EP0616865A1 - Verfahren und Vorrichtung zur magnetischen Eindämmung von Schmelze unter Verwendung von Konzentrationsrippen - Google Patents

Verfahren und Vorrichtung zur magnetischen Eindämmung von Schmelze unter Verwendung von Konzentrationsrippen Download PDF

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Publication number
EP0616865A1
EP0616865A1 EP93120635A EP93120635A EP0616865A1 EP 0616865 A1 EP0616865 A1 EP 0616865A1 EP 93120635 A EP93120635 A EP 93120635A EP 93120635 A EP93120635 A EP 93120635A EP 0616865 A1 EP0616865 A1 EP 0616865A1
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EP
European Patent Office
Prior art keywords
gap
coil part
recited
open side
fin
Prior art date
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Granted
Application number
EP93120635A
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English (en)
French (fr)
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EP0616865B1 (de
Inventor
Howard L. Gerber
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Inland Steel Co
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Inland Steel Co
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Priority claimed from US08/034,240 external-priority patent/US5279350A/en
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Publication of EP0616865A1 publication Critical patent/EP0616865A1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0637—Accessories therefor
    • B22D11/0648—Casting surfaces
    • B22D11/066—Side dams
    • B22D11/0662—Side dams having electromagnetic confining means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0637—Accessories therefor
    • B22D11/068—Accessories therefor for cooling the cast product during its passage through the mould surfaces
    • B22D11/0682—Accessories therefor for cooling the cast product during its passage through the mould surfaces by cooling the casting wheel

Definitions

  • the present invention relates generally to an improvement on the apparatuses and methods for magnetically confining molten metal which are disclosed in said antecedent applications. More particularly, this application discloses an improved method and apparatus for preventing the escape of molten metal through the open side of a vertically extending gap between two horizontally separated members and in which the molten metal is located.
  • the present invention is intended to operate in the same environment as that disclosed in the parent application, e.g., a twin-roll, continuous-casting apparatus. While the apparatus disclosed in the parent application is effective in preventing molten metal from escaping through the open side of a gap between two horizontally separated casting rollers, the improved apparatus of the present invention is designed to accomplish the same task more efficiently.
  • the twin-roll continuous casting environment in which the present invention is intended to operate typically comprises a pair of horizontally spaced rolls mounted for rotation in opposite rotational senses about respective horizontal axes.
  • the two rolls define a horizontally extending gap therebetween for receiving the molten metal.
  • the gap defined by the rolls tapers in a downward direction.
  • the rolls are cooled, and in turn cool the molten metal as the molten metal descends through the gap.
  • the gap has horizontally spaced, open opposite ends adjacent the ends of the two rolls.
  • the molten metal is unconfined by the rolls at the open ends of the gap.
  • mechanical dams or seals have been employed.
  • an electromagnet having a core encircled by a conductive coil through which an alternating electric current flows and having a pair of magnet poles located adjacent the open end of the gap.
  • the magnet is energized by the flow of alternating current through the coil, and the magnet generates an alternating or time-varying magnetic field extending across the open end of the gap between the poles of the magnet.
  • the magnetic field can be either horizontally disposed or vertically disposed, depending upon the disposition of the poles of the magnet. Examples of magnets which produce a horizontal field are described in the aforementioned Praeg U.S. Patent No. 4,936,374; and examples of magnets which produce a vertical magnetic field are described in the aforementioned Lari et al. U.S. Patent No. 4,974,661.
  • the alternating magnetic field induces eddy currents in the molten metal adjacent the open end of the gap creating a repulsive force which urges the molten metal away from the magnetic field generated by the magnet and thus away from the open end of the gap.
  • Another expedient for containing molten metal at the open end of a gap between a pair of members is to locate adjacent the open end of the gap a coil through which an alternating current flows. This causes the coil to generate a magnetic field which induces eddy currents in the molten metal adjacent the open end of the gap resulting in a repulsive force similar to that described above in connection with the magnetic field generated by an electromagnet.
  • Embodiments of this type of expedient are described in Olsson U.S. Patent No. 4,020,890, and the disclosure therein is incorporated herein by reference.
  • the use of a coil to directly generate the magnetic field adjacent the open end of the gap is more efficient than the use of an electromagnet because when employing an electromagnet, the coil is used to energize the core of a magnet through which magnetic flux must travel to the magnet poles which then generate a magnetic field adjacent the open end of the gap.
  • core loss when a coil is employed to energize an electromagnet; but core loss is not a significant factor when the coil is employed to directly generate the magnetic field at the open end of the gap. Even in that case, however, it is important to minimize the energy dissipated by the coil in producing a magnetic field sufficiently strong to confine the molten metal.
  • a drawback to the latter expedient is that the coil must be placed quite close to the open end of the gap in order to generate a magnetic field which will contain the molten metal there.
  • the coil can be relatively remote from the open end of the gap. The closer the coil is to the molten steel, the more severe the thermal conditions to which the coil is subjected.
  • Another drawback to the expedient employing a coil for directly generating the magnetic field at the open end of the gap is that part of the magnetic field is radiated in a direction away from the open end of the gap, thereby decreasing the efficiency of the coil.
  • the problem described in the preceding sentence can also be a problem when employing any electromagnet.
  • Gerber, et al., Serial No. 07/902,559 discloses a magnetic confining apparatus which employs a single turn coil to directly generate a magnetic field that extends through and is confined substantially to the open side of the gap.
  • magnetic material encloses all but the front working surface of the front half of the coil, and that magnetic material is used to concentrate current in the working surface of the coil that faces the open side of the gap.
  • Magnetic hysteresis loss a condition which is well-known to those of ordinary skill in the art, refers to energy that is dissipated in the form of heat in magnetic material when a time-varying magnetic field is applied to the magnetic material. Because this energy loss is characteristic of any magnetic material, a molten metal confining apparatus that does not employ magnetic material is desirable.
  • Each of the above-described energy losses causes heating of the magnetic material. If the current flowing in the coil is strong enough, the heat generated by the above-described energy losses can be severe enough to cause irreversible damage to the magnetic material. Accordingly, there is a limit on the amount of current that can be conducted through the coil, and as a result, there is a corresponding limit on the magnetic confining pressure that can be exerted by the coil. Thus, there is a limit on the amount of molten metal that may be confined by the coil employing magnetic material, in the manner described above, to concentrate current in the working surface. To confine molten metal in amounts exceeding this limit, it is necessary to employ a coil that does not employ magnetic material in such a manner.
  • this improved apparatus is essentially the same as that of the apparatus disclosed in the parent application, in a general sense, but the coil, used to generate the magnetic field which confines the molten metal within the gap, is modified to include fin-like structures on that part of the coil, termed the front coil part, that is directly opposite the open side of the gap.
  • the fin-like structures extend laterally outwardly from all surfaces of the front coil part except the working surface, which faces the open side of the gap.
  • the fin-like structures effectively concentrate current flowing in the front coil part in the working surface facing the open side of the gap. This, in turn, produces an increased magnetic flux concentration in the space between the working surface of the front coil part and the molten metal, thereby strengthening the confining pressure exerted on the molten metal in the gap.
  • alternating current is conducted through the coil to generate the horizontal magnetic field which extends from the working surface of the coil through the open side of the gap to the molten metal.
  • Dissipation of the magnetic field in a direction away from the open side of the gap is prevented by restricting the magnetic field generated by the coil substantially to the open side of the gap. This is accomplished by configuring the rear coil part, a nonmagnetic electrical conductor, not only to act as part of the return path for the current flowing through the front coil part, but also to confine the magnetic field substantially to the open side of the gap.
  • the working surface of the front coil part is configured to conform to the tapered shape of the gap so as to increase the magnetic pressure against the molten metal in accordance with increasing static pressure (i.e., depth) of the molten metal in the gap.
  • pieces of magnetic material are inserted in planar spaces vertically separating the fin-like structures to more fully spread out magnetic flux in the planar spaces between fin-like structures.
  • the fin-like structures include first and second portions which protrude forward of the coil to define a recess.
  • the recess receives portions of circumferential lips extending from the ends of the twin casting rolls with which the coil of the present invention is intended to be used.
  • Apparatus 20 produces a horizontally extending magnetic field which prevents the escape of molten metal through the open side 26 of a vertically extending gap 25 located between two horizontally separated, cylindrical metal rolls 21, 22 in a continuous strip caster. Due to the cylindrical shape of rolls 21, 22, the gap 25 narrows in width from the uppermost level of the gap downward to a level of minimum width at the nip 28 between the rolls ( Figures 2 and 5).
  • Rolls 21, 22 rotate in respective opposite, rotational senses about respective axes 23, 24. Molten metal is normally contained in gap 25. Rolls 21, 22 are cooled, in a conventional manner not disclosed here, and as molten metal descends vertically through gap 25, the metal is cooled and solidified into a metal strip 27 which descends downwardly from nip 28 ( Figure 5).
  • apparatus 20 comprises a current conducting coil 30 including a front coil part 31 and a rear coil part 32. Alternating current is conducted through coil 30, in a manner to be subsequently described, and this directly generates a horizontal magnetic field which, because of the proximity of coil 30 to open side 26 of gap 25, extends from the front surface 33 of coil 30, through open side 26 of gap 25, to the molten metal in the gap.
  • coil 30 and its associated structure are located sufficiently close to open side 26 of gap 25 to enable the directly generated magnetic field to contain the molten metal within the gap.
  • the possible adverse thermal effects of such close proximity to the hot, molten metal are offset by the employment of conventional protective structure, such as that described in detail in parent application serial Number 07/902,559, to protect the coil.
  • coil 30 may be insulated from the heat generated by the molten metal by positioning a refractory member 48 between coil 30 and open side 26 of gap 25 ( Figures 6 and 11).
  • front and rear coil parts 31, 32 are integral, and together they form coil 30 which is, in fact, a one-piece structure.
  • the integral connection of front coil part 31 to rear coil part 32 is indicated at 40 in Figures 4 and 9.
  • Front coil part 31 includes fins 44 to be described in more detail below; however, Figure 9 depicts the structure of one-piece coil 30 with fins 44 removed in order to clearly show lower body portion 35 of front coil part 31 and the integral connection 40 between front coil part 31 and rear coil part 32.
  • front coil part 31 and rear coil part 32 are separate structures electrically and structurally joined together in any conventional manner.
  • Front coil part 31 comprises an upper body portion 34 and a lower body portion 35.
  • the upper body portion 34 comprises a rectangular, mostly solid upper body structure 36 from which a neck 37 extends upwardly and integrally.
  • Neck 37, upper body structure 36, and lower body portion 35 have respective front surface portions which are contiguous and coplanar so as to form an uninterrupted front coil surface 33.
  • lower body portion 35 extends downwardly from upper body structure 36 and has a lateral width which decreases in a downward direction in conformity with the narrowing in width of open side 26 of gap 25.
  • Lower body portion 35 has two opposed side surfaces 41, 42 and a rearward facing surface 43 ( Figures 6 and 10). Contiguous with and extending laterally outward from side surfaces 41, 42 and rearward from surface 43 are a plurality of fins 44 vertically separated by planar spaces 45. The fins are planar members that are integral with lower body portion 35, and they extend away from open side 26 of gap 25.
  • rear coil part 32 comprises a box-like structure having a rear wall 60, side walls 61, 62, top wall portions 63, 64, and a bottom wall 65.
  • Walls 60-65 of rear coil part 32 define a cavity 46 that has an open front 47 and that is sized to receive front coil part 31 ( Figures 9 and 11).
  • Front surface 33 of front coil part 31 thus remains uncovered by rear coil part 32 and faces open side 26 of gap 25 through open front 47 of cavity 46.
  • Cavity 46 has a shape that conforms substantially to the shape of front coil part 31. Cavity 46 is larger than front coil part 31, however, so that fins 44 do not contact the inner surfaces of walls 60-65 of rear coil part 32 ( Figure 11).
  • a collar portion 66 Extending upwardly and integrally from rear coil part 32 is a collar portion 66 including collar side walls 67, 68 and collar rear wall 69. Walls 67-69 of collar 66 define an extension 72 of cavity 46. Cavity extension 72 has a shape that conforms substantially to the shape of neck 37 of front coil part 31. Cavity extension 72 receives neck 37, but collar 66 does not contact neck 37.
  • Figure 8 depicts a rear view of coil 30, wherein rear coil part 32 is partially cut away to expose fins 44 of front coil part 31. As indicated above, fins 44 are spaced apart from the inner surfaces of rear coil part 32 so that electric current flowing in the coil will flow downwardly through lower body portion 35, where it is concentrated in front surface 33, and then flows to rear coil part 32.
  • Coil 30 is positioned adjacent rolls 21, 22 so that the front surface of lower body portion 35 is directly opposite open side 26 of gap 25.
  • Coil 30 is dimensioned so that a portion 80 of coil 30 extends below roll nip 28, and the location of the lowermost fin 44 is also below nip 28 ( Figures 2 and 5).
  • Current flowing in portion 80 contributes to the intensity of the magnetic field in open side 26 of gap 25 just as does current flowing in the portion of coil 30 which is above nip 28.
  • the extension of coil 30 below nip 28 effectively strengthens the magnetic field at nip 28.
  • the strengthened magnetic field augments the magnetic confining pressure exerted on the molten metal in gap 25, at nip 28, where the static pressure urging the molten metal out of open side 26 of gap 25 is greatest.
  • Coil 30 may be supported in the desired position relative to the continuous casting rolls, and connected to a source of alternating current, in any conventional manner, e.g., in a manner similar to that described in detail in parent application serial Number 07/902,559.
  • An alternating current is conducted to front coil part 31, downwardly through front coil part 31, then upwardly through rear coil part 32 which is conductively and integrally attached to front coil part 31.
  • the current exits coil 30 through the conventional connecting structure mentioned above.
  • the alternating current flows in the coil, it generates a time-varying, horizontal magnetic field which tends to encircle each of front and rear coil parts 31, 32.
  • rear coil part 32 which is composed of a non-magnetic, electrically conductive material such as copper or copper base alloy, comprises a box-like structure which encloses all of front coil part 31 except front surface 33. Accordingly, because the structure enclosing front coil part 31 is non-magnetic, the horizontal magnetic field is substantially confined to the space in front of front surface 33 of front coil part 31, at open side 26 of gap 25, and the magnetic field is not dissipated in a direction away from open side 26 of gap 25.
  • lower body portion 35 has a shape that conforms substantially to open side 26 of gap 25.
  • both (a) the density of the current flowing in lower body portion 35 and (b) the intensity of the magnetic field along front coil part 31 (a parameter which is proportional to current density) increase in a downward direction along front coil part 31.
  • the coil produces a magnetic confining pressure that increases in a downward direction to match the increasing static pressure urging the molten metal out of open side 26 of gap 25.
  • Fins 44 serve to distribute the magnetic flux, which encircles that portion of front coil part 31 behind front surface 33, over substantially the entire area of each horizontal planar space 45.
  • the total amount of magnetic flux in front of front surface 33 (at open side 26 of gap 25) and the total amount of flux behind front surface 33 are the same.
  • the flux in front of front surface 33 is concentrated there.
  • the flux behind front surface 33 is spread out over an area corresponding to the area of planar spaces 45.
  • the flux density at open side 26 of gap 25, at any given vertical level of open side 26, is relatively greater than the flux density in any space 45 at the same vertical level.
  • Magnetic flux naturally tends to penetrate or diffuse through the surfaces of front coil part 31.
  • the polarity of the magnetic field which encircles front and rear coil parts 31, 32 varies sinusoidally in conformity with the changing polarity of the alternating current flowing in coil 30. Therefore, according to the skin effect (a phenomenon well-known to those of ordinary skill in the art), the magnetic flux only has time to penetrate a small depth into the surfaces of coil 30 and, in particular, into the surfaces of lower body portion 35 before the flux changes polarity.
  • the magnetic flux diffusing into front surface 33 of lower body portion 35 is more concentrated than the magnetic flux diffusing into side surfaces 41, 42 and rear surface 43. This is so because the flux is concentrated in front of front surface 33, at open side 26 of gap 25.
  • the distribution or concentration of current in various parts of lower body portion 35 is related to the concentration of magnetic flux at those parts. Accordingly, the current is concentrated in front surface 33, where the flux is most concentrated.
  • Fins 44 have a vertical thickness approximately four times as great as the skin depth of the material of which coil 30 is composed. Dimensioning fins 44 in this manner ensures that most of the current flows primarily along the surfaces of fins 44, as described above, rather than flowing directly through lower body portion 35. Because current is thus distributed along the surfaces of fins 44, the magnetic flux in planar spaces 45 (the distribution of which is related to the distribution of current) is spread out over the entire area corresponding to each planar space 45.
  • the skin depth, of the material of which coil 30 is composed, varies inversely with the frequency of the alternating current flowing in coil 30.
  • the thickness of fins 44 must be approximately four times the skin depth in order for current to flow substantially along the surfaces of fins 44. Therefore, the frequency of the current flowing in coil 30 must be high enough to produce a skin depth small enough that fins 44 can be about four skin depths thick, as described above, while permitting proper dimensioning of planar spaces 45 vertically separating fins 44.
  • planar spaces 45 are dimensioned to ensure that the magnetic flux density in planar spaces 45 is approximately constant throughout planar spaces 45.
  • the vertical dimension of each space 45 is between approximately fifty and approximately one hundred percent of the front-to-back thickness of lower body portion 35 (i.e., the distance from front surface 33 to rear surface 43 of lower body portion 35).
  • planar spaces 45 The exact dimensioning of planar spaces 45 depends upon several considerations, however. Magnetic flux density near a fin 44 varies inversely with distance from the fin. Moreover, at small distances from the fin, magnetic flux density is approximately constant. Thus, if planar spaces 45 separating fins 44 are sufficiently thin, the magnetic flux density in planar spaces 45 will be approximately constant as desired. Otherwise, the flux density will decrease toward the vertical center of each planar space 45. Where this occurs, the magnetic confining pressure exerted by coil 30, at open side 26 of gap 25, will also decrease. It is, therefore, desirable for planar spaces 45 to be thin.
  • planar spaces 45 are too thin, however, the inductance between fins 44 (which is proportional to the distance between fins) will also be small so that a greater portion of the total current flowing in coil 30 would flow along the surfaces of fins 44 than if planar spaces 45 are dimensioned properly. That, in turn, would reduce the portion of the total current that is concentrated in front surface 33 and would reduce the corresponding concentration of magnetic flux at open side 26 of gap 25. In other words, if planar spaces 45 are too thin, the coil will be inefficient.
  • fins 44 must be thick enough to ensure that current will flow substantially along the surfaces of fins 44.
  • the vertical dimension of planar spaces 45 must be small enough that the magnetic flux density is aproximately constant throughout each planar space 45, and large enough that most of the current is substantially concentrated in front surface 33.
  • the skin depth in fins composed of copper is approximately 1.2 mm. Fins 44 must therefore exceed approximately 4.8 mm in vertical thickness. In this same embodiment, adjacent fins 44 are vertically separated at intervening planar space 45 by approximately 12.5 mm.
  • fins 44 effectively lengthen the path through which current flows in front coil part 31 (i.e., current flows along the surfaces of fins 44), fins 44 increase the resistance to current flow through lower body portion 35 and, therefore, reduce the amount of current flowing through coil 30. Therefore, it would be desirable to keep the number of fins 44 as low as possible, while providing enough fins to spread out the magnetic flux behind lower body portion 35.
  • the downwardly increasing concentration of current flowing in front coil part 31 due to the downwardly tapering contour thereof further enhances the magnetic field and magnetic flux density at open side 26 of gap 25 near nip 28, as explained above.
  • the increased flux density at open side 26 of gap 25 enables coil 30 to exert a magnetic confining pressure on the molten metal in gap 25 that is relatively stronger, for a given amount of current flowing in the coil, than the pressure that could be exerted by a coil without fins.
  • pieces of magnetic material 70, 72, 74 may be placed in planar spaces 45 vertically separating adjacent fins 44. Individual pieces of magnetic material 70, 72, 74 may be horizontally separated by air gaps 71, 73 which are inherently less effective in conducting magnetic flux than is magnetic material.
  • the geometric configuration of magnetic material pieces 70, 72, 74 and intervening air gaps 71, 73 may be designed to maximize the dispersion of magnetic flux throughout planar spaces 45 between adjacent fins 44.
  • the total magnetic flux is distributed over a larger area in planar spaces 45 than it is in the embodiment that does not employ pieces of magnetic material 70, 72, 74 in planar spaces 45.
  • the magnetic flux density in magnetic material pieces 70, 72, 74 decreases. Consequently, the energy loss in magnetic material pieces 70, 72, 74 (which is proportional to magnetic flux density) also decreases.
  • pieces of magnetic material 70, 72, 74 produce the same types of energy losses as were produced by magnetic material enclosing the sides and back of the front half of the coil disclosed in parent application serial Number 07/902,559 (hereafter the "earlier coil”)
  • the energy losses in magnetic material pieces 70, 72, 74 are much less than the losses in the earlier coil. Therefore, in the embodiment of Figures 12-14, an enhanced magnetic field is produced by fins 44, but the energy losses in the form of generated heat are lower than those associated with the earlier coil. Because the coil of the present invention generates less heat than the earlier coil, the present coil can conduct a larger current and produce a stronger magnetic confining pressure than the earlier coil which uses magnetic material, but not fin structures, to concentrate current in the working surface.
  • a cooling channel 50 is provided in front coil part 31 and extends from top surface 38 of neck 37 through neck 37, upper body structure 36, and lower body portion 35, to bottom surface 39 of coil 30 (Figure 8). Cooling fluid is circulated through cooling channel 50 in order to cool front coil part 31. Heat generated by the current concentrated in front surface 33 of front coil part 31 is also dissipated by fins 44.
  • Rear coil part 32 may be cooled, as shown in Figure 4, by circulating cooling fluid through cooling tubes 51 (only one of which is shown) attached to rear coil part 32.
  • FIGS 15-18 illustrate another embodiment of the present invention wherein an apparatus indicated generally at 120 is positioned adjacent an open side 126 of a gap 125 between a pair of rolls 121, 122, similar to the positioning of apparatus 20 described above.
  • Apparatus 120 exerts a confining pressure, in a manner similar to that described in connection with apparatus 20, against the molten metal in gap 125, except for such differences as are noted below.
  • Apparatus 120 comprises a single turn coil 130 including a front coil part 131 integrally connected to a rear coil part 132.
  • Rear coil part 132 is very similar to rear coil part 32 described above but differs in some respects from rear coil part 32 as described below.
  • Rear coil part 132 includes walls 160-165 as well as walls 167-169 of collar 166 integrally connected thereto.
  • Front coil part 131 is similar to front coil part 31 described above but differs in some respects from front coil part 31 as described below.
  • Front coil part 131 comprises an upper body portion 134 and a lower body portion 135.
  • Upper body portion 134 comprises a rectangular, mostly solid upper body structure 136 from which a neck 137 extends upwardly and integrally.
  • Neck 137, upper body structure 136, and lower body portion 135 have respective front surface portions which are contiguous and coplanar so as to form an uninterrupted front surface 133.
  • lower body portion 135 extends downwardly from upper body structure 136 and has a lateral width which decreases in a downward direction in conformity with the narrowing in width of open side 126 of gap 125.
  • Lower body portion 135 has two opposed side surfaces 141, 142 and a rear surface 143. Contiguous with and extending laterally outward from side surfaces 141, 142 and rearward from rear surface 143 are a plurality of fins 144 vertically separated by planar spaces 145. Fins 144 are planar members that are integral with lower body portion 135, like fins 44 and lower body portion 35 in coil 30 described above.
  • each fin 144 comprises first and second portions 191, 192 which are disposed on opposite flanks of front surface 133 and which project forward of front surface 133 toward respective rolls 191, 192 ( Figures 16 and 18). Therefore, front surface 133 is not contiguous and coplanar with the front edge surfaces 149 of fins 144 as front surface 33 is with the front edge surfaces of fins 44 in coil 30. Rather, front surface 133 is recessed relative to surfaces 149 on first and second portions 191, 192 of fins 144.
  • Walls 160-165 of rear coil part 132 define a cavity 146 that has front opening 147 for receiving front coil part 131 ( Figures 15 and 16).
  • Front surface 133 of front coil part 131 remains uncovered by rear coil part 132 and faces open side 126 of gap 125 through front opening 147 of cavity 146 ( Figure 16).
  • Cavity 146 is larger than front coil part 131, however, so that fins 144 do not contact the inner surfaces of walls 160-165 of rear coil part 132 ( Figures 15 and 16).
  • Front edge surfaces 149 of first and second portions 191, 192 of fins 144 are coplanar with front opening 147 of cavity 146.
  • Front coil part 131 is disposed within cavity 146, and front surface 133 of front coil part 131 is recessed with respect to front opening 147 of cavity 146 ( Figures 15 and 18).
  • annular lip 190 is secured to each end surface 193 of each roll 121, 122.
  • Each lip 190 has an outer diameter equal to that of roll 121, 122 and extends outwardly from each end surface 193 of a roll in a direction parallel to the roll axis at 123 or 124.
  • Each lip 190 has an inner diameter such that the thickness of the lip is less than substantially one skin depth of the material of which lip 190 is composed at the particular frequency of the current flowing in coil 130.
  • Each lip 190 also defines the rim of an annular space 194 having an outer opening and an inner surface corresponding to roll end surface 193.
  • Each lip 190 also has an outer circumferential surface constituting a longitudinal extension of the circumferential casting surface of the roll (121 or 122) to which the lip is attached. Pairs of lips 190, counterrotating together with respective rolls 121 and 122, thus define a longitudinal extension 198 of gap 125. Accordingly, open side 126 of gap 125 is actually located at the open end of longitudinal gap extension 198 which, in this embodiment, is a part of gap 125 ( Figure 16). Naturally, static pressure urges the molten metal in gap 125 into longitudinal gap extension 198 from which, but for coil 130, the molten metal would escape through open side 126.
  • Each gap extension 198 is substantially one to substantially three times as long, and preferably about twice as long, as the skin depth of the particular molten metal being confined at the particular frequency of the current flowing in the coil. This dimensioning of extensions 198 ensures that sufficient magnetic flux is coupled with the molten metal to confine the molten metal in gap 125.
  • the amount of magnetic flux that can couple with the molten metal in gap 125 varies with the length of gap extensions 198 (and of annular spaces 194 into which portions 191, 192 of fins 144 protrude). If gap extensions 198 are too short, too little magnetic flux couples with the molten metal to produce a confining pressure sufficient to prevent escape of molten metal from gap 125. More total current is then required to enable coil 130 to couple enough magnetic flux to confine the molten metal.
  • the length of a cavity extension 198 typically is between approximately 1.5 and approximately 3 skin depths for the material of which lips 190 are composed at the frequency of the current flowing in coil 130. At a frequency of 3000 Hertz, for example, the length of each cavity extension 198 is substantially between sixteen and thirty-four millimeters (for lips 90 composed of steel).
  • first and second fin portions 191, 192 and coil front surface 133 effectively define a recess 196 ( Figure 15).
  • Coil 130 is positioned sufficiently close to rolls 121, 122 that an arc or segment of each circumferential lip 190 enters into recess 196 ( Figures 16 and 18).
  • top wall portions 163, 164 and bottom wall 165 of rear coil part 132 are notched to receive those segments of lips 190.
  • Each top wall portion 163, 164 includes a notch 183, 184 that is sized to allow a segment of a lip 190 to enter recess 196 without contacting top wall portion 163 or 164.
  • bottom wall 165 includes a notch 185 that is sized to allow a segment of a lip 190 on each roll 121, 122 to enter recess 196 without contacting bottom wall 163.
  • the distance that portions 191, 192 of fins 144 project forward of front surface 133 is approximately the length of cavity extensions 198. Sips 190 do not contact coil 130, however; and portions 191, 192 of fins 144 do not contact end surfaces 193 of rolls 121, 122 (or the annular discs, described below, that substantially cover end surfaces 193 of rolls 121, 122).
  • Lips 190 are composed of a non-magnetic material having a low electrical conductivity. This composition enables the magnetic flux generated by coil 130 to extend through those segments or arcs of lips 190 that are within recess 196 at any given rotational orientation of rolls 121, 122 (those segments obviously change as rolls 121, 122 rotate). The magnetic flux extending through those particular segments of lips 190 can then penetrate more deeply into, and magnetically couple more effectively with, the molten metal in gap 125 and longitudinal gap extensions 198 than if fins 144 did not project forward beyond front surface 133. This configuration therefore enables coil 130 to exert a stronger confining pressure on the molten metal than the coil could exert if portions 191, 192 of fins 144 did not project forward beyond front surface 133.
  • An annular disc 195 substantially covers each end surface 193 of each roll 121, 122. Each end surface 193 is also the inner surface of a respective annular space 194. Each disc 195 is composed of copper or other nonmagnetic material and therefore confines the magnetic field to the annular space 194 within lip 190 at each end of each roll 121, 122. In other words, the magnetic flux in annular space 194 does not penetrate end surface 193 of roll 121 because it is confined by nonmagnetic disc 195.
  • coil 130 is identical in structure and function to coil 30.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Continuous Casting (AREA)
  • General Induction Heating (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
EP93120635A 1993-03-22 1993-12-21 Verfahren und Vorrichtung zur magnetischen Eindämmung von Schmelze unter Verwendung von Konzentrationsrippen Expired - Lifetime EP0616865B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US08/034,240 US5279350A (en) 1991-08-01 1993-03-22 Apparatus and method for magnetically confining molten metal using concentrating fins
US34240 1993-03-22

Publications (2)

Publication Number Publication Date
EP0616865A1 true EP0616865A1 (de) 1994-09-28
EP0616865B1 EP0616865B1 (de) 1998-03-04

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JP (1) JP2968431B2 (de)
KR (1) KR0136751B1 (de)
DE (1) DE69317257T2 (de)
ES (1) ES2112952T3 (de)
RU (1) RU2116863C1 (de)
UA (1) UA27804C2 (de)
ZA (1) ZA938381B (de)

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SI2852391T1 (sl) 2012-05-21 2022-04-29 Insmed Incorporated Sistemi za obravnavo pljučnih infekcij
EP3466432B1 (de) 2014-05-15 2020-07-08 Insmed Incorporated Verfahren zur behandlung von pulmonaler mykobakterieller nichttuberkuloseinfektionen
WO2019191627A1 (en) 2018-03-30 2019-10-03 Insmed Incorporated Methods for continuous manufacture of liposomal drug products

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2289278A1 (fr) * 1974-11-01 1976-05-28 Olsson Erik Allan Procede pour assurer l'etancheite des joints d'assemblage
US4020890A (en) * 1974-11-01 1977-05-03 Erik Allan Olsson Method of and apparatus for excluding molten metal from escaping from or penetrating into openings or cavities
US4936374A (en) * 1988-11-17 1990-06-26 The United States Of America As Represented By The United States Department Of Energy Sidewall containment of liquid metal with horizontal alternating magnetic fields
US4974661A (en) * 1988-06-17 1990-12-04 Arch Development Corp. Sidewall containment of liquid metal with vertical alternating magnetic fields
EP0491641A1 (de) * 1990-12-17 1992-06-24 Usinor Sacilor Vorrichtung zum Stranggiessen von dünnen Metallbändern, insbesondere aus Stahl
EP0511550A1 (de) * 1991-04-17 1992-11-04 ACCIAI SPECIALI TERNI S.p.a. Verbesserung einer Bandgiessmaschine

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2289278A1 (fr) * 1974-11-01 1976-05-28 Olsson Erik Allan Procede pour assurer l'etancheite des joints d'assemblage
US4020890A (en) * 1974-11-01 1977-05-03 Erik Allan Olsson Method of and apparatus for excluding molten metal from escaping from or penetrating into openings or cavities
US4974661A (en) * 1988-06-17 1990-12-04 Arch Development Corp. Sidewall containment of liquid metal with vertical alternating magnetic fields
US4936374A (en) * 1988-11-17 1990-06-26 The United States Of America As Represented By The United States Department Of Energy Sidewall containment of liquid metal with horizontal alternating magnetic fields
WO1991018696A1 (en) * 1988-11-17 1991-12-12 Arch Development Corporation Sidewall containment of liquid metal with horizontal alternating magnetic fields
EP0491641A1 (de) * 1990-12-17 1992-06-24 Usinor Sacilor Vorrichtung zum Stranggiessen von dünnen Metallbändern, insbesondere aus Stahl
EP0511550A1 (de) * 1991-04-17 1992-11-04 ACCIAI SPECIALI TERNI S.p.a. Verbesserung einer Bandgiessmaschine

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DE69317257D1 (de) 1998-04-09
ES2112952T3 (es) 1998-04-16
AU5064193A (en) 1994-09-29
UA27804C2 (uk) 2000-10-16
RU2116863C1 (ru) 1998-08-10
KR940022596A (ko) 1994-10-21
EP0616865B1 (de) 1998-03-04
KR0136751B1 (ko) 1998-07-01
RU94010083A (ru) 1996-06-27
JPH06339756A (ja) 1994-12-13
ZA938381B (en) 1994-06-13
AU661955B2 (en) 1995-08-10
JP2968431B2 (ja) 1999-10-25
DE69317257T2 (de) 1998-07-09

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