US2169190A - Copper base alloy - Google Patents

Description

Patented Aug. 8, 1939 UNITED STATES COPPER BASE ALLOY James M. Kelly, Traflord, Pa., asaignor to Westingliouse Electric 3; Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application October 21, 1938,,

Serial No. 236,302

4 Claims.

This invention relates to alloys, and particularly to copper base alloys which have improved thermal, mechanical and electrical properties and the utilization of the alloys as articles of manufacture.

The present application comprises a continuation-in-part of my copending application Serial No. 149,146, filed June 19, 1937 now Patent #2147344.

Certain metals have been alloyed with coppe to produce an alloy having better mechanical properties, but generally such alloys have been inferior to copper as conductors of electricity and heat. In the copper base alloys which have been produced and which have the desired conductivity or mechanical strength, the characteristics are diflicult to duplicate.

An object of this invention is to produce a copper base alloy having high physical strength and good electrical and thermal conductivity.

Another object of this invention is to provide a copper base alloy which will have the characteristics of high physical strength and good electrical and thermal conductivity when precipitation hardened.

A further object of this invention is to pro- In order to produce a copper base alloy which will have desired mechanical and electrical properties, metals which can be precipitated to effect a dispersion of fine particles throughout a copper base when suitably heat treated are added to a copper melt. It has been found that a copper base alloy containing even small proportions of cobalt, iron and beryllium has excellent mechanical properties and good conductivity when heat treated.

In preparing the alloy the metals cobalt and iron may be added directly to the copper melt in any suitable form, such as powders or in lump form, since they are not easily oxidized as compared to the copper. The beryllium is added to the melt after the cobalt and iron have dissolved therein. By this practice, it is found that the alloying content may be maintained substantially constant during the hot forming operation.

In practice, the alloy may be prepared by heating a melt of copper such as electrolytic copper under a covering of charcoal in a graphite crucible and adding the alloying elements cobalt and iron in any suitable form to the copper melt. In order to permit complete deoxidization of the melt, it may be held at a temperature of between 1150" C. and 1200" C; for a period of time suflicient for the completion of the reaction of the graphite crucible with the oxygen. During this holding period, it is thought that the iron also aids in deoxidizing the melt. After the melt is deoxidized the beryllium is added to'the melt, which is then poured, giving an alloy in which substantially all the beryllium is recovered.

Where desired, the alloy may also be prepared by heating the melt in a ceramic crucible with a cover of lump charcoal over the surface of the melt. Small quantities of calcium or phmiphorus or other suitable deoxidizers may be addedto the melt of copper, cobalt and iron to insure complete deoxidation of the melt prior to the addition of the beryllium thereto. The alloying elements are readily soluble in copper and enter into solu-. tion providing an alioy'in which the alloying elements are uniformly distributed throughout the structure.

The alloy may be cast in massive, intricate or fine form in any suitable type of mold, such as a sand casting or chill cast mold. Where desired, the alloy may be cast directly into the predetermined shape of the article which is to be manufactured, after which it may easily be machined as required, or it may be cast to a pattern suitable for forging to the desired shape.- In its cast conditions, the copper, cobalt, iron and beryllium alloy is sufficiently ductile'to permit the forging or drawing of it to a predetermined shape.

Alloys comprising from small but effective amounts up to 3% by weight of each oi cobalt and iron and from asmall but eil'ective amount up to .5% by weight of beryllium with the balance substantially. all copper, when heat treated as hereinafter described to precipitation harden them, have high physical properties and good electrical and thermal conductivities. Through experiments it has been found that beryllium concentrations higher than .5% in the alloy do not sufhciently improve the properties of the alloy to justify their use.-

In order to develop the mechanical strength and electrical propertiesof the alloy it may be subjected to a precipitation hardening treatment comprising subjecting the alloy to a high temperature below the melting point of the alloy for obtaining a high solid solution of the alloying metals in the copper, quenching the alloy from the high temperature to retain the alloying metals in solid solution and then 're-heating the alloy to a lower or ageing temperature and holding it at this temperature for a period .of time sui'ilcient to precipitate the alloying elements from the solid solution state. In practice, heating at a. temperature of between 750 C. and 1075 C. is found to effect a high solid solution of the alloying metals in the copper while a reheat at a temperature of between 450 C. and 600 0. effects an efiicient precipitation of the alloying constituents.

Alloys comprising copper, cobalt, iron and beryllium within the ranges hereinbefore given when heat treated as described have a high Rockwell B hardness and good conductivity. The heat treatment is found to be of special benefit to alloys comprising between .5% to 3% of each of the elements cobalt and iron, and from a small but effective amount up to .5% of beryllium with the balance substantially all copper.

In the alloy of this invention, it is desired to maintain the ratio of the cobalt to iron content between .5 and 1.25 to 1 since it is found that such ratios produce the best combination of properties in the alloy. Since the conductivity and hardness values of the alloy may be taken as a criterion of the alloy, it is evident that the best alloying proportions which will give the highest value as a product of the hardness and conductivity, are to be preferred. In all cases the highest product of the conductivity and hardness values for different combined cobalt and iron contents within the limits given for the alloy of this invention is found to be obtained when the ratio of the cobalt to the iron content approximates 1.

The beryllium addition to the alloy gives it a very high hardness without detrimentally affecting its conductivity to the extent where it is undesirable. Further, the beryllium is found to effeet a refinement of the grain size of the alloy, rendering it exceptionally suitable for castings. These properties together with the finding that the beryllium in amounts up to .05 renders the alloy resistant to softening when exposed to high temperatures of about 500 C. for long periods of time, are of special value in certain applications of the alloy.

As representative of the benefits imparted to the alloy by the addition of the beryllium, the following table gives the results obalied with different beryllium contents in alloys in which the cobalt and iron contents are maintained constant at a preferred ratio of 1. In the table, the copper content is omitted, it being understood that the balance of the alloying content comprises copper with possible incidental impurities occurring during the alloying process:

I Composition Hardness Conduc- Alloy No. Rockwell tivity, Percent Percent Percent B percent Fe Cn Es The alloys given in the foregoing table were subjected to heat treatment consisting of quenching them from a temperature of 975 C. in water and reheating or ageing them at a temperature of 500 C. for a period of time of 18 hours. With approximately 25 to 50% of cold work inter spersed between the quenching and ageing treatments, the hardness may be further increased about over the values obtained by'the same heat treatment without the cold work. Further improvement in the conductivity is obtained by increasing the ageing time to about 35 hours, after which it is found that further ageing will not improve either hardness or conductivity.

The alloys of this invention are sufficiently ductile as cast to permit working them into the shape or form desired. Because of the action of the beryllium in refining the grain size of the alloy, it is particularly useful in the manufacture of large castings such as commutator segments. Since it is susceptible to age hardening, it is useful as castings in which the hardness cannot be developed by cold working. Other uses of the alloy are as welding electrode tips, welding wheels, fuse clamps and contactors were good conductivity is required, together with high physical strength.

It is, of course, to be understood that this in vention is described with reference to specific embodiments thereof and that other and various modifications may be made without in any way departing from. the spirit of the invention as set forth in the appended claims.

I claim as my invention:

1. An alloy comprising from about .5% to 3% of cobalt, from about .5% to 3% iron, from about 05% to .5% of beryllium, and the balance substantially all copper.

2. An alloy comprising from about .5% to 3% of cobalt, from about .5% to 3% of iron, from about 05% to .5% of beryllium, and the balance substantially all copper, the ratio of the cobalt to the iron being between .5 and 1.25 to l.

3. An age hardened alloy comprising from about 5% to 3% of cobalt, from about .5% to 3% of iron, from about .05% to 5% of beryllium with the balance substantially all copper which has been quenched from a temperature of between 750 C. and 1075 C. and aged at a temperature of between 450 C. and 600 C.

4. An alloy comprising about 2% of cobalt, about 2% ofiron, from about .05% to 5% of beryllium, and the balance substantially all copper.

JAMES M. KELLY.

CERTIFICATE OF CORRECTION.

Patent No. 2,169,190. August 8, 1959.

JAMES M. KELLY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 2, second column, lines b6 and 52, claims 5 and LL respectively, for "5%" read .573; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 50th day of January, A. D. 19h0.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.