EP2418032B1 - Flame-retardant ceramic impact absorber - Google Patents

Description

The invention relates to a refractory ceramic baffle pot.

A generic baffle is known for example from the following publications: DE 102 35 867 B3 . DE 102 02 537 C1 . US 5,358,551 . US 2004/0070123 A1 ,

In all cases, it is a matter of reducing turbulence in a metallurgical vessel that results when a molten metal hits a solid surface. This is the case, for example, when a molten metal from a ladle with a ferrostatic height of several meters strikes the bottom of a distributor (tundish).

The baffle according to US 5,358,551 has a classic pot shape, in which the upper free end portion of the wall is deflected inwards. The molten metal flows after hitting the bottom of the baffle first along the bottom, then up along the inside of the wall, and finally around the tapered baffle opening up into the tundish.

In the variant according to DE 102 35 867 B3 the baffle is formed at its upper open end with a so-called diffuser, that is, the cross section of the baffle becomes larger towards the upper outlet end to reduce the kinetic energy of the outflowing melt.

The proposal according to DE 102 02 537 C1 provides a baffle whose wall has at least one slot extending continuously from the edge (the upper free end of the wall) to the bottom, the slot width at the widest point being less than 10% of the widthwise dimension of the Floor plan should be.

The baffle according to US 2004/0070123 A1 has an inwardly broadened, protruded upper edge to redirect the flow of molten metal.

Usually baffles have a circular or rectangular base. Accordingly, the wall is endless or it consists of four wall sections. The base (the floor plan) may also be different, for example, oval or egg-shaped. According to the invention, it is particularly assumed that baffle pots are formed with mirror image (mirror-symmetrical) with respect to a vertical plane.

The following information relates in each case to a normal functional position of the impact pot (functional position), in which the bottom of the baffle is on or in a bottom of a metallurgical vessel and the wall of the baffle substantially perpendicular to the ground and thus substantially perpendicular from the bottom of the metallurgical Vessel extends upwards.

The baffle according to DE 102 02 537 C1 causes molten metal that enters the baffle, at least partially flows laterally through the wall-side slot. Due to the relatively small slot width, the melt flowing through the slot can have a considerable flow velocity. This causes additional flow turbulence.

The essay " Melt Flow Characterization in Continuous Casting Tundishes "(ISIJ International, Vol. 36 (1996), No. 6, pp. 667-672) ) defines a so-called plug flow, in which all fluid elements have the same residence time (residence time) in the tundish and a so-called dead volume. The dead volume characterizes the proportion of fluid whose residence time is more than twice the average residence time of the melt in the tundish.

These characterizations are phenomenologically transferred below to the flow of a molten metal in a tundish in which an impact pad (impact pot) according to the invention is integrated.

• gezielte Führung der Metallschmelze im Pralltopf und Tundish
• Minimierung von Strömungsturbulenzen im Tundish
• geringer Verschleiß des Pralltopfes
• hoher Fluidanteil mit Pfropfenströmung im Tundish
• kleines Totvolumen im Tundish
• günstige Herstellungskosten des Pralltopfes.

The object of the invention is to provide a baffle pot, which allows the following optimizations:

• targeted guidance of the molten metal in the baffle and tundish
• Minimization of tundish flow turbulence
• low wear of the baffle
• high fluid content with plug flow in the tundish
• small dead volume in the tundish
• favorable production costs of the baffle pot.

• das Strömungsverhalten der Schmelze nach Auftreffen auf dem Boden des Pralltopfes,
• der Strömungsverlauf der Schmelze im Pralltopf
• das Strömungsverhalten der Schmelze beim Verlassen des Pralltopfes,
• das Strömungsverhalten der Schmelze nach Verlassen des Pralltopfes im Schmelzbad des zugehörigen metallurgischen Gefäßes.

In order to create a baffle that meets as many of these requirements as possible, extensive experiments and investigations were carried out, especially with regard to an improved flow behavior of the molten metal. It was examined:

• the flow behavior of the melt after hitting the bottom of the baffle,
• the flow of the melt in the baffle
• the flow behavior of the melt when leaving the baffle,
• the flow behavior of the melt after leaving the baffle in the molten bath of the associated metallurgical vessel.

It has been found that the known impact pot geometries are in need of improvement, in particular with regard to the flow behavior of the melt when leaving the baffle pot and during subsequent entry into the molten bath of the associated metallurgical vessel.

It is advantageous if a portion of the melt in a volume flow of relatively large cross-sectional area is discharged laterally from the impact pot. The flow direction is substantially horizontal or at an angle <70 °, in particular <45 ° to the horizontal. It has also been found to be favorable to make the baffle so that the laterally exiting flow widens upwards (toward the free upper end portion of the baffle).

As a result, this resulted in a baffle geometry in which the baffle wall has at least one opening (for example a slot) with a specific cross-sectional profile. Viewed from the bottom of the baffle up to the free end portion of the wall, the width of the opening increases (in the circumferential direction of the baffle), that is, in a slit-shaped opening, the distance of the flanks which limit the slot laterally increases.

In this way, a relatively wide volume flow with relatively low flow velocity in the upper portion of the impact pot laterally led out of the baffle. Analogously, the volume flow, which exits laterally in the vicinity of the baffle bottom, is narrower and has a greater flow velocity. This flow profile reduces turbulence on entry into the molten metal in the metallurgical vessel.

This leads to a lower erosion of the refractory material of the baffle, in particular in the region of the flanks (boundaries) of the opening. Accordingly, less impurities (impurities) enter the molten metal in the tundish.

Another part of the volume flow leaves the baffle - as known - upwards.

The specific geometry of the orifice and the resulting specific melt flow laterally through the orifice in the baffle wall also result in the desired reduction in dead volume in the tundish and in a higher proportion of plug flow, as shown in the table below: dead volume plug flow Impact pot with closed wall analog US 5358551 28% 24% Impact pot with narrow, straight slot analog DE 10202537 C1 28% 26% Baffle according to claim 1 and Fig. 4 24% 30%

The formation of openings with a relatively large cross-section in the wall region of the baffle means that less refractory material must be used. This reduces the manufacturing costs.

In its most general embodiment, the invention relates to a refractory ceramic baffle with the features of the main claim.

In the side view results for the opening regularly a geometry in which the distance between flanks of the opening above is significantly larger than below. Possible cross-sectional profiles are shown and explained in the following description of the figures.

The opening can pass upwards, so that the free end of the wall is interrupted. However, the opening can also run as a discrete opening in the wall and be surrounded on all sides by wall sections. In the interests of optimized flow and flow distribution, cross-sectional profiles are preferred, which are mirror-symmetrical to a plane that projects perpendicularly from the inside of the wall, in other words: the plane of symmetry extends radially in a baffle with a circular floor plan (bottom), whose wall is a cylindrical peripheral surface having.

The flow is optimized when the opening has curved flanks, in particular between the sections of greatest width and smallest width. In the side view, this results in a profile of the opening similar to a funnel or a nozzle.

Further embodiments provide that the opening in the region between the largest width and the smallest width with respect to a central longitudinal axis of the opening has convexly or concavely curved flanks. This means that the width of the opening decreases steadily between the sections of greatest width and smallest width.

The opening ends according to one embodiment at a distance from the ground. It follows that within the baffle a bottom sump is formed, in which there is regularly molten metal during the casting process.

The opening extends over more than 40% of the height of the wall.

The flow pattern is optimized when the opening extends over a greater part of the height of the wall, for example more than 50%, more than 60% or more than 70%. The area of the baffle wall without lateral opening can be at least 20% of the height of the wall, calculated from the ground. This corresponds to a maximum extension of the opening over 80% of the height of the wall, calculated from its upper end.

In order to specifically guide the melt from the interior of the baffle to the opening, an embodiment of the invention provides for forming the inside of the wall, between the baffle surface of the base and the opening, with an inclination <90 ° to the horizontal. The result is a kind of "ramp" along which the melt, after being hit on the baffle, is led away not only laterally, but laterally upwards, specifically to the corresponding opening. This embodiment is also shown in more detail in the following description of the figures.

The latter embodiment requires that the opening ends at a distance from the bottom of the baffle pot.

The opening can also extend from the free end to the floor. This corresponds in principle to the embodiment according to FIG DE 102 02 537 C1 , The crucial difference to the known baffle is that the slot (the opening) in the wall of the baffle pot according to the invention is significantly larger and is characterized in particular by the fact that the cross section of the opening in the direction of the upper edge (the free edge) of Wall significantly enlarged.

The largest width of the opening is according to the invention more than 5% of the total circumference of the wall of the baffle pot. For a baffle with square base and corresponding four equal wall sections, this means that the largest width of the opening is more than 20% of the width of the corresponding wall section. This value also applies according to the invention for baffles with a rectangular plan, with the proviso that the value of the opening width refers to each of the wall portion in which the opening is located.

For baffles with a circular bottom and a correspondingly cylindrical wall surface, the following applies: the greatest width of the opening is more than 5% of the total circumference of the wall of the baffle. Dividing the wall into four equal sections, the value for the largest width of the opening, relative to each section, is again more than 20%.

This applies analogously to embodiments of baffles with an oval floor plan.

For other geometric shapes, in addition to the requirement that the largest width of the opening should be more than 5% of the total circumference of the wall, the following additional condition applies: the maximum width of the opening must be more than 20% of a quarter of the total circumference of the wall. The largest width is meaningfully limited to 25% of the total circumference of the baffle wall.

The smallest width of the opening (at the end of the opening / slot adjacent to the baffle bottom) is, for example, <4%, <2.5%, <1.5%, <1.0% of the total perimeter of the wall, and may also be, for example, with a V-shape of the slot, go to zero. The maximum value makes sense a maximum of 5%.

• für die größte Breite: > 100mm, > 150 mm, > 200 mm, > 250 mm, > 300 mm,
• für die kleinste Breite < 100 mm, < 75 mm, < 50 mm, < 25 mm, < 10mm.

Concrete values are exemplary:

• for the largest width:>100mm,> 150 mm,> 200 mm,> 250 mm,> 300 mm,
• for the smallest width <100 mm, <75 mm, <50 mm, <25 mm, <10 mm.

According to one embodiment of the invention, corresponding flanks of the opening are arranged between an inner side of the wall and a corresponding outer side of the wall with increasing distance. This creates a kind of "diffuser" with the result that the cross-sectional area of the opening between the inside and outside of the wall of the baffle pot increases (widens fan-shaped). In this way, a balloon-like volume flow is fed into the metal bath of the metallurgical vessel, which leads to a reduction of the turbulence in the metallurgical vessel.

In this embodiment, the flanks may be bowed to the outside environment, thereby assisting the effect.

Other features of the invention will become apparent from the features of the claims and the other application documents. The features mentioned may be essential individually or in any combination for the realization of the invention. Unless expressly excluded, features of individual embodiments, as far as technically possible in principle, combine with each other.

Figur 1:

eine perspektivische Ansicht eines Pralltopfes

Figur 2:

mögliche Querschnittsformen der Öffnung in der Wand des Pralltopfes

Figur 3:

eine perspektivische Ansicht einer weiteren Ausführungsform eines Pralltopfes

Figur 4:

eine Aufsicht, einen Längsschnitt sowie eine Seitenansicht einer dritten Ausführungsform des Pralltopfes.

The figures show, in each case in a schematic representation:

FIG. 1:

a perspective view of a baffle pot

FIG. 2:

possible cross-sectional shapes of the opening in the wall of the baffle pot

FIG. 3:

a perspective view of another embodiment of a baffle pot

FIG. 4:

a plan view, a longitudinal section and a side view of a third embodiment of the baffle pot.

The baffle according to FIG. 1 is constructed as follows: It has a rectangular bottom 10 with a lower base 10g and an upper baffle 10p. From the edge region of the bottom 10 extends a wall 20, which correspondingly comprises four wall sections 20a, 20b, 20c and 20d.

The wall 20 with its inner side 20i and the baffle 10p delimit a space 30 which is open towards the top, ie opposite the floor.

The free end 20k of the wall sections 20a to 20d is drawn inwardly, so that a corresponding undercut 20h results between the vertical regions of the wall sections 20a to 20d and the free end 20k (end section).

In the wall portion 20a, an opening 40 is formed, which extends from the free end 20k to over half the height H of the wall portion 20a. The vertical height h of the opening 40 corresponds to about 0.6 H. The opening has its greatest width Bg at its upper end and its smallest width Bk at the lower end. In between, the flanks 40f of the opening 40 are mirror-inverted relative to each other with respect to a central longitudinal axis M-M of the opening 40, resulting in a continuously decreasing cross-sectional geometry from the upper end to the lower end of the opening. The flanks 40f extend 90 ° to the inner side 20i of the wall 20.

The largest width Bg of the opening 40 is about 35% of the mean length L of the associated wall portion 20a and accordingly about 9% of the total circumference of the wall 20. The molten metal flowing into the baffle pot (indicated schematically by the arrow S) strikes the baffle surface first 10p and then spreads along the baffle 10p before going up along the inner side 20i of the wall 20. While the melt in the region of the wall sections 20b, 20c and 20d is subsequently deflected in the region of the undercut-formed free end 20k and led out of the baffle upwards (the same applies to the melt which flows along the wall 20a adjacent to the opening 40) , The flow rate is reduced analogously with increasing width of the opening 40. The flow direction is at the narrow end of the opening 40 largely horizontal, obliquely directed upward at the upper, wide end. In this way, an advantageous supply of the melt from the impact pot in the associated metallurgical vessel or in the melt located there.

FIG. 2 shows some possible cross-sectional shapes of the wall opening 40. Number 1 is similar to the example in FIG FIG. 1 formed, but the opening passes down to the bottom area. Variation No. 2 approximates the cross-sectional profile of a funnel. In No. 3, the flanks of the opening are bowl-shaped. The opening according to No. 4 is completely formed in the wall 20 and otherwise corresponds to the upper part according to No. 2. In No. 5, the flanks are not curved, but designed step-like. The cross-sectional geometry according to No. 6 is similar to that of a calyx.

The embodiment according to FIG. 3 differs from the according to FIG. 1 in that the opening 40 extends to the bottom 10, that is to say to the baffle surface 10p, and is formed in its lower portion in the manner of a slot with a constant width Bk. Another difference to the embodiment according to FIG. 1 is that the flanks 40f open to the outside 20s of the wall 20a, whereby an additional diffuser effect is achieved in the outflow of molten metal from the baffle.

According to the embodiment FIG. 4 There is a significant difference to the other illustrated embodiments is that the inner side 20i of the wall 20a at an angle α of about 45 ° (to the horizontal) of the baffle surface 10p in the direction of the opening 40 increases, creating a kind of ramp for the molten metal is formed towards the opening 40. The opening 40 ends, as the side view shows, similar to the embodiment according to FIG. 1 at a distance from the baffle 10p and points, similar to at FIG. 3 , a diffuser area on.

For all variants:

The baffle consists of a refractory ceramic material, for example based on magnesia, magnesia chromite, bauxite, A1 ₂ O ₃ or mixtures thereof.

Conveniently baffle pots, in which the upper free end portion of the wall (wall parts) is widened inwardly, so that the upward emerging from the baffle melt is redirected to the inside.

The base of the baffle pot is virtually arbitrary. Impact pots with circular bottom and cylindrical wall and baffle pots with rectangular, in particular square bottom and corresponding four, at right angles to each other extending wall sections, however, are clearly preferred in terms of production and flow behavior.

In each baffle at least one opening of the type described is formed on the wall side. In particular with baffles having a rectangular cross section, analogous openings can be formed in opposite wall sections.

Each aperture is significantly narrower in its portion adjacent the bottom than at its portion adjacent to the top edge (the upper edge) of the baffle wall. This results regularly in the side view, a cross-sectional profile, in which the width of the opening decreases from top to bottom. Only then can the desired volume flow be led away laterally and achieve the desired distribution of the flow velocity.

It is also essential that at least 70% of the total cross section of each opening run in a section defining the upper half of the wall, viewed in the vertical direction.

In all cases, this results for the outflowing molten metal, that the melt flow in the area of the opening becomes wider from bottom to top and above has a lower flow velocity than below. The flow direction can be adjusted by appropriate design of the flanks of the opening, in particular in the sense to guide the flow so that the cross-section of the volume flow increases with increasing distance from the baffle.

Claims (12)

1. Fireproof ceramic impact pad with the following features in its functional position:

   1.1 a bottom (10) with a lower base area (lOg) and an upper impact surface (10p),

   1.2 a wall consisting of multiple segments (20a-d), which extends from the bottom (10) up to a free end (20k), wherein the wall (20) with its inside (20i) and the impact area (10p) together border a space (30), which is open at its end opposite the bottom (10), 1.3 at least one segment (20a) of the wall (20) features at least one opening (40), which runs from the inside (20i) of the wall continuously to the outside (20s) of the wall (20) and which is bordered by opposite flanks (40f),

   1.4 the opening (40) features the following cross-sectional profile:

   1.4.1 regarding the perimeter direction of the wall (20) the opening (40) has its largest width (Bg) adjacent to the free end segment (20a),

   1.4.2 regarding the perimeter direction of the wall (20) the opening (40) has its smallest width (Bk) adjacent to the bottom (10),

   1.4.3 the opening (40) extends along more than 40% of the height (H) of the wall (40)

   characterized by the following further features:

   1.4.4 the largest width (Bg) of the opening (40) is more than 5% of the total perimeter of the wall (20) of the impact pad,

   1.4.5 in a longitudinal direction, from the upper free end segment (20k) of the wall (20) vertically downwards toward the bottom, the opening (40) extends in a profile with more than 70% of its cross-section in the upper half , adjacent to the free end segment (20k) of the wall (20).
2. Impact pad according to claim 1, wherein the opening (40) features curved flanks (40f) in an area between the largest width (Bg) and the smallest width (Bk).
3. Impact pad according to claim 1, wherein the opening (40) features curved flanks in relation to a central longitudinal axis of the opening (40) in the area between the largest width (Bg) and the smallest width (Bk).
4. Impact pad according to claim 1, wherein the opening (40) ends with a distance to the bottom (10).
5. Impact pad according to claim 4, wherein the inside (20i) of the wall (20), between the impact area (10p) of the bottom (10) and the opening (40), extends with a slope of < 90 degrees to the horizontal.
6. Impact pad according to claim 4, wherein the opening (40) extends over at most 90% of the height (H) of the wall (20).
7. Impact pad according to claim 1, wherein the opening (40) extends from the free end (20k) down to the bottom (10).
8. Impact pad according to claim 1, wherein corresponding flanks (40f) of the opening (40) are arranged with increasing distance between the inside (20i) of the wall (20) and a corresponding outside (20s) of the wall 40).
9. Impact pad according to claim 8, wherein the corresponding flanks (40f) of the opening (40) are curved in a direction towards the surrounding between an inside (20i) of the wall (20) and the corresponding outside (20s) of the wall (20).
10. Impact pad according to claim 1 with four segments (20 a-d) of the wall (20), wherein neighbouring segments (20a-20b, 20b-20c, 20c-20d, 20d-20a) are substantially arranged at a right angle to each other.
11. Impact pad according to claim 1, wherein the opening (40) is arranged mirror-inverted to a plane, which sticks out vertically from the inside (20i) of the wall (20).
12. Impact pad according to claim 1, wherein the upper free end (20k) of the wall (20) is widened towards the inside.

Images