Method for processing pump shell of nuclear power main pump

Abstract

The present application belongs to the technical field of nuclear power main pump, and relates to a machining method of a pump shell of a nuclear power main pump, which can reduce cost. In the process of finishing the inner cavity of the pump shell by a 6.3m numerical control vertical lathe, the stroke of the ram in the horizontal direction is very small, and the one-time machining forming of the inner spherical surface cannot be completed, so segmented machining is adopted. In order to ensure the machining precision of the segmented machining, a reference step is arranged at the middle position of the machining stroke of the inner cavity of the pump shell by using the excess of the workpiece, as the tool setting reference in the segmented machining. After the pump shell forging is finished, stainless steel surfacing is carried out on the inner cavity of the pump shell, and after the stainless steel surfacing, the middle reference step is welded at the same position of the inner cavity of the pump shell, as the reference transfer for the segmented machining. The expensive five-axis numerical control planer milling machine or the five-axis numerical control boring machine is avoided to machine the pump shell, and the existing 6.3m numerical control vertical lathe can be used to finish the machining of the pump shell, which has the advantages of cost saving and machining precision guarantee.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power main pump technology, specifically relating to a method for processing the pump casing of a nuclear power main pump. Background Technology

[0002] The main pump (hereinafter referred to as the main pump) is a pump in the primary loop system of the nuclear island used to drive the circulation of coolant within the RCP (Reactor Coolant System). Located in the heart of the nuclear island, the main pump pumps hot water into the evaporator for heat conversion. It is crucial for controlling the water circulation in nuclear power plant operations and is considered a Class I piece of equipment. Each evaporator has one main pump. The main pump casing is very large and is a single, integrally molded structure. The internal shape of the main pump casing is complex, requiring high dimensional and positional precision, making its manufacturing process challenging.

[0003] For example Figure 3 The pump casing 1 shown has a through hole 101 at the top, a water inlet hole 102 at the bottom, and a water outlet hole 103 on the side. The through hole 101, water inlet hole 102, and water outlet hole 103 are all connected to the internal cavity of the pump casing 1. The through hole 101 and water inlet hole 102 are coaxially arranged with the vertical axis L1 of the pump casing 1 as the center, and the diameter of the through hole 101 is larger than the diameter of the water inlet hole 102. The axis L3 of the water outlet hole 103 is parallel to the horizontal axis L2 of the pump casing 1.

[0004] Typically, five-axis CNC gantry milling machines or five-axis CNC boring machines are used to process pump casing forgings, but the equipment investment cost is high. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for processing the pump casing of a nuclear power plant main pump, which can reduce costs.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for processing the pump casing of a nuclear power plant main pump, comprising the following steps:

[0007] S1, based on the vertical axis L1 of the pump casing, set a finishing reference A for finishing the side wall of the inlet hole located at the bottom of the pump casing, and set a finishing reference B for finishing the side wall of the through hole located at the top of the pump casing.

[0008] Based on the machined surface of the water outlet, the allowance is evenly distributed, and a finishing reference D is set for finishing the sidewall of the water outlet located on the side of the pump casing.

[0009] Based on the finishing datum D and the return height dimension, set the finishing datum C for finishing the outer end face of the through hole;

[0010] S2, Weld a segmented intermediate reference step at the lower part of the pump casing cavity to make the upper surface of the intermediate reference step horizontal; The intermediate reference step is a horizontally arranged annular structure and the axis of the intermediate reference step coincides with the vertical axis L1 of the pump casing 1.

[0011] S3, move the tool post into the inner cavity of the pump housing; start the machine tool and extend the vertically positioned ram into the pump housing from top to bottom, and install the tool post horizontally at the lower end of the ram; install the lathe tool on the tool post, so that the cutting edge of the lathe tool is away from the tool post;

[0012] S4 uses finishing references A, B, C, and D as the finishing references for the pump casing, and finishes the through hole, inlet hole, and outlet hole respectively; installs tool holders of different lengths according to the different degrees of curvature of the inner surface of the pump casing; and finishes the inner cavity of the pump casing by using a segmented machining method from top to bottom.

[0013] S5, stainless steel corrosion-resistant layer is welded onto the inner cavity of the pump casing;

[0014] S6, Repeat steps S1-S4 to finish the stainless steel weld overlay.

[0015] Furthermore, step S4 specifically includes the following steps: using finishing datum A as a datum, finishing the sidewall of the through hole; using finishing datum C as a datum, finishing the outer end face of the through hole;

[0016] Depending on the degree of curvature of the pump casing's inner surface, tool holders of different lengths are installed; the pump casing's inner surface is precision-machined using a top-to-bottom segmented machining method.

[0017] Turn the pump casing over so that the inlet hole is on top and the through hole is on the bottom. Using the finishing reference B as the reference, finish machine the side wall of the inlet hole.

[0018] Using the finishing datum D as a reference, finish the sidewall of the water outlet.

[0019] Furthermore, in step S3, the tool holder is hoisted into the inner cavity of the pump casing using a steel wire rope.

[0020] Furthermore, in step S2, an intermediate reference step for segmented processing is welded to the lower part of the pump casing inner cavity by means of overlay welding.

[0021] Compared with existing technologies, the beneficial effects of this invention are: This invention provides a method for machining the pump casing of a nuclear power plant main pump, which can reduce costs. It avoids using expensive five-axis CNC gantry milling machines or five-axis CNC boring machines to machine the pump casing; instead, it can achieve precision machining of the pump casing using an existing 6.3m CNC vertical lathe, which has the advantage of cost savings and can also ensure machining accuracy. Attached Figure Description

[0022] Figure 1This is a structural schematic diagram of an existing 6.3m CNC vertical lathe;

[0023] Figure 2 This is a top view of the ram extending into the pump casing in this invention.

[0024] Figure 3 This is a schematic diagram of the vertical cross-sectional structure of the pump casing in this invention;

[0025] Figure 4 This is a schematic diagram of the invention in which the tool holder is hoisted into the inner cavity of the pump casing using a steel wire rope, and then the lathe is started to extend the vertically arranged slide into the pump casing from top to bottom.

[0026] Figure 5 This is a schematic diagram of the lathe tool performing finishing in this invention;

[0027] Reference numerals in the attached drawings: 1-Pump casing; 101-Through hole; 102-Inlet hole; 103-Outlet hole; 2-Intermediate reference step; 3-Slide block; 4-Tool holder; 5-Lathe tool; 6-Wire rope; 7-Screw rod; 8-Crossbeam; 9-Frame; 10-Worktable. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] The processing method for the pump casing of a nuclear power plant main pump includes the following steps:

[0030] S1, based on the vertical axis L1 of the pump housing 1, a finishing reference A is set for finishing the side wall of the water inlet hole 102 located at the bottom of the pump housing 1, and a finishing reference B is set for finishing the side wall of the through hole 101 located at the top of the pump housing 1.

[0031] Based on the machined surface of the water outlet 103, the allowance is evenly distributed, and a finishing reference D is set for finishing the side wall of the water outlet 103 located on the side of the pump casing 1.

[0032] Based on the finishing datum D and the return height dimension, a finishing datum C is set for finishing the outer end face of the through hole 101.

[0033] The pump casing 1 is positioned with the through hole 101 on top and the water inlet hole 102 on the bottom, and placed on the worktable 10 of an existing 6.3m CNC vertical lathe.

[0034] S2, weld the intermediate reference step 2 for segmented machining at the lower part of the inner cavity of the pump casing 1, so that the upper surface of the intermediate reference step 2 is horizontal; the intermediate reference step 2 is a horizontally arranged ring structure, and the axis of the intermediate reference step 2 coincides with the vertical axis L1 of the pump casing 1.

[0035] Specifically, in step S2, the intermediate reference step 2 for segmented processing is welded to the lower part of the inner cavity of the pump housing 1 by means of overlay welding.

[0036] S3, move the tool holder 4 into the inner cavity of the pump housing 1; start the lathe and extend the vertically arranged slide 3 into the pump housing 1 from top to bottom, and install the tool holder 4 horizontally at the lower end of the slide 3; install the cutting tool 5 on the tool holder 4, so that the cutting edge of the cutting tool 5 is away from the tool holder 4.

[0037] Preferably, in step S3, the tool holder 4 is hoisted into the inner cavity of the pump casing 1 using a steel wire rope 6.

[0038] S4, using finishing references A, B, C and D as finishing references for pump housing 1, respectively finish the through hole 101, water inlet hole 102 and water outlet hole 103; install tool holders 4 of different lengths according to the different degrees of curvature of the inner surface of pump housing 1; finish the inner cavity of pump housing 1 by using a segmented machining method from top to bottom.

[0039] Preferably, step S4 specifically includes the following steps: positioning the through hole 101 on top and the water inlet hole 102 on the bottom, and using the finishing reference A as a reference, finishing the sidewall of the through hole 101; using the finishing reference C as a reference, finishing the outer end face of the through hole 101; so that the sidewall and outer end face of the through hole 101 are consistent with the design drawing.

[0040] Depending on the degree of curvature of the inner surface of the pump casing 1, tool holders 4 of different lengths are installed; the inner cavity of the pump casing 1 is precision machined by segmenting along the vertical direction; this solves the technical problem that the 6.3m CNC vertical lathe is limited in the horizontal direction and cannot perform precision machining on the inner cavity of the pump casing 1.

[0041] Turn the pump casing 1 over so that the water inlet hole 102 is on top and the through hole 101 is on the bottom. Using the precision machining reference B as the reference, precision machine the side wall of the water inlet hole 102 so that the shape of the water inlet hole 102 matches the design drawing.

[0042] Using the precision machining datum D as the reference, a large floor-type boring machine is used to precision machine the side wall of the water outlet 103 so that the side wall of the water outlet 103 conforms to the design drawing.

[0043] The top-to-bottom segmented processing method specifically refers to dividing the inner cavity of the pump casing 1 into multiple segments along the vertical direction, and after finishing one segment, finishing the adjacent segment.

[0044] The purpose of installing tool holders 4 of different lengths is to adjust the horizontal extension of the cutting tool 5.

[0045] S5, stainless steel corrosion-resistant layer is welded onto the inner cavity of pump casing 1.

[0046] S6, Repeat steps S1-S4 to finish the stainless steel weld overlay.

[0047] like Figure 1As shown, the existing 6.3m CNC vertical lathe has a vertically arranged rectangular ram 3 with a 400mm × 400mm square cross-section. The ram 3 is mounted on the crossbeam 8 via a horizontally arranged lead screw 7, and can reciprocate linearly along the axis of the lead screw 7. The crossbeam 8 moves up and down via a drive mechanism, is mounted on the frame 9, and is guided by a vertical guide mechanism. Due to the limitations of the length and installation position of the lead screw 7, the horizontal stroke of the ram 3 is very small during the finishing of the pump housing 1's inner cavity on the 6.3m CNC vertical lathe, making it impossible to complete the inner spherical surface machining in one pass. Therefore, segmented machining is adopted. To ensure the accuracy of segmented machining, a reference step is set at the middle position of the machining stroke of the pump housing 1's inner cavity, utilizing the workpiece allowance, as a tool setting reference during segmented machining. After the pump casing forging is precision machined to meet the requirements, stainless steel overlay welding is performed on the inner cavity of pump casing 1. After stainless steel overlay welding, an intermediate reference step 2 is welded at the same position in the inner cavity of pump casing 1 as a reference for segmented machining. After the inner cavity of pump casing 1 is precision machined, the intermediate reference step 2 is removed, and then the connection between the outer edge of the intermediate reference step 2 and the inner wall of pump casing 1 is precision machined. Because the horizontal travel of the slide block 3 is limited, the tool holder 4 cannot be installed on the slide block 3 and then moved into the inner cavity of pump casing 1. The tool holder 4 can be hoisted into the inner cavity of pump casing 1 using a steel wire rope 6, and then the slide block 3 is moved into the inner cavity of pump casing 1. The operator enters the inner cavity of pump casing 1, straightens the tool holder 4 and installs it at the lower end of the slide block 3, and then horizontally installs the cutting tool 5 on the tool holder 4. The above solution avoids the need to use expensive five-axis CNC gantry milling machines or five-axis CNC boring machines to process the pump casing 1. The existing 6.3m CNC vertical lathe can be used to perform precision machining of the pump casing 1, which has the advantage of saving costs and can also ensure machining accuracy.

[0048] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent changes made to the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for processing the casing of a nuclear power plant main pump, characterized in that, Including the following steps: S1, based on the vertical axis L1 of the pump housing (1), a finishing reference A is set for finishing the side wall of the water inlet hole (102) located at the bottom of the pump housing (1), and a finishing reference B is set for finishing the side wall of the through hole (101) located at the top of the pump housing (1); Based on the machined surface of the water outlet (103), the allowance is evenly distributed, and a finishing reference D is set for finishing the side wall of the water outlet (103) located on the side of the pump casing (1); Based on the finishing datum D and the return height dimension, a finishing datum C is set for finishing the outer end face of the through hole (101); S2, weld the intermediate reference step (2) for segmented processing at the lower part of the inner cavity of the pump casing (1) so that the upper surface of the intermediate reference step (2) is horizontal; the intermediate reference step (2) is a horizontally arranged ring structure and the axis of the intermediate reference step (2) coincides with the vertical axis L1 of the pump casing (1); S3, transfer the tool holder (4) into the inner cavity of the pump housing (1); start the machine tool and extend the vertically arranged ram (3) into the pump housing (1) from top to bottom, and install the tool holder (4) horizontally at the lower end of the ram (3); install the lathe tool (5) on the tool holder (4) so ​​that the cutting edge of the lathe tool (5) is away from the tool holder (4). S4, using finishing references A, B, C and D as finishing references for the pump casing (1), respectively finish the through hole (101), water inlet hole (102) and water outlet hole (103); according to the different curvature of the inner cavity surface of the pump casing (1), install tool holders (4) of different lengths; adopt the method of segmented machining from top to bottom to finish the inner cavity of the pump casing (1); S5, stainless steel corrosion resistant layer is welded onto the inner cavity of the pump casing (1); S6, Repeat steps S1-S4 to finish the stainless steel weld overlay; Step S4 specifically includes the following steps: using finishing datum A as a datum, finishing the sidewall of the through hole (101); using finishing datum C as a datum, finishing the outer end face of the through hole (101); Depending on the degree of curvature of the inner surface of the pump casing (1), different lengths of tool holders (4) are installed; the inner cavity of the pump casing (1) is precision machined by a segmented machining method from top to bottom; Turn the pump casing (1) over so that the water inlet hole (102) is on top and the through hole (101) is on the bottom. Using the finishing reference B as the reference, finish the side wall of the water inlet hole (102). Using the finishing datum D as a reference, finish the sidewall of the water outlet (103).

2. The method for processing the pump casing of a nuclear power plant main pump as described in claim 1, characterized in that, In step S3, the tool holder (4) is hoisted into the inner cavity of the pump casing (1) using a steel wire rope (6).

3. The method for processing the pump casing of a nuclear power plant main pump as described in claim 1, characterized in that, In step S2, the intermediate reference step (2) for segmented processing is welded to the lower part of the inner cavity of the pump casing (1) by overlay welding.

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