EP3535071B1 - Method and system for producing a metal strip - Google Patents

Description

The invention relates to a method for producing a metallic strip, the strip being rolled in a rolling mill, the strip being subjected to a bending stretch straightening process in a bending straightener at a point downstream of the rolling mill, and the strip being subjected to a point downstream of the bending stretcher in the conveying direction on a reel. Furthermore, the invention relates to a plant for producing a metallic strip.

The requirements for cold strip flatness for thin hot strips, which are sold directly, for example, or for the hot strip flatness of hot strips, which are rolled and wound endlessly under tension and for which there are insufficient flatness measurements, are constantly increasing.

In the past, stretch straightening machines that can be used behind hot strip mills have been proposed to improve flatness. Such an application for continuous rolling is for example in the GB 2 163 689 A disclosed. An arrangement of stretch leveling machines in front of a reel driver or between the reel driver and reel is disclosed by the DE 2 537 188 A1 , the US 4,316,376 A , the EP 0 906 797 B1 , the DE 199 53 915 A1 , the EP 2 038 076 B1 and the EP 3 061 535 A1 . A stretching judge is located directly behind the hot strip mill in the US 4,539,830 A and inside the cooling section in the DE 10 2013 214 344 A1 disclosed. Show more solutions DE 10 2005 060 046 B4 and the EP 1 230 993 B1 .

The previously known solutions according to the publications mentioned have various disadvantages.

The object of the invention is therefore to provide a method and a system with which it is possible to increase the degree of flatness of the strip.

The solution to this problem by the invention is characterized in that the strip between the rolling mill and the bending straightener is kept at least temporarily under a first tension, that the strip is kept behind the bending stretcher at least temporarily under a second tension in the conveying direction, and that the strip in The area of the bending straightener is kept at least temporarily under a third tension, the third tension being greater than the first tension and the second tension.

The first tensile stress and the second tensile stress are preferably between 5 and 25 N / mm ² . The third tensile stress is preferably between 30 and 80 N / mm ² , particularly preferably between 40 and 60 N / mm ² . The head and the end of the band are exempt from said tension. The train level on the transport route before the bending straightener route and the transport route after the bending straightener route can be different.

The average tension level within the stretch straightening section is preferably determined as a function of the strip material, the strip temperature within the straightening section and the strip thickness and is preferably set and controlled using a process model. A train model also defines the train level in the neighboring transport routes.

The train level on the long transport route between the last active roll stand and the first driver of the bending stretcher and the transport route from the second driver of the bending stretcher and the reel driver or the reel is thus lower than the train level within the Bending straightener line. Accordingly, the trains in the area of the bending straightener line are decoupled from the neighboring lines.

The tension in the belt is preferably influenced, controlled or regulated by a first driver and a second driver, the first driver being arranged in front of the bending straightener in the conveying direction and the second driver being arranged behind the bending straightener in the conveying direction, or the two drivers extending the bending straightener in the conveying direction limit (in the latter case, the two drivers are therefore part of the bending straightener). The different train levels are set by the drivers in front of and behind the bending straightener. Instead of the second driver behind the bending straightener, a scissor driver or a reel driver can also take over their task. In this case, the increased third tensile stress is built up in the area of the bending straightener between the first driver and a reel driver. The distance a then applies between the first driver and the reel driver. The second driver is then open or not installed. The second tension then only applies between the reel driver and the reel. At least one further driver (e.g. a scissor driver) can also be arranged behind the second driver of the bending straightener unit.

The strip is preferably subjected to cooling in a cooling section between the rolling mill and the bending straightener. Cooling in the conveying direction behind the bending straightener preferably no longer takes place. The advantage of this type of cooling of the strip is that the cooling section no longer influences the flatness of the strip in this way.

The strip preferably has a temperature in its bending stretching process which is between 20 ° C. and 750 ° C., particularly preferably between 200 ° C. and 600 ° C.

A hot strip which has a thickness between 0.5 mm and 2.5 mm is particularly advantageously produced using the method mentioned.

The plant for producing a metallic strip comprises a rolling mill for rolling the strip, a bending straightener downstream of the rolling mill in the conveying direction of the strip and at least one reel downstream of the bending straightener and provides according to the invention that the bending straightener has a first driver arranged at the front in the conveying direction and one has second drivers arranged in the rear in the conveying direction, the two drivers limiting the extent of the bending straightener and the distance in the conveying direction between the first driver and the second driver being at most 20 m. The distance is preferably at most 5 m. This minimizes the throughput time through the bending straightener and the associated constriction of the belt as a result of the train.

A cooling section is preferably arranged between the rolling mill and the bending straightener; behind the bending straightener there is preferably no cooling section.

The bending straightener has a number of rollers for introducing a bending moment into the strip, the diameter of the rollers preferably being at least 50 mm, particularly preferably at least 100 mm.

The bending straightener section includes a bending straightener consisting of a number of rolls (for example 5 rolls) and / or a back bending unit consisting of further rolls (for example 3 rolls).

In the classic design, the driver can consist of two rollers standing one on top of the other or can be designed with an offset arrangement of the rollers in order to generate a wrap angle and, if appropriate, additional torque transmission.

In order that the strip is not excessively cooled as a result of the straightening roller cooling (which is particularly important in the case of endless rolling), the stretching judge rollers preferably have internal cooling and / or they are equipped with stripper plates for external cooling to shield the water from the strip so that the Reel temperature is not adversely affected. The strip cooling in the bending stretching section is also taken into account and is taken into account when determining the target strip temperature behind the cooling section, so that the desired reel temperature is generated.

The invention thus relates in particular to a hot bending straightener behind a hot strip mill.

The proposed solution thus provides an optimization of the bending straightener arrangement and the tension distribution, which subsequently leads to an improved flatness of the strip produced.

A good flatness improvement by means of a bending stretch straightening process results for a given strip material with high strip tension, high strip temperature and small bending radii of the strip, i. H. with small straightening roller diameters. However, straightening roller diameters that are too small are disadvantageous with regard to maintenance, service life and roller wear. Too high trains and / or too high strip temperatures result in large constrictions in width on the long route between the last rolling stand of the hot strip mill and the reel. The narrowing of the width due to tape tension is also dependent on the flatness condition itself and is therefore difficult to determine. The cooling section also influences the flatness of the belt.

When these findings are taken into account, an optimal straightening judge arrangement is obtained, which is characterized in particular by the above features.

Fig. 1

schematisch in der Seitenansicht eine Anlage zur Herstellung eines Bandes und

Fig. 2

den Verlauf der Zugspannung im Band über der Erstreckung in Längsrichtung der Anlage.

In the drawing, an embodiment of the invention is shown. Show it:

Fig. 1

schematically in side view a system for producing a tape and

Fig. 2

the course of the tension in the belt over the extension in the longitudinal direction of the system.

In Figure 1 A system for producing a steel strip 1 is shown, with only the last rolling stand being indicated by a rolling mill 2, from which the strip 1 runs in the direction of conveyance F in the direction of a reel 4 (two reels 4 are provided here by way of example). Between the rolling mill 2 and the reel 4, a bending straightener 3 is arranged, in which the strip is straightened by a bending stretching process.

The bending straightener 3 is limited in its extension in the conveying direction F by a first driver 5 and a second driver 6, a distance a being present between the two drivers 5, 6. The bending straightener 3 has a number of rollers 8, which are designed to apply corresponding bending stress to the belt 1 in a manner known per se.

A cooling section 7 is provided, which is arranged between the rolling mill 2 and the bending straightener 3 and with which the strip 1 can be cooled.

Furthermore, in Figure 1 indicated some components that are relevant for the implementation of the production process of the strip 1, namely a flatness measuring device 9, a temperature measuring device 10, a temperature measuring device 11, a pair of scissors 12 and a reel temperature measuring device 13.

The conveyance of the strip 1 between the rolling mill 2 and the reel 4 results from the interaction of the last rolling stand of the rolling mill, the first and the second driver 5, 6 and in the exemplary embodiment by a reel driver 14. By appropriate regulation of the components mentioned and in particular the first and second drivers 5, 6, the tension in the band can be influenced.

How this is done according to the invention can be seen from the illustration in FIG Figure 2 , where the course of the tensile stress over the distance s (running in the conveying direction F) is shown.

It can be seen that a first tensile stress σ ₁ is initially present between the rolling mill 2 and the bending straightener 3, which is preferably in a range between 5 and 25 N / mm ² .

There is a second tensile stress σ ₂ between the bending funnel 3 and the reel 4, which is also preferably in a range between 5 and 25 N / mm ² . The two tensile stresses σ ₁ and σ ₂ need not be the same.

However, the tensile stress in the area of the bending straightener 3 is at a higher level. The third tensile stress σ _{3 here} is in a preferred range between 40 and 60 N / mm ² .

It is advantageously provided that the distance a is relatively short and preferably only extends over approximately 5 m. As a result, the throughput time through the bending straightener 3 is short, which also results in only a small constriction of the band as a result of the train.

To cut the strips, the shears 12 are used in continuous rolling. The tensile stress σ ₂ is therefore = 0 for a short period of time. The driver 6 takes over the tension component σ ₂ in order to be able to maintain the tension σ ₃ in the area of the bending straightener.

The bending stretch straightening process is thereby significantly improved. This applies in particular if the process is operated with further parameters, as explained above.

This applies in particular with a view to the temperature control, which is preferably chosen so that the strip 1 in the area of the bending funnel 3 has a temperature between 200 ° C. and 600 ° C.

Reference symbol list:

1

tape

2nd

Rolling mill

3rd

Bending straightener

4th

reel

5

first driver

6

second driver

7

Cooling section

8th

role

9

Flatness measuring device

10th

Temperature measuring device

11

Temperature measuring device

12th

scissors

13

Coiler temperature measuring device

14

Reel driver

σ ₁

first tension

σ ₂

second tension

σ ₃

third tension

a

distance

s

route

F

Direction of conveyance

Claims (16)

1. Method of producing a metallic strip (1), wherein the strip (1) is rolled in a rolling mill (2), wherein the strip (1) is subjected to a bending/stretching straightening process in a bending/stretching straightener (3) at a position downstream of the rolling mill (2) in conveying direction (F) and wherein the strip (1) is wound up on a coiler (4) at a position downstream of the bending/stretching straightener (3) in conveying direction (F),
   characterised in that
   the strip (1) is held at least temporarily at a first tensile stress (σ₁) between the rolling mill (2) and the bending/stretching straightener (3),
   the strip (1) is held at least temporarily at a second tensile stress (σ₂) behind the bending/stretching straightener (3) in conveying direction (F) and
   the strip (1) is held at least temporarily at a third tensile stress (σ₃) in the region of the bending/stretching straightener (3),
   wherein the third tensile stress (σ₃) is greater than the first tensile stress (σ₁) and the second tensile stress (σ₂).
2. Method according to claim 1, characterised in that the first tensile stress (σ₁) and the second tensile stress (σ₂) are between 5 and 25 N/mm².
3. Method according to claim 1 or 2, characterised in that the third tensile stress (σ₃) is between 30 and 80 N/mm², preferably between 40 and 60 N/mm².
4. Method according to any one of claims 1 to 3, characterised in that the tensile stress in the strip (1) is influenced, controlled or regulated by a first driver (5) and a second driver (6), wherein the first driver (5) is arranged in front of the bending/stretching straightener (3) in conveying direction (F) and the second driver (6) is arranged behind the bending/stretching straightener (3) in conveying direction (F) or the two drivers (5, 6) limit the extent of the bending/stretching straightener (3) in conveying direction (F).
5. Method according to any one of claims 1 to 4, characterised in that the strip (1) is optionally kept temporarily below the third tensile stress (σ₃) between the first driver (5) and the coiler driver (14).
6. Method according to any one of claims 1 to 5, characterised in that the strip (1) is subjected to cooling in a cooling path (7) between the rolling mill (2) and the bending/stretching straightener (3).
7. Method according to any one of claims 1 to 6, characterised in that the strip (1) at the time of its bending/stretching straightening process has a temperature lying between 20° C and 750° C, preferably between 200° C and 600° C.
8. Method according to any one of claims 1 to 7, characterised in that a hot strip having a thickness between 0.5 mm and 2.5 mm is produced by it.
9. Method according to any one of claims 1 to 8, characterised in that the different tension levels σ₁, σ₂, σ₃ are predetermined by a process model in dependence on thickness, temperature and strip material.
10. Plant for producing a metallic strip (1), comprising a rolling mill (2) for rolling the strip (1), a bending/stretching straightener (3) downstream of the rolling mill (2) in conveying direction (F) of the strip (1) and at least one coiler (4) downstream of the bending/stretching straightener (3) in conveying direction (F), wherein the bending/stretching straightener (3) comprises a second driver (6) arranged behind in conveying direction,
    characterised in that
    the bending/stretching straightener (3) comprises a first driver (5) arranged in front in conveying direction (F), wherein the two drivers (5, 6) limit the extent of the bending/stretching straightener (3) and wherein the spacing (a) in conveying direction (F) between the first driver (5) and the second driver (6) is at most 20 m.
11. Plant according to claim 10, characterised in that the spacing (a) is at most 5 m.
12. Plant according to claim 10 or 11, characterised in that the second driver (6) in conveying direction (F) behind the bending/stretching straightener (3) is optionally a coiler driver (14) or a cutter driver.
13. Plant according to any one of claims 10 to 12, characterised in that a cooling path (7) is arranged between the rolling mill (2) and the bending/stretching straightener (3).
14. Plant according to any one of claims 10 to 13, characterised in that the bending/stretching straightener (3) comprises a number of rollers (8) for introducing a bending moment into the strip (1), wherein the diameter of the rollers (8) is at least 50 mm, preferably at least 100 mm.
15. Plant according to any one of claims 10 to 14, characterised in that the bending/stretching straightening path consisting of a bending/stretching straightener consists of a number of rollers and/or a reverse bending unit with more than one further roller.
16. Plant according to any one of claims 10 to 15, characterised in that the bending/stretching straightener (3) and/or the first driver (5) and/or the second driver (6) can be pushed into the transport line or moved near the transport line and replaced by a roller path depending upon the use or non-use of the bending/stretching straightening unit.

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