A continuous casting billet temperature measuring device and method based on electromagnetic induction

Abstract

The application relates to the field of steel continuous casting production, and particularly discloses a continuous casting billet temperature measuring device and method based on electromagnetic induction, which comprises an excitation coil and an induction coil. The excitation coil is composed of a first shell, a built-in iron core and a first coil wound on the iron core, the shell is provided with a first cooling water inlet and outlet to form an independent cooling loop. The induction coil is composed of a second shell and a second coil encapsulated in the second shell, the shell is provided with a second cooling water inlet and outlet to form another independent cooling loop. The excitation coil and the induction coil are coaxially arranged, and the induction coil is arranged between the excitation coil and a straightening section of the continuous casting billet to be measured. The structure ensures stable operation and temperature rise control of the coil under harsh working conditions through independent closed-loop cooling, and the optimized coaxial near-field arrangement enables the induction coil to more sensitively capture magnetic field disturbance caused by temperature change of the billet, so that high-precision and high-stability non-contact online measurement of the surface temperature of the continuous casting billet is realized.

Description

Technical Field

[0001] This invention relates to the field of continuous casting of steel, and in particular to a temperature measuring device and method for continuous casting billets based on electromagnetic induction. Background Technology

[0002] In the continuous casting process of steel, high-temperature molten steel enters the crystallizer through an immersion nozzle, where it rapidly forms an initial shell under the cooling effect of the copper crystallizer walls. Subsequently, the continuously cast billet is pulled out of the crystallizer by a straightening machine and enters the secondary cooling zone, where it is forcibly cooled by water spray or air mist, causing its surface temperature to continuously decrease and the shell thickness to gradually increase until it is completely solidified. The surface temperature of the continuously cast billet is a key parameter characterizing its solidification state and cooling process, and has a decisive influence on the quality of the final product (such as the uniformity of internal structure, and the tendency for surface and corner cracks). Therefore, accurate and reliable online monitoring of this temperature is crucial.

[0003] Currently, infrared thermometry (including point infrared thermometers and infrared thermal imagers) is widely used in industry to obtain the surface temperature of continuously cast billets. However, this technology faces significant challenges in the continuous casting production environment. First, the secondary cooling zone contains a large amount of water vapor generated by spraying, which has a strong absorption effect on infrared radiation, severely attenuating the infrared signal emitted by the measured target. Second, a layer of iron oxide scale with uneven composition and thickness continuously forms on the surface of the high-temperature continuously cast billet. This iron oxide scale not only has different radiation characteristics from the base steel, but its state (such as thickness and spalling) also changes dynamically, further introducing unpredictable measurement errors. These factors together make it difficult for traditional infrared thermometry methods to meet the requirements of high-precision quality control in continuous casting scenarios in terms of measurement accuracy and stability.

[0004] To overcome the aforementioned shortcomings, existing technologies have proposed various improvement schemes. For example, some schemes integrate a high-pressure gas purging device at the end of the infrared temperature measuring gun to try to dissipate water vapor in the temperature measuring path; others use multispectral imaging technology combined with algorithm correction to reduce the influence of iron oxide scale; still others attempt to embed contact temperature sensors in the support rollers or use electromagnetic emission to implant temperature measuring nails into the billet for measurement. However, these methods either fail to fundamentally eliminate the interference of water vapor and iron oxide scale, or require complex modifications to existing continuous casting equipment, resulting in high implementation costs and poor reliability, thus limiting their application in actual production.

[0005] Therefore, how to achieve a non-contact, high-precision, high-stability surface temperature measurement method that is easy to integrate online under the harsh conditions of continuous casting has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a continuous casting billet temperature measurement device and method based on electromagnetic induction. By installing an excitation coil and an induction coil above the continuous casting billet to be measured, the magnetic field formed near the induction coil is different according to the different relative permeability corresponding to different temperatures, thereby generating a difference in electromotive force and measuring the surface temperature of the continuous casting billet.

[0007] As a first aspect of the present invention, the present invention provides a continuous casting billet temperature measuring device based on electromagnetic induction, comprising: An excitation coil includes a first housing, an iron core disposed inside the first housing, and a first coil wound on the iron core. The first housing is provided with a first cooling water inlet and a first cooling water outlet to form a first cooling circuit. An induction coil includes a second housing and a second coil encapsulated within the second housing. The second housing is provided with a second cooling water inlet and a second cooling water outlet to form a second cooling circuit. The excitation coil and the induction coil are coaxially arranged, and the induction coil is located between the excitation coil and the straightening section of the continuous casting billet to be tested.

[0008] Optionally, the end face of the excitation coil is 20mm~30mm away from the surface of the straightening section of the continuous casting billet, and the induction coil is 5mm~10mm away from the surface of the straightening section of the continuous casting billet.

[0009] Optionally, the iron core is a cylindrical structure made of high-permeability silicon steel sheets stacked together, with a diameter of 20mm to 50mm.

[0010] Optionally, the first coil is an insulated copper wire wound around the periphery of the iron core, the diameter of the insulated copper wire being 0.5mm to 1.0mm and the number of turns being 50 to 150.

[0011] Optionally, the second coil is made of copper wire with a diameter of 0.2mm to 0.4mm wound into a ring with an inner diameter of 40mm to 80mm and 100 to 300 turns.

[0012] Optionally, the excitation coil is connected to an AC power source, which provides the first coil with an alternating current of 5Hz to 20Hz and a current intensity of 0.5A to 5A.

[0013] Optionally, the first cooling circuit and the second cooling circuit are configured such that, after cooling water is introduced, the temperature difference between the inlet and outlet water of the first cooling circuit and the second cooling circuit is less than 5°C.

[0014] As a second aspect of the present invention, the present invention provides a method for measuring the temperature of continuously cast billets based on electromagnetic induction, and based on the electromagnetic induction-based continuous casting billet temperature measuring device described in the first aspect above, the method comprising the following steps: Constructing a temperature-electromotive force calibration database: For the steel grade to be tested, prepare sample specimens and accurately monitor their temperature; place the heated specimens below the excitation coil and induction coil of the temperature measuring device, maintaining the same installation distance as during online measurement; pass an alternating current with preset parameters through the excitation coil, and simultaneously record the specimen temperature and the induced electromotive force output by the induction coil; change the specimen temperature, repeat the measurement, obtain the temperature-electromotive force relationship data for the steel grade, and store it; Online temperature measurement: Install the temperature measuring device on the continuous casting production line, and set the positions of the excitation coil and induction coil relative to the surface of the continuous casting billet according to the distance parameters during calibration; start the device and pass the same alternating current as in the calibration process to the excitation coil; Signal acquisition and processing: The induced electromotive force signal at both ends of the induction coil is acquired in real time, and the signal is filtered and averaged to obtain a stable electromotive force measurement value; Temperature inversion: The stable electromotive force measurement value is compared with a pre-stored temperature-electromotive force relationship database corresponding to the current casting steel grade, and the surface temperature of the continuous casting billet is obtained by querying or interpolation.

[0015] Furthermore, in the step of constructing the temperature-electromotive force calibration database, the sample specimen is heated to a temperature range of 700°C to 1100°C.

[0016] Furthermore, in the step of constructing the temperature-electromotive force calibration database, the frequency of the alternating current of the preset parameters is 5Hz~20Hz, and the current intensity is 0.5A~5A.

[0017] Compared with the prior art, the present invention discloses at least the following beneficial effects: The electromagnetic induction-based continuous casting billet temperature measurement device provided by this invention features a compact structure with coaxial and layered excitation coils and induction coils, each equipped with an independent closed-loop cooling water circuit. This ensures long-term stable operation of the entire measuring device under the harsh conditions of high temperature and high humidity in the secondary cooling zone of continuous casting, effectively controlling coil temperature rise and preventing magnetic drift or damage caused by self-heating. The induction coil is intentionally positioned closer to the surface of the continuous casting billet. This optimized spatial layout allows the induction coil to more sensitively capture subtle magnetic field disturbances caused by changes in the permeability of the billet's interior with temperature, significantly improving the sensitivity and resolution of temperature detection. This technical solution fundamentally avoids the inherent defects of traditional optical temperature measurement methods, such as interference from water vapor absorption and dynamically changing iron oxide scale, achieving truly non-contact, anti-interference measurement. Furthermore, the modular and compact structure, with high integration of cooling and measurement units, facilitates direct installation and subsequent maintenance on existing continuous casting production lines, providing a reliable and practical hardware foundation for online, real-time, and high-precision monitoring of the surface temperature of continuous casting billets. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the continuous casting billet temperature measuring device proposed in an embodiment of the present invention; Figure 2 A graph showing the relationship between electromotive force and temperature obtained by temperature measurement using the method of the present invention. Reference numerals: 1. Excitation coil; 11. First housing; 12. Iron core; 13. First coil; 101. First cooling water inlet; 102. First cooling water outlet; 2. Induction coil; 21. Second housing; 22. Second coil; 201. Second cooling water inlet; 202. Second cooling water outlet; 3. Continuous casting billet straightening section. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Reference Figure 1 As shown, this embodiment of the invention provides a continuous casting billet temperature measuring device based on electromagnetic induction, including an excitation coil 1 and an induction coil 2 disposed near the straightening section 3 of the continuous casting billet. This temperature measuring device is used for non-contact measurement of the surface temperature of high-temperature continuous casting billets.

[0023] In this embodiment, both the excitation coil 1 and the induction coil 2 are equipped with independent cooling water circuits to cope with the harsh environment of high temperature and high humidity in the secondary cooling zone of continuous casting.

[0024] Specifically, the excitation coil 1 mainly includes a first housing 11, an iron core 12 disposed inside the housing, and a first coil 13 wound around the iron core 12. The first coil 13 is made of insulated copper wire tightly wound around the iron core 12. The first housing 11 is provided with a first cooling water inlet 101 and a first cooling water outlet 102 for circulating and cooling the first coil 13 and the iron core 12 with pure cooling water to ensure stable operation in high-temperature environments. By controlling the cooling water flow rate, the temperature difference between the inlet and outlet water is maintained within 5°C.

[0025] In one specific embodiment, the iron core 12 is preferably a cylindrical structure made of stacked silicon steel sheets with high magnetic permeability, and its diameter can be between 20mm and 50mm.

[0026] In one specific embodiment, the first coil 13 is made of insulated copper wire tightly wound around the iron core 12. The diameter of the copper wire is in the range of 0.5mm to 1.0mm, and the number of turns is 50 to 150.

[0027] In this embodiment, the induction coil 2 mainly includes a second housing 21 and a second coil 22 encapsulated within the housing. The second housing 21 is provided with a second cooling water inlet 201 and a second cooling water outlet 202, so as to provide forced cooling to the second coil 22 through an independent cooling water path.

[0028] In one specific embodiment, the second coil 22 is made of thin-diameter copper wire (e.g., with a diameter of 0.2mm to 0.4mm) wound into a ring, with an inner diameter ranging from 40mm to 80mm and a number of turns ranging from 100 to 300.

[0029] Building upon the above embodiments, the excitation coil 1 and the induction coil 2 are further positioned in a specific spatial relationship. Their axes should coincide, and the induction coil 2 is positioned between the excitation coil 1 and the straightening section 3 of the continuously cast billet to be tested. This coaxial and layered arrangement optimizes the magnetic field distribution, enabling the induction coil 2 to more sensitively detect magnetic field disturbances caused by changes in the permeability of the continuously cast billet.

[0030] Furthermore, the distance between the end face of the excitation coil 1 and the surface of the continuous casting billet is set to 20mm~30mm, while the distance between the induction coil 2 and the surface of the continuous casting billet is closer, set to 5mm~10mm.

[0031] Building upon the above embodiment, the excitation coil 1 further requires connection to an AC power source (not shown in the figure). This AC power source provides an alternating current of a specific frequency and intensity to the first coil 13.

[0032] In a preferred embodiment, the frequency of the alternating current is controlled in the lower frequency range of 5~20Hz, and the current intensity is controlled between 0.5~5A. This low-frequency, moderate current parameter setting can generate a sufficiently strong induced signal at the induction coil 2, while avoiding excessive eddy current heating effects that could interfere with the measurement or damage the equipment itself.

[0033] The device in this embodiment utilizes the principle of electromagnetic induction to infer temperature by measuring the induced electromotive force, which is closely related to the material's magnetic permeability (a property that is a function of temperature). This fundamentally avoids the interference of water vapor and dynamically changing iron oxide scale on optical temperature measurement methods. It has the advantages of high measurement accuracy, strong environmental adaptability, and easy online integration and maintenance.

[0034] This invention also provides a method for measuring the temperature of continuously cast billets based on electromagnetic induction, which is implemented using the aforementioned temperature measuring device. (Refer to...) Figure 1 and Figure 2 As shown, the temperature measurement method includes the following steps: S1. Construct a temperature-electromotive force calibration database.

[0035] For each steel grade to be tested, the following calibration procedure is performed: A continuously cast billet sample containing the steel grade composition is cut into a flat specimen of a specified size (e.g., 20cm × 30cm × 3cm). Thermocouples are welded to the surface of the flat specimen to accurately monitor its temperature. The specimen is then placed in a heat treatment furnace and heated at a constant rate (e.g., 5°C / min) to the target temperature range (e.g., 700°C to 1100°C), and held at that temperature for a period of time (e.g., 10min to 60min) to ensure temperature uniformity. The heated specimen is placed below the excitation coil 1 and induction coil 2, which have been installed as described above, maintaining the same distance parameters as during online measurement. An alternating current of a preset frequency and current intensity is passed through the excitation coil 1, while the specimen temperature measured by the thermocouples and the induced electromotive force output by the induction coil 2 are continuously and synchronously recorded. By changing the set temperature of the heat treatment furnace, the above process is repeated to obtain the stable electromotive force values ​​corresponding to the steel grade at different temperature points, and finally, a graph is plotted as shown below. Figure 2 The temperature-electromotive force relationship curve of this steel grade is shown and stored in the database.

[0036] S2, Online temperature measurement.

[0037] On the continuous casting production line, the assembled temperature measuring equipment is installed in the target temperature measuring area, such as near the straightening section 3 of the continuous casting billet. During installation, the distance between the excitation coil 1 and the induction coil 2 and the surface of the continuous casting billet must be set strictly according to the distance parameters specified during calibration. The equipment is started, and an alternating current identical to that used in the calibration process is supplied to the excitation coil 1, and the cooling system is turned on.

[0038] S3. Signal Acquisition and Processing.

[0039] A high-precision voltage data acquisition system is used to acquire the induced electromotive force signal generated across induction coil 2 in real time. The acquired voltage signal is filtered and averaged to eliminate electromagnetic noise interference and obtain a stable time-averaged electromotive force value.

[0040] S4, Temperature Inversion.

[0041] The stable electromotive force value obtained in step S3 is compared with the temperature-electromotive force relationship database pre-established in step S1 for the current casting steel grade. By querying or interpolating, the surface temperature of the continuously cast billet uniquely corresponding to this electromotive force value can be determined, thereby realizing real-time, online, non-contact measurement of the surface temperature of the continuously cast billet.

[0042] The electromagnetic induction-based surface temperature measurement device and method for continuously cast billets proposed in this invention involves installing an excitation coil 1 and an induction coil 2 in the secondary cooling zone. Because the relative permeability of the continuously cast billet varies at different temperatures, the magnetic field strength passing through the induction coil 2 changes. By measuring the induced electromotive force and comparing it with experimental data, the surface temperature of continuously cast billets of different steel grades can be obtained. This method can avoid the influence of the iron oxide scale on the surface of the continuously cast billet.

[0043] Example 1 To illustrate the embodiments of the present invention more specifically, an application example is described below. This example uses the continuous casting production of 230mm×1450mm slabs of Q345 steel as an example. The electromagnetic induction-based continuous casting slab temperature measuring device of the above embodiment of the present invention is installed near the straightening section 3 of the continuous casting slab.

[0044] The composition of Q345 peritectic steel is: C: 0.15~0.17 wt.%, Si: 0.35~0.45 wt.%, Mn: 1.35~1.45 wt.%, P: ≤0.025 wt.%, S: ≤0.025 wt.%, V: 0.04~0.05 wt.%, liquidus temperature 1491℃, solidus temperature 1423℃, casting temperature 1520℃. This steel grade belongs to peritectic steel. If the surface temperature of the continuously cast billet is not properly controlled, corner cracks are prone to appear in the straightening section 3 of the continuously cast billet. To accurately obtain the surface temperature of the continuously cast billet, the surface temperature of the continuously cast billet is measured by excitation coil 1 and induction coil 2, which is achieved through the following steps: Step 1: Near the straightening section 3 of the continuously cast billet, install excitation coil 1 and induction coil 2, with excitation coil 1 20mm from the surface of the continuously cast billet and induction coil 2 10mm from the surface of the continuously cast billet. Figure 1 .

[0045] Step 2: The water flow rate through excitation coil 1 is 5L / min, the water flow rate through induction coil 2 is 8L / min, and the temperature difference between the inlet and outlet water is less than 5℃; Step 3: The core of excitation coil 1 is a 20mm diameter high-permeability silicon cylindrical iron core 12. The winding coil is made of 0.5mm diameter insulated copper wire, which is wound around the outer periphery of the iron core 12, with the number of turns controlled at 100. The induction coil 2 is made of 0.2mm diameter copper wire wound around the center, with an inner diameter of 40mm and 150 turns.

[0046] Step 4: Pass a 10Hz alternating current through excitation coil 1, with the current intensity controlled at 1.0A. Simultaneously, use a voltage data acquisition system to obtain an average electromotive force of 3.75V.

[0047] Step 5: The database of temperature-electromotive force relationship of Q345 steel was obtained through the following method: Step 501: Cut the continuous casting billet of Q345 steel into a plate of 20cm×30cm×3cm, weld a thermocouple on the surface of the plate, and monitor the temperature of the plate in real time. Step 502: Place the plate in a heat treatment furnace and heat it at 5℃ / min until it reaches 900℃, and hold it at that temperature for 30 minutes. Step 503: Take out the heated steel plate and place it under the excitation coil 1 and the induction coil 2. The excitation coil 1 is 20mm away from the surface of the continuous casting billet, and the induction coil 2 is 10mm away from the surface of the steel plate. Pass an alternating current of 1.0A and 10Hz through the excitation coil 1 and continuously record the thermocouple temperature and the electromotive force in the induction coil 2.

[0048] Step 504: Obtain the curve data between temperature and electromotive force, such as... Figure 2 As shown.

[0049] Step 6: Based on the electromotive force obtained from the online induction coil 2 and the relationship between the electromotive force and the temperature range, the surface temperature of the continuously cast billet in the straightening section is measured to be 857.5℃.

[0050] It should be understood that, in practical applications, the above-mentioned ranges of parameters such as frequency, current, coil size, and distance can be adaptively adjusted and optimized according to the specific working conditions of different steel properties and temperature measurement locations (such as the crystallizer outlet and different sections of the secondary cooling zone), and these adjustments are all within the protection scope of this invention.

[0051] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A continuous casting billet temperature measuring device based on electromagnetic induction, characterized in that, include: The excitation coil (1) includes a first housing (11), an iron core (12) disposed inside the first housing (11), and a first coil (13) wound on the iron core (12). The first housing (11) is provided with a first cooling water inlet (101) and a first cooling water outlet (102) to form a first cooling circuit. The induction coil (2) includes a second housing (21) and a second coil (22) encapsulated in the second housing (21). The second housing (21) is provided with a second cooling water inlet (201) and a second cooling water outlet (202) to form a second cooling circuit. The excitation coil (1) and the induction coil (2) are coaxially arranged, and the induction coil (2) is located between the excitation coil (1) and the straightening section (3) of the continuous casting billet to be tested.

2. The continuous casting billet temperature measuring device based on electromagnetic induction according to claim 1, characterized in that, The end face of the excitation coil (1) is 20mm to 30mm away from the surface of the straightening section (3) of the continuous casting billet, and the induction coil (2) is 5mm to 10mm away from the surface of the straightening section (3) of the continuous casting billet.

3. The continuous casting billet temperature measuring device based on electromagnetic induction according to claim 1, characterized in that, The iron core (12) is a cylindrical structure made of high permeability silicon steel sheets, with a diameter of 20mm~50mm.

4. The continuous casting billet temperature measuring device based on electromagnetic induction according to claim 1 or 3, characterized in that, The first coil (13) is an insulated copper wire wound around the outer periphery of the iron core (12). The diameter of the insulated copper wire is 0.5mm~1.0mm and the number of turns is 50~150.

5. The continuous casting billet temperature measuring device based on electromagnetic induction according to claim 1, characterized in that, The second coil (22) is made of copper wire with a diameter of 0.2mm to 0.4mm and wound into a ring with an inner diameter of 40mm to 80mm and a number of 100 to 300 turns.

6. The continuous casting billet temperature measuring device based on electromagnetic induction according to claim 1, characterized in that, The excitation coil (1) is connected to an AC power source, which provides the first coil (13) with an alternating current of 5Hz to 20Hz and a current intensity of 0.5A to 5A.

7. The continuous casting billet temperature measuring device based on electromagnetic induction according to claim 1, characterized in that, The first cooling circuit and the second cooling circuit are configured such that, after cooling water is introduced, the temperature difference between the inlet and outlet water of the first cooling circuit and the second cooling circuit is less than 5°C.

8. A method for measuring the temperature of continuously cast billets based on electromagnetic induction, based on the electromagnetic induction-based continuous casting billet temperature measuring device according to any one of claims 1 to 7, characterized in that, Includes the following steps: Constructing a temperature-electromotive force calibration database: For the steel grade to be tested, prepare a sample specimen and accurately monitor its temperature; place the heated specimen below the excitation coil (1) and induction coil (2) of the temperature measuring device, maintaining the same installation distance as during online measurement; pass an alternating current with preset parameters into the excitation coil (1), and simultaneously record the specimen temperature and the induced electromotive force output by the induction coil (2); change the specimen temperature, repeat the measurement, obtain the temperature-electromotive force relationship data of the steel grade, and store it; Online temperature measurement: Install the temperature measuring device on the continuous casting production line and set the positions of the excitation coil (1) and the induction coil (2) relative to the surface of the continuous casting billet according to the distance parameters during calibration; start the device and pass the same alternating current as the calibration process into the excitation coil (1); Signal acquisition and processing: The induced electromotive force signal at both ends of the induction coil (2) is acquired in real time, and the signal is filtered and averaged to obtain a stable electromotive force measurement value; Temperature inversion: The stable electromotive force measurement value is compared with a pre-stored temperature-electromotive force relationship database corresponding to the current casting steel grade, and the surface temperature of the continuous casting billet is obtained by querying or interpolation.

9. The method for measuring the temperature of continuously cast billets based on electromagnetic induction according to claim 8, characterized in that, In the step of constructing the temperature-electromotive force calibration database, the sample specimen is heated to a temperature range of 700°C to 1100°C.

10. The method for measuring the temperature of continuously cast billets based on electromagnetic induction according to claim 8, characterized in that, In the step of constructing the temperature-electromotive force calibration database, the frequency of the alternating current of the preset parameters is 5Hz~20Hz, and the current intensity is 0.5A~5A.

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