JP4700444B2 - Thickness control method when changing strip thickness of rolling mill - Google Patents

Description

  The present invention relates to a sheet thickness control method when changing the sheet thickness of a rolling mill in hot or cold conditions.

  When changing the running plate thickness with a rolling mill, it is necessary to change the roll gap of the rolling mill near the connection point between the preceding steel plate and the following steel plate. Conventionally, the roll gap setting value of the succeeding steel sheet is obtained by calculation, and as shown in the upper part of FIG. 1, roll gap control is performed so that the roll gap becomes this set value when the running plate thickness change starts. It was. However, the roll gap setting calculation has unavoidable errors due to actual material fluctuations of the rolled steel sheet, off-gauge contamination in the previous process, elastic deformation of the steel sheet, etc., and does not necessarily match the target thickness of the subsequent steel sheet. There were many things.

  In the rolling mill, AGC (automatic sheet thickness control) is always operating. For this reason, the roll gap setting error is corrected by AGC, and the roll gap is finally adjusted to match the target plate thickness of the succeeding steel plate while repeating hunting. However, as shown in the lower part of FIG. 1, a long plate thickness off gauge was generated until the target plate thickness of the succeeding steel plate was reached.

In order to solve this problem, Patent Document 1 proposes a plate thickness control method in which a monitor AGC of the entire rolling mill and a gauge meter AGC based on proportional-integral control based on the rolling load of each roll stand are combined. Patent Document 2 proposes a plate thickness control method that shortens a plate thickness off gauge generation section while correcting a roll gap setting error.
JP 60-177908 A Japanese Patent Laid-Open No. 11-226619

  However, none of the above-described conventional techniques can be a fundamental measure for minimizing the occurrence of sheet thickness off gauge. For example, when the gauge meter AGC is used, there is an inevitable plate thickness back calculation error due to a prediction error of mill rigidity, and when the proportional integral control is used, a sufficient off-gauge reduction effect cannot be obtained due to control overshoot. In the case of a tandem rolling mill, a monitor AGC using a thickness gauge on the rear surface of the entire rolling mill is generally used. Therefore, it is difficult to reduce the off gauge below the length corresponding to the distance.

  Accordingly, an object of the present invention is to provide a sheet thickness control method at the time of changing the sheet thickness of a rolling mill that can minimize the influence of overshoot in roll gap control and minimize the occurrence of sheet thickness off gauge. is there.

  As a result of intensive studies to solve the above-mentioned problems, the inventor does not set and control the target value of the roll gap, but the roll gap is open or closed at the start of the change of the running plate thickness. Alternatively, the roll gap opening or closing operation is started by setting only the direction, and the roll gap is reached when the subsequent steel plate thickness reaches the target plate thickness or a thickness within a predetermined error range with respect to the target plate thickness. It was found that the off-gauge generation is extremely reduced by stopping the operation and starting the monitor AGC using the stand rear surface thickness gauge.

The invention of claim 1 made on the basis of the above knowledge is the electric reduction in which the thickness of the succeeding steel plate is measured by mass flow calculation using the stand entrance side plate thickness meter, the entrance side plate speed meter, and the exit side plate speed meter. When changing the running plate thickness of a rolling mill of the type , the roll gap setting operation sets only the operation direction and operates in the operation direction simultaneously with the start of the running plate thickness change. The roll gap setting operation is stopped when the plate thickness is reached, and the plate thickness is controlled by AGC. In the invention of claim 2, the thickness of the following steel plate is measured by mass flow calculation using the stand entry side thickness meter, the entry side plate speed meter, and the exit side plate speed meter. When changing the plate thickness, the roll gap setting operation sets only the operation direction and operates in the operation direction simultaneously with the start of the running plate thickness change, immediately before the plate thickness of the succeeding steel plate reaches the target plate thickness. The roll gap setting operation is stopped, and the sheet thickness is controlled by AGC. During the roll gap setting operation, it is preferable to turn off the thickness control by AGC .

According to the first aspect of the present invention, when the thickness of the succeeding steel plate reaches the target plate thickness, the roll gap setting operation is stopped and the process shifts to plate thickness control by AGC. The thickness of the succeeding steel plate can be quickly controlled to the target thickness while avoiding the above. According to the invention of claim 2, since the roll gap setting operation is stopped immediately before the thickness of the succeeding steel plate reaches the target plate thickness, soft landing of the roll gap is possible. In this case, it is preferable to stop the roll gap setting operation when the plate thickness of the succeeding steel plate reaches a range of ± 5% of the target plate thickness. Furthermore, according to the invention of claim 3, the overshoot due to the overlap between the roll gap control and the AGC is eliminated, and the occurrence of the plate thickness off gauge can be minimized. Furthermore, according to the present invention , the timing at which the thickness of the succeeding steel plate reaches the target thickness can be detected without delay, which is preferable.

Embodiments of the present invention will be described below.
FIG. 2 is a conceptual diagram showing an embodiment of the present invention, and shows a state where a steel plate is continuously rolled cold or hot by a rolling mill equipped with a plurality of rolling stands. The first stand has a mass flow thickness calculator that calculates the rolling speed on the entrance side of the stand measured by the entrance side thickness meter 6, the entrance side plate speed meter 7, and the exit side plate speed meter 8 and the thickness on the entrance side of the stand. 1 is installed, and the roll gap during steady operation is controlled by the AGC 2 in conjunction with the roll gap to maintain the target plate thickness. The thickness measurement is not necessarily limited to the mass flow thickness calculation, and an X-ray thickness gauge or the like may be used. However, the mass flow plate thickness calculation is preferable because the plate thickness directly under the rolling roll is calculated and measured, and control delay is reduced. The reduction means may be either an electric reduction type or a hydraulic reduction type, but the present invention is particularly effective in the case of an electric reduction type that requires time to change the reduction.

  When changing the running plate thickness by connecting the preceding steel plate and the succeeding steel plate with different plate thicknesses, the roll gap target value corresponding to the plate thickness of the succeeding steel plate is calculated, and the running schedule changing device 3 performs the running. Simultaneously with the start of the change of the sheet thickness, the reduction changing device 4 starts the roll gap setting operation. Conventionally, as shown in FIG. 1, the roll gap has been changed to the target value of the subsequent steel plate roll gap, whereas in the present invention, the roll gap setting operation is performed without setting the absolute value of the roll gap. Only, and operates in the set direction at the same time as the start of the plate thickness change. That is, when the thickness of the succeeding steel plate is thin, the roll gap is closed as shown in the upper part of FIG. 3, and in the opposite case, the roll gap is opened.

  The rolling change finishing device 5 compares the plate thickness of the succeeding steel plate calculated by the mass flow plate thickness calculating device 1 with the target plate thickness, and stops the roll gap setting operation by the rolling change device 4 when the target plate thickness is reached. Change to plate thickness control by AGC2. After that, the monitor AGC is left to the control operation for maintaining the thickness of the succeeding steel plate at the set thickness as in the conventional case. With this method, as shown in the lower part of FIG. 3, the thickness of the succeeding steel plate quickly converges to the target value, and the occurrence of the plate thickness off gauge can be minimized.

  In the invention of claim 1 described above, the roll gap setting operation is stopped when the plate thickness of the succeeding steel plate reaches the target plate thickness. However, in the invention of claim 2, the plate thickness of the succeeding steel plate is the target plate thickness. Immediately before reaching, the rolling change end device 5 stops the roll gap setting operation and performs the plate thickness control by the monitor AGC. Specifically, it is preferable to stop the roll gap setting operation when the plate thickness of the succeeding steel plate reaches a range of ± 5% of the target plate thickness. Thus, by shifting to the plate thickness control by the monitor AGC immediately before reaching the target plate thickness, the disturbance at the time of control switching can be suppressed, and the soft landing of the roll gap can be achieved.

  The plate thickness control by the monitor AGC may be continued even during the running plate thickness change time, but if the plate thickness control by the monitor AGC is paralleled with the roll gap setting operation, an extra disturbance is introduced into the roll gap setting operation. There is a fear. Therefore, it is preferable to turn off the monitor AGC during the roll gap setting operation as shown in the lower part of FIG. As a result, overshoot after reaching the target plate thickness can be prevented, and the occurrence of the plate thickness off gauge can be further shortened.

  As described above, according to the plate thickness control method when changing the running plate thickness according to the present invention, the overgap of the roll gap setting operation is prevented and the plate thickness of the succeeding steel plate is quickly converged to the target plate thickness. Can be made. As a result, the generation amount of the plate thickness off gauge can be reduced to about half of the conventional one. FIG. 4 is a graph comparing the results of off-gauge length in the case of steel plates having a thickness tolerance of ± 5% with the results in the conventional method (this is set to 1), and the effect of the present invention is clear. .

It is a graph which shows the time change of the roll gap opening degree and steel plate board thickness in a conventional method. It is a conceptual diagram which shows embodiment of this invention. It is a graph which shows the time change of the roll gap opening degree and steel plate board thickness in this invention method. It is the graph which compared the track record of the off gauge length with the conventional method.

Explanation of symbols

1 Mass flow thickness calculator 2 AGC
3 Inter-run schedule change device 4 Rolling change device 5 Rolling change end device 6 Incoming plate thickness meter 7 Incoming plate speedometer 8 Outlet plate speedometer

Claims (3)

When measuring the plate thickness of the subsequent steel plate, changing the running plate thickness of the electric rolling type rolling mill that performs mass flow calculation using the stand entry side plate thickness meter, entry side plate speed meter, and exit side plate speed meter , The roll gap setting operation sets only the operation direction and operates in the operation direction simultaneously with the start of the change of the running plate thickness. When the thickness of the subsequent steel plate reaches the target plate thickness, the roll gap setting operation is stopped A sheet thickness control method at the time of changing the sheet thickness of the rolling mill, wherein the sheet thickness is controlled by AGC. When measuring the plate thickness of the subsequent steel plate, changing the running plate thickness of the electric rolling type rolling mill that performs mass flow calculation using the stand entry side plate thickness meter, entry side plate speed meter, and exit side plate speed meter , The roll gap setting operation sets only the operation direction and operates in the operation direction at the same time as the change of the running plate thickness is started. A sheet thickness control method at the time of changing the sheet thickness of the rolling mill, wherein the sheet thickness is controlled by AGC.   3. A method for controlling the thickness of a rolling mill when changing the running thickness of the rolling mill according to claim 1, wherein the thickness control by AGC is turned off during the roll gap setting operation.

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