EP0925850A2 - Method of rolling a metal strip - Google Patents

Abstract

The strip (1) is first upset in an upsetting roll stand (8), so that the strip cross section has a bone like contour with thickened ends. The strip edge regions primarily are next rolled in a compensating roll stand (9). The strip is cut into lengths by shears (10) after the upsetting roll stand (8) or after the compensating roll stand (9). After this it is rolled in at least one roll stand (11) with working rolls (12).

Description

The present invention relates to a rolling process for a metal strip with a band cross-section, a band beginning, a band end and an intermediate band middle section, in particular a Steel band.

Such tapes are first in the prior art in one Upsetter compressed, so that the strip cross-section is in the form of a Dog bone with bulges on the band edges. After that the metal strip is in at least one work stand Rollers rolled. After rolling, the tape will be on his Skipped the beginning and end of the tape. Accordingly, one Continuous rolling mill at least one roll stand and one Staucher upstream of the rolling stand and one downstream of the rolling stand Scissors.

There are many boundary conditions to be observed when rolling metal strip. One of the constraints is that the tape runs its entire length should have a width that is as uniform as possible. The width will again influenced by a variety of factors, for example Initial geometry of the band, the natural spread and the Constriction of the strip due to the strip tension within the rolling mill and on the way to the reel.

There are additional influences at the beginning and end of the band which change the width of the band. In particular, a Belt tension can only be built up when the belt is also in the following Scaffold is threaded. It is due to the lack of tape tension not for the first few meters of the tape, i.e. the beginning of the tape Constriction, and the tape becomes wider here than in the middle section of the tape. For the same reason, namely the lack of tape tension, the tape end also spreads more than the tape middle section.

To counteract the spread and the uneven spreads to compensate for the beginning of the band, the middle section and the end of the band, are usually the strips in front of the rolling mill by means of a Compression mill pre-compressed and then rolled. To the stronger To counteract the spread of the beginning and end of the band are used the beginning and end of the band are more compressed than the middle section of the band. After rolling, the unwanted ones are then Band shapes at the beginning and end of the band using cropping shears away. Such upsetting structures are also used in finished streets Direct processing of thin slabs (slab thickness below 100 mm) the finishing streets.

A so-called dog bone profile is formed by upsetting. This often leads to something special when passing through the rolling mill Forms of the beginning and end of the band. At the end of the line there are, for example, so-called Beaver tails, pancakes and fish tails typical. Especially the fish tails at the end of the strip tend to roll thin strips for double or one-sided tearing. This will ensure process reliability the rolling mill affected.

The possible degree of compression is also limited at the beginning of the strip, since that Belt must be threaded securely into the rolling mill. Will the tape too compressed at the beginning of the tape, it can happen that it does not gets into the roll gap, but hits and stops on a roll.

The previously known options for threading the tape lead either instability in the rolling process or loss of quality with the finished tape.

The object of the present invention is therefore a To provide rolling process for a metal strip in which the end product is high quality and especially uniform Has width over its entire length, being a A high degree of process reliability should be achieved or maintained.

The task is solved for the rolling process in that the Metal strip after upsetting in a compensating stand is rolled that essentially only the strip edges are rolled, that the metal strip after upsetting or after rolling the Tape edges is skimmed and that the metal tape only after Rolling the band edges and skimming in at least one work stand is rolled with work rolls.

Accordingly, the continuous rolling mill is characterized by that the scissors either between the edger and him immediately downstream compensating roll stand or at most 20 m behind the compensating roll stand.

Since the compensating roll stand only has comparatively low forces the band must exercise, it is preferably for reasons of cost Two-roll mill stand designed.

In order to be able to tap the beginning and end of the band differently, the scissors preferably have at least two pairs of knives. The beginning and end of the band can be skimmed off, for example, in such a way that the beginning or end of the band and the middle section of the band behind the work rolls have a uniform range. Alternatively the beginning or end of the band can also be skimmed off in this way be that threading the beginning of the strip into the work stand is facilitated or that when the metal strip emerges from the Work roll stand whose work rolls do not hit each other. This can be achieved in particular by changing the bandwidth seen continuously at the beginning of the strip in the direction of the strip increased and continuous at the end of the conveyor in the direction of travel decreases.

The rolling process is used particularly advantageously when the processed metal strip is taken directly from a continuous caster is, so that a continuous caster is arranged upstream of the edger.

Figur 1

ein Metallband,

Figur 2

einen Bandquerschnitt,

Figuren 3 bis 5

verschiedene Ausführungsformen einer kontinuierlichen Walzstraße.

Further advantages and details emerge from the further claims and the following description of an exemplary embodiment. Show

Figure 1

a metal band,

Figure 2

a band cross-section,

Figures 3 to 5

different embodiments of a continuous rolling mill.

1, a metal strip 1, e.g. a steel band, along a tape running direction x from a tape start 2 over a Band middle section 3 to a band end 4. The band 1 has one Band cross direction y a width. It runs from a band edge 13 to an opposite band edge 13. It also has one Cross section 5.

The tape 1 is in a continuous, shown schematically in Fig. 3 Rolled mill. 3, the tape is 1st first centered in a centering unit 6 in the belt transverse direction y. The strip 1 then passes through a descaler 7 in which the strip 1 is descaled. The strip 1 then passes through an edger 8 and a compensating roll stand 9. Between the edger 8 and the Compensating roll stand 9, scissors 10 are arranged, by means of which tape 1 at the beginning of the tape 2 and at the end of the tape 4 can. Behind the compensating roll stand 9 are work roll stands 11 arranged on a finishing train. The work stands 11 have of course work rolls 12 on.

The strip 1 is intended to pass through after passing through the work stands 11 if possible have a rectangular cross section 5. To this To reach strip cross-section 5, the metal strip 1 in the edger 8 initially compressed so that the band cross-section 5 the shape of a dog bone shown in FIG. 2. The metal band 1 therefore has 13 bulges at its band edges. It is on these places thicker than between the band edges 13. In the Compensating roll stand 9, the metal strip 1 is then rolled in such a way that essentially only the strip edges 13 are rolled. Outside the band edges 13 will either not or only a band thickness d reduced by a maximum of 5%.

The tapping of the metal strip 1 by the scissors 10 is used Increasing process security. In the present case, it happens before the compensating rollers, it could alternatively also be immediate done afterwards. After compensating rolling and tapping the strip 1 this is rolled by means of the work stands 11.

In the embodiment according to FIG. 3, a separate compensating roll stand is used 9 used. Since this mill stand 9 is only relatively small Must exert forces on the metal strip 1, it is for reasons of cost preferably designed as a two-roll mill stand. This is shown in Fig. 3 also shown in this way.

Alternatively, as shown in FIG. 4, the edger 8 can be arranged directly in front of the first of the work stands 11. This work roll stand 11 then serves as a compensating roll stand, because it is the rolling stand immediately downstream of the edger 8.

4 is between the two work stands 11 arranged. The scissors 10 is immediately behind the front of the work stands 11 at a distance D. The distance D between this work stand 11 and Scissors 10 is a maximum of 20 m, but is preferably less than 10 m, e.g. only 3 to 5 m.

In the exemplary embodiment according to FIG. 4, the scissors 10 also have two pairs of knives 14 so that the beginning of the band 2 and the end of the band 4 can be skimmed differently. Band start 2 and Band end 4 can be skimmed, for example, that they more or taper to a lesser arrow shape. This will make 2 threading this strip start 2 into the rear of the work stands 11 relieved. Furthermore, the beating of the Work rolls 12 of the rear work roll stand 11 when exiting the metal strip 1 avoided from this work stand 11. Alternatively, the beginning of the band 2 and the end of the band 4 can also be such be skimmed off that the entire strip 1 after the work rolling, that is, after exiting the rear work stand 11, one has a uniform bandwidth.

The unit described above from Staucher 8, compensating roll stand 9 and scissors 10 - the centering unit 6 and the descaler 7 are advantageous, but not absolutely necessary preferably, as shown in FIG. 5, a continuous caster 15 subordinate. The continuous caster 15 is therefore the edger 8 upstream. From it, tape 1 is removed and directly the Rolling mill fed. The Staucher 8, compensating roll stand 9 and scissors 10 existing unit is immediately behind the Continuous caster 15 arranged, so not only in front of the work stands 11, but even in front of a temperature compensation furnace 16. In this case too, the compensating roll stand 9 is preferred designed as a two-roll mill stand.

Reference list

1

Metal strap

2nd

Band start

3rd

Central band section

4th

Band end

5

Strip cross-section

6

Centering unit

7

Descaler

8th

Upsetter

9

Compensating roll stand

10th

scissors

11

Rolling stands

12th

Work rolls

13

Band edges

14

Pairs of knives

15

Continuous caster

16

Temperature compensation oven

d

Tape thickness

D

distance

x

Belt running direction

y

Band cross direction

Claims (14)

Rolling process for a metal strip (1) with a strip cross-section (5), a strip start (2), a strip end (4), strip edges (13) and an intermediate strip middle section (3), in particular a steel strip, with the following steps: The metal strip (1) is first compressed in an edger (8) so that the strip cross-section (5) takes the form of a dog's bone with bulges on the strip edges (13), the metal strip (1) is then rolled in a compensating roll stand (9) in such a way that essentially only the strip edges (13) are rolled, the metal strip (1) is skimmed after the upsetting or after the compensating rolling of the strip edges (13) by scissors (10) and the metal strip (1) is rolled with at least one work roll stand (11) with work rolls (12) after tapping and compensating rolling. Rolling method according to claim 1,
characterized,
that the beginning of the strip (2) is skimmed off in such a way that the threading of the beginning of the strip (2) into the work roll stand (11) is facilitated. Rolling method according to claim 1,
characterized,
that the beginning of the strip (2) is skimmed off in such a way that the beginning of the strip (2) and the middle section (3) of the strip have a uniform width after the work rolls. Rolling method according to claim 1, 2 or 3,
characterized,
that the strip end (4) is skimmed such that when the metal strip (1) emerges from the work roll stand (11), the work rolls (12) do not knock against one another. Rolling method according to claim 1, 2 or 3,
characterized,
that the strip end (4) is skimmed off such that the strip end (4) and the strip middle section (3) have a uniform strip width after the work rolling. Rolling method according to one of claims 1 to 5,
characterized,
that the processed metal strip (1) is taken directly from a continuous caster. Rolling method according to one of claims 1 to 6,
characterized,
that the metal strip (1) is centered before upsetting. Rolling method according to one of claims 1 to 7,
characterized,
that the metal strip (1) is descaled, preferably before upsetting. Continuous rolling mill with at least one compensating roll stand (9), an edger (8) directly upstream of the compensating roll stand (9) and scissors (10),
characterized,
that the scissors (10) either between the edger (8) and the compensating roll stand (9) or at most 20 m behind the compensating roll stand (9). Rolling mill according to claim 9,
characterized,
that the compensating roll stand (9) is preceded by a descaler. Rolling mill according to claim 9 or 10,
characterized,
that the edger (8) is preceded by a centering unit (6). Rolling mill according to claim 9, 10 or 11,
characterized,
that the compensating roll stand (9) is designed as a two-roll stand. Rolling mill according to one of claims 9 to 12,
characterized,
that the scissors (10) has at least two pairs of knives (14). Rolling mill according to one of claims 9 to 13,
characterized,
that the edger (8) is preceded by a continuous casting installation (15).

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