Global Info Research Product Code: PAEKs are thermoplastics that are crystalline in nature and are characterized by good mechanical properties, thermal stability, chemical and solvent resistance,
Brorkowskl 8 William Fischer. Bratirowslti, McKeesport, and William H. The invention has particular reference to processes for securing arc-resisting contact tips of certain refractory metals and their alloys to supporting structure of aluminum and like metals. The invention relates further to electrical contact members made by such processes.
There has been a need for a satisfactory method of brazing refractory metals, such as tungsten, molybdenum and tantalum, and their base alloys, to aluminum, magnesium and their base alloys. In the electrical industry, for instance, contact conductors adapted for use on high speed circuit interrupters generally are made of copper and copper alloys.
Since copper and copper alloys do not have suitable arc-resisting properties, it has been a common practice to secure a tip of arc-resisting material such as silver-tungsten, silver-molybdenum, or copper-tungsten to the main or supporting copper contact member to prevent excessive burning of the member.
It has been desirable to replace copper and alloys thereof with aluminum, aluminum alloys, magnesium alloys or the like to provide members which are lighter in Weight, yet which have comparable strength characteristics and electrical conductive properties.
Heretofore, attempts to replace copper and alloys thereof with metals such as aluminum, aluminum alloys, magnesium alloys or the like have not been satisfactory because no completely successful method has been found nor securing the arc-resisting contact tips to such metals. In an effort to obtain satisfactory mechanical and elec trical connection of arc-resisting tips to supporting structures of such metals, various mechanical joining methods have been resorted to, such as riveting, threading and swaging, and the like.
It has been found, however, that tips fastened according to these latter methods loosen relatively quickly under the repeated impacts resulting from continuous operation of the circuit interrupter.
The loosening of the contact tip from the support member, introduces high resistance regions wherein arcing occurs thereby impairing the efiiciency of the operation of the circuit interrupters.
It is difiicult, when utilizing any conventional brazing technique, to satisfactorily join a tip of arc-resisting ma terial such as silver-tungsten to an aluminum support member because of the presence of a layer of aluminum oxide present on the support member.
It is known that such surface oxide coatings can be removed by the ap plication thereto of strong reagents, such as fluorine-containing inorganic acids. As an example, it has been determined, however, that the utilization of such acids in the form of commercially available acid fluxes conventionally used in brazing techniques does not provide a satisfactory means for joining a silver-tungsten tip to an aluminum support member.
Corrosion frequently occuts in such joints, due to the inclusion therein of flux, with subsequent failure of the joint resulting. While the problem of joining refractory metals to aluminum has been emphasized in connection with circuit breaker contacts, it will be understood that there are numerous other instances where similar metal joining difficulties have arisen.
The object of the present invention is to provide a brazing process utilizing high frequency sound vibrations for joining refractory metals such as tungsten, molybdenum, tantalum, the platinum group metals, their base alloys, and carbides thereof, such as tungsten and molybdenum carbides, as well as mixtures embodying a refractory metal and good electrically conducting metals such as silver, copper and gold, to light, electrically conducting metals such as aluminum, magnesium and their base alloys.
It is a further object of the present invention to provide processes for preparing contact structures wherein arc-resistant tips of refractory metals are secured to support members of aluminum, aluminum alloys, magnesium alloys or the like by brazing techniques utilizing high frequency mechanically produced sound vibrations, to provide joints of maximum mechanical strength and members having excellent electrical conductivity.
Another object of the present invention is to provide improved electrical contact members having arc-resisting tips of refractory metals secured to supporting members by brazing techniques utilizing high frequency mechanically produced sound vibrations whereby member are provided having maximum mechanical strength and electrical conductivity characteristics.
Other and further objects of the invention will, in part, be obvious and will, in part, appear hereinafter. For a more complete understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawing, in which: It has now been discovered that refactory metals may be joined successfully to light, electrically conducting metals such as aluminum, aluminum alloys, magnesium alloys, and the like by fluxless brazing utilizing high frequency mechanically produced sound vibrations.
By refractory metals is meant metals such as tungsten, nickel, molybdenum, tantalum, the platinum group-metals and their base alloys and carbides thereof such as tungsten and molybdenum carbide.Brazing alloys from Grainger can let you join similar or dissimilar metals together without melting the base metal.
Find numerous sizes and materials here, including copper, nickel silver, bronze and various metal combinations.
High-temperature brazing materials consist of nickel-based alloys and silver-manganese alloys. They are used for brazing components intended to operate at temperatures well above normal ambient temperatures, such as parts for gas turbines or steam turbines.
On the basis of type of base metal use brazing material market can be segregated into four segments that are as follows aluminium, gold, copper, silver and other. The major contribution in revenue is expected to come from Copper and Gold segment owing to their extensive demands in .
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