EP3443131B1 - Blowing lance nozzle - Google Patents

Description

• un tube central d'alimentation en gaz de brassage, fermé à une extrémité tournée vers le bain par une première paroi frontale pourvue d'au moins deux ouvertures,
• un tube interne formant avec le tube central une première cavité annulaire pour le passage d'un liquide de refroidissement et terminé à une extrémité tournée vers le bain par une deuxième paroi frontale, appelée séparateur, présentant une ouverture centrale et un orifice de passage par ouverture prévue dans ladite première paroi frontale,
• un tube externe formant avec le tube interne une deuxième cavité annulaire pour le passage du liquide de refroidissement et fermé à une extrémité tournée vers le bain par une troisième paroi frontale présentant un orifice de sortie par ouverture prévue dans ladite première paroi frontale et présentant une surface interne comprenant une zone centrale conique qui est dirigée vers ladite ouverture centrale et qui présente une surface d'enveloppe incurvée en section axiale,
• un espace d'échange thermique qui est situé entre, d'une part, ladite deuxième paroi frontale et ladite surface interne de la troisième paroi frontale et, d'autre part, ladite ouverture centrale et ladite deuxième cavité annulaire, et dans lequel s'écoule le liquide de refroidissement, et
• un conduit de sortie pour le gaz de brassage appelé injecteur, partant de chaque ouverture dans ladite première paroi frontale et allant jusqu'audit orifice de sortie correspondant en passant par ledit orifice de passage correspondant d'une manière étanche au liquide de refroidissement.

The present invention relates to a blowing lance nose, intended for the mixing of baths, comprising

• a central brewing gas supply tube, closed at one end facing the bath by a first front wall provided with at least two openings,
• an internal tube forming with the central tube a first annular cavity for the passage of a coolant and terminated at one end facing the bath by a second front wall, called a separator, having a central opening and a passage opening per opening provided in said first front wall,
• an outer tube forming with the inner tube a second annular cavity for the passage of the coolant and closed at one end facing the bath by a third front wall having an outlet orifice by opening provided in said first front wall and having a surface internal comprising a conical central zone which is directed towards said central opening and which has a surface of a curved envelope in axial section,
• a heat exchange space which is located between, on the one hand, said second front wall and said internal surface of the third front wall and, on the other hand, said central opening and said second annular cavity, and in which s' drains the coolant, and
• an outlet duct for the stirring gas called an injector, starting from each opening in said first front wall and going up to said corresponding outlet orifice passing through said corresponding orifice in a sealed manner to the coolant.

In the following description, the terms “conical central zone which is directed towards said central opening and which has a surface of curved envelope in axial section ”will, for reasons of simplicity, sometimes only be expressed by the terms“ central depression ”.

The blowing lance nose as described in the present invention is used, inter alia, in oxygen converters for the manufacture of steel (BOF Basic Oxygen Furnace, AOD Argon Oxygen Decarburization). Converters make it possible to obtain steel by injecting oxygen into a liquid iron bath in order to burn the carbon contained therein. The basic principle in the field of oxygen blowing in converters (for example LD (for Linz-Donawitz)) is to propel 3 to 6 jets of oxygen arranged in a crown on a bath of liquid cast iron. The lance which allows the formation of these oxygen jets is then placed at a distance of 1 to 5 m above a bath of molten iron whose temperature can reach 1700 ° C.

The temperature of the nose of the lance can then increase rapidly to 400 ° C. and must remain in this environment for approximately 20 minutes. The nose is then removed and returns to room temperature, that is to say 20 ° C. These constraints damage the lance noses used for the baths of steelworks converters and typically, the lifetime of these is reduced following the significant stresses to which they are subjected, during a significant number of successive uses.

To improve the cooling of the lance noses, heat exchange spaces have been developed so that a coolant can circulate along the internal wall facing the bath of the lance nose. When a coolant, usually water, flows along the front wall, the calories from the metal forming that wall are transferred to this coolant. In this way, the temperature of the lance nose is uniform over the entire nose, and no longer particularly high only at the walls exposed to the bath.

Poor coolant circulation can also cause a local rise in coolant temperature. Consequently, locally the liquid can pass into the vapor phase under thermal stress. This results in the formation of cavities filled with trapped gases within the coolant. This formation of gas cavities in a liquid is known as the cavitation phenomenon. These cavitation phenomena then cause a decrease in the cooling efficiency of the front wall since the heat exchange between a gas phase and a solid phase is much less good than between a liquid phase and a solid phase. If the cooling is not uniform over the entire wall exposed to thermal variations, mechanical tensions appear between the different zones of this wall. This inhomogeneous distribution of the temperature generates, consequently, a reduction in the longevity of the lance nose. Indeed, the latter presents, after a few operating cycles, imbalances which considerably limit its lifespan.

The documents US4432534 and WO9623082 have, for example, lance noses designed to allow the flow of a coolant at high speed along the internal surface of the front wall, this same front wall has a slight central depression in order to optimize this flow .

The document EP0340207 provides for a significant depression in the central area of the lance nose on which are directed secondary jets of coolant causing a swirl in the flow of the liquid.

The document WO0222892 attempts to further improve the flow of coolant in the heat exchange space of the lance nose by developing a central depression in the face facing the bath having a well determined ratio between height and base of this depression. This ratio allows the heat exchange space to have a section for the passage of the coolant substantially constant so as to obtain a speed of passage of the coolant through this space which is approximately constant.

The document DE 19506718 describes a blowing lance nose used in or above liquid steel and having a cooling system based on the difference in roughness between the two walls of the heat exchange space, namely the separator and the internal surface of the third front wall. The ratio of the difference in roughness to the minimum radius of curvature of the surface exposed to the liquid steel must be kept constant to ensure good cooling. The document US2012 / 0211929 A1 discloses another example of the known prior art relating to a blowing lance nose.

When the cooling of the lance noses is not effective, in addition to the appearance of mechanical tensions, it has also been observed that an erosion phenomenon of the front wall appears at the periphery of the outlet orifices of the conduits for the gas brewing.

In the following description, the expression “stirring gas outlet pipe” will, for reasons of simplicity, sometimes be expressed only by the term injector.

The diameter of the outlet openings of the injectors tends to increase following the erosion of the edges thereof. This increase in diameter deforms the oxygen jets, which causes, in addition to the destruction of the lance nose, a dispersion of these jets and consequently a reduction in their effectiveness. The carbon oxidation reaction is, in fact, favored by the depth of penetration of the jets into the bath and by the mixing thereof. The lance noses being placed at a distance of 1 to 5 m above the cast iron bath, in order to be effective, the jets must have a coherent profile over the longest possible distance. The reaction yield is then reduced when these jets are dispersed because they penetrate less deeply into the melt. The reaction yield in the bath is therefore not optimal and moreover exhibits significant variability during the lifetime of the lance nose.

Efficient cooling is therefore important for the proper functioning of the lance noses, since it has the advantage of increasing the lifetime of the latter but also of guaranteeing better stability of reaction yield throughout their lifetime. and this by minimizing erosion at the edges of the front wall. However, such cooling is also very difficult to implement, under the extreme conditions encountered during the use of the lance noses.

Although the documents described above contribute to the improvement of the technique for cooling the noses, unfortunately, they still do not have a sufficient lifetime and do not provide a reaction yield in the bath which is stable at all times. along this lifespan.

The object of the present invention is to overcome these drawbacks of the state of the art by providing a lance nose which is simple to manufacture, the lifetime of which is increased and which makes it possible to ensure a reaction yield in the improved cast iron bath and stable throughout the life of the lance nose.

To solve this problem, there is provided according to the invention, a lance nose as indicated at the beginning in which the separator has at the central opening an edge in axial section which is curved such that a height H3 is defined between a front of said edge and said internal surface of the third front wall and that in the heat exchange space a predetermined minimum height H1 is present on the side of said central opening such that the ratio H1 / H3 is between 5% and 80 %, advantageously between 5% and 75%, preferably between 5% and 70%, preferably between 5% and 65%, particularly advantageously between 5% and 60%, preferably between 10% and 60% , advantageously between 15% and 60%, preferably between 20% and 60%, preferably between 25% and 60%, particularly advantageously between 25% and 55%, preferably between 30% and 55%.

Unlike the documents cited above, it has been discovered that the flow of coolant can be surprisingly improved by acting both on the configuration of the separator, in particular its edge at the central opening, and on its positioning relative to the third front wall.

In fact, on the one hand, the edge of the separator at the central opening, thanks to its curved axial section, allows the coolant, arriving from the first annular cavity, to carry out a progressive rotation between this curved edge and the central depression of the internal surface of the third front wall to arrive without disturbance in the heat exchange space.

The injectors in the lance nose represent obstacles which are in the path of the coolant, first between the first and the second front wall and then in the heat exchange space between the second and the third wall frontal. It is therefore necessary to "calm" the coolant after bypassing the first obstacle which are the injectors between the first and the second front wall. This role is achieved according to the present invention by the edge of the separator which is curved in axial section and which makes it possible to form at the central opening and in the heat exchange space passage sections for the coolant optimized.

In addition, this curved edge in axial section of the separator makes it possible to minimize the energy losses in the flow of the coolant which improves the acceleration of this liquid during its passage between the curved edge of the separator and the conical central zone. of the internal surface of the third front wall, before it arrives in the heat exchange space. This first acceleration is regulated by the section of the coolant passage between the edge of the separator and the central depression. In the volume contained in the cone passing through the axes of revolution of the injectors, H1 is the height minimal passage of water along the internal surface of the third front wall, in the heat exchange space. This first acceleration improves the cooling of the central part of the lance nose which is the part where the metal / liquid exchange surface is the least important and therefore the most difficult area to cool.

By the terms "passage section" is meant, according to the present invention, a section taken perpendicular to the direction of flow of the coolant.

On the other hand, the positioning of the separator relative to the third front wall makes it possible to form a heat exchange space having a predetermined height which regulates the acceleration of the coolant. The separator according to the present invention is substantially planar and substantially parallel to the third front wall thus ensuring a flow of the coolant with turbulence and reduced cavitation phenomenon.

The lance nose according to the present invention therefore makes it possible both to optimize the trajectory of the coolant, which minimizes turbulence, and to improve the acceleration of this liquid to effectively cool the wall exposed to thermal stresses. Consequently, the life of the lance nose according to the present invention is considerably increased and the erosion of the outlet edges of the injectors is minimized so that the reaction yield in the bath is improved and kept stable throughout the life of the lance nose. Indeed, good cooling reduces erosion of the outlet edges for the stirring gas, which makes it possible to obtain more coherent jets at the outlet of the injectors. These more coherent jets penetrate deeper into the cast iron bath and ensure better stirring thereof, thereby ensuring an improvement in the yield of the reaction in the bath. In addition, the gases and dusts emitted on the surface of the bath and going up towards the lance nose less impact the degradation of the nose when the cooling of this one is improved as for the nose of the present invention. As a result, the life of the nose according to the present invention is increased.

In another particular embodiment, the lance nose according to the present invention has a predetermined outer diameter D _ext and said edge of the separator is defined by a thickness e1 so that the ratio e1 / D _ext is between 3% and 30%, preferably between 4% and 25%, advantageously between 5% and 20%, preferably between 5% and 15%.

The thickness, e1, of the edge of the separator is the distance, taken parallel to the axis of revolution of the injectors, between the surface facing the first front wall and the surface facing the bath of the separator. This particular thickness of the edge of the separator allows on the one hand to further improve the rotation of the coolant around the edge of the separator which faces the central depression. On the other hand, the particular thickness of the edge of the separator advantageously reduces the energy losses during the flow of the coolant. The reduction in energy losses in turn leads to maintaining the acceleration of the liquid and therefore to optimizing the cooling of the nose.

Advantageously, the separator of the lance nose has a surface, facing the bath, substantially sinusoidal.

By the terms "sinusoidal surface" is meant a surface which forms a wavy curve, that is to say which has for example a convex part between two concave parts. The separator having a sinusoidal surface therefore has a convex part between two concave parts with respect to the third front wall. A minimum thickness is therefore located between two maximum thicknesses of the separator.

This sinusoidal surface has the advantage of offering the coolant a passage section in the improved heat exchange space. Indeed, as mentioned above, a first Acceleration of the coolant occurs before entering the heat exchange space. The sinusoidal surface of the separator has the effect of increasing the cross section of the coolant substantially in the center of the separator. Indeed, the injectors which pass through the separator substantially at its center, clutter the heat exchange space. This is where the separator is made concave (has an inward bulge) to leave room for the passage of coolant. The sinusoidal shape of the surface facing the separator bath therefore makes it possible to reduce the energy losses during the second bypass of the injectors between the separator and the internal surface of the third front wall. This sinusoidal surface is advantageous for the good cooling of the wall exposed to the liquid iron bath.

Preferably, said surface facing the substantially sinusoidal bath of said separator is such that the heat exchange space has a maximum height substantially at the center of said separator.

Preferably, the lance nose according to the invention has a pillar comprising a first end situated opposite the bath and a second end facing the bath connected to the central zone of the third front wall.

This pillar allows on the one hand to improve the circulation of the coolant when it plunges into the central opening. Indeed, the central opening can be a place of collision and the pillar present at the center of this central opening therefore makes it possible to minimize turbulence. The liquid will then go along the pillar before arriving in the heat exchange space.

Furthermore, this pillar advantageously made of a material with good thermal conductivity, such as copper, makes it possible to ensure a good transfer of the calories accumulated in the front wall exposed to the bath to the coolant. This phenomenon of calorie transfer is called "cold well". The heat transferred by the pillar then diffuses towards the coolant circulating around it.

In a particularly advantageous manner, the pillar has between said first and second ends a thinned part connected to the central zone which has a predetermined length L1 and an axial section continuously decreasing towards the central zone so that the pillar forms with the central zone from the internal surface of the third front wall a continuous curved surface.

According to the present invention by the terms "continuous curved surface" is meant a surface which has a "continuity of curves", preferably a "continuity of tangents".

By the terms "continuity of tangents" is meant, according to the present invention, that, in an axial section of the pillar, the curve of the thinned part of the pillar and the curve of the conical central zone of the internal surface of the third front wall have equal tangents at their common end, that is to say at their junction (second end of the pillar). Tangents are the first derivatives of curves at their common end.

A second degree of “continuity of curves” can possibly be a “continuity of curvatures”, which then means that the radii of curvature of the two curves (thinned part of the pillar and of the conical central zone of the internal surface of the third wall frontal) are equal at their common end, that is to say at their junction (second end of the pillar). In other words, the curves of the thinned part of the pillar and of the conical central zone of the internal surface of the third front wall have the same direction at their junction and also have the same radius at this point. The radii of curvature are the second derivatives of the curves at their common end, that is to say at their junction at the second end of the pillar.

The coolant arriving from the peripheral part of the nose (annular cavity) converges in the central opening where it performs a rotation of approximately 180 ° between the pillar and the edge of the separator before arriving in the exchange space thermal, for example frontal. The presence of this pillar having a particular geometry allows, on the one hand, to further optimize the flow of coolant passing through the central opening where it passes between the thinned part of the pillar and the edge of the separator and on the other part of accelerating the coolant before it arrives in the heat exchange space. Indeed, the edge of the separator according to the present invention has a complementary shape with the thinned part of the central pillar advantageously present in the center of the central opening. This complementary shape between these two elements is particularly advantageous for accompanying the coolant during its rotation of about 180 ° in the central opening, thus making it possible to lessen the turbulence in the liquid, to “calm it down”, and maintain good contact with the pillar serving as a "cold well" and then with the third front wall. Furthermore, this geometry also allows the acceleration of the coolant before it passes through the heat exchange space.

Advantageously, in the lance nose according to the present invention, the pillar has a second part of predetermined length L2 joining said thinned part and said first end, said second part having a circular cross section defined by a predetermined diameter D2, constant over the entire length L2 such that the ratio D2 / D _ext , is between 2% and 30%, advantageously between 7.5% and 17.5%, preferably between 10% and 15% of said outside diameter (D _ext ) of the nose of launch.

In this particular embodiment of the lance nose according to the present invention, given its diameter, the pillar can be considered as "massive" in view of the volume it occupies in the nose. This massive pillar made of a material with good thermal conductivity, such as copper, ensures good transfer of calories accumulated in the front wall exposed to the bath to the coolant, thus improving the phenomenon of "cold well". The heat transferred by the pillar then diffuses towards the coolant circulating around it and whose metal / liquid heat exchange surface is increased thanks to the thinned part having a curved profile. The heat is, therefore, better distributed within the lance nose which more particularly ensures good cooling of the area most exposed to extreme temperatures, namely the center of the third front wall. The lance nose according to this embodiment therefore results in an additional improvement in the cooling of the nose.

Advantageously, said thinned part I of the pillar has a predetermined minimum diameter D3 at its second end and said central zone has a height h and a base b such that the ratio h / (b-D3) is between 20% and 120%, preferably between 20% and 110%, advantageously between 30% and 110%, preferably between 30% and 100%, in particular between 40% and 100%, particularly advantageously between 40% and 90%, preferably between 45% and 85%, advantageously between 50% and 80%.

When no pillar is present at the top of the central conical zone, D3 is zero and h / (b-D3) = h / b.

The heat exchange surface is thus increased relative to the same surface of the heat front coming from the bath, and this without causing either swirling or cavitation in the liquid. In addition, the cross section of the liquid in the heat exchange space is such that the coolant has an adequate speed profile so that the cooling of the front wall exposed to the bath is further improved.

Preferably, the lance nose according to the present invention is characterized by a distance R, for the passage of the coolant, taken perpendicular to the longitudinal axis L of the nose in the central opening. When no pillar is present in the central opening, this passage distance is then called R ₁ and is measured between the front of the separator and the longitudinal axis of the nose, and therefore corresponds to the minimum radius of the central opening . When a pillar is present in the central opening, the passage distance R for the liquid is then measured between the front of the separator and the external surface of the thinned part I of the pillar, the distance is then called R ₂ . In both cases, this passage distance R is such that the ratio R / H3 is between 20% and 150%, preferably between 30% and 140%, advantageously between 30% and 130%, preferably between 40% and 130%, particularly advantageously between 50% and 130%, preferably between 60% and 120%, advantageously between 60% and 110%, reference between 70% and 110%, with R corresponding to R1 in the absence pillar or corresponding to R2 in the presence of a pillar.

This particular passage distance for the coolant makes it possible to further improve the flow of the coolant which will converge in the central opening before reaching the heat exchange space. The distance of passage of the liquid in the central opening in combination with the characteristics of the aforementioned nose, makes it possible to further improve the flow by improving the reduction of the disturbances and the acceleration of the coolant.

Advantageously, said separator has a surface facing said first substantially sinusoidal front wall.

In a particular embodiment, a deflector is present substantially in the center of said central tube for supplying stirring gas to the lance nose according to the present invention.

This deflector makes it possible to appropriately divert the gas leaving the central duct to engage in the outlet conduits for the stirring gas.

In a particularly advantageous embodiment of the device according to the invention, said outlet conduits for the gas stirring have axes of revolution placed obliquely to a longitudinal axis of the lance nose.

In a particular embodiment, the aforementioned elements of the nose are produced separately and fixed in the area of mutual connection by high energy welding, preferably an electron beam welding.

The aforementioned nose is made of several nose elements each consisting of a material chosen according to the function to be fulfilled. These elements are then fixed together by high energy welding, preferably by electron beam. This type of welding provides easily achievable copper-steel junctions with good liquid tightness, despite the fatigue stresses due to the successive thermal cycles to which the nose is subjected.

Other forms of device according to the invention are indicated in the appended claims.

• La figure 1 est une vue de face d'un nez de lance.
• La figure 2 illustre une vue en coupe suivant la ligne II-II de la Figure 1, d'une forme de réalisation particulière du nez de lance selon l'invention.
• La figure 3 représente un détail d'un nez de lance suivant l'invention, pour illustrer la partie caractérisante de l'invention.
• La figure 4 représente une vue analogue à la figure 2 d'une variante de nez de lance de soufflage selon l'invention.
• La figure 5 représente un détail d'un nez de lance selon l'invention, pour illustrer le mode de mesure des paramètres nécessaires à un mode de réalisation avantageux de l'invention.

Other details and advantages of the invention will emerge from the description given below, without implied limitation and with reference to the attached drawings.

• The figure 1 is a front view of a spear nose.
• The figure 2 illustrates a sectional view along line II-II of the Figure 1 , of a particular embodiment of the lance nose according to the invention.
• The figure 3 shows a detail of a lance nose according to the invention, to illustrate the characterizing part of the invention.
• The figure 4 represents a view similar to the figure 2 of a variant of the blowing lance nose according to the invention.
• The figure 5 shows a detail of a lance nose according to the invention, to illustrate the method of measuring the parameters necessary for an advantageous embodiment of the invention.

In the figures, identical or similar elements have the same references.

The figure 1 illustrates the third front wall 12 of the lance nose 1 which faces the bath. According to this embodiment, the lance nose 1 has six brewing gas outlet orifices 13 placed in a ring around a central zone 14 of the third front wall 12.

The figure 2 represents the lance nose according to the present invention in which the stirring gas is supplied by the central tube 2. This central tube 2 is closed by a front wall 3 directed towards the bath provided with at least two openings 4.

An internal tube 5 is arranged coaxially around the central tube 2 so as to form between them an annular cavity 6 serving for the supply of coolant in the direction of the arrow F ₁ . This internal tube 5 is terminated by a front wall 7 which is called a separator. This front wall 7 is provided with a central opening 8 and an orifice 9 in alignment with each opening 4 in the central tube 2. The separator 7, according to the present invention, has a geometry and an arrangement relative to the third particular front wall 12 which will be developed below.

An external tube 10 is arranged coaxially around the internal tube 5. This external tube forms with the internal tube 5 an annular cavity 11 which serves for the outlet of the coolant in the direction of the arrow F ₂ . This external tube is closed by a front wall 12 which faces the brewing bath and which has an internal surface 30. As shown in the figure 2 , the internal surface 30 of the third front wall 12 is provided with a conical central zone 14 which is directed towards the central opening 8 and which has a surface of a curved envelope in axial section.

The front wall 12 is also provided with an outlet orifice 13 in alignment with each opening 4 provided in the front wall 3 and with each passage orifice 9 provided in the front wall 7. In each of these aligned orifices and openings is arranged an outlet conduit 17 for the ejection of stirring gas outside the lance nose. The axes of revolution m of the conduits 17 are advantageously placed obliquely to the longitudinal axis L of the lance nose.

The cooling of this front wall 12 is ensured by the circulation of the cooling liquid in the heat exchange space 16 which is located between the separator 7 and the internal surface 30 of the front wall 12. In the illustrated embodiment , the coolant coming from the cavity 6 passes through the central opening 8 in the heat exchange zone 16 according to the arrow F ₃ . The liquid then flows in the direction of arrow F ₂ towards the outside, that is to say towards the cavity 11.

On the figure 3 , the separator 7, according to the present invention, is substantially planar and substantially parallel to the internal surface 30 of the third front wall 12. This separator 7 has, at the central opening 8, an edge 18 of curved axial section. A minimum diameter of the central opening 8 can then be measured from the front 19 of the edge 18 of the separator 7. The tangent passing through this front 19 and parallel to the longitudinal axis L of the lance nose makes it possible to measure the diameter the smallest of the central opening 8.

The height taken along the tangent passing through the front 19 and parallel to the longitudinal axis L of the lance nose and measured between said front 19 and the internal surface 30 of the third front wall 12 corresponds to the height H3, such that 'indicated on the figure 3 . The height H1 is in turn measured, parallel to the axis of revolution m of the injectors 17, between the surface facing the bath 20 of the separator 7 and the internal surface 30 of the third front wall 12, on the side of the opening central 8. This height H1 defines a minimum passage height for the coolant in the heat exchange space 16 at the central opening 8. In the volume contained in the cone passing through the axes of revolution m of the injectors, H1 is the minimum height of the passage of water along the internal surface of the third front wall, in space heat exchange. According to the present invention, the H ₁ / H ₃ ratio is advantageously between 30% and 55%.

The curved axial section of the edge 18 of the separator 7 has the advantage of accompanying the coolant when it converges in the central opening 8. In addition, as shown in the figure 3 , there is a complementary shape between the edge 18 of the separator 7 and the conical central zone 14 of the internal surface 30 of the third front wall 12. Therefore, the liquid is kept in contact with the internal surface of the third wall front 12 most exposed to thermal stresses. Consequently, a flow of coolant with reduced disturbance and cavitation phenomena can be obtained and maintained throughout its trajectory. The coolant thus "tranquilized" can then calmly bypass the obstacles represented by the injectors 17 in the heat exchange space 16 before emerging from the nose through the second annular cavity 11 along the arrow F ₂ .

The external diameter D _ext of the lance nose 1 according to the present invention corresponds to the diameter measured between the external surfaces of the external tube 10, as shown in the figure 2 .

Generally, a thickness of the separator 7 is measured between the surface 21 facing the first front wall 3 and the surface facing the bath 20 of the separator 7.

The thickness e1 of the edge 18 of the separator 7 is therefore measured parallel to the axis of revolution m of the injector 17 in continuity with the minimum height H1 of the heat exchange space 16 at the central opening 8. This thickness allows the separator to occupy a substantial volume in the lance nose and allows in combination with the curved section of the edge 18 to maintain a flow with reduced disturbance and good acceleration of the coolant. Preferably the ratio e1 / D _ext is between 5% and 15%,

In a particular embodiment of the lance nose shown in the figure 3 , the surface facing the bath 20 of the separator 7 is substantially sinusoidal. In the case where the surface facing the bath 20 of the separator 7 has a substantially sinusoidal shape, the maximum thickness, e1, is measured between the surface 21 facing the first front wall 3 and the tangent passing through the minimum of the part concave of the surface facing the bath 20. On the contrary, a minimum thickness is measured between the surface 21 facing the first front wall 3 and the tangent passing through the maximum of the convex part of the surface facing the bath 20.

This means that the separator 7 has, in addition to its thickness e1 at the central opening 8, a minimum thickness substantially at its center such that the heat exchange space 16 has a maximum height H _max substantially at the center of the separator 7. This height maximum H _max is intended to leave more space for the coolant when it passes through the injectors 17 in the heat exchange space 16.

The figure 4 represents a particular embodiment of the lance nose according to the present invention. In this embodiment, a central pillar 22 of particular configuration is present at the center of the central opening 8.

The pillar 22 has a first end E1 on the side of the first front wall 3 and a second end E2 connected to the central zone 14 of the internal surface 30 of the third front wall 12. This pillar preferably has a thinned part I between the first end E1 and the second end E2 which makes it possible to form a continuous curved surface 23 with the conical central zone 14 of the internal surface 30 of the third front wall 12. In this way, the coolant coming from the first cavity annular 6 along arrow F ₁ , runs along the upper face 21 of the separator 7 where it must bypass the injectors which represent a first obstacle on the trajectory of the liquid and then converges in the central opening 8. The pillar 22 present at the center of this central opening 8 then makes it possible to guide the coolant towards the internal surface 30 of the third front wall 12 where the thinned part I of the pillar ensures the passage of the liquid between this pillar 22 and the edge 18 of the separator 7, along the arrow F ₃ . Furthermore, the junction of the conical central zone 14 of the internal surface 30 of the third front wall 12 with the pillar 22 has a continuous curved surface 23 ensuring a progressive rotation of the liquid according to arrow F ₃ . The turbulence in the coolant then arriving in the heat exchange space 16 is reduced and the liquid can quietly bypass the injectors occupying a large volume in the heat exchange space 16. In this example, the calories accumulated in the front wall 12 exposed to the liquid iron bath are transferred to the pillar 22 whose contact surface with the coolant is increased thanks to its thinned part I, which improves the metal / liquid heat transfer

Furthermore, the pillar 22 advantageously has a second part II of predetermined length L2 joining said thinned part I and said first end E1, said second part II having a circular cross section defined by a predetermined diameter D2, constant over the entire length L2 , such that the ratio D2 / D _ext is advantageously between 10% and 15%.

Indeed, the pillar 22 being made of a material of good thermal conductivity, the heat coming from the bath and transmitted to the third front wall 12 and to its central zone 14 where it can then be led by the pillar 22 to the coolant. . The latter circulating around the pillar 22 ensures constant capture of the heat from the third front wall 12. In order to optimize the latter, the parts most exposed to the bath, namely the third front wall 12 and the pillar 22, are made of wrought copper which provides better thermal conductivity than cast copper.

Advantageously, the first thinned part I is further characterized by a predetermined diameter D1 which varies progressively from the diameter D2 at the junction with the second part II to a value preferably between 60% and 80% of D2 at the second end E2 of the pillar 22. The diameter D1 of the thinned part I of the pillar 22 therefore gradually decreases when one moves along the longitudinal axis L of the lance nose towards the bath until reaching a minimum value, then called D3 corresponding to the second end E2 of the pillar.

Preferably, the continuous curved surface 23 between the thinned part I of the pillar 22 and the conical central zone 14 of the internal surface 30 of the third front wall 12 is characterized by a radius of curvature greater than or equal to 30% of the diameter D2 of the second part II of pillar 22.

In the embodiment shown in figure 4 , the separator 7 and the thinned part I of the pillar 22 facing each other have a complementary shape thus ensuring the most delicate possible coolant support. Indeed, the edge 18 of the separator 7 and the thinned part I of the pillar 22 make it possible to form for the coolant a trajectory reducing the turbulence in the liquid.

A deflector 24 can also be placed in the center of the stirring gas supply tube 2. This deflector 24 makes it possible to appropriately divert the oxygen leaving the central pipe 2 to engage in the injectors 17.

The figure 5 represents a detail of the conical central zone 14 in order to explain how to measure the parameters relating to this central zone 14 of the internal surface 30 of the third front wall 12. The height h is measured between the tangent plane 32 of the wall internal 30 of the lance nose perpendicular to the longitudinal axis L and the parallel plane 31 tangent to the apex of the conical central zone 14. If an additional element to the conical central zone 14 is provided at the apex thereof, as for example pillar 22, plan 31 remains in the position it would have if this additional element did not exist. The apex of the conical central zone 14 coinciding with the cross section of the thinned part I of the pillar 18 having a minimum diameter D3, the plane 31 also passes through this section of minimum diameter D3 of the pillar 22.

The base b is situated in the tangent plane 32 of the internal wall 30. It is circumscribed by the points of intersection 33 with the extension of the internal wall 30.

Advantageously, the nose according to the present invention has an h / (b-D3) ratio of between 50% and 80%. Therefore, in the case where no additional element, such as for example a pillar, is present on the central zone 14, D3 is zero and the h / b ratio is preferably between 50% and 80%.

The figure 5 also represents the distance R for the passage of the coolant taken perpendicular to the longitudinal axis L of the nose in the central opening 8. When no pillar is present in the central opening 8, the distance R is measured between the front 19 of the separator 7 and the longitudinal axis L, this distance for the passage of the coolant is then called R ₁ and corresponds to the minimum radius of the central opening 8. When a pillar 22 is present in the opening central 8, the passage distance R for the liquid is then measured between the separating front 19 and the external surface of the thinned part I of the pillar 22, the distance is then called R ₂ . In both cases, this distance for the passage of the coolant is such that the ratio R / H3 is preferably between 70% and 110%, with R corresponding to R1 in the absence of a pillar or corresponding to R2 in the presence of a pillar.

It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made without departing from the scope of the appended claims.

Claims (10)

1. Blowing lance tip (1), intended for bath stirring, comprising:

   - a central tube for supplying stirring gas (2), closed at an end turned towards the bath by a first front wall (3) provided with at least two openings (4),

   - an internal tube (5) forming with the central tube (2) a first annular cavity (6) for the passage of a cooling liquid and ended at one end turned towards the bath by a second front wall, called a separator (7), having a central opening (8) and one passage orifice (9) per opening provided in said first front wall (4),

   - an external tube (10) forming with the internal tube (5) a second annular cavity (11) for the passage of the cooling liquid and closed at an end turned towards the bath by a third front wall (12) having one outlet orifice (13) per opening provided in said first front wall (4) and having an internal surface (30) comprising a tapered central area (14) which is directed towards said central opening (8) and which has a curved enveloped surface in axial section,

   - a heat exchange space (16) in which the cooling liquid flows, which is located between, on the one hand, said separator (7) and said third front wall (12) and, on the other hand, said central opening (8) and said second annular cavity (11), and in which the cooling liquid flows, and

   - an outlet conduit for the stirring gas, called an injector (17), leaving each opening (4) in said first front wall (3) and going as far as said corresponding outlet orifice (13) passing through said corresponding passage orifice (9) in a cooling liquid-tight manner,

   characterised in that said separator (7) has an edge (18) in axial section at the central opening (8) which is curved such that a height (H3) is defined between a front (19) of said edge (18) and said third front wall (12) and that in the heat exchange space (16) a minimum predetermined height (H1) is present on the side of said central opening (8), such that the ratio H1/H3 is between 5% and 80%, advantageously between 5% and 75%, preferably between 5% and 70%, preferentially between 5% and 65%, particularly advantageously between 5% and 60%, preferably between 10% and 60%, advantageously between 15% and 60%, preferably between 20% and 60%, preferentially between 25 and 60%, particularly advantageously between 25% and 55%, preferably between 30% and 55%.
2. Lance tip according to claim 1, characterised by a distance R, for the passage of the cooling liquid, taken perpendicularly to the longitudinal axis L of the tip between said front (19) of the edge (18) of the separator (7) and the longitudinal axis L of the tip, said distance R being such that the ratio R/H3 is between 20% and 150%, preferably between 30% and 140%, advantageously between 30% and 130%, preferentially between 40% and 130%, particularly advantageously between 50% and 130%, preferably between 60% and 120%, advantageously between 60% and 110%, preferably between 70% and 110%.
3. Lance tip according to any one of claims 1 and 2 having a predetermined external diameter (D_ext) and wherein said edge (18) of the separator (7) is defined by a thickness (e1) such that the ratio e1/D_ext is between 5% and 30%, preferably between 7% and 25%, advantageously between 7% and 20%, preferentially between 7% and 15%.
4. Lance tip according to any one of claims 1 to 3, wherein said separator (7) has a surface turned towards the bath (20) that is substantially sinusoidal.
5. Lance tip according to any one of claims 1 to 4, having a pillar (22) comprising a first end (E1) located opposite the bath and a second end (E2) turned towards the bath linked to the central area (14) of the internal surface (30) of the third front wall (12).
6. Lance tip according to claim 5, wherein the pillar (22) has a thinned part (I) between said first and second ends (E1 and E2) linked to the central area (14), which has a predetermined length L1 and an axial section decreasing in such a way that the pillar (18) forms a continuous curved section (23) with the central area (14) of the internal surface (30) of the third front wall (12).
7. Lance tip according to any one of claims 1 to 6, wherein said thinned part I of the pillar (22) has a minimum predetermined diameter D3 at said second end (E2) and said central area (14) of the internal surface (30) of the third front wall (12) has a height h and a base b so the ratio h/(b-D3) is between 20% and 120%, preferably between 20% and 110%, advantageously between 30% and 110%, preferentially between 30% and 100%, in particular between 40% and 100%, particularly advantageously between 40% and 90%, preferably between 45% and 85%, advantageously between 50% and 80%.
8. Lance tip according to any one of claims 1 to 7, wherein a deflector (24) is substantially present in the centre of said central stirring gas supply tube (2).
9. Lance tip according to any one of claims 1 to 8, wherein the injectors (17) have a revolution axis (m) oriented obliquely with respect to a longitudinal axis (L) of the lance tip.
10. Blowing lance tip according to any one of claims 1 to 9, characterised in that the above elements of the tip are produced separately and fixed in the mutual binding area by high energy welding, preferably electron beam welding.

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