EP3705202A1 - Conversion of a continuous casting plant for billet or bloom strands - Google Patents

Abstract

The invention relates to a method for converting a continuous casting plant for the continuous casting of a strand with a billet or bloom cross-section and the converted continuous casting plant. The object of the invention is to increase the productivity of the continuous caster as well as the metallurgical quality of the strands produced by the conversion. This object is achieved by the following steps: i) offsetting the flame cutting machine (6) in the casting direction so that a free space (F) is created between the last pull-out unit (5) and the offset flame cutting machine (6); ii) Installation of at least one soft-reduction unit (8) in the free space (F), each soft-reduction unit (8) having an adjusting device and a strand guide roller, which can be adjusted by the adjusting device, for reducing the thickness of the strand.

Description

Field of technology

The present invention relates to the technical field of continuous casting. Today, the majority of the world's steel produced annually is cast into strands with different cross-sections (slabs, billets, blooms, profiles, etc.) in continuously operated continuous casting plants.

Continuous casting machines for continuously casting molten steel into a strand with billet (engl. Billet) or Vorblockquerschnitt (engl. Bloom) are known.

On the one hand, the present invention relates to a method for converting a continuous casting plant for continuous casting of a strand with a billet or bloom cross-section.

On the other hand, the invention relates to the converted continuous caster for the continuous casting of a strand with a billet or bloom cross-section.

State of the art

The conversion of an existing continuous caster to continuously cast a strand with billet or bloom cross-section in order to increase the productivity of the continuous caster and / or the quality of the strands produced is often difficult, time-consuming and expensive due to the prevailing framework conditions. On the one hand, the arc radius of the strand guide cannot simply be changed due to structural conditions (e.g. the height of the hall or existing foundations) or financial limits. In existing continuous casting plants, the solidification point of the strand is typically in the area of the pull-out units. By increasing the casting speed the solidification point shifts backwards in the casting direction. If the solidification point is not to be shifted significantly, this requires either greater secondary cooling of the strand in the strand guide or a reduction in the casting speed. Stronger or harder cooling has a negative effect on the internal quality of the strand; a reduction in the casting speed reduces productivity. On the other hand, there is the possibility of increasing productivity by increasing the strand cross-section. However, this measure requires that the strand guide or the segments of the same have to be adapted to the changed strand cross-section, which greatly increases the costs. In addition, a format change is often not desired by the operator because this would change the product mix or other processing units.

How the conversion of an existing continuous caster for the continuous casting of a billet or bloom cross-section can be carried out with regard to low conversion costs, short conversion time and high reusability of existing components and also how the metallurgical quality of the strands produced can be increased is not possible from the prior art emerged.

Summary of the invention

The object of the invention is to find a method for converting an existing continuous caster to continuously cast a strand with a billet or bloom cross-section so that the conversion can be carried out with low conversion costs, a short conversion time and a high level of reusability of existing components. In addition, the metallurgical quality of the strands produced is to be increased.

This object is achieved by a method according to claim 1. Preferred embodiments are the subject of the dependent claims.

• eine Kokille zum Vergießen von flüssigem Stahl in einen Strang mit Knüppel- oder Vorblockquerschnitt und eine Oszilliereinheit zum Oszillieren der Kokille;
• eine bogenförmige Strangführung zum Stützen, Führen und Abkühlen des Strangs mit mehreren beiderseits des Strangs angeordneten Strangführungsrollen, wobei der Strang in der Strangführung durch Kühldüsen abgekühlt wird;
• zumindest eine Auszugseinheit mit je einer an den Strang anstellbaren angetriebenen Strangführungsrolle zum Ausziehen des Strangs aus der Kokille;
• eine Brennschneidemaschine zum Abschneiden des Strangs in Strangabschnitte; und
• einen Auslaufbereich zum Ablegen der Strangabschnitte auf einem Rollgang;

aufweisend die Verfahrensschritte:

1. i) Versetzten der Brennschneidemaschine in Gießrichtung, sodass zwischen der letzten Auszugseinheit und der versetzten Brennschneidemaschine ein Freiraum entsteht;
2. ii) Einbau zumindest einer Soft-Reduktions-Einheit in den Freiraum, wobei jede Soft-Reduktions-Einheit eine Anstelleinrichtung und eine durch die Anstelleinrichtung anstellbare Strangführungsrolle zur Dickenreduktion des Strangs aufweist.

Specifically, the technical problem is solved by a process for converting a continuous caster to continuously cast a strand with a billet or bloom cross-section, the continuous caster comprising before the conversion:

• a mold for pouring liquid steel into a strand with a billet or bloom cross-section and an oscillating unit for oscillating the mold;
• an arcuate strand guide for supporting, guiding and cooling the strand with several strand guide rollers arranged on both sides of the strand, the strand being cooled in the strand guide by cooling nozzles;
• at least one pull-out unit, each with a driven strand guide roller that can be adjusted to the strand for pulling the strand out of the mold;
• a flame cutting machine for cutting the strand into lengths of strand; and
• a run-out area for depositing the strand sections on a roller table;

comprising the process steps:

1. i) relocating the cutting machine in the casting direction, so that a free space is created between the last pull-out unit and the relocated cutting machine;
2. ii) Installation of at least one soft reduction unit in the free space, each soft reduction unit having an adjusting device and a strand guide roller which can be adjusted by the adjusting device for reducing the thickness of the strand.

The rebuilding process according to the invention can increase the productivity of the continuous caster on the one hand by increasing the casting speed, whereby the mold, at least parts of the strand guide, the pull-out unit and the outlet area can remain completely unchanged. Only the flame cutting machine is offset in the horizontal direction in the casting direction, so that at least one soft-reduction unit is inserted in the space that is created between the last pull-out unit in the casting direction and the offset flame cutting machine can be. The two strand shells of the partially solidified strand are pressed together by the soft reduction unit, which improves the internal quality of the strand. In this case, at least one strand guide roller of the soft-reduction unit is adjusted to the strand by an adjusting device (typically a hydraulic cylinder), whereby the thickness of the strand is reduced. If, in addition to increasing the casting speed, the cross-section of the billet or bloom strand is also increased, the mold and the strand guide must be adapted to the changed cross-section.

In an advantageous embodiment, a first insulation tunnel for thermal insulation of the strand is used between the rear end of the strand guide or the last segment of the strand guide in the casting direction and the pull-out unit.

In addition, it is advantageous if a second insulation tunnel is used for thermal insulation of the strand between the pull-out unit and the first soft-reduction unit in the casting direction.

In both cases, the solidification point of the strand is shifted in the casting direction, so that the strand enters the outlet area at a higher temperature.

It is advantageous if the casting speed and / or the cooling intensity of the converted continuous caster is set by a system control so that the solidification point of the strand is between the axis of rotation of the roll of the first soft-reduction unit and the axis of rotation of the roll of the last soft-reduction unit lies. As a result, the cross-section of the strand in the soft reduction units can be changed by moderate forces. Ideally, the freezing point of the strand lies in the area of the middle of the last soft reduction unit.

In general, it is possible for a cold-strand pull-out unit arranged after the last pull-out unit to continue to be used without being offset even after the conversion to the continuous caster.

It has been found to be advantageous that the strand leaves the mold already bent with a radius of curvature R ₁ . Such molds are referred to as arched molds.

The radius of curvature R _{1 of} the strand in the mold is 0.9.R ₁ R 1.1.R ₁ , preferably R = R ₁ , where R is the radius of curvature of the strand guide and R _{1 is} the radius of curvature of the strand in the mold is.

The object of the invention is also achieved by a continuous caster according to claim 9. Preferred embodiments are the subject of the dependent claims.

• eine Kokille, vorzugsweise eine Bogenkokille, zum Vergießen von flüssigem Stahl in einen Strang mit Knüppel- oder Vorblockquerschnitt und eine Oszilliereinheit zum Oszillieren der Kokille;
• eine bogenförmige Strangführung zum Stützen, Führen und Abkühlen des Strangs mit mehreren beiderseits des Strangs angeordneten Strangführungsrollen, wobei der Strang in der Strangführung durch Kühldüsen abgekühlt wird;
• zumindest eine Auszugseinheit mit je einer an den Strang anstellbaren angetriebenen Strangführungsrolle zum Ausziehen des Strangs aus der Kokille, wobei die Auszugseinheit nach dem hinteren Ende der bogenförmige Strangführung angeordnet ist;
• eine Kaltstrangauszugseinheit zum Ausziehen eines Kaltstrangs aus der Kokille;
• zumindest eine Soft-Reduktions-Einheit mit einer Anstelleinrichtung und ein durch die Anstelleinrichtung anstellbare Strangführungsrolle zur Dickenreduktion des Strangs, wobei die zumindest eine Soft-Reduktions-Einheit in einen Freiraum zwischen der an ihrer ursprünglichen Position verbleibenden letzten Auszugseinheit und der, in Auslaufrichtung des Stranges versetzten, neuen Position der Brennschneidmaschine angeordnet ist;
• eine Brennschneidemaschine zum Abschneiden des Strangs in Strangabschnitte; und
• einen Auslaufbereich zum Ablegen der Strangabschnitte auf einem Rollgang.

Specifically, the solution is provided by a continuous caster for the continuous casting of a strand with a billet or bloom cross-section, comprising:

• a mold, preferably an arched mold, for pouring liquid steel into a strand with a billet or bloom cross-section and an oscillating unit for oscillating the mold;
• an arcuate strand guide for supporting, guiding and cooling the strand with several strand guide rollers arranged on both sides of the strand, the strand being cooled in the strand guide by cooling nozzles;
• at least one pull-out unit, each with a driven strand guide roller that can be adjusted to the strand for pulling the strand out of the mold, the pull-out unit being arranged after the rear end of the curved strand guide;
• a cold strand pull-out unit for pulling a cold strand out of the mold;
• At least one soft-reduction unit with an adjusting device and a strand guide roller that can be adjusted by the adjusting device for reducing the thickness of the strand, the at least one soft-reduction unit in a free space between the last pull-out unit remaining in its original position and the one in the direction of exit of the strand offset, new position of the cutting machine is arranged;
• a flame cutting machine for cutting the strand into lengths of strand; and
• a run-out area for depositing the strand sections on a roller table.

It is preferred if a first insulation tunnel is arranged between the rear end of the strand guide or the last segment in the casting direction and a first pull-out unit or a second insulation tunnel for thermal insulation of the strand is arranged between the last pull-out unit and the first soft-reduction unit .

In addition, it is advantageous if a radius of curvature R of the curved strand guide is between 8 m and 12 m, preferably between 9 m and 11 m.

In order to reliably enable the thickness reduction even at different casting speeds, it is advantageous if the converted continuous caster has between 4 and 6 soft-reduction units.

Brief description of the drawings

• Fig 1 eine Darstellung einer Stranggießanlage zum Stranggießen eines Strangs mit Knüppel- oder Vorblockquerschnitt vor dem Umbau
• Fig 2 eine Darstellung der Stranggießanlage nach Fig 1 nach dem Umbau
• Fig 3 ein Detail zu Fig 2 mit der Darstellung der Strangführung
• Fig 4 ein weiteres Detail zu Fig 2 mit der Darstellung des Bereichs zwischen der Auszugseinheit und der Brennschneidemaschine
• Fig 5 eine Aufrissdarstellung der Soft-Reduktions-Einheit 8 aus den Figuren 2 und 4

Further advantages and features of the present invention emerge from the following description of non-limiting exemplary embodiments, the following figures showing:

• Fig 1 a representation of a continuous caster for the continuous casting of a strand with a billet or bloom cross-section before the conversion
• Fig 2 a representation of the continuous caster according to Fig 1 after the renovation
• Fig 3 a detail too Fig 2 with the representation of the strand guide
• Fig 4 one more detail too Fig 2 with the representation of the area between the pull-out unit and the flame cutting machine
• Fig 5 an elevation view of the soft reduction unit 8 from FIGS Figures 2 and 4th

Description of the embodiments

In Fig 1 a continuous caster 1 for the continuous casting of strands with billet or bloom cross-sections is shown schematically. A ladle turret with a ladle is shown in the upper left area of the figure. The continuous casting plant 1 is supplied with molten steel by means of the ladle via a crane shown at the very top. From the ladle, the molten steel in and of itself is conducted in a known manner via a shadow tube into the distributor and from there typically filled into the mold 2 via a dip tube ( SEN ). In the cooled mold 2, a constant pour level and a partially solidified strand with a liquid core and two solidified strand shells are formed. In order to prevent the strand shells from sticking to the mold 2, casting powder is applied to the meniscus and the mold 2 is oscillated essentially in the vertical direction via an oscillating unit 2a. The partially solidified strand is supported, guided and further cooled by cooling nozzles in the curved strand guide 3 following the mold 2. In the Fig 1 is a segment to support and guide the strand 4 shown with several strand guide rollers arranged on both sides of the strand. The arcuate strand is drawn out of the mold 2 by the pull-out unit 5 with at least one driven strand guide roller, here two or three pairs of driven pull-out rollers, and straightened in the horizontal direction. In order to enable the so-called "bottom feeding" of the cold strand, a cold strand pull-out unit 13 is provided, which can accommodate the likewise curved cold strand after the continuous casting installation 1 has been cast on. The strand is then transported on a roller table to the flame cutting machine 6, where it is cut into strand sections. The strand sections are either deposited in the run-out area 7 or are further processed by the roll stands following the run-out area 7 into wires, profiles or similar products.

Such continuous casting plants 1 are inexpensive to purchase and operate, but are unable to keep up with modern continuous casting plants either in terms of the productivity of the plant or the quality of the strands produced. Accordingly, there is a need to convert existing continuous casting plants in order to increase the quality of the strands produced and / or the productivity of the continuous casting plant.

Although modern continuous casting systems allow significantly higher casting speeds and qualities due to advances in the area of the permanent mold, the oscillating unit, strand guidance, better casting powder and, last but not least, greatly improved strand cooling and system automation, these advances cannot be directly transferred to existing continuous casting systems.

On the one hand, the solidification point of the strand in the strand guide shifts at higher casting speeds in the direction of the material to the rear, i.e. in the direction of the outlet area 7. In order to reliably prevent the cutting of a partially solidified strand, either the strand would have to be cooled more intensively by the strand cooling or the Curve radius of the strand guide can be increased. However, both measures are problematic because on the one hand more intensive strand cooling deteriorates the quality of the strand and on the other hand a larger arc radius increases the height of the continuous caster, which is very problematic in an existing hall with a given height.

According to the invention, the technical object is achieved in that the flame cutting machine 6 is offset backwards in the casting direction, so that a free space F is created between the last pull-out unit 5 and the offset flame cutting machine 6, and at least one soft reduction unit 8 is installed in the free space F , each soft-reduction unit 8 having an adjusting device 9 and a strand guide roller 10 which can be adjusted by the adjusting device for reducing the thickness of the strand.

These measures reliably prevent a partially solidified strand from being cut and also increase the internal quality of the strand.

The converted continuous caster 1 is in Fig 2 as well as further details in the Fig. 3 to 5 shown.

As in Fig 1 represented by an arrow, the flame cutting machine 6 is offset in the direction of material flow in the direction of the outlet area 7. By moving the cutting machine 6, a free space F (see Fig 2 ) formed between the rear end of the pull-out unit 5 and the front end of the flame cutting machine 6. The soft reduction unit 8 or a plurality of such units 8a ... 8e is used in this free space F. The soft reduction units 8 are typically inserted by a crane, as in the soft reduction units 8b, 8c in FIG Fig 4 indicated.

Due to the conversion method according to the invention, the pull-out unit 5 and the cold-strand pull-out unit 13 can typically be left in the same position (see FIG Fig 3 and 4th ), which further reduces the conversion time and effort. In order to move the freezing point of the strand even further in the direction of the outlet area 7, first and second insulation tunnels 11, 12 can be installed between the last segment 4 of the strand guide 3 and the pull-out unit 5 and between the pull-out unit 5 and the soft-reduction unit 8 (please refer Fig 2 ).

In the ideal case, the solidification point of the converted continuous caster lies in the area between the first soft-reduction unit 8a and the last soft-reduction unit 8e. This is ensured by a system control during operation.

In practice, it has been found to be advantageous if the mold 2 is designed as a curved mold and the radius of the mold 2 and the radius R of the curved guide 3 are between 8 m and 12 m, preferably between 9 m and 11 m.

In Fig 5 five soft reduction units 8a ... 8e are shown. Each reduction unit 8 has an adjusting device 9 (here a hydraulic cylinder) which can move an upper strand guide roller 10b in the direction of a lower strand guide roller 10a. By adjusting the upper strand guide roller 10b to the strand, not shown, the strand is reduced in its thickness. All reduction units 8a ... 8e are constructed identically and connected to the foundation via a base frame. Further details on soft reduction units are not necessary, since these are derived from the WO 2009/144107 A1 are known.

List of reference symbols

1

Continuous caster

2

Mold

2a

Oscillating unit

3

Strand guide

4th

Strand guide segment

5

Pull-out unit

6th

Flame cutting machine

7th

Run-out area

8.8a ... 8e

Soft reduction unit

9

Adjusting device

10,10a, 10b

Strand guide roller

11

first isolation tunnel

12

second isolation tunnel

13

Cold strand pull-out unit

F.

free space

R, R ₁

Radius of curvature

Claims (13)

Method for converting a continuous caster (1) for the continuous casting of a strand with a billet or bloom cross-section, the continuous caster (1) comprising before the conversion: - A mold (2) for casting liquid steel in a strand with a billet or bloom cross-section and an oscillating unit (2a) for oscillating the mold (2); - An arcuate strand guide (3) for supporting, guiding and cooling the strand with several strand guide rollers arranged on both sides of the strand, the strand in the strand guide (3) being cooled by cooling nozzles; - At least one pull-out unit (5), each with a driven strand guide roller that can be adjusted to the strand for pulling the strand out of the mold (2); - A flame cutting machine (6) for cutting the strand into strand sections; and - An outlet area (7) for depositing the strand sections; comprising the process steps: i) relocating the flame cutting machine (6) in the casting direction so that a free space (F) is created between the last pull-out unit (5) and the relocated flame cutting machine (6); ii) Installation of at least one soft reduction unit (8, 8a ... 8e) in the free space (F), each soft reduction unit (8) having an adjusting device (9) and a strand guide roller (10 ) to reduce the thickness of the strand. Method according to Claim 1, characterized in that a first insulation tunnel (11) for thermal insulation of the strand is used between the rear end of the strand guide (3) and the pull-out unit (5). Method according to Claim 2, characterized in that a second insulation tunnel is located between the pull-out unit (5) and the first soft-reduction unit (8, 8a) in the casting direction (12) is used for thermal insulation of the string. Method according to one of the preceding claims, characterized in that the casting speed and / or the cooling intensity of the converted continuous caster is adjusted by a system control so that the solidification point of the strand between the first soft reduction unit (8a) and the last soft reduction Unit (8e) lies. Method according to one of the preceding claims, characterized in that a cold-strand pull-out unit (13) arranged after the last pull-out unit (5) continues to be used after the conversion into the continuous caster. Method according to Claim 5, characterized in that the cold-strand pull-out unit (13) is not moved during the conversion. Method according to one of the preceding claims, characterized in that the strand leaves the mold (2) of the continuous casting machine (1) in a curved shape with a radius of curvature (R ₁ ). Method according to claim 8, characterized in that for the radius of curvature (R ₁ ) of the strand in the mold (2) the following applies: 0.9.R ₁ ≤ R ≤ 1.1.R ₁ , preferably R = R ₁ , where R is the The radius of curvature of the strand guide (3) is. Continuous casting plant (1) for continuous casting of a strand with a billet or bloom cross-section, comprising: - A mold (2), preferably an arched mold, for pouring liquid steel into a strand with a billet or bloom cross-section and an oscillating unit (2a) for oscillating the mold (2); - An arcuate strand guide (3) for supporting, guiding and cooling the strand with several on both sides of the Strand guide rollers arranged in a strand, the strand in the strand guide (3) being cooled by cooling nozzles; - At least one pull-out unit (5) each with a driven strand guide roller that can be adjusted to the strand for pulling the strand out of the mold (2), the pull-out unit (5) being arranged after the rear end of the curved strand guide (3); - A cold strand pull-out unit (13) for pulling a cold strand out of the mold (2); - At least one soft reduction unit (8) with an adjusting device (9) and a strand guide roller (10) that can be adjusted by the adjusting device for reducing the thickness of the strand, the at least one soft reduction unit (8) in a free space (F) is arranged between the last pull-out unit (5) remaining in its original position and the new position of the cutting machine (6) offset in the direction of discharge of the strand; - A flame cutting machine (6) for cutting the strand into strand sections; and - An outlet area (7) for depositing the strand sections. Continuous casting plant (1) according to claim 9, characterized in that a first insulation tunnel (11) for thermal insulation of the strand is arranged between the rear end of the strand guide (3) and a first pull-out unit (5). Continuous casting plant (1) according to claim 9 or 10, characterized in that a second insulation tunnel (12) for thermal insulation of the strand is arranged between the last pull-out unit (5) and the first soft-reduction unit (8, 8a). Continuous casting plant (1) according to one of Claims 9 to 11, characterized in that for a radius of curvature (R) of the curved strand guide, 12 m R 8 m, preferably 11 m R 9 m. Continuous casting plant (1) according to one of Claims 9 to 12, characterized in that the converted continuous casting plant (1) has between 4 and 6 soft-reduction units (8, 8a ... 8e).

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