EP0917922B1 - Process and plant for continuous casting slabs - Google Patents

Abstract

The increase in slab cross section due to bulging (10) between two rolls (3, 3') is compensated by a counter pressure applied to the slab (21) opposite to the bulge. The installation has rolls (3, 3') and (4, 4') which are offset relative to one another by at least of a fraction of the roll gap. An Independent claim is also included for a curved slab support unit in which roll segments with individual rolls mesh with one another.

Description

The invention relates to a method for the continuous casting of steel slabs with a Continuous mold, the partially solidified, from one strand shell and one partially liquid core existing strand after exiting from a mold the further solidification between roles on the inside and roles led to an outside of the strand guide and the strand shell in the area between two rollers on the inside spaced apart in the casting direction or the outside deformation in the form of a bulge with a cross-sectional enlargement formed. Furthermore, the invention relates to an implementation suitable for the process.

A strand guide suitable for safely guiding the casting strand includes in usually a larger number of individuals, but more closely interacting as a leadership Strand guide segments with one loose side and one fixed side Frame arranged guide and / or drive rollers, which together form a so-called Form a roll carpet. The roles can be continuous, but also at comparatively large strand widths can be temporarily stored.

The roles of the fixed and loose side point in the mold at a distance from the casting level different diameters in sections, opposite pairs of rollers have the same diameter.

With curved strand guidance between vertical and horizontal sections the segments lie in the radius beam, starting from the vertical course under the Chill mold up to the horizontal outlet.

EP 0 350 431 A2 describes a continuous casting process for slabs with a Continuous mold known. The strand, which partially solidifies in cross section, is between Guided pairs of rollers and is pulled off by means of driven rollers. The individual rolls of pairs of rolls are hydraulically deformed relative to the strand to actually employ.

EP 0 535 368 A1 describes a method and a plant for the production of Steel band known. In the process, a continuously cast steel strip, the consists of a solidified strand shell and a liquid core, in a roll deformation reduced in thickness and then rolled.

EP 0 041 498 A2 describes a continuous sheet caster.
In this case, a strand guide is arranged below the mold, which has two opposite roller conveyors, the rollers of which are mounted on scaffolding parts, the spacing of mutually opposite scaffolding parts and thus the spacing of the roller conveyors being variable in accordance with a rod cross section to be set.

To convert to adjust the distance between each other lying roller conveyors easy to design while allowing the distance to keep the end rolls of adjacent scaffolding parts approximately the same size Roll at least one of the roller tracks on the frame part in the longitudinal direction of this The roller conveyor is arranged so that it can be moved and in different lengths on the scaffolding fixable.

To avoid unwanted thickness deviations and improve the A steel strip strand is used to structure and to simplify the roll deformation unit cast from 40 - 80 mm thick, down to 15 - 40 mm thick and 2 - 15 mm Residual liquid roll-formed in a maximum of three stages and until it solidifies guided.

During the roll deformation of a partially solid steel strand, it turned out that this leads to strand deformations caused by bulges of the Strand shell can lead between two roller contact lines. there there are alternating zones of larger cross-section and zones of smaller size Cross-section, which lead to a pulsation of the residual melt inside the strand.

These bulges can particularly lead to critical shell deformations the liquid / solid phase boundary and thus for internal crack formation due to pulsating Residual melt movements as a result of periodic bulging of the strand shell as well as under the influence of the ferrostatic pressure of the liquid steel column, which extends into the mold in the mold.

• Temperatur, T [K]
• metallurgische Höhe, h [m]
• Rollenabstand, L [m]
• Gießgeschwindigkeit, V [m/min]
• Strangschalendicke, S [mm]
  in erster Näherung nach der Gleichung Wmax = 7,86 * 10-12 exp. (0,0046 * T) h2,25 * L6,1 * V-0,57 * S-5,26

bestimmt.The maximum bulge (W _max ) of the strand shell with a liquid core between two adjacent rolls in the casting direction is essentially determined by the following factors, such as

• Temperature, T [K]
• metallurgical height, h [m]
• Roller distance, L [m]
• Casting speed, V [m / min]
• Strand shell thickness, S [mm]
  in a first approximation according to the equation W Max = 7.86 * 10 -12 exp. (0.0046 * T) h 2.25 * L 6.1 * V -0.57 * P -5.26

certainly.

If you look at the bulging of the strand shell from pair of rollers to pair of rollers the liquid to be displaced (predominantly a two-phase mixture Crystals and melt), it can be seen that the volume to be displaced builds up a pressure sensor based on the ferrostatic pressure, the casting speed. depends on the volume and the path.

In a continuous caster, the volume is between two pairs of rollers Roller guides made of two half volumes, the fixed and loose side of each Are assigned to a segment. When this melting volume is displaced it exerts high pressure on the strand shell with its narrowing and promotes the formation of bulges while the system Strand / strand bulge negatively multiplied, superimposed and uncontrolled Movements of the melt in the mold level leads.

Starting from the aforementioned prior art, the object of the invention based on a process for the continuous casting of steel slabs in the preamble of claim 1 mentioned type and a trained to execute it Continuous caster, with which it is possible to achieve the aforementioned disadvantages and overcome difficulties, and especially the emergence of harmful, to suppress periodic bulges of the strand shell during roll deformation or to compensate.

The object is achieved according to the invention with a method or with a Continuous caster of the type mentioned in claims 1 and 4 with the characteristic features specified therein and with further refinements achieved according to the subclaims.

With the measure of the invention, according to which the entire roller conveyor of the strand guide either on the inside or on the outside in the longitudinal direction, and so that it is shifted in the casting direction, it is achieved that the Cross-sectional enlargement of a strand area affected by bulging the strand area opposite this from outside for training backpressure sufficient to reduce the cross section becomes. With this comparatively surprisingly uncomplicated measure succeeds in at least largely compensating for the effect of a bulge and thus the harmful pulsation of the residual melt in the casting strand is significant to suppress.

An embodiment of the method provides that the roles one side relative to the position of the other side in the casting direction by a maximum of half Roll distance to be offset from each other.

In a continuous caster for the production of steel slabs, in which the partially solidified strand containing a strand shell with a core Melt, after leaving the mold, during further solidification of strand guide segments between rollers spaced apart in the casting direction Is guided inside or an outside, and the strand shell deformations in the form of bulges between two spaced apart in the casting direction Roles of one side or roles of the other side are those role-bearing loss side and fixed side of this strand guide segment under ge mutual toothing by at least a partial amount of a roller spacing staggered.

This measure allows a continuous caster with a surprisingly uncomplicated construction and practically without additional costs to suppress the harmful bulges as far as possible by the rollers of each strand guide segment being offset from one another by at least a partial amount of this roller spacing
This is achieved, for example, in that the bearings on the inside or on the outside are preferably mirrored to one another in the case of intermediate rolls.

A further embodiment of the continuous caster provides that the mold with a flat design of their outlet on one side, for example opposite the strand guide fixed side, with n + 1 castors the loose side below Forming a toothing formed with the first strand guide segment is.

It can in a training of the invention in a continuous sheet caster interlocking segments each with a single-role cluster his.

Finally, use can be made of the measure that the Roll diameter of the first roll directly under the mold to the rolls increases at the end of the strand guide, for example of 100 mm diameter to max. 300 mm diameter.

Fig. 1a

im Querschnitt eine Strangführung nach dem Stand der Technik;

Fig. 1b

im Querschnitt eine Strangführung nach der Erfindung;

Fig. 2a

im Querschnitt und in vergrößerter Darstellung einen Teil der herkömmlichen Strangführung nach Fig. 1a;

Fig. 2b

im Querschnitt und in vergrößerter Darstellung einen Teil der erfindungsgemäßen Strangführung nach Fig. 1b;

Fig. 3

in Draufsicht zwischengelagerte Rollen relativ zur Position einer Querschnittsdarstellung eines von diesen geführten Gießstranges;

Fig. 4

in Ansicht eine verzahnte Senkrecht-Rollenführung mit geschnittenem Gießstrang;

Fig. 5

in Ansicht eine verzahnte Senkrecht-Abbiegestrecke einer Horizontal-Stranggießanlage.

Details, features and advantages of the invention result from the following explanation of some exemplary embodiments shown schematically in the drawings. Show it:

Fig. 1a

in cross section a strand guide according to the prior art;

Fig. 1b

in cross section a strand guide according to the invention;

Fig. 2a

in cross section and in an enlarged view part of the conventional strand guide according to Fig. 1a;

Fig. 2b

in cross section and in an enlarged view part of the strand guide according to the invention according to Fig. 1b;

Fig. 3

in plan view, intermediate rolls relative to the position of a cross-sectional representation of a casting strand guided by them;

Fig. 4

in view a toothed vertical roller guide with cut cast strand;

Fig. 5

in view a toothed vertical bending section of a horizontal continuous caster.

The strand guide shown in Fig. 1a according to the prior art has a mold 20 with a mold outlet 22. Among them is the casting strand 21 in solidification recognizable, its strand shell 1 increases in thickness with increasing solidification, whereas the the residual melt 2 enclosed therein decreases in relative volume, until it is completely frozen at last. In the solidification area is the Strand 21 between rollers 4, 4 'of the fixed side and rollers 3, 3' of Loss side led by management segments. Chill mold 20 and strand guide preferably belong to a continuous caster, not shown for casting steel slabs with a continuous mold with formats between 40 - 250 mm thick, widths between 500 to 3,500 mm and casting speeds between 1 to 10 m / min.

Seen in the casting direction between each two rollers 3, 3 ' above-described harmful bulges recognizable in their Volume enlargement of the residual melt content take place, that periodically with volume constrictions when transporting the strand 21 alternate between each pair of rollers and become extremely disadvantageous Perform "pumping movements" of the melt.

1b shows a strand guide design according to the invention. at this is to compensate for the cross-sectional enlargements affected strand areas each from outside for training a counter-pressure sufficient to reduce the cross section applied. For this, the rolls are over in the casting direction at least a partial amount of their roller spacing, and preferred by half the roller distance, offset from each other.

The compensation effect that can be achieved with great advantage the reduction in harmful volume increases between two spaced guide rollers 3, 3 'and 4, 4' is off Fig. 1b clearly recognizable. The result is as a result of the invention the bulge 10 and thus the increase in volume of the liquid Contents at most half as large as in Fig. 1a.

Figures 2a and 2b make it clear in detail that with a corresponding Arrangement of casting strand 21 and rollers 3, 3 'and 4, 4 'the residual melt to be displaced 2 with the shell 1 unchanged in the case of the strand guiding system according to the prior art (Fig. 2a) compared to the inventive design (Fig. 2b) Bulges 10 as a result of the opposing indentations 11 a maximum of half of the corresponding values relative to the figure Make out 2a. For clarification in FIG. 2a, the Places of increased volume designated 15, whereas the indentations are each designated 11.

FIG. 3 shows the arrangement of intermediate rolls 3, 4, the bearing 8, 9 of the loose and fixed side 6, 7 preferably mirrored in the center to stand by each other. Here are opposite Rolls 3, 4 also with mutually offset roles, z. B. with around 50 % of the roller spacing arranged offset, not surface symmetrical, but arranged symmetrically to each other, whereby these Arrangement for a bulge and minimized in time and place Melt volume movement leads.

Fig. 4 shows an arrangement of roller segments 5, 5 'of a vertical guide path for a casting strand 21 below one Mold 20. The segments 5, 5 'are due to their mutual Roll offset with teeth 14 lined up. It is one half each 22 and 22 'of the mold outlet of the mold 20 relative to the other half with teeth 14, 14 'with the subsequent strand guide segment 5 'by half a roller spacing shortened or lengthened. The same is true the roll-carrying loss side 6 of each strand guide segment 5 or 5 'with mutual interlocking 14 or 14' by at least offset a partial amount of a roller spacing. Also one can "Grid" plate, which normally connects to the exit of the mold, ensure the interlocking with the first roller segment. The figure 4 clearly shows the strand shell increasing in thickness 1 when the content of the melt decreases in the vertical direction 2.

For Figure 1b it must be added that the mold 20 at flat design of its outlet 22 on one side, for example. opposite strand guide fixed side 7 with n + 1 casters 12 opposite casters 13 of the loss side 6 producing one Teeth 14 formed with the first strand guide segment 5 ' is, as can be seen from Fig. 1b.

Figure 5 shows a vertical / horizontal bending system of the strand guide with the segments 5, 5 'associated with each other. This are in the area of the bend according to the visible radius rays strung together. The first, following the mold 20 Segment 5 'is with an offset connection length - fixed side shortens to the extended outlet part 22 of the mold 20 and extended on the loose side to the shortened outlet part 22 'of the mold 20 toothed connected. In the arch section there are one-roll clusters the fixed side arranged at the exit of the segment, the one allow rapid change of the roller segments.

LIST OF REFERENCE NUMBERS

1

strand shell

2

core

3

role

4

counter-roller

5

Strand guide segment

6

loose side

7

fixed side

8th

camp

9

camp

10

bulge

11

indentation

12

castor

13

castor

14

gearing

15

Places with larger volume

20

mold

21

strand

22

mold outlet

Claims (9)

1. Method for continuous casting steel slabs with an open-ended mould (20), wherein the partly hardened strip (21) consisting of a strip skin (1) and a partly liquid core (2) is after exit from the mould (20) guided, during the further hardening, between rollers (3, 3') respectively of an inner side (6) and rollers (4, 4') of an outer side (7) of the strip guidance and in that case the strip skin (1) forms, in the region between in each instance two rollers, which are spaced apart in casting direction, of the inner side (6) or the outer side (7), deformations in the form of a bulge (10) with a cross-sectional enlargement, characterised in that the entire roller path of the strip guidance is displaced in longitudinal direction, and thus in casting direction, either on the inner side (6) or on the outer side (7).
2. Method according to claim 1, characterised in that rollers in each case of one side are offset with respect to one another relative to the position of rollers of the other side in casting direction by at most half the roller spacing.
3. Method according to claim 1 or 2, characterised in that in order to provide compensation for the cross-sectional regions concerned in the cross-sectional enlargements a counter-pressure sufficient for formation of a cross-sectionally reducing depression (11) is applied in each instance from the outside.
4. Continuous casting plant for producing steel slabs, in which the partly hardened strip, containing a strip skin (1) with a core of molten material, after exit from the mould (20) is guided, during further hardening, by strip guide segments (5) between respective rollers, which are spaced apart in casting direction, of an inner side (6) or an outer side (7) and in that case the strip skin (1) forms deformations in the form of bulges (10) between in each instance two rollers (3, 3'), which are spaced apart in casting direction, of one side (6) or rollers (4, 4') of the other side (7), in particular for carrying out the method according to the invention, characterised in that the roller-supporting movable side (6) and fixed side (7) of each strip guidance segment (5) are arranged to be offset relative to one another, with mutual indenting (14, 14'), by at least a part of a roller spacing.
5. Continuous casting plant according to claim 4, characterised in that one half of the mould outlet (22) is constructed to be shortened or lengthened relative to the other half, with indenting (14, 14') with the adjoining strip guide segment (5'), by half a roller spacing.
6. Continuous casting plant according to claim 4 or 5, characterised in that in the case of interpositioned rollers (3, 4) the bearings (8, 9) of the inner side (6) or the outer side (7) are preferably disposed in mirror relationship at the centre point.
7. Continuous casting plant according to one or more of claims 4 to 6, characterised in that the mould (20) in case of planar execution of its outlet (22) is constructed at one side, for example opposite the strip guidance fixed side (7), with n + 1 foot rollers (12) of the movable side (6) with formation of an indenting (14) with the first strip guidance segment (5').
8. Continuous casting plant according to one or more of claims 4 to 7, characterised in that in the case of a curved continuous casting plant the mutually indenting segments (5, 5') are provided with a single roller cluster.
9. Continuous casting plant according to one or more of claims 4 to 8, characterised in that the roller diameter of the first roller (3, 4) increases below the mould (20) up to the rollers (3, 4) at the end of the strip guidance (5) from, for example, 100 mm diameter to at most 300 mm diameter.

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