Integrated nuclear power pump shaft and new shaft machining process and old shaft repairing process thereof

Abstract

The application discloses an integrated nuclear power pump shaft which is divided into a body section and a bearing section, the bearing section is located in the middle of the body section, the diameter of the bearing section is larger than that of the body section, and the bearing section and the body section are connected through a round angle R, and the outer circle of the bearing section is coated with a high wear resistance coating. The outer circle D of the bearing section is determined according to the size of the bearing sleeve matched with the nuclear power pump shaft. The integrated nuclear power pump shaft of the application replaces the shaft sleeve by designing the bearing section at the position of the original shaft sleeve, prolongs the service life of the nuclear power pump shaft, and improves the repair efficiency after the pump shaft is taken offline.

Description

Technical Field

[0001] This invention belongs to the field of mechanical design and material surface technology, specifically relating to the design of an integrated nuclear power pump shaft and its related processes. Background Technology

[0002] When a nuclear power plant pump shaft is in operation, its middle section needs to be fitted with a bearing. Traditionally, a detachable bearing sleeve (interference fit) is installed in the middle section. However, due to friction, this type of structure is prone to cracking. During use and after shutdown repair, the following problems arise: 1. When the bearing sleeve shows severe wear, most of the pump shafts that mesh with it no longer meet the requirements and cannot continue to be used, causing the pump shaft to be scrapped after one service cycle, resulting in extremely high operating costs (the lifespan of nuclear power plant pump shafts is limited by the bearing sleeve); 2. When the bearing sleeve wear is minor, a small number of pump shafts can be repaired after shutdown. The repair process requires the removal of the bushing. Since the bushing and pump shaft are interference fit, the bushing needs to be heated during disassembly. This operation will increase the deformation of the pump shaft, increasing the difficulty of repair. The bushing removal process can easily cause scratches on the surface of the pump shaft, increasing the workload and repair cycle. On the other hand, when the bearing bushing is reassembled after the pump shaft is repaired, it may cause scratches on other parts of the pump shaft, thereby reducing the accuracy of the pump shaft. In other words, in a few pump shafts, the disassembly and installation of the bearing bushing will cause secondary damage to the pump shaft during the offline repair and reassembly process, reducing the accuracy of the pump shaft. Summary of the Invention

[0003] The problem this invention aims to solve is to provide an integrated nuclear power pump shaft. It incorporates a bearing retainer at the original shaft sleeve location, replacing the original sleeve and extending the pump shaft's service life while improving post-production repair efficiency. Furthermore, this invention provides a new shaft machining process and a repair process for the integrated nuclear power pump shaft, enabling cyclical repair of the pump shaft.

[0004] The present invention discloses an integrated nuclear power pump shaft, which is divided into a body section and a bearing section. The bearing section is located in the middle of the body section, its diameter is larger than that of the body section, and it is connected to the body section by a fillet R. The outer circle of the bearing section is covered with a high wear-resistant coating.

[0005] Furthermore, the outer diameter D of the bearing bushing is determined based on the dimensions of the bearing bushing that the nuclear power pump shaft is to mate with.

[0006] When the integrated nuclear power pump shaft of this invention is a new component, the specific steps of its processing technology are as follows:

[0007] (1) Making the blank: The shaft blank is formed by forging;

[0008] (2) Machining: Machining the shaft blank to the dimensions and accuracy required by the drawing, with the middle section machined into a bearing stop;

[0009] (3) Bearing reinforcement: Select thermal spraying or laser cladding to prepare a high wear-resistant coating on the surface of the bearing;

[0010] (4) Grinding: Grind the bearing stop and body to the requirements of the drawing (dimensions, surface roughness);

[0011] (5) Post-inspection: After grinding, the bearing section is subjected to colorimetric and ultrasonic testing to ensure that the coating is free of defects such as cracks, pores, and peeling.

[0012] Furthermore, the specific preparation method of the bearing retainer coating in step (3) is as follows: for those with particularly severe vibration or impact during service, laser cladding is used; for the rest, supersonic flame spraying is used.

[0013] When the integrated nuclear power pump shaft of the present invention is used as a repair component, the specific steps of its repair process are as follows:

[0014] (1) Grinding: Grinding is performed on the worn areas according to the surface condition of the shaft to remove the surface corrosion layer and fatigue layer of the shaft. Different repair methods are determined according to the wear defect depth of the body and bearing.

[0015] (2) Pre-inspection: Perform dye penetrant testing and ultrasonic testing on the ground shaft to ensure that there are no defects such as cracks, pores, or corrosion.

[0016] (3) Coating preparation: The dimensions and surface are restored by preparing a coating on the ground body and bearing section. The preparation method is thermal spraying or laser cladding.

[0017] (4) Grinding: Precision grinding of bearing bearings and bearing bodies to the final required dimensions and tolerances;

[0018] (5) Post-inspection: After grinding, the shaft is subjected to dye penetrant testing and ultrasonic testing to ensure that the pump shaft is free of defects such as cracks, pores, and peeling.

[0019] Furthermore, in step 3: for areas with wear defect depth (grinding amount) > 0.3 mm, laser cladding is used for dimensional restoration and surface strengthening; for areas with wear defect depth (grinding amount) ≤ 0.3 mm, thermal spraying is used for dimensional restoration and surface strengthening.

[0020] Furthermore, when both the body and the bearing retainer are severely worn (wear defect depth > 0.3 mm), the wear defect of the shaft is first removed by grinding, and then the dimensions and reinforced surfaces of both the body and the bearing retainer are restored by laser cladding. Finally, they are ground to the final required dimensions and tolerances.

[0021] Furthermore, when the main body is severely worn (wear defect depth > 0.3 mm) and the bearing retainer is lightly worn (wear defect depth ≤ 0.3 mm), the wear defect of the shaft is first removed by grinding, then the main body is repaired by laser cladding, then the bearing retainer is repaired by thermal spraying, and finally, the bearing retainer and the main body are ground to the final required dimensions and tolerances based on the bearing retainer.

[0022] Furthermore, when the wear of the main body is relatively light (wear defect depth ≤ 0.3 mm) and the bearing retainer is severely worn (wear defect depth > 0.3 mm), the wear defect of the shaft is first removed by grinding, then the bearing retainer is repaired by laser cladding, then the main body is repaired by thermal spraying, and finally, the main body and bearing retainer are ground to the final required dimensions and tolerances based on the main body.

[0023] Furthermore, when the wear of both the body and the bearing retainer is relatively light (wear defect depth ≤ 0.3mm), the wear defect of the shaft is first removed by grinding, and then thermal spraying is used to restore the dimensions and strengthen the surface of both the body and the bearing retainer. Finally, they are ground to the final required dimensions and tolerances.

[0024] The advantages of the integrated nuclear power pump shaft of this invention are as follows: First, the bearing retainer and the pump shaft body are an integrated structure, and a high wear-resistant coating is prepared at the bearing retainer position, thereby replacing the existing bearing bushing. This significantly improves the wear resistance of the pump shaft bearing retainer, avoiding the pump shaft being taken off the production line in a short time due to wear failure of the original bearing bushing, thus extending the life of the nuclear power pump shaft and reducing production costs. Second, when the integrated pump shaft is taken off the production line for repair after wear, there is no increased deformation of the pump shaft due to heating and disassembling the bushing, nor is there any scratching of the pump shaft surface during disassembly and assembly. This improves the accuracy of the pump shaft, reduces the workload and difficulty of pump shaft repair, and shortens the repair cycle. Third, the pump shaft can be cyclically repaired, significantly extending the service life of the pump shaft.

[0025] Therefore, the integrated nuclear power pump shaft of the present invention solves the problems of short service life and high difficulty of offline repair. It can extend the service life of nuclear power pump shaft, increase the number of repairs, thereby significantly reducing the use cost of nuclear power pump shaft and improving the repair efficiency after pump shaft is offline. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the integrated nuclear power pump shaft of the present invention.

[0027] Figure 2 yes Figure 1 Enlarged diagram of point A in the middle. Detailed Implementation

[0028] To better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] from Figure 1 , Figure 2 As can be seen, the present invention provides an integrated nuclear power pump shaft, which is divided into a body section and a bearing section. The bearing section is located in the middle of the body section, its diameter is larger than the diameter of the body section, and it is connected to the body section by a fillet R. The outer circle of the bearing section is covered with a high wear-resistant coating.

[0031] The outer diameter D of the bearing bushing is determined based on the dimensions of the bearing bushing that the nuclear power pump shaft is to be fitted with.

[0032] The high wear-resistant coating for bearing bearings is prepared by supersonic flame spraying or laser cladding: laser cladding is used for bearings that experience particularly severe vibration or impact during service; supersonic flame spraying is used for other bearings.

[0033] This invention relates to an integrated nuclear power pump shaft. A step of the same size as the original bushing is designed on the shaft body at the corresponding position, serving as a bearing stop and becoming an integral part of the pump shaft. This bearing stop replaces the original bearing bushing, and a highly wear-resistant coating is applied to the bearing stop to improve wear resistance, significantly extending the service life of the integrated nuclear power pump shaft. Furthermore, when the bearing stop in the integrated structure wears, the pump shaft can be repaired after production to meet usage requirements. In addition, since there is no bearing bushing, various problems such as increased deformation, increased repair difficulty, and reduced pump shaft precision during bearing bushing assembly and disassembly are avoided. Repair can be performed quickly and with guaranteed quality. In summary, this invention significantly extends the service life of the integrated nuclear power pump shaft, allows for cyclic repair, and significantly reduces the operating cost of the integrated nuclear power pump shaft.

[0034] In this invention, the integrated nuclear power pump shaft is referred to as the shaft body, and the shaft body excluding the bearing section is referred to as the main body.

[0035] Example 2

[0036] When the integrated nuclear power pump shaft is a new component, the specific steps of its processing are as follows:

[0037] (1) Making the blank: The shaft blank is formed by forging;

[0038] (2) Machining: Machining the shaft blank to the dimensions and accuracy required by the drawing, with the middle section machined into a bearing stop;

[0039] (3) Bearing reinforcement: Select thermal spraying or laser cladding to prepare a high wear-resistant coating on the surface of the bearing;

[0040] (4) Grinding: Grind the bearing stop and body to the requirements of the drawing (dimensions, surface roughness);

[0041] (5) Post-inspection: After grinding, the bearing section is subjected to colorimetric and ultrasonic testing to ensure that the coating is free of defects such as cracks, pores, and peeling.

[0042] The specific preparation method of the bearing retainer coating in step (3) is as follows: for cases where vibration or impact is particularly severe during service, laser cladding is used; for other cases, supersonic flame spraying is used. The high wear-resistant coating at the bearing retainer improves the wear resistance of this location, thereby extending the service life of the pump shaft.

[0043] Example 3

[0044] When the integrated nuclear power pump shaft is a repair component, the specific steps of its repair process are as follows:

[0045] (1) Grinding: Grinding is performed on the worn areas according to the surface condition of the shaft to remove the surface corrosion layer and fatigue layer of the shaft. Different repair methods are determined according to the wear defect depth of the body and bearing.

[0046] (2) Pre-inspection: Perform dye penetrant testing and ultrasonic testing on the ground shaft to ensure that there are no defects such as cracks, pores, or corrosion.

[0047] (3) Coating preparation: The dimensions and surface are restored by preparing a coating on the ground body and bearing section. The preparation method is thermal spraying or laser cladding.

[0048] (4) Grinding: Precision grinding of bearing bearings and bearing bodies to the final required dimensions and tolerances;

[0049] (5) Post-inspection: After grinding, the shaft is subjected to dye penetrant testing and ultrasonic testing to ensure that the pump shaft is free of defects such as cracks, pores, and peeling.

[0050] In step 3: for areas with wear defect depth (grinding amount) > 0.3 mm, laser cladding is used for dimensional restoration and surface strengthening; for areas with wear defect depth (grinding amount) ≤ 0.3 mm, thermal spraying is used for dimensional restoration and surface strengthening.

[0051] Example 4

[0052] When repairing the integrated nuclear power pump shaft of Unit 1 of a nuclear power plant, the shaft body and bearing retainer were severely worn (wear defect depth > 0.3 mm). Therefore, the wear defects of the shaft body were first removed by grinding, and then the dimensions and reinforced surfaces of the shaft body and bearing retainer were restored by laser cladding. Finally, the shaft body was ground to the required dimensions and tolerances.

[0053] During the repair process, since the repair methods for the body and the bearing are the same, the order of repair is not restricted; during grinding, the shaft segment with the least deformation is used as the reference.

[0054] Example 5

[0055] When repairing the integrated nuclear power pump shaft of Unit 2 of a nuclear power plant, due to severe wear on the main body (wear defect depth > 0.3 mm) and relatively light wear on the bearing retainer (wear defect depth ≤ 0.3 mm), the wear defects on the shaft were first removed by grinding. Then, the main body was repaired by laser cladding. Next, the bearing retainer was repaired by thermal spraying. Finally, the bearing retainer and the main body were ground to the final required dimensions and tolerances, using the bearing retainer as a reference.

[0056] Since the deformation caused by laser cladding is greater than that caused by thermal spraying, the main body is laser clad first, and then the bearing retainer is thermally sprayed. This ensures that the bearing retainer is not affected by the laser cladding and will not undergo secondary deformation, thus serving as a grinding reference. If the bearing retainer is thermally sprayed first, and then the main body is laser clad, the bearing retainer will undergo secondary deformation due to the laser cladding. In addition, the thermal spray coating is relatively thin, which may cause the shaft repair to lose its reference and the coating to wear through, thus affecting the overall repair quality of the nuclear power pump shaft.

[0057] Example 6

[0058] When repairing the integrated nuclear power pump shaft of Unit 3 of a nuclear power plant, since the wear of the main body is relatively light (wear defect depth ≤ 0.3 mm) and the bearing retainer is severely worn (wear defect depth > 0.3 mm), the wear defects of the shaft body are first removed by grinding, then the bearing retainer is repaired by laser cladding, then the main body is repaired by thermal spraying, and finally, based on the main body, the main body and bearing retainer are ground to the final required dimensions and tolerances.

[0059] Since the deformation caused by laser cladding is greater than that caused by thermal spraying, the bearing support is laser clad first, and then the main body is thermally sprayed. This ensures that the main body is not affected by the laser cladding and will not undergo secondary deformation, thus serving as a grinding reference. If the main body is thermally sprayed first, and then the bearing support is laser clad, the main body will undergo secondary deformation due to the laser cladding. In addition, the thermal spray coating is relatively thin, which may cause the shaft repair to lose its reference and the coating to wear through, thus affecting the overall repair quality of the nuclear power pump shaft.

[0060] Example 7

[0061] When repairing the integrated nuclear power pump shaft of Unit 4 of a nuclear power plant, since the wear of the body and bearing was relatively light (wear defect depth ≤0.3mm), the wear defects of the shaft were first removed by grinding, and then thermal spraying was used to restore the size and strengthen the surface of both the body and bearing. Finally, it was ground to the final required size and tolerance.

[0062] During the repair process, since the repair methods for the body and the bearing are the same, the order of repair is not restricted; during grinding, the shaft segment with the least deformation is used as the reference.

[0063] Surface modification technology can significantly improve the corrosion resistance and wear resistance of workpieces. Common surface modification technologies include electroplating, laser cladding, and thermal spraying. Electroplating has the advantages of low cost, high production efficiency, and good coating thickness uniformity, but it causes environmental pollution and is gradually being phased out. Laser cladding has advantages such as simple operation, high bonding strength of the cladding layer, and a wide selection of materials. Thermal spraying has advantages such as a wide range of material selection, high coating preparation efficiency, low thermal impact on the substrate, high coating uniformity, and the ability to meet performance requirements under different working conditions. After the coating is prepared, it can be ground according to the surface roughness requirements of the workpiece to complete the repair. Therefore, this invention selects thermal spraying and laser cladding as surface strengthening and dimensional restoration technologies.

[0064] The advantages of the integrated nuclear power pump shaft of this invention are as follows: First, the bearing retainer and the pump shaft body are an integrated structure, and a high wear-resistant coating is prepared at the bearing retainer position, thereby replacing the existing bearing bushing. This significantly improves the wear resistance of the pump shaft bearing retainer, avoiding the pump shaft being taken off the production line in a short time due to wear failure of the original bearing bushing, thus extending the life of the nuclear power pump shaft and reducing production costs. Second, when the integrated pump shaft is taken off the production line for repair after wear, there is no increased deformation of the pump shaft due to heating and disassembling the bushing, nor is there any scratching of the pump shaft surface during disassembly and assembly. This improves the accuracy of the pump shaft, reduces the workload and difficulty of pump shaft repair, and shortens the repair cycle. Third, the pump shaft can be cyclically repaired, significantly extending the service life of the pump shaft.

[0065] Therefore, the integrated nuclear power pump shaft of the present invention solves the problems of short service life and high difficulty of offline repair. It can extend the service life of nuclear power pump shaft, increase the number of repairs, thereby significantly reducing the use cost of nuclear power pump shaft and improving the repair efficiency after pump shaft is offline.

Claims

1. A repair process for an integrated nuclear power plant pump shaft, characterized by: The integrated nuclear power pump shaft consists of a main body section and a bearing retainer. The bearing retainer is located in the middle of the main body section, its diameter is larger than that of the main body section, and it transitions to the main body section through a fillet radius (R). The outer circumference of the bearing retainer is covered with a highly wear-resistant coating. (Repair process...) The process includes the following steps: (1) Grinding: Grinding is performed on the worn areas according to the surface condition of the shaft to remove the surface corrosion layer and fatigue layer of the shaft. Different repair methods are determined according to the wear defect depth of the body and bearing. (2) Pre-inspection: Colorimetric and ultrasonic testing are performed on the ground shaft to ensure that there are no cracks, pores, or corrosion defects. (3) Coating preparation: The ground body and bearing are restored to their dimensions and surface strengthened by preparing a coating. The preparation method is thermal spraying or laser cladding. For areas with wear defect depth > 0.3 mm, laser cladding is used to restore dimensions and strengthen the surface. For areas with a depth ≤ 0.3mm, thermal spraying is used to restore dimensions and strengthen surfaces; (4) Grinding: Grind the bearing section and body to the final required dimensions and tolerances; (5) Post-flaw detection: Perform colorimetric and ultrasonic flaw detection on the ground shaft to ensure that the pump shaft is free of cracks, pores, and peeling defects; In step (3): When the wear defect depth of the body is > 0.3mm and the wear defect depth of the bearing section is ≤ 0.3mm, first grind to remove the wear defect of the shaft, then use laser cladding to repair the body, then use thermal spraying to repair the bearing section, and finally use the bearing section as a reference to grind the bearing section and body to the final required dimensions and tolerances.

2. The repair process according to claim 1, characterized in that: The outer diameter D of the bearing is determined based on the size of the bearing bushing that the nuclear power pump shaft needs to fit.

3. The repair process according to claim 1, characterized in that: When the wear defect depth of the body and bearing retainer is >0.3mm, the wear defect of the shaft is first removed by grinding, and then the dimensions and reinforced surfaces of the body and bearing retainer are restored by laser cladding. Finally, they are ground to the final required dimensions and tolerances.

4. The repair process according to claim 1, characterized in that: When the wear defect depth of the main body is ≤0.3mm and the wear defect depth of the bearing stop is >0.3mm, the wear defect of the shaft is first removed by grinding, then the bearing stop is repaired by laser cladding, then the main body is repaired by thermal spraying, and finally the main body and bearing stop are ground to the final required size and tolerance based on the main body.

5. The repair process according to claim 1, characterized in that: When the wear defect depth of the body and bearing retainer is ≤0.3mm, the wear defect of the shaft is first removed by grinding, and then the dimensions and surface of the body and bearing retainer are restored by thermal spraying. Finally, they are ground to the final required dimensions and tolerances.

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