Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1990-10-17
1993-09-21
Nelson, Peter A.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75238, 75239, 75244, 75247, 252514, 252516, 252519, 252520, 420501, C22C 2902
Patent
active
052464806
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a silver-based sintered contact material for use in switch-gears of the energy technology, and in particular for contact pieces in low-voltage switches, which contain in addition to silver, at least one higher melting point metal, metal alloy and/or a metal compound as an active component. Switch-gear of the energy technology is understood in the present instance as exclusively air switch-gear.
For contact pieces in low-voltage switch-gears of the energy technology, e.g., in power switches, as well as in DC and auxiliary contactors, contact materials of the silver-metal (AgMe) system have long proved successful. In the past, the silver-nickel (AgNi) system has had a major share of these contact materials. The advantageous properties of silver-nickel in contact systems are known and have been described together with the testing methods for contact materials, for example, in Int. J. Powder Metallurgy and Powder Technology, Vol. 12 (1976), pp 219-228.
Some time ago, however, it was found that nickel dust has carcinogenic effects. For this reason, endeavors have been under way for some time to replace the nickel by another metal or a metal alloy or metal compound. These new materials, however, must have a similar spectrum of contact properties as compared to AgNi materials.
It is, therefore, the object of the invention to provide a contact material of the initially mentioned kind wherein nickel as active component is replaced by a metal, metal alloy or metal compound without diminishing the contact properties.
According to the invention, the problem is solved by providing a contact material which contains in addition to silver (Ag), as an active component at least iron (Fe) and/or titanium (Ti). The active component may be present in the material in percentages by mass or weight of up to 50%.
In accordance with the invention, iron or titanium alone may be present in combination with silver. Preferably, the iron and the titanium are present in alloyed form. In particular, in the composition close to 50 atom-% (46 wt-% Ti) iron and titanium form an intermetallic phase in which the properties supplement each other ideally.
As a development of the invention, the contact material may additionally contain as further active components nitrides and/or carbides and/or borides of metals. In particular, titanium enters into consideration for this, but zirconium or tantalum may also be used. The nitrides and/or carbides and/or borides of the metal may have a mass or weight percentage of from 1 to 50% with reference to the iron-titanium content as the main active component. With the nitrides, carbides and/or borides, the proportion of the base constituents can be increased, i.e. the necessary proportion of silver may be reduced. As a whole, the material may contain the base constituents in percentages by weight up to at least 50%.
All active components are present in the contact material in a proportion in percent by volume of between 2% and 50%. In various embodiments of the present invention, the proportion of all active components is suitably less than 40%, less than 30%, or less than 20%.
Further details and advantages of the invention will become evident from the following description of an embodiment example for the production of contact pieces, with reference also being made to the attached table with specific examples for different materials compositions according to the invention.
The table lists measured values for the maximum welding force in N, for the volume burnoff in mm.sup.3, and for the contact resistance in m. These measured values characterize, in combination, the property spectrum of the particular contact material, wherein especially the volume burnoff is a significant measure for the possible number of switching operations of the contact, i.e., the life of the contact piece, and the contact resistance is a significant measure for the overtemperature at the contact piece. The values are compared in each instance with the measured values for AgNi10.
For the preparation o
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Grosse Joachim
Haufe Wolfgang
Rothkegel, deceased Bernhard
Mai Ngoclan T.
Nelson Peter A.
Siemens Aktiengesellschaft
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