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
  • H01H1/0233—Composite material having a noble metal as the basic material and containing carbides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
  • C22C27/04—Alloys based on tungsten or molybdenum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/12—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on oxides
• • 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
• • 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
  • C22C9/00—Alloys based on copper

Definitions

• the silver or copper is used to provide the contact material with a constituent of high electrical conductivity.
• the magnesium oxide constituent is used to provide the contact material with improved arc erosion resistance and improved arc interruption characteristics when compared to the same characteristics of a contact material consisting essentially of tungsten or its carbides, and silver or copper.
• the tungsten or its carbides with silver or copper type contact material of the present invention consists essentially of 90 to weight percent silver or copper, 0.25 to 7 weight percent magnesium oxide, the remainder essentially tungsten or carbides.
• the present invention relates to an electrical contact material and, more particularly, to an electrical contact material of the type including tungsten or its carbides, a metal having good electrical conductivity which is substantially mutually insoluble and non-reactive with tung sten or its carbides such as silver or copper, and magnesium oxide which improves the arc erosion resistance and improves the arc interruption characteristics of the contact material when compared to a contact material of the type consisting essentially of tungsten or its carbides with silver or copper.
• Electrical contacts of a high conductivity material such as silver or copper have poor arc erosion resistance and arc interruption characteristics and, therefore, among other things, tend to experience pitting of the working surface and to experience rapid arc erosion of the working surfaces of the contact material.
• composite contact materials have been made from tungsten with a matrix of either silver or copper.
• such composite contact materials tend to lose some of the matrix of silver or copper since under the action of heat normally associated with the operation of such composite contact materials, the silver or copper volatilizes creating tungsten nodules that act to increase the electrical transfer resistance of the working surface of the composite contact material and raise the temperature of the tungsten nodules.
• Additions of oxides of metals such as zirconium, aluminum and silicon in the composite contact material of tungsten and silver or copper type increases the hardness of the contact material and increases the electrical contact resistance of the contact material. None of the above metals or oxides of metals when added to the tungsten with silver or copper composite contact type material appears to have a substantial eifect on improving the arc erosion resistance and improving the arc interruption characteristics of such contact material.
• tungsten or its carbides with silver or copper composite contact type material which includes from about 0.25 to 7 weight percent magnesium oxide had significantly improved arc erosion resistance and decreased arc interruption characteristics.
• the addition of substantially the same Weight percent of magnesium oxide to an electrical composite material of molybdenum or its carbides with silver or copper did not significantly improve the arc erosion resistance and improve the arc interruption characteristics of such a composite contact material.
• a further feature of the electrical contact material is that the weight ratio of tungsten or its carbides to either silver or copper is 9:1 to 1:9 of the total weight of a composite and including from about 0.25 to 7 Weight percent magnesium oxide.
• the present invention relates to an electrical contact composite material of the type consisting essentially of tungsten or its carbides, a highly conductive metal which is substantially mutually insoluble and non-reactive wtih tungsten or its carbides such as silver or copper, and magnesium oxide (either light or heavy) wherein such material has improved arc erosion resistance and improved arc interruption characteristics.
• the contact material of the present invention can be made by any of several techniques including press techniques and press-sinter-infiltrate techniques.
• the infiltration temperature is above the sintering temperature of the compact but below the boiling point temperature of the infiltrant.
• Suitable temperatures for infiltration of the compact are in the range of up to 1400 C.
• An infiltration temperature of less than 1000 C. can be used, but the infiltration time is lengthened considerably.
• a suitable reducing atmosphere for use during infiltration is hydrogen or dissociated ammonia.
• Another method for preparing the electrical contact material of the present invention is to compact a blend of tungsten or its carbides, with silver or copper, and magnesium oxide, presinter the compact, sinter the compact and then infiltrate the sintered compact with a melt of either silver or copper, as the case may be.
• the weight content of tungsten or its carbides in the electrical contact material of the present invention is about to about 90 weight percent of the total weight of the contact material.
• a contact material including less than about 10 weight percent tungsten or its carbides tends to experience serious erosion of the working surfaces of the contact.
• a contact material including more than about 90 weight percent tungsten or its carbides experiences undesirable electrical characteristics such as high electrical contact resistance.
• the content of magnesium oxide in the electrical contact material of the present invention is about 0.25 to about 7 weight percent of the total weight of the contact material.
• a contact material including more than about 7 weight percent of magnesium oxide has a higher than desired electrical contact resistance.
• a contact material including less than about 0.25 weight percent magnesium oxide does not appear to significantly improve the arc erosion resistance and improve the arc interruption characteristics of the contact material.
• the preferred weight range in which the advantageous characteristics of arc erosion resistance and are interruption are associated with the composite material are from about 0.5 to about 3.5 weight percent magnesium oxide, with about 1.5 to about 2.5 weight percent magnesium oxide being the most preferred range.
• the most preferred composite material of the present invention is about 10 to 90 weight percent tungsten, about 90 to 10 weight percent silver and about 1.5 to 2.5 weight percent magnesium oxide.
• EXAMPLE 1 A blend of 90 weight percent silver powder, 8 weight percent tungsten powder, and 2 weight percent magnesium oxide is prepared by ball mill blending for 8 hours. The powders, prior to blending, have an average particle size of about 1 to 10 microns. The blend is compacted by any suitable means such as by pressing at a compacting pressure of about 11.5 tons per square inch. The compact is then sintered in a reducing atmosphere of hydrogen at about 825 C. for about 50 minutes. The sintered material is hot extruded into bar form.
• Example 1 The composite of 90 weight percent silver, 10 weight percent tungsten is made employing essentially the method of Example 1. The tests conducted on such material are essentially as outlined in Example 1.
• EXAMPLE 2 A mix of 81.6 weight percent tungsten carbide powder, 15 weight percent silver powder, and 3.4 weight percent magnesium oxide powder is blended by ball mill blending for 8 hours. The powders, prior to blending, have an average particle size of 1 to 10 microns. The blend is compacted at a pressure of 22 tons per square inch. The compact is sintered for about 30 minutes at about 1325 C. in a hydrogen atmosphere. The sintered compact is infiltrated with a melt of silver for about 30 minutes at about 1400 C. The final composition of the composite is 48 weight percent tungsten carbide, 50 weight percent silver and 2 weight percent magnesium oxide. Tests using the test procedure of Example 1 provide the following results:
• Average volume loss Material per operation 48% WC-50% Ag-2% MgO 3.871 cc. 1O" 50% WC-50% Ag 4.353 cc. 10-
• the composite of 50 weight percent tungsten carbide and 50 weight percent silver is made using essentially the method of Example 2.
• the test procedure of Example 1 is used to test the material.
• EXAMPLE 3 A blend of 88.2 weight percent tungsten, 10 weight percent silver, and 1.8 weight percent magnesium oxide is prepared by ball mill blending for 8 hours. The blend is compacted at a pressure of about 22 tons per square inch. The compact is presintered in a hydrogen atmosphere at 400 C. for 15 minutes, sintered in a hydrogen atmosphere at 1275 C. for 30 minutes and infiltrated with a melt of silver at 1400 C. for 30 minutes. The final composition of the composite is 36 weight percent silver, 1.3 Weight percent magnesium oxide, the remainder essentially tungsten. Tests using the test procedure of EXAMPLE 1, except that the current applied is 1400 amperes, provides the following results:
• Example 3 35% Ag-65% W 2.275 cc. 10'"
• the composite of 35 weight percent silver and 65 Weightpercent tungsten is made using essentially the method of Example 3.
• the test procedure of Example 1 is used to test the material.
• erosion resistance means and includes the ability of the composite contact material to withstand the effects of an electrical are without significant loss of the contact material.
• interruption means and includes the ability of the composite contact material not to sustain an electrical are for periods in the order of up to 2 electrical cycles depending on the type of switch device in which the contact material is used.
• magnesium oxide means and includes both light and heavy magnesium oxide.
• An electrical contact material of the tungsten or tungsten carbide with silver or copper type including from about 0.25 to about 7 weight percent magnesium oxide of the total weight of the electrical contact material, the addition of magnesium oxide improving the arc erosion and are interruption characteristics of the electrical contact material.
• An electrical contact material having improved arc erosion and arc interruption characteristics consisting essentially of about 90 to about 10 weight percent of a constituent selected from the group consisting of tungsten or its carbides, about 10 to about 90 weight percent of a constituent selected from the group consisting of silver or copper, and about 0.25 to about 7 weight percent of magnesium oxide with the possible inclusion of minor amounts of impurities.
• one constituent is about 90 to about 10 weight percent tungsten, one constituent is about 10 to about 90 weight percent silver, and about 0.25 to about 7 weight percent magnesium oxide with the possible inclusion of minor amounts of impurity constituents.
• An electrical contact material of the tungsten or tungsten carbide with a highly conductive metal which is substantially mutually insoluble and non-reactive with tungsten or its carbides type including from about 0.25 to about 7 weight percent magnesium oxide, the addition of magnesium oxide improving the arc erosion and are interruption characteristics of the contact material.
• Col, 1 line 32 delete "additives” and substitute therefore additions f 4 C' C; .Lli med and sealed this 15th day of iii- 175.1 1 7.

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

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23155875

Family Applications (1)

Country Status (5)

Cited By (8)

Families Citing this family (1)

• 1972
  • 1972-10-24 US US00299697A patent/US3827883A/en not_active Expired - Lifetime
• 1973
  • 1973-10-03 BR BR7684/73A patent/BR7307684D0/pt unknown
  • 1973-10-15 CA CA183,413A patent/CA1008117A/en not_active Expired
  • 1973-10-20 DE DE19732352796 patent/DE2352796A1/de active Pending
  • 1973-10-22 JP JP48118028A patent/JPS52234B2/ja not_active Expired

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