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

Abstract

The application discloses a manufacturing method of a high-cycle fatigue resistant impeller for a lead bismuth pump. The method is based on a multi-gradient fuse electric arc forming process, and the impeller blade is formed by sequentially connecting an intermediate layer and a hard layer from the root to the end of the blade. The intermediate layer is formed by 22Cr12NiWMoV surfacing, and the hard layer is formed by Fe310M surfacing. The intermediate 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. A transition layer formed by austenitic stainless steel surfacing is arranged between the adjacent two surfacing layers. The impeller blade is formed by multiple heterogeneous alloy gradient forming, so that the hardness increases from inside to outside. The transition layer is used for fusion welding connection of the heterogeneous alloys of the adjacent two surfacing layers, and the possibility of cracks in the heterogeneous hard alloy molten pool is reduced. The impeller blade prepared by the method has good anti-creep and erosion resistance performance at high strain parts, which is beneficial to reducing the wear and degradation speed of the tip of the impeller blade in a lead bismuth medium at high temperature and high speed, and improving the service life of the impeller for the lead bismuth pump.

Description

Technical Field

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

[0002] Lead-bismuth cooled fast reactors are among the most promising reactor types for Generation IV nuclear energy systems, with applications in offshore oil extraction, island development, power supply for big data centers, energy supply for remote areas, and special nuclear power applications. The lead-bismuth pump is the "heart" of the lead-bismuth reactor, the only rotating device within the reactor's nuclear island. It pumps lead-bismuth media that is a high-temperature (above 360°C), high-density, and highly corrosive liquid metal, operating under extremely harsh conditions. The impeller of the lead-bismuth pump must withstand high temperatures, high-cycle fatigue, and erosion.

[0003] Studies have shown that when the linear velocity of the impeller blades reaches 12 m / s under high-temperature conditions, blade creep and erosion begin at the tip, macroscopically manifesting as edge curling and dimensional degradation. Conventional impellers mostly use 304 or 316 stainless steel, and the degradation rate at the blade tips is shown in the attached figure. Figure 1 As shown in the table, the limit value of its blade wear thickness is 5000μm. When a conventional impeller operates at a linear speed of 12m / s for 6 months under high temperature conditions, the wear thickness of its blades is 3435.3μm. Therefore, its service life is estimated to be only 0.7 years. The design service life of the impeller for lead-bismuth pumps is 5 years. Therefore, conventional impellers cannot reach this design life and cannot meet the requirements of lead-bismuth pumps. 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 impeller material and manufacturing process. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of this invention is to provide a manufacturing method for a high-cycle fatigue resistant impeller for lead-bismuth pumps, thereby solving the technical problem of excessively rapid blade degradation in impellers for lead-bismuth pumps and improving the service life of impellers for lead-bismuth pumps.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for manufacturing an impeller for a high-cycle fatigue-resistant lead-bismuth pump includes the following steps: 1) obtaining an impeller hub; 2) using a multi-gradient fused wire arc forming process to fuse multiple dissimilar alloys on the impeller hub to obtain impeller blades with hardness increasing from the root to the tip.

[0006] Furthermore, the various dissimilar alloys include 22Cr12NiWMoV and Fe310M, and the impeller blades include a middle layer and a hard layer connected sequentially from the root to the tip. The middle layer is formed by welding 22Cr12NiWMoV, and the hard layer is formed by welding Fe310M.

[0007] Furthermore, in the direction from its root to its end, the intermediate layer is divided into a first weld overlay layer and a second weld overlay layer, and the hard layer is divided into a third weld overlay layer and a fourth weld overlay layer.

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

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

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

[0011] Furthermore, the dimensions 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 tip of the impeller blade, are respectively 0%-10%, 10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, and 80%-100%.

[0012] Further, step 1) includes the following sub-steps: 11) forging to obtain a hub blank; 12) performing a 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 further includes step 3) detecting the hardness of various parts on the impeller blades, and step 4) performing precision machining on the impeller blades, and selecting the precision machining tool according to the hardness of the machining part.

[0014] The present invention also includes an impeller for a high-cycle fatigue resistant lead-bismuth pump, the impeller being manufactured using the method 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 fused wire arc forming process, and uses a variety of dissimilar alloys to fuse and form impeller blades on the impeller hub. This makes the hardness of the impeller blades exhibit a gradient distribution in the width direction, so that the high-strain parts have better creep resistance and erosion resistance. This 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 lead-bismuth pump impeller.

[0016] 2. The manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention involves sequentially forming an intermediate layer and a hard layer using 22Cr12NiWMoV and Fe310M respectively in the direction from the root to the end of the impeller blade; under the premise of ensuring that the end hardness meets the usage requirements, the impeller blade is formed by gradient molding of various dissimilar alloys, and the hardness is distributed in a gradient, which can reduce the possibility of blade breakage during processing or use.

[0017] 3. The manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention includes an intermediate layer divided into a first weld overlay layer and a second weld overlay layer, a hard layer divided into a third weld overlay layer and a fourth weld overlay layer, and a transition layer is provided between two adjacent weld overlay layers. The transition layer is austenitic stainless steel and is used to weld dissimilar alloys between two adjacent weld overlay layers and to share the stress of the hard alloy under high and low temperature and stress conditions, which can effectively reduce the possibility of cracks appearing in the molten pool of dissimilar hard alloys. Attached Figure Description

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

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] Example: A method for manufacturing an impeller for a high-cycle fatigue resistant lead-bismuth pump, comprising the following steps: 1) obtaining an impeller hub; 2) using a multi-gradient fused wire arc forming process to fuse multiple dissimilar alloys on the impeller hub to obtain impeller blades with hardness increasing from the root to the tip.

[0021] The manufacturing method of the high-cycle fatigue resistant lead-bismuth pump impeller of the present invention is based on a multi-gradient fused wire arc forming process, and uses a variety of dissimilar alloys to fuse and form impeller blades on the impeller hub. This results in a gradient distribution of hardness in the impeller blades along their width, giving high-strain areas better creep resistance and erosion resistance. This helps reduce the wear and degradation rate of the impeller blade tips in high-temperature, high-speed lead-bismuth media, thereby increasing the service life of the lead-bismuth pump impeller. Therefore, the manufacturing method of the present invention can effectively solve the problem of excessively rapid blade degradation in lead-bismuth pump impellers, achieving the effect of improving the service life of lead-bismuth pump impellers.

[0022] Specifically, step 1) includes the following sub-steps: 11) Forging the shape to obtain the hub blank (determined according to the impeller size); 12) Performing a solution treatment on the hub blank; 13) Performing surface roughing on the hub blank to remove excess substrate (roughness and machining allowance are not limited) to obtain the impeller hub. In this way, the impeller hub is formed by forging, which helps to ensure the long-term stable operation of the impeller in the high-temperature lead-bismuth environment and avoids phenomena such as slag and gas spillage during multi-gradient melting. The surface of the hub blank is machined by CNC machining, strictly according to the three-dimensional dimensions, to ensure high dimensional accuracy and good surface finish.

[0023] Please see Figure 2 In step 2), the various dissimilar alloys include 22Cr12NiWMoV and Fe310M. The impeller blades include a middle layer and a hard layer connected sequentially from the root to the tip. The middle layer is formed by welding 22Cr12NiWMoV and the hard layer is formed by welding Fe310M.

[0024] Thus, due to the influence of the blade position angle, the lead-bismuth inlet and outlet edges experience the greatest angle of attack and creep deformation from the medium. Therefore, the inlet and outlet edges need to be hardened. 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 for the hardening area. Due to the angle of attack force, the weld layer thickness is relatively large, and multi-layer hard alloy welding will induce cracking tendency. Therefore, two types of hard alloy welding materials with different hardness are required to cooperate with the ER309 welding material for gradual dilution between each hard weld layer to achieve a gradient trend of gradually increasing hardness. This is to reduce the sensitivity of the impeller to high-cycle fatigue in the high angle of attack stress area when the impeller is subjected to high-frequency high and low temperature switching impact during the operation of the lead-bismuth pump, thereby improving the impeller life.

[0025] Specifically, in this embodiment, in the direction from its root to its end, the intermediate layer is divided into a first weld overlay layer and a second weld overlay layer, the hard layer is divided into a third weld overlay layer and a fourth weld overlay layer, and the hardness of the impeller blades increases sequentially from the inside to the outside to above 45 HRC. In this way, the hard layer adopts a "sandwich" gradient structure to facilitate the adjustment of the stress caused by the hardness gradient through welding dilution of the relatively low-hardness ER309, the relatively high-hardness 22Cr12NiWMoV, and the high-hardness F310M hard layer. ER309 acts as a soft layer to reduce the risk of cracking caused by the expansion force of the high-hardness weld layer under temperature fluctuations. The hardness is progressively increased layer by layer to prevent problems such as tool skipping during processing and joint cracking during creep.

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

[0027] Please see Figure 2 A first transition layer is formed by welding between the impeller hub and the first weld overlay layer; a second transition layer is formed by welding between the first and second weld overlay layers; a third transition layer is formed by welding between the second and third weld overlay layers; and a fourth transition layer is formed by welding between the third and fourth weld overlay layers. Each transition layer is made of austenitic stainless steel. In this embodiment, each transition layer is formed by welding with ER309 welding wire. ER309 welding wire is a type of stainless steel welding wire, characterized by its ability to form an ultra-low carbon austenitic structure. Thus, the present invention uses austenitic stainless steel as the transition layer for dissimilar alloy welding, and specifically uses ER309 welding wire with a relatively soft texture, so as to share the stress of the cemented carbide under high and low temperature and stress conditions, which can effectively reduce the possibility of cracks in dissimilar cemented carbide during welding, heat treatment, processing and other subsequent processes, as well as during use.

[0028] Please see Figure 2 In this embodiment, the impeller blades manufactured using the aforementioned manufacturing method have the following dimensions from the root to the tip: 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 have dimensions ranging from 0%-10%, 10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, and 80%-100%, respectively. These dimensions correspond to the dimensional ratio of the welding thickness of each weld overlay layer and transition layer. The average hardness values ​​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 are 18HRC, 35HRC, 23HRC, 38HRC, 29HRC, 45HRC, 31HRC, and 51HRC, respectively.

[0029] The manufacturing method of the present invention further includes step 3) detecting the hardness of various parts on the impeller blades, and step 4) performing finishing on the impeller blades and selecting the finishing tool according to the hardness of the machining part; in this way, the hardness of the impeller blades is first detected to ensure that the quality meets the standards, and then the corresponding tool is selected according to the different hardness to avoid damaging the tool and ensure that the finishing is carried out smoothly.

[0030] To verify the feasibility of the manufacturing method described in this invention, the impeller manufactured by this method was installed in a lead-bismuth pump to transport lead-bismuth media. The blade portion of the impeller was then subjected to high temperature conditions and operated at a linear velocity of 12 m / s for 6 months. The impeller was then removed for testing, and the test results are as follows: Figure 3 As shown, the wear thickness at the tip of the impeller blade is 304 μm. Based on the life loss limit of 5000 μm, the estimated lifespan is 8.22 years. The design lifespan of the impeller for the lead-bismuth pump is 5 years. Therefore, the impeller manufactured by the method described in this 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 solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within 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 process includes the following steps: 1) Obtaining the impeller hub; 2) Using a multi-gradient fused wire arc forming process, multiple dissimilar alloys are fused and formed on the impeller hub to obtain impeller blades with increasing hardness from the root to the tip. The various dissimilar alloys include 22Cr12NiWMoV and Fe310M. The impeller blades consist of a middle layer and a hard layer connected sequentially from the root to the tip. The middle layer is formed by welding 22Cr12NiWMoV, and the hard layer is formed by welding Fe310M. In the direction from its root to its end, the intermediate layer is divided into the first weld overlay layer and the second weld overlay layer, and the hard layer is divided into the third weld overlay layer and the fourth weld overlay layer. A first transition layer is formed by welding between the impeller hub and the first weld overlay layer; a second transition layer is formed by welding between the first and second weld overlay layers; a third transition layer is formed by welding between the second and third weld overlay layers; and a fourth transition layer is formed by welding between the third and fourth weld overlay layers. Each transition layer is made of austenitic stainless steel. The dimensions 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 tip of the impeller blade, are 0%-10%, 10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, and 80%-100%, respectively.

2. The manufacturing method of a high-cycle fatigue resistant lead-bismuth pump impeller according to claim 1, characterized in that: The hardness increase of the third and fourth weld layers is less than or equal to 20%.

3. The manufacturing method of a high-cycle fatigue resistant lead-bismuth pump impeller according to claim 1, characterized in that: Each transition layer is formed by ER309 overlay welding.

4. The manufacturing method of an impeller for a high-cycle fatigue resistant lead-bismuth pump according to claim 1, characterized in that: Step 1) includes the following sub-steps: 11) Forging to obtain a hub blank; 12) Solution treatment of the hub blank; 13) Surface machining of the hub blank and removal of excess substrate to obtain an impeller hub.

5. The method for manufacturing an impeller for a high-cycle fatigue resistant lead-bismuth pump according to claim 1, characterized in that: It also includes step 3) detecting the hardness of various parts of the impeller blades, and step 4) performing finishing on the impeller blades and selecting finishing tools according to the hardness of the machining area.

6. An impeller for a high-cycle fatigue resistant lead-bismuth pump, characterized in that: The impeller is manufactured using the manufacturing method described in any one of claims 1-5.

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