EP3969194B1 - Hot rolling with flexible configuration of the roll stands - Google Patents

Description

Field of technology

• wobei in der Warmwalzstraße nacheinander ein erstes und ein zweites Metallband gewalzt werden,
• wobei Abschnitte der Metallbänder jeweils zuerst das erste und erst danach das letzte Walzgerüst der Warmwalzstraße durchlaufen,
• wobei das letzte Walzgerüst zwischen dem Walzen des ersten Metallbandes und dem Walzen des zweiten Metallbandes umgerüstet wird,
• wobei das erste Walzgerüst sowohl während des Walzens des ersten Metallbandes als auch während des Walzens des zweiten Metallbandes als Quartogerüst konfiguriert ist,
• wobei die Warmwalzstraße zwischen dem ersten und dem letzten Walzgerüst eine Anzahl von weiteren Walzgerüsten aufweist.

The present invention is based on an operating method for a hot rolling mill which has at least a first and a last rolling stand,

• wherein a first and a second metal strip are rolled one after the other in the hot rolling mill,
• whereby sections of the metal strip first pass through the first and only then the last rolling stand of the hot rolling mill,
• wherein the last rolling stand is converted between the rolling of the first metal strip and the rolling of the second metal strip,
• wherein the first rolling stand is configured as a four-high stand both during the rolling of the first metal strip and during the rolling of the second metal strip,
• wherein the hot rolling mill has a number of further rolling stands between the first and the last rolling stand.

State of the art

The above-mentioned items are generally known. In particular, finishing lines for rolling metal strips (particularly made of steel) are usually operated in this way and finishing lines for rolling metal strips (particularly made of steel) are usually designed in this way. The last rolling stand (and usually also the other rolling stands of the finishing line) is converted in order to replace worn work rolls and, if necessary, worn backup rolls. The configuration of the The rolling stands are not changed. There is only a 1:1 exchange of roller pairs.

The rolling stands of hot rolling mills are usually designed as so-called four-high stands. Four-high stands are rolling stands that have backup rolls in addition to the work rolls, on which the work rolls are supported. In English-speaking countries, such rolling stands are often also referred to as 4-high.

In hot rolling, the trend is towards ever smaller final thicknesses, particularly for high-strength materials. For example, modern casting and rolling mills can produce a strip thickness of well under 1 mm for soft grades, sometimes even as little as 0.6 mm. Such final thicknesses cannot be achieved with harder materials. In practice, this requires work rolls with a very small diameter. However, the diameters of the work rolls used today limit the final thicknesses. In particular, as the work roll diameter decreases, the torque that can be transmitted also decreases. In addition, it must be possible to apply sufficient coolant to the work rolls so that the hot rolling mill can be operated in continuous operation.

The problem is usually solved by using work rolls with the smallest possible diameter. However, the smaller the diameter of the work rolls, the lower the torque with which the work rolls can be driven without risking the roll neck breaking. The torque is higher with harder materials. This creates the problem that on the one hand the diameter of the work rolls should be as small as possible in order to achieve the smallest possible final thickness, but on the other hand it must not be too small, otherwise the required torque cannot be transmitted.

In cold rolling, the problem is solved by rolling stands that have a large number of rolls, for example so-called 12-roll rolling stands or 20-roll rolling stands. Such rolling stands cannot be used in hot rolling because they take up too much space and do not allow sufficient cooling of the rolls - especially the work rolls.

From the US 2006/0 010 952 A1 It is known that individual rolling stands in a cold rolling mill can be converted so that they can be configured as four-high stands or as six-high stands as required. Six-high stands are rolling stands that have intermediate rolls in addition to the work rolls and the backup rolls, with the work rolls being supported by the intermediate rolls and the intermediate rolls being supported by the backup rolls. In English-speaking countries, such rolling stands are often referred to as 6-high.

From the US 2006/0 196 243 A1 It is also known to design a rolling stand so that it can be converted so that it can be configured as a four-high stand or a six-high stand as required. The rolling stand of the US 2006/0 196 243 A1 also appears to be a cold rolling mill.

From the JP 63 013 603 A It is known to design a rolling stand so that it can be converted so that it can be configured as a four-high stand or a six-high stand as required.

From the WO 2018/167 710 A1 A rolling mill is known which has three sequentially successive rolling mills. The first rolling mill is a roughing mill and has four-high rolling mill stands. The second rolling mill is a finishing mill and also has four-high rolling mill stands. The third rolling mill is connected to the finishing mill, with temperature control devices arranged between the finishing mill and the third rolling mill. The third rolling mill has four-high rolling mill stands or six-high rolling mill stands. The preamble of claim 1 is based on this document.

From the EP 0 281 782 A2 It is known to replace the work rolls and the intermediate rolls in a six-high rolling stand by thick work rolls and then to operate the rolling stand as a two-high stand or as a four-high stand.

From the US 2 039 959 A is a rolling mill stand designed as a six-high stand that can be operated as a four-high stand after the work rolls have been removed. In this state, the intermediate rolls serve as work rolls.

Summary of the invention

The object of the present invention is to create possibilities to produce materials with higher strength with low final thicknesses in a hot rolling mill.

The object is achieved by an operating method for a hot rolling mill with the features of claim 1. Advantageous embodiments of the operating method are the subject of the dependent claims 2 to 5.

According to the invention, an operating method of the type mentioned at the outset is designed in that, as part of the conversion of the last rolling stand, the last rolling stand is converted from a four-high stand to a six-high stand or vice versa between the rolling of the first metal strip and the rolling of the second metal strip, so that the last rolling stand is configured as a four-high stand with work rolls and backup rolls during the rolling of the first metal strip and as a six-high stand with work rolls, intermediate rolls and backup rolls during the rolling of the second metal strip, and that the further rolling stands are configured as four-high stands both during the rolling of the first metal strip and during the rolling of the second metal strip.

This conversion makes it possible to roll a metal strip made of a softer material or to roll a metal strip to a greater final thickness, while the last rolling stand - as in the prior art - is configured as a four-high stand. However, if a metal strip made of a harder material is to be rolled to a small final thickness, the last rolling stand can be converted to a six-high stand according to the invention.

It is possible to create the rolling plan (i.e. the sequence of metal strips to be rolled one after the other) in such a way that the last rolling stand is converted at a time when the work rolls currently in the last rolling stand would have to be removed anyway due to wear. This procedure leads to optimized productivity. In principle, however, the conversion can also be carried out regardless of the state of wear of the work rolls and thus regardless of a replacement of the work rolls (in a four-high stand) or the work rolls and possibly also the intermediate rolls (in a six-high stand) due to wear.

Preferably, the sum of the diameters of the work rolls and intermediate rolls of the last rolling stand configured as a six-high stand corresponds at least approximately - namely to within 20%, preferably to within 10% - to the diameter of the work rolls of the last rolling stand configured as a four-high stand. This allows the adjustment range of the last rolling stand to be optimally utilized both in the four-high stand configuration and in the six-high stand configuration.

The conversion of the last rolling stand from a four-high stand to a six-high stand is preferably carried out by removing work rolls from the last rolling stand configured as a four-high stand and installing work rolls and intermediate rolls from the last rolling stand configured as a six-high stand. Conversely, the conversion of the last rolling stand from a Converting a six-high stand into a four-high stand preferably by removing the work rolls and the intermediate rolls of the last rolling stand configured as a six-high stand and installing the work rolls of the last rolling stand configured as a four-high stand.

When converting the last rolling stand from a four-high stand to a six-high stand or vice versa, the work rolls and the intermediate rolls of the last rolling stand configured as a six-high stand are preferably installed or removed as a unit. This allows the conversion to be carried out particularly quickly.

In this case, the hot rolling mill has a number of additional rolling stands between the first and the last rolling stand, for example two additional rolling stands, three additional rolling stands or four additional rolling stands, so that - including the first rolling stand and the last rolling stand - there are a total of four, five or six rolling stands. In this case, the additional rolling stands are configured as four-high stands both during the rolling of the first metal strip and during the rolling of the second metal strip. This means that only the last rolling stand is converted.

It is possible for the work rolls of the last rolling stand configured as a six-high stand to be driven. In this case, these work rolls preferably have a diameter that is at least as large as the diameter of the intermediate rolls of the last rolling stand configured as a six-high stand. Alternatively, it is possible for the intermediate rolls of the last rolling stand configured as a six-high stand to be driven. In this case, the work rolls of the last rolling stand configured as a six-high stand preferably have a diameter that is between 50% and 70% of the diameter of the intermediate rolls of the last rolling stand configured as a six-high stand.

Short description of the drawings

FIG 1

eine Warmwalzstraße während des Walzens eines ersten Metallbandes,

FIG 2

die Warmwalzstraße von FIG 1 während eines nicht erfindungsgemäßen Walzens eines zweiten Metallbandes,

FIG 3

den Ausbau von Arbeitswalzen aus einem letzten Walzgerüst der Warmwalzstraße,

FIG 4

den Einbau von Arbeitswalzen und Zwischenwalzen in das letzte Walzgerüst der Warmwalzstraße,

FIG 5

das letzte Walzgerüst der Warmwalzstraße in zwei verschiedenen Konfigurationen und

FIG 6

eine Modifikation der Warmwalzstraße von FIG 1.

The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the embodiments, which are explained in more detail in conjunction with the drawings. Here, in a schematic representation:

FIG 1

a hot rolling mill during the rolling of a first metal strip,

FIG 2

the hot rolling mill of FIG 1 during a rolling of a second metal strip not according to the invention,

FIG 3

the removal of work rolls from a last rolling stand of the hot rolling mill,

FIG 4

the installation of work rolls and intermediate rolls in the last rolling stand of the hot rolling mill,

FIG 5

the last rolling stand of the hot rolling mill in two different configurations and

FIG 6

a modification of the hot rolling mill of FIG 1 .

Description of the embodiments

According to FIG 1 A hot rolling mill has several rolling stands 1a to 1d. The hot rolling mill can be designed in particular as a finishing mill.

According to FIG 1 There are four rolling stands 1a to 1d. However, the number of rolling stands 1a to 1d could also be greater, for example five, six or seven. However, there are at least three rolling stands 1a to 1d. Thus, a number of further rolling stands 1b, 1c are arranged between the first rolling stand 1a and the last rolling stand 1d.

At a certain point in time, a first metal strip 2 is hot rolled in the hot rolling mill. The first metal strip 2 can in particular be a steel strip. The first metal strip 2 runs through the hot rolling mill without stopping and without reversing direction in a transport direction x. The individual sections of the first metal strip 2 thus first pass through the first rolling stand 1a, then the second rolling stand 1b, then the third rolling stand 1c and finally the last rolling stand 1d. Before rolling in the first rolling stand 1a, the first metal strip 2 can be heated to the required rolling temperature, for example in a furnace (not shown). The rolling temperature for a steel strip is usually between 900 °C and 1200 °C. After rolling in the last rolling stand 1d, the first metal strip 2 can be wound up into a coil (not shown), for example.

In the FIG 1 In the state shown, i.e. during the rolling of the first metal strip 2, all rolling stands 1a to 1d of the hot rolling mill are configured as four-high stands. The rolling stands 1a to 1d each have work rolls 3 and backup rolls 4, but no further rolls. This also applies in particular to the first and last rolling stands 1a, 1d of the hot rolling mill.

FIG 2 shows the same hot rolling mill with the same rolling stands 1a to 1d during the rolling of a second metal strip 5. According to the illustration in FIG 2 the first rolling stand 1a is still configured as a four-high stand at this time, i.e. during the rolling of the second metal strip 5. However, at least the last rolling stand 1d is configured as a six-high stand. In addition to the backup rolls 4, it therefore has work rolls 6 and intermediate rolls 7. The intermediate rolls 7 are arranged between the backup rolls 4 and the work rolls 6.

The other rolling stands 1b, 1c are as shown in FIG 2 are still configured as four-high stands even during the rolling of the second metal strip 5.

In a four-high stand, the working rolls 3 are usually driven. In a six-high stand, the working rolls 6 are also usually driven. Additionally or alternatively However, in a six-high stand, the intermediate rolls 7 can also be driven - usually alternatively. These statements also apply to the last rolling stand 1d of the hot rolling mill in the respective configuration.

In the following, it is assumed that the first metal strip 2 is rolled first in the hot rolling mill and only then the second metal strip 5 is rolled. In principle, however, the reverse procedure is also possible.

In order to be able to roll both the first metal strip 2 and the second metal strip 5 in the same hot rolling mill, the last rolling stand 1d is converted from a four-high stand to a six-high stand between the rolling of the first metal strip 2 and the rolling of the second metal strip 5. Thus, as shown in FIG 3 , starting from the configuration of the last rolling stand 1d as a four-high stand, the working rolls 3 of the four-high stand are dismantled. The dismantling is carried out as is generally customary and in FIG 3 indicated by an arrow A, in the axial direction of the working rolls 3 through the window of the operator-side stand. Dashed lines are in FIG 3 the removed work rolls 3 are also shown.

After removing the working rolls 3, as shown in FIG 4 the working rolls 6 and the intermediate rolls 7 of the six-high stand are installed. The installation is carried out as is generally customary and in FIG 4 indicated by an arrow B, in the axial direction of the working rolls 6 and the intermediate rolls 7 through the window of the operator-side stand.

As a result, the last rolling stand 1d is used as required either as a four-high stand - see in FIG 5 left - or as a sexto frame - see in FIG 5 right - configured.

The backup rolls 4 are not changed when the last rolling stand 1d is converted. The backup rolls 4 are therefore the same in the configuration of the last rolling stand 1d as well as Both in the four-high stand and in the configuration of the last rolling stand 1d as a six-high stand, the same support rolls 4 are used.

Preferably, as shown in FIG 4 the working rolls 6 and the intermediate rolls 7 of the six-high stand are arranged in a cassette 8. This makes it possible to install the cassette 8 as such, i.e. as a unit. The working rolls 6 and the intermediate rolls 7 of the six-high stand can also be installed as a unit, ie in particular simultaneously.

In order to keep the adjustment range of the last rolling stand 1d - i.e. the roll gaps that can be formed between the work rolls 3 and between the work rolls 6 - as large as possible both in the configuration as a four-high stand and in the configuration as a six-high stand, the diameters D, D' and D" of the work rolls 3, the work rolls 6 and the intermediate rolls 7 should preferably be coordinated with one another in such a way that the sum of the diameters D', D" of the work rolls 6 and the intermediate rolls 7 of the six-high stand at least approximately corresponds to the diameter of the work rolls 3 of the four-high stand. Smaller deviations of a maximum of 20%, preferably a maximum of 10%, can, however, be tolerated.

The diameters D', D" of the work rolls 6 and the intermediate rolls 7 in the configuration of the last rolling stand 1d as a six-high stand should also be determined taking into account whether the work rolls 6 or the intermediate rolls 7 are driven. In the former case, the diameter D' of the work rolls 6 can be as large as the diameter D" of the intermediate rolls 7, possibly even larger than the diameter D" of the intermediate rolls 7. In the latter case, the diameter D' of the work rolls 6 is preferably significantly smaller than the diameter D" of the intermediate rolls 7. For example, the diameter D' of the work rolls 6 can be between 50% and 70% of the diameter D" of the intermediate rolls 7.

The conversion of the last rolling stand 1d from a four-high stand configuration to a six-high stand configuration was explained above. However, the reverse procedure, i.e. conversion from a six-high stand to a four-high stand, is also possible. The only thing that needs to be done is to follow the opposite procedure.

According to the presentation in FIG 6 the hot rolling mill can have a continuous casting plant 9. The continuous casting plant 9 is arranged upstream of the first rolling stand 1a. In the continuous casting plant, the metal strips 2, 5 are cast in the hot rolling mill before rolling. It is therefore possible to feed the metal strips 2, 5 to the first rolling stand 1a from the casting heat. The hot rolling mill is thus expanded in this case to a combined casting and rolling plant. Due to the presence of the continuous casting plant 9, it is particularly possible to operate the hot rolling mill in continuous operation. Alternatively, however, batch operation is also possible. It is also possible for the hot rolling mill - alternatively or in addition to the continuous casting plant 9 - to have a furnace (not shown in the FIGS). The furnace, if present, is arranged upstream of the first rolling stand 1a. If required, upstream rolling stands 10 can also be arranged upstream of the first rolling stand 1a, in particular roughing stands of a roughing train. The upstream rolling stands 10, if present, are arranged downstream of the continuous casting plant 9 and/or the furnace.

FIG 6 shows a state in which the rolling stands 1a to 1d are all configured as four-high stands. The continuous casting plant 9 and possibly also the upstream rolling stands 10 are also present when the last rolling stand 1d is configured as a six-high stand.

Further configurations of the rolling stands 1a to 1d can be made as required. In particular, the working rolls 3, 6 can be axially displaceable - both in the configuration as a four-high stand and in the configuration as a six-high stand. In the configuration as a six-high stand, alternatively or additionally the intermediate rolls 7 can also be displaceable relative to the work rolls 6. The bending of the work rolls 3, 6 and optionally also of the intermediate rolls 7 can also be as in the prior art. Furthermore, when the rolling stands 1a to 1d are configured as a four-high stand, the work rolls 3 can be arranged slightly offset relative to the support rolls 4, as seen in the transport direction x of the metal strips 2, 5. When the last rolling stand 1d is configured as a six-high stand, when the work rolls 6 are arranged slightly offset relative to the intermediate rolls 7, as seen in the transport direction x of the metal strips 2, 5. Likewise, when the last rolling stand 1d is configured as a six-high stand, the intermediate rolls 7 can be arranged slightly offset relative to the support rolls 4, as seen in the transport direction x of the metal strips 2, 5. The offset of the work rolls 6 relative to the intermediate rolls 7 and the offset of the intermediate rolls 7 relative to the support rolls 4 are preferably in the same direction. If necessary, any thrust forces can be absorbed by support rollers. The support rollers, if present, are arranged on the inlet side and/or outlet side of the work rolls 6. However, such support rollers should be dispensed with if possible.

In the last rolling stand 1d, the work rolls 3, 6 are generally cooled both in the four-high stand configuration and in the six-high stand configuration. Appropriate cooling beams are provided for cooling. For cooling the work rolls 6 in the six-high stand configuration, the cooling beams can be arranged on the inlet side and/or outlet side of the cassette 8 if necessary. Alternatively, the cooling beams can be a component of the last rolling stand 1d as such, so that they are not installed or removed when the configuration of the last rolling stand 1d is changed.

The present invention has many advantages. For example, due to the smaller diameter D' of the work rolls 6 compared to the diameter D of the work rolls 3, not only metal strips 2, 5 made of softer materials, but also metal strips 2, 5 made of harder materials can be rolled to low final thicknesses. Subsequent cold rolling can be omitted or can begin with a thinner input product, which in turn means that the output product of the cold rolling can have a lower thickness. Nevertheless, the range of products that can be produced is not impaired, and is often even expanded. In particular, for larger final thicknesses, the required bending stiffness during rolling can be achieved by configuring the last rolling stand 1d as a four-high stand. The pass reduction in the last rolling stand 1d can be maximized in the configuration as a six-high stand, although the rolling forces and rolling moments required for this can still be reduced. This also makes it possible to achieve improved material properties of the second metal strip 5. In particular, the microstructure of the second metal strip 5 can be homogenized and so-called shear bands can be prevented. Finally, ferritic rolling is possible in the hot rolling mill. This can have a positive effect on the so-called r-value, which characterizes the planar anisotropy and is important for the deep-drawability of the rolled metal strips 2, 5. In the prior art, this requires cold rolling followed by annealing. The present invention eliminates the need for cold rolling and annealing.

List of reference symbols

1a to 1d

Rolling mills

2, 5

Metal bands

3, 6

Work rolls

4

Support rollers

7

Intermediate rolls

8th

cassette

9

Continuous casting plant

10

upstream rolling stands

AWAY

Arrows

D, D', D"

diameter

x

Transport direction

Claims (5)

1. Operating method for a hot rolling line which has at least a first and a last roll stand (1a, 1d),

   - wherein in the hot rolling line a first and a second metal strip (2, 5) are rolled one after the other,

   - wherein portions of the metal strips (2, 5) in each case first pass through the first roll stand and only afterwards the last roll stand (1a, 1d) of the hot rolling line,

   - wherein the first roll stand (1a) is configured as a four-high stand both during the rolling of the first metal strip (2) and during the rolling of the second metal strip (5),

   - wherein the hot rolling line has a number of additional roll stands (1b, 1c) between the first and the last roll stand (1a, 1d),

   characterized in that the last roll stand (1d) is converted between the rolling of the first metal strip (2) and the rolling of the second metal strip (5) from a four-high stand to a six-high stand, or vice versa, so that the last roll stand (1d) during the rolling of the first metal strip (2) is configured as a four-high stand with working rollers (3) and support rollers (4) and is configured during the rolling of the second metal strip (5) as a six-high stand with working rollers (6), intermediate rollers (7) and support rollers (4), and in that the additional roll stands (1b, 1c) both during the rolling of the first metal strip (2) and during the rolling of the second metal strip (5) are configured as four-high stands.
2. Operating method according to claim 1, characterized in that
   the sum of the diameters (D', D") of working rollers (6) and intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand corresponds at a rate of precisely 20%, preferably at a rate of precisely 10% to the diameter (D) of the working rollers (3) of the last roll stand (1d) when configured as a four-high stand.
3. Operating method according to claim 1 or claim 2, characterized in that
   the conversion of the last roll stand (1d) from a four-high stand to a six-high stand is carried out by disassembling working rollers (3) of the last roll stand (1d) when configured as a four-high stand and installing working rollers (6) and intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand or, conversely, the conversion of the last roll stand (1d) from a six-high stand to a four-high stand is carried out by disassembling the working rollers (6) and the intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand and installing the working rollers (3) of the last roll stand (1d) when configured as a four-high stand.
4. Operating method according to claim 3, characterized in that,
   when the last roll stand (1d) is converted from a four-high stand to a six-high stand or, vice versa, the working rollers (6) and the intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand are installed or disassembled as a unit.
5. Operating method according to any one of the preceding claims,
   characterized in that
   the working rollers (6) of the last roll stand (1d) when configured as a six-high stand are driven and have a diameter (D') which is at least as large as the diameter (D") of the intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand or in that the intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand are driven and the working rollers (6) of the last roll stand (1d) when configured as a six-high stand have a diameter (D') which is between 50% and 70% of the diameter of the intermediate rollers (7) of the last roll stand (1d) when configured as a six-high stand.

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