Metal working – Method of mechanical manufacture – Combined manufacture including applying or shaping of fluent...
Reexamination Certificate
1999-07-12
2001-10-23
Echols, P. W. (Department: 3726)
Metal working
Method of mechanical manufacture
Combined manufacture including applying or shaping of fluent...
C164S413000, C164S454000, C072S146000, C072S214000, C029S254000
Reexamination Certificate
active
06305068
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a metal strip that can be coiled into a coil in a continuous horizontal strip casting installation, and a horizontal strip casting installation for carrying out this method.
A traditional continuous strip casting installation for producing a coiled metal strip includes first a furnace (holding furnace or hot top) with a chill mold, which determines the cross section of the metal strip. The chill mold typically is flange-mounted at the outlet of the furnace.
A draw-off unit with several draw-off rolls is arranged at a distance from the chill mold. The metal strip is guided horizontally through the draw-off unit between several draw-off rolls extending horizontally. Of the draw-off rolls, at least one draw-off roll is driven. As a rule, however, several draw-off rolls are driven.
If needed, a milling unit for machining the surface of the metal strip may be integrated between the chill mold and the draw-off unit.
The metal strip is guided further in a horizontal plane from the draw-off unit to a coiling unit. The coiling unit is provided with several coiling rolls, which bend the metal strip so that it is deposited in the form of a coil after leaving the coiling unit. The coil is stored on supporting rollers that extend horizontally and are provided above the coiling rolls in the coiling unit.
The coiling unit itself is mounted on rollers and is movable by the metal strip relative to a stationary machine stand.
Between the draw-off unit and the coiling unit there is a strip cutting unit, usually near the draw-off unit, which is movable in the longitudinal direction of the metal strip, is supported on rollers, and which cuts the metal strip when a coil has reached its predetermined diameter.
The drives for the draw-off rolls, the strip cutting unit and the coiling rolls are linked together by a programmable controller.
The coilable metal strip is produced in a Pilger-type reciprocating cycle having a forward stroke of approximately 15 mm and a return stroke of approximately 5 mm with a pause of approximately two seconds inserted between the individual strokes. The relative acceleration of the metal strip here amounts to approximately 4.5 cm/s
2
. During the entire production of the metal strip in a coil, the coiling unit is attached to the coil sitting on it, with the diameter of the coil increasing constantly, so the draw-off unit must overcome mass acceleration forces of up to approximately 25 tonnes (approximately 4 tonnes to 6 tonnes for the coiling unit, approximately 4 tonnes to 16 tonnes for the coil with its increasing diameter and approximately 2 tonnes for the strip cutting unit if the strip is to be cut). Furthermore, an inertial force of 250 kN must be accelerated and decelerated in each cycle, taking into account the strip draw-off force of approximately 2.5 tonnes.
The coiling unit is shifted by the metal strip between two positions starting from the draw-off unit. A limit switch causes the coiling drive to be turned on and the coiling unit to move back to the starting position along the metal strip. Once it reaches this starting position, another limit switch is operated, turning the coiling drive off again. The distance traveled by the coiling unit amounts to approximately 500 mm. In this procedure, the masses indicated above are accelerated and decelerated back and forth intermittently up to 30 times a minute. With an increase in diameter of the coil and consequently also an increase in weight, the opposing forces become progressively greater, thus causing considerable stresses on the bearings for the coiling rolls but also on the other bearings which must be serviced constantly for this reason and replaced frequently. In addition, the specified draw-off parameters are altered so that reproducibility of the cycles is impossible. An operation with a greater number of cycles per minute is impossible.
SUMMARY OF THE INVENTION
The object of the present invention is to create a method of producing a coiled metal strip and a continuous horizontal strip casting installation for carrying out the method which will avoid high mass acceleration forces and make each individual cycle reproducible.
The present invention meets this object in providing a method (and associated apparatus) for producing a metal strip that can be coiled into a coil in a continuous horizontal strip casting installation. The metal strip is drawn out of a chill mold assigned to a furnace by a draw-off unit having draw-off rolls in a Pilger-type reciprocating cycle with a forward stroke and a return stroke of a shorter length. The strip is conveyed via a strip cutting unit to a coiling unit, which is displaceable in the longitudinal direction of the metal strip, in which the metal strip is rolled into a coil supported by rollers. At least one coiling roll of the coiling unit and at least one draw-off roll of the draw-off unit are driven in synchronization in the cycle of the forward stroke and the return stroke of the metal strip.
A primary point of the present invention is the measure whereby at least one coiling roll of the coiling unit and at least one draw-off roll of the draw-off unit are driven in synchronization in the cycle of the forward stroke and the return stroke of the metal strip, i.e. the draw-off unit and the coiling unit are equipped with synchronized drives. The strip cutting unit is also included here if it is involved in this action. In this way, the Pilger-type reciprocating cycle consisting of a forward stroke and a return stroke of a shorter length takes place only in the metal strip. The unavoidably short strokes in the end phases of the cycles are compensated in the loop of the coil, which develops behind the last coiling rolls of the coiling unit and the coil. The coiling unit thus coils the strip in synchronization with the draw-off unit and need no longer be movable in principle. Only a slight traveling distance of approximately 50 mm is provided, intended for correcting the position of the coiling unit. The movement of the coiling unit along this path of approximately 50 mm, however, takes place over a period of approximately ten hours, so that the relative movement is insignificant.
In principle, within the scope of the present invention only the strip draw-off force of approximately 2.5 tonnes must be taken into account, and the weight of the strip cutting unit of approximately two tonnes must also be taken into account briefly for the time of cutting the metal strip. In other words, this yields a constant 2.5 tonnes upstream and downstream from the cutting of the metal strip at a maximum weight of only 4.5 tonnes. The weight of the coil on the coiling unit is thus of no importance. However, it is important within the scope of the present invention now, due to the method according to the present invention, because of the lack of mass surges in acceleration and deceleration, that all the bearings are protected so that their lifetime is greatly prolonged. The weight of the coil is limited only by the load-bearing capacity of the coiling unit and its machine stand.
Synchronous operation can be achieved with any desired drive unit. Purely electric drives (three-phase servo drives) as well as servo hydraulic drives or purely mechanical drives can be used.
In continuation of the basic idea according to the present invention, the drives of each driven draw-off roll of the draw-off unit and of each driven coiling roll of the coiling unit are linked together by a programmable controller. When there are multiple driven draw-off rolls and coiling rolls, all the draw-off rolls and all the coiling rolls are each controlled separately by a drive, which is then synchronized with the other drive by the programmable controller.
The longitudinal displacement of the strip cutting unit and the cutting mechanism is under the influence of the programmable controller in order to cut the metal strip at the intended time, so that the finished coil can then be removed from the coiling unit and a new coil can be pro
Brüning Hubertus
Oelmann Hartmut
Sroka Anwar von
Echols P. W.
Kenyon & Kenyon
KM Europa Metal AG
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