Classifications

• • 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
  • H01H1/0237—Composite material having a noble metal as the basic material and containing oxides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
  • C22C5/06—Alloys based on silver
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9265—Special properties
  • Y10S428/929—Electrical contact feature
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
  • Y10S75/95—Consolidated metal powder compositions of >95% theoretical density, e.g. wrought
  • Y10S75/951—Oxide containing, e.g. dispersion strengthened

Definitions

• ABSTRACT A light-duty electrical contact material which consists [30] Foreign Application Priority Data of a mixture of silver and ruthenium oxide, the ruthe- O t 21 1970 G tB 49 660/70 nium oxide contact being in the range 0.1 to 13.0 tea n am atomic per cent. For reasons of economy, the preferred ruthenium oxide content is 1.3%.
• the material is produced by powder metallurgical techniques from I fine, irregular Silver powder and preferably ultra fina [58] Fleld of Search 75/173, 200/166 C ruthenium metal powder Fine ruthenium oxide pow [56] References Cited der can be utilized in place of the ruthenium metal powder.
• the invention provides a light-duty electrical contact material which consists of a mixture of silver and ruthenium oxide, the ruthenium oxide content being in the range 0.1 to 13.0 atomic per cent.
• the preferred ruthenium oxide content is 1.3%.
• the invention also provides a method of producing a light-duty electrical contact including the steps of mixing fine, irregular silver powder with ultra fine ruthenium metal powder to provide a mixture having a fine, evenly dispersed ruthenium content in the range 0.1 to 10.0 atomic per cent; compacting the mixture into a desired shape; heating the compacted shape in a suitable atmosphere for a period of time to effect sintering of same; and internally oxidizing the sintered compacts to convert the ruthenium metal into ruthenium oxide.
• the invention further provides a light-duty electrical contact which is produced by the method outlined in the preceding paragraph.
• the electrical contact material according to the invention which, as previously stated, is suitable for lightduty applications, consists of a mixture of silver and ruthenium oxide, and the concentration of ruthenium oxide can vary from 0.1 to 13.0 atomic per cent.
• the contact material is best fabricated by powder metallurgical techniques and the preferred and most economical material is a material having a ruthenium oxide content of 1.3%. Vacuum and gas melting techniques are unsuitable because it is not possible to disperse the ruthenium phase finely and evenly throughout the silver.
• fine, irregular silver powder, and ultra fine ruthenium powder are initimately mixed together such that the ruthenium content of the mixture is in the range 0.1 to 10.0 atomic per cent.
• the intimate mixing can be effected by dry tumble milling for a period of time of the order of 2 to 24 hours.
• the intimate mixing of the powder particles can be effected by dry tumbling in the presence of glass spheres, or by milling under acetone.
• the size and shape of the metal powder particles is of prime importance in the manufacture of optimum silver-ruthenium oxide materials and both powders should preferably be as fine as is economically possible.
• This in practice involves the use of precipitated silver of less than 300 or 350 mesh (preferably less than 20 microns average intercept), and ruthenium powder in the sub-sieve size range (preferably less than 2 microns average intercept) with preferably no ruthenium powder particles of a size greater than 5 microns diameter.
• the use of fine powders ensures that a fine, even dispersion of the ruthenium is obtained in the finished contact material and facilitates the rapid oxidation of silver-ruthenium alloys which are to be internally oxidized to obtain a fine, even dispersion of ruthenium oxide in the silver.
• the powder mixture is then compacted, using molds, into the desired shape for the electrical contacts.
• the compacting can for example be effected at a pressure of the order of 10 to 20 tons per square inch to give green densities of the order of of the theoretical maximum density.
• the contact compacts are then sintered by being heated in a neutral or reducing atmosphere, for example 90%N /10%H for a period of time of not less than one hour.
• the upper temperature limit for the sintering operation is 960.5C i.e. the melting point of silver.
• a temperature just below the melting point temperature should be utilized, for example a temperature of the order of 930C.
• the sintering process increases the density of the contact material to between and of the theoretical maximum density, the actual density attained being dependent upon the sintering time and temperature.
• the sintered contact compacts are then internally oxidized by being heated in air at a temperature of the order of 930C for a period of time of not less than one hour.
• This oxidation process completely converts the sub-surface particles of ruthenium metal in the silver (Ag) to ruthenium oxide (RuO- Metal particles at greater depths will only be partially oxidised on their surfaces.
• Ruthenium oxide is a conducting oxide which exhibits very low electrical resistivity and is contained in the contact material as a fine, even dispersion.
• the density of the contact material may then, if dc sired, be increased to at least of the theoretical maximum density by a stamping operation at a pressure of the order of 40 to 45 tons per square inch.
• the material of the electrical contacts produced by this method exhibits low, stable contact resistance at low contact forces over a period of years under atmospheric conditions which would normally tarnish and corrode known silver base contact materials such as silver-cadmium oxide or silver alone.
• the green silver-ruthenium compacts can be compacted at a pressure of the order of 10 tons per square inch, and then sintered in air for a period of the order of one hour at a temperature of the order of 930C.
• This sintering process simultaneously sinters the contact material and oxidizes the ruthenium to RuO
• the ruthenium powder particles situated well below the surface of the compacts are oxidized and the density of the contact material is increased from 70% to 80% of the theoretical maximum density.
• the density of the contact material may then, if desired, be increased to at least 95% of the theoretical maximum density by a stamping operation at a pressure of the order of 40 to 45 tons per square inch.
• the contact material produced by this alternative method also exhibits low, stable contact resistance at low contact forces for long periods in tarnishing atmospheres.
• the silver recrystallized and grain growth begins, the grains grow until they meet a ruthenium oxide particle.
• the ruthenium oxide particles impede further grain growth and remain in the grain boundaries to effectively anchor them in position.
• the ruthenium oxide content of the contact materials produced by the methods according to the invention is mostly located in the grain boundaries in the silver.
• the contact resistance properties of the light-duty electrical contact materials according to the invention in comparison with silver (Ag) and silver-cadmium oxide (AgCdO) contact materials are indicated in the table given below:
• the contact resistance is shown as a function of contact force after 21 hours exposure to a moist H 8 atmosphere i.e. an atmosphere containing 700.0 mm H 5 and 17.0 mm of H 0.
• silver-ruthenium oxide is that it is readily solderable with soft solder, it is readily capable of heading to form a rivet, and it is capable of being brazed.
• the ruthenium metal powder utilized in the methods outlined in preceding paragraphs is replaced by ruthenium oxide powder such that the ruthenium oxide content of the silver-ruthenium oxide mixture is in the range 0.1 to 13.0 atomic per cent.
• the silverruthenium oxide mixture is then compacted and sintered in an inert atmosphere in the manner outlined in preceding paragraphs. While this production method produces a silver-ruthenium oxide material that may be suitable for certain applications it is not the preferred method because it results in a less favourable oxide particle size distribution and an inferior dispersion of oxide particles within the silver matrix.
• a light-duty electrical contact material which consists of a mixture of silver and ruthenium oxide, the ruthenium oxide content being in the range 0.1 to 13.0 atomic per cent.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Composite Materials (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Switches (AREA)
• Contacts (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=10454129

Family Applications (1)

Country Status (5)

Cited By (2)

Citations (2)

• 1970
  • 1970-10-21 GB GB4996070A patent/GB1313359A/en not_active Expired
• 1971
  • 1971-10-07 CA CA124,653A patent/CA967787A/en not_active Expired
  • 1971-10-19 FR FR7137511A patent/FR2111546A5/fr not_active Expired
  • 1971-10-20 DE DE2152327A patent/DE2152327C3/de not_active Expired
  • 1971-10-21 US US00191564A patent/US3778257A/en not_active Expired - Lifetime

Patent Citations (2)

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