US1157288A - Manufacture of fine refractory-metal wires. - Google Patents

Description

F. BLAU. I

MANUFACTURE OF FINE REFRACTORY METAL WIRE S.

' APPLICATION r'||.:n JAN- 31. 1912.

1,157,288. Patented Oct.19, 1915;

Figl. Z

MW lnvehtorz Fritz BLau,.

His Attorneg.

To all whom it concern:

rnrrz nmu, or f mmvm sexism, assreuon mo; semen-anaemic r comm,-a-conroaarron or new-roan, a V v I Be [it'known that I, Dr. Fnrrz Brno, a subject of the Emperor of Austria-Hungary, residing at Charlottenburg, Germany, have invented 'certain new and useful Imrovements in the Manufacture of Fine efractory-Metal Wires, of which the following is a specification.

-My invention relat to refractory metal. *wire and ribbon and to its production.

By my process of manufacturetungsten filaments or wires can be produced of a fineness and uniformity greatly superior to anything-heretofore made or obtainable in any way, and this wire is of remarkable uniformity of section for any length desired and of perfectly uniform surface; indeed, extremely small diameters for which the well known Wollaston process entirely fails can readily be obtained. in any "desired, lengths. Moreover, the process is easily carried out, and even when the wire is not reduced below what has hitherto been the extreme limit of fineness, the production of tungsten wire (especially ofthe finersizes) is. rendered very much easier and cheaper. Other advantages and valuable resultsobtainable through my invention will hereinafter be referred to or be apparent.

It mayhere be particularly mentioned that by the employment of my invention tungsten lamps of 16 candle power orless adapted for operation with an efiiciency of about one watt per Hefner candle at such high voltages as*220 or more may be produced very readily, whereas heretofore it has been diiiicult or impossible to make such lamps, and even I difiicult to produce 16 candle power lamps having tungsten wire filaments for 110 volts and thelikel- According to my invention, at least a tungsten wires or'filaments' of the desired finenessare finally obtained is efi'ected chem- 'ically. It is not, however,;necessa ry that the wires or filaments consist of chemlcally pure tungsten, but theymay contain small quantities of foreign componentsfdor example, phosphorus; or refractory,-. ox ids (lime, thorium). Indeed, theseadmixtures militate against the well-known; crystalline structure characteristic of ordinary tung- V sten metal,-which' interferes with the chemical treatment just referred to,-'-and so 5 Specification oi Letters Patent, I

are 'eyfen useful in my process as a meansof securing filaments 'or wire -without In my process, the crystalline of .the reduction in size bywhich "then not only. are the ab preserved in the chemical or electric-chemicalreducln process, but the diiferences become mum nnrnecronv -mnranwmns. p

: Patented oer; 19; Applicationnled'lanuaryfl;1912. iserialiqaigfle.

structure.

structure of ordinary tun sten. metal is got-j V rid of before the meta is subjected to chemical treatinent, which may be done by" mechanical wcrln'ngf of the metal while hot, as set forth in great detail No. 23,499 of 1909. 1

in British Patent 7 The tungsten metal which has been de- .prived of 1ts"cryst a llinestructure .by mech anical working in a heated condition may rolling or drawing and then' subjectedto the action of chemical means which (acting 7'0 .part ofthe mass of the wire or ribbon. The

upon the surface) removes a considerable wire may thus be drawn to asdiameter of about 5 /100 to 3/100millimeters-and the reduction in size carried'on chemically after that. Drawing to the diameter just menof "the fact that the manufacture of the:

,bored diamonds. necessary. for the very] "be brought to a very small diameter by smallest I diameters is no longen possiblaj Thus the second part of theprocess comes becomes uneconomical or fails.

Chemical treatment of the wire may also 'be carried out in several stages withintervening drawing operations. This has the advantage ofreducing the numberof dies required andj-the amount of die wear, as;

"into use where the ifirst part of the process;

well as various'oth'er advantages Furthermore,- the chemical treatment of the wire 7 7 cannot well be continued uninterrupted so far-that the wire is brought'to a verysmall fraction of its imtial cross section, because thenv the original inequalities in the wire previous to t chemical reduction become itself, If, forv example; the wire coming rominent, even without the produc tion 0 inequalities bythe chemical process from the die is'"100/1000 mm.- thick at one. I

end and 101 1000 mm. thick at theother (as a may'result from the enlargement of the die 3 by wear during the drawmg of the wire),

so u 105 I 1 te dilferences relative y greater when the wire is brought 1301a smaller diameter-for example, to Q 30/1000 mm. For whereas the inequality at first amounted to 1% of the diameter, at the end .of the chemical-reducing process it will amount to about 3% of the diameter; and the difference in sectional area at the ends of the wire will have increased in even.

---greater proportion. It is for these reasons ati'ons may consist of a single drawing opthat after'having been brought to a certain diameter by drawin the wire is.advanta-' geously reduced in size chemically, or elec-: tro-chemically, then drawn again to obivate or correct the relatively increased deviation 'incaliber, and then once more subjected to the chemical reducing process. This alternation of the stepsof the process may be carried out as often. as desired until the desired fineness of the wire is attained. The drawingwhich takesplace betweeneach two chemical or electro-chemical reducing opereration or of a plurality of such operations; and the process. may in general be so conducted that the available diamond dies shall be utilizedfto the best advantage. If, for

; example, a large numberof dies with the diameter-ahave accumulated in the course of work. and there is a deficiency of dies with a larger; or smaller diameter 1), then the chemical or .electro-chemical reduction will be carried 'so far that after it the dies may be used which are available in the greatest number. Thus not only is there a reduc tion in the work of drawing, but also an economy of stones.

My invention'wfllbest be understood in connection with the accompanying drawing which may 40 which; illustrates 1 one form of apparatus" vention, and in wh ch v Figure 1 is a longitudinal section of'the apparatus; and Fig. 2 is a transverse section along the line'22 of Fig. 1.

Inthe description (presently to. be given) of how the chemical reduction in size may be effected, I have referred to the wire treat ed as so far reduced by the prior mechanical working that the chemical reduction maybe carried out uninterrupteduntil the wire is brought to the final size, according. to the" mode of employing my invention first above referred to. Before entering upon this description, I desire to call attention to certain facts, the lmowledge of which may be gen- 'erally serviceable in the carrying on of my process. I p

It is necessary that the mechanical working result in the breaking up of the crystalline structureof the metal. If a' tun en wire of this'sort which has been. drawn own to about 5/100 millimeters or less is subiectedto a glowing operation, it will. generally change its structure again after a longer or shorter time and become c 'stallme,' usually in a few seconds. In this changed,

be used in carrying out my n1 amazes recrystallized condition, the second part of the process cannot be carried out with success; for although with suitable chemicals corrosion readily takes place, it does not go on uniformly, but scales out the crystals and attacks diflerent places between the crystals with different intensity, and gives an uneven product of very irregular cross-section,

'with projecting crystal-points and; edges, deep indentations and cracks-,in a word,

an unserviceable product. Again, if a tungsten-wire is made, for example, by drawing a nickel-tungsten alloy into wire and expelling the nickel by heating in an inert gas or in vacuum, a uniform slender-wire cannot be obtained therefrom by corrosion, since Wire produced in this way is attacked very irregularly in consequence of its crystalline structure. It will, therefore, be seen that the absence of the crystalline structure is a fundamental condition for the production of this very fine wire. I may now proceed to indicate in. some detail how the chemical reduction in size ma be effected.

After the completion of the-mechanical working in aglowing condition and the drawing to about 5/100 to3/100 millimeters,

the wire may for the further reduction in,

line solution offerro-cyanid of potassium (red'prussiate of potash),- which is used in 'astate of considerable dilution in order to allow the corrosion to go on slowly, because then the time whenthe process should be stopped in order to obtain the desired di-.

ameter can be gaged much more easily than if concentrated solutions which act. too rapidly are employed. Instead of the ferrocyanid of potassium solution, the most widely different; alkaline oxidizing means may be used,--as,- for example, persulfates, 1

peroxide, etc. Potassiumpermanganate may also be used, especially if provision is made in a suitable manner for removing the coatings of manganese which precipitate on the wire. 'It is very advantageous to pass the .wire throu h an. alkaline bath at a uniform rate. By t e speed of passage the rapidity of the corrosion and consequently the diameter that will be obtained are determined.

It is not necessary to put oxidizing means in the bath; the chemical reduction in size may also beefie ct'ed electrolytically. In this case the tun the anode.

en wire must, of course, forme w reis' passed through the As .tungwire is passed through an ammonia s'olubath at a slow, uniform rate and is properly to be taken over quite a large number of like polessfianodes) in such a manner that cient contact with them for curthere is rent to be supplied at various points on the wire, since by reason of thevery small diameter of. the wire potential difierences otherwise ariselwhich may cause a lack of uniformity'in the corrosion (though this tendency-is checked by the uniform rate of passage through the bath); The wire may, for example, be alternately taken vertically into the bath and out again in a rising and descending (zigzag) line, andoutside the vesselit may run over a number of contacts (anodes)-,rollers for -example,-which sup'-= I ply the positive current, so that uniform eatmg away of the relatively short loops which are in the liquid between each two rollers is insured. The loops are advantageously stretched in the bath over rollers, for example, which are non-conductors 'of electriclty, or wh ch consist of metal for which the voltage employed is not suficient to enable current to pass into the'liquid. The series'or row of contacts by which current issuppliedto'the wire duringits passage through the" bath may be 'in parallel electrically. Tlmgsten wire without crystalline structure can also be reduced in gases, as chlorin for example,if the temperature is maintained .sufliciently high to volatilize the chlorid formed. p

To describe anexample' of how the chemibe carried out electrolytically for sizes smaller than those above specifically referred to, '1-1/2 mil. drawn tungsten wire that is, wire of a diameter of one and onehalf one-thousandths of an inch-is passed through a dilute ammonia solution (20 parts concentrated 'ammonia to 80 parts water) at the rate of about 160 feet per hour. The

- apparatus illustrated inthe drawing is suitover suitably separated cylinders 12' and 13 arranged one above theother onan insulat ng frame 14 of ebonite or similar material,

able for carrying out this operation. The

tion containedin a' tin box 11 which serves as cathode for a current of 0.29 amperes and 2 volts of which thetwire is anode. The wound back and forthin ten loops about to seven feetlof wire being 'in the solution at once. u The lower roll 12' is made of glass, and the upper roll 13 is made with longitudinal or'bars15' on the surface so that the points of contact between the roll.

and the filament are electrically in parallel,

the contacting metal portions 15 being of platinum iridium. Current is led to the bars t ough afconducting core wand-conducting bearing 17 to which the positive ole of the battery is connected. By a sing e passage of 1-1/2 through the solucal reduction treatment of the wire may may cyanid of potassium) is verysuitable, or

tion under these conditions it will be reducedto a size of about one mil. or one one-thousandth of an inch. 4 The tungsten wire which is the subject of my invention finds the most diverse applications. As its tensile strength and also its resistance to heat andto acids isvery con-- siderable, it may serve for suspensionwires for fine measuring instruments (single and double-wire balances), torsion instruments of any kind, for. reticles in-optical instru-" ments, andfinally (as above referred to) for illuminating bodies for electric incandescent lamps and' the like.- 7

When the fine tungsten wire to be used in. incandescent lamps, it may after drawing to 5/100 to 3/100 mm. (for example) be placed upon the usual supporting means l of the lamp,which may have the form of the well known supporting frame used in tantalum'lamps and then put in the bath containing chemicals adapted by their action to reduce the wire in size uniformly, I

"so that a more slender wire of uniform surface and uniform cross-section throughout may result. On account of the material of the holders and the conducting wires, the reduction will in practice not be carriedon'in an acid. solution, since only the strongest oxidizing acids (as concentrated nitric acid) act on the tungsten filament. Such a course is not necessary, however, since alkaline I solut1ons are very well adapted to produce auniform reduction; A dilute alkaline-solution .of 'red prussiate of potash (ferrolow the constantly changing electrical resistance of the filament.- Thus the mounted filamentmaybe dipped in a solution of potas sium ferricyanid or potassiumferro-cyanid (about a-5-10% solution) until itscoldre- 1 sistance is doubled, which takes about fiveminutes. e o

The. chemical reduction in size may also be performed in a bath which itself does not attack the tungsten if'tlie tungsten wire is .made the'anode and a very weak current of a few milliamperes or even fractions thereof is conducted throu h the bath for aconsiderable time. Regar must be had for the fact that the resistance of the tungsten wire is so great that-with stronger currents the cur.- rent must be supplied at different points in: order to avoid an irregular reduction. Th'ough-in describing above how my invention can be carried out and applied. I

have referred to tlmgsten'wire' tungsten rib- 1 a can of course be..produeed'-in a similar manner. Such ribbonhas many uses more or IGSS llkQthOSfi of tungsten w1re.

What I claim asnew and desire to secure by Letters Patent of the United States, is

1. The method of producing very fine tungsten wire of uniform surface and crosssectlon which consists in reducing the size of slender tungsten wire free from the-ordinary crystalline structure of tungsten by electrolytic corrosion..

2. The method of producing very fine re-' fractory metal wire of uniform diameter and surface which consists in subjecting slender wire that has been deprived of its crystalline structure electrolyte.

3. The method of producing very fine tungsten wire of uniform diameter and sur-' face which consists in electrolytically cor roding slender tungsten wire which has been deprived of its crystalline structure by 'mechanical working while hot by passing it at a uniform rate-of speed through an alkaline bath as anode in such a mannerfthat a considerable length of wire is in the bath while supplying current to thewire at a number of points from a plurality of electrically parallel anode contacts traversed by the by mechanical working to electrolysis, as anode in a bath of suitable,

wire in its passage through the bath, so as to obtain a uniform corrosion.

4:. The method of producing very finetungsten-wire, the metal of which has been 'tungste'n wire of uniform diameter and surg fa ce: which consists in reducing the size of a 35.

deprived of its crystalline structure by mechanical working while hot by successive stages of electrolytic corrosionwith suitable magnification of the inequalities" of thewire resulting from this electrolytic reduction in size by drawing'Yof the wire between the stages of the'electrolytic treatment.

:5. The process of producing very fine A tungsten wire of uniform surface-andcrosssection which consists in repeatedly hotelectrolyte, and -Counteracting the relative. 40

working a body of tungsten to change it's I structure from crystalline to fibrous and at the'same time to reduce its cross-section andthen further reducing its cross-section by

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