US2120561A - Composite metallic bodies - Google Patents

Description

Patented June 14, 1938 COMPOSITE METALLIC BODIES Clemens A. Laise, Tenafly, N. J., and Jacob Kurtz, Brooklyn, N. Y., assignors to Eisler Electric Corporation, Union City,

ration of Delaware No Drawing.

N. J., a corpo- Application January 18, 1934,. Serial No. 707,106

9 Claims. (Cl. 29-182) The present invention relates to the production of composite metal bodies such as bars, rods or wires, and to their association with hard metal material. More particularly, it relates to such composite bodies as are adapted for-use for leadin wires or filament supports for electric incandescent lamps and radio tubes or for grids or grid supports for such tubes. It has special advantages when used for lead-in wires, grids and grid supports of multigrid thermionic valves and radio power tubes.

Such power tubes during operation generate a very considerable degree of heat which gives rise to undesired electronic emission from metal portions of the device that interferes withthe desired electronic emission from the cathode. Particularly is this undesired emission set up in the grids and connected parts when they become overheated and this so-called back-grid emission in a multigrid thermionic tube is a factor highly disturbing to the smooth operation of the device. Such undesired emission is substantially eliminated by the use of the metallic bodies of the present invention in forming the grid structure, and this desirable result is due to the high heat and electrical conductivity of such bodies.

In welding the leads,-supports or other connecting members to refractory metallic members of thermionic valves and incandescent lamps, such as tungsten, molybdenum or tantalum wires or rods used for conducting electric current through hard glass envelopes and for forming a tight seal therewith, it is diflicult to ensure the formation of a strong, unitary and conductive bond. For instance, when a copper lead wire is welded to a tungsten sealing-in member, the copper tends to become strongly oxidized at the temperatures required to form the union, and often becomes so weakened and embrittled that it is unable to withstand subsequent working, as in beading and forming in the case of radio power tubes. The result is that the joint is often broken and this causes a high percentage of waste, or

loss caused by defective joints. The bodies of the present invention, as will hereinafter appear, are very readily welded and united to refractory metallic members, with the formation of a strong, flexible and electrically conductive connection.

Other qualities rendering the composite body of the present invention suitable for formation into and use as a lead wire, a grid, or a filament or grid support, result from the fact that it has little tendency to oxidize, tarnish or corrode under heat, that it can within the invention be made reasonably rigid, and that it can be manufactured economically.

The product of the present invention may in form-be a bar, rod, wire, or strand, either by it- 7 self or integrally united with a refractory metal.

However, in whatever particular form it may be embodied, it comprises a central core of high electrical and thermal conductivity, and a sheath of a non-corrosive metal or metal alloy. The core may be of cuprousmaterial, and the sheath of nickelous material.- The core may be of pure copper, but for specific purposes additions suitable for the purpose may be added to the copper so v that the core may be a copper alloy or may contain beneficial additions in other form. The sheath, likewise, may be of pure nickel, but for specific purposes additions suitable for such purpose may be added to the nickel so that the sheath may be a nickel alloy or may contain beneficial additions in other form. Furthermore, the sheath may be nickelous and the, core pure cop per; or the sheath may be pure nickel and the core cuprous, i. e., mainly copper but alloy or havingbeneflcial additions. On the other hand, both core and sheath may be alloy or have beneficial additions as hereinafter described.

For purposes of illustration of the invention, merely, the following example is given of the preparation of a specific composite metal body:

Deoxidized bars of pure copper, three-quarters of an inch in diameter, as received from the mill, may be cut into lengths measuring, say, from thirty inches to four feet; These bars are then carefully cleaned and their surfaces polished to free them from'oxides or other corrosive inaterials. The copper bars are then provided with a sheath of pure nickel. This may be done by forcing the copper bars into nickel sleeves, such as seamless nickel tubes having at least the same length as the copperbars but preferably a slightly greater length. The sleeves, before this operation, have been carefully cleaned and their surfaces polished, both inside and outside, in a manner similar to that described above in reference to the copper bars. This results in a composite bar having a core of pure copper and a sheath of pure nickel. v

This composite bar may be then swaged in a suitable swaging machine so as to force the nickel sleeve into a very close contact with the copper core throughout the entire length of the core, and thus to put them in position .so that they may be welded and united in the manner which will I tremely intimate contact with the core throughout its length.

In this condition, the composite bar may be set on end on an adjustable platform in a verticalfurnace of sufficient dimensions to accommodate the bar, and subjected to temperatures high enough to cause the core and sleeve to fuse and weld together without melting either of them. This temperature is known in the art as the sweating temperature. In order to prevent the formation of oxides, this heating step may be carried out either in vacuum or in an atmosphere of non-oxidizing gas; but when it is desired to produce a thin film of hydride on the sleeve, as

described and claimed in the: patent to Laise No.

1,989,236, dated January 29, 1935, it may be carried out in an atmosphere of dry hydrogen.

The adjustable platform in the vertical furnace should be so disposed that only about one-half or not much more than two-thirds of the composite bar is subjected to the maximum temperature. After the desired union at this end is accomplished, the composite bar may be reversed so that the remainder of the bar may be subjected to the sweating temperature (of the copper core). This sweating temperature is readily observable by a skilled operator. In this way the core and sleeve are uniformly welded along the entire length of the core, the alloy of nickel and copper so formed between them serving as a brazing material.

After the constituents of the composite bar have been united, as above described; it may be removed from the furnace and rolled or swaged, which may be done either in the heat or in the cold. It is preferable, however, to swage it in the cold a number of times, with intermediate annealing as it,tends to become work hardened, until it is brought down to a diameter convenient for drawing, say three-quarters of an inch. The drawing may then be done in, well known manner and on well known apparatus. As the drawing progresses, the wire or rod tends to become work hardened and must be annealed; however, the last annealing should preferably always be done in reducing gases, such as hydrogen or gases containing hydrogen. Thus, the composite wire, the final product in the illustrative example, will have a bright, shiny surface, which may be metallic or may be coated with a thin hydride film. The temperature of annealing depends upon the sizes of the bars and may properly'be, for large bars, about 1000" C. or, for small wires, as low as 400 C. Care should be taken not to raise the annealing temperature sufliciently to cause the nickel or nickelous covering to become weak and brittle.

Instead of using a core of pure copper, a. core of copper alloy containing a small percentage of beryllium may be used, the beryllium constituting from .1% to 5% of the alloy. This does not materially reduce the conductivity of .the core, but hardens it somewhat. Instead of beryllium, a small percentage of other hardening metals, such as will not materially reduce the conductivity of the core, may be employed, the object being to harden the core slightly and increase its tensile strength, as well as the ultimate elongation of the composite wire. This elongation'should be from 10% to i. e., the core should be capable of elongation to this extent before rupture.

The sheath may, as previously indicated, be of composite construction. It may contain any non-corrosive metal or alloy such as nickel or cobalt, or nickel alloys of manganese, titanium, tantalum, platinum, gold, silver, etc., in the pro- The rod or wire, or a plurality of wires, twisted into a cable, may with great facility be welded to refractory metal such as tungsten, rhenium, molybdenum, tantalum, or the like,--for instance, to other parts of the tubes or lamps. Metals of this nature are often used to carry current through the press of such tubes or lamps, and to form a tight seal with the hard glass envelope thereof. A heat-conducting connection to such members is of distinct advantage, and a wire or cable exemplifying the metallic body of the present invention is very well adapted to be united with such hard metal members. When such a weld is adopted, there results a strong, flexible connection between the members, the composite body readily forming an alloy of lower melting point than either of its constituents, on the tungsten or molybdenum during the welding or uniting operation. The welding may be accomplished in any desired manner although I prefer to contact the members and spot-weld them. Thus, the novel metallic body of the present invention readily fuses and alloys with the tungsten or molybdenum, etc., of the refractory metallic members and makes a perfect union. The reason for this is because oxidation and resulting embrittling of the joint, which occurs when copper and similar metals are used to unite and weld with tungsten or molybdenum, are eliminated. Ordinary wire or strands of copper and the like are so weakened through heating and oxidation that they break away from the refractory metal and are not capable of withstanding beading and forming as is the case in making power tubes. With the welded union of the present invention, therefore, a great saving is achieved because of the reduction of loss from imperfect and embrittled products of this nature.

The sheath or covering of nickelous material may constitute from 10% to 50% of the weight of the composite bar, rod or wire, although for radio purposes the proportion is preferably 20% to 35% of the weight of the body.

Instead of fitting a sleeve of nickel around the cuprous core, covering of the core may be performed in other ways. For instance, the core may be coated by spraying the molten nickel or metal on to the same. In some circumstances it may be convenient actually to melt the copper or copper alloy in a seamless nickel tube closed at one end. It is also contemplated, if desired, to unite the-cuprous core to the outer sleeve by means of an intermediate layer of a brazing alloy such as brass or silver solder.

As previously indicated, the invention is also useful for producing a wire from which to form grids for thermionic valves for filaments in electric lamps. For such applications it is necessary to use wire which is non-corrosive, reasonably stifi and of high heat and electrical conductivity. The improved wire in accordance with the invention has a much greater heat conductivity than molybdenum nickel and nichrome wires used heretofore in this connection. Hence the improved wire will dissipate excess heat in thermionic valves and electric lamps much quicker 'proved dissipation of heat in such apparatus,

which results from forming the grids from the improved wire, lowers the operating temperature of the grids suiliciently to ensure the substantial absence of back-grid emission. Furthermore, the improved composite wire may be produced at a much lower cost than grid wires of molybdenum and molybdenum and tungsten alloys.

The composite metallic bodies of the invention may be used for heat-dissipating and non-corrosive purposes other than those alluded to above; for instance, they may be formed with wire and woven into meshed material for use as automobile brake linings. The bodies may also be used to advantage where their non-corrosive and electrically conductive qualities are desired to be utilized, as in the form of a stranded cable for use as storage battery cables.

In the main, these composite metallic bodies manifest their advantages and are best suited for use in the art of electricity, e. g., conductors. electrodes, and supports, and they, therefore, will be identified in the appended claims as electrical assemblies.

What we claim is:

l. A composite metallic body comprising a cuprous core and a covering of nickel metal, said covering constituting from 10% to of the weight of the body.

2. A composite metallic body comprising a cuprous core and a covering of nickel metal, said covering constituting from 20% to 35% of the weight of the body.

3. A composite metallic body comprising a core of high electrical and heat conductivity and a covering of a metallic material non-corrosive under normal conditions of oxidation and hydration, said covering constituting from 10% to 50% of the weight of the metallic body and adapted to form with said core a welding material readily covering of a. metallic material non-corrosive under normal conditions of oxidation and hydration, said covering constituting from 20% to 35% of the weight of the metallic body and adapted to form an alloy with said core for welding with refractory metals.

5. A composite metallic body comprising a core of high electrical and heat conductivity and a covering of a non-corrosive metallic material constituting from 10% to 50% of the ,weight of the metallic body and said covering containing a metal hydride, said body adapted to form an alloy for welding with refractory metals.

6. A composite wire consisting of a copper core and a nickel sheath, the sheath constituting from 10-50% of the weight of the wire.

'7. A composite wire consisting of a copper core and a nickel sheath, the sheath constituting from 20-35% of the weight of the wire.

8. A composite rod consisting of a copper core and a nickel sheath, the sheath constituting from 10-50% of the weight of the rod.

9. A composite rod consisting of a copper core and a nickel sheath, the sheath constituting from 20-35% of the weight of the rod.

CLEMENS A. JACOB