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
  • B22F3/1121—Making porous workpieces or articles by using decomposable, meltable or sublimatable fillers
  • B22F3/1125—Making porous workpieces or articles by using decomposable, meltable or sublimatable fillers involving a foaming process

Definitions

• the invention relates to a method for producing metal bodies an essentially homogeneous inner porosity made of metal powders and gas-releasing propellant powders.
• the invention further comprises porous, in particular metal bodies produced by the above method.
• metal foam bodies For a technical use of metallic bodies, especially in construction of devices are their mechanical properties and mostly their weight vital. Often, for example in the vehicle and Aviation industry, there is a desire for parts that have a high bending and / or Torsional strength, high energy absorption when deformed, low Thermal conductivity and the like with the lowest possible component weight exhibit. In order to reduce component weights in device and plant construction on the one hand there is the possibility of using light metals, on the other hand, the use of metal foam bodies can be particularly relevant in this regard be beneficial.
• Metal foam bodies are usually produced when using Light metals and the like alloys in that liquid metal is foamed and solidified. Bodies made in this way can be many have only simple geometric shapes for reasons of manufacturability and all have to be elaborately processed.
• DE-OS 1 201 559 describes another process for the production of Foam bodies with pores evenly distributed over the cross section are known in which a mixture of a crushed ductile metal and one at elevated temperature, but below the melting temperature of the metal gas-emitting additive is extruded and this welded mixture then to a temperature above the gas delivery temperature of the additive, however is heated below the melting point of the metal.
• This if necessary has a uniform porosity-producing method however, the disadvantage that only highly ductile metal powder, which is already through a Extrusions are weldable, can be used.
• a process for the largely continuous production of Metal foam bodies has become known from EP-0559097 A2, wherein a Metal blowing agent powder mixture introduced into a channel, with pre-compaction transported to and through a die at an elevated temperature is squeezed out.
• This has mainly been used for aluminum however, among other things, the problems of compliance with the required Manufacturing parameters and a high level of mechanical engineering.
• DE-4 018 360 C1 discloses another method for producing porous Metal body made of light metals using metal powder and at least one Propellant powder.
• a semi-finished product is made by hot compacting the Powder mixture at a temperature at which the compound of Metal powder particles are predominantly made by diffusion and at a pressure that is high enough to prevent the propellant from decomposing, that the metal particles are in a fixed connection with each other and represent a gas-tight seal for the particles of the blowing agent.
• the Consequence is by heating the semi-finished product to a temperature above that Decomposition temperature of the blowing agent, preferably in the temperature range of Melting point of the metal used, the porous metal body is formed.
• this complex process is quite suitable for one To manufacture light metal bodies with high and uniform porosity.
• this object is achieved by that from raw materials powder from at least one heavy metal and / or at least one heavy metal alloy, from at least one gas-forming and / or gas-releasing propellants and optionally from at least one non-metallic reaction and / or alloying agent and / or a mixing aid produced and the powders processed into a homogeneous mixture, which powder mixture under all-round pressure if necessary in one closable container and / or in the case of elevated, but below that for the Decomposition of the blowing agent temperature compacted into a blank after which the blank is subjected to a heat treatment, which at least partially in a temperature range between Solidus and Liquidus temperature due to chemical inhomogeneities Composition formed, lower melting heavy metal phase as well is in the range of the reaction and / or decomposition temperature of the blowing agent, where appropriate with a gas-generating and / or
• Particularly advantageous mechanical properties of the porous metal body increased temperature compared to its specific weight reached when the heavy metal and / or the heavy metal alloy Melting point interval of higher than 900 ° C, preferably higher than 1100 ° C having.
• the starting materials Metal powder with an average grain diameter of 11 ⁇ m to 400 ⁇ m and too a blowing agent powder and reaction and / or alloy powder with one processed average grain diameter of 1.1 to 200 microns and mixed the powder will be particularly advantageous conditions for compacting the Blank and a formation of homogeneous porosity with low specific Weight of the metal body reached.
• Powder with a lower melting thin layer the grain surfaces are, for example, annealed in one Reactive gas stream can be produced, whereby after compacting to a blank by at least partial melting of the temperature Surface areas and welding of the powder particles can take place.
• an essentially pure iron with a melting point of 1500 ° C. existing powder by adding or coating the Powder grains with carbon initially when heated or annealed Surface areas with a melting or. Get solidus temperature. Then diffuse the carbon arms into the The inside of the grain is experienced by the solidus and liquidus temperatures of the alloy in the Grain surface area an increase.
• the metal powder (s) and the blowing agent powder (s) as Reaction and / or alloying agent is a non-metallic element or the same compound, preferably carbon, especially graphite, before homogenizing mixing process is added.
• alloyed and high-alloyed heavy metals can also be beneficial especially for alloyed and high-alloyed heavy metals be if there is a layer in the area of the surface of the heavy metal powder grains is formed with increased nitrogen content, resulting in a heat treatment the blank is connected, because ultimately a high one Strength of the pore walls can be achieved.
• a carbon dioxide-releasing substance preferably at least one Carbonate, especially the elements from the second group of the periodic System or a heavy metal is used and by Exposed gas, possibly by reaction with the added carbon, which is experiencing an increase in volume, is used with highly effective Blowing agents, if appropriate with low blowing agent quantities, are particularly favorable trained porosity in the metal body reached.
• At least one oxide can also be used as blowing agent powder Heavy metal oxide, especially iron oxide, used and with at least one such an amount of carbon in the powder that the oxygen content of the oxide is reacted to CO gas.
• a highly crack-free inflation of the blank can be achieved if the Heating rate to the temperature at which the blowing agent gas cleaves, has a value that is greater than 4.05 ° C / s.
• At least two heavy metal powders and / or at least two blowing agent powders each with a different chemical Composition prepared and used to form the blank, can the conditions for a metallic connection of the powder particles to Formation of metal bodies with special mechanical properties and uniform small porosity can be optimized.
• the metal body is tight Has surface layer and is designed in particular as a composite body.
• the invention further comprises a porous metal body which has at least 40% by volume Has porosity, from at least one heavy metal and / or at least one Heavy metal alloy is formed and carbon contents of 0.05 to 4.1 wt .-% and / or has nitrogen contents of 0.002 to 0.3% by weight.
• a porous metal body which has at least 40% by volume Has porosity, from at least one heavy metal and / or at least one Heavy metal alloy is formed and carbon contents of 0.05 to 4.1 wt .-% and / or has nitrogen contents of 0.002 to 0.3% by weight.
• the metal body can be achieved if this essentially of an iron-based or nickel-based or one Cobalt-based alloy, in particular with chrome contents greater than 1.6 each % By weight or copper-based alloys and other heavy metals is formed and has a melting point greater than 900 ° C.
• the metal body consists essentially of at least one intermetallic Phase exists, so-called memory properties of this type can advantageously be used Materials are used.
• Table 1 show the effects of blowing agents with different dissociation temperatures (e.g. at 1 atm .: CaCO 3 : 900 ° C; SrCO 3 : 1289 ° C; BaCO 3 : 1360 ° C) on the one hand and carbon on the other according to a reaction process that increases the gas volume: MeCO 3 MeO + CO 2 CO 2 + C 2CO
• the propellant gas volume can be increased further if the metal oxides, in particular heavy metal oxides, formed from the carbonates by splitting off carbonic acid can be reduced by carbon at temperatures between 900 ° C. and 1250 ° C.
• heavy metal oxides for example iron oxides, in particular lamellar, that is to say non-amorphous hematite and carbon
• blowing agents and reactants with the formation of a blowing gas according to the formula: Fe 2 O 3 + 3C 2Fe + 3CO
• Powder additives made from lamellar hematite and graphite are particularly advantageous usable because a flaky structure of these particles good mixing and Distribution properties in the heavy metal powder as well as delayed reactions can effect.
• Stainless steel of the brand 304 L was produced by means of an inert gas atomization process and parts thereof with 0.1 wt.% CaCO 3 , with 0.15 wt.% SrCO 3 and with 0.15 wt.% SrCO 3 + 0 , 4 wt .-% C homogeneously mixed and the mixtures each filled in two sheet metal containers, these evacuated and sealed.
• a mixture series was hot isostatically pressed at a temperature of 1100 ° C., after which the blanks were then heated in an induction heating system to a temperature in the region of the melting temperature of the alloy in order to release the propellant gas, followed by cooling.
• a porosity of the metal bodies of over 62 vol.% could be determined, the carbon having a porosity-increasing and alloy-hardening effect.
• the pore volume or the pore size in the center of the part was larger and decreased towards the part surface.
• the second batch of mixtures was compacted in a hot isostatic press and then heated to near the melting point of the alloy. After holding the blanks at temperature for 30 minutes, the isostatic pressure was reduced to normal pressure with a homogeneous temperature distribution over the cross section and thus a porosity was formed in the metal body with simultaneous cooling of the same.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Powder Metallurgy (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Catalysts (AREA)

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• 1997
  • 1997-02-28 AT AT0034297A patent/AT406557B/de not_active IP Right Cessation
• 1998
  • 1998-02-26 EP EP98890051A patent/EP0868956B1/fr not_active Expired - Lifetime
  • 1998-02-26 AT AT98890051T patent/ATE248675T1/de not_active IP Right Cessation
  • 1998-02-26 ES ES98890051T patent/ES2202793T3/es not_active Expired - Lifetime
  • 1998-02-26 DE DE59809442T patent/DE59809442D1/de not_active Expired - Fee Related

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