US2161468A - Copper base alloy - Google Patents

Description

Patented June 6,. 1939 UNITED srATE's COPPER BASE ALLOY Franz R. Hensel and Earl I. Larsen, Indianapolis, Ind., assignors to P. R. Mallory &'Co., Inc., Indianapolis, Ind., a corporation of Delaware No Drawing.

1 Claim.

This invention relates to alloys and more particularly'c'opper bearing alloys of improved characteristics.

It is an object of the invention to improve the 5 electrical characteristics of the alloys such as electrical conductivity.

It is a further object to improve the pouring qualities and handling characteristics of the alloy during foundry treatment and later operations.

It is another object of the invention to improve the age hardening characteristics of such alloys.

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

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 claim.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method 5 of procedure and the combination of elements without departing from the spirit of the invention.

The present invention contemplates an alloy formed by the combination, in suitable proportions, of lithium with a zirconium bearing copper base alloy.

' In the prior art binary, ternary and quaternary copper-zirconium base alloys have been described. These alloys can be hardened by precipitation hardening. Zirconium is an element which will easily oxidize and which will be lost during the melting process if proper precautions are not taken. It is necessary to completely deoxidize the molten' bath before the zirconium is added.

40 A deoxidizer which is very frequently used is phosphor-copper, containing approximately 15% phosphorus. It has been found that the copperzirconium alloys which had been deoxidized with this material so that the residual phosphor content was .05% would not respond to heat treatment while material without phosphorus would reach, after aging, a Rockwell B hardness of 40 to 50. However, the loss of zirconium is excessive if it is added to a copper melt without using a suitable deoxidizer.

The present invention contemplates the improvement of the hardening ability of copper-zirconium-alloys and at the same time the improvement of electrical conductivity which comprises I adding from .005 to .3% of lithium to the copper- Al plication February 24, 1939, $811 31 N0. 258,185

zirconium base alloys in the molten state so that suflicient residual lithium remains to insure that the final product contains lithium in the proportions of .002 to .1%.

An example of our improved alloy is one con- 5 taining .02% lithium, 34% zirconium, 170% cadmium, balance copper. This material was quenched from 900 C. and cold-worked after quenching to 72 Rockwell B, the material was then aged at 400 C. for two hours, reaching a 10 hardness of 77 Rockwell B. Further cold-working after aging increased the hardness to 85 Rockwell B. By quenching the material from 925 C. the material was cold-worked after quenching to 68 Rockwell B, and aging for one 15 hour at 400 C. increased the hardness to 80 Rockwell B and further cold-working increased the hardness to Rockwell B. The electrical conductivity, after complete aging and coldworking was between 83 and 88%. The amount 20 of cold-working that was applied after quenching averaged 50% while after aging the additional cold-work amounted to 25%.

The use of lithium has also been found of similar advantage in copper-zirconium base alloys con- 25 taining such elements as iron, cobalt, nickel man-- ganese, silicon, tin, zinc, magnesium, beryllium, aluminum, silver, uranium, thorium and titani- A further advantage of the addition of lithium 30 to the alloys contemplated in the present invention, is that the refractory oxides such as zirconium oxide will be removed and that a material results which has clean grain boundaries and therefore increased ductility and impact strength. The 35 addition of lithium will also aid to get rid of any traces of phosphorus which is so objectionable in this class of alloy as far as hardening characteristics are concerned.

It should be pointed out that the present in- 40 vention does not contemplate the addition of lithium as a deoxdizer only. Suflicient lithium is added to the copper-zirconium base to insure that the residue thereof does not amount to less than a certain desired percentage.

' 45 In carrying out the present invention the alloys may be made according to the-following procedure. The copper is melted down first and to the molten copper a quantity of .005 to .3% lithium is added. The quantity of lithium de- 50 pends on the amount of oxygen, sulphur, phosphorous and other impurities contained in the copper and on the type of furnace used and on the melting conditions. The stronger aflinity of lithium for impurities causes the compounds with as any lithium alloys with the copper. The zirconium is added in the form of a master alloy containing above 10%'of zirconium. We have found it of advantage to use a 12 to 13% zirconium master alloy, which is prepared byesintering together zirconium hydride and copper powder in a reducing atmosphere. In the preparation of this hardener we have found it an advantage to add a certain amount of calcium on top of the pressed briquettes during sintering in order to prevent any oxidation. We have found it of great advantage to use a zirconium master :alloy containing 80 to 40% zirconium and the balance copper, which master alloy is prepared in a similar manner by sintering zirconium hydride and copper powder.

In order to obtain complete freedom from oxide inclusions of either copper oxide or zirconium oxide, it is advisable to add a definite percentage oflithium after all the alloying inzredients have been introduced and the melt is-ready for pourwhere other elements areto be added to the alloy they may be, originally melted in with the copper, or may be. added master alloy with ';copper.

The completed alloy may be cast in any form such as sand castings,

asintheformofa billets and plates. The

9,161,468 the latter to separate out from the bath before billets or plates may be worked into desirable shapes by extrudinsrhot rolling or similar process. A suitable temperature for extruding is 1600 F.

In the further treatment of the alloy it may be first heated to a. temperature of above ,700' C. and

subsequently after quenching to a temperature below 700' C. The alloys then may be coldworked in the manner indicated in the examples given above.

"I'he alloys are exceptionally well adapted because of the above properties to the production of electrical current carrying members, resistance welding electrodes, commutator segments, trolley shoes, contacts, contactors, applications where good thermal conductivity is required and the like.

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

What is claimed is: Analloy of .002 to .1% lithium, .l to 5% zirconium and the balance substantially all copper.

FRANZR. HENSEL. EARLI. LABS.