JP2005238310A - Method for controlling thickness in tandem mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the drop of yield due to deviation of thickness generated when performing shear cut while performing thickness control for controlling the thickness on the outlet side of the final N-th stand which comprises a tandem mill to the target thickness. <P>SOLUTION: By this method, when performing the shear cut of a metallic strip on the outlet side of the N-th stand while performing thickness control for controlling the thickness on the outlet side of the final N-th stand which comprises the tandem mill for rolling the metallic strip to the target thickness, the thickness on the outlet side of the (N-1)th stand is controlled at the holding value by operating the roll speed at the (N-2)th stand between the start of the holding state of the set value of the thickness on the outlet side of the (N-1)th stand just before tension on the outlet side of the N-th stand is eliminated by the shear-cut and the completion of the holding state of the set value of the thickness on the outlet side of the (N-1)th stand at the point of time when the tension on the outlet side of the N-th stand is restored. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sheet thickness control method for a tandem rolling mill for rolling a metal strip, and more particularly to a sheet thickness control method for a tandem rolling mill suitable for automatic sheet thickness control in a cold rolling mill for a steel strip.

  In a tandem rolling mill that cold-rolls a hot-rolled wide steel strip at room temperature to produce a thin plate, the thickness of the thin plate, which has been a conventional product, matches the target value, and the entire length of the thin plate Automatic plate thickness control is applied to keep the plate thickness uniform. Also, in that case, automatic tension control is also applied because stable operation is not possible unless the tension acting on the base material (steel strip) to be rolled is kept within the fracture limit during cold rolling. Is normal.

  For these two target values of plate thickness and tension, the two operation amounts of the rotation speed of the work roll (work roll) of the rolling mill and the gap of the work roll (interval between the upper and lower work rolls) are appropriately operated. By doing so, it is possible to simultaneously realize two controls of automatic plate thickness control and automatic tension control.

  FIG. 1 shows an outline of a conventional cold tandem rolling mill in which a plurality of rolling stands are arranged on a straight line, with three of the N-2 stands upstream from the N-th stand at the most downstream side as a representative. Show.

  In FIG. 1, each stand includes a pair of upper and lower work rolls 1 and a backup roll 2, and the steel strip S rolled by the upper and lower work rolls 1 of each stand is sequentially in the left direction indicated by an arrow in the figure. It is designed to be transported.

  In each stand, the work roll 1 is driven by an electric motor 3, and the electric motor 3 can be freely adjusted by a speed control device 4.

  Further, in this tandem rolling mill, the sheet thickness control device 5 is inputted with the sheet thickness measured on the outlet side measured by the sheet thickness detector 6 installed on the outlet side of the Nth stand. The plate thickness control signal is sent from the plate thickness control device 5 to the speed control device 4 of the N-1 stand upstream one stage so that the deviation between the side plate thickness and the target value becomes zero. Thickness setting value) is output, and the control device 4 controls the electric motor 3 that rotationally drives the work roll 1 of the stand.

  As described above, in cold rolling, it is not used for the control of the Nth stand, but the thickness of the outlet side of the final Nth stand is used for controlling the roll speed of the N-1 stand upstream, Patent Document 1 and so on have been implemented conventionally. This is because the Nth stand determines the surface quality (dull pattern, etc.) of the steel strip, so the thickness control using the speed, which is easy to get scratches etc., must be carried out at the N-1 stand. Because.

  Further, a tension detector 7 for measuring the tension between the stands is installed between the rolling stands, and the measured tension value by each detector 7 is input to the tension control device 8 of the downstream stand, The gap between the work rolls is structured such that the opening and closing of the gap can be freely adjusted by a reduction control device 9 driven by hydraulic pressure or an electric motor.

JP-A-7-68305

  Since the steel strip continuous by welding is wound in a coil shape, it is cut (shear cut) to a predetermined length by a shear (not shown) on the left side (exit side) of the Nth stand in FIG. For this reason, the tension between the Nth stand and the take-up reel disappears until the take-up of the steel strip is resumed by another take-up reel.

  However, when the above-described loss of tension occurs when controlling the thickness of the outlet side of the Nth stand by operating the roll speed of the (N-1) th stand, the thickness (target side of the Nth stand) is adjusted from the target. Two off-peaks occur. The section sandwiched between the two places becomes a defective part, resulting in a large yield reduction.

  FIG. 2A illustrates the two peaks A and B accompanying the disappearance of tension in the case of a tandem rolling mill with N = 5.

  The object of the present invention is to reduce the yield due to the deviation of the plate thickness that occurs during shear cutting while performing the plate thickness control to control the outlet plate thickness of the final Nth stand constituting the tandem rolling mill to the target plate thickness. It is to suppress.

  The present invention uses a tandem rolling mill consisting of 5 stands, and when performing shear cutting while performing the plate thickness control for controlling the exit side plate thickness of the final 5th stand constituting the tandem rolling mill to the target plate thickness. The cause of the thickness deviation that occurred was examined in detail.

  As a result, the causes A and B out of the plate thickness shown in FIG. That is, the cause of occurrence of the plate thickness deviation peak A is caused by a decrease in the rolling force of the fifth stand accompanying the disappearance of the tension, while the cause of occurrence of the plate thickness deviation B is based on the detected value of the plate thickness deviation peak A, The reason was that the control was performed in the direction in which the plate thickness decreased toward the fourth stand exit side. The negative peak C in FIG. 2C corresponds to this control.

  The present inventor considered that the decrease in yield can be suppressed by eliminating the peak B and changing the peak deviating from the target from two to one, and has reached the present invention.

  That is, the present invention provides the metal strip on the Nth stand outlet side while performing the plate thickness control for controlling the final plate thickness of the Nth stand constituting the tandem rolling mill for rolling the metal strip to the target plate thickness. When the N-th stand exit side plate thickness set value is held immediately before the N-th stand exit side tension disappears due to the shear cut, the N-th stand exit side tension is restored. In addition, the N-1 stand exit side plate thickness is controlled to the hold value by operating the roll speed of the N-2 stand until the hold state of the N-1 stand exit side plate thickness setting value is finished. The above-mentioned problems are solved by a sheet thickness control method for a tandem rolling mill.

  According to the present invention, the yield reduction due to the deviation of the plate thickness that occurs when shear cutting is performed while performing the plate thickness control to control the exit plate thickness of the final Nth stand constituting the tandem rolling mill to the target plate thickness. Can be suppressed.

  As described with reference to FIG. 1, the plate thickness control for controlling the final plate thickness of the Nth stand constituting the tandem rolling mill to the target plate thickness by operating the roll speed of the (N-1) th stand. When shear cutting is performed on the exit side of the Nth stand while performing the above, a deviation in the thickness of the exit side of the Nth stand occurs.

  In this embodiment, immediately before the Nth stand exit side tension disappears due to shear cutting, a hold state of the N-1th stand exit side plate thickness set value is started.

  For this reason, since it is possible to prevent the target plate thickness on the exit side of the (N-1) th stand from being reduced, the negative peak of the plate thickness set value in the direction of decreasing the plate thickness on the exit side of the (N-1) th stand. Does not occur.

  At the time when the tension on the Nth stand exit side is restored, specifically, the head of the subsequent shear-cut steel strip starts to be wound on the take-up reel, and the take-up reel and the N-th stand exit side When the tension is restored, the hold state of the N-1 stand exit side plate thickness set value is terminated, and the target plate thickness on the N-1 stand exit side is controlled based on the plate thickness detection value on the Nth stand exit side. It returns to the state to do.

  Note that the time point “just before the tension disappears” at which the hold state is started can be set to, for example, the control cycle immediately before the control cycle in which shear cutting is performed. Further, when the tension is restored at the time when the hold state is ended, the Nth stand exit side tension at the start of the hold is stored, and the Nth stand exit side tension is predetermined to the stored Nth stand exit side tension. It can be set as the time of approaching the size of.

  Further, in this embodiment, while the hold state of the N-1th stand exit side plate thickness set value is maintained, the stand exit side plate thickness is set to the target value and the roll of the N-2th stand The speed is controlled to control the held plate thickness. However, in that case, the control system is changed as shown in FIG.

  That is, the outlet side plate thickness actually measured by the plate thickness detector 6 installed on the outlet side of the Nth stand is input to the plate thickness control device 5, and the control signal from the plate thickness control device 5 and the first The exit side plate thickness of the stand actually measured by the plate thickness detector 6 </ b> A installed on the N-1 stand exit side is input to the plate thickness controller 5. Then, the plate thickness control device 5 changes the thicknesses of the measured output side plate thicknesses of the detectors 6 and 6A from the target values of the Nth stand output side and the N-1th stand output side. A plate thickness control signal is output to the speed control device 4 of the N-2 stand, and the control device 4 controls the electric motor 3 that rotationally drives the work roll 1 of the stand.

  Further, a tension detector 7 for measuring the tension between the stands is installed between the rolling stands, and the measured tension value by the detector 7 between the N-1th stand to the Nth stand is the speed of the N-1 stand. The tension measurement value input to the control device 4 and the other detectors 7 between the other stands is input to the tension control device 8 of the downstream stand, and the gap between the work rolls of each stand is hydraulic or electric. The opening / closing is freely adjusted by the driven reduction control device 9.

  An embodiment applied to a tandem rolling mill composed of five rolling mills will be described with reference to FIG.

  In the present embodiment, as in the case of FIG. 2, the thickness control for controlling the final delivery thickness of the fifth stand to the target thickness by manipulating the roll speed of the third tando is performed.

  As described above, when shear cutting is performed and the tension on the exit side of the fifth stand is lost (FIG. 3B), a peak A in which the plate thickness on the exit side of the fifth stand deviates from the target value occurs (FIG. 3). 3 (a), in the present embodiment, the hold state of the fourth stand exit side plate thickness set value was started in the control cycle immediately before the control cycle in which shear cutting is performed (FIG. 3 (c)). The negative peak of the fourth stand outlet side plate thickness setting value does not occur.

  In addition, while maintaining this hold state, the fourth stand outlet side thickness control for operating the roll speed of the third stand is carried out with respect to the held fourth stand outlet side thickness setting value. The fourth stand outlet side plate thickness (not shown) was not disturbed.

  In addition, the 5th stand delivery side tension | tensile_strength (actual value) is preserve | saved at the time of starting a hold state. Then, when the fifth stand exit side tension becomes 98% of the stored fifth stand exit side tension, the hold state of the fourth stand exit side plate thickness set value is terminated (FIG. 3C), Based on the thickness detection value on the stand exit side, the target plate thickness on the fourth stand exit side is controlled to return to the state before the start of holding.

  In the present embodiment, the peak at which the fifth stand exit side plate thickness deviates from the target can be made one location A, and the yield reduction can be significantly suppressed.

  According to the present invention, the yield reduction due to the deviation of the plate thickness that occurs when shear cutting is performed while performing the plate thickness control to control the exit plate thickness of the final Nth stand constituting the tandem rolling mill to the target plate thickness. Therefore, it can be used for rolling production of metal strips including steel strips.

Block diagram showing the main part of the control system of a conventional tandem rolling mill Diagram showing control results by conventional method Diagram showing control results by the method of the present invention The block diagram which shows the principal part of the control system of the tandem rolling mill which can apply this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Work roll 2 ... Backup roll 3 ... Electric motor (motor)
DESCRIPTION OF SYMBOLS 4 ... Speed control device 5 ... Plate thickness control device 6 ... Plate thickness detector 7 ... Tension detector 8 ... Tension control device 9 ... Roll-down control device

Claims (1)

When the metal strip is shear-cut on the exit side of the Nth stand while performing the plate thickness control for controlling the exit plate thickness of the final Nth stand constituting the tandem rolling mill for rolling the metal strip to the target plate thickness,
Just before the N-th stand exit side tension disappears due to the shear cut, the N-1 stand exit side plate thickness set value starts to be held, and when the N-th stand exit side tension is restored, the N-th stand exit side tension is restored. The roll thickness of the (N-2) th stand is operated to control the (N-1) th stand output side plate thickness to the hold value until the hold state of the one stand exit side plate thickness set value is finished. Thickness control method for tandem rolling mill.

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