Metal deforming – By use of roller or roller-like tool-element – With carrier for roller-couple or tool-couple
Reexamination Certificate
2000-08-07
2002-01-08
Tolan, Ed (Department: 3725)
Metal deforming
By use of roller or roller-like tool-element
With carrier for roller-couple or tool-couple
C072S009100, C072S011700, C072S241800, C072S366200
Reexamination Certificate
active
06336349
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for the flexible rolling of a metallic strip wherein, during the rolling procedure, the metallic strip is lead through a roll gap which is formed between two working rolls and during the rolling operation, the roll gap is deliberately changed in order to obtain different strip thicknesses over the length of the metallic strip.
2. Description of Related Art
Flexible rolling as a method for the production of planar metallic strips with different, default strip thicknesses over their length is known in practice. Flexible rolling is characterized in that the roll gap is deliberately changed during the rolling operation. While doing so, strip sections of different lengths are rolled with different thicknesses which can be connected to one another with different inclinations. The object of flexible rolling is to produce rolled stock with a load- and weight-optimized cross section. The method is designed, as is common, as strip rolling from coil to coil. Here, the winch-applied strip tension supports the rolling procedure and substantially improves the uniformity of the strip section in the longitudinal direction, i.e., in the rolling direction.
Rolling, in the context of the conventional strip rolling procedure, requires substantial energy for the deformation of the roll stock found in the intake zone leading to the roll gap—which leads to an elastic deflection of the roll. A deflection curve bending line which is almost parabolic and which corresponds to the axle center of the roll results through the deflection of the roll which is supported on both ends. Since the deflection causes a deviation from the uniform gap measure or the ideal gap, corrective measures are necessary.
One measure for correcting the deviation from the ideal gap—caused by the deflection of the rolls—consists of bowing the barrel-shaped or bellied construction of the roll body. With this type of correction, it is possible to bow only the working rolls, only the back-up rolls or both the working rolls and the back-up rolls. The bowing should compensate the deflection, which is caused by the roll force and the weight of the rolls, so that the gap between the rolls runs uniformly again, i.e., the gap is constant over the length of the rolls. Generally, the correction of the deflection curve bending line, however, is not complete and applies only to definite operational instances since the shape of the roll or the bowing is not changeable.
A further possibility for correction is seen in that, in each case, a roll body is placed oblique to its axis by a horizontal turning from the center of its line of contact with the corresponding roll. This oblique placement alters the gaps at the ends of the rolls while the center remains unchanged. Through its variation possibilities, the oblique placement of the rolls allows, particularly, for an approximated compensation of the deflection for almost all operational instances, but is comparable to the exactness obtainable with the already-mentioned parabolic surface of the roll body.
Furthermore, it is possible to create a moment of deflection through the application of forces on the bearing necks of the rolls which works against the moment of deflection in rolling. This biasing of the rolls also allows, like the oblique placement, an approximated compensation for almost all operational instances. The substantially increased stress on the bearing is, however, disadvantageous. In respect to the obtainable compensation, biasing can be compared with the parabolic surface.
Finally, a further possibility for correction exists in working roll cooling, which deals with thermal bowing.
It is understood that the already-mentioned correction possibilities for obtaining an ideal roll gap in rolling mills can be used alone or in combination with one another.
As opposed to the conventional strip rolling procedure, flexible rolling is especially problematic in that during the rolling process, large load fluctuations on the roll stand—which for one thing, no doubt, achieve the desired changes in strip thickness and for another, however, involve a substantial change of the roll load over the width particularly for wider metallic strips—constantly arise due to the frequent differences in thickness of the metallic strip. Through this, the deflection curve bending line of the working roll is influenced as is, consequently, the geometric formation of the roll gap and with it the planeness, as long as no correction to the implementation of a uniform gap measure follows. Should, in flexible rolling, the roll gap corresponding to the required strip section be run without correction, a characteristic, non-planar strip section develops over the width for this load change. Due to this non-planeness, there is the danger of corrugation on the edges or rips in the strip since the ordered alteration in height and the ordered alteration in length corresponding to it are not constant over the width. Because of this, different thickness result over the width and from this, different lengths which cause these flaws in the strip.
Planeness is a substantial requirement for a metallic strip. This is important in order to be able to insure the same proportions from the middle of the strip to the edge of the strip for further machining. Undesired effects can come about when winching strips that are not planar. This is expressed through frictional tension points on the contact areas in the winched coil either in the middle of the strip or at the edge of the strip depending on the strip section. This can lead the coiled strip to stick depending on the looping angle and the occurring frictional conditions, particularly if an annealing operation is performed afterward.
In the conventional strip rolling procedure for the production of planar metallic strips with a uniform thickness over the length, both the thickness of the strip and the planeness are constantly set, monitored over complex control loops and adjusted via corresponding correcting elements at occurring deviations. A control device for stabilizing the rolling-force-conditioned roll deflection in the conventional strip rolling procedure is known, for example, from German Patent DE 22 64 333 C3.
It is problematic that the known regulation needs a definite response time and a certain recovery time until it responds and until the effect of an alteration in the disturbance variable coming from the effect of the regulation withing the exactness of measurement is stabilized. This problem of the regulation response and the necessary recovery time plays a substantial role in flexible rolling since, in part, very short portions of strip with different thicknesses must be rolled at partially high rolling speeds and the planeness should, finally, be guaranteed over the entire length of the flexibly-rolled strip. This is particularly difficult, especially for wider metallic strips.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a method for flexible rolling of a metallic strip in which planeness can be well obtained, and particularly, also for relatively wide strips.
The above-mentioned and described object is met with a method of the type described above in which, during each setting of the roll gap or immediately thereafter, the deflection curve bending line is adjusted depending on the setting of the roll gap to obtain planeness in the metallic strip. It is thus substantial that the influence of the deflection curve bending line of the working roll while setting of the roll gap is not—at least not at first—achieved by feedback control, but instead from a control or an adjustment in which one variable—here, the deflection curve bending line of the working roll—is influenced by another variable—here, the roll gap in a pre-determined, fixed connection.
In the invention, the compensation of the deflection curve bending line alteration due to the load reversal from a roll gap alteration results through the knowledge of the dependence of the deflec
Hauger Andreas
Kopp Rainer
Muhr und Bender KG
Nixon & Peabody LLP
Safran David S.
Tolan Ed
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