EP0021861B1 - Gas-permeable refractory block and method of making this block - Google Patents

Description

The first invention relates to parts made of refractory material, permeable to gases and to their manufacturing process.

We know that certain industrial practices require the passage of a refractory piece by a gas.

This is the case, for example, in the field of the production of metals, in particular steel, where it has already been proposed, for metallurgical needs, to inject gases into a bath of molten metal through permeable refractory bricks incorporated into the masonry of the metallurgical vessel, at a level below that of the surface of the bath, and more generally at the bottom.

In this type of application, where the molten metal is in contact with the blowing face of the permeable part, it is of course desirable that the permeability of the latter be "selective", that is to say that 'It ensures the passage of gas in one direction without causing infiltration of liquid metal in the opposite direction and this, if possible, even in the absence of gas blowing. For this purpose, it is known to manufacture permeable refractory parts from raw material with special particle size, molded and sintered, giving the mass obtained a statistically isotropic open micro-porosity (French patents n ° 1.094.809 and n ° 1.162 .727).

Furthermore, it is no less desirable that this permeability should also be "oriented" since it involves directing the flow of the blown gas in such a way that it enters under pressure into the porous part by one face and so by the opposite face in contact with the molten metal, the other faces must remain completely sealed in order to prevent excessive lateral loss of the gas which naturally tends to grow with the height of the part. To this end, it has already been proposed to enclose this part in an appropriate manner in a sealed receptacle, constituted for example by a metallic envelope (French patent n ° 1.031.504), or by a layer of refractory concrete made waterproof by the choice of a finer grain size than that of the central region (French patents n ° 1,183,569 and n ° 1,350,751).

The realization of this type of composite structure elements is relatively easy. However, their use poses certain problems relating in particular to the phenomenon of hot differential expansion between the porous core and the sealed periphery and which lead to the undesired formation between the two of privileged passages for the blown gas, with all the consequences that this entails, both in terms of controlling insufflation and in terms of the service life of porous elements.

To overcome these difficulties, it has been suggested to manufacture monolithic elements with oriented permeability by passing through an intermediate stage during which a refractory piece which is naturally non-porous but internally and temporarily exhibits a tight network of links oriented in the blowing direction, the subsequent destruction of which reveals in its place an oriented network of thin and multiple channels (French patent n ° 1.271.201). These parts seem satisfactory in their use, but it is at the level of their manufacture that difficulties appear, because they require a complex and delicate apparatus of which we have not yet, it seems, precisely defined the appropriate characteristics. industrial production.

Finally, this permeability must still be high enough so as not to limit the gas flow rates too much, taking into account the pressure availability of the usual pneumatic installations in this field and which, to fix the ideas, usually cost around ten relative bars. about. However, as one can easily imagine, the greater the permeability of the porous part, the less it is "selective" and the more it is subject to wear out quickly by erosion on contact with the liquid metal. We are therefore faced with conflicting requirements in respect of which the solutions proposed so far, to the knowledge of the inventors, represent compromises that are not always satisfactory.

As an indication, it is in the field of metallurgical treatment in bags (addition, shading, etc.) that, it seems, was first applied the porous refractory parts previously mentioned. In this case, the necessary flow rates of stirring gas being relatively modest (of the order of 5 I / s per piece approximately), the permeable parts used generally have fairly good characteristics of selectivity and mechanical resistance, so that their wear speed is about the same as that of the surrounding refractory lining.

On the other hand, in the case of very large capacity containers, such as melting furnaces or converters, the specific flow rates of blown gas being much greater (of the order of ten times more), the parts used must be very permeable . Correlatively, their "selectivity" is degraded, which generally prohibits blowing in discontinuous operation. In addition, mechanical wear is accelerated and becomes significantly faster than that of the refractory lining, which is all the less acceptable as the bottoms are designed to last a much larger number of flows than for the pockets and that It is hardly conceivable at present to replace a part worn during a campaign.

The object of the present invention is to propose a refractory part whose gas permeability simultaneously presents all the requisite qualities of selectivity and orientation so as to have a lifetime. substantially equal to that of the refractory lining of the container intended to receive it, while making it possible to inject the desired gas flow rates.

Another object of the invention is to be able to produce a part of the aforementioned type retaining the cumulative advantages of an oriented permeability specific to parts of homogeneous structure with a network of fine internal channels, and of the simplicity of manufacture specific to porous parts of structure. composite and this must bear the respective disadvantages.

To this end, the invention relates to a refractory part permeable to gases, intended to constitute a means of pneumatic stirring of a metal bath in a metallurgical container by taking place in the refractory lining of this container at a level located under the surface of the bath so as to be brought into contact with said bath by one of its faces, permeable refractory part comprising a part made of non-porous refractory material and a metal part serving as a container for the refractory part, said metal part being formed of a lateral envelope and a closure plate placed opposite the face of the refractory part opposite to that intended to be brought into contact with the metal bath and provided with means for supplying gas under pressure, part characterized in that the part of non-porous refractory material consists of juxtaposed elements without material seals between them so as to provide between them passage zones for the e gases which are formed by slits which extend over its entire height in the direction of the gas blowing by connecting the side intended to be placed in contact with the bath to the opposite side opposite the closure plate, and in that a gas distribution chamber in said slots is provided at the base of the refractory portion and into which open the means for supplying gas under pressure.

According to another embodiment, the part made of non-porous refractory material is formed of a monolithic refractory block internally comprising recesses which pass right through in the direction of the gas blowing and in which are attached, without material seals sealing, smooth-walled elements, non-destructible when hot, so as to provide between each element and the refractory block passage zones for the gas which are formed by slots which extend over the entire height of said block in the direction blowing gas by connecting the face intended to be placed in contact with the metal bath to the opposite face opposite the closure plate and in that a gas distribution chamber in said slots is provided at the base of the refractory block and in which open the pressurized gas supply means.

As can be understood, the idea underlying the invention therefore consists in creating an artificial permeability in a piece of refractory material which is not naturally permeable, by providing in it discontinuities oriented in the direction of blowing. gaseous and produced by a particular design of the part, namely by an assembly of elements defining between them narrow slots through which the gas passes.

This assembly can be carried out in two distinct ways: either by incorporation in a refractory block of longitudinal dispersed metal or refractory elements, which pass right through the block in the direction of the blowing (that is to say according to the height of the part), either by a juxtaposition of independent refractory elements and also oriented in the direction of blowing.

In the first case, the gas passage slots are located on the periphery of the elements added in the refractory block, while, in the second case, they are more diffuse because they are distributed in the joint planes, that is to say according to more or less rectilinear narrow slots which go to the ends of the part and which, consequently, divide the latter into a plurality of unitary elements.

This new design of permeable refractory brick finally achieves the desired double objective, namely a durability of the part equal to that of the refractory lining of the metallurgical container in which it is installed and a high capacity in gas flow, adapted to the volume of the volume. bath contained in this container. This last particularity seems in particular due to the fact that the assembly of the constituent elements of the part being carried out without worrying about the tightness of the junction zones, it can pass in the latter a greater flow of gas than through the mass refractory, however porous it may be. This being the case, there is no need to have recourse to the extremely porous masses known previously, which allow fairly high gas flow rates, but which also wear out very quickly.

In accordance with practice, the refractory assembly is advantageously placed in a metal receptacle constituted by a lateral envelope open at one end so as to leave free the upper face of the refractory mass, intended to be brought into contact with the molten metal and leaving , of course, appear on its surface local discontinuities for the passage of gas, the other end of the metal casing being closed by a closure plate equipped with means for supplying the blowing gas.

It is recalled that the metal receptacle has the function in particular of ensuring a lateral seal at the periphery of the refractory mass. Furthermore, thanks to its more regular and smoother outer surface than that of the refractory, the metal envelope allows a narrow application of the part on the walls of the hole made in the refractory lining which receives it, or facilitates the extraction of this part with a view to its replacement, if necessary. We can also point out the role of this envelope as a reinforcement protecting the interior refractory mass against possible shocks during transport or handling.

In accordance with the invention, the part constructed by assembling juxtaposed unit elements can be produced according to several variants. A first category of variants takes into account the form of the juxtaposed refractory elements.

As such, the latter may have a flattened shape (plate, strip, etc.) the equal width of which, and therefore defines, that of the refractory piece. In this case, the elements are juxtaposed by their large lateral faces, succeeding each other parallel to each other along the length of the part. This produces a "sandwich" type assembly defining a plurality of joint planes whose surface traces are of unidirectional character (network of lines parallel in the direction of the width).

The refractory elements can also have a more compact and elongated shape (parallelepiped with square base or slightly rectangular) whose sides are of dimensions smaller than those of the part. In this case, the elements are juxtaposed parallel to each other by their four lateral faces, succeeding each other this time along the length and also according to the width of the part. One then obtains an assembly of “beam” type defining a plurality of intersecting joint planes uniformly oriented as before in the direction of the gas blowing, but whose traces on the surface have a bidirectional configuration (network of intersecting lines).

A second category of variants is based on the method of assembling the juxtaposed elements.

One possibility is to put them in mutual contact by their lateral faces. Another possibility consists in making a juxtaposition of refractory elements with interposition between them of separation means so as to keep them at a short distance from each other and thus be able to increase the blowing rates if necessary. These means can take many forms. These are, for example, calibrated spacers providing open joints between the refractory elements, such as metallic or other wires, oriented in the direction of the gas blowing, or refractory concrete inserts housed in longitudinal notches provided for this purpose. facing each other on the side faces of the juxtaposed refractory elements. These separation means can also consist of bulkheads inserted and inserted without any apparent play between the refractory elements, for example plates made of porous refractory material, therefore permeable, or simple metallic strips of flat or corrugated shape.

It is understood that the presence of strips makes it possible to increase the gas flow rate, because on the one hand the gas flow in the joint planes is facilitated against the smooth metal walls and, on the other hand, the number of joint planes between two juxtaposed refractory elements is multiplied by two.

Furthermore, if the strip is corrugated, the junction area is further increased, therefore also the blowing possibilities.

Similar results can be obtained when the refractory elements are juxtaposed in mutual contact.

In this case, in fact, the permeability of the part can be increased by providing surface grooves on the lateral faces of the elements which, once these have been assembled, will form fine rectilinear channels for the passage of the blowing gas.

The case can arise when you want to pass large gas flows, up to several tens of liters per second, for example 40 I / s, as this begins to be done with the cast iron converter of the oxygen blowing type. from above, after the actual refining period in order, for example, to overburden the metal bath. However, the permeability obtained by the simple joining of the elements is largely sufficient for the ironmaking operations of ladle brewing where the flow rates used are much lower, namely around 5 I / s approximately, therefore of the order of ten less than in the case mentioned above of the converter.

• - la figure 1 représente une vue en perspective, partiellement arrachée d'une pièce réfractaire perméable conforme à l'invention et constituée d'un assemblage du type "sandwich" d'éléments réfractaires juxtaposés en contact mutuel par leurs grandes faces latérales;
• - la figure 2 est une vue en coupe verticale selon la plan AA de la figure 1;
• - la figure 3 est une vue en coupe similaire à celle de la figure 2, représentant une variante de réalisation;
• - la figure 4 est une vue en perspective du dessus d'une pièce réfractaire perméable conforme à l'invention et constituée d'un assemblage type "faisceau" d'éléments réfractaires juxtaposés avec interposition entre eux de cales d'écartement;
• - ta figure 5 est une vue en perspective d'une variante de réalisation de la pièce représentée sur la figure 1.

The invention will be well understood and other aspects and advantages will emerge more clearly in the light of the description which follows, given by way of example and with reference to the plates of attached drawings in which:

• - Figure 1 shows a perspective view, partially cut away of a permeable refractory piece according to the invention and consisting of an assembly of the "sandwich" type of refractory elements juxtaposed in mutual contact by their large lateral faces;
• - Figure 2 is a vertical sectional view along the plane AA of Figure 1;
• - Figure 3 is a sectional view similar to that of Figure 2, showing an alternative embodiment;
• - Figure 4 is a perspective view from above of a permeable refractory part according to the invention and consisting of a "beam" type assembly of refractory elements juxtaposed with interposition of spacers between them;
• FIG. 5 is a perspective view of an alternative embodiment of the part shown in FIG. 1.

In the figures, the same elements are designated by identical references or supplemented by "'" in the case of homologous elements.

Figure 1 shows the entire permeable refractory piece as it can be presented to the user before being incorporated into the masonry of the metallurgical container intended to receive it, for example an oxygen blast converter from above . This part is essentially constituted by an assembly 1 of refractory plates 2 having the same height h and the same width 1 as the part. The refractory plates 2 are juxtaposed and pressed so as to be in mutual contact by their large faces, succeeding one another according to the length L of the part. In the example described, the tightening and cohesion of the assembly are ensured by shrinking, by means of an envelope 3 constituted by a steel sheet of approximately 1 mm thick. A closing plate 4 completes the envelope 3 so as to produce a sealed receptacle in which the assembly 1 is adjusted. The supply of the pressurized blowing gas takes place, in the direction indicated by the arrow, by a pipe 5 fixed in leaktight manner on the closure plate 4 around an orifice 6, which opens into a gas distribution channel 7 formed inside the assembly 1.

The plates 2 constituting the latter are made of refractory material of conventional composition and manufacture, for example in cooked magnesia without prior particle size selection, therefore non-porous. However, their juxtaposition without material seals, in accordance with the invention, defines in the room narrow slots parallel to each other, referenced 8 in Figure 1 and appearing on the surface in a rectilinear network according to the width of the room. These slots 8 constitute passage zones allowing the pressurized gas arriving in the distribution channel 7 to pass through the refractory assembly 1 and to come out at the end in contact with the liquid metal. It is understood that the presence of these permeable regions well located in the joint planes, gives the refractory assembly 1 thus formed an anisotropic permeability, that is to say oriented in the direction of gas blowing.

Of course, this permeability is also selective, because if the permeable nature of the slots 8 is sufficiently pronounced to ensure the passage of the blowing gas under pressure, it is nonetheless sufficiently attenuated to prevent infiltration of liquid metal. In this regard, it can be noted that, in the case of liquid steel, the limit permeability threshold corresponds to a micro-passage section of the order of 1 mm ² maximum.

The variant embodiment, illustrated in FIG. 3, consists in replacing the gas distribution channel, internal to the refractory assembly, by a space 7 ′ having the same function but disposed externally and below the refractory assembly 1. The immediate advantage of this type of embodiment lies in the fact that the gas distribution space this time affects the entire section of the refractory assembly 1, which was not the case with the previous variant.

The part of FIG. 3 is produced from that illustrated in FIGS. 1 and 2 by replacing the closure plate 4 with a base plate 12 with openwork perforations 14 which can be distributed at random, but preferably located at right joint planes designated at 8 in FIG. 1. The part thus obtained, composed of the assembly 1 buried by the envelope 3 and by the base plate 12, is placed in a lower frame 11 1 comprising a closure plate 4 'and an end ferrule 13 on which is placed, then welded for sealing reasons, the upper part. In this way, a distribution space 7 'is received between the base plate 12 and the closing plate 4' receiving the blowing gas through an opening 6 'made in the closing plate and extended by a supply line 5 ', and distributing it in the permeable assembly 1 through the perforations 14.

It is not essential that the envelope 3 extends over the entire height of the refractory plates. However, the envelope does not have the sole function of mechanically maintaining the assembly 1 but also serves to channel in the right direction the gases which would tend to escape laterally.

It should also be emphasized that the trapezoidal shape of the part illustrated in the figures in no way constitutes a necessary characteristic of the invention, but a relatively usual arrangement having the role of ensuring, under the pressure of the blowing gas, the blocking of assembly 1 in the masonry of the oven and thus avoid any risk of being propelled into the metal bath. Of course, other means ensuring such blocking may be suitable.

As regards now the number of refractory plates 2 (or 2 ') constituting the assembly 1, this number is left to the free choice of the user. As for the thickness of the refractory plates 2, it is advantageously around 3 to 5 cm. Under these conditions, if we choose, for the permeable part, a format equivalent to that of a conventional refractory brick (15x10 cm ² ) in order to be able to carry out a simple substitution, the number of plates juxtaposed according to the length of the part is then of five, as it is the case of figure 1.

We will now briefly indicate the operations to be carried out to manufacture the part permeable refractory which has just been described. At the start, there is the receptacle in which the assembly 1 will be assembled. This receptacle is however incomplete, that is to say that the envelope 3 lacks one of its side walls. Through this temporary opening, the refractory plates 2 are threaded by placing the plane of their large face perpendicular to the direction of introduction. The receptacle serves as a guide and the refractory plates 2 arranged on edge relative to the closure plate 4 are juxtaposed against one another by coming into contact with their respective large faces. The initial depth of the receptacle is determined so that it is almost completely occupied when the desired number of plates is reached. The missing face is then added by welding to the envelope 3 and, in order to ensure the cohesion of the assembly, a thin layer of refractory concrete is poured between this added face and the last plate introduced. The part thus produced is then ready for use.

Of course, this method of manufacture is in no way limiting and we will subsequently expose, with reference to Figures 4 and 5, a preferred manufacturing process which is perfectly applicable to the production of the part which has just been described.

Furthermore, this part is not limited to the examples illustrated by the figures.

Thus, the non-porous refractory elements, used for the construction of the part according to the invention, are not necessarily plates but can have other shapes or formats, insofar as it remains possible to assemble them in juxtaposing them against each other by their lateral faces, that is to say so as to give the joint planes a common direction, which is that of the crossing of the gas.

It is thus possible to use elongated elements, shaped for example in parallelepipeds with a square or slightly rectangular base, the meeting of which in the receptacle gives the assembly a permeability no longer limited to a series of parallel joint planes, but extended to all network of planes forming a more or less dense grid depending on the size of the elements.

Such an embodiment, which will moreover be described in more detail below, makes it possible to increase the gas flow rate.

It should be remembered that other means can be used in order to increase the permeability of the part. As already said, these means have the essential function of maintaining the refractory elements 2 at a short distance from each other. They can for example be constituted by thin sheets, preferably of thickness less than a millimeter, flat or undulated and interposed without apparent play between the refractory elements 2. When the permeable part is intended for a steelworks converter, the sheets of separation, as well as the outer casing, are advantageously coated with a protective layer against the risks of recarburization by contact with the cast iron.

These separating partitions can be put in place at the same time as the refractory elements 2 according to an alternating assembly process. However, it is also possible to use partitioning as a cell mold in which the non-porous refractory material is poured, which makes it possible to avoid, if desired, achieving the desired discontinuities in the refractory mass without having to assemble preformed refractory elements.

We will now describe, with reference to FIGS. 4 and 5, another category of variant embodiments of the invention, consisting of separating the refractory elements by means of spacers making open joints between them.

In order to illustrate the previously indicated variant, based on the geometric shape of the refractory elements, a part 16, 16 ′ is shown here produced by assembling parallelepipedic elements 18 of the same height h as the part and juxtaposed by their lateral faces, one after the other along the length L and the width 1 of the part. It is clear, however, that the presence of spacers between the elements is not linked to a particular shape of the latter and may very well be envisaged in the case of refractory elements shaped into plates extending over the entire width. of the part, as shown in FIG. 1. Referring to FIGS. 4 and 5, it can therefore be seen that the permeable refractory part 16 (16 ′) is essentially constituted by an assembly 17 of non-porous refractory elements 18, four in number in the two examples considered, and joined together in a non-contiguous manner by interposing spacers 19 (19 '). The cohesion of the assembly is ensured as before by compressive hooping by means of the lateral metal envelope 3. The closure plate 4 completes the envelope in the usual manner, in order to produce a sealed receptacle in which the assembly does not appears only by its free upper face intended to be brought into contact with the molten metal contained in the metallurgical container. The supply of pressurized insufflation gas is carried out, in the direction indicated by the arrow, by the supply pipe 5 mounted in leaktight manner on the closure plate 4 and connected to a power source not shown.

The elements 18 constituting the assembly are advantageously made of refractory material of conventional composition and manufacture, for example made of magnesia baked at high temperature to withstand chemical and mechanical wear well by contact with the slag, but without prior particle size selection, therefore non-porous naturally. However, their non-joining meeting by means spacers 19, (19 '), defines between them narrow spaces 20, constituting obligatory passage slots for the pressurized gas arriving at the base of the part via line 5 and passing through the refractory assembly 17 for emerge from the free upper end in contact with the molten metal. It is understood that the presence of these blowing spaces 20 located at the joint planes of the assembly gives the latter a "directed" permeability in the direction of the gas blowing.

Of course, this result is achieved if the conditions relating respectively to the spacers 19 (19 ′) and to the tightness in line with the lateral envelope 3 are met.

With regard to this last point, provision is made, in accordance with the invention, to interpose between the inner face of the envelope and the wall of the refractory elements 18, a layer 21 of a jointing product, of the usual type. in the field under consideration and the implementation of which will be described in more detail below.

As regards the spacers 19 (19 '), it is important that they are designed so as to provide narrow blowing slots 20, that is to say the width of which is preferably between 0.1 and 0 , 5 mm. Indeed, the permeability of the part 16 (16 ') depends only on the width of the slots 20. It can therefore, at least in principle, be increased or reduced at will by simply modifying the gauge of the spacers. However, since permeability varies in the opposite direction to "selectivity", the risk of infiltration of molten metal increases with the thickness of the shims. In this regard, it is therefore preferable that the thickness of the shims is as small as possible. The lower limit remains however conditioned by the unit flow of gas to be passed through the refractory piece, taking into account the pneumatic pressure which may be available upstream of the piece. On the other hand, if the thickness of the shims is increased too much, the pneumatic pressure, which must be maintained to avoid infiltration of molten metal, then generates a large gas flow, often in pure loss, of as much as this flow rate must then be maintained continuously even outside of the metal production phases requiring gas blowing.

In view of these indications, the thickness of the spacers is preferably close to 0.3 mm and in any case, between approximately 0.1 mm and 0.5 mm.

These characteristics are especially valid for the application of the refractory piece according to the invention to a metallurgical container such as a converter for refining cast iron. They can of course be modified for other applications, but the order of magnitude remains substantially the same if the specific gas flow rates exceed about ten liters per second.

These conditions being respected, the spacers can have multiple different embodiments insofar as they do not obstruct the passage section of the spaces 20 sufficiently large to prevent the flow of stirring gas that is wish to pass there.

In this regard, the spacers may be constituted for example by surface irregularities of the elements 18 deliberately pronounced, such as pins or protrusions in the form of pellets, obtained by molding during the manufacture of these elements.

Another embodiment consists in attaching the spacers between the elements at the time of the assembly operation.

In this case, the shims are advantageously in the form of elongated bodies, oriented longitudinally in the slots 20, that is to say in the direction of passage of the stirring gas so as not to hinder the passage thereof. Figures 4 and 5 respectively illustrate two different embodiments of spacers of this type. In the example of FIG. 4, the spacers 19 are simple commercial metal wires, preferably of steel, and calibrated to the desired dimension. There are four of them, one for each refractory element, and all oriented longitudinally so as to reduce their master-torque as much as possible in the gas flow. Their position can be arbitrary, however, it is preferable to locate them at the ends of the joint planes in order to minimize, as we understand, the functional clearances of the elements at the time of their assembly.

In the example of FIG. 5, the spacers 19 ′ are constituted by refractory concrete inserts housed in notches 22 provided at the ends of the joint planes and obtained during the assembly of the elements 18 which have at this effect a clearance along their edge.

The inserts can be cast on site after non-contiguous meeting of the elements 18 thanks to the spacers 23 arranged in the immediate vicinity of the notches and having the dual role of providing the blowing slots 20 and of constituting a sealing member allowing the casting of the inserts without risk of concrete infiltration into the slots 20.

The spacers 23 are advantageously of the same shape and the same size as the metal wires 19 (FIG. 4). However, unlike the latter, their function of spacer being only temporary since they serve as relays to the inserts 19 ′, they can be made of wires made of hot-destroyable material, for example polyamides such as that sold. under the "nylon" mark which can be eliminated either in the last phase of manufacturing the part, or allowed to destroy hot when commissioning the converter. It should be emphasized that the variant embodiments described with reference to the figures are characterized in particular by the fact that the spacers 19 or 19 ′ are bodies attached to the whole of the part and not, as indicated above, integral parts of the refractory elements preformed and specially designed for the manufacture of the part according to the invention, which is obviously not without influence on the cost price thereof. On the contrary, the installation of added spacers makes it possible to use refractory elements which are completely commonplace, or even "standard" in trade.

In this regard, a substantial advantage of the invention resides in the fact that the part 16 (16 ′) can be easily produced by taking as raw material a simple commercial refractory brick which is transformed according to the process which will be explained. . A commercial brick, made of non-porous refractory material, such as baked magnesia, is cut with a saw in the longitudinal direction. The elements obtained are then joined in a non-contiguous manner by placing between them the calibrated spacers 19 (FIG. 4) or, where appropriate, the temporary spacers 23 (FIG. 5). In the latter case, the edges of the elements located in the vicinity of the spacers are subjected beforehand to a removal of material, for example by milling, so as to be able to form the notches 22 in which a concrete insert 19 ′ is poured by any suitable means. .

In all cases, the cohesion of the assembly is then ensured by shrinking by means of the lateral metal casing 3 with the interposition of a layer of jointing product 21 which seals the gas at the level of the casing. The assembly is completed by the closure plate 4 added by welding on the lower edge of the envelope.

The performance that can be expected from the part thus produced as a blowing member is conditioned, in particular by the quality of the gas tightness at the envelope-refractory elements interface. This tightness directly linked to the nature of the jointing product 21 and / or to the way in which it is put in place. In this regard, the jointing product is advantageously a swelling refractory concrete which is poured in the liquid state in the interval initially provided between the metal casing and the refractory elements. The swelling, during the subsequent discharge, then causes, by reaction of the envelope and the elements, a jointing compression ensuring the desired tightness.

However, this variant of embodiment requires knowledge and therefore control, always delicate, of the mechanical stresses which develop in the part and which can, in particular, lead to deformations of the envelope by swelling which make it more difficult, even random. , the incorporation of the part in the masonry of the metallurgical container intended to receive it.

A preferred variant, which corresponds to the best embodiment that the inventors know how to do at present, consists in operating as follows: the metal casing 3 consisting of two half-shells 24 and 25 equal and in profile U-shaped. We begin by introducing the assembly 17 into any one of the half-shells, for example the half-shell 24 after having brushed its inner surface with a jointing product which naturally adheres to the metal wall. An identical basting is then carried out on the inner face of the half-shell 25 which is then arranged around half of the assembly protruding from the half-shell 24. The half-shells are dimensioned so that, at this stage of the operation, their respective edges are opposite in pairs.

The assembly is then compressed by exerting a push on the base of each half-shell using any suitable means, for example a vice, and the operation is completed by joining the two half-shells by their edges by means of cords of solder 26 in the middle of the face of the metal casing 3 thus reconstituted. Another advantageous variant of the invention consists in sawing the starting refractory brick according to a cross cut, so as to obtain, as shown in the figures, interlocking blowing slots 20. To do this, a saw blade is chosen whose thickness takes account of the thickness of the lateral envelope 3, so as to produce a permeable part which retains the same size as that of the initial brick, which in particular allows to be able to incorporate the permeable part without difficulty into the overall architecture of the refractory lining.

In accordance with another characteristic of the invention - not essential but useful when the initial refractory brick is impregnated with tar, for example a cooked magnesia brick impregnated with tar - the elements 18 are subjected to a temperate heating after cutting and before assembly, in order to eliminate the volatile elements which are inevitably present and which could subsequently leak and therefore clog the blowing spaces. The tempered heating operation can last a few hours and thus make it possible to go from a total carbon content of 8% to approximately 2% by weight.

It goes without saying that the invention cannot be limited to the examples described, but can have many other variant embodiments. This is particularly the case with wedges of spacing 19 between the elements and which can be of a very varied nature, for example piano wire, etc ... insofar as their size and their orientation respect the indications previously provided. In addition, their number is not necessarily limited to the proportion of one per refractory element.

Similarly, the number of refractory elements 18 constituting the assembly is not necessarily equal to four, but may be less than or greater than this number. Similarly, the notches, arranged opposite one another on the refractory elements and defining a housing for the concrete inserts, are not necessarily placed at the ends of the joint planes, but may be provided in places any inside the blowing slots.

In addition, it is recalled that, in accordance with another category of variants not shown in the figures, but the simple statement of which is sufficient to allow the skilled person to produce them, the part according to the invention may consist of a non-porous refractory mass, no longer formed of juxtaposed unitary elements, but of a single block having internally recesses which pass through it in the direction of the gas blowing and in which elements, without material seals, are attached with a smooth non-destructible hot wall, for example steel elements, so as to form with the refractory block surrounding the gas passage slots.

Finally, if the part according to the invention was specially designed originally as part of the refractory lining of a metallurgical container, such as a converter for refining cast iron into steel, in which a pneumatic stirring of the molten metal bath, it is nonetheless of general application to any industrial practice requiring the passage of a refractory piece by a fluid in the gaseous state.

Claims (14)

1. A gas-permeable refractory shape, designed as a means for pneumatically stirring a metal bath in a metal container, by setting it in the refractory lining of this container at a level below that of the surface of the bath so as to make contact with said bath on one of its faces, a permeable refractory shape comprising a portion (1) of a non-porous refractory material and a metal portion (3, 4) acting as a container for the refractory portion (1 said metal portion consisting of a side casing (3), and a cover plate (4) set opposite the face of the refractory portion (1) facing that that is to make contact with the metal bath and comprising a gas-pressure-feeding means (5), shape characterized in that the portion (1) of the non-porous refractory material consists of juxtaposed elements (2) with no in-between sealing means so as to provide between them gaps (8) through which the gas flows and which consist of slots extending throughout its height in the direction of the blown gas by connecting the face to make contact with the bath to the opposite face facing the cover-plate (4), and in that a gas-distributing chamber (7) in the said slots (8) is provided at the base of the refractory portion (1) and in which the gas-pressure feeding means open on into.

2. A gas permeable refractory shape, intended as a means for pneumatically stirring a metal bath in a metal container by setting it into the refractory lining of this container at a level below the bath surface so it makes contact with said bath on one of its faces, a permeable refractory shape comprising a portion (1), of non-porous material and a metal portion (3, 4) acting as container for the refractory portion (1), said metal portion consisting of a side casing (3) and a cover-plate (4) set opposite the face of the refractory portion (1) facing that to make contact with the metal bath and provided with gas-pressure feeding means (5), a shape characterized in that portion (1) of non-porous refractory material consists of a monolithic refractory block comprising internally recesses crossing it throughout in the direction in which the gas is blown and in which are inserted, with no sealing means, smooth-walled elements, non-destructible under heat, so as to provide, between each element and the refractory block, gaps for letting the gas through and which consists of slots extending throughout the height of said block in the direction in which the gas is blown by connecting the face to make contact with the metal-bath to the face opposite facing the cover-plate (4) and in that a gas-distribution chamber (7) in said slots is provided at the base of the refractory block and in which the gas-pressure feeding means (5) open onto.

3. A refractory shape according to claim 1 or 2, characterized in that the slots (8) through which the gas passes are provided with sized distance-pieces thus making up open joints (20).

4. A refractory shape according to claim 3, characterized in that the distance-pieces are filiform inserts (19) and set in the direction in which the gas is blown.

5. A permeable refractory shape, according to claim 1 or 2, characterized in that the slots are provided with partitions made up of thin, flat or corrugated metal-sheets.

6. A shape according to claim 1, characterized in that the refractory elements have a flat shape, in that they are juxtaposed by their longer side faces according to the length of the shape and in that their width defines the width of the shape.

7. A shape according to claim 1, characterized in that the refractory elements have an elongated shape, in that they are juxtaposed by their sidefaces according to the length and width of the shape.

8. A shape according to claim 1 or 2, characterized in that it exhibits a peripheral layer of non-porous refractory concrete interposed between the middle refractory portion (1) and. the metal casing (3).

9. A shape according to claims 1, 2 or 8, characterized in that the metal casing (3) consists of two U-shaped half-shells interconnected by their edges.

10. A process for manufacturing the shape according to claim 1, characterized in that a regular brick of non-porous refractory material is cut lengthwise, in that the initial brick is recreated by juxtaposing the resulting refractory elements (2) with no in-between seal, in that the whole is assembled by compressive stress in the side metal casing (3) and in that before or after having closed one end of the casing by means of the cover-plate (4) comprising the blown-gas inlet means (5), a peripheral coat of sealing compound is inserted between the side casing and the refractory elements.

11. A process according to claim 10, characterized in that during the juxtaposition operation of non-porous refractory elements, cut beforehand, segregating means consisting of sized (19) distance-pieces are interposed in-between the said refractory elements, thus providing open joints (20) in the direction in which the gas is blown.

12. A process according to claim 10, characterized in that during the juxtaposition operation of the non-porous refractory elements cut beforehand (2), separating means are interposed in-between them with no apparent play, the said means consisting of partitions in thin, flat or corrugated metal-sheets.

13. A process according to claim 10, 11 or 12, characterized in that use is made of a side casing consisting of two U-shaped half-shells, in that after having applied to their inner wall an adhering sealing compound, both half shells are adjusted around the treated beforehand assembly of refractory elements by fitting them one after the other, respectively by two opposite sides of the said assembly so as to place their edges opposite one another on both sides of the assembly and in that both half-shells are joined together by interlocking their respective edges while exerting a compressive stress by application of opposite thrusts on the base of the half-shells.

14. A process according to claim 10, characterized in that the initial non-porous refractory brick, which is to be cut up to element is of tar- impregnated refractory material and in that, after cutting, these elements are subjected to a phase of moderate heat in order to eliminate the more volatile constituents.

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