EP1897636B1 - Continuous casting machine and method - Google Patents

Description

The invention relates to a continuous casting plant, in particular for steel long products, according to the preamble of claim 1 and a process for continuous casting according to the preamble of claim 13.

When continuous casting is known, the liquid metal, eg. As the liquid steel, filled in a cooled mold and continuously led away from this mold with shell formation as Giessstrang continuously. This casting strand is guided by a further cooling device, a so-called secondary cooling, along a guideway formed by successively arranged guide rollers and further cooled by applying cooling agents (spraying of water, water-air mixture) and contact with the guide rollers as well as by a radiation of heat ,

For quality reasons, it is important that the cast strand is cooled symmetrically with respect to its cross section. For this purpose, on the one hand the cooling nozzles must be accurately positioned and aligned and have the same spray characteristics, but on the other hand, an exact guidance of the casting strand along its guideway is important. As soon as an asymmetrical temperature field arises in the cast strand for some reason, the strand tends to deflect laterally due to thermal deformation from the guideway. This shift leads immediately to uneven coolant-impingement and thus further displacement of the strand from its desired position. The problem is particularly critical when small-sized strands (billets, about 100-160 mm square) are poured using high-intensity spray water cooling, so-called hard cooling. Furthermore, when casting billet strands to lift the strand from its arcuate guideway come when in the Kokillenbereich increased frictional forces occur, while the relatively flexible strand is quasi stretched.

To guide the strand through the cooling device guide rollers are used, which are fixed or compliant (via spring assemblies, compressed air bellows, etc.) are mounted at a predetermined minimum distance from the strand, the compliant design is practically only used on the strand top.

It is disadvantageous in these solutions that due to the highly corrosive and humid environment of the cooling chamber, most of the roles stuck after a short period of time, since they are only sporadically touched by the strand and rotated by this, so quickly corrosion products and lime deposits can settle at the bearings , Fixed rollers are on the one hand thermally overloaded as a result of the heat radiation of the strand and on the other hand they often damage the strand surfaces with grooves and longitudinal scratches, which lead to product rejects. In addition - if in the same continuous casting line strands are cast with different sizes cross-sectional formats - each have either completely new guide elements installed or guide rollers are moved to a new position. Both means time expenditure and affects the availability of the casting plant. In practice, therefore, the leadership roles are often set to the largest format, and thereby led the smaller formats only within wide limits.

When casting disorders occur, e.g. Strand breakthroughs, fixedly positioned guide rollers and spray mats make it difficult to remove the breakthrough line, and restoring readiness for operation is time consuming.

In the publication JP-A-57130752 a continuous casting plant is described in which the extruded from the mold strand is deflected on pairs of rolls to form a bow and cooled accordingly by a water supply in these pairs of rolls. In this continuous casting plant primarily an energy recovery of the heated by the strand cooling water is provided. These pairs of rollers are each stored as on a cart. But it is not mentioned at any point that this Roll pairs or the water cooling are designed as modules and still controlled controlled.

The publication DE-A-33 05 660 refers to a horizontal continuous casting plant with a device for correcting the contour of the strand. For this purpose, there is provided a controllably operable cooling device which injects a cooling fluid on at least one of a plurality of corners of the cast strand to match the contour of the strand cross-section. With this cooling device but not the entire strand is cooled and it is not designed as a module with a controlled adjustability.

In the method and apparatus for continuous casting according to the published patent application DE-A-100 51 959 the strand is led away arcuate after leaving the mold, in which it is divided into several arc sections and the secondary cooling is adapted in its geometric configuration of the solidification profile. This is also a corresponding strand support, which should reduce along the arc sections. Subsequent to the bow sections, a soft-reduction segment and an intensive cooling device arranged upstream of the latter are also arranged. These soft-reduction segments consist of two or more roller stands whose pairs of rollers are without drive. An upper frame is hydraulically adjustable to a subframe. These roller stands serve only for the guidance of the already running in a straight lane strand. With them can not be achieved a total centering of the strand. In the case of secondary cooling, for example, the distance between the spray nozzles and the strand surface can be changed as a function of the self-setting profile that occurs.

The present invention has for its object to provide a continuous casting of the type mentioned above and to propose a method for continuous casting in particular steel, with which the quality of the cast strand can be significantly improved by a precise, with respect to the strand cross-section symmetrically distributed cooling. In addition, the non-productive times should be reduced when changing over the casting plant to another casting format and maintenance.

This object is achieved by a continuous casting with the features of claim 1 and by a method according to claim 13.

Further preferred embodiments of the continuous casting plant according to the invention and of the process according to the invention form the subject matter of the dependent claims.

In the inventive continuous casting with several consecutively arranged centering modules, each of which has a fixed, defining the desired course of the guideway role for a strand side and other leadership roles for the other strand sides, the other guide rollers are adjustable in a direction substantially perpendicular to the corresponding Giessstrangflächen and the contact pressure of the respective roller is adjustable to the casting strand, it is ensured that the guide rollers constantly run through the clamping of the strand and the casting strand is held in its desired position in the guideway. As a result, on the one hand the risk of thermal overloading of the rollers and damage to the strand surface is significantly reduced and ensures symmetrical cooling.

In addition, the contact pressure of the strand to the centering rollers can be measured and a signal derived therefrom can be delivered to a control device. For example, in the case of an increase in force on the lateral rollers as a result of a thermally induced deformation of the cast strand, a targeted change in the cooling can be carried out locally, for example on a specific strand side, so that a centric strand run is achieved virtually on the thermal path.

Likewise, conclusions can be drawn from the increase in the strand pressing force of the billet strand moved along its arcuate guide track to the upper centering rolls on the strand withdrawal forces and thus on the frictional forces in the mold region, which opens up new possibilities for monitoring the casting process, in particular the mold friction.

The continuous casting plant according to the invention makes it possible to cast strands of various sizes without impairing the availability of the plant, since the respective change of the guide rollers and / or the spraying organs or a manual, new positioning of the same is superfluous. The centric strand guidance guarantees high production quality in all strand formats and the changeover times are considerably shortened.

Fig. 1

schematisch einen Teil (Kokille mit der anschliessender Kühlkammer) einer erfindungsgemässen Stranggiessanlage in Seitenansicht;

Fig. 2

ein Zentriermodul als Teil der Stranggiessanlage nach Fig. 1 in perspektivischer Darstellung; und

Fig. 3

das Zentriermodul nach Fig. 2 mit einem Schutzkasten für eine Steuereinrichtung.

The invention will be explained in more detail with reference to the drawing. Show it:

Fig. 1

schematically a part (mold with the subsequent cooling chamber) of a continuous casting plant according to the invention in side view;

Fig. 2

a centering module as part of the continuous casting after Fig. 1 in perspective view; and

Fig. 3

the centering module after Fig. 2 with a protective box for a control device.

According to Fig.1 a continuous casting plant comprises a mold 1, into which the liquid metal, in particular steel, is filled and continuously led away below from this water-cooled mold 1 with the formation of a shell as cast strand 2. This casting strand is passed through a further cooling device, a so-called secondary cooling, and thereby further cooled. Depending on requirements, support rollers and spray elements 4 can be installed on the mold outlet as so-called foot roller stands or support segments. These are format-dependent and are replaced with the casting mold each time with the mold.

The cooling device comprises a plurality of spray modules 3 arranged one behind the other, in which the guided along a guideway Giessstrang 2 with coolants, usually with water or a water-air mixture is applied. For this purpose, each cooling module 3 is equipped with a multiplicity of spray nozzles 5 designed as spray elements, which are preferably mounted in water-conducting spray mats 7. The spray mats 7 are controlled via an adjusting member 6 substantially concentric to the cast strand axis adjustable. As an adjusting member 6 sliding arms 6a are advantageously provided for the spray mats 7 at the inner or outer radius of the strand, or corresponding pivot arms 6b for lateral spray mats 7. In addition, a drive 6c connected to the sliding arms 6a or the swivel arms 6b is provided for this adjusting element 6.

Under special circumstances, however, in the so-called dry casting, the strand without spray cooling, d h. be essentially cooled only by means of water-cooled rollers. It is all the more important in this case that the strand remains constantly in contact with all the guide rollers.

The casting strand 2 passes through a plurality of successively arranged centering modules 10, each of which has a fixed, the target course of the guideway defining roller 11 for a strand side 2a and other guide rollers for the other strand sides. These are in particular from Fig. 2 and 3 visible). In contrast to the roller 11, these further guide rollers 12, 13, 14 are arranged adjustable in a direction substantially perpendicular to the corresponding casting strand surfaces 2b, 2c, 2d independently of the casting strand cross-sectional shape (square, rectangle, round, double-T, etc.), as will be described below.

The respective centering module 10 has a stationary frame 20. One of the other guide rollers, the upper guide roller 12, is held by a bracket 20 pivotally mounted, bow-shaped holder 22 worn, such that it can be adjusted during its pivoting relative to the fixed mounted roller 11 and thereby pressed onto the strand side 2b. The pivoting of the holder 22 is preferably by means of a Fig. 2 apparent hydraulic cylinder 25 accomplished via a rotatably connected to a pivot shaft 21 lever 26. When adjusting the hydraulic cylinder 25 and the lever 26, the pivot shaft 21 and with it also the bow-shaped holder 22 is pivoted accordingly.

The two other lateral guide rollers 13, 14 are each supported by a respective fixed frame axis 31, 32 pivotable, sleeve-shaped part 33, 34, via two associated with the respective part flange 33a, 34a, in which the rollers are mounted , The two sleeve-shaped parts 33, 34 are rotatably connected to each other via intermeshing tooth segments 35, 36. One of the two parts, according to Fig. 2 the part 34 is actuated or pivoted by a further hydraulic cylinder 40, wherein its pivoting via the toothed segments 35, 36 is also transmitted to the other part 33, so that the two guide rollers 13, 14 via the pivotable flange 33a, 34a exclusively symmetrical to each other, ie adjusted concentrically to the desired axis of the strand guide path and can be pressed according to evenly on the two strand side surfaces 2c, 2d.

About the two hydraulic cylinders 25, 40, the contact pressure of the guide rollers 12, 13, 14 is controlled, and it is ensured that the guide rollers constantly run. As a result, the risk of thermal overload of the rollers and damage to the strand surface is significantly reduced.

In addition, the current contact pressure can be measured in the casting operation and at a pressure rise due to a thermally induced deformation of the casting strand a signal to a control device are issued, via which a targeted change in the cooling initiated and locally, for example on certain strand side, can be performed so that a centric strand run is achieved quasi on the thermal path.

Depending on requirements, a control or regulation of the position and / or the contact force of the guide rollers 12, 13, 14 may be provided on the casting strand (2). In a closed-loop control, this position and / or the contact force of the guide rollers can be set by comparing the setpoints with actual values.

It is also possible to fix a preceding position of the centering rollers via a corresponding circuit of the actuators, for example by regenerative switching of the hydraulic cylinders, up to a very high, adjustable discharge force. This position can be checked at predetermined intervals and corrected if necessary. This correction can be either controlled or even done in the form of an adaptive control that can accommodate the local geometric needs of the string.

Under the mentioned regenerative circuit of the control cylinder is meant a circuit in which the two cylinder pressure chamber are connected via line and the active pressure force results from the rod surface and the oil pressure. Only when the strand wants to escape from the desired position increases the pressure on the piston side and the cylinder is up to a predetermined max. Force blocked.

How out Fig. 3 can be seen, the actuators, preferably hydraulic cylinders 25, 40 and the control device with advantage in a water-cooled, sealed box 41 above the guide rollers housed and protected by the heat radiation and the corrosive environment.

The continuous casting plant according to the invention makes it possible to cast strands of various sizes without impairing the availability of the plant, since the respective change of the guide rolls or new positioning thereof is superfluous. This ensures high production quality in all strand formats.

It would be possible to couple the spray mats equipped with spray nozzles with the adjusting mechanisms of the guide rollers and thereby realize an automatic adjustment of the cooling elements in format changes, which would allow a fast, remote control of the casting plant to new casting format.

The complete centering modules can be quickly installed and removed in the cooling chamber by means of special manipulators positioned outside the cooling chamber. In this case, each module at the junction in the cooling chamber have a special connector unit by means of which all media and signals can be automatically connected.

In principle, within the scope of the invention, only spray nozzles according to the invention could also be provided in a special system, which are contained in a plurality of spray modules (3) arranged one behind the other and can be controlled substantially concentrically to the cast strand axis, during which the guide rollers would be arranged in the conventional sense.

Claims (19)

1. Continuous casting plant for long steel products, having a mould (1), from which a cast strand (2) having several strand sides (2a, 2b, 2c, 2d), is continuously cast, which strand is guided along a, in particular curved, guideway formed by guide rollers (11, 12, 13, 14) arranged one after the other, and at the same time in a cooling chamber having spray members, characterised in that
   the guide rollers (12, 13, 14) are contained in a plurality of centring modules (10) arranged one after the other and are adjustable in a controlled manner concentrically with respect to the axis of the cast strand, whereby the guide rollers (12, 13, 14) being adjustable by means of actuating members in perpendicular direction to the corresponding strand sides (2b, 2c, 2d) until the contact with the cast strand (2).
2. Continuous casting plant according to claim 1, characterised in that the respective centring module (10) has at least one fixedly mounted roller (11), defining the desired course of the guideway, for one strand side (2a) and further guide rollers (12, 13, 14) for the other strand sides (2b, 2c, 2d), whereby these further guide rollers (12, 13, 14) being adjustable by means of actuating members in a perpendicular direction to the corresponding strand sides (2b, 2c, 2d) to be continuously in contact with the cast strand (2) and the contact force of the respective roller against the cast strand (2) being adjustable.
3. Continuous casting plant according to claim 1, characterised in that the adjustment of the spray members is coupled to the adjustment of the guide rollers (12, 13, 14).
4. Continuous casting plant according to claim 2, characterised in that one of the further guide rollers (12, 13, 14) of the respective centring module (10) is adjustable relative to the fixedly mounted roller (11) and the two remaining guide rollers (13, 14) are adjustable concentrically with respect to the desired axis of the cast strand.
5. Continuous casting plant according to one of the claims 1 to 4, characterised in that the upper guide roller (12), adjustable relative to the fixedly mounted roller (11), of the respective centring module (10) is carried by a U-shaped holder (22) of the actuating member, which holder is pivotably held on a frame (20) of the centring module (10), whereby a hydraulic cylinder (25) or an actuator being present for pivoting the holder (22) or for pressing the guide roller (12) against the cast strand (2).
6. Continuous casting plant according to one of the claims 1 to 5, characterised in that the two remaining lateral guide rollers (13, 14) are carried by in each case one sleeve-shaped part (33, 34) of the actuating member, which sleeve-shaped part is pivotable about in each case one axle (31, 32) fixed to the frame, whereby the two sleeve-shaped parts (33, 34) being rotationally connected to one another via interengaging toothed segments (35, 36) and one of the two parts (33, 34) being actuable by a further hydraulic cylinder (40), for the purpose of symmetrically pivoting the parts (33, 34) or for concentrically pressing the guide rollers (13, 14) against the cast strand (2) running in its desired position.
7. Continuous casting plant according to claim 5 or 6, characterised in that an open-loop control or a closed-loop control of the position and/or of the contact force of the guide rollers (12, 13, 14) against the cast strand (2) is provided.
8. Continuous casting plant according to claim 5, 6 or 7, characterised in that the respective hydraulic cylinder (25, 40) of the actuating member is fixable by means of a control connection, preferably by means of a regenerative connection, in a preset position of the guide rollers (12, 13, 14) up to a very high adjustable limit force.
9. Continuous casting plant according to one of the claims 5 to 8, characterised in that the hydraulic cylinders (25, 40), operatively connected to a control device, are arranged together with the control device in a water-cooled box (41) above the guide rollers (11, 12, 13, 14).
10. Continuous casting plant according to one of the claims 1 to 9, characterised in that the centring modules (10) are installable and removable with the aid of a manipulator positioned outside the respective cooling chamber.
11. Continuous casting plant according to one of the claims 1 to 10, characterised in that, at the points of connection to the casting plant, the centring modules (10) have defined connector units, with the aid of which both cooling and control media as well as measuring and control signals are automatically connected on installation of the modules.
12. Continuous casting plant according to one of the claims 1 to 11, characterised in that spray battens (7), having the spray members embodied as spray nozzles (5) or the like, are assigned to the spray modules (3), whereby these spray battens (7) and with them the spray members being adjustable by means of actuating members in an approximately perpendicular direction to the corresponding strand sides (2b, 2c, 2d).
13. Method for the continuous casting of long steel products, in which the liquid steel is poured into a mould (1) and at the bottom is continuously withdrawn from this mould (1), with formation of a shell, whereby the cast strand (2) being guided along a guideway formed by guide rollers (11, 12, 13, 14) arranged one after the other and being further cooled by being subjected to the action of coolants, characterised in that
    that the cast strand (2) runs through a plurality of centring modules (10) arranged one after the other, the desired course of the guideway being predetermined by in each case one fixedly mounted roller (11), acting on one strand side (2a), of the respective centring module (10), and the cast strand (2) being centrally guided by means of further guide rollers (12, 13, 14) acting on the other strand sides (2b, 2c, 2d) and adjustable in a substantially perpendicular direction to these sides, whereby the contact force of the respective guide roller against the cast strand (2) being adjustable in a controlled manner, and the contact force of at least one part of the guide rollers (11, 12, 13, 14) against the cast strand (2) is measured and a signal is delivered to a control device.
14. Method according to claim 13, characterised in that the contact force of the strand against the lateral guide rollers (13, 14) is measured in each case and signals derived therefrom are delivered to a control device, via which, in the event of a thermal deformation of the cast strand (2), a targeted alteration of the cooling effected by the cooling device (3) is initiated and locally carried out.
15. Method according to claim 13 or 14, characterised in that the contact force of the strand against the upper guide rollers (12) as it moves along its curved guideway is measured in each case and signals derived therefrom are used to monitor the frictional forces in the region of the mould.
16. Method according to one of the claims 13 to 15, characterised in that the contact force measured by the water-cooled guide rollers (12, 13, 14) moved by the cast strand is used to control the strand cooling.
17. Method according to one of the claims 13 to 16, characterised in that the positions of the guide rollers (12, 13, 14) are measured and the current cross-sectional dimensions of the cast strand are calculated therefrom.
18. Method according to one of the claims 13 to 17, characterised in that, in the event of format changes of the cast strand (2), the adjustment of the guide rollers (12, 13, 14) can automatically trigger an adjustment of spray battens (7, 41) or the like, which are fitted with spray members (42) and form part of the cooling module (3).
19. Method according to one of the claims 13 to 18, characterised in that the guide rollers (12, 13, 14) are pressed against the cast strand (2) approximately with the same pressure.

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