EP1824617A1

EP1824617A1 - Method for continuous casting and rolling with an increased casting rate and subsequent hot-rolling of relatively thin metal strands, especially steel strands, and continuous casting and rolling device

Info

Publication number: EP1824617A1
Application number: EP06829594A
Authority: EP
Inventors: Jürgen Seidel; Jürgen Klöckner
Original assignee: SMS Demag AG
Current assignee: SMS Group GmbH
Priority date: 2006-01-10
Filing date: 2006-12-14
Publication date: 2007-08-29
Anticipated expiration: 2026-12-14
Also published as: RU2344889C1; ES2369292T3; PL1824617T3; KR20070089807A; TWI373386B; TW200734084A; ATE521425T1; MX2007007367A; UA89975C2; US20090193645A1; DE102006001195A1; US7958931B2; US20080093049A1; CA2636305C; ZA200707158B; CN101107085A; JP2008523998A; CN101107085B; KR100859291B1; AU2006324143A1

Abstract

The invention relates to a method for continuous casting and rolling with a high casting rate and subsequent hot-rolling of relatively thin metal strands, especially steel strands (1), the target temperatures (6) of the hot strip (2) being pre-defined. Said method enables temperature losses on the hot strip (2) to be reduced by increasing the temperatures of the work rolls (4) with a pre-determined rate of increase starting from a low initial temperature (5), and by adjusting the temperature (15) of the strip to a target roll temperature (6) of the hot strip (2) and/or by regulating or controlling the intensity of the roll cooling (18).

Description

Method for casting rolls with increased casting speed and subsequent hot rolling of relatively thin metal, in particular steel material strands, and casting-rolling device

The invention relates to a method for casting rolling with increased casting speed and subsequent hot rolling of relatively thin metal, especially steel material strands to thin hot strip in a multi-stand hot strip finishing train under the rules of the temperatures of the work rolls, and the associated casting-rolling device ,

Rolling at (high) casting speeds, ie a coupling of a continuous casting plant and a hot strip finishing train, leads to relatively low transport speeds within the hot strip finishing train following a continuous casting plant. Despite high initial temperatures (eg. From about 1250 ⁰ C) due to temperature losses to the environment and to the work rolls a required final rolling temperature of about 850 ⁰ C under normal conditions can not be met. Large amounts of energy are released to the work rolls.

Such conventional conditions exist, for example, in a continuous casting, which allows high casting speeds and high initial temperatures for the hot strip finishing train results.

It is also known (DE 198 30 034 A1) to regulate the work rolls by transverse field inducers on a setting of the temperature on a computer model, the bandwidth, material values, stitch loss, rolling speed, rolling temperatures and roll cooling detected. However, the result is used to control the temperature in the edge regions of the work rolls or the rolled strip to be adjusted. It is also known (EP 0 415 987 B2), so-called. Thin slabs (casting strands with about 50 mm thickness) inductively reheat in individual rolling stages before and within the finishing train, to which a considerable amount of electrical energy is needed.

It has also been proposed to reduce the diameters of the work rolls in order to reduce the heat flow to the rolls.

The invention is based on the objective of achieving a reduction in the temperature loss on the hot strip within the hot strip finishing train during casting rolling, so that the target rolling temperature can be set more precisely and in particular higher at the end of the rolling process.

The stated object is achieved in that at casting speeds of about 4 m / min to 12 m / min and taking into account relatively thin casting thicknesses of the casting strand, the rolling speeds, the temperatures of the work rolls are increased starting from a low initial temperature with a predetermined rate of increase and the strip temperature within the hot strip finishing train is adjusted to a target rolling temperature of the hot strip and / or by controlling or controlling the roll cooling intensity. This minimizes heat loss during continuous rolling (and coupling of the casting-rolling process) and achieves high-rolling-temperature rolling for all rolling mills of a hot strip finishing train. It can be derived from the process heat heating of the work rolls. In this case, the roll cooling is adjusted as a function of external boundary conditions such that the work roll slowly reaches the target temperature (of approximately 400 ^° C.) at the predetermined rate of increase and is within the tempering temperature of the roll material. A coupling of the casting-rolling process takes place, for example, at casting speeds between 4 and 12 m / min and usual casting thicknesses of 20 to 90 mm and at rolling speeds of about 0.3 to 18 m / sec. A further development consists in the fact that given given schedule data, a target temperature is set which is below the tempering temperature of the roll material of the work rolls.

A further development is that by applying a predetermined amount of cooling water to the work rolls, a maximum roll temperature and the belt speed are set by which the predetermined belt target temperature is achieved.

Advantageously, the temperature difference between the work roll core and the work roll surface of the work roll is adjusted so that the allowable stresses in the work roll are not exceeded.

Furthermore, a voltage monitoring within the work roll can be carried out both in the radial and in the axial direction on the basis of a calculated temperature and voltage field.

Other features of the invention provide that voltage monitoring is controlled via an online computer model.

The work roll may also be preheated to an initial temperature prior to use. At a preheating temperature of 200 ⁰ C, the stationary state is reached faster and / or the voltage level in the rollers is lower.

Other inventive features are that the work rolls are operated with respect to the intended temperature level excessive belt temperatures. As a result, belt heat losses can be specifically compensated. Practically, it is advisable that the work roll is preheated in an induction field under rotation. As a result, a localized and targeted heat supply is achieved depending on the mass distribution of the work roll.

An improvement of the process sequence provides that the inductive heating of the work roll surface is carried out on the inlet side of a roll stand. This increases the work roll contact temperature in the nip and minimizes the heat loss of the belt within the nip. The desired effect is achieved even before reaching a high core temperature.

It is also proposed that the inductive heating of a work roll be made differently over the length of the bale.

Other features to improve the process flow are that the work roll is preheated in the induction field within the hot strip finishing train or before installation adjacent to the hot strip finishing train.

One measure to be mentioned in particular is that during the starting process, in addition to the intensity of the roll cooling and / or the inductive heating, the rolling program structure is used as the controlled variable.

An improvement of the boundary conditions to reduce the strip temperature loss further occurs by the fact that intended scale scrubbers with minimum amount of water, in particular single-row, are operated.

Another approach to adjusting the cooling effect is that the cooling intensity of the work roll cooling is controlled by finely metered coolant and / or spray. In addition, it can be provided that only part of the rolling stands of the hot strip finishing train are operated at elevated temperatures of the respective work rolls.

Furthermore, the influence of a higher roller temperature and the influence of the expansion of the work rolls by heat from the work rolls to the strip shape in the region of the strip edge can be compensated by mechanical and / or thermal profile actuators.

The casting / rolling apparatus requires a known continuous casting apparatus and a hot strip finishing train, a heating device, and a work roll cooling means associated with each stand.

The training and development of the hot strip finishing train is that the length of the work rolls is tuned to an increase in temperature and that the work roll bearings are cooled and connected to an oil circulation lubrication or lubricated by special grease. As a result, the temperature increases (rates of increase) can be safely collected at the bearings.

Another measure to save heating energy and to increase the work roll service life is that the work rolls are ground while warm.

In this sense, it is further advantageous that are provided as a material for the work rolls heat-resistant and wear-resistant materials.

The higher temperatures of the work rolls is also taken into account by providing so-called HIP (hot isostatic pressing) rolls for the rolling mills of the hot strip finishing train. In other features, an on-line computing model includes a work roll temperature model based on the measured work roll surface temperatures, the initial temperature of the work roll, and the physical properties of the work roll.

In addition, the fact that the work roll temperature model takes into account the maximum average roll surface temperature, the maximum permissible temperature difference between the work roll core and the work roll surface and the maximum permissible stress in the work roll also has an effect.

Another measure to counteract a high temperature loss of the hot strip is that between the rolling stands roller shutter covers are installed.

An even better scaling reduction or oxide layer influencing of hot strip and work roll results from the fact that inert gas feeds are provided between the front roll stands under the roll cover covers.

A further embodiment provides that at least the rolling force, the inlet and outlet thickness, the rolling speed, the strip temperature, the scale layer thickness and the strip material are taken into account under the pass line parameters.

To this end, the thickness reduction in the pass schedule has been shifted to the rear of the hot strip finishing train.

Other measures which are conducive to the method result from the fact that a minimum outlet thickness is limited to a fixed value.

As an example for the data of a typical process or for a typical continuous strip finishing train, a hot strip finish rolling mill may be used. Road with approximately seven rolling stands for a Gießstrangdicke of H = 50 to 90 mm and a minimum outlet thickness of 0.6 to 1, 2 mm is provided.

In the drawing, embodiments of the method are shown, which are explained in more detail below.

Show it:

Fig. 1 is a diagram of the work roll temperature over time for the

Course without work roll cooling and with conventional work roll cooling,

2 shows the same diagram for a reduced work roll cooling for the purpose of setting specifically elevated work roll temperatures,

3 is a block diagram of the systematic structure of the work roll temperature model,

4 shows the hot strip finishing train and the strip temperature profile through the hot strip finishing train at different working roll temperature levels and

Fig. 5 is a graph of the course of the work roll cooling water amount over time.

In a conventional hot strip finishing train 3 for metal, in particular for a steel material strand 1, in discontinuous operation in the thin strip production, for example, about 180 sec rolled, followed by a rolling break of about 20 sec. To 19 during rolling provides a mean Ar- beitswalzen surface temperature of about 120 ⁰ C and in the break surface is cooled back to near water temperature. After a Variety of rolled hot strips 2 can be measured at the end of the rolling program roller temperatures of about 90 ⁰ C.

In a direct connection of the continuous casting and the hot strip finishing train 3 turns in continuous rolling in the hot strip finishing train 3, a strip temperature loss, which must be minimized by appropriate measures. For this reason, rolling with higher work roll temperatures is proposed for all stands 3a ... 3n or part.

The temperature profile without a work roll cooling 18 having an average surface temperature 19 and a core temperature 20 is preferably shown in the diagram of FIG. 1 (working roll temperature over time). A customary in rolling mills conventional work roll cooling 21 (lower part of the diagram) shows the approach of the core temperature 20 (of eg. 20 ⁰ C) to the average surface temperature of 19 (of, for example, 120 ° C). It can be seen that after the working time has progressed, the core temperature 20 approaches the average surface temperature 19 under otherwise identical rolling conditions and is then largely the same.

The goal is therefore to meter the roll cooling in dependence on external boundary conditions such that the work roll 4 reaches the target temperature 6 in FIG. 2 of approximately 400 ° C. at a predetermined rate of increase and is below the tempering temperature of the roll material. In this case, the temperature field within the work roll 4 or the temperature difference between Waiz- zenkern 4a and roll surface 4b must be set so that the allowable stresses in the work roll 4 are not exceeded. This process applies in the radial and also in the axial direction. For this purpose, the online calculation model in FIG. 3 is used.

In contrast, in FIG. 2, the dashed curve results in a reduced work roll cooling 22 according to the invention at elevated mean surface temperature. For a purpose of setting specifically elevated work roll temperatures in a preheated work roll 4 to an initial temperature 5 of, for example, 200 ⁰ C initially a temperature difference 23 to the core temperature 20. The warmer work roll 4 thus prevents unwanted lowering of the strip temperature 15 by the average surface temperature 19 a, the example at 400 ^° C.

In Fig. 3, the online calculation model 7 is shown in outline. In the work roll temperature model 9, the calculation of the work roll temperatures, the roll cooling water amounts and the stresses in the work roll 4 takes place. At least the following parameters are included in the calculation: a maximum mean surface temperature 19, a maximum permissible temperature difference 23 between core and surface and maximum permissible stress values 24 in the work roll 4.

As pass parameters 11 are provided: the rolling force 12, the inlet and outlet thickness 13, the rolling speed 14, the strip temperature 15, a scale layer thickness 16 and the strip material 17 itself.

4 shows an example of a hot strip finishing train 3 and the course of the strip temperature 15 for different boundary conditions. A scale scrubber 25, which is preferably single-row, is upstream. In the event that all the rolling stands are operated 3a ... 3n with increased work roll temperature, e.g., 400 ⁰ C to F1 -. F7, it affects to the local strip temperature 15 positive. It can be achieved by 6 910 ⁰ C in the illustrated example, then a 5 Anfangstempe- temperature of 1180 ⁰ C behind the scale washer 25 and a target temperature. When using standard work roll temperatures, an inadmissibly low strip temperature 15 of, for example, 805 ^C C arises, which can be seen in FIG. 4 by the dashed curve.

It is envisaged to heat or preheat the work roll 4 in an induction field 8a. This device is shown in FIG. 4 only on the running side of the mill stand F1. However, an arrangement is advantageous and feasible for all stands 3a..3n.

The intensity of the inductive heating 8a of the work roll 4 can also be predetermined differently over the roll length.

The procedure or course of the work roll cooling water amount 26 is shown in FIG. Compared to a "normal" amount of cooling water, a smaller amount is generally used in this process at the beginning of the illustrated endless rolling process and, as the roll core temperature 20 is increased, further reduced to a setpoint value specified by the online calculation model 7.

The method described for reducing the heat dissipation to the work rolls 4 is not limited to the illustrated application of continuous rolling with relatively long rolling times and low rolling speeds. The method can also be applied to conventional single or multi-stand hot strip rolling mills.

For temperature-sensitive materials, a lower subcooling of the strip surface is achieved by the roller contact at higher roller temperature. This results in homogeneous properties within the strip, for example over the strip thickness.

LIST OF REFERENCE NUMBERS

1 metal, in particular steel material strand

2 thin hot strip

3 hot strip finishing mill 3a ... 3n rolling mills

4 work roll 4a work roll core

4b Stripper surface

5 start temperature

6 target rolling temperature

7 online calculation model 8 Heating device

8a induction field

9 Stripper temperature model

10 strut surface temperature

11 Stitch plan parameters 12 Rolling force

13 inlet and outlet thickness

14 rolling speed

15 belt temperature

16 scale layer thickness 17 strip material

18 work roll cooling

19 mean surface temperature

19a increased mean surface temperature

20 core temperature 21 conventional work roll cooling

22 reduced work roll cooling Initial temperature difference Maximum permissible tension values in the work roll Scale washer Course of the work roll cooling water quantity

Claims

claims:

1. A method for casting rolls with increased casting speed and subsequent hot rolling of relatively thin metal, especially steel material strands (1) with relatively low belt speed to thin hot strip (2) in a multi-stand hot strip finishing train (3) under temperature control the work rolls (4), characterized in that at casting speeds of about 4 m / min to 12 m / min and taking into account relatively thin casting thicknesses of the cast strand, the rolling speeds are adjusted, the temperatures of the work rolls (4) starting from a low initial temperature (5) are increased at a predetermined rate of increase and the belt temperature (15) within the hot strip finishing train (3) set to a target rolling temperature (6) of the hot strip (2) and / or by controlling or controlling the intensity of the roll cooling (18) becomes.

2. The method according to claim 1, characterized in that for given stitch plan data, a target temperature (6) is set, which is below the tempering temperature of the roll material of the work rolls (4).

3. The method according to claims 1 or 2, characterized in that by applying a predetermined amount of cooling water (26) on the work rolls (4) has a maximum roll temperature and the belt be set speed by which the predetermined band target temperature (6) is reached.

4. The method according to claim 1, characterized in that the temperature difference between the work roll core (4a) and the work roll surface (4b) of the work roll (4) is set such that the allowable stresses in the work roll (4) are not exceeded.

5. The method according to claim 4, characterized in that a voltage monitoring is performed within the work roll both in the radial and in the axial direction due to a calculated temperature and voltage field.

6. The method according to claims 4 and 5, characterized in that the voltage monitoring via an online computer model (7) is controlled.

7. The method according to any one of claims 1 to 6, characterized in that the work roll (4) is preheated prior to its use to an initial temperature (5).

8. The method according to any one of claims 1 to 7, characterized in that the work rolls (4) are operated with respect to the intended temperature level excessive strip temperatures.

9. Process according to claims 5 or 6, characterized in that the work roll (4) is preheated in an induction field (8a) under rotation.

10. The method according to claim 9, characterized in that the inductive heating of the work roll surface (4b) on the inlet side of a roll stand (3a ... 3n) is made.

11. The method according to claims 9 and 10, characterized in that the inductive heating of a work roll (4) over the bale length is made different.

A method according to claim 9, characterized in that the work roll (4) is preheated in the induction field (8a) within the hot strip finishing train (3) or before installation adjacent to the hot strip finish rolling line (3).

13. The method according to any one of claims 1 to 9, characterized in that is used during the starting process in addition to the intensity of the roll cooling and / or the inductive heating of the rolling program structure as a controlled variable.

14. The method according to claims 1 to 9, characterized in that provided scale washer (25) with a minimum amount of water, in particular single row, are operated.

15. The method according to any one of claims 1 to 9, characterized in that the cooling intensity of the work roll cooling (18) is regulated by finely metered coolant and / or spray.

16. The method according to any one of claims 1 to 3, characterized in that only a part of the rolling mills (3a ... 3n) of the hot strip finishing train (3) with elevated temperatures of the respective work rolls (4) is operated.

17. The method according to any one of claims 1 to 16, characterized in that the influence of a higher roll temperature and the influence of the expansion of the work rolls (4) by heat from the work rolls (4) on the strip shape in the band edge by mechanical and / or thermal profile actuators is compensated.

18 casting-rolling device with a continuous casting apparatus and a hot strip finishing mill (3), a heating device (8) and each rolling mill (3a ... 3n) associated cooling device for the work rolls (4), characterized in that the length of the Work rolls (4) is tuned to an increase in temperature and that the work roll bearings are cooled and connected to an oil circulation lubrication or lubricated by special grease.

19. Casting rolling device according to claim 18, characterized in that the work rolls (4) are ground in the warm state.

20. Casting rolling device according to claims 18 and 19, characterized that as material for the work rolls (4) heat-resistant and wear-resistant materials are provided.

21. Casting rolling device according to claim 20, characterized in that for the rolling stands (3a ... 3n) of the hot strip finishing train (3) so-called. HIP rolls (hot isostatic pressing) are provided.

22 casting rolling device according to claims 18 to 21, characterized in that in an online computing model (7) a work roll

Temperature model (9) based on the measured work roll surface temperatures (10), the initial temperature (5) of the work roll (4) and the physical properties of the work roll (4) is included.

23. A casting / rolling apparatus according to claim 22, characterized in that in the work roll temperature model (9) the maximum mean roll surface temperature (19), the maximum allowable temperature difference (23) between work roll core (4a) and work roll surface ( 4b) and the maximum permissible tension (24) in the work roll (4) are taken into account.

24. Casting rolling device according to claims 18 to 23, characterized in that between the rolling stands (3a ... 3n) roller shutter covers are installed.

25. Casting rolling device according to claim 24, characterized that between the front rolling stands (3a ... 3n) are provided under the roller table covers inert gas supply.

26. Casting rolling device according to claims 17 to 22, characterized in that among the stitching parameters (11) at least the rolling force (12), the inlet and outlet thickness (13), the rolling speed (14), the strip temperature (15), the scale layer thickness (16) and the strip material (17) are taken into account.

27. Casting rolling device according to claim 25, characterized in that the thickness decrease in the pass schedule is shifted to the rear region of the hot strip finishing train (3).

28. Casting rolling device according to claim 1, characterized in that a minimum outlet thickness (13) is limited to a fixed value.

29. Casting rolling device according to claims 18 to 28, characterized in that a hot strip finishing train (3) with about seven rolling stands (F1 to F7) for a Gießstrangdicke of H = 50 to 90 mm and a minimum outlet thickness ( 13) of 0.6 to 1, 2 mm is provided.