US1969018A - Alloy - Google Patents

Description

Patented Aug. 7, I934 ALLOY Robert H. Leach, Fair-field, Conn assignor to Handy & Harman, New York, N. Y., a corporation of New York No Drawing. Application June 10, 1932, Serial No. 616,498

4 Claims. (Cl. 75-1) This invention relates to silver alloys and .is in this group have that effect. All the metals in concerned more particularly with a novel silver the group, however, do increase the tarnish realloy which may be used to especial advantage in sistance to a greater or less degree. Of the several the manufacture of table silver and hollow ware metals mentioned for use as hardeners, I prefer and for various other .purposes, because it has the to use nickel, as it offers certain advantages over property of strongly resisting tarnish and discolthe others in the group.v However, for the puroration. pose for which these metals are used in the new As is well known, silver alloys of ordinary comalloy, all four metals are substantial equivalents. positionandcontainingcopper as the base ingredi- Silver alloys which are now in widest use areent are susceptible to tarnish. Such discolorathose of sterling fineness containing not less than 65 tion of the metal is brought about by numerous 925 parts of silver per thousand, and in producagents, the most active being sulphur which is ing the new alloy of sterling fineness, I use appresent in various foods such as eggs, and is also proximately 92.5% silver, cadmium ranging from present to some extent in the atmosphere in the about 3% to about 4%, tin ranging from about form of gaseous compounds. Sulphur in both 3% to, 4 /g%, and a small amount of nickel, sili- 70 forms causes tarnishing at a rate which depends con, antimony, and/or magnesium as a hardener, on the length of contact or exposure of the nickel and/or silicon being especially desirable as metal, the concentration of the sulphur in the hardening ingredients. When any one of the food, or air, and the form in which the sulphur is hardening metals is used, the amount present is present. In any event, the necessity of frequent from about 4% to not to exceed about 1%, but 76 cleaning and polishing of silver articles to keep when two or more are employed, the total amount them in bright condition has led to numerous of the hardening ingredients is not to exceed attempts in the past to produce silver alloys which about 1.5%. are of good appearancahave the desired work- Instead of using cadmium as an element in the ing characteristics, and have a better resistance new alloy, I have found that approximately the 80 to tarnish than ordinary silver-copper alloys, same results may be obtained if zinc be substituted but up to the present, the proposed alloys with for part or all of the cadmium. I prefer to use which I am familiar, have not proven entirely satcadmium, however, and believe that the resistance isfactory. to tarnish of the new alloy in which cadmium is 80 The problem of producing a silver alloy which used instead of zinc is somewhat greater than that is resistant to tarnish is a difflcult one because inof an alloy in which zinc is present. vestigation has shown that binary alloys offer Typical examples of the new alloys of sterling little promise and the number of ternary and fineness have the following approximate analyses: quarternary alloys is very large. When it is un- 35 iierstood that small variations in the ingredients Example 1 in these alloys have an important effect on the re- Per cent sistance to tarnish and the amounts of the alloy- Silver ing ingredients used are highly critical with re- Cadmium spect to tarnish resistance, themagnitude and Tm 40 difficulty of the problem will be appreciated. Nickel 95 As a result of my investigations in this field, I Example Na 2 have found that a silver alloy which has excellent Per cent resistance to tarnish produced by various agencies Silver 92 5 may be produced by using cadmium and tin as a;

45 alloying metals, provided the cadmium and tin are Tin T confined within rather narrow limits, and the new gs; alloys may be given a somewhat improved resist- Nickel ance to tarnish and, in some cases better physical properties, if a small amount of a fourth ingre- Example No. 3

50 dient is added, which may be one or more of the Per cent metals, nickel, silicon, antimony and magnesium. Silver I 92.5 In most instances, the fourth ingredient has a Cadmium. 3,0 slight hardening effect and I shall, therefore, Tin 3,0 refer to it as a "hardener, although it is to be Nickel 0,5

55 derstood that not all of the metals mentioned Magnesium 1.0 1 0 T1 Nickel, antimony, magnesium, or silicon Example No. 4 I

Per cent As above mentioned, zinc may be substituted for all or part of the cadmium in the 800 fine alloy, but I prefer to employ cadmium.

I am aware that it has been proposed heretofore to make silver alloys which contain zinc, antimony, and tin, and tin and chromium, but after a large number of experiments involving the exposure of these alloys to various forms of tarnish, I have found that the ranges of cadmium and tin and the relative proportions used are quite critical and any substantial departure from the ranges given results in a lowered tarnish resistance. My tests indicate further that increasing the cadmium content improves the resistance of the alloy to certain forms of tarnish while increasing the tin improves the resistance to certain other forms of tarnish. An alloy which has the best resistance for tarnish from all sources is one in which the cadmium (or zinc) and tin are present in amounts within the ranges specified for an alloy of sterling fineness.

What I claim is:

1. A silver alloy which comprises silver ranging from about to 92.5%, cadmium ranging from about 14.5% to about 3%, tin ranging from about 5% to about 3% and nickel ranging from about 0.25% to about 1%.

2. A silver alloy which comprises silver ranging from about 80% to about 92.5%, cadmium ranging from about 14.5% to about 3%, tin ranging from about 5% to about 3% and about 0.5% of nickel.

3., A silver alloy of sterling fineness which comprises about 92.5% of silver, from about 4% to 3% of cadmium, from about 4.5% to about 3% of tin, and from about 0.25% to about 1% of nickel.

4. A silver alloy of sterling fineness which comprises about 92.5% of silver, about 3.5% of cadmium, about 3.5% of tin, and about 0.5% of nickel.

ROBERT H. LEACH.