EP0083920A2 - Method of casting steels with higher aluminium standards by continuous billet casting plants - Google Patents

Method of casting steels with higher aluminium standards by continuous billet casting plants Download PDF

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Publication number
EP0083920A2
EP0083920A2 EP83100005A EP83100005A EP0083920A2 EP 0083920 A2 EP0083920 A2 EP 0083920A2 EP 83100005 A EP83100005 A EP 83100005A EP 83100005 A EP83100005 A EP 83100005A EP 0083920 A2 EP0083920 A2 EP 0083920A2
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Prior art keywords
aluminum
tundish
casting
pan
amount
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German (de)
French (fr)
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EP0083920B1 (en
EP0083920A3 (en
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Dietfried Reiber
Klaus Längauer
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Von Roll AG
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Von Roll AG
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating 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
    • C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material

Definitions

  • the invention relates to a method for casting steel with over 0.02% metallic aluminum on billet continuous casting plants with free-running, calibrated tundish nozzles.
  • aluminum oxide compounds can be modified in the treatment of the liquid melt with alloys and / or slags of the metals calcium and magnesium.
  • the addition is expediently carried out by blowing into the casting ladle by means of an immersion lance.
  • Argon is normally used as the carrier gas.
  • ladle metallurgical treatment it is common to protect the melt in the ladle from further oxidation, e.g. thanks to protective gas, vacuum, special pan lid, keeping slag free, special slag compositions, pan deliveries made of refractories with low oxygen potential.
  • a method known from DE-AS 25 27 156 for preventing the addition of immersion spouts, as are usually used in bloom and slab caster systems, consists in "overblowing" the melt with calcium treatment agents. When “overblown”, aluminum oxide compounds are largely reduced to calcium oxide, which is said to be completely separated.
  • the invention is based on the object of metering the Ca amount in such a way that only liquid aluminum oxide compounds occur when casting steels with higher contents of metallic aluminum on billet continuous casting plants.
  • the melt is not overblown, but that the amount of solids blown in is matched precisely to the steel composition before the blown-in treatment, in particular to the Oxygen content (carbon content). It is advisable to determine the free oxygen content of the melt in the pan after adding Al and before blowing in; if this is higher than 15 ppm, additional aluminum (per ppm O 2 3.0 ppm Al) must be added.
  • the composition of the inclusion compounds calcium oxide - aluminum oxide is controlled so that - if there are no defined purity level requirements - a large part of the known fine grain steels can be cast between the ladle and the tundish without reoxidation protection.
  • this limit is already 0.020% Al. It may then be advisable to additionally seal the tundish airtight using a lid and before pouring it on using inert gases such as e.g. Keep nitrogen or argon oxygen free.
  • inert gases such as e.g. Keep nitrogen or argon oxygen free.
  • the reoxidation protection can consist of a known shadow pipe.
  • synthetic slags with a low oxidation potential for example Ca O with about 30% A1 2 ° 3 content, are additionally used to cover the steel surface in the tundish.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

1. Method of casting steels with more than 0.02 weight percent metallic aluminium by continuous billet casting plants with freewheeling, calibrated tundish jets, characterized in that from 0.8 to 0.1 weight percent aluminium is added to the ladle, dependent on the C-content, in an amount from 0.04 to 2.0 of the aluminium content, and that thereafter calcium alloys in an amount of 0.05 to 1.2 times the amount in the ladle, based on pure calcium, is added to the ladle.

Description

Die Erfindung betrifft ein Verfahren zum Vergiessen von Stählen mit über 0,02% metallischem Aluminium auf Knüppelstranggiessanlagen mit freilaufenden, kalibrierten Tundishdüsen.The invention relates to a method for casting steel with over 0.02% metallic aluminum on billet continuous casting plants with free-running, calibrated tundish nozzles.

Es ist bekannt, dass Stähle mit Gehalten an metallischem Aluminium über 0,02% an Knüppelstranggiessanlagen Schwierigkeiten beim Giessen bereiten, wenn das Aluminium bereits in der Giesspfanne zulegiert wird (alle %-Angaben sind Gewichtsprozente).It is known that steels with a metallic aluminum content of more than 0.02% in billet continuous casting plants cause difficulties when the aluminum is already alloyed in the ladle (all percentages are percentages by weight).

Der Grund dafür ist, dass die im Stahl suspendierten, nichtflüssigen Aluminiumoxydverbindungen sich beim Giessen an der Wandung der Tundishdüsen ansetzen und diese in kurzer Zeit vollständig zersetzen, so dass der Giessvorgang unterbrochen wird.The reason for this is that the non-liquid aluminum oxide compounds suspended in the steel attach themselves to the wall of the tundish nozzles during casting and completely decompose them in a short time, so that the casting process is interrupted.

Zur Herstellung von Feinkornstählen auf Aluminium-Basis wird das Einspulen von Aluminiumdraht in die Stranggiesskokille praktiziert. Diese Methode bringt unbefriedigende Ergebnisse, da die Aluminiumverteilung im Stranggussknüppel ungleichmässig ist und schlechte Strangoberflächen durch Aluminiumoxydnester entstehen.For the production of fine-grain steels based on aluminum, the winding of aluminum wire into the continuous casting mold is practiced. This method gives unsatisfactory results because the aluminum distribution in the continuous casting billet is uneven and poor strand surfaces are caused by aluminum oxide nests.

Es ist weiter bekannt, dass Aluminiumoxydverbindungen bei der Behandlung der flüssigen Schmelze mit Legierungen und/oder Schlacken der Metalle Calcium und Magnesium modifiziert werden können. Zur Erhöhung des Ausbringens dieser Metalle erfolgt die Zugabe zweckmässigerweise durch Einblasen in die Giesspfanne mittels Tauchlanze. Als Trägergas wird normalerweise Argon verwendet. Bei einer pfannenmetallurgischen Behandlung ist es üblich, die Schmelze in der Pfanne vor weiterer Oxydation zu schützen, z.B. durch Schutzgas, Vakuum, besonderen Pfannendeckel, Schlackenfreihalten, besondere Schlackenzusammensetzungen, Pfannenzustellungen aus Feuerfeststoffen mit niedrigem Sauerstoffpotential.It is further known that aluminum oxide compounds can be modified in the treatment of the liquid melt with alloys and / or slags of the metals calcium and magnesium. To increase the output of these metals, the addition is expediently carried out by blowing into the casting ladle by means of an immersion lance. Argon is normally used as the carrier gas. In ladle metallurgical treatment it is common to protect the melt in the ladle from further oxidation, e.g. thanks to protective gas, vacuum, special pan lid, keeping slag free, special slag compositions, pan deliveries made of refractories with low oxygen potential.

Eine aus DE-AS 25 27 156 bekannte Methode zur Verhinderung des Zusetzens von Tauchausgüssen, wie sie üblicherweise bei Vorblock- und Brammenstranggiessanlagen verwendet werden, besteht im "Ueberblasen" der Schmelze mit Kalziumbehandlungsmitteln. Beim "Ueberblasen" werden Aluminiumoxydverbindungen grösstenteils zu Calciumoxyd reduziert, das sich angeblich vollständig abscheiden soll.A method known from DE-AS 25 27 156 for preventing the addition of immersion spouts, as are usually used in bloom and slab caster systems, consists in "overblowing" the melt with calcium treatment agents. When "overblown", aluminum oxide compounds are largely reduced to calcium oxide, which is said to be completely separated.

Es werden aber auch noch Calcium-Aluminiumverbindungen mit hohen Calciumoxydgehalten gefunden, die bei Tauchausgüssen anscheinend keine Schwierigkeiten bereiten. Diese Einschlüsse sind infolge ihres hohen CaO-Gehaltes nichtflüssig.However, calcium-aluminum compounds with high calcium oxide contents are also found, which apparently do not cause any problems with diving spouts. These inclusions are not liquid due to their high CaO content.

Die vorgenannte Methode des "Ueberblasens" erbringt bei Knüppelstranggiessanlagen nichtreproduzierbare Ergebnisse, da bereits geringe Anteile nichtflüssiger Aluminiumoxydverbindungen das Zusetzen der freilaufenden, kalibrierten Tundishdüsen bewirken.The above-mentioned method of "overblowing" produces non-reproducible results in billet continuous casting plants, since even small amounts of non-liquid aluminum oxide compounds cause the free-running, calibrated tundish nozzles to clog.

Der Erfindung liegt die Aufgabe zugrunde, die Ca-Menge so zu dosieren, dass beim Giessen von Stählen mit höheren Gehalten an metallischem Aluminium auf Knüppelstranggiessanlagen nur flüssige Aluminiumoxydverbindungen auftreten.The invention is based on the object of metering the Ca amount in such a way that only liquid aluminum oxide compounds occur when casting steels with higher contents of metallic aluminum on billet continuous casting plants.

Zur Lösung dieser Aufgabe wird gemäss der Erfindung vorgeschlagen, dass in Abhängigkeit vom C-Gehalt im Bereich von 0,8 - 0,1% die 0,04- bis 2,0-fache Menge Aluminium in die Pfanne zugegeben wird und anschliessend Calcium-Legierungen in 0,05- bis 1,2-facher Menge Ca in die Pfanne eingeblasen werden, mit dem Zweck, ausschliesslich flüssige Calcium-Aluminiumoxyde zu bilden.To achieve this object, it is proposed according to the invention that, depending on the C content in the range of 0.8-0.1%, 0.04 to 2.0 times the amount of aluminum is added to the pan and then calcium Alloys are blown into the pan in 0.05 to 1.2 times the amount of Ca with the purpose of exclusively forming liquid calcium aluminum oxides.

Dies bedeutet, dass das Legieren von Aluminium in der Giesspfanne vor dem Einblasen von Ca-Mg-Legierungen und/ oder deren Schlacken so auf die Stahlzusammensetzung abgestimmt wird, dass durch die Behandlung der Schmelze mit diesen Einblasstoffen mit Sicherheit nur flüssige Calcium/ Magnesium-Aluminiumoxydverbindungen vorliegen und Gehalte von über 0,02% metallischem Aluminium in der Schmelze legiert bleiben.This means that the alloying of aluminum in the ladle before the blowing in of Ca-Mg alloys and / or their slags is matched to the steel composition in such a way that, by treating the melt with these blowing agents, it is certain that only liquid calcium / magnesium-aluminum oxide compounds are present and contents of more than 0.02% metallic aluminum remain alloyed in the melt.

Aus dem bekannten Zweistoffsystem Ca 0 - A12 03 ist ersichtlich, bei welchen Einschlusszusammensetzungen auch für Giesstemperaturen des Stahles im Tundish von z.B. 1480°C bis 1580°C die Einschlüsse noch in flüssiger Form vorliegen.From the known two-substance system Ca 0 - A1 2 0 3 it can be seen in which inclusion compositions, even for casting temperatures of the steel in the tundish, for example from 1480 ° C. to 1580 ° C., the inclusions are still in liquid form.

Für die Effektivität der Behandlung ist es gemäss der Erfindung von Wichtigkeit, dass die Schmelze nicht überblasen wird, sondern dass die Menge der eingeblasenen Feststoffe genau auf die Stahlzusammensetzung vor der Einblasbehandlung abgestimmt wird, insbesondere auf den Sauerstoffgehalt (Kohlenstoffgehalt). Es empfiehlt sich, nach der Al-Zugabe und vor Einblasen den freien Sauerstoffgehalt der Schmelze in der Pfanne zu bestimmen; liegt dieser höher als 15 ppm, ist weiteres Aluminium (pro ppm O2 3,0 ppm Al) zuzugeben.For the effectiveness of the treatment, it is important according to the invention that the melt is not overblown, but that the amount of solids blown in is matched precisely to the steel composition before the blown-in treatment, in particular to the Oxygen content (carbon content). It is advisable to determine the free oxygen content of the melt in the pan after adding Al and before blowing in; if this is higher than 15 ppm, additional aluminum (per ppm O 2 3.0 ppm Al) must be added.

Beispiel 1example 1

Qualität Ck 45, Chargen Nr. 49797

Figure imgb0001
Al-Zugabe bei Abstich: 24 kg = 0,6 kg/t Faktor Al-Zugabe = 0,142 · 168 = 24 freier Sauerstoffgehalt vor Einblasen: 11,1 ppm Feststoff eingeblasen: 100 kg Ca Si = 30 kg Ca = 0,75 kg Ca/t Faktor Ca-Zugabe = 0,178·168 = 30- freier Sauerstoffgehalt nach Einblasen: 2,76 ppmQuality Ck 45, batch No. 49797
Figure imgb0001
 Al addition at tapping: 24 kg = 0.6 kg / t factor Al addition = 0.142 · 168 = 24 free oxygen content before blowing: 11.1 ppm solid blown: 100 kg Ca Si = 30 kg Ca = 0.75 kg Ca / t factor Ca addition = 0.178 · 168 = 30- free oxygen content after blowing in: 2.76 ppm

Beispiel 2Example 2

Qualität: IE 1013 Chg.Nr. 54203

Figure imgb0002
Al-Zugabe bei Abstich: 45 kg = 1,125 kg/t freier Sauerstoffgehalt vor Einblasen: 12,75 ppm Feststoff eingeblasen: 120 kg Ca Si ≙ 0,9 kg Ca/t freier Sauerstoffgehalt nach Einblasen: 2,62 ppm % C = 30 = 120 kg CQuality: IE 1013 Chg.Nr. 54203
Figure imgb0002
 Al addition during tapping: 45 kg = 1.125 k g / t free oxygen content before injection: blown 12.75 ppm solids 120 kg Ca Si ≙ 0.9 kg Ca / t free oxygen content after injection: 2.62 ppm% C = 30 = 120 kg C.

Zugabe Al: 45 kg; Faktor Al-Zugabe = 0,375 · 120 = 45 Zugabe Ca: 36 kg; Faktor Ca-Zugabe = 0,3 · 120 = 36 Es ist weiter zu beachten, dass die in der Giesspfanne in flüssiger Form vorliegenden Einschlussverbindungen sich beim Giessprozess nicht wieder in einen nichtflüssigen Zustand verändern.Al addition: 45 kg; Factor Al addition = 0.375 * 120 = 45 addition Ca: 36 kg; Ca addition factor = 0.3 * 120 = 36 It should also be noted that the inclusion compounds present in liquid form in the ladle do not change back to a non-liquid state during the casting process.

Erfindungsgemäss wird die Zusammensetzung der Einschlussverbindungen Calciumoxyd - Aluminiumoxyd so gesteuert, dass - wenn keine definierten Reinheitsgradanforderungen vorliegen - ein grosser Teil der bekannten Feinkornstähle ohne Reoxydationsschutz zwischen Giesspfanne und Tundish vergossen werden kann.According to the invention, the composition of the inclusion compounds calcium oxide - aluminum oxide is controlled so that - if there are no defined purity level requirements - a large part of the known fine grain steels can be cast between the ladle and the tundish without reoxidation protection.

Ueberraschenderweise hat es sich gezeigt, dass bei kleineren Tundishen mit drei oder weniger Ausgüssen die Grenze für das Giessen ohne Giessstrahlschutz zwischen Pfanne und Tundish bei 0,03% metallischem Aluminium liegt. Liegen höhere Gehalte vor, ist zur Vermeidung der Reoxydation von Aluminium ein Giessstrahlschutz zwischen Pfanne und Tundish erforderlich.Surprisingly, it has been shown that in the case of smaller tundishes with three or fewer spouts, the limit for casting without pouring jet protection between the pan and the tundish is 0.03% metallic aluminum. If the contents are higher, pouring jet protection between the pan and the tundish is necessary to avoid reoxidation of aluminum.

Bei Tundishgrössen für vier und mehr Stränge liegt diese Grenze bereits bei 0,020% Al. Es kann dann zweckmässig sein, zusätzlich den Tundish luftdicht mittels Deckel abzuschliessen und vor dem Angiessen mittels Inertgasen wie z.B. Stickstoff oder Argon sauerstofffrei zu halten.For tundish sizes for four or more strands, this limit is already 0.020% Al. It may then be advisable to additionally seal the tundish airtight using a lid and before pouring it on using inert gases such as e.g. Keep nitrogen or argon oxygen free.

Der Reoxydationsschutz kann aus einem bekannten Schattenrohr bestehen.The reoxidation protection can consist of a known shadow pipe.

Erfindungsgemäss werden zusätzlich synthetische Schlacken mit niedrigem Oxydationspotential, z.B. Ca O mit etwa 30% A12 °3-Anteil, zum Abdecken der Stahloberfläche im Tundish verwendet.According to the invention, synthetic slags with a low oxidation potential, for example Ca O with about 30% A1 2 ° 3 content, are additionally used to cover the steel surface in the tundish.

Claims (7)

1. Verfahren zum Vergiessen von Stählen mit über 0,02% metallischem Aluminium auf Knüppelstranggiessanlagen mit freilaufenden, kalibrierten Tundishdüsen, dadurch gekennzeichnet, dass in Abhängigkeit vom C-Gehalt im Bereich von 0,8 - 0,1% die 0,04- bis 2,0-fache Menge Aluminium in die Pfanne zugegeben wird und anschliessend Calcium-Legierungen in 0,05- bis 1,2-facher Menge Ca in die Pfanne eingeblasen werden, mit dem Zweck, ausschliesslich flüssige Calcium-Aluminiumoxyde zu bilden.1. Process for casting steels with more than 0.02% metallic aluminum on billet continuous casting plants with free-running, calibrated tundish nozzles, characterized in that, depending on the C content in the range from 0.8 - 0.1%, the 0.04 to 2.0 times the amount of aluminum is added to the pan and then calcium alloys are blown into the pan in 0.05 to 1.2 times the amount of Ca, with the purpose of exclusively forming liquid calcium aluminum oxides. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass zusätzlich ein Gemisch von 50% Ca O und 50% A12 03 eingeblasen wird.2. The method according to claim 1, characterized in that a mixture of 50% Ca O and 50% A1 2 0 3 is additionally blown in. 3. Verfahren nach Anspruch 1 und 2, dadurch gekennzeichnet, dass in Abhängigkeit von der Höhe des Gehaltes an metallischem Aluminium und der Grösse des Tundishes ein Reoxydationsschutz zwischen Pfanne und Tundish zur Vermeidung der Aluminiumoxydation verwendet wird.3. The method according to claim 1 and 2, characterized in that depending on the level of the content of metallic aluminum and the size of the tundish, a reoxidation protection between pan and tundish is used to avoid aluminum oxidation. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass bei kleineren Tundishen mit drei oder weniger Ausgüssen und bei Al-Gehalten > 0,03% ein Reoxydationsschutz angewendet wird.4. The method according to claim 3, characterized in that a reoxidation protection is used for smaller tundishes with three or fewer spouts and for Al contents> 0.03%. 5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass bei grösseren Tundishen mit mehr als drei Ausgüssen und bei Al-Gehalten > 0,02% ein Reoxydationsschutz angewendet wird.5. The method according to claim 4, characterized in that a reoxidation protection is used for larger tundishes with more than three spouts and for Al contents> 0.02%. 6. Verfahren nach Anspruch 3, 4 und 5, dadurch gekennzeichnet, dass der Tundish mit synthetischen Schlacken mit niedrigem Oxydationspotential abgedeckt wird.6. The method according to claim 3, 4 and 5, characterized indicates that the tundish is covered with synthetic slags with low oxidation potential. 7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass die synthetischen Schlacken aus einer Mischung aus Ca 0 und etwa 30% Al2 03 bestehen.7. The method according to claim 6, characterized in that the synthetic slags consist of a mixture of Ca 0 and about 30% Al 2 0 3 .
EP83100005A 1982-01-08 1983-01-03 Method of casting steels with higher aluminium standards by continuous billet casting plants Expired EP0083920B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83100005T ATE23463T1 (en) 1982-01-08 1983-01-03 PROCESS FOR CASTING STEEL WITH HIGH ALUMINUM CONTENT ON BILLET CONTINUOUS CASTING PLANTS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH107/82 1982-01-08
CH10782 1982-01-08

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EP0083920A2 true EP0083920A2 (en) 1983-07-20
EP0083920A3 EP0083920A3 (en) 1983-10-26
EP0083920B1 EP0083920B1 (en) 1986-11-12

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2636400A1 (en) * 1976-08-11 1978-02-16 Mannesmann Ag PROCESS FOR IMPROVING THE CRYSTAL STRUCTURE OF STRIPPED STEEL
DE2527156B2 (en) * 1975-06-18 1980-09-04 Thyssen Niederrhein Ag Huetten- Und Walzwerke, 4200 Oberhausen Process for the pretreatment of molten steel in continuous casting
US4317678A (en) * 1980-09-26 1982-03-02 Union Carbide Corporation Process for continuous casting of aluminum-deoxidized steel

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2527156B2 (en) * 1975-06-18 1980-09-04 Thyssen Niederrhein Ag Huetten- Und Walzwerke, 4200 Oberhausen Process for the pretreatment of molten steel in continuous casting
DE2636400A1 (en) * 1976-08-11 1978-02-16 Mannesmann Ag PROCESS FOR IMPROVING THE CRYSTAL STRUCTURE OF STRIPPED STEEL
US4317678A (en) * 1980-09-26 1982-03-02 Union Carbide Corporation Process for continuous casting of aluminum-deoxidized steel

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EP0083920B1 (en) 1986-11-12
DE3367542D1 (en) 1987-01-02
EP0083920A3 (en) 1983-10-26
ATE23463T1 (en) 1986-11-15

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