Rolling mill for sizing tubes or cylindrical bodies in general i

Details Rolling mill for sizing tubes or cylindrical bodies in general i Rolling mill for sizing tubes or cylindrical bodies in general i

1999-05-10

2000-09-12

Butler, Rodney

Metal deforming

By use of roller or roller-like tool-element

Included in roller-cluster

72234, B21B 1310, B21B 1308

Patent

active

061160717

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a rolling mill of the type intended in particular for the iron and steel industry, for sizing tubes or cylindrical bodies.
The term "sizing" is here used to refer to that phase in the working of tubes, rods, bars or anything else in the iron and steel industry that can be described as a cylindrical body, in which a semi-finished product produced earlier is rolled out to its final dimensions.


BACKGROUND OF THE INVENTION

In the particular case of tubes, what takes place during sizing is essentially a reduction in the diameter of a semi-finished product, in order to reach its nominal value, because the thickness of the wall is usually reached through previous stages of the production cycle which can be carried out by rolling the material around a mandrel using rolling mills of a type commonly known by the abbreviation MPM, or on so-called push benches, or on machines known as "plug mills" etc. See for example on the matter the Japanese Patent Application No. 07314013.
Consequently the sizing of a tube may include the stage of withdrawing the mandrel, if this is made necessary by the previously executed process; that of reduction, whether by stretching or otherwise, and that of finishing with the aim of finally reaching the tolerances required in the production cycle.
Similar considerations to those indicated above with regard to tubes can also be applied, with the appropriate modifications, to the cylindrical bodies referred to earlier.
At present, the usual preference is for sizing to be carried out on rolling mills employing rolling units or stands (both of these terms will be used hereinafter with the same meaning) containing three driven rolls, as these have been found to give good performance as regards the surface finish of the wrought products.
With this type of rolling mill, a very common configuration is that in which the three rolls of the rolling stands are arranged with their respective axes of rotation lying along the sides of an equilateral triangle and are connected to each other via bevel gears, enabling them to be rotated simultaneously by the application of drive to only one of them; in this form the adjustment of the distance between the rolls and the rolling axis is small because the abovementioned configuration will not allow any large movement, it being necessary to keep the bevel gears in mesh. In practice, with this type of rolling mill it is possible to make only a very small adjustment in the positions of the rolls, by adjusting the supporting mechanisms of their bearings; most significantly, it should be pointed out that, under load, that is to say during the processing of a tube or cylindrical body, there is no possibility of making any adjustment.
Because of the low operational flexibility of rolling stands of this type, for brevity's sake they will be referred to below as fixed or fixed-type stands.
It should also be noted that the low flexibility of rolling mills made up of this type of stand requires that for output ranges of tubes comprising a large number of diameters, a large bank of rolling stands must be prepared, because in practice each diameter of tube to be made requires the availability of a set of stands set up specifically to form the rolling mill.
In order to remedy this situation, special rolling units with three or more driven rolls whose positions with respect to a rolling axis can be adjusted even under load, have recently been developed; examples of such rolling units are disclosed in the Italian Patent Applications Nos. MI92A000917 (also European Patent Application No. 92118389.3) and MI93A000704 (also International Patent Application No. PCT/EP/93/00898), both laid open and filed by the owner of this application. In these rolling units the rolls are mounted at the ends of respective lever-type arms which are hinged, at the opposite end from the rolls, to a container having the form essentially of a closed frame that can be removed from an external supporting structure of the rolling unit: each roll

REFERENCES:
patent: 4397169 (1983-08-01), Staat
patent: 5331835 (1994-07-01), Palma et al.
patent: 5765423 (1998-06-01), Cattaneo et al.
J. Ammerling, "Flexibility of 3-Roll Technology for Reducing and Sizing High-Quality Bars", Iron and Steel Engineer, Pittsburgh, US, vol. 67, No. 8, Aug. 1990, pp. 33-37.
W.-J. Ammerling, "Neue Generation Von Kombinierten 3-Walzen-Blocken in Stabstahl-Und Drahtstrassen", Stahl Und Eisen, vol. 115, No. 2, pp. 47-50.
E. Blos, "New Developments in Rod Mills", Iron and Steel Engineer, Pittsburgh, US, vol. 63, No. 12, Dec. 1986 pp. 35-46.

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