KR100605709B1 - Hot band control method and apparatus using brush roll in the strip casting process - Google Patents

Abstract

The present invention measures the brightness of the cast steel using a CCD camera and then analyzes the brightness difference between the center and the edge of the cast steel and adjusts the rotational force and the rolling force of the brush roll located at the edge of the casting roll accordingly, and the solidification ability of the edge portion. The present invention relates to a method and apparatus for preventing edge non-solidification by using brush roll control in a twin roll type thin plate manufacturing apparatus, and to manufacturing a thin plate through two casting rolls rotating in opposite directions. In the method of preventing edge non-solidification using brush roll control in an apparatus, a CCD camera is used to measure an image of a cast steel cast in a twin roll sheet metal fabrication apparatus, and an unsolidified edge portion using a threshold value in the measured cast image. After calculating the average distance of, calculates the difference in brightness between the center portion and the edge portion calculated above, the brightness Lice and calculating the rolling force of the brush roll and the rotation speed target value to reduce, and therefore is one to control the brush roll is located on the edge of the casting rolls.

Casting roll, black skin, brush roll, rolling force, edge non-solidification,

Description

HOT BAND CONTROL METHOD AND APPARATUS USING BRUSH ROLL IN THE STRIP CASTING PROCESS}

1 is a schematic diagram showing a thin plate casting process.

2 is a block diagram of an edge non-solidification prevention device using a brush roll control according to the present invention.

Figure 3 is a block flow diagram showing the processing of the edge non-solidification method using a brush roll control according to the present invention.

4 is an exemplary view of the brightness distribution of the cast steel cast in the thin plate casting process.

5 is a layout view of a brush roll and a casting roll.

6 is an exemplary view of the slab brightness interface using a threshold value.

* Description of the symbols for the main parts of the drawings *

21: fixed roll 22: moving roll

23 ~ 28: 1st ~ 6th Brush Roll

31, 36: 1st, 2nd load cell

33, 37: 1st, 2nd cylinder (Cylinder)

34, 38: 1st and 2nd servo valve

43: cast 44: CCD camera

45 monitor 46 Computer System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin roll type sheet manufacturing apparatus for casting thin sheets directly from a molten metal, and in particular, by adjusting a brush roll according to the brightness distribution of a cast photographed by a camera to maintain cleanliness of the surface of the casting roll. The present invention relates to an edge non-solidification prevention method and apparatus using brush roll control in a twin-roll thin sheet manufacturing apparatus for maintaining solidification uniformity in the width direction of a bias.

As shown in FIG. 1, the twin roll type sheet casting process includes two rolls 1 and 2 rotating in opposite directions to each other, and a sump of the molten steel between the rolls 1 and 2 is collected. (7), when molten steel is supplied from the tundish 3 above the rolls 1 and 2 to the sump 17 between the two rolls 1 and 2 through the nozzle 4, the molten steel is a few seconds. It is pressed down to the thin plate 10 by the two rolls 1 and 2 rotating while solidifying between the two rolls 1 and 2 (for example, 0.2 seconds). At this time, the sides of the two rolls (1, 2) are blocked by a ceramic side dam to prevent the molten steel to flow to the side of the roll.

Then, the roll separation force (RSF: Roll Separation Force) is generated on the two rolls 1 and 2 by the solidified thin plate. Therefore, in order to control the roll repulsion force generated during solidification, one of the two rolls is a fixed roll 1 having a fixed position, and the other roll is a moving roll 2 which is movable in the roll gap direction rather than in the rotational direction. After the configuration, the roll resilience is detected by a load cell (not shown) mounted on the back of the moving roll (2).

The solidification capacity of the molten steel is proportional to the cooling capacity of the casting rolls, and also in the distance between the two rolls 1 and 2, that is, the roll gap 9, the casting speed (rotation speed) of the roll, and the sump 7 It is affected by the height of the molten steel. In the above, the height of the molten steel is measured using the water surface height detection sensor 1-8. When molten steel solidifies, it generates a roll repulsion force (RSF) between the rolls (1, 2).

In addition, the solidification reduction rate is affected by the roll gap and the casting speed. For example, if the roll gap is too large or the casting speed is too fast, the solidification point will be lower than the center line of the roll nip, resulting in less roll repulsion, which causes unsolidification and plate failure of the molten steel. In the opposite case, the solidification point rises above the centerline of the roll nip, resulting in high roll repulsion.

Therefore, in the twin roll thin sheet casting apparatus, the roll gap, casting speed, and roll repulsion force are representative casting parameters indicating the solidification of the thin sheet. Basically, the height control of molten steel requires a high degree of precision and stability. Therefore, the height of molten steel is considered to maintain the target value immediately after the start of casting. Thus, the roll repulsion force can be seen as a result of the interrelationship between the roll gap and the casting speed.

By the way, when casting starts and molten steel flows into the pump 7, the molten steel is solidified between the two rolls 1 and 2 that rotate to form a cast steel. That is, due to the black skin formed on the surface of the roll and the wear of the edge dam deposited on the edge of the roll, the widthwise temperature distribution of the cast steel is not the same, which causes uneven solidification or hot band of the cast steel. Let's do it. This, of course, adversely affects the quality of the cast.

In other words, when the casting is started, the produced thin plate does not appear to have a cooling capacity evenly in the width of the plate due to the casting characteristics, and therefore, it tends to cause a hot band in the edge portion of the cast steel. There are various reasons for this, including contamination of the roll edge portion due to wear of the edge dam of the ceramic material, an unbalanced distribution of the roll cooling ability, and a roll crown considering the thermal expansion of the roll.

In addition, as the casting progresses, some of the components volatilized from molten steel form black skin on the surface of the roll. Thus, if there is a lot of black skin accumulated on the roll surface, the solidification slows down, and the casting speed decreases. It is relatively fast and the casting speed is increased.

In addition, in order to maintain a constant resilience force (RSF) between the casting rolls appearing due to the solidification between the roll and the roll, a high roll repulsion force to increase the casting speed, low roll repulsion force to control the slow casting speed Repulsive force control is carried out, wherein the change of the casting speed is determined in accordance with the conditions of the roll center representative of the solidification of the roll surface. Therefore, in general, the edge of the roll, in which the solidification delay occurs more than the center of the roll, is less solidified than the center of the roll.

Therefore, the present invention has been proposed to solve the above-described problems, the purpose of which is to measure the brightness of the cast using a CCD camera and then analyze the brightness difference between the center and the edge of the cast and accordingly By adjusting the rotational force and the pressing force of the brush roll located at the edge part, the black roll accumulated at the edge of the casting roll can be effectively removed to improve the solidification ability of the edge part and to improve the quality of the cast sheet. The present invention provides a method and apparatus for preventing edge coagulation using brush roll control.

The present invention is a technical means for achieving the above object, in the anti-coagulation prevention method using a brush roll control in a twin-roll thin plate manufacturing apparatus for producing a thin plate through two casting rolls rotating in opposite directions,

A) measuring an image of the cast steel cast in a twin roll type sheet manufacturing apparatus using a CCD camera;

B) obtaining an average distance of the unsolidified edge portion using the threshold value from the measured cast image;

C) calculating a difference in brightness between the center portion and the edge portion of the slab calculated in step b);

D) calculating a reduction force and a rotation speed target value of the brush roll so that the brightness difference calculated in step c) is reduced;

E) operating the brush roll at the calculated reduction force and rotation speed; And

F) while performing the step e) while moving the brush roll to the distance obtained in step b).

And, the edge non-solidification prevention device using the brush roll control in the twin-roll thin plate manufacturing apparatus as described above

First and second brush rolls respectively positioned on left and right edge portions of the lower part of the casting roll;

A CCD camera for photographing cast pieces cast from the two casting rolls;

First and second rotation driving units for rotating the first and second brush rolls, respectively;

First and second cylinders configured to apply pressure to the first and second brush rolls in a casting roll direction;

First and second servo valves controlling the operation of the first and second cylinders; And

In the cast image photographed by the CCD camera, the average distance of the unconsolidated edge portion is obtained by using a threshold value, the brightness difference between the center portion and the edge portion of the cast image is obtained, and the first and second brush rolls are proportional to the brightness difference. Calculate the rotational speed and the reduction force of the, control the first and second rotational drive and the first and second servo valves so that the calculated speed and pressure are applied, respectively, while moving the first and second brush rolls to the obtained average distance Characterized in that it consists of a computer system for operating at the calculated rotational speed and the reduction force.

In addition, the edge non-condensation preventing device further comprises a first and second load cells for detecting the pressure applied to the first and second brush rolls, the computer system is measured pressure reduction value detected in the first and second load cells And a first and second speed detection unit for comparing the calculated target pressure reduction force and feedback control and detecting a rotational speed applied to the first and second brush rolls, wherein the computer system includes the first and second speed detection units. The brush roll rotation speed detected by the speed detection unit is compared with the calculated target speed so as to control feedback to reach the target speed, so that the first and second brush rolls maintain the target speed and the pressing force.

The apparatus may further include first and second brush roll moving parts for moving the first and second brush rolls to the average distance from the edge portion under the control of the computer system in the longitudinal direction of the casting roll, respectively. do.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, the edge non-solidification prevention method and apparatus which used the brush roll control in the twin roll type thin plate manufacturing apparatus of this invention are demonstrated in detail.

Figure 5 shows the structure of the brush roll for effectively removing the black skin of the edge portion of the casting roll according to the present invention, the upper brush roll 52 located on the upper part of the casting roll 51, and the two lower parts located below Brush rolls 53 and 54. At this time, the upper brush roll 52 is the same length as the length of the casting roll 51, to remove contaminants over the entire surface of the casting roll 51, the lower brush roll (53, 54), respectively Located at the left and right edge portions of the casting rolls 53 and 54, the length thereof is set to approximate the length of the edge portion of the slab in which an unsolidified state occurs.

The basic purpose of the brush rolls 52 to 54 is to remove contaminants appearing on the surface of the roll 51 during casting. Therefore, in the present invention, the upper brush roll 52 is driven at a constant rolling force and rotational speed. On the other hand, the two lower brush rolls 53 and 54 vary the speed and the reduction force in proportion to the brightness difference between the central portion and the edge portion of the cast steel, in order to prevent edge coagulation. In addition, the lower brush rolls 53 and 54 may be configured to move left / right along the width direction length of the changing edge non-solidification.

That is, in the present invention, after detecting the solidified thin plate out of the roll nip using a CCD camera, the distance to the brightness deviation in the width direction of the slab is obtained, and the brightness deviation of the unsolidified and normal solidified portion is obtained. Therefore, by adjusting the rolling force and the rotational speed control state of the brush roll to induce the width direction solidification capacity of the casting roll to be uniform.

Accordingly, the apparatus for preventing slag edge non-solidification according to the present invention includes a means for measuring a slab image by using a CCD camera to detect brightness in the width direction of the slab, the rolling force of the brush roll based on the detected brightness information, and Means for calculating a rotational speed target value, and means for driving the brush roll with the calculated rotational speed and reduction force.

In addition, the method for preventing the non-solidification of the cast slab is 1) when the casting is started and the molten steel is injected into the sump, the molten steel is solidified between the casting rolls to form the cast steel, 2) the molten steel is solidified to between the two rotating rolls When pressed out, measure the image of the cast steel, 3) analyze the image measured by the CCD camera to find the distance to the section where the width deviation and brightness difference of the cast steel appears, 4) using the values obtained above And calculating a correction value of the reduction force and rotational speed of the lower brush roll, and 5) adding the calculated correction target value and a predetermined target value to operate the lower brush, wherein the brightness difference appears. The brush roll moves left / right according to the change of the section. At this time, the upper brush roll is rotating to a target value of a predetermined pressing force and a rotation speed regardless of the present algorithm for the purpose of cleaning the surface of the casting roll.

The apparatus and method as described above will be described in more detail with reference to FIGS. 2 and 3 as follows.

2 is an overall configuration diagram showing the edge non-condensation preventing apparatus according to the present invention, the casting rolls (21, 22), the casting rolls (21, 22) are installed on the casting rolls (21, 22) and First and second brush rolls 23 and 24 having the same length, third and fourth brush rolls 25 and 26 installed on the lower drive side of the casting rolls 21 and 22, and the casting roll 21 5, 6 brush rolls (27, 28) installed on the lower non-drive side of the 22, and the first brush roll driving portion 29 for controlling the rotational drive of the first and second brush rolls (23, 24) ), The first load cell 31 for detecting the pressure applied by the first and second brush rolls 23 and 24 to the casting rolls 21 and 22, and the first and second brush rolls 23 and 24. A first cylinder 33 for pushing toward the casting rolls 21 and 22, a first servo valve 34 for controlling the forward and backward movement of the first cylinder 33, and the third to sixth brush rolls 25. The second brush roll driving part 35 for rotating and driving the 28 to 28 and the third to sixth brush rolls 25 to 28 are cast. A second load cell 26 for detecting pressure applied to the 21 and 22, a second cylinder 37 for pushing the third to sixth brush rolls 25 to 28 toward the casting rolls 21 and 22; And a second servo valve 38 for controlling the forward and backward movement of the second cylinder 37, a CCD camera 39 for measuring an image of a cast piece discharged from the casting rolls 21 and 22, and the CCD camera ( 39) to display the image captured by the monitor 40, and the image of the slab photographed by the CCD camera 39 to calculate the brightness deviation and the length of the edge non-solidified portion of the center portion and the edge portion of the slab and calculated value According to the computer system 46 for outputting the rotational speed and the reduction force control signal of the third to sixth brush roll (25 to 28).

The operation of the apparatus will be described below. For the sake of simplicity, only the drive side of the casting rolls 21 and 22 will be selected and described. The non-driveside can also be understood by the above description since it is by the same method.

First, the image of the cast is photographed using the CCD camera 39. At this time, the CCD camera 39 has a resolution of 640 (pixel) x 480 (line). Each pixel is represented by gray levels of 0 to 255. For reference, brightness 0 means very dark color and brightness 255 means very bright color. The resolution and brightness per pixel may be finely divided.

That is, when casting starts, the image of the slab 42 manufactured from the casting rolls 21 and 22 is measured using the CCD camera 39. FIG. At this time, the position of the slab 42 is determined in preparation for the case where the slab 42 is shaken using the image measured initially. To do this, use a vertical 3x3 line detector.

Next, x _DS and x _NDS , which are widths of the unsolidified region, are obtained from the measured image data of the cast steel. FIG. 4 shows an example of cast steel images taken by the CCD camera 39. The detailed process is as follows. same.

Every line of image data is scanned in the width direction from the slab edge to the center of the slab, and the difference in brightness is obtained. That is, a specific threshold value is set, and the gray level of each pixel of each line from the edge portion to the center portion of the main surface image is compared with the threshold value, and if the pixel value is larger than the threshold value, it is classified as unsolidified and small. do.

In this case, the threshold for distinguishing the non-solidified portion from the solidified portion is obtained by an empirical value. Since the difference between the light and dark portions does not appear suddenly, about 70% of the maximum difference between the very bright and dark portions is used as the threshold. Set it.

FIG. 6 is a graph showing gray levels for one line of the cast image, with the driveside direction edge of the cast steel being zero on the x-axis, plotted on the x-axis to the non driveside edge of the cast steel, and the y-axis from 0 to 255. FIG. In the gray level of, a high gray level value of 255 levels from the edge portions of the cast pieces to a certain distance, and the central portion of the cast pieces have a gray level value within a predetermined value. Therefore, based on the arbitrarily determined threshold value, it can be seen that it is divided into the solidification region of both edge portions of the cast steel and the non-solidification region of the center of the cast steel.

As described above, the process of distinguishing the solidified portion from the non-solidified portion is applied to all the vertical lines of the cast image. In this way, aligning the obtained values in the longitudinal direction of each line will form a boundary between the light and dark portions of the cast steel. Thereafter, these values are averaged to obtain the representative values of the length x _DS of the non-solidified portion at the driveside edge and the length x _NDS of the non-solidified portion at the nondriveside edge.

Then, the width direction brightness is analyzed at the edge of the cast slab using the measured length values x _DS and x _NDS of the cast image and the non-solidified portion. First, the gray level sum of all the pixels of the cast is calculated as follows.

In Equation 1, S is a sum of gray levels (0 to 255) of all pixels of the slab, S _DS is a sum of gray levels of pixels from the drive side slab edge to x _DS in the center direction, and S _NDS is a non-driveside slab. The sum of gray levels of pixels from the edge to the center at x _NDS , and S _center is the sum of the gray levels of the slab center pixels.

Then, the gray level sum a of pixels from the center of the slab to the part where uncondensation starts in the driveside (DS) direction (normal consolidation part) is obtained as a = S / 2-S _DS .

In addition, the gray level sum b = S / 2-S _NDS from the center portion of the slab to the portion where the non-solidification starts in the non-driveside (NDS) direction (normal solidification portion) is obtained.

From the above, the difference in brightness per unit area of the normal solidified portion and the unsolidified portion is calculated by dividing the drive side / non drive side as shown in Equation 4 below.

Here, L represents the width of the cast steel, e _DS is the brightness deviation of the drive side, e _NDS is the brightness deviation of the non-drive side.

Using the values calculated as described above, it is possible to determine an increase ratio of the correction target value used to control the reduction force / rotation speed of the third to sixth brush rolls 25 to 28. At this time, the control panel stage increases the pressing force / rotation speed trim value of the third to sixth brush rolls 25 to 28 if the "e _DS " is large, and the third to sixth brush roll if the "e _DS " is small. The reduction force / rotation speed trim value of 25 to 28 is decreased, and if "e _DS " is 0, the reduction force / rotation speed trim values of the third to sixth brush rolls 25 to 28 are not adjusted.

An example of the algorithm for the control operation of the brush roll as described above is as follows.

algorithm start;

error_summation = error_summation + e _DS ;

If | e _DS  | > e

Load (speed) _trim = k _pload (k _pspeed ) * a + k _Iload (k _Ispeed ) * (e _DS  + error_summation);

Else

do nothing

Endif

If x _DS > x _center  -> move to right

Else If x _DS <x _center  -> move to left

Else

do nothing

Endif

Go to algorithm start for the next sampling time;

The above has been described based on the drive side of the sheet casting roll, and the same algorithm is applied to the non-drive side.

In the above algorithm, e is a predetermined experimental value.

Then, the target trimming values of the reduction force and rotational speed obtained as described above are added to the predetermined reduction force and rotational speed target values to the pressing force and rotational speed controllers of the third to sixth brush rolls 25 to 28. Allow it.

At this time, the control is performed while moving the third to sixth brush rolls 25 to 28 in the horizontal direction according to the values of the distances x _DS and x _NDS of the non-solidified parts.

As described above, the present invention is the rotation of the brush roll according to the slab width direction temperature deviation of the slab width direction temperature distribution is not the same due to the difference in the coagulation capacity of the casting roll and the black skin deposited on the roll edge portion. By controlling the speed / pressing force to induce the width direction solidification ability of the casting roll to be uniform, there is an excellent effect of improving the quality of the cast thin plate.

Claims (5)

In the edge roll non-solidification method using a brush roll control in a twin-roll thin plate manufacturing apparatus for producing a thin plate through two casting rolls that rotate in opposite directions to each other, A) measuring an image of the cast steel cast in a twin roll type sheet manufacturing apparatus using a CCD camera; B) obtaining an average distance of the unsolidified edge portion using the threshold value from the measured cast image; C) calculating a difference in brightness between the center portion and the edge portion of the slab calculated in step b); D) calculating a reduction force and a rotation speed target value of the brush roll so that the brightness difference calculated in step c) is reduced; E) operating the brush roll at the calculated reduction force and rotation speed; And (F) performing a step e) while moving the brush roll to the distance obtained in the step b). In an edge non-solidification prevention device using a brush roll control in a twin-roll thin plate manufacturing apparatus for rotating two casting rolls in different directions to cast a thin plate, First and second brush rolls respectively positioned on left and right edge portions of the lower part of the casting roll; A CCD camera for photographing cast pieces cast from the two casting rolls; First and second rotation driving units for rotating the first and second brush rolls, respectively; First and second cylinders configured to apply pressure to the first and second brush rolls in a casting roll direction; First and second servo valves controlling the operation of the first and second cylinders; And In the cast image photographed by the CCD camera, the average distance of the unconsolidated edge portion is obtained by using a threshold value, the brightness difference between the center portion and the edge portion of the cast image is obtained, and the first and second brush rolls are proportional to the brightness difference. Calculate the rotational speed and the reduction force of the, control the first and second rotational drive and the first and second servo valves so that the calculated speed and pressure are applied, respectively, while moving the first and second brush rolls to the obtained average distance An apparatus for preventing edge coagulation using brush roll control in a twin-roll thin sheet manufacturing apparatus, characterized by comprising a computer system operating at the calculated rotational speed and reduction force. The method of claim 2, And first and second load cells for detecting pressure applied to the first and second brush rolls. The computer system compares the measured pressure reduction value detected by the first and second load cells with the calculated target pressure reduction force to perform feedback control. . The method of claim 2, Further comprising a first and second speed detection unit for detecting the rotational speed applied to the first and second brush roll, The computer system feedback-controls the brush roll rotational speed detected by the first and second speed detection units to reach the target speed by comparing with the calculated target speed. Edge anti-solidification device. The method of claim 2, The first roll and the second brush roll, respectively, in the longitudinal direction of the casting roll, the first and second brush roll moving unit for moving the edge portion from the edge portion to the average distance under the control of the computer system, characterized in that further comprising Edge anti-solidification device using brush roll control on the device.

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