimilar alloys include 22Cr12NiWMoV and Fe310M, the multiple dissimilar alloys include 22Cr12NiWMoV and Fe310M, the impeller blades include an intermediate layer and a hard layer connected in sequence from their root to the end, the intermediate layer is formed by 22Cr12NiWMoV surfacing, and the hard layer is formed by Fe310M surfacing.

[0024] In this way, due to the influence of the blade position angle, the lead-bismuth inlet and outlet edges are subject to the largest medium attack angle and the largest creep deformation, so the inlet and outlet edges need to be hardened. The Co-based and Ni-based welding materials used in conventional hardening methods cannot be used in the fourth-generation lead-bismuth nuclear power reactor, and only Fe-based welding materials can be selected as the hardening part; and due to the problem of attack angle force, the thickness of the cladding layer is large, and at this time, multi-layer cemented carbide welding will cause crack tendency, so two types of cemented carbide welding materials with different hardness are required to cooperate with the layer-by-layer dilution of ER309 welding materials between each hard welding layer to achieve a gradient trend of gradually increasing hardness, so as to reduce the sensitivity of high-cycle fatigue in the high-attack angle stress zone when the impeller is subjected to high-frequency high-temperature conversion shock during the operation of the lead-bismuth pump, thereby improving the life of the impeller.

[0025] Specifically, in this embodiment, in the direction from the root to the end, the middle layer is divided into a first surfacing layer and a second surfacing layer, and the hard layer is divided into a third surfacing layer and a fourth surfacing layer, and the hardness of the impeller blade is increased from the inside to the outside to more than 45 HRC; In this way, the hard layer adopts a "sandwich" gradient structure to facilitate the low hardness ER309, high hardness 22Cr12NiWMoV and high hardness F310M hard layers. The stress caused by the hardness gradient is adjusted through welding dilution. ER309 is used as a soft layer to reduce the crack risk caused by the expansion force of the high hardness weld layer under temperature fluctuations; and the hardness is progressively increased layer by layer to prevent problems such as tool jumping during processing and seam cracking during creep.

[0026] And ensure that the hardness increase of the third and fourth cladding layers is less than or equal to 20%; in this embodiment, the hardness distribution of each cladding layer is as follows Figure 2 As shown; In this way, if the designed cladding thickness is small and the hardness of the two adjacent hard cladding layers is higher than 8-10HRC, the dilution effect of the softer transition layer formed by ER309 will become worse, and the effect of reducing the crack risk caused by the expansion force of the high-hardness weld layer will be greatly reduced.

[0027] See also Figure 2 A first transition layer is formed by surfacing welding between the impeller hub and the first surfacing layer, a second transition layer is formed by surfacing welding between the first surfacing layer and the second surfacing layer, a third transition layer is formed by surfacing welding between the second surfacing layer and the third surfacing layer, and a fourth transition layer is formed by surfacing welding between the third surfacing layer and the fourth surfacing layer, and each transition layer is austenitic stainless steel; in this embodiment, each transition layer is formed by surfacing welding with ER309 welding wire, which is a stainless steel welding wire characterized by being able to form a metal with an ultra-low carbon austenitic structure; In this way, the present invention adopts austenitic stainless steel as the transition layer for welding of dissimilar alloys, and specifically adopts softer ER309 welding wire to share the stress of cemented carbide under high and low temperature and stress conditions, which can effectively reduce the possibility of cracks in dissimilar cemented carbide during subsequent processes such as welding, heat treatment, processing and use.

[0028] See also Figure 2 In this embodiment, the impeller blades manufactured by the manufacturing method have a first transition layer, a first cladding layer, a second transition layer, a second cladding layer, a third transition layer, a third cladding layer, a fourth transition layer and a fourth cladding layer whose size ranges from the root to the end of the impeller blade are 0%-10%, 10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80% and 80%-100% respectively, and the size ranges correspond to the size ratios of the welding thicknesses of the cladding layers and the transition layers; the hardness averages of the first transition layer, the first cladding layer, the second transition layer, the second cladding layer, the third transition layer, the third cladding layer, the fourth transition layer and the fourth cladding layer are 18HRC, 35HRC, 23HRC, 38HRC, 29HRC, 45HRC, 31HRC and 51HRC respectively.

[0029] The manufacturing method of the present invention also includes the steps of 3) detecting the hardness of various locations on the impeller blades, and 4) fine-machining the impeller blades and selecting a tool for fine-machining according to the hardness of the processed parts; in this way, the hardness of the impeller blades is first detected to ensure that the quality meets the standard, and then the corresponding tool is selected according to the hardness to avoid damaging the tool and ensure smooth fine-machining.

[0030] In order to verify the feasibility of the manufacturing method of the present invention, the impeller manufactured by the manufacturing method was installed in a lead-bismuth pump to transport the lead-bismuth medium, and the blade part of the impeller was operated at a linear speed of 12m / s under high temperature conditions for 6 months. The impeller was then taken out for testing. The test results are as follows: Figure 3 As shown, the tip wear thickness of the impeller blade is 304 μm, and based on the life loss limit value of 5000 μm, the estimated limit life is 8.22 years, while the design life of the impeller for the lead-bismuth pump is 5 years. Therefore, the impeller manufactured by the manufacturing method of the present invention can better meet the requirements of the lead-bismuth pump.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for manufacturing an impeller for a high cycle fatigue resistant lead-bismuth pump, characterized in that: The method comprises the following steps: 1) obtaining an impeller hub; 2) using a multi-gradient fuse arc forming process to fuse and form a plurality of dissimilar alloys on the impeller hub to obtain an impeller blade whose hardness increases from the root to the end.

2. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 1, characterized in that: The multiple heterogeneous alloys include 22Cr12NiWMoV and Fe310M. The impeller blades include an intermediate layer and a hard layer connected in sequence from their root to the end. The intermediate layer is formed by 22Cr12NiWMoV surfacing, and the hard layer is formed by Fe310M surfacing.

3. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 2, characterized in that: In the direction from its root to the end, the middle layer is divided into a first surfacing layer and a second surfacing layer, and the hard layer is divided into a third surfacing layer and a fourth surfacing layer.

4. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 3, characterized in that: The hardness increase of the third weld overlay layer and the fourth weld overlay layer is less than or equal to 20%.

5. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 3, characterized in that: A first transition layer is formed by overlay welding between the impeller hub and the first overlay welding layer, a second transition layer is formed by overlay welding between the first overlay welding layer and the second overlay welding layer, a third transition layer is formed by overlay welding between the second overlay welding layer and the third overlay welding layer, and a fourth transition layer is formed by overlay welding between the third overlay welding layer and the fourth overlay welding layer, and each transition layer is austenitic stainless steel.

6. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 5, characterized in that: Each transition layer is formed by ER309 surfacing.

7. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 5, characterized in that: The size ranges of the first transition layer, the first weld overlay layer, the second transition layer, the second weld overlay layer, the third transition layer, the third weld overlay layer, the fourth transition layer and the fourth weld overlay layer from the root to the end of the impeller blade are 0%-10%, 10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80% and 80%-100% respectively.

8. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 1, characterized in that: Step 1) includes the following sub-steps: 11) forging to obtain a hub blank; 12) performing a solid solution treatment on the hub blank; 13) performing surface processing on the hub blank and removing excess substrate to obtain an impeller hub.

9. The method for manufacturing a high cycle fatigue resistant lead-bismuth pump impeller according to claim 1, characterized in that: The method also includes the steps of 3) detecting the hardness of various locations on the impeller blades, and 4) performing fine machining on the impeller blades, and selecting a tool for fine machining according to the hardness of the machining location.

10. An impeller for a high cycle fatigue resistant lead-bismuth pump, characterized in that: The impeller is manufactured by the manufacturing method according to any one of claims 1 to 9.

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