EP0943382A1 - Process and device for controlling the heat flow of a continuous casting mould during continuous slab casting - Google Patents

Abstract

The method with use of a submerged-entry nozzle, a casting powder and an oscillating mold further includes: a) measurement of the temperature of the copper plate surface over the mold width at least in the melt level region; b) control of the pressure and/or amount of some of the cooling water over the mold width to smooth and adjust the temperature of the copper plate surface in the melt level region. The apparatus includes water temperature probes in the connector openings (22) between the cooling slots (21) and the top distribution space (23) of the water box (16), as well as control elements (33, 34) located preferably in the top distribution space (23), for control of the throughput rate of the cooling water.

Description

The invention relates to a method for producing slabs especially made of steel, with the help of a plate mold, which is made of water-cooled, adjustable narrow side walls that between water-cooled broad side walls can be clamped. The The invention also relates to a device for carrying out the Procedure.

When continuously casting slabs, preferably made of steel, formats of the dimensional range are used
Cast 270-40mm thickness × 3,500-600mm width. This range of slab dimensions covers the so-called standard slabs with the dimensions
270-150 mm thickness × 3.000-600 mm width which are cast exclusively with rectangular mold formats.

The thin slabs of the size range
150-40 mm thickness × 3,500-600 mm width are preferably cast mainly with a funnel mold.

Both molds use a dipping spout, SEN ( S ubmerge E ntry N ozzle), and continuous casting powder. The media between the middle of the strand and the mold cooling water determine the heat flow, which can be determined for a given amount of mold cooling water by the temperature absorption of the cooling water.

The heat flow in the middle of the mold, i.e. in the area of the dip tube, SEN usually deviates from and is next to the SEN greater.

The cause of the different heat flows across the mold width are the various total resistances that affect the Formation of different partial resistances of the media steel / SEN / Slag film / copper plate / water boundary layer / water or Allow steel / slag film / copper plate / water to return. In this regard, is specific to the various Thermal conductivity and the different thicknesses pointed out.

- Kupfer

ca. 360 W/K . m

- Schlacke

ca. 1 W/K . m

- Stahl

ca. 50 W/K . m

- SEN

ca. 10 W/K . m,

womit die partiellen Gesamtwiderstände RX ges = Σ Ri = Σ I λ · q i über die Breite voneinander abweichen, d.h. sie können in den Bereichen des Tauchausgusses, SEN und neben dem Tauchrohr nicht gleich sein: RSEN ges ≠ Raußen ges This is the specific conductivity of individual media

- copper

approx. 360 W / K. m

- slag

approx. 1 W / K. m

- Stole

approx. 50 W / K. m

- SEN

approx. 10 W / K. m,

with which the partial total resistances R X total = Σ R i = Σ I. λ q i differ from each other across the width, ie they cannot be the same in the areas of the immersion spout, SEN and next to the immersion tube: R SEN total ≠ R Outside total

There is a need to equal these partial resistances set and also adjust to a certain value.

The prior art is described in the patents DE 41 17 073 and DE 195 29 931.

In the patent DE 41 17 073 the temperature recordings of the four water-cooled mold plates as integral values of each individual plate measured and evaluated. There will be no partial Values recorded across the mold width and, in principle, none Amounts of water changed for cooling.

A slab mold is described in the patent DE 195 29 931, that consists of at least three mutually independent cooling chamber segments exists, the separate in the mold exit Have connections for the independent supply of mold cooling water. With this arrangement, asymmetries of the specific heat flows are intended between the immersion area and the remaining mold areas be recognized and by conicity adjustment and cooling water control be balanced.

In contrast to the prior art, the object of the invention is to describe a process and a mold that enable the skin temperature of the Cu plates of the mold in the area of the mold level to be recorded 'online' in order to achieve an optimal level and distribution and constant temperature profile of the Cu plate skin in the mold level adjust even with changing copper plate thickness can.

• eine minimale thermische Belastung der Strangschale und damit gute Strangoberflächenqualität,
• ein gleichförmiges und krustenfreies Aufschmelzen des Gießpulvers im Gießspiegel zu Gießschlacke,
• eine gleichförmige Ausbildung des Schlackenschmierfilms zwischen Strangschale und Kupferplatten,
• einen gleichförmigen Wärmestrom über die Breite des Stranges in die Kokillenplatten,
• eine kontrollierte und geregelte Temperatur der Kupferplattenhaut im Gießspiegelbereich,
• eine gleichförmige thermische Belastung der Kupferplatte vor allem im Gießspiegel über die gesamte Kupferplattenbreite und damit
• eine maximale Standzeit der Kokillen-Kupferplatten.

A constant and optimal temperature profile in the copper plate skin over the entire mold width is a prerequisite for

• minimal thermal stress on the strand shell and thus good strand surface quality,
• a uniform and crust-free melting of the mold powder in the mold level to pour slag,
• uniform formation of the slag lubrication film between the strand shell and copper plates,
• a uniform heat flow across the width of the strand into the mold plates,
• a controlled and regulated temperature of the copper plate skin in the area of the mold level,
• a uniform thermal load on the copper plate, especially in the mold level, across the entire width of the copper plate and thus
• a maximum service life of the mold copper plates.

• Wassermenge
• Wasserdruck bzw.
• Wasserfließgeschwindigkeit

zu kontrollieren.This constant and optimized temperature profile of the copper plate skin can also be seen in the case of different or thinning copper plate thicknesses, e.g. due to reworking between two campaigns in the casting shop or with different copper qualities or, for example, with Ni-coated copper plates due to the corresponding changes in

• Amount of water
• Water pressure or
• Water flow rate

to control.

The object is achieved by the features of the claims.

The solution to the task is independent of the mold type, e.g. of the Vertical, vertical turn or circular mold. Also remains It does not matter whether the mold has a rectangular shape or a Has funnel shape in the mold level. The continuous casting speed when using the inventive mold, which preferably oscillates and is provided with a hydraulic oscillator drive between 0.5 and 10 m / min.

Figur 1

Darstellung des Temperaturprofiles zwischen den Kupferplatten einer Kokille und der Strangschale unter Berücksichtigung des Gießpulvers und der Gießschlacke im Badspiegel und zwischen der Kupferplatte und der Strangschale,

Figur 2

eine Rechteckkokille mit den Störungen der Kupferplattenhauttemperatur im Gießspiegel und der partiellen Wärmeströme über die Kupferplattenbreite,

Figur 3

eine Rechteckkokille mit den erfinderischen Merkmalen, die zu einer kontrollierten und über die Breite konstanten Kupferplattenhauttemperatur führt,

Figur 4

eine Trichterkokille mit den Störungen in der linken Hälfte des Bildes a) und mit den erfinderischen Merkmalen, Bilder b) bis f), die zu einer kontrollierten und über die Breite konstanten Kupferplattenhauttemperatur führt,

Figur 5

eine Rechteckkokille mit den Störungen in der linken Hälfte des Bildes a) und mit den erfinderischen Merkmalen, Bild b, die zu einer kontrollierten und über die Breite konstanten Kupferplattenhauttemperatur führt.

The figures serve to illustrate the following exemplary description of the invention. Show it:

Figure 1

Representation of the temperature profile between the copper plates of a mold and the strand shell, taking into account the casting powder and pouring slag in the bath level and between the copper plate and the strand shell,

Figure 2

a rectangular mold with the disturbances of the copper plate skin temperature in the mold level and the partial heat flows across the copper plate width,

Figure 3

a rectangular mold with the inventive features, which leads to a controlled and constant width of the copper plate skin temperature,

Figure 4

a funnel mold with the faults in the left half of picture a) and with the inventive features, pictures b) to f), which leads to a controlled and constant width of the copper plate skin temperature,

Figure 5

a rectangular mold with the disturbances in the left half of the picture a) and with the inventive features, picture b, which leads to a controlled and constant over the width copper plate skin temperature.

Figure 1 shows schematically a section through a mold plate 1 and a strand 2 in the casting direction. The strand is poured with immersion spout (SEN) 4 and casting powder 5. The bathroom mirror 6, which has a temperature of, for example, T _liq . = 1,500 ° C, is a first approximation of the isotherm (7 - 1,500 ° C), which also forms the inner strand shell. The mold 1 has the highest temperature 8 of, for example, 400 ° C at the level of the mold level (6) and represents the starting point for the 400 ° C isotherm (7 - 400 ° C), which is in the space between strand shells 9 and mold plate 1 , filled with solid and liquid pouring slag 10 expands. The copper plate skin temperature has, for example, a distribution as shown in FIG. 1 (temperature diagram). From the pouring level in point 8, the temperatures drop both in the pouring direction 3 and against the pouring direction towards the top edge of the copper plate 12. B. from 50 ° C.

This temperature field between the mold plate and the strand shell with its distinctive and maximum temperature 8 of 400 ° C at mold level can be changed by changing the water cooling and / or Copper plate thickness can be influenced.

• Erhöhung der Wassermengen (Druck, Fließgeschwindigkeit, Volumen) und/oder durch
• eine geringere Kupferplattendicke.

The temperature of the copper plate at the level of the mold level 8 can be reduced by

• Increase in water volumes (pressure, flow rate, volume) and / or through
• a lower copper plate thickness.

With such a measure, based on the heat flow Q ₂ > Q ₁ , the temperature of the Cu plate in the mold level 8 can be reduced (T - Q ₂ ) <(T - Q ₁ ) and, in connection with this, the melting behavior of the mold powder, accompanied by a Crust formation 13, are influenced.

These relationships make it clear that for an optimal procedure a temperature measurement and temperature control especially in the Casting mirrors are important. The relationships shown so far to influence the temperature field between the copper plate 1 and the strand shell 9 apply so far only in the casting direction 3, or there is an identical behavior across the casting width accepted. This requirement equal casting conditions over the Mold width cannot be assumed, because in the middle of the Slab z. B. a diving spout with the specific conductivity of e.g. B. 10 W / K m is used. This diving spout, for example has an outer shape of 120 × 200 mm, takes directly Influence on the heat flow, resulting in an asymmetry of the temperature field and the heat flow etc. over the mold width.

Figure 2 shows schematically the broadside copper plate with the Water box 6 of a rectangular mold. Part a) shows the View of the copper plate and drawing b) the section through the copper plate and water tank.

The copper plate 1 is on the water box via clamping screws 15 16 screwed. The water box is in the lower area with cooling media, preferably with cooling water, in quantity and pressure over the Inlet 17 supplied.

The cooling water 19 flows through at a desired speed Checked outlet openings 20 in the cooling slots 21 of the copper plates in pressure and quantity / time, then through transition openings 22, introduced uniformly across the width of the water tank (16) are to flow into the upper distribution space 23. From from here the water is fed to the mold circuit via an outlet line 24, which is adjustable in pressure and quantity, and the water treatment fed.

The partial picture a) gives the non-uniform temperature distribution 25 over the active mold width 26 between the narrow sides 27 again. The temperature rises in the area of the immersion nozzle, SEN 4 the Cu plate skin temperature. This partial increase can be caused by the temperature measurement 22.1 in the transition openings 22 when known the amount of water can be determined. The absolute temperature in the Copper plate skin and thus the partial temperature profile 28 over the mold length while using the partial Heat flows 22.1 in the ranges 1/1 'to n / n' can be adjusted using determined at least one thermocouple 29 in the copper plate become. The thermocouples of a breakdown protection can preferably be used here be used. Figure 2 does the task again clear.

In Figure 3 is the invention for a rectangular mold shown.

The partial mold a) shows the mold skin temperature of the casting mirror 8 in the areas next to the diving spout 30 or in the diving spout area 31 by reducing the partial amount of water in zones 32 1/1 'to n / n' of range 30 have been adjusted as well as the absolute Temperature level 8 has been set to a certain value. The combination of the thermocouples 29, the water temperature measurement 22.1 and the partial amounts of water in zones 32 allow the Check the temperature distribution 25 over the mold width and their absolute height.

The amounts of water in the respective water zones 32 can, for. B. by a slide plate 33 - Figure 3 b) - that a certain profile has the thermal profile with constant, partial water cooling corresponds and all the transition openings 22 in the upper Distribution room 23 of the water tank simultaneously detected, controlled become.

In sub-picture c) there is an example of a control valve 34 in the upper distributor space 34 of the water box 16 introduced that the water passage regulates in the transition opening 22. This valve could too be arranged in the lower distribution chamber 18 of the water tank 16. (Figure 2)

FIG. 4 shows the features of the invention in the case of a funnel mold, compared to the prior art in the left half of the sub-picture a).

Here, too, the partial is exemplarily similar to that in FIG Water in the water zones 32 next to the immersion pouring area 30 below Consideration of the funnel 35 with its envelope 36 partially detected. The water quantities can be controlled with the slide plate 33 or each transition opening 22 with a valve 34 be managed.

In sub-images b) and c) the slide plate is over the mold width and thickness and in section d) the control valve described 34 is shown schematically. The partial picture e) represents the funnel mold schematically represented by the supervision. In the drawing f) are mechanical Inserts 37 as a simple solution to throttling Transitional openings 22 shown, but no taxes or Allow rules of water quantities and only a static solution to the Represent task.

The advantage of the invention is again shown in FIG. 5 using the example of a Rectangular mold, compared with the prior art, shown. The left partial image a) represents the temperature profile that arises 25 of the Cu plate skin temperature in the mold level 8 over the The width of the mold is shown. In the right part b) is the temperature profile 25 shown using the inventive features. It puts a constant temperature 8 in the mold level and at the same time a constant temperature field between the copper plate and the Strand shell 9 over the entire mold width. This can the absolute temperature level 38 simultaneously within certain limits to get voted.

• die Qualität des Stranges zu verbessern und
• die Gießsicherheit sowie
• die Lebenszeit der Kokillenplatten zu erhöhen.

The procedural features are used with the aid of the partial heat flow measurement 22.1, the partial temperature measurement 29 and the partial devices 33 or 34 for water quantity control, which enable the described control circuit as mold device features

• to improve the quality of the strand and
• pouring security as well
• increase the lifetime of the mold plates.

Reference list

1

Broadside mold plate, cut in the casting direction

2nd

Strand, cut in the casting direction

4th

Diving spout, SEN

5

Mold powder

6

Bath mirror, casting mirror

7

Isotherms (i ° C)

8th

Mold skin at casting level with the highest temperature load of, for example, 400 ° C (TQ ₁ ), which is the starting point for the isotherm (7-400 ° C).

9

Strand shell

10th

solid and liquid pouring slag

11

Distribution of the copper plate skin temperature over the Mold height

12th

Top of copper plate

Q ₁

Heat flow with temperature at point (8) of (TQ ₁ ) = 400 ° C

Q ₂

Heat flow with temperature at point (8) of (TQ ₂ ) <TQ ₂

TQ ₁

Temperature of the copper plate in the mold at heat flow Q ₁

TQ ₂

Temperature of the copper plate in the mold at the heat flow Q ₂ , Q ₂ > Q ₁ , {TQ ₁ }> {TQ ₂ }

13

Crusting of the mold powder in the mold level

14

Broadside copper plate with a rectangular mold water box

15

Turnbuckles

16

Water tank

17th

Inlet for cooling water in quantity / time and pressure in the lower distribution space (18) of the water tank (16)

18th

lower distribution area of the water tank (16)

19th

Cooling water in quantity / time x pressure and m / sec

20th

Outlet openings from the lower distribution area of the water tank

21

Copper cooling slots

22

Transition openings in the upper distribution room

22.1

Water temperature measurement in the openings (22)

23

upper distribution area of the water tank (16)

24th

Outlet pipe for the mold cooling water

25th

Temperature distribution across the mold width in the mold level

26

active mold width

27

Narrow sides

28

partial temperature profile over the mold height

29

Thermocouple (s) in the copper plate

30th

Mold width area next to the immersion nozzle (4)

31

Mold width in the immersion pouring area

32

Water zones 1/1 'to 5/5' (n / n ')

33

Slider plate for controlling mold water

34

Control valve in the upper distributor chamber (23) of the water tank (16)

35

Pouring funnel

36

Envelope of the casting funnel in the mold width (1)

37

mechanical use in the transition opening (22)

38

Temperature level in the copper plate at mold level (8th)

Claims (9)

Method for producing slabs, in particular made of steel, with the aid of a plate mold, which consists of water-cooled, adjustable narrow side walls which can be clamped between water-cooled wide side walls, and which comprises the following steps: Pouring by means of a diving spout, Use of casting powder to form casting slag, Oscillation of the mold, Measurement of the temperature distribution of the copper plate skin temperature at least over the mold width in the area of the mold level, Regulation of the partial cooling water in pressure and / or quantity over the mold width to equalize and control the copper plate skin temperature in the area of the mold level. Method according to claim 1,
characterized,
that the partial heat flows are measured over the mold width and the integral heat flows over the mold height. The method of claim 1 or 2,
characterized,
that discrete temperature measurements for determining the copper plate skin temperature are carried out on the side facing the steel over the mold width. Method according to one of claims 1 to 3,
characterized,
that the partial temperature profiles and / or heat flow profiles over the mold height are determined over the mold width. Continuous casting mold consisting of water-cooled narrow side walls (27), which are between two water-cooled wide side walls (2), for carrying out the method according to one of claims 1 to 4, which contains the following elements: a diving spout (4), Pouring powder, powder or granules (5), oscillating mold, Water temperature sensor (22.1) in the transition openings (22) between the cooling slots and the upper distributor space (23) of the water tank (16), Control elements (33, 34), preferably in the upper distributor space (23) of the water tank (16), for the partial control of the cooling medium water in its flow rate. Continuous casting mold according to claim 5,
characterized,
that thermocouples (29) are installed in the narrow side walls (27) and / or in the wide side walls (1). Continuous casting mold according to claim 5 or 6,
characterized,
that with the help of the temperature sensors (22.1) and at least one thermocouple (29) over the mold width partial heat flow profiles and / or temperature profiles over the mold height are created, with which the desired temperature distribution over the mold width of the casting level (25) with the help of water quantity control valves (34) , which are provided in the transition openings (22) between the copper cooling slots (21) and the upper distributor space (23) of the water tank (16), are adjusted and checked during the casting process. Continuous casting mold according to one of claims 5 to 7,
characterized,
that instead of the water quantity control valves (34) a slide plate (33) is used to control the cooling water quantities. Continuous casting mold according to one of claims 5 to 8,
characterized,
that mechanical inserts (37) are used to preset the amounts of water at the transition openings (22).

Images