Device for indirect extrusion of a hollow section

A device for indirect extrusion of a hollow section from a billet, in particular a hollow aluminum billet, which is presented to a shape-giving orifice of a die, which is such that a container can be passed over it, thus enclosing the die, and features in its orifice a mandrel that determines the inner contour of the hollow section. A shaping recess is provided, with respect to the extrusion direction x, immediately in front of the shape-giving orifice of the die, the radial dimension of which recess is greater than the width of the shape-giving orifice. The shaping recess is provided either in the face of the die directed towards the extrusion stem or in the face of the extrusion stem directed towards face of the die.

BACKGROUND OF THE INVENTION 
The invention relates to a device for indirect extrusion of a hollow 
section from a billet, in particular a hollow aluminum billet which is 
presented to a shape-giving opening of a die by an extrusion stem, the die 
being such that a billet container can be moved over it, thus enclosing 
it, and a mandrel which determines the inner contour of the hollow section 
is provided in the shape-giving opening of the die. 
When hot forming a billet, pre-heated to the extrusion temperature, to 
strands or rods, the billet which is enclosed in the container is usually 
pressed by the extrusion stem of a hydraulic extrusion press into the 
stationary shaping die; the stem or a so-called dummy block on the 
extrusion stem forms the backing for the material which is to be extruded. 
When extruding by the so-called indirect extrusion method, either the 
shaping tool, the die, is pushed into the stationary container or the 
latter is moveable and can be pushed over the die thus enclosing it. In 
both cases, prior to extrusion, a new billet is placed in the container 
next to the backing and compressed to fill the space around it in the 
container. 
The die is mounted on a long tool stem which is subjected to high thermal 
and mechanical stresses; this tool stem must be hollow as the strand 
formed has to pass through it. By supporting the die the whole of the 
extrusion force acts on the tool stem during the extrusion stroke, this 
usually includes, besides the purely compressive forces, also torsional 
and bending forces. Furthermore, the mandrel projects into the tool stem. 
Applications exist for hollow sections in the form of seamless, hollow 
tubes featuring flanges at the end joined to the tube body with as little 
change in structure as possible. Such an application, for example, is to 
be found in containers used in uranium precipitation plants; these 
containers usually comprise a hollow tube body with a flange welded onto 
and machined at one end. 
SUMMARY OF THE INVENTION 
In view of the above the object of the present invention is to manufacture 
in one piece and as inexpensively as possible, via indirect extrusion, a 
hollow section with integral flange, and to develop a device for this 
purpose. 
This object is achieved by way of the invention in that a shaping recess is 
provided, with respect to the direction of extrusion, immediately before 
the shape-giving opening in the die, said recess having its radial 
dimension greater than the width of the die opening and being that place 
where the extruded matrix forms the flange that projects out beyond the 
side of the hollow section.

DETAILED DESCRIPTION 
It has been found particularly favorable to provide the shaping recess in 
the face of the die directed towards the extrusion stem so that the die 
shapes both the hollow section and the flange thereon in its full height. 
It is, however, also possible to provide for this shaping recess an 
extension recess running counter to the direction of extrusion, in the 
adjacent face of the extrusion stem; this is particularly useful if 
high-walled flanges are to be produced. 
It is also within the scope of the invention only to provide the extrusion 
stem with a shaping recess which is penetrated by the mandrel; according 
to another feature of the invention this shaping recess is formed by a 
ring-shaped collar and an insert. 
The shaping recess is thus a mold box for the flange, which in plan view is 
round, oval or preferably quadratic. 
When the flanged tube has been formed, the extrusion stem is drawn back and 
the said tube withdrawn from the tool stem. 
If the tool stem is likewise divided along a plane in its longitudinal axis 
as is the die, then, after moving the container back, the resultant 
flanged tube can be removed sideways, which permits relatively long tube 
lengths to be produced. 
As the contours of the shaping recess determine the shape of the flange, it 
is for example also possible to provide this with ring-shaped ribs or the 
like, if corresponding grooves are present in the floor of the shaping 
recess. 
Thanks to the invention it is now possible to extrude aluminum flanged 
tubes, which, up to now, has not been possible in the simple manner 
described above. 
Referring to the drawings, situated in front of the platen 1 of an 
extrusion press 2 for producing hollow sections is a container 3 for 
indirect extrusion arranged separate from the platen 1. The central bore 4 
in line with the main axis E of the press 2 allows the container 3 to be 
passed over a fixed, stationary tool stem 5, the head 6 of which is 
securely and directly mounted on the platen 1. 
Running through the tool stem 5 is a central stem channel 7 which extends 
from a shape-giving die 10, not shown in detail in FIG. 1, to an opening 9 
in the platen 1. The container 3 can be moved, counter to the direction of 
extrusion x, off the tool stem 5 held by slide 11. 
Facing the die front 12 and the face 13 of the container 3 remote from 
platen 1 is a pressure cylinder 14 in stand 15; an extrusion stem or ram 
16, and from this a mandrel 17, projects out from the cylinder 14 in the 
axis E of the press. 
The distance a between face 13 of the container 3 facing cylinder 14 and 
the end of the mandrel 17 in the non-operating position shown in FIG. 1 is 
such that, in this position, a light metal billet B can be placed in front 
of tool stem 5 by means of a billet loader 18; when the axis or billet B 
lies coaxial to the press axis E, the billet B can be pressed by extrusion 
stem 16 in the direction of extrusion x. 
FIG. 2 indicates the production of a hollow section 20 having a hollow tube 
part 21 of outer diameter d and flange 22 of height i. Billet B is pressed 
by face 24 of extrusion stem 16 against die 10 which features a shaping 
orifice or opening 25. The ring-shaped wall 26 of the die 10 determines 
the outer contour of the tube part 21; the inner contour of the tube part 
21 is determined by the mandrel 17 projecting into the orifice 25. Before 
the orifice, with respect to the extrusion direction x, is a shaping 
recess 30 in which the flange 22 resides at the end of the extrusion 
stroke. Face 24 of the extrusion stem 16 contacts face 12 of the die 10; a 
ring-shaped shoulder 28 on the extrusion stem 16 projects into a recess 29 
in container 3. 
In FIG. 2 it can be seen that the mandrel 17 is mounted in a mandrel 
channel 19 in extrusion stem 16. 
In the exemplified embodiment shown in FIG. 3 the shaping recess 30 is 
provided in the extrusion stem 16; it is made up of a ring-shaped 
projection 32 on the stem 16 and insert 33 mounted on the mandrel 17. 
Projecting ring 32 features a recess stop 35 which, in the shown end 
position, accommodates the ring-shaped edge 36 around the container bore 
4. 
As a result of the described device 2 it is now possible to extrude 
one-piece flanged pipes 20, which can be employed, for example, as 
centrifuge containers or receptacles for uranium separation plants. The 
shape of the flange 22, as seen in plan view, is determined by the shaping 
recess 30, and can be chosen at will, likewise the diameter d of flanged 
pipe 20. It can be decided according to the given conditions whether 
conventional hollow billets B are employed or whether these are 
heat-treated first. The facility for solution treatment of the billet B is 
not shown in the drawings.