EP0166908B1 - Process for the manufacture of boron-containing steels - Google Patents
Process for the manufacture of boron-containing steels Download PDFInfo
- Publication number
- EP0166908B1 EP0166908B1 EP85105505A EP85105505A EP0166908B1 EP 0166908 B1 EP0166908 B1 EP 0166908B1 EP 85105505 A EP85105505 A EP 85105505A EP 85105505 A EP85105505 A EP 85105505A EP 0166908 B1 EP0166908 B1 EP 0166908B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- boron
- calcium
- powder
- process according
- hexaboride
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- 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
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
-
- 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 production of steels alloyed with boron. It is known that by adding boron in small amounts, i.e. H. in the range of approximately 0.0005-0.05% by weight, the hardenability of steel can be improved depending on its carbon content. Steels with larger boron additions, d. H. more than 0.1% by weight have so far been of technical importance for atomic reactor construction. Boron is added to the steel either in the form of ferroboron, which according to the DIN standard has boron contents in the range of 10-20% by weight, or in the form of special master alloys with 0.2-2% by weight of boron (cf. "Ullmann's Encyclopedia der techn. Chemie ", 4th ed., Vol. 22 (1982), pp. 56-57).
- the boron in the steel must be in dissolved (metallic) form, which can generally be achieved by deoxidation and denitrification of the melt before the boron is added.
- nitride-forming elements such as titanium or zircon or alloys thereof
- a carrier gas e.g. calcium and titanium or zircon can also be added at the same time, e.g. B. in the form of an alloy.
- the final deoxidation and denitrification are carried out in one step.
- boron or a boron compound such as borax, ferroboron, NiB or FeSiB
- borax, ferroboron, NiB or FeSiB is then likewise supplied in precisely metered amounts and also in powder form using a carrier gas. It is also possible to blow in a mixture or an alloy of the nitride-forming element and boron or a boron compound.
- the introduction of the constituents mentioned is advantageously carried out by means of an immersion lance or via a slide attached to the pan, while the known addition of boron in wire form has proven less successful (cf. EP-B-12226).
- This object is achieved in that calcium hexaboride is used as the boron alloy carrier.
- Calcium hexaboride is a commercially available compound with a defined composition that is available in sufficient purity.
- Calcium borides have long been used in industry as reducing agents, for example for the deoxidation of copper melts. It is also known that a reducing agent for these oxides can be used in the production of iron and steel under predominantly acidic conditions for the introduction of basic oxides of rare earths.
- calcium silicide calcium boride is also mentioned as an example of such reducing agents (cf. US Pat. No. 2,799,575).
- the calcium hexaboride used as boron alloy carrier in the process according to the invention is advantageously used as a powder with particle sizes of approximately 0.01-1.00 mm.
- the introduction into the molten steel in the pan before the casting can be carried out using all measures known for this, such as by inserting with the aid of a hollow wire or by blowing in with the aid of an inert carrier gas.
- calcium hexaboride When introducing calcium hexaboride alone, it is advisable to pre-oxidize the steel melt in a known manner and, if necessary, to denitrify it. Because of its light specific weight, calcium hexaboride can advantageously also be introduced together in a mixture with likewise specifically light deoxidizing agents, such as aluminum or calcium silicide, the blowing in in admixture with additives having proven particularly useful for the final deoxidation.
- the selection according to the invention of using calcium hexaboride as the boron alloy carrier can decisively improve the accuracy of the targeted amounts of boron which remain dissolved in the steel.
- the calcium can preferentially react with locally enriched residual oxygen in the melt due to its greater affinity for oxygen, so that the added amounts of boron are protected from oxidation, remain dissolved in the steel and no longer partially Burning will be lost.
Abstract
Description
Gegenstand der Erfindung ist ein Verfahren zur Herstellung von mit Bor legierten Stählen. Es ist bekannt, daß durch Zulegierung von Bor in geringen Mengen, d. h. im Bereich von etwa 0,0005 - 0,05 Gew.-% die Härtbarkeit von Stahl in Abhängigkeit von dessen Kohlenstoffgehalt verbessert werden kann. Stähle mit größeren Borzusätzen, d. h. mehr als 0,1 Gew.-%, haben bisher für den Atomreaktorbau technische Bedeutung erlangt. Bor wird dem Stahl entweder in Form von Ferrobor zugesetzt, das nach DIN-Norm Borgehalte im Bereich von 10 - 20 Gew.-% aufweist oder in Form besonderer Vorlegierungen mit 0,2 - 2 Gew.-% Bor (vgl. "Ullmanns Encyklopädie der techn. Chemie", 4. Aufl., Bd. 22 (1982), S. 56 - 57).The invention relates to a process for the production of steels alloyed with boron. It is known that by adding boron in small amounts, i.e. H. in the range of approximately 0.0005-0.05% by weight, the hardenability of steel can be improved depending on its carbon content. Steels with larger boron additions, d. H. more than 0.1% by weight have so far been of technical importance for atomic reactor construction. Boron is added to the steel either in the form of ferroboron, which according to the DIN standard has boron contents in the range of 10-20% by weight, or in the form of special master alloys with 0.2-2% by weight of boron (cf. "Ullmann's Encyclopedia der techn. Chemie ", 4th ed., Vol. 22 (1982), pp. 56-57).
> Für die Steigerung der Härtbarkeit muß das Bor im Stahl in gelöster (metallischer) Form vorliegen, was im allgemeinen durch Desoxidation und Denitrierung der Schmelze vor der Borzugabe erreicht werden kann.> To increase hardenability, the boron in the steel must be in dissolved (metallic) form, which can generally be achieved by deoxidation and denitrification of the melt before the boron is added.
Es ist ferner bekannt, daß mit sehr geringen Borgehalten von 0,0001 - 0,03 Gew.-% in Stählen neben der bekannten Erhöhung der Härtbarkeit auch eine Steigerung der Zähigkeit erzielt werden kann, wenn die Schmelze vor der Borzugabe desoxidiert, nicht aber denitriert wird (vgl. DE-A-1608632).It is also known that with very low boron contents of 0.0001-0.03% by weight in steels, in addition to the known increase in hardenability, an increase in toughness can also be achieved if the melt deoxidizes before adding boron, but does not denitrify it will (see DE-A-1608632).
Unabhängig davon, ob diese Zähigkeitssteigerung des Stahles gewüscht wird oder nicht, ist beim Zulegieren von Bor in der Pfanne eine besonders sorgfältige Desoxidation erforderlich, wenn dabei der erforderliche enge Bereich von im Stahl gelöstem, metallischem Bor gewährleistet sein soll. Das kann beispielsweise dadurch erreicht werden, daß der Stahl in bekannter Weise mit Desoxidationsmitteln, wie Mangan, Silicium und Aluminium, vordesoxidiert und anschliessend Calcium, etwa in Form von CaSi oder CaC2, zur weiteren Desoxidation als Pulver in die Pfanne mit Hilfe eines inerten Trägergases, wie Argon oder Stickstoff, eingeblasen und dadurch der im Stahl gelöste Sauerstoff so weit erniedrigt wird, daß eine Oxidation des anschließend zugegebenen Bors im wesentlichen verhindert wird. Anschließend können Nitride bildende Elemente, wie Titan oder Zirkon oder Legierungen hiervon mittels eines Trägergases in die Pfanne eingeblasen werden, wobei Calcium und Titan oder Zirkon auch gleichzeitig zugegeben werden können, z. B. in Form einer Legierung. In diesem Fall wird somit die Enddesoxidation und die Denitrierung in einer Stufe durchgeführt. Nach erfolgter Abbindung des Sauerstoffs und gegebenenfalls des Stickstoffs wird dann ebenfalls mittels eines Trägergases Bor, bzw. eine Borverbindung, wie Borax, Ferrobor, NiB oder FeSiB, in genau dosierten Mengen und ebenfalls in Pulverform zugeführt. Es ist auch möglich, ein Gemisch oder eine Legierung aus dem Nitride bildenden Element und Bor bzw. einer Borverbindung einzublasen. Das Einbringen der genannten Bestandteile wird dabei vorteilhaft mittels einer Tauchlanze vorgenommen oder über einen an der Pfanne angebrachten Schieber, während sich die bekannte Zugabe von Bor in Drahtform weniger bewährt hat (vgl. EP-B-12226).Regardless of whether this increase in toughness of the steel is desired or not, particularly careful deoxidation is required when alloying boron in the pan if the required narrow range of metallic boron dissolved in the steel is to be ensured. This can be achieved, for example, by pre-deoxidizing the steel in a known manner with deoxidizing agents, such as manganese, silicon and aluminum, and then calcium, for example in the form of CaSi or CaC 2 , for further deoxidation as a powder in the pan using an inert carrier gas , such as argon or nitrogen, and the oxygen dissolved in the steel is reduced to such an extent that oxidation of the boron subsequently added is substantially prevented. Subsequently, nitride-forming elements, such as titanium or zircon or alloys thereof, can be blown into the pan by means of a carrier gas. Calcium and titanium or zircon can also be added at the same time, e.g. B. in the form of an alloy. In this case, the final deoxidation and denitrification are carried out in one step. After the oxygen and optionally the nitrogen have set, boron or a boron compound, such as borax, ferroboron, NiB or FeSiB, is then likewise supplied in precisely metered amounts and also in powder form using a carrier gas. It is also possible to blow in a mixture or an alloy of the nitride-forming element and boron or a boron compound. The introduction of the constituents mentioned is advantageously carried out by means of an immersion lance or via a slide attached to the pan, while the known addition of boron in wire form has proven less successful (cf. EP-B-12226).
Obwohl mit Hilfe dieser Verfahren wie Vordesoxidation der Stahlschmelze und Nachdesoxidation mittels Calcium in Form von Calciumlegierungen oder Calciumverbindungen, sowie den verbesserten Methoden des Einbringens der erforderlichen Bestandteile, wie Einblasen mit Hilfe eines inerten Trägergases, gute Ergebnisse bei der Herstellung von mit Bor legierten Stählen erzielt werden konnten, waren dennoch Schwankungen in der Borausbeute nicht zu vermeiden, d. h. die im fertigen Stahl gelösten geringen Bormengen konnten nicht mit hinreichender Sicherheit in den geforderten engen Toleranzen eingestellt werden.Although these processes, such as pre-deoxidation of the molten steel and post-deoxidation using calcium in the form of calcium alloys or calcium compounds, and the improved methods for introducing the necessary constituents, such as blowing in with the aid of an inert carrier gas, give good results in the production of steels alloyed with boron fluctuations in the boron yield could not be avoided. H. The small quantities of boron dissolved in the finished steel could not be set with sufficient certainty within the narrow tolerances required.
Das ist darauf zurückzuführen, daß auch durch Einsatz der schärfsten Desoxidationsmittel in der Praxis keine vollkommene Sauerstoiffreiheit in der Schmelze erreicht werden kann, so daß beim Einbringen ein Teil des Bors mit lokal angereichertem Restsauerstoff reagieren kann und somit nicht mehr für die Lösung im Stahl zur Verfügung steht. Darüberhinaus ist mit den bisher verwendeten Borlegierungsträgern, die entweder in Form von Sauerstoff enthaltenden Verbindungen, wie Borax oder Boraten, nicht mit ausreichender Reinheit verfügbar sind oder in Form von Legierungen mit herstellungsbedingten unterschiedlichen Borgehalten eine genaue Dosierung nur schwierig zu erreichen.This is due to the fact that, even in practice, the sharpest deoxidizing agents cannot achieve complete freedom from oxygen in the melt, so that part of the boron can react with locally enriched residual oxygen when it is introduced and is therefore no longer available for solution in the steel stands. In addition, with the boron alloy carriers used hitherto, which are either not available with sufficient purity in the form of oxygen-containing compounds, such as borax or borates, or in the form of alloys with different boron contents due to production, it is difficult to achieve an exact dosage.
Es stellt sich somit die Aufgabe, ein Verfahren zur Herstellung von mit Bor legierten Stählen zur Verfügung zu stellen, bei dem die Treffsicherheit der Einführung von Bor unter desoxidierenden Bedingungen in Stahlschmelzen in der Pfanne vor dem Vergießen nicht durch eine besondere Maßnahme des Einbringens selbst, sondern durch die Verwendung eines speziellen Borlegierungsträgers verbessert werden kann.It is therefore the task of providing a process for the production of steels alloyed with boron, in which the accuracy of the introduction of boron under deoxidizing conditions in molten steel in the ladle before casting is not achieved by a special measure of introduction itself, but rather can be improved by using a special boron alloy carrier.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß als Borlegierungsträger Calciumhexaborid verwendet wird.This object is achieved in that calcium hexaboride is used as the boron alloy carrier.
Calciumhexaborid ist eine handelsübliche Verbindung von definierter Zusammensetzung, die in ausreichender Reinheit zur Verfügung steht. In der Technik finden Calciumboride seit langem als Reduktionsmittel Verwendung, beispielsweise für die Desoxidation von Kupferschmelzen. Es ist ferner bekannt, daß bei der Herstellung von Eisen und Stahl unter vorwiegend sauren Bedingungen für das Einbringen von basischen Oxiden seltener Erden ein Reduktionsmittel für diese Oxide mitverwendet werden kann. Als Beispiel für derartige Reduktionsmittel wird u.a. neben Calciumsilicid auch Calciumborid genannt (vgl. US-A-2 799 575). Nach diesem Verfahren werden jedoch keine borlegierten Stähle erhalten, weil die Dosierung der Reduktionsmittel so bemessen ist, daß sie für die Reduktion der genannten Oxide vollständig verbraucht werden, wobei auch ggf. im ursprünglich eingesetzten Reduktionsmittel vorhandenes Bor vollständig unter Bildung von Boroxiden verbraucht worden ist, die durch Abbrand verloren gehen und somit das Bor nicht mehr für die Lösung im Stahl verfügbar ist. Die Verwendung von Calciumhexaborid als Borlegierungsträger wird hierdurch nicht nahegelegt.Calcium hexaboride is a commercially available compound with a defined composition that is available in sufficient purity. Calcium borides have long been used in industry as reducing agents, for example for the deoxidation of copper melts. It is also known that a reducing agent for these oxides can be used in the production of iron and steel under predominantly acidic conditions for the introduction of basic oxides of rare earths. In addition to calcium silicide, calcium boride is also mentioned as an example of such reducing agents (cf. US Pat. No. 2,799,575). According to this method, however, no boron-alloyed steels are obtained because the dosage of the reducing agents is such that they are completely consumed for the reduction of the oxides mentioned, including any boron present in the reducing agent originally used has been completely consumed with the formation of boron oxides, which are lost as a result of combustion and thus the boron is no longer available for the solution in the steel. This does not suggest the use of calcium hexaboride as a boron alloy carrier.
Das bei dem erfindungsgemäßen Verfahren als Borlegierungsträger verwendete Calciumhexaborid wird vorteilhaft als Pulver mit Teilchengrößen von etwa 0,01 -1,00 mm eingesetzt. Das Einbringen in die Stahlschmelze in der Pfanne vor dem Vergießen kann mit allen hierfür bekannten Maßnahmen vorgenommen werden, wie durch Einführen mit Hilfe eines Hohldrahtes oder durch Einblasen mit Hilfe eines inerten Trägergases.The calcium hexaboride used as boron alloy carrier in the process according to the invention is advantageously used as a powder with particle sizes of approximately 0.01-1.00 mm. The introduction into the molten steel in the pan before the casting can be carried out using all measures known for this, such as by inserting with the aid of a hollow wire or by blowing in with the aid of an inert carrier gas.
Beim Einbringen von Calciumhexaborid allein ist es zweckmäßig die Stahlschmelze in bekannter Weise vorzudesoxidieren und gegebenenfalls zu denitrieren. Aufgrund seines leichten spezifischen Gewichts kann Calciumhexaborid vorteilhaft auch im Gemisch mit ebenfalls spezifisch leichten Desoxidationsmitteln, wie Aluminium oder Calciumsilicid, gemeinsam eingebracht werden, wobei sich das Einblasen im Gemisch mit Zusätzen für die Enddesoxidation besonders bewährt hat.When introducing calcium hexaboride alone, it is advisable to pre-oxidize the steel melt in a known manner and, if necessary, to denitrify it. Because of its light specific weight, calcium hexaboride can advantageously also be introduced together in a mixture with likewise specifically light deoxidizing agents, such as aluminum or calcium silicide, the blowing in in admixture with additives having proven particularly useful for the final deoxidation.
Durch die erfindungsgemäße Auswahl, Calciumhexaborid als Borlegierungsträger zu verwenden, kann die Treffsicherheit der angestrebten Bormengen, die gelöst im Stahl verbleiben, entscheidend verbessert werden. Beim Einbringen dieser Verbindung, in der Calcium und Bor räumlich eng benachbart vorliegen, kann das Calcium aufgrund seiner größeren Sauerstoffaffinität bevorzugt mit lokal angereichertem Restsauerstoff in der Schmelze reagieren, so daß die zudosierten Bormengen vor Oxidation geschützt, gelöst im Stahl verbleiben und nicht mehr teilweise durch Abbrand verloren gehen.The selection according to the invention of using calcium hexaboride as the boron alloy carrier can decisively improve the accuracy of the targeted amounts of boron which remain dissolved in the steel. When introducing this compound, in which calcium and boron are spatially closely adjacent, the calcium can preferentially react with locally enriched residual oxygen in the melt due to its greater affinity for oxygen, so that the added amounts of boron are protected from oxidation, remain dissolved in the steel and no longer partially Burning will be lost.
Das ist insbesondere für die Herstellung von bormikrolegierten Stählen mit Borgehalten ab 0,0001 bis zu etwa 0,05 Gew.-% von entscheidender Bedeutung, da naturgemäß im Bereich dieser kleinen Borgehalte selbst geringe Schwankungen besonders störend sind. Aber auch für die Herstellung von Reaktorstählen mit beträchtlich höheren Borgehalten ist die durch die erfindungsgemäße Auswahl erzielte Treffsicherheit vorteilhaft.This is of crucial importance in particular for the production of boron-microalloyed steels with boron contents from 0.0001 up to approximately 0.05% by weight, since naturally even small fluctuations are particularly troublesome in the range of these small boron contents. But the accuracy achieved by the selection according to the invention is also advantageous for the production of reactor steels with considerably higher boron contents.
Claims (6)
- Process for the production of boron-alloyed steels by introducing boron in the form of boron compounds or boron alloys as a boron alloy carrier under deoxidizing conditions into the molten steel in the ladle before casting, characterized in that the boron alloy carrier used is calcium hexaboride.
- 2. Process according to Claim 1, characterized in that calcium hexaboride in powder form with particle sizes from 0.01 to 1.00 mm is used.
- 3. Process according to Claims 1 and 2, characterized in that the calcium hexaboride powder is introduced into the molten steel by means of a hollow wire or by means of an inert carrier gas.
- 4. Process according to Claim 3, characterized in that the calcium hexaboride powder is introduced as a mixture -with aluminium powder, calcium powder or calcium/silicon powder.
- 5. Process according to Claims 1, 2 and 4, characterized in that the calcium hexaboride is introduced in the form of pellets.
- 6. Process according to Claims 1, 2 and 4, characterized in that the calcium hexaboride is introduced in an encapsulated or microencapsulated form.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT85105505T ATE31081T1 (en) | 1984-05-08 | 1985-05-07 | PROCESS FOR THE MANUFACTURE OF STEELS ALLOYED WITH BORON. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19843416952 DE3416952A1 (en) | 1984-05-08 | 1984-05-08 | METHOD FOR PRODUCING STEEL ALLOYED WITH BOR |
| DE3416952 | 1984-05-08 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0166908A1 EP0166908A1 (en) | 1986-01-08 |
| EP0166908B1 true EP0166908B1 (en) | 1987-11-25 |
Family
ID=6235225
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP85105505A Expired EP0166908B1 (en) | 1984-05-08 | 1985-05-07 | Process for the manufacture of boron-containing steels |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0166908B1 (en) |
| AT (1) | ATE31081T1 (en) |
| DE (2) | DE3416952A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103695600B (en) * | 2013-12-19 | 2015-05-13 | 马钢(集团)控股有限公司 | Low-cost production method of boracic low-alloy-structured steel sheet billet |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1436945A (en) * | 1973-01-08 | 1976-05-26 | Borax Cons Ltd | Boriding compositions |
| FI793135A (en) * | 1978-11-17 | 1980-05-18 | Concast Ag | FOERFARANDE FOER BEHANDLING AV BORHALTIGT STAOL |
| US4353865A (en) * | 1981-04-24 | 1982-10-12 | Petrus Alex E | Boron containing, iron-manganese-zirconium master-alloy |
-
1984
- 1984-05-08 DE DE19843416952 patent/DE3416952A1/en not_active Withdrawn
-
1985
- 1985-05-07 EP EP85105505A patent/EP0166908B1/en not_active Expired
- 1985-05-07 DE DE8585105505T patent/DE3561071D1/en not_active Expired
- 1985-05-07 AT AT85105505T patent/ATE31081T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE3416952A1 (en) | 1985-11-14 |
| EP0166908A1 (en) | 1986-01-08 |
| ATE31081T1 (en) | 1987-12-15 |
| DE3561071D1 (en) | 1988-01-07 |
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