Alumina ceramic tube shell production device and preparation method

Abstract

This invention discloses an alumina ceramic tube shell production device, belonging to the field of advanced ceramic packaging technology. It includes a casting mechanism, an isostatic pressing mechanism, a sintering integrated furnace, a laser micro-textured metallurgical station, and a control system arranged sequentially along the process. The casting mechanism includes: a horizontal frame, a frame welded from rectangular steel pipes, with a base plate at the bottom, and two parallel guide rail supports fixed to the top surface of the frame; a slurry tank, configured as a U-shaped tank with an open top, the outer walls of the tank being bolted to the guide rail supports; and a casting steel strip wound between two sets of rollers upstream and downstream of the slurry tank, the upstream roller being the driving roller connected to the output shaft of a servo motor via a coupling. This invention, through process integration and linkage control, avoids the damage and contamination caused by repeated handling of the green body in traditional intermittent production, and can completely eliminate microbubbles in the slurry, preventing bubbles in the green body from forming surface bulges or internal voids after sintering, thus improving production quality.

Description

Technical Field

[0001] This invention belongs to the field of advanced ceramic packaging technology, specifically relating to an alumina ceramic tube shell production apparatus and preparation method. Background Technology

[0002] Alumina ceramic housings are widely used in the packaging of electronic devices such as integrated circuits, power modules, and vacuum interrupters due to their excellent insulation properties, thermal conductivity, and mechanical strength. As electronic devices evolve towards higher power density and higher reliability, increasingly stringent requirements are being placed on the airtightness, dimensional accuracy, and metallization bonding strength of alumina ceramic housings. Currently, the production process for alumina ceramic housings typically includes: slurry preparation, tape casting, isostatic pressing, debinding, sintering, and metallization. In existing technologies, microbubbles in the slurry are difficult to completely eliminate during tape casting. These residual bubbles in the green body form surface bulges or internal voids after sintering, leading to decreased airtightness and even rendering the housing unusable.

[0003] Patent Publication No. CN117719048B discloses a fully automated alumina ceramic vacuum tube shell forming production device and method. The disclosed fully automated isostatic pressing production line focuses on automated mechanical handling and does not address processes such as tape casting debubbling, binder removal, sintering atmosphere control, and metallization texturing. Patent Publication No. CN120941538A discloses an alumina ceramic tube shell production device and preparation method, where binder removal and sintering are performed independently in separate stages, failing to achieve precise control of oxygen partial pressure in the binder removal zone. Therefore, there is a need for an alumina ceramic tube shell production device and preparation method that can systematically solve the problem of surface bulges or internal voids formed by bubbles after sintering. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an alumina ceramic tube shell production apparatus and preparation method, thereby solving the technical problems mentioned in the background art.

[0005] The objective of this invention is achieved as follows: an alumina ceramic tube shell production apparatus includes a casting mechanism, an isostatic pressing mechanism, a sintering integrated furnace, a laser microtextured metallurgical station, and a control system arranged sequentially along the process steps. The casting mechanism includes: a horizontal frame, a frame welded from rectangular steel pipes, with a base plate at the bottom, and two parallel guide rail supports fixed to the top surface of the frame; and a slurry tank, configured as a U-shaped tank with an open top. The trough has two outer walls bolted to the guide rail support. The cast steel strip is wound between two sets of rollers at the upstream and downstream ends of the slurry trough. The upstream roller is a drive roller connected to the output shaft of a servo motor via a coupling. The downstream roller is a tension roller slidably mounted in the waist-shaped groove on the side wall of the frame via a slider. The scraper assembly includes a blade holder beam and scraper blades. The two ends of the blade holder beam are bolted to the side wall of the frame via L-shaped connecting seats. The scraper blades are clamped in the T-shaped groove of the blade holder beam and tightened by clamping bolts. A gap is provided between the bottom edge of the scraper blade and the upper surface of the cast steel strip. The gap is used to limit the casting thickness of the green billet.

[0006] Its working principle is as follows: Powder raw materials are made into a stable and uniform casting slurry, which is then cast into a strip of wet blank using a scraper. An isostatic press is used to perform isotropic densification on the wet blank. The blank is then fed into a segmented sintering furnace for debinding, pre-sintering, and high-temperature densification under specific temperature zones and atmospheres. Finally, end-face metallization is achieved through online laser processing and printing co-firing. In use, the casting mechanism supplies the prepared alumina slurry to the casting steel strip, controlling the thickness through the scraper gap to form a continuous tube-shell green blank. The isostatic pressing mechanism inserts the cast green blank into a rubber sleeve, applying pressure to the blank simultaneously radially and axially using a high-pressure liquid medium to homogenize its density. The integrated sintering furnace sequentially conveys the isostatically pressed blank through the debinding zone, pre-sintering zone, and high-temperature sintering zone, with each zone's temperature and atmosphere independently controllable. The entire process of alumina ceramic tube shell production, from green body preparation to final metallization, has been automated. Through process integration and linkage control, the damage and contamination caused by multiple handling of the green body in traditional intermittent production have been avoided. Micro bubbles in the slurry can be completely eliminated, preventing bubbles in the green body from forming surface bulges or internal voids after sintering, thus improving production quality.

[0007] Furthermore, the casting mechanism also includes an immersion ultrasonic transducer, which consists of three to five columnar piezoelectric transducers arranged at equal intervals along the length of the slurry tank. The outer shell of the immersion ultrasonic transducer is sealed with an O-ring and then inserted into the flange sleeve on the side wall of the slurry tank and locked. The immersion ultrasonic transducer is used to apply ultrasonic vibration to the casting slurry to break microbubbles.

[0008] Utilizing the cavitation effect (rapid generation and violent collapse of microbubbles) generated when high-frequency ultrasound propagates in liquid slurry, micron- or even nano-sized air bubbles in the slurry are broken up, preventing residual bubbles from causing sintering cracks inside the green body. Three to five columnar piezoelectric transducers are installed at the bottom or side wall of the slurry tank in the casting machine. The transducer housing is sealed with an O-ring and inserted into a flange sleeve to ensure no slurry leakage. During operation, the transducers vibrate at a frequency of 20-60 kHz, applying continuous ultrasonic vibration to the slurry above or below the cast steel strip. The green strip undergoes online debubbling as it passes through the vibration zone. This effectively eliminates microbubbles inside the cast green body, reducing the risk of bulging and cracking during sintering (the crack rate can be reduced to below 0.2%), while avoiding the time cost of an additional static debubbling process, thus improving production efficiency.

[0009] Furthermore, the isostatic pressing mechanism is located downstream of the casting mechanism and includes a wet-bag type isostatic press main unit, an axial pressurizing assembly, and a radial liquid chamber. The main body of the wet-bag type isostatic press main unit is a multi-layer prestressed steel wire wound thick-walled cylinder, which is arranged vertically. The bottom end is fixed to the base via a flange, and the top end is provided with a cylinder port sealing cover. The sealing cover and the inner cavity of the cylinder form a pressure-bearing cavity. The axial pressurizing assembly includes an axial piston rod and an upper end cover. The upper end cover is threaded to the top of the cylinder. The axial piston rod passes through the central hole of the upper end cover and is sealed by an O-ring. The lower end of the piston rod extends into the pressure-bearing cavity to apply pressure to the top of the rubber sleeve placed in the pressure-bearing cavity. The radial liquid chamber is filled with a mixture of ethylene glycol and water as a pressure medium. The lower part of the side wall of the cylinder is provided with a liquid inlet pipe, which is connected to the outlet flange of the booster pump via a high-pressure hose.

[0010] By utilizing the uniform pressure transmission properties of high-pressure liquids (such as water / ethylene glycol mixtures), the density gradient caused by friction on the mold sidewalls in traditional molding processes is overcome, enabling the tube preform to achieve a highly uniform density distribution both axially and radially. The cast tube preform is tightly encased in a rubber sleeve. First, the sleeve is placed in an isostatic pressing unit, and an axial pressure of 80-120 MPa is applied to the top using an axial pressurization component and maintained for 30-60 seconds. Subsequently, a booster pump injects pressure medium into the radial liquid chamber, applying a radial pressure of 100-150 MPa to the sleeve and maintaining it for 60-120 seconds, thus isotropically densifying the preform. This eliminates the density difference between the axial and radial directions, preventing warping and deformation of the tube preform after sintering.

[0011] Furthermore, the integrated sintering furnace is located downstream of the isostatic pressing mechanism and includes a horizontal furnace shell, furnace lining, a three-section furnace cavity, and an oxygen partial pressure distribution assembly. The horizontal furnace shell is a rectangular welded steel plate shell, and the inner wall of the shell is lined with heat-insulating fiber cotton to form the furnace lining. The inner cavity of the furnace lining is divided along its length into a sequentially connected glue removal zone, a pre-sintering zone, and a high-temperature sintering zone by two vertical heat-insulating plates. The bottoms of the glue removal zone, the pre-sintering zone, and the high-temperature sintering zone are connected in series by a continuous roller conveyor belt. The two ends of the roller are mounted on the side wall of the furnace shell via bearing seats and are connected to the conveyor motor by sprockets and chains. This belt is used to carry and transport the billet sequentially through the glue removal zone, the pre-sintering zone, and the high-temperature sintering zone. The oxygen partial pressure distribution assembly includes a needle valve and a mass flow controller. The inlet end of the needle valve is connected to the outlet of the air compressor via a parallel air pipe, and the outlet end is connected to the inlet pipe of the side wall of the glue removal zone via flanges.

[0012] The furnace employs a roller conveyor tunnel structure, dividing the furnace chamber into functionally independent temperature zones through physical partitions (insulation plates). It is equipped with a high-precision oxygen partial pressure distribution system to achieve programmed atmosphere control during the sintering process. In operation, the furnace body is welded from steel plates, with the inner walls lined with insulating fiber cotton. Two vertical insulation plates divide the furnace chamber along its length into a glue removal zone, a pre-sintering zone, and a high-temperature sintering zone. Each zone is connected to a roller conveyor belt at its bottom, driven by a motor for uniform speed operation. An air compressor provides the air source, which, after precise regulation by needle valves and a mass flow controller (MFC), is introduced into the respective air inlet pipes of each zone, achieving independent atmosphere control. This zoned control allows glue removal, pre-sintering, and high-temperature sintering to proceed under the optimal temperature / atmosphere profile, avoiding interference between different physicochemical reactions within the same temperature zone and ensuring the stability of the sintering quality.

[0013] Furthermore, the top wall of the furnace shell in the glue removal zone is equipped with an exhaust pipe, and the side wall is equipped with a multi-stage air inlet pipe; the top walls of the furnace shells in both the pre-sintering zone and the high-temperature sintering zone are equipped with hydrogen / nitrogen mixed gas inlet pipes; the furnace lining in the high-temperature sintering zone is embedded with... The heating element is fixed to the two side walls of the furnace cavity via a ceramic insulating base.

[0014] Based on the varying atmosphere requirements at different sintering stages, differentiated air intake methods and heat source locations are designed. The debinding stage requires strong exhaust to remove volatiles, the pre-sintering stage requires reducing gases to prevent oxidation, and the high-temperature sintering stage requires high heat loads. In operation, an exhaust pipe is installed on the furnace top in the debinding zone, and multi-stage air intake pipes are installed on the side walls to create an upward airflow that accelerates the removal of organic matter. In both the pre-sintering and high-temperature sintering zones, the furnace top is equipped with... A mixed gas inlet pipe is installed to create a protective atmosphere. Embedded within the furnace lining on both sides of the high-temperature sintering zone are... The heating element supplies heat to the center of the furnace through radiation and convection. Multi-stage air intake and exhaust effectively prevent volatiles from carbonizing on the surface of the billet or causing microcracks. The heating element is heat-resistant and oxidation-resistant, and has high thermal efficiency.

[0015] Furthermore, the laser microtextured metallization station includes a three-dimensional adjustment frame, a pulsed fiber laser, a galvanometer scanning head, and a tungsten paste screen printing table. The main unit of the pulsed fiber laser is located beside the frame, and the output fiber is connected to the galvanometer scanning head via a cable chain. The galvanometer scanning head is fixed to the end of the cantilever via a flange, and the lens optical axis is vertically downward aligned with the metallized surface of the tube shell on the roller. The tungsten paste screen printing table is located downstream of the galvanometer scanning head. The table surface is a granite reference plate, on which a tube shell positioning fixture is installed. A tungsten paste scraper mechanism is located on the side of the fixture. The scraper is driven by a cylinder to reciprocate, used to print tungsten and manganese metallized paste onto the laser-textured tube shell surface. High-energy-density pulsed lasers ablate a micron-scale pit array (microtexture) on the ceramic surface, destroying the surface inert layer and forming a mechanical anchoring effect. Subsequently, metal paste is filled into the pits using screen printing, and high-temperature co-firing forms a good metal-ceramic interface bond. The laser micro-pits solve the problem of poor metal layer adhesion caused by the low surface energy of ceramics.

[0016] Furthermore, the control system includes a PLC cabinet and an HMI touchscreen. The PLC cabinet is bolted to the electrical area next to the casting mechanism, and houses an S7-1500 series PLC main unit and analog modules. The HMI touchscreen is fixed to the operating side of the isostatic pressing mechanism via a cantilever bracket and is connected to the PLC cabinet via a shielded cable. The servo motor drivers of the casting mechanism, the power controllers of the immersion ultrasonic transducers, the pressure sensors and axial piston displacement sensors of the booster pump of the isostatic pressing mechanism, the temperature zone thermocouples and mass flow controllers of the sintering integrated furnace, and the module servo drivers of the laser microtextured metalworking station are all connected to the PLC cabinet via shielded cables to achieve temperature, pressure, gas, and position linkage control of the four stations. This is a distributed control system based on a PLC (Programmable Logic Controller). By collecting sensor signals (such as position, pressure, temperature, and flow) from each station, executing preset control algorithms (such as PID), and outputting control commands to drive servo motors, booster pumps, MFC and other actuators, the system achieves synchronous coordination throughout the entire process. It eliminates errors caused by manual operation and ensures the consistency of product performance in mass production.

[0017] A method for preparing an alumina ceramic tube shell includes the following steps:

[0018] Slurry preparation: at 92–96 wt% As the matrix, add 0.2–0.5 wt%, 0.1–0.3 wt% is used as a sintering aid, and is mixed with organic solvents, binders, and plasticizers to prepare a casting slurry with a solid content of 55–65%.

[0019] Defoaming casting: The slurry is sent into the casting mechanism after defoaming;

[0020] Isostatic pressing: Place the cast green body into a rubber sleeve, first apply axial pressure to 80–120 MPa and hold for 30–60s, then apply radial isostatic pressing to 100–150 MPa and hold for 60–120s.

[0021] Sintering Integration: The isostatically pressed green body is fed into the sintering integration furnace and processed according to the following curve:

[0022] Degreasing zone: The temperature is raised from room temperature to 600℃ at a rate of 0.5–1℃ / min, and the oxygen volume fraction is gradually reduced from 5% to 0.1%.

[0023] Pre-sintering zone: Temperature is increased from 600℃ to 1200℃ at a rate of 3–5℃ / min, and the atmosphere is switched to... Mixed reducing gas;

[0024] High-temperature sintering zone: The temperature is raised from 1200℃ to 1550℃, held for 2–4 hours, and then cooled down to 800℃ with the furnace.

[0025] Laser microtextured metallization: After the sintered body exits the furnace, an array of micropits is processed on the surface to be metallized using a pulsed fiber laser, followed by printing of tungsten and manganese metallization pastes, and then heated at 1450–1500℃. The alumina ceramic tube shell is co-fired for 30–60 min under a specific atmosphere to obtain the finished product.

[0026] After the high-temperature sintering zone is maintained at a certain temperature, the temperature is reduced to 1200℃ at a rate of 2–3℃ / min, and then reduced to 800℃ at a rate of 5–8℃ / min to suppress abnormal grain growth.

[0027] The beneficial effects of this invention are as follows: A strip of wet blank is formed by a scraper casting process, and isotropic densification is performed on the wet blank using an isostatic press. The blank is then fed into a segmented sintering furnace for debinding, pre-sintering, and high-temperature densification under specific temperature zones and atmospheres. Finally, end-face metallization is achieved through online laser processing and printing co-firing. In use, the casting mechanism supplies the prepared alumina slurry to the casting steel strip, controlling the thickness through the scraper gap to form a continuous tube-shell green blank strip. The isostatic pressing mechanism inserts the cast green blank into a rubber sleeve, applying pressure to the blank simultaneously radially and axially using a high-pressure liquid medium to homogenize its density. The integrated sintering furnace sequentially transports the isostatically pressed blank through the debinding zone, pre-sintering zone, and high-temperature sintering zone, with each zone's temperature and atmosphere independently controllable. The entire process of alumina ceramic tube shell production, from green body preparation to final metallization, has been automated. Through process integration and linkage control, the damage and contamination caused by multiple handling of the green body in traditional intermittent production have been avoided. Micro bubbles in the slurry can be completely eliminated, preventing bubbles in the green body from forming surface bulges or internal voids after sintering, thus improving production quality. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall process of the present invention;

[0029] Figure 2 This is a schematic diagram of the main structure of the horizontal frame of the present invention;

[0030] Figure 3 This is a top view schematic diagram of the horizontal frame structure of the present invention;

[0031] Figure 4 This is a schematic diagram of the three-dimensional structure of the horizontal frame of the present invention;

[0032] Figure 5 This is the invention Figure 4 Enlarged view of A in the middle;

[0033] Figure 6 This is a schematic diagram of the main structure of the isostatic pressing main unit of the present invention;

[0034] Figure 7 This is a schematic diagram of the internal structure of the isostatic pressing main unit of the present invention;

[0035] Figure 8 This is a schematic diagram of the main structure of the horizontal furnace shell of the present invention;

[0036] Figure 9 This is a top view schematic diagram of the horizontal furnace shell structure of the present invention;

[0037] Figure 10 This is a schematic diagram of the internal structure of the horizontal furnace shell of the present invention.

[0038] In the diagram: 1. Casting mechanism; 2. Isostatic pressing mechanism; 3. Sintering integrated furnace; 4. Laser microtextured metal processing station; 5. Control system; 6. Horizontal frame; 7. Foot plate; 8. U-shaped trough; 9. Coupling; 10. Tool holder beam; 11. T-slot; 12. Scraper blade; 13. Ultrasonic vibrator; 14. Isostatic pressing main unit; 15. Base; 16. Sealing cover; 17. Pressure chamber; 18. Piston rod; 19. Upper end cover; 20. Horizontal furnace shell; 21. Glue discharge area; 22. Pre-sintering area; 23. High-temperature sintering area; 26. Conveyor motor; 27. Exhaust pipe; 28. Multi-stage air inlet pipe; 29. ​​Mixed gas inlet pipe. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings. It should be noted that all directional terms such as up, down, front, back, left, and right appearing in the present invention are not intended to limit the present invention, but are only used to more clearly explain and interpret the present invention.

[0040] Example 1

[0041] like Figures 1-10 As shown, this embodiment discloses an alumina ceramic tube shell production device, including a casting mechanism 1, an isostatic pressing mechanism 2, a sintering integrated furnace 3, a laser microtextured metallurgical station 4, and a control system 5 arranged sequentially along the process. The casting mechanism 1 includes: a horizontal frame 6, a frame welded from rectangular steel pipes, with a base plate 7 at the bottom, and two parallel guide rail supports fixed to the top surface of the frame; a slurry tank, configured as a U-shaped tank with an open top, with the outer walls of both sides of the tank fixed to the guide rail supports by bolts; and a casting steel strip wound around the slurry. Between the two sets of rollers upstream and downstream of the material trough, the upstream roller is a drive roller connected to the output shaft of the servo motor via coupling 9, and the downstream roller is a tension roller slidably mounted in the waist-shaped groove on the side wall of the frame via a slider; the scraper assembly includes a blade holder beam 10 and a scraper blade 12. The two ends of the blade holder beam 10 are bolted to the side wall of the frame via L-shaped connecting seats. The scraper blade 12 is clamped in the T-shaped groove 11 of the blade holder beam 10 and tightened by clamping bolts. A gap is provided between the bottom edge of the scraper blade 12 and the upper surface of the cast steel strip. The gap is used to limit the thickness of the green billet casting.

[0042] Its working principle is as follows: Powder raw materials are made into a stable and uniform casting slurry, which is then cast into a strip of wet blank using a scraper. The wet blank is then isotropically densified using an isostatic press. Subsequently, the blank is fed into a segmented sintering furnace, where it undergoes debinding, pre-sintering, and high-temperature densification under specific temperature zones and atmospheres. Finally, end-face metallization is achieved through online laser processing and printing co-firing. In use, the casting mechanism 1 supplies the prepared alumina slurry to the casting steel strip, controlling the thickness through the scraper gap to form a continuous tube-shell green blank strip. The isostatic pressing mechanism 2 fits the cast green blank into a rubber sleeve, applying pressure to the blank simultaneously radially and axially using a high-pressure liquid medium to homogenize its density. The integrated sintering furnace 3 sequentially conveys the isostatically pressed blank through the debinding zone 21, the pre-sintering zone 22, and the high-temperature sintering zone 23, with each zone's temperature and atmosphere independently controllable. The entire process of alumina ceramic tube shell production, from green body preparation to final metallization, has been automated. Through process integration and linkage control, the damage and contamination caused by multiple handling of the green body in traditional intermittent production have been avoided. Micro bubbles in the slurry can be completely eliminated, preventing bubbles in the green body from forming surface bulges or internal voids after sintering, thus improving production quality.

[0043] The casting mechanism 1 also includes an immersion ultrasonic transducer 13, which consists of three to five columnar piezoelectric transducers arranged at equal intervals along the length of the slurry tank. The outer shell of the immersion ultrasonic transducer 13 is sealed with an O-ring and then inserted into the flange sleeve on the side wall of the slurry tank and locked. The immersion ultrasonic transducer 13 is used to apply ultrasonic vibration to the casting slurry to break microbubbles.

[0044] The cavitation effect (rapid generation and violent collapse of tiny bubbles) generated by high-frequency ultrasound propagating in liquid slurry is utilized to break up micron- or even nano-sized air bubbles in the slurry, preventing bubbles from remaining inside the green body and causing sintering cracks. Three to five columnar piezoelectric transducers are installed at the bottom or side wall of the slurry tank in the casting mechanism 1. The transducer housing is sealed with an O-ring and inserted into a flange sleeve to ensure no slurry leakage. During operation, the transducers vibrate at a frequency of 20-60 kHz, applying continuous ultrasonic vibration to the slurry above or below the cast steel strip. The green strip undergoes online debubbling as it passes through the vibration zone. This effectively eliminates microbubbles inside the cast green body, reducing the risk of bulging and cracking during sintering (the crack rate can be reduced to below 0.2%), while avoiding the time cost of an additional static debubbling process, thus improving production efficiency.

[0045] Example 2

[0046] like Figures 1-10 As shown, this embodiment discloses an alumina ceramic tube shell production device, including a casting mechanism 1, an isostatic pressing mechanism 2, a sintering integrated furnace 3, a laser microtextured metallurgical station 4, and a control system 5 arranged sequentially along the process. The casting mechanism 1 includes: a horizontal frame 6, a frame welded from rectangular steel pipes, with a base plate 7 at the bottom, and two parallel guide rail supports fixed to the top surface of the frame; a slurry tank, configured as a U-shaped tank with an open top, with the outer walls of both sides of the tank fixed to the guide rail supports by bolts; and a casting steel strip wound around the slurry. Between the two sets of rollers upstream and downstream of the material trough, the upstream roller is a drive roller connected to the output shaft of the servo motor via coupling 9, and the downstream roller is a tension roller slidably mounted in the waist-shaped groove on the side wall of the frame via a slider; the scraper assembly includes a blade holder beam 10 and a scraper blade 12. The two ends of the blade holder beam 10 are bolted to the side wall of the frame via L-shaped connecting seats. The scraper blade 12 is clamped in the T-shaped groove 11 of the blade holder beam 10 and tightened by clamping bolts. A gap is provided between the bottom edge of the scraper blade 12 and the upper surface of the cast steel strip. The gap is used to limit the thickness of the green billet casting.

[0047] Its working principle is as follows: Powder raw materials are made into a stable and uniform casting slurry, which is then cast into a strip of wet blank using a scraper. The wet blank is then isotropically densified using an isostatic press. Subsequently, the blank is fed into a segmented sintering furnace, where it undergoes debinding, pre-sintering, and high-temperature densification under specific temperature zones and atmospheres. Finally, end-face metallization is achieved through online laser processing and printing co-firing. In use, the casting mechanism 1 supplies the prepared alumina slurry to the casting steel strip, controlling the thickness through the scraper gap to form a continuous tube-shell green blank strip. The isostatic pressing mechanism 2 fits the cast green blank into a rubber sleeve, applying pressure to the blank simultaneously radially and axially using a high-pressure liquid medium to homogenize its density. The integrated sintering furnace 3 sequentially conveys the isostatically pressed blank through the debinding zone 21, the pre-sintering zone 22, and the high-temperature sintering zone 23, with each zone's temperature and atmosphere independently controllable. The entire process of alumina ceramic tube shell production, from green body preparation to final metallization, has been automated. Through process integration and linkage control, the damage and contamination caused by multiple handling of the green body in traditional intermittent production have been avoided. Micro bubbles in the slurry can be completely eliminated, preventing bubbles in the green body from forming surface bulges or internal voids after sintering, thus improving production quality.

[0048] The casting mechanism 1 also includes an immersion ultrasonic transducer 13, which consists of three to five columnar piezoelectric transducers arranged at equal intervals along the length of the slurry tank. The outer shell of the immersion ultrasonic transducer 13 is sealed with an O-ring and then inserted into the flange sleeve on the side wall of the slurry tank and locked. The immersion ultrasonic transducer 13 is used to apply ultrasonic vibration to the casting slurry to break microbubbles.

[0049] The cavitation effect (rapid generation and violent collapse of tiny bubbles) generated by high-frequency ultrasound propagating in liquid slurry is utilized to break up micron- or even nano-sized air bubbles in the slurry, preventing bubbles from remaining inside the green body and causing sintering cracks. Three to five columnar piezoelectric transducers are installed at the bottom or side wall of the slurry tank in the casting mechanism 1. The transducer housing is sealed with an O-ring and inserted into a flange sleeve to ensure no slurry leakage. During operation, the transducers vibrate at a frequency of 20-60 kHz, applying continuous ultrasonic vibration to the slurry above or below the cast steel strip. The green strip undergoes online debubbling as it passes through the vibration zone. This effectively eliminates microbubbles inside the cast green body, reducing the risk of bulging and cracking during sintering (the crack rate can be reduced to below 0.2%), while avoiding the time cost of an additional static debubbling process, thus improving production efficiency.

[0050] For better results, the isostatic pressing mechanism 2 is located downstream of the casting mechanism 1, and includes a wet bag type isostatic pressing host 14, an axial pressurizing assembly, and a radial liquid chamber. The main body of the wet bag type isostatic pressing host 14 is a multi-layer prestressed steel wire wound thick-walled cylinder, which is arranged vertically. The bottom end is fixed to the base 15 via a flange, and the top end is provided with a cylinder mouth sealing cover 16. The sealing cover 16 and the inner cavity of the cylinder form a pressure-bearing cavity 17. The axial pressurizing assembly includes an axial piston rod 18 and an upper end cover 19. The upper end cover 19 is threaded to the top of the cylinder. The axial piston rod 18 passes through the central hole of the upper end cover 19 and is sealed by an O-ring. The lower end of the piston rod 18 extends into the pressure-bearing cavity 17 to apply pressure to the top of the rubber sleeve placed in the pressure-bearing cavity 17. The radial liquid chamber is filled with a mixture of ethylene glycol and water as a pressure medium. The lower part of the side wall of the cylinder is provided with a liquid inlet pipe, which is connected to the outlet flange of the booster pump via a high-pressure hose.

[0051] By utilizing the uniform pressure transmission properties of high-pressure liquids (such as water / ethylene glycol mixtures), the density gradient caused by friction on the mold sidewalls in traditional molding processes is overcome, enabling the tube preform to achieve a highly uniform density distribution both axially and radially. The cast tube preform is tightly encased in a rubber sleeve. First, the sleeve is placed in an isostatic pressing unit 14, and an axial pressure of 80-120 MPa is applied to the top using an axial pressurization component and maintained for 30-60 seconds. Subsequently, a booster pump injects pressure medium into the radial liquid chamber, applying a radial pressure of 100-150 MPa to the sleeve and maintaining it for 60-120 seconds, thus isotropically densifying the preform. This eliminates the density difference between the axial and radial directions, preventing warping and deformation of the tube preform after sintering.

[0052] For better results, the integrated sintering furnace 3 is located downstream of the isostatic pressing mechanism and includes a horizontal furnace shell 20, a furnace lining, a three-section furnace cavity, and an oxygen partial pressure distribution assembly. The horizontal furnace shell 20 is a rectangular welded steel plate shell, and the inner wall of the shell is lined with heat-insulating fiber cotton to form the furnace lining. The inner cavity of the furnace lining is divided along its length into a glue removal zone 21, a pre-sintering zone 22, and a high-temperature sintering zone 23, which are connected sequentially by two vertical heat-insulating plates. The bottom of section 3 is connected by a continuous roller conveyor belt. The two ends of the roller are mounted on the side wall of the furnace shell via bearing seats and are connected to the conveyor motor 26 by sprockets and chains. This belt is used to carry and transport the billet through the glue removal zone 21, the pre-sintering zone 22 and the high-temperature sintering zone 23 in sequence. The oxygen partial pressure distribution assembly includes a needle valve and a mass flow controller. The air inlet end of the needle valve is connected to the air compressor outlet via a parallel air pipe. The air outlet end is connected to the air inlet pipe on the side wall of the glue removal zone 21 via flanges.

[0053] The furnace employs a roller conveyor tunnel structure, dividing the furnace chamber into functionally independent temperature zones through physical partitions (insulation plates). It is equipped with a high-precision oxygen partial pressure distribution system to achieve programmed atmosphere control during the sintering process. In operation, the furnace body is welded from steel plates, with the inner walls lined with insulating fiber cotton. Two vertical insulation plates divide the furnace chamber along its length into a debinding zone 21, a pre-sintering zone 22, and a high-temperature sintering zone 23. Each zone has a roller conveyor belt running at a constant speed, driven by a motor. An air compressor provides the air source, which, after precise regulation by a needle valve and a mass flow controller (MFC), is introduced into the air inlet pipes of each zone, achieving independent atmosphere control. This zoned control allows debinding, pre-sintering, and high-temperature sintering to proceed under the optimal temperature / atmosphere curves, avoiding interference between different physicochemical reactions in the same temperature zone and ensuring the stability of the sintering quality.

[0054] For better results, the top wall of the furnace shell in the glue removal zone 21 is equipped with an exhaust pipe 27, and the side wall is equipped with a multi-stage air inlet pipe 28; the top walls of the furnace shells in the pre-sintering zone 22 and the high-temperature sintering zone 23 are both equipped with hydrogen / nitrogen mixed gas inlet pipes 29; the furnace lining of the high-temperature sintering zone 23 is embedded with... The heating element is fixed to the two side walls of the furnace cavity via a ceramic insulating base.

[0055] Based on the different atmosphere requirements at different sintering stages, differentiated air intake methods and heat source locations are designed. The debinding stage requires strong exhaust to remove volatiles, the pre-sintering stage requires reducing gases to prevent oxidation, and the high-temperature sintering stage requires high heat loads. In operation, in the debinding zone 21, an exhaust pipe 27 is installed on the furnace top, and multi-stage air intake pipes 28 are installed on the side walls, forming an upward airflow to accelerate the removal of organic matter. In the pre-sintering zone 22 and the high-temperature sintering zone 23, the furnace top is equipped with... The mixed gas inlet pipe 29 forms a protective atmosphere. Embedded within the furnace lining on both sides of the high-temperature sintering zone 23 are... The heating element supplies heat to the center of the furnace through radiation and convection. Multi-stage air intake and exhaust effectively prevent volatiles from carbonizing on the surface of the billet or causing microcracks. The heating element is heat-resistant and oxidation-resistant, and has high thermal efficiency.

[0056] For better results, the laser microtextured metallization station 4 includes a three-dimensional adjustment frame, a pulsed fiber laser, a galvanometer scanning head, and a tungsten paste screen printing table. The main unit of the pulsed fiber laser is located beside the frame, and the output fiber is connected to the galvanometer scanning head via a cable chain. The galvanometer scanning head is fixed to the end of the cantilever via a flange, and the lens optical axis is vertically downward aligned with the metallized surface of the tube shell on the roller. The tungsten paste screen printing table is located downstream of the galvanometer scanning head. The table surface is a granite reference plate, and a tube shell positioning fixture is provided on the plate. A tungsten paste scraper mechanism is provided on the side of the fixture. The scraper is driven by a cylinder to reciprocate, used to print tungsten and manganese metallized paste onto the laser-textured tube shell surface. High-energy-density pulsed lasers ablate a micron-scale pit array (microtexture) on the ceramic surface, destroying the surface inert layer and forming a mechanical anchoring effect. Subsequently, metal paste is filled into the pits using screen printing, and a good metal-ceramic interface bond is formed after high-temperature co-firing. The laser micro-pits solve the problem of poor metal layer adhesion caused by the low surface energy of ceramics.

[0057] For better performance, the control system 5 includes a PLC cabinet and an HMI touchscreen. The PLC cabinet is bolted to the electrical area next to the casting mechanism 1, and houses an S7-1500 series PLC main unit and analog modules. The HMI touchscreen is fixed to the operating side of the isostatic pressing mechanism via a cantilever bracket and is connected to the PLC cabinet via a shielded cable. The servo motor driver of the casting mechanism 1, the power controller of the immersion ultrasonic transducer 13, the pressure sensor and axial piston displacement sensor of the booster pump of the isostatic pressing mechanism, the temperature zone thermocouple and mass flow controller of the sintering integrated furnace 3, and the module servo driver of the laser microtextured metalworking station 4 are all connected to the PLC cabinet via shielded cables to achieve temperature, pressure, gas, and position linkage control of the four stations. This is a distributed control system 5 based on a PLC (Programmable Logic Controller). By collecting sensor signals (such as position, pressure, temperature, and flow) from each station, executing preset control algorithms (such as PID), and outputting control commands to drive servo motors, booster pumps, MFC and other actuators, the system achieves synchronous coordination throughout the entire process. It eliminates errors caused by manual operation and ensures the consistency of product performance in mass production.

[0058] A method for preparing an alumina ceramic tube shell includes the following steps:

[0059] Slurry preparation: at 92–96 wt% As the matrix, add 0.2–0.5 wt%, 0.1–0.3 wt% is used as a sintering aid, and is mixed with organic solvents, binders, and plasticizers to prepare a casting slurry with a solid content of 55–65%.

[0060] Defoaming casting: The slurry is sent into casting mechanism 1 after defoaming;

[0061] Isostatic pressing: Place the cast green body into a rubber sleeve, first apply axial pressure to 80–120 MPa and hold for 30–60s, then apply radial isostatic pressing to 100–150 MPa and hold for 60–120s.

[0062] Sintering Integration: The isostatically pressed green body is fed into sintering integration furnace 3 and processed according to the following curve:

[0063] Degreasing zone 21: The temperature is raised from room temperature to 600℃ at a rate of 0.5–1℃ / min, and the oxygen volume fraction is gradually reduced from 5% to 0.1%.

[0064] Pre-sintering zone 22: Temperature is increased from 600℃ to 1200℃ at a rate of 3–5℃ / min, and the atmosphere is switched to... Mixed reducing gas;

[0065] High-temperature sintering zone 23: The temperature is raised from 1200℃ to 1550℃, held for 2–4 hours, and then cooled down to 800℃ and cooled with the furnace.

[0066] Laser microtextured metallization: After the sintered body exits the furnace, an array of micropits is processed on the surface to be metallized using a pulsed fiber laser, followed by printing of tungsten and manganese metallization pastes, and then heated at 1450–1500℃. The alumina ceramic tube shell is co-fired for 30–60 min under a specific atmosphere to obtain the finished product.

[0067] After the high-temperature sintering zone 23 is held at a temperature of 2–3℃ / min, the temperature is reduced to 1200℃, and then reduced to 800℃ at a rate of 5–8℃ / min to suppress abnormal grain growth.

[0068] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An alumina ceramic tube shell production apparatus, comprising a casting mechanism, an isostatic pressing mechanism, a sintering integrated furnace, a laser microtextured metallurgical stage, and a control system arranged sequentially along the process steps, characterized in that, The casting mechanism includes: The horizontal frame is a frame welded from rectangular steel pipes, with a base plate at the bottom. Two parallel guide rail supports are fixed to the top surface of the frame. The slurry tank is a U-shaped trough with an open top, and the outer walls of the trough are bolted to the guide rail supports. The cast steel strip is wound between two sets of rollers at the upstream and downstream ends of the slurry tank. The upstream roller is a drive roller connected to the output shaft of a servo motor via a coupling, and the downstream roller is a tension roller slidably mounted in a waist-shaped groove on the side wall of the frame via a slider. The scraper assembly includes a blade holder beam and scraper blades. The two ends of the blade holder beam are bolted to the side wall of the frame via L-shaped connecting seats. The scraper blades are clamped in the T-shaped grooves of the blade holder beam and tightened by clamping bolts. A gap is provided between the bottom edge of the scraper blade and the upper surface of the cast steel strip. The gap is used to limit the casting thickness of the green billet.

2. The alumina ceramic tube shell production apparatus according to claim 1, characterized in that, The casting mechanism also includes an immersion ultrasonic transducer, which consists of three to five columnar piezoelectric transducers arranged at equal intervals along the length of the slurry tank. The outer shell of the immersion ultrasonic transducer is sealed with an O-ring and then inserted into the flange sleeve on the side wall of the slurry tank and locked. The immersion ultrasonic transducer is used to apply ultrasonic vibration to the casting slurry to break microbubbles.

3. The alumina ceramic tube shell production apparatus according to claim 1, characterized in that, The isostatic pressing mechanism is located downstream of the casting mechanism and includes a wet bag type isostatic pressing host, an axial pressurizing component, and a radial liquid chamber. The main body of the wet bag type isostatic press is a multi-layer prestressed steel wire wound thick-walled cylinder. The cylinder is arranged vertically, and the bottom end is fixed to the base by a flange. The top end is provided with a cylinder mouth sealing cover. The sealing cover and the inner cavity of the cylinder form a pressure-bearing cavity. The axial pressurization assembly includes an axial piston rod and an upper end cap. The upper end cap is threaded to the top of the cylinder. The axial piston rod passes through the central hole of the upper end cap and is sealed by an O-ring. The lower end of the piston rod extends into the pressure chamber to apply pressure to the top of the rubber sleeve placed in the pressure chamber. The radial liquid chamber is filled with a mixture of ethylene glycol and water as the pressure medium. An inlet pipe is provided on the lower part of the side wall of the cylinder, which is connected to the outlet flange of the booster pump via a high-pressure hose.

4. The alumina ceramic tube shell production apparatus according to claim 1, characterized in that, The sintering integrated furnace is located downstream of the isostatic pressing mechanism and includes a horizontal furnace shell, furnace lining, three-section furnace cavity and oxygen partial pressure distribution assembly. The horizontal furnace shell is a rectangular steel plate welded shell, and the inner wall of the shell is lined with heat-insulating fiber cotton to form a furnace lining. The inner cavity of the furnace lining is divided into a glue discharge zone, a pre-sintering zone, and a high-temperature sintering zone by two vertical heat insulation plates along the length direction. The bottom of the glue discharge zone, the pre-sintering zone, and the high-temperature sintering zone are connected by a through roller conveyor belt. The two ends of the roller are mounted on the side wall of the furnace shell through bearing seats and connected to the conveyor motor by sprockets and chains. It is used to carry and transport the billet through the glue discharge zone, the pre-sintering zone, and the high-temperature sintering zone in sequence. The oxygen partial pressure distribution assembly includes a needle valve and a mass flow controller. The inlet end of the needle valve is connected to the outlet of the air compressor via a parallel air pipe, and the outlet end is connected to the inlet pipe of the glue discharge area via a flange.

5. The alumina ceramic tube shell production apparatus according to claim 4, characterized in that, The furnace shell top wall of the debinding zone is equipped with an exhaust pipe, and the side wall is equipped with a multi-stage air inlet pipe; the furnace shell top walls of both the pre-sintering zone and the high-temperature sintering zone are equipped with hydrogen / nitrogen mixed gas inlet pipes; the furnace lining of the high-temperature sintering zone is embedded with... The heating element is fixed to the two side walls of the furnace cavity via a ceramic insulating base.

6. The alumina ceramic tube shell production apparatus according to claim 1, characterized in that, The laser microtextured metallization station includes a three-dimensional adjustment frame, a pulsed fiber laser, a galvanometer scanning head, and a tungsten paste screen printing table; The main unit of the pulsed fiber laser is located on the side of the frame. The output fiber is connected to the galvanometer scanning head via a drag chain. The galvanometer scanning head is fixed to the end of the cantilever via a flange. The lens optical axis is vertically downward and aligned with the metallized surface of the tube shell on the roller. The tungsten paste screen printing table is located downstream of the galvanometer scanning head. The table surface is a granite reference plate. A tube positioning fixture is provided on the plate, and a tungsten paste scraper mechanism is provided on the side of the fixture. The scraper is driven by a cylinder to reciprocate, and is used to print tungsten and manganese metallized paste onto the laser-textured tube surface.

7. The alumina ceramic tube shell production apparatus according to claim 1, characterized in that, The control system includes a PLC cabinet and an HMI touch screen. The PLC cabinet is bolted to the electrical area next to the casting mechanism and is equipped with an S7-1500 series PLC host and analog modules. The HMI touch screen is fixed to the operating side of the isostatic pressing mechanism via a cantilever bracket and is connected to the PLC cabinet via a shielded cable. The servo motor driver of the casting mechanism, the power controller of the immersion ultrasonic transducer, the pressure sensor and axial piston displacement sensor of the booster pump of the isostatic pressing mechanism, the temperature zone thermocouple and mass flow controller of the sintering integrated furnace, and the module servo driver of the laser microtextured metal processing station are all connected to the PLC cabinet via shielded cables to realize the linkage control of temperature, pressure, gas and position of the four stations.

8. A method for preparing an alumina ceramic tube shell, using the apparatus described in any one of claims 1 to 7, characterized in that, Includes the following steps: Slurry preparation: at 92–96 wt% As the matrix, add 0.2–0.5 wt%, 0.1–0.3 wt% is used as a sintering aid, and is mixed with organic solvents, binders and plasticizers to prepare a casting slurry with a solid content of 55–65%; Defoaming casting: The slurry is sent into the casting mechanism after defoaming; Isostatic pressing: Place the cast green body into a rubber sleeve, first apply axial pressure to 80–120 MPa and hold for 30–60s, then apply radial isostatic pressing to 100–150 MPa and hold for 60–120s. Sintering Integration: The isostatically pressed green body is fed into the sintering integration furnace and processed according to the following curve: Degreasing zone: The temperature is raised from room temperature to 600℃ at a rate of 0.5–1℃ / min, and the oxygen volume fraction is gradually reduced from 5% to 0.1%. Pre-sintering zone: Temperature is increased from 600℃ to 1200℃ at a rate of 3–5℃ / min, and the atmosphere is switched to... Mixed reducing gas; High-temperature sintering zone: The temperature is raised from 1200℃ to 1550℃, held for 2–4 hours, and then cooled down to 800℃ and cooled with the furnace. Laser microtextured metallization: After the sintered body exits the furnace, an array of micropits is processed on the surface to be metallized using a pulsed fiber laser, followed by printing of tungsten and manganese metallization pastes, and then heated at 1450–1500℃. The alumina ceramic tube shell is co-fired for 30–60 min under a specific atmosphere to obtain the finished product.

9. The method for preparing the alumina ceramic tube shell according to claim 8, characterized in that, After the high-temperature sintering zone is maintained at a certain temperature, the temperature is reduced to 1200℃ at a rate of 2–3℃ / min, and then reduced to 800℃ at a rate of 5–8℃ / min to suppress abnormal grain growth.

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