US2711436A - Fluid material container with inclined slotted bottom having inductive stirring device adjacent thereto for an electric furnace - Google Patents

Description

2,711,436 OTTOM June 1955 M. F. JONES ETAL FLUID MATERIAL CONTAINER WITH INCLINED SLOTTED B HAVING INDUCTIVE STIRRING DEVICE ADJACENT THERETO FOR AN ELECTRIC FURNACE Filed Aug. 14, 1952 F l G. 1

5 m0 J wig w? NC a a Ma Y B atent @thce 2,711,436 ed June 21, 1%55 FLUID MATERIAL CGNTAKNER WITH INCLIVED SLOTTED BOTTOM HAVING INDUCTIVE STIR- RING DEVICE ADJACENT THERETO FOR AN ELECTRIC FURNACE Maurice F. Jones, Pittsburgh, and Isaac Harter, In, and Temple W. Ratclifie, Beaver, Pa., assignors, by direct and mesne assignments, to The Bahcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application August 14, 1952, Serial No. 394,252

11 Claims. (Cl. 13--2o) This invention relates to inductive stirring of fluid materials in a container and, more particularly, to an improved container construction and a novel combinati .1 of inductive stirring means therewith.

Stirring of fluid materials in containers is frequently practiced for various reasons, such as to obtain uniform temperatures and uniform composition, to speed up reaction rates, and to control the direction of movement of the fluid material. When heat is transmitted to the body of fluid material through its surface, a stirring action is desirable in order to obtain uniform heat throughout the body particularly when it is desire to avoid any substantial thermal gradient from top to bottom of the body.

It has been proposed to effect the stirring of the body of fluid material inductively instead of by the present marual or mechanical methods, and various arrangements have been suggested to provide such inductive stirring. These arrangements include those in which an electric flux is applied to the body at a predetermined zone in order to circulate the fluid material through this zone, the zone generally comprising a restricted passage or the like in communication with the main body of fluid material. Coils are used to provide the flux, being mounted in predetermined patterns on the container and suitably energized either with single or polyphase A. C.

While such inductive stirring is applicable to any electrically conductive fluid material in a container, it has found particular application in the metal founding and handling art. In this art, it has been applied principally to the stirring of the bath in melting furnaces, the term bath designating a body of hot metal with or without a protective slag coating. The inductive stirring is designed to assure equalization of temperatures in the bath, acceleration of reactions, and uniformity of mixing of the elements, ingredients or constituents of the bath. One advantage is that the stirring promotes uniform temperatures throughout the bath even when the latter is spot heated, by one or more electric arcs playing on its surface.

This stirring is particularly important in the case of continuous metal casting operations wherein, while molten metal is being poured into the mold from one ladle, one or more additional ladies of molten metal are kept in stand-by relation in order to utilize effectively available melting furnace capacity in which the tapping times of the melting furnaces may not be readily coordinated with the initiation of successive ladle pours into the continuous casting mold. in order to assure equalization of temperature in the molten metal and substantial uniformity of composition therethrough, it is particularly desirable to stir the metal both during the time a ladle is being held in stand-by relation and during the time molten metal is being poured therefrom.

It has been found that, when inductive stirring coils are applied to the usual type of ladle involving a metal shell having its inner surface lined with refractory, an excessive amount of power is required to effect the desired degree of stirring. This is due to the relatively large .ction in the effective field applied to the molten e "l as result of eddy current losses in the metal shell. However, attempts to correct this condition have not been satisfactory largely due to the fact that a suitable relatively rigid metal structure must be provided as a St ort for the refractory lining.

While the container and associated inductive stirring mech nism of the present invention is applicable to the stirring of any electrically conductive fluid material held in a container, the invention arrangement finds particular applicability in the stirring of molten metal held in a "sortie", holding or pouring ladle. The invention will, titer-store, be described, solely by way of giving a par cular example of the application of the invention ples, applied to the stirring of molten metal in refractory lined ladle.

nce with the present invention, the desired effect on the molten metal is produced with a ial reduction in power requirements over ed by prior art arrangements by interrupting the co tinuity of ma netic paths in the ladle lining shell and isolating magnetic components from each other, this being effected While still providing adequate support for the ladle lining. In addition, adequate cooling for the induction coils is provided. Both the electrical paths and the magnetic paths in the support structure are broken up into isolated sections. As a result, eddy current and 7 l in the ladle shell (re nearly eliminated, resul. u in lower power input to the induction coils being required to create the desir d stirring effect.

To this end, the shell structure within the desirably n strength portion of the field of the induction devices is made of nonmagnetic material and is formed of separate elements electrically and magnetically insulated from each other. Typically, at least the lower portion of the side wall of the ladle shell is formed of a nonm lilC metal, such as certain of the stainless steels. The bottom wall of the shell is formed or" spaced, substaniially parallel, metal slats supported at their ends, in electrically insulated relation, on the lower margin of the shell side Wall.

It has been found further that, when the inductive stirring coils are mounted immediately adjacent the ladle, which is the most effective position for insuring the maximum stirring effect on the molten metal, the coils become overheated. This is due to the combined elfect of the normal temperature rise due to current flow through the coils augmented by the relatively high ambient temperature in the immediate vicinity of the ladle. Further more, effective stirring with the usual flat bottomed ladle of the prior art requires rather complicated coil arrangements of relatively large size and also requires complicated and expensive low cycle A. C. generators of high amperage. This large amperage input required, in prior art devices, to produce the necessary field strength results in such heating of the coils as to require water cooling of the latter. This is undesirable, as it amounts to providing water under a molten steel bath with the attendant risk.

The particular inductive stirring arrangement of the invention permits the use of a relatively deep ladle which is advantageous from the standpoint of having, for equal molten metal capacity, less surface exposed for heat dissipation or oxidation, and requiring a lesser amount of slag for cover purposes thereby reducing the potentialities of changing the composition of the metal by re action with the slag while the metal is in storage. The effectiveness of the stirring action is further enhanced by providing a sloping bottom wall for the ladle with the inductive stirring arrangement disposed adjacent this Wall and so arranged that the field effect on the molten the and through the slats extending upwardly along the I under surface of the sloping bottom wall. The slats may comprise bars or may comprise rectangular or cylindrical tubes arranged in spaced relation. The cooling effect may be augmented by forcing air through or between the slats.

The inductive stirring arrangement preferably comprises a plurality of coils or coil sections arranged in a toothed or slotted magnetic structure, preferably laminated, supported immediately adjacent and parallel to the bars or tubes and with the open ends of the ma 1 netic structure slots facing the ladle bottom. The coils and the magnetic structure are so arranged that the inductive effect is concentrated over the length of the interior surface of the bottom wall, the stirring device extending in either direction beyond the bottom Wall, however.

For an understanding of the invention principles, reference is made to the following description to a typical embodiment thereof as illustrated in the accompanying drawing. In the drawing:

Fig. l is a vertical sectional view through a molten metal holding, refractory lined ladle embodying the invention;

Fig. 2 is a partial transverse sectional view of the bottom wall, taken on the line 22 of Fig. 1; and

Figs. 3 and 4 are views similar to Fig. 2 illustrating alternative constructions of the sloping bottom wall.

In the drawings, the invention is illustrated, by way of specific example only, as applied to the inductive stirring of molten steel in a refractory lined ladle, it being understood that the invention is not in any way limited to this particular application but may be used wherever it is desired to stir electrically conductive fluid material in any container. Referring to Fig. l, a ladle is shown as comprising a refractory lining 11 supported in an outer metal shell or casing generally indicated at 12. i

An angular cross section framework 13 at the upper end of ladle 1i and secured to shell 12, is provided to receive a suitable cover (not shown) for the ladle. The lining 11 is formed with a suitable pouring lip 14 adjacent which shell 12 is suitably cut away. If desired, pour lip or spout 14 may be provided with a water-cooled lintel, such as shown and described in the copending application of I. Harter et al., Serial No. 316,446, filed October 23, 1952, for the purpose of promoting development of a slag dam by chilling floating slag during pouring. The bath within ladle 10 may have its upper surface locally heated by arcs played thereon from arcing electrodes 50 which, in practice, may extend through the cover for the ladle into proximity with the upper surface of the bath.

Intermediate the height of casing 12, a shelf or support bracket 16 is secured peripherally thereto to removably support ladle ill on a supporting flange 17 of a suitable cradle or the like 15. Cradle may be a stationary holding station for ladle 10 or may be a tiltably mounted structure for tipping the ladle 10, about an axis passing transversely through lip 14, to pour molten metal from the ladle.

Ladle 10 is in the form of a truncated cone of substantial axial length. The frusto-conical lining 11 includes a relatively deep rear wall segment 18 diametrically opposite pouring lip 14, whereas the front wall segment 19 is substantially shorter than segment 18. The lower end of the ladle is closed by a bottom 21. In diametric cross section, ladle It) may be either circular or elliptical.

. eral member 24.

tic:

The inductor device, generally indicated at 30 and described more fully hereinafter, is mounted in cradle 15, to extend in parallel spaced relation to the bottom wall 20 of a ladle it) supported on cradle flange 17. The side wall portion of metal casing 12 is preferably divided into an upper section 2.2 and a lower section 23, the latter comprising substantially all that part of the casing sidewalls disposed within the high strength field of inductor 34). While upper casing portoin 22 may be any suitable metal or alloy, lower section 23, at least, if of a non-magnetic metal material, such as some of the stain less steels.

The casing support for bottom 2!? is necessarily interposed directly between inductor 39 and the molten metal ladle it). Thus, being completely in the inductor field and immediately adjacent the inductor this part of the casing has the most effect in absorbing or dissipating the l'nld flux.

in accordance with the invention, the field losses in the support for bottom 20 are minimized, if not substantially eliminated, by forming this support as a series of spaced, subst it' ly parallel slats or bars 25. These bars, which preferably re non-magnetic metal, are supported at each end in electrically insulated relation on a periph- Slats 25 may be solid or tubular, and of any desired cross sectional shape.

in the arrangement of Fig. 2, the slat structure may comprise a plurality of substantially parallel solid bars 25 extending forwardly and upwardly in supporting engagement with the outer surface of bottom it} and spaced to provide slots 26 therebetween. lternatively, the slat structure may comprise a plurality of spaced substantially parallel rectangular tubes 27 extending forwardly and upwardly in supporting engagement with bottom 2% and likewise forming slots 26 thcrebetween. This arrangement is shown in Fig. 3. A further slat arrangement is shown in Fig. 4 as comprising a plurality of cylindrical tubes 28, likewise arranged in substantially parallel spaced relation and extending forwardly and upwardly in supporting engagement with ladle bottom 20, the spaced tubes 23 forming slots 26 therebetween.

The slat structure supporting the refractory bottom 29 provides for flow of cooling air upwardly and forwardly along the under surface of bottom 2? and through the slots 26. Due to the upwardly extending relation of the bottom and the slats, there is a natural circulation of cooling air over the outer surface of bottom 2:) which tends to reduce the ambient temperature adjacent the ladle bottom wall. The bars 25, or tubes 2'7 or 28, may

, be bolted to flange 24 with the interposition of suitable insulating sleeves and washers. To enhance the cooling effect, air from a suitable source (not shown) may be blown through slats 27 or 28 or through the slots 26 between the slats 25, 27 or 28.

By dividing the support for the bottom 2% into spaced individual elements, the magnetic circuits are interrupted and the field absorption thus greatly reduced. Also, by insulating the slats from each other and from casing section 23, the paths for current flow are likewise incomplete. Hence, the field losses in the bottom wall support are at least minimized and may be substantially eliminated. Thus, the net power input required to produce a given stirring effect is greatly reduced.

The inductive stirring arrangement 31) is supported in the cradle 15, coming into operative relation with ladle ltl only when the latter is supported in cradle 15. Thus, the number of inductive stirring devices required is reduced, as only one is required at each holding station and at each pouring station. Also, the weight of the ladle structure is reduced by virtue of the fact that the inductive stirring arrangement does not form part of the ladle structure, and ladle lb can be moved without the necessity of disconnecting high amperage electrical leads.

Referring again to Fig. l, inductor 30 comprises a preferably laminated field structure secured at one end to the lower wall or platform 31 of cradle and extends upwardly and forwardly parallel to ladle bottom 20. The upper end of structure 3% is secured to the forward wall 32 of cradle 15. inductor St is so arranged in cradle 15 that, when ladle it) is supported in the cradle, there is a slight space or gap between adjacent parts of inductor 3i] and the slat structure 25 supporting the bottom of the ladle. Adjacent its lower end, inductor structure Si is provided with a plurality of winding slots 33 usually normal to bottom 2b and opening upwardly. T he intermediate portion of the field structure is provided with a plurality of deeper slots 34, likewise usually normal to and opening toward bottom 2%, and which have substantially twice the depth of slots 33. The upper end of structure 36 is provided with a plurality of shallower slots 36, substantially equal in depth to slots 33, and usually normal to and opening toward bottom 2%. it will be noted that the faces of slots 33 adjacent bottom 2d are in the same plane as the corresponding faces of the deep slots 34 whereas the bottoms of slots 36 are in the same plane as the bottoms of slots 34.

A first series of coils or coil sections 35 are placed in the inner ends of slots 34 and 3d, and a second series of coils or coil sections 41; are placed in the slots 33 and in the outer ends of slots as overlying the coils or coil sections 35. By reference to Fig. 1 it will be observed that, adjacent the lower rearmost portion of bottom 2t], is a first series of inductive windings relatively close to the slotted supporting structure. Beginning at a point in a plane which, if projected parallel to the side wall of slots 34 would substantially intersect the lower rear corner edge between wall segment 13 and bottom 2%, the concentration of the inductive windings is double in the slots 34, this concentrated winding extending to near the upper edge of bottom 2b where the latter merges with forward ladle wall segment 15 From this point onward, a single series of inductive windings is disposed in the slots 36 and is relatively more widely spaced from the slotted ladle bottom.

With the described inductive stirring arrangment, an inductive effect on the molten metal is provided which is at its greatest strength and concentration along the major portion of the upward length of bottom 20, beginning at the lower edge of this wall. In advance of this lower edge, a reduced inductive effect is provided which is, nevertheless, concentrated by being provided by coils closely adjacent the bottom wall. At the upper forward edge of bottoi 1 2b, the inductive effect is provided in substantially reduced amount by virtue of the single series of inductive windings in slots 36 which are spaced substantially from bottom Thereby, a variable inductive effeet is provided which acts on the molten metal as the latter approaches the junction between segment 18 and bottom 29 durin its circulation, this inductive effect being substantially increased as the metal begins to move upwardly along the bottom 2 Subsequently, the inductive effect is substantially reduced adjacent the upper end of bottom 20 so that less moving force is imparted to the circulating molten metal as it begins to move upwardly along the relatively short forward wall segment 19. This provides a substantially uniformly effective force on the molten metal, the coils in slots 33, by virtue of being immediately adjacent the bottom wall, exerting a greater effect on the metal than the coils in slots 36. The maximum moving effect on the molten metal is concentrated along the major portion of sloping bottom 26 by virtue of the double layers of coils laid in deep slots 34.

This arrangement is of particular importance in pro viding a sufficient motion for the molten metal in such a uniform manner as to eliminate or reduce the possibility of erosion of lining 12 due to the motion of the metal. Also, the moving efiect along wall segment 19, by being reduced compared to that along wall 26 and along wall 18, will also result in suiiicient motion to sweep the slag back from lip 14.

The coils 35 and 40 are suitably energized with either low frequency polyphase A. C. or progressively switched D. C. to produce an induced field substantially constant in strength moving upwardly along bottom 2%). In the case of energization with low frequency, polyphase A. C., the coils are so wired that, at any given instant, the coils 4t lying in shallow slots 33 would produce a pole of a given polarity (south, for example), the coils 35 and 4t lying in deep slots 3 3 would produce a north pole, and the coils 35 lying in shallow slots 35 would produce a south pole. With polyphase energization, there will thus be produced an induced polarity moving from left to right along bottom 2%. Approximately the same elfect is obtained by using D. C. energization with progressive mechanical switching.

During the described stirring motion of the molten metal, the latter sweeps upwardly along wall segment 19 and then rearwardly away from spout 14 and into the region of the are or arcs from electrode 50. Thus, the metal is continually circulated past the hot spot on the surface of the bath before returning to the bottom of the bath. This promotes uniformity of temperature throughout the bath and prevents there being any temperature gradient between the surface and the bottom of the bath. The rearward motion effected along the bath surface tends to keep the slag held back from lip 14. During pouring of ladle 1d, the intensity or speed of the field provided by inductor 3t may be temporarily increased, by raising the frequency if A. C. is used or speeding up the switching if D. C. is used, to insure the slag being held back from the pouring lip 14- by the stirring motion.

The sloping bottom 20 in association with wall segment 19 provides an easy transition Zone for the moving molten metal in passing from the bottom upwardly along wall segment 19. While arc electrodes Sll have been shown as the local heating means, it should be understood that the heating means may be other than the arcing electrodes, as for example a gas flame.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understod that the invention may be embodied otherwise without departing from such principles.

We claim:

1. A container for electrically conductive fluid material, having upwardly extending opposite wall portions and a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion; and electric field producing means arranged adjacent the under surface of said bottom wall to induce electromotive forces in the fluid material to stir the latter.

2. A container for electrically conductive fluid material, having upwardly eritending opposite wall portions and a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion; and electric field producing means arranged adjacent the under surface of said bottom wall to induce electromotive forces in the fluid material to move the latter upwardly along said bottom wall.

3. In combination, a container for electrically conductive fluid material, having upwardly extending opposite wall portions and a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion; a cradle removably supporting said container; coil means mounted in said cradle and arranged along the under surface of said bottom wall of a container supported in the cradle; and means for electrically energizing said coil means to induce electromotive forces in the fluid material to effect motion of the latter.

. 4. In combination, a container for electrically conductive fluid material, having upwardly extending opposite wall portions and a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion; a cradle removably supporting said container; coil means fixedly mounted in said cradle and arranged along the under surface of said bottom wall of a conta ner supported in said cradle; and means for electrically energizing said coil means to induce electrornotive forces in the fluid material to effect motion of the latter upwardly adjacent said bottom wall.

5. A container for electrically conductive fluid mate rial, having upwardly extending opposite wall portions and a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion and having slots in its under surface; and electric field producing means arranged adjacent said slots to induce electromotive forces in the fluid material to stir the latter.

6. In combination, a container for electrically conductive fluid material, having upwardly extending opposite wall portions and a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the ,lower periphery of the other wall portion and having slots in its under surface; a cradle removably supporting said container; coil means fixedly mounted in said cradle arranged along the under surface of said bottom wall of a container supported in said cradle; and means for electrically energizing said coil means to induce electromotive forces in the fluid material to eflect motion of the latter.

7. In combination, a pouring container for electrically conductive fluid material, having upwardly extending opposite wall portions, a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion and a pouring lip; a cradle removably supporting said container; electric field producing means arranged adjacent the under surface of said bottom wall of a container supported in said cradle to induce electrornotive forces in the fluid material to stir the latter, and supported for unitary movement with the container; and means mounting said cradle for tilting about an axis passing through the container pouring lip.

8. in combination, a pouring container for electrically conductive fluid material having upwardly extending opposite wall portions, a bottom wall sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion and having slots in its under surface, and a pouring lip; a cradle removably supporting said container; electric field producing means arranged adjacent said slots to induce electromotive forces in the fluid material to stir the latter,

8 and supported for unitary movement with the container; and means mounting said cradle for tilting about an axis passing through the container pouring lip.

9. A tiltable pouring container for electrically conduca tive fluid material having upwardly extending opposite wall portions formed with a pouring lip, and a bottom wall of non-magnetic material sloping upwardly from the lower periphery of one of said wall portions to the lower periphery of the other wall portion; and electric field roducing means arranged adjacent the under surface of said bottom wall to induce electromotive forces in the fluid material to move the latter upwardly along said bottom wall, and supported for tilting movement with the container.

10. A tiltable pouring container for electrically conductive fluid material having upwardly extending side walls formed with a pouring lip, and a sloping bottom wall, including non-magnetic, electrically isolated elements forming slots in the under surface of the bottom wall; and electric field producing means arranged adjacent said slots in the under surface of said bottom wall to induce electromotive forces in the fluid material to move the latter along said bottom wall, and independently supported for unitary tilt ng movement with the container.

11. in combination, a pouring container for electrically conductive fluid material having upwardly extending side walls formed with a pouring lip, and a sloping bottom wall, including non-magnetic, electrically isolated elements forming slots in the under surface of the bottom "'wall; a cradle removabb supporting said container; coil means arranged adjacent said slots along the under surface of said bottom wall and fixedly supported in said cradle, for inducing electromotive forces in the fluid ,material; and means mounting said cradle for tilting movement about an axis passing through the container pouring lip.

References tilted in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A CONTAINER FOR ELECTRICALLY CONDUCTIVE FLUID MATERIAL, HAVING UPWARDLY EXTENDING OPPOSITE WALL PORTIONS AND A BOTTOM WAL SLOPING UPWARDLY FRM THE LOWER PERIPHERY OF ONE OF SAID WALL PORTIONS TO THE LOWER PERIPHERY OF THE OTHER WALL PORTION; AND ELECTRIC FIELD PRODUCING MEANS ARRANGED ADJACENT THE UNDER SURFACE OF SAID BOTTOM

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