Classifications

• • 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
  • B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
• • 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
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
  • C22C2026/002—Carbon nanotubes

Definitions

• the invention relates to a method for producing a profile by extrusion of powder of metal and / or metal alloys, in which method a powder bed is heated to an extrusion temperature below the melting temperature of the powder and pressed under pressure through an opening of a die to the profile.
• a billet is pressed as a metallic block material through the opening of a die in an extrusion press normally.
• the powder beds are usually encapsulated in a container because of their low heat conduction prior to extrusion, and typically, e.g. by cold isostatic pressing, compacted.
• the poor heat conduction of the powder beds is made even more difficult by the oxide layers acting as an insulator on the metal particles. Due to the higher density and encapsulation during pressing, the heat transfer improves, and the entire powder bed can be heated by external heat homogeneously to the desired extrusion temperature, however, the time until the powder bed has set by heat conduction a uniform temperature distribution, relatively long is. For this reason, the direct processing of metallic powders in extrusion presses has not been successful.
• the intended for extrusion powder bed must be brought as homogeneous as possible to the desired extrusion temperature.
• the powder bed according to the prior art is heated in a suitable container either inductively or in a convection oven. It is important to ensure that the heating process takes long enough to a possible ensure uniform temperature distribution within the powder bed. As a result of this long wait to ensure the temperature homogeneity occurs an undesirable delay in the production process. Furthermore, the risk of excessive heating in the outer surface layers of the bed and / or too long a heat treatment time increases. This is of particular importance when from at least two different components existing powder, so-called composite powder whose components at elevated temperature, either individually, eg by oxidation, or among themselves tend to undesirable reactions to be processed.
• the invention has for its object to provide a method of the type mentioned, with which a rapid and uniform heating in all areas of the powder bed can be achieved.
• At least one metal or a metal alloy of the powder is a reactive metal which spontaneously forms a natural oxide protective layer on a free surface and / or the powder homogeneously contains fibrous particles which absorb microwaves, distributed in the bulk of the powder the powder bed is heated by microwave irradiation to extrusion temperature.
• the cavities between the powder particles including the oxide layers act as so-called "wave guides" for the microwaves, since they correspond in dimension to the wavelength of the microwave radiation.
• the microwave radiation can penetrate unhindered and with multiple reflection the entire area of the powder bed homogeneous.
• the density of the powder bed or the dimension of the cavities between the powder particles including the oxide layers can be tuned by an appropriate compression of the powder bed in addition to the wavelength of the microwave radiation.
• the powder in addition to the metal particles, also absorbs microwave radiation energy absorbing fibrous components, such as e.g. Contains carbon nanotubes (CNTs), they act locally as receiving antennas or absorber for the microwave radiation.
• fibrous components such as e.g. Contains carbon nanotubes (CNTs)
• they act locally as receiving antennas or absorber for the microwave radiation.
• the fibrous constituents are homogeneously distributed in the powder bed or, in the optimal case, even integrated at least partially into the metallic powder particles, a very effective and homogeneous heating of the entire bed can be achieved in this way. This effect can be enhanced by tuning the length of the fibrous components as closely as possible to the wavelength of the microwave radiation.
• the powder bed when heated to the extrusion temperature, is first irradiated with low microwave energy at a varying frequency and the absorbed energy is measured as a function of the frequency.
• the so-called resonance frequency results in a maximum of the absorbed energy. With this frequency, the powder bed is now irradiated with high microwave energy, resulting in an effective Energyeinkoppelung.
• the low frequency microwave sweep frequency sweep and the subsequent high microwave energy sweep at the resonant frequency to heat the powder bed to extrusion temperature can also be fully automated by control electronics so that the optimum frequency of injected microwave energy is always adjusted for different powder bulk and powder compositions.
• the powder bed can first be precompressed, for example, by means of a screw conveyor in an intermediate container. Subsequently, the thus pre-compressed powder bed in the intermediate container is irradiated with the resonant frequency and thereby heated quickly and uniformly to extrusion temperature. By means of a punch the precompressed and heated to extrusion temperature powder bed is pressed out of the intermediate container through the die opening. In this way, a continuous extrusion of metallic powder material can be realized.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Powder Metallurgy (AREA)
• Extrusion Of Metal (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Constitution Of High-Frequency Heating (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

Family

ID=38740313

Family Applications (2)

Family Applications After (1)

Country Status (7)

Families Citing this family (4)

Citations (1)

Family Cites Families (6)

• 2007
  • 2007-07-13 EP EP07405206A patent/EP2014394A1/fr not_active Withdrawn
• 2008
  • 2008-07-04 US US12/668,952 patent/US20100183469A1/en not_active Abandoned
  • 2008-07-04 CA CA 2692925 patent/CA2692925A1/fr not_active Abandoned
  • 2008-07-04 BR BRPI0813720-0A2A patent/BRPI0813720A2/pt not_active Application Discontinuation
  • 2008-07-04 WO PCT/EP2008/005489 patent/WO2009010201A2/fr not_active Ceased
  • 2008-07-04 EP EP08784627A patent/EP2178663A2/fr not_active Withdrawn
  • 2008-07-04 JP JP2010515393A patent/JP2010533238A/ja active Pending
  • 2008-07-04 CN CN200880024157.0A patent/CN101743080A/zh active Pending

Patent Citations (1)

Non-Patent Citations (1)

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