JPH07185630A - Control method for hot rolling machine - Google Patents

Abstract

PURPOSE:To obtain a control method for a hot rolling machine capable of changing draft setting only by target thickness and stably changing thickness by performing control by using different kinds of draft control parameters. CONSTITUTION:A controller is constituted of a thickness storage part 10, a change point tracking device 12, a thickness setting change device/gain compensator 14, a smoothing device 16, an abnormality detector 18, and an AGC device by BISRA system. The thickness storage device 10 stores the input/output side thickness target value of materials A, B found by draft schedule calculation, and calculates difference DELTAH, DELTAh. The change point tracking device 12 issues a setting switching timing when a flying thickness change point arrives at each stand. A draft setting correcting operation is started by such timing command. The thickness setting change device 14a starts the adding operation of thickness correction quantity by the input of the setting switching timing. In this way, it is possible to easily control a draft position when the thickness is changed with high accuracy by using the thickness target value calculation result of each stand.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a hot rolling mill control method,
Particularly, it relates to the control of the rolling position when changing the running plate thickness.

[0002]

2. Description of the Related Art In cold rolling, the strip thickness is changed, and its control has been established to some extent. However, if the control method of the cold rolling is directly applied to the hot rolling in which the change range of the plasticity coefficient (or deformation resistance) of the material is large, there is a problem that the control environment is different and stable control cannot be performed. By the way, if attention is paid to only the leading portion and the trailing portion, there is a BISRA type (or gauge meter type) automatic plate thickness control (AGC) as a control system for keeping the plate thickness constant. This control method controls the stand-out plate thickness to be constant against changes in the plastic coefficient (or deformation resistance) due to changes in the temperature of the rolled material, and unevenness of the entrance plate thickness due to plate thickness control errors. It is an object. By correcting roll deformation, oil film change, etc., the load on the rolling stand can be
The output plate thickness can be controlled to a constant value with the accuracy determined by the elongation characteristics.

[0003]

When changing the running plate thickness in hot rolling, there are the following two methods of using AGC.
There are two control methods. 1) The AGC is temporarily interrupted at the end of the preceding portion (material A), the rolling reduction of the succeeding portion (material B) is performed again, and the operation of the AGC is started again (Japanese Patent Laid-Open No. 56-114509, Japanese Patent Publication No. Japanese Unexamined Patent Publication No. 56-14510 and Japanese Unexamined Patent Publication No. 56-1
14511, JP-A-56-114512, etc.). Since there is an error in the estimated load, this control method has a problem in that the thickness cannot be changed in a short time because it needs to be corrected according to the actual value. In addition, this control method has a problem in that it is necessary to perform setting calculation of multivariables, and the size of the calculation device becomes large.

2) Normally, a constant target value of AGC is sequentially changed at the time of changing the plate thickness to perform the plate thickness changing operation (see Japanese Patent Laid-Open No. 60-177908 and Japanese Patent Publication No. 3-11847). With this control method, the AGC with a constant plate thickness target
No distinction is made between the operation and the operation at the time of changing the plate thickness in which the target plate thickness is changed and the entrance side plate thickness is significantly changed. For this reason, if this control method is used, the rolling position control in the sheet thickness changing operation becomes an excessive response or an excessive response, resulting in uneven rolling speed (main machine rotation speed) and looper movement, resulting in abnormal sheet thickness changing operation. Is likely to occur. In general, the AGC monitors the amount of reduction movement, the rate of reduction change, the position of reduction, etc. to protect the equipment during AGC operation with a constant plate thickness, but these settings are appropriately changed in this control method. However, there is a problem that the equipment cannot be protected at the time of the change.

The present invention has been made in order to solve such a problem, and is simple, accurate, and stable with a plate thickness target value (draft schedule) calculation result of each stand. An object of the present invention is to provide a hot rolling mill control method capable of realizing the change.

[0006]

A method for controlling a hot rolling mill according to one aspect of the present invention is a method for controlling a hot rolling mill which controls a rolling position of a mill by performing automatic plate thickness control,
The control is performed using different rolling reduction control parameters in the case of performing the plate thickness control with a constant target value and in the case of performing the plate thickness change control for changing the target plate thickness of the leading portion and the trailing portion during the running. A method for controlling a hot rolling mill according to another aspect of the present invention,
In the above control method for the hot rolling mill, when the plate thickness change control is performed, the reduction setting change amount that compensates the tuning rate of the automatic plate thickness control is given. A method for controlling a hot rolling mill according to another aspect of the present invention is the method for controlling a hot rolling mill, wherein the plastic coefficient of the material is converted on the assumption that the inlet side plate thickness is constant during the plate thickness change control. The reduction setting change amount is given using the apparent plasticity coefficient. A method for controlling a hot rolling mill according to another aspect of the present invention is a method for controlling a hot rolling mill described above, wherein a set value for abnormality detection is changed according to a rolling reduction condition during plate thickness change control for equipment protection. To do.

[0007]

As described above, the effect of the automatic plate thickness control (AGC) is primarily determined by the accuracy of the gauge meter system. However, in hot rolling, it is necessary to take into consideration the characteristics of the rolling reduction control device that accompanies changes in the plasticity coefficient. For that purpose, the optimum value may be switched and used when the plate thickness is changed and when the plate thickness is constant. When the entrance side plate thickness changes, the means for correcting the plasticity coefficient of the material further affects. By incorporating into AGC the difference in the plasticity coefficient between the preceding material (A material) and the following material (B material), the change in the apparent plasticity coefficient of the transition portion (C material) when the plate thickness is changed, and the difference in its correction means. , The reduction control operation during the plate thickness change and before and after the change is optimized.

[0008]

EXAMPLES The theoretical basis of the control method of the present invention will be first described before describing specific examples of the examples of the present invention. 1) AGC operation in A (leading) material and B (trailing) material FIG. 2 is a characteristic diagram of rolling, in which the elongation curve of the rolling mill and the plasticity curve of the material are shown. If the mill constant of the rolling stand is K between the delivery side plate thickness (h), the roll gap (S), and the rolling load (P),

## EQU1 ## There is a relationship of h = S + P / K (1). In the BISRA type AGC, lock-on values S ₀ , P ₀ ,
by setting h _0, deviations from these _{Δh = h-h 0, ΔS} = S-S 0, the thickness deviation Delta] h to be estimated by [Delta] P = P-P ₀ is controlled to be zero.

## EQU00002 ## .DELTA.h = .DELTA.S + .DELTA.P / K (2) Now, if the roll gap is controlled to correct the plate thickness by .DELTA.h ', the rolling load changes .DELTA.P' and the plate thickness changes accordingly. In order to change the plate thickness by Δh ', the roll gap can be calculated from the relation of the equation (2).

## EQU00003 ## .DELTA.S '=. DELTA.h'-. DELTA.P '/ K (3) must be changed. This change in load can be expressed as in equation (4) according to the plasticity coefficient of the material.

[0009]

[Equation 4] From now on, the roll gap change is

[0010]

[Equation 5]

It is obtained that only one has to be given. Further, as understood from the equation (2), the deviation Δh of the plate thickness from the lock-on value at the time of measurement can be estimated from the equation (2) by the deviation of the roll gap value and the rolling load from the lock-on value. That is,

Equation 6 Δh = ΔS + ΔP / K (6) Therefore, to control this deviation, the plate thickness
The roll gap change for changing Δh is expressed by the formula (5).
Than,

[0012]

[Equation 7]

Given only that, the deviation from the lock-on value of the new roll gap needs to be given by the following equation.

[0014]

[Equation 8]

Since M changes depending on the temperature of the material, processing history, composition, etc., it is difficult to accurately predict this.
If the predicted M exceeds the actual M, overcompensation occurs and an unstable state such as hunting occurs. If M that is too small is used, a sufficient AGC effect cannot be obtained. Therefore, in general, the AGC device does not control the plate thickness to the 100% target value by providing the tuning rate α of the following equation (9), but rather lowers the gain a little for stabilization. .

[0016]

[Equation 9]

M ₀ = predicted value of plasticity coefficient of material α = 0.7 to 0.9 When only AGC of A material and B material is considered, M predicted optimally for A material and B material, respectively. ₀ and constant α
It may be controlled by using.

2) Draft schedule calculation There are various methods for setting the rolling position after changing the plate thickness of each stand. For example, there is the following method. Of the actual rolling conditions of the preceding plate part just before the change in plate thickness bites into the rolling mill, the rolling speed and plate thickness at the entrance / exit side of each stand are measured or estimated, and the difference in the mass flow at the entrance / exit side of each stand is measured. And calculate
Next, based on the target finish plate thickness of the trailing plate part, the setting calculation of the rolling condition of the trailing plate part is performed under the condition that the change in the mass flow difference between each stand between the leading plate part and the trailing plate part is minimized. do. According to this setting method, it is possible to calculate the target value of the inlet and outlet side plate thickness of each stand after the plate thickness change based on the value before the plate thickness change, so the reduction position can be calculated from the difference between the plate thickness before and after the plate thickness change. If the setting is changed, it is possible to easily change the plate thickness without including an initial calculation error.

3) Rolling Reduction Setting Operation of C Material (Plate Thickness Change Part) and Apparent Plasticity Coefficient FIG. 3 is an explanatory diagram for setting the rolling reduction of C material. When changing the outlet plate thickness from hA to hB, if the inlet plate thickness is constant, SA
→ The rolling position of SB 'is corrected, but the inlet side plate thickness is HA → H
When changing to B, a correction operation of SA → SB is required. This can be considered as the plasticity coefficient of the material becomes M → M ′ when converted when the entrance side plate thickness is constant. The apparent plasticity coefficient M ′ of the material before and after changing the plate thickness is given by the following expression (10).

[0020]

[Equation 10]

Δh ^* : Output side target thickness change amount ΔH ^* : Input side target thickness change amount The values of M and K vary depending on the characteristics of each stand and the material temperature. In the case of the example of FIG. 3, M ′ is a value that is about 1/2 smaller than the plasticity coefficient M when the plate thickness is controlled to be constant. In controlling C material, M'determined in this way
By using, the accuracy of estimating the plasticity coefficient is improved,
The amount of reduction correction can be set appropriately.

Now that the principle of the present invention has been clarified by the above description, an embodiment of the present invention will be described. FIG. 1 is a block diagram showing the configuration of a control device that carries out a method for controlling a hot rolling mill according to an embodiment of the present invention. This control device includes a plate thickness storage unit 10, a change point tracking device 12, a plate thickness setting changing device / gain compensator 14, a smoothing device 16, an anomaly detection device 18, and a BISRA AGC device 20. In the figure, h _A is the target thickness of A material, h _B is the target thickness of B material, h
₀ is AGC lock-on plate thickness, hg is gauge meter plate thickness,
S is the rolling position (gap), ΔS is the rolling position deviation, P is the rolling load, G _COMP is the compensation gain, and G _AGC is AGC.
It is a gain.

The plate thickness storage unit 10 stores the target values of the inlet and outlet plate thicknesses of the A material and the B material obtained by the draft schedule calculation, and calculates the differences ΔH ^* and Δh ^* . The change point tracking device 12 issues a setting switching timing when the running plate thickness change point reaches each stand. This timing command starts the reduction setting correction operation. The plate thickness setting changing device 14a starts the addition operation of the plate thickness correction amount by inputting the setting switching timing. The gain compensator 14b inputs Δh ^* stored in the plate thickness storage unit 10 by the operation of the plate thickness setting changing device 14a. By the way, the AGC device 20 does not control the plate thickness to the 100% target value by providing the tuning rate (scale factor) α, but rather lowers the gain slightly for stabilization, and therefore Δ
Even if h ^* is directly added to the plate thickness target value of the AGC device 20,
The correction amount is not Δh ^* . Therefore, the AGC device 20
Plate AtsuOsamu proven to become Delta] h ^*, the gain compensator 14
b is arranged on the input side of the AGC device 20, and the function of the gain compensator 14a is expressed by the following equation (11) as a first-order approximation.

[Equation 11] G _COMP = (1−α) · (K + M ₀ ) / K (11) As a result, the target value Δhref input to the AGC device 20 is obtained.
Becomes the following expression (12).

Equation 12] ^{_{Δhref = G COMP · Δh * ...}} (12) The difference between Accordingly α or M thickness constant part of becomes possible to control the compensated.

The smoothing device 16 is composed of a ramp filter, a first-order lag filter, etc., and adjusts the length and shape of the C material by passing the Δh _ref . Of course, the running plate thickness may be changed by utilizing the maximum response of the rolling reduction system without using such a filter.

The abnormality detecting device 18 is a BISRA type A
It detects abnormalities such as the amount of pressure movement of the GC device 20, the rate of reduction change, the position of reduction, etc., and it is necessary to change the detection level according to the amount of plate thickness change during the running plate thickness operation. The abnormality detection level of the rolling movement amount is determined by the following equation (13).

[0026]

[Equation 13]

K: margin rate (about 1.5) Further, the reduction rate abnormality detection level is determined by the following equation (14).

[0028]

[Equation 14]

ΔS _ref : setting of the amount of reduction movement, Δτ: time, k: margin rate (about 1.5) The reduction position abnormality detection level is the following (15a), (15b).
Determined by the formula.

[ _Equation 15] S _refU = S ₀ + | ΔS _ref | (15a) [upper limit] S _refL = S ₀ + | ΔS _ref | (15b) [lower limit] S _refU : reduction upper limit position, S _refL : reduction lower limit Position S ₀ : initial reduction position, ΔS _ref : reduction movement amount setting The above setting values are changed during rolling by the running plate thickness change command.

FIG. 4 is a diagram showing an example of plate thickness change control in a 7-stand continuous rolling mill. In the figure, an FGC (finished plate thickness compensator) setup unit 30 is a storage unit 1 of FIG.
Includes 0, which pre-calculates the thickness schedule and set-up for material A. FGC
The (finished plate thickness compensator) 32 corresponds to the plate thickness setting changing device / gain compensator 14 and the smoothing device 16 in FIG. 1, and the AGC device 34 is a configuration in which the control system of the AGC device 20 in FIG. 1 is extracted. It consists of

FIG. 5 shows the run-off point tracking device 12 of FIG.
FIG. As shown in the figure, the predetermined run-off point position (on the exit side of the final stand, after rolling 300m from the tip)
Is converted to the exit side of the F ₁ stand, and this is used as the target value for plate length measurement. That is, the target value is calculated by the following equation (16). Then, after the F ₁ stand is bitten, the plate length is measured by the formula (17), and when the condition of the formula (18) is satisfied, the running plate thickness change command of F _{1 STD} is issued.

[0032]

[Equation 16]

[0033]

[Equation 17]

[0034]

[Equation 18]

According to this command, the correction amount is added to the target plate thickness of the F ₁ AGC device 34 (see FIG. 1). Furthermore, the arrival of the F ₂ stand is detected while calculating the movement amount of the travel change point position by the exit side length measuring system (see FIG. 5), and the run change command of the F ₂ stand is issued. F ₂ ~F ₇ stand is also the same logic. The length measuring system of the F ₁ stand in FIG. 5 inputs the rotational speed of the rolls and determines the plate length on condition that the rolling rolls are rotating and the presence of the running inflection point is detected. F ₂
In the case of the length measurement system after the stand, in addition to the rotation of the rolling roll and the detection of running deviation, the rotation speed of the roll is input and the strip length is calculated under the condition that the running deviation of the front stand is detected. There is. In addition, in each stand, learning control is applied to the length measurement system to improve its measurement accuracy.

FIG. 6 is a flow chart showing the operation of the embodiment shown in FIG. It is assumed that the FGC setup unit 30 calculates the thickness schedule and setup for the A material in advance, and also calculates the thickness schedule for the B material in advance and stores it. Then, the A material is set up and the A material is rolled (S1). The rolling control of the material A at this time is performed by the F ₁ AGC device 34. The running inflection point tracking device 12 changes (C
Material) is detected, the FGC circuit 32 is driven, and F ₁ A
The target value of the GC device 34 is changed, and the C material is rolled based on the changed target value (S2). That, FGC circuit 32 the operation result calculates the equation (12) is added to the target value of the F ₁ AGC device 34, F ₁ AGC unit 34 controls the pressing position of the mill on the basis of the target value. On the other hand, FIG.
The abnormality detecting device 18 calculates the set value as described above, and C
The presence or absence of abnormality is detected based on the set value according to the material (S
4). Then, when the running inflection point tracking device 12 detects the material B, the drive of the F ₁ FGC circuit 32 is stopped, and the F ₁ AGC circuit 32 is stopped.
The GC device 34 rolls the material B on the basis of the sheet thickness schedule without interrupting its operation (S5).

FIG. 7 is a timing chart showing the operation of each section in the prior art. This timing chart shows the characteristics when the parameters of the AGC device are corrected to optimum settings before and after the thickness change, and the AGC parameters related to the preceding material are used in the transition period of the thickness change. . That is, this is an example of the case where the rolling position correction amount is calculated by the equation (10) in the transition period of the plate thickness correction. As can be seen from this example, in the transition period of the plate thickness change, in the conventional rolling position correction method using the AGC device, as the plate thickness is thinner and the plasticity coefficient is higher, the rolling position is lowered too much, so that the tension fluctuation and the looper fluctuation are caused. You can see that is getting bigger.

On the other hand, FIG. 8 is a timing chart showing the operation of each part in the above-mentioned embodiment. Before and after changing the plate thickness, the optimum AGC parameters are used for each plate thickness, but during the transition period of plate thickness correction,
The reduction position correction amount is obtained as described above. According to the present embodiment, it can be seen that the tension fluctuation and the looper fluctuation are greatly reduced as compared with the above-mentioned example even in the latter stand where the reduction position correction amount is appropriate and the plate thickness is thin and the plasticity coefficient is large. When testing the actual machine, the final stand thickness is 4
We have succeeded in changing the running plate thickness to 00μ.

In the above embodiment, the BISRA type A
Although the GC has been described, as shown in FIG. 1, it can be easily implemented by combining it with the absolute value AGC before and after changing the plate thickness and switching it to the BISRA formula AGC.

[0040]

As described above, according to the present invention, the following effects can be obtained. 1) Since AGC is performed, the reduction setting can be changed only by the target thickness, and a new setting calculation is unnecessary. 2) It is possible to change the plate thickness with high accuracy without including errors such as estimated rolling load, roll expansion, and roll wear. However, when the present invention is applied to the gauge meter type control method, an error remains. 3) The AGC adjustment is optimized for all of A material, B material and C material, and the control operation for changing the plate thickness becomes stable. 4) By improving the prediction accuracy, fluctuations in the looper, roll speed, etc. can be reduced, and a stable plate thickness change is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control device that carries out a method for controlling a hot rolling mill according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of an elongation curve of a rolling mill and a plasticity curve of a material.

FIG. 3 is an explanatory diagram for setting a rolling reduction of a C material (a portion having a changed plate thickness).

FIG. 4 is a block diagram showing a configuration when the embodiment of FIG. 1 is applied to a 7-stand continuous rolling mill.

5 is an explanatory diagram of the running-inflection point tracking device in FIG. 4;

6 is a flowchart showing the operation of the embodiment of FIG.

FIG. 7 is a timing chart showing the operation of each unit in the conventional technique.

8 is a timing chart showing the operation of each part in the embodiment of FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B21B 37/18 BBM 8315-4E B21B 37/00 114 37/12 BBM 8315-4E 111 B (72) Inventor Fumio Fujita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (4)

[Claims] 1. A method for controlling a hot rolling mill that controls a rolling position of a mill by performing automatic plate thickness control, wherein a plate thickness control is performed with a constant target value, and a target plate of a leading portion and a trailing portion. A method for controlling a hot rolling mill, which is characterized in that control is performed by using different rolling reduction control parameters when performing plate thickness change control for changing the thickness during running. 2. The reduction setting change amount which compensates the tuning rate of the automatic plate thickness control when the plate thickness change control is performed.
Control method for hot rolling mill. 3. The hot working according to claim 1 or 2, wherein during the plate thickness change control, the reduction setting change amount is given by using the apparent plasticity coefficient obtained by converting the plasticity coefficient of the material on the assumption that the entrance side plate thickness is constant. Rolling mill control method. 4. A set value for abnormality detection for equipment protection,
The method for controlling a hot rolling mill according to claim 1, 2 or 3, wherein the hot rolling mill is changed according to a rolling reduction condition at the time of controlling the strip thickness change.