Method and system for non-contact on-line monitoring of solidification end point position and blank shell thickness

Abstract

The invention relates to the field of metallurgical casting blank monitoring, and provides a method and a system for non-contact online monitoring of a solidification end point position and a blank shell thickness, the method comprises the following steps: S1, carrying out vibration measurement on the surface of a casting blank by adopting a non-contact monitoring method to obtain an original vibration signal of the casting blank in a continuous casting process; s2, converting the original vibration signal from a time domain to a frequency domain through fast Fourier transform processing to obtain a vibration spectrum; s3, comparing the obtained vibration spectrum with the vibration spectrum of the casting blank of the same model in a standard database, and determining the position of the solidification end point of the casting blank; and S4, according to the obtained position of the solidification terminal point, in combination with a solidification heat transfer model, the blank shell thickness of the casting blank at each position before the solidification terminal point is determined. According to the method, a new way is provided for online, dynamic, non-contact and nondestructive detection of the continuous casting solidification process, reliable reference is provided for parameter optimization of the pulling speed, cooling, electromagnetic stirring, soft reduction and the like, and finally accurate control over the quality of the continuous casting billet is achieved.

Description

Technical Field

[0001] The invention relates to the field of metallurgical billet monitoring, and in particular to a system for non-contact online monitoring of a solidification endpoint position and billet shell thickness. Background Art

[0002] In the field of metallurgical engineering, quality control of the continuous casting process is the key to ensuring the solidification of metal materials and even the quality of the final product. The precise determination of the end point of solidification and the thickness of the billet shell is crucial to designing and optimizing the continuous casting process, improving production efficiency and improving material quality. During the continuous casting process, the liquid metal begins to form a billet shell from the meniscus of the crystallizer, and then continues to solidify downward until it is completely transformed into a solid phase. For metals with larger specifications and lower thermal conductivity, such as steel, the inside of the billet shell is still liquid when leaving the crystallizer, so it is necessary to release the latent heat through external spray cooling and rely on clamping rods for transportation. The length of the path that the billet passes before it is completely solidified depends on the thermal conductivity of the metal, the billet drawing speed and the cooling conditions. The position where it is completely solidified is called the end point of solidification. The evolution law of the continuous casting billet shell thickness and the end point of solidification are the core basis for the design of the drawing speed, electromagnetic stirring or soft reduction parameters.

[0003] Existing literature shows that the most commonly used technical means at home and abroad is to calculate the shell thickness or solidification end position of the continuous casting billet through mathematical models and verify it by nail shooting, white bright band method or lead pouring method. However, this method is destructive, and the test cycle is long and the cost is high, which affects production organization and safety. For non-destructive online monitoring to determine the end position of continuous casting solidification, the two technologies reported so far are mechanical method (CN117961018A) and ultrasonic method with electromagnetic excitation (CN111473752A). The mechanical method drives a hard material into the solidifying billet and determines the billet shell thickness by analyzing the morphological changes of the material in the billet; the ultrasonic method uses the method of actively exciting the billet vibration and analyzing the vibration signal returned by the billet to determine the billet shell thickness. These detection methods may introduce additional errors due to the high temperature environment of the material or equipment, and may also reduce the surface or internal quality of the billet. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a system for non-contact online monitoring of the solidification endpoint position and the shell thickness of the continuous casting billet. It only needs to monitor the vibrations on the surface of the continuous casting billet caused by equipment or process. The analysis of these vibrations is sufficient to accurately judge the solidification state of the continuous casting billet.

[0005] The present invention adopts the following technical solution:

[0006] In one aspect, the present invention provides a method for non-contact online monitoring of the solidification endpoint position and the shell thickness, comprising:

[0007] S1. Use a non-contact monitoring method to measure the vibration of the billet surface and obtain the original vibration signal of the billet during the continuous casting process;

[0008] S2. Converting the original vibration signal from the time domain to the frequency domain by fast Fourier transform (FFT) processing to obtain a vibration spectrum;

[0009] S3, comparing the vibration spectrum obtained in step S2 with the vibration spectrum of the same type of ingot in a standard database to determine the position of the solidification end point of the ingot;

[0010] S4. According to the position of the solidification endpoint obtained in step S3 and in combination with a solidification heat transfer model, determine the shell thickness of the ingot at various positions before the solidification endpoint.

[0011] According to the above aspects and any possible implementation, an implementation is further provided, wherein the method further comprises: S5, displaying and recording the result data obtained in step S4 through a display or a storage element.

[0012] According to the aspects and any possible implementation methods described above, an implementation method is further provided. In step S1, a non-contact vibration meter is used to measure the vibration of the ingot in the second cooling zone, the third cooling zone or the roller before cutting during the continuous casting process; the vibration is a natural vibration caused by the process or equipment.

[0013] According to the aspects and any possible implementation methods described above, an implementation method is further provided. In step S3, the standard database is a set of vibration spectra obtained after Fourier transform processing of original vibration signals of different models of ingots under different shell thickness conditions; the model parameters include ingot steel type, cross-sectional shape, cross-sectional size and drawing speed.

[0014] According to the aspects and any possible implementation methods described above, an implementation method is further provided, in which the corresponding relationship between the vibration spectrum of the ingot and the shell thickness of the ingot is determined through process tests, or obtained by comparing and screening the signals and results of different measurement points in the production process.

[0015] According to the aspects described above and any possible implementation method, an implementation method is further provided, in which the process test obtains the shell thickness or solidification end point position data of the ingot at different positions by nailing, pouring lead or leaking the ingot shell, and establishes a corresponding relationship between these data and the original vibration signal or vibration spectrum.

[0016] According to the aspects described above and any possible implementation method, an implementation method is further provided. In step S3, the specific method for determining the position of the end point of solidification of the ingot is: determining the amplitude threshold and the frequency peak number threshold of the vibration spectrum of a certain type of ingot through a standard database; the measured amplitude of the vibration spectrum of the ingot of this type is less than the amplitude threshold, and the number of frequency peaks is greater than the frequency peak number threshold. When both conditions are met at the same time, it is determined to be the end point of solidification of the ingot.

[0017] According to the aspects described above and any possible implementation method, an implementation method is further provided, wherein the number of non-contact vibrometers is 1 or several; when there is only one vibrometer, it is necessary to move the vibrometer near the solidification end point to monitor the signal; when there are two vibrometers, they are sandwiched and one is placed at a position where the ingot has been completely solidified before cutting to monitor the signal state of complete solidification of the ingot; the other is placed before solidification in the second cooling zone to monitor the signal state of the ingot containing a liquid core; when there are more than two vibrometers, multiple monitoring points are set near the solidification end point, and the position of the solidification end point is determined by comparing the change in the vibration signal under different liquid core ratios with the complete solidification signal.

[0018] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the cast billets include square billets, slabs, round billets and profile billets, and are not limited by size, steel type and drawing speed.

[0019] On the other hand, the present invention also provides a system for non-contact online monitoring of the solidification endpoint position and the shell thickness, the system is used to implement the above method, the system comprising:

[0020] Non-contact vibration meter, used to measure the vibration of the ingot surface and obtain the original vibration signal;

[0021] A standard database is used to store the original vibration signals of different types of ingots at different shell thickness states, and a collection of vibration spectra obtained after Fourier transform processing;

[0022] A signal conversion module receives the original vibration signal monitored by the non-contact vibration meter, processes it through fast Fourier transform, converts it from the time domain to the frequency domain, and obtains a vibration spectrum;

[0023] A solidification endpoint judgment module receives the vibration spectrum obtained by the signal conversion module, compares it with the vibration spectrum of the same type of ingot with different shell thickness states in the standard database, and determines the position of the ingot solidification endpoint;

[0024] The shell thickness calculation module determines the shell thickness of the ingot at various positions before the solidification endpoint according to the position of the solidification endpoint and in combination with the solidification heat transfer model.

[0025] The beneficial effects of the present invention are as follows: the present invention provides a new approach for online, dynamic, non-contact, non-destructive detection of the continuous casting solidification process, provides a reliable reference for the optimization of parameters such as casting speed, cooling, electromagnetic stirring and light pressure reduction, and ultimately achieves precise control of the quality of the continuous casting billet. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure shows a principle block diagram of a method for non-contact online monitoring of the solidification endpoint position and the shell thickness according to an embodiment of the present invention.

[0027] Figure 2 The diagram shows the monitoring positions of the vibration meters in Example 1 when the ingot is a round ingot or a square ingot; (a) one monitoring position of the vibration meter, (b) one monitoring position of the vibration meter, and (c) multiple monitoring positions of the vibration meters.

[0028] Figure 3 Shown is a schematic diagram of the monitoring positions of the vibrometers in Example 2 when the cast billet is a slab: (a) one monitoring position of the vibrometer, (b) one monitoring position of the vibrometer, and (c) multiple monitoring positions of the vibrometers. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention will be described in detail below in conjunction with specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects.

[0030] like Figure 1 As shown, a method for non-contact online monitoring of the solidification endpoint position and the shell thickness of a blank according to an embodiment of the present invention includes:

[0031] S1. Use a non-contact monitoring method to measure the vibration of the billet surface and obtain the original vibration signal of the billet during the continuous casting process;

[0032] In a specific embodiment, a non-contact vibrometer is used. The vibrometer needs to be installed on a slide rail so that it can slide to monitor different positions of the ingot. When the ingot is a round ingot or a square ingot, the vibration meter monitoring position diagram is shown in FIG. Figure 2 ; When the billet is a slab, the vibration meter monitoring position diagram is shown in Figure 3 .

[0033] S2. Converting the original vibration signal from the time domain to the frequency domain by fast Fourier transform (FFT) processing to obtain a vibration spectrum;

[0034] The Fourier principle shows that any continuously monitored time series or signal can be expressed as an infinite superposition of sinusoidal signals of different frequencies. The Fourier transform algorithm created based on this principle uses the original signal directly monitored to calculate the frequency, amplitude and phase of different sinusoidal signals in the signal in an accumulative manner. After being decomposed by Fourier transform, the time domain signal becomes a superposition of different sinusoidal signals. By analyzing the frequencies of these sinusoidal waves, a signal can be transformed into the frequency domain. It is difficult to see the characteristics of some signals in the time domain, but it is easy to see the characteristics after transforming to the frequency domain.

[0035] S3, comparing the vibration spectrum obtained in step S2 with the vibration spectrum of the same type of ingot in the standard database to determine whether there is a liquid phase at the position, and finally determining the position of the solidification end point of the ingot;

[0036] The standard database is a collection of vibration spectra obtained after Fourier transform processing of original vibration signals of different types of ingots under different shell thickness conditions; the model parameters include ingot steel type, cross-sectional shape, cross-sectional size and drawing speed.

[0037] The amplitude of the vibration spectrum of a billet containing a liquid core is significantly higher than that of a fully solidified billet. An amplitude that can reflect the vibration spectrum of a fully solidified billet is measured, and a vibration spectrum higher than this amplitude is judged to have a liquid phase. The billet containing a liquid core has fewer frequency peaks than the vibration spectrum of a fully solidified billet. An amplitude that can reflect the vibration spectrum of a fully solidified billet is measured, and a vibration spectrum less than this number of frequency peaks is judged to have a liquid phase.

[0038] The specific method for determining the position of the end point of solidification of the ingot is: determining the amplitude threshold and frequency peak number threshold of the vibration spectrum of a certain model of ingot through a standard database; the amplitude of the vibration spectrum of the model of ingot measured is less than the amplitude threshold, and the number of frequency peaks is greater than the frequency peak number threshold. When both conditions are met at the same time, it is determined to be the end point of solidification of the ingot.

[0039] S4. According to the position of the solidification endpoint obtained in step S3 and in combination with a solidification heat transfer model, determine the shell thickness of the ingot at various positions before the solidification endpoint.

[0040] When there is only one vibration meter, it is necessary to move the vibration meter near the solidification end point to monitor and compare the signal to determine the specific position of the solidification end point. When the billet is round or square, the vibration meter monitoring position is shown in Figure 2 (a), when the billet is a slab, the monitoring position of the vibration meter is shown in Figure 3 (a);

[0041] When there are two vibration meters, they can be placed side by side. One is placed at the position where the billet is completely solidified before cutting, showing the signal state of the billet being completely solidified. The other is placed before the second cooling zone solidifies, showing the signal state of the billet containing liquid core. When the device gradually moves toward the solidification end point, the signal changes at different liquid core ratios are compared until it is close to the signal of complete solidification, indicating that the position is the solidification end point. When the billet is round or square, the monitoring position of the vibration meter is shown in Figure 2 (b) When the billet is a slab, the monitoring position of the vibration meter is shown in Figure 3 (b);

[0042] When there are multiple vibration meters, multiple monitoring points can be set near the solidification end point. Based on the above principle and clamping method, the position of the solidification end point can be determined by comparing the change of the vibration signal under different liquid core ratios with the complete solidification signal. When the billet is round or square, the monitoring position of the vibration meter is shown in Figure 2 (c) When the billet is a slab, the monitoring position of the vibration meter is shown in Figure 3 (c).

[0043] When establishing the solidification heat transfer model of the continuous casting billet, in order to improve the accuracy and speed of the simulation calculation, it is necessary to simplify some factors that have little effect on the simulation results: ① Assume that the casting temperature (tundish temperature) is the initial temperature of the molten steel in the crystallizer; ② Ignore the heat transfer in the billet drawing direction; ③ Ignore the influence of the taper of the crystallizer, the protective slag film and the vibration on the heat transfer; ④ The change of the physical properties of the billet is only related to the temperature; ⑤ The heat transfer conditions of the outer arc and the inner arc of the billet are symmetrical; ⑥ Ignore the volume shrinkage during the solidification process of the billet.

[0044] The heat conduction phenomenon in the continuous casting process is relatively complex. The heat transfer equation and the boundary conditions of the continuous casting heat transfer process together constitute the mathematical model of heat transfer solidification of the continuous casting billet. The above problem is simplified to a two-dimensional unsteady-state heat transfer problem. The basic form of the heat transfer equation is shown in formula (1):

[0045]

[0046] Where: ρ is the density of the ingot, kg / m 3 ;c eff is the equivalent specific heat capacity, J / kg·K; λ is the thermal conductivity, W / (m·K); T is the temperature, K; t is the time, s; is the total derivative.

[0047] In the calculation process, whether the high-temperature physical property parameters of the continuous casting billet are selected reasonably will directly affect the calculation accuracy of the model. In order to calculate the solidification heat transfer process of the casting billet, it is necessary to know the liquidus temperature, solidus temperature, density, thermal conductivity, solidification latent heat, etc. The liquidus temperature, solidus temperature, density, thermal conductivity and other parameters are calculated by commercial software or empirical formulas, and their sizes change with changes in temperature. The continuous release of latent heat of solidification in the two-phase region increases the complexity of numerical calculations. In the solution process, the latent heat is considered to be an internal heat source. This model uses the equivalent specific heat method for processing, that is, the rate of change of temperature in this interval is slowed down in the form of amplifying the specific heat, thereby realizing the equivalent process of latent heat release. After processing, the equivalent specific heat C eff The calculation formula is shown in formula (2):

[0048]

[0049] For the two-dimensional unsteady heat transfer equation, the initial temperature is the pouring temperature, see formula (3):

[0050] T t＝0 =T C (3)

[0051] Where: T t＝0 is the initial temperature, K; T c is the pouring temperature, K.

[0052] The heat exchange in the crystallizer is usually calculated using the instantaneous heat flux density of the crystallizer:

[0053]

[0054] According to the law of conservation of heat:

[0055]

[0056]

[0057]

[0058] Where q is the average heat flux density of the crystallizer, W / m 2 ρ w is cooling water density, kg / m 3 ;c w is the specific heat capacity of cooling water, J / (kg·K); Q is the cooling water flow rate of the crystallizer, m 3 / s; △T is the temperature difference between the inlet and outlet water of the crystallizer, K; S is the effective contact area between the molten steel and the crystallizer, m 2 ; Where: q m is the instantaneous heat flux density of the crystallizer, W / m 2 ; β is a constant, depending on the cooling conditions of the crystallizer, W / m 2·s 1 / 2 ; q is the average heat flux density of the crystallizer, W / m 2 ;t m

[0059] is the residence time of molten steel in the crystallizer, s; L m is the effective length of the crystallizer, m; t is the casting time corresponding to a certain position of the crystallizer, s; v is the casting speed, m / s;

[0060] Second cooling zone. Since the boundary temperature and heat flux density of the second cooling zone are unknown, it belongs to the third type of boundary. When the boundary condition is the third type, the following formula can be used for calculation:

[0061] q1=h·(T S ―T w )(8)

[0062] h=a·w b +c(9)

[0063] Where: q 1 is the heat transfer in the second cooling zone, W / m 2 ; h is the comprehensive heat transfer coefficient, W / (m 2 ·K); T s is the surface temperature of the ingot, in K; T w is the water spray temperature, in K; w is the water flow density, L / (m 2 ·s); a and c are constants, and different values ​​are taken for different zones in the secondary cooling zone. The water spraying surface in the secondary cooling zone can cover most of the surface of the secondary cooling zone. The surface of the ingot that is not sprayed will actually dissipate heat through thermal radiation. This situation is taken into account in this paper by correcting the heat transfer coefficient h.

[0064] Radiation cooling area. The heat transfer in the radiation area and air cooling section is calculated using the radiation heat transfer formula:

[0065] q2=εδ(T S 4 ―T amb 4 )(10)

[0066] Where: q2 is the radiation heat transfer, W / m 2 ; ε is the blackness of the billet surface, which is taken as 0.8; δ is the Boltzmann constant, 5.67×10 ―8 W / (m 2 ·K 4 );T s is the surface temperature of the ingot, in K; T amb is the ambient temperature in K.

[0067] S6. Display and record data through display and storage elements, and continuously revise and update the standard database according to process tests or historical data;

[0068] Through process test determination, for example: by nailing, pouring lead or leaking the billet shell, the thickness of the billet shell at different positions or the position data of the solidification end point are obtained, and the corresponding relationship between these data and the vibration signal is established. Or by comparing and screening the signal results of different monitoring points in the production process, for example: under a certain continuous casting equipment and process conditions, the position of complete solidification is monitored and a data representing a completely solidified billet is generated, and the position where there is a liquid phase inside the billet shell is monitored and a data representing an incompletely solidified billet is generated, and the corresponding relationship between the solidification state and the vibration signal is established.

[0069] An embodiment of the present invention provides a system for non-contact online monitoring of the solidification endpoint position and the shell thickness, the system is used to implement the above method, and the system includes:

[0070] Non-contact vibration meter, used to measure the vibration of the ingot surface and obtain the original vibration signal;

[0071] A standard database is used to store the original vibration signals of different types of ingots at different shell thickness states, and a collection of vibration spectra obtained after Fourier transform processing;

[0072] A signal conversion module receives the original vibration signal monitored by the non-contact vibration meter, processes it through fast Fourier transform, converts it from the time domain to the frequency domain, and obtains a vibration spectrum;

[0073] A solidification endpoint judgment module receives the vibration spectrum obtained by the signal conversion module, compares it with the vibration spectrum of the same type of ingot with different shell thickness states in the standard database, and determines the position of the ingot solidification endpoint;

[0074] The shell thickness calculation module determines the shell thickness of the ingot at various positions before the solidification endpoint according to the position of the solidification endpoint and in combination with the solidification heat transfer model.

[0075] Example 1

[0076] The steel used in this embodiment is GCr15 bearing steel, the cross section of the ingot is 240mm×240mm, the basic parameters of the continuous casting machine are shown in Table 1, and the length and water distribution of the secondary cooling zone are shown in Table 2:

[0077] Table 1 Basic parameters of continuous casting machine

[0078]

[0079] Table 2 Length and water distribution of the secondary cooling zone

[0080]

[0081] The casting process under this production process is tested to obtain the shell thickness and solidification endpoint position signal data at different positions, and establish a corresponding standard database. For example, a vibration meter is used to measure the fully solidified area of ​​the continuous casting billet at 20m, and the vibration spectrum is obtained through fast Fourier transform (FFT) processing. The corresponding relationship between the vibration spectrum data here and the fully solidified state of the casting billet is established.

[0082] When there is only one vibration meter, it is necessary to move the vibration meter near the solidification end point to monitor and compare the signal and determine the solidification end point position as 16.15m. The monitoring position of one vibration meter is shown in Figure 2 (a).

[0083] Use two vibrometers, place them close together, one is placed at the position where the ingot has completely solidified before cutting, and displays the signal state of the ingot being completely solidified; the other is placed before the ingot has solidified in the secondary cooling zone, and displays the signal state of the ingot containing liquid core. Move the device gradually toward the solidification end point, and compare the signal changes at different liquid core ratios until it is close to the complete solidification signal. The monitoring position of the solidification end point is 16.15m. The monitoring positions of the two vibrometers are shown in Figure 2 (b).

[0084] Use three vibrometers and place them near the solidification endpoint. Make sure that one of them is placed at a position where the ingot has completely solidified before cutting, and display the signal state of the ingot being completely solidified; another one is placed before the second cooling zone solidifies, and display the signal state of the ingot containing liquid core. Move the device gradually toward the solidification endpoint, and compare the signal changes at different liquid core ratios until it is close to the complete solidification signal. The monitoring solidification endpoint position is 16.15m. The monitoring positions of multiple vibrometers are shown in Figure 2 (c).

[0085] By using the solidification endpoint position and combining the billet solidification heat transfer model, the relationship between the billet shell thickness and the distance from the meniscus is plotted, and the billet shell thickness at each position before the solidification endpoint is calculated. For example, when the distance from the meniscus is 10m, the billet shell thickness is 77mm. The data is displayed and recorded through the display and storage elements, and the standard database is continuously revised and updated according to process tests or historical data.

[0086] Example 2

[0087] The steel used in this embodiment is Q690 high-strength steel, the cross-section of the ingot is 230mm×1330mm, the casting speed is 1.4m / min, the intermediate ladle temperature is 1538℃, the liquidus temperature is 1512℃, and the superheat is 26℃. The calculated heat flow of the crystallizer is shown in Table 1, and the parameters of the secondary cooling zone and the cooling water volume are shown in Table 2:

[0088] Table 1 Calculated heat flow of crystallizer

[0089]

[0090] Table 2 Secondary cooling zone parameters and cooling water volume

[0091]

[0092] The casting process under this production process is tested to obtain the shell thickness and solidification endpoint position signal data at different positions, and establish a corresponding standard database. For example, the vibration meter is used to measure the completely solidified area of ​​the continuous casting billet 28m away from the meniscus, and the vibration spectrum is obtained through fast Fourier transform (FFT) processing. The corresponding relationship between the vibration spectrum data here and the completely solidified state of the casting billet is established.

[0093] When there is only one vibration meter, it is necessary to move the vibration meter near the solidification end point to monitor and compare the signal and determine the solidification end point position as 25.75m. The monitoring position of one vibration meter is shown in Figure 2 (a).

[0094] Use two vibrometers, place them in a sandwiched position, one placed at the position where the ingot has completely solidified before cutting, to display the signal state of the ingot being completely solidified; the other placed before the second cooling zone solidifies, to display the signal state of the ingot containing liquid core, and gradually move the device to the solidification end point, and compare the signal changes at different liquid core ratios until it is close to the complete solidification signal, and the monitoring solidification end point position is 25.75m. The monitoring positions of the two vibrometers are shown in Figure 2 (b).

[0095] Use three vibrometers and place them near the solidification endpoint. Make sure that one of them is placed at a position where the ingot has completely solidified before cutting, and display the signal state of the ingot being completely solidified; the other one is placed before the second cooling zone solidifies, and display the signal state of the ingot containing liquid core. Move the device gradually toward the solidification endpoint, and compare the signal changes at different liquid core ratios until it is close to the complete solidification signal. The monitoring solidification endpoint position is 25.75m. The monitoring positions of multiple vibrometers are shown in Figure 2 (c).

[0096] By using the solidification endpoint position and combining the billet solidification heat transfer model, the relationship between the billet shell thickness and the distance from the meniscus is plotted, and the billet shell thickness at each position before the solidification endpoint is calculated. For example, when the distance from the meniscus is 20m, the billet shell thickness is 91mm. The data is displayed and recorded through the display and storage elements, and the standard database is continuously revised and updated according to process tests or historical data.

[0097] The above is a detailed introduction to a method for non-contact, non-destructive, online dynamic monitoring of the position solidification endpoint and the thickness of the blank shell provided by the embodiment of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0098] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be subject to that defined in the attached claims.

[0099] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0100] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0101] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A method for non-contact online monitoring of the solidification endpoint position and the shell thickness, characterized in that: The method comprises: S1. Use a non-contact monitoring method to measure the vibration of the billet surface and obtain the original vibration signal of the billet during the continuous casting process; S2. Convert the original vibration signal from the time domain to the frequency domain by fast Fourier transform processing to obtain a vibration spectrum; S3, comparing the vibration spectrum obtained in step S2 with the vibration spectrum of the same type of ingot in a standard database to determine the position of the solidification end point of the ingot; S4. According to the position of the solidification endpoint obtained in step S3 and in combination with a solidification heat transfer model, determine the shell thickness of the ingot at various positions before the solidification endpoint.

2. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness according to claim 1, characterized in that: The method further comprises: S5, displaying and recording the result data obtained in step S4 via a display or a storage element.

3. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness according to claim 1, characterized in that: In step S1, a non-contact vibration meter is used to measure the vibration of the ingot in the second cooling zone, the third cooling zone or the roller before cutting during the continuous casting process; the vibration is a natural vibration caused by the process or equipment.

4. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness according to claim 1, characterized in that: In step S3, the standard database is a collection of vibration spectra obtained after Fourier transform processing of original vibration signals of different types of ingots under different shell thickness conditions; the model parameters include ingot steel type, cross-sectional shape, cross-sectional size and drawing speed.

5. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness according to claim 4, characterized in that: The corresponding relationship between the vibration spectrum of the ingot and the shell thickness of the ingot is determined through process tests, or obtained by comparing and screening the signals and results of different measuring points in the production process.

6. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness according to claim 5, characterized in that: The process test obtains the shell thickness or solidification end point position data at different positions of the ingot by nailing, pouring lead or leaking the ingot shell, and establishes a corresponding relationship between these data and the original vibration signal or vibration spectrum.

7. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness of claim 1, characterized in that: In step S3, the specific method for determining the position of the end point of solidification of the ingot is: determining the amplitude threshold and the frequency peak number threshold of the vibration spectrum of a certain model of ingot through a standard database; the amplitude of the vibration spectrum of the model of ingot measured is less than the amplitude threshold, and the number of frequency peaks is greater than the frequency peak number threshold. When both conditions are met at the same time, it is determined to be the end point of solidification of the ingot.

8. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness of claim 3, characterized in that: The number of non-contact vibrometers is one or more; when there is only one vibrometer, the vibrometer is moved near the solidification end point to monitor the signal; when there are two vibrometers, they are sandwiched and one is placed at a position that is completely solidified before cutting to monitor the signal state of complete solidification of the ingot; the other is placed before solidification in the secondary cooling zone to monitor the signal state of the ingot containing a liquid core; when there are more than two vibrometers, multiple monitoring points are set near the solidification end point to place the vibrometers, and the position of the solidification end point is determined by comparing the changes in the vibration signals under different liquid core ratios with the complete solidification signals.

9. The method for non-contact online monitoring of the solidification endpoint position and the shell thickness of claim 1, characterized in that: The casting billet includes square billet, slab billet, round billet and profile billet, and is not limited by size, steel type and drawing speed.

10. A system for non-contact online monitoring of the solidification endpoint position and the shell thickness, characterized in that: The system is used to implement the method according to any one of claims 1 to 9, and the system includes: Non-contact vibration meter, used to measure the vibration of the ingot surface and obtain the original vibration signal; A standard database is used to store the original vibration signals of different types of ingots at different shell thickness states, and a collection of vibration spectra obtained after Fourier transform processing; A signal conversion module receives the original vibration signal monitored by the non-contact vibration meter, processes it through fast Fourier transform, converts it from the time domain to the frequency domain, and obtains a vibration spectrum; A solidification endpoint judgment module receives the vibration spectrum obtained by the signal conversion module, compares it with the vibration spectrum of the same type of ingot with different shell thickness states in the standard database, and determines the position of the ingot solidification endpoint; The shell thickness calculation module determines the shell thickness of the ingot at various positions before the solidification endpoint according to the position of the solidification endpoint and in combination with the solidification heat transfer model.

Images