EP2046519B1 - Metal moulding and method for producing it - Google Patents

Abstract

A metal molding (10) comprises a metal foam region (12) composed of a metal foam consisting of a metal, a further region (14) in which the metal has fewer or smaller cavities than in the metal foam region, and an essentially sheet-like one-part or multipart insert element (16) with orifices or interspaces. The insert element (16) is arranged in a fringe region between the metal foam region (12) and the further region (14). The metal in the further region (14) is connected metallically to the metal in the metal foam region (12) in orifices or interspaces of the insert element (16).

Description

The present invention relates to a metal moldings consisting of metal-bonded areas of metal foam on the one hand and metal on the other hand and at least one insert element of a higher melting point than the base material of foam and metal exhibiting material, and to a process for its preparation.

Lightweight metal moldings or manufacturing method of the type mentioned are for example from AT 408317 B It is known, according to which, in a powder metallurgical process, a semifinished body of a compacted mixture of a matrix metal powder and a propellant powder in a foaming mold is heated together with at least one insert element to a temperature at which the matrix metal powder melts and the Propellant powder releases gas that forms gas bubbles in the matrix metal. The resulting metal foam encloses the insert element which does not melt at the temperatures used and which can fulfill a wide variety of functions, such as providing connections, cavities, reinforcements and the like. Disadvantages of such metal moldings or of the production process can be seen in the complexity with the resulting costs, and especially in the difficult or even uncontrollable division of the metal foam or metal regions and the wide distribution of the pore size in the metal foam itself, which is negative Influences on the quality of the molded body has.

In likewise known melt metallurgical processes for the production of metal foam itself (see, for example, US Pat. AT 410103 B or AT 411970 B ) gas is introduced into a particle-reinforced molten metal, whereby the gas bubbles formed collect to form flowable metal foam on the surface of the melt. This metal foam is then either cast or pressed into a mold or can also rise directly into a mold arranged above the melt. The foaming gas is by means of Nozzles (see eg AT 410104 B or AT 411768 B ) or by means of a so-called impeller (see eg US 2003/0051850 A1 ) are introduced into the melt. Metal foam is mainly made of aluminum composite material, but also made of composites of magnesium or other light metals. The most extensive industrial experience so far exists with aluminum foam, which is almost ideal in terms of the desired minimum mass density and also has excellent properties in terms of absorption of energy. Shaped metal foam therefore find use, for example, in the crumple zone of automobiles, as cavity reinforcements, but also as lost core parts of reinforced, light and hollow castings, wherein they additionally have a positive influence on the body acoustics. F., et al .; "Reinforced Aluminum Foams", in Cellular Metals and Meats Forming Technology (2001), pages 365-368 describes a process for the production of aluminum foam with insert elements.

Metal foam or moldings produced therefrom, however, are only able to absorb tensile stresses to a relatively small extent, which has already been attempted by the insert elements mentioned at the outset. Furthermore, it has not succeeded satisfactorily to provide the thickness or shape of a solid, dense, relatively foam-free exterior wall area as desired.

Object of the present invention is to improve a metal molding or a method of the type mentioned so that the opportunities given by the functional insert elements are optimally exploitable and that even a solid, foam-free outer wall area made of metal with a wide range of arbitrary design is possible ,

This object is achieved according to the present invention according to claim 1 and in a metal moldings of the type mentioned above in that / the metal foam area (s) (each) consists of metal foam with substantially monomodal bubble size / exist and opposite adjacent areas at least partially by means of Boundary region arranged insert elements which are formed substantially flat and having passage openings from one area to the other, which are formed in its cross section, that the substantially monomodal foam bubbles of one area are prevented from passing into the other, are delimited.

• Bereitstellen einer Kokille für den Metallformkörper;
• Anordnen zumindest eines ein- oder mehrteiligen Einlageelementes mit Öffnungen oder Zwischenräumen in der Kokille in zumindest einem Grenzbereich zwischen zumindest einem mit Metallschaum zu füllenden Metallschaumbereich und zumindest einem weiteren Bereich;
• Aufschmelzen eines Metalls;
• Einleiten von Gas in das aufgeschmolzene Metall, um das aufgeschmolzene Metall aufzuschäumen, wobei ein fließfähiger Metallschaum mit im wesentlichen monomodaler Blasengröße größer als die Öffnungen in dem Einlageelement entsteht;
• Verbringen des fließfähigen Metallschaums in den Metallschaumbereich und von im wesentlichen blasenfreiem Metall in den weiteren Bereich; und

The preparation according to the invention specified in claim II for such a metal molding is characterized by the following steps:

• Providing a mold for the metal molding;
• Arranging at least one single- or multi-part insert element with openings or intermediate spaces in the mold in at least one boundary region between at least one metal foam region to be filled with metal foam and at least one further region;
• Melting a metal;
• Introducing gas into the molten metal to foam the molten metal to form a flowable metal foam having a substantially monomodal bubble size greater than the openings in the liner;
• Placing the flowable metal foam in the metal foam region and substantially bubble-free metal in the wider region; and

Cooling the metal in the mold, wherein the metal solidifies to form the metal mold.

A casting according to the invention, which contains a shaped metal body of this kind in the form of a lost core, is also part of the invention.

The present invention is based on the idea of arranging one insert element or several insert elements in the metal molding, wherein each insert element may be one or more parts and preferably substantially flat, but not necessarily flat. This insert element or these insert elements have a melting point which is above the maximum temperature reached in the production of the metal molding, and preferably contain steel, another metal or another alloy or else ceramic or other materials, in particular fiber materials made of carbon, glass , Silicon carbide, alumina or other ceramic fibers. Furthermore, an insert element consist of aluminum alloy or aluminum, wherein it preferably has coated or glazed surfaces and / or an aluminum alloy having a melting point which is higher than the maximum temperature achieved in the production of the metal molding.

An insert element is preferably a net, a grid, a perforated sheet-like element, in particular a perforated sheet metal, a wire or fiber braid or consists of a plurality of substantially parallel straight or curved bars. It has openings or interspaces whose shape and / or size are selected so that, although the liquid metal, substantially no foam or its gas bubbles can pass through the openings or spaces. The insert element therefore forms a boundary between a metal foam region and a further region in which the metal has fewer or smaller or substantially no cavities.

The metal foam region is preferably arranged in the interior of the metal molding, while the further region forms the solid, foam-free surface of the metal molding. Through the openings or interspaces of the insert element, the metal in the metal foam region and the metal in the wider region are connected to one another metallically, d. H. they form a continuous crystal structure without an intermediate oxide, adhesive or other layer of a different material.

Due to the design and arrangement of the insert element or of the insert elements, the shape and in particular the thickness of the further region or of the solid wall region can be set as desired. The insert element defines the boundary between the metal foam region and the further region and is thus arranged in the boundary region between the same.

The insert element is also able to absorb tensile stresses and thus to perform a similar task as reinforcing steel in reinforced concrete. For this it can be mechanically biased. This preload can already be in the mold before the introduction of the flowable metal foam or before the cooling of the metal by suitable clamping devices are generated. Alternatively, the bias arises from the fact that the insert element consists of a material having a different, preferably higher thermal expansion coefficient than the metal in the metal foam region and in the wider region. The tensile stress in the insert element is in any case opposite a corresponding compressive stress of the metal foam region and the solid wall region.

Fig. 1 und 1a

jeweils schematische Darstellungen eines Schnitts durch einen Metall- formkörper;

Fig. 2

eine schematische Darstellung eines Schnitts durch einen weiteren Me- tallformkörper;

Fig. 3

eine schematische Darstellung eines Schnitts durch einen weiteren Me- tallformkörper;

Fig. 4

eine schematische Darstellung eines Gussvorganges im Querschnitt;

Fig. 5

eine schematische Darstellung eines Gussvorganges im Querschnitt;

Fig. 6

ein schematisches Flussdiagramm eines Herstellungsverfahrens.

Further embodiments are given in the dependent claims. Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying figures. Show it:

Fig. 1 and 1a

in each case schematic representations of a section through a metal molding;

Fig. 2

a schematic representation of a section through another metal shaped body;

Fig. 3

a schematic representation of a section through another metal shaped body;

Fig. 4

a schematic representation of a casting operation in cross section;

Fig. 5

a schematic representation of a casting operation in cross section;

Fig. 6

a schematic flow diagram of a manufacturing process.

Fig. 1 is a schematic representation of a shaped metal body 10 with a metal foam region 12 and a solid wall portion 14. In the boundary region between the metal foam region 12 and the solid wall portion 14, an insert member 16 is arranged. The insert element 16 is preferably a net, grid or braid of metal wire or strand of any cross-section or of carbon or other fibers, a perforated sheet or other sheet or an array of preferably substantially parallel bars or wires of any cross-section. Preferably, the insert element 16 is made of aluminum or another metal or an alloy or a other material having a melting point higher than the melting point of the metal of which the metal foam region 12 and the solid wall region 14 are formed. Steel in different qualities is particularly suitable because of its high strength, its high melting point, its good availability, its low price and the variety of processing and processing options. The insert element 16 may have coated or glazed surfaces.

The insert element 16 has openings or intermediate spaces in which the metal foam region 12 and the solid wall region 14 directly adjoin one another and merge homogeneously into one another. The metal foam region 12 and the solid wall region 14 are metallically connected to each other or have a continuous crystal structure without intervening layers of oxide or other materials. The metal foam region 12 and the solid wall region 14 are thus connected by the openings or interspaces of the insert member 16 cohesively.

The metal foam region 12 has cavities or gas bubbles with a substantially monomodal distribution of the dimensions. This means that all or almost all cavities of the metal foam region 12 have substantially the same diameter and the same volume. The cavities are approximately in the shape of multi-flattened balls or of polyhedra. Between each two adjacent cavities a substantially planar or plate-shaped metal web is arranged.

The solid wall portion 14 has in the in FIG. 1 Metal moldings 10 shown substantially in the form of a layer surrounding the metal foam region 12 and the insert member 16 with a constant thickness.

In a portion 18, the insert member 16 and the solid wall portion 14 have an opening, by the in the below with reference to FIG. 4 10 described more detailed production of the metal moldings flowable metal foam is placed in the metal foam region 12. In section 18, the metal foam region 12 directly adjoins the surface 20 of the metal molding 10. However, this can be done by special measures be avoided during manufacture or subsequently by milling and sealing with solid material.

The solid wall portion 14 has no or substantially no or at least (substantially) less or (substantially) smaller cavities than the metal foam portion 12. Like almost any casting, however, the solid wall portion 14 may also have at least isolated voids or other gas inclusions.

Fig. 1a differs from Fig. 1 only in that here now two different metal foam areas 12, 13 are provided, which are separated from each other by an additional insert element 16 and an additional part of the multi-piece insert element 16 and metal foam with different properties. For the sake of clarity, different bubble sizes are shown here - but it could also be metal foam of different base material, with different additions or similar differences. The insert element 16 inserted between the two metal foam regions 12, 13 at the interface substantially prevents thorough mixing of the two types of foam, so that different properties of the metal molding 10 can be predetermined in the two regions 12, 13. Also in the execution after Fig. 1a It is true that the metal foam areas 12, 13 with each other as well as these with the metal portion 14 through the insert elements 16 and the parts of the insert element 16 through metallic connection and thus by the insert elements 16 thus a reinforced metal moldings 10 is formed.

Apart from the fact that the areas 12, 13 and 14 consist of the same base material and differ essentially only in that in the area 14 virtually no gas bubbles, in area 13 many small gas bubbles and in the area 12 less large gas bubbles (as in Fig. 1a However, these differences could also go so far that the base materials differ in the areas 12, 13 and 14 - for example, different aluminum alloys could be used in the individual areas or to provide various additives to the foam areas or the metal area with certain desired properties.

Fig. 2 is a schematic representation of a portion of another metal shaped body 10 with a metal foam portion 12 and a solid wall portion 14, which are separated by an insert member 16. The example FIG. 2 is different from that FIG. 1 among other things, that the solid wall portion 14 due to the shape of the insert member 16 deviates from a simple layer with a constant thickness. In the solid wall portion 14, an eyelet 22 is disposed at one end of the metal molding 10. The shape and arrangement of the eyelet 22 is defined by the mold used for producing the metal mold body 10 or, for example, by a socket inserted in the mold. Alternatively, the eyelet 22 is made after the casting process on the cooled metal moldings 10 by drilling or milling. The insert element 16 has in the region of the eyelet 22 a greatly enlarged distance from the surface 20 of the metal shaped body 10. In the solid wall portion 14 therefore sufficient space for the eyelet 22 remains. The shape and arrangement of the insert member 16 ensures that the eyelet 22 is surrounded on all sides by solid material in the required strength. Furthermore, the insert element 16 is shaped and arranged in such a way that the solid wall region 14 is correspondingly reinforced towards the end and the eyelet 22 in the direction of the increased local mechanical stresses occurring there.

FIG. 3 Figure 3 is a schematic representation of a section through a casting 30 having an outer wall body 34. The outer wall body 34 has a shape and material thickness that correspond to the intended application. By way of example, eyelets 22 and a bore 36 are shown here. In the outer wall body 34, a core part is arranged, similar to the above with reference to FIGS. 1 to 3 shown metal moldings of a metal foam region 12, a solid wall portion 14 and an arranged in the boundary region between the same insert element 16 consists. The outer surface 20 of the core member which simultaneously corresponds to the inner surface of the outer wall body 34 is corrugated or has another structure which creates a connection between the core part and the outer wall body 34 by positive locking. Since the outer wall body 34 shrinks upon casting onto the core part, corrugation of the surface 20 of the core part or the interface between the core part and the outer wall body 34 may be dispensed with.

In the manufacture of the casting 30, first the core part is made and then placed and aligned in a mold defining the outer shape of the casting 30. In this mold, the core part is encapsulated with the outer wall body 34. By a suitable choice of the temperatures of the core part, the mold for the casting 30 and the liquid material of the outer wall body 34 and / or by the use of different metals with different melting temperatures for the core part and for the outer wall body 34 ensures that the core part during encapsulation not melted again.

At the in FIG. 3 The example shown thus serves a metal moldings, as above with reference to the FIGS. 1 and 2 represented as a lost core. Its size and arrangement defined the wall thicknesses of the outer wall body 34. In addition, the metal foam area 12 supports the outer wall body, thereby increasing the rigidity of the metal shaped body and absorbing structure-borne sound.

FIG. 4 is a schematic representation of a cross section of a mold 40 in a metal mold body or core part 10, as for example above with reference to FIGS. 1 or 2 was prepared is produced. The inner surface 42 of the mold 40 defines by its shape the shape of the metal moldings to be produced or the shape of the surface of the metal moldings. In the mold 40, a insert element 16 is arranged, as also above with reference to the FIGS. 1 to 3 already described.

Through an opening 44 of the insert element 16, flowable metal foam with a certain proportion of liquid metal is transferred into a metal foam region 12 defined by the insert element 16 (arrow 46). The metal foam fills the metal foam area 12. The insert element 16 has, as already mentioned above, openings or interspaces which are smaller than the gas bubbles of the flowable metal foam. This means, in particular, that in the case of elongate openings or spaces, at least the width thereof is smaller or substantially smaller than the diameters of most (for example 90% or 99%) of the gas bubbles. Therefore, the gas bubbles or the flowable metal foam can not pass through the openings or interstices of the insert member 16.

Excess liquid metal, d. H. liquid metal, which is not contained in webs of small or minimal thickness between two gas bubbles penetrates the openings or interstices of the insert member 16 and fills a gap 14 between the insert member 16 and the inner surface 42 of the mold 40. The flow movement of the liquid metal through the Insert element 16 and within the gap 14 is indicated by arrows 48.

After the metal foam region 12 is completely filled with flowable metal foam and the gap 14 is completely filled with liquid and substantially bubble-free metal, the mold 40 is cooled. After the metal foam in the metal foam region 12 and the metal in the intermediate space 14 have solidified, the mold 40 is opened or broken in order to remove a finished metal molding. For tempering before the casting process and during cooling, the mold 40 preferably has heating and / or cooling elements, which in FIG. 4 are not shown.

Alternatively to the above based on the FIG. 4 The method shown, the metal moldings similar to that in the AT 411 970 B described by means of a mold or mold 40, which has at least one small opening 52 in the vertical highest area in addition to an entry port 50, as in FIG. 5 is shown. In the mold 40, the insert element 16 is arranged. The mold 40 is brought to a temperature below the liquidus or melting temperature of a foamable alloy and / or left. An on the one hand in a melt 54 of this alloy protruding Eingieß- or Filler 56 is on the other hand liquid-sealingly connected to the mold 40. By means of an upward movement of the meniscus or liquid metal mirror 58 of the melt through the entry opening 50 into the at least one small-sized opening 52, the air is displaced or expelled from the mold 40.

In the melt 54 gas bubbles are formed and merged into metal foam. This displaces the initially bubble-free or at least largely bubble-free melt 54 within the insert element 16. The bubbles are produced with a diameter which is larger than the openings in the insert element 16 and therefore remain within the insert element 16 between the insert element 16 and the inner wall The mold thus remains bubble-free or substantially bubble-free melt 54 in a layer thickness which is defined by the shape of the inner wall of the mold 40 and by the shape and arrangement of the insert member 16.

After targeted removal of heat, the metal foam and the melt solidify in the mold 40. Before this heat removal, the entry opening 50 of the mold 40 can be closed and the mold 40 can be separated from the pouring or filling piece 56.

As already mentioned, the arrangement of the insert element 16 defines the shape of the solid wall region 14. In particular, the distance of the insert element 16 from the surface 20 of the metal mold body 10 determines the thickness of the solid wall region 14. In the limit case, the insert element 16 can directly adjoin the surface 20 of the metal article 10 may be arranged, wherein the insert element 16, for example, a mesh or a wire mesh. In this case, the solid wall portion 14 comprises the openings or interstices of the insert member 16, in particular the spaces between the wires of a wire mesh or mesh into which no or only very few or very small gas bubbles penetrate.

By means of a corresponding arrangement and shaping of one or more insert elements 16, it is also possible to produce solid areas with fewer or smaller or substantially no cavities are formed, which are not wall areas or not or not a large area adjacent to a surface 20 of the metal molding 10.

In addition to the insert element 16, the metal molding 10 may contain further deposits in the solid wall region 14 or in the metal foam region 12. In contrast to the insert element 16, these inserts can then serve not only for defining a boundary region between a metal foam region 12 and a solid wall region 14, but also preferably for reinforcing or mechanical reinforcement and / or as anchors or fastening elements for screwing, riveting, welding or otherwise connecting the metal molding 10 with other devices. For example, web or frame-shaped insert elements 16 serve to improve or increase the mechanical properties, in particular the strength (in particular the tensile strength) and the rigidity, of the metal foam region 12 and thus of the entire metal molded body 10. If such an insert is arranged in the metal foam, it must be arranged or designed with sufficiently large openings so that it does not prevent the complete filling of the metal foam area with flowable metal foam.

Insert elements can also be advantageously used to define metal foam regions 12 with different properties of the metal foam, in particular with different bubble or pore sizes (see also FIG Fig. 1a ). As a result, for example, within a single metal shaped body 10, the ability to absorb energy can be spatially modulated (setting of several energy absorption levels or plateau voltages). Among other things, this is particularly advantageous in components for crumple zones of automobiles or other vehicles, since it allows a precise adaptation to possible accident scenarios and an optimization of the protection of the occupants.

FIG. 6 is a schematic flow diagram of a method for producing a metal shaped body 10, as for example with reference to one of FIGS. 1 to 3 was presented. In a first step 82, a thickness of the solid wall portion 14 or a another area in which the metal shaped body 10 should contain fewer or smaller or substantially no voids. This is done, for example, due to the mechanical requirement, which the metal shaped body 10 should correspond to or due to a material thickness, which is required for further processing step (milling, drilling, welding, etc.).

In a second step 84, a mold 40 is provided, whose inner surface 42 defines the shape of the outer surface 20 of the metal shaped body 10 to be produced. In a third step 86, an insert element 16 is arranged in the mold 40, aligned and fastened, for example by clamping. The mold or at least its inner surface 42 is preferably preheated to a temperature close to the melting temperature of the material used.

In a fourth step 88, a foamable metal is provided, for example, by melting a finished alloy or producing it directly in the liquid state. The foamable metal preferably comprises composites with light metal such as aluminum or magnesium. The molten metal may be added with particles consisting of a material having a melting point higher than the melting point of the metal (such as SiC or Al ₂ O ₃ ). These particles serve in particular for the stabilization of the subsequently produced metal foam. Details are given in the patent literature mentioned in the introduction.

In a fifth step 90, gas is introduced into the molten metal to produce gas bubbles or metal foam. In this case, the gas is introduced so that metal foam is formed with a substantially monomodal distribution of the sizes of the gas bubbles or cavities. In a sixth step 92, the flowable metal foam is placed in the metal foam region 12 and substantially bubble-free liquid metal in the future solid wall region 14. The fifth and sixth steps 90, 92 are preferably carried out as described above with reference to FIGS. 4 and 5 has been described, and can also be performed in a different order.

In a seventh step 94, the mold 40 and the metal are cooled, so that the metal foam in the metal foam region 12 and the substantially bubble-free metal solidify in the future solid wall region 14 and form the metal molding 10.

Claims (16)

1. Metal molding (10) comprising metallically bonded regions (12, 14) made of metal foam on the one hand and metal on the other hand, and at least one insert element (16) made of a material having a higher melting point than the base material having metal foam and metal, characterized in that the metal foam region(s) (12) are (each) composed of metal foam having an essentially monomodal bubble size, and are delimited, at least partially, with respect to adjacent regions (14) by insert elements (16) situated in the boundary region which have an essentially flat design and have through openings from one region to the other which have a cross section such that the essentially monomodal foam bubbles of one region are prevented from passing into the other region, by means of which there are essentially no gas bubbles on the side of the insert element(s) (16) oppositely situated from the metal foam region(s) (12).
2. Metal molding according to Claim 1, characterized in that the insert element(s) (16) have a single- or multipart design, and preferably include a net and/or a lattice and/or perforated sheet metal and/or other perforated flat element and/or a plurality of essentially parallel rods and/or a wire mesh.
3. Metal molding according to one of Claims 1 or 2, characterized in that the base material for the metal foam and the metal is an aluminum composite material, and the material for the insert element(s) (16) contains steel, aluminum, ceramic, carbon, or glass in solid form or as a composite fiber material.
4. Metal molding according to one of Claims 1 through 3, characterized in that the insert element(s) (16) have essentially the same distance from the outer contour of the molding (10), at least in places, the region between the insert element(s) and the outer contour having essentially no foam bubbles or only very few/small foam bubbles.
5. Metal molding according to one of Claims 1 through 4, characterized in that at least one insert element (16) separates a metal foam region from at least one further metal foam region, the metal foams in these regions differing from one another in at least one characteristic, preferably the foam bubble size.
6. Metal molding according to one of Claims 1 through 5, characterized in that the insert element(s) (16) increase the mechanical strength or rigidity of the metal molding.
7. Metal molding according to one of Claims 1 through 6, characterized in that at least one insert element (16) is web-, strip-, or frame-shaped, or has a web-, strip-, or frame-shaped section.
8. Metal molding according to one of Claims 1 through 7, characterized in that at least one insert element (16) is mechanically pretensioned.
9. Metal molding according to one of Claims 1 through 8, characterized in that the materials of the metal foam and of the insert element (16) have different coefficients of thermal expansion, and due to the different coefficients of thermal expansion the pretension results during cooling of the metal molding (10) after it is manufactured.
10. Cast part having the following features:

    a core element; and

    an outer wall element which at least partially encloses the core element,

    wherein the core element is a metal molding according to one of Claims 1 through 9.
11. Method for manufacturing a metal molding (10), comprising the following steps:

    Providing (84) a mold (40) for the metal molding (10);

    Placing (86) a single- or multipart insert element (16) having openings or interspaces in the mold (40) in a boundary region between a metal foam region (12) to be filled with metal foam and a further region (14);

    Melting (88) a metal;

    Introducing (90) gas into the molten metal in order to foam the molten metal, resulting in a free-flowing metal foam having an essentially monomodal bubble size which is larger than the openings in the insert element (16);

    Introducing (92) the free-flowing metal foam into the mold (40), whereby metal foam collects in a metal foam region (12) on one side of the insert element (16), and metal collects essentially without gas bubbles on the other side of the insert element (16);

    and

    Cooling (94) the metal in the mold (40), whereupon the metal solidifies to form the metal molding (10).
12. Method for manufacturing a metal molding (10), comprising the following steps:

    Providing (84) a mold (40) with a charge opening (50) and at least one small opening (52) in the vertically highest region;

    Placing (86) an insert element (16) in the mold (40);

    Connecting a pouring or filling piece (56) to the mold (40) so as to be impermeable to molten metal, the pouring or filling piece (56) also projecting into a melt (54) of a metal;

    Moving a molten metal level (58) of the melt (54) upward through the charge opening (50) and into the at least one small opening (52);

    Introducing (90) gas into the melt (54) to form metal foam in the melt (54), whereby metal foam collects in a metal foam region (12) on one side of the insert element (16), and metal collects essentially without gas bubbles on the other side of the insert element (16); and

    Cooling (94) the metal in the mold (40), whereupon the metal solidifies to form the metal molding (10).
13. Method according to Claim 12, wherein the gas is introduced (90) into the melt (54) in such a way that the metal foam is formed within a single- or multipart insert element (16) having openings or interspaces.
14. Method according to one of Claims 11 through 13, wherein the insert element (16) includes a net or a lattice or perforated sheet metal or other perforated flat element or a plurality of essentially parallel rods or a wire mesh.
15. Method according to one of Claims 11 through 14, further comprising the following step:

    Pretensioning at least one of the insert elements (16) before introducing (92) the free-flowing metal foam or before cooling (94) the metal foam.
16. Method according to one of Claims 11 through 15, further comprising the following step:

    Predetermining (82) a thickness of a further region (14) of the metal molding (10) in which the metal molding (10) is to contain fewer or smaller cavities than in the metal foam region (12),

    wherein the insert element (16) is shaped and placed in the mold (40) in such a way that the further region (14) has the predetermined thickness.

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