Controlling a strip tension during the flexible rolling of metal strip

Abstract

An apparatus for controlling a strip tension during flexible rolling of metal strip comprises a roll arrangement with at least one dancer roll, the position of said dancer roll being adjustable for controlling the strip tension of the metal strip, at least one hydraulic drive coupled to the dancer roll for adjusting the dancer roll, a hydraulic tank for hydraulic fluid, which is fluidly connected to the hydraulic drive via a hydraulic supply line, a controllable valve arrangement between the hydraulic tank and the hydraulic drive for controlling the hydraulic drive, a hydraulic pump with which the hydraulic drive is supplied with hydraulic fluid from the hydraulic tank, and at least one hydraulic pressure accumulator for temporarily storing hydraulic fluid previously delivered by the hydraulic pump, the hydraulic pressure accumulator being arranged between the hydraulic pump and the valve arrangement, wherein a pressure sensor is arranged in the hydraulic drive for determining the hydraulic pressure.

Claims

1. A method for controlling a strip tension during flexible rolling of metal strip in a rolling mill with a dancer roll that is adjusted with a hydraulic drive, and further having a controllable valve arrangement disposed between a hydraulic pump and the hydraulic drive, and at least one hydraulic pressure accumulator arranged between the hydraulic pump and the valve arrangement, comprising the following steps: measuring a hydraulic pressure at the hydraulic drive, determining the strip tension in the metal strip based on the measured hydraulic pressure at the hydraulic drive; controlling the valve arrangement depending on the determined strip tension of the metal strip, storing hydraulic fluid in the at least one hydraulic pressure accumulator, feeding, at least partially, the hydraulic fluid previously stored in the at least one hydraulic pressure accumulator to the hydraulic drive for a short-term supply of hydraulic fluid, determining a position of the dancer roll of at least one strip guiding unit for coiling or uncoiling the metal strip, and varying a speed of a reel of the at least one strip guiding unit depending on the position of the dancer roll.

2. A method for controlling a strip tension during flexible rolling of metal strip in a rolling mill with a dancer roll that is adjusted with a hydraulic drive, and further having a controllable valve arrangement disposed between a hydraulic pump and the hydraulic drive, and at least one hydraulic pressure accumulator arranged between the hydraulic pump and the valve arrangement, comprising the following steps: measuring a hydraulic pressure at the hydraulic drive, determining the strip tension of the metal strip based on the measured hydraulic pressure at the hydraulic drive, controlling the valve arrangement depending on the strip tension of the metal strip, storing hydraulic fluid in the at least one hydraulic pressure accumulator, feeding, at least partially, the hydraulic fluid previously stored in the at least one hydraulic pressure accumulator to the hydraulic drive for a short-term supply of hydraulic fluid, determining a roll gap setting of a roll stand adjacent the roll arrangement; and controlling the valve arrangement in addition to the strip tension of the metal strip based on the roll gap.

3. An apparatus for controlling a strip tension during flexible rolling of metal strip, the apparatus comprising: a roll arrangement with at least one dancer roll, a position of said dancer roll being adjustable for controlling the strip tension of the metal strip, at least one hydraulic drive coupled to the dancer roll for adjusting the dancer roll, a hydraulic tank being fluidly connected to the hydraulic drive via a hydraulic supply line delivering hydraulic fluid to the hydraulic drive from the hydraulic tank and via a hydraulic return line returning hydraulic fluid from the hydraulic drive to the hydraulic tank, a hydraulic pump for supplying hydraulic fluid from the hydraulic tank to the hydraulic drive, a controllable valve arrangement disposed in the hydraulic supply line between the hydraulic pump and the hydraulic drive for controlling the hydraulic drive and disposed in the hydraulic return line between the hydraulic drive and the hydraulic tank, a pulsation damper arranged in the hydraulic return line between the controllable valve arrangement and the hydraulic tank, at least one hydraulic pressure accumulator for temporarily storing hydraulic fluid previously delivered by the hydraulic pump, the hydraulic pressure accumulator being arranged between the hydraulic pump and the valve arrangement, and a pressure sensor for determining a hydraulic pressure arranged in the hydraulic drive.

4. The apparatus according to claim 3, further comprising a compensation tank arranged downstream of the pulsation damper.

Description

BRIEF SUMMARY OF THE DRAWING

(1) One exemplary embodiment of a rolling mill is explained in more detail below with reference to a drawing.

(2) FIG. 1 schematically shows a rolling mill with hydraulic adjustment device in side view.

DESCRIPTION WITH REFERENCE TO THE DRAWING

(3) As seen in FIG. 1, a roll stand 2, in which two superimposed working rolls 3, 4 and two supporting rolls 5, 6 lying in vertical alignment with the working rolls 3, 4, is installed on a foundation 1. An adjustable and controllable roll gap 7 is formed between the working rolls 3, 4, through which a metal strip 8 passes from left to right in a production direction P in the illustration shown. The rolling mill may be a reversing mill in which, after a coil has passed through in the direction of production P, as shown in the FIGURE, a next coil passes through the rolling mill in the opposite direction.

(4) In the embodiment shown, the metal strip 8 comes from a first reel device 9 having a left-turning first reel 10 from which the metal strip 8 is uncoiled over the lower side of the first reel 10. For storing a certain length of the metal strip 8 and for introducing a strip tension into the metal strip 8, the metal strip 8 runs from the first reel device 9 in the direction of production P into a first roll arrangement 11 in the form of a double roll arrangement comprising a movable upper dancer roll 12 and a fixed lower roll 13. A horizontal double arrow indicates that the dancer roll 12 can be moved horizontally in the first roll arrangement 11 in a controlled manner. In principle, other orientations, such as a vertical or oblique adjustment, and other forms of movement, such as a swivel movement, are also conceivable. In the illustrated embodiment, a movement of the dancer roll 12 changes the length of the loop of metal strip 8 between an entry into the first roll arrangement 11 and an exit from the first roll arrangement 11.

(5) The lower, in principle stationary, roll 13 is to be pivoted by means of a rocker 14 from its operating position (solid representation 13) to an insertion position (dashed representation 13′) over a strip line 21. The dashed line indicates the insertion position of the stationary roll 13, in which the metal strip 8 can be inserted into the roll stand 2 along the strip line 21, which is also shown dashed. When the metal strip 8 is fixed for reeling, the roll 13 swivels back to its operating position shown with a solid line.

(6) Downstream of the roll stand 2 in the direction of production, and thus to the right of the roll stand 2, a second reel device 15 for coiling the metal strip 8 is shown, which has a left-turning rotating second reel 16 that coils the rolled metal strip 8 over the lower side. Between the roll stand 2 and the second reel device 15 is another second roll arrangement 17 for storing metal strip and applying a strip tension, comprising a movable upper dancer roll 18 and a stationary lower roll 19.

(7) In principle, the first reel 10 and the second reel 16 can be designed left-turning or right-turning, and the metal strip 8 can be uncoiled or coiled from above or from below.

(8) It is indicated by a horizontal double arrow that the dancer roll 18 is displaceable in a controlled manner relative to the stationary roll 19 in the second roll arrangement 17. Again, analogous to the dancer roll 12 of the first roll arrangement 11, it is conceivable that the dancer roll 18 is displaced or pivoted in a different direction. Adjusting the dancer roll 18 of the second roll arrangement 17 changes the length of the loop of metal strip 8 between an entry into the second roll arrangement 17 and an exit from the second roll arrangement 17.

(9) With dashed line, the roll 19 is shown in an insertion position 19′ over a strip line 21′ pivoted by means of a rocker 20 from its operating position 19, the insertion position serves to insert a beginning of the strip along the strip line 21, again shown with dashed line. When the beginning of the strip is fixed on the second reel 16, the roll 19 swivels back into its operating position 19 shown solid.

(10) Thus, by adjusting the dancer rolls 12, 18, the tensile force within the metal strip 8 can be varied. Additional tensile increase results when at least one of the rolls 12, 13, 18, 19 is provided with braking means and/or driving means not shown.

(11) In FIG. 1, a hydraulic drive for the dancer roll 18 of the second roll arrangement 17 is schematically shown, wherein the hydraulic drive comprises a double-acting hydraulic cylinder 22. The dancer roll 18 is connected to a piston rod 23 adjustably disposed in a cylinder 24 of the hydraulic cylinder 22, and is adjustable in position by the piston rod 23. The hydraulic cylinder 22 is actuated by a hydraulic actuating arrangement 25.

(12) The dancer roll 12 of the first roll arrangement 11 is adjustable, as the dancer roll 18 of the second roll arrangement 17, via a hydraulic cylinder and a hydraulic actuating arrangement, the hydraulic cylinder and the hydraulic actuating arrangement for the dancer roll 12 of the first roll arrangement 11 not being shown for clarity. Therefore, the hydraulic actuating arrangement 25 for the second roll arrangement 17 will also be described below as representative of the hydraulic actuating arrangement for the first roll arrangement 11.

(13) A hydraulic tank 27, in which hydraulic fluid is stored, is located in a mill cellar 26 below the level of the foundation 1. Furthermore, a hydraulic pump 28 is arranged in the mill cellar 26. The hydraulic pump 28 is fluidly connected to the hydraulic tank 27 via a hydraulic line 37 and delivers hydraulic fluid from the hydraulic tank 27 towards the hydraulic cylinder 22. In principle, multiple hydraulic pumps 28 may also be provided.

(14) The hydraulic cylinder 22 is in turn fluidly connected to the hydraulic tank 27 on the outlet side.

(15) For controlling the hydraulic cylinder 22, a controllable valve arrangement 29 is arranged between the hydraulic cylinder 22 and the hydraulic pump 28, which is fluidly connected to the hydraulic pump 28 via a supply line 38 and which comprises a hydraulic servo valve 30. The valve arrangement is further connected to the hydraulic tank 27 by a return line 39. The servo valve 30 can be controlled such that the supply line 38 from the hydraulic pump 28 is blocked, just as the return line 39 from the hydraulic cylinder 22 to the hydraulic tank 27 can be blocked. Further, the supply line 38 may optionally be fluidly connected to a first cylinder chamber 31 or a second cylinder chamber 32 of the hydraulic cylinder 22, with the return line 39 to the hydraulic tank 27 being connected to the respective other of the two cylinder chambers 32, 31. Thus, the piston rod 23 can be adjusted in the direction of the indicated double arrow.

(16) In order to enable the hydraulic cylinder 22 and thus the dancer roll 18 to be adjusted as quickly as possible, a hydraulic pressure accumulator 33 is arranged in the supply line 38 between the hydraulic pump 28 and the valve arrangement 29 in order to temporarily store hydraulic fluid previously delivered by the hydraulic pump 28 and to deliver it to the hydraulic cylinder 22 as required. In this case, the hydraulic pressure accumulator 33 is preferably arranged at a level of the foundation 1 or above and, moreover, is provided as close as possible to the hydraulic cylinder 22 in order to avoid line losses. In principle, it is also conceivable that several hydraulic pressure accumulators 33 are arranged in the supply line 38.

(17) A pulsation damper 34 is arranged in the return line 39 between the valve arrangement 29 and the hydraulic tank 27, although in principle several pulsation dampers 34 may be provided. The pulsation damper 34 serves to equalize the pressure fluctuations in the return line from the valve arrangement 29 to counteract cavitations. In addition, a compensation tank 35 is provided between the pulsation damper 34 and the hydraulic tank 27 to ensure that hydraulic fluid can flow from the compensation tank 35 into the hydraulic tank 27 without pressure so that cavitation cannot occur in this region of the hydraulic line. The pulsation damper 34 is arranged as close as possible to the hydraulic cylinder 22. In principle, however, it is also conceivable that no pulsation damper is provided in the return line 39.

(18) A force sensor in the form of a tension load cell 35 is provided between the hydraulic cylinder 22 and the coupling thereof to the dancer roll 18. This can be used to determine the tensile and compressive forces occurring between the hydraulic cylinder 22 and the dancer roll 18, so that the strip tension within the metal strip 8 can be inferred from this.

(19) Further, the hydraulic cylinder 22 includes a pressure sensor 36 for determining the hydraulic pressure within the second cylinder chamber 32. This determined pressure can also be used to infer the strip tension in the metal strip 8. The pressure sensor may also be located in the first cylinder chamber 31. Alternatively, multiple pressure sensors may be provided, for example one for the first cylinder chamber 31 and one for the second cylinder chamber 32 or for the hydraulic supply lines to the hydraulic cylinder 22.

(20) The hydraulic cylinder 22 is further provided with an integrated displacement measuring system 40, which can be used to determine the position of the dancer roll 18. The displacement measuring system 40 may alternatively be provided on another component that is moved with the dancer roll 18. The position of the dancer roll 18 makes it possible to determine whether the dancer roll 18 is already in an end position of its adjustment travel, in order to be able to adjust the speed of the metal strip 8 if necessary. By changing the speed of the metal strip 8, for example by changing the reel speed, the position of the dancer roll 18 can be changed. If the reel speed of the second reel 16 is increased, more metal strip 8 tends to be discharged from the second roll arrangement 17, so that a less long loop of metal strip 8 has to be stored in the second roll arrangement 17 to achieve a constant strip tension. In the embodiment shown, this is achieved by moving the dancer roll 18 to the left. Thus, when the dancer roll 18 of the second roll arrangement 17 is in an end position in the illustration on the right, the speed of the second reel 16 must be increased to tend to move the dancer roll 18 back to a center position. When the dancer roll 18 has reached a left end position, the speed of the second reel 16 must be reduced accordingly.

LIST OF REFERENCE NUMBERS

(21) 1 Foundation 2 Roll stand 3 Working roll 4 Working roll 5 Supporting roll 6 Supporting roll 7 Roll gap 8 Metal strip 9 First reel device 10 First reel 11 First roll arrangement 12 Dancer Roll 13 Roll 14 Rocker 15 Second reel device 16 Second reel 17 Second roll arrangement 18 Dancer Roll 19 Roll 20 Rocker 21 Strip line 22 Hydraulic cylinder 23 Piston rod 24 Cylinder 25 Actuating arrangement 26 Mill cellar 27 Hydraulic tank 28 Hydraulic pump 29 Valve arrangement 30 Servo valve 31 First cylinder chamber 32 Second cylinder chamber 33 Hydraulic pressure accumulator 34 Pulsation damper 35 Tension load cell 36 Pressure sensor 37 Hydraulic line 38 Supply line 39 Return line 40 Displacement measuring system