JPH05123726A - Plate thickness control method for cold tandem rolling mill - Google Patents

Abstract

(57) [Summary] [Purpose] The sheet thickness variation at the intermediate stand caused by rolling a material with rapid hardness variation such as the front and rear ends of the hot rolled coil is corrected, Stable manufacturing of cold-rolled strip products with high plate thickness accuracy. [Structure] In a cold tandem rolling mill, a plate thickness gauge 20 is provided on the entrance side of a stand located at a subsequent stage, and a low-frequency filter 21 separates and extracts the output of the plate thickness gauge 20. To simultaneously change the roll speed from the stand to the stand immediately before the stand and the rolling position of the stand, or the roll speed from the stand to the final stand and the rolling position of the stand by a feedforward method. It is the one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip thickness control method for a cold tandem rolling mill.

[0002]

2. Description of the Related Art Generally, a cold tandem rolling mill employs the following plate thickness control (AGC) method as shown in FIG. 2 (Steel Manual III (1) "Rolling Foundation / Steel Plate" P5).
74 ~ P579). In FIG. 2, 1 is a material to be rolled, 2
A, 2B and 2C are plate thickness gauges, and 3 is a rolling down device.

(1) AGC for controlling the plate thickness on the outlet side of the first stand to be constant (a) Feed-forward reduction AGC ... The pressing position of the first stand based on the deviation of the mother plate thickness measured by the first stand inlet side plate thickness gauge 2A To change. (b) Gauge meter rolling down AGC: The strip thickness is calculated from the rolling position of the first stand and the rolling load, and the rolling position is changed so that this becomes constant. (c) Feedback reduction AGC ... The first stand reduction position is changed based on the deviation of the first stand outlet thickness measured by the first stand outlet thickness gauge 2B.

(2) AGC feed-forward tension AGC for controlling the second stand outlet side plate thickness to a constant value ... Based on the first stand outlet side plate thickness deviation measured by the first stand outlet side plate thickness gauge 2B, the first stand roll speed To change.

(3) AGC feedback tension AGC for controlling the plate thickness on the delivery side of the final stand to be constant.
The final stand roll speed is changed based on the product thickness deviation measured in C.

That is, in the cold tandem rolling mill, the plate thickness control corrects the plate thickness fluctuation of the hot-rolled plate at the first stand, and thereafter passes through each stand as it is to obtain a high plate thickness accuracy. Therefore, in a normal cold tandem rolling mill, variations in the thickness and hardness of the hot-rolled sheet hardly affect the subsequent stands.

[0007]

However, in the completely continuous tandem rolling mill, since the hot rolling coil is welded and rolled at the entrance side of the tandem rolling mill, the front and rear ends of the hot rolling coil (hot tandem mill) are rolled. However, even if it has a rapid hardness change, it is necessary to roll with high accuracy as in the case of the steady part in the center of the coil. However, when rolling the front and rear ends of the hot-rolled coil with the above-described completely continuous tandem rolling mill, even if a relatively good strip thickness accuracy is obtained on the delivery side of the first stand, it is possible to heat it in the subsequent stand. The effect of a sudden change in hardness of the rolled coil appears, and at the final stand,
There is a problem that the plate thickness accuracy is significantly deteriorated.

The present invention corrects the plate thickness fluctuation at the intermediate stand caused by rolling a material having a rapid hardness change such as the front and rear ends of the hot rolled coil, and the plate thickness at the exit side of the final stand is corrected. The object is to stably manufacture cold-rolled strip products with high accuracy.

[0009]

According to the present invention, in a cold tandem rolling mill, a plate thickness gauge is provided on the inlet side of a stand located at the rear stage, and its output is separated and extracted by a low pass filter to separate low frequency components. , The roll speed from the first stand to the stand one before the stand and the rolled position of the stand based on the value, or the roll speed from the stand to the final stand and the rolled position of the stand, It is designed to be changed at the same time by the feedforward method.

[0010]

FIG. 1 shows a control system diagram of a plate thickness control device 10 used in an embodiment when the plate thickness control method according to the present invention is applied to a final stand.

The material 1 to be rolled has a variation in plate thickness due to a rapid hardness variation at the front and rear ends of the hot-rolled coil during rolling by the first to n-th (one stand before the final stand) stands. Occurs. This thickness variation is measured by the thickness gauge 20, and the low-pass filter 21 is provided with the measurement value Δh of the (n-1) th stand outlet side thickness variation.
Output _n-1 .

FIG. 3 shows the input Δh _n-1 of the low-pass filter 21.
And the output Δh ' _n-1 is shown in the diagram. The measured value Δh _n−1 of the outlet side plate thickness variation of the _n− 1th stand includes not only the plate thickness variation due to the front and rear ends of the hot-rolled coil but also high frequency components due to the influence of roll eccentricity at the 1st to n−1th stands. (1Hz or more) is naturally included.

However, when the plate thickness control is performed against this high frequency component, the response of the motor cannot be particularly followed, and (a) a trouble such as current trip is apt to occur. Since the rotation speed changes abruptly, torsional vibration of the spindle is likely to occur, (c) Slip is likely to occur between the work roll and the backup roll, and problems such as progress of roll wear occur. Therefore,
In the present invention, by using the low-pass filter 21, the plate thickness fluctuation component Δh ′ _n−1 obtained by removing the high frequency component of the plate thickness fluctuation due to roll eccentricity is calculated as the speed change amount calculation device 2
It outputs to 2. Then, the speed change amount calculation device 2
In 2, the speed change amount ΔV _Rn of the n-th stand is calculated by using the equation (1) so as to keep the final (n-th) stand outlet side plate thickness h _n constant.

[0014]

[Equation 1]

The speed change amount ΔV _Rn is sent to the speed control device 23 to change the roll speed. Further, by using the low-pass filter 21, the plate thickness fluctuation component Δh ′ _{n−1 obtained} by removing the high frequency component of the plate thickness fluctuation due to roll eccentricity is
In order to keep the tension T _n-1 between the n-1st stand and the nth stand constant, which is sent to the reduction position change amount calculation device 24.
The formula (2) is used to calculate the rolling position change amount ΔS _n of the n-th stand.

[0016]

[Equation 2]

The reduction position change amount ΔS _n is sent to the reduction position control device 25, and the reduction position by the reduction device 26 is changed.

The roll speed and the rolling position are changed at the same time when the plate thickness varying portion measured by the plate thickness gauge 20 reaches the n-th stand, as in the normal feedforward system. Further, when the responsiveness of the roll speed control and the responsiveness of the rolling position control are significantly different, it is natural that a delay circuit needs to be provided in the control system with fast responsiveness in order to match the responsiveness. In some cases, it may be possible to compensate for the apparent responsiveness shift by first changing the control system having the slow responsiveness.

According to the present method, the variation of the strip thickness on the delivery side of the n-1st stand (the variation of the sheet thickness caused by the rolling of the 1st to the nth-1st stands) between the n-1st stand and the nth stand. It is possible to improve the tension at the n-th stand without disturbing the tension, and as a result, compared with the case where the plate thickness is controlled simply by changing the speed, the occurrence of slips at the n-th stand due to the disturbance of the tension, the first to the n-th. It is possible to suppress the occurrence of new plate thickness variation in the -1 stand. Incidentally, in order to improve the plate thickness fluctuation in the n-stand due to the hardness fluctuation of the material to be rolled, it is naturally conceivable to correct the speed change amount ΔV _Rn and the rolling position change amount ΔS _{n accordingly} .

Further, instead of changing the speed changing stand to the nth stand, the speeds of the 1st to n-1st stands can be changed while maintaining the current speed ratio of the 1st to nth-1st stands. It is possible to obtain the same effect.

Further, the method of the present invention can of course be carried out in combination with the conventional method shown in FIG.

Further, FIG. 1 is only an example in which the method of the present invention is applied to the final stand. Since the purpose of the method of the present invention is to correct the plate thickness variation newly generated in the intermediate stand up to the final stand, it is naturally within the scope of the present invention to apply it to other stands in the subsequent stage.

Since the roll eccentricity component changes depending on the rolling speed, the cutoff frequency of the low-pass filter is naturally set to a high value (for example, 1 Hz) at a high speed and a low value according to the rolling speed at a low speed.

[0024]

[Example] A base plate having a plate width of 800 mm and a plate thickness of 2.0 mm was rolled at a rolling speed of 15
In a 5 stand cold tandem rolling mill train at 00mpm,
Cold rolled to 0.24 mm.

As the plate thickness control system, both the plate thickness control system of the present invention method of FIG. 1 and the conventional plate thickness control system of FIG. 2 were installed.

In the conventional method, the feed-forward reduction AGC of the first stand shown in FIG. 2, the gauge meter AGC, the feedback reduction AGC, and the feed-forward tension AG
C and control using the feedback tension AGC of the fifth stand (conventional method I), and addition of the feedforward tension AGC of the fifth stand shown in FIG. 4 to conventional method I of FIG. 2 (conventional method II). ) In addition, in the conventional method I of FIG. 2, the fifth stand shown in FIG. 1 is subjected to the control for simultaneously changing the rolling position and the roll speed by applying the low-pass filter with the cutoff frequency set to 1 Hz to the measured value of the plate thickness fluctuation. In each case of addition (method of the present invention), the welded portion of the hot rolled coil was rolled. The speed change amount by the feedforward tension AGC shown in FIG. 4 is calculated in the same manner as the equation (1).

FIG. 5 shows the fourth stand outlet side plate thickness deviation amount, the fifth stand
The stand-out side plate thickness deviation amount and the tension between the fourth and fifth stands are shown. On the delivery side of the fourth stand, due to a sudden change in hardness of the front and rear ends of the hot-rolled coil, a change in plate thickness occurs again in the intermediate stand, and a change of ± 10 μm or more occurs.

In the conventional method I, since the plate thickness control at the fifth stand is performed only by the feedback tension AGC, the steady deviation on the outlet side of the fifth stand is completely corrected, but the hot rolled coil near the welding point. It is impossible to deal with a sudden change in plate thickness due to a change in hardness at the front and rear ends. Further, due to this change in hardness, the tension between the fourth and fifth stands also changes.

In the conventional method II, since the plate thickness control is performed by the feed-forward method in which only the tension is changed, the tension between the 4th and 5th stands is largely changed as compared with the conventional method I, and the 5th at the high tension side. There is a risk of slippage and breakage on the stand and squeezing on the low tension side, so it is difficult to continue actual operation even if it can be done experimentally. Further, regarding the deviation of the plate thickness on the delivery side of the fifth stand, the tension between the fourth and fifth stands greatly changes. Therefore, if control is performed so as to keep the plate thickness on the delivery side of the fifth stand constant, the plate thickness due to the tension variation in the fourth stand will occur. It has not been completely corrected because it creates a new deviation. In addition, since the roll speed cannot follow even though the thickness variation component due to roll eccentricity is controlled,
Almost no variation in plate thickness has been improved.

On the other hand, in the method of the present invention, the roll speed is controlled so as to correct the plate thickness deviation, and at the same time, the rolling position is changed so as not to cause the tension fluctuation. Therefore, the tension between the fourth and fifth stands is made substantially constant. it can. As a result, since the plate thickness deviation due to the tension change in the fourth stand does not occur, the fifth stand outlet side plate thickness deviation can be controlled to be much smaller than in the conventional methods I and II.

After rolling, the roughness of each roll was measured in order to check the state of roll wear.
However, in the method of the present invention, Ra = 0.
However, in conventional method II, the roll speed is changed due to the roll thickness eccentricity component due to roll eccentricity, so Ra
I admitted that it would decrease to = 0.2.

That is, according to the method of the present invention, it is possible to correct the plate thickness fluctuation newly generated at the intermediate stand due to the hardness fluctuation or the like without causing the tension fluctuation, and for the high frequency component, Since it is not controlled forcibly, it does not cause troubles such as torsional vibration and roll wear, and it does not cause troubles such as plate slip, plate rupture, and squeezing, and cold rolling with a small plate thickness deviation. The strip product can be stably manufactured.

[0033]

As described above, according to the present invention, the plate thickness variation in the intermediate stand caused by rolling a material having a rapid hardness variation such as the front and rear ends of the hot rolled coil is corrected, On the delivery side of the final stand, it is possible to stably manufacture a cold-rolled strip product with high plate thickness accuracy.

[Brief description of drawings]

FIG. 1 is a control system diagram showing an example of a plate thickness control device for carrying out the present invention.

FIG. 2 is a control system diagram showing an example of a plate thickness control device used conventionally.

FIG. 3 is a diagram showing input / output by a low pass filter.

FIG. 4 is a control system diagram when a feedforward tension AGC is applied to the final stand.

FIG. 5 is a diagram showing a plate thickness accuracy improving effect according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material 10 Plate thickness control device 20 Plate thickness gauge 21 Low-pass filter 22 Speed change amount calculation device 23 Speed control device 24 Reduction position change amount calculation device 25 Reduction position control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruhiro Saito 1 Kawasaki-cho, Chiba-shi, Chiba Inside the Kawasaki Steel Co., Ltd. (72) Inventor Sadayuki Miyoshi 1 Kawasaki-cho, Chiba-shi, Chiba Steel Co. In-house

Claims (1)

[Claims] 1. In a cold tandem rolling mill, a plate thickness gauge is provided on the entrance side of a stand located at the latter stage, and a low-pass filter separates and extracts the low-frequency component from the output of the plate thickness gauge. To simultaneously change the roll speed from the stand to the stand immediately preceding the stand and the roll-down position of the stand, or the roll speed from the stand to the last stand and the roll-down position of the stand by a feedforward method. A method for controlling plate thickness of a cold tandem rolling mill, which is characterized by: