A method for detecting and determining the position and shape of a meniscus on a wide face of a slab crystallizer

Abstract

The application discloses a method for detecting and determining the position and shape of a meniscus on a slab crystallizer wide surface, and belongs to the technical field of continuous casting. The application aims to arrange temperature sensors on the upper and lower regions of the actual liquid level of molten steel on the wide surface of a slab crystallizer, and collect the temperature of the corresponding position of the copper plate of the crystallizer at a certain frequency. Firstly, the temperature gradient between two longitudinally adjacent temperature measuring points in the region near the actual liquid level of the molten steel is calculated. Since the temperature gradient near the steel-slag interface where the actual liquid level of the molten steel is located is extremely sharp, the coordinates of the two longitudinally adjacent temperature measuring points corresponding to the maximum value of the temperature gradient in the region can be determined. Then, the position of the meniscus at the place is selected between the two temperature measuring points, the center coordinates of the two temperature measuring points are selected, and the position coordinates of the meniscus corresponding to all the longitudinal temperature sensors in the wide surface direction are determined in this way. Finally, the shape of the meniscus on the wide surface of the slab crystallizer is obtained through interpolation. The application is easy to implement and maintain, has high prediction accuracy, and provides an effective way for developing closed-loop feedback control of the meniscus behavior of the crystallizer.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting production quality control in the iron and steel metallurgical industry, and specifically relates to a method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer. Background Technology

[0002] Because of the large span of the wide face of the slab continuous casting mold and the significant differences in the height of the meniscus, the steel-slag interface velocity at the meniscus is high, as well as the non-uniform heat transfer between the copper plate and the molten steel. This leads to quality problems such as slag entrainment and surface defects in the initial slab shell, especially during nozzle blockage, misalignment, or high-speed continuous casting processes. Therefore, determining the position and shape of the wide face meniscus of the slab mold is of great significance for efficient continuous casting.

[0003] Currently, there is a lack of methods for detecting and determining the position and shape of the wide meniscus of a slab crystallizer. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for detecting and determining the position and shape of the meniscus of a slab crystallizer. The aim is to achieve online monitoring or offline evaluation of the position and shape of the meniscus of the slab crystallizer, thereby forming a closed-loop feedback control of meniscus behavior such as crystallizer meniscus height, flow velocity, and heat transfer uniformity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer includes the following steps:

[0007] Step 1: Arrange multiple rows of temperature sensors in the upper to lower area of ​​the actual molten steel level on the wide side of the slab crystallizer.

[0008] Step 2: The temperature sensor collects the temperature of the copper plate during the continuous vibration cycle of the crystallizer at a certain frequency.

[0009] Step 3: Calculate the temperature gradient between two adjacent temperature measuring points along the billet pulling direction (longitudinal direction) near the actual liquid level of the molten steel based on the temperature of the copper plate, and determine the maximum value of the temperature gradient.

[0010] Step 4: Because the temperature gradient near the steel-slag interface where the actual molten steel level is located is very rapid, the coordinates of the two adjacent temperature measurement points corresponding to the maximum temperature gradient can be determined. The midpoint between two adjacent temperature measurement points in the longitudinal direction is selected as the corresponding coordinates of the meniscus in the wide plane of that column (one column).

[0011] Step 5: Determine the meniscus position coordinates of all columns of temperature sensors in the wide face direction using the above method.

[0012] Step 6: Interpolate the coordinates of all the wide meniscus positions obtained to determine the shape of the wide meniscus of the entire slab crystallizer.

[0013] Furthermore, in step 1, the temperature sensor can be a thermocouple, a fiber optic sensor, or any temperature measurement tool.

[0014] Furthermore, in step 1, the temperature sensors are positioned in an area 50-100 mm above and 100-500 mm below the actual molten steel level on the wide side of the mold. In the thickness direction, they are inserted 10-20 mm from the hot surface of the wide side of the mold. The spacing between the temperature measuring points of two rows of temperature sensors in the width direction is 20-100 mm. The spacing (L) between two adjacent temperature measuring points in the same column in the longitudinal direction is 2-10 mm, with the detection accuracy determined according to the process requirements of the continuous casting site.

[0015] Furthermore, in step 2, during the slab continuous casting process, the temperature sensor collects temperature at a frequency of 2 to 10 Hz, with a preferred frequency of 4 Hz for monitoring and collecting the temperature of the copper plate in the crystallizer.

[0016] Furthermore, in step 3, the temperature gradient is calculated by successively dividing the temperature difference of the copper plate at two consecutive temperature measuring points along the wide side of the crystallizer by the distance L between them. Mathematically, this is described as ΔT = (T... high -T low ) / L.

[0017] Furthermore, in step 4, the maximum temperature gradient (ΔG) max The maximum temperature gradient near the actual liquid level of the molten steel in the longitudinal direction is the maximum value of the temperature gradient. The coordinates of the two adjacent temperature measurement points corresponding to the maximum temperature gradient are also in the same column in the longitudinal direction.

[0018] Furthermore, in step 5, the coordinates corresponding to the position of the wide meniscus need to be determined based on the distance between the two longitudinal temperature measuring points, and generally the middle position of the two longitudinal temperature measuring points is selected.

[0019] Furthermore, in step 6, the interpolation method is selected as nonlinear interpolation, preferably cubic spline interpolation.

[0020] The above-mentioned method for determining the position and shape of the wide meniscus of the slab crystallizer can be used for online monitoring or offline evaluation. It is applicable to all continuous casting production, including slabs, square billets, and round billets, and is not limited to use on the wide and narrow faces of the crystallizer.

[0021] The beneficial effects of this invention are: it is easy to implement and maintain, has high prediction accuracy, provides a feasible method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer, and provides an effective way to develop closed-loop feedback control of the crystallizer meniscus behavior. Attached Figure Description

[0022] Figure 1 A schematic diagram of the arrangement of the wide-face fiber crystallizer in the slab crystallizer;

[0023] Figure 2 The temperature measurement results of the copper plate at the temperature measurement point near the meniscus;

[0024] Figure 3 The temperature gradient is calculated by subtracting two consecutive temperature measurement points in different columns.

[0025] Figure 4 The actual and test results of the meniscus at a pulling speed of 1.5 m / min without the action of FC-Mold;

[0026] Figure 5 The actual and test results of the meniscus at a pulling speed of 1.5 m / min under FC-Mold action;

[0027] Figure 6 The actual and test results of the meniscus at a pulling speed of 2.1 m / min without the action of FC-Mold;

[0028] Figure 7 The actual and test results of the meniscus at a pulling speed of 2.1 m / min under FC-Mold action. Detailed Implementation

[0029] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Example 1

[0031] The first step is to install fiber optic sensors on the wide face of the slab continuous casting crystallizer. The crystallizer is 1300mm wide, 247mm thick, and 900mm high. It is made of cast low-carbon steel, superheated to 25K, and has a casting speed range of 1.5m / min to 2.4m / min. It is equipped with electromagnetic braking (FC-Mold).

[0032] The second step involves placing the fiber optic sensors 50mm above the actual molten steel level on the wide side of the slab crystallizer and extending to 400mm below. The thickness direction is 15mm from the hot surface of the wide side of the crystallizer. The spacing between two rows of fiber optic sensors is 50mm, with two additional sensors placed 20mm from the corners on both sides. The longitudinal spacing between two temperature measuring points in the same row is 4mm. The specific arrangement of the fiber optic sensors on the wide side of the slab crystallizer is as follows... Figure 1 As shown.

[0033] The third step is to collect the temperature change of the copper plate during the crystallizer vibration cycle at a frequency of 4Hz.

[0034] Step 4: Select a moment in time to analyze the copper plate temperature collected by the fiber optic crystallizer. Determine the actual range of the molten steel level, such as... Figure 2 The image shows the temperature data collected from the upper 8mm to the lower 8mm of the molten steel level on the wide face of the crystallizer.

[0035] Step 5: Calculate the temperature gradient by dividing the difference between two consecutive temperature measurement points (8mm above and 8mm below the standard molten steel level in the wide-face crystallizer) by the distance between the measurement points, and determine the maximum value of the temperature gradient.

[0036] Step 6: The horizontal number between two consecutive temperature measurement points represents the maximum temperature gradient of the actual molten steel level at that location on the wide face. The midpoint between the two measurement points is selected as the corresponding coordinate of the meniscus on the wide face at that location. The coordinates of the meniscus at other locations on the wide face of the crystallizer are determined in the same way, as follows: Figure 3 As shown.

[0037] Step 7: Using cubic spline interpolation, regress the shape of the entire slab crystallizer's wide meniscus at casting speeds of 1.5 m / min and 2.1 m / min with and without FC-Mold, as shown in the following figure. Figures 4-7 As shown in the figure, the black dots represent the coordinates of the midpoint between the two temperature measurement points corresponding to the maximum temperature gradient in the same column, and the black dotted line represents the cubic spline interpolation result of the black dots. The detection results using the above method are in good agreement with the actual position and shape of the meniscus of the crystallizer.

[0038] The embodiments described above are merely specific implementations of the present invention, and the scope of protection of the present invention is not limited thereto. Any person skilled in the art can obviously obtain simple variations or equivalent substitutions of the technical solution within the scope of the technology disclosed in the present invention, and apply them to the technology of detecting and determining the position and shape of the wide meniscus of the slab crystallizer, all of which fall within the scope of protection of the present invention.

Claims

1. A method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer, characterized in that, Includes the following steps: Step 1: Arrange multiple rows of temperature sensors in the area from the upper to the lower part of the actual liquid level of molten steel on the wide side of the slab crystallizer; Step 2: The temperature sensor collects the temperature of the copper plate during the continuous vibration cycle of the crystallizer at a certain frequency; Step 3: Calculate the temperature gradient between two adjacent temperature measuring points along the billet pulling direction near the actual liquid level of the molten steel based on the copper plate temperature, and determine the maximum value of the temperature gradient; Step 4: Determine the coordinates of the two adjacent temperature measurement points in the vertical direction corresponding to the maximum temperature gradient, and take the midpoint of the two adjacent temperature measurement points as the corresponding coordinates of the meniscus in the wide plane. Step 5: Determine the meniscus position coordinates of all columns of temperature sensors in the wide face direction using the method described above; Step 6: Interpolate the coordinates of all the wide meniscus positions obtained to determine the shape of the wide meniscus of the entire slab crystallizer.

2. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 1, the temperature sensor can be a thermocouple, a fiber optic sensor, or any temperature measurement tool.

3. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 1, the temperature sensors are arranged in an area 50-100 mm above the actual molten steel level on the wide side and 100-500 mm below it; in the thickness direction, they are inserted 10-20 mm from the hot surface of the wide side of the crystallizer; the spacing between the temperature measuring points of two rows of temperature sensors in the width direction is 20-100 mm; the spacing between two adjacent temperature measuring points of the same column in the longitudinal direction is 2-10 mm, and the detection accuracy is determined according to the process requirements of the continuous casting site.

4. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 2, during the slab continuous casting process, the temperature sensor collects temperatures at a frequency of 2~10 Hz.

5. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 3, the temperature gradient is calculated by dividing the temperature difference of the copper plate at two consecutive longitudinal temperature measuring points by the distance between them along the wide side of the crystallizer.

6. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 4, the maximum temperature gradient is the maximum temperature gradient near the actual liquid level of the molten steel in the longitudinal direction, and the coordinates of the two adjacent temperature measuring points corresponding to the maximum temperature gradient are also in the same column in the longitudinal direction.

7. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 5, the coordinates corresponding to the position of the wide meniscus are determined based on the distance between the two longitudinal temperature measuring points, and the middle position of the two longitudinal temperature measuring points is selected.

8. The method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to claim 1, characterized in that, In step 6, the interpolation method selected is nonlinear interpolation.

9. A method for detecting and determining the position and shape of the wide meniscus of a slab crystallizer according to any one of claims 1-8, characterized in that, The method described can be used for online monitoring or offline evaluation, and is applicable to all continuous casting production, not limited to use on the wide and narrow faces of the crystallizer.

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