US2793423A - Compound metal stock - Google Patents

Description

May 28, 1957 M. J. STUMBOCK COMPOUND METAL STOCK Filed April 19, 1954 Fauna/0444140) A T'TORNE) 2,793,423 Patented May 28, 1957 COMPOUND METAL STOCK Max J. Stumbock, South Orange, N. J., assignor to Baker & Co., Inc., Newark, N. 1., a corporation of New Jersey Application April 19, 1954, Serial No. 423,956

5 Claims. (Cl. 29-194) The present invention deals with a compound metal stock and is concerned in particular with the provision of metal stock having a palladium alloy layer and a base metal backing.

In the manufacture of certain types of jewelry, watch cases, or palladium-surfaced equipment, it is customary to use a compound metal having a relatively thin palladium layer combined with a base layer of inexpensive metal. Base layers of brass, bronze, stainless steel, and German silver have been used for backings with palladium layers and the selection of such base metals has been largely dependent upon the particular use for which the composite or compound metal is intended. However, it has been found that, as in the case of gold alloys, the palladium develops a surface roughness upon annealing and working the composite metal for fabrication into palladium-clad articles or palladium-clad equipment. The surface roughness is referred to in the art as orange peel roughness. In order to overcome this disadvantage the art, in the case of gold alloys, resorts to somewhat complicated specific quaternary alloys or alloys such that substantial additions of base metals, including metals of the iron group, are necessary to preclude grain growth. In the case of a compound metal stock consisting of a thin layer of palladium on a base metal backing, the addition of any base metal of the iron group to the palladium does not satisfactorily prevent grain growth since the grain size depends upon the specific iron group metal used and more particularly to a specific range of such base metals for the prevention of the orange peel defect.

When palladium composite stock is employed for jewelry purposes, there is a limitation on the amount of base metals which may be legally employed. Usually the base metal content which would preclude the orange peel defect exceeds such base metal limitation.

It is an object of the present invention to provide a compound metal stock consisting of a thin layer of a palladium alloy on a base metal backing. It is another object of the present invention to provide a compound metal stock consisting of a palladium alloy on a base metal backing, wherein the palladium alloy may be annealed and worked without deleterious grain growth. Other objects of the present invention will become apparent from the description hereinafter following and the drawing forming a part hereof.

The drawing illustrates a cross-sectional view of a compound metal stock according to the present invention.

The present invention deals with a compound metal stock consisting of a thin layer of a binary palladium alloy on a base metal backing including preferably at least one of the backing metals brass, bronze, stainless steel, and German silver, wherein the palladium alloy after successive annealing and working consists of grains ranging in size from 0.005 mm. to 0.035 mm. and preferably a major portion of such grains ranging below 0.025

In forming a compound metal of the type contemplated by this invention, it is desirable to join the layers together before they are rolled to their final thinness, whereby it is possible to obtain thinner layers with a more suitable bond between the layers and with greater ease in handling. After a relatively thick compound metal stock is thus formed, it is subjected to the usual mechanical processes of rolling, pressing, bending, etc. to obtain a final product having the desired shape. It is well known, however, that when metals are so treated, they become hard and brittle and may not be further worked until they are again made soft as by annealing. A complete forming and shaping process, therefore, usually comprises several successive steps of rolling and annealing, during which successive steps the metal becomes first hand and then soft, there being a final annealing treatment after the reduced metal stock is bent or otherwise formed into the desired shape so that the metal will be in a durable, flexible and resilient condition. It is during such successive steps of annealing and working that the orange peel defect develops in the palladium alloy layer, unless the compound stock consists of a layer of palladium alloy consisting of palladium and from 1% to 5% cobalt in accordance with this invention.

The cobalt content is quite critical in the maintaining of the alloy grain size below 0.035 mm. and, surprisingly the cobalt content in the range specified is more than twice as efficient as the next best metal tested for elimination of the orange peel defect. For example, the iron group metal nickel which is widely used together with palladium as a binary alloy is only capable of maintaining less than one-half of the grain sizes below 0.035 mm. Specifically, the alloy palladium with 4% nickel maintains about 50% of the grain sizes in the neighborhood of 0.035 mm. On the other hand, in spite of the fact that nickel is closely related to cobalt, the alloy palladium with 4% cobalt provides grains such that 45% thereof range from 0.005 mm. to 0.008 mm., 30% range from 0.010 mm. to 0.015 mm., and 25% above 0.015 mm., but below 0.035 mm. With 5% cobalt, the optimum grain sizes are obtained since of such grain sizes are between 0.005 mm. and 0.10 mm. with 10% thereof being 0.015 mm. in size.

Furthermore, it has been found that the palladium alloy consisting of from 1% to 5% cobalt draws excellently and in a superior manner in comparison with the conventional palladium alloys, and the color of the 5% cobalt-palladium alloy is a pleasing bluish white, which compares favorably with that of the well known platinum and white gold alloys not only with respect to color characteristics but to oxidation and corrosion resistance as well.

What I claim is:

1. A compound metal stock comprising a layer of palladium alloy on a base metal backing, said palladium alloy consisting of palladium and from 1% to 5% cobalt.

2. A compound metal stock comprising a layer of palladium alloy on a base metal backing, said backing consisting of at least one of the metals brass, bronze, stainless steel, and German silver, said palladium alloy consisting of palladium and from 1% to 5% cobalt.

3. A compound metal stock comprising a layer of palladium alloy on a base metal backing, said palladium alloy consisting of 5% cobalt.

4. A compound metal stock comprising a layer of palladium alloy on a base metal backing, said palladium alloy consisting of palladium and from 1% to 5% cobalt, said alloy having grain sizes ranging between 0.005 mm. to 0.035 mm. with the major portion of said grains ranging below 0.025 mm.

5. A compound metal stock according to claim 3, 2,105,312 Cohn Jan. 11, 1938 wherein 90% 0f the grain sizes of said alloy are between 2,143,217 Truths Jan. 10, 1939 0.005 mm. to 0.010 mm. and 10% below 0.025 mm, 2,470,034 Hensel May 10, 1949 2,501,164 Durst Mar. 21, 1950 UNITED STATES PATENTS 5 2,539,096 Miller Jan. 23, 1951 References Cited in the file of this patent 2,074,996 Cohn Mar. 23, 1937

Claims (1)

1. A COMPOUND METAL STOCK COMPRISING A LAYER OF PALLADIUM ALLOY ON A BASE METAL BACKING, SAID PALLADIUM ALLOY CONSISTING OF PALLADIUM AND FROM 1% TO 5% COBALT.

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