US2861302A - Apparatus for continuous casting - Google Patents

Description

Nov. 25,1958 K, EJ MANN ETAL 2,861,302

APPARATUS FOR CONTINUOUS CASTING Filed Aug. 14, 1956 2 Sheets-Sheet 1 [271 Mar Kafl Ems"- Hann 4 s Erick Rcqnrf 3x5:

Nov. 25, 1958 K. E. MANN ETAL 2,8615302 APPARATUS FOR CONTINUOUS CASTING 2 Sheets-Sheet 2 Filed Aug. 14, 1956 Inventor's K a. r\ E ru t mm and Garick R u QrT B United States Patent APPARATUS FOR CONTINUOUS CASTING Karl Ernst Mann, Meinerzhagen,

Riepert, Frommersbach, near Gummersbach, Rhineland, Germany, assignors to Vereinigte Leichtmetall- Werke Gesellschaft mit beschraenkter Haftung, Bonn (Rhine), Germany Application August 14, 1956, Serial No. 603,915 5 Claims. (Cl. 22-572) The present invention relates to a new and improved method and apparatus for the continuous casting of molten metal. More particularly the present invention relates to a new and-improved apparatus for the continuous casting of molten metal to form a casting having a homogeneous and uniform structure.

The present application is a continuation-in-part of our copending application, now abandoned, Serial No. 544,786, filed on November 3, 1955 and entitled Continuous Casting Improvement.

There are conventional casting processes of molten metal known in the art which are identified as continuous casting processes wherein the molten material is poured into a mold in which it is solidified and the solidified material is continuously withdrawn from the mold. Therefore, there is always a portion of the material in the mold which is completely molten, a portion which is partially solidified, and a portion just before the exit from the mold which is fully solidified.

In one type of continuous casting process the solidified material leaving the mold is sprayed with cooling water in order to cool the same. This sudden cooling of the casting by the water sometimes causes the casting to break apart or causes other types of structural defects therein. One method of preventing such structural defects and splitting of the casting is to use cooling water whose temperature is not-too low. However, with such an arrangement one of the primary advantages of water cooling of a continuous casting is lost. That is, with cooling water having a relatively high temperature, the cooling of the casting takes a substantial amount of time and the texture of the casting becomes substantially thicker instead of the desirable finer texture. When it is desired to produce casting from metal alloys containing alloying metals which are at pouring or casting temperature partially or completely insoluble in the melt and cause liquation, it is difficult and often impossible to obtain an even distribution of these alloying metals in finely divided form throughout the entire crosssection of the casting. Accumulations or nests of such alloying metals impair the quality of ingots which are destined to be deformed to sheets, rods, profiles, forgings and the like in a. chipless manner. For instance, manganese which is desired in nearly all magnesium alloys because of its anticorrosive properties, easily forms undesirable manganese streaks in sheets and profiles when, for instance, to a magnesium alloy containing about 6% aluminum and 1% zinc, manganese is added in a quantity which exceeds its solubility at pouring temperature by about 0.1%. In the case of freecutting brass or free cutting aluminum alloys, the machinability of the work piece is impaired by an uneven and coarse distribution of lead or of the equivalent metals bismuth, cadmium, tin, etc.

It has been attempted to influence the crystallization processin the direction of increasing'the number and reducing the size of grains during production of continuous casting ingots by exposing the only partially solidified Westphalia, and Erich A 2,861,302 Patented Nov. 25, 1958 casting to the effect of a rotary magnetic field in order to equalize localized differences in temperature and heat content by causing a controlled circular movement.

However, such circular movement of the casting material is connected with disadvantages such as vortex formation in the vicinity of the center axis of the poured material and there exists the danger of tearing of the ingots and also of impairment of the ingot quality due to increased liquation.

It is therefore an object of the present invention to overcome the above described disadvantages in the continuous casting of molten metal.

A second object of the present invention is to provide a new and improved continuous casting apparatus.

Another object of the present invention is to provide a continuous casting apparatus wherein the casting made from the molten material has a fine structural texture.

Still another object of thepresent invention is to provide a Water cooled continuous casting apparatus using a magnetic field near the inlet of the mold into which the molten material is poured.

A further object of the present invention is to provide a new and improved continuous casting apparatus wherein the partially solidified material being cast is subjected to the action of a magnetic field.

Still a further object of the present invention is to provide a new and improved apparatus for the continuous casting of a molten material wherein the partially solidified material in the mold in subjected to an alternating magnetic field having its axis in a plane substantially perpendicular to the direction of flow of the molten metal in order to cause a stirring in the same for equalizing the temperature in the casting and to provide a desired structural texture.

With the above and other objects in view the present invention mainly consists of an apparatus for the continuous casting of molten material and including a mold for receiving the molten material to becast, the mold having an inlet through which the molten material is poured, and means for establishing an alternating magnetic field having lines of flux in the region of the mold inlet, the lines of flux extending through at least a portion of the material already poured into the mold and the axis of said magnetic field being perpendicular to the direction of flow of the molten material into and through the mold. v

In a preferred embodiment of the present invention the means for establishing the alternating magnetic field includes-a water cooled copper tubing formed in the shape of an annular member and-arranged near the inlet of the mold for establishing a magnetic flux when electrical current is passed therethrough. A secondary mag netic member is provided, substantially surrounding the copper tubing and distributing the magnetic flux into a predetermined pattern having the axis thereof arranged perpendicular to the direction of flow of the molten metal into the mold so that the magnetic flux flows through the partially solidified material in the mold.

The present invention also includes in a method for the continuous casting of molten material wherein the material is poured into a mold and continuously withdrawn therefrom, the improvement comprising subjecting partially solidified material within the mold to the action of an alternating magnetic field having its axis lying in a plane substantially perpendicular to the direction of flow of the material Where the material is subjected to the alternating magnetic field.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. 'The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will-be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is alongitudinal cross sectional view of oneembodiment capable, of carrying out the.-principles,..of the presentinvention;

Fig. 2 is a top, plan view of theembodiment shown in Fig. l;

Fig. 3 is a longitudinal cross sectional view of a second embodiment incorporating the principles of the present invention; and

Fig. 4 is a plan view of the apparatus illustrated in Fig. 3.

Referring to the drawings and more particularly to Figs/1 and '2, it can be seen that the molten material to be cast ispoured intothe cylindrical mold 3 from a spout 6. The mold 3 has an inlet 11 -and..an outlet 1.2.

Emerging from the outlet 12 of the cylindricalemold 3 is shown the solidified portion 4 .of the casting which has a partially molten andpantially solidified.i ortion.5 near 'theupper edge thereof adjacent the .inlet .11 of the mold. As the solidified, portion of the .casting emerges from the outlet 12 of the mold 3 it iscooled by cooling water supplied from an annular. channel. l3 connected to an annular reservoir 14 within the mold. An inlet channel 16 for the reservoir 14 is adaptedto becon'nected to a source of cooling water for-replenishing the water in the reservoir 14 as it, isused in cooling the casting.

Adjacent the inlet. 11 of the mold 3 is mounted a copper tubing-1 which is formed in the shape of an annular member-having an annular diameter substantially equal to the diameter of the circular inlet 11 of the mold. Partially surrounding the copper tubing 1 is a secondary magnetic member 2. The secondary magnetic member 2 is also shaped as an annular member and is made up of-a plurality of transformer laminations. This can best be seen in the plan view of Fig. 2. Each of the trans former laminations used in the secondary magnetic'mem' bet 2 has. a horseshoe-shaped cross section whentaken in a direction parallel to the annular axis of the annular member 2.

That is, the secondary annular magnetic member 2 is formed of a plurality of horseshoe-shaped transformer laminations. In Fig. 1 it can be seen that the open end of the horseshoe faces the inlet 11 of the mold 3.

In operation, the copper tubing 1 is connected to'a source .of alternating electrical current so that a magnetic field is established thereabout. Since the transformer laminations are made of a magnetic material, substantially all of the lines of fiux of the magnetic field established .by the current flowing through the copper tubing 1 flows through the horseshoe-shaped elements of the secondary magnetic member 2. However, there is an airgap between the open ends of the horseshoe. so that a substantial amount of the flux passes from one end of the i horseshoe through the partially solidified portion of the casting backinto the other leg of the horseshoe.

Accordingly, the secondary magnetic member 2 which is mounted in the region of the magnetic lines of flux distributes the lines of flux into a pattern extending through the partially solidified portion 5 of the material in the mold. As can be seen from the arrangement of the tubing 1. and the secondary magnetic member Zin Fig. 1, the pattern of thealternating magnetic field so established is. arranged with a substantially annular axis lyingin a plane perpendicular to thedirection of flow of the molten metal into 'themold. That is, each of the horseshoeshaped laminations of the secondary magnetic member 2 provides a substantially circular or annular magnetic field having an axis which is perpendicular to the direction of fiow of the molten material. The total of these magnetic fields is a substantially annularmagnetic ,field having an annular axis lyingima. plane-perpendicular to the direction of ,flow of .the ..molten Qmaterial -where such material is subjected to the .magnetic field. When this partially.

solidified portion 5 is subjected to the alternating magnetic field, a gentle stirring of this portion occurs which tends to eliminate any local variations of temperature within the solidified portion. Therefore, a uniform heating and cooling of the casting is provided since, by the time the partially solidified portion 5 becomes solidified as shown in the portion 4, any initial temperature variations within the molten material are dissipated due' to the action of the lines of flux established. bythe magnetic field.

It has been found that subjecting-the partially solidified material of the casting to such an alternating magnetic field results in a casting which has a desirable texture and which is free from any structural defects.

An experiment was carried out during the casting of a high-strength aluminum alloy of the type using aluminum, copper and magnesium. Castings having a diameter of 300 mm. were cast with a pouring velocity of. 45mm. per minute. In order to prove the effectiveness of the method and apparatus incorporating theprinciples of the present invention, two simultaneous castings were poured. One casting was made with the conventional distributing means and the second casting was made with the induction apparatus made up of the copper tubing land the transformer laminations 2 as illustrated in Figs. 1 and 2. During this experiment all other factors, such as the casting temperature, the shape of themold and the length thereof, the amount and temperature of the cooling water were all maintained exactly the same. That casting which was formed without. the alternating magnetic field provided by the present invention wasfull of structural cracks and fissures as well as other structural defects. On the other hand,. thecasting formed by the appara-. tus incorporating the principles ofthe present invention was completely uniform and homogeneous and had not structural defects at all.

A corresponding experiment was carried out in the same manner with an aluminum alloy formed of aluminum and manganese. That casting which was madewithout the alternating magnetic field was found to be full of voids andother structural defects while the casting made by the. principles -of the. present inventionwere freeof such defects.

Further experiments have also been carried ouLusing aluminum alloys made from aluminum, zinc, magnesium and copper and showing the same results. In theserlatter experiments. itwasalsofound thatin the castings made by the. principles of the present invention,..there was no segregation or liquationofchromium. v V

In further experiments aluminum alloy castingsofi the type including aluminum, .magne sium and silicon were produced having diameters in the order. ofmm.- without having any structural defects.

Referring now to Figs. 3 and 4 a second embodiment of the present invention is shown. The elements in Figs. 3 and 4 which, carry outthe same functions asin Figs. 1 and 2 are numbered with the same numerals. However, in this second embodiment the copper tubing 1 forms an annular member which-has a substantially smaller annular diameter than the diameter of the circular inlet 11 of the mold .3

Also, in this embodiment. the secondary magneticmemher 2', which surrounds. the copper tubing 1', also .is shaped as anannular member having an annular. di-. ameter substantially smaller than the diameter of the cir cular inlet 11 of the-mold 3.

In this second embodiment the members 1 andZ' are supported on the upper surface .of the mold 3 by asup'. porting member 17.

In operation this second. embodiment operates .substantially in the same manner as in the first embodiment. However it can be seen .in Fig. 4 that the spout 7 may be shaped with abifurcated .end having channels 8 and 9, in respective .end portions .thereot .so that the .molten material poured intorthemoldjs pouredoutside of the secondary magnetic member 2' closer to the sides of the mold 3 so that an even distribution of the molten material poured into the mold is provided.

In both of the embodiments described hereinabove it is possible to provide water-cooling for the copper tubing 1 and 1' since these tubings are hollow and permit the passage of cooling water therethrough.

According to the method of the present invention it is possible to produce continuous casting ingots, billets or the like from alloys which include alloy forming metals which at casting temperature are partially or completely insoluble in the melt and tend to cause liquation, in such a manner that these alloy forming metals are finely and evenly distributed throughout the entire ingot. This is achieved by subjecting the partially solidified melt to the action of an alternating magnetic field, such as can be produced with the apparatus of the present invention.

It has now further been found that an optimum of even and finely divided distribution of the liquating alloying metal can be achieved by super-heating the melt prior to casting to a sufliciently high temperature above the casting temperature so as to substantially dissolve the liquation-causing alloying metals, and by subsequently cooling to casting temperature. For instance, continuous casting ingots produced according to the methods of the present invention from an aluminum aly containing aluminum, copper, magnesium and lead have shown greatly improved machining properties. X-ray photographs of slices taken from such ingots show the completely even and very fine distribution of the lead.

The degree of super-heating of the melt above pouring temperature depends on the degree of solubility of the alloying metals in the melt at the respective temperatures. For instance, the solubility of lead in liquid aluminum, or of manganese in liquid magnesium is greater at temperatures which are above the normal casting temperatures for aluminum or magnesium alloys. The degree of superheating will have to be increased, according to the present invention, in accordance with increase in the relative quantity of, for instance, lead or manganese in the melt which would not be dissolved at casting temperature.

The percentage amount of liquating-causing alloy components which are dissolved at casting temperature depends on the type and relative quantity of the other al loying components; For instance, the solubility of manganese in magnesium (in binary alloys) is considerably reduced by the addition of aluminum. It follows'that the desirable degree of super-heating above the casting temperature of the respective alloy will have to be determined in each case, so as to achieve substantially complete dissolution of the alloy components which would not be dissolved at regular casting temperature.

Preferably, the diflicultly soluble alloy component is added last to the remainder of the alloy composition. The other alloying metals may be combined at lower temperature, and theliquating alloy component is then added last at the desired super-heating temperature. Immediately after dissolution of the liquating alloy component, the melt may be cooled to casting temperature and cast. This feature of the present invention is'described in detail further below in Examples 1, 2, 4 and 8,

The following examplesare given as illustrative only, the present invention however not being limited to the specific details of the examples.

All of the examples of continuous casting of alloys according to the method of the present invention were carried out in low frequency induction furnaces. It must be emphasized, however, that other types of furnaces such as gas or oil heated furnaces could also be employed for carrying out the method of the present invention.

In all examples, an induction device as herein described having a frequency of 50 cycles was used.

6 EXAMPLE 1 Magnesium alloy containing 7.5% aluminum, 1.2% zinc, 0.21% manganese, balance magnesium Magnesium pig is melted at 720 C. At this temperature the aluminum and zinc are alloyed with the magnesium, and the melt is then heated to 780 C. Upon reaching a temperature of 780 C. the manganese is added to the alloy. Thereafter, the melt is quickly cooled to 700 C. and cast. In a casting device, four continuous castings are made simultaneously with a casting speed of 60 mm. per minute. Each continuous cast ing has a diameter of mm. The series-connected induction devices have a total power of 4 kilowatts and a total voltage of 6 volts.

The thus-Obtained individual ingots of about 4 mm. lengths possess throughouttheir entire length and crosssection a fine-grained, even structure, completely free of manganese-nests, as shown by X-ray inspection.

EMMPLE II V Binary magnesium alloy containing 0. 75% Zirconium Magnesium pig is melted (the melting point of the magnesium is about 650 C.), the. melt is super-heated to 800 C. and zirconium is added in the form of a 50% magnesium-zirconium key -alloy. Thereafter, the melt is quickly cooled to 700 C. and cast. In a casting device two continuous castings are made simultaneously with a casting speed of 65 mm. per minute. Each continuous casting has a diameter of 180 mm. The seriesconnected inductiondevices have a total power of 2 kw. and a total voltage of 2.8 v. y

The thus-obtained ingots possess throughout their entire length and cross-section a fine-grained, even structure. The grain size is below 0.1 mm. X-ray examination shows complete absence of zirconium inclusions.

EXAMPLE III Binary magnesium alloy containing 1.9% manganese Magnesium pig is melted and super-heated to 740 C. At this temperature, the manganese is added in the form of water-free MnClwhereby the manganous chloride reacts with the molten magnesium under formation of manganese 1 and magnesium chloride. The melt is quickly cooled at 700 C. and cast. A continuous casting of 300 mm. diameter is formed ata casting speed of 40 mm. per minute. The induction device has a power of 4 kw. and a voltage of 5 v.

The thus-obtained ingots possess a fine-grained structure and are free of so-called columnar-structures and manganese nests, while similarly produced ingots which, however, were not exposed to the alternating magnetic field show both columnar-structures and manganese nests.

EXAMPLE 1v nesium, 1.0% manganese, 0.2% silicon, 0.3% iron, 2.0% lead, balance aluminumt The aluminum is molten and alloyed at 720 C. with all alloying elements except lead. The melt is then heated to 800 C. at which temperature the lead is added. Thereafter, the meltis cooled to 700 C. and cast. In a casting device four continuous castings of 170 mm. diameter each are made simultaneously with a casting speed of 60 mm. per minute. The induction device operates as described in Example I. j

The thus-obtained ingots possess an extraordinarily fine-grain structure. Lead is present in finest distribution throughout the entire cross-section and can hardly be recognized by X-ray examination. X-ray examination of similarly produced ingots which, however, havenot been exposed to the alternating magneticfield show ball.- like agglomerations of lead.

7 EXAMPLE y Aluminum alloy containing 3.8% copper, 0.9% magnesium, 0.9%. manganese, 0.2% silicon, 0.3% iron, 0.5% bismuth, 0.5% lead, balance aluminum The aluminumis molten and all alloying elements are added at a temperature of 720 (3., however, preferably lead and bismuth are added last. Thereafter, the melt is cooled'to 700 C., and-cast as described in Example IV. The thus-obtained ingot structure is comparable to the structure obtained according to Example IV.

EXAMPLE VI Aluminum alloy containing 4.5% zinc, 3.0% magnesium, 0.7% copper, 0.25% manganese, 0.3% iron, 0.2% silicon,,0.25.% chromium, balance. aluminum After melting-the aluminum, all-of the alloying elements are addedata temperature of 740C. Chromium in the form of an aluminumachromium key alloy containing chromium is added last. Casting takes place at 720 C. Aningot of 45.0mm. diameteris'cast at a speed of 28 mm. per minute. .The induction device has a power of 4L5' kw. and/a voltage of 6.3 v.

The thus-obtained ingot is of highly fine-grained'structure and, as can be shownby. X-ray tests the structure is free .of coarse chromium aluminides- (intermetallic compounds of chromium and aluminum).

EXAMPLE VII Aluminumalloy containing "8;1% zinc, 2.0% magnesium, 0.4% manganese, 0.1% silicon,.0.25% iron, 0.27% chromium, 0.07% vanadium, balance aluminum Alloying and casting temperatures'are thesame as described in Example VI; Two ingots of 300 mm; di ameter are'cast with a'speedof 37 mm; per minute. The series-connected induction devices have a total power of 4 kw. and a total voltage of 6 v. I

Thethus-obtained structure is similar to theonedescribed in Example VI and completely free of chromium aluminides and vanadium aluminides.

EXAMPLE VIII Aluminum alloy containing 0.82% -magnesium, 1.0% silicon, 0.21% iron, 0.91%--manganese, 0.2% chromium, 1.0% lead,-1.0% tin, balance aluminum After melting the aluminum, the alloying elements magnesium, silicon, manganese and chromium '(the latter in the form of a 10% key alloy) are added'at a temperature of 720 C. The melt is heated to 800 C, and at this temperature lead and'tin are added. The meltis now cooledto 710" C.,.and fouringots of 170 mm. diameter are cast at a casting speed of 57 per minute. The inductiondevicefisoperated as described in Example I. g

, Inspection of the ingot structure including X fray examination shows a fine-grained structure, absence of coarse chromium aluminides, and lead and tin in an extraordinarily fine distribution.

.EXAMPLE' IX V 7 Brass containing 58.0% copper, 2.8% lead, 39-.2-%' zinc The copper is molten at1050" C. and alloy edlat the same temperature with zinc and lead. A castingtemperature of 1000 C. is maintained. An ingot of 165 mm. diameter is cast at a speed of 70 mm. per minute. Tl'ieinduction device has a power of 3 kw. and operates at a voltage of 3.2 v.

In contrast to an ingot cast in similar manner but without exposure to an alternating magnetic field, the'ingot obtained asidescribed above is of evenfine-grained structure' withthclead very finelydistributed throughout the entire cross-section, as can bes'fe'en by Xray examination.

8? EXAMPLE X Aluminum brass containing 58.0% copper, 1.0% aluminum, 0.8% manganese, 1.5% lead, 0.3% iron, 38.4% zinc The copper is molten at 1050 C. and heated to 1200" C. At thistemperature manganese and iron are added in the form of 30% key alloys. The melt is cooled to 1050" C. and zinc, lead and aluminum are added. After further cooling to 1000 C., an ingot of mm. diameter is cast at a speed of 65 mm. per minute. The induction device operates as described in Example IX.

The result of structural examination of the thus-obtained ingot are similar to those described in Example IX.

It is therefore seen that by the improved method and apparatus incorporating the principles of the present invention it is possible to obtain in a continuous casting process a solid casting of wide diameter containing substantially no structural defects while permitting a high rate of production.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of casting operations difiering from the types described above.

While the invention has been illustrated and described as embodied in a continuous casting apparatus, it is not intended to be limitedto the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristicsof the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the'meaning and range ofequivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an apparatus for the continuous casting of molten material, in combination, a mold for receiving the molten material to be cast, said mold having an inlet'through which the molten material is poured to be solidified in the mold and an outlet from which the solidified material is continuously withdrawn; an annular current conducting member consisting essentially of a metaltubing disposed directlyab'ove and adjacent said mold inlet for establishing alternating magnetic lines of flux in the region of saidmold inlet when alternating current flows therethrough; and an annular magnetic member made up from a plurality of transformer laminations, each of said transformer laminations having a horseshoe-shaped cross section in a direction perpendicular to the axisof said annular magnetic member with the open end of the'horseshoe-shaped cross-section facing the mold inlet, said annular magnetic member being disposed in the region of said magnetic lines of fiux for distributing said lines of flux into a pattern extending through the solidification zone of the material poured into the mold wherein solidification of said material occurs.

2. In an apparatus for the continuous casting of molten material, in combination, a water-cooled mold for receiving the molten material to becast, said mold having an inlet through which the moltennmaterial is poured to be solidified in the mold and an outlet from which the solidified material is continuously withdrawm'an'annular current conducting member consisting essentially of a water-cooled metal tubing disposed directly above and adjacent said mold inlet for establishing alternating magnetic lines. of flux in the region of said mold inlet when alternating current flows therethrough; and an annular magnetic member made up from a plurality of transformer laminations, each of said transformer laminations having a horseshoe-shaped cross section in a direction perpendicular to the axis of said annular magnetic memher with the open end of the horseshoe-shaped cross section facing the mold inlet, said annular magnetic member being disposed in the region of said magnetic lines of flux for distributing said lines of flux into a pattern extending through the solidification zone of the material poured into the mold wherein solidification of said material occurs.

3. In an apparatus for the continuous casting of molten material, in combination, a mold for receiving the molten material to be cast, said mold having a substantially circular inlet through which the molten material is poured to be solidified in the mold; an annular current conducting metallic member having a diameter substantially equal to the diameter of said circular inlet disposed directly above and adjacent said mold inlet for establishing alternating magnetic lines of flux in the region of said mold inlet when alternating current flows therethrough; and an annular magnetic member made up from a plurality of transformer laminations, each of said transformer laminations having a horseshoe-shaped cross section in a direction perpendicular to the axis of said annular magnetic member with the other end of the horse shoe-shaped cross section facing the mold inlet, said annular magnetic member being disposed in the region of said magnetic lines of flux for distributing said lines of flux into a pattern extending through the solidification zone of the material poured into the mold wherein solidification of said material occurs.

4. In an apparatus for the continuous casting of molten material, in combination, a mold for receiving the molten material to be cast, said mold having a substantially circular inlet through which the molten material is poured; an annular current-conducting metallic member having a diameter substantially smaller than the diameter of said circular inlet disposed directly above and adjacent said mold inlet for establishing alternating magnetic lines of flux in the region of said mold inlet when alternating current flows therethrough; and an annular magnetic member made up from a plurality of transformer laminations, each of said transformer laminations having a horseshoe-shaped cross section in a direction perpendicular to the axis of said annular magnetic member with the open end of the horseshoe-shaped cross section facing the mold inlet, said annular magnetic member being disposed in the region of said magnetic lines of flux for distributing said lines of flux into a pattern extending through the solidification zone of the material poured into the mold wherein solidification of said material occurs.

5. In an apparatus for the continuous casting of molten material, in combination, a mold for receiving the molten material to be cast, said mold having an inlet through which the molten material is poured to be solidified in the mold; an annular current conducting member disposed directly above and adjacent said mold inlet for establishing alternating magnetic lines of flux in the region of said mold inlet when alternating current flows therethrough; and an annular magnetic member made up from a plurality of transformer laminations, each of said transformer laminations having a horseshoeshaped cross section in a direction perpendicular to the axis of said annular magnetic member with the open end of the horseshoe-shaped cross section facing said mold inlet, said annular magnetic member being disposed in the region of said magnetic lines of flux for distributing said lines of flux into a pattern extending through the solidification zone of the material poured into the mold wherein solidification of said material occurs.

References Cited in the file of this patent UNITED STATES PATENTS 1,518,321 Geyer Dec. 9, 1924 2,242,350 Eldred May 20, 1941 2,448,993 Mahoney et al Sept. 7, 1948 2,567,525 Morris Sept. 11, 1951 2,649,527 Chapman et al. Aug. 18, 1953 2,715,171 Williamson Aug. 9, 1955 FOREIGN PATENTS 343,648 Great Britain Feb. 26, 1931 504,519 Great Britain Apr. 26, 1939 705,762 Great Britain Mar. 17, 1954 159,282 Australia Oct. 13, 1954 1,064,849 France Dec. 30, 1953

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