Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1980-02-20
1981-03-10
Dean, R.
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
75165, 75173R, C22C 502
Patent
active
042551919
ABSTRACT:
Gold-silver alloys with good tarnish resistance for the dental art are prepared which, contrary to the known tarnish resistant alloys, still contain copper and thus have a deeper gold color and a high ductility. The alloys contain 33 to 48% gold, 0-5% platinum, 1-10% palladium, 0-0.2% iridium and/or ruthenium, 3-9% copper, 1-6% zinc, 0.5-4% tin and 2.5-10% indium, balance silver, wherein the mass ratio of copper to zinc is between 1:1 and 4:1, the content of copper is not higher than the sum of zinc, tin and indium, the content of palladium is at most three times as great as that of indium and does not exceed the sum of zinc, tin and indium. Under these provisions the copper content is not perceptibly disadvantageous to the resistance to discoloration.
REFERENCES:
patent: 3819366 (1974-06-01), Katz
patent: 3925073 (1975-12-01), Kohrn
patent: 4007040 (1977-02-01), Kropp
patent: 4008080 (1977-02-01), Wagner
patent: 4111690 (1978-09-01), Harmsen
Dean R.
Degussa - Aktiengesellschaft
Roy Upendra
LandOfFree
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