A method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature and a tungsten-rhenium thermocouple

Abstract

The present invention proposes a manufacturing method of a tungsten-rhenium thermocouple for radiation temperature measurement and a tungsten-rhenium thermocouple, including an insulating layer spin coating step, a sensitive core preparation step and a package shell assembly step. The insulating layer spin coating preparation process is used to evenly coat the hafnium oxide sol on the double end surfaces of the tungsten sheet and the tungsten-rhenium sheet, and form a stable insulating film after sintering; the sensitive core preparation process is used to stir and friction bond the tungsten sheet and the tungsten-rhenium sheet into a whole, and weld the tungsten wire and the tungsten-rhenium wire respectively to form a thermocouple temperature measurement sensitive core; the package shell assembly process is used to assemble the sensitive core into a stainless steel protective shell, and apply a high-emissivity coating on the probe surface. Through the manufacturing method provided by the present invention, an ultra-high temperature temperature sensor with an upper limit of 3000°C for transient radiation temperature measurement can be quickly prepared, which has good temperature measurement stability and response speed, and can be applied to temperature measurement in extreme radiation high temperature environments.

Description

Technical Field

[0001] The invention belongs to the technical field of sensor manufacturing, and in particular relates to a manufacturing method of a tungsten-rhenium thermocouple for measuring radiation temperature and the tungsten-rhenium thermocouple. Background Art

[0002] Radiation temperature measurement is crucial in many industries such as energy and metallurgy. Traditional radiation temperature measurement instruments such as radiation pyrometers and optical pyrometers have many defects.

[0003] Radiation pyrometers are greatly affected by the measuring distance and the intermediate medium, and their high temperature resistance is limited. They are difficult to work stably under ultra-high temperature conditions, resulting in poor measurement accuracy and low reliability. Although optical pyrometers can measure non-contact, they have extremely high requirements for the cleanliness of the measurement environment. Tiny dust or smoke will seriously affect the accuracy, and the measurement range is relatively narrow. In extremely high temperature scenarios, such as the moment of rocket engine ignition or the special stage of metallurgical furnace smelting, their reliability is significantly reduced.

[0004] In addition, most traditional radiation temperature measurement technologies have slow response speeds and cannot meet the rapidly changing high-temperature process requirements of modern industry. For example, the rapid temperature changes during high-speed metal processing are difficult for traditional equipment to capture in real time. At the same time, high material costs and complex manufacturing processes make the cost of traditional measurement equipment high, limiting its large-scale application and promotion, and making it difficult to meet the needs of industrial development for high-precision, high-reliability, and low-cost radiation temperature measurement.

[0005] In view of this, it is very meaningful to propose a manufacturing method of a tungsten-rhenium thermocouple for radiation temperature measurement and a tungsten-rhenium thermocouple. Summary of the invention

[0006] The present invention provides a method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature and a tungsten-rhenium thermocouple, which can overcome the problems of uneven thickness of the insulating layer and easy generation of thermal resistance in the prior art, and can achieve rapid preparation, have a high upper temperature measurement limit, good temperature measurement stability and response speed, and have a simple preparation process and low cost.

[0007] In the first aspect, the present invention provides a method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature, the method comprising an insulating layer spin coating step, a sensitive core preparation step and a packaging tube shell assembly step, wherein the insulating layer spin coating step is specifically as follows:

[0008] S1. Insulating layer spin coating step: hafnium tetrachloride is prepared into hafnium oxide sol with preset nanostructure and performance by sol-gel method, and a precursor solution is obtained and converted into sol by controlling water bath stirring, solution dripping and reaction conditions; then, on the tungsten sheet and tungsten-rhenium sheet that have been ultrasonically cleaned to remove impurities, the hafnium oxide sol is evenly and stably coated on the two end faces of the tungsten sheet and tungsten-rhenium sheet by setting multi-stage rotation speed and time control, and then sintered in a tubular furnace under controlled heating, insulation and cooling procedures to form hafnium oxide insulating films on the two end faces of the tungsten sheet and tungsten-rhenium sheet.

[0009] Preferably, the specific operation of the sol-gel method includes: placing the hafnium tetrachloride in ethanol with a purity of not less than 99%, magnetically stirring in a constant temperature water bath at 55 to 65°C for 1.5 to 2.5 hours, adding a sodium hydroxide solution with a concentration of 1 mol / L and continuing to stir at room temperature for 45 to 75 minutes to form the precursor solution, and then placing the precursor solution in a reactor in a microwave hydrothermal synthesizer with a microwave power of 4000 W to react for 3 to 5 hours, centrifugally washing at 3000 to 5000 rpm for 10 to 20 minutes, and freeze-drying at -40 to -20°C for 12 to 24 hours to obtain a nano hafnium oxide sol.

[0010] Preferably, in the insulating layer spin coating step, the parameters of the spin coater are set as follows: first, spin coating at a low speed of 400 to 600 rpm / min for 3 to 7 seconds, then spin coating at a medium speed of 1200 to 1800 rpm / min for 8 to 12 seconds, and finally, spin coating at a high speed of 3500 to 4500 rpm / min for 12 to 18 seconds, and during the spin coating process, the ambient temperature is maintained at 20 to 30°C and the humidity is maintained at 40% to 60%.

[0011] Preferably, in the insulating layer spin coating step, during the tubular furnace sintering, the heating rate in the range of 20 ~ 30 ° C to 350 ~ 450 ° C is 8 ~ 12 ° C / min, and it is kept at 350 ~ 450 ° C for 45 ~ 75 minutes, and the heating rate in the range of 350 ~ 450 ° C to 750 ~ 850 ° C is 10 ~ 15 ° C / min, and it is kept at 750 ~ 850 ° C for 60 ~ 90 minutes, followed by natural cooling. Argon gas with a purity of not less than 99.9% is introduced throughout the sintering process at a flow rate of 50 ~ 100 ml / min.

[0012] Preferably, the sensitive core preparation step specifically includes: S2, sensitive core preparation step: put the tungsten sheet and tungsten-rhenium sheet covered with the hafnium oxide insulating film into the slot of the alloy clamp bed and clamp them firmly, set the key parameters of the stir friction welding machine, make the stirring head vertically align with the upper end surface boundary line of the tungsten sheet and the tungsten-rhenium sheet, and use friction heat and mechanical force to achieve friction bonding of the upper end surfaces of the tungsten sheet and the tungsten-rhenium sheet to form a weld as a stable temperature measurement node through the rotation and movement of the stirring head along the boundary line; then remove the specific area of ​​the hafnium oxide insulating layer on the surface of the tungsten sheet and the tungsten-rhenium sheet through a grinding process, and use welding technology to firmly weld the tungsten wire and the tungsten-rhenium wire to the exposed metal surface respectively, so as to construct a thermocouple sensitive core; in the sensitive core preparation step, the key parameters of the stir friction welding machine include the rotation speed, movement speed and welding pressure of the stirring head, the rotation speed of the stirring head is 800~1200 rpm, and the movement speed is 3~ 7 mm / s, welding pressure is 150 ~ 250 Newtons.

[0013] Preferably, in the sensitive core preparation step, removing a specific area of ​​the hafnium oxide insulating layer on the surface of the tungsten sheet and the tungsten-rhenium sheet includes: grinding an area of ​​the hafnium oxide insulating layer of 5 to 15 square millimeters and a grinding depth of 0.3 to 0.7 millimeters.

[0014] Preferably, the packaging tube shell assembly step specifically includes: S3, packaging tube shell assembly step: insert the prepared sensitive core into the stainless steel protective tube, ensure that the head of the sensitive core is flush with the head of the protective tube, use a syringe to inject high-temperature glue from the tail of the stainless steel protective tube into the tube to achieve the connection between the sensitive core and the protective tube; uniformly apply a high-emissivity coating on the surface of the head of the thermocouple sensitive core; in the packaging tube shell assembly step, the stainless steel protective tube is made of 316L stainless steel with a wall thickness of 1.5 to 2.5 mm and a surface roughness Ra of no more than 0.8 microns.

[0015] Preferably, in the packaging tube shell assembly step, the high temperature glue has a temperature resistance of 1000-1200°C and an expansion coefficient of 5×10 - 6 ~ 8×10 - 6 / ℃, the filling amount error is controlled within ±5%.

[0016] Preferably, in the packaging tube shell assembly step, the material of the high emissivity coating is a boron carbide-based composite material, the emissivity of the high emissivity coating is not less than 0.9 in the wavelength range of 0.8 to 2.5 μm, the coating thickness is 10 to 20 microns, and the coating is performed using plasma spraying technology, the spraying pressure is 2 to 4 MPa, and the spraying distance is 150 to 200 mm.

[0017] In a second aspect, an embodiment of the present invention provides a tungsten-rhenium thermocouple for radiation temperature measurement, which is prepared according to the manufacturing method of the tungsten-rhenium thermocouple for radiation temperature measurement as described in the first aspect.

[0018] Compared with the prior art, the beneficial results of the present invention are:

[0019] Through the preparation process provided by the present invention, a tungsten-rhenium thermocouple for use in a high-temperature radiation environment can be quickly prepared. The hafnium oxide insulating layer formed by the sol-gel method and the spin coating method is thin and dense, and the thermocouple node formed by stir friction welding is stable, which improves the heat conduction speed, thereby accelerating the response speed. Further coating a high-emissivity coating on the probe surface can significantly enhance the sensitivity of the sensor to the radiation temperature. The prepared tungsten-rhenium thermocouple can measure radiation temperature up to 3000°C, which greatly improves the upper limit of temperature measurement, response speed and temperature measurement stability compared with other traditional radiation temperature measurement equipment. In addition, the preparation cost is low, the process is simple, and it is easy to popularize on a large scale. It can meet the strict requirements of energy, metallurgy and other industries for high-temperature radiation temperature measurement, and has broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and are used together with the description to explain the principles of the present invention. It will be easy to recognize other embodiments and many expected advantages of the embodiments because they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with each other. The same reference numerals refer to corresponding similar parts.

[0021] Figure 1 It is a schematic flow chart of a method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of a spin coating platform according to an embodiment of the present invention;

[0023] Figure 3 Schematic diagram of a friction stir welding platform according to an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of a sensitive core according to an embodiment of the present invention;

[0025] Figure 5 This is a diagram of a coaxial thermocouple according to an embodiment of the present invention;

[0026] Figure 6 This is a laser 3000°C test diagram of an embodiment of the present invention.

[0027] Figure numerals: 1. hafnium oxide sol; 2. tungsten sheet; 3. tungsten-rhenium sheet; 4. spin coater; 5. rotating platform; 6. hafnium oxide insulating film; 7. alloy clamp bed; 8. slot; 9. nut; 10. screw; 11. insert; 12. stirring head; 13. weld; 14. tungsten wire; 15. tungsten-rhenium wire; 16. stainless steel protection tube; 17. high-temperature glue; 18. high-emissivity coating. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0029] In a first aspect, an embodiment of the present invention discloses a method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature, such as Figure 1 As shown, the method includes an insulating layer spin coating step, a sensitive core preparation step and a packaging tube shell assembly step, and the specific steps are as follows:

[0030] S1, insulating layer spin coating step: hafnium tetrachloride is prepared into hafnium oxide sol 1 with preset nanostructure and performance by sol-gel method, and a precursor solution is obtained and converted into sol by controlling water bath stirring, solution dripping and reaction conditions; then, on the tungsten sheet 2 and tungsten-rhenium sheet 3 that have been ultrasonically cleaned to remove impurities, the hafnium oxide sol 1 is evenly and stably coated on the two end faces of the tungsten sheet 2 and the tungsten-rhenium sheet 3 by setting multi-stage rotation speed and time control, and then sintered in a tubular furnace under controlled heating, insulation and cooling procedures to form hafnium oxide insulating films 6 on the two end faces of the tungsten sheet 2 and the tungsten-rhenium sheet 3;

[0031] Specifically, Figure 2 As shown, in this embodiment, the specific operation of the sol-gel method includes: placing hafnium tetrachloride in ethanol with a purity of not less than 99%, and magnetically stirring in a constant temperature water bath at 55 to 65°C for 1.5 to 2.5 hours, dropping a sodium hydroxide solution with a concentration of 1 mol / L and continuing to stir at room temperature for 45 to 75 minutes to form a precursor solution. As shown in Table 1 below, it is found through experiments that within the temperature and time range of 65°C and 2.5 hours, the dissolution rate of hafnium tetrachloride can reach 98%, and at this sodium hydroxide solution concentration, the size of the generated precursor particles is relatively uniform, with an average particle size of 30nm.

[0032] First, hafnium tetrachloride is dissolved under specific conditions to ensure that the raw materials are fully and evenly dispersed in ethanol, laying a good foundation for subsequent reactions, helping to form a high-quality precursor solution and avoiding product defects caused by uneven dispersion of raw materials. Then, the uniform particle size distribution is conducive to the consistency and stability of subsequent reactions, making the performance of the final product more uniform. When constructing the insulating layer, it can ensure the balance of insulation performance everywhere, reduce local weak points, and improve the overall insulation effect.

[0033] The precursor solution is then placed in a reaction kettle in a microwave hydrothermal synthesizer with a microwave power of 4000 W to react for 3 to 5 hours, and then centrifuged and washed at 3000 to 5000 rpm for 10 to 20 minutes and freeze-dried at -40 to -20°C for 12 to 24 hours to obtain nano hafnium oxide sol 1. This can effectively remove impurities and moisture, accurately control the synthesis process of nano hafnium oxide sol 1, and obtain high-purity, high-quality nano hafnium oxide sol.

[0034] When this sol is used to prepare insulating films, it can form a dense and stable microstructure, which greatly enhances the high temperature resistance and corrosion resistance of the insulating layer, effectively ensures the stable operation of the thermocouple in extreme radiation and high temperature environments, and significantly improves the reliability and service life of the sensor. Compared with traditional insulating materials and preparation methods, the insulation performance retention time in the same high temperature environment is extended several times, providing key support for the high performance of the thermocouple.

[0035] Table 1

[0036] Experimental Grouping Dissolution rate of hafnium tetrachloride Stirring temperature (℃) Stirring time (h) Sodium hydroxide concentration (mol / L) Stirring time at room temperature (min) Average particle size of precursor (nm) Group 1 95% 55 1.5 1.0 45 20 Group 2 98% 65 2.5 1.0 75 30 Group 3 96% 60 2.0 1.0 60 25

[0037] The parameters of the spin coater 4 are set as follows: first, spin coating at a low speed of 400 to 600 rpm / min for 3 to 7 seconds, then spin coating at a medium speed of 1200 to 1800 rpm / min for 8 to 12 seconds, and finally spin coating at a high speed of 3500 to 4500 rpm / min for 12 to 18 seconds, and during the spin coating process, the ambient temperature is maintained at 20 to 30°C and the humidity is maintained at 40% to 60%. As shown in Table 2 below, after experimental testing, the thickness uniformity of the film layer obtained by spin coating under the above parameters can be controlled within ±5%, the surface flatness is high, and the roughness is less than 10nm.

[0038] The spin coater 4 operates according to specific parameters. Under suitable temperature and humidity conditions, the thickness uniformity of the spin-coated film can be controlled within a very small deviation range (±5%), and the surface is extremely flat and smooth (roughness less than 10nm), providing a high-quality film foundation for subsequent processes and effectively ensuring the stability and reliability of product performance.

[0039] Table 2

[0040] Experimental Grouping Low speed spin coating speed (rpm / min) Low speed spin coating time (s) Medium speed spin coating speed (rpm / min) Medium speed spin coating time (s) High speed spin coating speed (rpm / min) High speed spin coating time (s) Spin coating environment temperature (℃) Spin coating environment humidity Film thickness uniformity Film surface roughness (nm) Group 1 400 3 1200 8 3500 12 20 40% ±4% 8 Group 2 600 7 1800 12 4500 18 30 60% ±3% 5 Group 3 500 5 1500 10 4000 15 25 50% ±5% 7

[0041] Furthermore, during sintering in a tubular furnace, the heating rate in the range of 20 ~ 30 ° C to 350 ~ 450 ° C is 8 ~ 12 ° C / min, and the temperature is kept at 350 ~ 450 ° C for 45 ~ 75 minutes. The heating rate in the range of 350 ~ 450 ° C to 750 ~ 850 ° C is 10 ~ 15 ° C / min, and the temperature is kept at 750 ~ 850 ° C for 60 ~ 90 minutes, followed by natural cooling. Argon gas with a purity of not less than 99.9% is introduced throughout the sintering process at a flow rate of 50 ~ 100 ml / min.

[0042] Compared with the traditional insulating layer preparation method, the insulating layer spin coating in this embodiment can accurately control the thickness and uniformity of the insulating layer, making it thin and dense. In the sol-gel process, by optimizing the stirring, heat treatment, centrifugal washing and other steps, it is ensured that hafnium tetrachloride is converted into high-quality hafnium oxide sol 1, and then a uniform and defect-free insulating film can be formed when spin-coated on the tungsten sheet 2 and the tungsten-rhenium sheet 3. This thin and dense insulating layer can not only effectively guarantee the electrical insulation performance of the thermocouple, but also minimize the obstruction to heat conduction, which is significantly different from the problems of uneven thickness and easy thermal resistance of the insulating layer in the prior art, thereby improving the heat conduction efficiency and response speed.

[0043] The hafnium oxide sol 1 was carefully prepared by the sol-gel method, and combined with strict spin coating and precisely controlled tubular furnace sintering procedures, a dense insulating film was successfully formed on both sides of the tungsten sheet 2 and the tungsten-rhenium sheet 3. This insulating layer has a compact and uniform structure at the microscopic level, which effectively prevents the occurrence of leakage, provides a key guarantee for the stable operation of the thermocouple in high temperature and complex electromagnetic environments, greatly improves the reliability and stability of the sensor, ensures that the measurement signal is not disturbed, and maintains stable transmission.

[0044] For example, in the monitoring of high-temperature furnaces in the energy field, it can effectively resist the complex electromagnetic interference and high-temperature erosion in the furnace, ensure the accuracy and continuity of temperature measurement, and significantly improve the stability of the measurement system compared to traditional insulation methods, reducing measurement errors and equipment failures caused by insulation failure.

[0045] S2, sensitive core preparation step: put the tungsten sheet 2 and the tungsten-rhenium sheet 3 covered with the hafnium oxide insulating film 6 into the slot 8 of the alloy clamp bed 7 and clamp them firmly, set the key parameters of the stir friction welding machine, make the stirring head 12 vertically align with the upper end surface boundary line of the tungsten sheet 2 and the tungsten-rhenium sheet 3, and use the friction heat and mechanical force to realize the friction bonding of the upper end surfaces of the tungsten sheet 2 and the tungsten-rhenium sheet 3 by rotating the stirring head 12 along the boundary line to form a weld 13 as a stable temperature measurement node; then remove the specific area of ​​the hafnium oxide insulating layer on the surface of the tungsten sheet 2 and the tungsten-rhenium sheet 3 by grinding process, and use welding technology to firmly weld the tungsten wire 14 and the tungsten-rhenium wire 15 to the exposed metal surface respectively, so as to construct a thermocouple sensitive core;

[0046] like Figure 3 is a schematic diagram of the friction stir welding platform of this embodiment, Figure 4 Schematic diagram of the sensitive core of this embodiment. In this step, the key parameters of the friction stir welding machine include the rotation speed, moving speed and welding pressure of the stirring head 12, the rotation speed of the stirring head 12 is 800 to 1200 rpm, the moving speed is 3 to 7 mm / s, and the welding pressure is 150 to 250 Newtons.

[0047] As shown in Tables 3, 4 and 5 below, preferably, the rotation speed of the stirring head 12 is 1000 rpm, the moving speed is 5 mm / s, and the welding pressure is 200 N. After experimental comparison, this parameter combination helps to ensure welding quality and improve the performance of the sensitive core.

[0048] Table 3

[0049] Experimental Grouping Stirring head rotation speed (rpm) Welding joint strength (MPa) Number of welding defects Weld metal structure uniformity Group 1 800 300 3 Poor Group 2 1000 350 1 better Group 3 1200 320 2 generally

[0050] Table 4

[0051] Experimental Grouping Stirring head moving speed (mm / s) Welding efficiency (mm² / s) Weld seam quality Heat affected zone width (mm) Group 1 3 240 good 2.5 Group 2 5 300 excellent 2.0 Group 3 7 280 generally 3.0

[0052] Table 5

[0053] Experimental Grouping Welding pressure (Newton) Welding deformation (mm) Welding interface bonding tightness Internal residual stress (MPa) Group 1 150 0.5 better 150 Group 2 200 0.3 excellent 120 Group 3 250 0.4 good 130

[0054] Furthermore, the specific area of ​​the hafnium oxide insulating layer removed on the surface of the tungsten sheet 2 and the tungsten-rhenium sheet 3 includes: the grinding area of ​​the hafnium oxide insulating layer is 5 to 15 square millimeters, and the grinding depth is 0.3 to 0.7 millimeters. This ensures that the subsequent welding operation can be carried out smoothly and the performance of the sensitive core is stable and reliable.

[0055] In this embodiment, the process of stir friction welding is used to form the thermocouple temperature measurement node. After the tungsten sheet 2 and the tungsten-rhenium sheet 3 coated with the hafnium oxide insulating film 6 are coaxially aligned and clamped in the slot 8 of the alloy clamp bed 7, the high-quality friction bonding of the upper end surfaces of the two is achieved by accurately controlling the rotation and movement of the stirring head 12 along the upper end surface boundary line to form an extremely stable temperature measurement node. Different from traditional welding or connection methods, stir friction welding can achieve good metallurgical bonding of materials at the microscopic level, avoid the generation of defects such as pores and cracks, ensure the stability and reliability of the node, and greatly improve the accuracy and stability of temperature measurement.

[0056] By using the specific parameter settings of the friction stir welding machine, the stirring head 12 can be precisely operated on the boundary line of the end surfaces of the tungsten sheet 2 and the tungsten-rhenium sheet 3, achieving metallurgical bonding between the two and forming a high-quality weld 13. This bonding method forms a tight and uniform alloy connection in the microstructure, with high heat conduction efficiency, effectively improving the temperature response speed of the sensitive core, and can quickly and accurately sense temperature changes.

[0057] The subsequent precise grinding and reliable welding of the hafnium oxide insulating layer ensures the stable connection between the tungsten wire 14 and the tungsten-rhenium wire 15 and the sensitive core, further enhancing the stability of the sensitive core and the signal transmission performance, and ensuring the accuracy and reliability of the thermocouple temperature measurement. In the metal smelting process monitoring in the metallurgical industry, it can capture subtle changes in temperature in a timely manner, providing strong support for the precise control of the smelting process. Compared with the traditional connection method, the response speed is increased several times, significantly improving the production efficiency and product quality control level.

[0058] S3, packaging tube shell assembly steps: insert the prepared sensitive core into the stainless steel protective tube 16, ensure that the head of the sensitive core is flush with the head of the protective tube, use a syringe to inject high-temperature glue 17 from the tail of the stainless steel protective tube 16 into the tube to connect the sensitive core and the protective tube; evenly apply a high-emissivity coating 18 on the surface of the head of the thermocouple sensitive core.

[0059] Coaxial thermocouple diagram Figure 5 In this embodiment, the stainless steel protection tube 16 is made of 316L stainless steel, with a wall thickness of 1.5 to 2.5 mm and a surface roughness Ra of no more than 0.8 μm. The high temperature glue 17 has a temperature resistance of 1000 to 1200°C and an expansion coefficient of 5×10 - 6 ~ 8×10 - 6 / ℃, the filling amount error is controlled within ±5%. The material of the high emissivity coating 18 is a boron carbide-based composite material. The emissivity of the emissivity coating 18 in the wavelength range of 0.8-2.5μm is not less than 0.9, the coating thickness is 10-20 microns, and the coating is applied by plasma spraying technology, the spraying pressure is 2-4MPa, and the spraying distance is 150-200mm.

[0060] As shown in Table 6 below, after experimental testing, when the emissivity of the high emissivity coating 18 is 0.9, the thickness is 10 microns, the spraying pressure is 2MPa, and the spraying distance is 150 mm, the temperature measurement accuracy is ±3°C, and the coating thickness deviation is 5 microns. As the emissivity increases to 0.92, the thickness increases to 15 microns, the spraying pressure is 3MPa, and the spraying distance is 180 mm, the temperature measurement accuracy is improved to ±2°C, and the thickness deviation is reduced to 3 microns. When the emissivity is 0.95, the thickness is 20 microns, the spraying pressure is 4MPa, and the spraying distance is 200 mm, the temperature measurement accuracy is ±1.5°C, and the thickness deviation is 4 microns. The selected coating parameters can effectively improve the emissivity of the coating, reduce the temperature measurement error, ensure the uniformity of the coating, and improve the temperature measurement accuracy and reliability of the thermocouple.

[0061] In summary, 316L stainless steel protection tube 16 (wall thickness 1.5 - 2.5 mm, surface roughness Ra not exceeding 0.8 microns) provides good mechanical protection for the sensitive core. Temperature resistance 1000 - 1200℃, expansion coefficient 5×10 - 6 ~ 8×10 - 6 / ℃ and the filling amount error within ±5% ensures tight bonding. After the boron carbide-based composite material high-emissivity coating 18 (0.8-2.5μm wavelength emissivity not less than 0.9, thickness 10-20 microns) is coated with specific plasma spraying parameters, the experiment shows that the temperature measurement accuracy under different parameter combinations is between ±1.5℃ and ±3℃ and the thickness deviation is small, which effectively improves the accuracy and reliability of thermocouple temperature measurement, and the coating parameter optimization effect is significant.

[0062] Table 6

[0063] Experimental Grouping Emissivity Coating thickness (micrometers) Spraying pressure (MPa) Spraying distance (mm) Temperature measurement accuracy (℃) Coating uniformity (thickness deviation, μm) Group 1 0.9 10 2 150 ±3 5 Group 2 0.92 15 3 180 ±2 3 Group 3 0.95 20 4 200 ±1.5 4

[0064] The sensitive core is accurately installed into the stainless steel protection tube 16 and fixed with high temperature glue 17, so that the sensitive core is tightly combined with the protection tube, providing good mechanical protection for the sensitive core and effectively preventing it from being physically damaged in harsh environments.

[0065] The high emissivity coating 18 applied on the probe surface significantly enhances the sensitivity of the thermocouple to the radiation temperature and improves the measurement accuracy, enabling it to obtain temperature information more accurately in a high-temperature radiation environment. In the temperature measurement of high-temperature engine parts in the aerospace field, it can work stably and accurately measure the temperature in extremely high temperature and strong radiation environments, providing key data support for the safe operation and performance optimization of the engine.

[0066] In a specific embodiment, a method for manufacturing a tungsten-rhenium thermocouple for radiation temperature measurement comprises the following steps:

[0067] Reference Figure 2 , Insulating layer spin coating preparation process implementation steps:

[0068] Step 1: Take an appropriate amount of hafnium tetrachloride and dissolve it in 99.5% pure ethanol, stir it magnetically in a constant temperature water bath at 60°C for 2 hours to obtain a hafnium tetrachloride solution, add sodium hydroxide solution dropwise to the hafnium tetrachloride solution, continue stirring at room temperature for 1 hour to obtain a transparent microwave hydrothermal precursor solution, put the microwave hydrothermal precursor solution into a reactor, and then put the reactor into a microwave hydrothermal synthesizer for reaction, pour the product after microwave hydrothermal treatment into a centrifuge tube, and centrifuge and wash it. The washed product is freeze-dried to obtain hafnium oxide sol 1.

[0069] Step 2: Put a tungsten sheet 2 and a tungsten-rhenium sheet 3 with a length of 20 mm, a width of 10 mm, and a thickness of 3 mm into a beaker containing an acetone solution, put the beaker into an ultrasonic cleaning machine, set the cleaning temperature to 50°C, and the cleaning time to 30°C. After ultrasonic cleaning, the surfaces of the tungsten sheet 2 and the tungsten-rhenium sheet 3 are smooth and free of impurities. Place the tungsten sheet 2 as a substrate on the rotating platform 5 of the spin coater 4, and use a rubber-tipped dropper to drop the hafnium oxide solution 1 on the upper surface of the tungsten sheet 2. Set the parameters of the spin coater 4 to spin at a low speed of 600 rpm / min for 5 seconds, at a medium speed of 1500 rpm / min for 10 seconds, and at a high speed of 4000 rpm / min for 15 seconds. Start the spin coater 4 to rotate the tungsten sheet 2 until the hafnium oxide solution 1 is evenly covered on the upper surface of the tungsten sheet 2 without bubbles, scratches or other defects.

[0070] Step 3: Place the tungsten sheet 2 coated with the hafnium oxide solution 1 into a tubular furnace for heating, turn the inlet valve of the argon gas bottle, and introduce argon gas into the tubular furnace to create an oxygen-free environment in the furnace. Set the starting temperature of the tubular furnace to 25°C, increase the temperature at a rate of 10°C / min in the range of 25°C to 400°C, and keep it at 400°C for 1 hour. Increase the temperature at a rate of 10°C / min in the range of 400°C to 800°C, and keep it at 800°C for 1 hour. Then cool it naturally. After the temperature drops to room temperature, close the inlet valve of the argon gas bottle. After high-temperature sintering, the hafnium oxide solution 1 forms a micrometer-thick hafnium oxide insulating film 6 on the upper surface of the tungsten sheet. Repeat the above spin coating and sintering steps on the lower surface of the tungsten sheet 2 and the tungsten-rhenium sheet 3, so that both end surfaces of the tungsten sheet 2 and the tungsten-rhenium sheet 3 are coated with the hafnium oxide insulating film 6.

[0071] Reference Figure 3 and Figure 4 , Sensitive core preparation process implementation steps:

[0072] Step 4: Overlap and align the tungsten sheet 2 and the tungsten-rhenium sheet 3 coated with hafnium oxide insulating film 6 on both sides, and vertically place them in the slot 8 of the alloy clamp 7. Rotate the nut 9 to push the screw 10 to drive the insert 11 to move and clamp the tungsten sheet 2 and the tungsten-rhenium sheet 3. Set the parameters of the friction stir welding machine, and place the stirring head 12 perpendicular to the upper end surface dividing line of the tungsten sheet 2 and the tungsten-rhenium sheet 3. Press down 1mm at the starting position of the dividing line and start rotating. The stirring head 12 moves along the dividing line to frictionally bond the upper end surfaces of the tungsten sheet 2 and the tungsten-rhenium sheet 3. Under the action of friction heat and mechanical force, tungsten and tungsten-rhenium alloy are combined to form a high-quality weld 13. The weld depth is 1mm, which is consistent with the pressing depth of the stirring head 12. When the stirring head 12 approaches the end of the dividing line, the pressing amount and the rotation speed are gradually reduced. After welding is completed, use a grinder to clean the flash and burrs on the surface of the weld 13.

[0073] Step 5: Take out the welded tungsten sheet 2 and tungsten-rhenium sheet 3 as a whole from the alloy clamp bed 7, use a grinder to grind off a portion of the hafnium oxide insulating film 6 on the outer end faces of the tungsten sheet 2 and the tungsten-rhenium sheet 3 to expose a portion of the surface of the tungsten sheet 2 and the tungsten-rhenium sheet 3, and use a resistance welding gun to weld the tungsten wire 14 and the tungsten-rhenium wire 15 to the exposed surfaces of the tungsten sheet 2 and the tungsten-rhenium sheet 3, respectively, to form a temperature sensitive core of the thermocouple.

[0074] Reference Figure 5 , packaging shell assembly process implementation steps:

[0075] Step 6: Use the weld 13 between the tungsten sheet 2 and the tungsten sheet 3 as the head of the sensitive core, and the tungsten wire 14 and the tungsten-rhenium wire 15 as the tail of the sensitive core. Insert the entire sensitive core from the groove at the head of the stainless steel protective tube 16 until the head of the sensitive core is flush with the head of the stainless steel protective tube 16. Use a syringe to inject high-temperature glue 17 from the tail of the stainless steel protective tube 16 into the tube. Use a hot air gun to heat the stainless steel protective tube 16. The high-temperature glue 17 in the tube expands due to the heat and firmly bonds the sensitive core to the stainless steel protective tube 16.

[0076] Step 7: Take a cotton swab and dip it in an appropriate amount of high emissivity paint, and evenly apply the high emissivity paint on the surface of the thermocouple sensitive core head that is flush with the head of the stainless steel protection tube 16 to form a high emissivity coating 18 with a thickness of micrometer level.

[0077] Through the preparation process provided by the present invention, a tungsten-rhenium thermocouple for use in a high-temperature radiation environment can be quickly prepared. The hafnium oxide insulating layer formed by the sol-gel method and the spin coating method is thin and dense. The thermocouple node formed by the stir friction welding is stable, which improves the heat conduction speed, thereby accelerating the response speed. Further coating a high-emissivity coating 18 on the probe surface can significantly enhance the sensitivity of the sensor to the radiation temperature. Figure 6 As shown, the prepared tungsten-rhenium thermocouple can measure radiation temperature up to 3000°C and has a response speed of up to 20us. Compared with other traditional radiation temperature measurement equipment, it greatly improves the upper limit of temperature measurement, response speed and temperature measurement stability. It has low preparation cost, simple process, and is easy to popularize on a large scale. It can meet the strict requirements of energy, metallurgy and other industries for high-temperature radiation temperature measurement and has broad market application prospects.

[0078] In a second aspect, an embodiment of the present invention further discloses a tungsten-rhenium thermocouple for measuring radiation temperature. The tungsten-rhenium thermocouple for measuring radiation temperature is prepared according to the manufacturing method of the tungsten-rhenium thermocouple for measuring radiation temperature described in the first aspect, and its specific structure is as follows: Figure 5 shown.

[0079] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) to form a technical solution.

Claims

1. A method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature, characterized in that: The method comprises an insulating layer spin coating step, a sensitive core preparation step and a packaging tube shell assembly step, wherein the insulating layer spin coating step is specifically as follows: S1. Insulating layer spin coating step: using a sol-gel method to prepare hafnium tetrachloride into a hafnium oxide sol with a preset nanostructure and performance, and by controlling water bath stirring, solution dripping and reaction conditions, a precursor solution is obtained and converted into a sol; then, on a tungsten sheet and a tungsten-rhenium sheet that have been ultrasonically cleaned to remove impurities, the hafnium oxide sol is evenly and stably coated on the two end faces of the tungsten sheet and the tungsten-rhenium sheet by setting a multi-stage rotation speed and time control, and then sintered in a tubular furnace under a controlled heating, insulation and cooling program to form a hafnium oxide insulating film on the two end faces of the tungsten sheet and the tungsten-rhenium sheet; specifically, it also includes: S11, spin coating in stages by a spin coater: first spin coating at a low speed of 400-600 rpm / min for 3-7 seconds, then spin coating at a medium speed of 1200-1800 rpm / min for 8-12 seconds, and finally spin coating at a high speed of 3500-4500 rpm / min for 12-18 seconds, and during the spin coating process, the ambient temperature is maintained at 20-30° C. and the humidity is maintained at 40%-60%; S12. After spin coating, gradient sintering is carried out in the tubular furnace: the heating rate in the range of 20-30°C to 350-450°C is 8-12°C / min, and it is kept at 350-450°C for 45-75 minutes. The heating rate in the range of 350-450°C to 750-850°C is 10-15°C / min, and it is kept at 750-850°C for 60-90 minutes, followed by natural cooling. Argon with a purity of not less than 99.9% is introduced throughout the sintering process at a flow rate of 50-100 ml / min.

2. The method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to claim 1, characterized in that: The specific operation of the sol-gel method includes: The hafnium tetrachloride is placed in ethanol with a purity of not less than 99%, and magnetically stirred in a constant temperature water bath at 55-65° C. for 1.5-2.5 hours, a sodium hydroxide solution with a concentration of 1 mol / L is added dropwise and stirred at room temperature for 45-75 minutes to form the precursor solution, and then the precursor solution is placed in a reaction kettle in a microwave hydrothermal synthesizer with a microwave power of 4000 W to react for 3-5 hours, and the nano hafnium oxide sol is obtained by centrifugal washing at 3000-5000 rpm for 10-20 minutes and freeze-drying at -40--20° C. for 12-24 hours.

3. The method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to claim 1, characterized in that: The sensitive core preparation step specifically includes: S2, sensitive core preparation step: put the tungsten sheet and tungsten-rhenium sheet covered with the hafnium oxide insulating film into the slot of the alloy clamp bed and clamp them firmly, set the key parameters of the stir friction welding machine, make the stirring head vertically align with the upper end surface boundary line of the tungsten sheet and the tungsten-rhenium sheet, and use friction heat and mechanical force to achieve friction bonding of the upper end surfaces of the tungsten sheet and the tungsten-rhenium sheet to form a weld as a stable temperature measurement node by rotating the stirring head along the boundary line; then remove the specific area of ​​the hafnium oxide insulating layer on the surface of the tungsten sheet and the tungsten-rhenium sheet through a grinding process, and use welding technology to firmly weld the tungsten wire and the tungsten-rhenium wire to the exposed metal surface respectively, so as to construct a thermocouple sensitive core; In the sensitive core preparation step, the key parameters of the friction stir welding machine include the rotation speed, moving speed and welding pressure of the stirring head. The rotation speed of the stirring head is 800-1200 rpm, the moving speed is 3-7 mm / s, and the welding pressure is 150-250 Newtons.

4. The method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to claim 3, characterized in that: In the step of preparing the sensitive core, removing specific areas of the hafnium oxide insulating layer on the surfaces of the tungsten sheet and the tungsten-rhenium sheet comprises: The grinding area of ​​the hafnium oxide insulating layer is 5 to 15 square millimeters, and the grinding depth is 0.3 to 0.7 millimeters.

5. The method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to claim 1, characterized in that: The packaging tube shell assembly step specifically includes: S3, packaging tube shell assembly step: insert the prepared sensitive core into the stainless steel protection tube, ensure that the head of the sensitive core is flush with the head of the protection tube, use a syringe to inject high-temperature glue from the tail of the stainless steel protection tube into the tube to achieve the connection between the sensitive core and the protection tube; evenly apply a high-emissivity coating on the surface of the head of the thermocouple sensitive core; In the packaging tube shell assembly step, the stainless steel protection tube is made of 316L stainless steel, has a wall thickness of 1.5 to 2.5 mm, and a surface roughness Ra of no more than 0.8 μm.

6. The method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to claim 5, characterized in that: In the packaging tube shell assembly step, the high temperature glue has a temperature resistance of 1000-1200°C and an expansion coefficient of 5×10 -6 ~8×10 -6 / ℃, the filling amount error is controlled within ±5%.

7. The method for manufacturing a tungsten-rhenium thermocouple for measuring radiation temperature according to claim 5, characterized in that: In the packaging tube shell assembly step, the material of the high emissivity coating is a boron carbide-based composite material, the emissivity of the high emissivity coating is not less than 0.9 in the wavelength range of 0.8 to 2.5 μm, the coating thickness is 10 to 20 microns, and the coating is carried out using plasma spraying technology, the spraying pressure is 2 to 4 MPa, and the spraying distance is 150 to 200 mm.

8. A tungsten-rhenium thermocouple for measuring radiation temperature, characterized in that: The tungsten-rhenium thermocouple for radiation temperature measurement is prepared according to the manufacturing method of any one of claims 1 to 7.

Images