EP0012226A1 - Method for treating boron-containing steel - Google Patents

Method for treating boron-containing steel Download PDF

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Publication number
EP0012226A1
EP0012226A1 EP79104467A EP79104467A EP0012226A1 EP 0012226 A1 EP0012226 A1 EP 0012226A1 EP 79104467 A EP79104467 A EP 79104467A EP 79104467 A EP79104467 A EP 79104467A EP 0012226 A1 EP0012226 A1 EP 0012226A1
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Prior art keywords
boron
steel
nitride
calcium
casting
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German (de)
French (fr)
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EP0012226B1 (en
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Fritz Willim
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SMS Concast AG
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Concast Holding AG
Concast 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
    • C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material
    • 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
    • C21C7/0006—Adding metallic additives
    • 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
    • C21C2007/0018—Boron

Definitions

  • the invention relates to a process for the treatment of boron-containing steel for continuous casting, in particular for casting in small formats with unregulated spout, elements such as calcium and boron being pre-deoxidized with manganese, silicon and optionally aluminum by means of a carrier gas.
  • Boron is known to increase the hardenability of the steel; it is about 10 - 100 times more effective than other elements.
  • the required deoxidation of the steel is achieved with large amounts of aluminum, whereby it must be ensured that enough aluminum remains in the steel even if the oxygen content was particularly high before the deoxidation.
  • the addition of titanium, zirconium or the like binds the nitrogen dissolved in the steel so stably that it can no longer react with the boron added.
  • standards for metal steels of 0.020 - 0.040% are often prescribed for these steels, which means e.g. insensitivity to involuntary overheating during the heat treatment, in particular during hardening, is sought.
  • a process for continuous casting is also known in which various elements for deoxidizing, alloying, cooling, etc. are added as additives in powder form by means of a transport gas (oxidation, reduction or neutral gas) into a ladle and / or an intermediate container.
  • a transport gas oxygen, reduction or neutral gas
  • the problem of treating boron-containing steels, which should be particularly suitable for casting in small formats, is not dealt with.
  • the solution to this problem is characterized by least in the molten steel in the ladle before pouring into the mold by means of an inert carrier gas and in powder form the calcium or a compound thereof, at least one element which forms nitrides which is stable at the molten steel temperature and boron or a boron compound and the pouring jets from the ladle in the intermediate container and from the intermediate container into the mold are protected from contact with the air.
  • the steel is pre-deoxidized in a known manner with deoxidizers such as manganese, silicon and aluminum.
  • deoxidizers such as manganese, silicon and aluminum.
  • the aim is to achieve a metallic aluminum content of the melt of approximately 0.010-0.020%.
  • Calcium is then blown into the pan in the form of CaSi or CaC 2 for further deoxidation and the oxygen dissolved in the steel is lowered to such an extent that oxidation of the boron subsequently added is essentially prevented.
  • the calcium also causes a reduction in the sulfur content and a favorable influence on the sulfides.
  • At least one nitride-forming element which is stable at the steel melting temperature is also blown into the molten steel in the pan by means of a carrier gas, preferably argon.
  • a carrier gas preferably argon.
  • boron or a boron compound such as, for example, borax, ferro-boron, nickel-boron or ferro-silicon-boron, is likewise supplied in precisely metered amounts and also in powder form by means of a carrier gas.
  • the • pouring jets from the ladle to the intermediate container and from the intermediate container into the continuous casting mold are protected from contact with the air.
  • This protection against direct contact with the air can be provided, for example, by known ceramic protective tubes or by using protective gas in a liquid or gaseous state. Burning of the metallic boron is prevented.
  • the steel thus treated in the order described now contains the small amounts of effective, i.e. metallic or acid-soluble boron. Predeterminable application of boron within narrow limits is given. Above all, however, the steel treated in this way is now used for continuous casting of small formats, e.g. Billet, suitable, i.e. it can be used with free-running, non-plug-regulated and not oversized spouts, e.g. an intermediate container into which continuous casting molds are introduced. This also applies if increased aluminum contents, e.g. 0.020 - 0.040% of metallic aluminum are prescribed.
  • Zircon and / or titanium or their alloys in powder form are advantageously introduced as the nitride-forming element. Their high affinity ensures an effective Abbin- dun g of nitrogen as a nitride.
  • Calcium and zircon or titanium can also be added simultaneously, for example as a calcium-silicon-zirconium alloy and / or a calcium-silicon-titanium alloy.

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

Abstract

Verfahren zur Behandlung von borhaltigem Stahl zum Stranggießen, insbesondere zum Abgießen in kleinen Formaten mit ungeregeltem Ausguß. In die in der Gießpfanne befindlichen Stahlschmelze wird durch ein inertes Trägergas und in Pulverform Calcium oder eine Verbindung desselben, mindestens ein, bei Stahlschmelztemperatur stabile Nitride bildendes Element und Bor bzw. eine Bor-Verbindung eingebracht. Der so behandelte Stahl wird auf seinem Weg von der Pfanne in die Kokille vor erneuter Reaktion mit der Luft geschützt.Process for the treatment of boron-containing steel for continuous casting, in particular for casting in small formats with unregulated spout. Calcium or a compound thereof is introduced into the molten steel in the ladle by means of an inert carrier gas and in powder form, at least one nitride-forming element and boron or a boron compound which is stable at the molten steel temperature. The steel treated in this way is protected from renewed reaction with the air on its way from the ladle into the mold.

Description

Die Erfindung betrifft ein Verfahren zur Behandlung von borhaltigem Stahl zum Stranggiessen, insbesondere zum Abgiessen in kleinen Formaten mit ungeregeltem Ausguss, wobei einem, mit Mangan, Silizium und gegebenenfalls Aluminium vordesoxydierten Stahl Elemente wie Calcium und Bor mittels eines Trägergases zugegeben werden.The invention relates to a process for the treatment of boron-containing steel for continuous casting, in particular for casting in small formats with unregulated spout, elements such as calcium and boron being pre-deoxidized with manganese, silicon and optionally aluminum by means of a carrier gas.

Bekanntlich erhöht Bor die Härtbarkeit des Stahles; es ist dafür etwa 10 - 100 mal wirksamer als andere Elemente. Für manche Verwendungszwecke ist es von Vorteil, dass Borstähle in ungehärtetem Zustand besser verformbar sind als Stähle, bei denen gleiche Härte und Festigkeitseigenschaften durch andere Legierungselemente erreicht werden. Durch zu grosse Mengen von Bor wird der Stahl jedoch spröde, weshalb enge Grenzen, etwa 0,0008 - 0,0030% eingehalten werden müssen. Für eine optimale Wirkung müssen aber innerhalb dieser Grenzen, je nach Analyse und insbesondere je nach Kohlenstoffgehalt noch engere Bereiche sicher und vorherbestimmbar eingehalten werden können. Damit die gewünschte Wirkung auch erzielt wird, ist wesentlich, dass dieses Bor metallisch im Stahl vorliegt und nicht als Oxyd oder Nitrid gebunden ist. Es ist daher notwendig, dass der überschüssige Sauerstoff und Stickstoff durch andere Elemente stabil abgebunden werden. Die im Stahl üblicherweise enthaltenen Mengen an Silizium und Mangan reichen dafür nicht aus.Boron is known to increase the hardenability of the steel; it is about 10 - 100 times more effective than other elements. For some uses, it is advantageous that boron steels are more ductile in the unhardened state than steels in which the same hardness and strength properties are achieved by other alloying elements. Too large amounts of boron make the steel brittle, which is why narrow limits, around 0.0008 - 0.0030%, have to be observed. For an optimal effect, however, within these limits, depending on the analysis and in particular depending on the carbon content, even narrower ranges must be adhered to safely and in a predictable manner. In order for the desired effect to be achieved, it is essential that this boron is metallic in the steel and is not bound as an oxide or nitride. It is therefore necessary that the excess oxygen and nitrogen be stably bound by other elements. The amounts of silicon and manganese usually contained in steel are not sufficient for this.

Im Blockguss wird die benötigte Desoxydation des Stahles durch grosse Mengen an Aluminium erreicht, wobei sichergestellt werden muss, dass auch dann noch genügend Aluminium im Stahl verbleibt, wenn der Sauerstoffgehalt vor der Desoxydation besonders hoch war. Gleichzeitig wird dabei durch Zugabe von Titan, Zirkon oder dergleichen der im Stahl gelöste Stickstoff so stabil abgebunden, dass er nicht mehr mit zugeführtem Bor reagieren kann. Ausserdem werden für diese Stähle in Normen häufig Gehalte an metallischem Aluminium von 0,020 - 0,040% vorgeschrieben, wodurch z.B. eine Unempfindlichkeit gegen unfreiwillige Ueberhitzung bei der Wärmebehandlung, insbesondere beim Härten, angestrebt wird.In block casting, the required deoxidation of the steel is achieved with large amounts of aluminum, whereby it must be ensured that enough aluminum remains in the steel even if the oxygen content was particularly high before the deoxidation. At the same time, the addition of titanium, zirconium or the like binds the nitrogen dissolved in the steel so stably that it can no longer react with the boron added. In addition, standards for metal steels of 0.020 - 0.040% are often prescribed for these steels, which means e.g. insensitivity to involuntary overheating during the heat treatment, in particular during hardening, is sought.

Da beim Stranggiessen von Stählen mit einem Aluminiumgehalt von über 0,007% die Gefahr besteht, dass während des Giessvorganges Ausgüsse durch Anlagerungen von Aluminium-Oxyden zuschmieren, können solche Stähle nur mit Stopfenregulierten, überdimensionierten Ausgüssen vergossen wer-den. Zur Bündelung des bei der Drosselung durch den Zwischenbehälter-Stopfen zum Flattern neigenden Strahles müssen Tauchrohre verwendet werden; diese müssen ebenfalls überdimensioniert sein, um dadurch das Ansetzen von Tonerde zu kompensieren. Daher können solche Stähle beim Stranggiessen nur in grossen Formaten, z.B. zu Brammen oder Vorblöcken, gegossen werden.Since the continuous casting of steels with an aluminum content of more than 0.007% poses the risk of spills smearing during the casting process due to deposits of aluminum oxides, such steels can only be poured with plug-regulated, oversized spouts. Dip tubes must be used to bundle the jet that tends to flutter when throttled by the intermediate container stopper; these must also be oversized in order to compensate for the formation of alumina. Therefore, such steels can only be produced in large formats, e.g. into slabs or ingots.

Beim'Stranggiessen von kleinen Formaten, wie z.B. von Knüppeln, treten jedoch Schwierigkeiten wegen der Empfindlichkeit der Zufuhrregelung, der für diese Formate typischen, relativ hohen Giessgeschwindigkeiten und vor allem wegen der Grösse der in die Kokille einzuführenden Tauchrohre auf. Diese Schwierigkeiten können zu Störungen des Giessverlaufes führen. Daher werden kleine Formate üblicherweise mit sogenannten freilaufenden, ungeregelten Ausgüssen gegossen, bei denen die Durchflussmenge und damit die Abzugsgeschwindigkeit durch den Innendurchmesser der Ausgüsse bestimmt wird. Dieser darf sich daher während des Gusses nicht ändern, insbesondere darf der Ausguss nicht zuschmieren. Mit dem herkömmlichen Verfahren muss deswegen der Aluminium-Gehalt des Stahles je nach Analyse und Temperatur auf max. 0,004 - 0,007% beschränkt werden. Mit diesen niedrigen Gehalten an Aluminium kann der niedrige Gehalt an löslichem Sauerstoff nicht erreicht werden, der nötig ist, wenn man Bor in der Pfanne zulegieren will und dabei den erforderlichen engen Bereich an im Stahl gelösten, metallischen Bor gewährleisten muss.When continuously casting small formats, such as billets, however, difficulties arise due to the sensitivity of the feed control, the relatively high casting speeds typical of these formats and, above all, the size of the immersion tubes to be inserted into the mold. These difficulties can lead to disturbances in the pouring process. Therefore, small formats are usually cast with so-called free-running, unregulated spouts, in which the flow rate and thus the Pull-off speed is determined by the inside diameter of the spouts. Therefore, this must not change during the casting, in particular the spout must not smear. With the conventional method, the aluminum content of the steel must therefore be max. 0.004 - 0.007%. With these low levels of aluminum, the low level of soluble oxygen cannot be achieved, which is necessary if you want to alloy boron in the pan and thereby ensure the required narrow range of metallic boron dissolved in the steel.

Es ist aus der Praxis bekannt, beim Stranggiessen von borlegiertem Stahl zu Knüppeln, das Bor in Form von Draht in die Kokille, z.B. über den Giessstrahl des Zwischenbehälters, zuzuführen. Dies hat jedoch den Nachteil, dass die Zugabe weitgehend und in einem nicht eindeutig vorherbestimmbaren Ausmass unwirksam wird, weil das Bor mit dem im Stahl noch gelösten Sauerstoff und Stickstoff reagiert, und somit für die Verbesserung der Härtbarkeit unwirksam wird. Werden aber die Zugabemengen an Bor erhöht, um diesen zusätzlichen Abbrand zu kompensieren, besteht die Gefahr, dass unfreiwillig zu hohe Borgehal-te erreicht werden. Bei der bekannten Zugabe von Bor in Drahtform besteht weiter die Schwierigkeit, dass, um genügend Bor in die Schmelze einzuführen, die Drahtstärke und/oder die Drahteinführgeschwindigkeit sehr hoch gehalten werden muss. Ersteres bringt jedoch eine schwierige Handhabung wegen erhöhter Steifigkeit des Drahtes mit sich, und die hohe Einführgeschwindigkeit führt zu schwer beherrschbaren Ungenauigkeiten im Bor-Gehalt.It is known from practice, in the continuous casting of boron-alloy steel into billets, that the boron is in the form of wire in the mold, e.g. via the pouring stream of the intermediate container. However, this has the disadvantage that the addition is largely ineffective and to an extent that cannot be clearly predetermined, because the boron reacts with the oxygen and nitrogen still dissolved in the steel, and is therefore ineffective for improving the hardenability. However, if the addition amounts of boron are increased to compensate for this additional burn-up, there is a risk that the boron content will be reached involuntarily. With the known addition of boron in wire form, there is also the difficulty that in order to introduce enough boron into the melt, the wire thickness and / or the wire insertion speed must be kept very high. However, the former involves difficult handling due to the increased stiffness of the wire, and the high insertion speed leads to inaccuracies in the boron content that are difficult to control.

Es ist ebenfalls aus der Praxis bekannt, einen Stahl durch Einblasen von pulverförmigen Calcium in Form von CaSi oder CaC2 oder Aehnlichem mittels eines inerten Trägergases (Stickstoff oder Argon) zu desoxydieren. Neue Erkenntnisse haben gezeigt, dass es möglich ist, einen derart vorbehandelten Stahl auch dann noch mit freilaufendem Ausguss zu giessen, wenn er gleichzeitig noch erhöhte Mengen an metallischem Aluminium, z.B. 0,040% enthält. Bei diesen bekannten und bis jetzt vorzugsweise für den Blockguss ver- i wendeten Verfahren wird üblicherweise die grösste Menge des im Stahl gelösten Sauerstoffes zuerst durch Zugabe von Aluminium abgebunden, und erst danach der kleinere Teil durch Einblasen von Calcium. Einerseits ist Aluminium billiger als Calcium, und anderseits wurde erkannt, dass Einschlüsse aus Calcium-Aluminat leichter aus dem Stahl entfernt werden als Aluminium-freie Calcium-Oxyd-Einschlüsse.It is also known from practice to deoxidize a steel by blowing in powdered calcium in the form of CaSi or CaC 2 or the like using an inert carrier gas (nitrogen or argon). New insights have shown that it is possible to cast a steel that has been pretreated in this way with a free-running spout even if it also contains increased amounts of metallic aluminum, for example 0.040%. In these known processes, which have hitherto been used preferably for ingot casting, the largest amount of the oxygen dissolved in the steel is usually set first by adding aluminum, and only then is the smaller part made by blowing in calcium. On the one hand, aluminum is cheaper than calcium, and on the other hand, it has been recognized that calcium aluminate inclusions are easier to remove from steel than aluminum-free calcium oxide inclusions.

Es ist weiterhin ein Verfahren zum Stranggiessen bekannt, bei dem verschiedene Elemente zum Desoxydieren, Legieren, Kühlen etc. als Zusatzstoffe in Pulverform mittels eines Transportgases (Oxydations-, Reduktions- oder neutrales Gas) in eine Giesspfanne und/oder einem Zwischenbehälter zugeführt werden. Dadurch sollte ein gleichmässiges Verteilen des Zusatzstoffes in der Schmelze zwecks Erzielung eines homogenen Gussstückes möglich sein. Bei diesem bekannten Verfahren wird jedoch auf die Problematik des Behandelns von borhaltigen Stählen, die insbesondere zum Abgiessen in kleinen Formaten geeignet sein sollten, nicht eingegangen.A process for continuous casting is also known in which various elements for deoxidizing, alloying, cooling, etc. are added as additives in powder form by means of a transport gas (oxidation, reduction or neutral gas) into a ladle and / or an intermediate container. This should be possible a g facilitated even distribution of the additive in the melt in order to achieve a homogeneous casting. In this known method, however, the problem of treating boron-containing steels, which should be particularly suitable for casting in small formats, is not dealt with.

Es ist Aufgabe der Erfindung, ein Verfahren zur Behandlung von borhaltigen Stählen zum Stranggiessen zu schaffen, das es gestattet, das Bor ohne Beeinträchtigung der Giessbarkeit in genau dosierten Mengen in die Schmelze einzubringen und ein bestimmtes Ausbringen von Bor sicher zu gewährleisten. Insbesondere soll ermöglicht werden, den borhaltigen Stahl in kleinen Formaten auf einfache Art giessbar zu machen.It is an object of the invention to provide a process for the treatment of boron-containing steels for continuous casting, which allows the boron to be introduced into the melt in precisely metered quantities without impairing the castability and to ensure a certain discharge of boron. In particular, is intended to enable the boron steel in small formats easily g to make iessbar.

Die Lösung dieser Aufgabe ist dadurch gekennzeichnet, dest in die Stahlschmelze in der Pfanne vor dem Abgiessen in die Kokille durch ein inertes Trägergas und in Pulverform das Calcium oder eine Verbindung desselben, mindestens ein, bei Stahlschmelztemperatur stabile Nitride bildendes Element und Bor bzw. eine Bor-Verbindung eingebracht und die Giessstrahlen aus der Pfanne in den Zwischenbehälter und vom Zwischenbehälter in die Kokille vor Kontakt mit der Luft geschützt werden.The solution to this problem is characterized by least in the molten steel in the ladle before pouring into the mold by means of an inert carrier gas and in powder form the calcium or a compound thereof, at least one element which forms nitrides which is stable at the molten steel temperature and boron or a boron compound and the pouring jets from the ladle in the intermediate container and from the intermediate container into the mold are protected from contact with the air.

Der Stahl wird in bekannter Weise mit Desoxydationsmitteln, wie Mangan, Silizium und Aluminium vordesoxydiert. Dabei wird ein Gehalt der Schmelze an metallischem Aluminium von ungefähr 0,010 - 0,020% angestrebt. Hernach wird Calcium in Form von CaSi oder CaC2 zur weiteren Desoxydation als Pulver in die Pfanne eingeblasen und dadurch der im Stahl gelöste Sauerstoff soweit abgesenkt, dass eine Oxydation des anschliessend zugegebenen Bors im wesentlichen verhindert wird. Durch das Calcium wird auch eine Reduktion des Schwefelgehaltes sowie eine günstige Beeinflussung der Sulfide hervorgerufen.The steel is pre-deoxidized in a known manner with deoxidizers such as manganese, silicon and aluminum. The aim is to achieve a metallic aluminum content of the melt of approximately 0.010-0.020%. Calcium is then blown into the pan in the form of CaSi or CaC 2 for further deoxidation and the oxygen dissolved in the steel is lowered to such an extent that oxidation of the boron subsequently added is essentially prevented. The calcium also causes a reduction in the sulfur content and a favorable influence on the sulfides.

Hierauf wird in die Stahlschmelze in der Pfanne mindestens ein, bei der Stahlschmelztemperatur stabile.Nitride bildendes Element ebenfalls mittels eines Trägergases, vorzugsweise Argon, eingeblasen. Dadurch wird die Bildung des unerwünschten Bor-Nitrides verhindert, da der Stickstoff damit als Nitrid wirksam abgebunden ist. Nach erfolgter Abbindung des Sauerstoffes und des Stickstoffes wird ebenfalls mittels eines Trägergases Bor bzw. eine Bor-Verbindung, wie beispielsweise Borax, Ferro-Bor, Nickel-Bor oder Ferro-Silizium-Bor in genau dosierten Mengen und ebenfalls in Pulverform zugeführt.Then at least one nitride-forming element which is stable at the steel melting temperature is also blown into the molten steel in the pan by means of a carrier gas, preferably argon. This prevents the formation of the undesirable boron nitride, since the nitrogen is effectively bound as a nitride. After the oxygen and nitrogen have set, boron or a boron compound, such as, for example, borax, ferro-boron, nickel-boron or ferro-silicon-boron, is likewise supplied in precisely metered amounts and also in powder form by means of a carrier gas.

Durch das Einblasen des, Nitride bildenden Elementes und des Bors bzw. der Bor-Verbindung in Pulverform in die, in die Pfanne befindlichen Stahlschmelze, wird eine gleichmässige Verteilung sichergestellt.By blowing the nitride-forming element and the boron or boron compound in powder form into the steel melt located in the pan, one becomes the same moderate distribution ensured.

Zum gleichzeitigen Schutz des Bors während des Giessens vor einer Reaktion mit Sauerstoff und Stickstoff werden die • Giessstrahlen aus der Pfanne zum Zwischenbehälter und vom Zwischenbehälter in die Stranggiesskokille vor einem Kontakt mit der Luft geschützt. Dieser Schutz vor direktem Kontakt mit der Luft kann beispielsweise durch bekannte keramische Schutzrohre oder Anwendung von Schutzgas in flüssigem oder gasförmigen Zustand geschehen. Damit wird ein Abbrand des metallisch gelösten Bors verhindert.To simultaneously protect the boron during the casting against a reaction with oxygen and nitrogen, the • pouring jets from the ladle to the intermediate container and from the intermediate container into the continuous casting mold are protected from contact with the air. This protection against direct contact with the air can be provided, for example, by known ceramic protective tubes or by using protective gas in a liquid or gaseous state. Burning of the metallic boron is prevented.

Der so in der beschriebenen Reihenfolge behandelte Stahl enthält nunmehr die in sehr engen Grenzen benötigten, geringen Mengen an wirksamen, d.h. metallischem oder säurelöslichem Bor. Ein vorbestimmbares Ausbringen an Bor innerhalb enger Grenzen ist dabei gegeben. Vor allem jedoch ist der so behandelte Stahl nun zum Stranggiessen kleiner Formate, wie z.B. Knüppel, geeignet, d.h. er kann über frei laufende, nicht Stopfen-regulierte und nicht überdimensionierte Ausgüsse, z.B. eines Zwischenbehälters, in die Stranggiesskokille eingebracht werden. Dies auch dann, wenn erhöhte Aluminium-Gehalte, z.B. 0,020 - 0,040% an metallischem Aluminium vorgeschrieben sind.The steel thus treated in the order described now contains the small amounts of effective, i.e. metallic or acid-soluble boron. Predeterminable application of boron within narrow limits is given. Above all, however, the steel treated in this way is now used for continuous casting of small formats, e.g. Billet, suitable, i.e. it can be used with free-running, non-plug-regulated and not oversized spouts, e.g. an intermediate container into which continuous casting molds are introduced. This also applies if increased aluminum contents, e.g. 0.020 - 0.040% of metallic aluminum are prescribed.

Als Nitrid bildendes Element wird vorteilhaft Zirkon und/ oder Titan bzw. deren Legierungen in Pulverform eingebracht. Deren hohe Affinität sichert eine wirksame Abbin- dung des Stickstoffes als Nitrid. Calcium und Zirkon oder Titan können auch gleichzeitig zugegeben werden, beispielsweise als eine Calcium-Silizium-Zirkon-Legierung und/oder eine Calcium-Silizium-Titan-Legierung.Zircon and / or titanium or their alloys in powder form are advantageously introduced as the nitride-forming element. Their high affinity ensures an effective Abbin- dun g of nitrogen as a nitride. Calcium and zircon or titanium can also be added simultaneously, for example as a calcium-silicon-zirconium alloy and / or a calcium-silicon-titanium alloy.

Es kann aber auch angebracht sein, in die Schmelze ein Gemisch oder eine Legierung aus dem, Nitride bildenden Element und Bor bzw. einer Bor-Verbindung einzublasen.However, it may also be appropriate to blow a mixture or an alloy of the element which forms nitrides and boron or a boron compound into the melt.

Ein wirtschaftliches Einbringen und eine gute Verteilung wird vorteilhaft dadurch erreicht, dass die Zugabe des Calciums, des Nitride bildenden Elementes und des Bors bzw. der Bor-Verbindung über eine, mit axialem Zuleitungsrohr versehene Lanze erfolgt. Vorteilhaft kann die Zugabe auch über einen, an der Pfanne angebrachten Schieber erfolgen, wodurch eine besonders wirksame Vermischung erzielt wird.Economic introduction and good distribution is advantageously achieved by adding the calcium, the nitride-forming element and the boron or boron compound via a lance provided with an axial feed pipe. The addition can also advantageously be carried out via a slide attached to the pan, as a result of which particularly effective mixing is achieved.

Claims (5)

1. Verfahren zur Behandlung von borhaltigem Stahl zum Stranggiessen, insbesondere zum Abgiessen in kleinen Formaten mit ungeregeltem Ausguss, wobei einem, mit Mangan, Silizium und Aluminium vordesoxydierten Stahl Elemente wie Calcium und Bor mittels eines Trägergases zugegeben werden, dadurch gekennzeichnet, dass in die Stahlschmelze in der Pfanne vor dem Abgiessen in die Kokille durch ein inertes Trägergas und in Pulverform das Calcium oder eine Verbindung derselben, mindestens ein, bei Stahlschmelztemperatur stabile Nitride bildendes Element und Bor bzw. eine Bor-Verbindung eingebracht und die Giessstrahlen aus der Pfanne in den Zwischenbehälter und vom Zwischenbehälter in die Kokille vor Kontakt mit der Luft geschützt werden.1. A process for the treatment of steel containing boron for continuous casting, in particular for casting in small formats with unregulated spout, elements, such as calcium and boron, which have been pre-deoxidized with manganese, silicon and aluminum, being added by means of a carrier gas, characterized in that in the molten steel in the pan before pouring into the mold by means of an inert carrier gas and in powder form the calcium or a compound thereof, at least one element which forms nitrides which is stable at the melting point of steel and boron or a boron compound and the pouring jets from the pan into the intermediate container and be protected from contact with the air from the intermediate container into the mold. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass als Nitride bildendes Element Zirkon und/oder Titan bzw. eine Legierung derselben eingebracht wird.2. The method according to claim 1, characterized in that zirconium and / or titanium or an alloy thereof is introduced as the nitride-forming element. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass in die Stahlschmelze ein Gemisch oder eine Legierung aus dem, Nitride bildenden Element und Bor bzw. einer Bor-Verbindung eingebracht wird.3. The method according to claim 1 or 2, characterized in that a mixture or an alloy of the nitride-forming element and boron or a boron compound is introduced into the molten steel. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das, Nitride bildende Element und Bor bzw. die Bor-Verbindung über eine Lanze zugegeben werden.4. The method according to any one of claims 1 to 3, characterized in that the nitride-forming element and boron or the boron compound are added via a lance. 5. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Zugabe über einen Schieber erfolgt.5. The method according to any one of claims 1 to 3, characterized in that the addition takes place via a slide.
EP79104467A 1978-11-17 1979-11-13 Method for treating boron-containing steel Expired EP0012226B1 (en)

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EP0166908A1 (en) * 1984-05-08 1986-01-08 Elektroschmelzwerk Kempten GmbH Process for the manufacture of boron-containing steels

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US4440568A (en) * 1981-06-30 1984-04-03 Foote Mineral Company Boron alloying additive for continuously casting boron steel
US4575912A (en) * 1984-05-07 1986-03-18 Ssab Svenskt Stal Ab Spring steel
JPS62184909U (en) * 1986-05-15 1987-11-25
US6108932A (en) * 1998-05-05 2000-08-29 Steag Microtech Gmbh Method and apparatus for thermocapillary drying
US20030183041A1 (en) * 2002-03-28 2003-10-02 Sunao Takeuchi High-purity ferroboron, a mother alloy for iron-base amorphous alloy, an iron-base amorphous alloy, and methods for producing the same
US7717976B2 (en) * 2004-12-14 2010-05-18 L&P Property Management Company Method for making strain aging resistant steel
CN103341595B (en) * 2013-07-01 2015-09-16 广西大学 The long-acting alterant of high boron iron-based antifriction alloy and preparing process thereof and using method

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US4251268A (en) 1981-02-17
JPS6014810B2 (en) 1985-04-16
ES486598A0 (en) 1980-12-01
EP0012226B1 (en) 1982-01-20
CA1142761A (en) 1983-03-15
ZA795853B (en) 1980-10-29
DE2961903D1 (en) 1982-03-04
FI793135A (en) 1980-05-18
JPS5569214A (en) 1980-05-24
ES8101123A1 (en) 1980-12-01
TR20525A (en) 1981-10-05
AR217014A1 (en) 1980-02-15
BR7907238A (en) 1980-07-08
ATE591T1 (en) 1982-02-15

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