Direct or indirect metal pipe extrusion process, mandrel for extruding metal pipes, metal pipe extruder and extruded metal pipe

Abstract

If a mandrel for extruding metal pipes, having two axially offset pressing surfaces with different radial characteristics and having a transition region between these two pressing surfaces has a support surface in the transition region then the negative effect of narrowing, which arises owing to the mandrel shifting from a first pressing position, in which the first of the two pressing surfaces interacts with a die, to a second pressing position, in which the second pressing surface interacts with the die, can be minimized.

Claims

1. A method for extrusion of a metal pipe comprising the following steps: (a) providing a mandrel having a first end and a second end disposed opposite from each other, the mandrel having two pressing surfaces disposed at the first end and axially offset and having different radial characteristics, wherein the mandrel has a transition region between the two pressing surfaces and a supporting surface in the transition region; (b) pressing a metal block to form the metal pipe, through a die and by way of the mandrel; (c) moving the mandrel axially in a direction of the second end of the mandrel from a first pressing position to a second pressing position, in the first pressing position, a first one of the two pressing surfaces of the mandrel acts on the metal block, and in the second pressing position, a second of the two pressing surfaces of the mandrel acts on the metal block; and (d) supporting the metal block on a mandrel side of the metal block, at an axial height of the die, while the mandrel is moved from the first pressing position to the second position.

2. The metal pipe extrusion method according to claim 1, wherein the supporting takes place first after a free surface with regard to the mandrel is formed on the metal block.

3. The metal pipe extrusion method according to claim 2, wherein the supporting takes place when the free surface is displaced in the direction of the mandrel.

4. A method for extrusion of a metal pipe comprising the following steps: (a) providing a mandrel having a first end and two pressing surfaces disposed at the first end, the two pressing surfaces being axially offset and having different radial characteristics, wherein the mandrel has a transition region between the two pressing surfaces and a supporting surface in the transition region; (b) pressing a metal block to form the metal pipe, through a die and by way of the mandrel; (c) repositioning the die axially with reference to a block mount such that the mandrel is repositioned from a first pressing position to a second pressing position, in the first pressing position, a first one of the two pressing surfaces of the mandrel acts on the metal block, and in the second pressing position, a second of the two pressing surfaces of the mandrel acts on the metal block; and (d) supporting the metal block on a mandrel side of the metal block, at an axial height of the die, while the mandrel is repositioned from the first pressing position to the second position.

5. The metal pipe extrusion method according to claim 4, wherein the supporting takes place first after a free surface with regard to the mandrel has been formed on the metal block.

6. The metal pipe extrusion method according to claim 5, wherein the supporting takes place first when the free surface is displaced in the direction of the mandrel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, goals, and properties of the present invention will be explained using the following description of exemplary embodiments, which are also particularly shown in the attached drawing. The drawing shows:

(2) FIG. 1 a schematic overview of a direct metal pipe extruder having a mandrel situated in the first pressing position;

(3) FIG. 2 the arrangement according to FIG. 1, wherein the mandrel is being positioned in the second pressing position;

(4) FIG. 3 the arrangement according to FIGS. 1 and 2, with the mandrel situated in the second pressing position;

(5) FIG. 4 an indirect metal pipe extruder in representations similar to FIGS. 1 to 3, with the mandrel in the first pressing position;

(6) FIG. 5 a detail view of the mandrel tip of the mandrel according to FIGS. 1 to 4; and

(7) FIG. 6 a detail view of the mandrel tip similar to FIG. 5 showing two supporting surfaces.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(8) The two metal pipe extruders 10 and 20 each have a block mount 1, a die 2, a pressing punch 3 that can be displaced relative to the block mount 1, as well as a mandrel 6 that forms a gap, together with the die 2, through which a work piece is pressed from a metal block 5 into a metal pipe 9. This takes place, in each instance, in that the block mount 1 is displaced relative to the pressing punch 3, thereby causing the space in the block mount 1 to be reduced accordingly, and a metal block 5 situated there to be pressed through the gap between die 2 and mandrel 6, in each instance.

(9) For this purpose, the direct metal pipe extruder 10 shown in FIGS. 1 to 3 has a pressing punch 3 disposed ahead of the block mount 1 in the pressing direction P, which punch drives a pressing disk 4 into the block mount 1 in the pressing direction P, in known manner, thereby causing the space present in the block mount 1 to be reduced accordingly. In this connection, a die holder 7 is provided on the block mount 1, on which holder the die 2 is held in locally fixed manner, with reference to the block mount 1. If the pressing punch 3 is now moved in the pressing direction P, the work piece is pressed through the gap to form a metal pipe 9, which leaves the gap in the pressing direction P.

(10) The indirect metal pipe extruder 20 shown in FIG. 4 comprises a pressing punch 3 disposed behind the block mount 1 in the pressing direction P, which punch is moved counter to the pressing direction P for pressing and carries the die 2, wherein the block mount 1 has a closure piece 8 on its end facing away from the pressing punch 3, which closes off this mount counter to the pressing direction P. If the pressing punch 3 is now displaced counter to the pressing direction P, this punch presses the die 2 in the direction toward the closure piece 8, by way of the mandrel 6, so that the die 2 is displaced with reference to the block mount 1, in other words, does not remain fixed in place with reference to the block mount 1, in contrast to the case of direct metal pipe extruder 10. In this exemplary embodiment, the mandrel 6 is displaced with reference to the block mount 1, together with the pressing punch 3 or the die 2.

(11) It is understood that the relative movement between pressing punch 3 and block mount 1 can be implemented in different ways, for example in that the block mount 1 is held still and the pressing punch 3 is moved, or on the other hand, the pressing punch 3 is held still and the block mount 1 is moved. Likewise, it is possible to move both modules, as long as the relative movement between pressing punch 3 and block mount 1 required for pressing remains implemented.

(12) In the present exemplary embodiments, the mandrel is configured to have rotation symmetry with regard to its mandrel axis 68, but this is not absolutely necessary in all embodiments.

(13) As FIG. 5 particularly shows, the mandrel 6 narrows toward its mandrel tip 61 and has a first pressing surface 63 and a second pressing surface 64, which can be brought into a position in each instance in which they directly act on the material of the work piece, together with the die 2, forming it, and are able to shape the metal pipe 9 by axial displacement of the mandrel 6.

(14) A transition region 66 is disposed between the first pressing surface 63 and the second pressing surface 64, in which region is provided a supporting surface 62 (FIG. 5), or a supporting surface 62 and a further supporting surface 62 (FIG. 6), each of which is oriented cylindrically around the mandrel axis 68 in each of these exemplary embodiments. The support length 65 of supporting surface 62 in the embodiment shown in FIG. 5 is equal to the support length 65 of supporting surface 62 and the further supporting surface 62 in the embodiment shown in FIG. 6.

(15) In the axial direction, the first pressing surface 63 has a length 71 and the second pressing surface 64 has a length 72. A distance 73 can be found between the two pressing surfaces 63, 64, which distance defines the transition region 66.

(16) The mandrel rod 6 is held in place in known manner, at its mandrel foot 67, and can be displaced by way of the latter. In particular, it can be positioned from a first pressing position, in which the first pressing surface 63 interacts with the die 2, into a second pressing position, in which the second pressing surface 64 interacts with the die 2, as has been shown as an example in FIGS. 1 to 3.

(17) By means of this repositioning, the wall thickness can be changed in accordance with the different cross-sections of the two pressing surfaces 63, 64, whereby in the end result, a metal pipe 9 having different wall thicknesses and a transition region provided between them can be made available. In this connection, there is a constriction E in the transition region, which can be minimized by means of suitable support during repositioning of the mandrel, and can even be avoided entirely, if applicable.

(18) The present exemplary embodiments relate to aluminum pipes as the metal pipe 9, whereby other metals that can be pressed to form pipes, by means of extrusion methods, can also be used alternatively, accordingly, if applicable.

REFERENCE SYMBOL LIST

(19) 1 block mount 2 die 3 pressing punch 4 pressing disk 5 metal block 6 mandrel 7 die holder 8 closure piece 9 metal pipe 10 direct metal pipe extruder 20 indirect metal pipe extruder 61 mandrel tip 62 supporting surface 62 further supporting surface 63 first pressing surface 64 second pressing surface 65 support length 66 transition region 67 mandrel foot 68 mandrel axis 71 length of the first pressing surface 72 length of the second pressing surface 73 distance between the pressing surfaces E constriction P pressing direction