A method for preparing a copper alloy inner wall of a liquid rocket engine thrust chamber and application thereof

Abstract

The application discloses a preparation method and application of a liquid rocket engine thrust chamber copper alloy inner wall, and relates to the technical field of thin-walled component manufacturing of a rocket engine. The preparation method comprises the following steps: solid solution heat treatment, water quenching and surface pretreatment are performed on a copper alloy blank; after gradient preheating, the following steps are sequentially performed: first-pass coarse spinning, in-situ stress relief treatment, second-pass medium spinning, dynamic grain regulation and holding treatment and third-pass fine spinning; finally, the finished product is obtained through post-treatment, low-temperature aging heat treatment and detection. Through the cooperation of multi-pass variable-speed cross spinning and temperature control between passes, the application effectively eliminates interlayer delamination and microcracks, refines grains and releases residual stress, and significantly improves the high-temperature mechanical properties and service reliability of the thrust chamber inner wall.

Description

Technical Field

[0001] This invention relates to the field of rocket engine thin-walled component manufacturing technology, specifically to a method for preparing and applying a copper alloy inner wall for the thrust chamber of a liquid rocket engine. Background Technology

[0002] The thrust chamber of a liquid rocket engine is the core load-bearing and heat exchange component of the power system. During operation, it must withstand high-temperature gas impact of over 3000℃, high-pressure internal pressure of over 15MPa, and severe alternating thermal shock loads. The inner wall is under extreme high temperature, high pressure, and alternating stress coupling conditions for a long time.

[0003] Currently, the mainstream forming process for the inner wall of the thrust chamber is one-time spinning. Compared with welding and segmented machining processes, one-time spinning has core advantages such as good structural integrity, no welding joints, high heat exchange efficiency, and excellent structural strength, making it the preferred forming process for the inner wall of the thrust chamber of high-thrust launch vehicles.

[0004] While traditional spinning processes can achieve integral forming and avoid welding joints, the unidirectional feeding in actual production results in significant differences in the radial and circumferential flow of metal in the wall thickness direction. This leads to lag in metal flow in the central region, resulting in interlayer delamination and microcracks. At the same time, the local high temperature generated during spinning causes grain coarsening, anisotropy in the structure, and weakens the high-temperature thermal shock resistance. Summary of the Invention

[0005] This invention provides a method for preparing a copper alloy inner wall for the thrust chamber of a liquid rocket engine and its application, aiming to solve problems such as uneven metal flow in the wall thickness direction, coarse grains, and uneven microstructure that exist in traditional spinning processes.

[0006] The technical solution provided by this invention is as follows: This invention provides a method for preparing a copper alloy inner wall of the thrust chamber of a liquid rocket engine, comprising the following steps: The copper alloy billet is subjected to solution heat treatment at a temperature of 920℃-960℃ and a holding time of 50min-100min, followed by water quenching and surface pretreatment to make the surface roughness Ra≤3.2µm. The copper alloy billet after surface pretreatment is subjected to gradient preheating, with the heating temperature controlled at 280℃-300℃ and held for 15min-20min to ensure that the temperature difference in the wall thickness direction is ≤10℃. The first rough spinning process is carried out, with the spindle speed controlled at 50r / min-70r / min, the feed ratio at 100mm / r-120mm / r, and the total thinning rate at 30%-35%. After the rough spinning is completed, in-situ stress relief treatment is performed. After stress relief treatment, a second intermediate spinning process is performed. The spinning feed direction is switched, and the feed is reversed from the large diameter end of the thrust chamber to the small diameter end to achieve staggered spinning. The spindle speed is controlled at 70r / min-90r / min, the feed ratio is 70mm / r-90mm / r, the radial single reduction is 1mm-2mm, and the total thinning rate is 20%-30%. After the intermediate spinning is completed, dynamic grain control and heat preservation treatment is performed. After dynamic grain control and heat preservation treatment, a third fine spinning process is performed to restore the positive feed direction. The spindle speed is controlled at 70r / min-90r / min, the feed ratio is 100mm / r-700mm / r, the radial single reduction is 0.8mm-1mm, and the total thinning rate is 20%-30% to obtain the billet. The billet is subjected to post-processing, low-temperature aging heat treatment, ultrasonic non-destructive testing and metallographic structure testing in sequence to ensure that the internal porosity is ≤0.1% and the average grain size is ≤50µm, so as to obtain the finished copper alloy inner wall of the thrust chamber of liquid rocket engine.

[0007] Optionally, the method for performing in-situ stress relief is as follows: Keep the device in the clamped state and heat it at 500℃-600℃ for 25min-30min, then slowly cool it to room temperature to eliminate the axial residual stress caused by the large deformation of the coarse rotation.

[0008] Optionally, the method for performing dynamic grain control and heat preservation treatment is as follows: Dynamic recovery recrystallization was carried out by holding the temperature online at 600℃-700℃ for 25-35 minutes.

[0009] Optionally, before performing gradient preheating on the surface-pretreated copper alloy billet, the method further includes: coaxially clamping the surface-pretreated copper alloy billet onto the surface of a high-power CNC spinning die, and using a tail end to press and fix the end face of the billet to prevent axial movement during the spinning process; During the first pass of coarse spinning, the second pass of intermediate spinning, and the third pass of fine spinning, the circumferential symmetry of the two spinning wheels is always maintained at ≤0.02mm, and the radial synchronization error of the two spinning wheels is ≤0.01mm.

[0010] Optionally, the first coarse spinning pass is performed using a dual-rotor symmetrical synchronous spinning mode, with the rotary wheel radius being 30mm-40mm; During the third precision spinning process, the internal water-cooling circulation of the mandrel is synchronized to control the final forming temperature of the copper alloy billet to be stable at 300℃-350℃, suppressing secondary grain growth and completing the final wall thickness and contour dimensions of the thrust chamber.

[0011] Optionally, when performing the first pass of coarse spinning, the second pass of intermediate spinning, and the third pass of fine spinning, a water-based graphite high-temperature resistant lubricant is used throughout the process, and the lubricant coating thickness is 0.03mm-0.05mm.

[0012] Optionally, the post-processing method is as follows: air-cool the billet to room temperature and remove the flash and excess material at the ends; The method for performing the low-temperature aging heat treatment is as follows: the post-treated blank is held at a temperature of 380℃-420℃ for 60min-120min.

[0013] Optionally, the surface pretreatment method is as follows: rough machining is performed on the copper alloy billet after water quenching to remove surface oxide scale and forging surface inclusions.

[0014] Optionally, the room temperature tensile strength of the finished copper alloy inner wall of the liquid rocket engine thrust chamber is 400MPa-480MPa, and the high temperature tensile strength at 500℃ is 180MPa-300MPa.

[0015] The present invention also provides an application of the above-mentioned method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine in the aerospace field.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a method for preparing and applying a copper alloy inner wall for the thrust chamber of a liquid rocket engine. The method involves optimizing the initial microstructure of the copper alloy billet through solution heat treatment and water-cooled quenching, combined with gradient preheating to control the wall thickness temperature difference. This is followed by a three-pass, variable-speed, variable-thinning-rate roughing, intermediate, and finishing spinning process, with in-situ stress relief and dynamic grain control insulation treatment embedded between key passes. By precisely matching the spindle speed, feed ratio, and radial reduction, the metal achieves coordinated flow in the axial, circumferential, and radial directions. In particular, the staggered spinning in the second pass breaks the interlayer flow interface, promoting metallurgical bonding between metal layers. Simultaneously, the use of mandrel water-cooling circulation and lubricant for synergistic temperature control effectively suppresses secondary grain growth. Based on this, post-processing, low-temperature aging heat treatment, and dual non-destructive testing are used to further stabilize the microstructure and eliminate potential defects. This effectively solves the internal defect problems that existing technologies struggle to overcome during forming, such as uneven metal flow, core stress concentration, and large deformation gradients in the wall thickness direction, leading to interlayer delamination, microcracks, coarse grains, and excessive residual internal stress. Therefore, it avoids the risks of burn-through, cracking, and fatigue failure caused by hidden internal defects in traditional processes, significantly improving the high-temperature mechanical properties, thermal shock resistance, and service reliability of the components, and meeting the stringent requirements of the aerospace field for high-thrust liquid rocket engines under extreme operating conditions. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation method of the copper alloy inner wall of the thrust chamber of a liquid rocket engine in an embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit the invention.

[0019] To achieve the aforementioned objectives, this invention provides a method for preparing and applying a copper alloy inner wall for the thrust chamber of a liquid rocket engine. The overall technical solution, as described in the embodiments of this invention, mainly includes the following core technical elements: solution heat treatment and surface pretreatment of the copper alloy billet, gradient preheating and multi-pass spinning forming process, in-situ stress relief and dynamic grain control heat preservation treatment between passes, and subsequent aging heat treatment and non-destructive testing. These technical elements work together to constitute the overall technical solution of this invention.

[0020] like Figure 1 As shown, this invention provides a method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine, comprising the following steps: S1. The copper alloy billet is subjected to solution heat treatment at a temperature of 920℃-960℃ and a holding time of 50min-100min. Then, it is subjected to water quenching and surface pretreatment to make the surface roughness Ra≤3.2µm of the billet. S2. Perform gradient preheating on the surface-pretreated copper alloy billet, with the heating temperature controlled at 280℃-300℃ and held for 15min-20min to ensure that the temperature difference in the wall thickness direction is ≤10℃. S3. Perform the first rough spinning pass, controlling the spindle speed at 50r / min-70r / min, the feed ratio at 100mm / r-120mm / r, and the total thinning rate at 30%-35%. After the rough spinning is completed, perform in-situ stress relief treatment. S4. After stress relief treatment, perform the second intermediate spinning process, switch the spinning feed direction, feed from the large diameter end of the thrust chamber to the small diameter end to achieve staggered spinning, control the spindle speed to 70r / min-90r / min, the feed ratio to 70mm / r-90mm / r, the radial single reduction to 1mm-2mm, and the total thinning rate to 20%-30%. After intermediate spinning is completed, perform dynamic grain control and heat preservation treatment. S5. After dynamic grain control and heat preservation treatment, a third fine spinning process is performed to restore the positive feed direction. The spindle speed is controlled at 70r / min-90r / min, the feed ratio is 100mm / r-700mm / r, the radial single pressing amount is 0.8mm-1mm, and the total thinning rate is 20%-30% to obtain the billet. S6. The billet is subjected to post-processing, low-temperature aging heat treatment, ultrasonic non-destructive testing and metallographic structure testing in sequence to ensure that the internal porosity is ≤0.1% and the average grain size is ≤50µm, so as to obtain the finished copper alloy inner wall of the thrust chamber of the liquid rocket engine.

[0021] The method provided by this invention, by setting the process parameters of solution heat treatment, gradient preheating, and three-pass spinning, can effectively control the triaxial flow consistency of the metal in the wall thickness direction, break up the original casting porosity and pores, eliminate interlayer bonding interfaces, refine the matrix grains, and reduce residual internal stress during forming. This solves the problems of uneven metal flow, core stress concentration, large deformation gradient in the wall thickness direction, and easy generation of internal defects such as interlayer delamination, microcracks, coarse axial grains, and excessive residual internal stress in the single-pass spinning forming process of the inner wall of the thrust chamber of a liquid rocket engine in the prior art. It achieves high density and uniform microstructure of the inner wall of the thrust chamber, eliminating the need for subsequent hot isostatic pressing or welding repair, and significantly improving the high-temperature mechanical properties and thermal shock resistance of the component. For example, solution temperatures of 930℃ and 950℃ can be used, or spindle speeds of 60 r / min and 80 r / min can be used in the second and third spinning passes to adapt to the forming requirements of different specifications of billets.

[0022] This method, through the synergistic effects of solution heat treatment, gradient preheating, three-pass variable-speed and variable-thinning-rate spinning, in-situ stress relief between passes, and dynamic grain-controlled heat preservation, achieves the compaction and closure of internal pores and the complete elimination of interlayer delamination during the forming process of the copper alloy inner wall of the thrust chamber of a liquid rocket engine. Simultaneously, multi-stage temperature control achieves uniform and refined matrix microstructure. Furthermore, in-situ stress relief releases deformation stress step by step, preventing the initiation and propagation of internal microcracks, while dynamic grain-controlled heat preservation eliminates anisotropy in mechanical properties by dynamically restoring and recrystallizing long, strip-shaped deformed grains. Therefore, this preparation method significantly improves the overall forming quality and service stability of the inner wall of the thrust chamber of a liquid rocket engine, controlling the internal porosity to within 0.1% and the average grain size to ≤50µm, effectively solving the problems of cracking, burn-through, and fatigue failure of the inner wall under high-temperature and high-pressure conditions caused by internal defects in existing technologies.

[0023] In the actual spinning process, it may be difficult to completely eliminate axial movement and internal stress concentration caused by unstable clamping or asynchronous spinning wheels simply by optimizing the spinning process parameters. Therefore, the present invention provides the following preferred embodiments.

[0024] As a specific implementation method, in step S3, the in-situ stress relief treatment is performed by maintaining the clamped state and holding it at 500℃-600℃ for 25-30 minutes, followed by slow cooling to room temperature to eliminate the axial residual stress caused by the large rough-rotation deformation. By performing in-situ stress relief treatment, the residual stress introduced by plastic deformation can be eliminated through a thermal relaxation mechanism without disassembling the workpiece. This effectively blocks the path of internal microcrack initiation and propagation after the large rough-rotation deformation, further improving the service stability of the component. For example, a holding temperature of 550℃ or 580℃, or a holding time of 28 minutes or 30 minutes can be used.

[0025] As a specific implementation method, in step S4, the dynamic grain control heat preservation treatment is performed by holding the material online at a temperature of 600℃-700℃ for 25-35 minutes to achieve dynamic recovery recrystallization. Through dynamic grain control heat preservation, after spinning, high-temperature heat preservation promotes dislocation rearrangement and subgrain merging, achieving dynamic recrystallization. This breaks up the elongated deformed grains, initially refines the matrix structure, and avoids anisotropy in mechanical properties caused by residual deformed structures. For example, the online heat preservation temperature can be 620℃ or 680℃, or the heat preservation time can be 28 minutes or 33 minutes.

[0026] In one specific implementation, before gradient preheating the surface-pretreated copper alloy billet in step S2, the method further includes: coaxially clamping the surface-pretreated copper alloy billet onto the surface of a high-power CNC spinning die, and using a tail end to press and fix the end face of the billet to prevent axial movement during the spinning process; during the first pass of rough spinning, the second pass of intermediate spinning, and the third pass of fine spinning, the circumferential symmetry of the double spinning wheels is always maintained at ≤0.02mm, and the radial synchronization error of the double spinning wheels is ≤0.01mm. This embodiment ensures uniform force during the spinning process through high-precision clamping and synchronous control of the double spinning wheels, thereby preventing axial movement and ensuring consistent deformation in the wall thickness direction, and reducing internal stress concentration. For example, the circumferential symmetry of the double spinning wheels can be 0.01mm or 0.015mm, or the radial synchronization error of the double spinning wheels can be 0.005mm or 0.008mm.

[0027] As a specific implementation method, the first rough spinning pass can employ a dual-wheel symmetrical synchronous spinning mode with a wheel radius of 30mm-40mm. During the third fine spinning pass, a synchronized water-cooling circulation within the mandrel is used to control the final forming temperature of the copper alloy billet at 300℃-350℃, suppressing secondary grain growth and achieving precise forming of the final wall thickness and contour dimensions of the thrust chamber. By switching the spinning feed direction for staggered spinning, the interlayer flow interface in the wall thickness direction can be broken, strengthening the metallurgical bond. Simultaneously, the mandrel water cooling controls the final forming temperature, thereby completely eliminating interlayer delamination defects and preventing secondary grain growth, ensuring dimensional accuracy and microstructure stability. The first rough spinning pass can also use a wheel radius of 32mm or 38mm, or the third fine spinning pass can use a final forming temperature of 320℃ or 340℃.

[0028] In one specific implementation, water-based graphite high-temperature resistant lubricant is used throughout the first rough spinning pass, the second intermediate spinning pass, and the third fine spinning pass, with a lubricant coating thickness of 0.03mm-0.05mm. This water-based graphite high-temperature resistant lubricant combines friction reduction and heat dissipation functions, lowering the coefficient of friction between the spinning wheel and the blank and carrying away some heat, thereby preventing localized overheating that could lead to abnormal grain growth and maintaining uniform microstructure. For example, the lubricant coating thickness can be 0.035mm or 0.045mm.

[0029] As a specific implementation method, in step S6, the post-processing method is to air-cool the billet to room temperature and remove the flash and excess material at the ends.

[0030] The method for low-temperature aging heat treatment is as follows: the post-treated blank is held at 380℃-420℃ for 60min-120min.

[0031] Post-processing involves air cooling of the billet to prevent the generation of new stresses from rapid cooling, and aging treatment to precipitate strengthening phases, thereby stabilizing the microstructure and improving the overall mechanical properties of the finished product, especially its high-temperature strength. For example, aging temperatures of 390℃ or 410℃, or holding times of 80 min or 100 min, can be used.

[0032] As a specific implementation method, in step S1, the surface pretreatment method is as follows: rough machining is performed on the surface of the water-quenched copper alloy billet to remove the surface oxide scale and forging surface inclusions.

[0033] This embodiment removes the surface defect layer through mechanical processing, thereby ensuring a clean interface for subsequent spinning, improving the bonding quality of the spinning interface, and preventing impurities from inducing cracks.

[0034] As a specific implementation, the copper alloy inner wall of the thrust chamber of the liquid rocket engine prepared by this invention has a room temperature tensile strength of 400MPa-480MPa and a high temperature tensile strength of 180MPa-300MPa at 500℃. By controlling the uniformity of the microstructure and the fine grain strengthening through the aforementioned process, the product is ensured to meet the structural strength requirements of the liquid rocket engine under extreme service conditions.

[0035] This invention provides an application of the method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to any of the above embodiments in the aerospace field. By applying the copper alloy inner wall of the thrust chamber of a liquid rocket engine prepared by the above method to the aerospace field, the reliability and lifespan of aerospace propulsion systems can be improved, supporting the mission requirements of high thrust and long-term operation.

[0036] Unless otherwise specified, all materials, reagents and instruments used in the embodiments of this invention can be obtained through commercial channels.

[0037] 1. Materials and Reagents Copper alloy billet: Chromium-zirconium copper alloy thrust chamber inner wall special round forged billet, is an aerospace grade high strength and high conductivity chromium-zirconium copper alloy (CuCrZr / C18150 / TCr1-0.15), with pure copper as the base and trace amounts of chromium and zirconium added. It belongs to precipitation strengthened copper alloy, with a diameter of 600mm-1200mm and a thickness of 30mm-50mm.

[0038] Water-based graphite high-temperature resistant lubricant: commercially available industrial grade.

[0039] 2. Instruments and Equipment High-power CNC spinning machine: SY-400 model; Heating device: Medium frequency induction heating furnace; Ultrasonic non-destructive testing instrument: USM35X model; Metallurgical microscope: DM4M model; Electronic universal testing machine: AG-X Plus model.

[0040] Example 1 This embodiment prepares a high-performance copper alloy inner wall for the thrust chamber of a liquid rocket engine, and verifies the effect of a three-stage spinning process and intermediate heat treatment on eliminating internal defects and refining grains, including the following steps: (1) Select chromium zirconium copper alloy round forged billet, perform solution heat treatment on the billet, the solution temperature is 950℃, the holding time is 75min, and then perform water quenching. (2) The copper alloy billet after water quenching is rough machined to remove the surface oxide scale and forging surface inclusions, so that the surface roughness Ra of the billet is 2.5µm. (3) The pre-treated copper alloy billet is coaxially clamped on the surface of the core die of the high-power CNC spinning machine, and the end face of the billet is fixed by tail clamping. (4) The billet is preheated in a gradient manner, the heating temperature is controlled at 290℃, and the temperature is held for 18 minutes to make the temperature difference in the wall thickness direction 8℃. (5) Perform the first rough spinning, using a dual-rotor symmetrical synchronous spinning mode, with a rotary wheel radius of 35mm, controlling the spindle speed at 60r / min, a feed ratio of 110mm / r, and a total thinning rate of 32.5%. The spinning direction is unidirectional, from the small diameter end to the large diameter end of the thrust chamber wall. Water-based graphite high-temperature resistant lubricant is sprayed throughout the process, with a thickness of 0.04mm. (6) After rough spinning is completed, the clamped state is used for in-situ stress relief treatment. The temperature is kept at 550℃ for 28 minutes, and then slowly cooled to room temperature. (7) After stress relief treatment, perform the second intermediate spinning, switch the spinning feed direction, feed from the large diameter end of the thrust chamber to the small diameter end, control the spindle speed to 80 r / min, the feed ratio to 80 mm / r, the radial single pressing amount to 1.5 mm, and the total thinning rate to 25%; (8) After the spin forming is completed, dynamic grain control and heat preservation treatment is carried out. The temperature is kept online at 650℃ for 30 minutes to carry out dynamic recovery recrystallization; (9) After dynamic grain control and heat preservation treatment, the third fine spinning is carried out to restore the positive feed direction. The internal water cooling circulation of the core mold is matched synchronously to control the final forming temperature of the copper alloy billet to be stable at 320℃. The spindle speed is controlled at 80r / min, the feed ratio is 300mm / r, the radial single pressing amount is 0.9mm, and the total thinning rate is 25% to obtain the billet. (10) Post-process the billet by air cooling to room temperature and removing the flash and excess material at the ends; (11) Perform low-temperature aging heat treatment, and keep the post-treated billet at 400℃ for 90 min; (12) Perform ultrasonic non-destructive testing and metallographic structure testing on the workpiece after aging treatment.

[0041] Testing revealed that the prepared copper alloy inner wall of the liquid rocket engine thrust chamber had an internal porosity of 0.06%, an average grain size of 32µm, a room temperature tensile strength of 465MPa, and a high temperature tensile strength of 285MPa at 500℃.

[0042] The results show that the thrust chamber wall prepared using the process parameters of this embodiment can effectively achieve the compaction and closure of internal pores and the elimination of interlayer delamination, resulting in a uniform and refined matrix structure that meets the requirements of high performance indicators.

[0043] Example 2 The purpose of this embodiment is to verify the feasibility of the process at a solution temperature of 920°C.

[0044] Under the same preparation conditions as in Example 1, only the solution temperature was adjusted from 950℃ to 920℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.08%, an average grain size of 38µm, a room temperature tensile strength of 450MPa, and a high-temperature tensile strength of 268MPa at 500℃.

[0045] Example 3 The purpose of this embodiment is to verify the feasibility of the process at a solution temperature of 960°C.

[0046] Under the same preparation conditions as in Example 1, only the solution temperature was adjusted from 950℃ to 960℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.07%, an average grain size of 35µm, a room temperature tensile strength of 458MPa, and a high-temperature tensile strength of 276MPa at 500℃.

[0047] Example 4 The purpose of this embodiment is to verify the process feasibility when the total thinning rate of the first pass coarse spinning is 30%.

[0048] Under the same preparation conditions as in Example 1, only the total thinning rate of the first rough spinning pass was adjusted from 32.5% to 30% to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.08%, an average grain size of 36µm, a room temperature tensile strength of 452MPa, and a high-temperature tensile strength of 270MPa at 500℃.

[0049] Example 5 The purpose of this embodiment is to verify the feasibility of the process when the total thinning rate of the first pass coarse spinning is 35%.

[0050] Under the same preparation conditions as in Example 1, only the total thinning rate of the first rough spinning pass was adjusted from 32.5% to 35% to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.07%, an average grain size of 34µm, a room temperature tensile strength of 460MPa, and a high-temperature tensile strength of 278MPa at 500℃.

[0051] Example 6 The purpose of this embodiment is to verify the feasibility of the dynamic grain control heat preservation treatment at a temperature of 600°C.

[0052] Under the same preparation conditions as in Example 1, only the controlled dynamic grain size regulation temperature was adjusted from 650℃ to 600℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.09%, an average grain size of 42µm, a room temperature tensile strength of 442MPa, and a high-temperature tensile strength of 255MPa at 500℃.

[0053] Example 7 The purpose of this embodiment is to verify the feasibility of the dynamic grain control heat preservation treatment at a temperature of 700°C.

[0054] Under the same preparation conditions as in Example 1, only the controlled dynamic grain size regulation temperature was adjusted from 650℃ to 700℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.08%, an average grain size of 39µm, a room temperature tensile strength of 448MPa, and a high-temperature tensile strength of 262MPa at 500℃.

[0055] Example 8 The purpose of this embodiment is to verify the feasibility of the low-temperature aging heat treatment process at 380°C.

[0056] With all other preparation conditions the same as in Example 1, only the limited low-temperature aging heat treatment temperature was adjusted from 400℃ to 380℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.08%, an average grain size of 37µm, a room temperature tensile strength of 455MPa, and a high-temperature tensile strength of 272MPa at 500℃.

[0057] Example 9 The purpose of this embodiment is to verify the feasibility of the process when the low-temperature aging heat treatment temperature is 420°C.

[0058] Under the same preparation conditions as in Example 1, only the limited low-temperature aging heat treatment temperature was adjusted from 400℃ to 420℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.07%, an average grain size of 35µm, a room temperature tensile strength of 462MPa, and a high-temperature tensile strength of 280MPa at 500℃.

[0059] Example 10 The purpose of this embodiment is to verify the feasibility of the process at a final forming temperature of 300°C.

[0060] Under the same preparation conditions as in Example 1, only the final forming temperature was adjusted from 320℃ to 300℃ to obtain the product. The results show that the product still achieves the technical effects of the present invention, thus proving that the technical solution of the present invention has good feasibility and stability within the above parameter range. Testing revealed that the finished product has an internal porosity of 0.09%, an average grain size of 40µm, a room temperature tensile strength of 445MPa, and a high-temperature tensile strength of 258MPa at 500℃.

[0061] Comparative Example 1 This comparative example uses existing traditional processes to prepare the copper alloy inner wall of the thrust chamber of a liquid rocket engine. It is a conventional unidirectional continuous hot spinning forming method in the industry, without gradient preheating, misaligned spinning, intermediate in-situ stress relief, or dynamic grain control heat treatment. The specific preparation steps are as follows: (1) Select chromium zirconium copper alloy forged round billet of the same batch and specifications as in Example 1, unify the raw material standard, and eliminate the influence of material differences on the performance test results; (2) The billet is subjected to conventional solution heat treatment at a solution temperature of 950℃. After holding at the temperature for 75 minutes, it is water-quenched and then subjected to conventional surface rough machining to remove the surface oxide scale and control the surface roughness Ra≤3.2µm. (3) The billet is coaxially clamped in the core mold of the high-strength CNC spinning machine, and fixed by tail top clamping. Conventional preheating treatment is performed at a preheating temperature of 290℃ and a holding time of 18min. No gradient temperature control is performed in the wall thickness direction. The maximum temperature difference in the wall thickness direction of the billet can reach 22℃. (4) The traditional three-pass unidirectional hot spinning process is adopted. The entire process maintains a single feed direction with a small radial diameter and a large diameter. There is no staggered spinning process. The spinning parameters are as follows: First pass coarse spinning: spindle speed 60r / min, feed ratio 110mm / r, total thinning rate 32.5%, no in-situ stress relief treatment after spinning; Second pass medium spinning: spindle speed 80r / min, feed ratio 80mm / r, radial single reduction 1.5mm, total thinning rate 25%, no dynamic grain control and heat preservation treatment after spinning; Third pass fine spinning: spindle speed 80r / min, feed ratio 300mm / r, radial single reduction 0.9mm, total thinning rate 25%, no core mold water cooling temperature control during the forming process, and the final forming temperature is naturally cooled with a fluctuation range of 260℃-410℃. (5) The same water-based graphite high-temperature resistant lubricant was used throughout the spinning process, with a coating thickness of 0.04 mm, to ensure that the lubrication conditions were consistent with those in Example 1. (6) After forming, the blank is air-cooled to room temperature, the flash and excess at the ends are removed, and a low-temperature aging heat treatment process completely consistent with that in Example 1 is adopted: 400℃ for 90 min; (7) Finally, ultrasonic non-destructive testing and metallographic structure testing were performed to obtain the finished product of the copper alloy inner wall of the thrust chamber prepared by traditional process.

[0062] Testing revealed that the finished product of this comparative example had an internal porosity of 0.35%, an average grain size of 85µm, a room temperature tensile strength of 360MPa, and a high-temperature tensile strength of 150MPa at 500℃. Traditional unidirectional spinning processes result in a single direction of metal flow, a large gradient in wall thickness deformation, weak interlayer bonding, and the continuous accumulation of residual stress during the forming process, leading to coarse grains, poor microstructure uniformity, and numerous internal delamination and microcrack defects. Consequently, the high-temperature mechanical properties and structural stability of the finished product are far inferior to those of the product produced by the process of this invention.

[0063] Comparative Example 2 This comparative example, based on the traditional unidirectional multi-pass spinning process of Comparative Example 1, retains all spinning process parameters, pretreatment, and post-treatment processes. The only difference is the complete elimination of two core intermediate heat treatment processes: in-situ stress relief treatment after coarse spinning and dynamic grain control and heat preservation treatment after intermediate spinning. These processes are used to verify the key role of intermediate heat treatment in defect elimination, grain refinement, and performance improvement. The specific preparation steps are as follows: (1) Select chromium-zirconium-copper alloy billets of the same origin and specifications as those in Example 1 and Comparative Example 1 to ensure the principle of single variable in the experiment; (2) The solution heat treatment, water quenching, surface pretreatment, clamping and fixing, and gradient preheating processes are completely consistent with those in Example 1. The surface roughness of the billet, the preheating temperature, the holding time, and the wall thickness temperature difference are all kept at the same level. (3) The same three-pass variable speed and variable parameter spinning process as in Example 1 is adopted, including rough spinning, intermediate spinning with reverse feed, fine spinning with forward feed and core mold water cooling temperature control. The spinning wheel parameters, speed, feed ratio, pressing amount, total thinning rate, lubrication conditions and final forming temperature (320℃) are all the same as in Example 1. (4) Core difference process: After the first pass of coarse spinning is completed, no in-situ stress relief treatment is performed, and it directly enters the intermediate spinning process; after the second pass of intermediate spinning is completed, no dynamic grain control heat preservation treatment is performed, and it directly enters the fine spinning process. The residual stress of deformation and the deformation grains are not controlled and repaired throughout the process. (5) The post-processing of the billet, low-temperature aging heat treatment, non-destructive testing and metallographic testing procedures, parameters and standards are completely consistent with those in Example 1; (6) The final product of the thrust chamber copper alloy inner wall without intermediate heat treatment control is obtained.

[0064] Testing revealed that the finished product of this comparative example had an internal porosity of 0.28%, an average grain size of 70µm, a room temperature tensile strength of 380MPa, and a high-temperature tensile strength of 165MPa at 500℃. The results indicate that retaining the optimized spinning process and eliminating intermediate temperature control heat treatment resulted in product performance superior to Comparative Example 1 using the purely traditional process. However, compared to the complete process of this invention, it still exhibits problems such as high residual stress, residual deformed grains, significant microstructural anisotropy, and incomplete closure of internal micro-defects. Its high-temperature load-bearing capacity and component stability are significantly insufficient, verifying the synergistic effect of in-situ stress relief and dynamic grain-controlled heat treatment.

[0065] The properties of the copper alloy inner walls of the thrust chambers of liquid rocket engines prepared in Examples 1-10 and Comparative Examples 1-2 are shown in Table 1: Table 1

[0066] As shown in Table 1, the copper alloy inner walls of the liquid rocket engine thrust chambers prepared in Examples 1 to 10 all exhibit low internal porosity, significantly refined average grain size, and significantly superior room temperature and high temperature tensile strength compared to Comparative Examples 1 and 2. Example 1, in particular, demonstrates the lowest internal porosity, the finest grain size, and the best mechanical properties. This confirms that the synergistic effect of three-pass variable-speed, variable-thinning-rate offset spinning, in-situ stress relief between passes, and dynamic grain control and heat preservation treatment effectively eliminates internal defects and improves the overall performance of the material. Even at the boundary values ​​of the parameter range (such as the solution temperature of Examples 2 and 3, and the grain control temperature of Examples 6 and 7), the product performance remains at a high level, demonstrating the rationality and breadth of the process parameter window of this invention.

[0067] Example 11 This embodiment verifies the practical application effect of the preparation method of the present invention in the aerospace field. The copper alloy inner wall of the thrust chamber of a liquid rocket engine prepared in Example 1 was installed in a certain type of liquid rocket engine for ground hot-fire testing. The experimental results show that the copper alloy inner wall prepared by the present invention exhibits good thermal shock resistance and fatigue resistance under simulated high temperature and high pressure conditions of a rocket engine. The inner wall showed no cracking or burn-through, and good dimensional stability. Therefore, it can be used to prepare thrust chamber components for liquid rocket engines in the aerospace field.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a copper alloy inner wall of the thrust chamber of a liquid rocket engine, characterized in that, Includes the following steps: The copper alloy billet is subjected to solution heat treatment at a temperature of 920℃-960℃ and a holding time of 50min-100min, followed by water quenching and surface pretreatment to make the surface roughness Ra≤3.2µm. The copper alloy billet after surface pretreatment is subjected to gradient preheating, with the heating temperature controlled at 280℃-300℃ and held for 15min-20min to ensure that the temperature difference in the wall thickness direction is ≤10℃. The first rough spinning process is carried out, with the spindle speed controlled at 50r / min-70r / min, the feed ratio at 100mm / r-120mm / r, and the total thinning rate at 30%-35%. After the rough spinning is completed, in-situ stress relief treatment is performed. After stress relief treatment, a second intermediate spinning process is performed. The spinning feed direction is switched, and the feed is reversed from the large diameter end of the thrust chamber to the small diameter end to achieve staggered spinning. The spindle speed is controlled at 70r / min-90r / min, the feed ratio is 70mm / r-90mm / r, the radial single reduction is 1mm-2mm, and the total thinning rate is 20%-30%. After the intermediate spinning is completed, dynamic grain control and heat preservation treatment is performed. After dynamic grain control and heat preservation treatment, a third fine spinning process is performed to restore the positive feed direction. The spindle speed is controlled at 70r / min-90r / min, the feed ratio is 100mm / r-700mm / r, the radial single reduction is 0.8mm-1mm, and the total thinning rate is 20%-30% to obtain the billet. The billet is subjected to post-processing, low-temperature aging heat treatment, ultrasonic non-destructive testing and metallographic structure testing in sequence to ensure that the internal porosity is ≤0.1% and the average grain size is ≤50µm, so as to obtain the finished copper alloy inner wall of the thrust chamber of liquid rocket engine.

2. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to claim 1, characterized in that, The method for in-situ stress relief is as follows: Keep the device in the clamped state and heat it at 500℃-600℃ for 25-30 minutes, then slowly cool it to room temperature to eliminate the axial residual stress caused by the large deformation of the coarse rotation.

3. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to claim 1, characterized in that, The method for dynamic grain control and heat preservation treatment is as follows: Dynamic recovery recrystallization was carried out by holding the temperature online at 600℃-700℃ for 25-35 minutes.

4. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to claim 1, characterized in that, Before performing gradient preheating on the surface-pretreated copper alloy billet, the process further includes: coaxially clamping the surface-pretreated copper alloy billet onto the surface of the core die of a high-power CNC spinning machine, and using a tail tip to press and fix the end face of the billet to prevent axial movement during the spinning process; During the first pass of coarse spinning, the second pass of intermediate spinning, and the third pass of fine spinning, the circumferential symmetry of the two spinning wheels is always maintained at ≤0.02mm, and the radial synchronization error of the two spinning wheels is ≤0.01mm.

5. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to claim 4, characterized in that, The first rough spinning pass is performed using a dual-rotor symmetrical synchronous spinning mode, with a rotary wheel radius of 30mm-40mm. During the third precision spinning process, the internal water-cooling circulation of the mandrel is synchronized to control the final forming temperature of the copper alloy billet to be stable at 300℃-350℃, suppressing secondary grain growth and completing the final wall thickness and contour dimensions of the thrust chamber.

6. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to any one of claims 1-5, characterized in that, During the first pass of coarse spinning, the second pass of intermediate spinning, and the third pass of fine spinning, a water-based graphite high-temperature resistant lubricant is used throughout the process, with a lubricant coating thickness of 0.03mm-0.05mm.

7. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to claim 6, characterized in that, The post-processing method is as follows: air-cool the billet to room temperature and remove the flash and excess material at the ends; The method for performing the low-temperature aging heat treatment is as follows: the post-treated blank is held at 380℃-420℃ for 60min-120min.

8. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to claim 6, characterized in that, The surface pretreatment method is as follows: rough machining is performed on the copper alloy billet after water quenching to remove surface oxide scale and forging surface inclusions.

9. The method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to any one of claims 1-5, characterized in that, The room temperature tensile strength of the finished copper alloy inner wall of the thrust chamber of the liquid rocket engine is 400MPa-480MPa, and the high temperature tensile strength at 500℃ is 180MPa-300MPa.

10. The application of a method for preparing the copper alloy inner wall of the thrust chamber of a liquid rocket engine according to any one of claims 1-9 in the aerospace field.

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