US1162773A - Electric furnace. - Google Patents

Description

C. HERING.

ELECTRIC FURNACE.

APPLICATION FILED MAY I. 1913.

(1,162,773, Patented 1590.7, 1915.

' 276;. 1 Wadi/A UZ jfl R3 CARL HERING, lOIF PHILADELPHIA, PENNSYLVANIA.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Dec. 7, 1915.

Application led May 1, 1913. Serial No. 764,742.

To all 'whom it may concern Be it known that I, CARL HERING, a citizen of the United States, residing in the city of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

My invention relates to electric furnaces of the type in which a molten or fluid resistor is involved; and relates more particularly to furnaces in which the resistors are so proportioned as to produce the pinch effect described in my prior Letters Patent of the United States No. 988936. And my invention relates to features of electric furnace construction of general application, though such features are more particularly valuable in connection with a pinch effect furnace.

By my present invention I provide furnace structure whichis especially applicable to the heating of liquids or molten materials of relatively low electrical resistivity, such as silver, gold, copper, etc. or alloys rich in such high conductivity materials; and which is applicable to cases in which it is desirable to have the hearth or bath container divided into tvvo or more compartments; and it is applicable to cases in which it is desirable to use treating current of relatively higher voltage and, therefore, proportionately less current, for a given amount of energy; and it is applicable to cases in which bottom pouring of the liquid or molten material is desirable. And my improved structure has other advantages.

The hearth, bath container or melting chamber is divided into a plurality of compartments which are in communication with each other at or near the bottom of the fluid material through one or more circumferentially closed, completely submerged channels completely i'illed with the fluid or molten material. The electric current is made to pass through the fluid or molten material in these channels which latter are so proportioned that the desired amount of heat is set free in the molten or fluid material within them; and the cross section of the channel or channels is so small relatively to the current passed through it that the resulting pinch effect keeps the fluid or molten material circulating rapidly enough to prevent any such overheating as would cause rupture of circuit in the channel or channels, or as would cause any other undesirable state of affairs to arise. When the fluid or molten material has been sufciently treated, it may be poured from a channel branching from and communicating with a heating channel, or may be poured dir ctly from such a heating channel, or otherwise, thus securing bottom pouring, which prevents slag, floating impurities or other undesirable matter from leaving the furnace with the poured material. Furthermore the fluid or molten material may be super-heated immediately before or While being poured.

The several compartments of the furnace hearth, bath containing chamber or melting chamber, may contain different slags if desired, for example one compartment may contain an acid slag and another a basic slag, whereby the material under treatment may be first subjected to the effects of one of the slags of one compartment and then, without having to change the slag or Without having to pour the material into another hearth or chamber containing another slag, may be subjected to the eects of another slag. And by employment of a plurality of compartments, they may have refractory linings of different materials, each adapted to the slag used in the particular compartment. Furthermore the total length of the combined resistor channels in which the heat is mainly generated, may be made greater, since the total length may be broken up into several shorter separat/e'lengths and since one or more of the resistor channels may be open at both ends; and with greater total length of resistor channel the cross section of each channel may be made smaller, which features are particularly advantageous in the treatment of low resistance materials such as above referred to.

My invention resides in the method and apparatus hereinafter described and claimed.

For an illustration of some of the many forms my invention may take reference is to be had to the accompanying drawing, in which:

Figure 1 is a top plan view of a two compartment furnace embodying features of my invention. Fig. 2 is a vertical cross sectional view taken on the line X-X of Fig. 1. Fig. 3 is a side elevational view of the apparatus shown in Figs. l and 2. Fig. 4 is a top plan view of a live compartment furnace embodying features of my invention. Fig. 5 is a plan view of a three compartment furnace adapted for the application of three phase alternating current. Fig. 6 is a top plan view of a further form of furnace for the application of three phase alternating current. Fig. T is a top plan view of a third form of furnace applicable for a three phase alternating current. Fig. 8 shows several arrangements ot' resistors whereby circulation of the fluid or molten material may be caused to take place largely in one direction.l

Referring to Figs. l, 2 and 3, W represents the refractory wall or container of refractory material of an electric furnace, such refractory material being substantially a non-conductor of electricity, such as lire brick or other well known furnace material. 7Within the material lV are formed the two hearths, bath chambers or melting chambers H, H containing the mass of material M, which, during the normal operation of the furnace, is fluid or molten metal, particularly a metal or alloy of high electrical conductivity such as copper, silver, gold, brass, in fact any metal or alloy.

E, E are electrodes through which current is communicated to the material M, these electrodes being either' vertical, as indicated in full lines or disposed in any other suitable position, for example, inclined, as indicated in dotted lines in F ig. 2. With the inner end of each electrode communicates a fluid resistor R, of material M, preferably at or near the bottom of the chamber lvl, communicating therewith, but at any rate completely submerged so that the resistor .forming channel C, circumferentially closed, is always maintained completely filled with material M. And forming a communication between the two hearths H, H are the resistors R', R in the channels C, C. rlhe path of current is then, in through one electrode E, through its resistor l, through the main mass of material M in one of the hearths H, thence through the resistors it', R in succession to the material M in the other hearth H, thence through the remaining resistor R to the other electrode E, it being understood that the terminals of the current source are connected to these electrodes E, E.

The cross section of each of the resistors R and R is so small, with respect to the strength of the current passed through them, that the pinch eect ensues causing an automatic circulation, stirring or agitation of the material. And it will be seen that with the four resistors in series with each other the total resistor length is relatively great so that material of high electrical conductivity may be successfully treated without too greatly reducing the cross section of the resistors. And it is further apparent that by dividing the total resistor length into a plurality of shorter resistors, each resistor will not be so long as to interfere with the rapid circulation which is necessary in order to prevent rthe material in the resistor from reaching a temperature so high or excessive as to cause a rupture by vaporization, pinch effect or otherwise, in the material of the resistor, with attendant interference in operation and with damage to the channel walls and to the furnace as a Whole. It is to be understood however that the structure described is not limited in its use to low resistivity materials, since the resistors both as to their length and cross section may be suitably proportioned for the treatment of materials of high resistivity. And by the arrangement of resistors described, due to their great total combined length and to the greater length relatively to the cross section, whatever the material may be which is operated upon, the electrical energy may be delivered to the electrodes E, E at relatively higher voltage and therefore proportionately lower current strength, which among other advantages diminishes the loss of energy in the electrodes.

Communicating with both resistors R', R is a pouring hole P leading to the pouring lip or spout S. By this construction when the material M is ready for pouring, the furnace may be tilted, and the poured material is then that of highest temperature, or at any rate of a temperature higher than the main mass M in either hearth H, since the hole or channel P communicates directly with a resistor channel. Furthermore the bottom pouring thus made available insures that only clean metal or material M will be poured, as the slags, floating impurities, or other undesirable materials will remain floating upon the main bath M in the hearths H, H, and will therefore be retained in these hearths.

Just before the pouring, or during the pouring, the strength of the current passed through the resistors may be increased so as to superheat the material or metal M before or during the pouring, with the result that the material or metal M poured will remain fluid a longer time after pouring and will more easily liow into and properly fill a mold.

To prevent waste or loss of heat from the baths M, M the cover A, omitted from F ig. l, may be provided as in Figs. 2 and 3 to cover the hearths or chambers H, H.

The mass of material M in the hearths H, ll may be more or less mixed with each other, as by tilting the furnace as indicated b v the dotted lines in F ig. 3. the tilting be'- ing effected in this case by tipping the furnace upon its rounded bottom. Obviously however the tilting may be accomplished by pivoting the furnace and tilting it upon its ist pivots; and obviously the arrangement may be such that the furnace may be tilted not only in one plane but in planes at right angles to each other-,or in all planes. In any event the sidewise tilting will raiseyone hearth higher than the other and in consequence there,will be a flow of material M from the higher hearth to the lower hearth through resistors R. R, backward and forward according to the direction of tilting. This mixing of the materials in the two hearths is also attainable due to the pinch effect produced in the resistors R', R', causing more or of the circulating material to mix at the junction of these resistors. The pinch effect itself sometimes produces a higher level in one compartment and a lower one in the other, thus causing some mixing without tilting.

The channels C, C constitute in effect a single channel open at both ends, that is, communicating at both ends with a mass of material in a hearth or chamber. lith such a channel open at both ends the circulation of the material within the channel is chiefly outward from the channel at each cnd of the channel along its axis, and inward at each end of the channel along the periphery of the channel. In consequence, such a channel, open at both ends, may therefore be made substantially twice as long as a channel or resistor closed by or terminating at one end by an electrode, as in the case with the resistors and channels R, R and C. C. In consequence, such a resistor channel` open at both ends, and of substantially double the length of the resistor channel closed at one end` will operate. without materially overheating the material. In consequence' such a channel, open at both ends, is better adapted for treatment of low resistance materials or metals, like copper and its alloys, or other materia-l hereinbefore referred to, with which, to obtain the necessary resistance for the liberation of the necessary heat, a channel closed at one end would become so long that the attending pinch effect would not be able to carry the material out of the channel fast enough or before it was raised to dangerously high temperatures.

rl`his structure lends itself to the employment of relatively higher voltages, as above explained. whereby the losses of energy in the electrodes are reduced; and whereby the necessary energy may be transmitted to the electrodes with correspondingly less loss externally to the electrodes and furnace. Furthermore with a plurality of compartments H, H, different slags may be used. For eX- ampleas for refining steel, an acid slag may be used in one compartment, while a basic slag is used in another, thereby .avoiding the need for changing slags and saving heat that would otherwise be lost in changing slags. And since hearth or chamber linings of different materials are best suited to uses with different slags, by my arrangement of a plurality of compartments, each compartment may be lined with a ,material mo-st appropriate to the slag to be used in that compartment. Furthermore, a lfresh and therefore more active slag may be used inl one compartment for acting upon or getting out the impurities in the bath, while a staler, previously used or less active slag may be used in another compartment to do the gross preliminary refining and to remove or act upon the larger part of the impurities. Furthermore by usingl a plurality of compartments, cold metal or raw material may be inserted in one compartment for melting, while another compartment may be used for the refining by slag or other treatment, with the result that melting and refining may be simultaneously carried on, making the process a continuous one` and thereby avoiding freezing or chilling of the slag when cold metal or raw material is introduced.

In Fig. -l is shown in top plan view a furnace having features above described. Here the electrodes E, E communicate directly or through suitable resistors R, R with the baths in the chambers or compartments Il. H which in turn communicate through resistors R2, R2 in channels C2, C2, with the baths in compartments or chambers H1, IP. And between the bath in the compartment or chamber H2 and the baths in the compartments H1. H1 communication is afforded by resistors R3, R3 in the channels C3, C3. The channels C2 and C3 are of course always completely filled with fluid or molten material as described in connection with Figs. 1 to 3 inclusive` and lie preferably at or near the bottom of the baths. The pouring channel P in this case communicates with the bath in the chamber either at or near its bottom, or at the top. By this arrangement still greater total length of resistor may be obtained, while making practical use of the heating and pinch effect in each resistor. Obviously the number of resistors and number of baths may be further increased in any suitable number and manner.

In Fig. 5 is shown in plan view a form of my furnace having the three electrodes-E1. E2 and E3 to be connected to any suitable source of current, such as a transformer or generator delivering three phase alternating current. For example these three electrodes may be connected to the terminals of either a delta or Y connected source of three phase current. These electrodes connect by resistors R with the baths in the three compartments H1, H2 and H3 which are connected by the resistors R1, R2 and R3, the pouring channel P communicating with the latter and leading to the pouring spout S. A somewhat similar arrangement is shown lll in Fig. 6. Here however the resistors R1, R2 and R3 come to a. junction with which the pouring channel P communicates. Here again the electrodes may be connected to any suitable source of current, such as a source oIl three phase alternating current, either Y or delta connected.

ln Fig. 7 are shown three pairs of electrodes and three pairs of resistors and three compartments or chambers, with one of them, for example H8, communicating with the pouring channel P leading to the lip or spout S. The baths in the three chambers or compartments communicate with each other through the resistors R1, R2 and R8 while the resistors lt form communication between the electrodes and the baths in the hearths or chambers. One pair ofz electrodes, as El, El may be connected with any suitable source of current, direct or alternating, or with one phase of a three phase source, and similarly the pair of electrodes E2, E2 may communicate with another source, or with another phase of a three phase source; and similarly the electrodes E3, EB may communicate with any suitable source of current, as a third phase of a three phase source.

ln all of the structures above described all the resistor channels have been assumed to he of constant cross section throughout their length. and all of equal cross section. nd it is preferred that the channels which are open at both ends be substantially twice as long as any resistor which is closed at one end as by an electrode. However my invention is not to be understood as so limited, 'for the diflercnt resistors may diHer among themselves as to cross section or length, or both; and it is to be further understood that any or all of the resistors may change in cross section from end to end. And by suitably shaping the resistor channels, especially those open at both-ends` the direction of circulation caused by the pinch effect produced therein may be largely in one direction. For example in Fig. 8 the resistor channel is either conical, that is, tapering in cross section, or is composed of several parts inclined to each other with the result that the circulation of molten material or flow therethrough tends to be stronger in one direction than in the other.

What l claim is:

l. 'lhe method of treating molten metal of high conductivity, which consists in confining the molten metal in one or more circumferentially closed channels communicating with a plurality of separate masses of the material, passing current through the material in said channel or channels, the channel diameter being small with respect to the channel length, and the current passed through the material in the channel'or channels being great with respect to the channel cross section, whereby the pinch effect is produced.

2. The method of electrically treating molten material, which consists in confining said material in masses in communication with each other through a portion of said material confined in a circumferentially closed channel filled with said material, passing through the material confined in said channel an electric current whose strength is great with respect to the cross section of said confined material, whereby the pinch efi'ect is produced in said confined material, thereby stirring said masses of material, and changing the level of a mass of said material to cause a fiow of material between masses through said channel.

3. 'lhe method of electrically treating molten material, which consists in conning said material in masses in communication with each other through a portion of said material confined in a circumferentially closed channel filled with said material, passing through the material confined in said channel an electric current whose strength is great with respect to the cross section ot said confined material, whereby the pinch effect is'produced in said confined material, thereby stirring said masses of material, and subjecting the diiierent masses of material to dii'ereut re-agents.

4. irl`he method of electrically treating molten material, which consists in confining said material in masses in communication with each other through a portion of said material confined in a circumferentially closed channel filled with said material, passing through the material confined in said channel an electric current whose strength is great with respect to the cross section of said confined material, whereby the pinch effect is produced in said confined material, thereby stirring said masses ot material, and treating one osaid masses of material with re-agent and introducing raw material into another of said masses.

rlhe method of treating molten iron or steel, which consists in confining said iron or steel in masses in communication with each through a circumferentially confined mass of iron or steel, and passing through said confined molten iron or steel an electric' current Whose strength is great with respect to the cross section of said confined molten iron or steel, whereby the pinch eect is produced in said confined molten iron or steel, and thereby stirring said masses of molten iron or steel, treating one of said masses of molten iron or steel with at basic slag, and treating another of said masses of molten iron or steel with an acid slag.

6. The method of electrically treating molten material, which consists in confining said material in masses in communication with each other through a portion of said material confined in a circumferentially closed channel filled with said material, and passing through the material confined in said channel an electric current Whose strength is great with respect to the cross section of said confined material, whereby the pinch effect is produced in said confined material, thereby stirring said masses of material, treating one of Said masses of material with fresh or active re-agent, and treating another mass of said material with a artly spent re-agent.

The method of treating molten material, Which consists in confining said molten material in masses in communication With each other through a restricted section of said material, passing current through said restricted sectioniof material to heat and move the same to cause a mixing of said masses through said restricted section, treating one of said masses of molten material with a re-agent, and treating another of said masses of material with a different re-agent.

8. The method of treating molten material, which consists in confining said molten material in masses in communication With each other through a restricted section of said material causing a mixing of said masses through said restricted section, treating one of said masses of material with a fresh or active re-agent, and treating another of said masses of material With a partially spent reagent.

9. The method of treating molten material, which consists in confining said molten material in masses in communication with each other through a restricted section of said material, passing current through said restricted section of material to heat and move the same to cause a mixing of said masses through said restricted section, and

adding raw material to one of said masses.

10. The method of treating molten material, Which consists in confining said molten material in masses in communication with each other through a restricted section of said material, passing current through said restricted section of material to heat and move the same to cause a mixing of said massesthrough said restricted section, adding raw material to onel of'said masses, and treating another of said masses With a reagent.

11. The method of treating molten material, which consists in confining said molten material in masses in communication with each other through a plurality of serially connected restricted sections of said material, and passing current through said restricted sections of material to heat and move the same tocause a mixing of said masses through said restricted sections.

12. The method of treating molten material, Which consists in confining said molten material in masses in communication Vmove the same to cause a mixing of said masses through said restricted sections, treatmg one of said masses of molten material with a re-agent, and treatmg another of said masses of material with a different agent.

13. The method of treating molten material, which consists in confining said molten material in masses in communication with each other through a restricted section of said material causing a mixing of said masses through said restricted section, treating one of said vmasses of material with a fresh or active re-agent, and treating another of said masses of material with a partially spent reagent, and passing an electric current through said restricted section of material.

1li. The method of treating molten material, which consists in confining said molten material in masses in communication with each other through a plurality of serially connected restricted sections of said material, passing current through said restricted sections of material to heat and move the same to cause a mixing of said masses through said restricted section, adding rau7 material to one of said masses.

15. The method of treating molten material, which consists in confining said molten material in masses in communication with each other through a plurality of serially connected restricted sections of said material, passing current through said restricted sections of material to heat and move the same to cause a mixing of said masses through said restricted sections, adding raw material to one of said masses, and treating another of said masses With a reagent.

16. An electric furnace comprising two or more chambers adapted to contain molten material, means affording mechanical and electrical communication between the molten material in said chambers comprising circumferentially closed channels located below the level of said molten material and communicating with said chambers, a source of current external to said furnace, electrodes connected to said source of current and to said molten material, the cross section of a channel being such that the density of the current in the molten material in said channel is such as to cause so rapid a circulation of molten material in said channel by the pinch effect that dangerous temperatures in said channel are prevented.

17. An electric furnace comprising tWo or more chambers adapted to contain molten material, electrodes for conducting electric current into said molten material, a circumferentially closed channel connecting an electrode through the molten material in said channel with the molten material in a chamber, and a circumferentially closed channel connecting chalnbers with each other, the molten material in said channels and chambers forming a closed electric circuit including said electrodes.

18. An electric furnace comprising two or more chambers adapted to contain molten material, electrodes for conducting electric current into said molten material, a circumferentially closed channel connecting an electrode through the molten material in said channel with the molten material in a chamber, and a circumferentially closed channel connecting chambers with each other, the molten material in said channels and chambers forming a closed electric circuit including said electrodes, the current through one or more of said channels being so great with respect to the cross section thereof that rapid circulation of said molten material is produced therein by the pinch effect.

19. A tilting electric furnace comprising circumferentially closed resistor channels constituting sole communication between separated chambers, said chambers adapted to contain molten material filling said channels, means for passing current through the material in said channels, and a pouring outlet connecting with a channel.

20. An electric resistance furnace comprising electrodes, and a circuit Within said furnace having said electrodes as4 terminals, said circuit comprising molten conducting material disposed in circumferentially closed channels alternating with chambers, the current in the molten material in a channel being so great relatively to the cross section thereof that rapid circulation of said molten material is produced therein by the pinch effect.

21. A tilting electric furnace comprising a resistor included in circuit with electrodes, said resistor comprising molten conducting material disposed in a circumferentially closed channel having a plurality of enlargements constituting crucibles or hearths open at the top, said resistor forming the sole communication between said crucibles or hearths, and a pouring connection with said resistor.

22. An electric furnace comprising a plurality of hearths, circumferentially closed channels communicating with and connecting said hearths in series below the level of molten conducting material contained in said hearths, and channels connecting each of the l.two hearths forming the ends of the series with electrodes.

23. An electric furnace for treatment of molten metals of high conductivity comprising a resistor of molten high conductivity metal disposed in a circumferentially closed channel having a plurality of-enlargements constituting crucibles or hearths, the diameter of the channel being small compared to its length, and means for passing current through the resistor material, said current being great with respect to the cross section of the resistor, whereby the pinch effect is produced.

2-l. In an electric furnace a plurality of electrodes, a plurality of sections of molten resistor connected in series with each other between said electrodes, masses of molten material between resistor sections, said resistor sections adapted to have produced therein the pinch effect.

25. A tilting electric furnace comprising a circumferentially closed resistor channel constituting sole communication between separated chambers in all positions of said furnace, said chambers adapted to contain molten material filling said channel, means for passing current through the material in said channel, and a pouring outlet connecting with said channel.

26. A tilting electric furnace comprising circumferentially closed resistor channels constituting sole communication between separated chambers in all positions of said furnace, said chambers adapted to contain molten material filling said channels, means for passing current through the material in said channels, and a pouring outlet connecting directly with a channel.

27. An electric furnace comprising a plurality of chambers, resistor channels each opening at opposite ends into different of said chambers and forming means of communication between said chambers. and means for passing current of the different phases of a polyphase source through the material in said different resistor channels.

28. An electric furnace comprising a plurality of chambers, resistor channels interconnecting all of said chambers, said chambers and channels forming a closed loop system, and means for passing current through the material in said channels.

29. An electric furnace comprising a plurality of chambers, resistor channels interconnecting all of said chambers, said chambers and channels forming a closed loop system, and means for passing polyphase current through the different parts of said loop system.

30. An electric furnace comprising a plurality of chambers, resistor channels interconnecting all of said chambers, said chambers and channels forming a closed loop system, electrodes, and channel resistors forming connections between said electrodes and said loop system.

31. An electric furnace comprising a plurality of chambers, resistor channels interconnecting all of said chambers, said chambers and channels forming a closed loop system, means for passing current through the material in said channels, and a pouring outlet connecting with a channel.

32. The method of treating molten material, which consists in confining the molten material in one or more circumferentially closed channels forming sole communication between a plurality of separated masses of said material, passing current through the material in said channel or channels to heat the same, and pouring material directly from a channel during passage of current therethrough, whereby said material as it is poured is at higher temperature than the material in said masses.

33. The method of treating a mass of molten material, which consists in conning a part of the material in a circumferentially closed channel or channels forming a molten resistor or resistors, passing current through said resistor or resistors to heat the same, substantially all of the heat communicated to the mass of material being generated in said resistorl or resistors, pouring material directly from one or more of said resistors during the passage of current therethrough. In testimony whereof I have hereunto afliXed my signature in the presence of the two subscribing witnesses.

CARL HERING. Witnesses: v

ELEANOR T. MCCALL, NELLIE EVANS.

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