EP1530648B1 - Methods and device for decarbonising a steel melt - Google Patents

Methods and device for decarbonising a steel melt Download PDF

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Publication number
EP1530648B1
EP1530648B1 EP03792199A EP03792199A EP1530648B1 EP 1530648 B1 EP1530648 B1 EP 1530648B1 EP 03792199 A EP03792199 A EP 03792199A EP 03792199 A EP03792199 A EP 03792199A EP 1530648 B1 EP1530648 B1 EP 1530648B1
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EP
European Patent Office
Prior art keywords
steel melt
molten steel
lance
oxygen
blowing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP03792199A
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German (de)
French (fr)
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EP1530648A1 (en
Inventor
Yuyou Zhai
Johannes Müller
Johannes Spiess
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Primetals Technologies Austria GmbH
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Voest Alpine Industrienlagenbau GmbH
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Priority to EP06020935A priority Critical patent/EP1764421A3/en
Publication of EP1530648A1 publication Critical patent/EP1530648A1/en
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Classifications

    • 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
    • C21C7/068—Decarburising
    • C21C7/0685—Decarburising of stainless steel
    • 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
    • C21C5/005—Manufacture of stainless steel
    • 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
    • C21C5/32—Blowing from above
    • 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
    • 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
    • C21C5/42—Constructional features of converters
    • C21C5/46—Details or accessories
    • C21C5/4606—Lances or injectors
    • 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
    • C21C7/068—Decarburising
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/16—Introducing a fluid jet or current into the charge

Definitions

  • the invention relates to a method for decarburizing a molten steel in the course of the production of stainless steel in a metallurgical vessel, in particular in a converter, wherein the molten steel is treated with oxygen and optionally an inert gas, in particular argon and / or nitrogen.
  • a method for decarburizing a molten steel in particular by the AOD method, it is known to carry out decarburization by means of an oxygen blowing process above a carbon content of essentially 0.3% by weight in the molten steel, using a corresponding top lance. Below 0.3 wt% carbon content in molten steel, decarburization is continued by the operation of submerged nozzles. However, the operation of the lower bath nozzles is generally followed by insufficient mixing of the molten steel. Furthermore, there is a high ferrostatic pressure in the area of the lower bath nozzles, which has a negative effect on the decarburization.
  • Laval nozzles By Laval nozzles high flow rates can be realized in technically and economically efficient form. Since a slag layer normally floats on the molten steel, the flow rate of the gas stream directed to the same for treating the molten steel is of crucial importance. Only a high gas velocity, as it is particularly preferably achievable by use of a Laval nozzle, guarantees the contact of the gas stream, in particular the oxygen with the molten steel, and thus a sufficient mixing and decarburization of the molten steel. A major drawback with the use of Laval nozzles arises with regard to the controllability of the flow rate of oxygen, which varies depending on the carbon content in the molten steel during the blowing process.
  • the present invention has for its object to avoid the disadvantages of the prior art and a method according to the preamble of claim 1 to develop, with which a particularly economical and efficient decarburization of molten steel can be realized.
  • a particularly economical and efficient decarburization of molten steel is thus realized by above a carbon content of 0.3 wt%, oxygen in the molten steel through a lance equipped with a first Laval nozzle with a flow rate D1 and below a carbon content of 0.3% by weight in the molten steel Oxygen through a blow lance equipped with a second Laval nozzle with a flow rate D2, where D2 ⁇ D1, is blown onto the molten steel.
  • a particular measure for implementing the invention is that in the decarburization of the molten steel below a carbon content of 0.3 wt.%
  • oxygen and optionally inert gas, in particular argon and / or nitrogen, via an opening below the surface of the molten steel and via an above the surface of the molten steel arranged inflator is brought into contact with the molten steel.
  • the method according to the invention is in the decarburization of the molten steel below a carbon content of 0.3 wt% in the molten steel, the majority of the oxygen introduced through the inflator and the opening below the surface of the molten steel via the inflator with the molten steel in Brought in contact.
  • the present invention relates to a method for combined top and bottom injection of O 2 and / or inert gas in a metal vessel for the purpose of decarburization of a molten metal, in particular a molten steel, wherein the required O 2 amount mainly by one or several top lances are blown in, and the required adjustment of the O 2 and / or inert gas blow intensity by the change of the Lanzenkonfiguralion during operation, ideally by arrangement and operation a second lance is realized.
  • the second lance is designed for a lower blowing intensity or flow rate.
  • the specific blowing rate of the second lance is set to a value in the range of 0.5 to 1 Nm 3 / (t * min).
  • the lance used on the lance head on a Laval nozzle on a Laval nozzle.
  • oxygen and / or inert gas is blown onto the molten metal by the second top lance.
  • the second lance is operated at low C content in the melt with a lower blowing intensity.
  • the mixing ratio between oxygen and inert gas with which the molten metal is applied during the process is adjusted in accordance with the actual C content of the melt.
  • the critical C content (starting point for the use of the second lance) depends above all on the process conditions, in particular the chemical composition and the temperature of the molten metal, and / or other thermochemical conditions.
  • the working position and the blowing rate of the lances used are adjusted accordingly during the operation of the decarburization process.
  • the dimensions of the Unterbaddüsen are smaller interpretable with sufficient bath mixing than is the case in known from the prior art method.
  • an oxygen / inert gas mixture in particular with a blowing rate of 0.1 to 0.3 Nm3 / (t * min), is introduced to keep the nozzles free in the area of the subbubble nozzles.
  • the Unterbaddüsen are arranged on the bottom or on the side wall of the metallurgical vessel.
  • the Unterbaddüsen are designed as classic nozzles and / or flushing stones.
  • top lance is used during a first process step for decarburization.
  • the top lance becomes switched off and the further decarburization continued by blowing in oxygen and optionally inert gas via one or more Unterbaddüsen.
  • the duration of use of the lance is accordingly approximately 15-25% of the total process time.
  • This reaction is strongly influenced by the CO partial pressure.
  • the CO partial pressure is suppressed by introducing inert gas (Ar / N 2 ) into the molten steel.
  • the decarburization condition in the lower bath nozzle is less favorable because of the ferrostatic pressure over the lower bath nozzles. It is therefore proposed according to the invention to support the further decarburization by blowing (top-blowing) and to intensify the mixing.
  • a certain amount of inert gas may be added to the O 2 to be introduced via the lance, whereby the amount of gas required for the operation of the laval nozzle of the lance can be provided.
  • the Inertgas mecanicischung is limited in a given by the process requirement area to minimize the inert gas consumption, in particular the Ar / N 2 consumption.
  • the entire gas flow through the lance is to be selected so that a high Lanzenkopf- and / or nozzle wear is avoided, and a high utilization of the injected gas is ensured.
  • the invention relates to a process for decarburization in a refractory lined vessel, which is preferably in converter form, in the metal manufacturing industry, preferably in the steel and stainless steel producing industry.
  • a refractory lined vessel which is preferably in converter form, in the metal manufacturing industry, preferably in the steel and stainless steel producing industry.
  • blowing of a treatment gas below the surface of the molten metal is referred to as bottom-blowing.
  • blowing of treatment gas onto the surface of the molten metal is referred to as top blowing.
  • the decarburization in a metal vessel is subdivided into two process stages.
  • the first stage during which oxygen addition determines the rate of chemical evolution, decarburization at higher C content occurs through combined top and bottom blow, thus minimizing the amount of gas introduced into the metal bath through the bottom nozzles is that a laying of the floor nozzles is prevented.
  • a second process stage below a critical C content in the bath which, for example in the case of chromium-containing melts, is between 0.3-0.4% by weight of carbon in the molten steel, the mass transfer process taking place within the scope of the decarburization determines the reaction rate.
  • the O 2 bubble intensity is reduced accordingly.
  • the required amount of O 2 will be preferred Embodiment of the method according to the invention mainly blown through the top lance, preferably with the addition of inert gas.
  • the design of the lance head (with a Laval nozzle) is precisely configured for the requirements in this phase.
  • the lance used during the first bubble stage can be changed by mechanical adaptation (switching or conversion) so that the required blowing intensity and the required gas-jet character can be met.
  • the mixing ratios between O 2 and inert gas through the second lance are adjusted during the decarburization depending on the C content.
  • the underbath nozzles are subjected to an O 2 / inert gas mixture in order to prevent the nozzles from being laid or routed and to ensure optimum bath mixing.
  • a reduction phase can follow, with the inert gas being injected through the underbath nozzles and / or top lance.
  • the Laval nozzle has a mechanical and / or electromagnetic device for changing the characteristic of the Laval nozzle with regard to the set characteristic flow rate, for example by changing the cross-section of the nozzle.
  • FIG. 1 an apparatus for decarburizing a molten steel is shown by the AOD method.
  • the device I has a metallurgical vessel 2, in particular a. Converter, in which there is a molten steel 3, in particular a melt of a, preferably chromium-rich, stainless steel. On the molten steel 3 floats a slag 4.
  • the molten steel 3 is passed through bottom nozzles 5 with a treatment gas, which generally contains oxygen and optionally an inert gas, in particular with one or more of the gases: oxygen, nitrogen. Argon or air, treated.
  • a treatment gas which generally contains oxygen and optionally an inert gas, in particular with one or more of the gases: oxygen, nitrogen. Argon or air, treated.
  • a first blowing lance 6 is operated, by means of which likewise a treatment gas, in particular oxygen or an oxygen / inert gas mixture, particularly preferably an oxygen-argon mixture, is brought into contact with the molten steel.
  • a treatment gas in particular oxygen or an oxygen / inert gas mixture, particularly preferably an oxygen-argon mixture
  • the treatment gas is brought into contact with the molten steel.
  • the slag is forced back.
  • a sufficient intensity of the directed through the Laval nozzle of the lance on the molten metal gas stream also ensures good mixing of the liquids contained in the vessel.
  • a second lance 7 provided is not used in the first process step, which essentially corresponds to decarburization at a carbon content of more than 0.3% by weight.
  • a second process step 1 ' which corresponds to a decarburization at a carbon content preferably at or below 0.3% by weight in the molten steel
  • the steel melt 3' in the metallurgical vessel 2 ' is in turn fed via one or more bottom nozzles 5' a treatment gas
  • the second lance 7 ' is in operation in the second method step 1', which differs from the first lance 6 'in that this lance, which in turn is preferably equipped with a Laval nozzle, for a different, in particular smaller , Flow rate of treatment gas is designed.
  • the slag 4 ' is at least partially forced back by the operation of the lance 7' of the molten steel.
  • the lance 6 ' remains out of operation during the second process step.

Abstract

Decarburization of molten steel (3), especially in stainless steel production in a metallurgical vessel (2) and particularly a converter, involves treatment with oxygen and an inert gas if required and especially argon and/or nitrogen. To decarburize molten steel with carbon content of =0.3 wt.%, the gas is introduced through an opening (5) below the molten steel level and a blower lance (6, 7) over the molten steel surface, to bring the gas into contact with the metal.

Description

Die Erfindung betrifft ein Verfahren zur Entkohlung einer Stahlschmelze im Zuge der Herstellung von rostfreiem Stahl in einem metallurgischen Gefäß, insbesondere in einem Konverter, wobei die Stahlschmelze mit Sauerstoff und gegebenenfalls einem Inertgas, insbesondere Argon und/oder Stickstoff, behandelt wird.The invention relates to a method for decarburizing a molten steel in the course of the production of stainless steel in a metallurgical vessel, in particular in a converter, wherein the molten steel is treated with oxygen and optionally an inert gas, in particular argon and / or nitrogen.

Bei einem Verfahren zur Entkohlung einer Stahlschmelze, insbesondere nach dem AOD-Verfahren, ist bekannt, oberhalb eines Kohlenstoffgehaltes von im Wesentlichen 0,3 Gew % in der Stahlschmelze unter Benützung einer entsprechenden Top-Lanze eine Entkohlung mittels eines Sauerstoffaufblasprozesses durchzuführen. Unterhalb von 0,3 Gew% Kohlenstoffgehalt in der Stahlschmelze wird die Entkohlung durch den Betrieb von Unterbaddüsen fortgesetzt. Durch den Betrieb der Unterbaddüsen folgt im Allgemeinen jedoch eine unzureichende Durchmischung der Stahlschmelze. Weiters herrscht im Bereich der Unterbaddüsen ein hoher ferrostatischer Druck, der sich negativ auf die Entkohlung auswirkt.In a method for decarburizing a molten steel, in particular by the AOD method, it is known to carry out decarburization by means of an oxygen blowing process above a carbon content of essentially 0.3% by weight in the molten steel, using a corresponding top lance. Below 0.3 wt% carbon content in molten steel, decarburization is continued by the operation of submerged nozzles. However, the operation of the lower bath nozzles is generally followed by insufficient mixing of the molten steel. Furthermore, there is a high ferrostatic pressure in the area of the lower bath nozzles, which has a negative effect on the decarburization.

Eine weitere mögliche Verfahrensweisen zur Entkohlung einer chromhältigen Stahlschmelze durch einen kombinierten Blaseprozess ist aus der US-A 5,540,753 bereits bekannt. Durch den gemeinsamen Betrieb der Unterbaddüse und der Toplanze erfolgt eine besonders gute Durchmischung des Metallbades. Durch diese Maßnahme wird die Entkohlung des Stahlbades wesentlich beschleunigt. Für die Durchführung des Aufblaseprozess ist eine Aufblaselanze beschrieben, aus der der Sauerstoffstrahl bei bestimmten Bedingungen mit einer Geschwindigkeit austritt, die nicht kleiner als die Überschallgeschwindigkeit ist. Hierzu weist die Blaslanze eine Lavaldüse auf, und es wird der Sauerstoff durch die Lavaldüse auf die Oberfläche der Stahlschmelze geleitet.Another possible procedure for decarburizing a chromium-containing molten steel by a combined blowing process is already known from US-A 5,540,753. The joint operation of the Unterbaddüse and the top lance is a particularly good mixing of the metal bath. By this measure, the decarburization of the steel bath is significantly accelerated. For carrying out the inflation process, an inflation lance is described, from which the oxygen jet exits under certain conditions at a speed which is not less than the supersonic speed. For this purpose, the lance has a Laval nozzle, and the oxygen is passed through the Laval nozzle on the surface of the molten steel.

Durch Lavaldüsen sind in technisch und wirtschaftlich effizienter Form hohe Strömungsgeschwindigkeiten realisierbar. Da auf der Stahlschmelze im Normalfall eine Schlackenschicht aufschwimmt, ist die Strömungsgeschwindigkeit des zur Behandlung der Stahlschmelze auf dieselbe gerichteten Gasstromes von entscheidender Bedeutung. Erst eine hohe Gasgeschwindigkeit, wie sie besonders bevorzugt durch Anwendung einer Lavaldüse erzielbar ist, garantiert den Kontakt des Gasstromes, insbesondere des Sauerstoffes mit der Stahlschmelze, und damit eine ausreichende Durchmischung und Entkohlung der Stahlschmelze. Ein wesentlicher Nachteil beim Einsatz von Lavaldüsen ergibt sich hinsichtlich der Regelbarkeit der Durchflussmenge des Sauerstoffs, die in Abhängigkeit vom Kohlenstoffgehalt in der Stahlschmelze während des Blaseprozesses variiert.By Laval nozzles high flow rates can be realized in technically and economically efficient form. Since a slag layer normally floats on the molten steel, the flow rate of the gas stream directed to the same for treating the molten steel is of crucial importance. Only a high gas velocity, as it is particularly preferably achievable by use of a Laval nozzle, guarantees the contact of the gas stream, in particular the oxygen with the molten steel, and thus a sufficient mixing and decarburization of the molten steel. A major drawback with the use of Laval nozzles arises with regard to the controllability of the flow rate of oxygen, which varies depending on the carbon content in the molten steel during the blowing process.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, die Nachteile aus dem Stand der Technik zu vermeiden und ein Verfahren gemäß dem Oberbegriff des Anspruchs 1 zu entwickeln, womit eine besonders wirtschaftliche und effiziente Entkohlung der Stahlschmelze verwirklicht werden kann.The present invention has for its object to avoid the disadvantages of the prior art and a method according to the preamble of claim 1 to develop, with which a particularly economical and efficient decarburization of molten steel can be realized.

Diese Aufgabe wird entsprechend dem erfindungsgemäßen Verfahren nach dem kennzeichnenden Teil des Anspruchs 1.This object is achieved according to the inventive method according to the characterizing part of claim 1.

Eine besonders wirtschaftliche und effiziente Entkohlung der Stahlschmelze wird demnach verwirklicht, indem oberhalb eines Kohlenstoffgehalts von 0,3 Gew%, in der Stahlschmelze Sauerstoff durch eine mit einer ersten Lavaldüse ausgestatteten Blaslanze mit einer Durchflussmenge D1 und unterhalb eines Kohlenstoffgehaltes von 0.3 Gew% in der Stahlschmelze Sauerstoff durch eine, mit einer zweiten Lavaldüse ausgestatteten Blaslanze mit einer Durchflussmenge D2, wobei D2<D1, auf die Stahlschmelze aufgeblasen wird.A particularly economical and efficient decarburization of molten steel is thus realized by above a carbon content of 0.3 wt%, oxygen in the molten steel through a lance equipped with a first Laval nozzle with a flow rate D1 and below a carbon content of 0.3% by weight in the molten steel Oxygen through a blow lance equipped with a second Laval nozzle with a flow rate D2, where D2 <D1, is blown onto the molten steel.

Eine besondere Maßnahme zur Umsetzung der Erfindung besteht darin, dass bei der Entkohlung der Stahlschmelze unterhalb eines Kohlenstoffgehaltes von 0,3 Gew. % in der Stahlschmelze Sauerstoff und gegebenenfalls Inertgas, insbesondere Argon und/oder Stickstoff, über eine Öffnung unterhalb der Oberfläche der Stahlschmelze sowie über eine oberhalb der Oberfläche der Stahlschmelze angeordnete Aufblasvorrichtung mit der Stahlschmelze in Kontakt gebracht wird.A particular measure for implementing the invention is that in the decarburization of the molten steel below a carbon content of 0.3 wt.% In the molten steel, oxygen and optionally inert gas, in particular argon and / or nitrogen, via an opening below the surface of the molten steel and via an above the surface of the molten steel arranged inflator is brought into contact with the molten steel.

Nach einer besonderen Ausführungsform des erfindungsgemäßen Verfahrens wird bei der Entkohlung der Stahlschmelze unterhalb eines Kohlenstoffgehaltes von 0,3 Gew% in der Stahlschmelze, der überwiegende Teil des durch die Aufblasvorrichtung und die Öffnung unterhalb der Oberfläche der Stahlschmelze eingesetzten Sauerstoffs über die Aufblasvorrichtung mit der Stahlschmelze in Kontakt gebracht.According to a particular embodiment of the method according to the invention is in the decarburization of the molten steel below a carbon content of 0.3 wt% in the molten steel, the majority of the oxygen introduced through the inflator and the opening below the surface of the molten steel via the inflator with the molten steel in Brought in contact.

Durch diese erfindungsgemäße Maßnahme wird die Entkohlung gegenüber dem Stand der Technik wesentlich beschleunigt.By this measure, the decarburization of the invention is significantly accelerated compared to the prior art.

Nach einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens wird durch die Öffnung unterhalb der Oberfläche der Stahlschmelze gerade soviel Gas, insbesondere Sauerstoff, eingeblasen, dass eine Blockade der Öffnung verhindert und/oder gleichzeitig eine ausreichende Baddurchmischung sichergestellt wird.According to a preferred embodiment of the method according to the invention just as much gas, in particular oxygen, blown through the opening below the surface of the molten steel that prevents blockage of the opening and / or at the same time a sufficient bath mixing is ensured.

Nach einer besonderen Ausführungsform betrifft die vorliegende Erfindung ein Verfahren zur kombinierten Top- und Boden-Einblasung von O2 und/oder Inertgas in ein Metallgefäß zum Zwecke der Entkohlung einer Metallschmelze, insbesondere einer Stahlschmelze, wobei die erforderliche O2-Menge hauptsächlich durch eine oder mehrere Top-Lanzen eingeblasen wird, und die erforderliche Anpassung der O2- und/oder Inertgas-Blasintensität durch die Änderung der Lanzenkonfiguralion während des Betriebes, idealerweise durch Anordnung und Betrieb eine zweiten Blaslanze realisiert wird. Auf diese Weise erfolgt eine Sicherung des optimalen Gasstrahles (gute Durchmischung des Metallbades) und eine Erhöhung der Lanzenlebensdauer. Nach einer besonderen Ausführungsform der Erfindung wird die zweite Lanze auf eine niedrigere Blasintensität bzw. Durchflussmenge ausgelegt. Nach einer besonderen Ausführungsform der Erfindung ist die spezifische Blasrate der zweiten Lanze auf einen Wert im Bereich von 0,5 bis 1 Nm3/(t*min) eingestellt.According to a particular embodiment, the present invention relates to a method for combined top and bottom injection of O 2 and / or inert gas in a metal vessel for the purpose of decarburization of a molten metal, in particular a molten steel, wherein the required O 2 amount mainly by one or several top lances are blown in, and the required adjustment of the O 2 and / or inert gas blow intensity by the change of the Lanzenkonfiguralion during operation, ideally by arrangement and operation a second lance is realized. In this way, a backup of the optimal gas jet (good mixing of the metal bath) and an increase in the lance life. According to a particular embodiment of the invention, the second lance is designed for a lower blowing intensity or flow rate. According to a particular embodiment of the invention, the specific blowing rate of the second lance is set to a value in the range of 0.5 to 1 Nm 3 / (t * min).

Nach der besonderen Ausführungsform der Erfindung weist die verwendete Lanze am Lanzenkopf eine Laval-Düse auf.According to the particular embodiment of the invention, the lance used on the lance head on a Laval nozzle.

Nach einer weiteren Ausführungsform der Erfindung wird durch die zweite Top-Lanze Sauerstoff und/oder Inertgas auf die Metallschmelze aufgeblasen.According to a further embodiment of the invention, oxygen and / or inert gas is blown onto the molten metal by the second top lance.

Nach einer zusätzlichen Ausführungsform der Erfindung wird die zweite Lanze bei niedrigem C-Gehalt in der Schmelze mit einer niedrigeren Blasintensität betrieben. Nach einer weiteren besonderen Ausführungsform wird das Mischungsverhältnis zwischen Sauerstoff und Inertgas mit welchem die Metallschmelze beaufschlagt wird während dem Prozess entsprechend dem aktuellen C-Gehalt der Schmelze angepasst. Nach einer besonderen Ausführungsform der Erfindung hängt der kritische C-Gehalt (Startpunkt für den Einsatz der zweiten Lanze) vor allem von den Verfahrensbedingungen, insbesondere der chemischen Zusammensetzung und der Temperatur der Metallschmelze, und/oder anderen thermochemischen Bedingungen ab.According to an additional embodiment of the invention, the second lance is operated at low C content in the melt with a lower blowing intensity. According to a further particular embodiment, the mixing ratio between oxygen and inert gas with which the molten metal is applied during the process is adjusted in accordance with the actual C content of the melt. According to a particular embodiment of the invention, the critical C content (starting point for the use of the second lance) depends above all on the process conditions, in particular the chemical composition and the temperature of the molten metal, and / or other thermochemical conditions.

Nach einer besonderen Ausführungsform der Erfindung wird die Arbeitsposition und die Blasrate der verwendeten Lanzen während dem Betrieb des Entkohlungsverfahrens entsprechend eingestellt.According to a particular embodiment of the invention, the working position and the blowing rate of the lances used are adjusted accordingly during the operation of the decarburization process.

Nach einer besonderen Ausführungsform der Erfindung sind die Dimensionen der Unterbaddüsen bei ausreichender Baddurchmischung kleiner auslegbar als das bei aus dem Stand der Technik bekannten Verfahren der Fall ist. Nach einer besonderen Ausführungsform der Erfindung wird im Bereich der Unterbaddüsen ein Sauerstoff-/Inertgasgemisch, insbesondere mit einer Blasrate von 0,1 bis 0,3 Nm3/(t*min), zur Freihaltung der Düsen eingeleitet.According to a particular embodiment of the invention, the dimensions of the Unterbaddüsen are smaller interpretable with sufficient bath mixing than is the case in known from the prior art method. According to a particular embodiment of the invention, an oxygen / inert gas mixture, in particular with a blowing rate of 0.1 to 0.3 Nm3 / (t * min), is introduced to keep the nozzles free in the area of the subbubble nozzles.

Nach einer besonderen Ausführungsform der Erfindung sind die Unterbaddüsen am Boden oder an der Seitenwand des metallurgischen Gefäßes angeordnet.According to a particular embodiment of the invention, the Unterbaddüsen are arranged on the bottom or on the side wall of the metallurgical vessel.

Nach einer besonderen Ausführungsform der Erfindung sind die Unterbaddüsen als klassische Düsen und/oder Spülsteine ausgeführt.According to a particular embodiment of the invention, the Unterbaddüsen are designed as classic nozzles and / or flushing stones.

Bei einem aus dem Stand der Technik bekannten AOD-L oder K-OBM-S Prozess wird die mit einem Laval-Düsenkopf ausgestattete Top-Lanze während eines ersten Verfahrensschrittes zur Entkohlung eingesetzt. Bei einem Kohlenstoffgehalt von 0,3 Gew% in der Stahlschmelze wird die Top-Lanze abgeschaltet und die weitere Entkohlung durch Einblasen von Sauerstoff und gegebenenfalls Inertgas über eine oder mehrere Unterbaddüsen fortgesetzt. Die Einsatzdauer der Lanze beträgt demnach je nach dem Eingangskohlenstoffgehalt in der Vorschmelze ca. 15 - 25 % der gesamten Prozesszeit.In a known from the prior art AOD-L or K-OBM-S process equipped with a Laval nozzle head top lance is used during a first process step for decarburization. At a carbon content of 0.3% by weight in the molten steel, the top lance becomes switched off and the further decarburization continued by blowing in oxygen and optionally inert gas via one or more Unterbaddüsen. Depending on the input carbon content in the pre-melt, the duration of use of the lance is accordingly approximately 15-25% of the total process time.

Die Entkohlung folgt der Reaktion:

        Cr2O3 + 3C → 2Cr + 3CO

Decarburization follows the reaction:

Cr 2 O 3 + 3C → 2Cr + 3CO

Diese Reaktion wird stark durch den CO-Partialdruck beeinflusst. Um die Entkohlung zu begünstigen, wird der CO-Partialdruck durch Einleitung von Inertgas (Ar/N2) in die Stahlschmelze unterdrückt.This reaction is strongly influenced by the CO partial pressure. In order to promote decarburization, the CO partial pressure is suppressed by introducing inert gas (Ar / N 2 ) into the molten steel.

Diese Einleitung erfolgt nach dem Stand der Technik durch eine oder mehrere Unterbaddüsen und/oder eine Top-Lanze.This introduction is made according to the prior art by one or more Unterbaddüsen and / or a top lance.

Im Vergleich zum Aufblasen des Behandlungsgases (Top-Lance-Blowing) ist die Entkohlungsbedingung bei der Unterbaddüse wegen des ferrostatischen Druckes über die Unterbaddüsen ungünstiger. Es wird deshalb erfindungsgemäß vorgeschlagen, die weitere Entkohlung durch Aufblasen (Top-blowing) zu unterstützen und die Durchmischung zu intensivieren.Compared to top-lance blow-up, the decarburization condition in the lower bath nozzle is less favorable because of the ferrostatic pressure over the lower bath nozzles. It is therefore proposed according to the invention to support the further decarburization by blowing (top-blowing) and to intensify the mixing.

Hierbei könnte man nach einer besonderen Ausführungsform der Erfindung beispielsweise eine bestimmte Inertgasmenge zum dem über die Lanze einzuleitendem O2 beimischen, wodurch die für den Betrieb der Lavaldüse der Blaslanze erforderliche Gasmenge bereitgestellt werden kann. Die Inertgasbeimischung ist in einem durch den Prozessbedarf vorgegebenen Bereich einzuschränken, um den Inertgasverbrauch, insbesondere den Ar/N2-Verbrauch, zu minimieren. Der gesamte Gasdurchfluss über die Lanze ist dabei so auszuwählen, dass ein hoher Lanzenkopf- und/oder Düsenverschleiß vermieden wird, und eine hohe Ausnutzung des eingeblasenen Gases sichergestellt wird.In this case, according to a particular embodiment of the invention, for example, a certain amount of inert gas may be added to the O 2 to be introduced via the lance, whereby the amount of gas required for the operation of the laval nozzle of the lance can be provided. The Inertgasbeimischung is limited in a given by the process requirement area to minimize the inert gas consumption, in particular the Ar / N 2 consumption. The entire gas flow through the lance is to be selected so that a high Lanzenkopf- and / or nozzle wear is avoided, and a high utilization of the injected gas is ensured.

Die Erfindung bezieht sich auf ein Verfahren zur Entkohlung in einem mit feuerfest-ausgemauerten Gefäß, welches vorzugsweise in Konverterform vorliegt, in der Metallherstellungsindustrie, vorzugsweise in der Stahl- und Edelstahl erzeugenden Industrie. Durch das erfindungsgemäße Verfahren wird einerseits die bei kombiniertem Blowing (Top + Bottom) in einem entsprechendem Gefäß, insbesondere einem Konverter, auftretende optimale Durchmischung und somit auch ein verbesserter C-Transport zur CO-Bildung, und andererseits der bei dem Aufblasverfahren (Top-Lance-Blowing) niedrigere CO-Partialdruck, und die im Vergleich zum Bottom-Blowing somit günstigere Entkohlungsbedingung ausgenützt.The invention relates to a process for decarburization in a refractory lined vessel, which is preferably in converter form, in the metal manufacturing industry, preferably in the steel and stainless steel producing industry. By the method according to the invention, on the one hand, the optimum mixing occurring in a corresponding vessel, in particular a converter, in combined blowing (Top + Bottom) and thus also an improved C-transport for CO formation, and on the other hand in the inflation process (top-lance -Blowing) lower CO partial pressure, and thus exploited compared to the bottom-blowing thus more favorable decarburization condition.

Als Bottom-Blowing wird definitionsgemäß ein Einblasen eines Behandlungsgases unterhalb der Oberfläche der Metallschmelze bezeichnet. Als Top-Blowing wird definitionsgemäß ein Aufblasen von Behandlungsgas auf die Oberfläche der Metallschmelze bezeichnet.By definition, blowing of a treatment gas below the surface of the molten metal is referred to as bottom-blowing. By definition, blowing of treatment gas onto the surface of the molten metal is referred to as top blowing.

Erfindungsgemäß wird die Entkohlung in einem Metallgefäß in zwei Verfahrensstufen unterteilt. Während der ersten Stufe, während der die Sauerstoffzugabe die Geschwindigkeit der ablaufenden chemischen Reaktion bestimmt, erfolgt die Entkohlung bei höherem C-Gehalt durch kombiniertes Top- und Bottom-Blowing, wobei die Gasmenge, welche durch die Bodendüsen in das Metallbad eingeleitet wird, so minimiert wird, dass ein Verlegen der Bodendüsen verhindert wird. Während einer zweiten Verfahrensstufe unterhalb eines kritischen C-Gehaltes im Bad, welcher beispielsweise bei chromhaltigen Schmelzen zwischen 0.3-0.4 Gew% Kohlenstoff in der Stahlschmelze beträgt, bestimmt der im Rahmen der Entkohlung ablaufende Stofftransportvorgang die Reaktionsgeschwindigkeit. Um die Oxidation der Metallelemente im Bad zu minimieren und die gezielte Prozesstemperatur sicherzustellen, wird die O2-Blasenintensität dementsprechend reduziert. Während der zweiten Verfahrensstufe wird die erforderliche O2-Menge nach einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens hauptsächlich durch die Top-Lanze, vorzugsweise unter Beimischung von Inertgas, eingeblasen.According to the invention, the decarburization in a metal vessel is subdivided into two process stages. During the first stage, during which oxygen addition determines the rate of chemical evolution, decarburization at higher C content occurs through combined top and bottom blow, thus minimizing the amount of gas introduced into the metal bath through the bottom nozzles is that a laying of the floor nozzles is prevented. During a second process stage below a critical C content in the bath, which, for example in the case of chromium-containing melts, is between 0.3-0.4% by weight of carbon in the molten steel, the mass transfer process taking place within the scope of the decarburization determines the reaction rate. In order to minimize the oxidation of the metal elements in the bath and to ensure the targeted process temperature, the O 2 bubble intensity is reduced accordingly. During the second stage of the process, the required amount of O 2 will be preferred Embodiment of the method according to the invention mainly blown through the top lance, preferably with the addition of inert gas.

Da sich die während des zweiten Verfahrensschrittes gewünschte Gas-Durchflussmenge bzw. die gewünschte Blasintensität durch die Blaslanze von jener des ersten Verfahrensschrittes unterscheidet, wird nach einer besonderen Ausführungsform des erfindungsgemäßen Verfahrens eine zweite entsprechend ausgelegte Lanze installiert und eingesetzt, wobei die Auslegung des Lanzenkopfs (mit einer Laval-Düse) genau für die Erfordernisse in dieser Phase konfiguriert ist. Nach einer weiteren bevorzugten Ausführungsform kann erfindungsgemäß die während der ersten Blasenstufe eingesetzten Lanze durch mechanische Anpassung (Umschaltung bzw. Umstellung) so verändert werden, dass die erforderliche Blasintensität sowie der geforderte Gasstrahicharakter erfüllt werden kann. Die Mixhungsverhältnisse zwischen O2 und Inertgas durch die zweite Lanze werden während der Entkohlung je nach dem C-Gehalt angepasst. Die Unterbaddüsen werden dabei nach einer besonderen Ausführungsform mit einem O2/Inertgas-gemisch beaufschlagt, um ein Verlegen oder Zugehen der Düsen zu verhindern und eine optimale Baddurchmischung zu sichern. Nachdem der erforderliche C-Gehalt im Bad erreicht ist, kann eine Reduktionsphase folgen, wobei das Inertgas durch die Unterbaddüsen und/oder Toplanze eingeblasen wird.Since the gas flow rate desired during the second process step or the desired blowing intensity by the blowing lance is different from that of the first process step, according to a particular embodiment of the process according to the invention, a second suitably designed lance is installed and used, the design of the lance head (with a Laval nozzle) is precisely configured for the requirements in this phase. According to another preferred embodiment, according to the invention, the lance used during the first bubble stage can be changed by mechanical adaptation (switching or conversion) so that the required blowing intensity and the required gas-jet character can be met. The mixing ratios between O 2 and inert gas through the second lance are adjusted during the decarburization depending on the C content. According to a particular embodiment, the underbath nozzles are subjected to an O 2 / inert gas mixture in order to prevent the nozzles from being laid or routed and to ensure optimum bath mixing. After the required C content in the bath has been reached, a reduction phase can follow, with the inert gas being injected through the underbath nozzles and / or top lance.

Nach einer besonderen Ausführungsform weist die Lavaldüse eine mechanische und/oder elektromagnetische Einrichtung zur Veränderung der Charakteristik der Lavaldüse hinsichtlich der eingestellten charakteristischen Durchflussmenge, beispielsweise durch Veränderung des Querschnittes der Düse, auf.According to a particular embodiment, the Laval nozzle has a mechanical and / or electromagnetic device for changing the characteristic of the Laval nozzle with regard to the set characteristic flow rate, for example by changing the cross-section of the nozzle.

Entsprechend einer besonderen Ausführungsform der Erfindung ist nachfolgend ein nichteinschränkender Vergleich zwischen den Versuchsergebnisse einer nach dem Stand der Technik durchgeführten rostfreien Stahlerzeugung (konventionelles AOD-Verfahren) und einer nach dem vorgeschlagenen erfindungsgemäßen Verfahren durchgeführten rostfreien Stahlerzeugung:According to a particular embodiment of the invention, the following is a non-limiting comparison between the experimental results of a prior art stainless steel production (conventional AOD process) and a stainless steel production carried out according to the proposed inventive process:

Ausgansbedingungen:Ausgansbedingungen:

  • Vorschmelze: 3% C, 18.3% Cr, 3.5% NiPre-melt: 3% C, 18.3% Cr, 3.5% Ni
  • Abstichzielanalyse: 0.04%C, 18.3% Cr, 8.1% Ni, N < 450 ppm,Tapping target analysis: 0.04% C, 18.3% Cr, 8.1% Ni, N <450 ppm,
  • Abstichgewicht: 120 tTapping weight: 120 t
  • Umschaltpunkt N2 => Ar: 0.08% CSwitch point N 2 => Ar: 0.08% C
Verfahren nach dem Stand der Technik: Standard AOD Verfahren mit einem Stahlbadhöhe: 1.8 mPrior art method: Standard AOD method with steel bath height: 1.8 m

  • Ablauf: Die Top-lanze wird bis zu einem Kohlenstoffgehalt von 0,3 Gew% in der Stahlschmelze zur Entkohlung eingesetzt, ab einem Kohlenstoffgehalt von 0,3 Gew% in der Stahlschmelze erfolgt die O2 Eindüsung ausschließlich über BodendüsenProcedure: The top lance is used up to a carbon content of 0.3% by weight in the molten steel for decarburization; from a carbon content of 0.3% by weight in the molten steel, O 2 injection takes place exclusively via bottom nozzles
  • Gesamtbehandlungszeit: 55.2 min.Total treatment time: 55.2 min.
  • Ar: 8,5 Nm3/tAr: 8.5 Nm 3 / t
  • Si: 13 kg/tSi: 13 kg / t
  • Kalk: 51 kg/tLime: 51 kg / t
  • Feuerfest: circa 12 kg/tRefractory: about 12 kg / t
  • Cr-Ausbringung: 98%Cr output: 98%
Erfindungsgemäßes Verfahren:Inventive method:

  • Ablauf: Eine erste Lanze wird bei der Entkohlung bis zu einem Kohlenstoffgehalt von 0,3 Gew % in der Stahlschmelze eingesetzt. Nachfolgend wird eine zweite Lanze zum Aufblasen eines Ar/N2/O2 - Gemisches verwendet.Procedure: A first lance is used in the decarburization up to a carbon content of 0.3% by weight in the molten steel. Subsequently, a second lance is used to inflate an Ar / N 2 / O 2 mixture.

Der während des zweiten Verfahrensschrittes herrschende Gasfluß (Ar/N2/O2) bei dem Bottem-Blowing wird hinsichtlich der Prämisse, ein Zugehen der Düsen zu verhindern, minimiert.

  • Gesamtbehandlungszeit: 49.3 min.
  • Ar: 7.2 Nm3/t
  • Si: 8.6 kg/t
  • Kalk: 31 kg/t
  • Feuerfest: 8 kg/t
  • Cr-Ausbringung: 98,4%
The gas flow (Ar / N 2 / O 2 ) prevailing during the second process step in the bottem-blowing is minimized with respect to the premise of preventing nozzle leakage.
  • Total treatment time: 49.3 min.
  • Ar: 7.2 Nm3 / t
  • Si: 8.6 kg / t
  • Lime: 31 kg / t
  • Refractory: 8 kg / t
  • Cr output: 98.4%

Im Folgenden wird ein nicht einschränkendes Ausführungsbeispiel der Erfindung anhand einer Zeichnung näher erläutert. Es zeigt:

  • Fig. 1 eine Vorrichtung zur Behandlung einer Stahlschmelze
In the following, a non-limiting embodiment of the invention will be explained in more detail with reference to a drawing. It shows:
  • Fig. 1 shows an apparatus for treating a molten steel

In Fig. 1 ist eine Vorrichtung zur Entkohlung einer Stahlschmelze nach dem AOD-Verfahren dargestellt. Die Vorrichtung I weist dabei ein metallurgisches Gefäß 2, insbesondere einen. Konverter auf, in welchem sich eine Stahlschmelze 3, insbesondere eine Schmelze eines, vorzugsweise chromreichen, rostfreien Stahls befindet. Auf der Stahlschmelze 3 schwimmt eine Schlacke 4 auf. Die Stahlschmelze 3 wird durch Bodendüsen 5 mit einem Behandlungsgas, welches im allgemeinen Sauerstoff und gegebenenfalls ein Inertgas enthält, insbesondere mit einem oder mehreren der Gase: Sauerstoff, Stickstoff. Argon oder Luft, behandelt. Weiters wird eine erste Blaslanze 6 betrieben, durch welche ebenfalls ein Behandlungsgas, insbesondere Sauerstoff oder ein Sauerstoff-InertgasGemisch, besonders bevorzugt ein Sauerstoff-Argon-Gemisch, mit der Stahlschmelze in Kontakt gebracht wird. Wie anhand der schematischen Zeichnung ersichtlich, wird durch das Aufblasen des Behandlungsgases auf die Stahlschmelze, wenn dieses mit einer geeignet hohen Geschwindigkeit, wie das beispielsweise durch Anwendung einer Lavaldüse erreicht werden kann, geschieht, die Schlacke zurückgedrängt. Damit ist ein optimaler Kontakt des Behandlungsgases mit der Stahlschmelze gewährleistet. Eine ausreichende Intensität des durch die Lavaldüse der Blaslanze auf die Metallschmelze gerichteten Gasstromes sorgt zudem für eine gute Durchmischung der in dem Gefäß enthaltenen Flüssigkeiten. Eine zweite bereitgestellte Lanze 7 wird in dem ersten Verfahrensschritt, der im wesentlichen einer Entkohlung bei einem Kohlenstoffgehalt von über 0,3 Gew% entspricht, nicht eingesetzt.In Fig. 1, an apparatus for decarburizing a molten steel is shown by the AOD method. The device I has a metallurgical vessel 2, in particular a. Converter, in which there is a molten steel 3, in particular a melt of a, preferably chromium-rich, stainless steel. On the molten steel 3 floats a slag 4. The molten steel 3 is passed through bottom nozzles 5 with a treatment gas, which generally contains oxygen and optionally an inert gas, in particular with one or more of the gases: oxygen, nitrogen. Argon or air, treated. Furthermore, a first blowing lance 6 is operated, by means of which likewise a treatment gas, in particular oxygen or an oxygen / inert gas mixture, particularly preferably an oxygen-argon mixture, is brought into contact with the molten steel. As can be seen from the schematic drawing, by blowing the treatment gas onto the molten steel, if this happens at a suitably high speed, as can be achieved, for example, by using a Laval nozzle, the slag is forced back. This ensures optimal contact of the treatment gas with the molten steel. A sufficient intensity of the directed through the Laval nozzle of the lance on the molten metal gas stream also ensures good mixing of the liquids contained in the vessel. A second lance 7 provided is not used in the first process step, which essentially corresponds to decarburization at a carbon content of more than 0.3% by weight.

In einem zweiten Verfahrensschritt 1', welcher einer Entkohlung bei einem Kohlenstoffgehalt vorzugsweise bei oder unterhalb von 0,3 Gew% in der Stahlschmelze entspricht, wird der Stahlschmelze 3' in dem metallurgischen Gefäß 2' wiederum über eine oder mehrere Bodendüsen 5' ein Behandlungsgas zugeführt. Im Gegensatz zum Verfahrensschritt 1, ist im zweite Verfahrensschritt 1' die zweite Lanze 7' in Betrieb, die sich gegenüber der ersten Lanze 6' dadurch unterscheidet, dass diese Lanze, die wiederum bevorzugt mit einer Lavaldüse ausgestattet ist, für eine unterschiedliche, insbesondere kleinere, Durchflussmenge an Behandlungsgas ausgelegt ist. Wiederum wird die Schlacke 4' durch den Betrieb der Blaslanze 7' von der Stahlschmelze zumindest teilweise zurückgedrängt. Die Blaslanze 6' bleibt während des zweiten Verfahrensschrittes außer Betrieb.In a second process step 1 ', which corresponds to a decarburization at a carbon content preferably at or below 0.3% by weight in the molten steel, the steel melt 3' in the metallurgical vessel 2 'is in turn fed via one or more bottom nozzles 5' a treatment gas , In contrast to method step 1, the second lance 7 'is in operation in the second method step 1', which differs from the first lance 6 'in that this lance, which in turn is preferably equipped with a Laval nozzle, for a different, in particular smaller , Flow rate of treatment gas is designed. Again, the slag 4 'is at least partially forced back by the operation of the lance 7' of the molten steel. The lance 6 'remains out of operation during the second process step.

Claims (3)

  1. Method for decarbonizing a steel melt in the course of the production of stainless steel in a metallurgical vessel, in particular in a converter, the steel melt being treated with oxygen and, if appropriate, an inert gas, in particular argon and/or nitrogen, the top-blowing device having a blowing lance, and the oxygen being conducted through the blowing lance onto the surface of the steel melt, and the blowing lance having a Laval nozzle, and the oxygen being conducted through the Laval nozzle onto the surface of the steel melt, characterized in that oxygen is blown onto the steel melt with a throughflow quantity D1 through a blowing lance equipped with a first Laval nozzle, above a carbon content of 0.3% by weight in the steel melt, and is blown onto the steel melt with a throughflow quantity D2 through a blowing lance equipped with a second Laval nozzle, below a carbon content of 0.3% by weight in the steel melt, in which case D2 < D1.
  2. Method according to Claim 1, characterized in that, in the decarbonization of the steel melt, below a carbon content of 0.3% by weight in the steel melt, oxygen and, if appropriate, inert gas, in particular argon and/or nitrogen, are brought into contact with the steel melt via a port below the surface of the steel melt and via a top-blowing device arranged above the surface of the steel melt.
  3. Method according to Claim 1 or 2, characterized in that, in the decarbonization of the steel melt, below a carbon content of 0.3% by weight in the steel melt, the predominant part of the oxygen introduced through the top-blowing device and the port below the surface of the steel melt is brought into contact with the steel melt via the top-blowing device.
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EP1530648A1 (en) 2005-05-18
ATA12502002A (en) 2003-07-15
RU2319750C2 (en) 2008-03-20
EP1764421A3 (en) 2007-12-26
ATE363546T1 (en) 2007-06-15
WO2004018714A1 (en) 2004-03-04
DE50307383D1 (en) 2007-07-12

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