A method for spin forming of the inner wall of a large-size liquid rocket engine combustion chamber

Abstract

This invention discloses a spinning forming method for the inner wall of a large-size liquid rocket engine combustion chamber, comprising: pre-processing process steps on a CuCrZr alloy tube to obtain an alloy tube containing an effective portion and process steps; using a high-pressure spinning method to blank the CuCrZr alloy tube to obtain a cylindrical part with uniform wall thickness; assuming the thickness of the effective deformable portion of the CuCrZr alloy tube before blanking is δ0, and the wall thickness of the cylindrical part is δ1 = (0.4~0.6)δ0; performing solution heat treatment on the cylindrical part; and performing local high-pressure spinning on the workpiece to obtain a cylindrical part with variable wall thickness; assuming the wall thickness of the inner wall of the engine combustion chamber to be formed is δ f The wall thickness of the first part of the variable-thickness cylindrical component is δ. f The wall thickness of the second part is determined by δ f The thickness gradually increases to δ1, with the third part having a wall thickness of δ1; the cylindrical part is then spun and formed at the neck; the workpiece undergoes aging heat treatment to obtain the inner wall of the combustion chamber. This invention achieves a combustion chamber inner wall with good forming accuracy and mechanical strength using lower production costs and a shorter production cycle.

Description

Technical Field

[0001] This invention belongs to the field of plastic processing technology, specifically relating to a spinning forming method for the inner wall of a large-size liquid rocket engine combustion chamber. Background Technology

[0002] The thrust chamber of a liquid rocket engine is a core component of the rocket engine's propulsion system, responsible for converting the thermal energy of the high-temperature, high-pressure combustion gases generated by the liquid propellant into kinetic energy. The combustion chamber itself is a crucial part of the rocket thrust chamber. To ensure the reliability of the combustion chamber, its inner wall is typically made of a copper alloy material with good electrical conductivity and strength. In recent years, CuCrZr alloys have been increasingly used for the inner walls of combustion chambers. CuCrZr alloys are solid solution strengthened alloys, and the common process for preparing rocket combustion chamber inner wall blanks is forging, solution heat treatment, cold forging, and aging heat treatment. A major drawback of this process is low material utilization and poor performance uniformity. Furthermore, the large machining allowance leads to high costs for subsequent machining. Therefore, more researchers are considering spin forming as an alternative to forging for preparing liquid rocket combustion chambers.

[0003] Existing reports on the fabrication of combustors using spin forming methods mostly employ disc-shaped blanks as raw materials. These discs undergo significant thinning during the forming process, requiring a disc thickness far exceeding the combustor wall thickness, resulting in material waste. Forming combustors from discs often necessitates four or more sets of forming dies, multiple forming passes, and solution heat treatment between passes to obtain the target component, significantly increasing manufacturing costs and production cycles. Currently, reports on the fabrication of rocket engine combustors using copper alloy tubing are relatively few. Research is lacking on the crucial spin forming process and how to control the microstructure and properties of the workpiece through process methods. However, the microstructure and mechanical properties of the component are precisely what rocket thrust chamber designers and process engineers are most concerned with, which is why CuCrZr alloys are favored by thrust chamber designers compared to general copper alloys. The lack of a clear control relationship between existing process methods and material microstructure and properties prevents designers from fully utilizing the material advantages of CuCrZr alloys when using spin forming to fabricate combustors. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects and provide a spinning forming method for the inner wall of a large-size liquid rocket engine combustion chamber. This method solves the technical problems of high processing cost, low forming accuracy, and unsatisfactory product performance of traditional engine combustion chamber inner walls. This invention uses lower production cost and shorter production cycle to obtain a combustion chamber inner wall with good forming accuracy and mechanical strength.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention relates to a method for manufacturing the inner wall of a large-size liquid rocket engine combustion chamber. Using CuCrZr alloy thick-walled tubes as raw materials, the tubes are first spun and deformed, then subjected to multi-pass precision CNC spinning to form the combustion chamber inner wall blank. Solution treatment is applied between passes to eliminate deformation stress and restore material plasticity. After forming, the component undergoes aging heat treatment. By rationally setting and adjusting the spinning process parameters, precise control of component forming, dimensions, and microstructure properties is achieved. The inner surface of the formed workpiece is compared with the theoretical surface template; the single-sided gap is less than 0.2 mm, and the wall thickness deviation is less than 0.3 mm. The room temperature performance of the component meets the following requirements: tensile strength ≥ 450 MPa, yield strength ≥ 320 MPa, elongation ≥ 30%, grain size ≤ 50 μm. The mechanical properties of the component at 500℃ meet the following requirements: tensile strength ≥ 250 MPa, yield strength ≥ 180 MPa, elongation ≥ 20%.

[0007] A method for spin forming the inner wall of a large-size liquid rocket engine combustion chamber includes:

[0008] S1 pre-processes process steps on CuCrZr alloy tubes to obtain CuCrZr alloy tubes containing an effective portion and process steps; the process steps are used to cooperate with a spinning wheel, and the effective deformation portion is the portion that undergoes plastic deformation during the spinning process;

[0009] S2 uses a strong spinning method to open the CuCrZr alloy tube to obtain a cylindrical part with equal wall thickness; assuming that the thickness of the effective deformed part of the CuCrZr alloy tube before opening is δ0, then the wall thickness of the obtained cylindrical part with equal wall thickness is δ1=(0.4~0.6)δ0.

[0010] S3 performs solution heat treatment on cylindrical parts;

[0011] S4 performs localized high-intensity spinning on the workpiece obtained after solution heat treatment to obtain a cylindrical part with variable wall thickness; the cylindrical part with variable thickness consists of three parts, and the wall thickness of the inner wall of the engine combustion chamber to be formed is δ. f Then the wall thickness of the first part of the variable-thickness cylindrical component is δ. f The wall thickness of the second part is determined by δ f Gradually increasing to δ1, the wall thickness of the third part is δ1;

[0012] S5 is used for spin forming of cylindrical parts with varying thickness;

[0013] S6 performs aging heat treatment on the workpiece obtained by the spun forming process to obtain the inner wall of the combustion chamber.

[0014] Furthermore, in the CuCrZr alloy tube, the wall thickness δ0 of the effectively deformed portion is (3~5)δf ;

[0015] The length L0 of the effective deformable portion is determined based on the principle that the volume remains constant during the plastic deformation of the material.

[0016] The inner diameter of the CuCrZr alloy tube is Φ0 = Φ f1 , where Φ f1 The inner diameter of the large end of the combustion chamber wall of the engine to be formed.

[0017] Furthermore, the process steps include sections with uniform wall thickness and sloping sections;

[0018] The wall thickness of the uniform wall thickness section is δ f The length of the equal wall thickness section matches the size of the spinning wheel;

[0019] The ramp section connects to the effective deformation section, and the slope of the ramp section is 40° to 50°.

[0020] Furthermore, in step S2:

[0021] The CuCrZr alloy tube is blanked using a stepped spinning wheel, with the radius of the stepped spinning wheel R1 = (1~1.5)δ0;

[0022] The reduction per pass is not less than 0.3δ. i δ i The thickness of the alloy tube blank before deformation in this pass;

[0023] The feed ratio of the rotary wheel is f = 0.8 to 1.0, and the angle of attack of the rotary wheel is 0°;

[0024] In step S4:

[0025] Spinning is performed using a stepped spinning wheel, with the radius of the stepped spinning wheel R2 = (1~1.5)δ1;

[0026] The reduction per pass is not less than 0.3δ. i δ i The thickness of the alloy tube blank before deformation in this pass;

[0027] The feed ratio of the rotary wheel is f = 1.0 to 1.4, and the angle of attack of the rotary wheel is 0°.

[0028] Furthermore, in step S3, the solution heat treatment method is as follows:

[0029] Under an inert atmosphere, the temperature is kept at 950±10℃ for a holding time t=(2~3)δ1, where t is in min and δ1 is in mm;

[0030] After the heat preservation is completed, the furnace is removed and quenched. The transfer time for quenching should not exceed 20 seconds.

[0031] After quenching, inspect the surface condition of the workpiece. If oxide scale is present, remove it by mechanical grinding.

[0032] Furthermore, the lengths of the first and second parts of the variable-thickness cylindrical part obtained in step S4 are equal to the straight section and the converging section of the inner wall of the engine combustion chamber to be formed, respectively, and the length of the third part is longer than the length of the expanding section of the inner wall of the engine combustion chamber to be formed.

[0033] Furthermore, in step S5, the end is closed by spinning using a closing mold;

[0034] The closing mold is a split structure, consisting of a large-end mold and a small-end mold. The outer surface shape of the large-end mold matches the inner surface shape of the large end of the combustion chamber wall of the engine to be formed. The maximum diameter of the large-end mold is Φ. f1 The outer surface of the small-end mold includes a matching part and an overlapping part. The shape of the matching part matches the shape of the inner surface of the small end of the combustion chamber wall of the engine to be formed. The maximum diameter of the matching part is Φ. f2 The diameter of the overlapping part is Φ f2 Smooth transition to Φ f1 ;

[0035] At the beginning of step S5, the closing mold is installed inside the variable thickness cylindrical part. The inner surface of the first part of the variable thickness cylindrical part contacts the outer surface of the large end mold, and the inner surface of the third part of the variable thickness cylindrical part contacts the outer surface of the overlapping part of the small end mold.

[0036] At the end of step S5, the small end of the resulting workpiece is trimmed so that the maximum diameter of the remaining small end of the workpiece is Φ. f2 The length of the cut portion is equal to the length of the third part of the variable-thickness cylindrical part extending beyond the expansion section of the combustion chamber wall of the engine to be formed.

[0037] Furthermore, in step S5:

[0038] The cylindrical component with varying thickness is heated to a temperature of (0.6~0.8)T. a T a This refers to the aging heat treatment temperature.

[0039] Suppose that the spun forming process involves n spun passes, wherein the radial plastic deformation caused by each spun pass is equal, and the axial plastic deformation caused by each spun pass is equal;

[0040] The end is spun and formed by alternating forward and reverse rotation. Each forward or reverse rotation is completed by rotating to the throat position and then withdrawing the spinning wheel.

[0041] The rounded corner spinning wheel is used for the closing spinning forming. The rounded corner of the spinning wheel is R3 = (1~1.5)δ0; the angle of attack of the spinning wheel is 0°; when spinning forward, the feed ratio of the spinning wheel is f = 1.5~2.0; when spinning backward, the feed ratio of the spinning wheel is f = 1.0~1.5.

[0042] Furthermore, in step S6: the temperature of the aging heat treatment is 410±10℃, the holding time is 6~8h, and the furnace is removed and air-cooled after the holding time is completed; during the aging treatment, an inert protective gas is introduced into the furnace.

[0043] Furthermore, the inner diameter Φ of the large end of the combustion chamber wall f1 Not less than 400mm, small end inner diameter Φ f2 Not less than 300mm, throat inner diameter Φ f3 Not less than 200mm, total length L f Not less than 700mm, wall thickness δ f Not less than 8mm;

[0044] In step S1, the CuCrZr alloy tube has a room temperature tensile strength ≥200MPa, a yield strength ≥120MPa, an elongation ≥15%, and a grain size ≤150μm.

[0045] Compared with the prior art, the present invention has at least one of the following advantages:

[0046] (1) This invention uses CuCrZr alloy forged pipe as raw material and adopts precision spinning forming. The material utilization rate is higher than that of the traditional cold forging scheme or the scheme of spinning the disc material, and the requirements for the structure and properties of the raw material are lower.

[0047] (2) The present invention can form the engine combustion chamber wall blank by using two sets of spinning molds, three clamping processes, and one solution treatment, which has a low manufacturing cost and a short production cycle.

[0048] (3) The CuCrZr alloy engine combustion chamber blank obtained by the present invention has undergone at least one strong spinning deformation or closing spinning deformation in all parts after solution heat treatment, and the deformation amount is more than 30%, which further improves the structure and mechanical properties of the component.

[0049] (4) The CuCrZr alloy engine combustion chamber inner wall blank obtained by the present invention has better dimensional accuracy and wall thickness accuracy than the traditional preparation process.

[0050] (5) The process of this invention is simple, easy to implement, and has strong practicality, especially suitable for the production and preparation of large-scale products;

[0051] (6) The present invention has designed the structure of the closing mold so that it can provide good support for the small end of the workpiece, which is beneficial to improving the forming accuracy;

[0052] (7) In the process of closing the end, the present invention makes the deformation amount of each spinning pass consistent, so that the workpiece produces stable plastic deformation, which further improves the forming accuracy and reduces the generation of stress. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0054] Figure 2 This is a schematic diagram of a large-size liquid rocket engine combustion chamber inner wall blank prepared according to the present invention;

[0055] Figure 3 This is a schematic diagram of the CuCrZr alloy thick tube preform of the present invention;

[0056] Figure 4 This is a schematic diagram of the mold used for the end-forming spin molding of the present invention;

[0057] Figure 5 This is a schematic diagram of the variable wall thickness cylindrical part obtained by the high-pressure spinning of the present invention being mounted on the end-receiving spinning die;

[0058] Figure 6 This is a schematic diagram of the trajectory of the retracting spinning wheel of the present invention;

[0059] Figure 7 This is a schematic diagram of the closing spinning process of the present invention.

[0060] In the picture:

[0061] 1-Cylindrical part; 2-Large end mold; 3-Small end mold; 4-Connecting shaft; 5-Washer; 6-Locking nut; 7-Rolling wheel. Detailed Implementation

[0062] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0063] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0064] When manufacturing large-sized liquid rocket engine combustion chamber wall products, on the one hand, they need to have the dimensional accuracy of shape, position and wall thickness that meet the design requirements, and on the other hand, their microstructure and properties need to meet the requirements of service conditions. In addition, it is desirable that the forming conditions are easy to achieve, the process flow is simplified, the production efficiency is high and the manufacturing cost is low.

[0065] This invention provides a spin forming method for the inner wall of a large-size liquid rocket engine combustion chamber. This method has advantages such as low cost, short manufacturing cycle, low manufacturing difficulty, and excellent microstructure and properties of the prepared components.

[0066] This invention discloses a spin forming method for the inner wall of a large-size liquid rocket engine combustion chamber, comprising the following steps:

[0067] (1) Blank preparation: Pre-process the CuCrZr alloy thick tube to meet the requirements of the subsequent spinning forming process;

[0068] (2) Thick tube spinning blanking: CuCrZr alloy thick tube blanks are spun blanks with high force;

[0069] (3) Solution heat treatment: The billet obtained in step (2) is subjected to solution heat treatment;

[0070] (4) Precision high-pressure spinning: The blank obtained in step (3) is subjected to high-pressure spinning;

[0071] (5) Precision spinning forming: The blank obtained in step (4) is spun forming;

[0072] (6) Aging heat treatment: The spun component obtained in step (5) is subjected to aging treatment to obtain a large-size liquid rocket engine combustion chamber blank component that meets the requirements in terms of size and microstructure.

[0073] The blank component obtained by spinning is processed through machining and other processes to obtain the final combustion chamber wall product.

[0074] Preferably, the larger size refers to the inner diameter Φ of the larger end of the component. f1 Not less than 400mm, small end inner diameter Φ f2 Not less than 300mm, throat inner diameter Φ f3 Not less than 200mm, total length L f Not less than 600mm, wall thickness δ f Not less than 8mm.

[0075] Preferably, the combustion chamber wall has a typical Laval nozzle structure, wherein Φ f1 >Φ f2 >Φ f3 , and Φ f3 / Φ f1≥0.4; Total length of component L f =L a +L b +L c L a L is the length of the straight section. b L is the distance from the straight section to the throat. c This is the distance from the throat to the small end face of the component.

[0076] Preferably, in step (1), the CuCrZr alloy thick tube is forged. To ensure sufficient spinning deformation and considering economic efficiency, the wall thickness δ0 of the CuCrZr alloy thick tube is (3~5)δ f Inner diameter Φ0=Φ f1 The effective length L0 participating in subsequent spinning deformation should be calculated based on the principle that the volume remains unchanged during the plastic deformation of the material; the room temperature tensile strength of the CuCrZr alloy pipe (solution state) after forging is ≥200MPa, yield strength is ≥120MPa, elongation is ≥15%, and grain size is ≤150μm.

[0077] Preferably, in step (1), when pre-processing the CuCrZr alloy thick tube, a section with a thickness of δ should be processed outside the effective deformation length L0. f A 45° slope process step is required, and its length should be compatible with the size of the spinning wheel used in the spinning process. The purpose of this process step is to prevent excessive pressure from the spinning wheel at the starting position, which could lead to poor material flow and instability. Additionally, if the deformation resistance exceeds the spinning equipment's load-bearing capacity, spinning deformation will not be possible. If the slope is too steep, the excessive pressure from the spinning wheel will fail to achieve the intended purpose of the process step; if the slope is too shallow, the process step will be too long, reducing the effective material involved in deformation and resulting in material waste.

[0078] Preferably, in step (2), when performing high-pressure spinning on the CuCrZr alloy thick tube blank, a stepped spinning wheel should be selected, with a radius R1 = (1~1.5)δ0 and a single-pass reduction of not less than 0.3δ. i (δ i (The thickness of the blank before deformation in this pass). During the initial spinning process, the feed ratio of the spinning wheel is f = 0.8~1.0, and the angle of attack of the spinning wheel is 0°. At the end of the initial spinning, the blank is a cylindrical structure with uniform wall thickness. To ensure sufficient deformation during the initial spinning process and facilitate subsequent spinning, the wall thickness of the cylindrical part is required to be δ1 = (0.4~0.6)δ0. Furthermore, it should also satisfy the following condition: at the end of the subsequent high-pressure spinning, the free end of the cylindrical part can rest on the outer diameter of the small end of the closing die. The initial spinning should be carried out at room temperature without heating.

[0079] Preferably, in step (3), the solution heat treatment temperature is 950±10℃, the holding time is t(min)=(2~3)δ1(mm), inert gas is introduced during the solution treatment, and the workpiece is quenched after the holding time is completed. The transfer time for quenching should not be longer than 20s. After quenching, the surface condition of the workpiece should be inspected. The surface should have a metallic luster and no visible oxide scale. If oxide scale is present, it can be removed by mechanical grinding.

[0080] Preferably, in step (4), the workpiece obtained in step (3) is mounted on the die for blank spinning and subjected to localized high-pressure spinning. A stepped spinning wheel is used for high-pressure spinning, with a radius R2 of (1~1.5)δ1 and a single pass reduction of not less than 0.3δ. i (δ i (This refers to the thickness of the blank before deformation in this pass). During spinning, the feed ratio of the spinning wheel is f = 1.0~1.4, and the angle of attack of the spinning wheel is 0°. At the end of the heavy spinning process, a cylindrical part with variable wall thickness is obtained, in which the part that has undergone spinning deformation consists of three parts: ① a length of L a The wall thickness is δ f The section with uniform wall thickness corresponds to the straight cylindrical section of the target component; ② The length is L b Wall thickness from δ f The variable wall thickness portion gradually increases to δ1, corresponding to the convergence section of the target component; ③ The constant wall thickness portion with a wall thickness of δ1, the length of which is greater than the expansion section of the target component, to ensure that the free end of the cylindrical blank obtained by force spinning can rest on the outer diameter of the small end of the closing die. Force spinning should be carried out at room temperature without heating.

[0081] Preferably, in step (5), the variable wall thickness cylindrical blank obtained in step (4) is mounted on the closing spinning die. The closing die is a split structure, consisting of a large end die and a small end die, which are connected and fixed by a connecting shaft and corresponding washers and nuts. The interface of the die is machined into a wedge shape. The diameter of the large end die is the same as that of the small end die, both being Φ. f1 This is because the inner diameter of the variable wall thickness cylindrical part obtained in the previous step is Φ. f1 Set the diameter of the small end mold to Φ f1 During the closing process, the small-end mold can effectively support the small end of the variable-wall-thickness cylindrical part, which helps improve the forming quality. The length of the small-end mold is longer than the length of the small end of the target component. After closing, the excess length of the resulting workpiece is cut off, forming an inner diameter of Φ. f2 The little end.

[0082] Preferably, in step (5), the workpiece should be heated during the closing spinning process, and the heating temperature should be controlled at (0.6~0.8)T. a Within the range (T) a (This refers to the aging treatment temperature).

[0083] In one specific embodiment, during the finishing spinning process, the portion to be finished can be divided into n equal parts along the axial and radial directions of the mold, where n = 6 to 10, preferably n = 8, to determine the starting and ending positions of each spinning pass. A rounded-corner spinning wheel is used for finishing spinning, with a corner radius R3 = (3 to 4)δ1. The finishing spinning process employs alternating forward and reverse spinning, i.e., first pass reverse spinning → first pass forward spinning → second pass reverse spinning → second pass forward spinning → third pass reverse spinning → third pass forward spinning → fourth pass reverse spinning → fourth pass forward spinning → … → (n-1)th pass reverse spinning → (n-1)th pass forward spinning → nth pass reverse spinning → nth pass forward spinning. Each forward or reverse spinning pass is completed by reaching the throat position before the spinning wheel is withdrawn. The angle of attack of the spinning wheel during the spinning process is 0°. During forward rotation, the feed ratio of the rotating wheel is f = 1.5–2.0; during reverse rotation, the feed ratio is f = 1.0–1.5. The finishing trajectory of the first n-1 passes is a straight line segment, and the finishing trajectory of the nth pass is an offset line of the surface trajectory of the target component, with the offset distance being the thickness of the target component. This ensures that the deformation amount of the workpiece is evenly distributed in each pass during the finishing deformation process, avoiding material instability caused by excessive deformation in a single pass. Figure 6 The distances between A1B1, B1C1...G1H1 are equal, the distances between A2B2, B2C2...G2H2 are equal, and the radial intervals of each closing trajectory A1A2, B1B2...H1H2 are also equal.

[0084] Preferably, in step (6), the aging heat treatment temperature is 410±10℃, the holding time is 6~8h, and the furnace is removed and air-cooled after the holding time is completed. During the aging treatment, an inert protective gas is introduced into the furnace.

[0085] Example:

[0086] This invention provides a spin forming method for the inner wall of a large-size liquid rocket engine combustion chamber, such as... Figure 1 As shown, the steps are as follows:

[0087] (1) Blank preparation: The CuCrZr alloy thick tube is pre-processed to meet the requirements of the subsequent spinning forming process. Figure 3 The CuCrZr alloy thick tube is forged, and its wall thickness δ0 = (3~5)δ f Inner diameter Φ0=Φ f1 , where δ f Φ f1These represent the wall thickness and large-end inner diameter of the target component, respectively. The effective length L0 participating in subsequent spinning deformation should be calculated based on the principle of constant volume during the plastic deformation of the material. The room temperature tensile strength of the forged CuCrZr alloy tube (solution state) should be ≥200MPa, yield strength ≥120MPa, elongation ≥15%, and grain size ≤150μm. When pre-processing the CuCrZr alloy thick tube, a section with a thickness of δ should be machined outside the effective deformation length L0. f The process steps have a slope of 45°, and the length of the steps should be compatible with the size of the spinning wheel used for spinning.

[0088] (2) Thick tube spinning: For CuCrZr alloy thick tube blanks, a stepped spinning wheel should be used during spinning. The radius of the stepped spinning wheel R1 = (1~1.5)δ0, and the reduction per pass should not be less than 0.3δ0. i (δ i (The thickness of the blank before deformation in this pass is given). During the initial spinning process, the feed ratio of the spinning wheel is f = 0.8~1.0, and the angle of attack of the spinning wheel is 0°. At the end of the initial spinning, the blank is a cylindrical structure with uniform wall thickness, δ1 = (0.4~0.6)δ0, and it should also satisfy the following condition: at the end of the subsequent high-strength spinning, the free end of the cylindrical part can rest on the outer diameter of the small end of the closing die. The initial spinning should be carried out at room temperature without heating.

[0089] (3) Solution heat treatment: The billet obtained in step (2) is subjected to solution heat treatment at a temperature of 950±10℃ and a holding time of t (min) = (2~3)δ1 (mm). Inert gas is introduced during the solution treatment. After the holding time is completed, the billet is removed from the furnace and quenched. The transfer time for quenching should not exceed 20s. After quenching, the surface condition of the workpiece should be inspected. The surface should have a metallic luster and no visible oxide scale. If oxide scale is present, it can be removed by mechanical grinding.

[0090] (4) Precision high-pressure spinning: The blank obtained in step (3) is subjected to high-pressure spinning. The workpiece obtained in step (3) is mounted on the blank spinning die and subjected to local high-pressure spinning. A stepped spinning wheel is selected for high-pressure spinning. The radius of the stepped spinning wheel R2 = (1~1.5)δ1, and the reduction per pass is not less than 0.3δ. i (δ i (This refers to the thickness of the blank before deformation in this pass). During spinning, the feed ratio of the spinning wheel is f = 1.0~1.4, and the angle of attack of the spinning wheel is 0°. At the end of the heavy spinning process, a cylindrical part with variable wall thickness is obtained, in which the part that has undergone spinning deformation consists of three parts: ① a length of L a The wall thickness is δ f The section with uniform wall thickness corresponds to the straight cylindrical section of the target component; ② The length is L b Wall thickness from δf The variable wall thickness portion gradually increases to δ1, corresponding to the convergence segment of the target component; ③ the constant wall thickness portion with a wall thickness of δ1 ( Figure 5 Forced spinning should be performed at room temperature, without heating;

[0091] (5) Precision necking and spinning: The blank obtained in step (4) is necked and spun: The variable wall thickness cylindrical blank is mounted on the necking and spinning die. The necking die is a split structure, consisting of a large end die and a small end die. The two are connected and fixed by a connecting shaft and corresponding washers and nuts. To ensure a tight fit between the two dies, the interface of the dies is machined into a wedge shape. The diameter of the large end die 2 is the same as the diameter of the small end die 3, both being Φ. f1 ( Figure 4 The large-end mold 2 and the small-end mold 3 are connected by a connecting shaft 4 and locked by a locking nut 6. A gasket 5 is provided at the contact point between the connecting shaft and the mold. During the closing process, the closing mold is placed inside the cylindrical part 1, and a spinning wheel 7 is used for spinning and closing. The workpiece should be heated during the closing and spinning process, with the heating temperature controlled at (0.6~0.8)T. a Within the range (T) a (Aging treatment temperature). During the finishing spinning process, the section to be finished can be divided into 8 equal parts along the mold axis and radial direction respectively, thereby determining the starting and ending positions of each spinning pass. A rounded corner spinning wheel is selected for finishing spinning, with a radius R3 = (3~4)δ1. Finishing spinning adopts an alternating forward and reverse spinning method, that is, the first pass reverse spinning → the first pass forward spinning → the second pass reverse spinning → the second pass forward spinning → the third pass reverse spinning → the third pass forward spinning → the fourth pass reverse spinning → the fourth pass forward spinning → the fifth pass reverse spinning → the fifth pass forward spinning → the sixth pass reverse spinning → the sixth pass forward spinning → the seventh pass reverse spinning → the seventh pass forward spinning → the eighth pass reverse spinning → the eighth pass forward spinning. Each forward or reverse spinning pass is completed by spinning to the throat position and then withdrawing the spinning wheel. Figure 6 During spinning, the angle of attack of the spinning wheel is 0°. During forward spinning, the feed ratio of the spinning wheel is f = 1.5–2.0; during reverse spinning, the feed ratio of the spinning wheel is f = 1.0–1.5. The finishing trajectory of the first 7 passes is a straight line segment, and the finishing trajectory of the 8th pass is an offset line from the surface trajectory of the target component, with the offset distance being the thickness of the target component.

[0092] (6) Aging heat treatment: The combustion chamber inner wall blank obtained in step (5) is subjected to aging heat treatment at a temperature of 410±10℃ for 6-8 hours. After the holding time is completed, it is removed from the furnace and air-cooled. During the aging treatment, an inert protective gas is introduced into the furnace. After the aging treatment, a large-size liquid rocket engine combustion chamber inner wall spinning blank with dimensions, microstructure, and performance that meet the requirements is obtained.

[0093] Example 1

[0094] In this implementation case, the raw material used for the spin forming method of the inner wall of the large-size liquid rocket engine combustion chamber is CuCrZr forged tubing with a thickness δ0 = 31 mm, a length of 420 mm, and an inner diameter Φ0 = 380 mm. The measured mechanical properties are: room temperature tensile strength 250–260 MPa, yield strength 160–170 MPa, elongation 16%–17%, and grain size 100–150 μm. The target component is a rocket combustion chamber with a typical Laval nozzle structure. Figure 2 The component has a wall thickness of 10mm, an inner diameter of 380mm at the large end, an inner diameter of 300mm at the small end, an inner diameter of 200mm at the throat, a straight section length of 200mm, a converging section length of 300mm, and an expanding section length of 100mm. The following is the fabrication process of this component:

[0095] (1) Blank preparation: The CuCrZr pipe is processed into the shape shown in the figure. Figure 3 The structure shown has an effective deformation length L0 = 380 mm, a process step length of 30 mm, and a bevel angle of 45°.

[0096] (2) Thick-walled tube spinning: CuCrZr alloy thick-walled tube blanks are subjected to high-pressure spinning. A stepped spinning wheel with a radius R1 = 45mm should be used during spinning. The high-pressure spinning is performed in two passes, with single-pass reductions of 10mm and 6mm respectively. The feed ratio f = 1.0 and the wheel angle of attack is 0° during the spinning process. At the end of the spinning process, the blank is a cylindrical structure with a uniform wall thickness δ1 = 15mm. Spinning is performed at room temperature.

[0097] (3) Solution heat treatment: The billet obtained in step (2) is subjected to solution heat treatment at a temperature of 950℃ and a holding time of t = 30 min. Inert gas is introduced during the solution treatment. After the holding time is completed, the billet is removed from the furnace and quenched. The transfer time for quenching should be 10 s. After quenching, the surface condition of the workpiece is inspected. The surface should have a metallic luster and no visible oxide scale.

[0098] (4) Precision high-strength spinning: The blank obtained in step (3) is subjected to high-strength spinning. The workpiece obtained in step (3) is mounted on the blank spinning mold and subjected to local high-strength spinning. A stepped spinning wheel is used for high-strength spinning. The radius of the stepped spinning wheel is R2 = 15mm. The high-strength spinning is carried out in one pass. The wheel reduction is 5mm. During the spinning process, the feed ratio of the spinning wheel is f = 1.2 and the angle of attack of the spinning wheel is 0°. When the high-strength spinning is finished, a cylindrical part with variable wall thickness is obtained. The part that has undergone spinning deformation consists of three parts: ① a section with a length of 200mm and a wall thickness of 10mm with equal wall thickness, which corresponds to the straight section of the target component; ② a section with a length of 300mm and a wall thickness that gradually increases from 10mm to 15mm with variable wall thickness, which corresponds to the converging section of the target component; ③ a section with a wall thickness of 15mm with equal wall thickness ( Figure 5 Force spinning is performed at room temperature.

[0099] (5) Precision necking and spinning: The blank obtained in step (4) is necked and spun: The variable wall thickness cylindrical blank is mounted on the necking and spinning die. The necking die is a split structure, consisting of a large end die and a small end die. The two are connected and fixed by a connecting shaft and corresponding washers and nuts. The interface of the die is machined into a wedge shape. The diameter of the large end die is the same as that of the small end die, both being 380mm. Figure 4 During the finishing spinning process, the workpiece should be heated, with the heating temperature controlled within the range of 260-320℃. When finishing spinning, the section to be finished can be divided into 8 equal parts along both the axial and radial directions of the mold, thus determining the starting and ending positions of each spinning pass. A rounded corner spinning wheel with a radius R3 = 45mm is used for finishing spinning. The finishing spinning adopts an alternating forward and reverse spinning method, i.e., first pass reverse spinning → first pass forward spinning → second pass reverse spinning → second pass forward spinning → third pass reverse spinning → third pass forward spinning → fourth pass reverse spinning → fourth pass forward spinning → fifth pass reverse spinning → fifth pass forward spinning → sixth pass reverse spinning → sixth pass forward spinning → seventh pass reverse spinning → seventh pass forward spinning → eighth pass reverse spinning → eighth pass forward spinning. Each forward or reverse spinning pass is completed by rotating to the throat position before the spinning wheel is withdrawn. Figure 6 During the spinning process, the angle of attack of the spinning wheel is 0°. During forward spinning, the feed ratio of the spinning wheel is f = 1.5; during reverse spinning, the feed ratio of the spinning wheel is f = 1.2. The finishing trajectory of the first 7 passes is a straight line segment, and the finishing trajectory of the 8th pass is an offset line from the surface trajectory of the target component, with an offset distance equal to the thickness of the target component, i.e., 10mm.

[0100] (6) Aging heat treatment: The combustion chamber inner wall blank obtained in step (5) was subjected to aging heat treatment at a temperature of 420℃ for 6 hours. After the holding time, it was removed from the furnace and air-cooled. During the aging treatment, an inert protective gas was introduced into the furnace. After the aging treatment, the dimensions of the component were measured, and samples were taken from the component to test its microstructure and mechanical properties. The test results are shown in Table 1.

[0101] Table 1. Product size and performance test results of the examples.

[0102]

[0103] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0104] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for spin forming the inner wall of a large-size liquid rocket engine combustion chamber, characterized in that, include: S1 pre-processes process steps on CuCrZr alloy tubes to obtain CuCrZr alloy tubes containing effective parts and process steps; The process step is used to cooperate with the spinning wheel, and the effective deformation part is the part that undergoes plastic deformation during the spinning process; S2 uses a strong spinning method to blank the CuCrZr alloy tube to obtain a cylindrical part with equal wall thickness; assuming the thickness of the effective deformed part of the CuCrZr alloy tube before blanking is δ0, then the wall thickness of the obtained cylindrical part with equal wall thickness is δ1 = (0.4~0.6)δ0. S3 performs solution heat treatment on cylindrical parts; S4 performs localized high-intensity spinning on the workpiece obtained after solution heat treatment to obtain a cylindrical part with variable wall thickness; the cylindrical part with variable thickness consists of three parts, and the wall thickness of the inner wall of the engine combustion chamber to be formed is δ. f Then the wall thickness of the first part of the variable-thickness cylindrical component is δ. f The wall thickness of the second part is determined by δ f Gradually increasing to δ1, the wall thickness of the third part is δ1; S5 is used for spin forming of cylindrical parts with varying thickness; S6 performs aging heat treatment on the workpiece obtained by the spun forming process to obtain the inner wall of the combustion chamber. The lengths of the first and second parts of the variable-thickness cylindrical part obtained in step S4 are equal to the straight section and the converging section of the inner wall of the engine combustion chamber to be formed, respectively, and the length of the third part is longer than the length of the expanding section of the inner wall of the engine combustion chamber to be formed. In step S5, the end is closed and spun using a closing mold; The closing mold is a split structure, consisting of a large-end mold and a small-end mold. The outer surface shape of the large-end mold matches the inner surface shape of the large end of the combustion chamber wall of the engine to be formed. The maximum diameter of the large-end mold is Φ. f1 The outer surface of the small-end mold includes a matching part and an overlapping part. The shape of the matching part matches the shape of the inner surface of the small end of the combustion chamber wall of the engine to be formed. The maximum diameter of the matching part is Φ. f2 The diameter of the overlapping part is Φ f2 Smooth transition to Φ f1 ; At the beginning of step S5, the closing mold is installed inside the variable thickness cylindrical part. The inner surface of the first part of the variable thickness cylindrical part contacts the outer surface of the large end mold, and the inner surface of the third part of the variable thickness cylindrical part contacts the outer surface of the overlapping part of the small end mold. At the end of step S5, the small end of the resulting workpiece is trimmed so that the maximum diameter of the remaining small end of the workpiece is Φ. f2 The length of the cut portion is equal to the length of the third part of the variable-thickness cylindrical part extending beyond the expansion section of the combustion chamber wall of the engine to be formed.

2. The spinning forming method for the inner wall of a large-size liquid rocket engine combustion chamber according to claim 1, characterized in that, In CuCrZr alloy tubes, the wall thickness δ0 of the effectively deformed portion is (3~5)δ f ; The length L0 of the effective deformable portion is determined based on the principle that the volume remains constant during the plastic deformation of the material. The inner diameter of the CuCrZr alloy tube is Φ0=Φ f1 , where Φ f1 The inner diameter of the large end of the combustion chamber wall of the engine to be formed.

3. The spinning forming method for the inner wall of a large-size liquid rocket engine combustion chamber according to claim 2, characterized in that, The process steps include sections with uniform wall thickness and sloping sections; The wall thickness of the uniform wall thickness section is δ f The length of the equal wall thickness section matches the size of the spinning wheel; The ramp section connects to the effective deformation section, and the slope of the ramp section is 40°~50°.

4. The spin forming method for the inner wall of a large-size liquid rocket engine combustion chamber according to claim 1, characterized in that, In step S2: The CuCrZr alloy tube is blanked using a stepped spinning wheel, with the radius of the stepped spinning wheel R1 = (1~1.5)δ0; The reduction per pass is not less than 0.3δ. i δ i The thickness of the alloy tube blank before deformation in this pass; The feed ratio of the rotary wheel is f = 0.8~1.0, and the angle of attack of the rotary wheel is 0°; In step S4: Spinning is performed using a stepped spinning wheel, with the radius of the stepped spinning wheel R2 = (1~1.5)δ1; The reduction per pass is not less than 0.3δ. i δ i The thickness of the alloy tube blank before deformation in this pass; The feed ratio of the rotary wheel is f = 1.0~1.4, and the angle of attack of the rotary wheel is 0°.

5. The spin forming method for the inner wall of a large-size liquid rocket engine combustion chamber according to claim 1, characterized in that, In step S3, the solution heat treatment method is as follows: Under an inert atmosphere, the temperature is kept at 950±10℃ for a holding time t=(2~3)δ1, where t is in min and δ1 is in mm; After the heat preservation is completed, the furnace is removed and quenched. The transfer time for quenching should not exceed 20 seconds. After quenching, inspect the surface condition of the workpiece. If oxide scale is present, remove it by mechanical grinding.

6. The method for spin forming of the inner wall of a large-size liquid rocket engine combustion chamber according to claim 1, characterized in that, In step S5: The cylindrical component with varying thickness is heated to a temperature of (0.6~0.8) T. a T a This refers to the aging heat treatment temperature. Suppose that the spun forming process involves n spun passes, wherein the radial plastic deformation caused by each spun pass is equal, and the axial plastic deformation caused by each spun pass is equal; The necking and spinning process is carried out by alternating forward and reverse rotation. Each forward or reverse rotation is completed by rotating to the throat position and then withdrawing the spinning wheel. The rounded corner spinning wheel is used for the closing spinning forming. The rounded corner of the rounded corner spinning wheel is R3 = (1~1.5)δ0; the angle of attack of the spinning wheel is 0°; when spinning forward, the feed ratio of the spinning wheel is f = 1.5~2.0; when spinning backward, the feed ratio of the spinning wheel is f = 1.0~1.

5.

7. The method for spin forming of the inner wall of a large-size liquid rocket engine combustion chamber according to claim 1, characterized in that, In step S6: the temperature of the aging heat treatment is 410±10℃, the holding time is 6~8h, and the furnace is removed and air-cooled after the holding time is completed; during the aging treatment, an inert protective gas is introduced into the furnace.

8. The spin forming method for the inner wall of a large-size liquid rocket engine combustion chamber according to claim 1, characterized in that, The inner diameter Φ of the large end of the combustion chamber wall f1 Not less than 400mm, small end inner diameter Φ f2 Not less than 300mm, throat inner diameter Φ f3 Not less than 200mm, total length L f Not less than 700mm, wall thickness δ f Not less than 8mm; In step S1, the CuCrZr alloy tube has a room temperature tensile strength ≥200MPa, a yield strength ≥120MPa, an elongation ≥15%, and a grain size ≤150μm.

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