KR20030017110A - A methof for detecting edge skull in strip casting process - Google Patents

Abstract

PURPOSE: A method for detecting edge skull is provided to read information on size and position of edge skull by photographing cast strip coming out of the nip of casting rolls in strip casting process, thereby image processing the photographed images. CONSTITUTION: The method for detecting edge skull in strip casting process comprises the steps of photographing images of cast strip using CCD cameras installed between a position of the cast strip right after formation of cast strip and a point in which temperature distribution of cast strip is constant as continuously measuring load of edge dams at an edge dam load measuring part; obtaining picture data (B) consisting of cast strip outline and skull image and reading the number of pixels (Pc) between both sides of cast strip image by image processing the photographed picture data (A) of cast strip using an edge detection mask, and extracting picture data (C) of the skull image by removing straight line components representing the cast strip outline; obtaining differential absolute values for the edge dam load corresponding to the formation time point of skull in case that extraction results of the picture data (C) of the skull image is primarily judged to be skull, and reading the number of widthwise pixels (Px) and the number of lengthwise pixels (Py) of the extracted skull image by finally judging that is skull only when the absolute value is a certain value or more; and calculating width size (Sx) and length size (Sy) of actual skull using the following expression 1 (Sx=PxxCx/Pc) and expression 2 (Sy=PyxCy'/Pf) wherein Cx is actual horizontal length of a strip, Cy' is vertical length of CCD camera image and Pf is the number of lengthwise pixels of one frame.

Description

Edge scull searching method in sheet metal casting process {A METHOF FOR DETECTING EDGE SKULL IN STRIP CASTING PROCESS}

The present invention relates to an edge scull searching method for reading and storing information on the size and position of an edge scull by imaging a cast piece exiting the casting roll 에서 in a thin sheet casting process and image processing the photographed image. In detail, the image processing of the image of the cast slab to obtain the absolute value of the edge dam load derivative value at the time determined to be the edge skull, and is related to the edge skull search method that determines that the edge skull only when the absolute value is a certain value or more. will be.

Strip casting process is a technology that is more advanced than thin slab, and it is a technology that can produce cast steel (hot coil) directly from molten steel without making slab, and it can skip the hot rolling process in a short time. In addition to mass production, it is known as a process that can significantly reduce equipment investment costs, production costs and operating costs.

In the sheet casting process, hot molten steel is usually supplied between a pair of casting rolls through a nozzle to form a pair of casting rolls and a molten steel pool formed by edge dams, and then the casting rolls are rotated while rotating the casting rolls. The molten steel is rapidly solidified by heat leakage inside the roll through the contact between the molten steel and the cast steel.

However, in such a thin plate casting process, a scull may be generated in the slab at the end of the slab due to solidification unevenness in the width direction of the slab, and thus may be pressed together in a subsequent rolling process, thereby degrading the quality of the slab. A problem arises. Therefore, in order to prevent the deterioration of the cast steel due to the skull, it is necessary to perform post-treatment processes such as an edge cutting process and a subsequent rolling process to remove the skull from the cast steel. Accurate information about size and location is required.

In the related art, this has been visually determined or a follow-up step for treating the skull, such as an edge cutting step, with an arbitrary value obtained statistically has been difficult. Therefore, it is difficult to expect an efficient follow-up step.

As a technique for solving the above problems, the present inventors may include a Korean patent application (application number: 2000-41279). The patent application includes: a CCD camera installed between a point immediately after a cast is generated and a point where a temperature distribution of the cast is constant, to capture an image of the cast; The image data (A) of the photographed cast piece is image-processed with an edge detection mask to obtain image data (B) consisting of a slab outline and a skull image, reading the number of pixels (Pc) between both sides of the cast image, and the image data (B). ) Extracts the image data (C) of the skull image by erasing the linear component representing the slab outline, and reads the horizontal pixel number (Px) and vertical pixel number (Py) of the skull image from the image data of the extracted skull image. An image processing unit; And a horizontal pixel number (Px) and a vertical pixel number (Py) of the skull image, a pixel number (Pc) between both sides of the slab image, which is read by the image processor, and a preset horizontal size (Cx) of the slab, the CCD camera. And a calculation processing unit for calculating the horizontal size Sx and the vertical size Sy of the actual skull from the vertical size Cy 'of the actual cast image photographed in one frame of and the vertical pixel number Pf of the one frame. Disclosed is a method and apparatus for configuring edge scull search.

The method reads the information on the edge scull by simple image processing of the photographed image of the slab manufactured in the sheet casting process, and calculates the read information with a predetermined value to generate the skull and the position and width and length of the skull. This is useful in that it can be searched easily and quickly. However, in this method, even if scale is mixed in the cast steel, it is determined as a skull, so there is a problem that the portion where the scale is generated must be cut in a subsequent process.

The present invention is to solve the above-mentioned problems of the prior art, the edge dam measured at the time of occurrence of the skull when the size and position of the edge skull is detected by imaging the cast image using a CCD camera and image processing it It is an object of the present invention to provide an edge skull search method which can prevent the scale from being incorrectly determined as a skull by determining that the final skull is only when the absolute value of the load differential value is more than a predetermined value.

1 is a schematic explanatory diagram of an edge scull search apparatus of the present invention.

Fig. 2 is an example of an image of a slab photographed by a CCD camera of an edge scull search apparatus according to the present invention.

3 is an example of an image processed by an edge detection mask in an edge scull search apparatus according to the present invention.

4 is an example of an image showing a skull and scale start position and size read by an edge scull search apparatus according to the present invention.

5 is a graph showing a relationship between edge dam loads versus casting time,

Figure 5 (a) shows the relationship between the casting time and the edge dam load before the differential,

Fig. 5 (b) is a graph showing the relationship between casting time and edge dam load after differentiation.

Explanation of symbols on the main parts of the drawings

10: CCD camera 40: image processing unit

20: roll rotation speed measurement unit 50: calculation processing unit

30: edge dam load measuring unit 60: storage unit

Hereinafter, the present invention will be described.

In the sheet casting process, the slabs produced by pressing high-temperature molten steel between rotating rolls for casting are cooled to room temperature and start to turn black. The scull generated on the cast iron also begins to turn black as it cools, but the skull that cools faster than the cast steel turns black faster than the cast steel. Therefore, by detecting the difference in color caused by the difference in cooling rate by using a CCD camera it is possible to detect the skull during casting.

However, when scales (oxides generated on the metal surface) are generated by various causes during the sheet casting process, these scales also have a black color, and thus there is a problem that they may be confused with sculls in the CCD image.

Therefore, the present inventors have conducted numerous studies to solve the above problems, and as a result, the skull imparts more resistance to the edge dam located between the rolls when the skull is pressed with the liquid molten steel than without the skull. The present invention has been found.

That is, in the present invention, even if it is judged primarily as a skull by CCD image processing, the derivative value of the absolute value of the edge dam load at the time of the skull generation is obtained, and it is determined that the final skull is only when the derivative value is a certain value or more. It is characterized by providing an edge skull detection method for obtaining the size and position.

Therefore, the present invention,

Taking an image of the cast using a CCD camera installed between the point immediately after the cast is produced and the temperature distribution of the cast is constant, while continuously measuring the edge dam load in the edge dam load measuring unit;

The image data (A) of the photographed slab is image-processed with an edge detection mask to obtain an image data (B) consisting of a slab outline and a skull image, reading the number of pixels (Pc) between both sides of the slab image, and the image data (B). Extracting the image data (C) of the skull image by erasing the linear component representing the slab outline at

If it is determined that the skull is the result of the extraction of the skull image image data (C), the absolute value of the derivative value for the edge dam load corresponding to the time of the skull generation is obtained, and the final determination is made that the skull is only when the absolute value is a predetermined value or more. Reading horizontal pixel number (Px) and vertical pixel number (Py) of the skull image from the image data of the extracted skull image, and

An edge skull search method in a thin sheet casting process including calculating the horizontal size Sx and the vertical size Sy of an actual skull using Equations 1 and 2 below.

In addition, the present invention,

The edge dam load measuring unit and the roll speed measuring unit continuously measure the edge dam load and the casting roll speed, and use the CCD camera installed between the point immediately after the casting is made and the temperature distribution of the casting is constant. Imaging the image,

The image data (A) of the photographed cast piece is image-processed with an edge detection mask to obtain image data (B) consisting of a slab outline and a skull image, reading the number of pixels (Pc) between both sides of the cast image, and the image data (B). Extracting the image data (C) of the skull image by erasing the linear component representing the slab outline at

If it is determined that the skull is the result of the extraction of the skull image image data (C), the absolute value of the derivative value for the edge dam load corresponding to the time of the skull generation is obtained, and the final determination is made that the skull is only when the absolute value is a predetermined value or more. Reading the number of frames corresponding to the extracted skull image, and

Skull from the measured casting roll rotational speed (V), the interframe time interval preset according to the CCD camera, and the skull generation time (t) obtained in the frame in which the read skull image is generated An edge skull search method in a thin sheet casting process comprising the step of calculating the starting position Sp of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

1 is a schematic explanatory diagram of an edge scull search apparatus of the present invention. As shown in FIG. 1, the edge skull search apparatus of the present invention is largely divided into a CCD camera 10, a roll speed measuring unit 20, an edge dam load measuring unit 30, an image processing unit 40, and an arithmetic processing unit 50. It is configured to include.

First, the CCD camera 10 is preferably installed between the point immediately after the cast is generated from the point where the temperature distribution of the cast is constant to take an image of the cast. And the edge dam load measuring unit 30 for continuously measuring the edge dam load is provided, it is possible to install the roll speed measuring unit 20 for measuring the roll speed as needed.

The image processing unit 40 image-processes the image data A of the photographed slab with an edge detection mask to obtain image data B consisting of the slab outline and the skull image, and reads the number of pixels Pc between both sides of the slab image. The image data (C) of the skull image is extracted by erasing the linear components representing the slab outlines from the image data (B), and the horizontal pixel number (Px) and the vertical pixel number ( Serves to read Py).

The calculation processing unit 50 reads the number of horizontal pixels Px, the number of vertical pixels Py of the skull image, the number of pixels Pc between both sides of the slab image, and the preset, main, read by the image processing unit 40. From the horizontal size (Cx) of the convenience, the vertical size (Cy ') of the actual cast image picked up on one frame of the CCD camera, and the vertical pixel number (Pf) of the one frame, the actual size (Sx) and vertical size ( It is configured to serve to calculate Sy).

In addition, the calculation processing unit 50 obtains the absolute value of the derivative value of the edge dam load corresponding to the time point of the skull generation when the image processing unit 40 primarily determines that the skull is the extraction result of the skull image image data C. In other words, it only plays a role in determining that the skull is only valid when its absolute value is above a certain value.

Further, the edge scull search apparatus may further include a storage unit 60 for storing the image data of the skull image processed by the image processor and the horizontal and vertical size of the skull calculated by the arithmetic processor.

Therefore, according to the first aspect of the present invention, the present invention provides a skull search method capable of detecting the edge skull size.

That is, the edge dam load measuring unit 30 continuously measures the edge dam load, and uses the CCD camera 10 provided between the point where the temperature distribution of the cast steel is constant from the point immediately after the cast steel is produced. Image pickup In the present invention, since the skull and the slab can be distinguished due to the difference in color according to the cooling rate, the skull can be discriminated by a general image instead of a thermal image, and thus the image can be easily captured by using a CCD camera. An example of the image picked up by such a CCD camera 10 is shown in FIG.

In this way, the image data picked up by the CCD camera is transmitted to the image processing unit 40, and the load measured by the edge dam load measuring unit 30 is transferred to the arithmetic processing unit 50 in real time and embedded therein.

Next, in the present invention, the photographed image data A is subjected to two-stage image processing. In other words, step 1 is an image processing step using an edge detection mask to obtain image data (B) including the outline of the cast and the skull image, and step 2 is an outline component of the cast in the image data (B) processed in step 1. Image processing (C) consisting of only the skull image by erasing the image.

First, the mask for image processing used in step 1 has an advantage that the processing speed can be utilized quickly and simply by using an edge detection mask. The edge detection mask may be one of a robert operator, a sobel operator, a laplacian filter, and the like. In addition, although the size and shape of the mask may vary depending on the intended use, it is generally preferable to employ a 3 × 3 square shape for rapid image processing. 3 shows an example of image processing using a Sobel operator.

The pixel number Pc between both sides of the slab image is read from the image data B thus obtained. That is, the slab image is represented by two straight outlines or outlines close to a straight line. The number of pixels existing therebetween is read and provided to the calculation processing unit 50.

In the second step, the image data C including only the skull image is obtained by erasing the outline component of the cast steel from the image data B including the outline and the skull image of the cast steel processed in the first step. In general, since the slab is composed of linear components, the skull image can be obtained by eliminating continuous linear components.

In the second stage of image processing, when the cast steel is not moved to form a straight line component, the outline component of the cast steel does not appear as a single straight component in the image data. Therefore, using the line detection mask, the outline of the slab is obtained as a linear component and interpolated to eliminate the outline component of the slab. A 3 x 3 line detector can be used here.

Next, in the present invention, in order to solve the problem that the scale is misunderstood as a skull among the cast defects, if it is determined that the skull is the result of the extraction of the skull image image data (C) in step 2, the edge corresponding to the point of occurrence of the skull Obtain the absolute value of the derivative of the dam load and finally determine that it is a skull if the absolute value is above a certain value. This imparts more resistance to the edge dams located between the rolls and without the skull when the skull is pressed down with the molten steel in its original state, thus effectively measuring the scale that can be mistaken for the skull by measuring its edge dam load. To be identified.

FIG. 5 is a graph showing the relationship between edge dam load versus casting time. FIG. 5 (a) shows the relationship between casting time and edge dam load before pulverization, and FIG. 5 (b) shows the relationship between casting time and edge dam load after pulverization. A graph showing the relationship. In Figure 5 (a) it can be seen that the edge dam load shows a peak at a certain point, this point can be seen as the point when the skull is mixed in the slab (A) time is an example. It can be seen that the time (B) does not have any peak value when the scale is incorporated in the cast steel. Therefore, even after the step 2 is determined as a skull, as shown in Fig. 5 (b), it is possible to effectively distinguish the skull from the scale by judging by the skull only when the absolute value of the edge dam load derivative value is more than a predetermined value.

The calculation of the absolute value of the derivative and the final determination of whether the skull is a skull for the edge dam load is made in the calculation processing unit 50.

When finally determined as the skull, the horizontal pixel number Px and the vertical pixel number Py of the skull image obtained in step 2 are read. In other words, the number of pixels Px in the horizontal direction corresponding to each skull and the number of pixels Py in the vertical direction are read from the image-processed data, and the pixel number Pc between both sides of the obtained cast image is obtained by the calculation processing unit 50. Comes with).

Subsequently, the arithmetic processing unit 50 receives the number of pixels P of the read skulls, and the frame size Cx of the actual cast steel, which is set in advance in the arithmetic processing unit 50, on one frame of the CCD camera 10. The horizontal size Sx and the vertical size Sy of the actual skull are calculated using the actual vertical size Cy 'of the cast slab and the vertical pixel number Pf of one frame.

Here, the calculation of the skull size is based on the following equations (1) and (2).

[Equation 1]

[Equation 2]

In addition, according to a second aspect of the present invention, a skull search method capable of detecting an edge skull position is provided.

This method performs image processing on an image captured by a CCD camera in the same manner as the skull search method for calculating the horizontal and vertical size of the above-described skull, except that it calculates the starting position rather than the size of the skull. There is.

In other words, while continuously measuring the roll speed and the edge dam load in the roll speed measuring unit 20 and the edge dam load measuring unit 30, the temperature distribution of the cast steel is constant between the point immediately after the cast steel is produced. An image of the cast is imaged using the installed CCD camera 10. As such, the image data captured by the CCD camera is transmitted to the image processing unit 40, and the speed and the load measured by the roll speed measuring unit 20 and the edge dam load measuring unit 30 are calculated in real time. Is sent and built into.

Next, in the present invention, as described above, the image data A captured by the CCD camera is subjected to two-stage image processing. In other words, step 1 is an image processing step using an edge detection mask to obtain image data (B) including the outline of the cast and the skull image, and step 2 is an outline component of the cast in the image data (B) processed in step 1. Image processing (C) consisting of only the skull image by erasing the image.

Next, and as described above, in the present invention, in order to solve the problem that the scale is misunderstood as a skull during the main piece defect, if it is determined that the skull is the result of the extraction of the skull image image data (C) in the second step, The absolute value of the derivative value for the edge dam load corresponding to the time of skull occurrence is obtained and the final judgment is made that the skull is only when the absolute value is above a certain value. When finally determined to be a skull, the number of frames corresponding to the skull image extracted in step 2 is read.

Finally, the measurement roll rotation speed (V) measured by the calculation processing unit 50, the inter-frame time interval set in advance according to the CCD camera and the skull generation time (t) obtained from the corresponding frame in which the read skull image is generated The starting position Sp of the skull is calculated from. At this time, the interframe time determined by the CCD camera 10 selected to obtain the skull generation time t is preset in the calculation processing unit 50. In addition, the number of frames in which the skull is generated is read by the image processing unit 40 and provided to the calculation processing unit 50. Here, the frame number refers to a specific frame corresponding to a frame continuously captured at a predetermined time interval. Say number of turn. Therefore, the skull generation time is calculated based on the interframe time and the number of frames in which the skull is generated.

And the starting position Sp of the skull according to the skull generation time (t) can be calculated by Equation 3 below, in order to calculate the more accurate position can be included in the calculation of the shrinkage (C) of the cast during cooling. .

[Equation 3]

On the other hand, Figure 4 is an example of the image showing the size and the starting position of the skull detected in accordance with the above-described method of the present invention, not only the size and start position of the skull, but also the skull start position (A) scale start position ( It can be easily distinguished from B).

As described above, when detecting the size and position of the edge skull by imaging the slab image in the thin sheet casting process and detecting the size or position of the edge skull, only when the absolute value of the edge dam load differential measured at the point of occurrence of the skull is above a certain value. Judging by the final skull has a useful effect in preventing the scale from being incorrectly judged as a skull.

Claims (2)

Taking an image of the cast using a CCD camera installed between the point immediately after the cast is produced and the temperature distribution of the cast is constant, while continuously measuring the edge dam load in the edge dam load measuring unit; The image data (A) of the photographed cast piece is image-processed with an edge detection mask to obtain image data (B) consisting of a slab outline and a skull image, reading the number of pixels (Pc) between both sides of the cast image, and the image data (B). Extracting the image data (C) of the skull image by erasing the linear component representing the slab outline at If it is determined primarily that the skull is a result of the extraction of the skull image image data (C), the absolute value of the derivative value for the edge dam load corresponding to the time of the skull generation is obtained, and the skull is determined to be the skull only when the absolute value is a predetermined value or more. Judging and reading the number of horizontal pixels Px and the number of vertical pixels Py of the extracted skull image, and An edge skull search method in a thin sheet casting process comprising calculating the horizontal size Sx and the vertical size Sy of the actual skull using Equations 1 and 2 below. [Equation 1] [Equation 2] The edge dam load measuring unit and the roll speed measuring unit continuously measure the edge dam load and the casting roll speed, and use the CCD camera installed between the point immediately after the casting is made and the temperature distribution of the casting is constant. Imaging the image, The image data (A) of the photographed cast piece is image-processed with an edge detection mask to obtain image data (B) consisting of a slab outline and a skull image, reading the number of pixels (Pc) between both sides of the cast image, and the image data (B). Extracting the image data (C) of the skull image by erasing the linear component representing the slab outline at If it is determined that the skull is the result of the extraction of the skull image image data (C), the absolute value of the derivative value for the edge dam load corresponding to the time of the skull generation is obtained, and the final determination is made that the skull is only when the absolute value is a predetermined value or more. Reading the number of frames corresponding to the extracted skull image, and Skull from the measured casting roll rotational speed (V), the interframe time interval preset according to the CCD camera, and the skull generation time (t) obtained in the frame in which the read skull image is generated Edge scull searching method in the sheet casting process comprising the step of calculating the starting position (Sp). [Equation 3]