Preparation process of 0-shaped composite metal sealing element with large ring diameter ratio

Abstract

The invention relates to a large ring diameter ratio 0-shaped composite metal sealing element preparation technology, and relates to the technical field of metal sealing element preparation, and the technology comprises the following steps: S1, raw material preparation; s2, isostatic pressing forming of the metal rubber inner core; s3, preparing an integrated metal shell; s4, component preprocessing; s5, implanting the inner core; s6, radial compression locking; s7, overall stress relief annealing; and S8, finish machining and surface treatment. The preparation process of the large-ring-diameter-ratio O-shaped composite metal sealing element is combined with a radial compression locking process, the problems that a traditional slotted shell is low in strength at a seam position, an inner core is prone to being extruded out, and early failure is caused are fundamentally solved, the completely-closed O-shaped shell is prepared through a precision casting technology, full wrapping of the metal rubber inner core is achieved, and the sealing performance of the sealing element is improved. The integral structural strength and the sealing reliability of the sealing element are remarkably improved, and the sealing element is particularly suitable for extreme working condition environments with extremely high safety requirements such as aerospace and the nuclear industry and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of metal seal manufacturing technology, specifically a manufacturing process for a large annular ratio O-shaped composite metal seal. Background Technology

[0002] High-ratio O-ring composite metal seals are high-performance sealing elements with a special structure. The "high ratio" refers to the large ratio of the average diameter of the sealing ring to its cross-sectional diameter. These seals typically use a metal-rubber material with excellent elasticity and damping properties as the inner core, fully or partially encased by a dense metal shell, forming a composite structure that combines the strength of metal and the elasticity of rubber. Because they maintain reliable sealing performance under extreme conditions such as high temperature, high pressure, and strong vibration, they are widely used in aerospace, nuclear industry, and high-end chemical equipment—fields with extremely high requirements for sealing reliability.

[0003] In the literature on the fatigue mechanical properties and experimental research of O-ring metal-rubber seals with large ring diameter ratios, the preparation process of O-ring composite metal seals with large ring diameter ratios mainly includes: first, using stainless steel wire to spirally wind and wrap a blank, and then cold stamping it into a metal-rubber inner core; second, using flame heating to assist bending and rounding a slotted stainless steel tube to make a semi-enclosed outer shell; finally, placing the inner core into the outer shell to complete the assembly. This process uses the controlled variable method to study the influence of porosity, loading amplitude and other factors on the fatigue performance of the seal, providing basic data for related research.

[0004] However, this manufacturing process has significant defects: First, the outer shell made by "slotted steel pipe bending" has structural weaknesses at the joints, and the "semi-enclosed" design provides a direct overflow channel for the metal rubber inner core. Under alternating loads, the inner core is easily squeezed out of the gap, causing early failure. This is completely consistent with the "inner core overflow" phenomenon observed in the article, indicating that its structural design itself has fundamental defects. Second, the process is rough and lacks necessary post-processing steps, such as stress-relieving annealing for residual stress generated during cold stamping and assembly, resulting in high internal stress levels in the product, affecting long-term dimensional stability and fatigue life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a manufacturing process for O-ring composite metal seals with a large ring diameter ratio. This process offers advantages such as high sealing reliability, strong pressure resistance, low internal stress, good long-term dimensional stability, and long fatigue life. It solves the problems of high internal stress levels, poor dimensional stability, short fatigue life, and insufficient performance in high-sealing applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a manufacturing process for a large annular ratio O-ring composite metal seal, comprising the following steps:

[0007] S1 Raw Material Preparation: Stainless steel wire with a diameter of 0.15mm is selected as the metal rubber inner core material, and compatible stainless steel plates or discs are selected as the raw materials for the one-piece outer shell.

[0008] S2 Metal Rubber Core Isostatic Pressing: Stainless steel wire is filled into an O-shaped mold, and uniform high pressure is applied using cold isostatic pressing technology to form a dense and uniform O-shaped metal rubber core blank in one step.

[0009] S3 One-Piece Metal Shell Fabrication: A slotless, fully enclosed O-ring metal shell is manufactured by precision casting. Its inner diameter is designed to be slightly smaller than the outer diameter of the metal rubber inner core to form an interference fit.

[0010] S4 component pretreatment: The contact surfaces of the molded metal rubber inner core and the one-piece metal shell are ultrasonically cleaned to thoroughly remove oil and impurities;

[0011] S5 Core Implantation: The pre-treated metal rubber core is placed in the cavity of the one-piece metal shell to complete the initial assembly;

[0012] S6 Radial Compression Locking: The assembled components are placed in a special radial compression mold, and a hydraulic press is used to apply uniform and controllable radial pressure to deform the metal shell, thereby tightly and firmly wrapping and locking the internal metal rubber core.

[0013] S7 Overall Stress-Relief Annealing: The locked composite seal is placed in a vacuum or protective atmosphere furnace for stress-relief annealing. After holding at 350℃ for 1.5 hours, it is cooled with the furnace to eliminate residual stress and stabilize material properties and geometry.

[0014] S8 finishing and surface treatment: Polishing, plating, and passivation of the outer surface of the seal, and dimensional finishing to obtain the required surface quality and dimensional accuracy.

[0015] Furthermore, in step S1, the raw material preparation uses 0Cr18Ni9 stainless steel for both the stainless steel wire and the stainless steel plate.

[0016] Furthermore, in step S2, the 0Cr18Ni9 stainless steel wires that have undergone degreasing and cleaning are randomly and uniformly filled into a rigid O-ring mold cavity whose size matches the inner core of the target O-ring seal, according to a predetermined length and quantity. A uniform isotropic pressure of 200MPa to 400MPa is applied in a high-pressure vessel, and the pressure holding time is 5 to 10 minutes.

[0017] Furthermore, the precision casting in step S3 is specifically as follows:

[0018] 1) Low-melting-point wax is pressurized and cooled in a metal mold to create a wax model that is exactly the same in shape and size as the final O-ring metal shell;

[0019] 2) Connect multiple O-shaped wax models to a central wax gate bar through a wax gating system to form a wax model assembly resembling a "tree branch";

[0020] 3) Immerse the wax mold in silica sol, then evenly sprinkle refractory sand of different particle sizes on it, and dry and harden it at room temperature or under controlled humidity. Repeat this process 4-8 times to form the shell.

[0021] 4) Place the dried shell into hot water or a high-pressure steam autoclave to melt and flow out the wax inside, thus obtaining a completely sealed ceramic shell with an O-shaped cavity inside.

[0022] 5) The dewaxed ceramic shell is placed in a high-temperature furnace for firing to further improve its strength and remove residual moisture and impurities;

[0023] 6) Pour the molten 0Cr18Ni9 stainless steel into the preheated ceramic mold shell, and the molten metal fills the entire O-ring cavity.

[0024] 7) Allow the molten metal to cool naturally and solidify completely within the mold shell to form an O-shaped metal casting;

[0025] 8) Break or use water-based sandblasting to remove the outer ceramic shell, then remove the gating system by sandblasting, cutting, etc., and perform surface treatments such as grinding and polishing on the casting to finally obtain a groove-free, completely sealed, and dimensionally accurate O-shaped stainless steel shell.

[0026] Furthermore, in step S4, the cleaning solution is a water-based cleaning agent solution with a concentration of 3-5%. The cleaning process is as follows: the workpiece is completely immersed in the cleaning solution, the ultrasonic cleaning is performed, and then the workpiece is rinsed with deionized water 1-2 times with ultrasonic cleaning for 5 minutes each time to remove residual cleaning agent. The rinsed workpiece is then placed in a hot air circulating oven at 60-80℃ and dried for 10-15 minutes.

[0027] Furthermore, in step S5, non-metallic tweezers or special clamps are used to handle the metal rubber core gently, so that the metal rubber core is centered in the inner cavity of the metal outer shell without tilting or jamming, and its axis is basically coincident with the axis of the outer shell.

[0028] Furthermore, the radial pressure applied in step S6 should cause the metal shell to produce a radial compressive strain of 0.5%-2.0%, ensuring that the shell undergoes elastic or slight plastic deformation. The compression amount and pressure are monitored in real time by displacement and pressure sensors on the mold. After reaching the set pressure or displacement, the pressure is held for 30-60 seconds, and then the material is slowly and evenly unloaded.

[0029] Furthermore, step S7 includes the following:

[0030] Heating: The furnace temperature is uniformly increased from room temperature to 350℃ at a rate of 5-10℃ / min;

[0031] Insulation: Insulate at 350±10℃ for 1.5 hours to allow the residual stress inside the material to fully relax;

[0032] Cooling: After the heat preservation is completed, turn off the heating power and let the furnace cool down slowly to below 100°C. Then the workpiece can be taken out and cooled to room temperature in the air.

[0033] Furthermore, the polishing process employs a centerless cylindrical grinder or a precision grinding machine, using #400 to #800 mesh grinding wheels or abrasives, and undergoes 5-10μm electroless nickel plating (ENP) or electroplating nickel treatment.

[0034] Furthermore, in step S3, the inner diameter tolerance of the integrated metal shell is controlled within the range of -0.05mm to 0mm, and the outer diameter tolerance of the prefabricated metal rubber inner core is controlled within the range of +0.05mm to +0.10mm, thereby ensuring that there is an interference of 0.05mm to 0.15mm between the two.

[0035] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0036] 1. The manufacturing process of this large-ring-ratio O-ring composite metal seal, combined with radial compression locking technology, fundamentally solves the problems of low strength at the joints and easy extrusion of the inner core caused by traditional slotted shells, leading to early failure. By using precision casting technology to prepare a completely sealed O-ring shell, the metal rubber inner core is fully wrapped, which significantly improves the overall structural strength and sealing reliability of the seal. It is especially suitable for extreme working environments with extremely high safety requirements, such as aerospace and nuclear industry.

[0037] 2. The manufacturing process of this large ring diameter ratio O-ring composite metal seal incorporates steps such as cold isostatic pressing, ultrasonic cleaning, stress-relief annealing, and surface finishing. This effectively ensures the uniformity and density of the metal-rubber inner core, eliminates residual stress generated during processing and assembly, and improves the dimensional stability and fatigue life of the product. The overall process is scientific and reasonable, significantly improving the manufacturing precision and performance consistency of the large ring diameter ratio O-ring composite metal seal, and has good prospects for industrial application. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0039] The technical solutions of 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.

[0040] Please see Figure 1 The manufacturing process of a large annular ratio O-ring composite metal seal in this embodiment includes the following steps:

[0041] S1 Raw Material Preparation: Stainless steel wire with a diameter of 0.15mm is selected as the metal rubber inner core material, and compatible stainless steel plates or discs are selected as the raw materials for the one-piece outer shell.

[0042] S2 Metal Rubber Core Isostatic Pressing: Stainless steel wire is filled into an O-shaped mold, and uniform high pressure is applied using cold isostatic pressing technology to form a dense and uniform O-shaped metal rubber core blank in one step.

[0043] S3 One-Piece Metal Shell Fabrication: A slotless, fully enclosed O-ring metal shell is manufactured by precision casting. Its inner diameter is designed to be slightly smaller than the outer diameter of the metal rubber inner core to form an interference fit.

[0044] S4 component pretreatment: The contact surfaces of the molded metal rubber inner core and the one-piece metal shell are ultrasonically cleaned to thoroughly remove oil and impurities;

[0045] S5 Core Implantation: The pre-treated metal rubber core is placed in the cavity of the one-piece metal shell to complete the initial assembly;

[0046] S6 Radial Compression Locking: The assembled components are placed in a special radial compression mold, and a hydraulic press is used to apply uniform and controllable radial pressure to deform the metal shell, thereby tightly and firmly wrapping and locking the internal metal rubber core.

[0047] S7 Overall Stress-Relief Annealing: The locked composite seal is placed in a vacuum or protective atmosphere furnace for stress-relief annealing. After holding at 350℃ for 1.5 hours, it is cooled with the furnace to eliminate residual stress and stabilize material properties and geometry.

[0048] S8 finishing and surface treatment: Polishing, plating, and passivation of the outer surface of the seal, and dimensional finishing to obtain the required surface quality and dimensional accuracy.

[0049] It should be noted that by selecting high-performance stainless steel wire and compatible stainless steel plates, and combining cold isostatic pressing technology to prepare a dense and uniform metal-rubber inner core, and using precision casting technology to manufacture a slotless one-piece metal shell, the strength defects and inner core extrusion risks caused by traditional slotted structures are fundamentally avoided. Through key steps such as ultrasonic cleaning, interference fit assembly, radial compression locking, and stress-relief annealing, the tight connection between components is effectively guaranteed, residual stress from processing and assembly is eliminated, and structural stability and fatigue life are improved. Finally, precision machining and surface treatment further ensure the dimensional accuracy and surface quality of the seal. The overall process is scientific and systematic, significantly improving the reliability, consistency, and long-term service performance of large ring diameter ratio composite metal seals.

[0050] In step S1, raw material preparation, both stainless steel wire and stainless steel sheet are made of 0Cr18Ni9 stainless steel.

[0051] It should be noted that the use of 0Cr18Ni9 stainless steel as the uniform material for both the metal rubber inner core and outer shell ensures a good match between the internal and external components in terms of thermal expansion coefficient, mechanical properties, and corrosion resistance, thereby improving the overall structural compatibility and reliability.

[0052] In step S2, the 0Cr18Ni9 stainless steel wires that have undergone degreasing and cleaning are randomly and uniformly filled into a rigid O-ring mold cavity whose size matches the inner core of the target O-ring seal, according to a predetermined length and quantity. A uniform isotropic pressure of 200MPa to 400MPa is applied in a high-pressure vessel, and the pressure holding time is 5 to 10 minutes.

[0053] It should be noted that the isostatic pressing process of the metal rubber core has been refined. A random and uniform filling method is adopted, and the pressure is held at 200–400MPa for 5–10 minutes to ensure that the core is dense and has a uniform structure, which significantly improves its elasticity and resilience.

[0054] The precision casting in step S3 is as follows:

[0055] 1) Low-melting-point wax is pressurized and cooled in a metal mold to create a wax model that is exactly the same in shape and size as the final O-ring metal shell;

[0056] 2) Connect multiple O-shaped wax models to a central wax gate bar through a wax gating system to form a wax model assembly resembling a "tree branch";

[0057] 3) Immerse the wax mold in silica sol, then evenly sprinkle refractory sand of different particle sizes on it, and dry and harden it at room temperature or under controlled humidity. Repeat this process 4-8 times to form the shell.

[0058] 4) Place the dried shell into hot water or a high-pressure steam autoclave to melt and flow out the wax inside, thus obtaining a completely sealed ceramic shell with an O-shaped cavity inside.

[0059] 5) The dewaxed ceramic shell is placed in a high-temperature furnace for firing to improve its strength and remove residual moisture and impurities;

[0060] 6) Pour the molten 0Cr18Ni9 stainless steel into the preheated ceramic mold shell, and the molten metal fills the entire O-ring cavity.

[0061] 7) Allow the molten metal to cool naturally and solidify completely within the mold shell to form an O-shaped metal casting;

[0062] 8) Break or use water-based sandblasting to remove the outer ceramic shell, then remove the gating system by sandblasting, cutting, etc., and perform surface treatments such as grinding and polishing on the casting to finally obtain a groove-free, completely sealed, and dimensionally accurate O-shaped stainless steel shell.

[0063] It should be noted that the process of preparing a slotless one-piece metal shell through lost-wax precision casting is described in detail, including wax mold preparation, shell making, dewaxing, firing, casting and post-processing, to ensure the integrity of the shell structure and the accuracy of dimensions, fundamentally avoiding structural weaknesses caused by seams.

[0064] In step S4, the cleaning solution is a water-based cleaning agent solution with a concentration of 3-5%. The cleaning process is as follows: the workpiece is completely immersed in the cleaning solution, the ultrasonic cleaning is performed, and then the workpiece is rinsed with deionized water 1-2 times with ultrasonic cleaning for 5 minutes each time to remove residual cleaning agent. The rinsed workpiece is then placed in a hot air circulating oven at 60-80℃ and dried for 10-15 minutes.

[0065] It should be noted that the ultrasonic cleaning process parameters before component assembly are specified, using 3-5% water-based cleaning agent in combination with deionized water for rinsing, and drying under hot air at 60-80℃, which effectively removes surface oil and impurities, improving the cleanliness and reliability of subsequent assembly.

[0066] In step S5, non-metallic tweezers or special clamps are used to handle the metal rubber core gently, so that the metal rubber core is centered in the inner cavity of the metal outer shell without tilting or jamming, and its axis is basically coincident with the axis of the outer shell.

[0067] It should be noted that non-metallic tools or special fixtures are emphasized during the core implantation process to ensure that the metal rubber core is placed in the center without tilting or jamming, thus ensuring assembly accuracy and avoiding uneven force or local stress concentration caused by eccentricity.

[0068] In step S6, the radial pressure applied must cause the metal shell to produce a radial compressive strain of 0.5%-2.0% to ensure that the shell undergoes elastic or slight plastic deformation. The compression amount and pressure are monitored in real time by displacement and pressure sensors on the mold. After the set pressure or displacement is reached, the pressure is held for 30-60 seconds, and then the pressure is slowly and evenly released.

[0069] It should be noted that the process control parameters for radial compression locking are specified, requiring the outer shell to generate 0.5%–2.0% radial compression strain. Pressure and displacement are monitored in real time by sensors. After holding the pressure for 30–60 seconds, the pressure is slowly released to ensure that the locking process is controllable, uniform, and reliable.

[0070] Step S7 includes the following:

[0071] Heating: The furnace temperature is uniformly increased from room temperature to 350℃ at a rate of 5-10℃ / min;

[0072] Insulation: Insulate at 350±10℃ for 1.5 hours to allow the residual stress inside the material to fully relax;

[0073] Cooling: After the heat preservation is completed, turn off the heating power and let the furnace cool down slowly to below 100°C. Then the workpiece can be taken out and cooled to room temperature in the air.

[0074] It should be noted that the specific parameters of the stress-relief annealing process have been standardized. The process involves heating to 350±10℃ at a rate of 5–10℃ / min, holding at that temperature for 1.5 hours, and then cooling in the furnace. This effectively eliminates residual stress, stabilizes the material structure and geometry, and improves the long-term stability of the product.

[0075] During the polishing process, a centerless cylindrical grinder or precision grinding machine is used, with #400 to #800 mesh grinding wheels or abrasives, and 5-10μm electroless nickel plating (ENP) or electroplating nickel is performed.

[0076] It should be noted that specific requirements are put forward for finishing and surface treatment. Polishing is carried out using a centerless grinder or polishing machine, followed by a 5-10μm chemical or electroplating nickel treatment, which significantly improves the surface finish, wear resistance and corrosion resistance of the seal.

[0077] In step S3, the inner diameter tolerance of the integrated metal shell is controlled within the range of -0.05mm to 0mm, and the outer diameter tolerance of the prefabricated metal rubber inner core is controlled within the range of +0.05mm to +0.10mm, thereby ensuring that there is an interference of 0.05mm to 0.15mm between the two.

[0078] It should be noted that precise control of the inner diameter tolerance of the integrated housing (-0.05mm to 0mm) and the outer diameter tolerance of the metal rubber inner core (+0.05mm to +0.10mm) ensures that an interference fit of 0.05–0.15mm is formed between the two, providing reliable initial assembly conditions for subsequent radial locking.

[0079] This application provides a systematic, advanced, and highly reliable manufacturing process for large ring diameter ratio O-ring composite metal seals. The overall technical solution has significant innovation and practicality. First, by using precision casting to prepare a grooveless, fully enclosed one-piece metal shell, the structural weak points at the joints of traditional grooved shells are completely eliminated, effectively preventing the metal rubber core from extruding under high pressure or alternating loads, and greatly improving the structural integrity and long-term reliability of the seal. Second, the metal rubber core is formed using cold isostatic pressing technology, which achieves uniform densification of the material, giving it excellent elasticity, damping performance, and rebound stability. The process introduces interference fit design and radial compression locking technology to tightly bond the shell and the core, forming a strong mechanical enclosure, which enhances the overall load-bearing capacity and sealing preload.

[0080] Furthermore, the entire process emphasizes meticulous control, including using 0Cr18Ni9 stainless steel to ensure material consistency, ultrasonic cleaning to ensure interface cleanliness, stress-relief annealing to eliminate internal residual stress, and precision machining and surface treatment to improve dimensional accuracy and corrosion resistance. This comprehensively guarantees the high performance and high consistency of the product. The entire process design is scientific and rigorous, and the connection between each process is reasonable. It not only solves key technical problems such as obvious structural defects, high residual stress, and short service life in traditional processes, but also has good repeatability and industrialization potential. This seal is particularly suitable for extreme working conditions such as aerospace, nuclear energy equipment, and high-end chemical industry, and is of great significance for improving the sealing safety and service life of high-end equipment.

[0081] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0082] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A manufacturing process for a large annular ratio O-ring composite metal seal, characterized in that... Includes the following steps: S1 Raw Material Preparation: Stainless steel wire with a diameter of 0.15mm is selected as the metal rubber inner core material, and compatible stainless steel plates or discs are selected as the raw materials for the one-piece outer shell. S2 Metal Rubber Core Isostatic Pressing: Stainless steel wire is filled into an O-shaped mold, and uniform high pressure is applied using cold isostatic pressing technology to form a dense and uniform O-shaped metal rubber core blank in one step. S3 One-Piece Metal Shell Fabrication: A slotless, fully enclosed O-ring metal shell is manufactured by precision casting. Its inner diameter is designed to be slightly smaller than the outer diameter of the metal rubber inner core to form an interference fit. S4 component pretreatment: The contact surfaces of the molded metal rubber inner core and the one-piece metal shell are ultrasonically cleaned to thoroughly remove oil and impurities; S5 Core Implantation: The pre-treated metal rubber core is placed in the cavity of the one-piece metal shell to complete the initial assembly; S6 Radial Compression Locking: The assembled components are placed in a special radial compression mold, and a hydraulic press is used to apply uniform and controllable radial pressure to deform the metal shell, thereby tightly and firmly wrapping and locking the internal metal rubber core. S7 Overall Stress-Relief Annealing: The locked composite seal is placed in a vacuum or protective atmosphere furnace for stress-relief annealing. After holding at 350℃ for 1.5 hours, it is cooled with the furnace to eliminate residual stress and stabilize material properties and geometry. S8 finishing and surface treatment: Polishing, plating, and passivation of the outer surface of the seal, and dimensional finishing to obtain the required surface quality and dimensional accuracy.

2. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: In step S1, the raw material preparation process involves using 0Cr18Ni9 stainless steel for both the stainless steel wire and the stainless steel sheet.

3. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: In step S2, the 0Cr18Ni9 stainless steel wires that have undergone degreasing and cleaning are randomly and uniformly filled into a rigid O-ring mold cavity whose size matches the inner core of the target O-ring seal, according to a predetermined length and quantity. A uniform isotropic pressure of 200MPa to 400MPa is applied in a high-pressure vessel, and the pressure holding time is 5 to 10 minutes.

4. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: The precision casting in step S3 is as follows: 1) Low-melting-point wax is pressurized and cooled in a metal mold to create a wax model that is exactly the same in shape and size as the final O-ring metal shell; 2) Connect multiple O-shaped wax models to a central wax gate bar through a wax gating system to form a wax model assembly resembling a "tree branch"; 3) Immerse the wax mold in silica sol, then evenly sprinkle refractory sand of different particle sizes on it, and dry and harden it at room temperature or under controlled humidity. Repeat this process 4-8 times to form the shell. 4) Place the dried shell into hot water or a high-pressure steam autoclave to melt and flow out the wax inside, thus obtaining a completely sealed ceramic shell with an O-shaped cavity inside. 5) The dewaxed ceramic shell is placed in a high-temperature furnace for firing to further improve its strength and remove residual moisture and impurities; 6) Pour the molten 0Cr18Ni9 stainless steel into the preheated ceramic mold shell, and the molten metal fills the entire O-ring cavity. 7) Allow the molten metal to cool naturally and solidify completely within the mold shell to form an O-shaped metal casting; 8) Break or use water-based sandblasting to remove the outer ceramic shell, then remove the gating system by sandblasting, cutting, etc., and perform surface treatments such as grinding and polishing on the casting to finally obtain a groove-free, completely sealed, and dimensionally accurate O-shaped stainless steel shell.

5. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: In step S4, the cleaning solution is a 3-5% water-based cleaning agent solution. The cleaning process is as follows: the workpiece is completely immersed in the cleaning solution, the ultrasonic cleaning is performed, and then the workpiece is rinsed with deionized water 1-2 times with ultrasonic cleaning for 5 minutes each time to remove residual cleaning agent. The rinsed workpiece is then placed in a hot air circulating oven at 60-80℃ and dried for 10-15 minutes.

6. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: In step S5, non-metallic tweezers or special clamps are used to handle the metal rubber core gently, so that the metal rubber core is centered in the inner cavity of the metal outer shell without tilting or jamming, and its axis is basically coincident with the axis of the outer shell.

7. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: The radial pressure applied in step S6 should cause the metal shell to produce a radial compressive strain of 0.5%-2.0%, ensuring that the shell undergoes elastic or slight plastic deformation. The compression amount and pressure are monitored in real time by displacement and pressure sensors on the mold. After reaching the set pressure or displacement, the pressure is held for 30-60 seconds, and then the pressure is slowly and evenly released.

8. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: Step S7 includes the following: Heating: The furnace temperature is uniformly increased from room temperature to 350℃ at a rate of 5-10℃ / min; Insulation: Insulate at 350±10℃ for 1.5 hours to allow the residual stress inside the material to fully relax; Cooling: After the heat preservation is completed, turn off the heating power and let the furnace cool down slowly to below 100°C. Then the workpiece can be taken out and cooled to room temperature in the air.

9. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: The polishing process employs a centerless cylindrical grinder or a precision grinding machine, using #400 to #800 mesh grinding wheels or abrasives, and undergoes 5-10μm electroless nickel plating (ENP) or electroplating nickel treatment.

10. The manufacturing process of a large annular ratio O-shaped composite metal seal according to claim 1, characterized in that: In step S3, the inner diameter tolerance of the integrated metal shell is controlled within the range of -0.05mm to 0mm, and the outer diameter tolerance of the prefabricated metal rubber inner core is controlled within the range of +0.05mm to +0.10mm, thereby ensuring that there is an interference of 0.05mm to 0.15mm between the two.

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