US1273920A - Electric furnace. - Google Patents

Description

C. A. PFANSTIEHL.

ELECTRIC FURNACE.

APPLICATION FILED NOV. :9. 1914.

Patented July 30, 1918.

2 SHEETSSHEET I.

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f7 z tarneg C. A. PFANSTIEHL.

ELECTRIC FURNACE.

APPLICATION FILED NOV. 19, I914- 1 ,27 3 ,920. Patented July 30, 1918.

2 SHEETSSHEE T 2.

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a citizen of the United States,

" UNITED STATES PATENT OFFICE.

cam. A. rrans'rmnt, or wauxnoan, runners, ASSIGNOB 'ro rrans'rmnn comrm,

me, or NORTH cmca eo,

ELECTRIC FURNACE.

ILLINOIS, A CORPOBATION OF NEW YORK.

I Patented July so, 1918.

Application filed Novemberw, 1914. Serial No. 872,958.

A. PFANSTIEHL, residing at Waukegan, in the county of Lake and State of Illinois,-have invented certain new and useful Improvements in Electric Furnaces, of which the following is a full, clear, concise, and exact description, reference being Be it known that I, CARL 'had to the accompanying drawings, formin order later in a bell or ing a part of this specification.

My invention relates to. electric furnaces. One particular object of my invention is to provide a furnace adaptable for use in sintering ingots of tungsten metal in the proc- 'ess of producing ductile tungsten. My .improved sintering furnace makes it possible quickly and economically to sinter a tung sten ingot by a single heating operation in a single furnace, and this is accomplished without wasting any portion ofthe ingot under treatment. p

In one of the best processes of the prior art it has been customary to sinter ingots of compressed tungsten powder in two operations; first in a-tube furnacein which a fairly high degree of heat is employed, and bottle in which a heavy current is passed through the tungsten ingot. The-electric current is used in heating the ingot because that is the most feasible way in which to bring it to the requisite high temperature. The bell or bottle is employed an atmosphere of hydrogen, for tungsten when heated to a very high temperature in the air will oxidize rapi 1y. In these sintering furnaces of the prior art the upper end of the ingot is clamped in a water cooled terminal, fixed 'n'position. The lower end of the ingot is clamped in a copper terminal which floats in a bath of mercury, the currentbeing conveyed to or from the lower terminal through the mercury. There is necessarily tween the lower terminal and the mercury,

inorder to convey the heavy current em-'- ployed. The lower terminal is made to float in the mercury in order to permit'the lower terminal to move from' or up or down, to a slight degree, as may be necessary to accommodate. the movements of the lower end of the ingot. The lower or free end of the ingot tends to move up or down due-t0 the expansion or cont'racgive it that the tungsten may be heated in a large surface of contact beside to side,

' tofore tion of the metal when heated and cooled,

and there may be some'sidewise movement due to the warping of the ingot when heated. If the lower terminal were not free to accommodate itself to these movements the ingot would in all likelihood be broken when heated. It is necessary in these furnaces of the prior art to water cool the'mercury bath and bell or bottle which surrounds the mechanism previously described These elaborate devicesand precautions are provided because while it is necessary to heat the ingot to an extremely high temperature, the ingot has very little mechani-- ing to a minimum the strains imposed upon the ingot, it has still been necessary to heat the ingot at a moderate temperature and for a considerable period of time in order to suflicient strength handled in the sintering furnace being described. I Furthermore it'has been above to permit of its to supply hydrogen to theimpossible even with this elaborate furnace.

of the prior art to bring the l'ngot even in its final treatment that at which the tungsten will fuse, because at or extremely near the fusing point the tungsten does not have suflicient strength to support its own weight'or to withstand even the slight strains imposed upon it by; the terminal mechanism ofthe sintering furnace above described.

In these sintering furnaces of the prior art a considerablepart of each end of the tungsten ingot is clamped within the terifninals. The ends of the ingotare not, thereore,

to a temperature close to sult of which the ends of the ingot arenoteffectively sint ered and'must, therefore, be out or broken ofi' and wasted.

Under my improved process as carried out in the sintering furnace hereinafter described in detail, the tungsten bar or ingot under treatment is heated from end to endand to a higher temperature than has here been attained; Furthermore a single treatment in one sintering furnace takes the place of treatment intwo furnaces Jun:

der the prior practice.

. The ingot treated" heated to a high temperature, as a relit) till

7 extends through the b0 Broadly the sintering furnace hereinafter described and claimed comprises a heating chamber within which is disposed a cradle adapted to support an ingot under treatment. The cradle referred to is in the form of a pair of ductile tun sten rods of fibrous.

structure and arrange horizontally. and

parallel with one another,connected in any electric circuit when an ingot supported by the cradle is undergoing treatment.

My improved sintering furnace is more fully set forth in the following detailed description in. which reference is made to the accompanying drawings, in which so Figure 1 1s a longitudinal sectional view of the sintering furnace of my invention,

the electrical connections being diagrammatically illustrated;

Fig. 2 is a fragmentary cross-sectional view taken on the line 22 oi? Fig. 1 and looking in the direction indicated by the arrows;

Fig. 3 is a view taken on the line 33 of Fig. l. and lOOklllg in the direction indicated by the arrows, and

Fig. 4 is a fragmentary sectional view illustrating a slightly modified embodiment of my invention.

Similar reference numerals refer to similar parts throughout the several views.

Referring to the drawings, it will be seen that the sintering furnace of my invention comprises an alumina or alundum tube 10 provided with an outer sheath 11 of steel and constituting the heating chamber of the furnace. The tube 10 and its sheath 11 extend' through and are supported by a box or container 12 which is filled with a quantity of silica sand or other rial 13. A system of pi ing indicated at 28 d; of silica sand 13. Cooling water is supplied to this piping at 29 and flows out'at 30, a valve being provided, as indicated, to regulate the rate at the tube 10 and its "sheath 11.

in each end of the alumina or which heat is withdrawn from Located alundumtube 10 is a brass connector, said brass connectors being illustrated at 14 and 15 respectively. The connector 14 is substantially semi-circular in cross-section and is provided with a substantially lit-shaped passage 16 the-legs cooling illustrated. The right ends refractory mate-' the walls of of which are arrangedto be connected with a suitable source of belzept Water circulating through the mars es energy supply.

The connector 15, like the connector 14. is

substantially semi-circular in cross-section and is provided with a passage 18 through which water ma be circulated to keep the connector 15 sufticiently cool. The connector 15, however, differs from the connector M in that it is provided with a sliding terminal 19 having dove-tailed sliding connection with the connector 15 as is clearly illustrated in Fig. 2. This construction permits the rods 21 to expand and contract with changes of. temperature and without warping. Upon the right end of the sliding terminal 19 (Fig. l) is mounted a connector 20 arranged to be electrically connected with the source of electricity supply.

Formed in the inner end of the brass connector 14 is a pair or apertures into which extend the ends of a pair of parallel horizontal tungsten rods 21 which, as will presently be made apparent, form a cradle ,for the tungsten ingot to be-sintered. Suitable set screws, one of which is illustrated at 22, may be provided to retain the ends of the tungsten rods 21 in the connector It, as of the. tungsten rods 21 (Fig. 1) are fitted. in apertures formed in the left end minal 19, the rods 21 beingsecured in the sliding terminal by suitable set screws 23, as is' most- The rods 21 are'conveniently circular in cross-section and are formed of ductile metallic tungsten wire which has been swaged hammered or drawn to give it a high tensile strength and a fibrous structure. lln order to lend additional support to. the ductile tungsten rods 21 I provide a pair of transverse supporting rods 24 of ductile tungsten which bear in the alumina. or alundum tube 10, as is mose clearly illustrated in Fig. 3. The tungsten rods 24 are, of course, slipped into position before the sheath 11 is placed around the refractory tube 10.

During the sintering operation it is desirable that hydrogen be admitted to the heating chamber, and therefore I provide a hydrogen inlet pipe, illustrated at 25. This hydrogen inlet pipe is arranged to be connected by any suitable means with a source of hydrogen supply. During the sintering .or which is indicated at 27?, these blocks being disposed in the positions shown during the heating operation. The block 27 is desirably provided with an opening at 27 of the sliding ter clearly illustrated in Fig. 2.-

inents, i. e. t indicates that good results can be obtained closed bya mica window 27? through which the heating of the rods and the ingot may be observed. Theblock 27 may conveniently be rovided also with a small pipe 27 throng which the hydrogen may escape from the furnace chamber. The 0 erator ordinarily lights the hydrogen at t e end of the pipe 2 gas ma be indicated. The connector .14 and thesli ing terminal 19 are electrically connected with the terminals of the secondary winding of a suitable alternating current transformer, as illustrated, the primary winding of the transformer being electri cally connected with a generator, as suitable alternating current supply. In the primary circuit is preferably included a regulating. rheostat in order that any desired current may be supplied to the furnace heating ele-. e tungsten rods 21. Experience when each of the supporting and heating rods 21 has a cross-sectional .area substantially one-half that of the ingot to be sin tered; In .sintering' ingots of from i to of an inch square I have found it expedient to employ supporting and heating rods 21 of circular cross-section," approximately of an inch in diameter.

In the use of the sintering furnace of my 'pending application, Serial No. 39,500, filed July 12, 1915, and preferably of square or rectan larcross-section, is disposed upon the ro s 21, as is most clearly illustrated in Figs. 2 and 3. A current of electricity is now passed through the tungsten rods 21,- beating them to iricandescence. Part of the current will bediverted from the tungsten rods and flow through the ingot. The tungsten rods 21, having been swaged, hammered, drawn or otherwise treated to give them a fibrous structure of great strength and rigidity, will not when heated tend to sag to the same extent as will the ingot, the tungsten cross rods 24 coiiperatinlg also to prevent d e. In sintering that thetungsten ingotis heated tofusion by thepassa e of electricity through the members .of t e cradle,

,in order that the flow of the I V ;ithout the cradle members beingheat -ed to such'an extentthat they melt or seriously sag. I attribute this,

however, principally tothe fact that in the process of compression the tungsten ingot, which is made up of finely divided tungsten, a great amount of latent heat isstored in the ingot, which heat manifests itself, in mechanical action when the ingot has been.

raised to sucha temperature as to allow the deformed particles to move upon one an other due to their internal stress. It may parently heats to a higher temperature than the cradleupon which it is supported is due .in part to the rapid dissipation of heat from the members of the cradle into the water cooled terminals at the ends thereof. The Y through the ingot. I' am not certain that either of these explanations is the correct one, but I do know that the construction described herein accomplishes the satisfactory sintering of the ingot without melting the supporting cradle. V

In Fig. 4 I have illustrated in fragmentary section a slightly modified embodiment of my invention wherein an alumina or alundum tube is illustrated at 50. The re-- fractory tube 50 is not provided. with a steel sheath as is the tube 10 illustrated in Fig. 1, and therefore I find itdesirable to furnace illustrated in Fig. {1 have been given the same reference numerals as the corresponding parts illustrated in Figs. 1, 2 and 3.

Before hydrogen is'admitted to the furnace heating chamber as previously described, it is thoroughly purified byone of the processes commonlyemployed by persons skilled in the art to which my invention appertains. I do not deem it necessary to illustrate or describe in the'present application the apparatus or process whereby commercial hydrogen is purified to adapt it for use in my improved furnace.

I have illustratedthe furnace'of my inv'ention provided with but a single pair of cradle rods 21. Itwill be apparent at additional rods may be supplied. Thus three parallel rods will support two ingots and four rods will support "three ingots, et

cetera. The number of supporting rods and their cross-sectional shape may be ,varied to suit the particular purposes to which the furnace is to be applied.

Having described one embodiment of my '75 'be that the fact that the tungsten ingot ap-- invention in some detail it will heap arent this reason be heated to a higher tempera ture than would be feasible in the furnaces of the prior art; second, the furnace is extremel simple in its construction and in operation; third, the whole length of the ingot is heated to the high temperature reuired-for successful sintering, and there is, therefore, no waste; fourth, it is possibleto observe closely what is going on within the furnace at all times; and fifth, the heating and cooling of the cradle and the ingot may be closely regulated and controlled.

Having now described my invention, what 1 claim as new and desire to secum' hy, Lettors Patent oi the United l$*"-i"f 1. An electric furnace sintering irrg'ots oi compressed metallic tungsten powder at or near its iusmg-temperature comprising in combination a heatingcha nher of refractory material, a pair. of terminal blocks, one at either end of said chamber, a cradle of ductile metallic tungsten of tihrous structure extending horizontally from one terminal block to the other and adapted to support an, ingot of compressed tungsten powder in intimate contact with the cradle throughout the length of the ingot, and. means for passingthrough said cradle from terminal block to terminal block a current of electricity suiiicient to raise the temperature of the cradle substantially to the fusing point of metallic tungsten.

2. An electric furnaceior sintering; ingots of compressed metallic tungsten powder at or near its fusing temperature comprisingin combination a heating chamber of refractory material, a air of terminal blocks, one at either end 0 said chamber, a cradle of ductile metallic tungsten of fibrous structure extending horizontally from one terminal block to the other and adapted to support an ingot of compressed tungsten owder in intimate contact with the cradle throughout the length of the ingot, means for passing through said cradle from terminalhlocl: to terminal block a current of electricity Suficient to raise the temperature oi the cradle substantially to the fusing point or" metallic tungsten, and' reg'ulable means for cooling the walls of said heating chamber.

3.1% furnace of the class described comprising a cradle .forinedby a pair of parallel rods arranged to support in electric contact therewith. a conducting ingot to be sintered, and, means for passing an electric,

current through said cradle and ingot to heat the cradle and sinter an ingot carried thereby; Y i

d. A furnace of the class described comrising a cradle formed by a pair of paralelrods oi ductile tungsten of fibrous struceither. end of sai tarmac ture adapted tosupport in electric contact therewith an ingot to be sintered, and means for passing an electric current through the cradle and ingot to heat the cradle and sinter an ingot carried thereby.

5. A furnace of the class described comprising a heating chamber, a cradle Within said heating chamber, said cradle comprising a pair of parallel rods of ductile metallic tungsten of fibrous structure arranged to support an ingot of com ressed powdered tungsten to be sintere' and means for connecting said rods with a source of electric energy supply.

6., A furnace of the-class described comprising a heating chamber, a cradle within the heating chamber, said cradle comprising a air of arallel rods arraneed to su ort itor connecting, said rods with a source of electric'energy supply.

7, A furnace oi the class described contprising a heating chamber, a pair of terminals arranged to be connected with a source of electricity supply, and a pair of horizontal parallel rods oil ductile tungsten inter posed between said terminals and constituting a cradle for an ingot to be sir red,

8. A furnace of the class descrioed comprising a heating chamber, a pair of terminals disposed one at each end oil the heating chamber, said terminals arranged to be connected with a source of electricity supply, a pair of rods interposed between said term-inals constituting a cradle to support an n got tolbe sintered, and means for rnaintain ing an atmosphere of hydrogen within said heating chamberduring the heating operation. f

' 9; A furnace of the classdescribed comprising a heatin chamber, terminals at heatingchamber, means .aconducting ingot to be sintered, and means ill)- for passingcooling water through said terminals, a tungsten cradle interposed between said terminals, said cradle -arraruged to support an ingot to be 'sintere'd, and means for connecting-said terminals with a source of electricity supply 3 10. A furnace of the class described comprising a refractory tube constitutinga heatmg chamber, a pair of terminals disposed within the refractory tube, a cradle of due tile tungsten interposed between said terminals, means for maintaining an atmosphere of hydrogen within the heating chamber, and means for connecting said terminals with a source of electricity supply.

- 11., A furnace of the class describedcomprising in combination a refractory tube constituting a heating chamber, a air of terminals one at each end of-the re rectory tube," meansior passing cooling water, through each, of said terminals, a paircf rods of ductile metallic tungsten of fibrous structure interposed betweensaid terminals,

said rods constituting a cradle to support an ingot to be sintered, means for maintaining an atmosphere of hydrogen Within the heating chamber during the sintering operation, and means for connecting said terminals with a source of electricity supply.

In witness whereof I have hereunto sub- CARL A. PFANSTIEHL.

Witnesses:

H. A. NEIBURGER, ALBIN C. AHLBERG.

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