AT525111A1 - Stirring cast blooms with an oscillating strand stirrer - Google Patents

Abstract

Stirring cast blooms with an oscillating strand stirrer Liquid steel (1) is poured into a continuous mold (2) from above. At the bottom, a steel strand (3) with an already solidified strand shell (4) and a core (5) that is still liquid is withdrawn from the continuous mold (2). The steel strand (3) is introduced from above into a holding device (6) without changing direction, in which the steel strand (3) remains during a solidification time. During the solidification time, the steel strand (3) gradually solidifies into a bloom. During the solidification time, the liquid core (5) is stirred using a strand stirrer (9). Furthermore, the strand stirrer (9) is moved during the solidification time with an oscillation stroke (h) oscillating between an upper and a lower reversal point (P1, P2).

Description

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description

designation of the invention

Stirring of cast blooms with oscillating strand

stirrer

field of technology

The present invention is based on a manufacturing process

drive for an advance block,

- wherein liquid steel is poured from above into a continuous mold, a steel strand with an already solidified strand shell and a still liquid core is drawn from the continuous mold below and the steel strand with the already solidified strand shell and the still liquid core is drawn from above into a holding device without changing direction is introduced, in which the steel strand remains during a solidification period in which the steel strand gradually solidifies,

- wherein the liquid core during the solidification time means

a strand stirrer is stirred.

The present invention is also based on a control program that has machine code that can be processed by a control device of a continuous casting machine to produce a billet, the processing of the machine code by the control device causing the control device to activate a strand stirrer of a holding device in which a one already solidified strand shell and a still liquid core exhibiting steel strand during a solidification time gradually solidified to the billet, controlled in such a way that during the solidification time the liquid

core is stirred by means of the strand stirrer. The present invention is also based on a control

erection of a continuous casting machine for the production of a

Vorblocks, wherein the control device with such

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computer program is programmed so that during operation it controls a strand stirrer of a holding device, in which a steel strand, which has an already solidified strand shell and a still liquid core, gradually solidifies to form the bloom during a solidification time, in such a way that during the solidification time the liquid core is agitated by means of of

Strand stirrer is stirred.

The present invention is also based on a

continuous casting machine for producing a billet,

- wherein the continuous casting machine has a continuous mold into which liquid steel is poured from above and from which a steel strand with an already solidified strand shell and a still liquid core is drawn off at the bottom,

- wherein the continuous casting machine has a holding device below the continuous mold, into which the steel strand with the already solidified strand shell and the still liquid core is introduced from above without changing direction and in which the steel strand during a solidification time, in which the steel strand gradually to the bloom frozen, remains

- wherein the holding device has a strand stirrer which can be moved vertically along the steel strand and by means of which the liquid core is stirred during the solidification time,

- wherein the continuous casting machine has a control device

has, of which at least the strand stirrer is controlled.

State of the art

Such manufacturing processes are generally known. Purely by way of example, reference can be made to WO 2015/079 071 A2, to WO 2018 192 903 A1 and to EP 3 251 773 B1. Manufacturing processes of the type mentioned above are explained in detail in these publications.

Continuous casting machines with strand stirrers are well known.

Using the strand stirrer, the internal quality of the cast

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a strand improved. In particular, center

be reduced.

In the case of continuous casting plants, there are usually several strand stirrers. For example, there is often a mold stirrer that stirs the still liquid melt in the continuous mold. Even after exiting the continuous mold, stirring often takes place at one point or at several points. Seen in the direction of casting, the last strand stirrer is usually arranged in the vicinity of the location of the continuous casting machine where the bottom tip of the cast steel strand forms. The strand stirrers are usually stationary, i.e. not in the casting direction

movable or only slightly movable.

Strand stirrers are also often present in semi-continuous continuous casting installations, such as are typically used for casting blooms. In contrast to continuous casting plants, however, configurations are known in which there is only a single strand stirrer that can be moved in the casting direction. This is also explained in the patent documents mentioned at the outset.

Summary of the Invention

Despite the use of strand stirrers in semi-continuous continuous casting plants,

cast blooms still center segregation.

The object of the present invention is to create ways by which the center segregations in a simple and reliable way stronger than in the prior

technology can be reduced.

The task is through a manufacturing process with the

Features of claim 1 solved. Advantageous configuration

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of the manufacturing process are the subject of the dependent

Claims 2 to 11.

According to the invention, a manufacturing process of the type mentioned is designed in that the strand stirrer

during the solidification time with an oscillation stroke oscillating between an upper and a lower reversal point

will proceed.

Through this oscillation, center segregation can be efficiently avoided over the entire length of the cast steel strand by means of a single strand stirrer. The strand stirrer can function both as a typical strand stirrer in the narrower sense (i.e. a stirrer that stirs the steel strand in an area where the strand shell is still relatively thin) and as a final stirrer (i.e. a stirrer that stirs the steel strand in the area of the sump tip stirs) at the same time. A single stirrer thus takes on functions that are usually associated with two

stirrers can be realized.

In a simple embodiment, the upper reversal point is fixed. In particular, the upper reversal point can have a predetermined distance from the position of an upper edge of the completely cast steel strand, for example coincide with the upper edge of the completely cast steel strand or be up to approx. 30 cm below the upper edge or slightly

easily lie above the upper edge.

However, the upper reversal point is preferably variable. In this case, the position of the upper reversal point can be adapted in particular to the solidification behavior of the steel strand. For example, for this purpose the upper reversal point can be determined as a function of an upper location or as a function of a lower location. The upper location in this case is that location along the cast steel strand in the fixture where the liquidus tempera-

ture prevails. In an analogous way, the lower place is the one

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Location along the cast steel strand in the fixture where the solidus temperature prevails. With this procedure, the upper reversal point first moves down during the solidification time—namely when the steel strand is inserted into the holding device—and then gradually up. The top dead center can be determined, for example, in such a way that it is a predetermined distance above the upper location or a predetermined distance above

half of the lower place is arranged.

In a completely analogous manner, the lower reversal point is fixed in a simple embodiment. In particular, the lower reversal point can have a predetermined distance from the position of a lower edge of the completely cast steel strand, for example coincide with the lower edge of the completely cast steel strand or be up to approx. 30 cm above the lower edge or slightly below the lower edge lLie-

gene.

The lower reversal point is also preferably variable in a completely analogous manner. In this case, the position of the lower reversal point can also be adapted in particular to the solidification behavior of the steel strand. For example, for this purpose, the lower reversal point can be determined as a function of the upper location or as a function of the lower location. With this procedure - again completely analogous to the upper reversal point - the lower reversal point first moves downwards and then gradually upwards during the solidification time. The bottom reversal point can be determined, for example, in such a way that it is a predetermined distance above or below the upper location or a predetermined distance above or below the lower location.

tes is arranged.

The position of the upper and lower reversal point can in particular be matched to one another in such a way that, on the one hand, the upper reversal point is at an upper edge of the completely

cast steel strand or below and on the other hand,

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as long as the distance between the bottom dead center and the upper edge of the completely cast steel strand is at least as large as a fixed nominal lift, the top dead center is determined as a function of the bottom dead center in such a way that the oscillation lift is equal to the fixed nominal lift. On the other hand, if and as long as the bottom dead center is less than the fixed nominal stroke away from the top edge, the top dead center is set equal to the top edge of the steel strand. The latter case can occur both during the introduction of the steel strand into the holding device and when the steel strand has been completely introduced into the holding device. By appropriately coordinating the upper and lower reversal points, efficiency is increased

Stirring optimized.

The upper location and/or the lower location can be determined as required. For example, the top location and/or the bottom location may be determined as a function of time from the start of pouring or from the end of pouring. This approach is relatively easy to implement. However, it is preferable for the upper location and/or the lower location to be determined using a thermodynamic model of the steel strand. This results in an improved determination of the upper location and/or the lower

other place.

As a rule, the strand stirrer is designed as an electromagnetic stirring coil that is fed with at least one alternating current. The at least one alternating current is preferably varied during the oscillation of the strand stirrer as a function of the current position of the strand stirrer. Current strengths, frequencies, phase angles and others can characterize the at least one alternating current as required.

sizes can be varied.

The object is also achieved by a control program with the features of claim 12. According to the invention, the processing of the machine code by the control device

tion that the control device activates the strand stirrer

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controls that during the solidification time, the strand stirrer also oscillates with an oscillation stroke between

an upper and a lower reversal point is traversed.

Preferably, the processing of the machine code by the control device even causes the control device to carry out at least one of the advantageous operating modes of the device explained above in connection with the production method

strand stirrer realized.

The object is also achieved by a control device having the features of claim 14. According to the invention

programmed the control device with a control program according to the invention, so that the control device

stirrer as explained above.

The object is also achieved by a continuous casting machine having the features of claim 15. According to the invention, the control device is designed as a control device according to the invention in a continuous casting machine of the type mentioned, so that the strand stirrer during the solidification time with an oscillating oscillating between a

upper and a lower reversal point is moved.

Brief description of the drawings

The properties, features and advantages of this invention described above, and the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawings

will. This shows in a schematic representation:

1 to 5 different states during the casting of a steel strand,

6 shows a timing diagram,

7 to 9 longitudinal sections through various sections

a cast steel strand,

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10 shows a block diagram and FIGS. 11 to 14 show timing diagrams.

Description of the embodiments

In order to produce a bloom, according to FIGS. 1 to 5, liquid steel 1 is poured from above into a continuous mold 2 of a continuous casting machine and a steel strand 3 is drawn from the continuous mold 2 below. The steel strand 3 often has a large cross section, for example in the case of a circular cross section a diameter of 600 mm and more, sometimes up to over 1000 mm. Due to the relatively low rate of solidification, the steel strand 3--see in particular FIG. 7--has an already solidified strand shell 4 and a core 5 that is still liquid. In this state--that is, with the strand shell 4 already solidified and the core 5 still liquid--the steel strand 3 is introduced from above into a holding device 6 of the continuous casting machine. The holding device 6 is often referred to as tertiary cooling in the prior art. The holding device 6 is arranged below the continuous mold 2 . The insertion of the steel strand 3 into the holding device 6 is thus carried out in contrast to the pulling out of the

barrel mold 2 without changing direction.

1 to 5 show different phases of the casting process.

In the representation of FIG 1, casting has just begun. A strand head 7 of a dummy strand is still in the continuous mold 2 and seals it on its underside. In the illustration in FIG. 2, the strand head 7 has just passed through a secondary cooling zone of the continuous casting machine. In the secondary cooling zone, the steel strand 3 is withdrawn from the continuous mold 2 and supported by strand guide rollers. Furthermore, the steel strand 3 is cooled in the secondary cooling zone by means of cooling nozzles. In the representation of FIG. 2, the strand head 7 has just been inserted into the holding device 6.

step.

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In the illustration in FIG. 3, the feeding of the liquid steel 1 has just been completed. The strand head 7 is at this point in time in the holding device 6, but has not yet reached the bottom. The steel strand 3 itself, on the other hand, has now reached its full length 1 . It is usually in the range between 10 m and 20 m.

In the illustration in FIG. 4, the steel strand 3 is pulled further out of the continuous mold 2 . In the illustration in FIG. 5, the strand head 7 has reached the bottom of the holding device 6. An upper edge 8 of the steel strand 3 usually closes flush or almost flush with an upper edge of the half

tea facility 6 off.

With regard to the further details when casting the steel strand 3, reference is made to the prior art, for example to the already mentioned EP 3 251 773 BL.

FIG. 6 shows the location of the sump tip as a function of time t in a solid line. For example, an upper location O1 (see FIG. 10), at which the liquidus temperature TL prevails in the center of the steel strand 3, can be regarded as the sump tip. Alternatively, a lower location 02 (also see FIG. 10) can be regarded as the sump tip, at which in the center of the steel strand 3 the solidus temperature TS

reigns.

The casting of the steel strand 3 begins at a point in time t1 (compare FIG. 1). A base point of the steel strand 3 is therefore still above the holding device 6. The sump tip forms straight. In the further course, the base point of the steel strand 3 migrates downwards in accordance with the withdrawal of the steel strand 3 from the continuous mold 2 . The sump tip is a little above the base of the steel strand 3. At a point in time t2 (see FIG. 3), the liquid steel 1 is fed to the continuous mold 2

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completed. At time t2, the base of the steel strand 3 moves further down, ie has not yet reached its lowest point. In the meantime, the top of the swamp has moved up a little bit relative to the base. At a point in time t3 (compare FIG. 5), the strand head 7 and thus also the base point of the steel strand 3 has reached its lowest point. In the meantime, the top of the swamp has moved up a little bit relative to the base. However, it is located deep in the holding device 6. In the further course, the sump tip gradually migrates upwards until it reaches the upper edge 8 of the steel strand 3 at a point in time t4. Only at time t4 has the steel strand 3 solidified to form the bloom. The steel strand 3 remains in the holding device 6 at least up to time t4 (usually even beyond that). However, the thickness of the strand shell 4 gradually increases over the entire length of the steel strand 3, so that the sump tip moves upwards.

The period of time between the times t1 and t4 or between the times t3 and t4 can be regarded as the solidification time, as required. Irrespective of whether one or the other specification is made, the solidification time is generally in the range of a number of hours, for example between 5 hours and 15 hours, usually 10 hours and more. If required, the time span between the times t1 and t2 or between the times t1 and t3 can be regarded as the pouring time. Irrespective of whether one or the other specification is made, the pouring time is considerably shorter than the solidification time. As a rule, the casting time is a maximum of 3 hours, often in the range of approx. 1 hour.

Even while the steel strand 3 is in the holding device 6 , the steel strand 3 still has the strand shell 4 and the liquid core 5 . FIGS. 7 to 9 each show a cross section through the steel strand 3 directly

after complete insertion into the holding device 6.

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7 shows a cross section in the upper area of the steel strand 3, FIG. 8 shows a cross section in the central area of the steel strand 3. FIG. 9 shows a cross section in the area of the

Sump tip of steel strand 3.

During the solidification time, the liquid core 5 is stirred by means of a strand stirrer 9 of the holding device 6. The strand stirrer 9 is only shown in FIG. As indicated by a double arrow in FIG. 8, the strand stirrer 9 can be moved vertically along the steel strand 3 by means of a drive 10 . The drive 10 can be designed as a hydraulic cylinder. However, other configurations are also possible

Lich, especially as an electric drive.

According to FIG. 10, the strand stirrer 9 is controlled by a control device 11 of the continuous casting machine. If necessary, other components of the continuous casting machine can also be controlled by the control device 11, for example the feeding of the liquid steel 1 into the continuous mold 2, the withdrawal of the steel strand 3 from the continuous mold 2 and the associated insertion into the holding device 6 as well as various cooling systems, for example the continuous mold 2 and the steel strand 3 in the secondary cooling zone and the holding device 6. The control device 11 is programmed with a control program 12. The control program 12 includes machine code 13 which can be processed by the control device 11 . The processing of the machine code 13 by the control device 11 causes the control device 11 to control the strand stirrer 9 in a manner which

is explained in more detail below.

On the one hand, the liquid core 5 is stirred by means of the strand stirrer 9 during the solidification time. Especially in the case of the usual design of the strand stirrer 9, in which

the strand stirrer 9 is designed as an electromagnetic stirring coil, the stirring coil is fed with at least one alternating current I according to FIG. The further configuration can

be need. Advantageous configurations of a stirring coil,

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by means of which the liquid core 5 can be stirred in various ways are explained in more detail in WO 2017/162 418 A1, for example. The precise manner in which the liquid core 5 is stirred is of secondary importance within the scope of the present invention. The only decisive factor is that the exact effect on the liquid core 5 by the alternating current I (for example its current strength, its frequency and, in the case of several phases of the alternating current I, of phase relationships of the phases

to each other) is determined.

On the other hand - and this is the main subject of the present invention and is explained in connection with FIGS. 11 to 14 - the strand stirrer 9 is moved during the solidification time with an oscillation stroke h oscillating between an upper reversal point P1 and a lower reversal point P2. For this purpose, the drive 10 is given a position value p. The position value p is time-dependent accordingly

the desired oscillation.

Possible oscillations of the strand stirrer 9 are explained in more detail below in connection with FIGS. FIG 11 to 14 are based on FIG 6.

In the representation according to FIG. 11, both the upper reversal point P1 and the lower reversal point P2 are fixed. As a result, there is an oscillation with a uniform, time-constant oscillation swing h. The frequency of the oscillation can also be constant. However, it can also be varied over time. Furthermore, the oscillation can be sinusoidal or non-sinusoidal as required. A non-sinusoidal movement can exist, for example, if the oscillation stroke h and/or the oscillation frequency is relatively large (in particular the product exceeds a limit value), so that the strand stirrer 9 with a sinusoidal movement in the central area between the upper and lower reversal points P1, P2 would have to be moved at a speed that

can no longer be reached by the drive 10. From the

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For the same reason, it may also be possible that an acceleration required in the area of the upper and/or lower reversal point P1, P2 for a sinusoidal oscillation can no longer be achieved. However, other reasons for a non-sinusoidal movement of the strand stirrer 9 are also possible. If desired, the at least one alternating current I can continue to flow while the strand stirrer 9 is oscillating, depending on the current position p of the strand stirrer.

rers 9 can be varied.

The upper reversal point Pl can in particular have a predetermined distance al from the position of the upper edge 8 of the completely cast steel strand 3 . The distance al is usually in the range of less than 100 cm. The distance a1 can be positive or negative as required. In an analogous manner, the lower reversal point P2 can have a predetermined distance a2, in particular from the position of a lower edge of the completely cast steel strand 3. The distance a2 is usually also in the range of less than 100 cm. The distance a2 can also be positive or negative as required. The position of the lower edge of the fully cast steel strand 3 is correct

with the location of the strand head 7 coincide.

In the representation according to FIG. 12, the upper reversal point P1 is fixed. With regard to the exact position of the upper reversal point P1, the statements relating to FIG. 11 can be applied in an analogous manner. The lower reversal point P2, on the other hand, is variable. In particular, the bottom reversal point P2 in FIG. 12 is determined as a function of the top location O1. For example, the bottom reversal point P2 can be determined such that it coincides with the top location O1 or has a predetermined distance above or below the top location O1. Alternatively, the lower reversal point P2 can be determined as a function of the lower location 02. In this case, the lower reversal point P2 is generally determined in such a way that it lies above the lower location 02 and is at a predetermined distance from the lower location 02. Due to the

states that the upper reversal point Pl is fixed, the lower

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re reversal point P2 is variable, however, there is an oscillation with a time-varying oscillation stroke h. The comments on FIG. 11 on the frequency of the oscillation and the form of the oscillation as well as the possible variation of the alternating

current I also apply to FIG 12,

In order to determine the upper location 01 and/or the lower location 02, the control device 11 preferably implements a thermodynamic model 14 of the steel strand 3 according to FIG a phase transformation equation modeled online. At least the heat conduction equation is a differential equation. This often applies to the phase change equation as well. The heat conduction equation and the phase change equation are coupled and are solved iteratively. The model 14 is two-dimensional or three-dimensional. corresponding

Appropriate models are well known to those skilled in the art.

In the representation according to FIG. 13, both the upper reversal point P1 and the lower reversal point P2 are variable. In particular, the lower reversal point P2 in FIG. 13—as in FIG. 12—is determined as a function of the upper location O1. Alternatively, the lower reversal point P2 can be determined as a function of the lower location 02. The corresponding explanations for FIG. 12 can be applied in an analogous manner. A completely analogous procedure can be taken for the upper reversal point Pl. The determination only has to be made in such a way that the upper reversal point P1 is above the lower reversal point P2. The comments on FIG. 11 on the frequency of the oscillation and the form of the oscillation as well as the possible variation of the alternating current I also apply to FIG. 13.

The configuration explained in connection with FIG

which both the upper reversal point Pl and the lower

Reversal point P2 are variable is particularly preferred. in the

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Within the scope of this configuration, it is possible, in particular, for the bottom dead center P2 to be determined first and then (if possible) for the top dead center P1 to be determined as a function of the bottom dead center P2 in such a way that the oscillation stroke h is equal to a fixed nominal stroke hN, i.e. constant is. This determination is possible as long as the distance between the lower reversal point P2 and the upper edge 8 of the completely cast steel strand 3 is at least as great as the nominal stroke hN. If, on the other hand, the lower reversal point P2 is spaced less than the fixed nominal stroke hN from the upper edge 8 , the upper reversal point P1 is set equal to the upper edge 8 of the steel strand 3 . On the one hand, this state occurs briefly between times t1 and t2, while the steel strand 3 is being introduced into the holding device 6. On the other hand, this state occurs shortly before time t4. Therefore, during these two periods, the oscillation amplitude h is smaller than the nominal amplitude hN.

FIG. 14 shows a further embodiment in which both the upper reversal point P11 and the lower reversal point P2 are variable. The lower reversal point P2 as such and also the upper reversal point P1 as such are not shown in FIG. Instead, however, the position p

of the strand stirrer 9 as a function of time t.

In the context of the configuration according to FIG. 14, the lower reversal point P2 remains at an upper level N1 until the steel strand 3 has been introduced into the holding device 6 to a significant extent. Thereafter, the bottom dead center P2 is gradually lowered until it reaches a lower level N2. In particular, he can follow the introduction of the steel strand 3 into the holding device 6 during the lowering. After that, the lower reversal point P2 remains at the lower level N2 for some time. During a short period of time, the bottom dead center P2 is lowered below the lower level N2 and then gradually raised to the upper level N1. The top

Level N1 is preferably reached at time t4. in the

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Within the scope of the configuration according to FIG. 14, the strand

stirrer 9 preferably always with the nominal stroke nH.

The present invention has many advantages. In particular, there are usually several strand stirrers 9 in the prior art, each of which only covers a portion of the cast steel strand 3 . In the context of the present invention, on the other hand, one and the same strand stirrer 9 can stir the liquid core 5 over the entire length 1 or at least over almost the entire length 1 of the steel strand 3 . Nevertheless, a very high quality of the steel strand 3 can

can be achieved especially in its interior.

Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples and other variants can be derived therefrom by a person skilled in the art without violating the scope of protection of the invention.

to let.

17 List of reference symbols 1 liquid steel 2 continuous mold 3 steel strand 4 strand shell 5 liquid core 6 holding device 7 strand head 8 upper edge of the steel strand 9 strand stirrer 10 drive 11 control device 12 control program 13 machine code 14 model al, a2 distances h oscillation stroke hN nominal stroke 1 length of the steel strand I alternating current N1 upper Level N2 lower level p position value o1 upper location 02 lower location P1 upper reversal point P2 lower reversal point t time TL liquidus temperature TS solidus temperature

tl to t4 time points

Claims (15)

15 20 25 30 35 202100129 Claims 18 1. Manufacturing process for a bloom, - where liquid steel (1 ) from above into a continuous mold (2) is cast, below a steel strand (3) with a already solidified strand shell (4) and a still liquid Core (5) is withdrawn from the continuous mold (2) and the steel strand (3) with the already solidified strand shell (4) and the still liquid core (5) without changing direction is inserted from above into a holding device (6), in which the steel strand in which the steel strass block solidifies, remains - with the liquid core using a strand stirrer (3) during a solidification period, ng (3) gradually to the pre- t, (5) during the solidification period first (9) is stirred, characterized, that the strand stirrer (9) during the solidification time with nem Oszillationhub (h) oscillating between an upper and a lower reversal point (P1, P2) is moved. 2. Manufacturing method according to claim 1, characterized, that the upper turning point (P1) is fixed, especially by the Position of an upper edge (8) of the fully cast steel strand (3) has a predetermined distance (al). 3. Manufacturing method according to claim 1, characterized, that the upper turning point (P1) is variable. 4. Manufacturing method according to claim 3, characterized, that the upper turning point (P1) upper location (01) is determined, depending on one at which the liquidus temperature (TL) prevails, or depending on a lower place (02) is determined at which the solidus temperature (TS) reigns. 1 15 20 25 30 35 202100129 19 5. Production method according to one of claims 1 to 4, characterized, that the bottom reversal point (P2) is fixed, especially by the location of a bottom edge of the fully cast steel strand (3) has a predetermined distance (a2). 6. Production method according to one of claims 1 to 4, characterized in that that the bottom reversal point (P2) is variable. 7. Manufacturing method according to claim 6, characterized, that the bottom turning point (P2) is determined as a function of an upper location (01) at which the liquidus temperature (TL) prevails, or is determined as a function of a lower location (02) at which the solidus temperature ( TS) reigns. 8. Manufacturing method according to claim 1, characterized, - that the lower reversal point (P2) and the upper reversal point (Pl) are variable, - that the upper reversal point (P2) is at an upper edge (8) of the fully cast steel strand (3) or below, -- that as long as the distance between the bottom dead center (P2) and the upper edge (8) of the fully cast steel strand (3) is at least as large as a fixed nominal lift (hN), the top dead center (P1) depends on the bottom dead center ( P2) is determined such that the oscillation stroke (h) is equal to the fixed nominal stroke (hN), and -- that, if and as long as the bottom dead center (P2) is less than the fixed nominal lift (hN) away from the top edge (8), the top dead center (P1) is set equal to the top edge (8) of the steel strand (3). . 9. Manufacturing method according to claim 8, characterized, 15 20 25 30 35 202100129 20 that the lower reversal point (P2 upper location (01) is determined, ) depending on a at which the liquidus temperature (TL) prevails, or depending on a lower place (02) is determined on which the reigns. Solidus temperature (TS) 10. Manufacturing method according to claim 4, 7 or 9, characterized, that the upper location (01) and/ode of a thermodynamic model be averaged. 11. Manufacturing process according to r the lower location (02) by means (14) of the steel strand (3) one of the above claims, characterized, that the strand stirrer (9) as e is trained, with at least electromagnetic stirring coil at least one alternating current (I) is fed, and that the at least one alternating current (I) during the oscillation of the St ranking stirrers (9) in dependent from the current position of the strand stirrer (9) varies is ilated. 12. Control program having machine code (13) written by a control device (11) of a continuous casting machine for production of a bloom can be processed, the processing processing of machine code (13) by the controller (11) causes the control device (11) to stirrer (9) of a holding device (6), in which a one already solidified strand shell (4) and one that is still liquid Core (5) having steel strand (3) during a solidification tion time gradually solidifies to form the bloom, such controls that during the solidification of the liquid core (5) using the strand stirrer ( stirrer (9) with an oscillati 9) is stirred and the beach onshub (h) oscillating between an upper and a lower reversal point (P1, P2) will proceed. 13. Control program according to claim 12, characterized, that the processing of the machine code (13) by the control device (11) causes the control device (11) to carry out the additional method steps of at least one of the sayings 2 to 11 realized. 14. Control device of a continuous casting machine for producing a billet, wherein the control device is programmed with a computer program (12) according to claim 12 or 13, so that during operation it has a strand stirrer (9) of a holding device (6) in which a one has already solidified Strand shell (4) and a steel strand (3) containing a still liquid core (5) gradually solidifies during a solidification time to form the billet, at least controlled in such a way that the liquid core (5) is stirred by means of the strand stirrer (9) during the solidification time is and the strand stirrer (9) with an oscillation stroke (h) oscillating between an upper and a lower reversal point (P1, P2) is moved. 15. Continuous casting machine for producing a billet, 20 - the continuous casting machine having a continuous mold (2) into which liquid steel (1) is poured from above and from which a steel strand (3) with an already solidified strand shell (4) and a still liquid core (5) is drawn off from below , 25 - the continuous casting machine having a holding device (6) below the continuous mold (2), into which the steel strand (3) with the already solidified strand shell (4) and the still liquid core (5) is introduced from above without changing direction and in which the steel strand (3) 30 remains during a solidification time in which the steel strand (3) gradually solidifies to form the bloom, - wherein the holding device (6) has a strand stirrer (9) which can be moved vertically along the steel strand (3) and by means of which the liquid core (5) is stirred during the solidification 35 stirring time, - wherein the continuous casting machine has a control device (11) by which at least the strand stirrer (9) is controlled will, characterized, that the control device (11) is designed according to claim 14, so that the strand stirrer (9) during the solidification time with an oscillation stroke (h) oscillating between a upper and a lower reversal point (Pl, P2) is traversed.