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
  • H01H1/02372—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te
  • H01H1/02374—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te containing as major component CdO
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
  • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
  • C22C32/0021—Matrix based on noble metals, Cu or alloys thereof
• • 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
  • C22C5/10—Alloys based on silver with cadmium as the next major constituent
• • 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

Definitions

• the invention relates to a silver-metal oxide composite, in particular silver-cadmium oxide, for use on contact pieces in low voltage switching apparatus, and to a method for its manufacture.
• Silver-metal oxide composites preferably silvercadmium oxide with 6 to 15% by weight CdO, have been used for quite some time as contact-surfacing material in low voltage switch apparatus.
• the advantage of these materials in relation to pure silver is a considerably lesser likelihood of welding during the switching operation, an arc-quenching effect which is essentially based on prevention of the resistance sparking of alternating current switch arcs and normally a longer service life in the switching arc.
• the contact materials produced in this way have a favorable welding behavior but inadequate resistance to ignition loss (see Metall 6, 1952, page 369). Even the addition of other oxides increased the service life only by a small amount (US. Pat. No. 2,796,346, British Patent Specification No. 683,343).
• the method of single pressing always produces highly porous brittle compound bodies with coarse oxide coatings and is therefore used in cases in which it is of more importance to ensure a high resistance to welding than a high resistance to ignition loss of the contacts, for example, in aviation switch units with low switch voltages.
• silver-cadmium oxide materials can be made by internal oxidation of melted homogenous silver-cadmium alloys (this method hereinafter being referred to as 01).
• this oxidation method represents a marked advance, at least as regards the ignition loss of the contacts (see US Pat. No. 2,673,167; Metall 10, 1956, page 628).
• the quality of the contact materials AgCdO with A CdO content of 6 to 15% by weight which are produced by internal oxidation, is mainly determined by the form in which the CdO is precipitated. It is generally considered that the best material was that in which the CdO was finely granulated and uniformly distributed throughout the volume. Thus one hoped to avoid in the case of interruption of the oxidation the formation of linear CdO precipitates and/or with CdO concentrations in the grain boundaries and heterogenous confining of Cd() agglomerates the tendency towards zones of low material strength and increased friction.
• grain-refining additives such as Ni, Co, Fe, Mo, Cr, Ti, Sn, Zn and V should be added in very small quantities (0.001 to 1 weight to the AgCd alloy (see German Patent Specification No. 1,153,178; British Patent Specifications Nos. 1,032,398 and 2,796,346) and/or that there should be an increase in the partial oxygen pressure during oxidation in order to ensure uniform precipitation and to make the brittle material deformable.
• the micrograph of a material which was produced in accordance with the method 01 shows homogenous distribution of the CdO particles (grain size D 5 microns).
• Such a structure was generally considered a prerequisite for optimal resistance to ignition loss since CdO concentration in the grain boundaries of the silver considerably weakens the matrix and leads in the switching operation to a destruction of the contact pieces along the grain boundaries.
• P2 a more recent method of manufacture in which a mixture fillingof very finely distributed silver and cadmium oxide is sintered to blocksand then sealed by heat deformation using for example rollers or extrusion presses (see Metallisme 58, 1967, page 752; German Patent Publication P1,539,848,8).
• silver-metal oxide composites attain their highest degree of resistance to melting loss when the oxide particles were distributed as homogenously as possible in the silver matrix.
• the silver matrix is formed having in its structure concentrated metallic oxide grains at its grain boundaries, and the alloy comprises at least two of the following alloying metals: Ca, Sb, Mg, Be, Al, Sn, Mn, Bu and Zr.
• the oxide precipitation of the new contact material of the invention produces extremely finely granulated (D 0.1, micron) material, preferably in the grain boundaries of the silver matrix and in a considerably less extent in the Ag grain.
• This type of precipitation is obtained by an addition of at least two of the metals Ca, Li, Sb, Mg, Be, Al, Sn, Mn, Bi and Zr to the Ag/Cd base alloy.
• Ignition loss characteristics well above the average are shown by the following internally oxidized alloys (oxidation in oxygenated atmosphere at 600 to 850 C.):
• the materials produced are brittle and can be deformed only with great difficulty.
• the brittleness alone is, however, not an adequate criterion for a high resistance to ignition loss.
• An addition of for example 0.1 weight Mn alone to the AgCd alloy increases the hardness and the brittleness of the oxidized material considerably, but at the same time reduces the service life to about half that of a AgCdO material without additives which is easily deformable. Only the addition of a second element of the series listed above produces the unexpected effect.
• the material of the invention is suitable, in contrast to the known AgCdO materials as per Pl, P2and 01, for fast-switching low voltage switches.
• Method of manufacturing a brittle, homogeneous silver-cadmium oxide composite having grain boundaries and metal oxide grains enriched at said grain boundaries in a silver matrix which comprises: (1) mixing together to form an alloy silver, cadmium and at least two other alloy components selected from the group consisting of calcium, antimony, magnesium, beryllium, aluminum, tin, manganese, and zirconium, and (2) internally oxidizing said alloy in an oxidizing atmosphere at a temperature from about 600C to about 850C to precipitate extremely finely granulated oxide material in the grain boundaries of the silver matrix, the proportions by weight of components in said composite being from about 6% to about 15% of cadmium oxide, and from about 0.5% to about 6% of each oxide of said other alloy components.
• Met lfid according to claim 1 wherein the oxides of each of said other alloy components are present in amounts of from about 0.5% to about 2% by weight.
• Method of manufacturing contact pieces for low voltage switching which comprises (1) forming an alloy from silver, cadmium and at least two alloy metals selected from the group consisting of calcium, antimony, magnesium, beryllium, aluminum, tin, manganese, and zirconium, (2) shaping said alloy into electrical contact pieces of desired size and shape, (3) internally oxidizing the contact pieces of said aloy in an oxidizing atmosphere at a temperature from about 600C to about 850C to precipitate extremely fine granulated oxide material in the grain boundaries of the silver, the proportions by weight of components in said oxidized alloy being from about 6% to about 15% of cadmium oxide, and from about 0.5% to about 6% of each oxide of said alloy metals, and (4) recovering the oxidized contact pieces suitable for long life low voltage switching operations.
• alloy metals selected from the group consisting of calcium, antimony, magnesium, beryllium, aluminum, tin, manganese, and zirconium

Landscapes

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=5764522

Family Applications (1)

Country Status (6)

Cited By (9)

Families Citing this family (7)

• 1970
  • 1970-03-09 DE DE2011002A patent/DE2011002C3/de not_active Expired
• 1971
  • 1971-01-28 CH CH124571A patent/CH549864A/xx not_active IP Right Cessation
  • 1971-03-04 ES ES388906A patent/ES388906A1/es not_active Expired
  • 1971-03-09 FR FR7108023A patent/FR2084338A5/fr not_active Expired
  • 1971-04-19 GB GB2161071A patent/GB1336461A/en not_active Expired
  • 1971-12-22 US US00211038A patent/US3785810A/en not_active Expired - Lifetime

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