JP2000033409A - Method for controlling plate thickness in reversible rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a plate thickness deviation due to variation in deformation resistance as small as possible. SOLUTION: In a plate rolling in which rolling of not less than two passes is applied to a material 1 to be rolled which is pulled out of a coil, after measuring a plate thickness deviation to target plate thickness on the outlet side of the (n-1)th (n>=2) pass, the Fourier transformation of the signals of the obtained plate thickness deviation on the outlet side is executed and a frequency distribution is determined. Based on the diameter of the coil and the moving speed of the material to be rolled, the frequency due to variation in deformation resistance in the longitudinal direction which periodically appears, is determined. Using this frequency, the frequency determined before and preset threshold value, whether the periodic change in the deformation resistance has influence upon the thickness deviation on the outlet side or not, is judged. In the case that it is judged that the deviation is affected, a feed-forward AGC control gain at the n-th pass is corrected. Consequently, the thickness deviation caused by irregularity in the deformation resistance is drastically reduce. Further, the data to be stored can be reduced. Moreover, the higher accuracy of tracking is unnecessitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a thickness of a material to be rolled, particularly when a material to be rolled is rolled using a reverse rolling mill.

[0002]

2. Description of the Related Art As a method for controlling the thickness of a rolling mill,
Generally, the thickness deviation at the entrance to the rolling mill is measured (or estimated),
By changing the manipulated variable when this measurement point (or estimated point) passes through the rolling mill, feed-forward control that prevents the influence of the incoming side sheet thickness deviation from appearing on the outgoing side sheet thickness deviation, There is feedback control for measuring (or estimating) the sheet thickness deviation on the side and changing the manipulated variable so that the outlet sheet thickness matches the target value.

[0003] Here, as the manipulated variable, the rolling position of the rolling mill, the tension of the material to be rolled, or the roll speed of the rolling roll for changing this tension is used depending on the size of the material to be rolled and the rolling equipment. Have been. In particular, in the above-described feedforward control, the roll-down position adjustment amount or the tension adjustment amount is calculated using a preset gain so that the deviation between the delivery side plate thickness of the rolling mill and the target plate thickness becomes zero. It is necessary to set this gain with high accuracy.

[0004] In the cold rolling, thickness deviation occurs due to uneven deformation resistance in the longitudinal direction of the base material. Non-uniform deformation resistance in the longitudinal direction of the base material, when cooling the base metal coil placed on the coil stand rolled and wound by hot rolling, which is the upper process of cold rolling, by heat radiation, the coil stand This is caused by the difference between the cooling rate of the part that is in contact and the cooling rate of the part that is not in contact with the coil holder.

[0005] Also, in the case where the base material coil is annealed before the cold rolling step, deformation resistance non-uniformity also occurs because the coil outer peripheral portion is not uniformly annealed. Such deformation resistance unevenness causes a thickness deviation in cold rolling, so when cold rolling a high carbon steel sheet and a high silicon steel sheet in which the deformation resistance unevenness is conspicuous, it is caused by the deformation resistance unevenness. It is required to reduce the thickness deviation.

In response to this demand, a method is used in which the deformation resistance is determined from the thickness and rolling load at the entrance and exit of the rolling mill, and this value is used in the control of the next step or the next pass using this value (Japanese Patent Application Laid-Open No. 55-878)
No. 6616), a method of estimating or actually measuring the deformation resistance of a material being rolled from rolling data, and correcting the deviation from the previously considered deformation resistance by tension (Japanese Patent Laid-Open No. 57-19321).
No. 6, JP-A-58-3714), and using the estimated value of the deformation resistance based on the measured value at the i-1 stand in the tandem rolling mill, the rolling position of the i stand or the tension of the i-1 stand. (Japanese Patent Laid-Open No. 58-1)
No. 10113, JP-A-60-99421) and the like.

[0007]

However, in the method disclosed in Japanese Patent Application Laid-Open No. 55-86616, it is necessary to store the deformation resistance data of the entire length of the plate and to accurately track the longitudinal position. Therefore, the deformation resistance data becomes enormous and the system becomes complicated. Also,
On the contrary, there is a possibility that the deviation of the plate thickness becomes worse due to the tracking deviation, so that there is a problem that high accuracy is required for the tracking.

In the methods disclosed in JP-A-57-193216 and JP-A-58-3714, the displacement amount of the deformation resistance in the current rolling pass is determined by a tension based on an actually measured value. Since the correction is performed by the control, there is a problem that a time delay actually occurs similarly to the feedback control.

Further, the methods disclosed in JP-A-58-110113 and JP-A-60-99421 are limited to tandem rolling mills. When applied to a rolling mill, the same problem as the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 55-86616 occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides a method of controlling a sheet thickness in a reverse rolling mill capable of reducing a sheet thickness deviation caused by a change in deformation resistance as much as possible. To provide.

[0011]

In order to achieve the above-mentioned object, a method for controlling a thickness of a reverse rolling mill according to the present invention comprises the steps of:
The frequency due to the variation of the deformation resistance in the longitudinal direction of the material to be rolled, and whether or not the periodic change in the deformation resistance is affecting the exit side sheet thickness deviation using a preset threshold value is determined. If it is determined that there is, the feedforward AGC control gain of the next pass is corrected. By doing so, the thickness deviation due to the deformation resistance variation can be effectively reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A method for controlling a thickness of a reverse rolling mill according to the present invention is characterized in that, in plate rolling in which a material to be rolled out of a coil is rolled in two or more passes, n-1 (n ≧
2) After measuring the thickness deviation with respect to the exit target thickness at the pass, the obtained signal of the exit thickness deviation is Fourier-transformed to obtain a frequency distribution, and the diameter of the coil and the moving speed of the material to be rolled. The frequency due to the fluctuation of the deformation resistance in the longitudinal direction of the material to be rolled which appears periodically is obtained based on the above, and the periodic change of the deformation resistance is obtained using this frequency, the calculated frequency, and a preset threshold value. It is determined whether or not the side plate thickness deviation is affected. If it is determined that the side plate thickness deviation is affected, the feedforward AGC control gain of the nth pass is corrected.

Hereinafter, the principle of the thickness control method of the present invention will be described by taking as an example the case where the rolling position is adjusted. ΔH, the thickness difference between the thickness of the material to be rolled on the entry side of the rolling mill and a preset target thickness on the entry side, ΔH, the thickness of the material to be rolled on the exit side of the rolling mill, and the preset exit side Assuming that the deviation of the exit side plate thickness, which is the difference from the target thickness, is Δh, the rolling load variation ΔP when the deformation resistance unevenness Δkm is generated can be expressed by the following formula 1. It should be noted that the entry-side plate thickness deviation ΔH is simply used for characteristic analysis and is not always necessary for actual control.

[0014]

ΔP = (∂P / ∂H)） H + (） P / ∂h)）
h + (∂P / ∂km) Δkm where ∂P / ∂H: Influence coefficient of rolling load variation on entry side thickness ∂P / ∂h: Influence coefficient of rolling load variation on exit side thickness ∂P / ∂km : Influence coefficient of rolling load fluctuation on deformation resistance unevenness

In order to prevent the influence of the rolling load fluctuation ΔP from appearing in the exit side sheet thickness deviation Δh, the above equation 1 is substituted into the following equation 2 which is a gauge meter type, and the exit side sheet thickness deviation Δh The rolling position operation amount ΔS is determined by the following equation 3 so as to be zero, and the rolling position of the rolling mill may be operated so as to become the obtained rolling position operation amount ΔS.

[0016]

Δh = ΔS + (1 / M) ΔP where M: Mill stiffness coefficient

[0017]

ΔS = − (1 / M) ｛(∂P / ∂H) ΔH +
(∂P / ∂km) Δkm｝

Incidentally, when the entrance side thickness deviation ΔH is mainly caused by the deformation resistance irregularity Δkm, since the deformation resistance irregularity Δkm and the entrance side thickness deviation ΔH have the same phase, the relationship between the two is expressed by the following equation. 4 can be represented.

[0019]

Δkm = α · ΔH where α: proportional coefficient

From the above equation (4), the above equation (3) is replaced by the following equation (5).
By adjusting the value of α in Equation 5, it is possible to reduce the influence of the uneven deformation resistance Δkm on the outlet thickness deviation Δh.

[0021]

ΔS = −G · ΔH where G = (1 / M) ｛(∂P / ∂H) + α · (∂P /
∂km)｝

Based on this concept, a case is considered in which the (i + 1) th pass rolling is performed on the material to be subjected to the ith pass rolling with the gain Gi as in a reverse rolling mill. i
Non-uniform deformation resistance Δkm in the longitudinal direction of the coil during rolling in the pass
Is calculated by, for example, the following Expression 6.

[0023]

Δkm = [｛M- (∂Pi / ∂hi)｝ Δhi
+ ｛M · Gi − (∂Pi / ∂Hi)｝ ΔHi] / (∂P
i / ∂kmi) where ∂Pi / ∂hi is the coefficient of influence of the rolling load variation on the outgoing thickness at the i-th pass. ∂Pi / Hi is the coefficient of influence of the rolling load variation on the incoming thickness at the i-th pass. Pi / ∂kmi: Coefficient of influence of rolling load fluctuation on deformation resistance unevenness at the i-th pass

Also, the (i + 1) th pass-side sheet thickness deviation Δ in the pass
Since Hi + 1 is equal to the exit thickness deviation Δhi of the i-th pass,
From equation (4) above, the proportionality constant αi + of the (i + 1) th pass
1 can be expressed by the following equation 7, and from this equation 7, the gain of the (i + 1) th pass is obtained as in the following equation 8.

[0025]

Αi + 1 = [｛M− (∂Pi / ∂hi)｝ Δhi + ｛M · Gi− (∂P / ∂Hi)｝ ΔHi] / ｛(∂Pi / ∂kmi) ・ Δhi｝

[0026]

## EQU8 ## Gi + 1 = (1 / M). ｛∂Pi + 1 / ∂Hi + 1 +
αi + 1 · ({Pi + 1 / ∂kmi + 1)}

By setting the gain Gi + 1 in advance in the rolling of the (i + 1) th pass, it is possible to reduce the thickness deviation caused by uneven deformation resistance from the head of the material to be rolled.

The main cause of the deformation resistance unevenness in the longitudinal direction is as follows.
These include uneven cooling after hot rolling and uneven annealing when the base material coil is annealed before cold rolling.Deformation resistance unevenness due to these causes often occurs in one turn of the coil. In many cases, the degree of the deformation resistance unevenness differs between the outer diameter side and the inner diameter side.

Therefore, the same degree of deformation resistance nonuniformity does not occur over the entire length of the coil, but the degree of the change varies in the longitudinal direction of the coil. This deformation resistance unevenness is stored sequentially over the entire length in the coil longitudinal direction, and tracking of the coil longitudinal position must be performed with extremely high accuracy in order to reduce the thickness deviation due to the deformation resistance unevenness in the next pass. There is. It is also necessary to determine whether the exit side sheet thickness deviation after rolling is due to deformation resistance variation or thickness variation due to other disturbances.

Therefore, in the present invention, the frequency analysis of the sheet thickness deviation is performed based on the measured value of the delivery side thickness and the rolling speed, and
From the coil outer diameter and the rolling speed, a frequency due to the change in the deformation resistance of the material to be rolled which periodically appears is determined, and it is determined whether or not the frequency distribution of the sheet thickness deviation obtained by the calculation is due to the deformation resistance unevenness.

At this time, in order to perform frequency analysis, rolling data for a certain period of time is required. However, frequency calculation is performed in a form in which the longitudinal direction of the coil is divided into m (m ≧ 2) in time units, and the spectrum is calculated. If the strength exceeds a preset threshold value, it is determined that the deformation resistance unevenness is affecting the exit side plate thickness, and the thickness change caused by the deformation resistance unevenness is corrected based on Equation 7 above. Is calculated, and the rolling down position is adjusted using the correction gain obtained by equation (8).

Even if this correction gain is almost constant in the section where the above-mentioned frequency calculation is performed, it is possible to sufficiently correct the thickness fluctuation caused by the uneven deformation resistance. Also, less data needs to be stored. Furthermore, regarding the tracking, since the frequency of the entrance thickness is the same as the deformation resistance unevenness, in the conventional feedforward control, only the above-mentioned corrected gain need be used, so that a high tracking accuracy is required. Not even.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for controlling the thickness of a reverse rolling mill according to the present invention will be described with reference to an embodiment shown in FIG. FIG. 1 is a block diagram of a reverse rolling mill that implements the sheet thickness control method of the present invention.

In FIG. 1, reference numeral 1 denotes a rolled material, which is a rolled material 1 pulled out from a payoff reel 2 in the direction of the arrow.
Are the upper and lower work rolls 4 via the deflector rolls 3.
It is guided between the rolls and rolled by these upper and lower work rolls 4. The rolled material 1 passes through a deflector roll 5 and is wound on a tension reel 6. The above is the case of the odd-numbered path, and the flow is the reverse of the case of the even-numbered path.

Between the deflector roll 3 and the work roll 4, and between the work roll 4 and the deflector roll 5, there are thickness gauges 7 for measuring the incoming side thickness and the outgoing side thickness of the material 1 to be rolled, respectively.
8 are arranged. And these thickness gauges 7 and 8
Deviations ΔH and Δh between the measured values described above and predetermined entrance-side target thickness or exit-side target thickness are calculated, and these calculated values are output to the frequency analyzer 9. Frequency analyzer 9
Performs a frequency analysis of the inboard thickness deviation ΔH and the outboard thickness deviation Δh sent from the thickness gauges 7 and 8.

In the vicinity of the thickness gauges 7 and 8, there are touch rolls 10 and 11 for measuring the entrance speed and the exit speed of the material 1 to be rolled.
Are arranged, and the entrance speed and the exit speed measured by the touch rolls 10 and 11 are also sent to the frequency analyzer 9 described above. The frequency analyzer 9 Fourier-transforms the inlet-side sheet thickness deviation ΔH and the outlet-side sheet thickness deviation Δh to obtain a frequency distribution for each frequency, and provides the analysis result to the gain calculator 12.

The payoff reel 2 is provided with a diameter measuring instrument (not shown) for measuring the diameter of the coil, and the measured coil diameter is given to the gain calculator 12 via the frequency analyzer 9. . The gain calculator 12 calculates the frequency of the irregular deformation resistance on the input side and the frequency of the irregular deformation resistance on the basis of the coil diameter.
Using the analysis result given from the frequency analyzer 9,
It is determined whether the influence of the deformation resistance unevenness is large. In this determination, the threshold value set in advance is compared with the spectrum intensity of the thickness deviation of the above-mentioned frequency analysis result, and if the intensity exceeds the threshold value, it is determined that the influence is large.

When the gain calculator 12 determines that the influence of the deformation resistance unevenness is large, the gain of the next pass is calculated in advance by using the above-described equations 6, 7, and 8. This gain is sent to the rolling position operation amount calculator 13, which calculates the rolling position operation amount by using the gain necessary to reduce the influence of the deformation resistance unevenness, and calculates this amount. Given to the rolling position controller 14,
The position of the screw-down device 15 is adjusted. In addition, the signal from the tracking device 16 which receives the signal from the touch roll 10 and the thickness gauge 7 and tracks the longitudinal position of the material 1 to be rolled is also input to the rolling position operation amount calculator 13, and the rolling position operation is performed. It is used as a reference when determining the amount.

By the way, when the sampling period of each measured value is set to 20 msec, the sampling time required for the negative analysis is the time required for performing the frequency analysis as described above, which is 20.48 sec ( 1024 points of sampling data). Therefore, the total length in the coil longitudinal direction is divided into m (m ≧ 2) by the time required for each pass and the time (20.48 sec) required for the frequency analysis.

Next, an example of the case where rolling is actually performed by using the sheet thickness control method of the present invention will be described. FIG. 2 shows that the thickness is 2.0
mm, a high-carbon steel sheet that has undergone an annealing step before rolling is rolled through a plurality of passes (i-1 pass) of a base material having a width of 950 mm by a reverse rolling mill, and then a delivery plate when the i-th rolling is performed. This is the thickness deviation, and the sections (a), (b), and (c) in FIG. 2 indicate the sections in which the frequency calculation for 20.48 sec was performed as described above.

In this example, the thickness deviation differs in each section, and the result of the frequency calculation in each section is shown in FIG. In the sections (a) and (b) of FIG.
As shown in (b), the frequency distribution of the exit side plate thickness deviation of 0.42 Hz and 0.45 Hz is obtained. this is,
It is a frequency corresponding to the coil-winding calculated from the coil outer diameter and the rolling speed, and it is estimated that a sheet thickness deviation due to a change in deformation resistance appears (from 0.42 Hz to 0.4
The change to 5 Hz is due to the change in the coil outer diameter).

In the section (c) of FIG. 2, FIG.
As shown in FIG.
A frequency hardly appears at the portion of 47 Hz, and it is considered that there is no variation in deformation resistance in this section. In this case, the frequency intensity was set to 1 μm as the threshold value.
In sections (a) and (b), it is determined that a sheet thickness deviation due to deformation resistance unevenness has occurred, and using the above equations 7 and 8, the amount of gain correction in each section of FIG. Was calculated, and the (i + 1) th pass was rolled using the corrected gain obtained as a result of this calculation.

FIG. 4 shows the result of the deviation of the exit side plate thickness in the (i + 1) th pass at that time. When the sheet thickness control method of the present invention is applied, the sheet thickness deviation generated at the i-th pass as shown in FIG.
At the pass, the rolling has been significantly reduced by using the correction gain, and it is apparent that the thickness deviation due to uneven deformation resistance has been corrected. On the other hand, FIG. 5 shows a result when the conventional feedforward control is performed. In this case, the thickness deviation occurring at the i-th pass is not reduced at the (i + 1) -th pass.

The threshold value is set to 1 μm this time, but there are appropriate values depending on the material of the material to be rolled, the target thickness of the delivery side, and the like, and are set accordingly. In addition, in order to distinguish from a disturbance other than the deformation resistance unevenness, for example, the output side sheet thickness deviation caused by eccentricity of a roll of a rolling mill such as a backup roll or a work roll, a frequency estimated to occur periodically other than the deformation resistance unevenness is used. Can be calculated in advance and compared with this to easily classify.

In this embodiment, the case where the rolling position is adjusted has been described. However, in order to adjust the tension of the material to be rolled or to adjust the tension of the material to be rolled, the roll speed of the rolling roll is adjusted. You may do it.

[0046]

As described above, according to the method for controlling the thickness of the reverse rolling mill according to the present invention, the thickness deviation caused by uneven deformation resistance can be greatly reduced.
Also, less data needs to be stored. Further, regarding the tracking, since the frequency of the entrance thickness is the same as the deformation resistance unevenness, in the conventional feedforward control, it is sufficient to use only the corrected gain, and there is no need for a high tracking accuracy. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a reverse rolling mill for implementing a thickness control method of the present invention.

FIG. 2 is a drawing-side sheet thickness deviation when a high-carbon steel sheet that has undergone an annealing step before rolling is rolled in a plurality of passes (i-1 pass) by a reverse rolling mill and then subjected to an i-th pass rolling; ) ~
(C) shows a section.

3 (a) to 3 (c) show the results of frequency calculation in each section of FIG.

FIG. 4 is a diagram showing a result of calculating a correction gain in each section from a result of a frequency calculation, and performing a (i + 1) th pass rolling using the correction gain obtained as a result of the calculation.

FIG. 5 is a diagram showing the same result as FIG. 4 when conventional feedforward control is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material 7 Thickness gauge 8 Thickness gauge 9 Frequency analyzer 12 Gain calculator 13 Reduction position operation amount calculator

Claims (1)

[Claims] In a sheet rolling in which a material to be rolled out of a coil is subjected to rolling in two or more passes, a sheet thickness deviation with respect to an output target sheet thickness of an n-1 (n ≧ 2) pass is measured. The Fourier transform is performed on the output side plate thickness deviation signal to obtain a frequency distribution, and based on the diameter of the coil and the moving speed of the rolled material, the frequency due to the fluctuation of the deformation resistance in the longitudinal direction of the rolled material that periodically appears. Using this frequency and the calculated frequency, and a preset threshold value,
It is determined whether or not the periodic change in the deformation resistance is affecting the exit side sheet thickness deviation. If it is determined that the influence is affecting, the feedforward AGC control gain of the nth pass is corrected. A method for controlling the thickness of a reverse rolling mill.