Preparation method and application of cylindrical hot-pressing mold of carbon fiber woven structure

Abstract

The invention relates to the technical field of hot pressing mold preparation, in particular to a preparation method and application of a cylindrical hot pressing mold of a carbon fiber woven structure. The preparation method comprises the following steps: preparing a wood mold; eVA is pasted on the surface of the wood mold, and then the procedure of weaving the carbon fibers in a reciprocating mode is carried out; obtaining a first carbon fiber woven structure; then, the procedure of sewing carbon fibers on the surface of the first carbon fiber woven structure is conducted through a sewing needle and a positioning tool, and a second carbon fiber woven structure is obtained; then the second carbon fiber woven structure is subjected to densification treatment, and a cylindrical hot-pressing mold crude product is obtained; and finally, the cylindrical hot-pressing mold crude product is subjected to finishing forming, and a cylindrical hot-pressing mold product is obtained. The cylindrical hot-pressing die prepared by the invention has good mechanical properties and thermal stability.

Description

Technical Field

[0001] This invention relates to the field of hot pressing mold preparation technology, specifically to a method for preparing and applying a cylindrical hot pressing mold with a carbon fiber braided structure. Background Technology

[0002] Carbon-carbon hot pressing molds are cylindrical products made of high-density carbon / carbon composite materials, and are key tooling components designed specifically for high-temperature, high-pressure molding processes. Leveraging the high-temperature resistance, strong thermal shock resistance, and high strength of carbon / carbon composite materials, they can stably maintain the mold's shape and precision during the hot pressing and sintering of ceramics, composite materials, and other products, preventing cracking and deformation due to sudden temperature changes or high pressure. They are widely used in aerospace, new energy, and high-end materials manufacturing industries, where the molding process requirements are stringent.

[0003] Chinese patent document CN101797646A discloses a method for preparing a high-strength carbon-carbon hot pressing mold for a vacuum hot press furnace. The method involves continuously winding carbon cloth circumferentially and radially needle-punching to form a quasi-three-dimensional preform. The preform is then carbonized and densified through chemical vapor infiltration and resin pressure impregnation. After the densification process, high-temperature treatment and machining are performed to obtain the carbon / carbon hot pressing mold. Chinese patent document CN112225574A discloses a method for manufacturing a high-performance carbon-carbon composite hot pressing mold. This method includes preparing a component monomer of high-density carbon-carbon material; then: subjecting the component monomer to high-temperature treatment; performing a first CVD to increase density; preparing a preliminary carbon-carbon material molding body; winding a carbon fiber cloth layer onto the surface of the preliminary molding body to prepare a basic component; subjecting the basic component to pressure-oriented curing; performing a second high-temperature treatment; and performing a second CVD to increase density to obtain the final product. Chinese patent document CN113416087A discloses a method for preparing a high-strength composite carbon-carbon hot pressing mold, which includes preparing an inner cylinder preform and an outer cylinder preform; then, the method further includes: placing the inner cylinder preform and the outer cylinder preform in a deposition furnace to prepare the inner cylinder and the outer cylinder; preparing a winding layer, and obtaining a composite 1 after winding; placing the composite 1 in a carbonization furnace for carbonization treatment; preparing a composite 2, and carbonizing the composite 2; repeating the above steps until the density of the composite is >1.7 g / cm³. 3 The aforementioned combined body 2 is placed in a high-temperature furnace for high-temperature treatment; finally, the aforementioned combined body 2 is machined to obtain a high-strength combined carbon hot pressing mold.

[0004] However, carbon-carbon cylindrical hot pressing mold products are a typical application of high density, high strength and high temperature resistance in the field of carbon-carbon composite materials. Since the product mainly exhibits huge circumferential forces, even exceeding 100MPa, half of the carbon-carbon mold products are designed with relatively thick walls, some even reaching 200mm. The huge wall thickness makes the densification of carbon-carbon composite materials a challenge, and traditional gas-liquid bonding densification processes are difficult to achieve. Chinese patent document CN101797646A uses a continuous carbon cloth winding design for the carbon fiber preform to increase the circumferential bearing capacity of the carbon-carbon mold. However, the continuous carbon cloth is then formed by radial needle punching, which can break the continuous carbon fiber cloth to some extent, still posing a risk of insufficient strength. Chinese patent documents CN112225574A and CN113416087A use a combined molding method to solve the problem of densification for thick dimensions. They achieve high-density products by layering a thick cylinder into several thin-walled parts. However, because the densification of the parts is not synchronous, the thermal expansion states of each component are different, resulting in large stress in the overall assembly. The product is prone to delamination and ellipticization during high-temperature and high-pressure use. Summary of the Invention

[0005] This invention provides a method for preparing a cylindrical hot-pressing mold with a carbon fiber braided structure and its application, in order to overcome the shortcomings of related technologies.

[0006] According to a first aspect of the present disclosure, a method for preparing a cylindrical hot-pressing mold with a carbon fiber braided structure is provided, the method comprising the following steps: Step 1: Prepare a wooden mold according to the required dimensions of the cylindrical hot press mold product; first, attach EVA to the surface of the wooden mold, and then perform a reciprocating weaving process of carbon fiber; finally, remove the wooden mold to obtain the first carbon fiber woven structure; Step 2: Using a sewing needle and positioning fixture, perform a process of sewing carbon fibers onto the surface of the first carbon fiber braided structure to obtain the second carbon fiber braided structure. Step 3: The second carbon fiber braided structure is densified to obtain a cylindrical hot press mold rough product; wherein, the densification process includes, in sequence, a densification process, a first heating process, a peeling process, a liquid phase impregnation densification process, and a second heating process. Step 4: The rough cylindrical hot press mold is finished to obtain the cylindrical hot press mold product.

[0007] In one aspect of this disclosure, during the process of reciprocatingly weaving carbon fiber onto the surface of the wooden mold, 12K carbon fiber or 6K carbon fiber is used as the carbon fiber braiding thread and woven using a braiding machine; and: When using 12K carbon fiber, the weaving angle is selected from 120-140 degrees, the weaving speed is selected from 10-15 mm / min, and the weaving spool speed is selected from 200-300 min / revolution. When using 6K carbon fiber, the weaving angle is selected from 120-140 degrees, the weaving speed is selected from 5-8 mm / min, and the weaving spool speed is selected from 200-300 min / revolution.

[0008] In one aspect of this disclosure, the suture needle includes a tool needle tip, a straight bar, and a handle; the tip of the tool needle tip is provided with a hole; the sidewall of the straight bar is partially cut along the axial direction to form a circular groove, forming a through suture channel.

[0009] In one aspect of this disclosure, the positioning fixture has serrated teeth on one side.

[0010] In one aspect of the embodiments of this disclosure, the densification process is carried out by using natural gas as the deposition gas source for deposition densification; the deposition temperature is selected from 1000℃ to 1200℃; the deposition time is selected from 200 to 400h; and the vacuum degree during deposition is 1000 to 5000Pa.

[0011] In one aspect of this disclosure, the first heating process is carried out in an inert gas, and the temperature of the first heating process is selected from 2000°C to 2500°C. The second heating process is carried out in an inert gas, and the temperature of the second heating process is selected from 2000℃ to 2500℃.

[0012] In one aspect of this disclosure, the dimensions of the intermediate product obtained from the peeling process and the dimensions of the required cylindrical hot press mold product have the following relationship: The outer diameter D2 of the intermediate product is equal to the outer diameter D1 of the cylindrical hot press mold product plus (2~3) mm. The inner diameter d2 of the intermediate product is equal to the inner diameter d1 of the cylindrical hot press mold product - (5~6) mm; The height H2 of the intermediate product is equal to the height H1 of the cylindrical hot press mold product plus (10~13) mm.

[0013] In one aspect of the embodiments of this disclosure, the liquid phase impregnation densification treatment includes: vacuum impregnation treatment, pressure impregnation treatment, pressure curing treatment, and carbonization treatment; wherein, The vacuum impregnation process uses furan resin as the impregnating agent; and the vacuum degree in the vacuum impregnation process is selected from ≤100Pa; The pressure value in the pressure impregnation treatment is selected from 4~6MPa; The pressure value in the pressure curing process is selected from 1~3MPa, and the temperature is selected from 160℃~200℃; The carbonization temperature is selected from 900℃ to 1500℃.

[0014] In one aspect of this disclosure, the dimensions of the first carbon fiber braided structure and the dimensions of the required cylindrical hot press mold product have the following relationship: The outer diameter D3 of the first carbon fiber braided structure is equal to the outer diameter D1 of the cylindrical hot press mold product plus (5~6) mm. The inner diameter d3 of the first carbon fiber braided structure is equal to the inner diameter d1 of the cylindrical hot press mold product - (8~10) mm; The height H3 of the first carbon fiber braided structure is equal to the height H1 of the cylindrical hot press mold product plus (15~20) mm.

[0015] According to a second aspect of the present disclosure, a cylindrical hot pressing mold is provided, which is prepared by the aforementioned preparation method.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention adopts a three-dimensional woven structure + non-damaging continuous fiber structure, which improves the stress stability and mechanical properties. (2) The present invention adopts an integral weaving and integral densification process. The mold is an integrated structure from preform to finished product, with no splicing interface. The temperature field and pressure field are evenly distributed during the densification process, thereby improving the mechanical properties and thermal stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the positioning tooling of the present invention; Figure 2 This is a schematic diagram of the suture needle of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0019] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0020] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0021] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0022] Unless otherwise stated, the terms used in this disclosure have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this disclosure).

[0023] The term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0024] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0025] In this invention, the specific parameters of the positioning fixture and the suture needle are as follows: Figure 1 and Figure 2 As shown in the figure; where a is selected from 200~400mm and b is selected from 7.0~8.5mm; specifically, in Examples 1~3, a is 250mm and b is 7.9mm.

[0026] In this invention, a positioning fixture and a self-made suture needle are used for stitching. The self-made tool with the suture needle has a small hole at the tip and a suture thread channel designed in the straight section. The suture thread passes through the channel in the straight section to the small hole at the needle tip and exits from the small hole. Using the positioning fixture, the first puncture point is found, and the suture needle is inserted downwards through the carbon cloth layer, inserting the suture needle tip with the carbon fiber suture thread into the EVA. The high resilience of the EVA can clamp the carbon fiber suture thread, so one end of the suture thread is held in the EVA, while the other end continues along the suture needle channel to the outer surface of the braided body. As the suture needle is lifted, the inserted carbon fiber is fixed and can be kept in the thickness direction of the braided body, forming Z-direction fibers. Then, using the spacing designed by the positioning fixture, the next puncture position is found, and the needle is inserted again to penetrate the carbon cloth layer to the interior of the EVA, and then the suture needle is lifted. This process is repeated until the designed product size is fully covered. The braided body is continuously penetrated by the suture thread from top to bottom, forming an integral three-dimensional carbon fiber prefabricated body.

[0027] The continuous carbon fiber filament directly woven into a preform used in this invention achieves several advantages. First, by designing the direction and angle of the woven fibers, the carbon / carbon mold product can withstand maximum stress and maintain a highly stable structure. For mold products subjected to stress in specific directions, the fiber direction can be adjusted by controlling the woven angle to meet product requirements. Second, the entire mold achieves fully continuous carbon fiber filament molding without damage to the carbon fiber filaments, maximizing their strength characteristics. Traditional structures use needle punching, which leads to the breakage of some continuous carbon fiber filaments during molding, making it difficult to fully utilize the strength characteristics of the carbon filaments. This invention further proposes a stitching method that introduces a certain amount of long fibers in the radial direction of the cylindrical preform. This structure improves the integrity of the continuous carbon fiber woven body, preventing delamination, peeling, or twisting. Furthermore, the introduction of radial fibers significantly reduces the difficulty of subsequent densification processes, enabling the densification of products with larger wall thicknesses. Finally, the introduction of stitched radial fibers also improves the processing performance of the woven body, solving the risk of delamination during processing of two-dimensional structures such as carbon fiber winding or simple woven moldings in the final carbon-carbon product.

[0028] The present disclosure will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present disclosure are obtained through conventional commercial means. Unless otherwise specified, all contents mentioned below are mass contents. Unless otherwise specified, it is understood that the process is carried out at room temperature. Example

[0029] Example 1: Preparation of a carbon-carbon cylindrical hot press mold with an outer diameter of 500 mm, an inner diameter of 300 mm, and a height of 800 mm.

[0030] Preparation of the first carbon fiber braided structure: Wooden mold design and fabrication: Based on the dimensional parameters of the target carbon-carbon cylindrical hot press mold product (outer diameter D1=500mm, inner diameter d1=300mm, height H1=800mm), the dimensions of the first carbon fiber braided structure are calculated. According to the formula: the outer diameter of the first carbon fiber braided structure D3=D1+(5~6)mm, taking the middle value of 5.5mm, that is, D3=500+5.5=505.5mm; the inner diameter of the first carbon fiber braided structure d3=d1-(8~10)mm, taking the middle value of 9mm, that is, d3=300-9=291mm; the height of the first carbon fiber braided structure H3=H1+(15~20)mm, taking the middle value of 17.5mm, that is, H3=800+17.5=817.5mm.

[0031] The outer diameter of the wooden mold is the inner diameter of the precast body minus the thickness of the EVA felt. Using 5mm thick EVA felt, the outer diameter of the wooden mold is designed to be 291-5=286mm. The height of the wooden mold is consistent with the height of the first carbon fiber weaving structure, which is 817.5mm. The wooden mold is made of high-strength pine wood, and during processing, the surface of the wooden mold is ensured to be smooth and the dimensional accuracy error ≤±0.2mm to avoid affecting the stability of subsequent weaving processes.

[0032] EVA Soft Felt Application: Evenly apply the cut EVA soft felt to the surface of the wooden mold. Use high-temperature resistant and environmentally friendly adhesive during the application process to ensure a tight fit between the EVA soft felt and the wooden mold, without any bubbles or wrinkles. The EVA soft felt joints are overlapped, with the overlap width controlled at 12-15mm to prevent carbon fiber filaments from embedding into the gaps during weaving, which could lead to discontinuities in the woven structure.

[0033] Carbon fiber reciprocating weaving: Fix the wooden mold with EVA soft felt glued on it onto the chuck of the CNC weaving machine, and select 12K carbon fiber (fiber width approximately 4mm) as the weaving material. Set the weaving parameters: weaving angle 130 degrees, weaving travel speed 12mm / min, weaving spool travel speed 250min / revolution. Start the weaving machine and perform reciprocating weaving operations. During the weaving process, monitor the weaving tension in real time and maintain it stable at 5~8N to avoid tensile breakage or loosening of the carbon fiber filaments. When the outer diameter of the woven structure reaches the design value of 505.5mm, stop weaving, remove the wooden mold and the woven structure together, and let it stand for 24 hours. Then, slowly peel off the wooden mold to obtain the first carbon fiber woven structure. During the peeling process, take care to protect the woven structure and avoid external forces that could cause structural deformation.

[0034] Preparation of the second carbon fiber braided structure: Preparation of suture tools: The suture needle consists of a needle tip, a straight shaft, and a handle. The tip of the needle has a 1mm diameter hole. The straight shaft is made of stainless steel with a 3mm diameter. The side wall of the straight shaft is axially cut to form a 2mm wide circular groove, creating a through-flow suture channel. The handle is made of insulating and non-slip material for easy gripping and operation. One side of the positioning fixture has serrated teeth spaced 7.9mm apart for precise positioning of the suture puncture point, ensuring uniform suture spacing.

[0035] Suturing Operation: Fix the first carbon fiber braided structure on a dedicated workbench. Adjust the positioning fixture so that its serrated teeth align with the surface of the braided structure. Plan the suturing path according to the height and circumference of the braided structure, using a spiral suturing method with a suturing spacing of 15mm along the circumference and 20mm along the height. Pass the carbon fiber suture (using 12K carbon fiber yarn) through the straight channel of the suture needle until it emerges from the needle tip's fine orifice. Use the positioning fixture to locate the first puncture point, and puncture the carbon fiber layer vertically downwards with the suture needle, penetrating the EVA soft felt 5-8mm into the interior. Utilize the high resilience of the EVA soft felt to hold the carbon fiber suture, keeping one end fixed in the EVA soft felt and the other end extending along the suture needle channel to the outer surface of the braided structure. Slowly lift the suture needle, causing the carbon fiber suture to form Z-direction fibers in the thickness direction of the braid. Then move the positioning fixture to the next puncture point and repeat the above puncture, fixation, and needle lifting operations until the suture covers the entire surface of the first carbon fiber braided structure. During the sewing process, ensure the sutures are taut and not loose. After each round of sewing, cut the sutures and secure the joints with knots, keeping the knot length between 5 and 8 mm to prevent them from coming loose. After sewing, remove the EVA felt to obtain the second carbon fiber woven structure. This structure is a three-dimensional continuous woven structure with no fiber breakage and good overall integrity.

[0036] Densification treatment: Densification treatment: The second carbon fiber braided structure is placed in a chemical vapor deposition furnace, the furnace door is closed, and a vacuum is drawn until the vacuum level inside the furnace reaches 3000 Pa. Natural gas is introduced as the deposition gas source, and the gas flow rate is controlled at 7~8 m³ / s. 3 The temperature was increased to 1100℃ and maintained at this temperature and vacuum level for deposition densification for 300 hours. The density of the woven structure was monitored every 50 hours during deposition, and the density was increased to 1.25 g / cm³. 3 Stop the sedimentation process and allow it to cool naturally to room temperature before removing it.

[0037] First high-temperature treatment: The densified braided structure is placed in a high-temperature furnace, and argon gas is introduced as a protective gas at a flow rate of 14-15 m³ / h. 3 After purging the air from the furnace, the temperature is increased to 2200℃ at a rate of 5℃ / min and held for 5 hours. During the high-temperature treatment, the temperature uniformity within the furnace is monitored in real time, and temperature fluctuations are controlled within ±10℃ to prevent localized overheating and structural damage. After the holding period, the furnace is cooled to room temperature at a rate of 3℃ / min, completing the first high-temperature treatment.

[0038] Peeling Process: A CNC grinding machine is used to mechanically peel the blank after the first high-temperature treatment. According to the design requirements, the dimensional parameters of the intermediate product after peeling are: outer diameter D2 = 500 + 2.5mm = 502.5mm, inner diameter d2 = 300 - 5.5mm = 294.5mm, height H2 = 800 + 11.5mm = 811.5mm. A diamond grinding wheel is used during processing, with the grinding speed controlled at 15~20m / s and the feed rate at 0.05mm / pass, ensuring a surface roughness Ra ≤ 1.6μm and a dimensional accuracy error ≤ ±0.3mm. After processing, compressed air is used to blow away surface dust, obtaining the peeled intermediate product.

[0039] Liquid phase impregnation densification treatment: Vacuum impregnation treatment: Place the intermediate product into a vacuum impregnation tank, close the tank door, and evacuate to the ultimate vacuum degree ≤100Pa, maintaining the vacuum state for 30 minutes. Then, inject furan resin impregnating agent into the tank, ensuring that the impregnating agent completely submerges the product, and continue to maintain the vacuum for 3 hours to allow the furan resin to fully penetrate into the internal pores of the product.

[0040] Pressure impregnation treatment: Turn off the vacuum system, start the pressure system, and introduce compressed air into the impregnation tank to raise the pressure inside the tank to 5MPa. Maintain the pressure for 2 hours to further promote the penetration of the impregnating agent and remove residual air bubbles inside.

[0041] Pressure curing treatment: Remove the impregnated product and place it in a pressure curing oven. Heat the oven to 180℃ while applying a pressure of 1.5MPa and hold for 4 hours to cure the furan resin. During the curing process, control the heating rate to 2℃ / min to avoid excessively rapid heating that could cause the resin to crack.

[0042] Carbonization treatment: The cured product is placed in a carbonization furnace, and nitrogen is introduced as a protective gas at a flow rate of 8-10 m³ / h. The temperature is increased to 1200℃ at a rate of 3℃ / min and held for 6 hours to carbonize the cured resin and form a carbon matrix. After carbonization, the product is allowed to cool naturally to room temperature. Cyclic operation: The above vacuum impregnation-pressure impregnation-pressure curing-carbonization process is repeated once to increase the product density to 1.60 g / cm³. 3 above.

[0043] Second high-temperature treatment: The product, after liquid phase impregnation densification, is placed back into a high-temperature furnace under argon protection and heated to 2200℃ (the same as the product's operating temperature) at a heating rate of 5℃ / min. This temperature is maintained for 6 hours to further remove residual impurities and improve the crystallinity and structural stability of the carbon matrix. After the holding period, the product is cooled to room temperature at a cooling rate of 3℃ / min to obtain the rough carbon-carbon cylindrical hot press mold of this embodiment.

[0044] Finishing and Shaping: The rough carbon-carbon cylindrical hot press mold is fixed on a high-precision CNC machining center and finished according to the product drawings. Diamond tools are used for turning and milling, controlling the machining speed at 300~500 r / min and the feed rate at 0.1 mm / revolution. Cooling with cutting fluid is used during machining to prevent product deformation due to heat. The inner and outer cylindrical surfaces, end faces, and mounting and positioning structures of the mold are machined sequentially to ensure that the mold has an outer diameter of 500 mm, an inner diameter of 300 mm, and a height of 800 mm, achieving dimensional accuracy of IT6 grade and a surface roughness Ra≤0.8μm. After machining, non-destructive testing (ultrasonic testing and X-ray testing) is performed to ensure that the product is free of internal defects such as cracks, delamination, and porosity. After passing inspection, the product is cleaned and dried to obtain the final carbon-carbon cylindrical hot press mold product. Example 2: Preparation of a carbon-carbon cylindrical hot pressing mold with an outer diameter of 800 mm, an inner diameter of 500 mm, and a height of 1200 mm. Preparation of the first carbon fiber braided structure: Wooden Mold Design and Fabrication: The target mold product dimensions are outer diameter D1 = 800mm, inner diameter d1 = 500mm, and height H1 = 1200mm. Calculate the dimensions of the first carbon fiber braided structure: outer diameter D3 = 800 + 6 = 806mm (taking the upper limit of 6mm), inner diameter d3 = 500 - 10 = 490mm (taking the lower limit of 10mm), and height H3 = 1200 + 20 = 1220mm (taking the lower limit of 20mm). Select 6mm thick EVA soft felt. The outer diameter of the wooden mold is 490 - 6 = 484mm, and the height is 1220mm. The wooden mold is made of birch wood, dried (moisture content ≤ 8%), and then surface-polished to ensure dimensional accuracy error ≤ ±0.3mm.

[0045] EVA soft felt bonding: Use high-temperature resistant double-sided adhesive to bond the EVA soft felt to the surface of the wooden mold. When bonding, gradually push from one end of the wooden mold to the other end, and use a roller to roll out air bubbles. The overlap width of the EVA soft felt joints should be 20mm. After bonding, let it stand for 12 hours to ensure a firm bond.

[0046] Carbon fiber reciprocating weaving: 6K carbon fiber (fiber width approximately 2mm) was selected as the weaving material, and the wooden mold was mounted on a large CNC weaving machine. Weaving parameters were set as follows: weaving angle 140 degrees, weaving speed 6mm / min, and weaving spool speed 280min / revolution. An automatic tension control system was used during weaving to maintain a stable tension of 4~6N. The outer diameter of the weave was measured every 100mm, and the weaving parameters were adjusted accordingly to ensure the final weave structure reached an outer diameter of 806mm. After weaving, the structure was allowed to stand for 48 hours, and then the wooden mold was removed using a segmented peeling method to obtain the first carbon fiber woven structure.

[0047] Preparation of the second carbon fiber braided structure: Preparation of suture tools: This is the same as in Example 1.

[0048] Suturing Operation: Fix the first carbon fiber braided structure on a dedicated workbench. Adjust the positioning fixture so that its serrated teeth align with the surface of the braided structure. Plan the suturing path according to the height and circumference of the braided structure, using a spiral suturing method with a suturing spacing of 15mm along the circumference and 20mm along the height. Pass the carbon fiber suture (using 12K carbon fiber yarn) through the straight channel of the suture needle until it emerges from the needle tip's fine orifice. Use the positioning fixture to locate the first puncture point, and puncture the carbon fiber layer vertically downwards with the suture needle, penetrating the EVA soft felt 5-8mm into the interior. Utilize the high resilience of the EVA soft felt to hold the carbon fiber suture, keeping one end fixed in the EVA soft felt and the other end extending along the suture needle channel to the outer surface of the braided structure. Slowly lift the suture needle, causing the carbon fiber suture to form Z-direction fibers in the thickness direction of the braid. Then move the positioning fixture to the next puncture point and repeat the above puncture, fixation, and needle lifting operations until the suture covers the entire surface of the first carbon fiber braided structure. During the sewing process, ensure the sutures are taut and not loose. After each round of sewing, cut the sutures and secure the joints with knots, keeping the knot length between 5 and 8 mm to prevent them from coming loose. After sewing, remove the EVA felt to obtain the second carbon fiber woven structure. This structure is a three-dimensional continuous woven structure with no fiber breakage and good overall integrity.

[0049] Densification treatment: Densification treatment: The second carbon fiber braided structure is placed in a chemical vapor deposition furnace, the furnace door is closed, the vacuum is evacuated to 3000 Pa, natural gas is introduced, and the gas flow rate is controlled at 7~8 m³ / s. 3 The temperature was increased to 1100℃ at a constant rate of 1.25 g / cm³, and the deposition time was 300 h. Density was measured every 50 h during deposition, and the sedimentation rate was increased to 1.25 g / cm³. 3 Stop the deposition and cool to room temperature before removing.

[0050] First high-temperature treatment: The densified braided structure is placed in a high-temperature furnace, and argon gas is introduced as a protective gas at a flow rate of 14-15 m³ / h. 3 After purging the air from the furnace, the temperature is increased to 2200℃ at a rate of 5℃ / min and held for 5 hours. During the high-temperature treatment, the temperature uniformity within the furnace is monitored in real time, and temperature fluctuations are controlled within ±10℃ to prevent localized overheating and structural damage. After the holding period, the furnace is cooled to room temperature at a rate of 3℃ / min, completing the first high-temperature treatment.

[0051] Peeling process: A CNC grinding machine is used for peeling. The dimensions of the intermediate product after peeling are: outer diameter D2 = 800 + 3 = 803 mm, inner diameter d2 = 500 - 6 = 494 mm, height H2 = 1200 + 13 = 1213 mm. A diamond grinding wheel is used during processing, with a grinding speed controlled at 15~20 m / s and a feed rate of 0.05 mm / pass, ensuring a surface roughness Ra ≤ 1.6 μm and a dimensional accuracy error ≤ ±0.3 mm. After processing, compressed air is used to blow away surface dust, yielding the peeled intermediate product.

[0052] Liquid phase impregnation densification treatment: Vacuum impregnation treatment: Place the intermediate product into a vacuum impregnation tank, close the tank door, and evacuate to the ultimate vacuum degree ≤100Pa, maintaining the vacuum state for 30 minutes. Then, inject furan resin impregnating agent into the tank, ensuring that the impregnating agent completely submerges the product, and continue to maintain the vacuum for 3 hours to allow the furan resin to fully penetrate into the internal pores of the product.

[0053] Pressure impregnation treatment: Turn off the vacuum system, start the pressure system, and introduce compressed air into the impregnation tank to raise the pressure inside the tank to 5MPa. Maintain the pressure for 2 hours to further promote the penetration of the impregnating agent and remove residual air bubbles inside.

[0054] Pressure curing treatment: Remove the impregnated product and place it in a pressure curing oven. Heat the oven to 180℃ while applying a pressure of 1.5MPa and hold for 4 hours to cure the furan resin. During the curing process, control the heating rate to 2℃ / min to avoid excessively rapid heating that could cause the resin to crack.

[0055] Carbonization treatment: The cured product is placed in a carbonization furnace, and nitrogen is introduced as a protective gas at a flow rate of 8-10 m³ / h. The temperature is increased to 1200℃ at a rate of 3℃ / min and held for 6 hours to carbonize the cured resin and form a carbon matrix. After carbonization, the product is allowed to cool naturally to room temperature. Cyclic operation: The above vacuum impregnation-pressure impregnation-pressure curing-carbonization process is repeated once to increase the product density to 1.60 g / cm³. 3 above.

[0056] Second high-temperature treatment: The product, after liquid phase impregnation densification, is placed back into a high-temperature furnace under argon protection and heated to 2200℃ (the same as the product's operating temperature) at a heating rate of 5℃ / min. This temperature is maintained for 6 hours to further remove residual impurities and improve the crystallinity and structural stability of the carbon matrix. After the holding period, the product is cooled to room temperature at a cooling rate of 3℃ / min to obtain the rough carbon-carbon cylindrical hot press mold of this embodiment.

[0057] Finishing and shaping: The rough carbon-carbon cylindrical hot pressing mold is fixed on a high-precision CNC machining center and finished according to the product drawings. Diamond tools are used for turning and milling, controlling the machining speed at 300-500 rpm and the feed rate at 0.1 mm / revolution. Cooling with cutting fluid is used during machining to prevent product deformation due to heat. The inner and outer cylindrical surfaces, end faces, and mounting and positioning structures of the mold are machined sequentially to ensure that the mold has an outer diameter of 800 mm, an inner diameter of 500 mm, and a height of 1200 mm, achieving dimensional accuracy of IT7 grade and a surface roughness Ra≤1.0μm. After machining, comprehensive non-destructive testing is performed, including ultrasonic testing (for internal defects) and penetrant testing (for surface defects) to ensure product quality meets requirements. After passing inspection, the mold is cleaned and dried to obtain the final product. Example 3: Preparation of a carbon-carbon cylindrical hot pressing mold with an outer diameter of 300 mm, an inner diameter of 180 mm, and a height of 600 mm. Preparation of the first carbon fiber braided structure: Wooden mold design and fabrication: Target mold dimensions: outer diameter D1 = 300mm, inner diameter d1 = 180mm, height H1 = 600mm. First carbon fiber braided structure dimensions: outer diameter D3 = 300 + 5 = 305mm (lower limit 5mm), inner diameter d3 = 180 - 8 = 172mm (upper limit 8mm), height H3 = 600 + 15 = 615mm (upper limit 15mm). 4mm thick EVA soft felt is selected. Wooden mold outer diameter = 172 - 4 = 168mm, wooden mold height 615mm. The wooden mold is made of hardwood and undergoes stability treatment after processing to prevent deformation during use.

[0058] EVA soft felt bonding: Environmentally friendly high-temperature resistant adhesive is used to bond the EVA soft felt. During the bonding process, ensure that the soft felt is tightly bonded to the wooden mold without any curling edges. The overlap width at the splicing point is 12mm.

[0059] Carbon fiber reciprocating weaving: 12K carbon fiber was selected, and the weaving parameters were set as follows: weaving angle 120 degrees, weaving speed 10 mm / min, and weaving spool speed 200 min / revolution. The wooden mold was fixed on a small CNC weaving machine, and the machine was started for reciprocating weaving. The roundness of the woven structure was monitored in real time to ensure that the roundness error was ≤ ±0.5 mm. Weaving was stopped when the outer diameter reached 305 mm, and the wooden mold was peeled off to obtain the first carbon fiber woven structure.

[0060] Preparation of the second carbon fiber braided structure Preparation of suture tools: This is the same as in Example 1.

[0061] Suturing Operation: Fix the first carbon fiber braided structure on a dedicated workbench. Adjust the positioning fixture so that its serrated teeth align with the surface of the braided structure. Plan the suturing path according to the height and circumference of the braided structure, using a spiral suturing method with a suturing spacing of 15mm along the circumference and 20mm along the height. Pass the carbon fiber suture (using 12K carbon fiber yarn) through the straight channel of the suture needle until it emerges from the needle tip's fine orifice. Use the positioning fixture to locate the first puncture point, and puncture the carbon fiber layer vertically downwards with the suture needle, penetrating the EVA soft felt 5-8mm into the interior. Utilize the high resilience of the EVA soft felt to hold the carbon fiber suture, keeping one end fixed in the EVA soft felt and the other end extending along the suture needle channel to the outer surface of the braided structure. Slowly lift the suture needle, causing the carbon fiber suture to form Z-direction fibers in the thickness direction of the braid. Then move the positioning fixture to the next puncture point and repeat the above puncture, fixation, and needle lifting operations until the suture covers the entire surface of the first carbon fiber braided structure. During the sewing process, ensure the sutures are taut and not loose. After each round of sewing, cut the sutures and secure the joints with knots, keeping the knot length between 5 and 8 mm to prevent them from coming loose. After sewing, remove the EVA felt to obtain the second carbon fiber woven structure. This structure is a three-dimensional continuous woven structure with no fiber breakage and good overall integrity.

[0062] Densification treatment: Densification treatment: The second carbon fiber braided structure is placed in a small chemical vapor deposition furnace, evacuated to 1500 Pa, and natural gas is introduced at a flow rate of 5-6 m³ / h. 3 / h, heat to 1000℃, deposition time 200h. When the density reaches 1.22g / cm³ 3 Deposition ceases at that time.

[0063] First high-temperature treatment: Place in a high-temperature furnace, introduce argon gas at a flow rate of 8~10 m³ / h, raise the temperature to 2000℃, and hold for 4 hours.

[0064] Peeling process: Peeling is performed using a CNC lathe. The dimensions of the intermediate product after peeling are: outer diameter D2 = 300 + 2 = 302 mm, inner diameter d2 = 180 - 5 = 175 mm, height H2 = 600 + 10 = 610 mm. The surface roughness Ra after machining is ≤ 1.6 μm, and the dimensional accuracy error is ≤ ±0.3 mm.

[0065] Liquid phase impregnation densification treatment: Vacuum impregnation treatment: Place the intermediate product into a vacuum impregnation tank, close the tank door, and evacuate to the ultimate vacuum degree ≤100Pa, maintaining the vacuum state for 30 minutes. Then, inject furan resin impregnating agent into the tank, ensuring that the impregnating agent completely submerges the product, and continue to maintain the vacuum for 3 hours to allow the furan resin to fully penetrate into the internal pores of the product.

[0066] Pressure impregnation treatment: Turn off the vacuum system, start the pressure system, and introduce compressed air into the impregnation tank to raise the pressure inside the tank to 5MPa. Maintain the pressure for 2 hours to further promote the penetration of the impregnating agent and remove residual air bubbles inside.

[0067] Pressure curing treatment: Remove the impregnated product and place it in a pressure curing oven. Heat the oven to 180℃ while applying a pressure of 1.5MPa and hold for 4 hours to cure the furan resin. During the curing process, control the heating rate to 2℃ / min to avoid excessively rapid heating that could cause the resin to crack.

[0068] Carbonization treatment: The cured product is placed in a carbonization furnace, and nitrogen is introduced as a protective gas at a flow rate of 8-10 m³ / h. The temperature is increased to 1200℃ at a rate of 3℃ / min and held for 6 hours to carbonize the cured resin and form a carbon matrix. After carbonization, the product is allowed to cool naturally to room temperature. Cyclic operation: The above vacuum impregnation-pressure impregnation-pressure curing-carbonization process is repeated once to increase the product density to 1.60 g / cm³. 3 above.

[0069] Second high-temperature treatment: The product, after liquid phase impregnation densification, is placed back into a high-temperature furnace under argon protection and heated to 2200℃ (the same as the product's operating temperature) at a heating rate of 5℃ / min. This temperature is maintained for 6 hours to further remove residual impurities and improve the crystallinity and structural stability of the carbon matrix. After the holding period, the product is cooled to room temperature at a cooling rate of 3℃ / min to obtain the rough carbon-carbon cylindrical hot press mold of this embodiment.

[0070] Finishing and shaping: The rough carbon-carbon cylindrical hot pressing mold is fixed on a high-precision CNC machining center and finished according to the product drawings. Diamond tools are used for turning and milling, controlling the machining speed at 300-500 rpm and the feed rate at 0.1 mm / revolution. Cooling with cutting fluid is used during machining to prevent product deformation due to heat. The inner and outer cylindrical surfaces, end faces, and mounting and positioning structures of the mold are machined sequentially to ensure that the mold has an outer diameter of 800 mm, an inner diameter of 500 mm, and a height of 1200 mm, achieving dimensional accuracy of IT7 grade and a surface roughness Ra≤1.0μm. After machining, comprehensive non-destructive testing is performed, including ultrasonic testing (for internal defects) and penetrant testing (for surface defects) to ensure product quality meets requirements. After passing inspection, the mold is cleaned and dried to obtain the final product. Comparative Example 1: A carbon-carbon cylindrical hot press mold with an outer diameter of 500 mm, an inner diameter of 300 mm, and a height of 800 mm was prepared.

[0071] Preparation of the first carbon fiber braided structure: Wooden mold design and fabrication: Based on the dimensional parameters of the target carbon-carbon cylindrical hot press mold product (outer diameter D1=500mm, inner diameter d1=300mm, height H1=800mm), the dimensions of the first carbon fiber braided structure are calculated. According to the formula: the outer diameter of the first carbon fiber braided structure D3=D1+(5~6)mm, taking the middle value of 5.5mm, that is, D3=500+5.5=505.5mm; the inner diameter of the first carbon fiber braided structure d3=d1-(8~10)mm, taking the middle value of 9mm, that is, d3=300-9=291mm; the height of the first carbon fiber braided structure H3=H1+(15~20)mm, taking the middle value of 17.5mm, that is, H3=800+17.5=817.5mm.

[0072] The outer diameter of the wooden mold is the inner diameter of the precast body minus the thickness of the EVA felt. Using 5mm thick EVA felt, the outer diameter of the wooden mold is designed to be 291-5=286mm. The height of the wooden mold is consistent with the height of the first carbon fiber weaving structure, which is 817.5mm. The wooden mold is made of high-strength pine wood, and during processing, the surface of the wooden mold is ensured to be smooth and the dimensional accuracy error ≤±0.2mm to avoid affecting the stability of subsequent weaving processes.

[0073] EVA Soft Felt Application: Evenly apply the cut EVA soft felt to the surface of the wooden mold. Use high-temperature resistant and environmentally friendly adhesive during the application process to ensure a tight fit between the EVA soft felt and the wooden mold, without any bubbles or wrinkles. The EVA soft felt joints are overlapped, with the overlap width controlled at 12-15mm to prevent carbon fiber filaments from embedding into the gaps during weaving, which could lead to discontinuities in the woven structure.

[0074] Carbon fiber reciprocating weaving: Fix the wooden mold with EVA soft felt glued on it onto the chuck of the CNC weaving machine, and select 12K carbon fiber (fiber width approximately 4mm) as the weaving material. Set the weaving parameters: weaving angle 130 degrees, weaving travel speed 12mm / min, weaving spool travel speed 250min / revolution. Start the weaving machine and perform reciprocating weaving operations. During the weaving process, monitor the weaving tension in real time and maintain it stable at 5~8N to avoid tensile breakage or loosening of the carbon fiber filaments. When the outer diameter of the woven structure reaches the design value of 505.5mm, stop weaving, remove the wooden mold and the woven structure together, and let it stand for 24 hours. Then, slowly peel off the wooden mold to obtain the first carbon fiber woven structure. During the peeling process, take care to protect the woven structure and avoid external forces that could cause structural deformation.

[0075] Densification treatment: Densification treatment: The first carbon fiber braided structure is placed in a chemical vapor deposition furnace, the furnace door is closed, and a vacuum is drawn until the vacuum level inside the furnace reaches 3000 Pa. Natural gas is introduced as the deposition gas source, and the gas flow rate is controlled at 7~8 m³ / s. 3The temperature was increased to 1100℃ and maintained at this temperature and vacuum level for deposition densification for 300 hours. The density of the woven structure was monitored every 50 hours during deposition, and the density was increased to 1.25 g / cm³. 3 Stop the sedimentation process and allow it to cool naturally to room temperature before removing it.

[0076] First high-temperature treatment: The densified braided structure is placed in a high-temperature furnace, and argon gas is introduced as a protective gas at a flow rate of 14-15 m³ / h. 3 After purging the air from the furnace, the temperature is increased to 2200℃ at a rate of 5℃ / min and held for 5 hours. During the high-temperature treatment, the temperature uniformity within the furnace is monitored in real time, and temperature fluctuations are controlled within ±10℃ to prevent localized overheating and structural damage. After the holding period, the furnace is cooled to room temperature at a rate of 3℃ / min, completing the first high-temperature treatment.

[0077] Peeling Process: A CNC grinding machine is used to mechanically peel the blank after the first high-temperature treatment. According to the design requirements, the dimensional parameters of the intermediate product after peeling are: outer diameter D2 = 500 + 2.5mm = 502.5mm, inner diameter d2 = 300 - 5.5mm = 294.5mm, height H2 = 800 + 11.5mm = 811.5mm. A diamond grinding wheel is used during processing, with the grinding speed controlled at 15~20m / s and the feed rate at 0.05mm / pass, ensuring a surface roughness Ra ≤ 1.6μm and a dimensional accuracy error ≤ ±0.3mm. After processing, compressed air is used to blow away surface dust, obtaining the peeled intermediate product.

[0078] Liquid phase impregnation densification treatment: Vacuum impregnation treatment: Place the intermediate product into a vacuum impregnation tank, close the tank door, and evacuate to the ultimate vacuum degree ≤100Pa, maintaining the vacuum state for 30 minutes. Then, inject furan resin impregnating agent into the tank, ensuring that the impregnating agent completely submerges the product, and continue to maintain the vacuum for 3 hours to allow the furan resin to fully penetrate into the internal pores of the product.

[0079] Pressure impregnation treatment: Turn off the vacuum system, start the pressure system, and introduce compressed air into the impregnation tank to raise the pressure inside the tank to 5MPa. Maintain the pressure for 2 hours to further promote the penetration of the impregnating agent and remove residual air bubbles inside.

[0080] Pressure curing treatment: Remove the impregnated product and place it in a pressure curing oven. Heat the oven to 180℃ while applying a pressure of 1.5MPa and hold for 4 hours to cure the furan resin. During the curing process, control the heating rate to 2℃ / min to avoid excessively rapid heating that could cause the resin to crack.

[0081] Carbonization treatment: The cured product is placed in a carbonization furnace, and nitrogen is introduced as a protective gas at a flow rate of 8-10 m³ / h. The temperature is increased to 1200℃ at a rate of 3℃ / min and held for 6 hours to carbonize the cured resin and form a carbon matrix. After carbonization, the product is allowed to cool naturally to room temperature. Cyclic operation: The above vacuum impregnation-pressure impregnation-pressure curing-carbonization process is repeated once to increase the product density to 1.60 g / cm³. 3 above.

[0082] Second high-temperature treatment: The product, after liquid phase impregnation densification, is placed back into a high-temperature furnace under argon protection and heated to 2200℃ (the same as the product's operating temperature) at a heating rate of 5℃ / min. This temperature is maintained for 6 hours to further remove residual impurities and improve the crystallinity and structural stability of the carbon matrix. After the holding period, the product is cooled to room temperature at a cooling rate of 3℃ / min to obtain the rough carbon-carbon cylindrical hot press mold of this embodiment.

[0083] Finishing and Shaping: The rough carbon-carbon cylindrical hot press mold is fixed on a high-precision CNC machining center and finished according to the product drawings. Diamond tools are used for turning and milling, controlling the machining speed at 300~500 r / min and the feed rate at 0.1 mm / revolution. Cooling with cutting fluid is used during machining to prevent product deformation due to heat. The inner and outer cylindrical surfaces, end faces, and mounting and positioning structures of the mold are machined sequentially to ensure that the mold has an outer diameter of 500 mm, an inner diameter of 300 mm, and a height of 800 mm, achieving dimensional accuracy of IT6 grade and a surface roughness Ra≤0.8μm. After machining, non-destructive testing (ultrasonic testing and X-ray testing) is performed to ensure that the product is free of internal defects such as cracks, delamination, and porosity. After passing inspection, the product is cleaned and dried to obtain the final carbon-carbon cylindrical hot press mold product.

[0084] The main difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not include the process of sewing using suture needles and positioning fixtures. Performance testing: The carbon-carbon cylindrical hot-press mold products prepared in the above three embodiments were subjected to performance testing. The test items included density, tensile strength, flexural strength, and thermal shock stability. The test results are shown in Table 1 below. Among them, the thermal shock stability test was conducted by rapidly transferring the test sample from room temperature (20℃) to a high-temperature environment of 2000℃, holding it at that temperature for 1 hour, and then cooling it back to room temperature at a rate of 10℃ / min. This cycle was repeated 5 times, and the changes in appearance and size of the sample before and after the cycle were observed.

[0085] Table 1

[0086] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for preparing a cylindrical hot-pressing mold with a carbon fiber braided structure, characterized in that, The preparation method includes the following steps: Step 1: Prepare a wooden mold according to the required dimensions of the carbon-carbon cylindrical hot press mold product; first, attach EVA to the surface of the wooden mold, and then perform a reciprocating weaving process of carbon fiber; finally, remove the wooden mold to obtain the first carbon fiber woven structure; Step 2: Using a sewing needle and positioning fixture, perform a process of sewing carbon fibers onto the surface of the first carbon fiber braided structure to obtain the second carbon fiber braided structure. Step 3: The second carbon fiber braided structure is densified to obtain a cylindrical hot press mold rough product; wherein, the densification process includes, in sequence, a densification process, a first heating process, a peeling process, a liquid phase impregnation densification process, and a second heating process. Step 4: The rough cylindrical hot press mold is finished to obtain the cylindrical hot press mold product.

2. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, In the process of reciprocatingly weaving carbon fiber on the surface of the wooden mold, 12K carbon fiber or 6K carbon fiber is used as carbon fiber braiding thread by a braiding machine. and: When using 12K carbon fiber, the weaving angle is selected from 120-140 degrees, the weaving speed is selected from 10-15 mm / min, and the weaving spool speed is selected from 200-300 min / revolution. When using 6K carbon fiber, the weaving angle is selected from 120-140 degrees, the weaving speed is selected from 5-8 mm / min, and the weaving spool speed is selected from 200-300 min / revolution.

3. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, The suture needle includes a tool needle, a straight rod, and a handle; the tip of the tool needle is provided with a hole; the side wall of the straight rod is partially cut along the axial direction to form a circular groove, forming a through suture channel.

4. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 3, characterized in that, The positioning fixture has serrated teeth on one side.

5. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, The densification process involves using natural gas as the deposition gas source for deposition densification; the deposition temperature is selected from 1000℃ to 1200℃; the deposition time is selected from 200 to 400 hours; and the vacuum degree during deposition is 1000 to 5000 Pa.

6. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, The first heating process is carried out in an inert gas, and the temperature of the first heating process is selected from 2000℃ to 2500℃. The second heating process is carried out in an inert gas, and the temperature of the second heating process is selected from 2000℃ to 2500℃.

7. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, The dimensions of the intermediate product obtained from the peeling process and the dimensions of the required cylindrical hot press mold product have the following relationship: The outer diameter D2 of the intermediate product is equal to the outer diameter D1 of the cylindrical hot press mold product plus (2~3) mm. The inner diameter d2 of the intermediate product is equal to the inner diameter d1 of the cylindrical hot press mold product - (5~6) mm; The height H2 of the intermediate product is equal to the height H1 of the cylindrical hot press mold product plus (10~13) mm.

8. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, The liquid phase impregnation densification treatment includes: vacuum impregnation, pressure impregnation, pressure curing, and carbonization; wherein... The vacuum impregnation process uses furan resin as the impregnating agent; and the vacuum degree in the vacuum impregnation process is selected from ≤100Pa; The pressure value in the pressure impregnation treatment is selected from 4~6MPa; The pressure value in the pressure curing process is selected from 1~3MPa, and the temperature is selected from 160℃~200℃; The carbonization temperature is selected from 900℃ to 1500℃.

9. The method for preparing a cylindrical hot-pressing mold for a carbon fiber braided structure according to claim 1, characterized in that, The dimensions of the first carbon fiber braided structure and the required dimensions of the cylindrical hot press mold product have the following relationship: The outer diameter D3 of the first carbon fiber braided structure is equal to the outer diameter D1 of the cylindrical hot press mold product plus (5~6) mm. The inner diameter d3 of the first carbon fiber braided structure is equal to the inner diameter d1 of the cylindrical hot press mold product - (8~10) mm; The height H3 of the first carbon fiber braided structure is equal to the height H1 of the cylindrical hot press mold product plus (15~20) mm.

10. A cylindrical hot pressing mold, characterized in that, The cylindrical hot pressing mold is prepared by the preparation method described in any one of claims 1-9.

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