JP2009045635A - Method of controlling tension of rolled stock and rolling mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a stable operation possible by preventing variation of inter-stand tension when rolling the nose part of a rolled stock. <P>SOLUTION: In a method of controlling the tension of the rolled stock in which inter-stand tension is controlled by adjusting the roll speed of a rolling stand 5, a plurality of control gains G to the roll speed are beforehand determined by taking the inter-stand tension as a constraint condition and also a control-gain table 12 classifying the control gains G by the tension is prepared. When rolling the nose part of the rolled stock 6, the control gain G is determined from the control-gain table 12 and the actual value of tension deviation, the roll speed is determined on the basis of the control gain G, and it is applied to the rolling stand 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rolled material tension control method and a rolling apparatus to which the rolled material tension control method can be applied.

Conventionally, rolled materials such as thin steel plates and thin aluminum plates have been manufactured by a rolling mill having a plurality of rolling stands. In the rolling mill, the rolling load and the roll gap in the rolling stand are controlled in order to obtain a predetermined thickness of the rolled material. In addition, a looper is provided between the rolling stands, and the rising angle of the looper so that the tension of the rolled material between the rolling stands (simply called the tension between the stands) is within a predetermined range. Etc. were properly controlled.
Many “tension control methods” for controlling the tension between the stands have been developed.

For example, the technique disclosed in Patent Document 1 measures the height of a looper installed between rolling stands, controls the roll speed based on the difference between the actual height and the target height, and the tension between the stands. The looper current is controlled based on the difference between the actual value and the target value, and the tension is set to an appropriate value. Furthermore, while estimating the resonance frequency and damping coefficient of the looper control system, by changing the setting value of the roll speed according to this estimated value, the resonance frequency and damping coefficient are corrected to appropriate values, and the rolling mill is stabilized. We are planning to operate.
Moreover, there exists what is disclosed by patent document 2 as what suppresses the tension | tensile_strength between stands. The tension control method between the stands of patent document 2 detects the inlet side plate | board thickness fluctuation | variation in the entrance side of the rolling stand which generate | occur | produces for an unspecified cause by the thickness meter or the gauge meter plate thickness calculation value in a rolling stand, and the said entrance side plate Calculates rear tension fluctuation (variation of reverse rate of rolling stand) due to thickness fluctuation, calculates outlet side board thickness fluctuation to suppress rear tension fluctuation, and enters inlet side board thickness fluctuation based on said outlet side board thickness fluctuation The generation of tension due to is suppressed.
Japanese Patent No. 3041155 Japanese Patent No. 3451919

In recent years, demands for products from users have become stricter, for example, cost reduction. Therefore, in the rolling of thin plates, etc., it is not clearly controlled in the past, and it is adopted as a product by controlling strict tension between the stands even for the tip part of the rolled material that was not shipped as a product. Requests to do are raised from the field. Moreover, the importance of tension control at the tip of the rolled material is increasing from the viewpoint of stably rolling the rolled material tip, which is an unsteady part, and stably operating the entire continuous rolling mill.
However, the technique of Patent Document 1 is a control method that assumes only the stationary part after passing through the tip of the rolled material, and it is possible to perform tension control in the middle of the rolled material. It is difficult to suppress the tension.

Moreover, in the thing of patent document 2, since the main point is put on the stationary part where tension does not change so much similarly to the thing of patent document 1, it cannot control the plate | board thickness in the front-end | tip part of a rolling material. There's a problem.
Accordingly, in view of the above problems, the present invention provides a rolling material tension control method and rolling apparatus in a rolling mill that prevents fluctuations in tension between stands during rolling of the tip of the rolled material and enables stable operation. The purpose is to provide.

In order to achieve the above object, the present invention takes the following technical means.
In order to achieve the above object, the present invention has taken the following measures.
That is, the technical means for solving the problems in the present invention is a method of controlling the tension between the stands by adjusting the roll speed of the rolling stand when rolling the rolled material with a rolling mill having a plurality of rolling stands. In the material tension control method, a plurality of control gains for the roll speed are obtained in advance with the tension deviation of the tension between the stands as a constraint, and a control gain table in which each control gain is classified according to the tension between the stands is prepared. When rolling the tip of the rolled material, it is preferable to obtain a control gain from the control gain table and the actual value of the tension deviation, obtain a roll speed based on the control gain, and apply it to the rolling stand.

  It is preferable that the constraint condition is different when the tension between the stands is high, when the tension between the stands is near the target value, and when the tension between the stands is low.

In order to consider the influence of the tension deviation on the sheet thickness of the rolled material, an evaluation function with the product of the tension deviation and the sheet thickness as a parameter is defined, and the control gain is obtained so that the evaluation function is minimized. Is preferred.
In order to suppress a rapid change in the amount of change in the roll speed accompanying the change in the control gain, it is preferable to obtain a speed correction amount for the roll speed and obtain the roll speed based on the speed correction amount and the control gain.
Another technical means for solving the problems in the present invention is a rolling apparatus provided with a rolling mill having a plurality of rolling stands and a control device for controlling the tension between the stands by adjusting the roll speed of the rolling stand. The control device has a control gain table having the control gain for the roll speed obtained with the tension deviation between the stands as a constraint, classified for each tension deviation, and when rolling the tip of the rolled material In addition, a control gain determination unit that determines a control gain from the control gain table and the actual value of the tension deviation, and a roll speed calculation unit that calculates a roll speed based on the control gain are provided.

  According to the rolling material tension control method and rolling apparatus of the present invention, it is possible to prevent fluctuations in tension between stands during rolling of the tip of the rolled material. In addition, by appropriately controlling the tension at the tip of the rolled material, the thickness of the tip can be made appropriate, and the rolling mill can be operated stably.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a rolling apparatus according to the present invention. The rolling device 1 is for rolling a rolled material 6 (for example, slab) such as iron or aluminum into a thin plate, and controls a rough rolling machine and an intermediate rolling machine, a finishing rolling machine 2, a winding machine 3 and the like (not shown). And a control device 4 for performing the operation.
Hereinafter, for convenience of explanation, the finish rolling mill is simply referred to as the rolling mill 2. FIG. 1 shows a finish rolling mill 2.
The rolling mill 2 is a multi-stage rolling mill (tandem rolling mill), and the tension of the rolled material 6 between the plurality of rolling stands 5 and the rolling stands 5 and 5 (hereinafter referred to as tension between the stands or simply tension). A looper device 7 capable of measuring

Each rolling stand 5 includes a pair of work rolls 10 and 10 and a plurality of backup rolls 11 and 11 that back up the work rolls 10. The looper device 7 is arranged between the stands 5 and 5 and outputs the measured inter-stand tension to the control device 4. In this embodiment, the tension between the last rolling stand and the previous rolling stand 5 is measured by the looper device 7, and the roll speed of the previous rolling stand 5 is based on the actual value of the inter-stand tension. The tension between the stands is controlled by changing.
As shown in FIG. 2, the control device 4 is configured by a process computer. The process computer 4 includes a control gain table 12, a control gain determination unit 13, and a roll speed calculation unit 14.

The control gain table 12 stores a plurality of control gains G for controlling the roll speed of the work roll 10, and the control gain G is obtained with the tension deviation of the tension between the stands as a constraint condition.
First, the control gain stored in the control gain table 12 will be described.
The control gain G is obtained by applying an optimum control theory to the rolling control model represented by the equations (4) to (8).

Specifically, with respect to the rolling control model shown above, a plurality of evaluation functions shown in Expression (9) are minimized under the constraint conditions shown in Expression (1) to Expression (3). The control gain G is obtained. In Expressions (1) to (3), Δtf (i) _t ≧ 1 is assumed.

The constraint condition is that when the tension between the stands applied to the rolled material 6 is high (sometimes referred to as high tension), when the tension between the stands is in the middle of the target value, the tension between the stands is low (sometimes referred to as low tension). 3 patterns with the case. Equation (1) is the constraint when the stand tension is high, Equation (2) is the constraint when the stand tension is near the target value (sometimes referred to as medium tension), and the constraint when the tension between the stands is low The condition is represented by equation (3).
For example, high tension is when the inter-stand tension is greater than 10% of the target value, medium tension is when the inter-stand tension is in the range of ± 10% of the target value, and low tension is the inter-stand tension. Is less than 10% of the target value. These high tension, medium tension, and low tension standards are determined by the dimensions and strength of the rolling device 1 and the rolled material 6, and are appropriately changed.

In other words, the high tension is a state of rolling with the tension value of the tension insensitive body that can be regarded as having a slight influence on the sheet thickness fluctuation from the tension fluctuation, and the tension deviation is determined according to the constraint condition of the equation (1). Even if there is some variation, priority can be given to the control of the plate thickness.
Further, the low tension is a state in which rolling trouble such as the rolled material 6 may be separated from the looper device 7 when rolling is continued for a long time, and depending on the constraint condition of the formula (3). The tension control can be prioritized.

As shown in Table 1, the control gain G obtained in this way is classified into three groups for high tension, medium tension, and low tension, and is stored in the control gain table 12. Further, the control gain G divided for each group is classified according to the switching judgment criterion based on the tension deviation and stored in the control gain table.
As described above, the constraint condition is divided according to the tension between the stands, and the constraint condition of the tension deviation of the tension between the stands is determined. Therefore, in the case of high tension, the tension fluctuation is controlled by tension control by suppressing the occurrence of steep tension fluctuation. Can be relaxed. For medium tension near the target tension, the band width is set based on the idea that the influence on the thickness deviation is minimal if the tension changes within the band width. If the tension is low, the threading condition becomes unstable and rolling troubles occur. Therefore, priority should be given to tension control over the influence on sheet thickness deviation, and the tension should be controlled to follow the target tension as quickly as possible. Is possible.

In addition, as shown in Formula (9), the evaluation function uses the product of the tension deviation and the sheet thickness as a parameter, and this considers the influence of the tension deviation on the sheet thickness of the rolled material 6. It has become.
The control gain determination unit 13 determines the control gain G from the control gain table 12, the actual tension deviation value, and the actual tension value. Specifically, the control gain determination unit 13 includes the equation (10), and the tension deviation is determined by the difference between the actual tension value sent from the looper device 7 and a predetermined target tension value. Ask for. Then, the control gain determination unit 13 determines whether the tension is high tension, medium tension, or low tension from the actual tension value, selects a group from the control gain table 12, and switches the tension deviation obtained in advance. A control gain G belonging to the judgment criterion is selected.

  The roll speed calculation unit 14 obtains the roll speed based on the control gain G. The roll speed calculation unit 14 includes the equation (11), and obtains the change amount of the roll speed from the control gain G determined by the control gain determination unit 13 and the tension deviation. Moreover, the roll speed calculation part 14 is equipped with Formula (12), adds the variation | change_quantity of roll speed to an object rolling stand, and calculates | requires the roll speed (roll speed command value) controlled this time.

In addition, the roll speed calculation unit 14 includes a filter unit 15 that obtains a speed correction amount α with respect to the roll speed in order to suppress a rapid change in the change amount of the roll speed accompanying the change of the control gain G.
When the control gain deciding unit 13 decides the control gain G, the filter unit 15 looks at the flag where the control gain G shown in the equations (13) and (14) is switched, and the switching flag is raised. That is, at the time of the equation (13), the speed correction amount α is calculated based on the equation (15). The obtained speed correction amount α is applied when the change amount is obtained. G (Δtf (i) _t ) in equation (15) represents the roll speed command value ΔVr (i) _t when the velocity correction amount α is set to 0 in equation (11).

  Γ and β in the equation (15) are coefficients and threshold values for obtaining the speed correction amount α, and are for suppressing a sharp change in the command value for the roll speed. That is, the coefficient depends on the follow-up performance of the actual speed with respect to the roll speed command value, and can be appropriately determined depending on the rolling device 1 and rolling conditions.

Note that the switching flag described above indicates whether or not the control gain G determined by the current tension deviation has changed compared to the control gain G determined by the tension deviation before one sampling.
The operation of the rolling apparatus will be described based on the flowchart of FIG.
First, after the rolled material 6 is carried into the rolling mill 1 and the leading end of the rolled material 6 is bitten into the rolling stand i, and then bited into the next rolling stand i + 1, the rolling stand i and the next rolling stand. The tension between the stands between i + 1 and the stand i is measured using the looper device 7 several seconds after the stand i is bitten. Then, the control gain determination unit 13 calculates the tension deviation with respect to the inter-stand tension between the rolling stand i and the next rolling stand i + 1 based on the equation (10) (S1).

Further, the control gain determination unit 13 extracts the control gain G using the calculated tension deviation, the actual tension value, and the control gain table 12 (S2).
Next, it is determined whether or not the determined control gain G has changed compared to the previous control gain G, that is, whether or not a switching flag is set (S3). If the switching flag is not set, the speed correction amount α is set to 0 (S4). If the switching flag is set, the speed correction amount α is calculated based on the equation (15) (S5).
The roll speed calculation unit 14 uses the tension deviation obtained this time, the tension deviation one sampling before, the control gain G, and the speed correction amount α in the rolling stand i, and the change in the roll speed according to the equation (11). An amount is obtained (S6).

The roll speed calculation unit 14 adds the amount of change in the roll speed to the roll speed before one sampling in the rolling stand i to obtain the roll speed to be controlled this time (S7). The roll speed obtained for the rolling stand i is applied and controlled (S8). The roll speed is changed by the motor M that rotates the work roll 10.
It is determined whether or not the rolling of the tip of the rolled material 6 has been completed with respect to the rolling stand i to be controlled (S9).

4 and 5 show control results in the case of applying the rolling material tension control method and rolling apparatus according to the present invention. The control results shown in FIGS. 4 and 5 apply the tension between the stands of the final rolling stand (the rolling stand arranged at the final stage of the finish rolling mill) and the rolling stand immediately preceding this final rolling stand. The results at the final rolling stand are shown.
The broken line in each figure shows the example in case the tension control method of the rolling material of this invention is not applied (comparative example). In the comparative example shown in FIGS. 4 and 5, when the tip of the rolled material 6 bites into the final rolling stand, the tension between the stands rapidly rises to about 1.10, and the conventional roll speed accordingly. The calculation unit controls to change the roll speed.

As described above, in the comparative example, when the control for changing the roll speed is performed, the mass flow between the stands is greatly disturbed due to the abrupt roll speed change, so that the thickness deviation also changes greatly. When the change in the plate thickness deviation is large, the target tension is below, and the roll gap is corrected by the plate thickness control system accordingly. The correction of the roll gap further induces mass flow disturbance. As a result, the plate thickness deviation fluctuates for a while with the target plate thickness interposed therebetween, and then follows the target plate thickness.
On the other hand, in the embodiment shown by the solid line in FIG. 4, it can be seen that the tension value gradually changes from the high tension state when the plate is engaged to the vicinity of the target tension, and gradually changes in the vicinity of the target tension. Thereby, it can be confirmed that the roll speed command value is also changed gently without a steep change compared to the comparative example. As a result, the plate thickness deviation and the roll gap correction amount also change gradually, and the situation in which the plate thickness seen in the comparative example changes in vibration is not confirmed. Conversely, in the embodiment, the plate thickness fluctuation is suppressed even if the convergence to the target tension is sacrificed to some extent.

In the example shown by the solid line in FIG. 5, it can be confirmed that similar results can be obtained even in the case of low tension.
As a result of the above, it can be confirmed that the plate thickness deviation has been reduced and the off-gauge length has been shortened, and the plate thickness accuracy has been improved.
The present invention is not limited to the above embodiment.

It is the figure which showed the outline of the continuous rolling mill. It is a block diagram of a control apparatus. It is a flowchart which shows the tension control method of the rolling material which concerns on this invention. It is a figure which shows the result (1) which controlled the continuous rolling mill using the tension control method of the rolling material which concerns on this invention. It is a figure which shows the result (2) which controlled the continuous rolling mill using the tension control method of the rolling material which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling apparatus 2 Rolling mill 4 Control apparatus 6 Rolled material 7 Looper apparatus 12 Control gain table 13 Control gain determination part 14 Roll speed determination part

Claims (6)

In the rolling material tension control method of controlling the tension between the stands by adjusting the roll speed of the rolling stand when rolling the rolled material in a rolling mill having a plurality of rolling stands,
In advance, a plurality of control gains for the roll speed are obtained with the tension deviation of the tension between the stands as a constraint, and a control gain table in which each control gain is classified for each tension between the stands is prepared.
When rolling the tip of the rolled material, obtain a control gain from the control gain table and the actual value of the tension deviation,
A rolling material tension control method characterized by determining a roll speed based on the control gain and applying the roll speed to the rolling stand.   2. The constraint condition according to claim 1, wherein the constraint condition is different when the tension between the stands is high, when the tension between the stands is near the target value, and when the tension between the stands is low. Roll tension control method. The constraint condition when the tension between the stands is high is represented by Expression (1), the constraint condition when the tension between the stands is near the target value is represented by Expression (2), and the constraint condition when the tension between the stands is low is represented by Expression (2). The method for controlling the tension of the rolled material according to claim 2, wherein 3).

  In order to consider the influence of the tension deviation on the sheet thickness of the rolled material, an evaluation function is defined with the product of the tension deviation and the sheet thickness as a parameter, and the control gain is obtained so that the evaluation function is minimized. The tension control method for a rolled material according to any one of claims 1 to 3.   In order to suppress a rapid change in the amount of change in roll speed accompanying the change in the control gain, a speed correction amount for the roll speed is obtained, and the roll speed is obtained based on the speed correction amount and the control gain. The tension | tensile_strength control method of the rolling material in any one of Claims 1-4. In a rolling mill comprising a rolling mill having a plurality of rolling stands, and a control device that controls the tension between the stands by adjusting the roll speed of the rolling stand,
The controller is
A control gain table having a plurality of control gains with respect to the roll speed obtained with the tension deviation of the tension between the stands as a constraint, classified for each tension between the stands;
When rolling the tip of the rolled material, a control gain determining unit that determines a control gain from the control gain table and the actual value of the tension deviation;
A rolling apparatus comprising: a roll speed calculation unit that obtains a roll speed based on a control gain.

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