EP1432539B1 - Method and device for cooling the copper plates of a continuous casting ingot mould for liquid metals, especially liquid steel - Google Patents

Abstract

The invention relates to a device for cooling the copper plates (1.1) of a continuous casting ingot mould (1) for liquid metals, especially liquid steel, comprising an ingot mould coolant (2) which is guided in cooling channels. During the initial temperature rise to achieve a set casting speed or when said casting speed is exceeded for a deviating copper plate skin temperature (8), the copper plate skin temperature (8) is influenced, even when the casting speed is higher, in such a way that surface errors in the casting shell and/or cracks in the surface of the copper plates are prevented from occurring or occur in a significantly reduced manner by adjusting the copper plate skin temperature (8) at alternating casting speeds (6) of between 1 m/min and a maximum 12 m/min by means of quantitative correction of the amount of ingot mould coolant (4) and/or ingot mould coolant inflow temperature (5) according to the casting speed (6) and according to the thickness of the copper plates (9), to a desired constant value.

Description

The invention relates to a method and a device for cooling the copper plates of a continuous casting mold for liquid metals, in particular for liquid steel, with chill coolant guided in cooling channels and wherein during the speed ramp to target casting speed or exceeding the target casting speed or one of Kupferplatten- Target skin temperature deviating temperature, the amount or the flow rate of the coolant can be controlled.

The initially described method and device are known from EP-A-1 103 322 for the control of the internal temperature within the die plate thickness.

From DE 41 27 333 C2, a method is also known to direct the coolant at maximum speed in the region of the highest temperature load. As a result, the heat dissipation is improved and the temperature of the mold plate is reduced. In addition, a reduction of the temperature differences over the height of the mold and a consequent stress reduction and extension of the life of the mold walls is desired. However, this method does not take into account a changed, in particular an increased, very high casting speed.

Such continuous casting molds for casting liquid steel are cooled in generally used, known methods by the Kokillenkühlmittel is kept constant in the amount and temperature regardless of the casting speed when entering the continuous casting mold. The consequence of this procedure is that with increasing casting speed, the heat load, measured in W / m ² , and thus also the copper plate skin temperature and here especially during casting with casting speeds over 4 m / min increases sharply. This temperature increase at a given copper plate thickness of, for example, 20 mm between Kokillenkühlmittel and hot side leads in the case of the use of cast powder slag between strand shell and Kokillenkupferplatte on the one hand to different lubricity and different heat load and on the other shortened life of the Kokillenkupferplatten due to exceeding the recrystallization temperature of cold-rolled copper ,

These resulting disadvantages with increasing casting speed, but also with increasing copper plate thickness lead to disturbances of the casting process and / or surface defects in the strand shell and cracks in the copper plate surface.

The disturbances occur both in a watercourse in the continuous casting mold from bottom to top and from top to bottom. However, it can be seen that the watercourse from top to bottom, the copper plate skin temperature is lower than the watercourse from bottom to top.

The method referred to at the outset as known from EP 1 103 323 A2 determines an alternating copper plate temperature and corrects the mold coolant quantity and the actual casting speed by means of a computer.

However, the procedure for setting these sizes is not explained in detail.

The object of the invention is to propose specifications for a more exact control of the regulation of the controlled variables with regard to the copper plate skin temperature.

The stated object is achieved according to the invention in that, with changing casting speed between 1 m / min to a maximum of 12 m / min, the copper plate skin temperature by a quantitative correction of the mold coolant quantity and the mold coolant inlet temperature depending on the actual casting speed and depending on the copper plate thickness is set to a desired, constant size and that for controlling the Kokillen- coolant quantity and the Kokillenkühlmittel inlet temperature process data and system data, which are processed in controlled variables to an online simulation model, are used. As a result, depending on the casting speed, the copper plate skin temperature can be selected favorably even at different copper plate thicknesses and kept constant. In addition, constant conditions for the lubricity of cast powder slag, which is melted on the casting mirror from the casting powder used (if casting powder is used) are given. Furthermore, benefits are obtained by Kokillenkupferplatten, which no longer claimed until the recrystallization of copper and therefore less cracked. Other benefits include improved strand surface quality and casting security regardless of casting speed and copper plate thickness for selected working windows. This also increases the output.

Advantageously, it is thereby also possible for the desired, constant copper plate skin temperature in the casting mirror to be set constant.

The described effects can also be achieved either completely or partially when the mold coolant is passed from top to bottom or from bottom to top through the cooling channels.

According to further features, the continuous casting mold is oscillated.

Further advantages result from the fact that the cast strand is cast together when forming powdered powder slag.

The accuracy of the method can be further increased by using an immediate determination of the copper plate skin temperature in the Gießspiegelbereich addition or alternative to the online simulation model.

A device for cooling the copper plates of a continuous casting mold, in particular for liquid steel, with Kokillenkühlmittel guided in cooling channels, wherein at from the target temperature in copper plates between 4 mm to about 50 mm different temperatures, a computer and control means for the amount or the flow rate of the coolant, solves the task of proposing for the regulation of the controlled variables with respect to the copper plate skin temperature specifications for a more precise control, according to the invention, that a process computer, the process data and system data with an online simulation model for controlled variables for controlling the Kokülenkühlmittel inlet temperature and the mold coolant quantity created controls a three-way valve and a control valve and a variable-speed pump in the mold coolant circuit. As a result, the copper plate skin temperature on the hot side already at the start of casting much lower than previously observed and the copper plate is spared in a way that the recrystallization temperature of the copper is far from reached. This advantage affects large casting speeds.

According to another embodiment, the mold coolant inlet can be arranged at a distance above the casting mirror.

Moreover, it is advantageous if the continuous casting mold is oscillated by means of an oscillating device.

Furthermore, it serves to protect the strand shell of the cast strand that the cast strand is supplied during casting casting powder.

According to another embodiment, this regulation can also be carried out in such a way that, in addition to or instead of the process computer, a device is used for determining the copper plate skin temperature in the molten metal region for controlling the mold coolant inlet temperature and / or the mold coolant quantity.

In the drawing, an embodiment is shown, which will be explained in more detail below.

Fig. 1A

ein Blockschaltbild des Kühlkreislaufs einer klassischen Kokille,

Fig. 1 B

das zugehörige Blockschaltbild des Kühlkreislaufs einer sog. ISO-Kokille gemäß der Erfindung,

Fig. 2A

ein Gießgeschwindigkeits-Profil mit Wärmestrom über der Zeit,

Fig. 2B

der Wärmeverlauf bei einer herkömmlichen Kühlung,

Fig. 2C

der gewollte Wärmeverlauf gemäß der Erfindung,

Fig. 2D

der gewollte Wärmeverlauf bei eingeregelter Kupferplatten-Hauttemperatur und

Fig. 3

einen Vergleich des Standes der Technik mit der Erfindung anhand der Temperatur-Kurven über der Gießgeschwindigkeit unter Berücksichtigung des Kühlmittellaufs von oben nach unten und von unten nach oben in der Stranggießkokille.

Show it:

Fig. 1A

a block diagram of the cooling circuit of a classic mold,

Fig. 1 B

the associated block diagram of the cooling circuit of a so-called. ISO mold according to the invention,

Fig. 2A

a casting speed profile with heat flow over time,

Fig. 2B

the heat history in a conventional cooling,

Fig. 2C

the desired heat history according to the invention,

Fig. 2D

the desired heat history at adjusted copper plate skin temperature and

Fig. 3

a comparison of the prior art with the invention based on the temperature curves over the casting speed, taking into account the coolant run from top to bottom and from bottom to top in the continuous casting mold.

According to the prior art (FIG. 1A), a continuous casting mold 1, in which liquid steel is poured, is cooled in such a way that the mold coolant 2 at the mold coolant inlet 3 is introduced into the continuous casting mold 1 in its mold coolant quantity 4 and its mold coolant temperature. Inlet temperature 5 is kept constant regardless of the casting speed 6.

This procedure means that the heat load 7 in W / m ² (see Fig. 2A) and thus also the copper plate skin temperature 8 increases with increasing casting speed 6 and increases sharply, especially during casting with increasing casting speed 6 of up to 12 m / min , The increase in temperature at a given copper plate thickness 9, for example of 20 mm, between coolant and hot side leads in the presence of cast powder slag 10 between the strand shell of the cast strand 11 and mold copper 1.1 on the one hand to different lubricity and heat load 7 and on the other shortened life of Kokillenkupferplatten 1.1, what is due to the exceeding of the recrystallization temperature 12 of cold-rolled copper (see Fig. 3).

These resulting in increasing casting speed 6 and / or increasing copper plate thickness 9 disadvantages lead to disturbances of the casting process or surface defects in the strand shell and cracks in the copper plate surface.

The faults occur both from a watercourse 13.1 of the mold water 13 in the continuous casting mold 1 from bottom to top and in a watercourse 13.2 from top to bottom (see FIG. However, it can be noted that the watercourse 13.2 from top to bottom, the copper plate skin temperature 8 is lower than the watercourse 13.1 from bottom to top.

In Fig.1A (prior art), the continuous casting mold 1 is cooled by an inner coolant circuit 19 and an outer coolant circuit 20. Of the The outer coolant circuit 20, which runs over a heat exchanger 21, serves to cool the mold coolant 2 in the inner coolant circuit 19.

The inner coolant circuit 19 is guided over the heat exchanger 21 in such a way that the mold coolant quantity 4, which is set constant by means of a pump 22, is likewise kept constant in its inlet temperature 23 (T _in ) independently of the casting speed 6.

Serve this purpose, a three-way valve 24, a bypass 25 and a controlled system 26 between a T _in- measuring device for the inlet temperature 23 (T _in ) and the three-way valve 24. As a rule, the Kokillenkühlmittel 2 is performed as a watercourse 13.1 from bottom to top, in Dünnstranget also as watercourse 13.2 from top to bottom.

Referring to Fig. 1B, the coolant circuit in Fig. 1A is shown in block diagram, but with increasing casting speed 6 of 1 m / min to a maximum of 12 m / min, the copper plate skin temperature 8 by a quantitative correction of the mold coolant quantity 4 and 1 or the Kokillenkühlmittel inlet temperature 5 regardless of the casting speed 6 and regardless of the copper plate thickness 9 is set at a constant controlled Kokillenkühlmittel inlet temperature 5 to a desired, constant copper plate skin temperature 8. The regulation of the mold coolant quantity 4 and the mold coolant inlet temperature 5 can be achieved via a process computer 27 for an online simulation model 27.4 and process data 27.1 of the continuous casting mold 1 at a constant copper plate skin temperature 8 via an inlet speed window 6.2 (see FIG. For this, the process computer 27 requires process data 27.1 and system data 27.2 in order to control the mold coolant quantity 4 via a pump station 22.1 and / or control valves 29 and the mold coolant inlet temperature 5 through the three-way valve 24 via controlled variables 27.3. Before the pump station 22.1 is a surge tank 30th

In FIGS. 2A to 2D, the procedural relationships are explained.

Fig. 2A shows a heat flow 17 and a profile 16 of the casting speed 6 over the casting time 18. The graph describes a casting run from the start via a constant run-in speed window 6.2 with subsequent acceleration to a high speed level.

Fig. 2B shows the state of the art. The real copper plate skin temperature 8, denoted T _Cu-real , increases with the casting speed 6 and deviates from the desired copper plate skin temperature 8, referred to as the target copper plate temperature 8.1, (T _{Cu target} ) since the mold coolant quantity is 4 and the mold coolant inlet temperature 5 for cooling the continuous casting mold 1 is kept constant.

In Fig. 2C, the real copper plate skin temperature 8 (T _Cu-real ) is determined by a corresponding quantitative correction of the mold coolant quantity 4 irrespective of the casting speed 6 at a constant mold coolant inlet temperature 5 having the desired copper plate skin temperature 8, the copper plate target temperature 8.1 (T _{Cu target} ) brought to cover.

Referring to FIG. 2D, the copper plate skin temperature 8 (T _Cu-real ) with the target copper plate temperature 8.1 (T _{Cu target} ) is determined by the corresponding quantitative adjustment of the mold coolant quantity 4 and the mold coolant inlet temperature 5 as a function of the profile 16 the casting speed 6 over the casting time 18 brought to coincide. With the variation of both influencing variables, such as the mold coolant quantity 4 or the coolant velocity, which increases the heat transfer, and the mold coolant inlet temperature 5, which increases the potential and thus the heat flow 17, the inlet velocity windows 6.2 with respect to the casting speed 6 are for a desired, real copper plate skin temperature 8 at a given copper plate thickness 9 greater than in the case of variation of only one of the two influencing variables.

According to Fig. 3, the difference of the known method for the invention can be clearly read. It is the copper plate skin temperature 8 in response to the increasing casting speed 6, the max. 12 m / min., Based on. A horizontal straight line of the recrystallization temperature 12 represents the end of the heat load of the copper plate made of cold-rolled copper, at which the copper loses its strength and / or cold rolling structure and thus its properties important for the casting of molten steel. The temperature curve 14 in the prior art is described with the curve 14.1 (water flow from bottom to top) and the curve 14.2 (water flow from top to bottom). Both curves 14.1 and 14.2 increase steadily with increasing casting speed 6 to higher copper plate skin temperatures 8 in the region of the casting mirror, the copper plate skin temperature 8 in the case of the course of water 14.1 of the mold water 13 from bottom to top earlier recrystallization temperature 12 at a critical Casting speed 6.1 cuts as in the case of the course of water 14.2 from top to bottom.

The strongly increasing behavior of the copper plate skin temperature 8 in the casting mirror with increasing casting speed 6 and increasing copper plate thickness 9 is due to the constant in the prior art casting molds Kokillen- 4 and the constant Kokillenkühtmittet inlet temperature 5 at mold coolant inlet 3.

The control and constancy of the copper plate skin temperature 8 over the casting speed 6 is shown by the curve 15. In this case, it is clear that with increasing copper plate thickness 9, the copper plate skin temperature 8 at the same cooling conditions, expressed by the coolant velocity or the mold coolant quantity 4 and as Kokillenkühlmittel inlet temperature 5, increases. The same applies to the known method (see curve 13.1 - water flow from bottom to top and curve 13.2 - water flow from top to bottom).

The principle of the invention can also be applied to strip casters operating at up to 100 m / min casting speed. In this case, all measures applied to the height of the continuous casting mold 1 are applied to the circumference of the twin rolls.

LIST OF REFERENCE NUMBERS

1

continuous casting

1.1

Kokillenkupferplatte

2

mold coolant

3

Mold coolant inlet

4

Mold coolant quantity

5

Mold coolant inlet temperature

6

casting speed

6.1

critical casting speed

6.2

Entry speed window
(with same copper plate temperature)

7

Heat load (W / m ² )

8th

Copper plate skin temperature

8.1

Copper plate target temperature

9

Copper plate thickness

10

casting powder slag

11

cast strand

12

Recrystallization temperature

13

Kokillenwasser

13.1

Watercourse from bottom to top

13.2

Watercourse from top to bottom

14

Temperature profile in the prior art

14.1

Curve Kokillenkühlmittel from bottom to top

14.2

Curve Kokillenkühlmittel from top to bottom

15

Curve

16

Profile of the casting speed over the casting time

17

heat flow

18

pouring

19

inner coolant circuit

20

outer coolant circuit

21

heat exchangers

22

pump

22.1

pump station

23

Inlet temperature T _in

24

Three-way valve

25

bypass

26

controlled system

27

process computer

27.1

process data

27.2

plant data

27.3

controlled variable

27.4

online simulation model

28

temperature measurement

29

control valve

30

Surge tank

Claims (11)

1. A method for cooling the copper plates (1.1) of a continuous casting mould (1) for liquid metals, particularly for molten steel, with mould coolant (2) guided in cooling channels, and wherein the quantity and/or throughput speed of the cooling agent (2) are regulated during the starting speed ramp to the setpoint casting speed, or to a speed above the setpoint casting speed, or a temperature deviating from the setpoint skin temperature (8) of the copper plates,
   characterised in that
   when the casting speed (6) is changing from 1 m/ min to a maximum of 12 m/ min, the copper plate skin temperature (8) is set to a desired, constant value via quantitative correction of the mould coolant quantity (4) and the mould coolant inflow temperature (5), depending on the current casting speed (6) and depending on the copper plate thickness (9), and that process data (27.1) and system data (27.2), which are processed in controlled quantities to yield an online simulation model (27.4), are used to regulate the mould coolant quantity (4) and the mould coolant inflow temperature (5).
2. The method as cited in claim 1,
   characterised in that
   the desired, constant copper plate skin temperature (8) is constantly adjusted in the meniscus area.
3. The method as cited in claim 1,
   characterised in that
   the mould coolant (2) is guided through the cooling channels from top to bottom or from bottom to top.
4. The method as cited in any of claims 1 to 3,
   characterised in that
   the continuous casting mould (1) is oscillated.
5. The method as cited in claims 1 to 4,
   characterised in that
   the strand (11) is poured together with casting powder slag (10) as it is formed.
6. The method as cited in any of claims 1 to 5,
   characterised in that
   an immediate determination of the copper plate skin temperature (8) is used in the meniscus area in addition to or instead of that in the online simulation model (27.4).
7. A device for cooling the copper plates (1.1) of a continuous casting mould (1), particularly for liquid steel, with mould coolant (2) guided in cooling channels, wherein, when temperatures in the copper plates between 4 mm to approximately 50 mm deviate from the setpoint temperature, a computer and regulating means are provided for the quantity and / or the throughput speed of the cooling agent,
   characterised in that
   a process computer (27), which generates an online simulation model (27.4) for regulated quantities (27.3) with process data (27.1) and system data (27.2) to regulate the mould coolant inflow temperature (5) and the mould coolant quantity (4), controls a three-way valve (24) and a control valve (29) as well as a speed-regulated pump (22) in the mould coolant circuit (19; 20).
8. The device as cited in claim 7,
   characterised in that
   the mould coolant inflow (3) is arranged at a distance above the meniscus.
9. The device as cited in claim 7,
   characterised in that
   the continuous casting mould (1) is oscillated via an oscillation device.
10. The device as cited in either of claims 7 or 8,
    characterised in that
    casting powder is added to the strand (11) during casting.
11. The device as cited in any of claims 7 to 10,
    characterised in that
    in addition or instead of the process computer (27), a device for determining the copper plate skin temperature (8) in the meniscus area is used to regulate the mould coolant inflow temperature (5) and /or the mould coolant quantity (4).

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