EP2437900B1 - Energy-saving rolling mill train and energy-saving process for operating a combined casting and rolling station - Google Patents

Description

The invention relates to a rolling train, in particular hot rolling, hot strip mill and / or finishing mill of a hot rolling mill, for processing rolling stock, in particular consisting of steel, aluminum, copper or titanium, with a plurality of rolling stands immediately adjacent in a rolling direction, wherein the rolling stands in each case at least two Have work rolls between which the rolling stock is machinable. Furthermore, the invention relates to a cast-rolling composite plant and to a method for operating a cast-rolling composite plant.

Metallic precursors such as slabs, hot or cold strip, sheets, tubes, etc. of materials such as iron, steel, non-ferrous metals or other metallic materials are subjected to industrial processing in rolling mills various processing and finishing steps. Typical processing steps are the rolling of cast slabs to hot strip or the down rolling of the hot strip to the thickness desired by the customer in a cold rolling train, for example a tandem mill.

Rolling plants conventionally occur as separate plants which receive their rolling stock from, for example, a separate continuous casting device, eg a "continuous casting system". In modern cast-rolled composite plants, hot strip can be produced in a continuous process, in particular endlessly. A cast-rolled composite plant is eg in WO 96/01710 or in DE 694 08 595 T2 disclosed.

The decisive component for the processing of rolling stock is a roll stand with which, for example, slabs can be rolled out in successive rolling passes to form a strip. rolling mills are used in almost all rolling mills, especially in hot and cold rolling mills.

After hot rolling, the strips can be subjected to further processing steps. At the end of the rolling train, the rolled-down strip is usually rolled up with the aid of a reel to so-called "coils". Alternatively, a direct coupling with a cold rolling plant and / or treatment line takes place in the continuous process.

The hot strip can be subjected to further intermediate steps, such as a temperature treatment, before it is fed to a cold rolling line. At the end of a cold rolling line is usually a take-up reel for receiving the rolled strip, possibly combined in the continuous process with a pair of scissors.

When rolling high torques for processing the rolling stock must be applied. For this reason, powerful electric motors are used to drive the rollers, whose torque is often further increased by means of a reduction gear. DE 199 11 751 C1 describes a drive device for a roll stand. Powerful electric motors as well as correspondingly suitable transmissions are very heavy and voluminous.

The electric motors including gearboxes must be arranged laterally with respect to the processing direction of the rolling stock, thereby considerably increasing the space required to be overbuilt by a factory hall. JP 10-235416 alternatively proposes to integrate a compact superconducting electric motor into the interior of a roll of a roll stand. Such a design entails mechanical problems, since the roll in question, with its thus reduced stability, will suffer deformations at high rolling forces.

The object of the present invention is to provide a rolling mill for processing rolling stock and a cast-rolling composite plant with such a rolling mill and an operating method for the cast-rolling composite plant, which / which by means of his / her drive concept, the metallurgical and manufacturing processes simplify rolling, improve their energy efficiency and / or make it more flexible.

With regard to the rolling mill, the object of the invention is achieved by a rolling mill with the features of claim 1. With respect to the cast-rolling composite plant, the object of the invention is achieved by a cast-rolling composite plant according to claim 8, with respect to the operating method by a Method according to claim 11.

The rolling train comprises a plurality, in particular at least three or four, of roll stands immediately adjacent in the rolling direction, in particular in tandem operation.

The rolling train is either a roughing train and - with particular advantage - a finishing train of a hot rolling mill or hot strip rolling mill.

In this case, the rolling train comprises a plurality of laterally arranged electric motors with superconducting windings and at least three or at least four of the rolling stands each have at least one of the work rolls, preferably gearless, connected to the shaft of one of the electric motors.

As rolling stock, for example, slabs, hot strip, cold strip, coarse or thin sheets, pipes, etc. of iron, steel, non-ferrous metals such as aluminum, etc. into consideration.

An electric motor with electrically superconducting windings will be referred to as HTS motor in the following. Under an HTS motor, both a machine whose rotor winding is superconducting and whose stator winding is normally conducting, and a machine, so-called fully superconducting machines, in which both the rotor and the stator winding is made using superconducting material to understand.

The embodiment of the rolling train according to the invention is based on the following considerations:

In a rolling mill high powers or torques are required, which can be provided only by correspondingly large / voluminous electric motors. These must often be provided to further increase the torque with a gear. Accordingly, the drives have a large size. The large spatial extent of the gearbox and motor and their high weight mean that the construction of a compact rolling mill is so far only possible to a limited extent.

For example, resulting from the resulting space requirement of the conventional electric motors used so far stand distances, which must be bridged in an undesirable manner by means for material transport. Another consequence of the high stand spacing are lead times between the forming passes, which lead to significant and undesirable temperature losses, especially in the hot rolling process. In the example mentioned, this has the consequence that the product spectrum has to be limited, for example, with regard to the final millable thickness and / or the productivity (throughput) is reduced.

It was recognized that the rolling stands in a rolling mill, due to the spatial extent of rolling stand, gear and electric motors must comply with a minimum distance, the minimum distance of the rolling stands is due to the Size of the frame stand, of possibly necessary Zwischengerüsttransporteinrichtungen limited by electric motors or transmission. By using rolling stands, which are driven by a HTS motor, the minimum distance between immediately adjacent rolling stands and thus, for example, the unwanted cooling of the rolling stock can be reduced by reduced thermal radiation.

According to the invention it has been recognized that the above technical problems can be overcome by the use of HTS motors, which have a much smaller size with the same power compared to conventional electric motors. In addition, it was recognized that the use of a HTS motor in a rolling mill considerable energy savings (lower power dissipation) and because of possible reduced aggregate distances also brings cost advantages. This is particularly advantageous in cast-rolled composite systems.

The rolling mills of the rolling train have at least two work rolls, between which the rolling stock is machinable, wherein at least one of the work rolls is driven by a HTS motor. Such a rolling stand can be used both in hot and cold rolling mills. For example, while used in a hot rolling mill for slab rolling, a rolling stand in a cold rolling mill is used to roll down hot strip to the thickness desired by the customer. The rolling stand can be designed, for example, as a duo or as a quarto-rolling mill or as a hexagonal rolling mill.

Since the rolling mill is driven by a more compact HTS motor with the same power, the distances between the rolling stands can be selected smaller and the entire rolling train can be made shorter or more compact. The inventors have recognized that use of an HTS motor in the rolling mill thus brings with it significant cost reductions as well as technological advantages as a result of reduced cooling of the continuous rolling stock.

An HTS engine has a more stable, stiff performance (e.g., small rotor angle) and also reacts faster to changes in command values than a conventional electric motor. This case occurs frequently during rolling. In comparison to a conventional electric motor, an HTS motor is thus able to be regulated more quickly, which allows an improved and / or faster puncture behavior and / or an improved ski control particularly when it is used in a rolling train. This is particularly advantageous in heavy hot rolling reversing lines. As a "ski" is an unintentional deformation of the band up or down, i. referred to perpendicular to the transport direction.

According to one embodiment, at least one of the work rolls is gearless or connected by means of a reduced compared to a conventional electric drive gear with the shaft of one of the electric motors. In other words, in the first variant, the mechanical connection between the shaft of the HTS motor and the work roll of the rolling mill is carried out while dispensing with torque-converting mechanical intermediate elements (gear). For example, the shaft of the electric motor may be connected to the work roll via a common shaft or a spindle. As a spindle, e.g. a Doppelgelenkwelle understood with two end-side universal joints, which serves the torque transmission between the drive shaft of the motor and the work roll of the rolling stand. The absence of a gear not only brings a cost advantage, but also increases the reliability and variability of the mill. According to the property of the HTS engine to provide an increased torque compared to a conventional engine of comparable size, can - be reduced as a second variant - the size of the transmission. Both variants allow a cost reduction of the entire system. The variant without gearbox requires less maintenance.

A special configuration of the rolling stand, in which according to the invention the HTS motor is advantageously used, are the so-called twin drives, in which each of the work rolls is driven by an electric motor. Accordingly, according to a further embodiment, the rolling stand is configured such that it comprises a plurality of HTS motors, wherein each of the work rolls - preferably as described above directly or with a reduced gearbox - is mechanically connected to the shaft of one of the HTS motors. Since compared to conventional electric motors, the HTS motors with the same torque have a smaller size, eg due to a smaller stator diameter, the distance between the drive shafts of the motors can be reduced to each other. This is also positively noticeable that at the same time the existing inclination of the spindles can be reduced or the torque of the motors can be increased while maintaining the spindle angle. By reducing the spindle tilt their wear, especially in the universal joints, can be reduced. As a third measure / variant, the spindle length can be shortened with the result of a better control behavior, because long spindles act like springs.

In a twin drive, the electric motors are arranged directly next to one another or locally above one another (offset from each other). According to a further embodiment, these therefore advantageously have a common cooling system.

However, the use of an HTS motor is not only advantageous in directly driven rolling stands, such as the aforementioned twin drives, but also in a rolling mill, which according to a further embodiment comprises two work rolls, which are mechanically coupled via a branching gear, said this drive side with the shaft of one of the electric motors is coupled. According to a development, the branching gear is a pinion gear, since this withstands high torques.

The material of the windings of the HTS motor according to a further embodiment comprises metallic LTC superconductor material ("LTC" Low Temperature Conducting). For example, bismuth-based superconducting material which is technically proven, resistant and thus easy to process is suitable. The superconducting material for the windings of the HTS motor may be selected to have a critical current density of more than 300 A / mm ² at an operating temperature of 4.2K.

To reduce the cooling expense, it is expedient that the material of the windings of the HTS motor contains metal oxide HTC superconductor material ("HTC" = High Temperature Conducting). As HTC superconductor material, for example YBCuO is suitable, which has a higher transition temperature than metal oxide LTC superconductor material. The cooling overhead in the operation of a HTS motor with windings of HTC superconductor material is therefore correspondingly lower.

Preferably, therefore, an operating temperature between 10 and 40 K, preferably between 20 and 30 K, provided for the windings of the HTS motor. In the stated temperature range, metal oxide HTC superconductor material also has a high critical current density and a high critical field.

According to a further embodiment, the HTS motors, in particular those of adjacent rolling stands, have a common cooling system in a particularly advantageous manner.

Particularly in the case of continuous hot rolling mills, the distance between the rolling mills causes undesirable changes in the state variables of the rolling stock. The stand spacing of today's hot rolling mills in conventional construction is typically more than 5.0 m to 5.5 m. As a result of such distances, the rolling stock may, for example, cool down too much between the individual rolling passes or form scales on the surface. Such effects must be met by additional equipment such as an induction furnace or a descaling unit be compensated. The use of such additional units and their integration in the rolling mill is expensive on the one hand and resource-intensive on the other hand.

The spacing of the rolling stands can be reduced by the use of drive motors with superconducting windings, whereby additional aggregates, e.g. for descaling or for heating the rolling stock, can be omitted.

According to a preferred embodiment, in the rolling train, at least two of the rolling stands are designed for a maximum rolling force of more than 1500 t, in particular more than 2000 t, more than 2500 t, more than 3000 t, more than 3500 t or more than 4000 t and these two stands stand in the rolling direction at a distance of less than 5.0 m, preferably less than 4.5 m, less than 4.3 m, less than 4.0 m, less than 3.9 m, less than 3.7 m or less than 3.5 m.

The distance of the rolling stands is determined here as the distance of the axes of rotation of the work rolls of adjacent rolling stands in the rolling direction.

Furthermore, preferably, the rolling train has a control and / or regulating device-designed, for example, as part of process automation, in particular for controlling a heating device, a cooling section, a finishing stack and / or a speed of the rolling train, which is designed such that one as a result of the HTS -Motors is considered compared to a use of conventional engines reduced heat loss in the rolling stock. This can be done by implementation in an underlying model. Particularly appropriate is the consideration of the reduced heat loss in the process automation system of the finishing scale, including in the regulation of the finished strip temperature and / or on the reel temperature.

With preference, an optional - possibly existing between the rolling stands - transport device is designed as a vertical loop lifter. This achieves a further reduction in the distance between the stands.

According to a further preferred embodiment, the rolling train is part of a cast-rolling composite plant for the continuous production of hot strip. The processing speed of a cast-rolling composite plant is determined by the speed of the caster. Consequently, the state changes of the rolling stock occurring between the individual rolling passes, for example the cooling thereof, can not be compensated in a simple manner by increasing the rolling speed. The inventors have recognized that a reduction in the distance of the rolling stands thus represents a very advantageous possibility of effectively avoiding intermediate units, such as descaling systems or induction furnaces, for example, or making them less complicated. A reduced distance of the rolling stands can be achieved by using HTS motors.

Preferably, in the cast-rolling composite plant having a heating means arranged before or after the rolling mill for heating the belt cast from a casting apparatus, the heater is adjusted for heating power in consideration of a reduced heat loss in the rolling stock or strip due to the electric motors used ,

In the limit case, the cast-rolling composite plant can be carried out completely without such a heater.

wobei für den Faktor k gilt: k = 0,14(MW·h/t), insbesondere k = 0,13 (MW·h/t), k = 0,12 (MW·h/t) oder k = 0,11 (MW·h/t). Dabei steht MW für Megawatt, h für Stunden und t für (metrische) Tonnen.The method-related object is achieved according to the invention by a method for operating a cast-rolling composite plant, wherein rolled or strip material - preferably of steel - with a mass flow rate (m as mass per time) is transported through the mill train and wherein the heating device equipped with a heating power (P) and / or operated according to: $$\mathrm{0}\le \mathrm{P}<\mathrm{k}\cdot \dot{\mathrm{m}}$$

where k = 0.14 (MW × h / t), in particular k = 0.13 (MW × h / t), k = 0.12 (MW × h / t) or k = 0 for the factor k , 11 (MW · h / t). Here, MW stands for megawatts, h for hours and t for (metric) tons.

The device according to the invention can also be used for a method for increasing the performance of an existing rolling train comprising at least one rolling stand with non-superconducting and arranged in a limited space motor drive. In the performance enhancement method, the non-superconducting motor is replaced by a HTS motor that does not exceed the installation space limitation, ie an electric motor with superconducting windings, which is designed in such a way that the maximum rolling moment in the rolling stand is increased compared to the existing rolling line. It is designed either superconducting only the rotor, or only the stator, or both.

Figur 1

eine Kaltwalz-Tandemstraße in schematischer Perspektivansicht,

Figur 2

eine schematisierte Warmwalzstraße in Perspektivansicht,

Figur 3

einen Zwillingsantrieb ("Twin-Drive") eines Walzgerüsts in einer schematischen Querschnittsansicht,

Figur 4

eine schematisierte Tandemwalzstraße in (geschnittener) Draufsicht,

Figur 5

eine schematisch dargestellte Gieß-Walz-Verbundanlage,

Figur 6

ein Walzkraft-Gerüstabstands-Diagramm, und

Figur 7

eine Walzgerüstausführung mit Schlingenheber, in einem schematischem Längsschnitt.

In the following the invention will be explained in more detail with reference to embodiments shown in the drawing. It shows their

FIG. 1

a cold rolling tandem mill in schematic perspective view,

FIG. 2

a schematized hot rolling mill in perspective view,

FIG. 3

a twin drive of a roll stand in a schematic cross-sectional view,

FIG. 4

a schematic tandem rolling mill in (cut) plan view,

FIG. 5

a schematically illustrated cast-rolling composite plant,

FIG. 6

a rolling force stand distance diagram, and

FIG. 7

a rolling mill version with looper, in a schematic longitudinal section.

A tandem cold rolling mill 2, like her FIG. 1 shows, serves to roll down of hot strip 4 to the customer's desired thickness. For this purpose, the coiled to a hot rolled strip 4 of the tandem cold rolling mill 2 by means of a take-off reel 6 in a rolling direction W is supplied. The thickness of the hot strip 4 is first determined by means of a measuring device 8, then the strip is rolled down in several successive rolling passes by means of rolling stands 10 to the desired thickness. Each of the rolling stands 10 has at least two work rolls 12 and two support rolls 14, wherein the rolling stock, in this case the hot strip 4, is processed between the work rolls 12. At the end of the rolling process, the tape is rewound into a coil by means of a coiler 16. For the separation of the belt transversely to the rolling direction W, a dividing shear 18 is available. The reel 16 is driven by a HTS motor 20. The shaft of the HTS motor 20 is connected directly to the axis of the reel 16, that is, no transmission between the HTS motor 20 and the reel 16 is used. The same does not apply to the FIG. 1 shown drive the uncoiler 6 to. The work rolls 12 of the rolling stands 10 are either as twin drives, exemplified for the second rolling stand 10 in the rolling direction W, or using a branching gear, in this case a pinion gear 22, as exemplified for the third rolling stand 10 in the rolling direction W driven , In the rolling stand 10 designed as a twin-drive, both work rolls 12 are each directly connected to the shaft of a respective separate HTS motor 20 (both denoted by 20). Thus, there is a direct drive of the work rolls 12, being dispensed with a reduction gear.

Alternatively, as shown in the following roll stand 10 in the rolling direction W, the work rolls 12 on the pinion gear 22, which on the drive side turn with a (here only single) HTS motor 20 is connected to be driven.

The rewinding and reeling 16.6 and the rolling stands 10 are connected to a common control and / or regulating device 105, which will be discussed in detail later.

FIG. 2 shows a hot rolling mill 30 with the preheated slabs 32 are rolled to hot strip 4. For this purpose, the slabs 32 are first rolled in a roughing train 34 and later with a consisting of several (here: seven) rolling stands 10 finished stagger 36 (finishing mill) to hot strip 4. This is rolled up by means of a reel 16 to form a coil. The individual rolling stands 10, each in to FIG. 1 similar execution two work rolls 12 and two support rollers 14 are driven by HTS motors 20 both in the roughing 34 and in the finishing stack 36. The same applies to the Aufhaspel 16. The rolled strip has a width of 0.6 m to 1.8 m, typically 0.8 m to 1.6 m. The work rolls can be up to 5.5 m wide (= measured along the axis of rotation).

In both aforementioned embodiments, the HTS motors 20 are arranged laterally with respect to the rolling direction W and laterally of the rolling stands.

FIG. 3 shows a highly schematic (vertical) cross-sectional view of a rolling stand 10 of the tandem cold rolling line 2 of FIG. 1 or, more preferably, the hot rolling mill 30 of FIG. 2 , whose work rolls 12 are driven by a twin drive ("Twin Drive"). For this purpose, each of the work rolls 12 is connected with its shaft 23 via a spindle 24 to the motor shaft 25 of an HTS motor 20. The connection between the shaft 23 of the work roll 12 and the spindle 24 and between this and the motor shaft 25 takes place in each case by means of a universal joint or by means of waves with claws. Compared to conventional electric motors otherwise used in twin drives in the FIG. 3 shown HTS motors 20 a low height H on. This results in that the distance A of the motor shafts 25 is smaller than in conventional drives and thus the spindle pitch α is low. Under the spindle pitch α is the angle between the spindle 24 and the extension of the shaft 23 of the work roll 12 to understand. The spindle pitch α results from the offset between the shaft 23 of the work roll 12 and the motor shaft 25, which is bridged by the spindle 24. Preferably, the spindle pitch α <3 °, for example, 1.5 ° - 2.5 °.

The HTS motors 20 have a common cooling system 26, with which their superconducting windings are cooled. The cooling system 26 is an insulated pipe system generally known from cryotechnology, in which a refrigerant circulates and in which a refrigeration unit 28 is integrated. This usually includes a reservoir for the refrigerant, which is, for example, liquid helium, neon, nitrogen or a mixture of these gases. The refrigeration unit 28 also includes a compressor or a cold head for liquefying the coolant. The circulation of the coolant in the cooling system 26 may be by means of a pump or driven by a thermosiphon effect.

FIG. 4 shows a schematic representation of four rolling stands 10 of a running in tandem assembly hot strip finishing line of a hot rolling mill, as for example FIG. 2 as Fertigstaffel 36 of the hot rolling mill 30 shows, in plan (cross) view. The rolling stands 10 are waiving other units, such as induction heaters or Entzunderungsanlagen in the rolling direction W immediately adjacent to each other, which is possible due to the compact size of their used for driving HTS motors 20. The rolling stands 10 can thereby reach a distance B from one another, which can not be achieved with conventionally driven rolling stands 10. As distance B while the removal of Rotary axes D of the work rolls 12 defined in the rolling direction W.

The work rolls 12 are driven directly by the HTS motors 20, i. the shaft 23 of the work roll 12 and the motor shaft 25 of the HTS motors 20 form a common component. The HTS motors 20 of the rolling stands 10 arranged directly next to one another have a common cooling system 26 with an integrated refrigeration unit 28.

Due to the more compact design and narrower design, the heat losses are significantly reduced. This can be advantageously taken into account in a cooling model running for the rolling train in a superordinate (not explicitly drawn) control system for influencing the metallurgical changes in the rolling stock during rolling.

FIG. 5 shows a continuous casting belt-rolling plant 40 in which from a casting platform 42 in a Dünnbrammengießeinrichtung 44 continuously thin slabs are produced, which via a roller table 45 continuously, ie without cutting, winding and intermediate storage, a first rolling mill 46 ( "High Reduction Mill") are supplied. The motors of this rolling train 46 are designed as HTS motors. The same applies to the drives of the following optional device 48 for cutting and / or conveying, which may comprise a pendulum scissors and a "plate pusher". This device 48 is significant in particular in case of subsequent malfunctions in the direction of production. An optional crop shear can also have an HTS drive.

This is followed by a heating device 52, a descaling device 54, a second finishing mill 56 ("finishing mill"), a cooling section 58, an end shear 60 for cutting to desired product length and a windup device 62 for the finished product ("coil"). The drives of the rollers of the second rolling train 56 are designed as HTS engines, which just as in the rolls of the first rolling mill 46 brings special space advantages.

Due to the correspondingly compact and short design can be on means for supplying additional heat (eg "bar heater") to avoid unwanted premature cooling of the belt, either completely omitted or the corresponding devices are smaller in size than without the use of HTS motors , In the FIG. 5 For example, an induction furnace is shown as a heater 54, the heating power P - is chosen smaller - with the same mass flow rate - than with conventional electric motors. With a mass flow rate m of 180 tons of steel per hour (t / h), its heating power P = 25 megawatts (MW), preferably only 23 MW or only 19 MW.

The invention has not only effects on the dimensioning of a rolling mill, but also on the control of the system and its components. Therefore, a control and / or regulating device 105 (FIG. FIGS. 1 . 2 . 5 ) of the rolling train 2, 30, 46 and 56 or the cast-rolling composite plant 40 for controlling a heater 52, a finished relay 56, a cooling section 58 and / or a speed of the rolling train, designed such that a result of used superconducting electric motors compared with the use of conventional motors reduced heat loss is taken into account.

FIG. 6 shows in the hatched area 100, the preferred design according to the invention of rolling trains, for example, finishing lines of a hot strip mill, the distance B in the rolling direction of two rolling stands up and the maximum of the rolling stands producible rolling force F is given to the right. "Small plants" with a maximum rolling force of less than 1000 t (metric tons) are not considered in the example. The stand spacing B according to the invention is smaller than 5 m even with very large rolling forces (line 101). The straight line 102 clarifies the realization that with increasing Walzkraft more and more space for the drive systems and motors is needed because they have to work against increasing forces in the nip, so that ultimately increases the distance from the framework.

The straight line 102 can be described by the following equation: B max = a + F * b, in which a = 2 m, b = 1 m / 1000 t or a = 2.5 m, b = 1 m / 2000 t or a = 0 m, b = 1 m / 500 t

According to the invention, ie when using one or more HTS motors, for a certain rolling force F to be applied by the rolling stand, the distance B of the rolling stands is chosen to be smaller than the value for Bmax resulting from the formula: B = B max - c, in which c = 0.4m, 0.6m, 0.8m, 1.0m, 1.2m or 1.4m.

FIG. 7 shows an optional design for further reduction of the stand spacing B, in which between two rolling stands 10 a loop lifter 110 is present as a transport device. An actuating cylinder 112 performs essentially only a vertical or up and down movement to support the belt 4 and thus requires very little space.

Claims (11)

1. Rolling mill train (2; 30; 56), especially a hot rolling mill train, hot wide strip rolling mill train and/or finishing train of a hot rolling mill, for processing rolling stock (4, 32), especially consisting of steel, aluminum, copper or titanium,

   - with a plurality of rolling stands (10) immediately adjacent to one another in a rolling direction (W),

   - wherein the rolling stands (10) each have at least two working rolls (12) between which the rolling stock (4, 32) is able to be processed,

   - comprising a number of electric motors (20) with superconducting windings arranged to the side next to the rolling stands (10),

   - wherein, for at least three or at least four of the rolling stands (10), at least one of the working rolls (12) in each case is connected to the shaft (25) of one of the electric motors (20).
2. Rolling mill train (2; 30; 56) according to claim 1, in which at least one of the working rolls (12) has no gearing or is connected to the shaft (25) of one of the electric motors (20) by gearing reduced in size by comparison with a conventional electric drive.
3. Rolling mill train (2; 30; 56) according to claim 1, wherein two of the working rolls (12) are mechanically coupled via a branching transmission (22), wherein the branching transmission (22) is connected on the drive side to the shaft (25) of one of the electric motors (20).
4. Rolling mill train (2; 30; 56) according to one of claims 1 to 3, in which the electric motors (20), especially the electric motors (20) of neighbouring rolling stands (10), have a common cooling system (26).
5. Rolling mill train (2; 30; 56) according to one of claims 1 to 4, in which at least two of the rolling stands (10) are designed for maximum rolling force F of more than 1500 t, especially of more than 3000 t or more than 4000 t, and are at a distance B from one another of less than 5.0 m, preferably less than 4.5 m or less than 4.0 m.
6. Rolling mill train (2; 30; 56) according to one of claims 1 to 5, with an open-loop and/or closed-loop control device (105), especially for controlling a heating device (52), a finishing section, a cooling section (58) and/or a speed of the rolling mill train, being embodied such that a reduced heat loss of the rolling stock (4; 32) as a result of the superconducting electric motors (20) used compared to a use of conventional motors is taken into account.
7. Rolling mill train (2; 30; 56) according to one of claims 1 to 6, wherein a transport device is present between the rolling stands (10) which is embodied as a vertical looper (110).
8. Combined casting and rolling station (40) for continuous production of hot strip (4) with a rolling mill train (2, 30; 56) - arranged downstream from a caster (44) - according to one of claims 1 to 7.
9. Combined casting and rolling station (40) according to claim 8 without heating device (54) for heating the strip cast by the caster (44).
10. Combined casting and rolling station (40) according to claim 8, with a heating device (54) arranged before or after the rolling mill train (46) for heating the strip cast by the caster (44), with the heating device (54), as regards its heat output (P), being configured to take into account a reduced heat loss in the rolling stock (4; 32) or strip as a result of the electric motors (20) used.
11. Method for operating a combined casting and rolling station (40) according to claim 10, with rolling stock - preferably made of steel - being transmitted with a mass throughput ṁ through the rolling mill train (56) and with the heating device (54) able to be operated with a heat output P in accordance with: $$\mathrm{P}<\mathrm{k}\cdot \dot{\mathrm{m}}$$

    

    
    wherein the following applies for the factor k: k = 0.14 (MW·h/t), especially k = 0.13·MW·h/t, k = 0.12·MW·h/t or k = 0.11·MW·h/t.

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