US3385987A - Electrode for an arc furnace having a fluid cooled arcing surface and a continuouslymoving arc thereon - Google Patents

Description

May 28, 1968 c. B. WOLF ET AL 3,385.987

' ELECTRODE FOR AN ARC FURNACE HAVING A FLUID COOLED ARCING SURFACE AND A CONTINUOUSLY MOVING ARC THEREON Filed Oct. 24, 1966 2 Sheets-Sheet 1 WITNESSES INVENTORS Semfmo M. De Corso,George A. Kemeny I ATTORNEY MHUUG 221.2 LHLWUL, ummv. i-vv.

May 28, 1968 c WOLF ET AL 3,385,987

ELECTRODE FOR AN ARC FURNACE HAVING A FLUID COOLED ARCING SURFACE AND A CONTINUOUSLY MOVING ARC THEREON Filed Oct. 24, 1966 2 Sheets-Sheet 2 FIG.|B.

3,385,987 ELECTRODE FOR AN ARC FURNACE HAVING A FLUID COOLED ARCING SURFACE AND A CONTINUOUSLY MOVING ARC THEREON Charles B. Wolf, Irwin, George A. Kemeny, Export, and

Serafino M. De Corso, Media, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 24, 1966, Ser. No. 588,837 14 Claims. (Cl. 313-32) ABSTRACT OF THE DISCLOSURE An electrode having an annular or ring-shaped fluid cooled tip forming an arcing surface has a tip supporting structure including means for bringing cooling fluid to the tip and means for conducting fluid from the tip, the last-named fluid being hot relative to the first-named fluid, the last-named means including a tube slidable within a tube support secured to the tip whereby forces resulting from differential thermal expansion within the electrode are not applied to the tip. The central aperture of the annular tip is closed by a solid metallic hub. A field coil is disposed within the hollow annular tip and energized to set up a magnetic field at the arcing surface which causes the arc to substantially continuously rotate in an annular path around the ring-shaped tip. The supporting structure is at least partially composed of conductive material for bringing current to the tip to produce the arc. Novel means is provided for mounting the housing enclosing the field coil in predetermined desire-cl position within the tip. An expendable ring threaded at one end thereof to the outside annular edge of the tip is threaded at the other end thereof to the outer tube of the supporting structure and is easily removable and replaceable. A heat shield composed of a refractory material encloses at-least a substantial portion of the supporting structure The aforementioned outer metallic member of the supporting structure, tubular in shape, is removable from the electrode structure in case of damage thereto without necessitating the complete disassembly of the electrode structure.

This invention relates to improvements in electrodes, and more particularly to an improved fluid cooled elec trode for use in an arc furnace.

The invention described and claimed herein is an improvement over and a further development of electrodes described in several copending patent applications including application Ser. No. 440,425, filed Mar. 17, 1965, by S. M. De Corso and C. B. Wolf for Electrode and Tip; application Ser. No. 479,965, filed Aug. 16, 1965 by S. M. De Corso for Improved Electrode, and application Ser. No. 458,240, filed May 24, 1965 by S. M. De Corso and C. B. Wolf for Improved Non-consumable Electrode, all of the aforementioned copending applications being assigned to the assignee of the instant invention.

In those applications, there was described a non-consumable electrode including as essential parts thereof, a supporting structure including means forming fluid passageways for bringing a cooling fluid to the arcing tip or means forming the arcing surface, and conducting fluid therefrom, the supporting structure also providing for conducting current to the tip to produce and sustain an arc therefrom, and providing passageways for leads to energize a field coil and in some cases to pass a cooling fluid through a field coil composed of a number of turns of hollow conduit insulated from each other, with a cooling fluid flowing through the conduit.

To summarize some of the features of the instant invention not found in previous disclosures, the electrode 3,385,987 Patented May 28, 1968 tip of the instant invention is generally annular in shape and U-shaped in cross section and employs a solid hub so that if metal from the charge contacts the tiP n this region, electrical contact will be sensed by control circuitry and the electrode and tip will be raised. On the other hand, if the central aperture in the tip were closed by insulating material or formed the entrance of a tubular passageway, the electrical control circuitry would sense no contact and a heavy piece of metal might damage the bore area of the electrode, both due to mechanical forces and also due to eventual arcing to locations not well cooled, where are rotation would not be likely. The solid hub design represents an innovation or modification of a previously constructed nonconsumable electrode.

Another feature of the instant invention is that the electrode tip is threaded to an expendable ring which is in turn threaded to an outer tube of the supporting structure, the threading combining mechanical holding with good electrical contact. This threading eliminates the need for bolted flanges as are presently used in some prior art electrodes.

Furthermore, in some prior art electrodes damage to the lower end of the electrode column has been encountered at times and this has required remachining after welding at one end of the 15 foot structure weighing about one ton. Experience has shown that this damage appears to be concentrated near the lower end of the column and in the instant invention the lower end of the column is formed by the aforementioned expandable ring which has been made removable. In case of damage at the lower end of the column to this ring, it is only required to remove the ring and remachine or replace it, thereby reducing the downtime period.

Furthermore, the outer tube of the electrode column or supporting structure has been made removable so that if the column is damaged it is necessary to replace only the outer tube.

Furthermore in the instant apparatus the electrode tip is supported by mean-s of an expendable ring and the aforementioned outer tube. The inner tube of the supporting structure does not carry any load and is free to ex pand at its bottom end. This feature was adopted so that the differences in thermal expansion between the inner and outer water carrying passageways forming means produces no loads on the tip structure.

An additional feature of the instant invention is a split ring clamp collar which serves to both hold the column in the furnace crossarm and to conduct arcing current. The split ring clamp collar can be varied in outer diameter so as to fit different cross arm clamp sizes.

Accordingly, a. primary object of the instant invention is to provide a new and improved nonconsumable electrode.

Another object is toprovide a new and improved nonconsumable electrode having a structure which will per mit the free use of arc rotation sensing devices.

Another object is to provide a new and improved nonconsumable electrode in which the portions of the supporting structure which have been found by previous experience to be most frequently damaged may be removed and quickly replaced.

Another object is to provide a new and improved electrode so constructed that differences in the thermal expansion of inner and outer fluid conducting tubes do not place a strain on the electrode and specifically on the tip structure thereof.

These and other objects will become more clearly apparent after a study of the following specification when read in connection with the accompanying drawings, in which:

FIGS. 'lA. and 1B taken together constitute a cross-seetional iew through the electrode according to the pre ferred embodiment thereof.

As previously stated, the electrode includes a supporting structure, and in FIG. 1A, there is seen to be a manifold block 40 having an eye bolt 41 therein for lifting the electrode, the manifold block 40 having disposed therearound the upper end of a main electrode column tube 21, the upper end of which is externally threaded to make threaded engagement at 20 with a ring 24 which attaches the outer tube 21 to the manifold block, Disposed internally of the aforementioned tube 21 is a second main electrode column or tube 22 spaced therefrom to form a cylindrical or annular fluid inlet passageway 23, the aforementioned column 22 being secured to the manifold block 40 as by a series of peripherally spaced bolts, one of these being shown at 48. If desired the tubular column 22 could also be welded to the manifold block. A fluid input bushing 56 in threaded engagement in a threaded bore in the top of the block 40 brings cooling fluid to a strainer 42 which communicates with fluid flow passageway 58 which thereafter becomes somewhat smaller in cross section to form the aforementioned cylindrical fluid flow passageway 23. Referring still further to FIG. 1A, the fluid outlet passageway is shown at 61 formed by re turn fluid tube 44 communicating with a passageway 63 in the block 40. If will be understood that tube 44 could serve as a fluid inlet if desired. It will be understood that the passageway 63 communicates with a fluid outlet not shown in the particular cross section selected for illustration. Fluid outlet tube 44 is welded to tube 81 which is threaded at 82 in an internally threaded bore in manifold block 40.

Passing through an axial bore 68 in the aforementioned manifold block 40 is a sleeve 70 composed of electrically insulating material through which passes a conduit 72 for bringing a cooling fluid to a field coil generally designated 28, FIG. 1B; means symbolized by lead 73 is connected to the conduit 72 for connecting the conduit to a source of potential to energize the aforementioned field coil. The passageway 74 within the conduit communicates with a source of cooling fluid and is electrically insulated from the source by means of a suitable hydraulic insulator, not shown for convenience of illustration. A small gap 33 may exist between the outer wall of insulating sleeve 70 and the inner wall of column 22.

Passageway 74 could be a fluid outlet passageway if desired.

A removable clamp collar 26 composed of electrically conductive material is seen to be in electrical contact with the aforementioned main electrode column or tube 21, also composed of electrically conductive material, the column 21 providing one path for conducting current to the electrode tip generally designated to produce and sustain an are 77; lead 76 connected to the collar 26 is symbolically connected to a source of potential for producing the arc 77, FIG. 1B, from the electrode tip generally desig nated 10. Arc 77 may take place to a melt 78, or the are 77 may take place to any surface of opposite polarity within the furnace including an additional electrode,

With particular reference to FIG, 1B, and FIG. 1A, the upper portion of the outer column or tube 21 is seen to be protected from heat of radiation and convection within the furnace by a cylindrical heat shield generally desig nated 17 composed of two sections 84 and 85 supported by metallic support rings 14 and respectively, The heat shield may be composed of a ceramic if desired. The lower support ring 15 may be protected from heat. by ceramic plastered into the joint area.

The aforementioned intermediate expendable ring generally designated 13 is seen to be threaded at the upper end thereof at 87 to column 21, and the expendable ring is seen to be threaded at the lower end thereof at 90 to the electrode tip generally designated 10, The threaded connection at 90 provides the largest portion of support for the electrode tip. A large number of peripherally spaced holes drilled through ring 13, one hole being shown at 92, provide fluid flow passageways, but the passageways 92 do not necessarily extend 360 degrees and the ring 13 may have a solid portion 66. The passageways 92 within the ring member 13 extend a suflicient portion of the circumferential distance to bring ample cooling fluid from cylindrical fluid-in passageway 23 to annular fluid header 53. Passageway 96 is one of a number of passageways, U-shaped in cross-section, disposed at peripherally spaced intervals around the generally cup-shaped tip member 10, the inner and outer portions 100 and 101 of which are in effect formed integrally with each side. Another U-shaped passageway is seen at 97. The passageway 96 extends completely around the tip generally designated 10 near the arcing surface 98 from fluid inlet header 53 to fluid outlet header 54 at the other extremity thereof. Outlet header 54 communicates with the aforementioned fluid outlet passageway 61.

As taught in a copending patent application, passageways 96 and 97 may consist of a number of discrete means forming U-shaped passageways disposed at small spaced intervals around the entire periphery of the electrode tip, all spaces between the passageway forming means being brazed.

Mounted within the electrode tip is a magnetic field producing coil generally designated 28 composed of a number of turns of hollow conduit, the conduit being shown as square in cross-section, the aforementioned cooling fluid flowing through the turns, the coil being mounted within a coil housing 30 composed of electrically insulating material. A coil lead consisting of a portion. of the conduit is shown at 32, the end of which may be brazed to the round-to-square adapter or coupler 99 and thence make connection With fluid input tube 72. Tube 72 is composed of electrically conductive material and serves to bring electrical current to the field coil as well as cooling fluid.

At 104 there is shown a retainer member slidably mounted on the return flow pipe 44, surfaces 124 and sliding with respect to each other, and having O-rings disposed in annular grooves therein for providing a fluid tight seal, Retainer member 104 has a lower portion of increased outer diameter with the lower portion of the outer surface thereof threaded at 106 to attach 104 to tip member 10, the purpose of member 104 being to conduct coolant from manifold 54 to passageway 61.

A disc-shaped member 114, held in place by a number of peripherally spaced set screws, one of these being shown at 1'16, has a plurality of peripherally spaced bores 118 passing therethrough, through which pass a plurality of bolts, one of these being shown at 120, for supporting the structure of the field coil generally designated 28 by threaded engagement with the coil housing portion 127.

As previously stated, one of the desirable features of the invention includes the solid hub generally designated 11, shown seated in an annular groove 122 in the electrode tip generally designated 10, and having an O-ring disposed in an annular groove therein to provide a fluid tight seal. The solid hub 11 may be an integral part of member 104.

It will be seen that a number of other O-rings disposed in annular grooves are provided at various positions within the electrode structure wherever such a fluid seal is desirable between adjoining fluid flow passageways or wherever the O-ring prevents water leakage to exterior parts of the structure.

Another desirable feature of the invention includes the field coil lead assembly spacers 35, having aligned apertures 45, 46 and 47 therein, and which in cooperation with the inner main electrode column or tube 22 and the return flow tube 44 precisely space the magnetic field coil structure in the position shown to prevent damage to leads 72 induced by vibration or lack of supportt It will be understood that the conduit forming the field coil has a fluid outlet end and an adjoining fluid outlet. passageway, not shown in the cross-section. selected. for illustration.

It should be understood that water may enter through tube 44 and leave through passageway 23, if desired.

Whereas we have shown and described our invention with respect to an embodiment thereof which gives satisfactory results it should be understood that the drawings and written description are illustrative only and should not be interpreted in a limiting sense.

We claim as our invention:

1. A nonconsumable electrode comprising, in combination, an annular electrode tip generally U-shaped in cross section forming an arcing surface, a supporting structure including an outer column tube, the outer column tube being composed of electrically conductive material, an expendable ring in threaded engagement with the outer column tube and forming an extension thereof, the expendable ring being composed of electrically conductive material, the electrode tip being in threaded engagement with the lower end of the expendable ring, means adapted to electrically connect the column tube to a source of po tential to produce and Sustain an arc from the electrode tip to a surface of opposite polarity, the supporting structure including means forming fluid. flow passageways for conducting cooling fluid to the electrode tip and conducting fluid from the electrode tip, the electrode tip having a plurality of peripherally spaced generally U-shaped passageways for the flow of cooling fluid near the arcing surface thereof, a magnetic field coil disposed within the electrode tip and insulated therefrom, and lead means for the field coil extending through the supporting struc ture, the lead means being adapted to be connected to a source of potential to set up a magnetic field at the elec trode tip to cause the arc to rotate substantially continuously in an annular path around the annular arcing surface of the tip.

2. An electrode according to claim 1 in which the outer column tube is additionally characterized as being threaded to the supporting structure at the upper end thereof and removable from the remainder of the supporting structure.

3. An electrode according to claim 1 including in addition a solid hub disposed within the central aperture of the electrode tip.

4. An electrode according to claim 1 in which the mag netic field coil -is additionally characterized as being composed of hollow conduit with the turns of the field coil electrically insulated from each other, and the lead means conducts fluid to and from the field coil.

5. An electrode according to claim 1 including a disclike support member disposed within the supporting structure transverse to the longitudinal axis thereof, a p llrality of peripherally spaced set screws holding the disclike support structure in position therein, and means securing the magnetic field coil to the disc-like support: structure.

6. An electrode according to claim 1 including in ad dition an inner fluid flow tube slidable in a member attached to the electrode tip structure, the inner fluid flow tube and the supporting structure being constructed and arranged whereby the inner fluid flow tube does not carry any load and is free to expand at the bottom end thereof without placing any load on the electrode tip.

7. An electrode according to claim 1 including in ad dition, axially spaced parallel coil assembly spacers disposed within the supporting structure, the parallel assembly spacers having aligned central apertures therethrough and including in addition two passageways for leads to the magnetic field coil.

8. Electrode apparatus according to claim 1 including in addition a removable clamp collar at the upper end of the electrode supporting structure, the clamp collar being adapted to hold the electrode column in a furnace crossarm.

9. An electrode according to claim. 7 including in ad dition a retainer member slida'bly mounted on the lower end of the inner fluid flow tube, the retainer member having a lower portion of increased outer diameter in threaded engagement with a portion of the electrode tip.

10. An electrode for use in an arc furnace comprising, in combination, a supporting structure including outer tube means extending substantially from the top of the supporting structure to the bottom thereof, the outer tube means including a removable section, electrode tip means threaded to the lower end of the removable section, heat shield means disposed around at least a portion of the outer tube means, inner tube means disposed within the outer tube means and spaced therefrom to form a fluid flow passageway, an additional fluid flow tube disposed substantially midway of the supporting structure, the electrode tip having fluid flow passageways at spaced intervals around the periphery thereof communicating at adjacent ends thereof with the passageway betweenv the outer and inner tubes and communicating at the other ends thereof with the additional fluid flow tube, coil assembly spacers locating the additional fluid flow tube substantially centrally of the supporting structure, a retainer member slidably mounted on the lower end of the additional fluid flow tube, the retainer member having a portion of the electrode tip in threaded engagement therewith, a disc-like support member within the supporting structure extending substantially transverse to the axis thereof, means holding the disc-like support member in predetermined position within the supporting structure, a magnetic field coil annular in shape disposed within the electrode tip, means securing the magnetic field coil to the disc-like support member to maintain the field coil in fixed position, means extending through the supporting structure for bringing an energizing potential to the field coil, the supporting structure being additionally characterized as being composed at least in part of elec trically conductive material and being adapted to be connected to a source of electrical potential to produce an arc from the electrode tip to a surface of opposite polarity.

11. An electrode according to claim 10 including in addition a solid hub enclosing the central aperture of the electrode tip.

12. An electrode according to claim 10 in which the field coil is additionally characterized as being composed of hollow conduit and including in addition means for conducting a cooling fluid to the coil and means for co ducting fluid from the coil, both said last-named means being electrically insulated from the electrode tip and from the supporting structure.

13. An electrode according to claim 10 including in addition a heat shield composed of ceramic enclosing at least a portion of the outer tube of the supporting structure.

14. An electrode according to claim 13 including in addition at least one ring supporting the heat shield on the supporting structure.

References Cited UNITED STATES PATENTS 2,743,342 4/1956 Bettis 2l9123 2,941,821 6/1960 Klee 1318 3,130,292 4/1964 Gage 139 FOREIGN PATENTS 566,094 4/1958 Belgium.

JAMES W. LAWRENCE, Primary Examiner.

S. D. SCHLOSSER, Examiner.

S. A. SCHNEEBERGER, Assistant Examiner.

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