DE10160739C2 - Method and device for cooling the copper plates of a continuous casting mold for liquid metals, in particular for liquid steel - Google Patents

Description

The invention relates to a method and a device for cooling the copper plate with a continuous casting mold for liquid metals, in particular for liquid steel in coolant channeled coolant and during the speed start Driving ramp to the target casting speed or exceeding the target casting speed different skin plate temperature, with changing Casting speed between 1 m / min and a maximum of 12 m / min the copper plate Skin temperature through a quantitative correction of the amount of mold coolant and / or the mold coolant inlet temperature depending on the current casting speed and depending on the copper plate thickness to a desired, constant Size is set.

From DE 41 27 333 C2 a method is known in the area of the highest temperature the coolant at maximum speed. This will improves heat dissipation and reduces the temperature of the mold plate. Au In addition, a decrease in temperature differences over the height of the Ko kille and a consequent reduction in tension and extension of the Service life of the mold walls sought. However, this procedure takes into account not a changed, especially an increased, very high casting speed.  

Such continuous casting molds for the casting of liquid steel are cooled in generally known methods used by the mold coolant is kept constant regardless of the casting speed in the amount and its temperature when entering the continuous casting mold. The consequence of this procedure is that as the casting speed increases, the thermal load, measured in W / m ² , and thus also the copper plate skin temperature, and especially when casting at casting speeds above 4 m / min, increases sharply. This temperature rise for a given copper plate thickness of 20 mm between the mold coolant and the hot side, for example, results in different lubrication behavior and different heat loads when using powdered casting slag between the strand shell and the mold copper plate and, on the other hand, shortened tool life of the mold copper plates due to the recrystallization temperature being exceeded cold rolled copper.

The resulting disadvantages with increasing casting speed but also with increasing copper plate thickness lead to disruptions in the casting process and / or to surface defects in the strand shell and to cracks in the copper plate top area.

The disturbances occur both in a watercourse in the continuous casting mold of un th up and down from the top. But it can be determined that the copper plate skin temperature increases from top to bottom set lower than the water flow from bottom to top.

The method described at the outset is known from EP 1 103 323 A2. This The process takes into account a changing pouring speed and the process occurring, different copper plate skin temperature by correcting the knockout Killen coolant amount and / or the inlet temperature depending on the ak current casting speed and depending on the copper plate thickness. The pre However, setting these sizes is not explained in detail.

The object of the invention is to regulate the arithmetic variables The copper plate skin temperature prefers specifications for more precise control beat.

The object is achieved according to the invention in that the desired, con constant copper plate skin temperature is constantly set in the area of the mold level, by passing the mold coolant through the cooling channels from top to bottom and that to regulate the amount of mold coolant and / or the mold coolant Inlet temperature process data and plant data, which are controlled variables at one online simulation model are processed, used. This allows the Copper plate skin temperature depending on the casting speed even at un Different copper plate thicknesses are cheaply selected and kept constant the. There are also constant conditions for the lubrication behavior of casting powder slag that melted on the mold level from the mold powder used Zen is given (if mold powder is used). There are also advantages by mold copper plates, which no longer be until the recrystallization of the copper stressed and therefore less cracked to achieve. Other advantages are one improved strand surface quality and casting reliability regardless of the casting speed and the copper plate thickness for selected work windows. In order to output is also increased.

Further advantages result from the fact that the casting strand is potted with casting powder will.

The accuracy of the method can be increased even further by an immediate additional determination of the copper plate skin temperature in the area of the mold level is used for the online simulation model.

A device for cooling the copper plates of a continuous casting mold, in particular  for liquid steel, with cooling channels through which mold coolant flows, solves the Task for regulating the control variables with regard to the copper plate To propose skin temperature specifications for a more precise regulation, fiction according to the fact that a process computer with process data and system data for an online simulation model for controlled variables for controlling the mold cooling tel inlet temperature and / or the amount of mold coolant is supplied Three-way valve and a control valve as well as a speed-controlled pump in the mold Coolant circuit controls. This can cause the copper plate skin temperature on the The hot side can be kept much lower than before at the start of casting and the copper plate is spared in a way that the recrystallization temperature of copper is far from being achieved. This advantage affects large areas adjust the casting speed.

According to another embodiment, the mold coolant inlet can be spaced apart be arranged above the liquid level.

Furthermore, it serves to protect the strand shell of the casting strand that the casting strand is pourable when pouring mold powder.

According to a further embodiment, this regulation can also be provided in this way be taken that in addition a device for determining the copper plate skin temperature in the area of the mold level to regulate the mold coolant Inlet temperature and / or the amount of mold coolant can be used.

A further embodiment consists in the fact that the process data Data at the output of a heat exchanger can be fed to the process computer.

The control becomes even more precise in that the process data are the measurement data an immediate determination of the copper plate skin temperature in the mold level area can be fed to the process computer.  

Another improvement is the fact that the process data are the measurement data the inlet temperature of the mold coolant behind a pump station the Pro process computers can be fed.

It is also advantageous that the control valve controlled by the process computer Three-way valve of the heat exchanger is connected upstream.

In the drawing, an embodiment is shown, which he below in more detail is refined.

Show it:

Fig. 1A is a block diagram of the cooling circuit of a conventional mold,

FIG. 1B, the corresponding block diagram of the cooling circuit of a so-called. ISO mold according to the invention,

Fig. 2A is a Gießgeschwindigkeits profile with heat flow over the time,

Fig. 2B of the thermal history of a conventional cooling system,

FIG. 2C, the unwanted thermal history in accordance with the invention,

Fig. 2D the desired heat profile with regulated copper plate skin temperature and

Fig. 3 shows 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 , into which liquid steel is poured, is cooled in such a way that the mold coolant 2 at the Kokil len coolant inlet 3 into the continuous casting mold 1 in its mold coolant quantity 4 and its Chill coolant inlet temperature 5 regardless of the Gießge speed 6 is kept constant.

This procedure means that with increasing casting speed 6, the heat load 7 in W / m ² (see FIG. 2A) and thus also the copper plate skin temperature 8 increases, and especially when casting with increasing casting speed 6 of up to 12 m / min increases. The temperature rise for a given copper plate thickness 9 , z. B. 20 mm, between the coolant and heat-side leads in the presence of casting powder slag 10 between the strand shell the cast strand 11 and Kokillenkupferplatte 1.1 firstly to different lubricating performance and heat load 7, and on the other to shortened Standzei the mold copper plates th 1.1, which by exceeding the recrystallization temperature 12 is caused by cold-rolled copper (cf. FIG. 3).

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

The disturbances occur both with a water course 13.1 of the mold water 13 in the continuous casting mold 1 from bottom to top and with a water course 13.2 from top to bottom (see FIG. 3). However, it can be stated that the copper plate skin temperature 8 is set lower in the water course 13.2 from top to bottom than in the water course 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 . The outer coolant circuit 20 , which runs via a heat exchanger 21 , serves to cool the mold coolant 2 in the inner coolant circuit 19 .

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

A three-way valve 24 , a bypass 25 and a control path 26 serve between a T _in measuring device for the inlet temperature 23 (T _in ) and the three-way valve 24 . As a rule, the mold coolant 2 is guided as a water course 13.1 from bottom to top, in the case of thin-strand systems also as a water course 13.2 from top to bottom.

According to FIG. 1B, the refrigerant circuit as Fig. 1a in the block diagram, except that 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 Kokil len-refrigerant quantity 4 and / or the mold coolant inlet temperature 5 is set independently of the casting speed 6 and regardless of the copper plate thickness 9 with a constantly controlled mold coolant 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 carried out via a process computer 27 for an online simulation model 27.4 and process data 27.1 of the continuous casting mold 1 with a constant copper plate skin temperature 8 via a running-in speed window 6.2 (see FIG. 3). be realized. For this purpose, the process computer 27 requires process data 27.1 and system data 27.2 in order to regulate 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 control variables 27.3 . A pressure expansion tank 30 is located in front of the pump station 22.1 .

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

Fig. 2A shows a heat stream 17 and a profile 16 of the casting speed of about 6 pouring 18th The graph describes a pouring process from the start over a constant inlet speed window 6.2 with subsequent acceleration to a high speed level.

FIG. 2B are prior art again. The real copper plate skin temperature 8 , designated T _Cu-real , increases with the casting speed 6 and deviates from the desired copper plate skin temperature 8 , referred to as the copper plate target temperature 8.1 , (T _{Cu target} ) because the mold Coolant amount 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 ) by a corresponding quantitative correction of the mold coolant quantity 4 regardless of the casting speed 6 at constant mold coolant inlet temperature 5 with the desired copper plate skin temperature 8 , the copper plate Target temperature 8.1 (T _{Cu target} ) brought to congruence.

According to FIG. 2D, the copper plate skin temperature 8 (T _Cu-real ) with the copper plate target temperature 8.1 (T _{Cu target} ) by the corresponding quantitative setting of the mold coolant quantity 4 and the mold coolant inlet temperature 5 as a function of that Profile 16 of the casting speed over the casting time 18 brought to congruence. In the variation of both influencing variables, such as the amount of mold coolant 4 or the coolant speed, which increases the heat transfer, and the Ko coolant inlet temperature 5 , which increases the potential and thus the heat flow 17 , the inlet speed window 6.2 with respect to the Gießgeschwindig speed 6 for one wanted, real copper plate skin temperature 8 for a given copper plate thickness 9 larger than in the case of the variation of only one of the two influencing factors.

According to FIG. 3, the difference between the known method and the method according to the invention can be clearly read. It is the mold plate skin temperature 8 depending on the increasing casting speed 6 , the max. 12 m / min. A horizontal straight line of recrystallization temperature 12 represents the end of the thermal load on the copper plate made of cold-rolled copper, in which the copper adds strength and / or cold rolling and thus loses its properties which are important for the casting of liquid steel. The temperature profile 14 in the prior art is described with curve 14.1 (what the server runs from bottom to top) and curve 14.2 (water profile from top to bottom). Both curves 14.1 and 14.2 increase with increasing casting speed to higher copper plate skin temperatures 8 in the area of the pouring level, the copper plate skin temperature 8 in the case of water flow 14.1 of the mold coolant 13 from bottom to top earlier the recrystallization temperature 12 a critical pouring speed 6.1 cuts from top to bottom than in the case of water flow 14.2 .

The sharply rising behavior of the copper plate skin temperature 8 at the meniscus with increasing casting speed 6 and increasing copper plate thickness 9 is to recirculate to the casting constant in the prior art mold coolant quantity 4 and the constant mold coolant inlet temperature 5 at the mold coolant inflow. 3

The control and constancy of the copper plate skin temperature 8 on the Gießge speed 6 is shown with the curve 15 . It becomes clear that with increasing copper plate thickness 9, the copper plate skin temperature 8 with the same cooling conditions, expressed by the coolant speed or the mold coolant quantity 4 and as mold coolant inlet temperature 5 , increases. The same applies to the known method (cf. 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 casting devices which are operated at a casting speed of up to 100 m / min. All of the measures applied to the level of the continuous casting mold 1 are applied to the order of the twin rollers.

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 the same copper plate temperature)

7

Thermal 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

13.1

Watercourse from the bottom up

13.2

Watercourse from top to bottom

14

Temperature curve in the prior art

14.1

Curve mold coolant from bottom to top

14.2

Curve mold coolant from top to bottom

15

Curve

16

Profile of the casting speed over the casting time

17

heat flow

18

pouring

19

internal coolant circuit

20

external 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 mold ( 1 ) for liquid metals, in particular for liquid steel, with mold coolant ( 2 ) guided in cooling channels and during the speed ramp to the target casting speed or exceeding the target casting speed Target copper plate skin temperature ( 8 ), with changing casting speed ( 6 ) between 1 m / min to a maximum of 12 m / min, the copper plate skin temperature ( 8 ) by a quantitative correction of the amount of mold coolant ( 4 ) and / or Chill coolant inlet temperature ( 5 ) is set to a desired, constant size depending on the current casting speed ( 6 ) and depending on the copper plate thickness ( 9 ), characterized in that the desired, constant copper plate skin temperature ( 8 ) is set constant in the casting area is by the mold coolant ( 2 ) from top to bottom through the K cooling channels and that to regulate the mold coolant quantity ( 4 ) and / the mold coolant inlet temperature ( 5 ) process data ( 27.1 ) and system data ( 27.2 ), which are processed in control variables to an online simulation model ( 27.4 ), be used. 2. The method according to claim 1, characterized, that the casting strand is poured with casting powder.   3. The method according to any one of claims 1 or 2, characterized in that a direct determination of the copper plate skin temperature ( 8 ) in the mold level area is used in addition to the online simulation model ( 27.4 ). 4. Device for cooling the copper plates ( 1.1 ) of a continuous casting mold, in particular for liquid steel, with cooling channels through which mold coolant ( 2 ) flows, with casting speeds ( 6 ) between 1 m / min and a maximum of 12 m / min and copper plate thicknesses ( 9 ) from 4 mm to approx. 50 mm control sizes ( 27.3 ) for checking the mold coolant inlet temperature ( 5 ) and / or the mold coolant quantity ( 4 ) are provided, characterized in that a process computer ( 27 ) which is connected to process data ( 27.1 ) and system data ( 27.2 ) for an online simulation model ( 27.4 ) for controlled variables ( 27.3 ) for regulating the mold coolant inlet temperature and / or the mold coolant quantity ( 4 ), a three-way valve ( 24 ) and a control valve ( 29 ) and controls a speed-controlled pump ( 22 ) in the mold coolant circuit. 5. Device according to claim 4, characterized in that the mold coolant inlet ( 3 ) is arranged spaced above the casting level. 6. Device according to one of claims 4 or 5, characterized in that the casting strand ( 11 ) can be supplied with casting powder during casting. 7. Device according to one of claims 4 to 6, characterized in that additionally use a device for determining the copper plate skin temperature ( 8 ) in the area of the mold level for regulating the Kokillenkühlmit tel inlet temperature ( 5 ) and / or the amount of mold coolant ( 4 ) is cash. 8. Device according to one of claims 4 to 7, characterized in that the process data ( 27.1 ), the measurement data at the output of a heat exchanger ( 21 ) can be fed to the process computer ( 27 ). 9. Device according to one of claims 4 to 8, characterized in that the process data ( 27.1 ), the measurement data of a direct determination of the copper plate skin temperature in the area of the mold level can be fed to the process computer ( 27 ). 10. Device according to one of claims 4 to 9, characterized in that the process data ( 27.1 ), the measurement data of the inlet temperature ( 23 ) of the mold coolant ( 2 ) can be fed to the process computer behind a pump station ( 22.1 ). 11. Device according to one of claims 4 to 10, characterized in that the control valve ( 29 ) controlled via the process computer ( 27 ) is connected upstream of the three-way valve ( 24 ) of the heat exchanger ( 21 ).