US2243177A - Colored gold alloy - Google Patents

Description

Patented May 27, 1941 COLORED GOLD ALLOY Ludwig Weiss, Frankfort-on-the-Main, Germany, assignor to Chemical Marketing Company Inc., New York, N. Y., a corporation of New York No Drawing. Application May 1, 1940, Serial No. I 332,841. In Germany April 13, 1939 Claims.

My invention relates to the manufacture of a purple colored gold alloy containing thorium besides aluminum and gold.

It is known that gold combines with aluminum and forms an intermetallic composition of the formula AuAlz with a bluish or purple, amethystlike color, containing 78.5 parts of gold and 21.5 parts of Al. This alloy, known as amethyst or blue gold" is not workable because of its hardness, brittleness and its liability of break- Other gold alloys contain, besides gold and aluminum according to the formula AuAlz, additional quantities of aluminum or other soft metals such as silver, tin, zinc, cadmium, bismuth, thallium either alone or in combination in quantities which facilitate the workability of the alloy without a harmful influence to the color effect. The total amount of these additional soft metals should not exceed 40% of the alloy. With these additions of soft metals gold alloys of various shades are obtained, for instance, from red over a purple shade to a violet color, 1. e. especially amethyst colored red alloys which are workable and suitable for the manufacture of jewels.

Now it .was found that the qualities of the goldaluminum alloys, especially those of the formula AuAlz may be considerably improved with respect to the workability by adding thorium in suitable amounts.

These new alloys according to my invention may, for instance, also contain thorium in quantities up to about besides gold and aluminum. If a beautiful blue color is desired, the contents of thorium in the alloy must be kept below 7%. It is also possible to add very small amounts of thorium, for instance, such which do not exceed 1%- of the whole alloy. Gold aluminum alloys with a thorium content of, for instance, 0.5% to 1% have a beautiful shade, good workability and' ductility. The thorium content may even be kept lower, especially if other metals with improving qualities are present. The lower limit of the content of thorium is, for instance, about 0.5% of the total alloy.

Furthermore, I have found that the ductility of the alloys may be increased by adding tin in quantities of about 7% besides gold, aluminum and thorium.

Generally, it has proved advantageous to keep Gold Aluminum 24,25 Thorium 0.25 Tin 0.5

has a beautiful bluish color, good workability and may easily be hallmarked.

In carrying out my invention I may proceed as follows: The composition AuAlz, i. e. 78.5 parts of gold and 21.5 parts of aluminum, may serve as starting material, whereby one or both of these metals are partly substituted by thorium or thorium and tin.

It has proved advantageous to substitute one part of the aluminum by thorium or thorium and tin respectively. This makes it possible to obtain beautiful workable alloys with a high content of gold, for instance, 75% gold, corresponding to a hallmark of 18 karat.

The alloys, according to my invention, may als contain, besides the main constituents gold, aluminum and thorium or thorium and tin, small quantities of other metals such as silver, zinc,

cadmium and the like.

Other components of the alloy may be iron, nickel, cobalt, manganese, copper. The addition of small quantities of these metals either alone or in combination may influence the qualities of the alloys with respect to ductility and the like and'also in regard to the color shade. Of course, the quantity of these additional metals is proportioned in such manner that harmful influences may not occur. Generally, it was found advantageous to keep the amount of these metallic additions, alone or combined with each other, below 5% preferably below 2% of the total alloy. As the alloys are susceptible against oxygen, I prefer to work airsealed. For instance, I may proceed in such manner that at first the aluminum is molten under a salt layer whereupon the other ingredients are added in the following order: tin, gold, thorium.

Thealloys may be used for various purposes. They are especially suited for the manufacture of jewels.

What I claim is:

21.5% aluminum, and from about 0.5% to 10% thorium.

3. A workable gold alloy having a purple colored shade consisting of from about 71.5% to about 78.5% of gold, from about 14.5% to about 21.5% of aluminum, and from about 0.5% to about 7% or thorium.

4. A workable gold alloy having a purple oolored shade consisting of from about 75.5% to 78.5% of gold, from about 18.5% to about 21.5% of aluminum, and about,3% of thorium.

5. A workable gold alloy having a purple colored shade consisting of from about'68.5% to about 78.5% gold, from about 0.5% to about 10% thorium, and the remainder substantially all aluminum, the aluminum constituting not over 10 24.25% of the alloy.

LUDWIG wmss.