Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Patent
1998-09-11
1999-12-28
Hail, II, Joseph J.
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
B21B 1904
Patent
active
060065702
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a method for producing a hollow body from solid round steel that has been heated to shaping temperature.
2. Discussion of the Prior Art
The basic process for producing a hollow body from solid round steel by means of inclined rolls as a preliminary step in the production of seamless pipes is known (see Stradtmann, Stahlrohr-Handbuch, 7th edition, 1973, Vulkan-Verlag, Essen). In one of the known arrangements, a two-roll inclined rolling mill with Diescher disks is used for guiding the rolling stock (DE-PS 4308721).
A uniform wall thickness in the hollow bloom or ingot has decisive importance for the distribution of the wall thickness in the finished pipe, especially the eccentricity. Ideally, this is optimal when the ingot to be pierced, or the hollow ingot formed therefrom, is located with its center axis exactly on the center axis of the rolling mill and the center axis of the piercing mandrel likewise coincides precisely with the course of the center axis of the rolling mill. Interference can bring about deviations which become noticeable as deviations from the ideal position, wherein these deviations can be divided into components in the direction of the rolls and perpendicular thereto in the direction of the guides. Ideally, deviations of the piercing mandrel are compensated by the equilibrium of forces. Deviations in the position of the initial ingot result at the start of rolling in eccentric initial piercing which, particularly in the case of thick-walled hollow bodies in which the restoring forces brought about by the force equilibrium are small, leads to noticeably one-sided wall thicknesses and accordingly to waste.
In order to prevent eccentric piercing of the kind mentioned above, it is attempted to configure the piercing operation such that, immediately after the ingot is grasped by the rolls, the guides, for example, the rotating Diescher disks, guide the ingot centrally before the end face of the ingot contacts the piercing mandrel. However, this cannot always be guaranteed due to the radius of the Diescher disks.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a method for the production of a hollow body from solid round steel that has been heated to shaping temperature, by which the centering of the ingot can be ensured in a simple manner prior to the initial piercing operation, especially in the case of thick-walled hollow bodies.
According to the inventive method, immediately prior to the commencement of piercing, the clear distance between the pass-closing guides, preferably Diescher disks, is reduced in comparison to that of the stationary rolling phase. After initial rolling, the distance is adjusted to the customary value for the stationary rolling phase. The change in distance should advantageously be carried out automatically by the forces occurring in the direction of the guides (Diescher disks) during shaping.
With respect to the inventive device, the method according to the invention is realized in such a way that means which apply force to the guide so as to reduce the clear distance are arranged at the swinging or displacing arm of the pass-closing guides. These means preferably comprise a spring assembly which can be pretensioned. Alternatively, this action may be carried out by a hydraulically or pneumatically operating piston-cylinder unit which acts directly or indirectly, e.g., via an eccentric cam. The means exhibit a progressive characteristic such that the force for widening the guide clearance increases appreciably as the opening path increases, wherein the force for achieving the guide clearance under stationary conditions is less than the counterforce generated by shaping. The customary clear distance is accordingly reset automatically.
The advantage of the proposed method is that the desired centering for initial rolling is achieved by means of a very simple construction.
The method according to the invention is explained more fully in the drawing with refer
REFERENCES:
patent: 2535976 (1950-12-01), Wehman
patent: 4803861 (1989-02-01), Kummerling et al.
patent: 5406820 (1995-04-01), Mosey
patent: 5479805 (1996-01-01), Koenen et al.
Kindsgrab Adolf
Kummerling Rolf
Pieters Rolf
Hail, II Joseph J.
Mannesmann AG
Tolan Ed
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