US2196306A

US2196306A - Silver lithium alloy

Info

Publication number: US2196306A
Application number: US308996A
Authority: US
Inventors: Franz R Hensel; Kenneth L Emmert; James W Wiggs
Original assignee: PR Mallory and Co Inc
Current assignee: Duracell Inc USA
Priority date: 1939-12-13
Filing date: 1939-12-13
Publication date: 1940-04-09
Anticipated expiration: 1957-04-09

Description

Patented Apr. 9, 194i) UNITED STATES PATENT; OFFICE. I sILvEn LrrnnJM ALLOY I Fran! R; Hensel, Kenneth L. Emmett, andlllnel P. B. Mallory -82.

a corporation of It is an object of the present invention to provide an alloy which has improved electrical properties such as electrical conductivity.

It is a further object or the present invention to provide an alloy which shows great fluidity in the molten state and lends itself to casting ofvery intricate shapes. I

It is a still further object of the present in-' vention to produce an alloy which has improved wetting characteristics whenused as a silver solder. g

Another object of the present invention is to produce a new alloy which hassuperior electrical characteristics when used as an electrical makeand-break contact such as low material transfer,

low contact resistance and freedomfrom welding or sticking.

Other objects of the invention willbe apparent i'rcm the following description taken in connection with the appended claims. The present invention comprises the combination of elements,.

methods of manufacture and-the product thereof brought out and exemplified in the disclosure "hereinafter set forth, the scope of the invention being indicated in the appended claims. 4 While I a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the combination of elements with- 40 out departing from the spirit of the invention.

The present invention contemplates the addition to silver of lithium and metal from the group consisting of cadmium and zinc. .It is contemplated that alloys may be produced according to the invention ha'vlng the-ingredients combined in the following range of proportions:

1 Percent Lithium .002to 8 Metal selected from the group consisting of cadmium and zinc 1 mill) Balance, substantially all silver.

Wehave also mind that the addition of-the following elements-may improve the V gether in the correct proportions.

W. Wiggs, Indianapolis, Ind., assignorl to 00., Inc., Indianapolis, 1116.,

Application December 18, '1 939.

Serial No. 303,996 I K tics of the present alloyscovered by the present invention: I

. Per cent Tll'l Up to 11 Manganese Up to 20 3 Nickel Up to 10 Phosphor v p v Up to 8 Silicon Up to 2 It is also possible to substitute copper for a substantial part of the silver. I t

A A number of preferred compositions are given below: v a

Per'cent l. Cadmium 20 u Lithium .01 Silver Balance 3 Silver- 50 Cadmium 18 Zine Ooppe'r 15.2 ldthinm I v I 3 26' s. Silver .53. I

Zine 16 Copper 30.75

' Lithium .25

5. Silver 60 7.1 l5 Copper 20 Nickel 4.75 Lithium .25

- In addition to the baser elements, materials 35- from the palladium, platinum or gold group may also be present up to 10% each. The alloys of the present invention are preferably prepared by melting the ingredients to- The lithium 40 is preferably added in the form of a silverlithium master alloy, containing approximately 15% of lithium. This master alloy has a very low melting point which is in the neighborhood of 410 to 450 C. and therefore will so readily 4.5 into solution when added to the silver-copper melt.

The effect of lithium is to completely deoxidize the silver melt and to free same from other impurities which are harmful. Part of the lithium so will be eliminated together with these impurities and the remaining melt will be free from inclusions and oxides. The presence of lithium also prevents the further oxidization of the melt during the heating periods to which the melt may be u I it.

I subjected and the material retains a very high fluidity during pouring, resulting in extremely clean castings.

We have found that cadmium-silver alloys orv f silver-zinc alloys e. g. containing a small percentage of lithium such as, for instance, .01% or'less will lend themselves much more readily to rolling and wire drawing operations, resulting in a material which is entirely free from surfaceblemishes and oxide stringers. Furthermore if such silver wire is being spun or ii silver wire produced in that manner is being headed, a surface finish can be obtained with alloys of the new in-' vention that excels anything obtainable so far with alloys of the prior art. Very often in heading of silver alloys containing elements of the second group of the periodic system,' the formation of edge cracks or splits is encountered, causing a great number of rejects. By the addition of lithium to these alloys in the proportions specified these difilculties can be eliminated or materially reduced.

If lithium is used inhigher proportions such as .05 to 1% it was found that alloys of silver with elements of the cadmium-zinc group will show greatly improved-electrical characteristics. Contact alloys of this type have very improved characteristics as far as material transfer and contact resistance are concerned. It was also of great interest to find that the material transfer for this composition was from the cathode to the anode. In most silver base alloys the material transfer is in the opposite direction, therefore it seems desirable to use the material of the present invention in combination with another silver alloy having opposite transfer characteristics.

We have carried out ments with compositions containing zinc and cadmium, to which was added 25% lithium. After the material-was rolled into sheet or drawn a large number of experiinto wire, tests were made using these alloys for silver soldering purposes. It was found that most excellent results were produced by these new combinations. In order to cheapen the silver solders or to lower the melting point by the formation of ternary or quaternary eutectics, it was found that the addition of copper could be made to replace a substantial portion of the silver. It was also found that the addition of such elements, as particularly manganese, tin, phosphorus and silver would further improve the performance of the alloys containing 25% of lithium when used for silver soldering purposes. The alloys will flow very readily and will wet the metals to be joined readily and produce a joint of very high physical strength.

Since lithium decreases the melting point of silver very materially and since an eutectic is formed at 2.7% lithium, having a melting point of 610 C. care must be exercised when these materials are processed at elevated temperatures and if they contain higher percentages of lithium.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof,-it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An alloy containing .002 to 3% lithium, 1 to 30% of an element selected from the group consisting of cadmium and zinc and the balance substantially all silver. 7

2. An alloy composed of .05 to 1% lithium, 1 to 30% of an element selected from the group consisting of cadmium and zinc and the balance silver.

FRANZ R. HENSEL. KENNETH L. EMMERT. JAMES W. WIGGS.