US2117913A - Electric furnace - Google Patents

Description

May 17, 1938. G. ssn.

ELECTRIC FURNACE y Original Filed Ilarch 18, 1936 6 Sheets-Sheet l FN NN OM Nh Smxntor t G//f/Pr T "ST/L I Y Y w a g May 17, 1938. G. E. sElL 2,117,913

ELECTRIC FURNACE Original Filed March 18, 1936 6 Sheets-Sheet 2 ln n) Srwentor (Itfomeg May 17,v 1938.v G. E. sElL 2,117,913

ELECTRIC FURNACE Original Filed lax-ch 18, 1936 6 Sheets-Sheet 3 (Ittorneg May 17, 1938. G. E. SEH.

ELECTRIC FURNACE Original Filed llrch 18, 1936 6 SheetsfSheet 4 I r' l. ....J

(Ittomeg May 17, 1938 G. E SEH. 2,117,913

ELECTRIC FURNACE original tiled uren 1a, 1936 e sheets-sheet 5 May 17, 1938. G. E seu. 2,117,913:

' RLBc'rnIc FURNACE Original Filed laren 18, 1956 6 Sheets-Sheet 6 n "new". "'o o' nventar 'G/ifff i sfu Clttorneg lsatcnted May 17, 1938 UNITED STATES PATENT OFFICE assignments, to Builalo Electric Furnace Corporation, Buffalo, N. Y., a corporation of New York Original application March 18, 1936, Serial No. 69,450. Divided and this application August 21, 1937, Serial No. 180,194

4 Claims.

This `patent matures from a patent application carved from my parent patent application Serial No. 69,450,1iled March 18, 1936; and while the specification of that patent application is duplicated herein, it is thought that a reader hereof will be helped to a quicker understanding of the invention claimed herein as compared to the invention claimed in the parent case, by the following remarks that are in the nature of a prologue:

The invention of said parent patent applica- -tion was described, for the purpose of illustration, as an electric furnace having substantially horizontal rotatable hollow electrodes, through the bores of which were fed cores of starting materials convertible during their passage through the arc-heated zone of the electrodes into a metal refining reagent characterized by comprising a metal having a metal oxide in solution in the metal.

It became apparent during the time that said parent patent application was being prosecuted, that there was disclosed therein a multiplicity of inventions. The ilrst invention related to mechanism for supplying and feeding the cores to the hollow electrodes; whereas another invention related to a new type of electric furnace with particular reference to means for controlling the rate of feed of the cores in accordance with the speed of the chemical reaction taking place within the electrodes.

The present case is directed to the latter invention.

This finishes the prologue, so there now follows the main body of the specification copied from said parent patent application.

This present invention relates to electric furnaces of the type equipped with one or more hollow electrodes through which an loxidizing reagent for the material to be treated in the furnace is fed thereto by being impelled through the bore of the hollow electrode in the form of briquettes, or more often in the form of cylindrical cores, and relates more particularly to an improved conveying and propelling means for positively feeding the cylindrical cores through the bores of the hollow electrode.

In an electric furnace with which this present yinvention is adapted to cooperate, there is carried out the refining of ferro-alloys or other alloys and especially alloys containing chromium, and wherein the refining of the alloys is carried out by forming in a heated zone in the hollow electrode, under reducing conditions, a highly concentrated oxidizing reagent comprising essentiaily a reduced metal carrying therein a metal oxide. Suchr a reagent, when in liquefied condition and mixed with a molten bath of a metal mixture to be refined, exerts its oxidizing action on oxidizable impurities in the bath, such as carbon, thereby to reduce the content thereof in the bath. Since there is effected in the heated zone of the electrode a liquefying of the refining materials, fed thereto in core form, the speed of the cores to and through the bore of the electrode must be carefully controlled, as well as the positiveness of the torce used to impel the cores fed thereto and therethrough.

It is an object of my present invention to provide for such furnaces simple, eifective and dependable mechanisms for containing a supply ci? cores; for discharging cores from such source of supply in an orderly manner as they are required, and delivering the same to a positive feeding means; to a means for receiving the cores and positively feeding the same to and through the bore of the electrode in a continuous stream as required, and at a rate of speed which is carefully controllable in accordance with the speed of the reducing process being carried out within the furnace; and particularly to a feeding means for the cores which will permit relative movement of the feeding means with respect to the cores should the cores be stopped in their movement through the electrodes.

Other objects are that the assembly of the various instrumentalities for carrying out the above objects shall have proper cooperating relationship; shall have provision to allow for variations in the dimensions of the individual cores; and shall permit of ready access to all of the operating parts, in case of need. And a still further object is that said instrumentalities shall carri! out adequately,r the functions for which they were designed.

For the realization of these objects, the inven tion revolves about the various components oi core reservoir, discharging, conveying and feeding means for an electric furnace of the hollow electrode type wherein the hollow electrode thereof is both rotatable and reciprocable. The manner of carrying out the invention generally is to mount the hollow eiectrode on an automatically reoiprocable carriage provided also with means for rotating the electrode. A container or reservoir for a supply of the cores is provided and equipped with a discharging mechanism arranged to prevent jamming of the cores in the reservoir, or as they are discharged therefrom into a conveying mechanism.

The conveying mechanism coacts with a core IFeeding mechanism and delivers thereto a pluoi cores in succession, and arranged in axial alignment, and said core feeding mechanism subjects each core as received to a gripping or pinching action which prevents relative movenient oi the cores with respect to the feeding mechanism or to each other, and positively prosuch cores in succession into the bore of e electrode with the operative force necessary to positively orosei the saine through the bore. These various mechanisms derive their motivatif .1 er `from theirnotor or motors used 'for ocotlng the electrode supporting carriage g the electrode.

ly, with these ond other objects, as or advantage, one embodiment of invention will be hereinafter described for ative purposes, because obviously the in- ;lcn capable oi e, number oi embodiments. forni of invention chosen be described 'iustrated in the eccomponylng drawings in which:

l is e. side elevotion, partly in section, of fornace cheminer equipped with dlometrically/ ori/posed hollow electrodes, end with my present invention shown interposed between the core or reservoir .and the hollow electrodes; 2 a partial view oi l;

3 is o, side eievetion, inslgeleton form. ol the mlvirig mechanism "'or the material chsrgl devices, and the rototlng lor the hollow electrodes;

is pion view oi instrumentalities own in lillg. 3;

Fig. 5 is a section, teiten on the line d-l of lig. d is elevation, on an enlarged scale, oi the right hand end of? l, showing the core in elevation, and the core receiving conveyor at the discharge end thereof;

Fig. 2 is an end view oi liig. d;

Fig. 8 is a side elevation, on an enlarged scale, or the positive feeding ineens for the cores, ond located between the discharge end, of the core conveyor and the entrance end of the hollow electrode;

lig. 9 is an end elevation of Fig. ti;

Fig. 10 is a plan View of 9, and

Fig. l1 is a detail illustrating the construction oi the conveyor belt employed in structure shown in Figs. 8 and 9.

Referring' to the drawings, and particularly to Fig. l, there is shown a type of electric :furnace to which the present invention hss been applled. Such furnace comprises essentially a chamber I0, into which, and from the opposite sides thereof, extend tubular or hollow open ended electrodes Il and I2. The chamberl is usually a metal casing or shell lined with a. suitable relractory material Il, and supported on suitable base members, such as the base member I6. Within the chamber I0 is a hearth Il arranged 'to receive a bath oi metal I8 normally covered with a layer of slag I9. Oxidizing reagent material 20, in liquid form, drops onto the layer of slag I8 from hollow electrodes through the arc 2I formed in the gap 22 between the spaced ends of the electrodes II and I2. The reagent material is obtained from cores fed through the hollow electrodes I I and I2 and reduced to liquid form in the heated zone of the electrodes.

The reagent forming material 20, in the form 0I cores or briquettes, as will be apparent from an, inspection of Fig. 7, is fed into the entrance end of the hollow electrodes Il and I2, or the end remote from the gap 22, and is liquefied within the electrode. Due to the great heat generated by the arc 2I, and the consequent liqueiaction oi" the reagent material in the electrode, there is a tendency toward derangement of the normal ond continuous movement ol the cores or briquettes 20 through the bore or the electrodes il and l2 and the flow of liqueiied reagent therefrom. This invention therefore provides for the positive and uninterrupted movement of cores or briquettes through the bore ol the elec trodes so long as normal conditions that may exist therein both for the retardation ii not stoppage of that movement during abnormal conditions.

Esch electrode il and it has its own independent operating means for rotating the some, moving the same axially to compensate :for the inevitable erosion due to the maintenance oi the arc 2i, and means for receiving cores or briquettes from a magazine or reservoir and positively icedu ing the same through the bore of the electrode. llhese operating means are identical in charac ter and construction and therefore a description of but one necessary. Such independent oper ating may be so controlled as to operate in synchronism with each other, or may be interconnected, either by mechanical or electrical means,

i so as to operate as a unit. Also, each electrode is preierobly slightly inclined downwardly toward the furnace, as clearly shown in Fig. 1, the de of inclination trom the horizontal being approximately 3 degrees, in the preferred form oi constmctlon.

Each operating unit is mounted on a iramcwork or carriage 23 provided with wheels 23a which troclr. on spaced channel irons 2i and 25, and which constrain the carriage 23 to move toward and from the furnace i0 in a iixed path whereby the length of the arc may be varied as desired. Such channel irons 24 and 25 are supported, relative to the furnace Ill, on a iframework 2t* of structural shapes.

Mounted on a frame H8, suspended from the carriage 23, is a motor Il9. This motor has a drive shalt lill which extends outwardly from each end of the motor, and on each end is secured a pinion I2I. Secured to the channels 24 and 25, and extending for a distance commensurate with the desired length of travel of the carriage 23, are racks i522, with which the pinions IZI mesh. The motor H9, being fixed to the carriage 23, the rotation of the shaft 20, of the motor will cause a movement of the carriage 23, along the channels 24 and 25, toward and from the furnace IIB, it being assumed that the motor H9, is of the reversible type, and that control means is provided, not only for accomplishing this result, 'out also for controlling the speed of travel of the carriage 23, in accordance with the rate of erosion of the electrode I l or due to the maintenance of the desired extent of arc 2l.

' 'Ihe framework or carriage 23 is provided at the end adjacent the furnace I0, with spaced bearings 2l, in which is rotatably mounted a sleeve 28. This sleeve s provided at one end with a flange 29, for removable attachment to the entrance end of the hollow electrode II, and at the other end with a gear 30. Attached to the sleeve 28, is a. slip ring 3|, with which engages a brush 32, that is connected to a sultable source of power for supplying power or current to the electrode II. The bearings 21, and the Slip ring 3|, are so constructed as to permit lli shaft |04, brings the handle |04 to the full line position shown in Fig. 8, where it will be noted that the center of the eccentric portion of the shaft |04 is above the center of rotation of such shaft. The arms I0| are therefore locked in engaging position with shaft 88.

Attached to one end of the upright 04 is a casing IIB in which is a bearing IIS, in which turns the shaft 88. Secured to the shaft 04, within the casing IIB, is a worm wheel |20. Formed in the casing IIB are bearings I 2| in which is rotatably mounted one end of a shaft |22, this shaft being connected by the insulating coupling |23, tok the shaft 14, driven from the transmission 30. On the shaft |22, between the bearings I2i, is secured a worm |24 which meshes with and drives the worm wheel |20, and therefore the shaft 39.

Secured to the other end of the shaft 80 is a gear |25, which meshes with and drives a similar gear |25, secured to the shaft 95. The gears |25 and |20 are housed in a casing |21, secured to the upright 04. v

By means of the gears |25 and |26 and the worm and worm wheel |24 and |20 respectively, opposingk reaches of the conveyor belts 9i and 9e are driven in the same direction at the same speed, and in timed relation to the speed of the conveyor belt 68, by the power transmitted through the transmission 38.

Should it be desired to obtain access to conveyor 93, or to the entrance end of .the e trode II, or to any structure interposed betwe thesuperposed conveyors 93 and 99 and the e trance end of the electrode I, the si. moved in a counter-clockwise or upw tion, as viewed in Fig. 8, to relieve the the spring |08. This permits the arms released from the shaft 86, whereupon 96 may be rotated about the shaft 95 into the dash position shown in Fig. lowing access to the conveyor 93, or to parts of the mechanism.

Preferably the entrance end of the bore ci electrode il is spaced apart from the omino" end of the superposed conveyors 03 im. bridge the gap thus formed there :is proie-r provided a guide and support for the cores their passage from' the conveyors 93 and to the bore of the electrodes II. Such guide a ff' support is composed of some heat resistance terial like Alberene and is made in 'two pai a lower part I and an upper part i i2. i pivotally mounted on opposite sides of the lov part II I rest in vertical grooves in the sides the upper part H2, and are threaded to receive Wing nuts |I4 for maintaining the parte :in open ative relation with each other. Acting as a unit, the parts III and H2 are provided with here I I5 in alignment with the bore of the electrode i This bore H5 is chamfered at the end adjacent the conveyors 93 and 99, as indicated by reference niuneral I I6. The upper part is provid.n

' ed with a handle II'I.

With the apparatus constructed and arranged as above described,l and assuming the bath I, o1 molten metal, to be refined, to be located with- -in the furnace I0 and covered with a layer of source to the electrodes through the slip ring 3|,

gff'and brush 32, to the electrodes II and I2, to form the arc 2|, in the gap 22, between adjacent ends of such electrodes.

A supply of cores 20 is placed in the magazine 4I and power is then turned into the motor 3l, and also into the motor I I9. The speed of the Q; motor H3, is controlled to provide for the proper reciprocating longitudinal movement of the ele-ew trodes II and IE, to maintain the proper width of gap 22, therebetween. The speed of titre motor 3i, is controlled so as to maintain the proper slow' speed of rotation o the electrodes and also the proper rate of deiivery oi the cores 2li, t magazine 43, into and through the bore or the electrodes to bring the same into the iniiuen of the heat generated by the are 2|, wherein W both chemical and physicai action they are ce Y verted into an active oxidimng agent in form, and drop 'the slag bed I9, to v instrumentaiities on the carriage 2S, and op erated by the motor til, is auch that all auch in.m atrumentaiities operate in synchronism withd each other and at the proper speeds, such spea being predetermined in accordance with the spseg of iiquefaction of the cores in the arc'ti.

The cores 20, delivered in groups from t 'Y megamne 43, at time mism operated veg/"or t, and fr to the posi-tive atus is continuous ani erruptien until the ca some mechanic the he dot ma d i l n Eig. ii.

eiectric turn ce tif appiications ow Fatent eagent forming cited form.

l"uses a zone of f to a suilieientiy ii, reducing reaction reacts/tnt materiais in tine ci. e or burden in the eiectrode as Well as iirst a iiqueiying and a dissolving action so that there issues from. the enti of the electrodes a iiquid oxidizing reagent comprising a iitginid. re2 duced `metal having a metai-oxide carried thereby and therein. This .reagent formed in the elecd 'trede drops onto the molten metal bath on the furnace hearth and. through the slag thereon, by virtue of which the impurities or undesirable ox idizable constituents of the bath of metal on the hearth which is to be refined, are oxidized and removed therefrom.

Said oxidizing reagent is produced by having lili the cores fed to the electrode bores, made up of carefully proportioned starting materials of a metal oxide, insumcient carbon to reduce all of the metal oxide to metal, and a corrective. is cores approach the heated zone of the electrode,

lchemical reaction takes place between some or the metal oxide and the carbon which yields a reduced metal and carbon monoxide, leaving un reacted some met-al oxide and the corrective. The reduced metal becomes molten and would flow out from the open end of the electrode bore were it not for the corrective which being rionmobile the inciting point oi' the metal prevents it. ".lFoe molten metal is thus retained in the heated none until it attains a superlieat of some /idlio lil. above its melting point whereat it ex liiibil-s7 deilnite solvent properties for the unren duced metal oxide present, which goes into solo@ tion in the metal at those temperatures. At about this temperature the corrective becomes mobile or eren )fluid and permits the newly med oxidizing agent low from elec trow e. core ree-ding meansbelts S33 and liti-must feed the cores of starting material in oereuily timed relation 'to these chemical and physical actions otherwise these actions will not all have been completed before the material is forced from the electrode bore Soii there be slowing' down or retardation oi these actions, particularly the chemical reaction, the fe^ lng oi new cores to that zone must be cornespondingly lessened. This is done automatically due to slippage oi' the belts il@ and @ci past the cores therebetween to leave the cores stationary, as heretofore described. But as soon as any such abnormal vcondition passes, as indicated by a lessening ci the resistance to forward progress oi the cores, the belts grip the cores once more and iecontinue or restore their rate of feeding.

lFor preventing localization or erosion at the are ends or the electrodes, they are caused to be rotated during operation oi the furnace, and in order to control the desired length of the are (and thereby the heat generated by the arc) the electrodes are reciprocated toward and away from each other. For this double purpose, each electrode is mounted on a reciprocaiole carriage which is also equipped with driven mechanism forrotating the electrode. Also mounted on the propelled carriage and reciprocating therewith as a unit, are the various components of this invention, including the hollow electrode, means for rotating it, the core magazine, the core conveyor, the core discharger, and the core feeding means, all heretofore described both as to structure and operation.

What is claimed is:

l. An electric furnace having a pair of oppositely directed electrodes of which at least one is a rotatable, substantially horizontal, hollow electrede wherein chemical reaction takes place beaimais tween constituents of the electrode burden, which comprises a reservoir for cores of starting material adapted to provide the electrode burden; LOesitlve means :for feeding cores at a predetermined normal rate from lsaid reservoir to and into the bore oi said electrode in a contiguous sequence; means for automatically varying said rate of the feeding of the cores into the hollow electrode below and baci: to normal; a reciprocable carriage on which are mounted said hollow electrode, said reservoir, said feeding means and said controlling rieans; and means for recipron eating said carriage for thereby controlling the speed of the el cai reaction taking place with in the electrode b re.

2. fm electric rurriaee having a pair of opposltely directed electrodes of which at least one i a rotatable, substantially horizontal, hollow electrode wherein the electrode burden is treated, which com 'ses a reservoir for cores ci starting material adapted 'to provide the electrode burden; for lfeeding cores from said reservoir to and into the bore oi said hollow electrode in a contiguous sequence; and means for changing rate oi feed said cores without changing the speed oi operation oi? said feeding means automatically operable upon variation troni normal oi' resistance encountered by the cores entering said electrode be I.

in electric furnace having a pair of oppositely directed electrodes o which at least one is a rotatable, substantially horizontal, hollow electrede wherein is treated the electrode burden, which com' "ises a reservoir for cores of starting material adapted to provide the electrode burden; substantially uniformly speeded means for feeding cores from said reservoir to and into the bore oi said hollow electrode in a contiguous sequence against normal resistance; and means for varying the rate oi feed oi the cores automatically operable to lessen the rate due to greater than normal resistance encountered by the cores and to restore the rate upon return to normal of that resistance.

d. An electric furnace having a pair of oppo sitely directed electrodes of which at least one is a rotatable, substantially,horizontal, hollow electrode wherein the electrode burden is treated, which comprises a reservoir for cores of starting material adapted to provide the electrode burden; a substantially uniformly speeded pair of coacting conveyors for feeding cores from said reservoir to and into the bore of said hollow electrode against normal resistance; and means for render' ing said speeded conveyors inoperative to feed said cores against greater than normal resistance and for returning said conveyors to operative core feeding upon return of such resistance to normal.

GILBERT E. SEIL.

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