Alloys or metallic compositions – Silver base
Patent
1993-11-23
1995-06-06
Roy, Upendra
Alloys or metallic compositions
Silver base
148430, 148678, 420505, C22C 100, H01B 1300
Patent
active
054220653
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a contact material having a base of silver for use in power-engineering switchgear, particularly for contacts in low-voltage switches, which, in addition to silver, contains as a further active component at least one higher melting metal, a metal alloy or a metal compound. In addition, the invention also refers to a method for the manufacture of contacts from such material.
BACKGROUND OF THE INVENTION
For contacts in power-engineering switchgear, for instance in power switches as well as in direct current, motor and auxiliary contactors, contact materials of the silver/metal (AgMe) system have proven suitable for a long time. Representatives of this system are, for instance, silver-nickel (AgNi) and silver-iron (Ag--Fe).
Silver-nickel has advantageous contact properties which, together with the test methods for contact materials are described for instance in INT.J Powder Metallurgy and Powder Technology, Vol 12 (1976), pp. 219-228. There is the disadvantage, however, that nickel dust, in particular, has injurious effects on the human organism.
The use of iron in silver-based contact materials has been proposed on various occasions. It has, however, been found that silver-iron does not yet satisfy the requirements stipulated, since, upon the continuous passage of current through such contacts, excessive heating takes place which can be explained by the formation in this system of a cover layer, thus increasing the contact resistance. Furthermore, from Federal Republic of Germany OS 3 813 311 (WO-A-89/10417) a sintered contact material of the aforementioned type is known which, in addition to silver as active component, contains at least iron and/or titanium. Particularly when the iron and the titanium are present in alloyed form and form an intermetallic compound, good results were obtained in switching tests. Nitrides, carbides and/or borides of metals, in particular of titanium, can possibly be present as further active components.
Furthermore, in DE-C-38 16 895 the use of a silver-iron material having 3 to 30 wt.% iron and one or more of the additions manganese, copper, zinc, antimony, bismuth oxide, molybdenum oxide, tungsten oxide and chromium nitride in amounts of a total of 0.05 to 5 wt.%, balance silver, is proposed for electric contacts. Finally, from DE-A-39 11 904 a method of powder metallurgy is known for the manufacture of a semifinished product for electric contacts from a composite material having a base of silver with iron in which 5 to 50 wt.% iron is used as first secondary component and 0 to 5 wt.% of a second secondary component from one or more substances from the group which contains the metals titanium, zirconium, niobium, tantalum, molybdenum, manganese, copper and zinc as well as their oxides and carbides.
SUMMARY OF THE INVENTION
Starting from the above prior art, the object of the invention is to provide a further silver-based contact material and the corresponding method of manufacture. The new material is characterized by low contact heating with stable heating behavior, reasonable tendency towards welding together, and a long life with respect to predetermined switch current intensities.
This object is achieved, in accordance with the invention, with a material of the aforementioned type in the manner that iron in proportions of between 1 and 50% by weight and rhenium in proportions of between 0.01 and 5% by weight are present as active components in combination. For the fabricating of contacts from the material of the invention, the iron and the rhenium can be added to the silver in the form of pure metals and/or as alloy, the material being manufactured by powder metallurgy. The ratio of the proportions by weight of iron to rhenium can be between 4:1 and about 20:1.
DETAILED DESCRIPTION OF THE INVENTION
Within the scope of the present invention, it has been recognized that, in particular, rhenium in combination with iron and silver improves the spectrum of properties as contact material. The use of rhenium in c
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patent: 3511953 (1970-05-01), Schmidt, Jr.
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patent: 4859238 (1989-08-01), Weise et al.
patent: 4911769 (1990-03-01), Yamada et al.
patent: 5022932 (1991-06-01), Yamada et al.
Schreiner et al., "The Properties of P/M Electrical Contact Materials", The International Journal of Powder Metallurgy & Powder Technology, vol. 12, No. 3, Jul. 1976, pp. 219-228.
Horst Schreiner, "Pulvermetallurgie elektrischer Kontakte", Springer-Verlag, Berlin/Gottingen/ Heidelberg (1964), pp. 100-109-164-167.
Technische Rundschau Informations Palette.
Haufe Wolfgang
Hauner Franz
Roy Upendra
Siemens Aktiengesellschaft
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