US1735419A - Electric furnace - Google Patents

Description

5 Sheets-Sheet l INVENIQ F. w. BROOKE ELECTRIC FURNACE Filed June 1928 hi Q wfiwwwfiir F/ lnlllll IN i 1 1 l I l i 1|| Nov. 12, 1929.

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Patented Nov. 12,

um'raosTArEs I PATENT OFFICE] FRANK W. BROOKE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WILLIAM SWIN- nn'nn a nao'rnnns, snvmm, I Y

' nnnornro Application filed June 2,

The-present invention relates broadly to thwart of electric furnaces, and more particularly to electric arc melting furnaces.

It has heretofore been customary in the art to which this invention relates'to construct electric arc melting furnaces in such manner as to ,permit'tilting thereof for uroses' of .slagging and discharging. ghch urnaces are usually of substantially circular cross section, with either one or a plurality of electrodes. As the diameter of a circular furnace increases, the'difiiculties of operation -corres ondingly increase, not only with respect to t e proper supporting of the '15 electrodes, but also with respect to the sup- 1y to the electrodes of the current required.

n order to accommodate the tilting action, it has been necessary to support the electrodes. from one side of the furnace, and to supply the current through conductors supported on the same side and extending in proximity to the electrode supporting mechanism. The conductor construction has necessarily been such as to permit either the tilting with the electrodes in position, or the removal of the electrodes for tilting purposes, a considerable amount of slack having heretofore been required in either case.

This slack has usually assumed the form of a loop, and with extremely heavy currents of the character now encountered in the art, have presented a great many difliculties where such loops are used not only with respect to resistance losses, but by reason of distortion and weaving of the conductors under the heavy current surges to which they were subjected, such surges frequently varying from 0 to 50,000 amperes.

. Such a circular shape does not conveniently lend itself to use as a stationary furnace due to the difliculties encountered with the length of therabbles required for slagging and operating purposes, as well as by reason of the extremely detrimental action on the refractory walls resulting from any effort to effect melting of the fringes of the charge. This is unavoidable due to the fact that each of the electrodes is effective radially, and in order to effect melting of the fringes intermediate any two electrodes, the length of the OE PI'ITSPURGH, PENNSYLVANIA, A.GORPORATION OF PENN- FURNACE 1928. Serial N'o. 282,350.

radii throu h Whichthe electrodes act must be increase to such an extent as to project into the refractory itself.

The present invention contemplates an improved furnace shape and electrode arrangement enabling not only more uniform meltmg of the charge, but also overcoming the difficulties with respect to slagging and operating.

The present invention also contemplates a furnace construction which adapts itself either to use as a tilting furnace without any of the difficulties heretofore encountered, or which adapts itself to use as a stationary furnace with improved operating conditions.

In accordance with the present invention, there is preferably a division of the electrodes into sets, each ofwhich sets is supplied with current from its adjacent end of the furnace, thereby enabling the use of conductors havinga minimum length, the conductors in any case projecting at an angle to the direction of projection of the electrode supporting means whereby the inductive action therebetween is likewise reduced to a minimum.

It is well known to those skilled in the art that the reactance or impedance is a function of the area enclosed by the conductors of any one completed circuit. In accordance with the present invention there is provided an improved arrangement of conductors such that the area enclosed by any one completed circuit is materially reduced, thereby correspondingly reducing the reactance or impedance losses, Such an improved arran ement of conductors and electrodes is pre erably combined with a system of bracing such that a non-inductive circuit is formed thereby, the losses being further reduced in this manner.

In the accompanying drawings, I have shown more or less diagrammatically, a preferred embodiment of the present invention, it being understood that changes in the construction and arrangement of the parts may be made without departing either from the spirit of the invention or the scope of my broader claims.

In the drawings Figure 1 is a top plan view of a furnace constructed in accordance with my invention,

certain of the electrodes and electrode supporting and conducting means-being removed from a portion thereof.

Figure 2 is a partial elevational and sectional View, along the line II-II of Figure 1 Figure 3 is a transverse sectional view on the line IIIIII of Fig. 2, certain of the parts being broken away for sake of clearness;

Figure 4 is a transverse sectional view, on an enlarged scale, on the line IVIV of Fig. 3, looking in the direction of the arrows;

Figure 5 is a side elevational view of the construction illustrated in Fig. 4;

Figure 6 is a detail side elevational view, on an enlarged scale, a portion of the jib construction illustrating the insulation between the same and the mast; 1

Figure 7 is a view, similar to Fig. 3, illustrating a modified embodiment of the invention.

In carryin out the present invention, there may be provlded a furnace 2, preferably of materially greater length than width, thereby providing a charge receiving hearth 3, of generally similar contour.

The furnace may be strengthened and supported by any desired arrangement of buckstays 4, similar for example, to those utilized in the open hearth practice. These buckstays may be connected transversely and longitudinally of the furnace by bracing means of novel construction, providing non-inductive or non-magnetic paths. As illustrated more particularly in Fig. 1 of the drawings, desirable results in this respect may be obtained by providing each of the bracing means with suitable turn buckles 5, cooperating with a central or intermediate section 6, of non-magnetic material, preferably of high chromium or high magnanese steel, although any material having the required tensile strength may be employed. In this manner each of the bracing means provides an interrupted path for induced current flow, thereby cutting down any inductive losses to a minimum.

Located on one side of the furnace, preferably along one of its major sides, is a series of masts 7, with which cooperate jibs including electrode supporting arms 8, and carriages 9, the construction being such as to permit the jibs to travel vertically along the masts as required in order to properly position the electrode within the furnace, or to effect the removal thereof from the furnace.

Carried by each of the jibs is an electrode clamp 10 for cooperation with an electrode 11.

With a construction of the character herein illustrated, each of the jibs has a minimum overall length, with the length of all of the jibs the same, thereby disposing the electrodes in a line preferably substantially coinciding with the median longitudinal axis of the hearth. In this manner, all of the electrodes may be positioned at a uniform ductors leading therefrom. This construction lends itself to the provision of transformer bankslocatedadjacentoppositeendsofthefurnace, with conductors 13leading therefrom to the individual electrodes of a given set, the conductors extending substantially normally to the direction of extension of the jibs. This arrangement is extremely desirable in that it disposes the conductors out of proximity to the j ibs and thereby not only reduces induced current flow in the jibs, but also cuts down eddy current losses usually desig nated as I R losses, since it increases the distance between the metal of the jib and the conductors.

Inasmuch as such jibs are invariably constructed of ferrous material, the I R losses in cases where the conductors extend in proximity and parallel to them, are large. Not only. are such large losses avoided with the construction herein provided, but the resulting heating effect on the jibs is correspondingly decreased, with the result that it becomes easier to effect the desired lubrication of the parts and to maintain the desired insulation 14 between the different jibs and their respective masts, as indicated in Figure 6.

The provision of center sections 6, of nonmagnetic material in proximity to the electrodes, cooperates with the conductor arrangement referred to for cutting down I R losses which would result from the use of magnetic braces in proximity to the electrodes.

In order to cut down to a minimum the area embraced by the conductors constituting any completed circuit, I preferably provide an improved conductor construction and arrangement such that the conductors at one end always operate about a substantially fixed point, the amount of movement at the opposite end being determined by the travel of the electrodes. In obtaining the desired results in this respect, each transformer T, as illustrated in Figure 2, is connected to a conductor terminal 15, through a series of short flexible conductors 16, each terminal 15 being supported on a link 17, having a pivotal connection 18 with the terminal, and a pivotal support 19.

Cooperating with each terminal 15, and constituting each of the conductors 13, is a pair of water cooled conductors, preferably in the form of .tubes or pipes, cooperating at their opposite ends with a terminal 20, as illustrated in Figures 4 and 5. This terminal is constructed to receive a plurality of short flexible conductors 21, which are in turn connected to one of the electrode clamps 10. In

a order to relieve all mechanical loads from the conductors 21, each terminal 20 preferably has a pivotal connection 22 with the electrode clamp thereby permitting the desired relative ity of shic ds or plates 23, suitably disposed with respect to the conductors. The mechanical load at the opposite ends of the conductors 13 is carried by the links 17, so that the conductors and their associated connections have imposed thereon only the duty of carrying the current to the electrodes.

The pivotal connections 18 for the conductors define substantially fixed points about which the conductors move in accordance with the travel of the electrodes, thus resulting in an enclosed area for any completed circuit which is of substantially triangular shape, and necessarily only approximately one-half as large as would result from a substantially uniform movement of both ends of the conductors.

By dividing the electrodes into sets, it is also possible to maintain the overall length of any of the conductors 13 relatively short, as compared to that required by the use of a single bank of transformers located at one end of the furnace and connected to all of the electrodes.

' Although the furnace itself may be of any preferred construction with respect to charg in doors and slagging openings, I preferab y provide it on one side with three or more charging doors 24, and on the opposite side with a pair of slagging openings 25, the slagging openings being disposed symmetrically on opposite sides of a tapping opening 26. Due to this arrangement, the length of the rabbles required for slagging or operating purposes may be kept at a minimum, it being only necessary that the rabbles shall have a length substantially equal to the width of the furnace plus the additional amount required for their proper manipulation.

It will be further apparent to those skilled in the art that a furnace of the construction herein illustrated is adapted to be supported for tilting about its longitudinal axis, if desired, without the difficulties encountered in attempting to tilta furnace of corresponding capacity and of circular contour. Such an arrangement is illustrated in transverse section in Figure 7 of the drawings in which the furnace is shown as supported on cradles or rockers 27, cooperating with anti-friction supporting rollers 28. The desired tilting movement of the furnace. maybe obtained by means of a link or links 29, operated in any desired manner; The furnace itself, where of the tilting type, will preferably be provided with a discharge spout 30 projecting therefrom in order to Obtain a controlled path of discharge of the furnace contents.

Certain advantages of, the present invention arise from the provision of conductors and electrode supports contructed and disposed to reduce to a minimum the losses due to inductance and eddy currents either when used alone or in combination with a bracing system of such nature as to further cut down losses due to induced currents, the combination of the two resulting in a material saving in both respects and also in the maintenance of a uniform tension in the bracing means minimizing damage to the furnace such as would result from undue expansion and contraction of the bracing means.-

By a reduction in losses of the character herein referred to there is maintained a condition in which is brought more nearly to unity, thus insuring a power factor having desirable attributes with respect to open ating cost.

- Further advantages arise from the arrangement of electrodes insuring a greater uniformity of melting throughout the entire charge with a minimum deterioration of the refractory of the furnace.

' While advantages of the character referred to herein are obtained with a construction of the character described, it will be apparent that certain changes in the construction, arrangement and relation of the parts may be made in accordance with the spirit of this invention without departing from the scope of protection afforded by the claims.

I claim 2-- 1. in an electric furnace, a plurality of electrodes, supporting means for said electrodes located on one side of the furnace, and current supply means for said electrodes located on another side of said furnace.

2. In an electric furnace, a plurality of electrodes, supporting means for said electrodes extending across the furnace in one direction and substantially parallelly extended conductors for said electrodes extendmeans for one set of electrodes located at one end of the furnace, and current supply means for the other-set of electrodes located at the opposite end of the furnace.

5. In an electric furnace, a hearth of greater length than width, a plurality of electrodes disposed lengthwise of said furnace, and divided into sets, current supply means for one set of electrodes located at one end of the furnace, and current supply means for the other set of electrodes located at the opposite end of the furnace, there being sup porting means for the electrodes adjacent one side of the furnace.

6. In an electric furnace, a hearth of greater length than width, a plurality of electrodes disposed lengthwise of said furnace, and divided into sets, current supply means for one set of electrodes located at one end of the furnace, and current supply means for the other set of electrodes located at the opposite end of the furnace, said furnace being constructed for tilting movement about its major axis.

7. 'In an electric furnace, a hearth of greater length than width, a plurality of electrodes disposed lengthwise of said furnace and divided into sets, current supply means for one set of electrodes located at one end of the furnace, and current supply means for the other set of electrodes located atthe opposite end of the furnace, there being supporting means for the electrodes adjacent one side of the furnace, said furnace being constructed for tilting movement about its major axis.

8. In an electric furnace, an electrode, supporting means for said electrode extending across the furnace in one direction, and a conductor for said electrode extending across the furnace in another direction and substantially normal to said supporting means.

9. In an electric furnace, an electrode, supporting means for said electrode extending across the furnace in one direction, and a conductor for said electrode extending across the furnace in another direction, said conductor being mounted for movement at one end about a substantially fixed point.

10. In an electric furnace, an electrode, supporting means for said electrode extending across the furnace in one direction, and a conductor for said electrode extending across the furnace'in another direction and substantially normal to said supporting means, said conductor being mounted for movement at one end about a substantially fixed point.

11. Current supply means for electrodes, comprising a conductor having flexible connections adjacent the opposite ends thereof, and separate connections cooperating with the opposite ends for carrying the mechanical loads incident thereto.

12. In an electric furnace, an electrode, means for effectingtravel thereof, a conductor cooperating with said electrode, and a pivotal mounting forthe end of said conductor remote from the electrode, shiftable under the movement of the electrode,

13. In an electric furnace, an electrode,

my hand,

FRANK W. BROOKE.

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