Temperature sensor for warm compounding and manufacturing method thereof

Abstract

The application provides a temperature sensor for a warm-pressing composite working condition and a manufacturing method thereof. The temperature sensor comprises an insulating protection tube, a thermocouple, an insulating filling body, a thickened sealing head and a wiring terminal. The insulating protection tube has an end cavity inside. A temperature measuring junction of the thermocouple is located in the end cavity and is wrapped by the insulating filling body. The thickened sealing head has a semispherical structure. A flat bottom surface of the thickened sealing head is laser-sealed to an end of the insulating protection tube to seal the temperature measuring junction and the insulating filling body in the end cavity. The manufacturing method of the temperature sensor comprises the following steps: thermocouple wire welding, insulating powder vibration filling and high-temperature solidification, thickened sealing head laser welding and wiring terminal assembly. Through the above method, the pressure resistance and sealing performance of the temperature sensor measuring end are significantly improved, and the temperature measuring precision can be maintained for a long time in a high-temperature and high-pressure environment of the warm-pressing composite working condition.

Description

Technical Field

[0001] This invention relates to the field of temperature sensor technology, and in particular to a temperature sensor for combined temperature and pressure conditions and its manufacturing method. Background Technology

[0002] Temperature-pressure composite processing technology is a process for treating materials under high temperature and high pressure environments, widely used in high-end manufacturing fields such as aerospace, nuclear energy, and medical. Accurate temperature measurement is crucial for ensuring product quality and optimizing process parameters during temperature-pressure composite processing. However, this environment is characterized by high temperatures (typically 600℃-1000℃), high pressures (up to 20MPa), and highly corrosive media. Traditional thermocouples are prone to insulation degradation, measurement terminal damage, and signal drift under these conditions, failing to meet long-term stable temperature measurement requirements. N-type thermocouples, as a commonly used temperature sensor, offer advantages such as a wide temperature range (-270℃-1300℃), good stability, and strong oxidation resistance, theoretically making them suitable for temperature-pressure composite environments. However, the measurement terminal structure of existing temperature sensors is relatively weak, easily deformed or even broken under high pressure. Furthermore, media penetration under high temperature and high pressure environments reduces the insulation resistance between the thermocouple wire and the insulation layer, thus affecting measurement accuracy. Therefore, there is an urgent need to develop a temperature sensor and its fabrication method that can adapt to the harsh environment of combined temperature and pressure conditions, in order to solve technical problems such as easy deformation of the measuring end, poor sealing, and insufficient long-term stability. Summary of the Invention

[0003] To address the above problems, this invention proposes a temperature sensor for combined temperature and pressure conditions and its manufacturing method.

[0004] A temperature sensor for combined temperature and pressure conditions includes: an insulating protective tube extending axially, having a hollow cavity inside, and having an end cavity at the measuring end that communicates with the hollow cavity;

[0005] A thermocouple is installed inside the insulating protective tube. It consists of a positive thermocouple wire and a negative thermocouple wire. The ends of the two thermocouple wires are connected to form a temperature measuring contact, which is located in the end cavity.

[0006] An insulating filler, which fills the end cavity of the insulating protective tube and wraps the temperature measuring contact and part of the thermocouple, is composed of insulating powder that has been cured at high temperature.

[0007] The thickened end cap has a hemispherical structure, with its flat bottom surface sealed to the end of the insulating protective tube and its spherical surface facing outward. The thickened end cap encloses the insulating filler and temperature measuring contact within the end cavity.

[0008] A terminal block is located at the other end of the insulating protective tube and electrically connected to the cold junction of the thermocouple. The terminal block includes a terminal block, an insulating shell, and a sealing connector, and is used to realize electrical signal output.

[0009] Preferably, the height between the apex of the spherical surface and the flat bottom surface of the thickened end cap is in the range of 3.5mm-5.5mm, and this height constitutes the thickened dimension of the thickened end cap.

[0010] Preferably, the thickened end cap is made of GH2520 high-temperature alloy material, the insulating protective tube is made of corundum ceramic tube, and the ends of the thickened end cap and the insulating protective tube are connected by laser welding to form a sealed connection.

[0011] Preferably, the insulating powder is alumina ceramic powder, and the filling density of the insulating filler is ≥95%.

[0012] Preferably, the positive electrode thermocouple wire is a nickel-chromium-silicon alloy wire, and the negative electrode thermocouple wire is a nickel-silicon-magnesium alloy wire, with the wire diameter ranging from 0.5 mm to 1.0 mm.

[0013] A method for manufacturing the above-mentioned temperature sensor includes the following steps:

[0014] S1. Weld the ends of the positive and negative thermocouple wires to form a temperature measuring contact.

[0015] S2. Pass the welded thermocouple through the insulating protective tube so that the temperature measuring contact is located in the end cavity of the insulating protective tube;

[0016] S3. Insulating powder is filled into the end cavity by vibration and pressure, and then high temperature curing is performed to form an insulating filler.

[0017] S4. Connect the flat bottom surface of the thickened end cap to the end of the insulating protective tube, and use laser welding to seal the flat bottom surface to the end of the insulating protective tube so that the spherical surface faces outward, and use inert gas protection during the welding process.

[0018] S5. Weld the other end of the thermocouple to the terminal block, install the terminal block into the insulating housing, and then seal the insulating housing to the insulating protective tube through the sealing joint.

[0019] Preferably, the welding in step S1 is argon arc welding, with a welding current of 5A to 10A, an argon flow rate of 5L / min to 10L / min, and a welding time of 1s to 3s.

[0020] Preferably, in step S3, the high-temperature curing temperature is 800℃~1000℃, and the heat preservation time is 2h~3h.

[0021] Preferably, in step S4, the laser welding process parameters are: power 100W~200W, welding speed 5mm / s~10mm / s, shielding gas is argon, flow rate 8L / min~12L / min.

[0022] Preferably, after step S4, an airtightness test is performed on the weld, with a test pressure of 20 MPa and a holding time of 30 min.

[0023] The beneficial effects of this invention are as follows: By setting a hemispherical thickened end cap at the measuring end and using laser welding to seal it to the end of the insulating protective tube, the wall thickness and hemispherical structure of the thickened end cap can effectively disperse high pressure stress, significantly improve the pressure resistance of the measuring end, and prevent deformation or breakage of the measuring end under temperature and pressure combined working conditions; by laser welding the thickened end cap to the insulating protective tube, and combining it with the high-density insulating filler (filling density ≥95%) filled and cured inside the insulating protective tube, a fully sealed structure of the measuring end is achieved, which can effectively block the penetration of external corrosive media, ensure the insulation performance of the thermocouple, and extend the service life of the sensor. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the internal structure of the temperature sensor's measuring end.

[0025] Figure 2 This is a schematic diagram of the manufacturing process of a temperature sensor.

[0026] Figure label:

[0027] 1. Insulating protective tube; 2. Thermocouple; 21. Positive thermocouple wire; 22. Negative thermocouple wire; 23. Temperature measuring contact; 3. Insulating filler; 4. Thickened end cap. Detailed Implementation

[0028] The technical solution protected by this invention will be described in detail below with reference to the accompanying drawings.

[0029] This application provides a temperature sensor for combined temperature and pressure conditions, such as... Figure 1 As shown, the sensor mainly includes an insulating protective tube 1, a thermocouple 2, an insulating filler 3, a thickened end cap 4, and wiring terminals. It is suitable for temperature and pressure composite working conditions of 1200℃ and 20MPa. Compared with existing temperature sensors, it has better structural strength and sealing performance, which can effectively ensure the accuracy of temperature measurement.

[0030] The insulating protective tube 1 extends axially and has a hollow cavity inside. At one end of the insulating protective tube 1 (i.e., the measuring end), an end cavity communicating with the hollow cavity is provided to accommodate the temperature measuring contact 23 of the thermocouple 2 and the insulating filler 3. The diameter of the end cavity is set in the range of 3mm-5mm, and the wall thickness is set in the range of 1mm-2mm. In this embodiment, the insulating protective tube 1 is made of high-temperature resistant, high-strength corundum ceramic tube. Corundum ceramic tube has excellent high-temperature stability and can effectively protect the internal thermocouple 2 from the influence of the external environment.

[0031] Thermocouple 2 is housed within the hollow cavity of the insulating protective tube 1 and consists of a positive (NP) thermocouple wire 21 and a negative (NN) thermocouple wire 22. Specifically, the positive thermocouple wire 21 is made of nickel-chromium-silicon alloy, and the negative thermocouple wire 22 is made of nickel-silicon-magnesium alloy. Both thermocouple wires have a purity ≥99.99% and a wire diameter ranging from 0.5mm to 1.0mm (selectable according to the temperature measurement range and service life requirements). The ends of the two thermocouple wires are welded together to form a temperature sensing contact 23, which is located within the end cavity of the insulating protective tube 1. Argon arc welding is used to ensure a firm position of the temperature sensing contact 23 and to prevent defects such as pores and cracks that could affect measurement accuracy.

[0032] The insulating filler 3 fills the end cavity of the insulating protective tube 1 and wraps the temperature measuring contact 23 and part of the thermocouple 2. The insulating filler 3 is formed by filling high-purity alumina ceramic powder (particle size 10μm~20μm) under vibration and pressure, and then curing it at 900℃ for 2.5 hours, so that the filling density of the insulating filler 3 is ≥95%. This insulating filler 3 can not only fix the temperature measuring contact 23 and the two thermocouple wires in the end cavity to prevent displacement or vibration under high pressure, but also significantly improve the insulation performance of the measuring end and avoid signal interference.

[0033] The thickened end cap 4 has a hemispherical structure, with its flat bottom surface sealed to the end of the insulating protective tube 1, and the spherical surface facing outwards. The height H between the apex of the spherical surface and the flat bottom surface is 3.5mm-5.5mm, which constitutes the thickened dimension of the end cap (compared to the 0.5mm-1.0mm thickness of a conventional thin-walled end cap). The thickened end cap 4 is made of GH2520 high-temperature alloy material, giving it high-temperature and high-pressure resistance. Its hemispherical structure can evenly distribute external pressure to the end cap surface when subjected to high pressure, avoiding stress concentration. Furthermore, its thickened dimension provides compressive strength far exceeding that of ordinary thin-walled end caps. This allows the thickened end cap 4 to withstand the working pressure (20MPa) under combined temperature and pressure conditions, effectively preventing plastic deformation or cracking of the measuring end under high pressure.

[0034] The flat bottom surface of the thickened end cap 4 is laser-welded to the end of the insulating protective tube 1 to form a sealed connection. An inert gas (such as argon) is used for protection during the welding process to prevent weld oxidation and ensure a uniform, porosity-free weld. Preferably, the flat bottom surface of the thickened end cap 4 is polished before welding to achieve a surface roughness Ra≤0.8μm, ensuring a tight fit with the insulating filler 3. The welding of the thickened end cap 4 to the insulating protective tube 1, combined with the internal insulating filler 3, achieves a complete seal at the measuring end of the temperature sensor, effectively preventing the penetration of external corrosive media, ensuring the insulation performance of the internal thermocouple, and extending its service life.

[0035] A terminal (not shown) is located at the other end of the insulating protective tube 1 and is electrically connected to the thermocouple 2. The terminal includes a terminal block, an insulating shell, and a sealed connector. Specifically, the terminal block is made of copper alloy to ensure its conductivity; the insulating shell is made of polytetrafluoroethylene (PTFE), which has excellent insulation properties and corrosion resistance.

[0036] The cold end of the thermocouple wire is soldered to the terminal block, which is then installed in an insulating housing. The insulating housing is sealed to the insulating protective tube via a sealing joint. The sealing joint uses a threaded sealing structure and is combined with a high-temperature resistant sealing gasket to ensure sealing performance and prevent external media from seeping into the interior.

[0037] This application also provides a specific manufacturing method for the aforementioned temperature sensor, such as... Figure 2 As shown, it includes the following steps:

[0038] S1, Welding of thermocouple temperature sensing contacts

[0039] Thermocouple wires conforming to GB / T16839.1-2018 standard (including positive and negative electrodes) were selected. The positive electrode thermocouple wire 21 was made of nickel-chromium-silicon alloy, and the negative electrode thermocouple wire 22 was made of nickel-silicon-magnesium alloy. The ends of the two thermocouple wires were aligned and welded using argon arc welding. The welding parameters were set as follows: welding current 5A-10A, argon flow rate 5L / min-10L / min, and welding time 1s-3s. After welding, the weld joint 23 underwent visual inspection and non-destructive testing to ensure no defects were found.

[0040] S2, Pipe positioning

[0041] A corundum ceramic tube conforming to GB / T 10303-2015 standard is selected as the insulating protective tube. The welded thermocouple 2 is passed through the corundum ceramic protective tube so that the temperature measuring contact 23 is located in the end cavity of the insulating protective tube 1.

[0042] S3, Formation of insulating filler

[0043] High-purity alumina ceramic powder (particle size 10μm-20μm) is vibrated into the end cavity and appropriate pressure is applied during the filling process until the powder fills the cavity and is compacted, so that the filling density is ≥95%. After filling, high-temperature curing treatment is performed at a curing temperature of 800℃-1000℃ for 2h-3h to form a strong insulating filler 3.

[0044] S4, Laser welding of thickened end caps

[0045] Before welding, the flat bottom surface of the thickened end cap 4 and the end face of the insulating protective tube 1 are polished to a surface roughness Ra≤0.8μm and cleaned thoroughly. The flat bottom surface of the thickened end cap 4 is then butt-jointed and aligned with the end of the insulating protective tube 1. Laser welding is used to seal the flat bottom surface to the end of the insulating protective tube, with the spherical surface facing outwards. Inert gas protection is used during the welding process. Welding parameters are set as follows: power 100W-200W, welding speed 5mm / s-10mm / s, argon gas as the protective gas, flow rate 8L / min-12L / min. After welding, the weld is ground to ensure a smooth surface. An airtightness test is performed after welding, with a test pressure of 20 MPa and a pressure holding time of 30 minutes to ensure no leakage in the weld.

[0046] S5. Assembly of the terminal block

[0047] Solder the other end (cold junction) of thermocouple 2 to the terminal block (copper alloy). Then, insert the terminal block into the PTFE insulating shell. Finally, seal the insulating shell to the insulating protective tube using a threaded sealing joint, tighten the sealing joint, and use a high-temperature resistant sealing gasket to ensure overall sealing performance.

[0048] Furthermore, the following performance tests were performed on the manufactured temperature sensor:

[0049] (1) Insulation resistance test: The insulation resistance between the thermocouple wire and the thickened end cap and insulating protective tube is measured at room temperature using an insulation resistance tester. If the measured insulation resistance is ≥100MΩ, the design requirements are met.

[0050] (2) Temperature measurement accuracy test: The thermocouple is placed in a high-temperature calibration furnace and the temperature measurement accuracy is calibrated at different temperature points (such as 500℃, 1000℃, 1300℃). The measurement error is limited to ≤±0.5%t (t is the measured temperature), which meets the high-precision temperature measurement requirements of temperature and pressure composite working conditions.

[0051] (3) High temperature and high pressure performance test: The thermocouple is placed in a temperature and pressure composite working condition simulation device, and the temperature is set to 800℃ and the pressure to 20MPa, and the test is carried out continuously for 100h. During the test, the output signal of the thermocouple is monitored in real time. If the signal is stable and there is no obvious drift, the insulation resistance is still ≥50MΩ after the test, and there is no deformation or trace of medium penetration at the measuring end. Then it meets the requirements.

[0052] (4) Corrosion resistance test: The thermocouple is placed in a simulated corrosive medium (such as high-temperature water vapor or acidic gas) and tested continuously for 500 hours. After the test, the appearance of the measuring end and the insulating protective tube is checked. If there are no obvious corrosion marks and the temperature measurement accuracy error is still within the allowable range, then it meets the requirements.

[0053] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A temperature sensor for combined temperature and pressure conditions, characterized in that, include: An insulating protective tube (1) extends axially, has a hollow cavity inside, and has an end cavity at the measuring end that communicates with the hollow cavity; Thermocouple (2) is installed inside the insulating protective tube (1). It is composed of a positive thermocouple wire (21) and a negative thermocouple wire (22). The ends of the two thermocouple wires are connected to form a temperature measuring contact (23). The temperature measuring contact (23) is located in the end cavity. An insulating filler (3) is filled into the end cavity of the insulating protective tube (1) and wraps the temperature measuring contact (23) and part of the thermocouple (2). The insulating filler (3) is composed of insulating powder that has been cured at high temperature. The thickened end cap (4) has a hemispherical structure. Its flat bottom surface is sealed to the end of the insulating protective tube (1). Its spherical surface is set outward. The thickened end cap (4) encloses the insulating filler (3) and the temperature measuring contact (23) in the end cavity. A terminal block is located at the other end of the insulating protective tube and electrically connected to the cold junction of the thermocouple. The terminal block includes a terminal block, an insulating shell, and a sealing connector, and is used to realize electrical signal output.

2. The temperature sensor for combined temperature and pressure conditions according to claim 1, characterized in that, The height H between the apex of the spherical surface and the flat bottom surface of the thickened end cap (4) ranges from 3.5mm to 5.5mm, and this height constitutes the thickened dimension of the thickened end cap (4).

3. The temperature sensor for combined temperature and pressure conditions according to claim 1, characterized in that, The thickened end cap (4) is made of GH2520 high-temperature alloy material, and the insulating protective tube (1) is made of corundum ceramic tube. The ends of the thickened end cap (4) and the insulating protective tube (1) are connected by laser welding to form a sealed connection.

4. The temperature sensor for combined temperature and pressure conditions according to claim 1, characterized in that, The insulating powder is made of alumina ceramic powder, and the filling density of the insulating filler (3) is ≥95%.

5. The temperature sensor for combined temperature and pressure conditions according to claim 1, characterized in that, The positive electrode thermocouple wire (21) is a nickel-chromium-silicon alloy wire, and the negative electrode thermocouple wire (22) is a nickel-silicon-magnesium alloy wire, with a wire diameter range of 0.5 mm to 1.0 mm.

6. A method for manufacturing a temperature sensor as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Weld the ends of the positive electrode thermocouple wire (21) and the negative electrode thermocouple wire (22) to form a temperature measuring contact (23). S2. Pass the welded thermocouple (2) through the insulating protective tube (1) so that the temperature measuring contact (23) is located in the end cavity of the insulating protective tube (1); S3. Insulating powder is filled into the end cavity by vibration and pressure, and then high temperature curing is performed to form an insulating filler (3). S4. Connect the flat bottom surface of the thickened end cap (4) to the end of the insulating protective tube (1), and use laser welding to seal the flat bottom surface to the end of the insulating protective tube (1), so that the spherical surface faces outward, and use inert gas protection during the welding process. S5. Weld the other end of the thermocouple (2) to the terminal block, and install the terminal block into the insulating housing. Then, seal the insulating housing to the insulating protective tube (1) through the sealing joint.

7. The manufacturing method according to claim 6, characterized in that, The welding described in step S1 is argon arc welding, with a welding current of 5A to 10A, an argon flow rate of 5L / min to 10L / min, and a welding time of 1s to 3s.

8. The manufacturing method according to claim 6, characterized in that, In step S3, the high-temperature curing temperature is 800℃~1000℃, and the holding time is 2h~3h.

9. The manufacturing method according to claim 6, characterized in that, In step S4, the laser welding process parameters are: power 100W~200W, welding speed 5mm / s~10mm / s, shielding gas is argon, flow rate 8L / min~12L / min.

10. The manufacturing method according to claim 6, characterized in that, Step S4 is followed by an airtightness test of the weld, with a test pressure of 20 MPa and a holding time of 30 min.

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