EP1307305B1 - Method and strand guide for supporting, guiding and cooling casting strands made of steel, especially preliminary sections for girders - Google Patents

Abstract

A method and strand guide for supporting, guiding and cooling casting strands (1) made of steel, especially preliminary sections (2) for girders, which are cooled by injected water (29) and are drawn. The inventive method prevents cracks, especially surface cracks, from appearing in the microstructure by adapting the cooling conditions of the surface of the strand during secondary cooling. Undercooling of the chill of the strand is prevented by adapting the cooling and support of the beam blank format to the solidification range in order to avoid an undesirable solidification structure on the upper flange edges or in other cross-sectional areas so that cooling and support are provided exclusively where a crater is formed. The casting strand (1) is cooled by guiding the temperature in a specific manner in upper supporting segments (5, 6, 7) by means of injected water jets whose width at least matches the length of the supporting rollers on longitudinal and transversal sides (13, 14) of the cross section (1a) of the casting strand, and is decreasingly supported in an analogous manner with respect to the length of the casting path and the cooling state in core areas (15) of the cross section (1a) of the casting strand on the transversal sides (14) of said casting strand cross section (1a) and cooling occurs exclusively by means of water jets (8) which are oriented towards said core areas (15).

Description

The invention relates to a method and a strand guide for supporting, guiding and cooling of cast strands of steel, in particular of BBL pre-profiles for Support in which the cast strand after leaving the continuous casting mold in a Zero segment by means of secondary cooling and in subsequent support segments further cooled by water and pulled out.

From JP 42 00 844 it is known in a strand guide for Gießquerschnitts-longitudinal sides individual support rollers, partly as Tipprollen, partly as in Profilgrund arranged longitudinal rollers of short length to use. To the Cast cross-section broadsides are then arranged correspondingly long support rollers. However, this arrangement takes no account of the on relevant cast strand bodies existing strand shell thicknesses and the required cooling.

From the report "The casting of beam blanks in the electric steelworks of Stahlwerk Thüringen GmbH, Unterwellenborn "(Dengler, J-M et al, Stahl and Eisen, 1997, No. 5), a suitable strand guide is known. It teaches in addition to the water cooling of the strand the bridge, both flanges and the four flange tips to lead by means of unequal length support rollers. From the 11th Level to the end of the relevant support segment at the 20th roller level the cast strand is only on the bridge and on both flanges with 4 support rollers guided. The external cooling is only dependent on the Solidification state regulated.

It should be noted that the function of the strand guide not only the Supports the cast strand against the ferrostatic pressure includes, but also the withdrawal of solidification heat by the secondary cooling and the Maintaining the profile geometry generated in the continuous casting mold. It kick however, surface cracks still occur.

The goal of the strand guide must be a faultless surface quality of the Casting, an interior quality without cracks and without segregation at high Be true to profile.

The invention is based on the object, cracks in the microstructure, in particular surface cooling cracks, by adaptation of the cooling conditions the strand surface in the area of secondary cooling, and in this in particular to avoid hypothermia of the strand shell.

The object is achieved by a method according to the preamble of claim 1 according to the invention achieved in that to avoid an undesirable solidification structure on the flange upper edges or in other cross-sectional areas the cooling and support of the beam blank format the solidification areas adapted so that only in areas where sump formation is present, cooled and supported.

An embodiment of the method provides that the cast strand through Targeted temperature control in upper support segments with at least the length the support rollers corresponding widths of the spray water jets at Längsund Transverse sides of the Gießstrangquerschnitts cooled and analogous to Strangweglänge and the cooling state in core zones of Gießstrangquerschnitts supported on the transverse sides decreasing and only with on the liquid core zones directed spray water jets with the same or smaller Width of the bottom side is cooled. This will cause hypothermia Strand shell avoided, and the risk of cracks, especially surface cracks, is significantly reduced.

In a further embodiment of the invention, it is proposed that the cast strand through targeted temperature control in the zero support segment at its profile ends and in the longitudinal side center region of its cross section and on the Transverse sides supported, and thereby longitudinal sides and transverse sides of the Gießstrangquerschnitts, except the cast strand profile corner sections, cooled and that with strand shell formation progressing along the strand path length only the center area and the two transverse sides of the Gießstrangquerschnitts and in the area of the swamp tips of the core zones the transverse sides are restricted in the region of the sump tip or sump tips supported and cooled and on the long sides only on the Swamp zone directed spray water jets are used. This can a targeted temperature control depending on the cross-sectional zones of the Gießstrangquerschnitts not only in rectangular Gießstrangquerschnitt, but also be achieved in profile strands.

Further features of the invention provide that in the area of the swamp zone of the Gießstrangquerschnitt supported on its transverse sides without spray water cooling becomes. Advantageously, a heat flow of hotter takes place Zones in already cooled zones without a large temperature jump.

The targeted temperature control can also be completed to that the cast strand in the state of substantial solidification without Spray water jets and without top and side supports, on support rollers is guided on-the-floor.

The task will continue by means of guidance and cooling solved according to the invention in that the cast strand in individual Support segments targeted temperature-controlled, such that of support segment to support segment one to the solidification state of the extruded profile adapted secondary cooling is used, which consists of spray water jets a width equal to or greater than the length of support roller pairs and on the longitudinal side and in each case on the transverse side of the Gießstrangquerschnitts is provided and that following the zero segment Support segments are formed open, with excess water spray in a plurality of directions of Gießstrangquerschnitt through in the Frame open support segments can be derived. This will be over a Process-oriented secondary cooling through targeted support segment formation with an optimal arrangement of strand guide rollers the tendency to Hypothermia of strangles (flank corners) with bad Ductility behavior avoided and thus the emergence of cracks in the Microstructure and surface avoided. It can also be a homogeneous temperature distribution in Gießstrangquerschnitt be achieved.

• minimierte Wasserspritzmenge nur zur Abführung der Erstarrungswärme
• Reduzierung von Laufwasser wegen Unterkühlung der Flanschoberseiten und anderer Querschnittsbereiche
• Homogenes Temperaturbild im BBL-Querschnitt
• Temperaturführung von der Kokille bis in den Richttreiberbereich
• Einstellung von Oberflächentemperaturen im günstigen Duktilitätsbereich

By the temperature-controlled cooling and support in the form according to the invention the following effects are achieved:

• Minimized water injection quantity only to dissipate the solidification heat
• Reduction of running water due to hypothermia of the flange tops and other cross-sectional areas
• Homogeneous temperature image in BBL cross section
• Temperature control from the mold to the straightener area
• Adjustment of surface temperatures in the favorable ductility range

• Stützrollen, die nur im Sumpfbereich stützen
• Segmentausbildung so, dass die Flanschoberseiten nicht überdeckt werden
• Sicherstellung optimaler Wasserablaufeigenschaften
• Wasserauffang- und Leitbleche an den Segmentoberseiten, so dass möglichst wenig Laufwasser anfällt.

The strand guide segments should be adapted to the procedural requirements in training. Therefore the training takes place in the following way:

• Support rollers that support only in the sump area
• Segment formation so that the flange tops are not covered
• Ensuring optimal water drainage properties
• Water collecting and baffles on the top of the segment, so that the least possible running water is obtained.

The support and secondary cooling are designed according to further features such that in the zero support segment longitudinal sides of the Gießstrangquerschnitts by means of symmetrically arranged longer support roller pairs and the Gießstrang profile corner areas supported by Tipprollenpaaren shorter length are, and that the transverse sides of the Gießstrangquerschnitts means of about the Side length correspondingly long support roller pairs are supported. Such Support is e.g. advantageous for strand shell thicknesses between 30 and 50 mm. The support is practically from all sides only in the sump profile to unwanted To avoid hypothermia.

Another embodiment provides that in the following support segments to the Longitudinal sides of the Gießstrangquerschnitts only the center symmetrically arranged, longer support roller pairs, and on the transverse sides about the side length corresponding support roller pairs are provided. Here can the Strand shell thickness already assumed between 40 to 60 mm, so that the corner regions of the Gießstrangquerschnitts are no longer supported have to.

A further reduction of the support forces takes place according to other characteristics, in each of the following support segments on each of the transverse sides symmetrically arranged support roller pairs are shortened. It is assumed, that central areas of the cast strand are already solidified here, and the strand shell in outdoor areas approximately 50 to 70 mm thick.

With more advanced solidification is provided that in the following support segments only the symmetrically arranged on the transverse sides, shortened Support roller pairs are provided. For pre-profile casting strands is in the corner regions of the Gießstrangquerschnitts experience already a Strand shell thickness of 70 to 90 mm assumed.

It is proposed that the cast strand in sections more extensive Kernerstarrung rests only on the bottom on support rollers.

An improvement provides that the spray pattern of the secondary cooling analog designed for Gießsumpf core zone. As a result, too high a water supply be avoided.

It is provided with advantage that excess spray can be derived is. As a result, fall in the middle of the cast strand, e.g. on the profile web of a Preprofiles, only minimal amounts of water after the strand support on.

Another embodiment provides that a long support role as well wider or wider spray water jet is assigned. This measure is especially applicable for relatively thin strand shells of about 30 to 60 mm.

And finally, an embodiment may consist in that tapping rolls only still provided in a support segment following the zero support segment are.

In the drawing Ausführungsbeipiele the invention are shown and will explained in more detail below.

Fig. 1

einen Gießstrang in Seitenansicht mit dem Gießstrangweg zugeordneten Strangschalendicken für einen Vorprofil-Gießstrang,

Fig. 1 A

den Gießstrangquerschnitt in der Stranggießkokille,

Fig. 2A

den Gießstrangquerschnitt am Ausgang der Stranggießkokille,

Fig. 2B

den Gießstrangquerschnitt mit Stützrollenanordnung und Sekundärkühlung im Null-Segment,

Fig. 2C

den Gießstrangquerschnitt mit Stützrollenanordnung und Sekundärkühlung in einem nachfolgenden Stützsegment,

Fig. 2D

den Gießstrangquerschnitt mit Stützrollenanordnung und Sekundärkühlung in einem weiteren Stützsegment,

Fig. 2E

den Gießstrangquerschnitt mit Stützrollenanordnung und Sekundärkühlung im nächsten Stützsegment,

Fig. 2F

den Gießstrangquerschnitt vor der Durcherstarrung, ohne Sekundärkühlung,

Fig. 2G

den Gießstrangquerschnitt bei nahezu vollzogener Durcherstarrung,

Fig. 2H

den Gießstrangquerschnitt nach vollständiger Durcherstarrung auf dem Rollgang aufliegend,

Fig. 3

eine perspektivische Ansicht eines Stützsegmentes,

Fig. 4A

ein perspektivischer Schnitt durch das Stützsegment mit Tipprollen,

Fig. 4B

ein perspektivischer Schnitt durch das Stützsegment ohne Tipprollen,

Fig. 5

eine perspektivische Seiten-Ansicht im Querschnitt eines Null-Stützsegmentes in offener Ausbildung und

Fig. 6

eine perspektivische Ansicht des Null-Stützsegmentes in offener Ausbildung.

Show it:

Fig. 1

a cast strand in side view with the Gießstrangweg associated strand shell thicknesses for a pre-profile casting strand,

Fig. 1 A

the Gießstrangquerschnitt in the continuous casting mold,

Fig. 2A

the cast strand cross-section at the outlet of the continuous casting mold,

Fig. 2B

the cast strand cross section with support roller arrangement and secondary cooling in the zero segment,

Fig. 2C

the Gießstrangquerschnitt with support roller assembly and secondary cooling in a subsequent support segment,

Fig. 2D

the Gießstrangquerschnitt with support roller assembly and secondary cooling in another support segment,

Fig. 2E

the Gießstrangquerschnitt with support roller assembly and secondary cooling in the next support segment,

Fig. 2F

the cast strand cross-section before solidification, without secondary cooling,

Fig. 2G

the Gießstrangquerschnitt with almost completed Durcherstarrung,

Fig. 2H

the Gießstrangquerschnitt after complete solidification resting on the roller table,

Fig. 3

a perspective view of a support segment,

Fig. 4A

a perspective section through the support segment with Tipprollen,

Fig. 4B

a perspective section through the support segment without Tipprollen,

Fig. 5

a side perspective view in cross section of a zero support segment in the open and

Fig. 6

a perspective view of the zero support segment in open training.

As an exemplary embodiment, a cast strand 1 for a pre-profile 2, from the carrier rolled (Figures 1 and 1A). The casting strand 1 is after the Leaving the continuous casting mold 3 in a zero support segment 4 with a secondary cooling and subsequently in further support segments 5, 6 and 7 Spray water jets 8 cooled and powered rollers of a Ausziehmaschine 9 pulled out.

At a distance of 2 m to 2 m are the strand shell thicknesses with thickness information in mm indicated. The length L designates the entire plant length of the Continuous casting mold 3 up to the Ausziehmaschine 9. Also put the radii R1, R2 and R3 fix the arc of the strand course.

The cast strand 1 is replaced by a targeted temperature control in the (upper) Zero support segment 4 with spray water jets 8 applied, the width of a 10th which is equal to or greater than the length 11 of the support roller pairs 12th Such spray water jets 8 are on the longitudinal side 13 and on the transverse side 14 of Gießstrangquerschnitts 1 a used (Fig. 2A-2H). Analogous to the strand path length and the cooling state in core zones 15, which are still viscous Melt contained in the Gießstrangquerschnitt 1a, the transverse sides 14 decreasingly supported (FIGS. 2D-2F) and the spray water jets 8 become only directed to the core zones 15 (FIG. 2D).

According to the best possible method (FIGS. 2A-2H), the form-true, cast strand 1 produced in the continuous casting mold 3 into the zero support segment 4 (Fig. 2B), in which the casting strand 1 by means of the longitudinal side 13 arranged in the longitudinal side center region 16 support rollers 17 and to the Transverse sides 14 arranged support rollers 18 is supported. Here are the Gießstrang-Profileckbereiche 19 not cooled, but supported by means of 20 Tipprollen. The spray water jets 8 each form opposite, still in the liquid or viscous range strand and its strand width or strand thickness an opening in the flow direction angle. Thereby heat is extracted only to a greater extent there, where inside the Cast strand 1 is still liquid or viscous melt, while Already solidified areas, spared essentially the rest of strand shell 21 remains. This results in a gentler cooling of the strangeness and therefore there are fewer or no surface cracks. According to FIG. 2C, the spray water jets 8 are still widely maintained. In Fig. 2D is immediately recognizable that only the center region 16 of Gießstrangquerschnitts 1a is supported by support rollers 17, but no longer cooled becomes. The spray water jets 8 are directed only to the core zones 15. The support rollers 18 are kept considerably shorter. This targeted temperature control continues in the strand run (Fig. 2E) so far that only Spray water jets 8 directed on the longitudinal side 13 to the core zone 15 become. Finally, the core zone 15 (Figure 2F) is very small, leaving the cast strand 1 no longer needs to be cooled and only by means of Support rollers 18 is guided on the transverse sides 14. In Fig. 2G, the smaller Kemzonen 15 continues and the casting strand 1 is only on the horizontal Support rollers 22 out. According to FIG. 2H, the cast strand 1 is solidified. The Thickness of the strand shell 21 is, for example (depending on the respective Casting cross-section dimensions) in each case in FIG. 2B with 38.2 mm, in FIG. 2C with 54.0 mm, in Fig. 2D with 66.1 mm, in Fig. 2E with 76.4 mm, in Fig. 2F with 85.4 mm, 93.5 mm in FIG. 2G and 101.0 mm in FIG. 2H.

In Fig. 3 one of the support segments 5,6,7 is shown. After that are essential Assemblies each have a top frame 23, a bottom frame 24, side frames 25, removal rollers 26 and battens 27.

FIGS. 4A and 4B show the respective ones extending in the directions of the arrows 28 Outflow of spray water 29. The drain is in particular by a "open" design of the support segments 5,6,7, allows, wherein the Gießstrangquerschnitt 1a starting from an open frame in each case from the outside Ribs 30, reinforcements 31, inner ribs 32 and one nozzle 33 is surrounded on four sides.

The representation of FIG. 4A corresponds approximately to the strand path length in FIG Figs. 2B and 2C. The representation of FIG. 4B corresponds to the strand path length of FIG Fig. 2D.

Fig. 5 shows a vertical section through the drawn in operating position Support segment 5,6,7, wherein the open design of a support segment 5, 6, 7 is particularly easy to recognize. The nozzle sticks 33 through the Spray water jets 8 directed against the Gießstrangquerschnitt 1a splashing 29 can easily drain between the reinforcements 31 all around.

Referring to FIG. 6, a support roller stand 5, 6, 7 is described in FIG Training in operational position drawn in view.

LIST OF REFERENCE NUMBERS

1

cast strand

1a

Gießstrangquerschnitt

2

Preprofile (extruded profile)

3

continuous casting

4

Zero support segment

5

supporting segment

6

supporting segment

7

supporting segment

8th

splash-ray

9

Ausziehmaschine

10

Width (of spray water jet)

11

length

12

Support roller pairs

13

Longitudinal side (of the casting strand)

14

Transverse side of the casting strand

15

core zone

16

Longitudinal side center region

17

supporting role

18

supporting role

19

Cast strand-profile corner area

20

Tip role

21

strand shell

22

horizontal support roller

23

top frame

24

subframe

25

side frame

26

Construction roles

27

spray bar

28

arrow

29

splash

30

outer ribs

31

reinforcement

32

inner ribs

33

nozzle

Claims (15)

1. Method of supporting, guiding and cooling cast strips of steel, particularly of preliminary sections for girders, in which the cast strip after leaving the continuous casting mould is cooled and drawn out in a zero segment in a secondary cooling and in subsequent support segments again by spray water, characterised in that for avoidance of an undesired hardening structure on the flange upper edges or in other cross-sectional regions the cooling and supporting of the beam blank format is adapted to the hardening regions in such a manner that there is cooling and supporting only in regions in which liquid phase formation is present.
2. Method according to claim 1, characterised in that the cast strip is cooled by selective temperature guidance in upper support segments by widths, which correspond at least with the length of the support rollers, of the spray water jets at longitudinal and transverse sides of the cast strip cross-section and supported to decreasing extent analogously to the strip path length and to the state of cooling in core zones of the cast strip cross-section at transverse sides thereof and cooled only still by spray water jets, which are directed towards the liquid core zones, with the same width as or smaller width than the liquid phase side.
3. Method according to claim 1 or 2, characterised in that the cast strip is supported by selective temperature guidance in the zero support segment at the section ends and in the longitudinal side centre region of its cross-section and at its transverse sides, and the longitudinal and transverse sides, excluding the section corner regions, are cooled, that in the case of strip skin formation progressing on the strip path only still the centre region and the two transverse sides of the strip cross-section are supported, and that in the region of the liquid phase ends of the core zones the transverse sides are supported and cooled to limited extent in the region thereof, and only spray water jets directed towards the liquid phase zone are still used at the longitudinal sides.
4. Method according to one or more of claims 1 to 3, characterised in that the cast strip cross-section is supported in the region of the liquid phase zone at the transverse sides thereof again without spray water cooling.
5. Method according to one of claims 1 to 4, characterised in that the cast strip in the state of extensive hardening through is guided without spray water jets and lying on support rollers without upper and lateral support.
6. Strip guide for cast strips (1) of steel, particularly for preliminary sections (2) for girders, comprising a zero support segment (4) adjoining the continuous casting mould (3) and a secondary cooling with spray water jets (8) as well as successive further support segments (5 to 7) and a drawing-out machine (9), characterised in that the cast strip (1) is selectively guided in terms of temperature in individual support segments (4, 5, 6, 7) in such a manner that from support segment (4) to support segment (7) there is used a secondary cooling which is adapted to the state of hardening of the strip section (2) and consists of spray water jets (8) with a width (10) the same as or larger than the length (11) of support roller pairs (12) and which is provided at the longitudinal side (13) and each time at the transverse side (14) of the cast strip cross-section (1a) and that the support segments (5 to 7) following the zero segment (4) are constructed to be open, wherein excess spray water (29) can be conducted away in a plurality of directions (28) from the cast strip cross-section (1a) by the support segments (5 to 7) open in the frame.
7. Strip guide according to claim 6, characterised in that, in the zero support segment (4), longitudinal sides (13) of the cast strip cross-section (1a) are supported by means of longer support roller pairs (17) arranged to be symmetrical with respect to the centre, and cast strip section comer regions (19) are supported by means of tipping roller pairs (20), and that the transverse sides (14) of the cast strip cross-section (1a) are supported by means of support rollers (18) approximately corresponding in length with the side length.
8. Strip guide according to one of claims 6 and 7, characterised in that in following support segments (5, 6, 7) only longer support roller pairs (17), which are arranged centrally, are still provided at the longitudinal sides (13) of the cast strip cross-section (1a) and support roller pairs (18), which approximately correspond in length with the side length, are provided at the transverse sides (14) of the cast strip cross-section.
9. Strip guide according to one of claims 6 to 8, characterised in that in following support segments (5, 6, 7) support roller pairs (18) respectively arranged at the transverse sides (14) are shortened.
10. Strip guide according to one of claims 6 to 9, characterised in that in following support segments (5, 6, 7) only symmetrically shortened support roller pairs (18) are still provided at transverse sides (14).
11. Strip guide according to one of claims 6 to 10, characterised in that the cast strip (1) in portions of extensive core hardening only still rests at its underside on support rollers (22).
12. Strip guide according to one of claims 6 to 11, characterised in that the spray pattern of the secondary cooling is designed analogously to the cast liquid phase core zone (15).
13. Strip guide according to one of claims 6 to 12, characterised in that excess spray water (29) can be conducted away.
14. Strip guide according to one of claims 6 to 13, characterised in that a long support roller (17; 18) is respectively associated with a spray water jet (8) which is just as wide or is wider.
15. Strip guide according to one of claims 6 to 14, characterised in that tipping rollers (20) are only still provided in a support segment (5) which follows the zero support segment (4).

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