EP2624971A2

EP2624971A2 - Process and apparatus for producing a metal strip by casting and rolling

Info

Publication number: EP2624971A2
Application number: EP11763652.2A
Authority: EP
Inventors: Erich Hovestädt; Jürgen Seidel
Original assignee: SMS Siemag AG
Current assignee: SMS Group GmbH
Priority date: 2010-10-07
Filing date: 2011-09-28
Publication date: 2013-08-14
Anticipated expiration: 2031-09-28
Also published as: RU2013120545A; WO2012045629A2; WO2012045629A3; RU2537629C2; EP2624971B1; DE102011004245A1

Abstract

The invention relates to a process for producing a metal strip (1) by casting and rolling, in which process firstly a slab (3) with a nominal slab thickness (d) is cast in a casting machine (2) by discharging metal at a nominal casting speed (v) from a mould (4), wherein the slab (3) is subjected to thickness reduction in the region of a strand guide (5) by a number of rollers, wherein the temperature of the slab (3) is then controlled in a furnace (6) of a defined length, wherein the slab (3) is rolled downstream of the furnace (6) in a rolling mill train (7), and wherein in particular the slab (3) is subjected to thickness reduction to a nominal deformed slab thickness or preliminary strip thickness in a roughing rolling mill (8) downstream of the casting machine (2) and upstream of the furnace (6). In order firstly to provide an adequate buffer store in the event of interruptions to rolling and secondly to ensure the smallest possible furnace length in order to be able to work optimally in continuous operation, without high economical outlay, the invention provides that at least one of the following measures is carried out for temporarily reducing, in particular for temporarily interrupting, the supply of rolling stock into the rolling mill train (7): a) the slab thickness (d₀) is increased downstream of the casting machine (2) by reducing the thickness reduction of the slab (3) in the region of the strand guide (5); b) the casting speed is lowered from the nominal casting speed (v₀) to a reduced value; c) the thickness reduction of the slab (3) in the roughing rolling mill (8) is reduced. The invention further relates to a casting and rolling installation.

Description

Method and device for producing a metal strip by casting rolls

The invention relates to a method for producing a metal strip by casting rolls, in which first in a casting machine a slab with nominal slab thickness is poured by discharging metal at a nominal casting speed from a mold, wherein the slab in the region of a strand guide by a number rollers are subjected to a thickness reduction, wherein the slab is then tempered in a furnace of defined length, wherein the slab is rolled behind the furnace in a rolling train and wherein in particular the slab behind the casting machine and in front of the furnace in a roughing mill of a reduction in thickness to a nominal deformed slab thickness or Vorbanddicke is subjected. Furthermore, the invention relates to a casting rolling mill.

In cast rolling mills in the form of thin slab plants one can differentiate between batch processes and endless processes.

In batch processes, after casting or casting rolling, the slabs or pre-strips are separated into individual slabs or individual pre-slats so that coils of the desired size are produced after hot-rolling.

Thin slab plants mainly work as a slab process. For the slab process, it is characteristic that the conservation of energy and the required heating of the slab, for example in a roller hearth furnace, which is longer than the maximum slab length. This allows all slabs to be separated in such a way that the individual slab is completely in the oven within a certain period of time, ie neither in the casting machine nor in the casting machine. nenbereich still in the rolling range of the finishing train is engaged. Typical thicknesses of the slabs are between 40 mm and 100 mm.

In contrast, the so-called ISP process works with smaller intermediate strip thicknesses, which are typically in the range between 10 and 20 mm. The individual intermediate belts are always engaged either in the casting area or in the rolling area of the finishing train. The intermediate buffering of the pre-bands is carried out by means of two heated coiling ovens, which conserves the temperature of the pre-bands after reheating. Also known is the so-called ESP process. This is an endless process that originated from the ISP process. Since the ESP process must operate without a thermal intermediate buffer, all distances between the individual devices of the plant must be minimized in order to avoid the unprotected radiation of the heat of the intermediate strips to the environment. This inevitably results in small distances between the facilities. The advantages and disadvantages of the ESP process are as follows:

It is advantageous that uniform continuous rolling conditions can be maintained over several hot strips, which is very favorable, especially for thin hot strips.

The disadvantage, however, is as follows: It is difficult to adhere to the final rolling temperature, since the rolling speed in the finishing train is coupled directly to the mass flow from the casting machine. This can only be achieved by a consistently high casting performance and by reheating the intermediate belt to very high temperatures after roughing. Furthermore, the required final rolling temperatures can not be achieved for all steel grades, so that certain grades can not be produced in continuous operation. Then it is disadvantageous that in a required roll change, the sequence must be completely stopped. In case of faults, for example, in the casting operation, the continuous operation is interrupted, it must then be converted to batch mode. be switched. Due to the small distances between the casting plant and the finishing mill, if so-called "mini-coils" are converted in the ESP process, since they are not marketable products, their economic use is limited. weight is only about 35% to 40% of the coil size available in the marketplace.To maintain a consistently high casting performance, a high-performance steelworks is required, which can or must also work reproducibly at a high level from continuous operation to batch operation (too low finish rolling temperature) with the disadvantageous consequence that only "mini-coils" can be produced.

DE 10 2008 020 412 A1 describes a method for producing a metal strip by casting rolls, in which first a thin slab is cast in a casting machine. This is then rolled in a rolling mill using the primary heat of the casting process. In a first mode of operation can be carried out by direct coupling of the casting machine with the at least one rolling train, a continuous production of the metal strip (endless rolling); In a second operating mode, a discontinuous production of the metal strip can take place by decoupling the casting machine from the at least one rolling train (batch operation). In order to increase the flexibility of the system, it is provided that cast slabs or pre-belts casted behind the casting machine from the main transport line when driving the discontinuous production of the metal strip, stored and later transported back to the main transport line. The removed slabs or pre-bands can be brought to a desired temperature or kept at a desired temperature prior to being transported back into the main transport line. In order to avoid interruptions of casting during malfunctions or roll changes, an additional slab storage area - accessible by ferry - is created next to the main transport line. Although this makes it possible to solve the problem mentioned, ie to operate a method that overcomes the above-mentioned disadvantages of the ESP process, however, the device complexity is high and the casting rolling device is correspondingly cost-intensive, ie the intermediate storage of the slabs only with great effort to achieve.

The invention has for its object to provide a method of the type mentioned so or to create a corresponding device with which it is possible, without great effort on the one hand a sufficient buffer memory in the event of roll interruptions, z. B. due to a roll change, on the other hand to ensure the smallest possible furnace length to work optimally in continuous operation can. Thus, a combined continuous / batch process is to be provided which overcomes the above disadvantages of the ESP process with cost effective means. In particular, additional storage ovens adjacent to the transport line or oven extensions should be avoided.

The solution of this problem by the invention according to the method is characterized in that for temporary reduction, in particular for temporary interruption, the supply of rolling stock in the rolling mill at least one of the measures is performed: a) Increase the slab thickness behind the casting machine by reducing the thickness reduction of the slab in the field of strand guidance; b) lowering the casting speed from the nominal casting speed to a reduced value;

Reduction of the thickness reduction of the slab in the roughing mill. At least two of the measures a), b) or c) can also be used in combination in order to increase the desired effect.

In conjunction with the temporary reduction in the supply of rolling stock to the furnace, the slab may be cut (separated) on a pair of shears located in front of the furnace.

The inlet velocity of the slab into the furnace is preferably reduced by at least a factor of 2 compared to the nominal value.

The thickness reduction of the slab in the area of the strand guide is preferably reduced by up to 40 mm.

The thickness reduction of the slab in the roughing mill can be reduced to zero.

The temporary reduction, in particular the temporary interruption, the supply of rolling stock in the rolling train can be made while in the rolling mill a roll change is made or there is a different production delay in the rolling mill.

After making the temporary reduction in the supply of rolling stock in the rolling mill, the slab can be processed in batch batch operation. This is due to the process for the first slab after a Walzun- break.

The slab can, as long as a temporary reduction of the supply of rolling stock in the rolling train is not carried out, be processed in the continuous rolling process. However, the method is applicable to a rolling mill, which is operated in continuous mode or in batch mode. By means of the above measures a), b) or c), such a buffer time or rolling interruption in the rolling train can be created or made possible, so that no casting breakage must take place in the casting machine, with a short furnace being used in particular. The slab may also be subjected to heating by means of induction heating in front of or behind the furnace.

The casting rolling mill, which comprises a casting machine, an oven and a rolling mill connected downstream of the furnace, wherein the furnace has a number of heating elements in order to temper a cast slab, is inventively characterized in that the furnace has a total length between 30 and 120 m ,

The furnace is preferably formed as a roller hearth furnace or as roller-skating encapsulation, wherein it preferably has insulated roller conveyor rollers.

In front of the furnace and / or behind the furnace and / or inside the furnace, heating elements for heating the slab may be arranged, in particular inductive heating elements.

Behind the caster, a roughing mill or multiple roughing mills can be arranged.

The heating elements of the furnace are preferably arranged out of the transport line. In this case, insulation elements may be present, which can be retracted as needed in the area of the furnace instead of the heating elements.

Thus, the proposed method allows maximizing the slab puff mass or buffer time in a furnace (preferably in a roller hearth furnace or a walking beam furnace) by increasing the casting thickness in comparison with the (nominal) production thickness. Furthermore, alternatively or additionally, a lowering of the casting speed can be provided in comparison with the (nominal) production speed.

The method further provides alternatively or additionally that a reduction of the decrease in an in-line roughing stand or Vorgerüsten behind the casting plant and in front of the furnace in comparison with the (nominal) decrease takes place during regular production.

The method may provide for maximizing the oven bake time (in a hot strip and continuous hot rolling mill) where the feed rate of the slabs into the oven in the buffer phase is at least a factor of 2 over the nominal (normal) feed rate in the case of normal production is reduced. The change in the thickness decrease at the inline roughing stand is between ε = 0% to 70%. Alternatively or additionally, the casting thickness can be adjusted by LCR (liquid core reduction) of preferably 0 to 40 mm in order to influence the slab segment length in the furnace, preferably with the same ring weight.

Analogous to the change in the oven inlet thickness, the finished strip is changed to a desired practical finished strip thickness.

The process provides buffering time for a roll change or for bridging other production delays.

The proposed casting mill allows the combined batch and final rolling of hot strip. The oven - preferably designed as a roller hearth furnace - is preferably between 30 and 120 m long. The use of an inline roughing stand is preferred, but not mandatory. The use of the change in thickness in the caster and in the in-line scaffold for the purpose of increasing the buffer time or shortening the kiln length can be provided in a single-strand caster rolling mill, but also in a multi-strand caster rolling mill.

In addition, space can be provided for a ferry, as well as an additional logistically required furnace length for handling in the case of a 2-strand operation. The roller hearth furnace can be designed as a temperature holding furnace or alternatively serve for heating the slabs or intermediate bands. In addition, it is possible to inductively heat the slab or the preliminary slab in front of and / or behind the roller hearth furnace or within the same in order to move the slab to a temperature between 1.0050 ° C. and 1.400 ° C. before the scale washer of the finishing train bring.

In special cases, a roller table cover (roller table encapsulation) can also be used partially or instead of a roller hearth furnace. An induction heater, which is preferably arranged behind it, brings the pre-strip or the slab in front of the rolling train to the desired inlet temperature.

The induction heaters can be displaced laterally or upwards out of the line in order to be able to heat at a thin strip and to be able to drive out the induction heaters with a thick strip, in order to replace them with insulation elements (insulating elements, roller shutter encapsulation).

At least one inductive heating can also be provided between the stands of the finishing train. Thus, according to the invention, despite the use of a short furnace, a buffer time can be created or a rolling interruption can be realized in the rolling train (For example, to change a roller in the finishing train), without a casting demolition must be done in the casting machine.

In the drawings, embodiments of the invention are shown.

Show it:

1 is a schematic side view of a casting and rolling plant according to a first embodiment of the invention,

2 shows in the illustration according to FIG. 1 a cast roll mill according to an alternative embodiment of the invention and in the illustration according to FIG. 1 a cast roll mill according to the alternative embodiment of the invention.

FIGS. 1 to 3 each show a cast roll plant in which a metal strip 1 is produced.

For this purpose, a slab 3, preferably a thin slab with the thickness d, cast first in a conventional casting machine 2 by molten metal from a mold 4 with a casting speed v emerges vertically downwards. The cast strand is deflected by means of a strand guide 5 from the vertical to the horizontal. At the same time there is a reduction in the thickness of the cast slab 3. This is done by rollers which are arranged in the strand guide 5 and exert a normal force on both sides of the slab surface. The slab 3 leaves the casting machine 2 with the nominal thickness d ₀ and speed v ₀ in the belt conveying direction F.

The nominal values for the casting speed v ₀ and the slab thickness d ₀ are those values which are present in the scheduled production of the metal strip 1. At the end or behind the casting machine 2, an in-line roughing stand 8 (rough rolling mill) is directly arranged, with which the slab 3 is further reduced in thickness. Immediately behind the roughing stand 8 is a pair of scissors 9. Behind the pair of scissors 9, there follows an oven 6, which is designed, for example, as a roller hearth oven. At the position of the furnace 6 is also optionally the arrangement of a roller table cover or encapsulation preferably with insulated roller table rollers conceivable.

Behind the oven is followed by a finishing line 7, in which the strip is rolled to a desired final thickness.

The cast rolling mill still has various other elements, which are shown in the three embodiments. In Fig. 1 is located behind the furnace 6, an induction heater 10. This induction heating can optionally be arranged laterally displaced or heraushebbar from the working position. For thin tapes, the tape can be heated by the induction heater; then be provided with thicker slabs that the induction heater is moved out of the working position and replaced by insulating elements to reduce the heat radiation from the slab.

The exemplary six rolling mills of the finishing train 7 are designated F1 to F6. Within the finishing train 7 further induction heaters 1 1 can be provided between the rolling stands. Behind the finishing train 7 are a cooling section 12 and reels 13. Further scissors 14 and 15 are provided.

In Fig. 2 is a heat-insulating hood in the field of cold strand disposal 16 behind the roughing mill 8 and the scissors 9 mentioned. It can be equipped with a swiveling thermal insulation hood and insulated furnace rollers be. When casting the tape is observable here (pivoting the employment of the framework).

An induction heater 10 is provided here in front of the roller hearth furnace 6. In the solution according to FIG. 3 no induction heating is provided in the region of the furnace 6, however, in this embodiment the furnace 6 is made slightly longer.

In the system variants shown - preferably with an inline roughing stand 8, but alternatively also with several of these roughing stands - the intermediate thickness or the inlet thickness in the roller hearth furnace 6 (eg between 20 and 120 mm slab thickness) can be flexibly adjusted.

To produce a time buffer in the roller hearth furnace 6 at a roll interruption and / or in the case of a work roll change, by flexible changing the thickness decrease of the slab 3 on inline roughing 8 (thickness decrease ε = 0 to 70%) and / or by adjusting the casting thickness LCR (Liquid Core Reduction) in the area of strand guide 5 (between 0 and 40 mm) influences the slab length in the furnace. An increase in the intermediate thickness increases the furnace storage capacity or advantageously reduces the necessary furnace length.

If a roll change is planned, the slab 3 deformed on the roughing stand 8 is scooped up on the scissors 9 and then the intermediate thickness is purposefully raised for the following slab segment or for the following segments, specifically via the nominal values (production values). As a result of the lower transport speed, therefore, the oven 6 fills slower. An additional reduction of the casting speed supports this effect. The following table shows how the aspect ratio of the slab changes (example of a slab for a maximum ring weight of 18 kg / mm):

How fast a roller hearth furnace with a length of, for example, 60 m under different conditions (casting speed 3 or 5 m / min) is filled with and without decrease in the roughing stand 8) is shown in the following table:

Thickness [mm] Transport speed Fill time Boundary conditions

do not touch the [min]

Roughing stand [m / min]

50 1 1 5,5 Nominal (normal) production condition with thickness reduction on the roughing stand

Conditions for generating a time buffer:

1 10 5 12.0 No reduction in thickness

1 10 3 20.0 No reduction in thickness and reduced

casting speed The buffer time results from the Ofenfüllzeit given boundary conditions minus the rolling time in the finishing mill for the previously produced slab minus a reserve distance. Preferably, during rolling in the finishing train before the roll change, a final thickness is selected such that a high draw-in speed results in the finishing train.

If the slab thickness - z. B. in order to increase the buffer time - raised, the finished strip thickness is also increased accordingly to a desired practical finished strip thickness. The finishing train must therefore be prepared for decreases of, for example H = 1 10 - 5 mm and H = 50 - 1, 0 mm. For this purpose, the stator windows are to be dimensioned sufficiently, it is a large stroke of the thickness adjustment (long-stroke cylinder or additional mechanical employment in the front scaffolding or a wedge adjustment) provided further, the engine speed ranges are provided in the finishing mill accordingly.

The roller hearth furnace is designed for the mode of operation and the maximum and minimum thin slab thicknesses of, for example, 120 or 20 (25) mm, and corresponding roller spacings and diameters are used. The furnace length between the roughing stand 8 and the finishing train 7 is short and is preferably between 30 m and 120 m, depending on the required boundary conditions. Thus, the kiln length is shorter than with conventional CSP plants (where it is between 200 and 240 m). The shorter oven advantageously reduces the energy losses. The heating of the (transformed) slab 3 can take place with a roller hearth furnace or the roller hearth furnace is operated as a temperature holding furnace and assisted by inductive heaters upstream and / or behind or inside the roller hearth furnace (see the three exemplary embodiments according to FIGS. Parts of the furnace or the entire furnace may alternatively be designed in the form of a rolling cover or encapsulation with insulated roller table rollers. The above procedure applies to continuous and batch operation in a 1-line system. In order to make better use of the production capacity of the finishing train, it may be useful to integrate a second casting strand in the case of batch operation. In the case of a 2-line system, the above procedure of batch operation is also carried out on the second line in order to reduce the roller hearth furnace length in total. For this purpose, advantageously a flexible two-part ferry can be provided. The half parallel ferry transports the thick slabs and the whole double ferry is intended for the normal thinner, longer slabs. The ring weight of the slabs can be the same.

It should be noted that the slab 3 is understood to be the cast slab behind the casting machine 2 or else the deformed slab behind the rough rolling mill 8.

LIST OF REFERENCE NUMBERS

1 metal band

2 casting machine

3 slab

4 mold

5 strand guide

6 oven

7 rolling mill (finishing mill)

8 rough rolling mill (inline roughing stand)

9 scissors

10 induction heating

1 1 induction heating

12 cooling track

13 reel

14 scissors

15 scissors

16 Thermal insulation hood in the area of cold string disposal

d ₀ nominal slab thickness at the outlet of the casting machine v ₀ nominal casting speed at the outlet of the casting machine d slab thickness at the die exit

v Casting speed at Kokillenaustritt

F Slab, sliver or belt conveying direction

Claims

claims:

1 . A method for producing a metal strip (1) by casting rolls, wherein first in a casting machine (2) a slab (3) of nominal slab thickness (d) by casting metal with a nominal casting speed (v) from a mold (4) poured wherein the slab (3) in the region of a strand guide (5) is subjected to a reduction in thickness by a number of rolls, the slab (3) then being tempered in a furnace (6) of defined length, the slab (3) being behind the furnace (6) is rolled in a rolling train (7) and in particular the slab (3) behind the casting machine (2) and before the furnace (6) in a roughing mill (8) subjected to a reduction in thickness to a nominal reshaped slab thickness or pre-strip thickness is characterized in that for the temporary reduction, in particular for the temporary interruption, the supply of rolling stock in the rolling train (7) at least one of the measures is carried out: a) increase the slab thickness e (d ₀ ) behind the casting machine (2) by reducing the thickness reduction of the slab (3) in the region of the strand guide (5); b) lowering the casting speed from the nominal casting speed (v ₀ ) to a reduced value; c) reduction of the thickness reduction of the slab (3) in the roughing mill (8).

Method according to claim 1,

characterized,

at least two of the measures a), b) or c) according to claim 1 are used in combination.

Method according to claim 1 or 2,

characterized,

in that, in cooperation with the temporary reduction of the supply of rolling stock into the furnace (6), the slab (3) is cut on a scissors (9) arranged in front of the furnace (6).

Method according to one of claims 1 to 3,

characterized,

that the inlet velocity of the slab (3) into the furnace (6) is reduced by at least a factor of 2 compared to the nominal value.

Method according to one of claims 1 to 4,

characterized,

that the thickness reduction of the slab (3) in the region of the strand guide (5) is reduced by up to 40 mm.

Method according to one of claims 1 to 5,

characterized,

the reduction in thickness of the slab (3) in the rough rolling mill (8) is reduced to zero.

Method according to one of claims 1 to 6,

characterized,

that the temporary reduction, in particular the temporary interruption, the supply of rolling stock in the rolling train (7) is made while in the rolling train (7) a roll change is made o- in the rolling train (7) has a different production delay.

Method according to one of claims 1 to 7,

characterized,

in that after the temporary reduction of the supply of rolling stock into the rolling train (7) the slab (3) is processed in discontinuous batch mode.

Method according to one of claims 1 to 8,

characterized,

that the slab (3), as long as a temporary reduction of the supply of rolling stock in the rolling train (7) is not carried out, is processed in the continuous rolling process.

Method according to one of claims 1 to 9,

characterized,

that measures such a), b) or c) according to claim 1 such a buffer time or rolling interruption in the rolling train (7) created or made possible that no casting demolition must be done in the casting machine, in particular a short oven (6 ) is used.

Method according to one of claims 1 to 10,

characterized, the slab (3) is subjected to heating by means of an induction heater (10) in front of or behind the furnace (6).

12. Casting rolling mill comprising a casting machine (2), optionally a rough rolling mill (8), a furnace (6) and a rolling mill (7) connected downstream of the furnace (6), the furnace (6) having a number of heating elements to temper a cast slab (3), in particular for carrying out the method according to one of claims 1 to 1 1, characterized in that the furnace (6) has a total length of between 30 and 120 m.

13. Casting rolling mill according to claim 12,

characterized,

the oven (6) is designed as a roller hearth furnace or as a roller-skating encapsulation, wherein it preferably has insulated roller-conveyor rollers.

14. Cast rolling mill according to claim 12 or 13,

characterized,

in that heating elements for heating the slab (3) are arranged in front of the furnace (6) and / or behind the furnace (6) and / or inside the furnace (6), in particular inductive heating elements (10).

15. Cast rolling mill according to one of claims 12 to 14,

characterized,

that behind the caster (2) a roughing mill (8) or more roughing mills (8) are arranged.

16. Casting rolling mill according to one of claims 12 to 15,

characterized,

in that the heating elements of the furnace (6) or inductive heating elements (10) can be moved out of the transport line.

17. Cast rolling mill according to claim 16,

characterized,

that insulation elements are present, which can be retracted as needed in the area of the furnace (6, 10) instead of the heating elements.