AU2410299A

AU2410299A - Device for feeding molten metal

Info

Publication number: AU2410299A
Application number: AU24102/99A
Authority: AU
Inventors: Gerhard Bocher; Peter Muller; Wolfgang Reichelt; Ulrich Urlau
Original assignee: Salzgitter AG; SMS Demag AG
Current assignee: Salzgitter AG; SMS Siemag AG
Priority date: 1997-12-19
Filing date: 1998-12-14
Publication date: 1999-07-12
Anticipated expiration: 2018-12-14
Also published as: BR9813755A; DE59802177D1; CA2314076A1; ATE208671T1; EP1042087B1; ES2167963T3; JP2001526119A; AU744237B2; DE19758142A1; CN1098738C; CN1282279A; WO1999032248A1; EP1042087A1; KR20010033170A

Abstract

The invention relates to a device for feeding molten metal, especially liquid steel, through submerged casting tubes of an intermediate tank in a stationary permanent mold of a continuos slab casting installation. The intermediate tank (21) is configured as a casting chamber (22) fitted with a vacuum pump (27), said casting chamber being connected to a main chamber (23) into which the molten mass (S) is fed from the outside. The floor (24) of the casting chamber (22) is fitted with at least three adjacent submerged casting tubes (31-3n).

Description

72292 Device for feeding molten metal Description The invention relates to a device for feeding molten metal, in particular liquid steel, via submerged casting tubes in a tundish, into a stationary permanent mold of a continuous slab casting installation. DE 39 29 767 Al has disclosed a casting system for a steel-strip casting installation, in which two casting tubes are provided at a predetermined axial distance on a tundish. The main outlet openings from the casting tubes are arranged laterally opposite one another. The relatively large casting tubes, which require a widened casting-in area of the permanent mold, represent a drawback of this casting system. DE-A 24 28 060 has disclosed a continuous casting installation in which (Figure 1) steel flows continuously from a casting ladle into a tundish which has a bottom opening through which the steel flows into a refractory casting tube and, from this tube, into a-water-cooled, straight, vertically arranged, oscillating permanent mold. For extremely wide permanent molds, two casting tubes are used (Figure 5). Above the bottom opening, a refractory tube RA[/ an be moved to a distance from the top edge of the bottom

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-2 opening, and inert gas can be fed into the casting stream via this tube. The large geodetic height above the opening of the submerged casting tube and therefore the considerable kinetic energy which acts on the molten steel situated in the permanent mold via a casting tube or two casting tubes constitute drawbacks of this device. DE 195 12 209 has disclosed a method and a device in which molten metal, in particular steel, is passed via a submerged casting tube which is secured running out from a casting vessel into a vertically oscillating permanent mold. The cross sectional area of the submerged casting tube is not less than 0.3 times the clear internal cross section of the passage area of the permanent mold. The cross-sectional shape of the submerged casting tube used for this purpose resembles the permanent mold, and the tube therefore has a considerably greater width than thickness. A drawback of this design of the submerged casting tube is the relatively large unsuppor ted area and, in addition, the relatively sharp edges in the area of the narrow sides with regard to the resistance to fracture of the refractory material at the desired wall thickness. Furthermore, FR 2,675,411 has disclosed a device for feeding molten steel, having a bottom vessel and a top vessel which are connected to one another via a connecting line. A vacuum device, by means of which the molten material can be -3 raised from the bottom vessel, is provided on the cover of the top vessel, and via a submerged nozzle the steel is passed into a permanent mold. This installation is connected to gas supply elements and is used substantially to treat the steel before it is passed into the permanent mold via a submerged casting tube which is not described in more detail. The object of the invention is to provide a device for feeding molten metal, in particular liquid steel, in which the molten material can be fed safely and with little kinetic energy into a permanent mold using simple, inexpensive feed elements and with a high level of operational reliability. The invention achieves this object by means of the defining features of claim 1. Advantageous refinements of the invention are given in the subclaims. According to the invention, the molten material is passed into a permanent mold via a tundish which is held under a vacuum via at least three submerged casting tubes which are arranged next to one another. Dividing the total amount of molten material which is to be fed to the permanent mold into a number of partial amounts through a plurality of submerged casting tubes makes it possible to directly influence the direction and quantity of flow in the partial streams while, at the same time, incorporating the largest possible entry cross section for the feed elements into the kuJ -4 permanent mold. A large feed cross section combined, at the same time, with a low geodetic height of the liquid level enables a desired, low kinetic energy combined with a minimal penetration depth of the molten material supplied into the permanent mold to be achieved. The use of individual submerged casting tubes and the fact that they are arranged virtually in any desired way makes it possible, at the same time, to directly influence the flow conditions, in particular to set controlled return flows of molten material even in the upper part of the permanent mold. A further advantage of the device according to the invention is the use of geometrically simple elements, such as the round shape of the submerged casting tubes or virtually round shapes or alternatively rectangular shapes with very similar length/width ratios. The submerged casting tubes may be arranged in series next to one another on one line. In a further advantageous configuration, the submerged casting tubes are arranged on two lines, the odd-numbered tubes being provided on one line and the even-numbered tubes being provided on the other line. In this case, in addition, the distance between the submerged casting tubes in the center -of the permanent mold can be changed toward the narrow sides. The diameter of the submerged casting tubes may also be varied and adapted to the particular flow conditions. Z~NTO1 -5 To influence the flow of the molten material which is supplied, it is also proposed to adapt the angle of the submerged casting tubes to the main axis of the permanent mold according to the desired conditions of flow. A further variation consists in changing the length of the individual submerged casting tubes. In one variant, the shortest sub merged casting tube is in the center of the permanent mold. To achieve completely different flow conditions, the length of the submerged casting tubes is varied in such a way that the longest submerged casting tube is arranged in the middle of the permanent mold while the shorter tubes are arranged in the vicinity of the narrow side walls. In an advantageous configuration, submerged casting tubes which are rectangular in cross section and comprise submerged casting tubes which have elements are proposed, the individual submerged casting tubes, when designed the same way, being secured in a form-fitting manner in the tundish. In functional terms, this produces a submerged nozzle with a very high width to thickness ratio, yet the individual elements, since they are virtually square, have a particularly long service life. In a further advantageous configuration, control elements which can be used to vary or even completely close the flow through the individual submerged casting tubes are provided. In this way, the amount of material which flows through can be changed in operation or, in the event of -6 defects occurring in individual submerged casting tubes, the defective tube can be closed altogether without overall operation being impaired. Furthermore, a quick-acting closure for each individual submerged casting tube is provided for emergencies. One example of the invention is portrayed in the appended drawing, in which: Figure 1 shows a plan of the overall installation Figure 2 shows an uneven number of submerged casting tubes with the longest submerged casting tube in the center Figure 3 shows an even number of submerged casting tubes with the shorter submerged casting tube in the center Figure 4 shows submerged casting tubes which diverge out ward with respect to the central axis Figure 5 shows submerge casting tubes which diverge with respect to the central axis in the central area and converge in the outer area Figure 6 shows submerged casting tubes in series on one line Figure 7 shows submerged casting tubes of different dia meters on one line Figure 8 shows submerged casting tubes on two lines "Ik.

-7 Figure 9 shows non-circular submerged casting tubes on one line with a uniform orientation Figure 10 shows non-circular submerged casting tubes with different orientations Figure 11 shows a plan view and a side view of submerged casting tubes for a bow-type continuous casting installation Figure 12 shows a submerged casting tube with a quick acting closure Figure 13 shows an intermediate chamber with blocking device for individual submerged casting tubes Figure 14 shows submerged casting tubes which are rectangu lar in cross section, secured in a form-fitting manner Figure 15 shows rectangular submerged casting tubes with a conical opening. Figure 1 shows a ladle 11, the bottom opening 12 of which can be closed off by means of a stopper 14. A submerged nozzle 13, which projects into a principal chamber 23 of a tundish 21, is attached to the ladle 11. The tundish 21 also comprises a casting chamber which is arranged at a higher level than the principal chamber and to which a vacuum pump 27 for raising the molten liquid is connected. In the floor 24 of the casting chamber 22 there are bottom openings 25, to U; C0 -8 which submerged casting tubes 31 to 3n are connected, projecting into a permanent mold 41. Figure 2 shows the casting chamber 22, on which an odd number of submerged casting tubes 31 to 35, which project into the permanent mold 41, are arranged. The central tube 33 is the longest of these submerged casting tubes 31 to 35 which are arranged in series. Unlike Figure 2, Figure 3 shows an even number of submerged casting tubes 31 to 34, of which the central tubes 32, 33 are the shortest. In Figure 4, three submerged casting tubes 31 to 33 are provided, the outer tubes of which diverge conically with respect to the center axis of the permanent mold. In Figure,5, an even number of submerged casting tubes 31 to 34 are provided, the submerged casting tubes converging with respect to one another in pairs 31, 32 and 33, 34. In Figure 6, an odd number of submerged casting tubes 31 to 33 are arranged in series on one line L 1 , the distance ai between the tubes in the present case being greater than the distance a 2 from the outer submerged casting tube 31 or 33 from the narrow side 44 of the permanent mold. In Figure 7, an even number of submerged casting tubes 31 to 34 are arranged on one line Li, the individual submerged casting tubes 31 to 34 having different diameters; in the present case, the diameter of the middle submerged ALI 7 ' -9 casting tubes 32, 33 is larger than that of the outer submerged casting tubes 31, 34. In Figure 8, an odd number of submerged casting tubes 31 to 35 is provided, and these tubes are arranged on two lines L2, L3, the odd-numbered submerged casting tubes 31, 33, 35 being arranged on line L2 and the even-numbered submerged casting tubes 32 and 34 being arranged on line L3. In the present case, the distances between the individual submerged casting tubes 31 to 35, including the distance from the narrow side 44 of the permanent mold 41, and also the diameters of the submerged casting tubes 31 to 35, are constant. In Figure 9, an odd number of submerged casting tubes 31 to 35 are provided, having a diameter which differs from the circular shape, in this case being substantially oval. The individual submerged casting tubes 31 to 35 are arranged in series on one line L1 and in this case are aligned in the same direction. In Figure 10, an even number of submerged casting tubes 31 to 34 are arranged in series on one line L2; some of these substantially oval submerged casting tubes have their longitudinal direction on the line L2 (submerged casting tubes 31, 33), while the longitudinal extent of the other submerged casting tubes 32, 33 extends perpendicular to the line L2.

UAL

- 10 Figure 11 shows an arrangement of the submerged casting tubes 31 to 35 in a curved permanent mold 42 for a bow-type continuous casting installation. The free space inside the permanent mold 42 has a thickness d, and the submerged casting tubes 31 to 35, which are arranged on the line L1, are at a distance di = 0.2 to 0.4 x d from the inner wall of the inner radius Ri of the casting installation. Figure 12 shows part of the floor 24 of the casting chamber 22, specifically the bottom opening 25 which is surrounded by a bottom block 26. A quick-acting closure 53 is provided between the bottom block 26 and a submerged casting tube 31, the slide plate 54 of which closure, in the event of an emergency, closes the bottom opening 25 by means of an actuator 55. In Figure 13 there is, in addition to Figure 1 with the intermediate chamber 21 and the casting chamber 22, as well as the principal chamber 23 and the submerged casting tubes 31 to 33 projecting into the permanent mold 41, a device for closing the bottom openings 25, which in the present case can be closed off by means of stoppers 52. In Figure 14, the floor 24 of the casting chamber 22 is designed as a slot, into which submerged casting tubes 31 to 33 are fitted in such a manner that they are connected in a form-fitting manner to one another. These submerged casting tubes have molded elements which are supported on one AL

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- 11 another, and specifically a lug 36 which corresponds to a mating support 37. The shape of the submerged casting tubes 31 to 33 is rectangular, and in the present case these tubes are substantially square in cross section, which is kept constant over the entire length. Although not illustrated, it is possible for the submerged casting tubes to be of rectangular design at the foot end, i.e. in the area of the floor 24 of the casting chamber 22, and to merge into a circular shape towards the outlet, which provides more favorable conditions with regard to the stress ratios in the wall. Figure 15 shows a slot nozzle of modular design with submerged casting tubes 31 to 33 which are rectangular in shape, with the narrow side 38 being shorter than the wide side 39 of the submerged casting tube. The individual submerged casting tubes again have lugs 36 and mating supports 37 which enable them to be connected in a form fitting manner. In the case illustrated, the clear cross section of the submerged casting tubes 31 and 32 diverges in the direction of casting, while the outer wall is rectilinear and arranged parallel to the main axis I of the permanent mold 41. Furthermore, in the present case the walls of the

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- 12 submerged casting tubes 31 to 33 are shorter in the central area of the slot nozzle than in the vicinity of the permanent mold narrow side 44. In this way, it is possible to design a robust slot nozzle of any desired width/thickness ratio and, at the same time, to influence the flow conditions at any desired point of the slot nozzle.

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Claims

1. A device for feeding molten metal, in particular liquid steel, via submerged casting tubes leading from a tundish into a stationary permanent mold of a continuous slab casting installation, wherein the tundish (21) is designed as a casting chamber (22) which is provided with a vacuum pump and is connected to a principal chamber (23), into which the molten material (S) is fed from the outside, and wherein at least three submerged casting tubes (31-3n), which are arranged next to one another, are provided in the floor (24) of the casting chamber (22).

2. The device as claimed in claim 1, wherein, in a curved permanent mold (42) of a bow-type continuous casting installation, the submerged casting tubes (31-3n) are arranged in series on a line (L1) which is at a distance (di) of di = 0.2 to 0.4 x d, where d = the distance between the permanent mold wide sides (43), from the inner wall of the inner radius (Ri) of the casting installation.

3. The device as claimed in claim 1, wherein the submerged casting tubes (31-3n) are arranged on two parallel lines (L 1 , L 2 ) in relation to the permanent mold wide sides (43). - 14 4. The device as claimed in claim 3, wherein, if there is an uneven number of submerged casting tubes (31-3n), the submerged casting tubes (31-3n) which are denoted by even and odd numbers are each arranged on a respective line (L 1 or L 2 ) 5. The device as claimed in one of the preceding claims, wherein the submerged casting tubes (31-3n) are arranged in series on at least one line (LI or L 2 ) parallel to the permanent mold wide side (43) and, starting from the main axis (I) of the permanent mold, are arranged at a distance (an) from one another and from the permanent mold narrow side (44), in such a way that as the integer number (n) increases the distance (an) decreases.

6. The device as claimed in claim 5, wherein the actual distance (a,. 1 ) between two adjacent submerged casting tubes (31-3n) is an, 1 = 0.5 to 0.8 x an.

7. The device as claimed in at least one of the preceding claims, wherein the shape of the passage cross section (A) of the submerged casting tubes (31-3n) is not circular, and wherein the corresponding narrower side (38) is assigned to the permanent mold wide sides (43), the radii (r) of the wide side to the narrow side being no less than r =Y4 d. - 15 8. The device as claimed in one of claims 1 to 6, wherein the submerged casting tubes (31-3n) are rectangular in cross section and, in the area of the tundish (21), have molded elements (33, 37) which produce a form-fitting connection to one another and to the floor (24) of the casting chamber (22).

9. The device as claimed in at least one of the preceding claims, wherein at least one submerged casting tube, (31-3n) projects into the permanent mold at an angle (a) to the permanent mold main axis (I), where a = 10 to 450.

10. The device as claimed in claim 9, wherein at least two submerged casting tubes (31, 32) project into the permanent mold (41) at an angle (a) to the permanent mold main axis (I), and wherein these submerged casting tubes (31, 32) are arranged in a plane (E) which runs parallel to the permanent mold wide sides (43).

11. The device as claimed in at least one of the preceding claims, wherein the submerged casting tubes (31-3n) have different lengths (L).

12. The device as claimed in claim 11, wherein the length (1) of the submerged casting tubes (31-3n) is shorter in the submerged casting tubes (31-3n) arranged relatively close to - 16 the narrow sides (44) of the permanent mold (41) than the length (1) of those arranged in the center.

13. The device as claimed in claim 7 or 8, wherein the submerged casting tubes (31-3n) have different passage cross sections (A).

14. The device as claimed in claim 13, wherein the passage cross sections (A 1 ) of the submerged casting tubes (31-3n) in the case of the submerged casting tubes (31-3n) arranged relatively close to the narrow sides (44) of the permanent mold (41) are smaller than the passage cross section (A 2 ) of those arranged in the center.

15. The device as claimed in one of the preceding claims, wherein control elements (51) which can be used to control the flow through the individual submerged casting tubes (31 3n) are provided.

16. The device as claimed in claim 15, wherein the control elements (51) are stoppers (52) which can be used to restrict or close the passages through the submerged casting tubes (31-3n).

17. The device as claimed in claim 1, wherein quick acting closures (53) are provided, by means of which the - 17 individual bottom openings (25) leading from the casting chamber (22) to the submerged casting tubes (31-3n) can be blocked. - 18 List of reference symbols Feed 11 ladle 12 bottom opening 13 submerged nozzle 14 stopper for submerged nozzle 15 slide Intermediate passage 21 tundish 22 casting chamber 23 principal chamber 24 casting chamber floor 25 bottom opening 26 bottom block 27 vacuum pump Submerged arrangement

31-35 submerged casting tubes 36 lug 37 mating support 38 submerged casting tube narrow side 39 submerged casting tube wide side - 19 Continuous casting installation 41 (straight) permanent mold 42 (curved) permanent mold 43 permanent mold wide side 44 permanent mold narrow side Blocking arrangement 51 control element 52 stopper for submerged casting tube 53 quick-acting closure 54 slide plate' 55 actuator A passage cross section a distance between two submerged casting tubes d distance between two permanent mold wide side walls E plane L line 1 length of submerged casting tube Ri radium (internal) of continuous casting installation r radius of submerged casting tube S molten material I permanent mold main axis