WO2016029901A1

WO2016029901A1 - Method for extruding a metal, in particular a steel, and extrusion device

Info

Publication number: WO2016029901A1
Application number: PCT/DE2015/100343
Authority: WO
Inventors: Peter Valentin
Original assignee: Peter Valentin
Priority date: 2014-08-26
Filing date: 2015-08-19
Publication date: 2016-03-03
Also published as: DE102014112206A1; DE112015000327A5

Abstract

The invention relates to a method for extruding a metal, in particular a steel, in which a release agent is added to a melt of the metal, being provided to reduce the adhesion between the solidifying or the solidified metal and a mold cooled by means of a cooling medium, and in which the metal for forming a strand is led through the mold. According to the invention, in order to avoid material defects in the strand or on the surface of the latter, a quantity of heat which is transported away from the mold by means of the cooling medium is regulated. In a refinement of the invention, the quantity of heat to be transported away is regulated in a fixed manner on the basis of properties of the metal, preferably the liquidus temperature and/or the solidus temperature thereof, and/or of properties of the release agent, preferably the viscosity thereof, and/or of a temperature of the melt as the melt enters the mold and/or a rate at which the melt is put into the mold. Expediently, a maximum and/or a minimum quantity of heat to be transported away is fixed and the quantity of feed transported away is regulated in such a way that the maximum quantity of heat to be transported away is not exceeded and the quantity of heat to be transported away does not fall below the minimum. The invention further relates to an extrusion device.

Description

"Process for continuous casting of a metal, in particular a steel, and apparatus for continuous casting"

The invention relates to a method for the continuous casting of a metal, in particular a steel, in which a melt of the metal is a separating center! is added, which is provided to reduce the adhesion between the solidifying or the solidified metal and a middle of a ühimediums cooled mold and the metal is fed to form a strand through the mold.

The invention further relates to a continuous casting plant, mitteis which carries out the process eats. The method of the type mentioned and the continuous casting for performing the method are known by use. The known continuous casting plant comprises a pan, a distributor, from which the melt is optionally distributed in different molds, the mold, for which a cooling device and Kokillenosziliationseinrichtung are provided, and means for guiding the strand after leaving the mold. The melt is added from the ladle to the distributor, from which it is e.g. is passed through a dip tube into the mold. The surface of the melt in the mold is replaced by a

Slag covered, which is formed mitteis given in the mold release agent and on the one hand prevents reoxidation of the melt and on the other hand acts as a lubricant between the solidifying or solidified metal and the mold. The mold is oscillated to prevent caking of the metal on the cooled walls of the mold by means of the Kokiiienoszillationsvorrichtung. When the strand leaves the mold, it has a solidified shell of a few millimeters thick. After leaving the mold, the strand is cooled, inter alia, in a region designated as a casting arc from the outside by water and / or air. In the production of a raw strand by continuous casting in continuous casting, especially in continuous casting for the production of slabs, blooms or Knüppein, the generation of a defect-free surface of the raw strand and subsequent processing of the raw strand to a semifinished product or to a Fertigmaferial is of great importance. Defects on or near the surfaces of, for example, automotive safety parts can not be tolerated and must therefore be removed after or at each processing step. The removal of the defects of the raw string requires the construction and operation of appropriate Schieifanlagen with high quality testing equipment, is expensive and very time consuming and costly. It is also problematic that even after the removal of the surface fissures or damage there is no absolute certainty that there is a crack-free surface, in particular it can not be ruled out that there will be no fine cracks, which may later be the reason for the unusability of the products, since these are are very difficult or not defektierbar.

In addition, experience shows that in continuous casting, due to the defects, even strand breakthroughs can occur, which, in addition to impairments of qual- ity in the raw crush, lead to production disruptions with long downtimes and overly costly damage to the continuous casters.

For these reasons and in view of ever-increasing quality requirements, the production of metal strips with defect-free surfaces is becoming increasingly important. The invention has for its object to provide a method of the type mentioned, which allows the production of strands with improved quality.

According to the invention, this object is achieved with respect to the method in that to avoid material defects in the strand or on its surface, an amount of heat, which is removed by means of the cooling medium from the mold, is regulated.

With regard to the continuous casting plant, the object is achieved by a device for controlling a quantity of heat removed from the mold. Since the amount of heat transported away has a strong effect on the solidification of the forming structure of the strand, the control during the continuous casting can influence the structure in a surface area. In particular, it becomes possible to control the process in such a way that an increased giobulitic solidification in the surface region of the strand and a corresponding reduction in the formation of dendrites, which are frequently a cause of cracks or surface damage, is achieved.

Further, by the control during continuous casting, the properties of the lubricating film and thus the effect of lubrication can be influenced because the thickness of the lubricant formed between the mold and the strand is the viscosity of the lubricating film and hence the heat conductivity of the lubricating film Lubricating film are temperature dependent. In addition, it is advantageously possible by means of the control to avoid falling short of a minimum film thickness as well as the formation of aegglomerates from partially solidified phases of the release agent, which can be caused by formation of thicker lubricating films. The avoidance of falling below the Mindestfümdicke is important because high frictional forces between the strand and the mold, which can damage the surface and cause errors.

Expediently, a currently transported amount of heat is determined, in particular by determining the (amount of the transported per unit time cooling medium, which preferably comprises water or is formed by water, a measurement of a temperature at the inlet of the cooling medium in the mold and on discharge from the mold and optionally By determining the difference in the temperature at the supply line and during the discharge, a change in the heat flow density is expediently determined, taking into account that a reduction in the heat flow density leads to an increase in the lubricant thickness and an increase in the heat flow density Reduction of the lubricant film thickness has the consequence.

According to the invention, a high-frequency measurement, expediently with at least 1 Hz, preferably with at least 1000 Hz, is provided for determining the amount of heat transported away in order to be able to react quickly to changes, in particular to over- or undershrinking of the maximum or minimum quantity of heat transported away.

In one embodiment of the invention, the device for controlling the amount of heat removed from the mold is intended to change a volume flow of the cooling medium, by means of which a quantity of heat introduced into the mold by the temperature of the melt of the metal can be transported away. In a preferred embodiment of the invention, the volume flow, which is preferably guided within the ocular wall, settable by controlling the power of a pumping device or by operating valves for a conduit through which the cooling medium is passed. In one embodiment of the invention, the amount of heat to be removed is regulated as a function of the properties of the metal, preferably its liquefied temperature, its solidus temperature, its zero-degree of stability and / or its low viscosity temperature.

Alternatively or additionally, it is expediently provided to regulate the amount of heat to be removed as a function of the properties of the separating agent, preferably its temperature-dependent viscosity, in particular in the temperature range between 500 and 1600 ° C. The properties of the release agent, which is preferably formed by a Gießpuiver- or granulaf, further include specific gravity, bulk density, thermal conductivity, ristaliisationsart (glassy or amorphous / crystalline), crystallization temperature

(Transition liquid to solid or solidification start of a supercooled rheological mold slag as a result of the liquefaction of the casting powder / granules), softening, hemisphere and / or pour point and / or an onset temperature.

It has proven to be particularly advantageous to regulate the method such that the dynamic viscosity of the lubricating film at 1300 ° C between 0.1 and 5 Pa * s or that the lubricating film has a viscosity such that in the upper part of the mold a minimum lubricating film thickness, for example, of at least 10 to 100 pm forms.

Advantageously, the process can be adapted particularly easily on the basis of the properties of the metal or of the separating agent if, as explained below by way of example for sequence casting, different metals which differ in their composition during the process or if different separating agents are used. This proves to be particularly advantageous if differences in the respective properties are determined during continuous casting due to the use of the different batches of metallic raw material or of the casting powder, since the method can be adapted to the respective batches on the basis of information about the properties mentioned ,

In a preferred embodiment of the invention, a maximum and / or a minimum amount of heat to be removed is set and the amount of heat to be removed is regulated in such a way that the maximum amount of heat to be removed is removed. amount of heat not exceeded and the minimum amount of heat to be removed is not undershot. The maximum and / or the minimum quantity of heat to be removed is preferably determined on the basis of information about the metal or the casting powder and / or empirical values which are present through use of the continuous casting plant.

Since exceeding or falling short of the maximum or minimum amount of heat removed can be the cause of the formation of the errors, the production of strands which do not meet the required quality requirements can be avoided with this measure.

In one embodiment of the invention, it is provided to regulate the amount of heat to be removed as a function of a temperature of the melt on entry into the mold and / or a speed at which the melt is introduced into the mold. The continuous casting plant expediently has a device for determining this temperature and the regulating device is provided to regulate as a function of the temperature of the melt.

Such control of the amount of heat transported away proves to be particularly effective, since the sequence of continuous casting which has been customary for a long time and in which a casting time can take several hours or even several days, and in which different batches of raw material are cast successively, can be individual Change pouring parameters during the process. Thus, the individual batches have analytical differences, so that a pan setting must be adjusted in the pan. Accordingly, when casting each of the batches in the sequence continuous casting various temperatures in the distributor. Further, if there is no means for heating the liquid metal in the tundish, the tundish temperature will reach a maximum temperature shortly after the new batch has been run, and thereafter will fall to the respective batch end. Furthermore, the melt flows out when more of the molds are acted upon. Depending on the location of the respective outlet openings for the respective dies in the manifold different flow patterns and different residence times of the melt in the buttress exist and the melt therefore different temperatures depending on the mold when flowing into the mold. This leads to a different charge level from batch to batch and strand to strand temperature level in the respective mold, which in turn this different temperature level during the total casting time after passing through a maximum strives for a minimum, ie towards pouring end of each batch, the distributor channel temperature approaches more and more of the liquidus temperature.

These changes can be reacted thanks to the control according to the invention and thus a uniform and high quality of the strand, in particular the strand surface can be achieved. This is particularly advantageous if the strand is deformed after leaving the mold, as long as the core of the strand is still liquid (soft reduction). In one embodiment of the invention, the temperature of the cooling medium, preferably the temperature when fed into the mold, is controlled. On the one hand, the cooling medium determines the temperature of the inner wall of the mold and the

The viscosity of the release agent is temperature-dependent, on the other hand, the removed by the cooling medium amount of the absorbed by the cooling medium heat, which also depends on the temperature of the cooling medium, the control of the temperature of the cooling medium has proved to be suitable to influence the viscosity of the release agent , The continuous casting plant expediently comprises a cooling and / or heating device or a device for mixing the cooling medium in various temperatures to achieve a drawing temperature to regulate the temperature of the cooling medium. Conveniently, the temperature control, possibly by means of at least one heat exchanger, used in the continuous casting heat.

In a further development of the invention, the amount of release agent added per unit time is further regulated. In a preferred embodiment of the invention, it is provided to automatically add the release agent and to regulate the amount via a device provided for supplying the release agent.

Furthermore, it could be provided manually to give the release agent in the mold and to provide the continuous casting with a display device by means of which the manually added quantities per unit time are displayed.

Advantageously can be taken by the regulation on the one hand influence on the thickness of the lubricating film and thus as explained above errors on or in the strand can be avoided. On the other hand, a residence time of the release agent can be controlled on the melt in the upper region of the mold, wherein it has proved to be particularly advantageous depending on the residence time of the liquefied release agent on the melt above a meniscus in the upper region of the mold. This can ensure that on the Soil of the mold is always a sufficiently thick layer of slag, which is also referred to as Liquid Pooi, is present to protect the melt from reactions with the air. Furthermore, the residence time can be provided in such a way that it is ensured that the separating center! has reacted sufficiently long enough with the slag to be able to form a homogeneous and stable lubricating film.

In particular, it can be prevented that the mold is overfilled with the release agent, and that the release agent cakes on the mold or that release agent rings or wreaths of solidified mold slag form in the meniscus region (slag rlm formation). Furthermore, it can be avoided that the liquid pool is too small or idle.

Expediently, a frequency and / or an amplitude of an oscillation of the mold, the speed at which the metal is moved through the mold, and / or the temperature of the metal before it enters the mold are also controlled. Due to the oscillation of the mold caking of the strand is avoided on the mold, but it leads due to the relative movement to the formation of Oszlllationsmarken in the strand, which can be starting points of cracks, especially if they are too deep. By adjusting the frequency or the amplitude of the oscillation, it is possible to influence the formation of the oscillation marks. For example, it has been found suitable to reduce the frequency or amplitude as the viscosity of the lubricating film increases, e.g. due to an increase in the amount of heat removed or a decrease in the temperature of the melt upon entry into the mold. In a further embodiment of the invention, a volume flow, with which the melt is added to form the strand in the mold, regulated. For this purpose, a position of a stopper or slide provided on the distributor, by means of which the volume flow can be adjusted, is changed to this purpose.

In the preferred embodiment of the invention, the volume flow of the melt is controlled as a function of a height of the casting mirror and / or in dependence on the position of the plug or the slider.

This advantageously avoids fluctuations in the casting level, which have a negative effect on the surface quality of the strand. These

Variations occur, in particular, when deposits form on an outlet opening of the distributor, via which the melt is introduced into the mold, and the outlet opening becomes gradually clogged when the plug is opened. reason of reactions of refractory material it has, gradually changing its shape and / or when parts of the deposits or the refractory dissolve abruptly.

In particular, if the height of the casting mirror and / or the position of the plug or the slide in relatively short intervals, preferably with a frequency of at least two 2 Hz, preferably at least 5 Hz, is determined, beyond the Gießspiegelschwankungen can be determined very accurately. In particular, if the portion of the strand formed by the process, during the production of which it came to the Gießspiegelschwankungen, the strand assign after completion of the manufacturing process, this section of the strand can be removed from the strand to avoid that Materia! low quality is delivered. In a preferred embodiment of the invention, the Stranggießaniage for determining all, one or more of the following process parameters during continuous casting is set, the determination, if the Stranggießaniage is set up to produce several of the strands is provided for each strand, the determination preferably carried out continuously or in chronological order, preferably by measurement and / or by calculation:

- Temperature of the melt in the distributor

- Temperature of the melt entering the mold

- Temperature at the mold inner wall, preferably depending on a

Position inside the mold

- Temperature at the surface of the strand, preferably in the region of at least one surface and / or at least one edge of the strand

Strand shell thickness and / or strand shell growth constant in the entire Kokiilenberelch

- Casting speed of the melt

"Dwell time of the strand in the mold

- Amount of Trennmitfels added per unit time

Residence time of the mold slag in the mold in the area above the forming beach (liquid pool) and / or consumption of the separating agent,

- Bulk height of Trennmiftels in the mold, if necessary, stating solid

and / or liquid portion

- pouring mirror

- color of mold slag (black or red) - Recording of the emissivity of Kokillenschiacke

- Amplitude and / or frequency of Kokilienosziliation

Friction forces between the strand shell and the mold, it being possible to measure empty forces, upward driving forces and / or downward driving forces

Expediently, the method according to the invention is set up to perform the control as a function of one or more of the named process parameters.

Because the reactions that take place can be very short-term and very fast, for each or all of the aforementioned process parameters, a high-frequency data acquisition, expediently with at least 1 Hz, preferably at least 1000 Hz, provided to react quickly to avoid the formation of errors in the strand Furthermore, the control is carried out depending on all or some of the following process parameters, which are determined by the caster used: cube gutter structure, Sfranganzahl, geometric design of the mold (format, diameter), Kokilleniänge, in particular length of cooled areas, chemical composition of Kokilienmateriais and Thermal conductivity, coating (thickness of the coating and thermal conductivity) and / or structure and diameter of the dip tube.

In one embodiment of the invention, the continuous casting plant has devices for measuring and / or determining individual or all of the abovementioned process parameters. Furthermore, it is expediently provided with a database which has information about the respectively processed metal and / or the respectively processed release agent or can be provided with this information and which can be called up by the control device for the respective control.

The control device expediently has an evaluation and arithmetic unit which is set up to process the said information.

While the Stranggießaniage, in particular the Regeiungseinrichtung, according to the preferred embodiment of the invention is intended to regulate the amount of heat to be removed from the mold and can be set up in addition, the temperature of the cooling medium, the amount of release agent added per unit time and / or the frequency and / or the amplitude To regulate the oscillation of the mold is provided according to a development of the invention, the method regardless of the heat dissipated by the mold heat quantity by controlling the temperature of the cooling medium, the amount of release agent added per unit time and / or the frequency and / or the amplitude Oscillation of the mold to regulate. It has been shown that the control of one or more of the aforementioned process parameters has an advantageous effect. It is understood that the continuous casting, in particular the Regelelnelnrichtung, can be designed accordingly. It will be appreciated that the method and apparatus may be used to make billets or billets, preferably each having a rectangular or round, more preferably circular, cross-sectional shape, or slabs. The invention will be explained in more detail with reference to an embodiment and the accompanying drawings, which relate to the embodiment. Show it:

Fig. 1 shows a part of a Stranggießaniage invention in section, and Flg. 2 graphics for explaining the method according to the invention.

In Fig. 1, a mold 2 of a Stranggießaniage 1 according to the invention in carrying out the continuous casting according to the invention is shown in section from the side.

The mold 2, which has a rectangular cross-sectional shape is continuously fed from a distributor 1 4 via a dip tube 3 with liquid steel, in the Verleger 1 4 a plug 1 9 is provided, the position of which is adjustable to a volume flow, with the liquid steel 7 enters the mold 2 to be able to move. The plug 1 is provided with a device, not shown here, for determining the position of the plug 1 9 and / or for detecting movements of the plug 1 9. In the mold 2, a strand 4 is formed from the steel 7, which is led out of the bottom of the mold 2 and transported on via a pouring bow, not shown here. Optionally, a device for soft reduction not shown here may be provided.

During a movement of the strand 4 down through the mold 2, a sintered shell 5 is formed on the outer soaps of the strand 4 from a molten fraction 6 with the passage into the solid phase, which gradually becomes thicker. In a wall of the mold 2, a cooling line not shown here is provided by the pump 13 is continuously pumped by a pump water. A volume flow, with which the pump 13 pumps the cooling liquid through the cooling line, is regulated by a control device 21.

In the vicinity of an inlet 29, where the cooling water is added to the cooling line, a unit 26 for measuring a cooling water inlet temperature T = is provided. Furthermore, a device 25 for dividing the cooling water inlet temperature TE is provided, by means of which influence on the temperature of an inner wall of the mold 2 can be taken.

Behind an outlet 12, where the cooling water exits the Kühiieitung, a unit 27 for measuring a cooling water outlet temperature TA is provided.

By means of an evaluation and arithmetic unit 20 which is connected to the temperature measuring units 26,27 and which is adapted to detect TE and TA, can be based on the temperature difference dT = TA - TE and the flow rate, by means of which the pump 13 through the cooling liquid let the mold 2 flow, determine the amount of heat that removes the cooling liquid from the mold 2, and calculate the heat flow density.

In the vicinity of the inside of the mold 2 thermo elements 1 1 are provided in the wall of the mold 2, which serve for the location-dependent determination of the temperatures TKI to Τκό the mold 2. These are also connected to the evaluation and arithmetic unit 20 and can be read individually and assigned to their respective position in the mold 2, in particular depending on their vertical arrangement. An oscillating device 15 is provided for the mold 2, by means of which the mold 2 is moved oscillating vertically or in a circular arc during the execution of the method in order to prevent the strand 4 from adhering to an inner wall of the mold 2. A frequency and / or an amplitude with which the mold 2 is moved in an oscillating manner is regulated by the regulating device 21.

Below the mold 2, a unit 24 for measuring a speed at which the strand 4 emerges from the mold 2, is arranged. The unit 24, which preferably comprises a laser measuring unit, is connected to the evaluation and arithmetic unit 20 so that it can read the results of the speed measurement.

To determine the temperature Ts of the melt in the manifold 14, a thermocouple 23 is provided, which also with the evaluation and computing unit 20th is connected and its results can be read by the evaluation and processing unit 20.

Between the distributor 14 and the mold 2, there is provided a device 16 for the continuous supply of a casting powder 17 which comprises a conveyor belt and an adding device with which a defined quantity of the casting powder 17 can be applied to the conveyor belt. About the conveyor belt, the casting powder 1 7 is transported into the mold 2. An amount per unit time that is moved into the mold 2 is also controlled by the controller 21.

The casting powder 1 7 forms in the mold 2, first a Gießpulverschicht 8, in which the casting powder 1 7 is liquefied and from which immediately above the melt in the mold 2, a liquid slag layer, a so-called. Liquid pool 9 forms. This results from reaction of the casting powder 8 with the melt and protects against reactions with the air. The liquid pool 9 can also absorb deoxidation products of the molten metal and thereby change physically and chemically, in particular if the castability worsens due to high-melting Al 2 O 3. With the movement of the strand 4 through the mold 2, a lubricant film 10 is formed between the strand 4 and the inner wall of the mold 2 from the slag, which prevents the strand 4 from caking against the mold 2.

To determine the height of the casting powder layer 8, a laser measuring device 18 is provided, which is connected to the evaluation and arithmetic unit 20 and whose measurement results can be read out by the evaluation and arithmetic unit 20.

To determine the height of the casting mirror, the continuous casting plant 1 further comprises a measuring device 28 which comprises, for example, a cobalt radiator. The control device 21 is provided to read out the information acquired or determined by means of the evaluation and arithmetic unit 20 in order to access it for regulation. Furthermore, the Sfranggießanlage 1 includes a database 22, in which information about casting steels and to be used casting powder 1 7 are deposited. The information includes, inter alia, the liquidus temperatures of the steels and, depending on the temperature, viscosities of the casting powders 17 when the lubricant film 10 is formed between the strand 4 and the mold 2. Before starting the process, the control device 21 determines a minimum and a maximum heat flux density by retrieving the information about the steel 7 to be cast and the used casting powder 1 7 from the database 22, If the steel 7 or the casting powder 1 7 during the continuous casting For example, in sequence casting from sequence to sequence or from casting powder to change casting powder, because each used batches of steel 7 or the casting powder 17 have different properties, the Regeiungseinrichtung 21 fits the minimum and the maximum heat flux density to the respective steel 7 or the respective Casting powder 1 7 at. In addition, the desoxidization of the respective steel 7 is queried in the control device 21 and taken into account accordingly in the determination of the predetermined heat flux densities.

Concerning. of the steel 7, the heat flux density, which may occur at the strand 4 by cooling the mold 2, without any danger of dendrites in the structure of the strand 4, depends on a temperature To at the strand surface. The maximum heat flux density is determined for at least one of the four edges of the cross section rectangular strand 4, since the heat flux density is greatest in these areas.

Furthermore, a minimum heat flux density is determined in order to achieve a homogeneous formation of the solid phase and to report a rupture of the strand 4 during the guidance through and out of the mold 2. The minimum heat flux density relates to areas of the surface of the strand 4, which are spaced from the edges. A data set resulting from the determination, which shows the heat flow density as a function of the surface at the edges and at the surfaces as well as the minimum and the maximum heat flow density, is shown in Flg. 2a graphically reproduced. FIG. 2 a furthermore shows the heat flow density as a function of the temperature T o of the surface of the strand 4 by way of example for a steel of predetermined properties given predetermined process parameters, wherein different courses for the edge and the surface of the strand are shown.

In addition, by means of predetermined minimum and maximum thicknesses of the lubricating film 10, the control device 21 determines a minimum and a maximum viscosity to be set of the casting powder 1 7 by retrieving the information about the casting powder 1 7 from the database 22. The dependence of the thickness of the lubricating film 10 of the viscosity is shown in Fig. 2b. The viscosity of the casting powder 1 7 is temperature-dependent and is therefore suitable for One by changing the heat flow density, on the other hand by adjusting the cooling water inlet temperature Te regulate to take the temperature at the mold inner wall influence. As can be seen from FIG. 2b, the viscosity for achieving the minimum lubricant thickness in the present exemplary embodiment is set to greater than 62.5 dPa * s. The thickness of the lubricating film 10 can be further influenced by controlling the mean of the feeding device 16 per unit time of the injection mold powder 1 7 introduced into the mold 2.

Furthermore, the regulating device 21 regulates the feeding device 16 in dependence on the height of the casting film layer 8 determined by the laser measuring device 18 and / or the determined thickness of the lubricating film 10, so that the amount of casting powder] 7 introduced into the mold 2 per unit of tents is that of the consumed one equivalent. During continuous casting, the temperature To at the strand surface is calculated by means of the temperature Ts and the temperatures Τκι to Τκό, and the corresponding minimum and maximum heat flow density is determined from the data set and the pump 13 is controlled such that the volume flow of the cooling medium does not become so small or large that the maximum heat flow density is exceeded or the minimum heat flow density is exceeded.

On the other hand, by means of the adjusting device 25, the cooling water inlet temperature TE is controlled such that the maximum Schmierfiimdicke not exceeded or the minimum Schmierfiimdicke is not exceeded.

Finally, by the control device 21, the frequency and the

Amplitude of the oscillation of the mold 2 controlled such that it is adapted to the current viscosity of the lubricating film 10 and possibly to the speed of the strand 4. For example, As the viscosity of the lubricating film 10 increases, the frequency and amplitude are reduced to make the formation too deep

To avoid Gszillationsmarken, and reducing the viscosity of the lubricating film 10 which increases the frequency and the amplitude to prevent caking of the strand 4 to the mold 2. If fluctuations of the height of the casting mirror are detected by means of the cobalt radiator 28, the regulating device 20 regulates the position of the stopper 29 in such a way that the volume flow of the melt 7 introduced into the Kokiile 2 has such a size that a desired Gießspiegeihöhe is achieved.

If variations in the height of the casting mirror exceeding a certain limit value are determined by the cobalt radiator 28 or the device for determining the position or movements of the plug 19, a range of the strand 4 produced by means of the method according to the invention can be determined, during the production of which the fluctuations have taken place. In order to avoid that a strand 4 of poor quality is obtained, this region of the strand 4 can be separated from the strand 4.

Claims

iäns for ie: ;;

A method for continuously casting a metal, in particular a steel, in which a release agent is added to a melt of the metal, which is provided to reduce the adhesion of the solidifying or solidified metal and a cooled by a cooling medium mold and the metal! for the formation of a strand is passed through the mold, characterized

that in order to avoid material defects in the strand or on its surface, an amount of heat which is transported away from the mold by the coolant is regulated.

Method according to claim 1,

characterized,

in that the quantity of heat to be removed depends on properties of the metal, preferably its liquidus temperature and / or its solidus temperature, and / or properties of the release agent, preferably its viscosity, and / or a temperature of the melt upon entry into the mold and / or a speed with which the melt is placed in the mold, is regulated,

Method according to claim 1 or 2,

characterized,

that a maximum and / or a minimum amount of heat to be removed is fixed and the amount of heat removed is regulated in such a way that the maximum quantity of heat to be removed is not exceeded and the minimum amount of heat to be removed is not undershot.

Method according to one of claims 1 to 3,

characterized,

that a volume flow of the cooling medium, which removes an amount of heat introduced into the mold by the temperature of the melt of the metal, is regulated.

Method according to one of claims 1 to 4,

characterized. that the temperature of the ühlmediums, preferably temperature, with which the cooling medium is supplied, is regulated.

Method according to one of claims 1 to 5,

characterized,

in that the amount of release agent added per unit time is regulated, preferably as a function of a minimum residence time of the release agent in the mold.

Method according to one of claims I to 6,

characterized,

that a frequency and / or an amplitude of an oscillation of the mold, the speed at which the metal is moved through the mold and / or the temperature of the metal before entering the mold, is regulated.

Continuous casting apparatus comprising a mold cooled by a cooling medium, means for adding a release agent to the mold, and means for guiding the strand through the mold;

characterized by a device for controlling a quantity of heat removed from the mold.

Device according to claim 8,

characterized,

that the control device is provided for dividing a volume flow of the cooling medium, by means of which a quantity of heat introduced into the mold can be transported away.

Device according to claim 8 or 9,

characterized,

the device for determining a temperature of the melt entering the mold and / or a speed at which the melt enters the mold, a temperature of the cooling medium, preferably a supply temperature and / or a discharge temperature, and / or a difference between the Supply temperature and / or the discharge temperature, an amount of the release agent added per unit time, a frequency and / or amplitude of oscillation of the mold, a temperature of the melt in the buttress, a temperature of the melt at Entry into the mold, a temperature at the inner wall of the Kokirnien, a temperature at the surface of the strand, a strand shell thickness and / or a strand shell growth constant, a Gleßgeschwindig- kei † the melt, a residence time of the strand in the mold, a Verweiizeit the Kokiilenschlacke in the mold in the region above the forming strand ("liquid pool"), a consumption of the release agent, a bed height of the release agent in the mold, a height of a casting mirror, a color and / or an emissivity of Kokiilenschlacke, an amplitude and / or frequency Kokillenosziliation and / or a frictional force between the strand and the mold is set up.

Device according to one of claims 8 to 10,

characterized,

the control device is set up to control the temperature of the cooling medium, the frequency and / or the amplitude of the oscillation of the mold and / or the amount of release agent added per unit time.