EP0392239A1 - Process for production of alloyed steels - Google Patents

Process for production of alloyed steels Download PDF

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Publication number
EP0392239A1
EP0392239A1 EP90105648A EP90105648A EP0392239A1 EP 0392239 A1 EP0392239 A1 EP 0392239A1 EP 90105648 A EP90105648 A EP 90105648A EP 90105648 A EP90105648 A EP 90105648A EP 0392239 A1 EP0392239 A1 EP 0392239A1
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Prior art keywords
melt
gas
steel
oxygen
during
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German (de)
French (fr)
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Gerhard Dr. Gross
Marian Velikonja
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Messer Griesheim GmbH
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Messer Griesheim 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
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/30—Regulating or controlling the blowing
    • C21C5/35—Blowing from above and through the bath
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • 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
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases

Definitions

  • the invention relates to a method for producing unalloyed and alloyed steel brands with up to 10% alloying elements in a secondary steel refining converter according to the preamble of claim 1.
  • the post-treatment of alloy steel brands in the bottom-blowing converter is carried out with oxygen as process gas, as well as nitrogen and argon as treatment gas.
  • Such secondary steel refining processes are known under the abbreviations MRP (metal refining process) AOD (argon oxygen decarburization), UBD (under bottom blowing decarburization) and ASM (argon secondary metallurgy). They are used for refining low to high alloy steel brands in converter types of the same name with under bath nozzles, the steel brands be melted in the arc furnace. Unalloyed steels are usually not produced in these converters. However, there are manufacturers who, despite higher costs, refine unalloyed steels in such converters for quality reasons, although refining in an electric arc furnace would be cheaper.
  • DE-PS 934 772 shows a method for producing unalloyed steel in the Bessemer and Thomas converter, which is poor in harmful gases.
  • CO2 is introduced into the bath as a gas or by adding limestone alone or mixed with oxygen.
  • the steel melt for secondary steel refining is usually first melted in a melting furnace and then transferred to a fresh vessel, that is to say a converter. It is treated there by blowing the process and treatment gases into the melt through the bottom of the converter.
  • Metallic jacket gas nozzles are usually used for this purpose, in which the process gas is introduced through the central nozzle and the treatment gases are introduced through the ring nozzle.
  • the treatment gases introduced through the ring nozzle are inert gases and are used primarily to cool the metallic nozzles during the blowing process and to mix the melt. These are Ar and N2. By partially substituting these inert gases with CO2, the specific gas costs can be reduced.
  • the treatment of the melt in the converter takes place in 3 process phases, namely decarburization, heating and mixing. When heating, desulfurization is carried out at the same time and alloyed. These 3 phases are accompanied by sampling, temperature measurement and the addition of metallic and non-metallic solids and are separated in time.
  • FIG. 1 such a procedure of a treatment with the inert gases N2 and Ar for the alloy steel brand 42 CrMo 4 is shown schematically. Decarburization is indicated by area A, heating by area B, and mixing by area C. Below the line indicating the course of time in minutes, the measuring points x for the temperature measurement and y for the sampling are indicated. Below this, the concentration profiles of nitrogen and sulfur and carbon (N, S, C) are shown, as is the temperature profile T. In the lower part of FIG. 1, the temporal and quantitative use of the process gas oxygen and the protective or treatment gases argon and nitrogen are shown .
  • the invention has for its object to further reduce the specific gas costs in the secondary steel refining of alloy steel brands.
  • the inventive method is based on the surprising observation that the inert gases N2 and Ar can be substituted not only partially, but completely by CO2, which significantly reduces the specific gas costs in the secondary refining of steel.
  • the amount of CO2 introduced per unit of time in the melt must be so large that a sufficiently high mixing energy is introduced into the melt. Then all reactions can take place under equilibrium conditions.
  • N2 and Ar are completely replaced by CO2 in all 3 process phases of the steel treatment, that is to say during decarburization, heating and mixing.
  • FIG. 2 The schematic sequence of the method according to the invention is shown in FIG. 2, likewise for the steel brand 42 CrMo 4 as in FIG. 1. It is immediately apparent from this that essentially the same treatment result is achieved.
  • the CO2 has different effects in the individual process phases. This is described below.
  • the nozzles must be pressurized with inert gas in order to prevent the melt from penetrating.
  • the O2 can only be added when the blowing position is reached. Appropriate measures are required when the converter tilts back.
  • the quantities of gas that act on the nozzles during these converter movements are called safety quantities.
  • CO2 + C 2 CO
  • the CO2 is also used for decarburization of the melt, i.e. in the decarburization phase, CO2 is an additional oxygen carrier.
  • the melt is heated to the desired temperature by the exothermic reaction of added aluminum, silicon or an aluminum-silicon mixture with oxygen.
  • argon was used as the treatment gas in the heating phase because nitrogen would dissolve in the melt and would result in an undesired charging of the melt with nitrogen.
  • the melt is carburized during the heating phase.
  • This carburization can be calculated using the following equation: dC - carburizing rate in ppm C / min Q - flow rate of CO2 protective gas m3 / min Cf carburizing factor 0.3-0.5 G - Melt weight in tons
  • Table 1 which shows the degassing of the melt, measured on the nitrogen content, shows both the operating result of the conventional method with nitrogen and argon and the result of the method according to the invention.
  • the purity of the CO2 is essential for the effectiveness of the method according to the invention, especially during the heating phase.
  • the reduction of the melt by aluminum causes a higher solubility of nitrogen in the steel. Therefore, the nitrogen and hydrogen impurities in the CO2 are absorbed by the melt and can no longer be removed.
  • technical pure CO2 with a maximum of 500 vpm N2 and 50 vpm H2O must be used for the metallurgical treatment of steel according to the invention. This purity is preferably obtained by evaporating the CO2 from the liquid phase.
  • the CO2 also completely replaces the argon according to the invention.
  • the melt is mixed with argon shortly before tapping for about 1 to 2 minutes for temperature compensation.
  • the melt is oxidized immediately before tapping after the reactions mentioned in the description of the heating phase.
  • the carburization that takes place at the same time can be neglected, since it only max. Is 50 ppm and is therefore within the analysis tolerance.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)

Abstract

In secondary steel refining in a bottom-blown converter, nitrogen and argon are used as treatment gases in addition to oxygen as the process gas. Nitrogen and argon can be partially replaced by the inexpensive CO2. A process is indicated which allows complete replacement of nitrogen and argon by CO2. <IMAGE>

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von unlegierten und legierten Stahlmarken mit bis 10% Legierungselementen in einem Sekundärstahlraffinations­konverter nach dem Oberbegriff des Ansprüches 1.The invention relates to a method for producing unalloyed and alloyed steel brands with up to 10% alloying elements in a secondary steel refining converter according to the preamble of claim 1.

Die Nachbehandlung von legierten Stahlmarken im boden­blasenden Konverter erfolgt mit Sauerstoff als Prozeß­ges, sowie Stickstoff und Argon als Behandlungsgas. Derartige Sekundärstahlraffinationsverfahren sind unter den Kurzbezeichnungen MRP (Metall Raffinations Prozess) AOD (Argon Oxygen Decarburization) , UBD (Under Bottom Blowing Decarburization) und ASM (Argon Sekundär Metallurgie) bekannt. Sie dienen zur Raffination von niedrig- bis hochlegierten Stahlmarken in gleichnamigen Konvertertypen mit Unterbaddüsen, wobei die Stahlmarken im Lichtbogenofen erschmolzen werden. Unlegierte Stähle werden üblicherweise nicht in diesen Konvertern herge­stellt. Es gibt aber Hersteller, die trotz höherer Kosten aus Qualitätsgründen unlegierte Stähle auch in derartigen Konvertern raffinieren, obwohl die Raffina­tion im Lichtbogenofen kostengünstiger wäre.The post-treatment of alloy steel brands in the bottom-blowing converter is carried out with oxygen as process gas, as well as nitrogen and argon as treatment gas. Such secondary steel refining processes are known under the abbreviations MRP (metal refining process) AOD (argon oxygen decarburization), UBD (under bottom blowing decarburization) and ASM (argon secondary metallurgy). They are used for refining low to high alloy steel brands in converter types of the same name with under bath nozzles, the steel brands be melted in the arc furnace. Unalloyed steels are usually not produced in these converters. However, there are manufacturers who, despite higher costs, refine unalloyed steels in such converters for quality reasons, although refining in an electric arc furnace would be cheaper.

Aus der DE-PS 24 30 975 ist es bekannt, hierbei den Stickstoff und das Argon durch Mischen mit CO₂ teilwei­se zu ersetzen. Die DE-PS 934 772 zeigt ein Verfahren zum Herstellen von unlegiertem Stahl im Bessemer- und Thomas-Konverter, welcher an schädlichen Gasen arm ist. Hierbei wird CO₂ als Gas oder durch Zugabe von Kalk­stein allein oder gemischt mit Sauerstoff in das Bad eingeleitet.From DE-PS 24 30 975 it is known to partially replace the nitrogen and argon by mixing with CO₂. DE-PS 934 772 shows a method for producing unalloyed steel in the Bessemer and Thomas converter, which is poor in harmful gases. Here CO₂ is introduced into the bath as a gas or by adding limestone alone or mixed with oxygen.

Üblicherweise wird die Stahlschmelze für die Sekundär­stahlraffination zunächst in einem Schmelzofen einge­schmolzen und dann in ein Frischgefäß, also einen Kon­verter, überführt. Dort wird sie behandelt, indem durch den Boden des Konverters die Prozeß- und Behand­lungsgase in die Schmelze eingeblasen werden. Hierzu dienen gewöhnlich metallische Mantelgasdüsen, bei denen durch die Mitteldüse das Prozeßgas und durch die Ring­düse die Behandlungsgase eingeleitet werden. Die durch die Ringdüse eingeleiteten Behandlungsgase sind Inert­gase und dienen vor allem zur Kühlung der metallischen Düsen während des Blasverfahrens und zur Durchmischung der Schmelze . Es handelt sich hierbei um Ar und N₂. Durch die teilweise Substitution dieser Inertgase durch CO₂ können die spezifischen Gaskosten reduziert werden.The steel melt for secondary steel refining is usually first melted in a melting furnace and then transferred to a fresh vessel, that is to say a converter. It is treated there by blowing the process and treatment gases into the melt through the bottom of the converter. Metallic jacket gas nozzles are usually used for this purpose, in which the process gas is introduced through the central nozzle and the treatment gases are introduced through the ring nozzle. The treatment gases introduced through the ring nozzle are inert gases and are used primarily to cool the metallic nozzles during the blowing process and to mix the melt. These are Ar and N₂. By partially substituting these inert gases with CO₂, the specific gas costs can be reduced.

Die Behandlung der Schmelze im Konverter erfolgt in 3 Prozeßphasen, nämlich dem Entkohlen, dem Heizen und dem Mischen. Beim Heizen wird gleichzeitig entschwefelt und legiert. Diese 3 Phasen werden durch Probennahmen, Temperaturmessung und Zugabe von metallischen und nichtmetallischen Feststoffen begleitet und sind zeit­lich voneinander getrennt.The treatment of the melt in the converter takes place in 3 process phases, namely decarburization, heating and mixing. When heating, desulfurization is carried out at the same time and alloyed. These 3 phases are accompanied by sampling, temperature measurement and the addition of metallic and non-metallic solids and are separated in time.

In Figur 1 ist schematisch ein solcher Verfahrensab­lauf einer Behandlung mit den Inertgasen N₂ und Ar für die legierte Stahlmarke 42 CrMo 4 dargestellt. Hierin sind das Entkohlen durch den Bereich A, das Heizen durch den Bereich B und das Mischen durch den Bereich C angegeben. Unterhalb der den Zeitverlauf in Minuten angebenden Linie sind die Meßpunkte x für die Temperaturmessung und y für die Probennahme angegeben. Darunter sind die Konzentrationsverläufe von Stick­stoff und Schwefel sowie Kohlenstoff (N, S, C) darge­stellt, desgleichen der Temperaturverlauf T. Im unteren Teil von Figur 1 ist der zeitliche und mengen­mäßige Einsatz des Prozeßgases Sauerstoff und der Schutz- bzw. Behandlungsgase Argon und Stickstoff wie­dergegeben.In Figure 1, such a procedure of a treatment with the inert gases N₂ and Ar for the alloy steel brand 42 CrMo 4 is shown schematically. Decarburization is indicated by area A, heating by area B, and mixing by area C. Below the line indicating the course of time in minutes, the measuring points x for the temperature measurement and y for the sampling are indicated. Below this, the concentration profiles of nitrogen and sulfur and carbon (N, S, C) are shown, as is the temperature profile T. In the lower part of FIG. 1, the temporal and quantitative use of the process gas oxygen and the protective or treatment gases argon and nitrogen are shown .

Der Erfindung liegt die Aufgabe zugrunde, die spezifi­schen Gasekosten bei der Sekundärstahlraffination von legierten Stahlmarken weiter zu senken.The invention has for its object to further reduce the specific gas costs in the secondary steel refining of alloy steel brands.

Ausgehend von dem im Oberbegriff des Ansprüches 1 be­rücksichtigten Stand der Technik ist diese Aufgabe er­findungsgemäß gelöst mit den im kennzeichnenden Teil des Ansprüches 1 angegebenen Merkmalen.Starting from the prior art taken into account in the preamble of claim 1, this object is achieved according to the invention with the features specified in the characterizing part of claim 1.

Vorteilhafte Weiterbildungen der Erfindungen sind in den Unteransprüchen angegeben.Advantageous developments of the inventions are specified in the subclaims.

Das erfindungsgemäße Verfahren geht von der über­raschenden Beobachtung aus, daß die Inertgase N₂ und Ar nicht nur teilweise, sondern völlig durch CO₂ sub­stituiert werden können, wodurch die spezifischen Gasekosten bei der Sekundärraffination von Stahl er­heblich reduziert werden. Die pro Zeiteinheit in die Schmelze eingeführte Menge an CO₂ muß so groß sein, daß eine ausreichend hohe Mischenergie in die Schmelze eingebracht wird. Dann können sämtliche Reaktionen unter Gleichgewichtsbedingungen ablaufen. Bei dem erfindungsgemäßen Verfahren werden in allen 3 Prozeß­phasen der Stahlbehandlung, also beim Entkohlen, beim Heizen und beim Mischen N₂ und Ar vollständig durch CO₂ ersetzt.The inventive method is based on the surprising observation that the inert gases N₂ and Ar can be substituted not only partially, but completely by CO₂, which significantly reduces the specific gas costs in the secondary refining of steel. The amount of CO₂ introduced per unit of time in the melt must be so large that a sufficiently high mixing energy is introduced into the melt. Then all reactions can take place under equilibrium conditions. In the process according to the invention, N₂ and Ar are completely replaced by CO₂ in all 3 process phases of the steel treatment, that is to say during decarburization, heating and mixing.

Der schematische Ablauf des erfindungsgemäßen Verfah­rens ist in Figur 2 dargestellt, ebenfalls für die Stahlmarke 42 CrMo 4 wie in Figur 1. Es ist hieraus unmittelbar ersichtlich, daß im wesentlichen das glei­che Behandlungsergebnis erzielt wird.The schematic sequence of the method according to the invention is shown in FIG. 2, likewise for the steel brand 42 CrMo 4 as in FIG. 1. It is immediately apparent from this that essentially the same treatment result is achieved.

Das CO₂ hat in den einzelnen Prozeßphasen unterschied­liche Auswirkungen. Die wird nachfolgend beschrieben.The CO₂ has different effects in the individual process phases. This is described below.

Während des Aufrichtens des Konverters bei Beginn des Behandlungsverfahrens von der liegenden in die Blas­position müssen die Düsen mit Inertgas beaufschlagt werden, um das Eindringen der Schmelze zu verhindern. Der O₂ kann aus Sicherheitsgründen erst zugegeben wer­den, wenn die Blasposition erreicht ist. Entsprechende Maßnahmen sind beim Zurückkippen des Konverters erfor­derlich. Die Gasmengen, die während dieser Konverter­bewegungen die Düsen beaufschlagen, nennt man Sicher­heitsmengen.During the erection of the converter at the beginning of the treatment process from the lying to the blowing position, the nozzles must be pressurized with inert gas in order to prevent the melt from penetrating. For safety reasons, the O₂ can only be added when the blowing position is reached. Appropriate measures are required when the converter tilts back. The quantities of gas that act on the nozzles during these converter movements are called safety quantities.

Bei der Entkohlung der Schmelze durch Sauerstoff über­nimmt das CO₂ die Sicherheitsgasmenge während des Auf­ richtens des Konverters in die Blasposition. Danach wird durch die Mitteldüse der Sauerstoff geblasen und die Ringdüse dabei ständig durch CO₂ gekühlt. Durch diesen kombinierten Eintrag von Sauerstoff und CO₂ wird während der Entkohlungsphase der N₂- und H₂- Partialdruck gesenkt. Dies führt zur Entgasung der Schmelze. Gleichzeitig wird eine Aufladung der Schmelze mit den Gasen N₂ und H₂ verhindert, wodurch weitgehend N₂- und H₂-arme Stähle erhalten werden.When the melt is decarburized by oxygen, the CO₂ takes over the amount of safety gas during opening the converter into the blowing position. Then the oxygen is blown through the center nozzle and the ring nozzle is constantly cooled by CO₂. This combined entry of oxygen and CO₂ reduces the N₂ and H₂ partial pressure during the decarburization phase. This leads to degassing of the melt. At the same time, charging of the melt with the gases N₂ and H₂ is prevented, whereby largely low-N₂ and H₂ steels are obtained.

Durch die Reaktion CO₂ + C = 2 CO wird das CO₂ zu­sätzlich zur Entkohlung der Schmelze ausgenutzt, d.h. in der Entkohlungsphase ist CO₂ ein zusätzlicher Sauerstoffträger.Through the reaction CO₂ + C = 2 CO, the CO₂ is also used for decarburization of the melt, i.e. in the decarburization phase, CO₂ is an additional oxygen carrier.

Während der anschließenden Heizphase wirkt sich der Einsatz von CO₂ bei der Entschwefelung und Legierung anders aus. Hierbei wird die Schmelze durch die exo­therme Reaktion von zugegebenem Aluminium , Silizium oder einem Aluminium-Silizium-Gemisch mit Sauerstoff auf die gewünschte Temperatur aufgeheizt. In der Heiz­phase wurde bisher nur Argon als Behandlungsgas ver­wendet, weil sich Stickstoff in der Schmelze lösen würde und eine nicht gewünschte Aufladung der Schmelze mit Stickstoff zur Folge hätte.During the subsequent heating phase, the use of CO₂ in desulfurization and alloy has a different effect. Here, the melt is heated to the desired temperature by the exothermic reaction of added aluminum, silicon or an aluminum-silicon mixture with oxygen. Until now, only argon was used as the treatment gas in the heating phase because nitrogen would dissolve in the melt and would result in an undesired charging of the melt with nitrogen.

Bei dem erfindungsgemäßen Ersatz von Argon durch CO₂ sind folgende Reaktionen zu berücksichtigen: 3 CO₂ + 4 Al = 2 Al₂O₃ + 3 C      (1)
3 CO₂ + 2 Al = Al₂O₃ + 3 CO      (2)
oder
CO₂ + Si = SiO₂ + C      (3)
CO₂ + Si = SiO + CO      (4)
When replacing argon according to the invention with CO₂, the following reactions must be taken into account: 3 CO₂ + 4 Al = 2 Al₂O₃ + 3 C (1)
3 CO₂ + 2 Al = Al₂O₃ + 3 CO (2)
or
CO₂ + Si = SiO₂ + C (3)
CO₂ + Si = SiO + CO (4)

Beide Reaktionen finden während der Heizphase, in Ab­hängigkeit von der Aluminiumkonzentration in der Schmelze, statt. Analog Gleichung (1) oder (3) wird die Schmelze während der Aufheizphase aufgekohlt, das CO₂ durch Aluminium vollständig reduziert und ein Koh­lenstoffatom freigesetzt. Gleichzeitig läuft die Reak­tion (2) oder (4), d.h. die Teilreduktion von CO₂ ab, diese Reaktionen bewirken keine Aufkkohlung der Schmelze. Die Aufkohlung der Schmelze während der Heizphase kann für jede Schmelze im voraus berechnet und bei der Entkohlung durch tieferes Entkohlen der Schmelze berücksichtigt werden.Both reactions take place during the heating phase, depending on the aluminum concentration in the melt. Analogous to equation (1) or (3), the melt is carburized during the heating phase, the CO₂ is completely reduced by aluminum and a carbon atom is released. At the same time, reaction (2) or (4) takes place, i.e. the partial reduction of CO₂, these reactions do not cause carburization of the melt. The carburization of the melt during the heating phase can be calculated in advance for each melt and can be taken into account in the decarburization by deeper decarburization of the melt.

Wie aus den Figuren 1 und 2 ersichtlich, findet während der Heizphase eine Aufkohlung der Schmelze statt. Diese Aufkohlung kann nach folgender Gleichung berech­net werden:

Figure imgb0001
dC - Aufkohlungsgeschwindigkeit in ppm C/min
Q - Durchflußmenge CO₂-Schutzgas m³/min
Cf - Aufkohlungsfaktor 0,3 - 0,5
G - Schmelzgewicht in TonnenAs can be seen from FIGS. 1 and 2, the melt is carburized during the heating phase. This carburization can be calculated using the following equation:
Figure imgb0001
 dC - carburizing rate in ppm C / min
Q - flow rate of CO₂ protective gas m³ / min
Cf carburizing factor 0.3-0.5
G - Melt weight in tons

Bei einer Schutzgasmenge von 2 m³ CO₂/min beträgt die Aufkohlungsgeschwindigkeit in eimen 10-t-Konverter mit dem Aufkohlungsfaktor Cf = 0,5
dC = 536 x 2 x 0,5/10 = 53,6 ppm C/min.With a protective gas volume of 2 m³ CO₂ / min, the carburizing rate in a 10-t converter with the carburizing factor Cf = 0.5
dC = 536 x 2 x 0.5 / 10 = 53.6 ppm C / min.

Die Wirkung des CO₂ - Einsatzes gemäß der Erfindung in der Entkohlungs- und Heizphase ist für verschie­dene Stahlmarken in den nachfolgenden Tabellen 1 und 2 wiedergegeben. Die Tabelle 1, welche die Entgasung der Schmelze, gemessen am Stickstoffgehalt zeigt, zeigt hierbei sowohl das Betriebsergebnis des herkömm­lichen Verfahrens mit Stickstoff und Argon als auch das Ergebnis des erfindungsgemäßen Verfahrens. Tabelle 1 Entgasung der Schmelze, gemessen am Stickstoffgehalt Gas-Verbrauch Gas-Gehalt Schmelze O₂ N₂ Ar CO₂ Stickstoff Stahlmarke m³/t m³/t m³/t m³/t Start Ende 20 Mn 5 12,9 3,4 5,9 - 95 43 17 CrMo 55 12,1 3,7 6,0 - 122 75 42 CrMo 4 11,0 3,5 2,4 - 125 107 17 CrMoV 5.11 16,6 2,4 8,0 - 105 77 10 MnMo 74 16,1 - - 9,8 96 69 17 CrMo 5.11 17,1 - - 10,9 110 76 42 CrMo 4 12,6 - - 7,9 104 62 34 NiCrMo 14 18,6 - - 11,7 106 73 Tabelle 2 Aufkohlung der Schmelze während des Aufheizens Stahlmarke C-Gehalt Gas-Verbrauch Heizen mit Al Start Ende O₂ CO₂ % % m³/min m³/t m³/min m³/t kg/t 10 MnMo 74 0,04 0,08 9,0 6,0 2,4 3,0 10 17 CrMoV 5.11 0,12 0,16 3,0 9,0 2,3 3,0 10 42 CrMo 4 0,27 0,30 9,0 5,6 2,4 2,7 9 35 CrNiMo 14 0,27 0,32 9,0 6,6 2,4 3,5 11 The effect of CO₂ use according to the invention in the decarburization and heating phase is for different steel brands in the following tables 1 and 2 reproduced. Table 1, which shows the degassing of the melt, measured on the nitrogen content, shows both the operating result of the conventional method with nitrogen and argon and the result of the method according to the invention. Table 1 Degassing the melt, measured by nitrogen content Gas consumption Gas content melt O₂ N₂ Ar CO₂ nitrogen Steel brand m³ / t m³ / t m³ / t m³ / t begin The End 20 Mn 5 12.9 3.4 5.9 - 95 43 17 CrMo 55 12.1 3.7 6.0 - 122 75 42 CrMo 4 11.0 3.5 2.4 - 125 107 17 CrMoV 5.11 16.6 2.4 8.0 - 105 77 10 MnMo 74 16.1 - - 9.8 96 69 17 CrMo 5.11 17.1 - - 10.9 110 76 42 CrMo 4 12.6 - - 7.9 104 62 34 NiCrMo 14 18.6 - - 11.7 106 73 Carburization of the melt during heating Steel brand C content Gas consumption Heating with Al begin The End O₂ CO₂ % % m³ / min m³ / t m³ / min m³ / t kg / t 10 MnMo 74 0.04 0.08 9.0 6.0 2.4 3.0 10th 17 CrMoV 5.11 0.12 0.16 3.0 9.0 2.3 3.0 10th 42 CrMo 4 0.27 0.30 9.0 5.6 2.4 2.7 9 35 CrNiMo 14 0.27 0.32 9.0 6.6 2.4 3.5 11

Wesentlich für die Wirksamkeit des erfingungsgemäßen Verfahrens, insbesondere während der Heizphase, ist die Reinheit des CO₂. Die Reduktion der Schmelze durch Aluminium verursacht nämlich eine höhere Löslichkeit von Stickstoff im Stahl. Deshalb werden die Stickstoff- und Wasserstoff-Verunreinigungen im CO₂ von der Schmelze aufgenommen und können nicht mehr entfernt werden. Um dies zu verhindern, muß für die metallur­gische Behandlung von Stahl gemäß der Erfindung tech­nische reines CO₂ mit maximal 500 vpm N₂ und 50 vpm H₂O verwendet werden. Diese Reinheit wird vorzugsweise durch Verdampfen des CO₂ aus der flüssigen Phase erhal­ten.The purity of the CO₂ is essential for the effectiveness of the method according to the invention, especially during the heating phase. The reduction of the melt by aluminum causes a higher solubility of nitrogen in the steel. Therefore, the nitrogen and hydrogen impurities in the CO₂ are absorbed by the melt and can no longer be removed. To prevent this, technical pure CO₂ with a maximum of 500 vpm N₂ and 50 vpm H₂O must be used for the metallurgical treatment of steel according to the invention. This purity is preferably obtained by evaporating the CO₂ from the liquid phase.

In der Mischphase ersetzt das CO₂ ebenfalls erfindungs­gemäß das Argon vollständig. Nach dem Stand der Tech­nik wird die Schmelze kurz vor dem Abstich mit Argon etwa 1 bis 2 Minuten zum Temperaturausgleich durch­mischt. Bei der Substitution des Argons durch CO₂ fin­det hierbei unmittelbar vor dem Abstich eine Oxidation der Schmelze nach den bei der Beschreibung der Heiz­phase genannten Reaktionen statt. Durch die stöchio­ metrische Zugabe von etwa 1,0 kg Al/m³ CO₂ wird diese Veränderung der Analyse ausgeglichen. Die gleichzei­tig erfolgende Aufkohlung kann vernachlässigt werden, da sie nur max. 50 ppm beträgt und somit innerhalb der Analysentoleranz liegt.In the mixed phase, the CO₂ also completely replaces the argon according to the invention. According to the prior art, the melt is mixed with argon shortly before tapping for about 1 to 2 minutes for temperature compensation. When the argon is replaced by CO₂, the melt is oxidized immediately before tapping after the reactions mentioned in the description of the heating phase. Through the stoichio metric addition of about 1.0 kg Al / m³ CO₂ will compensate for this change in analysis. The carburization that takes place at the same time can be neglected, since it only max. Is 50 ppm and is therefore within the analysis tolerance.

Claims (8)

1. Verfahren zur Herstellung von unlegierten und legierten Stahlmarken mit bis 10% Legierungselementen in einem Sekundärstahlraffinationskonverter, in welchem während des aus den Phasen Entkohlen, Heizen und Mischen bestehenden Verfahrensablaufs durch im Boden des Konverters angeordnete Düsen zeitweilig Sauerstoff als Prozeßgas und/oder ein Behandlungsgas eingeblasen wird, dadurch gekennzeichnet, daß das Behandlungsgas gasförmiges CO₂ ist.1. Process for the production of unalloyed and alloyed steel brands with up to 10% alloying elements in a secondary steel refining converter, in which oxygen is temporarily blown in as process gas and / or a treatment gas through nozzles arranged in the bottom of the converter during the process sequence consisting of the decarburization, heating and mixing phases is characterized in that the treatment gas is gaseous CO₂. 2. Verfahren nach Anspruch 1, bei dem der Sauerstoff und das Behandlungsgas durch metallische Mantelgasdü­sen eingeblasen werden, dadurch gekennzeichnet, daß in den Zeiträumen mit alleiniger CO₂-Zufuhr das CO₂ sowohl durch die Ringdüse als auch durch die Mittel­düse eingeleitet wird.2. The method according to claim 1, in which the oxygen and the treatment gas are blown through metallic jacket gas nozzles, characterized in that the CO₂ is introduced both through the ring nozzle and through the central nozzle in the periods with sole CO₂ supply. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekenn­zeichnet, daß das CO₂ höchstens 500 vpm N₂ und höchstens 50 vpm H₂O enthält.3. The method according to claim 1 or 2, characterized in that the CO₂ contains at most 500 vpm N₂ and at most 50 vpm H₂O. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das gasförmige CO₂ durch Ver­dampfen aus der flüssigen Phase gewonnen wird.4. The method according to any one of claims 1 to 3, characterized in that the gaseous CO₂ is obtained by evaporation from the liquid phase. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß pro t Stahl 0.2 bis 1,0 m³/min CO₂ eingeblasen wird.5. The method according to any one of claims 1 to 4, characterized in that 0.2 to 1.0 m³ / min CO₂ is blown per ton of steel. 6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß während der Heizphase durch die notwendige Zugabe von Al oder Si eine Aufkohlung der Schmelze bewirkt wird.6. The method according to any one of claims 1 to 5, characterized in that carburization of the melt is effected during the heating phase by the necessary addition of Al or Si. 7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, daß die Aufkohlungsgeschwindigkeit dC durch die Formel
Figure imgb0002
 bestimmt ist, wobei
dC die Aufkohlungsgeschwindigkeit in ppm C/min,
Q der CO₂-Durchfluß in m³/min,
Cf der Aufkohlungsfaktor, 0,3 bis 0,5, und
G das Gewicht der Schmelze in t ist.7. The method according to claim 6, characterized in that the carburizing rate dC by the formula
Figure imgb0002
 is determined, whereby
dC is the carburizing rate in ppm C / min,
Q is the CO₂ flow in m³ / min,
Cf the carburizing factor, 0.3 to 0.5, and
G is the weight of the melt in t. 8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichent, daß eine Analysenänderung durch Re­oxidation der Schmelze während der Mischphase mit reinem CO₂ durch stöchiometrische Zugabe von 1,0 kg Aluminium/m³ CO₂ verhindert wird.8. The method according to any one of claims 1 to 7, characterized in that an analysis change by reoxidation of the melt during the mixing phase with pure CO₂ is prevented by stoichiometric addition of 1.0 kg aluminum / m³ CO₂.
EP90105648A 1989-04-13 1990-03-24 Process for production of alloyed steels Withdrawn EP0392239A1 (en)

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DE3912061A DE3912061A1 (en) 1989-04-13 1989-04-13 METHOD FOR PRODUCING ALLOY STEEL BRANDS

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US9045805B2 (en) 2013-03-12 2015-06-02 Ati Properties, Inc. Alloy refining methods
WO2016012003A1 (en) * 2014-07-23 2016-01-28 Sms Group Gmbh Method for nickel pig iron (npi) decarburization in an aod converter

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DE19608531C2 (en) * 1996-02-09 1998-02-26 Eisenbau Essen Gmbh Process for the treatment of steel, in particular for refining steel for the production of steel

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GB809407A (en) * 1956-10-09 1959-02-25 Union Carbide Corp Process for alloying steel
FR2235198A1 (en) * 1973-06-28 1975-01-24 Union Carbide Corp
FR2394610A1 (en) * 1977-06-13 1979-01-12 Siderurgie Fse Inst Rech Cooling converter tuyeres or lances - using liq. carbon di:oxide fed from reservoir by volumetric pump
EP0005506A1 (en) * 1978-05-11 1979-11-28 BASF Aktiengesellschaft Method for treating melts of pig iron and steel or steel alloys
EP0023759A1 (en) * 1979-06-29 1981-02-11 William H. Moore Method of recycling steel scrap
EP0170900A1 (en) * 1984-08-01 1986-02-12 Vasipari Kutato Es Fejlesztö Vallalat Process for the removal of contaminating elements from pig- iron, steel, other metals and metal alloys

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Publication number Priority date Publication date Assignee Title
GB809407A (en) * 1956-10-09 1959-02-25 Union Carbide Corp Process for alloying steel
FR2235198A1 (en) * 1973-06-28 1975-01-24 Union Carbide Corp
FR2394610A1 (en) * 1977-06-13 1979-01-12 Siderurgie Fse Inst Rech Cooling converter tuyeres or lances - using liq. carbon di:oxide fed from reservoir by volumetric pump
EP0005506A1 (en) * 1978-05-11 1979-11-28 BASF Aktiengesellschaft Method for treating melts of pig iron and steel or steel alloys
EP0023759A1 (en) * 1979-06-29 1981-02-11 William H. Moore Method of recycling steel scrap
EP0170900A1 (en) * 1984-08-01 1986-02-12 Vasipari Kutato Es Fejlesztö Vallalat Process for the removal of contaminating elements from pig- iron, steel, other metals and metal alloys

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9045805B2 (en) 2013-03-12 2015-06-02 Ati Properties, Inc. Alloy refining methods
US9683273B2 (en) 2013-03-12 2017-06-20 Ati Properties Llc Alloy refining methods
WO2016012003A1 (en) * 2014-07-23 2016-01-28 Sms Group Gmbh Method for nickel pig iron (npi) decarburization in an aod converter

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