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
  • B22F3/10—Sintering only
  • B22F3/11—Making porous workpieces or articles
  • B22F3/1103—Making porous workpieces or articles with particular physical characteristics
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• the invention relates to a method for powder metallurgy production of metal foam and of parts made of metal foam.
• Metal foam is also commonly called metal foam.
• Aqueous solutions, plastics or glass can be foamed.
• foam metals stands for elasticity, strength and temperature resistance
• Foam stands for low weight, cushioning, high porosity and a large specific surface area.
• Metal foam is a novel material with specifically introduced pore structure, it is non-flammable and has a high strength. Foams made of metal are airy materials that are light, stiff, but flexible and absorb a lot of energy in the event of a crash. Metal foam can also fulfill a wide range of other technical tasks and is particularly suitable for applications as thermal insulation, noise and vibration damping or as a compression element.
• Metal foams can be up to 85 percent air and only 15 percent metal, which makes them very light. They look like conventional plastic foams, but are much firmer. The manufacturing processes were too expensive, too expensive and too difficult to control until a few years ago, and the results were therefore rarely reproducible. But there are now melting and powder metallurgical processes that promise a high quality of the foamed metal.
• various methods are known and used. For example, for the production of steel foam from steel powder, water and a
• Stabilizer made a slip at room temperature. 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. On the one hand, in the reaction between steel powder and acid, hydrogen gas bubbles are produced which cause foaming. On the other hand, 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 harmful substances 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.
• at least one gas introduction tube with a defined gas outlet cross section protrudes into the melt through which individual bubbles are blown into the melt.
• the size of the bubbles is controlled by the adjustment of the Einströmparameter of the gas.
• EP 1 419 835 A1 discloses a method and an apparatus for producing flowable metal foam with a monomodal distribution of the dimensions of the cavities, which are likewise based on a melt metallurgical method.
• at least two adjacent identically dimensioned feed pipes protrude at a defined distance from one another into a metallurgical vessel with a foamable molten metal. Bubbles are formed in the regions of the protruding tube ends, with juxtaposition of regions of the bubble surfaces and formation of particles containing intermediate walls a continuous foam formation is formed.
• a disadvantage of these melt metallurgical processes is that a molten metal in the pure state can not be foamed.
• 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)
• ceramic particles EP 0 666 784 B
• a powder metallurgical process for producing porous metal bodies is described 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 a high temperature gas evolving propellant, wherein the metal forms a substantially closed matrix in which propellant particles are incorporated.
• An increased quality of a created metal foam body is to be achieved with a semi-finished product, in which the propellant particles einschumble metal matrix is formed by diffusion and / or pressure-welding of metal particles.
• a first step metal particles and at least one at elevated temperature gas (e) donating agent, so-called blowing agents, mixed, whereupon in a second step, the mixture formed under elevated pressure and elevated temperature to a semi-finished part and this while maintaining the Pressurization below the decomposition or outgassing temperature of the propellant is allowed to cool or cooled.
• JP 01-127631 (Abstract) a method is described in which analogously to the aforementioned solution under atmospheric pressure hydrogen, nitrogen, oxygen is introduced into the liquid metal or propellant particles, such as nitride, hydride or oxide, by thermal cracking gas in release the melt.
• the gasified liquid metal is placed in a mold and held under reduced pressure, at 400 to 760 mmHg for a period of time.
• metal foam bodies of high quality can be provided.
• these methods are extremely complicated with respect to the material used and the required devices, because it is necessary to use at least two powder components, namely metal particles and fuel particles.
• the individual powder components must be intimately mixed prior to heating and the powder grains are sintered together, for example by hot isostatic pressing, in order to achieve in the produced metal foam body pores with a homogeneous distribution as possible.
• a further disadvantage is that gas escapes from the blowing agent particles even before the metal melts and accumulates in cracks, defects, etc. This results in different sized and unevenly distributed pores in the metal foam. The pore size and volume expansion are difficult to control during the process.
• the object of the invention is to provide a method for the production of metal foam and parts made of metal foam, the easy to perform without the use of blowing agents and without expensive devices, the trapped pores are as small as possible pores, have a nearly the same volume and a homogeneous distribution.
• the metal foam parts produced by the process according to the invention should have a high dimensional stability.
• This object is achieved by a method having the features of claim 1 by a powdered metallic material containing at least one metal and / or a metal alloy, mixed and then under mechanical pressure and a temperature of up to 400 C to form a dimensionally stable semifinished product is pressed.
• This semi-finished product is placed in a pressure-tight sealable chamber, which is then sealed pressure-tight and the semifinished product is heated at the selected initial pressure to the melting or solidus temperature of the powdered metallic material.
• the pressure in the chamber is reduced to a selected final pressure.
• the semifinished product foams up and the metal foam formed thereby solidifies during the subsequent lowering of the temperature.
• the lowering of the temperature takes place after the beginning of the pressure reduction according to a predetermined gradient, wherein the selected final pressure is always achieved before the solidification of the powdery metallic material.
• a gas pressure up to approximately 50 bar is generated before or during the heating of the semifinished product in the closed chamber. After reaching the melting or solidus temperature of the pulverulent metallic material, the pressure in the closed chamber is reduced from the initial pressure to a predetermined gradient down to the final pressure of 1 bar.
• the heating of the semifinished product takes place in the closed chamber at an initial pressure of about 1 bar and after reaching the melting or solidus temperature of the powdered metallic material, the pressure in the closed chamber is reduced to a final pressure of about 0.1 to 0.01 bar after a predetermined gradient.
• a certain gas atmosphere can be created, for example an oxygen atmosphere or an atmosphere of moist air.
• the powdered metal material is preferably at a gas pressure between 1 and 50 bar, and a mechanical pressure of 200-400 MPa and a temperature of up to 400 0 C of konnpaktiert.
• the pulverulent metallic material is pretreated before being compacted into the semifinished product by modifying the surface of the individual granules of the pulverulent metallic material, for example by oxidizing or moistening.
• a reservoir provided in the molding tool ensures that the metal foam excess metal foam from the molding tool can escape through an opening to the reservoir. This also ensures that the molding tool is completely filled with the metal foam. With the reduction of pressure is also the Lowered temperature, so that the metal foam solidifies in the mold and thereby assumes the shape of the molding tool. After solidification of the metal foam, the metal foam body can be removed from the molding tool.
• the advantages of the method according to the invention are, in particular, that it is possible to produce metal foam or body made of metal foam, without complicated devices for introducing gas bubbles into the melt or the use of blowing agents, in a simple manner.
• a further advantage is that with the method according to the invention low-density metal foam can be produced in which the pores have small dimensions (volumes), are distributed almost uniformly and homogeneously throughout the metal foam.
• An additional advantage is that the pore size and the volume expansion can be adjusted within certain limits very easily and precisely or adjusted during the process by adjustable different pressure differences between the initial and final pressure, wherein there is a direct relationship between the pore size and the volume expansion. Ie. the pore size and the volume expansion can be predetermined by observing certain limit values by setting the initial pressure and the final pressure. But it is also possible that when observing the process, this can be terminated at any time upon reaching a desired pore size or volume expansion.
• a metal foam is made without the use of additional gas-imparting blowing agents.
• powder of AISi6Cu4 with an average particle size of about 20 microns with 0.5 wt.% TiH 2 , which has an average particle size of about 10 microns, homogeneously mixed This mixture is uni-axially compacted in a metal cylinder at a gas pressure of 1 bar and at a mechanical pressure of 300 MPa and at a temperature of about 400 ° C over a period of about 15 minutes to form a semifinished product. Thereafter, this semi-finished product is placed in a pressure-tight chamber and heated under an air atmosphere at an initial pressure of 8 bar to a temperature of about 550 ° C, which is thus slightly above the solidus temperature of AISi6Cu4 of about 516 ° C.
• the propellant begins to release hydrogen.
• the gas released and trapped in the molten aluminum of the semifinished product forms very small pores having an average diameter of less than 0.1 mm.
• the gas enclosed in the semi-finished product causes the sample to foam within 15 seconds.
• the temperature is reduced by about 5 K / s to below the solidus temperature of AISi6Cu4, so that the liquid AISi6Cu4 foam solidifies and thus the foam solidifies.
• An AISi6Cu4 foam produced by this method has pores which are homogeneously distributed in the metal foam, round and small, the average pore size being about 0.5 mm.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Powder Metallurgy (AREA)
• Cell Electrode Carriers And Collectors (AREA)

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• 2005
  • 2005-08-02 DE DE102005037305A patent/DE102005037305B4/de not_active Expired - Fee Related
• 2006
  • 2006-08-02 ES ES06775813T patent/ES2327066T3/es active Active
  • 2006-08-02 AT AT06775813T patent/ATE433814T1/de active
  • 2006-08-02 DE DE502006004012T patent/DE502006004012D1/de active Active
  • 2006-08-02 WO PCT/DE2006/001375 patent/WO2007014559A1/fr active Application Filing
  • 2006-08-02 EP EP06775813A patent/EP1915226B1/fr active Active
  • 2006-08-02 US US11/997,818 patent/US8562904B2/en not_active Expired - Fee Related
  • 2006-08-02 JP JP2008524357A patent/JP2009503260A/ja active Pending

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