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EP0857222A1 - Process for decarbonising a high-chromium steel melt - Google Patents

Process for decarbonising a high-chromium steel melt

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Publication number
EP0857222A1
EP0857222A1 EP96938964A EP96938964A EP0857222A1 EP 0857222 A1 EP0857222 A1 EP 0857222A1 EP 96938964 A EP96938964 A EP 96938964A EP 96938964 A EP96938964 A EP 96938964A EP 0857222 A1 EP0857222 A1 EP 0857222A1
Authority
EP
European Patent Office
Prior art keywords
decarburization
phase
oxygen
ctp
rate
Prior art date
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Granted
Application number
EP96938964A
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German (de)
French (fr)
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EP0857222B1 (en
Inventor
Johann Dr.-Ing. Reichel
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SMS Siemag AG
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Mannesmann AG
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • C21C7/0685—Decarburising of stainless steel
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • 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

Definitions

  • the invention relates to a method for decarburizing a molten steel for the production of high-chromium steels while blowing in oxygen, in which the decarburization rate is measured continuously and the amount of oxygen to be blown in is adjusted as a function of the measured values, the decarburization rate being determined from the CO 2 and CO 2 - Content in the exhaust gas and the exhaust gas flow is determined.
  • the proportion of the diluent gas and the amount of gas injected into the melt are changed in a predetermined manner.
  • the parameters entered in the model i.e. in a computer program, are compared with actual measured variables, and by comparing the predetermined target values and the determined actual variables, the decarburization process is controlled in such a way that the actual course of the process matches the process simulated in the computer to such an extent corresponds as possible.
  • this computer-controlled decarburization processes should be able to precisely control the decarburization process.
  • this method is suitable for decarburizing molten steel, due to the model used, this method is not suitable for precisely determining the point in time at which the transition point from the decarburization reaction to metal oxidation is reached.
  • control variables are calculated with the aid of a computer on the basis of measured or predetermined values: the duration of the Al-Si oxidation phase at the beginning of the decarburization process, the duration of a main decarburization phase immediately following the Al-Si oxidation phase until the transition point is reached from the decarburization reaction to metal oxidation, the decarburization rate in the main decarburization phase, the decarburization rate in turn being determined from the CO and CO 2 content in the exhaust gas and the exhaust gas flow.
  • the process is carried out in such a way that the amount of oxygen blown in immediately after the Al-Si oxidation phase to that amount of oxygen accelerated until the calculated decarburization rate is reached.
  • the decarburization rate is then kept substantially constant during the main decarburization phase by changing the amount of oxygen blown in.
  • the amount of oxygen blown in is continuously reduced in such a way that the decarburization rate decreases continuously with a predetermined time constant.
  • the method according to the invention for the production of high-chromium steels takes advantage of the knowledge that there is a critical decarburization state in the course of the process, i.e. a transition point from the decarburization reaction to metal oxidation, which can be calculated with sufficient accuracy beforehand using a special model, and the optimal process control depends is the timely detection of this state, after which the metal oxidation, especially the chromium oxidation, is favored in the melt to the disadvantage of the decarburization reaction.
  • a concrete embodiment of the model for determining the critical decarburization state which makes it possible to determine the duration of the Al-Si oxidation phase ⁇ tAl-Si, the duration of the main decarburization phase ⁇ tkr and the decarburization rate in the main decarburization phase, is given by equations (1) to ( 5).
  • This model assumes that there is an almost constant decarburization rate during the main decarburization phase which, after reaching the transition point from the decarburization reaction to metal oxidation, passes into the immediately subsequent post-critical phase.
  • the Oxygen inflow multiplied by the efficiency of the oxygen lance in the main decarburization phase constant.
  • a very low Cr burn-off is achieved in that, as the decarburization rate decreases, the oxygen supply is reduced continuously with the time constant ⁇ kr calculated using equations (1) to (5).
  • the control is very easy to implement by blowing in oxygen with the aid of adjustable gas flow control means.
  • the amount of oxygen blown in is adjusted to a predetermined flow rate for the duration of the Al-Si oxidation phase, so that the foaming of the slag does not exceed a certain thickness.
  • FIG. 2 shows the oxygen balance of the decarburization kinetics according to FIG. 1.
  • Fig. 1 shows schematically the decarburization kinetics of the underlying model.
  • the decarburization rate is plotted on the y-axis and the carbon content of the melt on the x-axis.
  • the main decarburization phase as can be seen in FIG. 1, is characterized by a constant decarburization rate which, after reaching the critical transition point from the decarburization reaction to metal oxidation, continuously passes into the post-critical phase. From this point of view, the critical transition point belongs to both the main decarburization phase and the post-critical phase. Accordingly, the different kinetics of the decarburization reaction that apply to these two phases are the same, ie. H.:
  • the energy balance of the melt is such that the instantaneous energy content of the melt is composed of the initial energy content of the primary metal and the stored energy, which is equal to the difference between the energy supply and the energy loss. Furthermore, it is assumed that the target temperature of the melt once reached at the critical point increases only slightly during the further treatment in the post-critical phase. The proposed process control is based on this assumption, in which only a small amount of chromium slagging takes place during the post-critical phase.
  • the right side of the energy balance equation (3) has several elements with a positive sign, which record the thermal energy released by the metal burnup (metal oxidation).
  • the intensity of the metal erosion is determined for the individual metals by the constant Konst. 1 to const. 7 characterized. These are parameters typical of the melting furnace and the melt.
  • the elements of equation (3) provided with a negative sign include the energy losses through the exhaust gas discharge, through the water cooling, through the heat radiation and the energy requirement for the melting of alloys and slags.
  • the essential quantity resulting from the solution of the system of equations (1), (2) and (3) is the critical carbon burn-up ⁇ Ckr.
  • the critical carbon content ⁇ Ckr that is the carbon content at the transition point of the melt according to FIG. 1, is obtained from the following equation:
  • CA is the initial carbon content of the melt.
  • the decarburization rate can be calculated taking into account the following equation according to FIG. 1:
  • the decarburization process is carried out in such a way that the relevant control variables are calculated at the beginning of decarburization using equations (1) to (5).
  • the further process flow is shown schematically in FIG. 2.
  • a predetermined oxygen flow and a predetermined inert gas flow (for example argon) are set and passed through the melt.
  • the predetermined values lie in a range in which the foaming of the metal slag does not exceed the permissible values.
  • the inert gas supply is switched off and the quantity of oxygen supplied is accelerated until the decarburization rate calculated for the main decarburization phase, which is determined from the CO and CO 2 content in the exhaust gas and the exhaust gas flow, is established.
  • This decarburization rate is kept essentially constant by regulating the oxygen supply during the main decarburization phase.
  • the critical transition point tkr is reached, the amount of oxygen supplied is reduced in proportion to the time with the time constant tkr.
  • the special feature of the invention lies in the determination of the metal bath concentrations of the chemical elements, the metal bath temperature at the critical point and the time of its occurrence. At the critical transition point, the chemical-thermodynamic relationships of the chemical reactions taking place in the metal bath are also calculated. With regard to the maximum instantaneous decarburization and the minimum metal slagging, these reaction processes are considered to be optimal.
  • the optimal reaction sequence is maintained in the postcritical decarburization phase by using the process variables calculated for the critical transition point on the basis of the model to control the postcritical phase, so that undesired chromium oxidation, oxygen consumption and the consumption of reducing agents, especially silicon, are significantly minimized can. As in the main decarburization phase, the oxygen flow rate is controlled via the decarburization rate.
  • the model-based determination of the critical condition also makes it possible to define the optimal input data for the melt.
  • the application possibilities of the method basically extend to all processes that take place with the reducing effect of the carbon against the chromium oxidation. These include both vacuum fresh processes (VOD) and AOD converter processes (Argon Oxigen Decarburization) with all technical modifications.

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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)
  • Coating With Molten Metal (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

PCT No. PCT/DE96/01970 Sec. 371 Date Apr. 23, 1998 Sec. 102(e) Date Apr. 23, 1998 PCT Filed Oct. 14, 1996 PCT Pub. No. WO97/15692 PCT Pub. Date May 1, 1997A process for decarburizing a steel melt for the production of high-chromium steels by blowing in oxygen in which the decarburization rate is continuously measured and the amount of oxygen to be injected is adjusted depending on the measured values. The following controlled quantities are calculated: a) the duration of the Al-Si oxidation phase at the start of the decarburization process, b) the duration of a principle decarburization phase immediately following the Al-Si oxidation phase until the transition point from the decarburization reaction to the metal oxidation is reached, and c) the decarburization rate in the principal decarburization phase. The injected oxygen quantity is increased at an accelerated rate immediately following the Al-Si oxidation phase to the oxygen quantity of the principal decarburization phase until the decarburization rate calculated in c) is reached. The decarburization rate is maintained substantially constant for the duration of the principal decarburization phase by the injected quantity of oxygen. The injected oxygen quantity is continuously reduced immediately following the principal decarburization phase so that the decarburization rate decreases continuously in time at a predetermined time constant.

Description

VERFAHREN ZUM ENTKOHLEN EINER HOCHCHROMHALTIGEN STAHLSCHMELZE METHOD FOR decarburizing a high-chromium steel melt
Beschreibungdescription
Die Erfindung betrifft ein Verfahren zum Entkohlen einer Stahlschmelze zur Herstellung von hochchromhaltigen Stählen unter Einblasen von Sauerstoff, bei welchem die Entkohlungsgeschwindigkeit fortlaufend gemessen werden und in Abhängigkeit von den gemessenen Werten die Menge des einzublasenden Sauerstoffs eingestellt wird, wobei die Entkohlungsgeschwindigkeit aus dem CO- und C02- Gehalt im Abgas und dem Abgasdurchfluß bestimmt wird.The invention relates to a method for decarburizing a molten steel for the production of high-chromium steels while blowing in oxygen, in which the decarburization rate is measured continuously and the amount of oxygen to be blown in is adjusted as a function of the measured values, the decarburization rate being determined from the CO 2 and CO 2 - Content in the exhaust gas and the exhaust gas flow is determined.
Aus der DE 33 11 232 C 2 ist ein Verfahren zum Entkohlen von Stahlschmelzen bekannt, bei dem auf der Grundlage eines theoretischen Modells, das den Verlauf der Entkohiung in der Stahlschmelze beschreibt, die Prozeßgrößen berechnet werden, anhand derer der Entkohlungsprozeß gesteuert werden soll. Dabei wird Sauerstoff und ein Verdünnungsgas in die Schmelze eingeblasen und die eingeblasenen Mengen entsprechend dem Entkohlungsveriauf mit Hilfe von einstellbaren Gasdurchfluß- kontrollmitteln gesteuert. Die Steuerung der eingeblasenen Mengen erfolgt so, daß das Ausmaß der Entkohlung und der Kohlenstoffgehalt der Schmelze während des Schmelzprozesses anhand des Modells berechnet und mit vorbestimmten Werten verglichen werden. Zu dem Zeitpunkt, an dem der berechnete mit dem vorbestimmten Wert übereinstimmt, wird der Anteil des Verdünnungsgases und die in die Schmelze eingeblasene Gasmenge in vorbestimmter Art und Weise geändert. Bei dem Verfahren werden also die in das Modell, d. h. in ein Rechenprogramm eingegebenen Kenngrößen mit tatsächlichen Meßgrößen verglichen und durch Vergleich der vorgegebenen Sollgrößen sowie der ermittelten Istgrößen wird die Steuerung des Entkohlungsprozesses derart vorgenommen, daß der Istverlauf des Prozesses dem im Rechner simulierten Prozeßvertauf so weit wie möglich entspricht. Mit diesem computergesteuerten Entkohiungsverfahren soll der Entkohiungsvorgang exakt gesteuert werden können.From DE 33 11 232 C 2 a method for decarburizing steel melts is known, in which on the basis of a theoretical model that describes the course of decarburization in the steel melt, the process variables are calculated, on the basis of which the decarburization process is to be controlled. Oxygen and a diluent gas are blown into the melt and the quantities blown in are controlled according to the decarburization process with the aid of adjustable gas flow control means. The quantities blown in are controlled in such a way that the extent of decarburization and the carbon content of the melt during the melting process are calculated on the basis of the model and compared with predetermined values. At the time when the calculated value coincides with the predetermined value, the proportion of the diluent gas and the amount of gas injected into the melt are changed in a predetermined manner. In the process, the parameters entered in the model, i.e. in a computer program, are compared with actual measured variables, and by comparing the predetermined target values and the determined actual variables, the decarburization process is controlled in such a way that the actual course of the process matches the process simulated in the computer to such an extent corresponds as possible. With this computer-controlled decarburization processes should be able to precisely control the decarburization process.
Dieses Verfahren ist zwar geeignet zum Entkohlen von Stahlschmelzen, jedoch ist dieses Verfahren aufgrund des verwendeten Modells nicht geeignet, exakt den Zeitpunkt des Erreichens des Übergangspunktes von der Entkohlungsreaktion zur Metalloxidation zu bestimmen.Although this method is suitable for decarburizing molten steel, due to the model used, this method is not suitable for precisely determining the point in time at which the transition point from the decarburization reaction to metal oxidation is reached.
Die Folge ist ein erhöhter Chromabbrand und dadurch zusätzlich erforderliche Mengen an Reduktionsstoffen, beispielsweise Ferrosiiizium und Kalk als basischeThe result is an increased chromium erosion and therefore additionally required amounts of reducing agents, for example ferrous silicon and lime as basic
Neutralisierung des Siliziumsgehalts in der Schlacke, sowie letztendlich eine verminderte Haltbarkeit der Pfanne oder des Konverters.Neutralization of the silicon content in the slag, and ultimately a reduced shelf life of the pan or the converter.
Es ist Aufgabe der vorliegenden Erfindung, das Entkohlen einer Stahlschmelze zur Herstellung von hochchromhaltigen Stählen durch Einblasen von Sauerstoff in die Schmelze exakt so zu steuern, daß insbesondere die unerwünschte Chromoxidation vermieden und trotzdem eine starke Entkohlung der Schmelze und eine minimale Metallverschlackung erzielt wird.It is an object of the present invention to control the decarburization of a steel melt for the production of high-chromium steels by blowing oxygen into the melt in such a way that, in particular, the undesirable chromium oxidation is avoided and nevertheless a strong decarburization of the melt and minimal metal slagging is achieved.
Die Lösung dieser Aufgabe hinsichtlich des Verfahrens ist erfindungsgemäß gekennzeichnet durch die im Patentanspruch 1 angegebenen Merkmale. Durch die kennzeichnenden Merkmale der Unteransprüche 2 bis 5 ist dieses Verfahren in vorteilhafter Weise weiter ausgestaltbar.The solution to this problem with regard to the method is characterized according to the invention by the features specified in claim 1. Due to the characterizing features of subclaims 2 to 5, this method can advantageously be further developed.
Erfindungsgemäß werden mit Hilfe eines Rechners auf der Grundlage gemessenener oder vorgegebener Werte die folgenden Regelgrößen berechnet: die Dauer der Al-Si- Oxidationsphase zu Beginn des Entkohlungsprozesses, die Dauer einer sich unmittelbar an die Al-Si-Oxidationsphase anschließenden Hauptentkohlungsphase bis zum Erreichen des Übergangspunktes von der Entkohlungsreaktion zur Metalloxidation, die Entkohlungsgeschwindigkeit in der Hauptentkohlungsphase, wobei die Entkohlungsgeschwindigkeit wiederum aus dem CO- und C02- Gehalt im Abgas und dem Abgasdurchfluß bestimmt wird.According to the invention, the following control variables are calculated with the aid of a computer on the basis of measured or predetermined values: the duration of the Al-Si oxidation phase at the beginning of the decarburization process, the duration of a main decarburization phase immediately following the Al-Si oxidation phase until the transition point is reached from the decarburization reaction to metal oxidation, the decarburization rate in the main decarburization phase, the decarburization rate in turn being determined from the CO and CO 2 content in the exhaust gas and the exhaust gas flow.
Das Verfahren wird so durchgeführt, daß die eingeblasene Sauerstoffmenge unmittelbar anschließend an die Al-Si-Oxidationsphase auf diejenige Sauerstoffmenge beschleunigt hochgefahren wird, bis sich die berechnete Entkohlungsgeschwindigkeit einstellt. Anschließend wird während der Dauer der Hauptentkohlungsphase durch Verändern der eingeblasenen Sauerstoffmenge die Entkohlungsgeschwindigkeit im wesentlichen konstant gehalten. In der sich an die Hauptentkohlungsphase unmittelbar anschließenden nachkritischen Phase wird die eingeblasene Sauerstoffmenge in der Weise kontinuierlich reduziert, daß die Entkohlungsgeschwindigkeit zeitkontinuierlich mit einer vorgegebenen Zeitkonbstanten abnimmt.The process is carried out in such a way that the amount of oxygen blown in immediately after the Al-Si oxidation phase to that amount of oxygen accelerated until the calculated decarburization rate is reached. The decarburization rate is then kept substantially constant during the main decarburization phase by changing the amount of oxygen blown in. In the post-critical phase immediately following the main decarburization phase, the amount of oxygen blown in is continuously reduced in such a way that the decarburization rate decreases continuously with a predetermined time constant.
Hierdurch wird erreicht, daß eine unter den gegebenen Bedingungen maximale Entkohlung und minimale Metallverschlackung, insbesondere eine minimale unerwünschte Chromoxidation, erzielt wird. Das erfindungsgemaße Verfahren zur Herstellung von hochchromhaltigen Stählen macht sich die Erkenntnis zunutze, daß es im Prozeßverlauf einen kritischen Entkohiungszustand gibt, also einen Übergangspunkt von der Entkohlungsreaktion zur Metalloxidation, der anhand eines speziellen Modells im Voraus hinreichend genau berechnet werden kann, und die optimale Prozeßführung abhängig ist vom rechtzeitigen Erkennen dieses Zustands, nach dessen Überschreiten die Metalloxidation, insbesondere die Chromoxidation, in der Schmelze zu Ungunsten der Entkohlungsreaktion begünstigt wird.This ensures that under the given conditions maximum decarburization and minimal metal slagging, in particular minimal undesired chromium oxidation, is achieved. The method according to the invention for the production of high-chromium steels takes advantage of the knowledge that there is a critical decarburization state in the course of the process, i.e. a transition point from the decarburization reaction to metal oxidation, which can be calculated with sufficient accuracy beforehand using a special model, and the optimal process control depends is the timely detection of this state, after which the metal oxidation, especially the chromium oxidation, is favored in the melt to the disadvantage of the decarburization reaction.
Erst die Bestimmung des kritischen Entkohlungszustands ermöglicht bezüglich der Prozeßführung eine Vorhersage des zeitlichen Prozeßablaufs. Bei bekannten Eingangsdaten des Vormetalls, insbesondere der chemischen Zusammensetzung, der Temperatur und des Gewichts, und der Vorgabe der gewünschten Enddaten in gleicher Form wie die Eingangsdaten der Schmelze können anhand des Modells die regelungstechnisch wichtigen Größen der Prozeßführung vorausberechnet werden.Only the determination of the critical decarburization state enables a prediction of the temporal process sequence with regard to the process control. In the case of known input data of the pre-metal, in particular the chemical composition, the temperature and the weight, and the specification of the desired end data in the same form as the input data of the melt, the parameters of the process control which are important in terms of control technology can be calculated in advance using the model.
Eine konkrete Ausgestaltung des Modells zur Bestimmung des kritischen Entkohlungszustands, das es ermöglicht, die Dauer der Al-Si-Oxidationsphase ΔtAl-Si, die Dauer der Hauptentkohlungsphase Δtkr und die Entkohlungsgeschwindigkeit in der Hauptentkohlungsphase zu bestimmen, wird durch die Gleichungen (1) bis (5) beschrieben. Dieses Modell geht davon aus, daß während der Hauptentkohlungs¬ phase eine nahezu konstante Entkohlungsgeschwindigkeit vorliegt, die nach dem Erreichen des Übergangspunktes von der Entkohlungsreaktion zur Metalloxidation in die sich unmittelbar anschließende nachkritische Phase übergeht. Dabei ist der Sauerstoffzufluß multipliziert mit dem Wirkungsgrad der Sauerstofflanze in der Hauptentkohlungsphase konstant.A concrete embodiment of the model for determining the critical decarburization state, which makes it possible to determine the duration of the Al-Si oxidation phase ΔtAl-Si, the duration of the main decarburization phase Δtkr and the decarburization rate in the main decarburization phase, is given by equations (1) to ( 5). This model assumes that there is an almost constant decarburization rate during the main decarburization phase which, after reaching the transition point from the decarburization reaction to metal oxidation, passes into the immediately subsequent post-critical phase. Here is the Oxygen inflow multiplied by the efficiency of the oxygen lance in the main decarburization phase constant.
Ein sehr geringer Cr-Abbrand wird dadurch erreicht, daß mit abnehmender Entkohlungsgeschwindigkeit zeitkontinuierlich mit der mittels der Gleichungen (1 ) bis (5) errechneten Zeitkonstanten τkr die Sauerstoffzufuhr verringert wird.A very low Cr burn-off is achieved in that, as the decarburization rate decreases, the oxygen supply is reduced continuously with the time constant τkr calculated using equations (1) to (5).
Die Steuerung ist durch das Einblasen von Sauerstoff mit Hilfe von einstellbaren Gasdurchflußkontrolimitteln sehr einfach zu realisieren.The control is very easy to implement by blowing in oxygen with the aid of adjustable gas flow control means.
Bei der Durchführung des Entkohlungsverfahrens ist es vorgesehen, für die Dauer der Al-Si-Oxidationsphase die Menge des eingeblasenen Sauerstoffs auf eine vorbestimmte Durchflußmenge einzustellen, so daß das Aufschäumen der Schlacke eine bestimmte Stärke nicht überschreitet.When carrying out the decarburization process, the amount of oxygen blown in is adjusted to a predetermined flow rate for the duration of the Al-Si oxidation phase, so that the foaming of the slag does not exceed a certain thickness.
Ein Beispiel der Erfindung wird anhand der beiliegenden Zeichnung näher erläutert. Die Figuren zeigen:An example of the invention is explained in more detail with reference to the accompanying drawing. The figures show:
Fig. 1 die Entkohlungskinetik des zugrundegeiegten Modells undFig. 1, the decarburization kinetics of the underlying model and
Fig. 2 die Sauerstoffbiianz der Entkohlungskinetik nach Fig. 1.2 shows the oxygen balance of the decarburization kinetics according to FIG. 1.
Fig. 1 zeigt schematisch die Entkohlungskinetik des zugrundegeiegten Modells. Dabei ist auf der y-Achse die Entkohlungsgeschwindigkeit und auf der x-Achse der Kohlenstoffgehalt der Schmelze aufgetragen. Die Hauptentkohlungsphase zeichnet sich, wie Fig. 1 erkennen läßt, durch eine konstante Entkohlungsgeschwindigkeit aus, die nach dem Erreichen des kritischen Übergangspunktes von der Entkohlungsreaktion zur Metalloxidation kontinuierlich in die nachkritische Phase übergeht. Unter diesem Gesichtspunkt ist der kritische Übergangspunkt sowohl zur Hauptentkohlungsphase als auch zur πachkritischen Phase zugehörig. Dement¬ sprechend ist die für diese beiden Phasen geltende unterschiedliche Kinetik der Entkohlungsreaktion gleich, d. h.:Fig. 1 shows schematically the decarburization kinetics of the underlying model. The decarburization rate is plotted on the y-axis and the carbon content of the melt on the x-axis. The main decarburization phase, as can be seen in FIG. 1, is characterized by a constant decarburization rate which, after reaching the critical transition point from the decarburization reaction to metal oxidation, continuously passes into the post-critical phase. From this point of view, the critical transition point belongs to both the main decarburization phase and the post-critical phase. Accordingly, the different kinetics of the decarburization reaction that apply to these two phases are the same, ie. H.:
mit With
ΔCkr Kohlenstoffabbrand bis zum kritischen Punkt in %ΔCkr carbon burn up to the critical point in%
Δtkr Dauer der HauptentkohlungsphaseΔtkr Duration of the main decarburization phase
Ckr kritischer Kohienstoffgehalt in % τkr Betriebsreaktionszeitkonstante in minCkr critical carbon content in% τkr operating reaction time constant in min
Die eigentliche Entkohlung findet während der Hauptentkohlungsphase, d. h. nach dem AI-, Sl-Abbrand bis zum Erreichen des kritischen Übergangspunktes statt. Parallel zur Kohienstoffoxidation findet bekanntermaßen eine Metalloxidation statt, vor allem die von Chrom, Mangan und Eisen. Daraus ergibt sich für die Sauerstoffbilanz die folgende Gleichung:The actual decarburization takes place during the main decarburization phase, i.e. H. after the AI, Sl burn up until the critical transition point is reached. As is known, metal oxidation takes place parallel to carbon oxidation, especially that of chromium, manganese and iron. This results in the following equation for the oxygen balance:
Δθ2,C + Δθ2,Me =ηHQθ2.H Δtkr (2)Δθ2, C + Δθ2, Me = ηHQθ2.H Δtkr (2)
mitWith
Δθ2,C Sauerstoffbedarf für Kohlenstoffabbrand bis zum kritischen Punkt in Nm3/min Δθ2,Me Sauerstoffbedarf beim Metallabbrand bis zum kritischen Punkt inΔθ2, C oxygen demand for carbon burn up to the critical point in Nm3 / min Δθ2, Me oxygen demand for metal burn up to the critical point in
Nm3/min T|H Wirkungsgrad der Sauerstofflanze in der HauptentkohlungsphaseNm3 / min T | H efficiency of the oxygen lance in the main decarburization phase
Qθ2,H Menge des eingeblasenen Sauerstoffs in derQθ2, H amount of oxygen blown in
Hauptentkohlungsphase in Nm3/minMain decarburization phase in Nm3 / min
Die Energiebilanz der Schmelze sieht so aus, daß der momentane Energieinhalt der Schmelze sich aus dem anfänglichen Energieinhalt des Vormetalls und der gespeicherten Energie, die gleich der Differenz zwischen der Energiezufuhr und dem Energieveriust ist, zusammensetzt. Weiterhin wird davon ausgegangen, daß die einmal am kritischen Punkt erreichte Solltemperatur der Schmelze während der weiteren Behandlung in der nachkritischen Phase nur leicht steigt. Auf dieser Annahme gründet sich die vorgeschlagene Prozeßsteuerung, bei der während der nachkritischen Phase nur noch eine geringe Chromverschlackuπg stattfindet. DieThe energy balance of the melt is such that the instantaneous energy content of the melt is composed of the initial energy content of the primary metal and the stored energy, which is equal to the difference between the energy supply and the energy loss. Furthermore, it is assumed that the target temperature of the melt once reached at the critical point increases only slightly during the further treatment in the post-critical phase. The proposed process control is based on this assumption, in which only a small amount of chromium slagging takes place during the post-critical phase. The
Energiefreisetzung beim Kohlenstoff- und Chromabbrand wird zum größten Teil durch die auftretenden Energieveriuste kompensiert. Die Energiebilanz stellt sich somit folgendermaßen dar CTP (GA/1000) ΔTSOII =The release of energy from carbon and chrome burns is largely compensated by the energy losses that occur. The energy balance is therefore as follows CTP (GA / 1000) ΔTSOII =
+ CTP (GA/1000) konstl ΔSi/0,1 + + CTP (GA/1000) konst2 ΔAI/0,1 + + CTP (GA /1000) (konst3 + λkonst4) ΔCkr/0, 1 + + CTP (GA/1000) konstδ ΔCkr/0,1 + + CTP (GA/1000) koπstδ ΔFekr/0,1 + + CTP (GA/1000) konst7 ΔMnkr/0,1 ++ CTP (GA / 1000) const ΔSi / 0.1 + + CTP (GA / 1000) const2 ΔAI / 0.1 + + CTP (GA / 1000) (const3 + λkonst4) ΔCkr / 0.1 + + CTP (GA / 1000) constδ ΔCkr / 0.1 + + CTP (GA / 1000) koπstδ ΔFekr / 0.1 + + CTP (GA / 1000) const7 ΔMnkr / 0.1 +
- (CGP /1000) (konstδ GA ΔCkr/100 + QAr,AI-Si ΔtAI-Si + QAΓ.H Δtkr)(Tθ + Tsoiι/2)- (CGP / 1000) (constδ GA ΔCkr / 100 + QAr, AI-Si ΔtAI-Si + QAΓ.H Δtkr) (Tθ + Tsoiι / 2)
-CTP ΔTw ΔQw (ΔtAi-Si + Δtkr) -CSP (ΔtAi-Si + Δtkr)/60 -Σ (Gi /1000) Q (3)-CTP ΔTw ΔQw (ΔtAi-Si + Δtkr) -CSP (ΔtAi-Si + Δtkr) / 60 -Σ (Gi / 1000) Q (3)
mitWith
GA Schmelzgewicht in KgGA melting weight in kg
ΔSi Si-Abbrand mit konstl =25 bis 40 K/0, 1 % Si-AbbrandΔSi Si burnup with constant = 25 to 40 K / 0.1% Si burnup
ΔAI Al-Abbrand mit konst2=25 bis 45 K/0, 1 % Al-AbbrandΔAI Al burn-up with const2 = 25 to 45 K / 0.1% Al burn-up
ΔCkr C-Abbrand mit konst3*5 bis 20 K/0,1% C-Abbrand und λ-AnteilΔCkr C-burn with const3 * 5 to 20 K / 0.1% C-burn and λ-part
(konst4=20 bis 40) der CO-Nachverbrennung(const4 = 20 to 40) CO post-combustion
ΔCrkr Cr-Abbrand mit konst5=5 bis 20 K/0, 1 % Cr-AbbrandΔCrkr Cr burnup with const5 = 5 to 20 K / 0.1% Cr burnup
ΔFβkr Fe-Abbrand mit konst6=1 bis 10 K/0, 1 % Fe-AbbrandΔF β kr Fe erosion with const6 = 1 to 10 K / 0.1% Fe erosion
ΔMnkr Mn-Abbrand mit konst7=5 bis 20 K/0, 1 % Mn-AbbrandΔMnkr Mn erosion with const7 = 5 to 20 K / 0, 1% Mn erosion
CTP spezifische Wärmekapazität der Schmelze in KWh/K/t λ Anteil der CO-Nachverbrennung im KesselCTP specific heat capacity of the melt in KWh / K / t λ Share of CO afterburning in the boiler
CGP spezifische Wärmekapazität des Abgases in KWh/Nm3/K QAr. Al;Si , QAΓ.H Ar-lnertgasdurchfluß in der At-Si-und Hauptentkohlungsphase inCGP specific heat capacity of the exhaust gas in KWh / Nm3 / K QAr. Al; Si, QAΓ.H Ar inert gas flow in the At-Si and main decarburization phase in
Nm3/minNm3 / min
CWP spezifische Wärmekapazität des Kühlwassers in KWM/KCWP specific heat capacity of the cooling water in KWM / K
ΔTw Temperaturdifferenz Einlauf/Auslauf in KΔTw temperature difference inlet / outlet in K
Qw mittlerer Kühlwasserdurchfluß in l/minQw mean cooling water flow in l / min
CSP Strahlungsleistung der Wandung in KWCSP radiation power of the wall in KW
Gi Zugabe T in KgGi addition T in kg
Ci Enthalpie der Legierung "i" in KWh/t To Temperatur des Vormetalls in "CCi enthalpy of alloy "i" in KWh / t To temperature of the pre-metal in "C
Die rechte Seite der Energiebilanzgleichung (3) weist mehrere mit einem positiven Vorzeichen versehene Glieder auf, die die durch den Metallabbrand (Metalloxidation) freigesetzte Wärmeenergie erfassen. Die Intensität des Metallabbrands wird für die einzelnen Metalle durch die Konstanten Konst. 1 bis Konst. 7 charakterisiert. Es handelt sich dabei um für den Schmelzofen und die Schmelze typische Parameter. Die mit einem negativen Vorzeichen versehenen Glieder von Gleichung (3) umfassen die Energieverluste durch die Abgasabführung, durch die Wasserkühlung, durch die Wärmeabstrahlung und den Energiebedarf für das Einschmelzen von Legierungen und Schlacken.The right side of the energy balance equation (3) has several elements with a positive sign, which record the thermal energy released by the metal burnup (metal oxidation). The intensity of the metal erosion is determined for the individual metals by the constant Konst. 1 to const. 7 characterized. These are parameters typical of the melting furnace and the melt. The elements of equation (3) provided with a negative sign include the energy losses through the exhaust gas discharge, through the water cooling, through the heat radiation and the energy requirement for the melting of alloys and slags.
Der Zusammenhang der prozeßrelevanten Temperaturen ergibt sich aus Gleichung (4):The relationship between the process-relevant temperatures results from equation (4):
TSoll = TSkr - To (4)TSoll = TSkr - To (4)
mitWith
Tskr Solltemperatur der Schmelze am kritischen Punkt in βCTskr target temperature of the melt at the critical point in β C
ΔTSoll Solltemperaturzuwachs der Schmelze am kritischen Punkt in "CΔTSoll target temperature increase of the melt at the critical point in "C
To Temperatur der Schmelze am Beginn der Behandlung in *CTo melt temperature at the start of treatment in * C
Die wesentliche Größe, die sich aus der Lösung des Gleichungssystems (1), (2) und (3) ergibt, ist der kritische Kohlenstoffabbrand ΔCkr. Mit diesem erhält man den kritischen Kohlenstoffgehalt ΔCkr, das ist der Kohlenstoffgehalt am Übergangspunkt der Schmelze gemäß Fig. 1 , aus folgender Gleichung:The essential quantity resulting from the solution of the system of equations (1), (2) and (3) is the critical carbon burn-up ΔCkr. With this, the critical carbon content ΔCkr, that is the carbon content at the transition point of the melt according to FIG. 1, is obtained from the following equation:
Ckr = CA - ΔCkr (6)Ckr = CA - ΔCkr (6)
wobei CA der Anfangskohlenstoffgehalt der Schmelze ist.where CA is the initial carbon content of the melt.
Die Entkohlungsgeschwindigkeit läßt sich berechnen unter Berücksichtigung der folgenden Gleichung gemäß Fig. 1:The decarburization rate can be calculated taking into account the following equation according to FIG. 1:
(-dC / dt) = ΔCkr / Δtkr = Ckr / τkr (5). Zusätzlich zum kritischen Kohlenstoffgehalt Ckr erhält man durch Lösung des Gleichungssystems (1) - (4) die regelungstechnisch sehr wichtigen Prozeßzeiten tkr und tAl-Si. Als vierte Unbekannte bestimmt das Gleichuπgssystem die Größe (To + ΔTsoll/2). Diesen Wert in Gleichung (4) eingesetzt ergibt Tskr - die Solltemperatur der Schmelze am kritischen Punkt.(-dC / dt) = ΔCkr / Δtkr = Ckr / τkr (5). In addition to the critical carbon content Ckr, solving the system of equations (1) - (4) gives the process times tkr and tAl-Si, which are very important in terms of control technology. As the fourth unknown, the equilibrium system determines the size (To + ΔTsoll / 2). Inserting this value in equation (4) gives Tskr - the target temperature of the melt at the critical point.
Das Modell zur Bestimmung des kritischen Entkohlungszustands wird durch die Gleichungen (1) bis (5) eindeutig beschrieben und ermöglicht es die für den Entkohlungsprozeß relevanten Steuerungsgrößen: die Dauer der Al-Si- Oxidationsphase ΔtAI-Si, die Dauer der Hauptentkohlungsphase Δtkr und dieThe model for determining the critical decarburization state is clearly described by equations (1) to (5) and enables the control variables relevant for the decarburization process: the duration of the Al-Si oxidation phase ΔtAI-Si, the duration of the main decarburization phase Δtkr and the
Entkohlungsgeschwindigkeit in der Hauptentkohlungsphase zu bestimmen.Determine decarburization rate in the main decarburization phase.
Die Durchführung des Entkohlungsverfahrens erfolgt so, daß zu Beginn der Entkohlung mit Hilfe der Gleichungen (1) bis (5) die relevanten Steuerungsgrößen berechnet werden. Der weitere Prozeßablauf ist in Fig. 2 schematisch dargestellt. In der AL-SI-Oxidationsphase wird ein vorbestimmter Sauerstoffdurchfluß und ein vorbestimmter Innertgasdurchfluß (beispielsweise Argon) eingestellt und durch die Schmelze geleitet. Die vorbestimmten Werte liegen dabei in einem Bereich, bei dem die Schäumung der Metallschlacke die zulässigen Werte nicht überschreitet.The decarburization process is carried out in such a way that the relevant control variables are calculated at the beginning of decarburization using equations (1) to (5). The further process flow is shown schematically in FIG. 2. In the AL-SI oxidation phase, a predetermined oxygen flow and a predetermined inert gas flow (for example argon) are set and passed through the melt. The predetermined values lie in a range in which the foaming of the metal slag does not exceed the permissible values.
Unmittelbar anschließend an die Al-Si-Oxidationsphase wird die Innertgaszuführung abgeschaltet und die zugeführte Sauerstoffmenge beschleunigt hochgefahren, bis sich die für die Hauptentkohlungsphase berechnete Entkohlungsgeschwindigkeit, die aus dem CO- und C02- Gehalt im Abgas und dem Abgasdurchfluß bestimmt wird, einstellt. Diese Entkohlungsgeschwindigkeit wird durch Regulierung der Sauerstoffzufuhr während der Hauptentkohlungsphase im wesentlichen konstant gehalten. Bei Erreichen des kritischen Übergangspunktes tkr wird die zugeführte Sauerstoffmenge zeitproportional mit der Zeitkonstanten tkr verringert.Immediately after the Al-Si oxidation phase, the inert gas supply is switched off and the quantity of oxygen supplied is accelerated until the decarburization rate calculated for the main decarburization phase, which is determined from the CO and CO 2 content in the exhaust gas and the exhaust gas flow, is established. This decarburization rate is kept essentially constant by regulating the oxygen supply during the main decarburization phase. When the critical transition point tkr is reached, the amount of oxygen supplied is reduced in proportion to the time with the time constant tkr.
Die Besonderheit der Erfindung liegt in der Bestimmung der Metallbadkonzentrationen der chemischen Elemente, der Metallbadtemperatur am kritischen Punkt und der Zeitpunkt seines Auftritts. Am kritischen Übergangspunkt werden außerdem die chemisch-thermodynamischen Verhältnisse der im Metallbad ablaufenden chemischen Reaktionen berechnet. Bezüglich der maximalen momentanen Entkohiung und der minimalen Metallverschlackung gelten diese Reaktionsabläufe als optimal. Der optimale Reaktionsablauf wird in der nachkritischen Entkohlungsphase dadurch beibehalten, daß die für den kritischen Übergangspunkt anhand des Modells berechneten Prozeßgrößen zur Steuerung der nachkritischen Phase herangezogen werden, sodaß die unerwünschte Chromoxidation, der Sauerstoffverbrauch und der Verbrauch an Reduktionsstoffen, vor allem des Siliziums, wesentlich minimiert werden können. Gesteuert wird wie in der Hauptentkohlungsphase die Sauerstoff- durchflußmenge über die Entkohlungsgeschwindigkeit.The special feature of the invention lies in the determination of the metal bath concentrations of the chemical elements, the metal bath temperature at the critical point and the time of its occurrence. At the critical transition point, the chemical-thermodynamic relationships of the chemical reactions taking place in the metal bath are also calculated. With regard to the maximum instantaneous decarburization and the minimum metal slagging, these reaction processes are considered to be optimal. The The optimal reaction sequence is maintained in the postcritical decarburization phase by using the process variables calculated for the critical transition point on the basis of the model to control the postcritical phase, so that undesired chromium oxidation, oxygen consumption and the consumption of reducing agents, especially silicon, are significantly minimized can. As in the main decarburization phase, the oxygen flow rate is controlled via the decarburization rate.
Die modellmäßige Bestimmung des kritischen Zustandes ertaubt außerdem die optimalen Eingangsdaten der Schmelze zu definieren. Die Anwendungsmöglichkeiten des Verfahrens erstrecken sich grundsätzlich auf alle Prozesse, die unter reduzierender Wirkung des Kohlenstoffs gegenüber der Chromoxidation ablaufen. Zu diesen gehören sowohl Vakuumfrischprozesse (VOD) als auch AOD- Konverterprozesse (Argon Oxigen Decarburization) mit allen technischen Abwandlungen. The model-based determination of the critical condition also makes it possible to define the optimal input data for the melt. The application possibilities of the method basically extend to all processes that take place with the reducing effect of the carbon against the chromium oxidation. These include both vacuum fresh processes (VOD) and AOD converter processes (Argon Oxigen Decarburization) with all technical modifications.

Claims

Pateπtansprüche Patent claims
1. Verfahren zum Entkohlen einer Stahlschmelze zur Herstellung von hochchromhaltigen Stählen unter Einblasen von Sauerstoff, bei welchem die Entkohlungsgeschwindigkeit fortlaufend gemessen werden und in Abhängigkeit von den gemessenen Werten die Menge des einzublasenden Sauerstoffs eingestellt wird, dadurch gekennzeichnet,1. A process for the decarburization of a molten steel for the production of high-chromium-containing steels while blowing in oxygen, in which the decarburization rate is measured continuously and the amount of the oxygen to be blown in is set as a function of the measured values, characterized in that
- daß folgende Regelgrößen berechnet werden:- that the following control variables are calculated:
a) die Dauer der Al-Si-Oxidationsphase zu Beginn des Entkohlungsprozesses,a) the duration of the Al-Si oxidation phase at the start of the decarburization process,
b) die Dauer einer sich unmittelbar an die Al-Si-Oxidationsphase anschließenden Hauptentkohlungsphase bis zum Erreichen des Übergangspunktes von derb) the duration of a main decarburization phase immediately following the Al-Si oxidation phase until the transition point from the
Entkohlungsreaktion zur Metalloxidation undDecarburization reaction for metal oxidation and
c) die Entkohlungsgeschwindigkeit in der Hauptentkohlungsphase undc) the decarburization rate in the main decarburization phase and
- daß die eingebiasene Sauerstoffmenge unmittelbar anschließend an die Al-Si-- that the amount of oxygen blown in immediately afterwards to the Al-Si
Oxidationsphase auf diejenige Sauerstoffmenge der Hauptentkohlungsphase beschleunigt hochgefahren wird, bis sich die gemäß c) berechnete Entkohlungsgeschwindigkeit einstellt,Oxidation phase is accelerated to that amount of oxygen in the main decarburization phase until the decarburization rate calculated according to c) is reached,
- daß für die Dauer der Hauptentkohlungsphase durch die eingeblasene- That for the duration of the main decarburization phase by the blown
Sauerstoffmenge die Entkohlungsgeschwindigkeit im wesentlichen konstant gehalten wird undAmount of oxygen the decarburization rate is kept substantially constant and
- daß unmittelbar anschließend an die Hauptentkohlungsphase die eingeblasene Sauerstoffmenge in der Weise kontinuierlich reduziert wird, daß sich die- That immediately after the main decarburization phase, the amount of oxygen blown in is continuously reduced in such a way that the
Entkohlungsgeschwindigkeit zeitkontinuierlich mit einer vorbestimmten Zeitkonstanten verringert.Decarburization rate is continuously reduced in time with a predetermined time constant.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Dauer der Al-Si-Oxidationsphase ΔtAI-Si , die Dauer der Hauptentkohlungsphase Δtkr und die Entkohlungsgeschwindigkeit in der Hauptentkohlungsphase anhand eines durch die folgenden Gleichungen (1) bis (5) beschriebenen Modells berechnet wird:2. The method according to claim 1, characterized in that that the duration of the Al-Si oxidation phase ΔtAI-Si, the duration of the main decarburization phase Δtkr and the decarburization rate in the main decarburization phase are calculated using a model described by the following equations (1) to (5):
mitWith
ΔCkr Kohlenstoffabbrand bis zum kritischen Punkt in %ΔCkr carbon burn up to the critical point in%
Δtkr Dauer der HauptentkohlungsphaseΔtkr Duration of the main decarburization phase
Ckr kritischer Kohlenstoffgehalt in % τkr Betriebsreaktionszeitkonstante in minCkr critical carbon content in% τkr operating reaction time constant in min
Δ02.C + Δθ2,Me =ηHQθ2,H Δtkr (2)Δ02.C + Δθ2, Me = ηHQθ2, H Δtkr (2)
mitWith
Δθ2,C Sauerstoffbedarf für Kohlenstoffabbrand bis zum kritischen Punkt in Nm3/min Δθ2,Me Sauerstoffbedarf beim Metallabbrand bis zum kritischen Punkt inΔθ2, C oxygen demand for carbon burn up to the critical point in Nm3 / min Δθ2, Me oxygen demand for metal burn up to the critical point in
Nm3/min T)H Wirkungsgrad der Lanze in der HauptentkohlungsphaseNm3 / min T) H Efficiency of the lance in the main decarburization phase
Qθ2,H Menge des eingeblasenen Sauerstoffs in derQθ2, H amount of oxygen blown in
Hauptentkohlungsphase in Nm3/minMain decarburization phase in Nm3 / min
CTP (GA/1000) ΔTSo!l =CTP (GA / 1000) ΔTSo! L =
+ CTP (GA /1000) konstl ΔSi/0,1 ++ CTP (GA / 1000) constant ΔSi / 0.1 +
+ CTP (GA/1000) konst2 ΔAI/0,1 ++ CTP (GA / 1000) const2 ΔAI / 0.1 +
+ CTP (GA/1000) (konst3 + λkonst4) ΔCkr/0,1 ++ CTP (GA / 1000) (const3 + λconst4) ΔCkr / 0.1 +
+ CTP (GA/1000) konstδ ΔCkr/0,1 + + CTP (GA /1000) konstβ ΔFekr/0, 1 ++ CTP (GA / 1000) constδ ΔCkr / 0.1 + + CTP (GA / 1000) const ΔFekr / 0.1 +
+ CTP (GA/1000) konst7 ΔMnkr/0,1 ++ CTP (GA / 1000) const7 ΔMnkr / 0.1 +
- (CGP /1000) (konstδ GA ΔCkr/100 + QAr,Ai-Si ΔtAi-Si + QAΓ.H Δtkr)(To- (CGP / 1000) (constδ GA ΔCkr / 100 + QAr, Ai-Si ΔtAi-Si + QAΓ.H Δtkr) (To
+ Tsoiι/2)+ Tsoiι / 2)
-CTP ΔTw ΔQw (ΔtAi-Si + Δtkr)-CTP ΔTw ΔQw (ΔtAi-Si + Δtkr)
- 12 - -CSP (ΔtAi-Si + Δtkr)/60 -Σ (Gi /1000) Ci (3)- 12 - -CSP (ΔtAi-Si + Δtkr) / 60 -Σ (Gi / 1000) Ci (3)
mitWith
ΔSi Si-Abbrand mit konstl =25 bis 40 K/0, 1 % Si-AbbrandΔSi Si burnup with constant = 25 to 40 K / 0.1% Si burnup
ΔAI Al-Abbrand mit konst2=25 bis 45 K/0, 1 % Al-AbbrandΔAI Al burn-up with const2 = 25 to 45 K / 0.1% Al burn-up
ΔCkr C-Abbrand mit konst3=5 bis 20 K/0, 1 % C-Abbrand und λ-AnteilΔCkr C-erosion with const3 = 5 to 20 K / 0, 1% C-erosion and λ portion
(konst4=20 bis 40) der CO-Nachverbrennung(const4 = 20 to 40) CO post-combustion
ΔCnxr Cr-Abbrand mit konst5=5 bis 20 K/0,1% Cr-AbbrandΔCnxr Cr burnup with const5 = 5 to 20 K / 0.1% Cr burnup
ΔFβkr Fe-Abbrand mit bis 10 K/0,1% Fe-AbbrandΔF β kr Fe erosion with up to 10 K / 0.1% Fe erosion
ΔMnkr Mn-Abbrand mit konst7=5 bis 20 K/0,1 % Mn-AbbrandΔMnkr Mn erosion with const7 = 5 to 20 K / 0.1% Mn erosion
CTP spezifische Wärmekapazität der Schmelze in KWh/K/t λ Anteil der CO-Nachverbrennung im KesselCTP specific heat capacity of the melt in KWh / K / t λ Share of CO afterburning in the boiler
CGP spezifische Wärmekapazität des Abgases in KWh/Nm3/K QAr ,AI;Si , QAΓ.H Ar-lnertgasdurchfluß in der Al-Si-und Hauptentkohlungsphase inCGP specific heat capacity of the exhaust gas in KWh / Nm3 / K QAr, AI; Si, QAΓ.H Ar inert gas flow in the Al-Si and main decarburization phase in
Nm3/minNm3 / min
CWP spezifische Wärmekapazität des Kühlwassers in KWh/l/KCWP specific heat capacity of the cooling water in KWh / l / K
ΔTw Temperaturdifferenz Einlauf/Auslauf in KΔTw temperature difference inlet / outlet in K
Qw mittlerer Kühlwasserdurchfluß in l/minQw mean cooling water flow in l / min
CSP Strahlungsleistung der Wandung in KWCSP radiation power of the wall in KW
Gi Zugabe "i" in KgGi addition "i" in kg
Ci Enthalpie der Legierung T in KWhΛCi enthalpy of the alloy T in KWhΛ
To Temperatur der Schmelze am Beginn der Behandlung in "CTo melt temperature at the start of treatment in "C
mitWith
ΔTSoll = TSkr - To (4)ΔTSoll = TSkr - To (4)
mitWith
TSkr Solltemperatur der Schmelze am kritischen Punkt in "CTSkr target temperature of the melt at the critical point in "C
ΔTSoll Solltemperaturzuwachs der Schmelze am kritischen Punkt in °CΔTset temperature increase of the melt at the critical point in ° C
, wobei die Entkohlungsgeschwindigkeit sich ergibt unter Berücksichtigung von (-dC / dt) = ΔCkr / Δtkr = Ckr / τkr (5). Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die Entkohlungsgeschwindigkeit nach dem Erreichen des kritischen Punktes zeitkontinuieriich mit der Zeitkonstanten τkr verringert wird. , whereby the decarburization rate results taking into account (-dC / dt) = ΔCkr / Δtkr = Ckr / τkr (5). A method according to claim 2, characterized in that the decarburization rate is reduced continuously after reaching the critical point with the time constant τkr.
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RU2139355C1 (en) 1999-10-10
US6093235A (en) 2000-07-25
PL186610B1 (en) 2004-01-30
JP3190351B2 (en) 2001-07-23
ES2140912T3 (en) 2000-03-01
AU701824B2 (en) 1999-02-04
DE19540490C1 (en) 1997-04-10
PL326503A1 (en) 1998-09-28
MX9802987A (en) 1998-09-30
CZ125298A3 (en) 1998-08-12
CN1063493C (en) 2001-03-21
KR19990044696A (en) 1999-06-25
AU7619796A (en) 1997-05-15
SK50198A3 (en) 1999-01-11
SK283186B6 (en) 2003-03-04
ATE188511T1 (en) 2000-01-15
BR9611224A (en) 1999-04-06
EP0857222B1 (en) 2000-01-05
KR100275100B1 (en) 2000-12-15
CN1200768A (en) 1998-12-02
WO1997015692A1 (en) 1997-05-01
JPH11504079A (en) 1999-04-06
DE59604131D1 (en) 2000-02-10

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