EP0032343B1 - Method for the gaseous stirring of a molten metal bath - Google Patents
Method for the gaseous stirring of a molten metal bath Download PDFInfo
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- EP0032343B1 EP0032343B1 EP80401859A EP80401859A EP0032343B1 EP 0032343 B1 EP0032343 B1 EP 0032343B1 EP 80401859 A EP80401859 A EP 80401859A EP 80401859 A EP80401859 A EP 80401859A EP 0032343 B1 EP0032343 B1 EP 0032343B1
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- Prior art keywords
- stirring
- bath
- fluid
- injection device
- molten metal
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/35—Blowing from above and through the bath
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
Definitions
- the present invention relates to the operations of pneumatic stirring of a bath of molten metal by injecting a gas under the surface of the bath.
- a handicap of this technique results from the fact that very often pneumatic stirring is useful or sought after, for the treatment of metal, only temporarily while the injection of gas, which provides this stirring, is necessary permanently to avoid that the molten metal clogs the injection device by solidifying it.
- the injection device is calibrated so as to obtain an optimal gas flow rate for stirring, the minimum flow rate necessarily to be observed outside of the stirring periods for protecting the injection device against the risk of blockage constitutes a substantial economic penalty which may not be justified for metallurgical reasons.
- the object of the present invention is to remedy these difficulties.
- the subject of the invention is a process for pneumatically stirring a bath of molten metal by introducing an inert fluid by means of an injection device opening out under the surface of the bath, according to which the effect brewing is only sought temporarily and characterized in that, outside the brewing periods, the injection device is supplied with an inert fluid in the gaseous state, and in that, during the brewing periods, the inert gaseous fluid is replaced with an inert fluid in the liquid state capable of vaporizing easily on contact with the molten metal.
- the fluids injected respectively in gaseous form and in liquid form can be either of the same chemical nature or of different chemical natures.
- the fluid injected in liquid form has a density / molecular mass ratio of high value.
- the method of the invention can be implemented both with an injection device constituted by nozzles opening out under the surface of the molten metal bath as with an injection device constituted by a plurality of refractory parts, selective and oriented internal permeability, incorporated into the bottom of the container containing the molten metal bath.
- an injection device constituted by nozzles opening out under the surface of the molten metal bath
- an injection device constituted by a plurality of refractory parts, selective and oriented internal permeability, incorporated into the bottom of the container containing the molten metal bath.
- Such permeable refractory parts have been described in patent application EP-0 021 861, in the name of the applicant.
- the invention therefore consists, in its essential characteristics, of modifying during operation the physical state of the stirring fluid - and possibly also its chemical nature - so as to inject a protective gas into the device. injection when the stirring of the bath is not necessary and to inject a stirring liquid when this need occurs.
- the invention provides an elegant solution to the problem posed by making it possible to reconcile the apparently contradictory imperatives of minimizing the protection flow and optimizing the stirring flow by means of the same injection device.
- FIG. 1 there is shown at 1 the converter with the lance 2 for blowing oxygen from above.
- the bottom 3 of the converter is provided with nozzles 4.
- the nozzles 4 consist of a central tube 5, through which liquid or gaseous nitrogen passes, and of an external tube 6 concentric with the tube 5 and defining with the tube 5 an annular space into which a cooling fluid is injected.
- the tubes 5 are connected to a manifold 7 supplied, either with liquid nitrogen coming from the source 8, or with gaseous nitrogen coming from the source 9.
- the placing of the manifold 7 in communication with the source 8 or with the source 9 takes place using the three-way valve symbolized at 10.
- the annular spaces defined between the tubes 5 and 6 are connected to a source 11 coolant through a line 12.
- the generally adopted criterion consists in obtaining a sonic velocity of the gas at the nose of the nozzle. Under these conditions, the minimum protection flow is close to 10 1 of nitrogen per second and this flow is obtained under a pressure of 2 ⁇ 10 5 Pascal.
- the treatment of the bath begins with stirring with nitrogen. Nitrogen in the liquefied state is then substituted for the previously blown nitrogen gas. Under the maximum pressure of 15. 105 Pascal, the flow of liquid nitrogen passing through the nozzle is 0.2 1 / sec. approximately which, on contact with the molten metal in the converter vaporizes rapidly, providing a gas flow rate close to 120 IIsec., which corresponds to the value sought for efficient stirring.
- the maximum gas flow rate that can be reached per nozzle is only 60 l / sec. about.
- the process according to the invention makes it possible, in the case of nitrogen mixing, to double the mixing flow at a given protection flow, or, expressed differently, to reduce the protection flow for half for a flow of brewing given.
- FIG. 2 there is shown at 1 the converter with the lance 2 for blowing oxygen from above.
- the permeable refractory pieces 13 are placed in the bottom 3 of the converter.
- Each piece 13 is constituted by an assembly 14 of refractory plates maintained laterally by a metal casing 15 completed by a closure plate 16.
- the pieces 13 are connected by conduits 17 to a nurse 7 supplied, either with liquid nitrogen coming from the source 8, or with gaseous nitrogen coming from the source 9.
- the nurse 7 is placed in communication with the source 8 or with the source 9 using of valve 10.
- nitrogen gas is injected at a minimum flow rate of less than 1 l / sec. ; this flow rate is obtained at a pressure of approximately 10 5 Pascal.
- nitrogen is then injected in the liquid state at a rate of approximately 0.3 l / sec. ; this flow rate is obtained at a pressure of approximately 6 ⁇ 10 5 Pascal.
- the liquid nitrogen vaporizes quickly and provides a gas flow close to 200 l / sec.
- the gaseous and liquid fluids are of different chemical nature.
- the shielding gas can be argon and the brewing liquid liquid nitrogen, whose cost price is lower than that of liquid argon and whose injection after the refining period, that is to say in a highly oxidized metal bath, no longer presents a great risk of nitriding of the latter.
- this passage from argon to liquid nitrogen makes it possible to achieve a flow rate of vaporized gas which, as we have seen, could not be obtained with liquid argon.
- This single source is then connected to the injection device by two parallel circuits, one of which includes an evaporator and which are activated alternately using a “bypass”, depending on whether one wishes to blow the gas or inject the brewing liquid.
- the invention is not limited to liquefied gases, but extends to any fluid in the liquid state under standard conditions of temperature and pressure, but insofar as it is obviously not not harmful to the development of the metal to be brewed.
- mixtures of fluids of different chemical natures are also possible.
- a brewing fluid which. per unit volume in the liquid state, provides the largest volume of gas by vaporization on contact with the molten metal.
- liquefied gases appear to be entirely suitable.
- the method according to the invention makes it possible to reduce the brewing period compared to the known technique. This is an appreciable advantage, in particular on the thermal level. because studies made by the inventors have shown that the cooling of a steel bath in a converter during brewing is less the result of the blowing of the brewing fluid than the calorific losses caused by the expectations for sampling and the duration of agitation of the bath, although these losses diminish when the converter capacity increases.
- stirring liquid can be under standard conditions of temperature and pressure, a gas which has been liquefied prior to its injection, the opposite is quite possible with regard to the shielding gas .
- the protective gas of the injection device is. under normal conditions of temperature and pressure, a liquid which has been vaporized prior to its passage through the injection device.
- the protection of the injection device with a gas originating from the prior vaporization of a liquid is combined with stirring of the bath by injection of a liquid originating from a previously liquefied gas. , which makes it possible to have a high flow rate of stirring gas, while reducing to a certain extent the cooling of the bath outside the brewing periods.
- the invention is not limited, as regards its applications, to mixing in a converter, but extends to other fields, such as the processing of steel in a ladle, and more generally, to any treatment.
- pneumatic stirring of a bath of molten metal by injecting a stirring fluid under the surface of the bath.
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- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
- Mixers With Rotating Receptacles And Mixers With Vibration Mechanisms (AREA)
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Abstract
Description
La présente invention concerne les opérations de brassage pneumatique d'un bain de métal en fusion par injection d'un gaz sous la surface du bain.The present invention relates to the operations of pneumatic stirring of a bath of molten metal by injecting a gas under the surface of the bath.
On sait que de telles opérations trouvent application dans divers secteurs industriels et en particulier en sidérurgie, où il a déjà été proposé (certificat d'utilité français n° 2 322 202) d'étendre les possibilités métallurgiques des procédés de conversion pneumatique de la fonte en associant, dans le convertisseur, un soufflage d'oxygène par le haut au moyen d'une lance émergée, avec une insufflation de gaz inerte dans le bain métallique pendant et après l'affinage à l'oxygène au moyen de dispositifs d'injection débouchant sous la surface et implantés en paroi ou plus généralement dans le fond du récipient.It is known that such operations find application in various industrial sectors and in particular in the steel industry, where it has already been proposed (French utility certificate no. 2,322,202) to extend the metallurgical possibilities of the processes for pneumatically converting cast iron. by combining, in the converter, a blowing of oxygen from the top by means of an emerged lance, with a blowing of inert gas in the metal bath during and after the refining with oxygen by means of injection devices emerging below the surface and implanted in the wall or more generally in the bottom of the container.
Un handicap de cette technique résulte du fait que bien souvent le brassage pneumatique n'est utile ou recherché, pour le traitement du métal, que temporairement alors que l'injection de gaz, qui procure ce brassage, est nécessaire en permanence pour éviter que le métal en fusion vienne boucher le dispositif d'injection en s'y solidifiant.A handicap of this technique results from the fact that very often pneumatic stirring is useful or sought after, for the treatment of metal, only temporarily while the injection of gas, which provides this stirring, is necessary permanently to avoid that the molten metal clogs the injection device by solidifying it.
A cet égard, si, compte tenu des disponibilités en pression de l'installation, on calibre le dispositif d'injection de manière à obtenir un débit de gaz optimal pour le brassage, le débit minimum à respecter nécessairement en dehors des périodes de brassage pour protéger le dispositif d'injection contre les risques de bouchage constitue une pénalité substantielle au plan économique qui peut ne pas être justifiée par des raisons métallurgiques.In this regard, if, taking into account the pressure available in the installation, the injection device is calibrated so as to obtain an optimal gas flow rate for stirring, the minimum flow rate necessarily to be observed outside of the stirring periods for protecting the injection device against the risk of blockage constitutes a substantial economic penalty which may not be justified for metallurgical reasons.
Inversement. si l'on calibre le dispositif d'injection de façon à minimiser le débit de protection, il est souvent difficile, voire impossible, d'atteindre ensuite les débits de gaz souhaitables pour un brassage efficace. On peut alors songer à multiplier le nombre de dispositifs d'injection, mais ce faisant, on est ramené au problème précédent.Conversely. if the injection device is calibrated so as to minimize the protection flow, it is often difficult, if not impossible, to then achieve the desired gas flow rates for efficient stirring. We can then think of increasing the number of injection devices, but in doing so, we are brought back to the previous problem.
La présente invention a pour but de remédier à ces difficultés.The object of the present invention is to remedy these difficulties.
A cet effet, l'invention a pour objet un procédé de brassage pneumatique d'un bain de métal en fusion par introduction d'un fluide inerte au moyen d'un dispositif d'injection débouchant sous la surface du bain selon lequel l'effet de brassage n'est recherché que temporairement et caractérisé en ce que, en dehors des périodes de brassage, on alimente le dispositif d'injection avec un fluide inerte à l'état gazeux, et en ce que, au cours des périodes de brassage, on substitue au fluide inerte gazeux un fluide inerte à l'état liquide susceptible de se vaporiser facilement au contact du métal en fusion.To this end, the subject of the invention is a process for pneumatically stirring a bath of molten metal by introducing an inert fluid by means of an injection device opening out under the surface of the bath, according to which the effect brewing is only sought temporarily and characterized in that, outside the brewing periods, the injection device is supplied with an inert fluid in the gaseous state, and in that, during the brewing periods, the inert gaseous fluid is replaced with an inert fluid in the liquid state capable of vaporizing easily on contact with the molten metal.
Les fluides injectés respectivement sous forme gazeuse et sous forme liquide peuvent être, soit de même nature chimique, soit de natures chimique différentes.The fluids injected respectively in gaseous form and in liquid form can be either of the same chemical nature or of different chemical natures.
Conformément à une variante, le fluide injecté sous forme liquide présente un rapport masse volumique/masse moléculaire de valeur élevée.According to a variant, the fluid injected in liquid form has a density / molecular mass ratio of high value.
Le procédé de l'invention peut être mis en oeuvre aussi bien avec un dispositif d'injection constitué par des tuyères débouchant sous la surface du bain de métal en fusion qu'avec un dispositif d'injection constitué par une pluralité de pièces réfractaires, à perméabilité interne sélective et orientée, incorporées dans le fond du récipient contenant le bain de métal en fusion. De telles pièces réfractaires perméables ont été décrites dans la demande de brevet EP-0 021 861, au nom du demandeur.The method of the invention can be implemented both with an injection device constituted by nozzles opening out under the surface of the molten metal bath as with an injection device constituted by a plurality of refractory parts, selective and oriented internal permeability, incorporated into the bottom of the container containing the molten metal bath. Such permeable refractory parts have been described in patent application EP-0 021 861, in the name of the applicant.
Comme on le comprend, l'invention consiste donc, dans ses caractéristiques essentielles, à modifier en cours d'opération l'état physique du fluide de brassage - et éventuellement sa nature chimique également - de manière à injecter un gaz de protection du dispositif d'injection lorsque le brassage du bain n'est pas nécessaire et à injecter un liquide de brassage lorsque cette nécessité a lieu.As can be understood, the invention therefore consists, in its essential characteristics, of modifying during operation the physical state of the stirring fluid - and possibly also its chemical nature - so as to inject a protective gas into the device. injection when the stirring of the bath is not necessary and to inject a stirring liquid when this need occurs.
Ainsi, l'invention apporte une solution élégante au problème posé en permettant de concilier les impératifs apparemment contradictoires de minimisation du débit de protection et d'optimisation du débit de brassage au moyen d'un même dispositif d'injection.Thus, the invention provides an elegant solution to the problem posed by making it possible to reconcile the apparently contradictory imperatives of minimizing the protection flow and optimizing the stirring flow by means of the same injection device.
L'invention sera mieux comprise dans ses différents aspects et avantages grâce à la description ci-après de deux exemples d'application du brassage au gaz inerte au cours d'une opération d'affinage pneumatique de la fonte dans un convertisseur à soufflage d'oxygène par le haut.The invention will be better understood in its various aspects and advantages thanks to the description below of two examples of application of inert gas mixing during a pneumatic refining operation of the cast iron in a blown converter. oxygen from above.
On considère un convertisseur de type LD d'une capacité de 60 t et dont le fond a été équipé d'un dispositif d'injection constitué par des tuyères en acier présentant un diamètre interne de 5 mm. Les tuyères sont au nombre de quatre uniformément réparties dans le fond et reliées à un système d'alimentation en azote dont la pression maximale permise est limitée à 105 Pascal.We consider an LD type converter with a capacity of 60 t and the bottom of which has been fitted with an injection device consisting of steel nozzles having an internal diameter of 5 mm. The nozzles are four in number uniformly distributed in the bottom and connected to a nitrogen supply system whose maximum allowable pressure is limited to 10 5 Pascal.
Sur la figure 1 jointe, on a représenté en 1 le convertisseur avec la lance 2 de soufflage d'oxygène par le haut. Le fond 3 du convertisseur est muni de tuyères 4. Les tuyères 4 sont constituées d'un tube central 5, à travers lequel passe l'azote liquide ou gazeux, et d'un tube extérieur 6 concentrique au tube 5 et définissant avec le tube 5 un espace annulaire dans lequel on injecte un fluide refroidissant. Les tubes 5 sont reliés à une nourrice 7 alimentée, soit en azote liquide provenant de la source 8, soit en azote gazeux provenant de la source 9. La mise en communication de la nourrice 7 avec la source 8 ou avec la source 9 se fait à l'aide de la vanne à trois voies symbolisée en 10. Les espaces annulaires définis entre les tubes 5 et 6 sont reliés à une source 11 de fluide refroidissant par l'intermédiaire d'une conduite 12.In Figure 1 attached, there is shown at 1 the converter with the
Au cours de la phase d'affinage à l'oxygène, le brassage à l'azote n'est pas nécessaire puisque la décarburation procure elle-même une agitation suffisante du bain métallique. Il s'agit donc, au cours de cette période, d'insuffler le minimum de gaz par tuyère, nécessaire pour éviter le bouchage de celle-ci. On sait que le critère généralement adopté consiste à obtenir au nez de la tuyère une vitesse sonique du gaz. Dans ces conditions, le débit minimal de protection est voisin de 10 1 d'azote par seconde et ce débit est obtenu sous une pression de 2 · 105 Pascal.During the oxygen refining phase, mixing with nitrogen is not necessary since the decarburization itself provides sufficient agitation of the metal bath. It is therefore, during this period, to inject the minimum amount of gas per nozzle, necessary to avoid clogging thereof. It is known that the generally adopted criterion consists in obtaining a sonic velocity of the gas at the nose of the nozzle. Under these conditions, the minimum protection flow is close to 10 1 of nitrogen per second and this flow is obtained under a pressure of 2 · 10 5 Pascal.
A la fin de la période d'affinage à l'oxygène, débute le traitement du bain par brassage à l'azote. On substitue alors de l'azote à l'état liquéfié à l'azote gazeux précédemment insufflé. Sous la pression maximale de 15. 105 Pascal, le débit d'azote liquide passant dans la tuyère est de 0,2 1/sec. environ qui, au contact du métal en fusion dans le convertisseur se vaporise rapidement en fournissant un débit de gaz voisin de 120 IIsec., ce qui correspond à la valeur recherchée pour un brassage efficace.At the end of the oxygen refining period, the treatment of the bath begins with stirring with nitrogen. Nitrogen in the liquefied state is then substituted for the previously blown nitrogen gas. Under the maximum pressure of 15. 105 Pascal, the flow of liquid nitrogen passing through the nozzle is 0.2 1 / sec. approximately which, on contact with the molten metal in the converter vaporizes rapidly, providing a gas flow rate close to 120 IIsec., which corresponds to the value sought for efficient stirring.
A titre comparatif, si l'on continue à alimenter les tuyères en azote gazeux après la période d'affinage, le débit maximal de gaz pouvant être atteint par tuyère est seulement de 60 I/sec. environ.By way of comparison, if one continues to supply the nozzles with nitrogen gas after the refining period, the maximum gas flow rate that can be reached per nozzle is only 60 l / sec. about.
Un tel débit pouvant être insuffisant pour assurer un brassage satisfaisant, on est alors amené, soit à doubler le nombre de tuyères, d'où un investissement et des frais d'exploitation supplémentaires, soit à utiliser des tuyères de plus grand diamètre interne, ce qui dans tous les cas, conduit à doubler la consommation d'azote nécessaire pour la protection des tuyères.As such a flow rate may be insufficient to ensure satisfactory stirring, it is then necessary either to double the number of nozzles, hence an investment and additional operating costs, or to use nozzles of larger internal diameter, this which in any case leads to double the consumption of nitrogen necessary for the protection of the nozzles.
On voit que le procédé selon l'invention permet, dans le cas d'un brassage à l'azote de doubler le débit de brassage à débit de protection donné, ou, exprimé différemment, à réduire de moitié le débit de protection pour un débit de brassage donné.It can be seen that the process according to the invention makes it possible, in the case of nitrogen mixing, to double the mixing flow at a given protection flow, or, expressed differently, to reduce the protection flow for half for a flow of brewing given.
Bien entendu, ces proportions sont valables pour l'azote et sont généralement modifiées avec la nature du gaz utilisé. Ainsi, si l'on utilise de l'argon liquéfié le débit maximum sera de 65 1/sec. environ, donc beaucoup plus défavorable que dans le cas de l'azote.Of course, these proportions are valid for nitrogen and are generally modified with the nature of the gas used. Thus, if liquefied argon is used, the maximum flow rate will be 65 l / sec. approximately, therefore much more unfavorable than in the case of nitrogen.
On considère un convertisseur du type LD d'une capacité de 60 t. Cinq pièces réfractaires perméables sont incorporées à la maçonnerie du fond du convertisseur. Chacune de ces pièces est constituée par un assemblage ordonné et jointif de plaques réfractaires non poreuses, juxtaposées sans joint matériel d'étanchéité entre elles ; le serrage et la cohésion de ces plaques est assuré par frettage, au moyen d'une enveloppe métallique ; une plaque de fermeture complète l'enveloppe métallique de façon à assurer l'étanchéité de chaque pièce vis-à-vis de l'extérieur du convertisseur ; une conduite d'amenée du fluide est fixée de façon étanche sur cette plaque de fermeture et débouche dans un canal de répartition du fluide ménagé à l'intérieur de l'assemblage des plaques réfractaires constituant chacune des pièces réfractaires perméables.We consider an LD type converter with a capacity of 60 t. Five permeable refractory pieces are incorporated into the masonry at the bottom of the converter. Each of these parts is made up of an ordered and joined assembly of non-porous refractory plates, juxtaposed without a material seal between them; the tightening and cohesion of these plates is ensured by shrinking, by means of a metal casing; a closing plate completes the metal envelope so as to seal each part vis-à-vis the outside of the converter; a fluid supply pipe is tightly fixed on this closure plate and opens into a fluid distribution channel formed inside the assembly of the refractory plates each constituting the permeable refractory parts.
Sur la figure 2 jointe, on a représenté en 1 le convertisseur avec la lance 2 de soufflage d'oxygène par le haut. Dans le fond 3 du convertisseur, sont placées les pièces réfractaires perméables 13. Chaque pièce 13 est constituée par un assemblage 14 de plaques réfractaires maintenu latéralement par une enveloppe métallique 15 complétée par une plaque de fermeture 16. Les pièces 13 sont reliées par des conduits 17 à une nourrice 7 alimentée, soit en azote liquide provenant de la source 8, soit en azote gazeux provenant de la source 9. La mise en communication de la nourrice 7 avec la source 8 ou avec la source 9 se fait à l'aide de la vanne 10.In Figure 2 attached, there is shown at 1 the converter with the
Au cours de la phase d'affinage à l'oxygène, on injecte de l'azote gazeux à un débit minimum inférieur à 1 1/sec. ; ce débit est obtenu à une pression d'environ 105 Pascal. A la fin de la période d'affinage à l'oxygène, on injecte alors de l'azote à l'état liquide à un débit d'environ 0,3 1/sec. ; ce débit est obtenu à une pression d'environ 6 ·105 Pascal. Au contact du métal en fusion, l'azote liquide se vaporise rapidement et fournit un débit de gaz voisin de 200 1/sec.During the oxygen refining phase, nitrogen gas is injected at a minimum flow rate of less than 1 l / sec. ; this flow rate is obtained at a pressure of approximately 10 5 Pascal. At the end of the oxygen refining period, nitrogen is then injected in the liquid state at a rate of approximately 0.3 l / sec. ; this flow rate is obtained at a pressure of approximately 6 · 10 5 Pascal. On contact with the molten metal, the liquid nitrogen vaporizes quickly and provides a gas flow close to 200 l / sec.
Conformément à une variante de l'invention, les fluides gazeux et liquides sont de nature chimique différente. Par exemple, dans une opération d'affinage de la fonte, le gaz de protection peut être de l'argon et le liquide de brassage de l'azote liquide, dont le prix de revient est inférieur à celui de l'argon liquide et dont l'injection après la période d'affinage, c'est-à-dire dans un bain métallique fortement oxydé, ne présente plus un gros risque de nitruration de ce dernier. Par ailleurs, ce passage de l'argon à l'azote liquide permet d'atteindre un débit de gaz vaporisé qui, comme on l'a vu, ne pourrait être obtenu avec l'argon liquide.According to a variant of the invention, the gaseous and liquid fluids are of different chemical nature. For example, in a pig iron refining operation, the shielding gas can be argon and the brewing liquid liquid nitrogen, whose cost price is lower than that of liquid argon and whose injection after the refining period, that is to say in a highly oxidized metal bath, no longer presents a great risk of nitriding of the latter. Furthermore, this passage from argon to liquid nitrogen makes it possible to achieve a flow rate of vaporized gas which, as we have seen, could not be obtained with liquid argon.
Toutefois, l'utilisation de fluides de même nature présente de son côté un avantage pratique appréciable, à savoir la possibilité de mettre en oeuvre l'invention avec une seule source de gaz liquéfié.However, the use of fluids of the same kind has an appreciable practical advantage, namely the possibility of implementing the invention with a single source of liquefied gas.
Cette source unique est alors reliée au dispositif d'injection par deux circuits en parallèle dont l'un comprend un évaporateur et qui sont activés alternativement à l'aide d'un « by-pass », selon que l'on désire souffler le gaz de protection ou injecter le liquide de brassage.This single source is then connected to the injection device by two parallel circuits, one of which includes an evaporator and which are activated alternately using a “bypass”, depending on whether one wishes to blow the gas or inject the brewing liquid.
Il va de soit que l'invention n'est pas limitée aux gaz liquéfiés, mais s'étend à tout fluide à l'état liquide dans les conditions standard de température et de pression, mais dans la mesure bien entendu où il n'est pas nuisible à l'élaboration du métal devant être brassé. Bien entendu, des mélanges de fluides de natures chimiques différentes sont également possibles.It goes without saying that the invention is not limited to liquefied gases, but extends to any fluid in the liquid state under standard conditions of temperature and pressure, but insofar as it is obviously not not harmful to the development of the metal to be brewed. Of course, mixtures of fluids of different chemical natures are also possible.
Compte tenu de ce qui précède, on a avantage à utiliser un fluide de brassage qui. par unité de volume à l'état liquide, procure le plus gros volume de gaz par vaporisation au contact du métal en fusion.In view of the above, it is advantageous to use a brewing fluid which. per unit volume in the liquid state, provides the largest volume of gas by vaporization on contact with the molten metal.
D'une façon générale. on a donc avantage à choisir un fluide de brassage qui présente un rapport masse volumique/masse moléculaire le plus élevé possible.Generally speaking. it is therefore advantageous to choose a stirring fluid which has the highest possible density / molecular weight ratio.
A cet égard, les gaz liquéfiés apparaissent tout- à-fait appropriés.In this respect, liquefied gases appear to be entirely suitable.
Ces considérations ne doivent pas en faire perdre de vue d'autres relatives à la viscosité du liquide de brassage dont dépend bien entendu le débit susceptible de pouvoir passer dans le dispositif d'injection sous une pression donnée.These considerations should not make us lose sight of others relating to the viscosity of the stirring liquid on which, of course, the flow rate likely to be able to pass through the injection device under a given pressure depends.
C'est ce qui explique que l'utilisation de l'argon liquide qui présente pourtant un rapport masse volumique/masse moléculaire sensiblement supérieur à celui de l'azote liquide (respectivement 35 et 29 1 ' environ) conduit à un débit de gaz vaporisé bien inférieur à ce dernier.This explains why the use of liquid argon which nevertheless presents a density / molecular mass ratio appreciably higher than that of liquid nitrogen (respectively 35 and 29 1 ′ approximately) leads to a flow of vaporized gas. much lower than the latter.
Par ailleurs. ces considérations ne tiennent pas compte des effets de refroidissement du bain occasionnés notamment par la vaporisation du fluide de brassage, mais on sait les contrebalancer le cas échéant par différents moyens d'apport calorifique d'appoint tels qu'un préchauffage du fluide lorsque cela est possible ou une prolongation du soufflage d'oxygène au-delà de la période d'affinage proprement dite.Otherwise. these considerations do not take into account the cooling effects of the bath caused in particular by the vaporization of the stirring fluid, but it is known to counterbalance them if necessary by various additional heat supply means such as preheating of the fluid when this is possible or an extension of the oxygen blowing beyond the actual refining period.
En outre. le procédé selon l'invention permet de réduire la période de brassage par rapport à la technique connue. Il s'agit là d'un avantage appréciable, en particulier sur le plan thermique. car des études faites par les inventeurs ont montré que le refroidissement d'un bain d'acier dans un convertisseur pendant le brassage est moins le fait de l'insufflation du fluide de brassage que des pertes calorifiques occasionnées par les attentes pour les échantillonnages et la durée d'agitation du bain, encore que ces pertes s'amenuisent lorsque la capacité de convertisseur augmente.In addition. the method according to the invention makes it possible to reduce the brewing period compared to the known technique. This is an appreciable advantage, in particular on the thermal level. because studies made by the inventors have shown that the cooling of a steel bath in a converter during brewing is less the result of the blowing of the brewing fluid than the calorific losses caused by the expectations for sampling and the duration of agitation of the bath, although these losses diminish when the converter capacity increases.
Par ailleurs. il doit être souligné que si le liquide de brassage peut être dans les conditions standards de températures et de pression, un gaz que l'on a liquéfié préalablement à son injection, le contraire est tout à fait possible à l'égard du gaz de protection.Otherwise. it should be emphasized that if the stirring liquid can be under standard conditions of temperature and pressure, a gas which has been liquefied prior to its injection, the opposite is quite possible with regard to the shielding gas .
En effet. conformément à une variante, le gaz de protection du dispositif d'injection est. dans les conditions normales de température et de pression, un liquide que l'on a vaporisé préalablement à son passage dans le dispositif d'injection.Indeed. according to a variant, the protective gas of the injection device is. under normal conditions of temperature and pressure, a liquid which has been vaporized prior to its passage through the injection device.
On comprend immédiatement les avantages particuliers de cette variante en ce qui concerne précisément l'aspect « thermique de l'opération.We immediately understand the particular advantages of this variant as regards precisely the “thermal” aspect of the operation.
Toutefois, conformément à une autre variante de réalisation, on associe à la protection du dispositif d'injection par un gaz provenant de la vaporisation préalable d'un liquide, un brassage du bain par injection d'un liquide provenant d'un gaz préalablement liquéfié, ce qui permet d'avoir du débit de gaz de brassage important, tout en réduisant dans une certaine mesure le refroidissement du bain en dehors des périodes de brassage.However, in accordance with another variant embodiment, the protection of the injection device with a gas originating from the prior vaporization of a liquid is combined with stirring of the bath by injection of a liquid originating from a previously liquefied gas. , which makes it possible to have a high flow rate of stirring gas, while reducing to a certain extent the cooling of the bath outside the brewing periods.
Enfin, l'invention ne se limite pas, quant à ses applications, au brassage en convertisseur, mais s'étend à d'autres domaines, tels que le traitement de l'acier en poche, et de façon plus générale, à tout traitement de brassage pneumatique d'un bain de métal en fusion par injection d'un fluide de brassage sous la surface du bain.Finally, the invention is not limited, as regards its applications, to mixing in a converter, but extends to other fields, such as the processing of steel in a ladle, and more generally, to any treatment. pneumatic stirring of a bath of molten metal by injecting a stirring fluid under the surface of the bath.
Claims (9)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT80401859T ATE18438T1 (en) | 1980-01-02 | 1980-12-23 | PROCESS FOR GAS FLUSHING A METAL BATH. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8000083A FR2473064A1 (en) | 1980-01-02 | 1980-01-02 | PROCESS FOR PNEUMATIC BREWING OF A FUSION METAL BATH |
FR8000083 | 1980-01-02 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0032343A1 EP0032343A1 (en) | 1981-07-22 |
EP0032343B1 true EP0032343B1 (en) | 1986-03-05 |
Family
ID=9237192
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP80401859A Expired EP0032343B1 (en) | 1980-01-02 | 1980-12-23 | Method for the gaseous stirring of a molten metal bath |
Country Status (8)
Country | Link |
---|---|
US (1) | US4382817A (en) |
EP (1) | EP0032343B1 (en) |
JP (1) | JPS56102689A (en) |
AT (1) | ATE18438T1 (en) |
AU (1) | AU535747B2 (en) |
CA (1) | CA1159653A (en) |
DE (1) | DE3071475D1 (en) |
FR (1) | FR2473064A1 (en) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2501722B1 (en) * | 1981-03-11 | 1986-08-14 | Siderurgie Fse Inst Rech | PROCESS FOR THE PNEUMATIC BREWING OF A METAL BATH |
US4780133A (en) * | 1986-11-10 | 1988-10-25 | Lazcano Navarro Arturo | Process to improve the refining of liquid metals by natural gas injection |
SE8702338L (en) * | 1987-06-05 | 1988-12-06 | Aga Ab | GAS RINSE OF MELMA IN SHAENK |
FR2632971B1 (en) * | 1988-06-17 | 1993-09-03 | Vallourec | PROCESS FOR TREATING LIQUID STEEL BY GAS INJECTION THROUGH THE BOTTOM OF POCKET |
FR2635789B1 (en) * | 1988-08-29 | 1993-04-23 | Air Liquide American | PROCESS FOR PRODUCING LOW NITROGEN STEEL IN A POCKET OVEN |
SE463876B (en) * | 1989-05-29 | 1991-02-04 | Aga Ab | SEATED AS TREATMENT OF A GAS MOLD AND DEVICE FOR SUCH TREATMENT |
FR2807066B1 (en) * | 2000-03-29 | 2002-10-11 | Usinor | PNEUMATIC BREWING PROCESS FOR POUCHED LIQUID METAL |
DE102009049896A1 (en) * | 2009-01-22 | 2010-08-05 | Sms Siemag Ag | Pulse flushing with inert gas in the BOF and AOD converter process |
CN111957251A (en) * | 2020-09-01 | 2020-11-20 | 云南锡业股份有限公司锡业分公司 | Liquid metal stirring device and using method thereof |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1189971A (en) * | 1956-10-19 | 1959-10-08 | Arbed | Steel making process |
BE609232A (en) * | 1961-10-16 | 1962-04-16 | Centre Nat Rech Metall | Improvements to cast iron refining processes |
GB1253581A (en) * | 1968-02-24 | 1971-11-17 | Maximilianshuette Eisenwerk | Improvements in processes and apparatus for making steel |
US4001009A (en) * | 1969-04-03 | 1977-01-04 | Hannsgeorg Bauer | Process for the manufacture of steels with a high chromium content |
BE752893A (en) * | 1969-07-08 | 1970-12-16 | Forges De La Loire St Chamond | METHOD AND DEVICE FOR COOLING A REFINING CONVERTER TUBE |
BE742079A (en) * | 1969-11-21 | 1970-05-21 | ||
US3819165A (en) * | 1972-12-08 | 1974-06-25 | Maximilianshuette Eisenwerk | Device for blowing-in oxygen through the refractory lining of a metallurgical converter |
AT337736B (en) * | 1973-02-12 | 1977-07-11 | Voest Ag | METHOD OF REFRESHING BIG IRON |
US3854932A (en) * | 1973-06-18 | 1974-12-17 | Allegheny Ludlum Ind Inc | Process for production of stainless steel |
FR2322202A1 (en) * | 1975-08-29 | 1977-03-25 | Siderurgie Fse Inst Rech | Steel refining by oxygen lancing and bottom blowing - for improved quality steel of various grades |
JPS5810967B2 (en) * | 1976-06-01 | 1983-02-28 | 新日本製鐵株式会社 | How to operate a converter |
US4174212A (en) * | 1978-03-10 | 1979-11-13 | A. Finkl & Sons Co. | Method for the refining of steel |
-
1980
- 1980-01-02 FR FR8000083A patent/FR2473064A1/en active Granted
- 1980-12-18 JP JP17965880A patent/JPS56102689A/en active Pending
- 1980-12-23 DE DE8080401859T patent/DE3071475D1/en not_active Expired
- 1980-12-23 AT AT80401859T patent/ATE18438T1/en not_active IP Right Cessation
- 1980-12-23 EP EP80401859A patent/EP0032343B1/en not_active Expired
- 1980-12-30 AU AU65884/80A patent/AU535747B2/en not_active Ceased
- 1980-12-30 CA CA000367690A patent/CA1159653A/en not_active Expired
-
1981
- 1981-01-02 US US06/222,513 patent/US4382817A/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
FR2473064B1 (en) | 1983-11-10 |
CA1159653A (en) | 1984-01-03 |
US4382817A (en) | 1983-05-10 |
AU535747B2 (en) | 1984-04-05 |
AU6588480A (en) | 1981-08-06 |
EP0032343A1 (en) | 1981-07-22 |
FR2473064A1 (en) | 1981-07-10 |
DE3071475D1 (en) | 1986-04-10 |
ATE18438T1 (en) | 1986-03-15 |
JPS56102689A (en) | 1981-08-17 |
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