JPH0235007B2 - - Google Patents

Abstract

1. A permeable device for introducing gas into a bath of liquid metal, comprising a case (1) in which is disposed an enclosure (3) which is open in its upper part, in which is placed at least one permeable refractory element (8) retained by a first refractory binder (10), the bottom (5) of the enclosure (3) having an orifice (6) connected to an inlet tube (2) for said gases, and the enclosure being fixed in the case by a second refractory binder (11), characterised in that the case is in the form of a box open in its upper part and having a bottom through which the gas inlet tube (2) extends in a sealed manner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permeable element for introducing gas into a bath of molten metal, and in particular for introducing stirring gas into molten steel. A brick with a rectangular cross section, approximately the same shape as the brick currently used for bricklaying a refractory lining at the nozzle or at the bottom of a converter for introducing stirring gas into the molten steel during its finishing or refining process. is used.
These permeable bricks are formed by a permeable element molded or encapsulated within a thin sheet metal housing, and a stirred gas is blown through a tube welded to the housing at the base of the housing.

However, this type of transparent element has the following drawbacks.

(a) Pipe welds made on thin metal sheets are relatively brittle and the converter brickwork forming the refractory lining is displaced relative to the bottom sheet of this converter jacket sheeting. This can result in the bond between the gas supply tube and the thin sheet breaking, creating cracks or openings in the thin sheet through which the stirring gas can escape. Furthermore, the leaked gas spreads to the bottom of the brickwork of the converter, creating an overpressure zone therein, pushing up the refractory lining and causing a breakdown accident.

(b) Transmission elements of the type hitherto described are usually incorporated into the brickwork of the converter, and these bricks are arranged in such a way as to hold the lining bricks in close contact with the thin sheets forming the housing. It is very firmly assembled around the element. During the operating process of a converter, it may occur that due to the influence of thermal and mechanical stresses, the bottom bricks are displaced relative to each other, so that the shape of the box and therefore of the bricks it contains is The thin sheet that makes up the box for the transparent element becomes loose. Such cracks between the housing sheet and the transparent element are the beginning of dangerous seepage of molten metal.

(c) Pressure applied to the bottom of the permeable element will tend to distort the thin metal walls forming the housing, causing the housing to separate from the permeable refractory element contained therein. This is especially true when brickwork as described above is to be relocated. When blowing in stirring gas, the gas finds its way to the molten bath through grooves formed along the casing. If the width of this groove becomes too large, then molten metal will seep through this passage opened between the metal sheet of the box and the transparent element housed therein. These seepages are dangerous. This is because the seepage can reach the lower part of the permeable element and destroy it, and it can also enter the gas supply pipe and even reach the outside of the converter, into the stirring gas supply pipe.

(d) Although the permeable element has exactly the same shape as the bricks of the refractory lining of the converter, the setback (i.e. conical slope) of this permeable element is relatively small. The pressure of the stirring gas acting over the bottom area of the permeable element has a thrusting effect that displaces the permeable element from the housing and gradually raises it above the level of the converter bottom. This considerably accelerates its wear.
This destruction mechanism is extremely dangerous. This is because when the bricks are completely worn out, this can result in molten steel seeping through the bottom of the converter.

The aim of the present invention is to obviate these drawbacks and to provide a permeation system for introducing gas into molten metal such that there is no risk of the permeation element becoming detached from the container containing such a permeation element. It is to submit sexual elements.

Accordingly, the present invention provides a permeable element for introducing gas into a molten metal bath, the upper part being open, a refractory element permeable to gas being arranged inside, and the bottom part being open. It consists of a box connected to the gas introduction pipe, the element is open at the top and placed inside the box, and a refractory element held by a first refractory binder is placed inside. an outer shell, the bottom of the outer shell having a hole connected to a gas inlet tube extending through the bottom of the housing, and the outer jacket being secured within the housing by a second refractory binder; It is characterized by the fact that

The envelope is preferably a substantially frustoconically shaped body of revolution, the smallest diameter of which is located at the top opening, the sides of which have inwardly projecting retaining means, and further comprising a housing. It has a convex coronal base facing the bottom of the body.

The retention means may consist of one or more circumferential grooves or may consist of a group of protrusions coined or otherwise formed on the side surface.

The invention will be explained in more detail below by means of accompanying drawings showing embodiments.

The transparent element of the invention shown in FIG.
It consists of a box 1 which is a parallel pipedock (a hexahedron in which each side is a parallelogram), is open at the top and has a flat bottom, and is made of a thin metal sheet. The bottom of this housing 1 has a gas supply tube 2 extending therethrough and hermetically welded to the bottom of the housing.

A rigid jacket 3 designed to resist the pressure of the gas is placed inside the housing 1 . This outer cover consists of a main body 4 substantially in the shape of a truncated cone and a crown-shaped bottom surface 5 that is convex facing the bottom of the box, and the upper part of the main body is open and the minimum diameter of the truncated conical main body corresponds to the opening. are doing. The coronal base has a hole 6 which is connected in a sealing manner to the tube 2 by welding.

The frusto-conical body 4 has two circumferential grooves 7 along its sides which project inwardly into the jacket 3.

As a variant, the circumferential groove 7 may be replaced by a protrusion 7a. Further, a suitable combination of grooves 7 and protrusions 7a can also be used.

The permeable refractory element 8 is placed on a bed of granular refractory material 9 within the jacket 3 which is adapted to distribute the stirring gas over the permeable element. They are the second
It is shown more clearly in the figure.

The permeable elements 8 are fitted into a first refractory binder 10 which imparts vibrations to the annular space located between these permeable materials and the jacket 3 above the bed of granular material 9. It is something that is injected while being given.

The refractory element 10 is compatible with the refractory material constituting the permeable element 8 and firmly adheres to the rough and/or textured walls of the latter refractory material.

In this way, on the one hand, due to the truncated conical shape of the jacket 3 and, on the other hand, provided on a plane parallel to the upper opening to prevent displacement of the refractory material 10 in relation to this jacket 3. The outer cover 3 is formed by a circumferential groove and/or a protrusion formed on the inner side of the outer cover.
The risk of displacing the internal transparent element assembly is reduced. The jacket 3 is made of a metal sheet of sufficient thickness to withstand the gas pressure, and its crowned base further serves to increase its resistance to the gas pressure.

An assembly consisting of a jacket 3 containing therein a transparent element 8 embedded in a refractory lining 10 is placed in the housing 1 and in the open space between the jacket 3 and the housing 1. The second refractory binder 11 is filled in the second refractory binder 11, thereby firmly adhering to the case. In this way a strong and unitary assembly is obtained between the envelope 3 and the components housed therein and the housing 1.

The housing 1 has a substantially parallel piped or truncated pyramid shape which is adapted to the shape of the brickwork normally used for converter housings.

The second refractory 11 is, for example, a refractory binder compatible with both the first refractory binder 11 and the refractory material forming the bricks of the refractory lining covering the bottom of the converter.

The structure of the permeable element for introducing gas according to the invention arranged in this way has the following advantages.

Incomplete joints between the tubes 2 and the jacket 3 do not cause damage to the bottom of the converter. This is because even if the gas escapes through the cracks and is released, it remains confined within the metal container constituting the box 1 and passes through the refractory material 11 into the molten metal bath contained in the converter. This is because it can only be slowly created and spread. These gases cannot enter the interior of the refractory mass constituted by the bricks at the bottom of the converter.

The pressure of the gas introduced by the passage of tube 2 is
For example, if the gas is a stirring gas, it can reach high values without causing damage.

This is because this gas is completely contained within the envelope 3, which is designed to withstand such high pressures. Stirring gas permeable element 8
and the refractory binder surrounding them cannot be extruded or displaced. This is because these components are firmly adhered to each other, and the groove 7
This is because it is firmly connected to the jacket 3 by the protrusion 7a and/or by the truncated conical shape of the jacket.

Furthermore, this construction makes it possible to utilize the most favorable geometry and cross-section for both the transparent element 8 and the housing 1, which must be placed in the brickwork at the bottom of the converter.

As an example, the permeable element is made from a porous sintered particulate refractory mixture shaped into small plates. These plates are then assembled and placed vertically within the envelope 3.

The plates, one of which is shown in detail in FIG. The large base surface 12 of the main surface 13 of is supported on a bed of granular refractory material 9.

Anchoring means in the form of projections 15 can also be provided on the side surfaces 14 of the plate 8.

In order to prevent extrusion of the plates 8 by the stirring gas, the main surfaces of the plates are trapezoidal and these side surfaces contribute to a reliable penetration of the plates into the refractory binder 10.

It is also possible to form microchannels 16 in the refractory mass formed by adjacent plates. The passageway is substantially vertical to facilitate gas flow and increase gas permeability and velocity through the permeable element.

To form these microchannels, it is possible, for example, to provide longitudinal grooves on one or both sides of the main surface 13 of the plates which are then to be adjacent, so that when the plates are stacked, the grooves form these vertical microchannels. This gives the permeable element excellent permeability and allows a large amount of gas to pass through.

In this way, for example, about 8 mm thick, 650 ~
Plates can be made with a length of 750mm and a width of 150-250mm. In order to ensure that the distance between two juxtaposed plates is not more than 0.5 mm, the grooves formed on one or both surfaces of the plates, i.e., the main surfaces, should be at most a few tenths of 1 mm.
It has a depth of 0.3mm. This dimensional restriction of the microchannels avoids the risk of metal seepage, which would have the effect of progressively impairing the transparency of the transparent element formed by the stacking of plates.

The refractory material constituting the permeable element 8 is selected to withstand thermal shock when heated by the converter environment and rapidly cooled when a sufficient amount of stirring gas is provided. This material must withstand the action of the gas moving through it.
These gases may be neutral, such as nitrogen or argon, reducing, such as carbon monoxide or hydrogen, or carbonizing, such as carbon dioxide or coexisting mixtures with these gases. These materials must also withstand the corrosive effects of the basic slag charged with the oxidized molten metal and iron oxides that come into contact during the stirring operation.

These substances are particularly magnesium, but
They cannot withstand the carbonizing effect of _CO2 , which can be used as stirring gas. If CO ₂ is used as the stirring gas, whether pure or mixed, aluminum with silicon nitride as a binder or zirconium oxide with chromium oxide as a binder are recommended.

The first refractory binder in which the permeable element 8 is embedded must of course be compatible with the permeable element and is a material commonly used for this purpose.

The second refractory binder material is also selected to be compatible with the first refractory binder and with the basic refractory material making up the bottom brickwork of the converter, such as a refractory binder material. It is a normal substance.

Indeed, upon contact with molten metal, the metal container and outer sheath 3 constituting the box 1 will be melted to at least that height and removed. The basic refractory material constituting the brickwork at the bottom of the converter then comes into contact with the second refractory binder 11 which is in contact with the first refractory binder 10.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a transparent element of the present invention, FIG.
The figure shows a sectional view of FIG. 1, and FIG. 3 shows a perspective view of the transparent element shown in FIG. 1...Case body, 3...Outer cover, 5...Coronal bottom surface, 7
...Groove, 7a...Protrusion, 8...Permeable refractory element, 10...First refractory material, 11...Second refractory material.

Claims (1)

[Scope of Claims] 1. A permeable element for introducing gas into a molten metal bath, the upper part of which is open, a refractory element that allows gas to permeate therein, and an inlet pipe for the gas. comprising a box having a connected bottom surface, the permeable element being open at the top and having a permeable refractory element disposed within the box and retained therein by a first refractory binder. an outer shell, the bottom surface of the outer shell having an aperture connected to a gas inlet tube extending through the bottom surface of the housing; Element for introducing gas into a molten metal bath, characterized in that it is fixed. 2. Substantially, the outer shell has a coronal bottom surface, the smallest diameter of which is located in the upper opening, has inwardly projecting retaining means on the sides and is convex towards the bottom surface of the box. 2. Element according to claim 1, characterized in that it consists of a frustoconical body. 3. Element according to claim 2, characterized in that the retaining means consist of at least one circumferential groove and/or a group of projections. 4. The device according to claim 1, characterized in that the box is substantially a parallel piped deck. 5. The transparent element is formed by a parallel pipe dic or a regular prismatic plate arranged vertically along its largest dimension, the sides of said plate having anchoring means and further comprising longitudinal microchannels. Element according to claim 1, characterized in that the plate is placed on a bed of granular refractory material. 6. Claim 5, characterized in that the micro passage is formed by a groove vertically formed on the surface of the plate, and the groove has a depth of 0.3 mm or less. Motoko. 7. Element according to claim 5, characterized in that the plate is made of magnesium, aluminum with a silicon nitride binder or of zirconium oxide with a chromium oxide binder.