An accurate forming method for an annular casing of an aeroengine

Abstract

This application relates to the field of manufacturing complex titanium alloy components, and specifically discloses a precise forming method for an annular casing of an aeroengine, including: producing metal powder through a powder-making process; using the metal powder to prepare a preform of the annular casing by cold isostatic pressing, where the structure and size of the preform correspond to those of the annular casing; setting the preform in a jacket of the annular casing and adding the metal powder into the jacket; performing hot isostatic pressing on the jacket with the preform to obtain the annular casing. The annular casing prepared by this method has fine and uniform microstructure, high comprehensive performance, good dimensional stability, high material utilization rate, and realizes high-precision net forming of the outer surface.

Description

Technical Field

[0001] The present application relates to the technical field of manufacturing complex titanium alloy components, and particularly to an accurate forming method for an annular casing of an aeroengine. Background Art

[0002] An aeroengine is the "heart" of an aircraft, the "pearl on the crown of modern industry", and an important symbol to measure the development level of a major country's modern industry. The casing is an important component of an aeroengine, the skeleton of the entire engine, and the main load-bearing component of the aeroengine. The shapes of aeroengine casings at different positions are different, but the basic feature is that they are composed of a cylindrical or conical shell and a support plate. Further subdivided, aeroengine casings can be divided into annular casings and box casings. Typical annular casings include combustion chamber casings, turbine casings, compressor casings, and outer casing casings, etc. The materials of typical annular casings mainly include titanium alloys and superalloys.

[0003] As a complex thin-walled component, the traditional forming methods of the annular casing include the following two: one is precision casting; the other is die forging + machining. Precision casting has more defects such as pores and looseness, and the structure is relatively coarse, which cannot meet the high-quality and high-performance casing forming. Secondly, die forging + machining. Since the annular casing generally has structures such as flange edges, stiffeners, and mounting seats, the size of the die forgings is very large, the material utilization rate is low, and there is a risk of machining deformation. Exploring new forming processes to achieve high-quality, high-precision, and high-efficiency manufacturing of annular casing parts has always been a research hotspot in the current military industry. Summary of the Invention

[0004] The present application provides an accurate forming method for an annular casing of an aeroengine. The annular casing prepared by this method has a fine and uniform structure, high comprehensive performance, good dimensional stability, high material utilization rate, and realizes high-precision net forming of the outer profile surface.

[0005] In a first aspect, an accurate forming method for an annular casing of an aeroengine is provided, including:

[0006] Producing metal powder through a powder-making process;

[0007] Preparing a preform of the annular casing by cold isostatic pressing with the metal powder, and the structure and size of the preform correspond to those of the annular casing;

[0008] Placing the preform in a jacket of the annular casing, and adding the metal powder in the jacket;

[0009] Performing hot isostatic pressing on the jacket with the preform to obtain the annular casing.

[0010] Compared with the prior art, the solution provided by this application has at least the following beneficial technical effects:

[0011] The annular casing refers to the single-layer casing part of an aeroengine. Its basic features are a thin-walled shell in the shape of a cylinder or a cone, with mounting flanges at the front and rear respectively. The outer surface is distributed with stiffeners and mounting seats. The thickness of the shell is generally 1-4 mm, and the materials are mainly titanium alloy or superalloy. The outer surface of the annular casing is distributed with stiffeners and mounting seats. The stiffener structure can be annular or grid-shaped, and the mounting seat structure also has various types. The forming and processing are very difficult. This method uses hot isostatic pressing near-net forming technology to achieve the precise net forming of the outer surface of the annular casing, without subsequent processing. The mounting flanges, stiffeners, and mounting seats of the annular casing are large in size, corresponding to a large powder loading amount and a large deformation amount. The conventional method of pre-placing solid blocks will have pre-placed interfaces in the structure after hot isostatic pressing, affecting the product quality. The cold isostatic pressing pre-placement method can not only control the precise deformation of the large-deformation positions, but also will not generate pre-placed interfaces brought by other pre-placement methods.

[0012] In combination with the first aspect, in some implementation manners of the first aspect, the preform of the annular casing includes an upper mounting flange preform, a lower mounting flange preform, a stiffener preform, and a mounting seat preform.

[0013] Designing multiple parts of the preform according to the structure of the annular casing is beneficial to improving the performance uniformity of the preform obtained by cold isostatic pressing.

[0014] In combination with the first aspect, in some implementation manners of the first aspect, the casing of the annular casing includes a casing outer wall, a casing inner core, a casing bottom, and a casing upper cover. The inner cavity formed by surrounding the casing outer wall, the casing inner core, the casing bottom, and the casing upper cover is used to set the preform. The outer ceramic ring is arranged on the outer periphery of the casing outer wall. The powder loading tube is arranged on the casing upper cover, and the degassing tube is arranged in the powder loading tube.

[0015] In combination with the first aspect, in some implementation manners of the first aspect, the thickness of the casing inner core, the casing bottom, and the casing upper cover is 6-10 mm.

[0016] Since the casing will participate in the deformation, in order to meet the structural strength requirements, slots need to be opened at the positions of the mounting flanges, stiffeners, and mounting seats of the casing outer wall, and local thinning may occur at the slot positions. A reasonable designed thickness can meet the structural requirements.

[0017] In combination with the first aspect, in some implementation manners of the first aspect, the inner diameter dimension α of the casing outer wall = the contour dimension β of the annular casing / (0.95-0.98).

[0018] The cold isostatic pressing pre-placement control deformation method reduces the subsequent deformation amount.

[0019] In combination with the first aspect, in some implementations of the first aspect, the annular casing includes a target portion, and the target portion is at the i-th position in the top-to-bottom order of the annular casing. The size γ of the central position of the jacket corresponding to the target portion i Satisfies:

[0020] The annular casing-jacket assembly shrinks from top to bottom in the height direction. Therefore, the sizes of the mounting edge, the reinforcing rib, and the mounting seat also move from bottom to top along with the shrinking direction. Therefore, when designing the jacket, the mounting edge, the reinforcing rib, and the mounting seat need to be designed to follow the movement in the height direction. Taking the upper side of the jacket groove corresponding to the upper side of the mounting edge as a reference, the central positions of the mounting edge, the reinforcing rib, and the mounting seat are adjusted following the movement, which is beneficial to making the finally obtained annular casing more matched with the design size.

[0021] In combination with the first aspect, in some implementations of the first aspect, the outer ceramic ring satisfies:

[0022] The material is silicon nitride ceramic, and the designed thickness is 50 - 100 mm.

[0023] In order to achieve precise net shaping of the outer profile surface, it is necessary to ensure precise controllability of shrinkage deformation. During the hot isostatic pressing process, the medium can exert pressure from the inside of the jacket to the outside. Therefore, the horizontal shrinkage of the entire annular casing-jacket is from the inside to the outside. The function of the outer ceramic ring is to control the size of the outer wall of the jacket after hot isostatic pressing to remain unchanged, thereby controlling the accuracy of the outer profile surface of the annular casing. The material of the outer ceramic ring is selected as silicon nitride ceramic, and its linear expansion coefficient under high temperature is very small. In order to facilitate assembly, the outer ceramic ring adopts a split structure, and the designed thickness is 50 - 100 mm.

[0024] In combination with the first aspect, in some implementations of the first aspect, setting the preform in the jacket of the annular casing and adding the metal powder in the jacket includes:

[0025] Loading spherical metal powder into the inner cavity formed by surrounding the outer wall of the jacket, the inner core of the jacket, the bottom of the jacket, and the upper cover of the jacket through the powder loading tube;

[0026] Compacting the powder by vibration and knocking;

[0027] After completing the powder loading, inserting the degassing tube into the powder loading tube and connecting the degassing tube and the jacket into one body by welding;

[0028] Assembling the split outer ceramic ring so that the outer circumference of the outer ceramic ring fits the outer wall of the jacket, and screwing and fixing the split outer ceramic ring.

[0029] In combination with the first aspect, in some implementations of the first aspect, the pressure of the cold isostatic pressing is 150-200 MPa, and the relative density is 90%-95%.

[0030] Use a cold isostatic press to press the annular casing mounting edge preform, the reinforcing rib preform, and the mounting seat preform. The dimensions of the preforms are exactly the same as those of the mounting edge, the reinforcing rib, and the mounting seat on the annular casing product.

[0031] In combination with the first aspect, in some implementations of the first aspect, the hot isostatic pressing of the jacket with the preform to obtain the annular casing includes:

[0032] Vacuumize at high temperature for degassing;

[0033] After degassing is completed, seal-weld the degassing pipe;

[0034] Perform hot isostatic pressing on the jacket with the preform, cool to below 200 °C after heat preservation and pressure holding, and then take out of the furnace;

[0035] After hot isostatic pressing is completed, take out the outer ceramic ring from the jacket, disassemble and assemble the jacket to obtain a rough annular casing;

[0036] Perform surface treatment and vacuum annealing treatment on the rough annular casing;

[0037] Machine the two end flanges and the inner profile with machining allowance to obtain the annular casing. Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of an annular casing.

[0039] Figure 2 It is a schematic structural diagram of an annular casing preform.

[0040] Figure 3 It is a schematic structural diagram of an annular casing jacket. Detailed Description of the Embodiments

[0041] The following further describes the present application in detail with reference to the drawings and specific embodiments.

[0042] The embodiment of the present application provides a precise forming method for an annular casing of an aeroengine. This method can adopt precise forming by hot isostatic pressing. The structure of the annular casing of the aeroengine is as Figure 1 shown. This method may include the following steps.

[0043] (1) Produce spherical powders of titanium alloy or superalloy by gas atomization or plasma rotating electrode powder making process. The composition, particle size, inclusions, and morphology of the powders can be detected to ensure that the powder properties meet the requirements.

[0044] (2) As Figure 2 shown, the upper mounting edge preform 11, lower mounting edge preform 12, reinforcing rib preform 13 and mounting seat preform 14 of the annular casing are pressed by the cold isostatic pressing method, and the titanium alloy or superalloy powder produced in step (1) is selected as the raw material.

[0045] (3) Design the jacket assembly according to the annular casing structure and the above-mentioned preform dimensions. As Figure 3 shown, the jacket assembly mainly includes a jacket outer wall 3, a jacket inner core 2, a jacket bottom 1, a jacket upper cover 5, an outer ceramic ring 4, a powder loading tube 6, and a degassing tube 7. The number of powder loading tubes 6 can be 1, 2 or more. A plurality of powder loading tubes 6 can be symmetrically and evenly spaced. The number of degassing tubes 7 can be 1, 2 or more. A plurality of degassing tubes 7 can be symmetrically and evenly spaced. After the design is completed, stainless steel or low-carbon steel can be selected to process the jacket outer wall 3, jacket inner core 2, jacket bottom 1, and jacket upper cover 5.

[0046] (4) Clean the processed jacket assembly parts, and transfer them to a clean workshop after completion. In the clean workshop, assemble and weld the jacket outer wall 3, jacket inner core 2, jacket bottom 1, jacket upper cover 5, and powder loading tube 6. Among them, the powder loading tube 6 is arranged on the jacket upper cover 5. During the process, Figure 2 the upper mounting edge preform 11, lower mounting edge preform 12, reinforcing rib preform 13 and mounting seat preform 14 shown are respectively loaded into the jacket to obtain an annular casing powder loading jacket.

[0047] (5) Load the metal spherical powder into the annular casing powder loading jacket obtained in step (4) through the powder loading tube 6 reserved on the jacket upper cover 5. Compact the powder by vibration and tapping. After the powder loading is completed, insert the degassing tube 7 into the powder loading tube 6, and connect the degassing tube 7 and the annular casing powder loading jacket into one body by argon arc welding. Finally, install the split outer ceramic rings respectively, and the outer surface of the outer ceramic ring is closely attached to the jacket outer wall 3. Finally, fix it with screws to obtain a complete annular casing jacket assembly.

[0048] (6) Put the complete annular casing jacket assembly in step (5) into a bench-type resistance furnace, connect the two degassing tubes 7 to the vacuum unit respectively, evacuate at high temperature for degassing, and after the degassing is completed, seal-weld the two degassing tubes 7 by argon arc welding.

[0049] (7) Perform hot isostatic pressing treatment on the sealed annular casing jacket assembly in step (6), cool it to below 200 °C after heat preservation and pressure holding, and then take it out of the furnace.

[0050] After hot isostatic pressing is completed, first remove the outer ceramic ring from the annular casing jacket assembly, then remove the jacket by combining machining and electrochemistry to obtain a rough annular casing blank, and then perform surface treatment and vacuum annealing treatment. Finally, machine the two flanges and the inner profile with a margin to obtain the final annular casing component.

[0051] In step (1), the annular casing refers to a single-layer casing part of an aeroengine. Its basic features are a thin-walled shell in the shape of a cylinder or a cone, with mounting flanges at the front and back respectively. The outer profile is distributed with stiffeners and mounting seats. The thickness of the shell is generally 1 - 4 mm, and the material is mainly titanium alloy or superalloy. The outer profile of the annular casing is distributed with stiffeners and mounting seats. The stiffener structure can be annular or grid-shaped, and the mounting seat structure also has various types. The forming and machining are very difficult. This method uses hot isostatic pressing near-net forming technology to achieve precise net forming of the outer profile of the annular casing, and no further machining is required.

[0052] In step (2), the mounting flanges, stiffeners, and mounting seats of the annular casing are large in size, corresponding to a large powder loading amount and a large deformation amount. The conventional method of pre-placing solid blocks will have pre-placement interfaces in the structure after hot isostatic pressing, which affects the product quality. The cold isostatic pressing pre-placement method can not only control the precise deformation of the large-deformation positions, but also will not generate pre-placement interfaces brought by other pre-placement methods. Use a cold isostatic press to press the pre-placement bodies of the mounting flanges, stiffeners, and mounting seats of the annular casing. The sizes of the pre-placement bodies are exactly the same as the sizes of the mounting flanges, stiffeners, and mounting seats on the annular casing product. The cold isostatic pressing pressure is 150 - 200 MPa, and the relative density is 90% - 95%.

[0053] In step (3), the designed thickness of the inner core 2 of the jacket, the bottom 1 of the jacket, and the upper cover 5 of the jacket is 6 - 10 mm. Since the jacket will participate in the deformation, in order to meet the structural strength requirements, slots need to be opened at the positions of the mounting flanges, stiffeners, and mounting seats on the outer wall 3 of the jacket, and local thinning may occur at the slot positions. Therefore, the thickness of each part of the outer wall is different, and the designed minimum thickness is 6 - 10 mm.

[0054] In step (3), the cold isostatic pressing pre-placement control deformation method reduces the subsequent deformation amount. When designing the jacket, the inner diameter size α of the outer wall 3 of the jacket corresponding to the mounting flanges, stiffeners, and mounting seats = the contour size β / (0.95 - 0.98). For example, the groove size α of the outer wall 3 of the jacket corresponding to the mounting seat i = the contour size β of the mounting seat i / (0.95 - 0.98), where the value of i ranges from 1 to n, and n is the number of mounting seats.

[0055] In step (3), the annular casing jacket assembly contracts from top to bottom in the height direction. Therefore, the dimensions of the mounting edge, reinforcing rib, and mounting seat also move from bottom to top along with the contraction direction. Therefore, when designing the jacket, the mounting edge, reinforcing rib, and mounting seat need to be designed to follow the movement in the height direction. Taking the upper side of the jacket groove corresponding to the upper side of the mounting edge as the reference, the positions of the mounting edge, reinforcing rib, and mounting seat are adjusted accordingly. i is the component order from top to bottom.

[0056] In step (3), in order to achieve precise net shaping of the external profile, it is necessary to ensure precise controllability of the shrinkage deformation. During the hot isostatic pressing process, the medium can exert pressure from the inside of the jacket to the outside. Therefore, the horizontal shrinkage of the entire annular casing jacket is from inside to outside. The function of the outer ceramic ring is to control the size of the outer wall 3 of the jacket after hot isostatic pressing unchanged, thereby controlling the accuracy of the external profile of the annular casing. The material of the outer ceramic ring is selected as silicon nitride ceramic, which has a very small linear expansion coefficient under high temperature. For ease of assembly, the outer ceramic ring adopts a split structure with a designed thickness of 50 - 100 mm.

[0057] Example 1

[0058] The structure of a certain new type of turbofan engine fan casing is as Figure 1 shown. The material selected is TA15 titanium alloy. The product thickness is 2.5 mm, the height is 800 mm, the maximum outer diameter of the flange is 782 mm, the thickness of the upper and lower mounting edges is 12 mm, the thickness of the middle reinforcing rib is 12 mm, the distance from the upper surface of the lower mounting edge is 356 mm, and there are two rows of circular mounting seats with a diameter of 40 mm. The center positions of the two rows of mounting seats are 83 mm and 442 mm respectively from the upper surface of the lower mounting edge. Taking this type of aeroengine fan casing as an example, a precise forming method for an aeroengine annular casing is described.

[0059] (1) Produce and detect titanium alloy spherical powder

[0060] The master alloy for powder production uses TA15 titanium alloy forging bars. The ingots for forging bars should undergo three times of vacuum consumable melting. Recycling materials are not allowed for ingot melting. TA15 spherical titanium alloy powder is produced by plasma rotating electrode powder making. The powder composition, particle size, inclusions, and morphology are detected to obtain qualified powder.

[0061] (2) Cold isostatic pressing to form a preform

[0062] The cold isostatic pressing method is used to press the mounting edge preform, reinforcing rib preform, and mounting seat preform of the fan casing. The dimensions of the preforms are exactly the same as those of the mounting edge, reinforcing rib, and mounting seat on the fan casing. The raw material selected is TA15 titanium alloy powder. The cold isostatic pressing pressure is 200 MPa, and the density of the cold isostatic pressing preform is measured to be 93%.

[0063] (3) Design and machine the fan casing cladding assembly

[0064] Design the cladding assembly according to the fan casing structure and the size of the preform, mainly including the outer cladding wall 3, the inner cladding core 2, the lower cladding base 1, the upper cladding cover 5, the outer ceramic ring, 2 powder loading pipes 6, and 2 degassing pipes 7. The designed thickness of the inner cladding core 2, the lower cladding base 1, and the upper cladding cover 5 is 10 mm. Grooves need to be machined at the installation edge, the reinforcing ribs, and the mounting seat positions of the outer cladding wall 3, so the thickness of each part of the outer wall is different. The designed minimum thickness is at the upper and lower installation edges, with a thickness of 10 mm. The thickness of the upper and lower installation edges and the reinforcing ribs is 12 mm. When designing the cladding, the groove size α1 of the outer cladding wall 3 corresponding to the installation edge and the reinforcing ribs is 12 / 0.96 = 12.5 mm, the diameter size of the mounting seat is 40 mm, and the groove size α2 of the outer cladding wall 3 corresponding to it is 40 / 0.96 = 41.7 mm. When designing the cladding, the installation edge, the reinforcing ribs, and the mounting seat need to be designed for follow-up in the height direction. Taking the upper side of the cladding groove corresponding to the upper surface of the lower installation edge as the reference, the center position dimension γ1 of the reinforcing rib is 356 + (12.5 - 12) / 2 = 356.25 mm. The center position dimension γ2 of the lower row of mounting seats is 83 + (41.7 - 40) / 2 = 83.85 mm, and the center dimension γ3 of the upper row of mounting seats is 442 + (41.7 - 40) / 2 = 442.85 mm. After the design is completed, select 304 stainless steel to machine the outer cladding wall 3, the inner cladding core 2, the lower cladding base 1, the upper cladding cover 5, the powder loading pipe 6, and the degassing pipe 7. The material of the outer ceramic ring is selected as silicon nitride ceramic, which has a very small linear expansion coefficient under high temperature. The outer ceramic ring is a split structure, and the designed thickness is 80 mm.

[0065] (4) Clean, assemble, and weld the powder-loading cladding of the fan casing

[0066] Clean the machined parts of the cladding assembly with a room-temperature metal cleaning agent, and then transfer them to a clean workshop. In the clean workshop, complete the assembly and welding of the outer cladding wall 3, the inner cladding core 2, the lower cladding base 1, the upper cladding cover 5, and 2 powder loading pipes 6. During the process, the preforms of the annular casing installation edge, the reinforcing ribs, and the mounting seats are respectively inserted into the cladding to obtain the powder-loading cladding of the fan casing;

[0067] (5) Powder loading, degassing, and sealing welding of the fan casing cladding assembly

[0068] Load TA15 spherical powder into the obtained powder-loading cladding of the fan casing through the 2 powder loading pipes 6 reserved on the upper cladding cover 5. Compact the powder by vibration and tapping, and record the powder loading weight as 24.8 kg. After the powder loading is completed, insert 2 degassing pipes 7 into the 2 powder loading pipes 6 respectively, and connect the degassing pipes 7 and the annular casing powder-loading cladding into one body by argon arc welding. Finally, insert the two halves of the outer ceramic ring respectively. The outer surface of the outer ceramic ring is closely fitted with the outer cladding wall 3 and fixed with screws to obtain a complete fan casing cladding assembly.

[0069] Place the fan casing jacket assembly with the welded exhaust pipe 7 in a pit resistance furnace and connect it to a vacuum unit to evacuate. When the reading is lower than 5×10 -3 Pa, start heating up. Heat up to 800°C. When the vacuum degree is lower than 5×10 -3 Pa, start heat preservation. The heat preservation time is 8 hours. After the heat preservation ends, close the pit resistance furnace, but continue to turn on the vacuum pump. When it cools down to 100°C, seal and weld the exhaust pipe 7.

[0070] (6) Hot isostatic pressing of the fan casing jacket assembly

[0071] Place the fan casing jacket in a hot isostatic press, carry out hot isostatic pressing treatment, and cool down to room temperature with the furnace. The process parameters of hot isostatic pressing are that the temperature is controlled at 920°C, the pressure is controlled at 140 MPa, heat preservation and pressure holding for 4 h. After the heat preservation and pressure holding end, cool down to 100°C with the furnace and then take out of the furnace.

[0072] (7) Removal of the fan casing jacket and product processing

[0073] Remove most of the steel jacket by mechanical processing according to the jacket removal drawing, leaving a margin of 3 - 5 mm on each side. Then remove the remaining steel jacket by electrolytic removal to obtain the fan casing blank. Machine the fan casing according to the product drawing to obtain the final fan casing product.

[0074] (8) Inspection and testing of the fan casing product

[0075] The room temperature mechanical properties and high temperature mechanical properties of the fan casing are respectively tested by processing the in-furnace test bars according to GB / T228.1 and GB / T228.2. The required values of the room temperature yield strength, tensile strength, elongation and reduction of area of the TA15 titanium alloy forgings specified in the "Specification for Titanium and Titanium Alloy Forgings for Aeronautical Use" (GJB2744-2007) are ≥855MPa, 930-1130MPa, ≥10% and ≥25% respectively, and the required tensile strength at 500°C is ≥635MPa. The actual test results are that the room temperature yield strengths are 935MPa, 938MPa, 943MPa, the room temperature tensile strengths are 1002MPa, 998MPa, 1008MPa, the room temperature elongations are 19.5%, 20.0%, 17.5%, the room temperature reductions of area are 43%, 41%, 39%, and the tensile strengths at 500°C are 668MPa, 662MPa, 672MPa. The fan casing is subjected to ultrasonic nondestructive testing by using the "Ultrasonic Testing Method for Deformed Metals" (GJB1580A-2004), and the judgment standard adopts Class A in GJB1580A-2004. The results show that no defects exceeding the equivalent of a φ1.2mm flat-bottomed hole are found. The fan casing is subjected to fluorescent inspection by using the "Penetrant Inspection" (GJB2367A-2005), and no surface cracks are found. The mechanical properties and nondestructive testing of the fan casing are all qualified.

[0076] The dimensions of the fan casing are measured, and the contour of the net-shaped outer surface is measured, and the result is 0.46mm, with high forming accuracy. The final weight of the fan casing is 16.5kg, the powder loading is 24.8kg, and the material utilization rate reaches 66.5%.

[0077] Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims of the present invention.

Claims

1. A precise forming method for an annular casing of an aero-engine, characterized in that Including: Producing metal powder through a powder-making process; Using the metal powder to prepare a preform of the annular casing by cold isostatic pressing, the structure and size of the preform corresponding to those of the annular casing; Placing the preform in a jacket of the annular casing and adding the metal powder into the jacket; Performing hot isostatic pressing on the jacket with the preform to obtain the annular casing; The jacket of the annular casing includes an outer jacket wall, an inner jacket core, a lower jacket bottom, and an upper jacket cover. The inner cavity formed by surrounding the outer jacket wall, the inner jacket core, the lower jacket bottom, and the upper jacket cover is used to arrange the preform. The outer ceramic ring is arranged on the outer periphery of the outer jacket wall. The powder loading pipe is arranged on the upper jacket cover, and the degassing pipe is arranged in the powder loading pipe. The inner diameter size α of the outer jacket wall = the contour size β of the annular casing / (0.95 - 0.98). The annular casing includes a target part, and the order of the target part from top to bottom in the annular casing is i, and the central position size γ of the jacket corresponding to the target part i Satisfies:

2. The method according to claim 1, wherein The preform of the annular casing includes an upper mounting edge preform, a lower mounting edge preform, a reinforcing rib preform, and a mounting seat preform.

3. The method according to claim 1, characterized in that, The thickness of the inner core of the jacket, the bottom of the jacket, and the upper cover of the jacket is 6 - 10 mm.

4. The method according to claim 1, characterized in that, The outer ceramic ring satisfies: The material is silicon nitride ceramic, and the designed thickness is 50 - 100 mm.

5. The method according to claim 1, characterized in that, The step of placing the preform in the jacket of the annular casing and adding the metal powder into the jacket includes: Loading spherical metal powder into the inner cavity formed by the outer wall of the jacket, the inner core of the jacket, the bottom of the jacket, and the upper cover of the jacket through the powder loading tube; Compacting the powder by vibration and tapping; After powder loading is completed, inserting the degassing tube into the powder loading tube and welding the degassing tube and the jacket into one body; Assembling the split outer ceramic ring so that the outer circumference of the outer ceramic ring fits the outer wall of the jacket, and fixing the split outer ceramic ring with screws.

6. The method according to claim 5, characterized in that, The pressure of the cold isostatic pressing is 150 - 200 MPa, and the relative density is 90% - 95%.

7. The method according to claim 1, characterized in that, The step of performing hot isostatic pressing on the jacket with the preform to obtain the annular casing includes: Performing degassing by evacuating to a high vacuum; After degassing is completed, sealing and welding the degassing tube; Performing hot isostatic pressing on the jacket with the preform, cooling to below 200 °C after heat preservation and pressure holding and then taking out of the furnace; after hot isostatic pressing is completed, taking out the outer ceramic ring from the jacket, disassembling and removing the jacket to obtain a rough blank of the annular casing; Performing surface treatment and vacuum annealing treatment on the rough blank of the annular casing; Machining the two end flanges and the inner profile with a machining allowance to obtain the annular casing.

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