US2136919A - Copper alloys of improved characteristics - Google Patents

Description

i atented Nov. 15, 1938 COPPER ALLoYs F IMPROVED CHARAC- mms'rrcs Franz R. Hcnsel and Earl I. Larsen, Indianapolis,

Ind., assignors to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware I No Drawing. Application July 13, 1938,

Serial No. 218,970

3 Claims.

This invention relates to alloys, and more particularly to copper alloys of improved characteristics.

An object of the invention is to produce an improved copper base alloy.

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

The present inventioncomprises a combinalO tion 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 without departing from the spirit of the invention. .Prior work on copper-silver-tin alloys has shown that these materials possess a number of desirable properties, particularly if tin and silver are present only in small percentages. Such alloys combine with a high annealing point excellent cold working properties. Preferred compositions for this type of alloy contain up to 1% tin and up to silver. By going to higher silver contents, such as 2 silver, certain aging phenomena can be obtained in these alloys; 0 such aging, however, is manifested more in improvements in electrical conductivity than in improvements in hardness. Due to the fact that the copper-silver system is inherently an age hardening system, the annealing point of copper- 5 silver-tin alloys, which have been severely cold Worked is fairly high. Silver furthermore has the outstanding advantage that it will not decrease the electrical conductivity materially when alloyed with copper. This is due to the limited 40 solid solubility of silver in copper at temperatures 'below 200 degrees C. We have found that at 600 degrees C. approximately 2 silver can be held in solid solution, while at 200 degrees C., only .3% silver is held in solid solution and at room temperature, this solubility is still less.

Alloys consisting of copper, tin and silver, have, in addition to the high annealing point andcold workability, also excellent corrosion resistance and particularly resistance to sea water corrosion. If the elements tin and silver are used in higher proportions, castings can be made in which tin is used to increase both the strength and yield point. It is impossible, however, to exceed the solubility of tin in copper, otherwise a constituent is formed which is generally known as the delta constituent, and forms hard spots which interfere with the machining properties. In order to overcome such difficulties, the present invention describes the addition of beryllium to an alloy of copper, silver and tin, and therewith combining the effects of the age hardening. characteristics of the copper-beryllium system with the desirable properties of the copper-silver-tin alloys.

The alloy of the present invention may preferably contain the essential ingredients in the following proportidns:

Per cent Beryllium .03-3 Silver .05-4 Tin .05-12 Copper Balance.

Within these composition ranges, there area number of specific alloys which have been found to be of particular importance. Four of the The alloys can be made according to standard alloying methods, such as melting the copper, adding the desired amounts of tin and silver, and afterwards adding the correct amount of beryllium, either in the form of a copper-beryllium .master alloy, or any other form. The material can be cast either in a chill mold or in sand molds, at the correct temperature, and the alloy can be used in the as cast condition, or can be further worked by means of rolling, extruding, drawing, forging or similar methods.

'After the alloy has been prepared according to standard alloying methods, the heat treatment may be carried out as follows:

The alloy in the form of a billet or a sand casting or any desired form, is raised in temperature to between 700 degrees C., and its melting point. The alloy is then quenched from this temperature and subsequently aged at temperatures below 600 degrees C. This heat treatment results in considerable improvements in the physical properties of the alloy.

If the alloy, after casting, is rolled, it has been found desirable to quench the alloy before rolling and aging same after rolling. The cold working operation between quenching and aging increases the hardness very considerably. It was found that in the new alloys disclosed, the addition of tin allows one to greatly reduce the beryllium content, in order to .obtain the same hardness. It is possible, for instance, to take an alloy of approximately 8% tin, .5% silver, .'15%

beryllium, balance copper, and obtain -a Brinell hardness of 350 by quenching the material, before rolling from approximately 800 degrees C. and subsequently aging same at between 250 and 800 degrees C. The amount of rolling between quenching and aging may vary from 25 to 75% cold reduction, the amount of cold reduction determining partly the final hardness which can .be reached. The alloy is particularly suitable for applications in which high elastic properties and high annealing temperatures are required. At the same time, the alloys show a good electrical and thermal conductivity. The alloys have found further extensive use in applications where the material is used for electrical contacting purposes, such as contactor contacts. where surface oxidation produces high resistance films on ordinary copper alloys.

The alloys have further found considerable use for wear resistance purposes and applications such as special welding electrodes and resistance welding dies in general.

The alloys are furthermore very suitable for springs, particularly springs which have to carry current, or which have to withstand certain temperature rises, without losing their elastic properties.

The materials are also suitable forspecial applications where springs of intricate desiln must be formed in the hardened condition, that is, after quenching and where high hardness can be reached after a suitable age hardening treatment. 5

The alloys are particularly suitable for any parts in electrical machinery, where the combination of silver, beryllium and tin produces the desirable characteristics required for such applications. 10

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 15 spirit and scope of the appended claims.

What is claimed is:

1. An age hardened alloy composed of:

' Per cent Beryllium .oa- 3 Silver .05- 4 Tin .05-12 Balance substantially all copper characterized by high hardness and electrical conductivity, and further characterized by the 25 fact that its hardness and conductivity are not permanently adversely afiected by elevated temperatures.

' 2, An alloy composed of:

FRANZ R. HENSEL. EARL I. LARSEN.