US 2026209 A
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D 1935- P. H. BRACE 2,026,209
COPPER ALLOY Filed Dec. 14, 1934 Fig. I.
WITNESSES: v INVENTOR Patented Dec. 31, 1935 UNITED STATES PATENT OFFICE COPPER. ALLOY Pennsylvania Application December 14, 1934, Serial No. 757,444
This invention relates to alloys and particularly to copper base alloys which have good physical properties and high thermal and electrical conductivity.
In constructing dynamo-electric machines, it is desirable to employ a metal or alloy for the complicated castings, such as the commutator castings, which is capable of being cast and which will have good physical properties and a. high rate of thermal conductivity. Copper is capable of being cast and has a high rate of thermal and electrical conductivity but does not possess the physical properties that are necessary for such purposes. It is, therefore, desirable to add alloying and hardening elements to the copper to produce a copper base alloy which will have the desired physical properties while maintaining a conductivity comparable to that of copper.
An object of this invention is to produce a 20 homogeneous copper base alloy which has good physical properties and a high thermal and electrical conductivity. I
This invention may be better understood by reference to the accompanying drawing, in which Figure l is a graph illustrating the effect of the alloying content on the conductivity of the resulting alloy, and
Fig. 2 is a graph illustrating the effect of the alloying content on the hardness of the resulting alloy where the alloy has been chill cast, annealed and cold worked.
In order to produce a copper base alloy which has good physical properties and high conductivity, certain alloying and hardening elements which will disperse in a finely divided state throughout the copper base are added to a copper melt. In practicing this invention, from .1% to 5% zirconium and from .05% to silver are added to the copper base as the alloying and hardening elements.
Zirconium, in addition to being a good alloying element in the copper base alloy, also acts as a deoxidizer for the copper melt. Zirconium is a far better deoxidizer than some of the more common deoxidizers such as magnesium and cadmium, since the heat of formation of the zir conium oxide which performs the deoxidizing process is greater than the heat of formation of the common deoxidizers. Also, by employing zirconium as the alloying and deoxidizing agent, only the desired elements will be taken up in solid solution with copper to increase the conductivity of the alloy.
silver is added to the copper base to increase the hardness of the resulting alloy, as will be described hereinafter.
It is preferred to add the silver and zirconium to the copper melt as a hardener in the form of a rod, pellet or cake. The hardener is produced as an alloy of zirconium and silver prepared ina reducing atmosphere, care being taken not to contaminate the alloy with impurities. The zirconium and silver content of the hardener varies in accordance with the respective amounts of zirconium and silver which it is desired to add to the copper melt as alloying elements.
It has been discovered that the hardness of the alloy is further increased where up to approximately 10% of titanium and/or 10% of nickel is add-ed to the copper, zirconium and silver melt. The addition of either, or both, titanium or nickel up to 10% of either element, materially increases the strength of the resulting alloy. Such additions, however, tend to lower the conductivity of the alloy. The titanium and nickel additions are thus desirable where increased strength is necessary and conductivity is of secondary importance.
These alloys are particularly desirable for commutator castings and compare favorably with straight copper castings which have no additional alloying elements. The straight copper castings as measured on said cast test bars have a conductivity of about 80%, and a Brinell hardness of only from 30 to 40. The alloys comprising a minor addition of the silver and zirconium alloying elements and prepared in accordance with this invention and chill cast have a Brinell hardness of above 65 and a conductivity of about 80% as compared to pure copper. An increase in the silver addition improves the hardness of the resulting alloy without materially decreasing its conductivity.
In investigating the copper base alloys produced, particular attention was directed to the relation of the hardness and the electrical conductivity values of the alloy. The chill cast in.. gots were hot forged to A" round bars and swaged cold to reduce the diameter approximately The electrical conductivity was determined on the swaged bars as cold worked 20% and as annealed in nitrogen at 750 C. The conductivity of the alloy as annealed corresponded to the conductivity of the cold worked alloy, a difference of not more than 1% being found. In Fig. 1 of the drawing, the conductivity of only those alloys which were annealed is, therefore, given.
The curves in Fig. 1 and Fig. 2 of the drawing Percent alloy content Alloy No. Copper Zirconium Silver These alloys when chill cast, cold worked and annealed have a Brinnell hardness and tensile strength and conductivity as indicated in the 01- 20 lowing tables:
As chill cast As cold worked Tensile strength, pounds per square inch Tensile 25 Brinell hardness Brinell hardness OVOI As annealed 35 Tensile Brinell strength, hardness pounds per square inch Conductivity, percent A method of heat treatment for the cast alloys for developing their physical and electrical properties where it is undesirable to employ deformation in complicated cast designs is to heat the casting to between 600 and 1075 C., quench 5 or quickly cool it and then reheat it to between 250 and 600 C. Where the casting is of such nature as to permit cold working, the cold working may follow the ageing of the alloy.
It is evident from the curves of Fig. 2 that the silver content of the alloy materially increases the hardness of the alloy and especially those alloys which are cold worked. It is to be noted that an increase in the silver addition does lower the conductivity of the resulting alloy slightly but not to a detrimental degree and that these alloys are still desirable because of their increase in hardness.
Although this invention has been disclosed with reference to certain specific alloys, it is, of course, to be understood that various modifications may be made in the alloying content as above described 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 .1% to 5% zirconium, from .05% to 10% silver and the balance copper.
2. An alloy comprising from .l% to 5% zirconium, from .05% to 5% silver and the balance copper.
3. An alloy comprising from .1% to 5% zirconium, from .5% to 2.5% silver with the balance copper.
4. An alloy comprising about .8% zirconi about .5% silver with the balance copper.
PORTER n. BRACE.