US2136548A - Copper-thorium alloys - Google Patents

Description

Patented Nov. 15, 1938 PATENT OFFICE.

2,136,548 corrEn-rnonrmu ALLOYS Franz R. Hensel and Earl I. Larsen, Indianapolis, Ind., assignors to P. B. Mallory & 00., Inc., Indianapolis, Ind., a corporation of Delaware No Drawing.

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

An object of the invention is to produce a copper alloy of high electrical and heat conductivity, combined with suitable hardness.

Another object of the invention is to provide an alloy which, in the form of a. casting, will have a very high electrical conductivity.

Further objects are to improve the cold worke ing and crystallizing characteristics of the alloy.

Other objects of the invention 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 the preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the combination of elements, without departing from the spirit of the invention.

The invention relates to alloys consisting basically of copper and thorium, to which third elements are added to further improve the characteristics. While these alloys may vary in their physical characteristics, according to the specific compositions, they will generally be characterized by high conductivity and improved hardness. The alloys are further characterized by desirable electrical properties, such as being a material of low work function, which might be useful for special contacting purposes, or applications, such as neon sign electrodes, and similar applications where highelectron emissivity is required.

It is contemplated that alloys may be produced according to the invention, having the ingredients combined in the following range of proportions:

It has also been possible to add small percentages of any one of the following ingredients manganese, iron, cobalt, nickel and tin.

Application September 15, 1937, Serial No. 164,034

without changing materially the characteristics of our new alloy: alumium, silicon, phosphorus In alloys consistingpredominantly of copper and thorium, it is found that additions of thorium to copper have very little efiect on lower ing the electrical conductivity. Alloys containing 1-1%% of thorium will have an electrical conductivity close to 90%, while alloys having as much thorium present as 5% will still have an electrical conductivity of 80%. With lesser amounts of thorium, higher values of electrical conductivity are obtainable.

We have found that alloys of. copper and thorium apparently show what is generally known as an eutectic structure. With higher percentages of thorium present, such as 10-20%, av microscopic analysis shows a definite copperthorium compound similar in structure to that noted in copper-thorium alloys of lower thorium content. This compound is one constituent of the eutectic. a

It appears that it is due to the formation of this eutectic and the small amount of thorium,

taken up in solid solution by the copper, which is responsible for the high electrical conductivity values. It is remarkable, however, to find that even with high thorium contents, the alloys remain easily workable and can be hot and cold worked. h

The addition of elements taken from the second group of the periodic system and particularly the element cadmium, tend to improve considerably the cold worked characteristics of the copper-thorium alloy. By adding both cadmium and thorium to our improved copper alloy, it is possible to produce a material for electrical purposes, of outstanding merit. Similar results are obtained by adding the other materials contained in this group, such as magnesium or zinc. By adding a high enough amount of beryllium, alloys can be made susceptible to heat treatment, generally known as age hardening, and characterized by the fact that the heat treatment consists in two steps; namely, the quenching operation, followed by the aging operation, with or without cold working.

In carrying out the present invention, an alloy of copper and an element taken from the second group of the periodic system may be made according to the conventional alloy making procedure of the prior art, and then thorium may be added in any convenient form, such as cupro-thorium, pure thorium, or any other thorium alloy or compound. We have found it even possible to use ferro- "thorium. provided that impurities of iron are not good deoxidizer, such as manganese, superiority is clearly shown. -The heat of formation of the fmanganese oxide is only 91,000 calories per gram of other ingredients which do .not substantially alter its characteristics is contemplated as within 7 the purview of the invention.

atomic weight of metal. Tmsmgh heat of formation of oxidesalso points to the fact that if alloys of copper and thorium are to be made which contain appreciable quantities of thorium, the molten bath must be free of oxides, particularly copper oxides; otherwise a certain quantity of oxide .to pure copper with the resulting formation of'thorium oxide.

The presence in the alloy of small proportions .While the present invention as to its objects and advantages has been described herein as carrled out in specific embodiments thereof, it is not desired to be limited thereby, but it is intended to cover within the spirit and scope of the appended copper.

What is claimed is:

1. An alloy consisting of copper and ,from 0.005% to 10% thorium, to which an element has been added, taken from the second group of the periodic system, the latter elements being present in quantities from the least useful amount up to 30%.

2. An alloy composed of 0.005% to.20% tho- 3. An. electric current conducting member formed of an alloy composed of 0.005% to 20% thorium, from the least useful amount up to 30% of a material selected from the group consisting the thorium will be lost in reducing the-copper ....f, cadmmm' zmmberymum' magnesmm' calcmm strontium and barium, and thebalance copper. 4. An electrical contacting member of the type comprising resistance welding electrodes and the like formed of an alloy composed of 0.005% to 20% thorium, from the least useful amount up to 30% of a material selected from the group consisting of cadmium, zinc, beryllium, magnesium, calcium, strontium and barium, and the balance R, HENSEL. EARL I; LARSEN.