Circulating degassing system and method based on desorption-condensation-adsorption

Abstract

The invention relates to the technical field of vacuum electronics, and discloses a desorption-condensation-adsorption-based circulating degassing system and method.The system comprises a vacuum cavity assembly, a heat insulation supporting table top arranged on a cavity bottom plate, a crucible contained in an internal heat preservation layer and an induction heating coil arranged outside in a sleeving mode; and a condensation plate with a water-cooling interlayer is arranged on the inner side of the top cover of the cavity and right opposite to the upper part of the crucible. The isolation ceramic is arranged between the crucible and the heat preservation layer to prevent sputtering pollution, and the positioning ceramic is used for limiting the concentric position of the coil and the crucible to guarantee heating uniformity. And in cooperation with the gradient heating process, gas and impurities released by the parts are rapidly adsorbed after making contact with the low-temperature condensation plate, the reverse deposition path of the impurities is effectively blocked, and the cleanliness and vacuum performance of the key parts of the traveling wave tube are improved.

Description

Technical Field

[0001] This invention relates to the field of home kitchen technology, specifically to a degassing system and method based on desorption-condensation-adsorption cycle. Background Technology

[0002] As a core microwave amplification device in satellite communication, radar reconnaissance, and electronic countermeasures systems, the lifespan and reliability of a space traveling wave tube (TWT) directly depend on the vacuum level inside the tube and the surface cleanliness of its components. During processing and storage, critical components inside the TWT (such as the electron gun's focusing electrode and anode, typically made of refractory metals like molybdenum and tungsten) accumulate large amounts of water vapor, organic matter, oxides, and other impurities on their surfaces and deep within their grain boundaries. If these impurities are not thoroughly removed through a rigorous degassing process before assembly, they will be released again under the high-temperature operating conditions of the TWT, leading to a deterioration of the vacuum level inside the tube and potentially causing serious consequences such as arcing, cathode poisoning, or even device failure.

[0003] Currently, the industry mainly uses vacuum high-temperature sintering furnaces or dedicated exhaust platforms to degas the aforementioned components. The basic principle is to use high-temperature heating to give the adsorbed gas molecules sufficient energy for desorption, which is then extracted by a vacuum pump. However, this traditional degassing method has insurmountable technical defects in practical applications. During conventional vacuum heating, although impurities on the component surface are forcibly desorbed by high temperature, the lack of immediate, directional capture methods for these high-temperature impurities within the vacuum chamber means that the desorbed impurity molecules often disperse disorderly within the vacuum cavity. When the heating process ends and the cooling phase begins, the saturated vapor pressure of these impurity gases decreases with the decrease in ambient temperature, making them prone to reverse migration, redeposition, or adsorption on the newly cleaned component surface. This results in incomplete degassing, and this secondary contamination severely restricts the achievement of ultra-high vacuum specifications for traveling wave tubes.

[0004] Furthermore, the heating structure design of existing degassing equipment also has shortcomings. In systems employing induction heating, the relative position between the induction coil and the heated components typically relies solely on visual alignment during manual installation or simple mechanical fixing, lacking a mandatory concentric positioning structure. This installation error can easily lead to uneven electromagnetic field distribution during the heating process, resulting in uneven heating of components, causing localized overheating or degassing dead zones, and even thermal stress deformation of precision parts. Therefore, developing a degassing system that can prevent the reverse deposition of impurities, ensure heating uniformity, and effectively protect thermal field components has become an urgent need to improve the manufacturing quality of space traveling wave tubes. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a degassing system and method based on desorption-condensation-adsorption cycles, which solves the technical problems in existing technologies such as secondary pollution during component cooling due to the lack of directional impurity collection methods, uneven heating due to inaccurate installation and positioning of induction heating coils, and easy contamination of insulation materials.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a desorption-condensation-adsorption cycle degassing system and method, comprising a reaction chamber, a chamber top cover, and a chamber bottom plate, wherein the chamber top cover is connected to the reaction chamber, and the reaction chamber is disposed on the chamber bottom plate; A bottom heat insulation plate is provided on the bottom plate of the cavity, and a crucible and an induction heating coil sleeved on the outside of the crucible are provided in the area above the bottom heat insulation plate. A condensation device is provided inside the top cover of the cavity. The condensation device includes a condensation plate, which is positioned directly above the crucible to adsorb gases and impurities desorbed from the crucible.

[0007] Preferably, the upper surface of the bottom heat insulation plate is provided with a heat insulation support platform, the heat insulation support platform is provided with an internal heat insulation layer, the crucible is housed inside the internal heat insulation layer, and a top heat insulation ceramic support is provided at the top opening of the crucible.

[0008] Preferably, an insulating ceramic is also provided on the heat-insulating support platform. The insulating ceramic is located between the crucible and the internal heat insulation layer to prevent sputtering during the material reaction process. The sidewall of the insulating ceramic is processed with a stepped structure, and one side of the insulating ceramic is processed with a through hole that fits the crucible.

[0009] Preferably, a coil support ceramic is provided on the heat-insulating support platform, the induction heating coil is fixedly installed on the coil support ceramic, and a positioning ceramic is provided between the induction heating coil and the top heat-insulating ceramic support. The positioning ceramic is used to define the concentric position of the induction heating coil and the top heat-insulating ceramic support.

[0010] Preferably, the condensation device further includes a vacuum flange and a cooling channel. The vacuum flange is connected to the top cover of the cavity, and the cooling channel passes through the vacuum flange. The condensation plate is an arc-shaped circular plate with an internal water-cooled jacket, and the cooling channel communicates with the water-cooled jacket of the condensation plate.

[0011] A degassing method based on desorption-condensation-adsorption cycle includes the following steps: Step S1: Place the parts to be processed into the crucible and seal the system; Step S2: Evacuate the reaction chamber using a vacuum system and introduce a cooling medium into the condenser plate of the condenser. Step S3: Activate the induction heating coil to perform gradient heating on the components, causing the gas and impurities on and inside the components to desorb and evaporate; the gradient heating includes a process sequence of heating to 200℃, 450℃, 950℃ and 1250℃ in sequence and holding at each temperature respectively; Step S4: The desorbed vaporized gas and impurities diffuse upwards in a vacuum environment, condense and are adsorbed after contacting the low-temperature condenser plate, thus completing the degassing process.

[0012] This invention provides a degassing system and method based on a desorption-condensation-adsorption cycle. It has the following beneficial effects: 1. This invention constructs a directional desorption-condensation-adsorption material transport path by placing a condensing plate with a water-cooled jacket directly above the heating crucible. Under vacuum conditions, high-temperature gas molecules and evaporated impurities desorbed from the surface of components and deep grain boundaries are rapidly condensed and firmly adsorbed upon upward diffusion and contact with the low-temperature condensing plate. This mechanism ensures that the environmental pressure within the reaction chamber remains below the saturated vapor pressure of the impurities, fundamentally cutting off the path for gaseous impurities to deposit back onto the surface of components during the cooling phase, thereby improving the vacuum cleanliness and insulation performance of key components of the traveling wave tube.

[0013] 2. This invention sets a positioning ceramic with limiting function between the induction heating coil and the top insulating ceramic support, which forcibly limits the concentric position of the induction heating coil and the internal crucible, effectively eliminating the eccentricity caused by installation errors, ensuring that the parts inside the crucible are always at the geometric center of the alternating magnetic field, so that they receive uniform radiant heating, avoiding thermal stress deformation caused by excessive local temperature difference, thereby ensuring the high consistency and reliability of degassing process parameters when batch processing parts.

[0014] 3. The present invention incorporates an insulating ceramic layer between the crucible and the internal porous insulation layer. This ceramic layer is machined with a stepped structure and through holes that fit the crucible. This physical isolation structure can effectively intercept and block metal vapors or splashes that may be generated during the high-temperature degassing process, preventing them from penetrating and contaminating the internal insulation material. This not only avoids a decrease in insulation performance but also prevents the contaminated insulation layer from becoming a new source of venting in subsequent use, thereby extending the service life of the core thermal field components and reducing the frequency of equipment maintenance. Attached Figure Description

[0015] Figure 1 This is a perspective view of the present invention; Figure 2 This is a cross-sectional view of the present invention; Figure 3 This is a schematic diagram of the induction coil heating structure of the present invention; Figure 4 This is a plan view of the present invention; Figure 5 This is a schematic diagram of the condenser plate structure of the present invention; Figure 6 This is a schematic diagram of the insulating ceramic structure of the present invention.

[0016] The components include: 1. Insulated support platform; 2. Crucible; 3. Reaction chamber; 4. Positioning ceramic; 5. Induction heating coil; 6. Top insulation ceramic support; 7. Chamber top cover; 8. Condensation plate; 9. Cooling channel; 10. Vacuum flange; 11. Insulation ceramic; 12. Internal insulation layer; 13. Coil support ceramic; 14. Bottom insulation plate; 15. Chamber bottom plate. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see the appendix Figure 1 -Appendix Figure 6 This invention provides a desorption-condensation-adsorption cycle degassing system, the main structure of which is constructed within a container capable of maintaining an ultra-high vacuum environment. The system includes a chamber base plate 15, a cylindrical reaction chamber 3 vertically mounted on the upper surface of the chamber base plate 15, and a chamber top cover 7 covering the top of the reaction chamber 3. To ensure the system can achieve a 10... -9 The ultimate vacuum index is in the Pa range. The connection interfaces of the reaction chamber 3, the top cover 7, and the bottom plate 15 are all machined with matching precision threaded holes and sealing grooves. They are fastened together by high-strength bolts and formed a tight physical sealed space with metal or high-temperature resistant rubber sealing rings.

[0019] In the bottom region of the cavity, a multi-layer thermal insulation support system is constructed to block the transmission of high temperature to the base plate and provide a stable installation reference. A bottom thermal insulation plate 14 is laid flat and fixed on the upper surface of the cavity base plate 15. The bottom thermal insulation plate 14 is made of a high temperature resistant and low thermal conductivity material. A thermal insulation support platform 1 is suspended above the bottom thermal insulation plate 14. The thermal insulation support platform 1 is firmly supported and locked by metal screws and matching nuts pre-welded to the cavity base plate 15. As the core load-bearing platform inside the system, the thermal insulation support platform 1 not only realizes multi-level heat blocking, but also provides a horizontal installation plane for the heating components above.

[0020] The core heating components of the system are centrally located in the area of ​​the insulated support platform 1. A hollow cylindrical internal insulation layer 12 is placed on the platform 1. A crucible 2 is vertically placed within the central cavity enclosed by the internal insulation layer 12 to hold the traveling wave tube components (such as molybdenum electrodes) to be processed. To prevent metal vapors or impurities generated during the high-temperature reaction from sputtering and contaminating the porous insulation material, an insulating ceramic 11 is specially installed on the insulated support platform 1 at the annular gap between the crucible 2 and the internal insulation layer 12. The sidewall of this insulating ceramic 11 is machined with a stepped structure of a specific size to enhance stability, and one side has a through-hole that fits into features of the outer wall of the crucible 2 (such as tungsten tube leads), thus forming an effective physical isolation barrier between the crucible 2 and the internal insulation layer 12. Furthermore, a top insulating ceramic support 6 is movably covered at the top opening of the crucible 2 to suppress heat loss from the top.

[0021] To achieve efficient and uniform heating of components, this system employs induction heating and is equipped with a positioning structure. The induction heating coil 5 is wrapped around the outer side of the inner insulation layer 12 and the top insulation ceramic support 6, and is insulated and supported by several coil support ceramics 13 vertically fixed to the heat-insulating support platform 1. To eliminate eccentricity errors during the installation of the induction heating coil 5, a positioning ceramic 4 is provided in the annular space between the induction heating coil 5 and the top insulation ceramic support 6. This positioning ceramic 4, through its specific structural dimensions, forcibly limits the induction heating coil 5 and the top insulation ceramic support 6 to being on the same axis, thereby ensuring that the crucible 2 located inside is always at the geometric center of the alternating magnetic field, greatly improving the uniformity of heating of the components.

[0022] The system's condensation and collection device is integrated inside the top cover 7 of the chamber, utilizing the cold wall effect to achieve unidirectional gas removal. A flange interface is welded to the top cover 7 and connected to a vacuum flange 10. The cooling channel 9 extends airtightly through the vacuum flange 10 into the reaction chamber. The condensing plate 8 is suspended and fixed inside the top cover 7, spatially facing the crucible 2 below. The condensing plate 8 is an arc-shaped circular plate with a hollow water-cooled jacket inside, its arc-shaped surface facing downwards. The cooling channel 9 communicates with this water-cooled jacket. During operation, external circulating cooling water continuously flows through the cooling channel 9 inside the condensing plate 8, maintaining its surface at a low temperature. When high-temperature gas molecules and evaporates desorbed from the crucible 2 below diffuse upwards, they directly collide with the surface of the opposite low-temperature condensing plate 8, rapidly losing thermal energy and condensing and adsorbing, thus preventing impurities from being deposited in the opposite direction, completing the degassing cycle of desorption-condensation-adsorption.

[0023] This invention provides a degassing method based on a desorption-condensation-adsorption cycle. This method fully utilizes the evaporation characteristics of residual gases, the temperature differences between gases adsorbed on material surfaces and at grain boundaries, and performs gradient heating and condensation adsorption cycles. The specific steps are as follows:

[0024] Step S1: Loading and System Closure Open the top cover 7 of the cavity, remove the top insulating ceramic support 6, and place the traveling wave tube components to be processed (such as key components of the electron gun, the molybdenum focusing electrode and anode) into the crucible 2. Then, sequentially reset the top insulating ceramic support 6, the positioning ceramic 4, and other components, close the top cover 7 of the cavity, and tighten the connecting threads to complete the physical sealing of the system.

[0025] Step S2: Vacuum Acquisition and Condensation Preparation The vacuum system is activated to evacuate the interior of reaction chamber 3. The specific operating procedure is as follows: First, the high-pressure valve, mechanical pump, and low-pressure valve are opened sequentially for initial evacuation. Once the vacuum level inside the furnace is detected to be below 10 Pa, the molecular pump is activated for secondary evacuation until the vacuum level inside the furnace reaches 1 × 10⁻⁶ Pa. -4 Pa.

[0026] At the same time, circulating cooling water is introduced into the cooling channel 9 to cool the condenser plate 8 and establish a low-temperature adsorption surface.

[0027] Step S3: Gradient heating for degassing The ultrasonic power supply is activated to energize the induction heating coil 5, and the temperature of the components inside the crucible 2 is monitored in real time using an optical pyrometer. Based on the material properties of the components, the following four-stage gradient heating process is executed: Dehydration stage: Control the heating temperature to 200℃ and maintain the temperature for 2 hours. This stage allows the water vapor adsorbed on the surface of the parts to be fully desorbed.

[0028] Excluding the macromolecular gas stage: Continue heating to 450℃ and hold for 1 hour. This stage mainly releases conventional macromolecular gases.

[0029] Surface oxide removal stage: Continue heating to 950℃ and hold for 1 hour. This stage allows the gases, oxides, and impurities adsorbed on the material surface to gain sufficient energy for evaporation and release.

[0030] Grain boundary impurity removal stage: The final temperature is raised to 1250℃ and held for 1 hour. In this stage, the high temperature forces the gases and impurities adsorbed deep within the grain boundaries of the molybdenum material to diffuse to the surface and evaporate.

[0031] Step S4: Desorption-condensation-adsorption cycle During the gradient heating process described above, gas molecules and vapors desorbed from the surface and interior of the components diffuse upwards in a vacuum environment. When these high-temperature particles come into contact with the low-temperature condenser plate 8 directly above, they lose thermal kinetic energy, condense, and adsorb onto the arc-shaped surface of the condenser plate 8, thus being removed from the reaction area around the components.

[0032] This process ensures that the pressure inside the reaction chamber 3 is always lower than the saturated vapor pressure of the impurities, preventing the impurities from being deposited back onto the surface of the parts during the cooling process, thus achieving complete degassing.

[0033] Step S5: Post-processing After the heating process is complete, turn off the ultrasonic power supply and keep the vacuum system and water cooling system running until the furnace temperature drops to a safe range. Then, close the vacuum valves and pump unit, open the top cover 7 of the chamber, and remove the components.

[0034] Working principle: When using this equipment, first, the key components of the traveling wave tube to be processed are securely placed inside crucible 2. Then, the device is sealed and the vacuum pump group is turned on sequentially. As the air in the reaction chamber 3 is evacuated, the ambient vacuum level gradually increases. When the vacuum level is detected to be below 10 Pa, the molecular pump is started to further evacuate the vacuum until it reaches 1 × 10 Pa. -4 Pa high vacuum state; At this time, the ultrasonic power supply is turned on, and the current generates an alternating magnetic field through the induction heating coil 5, which rapidly heats up the crucible 2 and its internal components. The operator controls the heating process according to the preset gradient heating process program. First, the temperature is raised to 200°C and held to promote the desorption of water vapor adsorbed on the surface of the components. Then, the temperature is raised to 450°C and held to release the adsorbed macromolecular gases. Next, the temperature is raised to 950°C and held to allow the oxides and impurities on the surface of the material to evaporate fully. Finally, the temperature is raised to 1250°C and held to force the gases and impurities hidden deep in the grain boundaries of the material to escape. Throughout the heating process, high-temperature gas molecules and evaporates desorbed from the surface and interior of the components diffuse upwards in a vacuum environment. When they come into contact with the low-temperature condenser plate 8 located directly above and circulated with cooling water, they are instantly cooled and condensed on the surface of the condenser plate 8. Through a continuous desorption-condensation-adsorption cycle, the partial pressure of impurities in the cavity is effectively reduced, preventing secondary pollution of volatiles during the component cooling stage.

Claims

1. A degassing system based on desorption-condensation-adsorption cycle, characterized in that, It includes a reaction chamber (3), a chamber top cover (7), and a chamber bottom plate (15); The top cover (7) of the cavity is connected to the reaction cavity (3), and the reaction cavity (3) is disposed on the bottom plate (15) of the cavity; A bottom heat insulation plate (14) is provided on the bottom plate (15) of the cavity, and a crucible (2) and an induction heating coil (5) sleeved on the outside of the crucible (2) are provided in the area above the bottom heat insulation plate (14). A condensation device is provided inside the cavity top cover (7), and the condensation device includes a condensation plate (8), which is located above the crucible (2).

2. The degassing system based on desorption-condensation-adsorption cycle according to claim 1, characterized in that, The bottom heat insulation plate (14) has a heat insulation support platform (1) on its upper surface. An internal heat insulation layer (12) is provided on the heat insulation support platform (1). The crucible (2) is placed inside the internal heat insulation layer (12). A top heat insulation ceramic support (6) is provided above the crucible (2).

3. The degassing system based on desorption-condensation-adsorption cycle according to claim 2, characterized in that, An insulating ceramic (11) is provided on the heat-insulating support platform (1). The insulating ceramic (11) is located between the crucible (2) and the internal heat insulation layer (12) to prevent sputtering during the material reaction process.

4. The degassing system based on desorption-condensation-adsorption cycle according to claim 2, characterized in that, A coil support ceramic (13) is provided on the heat-insulating support platform (1), and the induction heating coil (5) is fixedly installed on the coil support ceramic (13); A positioning ceramic (4) is provided between the induction heating coil (5) and the top heat-insulating ceramic support (6), and the positioning ceramic (4) is used to define the concentric position of the induction heating coil (5) and the top heat-insulating ceramic support (6).

5. The degassing system based on desorption-condensation-adsorption cycle according to claim 2, characterized in that, A vacuum flange (10) is connected to the top cover (7) of the cavity, and a cooling channel (9) is provided in the vacuum flange (10). The condenser plate (8) is an arc-shaped circular plate with an internal water-cooling interlayer, and the cooling channel (9) is connected to the water-cooling interlayer of the condenser plate (8).

6. The degassing system based on desorption-condensation-adsorption cycle according to claim 2, characterized in that, The reaction chamber (3), the top cover (7) and the bottom plate (15) are all provided with threaded holes and connected by a threaded structure. The cavity bottom plate (15) is provided with a welding screw, and the heat insulation support platform (1) is fixed by the welding screw and nut.

7. The degassing system based on desorption-condensation-adsorption cycle according to claim 3, characterized in that, The insulating ceramic (11) has a stepped structure on its sidewall, and one side of the insulating ceramic (11) has a through hole that fits the crucible (2).

8. A degassing method based on desorption-condensation-adsorption cycle, applied to the degassing system based on desorption-condensation-adsorption cycle as described in any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Place the parts to be processed into the crucible (2) and seal the system; Step S2: Evacuate the reaction chamber (3) using a vacuum system and introduce a cooling medium into the condenser plate (8) of the condenser. Step S3: Start the induction heating coil (5) to perform gradient heating on the parts, so that the gas and impurities on the surface and inside of the parts are desorbed and evaporated; Step S4: The desorbed gas and impurities come into contact with the low-temperature condenser plate (8), condense and are adsorbed, thus completing the degassing process.

9. The degassing method based on desorption-condensation-adsorption cycle according to claim 8, characterized in that, Step S2 specifically includes: sequentially opening the high valve, mechanical pump, and low valve to evacuate air; once the vacuum level reaches below 10 Pa, starting the molecular pump until the vacuum level reaches 1 × 10 Pa. -4 Pa.

10. The degassing method based on desorption-condensation-adsorption cycle according to claim 8, characterized in that, The gradient heating in step S3 specifically includes: Heat to 200℃ and keep warm for 2 hours; Heat to 450℃ and keep warm for 1 hour; Heat to 950℃ and keep warm for 1 hour; Heat to 1250℃ and keep warm for 1 hour.

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