Method for the static and dynamic control of the planarity...

Details Method for the static and dynamic control of the planarity... Method for the static and dynamic control of the planarity...

2000-07-20

2002-01-15

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

C072S009100, C072S241800, C072S247000, C072S366200

Reexamination Certificate

active

06338262

ABSTRACT:

FIELD OF THE INVENTION
This invention concerns a method for the static and dynamic control of the planarity of flat rolled products, such as strip or similar. The method is advantageously applied in five- or six-high stands, having a pair of working rolls (WR) associated with both negative and positive bending mechanisms and axial displacement, or shifting, mechanisms, a pair of back-up rolls (BUR), and at least an intermediate roll (IR) associated with a crossing mechanism and a positive and negative bending mechanism.
The method to control planarity provides that the second order components, the fourth order components and the edge-drop of the profile of the rolled strip are controlled independently. This control may occur both statically, (that is, during the initial setting or preset of the rolling mill, to set up the stand before rolling starts, to take it to adequate working conditions) and also dynamically, during rolling. To be more exact, the second order and fourth order components can be dynamically controlled, and even controlled with great efficiency.
BACKGROUND OF THE INVENTION
The state of the art includes a method to control the planarity of flat rolled products in six-high rolling stands, wherein both the working rolls and the intermediate rolls are associated both with bending systems, both negative and positive, and also with a system of long axial translation or shifting (macro shifting).
This method of control, however, has the disadvantage that it cannot completely and efficiently compensate edge-drop, and requires a particularly long axial translation of the intermediate rolls.
Another disadvantage of this method, which provides 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 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 final 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, various rolling stands and control systems have already been proposed which provide 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 method 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 the method to control the planarity of rolled products according to the invention to overcome the shortcomings described above and to improve the methods known in the state of the art.
SUMMARY OF THE INVENTION
One purpose of the invention is to achieve a method for the static and dynamic control of the planarity of flat rolled products, such as strip or similar, which will make possible to control and adjust, autonomously and independently, both statically and dynamically, that is to say, during rolling, both the x
2
component and the x
4
component, but 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 method for the static and dynamic control of the planarity of flat rolled 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 and bending means associated with the intermediate roll to arrange it with its longitudinal axis inclined, or rotated, with respect to the longitudinal axes of the working rolls and the back-up rolls and respectively bend it.
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, IR crossing and IR bending. 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.
In
FIG. 15
it can be seen how IR bending prevalently influences x
2
with collateral effects on x
4
(as for IR crossing), even though the action is less efficacious than that obtained with IR crossing. The x
4
/x
2
ratio is about {fraction (1/10)}.
The influence of IR crossing, IR bending, WR bending on the edges of the strip is very limited, and therefore when IR crossing, IR bending and WR bending is varied, it is not necessary to modify the set of WR shifting.
Therefore, the rolling stand which adopts the method according to the invention is equipped with means which allow IR crossing, IR bending, W

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