EP0721990B1 - Method of producing alloyed steels and arc furnace installation with positionable blowing lances therefor - Google Patents

Method of producing alloyed steels and arc furnace installation with positionable blowing lances therefor Download PDF

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Publication number
EP0721990B1
EP0721990B1 EP96890007A EP96890007A EP0721990B1 EP 0721990 B1 EP0721990 B1 EP 0721990B1 EP 96890007 A EP96890007 A EP 96890007A EP 96890007 A EP96890007 A EP 96890007A EP 0721990 B1 EP0721990 B1 EP 0721990B1
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EP
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Prior art keywords
manufacturing step
electric furnace
oxygen
several
during
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EP96890007A
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German (de)
French (fr)
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EP0721990A1 (en
Inventor
Ernst Dipl.-Ing. Fritz
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VAI Technometal GmbH
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VAI Technometal GmbH
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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
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5264—Manufacture of alloyed steels including ferro-alloys
    • 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
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5252—Manufacture of steel in electric furnaces in an electrically heated multi-chamber furnace, a combination of electric furnaces or an electric furnace arranged for associated working with a non electric furnace
    • 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
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
    • 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
    • C21C7/068—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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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
    • C21C2007/0093—Duplex process; Two stage processes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
    • Y10S75/961—Treating flue dust to obtain metal other than by consolidation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
    • Y10S75/962—Treating or using mill scale

Definitions

  • the invention relates to a method for producing alloy steels, in particular stainless steel or steel stock for stainless steel, being in a first Manufacturing step iron carrier largely decarburized and with the help of oxygen dephosphorated and the melt after removing the slag formed in one Another manufacturing step after the addition of alloy carriers to the desired one Alloy and carbon content is adjusted using oxygen and inert gas, and an installation for carrying out the method.
  • a method of this type is known from EP-A2 - 0 229 586. Both manufacturing steps are carried out in one and the same oxygen blowing converter. With this method, one is severely limited with regard to charging solids to be melted. Solid pig iron, alloying agents and scrap can be brought into the oxygen blowing converter in a maximum amount of 20% by weight of a batch. If you want to charge large quantities of solids, you are forced to add expensive exothermic chemical heating agents, but this entails the disadvantage of large quantities of slag (SiO 2 , Al 2 O 3 etc.). These large amounts of slag require high amounts of lime, and as a result there is a large loss of output of iron, chromium, manganese, etc.
  • the oxygen blowing converter has a floor flushing device to create a melt pool motion. This leads to the oxygen blowing converter high chrome slagging, so that the economy of the known method is not more is given.
  • the economically viable lower limit (with an even more viable one Chrome slag) for the carbon content is 0.2% C. In addition, do not set the lowest carbon content (e.g. less than 0.1% carbon).
  • the invention aims at avoiding these disadvantages and difficulties and presents itself the task, a method of the type described above and a system for Implementation of the process, which allow alloyed steels, especially stainless steels, in an economical way with high productivity to manufacture.
  • a gas inlet in the melt preferably with a minimum amount of 30 liters / min per point of introduction Introduction of inert gas and 300 liters / min when introducing oxygen or mixed gases containing oxygen.
  • the oxygen or oxygen-containing is expediently blown during the bath Mixed gas is an amount of inert gas that increases with the duration of the under bath blowing added.
  • a preferred embodiment is characterized in that the first Manufacturing step in a first electric furnace and the further manufacturing step in one different electric oven is carried out from the first electric oven.
  • the Placing the batch in a second electric furnace to carry out the further The manufacturing step enables the melt to be kept free of phosphorus Slag that still adheres to the brickwork despite being slagged in the first electric furnace. This results in an almost complete dephosphorization of the melt, so that the further manufacturing step, namely the alloy adjustment and further decarburization, in Absence of phosphorus can be done.
  • This can be, for example, at just above the normal melt level in the wall of the electric furnace arranged blow nozzles, which when tilting below the Melt surface come to rest, are carried out. As a result, these lie Blow nozzles when not in use above the melt (and slag) so that their Life is extended.
  • the metal yield is preferably increased and the consumption of reducing agent lowered if the further manufacturing step with the greatest possible exclusion of air is carried out.
  • the method according to the invention is particularly advantageous if of the iron carriers more than 20% by weight, preferably more than 40% by weight, of the batch of scrap become.
  • the further manufacturing step is expedient, leaving a subset of the Slag from the other one that took place before the further production step Manufacturing step carried out.
  • the slag containing Cr 2 O 3 which comes from the previous batch in the second electric furnace and which is formed by the partial oxidation of the silicon from the ferrochrome and the added lime etc., is primarily reduced by silicon and carbon from the ferrochrome and can be slagged off with high chrome output and minimal consumption of reducing agent, such as FeSi, before the fine decarburization in the electric furnace.
  • the slag during the further manufacturing step during a Flushing process with inert gas reduced by adding reducing agent, lime and flux and the melt is deoxidized and desulfurized, so that in the further production step final carbon content already required for the respective steel quality, the rest chemical analysis and the desired temperature of the melt can be achieved.
  • fine-grained ore e.g. Chrome ore as Cr and oxygen carrier (for Si oxidation) with or without mixing with reducing agent (e.g. FeSi, coal) and / or Carbon or nickel oxide are blown onto the arcs and onto the melt.
  • a system for carrying out the process with an electric furnace, in the bottom area of which jacket nozzles are provided, through the jacket of which hydrocarbon and / or inert gas can be fed in, is characterized by swiveling and longitudinally movable fresh lances arranged above the normal melt level and penetrating the side wall of the oven, and also in the bottom area provided jacket nozzles, through the jacket hydrocarbon and / or mixtures of hydrocarbon and inert gas and / or CO 2 and / or water vapor can be supplied.
  • FIGS. 1 and 2 each have an electric furnace in Illustrate cross section in a schematic representation.
  • An electric furnace 1 provided for the first manufacturing step has three sub-bath nozzles 4 in the refractory lining 2 of the lower part 3 of the stove, as shown in FIG.
  • the Unterbaddüsen 4 are nozzles, which are formed from two or three concentric tubes - in the manner of jacket nozzles - with the process gas flowing in the inner round central tube and protective gas for the nozzles flowing between the tubes in the annular or circular section cross sections.
  • the protective gas is preferably hydrocarbon, such as propane, butane or a mixture of hydrocarbon and inert gas. However, water vapor, CO 2 , light heating oil, CO, inert gas or mixtures thereof have also been successfully used as a protective medium.
  • Annular gap nozzles which were filled with refractory material in the central tube and in which the process gas was introduced through an interrupted annular gap, could also be successfully used as an under bath nozzle 4.
  • washing elements 6 are arranged, which are made of there are two pipes each.
  • the inner tube is made of fireproof material locked.
  • the annular gaps can also be formed from circular sections.
  • the Flushing elements 6 can also be made of porous, sheet metal-coated or with thin tubes provided refractory material.
  • fresh lances 9 are made of two or three concentric tubes or formed by a water-cooled tube.
  • the arrow direction 10 indicates that the fresh lances are inclined downwards as a tangent to an imaginary one Blow cylinder and at a relatively short distance from the bath surface 11.
  • the fresh lances 9 are inserted into water-cooled copper cooling boxes 12. It is also one of the three Electrodes 13 shown as a hollow electrode.
  • Three post-combustion / burner lances 14 are arranged in the upper part of the furnace side wall 8.
  • An opening 15 is used to add Slag formers and alloying agents.
  • FIG. 2 shows a second schematically illustrated electric furnace 16 according to the invention illustrated. This has a special feature - in contrast to that shown in Fig. 1 Electric furnace 1 - an exchangeable base part 17 in which the three rinsing elements 6 are provided.
  • An electrode 13 is designed as a hollow electrode, which is lined with a ceramic tube is. Alloying agents are passed through the opening 15 with a scrap basket (not shown) of the furnace cover 18 in the furnace (second electric furnace). Seals 19 are on the Separation point furnace side wall 8 to furnace cover 18, slag door 20 to furnace side wall 8 and at the opening 15 in the furnace cover 18 made of ceramic fiber. The furnace cover 18 will at least temporarily pressed against the furnace side wall 8 with a tensioning device.
  • the gas consumption per ton of liquid steel is determined as follows:
  • Fresh lances 9 are charged with 15 Nm 3 O 2 / t and the under bath nozzles 4 with 8 Nm 3 O 2 / t and 1.1 Nm 3 CH 4 / t.
  • the flushing elements 6 blow 1.2 Nm 3 N 2 plus 0.3 Nm 3 CH 4 / t to improve the bath movement and the application.
  • the electricity consumption on the electric furnace is 1 130 kWh / t of the liquid steel end product (from the second electric furnace). 50 kg of slag are slagged. 680 kg of premelt with 0.20% C, 0.020% P and 1590 ° C are passed on to the second electric furnace 16.
  • the tapping sequence time is 57 min.
  • the second electric furnace 16 100 t electric furnace with 70 MVA are per t liquid steel (AISI 304) approx. 60 kg slag recirculated from the pre-batch, 680 kg pre-melt, 350 kg Charged HCFeCr, FeMn, FeSi and 45 kg lime as well as 10 kg dolomite.
  • AISI 304 per t liquid steel
  • the fresh lances 9 apply 20 Nm 3 O 2 to the melt, 5 Nm 3 O 2 through self-consuming pipes and 4 8 Nm 3 O 2 + 2 Nm 3 Ar + 1 Nm 3 CH 4 through the under bath nozzles blown into the melt.
  • the entry of false air into the second electric furnace 16 is largely prevented (the furnace cover 18 is clamped against the furnace side wall 8).
  • 125 kg of slag are largely reduced and removed with the silicon from the HCFeCr and the carbon.
  • the melt in the second electric furnace 16 is blown to 0.04% C by blowing the O 2 + Ar / CH 4 + Ar with the aid of the under bath nozzles 4, and the slag is reduced during the inert gas blowing and the addition of FeSi and lime , the melt desulphurized, emptied, finely alloyed, rinsed and poured after an intermediate deslagging and another lime batching.
  • the treatment time in the second electric furnace 16 is approximately 70 minutes.
  • the dephosphorization of pig iron and scrap iron, recycled materials, FeNi etc. is carried out in first electric furnace 1 made.
  • the P 2 O 5 -containing slag is removed from the plant, ie the electric furnace 1, before this largely decarburized premelt is charged, alloyed, desilicated and decarburized in the second electric furnace 16.
  • Brief decarburization, deoxidation, desulphurization and rinsing can be carried out in a vacuum system (e.g. VOD system).
  • Decarburization with the lowest chrome slagging to medium or lowest Carbon content is with oxygen - or to reduce the CO partial pressure with oxygen containing mixed gases blowing stationary Unterbaddüsen 4 and / or 6 and partially with stationary and / or movable inflation nozzles 9 or lances.

Description

Die Erfindung betrifft ein Verfahren zum Herstellen von legierten Stählen, insbesondere von nichtrostenden Stählen oder Stahlvormaterial für nichtrostende Stähle, wobei in einem ersten Herstellungsschritt Eisenträger mit Hilfe von Sauerstoff weitgehend entkohlt und entphosphort und die Schmelze nach Entfernen der dabei gebildeten Schlacke in einem weiteren Herstellungsschritt nach Zufuhr von Legierungsträgern auf den gewünschten Legierungs- und Kohlenstoffgehalt mit Hilfe von Sauerstoff und Inertgas eingestellt wird, sowie eine Anlage zur Durchführung des Verfahrens.The invention relates to a method for producing alloy steels, in particular stainless steel or steel stock for stainless steel, being in a first Manufacturing step iron carrier largely decarburized and with the help of oxygen dephosphorated and the melt after removing the slag formed in one Another manufacturing step after the addition of alloy carriers to the desired one Alloy and carbon content is adjusted using oxygen and inert gas, and an installation for carrying out the method.

Ein Verfahren dieser Art ist aus der EP-A2 - 0 229 586 bekannt. Beide Herstellungsschritte werden hierbei in ein- und demselben Sauerstoffblaskonverter durchgeführt. Bei diesem Verfahren ist man hinsichtlich des Chargierens aufzuschmelzender Feststoffe stark begrenzt. Festes Roheisen, Legierungsmittel und Schrott lassen sich beim Sauerstoffblaskonverter maximal in Mengen von 20 Gew.% einer Charge einbringen. Will man größere Mengen an Feststoffen chargieren, ist man gezwungen, teure exotherme chemische Heizmittel zuzugeben, was jedoch den Nachteil großer Schlackenmengen (SiO2, Al2O3 etc.) mit sich bringt. Diese großen Schlackenmengen erfordern hohe Kalkzusätze, und es kommt in der Folge davon zu großen Ausbringungsverlusten an Eisen, Chrom, Mangan etc..A method of this type is known from EP-A2 - 0 229 586. Both manufacturing steps are carried out in one and the same oxygen blowing converter. With this method, one is severely limited with regard to charging solids to be melted. Solid pig iron, alloying agents and scrap can be brought into the oxygen blowing converter in a maximum amount of 20% by weight of a batch. If you want to charge large quantities of solids, you are forced to add expensive exothermic chemical heating agents, but this entails the disadvantage of large quantities of slag (SiO 2 , Al 2 O 3 etc.). These large amounts of slag require high amounts of lime, and as a result there is a large loss of output of iron, chromium, manganese, etc.

Gemäß der EP-A2 - 0 229 586 weist der Sauerstoffblaskonverter eine Bodenspüleinrichtung auf, um eine Schmelzbadbewegung zu erzeugen. Dies führt beim Sauerstoffblaskonverter zu hohen Chromverschlackungen, so daß die Wirtschaftlichkeit des bekannten Verfahrens nicht mehr gegeben ist. Die wirtschaftlich tragbare Untergrenze (bei noch tragbarer Chromverschlackung) für den Kohlenstoffgehalt liegt bei 0,2 % C. Zudem lassen sich niedrigste Kohlenstoffgehalte (z.B. kleiner als 0,1 % Kohlenstoff) nicht einstellen.According to EP-A2 - 0 229 586, the oxygen blowing converter has a floor flushing device to create a melt pool motion. This leads to the oxygen blowing converter high chrome slagging, so that the economy of the known method is not more is given. The economically viable lower limit (with an even more viable one Chrome slag) for the carbon content is 0.2% C. In addition, do not set the lowest carbon content (e.g. less than 0.1% carbon).

Bei der Herstellung von höherlegierten Stählen im Elektroofen, insbesondere chromlegierten nichtrostenden Stählen, ist man bisher auf Schwierigkeiten gestoßen, da es bei der Entkohlung im Elektroofen zu extrem hohen Chromverschlackungen kommt. Zur Vermeidung solcher Chromverschlackungen hat man vorgeschlagen, Temperaturen weit über 1700°C während der Entkohlung der Schmelze einzustellen. Das Ergebnis dieser Bemühungen war, daß weltweit ca. 80 % rostfreier Stähle mit Hilfe von Konverterverfahren hergestellt werden.In the manufacture of higher-alloy steels in an electric furnace, especially chrome-alloyed stainless steels, one has so far encountered difficulties as it involves decarburization extremely high chrome slagging occurs in the electric furnace. To avoid such Chrome slagging has been suggested, temperatures well above 1700 ° C during the Adjust decarburization of the melt. The result of this effort was that worldwide approx. 80% of stainless steels can be manufactured using converter processes.

Die Möglichkeiten der Verfahrensroute im Elektroofen - eventuell in Kombination mit einer nachgeschalteten Vakuumbehandlung - sind im Hinblick auf die wirtschaftlich anwendbaren Einsatzmaterialien stark begrenzt. So mußte das Phosphoreinbringen auf kleiner 0,030 % und das Kohlenstoffeinbringen auf unter z.B. 1 % begrenzt werden, da bei Anwesenheit von Chrom und wegen der Reduktion der Chromoxide fast keine Entphosphorung möglich ist und eine umfangreiche Entkohlung im Elektroofen wegen der langen Zeiten und der hohen Chromverschlackung bisher nicht erfolgreich war. Trotz des niedrigen Kohlenstoffeinbringens beim Einschmelzen von P-armem rostfreiem legiertem Schrott anstelle des Einschmelzens größerer hochkohlenstoffhaltiger Ferrochrommengen müssen die Vorschmelzen an den Elektroöfen üblicherweise mit C-Gehalten von 0,50 bis 1,2 % abgestochen werden und müssen daher einer langen Vakuumbehandlung unterzogen werden, um die notwendig niedrigen C-Gehalte etc. einzustellen. Die Kosten für diese lange Vakuumbehandlung sind hoch und ein Sequenzguß ist nicht möglich.The possibilities of the process route in the electric furnace - possibly in combination with one downstream vacuum treatment - are with regard to the economically applicable Feed materials severely limited. So the introduction of phosphorus had to be less than 0.030% and the introduction of carbon to e.g. 1% because in the presence of Chromium and because of the reduction of chromium oxides almost no dephosphorization is possible extensive decarburization in the electric furnace due to the long times and the high Chromium slagging has not been successful so far. Despite the low carbon input when melting P-poor stainless alloy scrap instead of melting Larger amounts of high-carbon ferrochrome have to be premelted to the Electric furnaces are usually tapped with C contents of 0.50 to 1.2% and must therefore be subjected to a long vacuum treatment in order to achieve the low C contents etc. The cost of this long vacuum treatment is high and a sequence casting is not possible.

Die Erfindung bezweckt die Vermeidung dieser Nachteile und Schwierigkeiten und stellt sich die Aufgabe, ein Verfahren der eingangs beschriebenen Art sowie eine Anlage zur Durchführung des Verfahrens zu schaffen, welche es ermöglichen, legierte Stähle, insbesondere nichtrostende Stähle, in wirtschaftlicher Weise bei hoher Produktivität herzustellen. Insbesondere soll es möglich sein, preiswertes energiereiches, jedoch phosphorhältiges flüssiges und/oder festes Roheisen mit über 0,03 % Phosphor einzusetzen. Weiters soll es erfindungsgemäß möglich sein, große Mengen an Feststoffen zu chargieren, insbesondere bis hinauf zu 100 %.The invention aims at avoiding these disadvantages and difficulties and presents itself the task, a method of the type described above and a system for Implementation of the process, which allow alloyed steels, especially stainless steels, in an economical way with high productivity to manufacture. In particular, it should be possible to use inexpensive, high-energy, however to use phosphorus-containing liquid and / or solid pig iron with over 0.03% phosphorus. Furthermore, it should be possible according to the invention to charge large amounts of solids, especially up to 100%.

Diese Aufgabe der Erfindung wird erfindungsgemäß dadurch gelöst,

  • daß der erste Herstellungsschritt unter Zufuhr von elektrischer Energie in einem Elektroofen (1) erfolgt und während des ersten Herstellungsschrittes eine Entkohlung durch Auf- und/oder Unterbadblasen durchgeführt wird und
  • daß der weitere Herstellungsschritt ebenfalls unter Zufuhr von elektrischer Energie in einem von phosphorhältiger Schlacke weitgehend freien Elektroofen (16) erfolgt, wobei während des weiteren Herstellungsschrittes eine Entkohlung durch Aufblasen von Sauerstoff oder einem sauerstoffhältigen Mischgas auf die Schmelze sowie eine Entkohlung durch Unterbadblasen mit Sauerstoff oder einem sauerstoffhältigen Mischgas durchgeführt wird.
This object of the invention is achieved in that
  • that the first manufacturing step takes place with the supply of electrical energy in an electric furnace (1) and during the first manufacturing step decarburization is carried out by blowing up and / or under bath and
  • that the further production step also takes place with the supply of electrical energy in an electric furnace (16) largely free of phosphorus-containing slag, during which decarburization by blowing oxygen or an oxygen-containing mixed gas onto the melt and decarburizing by blowing under bath with oxygen or a decarburization oxygen-containing mixed gas is carried out.

Mit Hilfe des erfindungsgemäßen Verfahrens gelingt es, mittlere und niedrigste Kohlenstoffgehalte unter Verzicht auf eine nachfolgende Vakuumbehandlung einzustellen. Falls bei niedrigsten Kohlenstoffgehalten doch eine Vakuumbehandlung durchgeführt werden soll, kann diese auf eine sehr kurze Behandlungszeit beschränkt sein. With the help of the method according to the invention, it is possible to achieve medium and lowest Adjust carbon levels without a subsequent vacuum treatment. If a vacuum treatment is carried out at the lowest carbon levels should be limited to a very short treatment time.

Vorzugsweise wird zur Erreichung hoher Reaktionsgeschwindigkeiten für das Entsilizieren, Entkohlen, das Auflösen von hochkohlenstoffhältigem Ferrochrom, etc., während des weiteren Herstellungsschrittes eine Badbewegung initiiert, u.zw. durch eine Gaseinleitung in die Schmelze, vorzugsweise mit einer Mindestmenge von 30 Liter/min je Einleitungsstelle bei Einleitung von Inertgas und 300 Liter/min bei Einleitung von Sauerstoff oder sauerstoffhältiger Mischgase.Preferably, in order to achieve high reaction rates for the desilication, Decarburization, the dissolution of high-carbon ferrochrome, etc., during the initiated a bath movement in a further manufacturing step, etc. through a gas inlet in the melt, preferably with a minimum amount of 30 liters / min per point of introduction Introduction of inert gas and 300 liters / min when introducing oxygen or mixed gases containing oxygen.

Zweckmäßig wird während des Unterbadblasens dem Sauerstoff bzw. dem sauerstoffhältigen Mischgas ein sich mit zunehmender Zeitdauer des Unterbadblasens erhöhender Inertgasanteil zugemischt.The oxygen or oxygen-containing is expediently blown during the bath Mixed gas is an amount of inert gas that increases with the duration of the under bath blowing added.

Eine bevorzugte Ausführungsform ist dadurch gekennzeichnet, daß der erste Herstellungsschritt in einem ersten Elektroofen und der weitere Herstellungsschritt in einem vom ersten Elektroofen unterschiedlichen weiteren Elektroofen durchgeführt wird. Die Einbringung der Charge in einen zweiten Elektroofen zur Durchführung des weiteren Herstellungsschrittes ermöglicht die einfache Freihaltung der Schmelze von phosphorhältiger Schlacke, die trotz Abschlackung im ersten Elektroofen noch an der Ausmauerung haftet. Hierdurch ergibt sich eine nahezu vollständige Entphosphorung der Schmelze, so daß der weitere Herstellungsschritt, nämlich die Legierungseinstellung und weitere Entkohlung, in Abwesenheit von Phosphor durchgeführt werden kann.A preferred embodiment is characterized in that the first Manufacturing step in a first electric furnace and the further manufacturing step in one different electric oven is carried out from the first electric oven. The Placing the batch in a second electric furnace to carry out the further The manufacturing step enables the melt to be kept free of phosphorus Slag that still adheres to the brickwork despite being slagged in the first electric furnace. This results in an almost complete dephosphorization of the melt, so that the further manufacturing step, namely the alloy adjustment and further decarburization, in Absence of phosphorus can be done.

Zur Einstellung der chemischen Analyse und Desoxidation sowie Entschwefelung und zur Durchführung einer Spülbehandlung kann es zweckmäßig sein, an den weiteren Herstellungsschritt einen zusätzlichen Herstellungsschritt mit einer Vakuumbehandlung der Schmelze anzuschließen.For setting the chemical analysis and deoxidation as well as desulfurization and It may be appropriate to carry out a rinsing treatment on the others Manufacturing step an additional manufacturing step with a vacuum treatment of the Connect melt.

Vorteilhaft wird während zumindest eines Teilschrittes des weiteren Herstellungsschrittes eine Spülung der Schmelze mit Inertgas oder einem Gemisch aus Inertgas und Kohlenwasserstoff durchgeführt. Dies kann beispielsweise mit knapp oberhalb des Normal-Schmelzenniveaus in der Wand des Elektroofens angeordneten Blasdüsen, die bei einem Kippvorgang unterhalb der Schmelzenoberfläche zu liegen kommen, durchgeführt werden. Hierdurch liegen diese Blasdüsen während der Nichtverwendung oberhalb der Schmelze (und Schlacke), so daß ihre Lebensdauer verlängert ist. One is advantageous during at least one substep of the further manufacturing step Flushing the melt with inert gas or a mixture of inert gas and hydrocarbon carried out. This can be, for example, at just above the normal melt level in the wall of the electric furnace arranged blow nozzles, which when tilting below the Melt surface come to rest, are carried out. As a result, these lie Blow nozzles when not in use above the melt (and slag) so that their Life is extended.

Vorzugsweise wird das Metallausbringen erhöht und der Verbrauch an Reduktionsmittel erniedrigt, wenn der weitere Herstellungsschritt unter weitestgehendem Luftabschluß durchgeführt wird. Die wirtschaftliche Vermeidung des Eindringens von Falschluft, insbesondere während der Reduktion der Schlacke und/oder Desoxidation der Schmelze, wird erzielt, indem die Schlackentüre und die Trennstelle zwischen Ofenwand und Ofendeckel z.B. mit Hilfe von Keramikfasern abgedichtet wird.The metal yield is preferably increased and the consumption of reducing agent lowered if the further manufacturing step with the greatest possible exclusion of air is carried out. The economical prevention of the ingress of false air, especially during the reduction of the slag and / or deoxidation of the melt achieved by the slag door and the separation point between the furnace wall and the furnace cover e.g. is sealed with the help of ceramic fibers.

Das erfindungsgemäße Verfahren ist besonders dann von Vorteil, wenn von den Eisenträgern mehr als 20 Gew.%, vorzugsweise mehr als 40 Gew.%, der Charge von Schrott gebildet werden.The method according to the invention is particularly advantageous if of the iron carriers more than 20% by weight, preferably more than 40% by weight, of the batch of scrap become.

Zweckmäßig wird der weitere Herstellungsschritt unter Belassung einer Teilmenge der Schlacke des vor dem weiteren Herstellungsschritt stattgefundenen weiteren Herstellungsschrittes durchgeführt.The further manufacturing step is expedient, leaving a subset of the Slag from the other one that took place before the further production step Manufacturing step carried out.

Die Cr2O3 enthaltende Schlacke, die im zweiten Elektroofen von der vorhergegangenen Charge stammt und die durch die teilweise Oxidation des Siliziums aus dem Ferrochrom und dem zugesetzten Kalk etc. gebildet wird, wird in erster Linie durch Silizium und Kohlenstoff aus dem Ferrochrom reduziert und kann bereits bei hohem Chromausbringen und minimalem Verbrauch an Reduktionsmittel, wie FeSi, vor der Feinentkohlung im Elektroofen abgeschlackt werden.The slag containing Cr 2 O 3 , which comes from the previous batch in the second electric furnace and which is formed by the partial oxidation of the silicon from the ferrochrome and the added lime etc., is primarily reduced by silicon and carbon from the ferrochrome and can be slagged off with high chrome output and minimal consumption of reducing agent, such as FeSi, before the fine decarburization in the electric furnace.

Vorzugsweise wird die Schlacke während des weiteren Herstellungsschrittes während eines Spülvorganges mit Inertgas unter Zugabe von Reduktionsmittel, Kalk und Flußmittel reduziert und die Schmelze desoxidiert und entschwefelt, so daß im weiteren Herstellungsschritt der bereits für die jeweilige Stahlqualität erforderliche Endkohlenstoffgehalt, die restliche chemische Analyse und die gewünschte Temperatur der Schmelze erzielbar sind.Preferably, the slag during the further manufacturing step during a Flushing process with inert gas reduced by adding reducing agent, lime and flux and the melt is deoxidized and desulfurized, so that in the further production step final carbon content already required for the respective steel quality, the rest chemical analysis and the desired temperature of the melt can be achieved.

Andere bevorzugte Verfahrensvarianten ergeben sich aus den weiteren Unteransprüchen.Other preferred process variants result from the further subclaims.

Es liegt auch im Sinne der Erfindung, daß während des ersten Herstellungsschrittes durch Hohlelektroden des Elektroofens Feststoffe, wie z.B. Elektroofen- oder Konverterstaub, Kohle zum Schlackenschäumen, Schlackenbildner, Erze, feinkörnige Legierungsmittel, Materialien, die entsorgt werden müssen, wie Klärschlamm, gekörnte Shredderleichtfraktion, Schleifstaub, Zunder etc., und während des weiteren Herstellungsschrittes durch Hohlelekroden des Elektroofens bevorzugt feinkörniges Erz, wie z.B. Chromerz als Cr- und Sauerstoffträger (für Si-Oxidation) ohne oder mit Vermischung mit Reduktionsmittel (z.B. FeSi, Kohle) und/oder Kohle bzw. Nickeloxid an die Lichtbögen und auf die Schmelze aufgeblasen werden.It is also within the scope of the invention that during the first manufacturing step Hollow electrodes of the electric furnace Electric furnace or converter dust, coal for slag foaming, slag formers, ores, fine-grained alloying agents, materials, that have to be disposed of, such as sewage sludge, granular light shredder fraction, grinding dust, Tinder etc., and during the further manufacturing step by hollow electrodes of the Electric furnace prefers fine-grained ore, e.g. Chrome ore as Cr and oxygen carrier (for Si oxidation) with or without mixing with reducing agent (e.g. FeSi, coal) and / or Carbon or nickel oxide are blown onto the arcs and onto the melt.

Eine Anlage zur Durchführung des Verfahrens mit einem Elektroofen, in dessen Bodenbereich Manteldüsen vorgesehen sind, durch deren Mantel Kohlenwasserstoff und/oder Inertgas zuleitbar ist, ist gekennzeichnet durch oberhalb des Normal-Schmelzenspiegels angeordneten und die Ofenseitenwand durchsetzenden schwenkbaren und längsbeweglichen Frischlanzen, sowie mit im Bodenbereich vorgesehenen Manteldüsen, durch deren Mantel Kohlenwasserstoff und/oder Gemische aus Kohlenwasserstoff und Inertgas und/oder CO2 und/oder Wasserdampf zuleitbar ist.A system for carrying out the process with an electric furnace, in the bottom area of which jacket nozzles are provided, through the jacket of which hydrocarbon and / or inert gas can be fed in, is characterized by swiveling and longitudinally movable fresh lances arranged above the normal melt level and penetrating the side wall of the oven, and also in the bottom area provided jacket nozzles, through the jacket hydrocarbon and / or mixtures of hydrocarbon and inert gas and / or CO 2 and / or water vapor can be supplied.

Es ist von besonderem Vorteil, wenn für den weiteren Herstellungsschritt ein weiterer Elektroofen vorgesehen ist.It is particularly advantageous if another is used for the further production step Electric oven is provided.

Die Erfindung ist nachfolgend anhand eines in der Zeichnung dargestellten Ausführungsbeispieles näher erläutert, wobei die Fig. 1 und 2 jeweils einen Elektroofen im Querschnitt in schematischer Darstellung veranschaulichen.The invention is described below with reference to one in the drawing Embodiment explained in more detail, wherein FIGS. 1 and 2 each have an electric furnace in Illustrate cross section in a schematic representation.

Ein für den ersten Herstellungsschritt vorgesehener Elektroofen 1 weist gemäß Fig. 1 in der feuerfesten Zustellung 2 des Herd-Unterteiles 3 drei Unterbaddüsen 4 auf. Die Unterbaddüsen 4 sind Düsen, die aus zwei oder drei konzentrischen Rohren - in der Art von Manteldüsen - gebildet werden, wobei im inneren runden Zentralrohr das Prozeßgas und in den kreisringförmigen oder kreisabschnittförmigen Blasquerschnitten zwischen den Rohren Schutzgas für die Düsen strömt. Das Schutzgas ist bevorzugt Kohlenwasserstoff, wie Propan, Butan oder eine Mischung aus Kohlenwasserstoff und Inertgas. Versuchsweise wurden jedoch auch Wasserdampf, CO2, leichtes Heizöl, CO, Inertgas bzw. Mischungen davon als Schutzmedium mit Erfolg angewandt. Auch Ringspaltdüsen, die im Zentralrohr mit feuerfestem Material gestopft waren und bei denen das Prozeßgas durch einen unterbrochenen Ringspalt eingeleitet wurde, konnten erfolgreich als Unterbaddüse 4 zum Einsatz gebracht werden. An electric furnace 1 provided for the first manufacturing step has three sub-bath nozzles 4 in the refractory lining 2 of the lower part 3 of the stove, as shown in FIG. The Unterbaddüsen 4 are nozzles, which are formed from two or three concentric tubes - in the manner of jacket nozzles - with the process gas flowing in the inner round central tube and protective gas for the nozzles flowing between the tubes in the annular or circular section cross sections. The protective gas is preferably hydrocarbon, such as propane, butane or a mixture of hydrocarbon and inert gas. However, water vapor, CO 2 , light heating oil, CO, inert gas or mixtures thereof have also been successfully used as a protective medium. Annular gap nozzles, which were filled with refractory material in the central tube and in which the process gas was introduced through an interrupted annular gap, could also be successfully used as an under bath nozzle 4.

Im Bodenbereich 5 des Herd-Unterteiles 3 sind drei Spülelemente 6 angeordnet, welche aus jeweils zwei Rohren bestehen. Das jeweils innere Rohr ist mit feuerfestem Material verschlossen. Die Ringspalte können auch aus Kreisabschnitten gebildet werden. Die Spülelemente 6 können auch aus porösem, blechummanteltem oder mit dünnen Röhrchen versehenem feuerfestem Material gebildet sein.In the bottom area 5 of the lower part 3 of the cooker, three washing elements 6 are arranged, which are made of there are two pipes each. The inner tube is made of fireproof material locked. The annular gaps can also be formed from circular sections. The Flushing elements 6 can also be made of porous, sheet metal-coated or with thin tubes provided refractory material.

Oberhalb der Normal-Schmelzenbadhöhe 7 bzw. der Schlacke sind in der Ofenseitenwand 8 stationäre Frischlanzen 9 angebracht. Diese Frischlanzen 9 sind aus zwei oder drei konzentrischen Rohren oder von einem wassergekühlten Rohr gebildet. Die Pfeilrichtung 10 weist darauf hin, daß die Frischlanzen schräg nach unten als Tangente zu einem gedachten Zylinder und in einem relativ geringen Abstand zur Badoberfläche 11 blasen. Die Frischlanzen 9 sind in wassergekühlte Kühlkästen 12 aus Kupfer eingesetzt. Weiterhin ist eine der drei Elektroden 13 als Hohlelektrode dargestellt. Drei Nachverbrennungs-/Brennerlanzen 14 sind im oberen Teil der Ofenseitenwand 8 angeordnet. Eine Öffnung 15 dient der Zugabe von Schlackenbildnern und Legierungsmitteln.Above the normal melt bath height 7 or the slag are 8 in the side wall of the furnace stationary fresh lances 9 attached. These fresh lances 9 are made of two or three concentric tubes or formed by a water-cooled tube. The arrow direction 10 indicates that the fresh lances are inclined downwards as a tangent to an imaginary one Blow cylinder and at a relatively short distance from the bath surface 11. The fresh lances 9 are inserted into water-cooled copper cooling boxes 12. It is also one of the three Electrodes 13 shown as a hollow electrode. Three post-combustion / burner lances 14 are arranged in the upper part of the furnace side wall 8. An opening 15 is used to add Slag formers and alloying agents.

In Fig. 2 ist ein zweiter schematisch dargestellter erfindungsgemäßer Elektroofen 16 veranschaulicht. Dieser weist als Besonderheit - im Unterschied zum in Fig. 1 dargestellten Elektroofen 1 - einen auswechselbaren Bodenteil 17 auf, in dem die drei Spülelemente 6 vorgesehen sind.FIG. 2 shows a second schematically illustrated electric furnace 16 according to the invention illustrated. This has a special feature - in contrast to that shown in Fig. 1 Electric furnace 1 - an exchangeable base part 17 in which the three rinsing elements 6 are provided.

Eine Elektrode 13 ist als Hohlelektrode ausgeführt, die mit einem Keramikrohr ausgekleidet ist. Legierungsmittel werden mit einem nicht dargestellten Schrottkorb durch die Öffnung 15 des Ofendeckels 18 in den Ofen (zweiter Elektroofen) eingebracht. Dichtungen 19 sind an der Trennstelle Ofenseitenwand 8 zu Ofendeckel 18, Schlackentür 20 zu Ofenseitenwand 8 und bei der Öffnung 15 im Ofendeckel 18 aus Keramikfaser gebildet. Der Ofendeckel 18 wird zumindest zeitweise mit einer Spannvorrichtung gegen die Ofenseitenwand 8 gepreßt.An electrode 13 is designed as a hollow electrode, which is lined with a ceramic tube is. Alloying agents are passed through the opening 15 with a scrap basket (not shown) of the furnace cover 18 in the furnace (second electric furnace). Seals 19 are on the Separation point furnace side wall 8 to furnace cover 18, slag door 20 to furnace side wall 8 and at the opening 15 in the furnace cover 18 made of ceramic fiber. The furnace cover 18 will at least temporarily pressed against the furnace side wall 8 with a tensioning device.

Das erfindungsgemäße Verfahren ist nachfolgend näher erläutert:The process according to the invention is explained in more detail below:

In einem 100 t Elektroofen 1 (erster Elektroofen) mit 70 MW Nennleistung werden an festen und flüssigen Materialien pro Tonne Flüssigstahl (AISI 304) chargiert:In a 100 t electric furnace 1 (first electric furnace) with a nominal output of 70 MW, fixed and liquid materials per ton of liquid steel (AISI 304):

400 kg flüssiges Roheisen mit 4,3 % C, 0,8 % Si und 0,10 % P, 30 kg festes Roheisen, 110 kg unlegierter Schrott, 20 kg Kalk, 15 kg Filterstaub (Einblasen durch Hohlelektrode) und 180 kg FeNi. 400 kg of molten pig iron with 4.3% C, 0.8% Si and 0.10% P, 30 kg of solid pig iron, 110 kg unalloyed scrap, 20 kg lime, 15 kg filter dust (blowing through a hollow electrode) and 180 kg FeNi.

Die Gasverbräuche pro Tonne Flüssigstahl werden wie folgt ermittelt:The gas consumption per ton of liquid steel is determined as follows:

Frischlanzen 9 werden mit 15 Nm3 O2/t und die Unterbaddüsen 4 mit 8 Nm3 O2/t und 1,1 Nm3 CH4/t beaufschlagt. Durch die Spülelemente 6 werden 1,2 Nm3 N2 plus 0,3 Nm3 CH4/t zur Verbesserung der Badbewegung und des Ausbringens geblasen. Der Stromverbrauch beträgt am Elektroofen 1 130 kWh/t des Flüssigstahl-Endproduktes (aus dem zweiten Elektroofen). 50 kg Schlacke werden abgeschlackt. An den zweiten Elektroofen 16 werden 680 kg Vorschmelze mit 0,20 % C, 0,020 % P und 1590°C weitergegeben. Die Abstichfolgezeit beträgt 57 min.Fresh lances 9 are charged with 15 Nm 3 O 2 / t and the under bath nozzles 4 with 8 Nm 3 O 2 / t and 1.1 Nm 3 CH 4 / t. The flushing elements 6 blow 1.2 Nm 3 N 2 plus 0.3 Nm 3 CH 4 / t to improve the bath movement and the application. The electricity consumption on the electric furnace is 1 130 kWh / t of the liquid steel end product (from the second electric furnace). 50 kg of slag are slagged. 680 kg of premelt with 0.20% C, 0.020% P and 1590 ° C are passed on to the second electric furnace 16. The tapping sequence time is 57 min.

In den zweiten Elektroofen 16 (100 t Elektroofen mit 70 MVA) werden pro t Flüssigstahl (AISI 304) ca. 60 kg Schlacke von der Vorcharge rezirkuliert, 680 kg Vorschmelze, 350 kg HCFeCr, FeMn, FeSi und 45 kg Kalk sowie 10 kg Dolomit chargiert. Durch die Hohlelektrode 13 werden 30 kg Chromerz zur Einsparung von FeCr und zur Siliziumoxidation eingeblasen.In the second electric furnace 16 (100 t electric furnace with 70 MVA) are per t liquid steel (AISI 304) approx. 60 kg slag recirculated from the pre-batch, 680 kg pre-melt, 350 kg Charged HCFeCr, FeMn, FeSi and 45 kg lime as well as 10 kg dolomite. Through the hollow electrode 13 30 kg of chrome ore are blown in to save FeCr and for silicon oxidation.

Pro t Flüssigstahl (AISI 304) werden durch die Frischlanzen 9 auf die Schmelze 20 Nm3O2, durch selbstverzehrende Rohre 5 Nm3 O2 und durch die Unterbaddüsen 4 8 Nm3 O2 + 2 Nm3 Ar + 1 Nm3 CH4 in die Schmelze geblasen. Der Eintritt von Falschluft in den zweiten Elektroofen 16 wird weitgehend verhindert (Anspannen des Ofendeckels 18 gegen die Ofenseitenwand 8). 125 kg Schlacke werden mit dem Silizium aus dem HCFeCr und dem Kohlenstoff weitgehend reduziert und abgeschlackt. 100 t Flüssigstahl mit 0,3 % C, 18,1 % Cr und 0,022 % P und 8,5 % Ni werden nach 55 min Behandlungszeit aus dem zweiten Elektroofen 16 abgestochen und in der Vakuumbehandlungs-Anlage unter Einsatz von 7 Nm3 O2 und 0,3 Nm3 Ar/t 48 min abschließend gefrischt, desoxidiert, feinlegiert, entschwefelt und gespült. Diese Chargen werden in Sequenzgüssen vergossen.Per ton of liquid steel (AISI 304) the fresh lances 9 apply 20 Nm 3 O 2 to the melt, 5 Nm 3 O 2 through self-consuming pipes and 4 8 Nm 3 O 2 + 2 Nm 3 Ar + 1 Nm 3 CH 4 through the under bath nozzles blown into the melt. The entry of false air into the second electric furnace 16 is largely prevented (the furnace cover 18 is clamped against the furnace side wall 8). 125 kg of slag are largely reduced and removed with the silicon from the HCFeCr and the carbon. 100 t of liquid steel with 0.3% C, 18.1% Cr and 0.022% P and 8.5% Ni are tapped from the second electric furnace 16 after a treatment time of 55 minutes and in the vacuum treatment system using 7 Nm 3 O 2 and 0.3 Nm 3 Ar / t 48 min finally fresh, deoxidized, finely alloyed, desulfurized and rinsed. These batches are cast in sequence castings.

Bei anderen Chargen wird bei ähnlichen Verbrauchszahlen die Schmelze im zweiten Elektroofen 16 mit Hilfe der Unterbaddüsen 4 durch Blasen von O2 + Ar/CH4 + Ar auf 0,04 % C gefrischt, die Schlacke während des Inertgasblasens und Zugabe von FeSi und Kalk reduziert, die Schmelze nach einem Zwischenabschlacken und erneutem Kalkchargieren entschwefelt, ausgeleert, feinlegiert, gespült und vergossen. Die Behandlungzeit im zweiten Elektroofen 16 beträgt ca. 70 min.In the case of other batches, with similar consumption figures, the melt in the second electric furnace 16 is blown to 0.04% C by blowing the O 2 + Ar / CH 4 + Ar with the aid of the under bath nozzles 4, and the slag is reduced during the inert gas blowing and the addition of FeSi and lime , the melt desulphurized, emptied, finely alloyed, rinsed and poured after an intermediate deslagging and another lime batching. The treatment time in the second electric furnace 16 is approximately 70 minutes.

Die Entphosphorung der Eisenträger Roheisen und Schrott, Kreislaufstoffe, FeNi etc. wird im ersten Elektroofen 1 vorgenommen. The dephosphorization of pig iron and scrap iron, recycled materials, FeNi etc. is carried out in first electric furnace 1 made.

Die P2O5-haltige Schlacke wird aus der Anlage, d.h. dem Elektroofen 1, entfernt, bevor diese weitgehend entkohlte Vorschmelze in den zweiten Elektroofen 16 chargiert, legiert, entsiliziert und entkohlt wird. Eine kurze Feinstentkohlung, Desoxidation, Entschwefelung und das Nachspülen kann in einer Vakuumanlage (z.B. VOD-Anlage) vorgenommen werden.The P 2 O 5 -containing slag is removed from the plant, ie the electric furnace 1, before this largely decarburized premelt is charged, alloyed, desilicated and decarburized in the second electric furnace 16. Brief decarburization, deoxidation, desulphurization and rinsing can be carried out in a vacuum system (e.g. VOD system).

Die Entkohlung bei niedrigster Chromverschlackung auf mittlere oder niedrigste Kohlenstoffgehalte wird mit Sauerstoff - bzw. zur CO-Partialdruckerniedrigung mit Sauerstoff enthaltenden Mischgasen blasenden stationären Unterbaddüsen 4 und/oder 6 sowie teilweise mit stationären und/oder beweglichen Aufblasdüsen 9 bzw. -lanzen ermöglicht.Decarburization with the lowest chrome slagging to medium or lowest Carbon content is with oxygen - or to reduce the CO partial pressure with oxygen containing mixed gases blowing stationary Unterbaddüsen 4 and / or 6 and partially with stationary and / or movable inflation nozzles 9 or lances.

Die Verfahrensschritte sind so aufgebaut, daß:

  • eine größtmögliche Flexibilität in der Verwendung großer Mengen an preiswerten Einsatzstoffen (P-haltiges Roheisen, HCFeCr etc.) gegeben ist,
  • ein Elektroofen 1 für das Einschmelzen, Überhitzen von P-haltigen Stoffen, wie Roheisen, sowie Entsilizieren, Entkohlen und Entphosphoren der Vorschmelze verwendet wird und der
  • zweite Elektroofen 16 für das schnelle Schmelzen von HCFeCr, Entsilizieren, Reduzieren der Schlacke, Entkohlen usw. verwendet wird,
  • die hohen Reaktionsgeschwindigkeiten für das Entsilizieren, Entkohlen, Entphosphoren, das Auflösen von HCFeCr usw. durch Anwendung eines intensiven Bodenspülens in Kombination mit stationären Frischlanzen 9 erreicht wird (die niedrige Cr-Oxidation wird durch das Unterbadblasen von oxidierenden Gasen erreicht),
  • kurze Betriebszeiten pro Verfahrensschritt zum Gießen von Sequenzen und
  • ein minimaler Verbrauch von Betriebsmittel gegeben ist. Die Cr2O3-haltige Schlacke wird z.B. in einer Verfahrensvariante im zweiten Elektroofen 16 nach dem Abstich der Schmelze belassen und mit dem Si bzw. C aus dem HCFeCr reduziert und danach abgeschlackt. Durch die kurze Feinentkohlung in der Vakuumanlage wird u.a. auch der Argonverbrauch vermindert.
The process steps are structured so that:
  • the greatest possible flexibility in the use of large quantities of inexpensive raw materials (P-containing pig iron, HCFeCr etc.) is given,
  • an electric furnace 1 is used for melting down, overheating P-containing substances, such as pig iron, as well as desilvering, decarburizing and dephosphors and the
  • second electric furnace 16 is used for the rapid melting of HCFeCr, desilvering, reducing the slag, decarburizing, etc.
  • the high reaction rates for desilvering, decarburizing, dephosphorus, dissolving HCFeCr etc. are achieved by using intensive floor washing in combination with stationary fresh lances 9 (the low Cr oxidation is achieved by blowing the oxidizing gases under the bath),
  • short operating times per process step for casting sequences and
  • there is minimal consumption of resources. In a process variant, the Cr 2 O 3 -containing slag is left in the second electric furnace 16 after tapping the melt and reduced with the Si or C from the HCFeCr and then slagged off. The short fine decarburization in the vacuum system also reduces argon consumption.

Es liegt im Sinne der Erfindung, die beschriebenen Merkmale beliebig zu kombinieren und den permanenten bzw. temporären Betriebsbedingungen (z.B. Zustellung eines der beiden Elektroöfen bzw. Reparatur an VOD-Anlage etc.) und Anlagen in den verschiedenen Stahlwerken anzupassen.It is in the spirit of the invention to combine the described features as desired and the permanent or temporary operating conditions (e.g. delivery of one of the two Electric ovens or repairs to VOD systems etc.) and systems in the various Steelworks.

Claims (26)

  1. A method of producing alloyed steels, particularly stainless steels or steel pre-material for stainless steels, wherein in a first manufacturing step iron carriers are largely decarburized and dephosphorized by oxygen and the melt, after removal of the slag resulting therefrom, is set to the desired alloy and carbon contents by means of oxygen and inert gas in a further manufacturing step under supply of alloy carriers, characterized in that
    the first manufacturing step is carried out under supply of electric energy in an electric furnace (1) and a decarburization by top blowing and/or submerged blowing is carried out during the first manufacturing step, and
    the further manufacturing step is also carried out under supply of electric energy, in an electric furnace (16) which is largely free from phosphorus-containing slag, wherein during the further manufacturing step a decarburization by top blowing of oxygen or an oxygen-containing mixed gas onto the melt as well as a decarburization by submerged blowing with oxygen or an oxygen-containing mixed gas is carried out.
  2. A method according to claim 1, characterized in that during the further manufacturing step a bath turbulence is initiated, namely by feeding gas into the melt, preferably in a minimum amount of 30 l/min per feed-in site when feeding inert gas and 300 l/min when feeding oxygen or oxygen-containing mixed gases.
  3. A method according to claim 1 or 2, characterized in that during submerged blowing an inert gas is admixed to the oxygen or the oxygen-containing mixed gas, respectively, at a percentage which increases as the submerged blowing progresses.
  4. A method according to one or several of claims 1 to 3, characterized in that the first manufacturing step is carried out in a first electric furnace (1) and the further manufacturing step in a further electric furnace (16) which is different from the first electric furnace (1).
  5. A method according to one or several of claims 1 to 4, characterized in that during an additional manufacturing step following the further manufacturing step, the melt is subjected to vacuum treatment.
  6. A method according to one or several of claims 1 to 5, characterized in that during at least one partial step of the further manufacturing step a flushing of the melt with inert gas or a mixture of inert gas and hydrocarbon is effected.
  7. A method according to one or several of claims 1 to 6, characterized in that the further manufacturing step is carried out under almost complete exclusion of air.
  8. A method according to one or several of claims 1 to 7, characterized in that more than 20% by weight, preferably more than 40% by weight, of the iron carriers in the charge consist of scrap.
  9. A method according to one or several of claims 1 to 8, characterized in that the further manufacturing step is carried out while retaining part of the slag obtained in the manufacturing step preceding the further manufacturing step.
  10. A method according to one or several of claims 1 to 9, characterized in that the slag is reduced in the further manufacturing step during flushing with inert gas under addition of reducing agent, lime and fluxing agent and the melt is deoxidized and desulfurized.
  11. A method according to claim 10, characterized in that the furnace atmosphere is adjusted during slag reduction by feeding in non- or, as compared with air, readily oxidizing gases while almost completely avoiding take-in of secondary air.
  12. A method according to claim 11, characterized in that the chemical analysis of the furnace atmosphere is checked and readjusted continuously.
  13. A method according to one or several of claims 10 to 12, characterized in that during the further manufacturing step a negative pressure is set in the electric furnace (16) at least during the reduction periods, particularly if the melt is low in carbon.
  14. A method according to one or several of claims 1 to 13, characterized in that during the further manufacturing step solid matter is introduced directly into the electric arc through hollow electrodes (13) of the electric furnace (16).
  15. A method according to claim 14, characterized in that, as solids, fine chrome ore or partially pre-reduced chrome ore are fed in as a chromium and oxygen carrier.
  16. A method according to one or several of claims 1 to 15, characterized in that during the first and/or further manufacturing step a bath turbulence is initiated by feeding inert gas into the melt and an oxidation of silicon and carbon is effected by top blowing oxygen or oxygen-containing mixed gas.
  17. A method according to one or several of claims 1 to 3 as well as 5 to 16, characterized in that the further manufacturing step is carried out in the electric furnace in which the first manufacturing step has been effected, but with the melt being tapped after the first manufacturing step, the phosphorus-containing slag being completely removed from the electric furnace, and the melt subsequently being charged back into the electric furnace.
  18. A method according to one or several of claims 1 to 17, characterized in that during the first manufacturing step and/or during the further manufacturing step solid matter such as filter dust from steel-making plants, ore, pre-reduced ore, iron carbide, alloying agents, residual substances, dust, scales, chips, slags, granular plastic material and/or liquids, as well as hazardous substances intended for disposal is introduced into the superheated melt individually or in mixtures, preferably by direct blowing-in and/or by top blowing and/or via hollow electrodes (13).
  19. A method according to one or several of claims 1 to 18, characterized in that a Cr2O3-containing slag formed during the further manufacturing step is tapped and is reduced in a further reaction vessel for chromium recovery by adding silicon carriers or other reducing agents, and the recovered chromium is used for alloying during the further manufacturing step.
  20. A method according to one or several of claims 1 to 19, characterized in that current consumption is reduced and foaming of the slag is stabilized by blowing in coal or coke along with oxidizing gases such as air, oxygen-enriched air, or an oxygen-containing mixed gas as a carrier gas, by direct blowing-in.
  21. A plant for carrying out the method according to one or several of claims 1 to 20, having an electric furnace (1, 16), in the bottom area (3) of which jacketed nozzles (4, 6) are provided, through the jacket of which it is feasible to feed hydrocarbon and/or inert gas, characterized by swivelling and lengthwise movable blowing-in lances (9) disposed above the normal molten bath level (7) and penetrating the furnace side wall (8), and having jacketed nozzles (4, 6) provided in the bottom area (3), through the jacket of which it is feasible to feed hydrocarbon and/or mixtures of hydrocarbon and inert gas and/or CO2 and/or water vapor.
  22. A plant according to claim 21, characterized in that a further electric furnace (16) is provided for carrying out the further manufacturing step.
  23. A plant according to claim 21 or 22, characterized in that the blowing-in lances (9) disposed above the normal molten bath level (7) consist of self-consuming pipes.
  24. A plant according to claim 22 or 23, characterized in that the further electric furnace (16) is provided with blowing-in lances (9) disposed above the normal molten bath level (7) as well as with submerged nozzles (6) provided in the lower part of the hearth (3) of the electric furnace (16).
  25. A plant according to one or several of claims 22 to 24, characterized in that the further electric furnace (16) is constructed to be almost completely airtight.
  26. A plant according to claim 25, characterized in that the furnace lid (18) is clampable relative to the furnace side wall (8) under insertion of a seal.
EP96890007A 1995-01-16 1996-01-11 Method of producing alloyed steels and arc furnace installation with positionable blowing lances therefor Expired - Lifetime EP0721990B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT5595 1995-01-16
AT55/95 1995-01-16
AT0005595A AT403293B (en) 1995-01-16 1995-01-16 METHOD AND INSTALLATION FOR THE PRODUCTION OF ALLOY STEELS

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EP0721990A1 EP0721990A1 (en) 1996-07-17
EP0721990B1 true EP0721990B1 (en) 2001-02-28

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EP (1) EP0721990B1 (en)
JP (1) JP4195106B2 (en)
KR (1) KR960029466A (en)
CN (1) CN1134984A (en)
AT (1) AT403293B (en)
BR (1) BR9600097A (en)
DE (1) DE59606475D1 (en)
TR (1) TR199600032A2 (en)
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ZA (1) ZA96281B (en)

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TW363081B (en) 1999-07-01
AT403293B (en) 1997-12-29
CN1134984A (en) 1996-11-06
EP0721990A1 (en) 1996-07-17
ATA5595A (en) 1997-05-15
DE59606475D1 (en) 2001-04-05
TR199600032A2 (en) 1996-08-21
JP4195106B2 (en) 2008-12-10
US6077324A (en) 2000-06-20
KR960029466A (en) 1996-08-17
BR9600097A (en) 1998-01-27
JPH08225880A (en) 1996-09-03
ZA96281B (en) 1996-07-31

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