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
C072S008500, C072S011300, C072S365200
Reexamination Certificate
active
06336350
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 that are set so that strip sections are obtained with 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 and is characterized in that the roll gap is diliberately altered during the rolling operation in order to obtain different band thicknesses over the length of the metallic strip. This can occur, on the one hand, directly by altering the tensile strength of the material via a heating or cooling of the metallic strip and a correspondingly altered swelling of the rolling stand during the rolling procedure. In this case, the temperature of the rolled stock can be not only above, but also below the recrystalization temperature. On the other hand, the alteration of the roll gap can be carried out with a direct method of the roll gap via the working rolls. Subsequently, both possibilities for obtaining a definite strip thickness pattern are understood by flexible rolling.
In flexible rolling—as explained above—strip sections are rolled with different strip thicknesses which can be connected to one another with different inclinations, from which multiple possibilities for a thickness profile result. The object of flexible rolling is to produce rolled stock with a load- and weight-optimized cross section. Flexible rolling allows the procedure-shortening manufacture of plates and sheets with a definite, component-individual thickness profile adapted to the load instance in the longitudinal direction of rolling. Such manufactured plates are not only suitable for automobile construction, but also for aeronautical and aerospace engineering and the construction of railroad cars. They can be re-shaped by corresponding processing steps, like, for example, internal pressure re-shaping or deep drawing. A profile manufacture with only one step substantially contributes to the high economic potential of this production technology. The thechnological advantages come especially from the continuity of the characteristics of the materials of the rolled stock, the applicability on all rollable materials as well as the flexibility of the manufacturing method.
The method is designed, as is common, as strip rolling from coil to coil, but variations such as coil to plate or plate to plate are also known. In coil to coil rolling, 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. By the way, flexible rolling from coil to coil guarantees a high productivity at the same time since the thickness profile is continuously generated in the strip.
It is of crucial importance in flexible rolling and also in the conventional rolling procedure to manufacture a planar metallic strip with a default thickness measure. In order to fulfil this specification, it is continuously tried, in rolling, to guarantee a uniform gap measure of the roll gap in rolling. This is not without problems since rolling requires substantial energy for the deformation of the roll stock found in the intake zone leading to the roll gap—which leads to a 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 length over the rolls is constant. Generally, the correction of the deflection curve bending line, however, is not complete and applies only to definite operational instance 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 he 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 defection 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.
Lastly, all the aforementioned measures serve the purpose of obtaining a planar metallic strip with a default thickness measure. To achieve this with flexible rolling is especially problematic since during the rolling procedure, 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 an even 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 thicknesses result over the width and from this, different lengths which cause these flaws in the strip.
In the conventional strip rolling procedure for the production of planar metallic strips with an even thickness over their length, both the thickness of the strip and the planeness are constantly set, monitored over complex control loops and controlled 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. Principally, such complex control loops can also be used in flexible rolling. However, 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 comin
Muhr und Bender KG
Nixon & Peabody LLP
Safran David S.
Tolan Ed
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