US2311436A - Electrical contacts - Google Patents

Description

Patented Feb. 16, 1943 ELECTRICAL CONTACTS Childress B. Gwyn, Jr., Deerfield, 111., assignor to Fansteel Metallurgical Corporation, North Chi cago, Ill., a corporation oi New York No Drawing. Application January 22, 1942,

Serial No. 427,680

Claims.

This invention relates to electrical contacts.

An object of this invention is to provide a silver-base contact alloy which is characterized by excellent inherent resistance to erosion and sticking.

Another object of the invention is to provide a silver-base contact alloy which is more readily and more economically produced than alloys for which it can be substituted to give at least as ood or better service.

It is a still further object of my invention to provide an alloy which is made from readily available materials not extensively employed for other purposes.

Other objects of the invention will be apparent from the following description taken in connection with the appended claims.

While certain preferred embodiments of the invention are described herein, it is readily apparent that some variation may be employed in the method of manufacture and combination of elements without departing from the spirit of the invention, all as outlined herein.

The present invention comprises an improvement in silver-base alloys, characterized by the addition to the silver base of considerable quantitles of iron, in amounts from 2.5 to 50 per cent. A portion of the iron may be advantageously replaced by other members of the iron group, which is herein defined as consisting of iron, nickel, cobalt, manganese and chromium; but it is an essential requirement of this invention that at least half of the iron group metal employed shall consist of iron itself.

It is likewise possible to improve the properties of my novel contact alloy by the addition 01 quantities of the precious metals, 1. e., gold and the platinum group metals in amounts of .1 to 20 per cent.

I have also found that in some instances it is desirable to further alter the composition of these alloys by the addition of from .1 to 30 per cent of one or more metals, e. g., cadmium, zirconium or indium.

Contacts made according to the teachings of this invention are characterized by excellent wear-resistance when employed on loads of substantial voltages. It is not advisable to employ contacts made in accordance with the teachings of this invention on loads below 5 volts, unless the exceptional suggestion of employing substantial quantities of precious metals is also employed.

Excellent results have been had from employing my new alloy in both resistance and inductive service.

Contacts of this type may be substituted, with desirable results, for contacts made of fine, sterling, or coin silver. They may also be desirably substituted for silver contact materials containing molybdenum, tungsten or nickel alloyed with silver.

My alloys are characterized by relatively higher contact resistance than certain other alloys provided for this purpose, and when substituted for such alloys are particularly characterized by their resistance to erosion due to electrical causes.

A particularly desirable feature of these alloys is the relative ease of procuring the necessary constituents of the alloy.

Manufacture of these alloys is carried out according to the more conventional principles. In some instances it is desirable to melt together some or all of the essential constituents, while in other cases it is desirable to provide the constituents in the form of powder particles which may be combined by the recognized technique of power metallurgy.

As an example of the results which may be expected from the employment of contacts described herein, a comparative testwas carried out on both A. C. and D. C. circuits at volts and 1500 watts. Contacts employed were all .25" in diameter. The results of the test were as follows:

A. C. test Material: Cycles before sticking Fine silver"; 1,370 Coin silver 1,709 Tungsten-silver 11,037 Molybdenum-silver 13,001 Cadmium-silver 558 Iron-silver 100,000 test stopped D. C. test Material: Cycles before sticking Fine silver "(0 Coin silver 73 Tungsten-silver 1'74 Molybdenum-silver 239 Cadmium-silver 202 Iron-silver 76,008

It is also significant to note that where sticking occurred, in most cases the contacts, after being separated and operated again, tended to stick readily thereafter. This was not the case with the iron-silver alloys.

What I claim and desire to secure by Letters Patent is: p

1. An electric contact member formed of an alloy containing as an essential ingredient, silver, to which has been added iron in amounts ranging from 2.5 to 50 percent.

2. An electric contact member formed of an alloy of 2.5 to 50 per cent iron. balance substantially all silver. 7

3. An electric contact member formed of silver, to which have been added at least two members of the iron group, one of which is iron itself, in amounts from 2.5 to 50 per cent.

4. An electric contact member formed of silver, to which have been added iron in amounts of 2.5 to 50 per cent, and a metal selected from the group consisting of cadmium, zinc, and indium in amounts from 0.1 to 30 per cent.

5. An electric contact member formed of silver, to which have been added iron in amounts of 2.5 to 50 per cent, and a precious metal selected from the group consisting of gold and the platinum group of metals in amounts of 0.1 to 20 per cent.

CHILDRESS B. GWYN, JR.