KR101568491B1

KR101568491B1 - Apparatus and method for controlling edge dam in twin roll strip casting process

Info

Publication number: KR101568491B1
Application number: KR1020130157952A
Authority: KR
Inventors: 김윤하; 황석균; 임지우
Original assignee: 주식회사 포스코
Priority date: 2013-12-18
Filing date: 2013-12-18
Publication date: 2015-11-11
Also published as: KR20150071204A

Abstract

According to an embodiment of the present invention, an edge dam control device is disclosed. An edge dam control device according to an embodiment of the present invention includes a pressure measuring sensor for measuring a pressure of at least one loading cylinder among a plurality of loading cylinders for applying pressure to an edge dam, An error accumulation unit for accumulating the pressure error, which is a difference between the target pressure and the target pressure, to calculate an accumulated error, and determining whether the measured pressure is greater than the target pressure using the accumulated error, And a pressure control section for controlling the casting rolls or the edge dam so that a contact area between the casting rolls and the edge dam is reduced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge dam control apparatus and a method for controlling an edge dam in a twin roll casting apparatus,

The present application relates to an apparatus and a method for controlling an edge dam in a twin roll thin sheet casting apparatus.

In a twin-roll thin sheet casting machine for casting thin plates directly from the melt, a ceramic side dam (ie, edge dam) is installed on both sides of the casting roll to prevent molten steel from flowing out to the side of the casting roll during the casting process. That is, by efficiently controlling the wear rate and the depressing force of the edge dam through the efficient position control of the edge dam, molten steel is prevented from flowing out between the side of the casting roll and the edge dam.

However, due to various reasons such as the type of steel, the surface characteristics of the casting roll, and the temperature change of the molten steel, there is a change in the reduction force between the edge of the casting roll and the edge dam. In some cases, even though a normal machining rate is applied, a large lowering force or a smaller pressing force higher than normal acts between the side of the casting roll and the edge dam.

When the lowering rate between the side of the casting roll and the edge dam becomes abnormally high, the lowering rate between the side of the casting roll and the edge dam can be reduced by applying a low wear rate, but there is a gap between the side of the casting roll and the edge dam, Molten steel may leak between the side and edge dams, which may deteriorate the quality of the cast strip edge.

In addition, even when the lowering force between the side of the casting roll and the edge dam becomes abnormally low, there is a gap between the side of the casting roll and the edge dam, and there is a risk that the molten steel leaks out between the side of the casting roll and the edge dam.

Horizontal vibration and vertical vibration are generated in the edge dam to prevent occurrence of edge skull. If a large downward force is applied between the edge of the casting roll and the edge of the casting roll due to the above-mentioned reason, the horizontal vibration and the vertical vibration are weakened, which causes the edge skull to be further induced.

According to the embodiment of the present invention, there is provided an edge dam control apparatus capable of lowering the descent force without adjusting the wear rate when the descent force between the edge of the casting roll and the edge dam becomes abnormally high.

According to another embodiment of the present invention, there is provided an edge dam control method capable of lowering the descent force without adjusting the wear rate when the descent force between the edge of the casting roll and the edge damper becomes abnormally high.

An edge dam control device according to an embodiment of the present invention includes a pressure measuring sensor for measuring a pressure of at least one loading cylinder among a plurality of loading cylinders for applying pressure to an edge dam, An error accumulation unit for accumulating the pressure error, which is a difference between the target pressure and the target pressure, to calculate an accumulated error, and determining whether the measured pressure is greater than the target pressure using the accumulated error, And a pressure control section for controlling the casting rolls or the edge dam so that a contact area between the casting rolls and the edge dam is reduced.

The plurality of loading cylinders of the edge dam control apparatus according to the embodiment of the present invention includes a lower loading cylinder, an upper FR loading cylinder, and an MR upper loading cylinder, and the pressure measuring sensor measures the pressure of the lower loading cylinder .

The error accumulation unit of the edge dam control apparatus according to an embodiment of the present invention includes a FIFO memory that sequentially receives the pressure error and stores the result in a first-in first-out (first-in first-out) manner, and adds the pressure errors stored in the FIFO memory An accumulator may be provided.

The pressure control portion of the edge dam control device according to the embodiment of the present invention may increase the interval between the casting rolls or raise the edge dam to reduce the contact area between the casting rolls and the edge dam have.

The apparatus for controlling an edge dam according to an embodiment of the present invention further includes a cylinder control unit for controlling the plurality of loading cylinders in response to a target wear rate, wherein, when the measured pressure is smaller than the target pressure, Can be increased.

The method of controlling an edge dam according to another embodiment of the present invention includes the steps of calculating a pressure error, which is a difference between a measured pressure and a target pressure, of a pressure of at least one loading cylinder among a plurality of loading cylinders which apply pressure to an edge dam Calculating cumulative error by accumulating the pressure error, determining whether the measured pressure is greater than the target pressure using the cumulative error, and if the measured pressure is greater than the target pressure, And controlling the contact area of the casting rolls and the edge dam to decrease.

The controlling step of the edge dam control method according to another embodiment of the present invention may increase the interval between the casting rolls or raise the edge dam to reduce the contact area between the casting rolls and the edge dam .

The method of controlling an edge dam according to another embodiment of the present invention includes the steps of increasing a target wear rate when it is determined that the measured pressure is smaller than the target pressure and controlling the plurality of loading cylinders in accordance with the increased target wear rate As shown in FIG.

Therefore, according to the edge dam control apparatus and method according to the embodiment of the present invention, when the descending force between the side of the casting roll and the edge dam becomes abnormally high, the area of the casting roll and the edge dam contact with each other, The lowering force can be lowered. Therefore, when the pressing force between the side of the casting roll and the edge dam becomes abnormally high, the downward force between the side of the casting roll and the edge dam can be reduced without concern that the molten steel flows out between the side of the casting roll and the edge dam. Also, the apparatus and method for controlling an edge dam according to an embodiment of the present invention have a new degree of freedom in wear control, and can be implemented without using additional hardware, which is also economically advantageous.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view schematically showing a configuration of a twin roll type thin plate casting apparatus. FIG.
Fig. 2 is a view schematically showing a configuration of an edge dam of the twin roll type thin sheet casting apparatus shown in Fig. 1. Fig.
3 is a diagram showing the configuration of an edge dam control apparatus according to an embodiment of the present invention.
4 is a flowchart illustrating an edge dam control method according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

Fig. 1 schematically shows a configuration of a twin roll type thin sheet casting apparatus. The twin roll casting apparatus 100 includes two casting rolls 1 and 2, a roll gap distance measuring device 3, a tundish 4, The immersion nozzle 5, the stopper 6, the bath surface height detection sensor 7, the edge dam 8, the molten steel sump 9, the load cell 10, the cylinder 11, the x- A roll 14, a rolling mill 15, a coiler 16, and the like. The two casting rolls 1, 2 can consist of a fixed roll 1 and a movable roll 2. 1 to 12 show strips.

Referring to FIG. 1, a process of casting a thin plate in the twin roll type thin sheet casting apparatus 100 will be briefly described below.

The molten steel stored in the ladle (not shown) is supplied to the tundish 4 through the openings of the ladders and the molten steel supplied to the tundish 4 is again fed through the immersion nozzle 5 to the two casting rolls 1, 2 And an edge dam 8 on the side surface of the casting rolls 1 and 2. As shown in Fig. The tundish 6 is provided in the tundish 4 and the stopper 6 serves as a valve for regulating the amount of molten steel flowing into the edge dam 8 from the tundish 4. Two casting rolls 1 and 2 rotating in opposite directions coagulate and press down the molten steel entering the ladle sump 9 from the tundish 4 to produce a strip 12. The resulting strip 12 is rolled by a rolling mill 15, and the rolled strip is wound by a coil 16.

An important process of sheet metal casting takes place in two casting rolls rotating in opposite directions shown in Fig. 1, namely a sump 9 between the stationary roll 1 and the moving roll 2. When molten steel is first supplied from the tundish 4 through the immersion nozzle 5 to the sump between two rolls, the molten steel is solidified and pressed down between the leader strip and the two rolls 1 and 2 within 0.2 seconds. At this time, the leader strip which solidifies with the molten steel, and the thin plate which follows after solidification, generates the roll repulsive force (RSF). This pressure is sensed by the load cell 10 mounted on the back of the roll.

The sides of the stationary roll 1 and the moving roll 2 are clogged by the edge dam 8 in order to prevent molten steel from flowing out to the sides of the casting rolls 1, The solidifying ability of the molten steel is proportional to the cooling ability of the casting rolls 1, 2.

The coagulation ability is determined by the distance between the two casting rolls 1 and 2, that is, the roll gap, the casting speed (rotation speed) of the casting rolls 1 and 2, and the height of molten steel in the sump get affected. The height of the molten steel is measured using the bath surface height detection sensor 7.

Basically, the height control of the steel requires high precision and stability. Therefore, in the present application, the height of the molten steel is regarded as maintaining the target value immediately after the start of casting.

Generally, when the molten steel solidifies, it creates a downward force between the casting rolls 1, 2. The solidification reduction rate is affected by the roll gap and the casting speed.

The roll gap is measured using the roll gap distance measuring device 3. [ For example, if the roll gap is too large, or if the casting speed is too fast, the freezing point will be lowered below the centerline of the roll nip and the pressure drop will be smaller, resulting in non-solidification and plate fracture of the molten steel. In the opposite case, the freezing point rises to the upper side and a high pressing force is generated. That is, the reduction force can be seen as a result of the correlation between the roll gap and the casting speed.

Fig. 2 is a view schematically showing a configuration of an edge dam of the twin roll type thin sheet casting apparatus shown in Fig. 1. Fig.

As shown in Fig. 2, edge dams 8-1 and 8-2 are provided on both sides of the fixed roll 1 and the moving roll 2, that is, on the drive side DS and the work side WS, respectively, Is prevented from flowing out to the side surfaces of the stationary roll 1 and the moving roll 2.

Each of the cylinders and sensors shown in Fig. 2 controls the position of the edge dam, thereby adjusting the depression force of the edge dam, and the position of the edge dam 8-1, 8-2 or the position of the edge dam 8-1, 8- 2) and the reduction forces between the casting rolls 1, 2 are detected.

Specifically, the DS horizontal vibration cylinder and the sensor 21, the WS horizontal vibration cylinder and the sensor 31 are connected to the edge dam 8-1 of the drive side DS and the edge dam 8- 2-2 so as to vibrate in the horizontal direction, that is, in the left-right direction when viewed from the side of the casting rolls 1, 2, and the edge dam 8-1, (8-1, 8-2).

The DS vertical cylinder and sensor 22 and the WS vertical cylinder and sensor 32 each have an edge dam 8-1 on the drive side DS and an edge dam 8-2 on the work side WS side, 8-2 in the vertical direction as viewed from the side of the casting rolls 1 and 2 and controls the positions of the edge dams 8-1 and 8-2 in the vertical direction, 2).

DS Lower Loading Cylinder and Sensor (23), DS FR Top Loading Cylinder and Sensor (24), DS MR Top Loading Cylinder and Sensor (25), WS Lower Loading Cylinder and Sensor (33) 34 and the WS MR top loading cylinder and sensor 35 respectively apply pressure to the corresponding positions of the edge dams 8-1 and 8-2 to cause the edge dam 8-1, Performs squeezing control between the side surfaces of the rolls 1 and 2, and senses pressure information at corresponding positions of the edge dams 8-1 and 8-2. Specifically, the DS lower loading cylinder applies pressure to the lower portion of the edge dam 8-1, the DS FR upper loading cylinder applies pressure to the upper portion of the edge dam 8-1 on the fixed roll 1 side, and DS The MR upper loading cylinder applies pressure to the upper portion of the edge dam 8-1 on the moving roll 2 side and the WS lower loading cylinder applies pressure to the lower portion of the edge dam 8-2, Applies a pressure to the upper portion of the edge dam 8-2 on the fixed roll 1 side and the WS MR upper loading cylinder can apply pressure to the upper portion of the edge dam 8-2 on the moving roll 2 side .

That is, the edge dam 8-1 provided on the drive side DS side of the fixed roll 1 and the moving roll 2 includes the DS horizontal vibration cylinder and the sensor 21, the DS vertical cylinder and the sensor 22, the DS The position in the horizontal and vertical directions and the positions of the stationary roll 1 and the moving roll 2 are detected by the lower loading cylinder and sensor 23, the DS FR top loading cylinder and sensor 24, and the DS MR top loading cylinder and sensor 25 2 and the edge dam 8-2 provided on the side of the fixed roll 1 and the work side WS of the moving roll 2 are controlled by the WS horizontal vibration cylinder and the sensor 31, Horizontal and vertical positions by WS vertical cylinder and sensor 32, WS bottom loading cylinder and sensor 33, WS FR top loading cylinder and sensor 34, and WS MR top loading cylinder and sensor 35 And the downward force on the side surfaces of the stationary roll 1 and the moving roll 2 are controlled.

3, the edge dam control device includes a pressure measurement sensor 23-1, an error accumulation unit 30, a pressure control unit 40, and a cylinder (not shown) A control unit 50 may be provided. The error accumulation unit 30 may include a FIFO memory 31 and an accumulator 32.

Fig. 3 shows the drive side DS side in the edge dam configuration shown in Fig. 2, and the work side WS side can have the same configuration.

The function of each of the blocks shown in FIG. 3 will be described as follows.

The pressure measuring sensor 23-1 measures the pressure of the lower loading cylinder of the edge dam. The pressure measurement sensor 23-1 may be the same as the sensor of the DS lower loading cylinder and the sensor 23 of Fig. The sampling time of the pressure measurement sensor 23-1 may be as fast as possible, and may be 1000 samples / sec or more.

The error accumulator 30 calculates a pressure error which is a difference between a target pressure and a measured pressure measured by the pressure measuring sensor, and accumulates the pressure error for a predetermined time to calculate an accumulated error. The target pressure can be preset and can be input from the outside. Further, the pressure error may be calculated as (target pressure-measured pressure).

The FIFO memory 31 of the error accumulating unit 30 stores the sequentially inputted pressure error in a first-in first-out manner. Therefore, the latest data can always be stored in the FIFO memory 31.

The accumulator 32 of the error accumulator 30 sums the data stored in the FIFO memory 31 to calculate the accumulated error. The accumulator 32 may calculate the accumulated error at predetermined time intervals after the data is completely filled in the FIFO memory 31. [

The pressure control unit 40 judges whether the measured pressure is greater than the target pressure by using the accumulated error, and if the measured pressure is larger than the target pressure, the contact area between the casting roll and the edge dam is reduced Edge dam or casting roll, and if the measured pressure is smaller than the target pressure, the corrected wear rate is calculated, and the calculated corrected wear rate is added to the target wear rate.

When the pressure error is calculated as (target pressure-measured pressure), the pressure control unit 40 can use the sign of the accumulated error to determine whether the measured pressure is greater than the target pressure. That is, the pressure controller 40 determines that the measured pressure is greater than the target pressure if the accumulated error has a negative value, and determines that the measured pressure is less than the target pressure if the accumulated error has a positive value .

The pressure control unit 40 may increase the interval between the casting rolls, i.e., the fixed roll 1 and the moving roll 2, or increase the distance between the edge dam 8 and the moving roll 2, The contact area between the casting rolls 1, 2 and the edge dam 8 can be reduced. As the contact area between the casting rolls 1, 2 and the edge dam 8 is reduced, the reduction force between the casting rolls 1, 2 and the edge dam 8 is substantially reduced The same effect occurs.

The pressure control unit 40 can calculate the roll gap compensation value obtained by multiplying the absolute value of the cumulative error by a predetermined casting roll gain and set the new casting roll gap by adding the roll gap compensation value to the current casting roll gap. That is, a new casting roll gap can be calculated by the following equation (1).

The pressure control unit 40 calculates a vertical cylinder compensation value obtained by multiplying the absolute value of the cumulative error by a predetermined edge dam vertical cylinder gain and adds the vertical cylinder compensation value to the current edge dam vertical cylinder height to obtain a new edge dam vertical The height of the cylinder can be set. That is, the height of the new edge dam vertical cylinder can be calculated by the following equation (2). The pressure control unit 40 can elevate the edge dam 8 by controlling the DS vertical cylinder 22 using the new edge dam vertical cylinder height.

When the measured pressure is smaller than the target pressure, the pressure control unit 40 increases the reduction load between the casting rolls 1, 2 and the edge dam 8 by adding the correction wear rate to the target wear rate . The correction duty ratio may be calculated by multiplying the absolute value of the cumulative error by the wear rate gain. That is, the new target wear rate can be calculated by the following equation (3).

The cylinder control unit 50 controls the DS lower loading cylinder in response to the target wear rate. 3, the cylinder control unit 50 may include a wear controller, a servo valve, a wear controller cylinder, a distance measuring sensor, and the like. The cylinder control unit 50 may include a side surface of the casting rolls 1 and 2, 8) can have a descent force corresponding to the target working ratio.

3, the cylinder control unit 50 controls the DS lower loading cylinder. However, the same cylinder control unit may be provided for each of the DS FR upper loading cylinder and the DS MR upper loading cylinder. That is, the target wear rate newly calculated by Equation (3) can be equally applied to the two upper loading cylinders.

3 illustrates the case where the lower loading cylinder and the upper loading cylinder are both controlled by measuring the lowering load of the lower loading cylinder. However, when the lowering cylinder is controlled by measuring the lowering load of any one of the upper loading cylinders, It is also possible to constitute such a control.

4 is a flowchart illustrating an edge dam control method according to another embodiment of the present invention.

The edge dam control method according to another embodiment of the present invention will be described with reference to FIG.

First, the pressing force of at least one of the loading cylinders for applying pressure to the edge dam is measured in real time, and a pressure error, which is a difference between the measured pressure and the target pressure, is calculated (S100). In this case, the loading cylinders may include a lower loading cylinder, an upper FR loading cylinder, and an MR upper loading cylinder, and the pressing force of the lower loading cylinder among the loading cylinders may be measured in real time. Further, the pressure error may be a value obtained by subtracting the measured pressure from the target pressure.

Next, the pressure error is integrated to calculate an accumulated error (step S200). Specifically, the cumulative error can be calculated by summing the pressure errors calculated for a predetermined time.

Next, it is determined whether the measured pressure is greater than the target pressure by using the accumulated error (step S300). Specifically, it is possible to determine whether the measured pressure is greater than the target pressure by discriminating the sign of the accumulated error. When the pressure error is a value obtained by subtracting the measured pressure from the target pressure as described above, And determines that the measured pressure is greater than the target pressure when the cumulative error is a negative value and determines that the measured pressure is less than the target pressure when the cumulative error is a positive value.

If it is determined in step S300 that the measured pressure is greater than the target pressure, the contact area between the casting rolls 1 and 2 and the edge dam 8 is reduced (step S400). Specifically, by increasing the distance between the casting rolls 1, 2, or by raising the edge dam 8, the contact area between the casting rolls 1, 2 and the edge dam 8 can be reduced .

If it is determined in step S300 that the measured pressure is smaller than the target pressure, the target wear rate is increased and the loading cylinders are controlled according to the increased wear rate (step S500).

The edge dam control method according to another embodiment of the present invention shown in Fig. 4 can be equally applied to both the drive side DS and the work side WS.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

100: twin roll type thin sheet casting apparatus 1: fixed roll
2: moving roll 8: edge dam
22: DS vertical cylinder and sensor 23: DS lower loading cylinder and sensor
24: DS FR Top Loading Cylinder and Sensor
25: DS MR Top Loading Cylinder and Sensor
32: WS Vertical Cylinder and Sensor 33: WS Lower Loading Cylinder and Sensor
34: WS FR Top Loading Cylinder and Sensor
35: WS MR Top Loading Cylinder and Sensor

Claims

A pressure measuring sensor for measuring a pressure of at least one of the plurality of loading cylinders which presses the edge dam;
An error accumulator for accumulating the pressure error, which is a difference between the measured pressure measured by the pressure measuring sensor and the target pressure, to calculate an accumulated error; And
Determining whether the measured pressure is greater than the target pressure using the cumulative error, and if the measured pressure is greater than the target pressure, reducing the contact area between the casting rolls and the edge dam, Or a pressure control section for controlling the edge dam.

The method according to claim 1,
The plurality of loading cylinders include a lower loading cylinder, an upper FR loading cylinder, and an upper MR loading cylinder,
Wherein the pressure measuring sensor measures the pressure of the lower loading cylinder.

The apparatus of claim 1, wherein the error accumulating unit
A FIFO memory for sequentially inputting the pressure error and storing the pressure error in a first-in first-out manner; And
And an accumulator for summing the pressure errors stored in the FIFO memory.

The apparatus of claim 1, wherein the pressure control unit
And increasing the spacing between the casting rolls to reduce the contact area between the casting rolls and the edge dam.

The apparatus of claim 1, wherein the pressure control unit
Wherein the edge dam is raised to reduce the contact area between the casting rolls and the edge dam.

The apparatus of claim 1, wherein the edge dam control device
Further comprising a cylinder control unit for controlling the plurality of loading cylinders in response to a target wear rate,
Wherein the pressure control unit increases the target wear rate when the measured pressure is smaller than the target pressure.

Calculating a pressure error, which is a difference between a measured pressure and a target pressure, from a pressure of at least one of the plurality of loading cylinders that pressurize the edge dam;
Accumulating the pressure error to calculate an accumulated error;
Determining whether the measured pressure is greater than the target pressure using the cumulative error; And
And controlling the contact area of the casting rolls and the edge dam to decrease when it is determined that the measured pressure is greater than the target pressure.

8. The method of claim 7, wherein the controlling
And increasing the spacing between the casting rolls to reduce the contact area between the casting rolls and the edge dam.

8. The method of claim 7, wherein the controlling
Wherein the edge dam is raised to reduce the contact area between the casting rolls and the edge dam.

8. The method of claim 7, wherein the edge dam control method
Increasing the target wear rate when it is determined that the measured pressure is less than the target pressure; And
And controlling the plurality of loading cylinders according to the increased target wear rate.