US2445670A - Apparatus for producing cast metal bodies - Google Patents

Description

R. KV HOPKINS Filed Feb. 3, 1944 l N V E NTO R Robert? l1. Hap/wins ATTORNEY July 20, 1948.

APPARATUS FOR PRODUCING CAST METAL BODIES Qflmmw IT' Patented July 20, 1948 APPARATUS FOR PRODUCING CAST METAL BODIES Robert K. Hopkins, New York, N. Y., assigner to The M. W. Kellogg Company, New York, N. Y., a corporation of Delaware Application February 3, 1944, Serial No. 520,986

2 Claims. 1

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 discharged 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 the 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 ailect the soundness of the casting.

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

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

Another object is to provide a new and improved apparatus for producing molten metal and depositing it free from atmospheric contamination and at high temperature into a mold having a cavity with a cross-section too restricted to permit effective use of a metal producing furnace therein.

Another object is to provide a new and improved continuous apparatus by which molten metal is produced and deposited free from atmospheric contamination and at high temperature. while the solidified ingot is withdrawn with respect to said mold.

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 embodies the structural features of the present invention;

Fig. 2 is a transverse section taken on line 2--2 of Fig. 1; and

Fig. 3 shows somewhat diagrammatically partly in vertical section and partly in front elevation another form of apparatus which embodies the structural features of the present invention.

In the form of the invention shown in Fig-s. 1 and 2, there is provided a mold Ill which may be of any suitable shape according to the desired shape of the metal to be produced. and which for the purpose of illustration is shown cylindrical for the casting of ingots. As far as certain aspects of the invention are concerned, this mold IU may be of unitary structure, but for continuous ca-sting operations it is desirably of split sectional construction as will be more fully described herelnafter.

For producing metal of the desired analysis, there is provided outside the mold I0 a furnace i2 in the form of a wide mouth vessel having a lower contracted desirably cylindrical spout or nozzle I3 extending into the upper end of said mold, and spaced from the inner periphery of said m-old by an annular clearance i4. Spout I3 connects into the furnace I2 by an overflow gate l5 raised a substantial distance above the bottom of said furnace to form therein a1 reservoir cavity or chamber i6 adapted to hold a substantial body of molten metal I1.

In the form of the invention shown in Fig. 1, the furnace i2 has concentric circular peripheral walls i8 and i9 integrally or otherwise rigidly connected together at the bottom. The reservoir furnace chamber i8 formed between these furnace walls I8 and I9 is annular in horizontal section and bowl-shaped in vertical radial section.

The walls of the furnace I2 and spout i3 are hollow to form a jacket 20 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 this jacket 20 by inlet and outlet pipes (not shown) connected into said jacket and arranged in any suitable manner.

The metal is produced and deposited in the furnace I 2 by the use of an electrode device which may be of the general type shown in my U. S. Patents Nos. 2.191,479 and 2,191,481. For that purpose, there is provided one or more consumable electrodes 22, two being shown, disposed in furnace I2 directly over its annular reservoir chamber I6. Electrodes 22 contain the base lngredients of the metal to be produced and deposited, and are desirably of hollow construction. Other constituents of the deposited metal may be furnished in the fluent form of granules, pellets. powders or the like through the hollows of the electrodes 22, so that these constituents in conjunction with said electrodes when fused produce a metal in the furnace I2 having the required analysis.

For creating a zone hot enough to fuse the metal as it is fed therein, the electrodes 22 are spaced by respective gaps 23 from the pool of deposited metal I1 in the furnace chamber I6, and current of sufficient intensity is discharged across said gaps to create a metal fusing zone in and around each of said gaps. For creating metal fusing current discharges across gaps 23, the electrodes 22 and the deposited metal I1 in the furnace chamber I6 are electrically connected in the same circuit from a suitable source 25 of electric power. The electrical connection to the deposited metal I1 in the furnace chamber I6 may be made from source of power 25 through the metal walls of said chamber.

The electrodes 22 and the granular metal constituents are fed at controlled rates towards the current discharge gaps 23 by suitable means, as for example that shown in my aforesaid Patent No` 2,191,479, to produce metal of the desired analysis, and to maintain said gaps substantially constant in length. The controlled downward feeding of the electrodes 22 may be effected by one or more feed motors regulated automatically in a suitable manner, as for example by the voltage drop across the current discharge gaps 23.

The hollow electrodes 22 may be continuously shaped from metal strips or skelps as shown in the aforesaid Patent No. 2,191,479, as said electrodes are fed continuously into the metal fusing zones in and around the current discharge gaps 23. The granular metal constituents may be delivered through the hoilows of electrodes 22 and into the current discharge gaps 23 at controlled rates and in desired proportions by means of metering devices (not shown) similar to those indicated in U. S. Patent No. 2,260,259. A number of these metering devices may be provided and arranged to feed the granular metal constituents at the desired rate to funnels leading into respective electrodes 22.

The furnace I2 contains a floating layer or blanket of flux 21 extending to a level above the inlet of the overflow gate I5. The lower ends of the electrodes 22 extend into flux 21, so that the current discharge gaps 23 are entirely submerged. Flux 21 fills the spout I3 through the overflow gate I and forms a protective blanket 28 over the surface of the molten metal 30 deposited in the mold I 0. On the outside of spout I3 in the annular clearance space I4, the protective flux blanket 28 extends above the lower end of said spout up to an approximate level A. Due to the heat conductive action of the mold I0, especially when liquid cooled, the flux in the annular clearance space I4 is frozen or solidified a comparatively short distance above the lower end of the spout I3 and forms thereby a solid seal 32, This solid flux seal 32 resists the static pressure of the flux in the furnace I 2 and prevents said flux from rising upwardly in the annular space I4.

The flux 21 arranged and distributed as described, maintains the molten metal from the time it is produced in the furnace I2 to the time it is deposited in the mold I0 out of contact with the air, so that this metal is effectively protected against air contamination while in the molten state. Flux 21 also serves as a heat insulating blanket around the metal from the time it is produced in the furnace I2 to the time it is deposited in the mold Iii, thereby allowing the use of extremely high temperatures in said furnace and effecting deposit of the molten metal at substantially the same high temperatures in mold I0.

The flux 21 also refines the metal, and comprises any suitable material having chemical and metallurgical properties necessary to carry out the method of the present invention. Silicates or components of silicates, such as magnesium silicate, calcium silicate, aluminum silicate and glass are suitable for the purpose.

Highly fluid superheated metal is continuously produced in furnace chamber I6 from the electrodes 22 and from the other metal ingredients delivered in fluent form. After the molten metal deposited in furnace chamber I6 reaches the level of pouring gate I5, it overflows the gate and discharges into the spout I3. The discharged molten metal flows thereafter as a continuous stream through the body offiux 21 in the spout I3, and is deposited in the mold I0 underneath the flux layer 28 as pool 30, the metal from the time it is produced to the time it is solidified is maintained by the protective action of the flux out of Contact with the air. The molten metal overflows the furnace chamber IB and is discharged into the mold IIJ at a rate which is substantially equal to the rate of its production.

Any solid particles which are not fused in the metal fusing zones in and around current discharge gaps 23 will eventually become fused before overflowing the gate I5. The unfused particles will sink towards the bottom of chamber I6 and, if they do not fuse as they sink, will settle at the bottom of chamber I6. As the unfused particles accumulate they will form piles that eventually will reach the level where the intense heat generated by the electrodes 22 will fuse the particles. Delivery of molten metal to the mold I0 free from unfused particles is thereby assured.

A heating electrode 31 is desirably disposed directly over the pouring gate I5 to maintain the overflowing metal highly fluid as it is discharged through said gate, and to prevent thereby freezing of the metal in said gate. Heating electrode 31 is desirably non-consumable, and for that purpose may be of copper hollowed to allow circulation of a cooling medium therethrough. Heating electrode 31 and the body of deposited metal I1 are connected in the same electric circuit to effect a current discharge from the lower end of said electrode to the metal overflowing the gate I5. For that purpose, electrode 31 may be connected to the source 25 of electric power.

As the molten metal overflows the pouring gate I5, the level of the deposited metal in mold I0 rises. At the same time, the metal deposited in the mold I0 solidifies progressively upwardly and inwardly as shown in the drawings.

In order to promote progressive solidication of the metal upwardly and to assure the maintenance of a body 30 of highly duid superheated metal in mold I0 to serve as a shrinkage feeder for the solidlfying metal below, heat is desirably transmitted continuously to the upper portion of the metal deposited in said mold. In the specific form shown, the pouring spout IJ serves as the electrode to discharge heating current across the annular gap40 intervening between the lower end of said spout and the surface of molten metal 30. Electrical connections from a source 4I of electric power to the furnace I2 and the mold l0 through leads 42 and 43, provide the necessary electrical tie-up for discharging current across the gap 4U. The current discharge across the gap 40 generates enough heat to maintain a supernatant body of highly fluid highly superheated metal 30, which feeds the shrinking solidifying metal below and thereby substantially eliminates shrink holes. cavities or pipes, floats out segregated impurities, and avoids the formation of cleavage planes. This so-called hot-topping" operation is carried out continuously and progressively upwardly, so that substantially the full length of the casting will be free from the defects indicated.

The heat input and the heat outgo of the operation are balanced to effect solldiflcation of the metal in mold i at a rate substantially equal to the rate at which the metal is produced in the furnace i2.

In the operation so far described, as the cast metal is poured in the mold lll and the level of the deposited metal risestherein the mold is moved gradually downwardly at a substantially uniform rate to maintain the current discharge gap substantially constant in length.

As far as certain aspects of the invention are concerned, the process described .may be applied to either still casting or continuous casting. By still casting" is meant a process in which the deposited metal in the mold is completely solidified before it is withdrawn from the mold. By continuous casting is intended a process in which the solidified metal is removed or withdrawn from the mold while the upper portion of the deposited metal is still in molten condition to form a casting of either finite or infinite length.

For still casting, the mold i0 may be supported on a platform which is movable downwardly at a substantially constant rate during metal producing operations, as for example by means of a screw feed drive.

In the specific form shown, the apparatus is employed to carry out a continuous casting operation. For that purpose, the mold I0 is desirably of split sectional construction as shown, and comprises a series of mold sections 45 tubularly stacked and diametrically split into complemental segments 4B. As far as certain aspects of the invention are concerned. these mold sections 45 may be oi' refractory material, and may be of solid construction.4 However, it is desirable to have these mold sections 45 of metal and of hcllow construction to permit liquid cooling thereof. For that purpose, the mold segments 46 are of a metal having high heat conductivity such as copper, and are provided with respective jackets 41. The cooling liquid is circulated through each of these jackets 4'lby means of an inlet 4l and an outlet 50 connected into each of said jackets. Inlets 4l and outlets 50 may be connected to respective hose or tubings 5i for circulating the cooling medium to and from the Jackets 41. The hose or tubings 5| may be flexible to permit movement of the mold segments 46 in a manner to be described, and may be detachably secured to the connections 4l and lll on the mold segments.

The solid ingot 55` formed by the casting op- 6 eration described is continuously withdrawn from the mold Ill during metal prodpcing. deposlting and hot-topping operations at .a rate which is substantially equal to the rate of solldlflcation of the metalin said mold. and which is correlated with the rate of metal production and deposition to maintain the spout I! in constant positional relationship with respect to the surface of the molten metal 30. The continuous withdrawal of the solid ingot 55 may be effected by means of pinch rollers 56 having drive engagement with the ingot 55..v and driven at substantially constant speed byany suitable means, and for instance from the motor and gear drive to one of said rollers.

To make the casting operations prolonged or continuous, the mold i0 is moved downwardly with the solidified ingot 55 during metal producing, depositing and hot-topping operations, and when the part of the solid cast metal embraced by the lower mold section 45 is cooled to the desired extent, this mold section is removed from the ingot andthe same mold section or another mold section is mounted on top of the 4tubular mold stack.

The frictional attachment between the ingot 55 and the mold i0 is sulllcient to hold said mold against downward relative gravitational movement with respect to said ingot. However, if the mold I0 is too heavy to prevent this relative movement or the cooling of the cast metal proceeds to a point where said metal is shrunk loose from said mold, then suitable mold supporting means may be provided-to prevent slippage of said mold along the ingot. ,Y

At the beginning of operations, the-.electrical connection 4.1 from the source 4i of electric power may be"attachedto one of the upper mold segments 4B. The connection 42 from the mold I0 to the power sourcef'li is long enough and flexible enough to permit movement of the mold segment 46 attached thereto from the top of the mold stack to the bottom. If the casting operation proceeds to the point where the mold segment 45 having this electrical connection 42 reaches the bottom of the mold stack and must be removed from the solidified ingot 55 in order to continue the casting operationsthis electrical connection may be removed from this bottom mold segment and readilyattached to the upper mold segment without interrupting operations. For that'vpurpose, there may be connected to the power source 4| branch leads. one of which may be attached to the upper mold segment 45 before the other lead is disconnected from the bottom mold segment.

If desired, after a solidified portion of the ingot 55 has been withdrawn from mold I0. electrical connection canbe continuously maintained between the bottom of the spout I3 and the body of molten metal 30 by attaching an electrical connection directly to the solidified ingot by means of a stationary contact shoe in slide engagement with said ingot.

If desired, the opposed moldsegments 4I instead of being bolted together as shown, may be 7 sure resisting function of this seal, so that flux ls prevented from overflowing the top of said mold.

It is seen that with the furnace construction of Figs. 1 and 2, it is possible to make a casting having a cross-section much smaller than that of the smallest furnace which can be emciently employed. The use of a furnace constructed and arranged with respect to the mold I as described, effects the continuous production and deposit of the metal in the furnace i2 and simultaneous continuous transfer of the metal from said furnace to said mold at a rate substantially equal to the rate of production of the metal in said furnace, while maintaining said metal free from atmospheric contamination, and substantially at the high temperature at which it is produced. At the same time, the furnace chamber I6 serves as a trap to prevent unfused particles of metal from being deposited in the mold I0 and forming bright spots in the casting.

In Fig. 3 is shown another form of .apparatus which embodies the features of the present invention. In this form of the invention, the furnace I2a is circular in cross-section, and instead of having an annular furnace chamber with a central overiiow gate connecting into a depending spout as in the construction of Fig. 1, it is formed with an overflow gate iSa on one side of the chamber merging into a depending spout Ila circular in cross-section. Overflow gate |5a is formed by a dam 60 constituting an upper extension of a portion of the circular wall of the spout |3a, and defining a reservoir furnace chamber 16a between said dam G and the outer peripheral circular wall section 6I of the furnace i2a. This furnace chamber IBa is approximately crescentic in horizontal section, and approximately bowl-shaped in vertical radial section, and has sufficient capacity to hold back a substantial amount of molten metal i'la before said metal starts to overow the gate |50.

The walls of the furnace I2a and spout l3a are desirably of copper, and are hollowed as in the construction of Fig. 1, to permit the circulation of a cooling medium in heat exchange relationship with said walls.

The metal is produced and deposited in the furnace i2a by the use of an electrode device similar to that employed in the method and construction of Fig. 1. For that purpose. a hollow consumable electrode 22a, containing the base ingredients of the metal to be produced and deposited extends directly over and substantially centrally of the furnace chamber lBa, and has its lower end submerged in a layer of flux 21a covering the deposited metal Ila in said chamber. Aithough only one consumable electrode 22a is shown. any number of these may beprovided according to the size of the furnace 12a.

The 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 22a, so that these constituents in conjunction with said electrode when fused, produce a metal in the furnace |2a having the required analysis. The electrode 22a is spaced from the upper surface of the deposited metal Ila by a gap 23a, and current of sufficient intensity is discharged through said gap to create a metal fusing zone as in the construction of Fig. 1. The electrode 22a and the body of metal ila in the furnace I2a are connected in the same circuit by connections to the power source 25a to The ux 21a forms a protective cover or blanket over the deposited metal Ila in the furnace chamber 16a, fills the spout i3a, and forms in the mold lila a protective iiux blanket 28a over the surface of said metal. The lower end of the spout 13a is submerged in this flux blanket 28a, and the solidification of the flux in the annular clearance space 14a between said spout and said mold I0a forms a solid seal 32a which serves as in the construction of Fig. 1 to resist the static pressure of the iiux in the furnace i2a, and thereby to prevent said flux from overowing the upper end of the mold Illa.

The deposited metal 30a in the mold iUa is heated to promote progressive solidiiication in said mold and to effect continuous hot-topping operations. For that purpose. heating current is discharged across the gap 40a intervening between the lower end of the spout 13a and the upper surface of the deposited metal 30a. The furnace |20, and the mold Ia may be connected to a suitable current source dla to eiTect the necessary current discharge across the gap 40a.

The mold lila is constructed as described in connection with the apparatus of Fig. 1, and is moved and progressively assembled and disassembled in a manner already made apparent in the description of said apparatus. The operation of the construction of Fig. 3 is in all respects the same as that described in connection with the construction of Figs. 1 and 2,

As many changes can be made in the above 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.

What is claimed is:

1. An apparatus for casting metal comprising a mold, a furnace outside said mold having a reservoir trap chamber and an overflow gate, a layer of flux over said chamber, a layer of i'lux in said mold, a. spout connected to said gate and extending into said mold with its lower end submerged in the iiux layer in said mold, said spout affording communication between the two flux layers, means for producing metal in said furnace under the protective action of the flux layer therein and depositing it in said furnace chamber under said latter flux layer. whereby the overflow from said furnace chamber passes over said gate through said spout and into said mold free from air contamination, while unfused particles of metal ingredients are trapped in said chamber. and means for solidifying the flux between said spout and the peripheral wall of said mold to form a substantially solid seal, whereby the flux is prevented from overflowing the upper end of the mold.

2. An apparatus for casting metal comprising a mold, a furnace outside said mold having a reservoir trap chamber and an overflow gate, a layer of flux over said chamber. a layer of flux in said mold, a spout connected to said gate and extending into said mold with its lower end submerged in the flux layer in said mold. said spout affording communication between the two flux layers, means for producing metal in said furnace under the protective action of the flux layer therein and depositing it in said furnace chamber under said latter ux layer, whereby the everilow from said furnace chamber passes over said gate through said spout and into said mold iree from air contamination, while unfused particles of metal ingredients are trapped in said chamber, `means for liquid cooling said mold. and means for liquid cooling said spout, the ux between said spout and the peripheral wall of said mold being solidiiled by both of said liquid cooling means and forming a solid seal to prevent overiiow of the flux from the upper end of said mold.

ROBERT K. HOPKINS.

REFERENCES CITED The following references are of record in the file of this patent:

0 UNITED s'xwms PATENTS Number Name Date King et al June 23, 1896 Monnot Dec. 28, 1909 Monnot Dec. 28, 1909 Mellen Nov. 11, 1919 Beck et al. Jan. 8, 1931 Hopkins Feb. 27, 1940 Junghans Dec. 15, 1942 Hopkins Feb. 9, 1943 Love July 20, 1943 Hopkins July 10, 1945

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