EP3437757A1 - Continuous casting of a metallic strand - Google Patents

Abstract

The invention relates to a method and a plant for continuous casting of a metallic strand (1) in a continuous casting machine. The object of the invention is to modify known continuous casting so that the formation of voids or cracks in the strand (1) is prevented. This object is achieved by the method according to claim 1, wherein the intensity of the secondary cooling (4) over the time t or the strand length s decreases, so that a strand beginning (1a) is cooled more intense than a strand end (1c).

Description

Field of engineering

The present invention relates to continuous casting, preferably semi-continuous, continuous casting of a metallic strand in a continuous casting machine.

• Einführen eines Kaltstrangs in die Kokille;
• Halten des Kaltstrangs in der Kokille, sodass ein Kopf des Kaltstrangs die Kokille fluiddicht verschließt;
• Angießen der Stranggießmaschine, wobei Metallschmelze in die Kokille gegossen wird und sich in der Kokille ein Gießspiegel und ein teilerstarrter Strang ausbildet;
• Beginnen des Ausziehens des Kaltstrangs aus der Kokille, wobei der Kaltstrang aus der Kokille ausgezogen wird;
• Stützen und Führen des teilerstarrten Strangs in der Strangführung, wobei der teilerstarrte Strang durch die Strangführungsrollen gestützt, geführt und durch Kühldüsen der Sekundärkühlung abgekühlt wird; und
• gesteuertes oder geregeltes Abkühlen des teilerstarrten Strangs bis zur Durcherstarrung des Strangs in der Tertiärkühlzone.

Specifically, the invention relates to a method for continuous casting, preferably for semi-continuous casting, a strand in a continuous casting machine, wherein the continuous casting a mold with a primary cooling, casting in the following direction a strand guide with several, preferably engageable with the strand, strand guide rollers for guiding and a Secondary cooling for cooling the strand, and in turn subsequently a Tertiärkühlzone for controlled or controlled cooling of the strand, comprising the steps of:

• Introducing a cold strand into the mold;
• Holding the dummy bar in the mold, so that a head of the dummy bar closes the mold fluid-tight;
• Casting the continuous casting machine, wherein molten metal is poured into the mold and forms in the mold a casting mirror and a partially solidified strand;
• Beginning to pull the cold strand out of the mold, pulling the cold strand out of the mold;
• Supporting and guiding the semi-solid strand in the strand guide, wherein the semi-solid strand is supported by the strand guide rollers, guided and cooled by cooling nozzles of the secondary cooling; and
• Controlled or controlled cooling of the partially solidified strand until the solidification of the strand in the tertiary cooling zone.

• eine Kokille mit einer Primärkühlung,
• in Gießrichtung nachfolgend eine Strangführung mit mehreren, vorzugsweise an den Strang anstellbaren, Strangführungsrollen zum Führen und Stützen des Strangs, sowie eine Sekundärkühlung zum Abkühlen des Strangs, und
• wiederum nachfolgend eine Tertiärkühlzone zum gesteuerten oder geregelten Abkühlen des Strangs aufweist.

Moreover, the invention relates to a continuous casting machine for continuous casting, preferably for semi-continuous casting, of a metallic strand, the

• a mold with a primary cooling,
• in the casting direction below a strand guide with several, preferably engageable with the strand, strand guide rollers for guiding and supporting the strand, and a secondary cooling to cool the strand, and
• in turn subsequently has a Tertiärkühlzone for controlled or controlled cooling of the strand.

State of the art

The generic method and a suitable system are from WO 2015/079071 known. Through the tertiary cooling zone with the adjustable insulation panels, the cooling rate of the strand can be fine-tuned from bottom to top. As a result, the formation of cavities in the strand is prevented, so that liquid molten steel can compensate for the solidification-induced volume jumps between the solid and liquid phase. The internal quality of the strand is thereby significantly improved. How the inner quality of the strand can be further improved, is not apparent from the Scriptures.

Summary of the invention

The object of the invention is to modify known continuous casting processes so that cavities or cracks in the strand are prevented even more consistently. This should further improve the internal quality of the cast strand.

The output according to the invention is solved by the subject matter of claim 1. Advantageous embodiments are the subject of the dependent claims.

Specifically, the solution is carried out by a generic method, wherein the intensity of the secondary cooling over the time t or the strand length s decreases, so that a Stranganfang is cooled more intense than a strand end.

By this measure, a strand, typically a steel strand or a strand of a so-called superalloy (see https://de.wikipedia.org/wiki/Superlegierung, for example, a nickel-based alloy), produced with a pronounced V-shaped configuration of the strand shells. In other words, the thickness growth of the strand shells in the casting direction increases rapidly, so that the strand shell at the lower end of the strand is substantially thicker than at the upper end. As a result, liquid molten metal can directly fill any voids caused by the solidification, which improves the internal quality of the strand.

It is expedient if a pressure p and / or a flow rate Q of a coolant discharged through a cooling nozzle onto the strand are influenced in order to set the intensity.

• einer chemischen Zusammensetzung der Metallschmelze,
• der Primärkühlung des Strangs in der Kokille,
• einer Auszugsgeschwindigkeit des Strangs aus der Kokille, ständig das Ist-Temperaturfeld des Strangs einschließlich der Ist-Phasengrenzen zwischen den festen, teigigen und flüssigen Phasen im Strang berechnet, wobei die Intensität der Sekundärkühlung, wie ein Druck p und/oder eine Durchflussrate Q eines durch eine Kühldüse auf den Strang ausgebrachten Kühlmittels, in Abhängigkeit des Ist-Temperaturfelds und/oder der Ist-Phasengrenzen, insbesondere der Ist-Position der Sumpfspitze, eingestellt wird.

It is particularly advantageous if a thermal calculation model during continuous casting in dependence

• a chemical composition of the molten metal,
• the primary cooling of the strand in the mold,
• an extraction rate of the strand from the mold, constantly the actual temperature field of the strand including the actual phase boundaries between the solid, doughy and liquid phases in the strand calculated, the intensity of the secondary cooling, such as a pressure p and / or a flow rate Q of a through a cooling nozzle on the strand discharged coolant, depending on the actual temperature field and / or the actual phase boundaries, in particular the actual position of the sump tip is set.

The calculation of the actual temperature field and the control of the secondary cooling is eg from the DE 44 17 808 or from the WO 2009/141205 known. Details will be in this application included by reference. By this embodiment, the intensity of the secondary cooling or the pressure p and / or the flow rate Q, for example, be set so that the actual position of a time-dependent desired position of the sump tip corresponds as possible.

In addition to changing the intensity of the secondary cooling during the casting process, it is advantageous to set a heat transfer coefficient U of a heat insulation in the tertiary cooling zone as a function of the actual temperature field and / or the actual phase boundaries, in particular the actual position of the sump tip.

Furthermore, it is favorable that after commencing the drawing, the cold strand is drawn out of the mold at a first drawing speed v ₁ and then the drawing speed v of the cold strand is increased to a second drawing speed v ₂ , where v ₂ > v ₁ .

Increasing the pull-out speed v takes place as a function of the time t or the strand length s. Preferably, the increase is piecewise continuous, preferably at least once continuously differentiable.

The latter measures also have a very positive effect on the V-shaped design of the strand shell.

In general, it is advantageous if the strand is thermally insulated in the tertiary cooling zone by a thermal insulation, wherein a heat transfer coefficient U of the heat insulation increases in the casting direction. This will cause the lower end of the strand, i. the strand head, more cooled than the top of the strand, i. the string foot.

A further improvement in the internal quality of the strand can be achieved if the continuous casting machine comprises a strand-movable in the casting direction, the Strand agitator during the extraction and after completing the withdrawal of the cold strand from the mold, the area of the bottom of the strand strand is electromagnetically stirred.

The object of the invention is also achieved by a continuous casting plant according to claim 10. Advantageous embodiments are the subject of the dependent claims.

Specifically, the solution is carried out by a generic continuous casting machine having a control or regulating device for time or strand length-dependent control or regulation of the intensity of the secondary cooling.

• einer chem. Zusammensetzung der Metallschmelze,
• einer Auszugsgeschwindigkeit des Strangs aus der Kokille,
• der Primärkühlung des Strangs in der Kokille, ständig das Ist-Temperaturfeld des Strangs einschließlich der Ist-Phasengrenzen zwischen den festen, teigigen und flüssigen Phasen im Strang zu berechnen, wobei die Intensität der Sekundärkühlung in Abhängigkeit des Ist-Temperaturfelds und/oder der Ist-Phasengrenzen, insbesondere der Ist-Position der Sumpfspitze, eingestellt werden kann.

It is advantageous if the control or regulating device comprises a thermal calculation model which is suitable during continuous casting in dependence

• a chem. Composition of molten metal,
• an extraction speed of the strand from the mold,
• the primary cooling of the strand in the mold to constantly calculate the actual temperature field of the strand including the actual phase boundaries between the solid, doughy and liquid phases in the strand, the intensity of the secondary cooling being dependent on the actual temperature field and / or the actual temperature. Phase boundaries, in particular the actual position of the sump tip, can be adjusted.

It is particularly advantageous if an extraction speed v of the strand from the mold and / or a heat transfer coefficient U of a heat insulation in the tertiary cooling zone can be set as a function of the actual temperature field and / or the actual phase boundaries, in particular the actual position of the sump tip ,

Brief description of the drawings

• Fig 1a bis 1h die Verfahrensschritte bei der Durchführung des Verfahrens,
• Fig 2a ein stranggegossener Strang nach dem Stand der Technik,
• Fig 2b ein stranggegossener Strang, der gemäß der Erfindung hergestellt wurde,
• Fig 3a ein Verlauf einer Ausziehgeschwindigkeit eines Strangs aus einer Kokille über der Zeit t,
• Fig 3b ein Verlauf einer Ausziehgeschwindigkeit eines Strangs aus einer Kokille über der Stranglänge s,
• Fig 4a ein Verlauf einer Durchflussrate Q eines Kühlmittels durch eine Kühldüse über der Zeit t,
• Fig 4b ein Verlauf einer Durchflussrate Q eines Kühlmittels durch eine Kühldüse über der Stranglänge s,
• Fig 5 ein Darstellung einer auf einen Strang akkumulierten Kühlmittelmenge,
• Fig 6 eine Darstellung einer variablen Isolierung in der Tertiärkühlzone,
• Fig 7a eine Darstellung einer variablen Wärmeisolation in der Tertiärkühlzone durch verschwenkbare Isolierklappen,
• Fig 7b eine Darstellung einer variablen Wärmeisolation in der Tertiärkühlzone durch verschiebbare Isolierklappen,
• Fig 8a eine Darstellung einer nicht erfindungsgemäßen Stranggießmaschine mit einer Steuer- und Regeleinrichtung zur Einstellung der Auszugsgeschwindigkeit v,
• Fig 8b eine Darstellung einer erfindungsgemäßen Stranggießmaschine mit einer Steuer- und Regeleinrichtung zur Einstellung der Intensität der Sekundärkühlung,
• Fig 8c eine Darstellung einer nicht erfindungsgemäßen Stranggießmaschine mit einer Steuer- und Regeleinrichtung zur Einstellung der Wärmeisolierung in der Tertiärkühlzone,
• Fig 9a bis 9e eine Darstellung von Verfahrensschritten auf einer alternativen Stranggießmaschine zu den Fig 1a...1h,
• Fig 10 eine Darstellung einer Kopfisolierung, und
• Fig 11 eine Darstellung der Position der Sumpfspitze im Strang über der Zeit gemäß dem Stand der Technik und der Erfindung.

Further advantages and features of the present invention will become apparent from the description of non-limiting Embodiments. The following schematically illustrated figures show:

• Fig 1a to 1h the process steps in carrying out the process,
• Fig. 2a a continuous casting strand according to the prior art,
• Fig. 2b a continuously cast strand made according to the invention,
• Fig. 3a a course of a withdrawal speed of a strand from a mold over the time t,
• Fig. 3b a course of a withdrawal speed of a strand from a mold over the strand length s,
• Fig. 4a a profile of a flow rate Q of a coolant through a cooling nozzle over the time t,
• 4b a profile of a flow rate Q of a coolant through a cooling nozzle over the strand length s,
• Fig. 5 an illustration of a quantity of coolant accumulated on a line,
• Fig. 6 a representation of a variable insulation in the tertiary cooling zone,
• Fig. 7a a representation of a variable heat insulation in the tertiary cooling zone by means of pivotable insulating flaps,
• Fig. 7b a representation of a variable heat insulation in the tertiary cooling zone by sliding insulating flaps,
• Fig. 8a a representation of a non-inventive continuous casting machine with a control and regulating device for adjusting the pull-out speed v,
• Fig. 8b a representation of a continuous casting machine according to the invention with a control and regulating device for adjusting the intensity of the secondary cooling,
• Fig. 8c a representation of a non-inventive continuous casting machine with a control and regulating device for adjusting the thermal insulation in the tertiary cooling zone,
• 9a to 9e a representation of process steps on an alternative continuous casting machine to the Fig. 1a ... 1h .
• FIG. 10 a representation of a head insulation, and
• Fig. 11 a representation of the position of the sump tip in the strand over time according to the prior art and the invention.

Description of the embodiments

In the FIGS. 1a ... 1h is the continuous casting, specifically the so-called semi-continuous continuous casting, a strand 1 shown in steel. The continuous casting machine is designed as a vertical installation and has as main components a water-cooled mold 2, a strand guide 3 comprising a plurality of strand guide rollers 3a engageable with the strand 1 and a secondary cooling 4 with a plurality of cooling nozzles 4a and a tertiary cooling zone 5 with a thermal insulation 9 and several insulation panels 9a on. The machine head of the continuous casting machine, comprising the mold 2 and the strand guide 3, are movable relative to the tertiary cooling zone 5, so that a single machine head can supply strands to several tertiary cooling zones. The strand guide rollers 3a need not necessarily be adjustable via an actuator to the strand 1. It is sufficient, if they can be adjusted mechanically, eg via washers or so-called shims .

In Fig. 1a the situation is shown before casting the continuous casting machine. A cold strand 6 was introduced into the mold 2, so that the stationary cold strand 6, the mold in the casting direction G fluid-tight seals.

In 1b is the casting of the continuous casting machine shown. A molten steel or a melt of a so-called superalloy is fed into the mold 2 either directly or via a distributor vessel, so that a casting level M is formed in the mold 2 and a strand 1 due to the primary cooling of the mold 2. After a somewhat constant pouring M has been set, is started with the extraction of the cold strand 6 from the mold 2. Initially, the drawing off takes place relatively slowly with a first drawing speed v ₁ of 0.12 m / min (see Fig. 3a ). The extraction speed v is determined according to Fig. 3a increased, so that a strand 1 forms with a pronounced V-shape of the strand shells (see Fig. 2b ). In contrast, the strand 1 in prior art continuous casting processes (see Fig. 2a ) does not have a pronounced V-shape, resulting in poor internal quality (such as cracks, voids, etc.). Due to the pronounced V-shape of the strand shells 11 of the strand 1 (see Fig. 2b ), the strand 1 during cooling in the Tertiärkühlzone 5 molten liquid melt from the upper portion of the partially solidified strand 1b so that any caused by the solidification cavities or cracks are refilled by melt. A thin strand shell 11 at the upper end of the strand 1c facilitates this crucial. The mold 2 is oscillated by an oscillator, not shown, in the vertical direction. A stirring coil, also not shown below the mold 2 stirs the partially solid strand. Both details are customary and eg from the WO 2015/079071 known.

In Fig. 1c the continuous casting is more advanced, wherein the strand 1 is supported and guided in the strand guide 3 by the strand guide rollers 3a and further cooled by the cooling nozzles 4a of the secondary cooling 4. According to the solid line of Fig. 3a is the extraction speed at the time of Fig. 1c in about 0.2 m / min.

In Fig. 1d is the time in continuous casting shown, in which the supply of molten steel was just stopped in the mold. The drawing speed v corresponds to the second drawing speed v ₂ of 0.36 m / min. This pull-out speed of the strand 1 is maintained until the end of the pull-out operation (see Fig. 3a ).

After the supply of molten steel has been stopped, the pouring mirror G in the mold 2 drops (see Fig. 1e ). At this time, the strand 1 has a strand length L of typically 6 to 12m. The diameter of the strand 1 is 600 mm.

The Fig. 1f shows the situation after the strand end 1c has passed the strand guide 3 and the secondary cooling 4 has been switched off. The partially solided strand 1b is then in the Tertiärkühlzone 5 and is slowly controlled or controlled cooled.

In the Fig. 1g and 1h the cooling of the partially solidified strand 1b in the tertiary cooling zone 5 is shown, the time of the Fig. 1g before the time of Fig. 1h is. As already indicated above, the machine head can serve several tertiary cooling zones 5 and, for example, can be moved in a horizontal direction to a further tertiary cooling zone 5. In order to further delay the solidification of the strand end 1 c, instead of the secondary cooling 4, the strand end 1 c can be heated by a head heater 13. The head heater 13 can be made, for example, inductively or by an exothermic powder (the process is referred to as "hot topping"), wherein the powder generates heat energy with the liquid molten steel. Since the partially solidified strand 1b in the region of the sump tip is particularly susceptible to cracks or cavities, it is advantageous if a strand agitator 14 in particular electromagnetically stirs this region.

The Fig. 2a shows a continuous cast semi-solid strand 1b according to the prior art. The strand end is almost completely solidified, so that any voids or cracks in the strand can not be filled by liquid melt 12.

In contrast, shows Fig. 2b a strand of the invention. The strand end 1 c is still largely liquid, so that any voids or cracks in the strand can be filled by liquid melt 12. As a result, the strand has a better internal quality.

As stated above, the shows Fig. 3a the extraction speed v over time t. It can be seen from the diagram that the pull-out speed v does not necessarily have to be increased linearly, but also, for example, under- or over-linear (see dashed lines). Even an increase, not shown, in discrete stages would be conceivable and could be useful.

The Fig. 3b shows another diagram for the extraction speed v, where v depends not on the time t but on the strand length s. This ensures that the strand beginning 1a is cooled more strongly than the strand end 1c, regardless of any interruptions in the casting process.

In both cases, not only the internal quality of the strand 1 is increased by increasing the extraction speed v, but also the economy of the Continuous casting process improved because more strands can be cast within the same time.

The internal quality of the strand is inventively by adjusting the intensity of the secondary cooling 4 as a function of time or the strand length s (see Fig. 1c ) improved. In both cases, this means that the strand beginning 1a is cooled more strongly in the secondary cooling 4 than the strand end 1c. This measure is in addition to increasing the Ausziehgeschwindigkeit v of the dummy bar 6 from the mold 2 or instead of it.

In the event that the adjustment of the intensity of the secondary cooling 4 takes place in addition to the change of the withdrawal speed v, the description of the Figures 1a-1h still fully valid. In addition, the intensity of the secondary cooling is varied as a function of the time t or the strand length s. The time-dependent change in the intensity of the secondary cooling by a change in the flow rate Q through the cooling nozzles 4a of the secondary cooling 4 is in Fig. 4a shown. The decrease of the flow rate Q or the intensity of the secondary cooling 4 can be linear (continuous line) but also sub-linear or superlinear (see dashed lines). Alternatively, the intensity of the secondary cooling can also be varied as a function of the strand length s (see 4b ). In this case, the strand length s during casting is calculated and the intensity of the secondary cooling 4 is determined according to the characteristic of 4b set.

In the event that the adjustment of the intensity of the secondary cooling 4 takes place instead of the change of the withdrawal speed v, the description of the Figures 1a-1h modify so that the extraction speed v remains constant. The drawn out of the mold 2 strand 1 is cooled in the secondary cooling zone 4 either time or strand length-dependent variable intensity, so that the strand beginning 1a is cooled more strongly than the strand end 1c.

In Fig. 5 schematically shows the accumulated on the different areas of a teilerstarrten strand 1b amounts of coolant in the time or strand length-dependent adjustment of the intensity of the secondary cooling (see Fig. 4a or 4b ). A high accumulated amount of refrigerant, such as at the lower run 1a, was finely screened and a low accumulated amount of refrigerant, as at the upper end of the line 1c, was shown roughly rastered. Due to the time or strand length-dependent change in the flow rate Q or a time or strand length-dependent change in the pressure p of the coolant, the intensity of the secondary cooling is changed so that the strand start is cooled more than the strand end.

In Fig. 6 Another way to improve the internal quality of the strand is shown. In this case, the heat insulation 9 is set in the tertiary cooling zone 5 as a function of the strand length L, wherein a heat transfer coefficient U of the heat insulation 9 in the casting direction G increases. In other words, the strand beginning 1a is cooled more strongly in the teritary cooling 5 than the strand end 1c. This measure can be done either in addition to or instead of increasing the Ausziehgeschwindigkeit v of the dummy bar 6 from the mold 2. It would also be possible for the change in the thermal insulation 9 in the tertiary cooling zone 5 to take place in addition to or instead of adjusting the intensity of the secondary cooling 4. The change in the heat transfer coefficient U of the heat insulation 9 is in Fig. 6 represented by a variable thickness of the insulation.

In Fig. 7a the strand length-dependent change of the thermal insulation 9 in the tertiary cooling zone 5 is represented by insulation panels 9a. In order to cool the strand beginning 1a stronger than the strand end 1c, the pivotable flaps of the insulation panels are different set, the upper flaps are largely closed and the lower flaps are largely open. As a result, a heat transfer coefficient U of the heat insulation 9 in the casting direction G increases. The change in the opening angle of the flaps can be preset either statically or dynamically, for example via pivoting drives for pivoting the flaps, during the cooling in the tertiary cooling zone 5.

The Fig. 7b shows an alternative to Fig. 7a , wherein the degree of coverage of the insulating flaps 9a of the strand at the strand end 1c is higher than at the strand beginning. This also increases the heat transfer coefficient U of the heat insulation 9 in the casting direction G.

In Fig. 8a is a non-inventive continuous casting machine with a control or regulating device 10 for controlling or regulating the pullout speed v shown. Taking into account the chemical composition 15 of the molten metal, the primary cooling 2a in the mold 2, the secondary cooling 4 and the strand length s, the control or regulating device 10 calculates the temperature field and the sump tip in the cast strand 1 and sets the withdrawal speed of the motor 16 as a function of Swamp tip. Optionally, it would also be possible to consider other parameters such as the position of the insulating panels 9a in the tertiary cooling zone.

The Fig. 8b shows a continuous casting machine according to the invention with a control or regulating device 10 for controlling or regulating the intensity of the secondary cooling 4 as a function of the strand length s. The controller 10 calculates, considering the chemical composition 15 of the molten metal and the primary cooling 2a in the mold and the strand length s, the temperature field and the sump tip in the cast strand 1 and adjusts the intensity of the secondary cooling 4 as a function of the sump tip. The sump tip is calculated in real time in a thermal calculation model.

The Fig. 8c shows a continuous casting machine not according to the invention with a control or regulating device 10 for controlling a heat transfer coefficient U of the heat insulation 9 in the Tertiärkühlzone 5. The control device 10 calculated taking into account the chemical composition 15 of the molten metal and the primary cooling 2a in the mold the temperature field and the sump tip in the cast strand 1 and sets the opening angle of the Isolierpanele 9 a depending on the sump tip. The sump tip is calculated in real time in a thermal calculation model.

In the 9a to 9e an alternative continuous casting machine for carrying out the method according to the invention is shown. In Fig. 9a we poured a strand 1 in the mold 2 and pulled out with variable withdrawal speed v from the mold. The strand 1 is supported and guided in the strand guide 3 and cooled by the secondary cooling. In Fig. 9b the casting in the mold was stopped and the strand 1 is located in a radiation area 17, where it can radiate heat to the environment over a certain time. On the way to the tertiary cooling zone 5, the strand passes through a stirring coil 14 and is electromagnetically stirred by this, see Fig. 9c , The strand is then introduced into the tertiary cooling zone 5, where it is cooled or controlled by the heat insulation 9. Since, in particular, the strand end 1 c is particularly sensitive, it is again thermally insulated by a lid, see 9d and 9e ,

In FIG. 10 schematically a head insulation 18 of a strand 1 is shown. The head insulation has a heat insulation 9 for the strand end 1c of the strand 1, so that the strand end 1c remains liquid longer. In addition to the thermal insulation 9, an exothermic powder 19 on the liquid strand end 1c be abandoned, which additionally heats the strand 1.

In Fig. 11 is schematically shown the result of the time- or distance-dependent adjustment of the extraction speed v and / or the time- or distance-dependent adjustment of the intensity of the secondary cooling and / or the setting of a heat transfer coefficient U of the heat insulation 9. All of these measures have the effect of slowing down the solidification of the partially solidified strand (see the dashed line indicating the position of the sump tip in the strand over time). In contrast, the solid line indicates the comparison with the prior art. As stated above, these measures lead to the strand of the invention having a pronounced V-shape of the strand shell (see Fig. 11 right) in contrast to strands of the prior art without pronounced V-shape of the strand shell (see Fig. 11 Left).

While the invention has been further illustrated and described in detail by the preferred embodiments, 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.

LIST OF REFERENCE NUMBERS

1

strand

1a

train early

1b

partially solid strand

1c

strand end

2

mold

2a

primary cooling

3

strand guide

3a

Strand guide rolls

4

Secondary cooling, secondary cooling zone

4a

cooling nozzle

5

Tertiary cooling, tertiary cooling zone

6

dummy bar

7

computer model

8th

crater tip

9

thermal insulation

9a

insulation panel

10

Control or regulating device

11

strand shell

12

liquid area of the strand

13

Heating head

14

Strangrührer

15

chemical composition

16

engine

17

radiation range

18

head insulation

19

exothermic powder

G

casting

L

strand length

M

meniscus

Q

Flow rate

S

strand length

t

Time

U

Heat transfer coefficient

v

Extraction speed, casting speed

Claims (12)

Method for continuous casting, preferably for semi-continuous casting, of a strand (1) in a continuous casting machine, wherein the continuous casting machine comprises a mold (2) with a primary cooling (2a), in the casting direction (G) subsequently a strand guide (3) with a plurality of strand guide rolls ( 3a) for guiding and a secondary cooling (4) for cooling the strand (1), and in turn subsequently a tertiary cooling zone (5) for the controlled or controlled cooling of the strand (1), comprising the method steps: - Introducing a cold strand (6) in the mold (2); - Keep the cold strand (6) in the mold (2), so that a head of the cold strand (6) the mold (2) closes fluid-tight; - Casting the continuous casting machine, wherein molten metal is poured into the mold (2) and in the mold (2) a casting mirror (M) and a partially solidified strand (1b) is formed; - Starting to pull out the cold strand (6) from the mold (2), wherein the cold strand (6) from the mold (2) is pulled out; Supporting and guiding the partially solidified strand (1b) in the strand guide (3), wherein the partially solidified strand (1b) is supported by the strand guiding rolls (3a) and cooled by cooling nozzles (4a) of the secondary cooling (4); - controlled or controlled cooling of the partially solidified strand (1b) until solidification of the strand (1) in the tertiary cooling zone (5); characterized in that the intensity of the secondary cooling (4) over the time t or the strand length s decreases, so that a strand beginning (1a) is cooled more intense than a strand end (1c). A method according to claim 1, characterized in that a thermal calculation model (7) during the continuous casting in dependence - a chem. Composition (15) of the molten metal, the primary cooling (2a) in the mold (2), a pull-out speed v of the strand (1) from the mold (2), continuously calculates the actual temperature field of the strand (1) including the actual phase boundaries between the solid, doughy and liquid phases in the strand (1), the intensity of the secondary cooling (4) being dependent on the actual temperature field and / or the actual temperature. Phase boundaries, in particular the actual position of the sump tip (8) is set. A method according to claim 2, characterized in that the intensity of the secondary cooling in dependence of the actual temperature field and / or the actual phase boundaries, in particular the actual position of the sump tip (8) is set. A method according to claim 2 or 3, wherein the strand (1) is thermally insulated in the tertiary cooling zone (5) by a thermal insulation (9), characterized in that a heat transfer coefficient U of the thermal insulation (9) as a function of the actual temperature field and / or the actual phase boundaries, in particular the actual position of the sump tip (8), is set. Method according to one of the preceding claims, characterized in that after the beginning of the drawing, the cold strand (6) is pulled out of the mold (2) at a first drawing speed v ₁ and then the drawing speed v of the cold strand (6) is extended to a second drawing speed v ₂ , where v ₂ > v ₁ . A method according to claim 5, characterized in that the raising of the extraction speed v as a function of the time t or the strand length s occurs. A method according to claim 6, characterized in that the raising of the extraction speed v piecewise continuous, preferably at least once continuously differentiable occurs. Method according to one of the preceding claims, characterized in that the strand (1) in the tertiary cooling zone (5) by a thermal insulation (9) is thermally insulated, wherein a heat transfer coefficient U of the heat insulation (9) in the casting direction (G) increases. Method according to one of the preceding claims, wherein the continuous casting machine comprises a strand agitator (14) which can be moved in the casting direction, characterized in that the strand agitator (14) moves out of the mold (2) during extraction and after completion of drawing out the cold strand (6) Area of the sump tip (8) of the strand (1) moves electromagnetically. Continuous casting machine for carrying out the method according to one of the preceding claims, wherein the continuous casting machine a mold (2) with a primary cooling (2a), - In the casting direction (G) below a strand guide (3) with a plurality of strand guide rollers (3a) for guiding and supporting the strand (1) and a secondary cooling (4) for cooling the strand (1), and - again below a Tertiärkühlzone (5) for controlled or controlled cooling of the strand (1), characterized by a control or regulating device (10) for time- or strand length-dependent control or regulation of the intensity of the secondary cooling (4). Continuous casting machine according to claim 10, characterized in that the control or regulating device (10) comprises a thermal calculation model (7) which is suitable during the continuous casting in dependence a chemical composition (15) of the molten metal, - An extraction speed (v) of the strand (1) from the mold (2), the primary cooling (2a) in the mold (2), constantly calculate the actual temperature field of the strand (1) including the actual phase boundaries between the solid, doughy and liquid phases in the strand (1), the intensity of the secondary cooling (4) depending on the actual temperature field and / or the actual Phase boundaries, in particular the actual position of the sump tip (8), can be adjusted. Continuous casting machine according to claim 11, characterized in that a drawing speed v of the strand (1) from the mold (2) and / or a heat transfer coefficient U of a thermal insulation (9) in the Tertiärkühlzone (5) in dependence of the actual temperature field and / or the Actual phase boundaries, in particular the actual position of the sump tip (8), can be adjusted.

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