US2259668A - Tarnish resistant silver alloy - Google Patents

Description

Patented Oct. 21, 1941 TARNISH RESISTANT SILVER ALLOY Jakob Spanner, Neu-Isenburg, Germany, assignor to Chemical Marketing Company Inc., New York, N. Y., a corporation of New York No Drawing. Application October 28, 1940, Serial No. 363,210. In Germany October 27, 1939 (Granted under the provisions of sec. 14, act of March 2, 1927: 357 0. G.

2 Claims.

My invention relates to the manufacture of silver alloys which are resistant against tarnishing, especially silver alloys containing also palladium, cadmium and copper.

Thorough investigations have shown that alloys containing. silver, palladium, cadmium and copper are resistant against tarnishing, even if the contents of silver are relatively high. They possess also some other good qualities if the ratio of the constituents is kept in the following ranges:

Per cent Silver 25-60 Palladium -50 Preferably about 20-35 Cadmium 10-40 Preferably about -25 Copper 5-30 Preferably about 10-20 Furthermore, the alloys may also contain gold or platinum, either alone or in combination, in quantities below 10%, preferably about 5%.

If the alloy has a high cadmium content, the

Metals of the iron group may also be contained in the above mentioned alloys, in quantities up to 10%, preferably not more than 5%.

If copper, zinc and metals of the iron, either alone or combined, are added to the silver alloy one part of the cadmium may generally be replaced by these metals.

Finally, small additions of deoxidising means may also be added to the silver alloys. As deoxidising substances I mean the following: phosphorous, calciumboride, silicium, thorium, cerium, lithium, titanium, manganese. In general, these additions should not exceed 5%; quantities between 0.05 and 5% have already a favorable influence.

The alloys may be used in difierent fields of commerce, so for instance, in the jewelry, for dental purposes or the like. The manufacture of these alloys is not expensive and yields to well workable, yellow white, tarnish resistant alloys.

The following table contains several alloys according to my invention. The alloys may also be utilized as solders.

Composition Heat ggfig Soft Rolling property treat- Au Pd Ag Cd Cu Zn Mn ment Percent Percent Percent Percent Percent Percent Percent C. KgJmm. KgJmm. Degrees 0 45 30 5 a-8 202 96 Cast good 750 5 15 5o 21 s 181 166 do 750 5 15 39 35 5 105 700 5 20 40 3O 5 199 750 10 10 45 3O 5 69 720 5 25 35 15 20 285 129 l .d0 650 5 25 5 177 104 Cast, sufficient- 750 5 30 25 25 15 147 Cast, good. 650 4. 5 27- 34. 75 18 15.75 155 Cast, very good...

sired degree, but if copper is present in large quantities, the allow will tend to a certain brittleness. It is therefore expedient to adapt the content of copper in each case to the requirements of the special alloy. In general, a content of copper varying between 5 and 20%, especially between 10 and 15% has yielded to good results.

Zinc may also be contained in the alloy, in quantities of, for instance, 0.5 to 10%, preferably 0.5 to 5%. Zinc as well as cadmium exert a favorable protecting effect against tarnishing of silver allows. Too high a content of zinc must be avoided since it would render the alloys brittle.

What I claim is:

1. A tarnish-resistant silver alloy comprising 25% to 60% silver, 10% to of palladium, 10% to 40% of cadmium, 5% to 30% of copper and 0.1% to 10% of a precious metal selected from the group consisting of gold and platinum,

said silver, palladium, cadmium, copper and precious metal constituting substantially all of the alloy.

2. A tarnish-resistant silver alloy comprising 25% to of silver, 20% to 35% of palladium, 15% to 25% of cadmium, 10% to 20% of copper and 0.1% to 10% of a precious-metal selected from the group consisting of gold and platinum, said silver, palladium, cadmium, copper and precious metal constituting substantially all of the alloy.

JAKOB SPANNER.