US2528209A - Apparatus for smelting metals - Google Patents

Description

Oct. 31, 1950 w, BQNSACK ETAL 2,528,209

APPARATUS FOR SMELTING METALS Original Filed July 12, 1946 3 Sheets-Sheet l vINVENTORS E?. E uralter M. W'il. Walter Bonsafek AT T RNEY .'5 Sheets-Sheet 2 fr l iled July l2 lgina Oct. 3l, 1950 INVENTOKS M. I'Vil ATTORNE W-alter Walter Bonqacr BY am "Obb 31, 195() w BONSACK ErAL 2,528,209

APPARATUS FoR SMELTING METALS original Filed July r2, 1946 5 sheets-sheet s Walter Bons ack ATT ORNE YS Patented Oct. 3l, 1950 FICE APPARATUS FOR SMELTING MEXTALS Walter Bonsack, Lyndhurst, and

Walter M. Weil,

Shaker Heights, Ohio, assignors, by mesne as- M. Weil, Cleveland, Ohio signments, to Walter Original application Jn 683,114. Divided and 1948, Serial No..30,963

1y 121946, serial No. this application June 3,

This invention relates to the smelting of metal and more particularly to the smelting of light metals for purposes of refining, purifying, modifying and mixing them. Reference is made to copending application for patent Serial No. 683,114, filed July l2, i946, of which this is a division. n f K In the smelting of light metals such as aluminum the metal is reduced to a liquid state for the removal of metal oxide coatings and impurities. The heating of metal for the purpose of bringing it to a molten state has the effect, in an oxidizing atmosphere such as air, of causing further oxidation of the metal with a resultant loss in recovery. It therefore becomes desirable /to heat the metal rapidly and bring it to a molten state with minimum exposure to an oxidizing atmosphere or environment while being heated.

To effect the rapid melting of light metals it has been customary in the smelting art to maintain a bath of molten metal into which solid metal is introduced. Submerging of the solid metal in the molten bath efl'ectsa rapid heat transfer from the molten metal to the solid metal particles or pieces, so that they are quickly reduced to a molten state. Large pieces of metal to be thus smelted are handled without undue difliculty, but in the case of small metal particles such as cuttings, turnings, filings and the like, immersion in the molten bath is diillcult. This diiculty arises not only by reason of the small light-weight and buoyant character oi' the particles or pieces, butr because on the surface of the molten bath a layer of oxide and slag material may be present which acts as a support for the small particles and resists their introduction or movement into the bath of molten material underneath. Hence small particles of light metal, when placed on the top of a smelting bath tend to be exposed for `an excessive length of time to the oxidizing atmosphere of the air and the contaminating impurities in the slag layer, while at the same time being subjected to the heat of the slag and the molten body of metal underneath.

Another problem encountered in the smelting of light metals is in connection with fluxing. 'Ilo separate the metal from v'oxides and other impurities various fluxes are added. Such materials are customarily employed in a powdered form and are of light weight, so that in associating themselves with the oxides and impurities they, buoy up these deleterious materials in the molten mass, vcausing the undesirable constituents torise to the surface and form the slag layer previously mentioned. Since theriiuxes are 2 themselveslight in weight, it is difllcult to introduce them into the metal through the slag layer or even when there is no slag layer. Much of the flux placed on the top ofa molten bath does not become thoroughly mixed into the molten metal and hence it is not employed to greatest efliciency. Accordingly, it is often necessary to employ a larger quantity of iluxing material when smelting by conventional methods than would be required if a more thorough and efficient mixing of the flux and metal couldv be obtained.

One practice in the smelting art is yto bring.

-example it is desirable under certain conditions to introduce gasesY such as nitrogen, chlorine,

fluorine and hydrogen fluoride into the metal during smelting and refining. These so-called refining gases, when introduced into a pasty mix of the metal, are physically entrained and the high viscosity of the metal retards the movement of the gas upwardly through the Ametal tothe surface, where'it escapes and is lost. 'Ihus a considerable economy in refining gas can be realized by carrying such gas into a pasty mix of the metal to be refined. Thus fluxes and refiners added to metal maintained in a slush or pasty state can be more readily commingled and the tendency of theiimpurities, contaminants, ux and other additives to separate out and either sink to the bottom or rise to the surface of the metal by reason of greater weight or buoyancy is minimized.

It is therefore one of the principal objects of the present invention to provide a new and improved apparatus suitable for ysmelting `metal, particularly light metal such as aluminum, which will largely overcome the difllculties mentioned above and which Will'obtain the advantages of simplicity, continuity, and economy of metal, fluxes. refiners and other additives; such apparatus to provide for the circulation of molten metal from one body thereof to another and back again, accompanied by the transfer of heat from molten metal in one of the bodies thereoi'.to solid metal being smelted, and to compensate for heat so lost or transferred or replenish the same by the application of heat to molten metal in the other body.

Another object of the invention is to provide a smelting apparatus in which heat is rapidly applied to solid metal being smelted to elevate the same quickly to its melting temperature while protecting it from oxidizing atmosphere so that oxidation thereof is minimized. More specincally, the invention contemplates the rapid immersion or engulfment of the solid metal in higher temperature liquid metal, so that the solid metal is by reason of such immersion or engulfment protected or shielded from exposure to the oxidizing air or atmosphere while being melted.

A further object of the invention is to provide an apparatus for smelting wherein a stream of molten metal is continuously withdrawn from a relatively large body of molten metal and poured or directed over, through or onto solid metal pieces or particles, so as to rapidly immerse, surround or engulf the solid metal and through intimate contact therewith effect a rapid heat transfer which quickly raises the solid metal to apasty state, its melting point, or substantially so. 1n its preferred form the apparatus of this invention is calculated to permit retention of the metal being s melted in a pasty mix, state or condition just short of completeliquefaction for a sufficient period of time to enable optimum fluxing and refining to take place. Thereafter and by the further addition of heat to the pasty mix, as by commingling additional quantities of relatively high temperature molten metal therewith, the mass is brought to skim in which condition impurities, contaminants and the like rise to the surface or are carried thereto by the action of the flux and are separated.

A still further object of the invention is the provision of an apparatus which maintains several bodies of metal in juxtaposition and provides for continuous circulation of molten metal between the bodies so that in refining or smelting, alloying and refining a large batch, all portions of such batch can be made homogeneous and uniform, permitting the introduction of alloying, refining and purifying ingredients in one region of the batch and obtaining proper distribution and incorporation of such ingredients throughout the mixture. i

As a still further feature and object of this invention an apparatus is contemplated in which a relatively large body of metal is maintained in a molten condition in a substantially closed furnace which serves to furnish to the metal the bulk of the heat used in smelting. A continuous stream of molten metal is withdrawn from the large body and directed into a separate and smaller body of metal where it commingles with solid metal introduced into the smaller body, supplying heat to the latter and forming apasty mix which is progressively built up or increased in size and maintained until refining, purifying and segregation of contaminants and impurities are substantially completed.

As an arrangement suitable for relatively large n scale operations, the present invention has as a further object the vprovision of an improved apparatus for substantially continuous smelting of light metal. In the sense that it is used in this specification, continuous denotes the addition of succeeding quantities of metal to be smelted while the purifying and refining of previously added quantities of metal is progressing.

The present invention includes a furnace similar to that employed in the intermittent or cyclicy batch method. Combined with the furnace is an auxiliary hearth upon which is maintained a body of metal. a part of such metal undergoing purification and'reflnement in a pasty mass condition, while another partis being brought to skim permitting slag and impurities to be removed from the top thereof. rlhe purified and refined metal flows back into the main furnace or heating chamber for re-circulation and re-use in the process until withdrawn from the smelter.

The fresh solid metal being added continuously or at regular intervals to the auxiliary hearth and which is being smelted, is heated to a pasty state by a continuous stream of molten metal from the large body thereof in the main heating chamber. Heat is added to that part or portion of the metal on the auxiliary hearth which is being brought to skim by continuously introducing thereinto a second or separate stream of relatively hot molten metal drawn from the large body of molten metal on the main hearth of the heating chamber. Thus heat is added to the body of metal on the auxiliary hearth at two separated points, one point being that at which the metal to be smelted ls introduced, and the other point being that at which it is desired to convert the pasty mass metal into a readily flowable liquid for separation of impurities, contaminants and for skimming. By correct proportioning of the rate of flow of the molten metal into the body of metal on the hearth at the several points mentioned, the correct amounts of heat can be added to maintain the metal in a pasty state after its initial introduction to the apparatus on the auxiliary hearth and to subsequently convert it to a liquid from the pasty mass for the separation oi impurities and for flowing it into the main furnace chamber.

For still further objects the invention con templates theprovision of an apparatus which is relatively simple and readily operated with maximum eiiieciency and economy. The invention resides in certain novel structural features and combinations. Other objects and advantages not specically mentioned above will become apparent from the following detailed description of thc invention which is made in connection with the accompanying drawings forming part of the specification. Like parts throughout the several views are indicated by the same letters and numerals of reference.

In the drawings:

Figure 1 is a plan view. partly diagrammatic, of a furnace embodying certain of the principles of the present invention;

Fis. 2 is a vertical, sectional view taken substantially on the line 2-2 of Fig. l;

Fig. 3 is a fragmentary, vertical, sectional view with parts removed taken substantially on the line 3-3 of Fig. l and enlarged with respect thereto;

Fig. 4; is a sectional detail taken substantially ou the line 4 4 of Fig. 3 and enlarged with respect thereto;

Fig. 5 is a sectional detail taken substantially on the line 5 5 of Fig. 3 and enlarged with respect thereto;

Fig. 6 is a fragmentary plan view, with parts broken away, showing the auxiliary hearth portion of a modified form of apparatus as contemplated by the present invention for use in a continuous process; and

Fig. 7 is a vertical section with parts broken away taken substantially on the line 'I-T oi' Fig. 6.

The present invention contemplates a modified furnace structure, preferably of the .reverberatory type, although other heaters may be employed. Such furnace includes, besides a suit-v able metal frame not shown, .a main hearth I enclosed by refractory lined side walls 3 and 5, refractory lined front and rear walls 4 and 2, and an arched refractory lined dome or ceiling 6. There is thus provided in the furnace an enclosed holding and heating chamber for molten metal B. Over such metal there is maintained a controlled atmosphere which in .practice is preferably slightly oxidizing in nature. Fuel such as gas and combustion air are introduced into the furnace chamber through openings I in the side wall 5 which accommodate conventional gas burners not shown. Spent or burned out gases are exhausted through ue 8, also located in the side wall 5.

In the side wall 3 there is formed an outlet opening communicating with the bottom of the main heating chamber adjacent the level of the hearth I and provided with a spout II). This outlet opening is plugged during the smelting -process and when the smelting is completed the plug is withdrawn so that the molten metal flows out through the spout I0 into ladles, ingot molds and the like, for subsequent use as desired. A number of clean-out or access openings II, I2 and I3 are formed in the walls 2, 4 and 5, respectively, of the furnace and can be removed or opened when it is desired to clean or repair the interior of the main furnace chamber or for initial charging of metal therein.

On the outside of the main furnace chamber, along the exterior side of the front wall, is an open or auxiliary hearth I8 which may be on substantially the same level as the mai or covered hearth I. The hearth I8 is enclosed by upright efractory lined side walls I'I, thus providing an open-topped receptacle disposed on the outside of the main hearth chamber and separated therefrom by the front wall 4.

At one end of the auxiliary hearth I8 an opening or passage 20 is formed through the front wall 4 adjacent the bottom thereof. The auxiliary hearth I8 thus communicates with the main "A of molten metal carried on the auxiliary or working hearth I8. From the larger body B of molten metal, heated to a relatively high temperature in the main or reverberatory portion of the furnace, a substantially continuous stream is flowed onto the hearth I8 through the opening or passage 20, from whence it emerges llrst into the small body C and is then pumped over a cross wall or welr 40 and into heat exchanging relation with the solid 4metal that has been lntroduced into the small body A on the auxiliary hearth I8. Thus heat is supplied to the solid metal to reduce it to a molten or pasty state or condition.

To effect a flow of metal between the 'relatively large body B contained in the main heating chamber on the hearth I and the smaller body A of metal in juxtaposition thereto on the auxiliary hearth I8 any suitable -pumping or flow inducing means or device may be utilized. One such device, illustrated in Figs. 1 through 5, comprises an electric induction pump.

This pump is located generally below the level :5 of the hearths and comprises a refractory lined hearth I through the passage 28, permitting the flowof` molten metal from one Yhearth to the other, thereby maintaining equal levels of molten metal fon the two hearths. The circulation of molten metal as contemplated by this invention involves a flow from the relatively large b ody B of metal on the main hearth I through the low relatively small passage er opening 20 onto the auxiliary hearth and return to the main hearth through a relatively `larger passage or opening 2I formedlthrough the front wall 4 at `theother, end of vthe auxiliary hearth Il. A

slidable or vertically movable closure or door 22 oi' refracto'y material is provided for the passage 2I. N Irmally the closure 22 is adjusted to or just below the surface of the metal in the openauxiliary hearth compartment. 'I'he gate orclosure 22 thus prevents the flow of slag or dross on the surface'of the auxiliary hearth metal into the main furnace chamber and seals the main chamber and the molten metal ,B" from the outside atmosphere, keeping the heat in and the air out.

In smelting solid .pieces of metal, particles or chunks are immersed in a relatively small body structure formed with upright passages 23 and 24, disposed in spaced preferably parallel relation and opening upwardly through the floor of the auxiliary hearth I8. The bottom or lower ends of the upright channels 23 and 24 are connected by a horizontal or transverse cross channel 25 which is preferably of larger cross sectional area than the upright channels so that it does not become blocked by settling of impurities or sediment. Midway between the upright channels 23 and 24 and preferably in parallel relation thereto is a central pumping channel 26, which also 4communicates at its lower end with the connecting or cross channel 25. Extending around the central or pumping channel 26 and through the refractory structure of the pump is a soft iron laminated core 28, which may be of rectangular shape as shown in Fig. 5. This core carries windings 30 and 3l of copper wire which constitute the primary of the pump transformer assembly and are connected to a suitable source of alternating current such as standard 'frequency power for the purpose of inducing alternating electro-magnetic flux in the iron core 28. 'I'he core 28 and the Iprimary coils 30 and 3l are insulated by refractory material 32 which separates and protects the coils from the heat of .the molten metal flowing through the passages of the pump structure formed in the refractory.

Extending as an upward continuation of the central or pumping channel 26 is a passage 31 formed in a conduit which includes an upper portion 36 of refractory material and a relatively short section 4I of electrically conductive. material such as carbon. The conductive section 4I is disposed at the upper end of the pumping channel 26 adjacent the level of the floor of the auxiliary hearth I8. y.

Referring to Fig. 4, the liquid metal in the passages 23, 24, -25 and 26, and the liquid metal on the auxiliary hearth I8 together with the conductive insert or portion 4I of the extension passage, constitutes the pair of merged secondary loops around a transformer core 28. Each loop has a leg common to the other loop and comprising the molten metal in the central passage 26. The effect of an alternating current imposed on `the primary coils 30 and 3l is to induce current 7 same to rise in the pumping channel 2l and in the extension passage 31. The direction oi windlng of the coils 30 and 3| is such that each induces current now in the same direction in the pumping passage 28.

'I'he upper end of the conduit ll is supported on a cross wall or weir 40, which divides the auxiliary hearth I8 into two zones one of which contains the working body o! metal indicated at A (and which is in communication with the metal B on the main hearth I through the opening 2l) and a smaller or ieeder" body of metal indicated at C" (which also is in communication with the metal B" on the main hearth I through the passage 20). The top oi the Weir or cross wall 40 is formed with a pouring lip 38 which extends as a continuation of the passage 31 in the conduit ll. Metal which is drawn into the pumping structure through the upright passages 23 and 24 from the feeder body C is thus forced around and upwardly through the pumping passage 2C, through the extension passage 31 and over the lip 38 of the weir or wall I to pour onto the mass of metal A and any solid metal pieces or particles which may have been placed adjacent the wall or weir 40. x

The pumping apparatus is illustrated as being disposed at an angle to the vertical, which iacilitates access for servicing or repair. It may, however, be disposed at other angles than that shown. A suitable enclosing and supporting metallic casing may be employed for the pumping structure and includes a housing 3l which is disposed n sealing relation around one end of the openings which' receive the iron core 28 and the primary coils 30 and 3|. A suitable ian or air blower (not shown) communicates with the interior of the housing 34 through an opening 35 to force or draw cooling air over the transformer coils to prevent excessive temperature rise. The metal casing or supporting structure for the pump may be separated from the refractory material constituting the walls of the passages by insulation indicated at 33. A removable cleanout or access door or plug 21 is provided at one end of the transverse or connecting passage 25.

In operating the furnace or smelter in accordance with the principles of the present invention, an initial starting or heel charge is provided as by leaving a small amount of metal from a preceding batch in the furnace or by introducing a quantity by pouring molten metal onto the auxiliary hearth I8 from whence it flows onto the hearth I through the opening 2l; or a quantity of solid metal may be charged directly into the main furnace chamber through the door opening II and melted by heat from the combustion of gases supplied through the burner openings L The initial quantity of metal placed or charged onto the hearths of the smelter may not and preferably will not be as large in quantity as indicated in the drawings, which represent an intermediate stage in the complete process. For descriptive purposes, however, the relative quantities shown in the drawings are used to indicate the cyclic operation. Actually, the relative levels will rise and fall depending on the rate of addition of fresh or solid metal, the viscosity or condition of the metal in the diierent bodies, the skimming of slag and contaminants, and the action of the pumping unit. The total metal charge in the furnace includes the main or relatively large body B," and a smaller body in juxtaposi- 8 tion thereto comprising the masses A and C in the two zones of the auxiliary hearth Il. The large body of metal B" under the controlled atmosphere in the main heating chamber is heated toa temperature substantially above its melting point in the manner previously mentioned.

Energization of the submerged induction pump structure nows molten metal from the mass indicated at 0" on one zone of the auxiliary hearth, over the weir or cross wall Il and onto the metal A in the other zone of the auxiliary hearth. The metal "A from the auxiliary hearth iiows into a metal "B" in the heating chamber through the opening Il. A continuous circulation or ilow of the molten metal is thus established, the metal being heated primarily in the controlled atmosphere chamber over the main hearth I, but also heated in a secondary manner in passing through the pumping structure by reason of the resistance of the metal to the now oi the electrical currents induced therein.

Metal to be smelted is submerged in the metal A on the auxiliary hearth where it rapidly absorbs heat from the relatively high temperature molten metal continuously supplied to this melting or mixing and commingling zone through circulation of the metal induced by the pumping structure. Small pieces or particles of metal to be smelted such as turnings, cuttings, spillings and the like are introduced into the mixing zone adjacent the cross wall or weir 4l, where the down ilowing metal from the pump outlet passage 31 promptly engulfs and submerges such small particles, carrying them below the surface ofthe metal A and minimizing oxidation of the solid metal. Fluxing materials, renners and the like can also be added to the metal A in the down flowing stream from the outlet of the pumping structure. In this manner the additives are thoroughly mixed and distributed in the metal A, so that uniform refining, purification and modication of the metal results.

The addition oi a large quantity oi solid metal to the metal A results in lowering the temperature of the molten or circulated metal so that a viscous pasty mass having a. slush-like consistency results. This pasty condition is benetlcial in the reiining process especially when the metal being smelted is scrap containing removable impurities and contaminants such as dirt and other foreign elements, as well as oxides of the metal being smelted. Flux added to the metal A for purification thereof is mixed through and entrained in the pasty mass and is evenly distributed by reason of being introduced at the region of the inilowing metal delivered by the pumping structure. The viscous nature of the pasty mass prevents rapid rising of the tluxing material upwardly through the metal being puried, allowing an intimate association of the ilux with the metal being puriiled for a relatively long period of time, resulting in more efllcient action of the ilux and improved purification, so that segregation of the impurities is substantially completed in the pasty state of the mass.

Rening materials added in a similar manner to the mass of metal A are evenly and thoroughly distributed therethrough and by reason of the viscosity of the metal in the pasty condition are prevented from separating out and being lost.

When the puriilcation, reilning and treatment of the metal A has been substantially completed in the pasty state, the addition of solid metal is suspended for a time while the flow of relatively the pasty mass of metal suillciently to liquefy the same. In this manner the metal A, with .the segregation of the impurities and contarn-` inants therein substantially completed is liquened, permitting the relatively light iluxlng materials to rise to the surface, carrying with them the segregated impurities and contaminants. This step is commonly known as bringing to skim.

vThe continued ow of molten metal over the weir or cross wall40 effects a flow of the purified metal through the opening 2| onto the main heating hearth i, where it is further raised in temperature and commingled with the larger mass of metal on the main hearth. s

The oxides and other contaminants carried to the surface of the metal A are separated therefrom by mechanical or hand skimming. When the contaminants are thus separated 'the smelting cycle is completed and the vapparatus is in condition for repetition of the cycle by the addition of ,solid metal introduced into the metal A on the auxiliary hearth. The cycle is repeated with the total mass of metal contained in the apparatus increasing each time until the furnace is full and ready to be tapped or emptied through the spout Ill. By reason of the continuous circulation of the molten metal under the influence of the pumping structure, all of the, metal in the furnace is brought to uniform composition regardless of the fact that it may include metal of widelyvarying composition added during different cycles of the smelting process. The metallurgise is therefore able by sampling at one point to determine accurately what refining and alloying materials should .-be added to bring the entire charge to the proper composition before tapping. Additionally the materials to be thus added in modifying the metal can be introduced rapidly, without waste or loss thereof, by placing them in the stream of metal flowing out of the pumping structure.

In Figs. 6 and 7 is illustrated a modification of the invention which includes a feature particularly useful when smelting metal in the form of relatively fine particles, such as turnings, cuttings, borings and the like. This modification also illustrates a suitable apparatus for performing the present process or method continuously in the manner previously mentioned. The main furnace structure used in this modiflcation may be the same as that shown in the preceding figures and a complete showing thereof has been omitted for simplicity. Front wall 4 of such furnaceis designated in Figs. 6 and 7, it being understood that the remainder of the structure not included in Figs. 6 and 7 corresponds generally to that previously described. Certain parts or portions of the modified structure and which correspond to parts described in connection with the preceding figures have been indicated by the same numerals of reference,

as for example, the auxiliary hearth Il, sidev and the adjustable walls I1, return passage 2| gate 22 for the return passage.

A cross wall or partition 10 of nre brick or similar material divides the of metal on the auxiliary hearth I8 into 'a feed portion D and the building up of a batchof metal in the furnace from the original heel, the general level of the metal will progressively rise.

The level of the-` feed yportion D of metal is maintained by gravity substantially equalto that of themolten metal on the main hearth inside the heating portion of the furnace by vflow through a low level opening or passage 1 I, which corresponds to the opening 2li previously described.

The position of the partition wall 10 is such that the refining portion -E of the outside or auxiliary hearthmetal is several times larger than the feed portion D, the latter serving merely to supply the pump which lifts the molten metal over the partition 10 for flow into different zones of the refining metal-E. y

At one end of the refining metal E and adjacent the partition 10, is a receiver or hopper into which metal to be smelted or refined is introduced. This receiver is constructed of heat resistant material such as graphite or silicon carbide and may include an upright cylindrical conlining pedestal portion 12 surmounted by an open topped funnel or cone 13. About'the upper peripheral edgeof the funnel 13 is a cylindrical -retaining flange 14 which prevents metal deposited on the receiving funnel 13 from over flowing. The parts of the receiver may be of integral molded construction and at the bottom of the pedestal portion a plurality of openings 15 are provided for the out-flow of metal from the interior of the retaining pedestal onto the hearth I8.

.wall 4, and a short guide wall 80, is "a manifold flume or duct structure comprising a cross conductor 82 and lateral conductors 83 and 8 4. The cross conductor 82 receives hot molten metal from the outlet 19 of the pump structure and f carries it to the lateral conductors 83 and 84.

/By reason ofthe .high temperatures to which the manifold and conductor structure is subjected, it is preferably made of heat resistant or refractory material and may be molded or machined from solid pieces. As shown in Fig. '1, the conductors or ilumes are inclined downwardly in the direction of flow of the molten metal, so that the metal moves by gravity therethroug f Adjustable gates 85 and 88 are provided to proportion ythe flow of metal through the cross conductors 83 and 84. These gates may be formed of refractory material, movable vertically through slots in the upper walls of the conductors, so as to vary the available cross section within the respective conductors for the ilow of molten metal -ductor to the cross conductor I2.

atrasos block 88 to hold the gates in desired adjusted vertical positions. The gate Il controlling the flow of molten metal through the lateral conductor 83 is disposed at the connection of such con- The gate It controlling the flow through the lateral conduit-- tor 84 is disposed in the cross conductor l2 Ilust beyond the connection of the lateral conductor 83. By thus positioning the gates relatively close to the pump outlet 19, the freezing of metal in the nume, should one or both of the gates be closed, is avoided.

The lateral conductor extends tangentially over the circular skirt or flange 14 of the funnelshaped receiver adjacent the periphery of the latter so that molten metal flowing out of the flume or conductor is discharged tangentially onto the outer edge of the conical funnel. Thus there is provided a continuous vortex or whirlpool of hot molten metal substantially covering the upwardly directed open topped cone or funnel of the receiver. Metal to be smelted and introduced into the receiver in relatively finely divided form, such as prevails in the case of turnings, borings, cuttings and the like, is quickly engulfed in a swirling vortex 90 of molten metal on the receiver and carried downwardly into and through the cylindrical retainer 12.

Refiners, purifiers, and iluxing materials to be added during the process are likewise introduced into the receiver vortex and are rapidly engulfed and carried below the surface of the molten metal in the cylindrical retainer. merged by the incoming fresh material.

The relative quantity of molten metal flowed onto the conical portion of the receiver through the lateral conductor 83 is so regulated by means of the adjustable gate 85 that the heat thus introduced into the receiver is just sufilcient to make a pasty mass or mix of all of the materials and metals added through the receiver. This pasty mix, which holds the metal to be retlned in intimate association with the refining materials and fluxes, moves continuously outwardly through the bottom of the receiver cylindrical portion 12 through the opening 15 in the latter and into the main mass of the refining portion E of the metal on the auxiliary hearth. A general flow over the auxiliary hearth I8 is thus induced in the metal. The level of the mixed metals rises somewhat in the cylindrical receiver 12 over the prevailing level outside of the receiver on the hearth I8 as shown in Fig. 7.

AHeat is added to the pasty mix by the molten metal flowing into the refining body E through the lateral conductor 84. The outlet of this conductor is relatively remote from the main outlet passage 2 l, which leads into the main hearth or heating chamber of the furnace, so that metal in a pasty mix or mush on the auxiliary hearth il is continuously being converted to a molten condition and brought to skim.

In the refining process the metal is agitated or worked during the heating and while being brought to skim, by hand puddling or by mechanical mixers or puddling devices lowered into the mass of metal on the auxiliary hearth. At this stage of the process when the metal is at a relatively high temperature, refiners or refining gases may be added to the liquid metal to effect refinement and purification which was not accomplished at the lower temperature of the pasty mush or mix. Such refiners may be introduced through the stream of molten high temperature metal issuing from the conductor I4 or They are kept subthey may be mixed directly into the body of metal on the auxiliary hearth.

The slag, dross land contaminants rising and carried to the surface of the molten metal adjacent the left-hand end of the auxiliary hearth, as viewed in Figs. 6 and '1, are separated or skimmed therefrom and the purified or refined metal flows into the main heating chamber through the passage 2l.. 'v

By thus utilizing separate streams of molten metal nowing' between the body of molten metal B and the body of molten or partially molten metal A on the auxiliary hearth, one stream for initial heating of solid metal to bring it to a pasty state and another stream to convert the pasty mix to liquid metal, a smelting furnace may be operated continuously. The metal to be smelted is introduced at uniform intervals or continuously into the swirling vortex in the receiver and is rapidly engulfed and reduced to a pasty mix condition with the refining materials and fluxes in the retainer portion of the receiver. The pasty mix mass thus produced travels forward over the auxiliary hearth during the refining process and while impurities and contaminants are segregated. Thereafter the addition of further heat by the other or second stream of molten metal flowing through the supplemental conduit or fiume lll completes the melting of the metal being smelted, bringing it to a liquid state or to skim, so that the segregated impurities and contaminants rise or are carried to the surface and can be separated or skimmed in the usual manner. Thus metal is being brought to a pasty state or condition in one zone of the auxiliary hearth and other metal is being changed from a pasty state or condition to a molten state in another zone of the auxiliary hearth.

'I'he large body of molten metal developed in the furnace may be tapped from time to time and a portion only of the smelted metal withdrawn at each tapping, the smelting process thus being carried on indennitely. If desired, the smelting process may be interrupted after a batch has been refined and purified and the entire body of molten metal removed during a single withdrawal or tapping. In either case and regardless of the manner of withdrawal of the smelted metal from the furnace, the process is continuous with respect to the smelting steps, inasmuch as the addition of metal to be smelted to the receiver may be continuous rather than cyclic.

In accordance with the patent statutes the principles of the present invention may be utilized in various ways, numerous modifications and alterations being contemplated, substitution of parts and changes in construction being resorted to as desired, it being understood that the embodiments shown in the drawings and described above are given merely for purposes of explanation and illustration without intending to limit the scope of the claims to the specific details disclosed.

What we claim and desire to secure by Letters Patent is:

l. Apparatus for melting and refining metals susceptible to rapid oxidation at elevated temperatures, which comprises a furnace having refractory lined side, top. and bottom walls defining a relatively large, enclosed, main hearth and refractory lined side and bottom walls deflning a relatively small, open, auxiliary hearth, said hearths being of substantial depths for hold- `ing baths of molten metal and the bottoms of i3 said heartlis being .at substantially the same level, .means for supplying heat to metal on the main hearth for maintaining it in a molten eonclition, a first passage connecting said Ineartns substantially at the level of their bottoms 'to permit free iiow of molten metal from one to tlie other, the

vertical height oi' said passage being suostanm tialiy less than the depths of said liearths for maintaining said passage entirely below 'the no1um 'mai ievel of molten metal on the lieartlis, a Binnen for molten metal, a second passage communicating" at one enel with said main lieartli through an opening disposed substantially at the level of the bottom thereof and having a vertical height substantially less than the tientlis of said hearths, whereby said opening may lee maintained entirely below the levels of molten metal on the hearths, said second passage being as soelated with the intake of saiil pump for son @lying molten metal thereto from said main hearth, and a third passage communicating at one end with the discharge of said ,uomo and ei:m tending above the auxiliary hearth for receiving molten metal from said pump and discharging it downwardly as a freely falling stream into a loatli of molten metal on the auxiliary hearth.

The apparatus of claim l including means or closing said ilrst 'passage during initial e'narg- :lng of the main hearth.

The apparatus ot' claim i including means for 'varying the vertical height oi time opening irom vsaid lrst passage into one oi salti heartlis.

The apparatus o claim l in wluioli third nassage is provided with a plurality oi discharge openings spaced therealong above sale", auxiliary lieartli for discharging molten metal downwardly spaced locations which are respectively acljacent and relatively' remote from the opening oi said first passage into the auxiliary hearth.

Apparatus for melting and reiining metals suseeptible to rapid oxidation at elevated temperatures, which eompriseg a furnace having re- ;*raotorg/,wails defining the sides, top, and loottom oi an enclosed, relatively large, main lieartli and the sides and bottom of an open, relatively small, auxiliary hearth, one of said walls being a common side wall of the main anni auxiliary l'leartlis, said lieartl'is being of substantial depths for holding Toaths of molten metal and the lootA toms of said hearths being at substantially the same level, means for supplying heet to metal on the main hearth ior maintaining it in a molten condition, a first passage through saisi eommon ISU side wail, the bottom of said @est emesse at eaeli enel thereof lying substantially in the plane of the bottoms of sani iieartlis, a second passage communicating at one enel with salti inain hearth through an opening in a wall thereof, a pomp having ite intaie disposed; yeeeive i 'lten metal from said seooml passage, and a tin passage oomznunieatlng at one end with the discharge of said pump and extending above the auxiliary lieai'tli for renewing molten .metal from the num-n and discharging it downwardly as a ireely i'all .ing stream into a loatli of molten metal on the am iliary hearth, the side Walla of salti lieartlea extending upwardly substantially above highest points of saisi ilrst anti second opening.. whereby the levels molten metal on eaiel lieartiie may lie maintained above the highest points of said liest and secano openings.,

o", Tne apparatus of claim 5, ineluding a mi@ eeiver resting upon the bottoni of said auxiliary hearth below salti third passage, saisi receiver comprising a hollow pedestal having eei'raotory walls andi an opening at its upper enel for re solving metal discharged from said third passage and solid metal and iiuxes to lie mixed. there with, and an opening in the side el salti pedestal adjacent the bottom theieof to permit free Plow of molten metal from the receiver onto eiijaeent portions of the auxiliary hearth.

WALTER rWAII'EFt WHXLQ REFERENCES @TELESE 'l'iie following references are of iecorel in the file oi this patent:

NETE@ STATES PATENTS

Claims (1)

1. APPARATUS FOR MELTING AND REFINING METALS SUSCEPTIBLE TO RAPID OXIDATION AT ELEVATED TEMPERATURES, WHICH COMPRISES A FURNACE HAVING REFRACTORY LINED SIDE, TOP, AND BOTTOM WALLS DEFINING A RELATIVELY LARGE, ENCLOSED, MAIN HEARTH AND REFRACTORY LINED SIDE AND BOTTOM WALLS DEFINING A RELATIVELY SMALL, OPEN, AUXILIARY HEARTH, SAID HEARTHS BEING OF SUBSTANTIAL DEPTHS FOR HOLDING BATHS OF MOLTEN METAL AND THE BOTTOMS OF SAID HEARTHS BEING AT SUBSTANTIALLY THE SAME LEVEL, MEANS FOR SUPPLYING HEAT TO METAL ON THE MAIN HEARTH FOR MAINTAINING IT IN A MOLTEN CONDITION, A FIRST PASSAGE CONNECTING SAID HEARTHS SUBSTANTIALLY AT THE LEVEL OF THEIR BOTTOMS TO PERMIT FREE FLOW OF MOLTEN METAL FROM ONE TO THE OTHER, THE VERTICAL HEIGHT OF SAID PASSAGE BEING SUBSTANTIALLY LESS THAN THE DEPTHS OF SAID HEARTHS FOR MAINTAINING SAID PASSAGE ENTIRELY BELOW THE NORMAL LEVEL OF MOLTEN METAL ON THE HEARTHS, A PUMP FOR MOLTEN METAL, A SECOND PASSAGE COMMUNICATING AT ONE END WITH SAID MAIN HEARTH THROUGH AN OPENING DISPOSED SUBSTANTIALLY AT THE LEVEL OF THE BOTTOM THEREOF AND HAVING A VERTICAL HEIGHT SUBSTANTIALLY LESS THAN THE DEPTHS OF SAID HEARTHS, WHEREBY SAID OPENING MAY BE MAINTAINED ENTIRELY BELOW THE LEVELS OF MOLTEN METAL ON THE HEARTHS, SAID SECOND PASSAGE BEING ASSOCIATED WITH THE INTAKE OF SAID PUMP FOR SUPPLYING MOLTEN METAL THERETO FROM SAID MAIN HEARTH, AND A THIRD PASSAGE COMMUNICATING AT ONE END WITH THE DISCHARGE OF SAID PUMP AND EXTENDING ABOVE THE AUXILIARY HEARTH FOR RECEIVING MOLTEN METAL FROM SAID PUMP AND DISCHARGING IT DOWNWARDLY AS A FREELY FALLING STREAM INTO A BATH OF MOLTEN METAL ON THE AUXILIARY HEARTH.

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