Metal deforming – By use of roller or roller-like tool-element – With carrier for roller-couple or tool-couple
Reexamination Certificate
2000-07-20
2002-04-23
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, C072S247000, C072S366200
Reexamination Certificate
active
06374656
ABSTRACT:
FIELD OF THE INVENTION
This invention refers to a rolling stand for plane products, such as strip or similar, and an associated method to control the planarity of said strip. The stand is advantageously of the six-high type, with a pair of working rolls (WR) bevelled at least at one end and associated with both negative and positive bending mechanisms and axial displacement, or shifting, mechanisms, a pair of back-up rolls (BUR), and a pair of intermediate rolls (IR) associated with crossing mechanisms.
The planarity control method provides that the quadratic components, the fourth order components and the edge-drop of the profile of the rolled strip are controlled in a coordinated manner. To be more exact, the quadratic and fourth order components can also be controlled with a high dynamic performance.
BACKGROUND OF THE INVENTION
The state of the art includes six-high rolling stands for plane products, comprising a pair of working rolls, a pair of back-up rolls and a pair of intermediate rolls, wherein, to control the planarity of the rolled product both the working rolls and the intermediate rolls are associated with both negative and positive bending systems, and wherein the intermediate rolls are also associated with a system of long axial translation (macro shifting).
These rolling stands, however, have the disadvantage that they cannot completely and efficiently compensate edge-drop, and require a particularly long axial translation of the intermediate rolls.
Another disadvantage of such rolling stands, which provide for the shifting of the intermediate rolls, is that the speed at which the shifting is performed is extremely slow compared with the rolling speed, that is to say, about {fraction (1/1000)} of the latter. Therefore, if the setting of the stand is not correct, since the inlet profile of the product being rolled is different from the aspected profile, or the rolling force is different from the initial expected one, there is a delay in the re-setting of the stand, for example because of the speed of shifting, with a resulting loss of planarity for a length of strip which is equal to the time taken to reset the stand multiplied by the rolling speed. To at least partly solve this problem of compensating the edges, there have already been proposals for rolling stands with a system of axial translation of the working rolls in the same direction as the intermediate rolls and wherein the working rolls are equipped with appropriate bevels or hollows at the ends.
Moreover, the state of the art also includes a rolling stand wherein the intermediate rolls (IR) are associated with crossing means suitable to reduce the so-called “strip walking”.
The present Applicant has devised, designed and perfected a rolling stand for plane products and a method to control the planarity of said products according to the invention to overcome the shortcomings described above and to perfect the rolling stands known in the state of the art.
SUMMARY OF THE INVENTION
The rolling stand for plane products and the method to control the planarity of said products according to the invention is set forth and characterised in the main claims, while the dependent claims describe other innovative features of the invention.
One purpose of the invention is to achieve a rolling stand for plane products, such as strip or similar, which will make possible to control and adjust, autonomously and independently, also during rolling, the x
2
component, the x
4
component and also components of a higher order, which consequently makes it possible to control the edge-drop of the rolled product, that is to say, components up to x
10
.
In accordance with this purpose, the rolling stand for plane products according to the invention comprises a pair of working rolls, a corresponding pair of back-up rolls and at least an intermediate roll located between one of the working rolls and a corresponding back-up roll, shifting means and bending means associated with at least one of the working rolls to translate it axially and respectively bend it, and crossing means associated with the intermediate roll to arrange it with its longitudinal axis inclined, that is, rotated, with respect to the longitudinal axes of the working rolls and the back-up rolls.
Before describing the invention in detail, it is appropriate to make the following premises.
The ability to control the profile of the strip being rolled is generally shown in the plane x
2
, x
4
(FIG.
5
), where x
2
and x
4
are the second and fourth order components of the function y(x)=a
0
+a
1
x+a
2
x
2
+a
3
x
3
+. . . +a
10
x
10
, which represents the thickness of the strip (FIG.
6
).
If the thickness is symmetrical, as it should be, the odd components should not be present. At most, we might find the component a
1
x which indicates the presence of strip with a wedge defect, that is, a profile which is on average trapezoid with edges of a different thickness, as shown in FIG.
7
.
The more efficient a stand is at controlling the shape, the wider is the zone x
2
, x
4
which can be controlled;
FIG. 8
shows two areas, the most extensive of which refers to a system with a higher control capacity than the more inward area.
If a stand has high dynamic performance in controlling the shape of the strip, this means that it is possible to pass quickly from a point A (
FIG. 9
) to a point B in the plane x
2
, x
4
. Then, together with an area of “static” or preset control, an area of “dynamic” control is also shown, clearly included in the area of static control which moves inside the area of global control (
FIG. 10
) according to the initial static functioning point “0”.
Since every actuator suitable to control the movements of the working rolls and intermediate rolls, in every operating condition (that is, roll diameters, strip width, inlet profile, rolling force, etc.) has its own “line of action”, to pass with complete freedom from a point A to a point B, it is generally necessary to have two actuators AT
1
and AT
2
which move in their own directions d
1
and respectively d
2
(FIG.
11
). Therefore, in the field of dynamic control, to have the possibility to pass from A to B without constraints on position B, the two necessary actuators must also have lines of action which are not parallel.
This having been said,
FIG. 12
shows the control of the crossing of an intermediate roll (IR) according to the invention, wherein it can be noticed how the influence of x
2
has limited collateral effects on x
4
, since the ratio between x
2
and x
4
is about {fraction (1/10)}. Therefore, by acting on IR crossing we have very limited effects on the x
4
component.
From the detail shown in
FIG. 13
, in which the two working rolls (WR) are shown, it can be seen how WR shifting prevalently influences the edges of the strip, if the working roll is appropriately bevelled.
WR shifting influences both x
2
and x
4
but in a very limited way compared with WR bending and IR crossing. WR shifting is practically defined by the width of the strip, with very small adjustments according to the actual edge-drop on the strip at outlet. The ratio between x
2
and x
4
is about 1.
As can be seen in
FIG. 14
, WR bending influences both x
2
and x
4
. The ratio x
4
/x
2
depends on the choice of the diameters of the rolls of the stand and on the width of the strip (rolling force, etc.), and is in any case near 1.
The influence of IR crossing and WR bending on the edges of the strip is very limited, and therefore when IR crossing and WR bending is varied, it is not necessary to modify the set of WR shifting.
Therefore, the rolling stand according to the invention is equipped with means which allow IR crossing, WR shifting and WR bending.
To be more exact, WR shifting is used to pre-set the working rolls according to the edge-drop.
The stand according to the invention provides to actuate a shifting action on the working rolls in order to allow an adequate control of the shape of the strip edges for all the strip width values provided for a given rolling stand.
Bobig Paolo
Donini Estore
Galletti Cesare
Danieli & C. Officine Meccaniche S.p.A.
Tolan Ed
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