Metal deforming – With use of control means energized in response to activator... – Metal deforming by use of roller or roller-like tool element
Reexamination Certificate
2000-01-07
2001-03-20
Tolan, Ed (Department: 3725)
Metal deforming
With use of control means energized in response to activator...
Metal deforming by use of roller or roller-like tool element
C072S011600, C072S012700, C072S012800
Reexamination Certificate
active
06202459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of rolling of a bar-shaped stock, e.g., a bar steel or wire to predetermined end height and end width measured transverse to the end height by application of rolling forces, and to a rolling mill train for implementing the method and including a plurality of arranged one after another active rolling mill stands having adjustable roll nips and forming rolling mill stand pairs.
2. Description of the Prior Art
The rolling mill trains of the type described above are generally known. The rolling mill stands are alternatively formed as horizontal rolling mill stands and vertical rolling mill stands, with the last rolling mill stand defining the end profile, e.g., round, square or hexagonal profile.
In the prior art, the roll nips of the rolling mill stands are adjusted with electric or hydraulic motors. However, the adjustment of the roll nip can be mostly effected in the unloaded condition only. The adjustment of the roll nip under a load is not possible. It is possible to change the rotational speed of the rolling mill stands during their operation. Other interventions, e.g., a correction of roll nips, is not possible.
A co-pending U.S. application Ser. No. 09/348,745 discloses a rolling mill train for rolling a bar-shaped stock including a plurality of active rolling mill stands through which a rolled stock passes one after another and the roll nips of which are adjusted with respective hydraulic cylinder units. There are further provided control units for controlling the operation of the respective hydraulic cylinder units so that a fraction of the rolling force-caused spring-offs of the rolling mill stands is compensated.
An object of the present invention is to provide a method of and a rolling mill train for rolling a bar-shaped stock with which the roll nips can be adjusted under load and the rolling characteristics of the rolling mill stands are adaptable to respective rolled stock.
SUMMARY OF THE INVENTION
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a rolling mill train having a plurality of arranged one after another, active rolling mill stands having adjustable roll nips and forming rolling mill stand pairs, a respective plurality of hydraulic cylinder units for adjusting the roll nips of respective rolling mill stands, and a respective plurality of roll nip control units for controlling the respective hydraulic cylinder units so that at least a fraction of rolling force-caused spring-offs of the respective rolling mill stands is compensated individually for each of the rolling mill stands. The provision of hydraulic cylinder units for adjusting of the roll nips permitted to adjust the roll nips under load. The capability to compensate the rolling force-caused spring-offs provided for an automatic compensation of the spring-offs. Because in this case, a possible rolling error would be completely transmitted to the width of the rolled stock, the spring-offs are only partially compensated. Due to the adjustability of the fractions to be compensated, the rolling mill stands can be adapted to their particular tasks in the rolling mill train.
The rolling mill stands in the rolling mill train perform different tasks, dependent on the rolled product, namely, they effect either a reduction of the rolled stock or so-called pre-sizing or sizing.
The primary task of the reduction stands is to reduce the stock cross-section to a most possible extent. These stands should be rather rigid. In connection with a monitor routine, the cross-section of the rolled stock can be optimized with such rolling mill stands.
The primary task of the pre-sizing stands is to bring the ratio of the stock height to the stock width to a certain value before the stock enters the following sizing stands. To this end, with a round end profile of the rolled stock, the stands with an oval pass should have a high rigidity, and the stands with a round pass should have an optimal rigidity. In such a case, the temperature and cross-sectional deviations will be uniformly distributed to both measurements.
The primary task of the sizing stands is to roll the rolled stock to the desired end dimensions and, at the same time, to insure a good ovality of the rolled stock. Here, with a round profile of the stock, the stands with oval passes should have a relatively high rigidity, and the stands with a round pass should have a smaller, optimal rigidity.
Thus, optimally, the following adjustments should be made:
The rolling force-caused spring-off of the last sizing stand should be compensated to a smaller degree than the spring-off of the preceding sizing stand;
The rolling force-caused spring-off of the last pre-sizing stand should be compensated to a smaller degree than the spring-off of the preceding pre-sizing stand; and
The rolling force-caused spring-offs of the reduction stands should be compensated almost completely.
The last two active rolling mill stands operate in a sizing mode. At least one rolling mill stand of a rolling mill stand pair immediately preceding the sizing stands operate in a pre-sizing mode. Due to the adjustability of the fraction of the rolling force-caused spring-offs of the rolling mill stands, it is easy to adjust the rolling mill stands for operation in a sizing, pre-sizing, or reduction made.
The ovality of the rolled stock is particularly good when the rolling force-caused spring-offs of the sizing stands are on average, compensated to a smaller degree than the spring-offs of the pre-sizing stands.
The tolerances are best maintained when the stock is so rolled in the pre-sizing stands that the sizing stands can operate in their most favorable dynamic region. This can be achieved, e.g., by determining the roll nips of the pre-sizing stands based on the roll nips of the sizing stands.
The dimension precision of the rolled stock can be increased by providing, downstream of the last sizing stand, a measuring device for measuring the end height and the end width of the rolled stock and by correcting the roll nips of the sizing stands based on the measured end height and width (monitor routine).
The precision of the dimension of the rolled stock can be further increased by providing further measuring devices arranged, respectively downstream of each pair of rolling mill stands for measuring the height and the width of the rolled stock as it leaves a respective pair. In this case, the roll nips of respective rolling mill stands can be directly determined from the measured height and width.
Usually, the draw of the rolled stock between separate rolling mill stands is determined, and their rotational speed is so controlled that the draw remains constant. In addition, it is possible to measure the cross-section of the rolled stock between the separate rolling mill stands. The measurements of the draw, heights and width during rolling can be used for optimizing the fractions of the rolling force-caused spring-offs which are to be compensated.
When a new stock is rolled, it could be possible to provide that the first billet of the charge has correct end dimensions. This can be achieved by providing memory means for storing material characteristics, end heights and end width of already rolled stocks, and for storing constant and set-up parameters of the rolling mill stands; by providing input means for inputting material characteristics, end height and end width of a new to-be-rolled stock, and by providing comparison means for comparing the material characteristics, the height and the width for the new to-be-rolled stock with the stored material characteristics, the end heights and the end width for the already rolled stocks, and for comparing instantaneous parameters of the rolling mill stands during rolling of the new rolled stock with the stored parameters of the rolling mill stands, whereby upon coincidence of the parameters for the new stock with the stored parameters for an already rolled stock, the rolling mill stands can be pre
Grossmann Erich
Muller Hubert
Palzer Otmar
Brown & Wood LLP
SMS Schloemann-Siemag AG
Tolan Ed
LandOfFree
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