Metal composite pipe for temperature sensor, preparation method and temperature sensor

Abstract

The invention provides a metal composite pipe for a temperature sensor, a preparation method of the metal composite pipe and the temperature sensor. The preparation method comprises the following steps: S1, providing a stainless steel inner sleeve and a nickel-based alloy outer sleeve; s2, depositing a precursor powder middle layer on the bonding surface of the inner sleeve or the outer sleeve subjected to surface pretreatment, wherein precursor powder comprises at least one of aluminum oxide, titanium dioxide or titanium black; s3, the inner sleeve is arranged in the outer sleeve, hole shrinkage deformation treatment is carried out, and a prefabricated composite pipe is prepared; and S4, the prefabricated composite pipe is subjected to diffusion treatment, a metallurgical bonding protection layer is formed between the precursor powder and the inner sleeve and between the precursor powder and the outer sleeve, and the metal composite pipe is prepared. According to the invention, a metallurgical bonding protective layer is formed between the inner sleeve and the outer sleeve of the metal composite tube by using the specific precursor powder, so that the high-temperature-resistant physical and chemical stability of the metal composite tube can be effectively improved, and the manufacturing cost is reduced while the service life of the thermocouple temperature sensor is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of high temperature resistant metal composite pipes, and in particular to a metal composite pipe for a temperature sensor, a preparation method thereof, and a temperature sensor. Background Art

[0002] Thermocouple temperature sensors have the advantages of high measurement accuracy, fast response speed, wide temperature measurement range, long-distance transmission of output signals, and high reliability. They are widely used in temperature detection and control in the fields of metallurgy, chemical industry, electric power, energy, military industry, aerospace, etc. The structure of the thermocouple mainly includes a thermocouple, an insulating structure, a protective tube, and a wiring structure. The thermocouple is composed of two conductors or semiconductors of different materials to form a loop. When there is a temperature gradient at both ends of the loop, a thermoelectric potential will be generated in the loop, and the electrical signal will be transmitted to the external measuring instrument through the wiring structure, and the thermoelectric potential will be converted into the corresponding measured temperature for display. The insulating structure, such as an insulating sleeve or an insulating powder filler, is arranged between the thermocouple and the protective tube to prevent short circuits between the thermocouples and between the thermocouple and the protective tube. The protective tube plays the role of installing, supporting and fixing the thermocouple, and protects the thermocouple from being eroded by the fluid in the test environment and isolating the stress and high pressure caused by the flow of the fluid. Since the protective tube is in direct contact with the fluid in the test environment, the protective tube plays a key and decisive role in extending the service life of the thermocouple temperature sensor.

[0003] Traditional protection tubes can be divided into metal protection tubes and non-metal protection tubes according to the different materials. Among them, metal protection tubes have been widely used in thermocouple industrial manufacturing due to their high mechanical strength, good thermal conductivity, machinability and easy installation. The materials of metal protection tubes include austenitic stainless steel, ferritic heat-resistant steel, nickel-based deformable high-temperature alloy, Inconel alloy, Hastelloy, wear-resistant alloy, heat-resistant alloy, etc. For fluid testing environments containing metal reactive atmospheres such as oxygen, sulfur, and phosphorus, under high temperature conditions, the stability of austenitic stainless steel and ferritic heat-resistant steel is not enough to effectively resist the hazards of reactive atmospheres. It is easy to react and stratify and fall off, causing the reactive atmosphere to enter the protection tube, corrode the hot electrode, and cause damage. Therefore, under the harsh conditions of high temperature and reactive atmosphere, nickel-based high-temperature alloys are usually used as protection tube materials. Nickel-based high-temperature alloys have the characteristics of high temperature resistance and stable physical and chemical properties, which can improve the service life of temperature sensors. However, nickel-based high-temperature alloys are expensive, and in order to resist deformation or breakage under high temperature conditions, the protection tube is required to have sufficient thickness, resulting in a significant increase in the manufacturing cost of the temperature sensor. To this end, researchers are committed to developing a metal protection tube that can reduce the manufacturing cost of the metal protection tube while meeting the requirements of using the temperature sensor in a high-temperature reactive atmosphere.

[0004] Patent document with application number 200720005757.5 discloses a thermocouple protection device with a sleeve structure. The thermocouple protection tube includes an inner sleeve and an outer sleeve which are threadedly connected. An inner hole is opened at the center of the inner sleeve. The outer sleeve is made of GH3039 alloy, which can ensure that the protective sleeve has the same high temperature resistance and good physical and chemical stability at high temperatures as the protective sleeve that completely uses GH3039 alloy as the sleeve; the inner sleeve is made of lCrl8Ni9Ti, which is cheap and has high temperature strength that can meet work requirements, thereby greatly reducing the manufacturing cost of the entire protective sleeve. The thickness of the outer sleeve is 2-5 mm, and the thickness of the inner sleeve is 4-10 mm.

[0005] The double-layer protective tube prepared by the above-mentioned related technology uses a nickel-based high-temperature alloy outer sleeve to react with a reactive atmosphere to form a stable compound, thereby forming a dense protective layer to prevent the reactive atmosphere from continuing to diffuse inward. However, under high temperature, fluid stress and high-pressure test environments, due to the presence of alloy surface stress, the dense protective layer may become loose, causing the reactive atmosphere to gradually diffuse inward and contact the inner sleeve. Since the chemical stability of the inner sleeve is not enough to resist the erosion of the reactive atmosphere, the protective effect of the inner sleeve will fail, causing damage to the hot electrode. It can be seen that there is an urgent need to provide a metal composite tube for temperature sensors, which can further improve the high temperature resistance and physical and chemical stability of the protective tube under high temperature while reducing the preparation cost of the protective tube. Summary of the invention

[0006] The object of the present invention is to provide a metal composite tube for a temperature sensor, a preparation method and a temperature sensor, which can reduce the preparation cost of the protection tube while further improving the high temperature resistance and the physical and chemical stability of the protection tube under high temperature.

[0007] In a first aspect, the present invention provides a method for preparing a metal composite tube for a temperature sensor, comprising the following steps:

[0008] S1. Providing an inner sleeve and an outer sleeve, wherein the inner sleeve is made of a stainless steel tube and the outer sleeve is made of a nickel-based alloy tube, and performing surface pretreatment on the outer surface of the inner sleeve and the inner surface of the outer sleeve, wherein the surface pretreatment includes at least one of surface grinding treatment, surface polishing treatment or surface cleaning treatment;

[0009] S2. Performing surface deposition treatment on the outer surface of the inner sleeve and / or the inner surface of the outer sleeve after the surface pretreatment, wherein the surface deposition treatment comprises depositing a precursor powder intermediate layer on the outer surface of the inner sleeve and / or the inner surface of the outer sleeve, wherein the precursor powder comprises at least one of aluminum oxide, titanium dioxide or titanium suboxide, wherein the chemical formula of the titanium suboxide is Ti n O 2n-1, 3 < n < 10, where n is an integer;

[0010] S3. Insert the inner sleeve into the outer sleeve and perform a diameter reduction deformation treatment, which includes at least one of drawing, rolling, or forging, so that the inner sleeve, the precursor powder intermediate layer, and the outer sleeve are tightly pressed together to prepare a prefabricated composite tube;

[0011] S4. Perform a diffusion treatment on the prefabricated composite tube so that a metallurgical bonding protective layer is formed between the precursor powder and the inner sleeve and the outer sleeve, and the metal composite tube is prepared.

[0012] Further, in step S1, the difference between the inner diameter of the outer sleeve and the outer diameter of the inner sleeve after the surface pretreatment is 0.1 mm to 0.5 mm.

[0013] Further, in step S2, the precursor powder is composed of at least one of titanium dioxide and / or titanium suboxide.

[0014] Further, in step S2, the surface deposition treatment includes the following steps:

[0015] S2-1. Prepare a prefabricated powder slurry by uniformly dispersing the precursor powder in a solvent to form the prefabricated powder slurry;

[0016] S2-2. Rotationally spray the prefabricated powder slurry, keep the inner sleeve or the outer sleeve rotating, and uniformly spray the prefabricated powder slurry onto the outer surface of the inner sleeve or the inner surface of the outer sleeve. After spraying, dry the slurry, and repeat the spraying-drying process until a precursor powder intermediate layer with a predetermined thickness is formed.

[0017] Further, in step S2-2, the predetermined thickness of the precursor powder intermediate layer is 15 μm to 40 μm.

[0018] Further, in step S3, the deformation amount of the total wall thickness of the inner sleeve and the outer sleeve after the diameter reduction deformation treatment is 20% to 40%.

[0019] Further, the diffusion treatment includes a first-stage diffusion reaction and a second-stage diffusion reaction. The temperature of the first-stage diffusion reaction is 200 to 600 °C, and the reaction time is 10 min to 5 h. The temperature of the second-stage diffusion reaction is 1000 to 1300 °C, and the reaction time is 6 h to 24 h.

[0020] Further, in step S4, the thickness of the protective layer is 2 to 12 μm.

[0021] In a second aspect, the present invention provides a metal composite tube for a temperature sensor, which is prepared by the preparation method of the metal composite tube for a temperature sensor described above.

[0022] In a third aspect, the present invention provides a temperature sensor, comprising a thermode, an insulating structure, a protection tube and a wiring structure, wherein the protection tube is made of the aforementioned metal composite tube for the temperature sensor.

[0023] In summary, the present invention has at least one of the following beneficial effects:

[0024] 1. The present invention provides a metal composite tube for a temperature sensor, a preparation method and a temperature sensor. A specific preparation method is used to form a metallurgically bonded protective layer between the inner and outer sleeves of the metal composite tube with a specific precursor powder, which can effectively improve the high-temperature resistant physical and chemical stability of the metal composite tube, increase the service life of the thermocouple temperature sensor, and reduce the manufacturing cost. In subsequent embodiments, the prepared temperature sensor is applied to the actual production diffusion furnace for temperature measurement. The working temperature is 1200°C. After the service life reaches 6 months, the temperature difference fluctuation can still be maintained at ≤1.5°C. Compared with the existing 310S stainless steel / GH3039 nickel-based alloy bimetallic composite tube with a service life of 5 months, the service life is significantly improved. In a preferred embodiment, the temperature difference fluctuation can still be maintained at ≤1.5°C after the service life reaches 6.5 months or even 7 months.

[0025] 2. The present invention provides a metal composite tube for a temperature sensor, a preparation method and a temperature sensor. Aluminum oxide, titanium dioxide or titanium suboxide powder forms a tightly bonded protective layer with the inner sleeve and the outer sleeve, which can, on the one hand, block the reactive gas under high temperature conditions from diffusing to the inner sleeve and reacting with it, and on the other hand, consume the active factors in the reactive gas, thereby significantly improving the protective effect of the metal composite tube and extending the service life of the temperature sensor. Furthermore, compared with aluminum oxide, the diffusion reaction of titanium dioxide with the inner sleeve and the outer sleeve is more sufficient, which can have a better protective effect. Furthermore, the diffusion reaction of titanium suboxide powder is more complete than that of titanium dioxide, which can have a better protective effect.

[0026] 3. The present invention provides a metal composite tube for a temperature sensor, a preparation method and a temperature sensor. The preparation method is simple, the controllability is strong, and it is easy to control. The raw materials are readily available, the manufacturing cost can be greatly reduced, and it is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is a schematic diagram of the microstructure of the metal composite tube of Example 1 of the present invention and a line scan diagram of Al and O elements;

[0028] Figure 2 1 is a schematic diagram of the microstructure of the metal composite tube of Example 2 of the present invention and a line scan diagram of Ti and O elements;

[0029] Figure 3 It is a schematic diagram of the microstructure of the metal composite tube of Example 3 of the present invention and a line scan diagram of Ti and O elements. DETAILED DESCRIPTION

[0030] The present invention provides a metal composite pipe for a temperature sensor, a preparation method and a temperature sensor. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In the description of the present invention, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection of two components, it can be a direct connection, or it can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0031] Thermocouples include thermocouples, insulation structures, protection tubes and wiring structures. Thermocouples are classified according to the positive and negative materials of the thermocouples, including R-type platinum-rhodium 13-platinum, S-type platinum-rhodium 10-platinum, B-type platinum-rhodium 30-platinum-rhodium 6, J-type iron-copper-nickel, T-type copper-copper-nickel, E-type nickel-chromium-copper-nickel, K-type nickel-chromium-nickel-aluminum, N-type nickel-chromium-silicon-nickel-silicon, C-type rhenium-tungsten 5-rhenium-tungsten 26, and A-type rhenium-tungsten 5-rhenium-tungsten 20. The positive electrode refers to the thermocouple with a positive potential relative to the other electrode when the temperature of the measuring end is higher than that of the reference end. The insulation structure plays a role in preventing the thermocouple from short circuiting. It can be a conventional insulating sleeve or insulating powder filler. The insulating sleeve can be made of corundum porcelain tube, high-aluminum porcelain tube, clay porcelain tube, etc., and the insulating powder filler can be magnesium oxide powder, aluminum oxide powder, etc. The metal protective tube plays the role of fixing, supporting and protecting the hot electrode. Reported studies have shown that the combination of a relatively cheap inner sleeve and an outer sleeve with high physical and chemical stability can reduce the preparation cost while improving the protection effect and extending the service life of the thermocouple. The inventor found in the long-term research process that the inner sleeve and the outer sleeve of the metal composite tube are only mechanically connected. Under the action of high pressure, fluid stress and reactive gas, the dense protective film formed on the surface of the outer sleeve has a tendency to loosen. During the long-term working process, the outer sleeve cannot completely block the reactive gas from diffusing inward, entering the inner sleeve and reacting with the inner sleeve, which causes the protective effect of the metal composite tube to be significantly reduced, and ultimately causes the surface of the internal thermocouple to be corroded by the reactive gas, resulting in inaccurate temperature measurement. To this end, the inventors found after a large number of experimental studies that by forming a specific intermediate protective layer between the inner sleeve and the outer sleeve of the metal composite pipe, a metallurgical bond is formed between the intermediate protective layer and the inner sleeve and the outer sleeve, which significantly improves the tightness of the inner sleeve-intermediate protective layer-outer sleeve. On the one hand, the intermediate protective layer can prevent the reactive gas from directly diffusing to the inner sleeve after passing through the outer sleeve to react with it. On the other hand, the intermediate protective layer can react with the reactive gas and consume the active factors in the highly reactive gas, thereby preventing the active factors from continuing to diffuse inward and corrode the inner sleeve, significantly improving the protective effect of the metal composite pipe, achieving the purpose of long-range effective protection of the thermocouple, and significantly improving the service life of the thermocouple. In addition, it can also prevent the defect of reduced temperature measurement accuracy caused by the thermoelectric potential drift caused by the reaction of the thermocouple, thereby further improving the temperature measurement accuracy of the thermocouple and the accuracy of temperature control. The present invention is obtained on the basis of this research.

[0032] In some embodiments of the present invention, a method for preparing a metal composite tube for a temperature sensor is provided, comprising the following steps:

[0033] S1. Provide an inner sleeve and an outer sleeve. The inner sleeve is made of a stainless steel tube, and the outer sleeve is made of a nickel-based alloy tube. Surface pretreatment is performed on the outer surface of the inner sleeve and the inner surface of the outer sleeve. The surface pretreatment includes at least one of surface grinding treatment, surface polishing treatment, or surface cleaning treatment. In the embodiments of the present invention, the material of the stainless steel tube can be selected from the conventional 200 series, 300 series, and 400 series stainless steels in the art, preferably the 300 series, including stainless steels with grades 301, 304, 304L, 304N, 305, 309, 310, 310S, 314, 316, 316L, 321, 347, 348, etc. The material of the nickel-based alloy tube can be selected from the conventional Monel series, Inconel series, Incoloy series, Hastelloy series, GH series, etc. in the art, preferably nickel-based alloys such as GH3030, GH3039, GH214, GH125, GH3044, GH2747, etc. The stainless steel tube and the nickel alloy tube can be commercially available finished pipe materials, or can be processed from bar materials by conventional deep processing hole-making processes in the art, or can also be prepared by methods for preparing pipes such as hot rolling, cold rolling, cold drawing, and extrusion, without specific limitations. It can be understood that the geometric dimensions of the inner sleeve and the outer sleeve are selected according to the needs of the temperature sensor. Preferably, the difference between the inner diameter of the outer sleeve and the outer diameter of the inner sleeve after surface pretreatment is 0.1 mm to 0.5 mm, more preferably 0.2 to 0.4 mm; preferably, the wall thickness of the inner sleeve after surface pretreatment is 0.625 to 2.5 mm, and the wall thickness of the outer sleeve is 0.5 to 2 mm.

[0034] S2. Perform surface deposition treatment on the outer surface of the inner sleeve and / or the inner surface of the outer sleeve that has undergone the surface pretreatment. The surface deposition treatment includes depositing a precursor powder intermediate layer on the outer surface of the inner sleeve and / or the inner surface of the outer sleeve. The precursor powder includes at least one of aluminum oxide, titanium dioxide, or titanium suboxide, preferably at least one of titanium dioxide or titanium suboxide. The chemical formula of the titanium suboxide is Ti n O 2n-1 , 3 < n < 10, where n is an integer; the precursor powder of this embodiment can be obtained commercially or can be prepared by conventional chemical synthesis methods; the titanium suboxide powder of this embodiment can be selected from Ti3O5, Ti4O7, Ti5O9, Ti6O 11 , Ti8O 15, preferably Ti3O5, Ti4O7, Ti5O9, further preferably Ti4O7; titanium dioxide powder can also be prepared by conventional hydrogen reduction method, carbon thermal reduction method, metal thermal reduction method; the particle size of the precursor powder in this embodiment is less than 10μm, preferably less than 5μm. In some embodiments of the present invention, the surface deposition treatment includes the following steps: S2-1. Prefabricated powder slurry is prepared, and the precursor powder is evenly dispersed in a solvent to form the prefabricated powder slurry; S2-2. Rotary spraying of the prefabricated powder slurry, keeping the inner sleeve or the outer sleeve rotating, and uniformly spraying the prefabricated powder slurry onto the outer surface of the inner sleeve or the inner surface of the outer sleeve. After spraying, the slurry is dried, and the spraying-drying process is repeated until a predetermined thickness of the precursor powder intermediate layer is formed, and the predetermined thickness is 15μm to 40μm, preferably 18 to 35μm.

[0035] S3. The inner sleeve is installed in the outer sleeve and subjected to a diameter reduction deformation treatment, wherein the diameter reduction deformation treatment includes at least one of drawing, rolling or forging, so that the inner sleeve, the precursor powder intermediate layer and the outer sleeve are tightly pressed together to prepare a prefabricated composite tube. In the embodiment of the present invention, drawing, rolling or forging can adopt at least one of conventional cold drawing, cold rolling, cold forging, hot drawing, hot rolling and hot forging. The deformation amount of the diameter reduction deformation treatment is set according to the degree of pressing after deformation. Preferably, the deformation amount of the total wall thickness of the inner sleeve and the outer sleeve after the diameter reduction deformation treatment is 20-40%, and more preferably 20-30%. The deformation amount of the total wall thickness of the inner sleeve and the outer sleeve refers to the amount of change of the total wall thickness of the inner sleeve and the outer sleeve before and after deformation, divided by the total wall thickness of the inner sleeve and the outer sleeve before deformation. It is understandable that before the cold deformation or hot deformation treatment is performed, the ends of the inner sleeve and the outer sleeve can also be welded or clad to seal the gap to prevent the precursor powder from overflowing during the deformation process.

[0036] S4. The prefabricated composite tube is subjected to diffusion treatment so that a metallurgical bonding protective layer is formed between the precursor powder and the inner sleeve and the outer sleeve to prepare the metal composite tube. In an embodiment of the present invention, the diffusion reaction includes a primary diffusion reaction and a secondary diffusion reaction. The temperature of the primary diffusion reaction is 200 to 600°C, preferably 300 to 500°C, and the reaction time is 10min to 5h, preferably 30min to 3h. The temperature of the secondary diffusion reaction is 1000 to 1300°C, preferably 1050 to 1250°C, and the reaction time is 6h to 24h, preferably 8 to 18h. After the diffusion reaction is completed, the thickness of the prepared protective layer is 2 to 12μm.

[0037] In some embodiments of the present invention, a temperature sensor is also provided, including a thermoelectrode, an insulating structure, a protective tube and a wiring structure. The thermoelectrode, the insulating structure and the wiring structure can all adopt the conventional structures in the art mentioned above, which will not be repeated here. The protective tube is prepared from the metal composite tube prepared above. Specifically, the metal composite tube prepared in step S4 is cut into the required length, and one end is completely welded and sealed to obtain a temperature sensor protective tube. The insulating sleeve is sleeved on the positive and negative electrodes of the thermoelectrode, and the measuring ends of the positive and negative electrodes are welded, and the measuring end is placed in the closed end of the protective tube, and the reference end of the thermoelectrode is led out of the protective tube and extended into the wiring structure and electrically connected to the wiring structure to prepare a thermocouple temperature sensor.

[0038] The present invention is further described in detail below in conjunction with specific embodiments.

[0039] Example 1

[0040] Embodiment 1 provides a metal composite tube for a temperature sensor, a preparation method and a temperature sensor, which specifically include the following steps:

[0041] S1. Provide an inner sleeve and an outer sleeve. The inner sleeve is made of 310S stainless steel and the outer sleeve is made of GH3039 nickel-based alloy. The outer surface of the inner sleeve and the inner surface of the outer sleeve are surface pretreated. Sandpapers ranging from 60 to 200 mesh are used to grind the outer surface of the inner sleeve and the inner surface of the outer sleeve until they are smooth. After grinding, they are sequentially alkali washed, acid washed, and washed with water. Finally, they are ultrasonically cleaned with anhydrous ethanol. After completion, they are dried. The outer diameter of the inner sleeve after surface pretreatment is measured to be 16mm, the wall thickness of the inner sleeve is 1.3mm, the outer diameter of the outer sleeve is 18.3mm, and the wall thickness of the outer sleeve is 1mm.

[0042] S2. Performing surface deposition treatment on the outer surface of the inner casing after surface pretreatment, the surface deposition treatment includes the following steps:

[0043] S2-1. Prefabricated powder slurry is configured. The precursor powder is Al2O3 powder, the powder particle size is 3 to 5μm, the powder purity is more than 99.5%, and the Al2O3 powder is evenly dispersed in anhydrous ethanol to form Al2O3 powder slurry, the mass volume ratio of Al2O3 powder to anhydrous ethanol is 1g / ml;

[0044] S2-2. Rotate and spray the prefabricated powder slurry, keep the inner sleeve rotating at a speed of 5 rad / min, and evenly spray the Al2O3 powder slurry onto the outer surface of the inner sleeve. After spraying, dry the slurry and repeat the spray-drying process three times until a predetermined thickness of the Al2O3 powder middle layer is formed. The thickness of the Al2O3 powder middle layer is 20 μm.

[0045] S3. The inner sleeve is installed into the outer sleeve, and the end gaps of the inner sleeve and the outer sleeve are welded closed. An exhaust gap is reserved during welding to remove residual air inside during subsequent drawing. Before drawing, a matching long core rod is placed in the inner sleeve. Subsequently, the inner sleeve and the outer sleeve are placed on a drawing machine and subjected to drawing and shrinking deformation treatment at room temperature. The long core rod is pulled out of the die hole of the drawing machine together with the inner sleeve and the outer sleeve. After the drawing is completed, the inner sleeve, the Al2O3 powder intermediate layer and the outer sleeve are tightly pressed together to prepare a prefabricated composite tube. After the drawing and shrinking deformation treatment, the wall thickness of the inner sleeve is 1 mm, the wall thickness of the outer sleeve is 0.77 mm, and the drawing deformation of the total wall thickness of the inner sleeve and the outer sleeve is 23%.

[0046] S4. The prefabricated composite pipe is subjected to a secondary diffusion reaction, wherein the reaction temperature of the primary diffusion is 300° C., the reaction time is 30 min, and the reaction temperature of the secondary diffusion is 1250° C., the reaction time is 10 h, to prepare a metal composite pipe.

[0047] The microstructure and element composition of the metal composite tube were tested using a scanning electron microscope with an energy dispersive spectrometer. Figure 1 The SEM image of the metal composite tube prepared in Example 1 and the line scanning results of Al and O elements are shown in FIG. Figure 1 It can be seen that a metallurgically bonded Al2O3 protective layer is formed between the inner casing and the outer casing. The thickness of the Al2O3 protective layer is measured to be 4 to 12 μm, and the inner casing-intermediate protective layer-outer casing are tightly bonded. The Al2O3 protective layer can prevent the reactive gas from passing through the outer casing and diffusing into the inner casing to react with it. In addition, under high temperature conditions, the Al2O3 protective layer can react with the active factors in the reactive gas and consume the highly active factors, thereby preventing the active factors from continuing to diffuse inward and corrode the inner casing.

[0048] The metal composite tube prepared in Example 1 is cut into a protective tube of the required length, one end is completely welded to form a closed end, the measuring end of the thermoelectrode (S-type platinum-rhodium 10-platinum) is installed in the closed end of the protective tube, the thermoelectrode is sleeved with an insulating sleeve (double-hole corundum core column), and then the reference end of the thermoelectrode is connected to the junction box and electrically connected to the junction box to prepare a thermocouple temperature sensor. The thermocouple temperature sensor prepared in Example 1 is applied to the actual production diffusion furnace for temperature measurement (working temperature 1200°C). After the service life reaches 6 months, the temperature difference fluctuation can still be maintained at ≤1.5°C, which is significantly improved compared to the existing 310S stainless steel / GH3039 nickel-based alloy bimetallic composite tube with a service life of 5 months.

[0049] Example 2

[0050] Embodiment 2 provides a metal composite tube for a temperature sensor, a preparation method and a temperature sensor, which specifically include the following steps:

[0051] S1. Provide an inner sleeve and an outer sleeve. The inner sleeve is made of 310S stainless steel and the outer sleeve is made of GH3039 nickel-based alloy. The outer surface of the inner sleeve and the inner surface of the outer sleeve are surface pretreated. Sandpapers ranging from 60 to 200 mesh are used to grind the outer surface of the inner sleeve and the inner surface of the outer sleeve until they are smooth. After grinding, they are sequentially alkali washed, acid washed, and washed with water. Finally, they are ultrasonically cleaned with anhydrous ethanol. After completion, they are dried. The outer diameter of the inner sleeve after surface pretreatment is measured to be 16mm, the wall thickness of the inner sleeve is 1.3mm, the outer diameter of the outer sleeve is 18.3mm, and the wall thickness of the outer sleeve is 1mm.

[0052] S2. Performing surface deposition treatment on the outer surface of the inner casing after surface pretreatment, the surface deposition treatment includes the following steps:

[0053] S2-1. Prefabricated powder slurry is configured. The precursor powder is TiO2 powder, the powder particle size is 3 to 5μm, the powder purity is more than 99.5%, and the TiO2 powder is evenly dispersed in anhydrous ethanol to form a TiO2 powder slurry. The mass volume ratio of TiO2 powder to anhydrous ethanol is 1g / ml;

[0054] S2-2. Rotate and spray the prefabricated powder slurry, keep the inner sleeve rotating at a speed of 5 rad / min, and evenly spray the TiO2 powder slurry onto the outer surface of the inner sleeve. After spraying, dry the slurry and repeat the spray-drying process three times until a TiO2 powder middle layer of a predetermined thickness is formed. The thickness of the TiO2 powder middle layer is 20 μm.

[0055] S3. Install the inner sleeve into the outer sleeve, and weld the gaps at the ends of the inner sleeve and the outer sleeve closed. During welding, an exhaust gap is reserved to remove the residual air inside during subsequent drawing. Before drawing, a matching long core rod is placed in the inner sleeve. Subsequently, the inner sleeve and the outer sleeve are placed on a drawing machine and subjected to drawing and shrinking deformation treatment at room temperature. The long core rod is pulled out of the die hole of the drawing machine together with the inner sleeve and the outer sleeve. After the drawing is completed, the inner sleeve, the TiO2 powder intermediate layer and the outer sleeve are tightly pressed together to prepare a prefabricated composite tube. After the drawing and shrinking deformation treatment, the wall thickness of the inner sleeve is 1 mm, and the wall thickness of the outer sleeve is 0.77 mm. The drawing deformation of the total wall thickness of the inner sleeve and the outer sleeve is 23%.

[0056] S4. The prefabricated composite pipe is subjected to a secondary diffusion reaction, wherein the reaction temperature of the primary diffusion is 300° C., the reaction time is 30 min, and the reaction temperature of the secondary diffusion is 1250° C., the reaction time is 10 h, to prepare a metal composite pipe.

[0057] The microstructure and element composition of the metal composite tube were tested using a scanning electron microscope with an energy dispersive spectrometer. Figure 2The SEM image of the metal composite tube prepared in Example 2 and the scanning results of Ti and O elements are shown in FIG. Figure 2 It can be seen that a metallurgically bonded TiO2 protective layer is formed between the inner sleeve and the outer sleeve. The thickness of the TiO2 protective layer is measured to be 2 to 12 μm, and the inner sleeve-intermediate protective layer-outer sleeve is tightly bonded. The TiO2 protective layer can prevent the reactive gas from passing through the outer sleeve and diffusing to the inner sleeve to react with it. In addition, under high temperature conditions, the TiO2 protective layer can react with the active factors in the reactive gas, consume the highly active factors, and thus prevent the active factors from continuing to diffuse inward and corrode the inner sleeve. Compared with the metal composite tube prepared in Example 1, the unmelted large particles of the intermediate protective layer of the metal composite tube prepared in Example 2 are significantly reduced, indicating that the diffusion reaction between the TiO2 protective layer of Example 2 and the inner sleeve and the outer sleeve is more sufficient, the bond is tighter, and it is more conducive to improving the protective effect.

[0058] The metal composite tube prepared in Example 2 is cut into a protective tube of the required length, one end is completely welded to form a closed end, the measuring end of the thermoelectrode (S-type platinum-rhodium 10-platinum) is installed in the closed end of the protective tube, and the thermoelectrode is sleeved with an insulating sleeve (double-hole corundum core column), and then the reference end of the thermoelectrode is connected to the junction box and electrically connected to the junction box to prepare a thermocouple temperature sensor. The temperature sensor prepared in Example 2 is applied to the actual production diffusion furnace for temperature measurement (working temperature 1200°C). After the service life reaches 6.5 months, the temperature difference fluctuation can still be maintained at ≤1.5°C. Compared with the existing 310S stainless steel / GH3039 nickel-based alloy bimetallic composite tube, the service life is 5 months, and the life is significantly improved, and the service life of the thermocouple temperature sensor in Example 2 is improved compared to that in Example 1.

[0059] Example 3

[0060] Embodiment 3 provides a metal composite tube for a temperature sensor, a preparation method and a temperature sensor, which specifically include the following steps:

[0061] S1. Provide an inner sleeve and an outer sleeve. The inner sleeve is made of 310S stainless steel and the outer sleeve is made of GH3039 nickel-based alloy. The outer surface of the inner sleeve and the inner surface of the outer sleeve are surface pretreated. Sandpapers ranging from 60 to 200 mesh are used to grind the outer surface of the inner sleeve and the inner surface of the outer sleeve until they are smooth. After grinding, they are sequentially alkali washed, acid washed, and washed with water. Finally, they are ultrasonically cleaned with anhydrous ethanol. After completion, they are dried. The outer diameter of the inner sleeve after surface pretreatment is measured to be 16mm, the wall thickness of the inner sleeve is 1.3mm, the outer diameter of the outer sleeve is 18.3mm, and the wall thickness of the outer sleeve is 1mm.

[0062] S2. Performing surface deposition treatment on the outer surface of the inner casing after surface pretreatment, the surface deposition treatment includes the following steps:

[0063] S2-1. Prefabricated powder slurry is configured. The precursor powder is Ti4O7 powder, the powder particle size is 3 to 5μm, the powder purity is more than 99.5%, and the Ti4O7 powder is evenly dispersed in anhydrous ethanol to form a Ti4O7 powder slurry. The mass volume ratio of Ti4O7 powder to anhydrous ethanol is 1g / ml;

[0064] S2-2. Rotate and spray the prefabricated powder slurry, keep the inner sleeve rotating at a speed of 5 rad / min, and evenly spray the Ti4O7 powder slurry onto the outer surface of the inner sleeve. After spraying, dry the slurry and repeat the spray-drying process three times until a Ti4O7 powder middle layer of a predetermined thickness is formed. The thickness of the Ti4O7 powder middle layer is 20 μm.

[0065] S3. The inner sleeve is installed into the outer sleeve, and the end gaps of the inner sleeve and the outer sleeve are welded closed. An exhaust gap is reserved during welding to remove residual air inside during subsequent drawing. Before drawing, a matching long core rod is placed in the inner sleeve. Subsequently, the inner sleeve and the outer sleeve are placed on a drawing machine and subjected to drawing and shrinking deformation treatment at room temperature. The long core rod is pulled out of the die hole of the drawing machine together with the inner sleeve and the outer sleeve. After the drawing is completed, the inner sleeve, the Ti4O7 powder intermediate layer and the outer sleeve are tightly pressed together to prepare a prefabricated composite tube. After the drawing and shrinking deformation treatment, the wall thickness of the inner sleeve is 1 mm, the wall thickness of the outer sleeve is 0.77 mm, and the drawing deformation of the total wall thickness of the inner sleeve and the outer sleeve is 23%.

[0066] S4. The prefabricated composite pipe is subjected to a secondary diffusion reaction, wherein the reaction temperature of the primary diffusion is 300° C., the reaction time is 30 min, and the reaction temperature of the secondary diffusion is 1250° C., the reaction time is 10 h, to prepare a metal composite pipe.

[0067] The microstructure and element composition of the metal composite tube were tested using a scanning electron microscope with an energy dispersive spectrometer. Figure 3 The SEM image of the metal composite tube prepared in Example 3 and the scanning results of Ti and O elements are shown in FIG. Figure 3It can be seen that a metallurgically bonded Ti4O7 protective layer is formed between the inner sleeve and the outer sleeve. The thickness of the Ti4O7 protective layer is measured to be 4 to 12 μm, and the inner sleeve-intermediate protective layer-outer sleeve is tightly bonded. The Ti4O7 protective layer can prevent the reactive gas from passing through the outer sleeve and diffusing to the inner sleeve to react with it. In addition, under high temperature conditions, the Ti4O7 protective layer can react with the active factors in the reactive gas, consume the highly active factors, and thus prevent the active factors from continuing to diffuse inward and corrode the inner sleeve. Compared with the metal composite tube prepared in Example 1, no particles are found in the intermediate protective layer of the metal composite tube prepared in Example 3, indicating that the diffusion reaction between the Ti4O7 in Example 3 and the inner sleeve and the outer sleeve is more complete, the bonding is tighter, and it is more conducive to further improving the protective effect.

[0068] The metal composite tube prepared in Example 3 is cut into a protective tube of the required length, one end is completely welded to form a closed end, the measuring end of the thermoelectrode (S-type platinum-rhodium 10-platinum) is installed in the closed end of the protective tube, and the thermoelectrode is sleeved with an insulating sleeve (double-hole corundum core column), and then the reference end of the thermoelectrode is connected to the junction box and electrically connected to the junction box to prepare a thermocouple temperature sensor. The thermocouple temperature sensor prepared in Example 3 is applied to the actual production diffusion furnace for temperature measurement (working temperature 1200°C). After the service life reaches 7 months, the temperature difference fluctuation can still be maintained at ≤1.5°C. Compared with the existing 310S stainless steel / GH3039 nickel-based alloy double-layer sleeve, the service life is 5 months, and the life is significantly improved, and the service life of the thermocouple temperature sensor in Example 3 is significantly improved compared with that in Example 1.

[0069] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a metal composite tube for a temperature sensor, characterized in that: The following steps are involved: S1. Providing an inner sleeve and an outer sleeve, wherein the inner sleeve is made of a stainless steel tube and the outer sleeve is made of a nickel-based alloy tube, and performing surface pretreatment on the outer surface of the inner sleeve and the inner surface of the outer sleeve, wherein the surface pretreatment includes at least one of surface grinding, surface polishing or surface cleaning; S2. Perform surface deposition treatment on the outer surface of the inner sleeve and / or the inner surface of the outer sleeve that have undergone the above-mentioned surface pretreatment. The surface deposition treatment includes depositing a precursor powder intermediate layer on the outer surface of the inner sleeve and / or the inner surface of the outer sleeve. The precursor powder includes at least one of aluminum trioxide, titanium dioxide, or titanium suboxide. The chemical formula of the titanium suboxide is Ti n O 2n-1 , 3 < n < 10, where n is an integer; S3. inserting the inner sleeve into the outer sleeve and performing a diameter reduction deformation process, wherein the diameter reduction deformation process includes at least one of drawing, rolling or forging, so that the inner sleeve, the precursor powder intermediate layer and the outer sleeve are tightly pressed together to prepare a prefabricated composite tube; S4. The prefabricated composite tube is subjected to diffusion treatment so that a metallurgically bonded protective layer is formed between the precursor powder and the inner sleeve and the outer sleeve, thereby preparing the metal composite tube.

2. The method for preparing a metal composite tube for a temperature sensor according to claim 1, characterized in that: In step S1, the difference between the inner diameter of the outer sleeve after the surface pretreatment and the outer diameter of the inner sleeve is 0.1 mm to 0.5 mm.

3. The method for preparing a metal composite tube for a temperature sensor according to claim 1 or 2, characterized in that: In step S2, the precursor powder is composed of at least one of titanium dioxide and / or titanium oxide.

4. The method for preparing a metal composite tube for a temperature sensor according to claim 1 or 2, characterized in that: In step S2, the surface deposition process includes the following steps: S2-1. Prepare a prefabricated powder slurry, and evenly disperse the precursor powder in a solvent to form the prefabricated powder slurry; S2-2. Rotate and spray the prefabricated powder slurry, keep the inner sleeve or the outer sleeve rotating, and evenly spray the prefabricated powder slurry onto the outer surface of the inner sleeve or the inner surface of the outer sleeve. After spraying, dry the slurry, and repeat the spraying-drying process until a precursor powder intermediate layer of a predetermined thickness is formed.

5. The method for preparing a metal composite tube for a temperature sensor according to claim 4, characterized in that: In step S2-2, the predetermined thickness of the intermediate layer of the precursor powder is 15 μm to 40 μm.

6. The method for preparing a metal composite tube for a temperature sensor according to claim 1 or 2, characterized in that: In step S3, the deformation amount of the total wall thickness of the inner sleeve and the outer sleeve after the diameter reduction deformation treatment is 20-40%.

7. The method for preparing a metal composite tube for a temperature sensor according to claim 1 or 2, characterized in that: In step S4, the diffusion treatment includes a primary diffusion reaction and a secondary diffusion reaction. The temperature of the primary diffusion reaction is 200-600°C, and the reaction time is 10min-5h. The temperature of the secondary diffusion reaction is 1000-1300°C, and the reaction time is 6h-24h.

8. The method for preparing a metal composite tube for a temperature sensor according to claim 1 or 2, characterized in that: In step S4, the thickness of the protective layer is 2-12 μm.

9. A metal composite tube for a temperature sensor, prepared by the method for preparing a metal composite tube for a temperature sensor according to any one of claims 1 to 8.

10. A temperature sensor, comprising a thermode, an insulating structure, a protection tube and a wiring structure, wherein the protection tube is made of the metal composite tube for the temperature sensor according to claim 9.

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