A temperature measuring thermocouple protective sleeve and temperature measuring device for continuously measuring high temperature copper liquid

Abstract

The utility model discloses a kind of temperature measuring thermocouple protective sleeve and temperature measuring device for continuous high-temperature copper liquid, belong to nonferrous smelting temperature measuring technical field, the protective sleeve adopts double-layer structure design, including high-purity corundum inner protective sleeve and high-temperature alloy outer protective sleeve, outer surface is coated with Al2O3-ZrO2 Compound coating. Multilayer graphite foil and metal mesh are alternately superimposed between inner and outer protective sleeve Heat stress buffer layer, end adopts conical sealing structure, the design effectively solves the technical problems such as short service life, poor thermal shock resistance, easy leakage of traditional protective sleeve in high-temperature copper liquid, realize in 1300 ℃ copper liquid Continuous work more than 8 months, thermal shock cycle number is more than 100 times, temperature measuring response time is less than 3 seconds, significantly improve temperature measuring reliability and service life, applicable to red copper continuous casting process Precision temperature monitoring.

Description

Technical Field

[0001] This utility model belongs to the field of continuous temperature measurement technology for copper liquid in non-ferrous metal smelting furnaces, specifically relating to a temperature measuring thermocouple protective sleeve and temperature measuring device for continuous measurement of high-temperature copper liquid, which is suitable for continuous monitoring of copper liquid temperature during continuous copper casting process. Background Technology

[0002] Temperature measurement of molten copper inside the furnace is a necessary procedure in the casting process. Its purpose is to ensure the stability and accuracy of temperature during heating and casting, thereby guaranteeing that the produced ingots meet certain quality standards. The temperature of the molten copper inside the furnace also affects the power consumption of the melting furnace inductor, thus influencing the power consumption per ton of product. Deviations in the molten copper temperature allow for timely detection and resolution of problems, preventing furnace leaks caused by temperature-related factors affecting the furnace refractory material.

[0003] For a long time, copper processing companies have used various temperature measurement methods, but all of them have the following technical problems:

[0004] 1. The protective sleeve has insufficient high temperature resistance and is prone to softening, deformation or corrosion in molten copper at temperatures above 1300℃.

[0005] 2. Insufficient mechanical strength; unable to withstand long-term scouring by molten copper and mechanical impact during feeding.

[0006] 3. Poor thermal shock resistance; prone to cracking under rapid cooling and heating conditions.

[0007] 4. Short service life; it generally needs to be replaced after only 2-3 months of use, which affects the continuity of production.

[0008] 5. The temperature measurement response is slow and cannot reflect changes in the temperature of the copper liquid in real time.

[0009] Patent CN220063201U discloses a COT thermocouple for stability measurement of an ethylene plant and its insertable protective sleeve, which adopts a double-layer protective tube structure, but does not solve the special technical problems in the high-temperature copper liquid environment, especially the problems of copper liquid corrosion resistance and thermal stress buffering. Utility Model Content

[0010] The purpose of this invention is to solve the above-mentioned technical problems and provide a temperature measuring thermocouple protection sleeve and temperature measuring device for continuous measurement of high-temperature copper liquid.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0012] A thermocouple protective sleeve for continuous high-temperature copper liquid measurement includes a thermocouple head shell, a connector, an outer protective sleeve, and an inner protective sleeve. The thermocouple head shell is fitted onto the outside of the thermocouple and is inserted into a mounting plate via the connector. The probe of the thermocouple extends through the thermocouple furnace lining brick from the other side of the mounting plate. The inner protective sleeve is fitted onto the probe, and the outer protective sleeve is fitted onto the inner protective sleeve. The inner protective sleeve is made of corundum tube with an alumina purity of not less than 99%. The outer protective sleeve is made of high-temperature alloy and has a coating on its outer surface. The inner protective sleeve and the outer protective sleeve are interference-fitted, and a thermal stress buffer layer is provided at the fit.

[0013] Furthermore, the buffer layer is composed of multiple layers of graphite foil and metal mesh, with 3-5 layers in total.

[0014] Furthermore, the outer protective sleeve has a conical sealing structure at its end, with a sealing angle α of 45±5°.

[0015] Furthermore, the coating is an Al2O3-ZrO2 composite coating, wherein the ZrO2 content is 20-30wt% and the coating thickness is 50-100μm.

[0016] Furthermore, the inner diameter of the inner protective sleeve is 4±0.1mm, the outer diameter is 6±0.1mm, and the wall thickness uniformity error is ≤0.05mm.

[0017] Furthermore, the temperature sensor head shell is provided with a display window.

[0018] Furthermore, the interference amount of the interference fit is 0.05-0.1 mm.

[0019] A continuous temperature measuring device includes a thermocouple protection sleeve as described above.

[0020] Compared with the prior art, the beneficial effects of this utility model are:

[0021] 1. This utility model, through the synergistic effect of the corundum inner sleeve (temperature resistance >1700℃) and the high-temperature alloy outer sleeve, combined with a special Al2O3-ZrO2 composite coating, can work continuously for more than 8 months in molten copper at 1300℃, which is more than twice the life of the prior art.

[0022] 2. The thermal stress buffer layer of this utility model can effectively alleviate thermal shock. Experiments show that it can withstand more than 100 cycles of rapid cooling and heating from room temperature to 1300℃.

[0023] 3. The high thermal conductivity and dimensional accuracy of the corundum material of this invention ensure that the temperature measurement response time is <3s, and the measurement accuracy is greatly improved;

[0024] 4. The unique conical sealing structure and composite coating of this utility model can effectively prevent copper liquid from penetrating, and it has been tested to work continuously for 5000 hours without leakage;

[0025] 5. The modular design of this utility model means that when the thermocouple is damaged, only the inner protective sleeve module needs to be replaced, without replacing the entire protective sleeve system, which greatly reduces maintenance costs and downtime. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of this utility model;

[0027] Figure 2 This is a schematic diagram of the internal structure of the present invention;

[0028] Figure 3 This is a schematic diagram of the buffer layer structure of this utility model;

[0029] Figure 4 for Figure 2 A magnified view of a portion of region A in the middle;

[0030] In the diagram: 1-Thermostat head shell; 2-Connector; 3-Mounting plate; 4-Thermocouple furnace lining brick; 5-Outer protective sleeve; 6-Conical sealing structure; 7-Buffer layer; 8-Inner protective sleeve; 9-Probe; 10-Display window. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0032] Example 1

[0033] A thermocouple protective sleeve for continuous high-temperature copper liquid measurement includes a thermocouple head shell 1, a connector 2, an outer protective sleeve 5, and an inner protective sleeve 8. The thermocouple head shell 1 is fitted over the outside of the thermocouple and is inserted into a mounting plate 3 via the connector 2. The thermocouple head shell 1 has a display window 10 for viewing the real-time temperature value. The probe 9 of the thermocouple extends from the other side of the mounting plate 3 through the thermocouple furnace lining brick 4. The probe 9 is made of 0.4mm platinum-rhodium wire. The inner protective sleeve 8 is fitted over the probe 9. The inner protective sleeve 8 is made of 99.6% high-purity corundum tube, with an inner diameter of 4.0mm, an outer diameter of 6.0mm, and a length of 232m after precision machining. The wall thickness uniformity error is controlled within 0.03mm. The outer protective sleeve 5 is made of GH3030 high-temperature alloy and is fitted on the inner protective sleeve 8. The outer surface is coated with an 80μm thick Al2O3-ZrO2 composite coating, in which the ZrO2 content is 25wt%. The end of the outer protective sleeve 5 is provided with a conical sealing structure 6 with a sealing angle α of 45°. When the inner protective sleeve 8 and the outer protective sleeve 5 are assembled, an interference fit of 0.08mm is adopted, and a thermal stress buffer layer 7 is provided at the mating point. The thermal stress buffer layer 7 is composed of 3 layers of 0.1mm thick graphite foil and 2 layers of 0.05mm thick stainless steel mesh (mesh wire diameter 0.05mm) alternately stacked.

[0034] The alumina purity of the inner protective sleeve 8 high-purity corundum tube can also be any value of ≥99%.

[0035] The number of layers in the buffer layer 7 can also be any value between 3 and 5.

[0036] The ZrO2 content in the coating can be any value between 20-30 wt%, and the coating thickness can also be any value between 50-100 μm.

[0037] The inner diameter of the inner protective sleeve 8 can be 4±0.1mm, the outer diameter can be 6±0.1mm, and the wall thickness uniformity error can be ≤0.05mm.

[0038] The interference amount of the interference fit can also be any value between 0.05 and 0.1 mm.

[0039] The outer protective sleeve 5 can also be made of GH3044 or Inconel 600 series high-temperature alloy materials.

[0040] The interference fit (0.05-0.1mm) between the inner and outer protective sleeves is mainly to ensure that the two are in close contact under high temperature working conditions, reduce the thermal resistance caused by air gaps, ensure the temperature measurement response speed, and prevent abnormal noise or loosening under vibration or fluid scouring in the furnace.

[0041] This interference fit is designed based on the hot operating temperature. When the system cools from a high temperature of 1300℃ to room temperature, the coefficient of thermal expansion of the outer protective sleeve 5 (high temperature alloy) is relatively large (typically 14-18×10⁻). 6 / ℃), the shrinkage is greater after cooling, and the inner protective sleeve 8 (corundum) has a smaller coefficient of thermal expansion (usually 6-8×10⁻). 6 / ℃), the shrinkage after cooling is small. After cooling, the original interference fit becomes very loose, and it even becomes easy to separate due to the greater shrinkage of the alloy. Therefore, the modules are easy to remove and replace during cold maintenance.

[0042] A continuous temperature measuring device includes a thermocouple protection sleeve as described above.

[0043] Test method:

[0044] Take 10 protective sleeves and 10 traditional graphite sleeves prepared in this embodiment;

[0045] Continuous operation tests were conducted in a 1300℃ copper liquid environment, and the service life was recorded.

[0046] Thermal shock cycling test: Place the furnace at 1300℃ from room temperature, hold for 5 minutes, then remove and air cool to room temperature, and record the number of cycles before cracking.

[0047] Response time measurement: The time taken to reach 63.2% of the final temperature was recorded when the sample was immersed in 1300℃ copper liquid from room temperature.

[0048] Conduct a leak-proof test: operate continuously in molten copper at 1300℃ and check regularly for copper leakage.

[0049] The test data of this embodiment are compared with those of the traditional graphite sleeve as follows:

[0050] Performance indicators Example 1 Traditional graphite sleeve Average service life 280 days 30 days thermal shock cycles 105 times 28 times Temperature measurement response time 2.8s 5.2s Copper corrosion resistance at 1300℃ 5000h no corrosion Corrosion begins after 1500 hours.

[0051] Test results show that the protective sleeve of this utility model is significantly superior to the traditional graphite sleeve in all performance indicators, especially in terms of service life and thermal shock resistance, and completely solves the technical problems mentioned in the background art.

[0052] Example 2:

[0053] It is basically the same as Example 1, except that:

[0054] The inner protective sleeve 8 is made of corundum tube with 99.7% pure alumina, the outer protective sleeve 5 is made of Inconel 600 alloy with a coating thickness of 100μm and an interference fit of 0.1mm, and the buffer layer 7 adopts a 5-layer structure (3 layers of graphite foil + 2 layers of metal mesh).

[0055] Test results: The protective sleeve of this embodiment can still work stably for more than 6 months in copper liquid at 1350℃, and can withstand 120 cycles of rapid cooling and heating from room temperature to 1350℃ in thermal shock cycle test.

[0056] Example 3

[0057] It is basically the same as Example 1, except that:

[0058] The Al2O3-ZrO2 composite coating contains 20wt% ZrO2 and has a coating thickness of 50μm. The buffer layer 7 has a 4-layer structure (2 layers of graphite foil + 2 layers of metal mesh) and an interference fit of 0.05mm.

[0059] Test results: The protective sleeve in this embodiment maintained good performance after working in molten copper at 1250℃ for 9 months, with a thermal response time of 2.9s.

[0060] Example 4

[0061] It is basically the same as Example 1, except that:

[0062] The Al2O3-ZrO2 composite coating contains 30wt% ZrO2 and has a coating thickness of 100μm. The buffer layer 7 has a 5-layer structure (3 layers of graphite foil + 2 layers of metal mesh) and an interference fit of 0.1mm.

[0063] Test results: The protective sleeve of this embodiment has stable performance after working in molten copper at 1320℃ for 7 months, and is particularly suitable for high-temperature conditions.

[0064] Comprehensive benefit analysis

[0065] The multi-layer structure introduces a slight delay in thermal response; however, considering all factors, the benefits of this invention far outweigh its disadvantages, as detailed below:

[0066] Trade-off between response speed and reliability: In the application scenario of continuous temperature measurement of molten copper in the furnace, a probe with a fast response (2-3 seconds) but which can only be used for 3 days and then fails is far less reliable than a probe with a slightly slower response (10-15 seconds) but which can work stably for 8 months. In the continuous casting temperature measurement process, the long-term trend stability of temperature is far more important than the instantaneous response in seconds.

[0067] The minor system errors introduced by this solution are stable and predictable, and can be compensated and calibrated by instruments or system software to eliminate their impact. In contrast, errors caused by bushing corrosion, thermocouple short circuits or breaks are random, abrupt, and uncompensable, which can lead to production accidents.

[0068] This invention sacrifices negligible response speed in exchange for exponentially improved measurement reliability, stability, and service life. It can ensure that the thermocouple can work in a stable environment for up to several months, thereby continuously outputting accurate and reliable temperature signals.

[0069] In summary, this design not only considered "whether it will have an impact," but also provided a comprehensive solution on "how to minimize the impact and make it far outweigh the benefits," transforming it from a consumable into a reliable industrial sensor component, ultimately greatly optimizing and ensuring the overall temperature measurement effect.

[0070] The working process of this utility model:

[0071] First, the assembled temperature measuring device is fixed to the predetermined installation position on the furnace wall by the mounting plate 3. The end of the outer protective sleeve 5 passes through the thermocouple furnace lining brick 4 embedded in the furnace wall and is precisely inserted into the copper liquid. By calculating and controlling the insertion depth, it is ensured that the temperature measuring end is located in the typical temperature measuring area of ​​150mm-200mm below the liquid surface. The temperature here is representative and can effectively avoid direct interference from liquid surface disturbance and feeding operation.

[0072] When the heat from the high-temperature molten copper (approximately 1080℃-1300℃) continuously acts on the end of the protective sleeve, the heat transfer process is as follows: The heat first passes through the outer protective sleeve 5, which has excellent resistance to high-temperature corrosion, and its surface Al2O3-ZrO2 composite coating; the heat then passes through the buffer layer 7, which is composed of multiple layers of graphite foil and metal mesh, effectively absorbing and buffering the thermal stress caused by rapid temperature changes, while efficiently transferring the heat inward due to the material's good thermal conductivity; the heat is conducted to the inner protective sleeve 8, where the high thermal conductivity of the corundum material and precise wall thickness control ensure that the heat can penetrate the tube wall quickly and uniformly; finally, the heat reaches the measurement contact of the probe 9;

[0073] When probe 9 is heated, it generates a weak millivolt-level thermoelectric electromotive force corresponding to the temperature height based on the Seebeck effect. This electrical signal is led out from the thermocouple through a high-temperature resistant compensating wire, passes through the entire protective sleeve, and is connected to the temperature measuring terminal located on the outside of the furnace body. The signal is then transmitted to an external temperature display instrument, recorder, or process control system (DCS / PLC) through a connecting cable, and converted into an intuitive digital temperature display or used in process control.

[0074] Resistance to mechanical shock and corrosion: The outer protective sleeve 5 serves as the first line of defense, with its high-strength alloy body and anti-corrosion coating, resisting the flow and erosion of molten copper, chemical corrosion, and physical collisions that may occur during feeding.

[0075] Thermal stress resistance and insulation: The thermal stress buffer layer 7 absorbs the expansion / contraction stress caused by drastic temperature changes, preventing brittle fracture of the corundum inner tube. The corundum inner protective sleeve 8 ensures reliable insulation between the thermocouple wire and the metal outer sleeve at all times, preventing signal short circuits.

[0076] Leakage-proof seal: The conical sealing structure 6 at the end of the sleeve and the overall interference fit and threaded connection together form a multi-layer sealing barrier, effectively preventing copper vapor or molten material from seeping in along the gaps and protecting the internal thermocouple from contamination and short circuits.

[0077] When the thermocouple itself reaches the end of its service life or is damaged due to accident, there is no need to replace the entire protective sleeve system. Simply loosen the connector 2 and the thermocouple head shell 1, along with the inner protective sleeve 8 and probe 9, can be pulled out from the fixed outer protective sleeve 5 as a module for replacement. This greatly reduces maintenance costs and downtime, demonstrating the superiority of its modular design.

Claims

1. A thermocouple protection sleeve for continuous high-temperature copper liquid measurement, characterized in that: The device includes a thermometer head shell (1), a connector (2), an outer protective sleeve (5), and an inner protective sleeve (8). The thermometer head shell (1) is fitted on the outside of the thermometer and is inserted into the mounting plate (3) through the connector (2). The probe (9) of the thermometer extends out from the other side of the mounting plate (3) through the thermocouple furnace lining brick (4). The inner protective sleeve (8) is fitted on the probe (9), and the outer protective sleeve (5) is fitted on the inner protective sleeve (8). The inner protective sleeve (8) is a corundum tube with an alumina purity of not less than 99%. The outer protective sleeve (5) is made of high-temperature alloy and has a coating on its outer surface. The inner protective sleeve (8) and the outer protective sleeve (5) are press-fitted together and a thermal stress buffer layer (7) is provided at the fit.

2. The thermocouple protection sleeve for continuous high-temperature copper liquid measurement according to claim 1, characterized in that, The buffer layer (7) is composed of multiple layers of graphite foil and metal mesh, with 3-5 layers.

3. The thermocouple protection sleeve for continuous high-temperature copper liquid measurement according to claim 1, characterized in that, The outer protective sleeve (5) has a conical sealing structure (6) at its end, with a sealing angle α of 45±5°.

4. The thermocouple protection sleeve for continuous high-temperature copper liquid measurement according to claim 1, characterized in that, The coating thickness is 50-100 μm.

5. A thermocouple protection sleeve for continuous high-temperature copper liquid measurement according to claim 1, characterized in that, The inner diameter of the inner protective sleeve (8) is 4±0.1mm, the outer diameter is 6±0.1mm, and the wall thickness uniformity error is ≤0.05mm.

6. A thermocouple protection sleeve for continuous high-temperature copper liquid measurement according to claim 1, characterized in that, The thermometer head shell (1) is provided with a display window (10).

7. A thermocouple protection sleeve for continuous high-temperature copper liquid measurement according to claim 1, characterized in that, The interference amount of the interference fit is 0.05-0.1 mm.

8. A continuous temperature measuring device, characterized in that: It includes a thermocouple protection sleeve as described in any one of claims 1-7.

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