Classifications

• • 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
• • 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

Definitions

• This invention relates to a composition of matter suitable for use as an electric current transmitting contact, and more particularly, to an iron containing silver composite material which, when employed as an electrical contact, does not generate objectionable radio interference, and to the method of making this material.
• a principal object of this invention is the provision of electric contact points for circuit making and breaking apparatus which virtually eliminate radio interference.
• a further object of this invention is the provision of a composition of matter having the ability to act as an arc-forming electrode without generating objectionable radio frequency interference signals.
• a further object of this invention is the provision of a method of manufacturing a metallic composite material which does not generate objectionable radio frequency interference when used as electric contact points in circuit making and breaking apparatus.
• the radio frequency signal generated by an arc may be virtually eliminated by providing at least one of the pair of electrodes between which the arc is formed with a contact point or surface at the location of the are composed essentially of a metallic composite material comprising a matrix of substantially pure silver through which is distributed about 2.5 percent to about 30 percent, by weight, iron in a finely divided dispersion, providing the iron particles have been subjected to a reduction treatment in situ, as will be more specifically described later.
• a switch which operates slower for example, one in which the movable contact comprises a thermally responsive bimetal element, will tend to are over longer periods of time and, therefore, generate signals of longer duration. There are unquestionably many other factors which infiuence these signals.
• an electrical contact material comprising a matrix of substantially pure silver containing a fine dispersion of metallic iron which has been subjected to a reducing treatment in situ has the property of virtually eliminating arc-generated radio frequency interference signals.
• the method by which this material is made determines whether or not the resulting composite material has this desirable property.
• One such method which I have found to be efficacious involves the following procedure. Powdered commercially fine silver is mixed with a solution of ferric nitrate, Fe(NO3)3-9H2O in alcohol to form aslurry. Sufficient ferric nitrate is present so that the iron content of the dry components of the slurry, calculated as pure iron, is in the range of about 2.5 percent to about 30 percent, by weight.
• the slurry is stirred constantly until dry to prevent caking.
• the dry mixture is then reduced in dry hydrogen at a temperature of about 500 to 550 C. for sufficient time to accomplish the reduction of the ferric nitrate to iron.
• the mixture of silver powder and finely divided iron particles is then pressed into a compact and sintered in a reducing atmosphere of pure dry hydrogen at a temperature of about 850 to 900 C.
• the iron particles are subjected to a reducing treatment in situ prior to and during the sintering of the silver matrix.
• the sintered material may then be cold-worked into rods or any other desired form form which contact points may be conveniently fabricated. It may be found necessary to anneal the material between cold-working operations. I have found it desirable to perform such anneals at about 850) C. in an atmosphere of pure dry hydrogen.
• my invention may be advantageously employed as the contacts of circuit making and breaking apparatus, such as a switch, for example, I also contemplate its usefulness to extend to such applications as a current carrying brush for motors and generators, wiper-arm type contactors for rheostats and slide-wire type potentiometers and the like.
• my invention is applicable to any electrical apparatus having current carrying components which are relatively movable with respect to each other in the normal operation of the apparatus and between which, incidental to the operation of the apparatus, arcs are formed which tend to generate objectionable radio frequency interference signals.
• a method of making electrical contact material comprising the steps of preparing a dry mixture composed of finely divided, substantially pure silver having a finely divided compound of iron capable of being reduced by pure dry hydrogen thoroughly distributed therethrough, the amount of the compound of iron constituting about 2.5 to about 30 percent, by weight, of the whole, calculated as pure iron, subjecting the dry mixture to a reducing treatment in an atmosphere of pure dry hydrogen at from 500 to 550 C., forming the treated mixture into a compacted mass and sintering the compacted mass into a composite in an atmosphere of pure dry hydrogen at a temperature between 850 to 900 C., the particles of the compound of iron thereby being subjected to a reducing treatment in situ.

Landscapes

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

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23705491

Family Applications (1)

Country Status (4)

Cited By (6)

Families Citing this family (2)

Citations (8)

• 1954
  • 1954-05-14 US US429966A patent/US2806786A/en not_active Expired - Lifetime
• 1955
  • 1955-03-29 GB GB9161/55A patent/GB771705A/en not_active Expired
  • 1955-05-11 FR FR1134382D patent/FR1134382A/fr not_active Expired
  • 1955-05-14 JP JP1337055A patent/JPS309537B1/ja active Pending

Patent Citations (8)

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