JPH06210338A - Sheet thickness controller for tandem rolling mill - Google Patents

Abstract

PURPOSE:To prevent the lag of acceleration and to keep a capacity high by replacing a target strip thickness to a target value calculated from a measured value when a measured strip thickness on the outlet side of each intermediate stand is remarkably difference from a target sheet thickness set in advance. CONSTITUTION:The sheet thickness hi is found by hi=(hi-1)X(Vi-1)/(Vi) in accordance with sheet speed meters 31-34 to detect the strip speed Vi on the outlet side of an i-th stand of a tandem rolling mill, the strip thickness hi-1 on the outlet side of a (i-1)th stand, the strip speed Vi-1 on the outlet side of an (i-1)th stand, the strip speed Vi on the outlet side of a i-th stand, a difference DELTAhi from a target sheet thickness hio set in advance is found by hi=(hio)-(hi). Whether a control target sheet thickness hio be replaced by this difference DELTAhi to the target value calculated from a measured value at that time or not is decided. When the replacement is needed, the roll speed of each stand is controlled by a mass flow AGC so that the finally decided DELTAhi takes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a tandem rolling mill, and more particularly to an improvement of an automatic plate thickness control device for a rolling mill for rolling metal strip such as a tandem cold rolling mill.

[0002]

2. Description of the Related Art Conventionally, a mass flow rate is measured by using a plate speed value of a plate speed gauge for detecting a strip speed provided between and before and after a stand of a tandem rolling mill and a plate thickness value of a plate thickness gauge installed in a preceding stage. According to the formula, the so-called mass flow AGC (Automatic Ga) for controlling the roll speed of the rolling mill so that the plate thickness on the stand exit side becomes the target plate thickness value.
after the passage, or in the continuous rolling, the control was started after the running plate thickness was changed, and the preset target value of each stand, that is, the setup value was set as the control target value.

[0003]

However, the conventional mass flow AGC has the following problems. For example, when changing the running plate thickness during continuous rolling, if there is an error between the preset conditions (setup) including the variation of material thickness and deformation resistance, and the plate actually passed, The plate thickness on the delivery side of the intermediate stand does not necessarily have a plate thickness set in advance or a value in the vicinity thereof. In such a case, when the control of the mass flow AGC is started, the roll speed is rapidly controlled in order to drive the actual value that largely deviates from the target value to the target value, and as a result, the inter-stand tension greatly changes.

In this state, not only the rolling speed cannot be increased, but in an extreme case, "narrowing" or "breakage" may occur, resulting in a loss of the rolling mill. The same problem as described above occurs when the mass flow AGC is controlled midway not only after changing the running plate thickness but also during normal rolling, and when the actual plate thickness on the stand-out side of each stand and the target value are significantly different.

An object of the present invention is to provide a strip thickness control device for a tandem rolling mill in which the fluctuation of the roll peripheral speed is small even in the case of a mass flow type AGC even when the preset setting condition and the actual value greatly differ.

[0006]

In order to solve these problems, the present invention provides a plate thickness detecting means for detecting the strip plate thickness h on the inlet side of a tandem rolling mill or on the outlet side of a preceding stand, and a tandem rolling mill. speed detecting means for detecting the strip speed Vi at the ith stand output side;

Strip plate thickness hi-1 at the (i-1) th stand outlet side, strip speed Vi-1 at the (i-1) th stand outlet side, strip speed V at the ith stand outlet side
In response to i, the plate thickness hi is

Hi = (hi−1) × (Vi−1) / (Vi) (1)

The target plate thickness hi0 set in advance obtained by
And the difference Δhi

Δhi = (hi0) − (hi) (2)

At the time of starting control of the plate thickness hi and the means for obtaining the control target plate thickness hi0.
A means for determining the necessity of replacing the target value calculated from the actual value at that time,

When the replacement is necessary, the plate thickness target value h
means for replacing i0 with a target value calculated from the actual value at that time;

Means for controlling the roll speed of each stand by the mass flow AGC so that the deviation Δhif between the finally determined target thickness hi0f and the actual thickness hi is 0. The present invention provides a plate thickness control device for a tandem rolling mill.

[0014]

In the mass flow AGC of the present invention, the product of the strip thickness and the speed is constant on the entrance side and the exit side of each stand of the tandem rolling mill, and the target value h on the exit side of each stand is set.
The roll speed of the stand is controlled so that the difference Δhi = hi0−hi from the actual plate thickness hi obtained by the calculation is set to 0 for i0.

According to the present invention, when the mass flow AGC control is started, if the actual output value at each stand and the preset target plate thickness are significantly different, the target plate thickness is calculated from the actual value at that time. Will be replaced with the target value
At the start of control, there is almost no AGC output for controlling the roll speed, and Δhi can be set to 0 with a comparatively small output for subsequent control.

As a result, at the time of starting the control of the conventional mass flow AGC, especially when the preset target value and the actual value are significantly different, the over tension or the low tension generated to drive the actual value to the target value is reduced. The tension fluctuation can be prevented. Therefore, the control of the mass flow AGC can be started freely.
You can make a stop.

[0017]

FIG. 1 is a block diagram showing an embodiment of the present invention. The strip 1, which is a steel strip to be rolled, sequentially passes through ST1 to ST4 of a plurality of stands (four in this embodiment) and is rolled. The plate thickness (ST1 output plate thickness in this embodiment) h1 of such a tandem rolling mill is the plate thickness detecting means 2
Detected by 1. Further, the plate speed between ST1 and ST2 is detected by the speed detecting means 31, and furthermore, the tracking between stands is performed based on the speed detection result. When a certain measurement point A (this actual thickness is h1A) reaches ST2, the speed V1 between ST1 and ST2 at that time is V1.
By the plate speed V2A between A and ST2 to ST3, the ST2 exit side plate thickness h2A

H2A = h1A × V1A / V2A (3)

The deviation Δ between the plate thickness h2A calculated by this calculation and the plate thickness target value h20 set in advance Δ
h2

Δh2 = h2A-h20 (4)

Calculating with In addition, the deviation rate R2, which is the relative error between the target thickness and the actual thickness,

R2 = | h2A-h20 | / h20 (5)

It is calculated by When the control of the mass flow AGC is started, its deviation Δh2 or the deviation rate R of the second stand
For 2 the determination is made as to whether the value is within the allowable range or not according to the equation (6) (α2 = 2.5% is used as the allowable standard in this embodiment).

R2 = | h2A-h20 | / h20 × 100> α2 (%) = 2.5% (6)

When the deviation rate R2 exceeds 2.5%,
The target value h20 is replaced with the actual target value. The above calculation and judgment are performed at each stand except the final stand. The deviation rate Ri is calculated at each stand. However, i is a natural number excluding the number corresponding to the final stage.

Examples are shown in Tables 1 and 2. In this example, an example in which a 3.6 mm original plate is rolled to a final target thickness of 1.224 mm is introduced. In Table 1, the difference between the actual plate thicknesses h2A and h3A of the second and third stands and h20 and h30 set as target values in advance is Δh2 = 18 μm (1.0%) Δh3 = 17 μm, respectively.
(1.2%), and in this case, it is not necessary to replace the target value because both stands are within the allowable range.

[0027]

[Table 1]

On the other hand, in the case of Table 2, the deviation rate R of the second stand
2 is 3.7%, the deviation rate R3 of the third stand is 3.5%, and it is necessary to replace the target value in both stands.

[0029]

[Table 2]

The above embodiment will be described with reference to the flowchart of FIG. The control of the mass flow AGC is started in step 2, but the plate thickness gauge 21 is used in the first stand in step 3.
The plate thickness control is performed according to and the target plate thickness is not replaced.

In step 4, the speed reaches the second stand, and the speeds of the second stand on the inlet side and the outlet side detected by the plate speed gauges 31 and 32 and the thickness of the inlet side detected by the plate thickness gauge 21
The outlet plate thickness is calculated by the equation (3). Furthermore (4),
The deviation rate R2 at the second stand is calculated by the equation (5),
A comparison operation is performed to determine whether or not it is within the allowable range α2. If it is within the allowable range, it is controlled according to the original target value, but if it is outside the allowable range, the target value is replaced with the actual value and control is performed.

In the following step 7, the third stand is reached, and like the second stand, it is judged whether the deviation ratio R3 is controlled by the target value or the actual value by controlling the deviation range R3. . If it is out of the allowable range, the target value is replaced with the actual value in step 9 and control is performed as in the above. Since step 10 is the fourth stand and the final stand in this embodiment, the target value cannot be changed.

Regarding the determination of the target value of each stand, for example, when Δh2 is a deviation on the plus side, that is, on the thick side as shown in equation (7), the roll speed of ST1 is reduced and the plate on the ST2 entry side is reduced. The speed is reduced from V1A to V1A ', and the deviation Δh2 is approximated to 0 as shown in equation 1, that is, the equation (8).

Δh2> 0 (7)

[0035]

[Equation 1]

Here, the allowable deviation rate α provided as the allowable range may be set separately for + and −. Further, the absolute value may be set instead of the ratio. Further, fine control can be performed by layering according to specifications such as material and thickness of rolled material.

On the actual control side, the gain that determines the output amount after the control is started can be set as a function of the deviation, speed, time after the start, etc., and optimal control can be performed. In the present invention,
If the allowable range is set small, the target value will be replaced under all conditions. Normally, X-rays and the like are used as a thickness meter and are installed around ST1, but since the AGC by these thickness meters is controlled separately from the mass flow-AGC, these target values are not replaced. Further, it is needless to say that the target plate thickness on the delivery side of the final stand is originally intended to be finally rolled to that plate thickness, is actually measured by X-ray or the like, and the target value is not replaced under any condition.

[0038]

The plate thickness control device of the tandem rolling mill according to the present invention has the following effects. When the actual target plate thickness on the output side of each intermediate stand greatly differs from the preset target thickness due to variations in deformation resistance after passing the plate or after changing the running plate thickness during continuous rolling, the conventional system mass flow-AGC It is possible to prevent the rolling mill from being stopped due to a delay in acceleration due to fluctuations in tension on the over-tension side or extremely low-tension side, which inevitably occurred in the above, or in extreme cases, such as narrowing or breakage. Can be kept high.

Further, the control of the mass flow-AGC can be started at any time during rolling, not only after the thickness of the threaded plate or the running plate thickness is changed but also at the time of starting the control, since there is no particular fluctuation in the tension. From the above, the ability of the rolling mill can be maintained at a high level, and good plate thickness accuracy can always be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the control device.

[Explanation of symbols]

 1 Strip 4 Control Device 20, 21, 24 Plate Thickness Meter 31, 32, 33, 34 Plate Speed Meter 41, 42, 43, 44 Motor ST1, ST2, ST3, ST4 Stand

Claims (1)

[Claims] 1. A plate thickness detecting means for detecting a strip plate thickness h on an inlet side of a tandem rolling mill or on an outlet side of a preceding stand, and a velocity detection for detecting a strip velocity Vi on an ith stand outlet side of a tandem rolling mill. And a strip plate thickness hi-1 on the outlet side of the (i-1) th stand,
Strip speed Vi−1 on the output side of the (i−1) th stand,
In response to the strip speed Vi on the outlet side of the i-th stand, the plate thickness hi hi = (hi−1) × (Vi−1) / (Vi) is obtained, and the difference from the preset target plate thickness hi0 is obtained. △ hi
Is calculated by Δhi = (hi0) − (hi), and when the control of the plate thickness hi is started, the control target plate thickness hi0 is set to a target value calculated from the actual value at that time by the calculated difference Δhi. A means for determining the necessity of replacement, a means for replacing the plate thickness target value hi0 with a target value calculated from the actual value at that time when the replacement is necessary, and a finally determined plate thickness target. Value hi0f and actual thickness hi
And a means for controlling the roll speed of each stand by a mass flow AGC so that the deviation Δhif from the value becomes zero.