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
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/30—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis
• • 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
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0466—Alloys based on noble metals
• • 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
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
  • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
  • B22F9/26—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions using gaseous reductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
  • H01H1/021—Composite material
  • H01H1/023—Composite material having a noble metal as the basic material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
  • H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
  • H01H11/048—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by powder-metallurgical processes

Definitions

• the invention is based on a powder-metallurgical method for producing a semi-finished product for electrical contacts from a composite material based on silver 5 to 50 wt .-% iron as the first secondary component and 0 to 5% by weight of a second secondary constituent from one or more substances from the group which contains the metals titanium, zircon, niobium, tantalum, molybdenum, tungsten, manganese, copper and zinc, their oxides and their carbides, and the rest of silver as the main component, which is disclosed in the older, but not prepublished DE-A-38 16 895.
• the individual constituents of the composite material are mixed with one another in powder form, pressed into shaped bodies and sintered, that is to say produced by a conventional powder metallurgical process.
• the composite material cannot be produced by melt metallurgy, because iron is not significantly soluble in silver even in the molten state.
• the invention has for its object to find a way in which the frequency of such spontaneously occurring increases in contact resistance can be reduced.
• the alloy or composite powder by adding compounds present in aqueous solution for the alloying or ver Metals provided in the powder are pyrolytically decomposed by the process of spray pyrolysis.
• the method of spray pyrolysis is described, for example, in US Pat. No. 3,510,291, in EP 0 012 202 A1 and in DE 29 29 630 C2. Salts of the metals intended for the alloy or composite powder are dissolved in a liquid and the solution is atomized in a hot reactor or in a flame, so that the solvent evaporates suddenly, at a temperature below the melting temperature of the dissolved Metals lies. The sudden evaporation of the solvent results in composite powder particles in which the metals are bound together in a very fine and uniform distribution.
• the composite powders are usually created by spray pyrolysis with particles that are smaller than 100 ⁇ m (diameter). For the process according to the invention, preference is given to using powders whose particles are not larger than 40 ⁇ m. In the composite powder produced by spray pyrolysis, the individual constituents are predominantly in the form of 0.1 ⁇ m to 1 ⁇ m (diameter) large particles which are connected to one another. The use of such finely structured powder particles favors the formation of the desired properties of the contact pieces (low erosion, low tendency to weld, consistently low contact resistance).
• the spray-pyrolytically produced composite powder can contain not only metallic components, but also oxides or carbides if the oxide-forming or carbide-forming metals are added to the solution to be sprayed from the outset in the form of a soluble salt.
• the atmosphere In order for oxides or carbides to form in the hot atmosphere in which the metal salt solution is sprayed, the atmosphere must of course contain free oxygen or oxygen in a reactive compound or a gaseous carbon compound, for example a gaseous hydrocarbon, with which the spray pyrolysis is used initially formed, reactive metals can react with the formation of oxide or carbide.
• the oxidic or carbidic constituents that may be provided bring about, in part, a lowering of the contact point temperature in switching operation and, in part, an extension of the service life of the contact pieces not only in the case of small and medium current loads, but also in the heavy load range, as described in IEC standard 158-1 for AC4 Test conditions is specified (switch-off current equals switch-on current).
• switch-off current equals switch-on current.
• Molybdenum oxide, molybdenum carbide, tungsten oxide and tungsten carbide work even in small quantities (in the order of magnitude from 0.1% by weight).
• Alloy powders and composite powders that can be used in the process according to the invention can be produced not only by spray pyrolysis, but also in other ways, for example by chemical mixed precipitation of the metals intended for the alloy or composite powders from a solution of their salts or by atomizing of molten metals. Chemical mixed precipitation is an option for the production of composite powders from components that can be dissolved and chemically precipitated under similar conditions.
• the atomization of molten metals is primarily considered for the production of alloy or composite powders from metals which are soluble in one another at least in the molten state in the quantitative ratios of interest here, which applies to iron pairings with most of the metals intended for the second secondary constituent;
• manganese is also firmly soluble in an amount of up to a few percent, whereas titanium and zircon in silver are not soluble in the solid state, but are to a certain extent soluble in the molten state.
• a composite powder can only be formed by atomization if the molten metals are mixed intensively with one another by stirring or if the spray jets of the molten metals are allowed to penetrate one another.
• Alloy or composite powders obtained by mixed precipitation or atomization can subsequently be subjected to an internal process Undergo oxidation and thereby produce an oxide composite powder or carburize and thereby produce a carbide-containing composite powder.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Powder Metallurgy (AREA)
• Contacts (AREA)

Applications Claiming Priority (2)

Publications (2)

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Citations (8)

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• 1989
  • 1989-04-12 EP EP89106490A patent/EP0338401B1/fr not_active Expired - Lifetime
  • 1989-04-12 DE DE58909449T patent/DE58909449D1/de not_active Expired - Fee Related
  • 1989-04-12 ES ES89106490T patent/ES2080052T3/es not_active Expired - Lifetime

Patent Citations (8)

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