Vacuum centrifugal preparation method of aluminum bronze leakage stop ring of water turbine set

Abstract

The application discloses a vacuum centrifugal preparation method of an aluminum bronze leak-stopping ring of a hydraulic turbine unit, and steps of the method comprise the following: ingredients are prepared according to Al: 8.5-10.0 wt%, Fe 4.0-5.0 wt%, Ni 4.0-5.0 wt%, Mn 1.5-2.5 wt%, and the rest is Cu; each raw material is added into a vacuum melting furnace for smelting, and after refining, heat preservation and stirring, the material is transferred into a tundish; the copper alloy liquid in the tundish is subjected to vacuum centrifugal casting to obtain a ring-shaped blank, and the blank is immediately cooled in a cooling water pool after being discharged; the ring-shaped blank is subjected to mechanical processing 1 to remove defects, is subjected to hot ring rolling by using a hot ring rolling process and is subjected to water cooling; and then, the ring-shaped blank is subjected to mechanical processing 2 to obtain a finished product with a sampling position on the outer side of the upper surface. The preparation method has the advantages of simple process, high production efficiency, no internal defects of the finished product, uniform composition, compact and stable structure of the prepared aluminum bronze leak-stopping ring and the like, and the service life of the leak-stopping ring is guaranteed.

Description

Technical Field

[0001] This invention belongs to the technical field of aluminum bronze leak-stopping rings, specifically relating to a vacuum centrifugal preparation method for aluminum bronze leak-stopping rings for water turbine units. Background Technology

[0002] Pumped storage is an important method for ensuring the safe and stable operation of power systems in countries around the world. my country's development of pumped storage began in the late 1960s with the Gangnan Hydropower Station in Hebei Province. Subsequent projects, including the Guangzhou Pumped Storage Station, the Ming Tombs Pumped Storage Station in Beijing, and the Tianhuangping Pumped Storage Station in Zhejiang Province, solidified the foundation for its development. With the rapid development of my country's economy and society, the development of pumped storage has accelerated, and the number of projects has increased significantly. Currently, my country has a total installed capacity of 32.49 million kilowatts of pumped storage power stations and 55.13 million kilowatts under construction. Approximately 60% of these are located in East and North China, making China the world's largest pumped storage power station in both completed and under-construction capacity.

[0003] A leak-proof ring is a replaceable sealing structure installed between the runner and the top and bottom rings of a mixed-flow turbine to reduce leakage. Its main purpose is to minimize turbine volumetric losses and protect the runner's upper crown and lower rings from wear. Before 2017, my country primarily used stainless steel leak-proof rings for turbid water power generation turbines. In recent years, my country's hydropower stations have mainly focused on energy storage-type clear water power stations. Due to aluminum bronze's resistance to cavitation, wear, and high strength, as well as its ease of installation during both cold and hot fitting, leak-proof rings have begun to be manufactured using aluminum bronze.

[0004] Centrifugal casting is both a traditional and a modern casting method. As a special casting method, it occupies a very important position in the modern casting industry. Compared with other casting methods, centrifugal casting has the following advantages: 1. It can produce hollow cylindrical and ring castings, as well as pipes of different diameters and lengths, without the need for any sand molds, resulting in high production efficiency and low production costs. 2. Some castings do not require any risers or gating systems, improving the utilization rate of molten metal. 3. The molten metal solidifies under centrifugal force, resulting in a fine microstructure. Lighter inclusions such as slag and oxides float to the surface of the molten metal and can be removed by machining. 4. Within a defined casting wall thickness range, a directional solidification structure can be obtained from the mold wall to the inner wall of the casting. Centrifugal casting of copper alloys is mainly used to produce various bushings, rollers, rims, and steel-backed copper alloy bearings. Compared with other casting methods, the copper alloy castings produced by this process have fewer or even no porosity and inclusions, and a dense microstructure, which can significantly improve the casting yield and mechanical properties. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a leak-proof ring suitable for a pumped storage power station turbine unit. Specifically, it relates to a vacuum centrifugal preparation method for an aluminum bronze leak-proof ring for a turbine unit, which has the characteristics of uniform and stable elements, dense structure, simple process route, high processing efficiency and low cost.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A vacuum centrifugal preparation method for an aluminum bronze leak-proof ring for a water turbine unit includes the following steps:

[0008] 1) Material formulation: The leak-stop ring is made of aluminum bronze, with the following proportions: Al: 8.5-10.0wt%, Fe: 4.0-5.0wt%, Ni: 4.0-5.0wt%, Mn: 1.5-2.5wt%, and the remainder being Cu.

[0009] 2) Melting: Add the various materials from step 1) into a vacuum melting furnace for melting. After melting, heat preservation and stirring, transfer to an intermediate ladle.

[0010] 3) Vacuum centrifugal casting: When the temperature of the copper alloy liquid after melting in step 2) reaches 1150-1200℃, the copper alloy liquid in the tundish is poured into the centrifugal mold in the vacuum vertical centrifuge for casting. Immediately after the copper alloy liquid is poured, a heating covering agent is added to the inside of the copper alloy liquid. After the covering agent is completed, carbonized rice husk is added to cover it to obtain a ring-shaped billet. After the billet is demolded, it is immediately hoisted into the cooling water tank for cooling.

[0011] 4) Machining 1: Machining the ring-shaped billet obtained in step 3); first remove the defects on the inner surface, then remove the defects on the outer surface and the upper and lower surfaces, and then process it to the specified dimensions to obtain the ring-shaped billet before hot ring rolling;

[0012] 5) Hot ring rolling: The ring-shaped billet obtained in step 4) is used as the raw material for the hot ring rolling process. It is first heated by a bogie furnace, and then hot ring rolled by a CNC ring rolling mill. After the hot ring rolling is completed, it is immediately cooled in a water tank.

[0013] 6) Machining after hot ring rolling 2:

[0014] The ring-shaped billet that has been hot rolled and cooled is machined to the required dimensions, and a sampling position is left on the outer side of the upper surface.

[0015] Furthermore, in step 2), the melting temperature is 1300-1350℃, and the holding time is 5-10 minutes.

[0016] Furthermore, in step 1), Cu is added in the form of electrolytic copper pure copper plates, Al is added in the form of aluminum ingots, Fe is added in the form of iron nails, Ni is added in the form of nickel plates, and Mn is added in the form of metallic manganese.

[0017] Furthermore, in step 3), the thickness of the heating covering agent is 20-40 mm, and the thickness of the carbonized rice husk covering is 60-80 mm.

[0018] Further, the dimensions of the annular blank in step 3) are: outer diameter 2500-2600mm, inner diameter 1850-1950mm, and height 220-240mm.

[0019] Furthermore, in step 4), the defects on the inner surface include oxide scale and shrinkage pores; the defects on the outer surface and the upper and lower surfaces include oxide scale, pores, and cracks.

[0020] Furthermore, the hot ring rolling process in step 5) is as follows: first, place the ring-shaped billet in the bogie furnace, preheat it to 450-500℃, then heat it to 850-900℃, and hold it for ≥3h; the hot ring rolling process is rapid, ensuring that the final rolling temperature is >700℃, and the entire hot ring rolling process must ensure that the rolling is completed in one go.

[0021] Furthermore, after step 5) hot ring rolling, the dimensions of the billet after ring rolling must be guaranteed to be: outer diameter 3060±10mm; inner diameter 2570±10mm; height 190±6mm.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) Aluminum bronze alloy material is used. Compared with conventional materials, it has the advantages of cavitation resistance, wear resistance and high strength, which can meet the working environment of the turbine unit.

[0024] (2) The production of aluminum bronze alloy leak-proof rings by vacuum centrifugal casting reduces the absorption of copper alloy liquid during the smelting process, ensuring fewer or even no defects inside the billet; vacuum centrifugal casting can also ensure the uniformity of each element inside the billet and ensure a dense internal structure.

[0025] (3) By adopting the process of vacuum centrifugal casting → machining → hot ring rolling → machining, it is possible to produce products of multiple specifications with one mold, thereby reducing production costs.

[0026] (4) The preparation method of the present invention has simple process, high production efficiency, no defects in the finished product, and the prepared aluminum bronze leak-proof ring has the advantages of uniform composition, dense and stable structure, which ensures the service life of the leak-proof ring. Attached Figure Description

[0027] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation thereof. The spacing or dimensions between parts in the drawings are exaggerated to show their positions; these schematic diagrams are for illustrative purposes only.

[0028] Figure 1 This is a cross-sectional view of the vacuum centrifugal casting aluminum bronze leak-stopping ring blank after machining 1.

[0029] Figure 2 This is a cross-sectional view of the specific sample retention location of the vacuum centrifugal casting aluminum bronze leak-stopping ring billet after hot ring rolling and machining. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0031] Example 1

[0032] (1) Batching: The leak-proof ring of the copper-based alloy turbine unit is made of aluminum bronze, with a weight percentage of 9.7% Al, 4.5% Fe, 4.7% Ni, 2.1% Mn, and the remainder Cu. Cu is added as pure copper plates from electrolytic copper, Al is added as aluminum ingots, Fe is added as iron nails, Ni is added as nickel plates, and Mn is added as metallic manganese.

[0033] (2) Melting: Add the prepared materials in (1) into a vacuum melting furnace and melt them at a temperature of 1320℃. After the copper alloy liquid is melted and cleared, keep it at a constant temperature for 10 minutes. After it is fully stirred and evenly mixed, transfer the copper alloy liquid into an intermediate ladle.

[0034] (3) Vacuum centrifugal casting: When the temperature of the copper alloy liquid obtained in (2) reaches 1160℃, the copper alloy liquid in the intermediate ladle is poured into the centrifugal casting mold in the vacuum vertical centrifuge for casting. After the copper alloy liquid is poured, a heating covering agent with a thickness of 40mm is immediately added to the inside of the copper alloy liquid. After the covering agent is completed, carbonized rice husk is added to cover the material with a thickness of 60mm. Through centrifugal casting, an annular billet with an outer diameter of 2530mm, an inner diameter of 1880mm, and a height of 230mm is finally obtained. After the billet is demolded, it is immediately placed in a cooling water pool for cooling.

[0035] (4) Machining 1. The annular billet obtained in (3) is machined. The oxide scale and shrinkage defects on the inner surface are removed by CNC vertical lathe. Then, the oxide scale, pores, cracks and other defects on the outer surface and the upper and lower surfaces are removed. The billet is machined to the dimensions specified in the drawing, with an outer diameter of 2522 mm, an inner diameter of 1990 mm and a height of 220 mm. Finally, the annular billet before hot ring rolling is obtained. Figure 1 As shown.

[0036] (5) Hot ring rolling: The ring-shaped billet obtained in (4) is rolled into a ring using hot ring rolling. First, the ring-shaped billet is placed in a bogie furnace and preheated to 460℃, then heated to 860℃ and held for ≥3h. The ring rolling process should be rapid to ensure that the final rolling temperature after ring rolling is >700℃. After hot ring rolling, it is directly cooled by cooling water. The dimensions of the billet after hot ring rolling are: outer diameter 3060mm, inner diameter 2570mm, and height 190mm.

[0037] (6) Machining after hot ring rolling 2. After hot ring rolling, machining is performed again according to the specified dimensions, and the outer side of the upper surface of the billet is machined according to... Figure 2 Process the material and leave sampling locations to test the relevant performance.

[0038] The composition comparison between the aluminum bronze leak-stopping ring of Example 1 of the present invention and that produced by conventional processes is shown in Table 1 below:

[0039] Table 1. Comparison of composition between aluminum bronze sealing rings produced in Example 1 and those produced by conventional processes.

[0040]

[0041] As shown in Table 1, the composition samples of aluminum bronze leak-stopping rings produced by conventional processes show a large difference at the three points, with the Al element deviation reaching about 2.7%. In contrast, the composition samples of aluminum bronze leak-stopping rings produced using Example 1 show a smaller difference at the three points, with the Al element content deviation being only 0.92%.

[0042] Table 2 below shows a comparison of the mechanical properties of Embodiment 1 of the present invention with those of conventional production processes:

[0043] Table 2. Comparison of mechanical properties of aluminum bronze leak-stopping rings produced in Example 1 and those produced by conventional processes.

[0044]

[0045] Example 2

[0046] Steps (1), (2), (4) and (6) of Example 2 are the same as those of Example 1.

[0047] (3) Centrifugal casting: When the temperature of the copper alloy liquid obtained in (2) reaches 1180℃, the copper alloy liquid in the tundish is poured into the centrifugal casting mold for casting. After the copper alloy liquid is poured, a heating covering agent with a thickness of 40mm is added to the inside. After the covering agent is completed, carbonized rice husk is added to cover the inside with a thickness of 60mm. Through centrifugal casting, a ring-shaped billet with an outer diameter of 2530mm, an inner diameter of 1880mm, and a height of 230mm is finally obtained. After the billet is demolded, it is immediately placed in a cooling water tank for cooling.

[0048] (5) Hot ring rolling: The ring-shaped billet obtained in (4) is rolled into a ring using hot ring rolling. First, the ring-shaped billet is placed in a bogie furnace and preheated to 460℃, then heated to 900℃ and held for ≥3h. The ring rolling process should be rapid to ensure that the final rolling temperature is >700℃ after ring rolling. After ring rolling, it is directly cooled in water. The dimensions of the billet after hot ring rolling are: outer diameter 3060mm, inner diameter 2570mm, and height 190mm.

[0049] The composition comparison of the aluminum bronze leak-stopping ring produced by Example 2 of the present invention and that produced by conventional production processes is shown in Table 3 below:

[0050] Table 3. Comparison of composition between aluminum bronze sealing rings produced in Example 2 and those produced by conventional processes.

[0051]

[0052] Table 4 shows a comparison of the mechanical properties of Embodiment 2 of the present invention with those of conventional production processes:

[0053] Table 4. Comparison of mechanical properties of aluminum bronze leak-stopping rings produced in Example 2 and those produced by conventional processes.

[0054]

[0055] When using conventional processes for production, due to the instability of casting + hot forging, there will be certain defects in the ingots during the production process, resulting in a certain rate of non-conforming products during hot forging. Therefore, the total production cost is higher than that of the method of this invention. It can be seen that the method of this application can also effectively reduce production costs.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A vacuum centrifugal preparation method for an aluminum bronze leak-proof ring for a water turbine unit, characterized in that, Includes the following steps: (1) Batching: The leak-proof ring of the copper-based alloy turbine unit is made of aluminum bronze, with a weight percentage of 9.7% Al, 4.5% Fe, 4.7% Ni, 2.1% Mn, and the remainder Cu. Cu is added in the form of electrolytic copper pure copper plates, Al is added in the form of aluminum ingots, Fe is added in the form of iron nails, Ni is added in the form of nickel plates, and Mn is added in the form of metallic manganese. (2) Melting: Add the prepared materials in (1) into a vacuum melting furnace and melt them. The melting temperature is 1320℃. After the copper alloy liquid is melted and cleared, keep it at a constant temperature for 10 minutes. After it is fully stirred and evenly mixed, transfer the copper alloy liquid into an intermediate ladle. (3) Centrifugal casting: When the temperature of the copper alloy liquid obtained in (2) reaches 1180℃, the copper alloy liquid in the tundish is poured into the centrifugal casting mold for casting. After the copper alloy liquid is poured, a heating covering agent with a thickness of 40mm is added to the inside. After the covering agent is applied, carbonized rice husk is added to cover the inside with a thickness of 60mm. Through centrifugal casting, a ring-shaped billet with an outer diameter of 2530mm, an inner diameter of 1880mm, and a height of 230mm is finally obtained. After the billet is demolded, it is immediately placed in a cooling water tank for cooling. (4) Machining 1. Machining the ring-shaped billet obtained in (3) by using a CNC vertical lathe to remove the oxide black scale and shrinkage defects on the inner surface, and then removing the oxide black scale, pores, cracks and other defects on the outer surface and the upper and lower surfaces. Machining to an outer diameter of 2522mm, an inner diameter of 1990mm and a height of 220mm according to the dimensions specified in the drawing, and finally obtaining the ring-shaped billet before hot ring rolling; (5) Hot ring rolling: The ring billet obtained in (4) is rolled into a ring by hot ring rolling. First, the ring billet is placed in a bogie furnace and preheated to 460°C, then heated to 900°C and held for ≥3h. The ring rolling process should be rapid to ensure that the final rolling temperature after the ring rolling is >700°C. After the ring rolling is completed, it is directly cooled in water. The dimensions of the billet after hot ring rolling are 3060mm outer diameter, 2570mm inner diameter, and 190mm height. (6) Machining after hot ring rolling 2. After hot ring rolling, the machine is machined again according to the specified dimensions.

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