US2169187A - Copper base alloy - Google Patents

Description

, 2,169,187 PATENT OFFICE corPEa BASE ALLOY James M. Kelly, Trafiord, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa... a corporation of Pennsylvania No Drawing.

6 Claims.

This invention relates to alloys, and particularly to copper alloys which have improved mechanical thermal 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 #2,- 147,844.

Certain metals have been alloyed with copper 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 difiicult to duplicate since a hardener alloying element is usually employed and deoxidation of the elements must beclosely controlled. A hardener is usually easily oxidized and, therefore, diificult to get into liquid solution while the recovery of the alloying elements introduced into the copper melt is difiicult.

An object of this invention is to provide 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 high electrical and thermal conductivity when precipitation hardened.

A further object of this invention is to utilize a copper base alloy formed to shape and precipitation hardened to give high physical strength and high electrical and thermal conductivity.

A more specific object of this invention is to produce a copper base alloy which may be precipitation hardened to givethe high physical strength and conductivity and which will retain its strength and resistance to creep whensubjected to elevated temperatures.

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

In order to produce a copper base alloy which will have desired mechanical and electrical properties, metals which can be precipitated to efiect the dispersion of fine particles throughout a copper base alloy 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 zirconium has excellent mechanical and electrical properties when heat treated.

In preparing the alloy the metals cobalt, iron and zirconium may be added directly to the copper melt in any suitable form such as compacted powders or lump, since they are not easily oxidized as compared to copper. The alloying contcntmaythulbemaintalnedsuhltanflallycon- Application October 21, 1938, Serial No. 236,239

stant during the hot forming operations, since the alloying elements will notbe lost by oxidation at the surface of the alloy.

In practice the alloy may be prepared by heating a melt of copper, such as commercial electrolytic copper under a covering of charcoal in a graphite crucible and adding the alloying ele-: ments in any suitable form to the copper melt. In order to permit complete deoxidation of the melt, it may be held at a temperature of between 1150 C. and 1200 C. for a. period of time suificient for the completion of the reaction of the graphite crucible with the oxygen. 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. Although not always necessary, as in the making of other copper base alloys where desired small quantities of calcium or phosphorus or other suitable deoxidizers may be added to the melt of copper cobalt, iron and zirconium to insure complete deoxidation of the melt. The alloying elements are readily soluble in copper and enter into solution providing an alloy in which the alloying elements are uniformly distributed thrroughout the structure.

The alloy may be cast in massive,integrate 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 be easily machined as required or it may be cast to a pattern suitable for forging to the desired shape. In its cast condition the copper, cobalt, iron and zirconium alloy is comparatively ductile being easily forged or drawn to shape.

Alloys comprising from small but efiective amounts up to 5% of each of cobalt and iron and from a small but eiiective amount up to 5% of zirconium with the balance substantially all copper when heat treated, as hereinbefore described, to precipitation harden them, have been found to have high physical strength and good electrical and thermal conductivities.

In order to develop the mechanical strength and the electrical properties of 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 1075 C. is found to eflect a blah solid solution 0 of the alloying metals in the copper while a reheat at a temperature oi! between 450 C. and 600 C. eifects an efficient precipitation of the alloying constituents.

Alloys comprising copper, cobalt, iron and zirconium within the ranges hereinbefore given when heat treated as described, have a high Rock well B hardness, high ultimate strength 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 2% of zirconium 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 is to be preferred. In all cases the highest product of the conductivity and hardness values for different combined cobalt and iron contents within the ranges given is found to be obtained when the ratio of the cobalt to the iron content approximates l.

The zirconium additions to the alloy gives it a high ultimate strength without detrimentally affecting its conductivity and hardness. Further, the zirconium additions within the preferred range of from small but eiiective amounts up to 2% improves the elongation characteristics of the alloy, giving an alloy which has an elongation of about 18%. Since the zirconium has strong deoxidizing properties, it functions in the alloy to give a dense alloy free from porosity. In addition, zirconium possesses the property of refining the grain of this particular alloy in the as cast condition, micro examinations showing that the general grain structure compares to that which is obtained in cold rolled materials. As representative of the benefits aflorded the alloy by the addition of zirconium, the following table gives the results obtained with difierent zirconium additions to an alloy in which the cobalt and iron contents are maintained constant at a preferred ratio of one. In the table the copper content is omitted, it being understood that the balance of the alloying content comprises copper with posslble incidental impurities occurring during the alloying process.

Composition Percent Ultimate Alloy Hardness oonducstrength No. 5&- 5g; :3; RWKWUB tivity lbs./sq.in.

Fe 00 Zr 371s 2 2 2 s3 03 70,500 3710 2 2 .0 so 59 70,000 3717 2 2 1.0 83 57 77.000

The alloys identified in the above given table were subjected to a heat treatment consisting of quenching them from a temperature of 1000 C. and reheating or aging them at a temperature of 500 C. for a period of time of 18 hours. In some cases conductivity values of over 70% have been obtained by aging the alloys for a period of time of about hours. In connection with the aging treatment it is noted that the zirconium content tends to restrain grain growth during the heating or the alloy.

With the alloys of copper, cobalt, iron and zirconium it is possible to employ them in the quenced state for it is noted that where zirconium is included as an essential element of the alloy, the alloy has a hardness of about '70 Rockwell B when quenched in water from 1000 C. This property is important for such applications where it is necessary to braze parts together and retain high hardness, because the alloy is not softened appreciably when subjected to the heat necessary in performing the brazing operation.

Although the alloys produced in accordance with this invention have an extremely high Rochwell B hardness when quenched or heat treated, as castthey are quite ductile and may be readily worked into the shape or form desired. The alloys prepared from. the different alloying elements and within the ranges given hereinbeiore are particularly useful in the manufacture of large castings such as commutator segments. Other uses of the alloy are as welding electrode tips or welding wheels or other articles where a conductivity of about 60% or greater is required together with. high physical strength. These alloys may also be efficiently employed in applications such as cylinder heads for internal combustion engines and where high thermal concluctivity is desired combined with high physical strength. The alloys may be cast directly into the predetermined shape 01. the article of manuiacture or into a pattern suitable for forging or drawing.

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

I claim as my invention:

1. An alloy comprising from a small but effective amount up to 5% of cobalt, from a small but efiective amount up to 5% of iron, from a small but effective amount up to 5% of zirconium, with the balance substantially all copper.

2. An alloy comprising from about .5% to 3% of cobalt, from about .5% to 3% of iron, from a small but effective amount up to 2% of zirconium, with the balance substantially all copper.

3. An alloy comprising from about .5% to 3% of cobalt, from about .5% to 3% of iron, from a small but effective amount up to 2% of zirconium, with the balance substantially all copper, the ratio or the cobalt to the iron being between .5 and 1.25 to 1.

4. An age hardened alloy comprising from about .5% to 3%'of cobalt, from about .5% to 3% of iron, from a small but effective amount up to 2% of zirconium 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.

5. As an article of manufacture, an alloy comprising from about .5% to 3% of cobalt, from about .5% to 3% of iron, from a small but effective amount up to 2% of zirconium with the balance substantially all copper, formed to a predetermined shape and precipitation hardened to give high physical strength and good conductivity.

6. An alloy comprising about 2% of cobalt, about 2% of iron,Iro1n .2% to 1% of zirconium, and the balance substantially all copper.

JAMES M. KELLY.