US2272063A - Electric contacting member - Google Patents

Description

I Patented Feb. 3,

ELECTRIC comacrnfwe- I Hensel and Kenneth 1..

assignors tol' .-1t.-Malloryv &"O0.,f

fl ranz R.

. apolis, Ind.,

lnc., Indianapolis, Ind.

aware No Drawing. Application Serial Neeuse 3 Claims. (01. zoo-515s) This invention relates to electric contacts. I

An object of the invention is to improve the characteristics of an electrical contacting element containing silver.

Another object of,.the invention is to provide a silver base contact material which will retain a low contact resistance.

A still further object is to provide a-new contact material which can be used under severe electrical conditions, without welding.

Other objects 01' the invention will be apparent from the following description, taken in connection with the appended claims.

. The present invention relates to an electric contact and the combination of elements there-- for, methods of manufacture and the product thereof, brought out and exemplifiedin the disclosure hereinafter set forth, the scope of the invention being indicated in the appended claims.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may b made in the method of procedure and the combination of elements,

without departing from the spirit of the invention.

The present invention comprises an improvement in silver electric contact elements. According to the invention, the contacts are improved by I the addition of beryllium.

The contacts may be composed of silver and beryllium accordingly. The ingredients may be present in approximately the following proportions: Beryllium Percent by weight .05 to4 Silver Balance One of the experimental alloys, containing .94,% beryllium,.had a conductivity in the ascast condition or 67.2%, a hardness in the as'cast condition of 43 Rockwell'E'which increased to 87 Rockwell F, after 25% cold swaging. The speciflc gravity of this material was 10.12 grams per c. c., as compared to 10.5 grams per c; c. for fine silver. The beryllium has a much lower specific ,gravity than fine silver. and therefore the addition of beryllium lowers the density of the finished alloy, which is of considerable commercial importance, because it is possible to obtain a larger number of finished pieces, and more par ticularly finished contacts, most constitutional diagrams thepercentages are given by weight percentages. A much clearer picture, however, can be obtained, if the atomic I sistedoi sodiumnuoride and Q I The additioncof small percentages to silver I causes a -very marked decrease in the freezing.

electrical conductivity.

sheet. also very readily v material on the'other side.

per unit weight. In-

percenta'ges are used, because there is an enormous diilerence .in the atomic weights 01' silver 'bllity decreasesslowly ture- This indicated that the materials can be I hardening, which can I heat treatment of the alloys,, consisting usually in a quenching operation and -a subsequent aging operation.

.freadily to be prepared In order to avoid segregation during melting,

a master alloy-wasused containing 4 to 6% of. I

beryllium. Nodimculty was'encounteredinmelting and pouringithe'se alloys; It was found advisable, inicertain cases to ad a flux which conpoint. the liquidus' curve ialling' steeply, until a beryllium content'or.9'l is reached. This corresponds to an atomic percentage of I I the'liquidus first rises very sharply, then flattensout atomic percent of p-berylliumat the temperature or the treezing pointof the eutectic. The soluth decreasing temperaimproved slightly ;by age be obtained by a raiseboth the hardness of beryllium, shows a typical structure of an eutectic, the matrixconsisting or silver and a free con stituent consisting of the beryllium rich solid solution.. In thepreparation or the alloys it has dizers' and degasiflers, such as, or instance, lithium. Alloys produced in such a manner are oxide and therefore show improved ductility, impact strength and it used I tact, show a decreased tendency to transter.

Silver-beryllium alloys lend themselvesv very in the form ohco'ntacts from either swaged' material, drawn wire or rolled to be prepa'red in the form or contact bimetals in which one side consists of abaselmetah'such as an alloy omen, or nickel.

or a copper base material and asilvehberyllium tic composition containing beryllium was tested in a I rent test. In this test, contacts of similar physical dimensions are studied on a resistive. inductive circuit at 470- cycles per minute, wherein. q in the circuit was increased peri-- currentvalues. in 4 current flowin to obtain the dennite ryllium fluoride.: I

10.4 beryllium. .Themelting point of .the eutectic is 881 degrees C. With increasingberyllium,

1 I It was foundithat themaximum solidsolubility was3.5

It was powble to 3' I the material and the Under the, microscope," the material containing 10.4 atomic percent of.

tree from beryllium as an electrical con- Silver-:beryllium alloys lendthemselves Ana oyoftheeutecweisht percent. o1 standard critical curcomparison with contact materials produced in the prior art. The alloy tested gave a critical current of 15 amps. and a negative transfer of v critical current was a maximum and the transfer, a minimum. The peak was located between a beryllium content of about 1 to 3%.

It was found that after completing the tests, the material retained an abnormally low contact resistance, the eutectic material retained an abnormally low contact resistance, the eutectic material showing a contact resistance of only .05 milliohm, after 30,000 cycles. This is considerably below coin silver, standard silver and even fine silver.

The alloy of the present invention has been found useful for a large number of electric conhigh speed production and corrosion resistance are required.

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 electric contact element consisting of .05

' to 4% beryllium by weight and the balance silver.

' 10.4 atomic percent of beryllium and the balance tact applicationssuch as for instance, sensitive direct current relays, overload cutouts, voltage regulators, thermostats, indicating and recording gaugers, and the like. I v

The alloys of the present invention have been found to have excellent free machining properties for the production of commercial parts where silver, said contact element being characterized by low specific resistance, low contact resistance and low tendency to weld in service.

FRANZ R. HENSEL. KENNETH L. EMIVIERT.