US1499922A - Electric-arc furnace - Google Patents

Description

July 1 1924.

W. S. HADAWAY, JR

ELECTRIC ARC FURNACE Filed Dec. 10 1921 BY a INVEN TOR.

ATTORNEY.

Patented July 1,1924.

PATENT OFFICE.

WILLIAM S. H ADAWAY, JR, .0! NE'W'ROCHELLE, NEW YORK.

' ELECTRIC-ARC FURNACE Application filed December 10, 1921. Serial 170. 521,333.

To all whom it may concern:

Be it known that I, WILLIAM S. HADA- WAY, Jr., a. citizen of the United States,

and a residentof New Rochelle, county of Westchester, and State of New York, have invented certain new and useful Improvements in Electric-Arc Furnaces, of which the following is a specification.

This invention relates to electric arc "furnaces, and more particularly to such furnaces employing electrodes arranged to form an arc in proximity to a quantity of metal or the like to be heat treated.

Broadly stated it is an object of the present invention to provide an electric arc furnace in which the efficiency of operation is greatly improvedby supplying a gaseous material directly to the arc.

Another object relates to the improvement of means for producing heat for the treatment of metals requiring high degrees of heat with substantially no reaction or interference with the chemical constituents change in the amount of carbon in a steel:

makes a greatly amplified change in the characteristics thereof, and thus the production of certain high grade steels, requiring' definite, critical proportions of carbon, is uncertain, and production schedules relating-thereto erratic.

In'its broader aspects, therefore, this invention is intended to reduce cost and to overcome these difiiculties, and in furtherance of these objects various other important features are provided, which will appear from the following description taken in connection with the accompanying drawing, in which- Figure 1 shows a sectional elevation of a furnace;

'Figure 2 shows an enlarged sectional view of a portion of the apparatus; and

Figure 3 shows a section taken on the line 3-3 of Fig. 2.

Like reference characters refer to like parts in the several figures of the drawing.

For the purpose of showing more or less diagrammatically an apparatus embodying the invention, there is shown in the drawing a retort 10 comprising a frame work 11 and a crucible 12 supported therein. The framework 11 is constructed of metal plates suitably secured together. The crucible is made of a refractory material in the form of a bowl having an outlet which may be sealed by a detachable plug 13 also of refractory material. The upper surface of the furnace comprises a cover plate 14, also of refractory material, having a substantially centrally disposed orifice for the re-' ception of a heater sleeve 15. The sleeve 15 has a peripheral shoulder or flange 16 for positioning the sleeve upon the plate 14,. 7 and is preferably .formed of refractory material capable of withstanding very high temperatures. The lower extremity of 'thesleeve 15 is open. The upper end of the sleeve 15 is closed by a cover plate 17 made of refractory material and resting on an internal shoulder in the sleeve 15 and is re? enforced by a second plate 18. The plate 18 is made ofa material which is an insulator of electricity, and which is capable of withstanding the degree of heat necessary.

A plurality of electrodes such as 20, 21 extend through slots in the plates 17, 18 the supports therefor being secured to the insulating plate 18, in any desired manner. Each of these supports (Figure 2) comprises a yoke or bridge 22 for pivotally supporting upon trunnion bearings the respective electrode and its carriage 23 (Figure 3). Thus the electrodes maybe rocked 0r tilted into and out of contact with each other. Each of the yokes 22has an extension 24 with an upright toothed segment 25, and the corresponding electrode carriage 23 has an arm 26 movable in proximity to the segment 25. The free end of each arm- 26 is shaped in the form of a handle and suitable latching means 27 may be provided for maintaining the electrode in a given position when desired. It 15 understood however that any suitable form 'of i or maintaining means, automatic,

manual or semi-automatic, may be employed for these purposes.

, The electrode supports and carriage are preferably made of nickel chromium or other suitable material.

The electrodes 20, 2l are made of a fulgarite such as oxide of magnesia, which is a conductor of electricity only when hot. They are made hollow in the form of tubes, the upper extremity of each being provided with a suitable binding post 30. Each electrode is mounted or clamped on the carriage 23 in any suitable manner and a transverse passage 31 leads through the wall of the electrode, one flange of the carriage member 23 and through a stufling box' 32, connecting to a supply 33 for supplying a suitable gas or vapor to the electrode. The binding posts each may comprise a split collar of electrically conducting material fitted over the upper end of the respective electrode, and fastened by means of a suitable set screw. Leading from the electrodes is a corresponding plurality of conductors connected to a source of current 34. The source 34 may supply either direct or alternating current and as shown a single phase alternating current is supplied; it is understood however that two or three phase current may be employed, the number of conductors and electrodes being then increased to four and three each respectively.

The supply 33. is connected to a main passage 35 leading to one of the electrodesupports for supplying active medium thereto. A bypass therefrom (see Fig. 1) leads to one part of a valve 36. A second part of the valve is. connected by means of a passage 37 to another of the electrode supports, andserves to supply or to withdraw active medium therefrom depending upon the position of the valve 36. A third part of the valve 36 is connected by means of a passage 38to the source 33.

In the interior of the bowl 12 is placed a suitable quantity of material 40 which is to be heat treated. When molten, the material may be removed by removin the plug 13 and tilting'the frame 11, the e being provided for that purpose suitable trunnion bearings in the sides thereof supported on upright brackets such as 41.

In operation, assuming that the source 34 is active, the electrodes are brought into contact at their lowerends. On account of the high resistance of the electrodes when cold little'or no current flows. The valve 36 is set in the position shown in Figurel.

A supply of hot gas or vapor, such as superheated steam for example, is now supplied through the passage 31 and the interior passage of each of the electrodes to the lower extremities thereof. The heat of the vapor is imparted to the electrodes, whose or crevices in the device.

resistance is reduced thereby, and current flows;

The electrodes are now separated, drawing an arc which produces an intense heat. A peculiar action now takes place, the theoretical explanation of which is in some doubt on account of obvious-difiiculties of observation; but it is thought that the action may be that the oxide of magnesia of which. the electrodes are formed is decomposed, and almost immediately recombines, so that there is substantially no real or permanent combustion thereof. While in its decomposed state, however, it forins, in combination with the vapor emitted by the electrode ends, a gaseous conducting path for th -current, so that a greatly extended arc can be formed with constant voltage and current factors.

The heat is imparted to the material 40 by radiation and reflection. Temperatures approximating. 5000 F. can be produced by such an arc, which is ample to raise the temperature of the material being treated to desired degrees.

'The heat transmitted by conduction through the electrodes 20, 21'to their respective supports is imparted, to the incoming stream of vapor. The vapor, although hot, is at a temperature considerably below the melting point of nickel chromium or other material of which the supports are made, and serves to limit the rise of temperature therein and prevent damage thereto. Thus it will be seen that the vapor performs a three-fold purpose: it heats the electrodes to make them conductors of electricity; it provides a path of electric conductivity for the current in the arc; and after the arc has been started, the vapor limits the rise of temperature of the electrode supports.

During the early period of the operation, the vapor after serving-its purpose, or the residue of the vapor, escapes throughv leaks 1 Later the valve 36 may be shifted to interconnect passages 37 and 38, thus permitting circulation of the vapor in through one electrode and out loss. Furthermore, the lack of combustion,

imparts stability to the are not found with carbon arcs, the electrodes of which necessarily are continually consumed, thus varying the arc, and requiring continualoperation of the regulating devices, and emitting an undesirable material in the-furnace.

When it is desired to remove contents of the crucible the source of current 34 and the supply of vapor are discontinued. The material 40 may then be emptied out, and the. apparatus made -ready for subsequent use. 7

electrodes.

Illustrativesapparatus has been described but itis ex-presly understood that the scope of the invention is not to be limited thereby,

reference being had to the appended claims vapor longitudinally through the electrodes.

3. An electric arc device comprising hols low electrodes of a material which is a nonconductor of electricity when cold, and means for passing a hot vapor longitudinally through the electrodes.

4. An electric arc device comprising hol.

low electrodes of an oxide ,of magnesia, and. means for passing a hot vapor through said 5. An electric arc device comprising hol low electrodes of an oxide of magnesia, and a single means for conducting a medium to each of the electrodes for initially raising the temperature thereof and for providing a gaseous ath for conducting electricity throu h t e arc.

6. electric arc device comprising means for introducing a flow of vapor for providing a gaseous path of conductivity for the are.

7. An electric arc device comprising a plurality of. electrodes and means for introducing a flow of vaporfor providing a gaseous path of conductivity for the arc.

8. An electric arc device comprising a plurality of hollow electrodes and means for introducing a flow of vapor through the electrodes for providing a gaseous path of conductivity for electricity.

9. An electric arc device comprising a plurality of hollow electrodes and supports therefor, and means for introducing a flow of vapor through the supports and the electrodes to the are.

10. The method of maintaining an are which consists of supplying a flow of vapor and a current of electricity to the arc.

11. The method 'of initiating and maintaining an electric are which consists .of supplying a potential of electricity, supplying a hot vapor to initiate conduction of electricity and to form a gaseous path at the are for the electric current. i

- 12. The method of operating an electric are which consists of passing a vapor to the arc in such "manner as to cool the ends of the electrodes spaced from the arc ends, and imparting the heat of the electrodes to the incoming vapor as it approaches the arc.

13. An electric furnace comprising electrodes composed of an oxide of magnesia.

14. An electric furnace comprisin hollow electrodes, means for supplying e ectric means for energy thereto, and means for passing a vapor through the. electrodes. 7

15. An electric furnace comprising ho low electrodes of a material which is a nonconductor of electricity when cold, and means for passing a hot gaseous medium through the electrodes.

16. An electric furnace comprising hol low electrodes of an oxide of magnesia, and passing a hot' vapor through said electrodes.

17. An electric furnace comprising hollow electrodes of an oxide of magnesia, and a single means for conductin a medium to each of the electrodes for initially raising the temperature thereof and for providing a gaseous path for conducting electricity through the arc.

18. An electric furnace, comprising means forintroducing a vapor for providing a gaseous path of conductivity for the arc.

19. An electric furnace comprising a plurality of electrodes and means for introducing a vapor for providing a gaseous path of conductivity for the are.

20., An electric arc comprising a casing forming a substantially closed space, and electrodes protruding into the closed space, said electrodes being non-conductors of electricity at ordinary temperatures and conductors of electricity when hot.

21. An electric, arc furnace comprising a structure vforming a substantially closed space, and electrodes which are non-conductors of electricity at ordinary temperatures and conductors of electricity when hot, said electrodes being positioned to protrude into the closed space, and means for heating the electrodes.

22. An electric arc comprising a structure forming a substantially enclosed space, and electrodes protruding into the enclosed space, said electrodes being nonconductors of electricity at ordinary temperatures and conductors of electricity when hot, and means for conducting a heating medium to said electrodes for'raising their temperature to a point where they become conductors.

23. Any electric arcdevice comprising a furnace havin an enclosed space, and electrodes protru ing into the space and formed of a material which decomposes and recombines in the arc. 24. The method of initiating andgmaintaining an electric are which consists of supplying a potential of electricity, supplying WILLIAM s. HADAWAY,

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