Rolling Mill for Rolling a Metallic Strip

Abstract

In a rolling mill for rolling metal strip (1), especially steel strip, which has at least one rolling stand (2), an upstream coiler (3), and a downstream coiler (4), wherein an “S” roll unit (5, 6), which has two rolls (7, 8; 9, 10) that guide the strip (1) in the form of an “S”, is arranged between the upstream coiler (3) and the rolling stand (2) and/or between the rolling stand (2) and the downstream coiler (4), the invention provides that a first roll (7, 9) of the “S” roll unit (5, 6) is arranged in a fixed manner, and a second roll (8, 10) of the “S” roll unit (5, 6) is arranged in such a way that it can move relative to the first roll (7, 9).

Description

The invention concerns a rolling mill for rolling metal strip, especially steel strip, which has at least one rolling stand, an upstream coiler, and a downstream coiler, wherein an “S” roll unit, which has two rolls that guide the strip in the form of an “S”, is arranged between the upstream coiler and the rolling stand and/or between the rolling stand and the downstream coiler.

The increasing necessity for weight savings, especially in the automobile industry, has led to the development and use of load-adapted parts, so-called tailored blanks. The essential feature of these parts that is of special importance in this connection is that they have a variable thickness. Tailored blanks-were originally produced mainly by welding. However, it was found that they can also be produced in an especially favorable way by flexible cold rolling, which can be used to produce tailored blanks.

In flexible cold rolling, the thickness of the rolling stock is varied during rolling. In this regard, the roll gap can be periodically varied. The thickness variation results in mass flow disturbances and tension fluctuations, especially on the entry side of the rolling stand but also on the delivery side of the rolling stand. At the rolling speeds necessary for profitable production, these mass flow disturbances and tension fluctuations can no longer be compensated by the dynamics of the coiler motors, so that so-called dancer rolls are used between the rolling stand and the coilers in installations of this type.

WO 03/008,122 A1 describes a solution of this type. It discloses a cold rolling mill for cold rolling metal strip, which has a single stand with means for adjusting the roll gap, a coiler for uncoiling the strip upstream of the single cold rolling stand, and a coiler for coiling the strip downstream of the rolling stand. To achieve flexible rolling, a strip accumulator is arranged between the upstream coiler and the rolling stand for controlling the mass flow and the strip tension. This strip accumulator consists of at least three rolls. The middle roll is designed as a dancer roll and can be moved perpendicularly to the direction of conveyance of the strip.

EP 1 121 990 A2 discloses a similar solution—but with the use of a larger number of rolls. The same is true of a design disclosed by JP 10-034,204 A1.

The dancer rolls described in the cited documents are connected with a linear actuator, with which they can be moved perpendicularly to the direction of conveyance of the strip under open-loop or closed-loop control. The strip accumulator function that is essential for flexible cold rolling can be fulfilled in this way.

DE 198 18 207 C2 and JP 60-231,516 disclose so-called loopers, i.e., rolls which are applied to the strip fed to the rolling stand or carried away from the rolling stand, in order, for example, to be able to undertake a determination of the tensile force in the strip.

During rolling, the rolling force can be reduced by tensile forces on each side of the roll gap. However, it is only in the last pass that it must not be too high, since otherwise, as is known from experience, problems can arise in the subsequent process steps, especially during annealing. “S” roll units (“S” rolls) can be used to develop a tension difference between the rolling stand and coiler.

When both a strip accumulator function is to be realized, generally with dancer rolls, and a desired tension difference between the rolling stand and the coiler is to be produced, generally by “S” roll units, considerable equipment expense is required in the prior-art solutions.

Therefore, the objective of the invention is to modify a metal strip rolling mill of the aforementioned type in such a way that simple and thus economical means can be employed both to realize a strip accumulator function, especially in the case of flexible rolling, and to maintain a tension difference between the rolling stand and coilers that can be controlled in a well-defined way.

In accordance with the invention, this objective is achieved by arranging a first roll of the “S” roll unit in a fixed manner and arranging a second roll of the “S” roll unit in such a way that it can move relative to the first roll.

Apart from guide rolls for the strip that may additionally be present, only the “S” roll unit is intended, in accordance with the invention, to be provided between the coiler and rolling stand, but both the strip accumulator function can be provided and the required tension on the strip can be exerted with the proposed design of the “S” roll unit.

In a preferred embodiment, the second roll, which can move relative to the first roll, is rotatably mounted on a swivel arm, which is supported at one end in a stationary axis. The two axes of the rolls of the “S” roll unit are arranged parallel to each other. It is advantageous for the stationary axis to coincide with the axis of rotation of the first roll.

To swivel the second roll relative to the first roll, a linear actuator articulates with the swivel arm, preferably in a pivot some distance from the stationary axis. It is advantageous to use a hydraulic piston-cylinder system as the linear actuator.

To be able to influence the development of tension in the strip in an optimum way, means can be provided for driving at least one of the rolls of the “S” roll unit.

The proposal of the invention can be used to advantage in a cold rolling mill. In addition, the rolling stand is preferably a single stand. The proposed system is suitable especially for flexible rolling, which is why the rolling stand can have means for flexible adjustment of the roll gap.

Finally, strip conveyance or handling is improved by equipping at least one of the coilers with means that allow rotational speed control.

The proposed system makes it possible in a very simple and thus inexpensive way to provide a rolling plant for flexible rolling that makes available a strip accumulator, which is essential in this type of operation. In addition, the strip is also maintained at the required tension, so that the rolling itself can be carried out in an advantageous way from the standpoint of process engineering.

A specific embodiment of the invention is illustrated in the drawings.

FIG. 1 shows a schematic side view of a rolling mill for the flexible rolling of metal strip.

FIG. 2 shows an enlarged view of an “S” roll unit on the discharge side of the rolling mill.

FIG. 1 shows a schematic view of a rolling mill, in which a coiled steel strip 1 is uncoiled from an upstream coiler 3 and fed to a single cold rolling stand 2. Another coiler 4, which re-coils the rolled metal strip 1, is installed downstream of the rolling stand 2 in the direction of conveyance R of the metal strip 1. The coilers 3, 4 are provided with drives (not shown), so that the strip 1 can be uncoiled and coiled under open-loop or closed-loop control.

Flexible cold rolling of the strip is carried out in the rolling stand 2. The strip 1 has a nonconstant thickness—as viewed in its longitudinal direction. This means that, during the rolling process, the roll gap is varied in accordance with a preset profile to produce a strip whose thickness varies periodically.

To allow this process to be carried out under conditions that are favorable from the standpoint of process engineering, it is necessary to compensate the change in mass flow in the strip that results from the variable strip thickness. Furthermore, a well-defined tension must be developed and maintained in the strip 1 to keep the rolling force low.

To accomplish this, an “S” roll unit 5, 6 is installed between the upstream coiler 3 and the rolling stand 2 and between the rolling stand 2 and the downstream coiler 4, respectively. Each “S” roll unit has two rolls 7, 8 and 9, 10, respectively, which are arranged relative to each other in a well-known way, so that the strip 1 is guided in an S-shaped path. The resulting wrapping of the rolls 7, 8, 9, 10 makes it possible, with suitable driving of the rolls, to transmit a force to the strip 1 and thus to maintain the desired tension in the strip 1 between the “S” roll unit 5, 6 and the rolling stand 2.

To be able to achieve both the application of tension in the strip and the strip accumulator function, the “S” roll units 5 and 6 are constructed as shown in FIG. 2. Each unit has one roll 9 (or 7) that feeds the strip 1 to or guides it away from the rolling stand 2. This roll 9 (or 7) is supported in a fixed position. By contrast, the other roll 10 (or 8), is movably supported and can swivel relative to the first roll 9, 7. To this end, it is mounted at the end of a swivel arm 11. The other end of the swivel arm 11 is supported in a stationary axis 12, which coincides with the axis of rotation of the first roll 9, 7.

One end of a linear actuator 14, which is realized as a hydraulic piston-cylinder system, articulates with the swivel arm, namely, in a pivot 13 some distance from the axis of rotation of the second roll 8, 10. The actuator 14 is supplied with hydraulic oil as indicated in FIG. 2.

When the piston-cylinder system 14 is acted upon by hydraulic oil under open-loop or closed-loop control, the pivot 13 can be raised or lowered, so that the second roll 8, 10 can be swiveled about its axis of rotation 12. This results in a longer or shorter distance for the strip 1 between the rolling stand 2 and coilers 3 or 4, thereby enabling the “S” roll units 5, 6 to carry out a strip accumulator function.

The above-described construction of the rolling mill and especially of the two “S” roll units 5, 6 makes it possible, with a very simple design, to compensate the mass flow variation that occurs during flexible cold rolling and at the same time to develop the tension difference between the rolling stand 2 and coilers 3, 4 that allows an optimum rolling operation. With suitably fast automatic control of the linear actuator 14, it is possible to compensate the mass flow disturbances without any appreciable tension fluctuations.

To achieve this goal in the past, it was necessary to use a large number of rolls, which made these installations expensive.

As a result of the compensation of the mass flow disturbances and the associated reduction of the tension fluctuations, the automatic control of strip thickness can be improved. It becomes possible to make adjustments of the tensile stresses favorable for the rolling process without regard to the tensile stresses present at the coilers.

The compensation of the mass flow disturbances and the strip accumulator function are now realized in one piece of equipment, namely, the “S” roll unit described above, for which separate pieces of equipment were previously needed.

List of Reference Symbols

• 1 metal strip (steel strip)
• 2 rolling stand
• 3 upstream coiler
• 4 downstream coiler
• 5 “S” roll unit
• 6 “S” roll unit
• 7 roll
• 8 roll
• 9 roll
• 10 roll
• 11 swivel arm
• 12 stationary axis
• 13 pivot
• 14 linear actuator
• R direction of conveyance of the strip

Claims

1. Rolling mill for rolling metal strip (1), especially steel strip, which has at least one rolling stand (2), an upstream coiler (3), and a downstream coiler (4), wherein an “S” roll unit (5, 6), which has two rolls (7, 8; 9, 10) that guide the strip (1) in the form of an “S”, is arranged between the upstream coiler (3) and the rolling stand (2) and/or between the rolling stand (2) and the downstream coiler (4), characterized by the fact that a first roll (7, 9) of the “S” roll unit (5, 6) is arranged in a fixed manner, and a second roll (8, 10) of the “S” roll unit (5, 6) is arranged in such a way that it can move relative to the first roll (7, 9).

2. Rolling mill in accordance with claim 1, characterized by the fact that the second roll (8, 10), which can move relative to the first roll (7, 9), is rotatably mounted on a swivel arm (11), which is supported at one end in a stationary axis (12).

3. Rolling mill in accordance with claim 2, characterized by the fact that the stationary axis (12) coincides with the axis of rotation of the first roll (7, 9).

4. Rolling mill in accordance with claim 2 or claim 3, characterized by the fact that a linear actuator (14) articulates with the swivel arm (11) in a pivot (13) some distance from the stationary axis (12).

5. Rolling mill in accordance with claim 4, characterized by the fact that the linear actuator (14) is a hydraulic piston-cylinder system.

6. Rolling mill in accordance with any of claims 1 to 5, characterized by means for driving at least one of the rolls (7, 8, 9, 10) of the “S” roll unit (5, 6).

7. Rolling mill in accordance with any of claims 1 to 6, characterized by the fact that it is designed as a cold rolling mill.

8. Rolling mill in accordance with any of claims 1 to 7, characterized by the fact that the rolling stand (2) is a single stand.

9. Rolling mill in accordance with any of claims 1 to 8, characterized by the fact that the rolling stand (2) is equipped with means for flexible adjustment of the roll gap.

10. Rolling mill in accordance with any of claims 1 to 9, characterized by the fact that at least one of the coilers (3, 4) is equipped with means for rotational speed control.