US3344839A - Process for obtaining a metallic mass by fusion - Google Patents

Description

Oct. 3, 1967 J. A. F. SUNNEN 3,344,839

PROCESS FOR OBTAINING A METALLIC MASS BY FUSION 3 Sheets-Sheet 1 Filed May 18, 1964 PRIOR ART 32 PRIOR ART fl INVENTOR ATTORNEY Oct. 3, 1967 J. A. F. SUNNEN 3,344,839

PROCESS FOR OBTAINING A METALLIC MASS BY FUSION 3 Sheets-Sheet 2 Filed May 18, 1964 INVENTOR 7260415 fume 3 .7: m 1- II v F r L a. u, zii... 2.4

v r L 5 .Tit: 2 \I n u u I I ATTORN EY Oct. 3, 1967 J. A. F. YSUNNEN 3,344,839

PROCESS FOR OBTAINING A METALLIC MASS BY FUSION Filed May 18, 1964 3 Sheets-Sheet 5 United States Patent 3,344,839 PROCESS FOR OBTAENING A METALLIC MASS BY FUSION Jean Albert Francois Sunnen, Uccle, Brussels, Belgium, assignor to La Soudure Electrique Autogene, Procedes Arcos, Brussels, Belgium, a corporation of Belgium Filed May 18, 1%4, Ser. No. 368,124 Claims priority, application Belgium, Nov. 28, 1963, 513,653, Patent 640,541 8 Claims. (Cl. 164-52) The present invention relates to a process for obtaining a metallic mass by fusion, in which at least one fusible electrode penetrates in a continuous manner into a pool of molten slag which covers a pool of metal contained in a cooled mold, the electrode comprising compacted metallic powder and an electric current being fed into the slag and causing, through heat resulting from its passage across the slag, the progressive melting of the electrode and keeping the slag and the nearby metal covered by the slag in molten condition.

A purpose of the invention is to maintain a pool molten by electric current passing from an electrode through a molten slag, and to continuously progress into the molten pool an electrode formed in whole or in part by compacted metallic powder which is continuously melted as the electrode progresses.

A further purpose is to cool the pool suitably by cooling the mold, and permissibly to continuously extract solidified metal from the end of the mold opposite to the electrode.

A further purpose is to progress the electrode including the compacted metal powder continuously and evenly into the molten slag and to expose the metallic powder at the least one portion of the periphery of the electrode, preferably at least one-half of the periphery.

A further purpose is to provide a solid metallic core as well as agglomerated metallic powder in the electrode, making the weight of the agglomerated powder at least several times the weight of the core, preferably at least four times the weight of the core.

A further purpose is to introduce electric current to the solid metallic core of the electrode at a location at which the metallic powder has not yet been agglomerated.

A further purpose is to employ at least three electrodes submerged between the molten slag, fed from a source of three phase current, each phase being connected to one of the electrodes and a neutral point being connected to the metallic mass which is being produced.

A further purpose is to make a mold of a plurality of parts, cooling at least one of these parts and adhering to the solidified molten mass at least one of the mold parts.

A further purpose is to cause stirring of molten metal in the pool by connecting the electrode to a source of alternating current having a frequnecy higher than industrial frequency.

A further purpose is to cause rotation of the molten pool by subjecting the pool to a magnetic field parallel to the axis of the mold, the magnetic field reacting with the electric current flowing between the electrode or electrodes and the mold.

A further purpose is to subject the molten metal during cooling and solidification to ultra-sonic vibrations.

A further purpose is to produce mechanism for forming a metallic mass such as an ingot, by providing a mold which is cooled and which can contain a molten pool, molten slag on the molten pool, and a solidified mass below the molten pool, projecting at least one electrode into and beneath the molten slag, passing electric current between the electrode and the solidifying molten metal to generate resistance heating in the slag and thus melt the adjoining metal and the electrode and agglomerating over at least one portion of the periphery of the electrode metallic powder above the molten pool as the electrode is progressively introduced into the pool of slag which causes it to melt.

A further purpose is to make the mold with an enlarged upper portion in which the metal solidifies and to extract the solidified mass from the lower end of the mold.

A further purpose is to provide a slanted extraction portion at the lower end of the mold.

Further purposes appear in the specification and in the claims.

Ingot manufacturing processes known in the prior art involve an electric arc striking between a fusible electrode and a metallic pool contained in an ingot mold consisting of a cooled copper shell. In a variant of this prior art process, a non-fusible electrode is used and the material to be fused, for instance metallic powder, is introduced on one side of the pool. Unfortunately, an inert atmosphere must be used to protect the metal brought to high temperature and it is often necessary to maintain by expensive means the entire area under a low pressure to improve the degassing of the pool. Furthermore, it is difiicult to control the tendency of the arc to wander. The are may jump from the electrode to the water cooled ingot mold, involving a risk of piercing its wall which would result in aviolent explosion because water would then enter the metallic pool. Finally, the fusion of the metal is accompanied by an abundant spatter and the spatter sticks to the upper part of the ingot mold and later on during subsequent stages of filling the mold, cold shuts and surface defects are produced so frequently that it becomes necessary, before rolling the ingot, to remove a large amount of metal to a depth which sometimes is as great as one centimeter.

It has also been proposed in the prior art to produce an ingot by an arc striking between an electrode and a pool under the protection of a layer of slag. In a variant of this process, a thick layer of flux is fused and becomes thereby electrically conductive as well as very hot. The electrode no longer arcs under these conditions and the electric current passes from one or more electrodes to the metallic pool through the molten slag. As a result of eddy currents within the electrode of electrodes, and mostly in the slag, the electrode or electrodes melt progressively. In this process, most of the tendency to form spatter is avoided and the surface condition of the ingot is greatly improved, and moreover it is possible to employ a refining operation by chemical reactions between the slag and the metal. Finally, the erratic wandering of the arc is no longer to be feared and it is unnecessary to operate costly vacuum pumps.

It has been proposed to use one or more non-fusible electrodes and to bring the metallic powders and the slag ingredients into the pool independently from the electrode or electrodes.

When using one or more non-fusible electrodes, such as graphite electrodes for example, there is danger of contaminating the pool by carbon. If, on the other hand, one or more electrodes are made of fusible materials such as copper or tungsten, it is necessary to cool them very vigorously to prevent melting. A very large amount of heat is then lost, and four to five kilowatt hours are required to melt one kilogram of steel. Furthermore, the powder which is depositedupon the pool has a tendency to float on it. As a result of powder accumulation at a single spot, a time is reached when short circuits develop between the electrode or electrodes and the ingot mold or between the electrodes themselves. In addition, the powder reacts with air at the upper surface of the pool. This latter difliculty can only be overcome by additional gas protection, which is of course costly.

It has been proposed in the prior art to use metallic granules instead of fine powders, to facilitate flow, but such granules, because of their relatively large mass and small surface, receive very little heat by transfer during their fall through the slag. Therefore, they penetrate the molten metal pool in a solid condition, causing intense localized cooling and agglomerating together Without melting throughout.

These difficulties have been remedied by using several fusible electrodes of different shapes, such as wires, strips, bars and even ingots. Nevertheless, the composition of the ingot is limited to that of the electrodes, and furthermore high energy must be used, about 1.2 to 1.7 kilowatt hours per kilogram of remelted metal or an average of 1.5 kilowatt hours per kilogram of melted met-a1. If an attempt is made to increase the melting speed by increasing the current intensity, dendrites are found to form at the surface of separation between the liquid metal and solid metal, growing perpendicularly to the axis of the ingot mold as a result of the very elongated depth of the metallic pool. Impurities then gather in the center of the ingot, tending to cause cracks to formIIf it is desired to obtain a high hourly output of metal by increasing the amperage, an electrode of very large diameter must be used, which is heavy and difiicult to handle. This process leads to the use of a 0.4 ratio between the electrode diameter and the ingot mold diameter when the latter is cylindrical. Also there must be provided above the mechanism for feeding the current a device to connect successive electrodes to avoid interruption of the melting operation.

In order to permit a change in composition during the manufacture of an ingot, it has been proposed to drop upon the layer of molten slag independently of the penetration of an electrode into the slag, metallic powders having different composition. However, these powders have a tendency to freeze on the slag pool as in the process above mentioned where a non-fusible electrode is used, and therefore this method has the same drawbacks as in the process previously discussed. These difficulties are the more serious when the electrode has a larger diameter. This diameter is large because it is generally close to onehalf of the ingot mold diameter when the latter is cylindrical. Furthermore, it is difficult to obtain an even composition of the ingot and this process has been abandoned.

It has also been proposed in the prior art to replace a bar or a wire electrode by an electrode consisting of a tube or a strip containing a core of metallic powder. However, it is not possible to produce in this way a composite electrode where the volume of sufficiently compacted pow der amounts to more than one-third of the total volume of the electrode, and this greatly reduces the number of chemical compositions which can be used. Moreover it is found that it is also necessary, as in the case of solid bars and wires, to supply energies of 1.2 to 1.7 kilowatt hours per kilogram of metal, and that it is not possible to increase the amperage above certain limits without causing segregation and cracking along the axis of the ingot.

In the process of the invention these difficulties are overcome by delivering continuously and at constant speed into the molten slag, at least one fusible electrode having over at least one portion of its periphery metallic powder which is agglomerated above the slag pool so that this agglomerated powder is carried by the electrode deep into the core of the molten slag as the electrode melts progressively into the pool.

The agglomerated condition and the securing in position of the powder can be obtained either by mechanical action, or by magnetic action provided the powder possesses magnetic properties. The powder is carried in an agglomerated condition, in a continuous and even man ner, into the molten slag where'it melts by alloying itself to the metal of the electrode which is carrying it. This feature cannot be obtained by simply dropping powder into the slag pool.

In this manner the powder which is carried deep into 4 the interior of the slag pool by the downward motion of the electrode, melts much faster by contact with the slag pool.

The metallic mass which is fused by the process of the invention can be contained in an ingot mold to form an ingot after complete solidification. It can also be melted in a bottomless mold from which it is extracted at the rate of its production out of the end of the mold opposite that nearest to the electrode or electrodes. It also can be melted in a mold closing around metallic parts intended to be joined.

The invention also relates to mechanism by which the process of the invention can be carried out. In this mechanism the mold is cooled sufficiently to cool a mass of molten metal which is brought into it by the fusion of at least one electrode comprising compacted metallic powder, through a layer of slag heated by the passage of electric current fed by the electrode or electrodes.

The mechanism as per the invention provides above the mold, means to agglomerate, on at least one portion of the periphery of the electrode, metallic powder gradually as the electrode penetrates into the slag pool which melts it.

In a particular embodiment of the invention, the mold comprises an upper portion where melting takes place having a larger cross section than the lower portion where the molten mass solidifies, as Well as means to extract the solidified mass from the lower end of the mold.

Other features of the invention will be evident from the description of the drawings attached to the specification which illustrate schematically and only by way of example a prior art mechanism to produce ingots as well as several new mechanisms for carrying out the invention.

FIGURE 1 is a vertical section of an ingot mold in which an ingot is being formed by a prior art process using a solid electrode.

FIGURE 2 is a vertical section of the solidified portion of the metal of FIGURE 1, illustrating the arrangement of crystals formed.

FIGURE 3 is a diagrammatic vertical section showing formation of an ingot by the process of the invention using a consumable electrode composed of a wire surrounded by powder.

FIGURE 4 is a vertical section of a solidified portion of the metal of FIGURE 3, illustrating the arrangement of the crystals formed.

FIGURE 5 is a vertical section of an embodiment of the invention which includes a compression chamber surrounding a continuous electrode and provided with means for feeding powder and an outlet for powder extrusion around the central wire.

FIGURE 6 is an enlarged cross section of the electrode on the line 6-6 of FIGURE 5 showing the electrode at the point at which it penetrates into the ingot mold.

FIGURE 7 is an enlarged cross section of another form of coated electrode penetrating into the ingot mold as in FIGURE 5.

FIGURE 8 is a vertical section of an embodiment of the invention in which the powder is compacted against a strip by rolling.

FIGURE 9 is an enlarged plan section on the line 9-9 of FIGURE 8.

FIGURE 10 is a view similar to FIGURE 9 of an embodiment in which the rolling mill rolls have semicircular grooves.

FIGURE 11 is a vertical section of an embodiment in which electromagnetic means is used to compact the powder around a continuous electrode. 1

FIGURE 12 is a vertical section of a form of the invention which uses a compacting rolling mill for powder only which is shaped as a bar fed by a pair of rolls.

FIGURE 13 is a vertical section of an illustration similar to that of FIGURE 5 in which the cooled metallic mass is extracted in a continuous manner from the mold after it freezes, by a pair of driving rolls.

FIGURE 14 is a plan view of an ingot surrounded by the cooling shell, and above which there is a strip electrode coated with powder, shown in cross section.

FIGURE 15 is a vertical section of one embodiment of the invention for continuous production of bars and shapes, using three melting electrodes.

FIGURE 16 is a plan view showing the connections of the three electrodes of the form of FIGURE 15, each being connected to one phase of a three phase alternating current power source, and showing their relative positions to each other, omitting the neutral connection shown in FIGURE 15.

FIGURE 17 is a vertical section of an embodiment similar to FIGURE 15 but with the outlet slanted with respect to the vertical.

FIGURE 18 is a vertical section of a device of the invention which includes an ingot mold provided with an electromagnetic wiring to create circulation inside the molten pool.

FIGURE 19 is a vertical section of an embodiment of the invention intended to create composite articles.

In the process of the invention, in which at least one electrode melts in a pool of molten slag, this electrode has at least part of its peripheral surface covered with metallic powder agglomerated above the pool of molten slag and carried deep into the interior of the molten slag as the electrode melts. This offers the advantage of providing a much greater speed of fusion of the electrode than in the case of a solid electrode or an electrode having a core of powder and fed with the same current under the same voltage. The amount of electrical energy consumed in the process as per the invention is in some cases no more than 0.5 kilowatt per hour per kilogram of molten steel.

During comporative testing, a solid wire having diameter of 3.2 millimeters and of known composition, was first melted in a pool of slag, to deposit a stainless steel containing about 18% chromium and 8% nickel by Weight. The fusion took place in a basic slag covering the metal pool deposited in an ingot mold, by a current of 625 amperes under a voltage drop of 40 volts.

An ingot of 6.7 kilograms was obtained by melting a wire weighing 6.850 kilograms in 23 minutes. The fusion speed Was 17.470 kilograms per hour and the electrical energy consumed was 1.450 kilowatt hours per kilogram of melted material.

With the same current and the same voltage drop, an electrode designed to produce the same stainless steel was melted consisting of an open hearth steel strip surrounding a nickel wire and a mixture of metallic powder. The weight of the strip was equal to 61.16% of the total weight of the electrode; that of the nickel wire was 9.17% and that of the mixture of metallic powders was 29.67%. The external diameter of the electrode was the same as the diameter of the solid wire used in the previous experiment, namely 3.2 millimeters. The slag covering the metal pool was the same as that in the previous case. An ingot of 6.6 kilograms was obtained by melting 6.650 kilograms of composite electrode in 22 minutes. The melting speed was 18 kilograms per hour and the energy consumption was 1.390 kilowatt hours per kilogram of melted material.

The melting speed and the energy consumption were, therefore, substantially the same as in the previous case even though the electrode contained about 30% of metallic powder.

In a third test, a composite electrode designed to deposit the same stainless steel and consisting of a steel wire surrounded on its entire periphery with a mixture of compacted powders was melted with the same current and voltage drop as used previously. This wire had a diameter of 2.4 millimeters and had a cross section practically identical with that of the strip used in the previous test. The mixture of powder comprised, in addition to the mixture used in the previous test and corresponding to 30% of the total weight of the electrode, an amount of nickel 6 powder of a weight equal to that of the nickel wire previously used (9.17%). The total proportion of powder was thus about 38.84% of the total weight and the weight of the central wire was about 61.16%

The slag used was the same as in the first two cases.

An ingot of 6.700 kilograms was obtained by melting 6.755 kilograms of the composite electrode in 16 minutes. The melting speed was 25.120 kilograms per hour and the energy consumption was slightly below 1 kilowatt hour per kilogram of melted material.

Therefore, the arrangement of the same amount of powder outside the core having the same weight as that of the strip which surrounded the powder in the second test resulted in a melting speed of about 140% of that obtained in the second test with an electrical energy consumption of about 70% of that of the second test.

Later a composite electrode Was made from a steel wire identical to the one used in the electrode in the third test and surrounded by a mixture of compacted powders weighing about four times the weight of the wire. This was melted with the same current and the same voltage drop as in the previous test. The metal powders were made up of a proportion of iron powder such that the deposited metal would contain about 18% chromium and 8% nickel by weight, even though the central wire was no bigger than in the case of the third test. The slag used was the same for the three previous tests.

In ingot of 2.790 kilograms was obtained by fusion in 3 minutes and 22 seconds from a composite electrode Whose central wire weighed 0.530 kilogram while the powder layer weighed 2,260 kilograms. The melting speed was, therefore 49.673 kilograms per hour and the energy consumption was 0.542 kilowatt hour per kilogram of melted material.

This melting speed is much higher than that obtained by known processes and the energy consumption is much lower. It does not reach 40% of the energy consumption for a solid wire or for a wire containing a core of powders weighing 30% of the total weight of the electrode.

In a test where the amount of powder coating the electrode amounted to only 10% of the wire weight, it was obvious that the melting speed was already 10% higher than that obtained under identical conditions with a solid electrode or with an electrode of the same diameter provided with a core. The wire of the electrode consisted of mild steel and the powder was ferrochromium to obtain a steel ingot of the 2% by weight chromium type.

The process of the invention makes it possible to vary the composition of the metallic masses obtained within very large limits, since it is possible to obtain sound masses with less than 20% of the electrode weight consisting of wire, bar or strip, while more than of the weight consists of powders. The process no longer requires, when using very high current, solid electrodes having such big diameters, since the solid portion need amount to only one-fifth of the deposited metal. The process is, therefore, suitable for continuous operation with a wire or strip and a powder feeder, instead of requiring big heavy bars diflicult to handle and needing junctions to one another.

An important feature also is that there is a different method of fusion.

In FIGURE 1 a prior art embodiment is shown schematically, in which a solid or core electrode 1 or an electrode formed by wrapping a strip around a core of powder, is driven in the direction of arrow X by rolls 2 and plunges into a pool of molten slag 3, floating over a metallic ingot 4. The upper part of the metallic ingot comprises a pool of molten metal. The metallic ingot and the pool of molten metal and slag are contained within a double walled ingot mold 5 connected to the electrode 1 by an electric circuit 6 including a current source 7. The ingot mold is cooled by water circulation at 8 introduced at 9 and discharging at 10.

The metal of the electrode, or the sheath of the cored electrode, is brought to high temperature by the eddy currents due to its own electrical resistance, but it also receives through its surface of contact with the slag where it is immersed beneath the level of the slag a more substantial amount of heat, due to the electrical resistance of the slag-to-metal contact surface.

As shown in FIGURE 2, illustrating the ingot of FIG- URE 1 without the metal and slag pools, the driving rolls the electrodes and the electrical circuit, a growth of crystal dendrites 11 develops perpendicularly to the solidifying line 12 as shown and since this line dips deep in the center, the dendrites tend to grow radially, collecting impurities along the axis of the ingot and causing danger of cracking.

In FIGURE 3, powder is added to the periphery of a wire 14. Other conditions are the same. It is observed that the melting speed increases considerably. This is explained by the powder-to-slag surface contact being much greater than in FIGURE 1. It is also noticed that the metallic pool 15 in FIGURE 3 dips less deeply in the center than in FIGURE 1. The contact surface 12 tends to flatten. As a result, if, as shown in FIGURE 4, the metallic pool is slightly depressed at the center, the dendrites grow nearly axially throwing the impurities into the liquid metal where a refining action of the slag can still take place.

Examining voltage oscillograms, it was possible to count the number of drops of molten metal passing in one unit of time and, from the knowledge of the amount melted, the average weights of the drops could be determined to be 2 to 4 grams for a 1600 ampere current, and for solid electrodes of 30 to 60 millimeters diameter. Under these conditions, the total developing surface, and therefore the reaction surface between drops of molten metal and slag, was computed to be about 0.3 square meter per kilogram. On the other hand, when using an electrode of the same outside diameter but consisting for instance of a 10 millimeter wire surrounded by agglomerated iron powder, the fusion was known to be much smoother due to the powder grains dissolving into the slag. The developed surface of a powder whose grains are supposed to be all spherical having a density of 8 grams per centimeter and being in con-tact with the slag is about 4 square meters per kilogram for a 60 to 100 ASTM mesh powder and 10 square meters per kilogram for 100 to 270 ASTM mesh powder.

The refining reactions by the slag are thus considerably assisted.

It is also observed that with an electrode coated with powder, the center dipping of the metallic pool is less pronounced and this permits, for very high currents, reduction of the risk of segregation and cracking in the center of the molten mass.

The coating of wire 14 by powder 13 can be produced in the manner shown in FIGURE where the wire penetrates into a container 19 filled with powder compacted by the rotation of a feeding screw 20 in a side cylinder 21. The wire emerges from the container 19 through an aperture 22 together with a ring of powder 13. The diameter of the aperture 22 is larger than the diameter of the wire 14 and it is selected by the thickness of the layer of powder desired to be obtained around the wire. A dieholder device may be provided to vary the thickness at will.

In some cases it is necessary to protect the coated electrode against the surrounding atmosphere. The electrode emerging from the container 19 through the aperture 22 is then enclosed until it enters the ingot mold 5 by a protecting nozzle 23 acting as a shield around the electrode. The upper portion of this nozzle is provided with a gas inlet 24. The diameter of this nozzle is smaller than the inside diameter of the ingot mold to permit the protecting gases as well as those evolved during the fusion of the electrode to escape.

The electrode shown in FIGURE 7 consists of a metallic strip 25 between two layers of metallic powder 13 and 13 applied on both broad faces.

Compacting of the powder may be obtained by rolling mills containing the powder and shown in FIGURE 8. The latter illustrates a hopper26 at the bottom of which two rolling mill rolls 27 and 28 are installed, having grooves of different depths 29 and 30 (FIGURE 9) within contacting flanges 31 and 32. These rolls leave between themselves a rectangular space due to the junction of both grooves. A metallic strip 25 delivered from a roll 33 is fed around roll cylinder 27 and leaves the mill loaded with compacted powder 13 under pressure of rolls 27 and 28. i

In an embodiment similar to that of FIGURES 8 and 9 but somewhat modified as shown in FIGURE 10, the wire is coated completely. Rolls 27 and 28 have semi-circular grooves 34. The wire 14 passes in the center of the circular area formed by the contacting grooves and is completely surrounded with compacted powder 13 when it emerges from the rolling mill.

If the powder is sufficiently magnetic, the agglomeration can be accomplished magnetically. In the embodiment shown in FIGURE 11, the powder feeds from a hopper 35 provided with a vibrator 36 to an endless belt 37 and later it falls on an inclined trough 38 for delivery to the container 19. Under the action of a magnetic field produced by passing a current in the electrode wire 14, the powder adheres around the wire and is carried with it through the aperture 22. Magnetic coils 4t) and 41 are arranged facing each other to reinforce the magnetic field to compact the powder.

Non-magnetic powders can be agglomerated advantageously with magnetic powders. The mixture can be fed by an extruder screw or by means of a belt feeder or by any other known means. Should the feeder be located too far from the location of the fusion operation, the powder can be fed pneumatically by means of a suitable gas. This device is of interest because it permits reducing the crowding of parts above the pool.

It will be evident that the ingot formed in an ingot mold such as 5 may be circular as well as any other shape, and that the extrusion die for the compacted powder may have whatever shape is most suitable for the ingot shape.

As shown in FIGURE 12, the electrode 13 can consist solely of powder compacted by passing between groove rolls 27 and 28 of a mill. These rolls are followed by a pair of metallic guiding rolls 42, one of which is electrically connected to the current source 7.

The cross section of the ingots may be of any desired shape to obtain any profile desired.

In FIGURE 14 a plan view is shown of an ingot mold 5 of rectangular cross section, in which a coated electrode having a shape similar to the ingot mold plunges into the slag layer. The electrode has a rectangular metallic core 25 and a coating of powder 13.

The process of the invention is not limited to pouring ingots or other masses of short length, but can be applied to the continuous production of simple bars or shapes.

The installation shown in FIGURE 13 illustrates this possibility schematically. This sketch shows a mold 5 in which the deposited metal solidifies and is being extracted downward by a pair of driving rolls 43 in the shape of a bar 4' cooled in said mold. The bar emerges from the end of mold 5' which is opposite to the end nearest to the electrode and progresses as the electrode melts.

In the installation shown in FIGURE 15, a bottomless mold 5 comprises an upper portion 44 having a larger cross section than the lower portion 45 in which the molten metallic mass solidifies. Three composite electrodes 46 with peripheral powder are fed each from one phase of a three-phase current source 47 (see FIGURES 15 and 16) whose neutral center 48 is connected to the bar 4' being extracted in a continuous manner from the reduced section 45 of a mold 5 by rollers 43.

In order to prevent solidification which might accidentally partially invade the tapered portion 49 adjoining the large portion 44 to the small portion 45 in FIGURE 15, the lower portion having a smaller cross section can be extended to the side as shown in FIGURE 17. In this embodiment, two composite electrodes 46 are connected in parallel to the current source.

An electric current passing through a conductive molten mass generates in this mass circular magnetic lines Which react with the main and with induced electric currents to cause motions in the mass. In the mechanism of the invention the current emerges from the electrode and spreads out in the mass, toward the conductive walls of the mold. The beneficial stirring action so created will be increased in intensity by using a medium frequency alternating current, for example 300 cycles per second, instead of the usual industrial frequency.

However, the known method of mixing by an induction furnace may be used as shown schematically in FIG- URE 18. An ingot mold of non-magnetic metal 50 and having a double wall is shown as a cooled chamber. Around it there is a winding 51 of fine wire suitably insulated. A composite electrode plunges inside the ingot mold 50. The current lines illustrated by arrows Y move down the walls of the ingot mold, penetrate into the slag pool 3 and the metal pool 15 and then enter the electrode. On the other hand, the lines of force of the magnetic field developed :by current passing through the winding 51 follow the arrows Z and are parallel to the axis of the ingot in the ingot mold. The action of the magnetic field upon the current lines causes the molten mass to rotate around the axis of the ingot mold.

When a fine crystalline structure is desired, ultrasonic vibrations can be introduced into the ingot.

To compensate for variations in composition due to deterioration of the slag, fresh slag is introduced, or else the amount of powder is increased or decreased. The same is true of alloying ingredients introduced in the pool as the pool increases in height.

It is desirable to give the coating of powder around the electrode a shape similar to that of the ingot mold.

The flux consumed and which forms a skin around the ingot, is replaced gradually as it is consumed, either by a separate feeding from the electrode or electrodes, or by mixing with metallic powders at the periphery of the electrodes or electrodes, or by feeding of a metallic sheath containing the flux as a core.

In FIGURE 19, the process is shown for producing, in a manner which is known per se, composite articles. The schematic installation comprises two bottomless molds 5' and 5 which are cooled and placed at diiferent levels. The cross sections of these molds are diiferent from one another. The one having the smaller area 5' penetrates inside the one having the larger area 5 The metal 52 melted in the one having the larger area from electrodes 13" surrounds the product 53 emerging from the mold 5'. The product 53 is formed in mold 5' from an electrode 13'.

The process of the invention may be applied in a mold consisting of several pieces some of which only are cooled, so that those which are not cooled can be joined by means of the metallic mass deposited between them when said mass is cooled.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or part of the benefits of my invention without copying the process and mechanism shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A process of obtaining a metallic mass by fusion, which comprises maintaining a pool of molten metal in a mold, maintaining a pool of molten slag on said pool of molten metal in said mold, merely compacting metallic powders, directly above the pool of molten slag, in order to form at least one fusible electrode presenting compacted metallic powder on at least a portion of its periphery, said electrode being a composite electrode comprising a solid metallic core and a layer of metallic powder compacted on said core having a weight at least several times the weight of the core, continuously forcing said fusible electrode into the pool of molten slag, passing electric current from said fusible electrode through said molten slag in order that by the heat resulting from its passage through the molten slag, it progressively melts the electrode and keeps the slag and the nearby metal covered by the slag in a molten condition, and cooling the mold to cause the molten metal to solidify.

2. A process of claim 1, in which the metallic powders are compacted on at least one half of the periphery of said electrode.

3. A process of claim 1, in which the weight of the compacted powder is at least four times the weight of the solid metallic core.

4. A process of claim 1, which comprises extracting the metallic mass from the mold in which it has cooled out of an end of the mold opposite to that nearest to the electrode, as fusion of the electrode progresses.

5. A process of claim 4, in which three electrodes are introduced into the slag pool, which comprises passing alternating current to said electrodes each from one phase of a source of three-phase current and connecting a neutral point of said phases to the cooling mass which is continuously extracted from the mold.

6. A process of claim 1, which comprises impressing a magnetic field on the pool of molten metal and slag parallel to the axis of the mold and thereby subjecting the pool to rotation by having the magnetic field react with the electric current flowing between the mold and the electrode.

7. A process of claim 1, which comprises subjecting the molten metal to ultrasonic vibrations during cooling.

3. A process of Obtaining a metallic mass by fusion, which comprises maintaining a pool of molten metal in a mold, maintaining a pool of molten slag on said pool of molten metal and in said mold, merely compacting metallic powders, directly above the pool of molten slag, in order to form at least one fusible electrode presenting compacted metallic powders on at least a portion of its periphery, said electrode being a composite electrode consisting of a solid metallic core and metallic powder, continuously forcing said fusible electrode into the pool of molten slag, passing electric current to said electrode at a location at which the metallic powder has not yet been compacted on the electrode, passing electric current from said fusible electrode through said molten slag in order that by the heat resulting from its passage through the molten slag it progressively melts the electrode and keeps the slag and the nearby metal covered by the slag in a molten condition, and cooling the mold to cause the molten metal to solidify.

References Cited UNITED STATES PATENTS 1,391,507 9/1921 Riveroll 7512 2,369,233 2/1945 Hopkins 22 57.2 2,375,107 5/ 1945 Hopkins 2257.2 XR 2,541,764 2/1951 Herres et al 13-9 2,727,937 12/1955 Boyer 22-572 2,800,519 7/1957 Garmy 13-9 X 2,813,921 11/1957 Vordahl et a1 75-l0 XR 2,891,294 6/1959 Muller et a1. 22216 3,067,473 12/ 1962 Hopkins 22-212 3,193,889 7/1965 Lane et al 22-216 FOREIGN PATENTS 135,344 11/ 1949 Australia. 1,174,959 11/ 1958 France.

WILLIAM J. STEPHENSON, Primary Examiner. V. K. RISING, Assistant Examiner.

Claims (1)

1. A PROCESS FOR OBTAINING A METALLIC MASS BY FUSION, WHICH COMPRISES MAINTAINING A POOL OF MOLTEN METAL IN A MOLD, MAINTAINING A POOL OF MOLTEN SLAG ON SAID POOL OF MOLTEN METAL IN SAID MOLD, MERELY COMPACTING METALLIC POWDERS, DIRECTLY ABOVE THE POOL OF MOLTEN SLAG, IN ORDER TO FORM AT LEAST ONE FUSIBLE ELECTRODE PRESENTING COMPACTED METALLIC POWDER ON AT LEAST A PORTION OF ITS PERIPHERY, AID ELECTRODE BEING A COMPOSITE ELECTRODE COMPRISING A SOLID METALLIC CORE AND A LAYER OF METALLIC POWDER COMPACTED ON SAID CORE HAVING A WEIGHT AT LEAST SEVERAL TIMES THE WEIGHT OF THE CORE, CONTINUOUSLY FORCING SAID FUSIBLE ELECTRODE INTO THE POOL OF MOLTEN SLAG, PASSING ELECTRIC CURRENT FROM SAID FUSIBLE ELECTRODE THROUGH SAID MOLTEN SLAG IN ORDER THAT BY THE HEAT RESULTING FROM ITS PASSAGE THROUGHT THE MOLTEN SLAG, IT PROGRESIVELY MELTS THE ELECTRODE AND KEEPS THE SLAG AND TE NEARBY METAL COVERED BY THE SLAG IN A MOLTEN CONDITION, AND COOLING THE MOLD TO CAUSE THE MOLTEN METAL TO SOLIDIFY.

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