KR20040003296A - Control method for roll separation force and roll gap in twin roll strip casting process - Google Patents

Abstract

PURPOSE: A method for controlling roll force and roll gap in twin roll strip casting process is provided to prevent damage of casting rolls by adopting repulsive force/gap control method if variation of repulsive force is maintained to a certain level or more and adopting repulsive force/speed control method if variation of repulsive force is maintained to a certain level or less. CONSTITUTION: The method comprises first step (S61,S62) of performing repulsive force/gap control for controlling repulsive force of casting rolls by initiating manufacture of strip, thereby adjusting gap between the rolls through cylinder as increasing casting speed of a twin roll strip casting machine before a normal speed, that is, a set time (t0); second step (S63) of measuring repulsive force values of the rolls; third step (S64) of comparing the measured repulsive force values (RSF) with preset repulsive force value (RSF-th) after the set time (t0) from the strip manufacturing initiation time point; fourth step (S65) of performing repulsive force/speed control for controlling repulsive force by adjusting speed of motor as constantly maintaining a gap between the casting rolls if the measured repulsive force values (RSF) are less than the preset repulsive force value (RSF-th) in the second step; and fifth step (S66) of performing repulsive force/gap control for controlling repulsive force by adjusting a gap between the casting rolls through the cylinder as constantly maintaining a speed of the twin roll strip casting machine if the measured repulsive force values (RSF) are more than the preset repulsive force value (RSF-th) in the second step.

Description

CONTROL METHOD FOR ROLL SEPARATION FORCE AND ROLL GAP IN TWIN ROLL STRIP CASTING PROCESS}

The present invention relates to a roll reduction force and a roll gap control method in a twin-roll thin sheet casting process, in particular, while performing a control method for maintaining the roll gap constant in the repulsion force / speed (RSF / speed) method during casting, While the change of repulsive force is over a certain level due to the inflow of foreign substances such as Escal, switch to the repulsive force / gap control method, and when the change of repulsive force is below a certain level, rebound force / speed (RSF / speed) The present invention relates to a roll reduction force and a roll gap control method in a twin roll sheet metal casting process to be controlled by switching to a control method.

In general, the twin roll sheet metal casting technology is a thin plate having a thickness of 2-6 mm through the reduction of the molten steel injected between the two cylindrical casting rolls interlocking with each other and the edge dam blocking the casting rolls back and forth through the casting rolls. It is a technology that produces. One of the two casting rolls is equipped with a repulsive force detector such as a load cell to measure roll reduction force or roll repulsion force of molten steel and is located in a fixed position. Measure the applied load or the repelling force of the cast solids.

As such, as a method for maintaining a constant thickness and quality of the produced thin plate, a roll crown is formed to reduce the difference in the solidification rate of the molten steel at the center portion and the edge of the casting roll, or at the same time A method of adjusting a gas near the molten steel between the casting rolls is used, but nevertheless molten steel that is solidified before other portions at the contact surface of the edge dam and the edge dam of the casting roll is generated as a skull. When an almost solid skull flows between the casting rolls, the repulsive force due to the skull is transmitted to the load cell, although the reduction force applied to the entire casting roll is smaller, whereby the molten steel at the center of the roll becomes less solidified and reduced. In severe cases, there is a disadvantage of causing a short circuit of the cast.

The sheet produced in such a twin roll sheet metal casting process maintains the height of the molten steel between the casting rolls at the same time, and simultaneously maintains the gap between the casting rolls and the repulsive force (RSF) of the molten steel being reduced to a desired value. Can improve the quality.

1 is a configuration diagram of a roll gap and a roll pressure reduction control apparatus of a conventional twin roll sheet casting process, referring to FIG. 1, a conventional twin roll sheet casting process equipment includes two cylindrical casting rolls 1 engaged with and rotated opposite to each other. And an edge dam 2 formed by blocking the front and rear between the casting rolls 1, wherein the molten steel 3 is injected into and stored in the edge dam 2, and the casting roll 1 As the molten steel (3) of the edge dam (2) in accordance with the rotation of the engagement proceeds to the bottom by the pressing force through the casting roll (1) is a facility that is made of thin plate.

The roll gap and roll pressure reduction control apparatus of the conventional twin roll type sheet casting process applied to such a facility includes a motor for rotating the casting roll 1 and a cylinder for providing a pressing force to the casting roll 1. (5), the speed sensor 11 for measuring the speed of the motor 4, the roll gap sensor 12 for measuring the gap of the casting roll 1, and the reduction force of the casting roll 1 Load cell 13 for measurement and repulsion / gap control is performed at the start of casting, increasing the speed until the casting speed reaches the normal speed, and the gap is kept constant after the casting speed reaches the normal speed. Main retarder 20 to perform repulsive force / speed control, a repulsive force / gap controller 21 to control repulsive force using a gap, a gap controller 22 to control a cylinder according to a roll gap, and speed Repulsive force / speed controller 23 for controlling the repelling force by A speed controller 24 for controlling the rotation.

Referring to the conventional method of controlling such a roll gap and the repulsive force (RSF), there are four types of conventional control methods, which will be described later.

First, the speed controller 24 receives the linear speed of the casting roll into a speed sensor 11 such as an encoder, and casts it through the motor 4 driving the casting roll 1. The linear velocity of the roll 1 is controlled using Equation 1 below.

Here, e means error, E means casting roll motor input, and Kp and Ki represent the proportional and integral constants of the PID controller, respectively.

Secondly, the gap controller 22 receives a gap between the casting rolls into a roll gap sensor 12 such as LVDT, and a hydraulic cylinder acting on a moving roll of the casting roll 1. 5) to control the roll gap using the following equation (2).

Here, e denotes an error, E denotes a hydraulic cylinder input, and Kp and Ki denote proportional and integral constants of the PID controller, respectively.

Third, the RSF / speed controller 23 uses the roll speed to control the RSF. In other words, if the roll speed is increased, the contact time between the roll and the molten steel is shortened, and as a result, the solidification of the molten steel is less, and thus the repulsive force (RSF) is lowered. Repulsive force (RSF) can be controlled using the following equation (3).

Here, e means error, E means casting roll motor input, and Kp and Ki represent the proportional and integral constants of the PID controller, respectively.

And fourthly, the repulsive force / gap controller 21 controls the roll gap to control the repulsive force RSF. That is, in the case where casts are formed between the rolls, the smaller the roll gap, the higher the resilience force (RSF) applied to the casting roll, and conversely, the larger the roll gap, the lower the repulsive force (RSF). Can be controlled using Equation 4 below.

Here, e denotes an error, E denotes a hydraulic cylinder input, and Kp and Ki denote proportional and integral constants of the PID controller, respectively.

FIG. 2 is a flowchart illustrating a conventional roll gap and roll pressure reduction control process. Referring to FIG. 2, a conventional roll gap and roll pressure reduction control process is described, while increasing the speed before the normal speed, that is, before the set time (to). Repulsive force / gap control is performed (S21, S22), and after the set time (to), the repulsive force / speed control is performed while maintaining the gap until the end of the address (S23, S24).

According to this, the speed controller controls the linear speed of the roll to match a given command value, and the gap controller controls only the gap, which is the linear speed at which the desired initial condition, i.e., the stationary roll is constant at the beginning of casting. It is used to slowly increase the speed in order to rotate and to move the gaps of the roll gap open near the desired cast thickness. In addition, since the repulsive force (RSF) and the roll gap must be controlled at the same time during casting, a repulsive force / speed control method or a repulsive force / gap control method is used, which has advantages and disadvantages. .

However, according to the conventional repulsive force / gap control method, the repulsive force (RSF) is controlled by using the roll gap while first controlling the linear speed of the roll to match the command value. While it is fast and effective in controlling the repulsive force (RSF), it leads to thickness variation of the produced cast, which adversely affects the quality of the cast. In addition, when the skull is formed intermittently at the roll edge that is relatively solidified faster than the center of the roll, the repulsive force (RSF) is increased to increase the roll gap, thereby reducing the repulsive force (RSF). Because of this increase, less solidified parts of the molten steel may exist, which may cause short circuiting of the cast steel, and thus an upper limit of roll gap variation must be set, which is dependent on the experience value. At this time, the less coagulated portion is brighter because the temperature is higher than the surroundings, which is called a hot band, and there is a problem that appears clearly each time the inflow of the skull.

In other words, according to the conventional RSF / speed control method, the roll gap is kept constant according to the desired thickness of the cast steel, so that the thickness of the produced cast steel is hardly changed. In order to control the roll speed, the influence of the roll speed on the repulsive force (RSF) is not so fast, so the control performance of the repulsive force (RSF) is relatively poor. Even if a scull occurs, the roll gap is kept constant so that the thickness variation of the cast steel does not occur much.The reaction speed of the roll speed for the control of the repulsive force (RSF) is slow, so that even when the scull is pressed down and pulled out, There is no reduction in rolling force, so there is no risk of casting short. However, since excessive repulsive force (RSF) due to the skull is transmitted to the casting roll as it is, the casting roll can be damaged if the material of the casting roll is not made strong. Since the hot band appears, but was weak compared to the repulsion / gap (RSF / gap) method.

3A and 3B are graphs of driving and non-driving side roll repulsion when mixing foreign substances on the casting roll, and FIGS. 4A and 4B are differential processing graphs for the data of FIG. 3.

3A and 3B, the horizontal axis means address time in seconds, the number in parentheses means the length of the produced cast steel, and the vertical axis shows the repulsive force (RSF) in tons. The drive side repulsion (RSF) and the non-drive side repulsion (RSF) are the abbreviations for drive side repulsion and non drive side repulsion respectively, one load cell on each side of the fixed roll. Was installed and the value was measured. As shown in FIGS. 3A and 3B, a sudden change in the compositional repulsive force was detected at 120, 150, and 190 seconds, and a change in the non-driven side (NDS) repulsive force was detected at 150 and 190 seconds. Since the RSF / speed method cannot quickly compensate as a roll speed when there is a sudden change in repulsive force, a situation arises in which the roll must withstand this repulsive force (RSF). This can be seen more clearly with reference to Figures 4a, 4b, the change in repulsive force (RSF).

The present invention has been made to solve the above problems, the object of the present invention is to perform a control method to maintain a constant roll gap in the repelling force / speed control method during casting, while the repulsive force due to the inflow of foreign matter such as scull between the rolls While the change of rebounding force is over a certain level, switch to the repulsive force / gap control method, and when the change of repulsive force becomes below a certain level, switch to control to the repulsive force / speed control method again to prevent damage to the casting roll. To provide a roll reduction force and a roll gap control method in a twin roll sheet metal casting process.

1 is a configuration diagram of a roll gap and roll pressure reduction control apparatus of a conventional twin roll type sheet casting process.

2 is a flowchart illustrating a conventional roll gap and roll pressure reduction control process.

3A and 3B are graphs showing the driving and non-driving side roll repulsion force when mixing the casting roll foreign matter.

4A and 4B are differential processing graphs for the data of FIG. 3.

5 is a configuration diagram of a roll gap and roll pressure reduction control device of a twin roll sheet metal casting process for carrying out the present invention.

Figure 6 is a flow chart showing a roll gap and roll pressure reduction control method of a twin roll thin plate casting process according to the present invention.

Explanation of symbols on the main parts of the drawings

1: roll 2: edge dam

3: molten steel 4: motor

5: cylinder 11: speed sensor

12: roll gap sensor 13: load cell

200: giving the main 210: repulsive force / gap controller

220: gap controller 230: repulsive force / speed controller

240: speed controller SW1: first switch

SW2: second switch

As a technical means for achieving the above object of the present invention, the present invention is a motor for rotating the pair of rolls on both sides, a cylinder for providing a reduction force on one side of the pair of rolls, and a speed sensor for measuring the speed of the motor And a main controller installed in a twin roll sheet metal casting process including a roll gap sensor for measuring a gap of the pair of rolls and a load cell for measuring a rolling force on the other side of the pair of rolls. A first step of starting the sheet production and performing a repulsion force / gap control to control the repulsive force of the roll by adjusting the roll gap through the cylinder while increasing the speed before the normal speed, that is, before the set time; A second step of measuring the repulsive force of the roll; A third step of comparing the measured repulsive force with a previously set repulsive force after a set time (to) from a thin plate production start time; In the second step, when the measured repulsive force is less than the set repulsive force, performing a repulsive force / speed control to control the repulsive force by adjusting the speed of the motor while maintaining a constant gap; In the second step, if the measured repulsive force is greater than the set repulsive force, a fifth step of performing a repulsive force / gap control to control the repelling force by adjusting the roll gap through the cylinder while maintaining a constant speed It provides a roll reduction force and a roll gap control method in a twin roll thin plate casting process.

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the apparatus for performing the roll reduction force and the roll gap control method in the twin-roll thin plate casting process according to the present invention will be described in detail.

The present invention is a control method to maintain a constant roll gap in the repulsive force / speed (RSF / speed) method, when the change in the repulsive force (RSF), the control method for a while the repulsive force / gap (RSF / gap) method The present invention proposes a method for preventing the damage of the casting roll by changing to.

FIG. 5 is a configuration diagram of a roll gap and roll pressure reduction control apparatus of a twin-roll thin sheet casting process for carrying out the present invention. Referring to FIG. 5, an apparatus for carrying out the method of the present invention will be described.

The method of the present invention comprises two cylindrical casting rolls (1) interlocking and rotating opposite to each other, and an edge dam (2) formed by blocking front and rear between the casting rolls (1), wherein the edge dam (2) includes: The molten steel 3 of high temperature is injected and stored, and the molten steel 3 of the edge dam 2 travels downward by the pressing force between the casting rolls 1 as the interlocking rotation of the casting roll 1 is carried out. While being applied to the process of manufacturing a thin plate, in order to control such a thin plate manufacturing process, the apparatus for performing the method of the present invention is a motor (4) for rotating the casting roll (1), and the casting roll (1) And a cylinder 5 for providing a pressure reduction force, a speed sensor 11 for measuring the speed of the motor 4, and a roll gap sensor 12 for measuring a gap of the casting roll 1.

In addition, the apparatus for carrying out the present invention performs the repulsive force / gap control while increasing the speed, before the set time (to) from the start of manufacturing the thin plate, measuring the repulsive force (RSF) of the roll (1) to start the thin plate manufacturing After the set time (to) from the time point, the measured reaction force (RSF) and the previously set reaction force (RSF_th) are compared, and according to the comparison result, the reaction force / speed control is performed while maintaining the gap constant, or the speed Main repertoire 200 to perform the repulsive force / gap control while maintaining a constant, a repulsive force / gap controller 210 for controlling the repulsive force using the gap, a gap controller 220 for controlling the cylinder according to the roll gap and , A repulsive force / speed controller 230 for controlling the repulsive force using the speed, and a speed controller 240 for controlling the rotation of the motor in accordance with the linear speed of the roll. The cylinder control signal of the gap controller 220 and the cylinder control signal of the reaction force / gap controller 210 are selected and provided to the cylinder 5 according to the selection signal SC1 of the main controller 200. The motor control signal of the speed controller 240 and the motor control signal of the reaction force / speed controller 230 are selected according to the first switch SW1 and the selection signal SC2 of the main controller 200. And a second switch SW2 provided to (4).

The repulsive force / gap controller 210, the gap controller 220, the repulsive force / speed controller 230, and the speed controller 240 may operate under the control of the main controller 200, in this case, the selection signal. It is preferable to operate in synchronization with (SC1, SC2).

Operation of the preferred embodiment of the present invention configured as described above will be described in detail below based on the accompanying drawings.

The present invention can control the thickness of the cast slab produced more precisely because the RSF / speed method can keep the roll gap constant regardless of the roll repulsion force (RSF) value. Algorithms for compensating for roll eccentricity can be implemented regardless of repulsive force (RSF) for more precise roll gap control, thereby enabling more precise thickness control. In addition, the present invention can prevent the excessive transfer of the repulsive force (RSF) to the casting roll by the foreign matter such as skull in the control of the repulsion force / speed (RSF / speed) method described later and thereby damage to the casting roll.

Figure 6 is a flow chart showing a roll gap and roll pressure reduction control method of a twin roll thin plate casting process according to the present invention.

Referring to Figure 6, the present invention is a motor (4) for rotating the casting roll (1) on both sides, a cylinder (5) for providing a reduction force on one side of the casting roll 1, and the motor (4) Speed sensor 11 for measuring the speed of the), the roll gap sensor 12 for measuring the gap of the casting roll 1, and the load cell 13 for measuring the rolling force on the other side of the casting roll (1) Roll rolling force and roll gap control method in a twin-roll thin plate casting process comprising a, first, in the first step (S61, S62) to start the sheet production, the speed before the normal speed, that is, before the set time (to) A reaction force / gap control is performed to control the reaction force of the roll 1 by adjusting the roll gap through the cylinder while increasing.

In detail, the main controller 200 of the present invention selects the speed controller 240 from the second switch SW1 using the selection signal SC2 of the speed of the casting roll which is stopped when the casting starts. By using the speed controller 240, the control signal is gradually raised to a predetermined set speed for a predetermined time (to), and at the same time, the selection signal SW1 is used so that molten steel can be pressed between two rolls to ensure plate formation. By selecting the repulsion force / gap controller 210 in the first switch (SW1) by using the repulsion force / gap controller 210, to control to maintain a higher pressing force than in the normal state.

Next, in the second step S63, the main controller 200 measures the repulsive force of the roll 1, which is a setting corresponding to a predetermined time, that is, a time taken for the speed of the motor to reach a steady state. When the time to elapses, it is recognized as a steady state, and then the repulsive force (RSF) is measured through the load cell 13.

Next, in the third step (S64), after the set time (to) from the start point of sheet production, the measured reaction force and the previously set reaction force are compared, which is determined by the main controller 200. Is compared with a predetermined limit reaction force (RSF_th) to determine the control method as follows.

Next, in the fourth step S65, in the second step, when the measured reaction force is less than the set reaction force, the main controller 200 sets the selection signal SC1 to the gap controller 220 at the first switch SW1. ) To control the thickness of the cast steel to maintain a constant thickness using the gap controller 220, and the repulsive force / speed at the second switch (SW2) by the selection signal (SC2) The controller 230 is selected to control the repulsive force by adjusting the casting speed, that is, the rotational speed of the motor, by using the repulsive force / speed controller 230.

Next, in the fifth step S66, in the second step, when the measured reaction force is greater than the set reaction force, the main controller 200 sets the speed controller 240 at the second switch SW2 by the selection signal SC2. Is selected to keep the speed constant for the purpose of protecting the roll, and at the same time, the reaction force / gap controller 210 is selected by selecting the reaction force / gap controller 210 at the first switch SW1 as the selection signal SC1. ) Adjusts the roll gap through the cylinder to control the repelling force.

On the other hand, as shown in Figure 5, using the change in the reaction force (RSF) it is easy to determine the drive of the reaction force / speed (RSF / speed) controller and the reaction force / gap (RSF / gap) controller, in this case, noise It is desirable to pass through a low pass filter or the like first to withstand it.

As described above, the present invention maintains a method of maintaining a constant roll gap by using a repulsive force / speed method, but as shown in FIG. 3, when a foreign material such as a skull is introduced and a sudden change in repulsive force occurs, a control method By preventing the damage of the casting roll by changing the repulsive force / gap method for a while, when the change in the repulsive force is small, the control method of returning to the repulsive force / speed (RSF / speed) method again.

According to the present invention as described above, while performing a control method to maintain a constant roll gap in the repulsive force / speed (RSF / speed) control method during casting, the change in the repulsive force due to the inflow of foreign matter such as scull between the rolls to a certain level During the abnormality, the casting roll is damaged by switching to the repulsive force / gap control method and switching back to the repulsive force / speed control method when the change of the repulsive force becomes below a certain level. It is effective to prevent this.

In addition, another effect of the present invention is the repulsive force (RSF), which plays an important role in determining the quality of the thin plate produced in the thin plate casting process, and the method of controlling the thickness at the same time, the repulsive force less risk of casting interruption due to the short circuit of the cast steel By using the RSF / speed method, damage to the casting rolls can be significantly reduced compared to the previous method. This can greatly reduce the quality degradation due to the damage of the casting roll in the thin plate casting process, and can greatly reduce the production cost of the thin plate by extending the life of the roll.

The above description is only a description of specific embodiments of the present invention, and the present invention is not limited to these specific embodiments, and various changes and modifications of the configuration are possible from the above-described specific embodiments of the present invention. It will be apparent to those skilled in the art to which the present invention pertains.

Claims (3)

A motor 4 for rotating the casting rolls 1 on both sides, a cylinder 5 for providing a reduction force on one side of the casting roll 1, and a speed sensor for measuring the speed of the motor 4 ( 11), a roll roll sensor 12 for measuring the gap of the casting roll 1, and a load cell 13 for measuring the rolling force on the other side of the casting roll (1) In the installed main controller 200 to control the roll reduction force and the roll gap, The first step of starting the sheet production and performing the reaction force / gap control to control the reaction force of the roll 1 by adjusting the roll gap through the cylinder while increasing the speed before the normal speed, that is, before the set time (to) ( S61, S62); A second step (S63) of measuring the repulsive force (RSF) of the roll (1); A third step (S64) of comparing the measured repulsive force (RSF) with a previously set repulsive force (RSF_th) after a set time (to) from the start of thin plate production; In the second step, when the measured repulsive force is less than the set repulsive force (S65) to perform a repulsive force / speed control to control the repulsive force by adjusting the speed of the motor while maintaining a gap; In the second step, if the measured repulsive force is greater than the set repulsive force, a fifth step (S66) for performing the repulsive force / gap control to control the repelling force by adjusting the roll gap through the cylinder while maintaining the speed constant Roll rolling force and roll gap control method in a twin-roll thin plate casting process characterized in that. The method of claim 1, wherein the fourth step (S65) When the measured repulsive force is smaller than the set repulsive force, the main controller 200 selects the gap controller 220 at the first switch SW1 as the selection signal SC1 to maintain the thickness of the cast steel in a constant manner. Using 220 to control the gap to be kept constant; Then, the main controller 200 selects the reaction force / speed controller 230 at the second switch SW2 as the selection signal SC2 and uses the reaction force / speed controller 230 to rotate the casting speed, that is, the rotation of the motor. Roll pressing force and roll gap control method in a twin-roll thin plate casting process comprising the step of controlling the repulsive force by adjusting the speed. The method of claim 1, wherein the fifth step (S66) In the second step, when the measured reaction force is greater than the set reaction force, the main controller 200 selects the speed controller 240 at the second switch SW2 as the selection signal SC2 for the purpose of protecting the roll. Keeping the speed constant; Then, the main controller 200 selects the reaction force / gap controller 210 at the first switch SW1 by the selection signal SC1, and the reaction force / gap controller 210 adjusts the roll gap through the cylinder to adjust the reaction force. Roll rolling force and roll gap control method in a twin-roll thin plate casting process comprising the step of controlling the.