Classifications

• • 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
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F33/00—Other mixers; Mixing plants; Combinations of mixers
  • B01F33/45—Magnetic mixers; Mixers with magnetically driven stirrers
• • 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
• • 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

Definitions

• the movements imparted to molten metal during continuous casting can schematically be classified into two distinct categories, depending on whether one considers the ingot mold or, below, the stages of the secondary cooling of the casting machine.
• loops 42, 43 are established parallel to the large faces and are staggered according to the height of the product poured on either side of a common transverse motor action area of the magnetic field, the currents of each loop going up along of a small face and descending along the small opposite face.
• Such a configuration of movements is conventionally referred to as a "butterfly wing configuration”. It is possible, as shown in the attached figure 4 extracted from the document FR 82.10844, to multiply the transverse motor action zones 51, 52 ... of the magnetic fields according to the height of the casting machine. In this case, they are given opposite directions of rotation two by two between the nearest neighboring loops, in order for example to concern a volume stirred as large as possible for a given available stirring power.
• horizontally movable magnetic fields are produced by polyphase linear inductors 30a, 30b and 30a ', 30b' arranged on the large walls of the mold 32 opposite the exit path of the metal jets on either side of the nozzle 31.
• polyphase linear inductors 30a, 30b and 30a ', 30b' arranged on the large walls of the mold 32 opposite the exit path of the metal jets on either side of the nozzle 31.
• it is then possible to slow the current of the jet concerned sliding of the fields against current, going from the small wall to the nozzle -fig 3b j
• accelerate it sliding in co-current in the direction going from the nozzle to the small wall-fig 3b 2 ).
• the invention aims, via an overall mixing movement studied of the molten metal according to the metallurgical height, to provide a good exchange of the metal still liquid in both directions between the secondary cooling zone and the mold. Therefore, both thermal and chemical homogeneity will be achieved between the top and bottom of the poured liquid metal well without disturbing the flow mode in the ingot mold and, if necessary, without depriving itself of the cumulative beneficial effects proper mixing in an ingot mold and mixing in secondary cooling respectively.
• a further aim of the invention is to contribute to the improvement of the metallurgical quality of steel grades for which good internal health is sought, such as grades for heavy plates or for large welded tubes, ferritic stainless steels, or electrical steels with silicon.
• Another additional aim is to be able to act on the flows in the secondary to use them at the level of the casting jets coming from the nozzle either as an accelerating agent, or on the contrary as a braking agent for the metal arriving in the ingot mold, or even as a means to counteract the inclinations of "left-right" asymmetry of the movements of the metal within the ingot mold.
• the invention relates to an electromagnetic stirring process in the secondary cooling zone of an installation for continuous casting of slabs, or other similar products with an elongated straight section, the ingot mold of which has a immersed pouring nozzle with lateral outlet openings directed towards the small faces, stirring process implemented using sliding magnetic fields generated by polyphase inductors placed near the cast metal, characterized in that one forces, in said secondary cooling zone, the establishment of a longitudinal flow of the liquid metal located in the middle region of the product poured according to two antagonistic collinear currents.
• these two longitudinal antagonistic collinear currents are created in the middle part of the product which converge towards one another so that the two upper lobes which extend in the mold up to the level of the jets coming from the Outlets of the pouring nozzle are superimposed on them against the current to brake them.
• the location of the longitudinal flow in the secondary is shifted laterally towards one or the other of the small walls of the cast product in order to counteract the tendencies to the "left-right" asymmetry of the movements of metal within the mold.
• the longitudinal metal flow is created in the middle region of the product poured according to two antagonistic collinear currents using collinear mobile magnetic fields sliding longitudinally in said median region, or by approaching the from each other, either by moving away.
• the longitudinal metal flow is created in the middle region of the cast product according to two antagonistic collinear currents using mobile collinear magnetic fields sliding transversely along the width of the cast product, ie by approaching the 'from each other from the edge towards the center of the cast product, or by moving away from each other from the center towards the edge of the cast product.
• the sliding magnetic fields are generated using polyphase linear inductors which are placed opposite the large faces of the cast product.
• the inductors are supplied with electric currents of different intensities, in order to regulate differently the action on the two antagonistic collinear metallic currents created by the sliding magnetic fields which they generate.
• colllinear sliding of the metal fields or flows it should be understood that the magnetic fields, respectively the currents of metal, slide not in parallel with each other but in the same line, like two collinear vectors with respect to two parallel vectors.
• the invention consists, in its main foundations, in creating in the secondary cooling zone a cross-stitch with two transverse branches and two longitudinal branches.
• This zone is provided with a pair of linear inductors arranged opposite one on the other on each side of the product along the width thereof and generating a horizontally sliding magnetic field so as to achieve an electromagnetic mixing mode in the form of "butterfly wings" known is for example from the document FR 72.20546 cited above
• Figure 4 is a diagram similar to the previous one in Fig. 3, but showing a mode of electromagnetic mixing in "triple loop", as achieved for example by implementing the teaching of the document FR 82.10844 pre- - the other figures, numbered from 5 to 9 are specific to the invention.
• FIGS. 1 to 4 served as a support for the presentation of the prior art already made at the start of this thesis. We will not come back to this in the following.
• FIGS. 5 to 9 representative of the mode of mixing in the secondary proper to the invention in these two variants (divergent or convergent in the center), the sliding magnetic fields, just like the linear inductors which produce them, are represented by thick vertical or horizontal arrows.
• the convection movements produced are themselves represented by their main trajectories in the form of lines carrying arrowheads indicating the direction of movement movement on the carrier path.
• the solid lines represent active convection zones, therefore of circulation subjected to the action of sliding magnetic fields.
• a submerged nozzle 4 centered on the casting axis A feeds the ingot mold in molten metal from a distributor not shown located above.
• This nozzle is provided with gills of lateral outlets 5 and 5 ′ each turned opposite one and the other of the small walls 3 and 3 ′ respectively.
• the form of the cast product is determined by the internal dimensions of the mold defining the casting space into which the molten metal arrives in the form of jets 7, 7 ′ emerging from the openings of the nozzle 4 conventionally in a more or less average direction. horizontal, or slightly tilted downwards.
• the cast product thus progresses from the top, from the level of the meniscus 8, downwards, in the direction of extraction of the casting machine, vertically or along a curved path in a plane orthogonal to that of the figure, with an extraction speed (casting speed) usually of the order of one meter per minute.
• these branches Due to the necessarily “finished” dimensional nature of the cast product, these branches, as can be seen, are connected in a way with each other by recirculation loops to form an overall flow developing in the plane of the large faces of the product cast in the shape of a four-leaf clover, the leaves constituting lobes L1, L2, L3, L4, the upper two of which, L1 and L4, extend to the mold at the outlet jets 7 and 7 '.
• the pair of vertical branches is in "divergent" type convection. The metal streams move away from each other from the center P.
• the convection of the metal is then of the "convergent" type: the metallic currents converge towards each other in the direction of the center of confluence P by flowing from the small lateral faces of the product towards the longitudinal axis A.
• the metal currents which form these branches are created by sliding magnetic fields, themselves generated by linear inductors arranged in the immediate vicinity of the product cast opposite these large faces (preferably the two faces) .
• the implementation of the invention maximizes the exchanges of metallic material between the bottom and the top of the liquid well.
• the looping circulation of the metal in any lobe takes place in a direction of rotation opposite to that which is established in the two closest neighboring lobes.
• the strength of the casting jets 7 and 7 ′ then being systematically reinforced by the central flow 10a rising co-current, the recirculation loops L5 and L6 in the mold towards the meniscus 8 will be reinforced in their turn. Consequently, the "double loop" mode L5, L1, L4 and L6 present within the mold is thus moreover stabilized.
• FIG. 9 similar to FIG. 5, is essentially distinguished from it by the fact that the directions of circulation of the metal in each of the four " branches of the cross 9 are reversed. This FIG.
• FIG. 9 thus illustrates the second main variant for implementing the invention which consists in creating longitudinal antagonistic collinear currents 20a, 20b in the middle part of the cast product 6 which this time converge towards each other in the direction of point P so as to provide circulation of the liquid metal which extends into the mold 1 by currents rising along the small faces 18, 18 'up to the level of the metal jets 7, 7' coming from the outlet gills 5, 5 'of the nozzle with which they oppose against the current to slow them down.
• the invention consists, in short, in judiciously using the electromagnetic stirring means currently available to carry out in the secondary a cutting in the long direction of the product into two strands juxtaposed and, in each strand, to install a butterfly wing type brewing configuration. In doing so, an overall flow system is created in the secondary with four lobes, the heart of which is the cross cross 9 with its center P.
• this division into two strands will be made half-width of the cast product, that is to say along the longitudinal axis thereof, since this axis generally merges with the casting axis. That said, it will suffice to unbalance the stirring forces between the two transverse branches 11 a, 11 b, for example via a differentiated adjustment of the intensities of the electric currents supplying the inductors 12, 13, to laterally move the middle position from the center P towards a small face 5 or towards the other 5 ′ and thus obtain a more selective effect on one side of the nozzle on the mold movements than on the other.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Continuous Casting (AREA)
• Alcoholic Beverages (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Treatment Of Steel In Its Molten State (AREA)

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• 2003
  • 2003-10-27 FR FR0312555A patent/FR2861324B1/fr not_active Expired - Fee Related
• 2004
  • 2004-10-22 US US10/577,461 patent/US20070074845A1/en not_active Abandoned
  • 2004-10-22 RU RU2006118350/02A patent/RU2357833C2/ru active
  • 2004-10-22 EP EP04805290A patent/EP1677928B1/de active Active
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  • 2004-10-22 CA CA002543368A patent/CA2543368A1/fr not_active Abandoned
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