FR3151850A1 - Industrial process for heat treatment of preforms made of carbon precursor material for the manufacture of C/C parts - Google Patents

Abstract

Industrial method for heat treatment of preforms made of carbon precursor material for the manufacture of C/C parts Industrial method for heat treatment of preforms made of carbon precursor material comprising the following steps in sequence: - introduction (S10) of a load of preforms made of carbon precursor material into a first sealed airlock in selective communication with a first furnace, - replacement (S20) of the air present in the first airlock with a neutral gas, - transfer (S30) of said load into the first furnace, - first carbonization treatment (S40) in the first furnace, - transfer (S50) of said load into a second sealed airlock in selective communication with the first and second furnaces, - placing the second sealed airlock under vacuum (S60), - transfer (S70) of said load into the second furnace, - second carbonization treatment (S80) in the second furnace, - transfer (S80) of said load into a third sealed airlock in selective communication with the second furnace and with an outlet to the open air. Figure for abstract: Fig. 5

Description

Industrial process for heat treatment of preforms made of carbon precursor material for the manufacture of C/C parts

The present invention relates to the general field of manufacturing parts made of carbon-carbon (C/C) composite material.

Document US 6,183,583 discloses a method for obtaining C/C composite material parts comprising the following steps:

- manufacture of fibrous preforms with carbon precursor fibers such as polyacrylonitrile or PAN,

- heat treatment called carbonization consisting of purifying the PAN fibers and the carbon which makes up the preforms,

- densification of preforms by chemical infiltration in the gas phase.

The heat treatment of fibrous preforms consists of two steps: primary carbonization and secondary carbonization. The primary carbonization step is carried out at high temperature in dedicated batch furnaces. Large quantities of gaseous effluents must be evacuated during primary carbonization. The secondary carbonization step of fibrous preforms is carried out at very high temperature and low pressure also in dedicated batch furnaces different from the furnaces used for primary carbonization. Small quantities of gaseous effluents must be evacuated during secondary carbonization.

The duration of the treatment cycles is of the order of two to three days for primary carbonization and four to five days for secondary carbonization.

Even if the furnaces used for primary and secondary carbonizations respectively can be large in order to process several hundred preforms at the same time, the implementation of these two carbonizations requires the loading and unloading of a large number of preforms which are difficult to handle. These operations are complex to automate and can generate non-quality. Each carbonization also requires a heating step of the furnace to reach the preform treatment temperature and a cooling step of the furnace and the equipment used in order to allow the unloading of the preforms after treatment. These steps are costly in energy and their duration reduces the production capacity of the furnace. In addition, the size of a batch furnace is limited by the loading and unloading constraints, but also by the requirements for temperature homogeneity in the furnace enclosure. The same is true for the high-temperature treatment of part blanks after densification.

Therefore, when the production capacity needs to be increased, this requires using more dedicated furnaces at the same time. This solution is not optimal because it leads to high investment levels and a significant increase in the overall energy cost.

There is therefore a need to increase production capacity for the carbonization of fiber preforms and the high temperature treatment of blanks after densification while controlling investment costs and energy consumption.

To this end, the invention proposes an industrial method for the heat treatment of preforms made of carbon precursor material, the method comprising the following steps in sequence:
- introduction of a load of one or more preforms made of carbon precursor material into a first sealed airlock in selective communication with a first oven,
- replacement of the air present in the first airlock with a neutral gas,
- transfer of said load into the first oven,
- first carbonization treatment of each preform of said load in the first oven,
- transfer of said load into a second sealed airlock in selective communication with the first oven and with a second oven,
- vacuuming of the second airlock,
- transfer of said load to the second oven,
- second carbonization treatment of each preform of said load in the second furnace,
- transfer of said load into a third sealed airlock in selective communication with the second oven and with an outlet to the open air.

The use of two furnaces in combination with airlocks makes it possible to create a continuous carbonization treatment line. This increases the production capacity of carbonized preforms without having to increase the number of furnaces or their size, i.e. at a controlled investment cost.

In addition, the method of the invention does not require interruption of the heating of the furnaces used for the carbonization treatments. This makes it possible to both improve the production rate and optimize energy consumption since the energy used to heat the furnaces is almost entirely used for the carbonization treatments, whereas with the batch treatment furnaces of the prior art a significant amount of energy is used outside the carbonization treatment to reheat the furnaces after each unloading of preforms.

According to a particular characteristic of the industrial process of the invention, loads of one or more preforms made of carbon precursor material are introduced into the first airlock at a determined time interval. It is thus possible to define a production rate.

According to another particular characteristic of the industrial process of the invention, the gaseous effluents released by each preform during the first and second treatments are burned in the same thermal oxidizer. Since the furnaces used by the process of the invention operate without interruption, the thermal oxidizer is continuously supplied by the combustion of the gaseous effluents. The thermal oxidizer is thus always maintained at its operating temperature without the need for natural gas, which is usually added during the phases without gaseous effluent emissions, corresponding in particular to the cooling, unloading, inter-cycle and loading phases in the batch furnaces of the prior art to maintain the oxidizer at its operating temperature, these phases corresponding to more than 70% of the production time. Furthermore, even if the flow rate of the effluents released by the second carbonization treatment is too low to maintain the oxidizer at the correct temperature, the temperature of the oxidizer is still maintained by the effluents released by the first carbonization treatment, the flow rate of which is much higher.

According to another particular characteristic of the industrial process of the invention, the first and second furnaces are swept by a neutral gas. This facilitates the evacuation of the gaseous effluents released during the first and second carbonization treatments. The mass flow rate of neutral gas in at least the first furnace can be determined as a function of a mass flow rate of the gaseous effluents in order to limit the impact of the neutral gas (dilution) on the heat input of the effluents to the oxidizer.

According to another particular characteristic of the industrial process of the invention, the second furnace is alternately connected to a first cold trap and to a second cold trap each configured to condense the gaseous effluents released by each preform during the second carbonization treatment, the process comprising a step of cleaning the first cold trap when the second cold trap is connected to the second furnace (second operational cold trap) and vice versa.

According to another particular characteristic of the industrial method of the invention, during the first and second carbonization treatments, the load successively passes through a plurality of heating zones present respectively in the first and second furnaces, a heating temperature gradually increasing to a maximum heating temperature between a first heating zone of the plurality of heating zones and a last heating zone of said plurality of heating zones. The loads of preforms moving inside each furnace, the temperature rise conditions (thermal ramp) encountered in the static furnaces of the prior art are thus recreated.

According to another particular characteristic of the industrial process of the invention, during the first carbonization treatment, the maximum heating temperature in the last heating zone of said plurality of heating zones is between 700°C and 1000°C with a temperature rise rate between the first heating zone and the last heating zone of said plurality of heating zones of less than 400°C/h.

According to another particular characteristic of the industrial process of the invention, during the second carbonization treatment, the maximum heating temperature in the last heating zone of said plurality of heating zones is between 1500°C and 2600°C with a temperature rise rate between the first heating zone and the last heating zone of said plurality of heating zones of less than 1500°C/h.

According to another particular characteristic of the industrial process of the invention, the process further comprises, after the second carbonization treatment step and before the step of transferring the load into a third sealed airlock, a step of cooling each preform of said load.

The invention also relates to a method for manufacturing a part made of carbon-carbon composite material comprising the following steps:

- heat treatment of preforms made of carbon precursor material according to the industrial process for heat treatment of preforms made of carbon precursor material of the invention,

- densification of preforms by a carbon matrix in order to obtain rough parts,

- high temperature treatment of part blanks.

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the attached drawings which illustrate exemplary embodiments thereof which are not in any limiting nature.

There schematically represents an installation for implementing an industrial heat treatment process according to one embodiment of the invention,

There represents, schematically and in section, a first section of the installation of the ,

There represents, schematically and in section, a second section of the installation of the ,

There represents, schematically and in section, an example of loading preforms made of carbon precursor material which can be used in the industrial process of the invention,

There is a flowchart showing the steps of an industrial process of a method for manufacturing parts made of carbon-carbon composite material comprising a heat treatment of preforms made of carbon precursor material according to one embodiment of the invention.

There shows very schematically a heat treatment installation 1 in which an industrial process for heat treatment of preforms made of carbon precursor material according to the invention can be implemented.

The installation 1 comprises from upstream to downstream in a direction of travel D _P a loading device 10 in the open air, a first sealed airlock 20, a first oven 100, a second sealed airlock 30, a second oven 200, a third sealed airlock 40 and an unloading device 50 in the open air.

The first furnace 100 is in particular intended to carry out a first carbonization treatment, also called primary carbonization. The second furnace 200 is in particular intended to carry out a second carbonization treatment, also called secondary carbonization.

The first sealed airlock 20 is in selective communication with the loading device 10 and the first oven 100 by first and second movable doors 21 and 22 respectively ( ) according to three configurations. In a first configuration, the first airlock 20 is in communication with the loading device 10 in the open air by opening the first movable door 21 in order to allow the introduction of a load of preforms into said airlock while being isolated from the first oven 100 by closing the second movable door 22. In a second configuration, the airlock 20 is isolated from both the loading device 10 and the first oven 100 by closing the two movable doors 21 and 22, the airlock then forming a sealed enclosure around the load of preforms. In a third configuration, the airlock 20 is in communication with the first oven 100 by opening the second movable door 22 while being isolated from the loading device 10 by closing the first movable door 21 in order to allow the transfer of the load of preforms into the first oven 100.

The second sealed airlock 30 is in selective communication with the first furnace 100 and the second furnace 200 by first and second movable doors 31 and 32 respectively (FIGS. 2 and 3) according to three configurations. In a first configuration, the second airlock 30 is in communication with the first furnace 100 by opening the first movable door 31 in order to allow the introduction of a load of preforms having undergone the first carbonization treatment into said airlock while being isolated from the second furnace 200 by closing the second movable door 32. In a second configuration, the airlock 30 is isolated from both the first furnace 100 and the second furnace 200 by closing the two movable doors 31 and 32, the airlock then forming a sealed enclosure around the load of preforms. In a third configuration, the airlock 30 is in communication with the second oven 200 by opening the second movable door 32 while being isolated from the first oven 100 by closing the first movable door 31 in order to allow the transfer of the load of preforms into the second oven 200.

The third sealed airlock 40 is in selective communication with the second oven 200 and the unloading device 50 by first and second movable doors 41 and 42 respectively ( ) according to three configurations. In a first configuration, the third airlock 40 is in communication with the second furnace 200 by opening the first movable door 41 in order to allow the introduction of a load of preforms having undergone the second carbonization treatment into said airlock while being isolated from the unloading device 50 by closing the second movable door 42. In a second configuration, the airlock 40 is isolated both from the second furnace 200 and from the unloading device 50 by closing the two movable doors 41 and 42. In a third configuration, the airlock 40 is in communication with the unloading device 50 to the open air by opening the second movable door 42 while being isolated from the second furnace 200 by closing the first movable door 41 in order to allow the load of preforms to exit the installation 1.

There illustrates a first section of the installation 1 comprising the loading device 10 in the open air, the first sealed airlock 20, the first oven 100 and the second sealed airlock 30.

The first furnace 100 is delimited by a cylindrical enclosure 101 interposed between the first and second sealed airlocks 20 and 30. The furnace 100 comprises a treatment chamber 140 inside which circulate loads 300 of preforms made of carbon precursor material in the direction of travel D _P . The treatment chamber 140 is surrounded by a heating device 110 and an insulator 102 arranged between the enclosure 101 and the heating device 110. The first furnace 100 has a tunnel shape which extends between an inlet 103 in selective communication with the first sealed airlock 20 and an outlet 104 in selective communication with the second sealed airlock 30.

The first oven 100 also comprises a movement device 150, for example a conveyor belt, a pusher or any other suitable system, which makes it possible to move the loads 300 in the treatment chamber 140 at a determined movement speed and in the direction of travel D _P .

In the example described here, the treatment chamber 140 comprises several heating zones Z ₁ to Z ₆ which are independently temperature-controlled by the heating device 110. In the example described here, the heating device 110 comprises resistive heating elements (not shown in the ) distributed around each of the heating zones Z ₁ to Z ₆ and which are controlled to control the temperature in each of the heating zones. Other heating means capable of controlling the temperature in each of the heating zones can of course be used. The heating of the heating zones can for example be carried out by induction. In this case, the reaction chamber is surrounded by an armature, or susceptor, for example made of graphite, which is coupled with inductors present located outside the reaction chamber and formed of at least one induction coil each.

The heating zones make it possible to gradually increase the treatment temperature of the preforms as they move in the treatment chamber 140. The length of the heating zones defines the residence time (stage) of the loads 300 in each of the heating zones for a given speed of movement of said loads in the direction of travel D _P .

The first furnace 100 further comprises an extraction system 130 for evacuating the gaseous effluents released by the preforms during their carbonization treatment. More specifically, the extraction system 130 comprises a suction pipe 131 present in the treatment chamber 140, the suction pipe 131 being extended by an evacuation pipe 132 which is itself connected to a thermal oxidizer 133, also called a thermal incinerator. The treatment chamber 140 is further provided with a source of neutral gas (not shown in the ) allowing the treatment chamber to be swept with a neutral gas in order to facilitate the evacuation of gaseous effluents by the extraction system 130.

There illustrates a second section of the installation 1 comprising the second sealed airlock 30, the second oven 200, the third sealed airlock 40 and the unloading device 50 in the open air.

The second oven 200 is delimited by a cylindrical enclosure 201 interposed between the second and third sealed airlocks 30 and 40. The oven 200 comprises a treatment chamber 240 inside which the loads 300 of preforms made of carbon precursor material circulate in the direction of travel D _P . The treatment chamber 240 is surrounded by a heating device 210 and an insulator 202 disposed between the enclosure 201 and the heating device 210. The oven 200 has a tunnel shape that extends between an inlet 203 in selective communication with the second sealed airlock 30 and an outlet 204 in selective communication with the third sealed airlock 40. In the example described here, the second oven 200 further comprises a cooling cell 260 present inside the enclosure 201 and placed between the treatment chamber 240 and the third outlet airlock. The cooling cell 260 may be provided with a heat exchange system (not shown in the ) to accelerate the cooling of 300 loads in the cooling cell.

The second oven 200 also comprises a movement device 250, for example a conveyor belt, a pusher or any other suitable system, which makes it possible to move the loads 300 in the treatment chamber 240 and in the cooling cell 260 at a determined movement speed and in the direction of travel D _P .

In the example described here, the treatment chamber 240 comprises several heating zones Z ₇ to Z ₁₄ which are independently temperature-controlled by the heating device 210. In the example described here, the heating device 210 comprises resistive heating elements (not shown in the ) distributed around each of the heating zones Z ₇ to Z ₁₄ and which are controlled to control the temperature in each of the heating zones. Other heating means capable of controlling the temperature in each of the heating zones can of course be used. The heating of the heating zones can for example be carried out by induction. In this case, the reaction chamber is surrounded by an armature, or susceptor, for example made of graphite, which is coupled with inductors present located outside the reaction chamber and formed of at least one induction coil each.

The heating zones make it possible to gradually increase the treatment temperature of the preforms as they move in the treatment chamber 240. The length of the heating zones defines the residence time (stage) of the loads 300 in each of the heating zones for a given speed of movement of said loads in the direction of travel D _P .

The second furnace 200 further comprises an extraction system 230 for evacuating the gaseous effluents released by the preforms during their carbonization treatment. More specifically, the extraction system 230 comprises a suction pipe 231 present in the treatment chamber 240, the suction pipe 231 being extended by an evacuation pipe 232 which is itself connected to first and second cold traps 234 and 235 each configured to condense the gaseous effluents released by each preform during the second carbonization treatment. In the example described here, the evacuation pipe 232 is selectively connected to the first and second cold traps 234 and 235 by a three-way valve 233. Any other selective connection device can be envisaged. The outlet of the cold traps 234 and 235 is connected to a vacuum pump 236 for pumping the treatment chamber 240 in order to carry out the second carbonization treatment under reduced pressure, typically under a pressure of between 1 mbar and 100 mbar. The outlet 237 of the vacuum pump 236 is connected to the thermal oxidizer 133.

The operating principle of cold traps is that of a shell-and-tube heat exchanger. The tubes through which the gaseous effluents pass are cooled by the water circulating in the shell. Once the tubes are filled, these tubes are cleaned by injecting water into the tube and then drying it under vacuum.

When the first cold trap is operational to capture solid deposits (silicon, alkalis, etc.) contained in the gas effluents, the second cold trap which is not connected to the second furnace is cleaned. Conversely, when the second cold trap is operational, the first cold trap which is not connected to the second furnace is cleaned. Thus, the cleaning of the cold traps can be carried out without interrupting the heat treatment.

The treatment chamber 240 is further provided with a source of neutral gas (not shown in the ) allowing the treatment chamber to be swept with a neutral gas in order to facilitate the evacuation of gaseous effluents by the extraction system 230.

THE illustrates an example of loading 300 of carbon precursor material preforms. The loading 300 comprises a loading tool 310 comprising a support plate 311 configured to cooperate with the displacement devices 150 and 250, a support cylinder 312 extending from the support plate 311 and intermediate plates 313 extending from the support cylinder 312. A plurality of annular carbon precursor material preforms 350 are stacked respectively on the support plate 311 and the intermediate plates 313. A loading disk 314 is placed on the top of each stack of preforms 350 in order to control the deformations and warping of the preforms during their processing.

The preforms 350 are made from carbon precursor fibers, which precursor may be, for example, pre-oxidized polyacrylonitrile (PAN), a pitch, a rayon, or a phenolic compound. Each preform 350 may, for example, be made at least in part with continuous elements forming a multidirectional two-dimensional texture. It may be a fabric, a braid, a knit, a unidirectional sheet, or a superposition of several unidirectional sheets of wires, cables, or strands. The sheets are superimposed with different directions and assembled by light needling. For example, the basic texture may be formed from three unidirectional sheets arranged respectively at 0°, +60°, and -60° relative to an axis of the texture. Optionally, the basic texture may be supplemented by a thin veil of fibers pre-needled onto the texture. Examples of embodiments of such annular preforms are described in particular in document US 6,767,602. The preforms described here may be intended for the manufacture of brake discs made of carbon-carbon material.

We now describe in relation to the an industrial method for manufacturing parts made of carbon-carbon material comprising a heat treatment of preforms made of carbon precursor material and a high temperature treatment of part blanks according to one embodiment of the invention.

The industrial method of the invention applies in particular to the treatment of the preforms 350 packaged in the load 300 as described above. However, the industrial method of the invention applies generally to any type of preform made of carbon precursor material and to any type of load. Each load can for example carry one or more preforms, the preforms being able to have a shape and dimensions different from the annular preforms 350 and/or have a shape and dimensions different from each other.

An industrial process for the heat treatment of preforms made of carbon precursor material is described herein, which is implemented in the heat treatment installation 1 described above and following the path of a load 300 of preforms made of carbon precursor material 350 also described above.

The industrial heat treatment process begins with the introduction from the loading device 10 into the open air of a load 300 of preforms made of carbon precursor material 350 into the first sealed airlock 20 with the first movable door 21 open and the second movable door 22 closed (step S10).

The airtight airlock 20 is then closed (first and second movable doors 21 and 22 closed) and the air present inside it is pumped out and replaced by a neutral gas such as nitrogen or argon (step S20). At this stage, the load 300 is in an atmosphere compatible with that of the first furnace 100 because it no longer contains oxygen.

Once the air present in the first airlock 20 has been replaced by a neutral gas, the second movable door 22 of the airlock 20 can be opened. The load 300 is then transferred to the first oven 100 (step S30).

The load 300 passes through the treatment chamber 140 of the furnace 100 in the direction of travel D _P in order to carry out a first carbonization treatment of the preforms made of carbon precursor material 350 (step S40). The load 300 successively passes through the heating zones Z ₁ to Z ₆ , the heating temperature gradually increasing from a starting temperature, for example 300°C, in the first heating zone Z ₁ up to a maximum heating temperature in the last heating zone Z ₆ . The maximum heating temperature in the last heating zone Z ₆ is between 700°C and 1000°C with a temperature rise rate between the first heating zone Z ₁ and the last heating zone Z ₆ of less than 400°C/h. The first carbonization treatment is carried out at a pressure close to atmospheric pressure.

During the first carbonization treatment, the temperature rise of the preforms 350 results in a strong release of gaseous species HCN, NH ₃ , CO, CO ₂ and H ₂ . In the case of preforms comprising pre-oxidized Pan fibers, these lose approximately 51% of their mass during their carbonization. The mass flow rate of the gaseous effluents released is linked to the time interval (also called “takt time”) which corresponds to the time interval for a load to pass between a position n and a position n+1 in the heat treatment installation. This time interval (“takt time”) may for example correspond to the time interval for a load to pass between the first airlock (position n) and the entry into the first furnace (position n+1) or to the time interval for a load to pass between the outlet of the cooling cell (position n) and the third airlock (position n+1). The effluent mass flow rate Dme can be determined from the formula Dme=ρ.m/τ where ρ is the mass loss, m is the mass of pre-oxidized Pan in the stack and τ is the transfer time interval.

The gaseous effluents resulting from the carbonization of the preforms are destroyed by a thermal oxidizer, here the thermal oxidizer 133. Thanks to the continuous treatment in the furnace 100, the thermal oxidizer 133 can be maintained at its operating temperature by the sole heat input of the gaseous effluents without adding natural gas. This constitutes an advantage compared to the carbonization treatments carried out in discontinuous or “batch” type furnaces where the consumption of natural gas is very high to maintain the thermal oxidizer at its operating temperature during the phases without effluent emission as is the case during the phases of loading, heating, cooling and unloading of the preforms.

The gaseous effluents are preferably entrained by sweeping the treatment chamber of the furnace with a neutral gas, for example nitrogen. Too low a flow rate of neutral gas can lead to the formation of tars on the fibres while too high a flow rate of neutral gas can be harmful to the combustion of the thermal oxidiser (dilution of the heat input of the effluents). The mass flow rate of neutral gas Dmg can be defined as a function of the mass flow rate of gaseous effluents Dme according to the rule Dmg=k.Dme with k between 0.3 and 3.

On leaving the treatment chamber 140 of the first furnace 100, that is to say after the first carbonization treatment, the load 300 is transferred into the second sealed airlock 30 with the first movable door 31 open and the second movable door 32 closed (step S50).

The airlock 30 is then closed (first and second movable doors 31 and 32 closed). The airlock 30 is then placed under vacuum (step S60). At this stage, the load 300 is in an atmosphere compatible with that of the second furnace 200, the second carbonization treatment being carried out under vacuum in the second furnace.

Once the vacuum has been achieved in the second airlock 30, the second movable door 32 of the airlock 30 can be opened. The load 300 is then transferred to the second oven 200 (step S70).

The load 300 passes through the treatment chamber 240 of the furnace 200 in the direction of travel D _P in order to carry out a second carbonization treatment of the preforms made of carbon precursor material 350 (step S80). The load 300 successively passes through the heating zones Z ₇ to Z ₁₄ , the heating temperature gradually increasing from a starting temperature, for example 800°C, in the first heating zone Z ₇ to a maximum heating temperature in the last heating zone Z ₁₄ . The maximum heating temperature in the last heating zone Z ₁₆ is between 1500°C and 2600°C with a temperature rise rate between the first heating zone Z ₇ and the last heating zone Z ₁₄ of less than 1500°C/h.

The amount of gaseous effluents released during the second carbonization treatment is significantly less than that of the effluents released during the second carbonization treatment.

The gaseous effluents from the second carbonization treatment of the preforms are destroyed by the same thermal oxidizer as that used to destroy the effluents from the first carbonization treatment, here the thermal oxidizer 133. Thus, even if the heat input of the effluents from the second carbonization treatment could be insufficient (flow rate too low) to maintain the oxidizer at its operating temperature, this does not pose a problem because the oxidizer is already sufficiently heated by the heat input of the effluents from the first carbonization treatment. The gaseous effluents are preferably entrained by sweeping the treatment chamber of the furnace with a neutral gas, for example nitrogen.

The suction pipes and exhaust lines of both furnaces are preferably kept at a temperature above 350°C in order to avoid the formation of deposits in the pipes and/or lines. This can be achieved by insulating and/or heating the pipes and lines.

At its outlet from the treatment chamber 240 of the second furnace 200, i.e. after the second carbonization treatment, the load 300 passes through the cooling cell 260 which makes it possible to accelerate the cooling of the preforms (step S90). The cooling cell is configured to allow the preforms to be released into the open air at a temperature below 300°C in order to avoid oxidation of the preforms.

Upon exiting the cooling cell, the load 300 is transferred into the third sealed airlock 40 with the first movable door 41 open and the second movable door 42 closed (step S100).

The first movable door 41 of the watertight airlock 40 is closed and then the second movable door 42 is opened, which allows the load 300 to be released into the open air, in the example here via the unloading device 50 (step S110).

Steps S10 to S110 described above are carried out in a chained manner for each preform loading starting from step S10 of introducing a load of preforms into the first sealed airlock. Steps S20 to S100 can be fully automated. The steps of loading (step S10) and unloading (step S110) the loads of preforms into the heat treatment installation can also be automated. It is thus possible to implement continuous carbonization treatments of preforms made of carbon precursor material by introducing loads of preforms into the first sealed airlock at regular intervals.

The process for manufacturing parts made of C/C material continues with the densification of the preforms thus treated (step S120). In a known manner, the preforms can for example be densified by chemical vapor infiltration (CVI) in order to produce blanks of parts made of carbon-carbon composite material (C/C), i.e. blanks of parts comprising a carbon fiber reinforcement densified by a carbon matrix.

The part blanks are then subjected to a high temperature treatment (step S130) which can be carried out as already described previously for the carbonization of the fiber preforms, the temperature conditions (maximum temperatures and temperature rise ramps) in the first and second furnaces being adapted for the high temperature treatment.

The expression “between … and …” must be understood as including the limits.

Claims (11)

Industrial process for the heat treatment of preforms made of carbon precursor material (350), the process comprising the following steps in sequence:
- introduction (S10) of a load (300) of one or more preforms made of carbon precursor material (350) into a first sealed airlock (20) in selective communication with a first oven (100),
- replacement (S20) of the air present in the first airlock with a neutral gas,
- transfer (S30) of said load (300) into the first oven (100),
- first carbonization treatment (S40) of each preform of said load in the first furnace (100),
- transfer (S50) of said load (300) into a second sealed airlock (30) in selective communication with the first oven (100) and with a second oven (200),
- vacuuming (S60) of the second airlock (30),
- transfer (S70) of said load into the second oven (200),
- second carbonization treatment (S80) of each preform of said load in the second furnace (200),
- transfer (S100) of said load (300) into a third sealed airlock (40) in selective communication with the second oven (200) and with an outlet to the open air. Manufacturing method according to claim 1, in which loads (300) of one or more preforms made of carbon precursor material (350) are introduced into the first sealed airlock (20) at a determined time interval. Method according to claim 1 or 2, in which the gaseous effluents released by each preform during the first and second treatments are burned in the same thermal oxidizer (133). A method according to claim 3, wherein the first and second ovens (100, 200) are swept with a neutral gas. The method of claim 4, wherein the mass flow rate of neutral gas in at least the first furnace (100) is determined as a function of a mass flow rate of the gaseous effluents. Method according to any one of claims 1 to 5, in which the second furnace (100, 300) is alternately connected to a first cold trap and to a second cold trap each configured to condense the gaseous effluents released by each preform during the second carbonization treatment, the method comprising a step of cleaning the first cold trap when the second cold trap is connected to the second furnace and vice versa. A method according to any one of claims 1 to 6, wherein, during the first and second carbonization treatments, the charge successively passes through a plurality of heating zones (Z ₁ -Z ₆ , Z ₇ -Z ₁₄ ) present respectively in the first and second furnaces (100, 200), a heating temperature gradually increasing to a maximum heating temperature between a first heating zone (Z ₁ , Z ₇ ) of the plurality of heating zones and a last heating zone (Z ₆ , Z ₁₄ ) of said plurality of heating zones. A method according to claim 7, wherein, during the first carbonization treatment, the maximum heating temperature in the last heating zone (Z ₆ ) of said plurality of heating zones (Z ₁ -Z ₆ ) is between 700°C and 1000°C and wherein the temperature rise rate between the first heating zone and the last heating zone (Z ₆ ) of said plurality of heating zones is less than 400°C/h. A method according to claim 7 or 8, wherein, during the second carbonization treatment, the maximum heating temperature in the last heating zone (Z ₁₄ ) of said plurality of heating zones (Z ₇ -Z ₁₄ ) is between 1500°C and 2600°C and wherein the temperature rise rate between the first heating zone and the last heating zone (Z ₁₄ ) of said plurality of heating zones is less than 1500°C/h. Method according to any one of claims 1 to 9, the method further comprising, after the second carbonization treatment step and before the step of transferring the load into a third sealed airlock (40), a step of cooling each preform of said load. Method for manufacturing a part in carbon-carbon composite material comprising the following steps:
- heat treatment of preforms made of carbon precursor material in accordance with the method as defined in any one of claims 1 to 10,
- densification of preforms by a carbon matrix in order to obtain rough parts,
- high temperature treatment of part blanks