US2380238A

US2380238A - Method and apparatus for producing cast metal bodies

Info

Publication number: US2380238A
Application number: US519230A
Authority: US
Inventors: Robert K Hopkins
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1944-01-21
Filing date: 1944-01-21
Publication date: 1945-07-10
Anticipated expiration: 1962-07-10

Description

July 10, 1945. R. K. HOPKINS 2,380,

METHOD AND APPARATUS FOR PRODUCING CAST METAL BODIES Filed Jan. 21, 1944 2 Sheets-Sheet 1 INVENTOR Koberi 1f. Hqa/i'zims" Wag/X301 2 ATTORN Patented July 10, 1945 METHOD AND APPARATUS FOR PRODUCING CAST METAL BODIES I Robert K. Hopkins, New York, N. Y., assignor to The M. W. Kellogg Company, New York, N. Y., a

corporation of Delaware Application January 21, 1944, Serial No. 519,230

9 Claims. -(01. 22 c1) The present invention relates to the art of producing cast metal bodies.

In the electric fusion method of producing cast metal bodies, such as ingots, current is dis-. charged from an electrode through a flux submerged gap separating said electrode from the body of deposited molten metal, to create a metal fusing zone in and around said gap. At the same time, solid ingredients of the metal to be produced are fed into this fusing zone at controlled rates. The electrode may be of consumable hollow construction, and may contain some of the metal ingredients of the ingot to be produced, while the other ingredients may be delivered into the metal fusing zone in the fluent form of granules, pellets, powders or the like, through the hollow of said electrode. Some of th particles from these fluent metal ingredients having high fusion points may pass through the metal fusing zone, and may settle towards the bottom of the deposited molten metal without being completely fused. These solid unfused particles imbedded in the casting will produce therein so-called bright spots which adversely affect the soundness of the casting.

One object of the present invention is to provide a new and improved method and apparatus for producing and depositing metal in a mold in a manner to assure complete fusion of the metal ingredients deposited in said mold.

Another object of the present invention is to provide a, new and improved method and apparatus for producing highly superheated metal and depositing said metal in said mold in substantially said highly superheated condition without allowing the molten metal to come in contact with the air.

Various other objects, features and advantages of the invention will be apparent from the following particular description, and from an inspection of the accompanying drawings, in which:

Fig. 1 shows somewhat diagrammatically partly in vertical section and partly in front elevation one form of apparatus which may be employed to carry out the method of the present invention, and which embodies the structural features of the present invention:

Fig. 2 is a vertical section taken on the line 22 of Fig. l. but on a larger scale;

Fig. 3 is a horizontal section taken on line 3-3 of Fig. 2;

Fig. 4 shows somewhat diagrammatically in vertical section another form of apparatus which may be employed to carry out the method of the present invention, and which embodies the structural features of the present invention; and

Fig. 5 is a horizontal section taken on line 5-5 of Fig. 4.

In the form of the invention shown in Figs. 1 to 3, there is provided a mold III which may be of any suitable shape, according to the desired shape of the metal body to be produced, and which for the purpose of illustration, is shown cylindrical. Moldl0 may be of any suitable material such as cast iron, and is constructed and dimensioned to effect solidification of the deposited metal progressively upwardly and inwardly therein in the manner well-known in the art. Mold I0 is closed at its bottom end, as for example by means of a stool of suitable material, such as cast iron.

For producing metal in the interior of the mold Hi, there is provided therein a vessel ll serving as a furnace or crucible. This crucible ll may be of any suitable shape, and is shown cupshaped and specifically in the form of a bowl with a, substantially hemispherical cavity. The walls of crucible H are hollowed to form a jacket I2 through which a suitable cooling liquid is circulated, and are made of a metal having high heat conductive capacity, as for example copper. The cooling liquid is circulated through the jacket l2 of the crucible wall by an inlet pipe l3 and an outlet pipe l4. These pipes 13 and I4 are desirably diametrically or otherwise symmetrically disposed with respect to the cricible H, and are connected int said jacket by any suitable means, as for example by threading or welding, or both The crucible l l is advantageously suspended and supported in the mold I0 through the medium of these pipes l3 and M, in a manner to be made apparent.

The crucible II is provided with an overflow pouring gate I5 comprising a substantially radial channel IS in the wall of said crucible, and a runner H in said channel desirably of refractory material. When the molten metal deposited in the crucible ll reaches a predetermined level therein, it overflows through the pouring gat l5 and into the mold Ill.

The metal is produced and deposited in the crucible I l by the use of an electrode device which may be of the general type shown in my U. S. Patents 2,191,479 and 2,191,481. For that purpose, there may be provided a consumable electrode I8 extending in the mold I0 directly above the crucible I I, and containing ingredients of the metal to be produced and deposited in said mold.

Other constituents of the deposited metal may be furnished-in the fluent form of granules, pellets, powders or the like, through the hollow of the electrode I8, so that these other constituents in conjunction with said electrode produce a metal in the crucible ll having the required analysis. The electrode l8 and the granular metal constituents are fed at controlled rates to the current discharge gap between the end of said electrode and the pool of molten metal 2i in said crucible by suitable means, as for instance that;

shown in my Patent No. 2,191,479 above referred to, to produce metal'of the desired analysis, and to maintain said gap substantially constant in length.

The controlled downward feeding of the electrode It may be effected through a pair of feed wheels 22 on opposite sides of said electrode and in frictional engagement therewith. At least one of these feed wheels 22 is driven from a motor 23 through a suitable reduction gearing, while the other wheel may be positively driven from said motor or may be merely an idler serving as a guide for the electrode IB. This motor 23 may be regulated automatically by the voltage drop across the current discharge gap 20 in any well- ,known manner, 50 that the feed Wheels 22 are automatically operated and controlled to feed the electrode [8 downwardly as it is continuously consumed. The current discharge gap 20 is thereby maintained substantially constant in length.

The hollow electrode l8 may be continuously shaped from a metal strip or skelp 24 as shown in the aforesaid Patent No. 2,19l,479 as said electrode is fed continuously into the metal fusing zone.

The granular metal constituents may be delivered through the hollow of the electrode l8 and into the current discharge gap 20 at controlled rates and at desired proportions by means of metering devices (not shown) that feed it at the desired rate to a funnel tube 25 leading into the electrode [8 as it is formed.

The electrode l8 and the deposited metal 2| in the crucible H are electrically connected in the same circuit, so that current as it is discharged from said electrode, passes through the gap 20, and thereby creates a high temperature zone in which the solid metal ingredients are readily fused. The electrical connection to the electrode I8 may be effected, as for example, through a contact nozzle 21, connected to a suitable source of current and embracing said electrode with a snug slide fit loose enough to permit the feeding of said electrode through said nozzle, but tight enough to maintain electrical contact between said nozzle and said electrode.

The electrical connection of the deposited metal 2| into the circuit of the contact nozzle 21 may be effected by grounding the metal walls of the crucible H through the water circulating pipes l3 and/or [4.

During metal producing and depositing operations, the crucible II is entirely submerged in a floating layer or blanket of flux 28 of any suitable composition, and the lower end of the electrode I8 is submerged in this flux, so that the current discharge gap 20 is also entirely submerged in this flux. Flux 28 refines the metal as it is produced, promotes fusion, and maintains the molten metal from the time it is produced to the time it is deposited in the mold I0 out of contact with the air. Flux 28 also serves as a heat insulating blanket around the crucible I I and the metal being produced and deposited in the mold to, thereby allowing the use of extremely method of the present invention.

Highly superheated molten metal is continu- 'ously produced from the electrode I8 and the other metal ingredients delivered in fluent state into the metal fusing zone in and around the current discharge gap 20; thi metal is continuously deposited in the crucible ii. After the metal in the crucible ll reaches the level of the pouring gate IE it overflows into the mold I 0 as a steady continuous stream under the protective action of the encompassing flux 28, to form the D001 of molten metal 29. The molten metal overflows into the mold I0 at a rate substantially equal to its rate of production.

Any solid particles supplied to the current discharge gap 20 which are not fused therein, and which are deposited in the crucible II in unfused condition will eventually become fused because of the intense heat concentrated in the comparatively restricted space afforded by the crucible cavity. These unfused particles will not overflow into the mold I0, but will sink towards the bottom of crucible II. If these particles do not all fuse as they sink in the crucible ll, they will settle and accumulate at the bottom of said crucible to form a pile whose peak will eventually reach a level where the intense heat generated by the electrode [8 will fuse the particles. Delivcry of molten metal to the mold l0 free from unfused particles is thereby assured.

As the molten metal overflows the crucible II, and is deposited in the mold Ill, the level of the deposited metal in the mold rises and the metal deposited in the mold l0 solidifies progressively upwardly and inwardly, as shown in the drawings.

In order to promote progressive solidification of the metal upwardly, and to assure the maintenance of a substantial body of molten metal 29 in the upper portion of the deposited metal in the mold In to serve as a shrinkage feeder for the solidifying metal below, heat is continuously transmitted to the upper portion of the deposited metal. In the specific form shown, this heating of the upper portion of the deposited metal 29 is carried out by means of an electrode device comprising an electrode 3| extending into the mold In with its lower end'submerged in the flux 28, but spaced from the surface of metal 29 by a current discharge gap 32. Electrode 3| is desirably non-consumable, and for that purpose may be of copper hollowed to allow circulation of a cooling medium therethrough, whereby the temperature of said electrode is maintained below its fusion point.

The electrode 3| and the body of deposited metal 29 in the mold ID are connected in the same circuit to effect a current discharge across the gas 32 of sufficient intensity to maintain said .metal fluid for the purpose indicated, and to promote progressive solidification. Non-consumable electrode 3| is desirably disposed diametrically opposite the pouring gate I5 to promote equalization of the temperature of metal 29 and solidification of the metal in the mold l0 substantially symmetrically with respectto the vertical axis of said mold.

The rate of inputof heat into the mold metal 29 through the medium of the electrode II is desirably so controlled and correlated with respect to the rate of production and deposition of metal in the crucible II, as to effect progressive solidification of the etal in the mold Id at a rate substantially equal to said rate of metal production and deposition.

shown, as far as certain'aspects of the invention are concerned, any number of these electrodes can be provided according to the size of the mold I0, and these may be distributed over the surface of the deposited metal-29 in the mold III according to any desired pattern.

As the metal producing operation progresses, the level of the deposited metal 29 in the mold In gradually rises. It is therefore necessary to move the crucible I I and the two electrodes I8 and 3| relatively with respect to the mold I to maintain a constant positional relationship between said crucible and electrodes on the one hand, and the upper surface of the deposited metal 29 in the mold I0 on the other hand. This relative movement may be effected either by moving the mold I 0 continuously downwardly while the crucible II and electrodes I8 and 3| are held stationary, or by maintaining the mold I 0 fixed in position while said crucible and electrodes are moved continuously upwardly as a unit. In Fig. 1 there is shown for the purpose of illustration means which may be employed to effect the desired relative movement, and which comprise a hoist 35 to which the contact nozzle 21 and the water circulating pipes l3 and I4 for the crucible jacket I2 are fastened, as for example by a clamp 36, and to which the electrode 3| may be similarly fastened. Hoist" may be moved vertically by any suitable means, as for example that shown in my U. S. Patent 2,191,478. or may be moved in the manner indicated in the drawings through a pair of vertical feed screws 34 threaded therein and journalled in suitable fixed bearings (not shown) arrangedto' hold these feed screws against axial movement. The two feed screws 34 are driven in unison and in the same direction through a motor 31, and a speed reducing transmission between said motor and said feed screws, This transmission may comprise worm wheels 38 keyed or otherwise fixed to the feed screws 34 respectively for rotation therewith, and meshing with respective worm wheels on the shaft of the motor 31.

' The motor 31 is desirably automatically controlled, to maintain a constant positional relationship between the crucible II and electrodes I8 and 3| on the one hand, and the surface of the depositedmetal 29 in the mold III on the other hand. For that purpose, this motor 31. may be automatically controlled in accordance with the voltage drop across the current discharge gap 32.

The

feed device

22 and 23 for the electrode I8 may, if desired, be supported on the hoist 35 as shown. With this construction, the electrode I8 will be moved upwardly with its contact nozzle 21, but will still be subject to the control of the feed wheels 22 according to the voltage drop across the gap 20, or according to any other regulating factor selected, so that the length of this gap will be kept substantially constant.

The use of the crucible II permits the production of metal at extremely high temperatures. This highly fluid highly superheated metal as fast as it is produced is deposited as a continuous stream into the mold III, and during its transfer from the crucible I I to said mold II is maintained under the protective action of the flux 28. The metal, during its transfer to the mold III, is further refined by the flux 28 and as a result of the heat insulating action of said flux, is added to the pool of molten metal 29 in. said mold at substantially the same high temperature it had in.

the crucible II. At the same time, the transfer Although only one heating electrode ll is is effected without atmospheric contamination. The metal deposited in the mold III is maintained free from air contact during its solidification.

At the beginning-of casting operations, the crucible I I maybe empty of metal and submerged in the flux 28 near the bottom of the mold III. Under these conditions, the metal producing operation in the crucible II may be initiated with the electrode II sumciently close to the bottom of said crucible to produce the necessary metal fusing heat. During this initial metal producing stage, the crucible II and the mold III are kept in fixed relative positions until the molten metal deposited in the crucible II begins to overflow the pouring gate I5. During this initial metal producing stage, the feed of the electrode I8 may be under manual control, or may be under the automatic contfol described. After the overflow of metal from the crucible II begins, said crucible can be moved at a controlled rate with respect to the mold III, as the level of the metal deposited in said mold rises in a manner already described.

If desired, instead of initiating the metal producing operation with the crucible II empty of metal and near the bottom of the mold III, the operation may be initiated with the crucible I I out of the mold and in the presence of a protec-' tive layer of flux in said crucible. When metal to the desired level has been produced in the crucible I I, it may be lowered with its protective layer of flux into "and relatively with respect to the mold I0, and the metal producing operation continued with the crucible in said mold.

Where a number of molds are being filled in succession with molten metal, the crucible II containing this metal is raised with respect to and out of the filled mold, and maybe lowered relatively into the next mold to be filled. As crucible II is so raised out of the mold, it carries with it a layer of flux'which protects the metal in said crucible against atmosphericcontamination while said crucible is being transferred into the next flux containing mold.

In Figs. 4 and dis shown another form of apparatus which may be employed to carry out the method of the present invention, and which comprises an endless or annular crucible or furnace Ila, desirably of circular shape and disposed in the mold III. This crucible Ila has a circular outer peripheral wall 4I and a circular inner peripheral wall 42 integrally or otherwise rigidly connected concentrically together at the bottom. and forming therebetween an annular cavity 43 substantially bowl-shaped in radial section. The topgof the inner crucible wall 42 extends below the top of the outer crucible wall 4I, and defines a substantially horizontal circular seat 44 around a central circular opening 45. Resting on and 'secured to this seat 44 is a circular runner 46,

opening 41 when the level of this metal reaches the top of said runner. This overflow metal from the crucible Ila is deposited substantially centrally in the mold Ill, so that all the advantages inherent in pouring the metal in said mold in a Molten metal of the required analysis is pro duced in the crucible Ila desirably by the use of an electrode device similar to that described in connection with the construction of Figs. 1 to 3. For that purpose, one or more consumable electrodes We are provided, two being shown, diametrically disposed directly over the crucible cavity 43, and spaced by current discharge gaps 200 above the surface of the deposited metal 2m in the crucible Ila. These electrodes l8a which are connected into the circuit of the molten metal Zia as in the construction of Figs. 1 to 3, contain at least some of the ingredients of the metal to be produced, and are desirably hollow. Other metal ingredients in the fluent form of granules, pellets or powders, are delivered to the metal fusing zones created by the current discharge across the gaps a, as for example through the hollows of the electrodes l8a.

The feeding of the electrodes I8a and the fluent metal ingredients into the metal fusing zone may be effected at controlled rates in a manner already indicated in connection with the construction of Figs. 1 to 3.

The molten metal 2Ia in the crucible Ha, besides being heated by the consumable electrodes l8a, may be further heated by the use of one or more electrodes 48, two being shown diametrically disposed directly over the surface of the deposited metal 2 la in quadrant relationship with the electrodes "la, and spaced from said surface by current discharge gaps 49. These electrodes 48, which are connected into the circuit of the crucible metal 2la, are desirably non-consumable, and are constructed like the electrodes 3| of Figs. 1 to 3.

Instead of employing the heating electrodes 48 in the position shown, as far as certain aspects of the invention are concerned, a single heating electrode may be used, disposed directly over the pouring hole 41 to maintain the overflowing metal highly fluid as it is discharged through said hole, and to prevent thereby freezing of said metal in said hole. This single central heating electrode may replace the two heating electrodes 48 shown,

or may supplement the heating action of these latter electrodes.

Also, if desired, as far as certain aspects of the invention are concerned, if the clearance between the crucible Ho and the mold walls permits, one or more non-consumable heating electrodes may be employed between said crucible and said mold walls directly over the metal 29a deposited in the mold I0 to serve the same purpose as the heating electrodes 3| in the construction of Figs. 1 to 3.

The crucible I la and the lower ends of the electrodes [8a and 48 are submerged in the flux 28a in the manner and for the purpose indicated in connection with the construction of Figs. 1 to 3, and these members are supported for movement in unison with respect to the mold Illa as shown in said construction. l

The process illustrated in Figs. 4 and 5 is carried out in the manner already made apparent in connection with the method shown in Figs. 1 to 3, the molten metal being deposited in the mold l0 from-crucible Ha at a rate which is substantially equal to the rate of production and deposition of the metal in said crucible.

In the two constructions of Figs. 1 to 5, the furnace or crucible II or Ha is disposed in the mold IEi. However, as far as certain aspects of the invention are concerned, the furnace or crucible may have its metal producing section outside of the mold l0, and the metal may be transferred from said furnace section to the mold continuously while the metal is being produced in said furnace section. This transfer would be effected at a rate substantially equal to the rate of metal production in said furnace while the metal being transferred is maintained out of contact with the air. Such a construction is shown in my copending application, Serial No. 534,829, filed May 9, 1944.

As many changes can be made in the above method and apparatus, and many apparently widely different embodiments of this invention can be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A method of casting metal which comprises the steps of producing and depositin metal in a furnace immersed in a layer of flux in a mold,

from said furnace through said layer of flux and into said mold.

2. A method of casting metal which comprises the steps of continuously depositing metal in a crucible immersed in a layer of flux in a mold,

and simultaneously overflowing metal from said crucible through said layer of flux and into said mold when the level of metal in said crucible reaches a substantial distance about the bottom of said crucible.

3. A method of casting metal which comprises the steps of continuously depositing metal in a crucible immersed in a layer of flux in a mold. overflowing metal from said crucible through said layer of flux and into said mold, and simultaneously moving said mold and said crucible relatively apart as the level of deposited metal in said mold rises, to maintain a substantial constant positional relationship between said crucible and the surface of said latter metal.

4. An apparatus for casting metal comprising a mold, flux in said mold, a crucible immersed in said flux, means for producing and depositing metal in said crucible below a layer of said flux, and means for discharging metal from said crucible through said flux and into said mold below said flux.

5. An apparatus for casting metal comprising a mold, flux in said mold, a crucible immersed in said flux, and means for continuously producing and depositing metal in said crucible, said crucible having an overflow pouring gate disposed a substantial distance above the bottom thereof, whereby metal deposited in said crucible as it reaches the level of said pouring gate overflows said gate and discharges through said flux and into said mold below said flux.

6. An apparatus for casting metal comprising a mold, flux in said mold, a crucible immersed in said flux, current discharge electrode means tor continuously producing metal under a layer or said flux and depositing it in said crucible, and means for discharging metal from said crucible through said flux and into said mold below said flux.

7. An apparatus for casting metal comprising a mold, flux in said mold, a crucible immersedin said flux, means for continuously producing metal under a layer of said flux and depositing it in said crucible, means for overflowing metal from said crucible through said flux and into said mold below said flux while metal is being produced and deposited in saidcrucible, and means for moving said mold and said crucible relatively while said metal is being discharged into said mold to maintain said crucible in constant positional relationship with respect to the rising surface of the metal in said mold.

8. An apparatus tor casting metal comprising a mold, flux in said mold, a cup-shaped crucible immersed in said flux and having an overflow pouring gate on one side thereof, and means for continuously producing metal in said flux and depositing it in said crucible.

9. An apparatus for casting metal comprising a mold, flux in said mold, an annular crucible immersed in said flux and having an overflow gate positioned substantially centrally of its outer wall a substantial distance above the bottom of said crucible, and means for producing metal in said flux and depositing it in said crucible.

ROBERT K. l-IOPKINS.