US1089757A - Tungsten manufacture. - Google Patents

Description

UNITED STATES PATENT OFFICE.

THEODORE W. FREGH, JR., .0]? CLEVELAND, OHIO, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TUNGSTEN MANUFACTURE.

Ho Drawing.

Specification of Letters Patent.

1 Application filed october 9, 1912. Serial No. 724,825.

To all whom it may concern 7 Be it known that I, THnononnW. Freon, .Jr., a citizen of the United States,,residing at Cleveland, in the county of Cuyahoga,

State of Ohio, have invented certain new and useful Improvements in Tungsten Manufacture, of which the following is a specification. V

My invention relates to the manufacture 1 of tungsten for use in the filaments of incandescent electric lamps and for other purposes. Incandescent lamp filaments made of tungsten such as can be produced by my process can be operated on alternating current for an indefinite time without the transverse faulting or displacement of adjacent sections of filament known as olfsetting and give very uniform and good re- ,sults as regards length of life, maintenance ga'of candle-power, and strength after buming. By this process, also, can be produced tungsten which possesses'a greater or less degree of ductility and pliability even after v prolonged exposure to high temperature, as in the incandescence of electric lamp filaments and of electric furnace resistors, etc. .By my process, furthermore, can be produced coherent tungsten capable of mechanical working while hot and which if such so hot workingis sulficientlyprolonged becomes freely capable of mechanical working and shaping when cold by. reason ofproperties of ductility, malleabllity, pliability, etc.,- or, in general, of undergoing permanent de formation in any wa under the application of force below the ultimate breaking strength of the materiaL-acquired during the hot working or'(if the-material possessed any such properties before) greatly increased by a change in the material which occurs during the hot working. Different lots of such metal, also, exhibit great uniformity and reliability as regards their capacity for drawing down to the very finest sizes,as for example, that required for a 10 watt 110 volt sign lamp. Tungsten produced in accordance with my invention and'thus hot worked also tends when subjected to high temperatureto retain the ductility, etc., ac-

i quired during the hot ;working,-or, at. least,

loses the same but gradually.

I have hereinafter described my process with particularreference to its employment for the reduction of coherent tungsten out ofnwhic electric lamp filaments are to be ticular,.coherent tungsten Patents 23,499 of ments can be prevented by theaddition of foreign material to the metal; and in parpossessing some or all of the roperties above set forth has been produced which-has been fired in a Hessian or Battersea crucible, and also from powderedmaterial to which have, been added one or more of various refractory oxids such as those of thorium, zirconium, yttrium, erbium, di-

dymium, or ytterbium, or substances which when decomposed by heating give such oxids, particularly thorium nitrate. The crucible firing, indeed, owes its efficacy in part to. substances such as these (consisting largely of alumina and silica) found in the oxid after the. firing and probably volatilized into it from the crucible, and in part from tungsticg 3) to a coarsening of the tungstic oxid which results from the firing. While thoroughly eflicacious and more reliable than the other modes of addition as heretofore employed, this firing treatment is expensive, because for the'best results a crucible can be used only once and 1 because" when carried out at the most effective temperatures it generally involves the loss of a substantial amount of tungstic oxid by volatilization, and does not always produce a definite quantitative effect as to the amount of the addition thus made to the oxid.

My process possesses all the eflicacy and reliability of the crucible firing above mentioned without any of its disadvantages, being simple, economical, easy to carry out and control, and perfectly'definite in its effects. In this process, suitable substances or addition material whose introduction makes the metal filaments finally produced capable of incandescence on alternating current without ofl'setting (such as: the oxide and compounds above referred to) are employed. This addition material is introduced into the material from which the filaments are eventually to be produced at a suitable stage and the whole is then heated, especially good results being obtained when this heating is carried out under oxidizing conditions. By this mode of procedure the effect of such substances'in .giving to the metal eventually obtained the property of not offsetting and of retaining its ductility even when highly heated is improved; and the degree of coarseness or fineness of the tungsten-hitherto found to be a matter of considerable moment as regards the facility with which material to which such additions as above mentioned have been made can be hot worked-oeases to be of prime importance. The treatment (fan advantageously be carried out with the compounds from which tungsten is produced, preparatory to their reduction, though it can also be carried out in other ways. Superior results are obtained by employing thorium nitrate and introducing it into the material when the latter is in the form of tungstic oxid, and afterward heating the oxid with this addi tion in an oxidizing atmosphere. This mode of procedure greatly intensifies and improves the final efi'ects of the thorium nitrate addition as regards the non-offsetting properties of the filament and its retention of ductility after high heating. The good results may possibly be due to some sort of chemical reaction between the tungstic oxid and the thorium nitrate, or to elimination of impurities present in the tungstic 'oxid; or it may be t at the thorium nitrate or the'thoria under these conditions in some way facilitates some molecular or intermolecular chan e in the tungstic oxid; or the action may e of some still difi'erent character, or a combination of various effects.

I will now describe in detail how my invention can be successfully carried out commercially. A satisfactor quality of tungstic oxid can be produced y. dissolving tungstic oxid (W0 as pure as commercially obtainable in ammonia water, purifyingthe ammonium tungstate thus formed by crystallization overa steam bathyand-the-n; after washing with distilled water and drying,

decomposing the ammonium tungstate by the application of moderate heat, say 400 to, 500 0., which drivesofifthe ammonia and leaves tungstic oxid. -A1ternatively, and with very good results, the ammonium tungstate solution ma be precipitated with concentrated hydroc oric acid-care being taken in the addition of the hydrochloric acid to the solution not to pass the neutral pointthe resulting crystals of ammonium tungstate filtered ofi, washed with distilled water, and heated as before toconvert to.

I tungstic' oxid.

The tungstic oxid purified as just described or in any adequate manner is mixed tubular mold of about 1% internal diameter with thorium nitrate solution. Though the proportions can be varied, good results are obtained by using, with a kilogram of tung-' stic oxid, 75 cubic centimeters of thorium nitrate solution of such strength that 10 cubic centimeters of it contain 1 ram of thorium oxid (ThO The weig t of a thorium nitrate solutionrof this strength is 1.1484 times that of an'equal volume of water,-- which fact alfords a convenient test. The mixture obtained by the addition of the thorium nitrate solution to the tungstic oxid as just described contains approximately three-fourths of one per cent. of thorium oxid by weight. To this mixture sufficient water is added to make a thick solution or paste, water bath, so that the materials are thoroughly, intimately, and uniformly incorporated together. According to one mode of procedure, this stirring over the water bath is continued until the material becomes a thick mud that can be molded like clay, and

this mud is packed with a ram-rod into a and about 10" long. The material is then pushed from the mold and the slug or rod thus obtained is dried in an ordinary gas oven until it will hold together sufficiently to bear handling. Alternatively, the heating of the material over the water bath may be continued until it is'evaporated to dryness and the tungstic oxid powder thus obtained may be pressed dry in a mold into a rectangular slug or briquet about 1" or 5} square and 9" long,-the mold being sufliciently reinforced to withstand high pressure and a hydraulic press being employed. It will be understood that the formation of the oxid into a slug in either of these ways is merely "to put it in a convenient form for the subsequent heating operation and to obviate the necessity of employing boats to contain the loose powder, since most of the materials which would be convenient for such boats would be liable to contaminate it or would be rapidlyjdeteriorated by it, or are unduly expensive.

which is thoroughly stirred over a The firing of'the slugimay 'conveni'ently be carried out in a porcelain tube furnace about 24 long and of 1;. internal diameter electrically heated by a suitable external winding, the slug being pushed through this furnace at the rate 0 every four minutes. The ends of this furnace being open to the atmosphere, oxidizing conditions will exist within it without any special steps being taken taint-reduce oxidizing as into-it. The furnace may to advantage e-maintained atsuch a temperature that its interior matches in color with the carbon filament of an ordinary carbon.

filament lamp operated at 45% of the voltabout 1" age for vwhich it would operate at the stand- 4.

ard efliciency of 3.1 watts per candle. The

slugs shrink slightly during this firing operation, and when they come from the furnace they are green in color. This change in color may possibly be due to the formation of a low thorium tungstate or tungsten thoriate by reaction between the tungsten trioxid and the thorium nitrate, or to other causes.

' The fired slug may be pulverized in an ore crusher and the oxid powder then reduced in a porcelain tube furnace electrically heated by an external platinum winding, hydrogen being passed over the surface of the oxid in the tube and'the temperature gradually raised until the interior of the furnace matches in color with the carbon filament of an ordinary carbon filament lamp burning at 45% of its voltage for a 3.1 watt. per. candle efiiciency,though a temperature at which the interior of the tube will match with such a filament burning at 30%. of the rated voltage as just stated will sutfice. Alternatively,-the slug may be reduced with hydrogen in the same way without crushing; this will give a mass of tungsten particles so soft and friable that it can .be pulverized between the fingers. This mass may be reduced. to powder in any suitable way, as by grinding in a porcelain mortar.

The tungsten powder obtained into a rod and worked into filament form or into any other desired shape as described ining material a relatively small amount or a compound of thorium and heating the mixture under oxidizlng conditions.

.OXICl under oxidizing conditions in any of the ways above indicated may be pressed up 2. The process of preparing a compound containing tungsten for subsequent reduction to tungsten and the drawing of the said tungsten down to wire which consists in heating said compound under oxidizing c011- ditions with a compound of thorium.

3. The tungsten for subsequent reduction to tungsten and the drawing of the said tungsten down to wire which consists in heating said with a compound of thorium.

4. The process of preparing an oxid of tungsten for subsequent reduction to tungsten and thedrawing of the said tungsten down to wire which consists in heating said oxid under oxidizing conditions with a compound of thorium which is broken up upon heating to produce an oxid of thorium.

. 5. The process of preparing tungstic oxid for subsequent reduction to tungsten and .50 process of preparing an oxid of the drawing of the said tungsten down to v wire which consists in heatlng said oxid under oxidizing conditions wit-ha compound of thorium.

6. The process of preparing tungstic oxid for subsequent reduction to tungsten and the drawing of the said tun ten down to wire which consists in heatln said oxid under oxidizing conditions with a compound of thorium which is broken up upon heatin to produce an oxid of thorium.

7. Tie method which consists in heating to a suitable temperature in an oxldizing atmosphere tungstlc oxid with which is intimately incorporated a comparativelysmall proportion of.-thor1um mtrate.

In witness whereof, I have hereunto set my hand this 28th day of'September, 1912,

THEODORE W. FRECH, JR.

Witnesses:

JOHN M. SmoNe, RALPH B. HUNTER.