Alloys or metallic compositions – Copper base – Titanium – zirconium or hafnium containing
Patent
1989-12-18
1992-09-22
Dean, R.
Alloys or metallic compositions
Copper base
Titanium, zirconium or hafnium containing
420501, 164 551, 164 561, 164 571, C22C 102, C22C 900, C22C 506
Patent
active
051494981
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of producing tarnish- and oxidation-resistant alloys on the basis of copper or silver, small additions of boron and zirconium being added to the melt.
2. Background Art
A method of dispersion hardening of copper, silver or gold as well as of their alloys as matrix material with metal borides as dispersoid, is already known (German Published Patent Application No. 3,522,341); according to this method, the melt on the basis of the matrix metals with stoichiometric additions of boron and boride-forming metals is superheated by 300.degree. to 750.degree. C. to form metal boride in an amount of 1 to 5 volume %, and subsequently subjected to extremely rapid solidification. The necessary superheating of the melt requires high-priced crucible material, and the extremely rapid solidification requires sophisticated powder-metallurgical processes.
BROAD DESCRIPTION OF THE INVENTION
The object of the invention is to provide a method which functions without high superheating of the melt, and which does not make demands concerning rapid solidification, but operates with low alloying additions. This object is achieved by the process of the invention. The invention involves a method of producing tarnish-resistant and oxidation-resistant alloys on the basis of copper or silver with a high electrical conductivity of more than 90 percent IACS and a softening temperature of more than 550.degree. C. Stoichiometric amounts of boron and zirconium are added to the copper or silver melt. A copper or silver melt containing additions of preferably 0.3 to 0.6 weight percent of zirconium and 0.1 to 0.2 weight percent of boron to form a fine dispersion of less than 1, preferably 0.4 to 0.8 volume percent, such that the melt can be processed into seminfinished products using continuous casting and rolling units. The method according to the invention leads to a very high resistance to tarnishing and oxidation. As this method requires only very low alloying additions, which combine to give the insoluble boride, the electrical conductivity corresponds practically to that of pure copper. This also results in excellent formability of the material produced according to this method. This method can be used to produce tarnish- and oxidation-resistant sheets and profiles, for example tubes, rods or wires, which have electrical conductivities between 97 and 99% IACS of that of pure copper, permitting softening temperatures above 550.degree. C. The material produced according to this method is suitable in particular for thermally stressed electrical conductors, contacts, connectors, as well as for semiconductor carriers. In addition, the principle of the invention can be transferred to silver. If, for example, the silver melt or the silver-alloy melt contains additions of zirconium and boron in order to form zirconium boride in an amount of less than 1 volume %, preferably 0.4 to 0.8 volume %, this, too, will essentially improve the resistance of silver to tarnishing.
Another advantageous development of the invention results, when in the invention method, excess calcium hexaboride CaB.sub.6 is used as deoxidant, such that the excess serves for introducing the necessary boron proportion into the copper or silver melt. A further advantageous development of the invention results, when in the invention method, sheets, profiles and wires for tarnish-resistant and oxidation-resistant structural components tolerating thermal and mechanical stresses are produced for application in pollutant-containing atmospheres. A further advantageous development of the invention results, when in the invention method, semiconductor carriers, electrical contacts, connectors and wire for highly stressed engines and generators are produced. Another advantageous development of the invention results, when in the invention method, silver alloys are produced which are tarnish-resistant in a sulfur-containing environment.
DETAILED DESCRIPTION OF THE INVENTION
The materials produced ac
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Nilmen Fehmi
Winter Heinrich
Battelle-Institut e.V.
Dean R.
Phipps Margery S.
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