Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Making porous product
Reexamination Certificate
2000-11-30
2002-05-21
Jenkins, Daniel J. (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Making porous product
Reexamination Certificate
active
06391250
ABSTRACT:
The present invention relates generally to novel foamed metal moldings, and in particular to a novel process for the specific and reproducible production of these novel moldings.
In recent years a large number of publications and patents have been issued concerning the production of foamed metals, devices for carrying out the process and also concerning the metal/foaming agent mixtures required for foamed metal production or the semifinished products for use in a metal foaming production process and concerning the production of said semifinished product.
Reference is made only by way of example and by no means exhaustively to the following documents with regard to the proposals and activities which have become known in this area.
DE 1 164 102 A, DE 196 12 781 C1, DE 43 40 791A1, DE 44 26 627 A1, EP 460 392 A1, EP588 182A2.
Reference is also to be made here to a known technique of foaming metals, in which semifinished products formed from compacted metal particle/foaming agent particle mixtures are placed in foaming molds, for example of steel, and made to expand by heating.
According to EP 804 982 A2, the powder-metallurgical starting material is heated in a heated chamber outside a foam casting mold and made to expand, after which the metal foam, adjusted in its amount to match the volume capacity of the casting mold, is pressed in its entirety into the casting mold, a relatively complex technique.
In U.S. Pat. No. 3,087,807 A there is a description of a process according to which a semifinished product, formed to correspond approximately in its shape to the desired final form of the finished foamed metal body, is introduced into a hollow enclosure and expanded there by heating.
DE 44 24 15 A1 describes foamed metals with anisotropic properties, which are produced by heating the foamable semifinished product in the foaming and casting mold and subsequent deformation. It is stated there that, for destroying the walls between the pores for the purpose of further reducing their number, said walls representing the means by which the electrical and thermal conduction of the foamed metal, in itself reduced by the pores, takes place, it is possible to provide for the integration of small ceramic or hard-metal particles, short fibers or the like, which serve as crack starters during the deformation.
The number and variability of the application possibilities of foamed metals or of moldings, workpieces, structural elements or the like produced from them is high. Mention is to be made at this point, just as examples, of the stiffening of hollow forms, all structural elements used for sound and vibration damping of the widest variety of types, also structural elements inhibiting energy flows, such as heat flow for example, and not least use as decorative and covering structural elements, increasingly valued on account of their low density, such as for example wall plates and panels or the like, the foam structure itself, or else foam-structure limits within the structural elements, sometimes providing ist surface with attractive esthetic aspects, which may serve for decorative purposes.
In many cases, however, it is a fact that the individual foamed metal molding by itself is not functional and, as for example in the case of soundproofing structural elements, wall panels or the like, requires some sort of securing means or else, for example, is to have cavities, openings or the like, which are intended for example for receiving securing, connecting and/or joining elements.
It is consequently necessary after completion of the foamed metal body to perform finishing work on it, such that the required clearances are made in it, such that, for example, retaining elements have to be screwed into the previously made holes or that clamping and position-retaining elements, for example reaching around the edges of the structural element, have to be attached.
If, for example, foamed metal composite structural elements are to be realized, that is to say for example sandwich structural elements, for example with a lower and upper solid covering metal sheet and a foamed metal structure in between, it has previously been the procedure to introduce a metal powder/foaming-agent powder mixture between the two metal sheets and then produce an essentially compact preform or semifinished body with outer covering layers, for example by rolling, pressing or the like, which body is expanded at elevated temperature, for example in a mold, the bottom sheet then for example remaining in position and the covering sheet being “lifted” into a final position by the expanding foamed metal. A disadvantage of this technology, cited here as an example, is that it allows an exact final positioning of the sheets to be achieved only with difficulty.
The object of the invention is to provide a process in which there is essentially no longer any need, such as that described above, for the subsequent provision of structural elements, retaining elements, cavities, clearances or the like. The novel process should, furthermore, save the use of costly-to-produce pre-material, such as for example the semifinished product as described above, on the basis of a compacted metal powder/foaming agent/covering metal sheet composite and should lead to foamed metal products with integrated-in or integrated-on solid elements with exactly controllable final positioning.
The novel process is finally intended to enable the production of finished foamed metal moldings and structural elements suitable right away for technical operation and use, in essentially a single process step.
The invention consequently relates to a novel process for producing moldings, workpieces or structural elements from or with foamed metal on the basis of aluminum or aluminum alloys or other metals or alloys, in which process semifinished bodies, bars, profiles, plates or the like of foamable semifinished material, obtained by powder-metallurgical means by compacting a mixture of at least one powder of the matrix metal with at least one foaming agent which releases a foaming gas at elevated temperature and is base d on at least one metal hydride or some other foaming agent, are introduced into a foaming and shaping mold or the like, are arranged there in the respectively desired geometrical arrangement and two-dimensional and/or three-dimensional distribution, and are brought to a temperature in the range of the melting temperature of the matrix metal in the said mold by heating, the foaming operation is ended after filling of the cavity of said mold to a desired degree with the foamed metal formed and, finally, the foamed metal moldings, workpieces or structural elements obtained in this way are demolded or removed, characterized therein, that
at least one foamable, compacted semifinished body or a plurality of semifinished bodies of this type is/are introduced into the foaming and shaping mold, together with at least one structure or body formed from a material or solid material or metal not foamable at the melting temperature of the matrix metal o r foaming temperature and/or a (technical) functional structural element from the group comprising wires, cables, bars, networks, gratings, foils, plates, sheets, honeycomb bodies, profiles, tubes, bushes, anchoring elements, screw shanks or the like, and is/are held in the desired Position, after which the heating is performed with formation of the foamed metal, enclosing the structure or the (solid) body and/or functional structural element integrally and snugly in the form or shape corresponding to the mold cavity,
the material or matrix metal of the foamed metal formed at the respective foaming temperature being brought into contact with the entire structure or (solid) body and/or functional structural element or with a part of the same, and
after appropriate cooling, the composite molding or structural element obtained, with a structure firmly bonded in the foamed metal, or firmly bonded (solid) body and/or functional structural element, is demolded.
Consequently, the essence of the invention is not only in particula
Simanĉik Frantisèk
Wolfsgruber Eric
Wörz Helmut
Bachman & LaPointe P.C.
Jenkins Daniel J.
Mepura Metallpulvergesellschaft mbH Ranshofen
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