JPH10305352A - Control of continuous casting machine with twin rolls - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a controlling method of a continuous sheet casing machine with twin rolls which controls the estimated error and the time delay, and stabilizes the sheet thickness by compensating the roll gap adjusting volume based on the estimated sheet thickness value using the measured value of the sheet thickness, and by adjusting the roll gap based on the compensated value. SOLUTION: A sheet thickness controlling part 5 outputs a roll gap changing volume Sref to a servo controller 5a, and a peripheral velocity changing volume Vref to a velocity regulator 5b respectively, while a roll load measured value Pact provided from a load meter 14, a sheet thickness measured value Hact provided from a sheet thickness meter 15, and additionally a roll load desired value Paim, and a sheet thickness desired value Haim are functioning as input ends. The servo controller 5a adjusts the roll gap by transferring a horizontal roll 11 through increasing/decreasing the servo current conductivity in the servo 12. The velocity regulator 5b adjusts the rotational speed of twin rolls 1 by increasing/decreasing the motor current conducted in a main motor 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling a twin-roll continuous caster.

[0002]

2. Description of the Related Art As a method of casting a thin sheet of steel or non-ferrous metal, various strip casting methods have attracted attention.
It is applied to the casting of various metal plates including steel plates.
Among them, when casting a thin plate with a thickness of several mm,
A twin-roll continuous casting method (hereinafter referred to as a twin-roll method) is used as a typical method.

In the twin roll method, a pair of horizontal rolls (twin rolls) having internal cooling means are arranged side by side at a distance of several mm, and each horizontal roll is rotated from the upper side in a winding direction so as to be interposed between the horizontal rolls. By injecting the molten metal into the gap from the upper side, the molten metal is continuously cooled by contact with the peripheral surface of each horizontal roll, and the solidified shell, which increases its thickness at the outer portion, is moved to the closest position of the horizontal roll ( At the vicinity of the kiss point), pressure is applied by pressing between the horizontal rolls to form a thin slab on the horizontal roll exit side.

By taking advantage of the advantage that a very thin slab having a thickness of several mm can be continuously cast by this twin-roll method, from the viewpoint of working efficiency and energy saving, the product is cold-rolled as it is and the product thickness is reduced. Attempts have been made to perform processing to such an extent that high plate thickness accuracy at the casting stage has been required.

[0005] The thickness accuracy in the twin-roll method varies depending on the state of formation of a solidified shell at the center of the slab, and the molten metal level,
It varies in a complicated manner depending on various operating conditions such as the melt temperature, roll peripheral speed, roll gap, and roll load. In order to stably obtain a thin plate slab with high plate thickness accuracy, it is necessary to appropriately control these operating conditions, and several control methods have been introduced so far.

For example, in Japanese Patent Application Laid-Open No. 4-167950, the roll gap is changed by detecting the roll load and moving the twin rolls in the horizontal direction so that the roll load matches the target value. At the same time, detect the slab thickness and molten metal level,
A control method for making the slab thickness constant by increasing or decreasing the roll peripheral speed based on the deviation between the detected plate thickness and the target plate thickness and the detected deviation between the molten metal level and the target molten metal level is disclosed. ing.

As a thickness gauge for detecting the thickness in this control method, various thickness gauges such as a radiation type using X-rays, a differential transformer, an air micro type, and a laser type may be used. Since there is a possibility that the molten metal may be incurred due to troubles during the operation such as breakout, etc., any type of thickness gauge is installed as far away as possible on the downstream side of the twin rolls.

However, since the detected value of the sheet thickness detected from the sheet thickness gauge is fed back and used for the control as described above, a time delay occurs in the control in accordance with the installation distance from the twin rolls. In order to suppress the decrease in control accuracy due to the time delay, it is conceivable to increase the control gain.However, since the control is likely to be unstable, the control value must be reduced to the same level as when there is no time delay in the detected value. The gain cannot be increased. As described above, there is a disadvantage that it is difficult to improve the controllability of the sheet thickness control based on the actually measured value of the sheet thickness.

In Japanese Patent Publication No. 7-51256,
Without actually measuring the plate thickness, from the roll gap, roll load, roll cooling water temperature, and cooling water temperature of the frame supporting the twin rolls, calculate the amount of frame deflection, the amount of thermal deformation of the frame and twin rolls, There is disclosed a method of estimating a plate thickness from a calculated theoretical roll gap and performing control using the estimation result. This method does not cause a time delay of the thickness control, but the average thickness in the casting direction does not match the target thickness due to an estimation error.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and corrects a roll gap adjustment amount based on an estimated thickness value using an actual measured thickness value to obtain a corrected value. By adjusting the roll gap based on
An object of the present invention is to provide a control method of a twin-roll type continuous sheet casting machine capable of suppressing an estimation error, suppressing a time delay inevitably included in a measured sheet thickness, and stabilizing the sheet thickness.

[0011]

According to a first aspect of the present invention, there is provided a control method for a twin-roll type continuous casting machine, wherein a molten metal is injected into a gap between the twin rolls while rotating twin rolls juxtaposed at an appropriate distance. In the control method of a twin-roll continuous caster, which lowers the molten metal solidified by contact with the twin rolls provided with internal cooling means and obtains a plate-shaped slab of a desired thickness, the actually measured twin-roll reduction load and A first step of taking in the measured thickness of the slab, a second step of estimating the thickness of the slab based on the taken down load, and a deviation of the estimated thickness and the target thickness, A third step of calculating a first gap correction amount for correcting the gap size of the twin rolls; and a gap size of the twin rolls based on the deviation of the target thickness and the sheet thickness taken in the first step. Calculate the second gap correction amount for correction Fourth step, a fifth step of calculating a gap change amount for correcting the gap dimension of the twin roll based on the first gap correction amount and the second gap correction amount, and a fifth step of calculating the twin roll based on the gap change amount. And a sixth step of adjusting the gap size.

The control method of the twin-roll continuous casting machine according to the second invention is the same as the control method of the twin-roll continuous casting machine according to the first invention, and further includes a rolling load and a rolling load taken in the first step. A seventh step of calculating a circumferential speed correction value of the twin roll based on the deviation of the target rolling load; and an eighth step of adjusting the circumferential speed of the twin roll based on the circumferential speed correction value. .

The control method of the twin-roll type continuous casting machine according to the first invention will be described below. First, a sheet thickness is estimated based on a roll load actual measurement value that does not include a time delay, and a first gap correction amount is calculated based on a deviation between the sheet thickness estimation value and a sheet thickness target value.

By adjusting the roll gap, which is the gap size between the twin rolls, based on the first gap correction amount, the change due to the elastic deformation of the twin roll and the frame caused by the change in the roll load without being affected by the time delay. Can be corrected to stabilize the sheet thickness, but in the control based on the sheet thickness estimation value based on the roll load, it is inevitable that an estimation error occurs between the sheet thickness estimation value and the actual sheet thickness.

Then, the sheet thickness is actually measured, and a second gap correction amount is calculated based on the deviation between the actual measured value of the sheet thickness and the sheet thickness target value. The first gap correction amount is calculated based on the second gap correction amount. A gap change amount in which the estimation error included in the amount is corrected is calculated. Then, by adjusting the roll gap based on the gap change amount, the above-described estimation error of the plate thickness can be eliminated.

According to the control method of the twin-roll type continuous casting machine according to the second invention, the twin-roll type continuous casting machine according to the first aspect of the present invention utilizes the characteristic of the roll load which becomes small and large according to the level of the peripheral speed of the roll. In addition to the control method of the casting machine, the load can be stabilized by adjusting the peripheral speed of the roll based on the deviation between the measured load value and the target load value. Breaking of the piece can be suppressed.

FIG. 4 is a flowchart showing a control method of the twin-roll type continuous casting machine according to the first invention. First, the actually measured roll load and the actually measured sheet thickness are taken in (step 1), and the sheet thickness is estimated based on the taken roll load actual measurement value (step 2).

The relationship between the plate thickness and the roll load can be expressed by the following relational expression. Here, h is the plate thickness, P is the roll load, S is the roll gap, H is the level of the molten metal, V is
c indicates the roll peripheral speed, respectively.

H = h (P, S, H, Vc) (1)

When the equation (1) is linearized within a small change range, it is expressed as the equation (2), and the sheet thickness can be estimated from the change in the roll load. In addition, Δh indicates a sheet thickness variation, ΔP indicates a roll load variation, ΔS indicates a roll gap variation, ΔH indicates a molten metal level variation, and ΔVc indicates a roll peripheral speed variation.

[0021]

(Equation 1)

Here, by making the level H independent of the control system of the present invention, the level change ΔH can be neglected as small. Further, it is assumed that appropriate values experimentally obtained in advance are used for the roll gap S and the roll peripheral speed Vc, and the influence of these fluctuation amounts on the sheet thickness fluctuation amount Δh is very small. Therefore, the roll gap variation ΔS and the roll peripheral speed variation ΔVc can be ignored. Thus, the thickness variation Δh can be estimated by knowing the roll load variation ΔP.

Next, based on the deviation between the sheet thickness and the target value of the sheet thickness estimated in step 2, the first value is calculated by PI calculation or the like.
The gap correction amount is calculated (step 3).

Then, a second gap correction amount is calculated by a calculation such as a PI calculation based on the deviation between the actual measured thickness value and the target thickness value taken in step 1 (step 4). In order to further suppress the influence of the time delay caused by the measured thickness of the sheet used in step 4, the control system design such as the Smith method for removing the time delay from the closed loop by incorporating the model to be controlled into the calculation. It is desirable to perform time delay compensation by the method.

Based on the second gap correction amount calculated in step 4 and the first gap correction amount calculated in step 3, a gap change amount is calculated by calculation such as PI calculation (step 5), and the calculated gap change amount is calculated. The roll gap is adjusted based on (step 6).

With the above configuration, the effect of the time delay caused by using the measured thickness value is suppressed, the influence of the estimation error caused by using the estimated thickness value is suppressed, and the thickness of the slab is stabilized. be able to.

FIG. 5 is a flowchart showing a control method of the twin-roll type continuous casting machine according to the second invention. In addition to the above steps 1 to 6, a peripheral speed change amount which is a change amount of the roll peripheral speed is calculated based on the deviation between the actual measured roll load value and the target roll load value taken in step 1 (step 7). The peripheral speed of the twin roll is adjusted based on the calculated peripheral speed change amount (step 8). Thereby, the roll load is stabilized, and the plate thickness can be further stabilized.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a configuration of a main part of a twin-roll continuous casting machine according to the present invention.

In FIG. 1, the twin-roll type continuous casting machine has a pair of horizontal rolls 11, 11 provided with internal cooling means, having a length of several mm.
The twin rolls 1 arranged in parallel at a distance are supported by a pair of frames (not shown), and while the horizontal rolls 11 are rotated in the direction of winding in from above, a tank provided above and storing the molten metal 21 is provided. The molten metal 21 is poured from the dish 2 into the gap between the horizontal rolls 11 and 11 through the immersion nozzle 3 extending downward, and
By continuously cooling the molten metal 21 by contact with the peripheral surfaces of the horizontal rolls 11, 11, the solidified shell whose thickness increases at the outer portion thereof is moved near the closest position of the horizontal rolls 11, 11. The thin plate-shaped cast piece 4 is formed on the exit side of the twin rolls 1 by pressure contact between the two rolls.

One of the horizontal rolls 11 is provided so as to allow its rotation axis to move in a direction opposite to the horizontal rolls 11 and 11, and is driven in this direction by a servo 12 provided on the rotation axis. Thus, the roll gap, which is the gap size between the horizontal rolls 11, 11, is changed.
The twin roll 1 is a main motor 1 for driving the rotation shaft.
3 and drives the twin rolls 1 at a predetermined rotational speed.

A load cell 14 comprising a load cell, a strain gauge, and the like is provided on the rotating shaft of the twin roll 1, detects a roll load as a rolling load of the twin roll 1, and gives the detection result to the plate thickness control unit 5. ing.

A thickness gauge 15 of a radiation type, a laser type, or the like is provided at an appropriate position on the exit side of the twin roll 1.
The thickness (thickness) of the slab 4 is detected, and the detection result is given to the thickness control unit 5.

The thickness control unit 5 composed of an online computer, not shown, in addition to the measured roll load value Pact given from the load meter 14 and the measured thickness value Hact given from the thickness gauge 15 as described above. Roll load target value Paim and sheet thickness target value H given from the host computer
aim is set as an input terminal, and based on these input results, the roll gap change amount Sref, which is the change amount of the gap size of the horizontal rolls 11, 11, is sent to the servo controller 5a, and the peripheral speed change amount, which is the change amount of the peripheral speed of the twin rolls 1, is provided. Vref is output to each of the speed regulators (ASR) 5b.

The servo controller 5a adjusts the roll gap by moving the horizontal roll 11 by increasing or decreasing the servo current supplied to the servo 12 according to the applied roll gap change amount Sref.

The speed regulator 5b adjusts the rotation speed of the twin roll 1 by increasing or decreasing the motor current supplied to the main motor 13 in accordance with the given peripheral speed change amount Vref.

In addition to the above control system, a control system for controlling the level of the molten metal is provided, and the level of the molten metal is kept constant. In this control system, a molten metal level measured value Fact is detected from the surface height of the molten metal 21 in the molten metal pool by a molten metal level detecting means 61 such as a camera provided directly above the molten metal pool between the horizontal rolls 11 and 11. The molten metal level control unit 6 taking in the detection result calculates the opening degree of the stopper 22 based on a deviation from a predetermined molten metal level target value Faim. The opening / closing signal is supplied to a stopper control means 23 for operating the stopper 22, whereby the opening of the stopper 22 is adjusted and the molten metal level is kept constant.

FIG. 2 is a block diagram showing details of the sheet thickness control unit 5. As shown in FIG. The sheet thickness estimating unit 51 estimates the sheet thickness from the deformation amount of the twin roll 1 and the frame based on the actual roll load value Pact given from the load cell 14, and estimates the sheet thickness Hpr.
d is given to the first gap correction amount calculation unit 52. The first gap correction amount calculation unit 52 calculates the given estimated thickness value Hpr.
Based on d and a target thickness Haim given from a higher-level computer (not shown), the first gap correction amount S1 is calculated using a calculation rule such as a PI calculation, for example, using a relational expression of input / output characteristics such as the following expression. I do. Kp ₁ and Ti ₁ are constants.

[0038]

(Equation 2)

Based on the target thickness Haim and the deviation ΔH of the measured thickness Hact given from the thickness gauge 15, the second gap correction amount calculating section 53 uses a calculation rule such as PI calculation. The second gap correction amount S2 is calculated using a relational expression of input / output characteristics such as the following expression. Note that Kp ₂ ,
Ti ₂ indicates a constant.

[0040]

(Equation 3)

Based on the first gap correction amount S1 and the second gap correction amount S2, the gap change amount calculating section 54 calculates P
The gap change amount Sref is calculated using an operation rule such as the I operation, for example, using a relational expression of the input / output characteristics such as the following expression, and is output to the servo controller 5a. Kp and Ti indicate constants.

[0042]

(Equation 4)

Based on the actual roll load value Pact given from the load meter 14 and the deviation ΔP between the roll load target value Paim given from the host computer (not shown), the peripheral speed change amount calculating section 55 calculates the peripheral speed change amount Vref. Calculate and output to the speed regulator 5b.

FIG. 3 is a graph showing the control results of the twin-roll type continuous casting machine. The horizontal axis shows the casting time (sec), the thickness variation (mm) and the roll load variation (to).
n) and the roll peripheral speed variation (m / min) are also shown along the vertical axis, corresponding to the horizontal axis.

In the figure, the waveform indicated by a solid line indicates the control result of the present embodiment, and the waveform indicated by a broken line indicates a conventional example.
6 shows a control result of JP-A-67950. The target thickness is 2 (mm) and the target roll load is 10 (to
n), the peripheral speed target value is 50 (m / min).

As shown in FIG. 3, in the conventional control method, the thickness variation is ± 0.054 with respect to the target thickness.
(Mm), but in the control method of the present invention, ± 0.
022 (mm), indicating that the plate thickness accuracy has been further improved. The roll load variation and the roll peripheral speed are also ± 1.20 (to
n), ± 3.30 (m / min), but ± 1.0 (ton), ± 2.98 (m) in the control method of the present invention.
/ Min), and it can be seen that the fluctuations of the roll load and the roll peripheral speed are also suppressed. Thus, according to the present invention, not only can the plate thickness be stabilized, but also fluctuations in roll load and roll peripheral speed can be suppressed.

[0047]

As described above in detail, in the control method of the twin-roll type continuous casting machine according to the present invention, the influence of the time delay on the control is small even if the measured thickness is used, and the thickness estimation is performed. Even if the value is used, the influence of the estimation error on the control is small, and the plate thickness of the slab can be stabilized with high accuracy.

Further, by stabilizing the peripheral speed of the twin rolls based on the twin rolls' rolling load, fluctuations in the rolling load are suppressed, and slab breakage, breakout, etc. are suppressed, and operation is stabilized. For example, the present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a twin-roll continuous casting machine according to the present invention.

FIG. 2 is a block diagram illustrating details of a sheet thickness control unit.

FIG. 3 is a graph showing a control result of a twin-roll type continuous casting machine.

FIG. 4 is a flowchart showing a control method of the twin-roll continuous casting machine according to the first invention.

FIG. 5 is a flowchart showing a control method of the twin-roll continuous casting machine according to the second invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Twin roll 2 Tundish 3 Immersion nozzle 4 Cast piece 5 Sheet thickness control part 6 Molten metal level control part 12 Servo 13 Main motor 14 Load meter 15 Thickness gauge 21 Molten metal 22 Stopper 23 Stopper opening / closing means

Claims (2)

[Claims] 1. A molten metal is poured into a gap between twin rolls while rotating twin rolls juxtaposed at an appropriate distance from each other, and the molten metal solidified by contact with the twin rolls provided with internal cooling means is reduced. In a control method of a twin-roll continuous casting machine for obtaining a plate-like slab having a desired thickness, a first step of taking in a measured roll-down load of a twin roll and a measured thickness of a cast slab, A second step of estimating the thickness of the cast slab based on the above, and a third step of calculating a first gap correction amount for correcting the gap size of the twin rolls based on the deviation between the estimated thickness and the target thickness. And a fourth step of calculating a second gap correction amount for correcting the gap size between the twin rolls based on the deviation of the target thickness and the thickness taken in the first step; Based on the correction amount and the second gap correction amount A fifth step of calculating a gap change amount for correcting the gap size of the twin rolls, and a sixth step of adjusting the gap size of the twin rolls based on the gap change amount. Control method of roll type continuous casting machine. A seventh step of calculating a peripheral speed correction value of the twin roll based on a deviation between the rolling load and the target rolling load taken in the first step; The method according to claim 1, further comprising an eighth step of adjusting a peripheral speed.