Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/08—Alloys with open or closed pores
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D25/00—Special casting characterised by the nature of the product
  • B22D25/005—Casting metal foams
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/08—Alloys with open or closed pores
  • C22C1/083—Foaming process in molten metal other than by powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/08—Alloys with open or closed pores
  • C22C1/083—Foaming process in molten metal other than by powder metallurgy
  • C22C1/086—Gas foaming process
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/11—Making porous workpieces or articles
  • B22F3/1103—Making porous workpieces or articles with particular physical characteristics
  • B22F2003/1106—Product comprising closed porosity

Definitions

• the invention relates to a process for the production of metal foams with stabilizing particles and metal foam.
• Metal foams are of great interest as materials because of their possible combinations of different properties.
• metal foams are very light on the one hand, and on the other hand have high rigidity and considerable strength. You can z. B. are used for thermal insulation, noise and vibration damping or compression element.
• a slurry is prepared at room temperature to produce steel foam from steel powder, water and a stabilizer.
• Phosphoric acid is added to this mixture as a binding and blowing agent.
• Two reactions then take place in the slurry, leading to the formation of a stable foam structure.
• hydrogen gas bubbles are produced which cause foaming.
• a metal phosphate is formed, which solidifies the pore structure by its adhesive effect. The foam thus produced is dried and then sintered free of pollutants to the metallic composite.
• a melt metallurgical process is described, for example, in EP 1 288 320 A2 by introducing gas bubbles into a melt.
• the size of the bubbles is controlled by the adjustment of the Einströmparameter of the gas.
• Distribution of the dimensions of the cavities presented which is also based on a melt metallurgical process.
• at least two adjacent identically dimensioned feed pipes protrude at a defined distance from one another into a vessel with a foamable molten metal.
• Bubbles are formed in each case in the regions of the projecting tube ends, a continuous foam formation being formed by juxtaposition of regions of the bubble surfaces and formation of particle-containing intermediate walls.
• Metal melt in the pure state is not foamable.
• the melt must be mixed with a viscosity-increasing agent, for example an inert gas (GB 1, 287,994) or with ceramic particles (EP 0 666 784 B), prior to carrying out the foaming.
• a viscosity-increasing agent for example an inert gas (GB 1, 287,994) or with ceramic particles (EP 0 666 784 B)
• a viscosity-increasing agent for example an inert gas (GB 1, 287,994) or with ceramic particles (EP 0 666 784 B)
• a powder metallurgical process for the production of porous metal bodies is presented in DE 101 15 230 C2, in which a mixture which comprises a pulverulent metallic material which contains at least one metal and / or one metal alloy and a gas-releasing propellant-containing powder is compacted to form a semifinished product.
• This semifinished product is foamed under the action of temperature, wherein a propellant-containing powder is used, in which the temperature of the maximum decomposition is less than 120 K below the melting temperature of the metal or the solidus temperature of the metal alloy.
• WO 2005/011901 A1 it is proposed that, for the production of metal parts with internal porosity, first a foamable semifinished product consisting of metal and at least one blowing agent releasing gas at elevated temperature is produced.
• the foamable semifinished product contains a substantially closed matrix in which propellant particles are embedded.
• Foam particle enclosing metal matrix is formed by diffusion and / or pressure welding of metal particles.
• JP 01-1273131 also describes a process in which hydrogen, nitrogen, oxygen is introduced into the liquid metal analogously to the abovementioned solution under atmospheric pressure or propellant particles, such as nitride, hydride or oxide, by thermal cracking gas into the Release melt.
• the gasified liquid metal is placed in a mold and held under reduced pressure, 53.320 to 101, 308 kPa for a period of time.
• US 4,713,277 describes a process for producing a metal foam having a specific gravity of 0.2 to 0.8 and uniformly distributed polygonal cavities of an average size of 2 to 10 mm, in which first the starting materials for the molten metal (Al or alloys thereof) and Ca are mixed as a binder (to increase the viscosity) and heated to melting temperature, then a frother, titanium hydride with 1 to 3 wt .-%, is mixed in air.
• a process for producing stabilized metal foams is disclosed in US 5,112,697.
• solid stabilizing particles are added to the starting material for the metal matrix, mixed and heated to a temperature greater than the liquidus temperature of the metal matrix. Subsequently, gas is added to the mixture and the mixture is cooled. The stabilizing particles are then incorporated into the metal matrix.
• attention is drawn to the correct selection of these solid stabilizing particles, since these can lose their form and their identity by dissolution in the metal or chemical combination with the metal.
• stabilizing particles are called: metal oxides, carbides, nitrides or borides, in particular Al, TiB 2 , Zr, SiC, SiN, which are contained in the metal foam to ⁇ 25%, preferably 5 to 15%.
• the size of the particles is given as 0.1 to 100 ⁇ m. It should be noted that the right size selection is important because too small particles are very difficult to mix. On the other hand, particles that are too large precipitate. If the volume fraction of these stabilizing particles is too low, the foam stability is too weak; if the volume fraction is too high, the viscosity is too high.
• the method described produces a metal foam having typical cell sizes of 250 ⁇ m to 50 mm.
• Such metal foams containing ⁇ m-sized stabilizing particles in their metal matrix are brittle and are difficult to cut clean with a saw.
• the starting materials are very expensive and a large amount of these particles is necessary to achieve good stability.
• the object of the invention is to provide a further process for producing metal foams comprising stabilizing particles, in particular the amount of stabilizing particles necessarily used should be reduced and the metal foams produced should be easier to process.
• the object is achieved for a method of the type mentioned in that the stabilizing particles are generated in the preparation of the foamable starting material in an in situ reaction of molten reactive liquids and a molten metal, wherein the molten metal, the components of the submicroscopic particles or Nanoparticles are added at least as fluoride salt, then mixed and heated above the melting temperature of the mixture components.
• the solution according to the invention in which the stabilizing submicroscopic particles or nanoparticles are produced during the preparation of the foamable starting material by means of an in situ reaction, makes it possible to provide and cooperate with such elements which are required for the formation of an interface layer between the melt and the stabilizing particles a contact angle of 10 to 100 grd, preferably from 60 to 80 grd are necessary. As has surprisingly been found, this angle is essential for the formation of metal foams according to the inventive solution and depending on the alloys used and also essential for the grain refining during solidification.
• the stabilizing particles produced in an in situ step have a larger specific surface area.
• the metal foams produced in this way are less brittle, since their metal matrix has better mechanical properties, and can be processed more easily.
• K x AF y is used as fluoride salt, where A is an element of Ti, B, Zr, Nb, V, W, Ta or Ce, preferably K 2 TiF 6 or KBF 4 is used or both salts are used as a mixture.
• a further constituent of the stabilizing particles to be produced in the in situ reaction for example carbon in the form of graphite, is added.
• the metal used for the melt is aluminum or an aluminum alloy.
• the starting material is cooled to 700 0 C and for foaming the same powdered metal hydride, preferably TiH 2 , from 1 to 3 wt. % added as an intumescent at 700 ° C.
• the same powdered metal hydride preferably TiH 2 , from 1 to 3 wt. % added as an intumescent at 700 ° C.
• reactive gases can also be used for foaming, for example CH 4 , NH 3 and O 2 , preferably O 2 in a concentration of 0.1 to 10 vol.%, In particular of 1 to 2 vol.%.
• the temperature is in this case 600 to 1000 0 C, preferably 700 ° C.
• the foaming of the starting material can also be carried out by other methods known from the prior art, for example by means of a gas injection directly into the melt.
• the invention also comprises a metal foam according to claim 15. Thereafter, the metal foam stabilizing particles in a metal matrix, wherein the stabilizing particles less than 10 vol. % are contained in the metal matrix, have a size of less than 1 ⁇ m and are arranged at a contact angle of 10 to 100 °, and the metal matrix is formed of uniformly arranged polygonal closed cells with an average diameter of 2 to 10 mm and the metal foam has a porosity of at least 75%, preparable by a process comprising the following steps: producing the stabilizing particles in an in situ reaction of molten reactive liquids and a molten metal, the molten metal being the constituents of the submicroscopic particles to be produced Particles or nanoparticles are added at least as a fluoride salt, then mixed and heated above the melting temperature of the mixture components to form an interfacial layer in which the stabilizing particles are arranged at a contact angle of 10 to 100 °, preferably 60 to 80 °, subsequently the enplanetaryen melt all unwanted constituents
• the stabilizing particles contain Ti or B or Zr or Nb or V or W or Ta or Ce or C or Al in combination with a second element of this group and are preferably formed from TiC or AIB 2 or TiB 2 .
• Fig. 1 is a SEM image of a cut Al foam cell whose
• Fig. 2 is an X-ray of the same AI foam.
• Fig. 1 shows an SEM photograph of a section through a cell of the AI foam, on its surface, i. on their cell wall, the TiC particles are very well recognizable in their dense and relatively homogeneous arrangement.
• FIG. 2 the entire sample of the same AI foam with TiC particles is shown. The diameter of this sample is 40 mm.
• EMBODIMENT 2 A mixture of KBF 4 and K 2 TiF 6 is added to an Al melt produced at 800 ° C. and mixed. After the reaction, the unwanted components are again removed except for the Al-TiB 2 mixture. Cooling and foaming process is carried out as in Example 1.
• the Al foam thus produced with a porosity of about 75% contains TiB 2 particles in a concentration of 4 vol.% And a size of less than 1 micron.
• Al is melted at 800 ° C. This melt is added to KBF 4 and mixed again. After removal of the undesirable components after the reaction, the Al-AIB 2 mixture - as described - cooled and foamed. The result of this process is once again an Al foam with a porosity of about 75%, the stabilizing particles of which are formed here from AIB 2 and are contained in the foam in a concentration of 4.3% by volume.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Powder Metallurgy (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

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Cited By (5)

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• 2006
  • 2006-07-03 DE DE102006031213A patent/DE102006031213B3/de not_active Expired - Fee Related
• 2007
  • 2007-06-27 WO PCT/DE2007/001140 patent/WO2008003290A2/de not_active Ceased
  • 2007-06-27 DE DE502007005568T patent/DE502007005568D1/de active Active
  • 2007-06-27 EP EP07785573A patent/EP2044230B1/de not_active Not-in-force
  • 2007-06-27 AT AT07785573T patent/ATE486971T1/de active

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