A method and system for measuring the thickness of a liquid slag layer of a continuous casting protective slag in real time

Abstract

This invention provides a method and system for real-time measurement of the thickness of the molten slag layer in continuous casting, relating to the field of continuous casting technology in iron and steel metallurgy. The method includes: emitting electromagnetic waves into the molded slag and receiving the reflected echoes; using the echo from the molten steel surface with the largest amplitude as a reference anchor point; sequentially identifying the echo times of the powdery slag layer, sintered layer, and upper surface of the molten slag layer; collecting mold vibration displacement data to compensate for the measurement distance; and calculating the thicknesses of the powdery slag layer, sintered layer, and molten slag layer based on the compensated distances. This invention achieves non-contact, real-time, and high-precision measurement of the thickness of the three layers of molded slag through four-layer interface identification and vibration compensation.

Description

Technical Field

[0001] This invention relates to the field of continuous casting technology in iron and steel metallurgy, specifically to a method and system for real-time measurement of the thickness of the protective slag layer in continuous casting. Background Technology

[0002] In continuous steel casting, protective slag is added to the surface of the molten steel in the crystallizer. After heating and melting, it forms a powdery slag layer, a sintered layer, and a liquid slag layer (distributed sequentially from the powdery slag layer towards the molten steel). The liquid slag layer, covering the molten steel surface, flows into the space between the copper plate wall and the solidified billet shell under the vibration of the crystallizer, forming a slag film that lubricates the billet shell and prevents adhesion. The thickness of the liquid slag layer is a key indicator for evaluating the lubrication effect of the protective slag and predicting the risk of sticking and leakage.

[0003] Traditional methods for measuring the thickness of protective slag in continuous casting production mainly employ manual contact methods, such as the double-wire method or the panel method. The double-wire method utilizes the difference in melting points between steel and copper wires, estimating the slag layer thickness by manually inserting the wire into the protective slag and measuring the melting marks. The panel method involves inserting a coated thin steel sheet into the protective slag, using the temperature difference to leave a mark on the steel sheet for measurement. Both methods have the following drawbacks: they require manual insertion of the measuring tool, necessitating the replacement of consumables after each measurement, and pose safety risks such as burns during operation; the measurement process is affected by fluctuations in the slag layer, resulting in significant errors; and they can only perform single-point, point-based measurements, failing to achieve continuous real-time monitoring and making it difficult to promptly detect abnormal changes in the slag layer thickness.

[0004] Related research has attempted to use electromagnetic wave technology for non-contact measurement of mold flux thickness. This type of method measures the thickness of the mold flux by emitting electromagnetic waves and receiving the reflected echoes, utilizing the differences in the propagation characteristics of electromagnetic waves in different media. However, existing electromagnetic wave measurement schemes can only measure the thickness of the powdery slag layer (solid layer), and cannot distinguish or measure the thickness of the sintered layer and the liquid slag layer. Since the liquid slag layer is a critical layer determining lubrication effectiveness and the risk of sticking and leakage, and its echo signal is weak and easily affected by mold vibration and on-site noise, these schemes struggle to achieve stable and accurate measurement of the liquid slag layer thickness in the harsh environment of continuous casting. Therefore, how to achieve non-contact, real-time, and accurate measurement of the liquid slag layer thickness during continuous casting is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a method and system for real-time measurement of the thickness of the protective slag layer in continuous casting. Through four-layer interface identification and vibration compensation, it achieves non-contact, real-time, and high-precision measurement of the thickness of the three protective slag layers.

[0006] In a first aspect, the technical solution of the present invention provides a method for real-time measurement of the thickness of the protective slag layer in continuous casting, comprising the following steps: Electromagnetic waves are emitted into the protective slag inside the crystallizer, and the reflected echoes are received; The echo times of the four interfaces—the upper surface of the slag layer, the upper surface of the sintered layer, the upper surface of the liquid slag layer, and the surface of the molten steel—are identified based on the amplitude characteristics of the reflected echoes. Among them, the echo with the largest amplitude is determined to be the echo of the molten steel surface, and the echo times of the molten steel surface echo are determined sequentially backward from the reference anchor point to the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the slag layer. The vibration displacement data of the crystallizer is collected, and the distance calculated based on the echo time is compensated based on the vibration displacement data to obtain the compensated distance. The thickness of the slag layer, the sintering layer, and the liquid slag layer are calculated based on the compensated distance.

[0007] Secondly, the technical solution of the present invention provides a system for real-time measurement of the thickness of the protective slag layer in continuous casting, comprising: An electromagnetic wave probe, installed above the crystallizer, is used to emit electromagnetic waves into the protective slag inside the crystallizer and receive the reflected echoes. A displacement sensor, installed on the crystallizer, is used to collect vibration displacement data of the crystallizer; The processor is connected to the electromagnetic wave probe and the displacement sensor, and includes an interface recognition module, a distance compensation module and a thickness calculation module. The interface recognition module is used to identify the echo times of four interfaces—the upper surface of the slag layer, the upper surface of the sintered layer, the upper surface of the liquid slag layer, and the surface of the molten steel—based on the amplitude characteristics of the reflected echoes. The echo with the largest amplitude is identified as the molten steel surface echo, and the echo times of the molten steel surface echo are used as the reference anchor point to sequentially determine the echo times of the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the slag layer. The distance compensation module is used to calculate the original distance from each interface to the probe based on the echo time of each interface, and to compensate the original distance based on the vibration displacement data to obtain the compensated distance. The thickness calculation module is used to calculate the thickness of the slag layer, the sintering layer, and the liquid slag layer based on the compensated distance.

[0008] As can be seen from the above technical solutions, this application has the following advantages: This method can continuously emit electromagnetic waves into the protective slag inside the crystallizer, receive the reflected echoes from the four interfaces in real time, and use the strong echo formed on the surface of the molten steel as a reference anchor point to calculate the position of the upper surface of the liquid slag layer, thereby directly obtaining the thickness value of the liquid slag layer. The thickness value can then be refreshed and displayed on the display screen in the control room in real time. Operators can monitor the changes in the thickness of the liquid slag layer at any time without having to approach the crystallizer. There is no need to manually approach the crystallizer to insert or remove measuring tools, nor is it necessary to replace consumables such as steel wire and steel plate each time. This eliminates the risk of burns and the cost of consumables, and realizes non-contact, continuous, and real-time measurement of the thickness of the liquid slag layer. By installing displacement sensors on the crystallizer, vibration displacement data is collected in real time, and the vibration displacement value is deducted in the distance calculation process, so that the relative distance between the probe and each slag layer interface returns to the true value when the crystallizer is stationary. The compensation accuracy is high and can meet the requirements of online continuous casting inspection for measurement stability and repeatability. By identifying the echoes from the four interfaces, the thicknesses of the powdered slag layer, sintered layer, and liquid slag layer can be calculated separately. The thickness of the liquid slag layer directly determines the lubrication effect of the protective slag and the risk of sticking and leakage. The thicknesses of the powdered slag layer and the sintered layer reflect the thermal melting behavior of the protective slag. An excessively thick powdered slag layer indicates that the amount of protective slag added is too large or the melting rate is too slow. An abnormally thick sintered layer may indicate a change in the sintering performance of the protective slag. Operators can comprehensively assess the usage status of the protective slag by combining the data from these three layers, providing more multi-dimensional references for the refined control of the continuous casting process. Attached Figure Description

[0009] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of a system structure for real-time measurement of the thickness of the protective slag layer in continuous casting, provided as an embodiment of the present invention.

[0011] Figure 2 This is a schematic flowchart of a method for real-time measurement of the thickness of the protective slag layer in continuous casting, provided as an embodiment of the present invention. Detailed Implementation

[0012] To make the purpose, features, and advantages of this application more apparent and understandable, specific embodiments and accompanying drawings will be used to clearly and completely describe the technical solution protected by this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0013] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this application and in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0014] Figure 1 A schematic diagram of a system structure for real-time measurement of the thickness of the protective slag layer in continuous casting is provided as an embodiment of the present invention, as shown below. Figure 1 As shown, the system includes an electromagnetic wave probe, a displacement sensor, and a processor. The processor further includes multiple functional modules, namely an interface recognition module, a distance compensation module, and a thickness calculation module. The system also includes a display unit. The module referred to in this invention is a series of computer program segments that can be executed by the processor and perform a fixed function, and which are stored in memory.

[0015] An electromagnetic wave probe, installed above the crystallizer with its axis perpendicular to the protective slag surface, is used to transmit electromagnetic waves into the protective slag inside the crystallizer and receive reflected echoes. A high-temperature resistant antenna can be used. The electromagnetic wave probe operates in the frequency range of 6GHz to 80GHz, transmitting electromagnetic waves using a pulse or frequency-modulated continuous wave system, and receiving reflected echoes from four interfaces: the upper surface of the powdered slag layer, the upper surface of the sintered layer, the upper surface of the liquid slag layer, and the surface of the molten steel.

[0016] Displacement sensors are installed on the back of the copper wall of the crystallizer or on the vibration device to collect vibration displacement data of the crystallizer in real time.

[0017] The processor is connected to both the electromagnetic wave probe and the displacement sensor. The processor's interface recognition module identifies the echo times of the four interfaces based on the amplitude characteristics of the reflected echoes: the echo with the largest amplitude is identified as the steel surface echo, and using this echo's time as a reference anchor point, the echo times of the upper surfaces of the liquid slag layer, sintered layer, and powdered slag layer are determined sequentially forward. The distance compensation module calculates the original distance from each interface to the probe based on the echo times of each interface, and compensates for the original distance based on the vibration displacement data collected by the displacement sensor to obtain the compensated distance. The thickness calculation module calculates the thickness of the powdered slag layer, sintered layer, and liquid slag layer based on the compensated distances.

[0018] The display unit is connected to the processor and is used to display the thickness values ​​of each layer in real time. In a preferred embodiment, the display unit adopts a touch-screen industrial display screen, which, in addition to real-time display, also provides interactive functions such as historical trend curve query, alarm threshold setting, and data export.

[0019] After system power-on initialization, the electromagnetic wave probe emits electromagnetic waves into the protective slag inside the crystallizer at a set frequency and power. The electromagnetic waves sequentially penetrate the powdered slag layer, sintered layer, and liquid slag layer, generating reflected echoes at each layer interface and the surface of the molten steel. The receiving antenna receives the echo signals and transmits them to the processor. This module of the processor calculates and displays the thicknesses of the powdered slag layer, sintered layer, and liquid slag layer based on the collected data. This includes: an interface recognition module extracting candidate echoes from the echo signals and determining the interface based on a strategy of "using the echo from the molten steel surface as a reference anchor point and identifying them sequentially forward." Four echo times. The distance compensation module is based on... The original distance is calculated and then compensated by combining it with vibration displacement data collected by displacement sensors to obtain the compensated distance. The thickness calculation module is based on... The thickness of each layer is calculated, and the final thickness of each layer is output to the display unit. The data processing procedure is detailed in the subsequent implementation example of a method for real-time measurement of the slag layer thickness in continuous casting, and will not be repeated here.

[0020] It should be noted that, Figure 1 The diagram also shows the use of a layered calculation model to determine the thickness of each layer, with the distance from the electromagnetic wave probe to the upper edge of the copper plate in the crystallizer serving as the detection reference point. (Not shown in the diagram), the distance from the electromagnetic wave probe to the upper surface of the slag layer was calculated to be: The distance from the electromagnetic wave probe to the upper surface of the sintered layer is The distance from the electromagnetic wave probe to the upper surface of the liquid slag layer is The distance from the electromagnetic wave probe to the surface of the molten steel is The above distance All distance values ​​are after vibration compensation. The thickness of each layer is then calculated using the following formula: Thickness of powder and slag layer: ; Sintered layer thickness: ; Liquid slag layer thickness: .

[0021] The foregoing described an embodiment of a system for real-time measurement of the thickness of the protective slag layer in continuous casting. Based on the system described above, this invention also provides a method for real-time measurement of the thickness of the protective slag layer in continuous casting, corresponding to the system.

[0022] Figure 2 This is a schematic flowchart of a method for real-time measurement of the thickness of the protective slag layer in continuous casting, provided by an embodiment of the present invention. Figure 2 As shown, the method includes the following steps.

[0023] S1 emits electromagnetic waves into the protective slag inside the crystallizer and receives the reflected echoes.

[0024] As shown in Table 1, electromagnetic waves generate reflected echoes when they encounter the following four interfaces where the dielectric constant changes abruptly during propagation.

[0025] Table 1: Interfaces where dielectric constant changes abruptly

[0026] The fourth interface (the slag layer-molten steel interface) is impenetrable to electromagnetic waves due to the excellent conductivity of molten steel, resulting in a reflectivity close to 100%. Its echo intensity is several decibels higher than the previous three interfaces, forming a characteristic strong echo. The receiving antenna inside the electromagnetic wave probe receives the reflected echoes from all four interfaces and transmits the echo signals to the processor.

[0027] S2. Identify the echo times of the four interfaces—the upper surface of the slag layer, the upper surface of the sintered layer, the upper surface of the liquid slag layer, and the surface of the molten steel—based on the amplitude characteristics of the reflected echoes. Among them, the echo with the largest amplitude is determined to be the echo of the molten steel surface, and the echo times of the molten steel surface echo are determined sequentially forward from the reference anchor point to the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the slag layer.

[0028] S2.1, preprocess the received raw echo signal to obtain candidate echoes.

[0029] Before identifying the echo times of each interface, the original echo signal received by the electromagnetic wave probe is first preprocessed to suppress ambient noise and enhance weak echo signals. Specifically, this includes the following steps S2.11 to S2.15.

[0030] S2.11 uses a bandpass filter to filter the original echo signal, removing noise signals from outside the transmission frequency band.

[0031] The original echo signal contains various noise interferences from the crystallizer copper plate, molten steel flow, and on-site industrial equipment. To filter out noise signals outside the transmission frequency band, a bandpass filter is used to filter the original echo signal.

[0032] Specifically, the passband frequency range of the bandpass filter is matched with the frequency band of the electromagnetic wave probe's transmitted signal, preferably set to 1.2 to 1.5 times the bandwidth of the transmitted signal. Through bandpass filtering, low-frequency reflection interference generated by the copper plate of the crystallizer and electromagnetic interference from the industrial site can be effectively filtered out, while retaining the effective echo signals generated at the interfaces of each layer of the protective slag.

[0033] S2.12 employs automatic gain control to adjust the gain of the filtered signal, automatically adjusting the amplification factor according to the intensity of the echo from the molten steel surface to prevent strong echoes from causing signal saturation.

[0034] In the bandpass filtered echo signal, the intensity of the echo from the molten steel surface is much greater than that from the other three interfaces. Without gain adjustment, the strong echo may saturate the signal receiver, distorting or drowning out the weak echo signal. Therefore, Automatic Gain Control (AGC) is used to adjust the gain of the filtered signal. The AGC circuit monitors the intensity of the molten steel surface echo in real time and automatically adjusts the amplifier's gain coefficient accordingly: when the molten steel echo intensity is too high, the gain is automatically reduced to prevent signal saturation; when the echo intensity is too low, the gain is automatically increased to ensure the detection capability of weak signals.

[0035] S2.13, acquire the ambient noise of the signal after gain adjustment within the silent window, calculate the adaptive noise threshold, determine the signal components with amplitudes lower than the adaptive noise threshold as noise and remove them, and the remaining signal components constitute the initial candidate echo.

[0036] Even after AGC adjustment, a certain degree of background noise still exists in the signal. To distinguish between valid echoes and noise, this embodiment collects the ambient noise of the signal within a silent window, calculates an adaptive noise threshold, and discards signal components with amplitudes below the threshold as noise.

[0037] Specifically, at the beginning of each measurement cycle, a silent window is set during which the electromagnetic wave probe does not emit signals but only receives ambient noise; the ambient noise signal within the silent window is collected, and the mean μ and standard deviation σ of the noise amplitude are calculated; according to the formula... Calculate the adaptive noise threshold , where k is a preset coefficient.

[0038] Calculated Then, the amplitude of the signal adjusted by AGC is lower than The components were identified as noise and removed, with an amplitude not less than [amount missing]. The components are preserved, forming the initial candidate echo.

[0039] S2.14 employs multi-pulse coherent accumulation, which aligns the initial candidate echo signals corresponding to multiple consecutive transmitted pulses in the time domain and then superimposes and averages them to improve the signal-to-noise ratio of weak echoes.

[0040] The reflected echoes generated on the upper surface of the sintered layer and the upper surface of the liquid slag layer have weak amplitudes, and the signal-to-noise ratio of a single measurement is usually low in decibels, which is insufficient for stable identification. Therefore, this embodiment uses multi-pulse coherent accumulation to improve the signal-to-noise ratio of weak echoes.

[0041] Specifically, N electromagnetic pulses with identical parameters are emitted consecutively. The initial candidate echo signals corresponding to these N pulses are aligned in the time domain and then superimposed and averaged. The effective echo signals have the same phase and arrival time in each pulse, while the noise components are random. After superposition and averaging, the amplitude of the effective signal remains unchanged, while the noise amplitude is reduced. times.

[0042] S2.15 uses matched filtering to perform cross-correlation calculations between the superimposed and averaged signals and the preset transmitted pulse template in order to suppress residual noise and enhance the effective echo signal, thereby obtaining candidate echoes.

[0043] To further suppress noise and enhance the effective echo signal, a matched filter is used to process residual noise.

[0044] Specifically, the averaged signal is cross-correlated with a preset transmitted pulse template. Let the transmitted pulse template be s(t) and the received signal be r(t), then the output of the matched filter is:

[0045] Matched filtering is the optimal linear filter, maximizing the signal-to-noise ratio against a white noise background. Through matched filtering, the effective echo signal is further enhanced, while residual noise is effectively suppressed. The signal obtained after matched filtering is the candidate echo, used for subsequent interface identification.

[0046] This preprocessing procedure can effectively extract echoes from the upper surface of the sintered layer and the upper surface of the liquid slag layer that are submerged by noise, providing reliable candidate echo data to improve the accuracy of the liquid slag layer thickness.

[0047] S2.2, among all candidate echoes, the echo with the largest amplitude is determined to be the steel surface echo.

[0048] Among all candidate echoes, the echo with the largest amplitude is selected and determined to be the surface echo of molten steel.

[0049] Molten steel is a good conductor, and electromagnetic waves undergo total reflection at its surface, with a reflectivity approaching 100%. Therefore, the amplitude of the echo from the molten steel surface is much larger than that from the other three interfaces, forming a characteristic spike. Based on this physical characteristic, using the candidate echo with the largest amplitude as the molten steel surface echo has high reliability.

[0050] The moment of the surface echo of the molten steel is denoted as . and with As a reference anchor point for subsequent identification.

[0051] S2.3, using the time of the echo on the surface of molten steel as the reference anchor point, select the echo to be verified, and sequentially determine the echo on the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the powdered slag layer that meet the preset conditions, and then determine the time of each echo.

[0052] S2.31, with Using the time axis as a reference, the echoes that meet the first preset condition are determined to be echoes from the upper surface of the liquid slag layer, and their times are recorded as follows: .

[0053] It should be noted that the echo time of electromagnetic waves propagating from the probe to each interface and back to the probe is positively correlated with the interface depth: the deeper the interface, the later the echo time. Therefore, the echo time at the surface of molten steel (the deepest point) is... Maximum echo time of the upper surface (second deepest) of the liquid slag layer Secondly, and so on. From Starting in the opposite direction, that is, searching in the direction of decreasing time, allows us to find the echoes of each interface in order of depth from deep to shallow, which conforms to the laws of physics.

[0054] Specifically, with Using this as a baseline, the echo to be verified is searched in reverse direction along the time axis. The echoes are sorted from largest to smallest amplitude. It is determined whether the amplitude difference between the current echo and the echo from the molten steel surface is greater than a first amplitude threshold, and whether the slag layer thickness corresponding to the time difference between the current echo and the molten steel surface echo is within a preset slag layer thickness threshold range. If so, the first echo that meets the conditions is identified as the upper surface echo of the slag layer, and its time is recorded as [time value missing]. If none of the candidate echoes meet the conditions, the current frame data is deemed invalid and discarded.

[0055] In this embodiment, the first preset condition includes two sub-conditions, namely the amplitude condition and the thickness condition, which must be satisfied simultaneously.

[0056] Sub-condition one is the amplitude condition: the amplitude difference between the echo to be verified and the echo from the molten steel surface is greater than the first amplitude threshold. Although the amplitude of the echo from the upper surface of the slag layer is smaller than that from the molten steel surface, it is still significantly greater than that from the sintered layer and the pulverized slag layer. This embodiment, by setting an appropriate amplitude threshold, can eliminate interference from the echoes from the sintered layer and the pulverized slag layer, avoiding misjudging weaker echoes as originating from the upper surface of the slag layer. First amplitude threshold. The value should be determined based on statistical analysis of on-site measured data. For example, the echo amplitude of molten steel surface... Echo amplitude of the upper surface of the liquid slag layer The difference is between 6dB and 10dB, while With sintered layer echo amplitude The difference is between 3dB and 5dB. Therefore, Setting it to 6dB–8dB ensures that only candidates with amplitudes significantly greater than other echoes are identified. .

[0057] Sub-condition two is the thickness condition: the time difference between the echo to be verified and the echo from the molten steel surface. According to the propagation speed of electromagnetic waves in the liquid slag layer Calculate the corresponding liquid slag layer thickness This thickness value should be within the preset threshold range for liquid slag layer thickness. The thickness of the slag layer is constrained by process parameters such as the melting rate of the protective slag, the temperature of the molten steel, and the casting speed. Values ​​exceeding the typical range of slag layer thickness in actual continuous casting production are either due to echo recognition errors or abnormal protective slag conditions. Setting thickness conditions can filter out invalid data generated by recognition errors, and can also retain the data for alarm purposes when the slag layer thickness is truly abnormal. The specific values ​​of the slag layer thickness threshold range can be adjusted according to the process requirements of different steel grades and different protective slag grades.

[0058] The amplitude of the echo from the upper surface of the liquid slag layer is usually greater than that from the sintered layer and the powdered slag layer. Therefore, in this embodiment, the echoes to be verified are sorted from largest to smallest amplitude, prioritizing the verification of candidates with larger amplitudes to improve search efficiency. For the current echo to be verified, it is sequentially determined whether it meets the above two sub-conditions. If both conditions are met, the first echo that meets the conditions is identified as the upper surface echo of the liquid slag layer, and its time is recorded as _____. The search is terminated. If the current echo does not meet any of the sub-conditions, the next candidate echo is verified. If no echo that meets the conditions is found after traversing all candidate echoes, the current frame data is deemed invalid and discarded.

[0059] S2.32, with Using this as a baseline, a reverse search is performed along the time axis. Two adjacent echoes that meet the second preset condition are respectively identified as echoes from the upper surface of the sintered layer and echoes from the upper surface of the slag layer, and their times are recorded as follows: and .

[0060] Considering that the sintered layer and the slag layer are physically adjacent and there is no other medium layer between them, the surface echo of the sintered layer ( ) and echo on the upper surface of the slag layer ( In an echo sequence, two echoes must be temporally adjacent. Therefore, this embodiment uses a combination of adjacent echoes for detection, which can eliminate interference from non-adjacent echo combinations.

[0061] Specifically, in Based on successful identification, Previously, adjacent echo combinations were searched in the reverse direction of the time axis, and each group of adjacent echoes was selected as the next group of echoes in order of time from nearest to farthest. and The combination to be verified is used to verify whether the amplitude difference between the two echoes in this group is less than the second amplitude threshold, and whether the two echoes are respectively compared with... The time difference is used to determine whether the thickness of the sintered layer and the thickness of the slag layer are within the preset threshold ranges for sintered layer thickness and slag layer thickness, respectively. The first adjacent echo combination that meets the conditions is then determined as the upper surface echo of the sintered layer and the upper surface echo of the slag layer, respectively, according to their time sequence. The times are recorded as follows: and If none of the adjacent echo combinations meet the conditions, then it is determined that... and If recognition fails, the current frame data is deemed invalid and discarded, or only output... and .

[0062] In this embodiment, the second preset condition includes three sub-conditions: similar amplitude condition, sintered layer thickness condition, and slag layer thickness condition, all of which must be met simultaneously.

[0063] Sub-condition one is the similar amplitude condition: the amplitude difference between the two echoes is less than the second amplitude threshold. The dielectric constants of the slag layer and the sintered layer are not significantly different, and both are solid or semi-solid with similar reflection characteristics. Therefore, the echo amplitudes generated on the upper surfaces of the slag layer and the sintered layer are similar, and the amplitude difference between them is usually small. However, the dielectric constants of the sintered layer and the liquid slag layer differ slightly, therefore... and The amplitude difference is usually greater than and The amplitude difference. This embodiment utilizes this characteristic, and by setting a similar amplitude condition, it can distinguish between "... "Combination" with other possible echo combinations. Second amplitude threshold. It can be set to an absolute value or a relative value.

[0064] Sub-condition two: Sintered layer thickness condition: Echo on the upper surface of the sintered layer ( ) and echo on the upper surface of the liquid slag layer ( (time difference) According to the propagation speed of electromagnetic waves in the sintered layer Calculate the corresponding sintered layer thickness This thickness value should be within the preset threshold range for sintered layer thickness. The sintered layer is a semi-molten layer that transitions from the powdered slag layer to the liquid slag layer. Its thickness is affected by the melting rate of the protective slag and the temperature gradient. Values ​​exceeding the typical range for sintered layer thickness may originate from identification errors or abnormal sintering performance of the protective slag. Setting sintered layer thickness conditions can verify... Correctness of identification.

[0065] Sub-condition three: slag layer thickness condition: echo on the upper surface of the slag layer ( ) and echo on the upper surface of the sintered layer ( (time difference) According to the propagation speed of electromagnetic waves in the slag layer Calculate the corresponding slag layer thickness This thickness value should be within the preset threshold range for slag layer thickness. The slag layer is the unmelted solid protective slag layer, and its thickness is affected by the amount of slag added and the melting rate of the protective slag. Values ​​exceeding the typical range for slag layer thickness may originate from identification errors, abnormal slag addition, or abnormal melting rates of the protective slag. Setting slag layer thickness conditions can verify... and Correctness of identification.

[0066] The sintered layer and the slag layer are directly above the liquid slag layer, and their echo times are closest. Therefore, those that meet the conditions Combinations are most likely to occur near The location. This embodiment uses... Using this as a reference point, search for adjacent echo combinations in the reverse direction of the time axis. Each group of adjacent echoes is selected as a combination to be verified, arranged from most recent to furthest in time, prioritizing those closest to the source. Combining these methods can improve search efficiency and reduce computational load.

[0067] For the current adjacent echo combinations to be verified, determine in turn whether they satisfy the above three sub-conditions. If they are satisfied simultaneously, the later echo is identified as the upper surface echo of the sintered layer. The earliest echo was identified as the echo from the upper surface of the slag layer. If the current combination does not satisfy any of the sub-conditions, then continue to verify the next set of adjacent echo combinations.

[0068] If iterate If no combination meeting the conditions is found after combining all adjacent echoes, then it is determined that... and Recognition failed. At this point, one of two processing methods can be selected based on the actual application requirements: 1) Determine the current frame data as invalid and discard it; 2) Output only... and No output and .

[0069] When electromagnetic waves propagate in different media, the echo time is strictly positively correlated with the interface depth; that is, the deeper the interface, the later the echo time. Based on this, in this embodiment, only the echo time is output. and At that time, verify whether and The chronological order must be satisfied, i.e., verification. If the condition is not met, it indicates that the echo from the upper surface of the slag layer appears after the echo from the molten steel surface, which does not conform to physical laws. Therefore, the current frame data should be discarded. Output At that time, verification Whether the time sequence is satisfied, i.e., verification. If the condition is not met, it indicates that the time sequence of the echoes from each interface does not match the actual layering sequence of the protective slag layer in the crystallizer, and the current frame data is discarded.

[0070] S3: Collect vibration displacement data of the crystallizer, and compensate for the distance calculated based on the echo time based on the vibration displacement data to obtain the compensated distance.

[0071] In continuous casting, the mold vibrates periodically at a certain frequency and amplitude to facilitate the demolding of the billet from the copper wall of the mold. This vibration directly affects the accuracy of electromagnetic wave ranging. Let's assume that when the mold is stationary, the true distance from the electromagnetic wave probe to a certain interface is... When the crystallizer vibrates, the probe vibrates along with the crystallizer, and the actual distance from the probe to the interface becomes:

[0072] in, Let be the vibration displacement of the crystallizer at time t, with the crystallizer's stationary position as the reference; upward movement is positive, and downward movement is negative. Correspondingly, the original distance is calculated based on the echo time. for:

[0073] That is, vibration displacement It is directly superimposed on the distance measurement value.

[0074] This embodiment uses a displacement sensor to collect crystallizer vibration displacement data in real time and performs compensation in the distance calculation stage to eliminate the influence of vibration on distance measurement. Specifically, it includes the following steps S3.1 to S3.3.

[0075] S3.1, Install a displacement sensor on the crystallizer to collect the vibration displacement data of the crystallizer in real time.

[0076] S3.2 For each electromagnetic wave emission measurement, record the emission time of that measurement, and obtain the corresponding vibration displacement value δ from the vibration displacement data based on the emission time.

[0077] Specifically, for each electromagnetic wave emission measurement, the emission time of that measurement is recorded. Because the crystallizer's vibration is periodic, the vibration displacement values ​​corresponding to the electromagnetic waves emitted at different times are different. Therefore, it is necessary to obtain the corresponding vibration displacement value from the vibration displacement data based on the emission time. .

[0078] S3.3 Calculate the original distance from each interface to the probe based on the echo time of each interface, and subtract the vibration displacement value δ from the original distance to obtain the compensated distance.

[0079] According to the formula Calculate the original distance from the j-th interface to the probe, where: When j=1 , The moment of electromagnetic wave emission. , The relative permittivity of the slag layer; When j=2 , The relative permittivity of the sintered layer; When j=3 , The relative permittivity of the liquid slag layer; When j=4 C is the speed of light in a vacuum.

[0080] It should be noted that for electromagnetic waves to propagate from the probe to the surface of molten steel, they must successively pass through the air layer, slag layer, sintered layer, and liquid slag layer. Molten steel is a good conductor, and the electromagnetic waves undergo total internal reflection at the surface of the molten steel, failing to penetrate its interior. Therefore, the propagation medium for electromagnetic waves is the entire slag layer and air above the molten steel. The initial distance can be expressed as… . This does not mean that electromagnetic waves travel at the speed of light, but rather that the combined effects of the various media layers are transmitted through… It is manifested in itself. In other words, The propagation delay of electromagnetic waves in each layer of the medium has already been included, so the velocity can be taken as C. The accuracy of the distance calculation is determined by... ensure.

[0081] Obtain the raw distance from each interface to the probe. and the currently measured vibration displacement value Then, compensation is performed according to the following formula:

[0082] In the formula, This is the compensated distance from the j-th interface to the probe, i.e., the true distance when the crystallizer is stationary. The method subtracts the additional displacement caused by crystallizer vibration at the measurement moment from the original distance, restoring the true distance when the crystallizer is stationary.

[0083] S4. Calculate the thickness of the powder slag layer, the sintered layer, and the liquid slag layer based on the compensated distance.

[0084] The thickness of the slag layer is the difference between the distance between the upper and lower surfaces of the compensated slag layer; the thickness of the sintered layer is the difference between the distance between the upper and lower surfaces of the compensated sintered layer; and the thickness of the liquid slag layer is the difference between the distance between the upper and lower surfaces of the compensated liquid slag layer and the distance between the compensated molten steel surface.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for real-time measurement of the thickness of the protective slag layer in continuous casting, characterized in that, Includes the following steps: Electromagnetic waves are emitted into the protective slag inside the crystallizer, and the reflected echoes are received; The echo times of the four interfaces—the upper surface of the slag layer, the upper surface of the sintered layer, the upper surface of the liquid slag layer, and the surface of the molten steel—are identified based on the amplitude characteristics of the reflected echoes. Among them, the echo with the largest amplitude is determined to be the echo of the molten steel surface, and the echo times of the molten steel surface echo are determined sequentially backward from the reference anchor point to the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the slag layer. The vibration displacement data of the crystallizer is collected, and the distance calculated based on the echo time is compensated based on the vibration displacement data to obtain the compensated distance. The thickness of the slag layer, the sintering layer, and the liquid slag layer are calculated based on the compensated distance.

2. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 1, characterized in that, The echo times of four interfaces—the upper surface of the slag layer, the upper surface of the sintered layer, the upper surface of the molten slag layer, and the surface of the molten steel—are identified based on the amplitude characteristics of the reflected echoes. Specifically, this includes: The received raw echo signal is preprocessed to obtain candidate echoes; Among all candidate echoes, the echo with the largest amplitude is determined to be the steel surface echo; Using the time of the echo on the surface of molten steel as the reference anchor point, the echo to be verified is selected, and the echoes on the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the powdered slag layer that meet the preset conditions are determined in sequence, thereby determining the time of each echo.

3. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 2, characterized in that, The received raw echo signal is preprocessed, specifically including: A bandpass filter is used to filter the original echo signal to remove noise signals outside the transmission frequency band; Automatic gain control is used to adjust the gain of the filtered signal, and the amplification factor is automatically adjusted according to the intensity of the echo from the molten steel surface to prevent strong echoes from causing signal saturation. The ambient noise within the silent window is collected after gain adjustment of the signal. An adaptive noise threshold is calculated. Signal components with amplitudes lower than the adaptive noise threshold are identified as noise and removed. The remaining signal components constitute the initial candidate echo. Multi-pulse coherent accumulation is used to align the initial candidate echo signals corresponding to multiple consecutive transmitted pulses in the time domain and then superimpose and average them to improve the signal-to-noise ratio of weak echoes. Matched filtering is used to cross-correlate the superimposed and averaged signals with a preset transmit pulse template to suppress residual noise and enhance the effective echo signal, thereby obtaining candidate echoes.

4. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 3, characterized in that, The calculation of the adaptive noise threshold specifically includes: At the beginning of each measurement cycle, a silent window is set during which the electromagnetic wave probe does not emit signals and only receives ambient noise. Collect ambient noise signals within a silent window, and calculate the mean μ and standard deviation σ of the noise amplitude; According to the formula Calculate the adaptive noise threshold , where k is a preset coefficient.

5. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 2, characterized in that, Using the time of the molten steel surface echo as the reference anchor point, the echo to be verified is selected, and the echoes on the upper surface of the molten slag layer, the upper surface of the sintered layer, and the upper surface of the powdered slag layer that meet the preset conditions are determined sequentially. Then, the time of each echo is determined, specifically including: The echo with the largest amplitude among all candidate echoes is identified as the steel surface echo, and its time is recorded as . and with Used as the reference anchor point; by Using this as a baseline, the echo to be verified is searched in reverse direction along the time axis. The echoes are sorted from largest to smallest amplitude. It is determined whether the amplitude difference between the current echo and the echo from the molten steel surface is greater than a first amplitude threshold, and whether the slag layer thickness corresponding to the time difference between the current echo and the molten steel surface echo is within a preset slag layer thickness threshold range. If so, the first echo that meets the conditions is identified as the upper surface echo of the slag layer, and its time is recorded as [time value missing]. If none of the candidate echoes meet the conditions, the current frame data is deemed invalid and discarded. exist Based on successful identification, Previously, adjacent echo combinations were searched in the reverse direction of the time axis, and each group of adjacent echoes was selected as the next group of echoes in order of time from nearest to farthest. and The combination to be verified is used to verify whether the amplitude difference between the two echoes in this group is less than the second amplitude threshold, and whether the two echoes are respectively compared with... The time difference is used to determine whether the thickness of the sintered layer and the thickness of the slag layer are within the preset threshold ranges for sintered layer thickness and slag layer thickness, respectively. The first adjacent echo combination that meets the conditions is then determined as the upper surface echo of the sintered layer and the upper surface echo of the slag layer, respectively, according to their time sequence. The times are recorded as follows: and If none of the adjacent echo combinations meet the conditions, then it is determined that... and If recognition fails, the current frame data is deemed invalid and discarded, or only output... and .

6. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 5, characterized in that, The method also includes the following steps: Output only and At that time, verify whether and The time sequence must be satisfied; otherwise, the current frame data must be discarded. Output At that time, verification Check if the time sequence is satisfied; if not, discard the current frame data.

7. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 1, characterized in that, The vibration displacement data of the crystallizer is collected, and the distance calculated based on the echo time is compensated based on this vibration displacement data to obtain the compensated distance. Specifically, this includes: Install displacement sensors on the crystallizer to collect vibration displacement data of the crystallizer in real time; For each electromagnetic wave emission measurement, the emission time of that measurement is recorded, and the corresponding vibration displacement value δ is obtained from the vibration displacement data based on the emission time. Calculate the original distance from each interface to the probe based on the echo time of each interface, and subtract the vibration displacement value δ from the original distance to obtain the compensated distance.

8. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 7, characterized in that, The original distance from each interface to the probe is calculated based on the echo times of each interface, specifically including: According to the formula Calculate the original distance from the j-th interface to the probe, where: When j=1 , The moment of electromagnetic wave emission. , The relative permittivity of the slag layer; When j=2 , The relative permittivity of the sintered layer; When j=3 , The relative permittivity of the liquid slag layer; When j=4 ; C is the speed of light in a vacuum.

9. The method for real-time measurement of the thickness of the protective slag layer in continuous casting according to claim 1, characterized in that, The thicknesses of the slag layer, sintered layer, and liquid slag layer are calculated based on the compensated distance, specifically including: The thickness of the slag layer is the difference between the distance between the upper and lower surfaces of the compensated slag layer; the thickness of the sintered layer is the difference between the distance between the upper and lower surfaces of the compensated sintered layer; and the thickness of the liquid slag layer is the difference between the distance between the upper and lower surfaces of the compensated liquid slag layer and the distance between the compensated molten steel surface.

10. A system for real-time measurement of the thickness of the protective slag layer in continuous casting, characterized in that, include: An electromagnetic wave probe, installed above the crystallizer, is used to emit electromagnetic waves into the protective slag inside the crystallizer and receive the reflected echoes. A displacement sensor, installed on the crystallizer, is used to collect vibration displacement data of the crystallizer; The processor is connected to the electromagnetic wave probe and the displacement sensor, and includes an interface recognition module, a distance compensation module and a thickness calculation module. The interface recognition module is used to identify the echo times of four interfaces—the upper surface of the slag layer, the upper surface of the sintered layer, the upper surface of the liquid slag layer, and the surface of the molten steel—based on the amplitude characteristics of the reflected echoes. The echo with the largest amplitude is identified as the molten steel surface echo, and the echo times of the molten steel surface echo are used as the reference anchor point to sequentially determine the echo times of the upper surface of the liquid slag layer, the upper surface of the sintered layer, and the upper surface of the slag layer. The distance compensation module is used to calculate the original distance from each interface to the probe based on the echo time of each interface, and to compensate the original distance based on the vibration displacement data to obtain the compensated distance. The thickness calculation module is used to calculate the thickness of the slag layer, the sintering layer, and the liquid slag layer based on the compensated distance.

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