EP0292670B1 - Refractory ceramic molded body - Google Patents

Abstract

A refractory, ceramic, shaped member or nozzle. The shaped member is provided with a passage, preferably in the center. To prevent molten material that might penetrate the passage from penetrating therethrough and solidifying at such a later point, a cooling device may be provided in the passage.

Description

The invention relates to a refractory ceramic molded body according to the preamble of claim 1. Such molded bodies are generally referred to as " _flushing stones".

Flushing stones are preferably inserted into the wall or the bottom of a metallurgical melting vessel (e.g. converter, pan) and here mostly by means of a perforated brick and are used for blowing in flushing gases, in particular inert flushing gases such as argon, for melt treatment in order to optimize the quality.

Flushing stones of this type have been described many times, for example reference is made to German Offenlegungsschriften 3,531,533, 3,527,793, 3,531,534 and 3,520,783.

DE-OS 3 520 207 also describes a sink which is intended to blow gases or solids into a pan containing molten metal. The published application, which deals exclusively with the mounting of the sink in the perforated block, shows in the single figure a sink with a central, large passage channel through which gases or solids are to be blown. The embodiment shown with a particularly large passage channel cannot be used in practice because, with this size of a passage channel, molten metal would easily penetrate into the sink and destroy the device.

However, there is an urgent need to inject solids into the molten metal, especially for desulfurization. Such solids are fine lime or mixtures of fine lime and soda, but also calcium carbide (CaC ₂ ) or calcium cyanamide (CaCN ₂ ).

Known gas purging plugs, as described in summary, for example, in «Radex-Rundschau, 1987, 288», do not allow solids to be blown in, no matter how fine, because the fine porosity of such gas purging plugs quickly leads to constipation and thus inoperability would lead to the establishment. In addition, there would be a great risk of molten metal infiltration as soon as the gas pressure was reduced somewhat.

A multi-part gas purging plug is known from EP-A 87 261, a common cavity being formed between two sections arranged one above the other, in which a valve body is movably guided. The valve body is manipulated externally via a spindle. The respective valve position must therefore be set manually, which, in addition to the multi-part form, is a major disadvantage of the known device. Blockages can also occur when solids are injected.

So-called blowing or immersion lances, such as are described, for example, in German utility models 8 622 299 or 8 626 930, are largely used for blowing in solids. Both inert gases and additives of the type mentioned are introduced into the molten metal via blowing lances of this type. To do this, the blow lance with the blow head and most of its casing is immersed in the molten metal. The gas and / or the solid is injected into the molten metal via the so-called lance core, usually a steel tube that opens into the blow head with corresponding outlet openings.

The part of the blow lance immersed in the molten metal is exposed to considerable thermal and mechanical stresses, which is mentioned several times in the German utility models mentioned. If, for example, cracks reach the lance core, the blowing lance is unusable and must be replaced. The spent lance can not be used again, although a not inconsiderable portion of the sheath would be funktionsfä- hi ^g if necessary.

Numerous attempts in the past have therefore dealt with the mechanical stabilization of such blowing lances.

A particular problem is that when the lance is immersed in the liquid metal bath and during the blowing process, the displacement of the liquid results in strong oscillatory movements and thus large flexing forces which have to be absorbed without damaging the lance and in particular the refractory casing. However, this problem can practically not be dealt with in the case of a blowing lance which is freely immersed in a molten metal by means of a so-called lance stand.

The invention has for its object to provide a way for simple and safe supply of gas and / or solid in the molten metal of a metallurgical vessel, which does not lead to the known mechanical problems with blowing lances, but in which there is also no risk of clogging or a breakthrough of the molten metal can be added to the molten metal without further solids. In accordance with the invention, the aim is to be able to supply both gases and solids, if appropriate in combination, if possible via one device.

For this purpose, the invention provides a molded body according to the preamble of claim 1, in which the valve comprises a closing body which seals the passage channel in the starting position (without gas / solid passage) and which seals when a predeterminable gas and / or solid stream is reached Position can be removed and the passage channel releases.

Preferred embodiments are set out in dependent claims 2-14. In addition, the invention also consists in a method according to claim 15 for blowing solid, powdery or granular additives into a molten metal.

The invention has recognized that, for example, the channels of gas purging stones with "directed porosity" (Radex-Rundschau, loc. Cit.) Are no more sufficient for transporting solids than the pores in a gas purging plug with "non-directional porosity _" . The channel must rather be larger, for example the average diameter is 2 to 10 mm, preferably 4 to 6 mm. With such an open cross section, of course, the risk of penetration of molten metal is greater, which is now reliably prevented by the aforementioned valve formation in the flow channel.

It goes without saying that the closing body must be larger than the cross section of the passage to ensure a secure seal.

• Eine Möglichkeit besteht darin, bei der Herstellung des Formkörpers entlang des Weges des Durchlaßkanals einen, aus einem verbrennbaren Material, zum Beispiel einem Schaumkunststoff, bestehenden Körper miteinzuformen, in dem wiederum der Schließkörper enthalten ist. Dabei weist der verbrennbare Körper die Form der später auszubildenden Kammer des als Rückschlagventil gestalteten Ventils auf.

In order to be able to insert the closing body into the molded body or the valve, the invention proposes various further alternatives:

• One possibility is to co-mold a body made of a combustible material, for example a foam plastic, in the manufacture of the shaped body along the path of the through-channel, which body in turn contains the closing body. The combustible body has the shape of the chamber to be formed later of the valve designed as a check valve.

After the body has burned out, only the closing body remains as such, which preferably consists of a high-quality refractory ceramic, for example of zirconium dioxide (Zr0 ₂ ) or titanium dioxide (Ti0 ₂ ).

Another alternative is to manufacture the part of the sink that receives the check valve separately. This part can in turn consist of two parts, which together form the space of the check valve and have corresponding connection openings for the passage channel. The “block” produced separately in this way is then preferably inserted into the flushing block at the connection end and mortared there, for example.

In order to achieve a particularly secure seal, the invention proposes to design the closing body as a ball, so that, regardless of the particular orientation, a secure contact against the passage channel in the closed position is always ensured.

In order to further optimize the contact area between the closing body and the passage channel - for example when the valve chamber is designed as a separate component - this can also be produced from high-quality, highly abrasion-resistant, refractory ceramic of the type mentioned.

Safe sealing, for example in the event of an interruption in the blowing process, also ensures that a closed space is created above the valve, the gas column built up therein making it difficult for metal melt to penetrate.

Should metal melt nevertheless penetrate, the valve ensures that the metal flow is stopped in the area of the sink and the metal melt then freezes for a short time.

By additionally arranging a cooling device, it can also be achieved that molten metal penetrates only in the uppermost regions of the passage channel and freezes there immediately, which has the advantage that such a sink can be used again. Instead of changing the sink, only the upper, frozen area needs to be drilled out, and the sink is then available for further use.

The cooling device can be designed in various ways and can consist, for example, of a cooling line through which liquid or gas can flow and which is arranged directly adjacent to the passage channel.

This cooling line can, for example, be helically guided around the through-channel and thus enables intensive cooling which, during normal operation, i.e. when an inert gas and / or a preferably powdery solid is blown through the through-channel, does not disturb the operation, on the other hand immediately in the event that molten metal penetrates the channel, causing it to solidify.

The cooling line can be arranged so that it forms a closed circuit, in an alternative embodiment it is provided that the cooling line with the section opposite the connection-side end opens into the surface of the shaped body facing the molten metal of the metallurgical vessel, that is to say the cooling gas sent through is blown into the molten metal. This embodiment can be used, for example, to send the inert gas for purging through the cooling line, while the powdery solids themselves are passed through the passage channel, possibly together with further purging gas.

The cooling line is preferably designed as a copper line, which further enhances the desired cooling effect due to excellent heat conduction.

This cooling line can also be used to display residual strength at the same time, whereby exemplary residual strength display devices are described, for example, in the Radex Rundschau (loc. Cit.). In this case, the electrical conductivity of the copper material of the line can be used, for example, to close or interrupt an electrical circuit when molten metal penetrates and to simultaneously actuate a corresponding signal device.

The advantages of a molded body according to the invention are obvious. Gas purging plugs of a known type need only be converted slightly, namely by forming a passage with the valve described. This does not change the shape or the function of conventional gas purging stones. Nevertheless, the blowing in of solids is made possible. It is obvious that the additional devices can be carried out both for joint flushers and for gas flushing stones with undirected or directed porosity.

Like a conventional gas purging plug, the purging plug is inserted, for example, into a perforated block (possibly via a perforated block sleeve) and is rigidly arranged there. Problems related to mechanical stress, such as occur with blowing lances and described above, omitted. In this respect, the molded body is no longer exposed to mechanical loads, which significantly increases its service life. Furthermore, complex measures to set up a lance stand can be dispensed with. The flushing in of gases and solids in particular at the bottom makes the melt treatment more uniform than processes using blowing lances. Above all, a molded body according to the invention is much cheaper than a known lance arrangement.

The molded body can also be combined with a breakthrough protection, as described for example in the Radex-Rundschau (loc. Cit.). According to a further embodiment, the passage channel can be designed like a siphon. The "knee" formed in the connection-side end results in a kind of pressure cushion when the gas / solids supply is reduced or switched off, while in the upper section facing the molten metal in the vessel, any penetrating molten metal is stopped in its flow and thus even faster can freeze, especially when arranging a cooling device. The point of discontinuity in the passage channel, generally referred to as a siphon, can be designed in various ways, for example S-shaped.

• a) Zunächst wird die Inertgasleitung zugeschaltet, die Gas durch den Durchlaßkanal und/oder die Kühleinrichtung und/oder das poröse feuerfeste Material des Spülsteines drückt. Durch den Inertgasfluß durch den Durchlaßkanal wird das Rückschlagventil weggeführt, so daß der freie Querschnitt des Durchlaßkanals zur Verfügung steht.
• b) Anschließend wird eine bestimmte Menge des pulverförmigen oder körnigen Zusatzmittels in und durch den Durchlaßkanal geblasen, gegebenenfalls in Kombination mit Inertgas.
• c) Während des Betriebes können die Gas-und/oder Feststoffmengen durch entsprechende Regelung/Steuerung der Zuführleitungen geregelt werden.
• d) Beispielsweise nach Abschalten der Feststoffzufuhr wird mit einer reinen Inertgasspülung weitergearbeitet, bis
• e) schließlich auch die Inertgaszufuhr abgeschaltet wird. In diesem Moment entfaltet das Rückschlagventil wieder seine Wirkung, der Schließkörper dichtet den Durchlaßkanal ab und etwaig in den Durchlaßkanal eindringende Metallschmelze dringt bis maximal zum Rückschlagventil vor und friert dann, in der Regel sehr viel weiter vorher aufgrund der Kühlleitung, ein.

The following procedure is used to blow solid additives into a molten metal:

• a) First, the inert gas line is switched on, which presses gas through the passage channel and / or the cooling device and / or the porous refractory material of the sink. The check valve is guided away by the inert gas flow through the passage channel, so that the free cross section of the passage channel is available.
• b) A certain amount of the powdery or granular additive is then blown into and through the passage channel, optionally in combination with inert gas.
• c) During operation, the gas and / or solids quantities can be regulated by appropriate regulation / control of the supply lines.
• d) For example after switching off the solids supply, the process is continued with a pure inert gas flushing until
• e) finally the inert gas supply is switched off. At this moment, the check valve takes effect again, the closing body seals the passage channel and any metal melt penetrating into the passage channel penetrates as far as possible to the check valve and then freezes, usually much earlier due to the cooling line.

The invention is explained in more detail below on the basis of an exemplary embodiment, the single drawing representing a longitudinal section through a refractory molded body according to the invention with a check valve and cooling device.

• Der Spülstein besteht aus einem üblichen feuerfesten Material, das je nach zum Beispiel Pfannentyp, Abstichtemperatur, Pfannenbehandlung, Spülzeit oder dergleichen, ausgewählt wird, hier aus einem Material auf der Basis 97 Gew.-% A1₂0₃.

In the figure, the reference numeral 10 designates a sink which has the following features in detail:

• The sink consists of a conventional refractory material, which is selected depending on, for example, pan type, tapping temperature, pan treatment, rinsing time or the like, here from a material based on 97% by weight A1 ₂ 0 ₃ .

The sink is frustoconical in shape, its upper, narrower end 12 facing the molten metal in the melting vessel and its lower, wider end 14 forming the connection-side end.

The sink 10 has a plurality of channels 16, which run essentially parallel to the peripheral surface 18 and have a small diameter (maximum about 1 mm). The dense material between the channels 16 consists essentially of the above-mentioned corundum qualities.

A sheet metal casing 20 comprises a sheet metal jacket 22 which extends around the peripheral surface 18 of the sink 10 and a circular base 26 which covers the lower end face of the sink 10 and is welded to the sheet jacket 22 in a gas-tight manner on its outer periphery. The ceramic molded body is inserted into the sheet metal jacket 22 via a mortar layer 28, in such a way that a space 30 remains between the lower end face 24 and the bottom 26, which is achieved by two spacers 32 which run crosswise to one another (in the figure, this is parallel to see spacers 32 extending to the plane of the drawing). A connecting line 34 (gas-tight connection) runs in the center from the bottom 26, via which an inert gas such as argon can be blown into the pressure chamber 30 and there through the channels 16. The gas flow runs through the lower, front opening of the channels 16 through the channels 16 to the opposite, upper front end 36 and from there into the molten metal (not shown).

The gas connection for line 34 is made in a known manner.

It is also a matter of course that the sink 10 is used in a suitable manner in the bottom or the wall of the metallurgical melting vessel, for example in a perforated stone or via a perforated stone sleeve.

Concentric to the central longitudinal axis of the sink 10 is arranged in this a passage 38, which can either be drilled out or formed by a metal or dense refractory tube.

The passage channel 38 runs from the upper end face 36 to the lower end face 24 and continues from there in a connecting line 40 which in the first part runs concentrically to the connecting line 34 and then passes through it in a gastight manner.

A copper line 43, which forms a ring line with a supply line 42 and a discharge line 44, extends helically around the passage channel. It is obvious that cooling air supplied via the supply line 42 is helical due to the forced guidance around the passage channel 38 up to the upper end 36 of the molded body flows and from there back to the discharge line 44 and due to the tight order Closure of the passage 38 causes a high cooling effect.

A valve 46 is arranged somewhat above the lower end face 24 in the course of the passage 38. This consists of a chamber 48 widening on both sides of the passage 38, which has approximately a kidney shape in the sectional drawing, which extends from a section directly above the inlet opening of the passage line 38 at 50 offset laterally into the refractory ceramic.

Arranged within the chamber 48 is a ball 52 which, in the illustration according to the drawing, lies directly on the inlet opening of the passage channel 38 at 50 and seals it.

The design of the chamber 48 is such that when a specific gas pressure is applied, the ball 52 is pushed away from its sealing position at 50 and is guided out of engagement with the passage channel 38 into the position 54 shown in dashed lines in the figure along a constrained guide indicated by the arrow. whereby the path of the passage 38 is completely cleared.

• Bei der Herstellung des feuerfesten Formkörpers wird ein entsprechend geformter Teil aus einem verbrennbaren Material mit eingeformt, in dem wiederum die Kugel 52 angeordnet ist. Durch entsprechende Temperaturbelastung brennt das Material weg und gibt den Raum der Kammer 48 mit der Kugel 52 frei.

The chamber 48 with the ball 52 can be introduced as follows, for example:

• In the manufacture of the refractory molded body, a correspondingly shaped part made of a combustible material is also molded in, in which the ball 52 is in turn arranged. The material burns away due to a corresponding temperature load and exposes the chamber 48 with the ball 52.

However, it is also possible to design the area marked with dash-dotted lines around the valve 46 as a separate component (this component 56 itself may in turn consist of two halves) and it will be inserted (mortared in) in the correspondingly drilled or recessed matrix material of the molded body 10 ).

• Zunächst kann ein normaler Gasspülvorgang initiiert werden, indem ein Inertgas über die Zuführleitung 34 in den Druckraum 30 und von dort durch die Kanäle 16 in die Metallschmelze geblasen wird.

The functioning of the molded body is as follows:

• First, a normal gas purging process can be initiated by blowing an inert gas into the pressure chamber 30 via the feed line 34 and from there through the channels 16 into the molten metal.

By connecting a gas reservoir, which is also not shown, argon, for example, is then blown via the feed line 40 into the lower part of the passage 38, the gas flow, when the ball 52 is reached, leading it away from the closed position into the upper position shown in broken lines in the figure, the cross section of the passage 38 is released. The gas then continues to flow through the channel 38 into the molten metal. At the same time or, preferably, with a time delay, a powdery or granular additive, such as lime or the like, is blown into the feed line 40 and in the same way fed through the channel 38 into the melt.

When falling below a certain flow rate of the solid or gas guided through the channel 38, the ball 52 falls back into its closed position at 50 and thus seals the channel 38 downward.

Any metal melt penetrating into the channel 38 is stopped here at the latest and freezes.

Due to the arrangement of the cooling line 43 it can be achieved that any metal melt which has penetrated solidifies much earlier, namely in the region of the upper end face 36, and thus further penetration of metal melt is prevented.

The copper line 43 also offers a safety function, namely if the upper region 12 of the sink is eroded to a certain depth, the metal melt reaches the copper line 43 and melts it; at the same time, the pressure in the lines 42, 44 drops, which can be registered by a corresponding display device.

Then it is time to change the sink.

Likewise, however, the metallic conductivity of the copper material can also be used to connect corresponding residual strength display devices, as described, for example, in German Offenlegungsschriften 3,424,466 or 3,503,221.

Claims (15)

1. Refractory, ceramic shaped member with at least one passage (38) for the supply of gas and/or solids to the molten metal of a metallurgical vessel wherein the passage (38) opens out with an open end in a surface (36) of the shaped member (10) facing the molten metal, and being connectable at its opposite end to a gas and/or solids pipe (40) with a valve being arranged in that passage (38), characterized in that the valve (46) comprises a closing member (52) sealing off the passage (38) in the inital position (without the conveyance of gas/solids), which closing member (52) can be moved out of its sealing position when the passage (38) receives a given stream of gas and/or solids.

2. Shaped member according to claim 1, characterized in that the closing member (52) is a ball, which can be guided along a movement path out of the passage (38).

3. Shaped member according to claim 1 or 2, characterized in that the valve is located as a separate component in the shaped member.

4. Shaped member according to one of claims 1 to 3, characterized in that the closing member (52) and/or the valve (46) consist of a refractory, ceramic material which is highly resistant to abrasion, for example Zr0₂ or Ti0₂.

5. Shaped member according to one of claims 1 to 4, characterized in that the passage (38) passes through the shaped member (10) from its end adjacent the connection to its opposite, open end.

6. Shaped member according to one of claims 1 to 5, characterized in that the passage (38) has a diameter of between 2 and 10 mm, preferably between 4 and 6 mm.

7. Shaped member according to one of claims 1 to 6, characterized in that the part surrounding the passage (38) is designed as a conventional gas nozzle.

8. Shaped member according to one of claims 1 to 7, characterized in that the passage (38) can be cooled by a cooling device (43) at least at its end facing the metallurgical smelting vessel.

9. Shaped member according to claim 8, characterized in that the cooling device consists of a cooling pipe (43) arranged directly adjacent to the passage (38) and through which liquid or gas are able to flow.

10. Shaped member according to claim 8 or 9, characterized in that the cooling pipe (43) opens out in the surface (36) of the shaped member (10) with the section located opposite the end adjacent of the connection.

11. Shaped member according to one of claims 9 or 10, characterized in that the cooling pipe (43) surrounds the passage (38) helically.

12. Shaped member according to one of claims 8 to 11, characterized in that the cooling pipe (43) is a copper pipe.

13. Shaped member according to one of claims 1 to 12, characterized by an additional safety device against a break-out and/or residual intensity indicating device.

14. Shaped member according to one of claims 1 to 13, characterized in that the passage (38) is constructed in the manner of a syphon.

15. Method for blowing in solid, pulverulent or granular additives into molten metal by way of a shaped member according to one of claims 1 to 14, characterized by the following steps:

a) blowing-in a stream of inert gas and/or solids into the passage (38) and opening of the valve (46) caused thereby,

b) blowing at least one additive through the passage (38), preferably with the assistance of a stream of inert gas,

c) if neccesary subsequent interruption of the stream of additives and further flushing solely with inert gas,

d) interrupting the supply of inert gas and/or solids until the valve (46) is closed.

Images