JP2002346616A - Method for controlling sheet thickness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that no good feedforward control of sheet thickness can be done in a conventional sheet thickness control method wherein the thickness of a sheet to be rolled is controlled by feedforward of the correction amount of a reduction position predicted for the rolling of the following pass because high predicted accuracy of a sheet temperature is not obtainable and/or deviation in tracking has a great effect and/or for other reason. SOLUTION: According to the invented method, the sheet temperature distribution in the longitudinal direction for the following pass is predicted from the entering sheet thickness, leaving sheet thickness and sheet temperature distribution in the longitudinal direction at the time of the rolling of the preceding pass. The rolling load distribution in the longitudinal direction of the sheet at the time of the rolling of the following pass is predicted based on the sheet temperature distribution in the longitudinal direction of the sheet for the following pass and the leaving sheet thickness distribution in the longitudinal direction of the sheet. Then the correction amount of the reduction position for the rolling of the following pass is predicted, whereby good feedforward control is done. This feedforward control method is also applicable to the rolling of a tapered sheet.

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, and more particularly, to a method for controlling the thickness of a material to be rolled by feeding forward a reduction position correction amount predicted for rolling in the next pass. The present invention relates to a control method which is particularly suitable for rolling a tapered plate.

[0002]

2. Description of the Related Art In a sheet rolling process such as a thick plate rolling, various types of automatic thickness control (AG) are used to reduce the thickness variation in the longitudinal direction of a sheet material, which greatly affects the quality of a product.
C) has been used. The AGC is BISRA-A
Feedback control (FB-AGC) represented by GC and absolute value AGC and feedforward control (FF-A
GC). Among the FB-AGCs, the BISRA-AGC is an FB control that adjusts a roll gap by multiplying a load variation from a lock-on value by a proportional gain, and the absolute value AGC is an absolute value of an output side plate thickness from an actually measured load. Value, and I or P is calculated from the difference between the target thickness and the predicted thickness.
The roll gap is adjusted by the I controller. In the past, the above-mentioned FB-AGC has been basically used. However, in the FB-AGC, due to a response delay of a hydraulic system or the like for adjusting a roll gap, temperature disturbance cannot be compensated or transformation occurs during rolling. For example, even if there is a sudden change in the load, there is a problem that the change cannot be followed. In recent years, the FF-A
GC is adopted or the FF-AGC and the FB-A
It is often used in combination with GC. The FF-AG
C is for obtaining a gap distribution to be corrected from the entry-side sheet thickness distribution in advance before actual rolling, and adjusting the gap at a designated timing by a tracking device according to the gap distribution. When controlling the thickness variation, high tracking accuracy is required. For example, Japanese Patent Application Laid-Open No. 6-304635 (hereinafter referred to as
The technology described in Japanese Patent Application Laid-Open No. 9-253723 (hereinafter referred to as Reference 2) is disclosed in FB-A.
This is a combination of GC and FF-AGC. The technique described in the above-mentioned Reference Publication 1 obtains a plastic coefficient of a plate end of a previous pass from a load and a roll gap of a plate end of a two-pass before and a previous pass, and obtains a plastic coefficient at the time of the next pass biting from the obtained plastic coefficient. The load fluctuation is predicted, and AGC is performed based on the predicted load fluctuation.
The response delay is predicted, and the set gap and the steady-state gap are corrected. The technique disclosed in Reference 2 predicts a load distribution from a temperature distribution and a sheet thickness distribution obtained in advance, and calculates a gap correction amount in consideration of a delay in the absolute value AGC.

[0003]

In the technique disclosed in the above-mentioned reference 1, the entire compensation amount is compensated by feedforward, so that if the tracking shifts, the influence on the sheet thickness is large. There is a problem that metamorphosis cannot be considered. Further, in the technique described in Reference Publication 2, it is necessary to accurately predict the temperature distribution.
Reference 2 does not specifically disclose the identification of the temperature distribution. Although only calculation using a temperature model or actual measurement using a thermometer is described, it is not easy to obtain an accurate temperature distribution in any case. Further, all of the conventional techniques only consider a model having a constant thickness, and cannot deal with an arbitrary tapered thickness. In order to solve such problems in the conventional technology, the present invention improves the thickness control method, feed-forwards the reduction position correction amount predicted for the rolling in the next pass, and increases the thickness of the material to be rolled. In controlling the sheet thickness, the thickness distribution of the inlet side, the thickness of the outlet side, and the sheet temperature at the time of rolling in the previous pass of the next pass are determined. The longitudinal distribution of the sheet temperature for the next pass is predicted by compensating for the air-cooling component due to the inter-pass time between the pass and the next pass, and the sheet longitudinal distribution of the sheet temperature for the next pass and the output for the previous pass. Based on the distribution of the side plate thickness in the longitudinal direction of the plate, the distribution of the rolling load at the time of rolling in the next pass is predicted in the longitudinal direction of the plate. Against pass rolling By predicting the amount of correction of the recording position, it is possible to accurately predict the plate temperature distribution in the plate longitudinal direction, respond to transformation during rolling, and have a large tolerance for errors in tracking deviations and load fluctuation prediction errors. It is an object of the present invention to provide a control method and a control method suitable for controlling the thickness of a tapered plate having an arbitrary shape.

[0004]

In order to achieve the above object, the invention according to claim 1 is to feed forward a reduction amount correction amount predicted for rolling in the next pass to reduce the thickness of a material to be rolled. In the thickness control method for controlling, a distribution in the longitudinal direction of the thickness of the inlet side, a thickness of the exit side, and the temperature of the plate at the time of rolling in the preceding pass of the next pass is determined. The air-cooling component due to the inter-pass time between the previous pass and the next pass is corrected to predict the plate temperature longitudinal distribution for the next pass, and the plate temperature distribution for the next pass in the plate longitudinal direction. The longitudinal distribution of the rolling load during the rolling of the next pass is predicted based on the longitudinal distribution of the thickness of the exit side for the pass and the target value of the exit thickness for the next pass. Rolling load plate longitudinal direction Based on the distribution, the amount of correction of the rolling position for the rolling of the next pass is predicted, and the taper shape is set as a target value of the outlet side thickness for the next pass used in predicting the distribution of the rolling load at the time of rolling in the next pass. The thickness control method is characterized in that the thickness target value is used together with the absolute value AGC using the tapered target value. According to a second aspect of the present invention, the rolling load and the roll gap in each of the rolling before the next pass and the rolling in the preceding pass are actually measured, and based on the actually measured rolling load and the roll gap, the preceding load is determined. 2. The sheet thickness control method according to claim 1, wherein a distribution in the sheet longitudinal direction of an incoming side sheet thickness, an outgoing side sheet thickness, and a sheet temperature during rolling of the pass is determined. In the thickness control method according to the first aspect, when the thickness of the material to be rolled is controlled by feeding forward the reduction position correction amount predicted for the rolling in the next pass, the rolling in the previous pass of the next pass is performed. The distribution in the longitudinal direction of the sheet thickness at the entrance, the sheet thickness at the exit, and the sheet temperature at the time are determined. Next, for the longitudinal distribution of the plate temperature determined for the previous pass, the air-cooling component due to the inter-pass time between the previous pass and the next pass is corrected,
The longitudinal distribution of the plate temperature for the next pass is predicted. Then, based on the distribution of the sheet temperature in the longitudinal direction of the next pass, the distribution of the exit side thickness in the longitudinal direction of the preceding pass, and the target value of the exit side thickness in a tapered shape for the next pass, And the rolling position correction amount for the next pass rolling is predicted based on the predicted rolling longitudinal load distribution for the next pass rolling. As described above, in the sheet thickness control method according to the first aspect, the temperature prediction accuracy can be improved by predicting the longitudinal distribution of the sheet temperature for the next pass using the process data immediately before rolling. In addition, it becomes possible to predict deformation resistance via temperature during controlled rolling, and it is possible to cope with transformation plasticity. In addition, it is not necessary to compensate for the entire compensation amount by feedforward, and a large permissible range for tracking deviation and load fluctuation prediction error can be secured. Also, as described above, in predicting the distribution of the rolling load in the longitudinal direction of the rolling at the time of rolling in the next pass, the target value of the tapered exit side thickness for the next pass is referred to, so that the rolled plate thickness is formed into an arbitrary tapered shape. It becomes possible. Further, in the first aspect, a feedback circuit that uses the tapered target plate thickness as a target value is also used, so that a model shift that is difficult to delete only by feedforward control (a target value due to a taper plate shape or the like) is obtained. It is possible to correct the integration of the error accompanying the change in the sheet thickness). In the sheet thickness control method according to the second aspect, based on actual measurement data of a rolling load and a roll gap in each of the rolling before the next pass and the rolling in the previous pass of the next pass, the input side plate at the time of rolling in the preceding pass. Since the thickness, delivery side thickness, and plate temperature distribution in the plate length direction are determined, it is not necessary to use a gamma-ray thickness gauge close to the rolling mill for FF-AGC.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiment is a specific example of the present invention and does not limit the technical scope of the present invention. Here, FIG. 1 is a flowchart for explaining a sheet thickness control method according to an embodiment of the present invention, and FIG. 2 is an F-number suitable for implementing the sheet thickness control method according to the embodiment of the present invention.
FIG. 3 is a configuration diagram for explaining F-AGC. A thickness control method according to an embodiment of the present invention includes, for example, a thickness control of a reversible rolling mill that controls a thickness of a material to be rolled by feeding forward a reduction position correction amount predicted for the next pass rolling. The method is characterized in that, as shown in FIG. 1, the rolling load and the roll gap in each of the rolling before the next pass and the rolling in the previous pass are actually measured (S
1), the distribution of the sheet thickness in the longitudinal direction of the sheet at the entrance side, the thickness of the exit side, and the sheet temperature at the time of rolling of the previous pass of the next pass is determined (S2). The longitudinal distribution of the plate temperature for the next pass is predicted by correcting the air-cooling component due to the inter-pass time between the previous pass and the next pass (S3). Based on the distribution of the thickness of the delivery side sheet thickness in the longitudinal direction of the preceding pass, the distribution of the rolling load in the rolling of the next pass is predicted in the longitudinal direction of the plate (S4). Based on the distribution, the amount of correction of the rolling position for the rolling of the next pass is predicted (S
5) By the way. Further, as shown in FIG. 2, a feed-forward control device (FF-AGC) 1 suitable for carrying out the sheet thickness control method according to the embodiment of the present invention has, for example, an absolute value AGC 2 For the set rolling position, the rolling position correction amount determined by the sheet thickness control method according to the embodiment of the present invention is fed forward. As will be described later, one of the features of the present invention is that a tapered target value of the thickness is adopted as the target thickness given to the feedforward control device (FF-AGC). Since such a target plate thickness value can be arbitrarily selected, a taper plate having an arbitrary shape can be rolled. The absolute value AGC2 is intended for, for example, a reversible finishing mill 5 that performs finish rolling of a plate (corresponding to a material to be rolled) 4, and adjusts a roll gap between upper and lower work rolls 5a and 5b. , Used to set the roll speed. Since the configuration of the absolute value AGC2 is well known, a detailed description thereof will be omitted. However, another feature of the present invention is that a tapered target value for the target thickness to be given to the absolute value AGC2 is adopted. It is. As a result, the deviation caused by adopting the tapered model (target value) which cannot be eliminated only by the feedforward control is eliminated. Above the backup roll 51a supporting the upper work roll 5a of the finishing mill 5, a load cell 6 and a position meter 7 are provided, from each of which a rolling load P and a roll gap S (corresponding to a rolling position) are provided. , FF-AGC1.

Hereinafter, the operation of the above thickness control apparatus, that is, the details of the thickness control method according to the embodiment of the present invention will be described. The above-mentioned FF-AGC1 is a reduction amount ΔS
The path before the next path i for which (i) is to be predicted (i−
2) Using the actual data of the previous pass (i-1) and the data obtained from other calculations and settings, the reduction position correction amount Δ
The calculation of S (i) is performed. The rolling position correction amount ΔS (i)
Of the two passes performed prior to the next pass i to predict the rolling load P and the roll gap S by the load cell 6 and the position meter 7 in the rolling of the pass before (i-2). Are collected in the plate longitudinal direction. From the rolling load P (i-2) and the longitudinal distribution of the roll gap S (i-2) collected in the rolling before the previous pass (i-2), for example, according to the following equation (1), In the rolling in i-2), the distribution in the plate longitudinal direction of the exit side plate thickness h (i-2) is obtained. h = S + P / M (1) where M is a Mill constant. Also, the next previous pass (i-
Also in the rolling of 1), the load cell P and the position meter 7 determine the rolling load P (i-1) and the roll gap S.
The distribution in the plate longitudinal direction of (i-1) is collected. In the same manner as in the case of the pass before (i-2), from the rolling load P and the roll gap S distribution in the plate longitudinal direction obtained in the rolling of the pass before (i-1), according to the above equation (1), In the rolling of (i-1), the distribution of the exit side thickness h (i-1) in the plate longitudinal direction is obtained. In the two-pass rolling, in each of the passes (i-2) and (i-1), the distribution in the plate longitudinal direction of the exit side plate thickness h is collected.
The outgoing side plate thickness h (i-2) collected in the rolling of No. 1 is used as the incoming side plate thickness H (i-1) in the previous pass (i-1). Then, the rolling load P (i−
1), the thickness H (i-1) of the inlet side, and the thickness data h (i-
In addition to 1), the deformation resistance Kf (i-1) with respect to the previous pass (i-1) is determined from the set plate width B and the roll radius using, for example, a rolling load equation represented by the following equation (2). The distribution in the plate longitudinal direction is calculated analytically or numerically. P = B · Qp · ld · Kf (2) where Qp is the rolling force function (sheet thickness, roll radius, load,
Ld is a contact arc length (a function of load, roll radius, and plate thickness). Next, based on the deformation resistance Kf (i-1) for the previous pass (i-1), the distribution in the plate longitudinal direction of the plate temperature T (i-1) for the previous pass (i-1) is analytically or numerically calculated. Is calculated. Deformation resistance Kf and plate temperature T
Is expressed, for example, by the following equation (3). Kf = exp (c1 + c2 / T) · ε C3 · h C4 (3) where, epsilon is strain (plate thickness, a function of plate width), (c1.about.c4) is a coefficient which is stratified for each steel grade. Incidentally, the relationship between the rolling load P and the plate temperature T as expressed by the above equations (2) and (3) is based on the test performed on the rolled material of the same material as the plate 4 before the actual rolling. Is determined in advance by dynamic rolling. In this way, the rolling of the pass before (i-2) and the rolling of the previous pass (i-1)
Rolling loads P (i-2), P (i
-1), actual measurements of the roll gaps S (i-2) and S (i-1) are performed (S1), and the incoming side thickness H (i-1) and the outgoing side plate in the rolling of the previous pass (i-1). The thickness h (i-1) and the plate temperature T (i-1) are calculated (S2).

Next, the longitudinal distribution of the plate temperature T (i) for the next pass i to be predicted is predicted from the data of the plate temperature T (i-1) for the previous pass (i-1) ( S3). For example, the temperature drop due to air cooling may be corrected from the inter-pass time between the previous pass (i-1) and the pass i using a general equation of radiative heat transfer or convective heat transfer. The data of the sheet temperature T corresponds to the average temperature in the sheet width direction immediately below the roll bite in the rolling of the previous pass (i-1), and the calculation is performed as described above. Is used, the plate temperature T for the next pass i
High prediction accuracy can be obtained for (i). Further, since the exit side plate thickness h and the entrance side plate thickness H are calculated from the rolling load P and the roll gap S, when predicting the plate temperature T (i), the γ-ray plate thickness is close to the finishing mill 4. There is no need to provide a meter. Next, the distribution of the predicted plate temperature T (i) in the plate longitudinal direction, the distribution of the incoming plate thickness H (i) for the next pass i in the plate longitudinal direction (the exit plate thickness h (i) of the previous pass (i-1)). -1)
The distribution in the longitudinal direction of the rolling load P (i) in the rolling of the next pass i is predicted from the target longitudinal thickness value for the next pass i, the set sheet width, and the roll radius (S).
4). At this time, the target thickness target value of the tapered plate is used as the exit thickness target value for the next pass i. The prediction of the distribution of the rolling load P in the plate longitudinal direction in the rolling of the next pass i is performed by, for example, obtaining the deformation resistance Kf according to the above equation (3), and calculating the above equation ( What is necessary is just to follow 2). Further, the rolling load P (i) and the rolling load P predicted for the next pass i
From the difference from the average value Pave of (i), ΔP (i), the rolling position correction amount ΔS (i) at each point in the longitudinal direction for the next pass i is calculated according to the following equation (4) (S5). . ΔS (i) = haim (i) −g · ΔP (i) / M (4) where g is a control gain, haim (i) is a tapered target plate thickness, and M is a mill constant. The rolling position correction amount ΔSi with respect to the next pass i thus obtained is determined as a feedforward correction amount of the rolling position at a predetermined timing determined by tracking each point in the longitudinal direction of the sheet by a rolling speed or the like. Used in Thereby, an arbitrary tapered target plate thickness can be obtained. In the subsequent passes, similarly, the rolling position correction amount ΔS is sequentially predicted, and
Until all the passes to the plate 4 have been completed, the feedforward control is performed on the screw-down device 3. In the sheet thickness control method according to the embodiment of the present invention, when the reduction position correction amount ΔS (i) is obtained from the rolling load difference ΔP (i), a control gain g serving as an adjusting element is used. Since the correction amount ΔS (i) is fed forward,
It is possible to secure a large allowable range for tracking deviation and load fluctuation prediction error. As shown in FIG. 2, the target value of the tapered plate thickness is given to a feedback control device such as an absolute value AGC, and it is desirable that feedback control based on the absolute value AGC is also used. This is because the feedforward control alone can correct the integration of the error due to the model deviation due to the variation of the target plate thickness due to the tapered plate shape or the like by using the feedback control together. Here, FIG. 3 shows an example in which the case where feedforward control is performed by the plate thickness control method according to the embodiment of the present invention is compared with the case where feedforward control is not performed. In FIG. 3, the vertical axis represents the plate thickness, and the horizontal axis represents the position (or time) in the plate longitudinal direction. FIG. 3 (a) shows an example in which the feedforward control by the sheet thickness control method according to the embodiment of the present invention is not performed. I have. On the other hand, FIG. 3B shows an example in the case where feedforward control is performed by the sheet thickness control method according to the embodiment of the present invention when the same temperature fluctuation is applied. Compared with the example of a), the variation of the plate thickness is greatly suppressed. As described above, in the sheet thickness control method according to the embodiment of the present invention, the temperature prediction accuracy can be improved by predicting the longitudinal distribution of the sheet temperature for the next pass using the process data immediately before rolling. . In addition, it becomes possible to predict deformation resistance via temperature during controlled rolling, and it is possible to cope with transformation plasticity. In addition, it is not necessary to compensate for the entire compensation amount by feedforward, and a large permissible range with respect to tracking deviation and load fluctuation prediction error can be secured. In addition, based on the measured data of the rolling load and the roll gap in the two-pass rolling before the next pass and the rolling in the preceding pass, the inlet thickness, the outlet thickness,
Since the plate temperature distribution in the plate longitudinal direction is determined, FF-AG
For C, there is no need to use a gamma-ray thickness gauge close to the rolling mill. In the above embodiment, the sheet thickness control method according to the present invention is used together with the feedback control based on the absolute value AGC, but may be combined with another FB-AGC or may be used alone. Is also good. Also,
If a thickness gauge is already prepared, the entry side thickness and the exit side thickness at the time of rolling in the preceding pass are not calculated as in the above-described embodiment, but the actual thickness may be measured by the thickness gauge. .

[0008]

As described above, in the sheet thickness control method of the present invention, the accuracy of temperature prediction is improved by predicting the longitudinal distribution of the sheet temperature for the next pass using the process data immediately before rolling. Can be. In addition, it becomes possible to predict deformation resistance via temperature during controlled rolling, and it is possible to cope with transformation plasticity. In addition, it is not necessary to compensate for the entire compensation amount by feedforward, and a large permissible range for tracking deviation and load fluctuation prediction error can be secured. In addition, based on the measured data of the rolling load and the roll gap in each of the two-pass rolling before the next pass and the rolling in the preceding pass, the sheet thickness of the incoming side sheet thickness, the outgoing side sheet thickness and the sheet temperature at the time of the rolling of the preceding pass are determined. In the case where the directional distribution is determined, it is not necessary to use a gamma-ray thickness gauge close to a rolling mill for FF-AGC. FIG. 4 shows the difference in effect between the case of only the absolute value AGC and the case of the present invention. Compared to the case of only the absolute value AGC shown in FIG. In this case, it can be seen that the simulation value (thick line) follows the target plate thickness (thin line) without deviation. Further, a tapered target thickness value is used as a delivery-side target thickness value for the next pass, which is used in predicting the rolling direction distribution of the rolling load during the rolling of the next pass.
Thus, the present invention can be applied to any tapered plate. The present invention is also configured using the absolute value AGC using the tapered target value of the thickness. As a result, it is possible to correct the accumulation of errors due to model deviation (change in target plate thickness due to tapered plate shape or the like) that is difficult to delete only by feedforward control.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining a sheet thickness control method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram for explaining an FF-AGC suitable for performing the thickness control method according to the embodiment of the present invention.

FIG. 3 is a diagram showing an example in which sheet thickness control accuracy is compared between a case where the sheet thickness control method according to the embodiment of the present invention is not applied and a case where the method is applied.

FIG. 4 shows a case where the control method according to the present invention is not used;
The graph which shows the difference at the time of using.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... FF-AGC 2 ... FB-AGC 3 ... Reduction device 4 ... Plate 5 ... Finishing rolling machine 6 ... Load cell 7 ... Position meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Akira Kitamura 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Sadao Morimoto Kanazawacho, Kakogawa City, Hyogo Prefecture No. 1 Kobe Steel, Ltd. Kakogawa Works F-term (reference) 4E024 AA07 BB07 CC01 CC02 EE02

Claims (2)

[Claims] In a thickness control method for controlling a thickness of a material to be rolled by feeding forward a rolling position correction amount predicted for a rolling in a next pass, an input side plate at the time of rolling in a preceding pass of the next pass. The distribution in the plate longitudinal direction of thickness, delivery side plate thickness, and plate temperature is determined, and the air cooling component due to the inter-pass time between the previous pass and the next pass is corrected for the distribution of plate temperature in the plate longitudinal direction determined for the previous pass. Predicting the longitudinal distribution of the plate temperature for the next pass, the longitudinal distribution of the plate temperature for the next pass, the longitudinal distribution of the exit thickness for the previous pass, and the target exit thickness for the next pass. On the basis of the,
The rolling direction distribution of the rolling load at the time of rolling in the next pass is predicted, and the rolling position correction amount for the rolling in the next pass is predicted based on the predicted rolling direction distribution of the rolling load for the rolling in the next pass. In addition, a tapered target thickness value is used as a delivery-side target thickness value for the next pass, which is used for predicting a rolling direction distribution of a rolling load in the rolling of the next pass, and the tapered target thickness value is used. A sheet thickness control method characterized by using an absolute value AGC using a combination. 2. A rolling load and a roll gap in each of the rolling before the next pass of the next pass and a rolling in the preceding pass are measured, and based on the actually measured rolling load and the roll gap, the rolling load and the roll gap during the rolling in the preceding pass are measured. 2. The thickness control method according to claim 1, wherein the distribution of the thickness of the inlet side, the thickness of the outlet side, and the temperature of the sheet in the longitudinal direction are determined.