US3035106A - Construction and operation of electric tilting furnaces - Google Patents

Description

J. MERCIER 3,035,106

CONSTRUCTION AND OPERATION OF ELECTRIC TILTING FURNACES May 15, 1962 2 Sheets-Sheet 1 Filed Aug. 27, 1959 INV EN TOR JEAN MERC/ER BY W 7 ATTORNEY J. MERCIER 3,035,106

NG FURNACES May 15, 1962 CONSTRUCTION AND OPERATION OF ELECTRIC TILTI 2 Sheets-Sheet 2 Filed Aug. 27, 1959 INVENTOR JEA N MERC/ER ATTORNEY United rates The present invention which is based upon applioants researches relates to Ia method of constructing electric furnaces and concerns, more especially, novel tilting electric furnaces using electrodes. It is already known to tap molten materials contained in a furnace, electric or otherwise, through a tap hole placed at the bottom of the furnace; however, this technique presents the serious drawback of producing a nonuniform flow, which varies widely as the level of the molten mass is lowered and, correspondingly, the hydrostatic pressure. This arrangement, frequently utilized industrially, is therefore inadequate in thoses cases where it is important to have a controlled flow during the tapping operation.

Further, it is known to pour out molten materials contained in an electric furnace comprising electrodes by inclining the electrode-pot assembly while the electrodes are, or are not, maintained under voltage. Furnaces of this kindcurrently used in steel plants-present, however, major drawbacks, among others, the following: first, since the electrodes tilt together with the pot (crucible), the furnaces comprise a heavy, moving mass and, hence, involve high erection costs and, second, when the electrodes are in the tapping i.e. discharge position, they make a more or less acute angle with the surface of the molten bath so that, in the case where they remain under voltage, they work at a part only of their cross section normally in contact with the bath.

Applicants work has led to the development of a system of construction which eliminates the various drawbacks of the prior tilting electric furnace comprising electrode(s).

The present invention has for its object a method of constructing tilting electric furnaces provided with an electrode or electrodes, wherein the plane of the working section of said electrode(s) remains continuously horizontal; the invention also comprehends the novel furnaces built according to the method disclosed herein.

Other objects of the present invention will be disclosed in the course of the following exposition taken in conjunction'with the annexed drawing.

The figures in the drawing, which are in no way limiting, have for their sole purpose to illustrate the various features of the novel method of constructing electric furnaces provided with electrode(s) and, also, the novel furnaces themselves. In these drawings:

FIGURES l, 2 and 3 represent diagrammatically, and in longitudinal section along the tilting plane, one embodiment of an electric furnace according to this invention; in these figures, FIGURE 1 shows the furnace tilted backward; FIGURE 2 shows it in horizontal position, and FIGURE 3 shows it tilted forward.

. FIGURES 4, 5 and 6 represent, likwise diagrammatically and in longitudinal section along the tilting plane, a different embodiment of an electric furnace of this invention in the respective backward-tilted position, horizontal position, and forward-tilted position.

- FIGURES 7, 8 and 9 represent similar diagrammatic views of a still different embodiment of the furnace of this invention, in the respective backward-tilted position, horizontal position, and forward-tilted position.

' FIGURE 10 is 'a general perspective view of a tilting system comprising a train of rollers for the furnace pot.

FIGURE 11 is an explanatory diagram to illustrate the location of the axis about which the furnace pot tilts, according to the invention.

In the various figures of the drawing, the same or similar parts are designated by the same reference numerals.

Applicant has discovered first, that by making the electrode(s) of a tilting electric furnace independent of the position of the furnace pot, it is possible, on the one hand, to maintain the plane of their working section continuously horizontal and, on the other, to mm'ntain always a maximum operating efficiency of the electrode(s) since, whatever the operating condition, the planes of the section of the electrode(s) and of the surface of the molten materials will always remain parallel to one another. By a simple longitudinal or vertical displacement, the electrodes are made to follow the level variations of said surface during the tapping process; hence, their constant nate of operation enables them to supply continuously the calories required to maintain the materials in the state of fluidity suitable for uniform and controlled tapping.

Applicant has further established that, in the course of the various operations, the furnace pot alone can be inclined by tilting; such tilting is carried out about an axis of rotation approximately defined by the intersection of (a) the horizontal plane passing through the origin of the pouring spout of the furnace, with (b) the vertical plane perpendicular to the plane of tilt and substantially passing through the geometrical center of the working (cross) section or surface of the electrode, or of the surface delimited by the working section (surface) of said electrodes.

The location of the axis about which the pot tilts, in accordance with the foregoing definition, will become clearer by reference to FIGURE 11 of the attached drawing. In this figure,

A is the horizontal plane passing through the origin, i.e. lower level of the pouring spout of the furnace pot;

E E B are the working sections of the electrodes; these sections are always disposed substantially in the plane A. By the phrase working section of an electrode is understood its terminal section, that is, the end from which the arc breaks out and which is substantially in contact with the molten material;

X--Y is the axis of rotation of the pot, which corre-v sponds to the intersection of B, the plane of tilt, passing substantially through the geometric center O of the working section of the electrodes (in the case illustrated in FIGURE 11, there are three electrodes), and of C, the vertical plane passing through O-- and perpendicular to the plane B.

In practice, the said axis of rotation, whether real or imaginary, is situated in the vicinity of the one theoretically defined above, for example, depending on the various dimensions of the pot and/or the electrode(s), it will be spaced therefrom by an amount which Wllll'lOt exceed by a few percent, or tens percent, that of the diameter, or of the major axis, or of the major diagonal, of the surface of the upper section of the pot.

According to a preferred, but not limiting embodiment of the present invention, the furnace is constructed as follows: the electrode or electrodeswhich can, if desired, have an inclined positionare placed vertically along or in the vicinity of the axis of symmetry of the pot when in a horizontal position, and are held or supported by their own framework; the pot which can eventually be suspended by any known means about it axis of rotation as defined above, is seated on a base comprising a train of rollers. This train of rollers is such as to permit the tank to tilt about an imaginary axis, as defined above. The electrode or electrodes can'be displaced separately or simultaneously with a longitudinal or vertical motion in order to bring their Working surface into contact with the materials treated in the furnace. I

The method of constructing tilting electric furnaces according to the present invention possesses, additionally, the fundamental characteristic of being capable of treating for a given pot capacity a volume of materials larger than that treated in the furnaces of the prior art. Indeed, the furnaces built according to the invention are capable of being tilted in a backward position, as illustrated in FIGURES 1, 4 and 7, opposite and symmetrical to the pouring position, which makes it possible to charge and treat in the pot an additional quantity of materials as compared with that filling the pot when in the normal horizontal position; moreover, this advantageous result is achieved with a constant and maximum operating efficiency of the electrode(s). Specifically, the roller train or gear on which the pot rests is constructed in such a way that the pot can tilt forward as well as backward, and by an angle relative to the horizontal which is calculated as a function of the other constructional characteristics of the pot e.g. shape, volume, height, etc.

Moreover, the independence of the pot of such furnaces of their heating system by means of electrodes, and the symmetry of such furnaces with regard to the axis of the electrode or electrode assembly, makes it possible to construct furnace pots which are seated, for example, on a double roller gear; one of these enables, as has been said above, the tilting of the cells forward and/or backward, while the other makes it possible to turn (pivot) the tank about itself, for example, on a circular platform, with a View to effecting different tappings into separate apparatus.

The present invention has also for its object a special form of hearth for such pots. Applicant has established that since the furnace tilts backward, it is important, in certain cases, that the depth of the pot be greater in the rear portion than in the front of the pot. For a given volume of molten materials, such a construction makes tapping both easier and more complete.

Additionally, the furnace pots according to the invention can be provided with one or more tap holes, placed in the lower part of the crucible and, even, in the vicinity of the lowest point thereof. In the case where the molten materials comprise two products which separate from one another, for example, into slag and a ferroalloy, the slag can be recovered by pouring it off through the upper spout, while the ferroalloy is removed by tapping or pouring it off through a lower tap hole. The latter can, according to the invention, be provided in the front as well as in the rear portion of the tank, particularly, in the case of a hearth having the special shape described above.

The various embodiments of the invention are illustrated diagrammatically in the drawing. Referring to FIGURES 1, 2 and 3: The furnace is provided with a pot 1 seated on a train of rollers 2 so disposed that the pot when moved thereon, tilts about an axis 11 as defined above. The materials 3 in the pot are kept in a molten state by being heated by means of two or more electrodes 4-. These electrodes can be displaced along their longitudinal i.e. vertical axis by any suitable means as shown in FIGURE 1. In accordance with the invention, the working surfaces or planes 4 4 of the electrodes are maintained horizontal in all positions of the pot, as is clearly shown in FIGURES 1, 2 and 3'. The molten materials are tapped by being poured out through spout 5.

FIGURES 4, 5 and 6 illustrate an embodiment of applicants invention similar to the foregoing but wherein the pot is provided with a special form of hearth. More particularly, here, the rear portion of 6 of the hearth is of greater depth than the front portion 6 By reference to FIGURE 6, it will be seen that with this special hearth construction, the pot can be substantially comi pletely emptied of its contents when tilted in its forward position.

FIGURES 7, 8 and 9 represent a furnace similar to that shown on FIGURES 1, 2 and 3, but which is additionally provided with a tap hole 7 situated on the rear portion and in the vicinity of the bottom of the pot, and through which the lower layer 3 of the contained molten materials can be tapped.

Referring now to FIGURE 10: Pot 1 is seated on a base 8 consisting of a metallic frame provided with a quadruple set of wheels or rollers 2; the pot rests on these rollers by means of two parallel rails 10' attached to the pot. The rails are constituted of two sectors forming portions of two parallel circles of the same diameter, the centers of which are so located that they define an axis of rotation 11 for the pot in accordance with the principle explained above. Tilting can be produced by any suitable means, for example, by means of a hydraulic jack 12. The base 8 itself can be placed on a train of rollers 13 whereby the pot can be turned around on a circular platform 14 about a vertical axis passing through the center of symmetry of the pot when in its horizontal position.

The furnaces of the invention can be built of any known material, depending on the processes for which they are intended; they can be used to carry out any electrothermal and/or electrometallurgical process, continuously or batch-wise.

I claim: a v v I,

1. A tiltable electric furnace for molten material from which the molten material is discharged by tilting the furnace, comprising in combination: a pot; a pouring outlet in said pot; an electrode system comprising a horizontal working surface, said system being disposed vertically in the vicinity of the center of symmetry of the pot 'when the latter is in a horizontal position; means for displacing said electrode system along its longitudinal axis, whereby the working surface of the electrode remains continuous ly horizontal and parallel to the level of the molten ma- -t eria1; a pouring outlet disposed in the upper portion of the pot; means for tilting said pot, independentlyof said electrode system, about an axis substantially defined by the intersection of (a) a horizontal plane passing through the lower edge of the pouring outlet, and (b) a vertical plane perpendicular to the plane of tilt and substantially passing in the neighborhood of the geometrical center of the working surface of the electrode system whereby, during tilting, the working surface of the electrode system remains constantly horizontal and parallel to the level of the molten material.

2. Furnace according to claim 1, wherein the potis mounted on a tiltable support, and means for tilting the pot.

3. In the method of operating a tiltable electric furnace for molten material, comprising a pot provided with a pouring outlet disposed in its upper portion, and through which the molten material is discharged by tilting the furnace, and a displaceable electrode system comprising a horizontal working surface and connected to a current supply, the improvement which comprises the steps of tilting the pot independently of the electrode system while maintaining the supply of current to the electrodes about an axis substantially defined by the intersection of (a) a horizontal plane passing through the lower edge of the pouring outlet, and (b) a vertical plane perpendicular to the plane of tilt and substantially passing in the neighborhood of the geometrical center of the working surface of the electrode system, whereby the working sur-face'of the electrodes remains continuously horizontal and parallel to the level of the molten material.

4. The method of operating a tiltable electric furnace for treating material and comprising a pot provided with a pouring outlet disposed in its upper portion, and through which molten material is discharged by tilting'the furnace,

and a displaceable electrode system comprising a horizontal working surface and connected to a current supply,

comprising the steps of: tilting the pot backward in a position opposite and symmetrical to the pouring position and independently of the electrode system; filling the pot with material to be treated, and applying current to the electrode system whereby the material in the pot is heated and melted, and the level of the molten metal remains continuously parallel to the horizontal working surface of the electrode system.

5. Furnace according to claim 1, wherein an additional outlet is disposed at a lower level on the opposite side of the pot, and means for tilting the pot to selectively discharge molten mater-ial through either of said outlets.

6. Furnace according to claim 1, provided with a hearth of varying depth in said pot, the greatest depth 6 being located on the side remote from the pouring outlet. 7. Furnace according to claim 1, wherein an additional outlet is disposed at a lower level of the pot.

References Cited in the file of this patent UNITED STATES PATENTS 1,080,940 Massip Dec. 9, 1913 1,189,356 Eyermann July 4, 1916 1,313,890 Gray Aug. 22, 1919 10 2,406,147 Hopkins Aug. 20, 1946 FOREIGN PATENTS 548,737 Great Britain Oct. 22, 1942 910,418 Germany July 8, 1949

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