An Eddy Current Detection System and Detection Method for Molten Steel Level in a Mould

Abstract

The present invention discloses an eddy current detection system and a detection method for the molten steel level in a mold. The system includes: a mold device, which includes a main housing and a mounting housing protruding from the main housing; an air layer, a powder slag layer, a molten slag layer and a molten steel layer are arranged in the main housing; a low-frequency coil group and a high-frequency coil group are arranged in the mounting housing, and the low-frequency coil group and the high-frequency coil group are used to generate a magnetic field to generate eddy current signals in the molten steel layer and the molten slag layer; a sensor module, which includes an eddy current sensor, and the eddy current sensor is arranged on the inner side wall of the main housing and is used to detect the eddy current signals generated in the molten steel layer and the molten slag layer; a controller, which is used to receive the eddy current signals detected by the eddy current sensor, and perform fusion analysis on the eddy current signals, the attribute parameters of the molten steel layer and the molten slag layer, and the parameters of the low-frequency coil group and the high-frequency coil group to obtain the detection distance of the molten steel layer and the thickness of the molten slag layer.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting production of steel, and particularly relates to an eddy current detection system and a detection method for the molten steel level in a mold. Background Art

[0002] In the detection technology of distance and displacement by eddy current, the measurement technology for a range of 1 mm - 30 mm is relatively mature. For sensors with a measurement range above 80 mm, there are only a small number of immature products, and at the same time, the measurement accuracy of such sensors is not particularly high.

[0003] When producing molten steel, due to high temperature, the protective slag covering the surface of the molten steel will melt to form a slag layer. This slag layer plays an important role and is closely related to the quality of the continuous casting billet. However, currently, there are few devices that can accurately measure the thickness of this slag layer or they are in the experimental stage.

[0004] In the continuous casting production of steel, the mold plays an unparalleled role. If the molten steel in the mold fluctuates greatly, subcutaneous slag inclusions and slag entrainment will occur in the continuously cast billet, seriously affecting the quality and production speed of the billet. In severe cases, major safety accidents such as overflow of molten steel and leakage of molten steel will occur. Therefore, accurately controlling the molten steel level in the mold can not only improve the production quality and production speed of continuous casting but also improve production safety. Therefore, the research on high-performance detection and control technology for the molten steel level in the mold has become an important research direction in the field of continuous casting production.

[0005] There are various methods for layer-by-layer detection of the molten steel level in the mold, such as the thermocouple method, the infrared method, the ultrasonic method, etc. However, due to the relatively harsh on-site environment of continuous casting, there is a certain impact on the detection accuracy of the thermocouple method, the infrared method, the ultrasonic method, etc. However, the eddy current detection method can overcome these influencing factors. Therefore, how to design an eddy current detection means for the molten steel level in the mold is still a technical problem to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention proposes an eddy current detection system and a detection method for the molten steel level in a mold, so as to realize the measurement of the distance of the molten steel layer and the thickness of the slag layer in the mold.

[0007] In the first aspect of the present invention, an eddy current detection system for the molten steel level in a mold is provided. The system includes: a mold device, the mold device includes a main housing and an installation housing protruding from the main housing; an air layer, a powder slag layer, a molten slag layer, and a molten steel layer are sequentially arranged in the main housing from top to bottom; a low-frequency coil group and a high-frequency coil group are arranged in the installation housing, the low-frequency coil group is used to generate a first magnetic field to generate a first eddy current signal in the molten steel layer; the high-frequency coil group is used to generate a second magnetic field to generate a second eddy current signal in the molten slag layer; a sensor module, the sensor module includes an eddy current sensor, and the eddy current sensor is arranged on the inner side wall of the main housing to detect the first eddy current signal generated by the molten steel layer and the second eddy current signal generated by the molten slag layer; a controller, the controller is used to receive the first eddy current signal and the second eddy current signal detected by the eddy current sensor, and perform fusion analysis on the first eddy current signal, the second eddy current signal, the attribute parameters of the molten steel layer and the molten slag layer, and the parameters of the low-frequency coil group and the high-frequency coil group to obtain the detection distance of the molten steel layer and the thickness of the molten slag layer.

[0008] Further, the low-frequency coil group includes a concentrically arranged low-frequency excitation coil and a low-frequency detection coil. The low-frequency excitation coil is used to generate a first magnetic field to generate a first eddy current signal in the molten steel layer; the low-frequency detection coil is used to detect the changing first voltage value in the molten steel layer.

[0009] Further, the high-frequency coil group includes a concentrically arranged high-frequency excitation coil and a high-frequency detection coil. The high-frequency excitation coil is used to generate a second magnetic field to generate a second eddy current signal in the molten slag layer, and the high-frequency detection coil is used to detect the changing second voltage value in the molten slag layer.

[0010] Further, the radius of the low-frequency excitation coil is greater than the radius of the high-frequency excitation coil, and the excitation frequency of the low-frequency excitation coil is greater than the excitation frequency of the high-frequency excitation coil.

[0011] Further, the radius of the low-frequency excitation coil is less than the radius of the low-frequency detection coil, the number of turns of the low-frequency excitation coil is less than the number of turns of the low-frequency detection coil, and the thickness of the low-frequency excitation coil is less than the thickness of the low-frequency detection coil.

[0012] Further, the radius of the high-frequency excitation coil is less than the radius of the high-frequency detection coil, the number of turns of the high-frequency excitation coil is less than the number of turns of the high-frequency detection coil, and the thickness of the high-frequency excitation coil is equal to the thickness of the high-frequency detection coil.

[0013] Further, the controller performs fusion analysis on the first eddy current signal, the second eddy current signal, the property parameters of the molten steel layer and the slag layer, and the parameters of the low-frequency coil group and the high-frequency coil group to obtain the thicknesses of the molten steel layer and the slag layer, including: establishing an impedance change function for the molten steel layer and the slag layer, calculating the impedances of the molten steel layer and the slag layer; based on the impedances of the molten steel layer and the slag layer, constructing an equivalent circuit, determining an expression for the relationship between the change in eddy current intensity of the molten steel layer and the detection distance and an expression for the relationship between the change in eddy current intensity of the slag layer and its thickness; according to the expression for the relationship between the change in eddy current intensity of the molten steel layer and the detection distance and the expression for the relationship between the change in eddy current intensity of the slag layer and its thickness, using the first eddy current signal and the second eddy current signal of the molten steel layer and the slag layer, calculating the detection distance of the molten steel layer and the thickness of the slag layer.

[0014] The second aspect of the present invention provides an eddy current detection method for the molten steel level in a mold, and the method includes: exciting a low-frequency coil group with a sine voltage wave signal to generate a first magnetic field, so that a first eddy current signal is generated in the molten steel layer; exciting a high-frequency coil group with a sine current wave signal to generate a second magnetic field, so that a second eddy current signal is generated in the slag layer; detecting the first eddy current signal generated in the molten steel layer and the second eddy current signal generated in the slag layer through an eddy current sensor; the controller performs fusion analysis on the first eddy current signal, the second eddy current signal, the property parameters of the molten steel layer and the slag layer, and the parameters of the low-frequency coil group and the high-frequency coil group to obtain the detection distance of the molten steel layer and the thickness of the slag layer.

[0015] Further, the steps for the controller to perform fusion analysis on the first eddy current signal, the second eddy current signal, the property parameters of the molten steel layer and the slag layer, and the parameters of the low-frequency coil group and the high-frequency coil group to obtain the thicknesses of the molten steel layer and the slag layer include: establishing an impedance change function for the molten steel layer and the slag layer, calculating the impedances of the molten steel layer and the slag layer; based on the impedances of the molten steel layer and the slag layer, constructing an equivalent circuit, determining an expression for the relationship between the change in eddy current intensity of the molten steel layer and the detection distance and an expression for the relationship between the change in eddy current intensity of the slag layer and its thickness; according to the expression for the relationship between the change in eddy current intensity of the molten steel layer and the detection distance and the expression for the relationship between the change in eddy current intensity of the slag layer and its thickness, using the first eddy current signal and the second eddy current signal of the molten steel layer and the slag layer, calculating the detection distance of the molten steel layer and the thickness of the slag layer.

[0016] The above eddy current detection system and method for the molten steel level in the mold generate different magnetic fields in the molten steel layer and the slag layer through the low-frequency excitation coil and the high-frequency excitation coil, detect different voltage values in the molten steel layer and the slag layer through the low-frequency detection coil and the high-frequency detection coil, and detect different eddy current signals in the molten steel layer and the slag layer through the eddy current sensor. The detection distance of the molten steel layer and the thickness of the slag layer are obtained through the fusion analysis of different voltage values, different eddy current signals, the attribute parameters of the molten steel layer and the slag layer, and the coil parameters, realizing the measurement of the layered structure in the mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] For purposes of illustration and not limitation, the present invention will now be described with reference to the preferred embodiments of the present invention, particularly with reference to the accompanying drawings, in which:

[0018] Figure 1 is a three-dimensional structural schematic diagram of an eddy current detection system for the molten steel level in the mold provided by an embodiment of the present invention;

[0019] Figure 2 is a two-dimensional schematic diagram of an eddy current detection system for the molten steel level in the mold provided by an embodiment of the present invention;

[0020] Figure 3 is a flowchart of an eddy current detection method for the molten steel level in the mold provided by another embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of an equivalent circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0023] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art belonging to the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0025] Figure 1It is a three-dimensional structural schematic diagram of an eddy current detection system for the molten steel level in a mold provided by an embodiment of the present invention. Figure 2 It is a two-dimensional schematic diagram of an eddy current detection system for the molten steel level in a mold provided by an embodiment of the present invention. The eddy current detection system for the molten steel level in the mold generates a magnetic field through a coil and detects the eddy current intensity generated by different structural layers in the mold through an eddy current sensor, so as to realize the measurement of the thickness of different structural layers in the mold.

[0026] Please refer to Figure 1 and Figure 2 , the eddy current detection system for the molten steel level in the mold includes a mold device 10, a sensor module 20 and a controller 30.

[0027] The mold device 10 includes a main housing 11 and a mounting housing 12 protruding from the main housing 11.

[0028] An air layer 111, a powder slag layer 112, a slag layer 113 and a molten steel layer 114 are sequentially arranged in the main housing 11 from top to bottom. The air layer 111 contains air, the powder slag layer 112 contains a substitute for powder slag, the slag layer 113 contains a substitute for slag, and the molten steel layer 114 contains simulated molten steel.

[0029] A low-frequency coil group 13 and a high-frequency coil group 14 are arranged in the mounting housing 12. The low-frequency coil group 13 includes a concentrically arranged low-frequency excitation coil 131 and a low-frequency detection coil 132. The low-frequency excitation coil 131 is used to generate a first magnetic field to make the molten steel layer 114 generate a first eddy current signal; the low-frequency detection coil 132 is used to detect the changing first voltage value in the molten steel layer 114; the high-frequency coil group 14 includes a concentrically arranged high-frequency excitation coil 141 and a high-frequency detection coil 142; the high-frequency excitation coil 141 is used to generate a second magnetic field to make the slag layer 113 generate a second eddy current signal, and the high-frequency detection coil 142 is used to detect the changing second voltage value in the slag layer 113.

[0030] The sensor module 20 includes an eddy current sensor 21. The eddy current sensor 21 is arranged on the inner side wall of the main housing 11 and is used to emit an electromagnetic signal and receive the first eddy current signal returned by the molten steel layer 114 and the second eddy current signal returned by the slag layer 113.

[0031] The controller 30 is configured to receive the first eddy current signal and the second eddy current signal detected by the eddy current sensor 21, the first voltage value detected by the low-frequency detection coil 132, and the second voltage value monitored by the high-frequency detection coil 142. The controller 30 performs fusion analysis on the first eddy current signal, the second eddy current signal, the first voltage value, the second voltage value, as well as the attribute parameters of the molten steel layer and the slag layer, and the parameters of the low-frequency excitation coil and the high-frequency excitation coil, to obtain the detection distance of the molten steel layer and the thickness of the slag layer. Herein, the detection distance of the molten steel layer is the distance between the molten steel layer and the upper end of the main housing 11 of the mold device 10.

[0032] For the above-mentioned eddy current detection system for the molten steel level in the mold, different magnetic fields are generated in the molten steel layer 114 and the slag layer 113 by the low-frequency excitation coil 131 and the high-frequency excitation coil 141, and different voltage values are detected in the molten steel layer 114 and the slag layer 113 by the low-frequency detection coil 132 and the high-frequency detection coil 142. Different eddy current signals are detected in the molten steel layer 114 and the slag layer 113 by the eddy current sensor 21. The detection distance of the molten steel layer and the thickness of the slag layer are obtained through the fusion analysis of different voltage values, different eddy current signals, the attribute parameters of the molten steel layer and the slag layer, and the coil parameters, so as to realize the measurement of the layered structure in the mold.

[0033] In some embodiments, since the main components of the solid mold powder are silicon dioxide and calcium oxide, this layer is similar to glass. Therefore, a 1-mm-thick glass is used to replace the solid slag layer to support the powder slag layer 112. Neither the glass nor the powder slag is conductive, and its thickness can be regarded as the thickness of the powder slag layer. The conductivity of tap water is 0.5 - 5.0 S / cm.

[0034] The conductivity of the molten steel layer 114 is 0.1 - 0.3 S / cm. Tap water is used to replace the weakly conductive molten steel film, and an aluminum plate is used to replace the molten steel to establish a simulation object of the molten steel.

[0035] In some embodiments, the outer wall of the main housing 11 is made of steel, and the shape of the main housing 11 is generally square.

[0036] In some embodiments, the material of the mounting housing 12 is stainless steel 304, and a shielding layer is provided on the outside of the mounting housing 12.

[0037] In some embodiments, the number of the low-frequency coil groups 13 is two. The two low-frequency coil groups 13 are arranged at intervals, and the leads of the two low-frequency coil groups 13 are led out through the through holes at the rear of the mounting housing 12. The shapes of the two low-frequency coil groups 13 are generally cylindrical.

[0038] The low-frequency excitation coil 131 and the low-frequency detection coil 132 are generally in an annular shape, and the radius of the low-frequency excitation coil 131 is smaller than that of the low-frequency detection coil 132. Preferably, the difference between the radius of the low-frequency excitation coil 131 and the radius of the low-frequency detection coil 132 is 250 mm.

[0039] The number of turns of the low-frequency excitation coil 131 is smaller than that of the low-frequency detection coil 132. Preferably, the number of turns of the low-frequency excitation coil 131 is 400 turns, and the number of turns of the low-frequency detection coil 132 is 4500 turns.

[0040] For the low-frequency coil group, considering the influencing factors of its measurement range, coils with a larger radius need to be preferentially used. Therefore, a low-frequency coil group 13 with an inner diameter of 60 mm and an outer diameter of 80 mm is used. Among them, the thickness of the low-frequency excitation coil 131 is smaller than that of the low-frequency detection coil 132. Preferably, the thickness of the low-frequency excitation coil is 5 mm, and the thickness of the low-frequency detection coil is 15 mm.

[0041] In some embodiments, the number of the high-frequency coil groups 14 is two, and the leads of the two high-frequency coil groups 14 are led out through the through holes at the rear of the mounting housing 12. The shapes of the two high-frequency coil groups 14 are generally cylindrical.

[0042] The radius of the high-frequency excitation coil 141 is smaller than that of the high-frequency detection coil 142. Preferably, the difference between the radius of the high-frequency excitation coil 141 and the radius of the high-frequency detection coil 142 is 150 mm.

[0043] The number of turns of the high-frequency excitation coil 141 is smaller than that of the high-frequency detection coil 142. Preferably, the number of turns of the high-frequency excitation coil is 100 turns, and the number of turns of the high-frequency detection coil is 1000 turns.

[0044] For the detection of the slag layer, since the slag layer is relatively close to the coil and the change range of the slag layer is relatively small, smaller coils are selected when designing the high-frequency coil group. The thickness of the high-frequency excitation coil 141 is equal to the thickness of the high-frequency detection coil 142. Preferably, the thickness of the high-frequency excitation coil 141 is 5 mm, and the thickness of the high-frequency detection coil 142 is 5 mm.

[0045] In some embodiments, the radius of the low-frequency detection coil 132 is larger than that of the high-frequency detection coil 142, and the radius of the low-frequency excitation coil 131 is larger than that of the high-frequency excitation coil 141.

[0046] The excitation frequency of the low-frequency excitation coil 131 is higher than that of the high-frequency excitation coil 141. The excitation frequency of the low-frequency excitation coil 131 is 800 Hz, and the excitation frequency of the high-frequency excitation coil 141 is 5 MHz.

[0047] The low-frequency excitation coil 131 and the high-frequency excitation coil 141 generate different magnetic fields due to different excitation frequencies. At the same time, due to the different conductivities of the stratified structures in the measured mold, the eddy current signals generated will also be different. Therefore, the voltage values of the respective stratification changes are obtained by the different effects of the eddy current signals on the detection coils. The voltage value of the molten steel layer 114 changing within a large range is detected by the low-frequency detection coil 132 with a large radius, and the change within a small range of the slag layer 113 is obtained by the high-frequency detection coil 142 with a small radius. When the molten steel layer 114 changes at different heights, the slag layer 113 also changes, and different values of changes at different positions within the full range of the mold are detected.

[0048] In some embodiments, the sensor module 20 further includes a millimeter-wave sensor disposed in the main housing 11, and the millimeter-wave sensor is used to measure the lengths of the low-frequency coil group and the high-frequency coil group.

[0049] Figure 3 It is a flowchart of the eddy current detection method for the molten steel level in the mold provided by another embodiment of the present invention. The eddy current detection method for the molten steel level in the mold is implemented based on the above-mentioned eddy current detection system for the molten steel level in the mold.

[0050] Please refer to Figure 3 , the eddy current detection method for the molten steel level in the mold includes the following steps:

[0051] S100, a first magnetic field is generated by exciting the low-frequency excitation coil with a sine voltage wave signal to generate a first eddy current signal in the molten steel layer; a second magnetic field is generated by exciting the high-frequency excitation coil with a sine current wave signal to generate a second eddy current signal in the slag layer.

[0052] In this embodiment, a 10V sine voltage wave signal is used as the excitation signal source for the low-frequency excitation coil, and a 0.5A sine current wave signal is used as the excitation signal source for the high-frequency excitation coil.

[0053] S200, the first voltage value changing in the molten steel layer is detected by the low-frequency detection coil; the second voltage value changing in the slag layer is detected by the high-frequency detection coil.

[0054] S300, the first eddy current signal generated by the molten steel layer and the second eddy current signal generated by the slag layer are detected by the eddy current sensor. The distance between the eddy current sensor and the center of the low-frequency coil group is collected by the millimeter-wave sensor.

[0055] S400, the first voltage value, the second voltage value, the first eddy current signal, the second eddy current signal, and the attribute parameters and coil parameters of the molten steel layer and the slag layer are fused and analyzed to obtain the detection distance of the slag layer and the thickness of the molten steel layer. Among them, the detection distance of the molten steel layer is the distance between the molten steel layer and the upper end of the main housing of the mold device

[0056] In this embodiment, the method for fusing and analyzing the first voltage value, the second voltage value, the first eddy current signal, the second eddy current signal, and the property parameters and coil parameters of the molten steel layer and the slag layer is as follows:

[0057] S401. Establish an impedance change function for the molten steel layer and the slag layer, and calculate the impedance of the molten steel layer and the slag layer.

[0058] In this embodiment, the property parameters of the molten steel layer and the slag layer are conductivity and permeability; the coil parameters are excitation angular frequency and excitation frequency.

[0059] In this embodiment, the impedance change function of the molten steel layer and the slag layer is:

[0060] Z = f(r1, r2, L1, L2, L3, σ1, σ2, …, σ m , μ1, μ2, …, μ m , H1, H2, …, H m , ω) (1)

[0061] In the formula, r1 and r2 are the inner diameter and outer diameter of the low-frequency coil group, L1 is the length of the low-frequency coil group, L2 is the length of the high-frequency coil group, and L3 is the distance between the eddy current sensor and the powder slag layer in the mold; σ1, σ2, …, σ m are the conductivities of the powder slag layer, the slag layer, and the molten steel layer; μ1, μ2, …, μ m are the permeabilities of the powder slag layer, the slag layer, and the molten steel layer; H1, H2, … H m-1 , H m are the thicknesses of the powder slag layer, the slag layer, and the molten steel layer, and ω is the excitation angular frequency. When the coil parameters and the properties of the object to be measured are determined, the impedance Z obtained from the function is only related to the magnitude of L3. Therefore, the relationship between the change of molten steel and the distance can be obtained.

[0062] S402. Based on the impedance of the molten steel layer and the slag layer, construct an equivalent circuit, and determine the relationship expression between the change of eddy current intensity in the molten steel layer and the detection distance, and the relationship expression between the change of eddy current intensity in the slag layer and the thickness of the slag layer itself.

[0063] In this embodiment, the specific implementation method for determining the relationship expression between the change of eddy current intensity in the molten steel layer and the detection distance, and the relationship expression between the change of eddy current intensity in the slag layer and the thickness of the slag layer itself is as follows:

[0064] For an eddy current sensor, it is usually equivalent to the two coils on both sides of a transformer, that is, the low-frequency excitation coil or the high-frequency excitation coil is regarded as the primary side of the transformer, and the eddy currents generated in the molten steel layer and the slag layer are regarded as the secondary side of the transformer. For two mutually coupled coils, the primary coil is at voltage U srUnder the action of [I1], an induced current I2 will be generated in the secondary side coil under electromagnetic induction, and the generated induced current will affect the current I1 and voltage U in the primary coil. sr , and its equivalent diagram is as Figure 4 shown.

[0065] According to Kirchhoff's voltage balance equation:

[0066]

[0067] In the formula, R1 is the impedance of the low-frequency excitation coil or high-frequency excitation coil; R2 is the resistance of the molten steel layer and the slag layer; M is the mutual inductance coefficient; Usr is the excitation voltage; L1 is the inductance of the eddy current sensor; L2 is the eddy current inductance of the molten steel layer and the slag layer.

[0068] From the above formula (2), we can get:

[0069]

[0070] Therefore:

[0071]

[0072] From the above formula (4), we can get:

[0073] The relational expression of the eddy current intensity I2 of the molten steel layer and the slag layer and the excitation frequency f of the low-frequency excitation coil or high-frequency excitation coil;

[0074] The relational expression of the eddy current intensity I2 of the molten steel layer and the detection distance d and the relational expression of the eddy current intensity I2 of the slag layer and the thickness d1 of the molten layer itself.

[0075] The change in the eddy current intensity of the molten steel layer causes a change in the induced voltage of the detection coil. That is, the relationship between the eddy current intensity and the detection distance can be regarded as the relationship between the induced voltage U and the detection distance d. By fitting the measurement data, the relational expression between the two is obtained:

[0076] U = 0.000362d 2 - 0.4263d + 1429.4

[0077] The eddy current intensity of the slag layer is affected by the change of the molten steel and the change of the slag layer itself. The change in the eddy current intensity of the slag layer can be regarded as the change in the induced voltage U1 of the detection coil. By establishing a regression mathematical model, the relationship among the three is obtained:

[0078] U1 = 0.4454d + 13.0292d1 - 0.6940

[0079] where d1 is the thickness of the molten layer itself.

[0080] S403, according to the relationship expression between the change of eddy current intensity of the molten steel layer and the detection distance, and the relationship expression between the change of eddy current intensity of the slag layer and the thickness of the slag layer itself, the detection distance of the slag layer and the thickness of the molten steel layer are calculated using the collected first eddy current signal and second eddy current signal of the molten steel layer and the slag layer.

[0081] The above-mentioned eddy current detection method for molten steel level in the crystallizer generates different magnetic fields in the molten steel layer and the slag layer through low-frequency excitation coils and high-frequency excitation coils, and detects different voltage values ​​generated in the molten steel layer and the slag layer through low-frequency detection coils and high-frequency detection coils, and detects different eddy current signals generated in the molten steel layer and the slag layer through eddy current sensors. The detection distance of the molten steel layer and the thickness of the slag layer are obtained through a fusion analysis of different voltage values, different eddy current signals, property parameters of the molten steel layer and the slag layer, and coil parameters, thereby realizing the measurement of the layered structure in the crystallizer.

[0082] The above-mentioned eddy current detection method of molten steel level in the crystallizer is verified below.

[0083] Place a steel plate or aluminum plate at the bottom of the crucible, and cover it with protective slag or crystals with a lower melting point, such as sodium chloride. Put the crucible and protective slag into a heating furnace and heat until the protective slag or sodium chloride is melted. Then withdraw from the heating furnace and align with the edge of the crystallizer device equipped with eddy current sensors and millimeter wave sensors and place it on a refractory brick platform. Add powder slag to the molten protective slag and use a rotating scraper to flatten the powder slag, and measure with the sensor at the same time. The melting point of the selected protective slag is about 1065 degrees Celsius, and the melting point of sodium chloride is 865 degrees Celsius. The conductive properties after melting are close to those of the protective slag (its melting point and conductive properties can be adjusted by adding other materials). After the eddy current sensor collects data, the crucible can be cut open after natural cooling, and the layer thickness during the measurement period can be compared with the data measured by the eddy current detection method of the molten steel level in the crystallizer mentioned above.

[0084] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An eddy current detection system for molten steel level in a mold, characterized in that, Comprising: A mold device, the mold device includes a main housing and a mounting housing protruding from the main housing; an air layer, a powder slag layer, a molten slag layer, and a molten steel layer are sequentially arranged in the main housing from top to bottom; a low-frequency coil group and a high-frequency coil group are arranged in the mounting housing, the low-frequency coil group is used to generate a first magnetic field to make the molten steel layer generate a first eddy current signal; the high-frequency coil group is used to generate a second magnetic field to make the molten slag layer generate a second eddy current signal; Further, the low-frequency coil group is excited by a sine voltage wave signal to generate a first magnetic field, so that the molten steel layer generates a first eddy current signal; the high-frequency coil group is excited by a sine current wave signal to generate a second magnetic field, so that the molten slag layer generates a second eddy current signal; A sensor module, the sensor module includes an eddy current sensor, and the eddy current sensor is arranged on the inner side wall of the main housing for detecting the first eddy current signal generated by the molten steel layer and the second eddy current signal generated by the molten slag layer; A controller, the controller is used to receive the first eddy current signal and the second eddy current signal detected by the eddy current sensor, and perform fusion analysis on the first eddy current signal, the second eddy current signal, and the attribute parameters of the molten steel layer and the molten slag layer, and the parameters of the low-frequency coil group and the high-frequency coil group to obtain the detection distance of the molten steel layer and the thickness of the molten slag layer, specifically including: Establish an impedance change function of the molten steel layer and the molten slag layer, and calculate the impedance of the molten steel layer and the molten slag layer; Based on the impedance of the molten steel layer and the molten slag layer, construct an equivalent circuit, and determine the relationship expression between the change in eddy current intensity of the molten steel layer and the detection distance and the relationship expression between the change in eddy current intensity of the molten slag layer and its thickness; The relationship expression of the equivalent circuit is: （2） Wherein, R1 is the impedance of the low-frequency excitation coil or the high-frequency excitation coil; R2 is the resistance of the molten steel layer and the slag layer; ω is the excitation angular frequency, M is the mutual inductance coefficient; U sr is the excitation voltage; L1 is the inductance of the eddy current sensor; L2 is the eddy current inductance of the molten steel layer and the slag layer, I1 represents the current generated after the primary coil is energized, and I2 represents the eddy current intensity of the molten steel layer and the slag layer.

2. The eddy current detection system for the molten steel level in the mold according to claim 1, wherein, The low-frequency coil group includes a concentrically arranged low-frequency excitation coil and a low-frequency detection coil, the low-frequency excitation coil is used to generate a first magnetic field to make the molten steel layer generate a first eddy current signal; the low-frequency detection coil is used to detect the changing first voltage value in the molten steel layer.

3. The eddy current detection system for the molten steel level in the mold according to claim 2, wherein The high-frequency coil group includes a concentrically arranged high-frequency excitation coil and a high-frequency detection coil, the high-frequency excitation coil is used to generate a second magnetic field to make the molten slag layer generate a second eddy current signal, and the high-frequency detection coil is used to detect the changing second voltage value in the molten slag layer.

4. The eddy current detection system for the molten steel level in the mold according to claim 3, wherein The radius of the low-frequency excitation coil is greater than the radius of the high-frequency excitation coil, and the excitation frequency of the low-frequency excitation coil is less than the excitation frequency of the high-frequency excitation coil.

5. The eddy current detection system for the molten steel level in the mold according to claim 2, characterized in that, The radius of the low-frequency excitation coil is less than the radius of the low-frequency detection coil, the number of turns of the low-frequency excitation coil is less than the number of turns of the low-frequency detection coil, and the thickness of the low-frequency excitation coil is less than the thickness of the low-frequency detection coil.

6. The eddy current detection system for the molten steel level in the mold according to claim 3, wherein, The radius of the high-frequency excitation coil is less than the radius of the high-frequency detection coil, the number of turns of the high-frequency excitation coil is less than the number of turns of the high-frequency detection coil, and the thickness of the high-frequency excitation coil is equal to the thickness of the high-frequency detection coil.

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