Metal deforming – By extruding through orifice – With metal-deforming other than by extrusion
Patent
1992-03-03
1994-05-10
Larson, Lowell A.
Metal deforming
By extruding through orifice
With metal-deforming other than by extrusion
428585, B21C 2301
Patent
active
053097483
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is concerned with a method of producing extrusions and particularly with the production of long metal extrusions having uniform mechanical properties along the entire length of the extruded section.
BACKGROUND OF THE INVENTION
There is a need within the aircraft and construction industries for long aluminium extrusions having a high and uniform fracture toughness throughout the length of the extrusion. However using conventional extrusion processes it is found that the fracture toughness may be reduced towards the back-end of the extrusion. The longer the extrusion the worse the problem becomes. In order to obtain extrusions having adequate fracture toughness along their length it is necessary either to discard a large portion from the back-end of the extrusion or for ease of production to discard a large part from the rear end of the billet. Since the size of billets is limited to those which can be accommodated by the extrusion press, the size of extrusions which can be reliably produced is also limited.
If a billet of smaller diameter than the internal diameter of the container of the extrusion press is used the extrusion ram compresses the billet along its length and the billet metal is displaced in a transverse direction to fill the container. This process is known as upsetting. It is known to increase the transverse ductility of extrusions by introducing a small degree of upset along the entire length of the extrusion billet.
U.S. Pat. No. 3455134 describes the use of tapered billets in a hydrostatic extrusion process. The billets remain tapered during extrusion and are not upset.
GB 769604 is concerned with the hot working of alloys which are not normally extrudable. A billet which may be frusto-conical is compressed axially, and then extruded with the head of the ingot extruded last. The purpose of the method is to reduce loss of metal as scrap.
SUMMARY OF THE INVENTION
The present inventors have now discovered that by use of billets having a tapered back-end a differential upset may be applied to the billet and extrusions may be produced which have improved fracture toughness along their length. Accordingly, the present invention provides a method of producing an extrusion which method comprises providing a billet of extrudable metal, said billet having an untapered part and a back end which has a reduced cross-section along at least part of its length, the cross-sectional area of the billet at the back-end being up to 90% of the cross-sectional area of the untapered part of the billet, compressing the billet along its length such that the metal of the back-end of the billet is upset in a transverse direction, and extruding the compressed billet.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the invention will become apparent to those of ordinary skill in the art upon reviewing the detailed description of the invention in conjunction with the appended drawings in which:
FIGS. 1A through D are side views of tapered metal extrusion billets prepared in accordance with the present invention.
FIG. 2A and B are views of another tapered metal extrusion billet prepared in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is illustrated with particular reference to aluminium and aluminium alloys. However the present invention is not limited to aluminium but is applicable to other extrudable metals.
The invention also provides a billet of extrudable metal for use in the extrusion process which has a reduced cross-section along at least part of its length such that the cross-sectional area at one end is up to 90% of the cross-sectional area of the untapered part of the billet wherein the billet is of a 2000, 5000, 6000, 7000 series alloy or 8090 or 8091 aluminium alloy or that sold under the Trade Mark Weldalite 049.
In a further aspect of the invention there is provided an extrusion of a metal having a volume of metal of at least 60% of that of the billet from which it was extrud
REFERENCES:
patent: 2080640 (1937-05-01), Templin
patent: 2781903 (1957-02-01), Buffet et al.
patent: 3802243 (1974-04-01), Wessel
patent: 3874213 (1975-04-01), Sperry et al.
Dixon William
Jarrett Martin R.
Alcan International Limited
Larson Lowell A.
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