DE102011004245A1 - Method and device for producing a metal strip by casting rolls - Google Patents

Abstract

The invention relates to a method for producing a metal strip (1) by casting rolling, in which a slab (3) with a nominal slab thickness (d) is first of all produced in a casting machine (2) by dispensing metal with a nominal casting speed (v) from a mold ( 4) is poured, the slab (3) being subjected to a reduction in thickness in the area of a strand guide (5) by a number of rollers, the slab (3) then being tempered in a furnace (6) of a defined length, the slab ( 3) is rolled behind the furnace (6) 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) a reduction in thickness to a nominal formed slab thickness or pre-strip thickness is subjected. In order on the one hand to create a sufficient buffer store in the event of roll interruptions without high economic outlay and on the other hand to ensure the shortest possible furnace length in order to be able to work optimally in continuous operation, the invention provides that the supply of Rolled material into the rolling train (7) at least one of the measures is carried out: a) increasing the slab thickness (d0) 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 (v0) to a reduced value; c) Reduction in the thickness reduction of the slab (3) in the roughing mill (8). The invention further relates to a casting and rolling plant.

Description

The invention relates to a method for producing a metal strip by casting rolls, in which first in a casting machine a slab of 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 of roles of a Wherein the slab is subsequently tempered in a furnace of defined length, the slab being rolled behind the furnace in a rolling train and, in particular, the slab behind the casting machine and in front of the furnace in a roughing mill reducing thickness to a nominal reshaped slab thickness or thickness Substrate thickness 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 you to separate all slabs so that in a certain period of time, the individual slab is completely in the oven, d. H. neither in the casting machine area nor in the rolling area 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 the following: It is difficult to comply with the final rolling temperature, since the rolling speed in the finishing train is directly coupled 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 endless operation is interrupted, it must then be switched to batch mode. When switching to batch mode in the ESP process, only so-called "mini-coils" can be produced due to the small distances between the caster and the finishing train. Since these are not marketable products, their economic use is limited. Their specific coil weight is only about 35% to 40% of the marketable coil size. In order to maintain a consistently high casting performance, a high-performance steelworks is needed, which also can or must work reproducibly at a high level. Disturbances in the steelworks also lead directly to the need to switch from continuous operation to batch operation (too low final rolling temperature) with the disadvantageous consequence that only "mini-coils" can be produced.

In the DE 10 2008 020 412 A1 a method for producing a metal strip by casting rollers is described, 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 mode, by decoupling the caster from the at least one rolling train, a discontinuous production of the metal strip done (batch mode). 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 before being transported back into the main transport line. In order to avoid interruptions in the event of faults or roll changes, an additional slab storage area - accessible by ferry - is thus created next to the main transport line.

This makes it possible to solve the problem mentioned, that is to operate a method that overcomes the above-mentioned disadvantages of the ESP process, but the device complexity is high and the Gießwalzvorrichtung correspondingly expensive, d. H. the intermediate storage of the slabs can only be achieved with great effort.

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.

• a) Erhöhen der Brammendicke hinter der Gießmaschine durch Verminderung der Dickenreduktion der Bramme im Bereich der Strangführung;
• b) Absenken der Gießgeschwindigkeit von der nominalen Gießgeschwindigkeit auf einen verminderten Wert;
• c) Verminderung der Dickenreduktion der Bramme in dem Vorwalzwerk.

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 carried out:

• a) Increase the slab thickness behind the casting machine by reducing the thickness reduction of the slab in the strand guide;
• b) lowering the casting speed from the nominal casting speed to a reduced value;
• c) 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 roll interruption.

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 continuous casting plant, 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 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 designed as a roller hearth furnace or as roller-skated 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 buffer mass in a furnace (preferably in a roller hearth furnace or a walking beam furnace) by increasing the casting thickness as compared to 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 in addition, that a reduction in the decrease in an in-line roughing stand or behind the caster and before 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 method provides buffering time for a roll change or to bridge other production delays.

The proposed casting mill allows combined batch and continuous 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 in-line roughing stand is preferred, but not mandatory.

The use of the change in thickness in the casting machine 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 casting-rolling plant, but also in a multi-strand casting-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, before and / or behind the roller hearth furnace or inductively heat the slab or the pre-band to bring the slab to a temperature between 1050 ° C and 1400 ° C before the scale scrubber of the finishing train.

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 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 (dam elements, roller box 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 roll interruption can be realized in the rolling train (for example, to change a roll in the finishing train), without having to make a casting break in the casting machine.

In the drawings, embodiments of the invention are shown.

Show it:

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

2 in the illustration 1 a casting rolling mill according to an alternative embodiment of the invention and

3 in the illustration 1 a casting rolling mill according to another alternative embodiment of the invention.

In the 1 to 3 In each case a casting rolling plant is to be seen, in which a metal band 1 will be produced.

For this purpose, first in a known casting machine 2 a slab 3 , preferably a thin slab of thickness d, cast by molten metal from a mold 4 emerges vertically downwards at a casting speed v. The cast strand is made by means of a strand guide 5 redirected from the vertical to the horizontal. At the same time, there is a reduction in the thickness of the cast slab 3 , For this roles serve, in the strand guide 5 are arranged 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 to be understood as the values which occur during the scheduled production of the metal strip 1 available.

At the end or behind the caster 2 is immediately an inline roughing stand 8th (Roughing mill) arranged with which the slab 3 continues to be reduced in thickness. Immediately behind the roughing frame 8th there is a pair of scissors 9 , Behind the scissors 9 closes a stove 6 on, which is designed for example as a roller hearth furnace. At the position of the furnace 6 Optionally, the arrangement of a roller table cover or encapsulation is preferably conceivable with insulated roller table rollers.

Behind the stove is a finishing road 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 1 is behind the stove 6 an induction heater 10 , This induction heater can optionally be arranged laterally displaceable 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 stands of the finishing train 7 are designated F1 to F6. Inside the finishing train 7 can between the rolling stands more induction heaters 11 be provided. Behind the finishing train 7 There is a cooling section 12 and reels 13 , There are also more scissors 14 and 15 intended.

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

An induction heater 10 is here in front of the roller hearth furnace 6 intended.

In the solution according to 3 is in the range of the furnace 6 no induction heating provided, however, in this embodiment, the oven 6 run a little longer.

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

In the roller hearth furnace 6 During a roll interruption and / or in the case of a work roll change to produce a time buffer is by flexibly changing the thickness decrease of the slab 3 on the in-line roughing stand 8th (Thickness decrease ε = 0 to 70%) and / or by adjusting the casting thickness by LCR (Liquid Core Reduction) in the strand guide 5 (between 0 and 40 mm) affects the slab length in the oven. Increasing the intermediate thickness increases the furnace storage capacity or advantageously reduces the necessary furnace length.

If a roll change is planned, the on the roughing stand 8th deformed slab 3 on the scissors 9 Then, for the following slab segment or for the following segments, the intermediate thickness is purposefully raised above the nominal values (production values). Due to the lower transport speed, therefore, the furnace fills 6 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): Area Thickness [mm] Length of a slab segment [m] comment mold 110 21.5 Nominal (normal) production condition Outlet casting machine 80 29.6 after LCR Behind inline scaffolding 50 47.4 after thickness reduction Behind inline roughing stand (increased thickness reduction on LCR and roughing stand) 35 67.7 Special case with a short oven: Slab is partly outside the oven and fits between scissors 9 and finishing tipper scrubber

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 behind the roughing stand [m / min] Oven filling time [min] boundary conditions 50 11 5.5 Nominal (normal) production condition with thickness reduction on the rough stand Conditions for generating a time buffer: 110 5 12.0 No reduction in thickness 110 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, when rolling in the finishing train before the roll change so selected a final thickness that results in a high feed rate 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 = 110 → 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 kiln length between the roughing stand 8th 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.

Heating of the (transformed) slab 3 can be done with a roller hearth furnace or the roller hearth furnace is operated as a temperature holding furnace and supported by inductive heaters forward and / or behind or inside the roller hearth furnace (see the three embodiments according to 1 to 3 ). Parts of the furnace or the entire furnace may alternatively be designed in the form of a roller table 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 a 2-strand plant, the above procedure of the batch operation is also performed on the second strand to reduce in total the roller hearth furnace length. 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 as a slab 3 the cast slab behind the casting machine 2 or the formed slab behind the roughing mill 8th is understood.

LIST OF REFERENCE NUMBERS

1

metal band

2

casting machine

3

slab

4

mold

5

strand guide

6

oven

7

Rolling mill (finishing mill)

8th

Pre-rolling mill (inline roughing stand)

9

scissors

10

induction heating

11

induction heating

12

cooling section

13

reel

14

scissors

15

scissors

16

Heat-insulating 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 Kokillenaustritt

v

Casting speed at Kokillenaustritt

F

Slab, pre-strip or belt conveying direction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008020412 A1 [0008]

Claims (17)

Method for producing a metal strip ( 1 ) by casting rolls, in which first in a casting machine ( 2 ) a slab ( 3 ) with nominal slab thickness (d) by applying metal with a nominal casting speed (v) from a mold ( 4 ) is poured, the slab ( 3 ) in the region of a strand guide ( 5 ) is subjected to a reduction in thickness by a number of rollers, the slab ( 3 ) in an oven ( 6 ) of defined length, wherein the slab ( 3 ) behind the stove ( 6 ) in a rolling mill ( 7 ) and in particular the slab ( 3 ) behind the casting machine ( 2 ) and in front of the stove ( 6 ) in a roughing mill ( 8th ) is subjected to a reduction in thickness to a nominal reshaped slab thickness or pre-strip thickness, characterized in that for the temporary reduction, in particular for temporary interruption, the supply of rolling stock into the rolling train ( 7 ) at least one of the measures is carried out: a) increasing the slab thickness (d ₀ ) behind the casting machine ( 2 ) by reducing the thickness reduction of the slab ( 3 ) in the field of strand guidance ( 5 ); b) lowering the casting speed from the nominal casting speed (v ₀ ) to a reduced value; c) reduction, the thickness reduction of the slab ( 3 ) in the roughing mill ( 8th ). A method according to claim 1, characterized in that at least two of the measures a), b) or c) are used in combination according to claim 1. A method according to claim 1 or 2, characterized in that in cooperation with the making of the temporary reduction of the supply of rolling stock in the furnace ( 6 ) the slab ( 3 ) in front of the stove ( 6 ) arranged scissors ( 9 ) is cut. Method according to one of claims 1 to 3, characterized in that the inlet velocity of the slab ( 3 ) in the oven ( 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 in that the thickness reduction of the slab ( 3 ) in the field of strand guidance ( 5 ) is withdrawn by up to 40 mm. Method according to one of claims 1 to 5, characterized in that the thickness reduction of the slab ( 3 ) in the roughing mill ( 8th ) is reduced to zero. Method according to one of claims 1 to 6, characterized in that the temporary reduction, in particular the temporary interruption, the supply of rolling stock in the rolling train ( 7 ) while in the rolling mill ( 7 ) a roll change is made or in the rolling mill ( 7 ) another production delay exists. Method according to one of claims 1 to 7, characterized in that after the temporary reduction of the supply of rolling stock in the rolling train ( 7 ) the slab ( 3 ) is processed in discontinuous batch mode. Method according to one of claims 1 to 8, characterized in that the slab ( 3 ), as long as a temporary reduction in the supply of rolling stock to the rolling mill ( 7 ) is not carried out, is processed in the continuous rolling process. Method according to one of claims 1 to 9, characterized in that by the measures a), b) or c) according to claim 1 such a buffer time or rolling interruption in the rolling mill ( 7 ) is created or made possible that no casting demolition must be done in the casting machine, in particular a short furnace ( 6 ) is used. Method according to one of claims 1 to 10, characterized in that the slab ( 3 ) in front of or behind the stove ( 6 ) heating by means of an induction heater ( 10 ). Cast rolling mill, which is a casting machine ( 2 ), possibly a roughing mill ( 8th ), a stove ( 6 ) and one oven ( 6 ) downstream rolling mill ( 7 ), wherein the furnace ( 6 ) has a number of heating elements to a cast slab ( 3 ), in particular for carrying out the method according to one of Claims 1 to 11, characterized in that the furnace ( 6 ) has a total length between 30 and 120 m. Casting rolling plant according to claim 12, characterized in that the furnace ( 6 ) is designed as a roller hearth furnace or as a roller-skated encapsulation, wherein it preferably has insulated roller conveyor rollers. Cast rolling mill according to claim 12 or 13, characterized in that in front of the furnace ( 6 ) and / or behind the oven ( 6 ) and / or within the furnace ( 6 ) Heating elements for heating the slab ( 3 ) are arranged, in particular inductive heating elements ( 10 ). Cast rolling mill according to one of claims 12 to 14, characterized in that behind the casting machine ( 2 ) a roughing mill ( 8th ) or several roughing mills ( 8th ) are arranged. Cast 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 ) are arranged out of the transport line. Casting rolling plant according to claim 16, characterized in that there are insulation elements which, if necessary, are in the area of the furnace ( 6 . 10 ) can be retracted instead of the heating elements.

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