Mill stand

Abstract

A device for stabilizing of working rollers and back-up rollers of a mill stand that has, for each bending block, first hydraulic pressing units being arranged upstream of the working roller, each first hydraulic pressing unit having a piston with a piston rod and a pressure plate, the piston and the piston rod being integrated in the bending block and the pressure plate being pressable against a working roller chock, and for each stand column, at least one second hydraulic pressing unit, the second hydraulic pressing unit being arranged downstream of the back-up roller and having a piston with a piston rod and a pressure plate, the piston and the piston rod being integrated in the stand column and the pressure plate being pressable against the back-up roller chock, and a first hydraulic pressing unit containing a first oscillation absorber.

Claims

1. A mill stand having a device for stabilizing the working rollers and back-up rollers of the mill stand while a rolling stock is being rolled to form a strip, the mill stand comprising: an upper and a lower working roller for rolling the rolling stock to form the strip, an upper and a lower back-up roller for supporting the working rollers in the mill stand, an operator-side and a drive-side mill stand housing, an operator-side and a drive-side working roller chock, the working rollers being rotatably mounted in the working roller chocks, operator-side and drive-side bending blocks for deflecting the working rollers, an operator-side and a drive-side back-up roller chock, the back-up rollers being rotatably mounted in the back-up roller chocks, wherein, for each bending block, there are at least two first hydraulic pressing units for stabilizing the working rollers in the mill stand housing, the first hydraulic pressing units being arranged upstream of the working roller in the transport direction of the rolling stock (TR), each first hydraulic pressing unit comprising a piston with a piston rod and a pressure plate, the piston and the piston rod being integrated in the bending block and the pressure plate being able to be pressed hydraulically against a working roller chock; for each mill stand housing, there is at least one second hydraulic pressing unit for stabilizing the back-up rollers in the mill stand housing, the second hydraulic pressing unit being arranged downstream of the back-up roller in the transport direction of the rolling stock (TR), the second hydraulic pressing unit comprising a piston with a piston rod and a pressure plate, the piston and the piston rod being integrated in the mill stand housing and the pressure plate being able to be pressed hydraulically against the back-up roller chock, at least one of the first hydraulic pressing units contains a first oscillation absorber, which reduces pressure oscillations that occur in a pressure chamber of the at least one first hydraulic pressing unit.

2. The mill stand as claimed in claim 1, wherein at least one of the second hydraulic pressing units contains a second oscillation absorber, which reduces pressure oscillations that occur in a pressure chamber of the at least one of the second hydraulic pressing unit.

3. The mill stand as claimed in claim 2, wherein the first or second oscillation absorber is in the form of a Helmholtz resonator having a longitudinal channel forming a hydraulic inductance (L) and a volume forming a hydraulic capacity (C), the pressure chamber of one of the first hydraulic pressing units or the pressure chamber of one of the second hydraulic pressing units being connected to the longitudinal channel and the longitudinal channel being connected to the volume of the Helmholtz resonator.

4. The mill stand as claimed in claim 3, wherein the longitudinal channel has a settable throttle, with the result that the damping of the first or second oscillation absorber can be set.

5. The mill stand as claimed in claim 2, wherein the first or second oscillation absorber is in the form of a λ/4 resonator, the pressure chamber of one of the first hydraulic pressing units or the pressure chamber of one of the second hydraulic pressing units being connected to the λ/4 resonator.

6. The mill stand as claimed in claim 2, wherein the first or second oscillation absorber is in the form of a spring-mass oscillator.

7. The mill stand as claimed in claim 2, wherein 0.75*fT≤fC≤1.33*fT, wherein fC is a characteristic frequency occurring in the mill stand, and fr is a natural frequency of the first or second oscillation absorber.

8. The rolling stand as claimed in claim 2, wherein the piston rod of one of the first hydraulic pressing units and/or one of the second hydraulic pressing units has a first longitudinal bore being connected to a piston-side pressure chamber and a second longitudinal bore being connected to a rod-side pressure chamber.

9. The mill stand as claimed in claim 1, wherein the piston rod of one of the first hydraulic pressing units and/or one of the second hydraulic pressing units has a first longitudinal bore being connected to a piston-side pressure chamber and a second longitudinal bore being connected to a rod-side pressure chamber.

10. The mill stand as claimed in claim 1, wherein the piston rod of at least one of the first hydraulic pressing units is supported on one of the bending blocks and/or wherein the piston rod of at least one of the second hydraulic pressing units is supported on one of the mill stand housings.

11. A method for stabilizing the working rollers and back-up rollers of a mill stand, while a rolling stock is being rolled to form a strip in the mill stand, in particular by means of a device for stabilizing the working rollers and back-up rollers as claimed in claim 1, comprising the following method steps: setting a rolling gap in the vertical direction between the lower and the upper working roller; stabilizing the working rollers by applying a first hydraulic pressure to the first hydraulic pressing units, the first hydraulic pressing units being pressed against the working roller chocks; stabilizing the back-up rollers by applying a second hydraulic pressure to the second hydraulic pressing units, the second hydraulic pressing units being pressed against the back-up roller chocks; absorbing pressure oscillations in a pressure chamber of the first hydraulic pressing units by means of multiple first oscillation absorbers, absorbing pressure oscillations in a pressure chamber of the second hydraulic pressing unit by means of multiple second oscillation absorbers.

12. The method as claimed in claim 11, wherein the mill stand carries out three rolling passes in a finishing train and the first oscillation absorbers and a second oscillation absorbers are set to a natural frequency of between f.sub.Low and f.sub.High TABLE-US-00002 nth rolling pass f.sub.Low [Hz] f.sub.High [Hz] 1 22 40 2 48 87 3 75 133.

13. The method as claimed in claim 12, wherein a pressing force of at least one of the first hydraulic pressing units during operation is set by way of a pressure regulator with a continuously adjustable valve.

14. The method as claimed in claim 11, wherein a pressing force of at least one of the first hydraulic pressing units during operation is set by way of a pressure regulator with a continuously adjustable valve.

15. The method as claimed in claim 14, wherein a pressing force of at least one of the second hydraulic pressing units during operation is set by way of a pressure regulator with a continuously adjustable valve.

16. The method as claimed in claim 11, wherein a pressing force of at least one of the second hydraulic pressing units during operation is set by way of a pressure regulator with a continuously adjustable valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-described properties, features and advantages of the present invention and the manner in which they are achieved will become clearer and more clearly understandable in connection with the following description of multiple drawings, in which:

(2) FIG. 1 shows a partial sectional front view of a mill stand with a device for stabilizing the working rollers and back-up rollers,

(3) FIG. 2 shows a partially sectional illustration along the line A-A from FIG. 1,

(4) FIG. 3 shows a partially sectional illustration along the line B-B from FIG. 1,

(5) FIG. 4 shows a sectional illustration of a working roller chock with a first hydraulic pressing unit,

(6) FIG. 5 shows an axonometric illustration of the bending block with four first hydraulic pressing units from FIG. 4,

(7) FIG. 6 shows a hydraulic layout for the first hydraulic pressing unit from FIG. 4,

(8) FIG. 7 shows an axonometric illustration of a mill stand housing with a second hydraulic pressing unit,

(9) FIG. 8 shows a hydraulic layout for the second hydraulic pressing unit from FIG. 7, and

(10) FIG. 9 shows a functional layout for a first hydraulic pressing unit in the retracted and extended state.

DESCRIPTION OF THE EMBODIMENTS

(11) FIG. 1 schematically shows a front view of a mill stand 30, specifically the third hot-mill stand F3, of a finishing train of an Arvedi ESP plant. The rolling stock 31 of steel is hot rolled to form a strip 32 in the rolling gap between the working rollers 1 of the mill stand 30. Each working roller 1 is rotatably mounted in two working roller chocks 4. The working rollers 1 are supported on back-up rollers 2. It is also the case that each back-up roller 2 is rotatably mounted in two back-up roller chocks 5. The working roller chocks 4 and the back-up roller chocks 5 are displacable in the vertical direction in the mill stand housings 3. The rolling gap between the two working rollers 1 is set by at least one hydraulic cylinder 33. The working rollers 1 can be deflected by way of the bending blocks 4a, which are arranged between the mill stand housings 3 and the working roller chocks 4. This makes it possible, among other things, to change the profile and/or the evenness of the rolled strip 32. Bending blocks are known in principle from the prior art. In order to enhance clarity, in FIGS. 1 and 3 the bending blocks 4a are illustrated without the hydraulic cylinders for deflecting the working rollers 1. To reduce stand oscillations in the mill stand 3 or to stabilize the working rollers 1 and the back-up rollers 2 while the rolling stock 31 is being rolled to form the strip 32, the first hydraulic pressing units 6 are pressed against the working roller chocks 4. The first hydraulic pressing units 6 are integrated in the bending block 4a illustrated on the left-hand side and are arranged on the run-in side with respect to the transport direction TR of the rolling stock 31. The second hydraulic pressing units can be pressed against the back-up roller chocks 5. The second hydraulic pressing units 7 are integrated in the mill stand housing 3 and are arranged on the run-out side with respect to the transport direction TR of the rolling stock 31.

(12) FIGS. 2 and 3 respectively show a partial sectional illustration along the sectional line A-A (FIG. 2) and along the sectional line B-B (FIG. 3).

(13) It is clear from FIG. 2 that the back-up roller 2 is mounted in the mill stand housings 3 by way of two back-up roller chocks 5. The back-up roller chocks 5 can be braced against the mill stand housings 3 by the second hydraulic pressing units 7. The second hydraulic pressing units 7 mechanically stabilize the back-up rollers 2.

(14) In a similar way, FIG. 3 shows that the bending blocks 4a can be braced against the working roller chocks 4 by two respective first hydraulic pressing units 6. The first hydraulic pressing units 6 mechanically stabilize the working rollers 1.

(15) FIG. 4 shows a sectional illustration of a first hydraulic pressing unit 6. In order to be able to introduce the compressive forces of the pressure plate 10 directly into the bending block 4a, and for reasons of compactness, the piston rod 9 and the piston 8 of the first hydraulic pressing unit 6 are integrated in the bending block 4a. The piston rod 9 has for example a diameter D1 of 60 mm, the piston 8 has a diameter D2 of 80 mm and the pressure plate 10 has a diameter D3 of 250 mm. The first hydraulic pressing unit 6 has four ports: an oil supply for the piston side 34, an oil supply for the rod side 35, a leakage port 36, and a lubricant supply 37. The oil supply for the piston side 34 leads into a first longitudinal bore in the piston rod 9, which is connected to the piston-side pressure chamber of the first hydraulic pressing unit 6. The oil supply for the rod side 35 leads into a second longitudinal bore in the piston rod 9, which is connected to the rod-side pressure chamber of the first hydraulic pressing unit 6. The leakage port 36 ensures that any leakages from the first hydraulic pressing unit 6 are withdrawn. Lastly, the lubricant supply 37 ensures that the pressure plate 10 is supplied with enough lubricant. The specified dimensions of the first hydraulic pressing unit 6 serve only for illustrative purposes and are not limiting. The first hydraulic pressing unit 6 can apply a stroke of 6 mm and a maximum clamping force of 125 kN. Each bending block 4a on the run-in side has four first hydraulic pressing units 6 (see FIG. 5).

(16) Except for the specified diameters D1 to D3, the specified stroke and the maximum clamping force, the structure of a second hydraulic pressing unit is identical to the structure of a first hydraulic pressing unit 6.

(17) FIG. 5 shows an exterior view of a bending block 4a with four first hydraulic pressing units 6. The bending block 4a is fixed to the mill stand housing 3.

(18) FIG. 6 shows a hydraulic layout for the actuation of two first hydraulic pressing units 6, which are activated by way of a switching valve 39. The proportional/regulating or servo valve (valves of this type are also referred to as continuously adjustable valves) 38 has the function of setting a particular pressure level on the piston side of the two first hydraulic pressing units 6, with the result that a working roller chock is pressed against a working roller chock with a defined pressing force. The two pressure limiting valves 41 serve to limit the maximum pressure. Lastly, it can be seen from FIG. 6 that the piston sides of the two first hydraulic pressing units 6 are connected to a first oscillation absorber 11a, the oscillation absorber being in the form of a Helmholtz resonator with a hydraulic inductance L and a volume 17 as hydraulic capacity C. The natural frequency f.sub.T of a Helmholz resonator is

(19) $f_T=\frac{1}{2\pi \sqrt{L.Math.C}},$
such that the natural frequency f.sub.T can be easily adapted to the stand oscillations occurring during operation.

(20) FIG. 7 shows an exterior view of a second hydraulic pressing unit 7, which is integrated in a mill stand housing 3. The piston rod has for example a diameter of 140 mm, the piston has a diameter of 160 mm and the pressure plate has a diameter of 350 mm. The second hydraulic pressing unit 7 also has four ports: an oil supply for the piston side 34, an oil supply for the rod side 35, a leakage port 36, and a lubricant supply 37. The specified dimensions of the second hydraulic pressing unit 7 serve only for illustrative purposes and are not limiting. The second hydraulic pressing unit 7 can apply a stroke of 6 mm and a clamping force of 500 kN. A second hydraulic pressing unit 7 can therefore press against a back-up roller chock 5 with a force of 500 kN.

(21) FIG. 8 shows a hydraulic layout for the actuation of a second hydraulic pressing unit 7. A switching valve 39 activates the pressure supply for the proportional/regulating/servo or continuously adjustable valve 38. The proportional/regulating/servo or continuously adjustable valve 38 has the function of setting a particular pressure level on the piston side of the second hydraulic pressing unit 7, with the result that a back-up roller chock 5 is pressed against the mill stand housing with a defined pressing force. The two pressure limiting valves 41 serve to limit the maximum pressure. Lastly, it can be seen from FIG. 8 that the piston side of the second hydraulic pressing unit 7 is connected to a second oscillation absorber 11b, the oscillation absorber being in the form of a λ/4 resonator with a length of λ/4.

(22) The length of the one λ/4 resonator is calculated as follows: The speed of sound c.sub.S in oil results from the formula c.sub.S=√{square root over (B/ρ)}, B specifying the compressive modulus and r specifying the density of the oil. In the case of oil, B is approx. 12 000 bar and r is approx. 850 kg/m.sup.3. Therefore, the result is c.sub.S=1188 m/s. As described above, the frequency of the stand oscillation in the third finishing stand is approx. 100 Hz. The wavelength λ of an oscillation at 100 Hz in oil is produced by λ=c.sub.S/f=11.88 m. A λ/4 resonator therefore has a length of λ/4=2.97 m. The λ/4 resonator may be configured either as a straight tube or hose piece, as illustrated, or as a curved tube or hose piece. By way of the length, the λ/4 resonator can be adapted very easily.

(23) FIG. 9 shows the mode of operation of a first hydraulic pressing unit 6 in the retracted state (shown at the top) and in the extended state (shown at the bottom) on the basis of two half-sections. By applying pressure to the oil supply of the piston side 34, the pressure plate 10 moves to the right by the travel x. The piston rod is supported on the housing of the bending block 4a and only the cylinder barrel with the pressure plate 10 moves. This results in an especially compact structure, with the result that the piston and the piston rod can be easily integrated into the bending block 4a. In the extended state, the pressure plate 10 bears against the working roller chock 4, with the result that the working roller chock 4 with the working roller 1, which is not illustrated, the bending block 4a and the mill stand housing 3 are mechanically braced.

(24) It is not important for the invention whether the bending blocks 4a in the mill stand housings 3 are vertically displaceable or are installed non-displaceably in the mill stand housings 3.

(25) Although the invention has been illustrated and described in more detail by the preferred exemplary embodiments, the invention is not limited by the examples disclosed, and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

LIST OF REFERENCE SIGNS

(26) 1 Working roller 2 Back-up roller 3 Mill stand housing 4 Working roller chock 4a Bending block 5 Back-up roller chock 6 First hydraulic pressing unit 7 Second hydraulic pressing unit 8 Piston 9 Piston rod 10 Pressure plate 11a First oscillation absorber 11b Second oscillation absorber 14 Longitudinal bore 15 Helmholtz resonator 16 Longitudinal channel 17 Volume 19 λ/4 resonator 30 Mill stand 31 Rolling stock 32 Strip 33 HGC hydraulic cylinder 34 Oil supply, piston side 35 Oil supply, rod side 36 Leakage port 37 Lubricant supply 38 Proportional/regulating/servo valve or continuously adjustable valve 39 Switching valve 41 Pressure limiting valve A, B Port of a hydraulic valve C Hydraulic capacity D1, D2, Diameter D3 L Hydraulic inductance HL Leakage port of the hydraulic system HP Pressure port of the hydraulic system HT Tank port of the hydraulic system P Pressure port of a hydraulic valve T Tank port of a hydraulic valve TR Transport direction of the rolling stock x Travel