US1411158A - Electric-furnace construction - Google Patents

Description

W. E. F. AND A. B. BRADLEY.

ELECTRIC FURNACE CONSTRUCTION.

APPLICATION HLED AUG.27,19I81 RENEWED AUG. 26. 1921- Patented Mar. 28, 1922.

w..E. F. AND A. B. BRADLEY.

ELECTRIC FURNACE CONSTRUCTION. APPLICATION FILED, Aue.27, 191s. RENEWED AUG. 26, 1921.

1 ,411 ,1 5 Patented Mar. 28,1922.

4 SHhETSSHEET 2.

$1 alta /Mei P W. E. F. AND A. B. BRADLEY.

ELECTRIC FURNACE CONSTRUCTION.

APPLICATION FILED AUG.27, 191s. RENEWED AUG. 26. 1921.

1 ,41 1 1 58 Patented Mar. 28, 1922.

4 SHEETS-SHEET 3.

Sum

$1, amma 5.

W. E. F. AND A. B. BRADLEY.

ELECTRIC FURNACE CONSTRUCTION. APPLICATION FILED 1116.27, 1918. RENEWED AUG. 26, 1921.

Patented Mar. 28, 1922.

4 SHEETS-SHEET 4. ,610

SI nviwvtoz UNITED STATES PATENT OFFICE.

WALTER E. F. BRADLEY, OF LOS ANGELES CALIFORNIA, AND ALONZO B. BRADLEY,

OF NEW YORK, N. Y.

ELECTRIC-FURNACE CONSTRUCTION.

Specification ofLetters Patent.

Patented Mar. 28, 1922..

Application file-d August 27, 1918, Serial No. 251,666. Renewed August 26, 1921. Serial No. 495,720.

To all whom it may concern Be it known that we, WALTER E. F. BRAD- LEY and ALONZO B. BRADLEY, both citizens of the United States, and residing,-respectively, in Los Angeles, county of Los Angeles, State of California, and in the city, county, and State of New York, have invented certain new and useful Improveples involved in the invention.

ments in Electric-Furnace Construction, of which the following is a specification.

Our invention relates in general to electric furnaces, and more particularly to those of they electric arc type for metallurgical operations. In a more limitedsense, the invention is especially applicable to electric arc furnaces for performing metallurgical reduction by means of a gaseous reducing agent, and a construction of the furnace for this particular purpose will perhaps serve as the best example to illustrate the princi- Furnaces of the type above set forth re- 11118 'a main crucible or hearth to receive t e charge of, for example, ore and flux,

an opening or passageway through which the charge may be introduced, electrodes for developing heat within theinterior chamber of the furnace, atuyere or some form of device for applying the gaseous reducing agent to the charge, and an opening or passageway through which the slag and reduced metal may be discharged from the furnace. It is not always necessary that this latter element be separate and distinct from the opening or passageway through which the charge is introduced into the furnace for treatment. In the operation of the furnace the electrodes must be suitably suplied with electric power and must be capa- Ele of adjustment to maintain the proper respective positions of the electrodes between which the arc is drawn. Also the supply of the gaseous reducing agent should be capable of manipulation to control the application of the reducing agent ,to the charge with respect to regulating the rate of supply and with respect to discontinuing the supply of gas as desired, as for example on completion of the reducing operation. The discharge of the sla and reduced ore is ordinarily accomplishe by a pouring action as by tilting the furnace bodily upon a horizontal axis or by rocking the furnace upon a generally horizontal base.

According to the present invention the.

introduced into the charge and the door through which the charge is to be poured from the furnace, are disposed in proper relation to each other and at points in the furnace wall at suitable distances from the inclined axis so that when the furnace has been turned to one position the tuyere is beneath the molten charge and the door is above the charge, in a second position both are above the charge, and in a third position the door is beneath the char e while the tuyere is above the charge. f he elec trodes are mounted in the upper portion of the furnace so as to project 1nto the iriterior chamber above the charge and they are set at the proper angle to the axis so as to gain the most advantageous deflection of the arc downward without the are becoming interrupted. On the other hand, the electrodes are symmetrically disposed in radial planes at equal angles from each other. With this arrangement of the electrodes in symmetrical relation, we are enabled to automatically regulate the feed of the electrodes by, individual controls dependent upon the respective ciirrent passing through.

position in whichboth the tuyere and the door are above the level of the charge; Figure 3 is an outside view of the furnace as it appears when in the pouring position; and Figure 4 is a diagram illustrating how the feed of the electrodes may be accomplished automatically.

. Referring specifically to the drawings (Figure '1- 10 indicates the inner linin of highly re ractory material, 11 the bee 'ng thereof which may for exam le be fire brick,- and 12 the outer shell of s eet metal. As

shown in the present example, the furnace has an'intermediate cylindrical portion and upper and lower conical portions, the common axis of these parts being inclined to the vertical, with the lowest element of the conical surface horizontal. The relation between the altitude and base of this lower cone is chosen to provide the maximum interior capacity for a given radiating surface, whereas the inclination of the axis of the furnace is chosen to bring the lowermost element of the conical surface into a horizontal plane. The charge of material such as ore and flux, is represented at 13. The tuyere through which the reducing gas is supplied to the charge 13 is mounted in the lower conical wall of the furnace and comrises a removable carbon tube 14, inserted in a highly refractory socket or sleeve 15,

communicating at the bottom with a supply ipe 16 through which the reducing gas is a mitted under the control of hand valve 17. Pipe 16 ispresumed to be flexibly connected with a source of gas, such as for example a natural gas main.

The charge 13 is introduced into the furnace through the inlet 18 mounted in the upper cone of the furnace body. During the reducing action the gas admitted through the tuyere 14 passes upwardly through the charge and the gaseous prod ucts rising from the surface of the charge rise through the interior furnace chamber and pass out through the charge inlet 18.

In the example selected for purposes of illustration, three phase alternating current is employed, with one electrode for each phase. The electrodes are indicated at 19, and their supply conductors at 20 leading off from the three phase cable 21. As seen clearl in Figure 1, the electrodes are incline to the main axis of the furnace, the construction being such as to deflect the arc downward as far as possible with a given volta e. The desired angle is taken into consideration in determining the height of the upper ,cone or roof of the furnace body, so that the electrodes may pass through the furnace roof at right angles thereto. The distance at which the electrodes are disposed from the apex of the upper cone is so chosen as to bring the point toward which the electrodes converge approximately in the centre of the interior furnace chamber so as to apply heat as uniformly as possible to the charge of ore and slag. It is also to be noted that the design. calls for such dimensions as to avoid projection of the electrodes into the gpagg immediately beneath the charge in- By referring to Figure 4, which shows one way in which the feed of the electrodes can be accomplished automatically, it will be seen that the electrodes are distributed at equal circumferential distances about the main tion to advance the electrode.

axis of the furnace. It has also been stated that the several electrodes have the same inclination to the main axis of the furnace. With this symmetrical arrangement, the three phase are will be maintained between their tips, with an equal load in each electrode so long as their tips are equidistant from the imaginary point toward which they converge. Unequal consumption of one electrode may for example increase its distance from the centre with the result that its phase meets abnormally high resistance. To restore equilibrium the individual controls shown in Figure 4 may be employed. Theelectrodes 19 are shown in the diagram as separately supplied with current from the individual conductors 20. Each individual conductor 20 passes through or in inductive relation with a coil 22 which is connected with a solenoid coil 23, whose armature 24 actuates switch 25 against the influence of spring 26. Switch 25 mav thus be caused to make contact with a terminal 27 connected with a negative line wire 28 or with a terminal 29 connected with a positive line wire 30. The circuit leading to or from the switch arm 25 comprises a conductor 31 which leads to a motor 32 from which a conductor 33 leads to a neutral line wire 34. The shaft of motor 32 carries a pinion 35 which meshes-with a rack 36 on electrode 19 so that upon the motor being energized the electrode will be moved in one direction or the other depending upon the direction of the current flowing through the windings of the motor. If we assume that the current in one of the electrodes 19 has decreased so that the current induced in coil 22 is less, the current in coils 22 and 23 will be weakened so that spring 26 may pull the switch arm 25 into contact with the terminal 29. Thereupon current flows from line wire 30 into the motor 32 by way'of conductor 31 which we may assume drives the motor 32 in a direc- When the electrode has been advanced to the point where the current. of its phase becomes normal, the increased current flowing through coils 22 and 23 has the effect of withdrawing the switch arm 25 from the terminal 29 and the motor comes to rest. Excessive current passing through electrode 19 increases the current In coils 22 and 23 to such an extent that armature 24 is caused to draw the switch arm 25 into contact with the terminal 27 and establish a circuit through motor 32 in the opposite direction, whereupon the electrode is withdrawn until its current becomes normal. With the automatic regulation described, it is apparent that the feed of the electrodes will take place during the ordinary running of the furnace without requiring the constant shifting of the electrodes by the furnace attendant. It will however be understood that while the inmanual adjustment and none is shown, the

automatic regulation is in practice intended to be a feature additional to any suitable construction and arrangement by which the parts can be set in their normal position by the operator and by which any required manual shifting or adjustment of the electrodes can be accomplished.

As explained in the introduction to this specification, the furnace is designed to have a plurality of positions, and movement into these positions is accomplished by rotating the furnace about aninclined axis. To provide for this shifting operation, the furnace is supported in the embodiment shown upon a circumferential series of rollers 35, which are suitably mounted in an annular runway 36, and have resting upon them a collar 37, which surrounds the furnace and is suitably secured thereon. .Power for turning the furnace may be applied for example by a pinion 38 meshing with gear ring mounted on the upper face of collar 37.

In operation, the furnace receives its charge while in the position shown in Figure 1, in which it willbe noted the inlet 18 is vertical, the tuyere 14-is at the lowest level and the door 40 is above the charge level. With the are burning between electrodes 19 and the reducing gas delivered through tuyere 14, fusion and reduction of the charge and slagging of impurities occur. Upon completion of the reducing operation, the furnace is rotated upon its inclined axis until the tuyere 14 is removed from beneath the charge but with the door still above the level of the charge, as shown in Figure 2. By having the door and tuyere less than 180 apart, the space below them is thus increased. The gas may then be partially or entirely shut off without danger of the molten metal running into the tuyere. The heating may be continued or not, as desired, for a further period of time with the furnace in this position, to ermit the charge to become as free as possi le of gas. Preferably a reduced quantity of gas is permitted to continue flowing through the tuyere 14: to maintain a reducing atmosphere above the charge and avoid oxidation of the electrodes. When it is desired to pour ofi' slag and reduced metal, the furnace is turned further toward the position shown in Figure 3, in which the door 40 is brought below the level of the charge, but with the tuyere 14 still above the charge. Figure 3 is intended to show how the charge can be completely removed from the furnace, as'the door 40 preferably has its lower edge substantially in the plane of the base of the bottom cone.

Additions may be made either before or after pouring off the slag, for producing a particular quality of steel. It will also be understood that it may be desired in many cases to leave a certain quantity of molten charge in the furnace and introduce the fresh charge into this. Thus the furnace would not necessarily be turned as far as shown in Figure 3 in pouring off the reduced metal. \Vhen ready for the new charge, the furnace is returned to the position shown in Figure 1, preferably by rotation in the opposite direction. The carbon tube14 which serves as the tuyere through which the reducing gas is introduced, is removable so as to be readily replaced when necessary. The gas passing through it protects it from oxidation, and it is found to Wear better than metal or any of the ordinary refraotory materials. Should the supply of gascease or fall below a certain pressure, however, while the tuyere is beneath the molten charge, the metal flows into it and solidifies. Being removable it may in Such cases be easily withdrawn and replaced.

The illustration of threeelectrodes is only to show the principle of operation where a plurality of electrodes in symmetrical re lation are employed. Obviously the number may be varied without departing from the principle involved. Also the current may be either alternating or direct, but alternating is preferred.

We claim:

1. An electric furnace comprising a furnace body, with its .main axis inclined, and having a door provided in its wall at a distancefrom the inclined main axis, and means of, and means for rotating said furnace body with its axis inclined to raise and lower said door with respect to a horizontal plane.

3. An electric furnace comprising a furnace body with its main axis inclined, and

having a tuyere provided in its wall at a distance from, the inclined, main axis, and means for rotatably supporting the said furnace body.

4. An electric furnace comprising in combination a generall symmetrical furnace body having a tuyere in its wall at a point removed from the main geometrical axis thereof, and means for rotating said furnace body with its axis inclined to raise and lower said tuyere with respect to a horizontal plane.

5. An electric furnace comprising in combination a furnace body having a door and a tuyere, both of which are removed from the main axis of the furnace, and means for rotatably supporting the said furnace body with its main axis inclined.

6. An electric furnace comprising in combination a furnace body having a door and a-tuyere circumferentially spaced apart and both removed from the main axis of the furnace, means for rotatably supportin the furnace body with its main axis incline and means for turning the furnace body upon its support to raise and lower the tuyere and door. I

7. An electric furnace comprising in combination a furnace body, having a door and a tuyere, circumferentially spaced apart and at different distances from the main axis of the furnace, and means for rotatably supporting the said furnace body with its main axis inclined,

8. An electricfurnace comprising in combination a furnace body having a door and a tuyere circumferentially spaced less than 180 apart and at different distances from the main axis of the furnace, and means for rotatably supporting the said furnace body with its main axis inclined.

9. An electric furnace having a conical bottom and means for rotatably supporting the same on an inclined axis with the lowest element of the conical surface horizontal.

10. An electric furnace having a body with cylindrical intermediate ortion and a co-axial conical bottom, the cylindrical portion havin a door with its lower edge substantially 1n the plane of the base'of the conical surface, and means for rotatably supportin the furnace body on an inclined axis with t e lowermost element of the conical surface horizontal.

11. An electric furnace for reduction of ores, comprising a furnace body with interior chamber to contain the charge, a plurality of symmetrically arranged electrodes projecting into the said interior chamber but terminating above the charge of ore therein, said electrodes being inclined toward a common axis, means for supplying current to said electrodes, and individual feed devices controlled by the current passing through the respective electrodes for maintaining their ends at equal distances from their common axis.

WALTER E. F. BRADLEY. ALONZO B. BRADLEY.

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