EP3251773B1 - Semi-continuous strand casting of a steel bar - Google Patents

Semi-continuous strand casting of a steel bar Download PDF

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Publication number
EP3251773B1
EP3251773B1 EP17173954.3A EP17173954A EP3251773B1 EP 3251773 B1 EP3251773 B1 EP 3251773B1 EP 17173954 A EP17173954 A EP 17173954A EP 3251773 B1 EP3251773 B1 EP 3251773B1
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EP
European Patent Office
Prior art keywords
strand
cooling
continuous casting
casting machine
tertiary
Prior art date
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Application number
EP17173954.3A
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German (de)
French (fr)
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EP3251773A1 (en
Inventor
Christian Brugger
Susanne Hahn
Jens Kluge
Hans-Peter KOGLER
Johann Poeppl
Guoxin Shan
Susanne Tanzer
Heinrich Thoene
Franz Wimmer
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Primetals Technologies Austria GmbH
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Primetals Technologies Austria GmbH
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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
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
    • 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
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/041—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds for vertical casting
    • 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
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/055—Cooling the moulds
    • 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
    • B22D11/08—Accessories for starting the casting procedure
    • 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
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1213—Accessories for subsequent treating or working cast stock in situ for heating or insulating strands
    • 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
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling
    • 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
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
    • B22D11/1281—Vertical removing
    • 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
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • 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
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling

Definitions

  • the present invention relates to a method for the semi-continuous casting of a strand, preferably a bloom, from steel in a continuous casting machine and a continuous casting machine suitable therefor.
  • the continuous casting machine has a continuous mold, a device for pulling a strand out of the continuous mold and a device for conveying the strand out of the continuous casting machine in the form of a cast part elevator.
  • the continuous casting machine has a cooled continuous mold, a strand guide with secondary cooling and a device for pulling a strand out of the continuous mold and a device for conveying the strand out of the continuous casting machine. After undressing of the strand can be cooled further in half-shells.
  • the continuous casting machine used is divided into three parts.
  • the cooled continuous mold which is typically made of copper or a copper alloy, for primary cooling of the strand is followed by a strand guide for supporting and guiding the strand with secondary cooling, typically comprising a plurality of single-substance (mostly so-called water-only nozzles) and / or multi-substance nozzles (mostly so-called. airmist nozzles), for cooling the partially solidified strand shell, and a tertiary cooling zone for further cooling the strand.
  • the continuous casting machine is designed as a vertical continuous casting machine with a vertical mold, a vertical strand guide and a vertical tertiary cooling zone.
  • liquid steel typically from a metallurgical vessel, such as a ladle or a pouring distributor
  • a metallurgical vessel such as a ladle or a pouring distributor
  • the liquid steel with the cold strand having a solidified beginning of the strand and one forms the partially solidified strand following the strand start (ie a solidified strand shell and a liquid core).
  • the flow from the metallurgical vessel into the continuous mold can be set, for example, using a slide valve or a plug drive.
  • the partially solidified strand is then pulled out of the continuous mold, the casting level in the mold, which is established by the inflow of liquid steel into the mold and the extraction of the partially solidified strand by driven strand guide rollers, being kept approximately constant.
  • the partially solidified strand is supported in the strand guide, guided and further cooled by the secondary cooling.
  • the secondary cooling has a plurality of cooling nozzles; at slow casting speeds, however, cooling by radiation can already be sufficient to form a stable strand shell.
  • the cooling intensities in the primary and secondary cooling are adjusted depending on the pull-out speed so that the shell of the partially solidified strand withstands the maximum ferrostatic pressure that occurs in the continuous casting machine.
  • the casting process is ended, for example by closing the metallurgical vessel.
  • a strand end of the strand which is typically not completely solidified, is formed.
  • the end of the strand is now pulled out of the continuous mold at least to such an extent that it comes to rest in the area of the secondary cooling or the tertiary cooling of the continuous casting machine.
  • secondary cooling zone secondary cooling is ended.
  • the partially solidified strand is now slowly, controlled or regulated in the tertiary cooling zone of the continuous casting machine until completely solidified, in comparison to continuous casting.
  • the cooling takes place in a controlled manner - decreasing more in the foot area (ie in the area of the start of the strand) and towards the end of the strand ie in the area of the end of the strand.
  • the center of the partially solidified strand there is either a globular or dendritic structure with only extremely low segregations and porosities. With dendritic solidification, the dendrites in the strand center cannot grow together, which avoids the thread porosity in the strand center. Finally, the solidified strand is removed from the continuous casting machine.
  • the cooling of the partially solidified strand in the tertiary cooling zone is either controlled or regulated.
  • the target temperature for the cooling can be the surface temperature of the strand, or preferably a - in a 2 or 3-dimensional model containing the heat conduction equation for the strand and, if necessary, taking into account the processes involved in structural transformation - a structure composition calculated in real time in the center of the strand be used. This allows the cooling and the microstructure formation in the strand to be set very precisely.
  • the strand is cooled primarily by heat radiation and possibly by convection; spray cooling is typically not required.
  • the cooling at the start of the strand can be adjusted more than at the end of the strand without additional energy. Through targeted heating of the line, this can be ensured with additional energy. Finally, a slow cooling of the strand, possibly only locally, can be remedied by surface cooling of the strand.
  • the partially solidified strand In order to prevent the partially solidified strand from cooling too quickly in the tertiary cooling zone, it is advantageous if the partially solidified strand, preferably its outer surface, is heated in the tertiary cooling zone by a, preferably inductive, heating device. Alternatively, the strand can also be heated by a burner.
  • cooling of the partially solidified strand according to the invention should not occur too slowly, locally too slow cooling can be prevented if the partially solidified strand is cooled in the tertiary cooling zone by a, preferably movable, cooling device.
  • the heating device can be moved in the pull-out direction of the continuous casting machine.
  • the temperature of the strand can only be influenced by a single heating device without the need for distributed devices.
  • the partially solidified strand in the tertiary cooling zone is protected against rapid cooling by thermal insulation. It is advantageous if the Thermal insulation is preheated before the start of casting.
  • a particularly effective thermal insulation that also promotes the degassing of the melt that has not yet solidified and also protects against scaling consists in holding the strand in a vacuum or in an atmosphere of protective gas.
  • the insulation effect is either preset statically or is controlled or regulated during operation.
  • the setting can e.g. by swiveling insulation slats.
  • the insulation fins can be adjusted to different, but statically constant, swivel angles over the length of the strand.
  • the swivel angle can also be adjusted dynamically during the cooling phase. E.g. the swivel angle below - i.e. in the area of the beginning of the strand - larger than above, whereby the end of the strand is cooled more slowly than the beginning of the strand.
  • the cooled continuous mold preferably the continuous mold and the secondary cooling zone
  • the cooled continuous mold and the secondary cooling zone are separated (e.g. lifted off) from the tertiary cooling zone and the separated components transverse to the direction of extension of the continuous casting machine to another casting station, ie to another tertiary cooling zone.
  • a further strand can be cast, during which the strand previously produced is slowly cooled in the tertiary cooling zone.
  • the end of the strand is heated by a heating device, in particular an inductive heating device, an arc furnace, a plasma heater or by burning off exothermic covering powder.
  • a heating device in particular an inductive heating device, an arc furnace, a plasma heater or by burning off exothermic covering powder.
  • a stirring device such as a stirring coil is advantageous. This can advantageously be moved along the strand axis.
  • the partially solidified strand in the tertiary cooling zone can be rotated alternately clockwise and counterclockwise about its own axis. The reversal of direction ensures particularly intimate mixing inside the strand.
  • the cast strand is given a load-bearing shell as quickly as possible and the length of the secondary cooling can thereby be kept as short as possible, it is advantageous if the strand has a round cross section.
  • a similar effect can also be achieved with a strand with a three-round, four-round, etc. cross-section.
  • the outer surface of the strand can be heated by the heating device, as a result of which the cooling (and thus the microstructure formation) in the central region of the partially solidified strand in the tertiary cooling zone of the continuous casting machine can be set very precisely.
  • the tertiary cooling zone has, in particular statically adjustable or dynamically controlled or regulated, heat insulation.
  • the continuous mold, the secondary and the tertiary cooling zone are arranged in a row (so-called in-line).
  • the productivity of the semi-continuous continuous casting machine is significantly increased if the continuous casting machine has several, transverse to the direction of extension
  • Continuous casting machine has offset tertiary cooling zones, the machine head of the continuous casting machine, comprising the continuous mold and preferably the secondary cooling zone, being connectable and separable to a tertiary cooling zone and at least the machine head being movable transversely to the pull-out direction.
  • a single machine head can serve several tertiary cooling zones, so that a high throughput is achieved despite the slow cooling of the partially solidified strands.
  • the machine head is preferably moved to a further tertiary cooling zone, during which the strand is stationary. This does not interfere with the controlled or regulated slow cooling in the central area of the strand.
  • the strand can also be moved away from the machine head, if necessary with tertiary cooling.
  • the adjustable heat insulation has at least one - advantageously several - insulation panels (also called lamella) that can be moved in the pull-out direction of the continuous casting machine or pivoted to the pull-out direction. This allows the cooling rate of the partially solidified strand to be passive, i.e. without additional energy input.
  • a simple and robust continuous casting machine has a continuous pull-off carriage for pulling out the strand, the continuous pull-off carriage being movable in the pull-out direction, for example by spindle, rack or cylinder drives.
  • the beginning of the strand is supported on the strand puller wagon via the cold strand.
  • the continuous pull-off carriage is connected to the machine head, the continuous pull-off carriage being movable with the machine head transversely to the pull-out direction.
  • the cast strand after the casting end is e.g. parked on a pedestal on the hall floor and the machine head is moved to another tertiary cooling with the strand puller.
  • the slow cooling of the parked strand can e.g. be ensured by a thermal hood placed over the strand.
  • the machine head it would also be possible for the machine head to be stationary and for the cast strand to be moved transversely to the pull-out direction.
  • the cast strand is e.g. placed on a pedestal, whereby the pedestal and the strand can be moved to a further tertiary cooling zone.
  • Fig 1a is poured from a ladle distributor, not shown, of liquid steel via a dip tube into a cooled continuous mold 2, with the continuous mold 2 being fluid-tightly closed by the cold strand 6 at the start of casting of the continuous casting machine, so that a mold level M (also called a meniscus) is established in the mold.
  • a mold level M also called a meniscus
  • a solidified strand start 1a is formed (see Fig 1c ) out. Due to the primary cooling of the cooled continuous mold 2, the partially solidified strand 1b following the solidified strand start 1a against the pull-out direction A is not solidified, but rather has only a thin strand shell and a liquid core.
  • the continuous casting machine has a continuous take-off carriage 11 which comprises the cold strand 6 itself, a threaded spindle 12, a threaded nut 13 and a motor 14 for moving the strand pull-off carriage 11 in the pull-out direction A.
  • the motor 14 is connected via a gear and the threaded spindle 12 to the threaded nut 13 and has a through drive for the threaded spindle 12.
  • strand 1 has already been pulled further out of the continuous mold 2, the strand 1 in the strand guide 3 following the mold 2 being supported by several strand guide rollers 3a, guided and cooled by a plurality of cooling nozzles 4a in the secondary cooling 4.
  • the strand 1 forms a load-bearing strand shell that can withstand the ferrostatic pressure. A breakdown of strand 1 is thus prevented.
  • Fig 1c the beginning of the strand 1a has already passed the secondary cooling 3 of the continuous casting machine and has entered the tertiary cooling zone 5.
  • the strand 1 is further slowly controlled or regulatedly cooled, so that solidification takes place in the center of the partially solidified strand 1b with an upward direction.
  • the tertiary cooling zone 5 has a thermal insulation 9 and an in Fig 1f heater 7 shown.
  • FIG 2a An example of a thermal insulation 9 for tertiary cooling is shown, the atmosphere between the strand 1 and the heat hood 9 being evacuated by a vacuum pump (here a jet pump 15).
  • a vacuum pump here a jet pump 15
  • a pressure connection of the jet pump 15 is connected to a compressed air network and the suction connection of the jet pump 15 to the space inside the heat insulation 9.
  • This measure also prevents oxidation, ie scaling, of strand 1; the vacuum treatment also degasses the melt which has not yet solidified in the strand.
  • the heat insulation 9 has several Isolation panels 9a, which can be closed independently of one another (opening angle 0 °), opened (opening angle 90 °) or partially opened (90 °> opening angle> 0 °).
  • Fig 1d the casting was ended in the continuous casting machine, so that a strand end 1c is formed.
  • the casting level M lies below the casting level shown in broken lines according to the method steps 1a-1c.
  • the Fig 1e shows the situation after the strand end 1c of the strand 1 has passed the secondary cooling zone 3, the secondary cooling has ended and the strand end 1c is flush with the upper end of the tertiary cooling zone 5.
  • the slow, controlled or regulated cooling of the partially solidified strand 1b is ensured by the thermal insulation 9 and the heating of the strand by the heating device 7 which can be moved in the pull-out direction A (see Fig 1f ).
  • the strand end 1c is heated by an inductive head heater 10, so that the strand end 1c is prevented from cooling too quickly.
  • a round steel strand 1 with a diameter of 1200 mm and a length of 10 m was produced.
  • the pull-out speed of the strand 1 from the continuous mold 2 is 0.25 m / min. Due to the heat insulation 9 and the reheating of the strand 1 by the movable heating device 7, the complete solidification of the strand 1 is only achieved after 13 hours.
  • the casting of the strand - without the slow cooling of the strand in the tertiary cooling zone 5 - was ended after only 46 minutes.
  • the casting process is completed quickly, which is why it increases the throughput of the semi-continuous continuous casting process advantageous if the in Fig 1f Machine head, no longer shown, is separated from the tertiary cooling zone 5 and is moved transversely to the pull-out direction A to a further tertiary cooling zone 5.
  • a new strand can be cast there, while the in Fig 1f strand 1 shown is cooled further slowly. After slow cooling of the strand 1 until it has completely solidified, the strand is conveyed out of the continuous casting machine, for example by a device according to the 8a and 8b .
  • FIG. 4 is a first alternative embodiment of the tertiary cooling zone 5 of FIG Fig. 1 shown.
  • the space between the strand 1 and the heat insulation 9 is evacuated by a jet pump 15, as a result of which good heat insulation and slow cooling are achieved.
  • the surface of the strand 1 is protected against scaling and the residual melt is degassed.
  • the jet pump is simple and wear-free; its pressure connection is connected to a compressed air connection P and its suction connection to the room to be evacuated within the tertiary cooling zone.
  • the blowing off can take place against ambient pressure U.
  • the inductive head heater 10 is advantageous over a plasma heater, since the magnetic field also acts through the thermal insulation of the strand end 1c.
  • the Fig. 2b shows a second alternative of the tertiary cooling zone 5 of FIG Fig. 1 .
  • the insulation lamellae 9a of the heat insulation 9 can be pivoted to the pull-out direction, so that the air change between the ambient air and the strand 1 can be set inside the tertiary cooling zone 9.
  • the insulation slats 9a on the right side of the strand 1 were closed and shown on the left side opened by 10 ° to the pull-out direction A.
  • the slats 9a can be adjusted either manually or by actuators.
  • the Fig 3 shows schematically the time course of the travel path s of the inductive heating device 7 for reheating the outer surface of the strand 1.
  • the heating device 7 is drawn through in the upper region of the strand 1 and shown in dashed lines in the lower region. Since the solidification front shifts from the bottom to the top during cooling (ie from the start of the strand 1a to the end of the strand 1c), the travel path s of the heating device 7 also decreases over time.
  • a plurality of heating devices for example burners
  • a plurality of heating devices for example burners
  • the Fig. 4 shows the temperatures in ° C according to Fig. 1 produced strand 1 in a sectional view 3h after casting start (part figure 1), 8.3h after casting start (part figure 2) and when the strand 1 has solidified, about 13h after casting start (part figure 3).
  • the time course of the temperatures of strand 1 at different positions on the surface and in the center of the strand are shown in Fig. 5 shown. It can be seen from this that the casting of the strand and thus also the primary and secondary cooling is ended 46 minutes after the start of casting and then the strand 1 is cooled in a controlled manner only by the tertiary cooling 5.
  • a vertical continuous casting machine according to the invention is shown in two views.
  • the liquid steel is poured from a pan 30 into the pouring manifold 31 via a shadow pipe, then the melt flows into the continuous mold 2 via a dip pipe ( SEN ), not shown.
  • the primary cooling in the mold 2 forms a partially rigid strand 1 with a load-bearing strand shell.
  • the melt is influenced even further by an optional stirring device 32.
  • the strand 1 is supported in the strand guide 3, guided and further cooled in the secondary cooling zone 4.
  • At least the continuous mold 2, the stirring coil 32, the strand guide 3 with the secondary cooling zone 4, and optionally also the tertiary cooling zone 5, can be moved on a casting car 33 on the casting platform G.
  • the strand 1 with the cold strand 6 is pulled out of the continuous mold 2 via the strand withdrawal carriage 11.
  • the strand take-off carriage 11 is driven via four threaded spindles 12 and guided by additional guide rails 34, a motor being connected to the threaded nut 13 via a gear and the threaded spindle 12.
  • the casting carriage 33 can be moved transversely to the pull-out direction A to a further casting station, since the casting of the partially solidified strand, ie without the tertiary cooling of the strand 1, takes considerably less time than the tertiary cooling of strand 1 until it solidifies.
  • the strand 1 is slowly cooled by the thermal insulation 9 and possibly by a heating device (not shown here), so that the solidification takes place in the center of the strand with an upwardly oriented solidification front.
  • FIG. 7 A more detailed representation of the machine head of the continuous casting machine from the Fig. 6a , 6b is in Fig. 7 shown.
  • the Fig. 8a, 8b schematically show an embodiment for the conveying of the solidified strand 1 from the tertiary cooling zone.
  • the strand 1 is laterally supported by two brackets 38, so that on the continuous casting machine there are also very different diameters (see floor plan of Fig 8a ) can be shed.
  • Fig 8a the strand 1 has already been swung out with respect to the vertical and lies on the brackets 38.
  • Fig 8b the strand 1 is placed on the roller drive 39 on a roller table 37, where it can be removed in the direction of the arrow.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Description

Gebiet der TechnikTechnical field

Die vorliegende Erfindung betrifft ein Verfahren zum semi-kontinuierlichen Stranggießen eines Strangs, vorzugsweise eines Vorblocks, aus Stahl in einer Stranggießmaschine und eine dazu geeignete Stranggießmaschine.The present invention relates to a method for the semi-continuous casting of a strand, preferably a bloom, from steel in a continuous casting machine and a continuous casting machine suitable therefor.

Stand der TechnikState of the art

Der überwiegende Teil der heute produzierten Gesamtstahlmenge wird in kontinuierlich betriebenen Stranggießmaschinen mit hohem Durchsatz zu Strängen vergossen. Nur ca. 5% der Gesamtstahlmenge wird zu Vorblöcken (engl. ingots) vergossen. Das Vorblockgießen ist bspw. beschrieben im ASM Handbook, Volume 15: Casting, Kapitel "Steel Ingot Casting", Seiten 911-917, DOI: 10.1361/asmhba0005295 . Obwohl der Anteil von flüssigem Stahl der über die sog. Ingotroute zu Vorblöcken vergossen wird klein ist, ist die Ingotroute aber wegen der Eignung für spezielle Stahlsorten und -formate sehr profitabel.The majority of the total amount of steel produced today is cast into strands in continuously operated continuous casting machines with high throughput. Only about 5% of the total amount of steel is cast into ingots. The blooming is described, for example, in ASM Handbook, Volume 15: Casting, chapter "Steel Ingot Casting", pages 911-917, DOI: 10.1361 / asmhba0005295 . Although the proportion of liquid steel that is cast into blooms via the so-called ingot route is small, the ingot route is very profitable due to its suitability for special steel types and formats.

Vorteile des Vorblockgießens sind:

  • Hohe Flexibilität in den Produktabmessungen, günstig bei kleinen Losgrößen, einzigartig bei großen Formaten;
  • Eignung für spezielle Stahlsorten (z.B. für Kaltformstähle CHQ; HSLA Stähle; hochlegierte Stähle mit ca. 5% Legierungsanteilen, wie Cr, Ni, Mo; Kettenstähle; Automatenstähle mit einem hohen Anteil von S, Pb, Bi; Lagerstähle mit ca. 1% C, 1,2% Cr, 0,25% Ni, 0,25% Mo; etc.); und
  • höhere Qualität in punkto Vermeidung von Zentrumsseigerung und Porosität, insbesondere von Fadenporosität im Zentrum des Strangs.
Advantages of blooming are:
  • High flexibility in product dimensions, inexpensive for small lot sizes, unique for large formats;
  • Suitability for special steel grades (e.g. for cold-formed steels CHQ; HSLA steels; high-alloy steels with approx. 5% alloy components, such as Cr, Ni, Mo; chain steels; free-cutting steels with a high proportion of S, Pb, Bi; bearing steels with approx. 1% C , 1.2% Cr, 0.25% Ni, 0.25% Mo; etc.); and
  • higher quality in terms of avoidance of center elevation and porosity, especially thread porosity in the center of the strand.

Nachteile des Vorblockgießens sind:

  • langsame aber nur unzureichend kontrollierbare Abkühlgeschwindigkeiten in der Vorblockkokille;
  • höhere Ausbringverluste durch das Abtrennen des Kopfund Fußteils des Vorblocks;
  • höhere Betriebskosten; und
  • geringere Gefügesymmetrie und Reinheit.
Disadvantages of ingot casting are:
  • slow but insufficiently controllable cooling speeds in the bloom block;
  • higher yield losses due to the separation of the head and foot section of the bloom;
  • higher operating costs; and
  • less structural symmetry and purity.

Aus der DE 2042546 A1 ist ein Verfahren zum kontinuierlichen Stranggießen eines metallischen Strangs 2 in einer Stranggießmaschine bekannt, wobei die Stranggießmaschine eine gekühlte Durchlaufkokille 3 zur Primärkühlung des Strangs, eine Sekundärkühlung zum Abkühlen des Strangs und Ausziehwalzen 4 aufweist, umfassend die Verfahrensschritte:

  • Gießstart der Stranggießmaschine, wobei flüssiges Metall 6 in die Durchlaufkokille gegossen wird und das flüssige Metall einen teilerstarrten Strang ausbildet;
  • Ausziehen des teilerstarrten Strangs aus der Durchlaufkokille; und
  • Abkühlen des teilerstarrten Strangs in der Sekundärkühlzone.
From the DE 2042546 A1 A method for the continuous continuous casting of a metallic strand 2 in a continuous casting machine is known, the continuous casting machine having a cooled continuous mold 3 for primary cooling of the strand, a secondary cooling for cooling the strand and pull-out rolls 4, comprising the method steps:
  • Casting start of the continuous casting machine, liquid metal 6 being poured into the continuous mold and the liquid metal forming a partially solidified strand;
  • Pulling out the partially solidified strand from the continuous mold; and
  • Cooling of the partially solidified strand in the secondary cooling zone.

Aus der DE 4108785 A1 ist ein Verfahren zum semi-kontinuierlichen Stranggießen und eine Stranggießmaschine bekannt. Die Stranggießmaschine weist eine Durchlaufkokille, eine Einrichtung zum Ausziehen eines Strangs aus der Durchlaufkokille und eine Einrichtung zum Ausfördern des Strangs aus der Stranggießmaschine in Form eines Gießteil-Aufzugs auf.From the DE 4108785 A1 a method for semi-continuous continuous casting and a continuous casting machine is known. The continuous casting machine has a continuous mold, a device for pulling a strand out of the continuous mold and a device for conveying the strand out of the continuous casting machine in the form of a cast part elevator.

Schließlich ist aus der DE 3542418 A1 ein Verfahren zum kontinuierlichen vertikalen Stranggießen und eine kontinuierliche Vertikalstranggießanlage bekannt. Die Stranggießmaschine weist eine gekühlte Durchlaufkokille, eine Strangführung mit einer Sekundärkühlung sowie eine Einrichtung zum Ausziehen eines Strangs aus der Durchlaufkokille und eine Einrichtung zum Ausfördern des Strangs aus der Stranggießmaschine auf. Nach dem Ausziehen des Strangs kann dieser in Halbschalen weiter abgekühlt werden.After all, is out of DE 3542418 A1 a method for continuous vertical continuous casting and a continuous vertical continuous caster known. The continuous casting machine has a cooled continuous mold, a strand guide with secondary cooling and a device for pulling a strand out of the continuous mold and a device for conveying the strand out of the continuous casting machine. After undressing of the strand can be cooled further in half-shells.

Zusammenfassung der ErfindungSummary of the invention

Untersuchungen der Anmelderin haben ergeben, dass die höhere Qualität des Vorblockgießens in Bezug auf Zentrumsseigerung und Porosität hauptsächlich durch die langsame Erstarrungsgeschwindigkeit und die vom Stranganfang zum Strangende hin gerichtete Erstarrung im Zentrumsbereich des Vorblocks bewirkt wird. Die Erstarrung im Zentrum erfolgt globular bzw. mit einer axial ausgerichteten Erstarrungsfront, sodass eventuell auftretende Dendriten vermieden werden, welche im Zentrum Brücken bilden und das Nachsaugen der Schmelze behindern. Eine Fadenporosität im Zentrum ist somit weitgehend ausgeschlossen. Im Gegensatz dazu sind die Eigenschaften beim kontinuierlichen Stranggießen genau umgekehrt. Extrem niedrige Abkühlraten wie beim Vorblockgießen sind bei kontinuierlich betriebenen Stranggießmaschinen nicht realisierbar, da die Maschinenlänge aus wirtschaftlichen Gründen beschränkt ist. Durch die höhere Abkühlgeschwindigkeit verbunden mit der eher radial von außen nach Innen gerichteten Erstarrung beim kontinuierlichen Stranggießen wird eine dendritische Erstarrung und damit Zentrumsseigerung und Porosität verursacht. Daher werden nach dem Stand der Technik große Formate, die im Wesentlichen frei von Zentrumsseigerungen und Porositäten, insbesondere von Fadenporositäten, sein sollen, über die Ingotroute hergestellt. Die höheren Betriebskosten, geringere Ausbringung und Nachteile in der Gefügesymmetrie und Reinheit des Vorblocks werden dabei in Kauf genommen.Investigations by the applicant have shown that the higher quality of the ingot casting with regard to center elevation and porosity is mainly caused by the slow solidification speed and the solidification in the central area of the ingot from the beginning of the strand to the end of the strand. The solidification in the center is globular or with an axially oriented solidification front, so that any dendrites that may occur are avoided, which form bridges in the center and hinder the suction of the melt. A thread porosity in the center is therefore largely excluded. In contrast, the properties of continuous continuous casting are exactly the opposite. Extremely low cooling rates, such as with blooms, cannot be achieved with continuously operated continuous casting machines because the length of the machine is limited for economic reasons. The higher cooling rate combined with the more radial solidification from the outside towards the inside during continuous casting results in dendritic solidification and thus an increase in center and porosity. Therefore, according to the prior art, large formats, which should be essentially free of center segregation and porosity, in particular of thread porosity, are produced via the ingot route. The higher operating costs, lower output and disadvantages in the structural symmetry and purity of the bloom are accepted.

Die Aufgabe der Erfindung ist es, die Nachteile des Stands der Technik zu überwinden und ein Verfahren zum semi-kontinuierlichen Stranggießen eines Strangs, vorzugsweise eines Vorblocks, aus Stahl darzustellen, bei dem der Strang

  • eine geringe Zentrumsseigerung und Porosität aufweist, und
  • dennoch rasch, d.h. mit hohem Durchsatz, vergossen werden kann. Dadurch soll der semi-kontinuierlich vergossene Strang einerseits ähnliche bzw. sogar bessere metallurgische Eigenschaften wie ein durch die klassische Ingotroute hergestellter Vorblock haben; andererseits soll der Strang aber mit einem ähnlich hohen Durchsatz produziert werden können wie in einer kontinuierlich betriebenen Stranggießmaschine.
The object of the invention is to overcome the disadvantages of the prior art and to provide a method for the semi-continuous casting of a strand, preferably a bloom, from steel, in which the strand
  • has a low center segregation and porosity, and
  • can nevertheless be poured quickly, ie with a high throughput. As a result, the semi-continuously cast strand should on the one hand have similar or even better metallurgical properties than a preliminary block produced by the classic ingot route; on the other hand, the strand should be able to be produced at a similarly high throughput as in a continuously operated continuous casting machine.

Schließlich soll eine dafür geeignete Stranggießmaschine angegeben werden.Finally, a suitable continuous casting machine should be specified.

Diese Aufgabe wird durch ein Verfahren nach Anspruch 1 gelöst, vorteilhafte Ausführungsformen sind Gegenstand der abhängigen Ansprüche.This object is achieved by a method according to claim 1, advantageous embodiments are the subject of the dependent claims.

Erfindungsgemäß werden beim Verfahren zum semi-kontinuierlichen Stranggießen eines Strangs, vorzugsweise eines Vorblocks, aus Stahl in einer Stranggießmaschine, wobei die Stranggießmaschine eine gekühlte Durchlaufkokille zur Primärkühlung des Strangs, nachfolgend eine Strangführung zum Stützen und Führen des Strangs mit einer - typischerweise mehrere Kühldüsen umfassenden - Sekundärkühlung zum Abkühlen des Strangs, und wiederum nachfolgend eine Tertiärkühlung zum weiteren Abkühlen des Strangs aufweist, folgende Verfahrensschritte durchgeführt:

  • Gießstart der Stranggießmaschine, wobei flüssiger Stahl in die durch einen Kaltstrang verschlossene Durchlaufkokille gegossen wird und der flüssige Stahl mit dem Kaltstrang einen durcherstarrten Stranganfang und nachfolgend einen teilerstarrten Strang ausbildet;
  • Ausziehen des teilerstarrten Strangs aus der Durchlaufkokille;
  • Stützen und Führen des teilerstarrten Strangs in der Strangführung, wobei der teilerstarrte Strang durch die Sekundärkühlung abgekühlt wird;
  • Gießende der Stranggießmaschine, wobei das Vergießen von flüssigem Stahl in die Durchlaufkokille beendet wird und sich ein Strangende ausbildet;
  • Ausziehen des Strangendes aus der Durchlaufkokille;
  • Beenden des Ausziehens, sodass das Strangende außerhalb der Durchlaufkokille (d.h. im Bereich der Sekundärkühlzone oder der Tertiärkühlzone der Stranggießmaschine) liegt;
  • Beenden der Sekundärkühlung;
  • gesteuertes oder geregeltes Abkühlen des teilerstarrten Strangs bis zur Durcherstarrung des Strangs in der Tertiärkühlzone der Stranggießmaschine, wobei das Abkühlen am Stranganfang stärker und zum Strangende hin abnehmend eingestellt wird und die Abkühlung des teilerstarrten Strangs in der Tertiärkühlzone durch die Beeinflussung zumindest eines aus der Gruppe:
  • Wärmeisolation des Strangs,
  • Heizung des Strangs,
  • Oberflächenkühlung des Strangs
    eingestellt wird;
  • Ausfördern des Strangs aus der Stranggießmaschine.
According to the invention, in the process for the semi-continuous casting of a strand, preferably a bloom, made of steel in a continuous casting machine, the continuous casting machine being a cooled continuous mold for primary cooling of the strand, subsequently a strand guide for supporting and guiding the strand with a - typically comprising several cooling nozzles - Secondary cooling for cooling the strand, and in turn subsequently having a tertiary cooling for further cooling the strand, carried out the following process steps:
  • Casting start of the continuous casting machine, liquid steel being poured into the continuous mold closed by a cold strand, and the liquid steel with the cold strand forming a solidified start of the strand and subsequently a partially solidified strand;
  • Pulling out the partially solidified strand from the continuous mold;
  • Supporting and guiding the partially solidified strand in the strand guide, the partially solidified strand being cooled by the secondary cooling;
  • Pouring end of the continuous casting machine, the pouring of liquid steel into the continuous mold being ended and a strand end being formed;
  • Pulling the end of the strand out of the continuous mold;
  • Stopping the pulling out so that the strand end lies outside the continuous mold (ie in the area of the secondary cooling zone or the tertiary cooling zone of the continuous casting machine);
  • Termination of secondary cooling;
  • Controlled or regulated cooling of the partially solidified strand until solidification of the strand in the tertiary cooling zone of the continuous casting machine, the cooling at the beginning of the strand being set to be stronger and decreasing towards the end of the strand, and the cooling of the partially solidified strand in the tertiary cooling zone by influencing at least one of the group:
  • Heat insulation of the strand,
  • Heating the strand,
  • Surface cooling of the strand
    is set;
  • Conveying the strand from the continuous casting machine.

Die dabei verwendete Stranggießmaschine ist dreiteilig gegliedert. An die typischerweise aus Kupfer bzw. einer Kupferlegierung bestehende gekühlte Durchlaufkokille zur Primärkühlung des Strangs folgt eine Strangführung zum Stützen und Führen des Strangs mit einer Sekundärkühlung, typischerweise umfassend mehrere Einstoff- (meistens sog. water only Düsen) und/oder Mehrstoffdüsen (meistens sog. airmist Düsen), zum Abkühlen der teilerstarrten Strangschale, und eine Tertiärkühlzone zum weiteren Abkühlen des Strangs nach.The continuous casting machine used is divided into three parts. The cooled continuous mold, which is typically made of copper or a copper alloy, for primary cooling of the strand is followed by a strand guide for supporting and guiding the strand with secondary cooling, typically comprising a plurality of single-substance (mostly so-called water-only nozzles) and / or multi-substance nozzles (mostly so-called. airmist nozzles), for cooling the partially solidified strand shell, and a tertiary cooling zone for further cooling the strand.

Um das Biegen bzw. das Rückbiegen des Strangs zu vermeiden, ist es vorteilhaft, wenn die Stranggießmaschine als eine Vertikalstranggießmaschine mit einer senkrechten Kokille, einer senkrechten Strangführung und einer senkrechten Tertiärkühlzone ausgebildet ist.In order to avoid the bending or the back bending of the strand, it is advantageous if the continuous casting machine is designed as a vertical continuous casting machine with a vertical mold, a vertical strand guide and a vertical tertiary cooling zone.

Das erfindungsgemäße Verfahren läuft wie folgt ab: Beim Gießstart der Stranggießmaschine wird flüssiger Stahl (typischerweise von einem metallurgischen Gefäß, wie einer Pfanne oder einem Gießverteiler) in die durch einen Kaltstrang verschlossene Durchlaufkokille vergossen, wobei der flüssige Stahl mit dem Kaltstrang einen durcherstarrten Stranganfang und einen dem Stranganfang nachfolgenden teilerstarrten Strang (d.h. eine erstarrte Strangschale und einen flüssigen Kern) ausbildet. Der Durchfluss vom metallurgischen Gefäß in die Durchlaufkokille kann bspw. über einen Schieberverschluss oder einen Stopfenantrieb eingestellt werden. Anschließend wird der teilerstarrte Strang aus der Durchlaufkokille ausgezogen, wobei der Gießspiegel in der Kokille, der sich durch den Zufluss von flüssigem Stahl in die Kokille und das Ausziehen des teilerstarrten Strangs durch angetriebene Strangführungsrollen einstellt, in etwa konstant gehalten wird. Der teilerstarrte Strang wird nach der Durchlaufkokille in der Strangführung gestützt, geführt und durch die Sekundärkühlung weiter abgekühlt. Insbesondere bei höheren Gießgeschwindigkeiten ist es vorteilhaft, wenn die Sekundärkühlung mehrere Kühldüsen aufweist; bei langsamen Gießgeschwindigkeiten kann jedoch die Kühlung durch Strahlung bereits ausreichen, eine tragfähige Strangschale zu bilden. Die Kühlintensitäten in der Primär- und Sekundärkühlung werden je nach Auszugsgeschwindigkeit so eingestellt, dass die Schale des teilerstarrten Strangs dem maximal auftretenden ferrostatischen Druck in der Stranggießmaschine standhält. Wenn der Strang die gewünschte Länge bzw. das gewünschte Gewicht erreicht hat, wird der Gießvorgang beendet, bspw. durch das Verschließen des metallurgischen Gefäßes. Dadurch bildet sich ein typischerweise nicht völlig durcherstarrtes Strangende des Strangs aus. Das Strangende wird nun zumindest soweit aus der Durchlaufkokille ausgezogen, dass es im Bereich der Sekundärkühlung oder der Tertiärkühlung der Stranggießmaschine zu liegen kommt. Spätestens wenn das Strangende die Sekundärkühlzone passiert hat, wird die Sekundärkühlung beendet. Der teilerstarrte Strang wird nun - im Vergleich zum kontinuierlichen Stranggießen - langsam, gesteuert oder geregelt in der Tertiärkühlzone der Stranggießmaschine bis zur völligen Durcherstarrung abgekühlt. Dabei erfolgt die Abkühlung kontrolliert - stärker im Fußbereich (d.h. im Bereich des Stranganfangs) des Stranges und zum Strangkopf d.h. im Bereich des Strangendes) hin abnehmend. Damit wird im Zentrumsbereich eine von unten nach oben gerichtete Erstarrungsfront bewirkt. Im Zentrum des teilerstarrten Strangs stellt sich so entweder ein globulares oder dendritisches Gefüge mit nur äußerst geringen Seigerungen und Porositäten ein. Bei dendritischer Erstarrung können die Dendriten im Strangzentrum nicht zusammenwachsen, wodurch die Fadenporosität im Strangzentrum vermieden wird. Schließlich wird der durcherstarrte Strang aus der Stranggießmaschine ausgefördert.The process according to the invention proceeds as follows: At the start of casting of the continuous casting machine, liquid steel (typically from a metallurgical vessel, such as a ladle or a pouring distributor) is poured into the continuous mold closed by a cold strand, the liquid steel with the cold strand having a solidified beginning of the strand and one forms the partially solidified strand following the strand start (ie a solidified strand shell and a liquid core). The flow from the metallurgical vessel into the continuous mold can be set, for example, using a slide valve or a plug drive. The partially solidified strand is then pulled out of the continuous mold, the casting level in the mold, which is established by the inflow of liquid steel into the mold and the extraction of the partially solidified strand by driven strand guide rollers, being kept approximately constant. After the continuous mold, the partially solidified strand is supported in the strand guide, guided and further cooled by the secondary cooling. In particular at higher casting speeds, it is advantageous if the secondary cooling has a plurality of cooling nozzles; at slow casting speeds, however, cooling by radiation can already be sufficient to form a stable strand shell. The cooling intensities in the primary and secondary cooling are adjusted depending on the pull-out speed so that the shell of the partially solidified strand withstands the maximum ferrostatic pressure that occurs in the continuous casting machine. When the strand has reached the desired length or weight, the casting process is ended, for example by closing the metallurgical vessel. As a result, a strand end of the strand, which is typically not completely solidified, is formed. The end of the strand is now pulled out of the continuous mold at least to such an extent that it comes to rest in the area of the secondary cooling or the tertiary cooling of the continuous casting machine. At the latest when the end of the strand passes the secondary cooling zone secondary cooling is ended. The partially solidified strand is now slowly, controlled or regulated in the tertiary cooling zone of the continuous casting machine until completely solidified, in comparison to continuous casting. The cooling takes place in a controlled manner - decreasing more in the foot area (ie in the area of the start of the strand) and towards the end of the strand ie in the area of the end of the strand. This creates a solidification front from bottom to top in the center area. In the center of the partially solidified strand there is either a globular or dendritic structure with only extremely low segregations and porosities. With dendritic solidification, the dendrites in the strand center cannot grow together, which avoids the thread porosity in the strand center. Finally, the solidified strand is removed from the continuous casting machine.

Das Abkühlen des teilerstarrten Strangs in der Tertiärkühlzone erfolgt entweder gesteuert oder geregelt. Als Soll-Wert für die Abkühlung kann die Oberflächentemperatur des Strangs, oder bevorzugt eine - in einem 2- oder 3-dimensionalen Modell beinhaltend die Wärmeleitungsgleichung für den Strang und gegebenenfalls unter Berücksichtigung der Vorgänge bei der Gefügeumwandlung - in Echtzeit berechnete Gefügezusammensetzung im Zentrum des Strangs herangezogen werden. Dadurch kann die Abkühlung und die Gefügeausbildung im Strang sehr genau eingestellt werden. In der Tertiärkühlung wird der Strang primär durch Wärmestrahlung und ggf. durch Konvektion abgekühlt; eine Spritzkühlung ist typischerweise nicht erforderlich.The cooling of the partially solidified strand in the tertiary cooling zone is either controlled or regulated. The target temperature for the cooling can be the surface temperature of the strand, or preferably a - in a 2 or 3-dimensional model containing the heat conduction equation for the strand and, if necessary, taking into account the processes involved in structural transformation - a structure composition calculated in real time in the center of the strand be used. This allows the cooling and the microstructure formation in the strand to be set very precisely. In tertiary cooling, the strand is cooled primarily by heat radiation and possibly by convection; spray cooling is typically not required.

Durch die langsame Abkühlung des Strangs können eventuell notwendige Glühbehandlungen des Strangs zwecks Spannungsabbau und weiterer Strukturverbesserung bereits in der Tertiärkühlzone der Stranggießmaschine durchgeführt werden. Erfindungsgemäß wird das langsame, geregelte oder gesteuerte, Abkühlen des Strangs durch zumindest eine der folgenden Maßnahmen beeinflusst:

  1. a) Beeinflussung der Wärmeisolation des Strangs,
  2. b) Heizung des Strangs,
  3. c) Oberflächenkühlung des Strangs.
Due to the slow cooling of the strand, any necessary annealing treatments of the strand for the purpose of relieving tension and further improving the structure can already be carried out in the tertiary cooling zone of the continuous casting machine. According to the invention, the slow, regulated or controlled cooling of the strand is influenced by at least one of the following measures:
  1. a) influencing the heat insulation of the strand,
  2. b) heating the strand,
  3. c) surface cooling of the strand.

Durch die gezielte Beeinflussung der Wärmeisolation kann ohne zusätzliche Energie die Abkühlung am Stranganfang stärker als am Strangende eingestellt werden. Durch eine gezielte Heizung des Strangs kann dies mit zusätzlicher Energie sichergestellt werden. Schließlich kann eine - ggf. nur lokal - vorliegende - zu langsame Abkühlung des Strangs durch eine Oberflächenkühlung des Strangs behoben werden.By specifically influencing the heat insulation, the cooling at the start of the strand can be adjusted more than at the end of the strand without additional energy. Through targeted heating of the line, this can be ensured with additional energy. Finally, a slow cooling of the strand, possibly only locally, can be remedied by surface cooling of the strand.

Um ein zu rasches Abkühlen des teilerstarrten Strangs in der Tertiärkühlzone zu verhindern, ist es vorteilhaft, wenn der teilerstarrte Strang, vorzugsweise dessen Mantelfläche, in der Tertiärkühlzone durch eine, bevorzugt induktive, Heizvorrichtung aufgeheizt wird. Alternativ kann der Strang aber auch durch Brenner aufgeheizt werden.In order to prevent the partially solidified strand from cooling too quickly in the tertiary cooling zone, it is advantageous if the partially solidified strand, preferably its outer surface, is heated in the tertiary cooling zone by a, preferably inductive, heating device. Alternatively, the strand can also be heated by a burner.

Obwohl ein zu langsames Abkühlen des teilerstarrten Strangs gemäß der Erfindung nicht auftreten sollte, kann ein lokal zu langsames Abkühlen verhindert werden, wenn der teilerstarrte Strang in der Tertiärkühlzone durch eine, bevorzugt verfahrbare, Kühlvorrichtung abgekühlt wird.Although cooling of the partially solidified strand according to the invention should not occur too slowly, locally too slow cooling can be prevented if the partially solidified strand is cooled in the tertiary cooling zone by a, preferably movable, cooling device.

Besonders vorteilhaft ist es, wenn die Heizvorrichtung in Auszugsrichtung der Stranggießmaschine verfahrbar ist. Dadurch kann die Temperatur des Strangs nur durch eine einzige Heizvorrichtung beeinflusst werden, ohne dass hierzu verteilt angeordnete Vorrichtungen benötigt werden.It is particularly advantageous if the heating device can be moved in the pull-out direction of the continuous casting machine. As a result, the temperature of the strand can only be influenced by a single heating device without the need for distributed devices.

Für die Einstellung der Erstarrung ist es besonders vorteilhaft, wenn der teilerstarrte Strang in der Tertiärkühlzone durch eine Wärmeisolation vor zu rascher Abkühlung geschützt wird. Vorteilhaft ist es, wenn die Wärmeisolation vor dem Gießstart vorgeheizt wird. Eine besonders effektive Wärmeisolation die zudem die Entgasung der noch nicht erstarrten Schmelze fördert und außerdem vor Verzunderung schützt, besteht darin, den Strang in einem Vakuum oder in einer Atmosphäre aus Schutzgas zu halten.For setting the solidification, it is particularly advantageous if the partially solidified strand in the tertiary cooling zone is protected against rapid cooling by thermal insulation. It is advantageous if the Thermal insulation is preheated before the start of casting. A particularly effective thermal insulation that also promotes the degassing of the melt that has not yet solidified and also protects against scaling consists in holding the strand in a vacuum or in an atmosphere of protective gas.

Bei der Wärmeisolation ist es vorteilhaft, wenn die Isolationswirkung entweder statisch voreingestellt wird oder während des Betriebs gesteuert oder geregelt eingestellt wird ist. Die Einstellung kann z.B. durch schwenkbare Isolationslamellen erfolgen. Die Isolationslamellen können während der Tertiärkühlphase über die Stranglänge auf verschiedene, jedoch statisch gleichbleibende, Schwenkwinkel eingestellt werden. Die Schwenkwinkel können aber auch je nach Produktionsprogramm während der Abkühlphase dynamisch verstellt werden. Bspw. können die Schwenkwinkel unten - d.h. im Bereich des Stranganfangs - größer als oben eingestellt werden, wodurch der Strangendbereich langsamer als der Stranganfangsbereich abgekühlt wird.With thermal insulation, it is advantageous if the insulation effect is either preset statically or is controlled or regulated during operation. The setting can e.g. by swiveling insulation slats. During the tertiary cooling phase, the insulation fins can be adjusted to different, but statically constant, swivel angles over the length of the strand. Depending on the production program, the swivel angle can also be adjusted dynamically during the cooling phase. E.g. the swivel angle below - i.e. in the area of the beginning of the strand - larger than above, whereby the end of the strand is cooled more slowly than the beginning of the strand.

Um den Durchsatz im semi-kontinuierlichen Gießbetrieb zu erhöhen, ist es äußerst vorteilhaft, wenn nachdem das Strangende die Sekundärkühlung passiert hat, die gekühlte Durchlaufkokille, bevorzugt die Durchlaufkokille und die Sekundärkühlzone, von der Tertiärkühlzone getrennt (bspw. abgehoben) werden und die abgetrennten Bauteile quer zur Auszugsrichtung der Stranggießmaschine zu einer anderen Gießstation, d.h. zu einer weiteren Tertiärkühlzone, verfahren werden. Bei der weiteren Tertiärkühlzone kann ein weiterer Strang gegossen werden, währenddessen der zuvor erzeugte Strang in der Tertiärkühlzone langsam abgekühlt wird. Durch diese Maßnahmen wird die hohe Qualität des Vorblockgießens mit der hohen Produktivität des kontinuierlichen Stranggießens vereint.In order to increase the throughput in the semi-continuous casting operation, it is extremely advantageous if after the strand end has passed through the secondary cooling, the cooled continuous mold, preferably the continuous mold and the secondary cooling zone, are separated (e.g. lifted off) from the tertiary cooling zone and the separated components transverse to the direction of extension of the continuous casting machine to another casting station, ie to another tertiary cooling zone. In the further tertiary cooling zone, a further strand can be cast, during which the strand previously produced is slowly cooled in the tertiary cooling zone. These measures combine the high quality of the ingot casting with the high productivity of continuous continuous casting.

Nach dem Trennen der gekühlten Durchlaufkokille, bzw. der Durchlaufkokille mit der Sekundärkühlzone, von der Tertiärkühlzone ist es vorteilhaft, wenn das Strangende durch eine Wärmeisolation vor zu rascher Abkühlung geschützt wird.After separating the cooled continuous mold, or the continuous mold with the secondary cooling zone, from the Tertiary cooling zone, it is advantageous if the end of the strand is protected by thermal insulation from cooling too quickly.

Weiters ist es vorteilhaft, wenn das Strangende durch eine Heizeinrichtung, insbesondere eine induktive Heizeinrichtung, einen Lichtbogenofen, eine Plasmaheizung oder durch das Abbrennen von exothermem Abdeckpulver, erwärmt wird.It is also advantageous if the end of the strand is heated by a heating device, in particular an inductive heating device, an arc furnace, a plasma heater or by burning off exothermic covering powder.

Durch das Isolieren und das Erwärmen des Strangendes wird der obere Bereich des Strangs bis zum Durcherstarrungsende mit flüssigem Sumpf gehalten und das Nachsaugen der Schmelze in das Strangzentrum sichergestellt. Durch diese Maßnahmen wird eine hohe Qualität erzielt und eine zu große Trichterbildung im Strangende vermieden. Ähnliche Maßnahmen sind aber auch im unteren Bereich des Strangs möglich. Durch diese Maßnahmen werden die Ausbringverluste reduziert, da nur ein kürzerer Abschnitt vom Stranganfang und -ende abgetrennt werden muss.By insulating and heating the end of the strand, the upper region of the strand is held with liquid sump up to the solidification end and the melt is sucked into the center of the strand. These measures ensure high quality and avoid excessive funnel formation at the end of the strand. Similar measures are also possible in the lower area of the strand. These measures reduce the output losses since only a shorter section has to be separated from the start and end of the strand.

Zur Erzielung einer gleichmäßigen Innenstruktur ist eine Rühreinrichtung wie eine Rührspule vorteilhaft. Diese ist günstigerweise entlang der Strangachse verfahrbar. Alternativ dazu kann der teilerstarrte Strang in der Tertiärkühlzone um seine eigene Achse abwechselnd im Uhrzeigersinn und gegen den Uhrzeigersinn gedreht werden. Durch die Richtungsumkehr wird eine besonders innige Vermischung im Inneren des Strangs sichergestellt.To achieve a uniform internal structure, a stirring device such as a stirring coil is advantageous. This can advantageously be moved along the strand axis. Alternatively, the partially solidified strand in the tertiary cooling zone can be rotated alternately clockwise and counterclockwise about its own axis. The reversal of direction ensures particularly intimate mixing inside the strand.

Damit der gegossene Strang möglichst schnell eine tragfähige Schale erhält und dadurch die Länge der Sekundärkühlung möglichst kurz gehalten werden kann, ist es vorteilhaft, wenn der Strang einen runden Querschnitt hat. Ein ähnlicher Effekt kann auch bei einem Strang mit einem dreirunden, vierrunden etc. Querschnitt erzielt werden.So that the cast strand is given a load-bearing shell as quickly as possible and the length of the secondary cooling can thereby be kept as short as possible, it is advantageous if the strand has a round cross section. A similar effect can also be achieved with a strand with a three-round, four-round, etc. cross-section.

Die erfindungsgemäße Aufgabe wird ebenfalls durch eine Vorrichtung nach Anspruch 9 gelöst. Vorteilhafte Ausführungsformen sind Gegenstand der abhängigen Ansprüche.The object of the invention is also achieved by a device according to claim 9. Advantageous embodiments are the subject of the dependent claims.

Die erfindungsgemäße Stranggießmaschine umfasst

  • eine Einrichtung zum Ausziehen eines Strangs aus einer Durchlaufkokille und eine Einrichtung zum Ausfördern des Strangs aus der Stranggießmaschine,
  • die gekühlte Durchlaufkokille zur Primärkühlung des Strangs, nachfolgend
  • eine Strangführung zum Stützen und Führen des Strangs mit einer Sekundärkühlzone, typischerweise umfassend mehrere Kühldüsen, zum Abkühlen des Strangs, und wiederum nachfolgend
  • eine Tertiärkühlzone zum weiteren Abkühlen des Strangs, dadurch gekennzeichnet,
dass die Tertiärkühlzone eine statisch voreinstellbare oder eine dynamisch (d.h. während des Betriebs) gesteuert oder geregelt einstellbare Wärmeisolation aufweist, wobei die verstellbare Wärmeisolation zumindest ein Isolationspanel aufweist, dass in Auszugsrichtung verlagerbar oder zur Auszugsrichtung verschwenkbar ist.The continuous casting machine according to the invention comprises
  • a device for extracting a strand from a continuous mold and a device for conveying the strand out of the continuous casting machine,
  • the cooled continuous mold for primary cooling of the strand, below
  • a strand guide for supporting and guiding the strand with a secondary cooling zone, typically comprising a plurality of cooling nozzles, for cooling the strand, and again in turn
  • a tertiary cooling zone for further cooling the strand, characterized in that
that the tertiary cooling zone has a statically presettable or dynamically (ie during operation) controlled or regulated adjustable heat insulation, the adjustable heat insulation having at least one insulation panel that can be displaced in the pull-out direction or pivotable to the pull-out direction.

Durch die Heizvorrichtung kann die Mantelfläche des Strangs aufgeheizt werden, wodurch die Abkühlung (und dadurch die Gefügeausbildung) im Zentrumsbereich des teilerstarrten Strangs in der Tertiärkühlzone der Stranggießmaschine sehr genau eingestellt werden kann.The outer surface of the strand can be heated by the heating device, as a result of which the cooling (and thus the microstructure formation) in the central region of the partially solidified strand in the tertiary cooling zone of the continuous casting machine can be set very precisely.

Um die langsame Abkühlung des teilerstarrten Strangs bei einem niedrigen Energieverbrauch für die Heizvorrichtung zu ermöglichen, ist es vorteilhaft, wenn die Tertiärkühlzone eine, insbesondere statisch einstellbare oder eine dynamisch gesteuert oder geregelt einstellbare, Wärmeisolation aufweist.In order to enable slow cooling of the partially solidified strand with a low energy consumption for the heating device, it is advantageous if the tertiary cooling zone has, in particular statically adjustable or dynamically controlled or regulated, heat insulation.

Zweckmäßig ist es, wenn die Durchlaufkokille, die Sekundärund die Tertiärkühlzone in einer Reihe (sog. in-line) angeordnet sind.It is expedient if the continuous mold, the secondary and the tertiary cooling zone are arranged in a row (so-called in-line).

Die Produktivität der semi-kontinuierlichen Stranggießmaschine wird wesentlich erhöht, wenn die Stranggießmaschine mehrere, quer zur Auszugsrichtung der Stranggießmaschine, versetzte Tertiärkühlzonen aufweist, wobei der Maschinenkopf der Stranggießmaschine, umfassend die Durchlaufkokille und vorzugsweise die Sekundärkühlzone, mit einer Tertiärkühlzone verbindbar und trennbar sind und zumindest der Maschinenkopf quer zur Auszugsrichtung verfahrbar ist. Wie oben beschrieben, kann ein einziger Maschinenkopf mehrere Tertiärkühlzonen bedienen, sodass ein hoher Durchsatz trotz der langsamen Abkühlung der teilerstarrten Stränge erreicht wird.The productivity of the semi-continuous continuous casting machine is significantly increased if the continuous casting machine has several, transverse to the direction of extension Continuous casting machine has offset tertiary cooling zones, the machine head of the continuous casting machine, comprising the continuous mold and preferably the secondary cooling zone, being connectable and separable to a tertiary cooling zone and at least the machine head being movable transversely to the pull-out direction. As described above, a single machine head can serve several tertiary cooling zones, so that a high throughput is achieved despite the slow cooling of the partially solidified strands.

Vorzugsweise wird der Maschinenkopf zu einer weiteren Tertiärkühlzone verfahren, währenddessen der Strang stationär ist. Dadurch wird die gesteuert oder geregelte, langsame Abkühlung im Zentrumsbereich des Strangs nicht gestört. Alternativ dazu kann aber auch der Strang, ggf. mit der Tertiärkühlung, vom Maschinenkopf weggefahren werden.The machine head is preferably moved to a further tertiary cooling zone, during which the strand is stationary. This does not interfere with the controlled or regulated slow cooling in the central area of the strand. As an alternative, the strand can also be moved away from the machine head, if necessary with tertiary cooling.

Erfindungsgemäß ist vorgesehen, dass die verstellbare Wärmeisolation zumindest ein - vorteilhafterweise mehrere - Isolationspanel (auch Lamelle genannt) aufweist, dass in der Auszugsrichtung der Stranggießmaschine verlagerbar oder zur Auszugsrichtung schwenkbar ist. Dadurch kann die Abkühlgeschwindigkeit des teilerstarrten Strangs passiv, d.h. ohne zusätzlichen Energieeintrag, eingestellt werden.According to the invention, it is provided that the adjustable heat insulation has at least one - advantageously several - insulation panels (also called lamella) that can be moved in the pull-out direction of the continuous casting machine or pivoted to the pull-out direction. This allows the cooling rate of the partially solidified strand to be passive, i.e. without additional energy input.

Mehrere Stränge mit kleinem Format können gleichzeitig erzeugt werden, wenn der Maschinenkopf der Stranggießmaschine mehrere gekühlte Durchlaufkokillen und mehrere dahinter angeordnete Strangführungen mit Sekundärkühlzonen aufweist.Several strands with a small format can be produced at the same time if the machine head of the continuous casting machine has several cooled continuous molds and several strand guides arranged behind them with secondary cooling zones.

Eine einfache und robuste Stranggießmaschine weist einen Strangabzugswagen zum Ausziehen des Strangs auf, wobei der Strangabzugswagen in Auszugsrichtung, beispielsweise durch Spindel-, Zahnstangen- oder Zylinderantriebe, verfahrbar ist. Dabei stützt sich der Stranganfang über den Kaltstrang auf dem Strangabzugswagen ab.A simple and robust continuous casting machine has a continuous pull-off carriage for pulling out the strand, the continuous pull-off carriage being movable in the pull-out direction, for example by spindle, rack or cylinder drives. The beginning of the strand is supported on the strand puller wagon via the cold strand.

Bei einer Ausführungsform der erfindungsgemäßen Stranggießmaschine ist der Strangabzugswagen mit dem Maschinenkopf verbunden, wobei der Strangabzugswagen mit dem Maschinenkopf quer zur Auszugsrichtung verfahrbar ist. Dabei wird der gegossene Strang nach dem Gießende z.B. auf einem Podest auf dem Hallenboden abgestellt und der Maschinenkopf mit dem Strangabzugswagen zur einer anderen Tertiärkühlung verfahren. Die langsame Abkühlung des abgestellten Strangs kann z.B. durch eine über den Strang gestülpte Thermohaube sichergestellt werden.In one embodiment of the continuous casting machine according to the invention, the continuous pull-off carriage is connected to the machine head, the continuous pull-off carriage being movable with the machine head transversely to the pull-out direction. The cast strand after the casting end is e.g. parked on a pedestal on the hall floor and the machine head is moved to another tertiary cooling with the strand puller. The slow cooling of the parked strand can e.g. be ensured by a thermal hood placed over the strand.

Alternativ dazu wäre es auch möglich, dass der Maschinenkopf stationär ist und der gegossene Strang quer zur Auszugsrichtung verfahrbar ist. Hier wird der gegossene Strang z.B. auf einem Podest abgestellt, wobei das Podest samt dem Strang zu einer weiteren Tertiärkühlzone verfahren werden kann.Alternatively, it would also be possible for the machine head to be stationary and for the cast strand to be moved transversely to the pull-out direction. Here the cast strand is e.g. placed on a pedestal, whereby the pedestal and the strand can be moved to a further tertiary cooling zone.

Kurze Beschreibung der ZeichnungenBrief description of the drawings

Weitere Vorteile und Merkmale der vorliegenden Erfindung ergeben sich aus der nachfolgenden Beschreibung nicht einschränkender Ausführungsbeispiele, wobei die Figuren zeigen:

  • Fig 1 mit den Teilfiguren la...lf zeigen schematisch die Verfahrensschritte beim semi-kontinuierlichen Stranggießen eines Vorblocks aus Stahl.
  • Fig 2a und 2b zeigen zwei alternative Ausführungsformen einer Tertiärkühlung für das semi-kontinuierlichen Stranggießen eines Vorblocks aus Stahl.
  • Fig 3 zeigt den zeitlichen Verlauf eines Heizaggregats zum Erwärmen eines Vorblocks in einer Tertiärkühlung.
  • Fig 4 zeigt die Temperaturen bei der Abkühlung des Strangs 1 in der Tertiärkühlzone 5.
  • Fig 5 zeigt die Temperaturverläufe über der Zeit zu Fig 4. Fig 6a und 6b zeigen eine erfindungsgemäße Stranggießmaschine in einem Auf- und einem Kreuzriss.
  • Fig 7 zeigt einen Maschinenkopf einer erfindungsgemäßen Stranggießmaschine in zwei Rissen.
  • Fig 8a, 8b zeigen schematisch das Ausfördern eines durcherstarrten Strangs aus einer Tertiärkühlzone.
Further advantages and features of the present invention result from the following description of non-limiting exemplary embodiments, the figures showing:
  • Fig. 1 with the partial figures la ... lf schematically show the process steps in semi-continuous continuous casting of a steel ingot.
  • Figures 2a and 2b show two alternative embodiments of a tertiary cooling for the semi-continuous continuous casting of a steel ingot.
  • Fig 3 shows the time course of a heating unit for heating a bloom in a tertiary cooling.
  • Fig. 4 shows the temperatures during the cooling of the strand 1 in the tertiary cooling zone 5.
  • Fig. 5 shows the temperature profiles over time Fig. 4 . Fig. 6a and 6b show a continuous casting machine according to the invention in an elevation and a cross-section.
  • Fig. 7 shows a machine head of a continuous casting machine according to the invention in two cracks.
  • Fig. 8a, 8b schematically show the discharge of a solidified strand from a tertiary cooling zone.

Beschreibung der AusführungsformenDescription of the embodiments

In den Fig la...lf sind die Verfahrensschritte beim semikontinuierlichen Stranggießen eines Strangs 1 in einer Stranggießmaschine gezeigt.The process steps in the semi-continuous continuous casting of a strand 1 in a continuous casting machine are shown in FIGS.

In Fig 1a wird aus einem nicht extra dargestellten Pfannenverteiler flüssiger Stahl über ein Tauchrohr in eine gekühlte Durchlaufkokille 2 gegossen, wobei beim Gießstart der Stranggießmaschine die Durchlaufkokille 2 durch den Kaltstrang 6 fluiddicht verschlossen ist, sodass sich in der Kokille ein Gießspiegel M (auch Meniskus genannt) einstellt. Durch das Verbinden des flüssigen Stahls mit dem Kopf des Kaltstrangs 6 bildet sich ein durcherstarrter Stranganfang 1a (siehe Fig 1c) aus. Durch die Primärkühlung der gekühlten Durchlaufkokille 2 ist der dem durcherstarrten Stranganfang 1a entgegen der Auszugsrichtung A nachfolgende teilerstarrte Strang 1b nicht durcherstarrt, sondern weist lediglich eine dünne Strangschale und einen flüssigen Kern auf. Um den Gießspiegel M in der Kokille 2 trotz des über das Tauchrohr nachströmenden flüssigen Stahls in etwa konstant zu halten, wird der Strang 1 aus der Kokille 2 ausgezogen. Dazu weist die Stranggießmaschine einen Strangabzugswagen 11 auf, der den Kaltstrang 6 selbst, eine Gewindespindel 12, eine Gewindemutter 13 und einen Motor 14 zum Verfahren des Strangabzugswagens 11 in die Auszugsrichtung A umfasst. Der Motor 14 ist über ein Getriebe und die Gewindespindel 12 mit der Gewindemutter 13 verbunden und weist einen Durchtrieb für die Gewindespindel 12 auf.In Fig 1a is poured from a ladle distributor, not shown, of liquid steel via a dip tube into a cooled continuous mold 2, with the continuous mold 2 being fluid-tightly closed by the cold strand 6 at the start of casting of the continuous casting machine, so that a mold level M (also called a meniscus) is established in the mold. By connecting the liquid steel to the head of the cold strand 6, a solidified strand start 1a is formed (see Fig 1c ) out. Due to the primary cooling of the cooled continuous mold 2, the partially solidified strand 1b following the solidified strand start 1a against the pull-out direction A is not solidified, but rather has only a thin strand shell and a liquid core. In order to keep the casting level M in the mold 2 approximately constant despite the liquid steel flowing in via the dip tube, the strand 1 is pulled out of the mold 2. For this purpose, the continuous casting machine has a continuous take-off carriage 11 which comprises the cold strand 6 itself, a threaded spindle 12, a threaded nut 13 and a motor 14 for moving the strand pull-off carriage 11 in the pull-out direction A. The motor 14 is connected via a gear and the threaded spindle 12 to the threaded nut 13 and has a through drive for the threaded spindle 12.

In Fig 1b wurde der Strang 1 bereits weiter aus der Durchlaufkokille 2 ausgezogen, wobei der Strang 1 in der der Kokille 2 nachfolgenden Strangführung 3 durch mehrere Strangführungsrollen 3a gestützt, geführt und durch mehrere Kühldüsen 4a in der Sekundärkühlung 4 abgekühlt wird. Dabei bildet der Strang 1 eine tragfähige Strangschale aus, die dem ferrostatischen Druck standhalten kann. Somit wird ein Durchbruch des Strangs 1 verhindert.In Fig 1b the strand 1 has already been pulled further out of the continuous mold 2, the strand 1 in the strand guide 3 following the mold 2 being supported by several strand guide rollers 3a, guided and cooled by a plurality of cooling nozzles 4a in the secondary cooling 4. The strand 1 forms a load-bearing strand shell that can withstand the ferrostatic pressure. A breakdown of strand 1 is thus prevented.

In Fig 1c hat der Stranganfang 1a bereits die Sekundärkühlung 3 der Stranggießmaschine passiert und ist in die Tertiärkühlzone 5 eingetreten. In der Tertiärkühlzone 5 wird der Strang 1 weiter langsam gesteuert oder geregelt abgekühlt, sodass im Zentrum des teilerstarrten Strangs 1b die Durcherstarrung mit einer nach oben orientierten Richtung erfolgt. Dadurch bildet sich entweder ein globulares bzw. zumindest ein dendritisches, die Fadenporosität vermeidendes, Gefüge aus. Um das zu rasche Abkühlen des teilerstarrten Strangs 1b zu verhindern, weist die Tertiärkühlzone 5 eine Wärmeisolierung 9 und eine in Fig 1f dargestellte Heizeinrichtung 7 auf. In der Fig 2a ist ein Beispiel einer Wärmeisolierung 9 für eine Tertiärkühlung gezeigt, wobei die Atmosphäre zwischen dem Strang 1 und der Wärmehaube 9 durch eine Vakuumpumpe (hier eine Strahlpumpe 15) evakuiert wird. Hierzu wird ein Druckanschluss der Strahlpumpe 15 mit einem Druckluftnetz und der Sauganschluss der Strahlpumpe 15 mit dem Raum innerhalb der Wärmeisolierung 9 verbunden. Durch diese Maßnahme wird zudem auch eine Oxidation, d.h. Verzunderung, des Strangs 1 verhindert; außerdem wird durch die Vakuumbehandlung die noch nicht durcherstarrte Schmelze im Strang entgast. Die Wärmeisolation 9 weist mehrere Isolationspanele 9a auf, die unabhängig voneinander geschlossen (Öffnungswinkel 0°), geöffnet (Öffnungswinkel 90°) oder teilweise geöffnet (90° > Öffnungswinkel > 0°) werden können.In Fig 1c the beginning of the strand 1a has already passed the secondary cooling 3 of the continuous casting machine and has entered the tertiary cooling zone 5. In the tertiary cooling zone 5, the strand 1 is further slowly controlled or regulatedly cooled, so that solidification takes place in the center of the partially solidified strand 1b with an upward direction. As a result, either a globular or at least a dendritic structure that avoids thread porosity is formed. In order to prevent the partially solidified strand 1b from cooling too rapidly, the tertiary cooling zone 5 has a thermal insulation 9 and an in Fig 1f heater 7 shown. In the Fig 2a An example of a thermal insulation 9 for tertiary cooling is shown, the atmosphere between the strand 1 and the heat hood 9 being evacuated by a vacuum pump (here a jet pump 15). For this purpose, a pressure connection of the jet pump 15 is connected to a compressed air network and the suction connection of the jet pump 15 to the space inside the heat insulation 9. This measure also prevents oxidation, ie scaling, of strand 1; the vacuum treatment also degasses the melt which has not yet solidified in the strand. The heat insulation 9 has several Isolation panels 9a, which can be closed independently of one another (opening angle 0 °), opened (opening angle 90 °) or partially opened (90 °> opening angle> 0 °).

In Fig 1d wurde das Gießen in der Stranggießmaschine beendet, sodass sich ein Strangende 1c ausbildet. Durch das Ausziehen des Strangendes 1c aus der Kokille 2, liegt der Gießspiegel M unterhalb des strichliert dargestellten Gießspiegels gemäß den Verfahrensschritten 1a-1c.In Fig 1d the casting was ended in the continuous casting machine, so that a strand end 1c is formed. By pulling the end of the strand 1c out of the mold 2, the casting level M lies below the casting level shown in broken lines according to the method steps 1a-1c.

Die Fig 1e zeigt die Situation nachdem das Strangende 1c des Strangs 1 die Sekundärkühlzone 3 passiert hat, die Sekundärkühlung beendet wurde und das Strangende 1c bündig mit dem oberen Ende der Tertiärkühlzone 5 abschließt. In der Tertiärkühlzone 5 wird die langsame, gesteuert oder geregelte Abkühlung des teilerstarrten Strangs 1b durch die Wärmeisolation 9 und die Erwärmung des Strangs durch die in der Auszugsrichtung A verfahrbare Heizeinrichtung 7 sichergestellt (siehe Fig 1f). Nach dem Trennen und Abheben des Maschinenkopfs, umfassend die Durchlaufkokille 2, die Strangführung 3 und die Sekundärkühlung 4, von der Tertiärkühlung 5, wird das Strangende 1c durch eine induktive Kopfheizung 10 erwärmt, sodass eine zu rasche Abkühlung des Strangendes 1c verhindert wird.The Fig 1e shows the situation after the strand end 1c of the strand 1 has passed the secondary cooling zone 3, the secondary cooling has ended and the strand end 1c is flush with the upper end of the tertiary cooling zone 5. In the tertiary cooling zone 5, the slow, controlled or regulated cooling of the partially solidified strand 1b is ensured by the thermal insulation 9 and the heating of the strand by the heating device 7 which can be moved in the pull-out direction A (see Fig 1f ). After the machine head has been separated and lifted off, comprising the continuous mold 2, the strand guide 3 and the secondary cooling 4, from the tertiary cooling 5, the strand end 1c is heated by an inductive head heater 10, so that the strand end 1c is prevented from cooling too quickly.

Gemäß den Figuren la...lf wurde ein runder Stahlstrang 1 mit einem Durchmesser von 1200 mm und einer Länge von 10 m produziert. Die Auszugsgeschwindigkeit des Strangs 1 aus der Durchlaufkokille 2 beträgt 0,25 m/min. Durch die Wärmeisolation 9 und das Wiedererwärmen des Strangs 1 durch die verfahrbare Heizeinrichtung 7 wird die vollständige Durcherstarrung des Strangs 1 erst nach 13 h erreicht. Das Vergießen des Strangs - ohne dem langsamen Abkühlen des Strangs in der Tertiärkühlzone 5 - wurde aber bereits nach 46 min beendet. Da das Vergießen im Gegensatz zur langsamen Durcherstarrung rasch beendet ist, ist es zur Erhöhung des Durchsatzes des semi-kontinuierlichen Stranggießverfahrens vorteilhaft, wenn der in Fig 1f nicht mehr dargestellte Maschinenkopf von der Tertiärkühlzone 5 getrennt und quer zur Auszugsrichtung A zu einer weiteren Tertiärkühlzone 5 verfahren wird. Dort kann ein neuer Strang vergossen werden, währenddessen der in Fig 1f dargestellte Strang 1 weiter langsam abgekühlt wird. Nach dem langsamen Abkühlen des Strangs 1 bis zu dessen vollständiger Durcherstarrung wird der Strang aus der Stranggießmaschine ausgefördert, bspw. durch eine Vorrichtung gem. den Fig 8a und 8b.According to the figures la ... lf, a round steel strand 1 with a diameter of 1200 mm and a length of 10 m was produced. The pull-out speed of the strand 1 from the continuous mold 2 is 0.25 m / min. Due to the heat insulation 9 and the reheating of the strand 1 by the movable heating device 7, the complete solidification of the strand 1 is only achieved after 13 hours. The casting of the strand - without the slow cooling of the strand in the tertiary cooling zone 5 - was ended after only 46 minutes. In contrast to the slow solidification, the casting process is completed quickly, which is why it increases the throughput of the semi-continuous continuous casting process advantageous if the in Fig 1f Machine head, no longer shown, is separated from the tertiary cooling zone 5 and is moved transversely to the pull-out direction A to a further tertiary cooling zone 5. A new strand can be cast there, while the in Fig 1f strand 1 shown is cooled further slowly. After slow cooling of the strand 1 until it has completely solidified, the strand is conveyed out of the continuous casting machine, for example by a device according to the 8a and 8b .

In der Fig 2a ist eine erste alternative Ausführungsform der Tertiärkühlzone 5 von Fig 1 dargestellt. Dabei wird der Raum zwischen dem Strang 1 und der Wärmeisolierung 9 durch eine Strahlpumpe 15 evakuiert, wodurch eine gute Wärmeisolation und eine langsame Abkühlung erreicht wird. Außerdem wird die Oberfläche des Strangs 1 vor Verzunderung geschützt und die Restschmelze entgast. Die Strahlpumpe ist einfach und verschleißfrei; dessen Druckanschluss wird mit einem Druckluftanschluss P und dessen Sauganschluss mit dem zu evakuierenden Raum innerhalb der Tertiärkühlzone verbunden. Das Abblasen kann gegen Umgebungsdruck U erfolgen. Die induktive Kopfheizung 10 ist gegenüber einer Plasmaheizung vorteilhaft, da das magnetische Feld auch durch die Wärmisolierung des Strangendes 1c wirkt.In the Fig 2a FIG. 4 is a first alternative embodiment of the tertiary cooling zone 5 of FIG Fig. 1 shown. The space between the strand 1 and the heat insulation 9 is evacuated by a jet pump 15, as a result of which good heat insulation and slow cooling are achieved. In addition, the surface of the strand 1 is protected against scaling and the residual melt is degassed. The jet pump is simple and wear-free; its pressure connection is connected to a compressed air connection P and its suction connection to the room to be evacuated within the tertiary cooling zone. The blowing off can take place against ambient pressure U. The inductive head heater 10 is advantageous over a plasma heater, since the magnetic field also acts through the thermal insulation of the strand end 1c.

Die Fig 2b zeigt eine zweite Alternative der Tertiärkühlzone 5 von Fig 1. Dabei sind die Isolationslamellen 9a der Wärmeisolierung 9 zur Auszugsrichtung verschwenkbar, sodass der Luftwechsel zwischen der Umgebungsluft und dem Strang 1 im Inneren der Tertiärkühlzone 9 einstellbar ist. Lediglich zur Illustration der Funktion der Isolationslamellen 9a wurden die Isolationslamellen 9a auf der rechten Seite des Strangs 1 geschlossen und auf der linken Seite um 10° zur Auszugsrichtung A geöffnet dargestellt. Die Verstellung der Lamellen 9a kann entweder manuell oder durch Aktoren erfolgen.The Fig. 2b shows a second alternative of the tertiary cooling zone 5 of FIG Fig. 1 . The insulation lamellae 9a of the heat insulation 9 can be pivoted to the pull-out direction, so that the air change between the ambient air and the strand 1 can be set inside the tertiary cooling zone 9. Only to illustrate the function of the insulation slats 9a, the insulation slats 9a on the right side of the strand 1 were closed and shown on the left side opened by 10 ° to the pull-out direction A. The slats 9a can be adjusted either manually or by actuators.

Die Fig 3 zeigt schematisch den zeitlichen Verlauf des Verfahrwegs s der induktiven Heizvorrichtung 7 zum Wiedererwärmen der Mantelfläche des Strangs 1. Hierbei ist die Heizvorrichtung 7 im oberen Bereich des Strangs 1 durchgezogen und im unteren Bereich strichliert dargestellt. Da sich die Erstarrungsfront während der Abkühlung von unten nach oben (d.h. vom Stranganfang 1a zum Strangende 1c) verschiebt, verringert sich auch der Verfahrweg s der Heizvorrichtung 7 über der Zeit. Alternativ zu einer verfahrbaren Heizvorrichtung 7 könnten auch mehrere, in Auszugsrichtung A verteilt über die Länge der Tertiärkühlzone 5 angeordnete Heizeinrichtungen (z.B. Brenner) verwendet werden.The Fig 3 shows schematically the time course of the travel path s of the inductive heating device 7 for reheating the outer surface of the strand 1. Here, the heating device 7 is drawn through in the upper region of the strand 1 and shown in dashed lines in the lower region. Since the solidification front shifts from the bottom to the top during cooling (ie from the start of the strand 1a to the end of the strand 1c), the travel path s of the heating device 7 also decreases over time. As an alternative to a movable heating device 7, it would also be possible to use a plurality of heating devices (for example burners) arranged in the pull-out direction A and distributed over the length of the tertiary cooling zone 5.

Die Fig 4 zeigt die Temperaturen in °C des gemäß Fig 1 erzeugten Strangs 1 in einer Schnittdarstellung 3h nach Gießstart (Teilfigur 1), 8,3h nach Gießstart (Teilfigur 2) und bei Durcherstarrung des Strangs 1, ca. 13h nach Gießstart (Teilfigur 3). Der zeitliche Verlauf der Temperaturen des Strangs 1 an unterschiedlichen Positionen an der Oberfläche und im Zentrum des Strangs sind in Fig 5 dargestellt. Daraus geht hervor, dass das Vergießen des Strangs und damit auch die Primär- und die Sekundärkühlung 46 min nach dem Gießstart beendet wird und anschließend der Strang 1 lediglich durch die Tertiärkühlung 5 kontrolliert abgekühlt wird.The Fig. 4 shows the temperatures in ° C according to Fig. 1 produced strand 1 in a sectional view 3h after casting start (part figure 1), 8.3h after casting start (part figure 2) and when the strand 1 has solidified, about 13h after casting start (part figure 3). The time course of the temperatures of strand 1 at different positions on the surface and in the center of the strand are shown in Fig. 5 shown. It can be seen from this that the casting of the strand and thus also the primary and secondary cooling is ended 46 minutes after the start of casting and then the strand 1 is cooled in a controlled manner only by the tertiary cooling 5.

In den Figuren 6a, 6b ist eine erfindungsgemäße VertikalStranggießmaschine in zwei Ansichten dargestellt. Der flüssige Stahl wird von einer Pfanne 30 über ein Schattenrohr in den Gießverteiler 31 gegossen, anschließend strömt die Schmelze über ein nicht dargestelltes Tauchrohr (SEN) in die Durchlaufkokille 2 ein. Durch die Primärkühlung in der Kokille 2 bildet sich ein teilerstarrter Strang 1 mit einer tragfähigen Strangschale aus. In der Kokille 2 wird die Schmelze durch eine optionale Rühreinrichtung 32 noch weiter beeinflusst. Der Strang 1 wird in der Strangführung 3 gestützt, geführt und in der Sekundärkühlzone 4 weiter abgekühlt. Zumindest die Durchlaufkokille 2, die Rührspule 32, die Strangführung 3 mit der Sekundärkühlzone 4, und optional auch die Tertiärkühlzone 5, sind auf einem Gießwagen 33 auf der Gießbühne G verfahrbar. Der Strang 1 mit dem Kaltstrang 6 wird über den Strangabzugswagen 11 aus der Durchlaufkokille 2 ausgezogen. Dazu wird der Strangabzugswagen 11 über vier Gewindespindeln 12 angetrieben und durch zusätzliche Führungsschienen 34 geführt, wobei ein Motor über ein Getriebe und die Gewindespindel 12 mit der Gewindemutter 13 verbunden ist. Nachdem der Gießvorgang beendet und der Strang 1 auf dem Amboss 40 abgestellt worden ist, kann der Gießwagen 33 quer zur Auszugsrichtung A zu einer weiteren Gießstation verfahren werden, da das Gießen des teilerstarrten Strangs, d.h. ohne der Tertiärkühlung des Strangs 1, wesentlich weniger Zeit benötigt als die Tertiärkühlung des Strangs 1 bis zu dessen Durcherstarrung. In der Tertiärkühlzone 5 wird der Strang 1 durch die Wärmeisolierung 9 und ggf. durch eine hier nicht dargestellte Heizeinrichtung langsam abgekühlt, sodass die Erstarrung im Zentrum des Strangs mit einer nach oben orientierten Erstarrungsfront erfolgt.In the Figures 6a , 6b a vertical continuous casting machine according to the invention is shown in two views. The liquid steel is poured from a pan 30 into the pouring manifold 31 via a shadow pipe, then the melt flows into the continuous mold 2 via a dip pipe ( SEN ), not shown. The primary cooling in the mold 2 forms a partially rigid strand 1 with a load-bearing strand shell. In the mold 2, the melt is influenced even further by an optional stirring device 32. The strand 1 is supported in the strand guide 3, guided and further cooled in the secondary cooling zone 4. At least the continuous mold 2, the stirring coil 32, the strand guide 3 with the secondary cooling zone 4, and optionally also the tertiary cooling zone 5, can be moved on a casting car 33 on the casting platform G. The strand 1 with the cold strand 6 is pulled out of the continuous mold 2 via the strand withdrawal carriage 11. For this purpose, the strand take-off carriage 11 is driven via four threaded spindles 12 and guided by additional guide rails 34, a motor being connected to the threaded nut 13 via a gear and the threaded spindle 12. After the casting process has ended and the strand 1 has been placed on the anvil 40, the casting carriage 33 can be moved transversely to the pull-out direction A to a further casting station, since the casting of the partially solidified strand, ie without the tertiary cooling of the strand 1, takes considerably less time than the tertiary cooling of strand 1 until it solidifies. In the tertiary cooling zone 5, the strand 1 is slowly cooled by the thermal insulation 9 and possibly by a heating device (not shown here), so that the solidification takes place in the center of the strand with an upwardly oriented solidification front.

Eine detailliertere Darstellung des Maschinenkopfes der Stranggießmaschine aus den Fig 6a, 6b ist in Fig 7 dargestellt.A more detailed representation of the machine head of the continuous casting machine from the Fig. 6a , 6b is in Fig. 7 shown.

Die Fig 8a, 8b zeigen schematisch eine Ausführungsform für das Ausfördern des durcherstarrten Strangs 1 aus der Tertiärkühlzone. Der Strang 1 wird durch zwei Bügel 38 seitlich gestützt, sodass auf der Stranggießmaschine auch stark unterschiedliche Durchmesser (siehe Grundriss von Fig 8a) vergossen werden können. In Fig 8a ist der Strang 1 gegenüber der Vertikalen bereits ausgeschwenkt worden und liegt an den Bügeln 38 auf. In Fig 8b wird der Strang 1 über den Schwenkantrieb 39 auf einen Rollgang 37 abgelegt, wo er in Pfeilrichtung entnommen werden kann.The Fig. 8a, 8b schematically show an embodiment for the conveying of the solidified strand 1 from the tertiary cooling zone. The strand 1 is laterally supported by two brackets 38, so that on the continuous casting machine there are also very different diameters (see floor plan of Fig 8a ) can be shed. In Fig 8a the strand 1 has already been swung out with respect to the vertical and lies on the brackets 38. In Fig 8b the strand 1 is placed on the roller drive 39 on a roller table 37, where it can be removed in the direction of the arrow.

Obwohl die Erfindung im Detail durch die bevorzugten Ausführungsbeispiele näher illustriert und beschrieben wurde, so ist die Erfindung nicht durch die offenbarten Beispiele eingeschränkt und andere Variationen können vom Fachmann hieraus abgeleitet werden, ohne den Schutzumfang der Erfindung wie in den beigefügten Ansprüchen definiert zu verlassen.Although the invention has been illustrated and described in detail by the preferred exemplary embodiments, so the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention as defined in the appended claims.

BezugszeichenlisteReference list

11
Strangstrand
1a1a
StranganfangStart of strand
1b1b
teilerstarrter Strangsemi-rigid strand
1c1c
StrangendeStrand end
22nd
Durchlaufkokille, PrimärkühlungContinuous mold, primary cooling
33rd
StrangführungStrand guide
3a3a
StrangführungsrollenStrand guide rollers
44th
Sekundärkühlung, SekundärkühlzoneSecondary cooling, secondary cooling zone
4a4a
KühldüseCooling nozzle
55
Tertiärkühlung, TertiärkühlzoneTertiary cooling, tertiary cooling zone
66
KaltstrangCold strand
77
HeizvorrichtungHeater
99
WärmeisolationThermal insulation
9a9a
IsolationspanelInsulation panel
1010th
KopfheizungHead heating
1111
StrangabzugswagenExtractor coach
1212th
GewindespindelThreaded spindle
1313
GewindemutterThreaded nut
1414
Motorengine
1515
StrahlpumpeJet pump
30, 30'30, 30 '
Pfannepan
3131
GießverteilerPouring distributor
3232
RührspuleStirring coil
3333
GießwagenWatering car
3434
FührungsschieneGuide rail
3535
OszilliereinrichtungOscillating device
3636
WasserabstreiferWater scraper
3737
RollgangRoller table
3838
Bügelhanger
3939
SchwenkantriebSwivel drive
4040
Ambossanvil
AA
AuszugsrichtungExtension direction
GG
GießbühneCasting platform
MM
GießspiegelCasting level
PP
Druck in einem DruckluftnetzPressure in a compressed air network
SS
VerfahrwegTravel
UU
UmgebungsdruckAmbient pressure

Claims (15)

  1. Method for the semi-continuous casting of a strand (1) made of steel in a continuous casting machine, wherein the continuous casting machine has
    - a cooled open-ended mold (2) for the primary cooling of the strand (1), followed by
    - a strand guide (3) for supporting and guiding the strand (1), having secondary cooling (4) for cooling the strand (1), followed in turn by
    - tertiary cooling (5) for cooling the strand (1) further, comprising the method steps:
    - start of casting in the continuous casting machine, wherein liquid steel is poured into the open-ended mold (2) closed off by a dummy bar (6) and the liquid steel forms with the dummy bar (6) a fully solidified strand start (1a) and then a partially solidified strand (1b);
    - extracting the partially solidified strand (1b) from the open-ended mold (2);
    - supporting and guiding the partially solidified strand (1b) in the strand guide (3), wherein the partially solidified strand (1b) is cooled by the secondary cooling (4);
    - end of casting in the continuous casting machine, wherein the pouring of liquid steel into the open-ended mold (2) is ended and a strand end (1c) forms;
    - extracting the strand end (1c) from the open-ended mold (2);
    - ending extraction, such that the strand end (1c) is located outside the open-ended mold (2);
    - ending secondary cooling (4);
    - controlled or regulated cooling of the partially solidified strand (1b) until full solidification of the strand (1) in the tertiary cooling zone (5) of the continuous casting machine, wherein the cooling takes place more strongly at the strand start (1a) and in a decreasing manner toward the strand end (1c) and the cooling of the partially solidified strand (1b) in the tertiary cooling zone (5) is set by influencing at least one from the group of:
    - thermal insulation of the strand (1, 1b),
    - heating of the strand (1, 1b),
    - surface cooling of the strand (1, 1b);
    - discharging the strand (1) from the continuous casting machine.
  2. Method according to Claim 1, characterized in that the partially solidified strand (1b) is heated in the tertiary cooling zone (5) by a heating device (7).
  3. Method according to Claim 2, characterized in that the heating device (7) is displaceable in the extraction direction (A) of the continuous casting machine.
  4. Method according to one of Claims 1 to 3, characterized in that the partially solidified strand (1b) is protected from cooling too rapidly in the tertiary cooling zone (5) by thermal insulation (9).
  5. Method according to Claim 4, characterized in that the insulating effect of the thermal insulation (9) is set.
  6. Method according to one of Claims 1 to 5, characterized in that the strand end (1c) is heated by head heating (10).
  7. Method according to one of Claims 1 to 6, characterized in that the surface of the partially solidified strand (1b) is cooled by a cooling device (4a) in the tertiary cooling zone (5) .
  8. Method according to one of the preceding claims, characterized in that the partially solidified strand (1b) is stirred in the tertiary cooling zone (5) by a stirring coil (32) that is stationary or displaceable in the extraction direction (A), or the partially solidified strand (1b) is rotated about its own axis alternately in the clockwise direction and the counterclockwise direction in the tertiary cooling zone (5).
  9. Continuous casting machine for carrying out the method according to one of Claims 1 to 8, having
    - a device (12) for extracting a strand (1) from an open-ended mold (2) and a device (37, 38, 39) for discharging the strand (1) from the continuous casting machine,
    - the cooled open-ended mold (2) for the primary cooling of the strand (1), followed by
    - a strand guide (3) for supporting and guiding the strand (1), having a secondary cooling zone (4) for cooling the strand (1), followed in turn by
    - a tertiary cooling zone (5) for cooling the strand (1) further, characterized
    in that the tertiary cooling zone (5) has thermal insulation (9) that is statically presettable or settable in a dynamically controlled or regulated manner for the controlled or regulated cooling of the partially solidified strand (1b), wherein the adjustable thermal insulation (9) has at least one insulation panel (9a) which is displaceable in the extraction direction (A) or pivotable with respect to the extraction direction (A).
  10. Continuous casting machine according to Claim 9, characterized in that the tertiary cooling zone (5) has a heating device (7).
  11. Continuous casting machine according to either of Claims 9 and 10, characterized by a plurality of tertiary cooling zones (5) that are offset transversely to the extraction direction (A) of the continuous casting machine, wherein the machine head of the continuous casting machine, comprising the open-ended mold (2), is connectable to and separable from a tertiary cooling zone (5).
  12. Continuous casting machine according to Claim 11, characterized in that a plurality of tertiary cooling zones (5) are arranged one after another in an arcuate or linear manner.
  13. Continuous casting machine according to one of Claims 10 to 12, characterized in that the continuous casting machine has a strand extraction carriage (11) for extracting the strand (1), wherein the strand extraction carriage (11) is displaceable in the extraction direction (A).
  14. Continuous casting machine according to Claims 10 and 13, characterized in that the strand extraction carriage (11) is connected to the machine head and both are displaceable transversely to the extraction direction (A).
  15. Continuous casting machine according to one of Claims 10 to 14, characterized in that the machine head is stationary and the strand (1) is displaceable transversely to the extraction direction (A).
EP17173954.3A 2014-03-27 2015-01-27 Semi-continuous strand casting of a steel bar Active EP3251773B1 (en)

Applications Claiming Priority (3)

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EP14162061 2014-03-27
PCT/EP2015/051619 WO2015079071A2 (en) 2014-03-27 2015-01-27 Semi-continuous casting of a steel strip
EP15702712.9A EP3122492B2 (en) 2014-03-27 2015-01-27 Semi-continuous casting of a steel ingot

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EP15702712.9A Division EP3122492B2 (en) 2014-03-27 2015-01-27 Semi-continuous casting of a steel ingot

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RU2016141648A (en) 2018-04-27
US10307819B2 (en) 2019-06-04
EP3122492B1 (en) 2017-07-05
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AT515731B1 (en) 2018-08-15
CN106457371B (en) 2019-05-07
AT15215U1 (en) 2017-03-15
AT515731A2 (en) 2015-11-15
WO2015079071A2 (en) 2015-06-04
EP3122492B2 (en) 2020-06-10
EP3122492A2 (en) 2017-02-01
US20170216908A1 (en) 2017-08-03
EP3251773A1 (en) 2017-12-06

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