US2180137A - Metallic alloy - Google Patents

Description

Patented Nov. 14, 1939 UNITED STATES PATENT OFFICE METALLIC ALLOY No Drawing. Application January 7, 1938, Serial No. 183,832

9 Claims.

This invention relates to a metallic alloy and a method of making -it, and more particularly to an alloy and a method ofmaking it, especially adapted for use in the manufacture of orna- 5 mental articles.

Various alloys, especially of tin, hire been long used for casting articles such as o namental buckles, clips, picture frames, theatrical and the like,which are inexpensive andt will 10 maintain a brilliant appearance for a considerable time.

from these alloys, a quantity of the material may be kept molten for considerable lengths of time with additions both of new material and of scrap to beremelted. Also a kettle containing a supply of the alloymay be periodically cooled and reheated when a need for a new period of casting arises, so that the contents of such a kettle may be remelted several times. In some cases 20 these facts effect changes in the composition of the alloy which adversely affect the appearance or mechanical properties or both of articles cast. An object of the present invention is to provide an alloy of the general character and purpose de- 25 scribed, and a method of preparing the alloy,

such that the material thus composed and compounded will maintain its desirable characteris-' tics unchanged through a considerable series of remeltings, and such that, when deterioration eventually sets in, the pristine character of the alloy may be restored in a simple and effective manner.

With the above and other objects in view the invention may be embodied inan alloy of about 35 0.90% to 1.05% copper and not more than about 0.10% cadmium, with the balance substantially all tin comprising lead not in excess of 0.50%

and traces of antimony and bismuth, permissible as harmless impurities, which alloy is preferably 40 compounded by melting commercial refined tin in a suitable kettle, adding a prescribed amount of a suitable copper tin alloy to make the desired copper content and adding about fourteen ounces of metallic cadmium per ton of alloy, the alloy 45 being then stirred and cast into bars or pigs.

Other objects and features of the invention will appear from the following detailed description of an embodiment thereof in an alloy of the general character described, a method of making the 50 alloy, and a method of restoring the frequently remelted alloy to its original characteristics.

To prepare the alloy, commercial refined tin is melted in a suitable kettle and a sufllcient amount of a copper-tin alloy, sufficiently rich in copper,

55 is stirred into the molten charge of tin to give a In the manufacture of such articles,

final copper content to the alloy of from 0.90% to 1.05% copper with the balance tin except for minor impurities. Preferably the final copper content should be from 0.95% to 1.00% copper. It is found that a preferably convenient copper- 5 tin alloy for thus introducing the copper is one consisting essentially of about 33% copper and 67% tin.

This preliminary alloy may then be preferably tested for physical properties by casting test samples and testing these for polished seeming -*brilliance of surface, toughness and ability to be deformed without cracking.

Should the preliminary alloy show excessive brittleness, which. may sometimes occur from causes not at present wholly clear or known, the molten chargeis brought to a temperature preferably .of about 550 F. to 600 F. and sulfur to the extent of about two to four ounces per ton of alloy is stirred in, and a second lot of test specimens cast. If necessary to remove brittleness such addition of sulfur may be repeated.

Sulfur, besides removing the brittleness, may, especially if the sulfur treatment be repeated, reduce the copper content below the point where the copper is effective to produce the desired polished seeming brilliance of surface. Hence the test specimens are analysed for copper content, and if this be too low, it'is restored by addition of the copper-tin alloy used before to introduce co'pper.

It is found that the liability of the preliminary alloy to be brittle and hence to require treatment with sulfur, as well as the extent of sulfur treatment required, are both markedly diminished if the copper-tin alloy used to introduce the copper be carefully deoxidized before being added to the molten tin charge, preferably by adding a small amount of a phosphor copper alloy to the copper-tin alloy in ,question when the latter is being compounded.

When the preliminary alloy thus prepared has both the desired characteristics and composition, cadmium is added in metallic form and stirred in, in sumcient amount to bring the proportion of cadmium present in the finished alloy preferably to from 0.04% to 0.05% but in any event not over about 0.10%.

The alloy thus prepared, when cast in suitable molds,-makes articles of the general kind described having a brilliant silver white surface which not only come out of the mold with this polished seeming brilliance of surface but retain this appearance for an unusually great length of time before eventually becoming tarnished in the air. Furthermore, the alloy flows smoothly and will fill even an intricate mold in accurately complete detail. Where it is needful, sheet or bar like members of such articles cast from this alloy are notably pliable and may be bent closely double without visibly or seriously weakening or'damaging the metal at the bend.

It is also found that this alloy, especially when produced in the manner described, can be remelted repeatedly either alone or with additions of scrap metal of the same alloy, without such deterioration as to harmfully affect the visible or mechanical properties of articles cast from it.

If a batch of the alloy after a too extended series of remeltings finally does produce frosted or brittle castings, it may be regenerated in a simple manner by treatment with sulfur as above described and, if necessary, by restoration of a lost copper content by addition of such copper-tin alloy as was originally used in preparing the material.

While it is preferred to add the cadmium after the preliminary copper-tin alloy has been cleansed and stabilized with sulfur as described, this is not essential. The cadmium may be added immediately after or with the high copper-tin and the sulfur treatment applied afterward, if desired.

While the presence of lead in amounts up to 0.50% and of antimony and bismuth in smaller proportions is not in general harmful, it is preferred to have none of these present in amount exceeding 0.10%.

Other variations in the invention as disclosed will readily occur to those skilled in the art and the illustrative embodiments herein disclosed may be modified and departed from in various ways without departing from the spirit and scope of the invention as pointed out in and limited solely by the appended claims.

What is claimed is:

1. An alloy for use in casting articles and consisting of from 0.90% to 1.05% copper, from 0.01% to 0.10 cadmium, and the balance tin except for harmless impurities.

2. An alloy for use in casting articles and consisting of from 0.95% to 1.00% copper, from 0.02% to 0.07% cadmium, and the balance tin except for harmless impurities.

3. An alloy for use in casting articles and consisting of about 0.98% copper, about 0.045% cadmium, and the balance tin except for harmless impurities.

4. A method of making an alloy for use in casting pliable articles, which method comprises the steps of melting a quantity of substantially pure tin, adding a sufficient quantity of deoxidized copper-tin alloy to introduce copper to the extent of 0.90% to 1.05% of the total charge, and adding a sufficient quantity of cadmium to make a cadmium content of 0.01% to 0.10% of the total charge.

5. A method of making an alloy for use in casting pliable articles, which method comprises the steps of melting a quantity of substantially pure tin, adding a small portion of copper thereto, treating the resulting molten alloy with sulfur to increase the surface brilliancy and lessen the brittleness of articles cast therefrom, and adding a small portion of cadmium to improve the surface brilliance and untarnishing character of articles cast from the alloy.

6. A method of making an alloy for use in casting pliable articles, which method comprises the steps of melting a quantity of substantially pure tin, adding a small portion of deoxidized copper-tin mixture thereto, treating the resulting molten alloy with sulfur to increase the surface brilliancy and lessen the brittleness of articles cast therefrom, and adding a small portion of cadmium to improve the surface brilliance and untarnishing character of articles cast from the alloy.

'7. A method of making an alloy for use in casting pliable articles, which method comprises the steps of melting a quantity of substantially pure tin, adding about one thousand ounces of a mixture of about one third copper and two thirds tin per ton of tin melted, treating the molten charge with about two to four ounces of sulfur per ton of charge, and adding about fourteen ounces of metallic cadmium per ton of the resultant alloy.

8. A method of making an alloyfor use in casting pliable articles, which method comprises the steps of melting a quantity of substantially pure tin, adding a small portion of deoxldized copper-tin mixture thereto, and adding a small portion of cadmium to improve the surface brilliance and untarnishing character of articles cast from the alloy.

9. A method of making an alloy for use in casting pliable articles, which method comprises the steps of melting a quantity of substantially pure tin, adding a small portion of copper thereto, treating the resulting molten alloy with a small portion of sulfur sufficient to increase the surface brilliancy and lessen the brittleness of articles cast therefrom, and adding a small portion of cadmium to improve the surface brilliance and untarnishing character of articles cast from the alloy.

CHARLES H. BELL. LOUIS S. DEITZ, JR. ABRAHAM I. STEIN.