WO2022090135A1

WO2022090135A1 - Forming tool and method for the impact extrusion of metallic workpieces

Info

Publication number: WO2022090135A1
Application number: PCT/EP2021/079504
Authority: WO
Inventors: Noomane Ben Khalifa; Jonas Isakovic; Jan Bohlen
Original assignee: Helmholtz-Zentrum Hereon Gmbh; Leuphana Universität Lüneburg
Priority date: 2020-10-27
Filing date: 2021-10-25
Publication date: 2022-05-05
Also published as: DE102020128163B3

Abstract

The present invention relates to a forming tool and to a method for the impact extrusion of metallic workpieces to produce largely isotropic impact-extruded parts. In the forming tools according to the invention, the forming process of the metallic material takes place substantially within the die. In addition, in contrast to conventional impact extrusion, the entire material flow in the inner laminar layers and the outer laminar layers takes place in the normal direction and in the transverse direction to the impact extrusion direction. According to the invention, a forming tool with a die is also used, which has at least one die channel wall which curves into the die channel, and wherein the channel cross-sectional areas defined by die channel walls remain substantially constant in size within the die channel.

Description

Forming tool and process for the extrusion of metal workpieces

FIELD OF THE INVENTION

The present invention relates to a forming tool according to the preamble of claim 1 and a method for the extrusion of metallic workpieces.

DESCRIPTION OF THE PRIOR ART

Extrusion is a pressure forming process used to produce rods, wires, tubes and irregularly shaped profiles. A workpiece, which is usually used as a cylindrical or cuboid profile, is introduced into a feed channel and pressed by means of a punch through a mold, in particular through a nozzle channel in the mold, also known as the running surface, so that the material is deformed by plastic deformation takes a desired shape to produce an extrusion. In direct or forward extrusion, the ram moves in the direction of the flow of the resulting profile towards the nozzle channel in the die; in indirect or reverse extrusion, the material is pressed against the direction of the punch by a die attached to the hollow punch.

DE 10 2010 006 387 A2 discloses a method for extruding wires made of magnesium material, in which the magnesium material is introduced into a feed channel and pressed by means of a punch through a mold with plastic deformation, with the magnesium active substance being extruded through the Mold is lubricated with a lubricant. The disadvantage is that the extruded parts produced often show a strong anisotropic mechanical behavior, such as a tension-compression anisotropy and / or a bending anisotropy based on the position of the stress direction along or transverse to the direction of extrusion. This applies, among other things, to extruded parts made from magnesium materials. These differences impede the use of profiles for structural components. It would therefore be desirable to achieve improved isotropic mechanical behavior in the extruded parts produced. This can be, for example, a tension/compression isotropy and/or a bending isotropy independent of the position of the stress direction in relation to the extrusion direction.

In order to improve the isotropic behavior of an extruded part, attempts have been made to add alloy components to the extruded material. However, improved isotropic mechanical properties of such alloys are "bought" by poorer extrudability due to sharply increasing extrusion forces. Attempts have also been made to produce isotropy by multiple extrusion of the same profile with an angled feed channel (ECAE method). Also These methods are associated with disadvantages, however, the practical implementation of this method is disadvantageous because an angled feed channel cannot be easily realized with the existing presses.

DE 102 30 553 A1 discloses a method and a device for the extrusion of magnesium materials, in which a particularly cylindrical profile made of a magnesium material is introduced into a feed channel and pressed by means of a stamp under plastic deformation through a mold, with a plasti cal deformation of the profile is provided immediately before the mold transverse to the direction of movement by the feed movement of the Stamp is reached. For this purpose, the profile is initially displaced by means of the stamp until it rests against the forming tool. As a result of the continued feed movement, the profile is compressed, ie deformed with expansion in the transverse direction, so that there is no central axis aligned in the extrusion direction, but an orientation of the central axis that is folded out in different directions. This increases the compressive stress to the level of the tensile stress. However, the proposed method is not very economical because the feed channel is not completely filled with material. In addition, the extruded parts produced using the method in DE 102 30 553 A1 have improved isotropic properties, which, however, are often insufficient.

The invention is therefore based on the object of providing a mold for the production of extruded parts with further improved isotropic properties, which enables a method without the disadvantages mentioned above. In particular, the greatest possible reduction of the anisotropic mechanical behavior should be realized. Furthermore, it is the object of the present invention to provide a method for producing largely isotropic extruded parts that can be carried out using conventional extrusion presses.

SUMMARY OF THE INVENTION

The first-mentioned object is achieved according to the invention with a mold for an extrusion process according to the features of patent claim 1 . The further configuration of the mold can be found in dependent claims 2 to 7 .

According to the invention, a mold for the extrusion of metallic materials is provided with at least one extrusion die that extends along a longitudinal axis, the extrusion die in the direction of its longitudinal axis. axis comprises a die channel having a die channel inlet, a die channel outlet, and die channel walls extending from the die channel inlet to the die channel outlet to form a die channel nozzle for plastically deforming the metallic material into a desired shape to produce an extrusion, the die channel walls on each define a channel cross-sectional area in a cross-sectional plane transverse to the longitudinal axis of the extrusion die, and wherein the channel cross-sectional area has an extension in a first direction normal to the direction of the longitudinal axis and in a second direction normal to the direction of the longitudinal axis and transverse to the first normal direction. The extrusion die according to the invention is characterized in that the expansion of the channel cross-sectional area increases in the first normal direction and decreases in the second normal direction. In other words, the die channel nozzle forms a confuser in a first normal direction to the longitudinal axis of the extrusion die and a diffuser in a second normal direction to the longitudinal axis of the extrusion die, transverse to the first normal direction.

At least one die channel wall is preferably arched into the die channel. At least two, three or four are preferred, and all die channel walls are more preferably curved into the die channel. The curvatures of the matrix walls can be designed discontinuously over polyhedron surfaces or continuously over free-form surfaces.

It is furthermore preferred that the surface area, ie the size, of the channel cross-sectional areas decreases from the die channel entrance to the die channel exit. The consequence of this is that the hydrostatic pressure that acts on and in the material increases within the die channel as it progresses through the die and the metallic material completely fills the die channel during extrusion.

In the forming tools according to the invention, the forming process of the metallic material takes place essentially inside the die.

The object is also achieved by a method with the features of claim 9 for the production of extruded parts, in which a profile made of a metallic material is introduced into a feed channel and pressed by means of a stamp with plastic deformation through a mold, the mold having at least one extrusion die as described above.

According to one aspect of the invention, these are common, extrudable metallic materials such as aluminum and magnesium alloys in particular.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is explained by way of example with reference to the accompanying figures. The figures do not restrict the scope of protection of the invention defined by patent claims. The figures show:

FIGS. la to ld: a first perspective view of a first extrusion die according to the invention for producing a strip profile in the direction from the die channel inlet to the die channel outlet;

FIGS. 2a to 2b: a second perspective view of a first extrusion die according to the invention for producing a strip profile in the direction from the die channel outlet to the die channel inlet; FIG. 3a: a perspective view of a central section through a second extrusion die according to the invention for producing a strip profile in the direction from the die channel inlet to the die channel outlet;

FIG. 3b: a perspective view of a further section through the second extrusion die according to the invention shown in FIG. 3;

FIG. 4: a perspective view of a central section through an extrusion die according to the prior art for producing a strip profile in the direction from the die channel inlet to the die channel outlet;

FIGS. 5a to 5d: a perspective view of a third extrusion die according to the invention for producing an L-profile in the direction from the die channel inlet to the die channel outlet;

FIG. 6a: a first perspective view of a fourth extrusion die according to the invention, production of a hollow profile in the direction from the die channel inlet to the die channel outlet;

FIGS. 6b to 6d: a schematic view of the fourth extrusion die according to the invention according to FIG. 6a in the direction from the die channel inlet to the die channel outlet.

In a first embodiment of the present invention according to FIGS. In the direction of its longitudinal axis 3, the extrusion die 1 comprises a die channel with a die channel lass 4 and a die channel outlet 5. Furthermore, the die channel comprises die channel walls. Two opposing die channel walls 11 and 12 are shown in FIG. 1b for better understanding; two further matrix channel walls 13, 14 are perpendicular thereto (not emphasized). The die channel walls 11, 12, 13, 14 extend from the die channel inlet 4 to the die channel outlet 5 to form a running surface in order to convert the metallic material during flow through plastic deformation with the production of an extruded part - in this embodiment into a metallic strip. According to the embodiment shown in FIGS. 1a to 1d, the die channel inlet 4 has a square shape and the die channel outlet 5 has a rectangular shape. The die channel walls 11, 12, 13, 14 are all curved into the die channel, with the curvature of the die channel walls 11, 12 being differently pronounced than the curvature of the die channel walls 13, 14 lying perpendicular thereto. In this case, the curvatures of the die channel walls 11, 12, 13, 14 are constructed continuously over free-form surfaces. The profile of the die channel tapers in the direction of the opposing die channel walls 13, 14, forming a confusor in this first direction normal to the longitudinal axis of the extrusion die, and it widens at the same time in the direction of the opposing die channel walls 11, 12, forming a diffuser in this second direction normal to the longitudinal axis of the extrusion die .

The die channel walls 11, 12, 13, 14 define a channel cross-sectional area 21, 23 (FIG. 1c) or 22 (FIG. 1d) on each cross-sectional plane transverse to the longitudinal axis of the extrusion die. The size of these channel cross-sectional areas 21, 22, 23, which are defined by the die channel walls 11, 12, 13, 14, decreases from the die channel entrance to the die channel exit, ie the surface area of the through the die channel walls 11, 12, 13, 14 defined channel cross-sectional areas on each cross-sectional plane transverse to the longitudinal axis of the extrusion die remains in the direction from the die channel inlet 4 to the die channel outlet 5 decreases. In other words, the square footage of the faces shown is: 21 > 22 > 23.

FIG. 2a shows the extrusion die 1 of the first embodiment according to the invention in a second perspective view, which is tilted by 180° and rotated by 90° compared to the first perspective view. In the direction of its longitudinal axis 3, the extrusion die 1 comprises a die channel with a die channel outlet 5—which is now shown lying on top—and a die channel inlet 5. In FIG. 2b, the die channel wall 14 is shown highlighted as an example for better understanding.

In a second embodiment of the present invention according to FIG. In the direction of its longitudinal axis 103, the extrusion die 101 comprises a die channel with a die channel inlet 104 and a die channel outlet 105. The die channel also comprises die channel walls 111, 112, 113. The die channel wall 111 is curved in the direction of the die channel. A die channel wall opposite the die channel wall--not shown in this view--is also curved in the direction of the die channel. According to the second embodiment, the die channel walls 112, 113 are not curved in the direction of the die channel. The wall of the arched die channel wall 111 of the second embodiment of the present invention shown in FIG. 3a is illustrated in the quarter section according to FIG. 3b. In this embodiment, the curvature of the matrix channel wall 111 is built up discontinuously over a polyhedron surface. A conventional extrusion die 901 for extruding metal strip is shown in FIG. In the direction of its longitudinal axis 903, the extrusion die 901 comprises a die channel with a die channel inlet 904 and a die channel outlet 905 as well as die channel walls 911, 912, 913. However, these are not profiled, so that the actual forming process of the metallic material does not take place in the die, but exclusively in the upstream supply channel takes place. The die channel defined by the die channel walls 911, 912, 913 only serves to maintain the band geometry.

In the forming tools according to the invention, the forming process of the metallic material essentially takes place inside the die. In addition—in contrast to conventional extrusion—the entire material flow in the inner laminar layers and the outer laminar layers is moved in the normal direction and in the transverse direction to the direction of extrusion.

In a third embodiment of the present invention according to FIG. 5a, the mold for the extrusion of metallic L-profiles has an extrusion die 201 that extends along a longitudinal axis 203. In the direction of its longitudinal axis 203, the extrusion die 201 comprises a die channel with a square die channel inlet 204 and an L-shaped die channel outlet 205. The die channel also comprises die channel walls 211, 212, 213, 214, 215. Die channel walls 213, 214 are shown in FIG. 5b for better understanding highlighted as an example.

The die channel walls 211, 212 are curved into the die channel, the curvature of the die channel walls 211, 212 being opposite to the curvature of the die channel walls 213, 214 are differently pronounced. The die channel walls 213, 214 are curved outwards. The curvature of the material channel wall, which forms the inside of the L-profile, is particularly pronounced.

The die channel walls 211, 212, 213, 214, and the material channel wall that forms the insides of the L-profile, define a channel cross-sectional area 221, 223 (Figure 5c) and 222 (Figure 5d) on each cross-sectional plane transverse to the longitudinal axis of the extrusion die. The size of these channel cross-sectional areas 221, 222, 223, which are defined by the die channel walls, decreases, i.e. the area of the channel cross-sectional areas defined by the die channel walls on each cross-sectional plane transverse to the longitudinal axis of the extrusion die decreases in the direction from the die channel inlet 204 to the die channel outlet 205 ; In other words, the square measure of the faces shown is: 221 > 222 > 223.

The person skilled in the art recognizes that other profiles such as V-profiles, U-profiles, cross profiles, star profiles and also hollow profiles can be produced in a similar way.

Hollow profiles can also be produced according to the invention. For this purpose, the mold consists of two parts, which can either be joined together in a separable manner or manufactured in one piece. A first part for forming a mandrel, which forms the inner contour of the profile, has at least two hollow chambers, which are arranged around a core and open into a welding chamber. The core ends in a mandrel that is attached to the outer edge of the mold via bridges and protrudes into the running surface of the die. At least one of the outer die channel walls of the tread, preferably also at least one die channel wall of the mandrel, is curved into the die channel, with the channel cross-sectional areas defined by the inner and outer die channel walls in the die channel, ie the channel cross-sectional areas defined by the outer die channel walls minus the cross-sectional area defined by the die channel walls of the mandrel, remain substantially constant in size. Preferably all die channel walls of the running surface, more preferably also all die channel walls of the mandrel, are curved into the die channel.

In a fourth embodiment of the present invention according to FIGS. 6a to 6d, the mold for the extrusion of metallic hollow profiles has an extrusion die 601.

A first part of the extrusion die 601 for forming a mandrel 642 which forms the inner contour of the profile, has four hollow chambers 631 which are arranged around a core and open into a welding chamber 641 which has an inlet and a bottom. A die channel with a die channel inlet 604 and a die channel outlet 605 extends from the bottom of the welding chamber.

Furthermore, the die channel includes inner and outer die channel walls. Two inner die channel walls 613, 614 of the four inner die channel walls according to this embodiment are highlighted in FIG. 6c for better understanding. Two outer die channel walls 615, 616 of the four outer die channel walls according to this embodiment are exemplified in FIG. 6d for better understanding.

The die channel walls 613, 614, 615, 616 are all curved into the die channel.

Various variants are known for extruding hollow profiles. The die concept we have described here reflects the structure of a chamber tool. The conventional nally manufactured chamber tools are multi-part. A component of the tool defines the inner contour of the hollow profile. Another variant for manufacturing hollow profiles is extrusion with an integrated mandrel. These machines are usually loaded with a hollow pin instead of a solid pin. The mandrel integrated into the machine and the hollow bolt replace the need to first split the material and then join it again in the welding chamber with a chamber tool. A tool design according to the invention that displaces the material transversely to the direction of extrusion is also possible in an extrusion press with an integrated mandrel. For this, only the mandrel of the machine would have to be designed with the corresponding curvatures.

The molds according to the invention can be produced using 3D metal printing processes, for example using known powder bed melting processes.

Claims

Claims Mold for the extrusion of metallic materials with at least one extrusion die (1, 101, 201, 601) which extends along a longitudinal axis (3, 103, 203), the extrusion die (1, 101, 201, 601) in the direction of its longitudinal axis (3, 103, 203) has a die channel through which the metallic material can flow and which has a die channel inlet (4, 104, 204,

604), a die channel outlet (5, 105, 205, 605) and die channel walls (11, 12, 13, 14), (211, 212, 213,

214), (311, 312, 313, 314, 315), (613, 614, 615, 616) extending from the die channel inlet (4, 104, 204, 604) to the die channel outlet (5, 105, 205, 605) to form a die channel nozzle in order to convert the metallic material into a desired shape by plastic deformation while producing an extruded part, the die channel walls (11, 12, 13, 14), (211, 212, 213, 214), ( 311, 312, 313, 314, 315), (613, 614, 615, 616) on each cross-sectional plane transverse to the longitudinal axis (3, 103, 203) of the extrusion die (1, 101, 201, 601) a channel cross-sectional area (21, 22 , 23) , (221, 222, 223) and wherein the channel cross-sectional area (21, 22, 23) , (221, 222, 223) has an extension in a first

Direction normal to the direction of the longitudinal axis (3, 103,

203) and in a second direction normal to the direction of the longitudinal axis (3, 103, 203) and transverse to the first

Has normal direction, characterized in that the extension of the channel cross-sectional area (21, 22, 23), (221, 222, 223) increases in the first normal direction and decreases in the second normal direction. Mold tool according to Claim 1, characterized in that at least one die channel wall is curved into the die channel. Mold according to claim 2, characterized in that two, three, four, five or six die channel walls (11, 12, 13, 14), (211, 212, 213, 214), (311, 312, 313, 314,

315), (613, 614, 615, 616) are arched into the matrix channel. Mold according to one or more of claims 1 to

3, characterized in that the curvatures of the die channel walls (11, 12, 13, 14), (211, 212, 213, 214),

(311, 312, 313, 314, 315), (613, 614, 615, 616) are built up discontinuously over polyhedron faces. Mold according to one or more of claims 1 to

(311, 312, 313, 314, 315), (613, 614, 615, 616) are built up continuously over freeform surfaces. Forming tool according to one of the preceding claims, characterized in that the size of the cavity walls (11, 12, 13, 14), (211, 212, 213, 214), (311, 312, 313, 314, 315), ( 613, 614, 615, 616)n defined channel cross-sectional area (21, 22, 23), (221, 222, 223) in the

Die channel decreases from the die channel inlet (4, 104, 204, 604) to the die channel outlet (5, 105, 205, 605). Mold according to one or more of Claims 1 to 6 for the extrusion of metallic materials in the form of strips, L profiles, V profiles, U profiles, cross profiles, star profiles or hollow profiles. Mold according to one or more of Claims 1 to 6 for the extrusion of metallic materials in the form of hollow profiles, characterized in that a first part of the extrusion die (1, 101, 201, 601) for forming a mandrel (642) is connected upstream of the die channel, which forms the inner contour of the profile, the first part of the extrusion die (1, 101, 201, 601) having at least two hollow chambers (631) which are arranged around a core and open into a welding chamber (641), and the core in the Mandrel (642) opens, which is attached via bridges to an outer edge of the mold and projects into the die channel inlet (604). Process for the production of extruded parts, in which a profile made of a metallic material is introduced into a feed channel and is pressed by means of a stamp with plastic deformation through a mold according to claims 1 to 8. Method according to Claim 9, characterized in that magnesium, a magnesium alloy, aluminum or an aluminum alloy is used as the metallic material.