A sealing glass for extremely low temperature environment, a preparation method and applications thereof

Abstract

This invention relates to the field of sealing materials for electrical equipment, specifically to a sealing glass for extremely low temperature environments, its preparation method, and its application. The sealing glass, by mass percentage, comprises the following components: SiO2: 50-55%, B2O3: 14-17%, Na2O: 10-13%, Al2O3: 5-7%, K2O: 1-3%, BaO: 1-2%, ZrO2: 1-1.5%, La2O3: 0.5-1%, with the balance being unavoidable impurities. The boron oxide is introduced by boric acid, and the remaining components are introduced by their respective oxides. The coefficient of thermal expansion of the sealing glass in the temperature range of 20-300°C is 90 × 10⁻⁶. ‑7 ~100×10 ‑7 The glass exhibits no brittle fracture at an extremely low temperature of -196℃. The preparation method includes six steps: ingredient mixing, high-temperature melting, ball milling and sieving, slurry preparation, spray granulation, and vitrification. The sealing glass prepared by this invention ensures long-term sealing of the interface, solving the problem of low-temperature failure of existing sealing materials in electrical penetrations.

Description

Technical Field

[0001] This invention relates to the field of sealing materials for electrical equipment, specifically to a sealing glass for extremely low temperature environments, its preparation method, and its application. Background Technology

[0002] With the rapid development of energy, aerospace, deep space exploration, superconductivity, and large scientific facilities, the application of cryogenic technology is becoming increasingly widespread. For example, liquefied natural gas (LNG, approximately -162°C) storage and transportation facilities, liquid hydrogen (-253°C) energy systems, superconducting equipment cooled by liquid nitrogen (-196°C), and the cryogenic environment of space probes all place extremely stringent requirements on the sealing and safety of electrical systems operating stably within them.

[0003] Electrical penetrations serve as a "lifeline" connecting different temperature zones and transmitting electrical energy and signals. Their core function is to penetrate and connect internal and external conductors while simultaneously ensuring the airtightness and integrity of the container itself. Once the sealing function of an electrical penetration fails, it will endanger the electrical insulation performance, causing signal transmission interruption, and in more serious cases, it can cause equipment damage and lead to catastrophic safety accidents such as media leakage.

[0004] Currently, organic sealing materials are commonly used in extremely low temperature applications. For example, utility model application CN201621134868.1 discloses an ultra-low temperature low-pressure electrical penetration component, including a spun assembly, a sealing nut, a guide ring, a sealing ring, a first flange, and a second flange; multiple fillers are disposed between the insulating sleeve and the stainless steel pipe; the insulating sleeve and fillers are made of polytetrafluoroethylene (PTFE). Organic materials are at risk of aging in long-term ambient and high-temperature service environments. Furthermore, the bond between organic materials and metals is a van der Waals force, with low bond energy and insufficient tightness, posing a risk of sealing failure during long-term operation. Simultaneously, organic materials become embrittled in low-temperature environments, significantly reducing the sealing performance, electrical performance, and pressure-bearing capacity of the electrical penetration component, failing to meet the requirements for long-term use in extremely low temperature environments.

[0005] Therefore, developing a sealing glass that can provide good sealing performance, stable performance, and good thermal expansion matching in extremely low temperature environments has become a key technical challenge in this field. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a sealing glass for extremely low temperature environments, its preparation method, and its application. The goal is to achieve a sealing glass that exhibits no brittle fracture and stable physicochemical properties at an extremely low temperature of -196℃, ensuring long-term sealing performance of the sealing interface during application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A sealing glass for use in extremely low temperature environments comprises, by weight percentage, the following components: SiO2: 50-55%, B2O3: 14-17%, Na2O: 10-13%, Al2O3: 5-7%, K2O: 1-3%, BaO: 1-2%, ZrO2: 1-1.5%, La2O3: 0.5-1%, boron oxide is introduced by boric acid, and the remaining components are introduced by their respective oxides.

[0008] Preferably, the coefficient of thermal expansion of the sealing glass in the temperature range of 20~300℃ is 90×10⁻⁶. -7 ~100×10 -7 / K, no brittle fracture at extremely low temperatures of -196℃.

[0009] A method for preparing sealing glass for extremely low temperature environments includes the following steps: S1. Ingredient Mixing: Weigh the raw materials according to the sealing glass ratio and mix them thoroughly; S2. High-temperature melting: After the raw materials mixed in S1 are melted at high temperature, they are quenched in water to obtain glass slag; S3. Ball milling and sieving: The glass slag obtained from ball milling S2 is sieved to obtain glass powder; S4. Slurry preparation: The glass powder obtained in S3 is dispersed in a liquid phase composed of solvent, dispersant and binder, and ball-milled to obtain glass powder slurry; S5. Spray granulation: The glass powder slurry obtained in S4 is spray granulated to obtain granulated powder, which is then sieved; S6. Forming and Vitrification: After the granulated powder after sieving S5 is pressed into a glass blank, it is debonded and vitrified to obtain the desired glass beads.

[0010] Preferably, in step S2, the high-temperature melting conditions are: holding at 1600–1650°C for 90–100 minutes.

[0011] Preferably, in step S3, the ball-to-material ratio during ball milling is 1:1 to 1.2, and the ball milling time is 140 to 150 minutes.

[0012] Preferably, in step S4, the mass ratio of glass powder, solvent, dispersant, binder, and grinding balls is 110:70-76:1:11-14:170-180.

[0013] Preferably, the solvent is water, the dispersant is sodium polyacrylate, and the binder is carboxylated polyvinyl alcohol.

[0014] Preferably, in step S4, the ball milling time is 100–120 min.

[0015] Preferably, in step S6, the temperature during adhesive removal is 480~560℃, and the temperature during vitrification is 620~630℃.

[0016] The present invention also provides the application of sealing glass in the preparation of electrical penetrations for extremely low temperatures.

[0017] Beneficial effects: 1) By adding B2O3, the sealing glass of the present invention effectively reduces the thermal expansion coefficient of the sealing glass network, which is one of the key components for achieving the matching of sealing glass and alloy conductor; at the same time, the addition of Al2O3 works synergistically with B2O3 to further finely control the thermal expansion coefficient of the sealing glass and enhance network stability.

[0018] 2) The introduction of ZrO2 significantly improves the mechanical strength and toughness of the sealing glass at extremely low temperatures, inhibits brittle fracture, and ensures the long-term sealing performance of the sealing interface. Even after undergoing severe temperature cycling, it maintains structural integrity and reliable sealing. La2O3, as a high-performance network optimizer, plays a crucial role in utilizing La... 3+ The high field strength effect of ions significantly enhances the cross-linking density and structural stability of the glass network, thereby improving the mechanical strength and chemical durability of the sealing glass in extremely low temperature environments. This dual effect ensures that the product can withstand severe thermal stress shocks and prevent microcrack formation, while also resisting environmental erosion over a long period, guaranteeing its ultra-long lifespan and reliability under harsh operating conditions.

[0019] 3) The sealing glass prepared by this invention has a coefficient of thermal expansion of 90 × 10⁻⁶ in the temperature range of 20–300°C. -7 ~100×10 -7 / K exhibits no brittle fracture and stable physicochemical properties at extremely low temperatures of -196℃, ensuring long-term sealing of the sealing interface. Attached Figure Description

[0020] Figure 1 This invention provides a process for preparing sealing glass for extremely low temperature environments.

[0021] Figure 2 This is the manufacturing process for the electrical penetration component used in the ultra-low temperature application of the present invention.

[0022] Figure 3 This is a schematic diagram of the structure of the electrical penetration component for extremely low temperatures of the present invention.

[0023] Figure 4 This is a cross-sectional view of the structure of the electrical penetration component for extremely low temperatures of the present invention.

[0024] Among them, 1. flange; 2. metal conductor; 3. sealing glass; 4. elastic sealant; 5. insulating sleeve. Detailed Implementation

[0025] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Unless otherwise specified, the reagents used are conventional commercially available reagents or prepared according to existing technology; unless otherwise specified, the operating methods used are conventional operations in the art.

[0026] The sealing glass for ultra-low temperature environments provided by the present invention comprises, by mass percentage, the following components: SiO2: 50-55%, B2O3: 14-17%, Na2O: 10-13%, Al2O3: 5-7%, K2O: 1-3%, BaO: 1-2%, ZrO2: 1-1.5%, La2O3: 0.5-1%, boron oxide is introduced by boric acid, and the remaining components are introduced by their respective oxides.

[0027] Preferably, the sealing glass comprises the following components by weight percentage: SiO2: 50-55%, B2O3: 14-17%, Na2O: 12%, Al2O3: 5-7%, K2O: 1-3%, BaO: 1-2%, ZrO2: 1-1.5%, La2O3: 0.5-1%.

[0028] The sealing glass of this invention effectively reduces the coefficient of thermal expansion of the sealing glass network by adding B2O3, which is one of the key components for achieving matching between the sealing glass and the alloy conductor; at the same time, the addition of Al2O3 works synergistically with B2O3 to further finely control the coefficient of thermal expansion of the sealing glass and enhance the network stability.

[0029] Furthermore, the introduction of ZrO2 significantly improves the mechanical strength and toughness of the sealing glass at extremely low temperatures, suppresses brittle fracture, and ensures the long-term sealing performance of the sealing interface. Even after undergoing severe temperature cycling, it maintains structural integrity and reliable sealing. La2O3, as a high-performance network optimizer, plays a crucial role in utilizing La... 3+ The high field strength effect of ions significantly enhances the cross-linking density and structural stability of the glass network, thereby improving the mechanical strength and chemical durability of the sealing glass in extremely low temperature environments. This dual effect ensures that the product can withstand severe thermal stress shocks and prevent microcrack formation, while also resisting environmental erosion over a long period, guaranteeing its ultra-long lifespan and reliability under harsh operating conditions.

[0030] In this invention, the linear thermal expansion coefficient of the sealing glass in the temperature range of 20~300℃ is 90×10⁻⁶. -7 ~100×10 -7 / K, the linear thermal expansion coefficient, was measured by a thermal expansion coefficient tester; the test sample was a defect-free standard glass rod, the heating rate was 5℃ / min, and the average of three parallel tests was taken; this coefficient can ensure that the sealing glass and the matching metal conductor expand and contract synchronously during temperature cycling, avoiding excessive stress at the interface that could lead to cracking and airtightness failure, and is suitable for long-term use in extremely low temperature environments.

[0031] This invention also provides a method for preparing sealing glass for extremely low temperature environments, such as... Figure 1 As shown, it includes the following steps: S1. Ingredient mixing: Weigh the raw materials according to the sealing glass ratio: SiO2: 50~55%, B2O3: 14~17%, Na2O: 12%, Al2O3: 5~7%, K2O: 1~3%, BaO: 1~2%, ZrO2: 1~1.5%, La2O3: 0.5~1%, and mix the raw materials in a V-type mixer for 35~40 minutes; S2. High-temperature melting: The raw materials after S1 are mixed are melted at 1600-1650℃ for 90-100 minutes, and then water-quenched to obtain glass slag; at the same time, glass rods are cast and the coefficient of thermal expansion is tested. S3. Ball milling and sieving: In a planetary ball mill, add grinding balls and glass slag obtained in S2 at a material-to-ball ratio of 1:1 to 1.2, ball mill for 140 to 150 minutes, and sieve through a 150-mesh sieve to obtain glass powder; S4. Slurry preparation: The glass powder obtained in S3 is dispersed in a liquid phase composed of solvent water, dispersant sodium polyacrylate and binder carboxyvinyl alcohol, and grinding balls are added. The mixture is ball-milled for 100-120 min to obtain a glass powder slurry. The mass ratio of glass powder, solvent, dispersant, binder and grinding balls is 110:70-76:1:11-14:170-180.

[0032] S5. Spray granulation: The glass powder slurry obtained in S4 is placed in a spray granulation tower for spray granulation. The granulated powder obtained is sieved and 80-240 mesh granulated powder is taken. S6. Forming and Vitrification: The granulated powder obtained in S5 is pressed into the required glass blank under a pressure of 0.2~0.4t using compression molding. The glass blank is debonded at 480~560℃ and vitrified at 620~630℃ to obtain the required glass beads, which are the sealing glass used for sealing.

[0033] The sealing glass provided by this invention is used to prepare electrical penetration components for extremely low temperatures.

[0034] like Figure 3-4As shown, the cryogenic electrical penetration device includes a flange 1 with multiple sealing holes and multiple sealing assemblies. One sealing assembly is installed in one sealing hole. The sealing assembly includes a metal conductor 2, a sealing glass 3 located on the outer periphery of the metal conductor, two sealants 4, and two insulating sleeves 5. The space inside the sealing hole includes a sealing section and sealing sections located at both ends of the sealing section. The sealing glass 3 is located in the sealing section, and the sealant 4 is sleeved on the partial insulating sleeves 5, and both are located in the sealing section. The two ends of the metal conductor 2 and the remaining insulating sleeves 5 pass through the sealing hole.

[0035] Specifically, the inner diameter of the insulating sleeve 5 matches the outer diameter of the metal conductor 2, and the length of the metal conductor 2 extending beyond the sealing hole of the flange 1 at both ends is much greater than that of the insulating sleeve 5.

[0036] Furthermore, the mounting end face of flange 1 is provided with threaded holes, the number of which is at least 6, and they are symmetrically distributed around the central axis of flange 1, taking into account both installation convenience and fixing stability, facilitating fixed installation with cryogenic equipment and improving product practicality.

[0037] In this embodiment of the invention, the flange 1 is made of 304 stainless steel, which has excellent corrosion resistance. The metal conductor 2 is made of 4J50 Kovar alloy, whose coefficient of thermal expansion is highly matched with the sealing glass 3 of the invention, which can effectively avoid interface cracking caused by thermal stress during extreme low temperature temperature changes. The ends of the metal conductor 2 are gold-plated to improve corrosion resistance and conductivity, ensuring stable electrical connection and signal transmission. The insulating sleeve 5 is made of polytetrafluoroethylene or polyetheretherketone, which is resistant to high and low temperatures, chemical corrosion, and has excellent insulation performance. It does not become brittle in an extreme low temperature environment of -196℃. The elastic sealant 4 is silicone rubber, which is used to protect the sealing glass from corrosion by water vapor and acid and alkali gases. It is a silicone rubber resistant to extreme low temperatures of -196℃, which does not become brittle or shrink in an extreme low temperature environment, maintaining elastic sealing performance.

[0038] For example, the sealing glass 3 of the present invention is a glass bead. A plurality of sealing holes of the same specifications and depth are opened on the 304 stainless steel flange 1. The 4J50 Kovar alloy metal conductor 2 is coaxially inserted into the sealing hole. The glass bead is embedded between the sealing hole and the sealing section of the 4J50 Kovar alloy metal conductor 2. The glass bead, the 4J50 Kovar alloy metal conductor 2 and the 304 stainless steel flange 1 are integrated into a sealed and insulating structure by high temperature sintering. Polytetrafluoroethylene insulating sleeves 5 are sleeved on both ends of the 4J50 Kovar alloy metal conductor 2 and the polytetrafluoroethylene insulating sleeves 5 abut against the corresponding end faces of the glass beads. Silicone rubber is injected into both end faces of the glass beads. After the silicone rubber cures, the polytetrafluoroethylene insulating sleeves 5 and the glass beads are firmly bonded together to form a complete electrical penetration component.

[0039] The integrated sintered structure of "flange-sealing glass-metal conductor" of the present invention, combined with the composite protective structure of insulating sleeves at both ends and elastic sealant potting, forms a dual-sealed insulation system through sintered sealing of sealing glass and protection by sealant, which can meet the sealing and pressure bearing performance, high insulation and high voltage withstand electrical performance in extremely low temperature environments.

[0040] Methods for fabricating electrical penetration components for extremely low temperatures, such as... Figure 2 As shown, it includes the following steps: S1. Substrate pretreatment: The flange 1 and the metal conductor 2 are sequentially degreased, pickled, and sandblasted to remove surface oil, oxide layer and impurities, so that the surface roughness of the substrate meets the sealing requirements and improves the bonding force with the sealing glass 3. S2. Assembly and Positioning: Use graphite clamps to coaxially assemble and position the flange 1, sealing glass 3, and metal conductor 2, so that the sealing glass 3 is located between the sealing hole of the flange 1 and the sealing section of the metal conductor 2; and ensure that the sealing glass completely fills the gap between the flange sealing hole and the metal conductor to avoid filling gaps; S3. High-temperature sintering: The S2 assembly is placed in a nitrogen atmosphere sintering furnace and sintered at 900~930℃ for 20~25min. At high temperature, the sealing glass 3 melts and fully wets the sealing hole of the flange 1 and the surface of the metal conductor 2. The flange 1 and the metal conductor 2 are sealed and insulated through the sealing glass 3. After cooling, an integrated sealed and insulated structure is formed. The nitrogen atmosphere can effectively prevent the substrate from oxidizing at high temperature. S4. Post-treatment: The integrated structure after S3 sintering is surface treated to remove the oxide layer on the surface of flange 1, making the flange surface clean and bright. The ends of the metal conductor 3 are gold-plated to further improve its corrosion resistance and conductivity. S5. Composite protection: Insulating sleeves 5 are fitted at both ends of the metal conductor 2, so that the insulating sleeves 5 abut against the corresponding end faces of the sealing glass 3, and elastic sealant 4 is injected into the end faces of both ends of the sealing glass 3. After curing, a complete electrical penetration component is formed.

[0041] Example 1 A method for preparing sealing glass for extremely low temperature environments includes the following steps: S1. Ingredient mixing: Weigh the raw materials according to the sealing glass ratio: SiO2: 55%, B2O3: 14%, Na2O: 12%, Al2O3: 7%, K2O: 3%, BaO: 2%, ZrO2: 1.5%, La2O3: 1%, and mix the raw materials in a V-type mixer for 40 minutes; S2. High-temperature melting: The raw materials after S1 are mixed are melted at 1600℃ for 90 minutes and then water-quenched to obtain glass slag; at the same time, glass rods are cast and the coefficient of thermal expansion is tested. S3. Ball milling and sieving: In a planetary ball mill, add the glass slag obtained in S2 and grinding balls at a material-to-ball ratio of 1:1, ball mill for 150 minutes, and sieve through a 150-mesh sieve to obtain glass powder; S4. Slurry preparation: The glass powder obtained in S3 is dispersed in a liquid phase composed of solvent water, dispersant sodium polyacrylate and binder carboxyvinyl alcohol, and grinding balls are added. The mixture is ball-milled for 100 min to obtain glass powder slurry. The mass ratio of glass powder, solvent, dispersant, binder and grinding balls is 110:70:1:11:170. S5. Spray granulation: The glass powder slurry obtained in S4 is placed in a spray granulation tower for spray granulation. The granulated powder obtained is sieved and 80-240 mesh granulated powder is taken. S6. Forming and Vitrification: The granulated powder obtained in S5 is pressed into the required glass blank using compression molding. The glass blank is debonded at 480°C and vitrified at 620°C to obtain the required glass beads.

[0042] The specific steps for preparing an electrical penetration device for ultra-low temperature applications using the sealing glass prepared above are as follows: S1. Substrate pretreatment: The 304 stainless steel flange and the 4J50 Kovar alloy metal conductor are sequentially degreased, pickled and sandblasted. S2. Assembly and positioning: The flange, sealing glass, and metal conductor are coaxially assembled and positioned using graphite clamps, so that the sealing glass is located between the sealing hole of the 304 stainless steel flange and the sealing section of the 4J50 Kovar alloy metal conductor. S3. High-temperature sintering: The S2 assembly is placed in a nitrogen atmosphere sintering furnace and sintered at 900℃ for 20 minutes; after cooling, an integrated sealed insulation structure is formed. S4. Post-treatment: Surface treatment is performed on the integrated structure after S3 sintering to remove the oxide layer on the flange surface and to plate the ends of the metal conductors with gold. S5. Composite protection: Insulating sleeves are fitted at both ends of the metal conductor, so that the insulating sleeves abut against the corresponding end faces of the sealing glass. Elastic sealant is poured into both end faces of the sealing glass, and after curing, a complete electrical penetration is formed.

[0043] Example 2 A method for preparing sealing glass for extremely low temperature environments includes the following steps: S1. Mixing of ingredients: Weigh the raw materials according to the sealing glass ratio: SiO2: 52%, B2O3: 17%, Na2O: 12%, Al2O3: 5%, K2O: 1%, BaO: 1%, ZrO2: 1%, La2O3: 0.5%, and mix the raw materials in a V-type mixer for 35 minutes; S2. High-temperature melting: The raw materials after S1 are mixed are melted at 1650℃ for 100 minutes and then water-quenched to obtain glass slag; at the same time, glass rods are cast and the coefficient of thermal expansion is tested. S3. Ball milling and sieving: In a planetary ball mill, add the glass slag obtained in S2 and grinding balls at a material-to-ball ratio of 1:1.2, ball mill for 150 minutes, and sieve through a 150-mesh sieve to obtain glass powder; S4. Slurry preparation: The glass powder obtained in S3 is dispersed in a liquid phase composed of solvent water, dispersant sodium polyacrylate and binder carboxyvinyl alcohol, and grinding balls are added. The mixture is ball-milled for 120 min to obtain glass powder slurry. The mass ratio of glass powder, solvent, dispersant, binder and grinding balls is 110:76:1:14:180. S5. Spray granulation: The glass powder slurry obtained in S4 is placed in a spray granulation tower for spray granulation. The granulated powder obtained is sieved and 80-240 mesh granulated powder is taken. S6. Forming and Vitrification: The granulated powder obtained in S5 is pressed into the required glass blank using compression molding. The glass blank is debonded at 520°C and vitrified at 630°C to obtain the required glass beads.

[0044] The specific steps for preparing an electrical penetration device for ultra-low temperature applications using the sealing glass prepared above are as follows: S1. Substrate pretreatment: The 304 stainless steel flange and the 4J50 Kovar alloy metal conductor are sequentially degreased, pickled and sandblasted. S2. Assembly and positioning: The flange, sealing glass, and metal conductor are coaxially assembled and positioned using graphite clamps, so that the sealing glass is located between the sealing hole of the 304 stainless steel flange and the sealing section of the 4J50 Kovar alloy metal conductor. S3. High-temperature sintering: The S2 assembly is placed in a nitrogen atmosphere sintering furnace and sintered at 930℃ for 25 minutes; after cooling, an integrated sealed and insulating structure is formed. S4. Post-treatment: Surface treatment is performed on the integrated structure after S3 sintering to remove the oxide layer on the flange surface and to plate the ends of the metal conductors with gold. S5. Composite protection: Insulating sleeves are fitted at both ends of the metal conductor, so that the insulating sleeves abut against the corresponding end faces of the sealing glass. Elastic sealant is poured into both end faces of the sealing glass, and after curing, a complete electrical penetration is formed.

[0045] Example 3 A method for preparing sealing glass for extremely low temperature environments includes the following steps: S1. Ingredient Mixing: Weigh the raw materials according to the sealing glass ratio: SiO2: 50%, B2O3: 16%, Na2O: 12%, Al2O3: 6%, K2O: 2%, BaO: 1.5%, ZrO2: 1.3%, La2O3: 0.8%, with the remainder being unavoidable impurities; place the raw materials in a V-type mixer and mix for 35 minutes; S2. High-temperature melting: The raw materials after S1 are mixed are melted at 1620℃ for 90 minutes and then water-quenched to obtain glass slag; at the same time, glass rods are cast and the coefficient of thermal expansion is tested. S3. Ball milling and sieving: In a planetary ball mill, add the glass slag obtained in S2 and grinding balls at a material-to-ball ratio of 1:1.1, ball mill for 140 minutes, and then pass through a 150-mesh sieve to obtain glass powder; S4. Slurry preparation: The glass powder obtained in S3 is dispersed in a liquid phase composed of solvent water, dispersant sodium polyacrylate and binder carboxylated polyvinyl alcohol, and grinding balls are added. The mixture is ball-milled for 110 min to obtain a glass powder slurry. The mass ratio of glass powder, solvent, dispersant, binder and grinding balls is 110:73:1:13:175. S5. Spray granulation: The glass powder slurry obtained in S4 is placed in a spray granulation tower for spray granulation. The granulated powder obtained is sieved and 80-240 mesh granulated powder is taken. S6. Forming and Vitrification: The granulated powder obtained in S5 is pressed into the required glass blank using compression molding. The glass blank is debonded at 560°C and vitrified at 625°C to obtain the required glass beads.

[0046] The specific steps for preparing an electrical penetration device for ultra-low temperature applications using the sealing glass prepared above are as follows: S1. Substrate pretreatment: The 304 stainless steel flange and the 4J50 Kovar alloy metal conductor are sequentially degreased, pickled and sandblasted. S2. Assembly and positioning: The flange, sealing glass, and metal conductor are coaxially assembled and positioned using graphite clamps, so that the sealing glass is located between the sealing hole of the 304 stainless steel flange and the sealing section of the 4J50 Kovar alloy metal conductor. S3. High-temperature sintering: The S2 assembly is placed in a nitrogen atmosphere sintering furnace and sintered at 910℃ for 20 minutes; after cooling, an integrated sealed and insulating structure is formed. S4. Post-treatment: Surface treatment is performed on the integrated structure after S3 sintering to remove the oxide layer on the flange surface and to plate the ends of the metal conductors with gold. S5. Composite protection: Insulating sleeves are fitted at both ends of the metal conductor, so that the insulating sleeves abut against the corresponding end faces of the sealing glass. Elastic sealant is poured into both end faces of the sealing glass, and after curing, a complete electrical penetration is formed.

[0047] The thermal expansion coefficient of the cryogenic sealing glass prepared in Examples 1-3, as well as the gas leakage rate, insulation resistance, withstand voltage, and withstand pressure value after immersion in cryogenic liquid nitrogen for 30 minutes, were measured. The results are shown in Table 1. The thermal expansion coefficient of the glass was measured by a thermal expansion coefficient tester, the gas leakage rate was measured by a helium mass spectrometer leak detector, the insulation resistance was measured by an insulation resistance tester, the withstand voltage value was measured by a withstand pressure tester, and the withstand pressure value was measured by a pressure testing platform.

[0048] Table 1

[0049] The test results show that the coefficient of thermal expansion of the sealing glass prepared in this embodiment of the invention is 94.1 × 10⁻⁶. -7 ~98.5×10 -7 / K, through the preparation of sealing glass, a sealed and insulated connection is made between the flange and the conductor, enabling the electrical penetration to meet high sealing performance and high pressure resistance in extremely low temperature environments, significantly improving the service life of the electrical penetration; the overall structure forms a dual sealing and insulation system of sintered sealing + adhesive sealing protection, which can ensure that the electrical penetration has a highly reliable sealing function in an extremely low temperature environment of -196℃, and can withstand a pressure of not less than 7.5MPa, maintaining normal electrical connection and signal transmission functions.

Claims

1. A sealing glass for use in extremely low temperature environments, characterized in that, The sealing glass comprises, by weight percentage, the following components: SiO2: 50-55%, B2O3: 14-17%, Na2O: 10-13%, Al2O3: 5-7%, K2O: 1-3%, BaO: 1-2%, ZrO2: 1-1.5%, La2O3: 0.5-1%, with the balance being unavoidable impurities; the boron oxide is introduced by boric acid, and the remaining components are introduced by their respective oxides.

2. The sealing glass for ultra-low temperature environments according to claim 1, characterized in that, The sealing glass has a coefficient of thermal expansion of 90*10 -7 ~100*10 -7 / K in the range of 20-300 DEG C, and no brittle fracture at -196 DEG C.

3. The method for preparing sealing glass for ultra-low temperature environments according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Ingredient Mixing: Weigh the raw materials according to the sealing glass ratio and mix them thoroughly; S2. High-temperature melting: After the raw materials mixed in S1 are melted at high temperature, they are quenched in water to obtain glass slag; S3. Ball milling and sieving: The glass slag obtained from ball milling S2 is sieved to obtain glass powder; S4. Slurry preparation: The glass powder obtained in S3 is dispersed in a liquid phase composed of solvent, dispersant and binder, and ball-milled to obtain glass powder slurry; S5. Spray granulation: The glass powder slurry obtained in S4 is spray granulated to obtain granulated powder, which is then sieved; S6. Forming and Vitrification: After the granulated powder after sieving S5 is pressed into a glass blank, it is debonded and vitrified to obtain the desired glass beads.

4. The production method according to claim 3, characterized by, In S2, the high-temperature melting conditions are: holding at 1600-1650℃ for 90-100 minutes.

5. The preparation method according to claim 3, characterized in that, In S3, the ball-to-material ratio during ball milling is 1:1 to 1.2, and the ball milling time is 140 to 150 minutes.

6. The preparation method according to claim 3, characterized in that, In step S4, the mass ratio of glass powder, solvent, dispersant, binder, and grinding balls is 110:70~76:1:11~14:170~180.

7. The preparation method according to claim 6, characterized in that, The solvent is water, the dispersant is sodium polyacrylate, and the binder is carboxylated polyvinyl alcohol.

8. The preparation method according to claim 3, characterized in that, In step S4, the ball milling time is 100–120 min.

9. The preparation method according to claim 3, characterized in that, In S6, the temperature during adhesive removal is 480~560℃, and the temperature during vitrification is 620~630℃.

10. The use of the sealing glass according to any one of claims 1-2 in the preparation of electrical penetrations for cryogenic applications.

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