US2241815A - Method of treating copper alloy castings - Google Patents

Description

Patented May 13, 1941 UNITED STATES PATENT. OFFICE METHOD OF TREATING COPPER. ALLOY CASTINGS Franc R. Hensel and Earl I. Larsen, Indianapolis, Ind., assignors to R. R. Mallory & Co. Inc., Indianapolis, had, a corporation of Delaware No Drawing. Application August 12, 1938, Serial No. 224,497

2 Claims.

This invention relates to the production of copper alloy castings, containing high percentages of copper.

It is an object of the invention to produce castings of improved hardness, electrical and structural parts and in the mechanical held, in-

applications where. high thermal conductivity is required, together with improved strength. It is a further object of this invention to produce castings which will not anneal at elevated temperatures.

It is a further object of this invention to produce castings which have a high ratio of elastic limit to tensile strength.

Another object of the present invention is to produce castings which can be readily brazed, soldered or welded, without destroying their physical properties.

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

The present invention comprises a 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 claims.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and a combination of elements, githout departing from the spirit of the inven- In the prior art, alloys have been described containing hardening elements, such as the silicides of the iron group metals. harden materials of this type, it has been necessary to apply a double heat treatment, the first part of which is generally classified as a solution treatment, and which consists in heating the material to a high temperature and then rapidly quenching. In addition to this first treatment, a second treatment is employed, comprising a prolonged heating at a lower temperature. This is usually called the aging or precipitation treatment because this treatment causes the decomposition of a super-saturated solid solution, the precipitated particles being so small in most cases that they cannot be detected under a microscope.

Heretofore, attempts have been made to manu- I iacture castings commercially 01' copper hard- In order to ened with nickel silicide, using the double heat treatment of the prior art just described. The result was such a large number of failures of the castings that manufacture of this alloy was discontinued.

We have found that for many uses the above double heat treatment will not produce the desired results when applied to copper alloys hardened with nickel or cobalt silicide.

While the castings show a considerable increase in hardness and conductivity, after such a double treatment, at the same time they become, very frequently, extremely brittle, and show very low tensile strength. In a large number of castings treated that way, the ultimate tensile strength was only 5,000 p. s, i., and in many instances, it was so low that the castings broke as a result of this heat treatment. Numerous tests were made, in which melting conditions and alloying conditions were variedffiowever,

the inconsistency of physical properties could not be eliminated or correlated with composition. In addition to copper and nickel silicide, other elements were added, such as magnesium, aluminum, zinc, tin, phosphorus and cadmium, in percentages up to 5% without, however, resulting in improvement of the ultimate strength as long as the double heat treatment was employed.

We then made experiments in which the heat treatment was completely changed in such a manner that the solution treatment was entirely eliminated and only a single heat treatment, corresponding to an anneal, was used. The result was that hardness values could be obtained closely approaching those and in some cases equivalent to the ones obtained with the double heat 1 treatment. The electrical conductivity, resulting from the single annealing treatment, was

additions of nickel and silicon, are approximately as follows:

Tensile strength p. s. i.-- 60,000 Brinell hardness -200 Electrical conductivity ..per cent 40-45 The ductility is a function of the chemical composition only and will vary from 5 to 35%, after our annealing treatment.

The process of annealing is applied to sand castings or chill castings, irrespective of cross section. It usually consists in heating alloys for the present invention can be prepared without taking any special precautions. Usually the copper is melted first, then the alloy additions are made, preferably in the form of a suitable hardener and the melt is poured in either sand, chill or other molds. The castings should then be used without any application of hot working because such hot working operationswill partly destroy the beneficial eifect of the single heat treatment described in this application.

The castings prepared as indicated above are well suited for such parts as electrode wheels, current carrying members, heat carrying members, axles, shafts and corrosion resistant parts.

The preferred composition of the castings is as follows:

. v Per cent Nickel 0.5 to 5 Silicon 0.1 to 2 Copper Balance It is possible likewise to improve alloys containing small percentages of aditional ingredients by the single heat treatment described above; thus copper alloys containing nickel and silicon may also contain such elements as zinc, tin, silver, cadmium, magnesium, beryllium, aluminum,- titanium, zirconium, chromium, manganese, iron and cobalt.

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:

l. The method of improving the properties of copper which comprises alloying with copper 0.5 to 5% of an element selected from the group consisting of nickel and cobalt and 0.1 to 2% silicon, casting the resulting alloy and then annealing the alloy in the as cast condition at a temperature between 400 C. and 600 C. for a period of from several minutes to several hours to improve the hardness and tensile strength.

2. The method of improving the physical properties and particularly the tensile strength of castings consisting of 0.5 to 5% nickel, 0.1 toi 2% silicon and the balance copp r which comprises applying a single heat treatment to said castings in the as cast condition, said heat treatment consisting of an anneal for a period of from several minutes to several hours at a temperature within the range 400 C. and 600 C.

FRANZ R. I-IENSEL.

EARL I. LARSEN.