Boots – shoes – and leggings
Patent
1994-11-29
1996-07-09
Gordon, Paul P.
Boots, shoes, and leggings
364469, B21B 3700
Patent
active
055351298
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The flatness of a rolled product is determined, inter alia, by the work rolls of the rolling mill, and the flatness can thereby be influenced by the setting of the different control members of the rolls which may comprise screws, bending cylinders, shifting devices, etc. The present invention relates to a method and a device for evaluation of the input signals to the control devices of the control members which are needed to influence the flatness such that the desired accuracy with regard to flatness is attained.
BACKGROUND ART, THE PROBLEMS
The control members which are included in a rolling mill influence the flatness of the strip in different ways. The screws of the rolling mill are used for setting the roll gap across the strip or for adjustment or intentional angular adjustment of the roll gap. Normally bending cylinders are provided, both for bending of the work rolls and for bending of intermediate rolls in a 6-high rolling mill. Normally, also so-called shifting devices are included for axial shifting of the rolls.
A condition for achieving the desired flatness of the rolled product is to have a more or less continuous access to a measure of actual flatness across the strip, that is, a flatness curve. With a known flatness curve, the rolling mill can be provided with a closed-loop flatness control. In a classical manner, the flatness curve obtained is compared with the desired flatness. The flatness errors which thereby arise are then used, in accordance with different models, for influencing the control members to minimize the flatness errors. Thus, the flatness control comprises several executing devices, which means a relatively extensive evaluation process to decide on the magnitude of the various actions by the control members which provide the best result.
A very suitable measurement device--which is often used in these applications--for determining the flatness curve of the rolled strip is the "STRESSOMETER", developed by Asea Brown Boveri AB, which has been available on the market since the middle of the 60's and which has been described in a large number of pamphlets and other publications. The measurement device is designed as a measuring roll, with approximately 50 measuring points across the strip, which in most cases can be placed between the mill stand and the wind-up reel without the use of deflector rolls. The measurement takes place with the aid of force transducers, based on the magnetoelastic principle, and primarily provides the stress distribution of the strip along the measuring roll. If the stress is greater than the buckling stress for the material, the sheet buckles when the strip is left free with no influence by any tensile force. The stress distribution is a flatness curve for the strip across the rolling direction. A more detailed description of the measurement principle is given, inter alia, in an article in IRON AND STEEL ENGINEER, April, 1991, pp. 34- 37, "Modern approach to flatness measurement and control in cold mill" by A. G. Carlstedt and O. Keijser. The article discloses that, because of the relatively extensive signal processing which is required to obtain the flatness curve, this will be updated at intervals of about 50 ms.
When rolling strip, it is important to check and to have the correct roll gap since small variations along the work rolls give a varying reduction of the thickness across the strip, which in turn leads to an inferior flatness curve. The task of the flatness control is thus to maintain an existing curve constant during the whole rolling operation.
As is clear, among other things from the above-mentioned article in IRON AND STEEL ENGINEER, a technique is often used which comprises modifying, with the aid of the bending cylinders, the shape of the work rolls to influence the flatness of the strip. As will have been clear, however, there are several other control possibilities which can be used to influence the flatness curve. A concept for flatness control, in which several control members can be activated, is also descri
REFERENCES:
patent: 3936665 (1976-02-01), Donoghue
patent: 4537050 (1985-08-01), Bryant et al.
patent: 4576027 (1986-03-01), Yoshida et al.
patent: 4587819 (1986-05-01), Hausen
patent: 5267170 (1993-11-01), Anbe
Asea Brown Boveri AB
Garland Steven R.
Gordon Paul P.
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