US1422019A - Alloy of refractory metals and process of forming same - Google Patents

Description

UNHTEE STATES JOHN ADAM YUNCK, OF SOUTH ORANGE, NEW JERSEY.

ALLOY OF REFRACTORY METALS AND PROCESS OF FORMING SAME.

No Drawing. Application filed January 17, 1913, Serial No. 742,711. Renewed July 14, 1921.

Specification of Letters Patent.

Serial To all whom it may cmwem:

Be it known that 1, JOHN A. YUNoK, a citizen of the United States of America, residing at South Orange, county of Essex, State of New Jersey, have invented certain new and useful Improvements in Alloy of Refractory Metals and Processes of Forming Same, of which the following is a specification.

My invention relates to an alloy of tungsten and thorium particularly useful in making metal filaments for incandescent lamps, and a method of making same. Various alloys of the refractory metals have been proposed for this purpose because the alloys are usually more ductile than their constituents taken separately, but none of such alloys heretofore proposed have been successful for the purpose because they either had too low a fusing point, or volatilized at high temperatures'and discolored the lamp bulb.

I have discovered that an alloy of tungsten, 95 to 99 parts, and thorium, 5 to 1 fparts, can be swaged and drawn down to lament size, and produces a filament of high eificiency, high melting point and one which does not discolor the lamp bulb. In making such alloy I employ the following process:

I dissolve from 1 to 5 parts by weight of thorium nitrate in distilled water and mix into a thick paste with from 99 to 95 parts of powdered tungsten oxide, or equivalent compound of tungsten, or with pure powdered tungsten. This paste is dried and heated until the moisture is driven off, then crushed to powder, put into a crucible and fired for eight hours. The temperature is gradually raised to about 1200 degrees centigrade, maintained-for about three hours at that point, and then gradually lowered. When the crucible and contents are reduced to atmospheric temperature, which usually does not occur until about 20 hours after the beginning of the firing, the contents are taken out, ground and sifted through bolting cloth.

The fine material which has passed through the bolting cloth is then preferably placed in a nickel tube of say about 2 inches internal diameter and rovided with connections for passing by rogen gas through to cool gradually, this entire portion of the process usually consuming about seven hours time. During the entire period a current of hydrogen gas is kept flowing through the tube, over the powdered mixture.

After the material has been treated as above described it is again sieved or bolted and the fine powder resulting from this operation is mixed with any suitable binder and squirted from a mold to form a rod. These rods I place in a suitable receptacle, of highly refractory material, which is placed in an oven where it is gradually raised to a temperature of about 1200 degrees centigrade, maintained there for about an hour and a half and then gradually cooled off. A stream of hydrogen gas is continually passed through the oven in contact with the material during this operation.

The rod so formed and baked is next sintered by placing it in a treating bottle through which a supply of dry hydrogen gas is continually flowing and subjecting it to the passage of an electric current of about the following strength:

Amperes. First five minutes 500 Second five minutes 750 Third five minutes 1000 Next ten minutes 1500 Last five minutes 2000 The current is then gradually turned off reducin it to zero in about 5 minutes. As at ,present advised, I believe the fact that both constituents of the alloy are liberated from their respective compounds during the formation of the alloy, so that they may combine while in the nascent condition so resulting, has an important efl ect on the perfection of the alloying action, and on the durability of the product under the conditions of its use.

The sintered ingot thus produced may be worked down to filament form by known processes. a

"The filament so produced is tough and can be safely handled in making lamps, is of practically the same efficiency as pure tungsten, has a high melting point and will not volatilize and blacken the lamp bulb when run at high incandescence.

Having, therefore, described my invention, I claim:

1: An alloy for use in making metal filaments and the like, composed of at least 95 per cent of metallic tungsten and the rest pure thorium. v

2. The product of the invention herein set forth, being an alloy of more than 95 per cent tungsten and less than 5 per cent thorium. I I

3. As a step in the herein described process offorming alloys of tungsten and thorium, heating a mixture of a finely powdered oxide of tungsten and thorium nitrate in such manner as to entirely reduce the thorium nitrate.

4. The process of forming an alloy of tungsten and thorium which consists in mix in an'oxide of tungsten and thorium nitrate, reducing the mixture to a fine powder, subjecting the powder to high heat for a period of hours in a non-reducing atmosphere, regrinding and subjecting the powder for several hours in a reducing atmosphere to heat suflicient to reduce the compounds forming said powder, then mixing said powder with a suitable binder, forming into rods or wire, and heating and sintering the same.

5. The method which consists in drying tungstic oxide uniformly moistened with a thorium salt solution, pulverizing the dry residue, heating said .ulverized residue to convert all sald thorlum salt to thorium oxide, and completely reducing said residue by maintaining it at the highest possible temperature-in a dry reducing atmosphere for a prolonged period until the last trace of 'oxide is removed and a ductile alloy is proof oxide.

JOHN ADAM YUNCK. Witnesses:

A. PARKER SMITH, M. G. CRAWFORD.