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Publication numberUS3914981 A
Publication typeGrant
Publication dateOct 28, 1975
Filing dateJan 23, 1975
Priority dateJan 29, 1974
Also published asCA1021288A, CA1021288A1, DE2501485A1
Publication numberUS 3914981 A, US 3914981A, US-A-3914981, US3914981 A, US3914981A
InventorsNilsson Jan, Syvakari Pertti
Original AssigneeAsea Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Die for hydrostatic extrusion
US 3914981 A
Abstract
A composite die for hydrostatic extrusion is composed of a preforming portion with a conical inlet portion and an end-forming portion, separated from each other along a radially dividing plane. A force-absorbing support ring surrounds that part of the end-forming portion which is in contact with and nearest the pre-forming portion. There is a gap on the outside of the part of the end-forming portion remote from the pre-forming portion. Separate rings surround and abut the calibrating end-forming portion and the support ring.
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nited States Patent Nilsson et a1.

[451 Oct. 28, 1975 DIE FOR HYDROSTATIC EXTRUSION Inventors: Jan Nilsson, Robertsfors; Pertti Syvakari, Helsingborg, both of Sweden Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden Filed: Jan. 23, 1975 Appl. N0.: 543,473

Assignee:

Foreign Application Priority Data Jan. 29, 1974 Sweden 74011107 U.S. Cl 72/467; 72/60 Int. Cl. B21C 25/02 Field of Search 72/467, 60, 253

References Cited UNITED STATES PATENTS l/1912 Stratton et al. 72/481 X 3,109,663 11/1963 Phillips, Jr. 279/41 3,191,374 6/1965 Ege 72/467 X 3,691,816 9/1972 Strandell 72/467 Primary Examiner-Milton S. Mehr [57] ABSTRACT A composite die for hydrostatic extrusion is composed of a preforming portion with a conical inlet portion and an end-forming portion, separated from each other along a radially dividing plane. A forceabsorbing support ring surrounds that part of the andforming portion which is in contact with and nearest the pre-forming portion. There is a gap on the outside of the part of the end-forming portion remote from the pre-forming portion. Separate rings surround and abut the calibrating end-forming portion and the support ring.

5 Claims, 2 Drawing Figures Sheet 1 of 2 US. Patent 0m. 28, 1975 DIE FOR HYDROSTATIC EXTRUSION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for hydrostatic extrusion which is composed of two or more individual parts. The purpose of the invention is to reduce the stresses in and around the die opening and accordingly reduce the risk of rupture and increase the life, and also to facilitate and reduce the cost of the manufacture of the die. The die is particularly intended for hot extrusion where the high temperature of the billet increases the stresses in the die. Different kinds of equipment in which the die may be used are described more fully in, for example, US. Pat. Nos. 3,702,555 and 3,751,958.

2. The Prior Art In a press for hydrostatic extrusion, a die projects into a pressure chamber and rests on a die support which takes up axial forces operating outwardly on the die. Usually the die support also projects somewhat into a cylinder which forms part of the pressure cham' ber. The die is surrounded by the pressure medium which acts on the billet to be extruded. The pressure medium brings about forces acting radially inwardly on the outer surface of the die. The billet to be extruded produces outwardly acting radial forces in the inlet portion of the die. As far as up to the die opening these radial forces balance each other, but beyond the smallest calibrating cross-section of the die the radial inner pressure ceases, so the forces produced by the pressure medium give rise to very great stresses at the inner surface of the die. A stress factor greater than two is obtained for thick-walled tubes in case of an outer load, that is, the stresses at the inner surface are more than twice as great as at the outer surface. The outer load itself is great, usually from to kbar. A die manufactured in one piece has also a shape which is less suitable from the point of view of hardening, and must of course have the same high-tensile material in the inlet portion as at the die opening, in spite of the fact that the material in the inlet portion is not subjected to the same high stresses. This results in a bad utilization of the material in the inlet portion of the die.

SUMMARY OF THE INVENTION According to the invention, the die is composed of two or more annular portions which are separated by substantially radial dividing lines. A first portion has a conical opening and forms a preforming portion, and a second portion having an opening which closely follows the first portion forms an end-forming and calibrating portion. The end-forming and calibrating portion is surrounded by a third ring and is attached in this ring in a prestressed manner. The prestressing may vary axially so that it is lower at its outer surface than at its inner portion. The same effect can be attained by giving the third ring a smaller axial extension than the endforming and calibrating portion, thus obtaining a suitable balancing of outwardly directed radial forces. The outer limit surface of the end-forming and calibrating portion can advantageously be located immediately behind the smallest cross-section of the die opening. It may then be appropriate to form the die with a third and a fourth ring which make contact with the endforming and calibrating portion and the surrounding prestress ring, respectively. These third and fourth rings are given such dimensions that a radial gap is formed between them. In this way the stress caused by the pressure medium at the opening of the inner ring is reduced. The rings can be made with different thicknesses so that a radial gap is formed between the endforming ring and the ring below the prestress ring. All the annular parts mentioned are held together by a surrounding ring and by locking rings.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described more fully with reference to the accompanying drawing. FIGS. 1 and 2 show dies of different embodiments placed in a pressure chamber in a press of the kind described in US. Pat. No. 3,751,958.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the FIGS., 1 designates a press table in a press stand, the rest of which is not shown, and 2 a highpressure cylinder which is part of a high-pressure chamber. In the cylinder there are a support cylinder 3 for taking up forces from a tube mandrel, a seal 4 consisting of an inner sealing ring 4a and an outer sealing ring 4b, and a spacing tube 5 which holds the seal 4a, 4b axially fixed to the seal holder 6. A die support 7 rests on the press table 1 and projects into the cylinder 2. The die support is provided with a guide ring 8 for centering a die 9a, which rests on the die support 7.

In the embodiment according to FIG. 1, the die 9a consists of a plurality of annular parts. The part 10 forms a preforming portion and has a concial opening 11. Below this there is an annular end-forming and calibrating portion 12 with a conical opening 13 which closely conforms to the opening 11 in the preforming portion 10. Furthermore, there are a substantially cylindrical opening 14 and, below this, a portion 15 with a somewhat larger diameter than the opening 14. The part 12 is surrouonded by a ring 16 and is attached into this ring at least along part of its axial extension. In the embodiment shown, the support ring 16 has a smaller thickness than the end-forming portion 12, so that the ring is engaged into the part of the portion 12 nearest to the preforming portion 10 but not in its outermost part. The preforming portion 10, the end-forming and calibrating portion 12 and the attachment ring 16 are held together by a ring 17 and by locking rings 18 and -19. The die support 7 is formed with support surfaces 21 and 22 in different planes at the same axial spacing as the outer surfaces of the parts 12 and 16. Between the outer cylindrical surface of the end-forming portion 12 and the step between the surfaces 21 and 22 there is a gap 23 so that the die support 7 can be compressed radially without coming into contact with the outer cylindrical surface of the end-forming portion 12. Because the end-forming portion 12 is attached in the support ring 16 in a prestressed manner, the billet, when it is pressed against the conical openings 11 and 13 of the die during insertion, is prevented from giving rise to tensile stresses in the end-forming portion 12, which stresses might cause said portion to burst. Further, the shape of the die causes the ring 16 and the pressure medium acting thereon to operate only on that part of the end-forming portion 12 which is exposed to outwardly directed radial forces during the pressing, that is, substantially only on the part which is located outside the conical portion 13 and the die opening portion 14. The shape of the die also means that the pressure medium is prevented from causing dangerous compressive stresses in the clearance portion in the die opening where there are no radially outwardly directed forces during the pressing.

In the embodiment according to FIG. 2, the die 9b contains a preforming portion 10, an end-forming portion 12 with a prestressed support ring 16 and also two rings and 26. The outer end surfaces of these rings are located at the same plane. The ring 26 has thus a greater thickness than the ring 25.

The outer diameter of the ring 25 is smaller than the inner diameter of the ring 26, so that a radial gap 27 is formed. The ring 26 is formed with a radially inwardly directed flange 28 which projects into a recess 29 in the ring 25 in order to fix this ring axially. The parts of the die are held together by a ring 30 and two locking rings 31 and 32. Because of the gap 27 between the ring 25 and the ring 26, the ring 26 must be deformed radially under the action of the pressure medium around the die before it is pressed against the ring 25. If possible, the play between the ring 26 and the ring 12 should be so large that said rings do not make contact with each other during the pressing. In this way it is possible to limit the stress caused by the pressure medium in the ring 12 and in the opening in the ring 25. When a die of this design is used, the end surface 34 of the die is of course completely plane.

One further advantage of a composite die according to the invention is that different materials can be chosen for different parts of the die. This means that a material of very high strength can be chosen in the endforming and calibrating portion of the die, and that this part can be given improved properties more easily by heat treatment because of its relatively small dimensions, which results in a reduced risk of dangerous stresses due to the heat treatment, and thus higher strength. It will also be possible to use hard metal in the die, or other materials which can be manufactured in the large sizes required for an undivided die only with considerable difficulty. The die will also be less sensi tive to such heat shocks which arise from contact with a heated extrusion billet. The cost of the die is also reduced by the fact that relatively inexpensive materials can be used in the main part of the die. In case of damage to the die, normally only the end-forming and calibrating portion of the die needs to be replaced. Further, the same elements can be used to a great extent for extruding products of different cross-sectional areas.

We claim:

1. Composite die for hydrostatic extrusion with a preforming portion (10) with a conical inlet portion (11) and an end-forming portion (12) separated along at least one substantially radial dividing plane, and a prestressed solid closed force-absorbing/support ring (16) surrounding and contacting the end-forming portion and supporting the end-forming portion (12) only in that part of its height nearest the pre-forming portion (10).

2. Composite die according to claim 1, in which a gap is provided around the part of the end-forming portion remote from the pre-forming portion.

3. Composite die according to claim 1, in which the thickness of the support ring (16) is smaller than that of the end-forming portion (12).

4. Composite die according to claim 1, which comprises a fourth ring (25) and a fifth ring (26) on the outside of the fourth ring, said fourth and fifth rings axially abutting the calibrating portion (12) and the support ring (16), respectively.

5. Composite die according to claim 4, in which a radial gap (27) is provided between the fourth ring (25) and the fifth ring (26).

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1015913 *Jan 4, 1910Jan 30, 1912 Apparatus for drawing wire.
US3109663 *Mar 27, 1962Nov 5, 1963American Carbide CompanyDie assemblies
US3191374 *Dec 15, 1961Jun 29, 1965Anaconda Wire & Cable CoForming die
US3691816 *Jun 19, 1970Sep 19, 1972Strandell Per-OlofMoulds
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4016737 *Dec 11, 1975Apr 12, 1977Allmanna Svenska Elektriska AktiebolagetHigh pressure press
US4038849 *Dec 1, 1975Aug 2, 1977Asea AktiebolagHigh pressure press
US4041743 *Nov 20, 1975Aug 16, 1977Asea AktiebolagHigh pressure press
US4041744 *Nov 20, 1975Aug 16, 1977Asea AktiebolagHigh pressure press
US4195505 *Nov 17, 1978Apr 1, 1980Asea AbPress for hydrostatic extrusion of tubes
US4397080 *Nov 10, 1980Aug 9, 1983Me-U-Sea, Inc.Process for preparation of support tooling for extrusion dies
US4543812 *Aug 6, 1984Oct 1, 1985The Harris-Thomas Drop Forge CompanyForging apparatus
Classifications
U.S. Classification72/467, 72/60
International ClassificationB21C25/00, B21C25/02, B21C23/00
Cooperative ClassificationB21C25/02, B21C23/007
European ClassificationB21C25/02, B21C23/00H