US1768881A - Induction furnace - Google Patents

Description

July 1, 1930. P. H. BRAcE INDUCTION FURNACE 2 Shania-sheet 1 Filed Aug. 14. 1929 INVENTOR Porer/fBrace.

ATTORNEY 2 Sheets-Sheet 2 l N v E N To R Porer/ Brace.

TTORNEY Patented July 1, 1930 UNITED STATES PATENT OFFICE PORTER H. BRACE, 0F FOREST HILLS, PENNSYLVANIA, `ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA INDUCTION FURNACE Application led August 14, 1929. Serial No. 385,764.

My invention relates to electric furnaces and particularly to electric induction furnaces of relatively large size.

An obj ect of my invention is to provide an induction furnace that shall embody means for establishing a plurality of substantially separate secondary electric circuits, whereby the length of effective current path and of energy input is increased.

Another object of my invention is to provide a crucible for a surrounded-pool-type induction furnace that shall embody a plurality of refractory walls disposed in substantially radial positions and cooperating with the crucible wall to divide material located in the crucible into a number of substantially separate sections. i

Another object of my invention is to provide the refractory dividing or separating walls with metallic strengthening and cooling means interfitting therewith and substantially covered thereby.

In practicing my invention, I provide a refractory crucible of the surrounded-pool type with a plurality of intermediate refractory walls disposed in substantially axial and'radial positions to cooperate with the crucible to provide a plurality of substantially similar and substantially separated sections within the crucible distributed peripherally thereof `to increase the effective length of the path of the secondary current induced in the material to be melted. Means are rovided in one or more of the Walls to permit of emptying the crucible at one time.

In the drawings,

Figure 1 is a top plan View of an electric induction furnace embodying my invention,

a portion of the cover being shown in place;

Fig. 2 is a vertical section taken on the line II-II of Fig. 1;

Fig. 3 is a schematic top plan view of a modified form of device embodying my invention;

Fig. 4 is a schematic top plan View of a further modification;

Fig. 5 is a top plan View of a still further modification of a device embodying my invention, and

Fig. 6 is a view, in lateral vertical section, taken on the line VI-VI of Fig. 5.

Referring more particularly to Figs. 1 and 2 of the drawings, I have there shown an outer metal casing 11 which may be provided with short shafts or trunnions 12 and 13 to permit of tilting the furnace. A builtup lining or crucible 14 is provided as may be necessary or desirable in case of furnaces of relatively large capacity. Immediately surrounding the crucible 14, is a layer 16 of granular refractory material which is maintained in its proper operative position by a casin 17 of electric-insulating material and of su stantially the same general shape as the crucible.

An energizing coil 18 includes a plurality of turns of an electric-conducting member and a fluid-conducting member shown in section in Fig. 2 of the drawings. Granular electric and heat-insulating material 19 is located Within the casing 11 and is adapted to support the coil 18 and the members 17 and 14 and the granular material 16. A cover 20 may be provided at the top of the furnace structure.

A plurality of axially and radially-disposed refractory walls 21, 22 and 23 are symmetrically spaced peripherady within the.

crucible 14 and extend from substantially the 80 center or axis of the crucible to the crucible wall itself and are interfitted therewith, substantially as shown in Fig. 1 of the drawings,

Figs. 3 and 4 show, respectively, modifications of the idea of subdividing the material to be located in the crucible 14, Fig. 1 showing a lining or crucible 26 having a plurality of radially extending walls 27, also of refractory material, located therein but not engaging each other at their inner ends. In this case, the sections of material within the crucible being heated Will not be entirely separated.

Fig. 4 shows a substantially circular lining or crucible 28 of a refractory material having located therein a plurality of radially extending refractory walls 29, the outer ends of which interfit with the wall 28, and a substantially solid central core member 31 also of refractory material. In this case, the respective ICO sections within the crucible 28 will be entirely separate from each other. i

Referring more particularly to Flgs. 5 and 6 of the drawings, I have there illustrated an rial 37 and a shroud 38 of electric-insulatin material are located between the crucible an the energizing coil. Granular material 39 is located between the shroud 38 and the casing 32 and has electric and heat-insulating characteristics. A cover 40 may be provided.

A pluralitty of spaced and substantially radial refractory wa ls 41, 42 and 43 are provided, the ends of which interfit with the walls of the crucible 33.

The respective walls 41 to 43, inclusive, are built up of a plurality of relatively thin bricks or blocks of refractory material adapted to withstand the chemical action of the materal being melted and also the relatively high temperature of the molten material.

As these walls provide paths for flux which will not be effective in heatin the material, it is desirable that the thic ess of these walls be reduced as much as possible, consistent with the necessar mechanical strength. I, therefore, provi e an interlitting metal structure for each of these walls which, as shown more particularly in Fig. 6 of the drawings, includes a bottom ortion 44 of metal upon which the wall is built as well as upwardly extendin portions 46 between which the bricks or b ocks constituting the walls 41, 42 and 43 are fitted. The upper end portion of each of the members 46 may be headed over, as shown in Fig. 6 in order to maintain the bricks or blocks of the respective walls in their proper operative positions on the portions 44.

Means for cooling the respective walls 4l to 43, and, more particularly, the metal bases 44, are provided in the form of conduits 47 which extend outwardl through suitable openings in the wall of t e casing 32 and are connected to a source of supply of a cooling fluid, in the manner shown generally in Fig. 5 of the drawings.

In the case of relatively large furnaces operating at commercial frequencies, such as 25 to cycles, as well as in small furnaces, of the surrounded-po@ t pe, operating at higher frequencies, it usuallyy happens that the current-carrying zone of the charge is of relatively small depth radially, as compared to the diameter of the charge. This means that only a relatively small portion of the total volume undesirable electrical an mechanical complications which limit the permissible amount of energy input and, in the case of large furnaces, it may happen that this energy input is undesirably low, when related to the metalholding capacity of the furnace chamber.

Tht provision of a plurality of refractory walls within a lining or crucible extending axially thereof in one direction and radially thereof in another direction, ensures substantially separate material-holding compartments, so that the original circumferential zone of the secondary current is replaced by a system including a plurality of current zones which conform, 1n a general way, to the outer wall of the melting chamber or crucible and the corresponding surfaces of the partition walls.

By dividing a substantially circular furnace chamber into three smaller chambers, as shown in Fig. 1 of the drawings, the total length of effective current zone is approximately doubled and the ower intake of the furnace with a given coi and with a predetermined current traversing said coil is correspondingly increased. This has the result that both the efliciency and the power factor of a furnace of my new type are improved, the efficiency being particularly improved because the energy transfer to, and received by, the material being heated has been substanf tially doubled without increasing the amount of energy ex ended in the coil or without increasing the lieat loss from the material in the crucible and from the crucible itself.

The im rovement in the power factor will be depen ent upon the thickness of the refractory-partitions for the reason that idle ma netic flux passes through the space occupie by these non-conducting walls and, hence, I prefer, wherever possible, to use the structure shown in Figs. 5 and 6 which not onl cools the refractory artitions but also ena les me to make them o a minimum effective thickness.

Openings are provided in the partitions at spaced points, such as the junction of each partition with the outer periphery of the furnace chamber, these beinnr shown by numeral 51 in Fig. 2 of the drawing and by numeral 52 in Fig. 6 of the drawing. This permits of emptying substantially all of the molten material in a crucible at any one time and these openings have the further effect of diminishing the effective thickness of the partition walls, because the metal filling the perforations in the walls obstructs passage of idle ux through the axial-space volumes occupied by the partitions and, by so doing, it absorbs ener y. I have, thmerefore, shown a pluraliy o such openings, it being understood fil that the number of such openings may be such as may be found suitable or desirable in accordance with the above noted considerations.

The use of interfitting metallic members with the refractory partitions provides a much stronger partition than would otherwise be the case, and the use of fluid cooling means aids in lengthening the life of these partitions.

Various modifications may be made in the device embodying my invention Without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the l prior art or are set forth in the appended claims.

I claim as my invention:

1. In an electric heating device including a crucible and a helical energizing coil surrounding it, means in said Crucible cooperating therewith to provide a plurality of substantially separate secondary electric circuits in a mass of material located in said crucible.

2. In an induction furnace of the surrounded-pool type having a refractory lining and a helically-wound energizing coil, refractory means in said lining cooperating therewith to largely increase the total length of effective current path in material to be heated therein.

.3. In an induction furnace of the surrounded-pool type having a refractory Crucible and a helically-Wound energizing Coil, a plurality of refractory Walls connecting peripherally spaced points of the refractory cru- Cible to provide a plurality of substantially separate secondary electric circuits in a mass of material located in said Crucible.

4. In an induction furnace of the surroundecl-pool type having a refractory Crucible and a helically Wound energizing coil, a plurality of refractory Walls disposed in substantially radial and axial positions in the crucible and joined therewith to establish a plurality of substantially separate secondary electric Circuits in a mass of material located in said cru- Cible.

5. In an induction furnace, in combination, a pot-type Crucible of refractory material, a plurality of refractory Walls therein cooperating with the Crucible to provide aplurality of similar, substantially separate and uniformly spaced furnace sections for receiving material to be heated, and a single energizing coil surrounding the Crucible.

6. In an induction furnace, a single helically-Wound energizing coil and a plurality of substantially separate and similar crucible sections located Within the coil, extending peripherally of the axis thereof and energized simultaneously thereby.

7. In an induction furnace, in combination, a lining of refractory material, a plurality of refractory Walls therein cooperating with the lining to provide a plurality of similar, substantially separate and uniformly spaced furnace sections for receiving material to be heated, a single energizing coil surrounding the lining, and means in certain of said refractory walls for effecting emptying of all of said furnace sections at one time and for reducing the stray flux traversing said refractory Walls 8. In an induction furnace of the surrounded-pool type having a refractory lining and a helically Wound energizing coil therearound, a plurality of refractory Walls radially disposed in the lining and joined thereto to establish a plurality of substantially separate sec,- ondary electric circuits in a mass of material located in said lining, means in said refractory Walls for strengthening the same, and means for artificially cooling said strengthening means.

9. In an induction furnace, a single helically-Wound energizing Coil, a refractory lining, of pot-type, Within said energizing coil, and refractory means in said lining to cooperate therewith to increase the energy transfer from the energizing coil to material located in the lining relatively to that transferred inthe absence of said means.

10. In an induction furnace of the surrounded-pool type having a refractory lining and a helically Wound energizing coil therearound, a plurality of substantially radial and l axial refractory Walls cooperating with therefractory lining to establish a plurality of substantially separate secondary electric circuits in a mass of material located in the lining, said circuits being symmetrically spaced peripherally of the axis of the coil and the lin- Il. In an induction furnace,l in combination, a pot-type crucible of refractory material, a pluralityof refractory walls therein cooperating with the Crucible to provide a plurality of similar, substantially separate and uniformlyvspaced furnace sections for receiving material to be heated, a single energizing coil surrounding the Crucible, a

metal member at the bottom of each refrac-

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