Ceramic refractory stopper

Abstract

The invention relates to a ceramic refractory stopper (a stopper device) for controlling a flow of molten metal at an outlet opening of a metallurgical vessel, such as a tundish.

Claims

1. Ceramic refractory stopper, comprising a) a rod-shaped stopper body (12) defining a central longitudinal stopper axis (A) including: b) at least one fitting (16) for connecting a gas supply line (30), and c) at least one gas channel (14) of a total length (L) within said stopper body (12), extending between an inlet section at a first end (12u) of the stopper body (12) and an outlet section in a free outer surface area (12o) at a second end of the stopper body, which second end defining a stopper head (12h), wherein d) a filling material is arranged within the gas channel (14) according to the following conditions: e) the filling material is a high temperature resistant and particulate material which is defined by solid parts and an open porosity, and arranged as a packed bed which extends along a distance (R) of the gas channel (14) being ≧25% of the total length (L) of the gas channel (14) and f) said solid parts of the high temperature resistant and particulate material infill between 10 and 90% by volume of the gas channel (14) along said respective distance (R).

2. Ceramic refractory stopper according to claim 1, wherein the gas channel (14) extends along more than 50% of its total length (L), parallel to the central longitudinal stopper axis (A).

3. Ceramic refractory stopper according to claim 1, wherein the gas channel (14) has a smaller cross-section at its part (14l) within the stopper head (12h) and the high temperature resistant and particulate material (20) is only present in the remaining part (14u, 14m) of the gas channel (14) of larger cross-section.

4. Ceramic refractory stopper according to claim 1, wherein the gas channel (14) has a cylindrical shape.

5. Ceramic refractory stopper according to claim 1, wherein said part of the gas channel (14u, 14m), filled with the high temperature resistant and particulate material, has a cross-section of >500 mm.sup.2.

6. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material (20) is selected from the group complying with at least one of the following properties: a) thermal capacity, established in accordance with EN 993-14,15 of more than 0.4 J/gK b) thermal conductivity, established in accordance with EN 993-14,15 of more than 0.04 W/mK c) temperature resistance of more than 1000° C.

7. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material is selected from the group consisting of: charcoal, oxidic refractory materials, and non-oxidic refractory materials.

8. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material (20) is provided by particles with a grain size d90 of 1-10 mm.

9. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material (20) is arranged as one continuous filling.

10. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material (20) is arranged as two or more continuous fillings (20.1, 20.2) with a clearance (14i) between the respective fillings (20.1, 20.2).

11. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material (20) is covered, as least at one of its free ends, by a high temperature resistant, gas permeable filter (22u, 22o, 22.1u, 22.2u).

12. Ceramic refractory stopper according to claim 1, wherein the solid parts of the high temperature resistant and particulate material infill between 20 and 60% by volume of the gas channel (14) along said respective distance (R).

13. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material extends along a distance (D) of the gas channel (14) being ≧50% of the total length (L) of the gas channel (14).

14. Ceramic refractory stopper according to claim 1, wherein the high temperature resistant and particulate material (20) is provided as a preparation comprising: three-dimensional shapes, granules, pellets, fibres, pyramids, cones, spheres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with respect to the attached schematic drawing, showing in:

(2) FIG. 1: A sectional view of a first embodiment of new stopper.

(3) FIG. 2: A sectional view of a second embodiment of the new stopper.

DETAILED DESCRIPTION

(4) FIG. 1 shows a longitudinal sectional view of a stopper rod 10 according to the invention in its working position. In accordance with prior art it is made of a refractory ceramic stopper body 12, shaped as a rod, comprising a substantially cylindrical main section 12m (in FIG. 1 the upper section) and a head section 12h at its lower end, typically called a stopper head.

(5) The rod-shaped stopper body 12 defines a central longitudinal stopper axis A (FIG. 2) and comprises a cylindrical gas channel 14, running within said stopper body 12, concentrically with respect to axis A, from an upper end 12u of stopper body 12 toward said stopper head 12h (thus defining an upper section 14u of cylindrical gas channel 14 of inner diameter D) and extending into said stopper head 12h and finally extending into a free outer surface area 120 of said stopper head 12h (thus defining a lower section 14l of cylindrical gas channel 14 of inner diameter d).

(6) At its upper end 12u a metallic fitting 16 is arranged around said gas channel 14 within the refractory ceramic material.

(7) Said fitting 16 comprises an inner thread for a form-fit connection to a gas supply line 30.

(8) While total length of said gas channel 14 between a free top surface 12t and its outlet opening 14o at the lower end of stopper 10 is defined as L, about 0.4 L (represented in FIG. 1 as distance R) of said gas channel are filled with a particulate charcoal, schematically illustrated by cuboids 20.

(9) The distance R, and insofar the height of the filler material 20 in the gas channel 14 is defined at its upper and lower end by a fibre filter 22o,u shaped as plates, wherein the cross section of said filter plates 22o,u is slightly larger than the said diameter D to keep the filters 22o,u (with the charcoal in between) at place (by friction).

(10) This arrangement may be compared with a cartridge and indeed one option to arrange the said particulate material within gas channel 14 is to prepare the filler material like a cartridge, which cartridge being made of a cylindrical envelope, for example made of paper and limited at its ends by said filter plates.

(11) During use the envelope may burn off, while the said filter plates 22o,u are made of ceramic fibres, which withstand the temperatures within said stopper rod during use, as the charcoal does.

(12) The example according to FIG. 1 is characterized by the following dimensions after final preparation for use (possible alternatives with typical upper and lower limitations, valid as well for other embodiments and other filler materials are stated in brackets, although data outside these ranges do fall as well under the general idea of the invention): L=1065 mm [800 to 1200 mm] D=28 mm [20 to 50 mm] d=2 mm [1 to 6 mm] particle size of filler material: d.sub.90=3.0 mm [d.sub.90=2 to 6 mm] bulk density of charcoal: 0.2 kg/m.sup.3 [0.1-0.6 kg/m.sup.3] thermal conductivity of filler material: 1 W/mK thermal capacity of filler material: 1 J/gK

(13) In a practice test with this stopper it could be proved that the desired gas flow (Argon: 9 l/min) could be maintained over the complete period of use without any distracting back-pressure or other negative effects.

(14) The embodiment according to FIG. 2 is similar to that of FIG. 1 so that only the distinguishing features are described hereinafter:

(15) Instead of one continuous column of filler material (of a length of 0.4 L according to FIG. 1) the embodiment of FIG. 2 comprises two filler section 20.1 and 20.2 (defining 2 cartridges) each roughly of about half the length (0.2 L) of that according to FIG. 1 and each with a filter plate 22.1u, 22.2u only at its lower end.

(16) Accordingly a space 14i defined by a corresponding section of the gas channel 14 is arranged between both said filler sections 20.1, 20.1 and a gas channel section 14m is defined between filter 22.2u and gas channel section 14l.

(17) Finally a particulate MgO sinter material is used instead of charcoal (according to the example of FIG. 1) and the filter is made of mineral fibres.

(18) In other words, the gas, entering the gas channel 14 at fitting 16 takes the following way toward outlet opening 14o: gas channel section 14u MgO (filler) section 20.1 filter plate 22.1u gas channel section 14i MgO (filler) section 20.2 filter plate 22.2u gas channel section 14m gas channel section 14l outlet opening 14o.

(19) The filler section(s) are responsible to achieve the following characteristics: a redirection of the gas flow an increased hot solid surface in contact with the gas a more or less uniform temperature of the treatment gas (here: Argon) within gas channel 14 no relevant condensations of treatment gas along gas channel 14 any abrasions and/or other solid impurities are collected within said filler sections and/or the adjacent filter plates and hindered to enter into gas channel section 14l of reduced diameter.