CN103058700A - Insulating sealed metal air pipe as well as sealed connection method of metal pipes and ceramic pipe - Google Patents

Abstract

The present invention provides an insulated and sealed metal air pipe, comprising: a first metal pipe, a second metal pipe and a ceramic pipe; the inner wall of the ceramic pipe and the outer wall of the first metal pipe form a first space, and the first space The two ends of the ceramic tube are provided with an oxide sealing layer, and the inside of the first space is filled with a metal sealing layer; the inner wall of the ceramic tube and the outer wall of the second metal tube form a second space, and the two ends of the second space An oxide sealing layer is provided, and the second space is filled with a metal sealing layer. The present invention also relates to a method for insulating and sealing metal pipes and ceramic pipes: forming a first metal sealing layer and a second metal sealing layer on the inner wall of the ceramic pipe; The ends are respectively coated with oxide sealing slurry; the two metal pipes are respectively welded to the metal sealing layer. The insulated and sealed metal gas pipe is suitable for various ambient atmospheres under high temperature conditions.

Description

Insulated and sealed metal air pipe and sealing connection method between metal pipe and ceramic pipe

technical field

The invention relates to the field of metal connection, in particular to an insulated and sealed metal air pipe and a method for sealing connection between the metal pipe and the ceramic pipe.

Background technique

Metal and ceramic sealing is a technology that uses ceramic media to connect metals. This technology keeps metals working at high temperatures insulated. It is mainly used in vacuum electronic devices, semiconductors, integrated circuits, electric light sources, laser atomic energy, chemical industry, Metallurgy, power equipment and other industries.

There are three main methods of sealing between metal and ceramics:

One is the oxide solder method, also known as the glass solder method, which uses the melting of solder to form glass that penetrates into the ceramic and infiltrates the metal surface, thereby completing the sealing of the ceramic and the metal.

One is the sintered metal powder method, that is, firstly, a metal layer is sintered on the ceramic at high temperature in a reducing atmosphere, so that the surface of the ceramic has metallic properties, and then it is welded with the metal to complete the bonding between the ceramic and the metal. seal.

One is the active metal method, which uses transition metal elements such as titanium, zirconium, and hafnium to form alloys with metals such as copper, nickel, and silver at temperatures lower than their respective melting points. These alloys react with the ceramic surface in the liquid phase and Infiltration of various metals to complete the sealing of ceramics and metals.

Since the sintered metal powder method or active metal method involves applicable metals, such as copper, nickel, titanium and other metals, these metals will undergo oxidation reactions at high temperatures, which will easily cause aging of the seal, so the sintered metal powder method or active metal method in It can only work in neutral or reducing atmosphere at high temperature, but not in oxidizing atmosphere.

Contents of the invention

The technical problem to be solved by the present invention is to provide an insulated and sealed metal air pipe and a method for sealing connection between the metal pipe and the ceramic pipe, which is suitable for various ambient atmospheres under high temperature conditions.

The present invention provides an insulated and sealed metal air pipe, comprising: a first metal pipe, a second metal pipe and a ceramic pipe whose inner wall is respectively connected to the outer wall of the first metal pipe and the outer wall of the second metal pipe;

The inner wall of the ceramic tube and the outer wall of the first metal tube form a first space, both ends of the first space are provided with an oxide sealing layer, and the inside of the first space is filled with a metal sealing layer;

The inner wall of the ceramic tube and the outer wall of the second metal tube form a second space, both ends of the second space are provided with an oxide sealing layer, and the inside of the second space is filled with a metal sealing layer.

Preferably, the metal sealing layer includes one or more of Mo, Mn, W, Cu, Ti, Ag, Au, Ni, Zr, Nb, Be, V, Zn, Sn and Pb.

Preferably, the oxide sealing layer includes one or more of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , ZnO, RO and A ₂ O, and the RO is MgO, CaO, SrO or BaO, The A ₂ O is K ₂ O, Na ₂ O or Li ₂ O.

Preferably, the expansion coefficients of the first metal tube and the second metal tube are greater than the thermal expansion coefficient of the ceramic tube.

Preferably, the cross-sectional area of each place in the ceramic tube is consistent.

Preferably, the cross-sectional area of the two ends of the ceramic tube is larger than the cross-sectional area of the middle part.

The present invention also provides a method for insulating and sealing metal pipes and ceramic pipes, comprising the following steps:

(A) Coating metal sealing slurry on both ends of the inner wall of the ceramic tube, and sintering to form the first metal sealing layer and the second metal sealing layer;

(B) Coating oxide sealing slurry on both ends of the first metal sealing layer to isolate both ends of the first metal sealing layer from air;

Coating oxide sealing slurry on both ends of the second metal sealing layer, so that the two ends of the second metal sealing layer are isolated from the air;

(C) welding the first metal tube to the first metal sealing layer to isolate the first metal sealing layer from the air; welding the second metal tube to the second metal sealing layer to isolate the second metal sealing layer from the air.

Preferably, in the step (A), the sintering temperature is 1400-1600° C., and the sintering time is 50-70 minutes.

Preferably, nickel plating on the first metal layer and the second metal layer is also included after the step (A).

Preferably, in the step (C), the welding method is brazing, and the brazing temperature is 1000-1200°C.

Compared with the prior art, the insulating and sealed metal air pipe of the present invention comprises: a first metal pipe, a second metal pipe and a ceramic pipe whose inner wall is connected to the outer wall of the first metal pipe and the outer wall of the second metal pipe respectively; The inner wall of the ceramic tube and the outer wall of the first metal tube form a first space, the two ends of the first space are provided with an oxide sealing layer, and the inside of the first space is filled with a metal sealing layer; the ceramic tube The inner wall of the second metal tube and the outer wall of the second metal pipe form a second space, and the two ends of the second space are provided with an oxide sealing layer, and the inside of the first space is filled with a metal sealing layer.

Since the connection between the metal tube and the ceramic tube has both an oxidized sealing layer and a metal sealing layer, the connection is tight, it is not easy to disengage, and the sealing is excellent. And because the metal sealing layer is filled between the oxide sealing materials, the metal sealing layer is not in direct contact with the air, it is not easy to oxidize at high temperature, and the aging speed is slow, so it is suitable for various ambient atmospheres under high temperature conditions, and no longer For use in neutral or reducing atmospheres only.

Description of drawings

Fig. 1 is the cross-sectional view of the insulated and sealed metal air pipe of the cylindrical shape for the inner wall of the ceramic pipe;

Fig. 2 is a cross-sectional view of an insulated and sealed metal air pipe whose inner wall of the ceramic pipe is "I" type.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than limiting the claims of the present invention.

The embodiment of the present invention discloses an insulated and sealed metal air pipe, comprising: a first metal pipe, a second metal pipe, and a ceramic pipe whose inner walls are respectively connected to the outer wall of the first metal pipe and the outer wall of the second metal pipe;

The inner wall of the ceramic tube and the outer wall of the first metal tube form a first space, both ends of the first space are provided with an oxide sealing layer, and the inside of the first space is filled with a metal sealing layer;

The inner wall of the ceramic tube and the outer wall of the second metal tube form a second space, both ends of the second space are provided with an oxide sealing layer, and the inside of the second space is filled with a metal sealing layer.

In the present invention, the insulated and sealed metal gas pipe includes: a first metal pipe, a second metal pipe and a ceramic pipe whose inner wall is connected to the outer wall of the first metal pipe and the outer wall of the second metal pipe respectively.

The first metal tube is inserted into one end of the ceramic tube, and its outer wall is connected to the inner wall of the ceramic tube; the second metal tube is inserted into the other end of the ceramic tube, and the outer wall of the second metal tube is connected to the inner wall of the ceramic tube. The ends of the first metal tube and the second metal tube are not in contact, and the inner tubes of the first metal tube, the ceramic tube and the second metal tube communicate in sequence.

The present invention has no special limitation on the materials of the first metal pipe and the second metal pipe, and the expansion coefficient thereof is preferably greater than that of the ceramic pipe. During high-temperature use, the metal sealing layer is subjected to radial compressive stress between the metal tube and the ceramic tube, which is conducive to sealing.

The ceramic tube connects the first metal tube and the second metal tube, and since the ceramic is non-conductive at 600-1000°C, it can function as an insulating connection. The present invention has no special limitation on the shape of the inner wall of the ceramic tube, preferably "I" shape or cylindrical shape. The "I" type means that the cross-sectional area at both ends of the ceramic tube is larger than the cross-sectional area in the middle; the cylindrical type means that the cross-sectional area of each place in the ceramic tube is consistent.

The inner wall of the ceramic tube and the outer wall of the first metal tube form a first space, and the first space surrounds the outer wall of the first metal tube. In order to ensure the tightness, there are two ends of the first space An oxide sealing layer, the inside of the first space is filled with a metal sealing layer. The inner wall of the ceramic tube and the outer wall of the second metal tube form a second space. In order to ensure airtightness, both ends of the second space are also provided with an oxide sealing layer, and the inside of the second space is filled with metal Sealing layer.

In the present invention, the metal pipe is connected with the ceramic pipe through the metal sealing layer and the oxide sealing layer. In both the first space and the second space, the oxide sealing layer wraps the metal sealing layer in the middle to isolate the metal sealing layer from air and prevent the metal sealing layer from being oxidized in an oxidizing environment.

Refer to Fig. 1 and Fig. 2 for the specific structure of the insulated and sealed metal gas pipe of the present invention. Figure 1 is a cross-sectional view of a cylindrical insulated and sealed metal gas pipe with a ceramic tube inner wall, including a first metal tube 1, a ceramic tube 2, a metal sealing layer 3, an oxide sealing layer 4a, an oxide sealing layer 4b and a second metal tube 5. The inner wall of the ceramic tube 2 is cylindrical, and the inner wall of the ceramic tube 2 and the outer wall of the first metal tube 1 form a first space, and one end of the first space is the top of the ceramic tube connected to the first metal tube. An oxide sealing layer 4a is provided at the part, and an oxide sealing layer 4b is provided at the other end of the first space, that is, the part where the middle part of the ceramic tube connects with the bottom of the outer wall of the first metal tube 1 . The metal dense layer 3 is filled between the oxide sealing layer 4 a and the oxide sealing layer 4 b. The connection mode between the second metal tube 5 and the ceramic is the same as the connection mode between the first metal tube 4 and the ceramic tube 2 , and the second metal tube 5 is not in contact with the first metal tube 1 . In a high-temperature environment, the metal sealing layer 3 is subjected to radial compressive stress between the metal tube 1 and the ceramic tube 2, which is beneficial for sealing.

Figure 2 is a sectional view of an insulating and sealed metal gas pipe whose inner wall is an "I" type of ceramic tube, including a first metal tube 1, a ceramic tube 2, a metal sealing layer 3, an oxide sealing layer 4a, an oxide sealing layer 4b and a second Metal tube 5; the inner wall of ceramic tube 2 is "I" type, the cross-sectional area of both ends is greater than the cross-sectional area of the middle part, and the cross-sectional area of the inner wall of the first metal tube 1 is equal to the cross-sectional area of the middle part of the inner wall of ceramic tube 2. The outer wall of the first metal tube 1 is connected to the inner wall of the ceramic tube 2 to form a first space. One end of the first space, that is, the part where the top of the ceramic tube is connected to the first metal tube is provided with an oxide sealing layer 4a. The other end of the space, that is, the part where the middle part of the ceramic tube connects with the bottom of the outer wall of the first metal tube 1 is provided with an oxide sealing layer 4b. The metal sealing layer 3 is filled between the oxide sealing layer 4a and the oxide sealing layer 4b. The connection mode between the second metal tube 5 and the ceramic is the same as the connection mode between the first metal tube 4 and the ceramic tube 2 , and the second metal tube 5 is not in contact with the first metal tube 1 . In a high-temperature environment, the metal sealing layer 3 is subjected to radial compressive stress between the metal tube 1 and the ceramic tube 2, which is beneficial for sealing.

The difference between FIG. 1 and FIG. 2 is that the shape of the oxide sealing layer 4b is different. The present invention does not limit the shape of the oxide sealing layer 4b, as long as the metal sealing layer 3 can be isolated from the air.

The metal sealing layer filled in the first space and the metal sealing layer filled in the second space may use the same metal sealing material, or different metal sealing materials, preferably both are the same. The metal sealing layer preferably includes one or more of Mo, Mn, W, Cu, Ti, Ag, Au, Ni, Zr, Nb, Be, V, Zn, Sn and Pb, more preferably Mo and Mn . The metal sealing layer can tightly connect the metal tube and the ceramic tube, and has a high bonding force. Moreover, the metal sealing layer is located between the oxide sealing layers and is not in contact with the air, so as to ensure that it will not be oxidized when it is in an oxidizing atmosphere at a high temperature.

The oxide sealing layer at both ends of the first space and the oxide sealing layer at both ends of the second space may use the same oxide sealing material, or different oxide sealing materials, preferably both are the same. The oxide sealing layer preferably includes one or more of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , ZnO, RO and A ₂ O, and the RO is MgO, CaO, SrO or BaO, A ₂ O is K ₂ O, Na ₂ O or Li ₂ O, and more preferably includes SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ .

The present invention also provides a method for insulating and sealing metal pipes and ceramic pipes, comprising the following steps:

(A) Coating metal sealing slurry on both ends of the inner wall of the ceramic tube, and sintering to form the first metal sealing layer and the second metal sealing layer;

(B) Coating oxide sealing slurry on both ends of the first metal sealing layer to isolate both ends of the first metal sealing layer from air;

Coating oxide sealing slurry on both ends of the second metal sealing layer to isolate the two ends of the second metal sealing layer from air;

(C) welding the first metal tube to the first metal layer to isolate the first metal layer from the air; welding the second metal tube to the second metal layer to isolate the second metal layer from the air.

In the present invention, firstly, the metal sealing slurry is coated on one end of the inner wall of the ceramic tube, and then sintered to form the first metal sealing layer. The present invention has no special limitation on the area coated with the metal sealing slurry, which can be selected by those skilled in the art according to the connection between the metal tube and the ceramic tube. The method for preparing the metal sealing slurry is preferably uniformly mixing metal powder with an organic solvent, and grinding to obtain a metal slurry. The metal powder is preferably one or more of Mo, Mn, W, Cu, Ti, Ag, Au, Ni, Zr, Nb, Be, V, Zn, Sn and Pb, more preferably Mo and Mn. The metal powder can always be added with other types of powders to assist sintering, preferably alumina powders. The organic solvent is preferably cellulose and terpineol. The present invention has no special limitation on the mixing ratio of the metal powder and the organic solvent, and those skilled in the art can mix according to well-known ratios. The present invention has no special limitation on the grinding method, and a three-roll mill is preferably used for grinding.

The first metal layer surrounds the inside of the ceramic tube. The sintering is preferably carried out in a hydrogen atmosphere; the sintering temperature is preferably 1400-1600°C, more preferably 1450-1550°C; the sintering time is preferably 50-70 minutes, more preferably 55-65 minutes.

After the first metal sealing layer is formed, it is preferable to plate nickel on the first metal sealing layer. The thickness of the nickel is 4-10 μm. The nickel-plated layer can improve the flow of solder in the metal layer, slow down the residual stress in the joint, and improve connection strength.

In the present invention, after the first metal sealing layer is formed in the ceramic tube, oxide sealing slurry is coated on both ends of the first metal layer to isolate the two ends of the first metal sealing layer from the air. The oxide sealing slurry is a mixture of oxide powder and solvent, and its preparation method is preferably:

The oxide powder is ball milled and mixed evenly, melted and cooled to obtain glass;

The glass is pulverized, mixed with an organic solvent, and ground to obtain an oxide sealing slurry.

The oxide powder is preferably one or more of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , ZnO, RO and A ₂ O, and the RO is MgO, CaO, SrO or BaO, A ₂ O is K ₂ O, Na ₂ O or Li ₂ O, more preferably SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ . The melting temperature is preferably 1300-1500°C, more preferably 1350-1450°C.

The organic solvent is preferably cellulose and terpineol. The present invention has no special limitation on the mixing ratio of the metal powder and the organic solvent, and those skilled in the art can mix according to well-known ratios. The present invention has no special limitation on the grinding method, and a three-roll mill is preferably used for grinding.

In the present invention, after the two ends of the first metal layer are isolated from the air, the first metal tube is welded to the first metal sealing layer, so that the first metal sealing layer is isolated from the air. After welding, the outer wall of the first metal tube is connected to the inner wall of the ceramic tube through the first metal sealing layer, and both ends of the first metal sealing layer are oxide sealing layers. Due to the high welding temperature, the oxide sealing slurry is tightly sealed with the inner wall of the ceramic tube after drying. The welding is preferably brazing, the brazing preferably uses a copper solder ring, the brazing is preferably performed in a hydrogen atmosphere, and the brazing temperature is preferably 1000-1200°C, more preferably 1050-1150°C.

After the welding is completed, the first metal tube is insulated and hermetically connected to the ceramic tube.

The sealing connection method of the second metal tube and the ceramic tube is the same as the above-mentioned sealing connection method of the first metal tube and the ceramic tube. The other end of the inner wall of the ceramic tube is coated with a metal sealing slurry and sintered to form a second metal sealing layer. The present invention has no special limitation on the area coated with the metal sealing slurry, which can be selected by those skilled in the art according to the connection between the metal tube and the ceramic tube. The metal sealing slurry selected for the second metal sealing layer may be the same as the metal sealing slurry selected for the first sealing layer, or may be different. The preparation method of the second metal sealing layer is the same as that of the first sealing layer.

The second metal layer surrounds the inside of the ceramic tube. The sintering is preferably carried out in a hydrogen atmosphere; the sintering temperature is preferably 1400-1600°C, more preferably 1450-1550°C; the sintering time is preferably 50-70 minutes, more preferably 55-65 minutes.

After forming the second metal sealing layer, it is preferable to plate nickel on the first metal sealing layer. The thickness of the nickel is 4-10 μm. The nickel plating layer can improve the flow of solder in the metal layer, slow down the residual stress in the joint, and improve connection strength.

In the present invention, after the second metal sealing layer is formed in the ceramic tube, oxide sealing slurry is coated on both ends of the second metal layer to isolate the two ends of the second metal sealing layer from the air. The oxide sealing slurry is a mixture of oxide powder and solvent, and its preparation method is preferably:

The oxide powder is ball milled and mixed evenly, melted and cooled to obtain glass;

The glass is pulverized, mixed with an organic solvent, and ground to obtain an oxide sealing slurry.

The oxide powder is preferably one or more of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , ZnO, RO and A ₂ O, and the RO is MgO, CaO, SrO or BaO, A ₂ O is K ₂ O, Na ₂ O or Li ₂ O, more preferably SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ . The melting temperature is preferably 1300-1500°C, more preferably 1350-1450°C.

The organic solvent is preferably cellulose and terpineol. The present invention has no special limitation on the mixing ratio of the metal powder and the organic solvent, and those skilled in the art can mix according to well-known ratios. The present invention has no special limitation on the grinding method, and a three-roll mill is preferably used for grinding.

In the present invention, after the two ends of the second metal layer are isolated from the air, the second metal tube is welded to the second metal sealing layer, so that the second metal sealing layer is isolated from the air. After welding, the outer wall of the first metal tube is connected to the inner wall of the ceramic tube through the first metal sealing layer, and both ends of the first metal sealing layer are oxide sealing layers. Due to the high welding temperature, the oxide sealing slurry is tightly sealed with the inner wall of the ceramic tube after drying. The welding is preferably brazing, the brazing preferably uses a copper solder ring, the brazing is preferably performed in a hydrogen atmosphere, and the brazing temperature is preferably 1000-1200°C, more preferably 1050-1150°C.

In actual operation, for the sake of simple operation, the metal sealing slurry can be coated on both ends of the inner wall of the ceramic tube at the same time, and after sintering, the first metal sealing layer and the second metal sealing layer are respectively obtained. Then, the two ends of the first metal layer and the two ends of the second metal layer on the inner wall of the ceramic tube are respectively coated with oxide sealing slurry. Finally, the first metal tube and the second metal tube are inserted into the two ends of the ceramic tube respectively for welding.

The insulation and airtightness test of the insulated and sealed metal air pipe obtained by the insulating and sealing method shows that the insulation resistance at both ends of the metal pipe is 1.8×10 ¹² to 2.2×10 ¹² ohms, and the airtightness is good.

In order to further understand the present invention, the insulated and sealed metal air pipe provided by the present invention and the sealing connection method between the metal pipe and the ceramic pipe are described below in conjunction with the examples, and the scope of protection of the present invention is not limited by the following examples.

Example 1

20 grams of SiO ₂ , 55 grams of B ₂ O ₃ , and 25 grams of Al ₂ O ₃ were ball milled and mixed uniformly, melted at 1400°C, and poured into cold water to form a glass. The glass is crushed and passed through a 40-mesh sieve to obtain glass sealing filler powder. 80 grams of glass sealing filler powder, 1 gram of ethyl cellulose, and 19 grams of terpineol were uniformly mixed and ground by a three-roll mill to prepare an oxide sealing slurry.

Mix 52 grams of Mo powder, 14 grams of Mn powder, 14 grams of Al ₂ O ₃ powder, 1 gram of ethyl cellulose, and 19 grams of terpineol and grind them with a three-roll mill to make a metal sealing slurry.

The inner wall of the ceramic tube is cleaned, and the two ends of the inner wall of the ceramic tube are uniformly coated with the metal sealing slurry, and then sintered at 1500° C. for 60 minutes in a hydrogen atmosphere to obtain the first metal layer and the second metal layer.

After polishing the ceramic tube with the sintered first metal layer and the second layer, a nickel layer of about 5 μm is plated on the metallized inner wall.

Copper solder rings are placed on the outer walls of the first metal pipe and the second metal pipe, and the two ends of the first metal layer and the two ends of the second metal layer are respectively coated with oxide sealing paste, so that the first metal layer Both ends of the first metal layer and the second metal layer are isolated from air. Then put the first metal tube and the second metal tube into the ceramic tube respectively and fix them with a clamp. The first metal tube and the first metal layer are brazed at 1100°C in a hydrogen atmosphere, so that the first metal layer is isolated from the air; the second The two metal tubes and the second metal layer are brazed in a hydrogen atmosphere at 1100°C, so that the second metal layer is isolated from the air.

At a temperature of 830°C, air, nitrogen, and hydrogen are introduced respectively, and the inlet and outlet are cooled by water circulation. Use an insulation tester to measure the insulation resistance at both ends of the metal pipe. The measurement time is 30 seconds. Use a gas flowmeter to measure the airflow of the inlet and outlet. flow. See Table 1 for the experimental results. Table 1 shows the sealing and insulating performance of insulating and sealing metal gas pipes in various atmospheres.

Table 1 Sealing and insulating properties of insulating and sealing metal gas pipes in various atmospheres

30 seconds insulation resistance (ohms) Inlet flow (sccm) Outlet flow (sccm) Air 1.8×10 ¹² 1003 997 Nitrogen 2.1×10 ¹² 998 1001 hydrogen 1.9×10 ¹² 997 995

It can be known from Table 1 that the insulating and sealed metal air pipe obtained by the present invention has good insulation and good sealing.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. An insulated and sealed metal gas pipe, comprising: a first metal pipe, a second metal pipe and a ceramic pipe whose inner wall is connected to the outer wall of the first metal pipe and the outer wall of the second metal pipe; The inner wall of the ceramic tube and the outer wall of the first metal tube form a first space, both ends of the first space are provided with an oxide sealing layer, and the inside of the first space is filled with a metal sealing layer; The inner wall of the ceramic tube and the outer wall of the second metal tube form a second space, both ends of the second space are provided with an oxide sealing layer, and the inside of the second space is filled with a metal sealing layer. 2. The metal air pipe according to claim 1, wherein the metal sealing layer comprises Mo, Mn, W, Cu, Ti, Ag, Au, Ni, Zr, Nb, Be, V, Zn, Sn and One or more of Pb. 3. The metal gas pipe according to claim 1, wherein the oxide sealing layer comprises one or more of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , ZnO, RO and A ₂ O , the RO is MgO, CaO, SrO or BaO, and the A ₂ O is K ₂ O, Na ₂ O or Li ₂ O. 4. The metal air pipe according to claim 1, characterized in that the expansion coefficients of the first metal pipe and the second metal pipe are greater than the thermal expansion coefficient of the ceramic pipe. 5. The metal gas pipe according to claim 1, characterized in that, the cross-sectional area of each place in the ceramic pipe is the same. 6 . The metal gas pipe according to claim 1 , wherein the cross-sectional area of the two ends of the ceramic pipe is larger than that of the middle part. 7 . 7. A method for insulating and sealing metal pipes and ceramic pipes, comprising the following steps: (A) Coating metal sealing slurry on both ends of the inner wall of the ceramic tube, and sintering to form the first metal sealing layer and the second metal sealing layer; (B) Coating oxide sealing slurry on both ends of the first metal sealing layer to isolate both ends of the first metal sealing layer from air; Coating oxide sealing slurry on both ends of the second metal sealing layer, so that the two ends of the second metal sealing layer are isolated from the air; (C) welding the first metal tube to the first metal sealing layer to isolate the first metal sealing layer from the air; welding the second metal tube to the second metal sealing layer to isolate the second metal sealing layer from the air. 8 . The insulation sealing method according to claim 7 , wherein in the step (A), the sintering temperature is 1400-1600° C., and the sintering time is 50-70 minutes. 9 . The insulating and sealing method according to claim 7 , further comprising plating nickel on the first metal layer and the second metal layer after step (A). 10 . 10 . The insulating and sealing method according to claim 7 , wherein in the step (C), the welding method is brazing, and the brazing temperature is 1000-1200° C. 11 .

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