A manufacturing process for aircraft carbon brake discs

Abstract

This application discloses a manufacturing process for an aircraft carbon brake disc, comprising the following steps: S1, densifying a preform of the aircraft carbon brake disc using a liquid-phase impregnation method; S2, graphitizing the preform after densification in S1; before the liquid-phase impregnation method, preheating the preform and the impregnation liquid to reach the same temperature; using partial pressure impregnation during the liquid-phase impregnation method; using graded temperature-increasing curing during the curing stage of the liquid-phase impregnation method; and maintaining a flow rate of 0.5–1.0 m³ / s throughout the graphitization process. 3 Under inert gas protection, the process involves staged heating and switching the corresponding protective gas. In this application, during the liquid-phase impregnation densification process, the impregnation liquid and the preform are preheated simultaneously. Partial pressure impregnation is used during impregnation, and staged heating is employed during curing. During graphitization, staged heating is used while simultaneously switching the corresponding gas to improve the densification degree and yield of the carbon brake disc.

Description

Technical Field

[0001] This application relates to a manufacturing process for aircraft carbon brake discs, belonging to the field of composite materials / aviation braking materials / carbon / carbon composite materials. Background Technology

[0002] Carbon brake discs, due to their advantages such as low density, high temperature resistance, and stable friction performance, have been widely used in the braking systems of modern aircraft. The fabrication of carbon brake discs typically employs a densification process combining liquid-phase impregnation with high-temperature heat treatment (carbonization and graphitization). This involves using a carbon fiber preform as a skeleton, introducing carbon precursors such as resin into the pores of the preform via liquid-phase impregnation, followed by curing and carbonization cycles, and finally, high-temperature graphitization treatment to obtain a dense, high-performance carbon / carbon composite brake disc.

[0003] In the liquid-phase impregnation densification stage, existing processes typically heat the preform and the impregnation liquid separately or only one of them. During impregnation, a single constant pressure, such as around 1.5 MPa, is often used. In the curing stage, the temperature is typically raised directly to the curing temperature at a fixed rate, such as 20°C / h, and then held. This traditional approach has significant shortcomings: Firstly, if there is a large temperature difference between the preform and the impregnation liquid, or if the impregnation liquid viscosity is high, the penetration depth and uniformity of the impregnation liquid within the preform are easily limited, making it difficult for the resin to fully fill the micropores. Secondly, rapid and uncontrolled heating during curing can lead to a violent resin curing reaction, concentrated heat generation, and significant volume shrinkage, easily generating thermal stress, bubbles, and microcracks within the cured body. This results in low preform density and numerous internal defects, creating potential quality problems for subsequent processing. In the graphitization stage, existing processes typically use a single protective gas, such as pure nitrogen, and raise the temperature directly from room temperature to the graphitization temperature at a constant rate, such as approximately 200°C / h, with little consideration given to the specific requirements of the protective atmosphere and temperature measurement methods for different temperature ranges. However, nitrogen reacts chemically with the carbon matrix at ultra-high temperatures to form nitrides, consuming both carbon fibers and matrix carbon, and affecting material purity. Simultaneously, a uniform heating rate throughout the process is difficult to match the varying energy input and mass migration rates required for thermal decomposition of carbon precursors, volatile release, and graphite crystal growth at different temperature ranges. Excessively rapid or uniform heating procedures can lead to gas accumulation and thermal stress concentration within the preform, resulting in cracking, spalling, and insufficient density. These issues collectively impact the improvement of density and the control of quality stability in aircraft carbon brake disc products. Summary of the Invention

[0004] In view of this, this application addresses the problems of low resin impregnation, uneven curing, bubbles, and microcracks by simultaneously preheating the impregnation liquid and the preform during the liquid-phase impregnation densification process, employing partial pressure impregnation during impregnation, and using graded temperature rise curing during curing. This improves the pore filling rate and structural stability of the preform after curing. Furthermore, during the graphitization process, precise switching of the corresponding gas and flexible adjustment of the temperature measurement method during graded temperature rise address the problems of uneven thermal stress, oxidation, and low density in the preform. This provides a manufacturing process for aircraft carbon brake discs to improve the densification degree and yield of carbon brake discs. The specific scheme is as follows: A manufacturing process for an aircraft carbon brake disc, the manufacturing process comprising the following steps: S1, the preform of the aircraft carbon brake disc is densified by liquid phase impregnation method; S2, graphitization treatment is performed on the preform that has been densified by S1; In S1, before performing the liquid phase impregnation method, the preform and the impregnation liquid are preheated to the same temperature; during the liquid phase impregnation method, partial pressure impregnation is used; the curing stage of the liquid phase impregnation method uses graded temperature rise curing. During the graphitization process of S2, the flow rate is maintained at 0.5–1.0 m³ / s throughout the entire process. 3 Under inert gas protection, a staged heating process is adopted, with the corresponding protective gas being switched at each stage.

[0005] Preferably, in S1, the preform and the impregnation liquid used to impregnate the preform are preheated to 60±10°C.

[0006] Preferably, the partial pressure impregnation in S1 is specifically as follows: after the impregnation liquid is fully injected, the pressure is maintained at 2.0 to 2.5 MPa, the pressure is released to 0.2 MPa after impregnation is completed, and the pressure is raised to 1.0 MPa and maintained throughout the curing process.

[0007] Preferably, in S1, the staged temperature rise curing specifically involves: Under a pressure of 1.0 MPa, the temperature was increased from 60℃ to 120℃±10℃ at a heating rate of 20℃ / h. Keep warm for 1 hour; Then the temperature was increased from 120℃ to 180±10℃ at a rate of 10℃ / h, and held for 2h.

[0008] Preferably, in S2, the graphitization process includes the following steps: S21, the preform after S1 densification treatment is loaded into the graphitization furnace and the airtightness of the furnace is checked. S22. After the airtightness of the graphitization furnace is checked and found to be qualified, prepare for heating by turning on the circulating water in the furnace and keeping the pressure inside the furnace in a slightly positive state, i.e., 0.01~0.05MPa. S23 maintains a flow rate of 0.5–1.0 m³ throughout the entire process. 3 Under / h gas protection, the corresponding protective gas is used to gradually increase the temperature to 2200±30℃ and switch during the heating process; S24, after the heat preservation is completed, the power is turned off and the temperature is reduced. The temperature is recorded every 1 hour throughout the process, and a slight positive pressure is maintained in the furnace. When the temperature drops to 1550±50℃, pure argon is switched to pure nitrogen. When the temperature drops to 1000℃, the infrared thermometer is switched to thermocouple temperature measurement. When the temperature drops below 150℃, the charging of pure nitrogen is stopped, and the furnace is removed when the temperature drops below 100℃. S25, after exiting the furnace, each precast body is inspected for appearance, dimensions, and weight, and the density of the billet is calculated. The density of a qualified billet is ≥1.85g / cm³. 3 No scratches or chipping defects.

[0009] Preferably, in S23, the process of graded heating and corresponding switching of protective gas is as follows: from room temperature to 1000±50℃: heating rate 400℃ / h, when the temperature reaches 1000℃, the thermocouple temperature measurement is switched to the infrared thermometer temperature measurement. From 1000℃ to 1600±50℃: heating rate 200℃ / h, when the temperature rises to 1550±50℃, switch pure nitrogen to pure argon and fill the furnace with pure argon to a slightly positive pressure state; From 1600℃ to 2200±30℃: heating rate 140℃ / h, hold for 2h after reaching the target temperature.

[0010] Preferably, in step S24, the gas flow rate during the heat preservation process is consistent with that during the heating process, maintaining a flow rate of 0.5–1.0 m³ / h. 3 / h, to ensure a stable atmosphere inside the furnace.

[0011] Preferably, in S25, the appearance inspection requirements are: the edges and surfaces of the blank are free from scratches or damage, and there are no chips or defects with a length greater than 5mm, a width greater than 5mm, or a depth greater than 2mm.

[0012] Compared with the prior art, the beneficial effects of this application are as follows: In the densification stage, this application employs simultaneous preheating of the preform and the impregnating liquid to maintain the same preset temperature. This reduces the viscosity of the impregnating liquid and avoids uneven filling caused by temperature differences at the contact interface, allowing the impregnating liquid to penetrate evenly and deeply into the pores inside the preform, thus improving impregnation efficiency. Simultaneously, a pressure-partial impregnation process—high-pressure impregnation, medium-pressure degassing, and low-pressure curing—is used. This process forces the impregnating liquid into the micropores under high pressure, followed by depressurization to facilitate the removal of compressed gas and excess resin. Finally, the preform is solidified under appropriate curing pressure, improving pore filling rate and the density of the cured structure. During the curing stage, a staged heating process with controlled heating rate is used. First, the temperature is raised to an intermediate temperature at a slower rate and held, allowing the resin to undergo initial cross-linking and smoothly release reaction heat and volatiles. Then, the temperature is raised to the curing temperature at an even slower rate to complete deep cross-linking. This method effectively prevents explosive polymerization, microcracks, and internal bubble defects caused by violent reactions and volume shrinkage, resulting in a solidified body with uniform structure and low internal stress, providing a high-quality preform for subsequent graphitization treatment.

[0013] During the graphitization process, this application employs differentiated heating rates based on the thermal decomposition and structural transformation characteristics of the material in different temperature ranges throughout the entire process from room temperature to processing temperature. This involves graded heating and heat preservation, particularly by appropriately slowing down the heating rate in the temperature range where volatiles are concentrated and in the high-temperature range where graphite crystals grow. This provides sufficient time for gas escape and atomic diffusion, effectively preventing the preform from cracking due to thermal stress concentration and gas accumulation, thus ensuring the full growth of graphite microcrystals and the high density of the product.

[0014] Specifically, at approximately 1550℃, pure nitrogen was switched to pure argon, and the temperature measurement method was changed, switching between thermocouples and infrared thermometers at approximately 1000℃. By switching the protective gas according to the temperature range during the heating and holding process, on the one hand, low-cost nitrogen was used as the protective atmosphere in the low-temperature range, while argon, which has stronger chemical inertness, was switched in the high-temperature range, eliminating the risk of carbon materials undergoing nitriding reaction with nitrogen at ultra-high temperatures; on the other hand, the accuracy of temperature measurement and equipment safety were ensured throughout the entire temperature range, and ultimately a carbon brake disc blank with high purity, stable structure, and uniform performance was obtained.

[0015] Meanwhile, a slight positive pressure is maintained inside the furnace throughout the heating and cooling process, meaning the pressure is slightly higher than the atmospheric pressure outside the furnace. This is combined with a continuous and stable flow of protective gas to prevent the risk of high-temperature oxidation and ablation caused by the backflow of outside air into the furnace. At the same time, the protective gas is stopped in a timely manner as the temperature decreases during the cooling process, and the product is taken out of the furnace below 100°C. This ensures the safety of the product when exposed to the atmosphere and further guarantees the surface and internal quality of the billet.

[0016] This application achieves a stable density of 1.85 g / cm³ in the preform after graphitization by controlling the densification and graphitization process conditions. 3 The above results are achieved without scratches, chips, or other defects, effectively solving the problems of low densification, numerous curing defects, and high-temperature oxidation weight loss in existing technologies, and significantly improving the manufacturing quality and yield of aircraft carbon brake discs. Detailed Implementation

[0017] A manufacturing process for an aircraft carbon brake disc, the manufacturing process comprising the following steps: S1, the preform of the aircraft carbon brake disc is densified by liquid phase impregnation method; S2, graphitization treatment is performed on the preform after densification treatment by S1; In S1, the preform and the impregnation liquid are preheated to the same temperature before the liquid phase impregnation method is performed; partial pressure impregnation is used during the liquid phase impregnation method; and graded temperature rise curing is used during the curing stage of the liquid phase impregnation method. During the graphitization process of S2, the flow rate was maintained at 0.5–1.0 m³ / s throughout the process. 3 Under inert gas protection, a staged heating method is used with corresponding switching of the protective gas.

[0018] In this application S1: The preform has a density ≥1.62 g / cm³ after two intermediate processing steps. 3 The carbon brake discs for aircraft, after being impregnated and densified with S1, have a preform density ≥1.65g / cm³. 3 .

[0019] The impregnation solution used to impregnate the preform is an impregnation solution prepared with FA-2 furan resin as impregnating agent and industrial-grade phosphoric acid as curing agent, wherein the weight ratio of phosphoric acid to FA-2 furan resin is 6:100.

[0020] The preform and the impregnation liquid used to impregnate the preform are preheated to 60±10℃, and the impregnation liquid needs to be continuously stirred during preheating.

[0021] In S1, before the sealing test, it must be confirmed that the furnace body sealing ring is not twisted, deformed or damaged, and that there is no air leakage at the pipe and valve connection.

[0022] The partial pressure impregnation in S1 is as follows: after the impregnation liquid is completely injected (i.e., completely injected into the impregnation tank), the pressure is maintained at 2.0 to 2.5 MPa; after impregnation, the pressure in the impregnation tank is slowly released to 0.2 MPa; during curing, the pressure is increased to 1.0 MPa and maintained throughout the process.

[0023] It should be noted that when filling with the impregnation liquid, the impregnation system should be kept under negative pressure to perform negative pressure filling (i.e., filling with impregnation liquid) until the impregnation liquid completely submerges the preform and is 100mm above it. The impregnation liquid (resin) can be reused ≤3 times. Before each use, it should be preheated to 60±10℃ and stirred evenly.

[0024] The specific steps of graded temperature rise curing in S1 are as follows: under a pressure of 1.0 MPa, the temperature is raised from 60℃ to 120℃±10℃ at a rate of 20℃ / h and held for 1h; then, the temperature is raised from 120℃ to 180±10℃ at a rate of 10℃ / h and held for 2h.

[0025] It should be noted that during the graded heating and curing process, the pressure of the impregnation tank should be adjusted in a timely manner using the venting valve to ensure that the pressure is stable at 1.0 MPa.

[0026] Both the impregnation and curing processes are carried out in a nitrogen atmosphere. The nitrogen used is pure nitrogen that conforms to the GB / T8979-2008 standard. Pressure changes are monitored in real time during the filling process, and the pressure fluctuation is ≤±0.1MPa.

[0027] After curing, disconnect the power, release the gas, and depressurize. Allow the precast body to cool to below 50°C before removing it from the furnace. After removal, inspect the appearance of the precast body, weigh it, and calculate its density. A qualified precast body must be free of bubbles and cracks, and have a density ≥1.65 g / cm³. 3 .

[0028] In S2 of this application: The preform density after S1 densification treatment is ≥1.65 g / cm³. 3 The preform density after S2 graphitization treatment is ≥1.85 g / cm³. 3 .

[0029] The specific graphitization process of S2 includes the following steps: S21, the preform after S1 densification treatment is loaded into the graphitization furnace and the airtightness of the furnace is checked. S22. After the airtightness of the graphitization furnace is checked and found to be qualified, prepare for heating by turning on the circulating water in the furnace and keeping the pressure inside the furnace at 0.01~0.05MPa to maintain a slightly positive pressure. S23 maintains a flow rate of 0.5–1.0 m³ throughout the entire process. 3 Under / h gas protection, the temperature is gradually increased to 2200±30℃ and the corresponding protective gas is switched during the heating process; S24, after the heat preservation is completed, the power is turned off and the temperature is reduced. The temperature is recorded every 1 hour throughout the process, and a slight positive pressure is maintained in the furnace. When the temperature drops to 1550±50℃, pure argon is switched to pure nitrogen. When the temperature drops to 1000℃, the infrared thermometer is switched to thermocouple temperature measurement. When the temperature drops below 150℃, the charging of pure nitrogen is stopped, and the furnace is removed when the temperature drops below 100℃. S25, after exiting the furnace, each precast body is inspected for appearance, dimensions, and weight, and the density of the billet is calculated. The density of a qualified billet is ≥1.85g / cm³. 3 It has no defects such as scratches or chipping, and the preform after graphitization treatment is a carbon brake disc blank.

[0030] In S23, the process of graded heating and corresponding switching of protective gas is as follows: from room temperature to 1000±50℃: heating rate 400℃ / h, when the temperature reaches 1000℃, the thermocouple temperature measurement is switched to the infrared thermometer temperature measurement. From 1000℃ to 1600±50℃: heating rate 200℃ / h, when the temperature rises to 1550±50℃, switch pure nitrogen to pure argon and fill the furnace with pure argon to a slightly positive pressure; From 1600℃ to 2200±30℃: heating rate 140℃ / h, hold for 2h after reaching the target temperature.

[0031] Both the pure nitrogen and pure argon meet national standards, with pure nitrogen conforming to GB / T8979-2008 and pure argon conforming to GB / T4842-2006.

[0032] In S24, the gas flow rate during the heat preservation process is the same as that during the heating process, maintained at 0.5–1.0 m³ / h. 3 / h, to ensure a stable atmosphere inside the furnace.

[0033] In S25, the visual inspection requirements are: the edges and surfaces of the blank should be free of scratches or damage, and there should be no chips or defects with a length greater than 5mm, a width greater than 5mm, or a depth greater than 2mm.

[0034] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0035] Example 1 This embodiment uses a carbon brake disc specifically designed for wide-body aircraft like the B767-300 as an example to illustrate the liquid-phase impregnation method employed in S1. In this embodiment, an LK-QZ610×900 type vacuum pressure resin impregnation tank is used, and 10 discs with a density ≥1.62 g / cm³ after two intermediate processing are taken. 3 Taking the B767-300 type carbon brake disc bearing plate preform as the object of treatment, using FA-2 furan resin as the impregnating agent and industrial-grade phosphoric acid as the curing agent, the specific process of the liquid phase impregnation method is as follows: 1.1 Raw material preparation: Prepare impregnation solution by mixing phosphoric acid and FA-2 furan resin at a weight ratio of 6:100. The resin used is FA-2 furan resin from Changshu Dewey Huagong (compliant with Q / 320581EKN001-2014), and the phosphoric acid is compliant with GB / T2091-2008 standard. Take 120kg of FA-2 furan resin and 7.2kg of industrial grade phosphoric acid, and stir evenly to obtain impregnation solution. 1.2 Furnace loading: Stack 10 preforms in the impregnation tank according to their numbers, and separate adjacent preforms with 1.5-2.5mm graphite gaskets to prevent sticking; hoist the impregnation tank into the impregnation vessel, aligning the impregnation tank with the center of the impregnation vessel. It should be noted that the actual number of preforms loaded into the furnace is determined based on the height of the effective temperature control zone of the impregnation vessel. 1.3 Sealing test: Check the sealing ring and valve of the impregnation tank, close the furnace cover and tighten the screws to ensure there is no air leakage; 1.4 Preheating and vacuuming of the preform: Heat the impregnation tank to 60±10℃ and keep it at that temperature for 1 hour to ensure uniform preheating of the preform; turn on the vacuum pump to evacuate the tank until the gauge pressure inside the tank is below -0.093Mpa, such as -0.094Mpa, and keep it for 30 minutes to remove the air from the pores inside the preform and improve the impregnation effect. 1.5 Resin preheating and preparation: Add 120 kg of FA-2 furan resin to the resin tank, ensuring that the resin completely submerges the preform and is 100 mm above it after entering the impregnation tank; heat the resin tank to 60±10℃, keep it at this temperature for 30 min and stir continuously; just before impregnation, add 7.2 kg of industrial-grade phosphoric acid in proportion, stir evenly to obtain the impregnation solution, and maintain the temperature of the impregnation solution at 60±10℃. 1.6. Resin filling under negative pressure: After checking that the temperature of both the impregnation tank and the resin tank is 60±10℃, open the valve between the two tanks and use the negative pressure of the impregnation tank to automatically fill the impregnation liquid into the impregnation bucket inside the impregnation tank; after the resin is completely filled, close the valve and continue to evacuate for 60 minutes to remove the air bubbles generated during the impregnation process. 1.7 Pressure Impregnation: Fill the impregnation tank with pure nitrogen to raise the pressure inside the tank to 2.0-2.5 MPa, maintain the temperature at 60-70℃, and impregnate for 2 hours; during the impregnation process, monitor the pressure and temperature in real time to ensure that the pressure is stable within the above range and there is no pressure release or temperature drop; 1.8 Pressure Relief and Resin Recovery: After impregnation, slowly depressurize the impregnation tank to 0.2MPa, open the valve, and use the residual pressure in the tank to recover the unimpregnated resin into the resin tank. Check the amount of resin recovered to confirm that there is no residual resin in the impregnation tank. 1.9, Staged Heating and Curing: Refill the impregnation tank with pure nitrogen to raise the pressure to 1.0 MPa and maintain it throughout the process; heat and cure at the following staged rates, adjusting the pressure in real time to ensure the pressure inside the tank remains stable at 1.0 MPa: Heating from 60℃ to 120±10℃: heating rate 20℃ / h, hold at the temperature for 1 hour after reaching the temperature to allow the resin to initially cure; Heating from 120℃ to 180±10℃: heating rate 10℃ / h, hold at the temperature for 2 hours after reaching the temperature to allow the resin to fully cure; 1.10. Unloading and Inspection: After curing, disconnect the power, release the gas, and depressurize. Cool the precast body in the furnace to 45℃ (below 50℃) before unloading. After unloading, inspect the appearance of the precast body, weigh it, and calculate its density. All 10 precast bodies should be free of bubbles and cracks, and have a density of 1.65–1.68 g / cm³. 3 All of them passed the test and can proceed to the carbonization process.

[0036] Example 2 This embodiment uses 10 preforms that have undergone densification treatment in Example 1 as the processing object, and provides a specific example of the graphitization process. The graphite furnace used in this embodiment is a KGPS350-1 type high-temperature graphitization furnace with an effective temperature control zone of Φ600×1600mm. The specific steps are as follows: 2.1 Furnace loading: Arrange 10 preforms neatly vertically according to their numbers and stack them in the effective temperature control zone of the KGPS350-1 high-temperature graphitization furnace without spacers to ensure uniform heating of the preforms; the number of preforms loaded in actual production is flexibly adjusted according to the thickness of the preforms and the height of the furnace.

[0037] 2.2 Sealing test: Check the sealing of the furnace body sealing ring and pipeline valves. Turn on the vacuum pump to evacuate to a pressure below -0.096 MPa, such as -0.097 MPa. Then close the valves and vacuum pump and maintain the pressure for 20 minutes. If the pressure is below -0.094 MPa after the pressure maintenance, such as -0.095 MPa, the seal is qualified. Otherwise, re-inspect and repeat the operation.

[0038] 2.3 Preparations before heating: Turn on the furnace circulating water and fill the furnace with pure nitrogen to a slight positive pressure (the pressure vacuum gauge returns to zero slightly above the pressure, which is a slight positive pressure far below 0.1 MPa to ensure that there is no air residue in the furnace).

[0039] 2.4, Staged Heating and Gas Switching: Power-on heating, with gas protection maintained throughout the process, flow rate 0.5–1.0 m³ / h. 3 / h, control the heating rate according to the following stages and switch the protective gas accordingly: Temperature rise from room temperature to 1000±50℃: heating rate 400℃ / h. When the temperature is reached, switch the thermocouple temperature measurement to an infrared thermometer to avoid high temperature damage to the thermocouple. Pure nitrogen gas is used throughout the process. Nitrogen is used to purge the temperature from 1000℃ to 1550℃. When the temperature reaches 1550℃, pure nitrogen is switched to pure argon and pure argon is purged to create a slight positive pressure inside the furnace to improve the high-temperature protection effect. The heating rate throughout the process is 200℃ / h. Heating from 1550℃ to 1600±50℃: heating rate 200℃ / h, pure argon gas throughout the process; Heating from 1600℃ to 2200±30℃: heating rate 140℃ / h, holding at the target temperature for 2h to ensure full graphitization of the preform; Throughout the entire heating process, the gas flow rate is 0.8 m³ / s. 3 / h.

[0040] 2.5 Cooling and Gas Reversal: After the heat preservation is completed, the power is cut off at 2200℃ to cool down. The temperature is recorded every 1 hour throughout the process, and a slight positive pressure is maintained inside the furnace. When the temperature drops to 1550±50℃, pure argon is switched to pure nitrogen. When the temperature drops to 1000℃, the infrared thermometer is switched to thermocouple temperature measurement.

[0041] 2.6. Furnace Tapping and Inspection: Continue cooling in the furnace. Stop charging with pure nitrogen when the temperature drops below 150℃. Tapping the preforms when the temperature drops below 100℃. After tapping, inspect the appearance, measure the dimensions, and weigh each preform to calculate the density. The density of all 10 preforms (billets) measured was between 1.85 and 1.87 g / cm³. 3 Furthermore, all 10 blanks were free of defects such as scratches and chipping.

[0042] Comparative Example 1 This comparative example serves as a comparison with Example 1. Ten preforms from the same batch were treated using existing common processes: the preforms were preheated to 80°C, the resin was not preheated, the impregnation pressure was 1.5 MPa, and the curing temperature rise rate was 20°C / h throughout the process, without grading. After curing, the preform density was measured to be 1.60–1.62 g / cm³. 3 Of these, 5 pieces contained internal microbubbles, 3 pieces had microcracks at the edges, and after carbonization, only 4 pieces had a density ≥1.86 g / cm³. 3 Only 40% passed the test.

[0043] Comparative Example 2 This comparative example serves as a comparison with Example 2. Ten preforms from the same batch were treated using a conventional graphitization process: single pure nitrogen protection, a continuous heating rate of 200℃ / h, no temperature measurement mode switching, and a vacuum test to -0.090 MPa for 10 minutes to check for airtightness. After treatment, the preform density was measured to be 1.80–1.83 g / cm³. 3 Of the 5 pieces, 3 had minor cracks and 2 had edge chipping defects, resulting in a scrap rate of 50%.

[0044] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and are all considered technical.

Claims

1. A manufacturing process for an aircraft carbon brake disc, characterized in that, The preparation process includes the following steps: S1, the preform of the aircraft carbon brake disc is densified by liquid phase impregnation method; S2, graphitization treatment is performed on the preform that has been densified by S1; In S1, before performing the liquid phase impregnation method, the preform and the impregnation liquid are preheated to the same temperature; during the liquid phase impregnation method, partial pressure impregnation is used; the curing stage of the liquid phase impregnation method uses graded temperature rise curing. During the graphitization process of S2, the flow rate was maintained at 0.5–1.0 m³ / s throughout the entire process. 3 Under inert gas protection, a staged heating process is adopted, with the corresponding protective gas being switched at each stage.

2. The manufacturing process of an aircraft carbon brake disc according to claim 1, characterized in that, In S1, the preform and the impregnation liquid used to impregnate the preform are preheated to 60±10℃.

3. The manufacturing process of an aircraft carbon brake disc according to claim 1, characterized in that, The partial pressure impregnation in S1 specifically involves maintaining the pressure at 2.0 after the impregnation liquid is fully injected. The pressure is initially set at 2.5 MPa, then reduced to 0.2 MPa after impregnation. During curing, the pressure is increased to 1.0 MPa and maintained throughout the process.

4. The manufacturing process of an aircraft carbon brake disc according to claim 1, characterized in that, In S1, the step-by-step temperature-increase curing process is specifically as follows: Under a pressure of 1.0 MPa, the temperature was increased from 60℃ to 120℃±10℃ at a heating rate of 20℃ / h. Keep warm for 1 hour; Then the temperature was increased from 120℃ to 180±10℃ at a rate of 10℃ / h, and held for 2h.

5. The manufacturing process of an aircraft carbon brake disc according to claim 1, characterized in that, In S2, the graphitization process includes the following steps: S21, the preform after S1 densification treatment is loaded into the graphitization furnace and the airtightness of the furnace is checked. S22. After the airtightness of the graphitization furnace is checked and found to be qualified, prepare for heating by turning on the circulating water in the furnace and keeping the pressure inside the furnace in a slightly positive state, i.e., 0.01~0.05MPa. S23 maintains a flow rate of 0.5–1.0 m³ throughout the entire process. 3 Under the protection of an inert gas of / h, the temperature is gradually increased to 2200±30℃ and the corresponding protective gas is switched during the heating process; S24, after the heat preservation is completed, the power is turned off and the temperature is reduced. The temperature is recorded every 1 hour throughout the process, and a slight positive pressure is maintained in the furnace. When the temperature drops to 1550±50℃, pure argon is switched to pure nitrogen. When the temperature drops to 1000℃, the infrared thermometer is switched to thermocouple temperature measurement. When the temperature drops below 150℃, the charging of pure nitrogen is stopped, and the furnace is removed when the temperature drops below 100℃. S25, after exiting the furnace, each precast body is inspected for appearance, dimensions, and weight, and the density of the billet is calculated. The density of a qualified billet is ≥1.85g / cm³. 3 No scratches or chipping defects.

6. The manufacturing process of an aircraft carbon brake disc according to claim 5, characterized in that, In S23, the process of graded heating and corresponding switching of protective gas is as follows: from room temperature to 1000±50℃: heating rate 400℃ / h, when the temperature reaches 1000℃, the thermocouple temperature measurement is switched to the infrared thermometer temperature measurement. From 1000℃ to 1600±50℃: heating rate 200℃ / h, when the temperature rises to 1550±50℃, switch pure nitrogen to pure argon and fill the furnace with pure argon to a slightly positive pressure state; From 1600℃ to 2200±30℃: heating rate 140℃ / h, hold for 2h after reaching the target temperature.

7. The manufacturing process of an aircraft carbon brake disc according to claim 5, characterized in that, In S24, the gas flow rate during the heat preservation process is the same as that during the heating process, maintained at 0.5–1.0 m³ / h. 3 / h, to ensure a stable atmosphere inside the furnace.

8. The manufacturing process of an aircraft carbon brake disc according to claim 5, characterized in that, In S25, the visual inspection requirements are: the edges and surfaces of the billet are free from scratches or damage, and there are no chips or defects with a length greater than 5mm, a width greater than 5mm, or a depth greater than 2mm.