Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/50—Pouring-nozzles
  • B22D41/62—Pouring-nozzles with stirring or vibrating 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
  • B22D11/16—Controlling or regulating processes or operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/02—Use of electric or magnetic effects
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H2250/00—Electrical heat generating means
  • F24H2250/08—Induction

Definitions

• Continuous casting apparatus for electromagnetic rotation of the liquid metal in transit through the casting nozzle.
• the present invention relates to the continuous casting of metals, steel in particular, implementing a submerged casting nozzle which is immersed in a mold placed underneath. More specifically, the invention relates to the axial rotation of the liquid metal in transit in such a nozzle between the tundish and the mold. It is known that the axial rotation of the metal already within the casting nozzle is a recognized means for controlling the flows in the mold by modifying the distribution of the gas bubbles and inclusions present in the liquid metal before it arrives in the mold.
• the rotation of the flows in the pouring nozzle thus appears as an effective means for combating the appearance of surface appearance defects, such as blistering and exfoliations, on cold-lined sheets of steel grades for application. automotive and packaging steels.
• This technique therefore enables the reduction of the writing operations on continuously cast slabs (reduction or even elimination of surface defects on exfoliation-type sheets), the elimination of downgrades and disputes for blistered defects, as well as the increase in productivity. machines by lengthening sequences and increasing casting speeds.
• the rotating of the liquid metal in the pouring nozzle has already been proposed using different types of actuators. Two types of actuators can be schematically distinguished: "passive" actuators and "active" ones.
• the "passive" actuators are, among other things, the design modifications of the inner wall of the nozzle (for example: spirals), the members such as the helix, the internal helical nozzle, etc. which are implanted in the body of the nozzle itself. , or the modifications of the upper portion of the nozzle at the junction with the distributor (for example: acceleration cone) or the modifications of the actual body for regulating the metal flow in the nozzle.
• the major disadvantages of this type actuators are to generate a rotation speed directly dependent on the metal flow passing through the nozzle and to constitute preferred sites of deposits of inclusions in the nozzle, resulting in a potential increase in the risk of clogging.
• the "active" actuators are essentially of electromagnetic nature: a polyphase type static annular electromagnetic inductor surrounds the nozzle at a small distance over part of its length and generates a magnetic field rotating around the casting axis intended to drive in axial rotation with him the liquid metal present in the nozzle. Examples are described in JP 06 023498 or JP 07 108355 or JP 07 148561. However, the electromagnetic devices heretofore proposed are, for the most part, based on the tangential rotating field linear stators technology operating at low or very low frequency ( ⁇ 10 Hz).
• the others are magnetic field through, so salient poles wound to a pair of poles by phases facing one another on either side of the axis of the nozzle.
• the invention falls within this category. They make it possible to overcome some of the disadvantages mentioned above, in particular the phenomenon of central depression. However, the smallness of the location combined with a necessarily high electrical power installed, as well as the desired reduction of the air gap by bringing the protruding inward polar tooth protruding beyond the winding and the nozzle to maximize the electromagnetic coupling.
• the object of the present invention is to propose a solution for an electromagnetic rotation of the liquid metal within a casting nozzle which does not have the drawbacks of known solutions.
• the subject of the invention is a continuous casting plant for metals, in particular steel, in which the submerged nozzle through which the molten metal to be poured arrives in the mold from a pouring distributor located above is surrounded by an electromagnetic annular magnetic field inductor rotating around the casting axis for driving in axial rotation with it the molten metal, said inductor being of polyphase type with a magnetic field having a pair of poles per phase and each pole of which is formed by an electric winding wound around an inwardly projecting pole tooth terminating in a polar face disposed opposite and in proximity to the nozzle, the pole teeth being interconnected by a bolt external magnetic magnetic flux closing device, characterized in that each polar tooth has a lateral narrowing (a bevel for example) at the end of its projecting portion, which increases the distance separating the polar faces between them.
• a lateral narrowing a bevel for example
• the annular inductor is formed in two pivotally articulated half-shells that can close around the nozzle.
• the invention implements a so-called "through” magnetic field, that is to say passing through the axis of the nozzle without noticeable weakening of its intensity between the edge and the center of that -this. Due to the technological base chosen, namely that with a pair of poles per phase of the power supply supplying a polyphase annular inductor with wound salient poles distributed around the nozzle, the rotating magnetic field produced is of the desired "through” type .
• the casting axis is at the center of the air gap of the inductor and the produced field prospers in this gap through the casting axis for, from a given magnetic pole, join the magnetic pole paired opposite sign located opposite and not next to it as it would be the case with an inductor with distributed poles or several pairs of poles per phase.
• this type of technology is not new in itself. It is even quite widely used for the rotation of the liquid metal cast, not in a nozzle, but in the mold itself, so in the case of inductors to rotate (the liquid metal column) much larger apparent diameter than that of the metal jet in the nozzle and with a correspondingly much lower rotational angular velocity requirement (see for example USP 4,462,458).
• FIG. 1 is a diagram representative, seen in cross section, the inductor in two butted half-shells provided with its internal heat shield bordering the gap
• - Figure 2 is a diagram similar to the previous one but intended to show the propagation of the lines of force of the magnetic field through the gap as frozen at any given time of the operation of the inductor
• FIG. 3 is a block diagram showing the articulation of the two half-shells constituting the inductor
• FIG. 4 shows the map of the velocities of the liquid metal rotating within the casting nozzle under the effect of the magnetic field in a plane of cross section of the nozzle;
• FIG. 5 shows the evolution of the intensity B of the magnetic field in the air gap along a diameter D of the nozzle taken in a plane situated at half height of the inductor;
• FIG. 6 shows, in correspondence with the representation of FIG. 5, the correlative evolution of the magnetic force field F B along a diameter D of the nozzle according to a radial profile R and according to a orthoradial profile OR.
• the same elements are designated by identical references. As can be seen with reference to FIGS.
• the inductor 1 is a linear motor stator closed on itself, constituted for this purpose by two independent, equal semicubular portions 2a and 2b, shells).
• Each half-shell comprises three coiled protruding poles 3, the polar face 4 of which faces inwards, these magnetic poles, made of assembled stacked soft iron sheets, being conventionally connected to each other by an outer peripheral hemi-tubular yoke 5, 5b.
• the set is sized so that the two paired heads come together in the junction plane J when the inductor is in the closed working position shown in Figures 1 and 2.
• a cap 7a, 7b, also of corresponding hemi-tubular form internally cape the polar faces of each half-shell and form, once the inductor in the closed position, a thermal protection screen 7 which surrounds at a short distance the casting nozzle.
• This thermal protection is desirable for the electric windings 3 of the inductor with respect to the radiation emitted by the pouring nozzle 8 shown in FIG. 3 and channeling the flow of molten metal towards the mold. Details on the possible constitution of this screen will be given later.
• the electrical winding 6 of each coiled pole 3 is connected to a phase of a three-phase power supply (not shown) intended to supply the primary current of the inductor.
• any protruding pole of one of the half-shells 2a is diametrically opposite a projecting pole of the other half-shell 2b.
• These two poles form a "pair of poles" in the sense that they are both connected to the same phase of the power supply, but in opposition (for example via a different winding direction) so that, at every moment, their active faces are of opposite signs. This condition is necessary for the magnetic field produced to be of the through type.
• the magnetic flux return poles 3 and 5a, 5b are laminated into grain-oriented Fe-Si plates having an initial thickness of 0.3 mm in order to minimize the hysteresis losses.
• Their operating height is between 50 (minimum value) and 500 mm, depending on the space available between the distributor and the top of the mold between which the inductor will take place.
• Their internal diameter is of the order of the outer diameter of the casting nozzle increased by a few tens of mm to preserve a separation but in order to ensure the best possible inductive coupling.
• the primary windings 6 consist of a large number (several hundred) of very small copper wire turns supporting high current densities (> 10 A / mm). They are provided within them water-cooled copper heat extractors (not shown). These coils are supplied with three-phase currents at medium frequency ranging from 50 Hz to 600 Hz.
• this static motor constituting the inductor 1 can generate in its gap occupied by the nozzle a transverse electromagnetic field (said through) of high intensity (between 1000 and 1500 gauss) for low values. inductive currents (a few tens of amperes). This field, as seen in the diagram, is almost uniform in the central part of the gap.
• This essential characteristic of the invention makes it possible to generate in the liquid metal a field of forces uniformly decreasing from the wall to the center, as shown in the diagram of FIG. 6. This allows, as the speed chart also clearly shows. of Figure 4, to rotate the liquid metal with a speed that remains high even in the axial portion of the nozzle. This specificity is necessary to avoid a too strong depression in the central part of the nozzle where the metal would then tend to "leak" and undergo a strong downward vertical acceleration, thus canceling part of the beneficial effect of rotating . As clearly shown in FIG.
• the intensity of the primary currents can be greatly increased.
• the proposed technique makes it possible, in a wide range of intensity of the primary currents, to increase very strongly the intensity of the electromagnetic field in the gap, by increasing the intensity of these currents to values well beyond the threshold intensity corresponding to the magnetic saturation of the cylinder head 5. This allows to channel the magnetic field lines and increase, in the air gap of the motor, the intensity of this magnetic field until the latter reaches its saturation value in the cylinder head.
• the inductor is very close (at about 5 mm distance) from the casting nozzle 8 whose outside temperature is of the order of 1100 to 1200 ° C. Its thermal protection, vis-à-vis the radiation emitted by the nozzle, is then provided by the segmented copper screen 7, of thin thickness, cooled by water circulation and transparent to the electromagnetic field through this segmentation.
• the inductor is advantageously held by a support consisting of two arms 9 articulated about a pivoting axis 10.
• the arms are driven by jacks 11 which ensure their closing-opening and allow to exert a sufficient contact force (greater than 200 kgf) between the yokes 5a and 5b of the two hemi-tubular parts 2a and

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (2)

Family

ID=33484516

Family Applications (1)

Country Status (12)

Families Citing this family (14)

Family Cites Families (10)

• 2003
  • 2003-06-17 FR FR0307307A patent/FR2856321B1/fr not_active Expired - Fee Related
• 2004
  • 2004-06-08 WO PCT/FR2004/001418 patent/WO2005002763A2/fr not_active Ceased
  • 2004-06-08 JP JP2006516265A patent/JP4435781B2/ja not_active Expired - Fee Related
  • 2004-06-08 EP EP04767284A patent/EP1633512B1/de not_active Expired - Lifetime
  • 2004-06-08 KR KR1020057023978A patent/KR101004065B1/ko not_active Expired - Fee Related
  • 2004-06-08 CN CNB2004800172286A patent/CN100406165C/zh not_active Expired - Fee Related
  • 2004-06-08 US US10/561,067 patent/US20060124272A1/en not_active Abandoned
  • 2004-06-08 ES ES04767284T patent/ES2279430T3/es not_active Expired - Lifetime
  • 2004-06-08 SI SI200430240T patent/SI1633512T1/sl unknown
  • 2004-06-08 DE DE602004004270T patent/DE602004004270T2/de not_active Expired - Lifetime
  • 2004-06-08 PL PL04767284T patent/PL1633512T3/pl unknown
  • 2004-06-08 CA CA2529384A patent/CA2529384C/fr not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events