US1531666A - Refractory metallic body of high density and process for making the same - Google Patents

Description

March 31. 1925. 1,531,666

- c. A. LAISE REFRACTORY METALLIC BODY OF HIGH DENSITY AND PROCESS FOR MAKING THE SAME Filed June 12, 1922 :rrgi.

2 L r INVENTOR.

2 2'7 16 a Cleans HLcuse W AD -M '76 Z4. ATTORNEYC Patented To all whom it may o. r s A. miss; or Awxmz; new mam. cromr mmfanirc Bony or men nmesrrr am) PM. son.

Be it known that I, CLEMENS A. lia se, a citizen of the United States, and a resident of Wee'hawkemfcounty of Hudson, State of New J erseyrha've invented certain new and useful Improvements in Refractory Metallic Bodies of High Density and Processes for Making the Same, of. which thefioll'owing is a specification. m i

his invention relates to the production ofmetallic bodies of refractory metals of a density or specific gravity above 18, such bodiesbeing of'small dimensions usually not exceeding 5- to 10 grams in weight. V

I have discovered that instea of mechanically working metallic bars of refractory metals by hammering, swaging, rolling or drawing the said metals and then shaping them into small bodies by cutting or punching, I can press up the refractory metallic powders into any desired sha pe, then fuse or sinter the pressed up bodies into solid ordinarily desired for use I which the products are to use of specific gravity of approximately 18 and sirable to produce are platinu m'iridium, gold?" coherent forms and then finish the said bodies for commercial use by my improved rotary impact finishing process.

have found that by carrying out these steps, not only. a superior product is obtained, but a product can be manufactured much more economically than by means of processes now known. The refractory metallic bodieswhich are in the arts may of any but are usually insuitable shape,

the form of cylindrical discs having-a thickness not exceeding f to 4" and a diameterranging between to As it is well known, the dimensions and shapes may, however, vary according to the purposes-for be used. -The desired shapes or bodies are commonly used as face plates for contacts or contacts for telephony or telegraphy, for

X-ray targets, circuit controllers, rectifiers, other purposes [which will an for many readily suggest themselves.

My invention especially appertains to the refractory metals having a normal above, ande'specially these metals which do not acted upon metallicbodies which are particularly de-,, bodies of tungsten, thorium, tantalum,

ignition points in. gas-engine installationsfor-magneto points,

metals can be Application medium 12, r922. Sci- 811%. 587,619.

.uraniumand alloysor mixtures of these temperature being reduced atstated times as the bodies became drawn down into with intermediate drawing, the temperature being-likewise reduced at intervals as the cross section of the rod becomes smaller. The discs were then cut from the rods or else punched from the rolled plates. Que of these processes is in practice today by the General Electric Company and it is set forth at great length in Patent N 0. 1,082,933 of December 30th, 1913, to William l). Coolidge, as'signor to General Electrio Company.

In order to overcome the great difficulties and to save the enormous expense .resultin from the mechanical working of refractory metallic bodies havin a normal specific gravity above 18, and urthermore, to overcome the great difficulties of shaping these bodies into. definite forms to make them smaller, and then either a rod by cold drawin s g annealings, or else by hot suitable as face plates for various purposes I have invented a newprocess and product which will be hereinafter set forth.- Since the bodies to be roduced are usually very small and thin, the process can be effectively carried out on a very large scale.

I have discovered a process by which dies made from y one of the metals specified or alloys of these metals, including tungsten, and alloys of tungsten, in which, instead of mechanically working the metal by hammering, rolling or drawing into the shape desired, I am enabled. to eliminate this long expensive proceeding. 1 have found that commercial bodies of tungsten produced by a process diflermg essentiall from the'special processes of the prior art in all which the forms required for industrial use were produced by a special mechanical working. my process the metallic bodies are 'first shaped into the desired forms by pressing the metallic powder I subject the sintered body to a finishin heat is an operative temperature.

are used the tumbling 1mpact process for a considerable lengt of time under a constant temperature by placing the sintered shapes of tungsten with impact balls, such as tungsten steel in a tumbling barrel, and subjecting them during the tumbling to a heat treatment. The temperature during this heat treatment is but is maintained at' a below the melting ull red When not only constant temperature much of the metal. I have found that a the recious metals and impact step may be carried out at room temperature.

In the accompanying. drawings I have illustrated mechanisms which I have found very suitable for use in aiding in the performance of the several steps of my-process.

' having a convex surface.

' sten face plate.

- and 52, as shown, to

which Fig. 4

Fig. 6 1s a cross section of a disc, one surface of which is concave and the other convex. i I

Fig. 7 is a contact having a face plate of tungsten and a backing of iron or steel.

Fig. 8 is a contact consisting wholly of tungsten.

Fig. 9 is a screw contact having a tung- Briefly referring to the drawings:

The slntering furnace illustrated in Fig, 1 consists essentially of a refractory metal tube or slab of tungsten or tungsten alloy,

which has'a stationary water cooled copperelectrode 51 attached to one end, and a .movable water cooled copper electrode 52 attached to the other end so as to allow for the expansion or contraction of the metal tube or slab 50 during the heating operation. The ends of the tungsten tube 50 fit into the water cooled electrodes 51 which the main leads 53 and 5a are attached, these leads being connected incircuit to atransformer' 55, conventionally shown. The entire chamber is enclosed by a. water cooled cylindrical casin which rests on supports of insulating material 62 and 63. The pressed up forms or shapes L tobe sintered are placed upon a boat B of suitable material and are then introduced into the tube or point 19 meshing with a on .to'a slab throu h the opening 65. p The refractory metal s ab or tube is supported by refractry metal rods 66 of the same material as the heating element. The shapes to be sintered are allowed to remain in the heating element after it has reached its maximum temperature approximately 2700 degrees C., for about ten minutes. The current passing through the heating element is then interrupted, the boat .is shoved into the water cooled chamber 67 by means of a tungsten rod and then removed through the opening 68. The operation is carried out in an atmosphere'of hydrogen or in .1 low pressurehydrogen vacuum. In the latter case long rubber stoppers are placed into each end and the chamber is evacuated through a. glass tube in one of these rubber stoppers. The forms or shapes being heated by external means no blow holes are formed in the center and a much more compact mass is therefore obtained.

In Fig. 2 is shown a tumbling barrel 10, the hexagonal sides being to more eflectually throw the contacts about during its rotation, as readily understood.

rovided with a coverll and a fixed hearing 12'on its underside through which the shaft 13 extends and to which it is secured. The supporting plate 20 is provided with legs 21 and 22 of diflerent length in order' that the support may be held vat an angle The barrel 10' is to the horizontal. On. the shaft 13 is a pulley 14 which operates a belt 15 which engages a pulley 16 on a. support 17 towhich 's secured a shaft 18 carrying a gear gear 19 secured to the shaft of the motor M. The rotating drum is mounted within a casing C which rests upon the supporting plate 20, as shown. Within the casing are provided air and gas burners 30 and 40 arranged with apertures,

as shown, the burner LO'being especially arranged so that the flames may impinge against the lower portion of the tumbling barrel.

The products shown in Figs. to 9 are clearl illustrated, having the shapes above speci ed. a

The essential steps of my invention are as follows:

First: The production of a very fine or fine grained metallic powder of high density the great fineness ofthe powder tending to produce a body of high specific gravity.

Second: The pressing of this dense powder into coherent bodies in the desired shape at high pressures, thus forming the bodyinto its desired shape and at the same time increasing the density.

Third: .The fusing or sintering of these compressed bodies in an inert or reducing atmosphere or even in vacuum or under pressure at a temperature near their melting I duce as nearly of about tile' constituents which may purposely have been introduced to draw the particles of refractory metal together. This step further increases the density.

Fourth: The mechanical tumbling of the above metallic bodies either at room temperature or at a higher temperature, which higher temperature, however, is constant but which is much below the melting point of the metal being acted upon sothat by means of this impact with hard bodies, such astungsten or vanadium steel balls',-theirjdensi ty isstill further increased.

While my process is applicable to the production of bodies or shapes of the kind adapted for use in the arts, it is particularly applicable for the production of dense face plates of tungsten, platinum,- iridium and their alloys.

In order to produce face plates of tungstem or platinum or their alloysI first proa chemically pure tungsten or platinum powder as possible, preferably by the reduction of the pure tungsten oxide with hydrogen, if tungsten powder is'desired, or by the ignition of ammonium chlorplatinate if platinum is desired. These metallic powders should be as void talline structure as possible, cases I may'add a certain percentage of crystalline powder in order to have the metal flow better at the tablet machine. To the chemically pure metallic powders I then add a small percentage of a fluxing metal which alloys with: the main constituent at low temperatures but which is volatilized' out at the higher temperatures and thereby has a tendencyto draw particles of the main constituents together. For tungsten, I prefer to use about 1 to 2 per cent of copper, iron, 'gold or nickel.

though in some To the chemically pure tungsten powder I prefer to add 1 per cent'to 1.5 per cent of chemically-pure nickel powder.and the mixture of tungsten ball-milled from 10 hours to 24 hours. The ball milling may be done in nickel contain ers usin'g balls or discs of coherent tungsten so that there is no contamination of impurities. After this metallic powder has 'attained a weight'of about to cubic inch it is ready for pressing. The pressing step is preferabl carried out on a Stokestabletmachine or #0, the

shape of the disc depending upon the pur-- pose for which the'body is to be used. As

above stated, the metal powder should be of such a'structure that it will readily flow from the hopper and is compressed at a pressure 50 tons to 100 tons per square inch. The bodies of pressed tungsten powder are placed into nickel boats and heated in hydrogen at a temperature of 1000 degrees C. to 1200 degrees C. for about a quarter to as shown in Fig. 1.

of crys-- and nickel powder is then 100 grams per half an hour. This strength to them so that they-can be handled and still retain their shar edges. If the metal has the proper physical structureso as to produce a strong disc'this step is-not necessary.

These small bodies are then placed into the tungsten boats B andsubjected to a heat treatment in a tungsten tube furnace such This treatment is referably carried out'in an atmosphereof hyimparts suflicient drogen at a temperature of about 2700 de-- -f grees C if tungsten bodies are produced, C. to 1700 degrees C. if platinum or platinum alloy bodies are produced. This treatment consists of a combination -sintering, volatilization and fusing action; above temperatures a treatment of- 5 to 10 minutes duration is sufiicient. During this treatmentthe volatile. constituents whichdistilled out. e particles of refractory metals are draw the vmetal together are and th .and at a temperature of about 1600 degrees and at the fused together to dense coherent bodies. a

fter cooling i'n'hydrogen they are removedfrom the furnace.

They are then subjected tomy impact finishing process whereb they are tumbled in a revolving barrel suc as shown in Figs.

2 and 3 with hardened I balls or impact bodies, which may be round or sharp e ged depending upon the purpose for which they are to be used. The ings which are made of Vanadium or tungsten-steel or of other toolsteel or alloys suchwill not readily softenasstellite, etc., which under heat, are commonly used. The tumbling may be done at elevated temperatures. In the latter case the tumbling barrel may be heated by means otgas as shown. in Fig. 2, a metal casing C belngplaced around'the barrel A which encloses the heat and keeps it at a uniform temperature approximately at 400 degrees C. The heating of the barrel may also be done electrically. When treating substantially pure tungsten discs,.a,dull red-heat is preferable whereas when the platinum metals are subjected to this treatment the operation may be carried. out at room tempera ture. During this impact finishing process the pores of the discs are-closed, the surface of the discs are compacted and made denser, the surface of the metallic bodies is polished and the'density of the metallic bodies themselves is considerably'increased.

a period of from four hours to at room temperature orballs as used in bear- The tumbling is usually carried out over thirty hours depending upon the character of'the metals 1 that are being tumbled or until the metallic bodies attainthe desired density. The turnbling may also be carried out in an inert reducing or hydrogen atmosphere.

. 'After' tumbling operation is completed the metallic bodies are treated with weak I acids or alkalies to cleanse the surface and are then tumbled in saw-dust after which they are ready for welding or for the market.

The impact finishing treatment is carried I out at one temperature and not-at a gradaful face plate of a refractory metal for uniformly heated from and therefore are uniform in structure.

contacts or X ray work is that the same be of the highest density obtainable and that it be 01? fine grain structure. Both of these features are attained through my process. Furthermore, the face-plates of tungsten or similar metals as made to-day varydecidedly in structure owing to the non-uniform heating process to which they are subjected during the process of manufacture whereas by my process all discs are an external source Thus for instance in the prior art bars of pressed tungsten are 'sintered by sending a current through the same equivalent to about 90 per cent of the fusing current in an atmosphere of hydrogen. By this means a temperature gradient is produced between the interior of the slug and the outsidefrom which the heat is carried by the hydrogen. This produces non-uniformity across the slug and furthermore since the ends'are held at water cooled electrodes there is a decided diiference in structure between the metal near the water-cooled electrodes and the metal near the center of the slug. All of these factors cause a non-uniformity in the structure of the discs made from rods or plates of such material so that it has giventhe manufacturer of ignition systems considerable trouble. Since my process subjects the-metallic bodies to a more heat treatment most of these undesirable features are eliminated.

Furthermore, any pores that may be in the metallic bodies madeaccording to the old process remain open hich causes pitting whereas any pores in the metallic bodies produced by my process are closed during the impact treatment.

Another advantage of my process is also manifested in that I find that instead of merely making adisc I can make a complete rivet by my process such as shown in Fig. 8 thereby avoiding the extra operation 0 welding the disc on to the steel or nickel blank; This is especially desirable when working with tungsten or tungsten alloys or mixtures where the cost ofthe material I Y of which the contact is made is low enough so as to permit of this procedure. I

M process also enables me to make discs or rlvets of alloys or mixturesof the precuniform f stantially dullred heat.

ious metals and metals of the tungsten' group thereby enabling me to produce a contact of these metals which may be substit-uted for platinum or platinum-iridium and which is equally asgood and decidedly cheaper.

Having thus described my invention, what I claim and desire'to secure by Letters Patent is: v

1. A method of forming articles of the kind described which comprises pressing fine powders of metal into a desired form, sintering the formed article at a high tem perature and compacting the articles at a substantially uniform but lower temperature by an impact, tumbling action. T

2. A method of forming articles of the kind described which comprises a metal powder containing a small quantity of a 'comparatively volatile substance under pressure to a desired form, volatilizing said substance at a high temperature and compacting the article at a lower temperature an impact, tumbling action. .3. A method of forming articles of the kind described which comprises compacting a metal powder into a desired form, sintering theformed article at a high temperature and compacting said article by an impact, tumbling action at .a temperature of approximately 400 degrees C.

4. A method of forming .articles of the kind described whichcomprises compacting' a metal powder containing a. small quantity-of a comparatively volatilesubstance under pressureto a desired form,-volatilizing said substance from said article at a high temperature and compacting said'article by an impact, tumbling action at a temperature ofapproximately 400 degrees C. in a reducing atmosphere.

5. A-me'thod of forming 'metallic articles of the kind described which comprises compacting a powder of metals of a density of over 18 to a desired form, metals and compacting said sintered article at a substantially uniform lower temperature by an impact, tumbling action.

6. A method of forming metallic articles of the kind described which comprises comsintering sai pacting a powder of metals of a density of over 18 with a small amount of a more vola tile metal, heating said compacted article to a temperature suflicient to volatilize saidmore volatile metal, and compacting said article by an impact, tumbling. action at a sub 7. A method of forming articles of the kind described which comprises compacting a powder of metals of a ensity of over 18' with a small amount of a more volatile metal. to a desired form,

and heating said articles to a temperature suflicient to volatilize said more volatile metal and then compact'said article by an impact, tumbling compacting action at ture.

a substantially I uniform tempera;

8. A method of forming articles of. the

kind described which comprises compacting said article to tungsten powder containing a small amount of nickel powder to a desired form, heating a temperature suflicientto volatilizesaid nickel and compacting saidarticle at a lower temperature by an' impacg tumbling action.

9. An article pf manufacture comprising a body of tungsten of high density which is free from a fibrous structure, the surface of which has been still further densified by an impact, tumbling action. Y

10. An article of manufacture comprising a refractory metal of high specific gravity,- the density of the surface of which is increased over that on the inside of the body by an impact, tumbling action at a tempera- 20 ture approximating a dull red heat.

11. An article of manufacture comprising a contact oftungsten of high density which is free from a fibrousstructure, the surface of which being denser than'theinside, the said surface being formed by an impact, tumbling action.

In witness whereof I have hereunto set myhand at the borough'of Manhattan, city and State of New York, this 6th day of 30 June, 1922.

' one A. SE.

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