US 3905417 A
An electromagnetic rabbling mechanism associated with continuously poured molten metal forming an ingot comprises an inductor coil mounted on a stationary annular laminated magnetic structure providing a rotating magnetic field which surrounds the slowly descending column of solidifying metal and induces rotation of the central and still liquid metal within the solidified outer crust portion of the ingot. Cooling of the inductor coil and its rotary magnetic field producing structure is effected by immersion thereof within a water-filled annular tank co-axially surrounding the descending metal column, the water or other liquid coolant being continuously circulated through the tank along a path designed to establish an optimum amount of heat transfer contact surfaces with all exposed parts of the magnetic structure and the coil.
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Description (OCR text may contain errors)
United States Patent Delassus [451 Sept. 16, 1975 ELECTROMAGNETIC RABBLING MECHANISM FOR CONTINUOUSLY POURING MOLTEN METAL  Inventor: Jean Delassus, Montmorency.
France  Assignee: Compagnie Electro-Mecanique, Paris, France 122] Filed: Dec. 6, 1973  Appl. No.: 422,128
 Foreign Application Priority Data Dec. 21. 1972 France 72.45725 7 I It "14pm 4 "1 g  US. Cl. 164/147; 164/250; 335/300  Int. Cl? B22D 11/12; B22D 27/02  Field of Search 164/49, I47, 250, 251. 164/273 R; 335/300  References Cited UNITED STATES PATENTS 2,877,525 3/1959 Schaaber 164/49 3,056,071 9/1962 Baker et al. 335/300 Primary Examiner-Robert D. Baldwin Attorney, Agent, or Firm-Pierce, Scheffler & Parker 5 7 ABSTRACT An electromagnetic rabbling mechanism associated with continuously poured molten metal forming an ingot comprises an inductor coil mounted on a stationary annular laminated magnetic structure providing a rotating magnetic field which surrounds the slowly descending column of solidifying metal and induces rotation of the central and still liquid metal within the solidified outer crust portion of the ingot. Cooling of the inductor coil and its rotary magnetic field producing structure is effected by immersion thereof within a water-filled annular tank co-axially surrounding the descending metal column, the water or other liquid coolant being continuously circulated through the tank along a path designed to establish an optimum amount of heat transfer contact surfaces with all exposed parts of the magnetic structure and the coil.
8 Claims, 5 Drawing Figures PATENTED SEP 1 6 I975 SHEET 3 BF 3 ELECTROMAGNETIC RABBLING MECHANISM FOR CONTINUOUSLY POURING MOLTEN METAL The present invention relates to mechanisms for continuously pouring molten metals and wherein the ingot 5 leaving the ingot mold where it was shaped continuously descends at a constant and very low speed, the ingot then consisting of an outer crust already solidified at the mold exit and of a central, still liquid part, called the molten well or shaft, ofwhich the cross-section progressively narrows during ingot descent into a so-called secondary cooling zone.
It is known that by setting this liquid metal in motion during its solidification, a technique known as rabbling, the structure and homogeneity of the solidified product will be improved; proposals already have been advanced to make use of a rotating magnetic field to stir and cause the liquid column to revolve at moderate speed about the longtitudinal pouring axis.
Such a rotary magnetic field may be achieved by means of a wound magnetic toroid, which functions as an inductor, of the type used in the stators for electric rotating field motors, with a hollowed central part traversed by the ingot being solidified and transversely crossed by the rotating magnetic field.
However, a magnetic toroid is subjected to the in tense radiation from the partially solid ingot still at very high temperature and passing through said toroid, which therefore is in danger of being very rapidly de stroyed unless effective means are provided to ensure its cooling.
To that end, and in conformity with the present invention, adequate cooling is ensured by completely immersing the toroidal inductor in a tank subjected to strong circulation of a liquid coolant preferably water; in order to achieve this result, the magnetic toroid is mounted in an impermeable annular tank provided with a cooling water inlet and an outlet for the water having provided the cooling, the tank being so designed, that the water will first circulate from top to bottom through an annular passage provided between the outer wall of the tank and the periphery of the stack of annular laminations comprising along their inner rims the slots holding the inductor winding, then horizontally and radially inward around the conductors at the lower winding heads, then from the bottom towards the top through these winding slots and through the narrow annular passage provided between the lower rim of the lamination stack and the inner tank wall, and lastly horizontally and radially outward above the stack around the conductors at the upper winding heads and out through the outlet.
To prevent that the winding conductors be degraded by the cooling water, they consist of a flexible conductor comprising a central stranded conductor covered by an insulator impermeable to water; one may for instance use a flexible conductor structure of circular cross-section and 6mm in diameter, comprising a 3 mm copper core; while such conductor will not efficiently fill the slots, they do allow obtaining the desired field intensity and ensure effective cooling water passage be tween them in the remaining clear spaces between their cylindrical walls, even though they are adjoining.
Another difficulty consists in achieving conductor cable lead-outs that are impermeable with respect to the cooling water; to that end, and in conformity with a characteristic of the present invention, the lead-outs are solid conductors traversing an insulating plate provided in the wall of the tank and connected inside the latter to the carefully insulated ends of the winding.
In order to ensure the desired hermeticity and insulation of the connections between the ends of the cables and those of the solid and massive conductors, the bared cable ends will be soldered into bores fashioned in the solid and massive conductors. heat-setting sleeves surrounding the cable ends and the corresponding ones of the solid conductors, the whole being immersed in a filling resin or potting compound inside an insulating sleeve of which the outer rim is sunk in a corresponding groove made to that end in the lower side of the insulating plate; furthermore, the solid and massive conductors are provided with an inner shoulder which is pressed against an interposed toroidal seal against the lower side of the insulating plate by means of a tightening screw.
Lastly, the tank is so designed that it may be easily dismantled to permit inside cleaning and to provide easy access to the cables and connections.
The accompanying drawings illustrate a preferred embodiment of the present invention wherein:
FIG. 1 is a vertical cross-section of the electromagnetic rabbling mechanism for the continuous pouring of a molten metal;
FIG. 2 is a top view of a cross-section along line llll of FIG. 1',
FIG. 3 is a diametrical section of the electromagnetic mechanism being used;
FIG. 4 is a section along line lVlV of FIG. 3; and
FIG. 5 is a cross-section on a larger scale, of the winding cable terminals.
With reference now to FIG. 1, the column of molten metal leaving a ladle (not shown) and which descends slowly along a vertical path comprises first an already solid part of ingot 1 within which liquid metal 2 forms a fusion well or shaft; the ingot passes through the interior hollow part of an annular tank 3 within which is mounted an inductor coil L with lower and upper heads 6 and 7 resp., in the circumferentially spaced slots 5 of an annular magnetic lamination stack 4.
Cooling water flowing in the tank from top to bottom passes through inlet 8 and reaches tank 3; it then passes between the outer rim of the annular lamination stack 4 and the outer wall 9 of tank 3 to the lower part of the tank, then flows horizontally radially inward while cooling the lower winding heads 6, next moving from bottom to top in slots 5 of lamination stack 4 and also in the annular clear space 10 left between the inner rim of the annular lamination stack 4 and inner wall 11 of the tank, and lastly horizontally and radially outward at the upper tank part, where it cools the conductors of the upper winding heads 7, and finally discharges through outlet 12.
FIG. 3 shows in greater detail several radial passages 14 in the lower clamping plate 13 of lamination stack 4, which supply cooling water to the center and direct it towards the winding terminals 6 through orifices 15 designed for that purpose; the figure also shows the radial spaces 16 provided between plates separating the various winding heads 6 from one another; similarly, as regards the upper part of the tank, after the water has come up through slots 5 holding the conductor winding and through space 10 between the inner surface of lamination stack 4 and inner wall 11 of the tank, it will cool the upper winding heads 7, passing through the radial 3 spaces 19 between the plates separating the several upper winding heads 7, then discharging through outlet 12. Direct through-holes 17 of small diameter and drilled in upper clamping plate 18 prevent formation of air pockets in the upper annular space between tank 9 and lamination stack 4.
The annular tank 3 is sectionalized in order to permit easy access to the space between the inner and outer walls for inspection of the electrical components as well as to facilitate cleaning of the interior of the tank. For this purpose the inner wall ll is continuous from the top to the bottom. but the outer wall 9 is divided into upper and lower sections joined together by means of connection flanges provided with sealing rings 22 therebetween and which are fastened by means of cir cumferentially spaced bolt-and-nut connections 20. The upper end of the outer wall 9 terminates in a radially inward wall reaching to the inner wall 11 and which is joined to the latter by means of a sealing ring 23 and circumferentially spaced connection screws 21. Upon removal of the connection bolts and screws 21, the upper part of the tank may be lifted off, thereby providing full access to the interior of the tank.
In order to achieve good electrical insulation simultaneously with satisfactory hermeticity with respect to the cooling water. the winding conductor lead-outs may be designed in the manner shown in FIGS. 4 and 5, namely. as solid and massive conductors 24 which traverse an insulating plate 25 installed in a junction neck 26 extending outward from the tank 3 as illustrated in FIG. 4. As illustrated in a larger scale in FIG. 5, each of the massive conductor parts 24 includes bores 29 in the upper portions 30 for receiving and sol dering the bared ends 27 of the flexible inductor con ductors 28, hermeticity of the assembly being achieved by means of heat-shrinking sleeves 31; the whole is immersed in a potting resin 32 inside a circular insulating sleeve 33 of which the end 34 is pushed into a circular groove in insulating plate 25', a tightening nut 35 screwed onto a threaded stern portion of the conductor part 24 clamps the integrated set of cable lead-outs 28 to insulating plate 25 by compressing a toroidal seal ring 36 which provides the desired hermeticity; cablelugs 37 may thereafter be tightened by nuts 38.
While the embodiment of the invention described herein and referring to the accompanying drawings is preferred, it is considered illustrative only and hence verious modifications may be resorted to without thereby departing from the scope of the appended claims.
1. A liquid-cooled electromagnetic rabbling mecha nism associated with a continuously poured and descending column of molten metal forming an ingot which comprises an annular cooling tank adapted to co-axially surround the descending column of metal an annular laminated magnetic structure located coaxially within said cooling tank and having a cylindric array of axially extending coil-receiving slots located at the inner periphery thereof, an inductor coil located in said slots, said inductor coil being constituted by a winding of an electrical conductor covered by a sheath which is impermeable to the liquid coolant, a lead-out structure from the terminal ends of said coil through the wall of said cooling tank to an energizing source thereby enabling production of a rotating magnetic field which induces rotation of the centrally located and still molten metal within the outer crust portion of the ingot being formed, and means for effecting forced circulation of a liquid coolant through said tank which includes means establishing a flow path therefor which provides passage of the coolant from an inlet downwardly through an annular passage provided between the outer wall of said tank and the outer periphery of said annular magnetic structure to the bottom of the coil. thence inwardly to the inner periphery of said annular magnetic structure. thence upwardly through said slots and an annular passage provided between the inner periphery of said annular magnetic structure and the inner wall of said tank to the top of the coil, and thence outwardly from said tank through a discharge outlet.
2. A liquid-cooled electromagnetic rabbling mechanism as defined in claim 1 wherein said annular laminated magnetic structure includes clamping plates at the upper and lower ends thereof, said lower clamping plate including radially extending passages therein for directling the liquid coolant radially inward to the inner periphery of said annular magnetic structure and said upper clamping plate including a multiplicity of through-holes to prevent formation of air pockets in the upper annular space between said tank and said annular laminated magnetic structure.
3. A liquid-cooled electromagnetic rabbling mechanism as defined in claim 1 wherein the conductor from which said inductor coil is wound has a flexible characteristic and is constituted by stranded cable covered by the sheath of material impermeable to the liquid coolant.
4. A liquid-cooled electromagnetic rabbling mecha nism as defined in claim 3 wherein said flexible stranded cable which forms the coil conductor has a circular cross-section of 6mm in diameter and includes a 3 mm diameter copper core.
5. A liquid-cooled electromagnetic rabbling mechanism as defined in claim I wherein said tank includes a junction neck and a transversely extending insulator plate therein through which are passed and supported the lead-out terminal structures for the various parts of said inductor coil.
6. A liquid-cooled electromagnetic rabbling mecha' nism as defined in claim 5 wherein the lead-out structures for the various conductor members of said inductor coil include massive parts of conductive material including bores for receiving and connection by soldering of the bared ends of the conductor parts. heat shrinkable sleeves enclosing and sealing off the connections between the conductor ends and said bored massive parts, said sealed-off connections being immersed in a potting resin and covered by an insulating sleeve the end of which is embedded in a corresponding groove provided in said insulator plate.
7. A liquid-cooled electromagnetic rabbling mechanism as defined in claim 6 wherein said massive conductor part includes a threaded stem portion projecting through said insulator plate and secured thereto by a out, said stern portion establishing a shouldered portion and a sealing ring surrounding said stem portion and which forms a seal between said shouldered portion and the adjacent surface of said insulator plate.
8. A liquid-cooled electromagnetic rabbling mechanism as defined in claim 1 wherein said annular tank is sectionalized into upper and lower parts which are disconnectible to permit removal of the upper part for access to the interior of the tank.