Classifications

• • 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
• • 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
  • C22C1/087—Foaming process in molten metal other than by powder metallurgy after casting in solidified or solidifying metal to make porous metals

Definitions

• the invention relates to a method for producing metal foam in a metal die casting machine, in particular metal foam made from aluminum materials, and to a metal body produced by this method, for example a component made from such an aluminum material.
• foamable semi-finished aluminum products is atomized aluminum powder, to which a blowing agent is added.
• a blowing agent is added.
• a body pressed from a powder mixture is heated in a heatable, closed vessel to temperatures above the decomposition temperature of the blowing agent and / or the melting temperature of the metal.
• the powder is compacted and the molded part thus created is placed in the area of a component to be foamed and foamed by heating up to 650 ° C. It can the "envelope" is subject to unacceptable deformations or the foaming process is uneven.
• metallic articles with cavities are produced in that gases are dissolved in a metal melt and the foaming process is initiated by a sudden reduction in pressure.
• the foam is stabilized by cooling the melt.
• metallic foam is obtained with the controlled release of propellant gases by first melting a metal at temperatures below the decomposition temperature of the propellant used. A metal foam is established by subsequently dispersing the blowing agent in the molten metal and heating the matrix above the temperature then required to release blowing gases.
• W.Thiele Filler-containing aluminum sponge - a compressible cast material for the absorption of impact energy, in: Metall 28, 1974, Issue 1, pp. 39 to 42 describes the production of foam aluminum.
• the desired cavities are specified in size, shape and position in the form of a loose bed of easily compressible inorganic light materials, such as expanded clay minerals, expanded clay, glass foam balls or hollow-cored spheres etc.
• the light material fill is placed in a casting mold. The remaining spaces in the fill are filled with metal.
• the aluminum sponge obtained in this way is relatively poorly mechanically loadable and contains the material of the bed.
• DE-B-11 64 103 relates to a process for the production of metal foam bodies.
• a solid that decomposes when heated to form gas is mixed with a molten metal so that the solid is wetted by the metal.
• a molten metal for example, powdered titanium hydride is added to a molten alloy of aluminum and magnesium at a temperature of 600 ° C.
• the closed foam thus formed is then poured into a mold in order to cool and solidify there.
• the work is obviously not in a closed system, but in an open system.
• GB-A-892934 relates to the production of complex structures with a foamed metal core and a closed, non-porous surface, the implementation of the described method depending on the filling of the metal blowing agent mixture into the mold before the start of the foaming process.
• DE-C-198 32 794 describes a process for producing a hollow profile which is filled with metal foam.
• This method comprises the steps of pressing the hollow profile made of a shell material with an extrusion press, which has an extrusion tool with a die and a mandrel, feeding the metal foam made of a foam material through a feed channel to the hollow profile which is formed in the mandrel.
• WO 92/21457 describes the production of aluminum foam in such a way that gas is blown in under the surface of a molten metal, whereby
• Abrasives serve as stabilizers.
• EP-B-0 666 784 describes a method for molding a metal foam stabilized by means of particles, in particular an aluminum alloy by heating a composite of a metal matrix and finely divided solid stabilizing particles above the solidus temperature of the metal matrix, and gas bubbles are released into the molten metal composite below its surface, thereby forming a stabilized liquid foam on the surface of the molten metal composite. It is characterized by a molding of the metal foam by pressing the stabilized liquid foam into a mold and with a pressure which is only sufficient for the liquid foam to take the shape of the mold without the cells of the foam being substantially compressed and subsequent cooling and solidification of the foam to obtain a shaped object. The foam is pressed into the mold using a movable plate.
• a first movable plate presses the liquid foam into the mold and a smooth surface is formed on the molded foam article.
• a second movable plate is pressed into the foam within the mold to form smooth inner surfaces on the foam article.
• the shaping can also be done by means of rollers.
• EP-A-0 804 982 teaches a further process for producing molded parts from metal foam. Foaming takes place in a heatable chamber outside a casting mold, the volume of the powder metallurgical starting material for the metal foam introduced into the chamber being equal to the total foaming capacity foamed phase essentially corresponds to the volume of a filling of the mold. All metal foam in the chamber is pressed into the mold, in which foaming is continued with the remaining foaming capacity until the mold is completely filled.
• the mold is a sand or ceramic mold, the metal foam is introduced into the chamber as a semi-finished product and only pressed into the mold after foaming, for example using a piston. At the Pressing the foam into the mold shears it. The mold is not filled with a foam of an inherently inhomogeneous structure.
• DE-A-19 501 508 discloses a method for producing a cavity profile with reduced weight and increased rigidity, for example a component for the chassis of a motor vehicle.
• This consists of die-cast aluminum and in the cavities there is a core made of aluminum foam.
• the integrated foam core is manufactured using powder metallurgy and then fixed to the inner wall of a casting tool and cast with metal using a die-casting process.
• the dissolving or blowing in of propellant gases in molten metal is not suitable for the production of near-net-shape components, since a system consisting of melt with occluded gas bubbles is not sufficiently stable in time to be processed in shaping tools.
• the solution to the aforementioned problem consists in a first embodiment in a process for producing metal foam by adding a blowing agent to a molten metal, which is characterized in that the molten metal is introduced into the mold cavity of a metal die-casting machine and fixed with a gas-releasing, solid at room temperature Foaming agent foams.
• light metal foams for example made of aluminum or aluminum alloys
• a closed outer skin specifically as a gradient material and close to the final contour in one step by a casting process in a commercially available die-casting machine, based on the use of solid, gas-releasing propellants
• a metal hydride especially a light metal hydride.
• liquid or pasty metal is pressed under high pressure into a mold which represents the mold cavity.
• the metal is injected directly from the melting chamber into the mold at up to approx. 10 7 Pa; in the cold chamber process preferred according to the invention, for example for materials made of Al and Mg alloys, the melt is first poured into a cold intermediate chamber and thence pressed into the mold with more than 10 8 Pa.
• the casting performance of the hot chamber process is higher, but so is the wear on the system.
• the advantages of die casting are the good material strength, the clean one
• the process sequence preferred according to the invention comprises filling the required volume of molten metal into the filling or casting chamber and introducing it into a mold cavity while adding the blowing agent to the molten metal.
• molten metal and blowing agent are brought together in the mold cavity, the Volume is defined or filled with the melt-blowing agent mixture or underfilled.
• the blowing agent is not brought into contact with the molten metal directly in the mold cavity, but in a filling or casting chamber, and the mixture is then introduced into the mold cavity.
• the blowing agent can be introduced into the filling or casting chamber on the one hand and / or the mold cavity on the other hand before, during and / or after the metal melt has been introduced into the respective chamber.
• a special mixing process is not necessary when bringing the molten metal and blowing agent together. Rather, the mixing in the process according to the invention takes place by introducing the molten metal into the molding chamber at high speed in the die casting machine, regardless of the time at which the blowing agent is added to the molten metal.
• the foaming itself takes place in the mold cavity, which is a closed mold. However, as is usual in die casting or the like, this can have riser channels for ventilation.
• the essentially foamed metal body is then ejected.
• the blowing agent is added directly to the molten metal in the filling or casting chamber or in the mold cavity, integrally foamed metal bodies being produced in one operation.
• These have a smooth surface, the formation of which is easily reproducible is. Due to the possible spray filling, different wall thicknesses can be easily adjusted. The walls are closed on all sides, clean, tight and homogeneous. Post-treatment is usually not necessary.
• the metal bodies produced are increasingly porous on the inside and have a density gradient.
• the decomposition temperature of the blowing agent should be matched to the melting temperature of the casting material (metal melt).
• the decomposition may only start above 100 ° C and should not be higher than approx. 150 ° C above the melting temperature.
• the proportion of metal in the metal body produced can be in the range from 5 to 95% by volume or% by weight, depending on the volume or thickness of the metal body, a lower volume to surface ratio indicating higher filling levels.
• a vehicle part should be made from an aluminum material as an integrally foamed metal body.
• a casting chamber of the die casting machine was filled with a corresponding amount of molten metal.
• the "shot” took place before the foam was formed; the foaming process took place in situ in the mold cavity. It was quickly foamed into the cold mold.
• the component had a mass of only about 40% compared to conventional die-cast parts.
• the metal body made of an aluminum material according to the example had a lower density than magnesium, but its torsional rigidity, for example.

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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)
• Superconductors And Manufacturing Methods Therefor (AREA)

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• 2001
  • 2001-02-01 DE DE10104339A patent/DE10104339A1/de not_active Withdrawn
• 2002
  • 2002-01-12 DE DE50202904T patent/DE50202904D1/de not_active Expired - Lifetime
  • 2002-01-12 EP EP02708278A patent/EP1356131B1/fr not_active Expired - Lifetime
  • 2002-01-12 WO PCT/EP2002/000245 patent/WO2002060621A2/fr not_active Application Discontinuation
  • 2002-01-12 AT AT02708278T patent/ATE294251T1/de active
  • 2002-01-12 ES ES02708278T patent/ES2240704T3/es not_active Expired - Lifetime
  • 2002-01-12 AU AU2002242664A patent/AU2002242664A1/en not_active Abandoned

Non-Patent Citations (1)

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