EP0332939B1 - Bow-type continuous casting plant for billets - Google Patents

Abstract

In bow-type continuous casting plants for billets, blooms and sheet bars which use a rigid dummy bar (10) for initial casting, structural and/or surface defects, such as cracks, in the cast strand (12) are to be avoided even in the case of small arc radii, e.g. </= 3 m. For this purpose, an oval-arc-shaped straightening section (18) with bending reaction rolls (8) is provided for the cast strand (12) underneath the guideway (17) for the circular-arc-shaped dummy bar (10), between a pair (6, 6') of driving rolls arranged on a circular-arc-shaped strand path and the decoupling point (15). <IMAGE>

Description

The invention relates to a continuous sheet caster according to the preamble of claim 1.

In order to achieve a low overall height in continuous steel casting plants, molds with a curved mold cavity are used. The overall height could be further reduced by reducing the arc radii of such molds. As the mold radii become smaller, however, the stretch in the strand crust in the straightening machine increases when the strand is straightened. It has therefore been proposed to combine circular arc molds with oval-arc-shaped strand guides. Such systems require a flexible start-up line for casting, which usually consists of articulated links.

For smaller formats, in particular for billet systems, so-called rigid, circular-arc-shaped starting strands are advantageously used in the case of continuous-arc casting systems instead of flexible starting strands. In DE-OS 2'629'453, which forms the preamble of the main claim, an arc continuous casting system for billets or blooms with a rigid starting strand is described. The length of the start-up line is dimensioned such that the head end is inserted into the bow mold and the foot end is engaged in the leveler. A pair of driving rollers of the leveling machine is arranged at the tangent point. A straightening roller, which is also a decoupling between the starting line and cast strand, aligns the arcuate strand at the tangent point according to the single-point straightening process. After uncoupling, the rigid start-up line is brought into a parking device above the horizontal conveying path by means of a drive. With a correspondingly large circular arc, for example between 4 and 8 m radius, such systems are also suitable for crack-sensitive steels or larger strand formats, because the elongation during straightening decreases with increasing circular arc radius. If a radius of the circular arc of 3 m or less is provided, the elongation increases when straightening at the tangent point. The distance between the pair of driving rollers at the tangent point and the decoupling and straightening roller is also becoming shorter. This leads to structural and / or surface defects on the cast strands.

The invention has for its object to provide a continuous casting system with a rigid start-up strand, which on the one hand has a low overall height with an arc radius of, for example, R ≦ 3 m and at the same time avoids structural and / or surface defects, such as cracks, etc. on the cast strand.

To achieve this object, the invention proposes a continuous sheet caster according to the sum of the features of claim 1.

The continuous strand casting installation according to the invention allows a rigid, circular-arc-shaped starting strand to be passed through an oval-arc-shaped strand guiding part without radial bending forces acting on the starting strand. Furthermore, the basic concept according to the invention makes it possible to replace part of the circular-arc-shaped strand guideway by the oval-arc-shaped straightening section, as a result of which the cast arc-shaped strand can be gently bent open in two or more stages early, for example before reaching the tangent point. The bending reaction roll (s) ensure that the strand, regardless of its possibly irregular temperature, especially during the pouring period, is exposed to precisely defined changes in elongation along the straightening section. In contrast to the straightening concept according to the invention, in the known single-point straightening the strand is straightened in one step in an uncontrolled manner. The strand is not directed along a curve, but according to its current local bending resistance. According to the invention, bulky sheet continuous casting plants with a rigid start-up strand can therefore be significantly reduced in structure for the first time without disadvantages for the cast strand, which has a positive effect both on the overall height of the installation and on the length of the parking facility for the rigid start-up strand.

The oval-arched straightening section can be seen in the direction of the strand, e.g. start with a vertical beam of radii and the outfeed section for cast strands following the straightening section can rise slightly or be arranged horizontally. An advantageous embodiment is obtained when the pair of drive rollers is arranged on a radius beam which lies in front of the vertical radius beam in the strand running direction and an angle of up to 30 degrees, preferably between 5-20 degrees, is provided between the two radius rays. As a further alternative solution, it is proposed to arrange a bending reaction roller of the oval-arch-shaped straightening section on the vertical radiant beam.

The start of the bending process along the strand guide can be freely selected depending on the size of the intended casting format, steel quality, etc. by placing the pair of drive rollers. The design principle also enables the number of straightening stages to be freely designed between the pair of drive rollers and the straightening roller. According to a further proposed solution, the straightening roller arranged in the strand conveying direction after the vertical radius beam can be used Separate the cast strand at the decoupling point from the start-up strand at the same time and transfer it from the circular arc via an oval arc to a straight line in at least two straightening stages. Any number of bending reaction rollers can be arranged between the pair of drive rollers and the straightening roller along the outside of the oval-curved straightening path.

It is at the discretion of the person skilled in the art to distribute the format- and steel quality-specific strains on the strand surface on bending sections before and after the vertical radius beam. In the sense of an additional alternative solution, it is proposed that the position of the bending reaction roller arranged on the vertical radius beam is fixed in such a way that the straightening section is divided into two partial straightening sections with essentially the same partial expansions on the strand surface. The change in elongation along the straightening section on the strand surface with a strand thickness of, for example, 100 mm can advantageously be set to a maximum of 0.002% / mm.

The start head with the coupling element for the cast strand can be attached directly to the rigid start strand. Variants are also known which provide an additional coupling element between the starting head and the rigid starting strand, which ensures a separation between the cast strand and the starting strand during each casting cycle. In a particularly advantageous embodiment, the rigid starting strand has a pivotable starting head member with a pivot axis parallel to the pivoting axis of the starting strand. The role for decoupling the starting strand from the cast strand exerts a force essentially radially directed to the circular arc-shaped strand path on this starting head member. A decoupling is initiated before the cast strand reaches the straightening and uncoupling roll. Such a start-up line can also then also be trouble-free be moved into the mold if the start-up strand or the strand guide have certain dimensional tolerances to the nominal dimension due to wear. When moving in through the mold, the start-up head can be swiveled slightly and centered. Modern sealing methods that pinch a seal when retracting, as described for example in EP-PS 0'114'309, can also be used in such systems.

The precision of the introduction of the start-up line can be further increased if the start-up line is guided at its end opposite the start-up head by means of a pivot lever articulated in the center of the circular arc.

Exemplary embodiments of the invention are described below with reference to figures.

Fig. 1

eine Seitenansicht auf eine schematisch dargestellte Bogenstranggiessanlage und

Fig. 2

eine Seitenansicht auf eine oval-bogenförmige Richtstrecke.

Show it:

Fig. 1

a side view of a schematically illustrated continuous casting and

Fig. 2

a side view of an oval-arched straightening section.

In Fig. 1, a continuous sheet caster with an arc mold 3, an oscillation device 4 and a secondary cooling device 5 is shown. The center of the circular arc is designated 9. A driving straightening machine is constructed from a pair of driving rollers 6, 6 ', a straightening roller 7 and a bending reaction roller 8. An arc-shaped, rigid starting strand 10, which is held and guided by a pivot lever 11 articulated in the circular arc center 9 during the movement, is shown in a decoupling position by a cast strand 12. A support 13 represents part of a parking device. The swivel lever 11, which can be connected fixedly or coupled to the starting line 10, has a swivel drive, not shown, which is known per se.

He can pivot the starting strand around the center of the arc 9 and insert it into the drive roller pair 6, 6 'or lead it out of it. An arrow 15 points to a decoupling point at which the straightening roller 7 separates or uncouples the cast strand 12 from the starting strand 10. Below the guideway 17 for the arc-shaped starting strand 10 between the drive roller pair 6, 6 'and the decoupling point 15, an oval-arc-shaped straightening path 18 is provided with the bending reaction roller 8 for the cast strand. The Teibrollenpaar 6, 6 'lies on the circular arc, which has a radius of 2.5 m, for example. The bending reaction roller 8 is positioned so that a first bending radius of e.g. 4.5 m results. A subsequent roller 20 is already arranged in the horizontal plane of a cooling bed. With 7 'dash-dotted line roller 7 is shown in a position after decoupling. In this position she acts as a judge.

The rollers 20 belong to the discharge path, which can be arranged horizontally or slightly inclined. The pair of driving rollers 6, 6 'lies on a radiant beam 21 which begins at the center 9 of the guideway 17 of the arc-shaped starting strand 10. This radiate beam 21 lies in the strand running direction 22 in front of a vertical radiate beam 23. Between the two radiate beams 21, 23 there is an angle alpha of, for example, up to 30 degrees, preferably between 5-20 degrees.

The bending reaction roller 8 of the oval-arc-shaped straightening path 18 is also arranged on the vertical radiant beam 23. It lies below the guideway 17 of the arc-shaped starting strand 10, approximately in the middle of the oval-arc-shaped straightening section 18. Between the rollers 6, 6 'and this bending reaction roller 8, the strand is bent in a first step. Separates in the line conveying direction 22 after the vertical radius beam 23 at the decoupling point 15 the straightening roller 7 the cast strand from the starting strand and bends the cast strand in the two straightening stages mentioned from the circular arc over an oval arc into a straight line. The position of the bending reaction roller 8 or the radius of the first bending step can be calculated such that there are two partial straightening sections along the straightening section 18 with essentially the same strains on the strand surface. For example, with a 100 mm thick strand, an arc radius of 2500 mm, a length of the straightening path of at least 1000 mm, elongation changes Epsilon in% / mm on the strand surface of a maximum of 0.002 can easily be realized.

In FIG. 2, the same reference numbers as in FIG. 1 are used for the same parts. The rigid starting line 10 is provided with a pivotable starting head member 25 with a pivot axis 26 parallel to the pivot axis in the circular arc center 9 (FIG. 1) of the starting line 10. The roller 7 for decoupling the starting strand 10 from the cast strand 12 exerts a force which is essentially radially directed to the arcuate strand path on the starting head member 25. In this example, the uncoupling can be initiated earlier and the foot end of the strand 12 can thereby be better directed. The starting head member 25 is provided with means which ensure that the member 25 tilts back into the arc shape of the starting strand 10.

In addition to the role 8, a further bending reaction role 8 'is included in this example, which gives an additional straightening level. In this example, the cast strand 12 is directed simultaneously in three straightening stages by means of the roller 7. The circular-arc-shaped guideway 17 of the starting strand 10 is shown in dash-dotted lines.

Claims (8)

1. A bow-type continuous casting plant for billets, blooms and sheet bars comprising a bow-shaped mold (3), a secondary cooling device (5), a driving straightening machine with driving rollers (6) and straightening rollers (7, 8) and a circular bow-shaped rigid starting billet (10) with a drive device (11) and a parking device (13), the starting billet (10) being separable from the cast billet (12) at an uncoupling site (15) by means of the straightening roller (7), characterised in that an oval bow-shaped straightening stage (18) with bending reaction rollers (8) for the cast billet (12) is provided beneath the guide path (17) for the circular bow-shaped starting billet (10) between a driving roller pair (6, 6′) arranged on a circular bow-shaped billet path and the uncoupling site (15).

2. A bow-type continuous casting plant according to claim 1, characterised in that a substantially horizontal extraction stage (20, 20′) is provided for the straightened billets and the driving roller pair (6, 6′) is arranged on a radius (21) lying upstream of the vertical radius (23) in the billet running direction and an angle (alpha) of up to 30 degrees, preferably between 5 and 20 degrees, is provided between the two radii (21, 23).

3. A bow-type continuous casting plant according to claim 2, characterised in that a bending reaction roller (8) of the oval bow-shaped straightening stage (18) is arranged on the vertical radius (23).

4. A bow-type continuous casting plant according to claim 2 or 3, characterised in that the straightening roller (7) arranged downstream of the vertical radius (23) in the billet conveying direction (22) simultaneously separates the cast billet (12) from the starting billet (10) at the uncoupling site (15) and converts the cast billet (12) in at least two straightening stages from the circular bow shape, through an oval bow shape into a straight line.

5. A bow-type continuous casting plant according to claim 3 or 4, characterised in that the bending reaction roller (80 arranged on the vertical radius (23) divides the straightening stage (18) into two partial straightening stages with essentially equal partial stretching of the billet surface.

6. A bow-type continuous casting plant according to claim 5, characterised in that the stretching variation epsilon in the billet surface along the straightening stage (18) is calculated at a maximum of 0.002%/mm with a billet thickness of 100 mm.

7. A bow-type continuous casting plant according to one of claims 1 to 6, characterised in that the rigid starting billet (10) comprises a pivotable starting head member (25) with a pivot axis (26) parallel to the pivot axis (9) of the starting billet (10) and the roller (7) for uncoupling the starting billet (10) from the cast billet (12) exerts a force on the starting head member (25) substantially radial to the circular bow-shaped billet path (17).

8. A bow-type continuous casting plant according to one of claims 1 to 7, characterised in that, at its opposite end to the starting head (25), the starting billet (10) is guided by means of a pivot lever (11) articulated at the arc centre (9).

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