EP0865849B1 - Oscillating mould with an immersion nozzle for continuous casting of slabs - Google Patents

Abstract

Oscillating mould intended for continuous casting preferably of steel slabs with an a submerged melt outlet and use of casting powder incorporates a submerged melt outlet pipe (8) with a flow cross section (8.4) and an outlet cross section (8.3.1). It further incorporates freely movable narrow-side plates (1.3), and broad-side plates (1) which are plane in the direction of the mould length and are concave with a central symmetry in the direction of the mould with. The broad-side plates are additionally provided with a funnel section (5) corresponding to the cross section (8.1) of the melt outlet pipe at least in the melt level zone. This funnel section is at least partially reduced towards the mould outlet.

Description

The invention relates to an oscillating mold for the continuous casting of slabs, preferably made of steel, with immersion spout with internal flow cross-section, Wall thickness, outlet cross-section and outer cross-sectional format with a width and thickness with broad sides with freely movable narrow sides with a pouring funnel, of the outer cross-sectional shape of the immersion nozzle at least in Casting area corresponds and at least in the direction of the mold exit is partially withdrawn.

The continuous casting is carried out in particular in formats of the thickness range between 20 and 250 mm, preferably 40 - 150 mm (thin slabs), and the width format between 500 and 3,300 mm, preferably 500 - 1,800 mm, with casting speeds of maximum 10 m / min.

The previously known opened by means of a funnel or trough in the mold level Slab or thin slab molds can be divided into the following groups with preliminary and Divide disadvantages.

In the patent DE 887 990 a funnel mold is described in which the There is a risk that the strand shell jams in the mold, which can be torn off the strand shell leads during conveying.

The patent DE 34 00 220 describes a funnel mold with broad sides and Narrow side walls, at the side of the funnel-shaped pouring area Is arranged parallel area, at least the thickness of the cast tape or corresponds to the thin slab. With this mold the disadvantages of the mold become corrected according to the above patent DE 887 990.

JP-OS 58-86906 describes a mold which is independent of the immersion mold is concave and there is a residual concavity at the mold outlet having. At the same time, the concavity is withdrawn over the length of the mold larger than the shrinkage of the slab across the mold width, so that the taper of the narrow sides is negative or the strand width at the mold outlet is larger than in the area of the mold level. In addition, this solution does not provide uniform slag formation across the strand width, because the active Strand thickness in the mold level for melting mold powder is not uniform. This unequal formation of slag is also evident in the patent DE 36 27 991 detect.

In the patent DE 41 31 829 is a 4-plate thin slab mold described, which is concave in the narrowest slab width. This Opening in the area of the casting level and in the middle of the slab is max. 12 mm each 1,000 mm slab width.

This mold shape has the disadvantage that in the area between the Chill broadside and the dip tube, which is opposite the area outside the Dip tube is only very narrow (maximum 2 x 0.25 slab thickness + 12 mm), a lack of pouring slag and a lack of fresh melt occurs, which lead to increased heat flow and shrinking behavior as well as hypothermia and Bridge formation between strand shell and immersion spout leads. These disadvantages culminate in a high susceptibility of the slab surface to longitudinal cracks in the area the middle of the slab.

The patent specifications DE 44 03 045 and DE 44 03 050 describe concave Mold shapes that do not indicate a connection between the make concave mold and the outer and inner immersion mold. This lack of optimization of the forms to one another leads to disturbances in the Heat flow over the mold width and height as well as the steel flow in and below the casting level, which in turn promote the risk of longitudinal cracking.

In European patent application 0 109 357 A1 the choice of concave mold shape, the immersion nozzle or the immersion tube none Consideration. In addition, these are molds for casting Aluminum using electromagnetic fields, that is, the strand has no contact with the mold when the strand shell is formed. Furthermore no mold powder is used and the mold does not oscillate. Will continue not continuously, but poured into a kind of ingot mold.

WO-A-89/12 516 relates to a so-called funnel mold with an upper one widened pouring area, which in the direction of casting to the format of the cast Thin slab is returned. The dip tube extends into the pouring area Distributor for molten steel arranged above the mold. From one necessary optimization of the shapes of mold plates, funnels and Diving spout is out of the question.

• eine ungleichförmige Schlackenbildung über die Strangbreite im Bereich des Tauchrohres,
• eine Unterkühlung des Stahles im Bereich des Tauchrohres gegenüber dem Bereich neben dem Tauchrohr,
• eine Behinderung des Schrumpfens der Strangschale in horizontaler Richtung durch die parallele Kokillenform und dies besonders bei breiten Brammenformaten.

In addition to these thin slab molds, the classic slab mold with the rectangular format of, for example, 200 x 200 mm should also be discussed. Apart from the fact that the casting speed is only a maximum of 2 m / min and the heat flow and thus shrinkage is only approx. 1 MW / m ² and approx. 1%, this standard mold system has a relatively thick slag film between the strand shell and the mold of e.g. 1 - 2 mm thick the following defects:

• a non-uniform formation of slag over the strand width in the area of the dip tube,
• subcooling of the steel in the area of the dip tube compared to the area next to the dip tube,
• a hindrance to the shrinking of the strand shell in the horizontal direction due to the parallel mold shape and this is particularly the case with wide slab formats.

• der Gießleistung
• der inneren und äußeren Form,
• der Fließquerschnitte,
• der Auslaßöffnungen in Größe und Anordnung und
• Wandstärke (maximale Gießzeit, Anzahl der Schmelzen in Sequenzguß)

folgenden Anforderungen gerecht wird:

• gleichförmige Schlackenbildung über die Brammenbreite,
• gleichförmige und ruhige Badbewegung,
• reibungsarmes und gleichförmiges Schrumpfen der Strangschale über die Brammenbreite,
• Gießen von unterschiedlichen Brammenbreiten mit einer Kokille (großer Verstellbereich),
• Einstellen von unterschiedlichen konischen Anstellungen der Schmalseiten durch Steuerung, aber auch Regelung.

The object of the invention is to find a mold that with respect to a defined immersion nozzle

• the casting performance
• the inner and outer form,
• the flow cross-sections,
• the outlet openings in size and arrangement and
• Wall thickness (maximum casting time, number of melts in sequence casting)

meets the following requirements:

• uniform slag formation across the slab width,
• uniform and calm bath movement,
• low-friction and uniform shrinking of the strand shell across the slab width,
• Casting of different slab widths with a mold (large adjustment range),
• Setting of different conical positions of the narrow sides by control, but also regulation.

The object is achieved by the features of claim 1 The task is independent of the mold type, e.g. the vertical, vertical turn or circular arc mold. Define the dependent claims Developments of the device according to claim 1.

Foundry experience has shown that breakthrough-safe casting and Sequence casting over a desired long casting time of e.g. 24 hours maximum and a casting speed of maximum 10 m / min for the production of error-free The surface of the mold in connection with the mold Interpretation / design (shape) of the immersion nozzle for the desired casting performance is essential.

Fig. 1

Draufsicht der Trichterkokille mit zwei Tauchausgußvarianten,

Fig. 2

Seitenansicht der Trichterkokille mit drei unterschiedlichen Trichterformen,

Fig. 3

Draufsicht der Trichterkokille am Kokillenaustritt mit zwei Austrittsformen,

Fig. 4

Seitenansicht der Trichterkokille mit drei unterschiedlichen Trichterformen und zwei Tauchausgußvarianten.

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

Fig. 1

Top view of the funnel mold with two immersion pouring variants,

Fig. 2

Side view of the funnel mold with three different funnel shapes,

Fig. 3

Top view of the funnel mold at the mold outlet with two exit forms,

Fig. 4

Side view of the funnel mold with three different funnel shapes and two immersion pouring variants.

The wide mold sides 1 have a concave, symmetrical to the central axis 2 linear or flat shape 1.1 over the entire mold height 3. This concave, linear form extends over the area of the broadside adjustment to the Edge 5.1 of the funnel 5 in the casting area 6 or on the upper edge of the mold 7. This concave and flat opening of the mold 1.2, which corresponds to a diamond, should compared to the rectangular mold, a maximum of about 4% of the thickness of the narrow sides 1.3 or casting thickness in the narrow side area.

In order to ensure an optimal width adjustment and conicity control, should the broad sides 1 hydraulically position and force controlled on the narrow sides 1.3 be brought up.

The shape 5.2 of the funnel 5 in the mold level corresponds to the shape 8.1 of the Immersion spout 8 and has an opening 5.3 of preferably 140% of the half Immersion nozzle thickness 8.2 or 70% of the immersion nozzle thickness 8.2.1.

The immersion nozzle itself, due to the desired maximum pouring time (sequence pouring of, for example, 24 hours) and the pouring performance in t / min of, for example, 5 t / min and the associated optimal flow speed of, for example, 1 m / sec at the immersion nozzle openings 8.3 with the Opening cross section 8.3.1, has a desired inner flow cross section 8.4 of, for example, 9,000 mm ² , a desired immersion spout wall thickness 8.5 of, for example, 30 mm and an opening cross section 8.3.1 of, for example, 7,000 mm ² .

The immersion mold, essentially determined by the casting performance and the maximum desired casting time, determines the shape of the funnel 5 both in Casting level area 6 as well as below the casting level. Preferably the Opening of the funnel 5.3 in the area of the mold level about half Immersion nozzle thickness 8.2 and the funnel width 5.4 approx. The immersion nozzle width 8.6 correspond to the casting powder 9 to a uniform slag thickness 10 the bath level and thus to a uniform slag film 11 between the To build the strand shell and the mold broadside 1. The maximum should be the opening 70% of the total immersion pouring thickness of the funnel in the area of the mold level on each broad side 8.2.1, since the specific thermal conductivity of the Refractory material (based on alumina graphite) at approx. 7 - 10 W / ° K. m compared to steel of approx. 50, slag of approx. 1 and Cu of approx. 360 W / ° K and this is relative low conductivity for strong hypothermia, especially in the case a rectangular mold. The opening of the mold through a funnel acts on it Hypothermia between immersion nozzle 8 and mold wall 1, due to the low conductivity of the immersion pouring material, counteracts and compensates them in In the case of a funnel opening 5.3> 50% of the dip tube thickness.

This is the concave, linear and flat broadside shape in the middle of the broad sides superimposed funnel shape 5.2 in the area 4 can alternatively over three Species are withdrawn that are essentially from the immersion mold 5.2 below the bath level.

The return of the funnel to the concave, flat broadside form 1.1 is done by the envelope 13 described. So the funnel can over part of the mold height 13.1 - preferably 75% - with a total mold height 3 of e.g. 1,200 mm be withdrawn. It is also the case with shorter molds or sensitive ones Steel grades possible to take back the funnel shape more gently.

This can be realized in that the envelope curve 13.2 over the entire Mold height 3 or even extends beyond mold exit 14, i.e. that at the mold exit a residual funnel 15 is the concave, linear Broad side shape 1.1 superimposed symmetrically.

If the funnel 5 is withdrawn, the strand can be within the mold height 3 via the envelopes 13.1 or 13.2 with its convex, center-symmetrical 1.1, linear cross-sectional shape up to the end of the strand guide 16 or into the rolling mill be performed, or it is in the strand guide 16 on a rectangular format molded.

In the case of a convex strand format at the mold exit 4, the one Has residual crowning corresponding to the residual funnel 15, the format can to the point Preserved end of strand guidance, partially preserved or even on one rectangular shape.

• der Strömung,
• der Badbewegung,
• der Schlackenführung,
• des Wärmestromes und
• des Schrumpfverhaltens

zu einer Zentrierung des Stranges in der Kokille und in der Strangführung und mit zu einer hohen Gießsicherheit (Vermeidung von Durchbrüchen) bei und dies besonders bei hohen Gießgeschwindigkeiten von bis zu 10 m/min.In addition to the optimized conditions, this type of mold according to the invention with its specific funnel shape also helps

• the current,
• the bath movement,
• the slag guide,
• of the heat flow and
• of shrinkage behavior

centering of the strand in the mold and in the strand guide and with a high casting reliability (avoidance of breakthroughs), especially at high casting speeds of up to 10 m / min.

• Das Merkmal 'konkave lineare und plane Breitseitenform' führt zu
  • reibungsarmem Schrumpfen des Strangschale in horizontaler Richtung,
  • maximalem Breitenverstellbereich durch minimale Trichterform unabhängig von der gesamten Strangbreite (z.B. 500 - 2.000 mm).
  • Breitenverstellung auch während des Gießens,
  • Konizitätssteuerung oder Regelung der Schmalseiten während des Gießens,
  • längsrißfreie Brammenoberflächen.
• Das Merkmal 'Trichter' führt zu
  • freier Wahl der Tauchausgußform hinsichtlich
    • maximaler Gießleistung, t/min
    • Strömungsgeschwindigkeiten m/s durch
      • Strömungsquerschnitte im Tauchausguß und an den Tauchausgußöffnungen
    • maximaler Gießzeit/Sequenzguß (z.B. 24 h) durch freie Wahl der Tauchausgußwandstärke (30 mm bei 1 mm/h Schlackenverschleiß),
  • gleichförmiger Badspiegelbewegung, Unterdrückung von Turbulenzen,
  • gleichförmigem Temperaturgradienten im Badspiegel von Kokillenmitte zur Strangschale über die gesamte Kokillenbreite,
  • keiner Gefahr der Brückenbildung zwischen Strangschale und Tauchausgußwand,
  • gleichförmigem Schmelzen von Schlacke über die Breite des Badspiegels,
  • gleichförmiger Ausbildung des Schlackenfilms zwischen Strangschale und den Breitseiten-Kokillenplatten,
  • gleichförmiger Wärmestromdichte über die Kokillenbreite,
  • gleichförmigem Schrumpfverhalten der Strangschale über die Kokillenbreite, vor allem in horizontaler Richtung,
  • guter und rißfreier Brammenoberfläche selbst bei längsrißempfindlichen Stahlgüten wie z.B. peritektischen Stählen,
  • Zentrierung des Stranges in der Kokille und der Strangführung,
  • hoher Gießsicherheit oder geringste Durchbruchsraten,
  • Möglichkeit der Erzeugung einer konkaven, mittensymmetrischen Bramme.

These very complex processes when casting thin slabs and slabs, especially at high casting speeds, are taken into account by the features described in the patent claims. Compared to the prior art, the invention leads to the following feature-specific advantages both in thin slab casting and in slab casting, such as:

• The characteristic 'concave linear and flat broadside shape' leads to
  • low-friction shrinkage of the strand shell in the horizontal direction,
  • Maximum width adjustment range thanks to the minimal funnel shape, regardless of the total strand width (e.g. 500 - 2,000 mm)
  • Width adjustment also during casting,
  • Conicity control or regulation of the narrow sides during casting,
  • slab surfaces without longitudinal cracks.
• The feature 'funnel' leads to
  • free choice of diving mold with regard to
    • maximum casting performance, t / min
    • Flow velocities m / s through
      • Flow cross sections in the immersion nozzle and at the immersion nozzle openings
    • maximum casting time / sequence casting (e.g. 24 h) through free choice of immersion pouring wall thickness (30 mm at 1 mm / h slag wear),
  • uniform bath level movement, suppression of turbulence,
  • uniform temperature gradient in the bath level from the center of the mold to the strand shell over the entire width of the mold,
  • no danger of bridging between strand shell and immersion pouring wall,
  • uniform melting of slag across the width of the bath level,
  • uniform formation of the slag film between the strand shell and the broadside mold plates,
  • uniform heat flow density across the mold width,
  • uniform shrinkage behavior of the strand shell across the mold width, especially in the horizontal direction,
  • good and crack-free slab surface, even with steel grades sensitive to longitudinal cracks such as peritectic steels,
  • Centering of the strand in the mold and the strand guide,
  • high casting reliability or lowest breakthrough rates,
  • Possibility of producing a concave, symmetrical slab.

Reference list

1

Broadside mold plates

1.1

concave, center-symmetrical, linear and flat broadside shape

1.2

Opening of the concave, linear and flat broadside shape

1.3

Narrow side

2nd

Center axes in the casting direction

2.1

Center axis in the casting direction, parallel to the broadside

2.2

Center axis in the casting direction, perpendicular to the broad sides

3rd

Mold height

4th

Area of broadside adjustment

5

funnel

5.1

Transition between concave, linear broadside and Funnel shape

5.2

Funnel shape

5.3

Opening of the funnel in the area of the mold level

5.4

Funnel width in the mold level

6

Casting level

7

Upper edge of the mold

8th

Diving spout

8.1

Immersion mold

8.2

half immersion pouring thickness

8.2.1

Immersion pouring thickness

8.3

Diving spout openings

8.3.1

Opening cross-section

8.4

inner flow cross-section

8.5

Immersion pouring wall thickness

8.6

Immersion spout width

9

Pouring powder layer on the bathroom mirror

10th

Slag thickness on the bathroom mirror

11

Slag film between strand shell and broadside mold plates

12th

Strand shell

13

Envelopes between funnel 5 and opening of the concave, plan broadside form 1.2

13.1

Envelope curve, withdrawal over part of the mold height 3

13.2

Envelope curve, withdrawal over the entire mold height 3

13.3

Envelope, residual funnel at the mold exit

14

Mold exit

15

Shape of the residual funnel at the mold exit

16

Strand guide

Claims (8)

1. Oscillating chill mould for continuous casting of slabs, preferably of steel, with an immersion spout (8) having an inner flow cross-section (8.4), a wall thickness (8.5), an outlet cross-section (8.3.1) and an outer cross-sectional format (8.1) with a width (8.6) and thickness (8.2.1) with wide sides (1) which define a pouring gate (5), which corresponds with the outer cross-sectional shape (8.1) of the immersion spout (8) at least at the region of the casting surface (6) and which is at least partly drawn back in the direction of the chill mould outlet and with freely movable narrow sides (1.3),
   characterised by
   a shape (1.1), which is linear and, planarly over the chill mould length, concave symmetrically with respect to the centre, of the wide sides (1.1), with a maximum opening (1,2) of 4% of the thickness of the narrow sides (1.3), wherein the pouring gate (5) is mounted symmetrically with respect to the centre in the wide sides and wherein the gate shape (5.2) is so selected that said gate shape follows not only at the region of the casting surface (6) but also below of the casting surface the outer shape (8.1) of the immersion spout, wherein the opening (5.3) of the gate in the region of the casting surface (6) constitutes at each wide side at most 70% of the thickness (8.2.1) of the immersion spout or at most 140% of half the thickness (8.2) of the immersion spout.
2. Chill method according to claim 1, characterised in that the gate shape (5.2) in the chill mould is fully drawn back in such a manner that the body curves (13.1, 13.2) thereof end in the wide sides (1) above the chill mould outlet (14) or at the chill mould outlet (14) and the chill mould has a concave, linear shape (1.1) at the chill mould outlet (14).
3. Chill mould according to claim 1, characterised in that the gate shape (5.2) in the chill mould is in part (13.3) drawn back as far as the chill mould outlet (14) in such a manner that the body curve (13.3) thereof has a residual gate (15) and the chill mould has at the chill mould outlet (14), apart from the concave, linear shape (1.1), also a spherical form which is symmetrical with respect to the centre and corresponds with the residual gate shape (15).
4. Chill mould according to at least one of claims 1 to 3, characterised in that the pouring gate (5) in the chill mould has a minimum width (5.4) of 500 mm.
5. Chill mould according to at least one of claims 1 to 4, characterised in that the immersion spout (8) has an inner flow cross-section (8.4) with up to 20,000 mm², preferably about 9,000 mm², an immersion spout wall thickness (8.5) of 20 mm to 40 mm, preferably 30 mm, and an overall opening cross-section (8.3.1) with up to 15,000 mm², preferably about 7,000 mm², at the outlet of the immersion spout.
6. Chill mould according to at least one of claims 1 to 5, characterised in that the opening or openings (8.3) of the immersion spout are optimised in cross-section with respect to the predeterminable casting performance in such a manner that a flow speed of up to 2 m/sec, preferably about 1 m/sec, prevails at the opening or openings (8.3).
7. Chill mould according to at least one of claims 1 to 6, characterised in that the narrow sides (1.3) and thus the strip width adjustment range are designed to be movable to a minimum to the transition (5.1) between the concave, linear wide sides and the pouring gate (5).
8. Chill mould according to at least one of claims 1 to 7, characterised in that the wide sides (1) of the chill mould are designed to be movable against the narrow sides (1.3) in hydraulically position-regulated force-regulated manner.

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