Shaping and pre-tightening device and shaping and pre-tightening method for thin-wall ceramic matrix composite pipe fitting

Abstract

The invention discloses a shaping and pre-tightening device and a shaping and pre-tightening method for a thin-wall ceramic-based composite material pipe fitting. The technical problems that in the CVI deposition densification process of a ceramic-based composite material, deposition stress of the thin-wall ceramic-based composite material pipe fitting is not uniform, growth internal stress is not dispersed, the bending deformation degree is large, and the straightness cannot be guaranteed are solved. The device comprises a core mold and two end part pre-tightening assemblies, the shape and the size of the core mold are designed according to the shape of the inner wall of the thin-wall ceramic matrix composite pipe fitting, threads are formed in the two ends of the core mold, and the middle of the core mold is used for supporting and shaping the thin-wall ceramic matrix composite pipe fitting; one end of each end pre-tightening assembly is used for being connected with the end of the thin-wall ceramic matrix composite pipe in a sleeving mode, the other end of each end pre-tightening assembly is connected to the end of the core mold through threads, the end pre-tightening assemblies are used for providing pre-tightening axial tensile stress for the thin-wall ceramic matrix composite pipe, and the size precision uniformity and the shape stability of the thin-wall ceramic matrix composite pipe can be effectively guaranteed.

Description

Technical Field

[0001] The invention relates to a ceramic matrix composite material preparation device, in particular to a shaping pre-tightening device and a shaping pre-tightening method for a thin-wall ceramic matrix composite material pipe fitting. Background Art

[0002] Ceramic-based composite materials have excellent properties such as high specific strength, high specific modulus, high temperature resistance, and corrosion resistance, and have broad application prospects in the fields of aerospace, energy, and chemical industry. As an important structural component, the performance and quality of thin-walled ceramic-based composite pipe fittings directly affect the reliability and service life of related equipment. However, since thin-walled ceramic-based composite pipe fittings are prone to deformation and cracking during the preparation process, effective shaping and pre-tightening devices and preparation methods are required to ensure their quality.

[0003] At present, the commonly used methods for preparing thin-walled ceramic-based composite pipe fittings mainly include winding method, layering method, chemical vapor infiltration method, nano-impregnation and transient eutectic phase synthesis, polymer precursor conversion method, reactive infiltration method, etc. Among them, the chemical phase infiltration process (CVI) is actually an extension of the chemical vapor deposition method, which is a gas-solid surface multiphase chemical reaction. Since it is difficult to form large-sized components with complex shapes in one time, the breakthrough of ceramic-based composite materials in deposition processing technology is also one of the key problems that must be solved for its application. The straightness problem in the CVI deposition densification process of ceramic-based composite materials is an urgent problem to be solved in order to achieve the processing and deposition of thin-walled ceramic-based composite materials with a radial ratio. However, these methods often cannot ensure the dimensional accuracy and shape stability of pipe fittings during the preparation process, and are also prone to defects such as delamination, pores, and bending. In addition, the existing shaping and pre-tightening devices also have some shortcomings, such as complex structure, inconvenient operation, uneven pre-tightening force, etc., which seriously affect the preparation quality and efficiency of thin-walled ceramic-based composite pipe fittings. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems of uneven deposition force, non-dispersion of growth internal stress, large bending deformation and lack of straightness guarantee in thin-walled ceramic-based composite material pipe fittings during the CVI deposition densification process of ceramic-based composite materials, and to provide a shaping pre-tightening device and a shaping pre-tightening method for thin-walled ceramic-based composite material pipe fittings.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A shaping pre-tightening device for thin-walled ceramic-based composite pipe fittings, which is special in that it includes a core mold and two end pre-tightening components;

[0007] The shape and size of the core mold are designed according to the inner wall shape of the thin-walled ceramic-based composite pipe fitting. Both ends of the core mold are provided with threads. The middle part of the core mold is used to closely fit the inner wall of the thin-walled ceramic-based composite pipe fitting, support and shape the thin-walled ceramic-based composite pipe fitting, and ensure the inner wall size accuracy and straightness of the thin-walled ceramic-based composite pipe fitting;

[0008] One end of each end pre-tightening assembly is used to sleeve the end of a thin-walled ceramic-based composite material pipe fitting, and the other end is connected to the end of the core mold through a thread, and is used to provide pre-tightening axial tensile stress for the thin-walled ceramic-based composite material pipe fitting, which can ensure that the end fibers of the thin-walled ceramic-based composite material pipe fitting are tightly connected to the core mold and that the thin-walled ceramic-based composite material pipe fitting is in a linear tensile state.

[0009] Further, the end pre-tightening assembly includes a coaxially arranged positioning assembly, a fastening assembly, a pre-tightening assembly and a fixing assembly;

[0010] A through hole is opened in the middle of the positioning component, and the inner wall of the through hole is smooth. The positioning component is sleeved on the end of the thin-walled ceramic-based composite material pipe fitting through the through hole. A thread is opened on the outer wall of one end of the positioning component, and the fastening component is connected through the thread. The outer wall of the other end is sleeved on the pre-tightening component. The inner wall of the pre-tightening component has an internal threaded hole, and the outer wall has an external thread. The pre-tightening component is connected to the end thread of the core mold through the internal threaded hole, and is connected to the fixing component through the external thread.

[0011] The fastening assembly is used to ensure that the positioning assembly is tightly connected to the end fibers of the ceramic-based composite material pipe fitting, and to position and fix the positioning assembly to prevent sliding.

[0012] The pre-tightening component is mainly used to clamp one side of the positioning component, while ensuring the fit with the core mold, pre-tightening and stretching the end fibers of the ceramic-based composite material pipe fittings to ensure straightness and pre-tightening axial tensile stress.

[0013] The fixing assembly is used to lock the pre-tightening assembly to ensure a tight fit between the pre-tightening assembly and the core mold.

[0014] Each ceramic matrix composite material pipe fitting can be installed and fixed by a pre-tightening assembly, which applies tensile stress to the ceramic matrix composite material pipe fitting along the axial direction and places it at the optimal atmosphere reaction position in the CVI deposition furnace area.

[0015] By pre-tightening the components in the CVI deposition atmosphere area, the uneven weaving of the preform can be reduced and the convex point phenomenon of CVI deposition can be prevented.

[0016] Due to the shaping effect of the thin-walled ceramic matrix composite pipe fittings, it is further beneficial to ensure the straightness of the substrate and coating deposition.

[0017] Under the device, a pre-tightening force can be applied to the ceramic-based composite material pipe fitting along the axial direction, thereby enhancing the tensile strength of the material and ensuring the inner diameter dimensional accuracy of the thin-walled ceramic-based composite material pipe fitting.

[0018] Furthermore, the positioning assembly includes a tubular sleeve and a circular baffle, the inner wall of the tubular sleeve is smooth, a thread is provided on the outer wall at one end, and the fastening assembly is connected by thread, and the outer wall at the other end is sleeved with a circular baffle, and the pre-tightening assembly is sleeved on the circular baffle; by sleeve-fitting the circular baffle in the pre-tightening assembly, the circular baffle can move axially with the pre-tightening assembly.

[0019] Furthermore, the pre-tightening assembly includes two semicircular tubes arranged opposite to each other, the inner walls of the two semicircular tubes are provided with internal threaded holes, one end of the outer wall is connected to the boss, the other end of the outer wall is provided with external threads, each of the bosses is provided with a semicircular groove, the semicircular grooves of the two bosses are connected with a circular baffle, the external threads of the two semicircular tubes are connected to the fixing assembly, and the threads at the ends of the core mold are connected to the two semicircular tubes. The circular baffle is in the semicircular groove of the boss, so that the circular baffle moves axially with the boss, and when the boss rotates, the circular baffle only moves axially under the friction between the tubular sleeve and the thin-walled ceramic-based composite material.

[0020] At the same time, the present invention also provides a shaping and pre-tightening method for thin-walled ceramic-based composite pipe fittings. The shaping and pre-tightening device for thin-walled ceramic-based composite pipe fittings described above is special in that it includes the following steps:

[0021] Step 1, select a suitable mandrel so that the distance between the two threads of the mandrel is slightly larger than the length of the thin-walled ceramic matrix composite pipe;

[0022] Step 2: Apply a release agent on the core mold, put the thin-walled ceramic-based composite pipe fitting to be formed on the core mold, and then put it on the two ends of the thin-walled ceramic-based composite pipe fitting through two end pre-tightening components, and each end pre-tightening component is also connected to one end of the core mold through a thread;

[0023] Step 3, respectively rotate the two end pre-tightening components to move toward both ends along the threads of the core mold, and at the same time apply axial tensile stress to the ends of the thin-walled ceramic-based composite pipe fittings through the end pre-tightening components, so that the thin-walled ceramic-based composite pipe fittings are in a pre-tightened state, thereby applying pre-tightening force to the thin-walled ceramic-based composite pipe fittings to be formed and ensuring the straightness of the thin-walled ceramic-based composite pipe fittings. The role of the axial tensile stress is to keep the pipe fittings in the desired shape and size during the deposition and heat treatment process to prevent deformation and cracking.

[0024] Furthermore, step 3 is specifically as follows:

[0025] The pre-tightening assembly is rotated to move the pre-tightening assembly toward the end of the core mold, and at the same time, the positioning assembly is driven to move along the axial direction of the core mold.

[0026] When tightening the pre-tightening assembly, the axial force of the bolt is transmitted to the end of the thin-walled ceramic matrix composite pipe through the positioning assembly, so that the two ends of the thin-walled ceramic matrix composite pipe are opposite to each other, thereby applying tensile stress to the pipe. Since the positions of the pre-tightening assembly and the positioning assembly are reasonably arranged according to the size and shape of the pipe, the uniform distribution of the pre-tightening force on the pipe can be ensured. At the same time, by adjusting the tightening degree of the pre-tightening assembly, the size of the pre-tightening force can be controlled to adapt to pipes of different sizes and shapes.

[0027] Beneficial effects of the present invention:

[0028] 1. In a shaping pre-tightening device and shaping pre-tightening method for a thin-walled ceramic-based composite material pipe fitting of the present invention, an axial tensile stress is applied to the thin-walled ceramic-based composite material pipe fitting by rotating the end pre-tightening component, thereby placing the thin-walled ceramic-based composite material pipe fitting in a shaping pre-tightening state; the device has a simple structure, is easy to operate, and has uniform pre-tightening force, and can effectively ensure the uniformity of dimensional accuracy and shape stability of the thin-walled ceramic-based composite material pipe fitting.

[0029] 2. The present invention provides a shaping and pre-tightening device and shaping and pre-tightening method for thin-walled ceramic-based composite material pipe fittings, which adopt a process combining CVI molding and shaping and pre-tightening, and can effectively avoid deformation, cracking and other problems of the pipe fittings during the preparation process, and can also improve the preparation quality and efficiency of the pipe fittings, and facilitate mass production.

[0030] 3. The shaping pre-tightening device and shaping pre-tightening method of thin-walled ceramic-based composite pipe fittings of the present invention solve the problems of inaccurate positioning, uncontrollable force and bending deformation caused by conventional reliance on manual autonomous tightening and positioning.

[0031] 4. The present invention provides a shaping and pre-tightening device and shaping and pre-tightening method for thin-walled ceramic-based composite pipe fittings, which are suitable for the size and shape control during the deposition processing and heat treatment of thin-walled ceramic-based composite parts, and are particularly suitable for the deposition processing of long-sized thin-walled ceramic-based composite parts, and are of great significance for improving the deposition preparation effect of such ceramic-based composite parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a partial structural schematic diagram of a core mold in an embodiment of a shaping and pre-tightening device for a thin-walled ceramic-based composite material pipe fitting of the present invention;

[0033] Figure 2 It is a schematic structural diagram of a thin-walled ceramic-based composite material pipe fitting in an embodiment of a shaping and pre-tightening device for a thin-walled ceramic-based composite material pipe fitting of the present invention;

[0034] Figure 3 It is a schematic diagram of the structure of an end portion of an embodiment of a shaping and pre-tightening device for a thin-walled ceramic-based composite pipe fitting of the present invention;

[0035] Figure 4 It is a structural schematic diagram of a positioning assembly in an embodiment of a shaping and pre-tightening device for a thin-walled ceramic-based composite material pipe fitting of the present invention;

[0036] Figure 5 It is a structural schematic diagram of a fastening assembly in an embodiment of a shaping and pre-tightening device for a thin-walled ceramic-based composite material pipe fitting of the present invention;

[0037] Figure 6 It is a structural schematic diagram of a pre-tightening assembly in an embodiment of a shaping pre-tightening device for a thin-walled ceramic-based composite material pipe fitting of the present invention;

[0038] Figure 7 It is a schematic structural diagram of a fixing assembly in an embodiment of a shaping and pre-tightening device for a thin-walled ceramic-based composite material pipe fitting of the present invention.

[0039] In the figure, 1-core mold, 2-positioning assembly, 3-fastening assembly, 4-pre-tightening assembly, 5-fixing assembly. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention provides a shaping and pre-tightening device for thin-walled ceramic-based composite pipe fittings, such as Figure 1 As shown, it includes a core mold 1, a positioning component 2, a fastening component 3, a pre-tightening component 4 and a fixing component 5;

[0042] In this embodiment, the length of the thin-walled ceramic-based composite pipe is L=1200-2400 mm. Figure 2 As shown, the connection relationship of the preload device is:

[0043] The thin-walled ceramic-based composite pipe is sleeved on the core mold 1. The shape and size of the core mold 1 are designed according to the inner wall shape of the thin-walled ceramic-based composite pipe. Figure 3As shown, threads are provided at both ends of the core mold 1, and the middle part of the core mold 1 is used to support and shape the thin-walled ceramic-based composite material pipe fittings; positioning components 2 are respectively sleeved at both ends of the thin-walled ceramic-based composite material pipe fittings, the inner wall of the positioning component 2 is smooth, and the inner wall is sleeved on the end of the thin-walled ceramic-based composite material pipe fitting, a thread is provided on the outer wall of one end of the positioning component 2, and the fastening component 3 is connected through the thread of the outer wall, and the outer wall of the other end of the positioning component 2 is sleeved in the pre-tightening component 4, the inner wall of the pre-tightening component 4 is provided with an internal threaded hole, and the outer wall is provided with an external thread, the pre-tightening component 4 is connected to the end thread of the core mold 1 through the internal threaded hole, and is connected to the fixing component 5 through the external thread.

[0044] like Figure 4 As shown, the positioning component 2 includes a tubular sleeve and a circular baffle. The inner wall of the tubular sleeve is smooth, and a thread is provided on the outer wall at one end, and the fastening component 3 is connected by thread. The outer wall at the other end is sleeved with a circular baffle, and the pre-tightening component 4 is sleeved on the circular baffle. The positioning component 2 refers to the end boundary limit of the thin-walled ceramic matrix composite material pipe fitting, which is used to ensure that the end fiber of the thin-walled ceramic matrix composite material pipe fitting is closely connected with the core mold 1.

[0045] The structure of the fastening assembly 3 is as follows Figure 5 As shown, the fastening component 3 is used to ensure that the positioning component 2 is tightly connected to the end fibers of the ceramic matrix composite material pipe fitting, and is positioned and fixed to prevent sliding.

[0046] The pre-tightening assembly 4 is sleeved on the circular baffle; by sleeved in the pre-tightening assembly 4, the circular baffle can move axially with the pre-tightening assembly.

[0047] like Figure 6 As shown, in this embodiment, the pre-tightening component 4 includes two semi-circular tubes arranged opposite to each other, the inner walls of the two semi-circular tubes are provided with internal threaded holes, one end of the outer wall is connected to the boss, and the other end of the outer wall is provided with external threads, a semi-circular groove is provided in each boss, and a circular baffle is connected in the semi-circular grooves of the two bosses, and the external threads of the two semi-circular tubes are connected to the fixing component 5, and the threads at the end of the core mold 1 are connected in the two semi-circular tubes. The circular baffle is in the semi-circular groove of the boss, so that the circular baffle moves axially with the boss, and when the boss rotates, the circular baffle only moves axially under the friction between the tubular sleeve and the thin-walled ceramic-based composite material. The pre-tightening component 4 is mainly used to clamp one side of the positioning component 2, while ensuring the fit with the core mold 1, pre-tightening and stretching the end fibers of the ceramic-based composite pipe fitting, and ensuring the straightness and pre-tightening axial tensile stress.

[0048] The structure of the fixing assembly 5 is as follows: Figure 7 As shown, the two semicircular tubes used for sleeve connection of the pre-tightening component 4 are mainly used for locking the pre-tightening component 4 to ensure a tight fit between the pre-tightening component 4 and the core mold 1 .

[0049] Since CVI (chemical vapor infiltration) commonly used in the preparation and molding process of ceramic-based composite materials is suitable for the preparation of composite parts with a wall thickness not exceeding 6 mm, in order to ensure the material preparation performance while taking into account the preparation efficiency and cost, the thin-walled ceramic-based composite pipe shaping pre-tightening component 4 in this embodiment is designed to adapt to the performance of different pipes and the needs of use conditions, and to solve the problems of surface protrusions, poor uniformity, bending deformation, etc. during the CVI deposition process of multiple thin-walled pipes. The present invention prevents bending deformation of thin-walled ceramic-based composite pipes during the processes of processing, deposition and heat treatment of thin-walled ceramic-based composite parts, and reduces the impact of uneven deposition diameter of thin-walled pipes on performance.

[0050] Each ceramic matrix composite material pipe can be installed and fixed by a shaping pre-tightening assembly 4, which applies tensile stress to the ceramic matrix composite material pipe along the axial direction and places it at the optimal atmosphere reaction position in the CVI deposition furnace area.

[0051] In the CVI deposition atmosphere region of the shaping pre-tightening component 4, the uneven weaving phenomenon of the shaped thin-walled ceramic-based material pipe fittings can be reduced, and the convex point phenomenon of CVI deposition can be prevented.

[0052] Due to the shaping effect of the thin-walled ceramic matrix composite pipe fittings, it is further beneficial to ensure the straightness of the substrate and coating deposition.

[0053] Under the shaping pre-tightening device of the thin-walled ceramic-based composite pipe fitting, a pre-tightening force can be applied to the ceramic-based composite pipe fitting in the axial direction, thereby enhancing the tensile strength of the material and ensuring the inner diameter dimensional accuracy of the thin-walled ceramic-based composite pipe fitting.

[0054] A shaping and pre-tightening method for thin-walled ceramic-based composite pipe fittings, using a shaping and pre-tightening device for thin-walled ceramic-based composite pipe fittings, characterized in that it includes the following steps:

[0055] Step 1, selecting a suitable mandrel 1 so that the distance between two threads of the mandrel 1 is slightly larger than the length of the thin-walled ceramic matrix composite pipe;

[0056] Step 2: Apply a release agent on the core mold 1, put the thin-walled ceramic-based composite pipe fitting to be formed on the core mold 1, and then put it on the two ends of the thin-walled ceramic-based composite pipe fitting through two end pre-tightening components, and each end pre-tightening component is also connected to one end of the core mold 1 through a thread; specifically:

[0057] Apply a release agent on the core mold 1, put the thin-walled ceramic-based composite material pipe fitting to be formed on the core mold 1, put the tubular sleeve of the positioning component 2 on the end of the thin-walled ceramic-based composite material pipe fitting, and then respectively put the two semicircular tubes of the pre-tightening component 4 into the threaded end of the core mold 1, and extend each circular baffle to the semicircular groove of the boss of each pre-tightening component 4, and then lock the two semicircular tubes through the fixing component 5 to ensure that the two semicircular tubes are tightly fitted to the core mold 1, while ensuring the inner diameter size accuracy and straightness of the thin-walled ceramic-based composite material pipe fitting.

[0058] When the pre-tightening component 4 is tightened, the axial force of the fixing component 5 is transmitted to the end of the thin-walled ceramic-based composite material pipe through the positioning component 2, so that the two ends of the thin-walled ceramic-based composite material pipe are opposite to each other, thereby applying tensile stress to the pipe. Since the positions of the pre-tightening component 4 and the positioning component 2 are reasonably arranged according to the size and shape of the pipe, the uniform distribution of the pre-tightening force on the pipe can be ensured. At the same time, by adjusting the tightening degree of the pre-tightening component 4, the size of the pre-tightening force can be controlled to adapt to pipes of different sizes and shapes.

[0059] Step 3: Rotate the two end pre-tightening components to move toward both ends along the threads of the core mold 1, and apply axial tensile stress to the ends of the thin-walled ceramic-based composite pipe fittings through the end pre-tightening components, so that the thin-walled ceramic-based composite pipe fittings are in a pre-tightened state, and the shaping pre-tightening of the thin-walled ceramic-based composite pipe fittings is completed. Specifically: rotate the pre-tightening component 4 to move the pre-tightening component 4 toward the end direction of the core mold 1, and at the same time drive the positioning component 2 to move along the axial direction of the core mold 1.

[0060] The principle of the shaping pre-tightening method of a thin-walled ceramic-based composite pipe fitting of the present invention is: through the cooperation of the pre-tightening component 4 and the positioning component 2, an axial tensile force is generated on the core mold 1, thereby applying a pre-tightening force to the semi-finished thin-walled ceramic-based composite pipe fitting placed therein, and ensuring the straightness of the thin-walled ceramic-based composite pipe fitting. The function of the pre-tightening force is to keep the pipe fitting in the desired shape and size during the deposition and heat treatment process, and prevent problems such as deformation and cracking.

[0061] Due to the problems of multiple rounds of CVI deposition and long cycle in the processing and deposition of thin-walled ceramic-based composite materials, in order to improve the industrial efficiency of production and preparation and improve the utilization rate of deposition, each thin-walled pipe is placed directly below the node of the deposition positioning component 2, and the deposition positioning component 2 and the thin-walled deposition pipe are placed in the CVI deposition furnace together by hoisting and fixing. The pipe loading direction is kept parallel to the flow direction of the reaction atmosphere to ensure that the reaction amount of the reaction atmosphere and the inner and outer contact surfaces of the pipe tend to be consistent, and the chemical vapor deposition process is used for densification. The multiple rounds of deposition are hoisted in the opposite direction in turn, and the above-mentioned deposition cycle is used to perform multiple rounds of CVI deposition processing.

[0062] The deposition quality of each thin-walled pipe fitting in the present invention is greatly improved, mainly because the axial tensile stress of the thin-walled ceramic-based composite material pipe fitting is applied by shaping and pre-tightening the thin-walled ceramic composite pipe fitting in this embodiment, so that the deposition atmosphere airflow of the thin-walled ceramic composite part in the furnace is parallel to the hoisting diameter direction, reducing the uneven deposition growth of the preform weaving, avoiding the unevenness of radial growth, improving the atmosphere reaction efficiency of the deposition interface layer, and uniform surface deposition, ensuring that the inner wall dimensional accuracy of the thin-walled ceramic composite pipe fitting is qualified, and the straightness of the thin-walled ceramic composite pipe fitting meets the quality requirements, and the deposition efficiency and axial tensile stress quality are significantly improved. The surface deposition is uniform, which can significantly improve the deposition efficiency and quality of the CVI matrix.

[0063] The above description is only a specific embodiment of the present invention, and a comparison of the effects of the specific embodiments and the related comparative examples, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A shaping and pre-tightening device for thin-walled ceramic-based composite pipe fittings, characterized in that: It comprises a core mold (1) and two end pre-tightening components; The shape and size of the core mold (1) are designed according to the inner wall shape of the thin-walled ceramic-based composite material pipe fitting, threads are provided at both ends of the core mold (1), and the middle part of the core mold (1) is used to support and shape the thin-walled ceramic-based composite material pipe fitting; One end of each end pre-tightening assembly is used to sleeve the end of a thin-walled ceramic-based composite material pipe fitting, and the other end is connected to the end of the core mold (1) through a thread. The end pre-tightening assembly is used to provide pre-tightening axial tensile stress for the thin-walled ceramic-based composite material pipe fitting.

2. According to claim 1, a shaping and pre-tightening device for thin-walled ceramic matrix composite pipe fittings is characterized in that: The end pre-tightening assembly comprises a coaxially arranged positioning assembly (2), a fastening assembly (3), a pre-tightening assembly (4) and a fixing assembly (5); A through hole is provided in the middle of the positioning component (2), and the inner wall of the through hole is smooth. The positioning component (2) is sleeved on the end of the thin-walled ceramic-based composite material pipe through the through hole. A thread is provided on the outer wall of one end of the positioning component (2) and is connected to the fastening component (3) through the thread. The outer wall of the other end is sleeved on the pre-tightening component (4). The inner wall of the pre-tightening component (4) is provided with an internal threaded hole, and the outer wall is provided with an external thread. The pre-tightening component (4) is connected to the end thread of the core mold (1) through the internal threaded hole, and is connected to the fixing component (5) through the external thread.

3. The shaping and pre-tightening device for thin-walled ceramic matrix composite pipe fittings according to claim 2, characterized in that: The positioning assembly (2) comprises a tubular sleeve and a circular baffle. The inner wall of the tubular sleeve is smooth. One end of the outer wall is provided with a thread and is connected to the fastening assembly (3) via the thread. The outer wall of the other end is sleeved with the circular baffle. The pre-tightening assembly (4) is sleeved on the circular baffle.

4. The shaping and pre-tightening device for thin-walled ceramic matrix composite pipe fittings according to claim 3, characterized in that: The pre-tightening assembly (4) comprises two semicircular tubes arranged opposite to each other, the inner walls of the two semicircular tubes are provided with internal threaded holes, one end of the outer wall is connected to a boss, and the other end of the outer wall is provided with external threads, each of the bosses is provided with a semicircular groove, and the semicircular grooves of the two bosses are connected to a circular baffle, the external threads of the two semicircular tubes are connected to the fixing assembly (5), and the threads of the ends of the two semicircular tubes are connected to the core mold (1).

5. A shaping and pre-tightening method for thin-walled ceramic-based composite pipe fittings, using a shaping and pre-tightening device for thin-walled ceramic-based composite pipe fittings according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1, selecting a suitable mandrel (1) so that the distance between two threads of the mandrel (1) is slightly larger than the length of the thin-walled ceramic matrix composite pipe; Step 2: Apply a release agent on the core mold (1), put the thin-walled ceramic-based composite material pipe fitting to be formed on the core mold (1), and then put it on the two ends of the thin-walled ceramic-based composite material pipe fitting through two end pre-tightening components, and each end pre-tightening component is also connected to one end of the core mold (1) through a thread; Step 3, respectively rotate the two end pre-tightening components to move along the thread of the core mold (1) toward both ends, and at the same time apply axial tensile stress to the ends of the thin-walled ceramic-based composite material pipe fittings through the end pre-tightening components, so that the thin-walled ceramic-based composite material pipe fittings are in a pre-tightened state, thereby completing the shaping pre-tightening of the thin-walled ceramic-based composite material pipe fittings.

6. According to the method for shaping and pre-tightening a thin-walled ceramic matrix composite pipe fitting according to claim 5, step 3 specifically comprises: The pre-tightening component (4) is rotated to move the pre-tightening component (4) toward the end of the core mold (1), and at the same time, the positioning component (2) is driven to move along the axial direction of the core mold (1).

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