JPH05123728A - 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, plate thickness gauges 20 are provided on the entrance side of the stand located at the rear stage and the entrance side of the stand immediately before the stand, and at the time of low speed, the output of the entrance side plate thickness gauge 20 of the stand. Based on a value obtained by correcting the output of the entrance-side thickness gauge 20 of the stand immediately before the stand at a high speed by the output of the entrance-side thickness gauge 20 of the stand, the first stand is moved to the front of the stand by one. The roll speed to 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 are changed at the same time by the feedforward method.

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]

DISCLOSURE OF THE INVENTION The present invention provides a cold tandem rolling mill with plate thickness gauges on the entrance side of the stand located at the rear stage and the entrance side of the stand immediately before the stand.
At low speed, based on the output of the input side thickness gauge of the stand, at high speed, based on the value of the output of the input side thickness gauge of the stand one before the stand corrected by the output of the input side thickness gauge of the stand, The roll speed from the first stand to the stand one before the stand and the rolled position of the stand, 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 to be rolled 1 has a plate thickness variation 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 (two stands before the final stand) stands. Occurs. This sheet thickness variation Δh _n-2 is measured by the sheet thickness gauge 20, and further, the sheet thickness variation Δ after rolling on the n-1th stand Δ.
h _n-1 is measured with a plate thickness gauge 30. Based on these plate thickness fluctuation measured values Δh _n-2 and Δh _n-1 , the corrected plate thickness fluctuation amount calculating device 21 uses the formulas (1) and (2) to correct the corrected plate thickness fluctuation amount Δh _n ' _- Calculate ₁

[0012]

[Equation 1]

At low speed, the actual thickness variation Δh _n-1 on the final stand entrance side is measured by the thickness gauge 30 and then this measured value is reached within the time when the measuring section reaches the final stand. Therefore, the rolling speed is so slow that each control amount is calculated and the control is actually performed. In this case, the corrected plate thickness fluctuation amount Δh _n ' _-1 is of course the measured value, as shown in equation (1). Δh _n-1 can be used as it is. However, at high speeds, the arrival time from the thickness gauge 30 to the final stand becomes very short, and the measured value Δh _n-1 cannot be used in time, so it cannot be used. Therefore, the n-1th stand (one stand before the last stand)
The corrected plate thickness fluctuation amount Δh _n ' _-1 is calculated using the equation (2) from the measured value Δh _n-2 of the plate thickness fluctuation amount on the inlet side. The expression (2) means that the measured value of the thickness variation of the (n-1) th stand-in side is Δh.
_n-2 is multiplied by the plate thickness ratio h _n-1 / h _n-2 to estimate the plate thickness fluctuation amount on the final stand side, and this value is corrected to the plate thickness fluctuation correction coefficient α.
It is a product of The plate thickness variation correction coefficient α is represented by a ratio of the estimated plate thickness variation and the actually measured plate thickness variation, and a value calculated previously or a learning value (estimated from past data) is used.

The corrected plate thickness variation amount Δh _n ' _-1 calculated by the above equations (1) and (2) is output to the speed change amount calculation device 22. The speed calculation device 22 calculates the speed change amount ΔV _Rn of the n-th stand in order to keep the final (n-th) stand outlet side plate thickness h _n constant using the equation (3).

[0015]

[Equation 2]

The speed change amount ΔV _Rn is sent to the speed controller 23 to change the roll speed. Further, the corrected plate thickness variation amount Δh _n ' _-1 is sent to the reduction position change amount calculation device 24 to keep the tension T _n-1 between the ( _n-1) th stand and the nth stand constant ( 4) The formula is used to calculate the rolling position change amount ΔS _n of the n-th stand.

[0017]

[Equation 3]

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 or the plate thickness gauge 30 reaches the n-th stand, as in the normal feedforward system. Be done. Further, when the responsiveness of the roll speed control and the responsiveness of the rolling position control are significantly different, it is natural that it is necessary to provide a delay circuit in the control system having a 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 this method, the variation of the plate thickness on the delivery side of the (n-1) th stand (the plate thickness variation caused by the rolling of the 1st to (n-1) th 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 the slip at the n-th stand due to the disturbance of the tension, the 1st 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 variation in the n-stand due to the hardness variation 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 the speed changing stand being the nth stand, the speeds of the 1st to n-1st stands are set to the current 1st stand.
The exact same effect can be obtained by changing the speed ratio of the (n-1) th stand.

Furthermore, 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.

[0024]

[Example] A mother plate having a plate width of 800 mm and a plate thickness of 2.0 mm was cold-rolled to 0.24 mm in a 5-stand cold tandem rolling mill train.

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 the feedback tension AGC of the 5th stand (conventional method I), the feedforward tension A of the 5th stand shown in FIG. 3 in the conventional method I of FIG.
When GC is added (conventional method II), and also in conventional method I of FIG.
In the case where the control for simultaneously changing the rolling position and the roll speed of the fifth stand using the plate thickness gauges of the fourth and fifth stands shown in FIG. Parts were rolled. In addition, the speed change amount by the feedforward tension AGC shown in FIG.
It is calculated in the same way as equation (3).

FIG. 4 shows the fourth stand outlet side plate thickness deviation amount, the fifth stand outlet side plate thickness deviation amount at the low speed (500 mpm), and the fourth to fifth parts.
Indicates the tension between stands. 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 only by changing the tension, the tension between the fourth and fifth stands fluctuates significantly as compared with the conventional method I, and on the high tension side, There is a risk of slippage and breakage on the 5 stand, and a risk of squeezing on the low tension side, so it is difficult to continue the actual operation even if it can be experimentally performed. 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.

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 fluctuation in the fourth stand does not occur, the fifth stand exit side plate thickness deviation can be controlled to be much smaller than in the conventional methods I and II.

FIG. 5 shows the deviation amount of the fourth stand outlet side plate thickness at the time of high speed (2000 mpm), the fifth stand outlet side plate thickness deviation amount, the fourth to
The tension between 5 stands is shown. The fourth stand exit side plate thickness deviation amount has the same plate thickness fluctuation as at the low speed, but since it is high speed, the plate thickness fluctuation due to roll eccentricity and the plate thickness due to hardness fluctuation of the hot rolled plate front / rear end part The fluctuations are very short periods.

Although the conventional method I behaves similarly to the low speed, in the conventional method II, the hardness variation part is already used before the control is performed by the feedforward tension AGC using the output of the plate thickness gauge on the entrance side of the final stand. Since the sheet thickness deviation at the welding point remains as it is, the sheet thickness deviation at the welding point remains as it is, and the sheet thickness variation is separately generated by the output of the feedforward tension AGC. The tension between the 4th and 5th stands is also affected by the feedforward tension AGC, which causes a separate tension variation.

On the other hand, in the method of the present invention, at the time of high speed, the fifth stand entrance side plate thickness is estimated and used for control from the output of the entrance side plate thickness gauge of the fourth stand according to the equation (2). There is sufficient time from the measurement of the plate thickness until the measurement unit reaches the final stand, and since control can be performed without delay, even at high speeds, similarly to low speeds, there is no fluctuation in tension between the 4th and 5th stands, It is possible to control the thickness deviation on the delivery side of the fifth stand to be extremely small.

That is, according to the method of the present invention, it is possible to correct a sheet thickness variation newly generated at the intermediate stand due to a hardness variation or the like regardless of the rolling speed and without causing tension variation at any speed. Yes, as a result, cold-rolled strip products with less thickness deviation can be used for slipping, breaking,
It is possible to stably manufacture without trouble such as squeezing.

[0035]

As described above, according to the method of the present invention, it is possible to correct the plate thickness variation in the intermediate stand caused by rolling the material having the rapid hardness variation such as the front and rear ends of the hot rolled coil. On the outlet 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 control system diagram when a feedforward tension AGC is applied to a final stand.

FIG. 4 is a diagram showing a plate thickness accuracy improving effect according to the present invention at a low speed.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material 10 Plate thickness control device 20 Plate thickness gauge 21 Corrected plate thickness variation calculation device 22 Speed change amount calculation device 23 Speed control device 24 Reduction position change amount calculation device 25 Reduction position control device 30 Plate thickness gauge

 ─────────────────────────────────────────────────── ─── 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, plate thickness gauges are provided on the entrance side of the stand located at the rear stage and the entrance side of the stand immediately before the stand, and the output of the entrance side plate thickness gauge of the stand at low speed is provided. Based on the value obtained by correcting the output of the entrance side thickness gauge of the stand immediately before the stand at the high speed by the output of the entrance side thickness gauge of the stand, the first stand to the stand immediately before the stand. Up to the roll speed 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, the cold tandem rolling mill characterized by simultaneously changing by a feedforward method. Plate thickness control method.