Method for producing a metal foam product from an aluminium-containing material with the aid of a tool mould having a mould core coated with a release agent, and tool mould

Abstract

The invention relates to a method (100) for producing a metal foam product (1) having a cavity (4) of predetermined shape with a metal foam (2) made of an aluminium-containing material, comprising the following method steps (102, 104, 106, 108, 110): providing a tool mould (1000) with a mould core (1004) having the predetermined shape; coating at least some portions of an outer surface (1006) of the mould core facing the part (1008) of the mould interior (1002) that is accessible to the metal foam with a release agent (1010); filling the mould interior of the tool mould with the aluminium-containing material and a blowing agent; heating the tool mould with the material and blowing agent located therein, so that the material is foamed; removing the mould core from the metal foam product. By means of the method according to the invention and the tool mould according to the invention, metal foam products having complex geometries can be produced cost-effectively and with little effort.

Description

The invention relates to a method for producing a metal foam product from an aluminium-contain-ing material with the aid of a tool mould having a mould core coated, at least in sections, with a release agent, as well as to a tool mould and a metal foam product. Metal foam products made of aluminium are becoming increasingly widespread, as they are resilient and energy-absorbing while requiring little material, and exhibit high heat conductivity. Such metal foam products are produced by foaming the aluminium-containing material by applying heat, using a heat-activated release agent such as Ti2O. Complex geometries can only be produced at considerable cost. The underlying object of the invention is therefore to enable the cost-effective and efficient production of metal foam products with complex geometries. According to the invention, this problem is solved by a method for producing a metal foam product having a cavity of a predetermined shape, with a metal foam made of an aluminium-containing material, comprising the following method steps: - providing a tool mould with a mould core having the predetermined shape; - coating at least some portions of an outer surface of the mould core with a release agent, the outer surface facing the part of the mould interior that is accessible to the metal foam; - filling the mould interior of the tool mould with the aluminium-containing material and a blowing agent; - heating the tool mould with the material and blowing agent located therein, so that the material is foamed; - removing the mould core from the metal foam product. This problem is further solved by a tool mould for producing a metal foam product comprising a cavity of a predetermined shape from an aluminium-containing material, wherein the tool mould comprises a mould core having the predetermined shape, wherein an outer surface of the mould core, the outer surface facing the part of the mould interior that is accessible to the metal foam, is coated at least in some portions with a release agent. The advantage of these two solutions is that metal foam products containing cavities can be produced in a simple and cost-effective manner. Such cavities reduce the density and, consequently, the production costs of the metal foam product. Furthermore, the metal foam product according to the invention offers a high degree of functional integration and a wide range of possible applications. For example, the cavities in the metal foam product can be used to house electrical cables or cooling lines. With the aid of the solutions described above, it is furthermore possible to produce ducts directly within the metal foam. In particular, the walls of the ducts are formed by the metal foam itself, thereby saving material. Furthermore, this configuration enables direct heat exchange between the ducts and the metal foam from which they are formed, without any intermediate components. This increases energy efficiency. The invention can be further improved by the following advanced features, each of which is preferred in its own right and can be combined with any other as desired. The features described below can be used indiscriminately both to improve the method and to improve the tool mould. Thus, in one configuration, the release agent may comprise or consist of boron nitride, graphite and / or a ceramic, in particular aluminium oxide or a carbide such as tungsten carbide. These release agents are heat-resistant and reliably prevent the metal foam from bonding to the mould core. The tool mould is preferably reusable, or is reused. This reduces production costs. In order to simplify the assembly and disassembly of the tool mould, the tool mould may, according to one configuration, comprise at least one receptacle that is accessible for the mould core from outside the tool mould, in which receptacle the mould core can be received at least in sections. The mould core can be inserted into the tool mould and / or removed from it through the receptacle. A mould core that is housed in the receptacle of the tool mould may be accessible from outside the tool mould. In order to improve accessibility to the mould core, at least one section of the mould core may be arranged outside a part of the mould, which part surrounds the mould interior. The mould core may thus extend from the mould interior to the outside of the mould interior, for example through a wall, in particular a top or bottom of the tool mould. In order to make the production process more energy-efficient, in one configuration, the energy required to heat the tool mould and / or to foam the material may be supplied at least in part via the mould core, and according to another embodiment, even entirely via the mould core. In order to further reduce energy losses, the energy, in particular thermal energy, required to heat the tool mould may, according to one configuration, be supplied exclusively via that section of the mould core which is arranged outside the part of the tool mould that sourrounds the mould interior. In order to reduce the mass of the mould core and thus the production costs, as well as to improve the manageability of the tool mould, the mould core may be hollow. The mould core may have an opening, in particular a through-opening, which may extend through the entire mould core along a longitudinal axis of the mould core. In one embodiment, the mould core is tubular, preferably in the form of a metal tube. The cavity within the mould core may be accessible from outside the tool mould. According to one configuration, the mould core may be cylindrical, at least in sections. Such a mould core can be produced easily and with a high degree of accuracy. Of course, the mould core may also be entirely cylindrically shaped. Furthermore, the mould core may be prismatic, conical and / or hollow-cylindrical, at least in sections. In particular, a conical shape of the mould core may simplify the insertion and / or removal of the mould core into or from the mould interior. In a further embodiment, the mould core may comprise or consist of a cast aluminium material. The high heat conductivity of cast aluminium materials ensures that the thermal energy supplied via the mould core is distributed evenly across the outer surface of the mould core and conducted with minimal loss into the mould interior. Naturally, the mould core may alternatively or cumulatively also comprise or consist of other metallic materials. In order not to impair the stability of the produced metal foam product, the mould core may extend to different side surfaces of the mould interior. Thus, the points at which the mould core abuts the inner surface of the tool mould facing the mould interior may each be located on different side surfaces of the mould interior. The different side surfaces may be opposite, in particular parallel, side surfaces arranged in the mould interior of the tool mould. The mould core may be assembled in one piece or in several parts, and thus, for example, consist of individual segments, so that cavities of various geometric shapes can be produced in the metal foam product. The individual segments may be, or will be, coated with a release agent independently of one another. For example, at least one segment may remain uncoated, so that it bonds with the metal foam and becomes part of a composite structure. This segment is, of course, not reusable, but forms part of the metal foam product. The segments may be made of different materials. For example, materials with different heat conductivities may be used. In this way, the heat input into the mould interior can be influenced by the arrangement of the segments. This makes it possible to compensate for uneven heat input, which is predetermined by the furnace, or to specifically influence the structure of the metal foam in individual areas. According to a further configuration, even those segments that become part of the metal foam product because they bond with the metal foam may be made of a different material compared to the segments that remain within the tool mould. The tool mould may be configured to produce a metal foam product with several intersecting or interpenetrating cavities. In particular, the cavities may be defined by different segments of the mould core, each of which may have different cross-sections or three-dimensional shapes. The mould core may comprise several struts or branches, for example extending at right angles or acute angles to one another, which define the cavities in the metal foam product to be produced. Naturally, the mould core may also be configured to produce several cavities that do not intersect or interpenetrate, such as cavities arranged in parallel to one another. The shape and position of the mould core can influence the direction along which thermal energy is transmitted between the mould core and the material or the blowing agent during heating and / or cooling of the tool mould. Should the metal foam product produced with this tool mould have cooling or heating devices in its subsequent use, in particular cooling lines running through the cavities, the direction of heat transfer or heat dissipation between the cooling lines and the metal foam product may analogously be influenced by the shape and position of the cavities. The problem is further solved by a metal foam product made of a metal foam made of an alumin-ium-containing material, having a cavity, wherein an average cell size decreases towards an interface directly surrounding the cavity. Such a metal foam product is both resilient and lightweight. The material density of the metal foam product may thus increase towards an interface immediately surrounding the cavity. In particular, the density distribution may increase parabolically towards the interface. The metal foam product, or the metal foam, may have a closed foam surface at the interface and, in particular, may be completely smooth. The metal foam may be an integral foam, or the metal foam product may consist of an integral foam. The term “integral foam” may refer to a metal foam, the cell structure of which becomes denser towards an interface and which has an outer skin at the interface that is preferably closed and / or smooth. The invention is explained below by way of example with reference to the Figures. In accordance with the above explanations, individual features described below may be omitted in the relevant embodiment if the technical effect of these features is not essential for a particular application. Conversely, a feature described above but not described below may be added to the relevant embodiment if the technical effect of this feature is essential for a particular application. It is shown by: Fig. 1 a schematic view of a metal foam product; Fig. 2 a schematic cross-sectional view of another metal foam product; Fig. 3 a schematic view of a method for producing a metal foam product; Fig. 4 a schematic view of a tool mould for producing a metal foam product; and Fig. 5 a schematic perspective view of another metal foam product. Fig. 1 shows a metal foam product 1 comprising a metal foam 2. The metal foam product 1 has at least one cavity 4 which extends, at least in sections, through the metal foam product 1. Both the metal foam product 1 and the cavity 4 may have virtually any three-dimensional shape. In the illustrated embodiment, the metal foam product 1 has a cuboid shape, which is traversed by a substantially cylindrical cavity 4. The cavity 4 may extend from a first side surface 6 of the metal foam product 1 to a second side surface 8 of the metal foam product 1, which is arranged parallel to the first side surface 6. Naturally, the cavity 4 may also extend between side surfaces 10 that are not opposite one another. At one or more points, in particular in the region of the cavity 4, the metal foam product 1 may comprise a cover layer 12, so that a composite material is formed. Preferably, there is a metallic bond between a cover layer 12 and the metal foam 2. In the embodiment shown, the cover layer 12 extends along an interface 14 immediately surrounding the cavity 4, however, the cover layer 12 may also cover the entire interface 14. As shown in Fig. 5, the metal foam product 1 may also have several cavities 4. In the embodiment shown, the cavities 4 have different three-dimensional shapes resulting from various cross-sections, namely rectangular, circular and polygonal. Of course, other cross-sections or three-dimensional shapes are also conceivable. The cross-sections of the cavities 4 need not be constant along the longitudinal extension of the cavities 4, as shown in Fig. 5, but may also vary, thereby defining, for example, a conical cavity 4. The cavities 4 shown in Fig. 5 intersect, so that the cavities 4 interpenetrate in sections or are connected to one another. In the embodiment shown, two cavities 4 intersect at right angles; however, the cavities 4 may also be arranged at an obtuse or acute angle to one another. According to other configurations, the cavities 4 may not intersect or interpenetrate at all and, in particular, may be arranged parallel to one another. Fig. 2 shows a schematic cross-sectional view of a further metal foam product 1 with a cavity 4. The metal foam product 1 comprises a plurality of adjacent cells 16, the average size 18 of which varies along the length of the metal foam product 1. In the embodiment shown, the average cell size 18 decreases towards the interface 14 immediately surrounding the cavity 4, so that the density of the metal foam product 1 increases towards the cavity 4. The density distribution of the metal foam product 1 may, for example, increase in a parabolic manner towards the cavity 4 or the interface 14. At the interface 14, the metal foam product 1 may have a closed, preferably smooth foam surface 20, which may form a solid wall or outer skin surrounding the cavity 4. For the production of the metal foam product 1, the method 100 shown schematically in Fig. 3 is carried out. In a first step 102 of the method 100, a tool mould 1000 is provided. In this context, a mould interior 1002 of the tool mould 1000 has the same geometric three-dimensional shape as the metal foam 2 in the metal foam product 1. It should be noted that the metal foam product 1 can be machined using either cutting or non-cutting processes, if this is necessary for individual applications. For example, the metal foam product 1 can be reshaped in order to bring it into a different shape for an application. Additionally or cumulatively, the metal foam product 1 can be provided with bores and milled-out portions, punched holes and / or additional parts. The tool mould 1000 comprises a mould core 1004, which is arranged at least in sections within the mould interior 1002 and which has a predetermined shape corresponding to the cavity 4 of the metal foam product 1 to be produced. The nature of the mould core 1004 is explained in more detail below with reference to Fig. 4. In a second step 104, an outer surface 1006 of the mould core 1004, which faces a part 1008 of the mould cavity 1002 that is accessible to the metal foam 2, is coated, at least in portions, with a release agent 1010. The release agent 1010 is, for example, a ceramic such as aluminium oxide, in particular Al2O3, or a carbide such as tungsten carbide. Graphite or boron nitride may also be used as the release agent 1010. Where the mould core 1004 is coated with the release agent 1010, the metal foam 2 does not bond with the mould core 1004. Thus, if, for example, a segment 1012 of the mould core 1004 is not coated with the release agent 1010, it can form a cover layer 12 of the metal foam product 1. In step 106, the tool mould 1000 is filled with the aluminium-containing material and a blowing agent. The aluminium-containing material may be in the form of strips. The blowing agent may be added in the form of strip- or strand-shaped compacts. The tool mould 1000 is then sealed and heated in step 108, so that the blowing agent is activated and the aluminium-containing material is melted, thereby producing the metal foam 2. Infrared rays are preferably used to heat the tool mould 1000. In one configuration, the energy required to heat the tool mould 1000 or to foam the material can be supplied, at least in part, via the mould core 1004. The tool mould 1000 is then cooled, either actively or passively, and subsequently, in a further step 110, the mould core 1004 is removed from the metal foam product 1. In order to simplify this process, the mould core may, in one configuration, have a slight taper. The metal foam product 1, which is now ready for any further processing, can then be removed. The mould core 1004 can then be reused, provided that no individual segments 1012 have remained as the cover layer 12 of the metal foam product 1. However, at least those segments 1012 of the mould core 1004 that have not become part of the cover layer 12 of the metal foam product 1 can be reused. Fig. 4 shows the tool mould 1000 with a bottom 1014 and a separate top 1016, which surround a mould interior 1002 of the tool mould 1000 between them. The tool mould 1000 comprises the mould core 1004, which, in the embodiment shown, extends through the mould interior 1002 between the bottom 1014 and the top 1016, that is, towards two different side surfaces 10 of the mould interior 1002. The mould core 1004 need not, as shown in Fig. 4, be housed in a receptacle 1018 of the tool mould 1000 that is accessible from outside the tool mould 1000 and, in particular, need not extend through the bottom 1014 and / or top 1016 of the tool mould 1000. The mould core 1004 may comprise a section 1020 which is arranged outside the part 1022 of the tool mould 1000 that surrounds the mould interior 1002. For example, as can be seen from Fig. 4, the mould core 1004 may protrude outwards through the top 1016 of the tool mould 1000. In a configuration, the energy required for heating can be supplied, preferably in its entirety, via this section 1020 of the mould core 1004. The mould core 1004 has the predetermined shape of the cavity 4 of the metal foam product 1, which can be produced using the tool mould 1000. The mould core 1004 shown in Fig. 4 is hollow-cylindrical in shape. Naturally, the mould core 1004 may also have other shapes, such as a shape that is at least in sections cylindrical, conical or prismatic. Furthermore, the mould core 1004 may, of course, also be solid at least in sections and thus not hollow at least in sections. According to Fig. 4, the mould core 1004 may be constructed from individual segments 1012. The segments 1012 may form part of a modular system comprising more segments 1012 than those 5 currently used in the tool mould 1000. Different moulds can be assembled from different segments 1012. The segments 1012 may be made of different materials. In particular, a segment 1012 may be made of a cast aluminium material. However, at least one segment 1012 is coated, at least in portions, with a release agent 1010, which is applied to an outer surface 1006 of the mould core 10   1004 or a segment 1012 of the mould core 1004 facing the part 1008 of the mould interior 1002 that is accessible to the metal foam 2. For example, a segment 1012 that is intended to remain as the cover layer 12 of the metal foam product 1 may be made of steel, while a segment 1012 coated with a release agent 1010 may be made of the cast aluminium material. Reference signs 1 metal foam product 2 metal foam 4 cavity 6 first side surface 8 second side surface 10 side surface 12 cover layer 14 interface 16 cells 18 cell size 20 foam surface 100 method 102 first step 104 second step 106 third step 108 fourth step 110 fifth step 1000 tool mould 1002 mould interior 1004 mould core 1006 outer surface 1008 accessible part of the mould interior 1010 release agent 1012 segment 1014 bottom 1016 top 1018 receptacle 1020 section that is arranged outside 1022 part of the tool mould that surrounds the mould interior

Claims

1. Method (100) for producing a metal foam product (1) having a cavity (4) of a predetermined shape, with a metal foam (2) made of an aluminium-containing material, comprising the method steps (102, 104, 106, 108, 110):- providing a tool mould (1) with a mould core (1004) having the predetermined shape;- coating at least some portions of an outer surface (1006) of the mould core (1004) with a release agent (1010), the outer surface (1006) facing the part (1008) of the mould interior (1002) that is accessible to the metal foam (2);- filling the mould interior (1002) of the tool mould (1000) with the aluminium-con-taining material and a blowing agent;- heating the tool mould (1000) with the material and blowing agent located therein, so that the material is foamed;- removing the mould core (1004) from the metal foam product (1).

2. Method (100) according to claim 1, wherein the release agent (1010) comprises or consists of- boron nitride;- graphite;- a ceramic, in particular aluminium oxide or a carbide such as tungsten carbide.

3. Method (100) according to claim 1 or 2, comprising the following method step:- reusing the mould core (1004) of the tool mould (1000).

4. Method (100) according to one of claims 1 to 3, wherein the energy required to heat the tool mould (1000) and / or to foam the material is supplied at least in part via the mould core (1004).

5. Tool mould (1000) for producing a metal foam product (1) having a cavity (4) of a predetermined shape from an aluminium-containing material, wherein the tool mould (1000) comprises a mould core (1004) having the predetermined shape, wherein an outer surface (1006) of the mould core (1004), the outer surface (1006) facing the part (1008) of themould interior (1002) that is accessible to the metal foam (2), is coated at least in some portions with a release agent (1010).

6. Tool mould (1000) according to claim 5, wherein the release agent (1010) comprises or consists of- boron nitride;- graphite;- a ceramic, in particular aluminium oxide or a carbide such as tungsten carbide.

7. Tool mould (1000) according to claim 5 or 6, wherein the tool mould (1000) is reusable.

8. Tool mould (1000) according to one of claims 5 to 7, wherein the mould core (1004) is hollow.

9. Tool mould (1000) according to one of claims 5 to 8, wherein the mould core (1004) extends to different side surfaces (10) of the mould interior (1002).

10. Tool mould (1000) according to one of claims 5 to 9, wherein the tool mould (1000) comprises at least one receptacle (1018) that is accessible from outside the tool mould (1000) for the mould core (1004), in which receptacle (1018) the mould core (1004) can be accommodated at least in sections.

11. Tool mould (1000) according to one of claims 5 to 10, wherein at least one section (1020) of the mould core (1004) is arranged outside a part (1022) of the tool mould (1000), which part (1022) surrounds the mould interior (1002).

12. Tool mould (1000) according to claim 11,wherein the energy required to heat the tool mould (1000) is supplied exclusively via the section (1020) arranged outside the part (1022) of the tool mould (1000), which part (1022) surrounds the mould interior (1002).

13. Tool mould (1000) according to one of claims 5 to 12, wherein the mould core (1004) is cylindrical at least in sections.

14. Tool mould (1000) according to one of claims 5 to 13, wherein the mould core (1004) comprises or consists of a cast aluminium material.

15. Metal foam product (1) made of a metal foam (2) made of an aluminium-containing material, having a cavity (4), wherein an average cell size (18) decreases towards an interface (14) directly surrounding the cavity (4).

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