US1202535A - Production of metallic tungsten. - Google Patents

Description

FREDERICK G. KEYES AND ROBERT B. BROWNLEE, 0F HOBOKEN, NEW JERSEY, ASSIGN- ORS T0 COOPER HEWITT ELECTRIC COMPANY, OF HOBOKEN, NEW JERSEY, A COR- PORATION OF NEW JERSEY.

PRODUCTION OF METALLIC TUNGSTEN.

mosses.

Specification of Letters Patent.

Patented (let. 2%, 19146.

No Drawing. Original application filed July 6, 1914, Serial No. 849,137. Divided and this application filed April 10, 1915.

To all whom itmay concern Be it known that We, FREDERICK G. KEYES and ROBERT B. BROWNLEE, citizens of the United States, and residents of Hoboken, county of Hudson, State of New Jersey, have invented certain new and useful Improvements in the Production of Metallic Tungsten, of which the following is a specification.

The attempt to produce metallic tungsten by electrolytic processes has hitherto shown very meager results. It has been found, for example, that it is impossible to obtain tungsten electrolytically from an aqueous solution of its salts. Ithas also been found that only the so-called tungsten-bronzes can be obtained from molten para-tungstates. Moreover, while we have found that tungsten tri-oxid gives a clear solution in boric acid at 1000 to 1200 degrees centigrade, even with a high concentration of the tri-oxid, yet such a solution submitted to a tension of from 110 to 500 volts at temperatures from 1000 to 1300 degrees centigrade permits only a fraction of an ampere to pass. Separation of tungsten took place when the electrolytic action was prolonged, but the.

The substance is fluid at about 2000 degrees centigrade and in its fluid condition may be utilized as an electrolytic bath from which metallic tungsten can be separated by the observance of a proper mode of procedure.

lln general we prefer to employ a rotating cathode of tungsten and an anode in the form of a sintered rod of tungsten, through which and through the oxid bath an electric current is passed. Varying current densities may be employed according to the character of the deposit desired, the dimensions of the bath, the volume of the electrolyzing Serial No. 20,446.

fluid, and the area of the electrodes. The crucible itself should be of such a character as not to contaminate the bath with impurities if it is desired to produce pure tungsten. If, however, it be desired to produce, for example, a carbon bearing deposit, the crucible material may contain carbon.

In order to bring the electrolytic substance that the heat of formation of this oXid is 131,000 calories per gram molecule; hence, about one volt is the decomposition or deposition potential. Sufiicient energy in addition to this mustbe applied to maintain the material in a fluid condition.

Recapitulating the foregoing description of the novel process herein described, the steps consist, first, of a more or less prolonged ignition of WO at 1800 to 2000 degrees Centigrade. This results in the liberation of a portion of the oxygen, leaving a lower oxyg'en compound or a mixture of such oxygen compounds. Thus, the. first step in the process may leave VVO or WO .or a mixture of these two oxids. The substance resulting from this part of the process is then brought to a fluid state and maintained in said state, preferably by means of the PR heat, and a surplus of energy is applied to the material for maintaining it in a fluid condition. The application of electric current to this fluid material causes a compact deposit of metallic tungsten upon the oathode. As already stated, the cathode is of tungsten, and preferably a rotating cathode, while the anode is, for example, a tungsten anode consisting of a sintered rod of tungsten. The density of the current applied to the bath varies according to conditions already stated. It has been found that at high temperatures anodes of high melting metals, as iridium, become oxidized at the anode in this bath since oxygen is liberated, and that, moreover, such oXid passing into the solution, the metal ion is deposited upon the cathode, thereby producing an alloy, or at any rate, contaminating the deposit of pure tungsten which it is desired to obtain. Of course, an ideal electrode would consist of a cast bar of lower tungsten oxids since they conduct the electric current with facility. As a matter of course, the melting point of such an oXid would be the same as the bath in which the electrolysis is being carried out and hence the use of such an anode is precluded. The melting point of the anode, however, may be adjusted by mixing the lower tungsten oxid and tungsten powder and casting this into the form of an anode bar. Obviously, such an anode or, at least the particles of tungsten composing it, will be attacked by the anion, in the present instance oxygen, forming oxid in all probability and thereby becoming a portion of the bath itself. lhis is desirable and forms as will be readily perceived, a means of'renewing the electrolytic bath. Other anodes, of course, may be used depending upon the character of the cathode deposit desired. For example, a graphite anode might be used within and wholly surrounded by a porous cup material, the interstices of which would prevent the wandering of objectionable anode particles to the cathode. The cup serves as a screen or filter.

It is convenient to use as the cathode a tungsten wire about one-sixteenth of an inch in diameter. The first wire used in the formation of subsequent tungsten wires may be of iridium, for example, and after a deposit of considerable thickness of metallic tungsten has been formed upon this iridium I wire the ingot thus created may be swaged down and a part of the resulting wire agaln used as a cathode. By repeating this process the iridium is finally eliminated and a pure tungsten wire to form the cathode is obtained.

It will be understood that we have mentioned the use of an original iridium cathode simply to explain how we may produce subsequent materials for cathodes which are made in accordance with the herein described process. After the iridium has been removed by repeated operations such as have been described, wires or other shapes of our grade or quality of tungsten may be utilized as cathodes. There is, of course, no controlling reason why ordinary commercial tungsten should not constitute the cathode, if desired or if suited to special needs or requirements. When suflicient tungsten has been deposited upon the cathode, the wire may be removed and another substituted. In practice, to prevent the bath from cooling, it is recommended to use two rotating cathodes, one of which may be removed and a new cathode placed in the electrode holder. The electrode, with its tungsten deposit, 15 then swaged down to a diameter where it is practical to reduce the diameter still further by drawing dies.

Applicants case Serial Number 849,137, filed July 6th, 1914, of which this application is a division, contains claims relating more particularly to the method of producing pure tungsten.

We claim as our invention:

In an electrolyzing bath a suitable cathode and an anode consisting of a sintcred mixture of tungsten powder and low tungsJten oxids cast into the form of an anode Signed at New York in the county of New York and State of New York this ninth day of April, A. D. 1915.

FREDERICK G. KEYES. ROBT. B. BROWNLEE. Witnesses:

HAROLD B. WOODWARD, THOS. H. BROWN.