WO2009149903A1 - Process for the high-temperature annealing of grain-oriented magnetic steel strip in an inert gas atmosphere in a heat treatment furnace - Google Patents

Process for the high-temperature annealing of grain-oriented magnetic steel strip in an inert gas atmosphere in a heat treatment furnace Download PDF

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Publication number
WO2009149903A1
WO2009149903A1 PCT/EP2009/004149 EP2009004149W WO2009149903A1 WO 2009149903 A1 WO2009149903 A1 WO 2009149903A1 EP 2009004149 W EP2009004149 W EP 2009004149W WO 2009149903 A1 WO2009149903 A1 WO 2009149903A1
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Prior art keywords
inert gas
hydrogen
gas atmosphere
temperature
heat treatment
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PCT/EP2009/004149
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German (de)
French (fr)
Inventor
Frank Maschler
Peter Wendt
Erik Micek
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Loi Thermoprocess Gmbh
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Priority to EP09761466A priority Critical patent/EP2304061A1/en
Publication of WO2009149903A1 publication Critical patent/WO2009149903A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/663—Bell-type furnaces
    • C21D9/667—Multi-station furnaces
    • C21D9/67—Multi-station furnaces adapted for treating the charge in vacuum or special atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/663—Bell-type furnaces

Definitions

  • the invention relates to a method for high-temperature annealing of grain-oriented electrical steel strip in a protective gas atmosphere in a heat treatment furnace, wherein the inert gas atmosphere contains hydrogen and wherein a security medium is used to flush the hydrogen-containing inert gas atmosphere.
  • Grain-oriented electrical steel is used for the iron core or wound cores of transformers or generators. It is silicon-alloyed steel sheet, which has good magnetic properties. The electrical steel is wound into batches or coils or stacked.
  • the annealing process is carried out in a heat treatment furnace, usually in a hood furnace or a rotary hearth furnace under protective gas or in a protective gas atmosphere.
  • a typical non-continuous heat treatment furnace for high temperature annealing of grain oriented electrical steel in the form of a hood furnace has a hearth with one or more heaters, heating and possibly cooling devices.
  • On an incandescent base are one or more coils or batches. As a rule, the coils are covered with a protective cover so that a glow chamber is formed.
  • the protective cover seals the combustion chamber with a sand cup in front of a boiler room, which forms under a heating hood.
  • the protective gas in the annealing space under the protective hood is passed through the sand cup seal in the boiler room.
  • the high-temperature annealing process has four phases with different inert gas atmosphere in the annealing space:
  • Phase 1 The annealing space is purged with nitrogen (N 2 ) to remove the atmospheric oxygen. The heating is started and it is heated to a temperature of 600 to 850 0 C and possibly held for a few hours. During this time, it is purged with nitrogen. During purging, protective gas is introduced into the annealing space continuously or at predetermined intervals, while the inert gas atmosphere flows out with a defined volume flow.
  • Phase 2 After leaving phase 1, in phase 2 the annealing space is rinsed with a mixture of nitrogen (N 2 ) and hydrogen (H 2 ). The heat treatment furnace is heated slowly at 10 to 20 K / h. During this time, the orientation of the crystals in the form of the GOSS texture develops in the electrical steel strip.
  • Phase 3 After completing the crystal alignment, the purge is switched to pure hydrogen (H 2 ). The heating is at about 1200 0 C for about 20 to 30 hours (h) in the holding operation. At these temperatures, nitrogen must no longer be present in the protective gas atmosphere in order to avoid nitrogen uptake by the charge. Then it is heated with adjustable gradient, ie the temperature down to 650 0 C and lowered below (cooling period).
  • Phase 4 The hydrogen (H 2 ) in the annealing space under the protective hood is purged with nitrogen (N 2 ). Afterwards the heating hood can be removed. Under the protective hood, an overpressure is maintained by introducing a small amount of nitrogen. For safety reasons, it must be possible at any time during the annealing process, ie even at high furnace temperatures (phase 3), to rinse out the protective gas atmosphere in the heat treatment furnace, which consists of hydrogen or a mixture of hydrogen and nitrogen, with a safety medium. From practice it is known to use as security medium nitrogen (N 2 ). However, when using nitrogen as the safety medium, there is the danger that the batch will be adversely affected by nitrogen uptake at a batch temperature of approx. 950 ° C.
  • phase 3 hydrogen exits into the boiler room because the sand cup seal does not completely seal off the combustion chamber from the boiler room. If the temperature in the boiler room falls below the safety limit of 750 ° C, safety precautions must be taken to reliably prevent the formation and accumulation of an explosive atmosphere. These security measures can be very expensive.
  • the object of the invention is therefore to develop a method of the type mentioned, so the plant and process safety is guaranteed at any time during the annealing process with little effort and at the same time an impairment of the batch is avoided.
  • the safety medium for rinsing the hydrogen-containing inert gas inert gas may consist of pure noble gas and / or a mixture of mainly noble gas and hydrogen.
  • the inert gas containing security medium is preferably used for rinsing the hydrogen-containing protective gas atmosphere when the temperature of the batch 950 0 C exceeds, ie, when the temperature of the batch is at least 950 0 C. It is rinsed with inert gas and / or a mixture of mainly noble gas and hydrogen until the temperature of the charge is below the temperature at which the electrical steel no longer absorbs nitrogen. This prevents the batch from taking up nitrogen, especially during the cooling period.
  • argon or helium is used as the security medium.
  • Fig. 1 shows a conventional high-temperature annealing method
  • Fig. 2 is a high-temperature annealing method according to the invention.
  • the high-temperature annealing process is divided into four phases. In each phase, the inert gas atmosphere in the annealing space is different.
  • phase 1 the annealing space is purged with nitrogen (N 2 ) to remove atmospheric oxygen.
  • N 2 nitrogen
  • the heating is started and it is heated to a temperature of 600 to 850 0 C and possibly held for a few hours. During this time, it is purged with nitrogen.
  • purging inert gas is introduced into the annealing space continuously or at predetermined intervals, while the inert gas atmosphere flows with a defined volume flow.
  • phase 2 the annealing space is rinsed in phase 2 with a mixture of nitrogen (N 2 ) and hydrogen (H 2 ).
  • the heat treatment furnace is heated slowly at 10 to 20 K / h. In this Time is the formation of the crystals in the form of the GOSS texture in the electrical steel.
  • the purge is switched to pure hydrogen (H 2 ) in phase 3.
  • the heating is at about 1200 0 C for about 20 to 30 h in the holding operation.
  • it is heated with adjustable gradient, ie the temperature down to 650 0 C and lowered below (cooling period).
  • FIG. 1 shows that at the end of phase 3 the hydrogen-containing protective gas atmosphere is flushed out by means of nitrogen as the safety medium. This is shown as an extended bar at the beginning of Phase 4.
  • Fig. 2 it is shown that at the end of phase 3 at a temperature above 950 0 C started with a purge with a noble gas E and continued during a phase 3 a.
  • the hydrogen is flushed out with inert gas within 1 to 2 h.
  • the flushing rate depends on the free volume in the annealing space and is typically approx. 10 m 3 / h to 20 m 3 / h. Then it is flushed with a lower volume flow to ensure a safe overpressure to the boiler room.
  • the necessary volume flow depends mainly on the leak rate of the sand cup.
  • the volumetric flow can also remain constant or otherwise be varied in a sensible way.
  • the inert gas used is argon.
  • the noble gas can be mixed with up to 5% hydrogen. It is advantageous that in the boiler room at the end of phase 3, when the temperature falls below the safety limit of 750 0 C, even in the presence of oxygen can not form an explosive atmosphere. Due to the use of a noble gas-containing safety medium for rinsing the hydrogen-containing inert gas atmosischenre an impairment of the batch during rinsing is avoided.

Abstract

The invention relates to a process for the high-temperature annealing of grain-oriented magnetic steel strip in an inert gas atmosphere in a heat treatment furnace, wherein the inert gas atmosphere contains hydrogen and wherein a safety medium is used to flush out the hydrogen-containing inert gas atmosphere. According to the invention, the safety medium for flushing out the hydrogen-containing inert gas atmosphere contains noble gas. In the context of the invention, the safety medium may consist of pure noble gas and/or a mixture of mainly noble gas and hydrogen. In order to obtain a reduction potential that may be required, up to 5% hydrogen can be admixed with this noble gas, this posing no safety problems. As a result, no explosive mixture can form in the system and the charge is prevented from becoming damaged by the uptake of nitrogen.

Description

Verfahren zum Hochtemperatur-Glühen von kornorientiertem Elektroband in einer Schutzgasatmospäre in einem Wärmebehandlungsofen Process for high-temperature annealing of grain-oriented electrical steel strip in a protective gas atmosphere in a heat treatment furnace
Die Erfindung betrifft ein Verfahren zum Hochtemperatur-Glühen von kornorien- tiertem Elektroband in einer Schutzgasatmospäre in einem Wärmebehandlungsofen, wobei die Schutzgasatmospäre Wasserstoff enthält und wobei ein Sicherheitsmedium zum Ausspülen der wasserstoffhaltiger Schutzgasatmosphäre verwendet wird.The invention relates to a method for high-temperature annealing of grain-oriented electrical steel strip in a protective gas atmosphere in a heat treatment furnace, wherein the inert gas atmosphere contains hydrogen and wherein a security medium is used to flush the hydrogen-containing inert gas atmosphere.
Kornorientiertes Elektroband wird für den Eisenkern bzw. gewickelte Kerne von Transformatoren oder Generatoren verwendet. Es handelt sich um Silizium-legiertes Stahlblech, das gute magnetische Eigenschaften besitzt. Das Elektroband ist zu Chargen bzw. Coils gewickelt oder gestapelt.Grain-oriented electrical steel is used for the iron core or wound cores of transformers or generators. It is silicon-alloyed steel sheet, which has good magnetic properties. The electrical steel is wound into batches or coils or stacked.
Das Glühverfahren wird in Wärmebehandlungsofen, meistens in einem Haubenofen oder einem Drehherdofen unter Schutzgas beziehungsweise in einer Schutzgasatmospäre durchgeführt. Ein typischer nicht kontinuierlich arbeitender Wärmebehandlungsofen zum Hochtemperatur-Glühen von kornorientiertem Elektroband in Form eines Haubenofens weist einen Herd mit einem oder mehreren Glühsockeln, Beheizungs- und ggf. Kühleinrichtungen auf. Auf einem Glühsockel befinden sich ein oder mehreren Coils oder Chargen. Die Coils wer- den in der Regel mit einer Schutzhaube abgedeckt, so dass sich ein Glühraum bildet. Die Schutzhaube dichtet den Glühraum mit einer Sandtasse gegenüber einem Heizraum ab, der sich unter einer Heizhaube bildet. Das Schutzgas in den Glühraum unter der Schutzhaube wird über die Sandtasse-Abdichtung in den Heizraum geleitet. Das Hochtemperaturglühen nach dem Stand der Technik wird anhand derThe annealing process is carried out in a heat treatment furnace, usually in a hood furnace or a rotary hearth furnace under protective gas or in a protective gas atmosphere. A typical non-continuous heat treatment furnace for high temperature annealing of grain oriented electrical steel in the form of a hood furnace has a hearth with one or more heaters, heating and possibly cooling devices. On an incandescent base are one or more coils or batches. As a rule, the coils are covered with a protective cover so that a glow chamber is formed. The protective cover seals the combustion chamber with a sand cup in front of a boiler room, which forms under a heating hood. The protective gas in the annealing space under the protective hood is passed through the sand cup seal in the boiler room. The high-temperature annealing according to the prior art is based on the
Zeichnung erläutert, die in Fig. 1 ein Diagramm zeigt, in dem die Temperatur im Wärmebehandlungsofen bzw. die Ofentemperatur T (Ordinate; in 0C) in Abhängigkeit von der Zeit (Abszisse; in Stunden h) dargestellt ist. Das Hochtemperatur-Glühverfahren weist vier Phasen mit unterschiedlicher Schutzgasatmospäre im Glühraum auf:1, which shows the temperature in the heat treatment furnace or the furnace temperature T (ordinate, in O C) as a function of time (abscissa, in hours h). The high-temperature annealing process has four phases with different inert gas atmosphere in the annealing space:
Phase 1 : Der Glühraum wird mit Stickstoff (N2) gespült, um den Luftsauerstoff zu entfernen. Die Heizung wird gestartet und es wird auf eine Temperatur von 600 bis 850 0C aufgeheizt und ggf. einige Stunden gehalten. In dieser Zeit wird mit Stickstoff gespült. Beim Spülen wird kontinuierlich oder in vorgegebenen In- tervallen Schutzgas in den Glühraum eingeleitet, während die Schutzgasatmosphäre mit einem definierten Volumenstrom abströmt. Phase 2: Nach Verlassen der Phase 1 wird in Phase 2 der Glühraum mit einem Gemisch aus Stickstoff (N2) und Wasserstoff (H2) gespült. Der Wärmebehandlungsofen wird mit 10 bis 20 K/h langsam aufgeheizt. In dieser Zeit bildet sich in dem Elektroband die Ausrichtung der Kristalle in Form der GOSS-Textur aus. Phase 3: Nach Beendigung der Kristall-Ausrichtung wird die Spülung auf reinen Wasserstoff (H2) umgestellt. Die Heizung geht bei ca. 1200 0C für ca. 20 bis 30 Stunden (h) in den Haltebetrieb. Bei diesen Temperaturen darf kein Stickstoff mehr in der Schutzgasatmosphäre vorliegen, um eine Stickstoffaufnahme durch die Charge zu vermeiden. Danach wird mit regelbarem Gradienten abgeheizt, d. h. die Temperatur bis auf 650 0C und darunter gesenkt (Abkühlperiode).Phase 1: The annealing space is purged with nitrogen (N 2 ) to remove the atmospheric oxygen. The heating is started and it is heated to a temperature of 600 to 850 0 C and possibly held for a few hours. During this time, it is purged with nitrogen. During purging, protective gas is introduced into the annealing space continuously or at predetermined intervals, while the inert gas atmosphere flows out with a defined volume flow. Phase 2: After leaving phase 1, in phase 2 the annealing space is rinsed with a mixture of nitrogen (N 2 ) and hydrogen (H 2 ). The heat treatment furnace is heated slowly at 10 to 20 K / h. During this time, the orientation of the crystals in the form of the GOSS texture develops in the electrical steel strip. Phase 3: After completing the crystal alignment, the purge is switched to pure hydrogen (H 2 ). The heating is at about 1200 0 C for about 20 to 30 hours (h) in the holding operation. At these temperatures, nitrogen must no longer be present in the protective gas atmosphere in order to avoid nitrogen uptake by the charge. Then it is heated with adjustable gradient, ie the temperature down to 650 0 C and lowered below (cooling period).
Phase 4: Der im Glühraum unter der Schutzhaube befindliche Wasserstoff (H2) wird mit Stickstoff (N2)ausgespült. Danach kann die Heizhaube entfernt werden. Unter der Schutzhaube wird ein Überdruck gehalten, indem eine geringe Menge Stickstoff eingeleitet wird. Aus Sicherheitsgründen muss es möglich sein, zu jeder Zeit während des Glühprozesses, d. h. auch bei hohen Ofentemperaturen (Phase 3) die Schutzgasat- mospäre im Wärmebehandlungsofen, die aus Wasserstoff oder einem Gemisch aus Wasserstoff und Stickstoff besteht, mit einem Sicherheitsmedium auszuspülen. Aus der Praxis ist bekannt, als Sicherheitsmedium Stickstoff (N2) zu verwenden. Allerdings besteht bei der Verwendung von Stickstoff als Sicherheitsmedium die Gefahr, dass ab einer Chargentemperatur von ca. 950 0C die Charge durch Stickstoff-Aufnahme beeinträchtigt wird.Phase 4: The hydrogen (H 2 ) in the annealing space under the protective hood is purged with nitrogen (N 2 ). Afterwards the heating hood can be removed. Under the protective hood, an overpressure is maintained by introducing a small amount of nitrogen. For safety reasons, it must be possible at any time during the annealing process, ie even at high furnace temperatures (phase 3), to rinse out the protective gas atmosphere in the heat treatment furnace, which consists of hydrogen or a mixture of hydrogen and nitrogen, with a safety medium. From practice it is known to use as security medium nitrogen (N 2 ). However, when using nitrogen as the safety medium, there is the danger that the batch will be adversely affected by nitrogen uptake at a batch temperature of approx. 950 ° C.
Ferner besteht folgende Problematik: In der Phase 3 tritt Wasserstoff in den Heizraum aus, weil die Sandtassen-Abdichtung den Glühraum nicht vollständig gegenüber dem Heizraum abdichtet. Sofern die Temperatur im Heizraum die Sicherheitsgrenze von 750 °C unterschreitet, müssen Sicherheitsvorkehrungen getroffen werden, um die Bildung und Ansammlung einer explosionsfähigen Atmosphäre sicher auszuschließen. Diese Sicherheitsvorkehrungen können sehr aufwendig sein.There is also the following problem: In phase 3, hydrogen exits into the boiler room because the sand cup seal does not completely seal off the combustion chamber from the boiler room. If the temperature in the boiler room falls below the safety limit of 750 ° C, safety precautions must be taken to reliably prevent the formation and accumulation of an explosive atmosphere. These security measures can be very expensive.
Aufgabe der Erfindung ist es demgemäß, ein Verfahren der eingangs genannten Art weiterzuentwickeln, so die Anlagen- und Prozess-Sicherheit jederzeit während des Glühverfahrens mit geringem Aufwand gewährleistet ist und gleichzeitig eine Beeinträchtigung der Charge vermieden wird. Zur Lösung der Aufgabe enthält das Sicherheitsmedium zum Ausspülen der wasserstoffhaltigen Schutzgasatmosphäre Edelgas. Im Rahmen der Erfindung kann das Sicherheitsmedium aus reinem Edelgas und/oder einem Gemisch aus hauptsächlich Edelgas und Wasserstoff bestehen.The object of the invention is therefore to develop a method of the type mentioned, so the plant and process safety is guaranteed at any time during the annealing process with little effort and at the same time an impairment of the batch is avoided. To solve the problem contains the safety medium for rinsing the hydrogen-containing inert gas inert gas. Within the scope of the invention the safety medium may consist of pure noble gas and / or a mixture of mainly noble gas and hydrogen.
Um ein ggf. erforderliches Reduktionspotential zu erhalten, kann diesem Edelgas bis zu 5 % Wasserstoff beigemischt werden, was sicherheitstechnisch un- bedenklich ist. Damit kann sich in der Anlage kein explosionsfähiges Gemisch bilden und es wird eine Schädigung der Charge durch Stickstoff-Aufnahme verhindert.In order to obtain a possibly required reduction potential, up to 5% of hydrogen can be added to this inert gas, which is safety-friendly. This can not form an explosive mixture in the system and it is a damage to the batch prevented by nitrogen uptake.
Das edelgashaltige Sicherheitsmedium wird vorzugsweise zum Ausspülen der wasserstoffhaltigen Schutzgasatmosphäre verwendet, wenn die Temperatur der Charge 950 0C überschreitet, d. h. wenn die Temperatur der Charge mindestens 950 0C beträgt. Es wird so lange mit Edelgas und/oder einem Gemisch aus hauptsächlich Edelgas und Wasserstoff gespült, bis die Temperatur der Charge unterhalb der Temperatur liegt, ab der das Elektroband keinen Stickstoff mehr aufnimmt. Damit wird verhindert, dass die Charge, insbesondere in der Abkühl- periode, Stickstoff aufnimmt.The inert gas containing security medium is preferably used for rinsing the hydrogen-containing protective gas atmosphere when the temperature of the batch 950 0 C exceeds, ie, when the temperature of the batch is at least 950 0 C. It is rinsed with inert gas and / or a mixture of mainly noble gas and hydrogen until the temperature of the charge is below the temperature at which the electrical steel no longer absorbs nitrogen. This prevents the batch from taking up nitrogen, especially during the cooling period.
Vorzugsweise wird Argon oder Helium als Sicherheitsmedium verwendet.Preferably, argon or helium is used as the security medium.
Das Hochtemperatur-Glühen nach der Erfindung wird anhand der Zeichnung erläutert.The high-temperature annealing according to the invention will be explained with reference to the drawing.
In der Zeichnung zeigt Fig. 1 ein konventionelles Hochtemperatur-Glühverfahren;In the drawing, Fig. 1 shows a conventional high-temperature annealing method;
Fig. 2 ein Hochtemperatur-Glühverfahren nach der Erfindung.Fig. 2 is a high-temperature annealing method according to the invention.
In der Zeichnung zeigen Fig. 1 und Fig. 2 jeweils ein Diagramm, in dem die Temperatur im Wärmebehandlungsofen bzw. die Ofentemperatur T (Ordinate; in 0C) in Abhängigkeit von der Zeit (Abszisse; in Stunden (h)) dargestellt ist. Das Hochtemperatur-Glühverfahren ist in vier Phasen unterteilt. In jeder Phase setzt sich die Schutzgasatmospäre im Glühraum anders zusammen.1 and 2 each show a diagram showing the temperature in the heat treatment furnace or the furnace temperature T (ordinate, in C 0 ) as a function of time (abscissa, in hours (h)). The high-temperature annealing process is divided into four phases. In each phase, the inert gas atmosphere in the annealing space is different.
Der Ablauf des Hochtemperatur-Glühverfahrens in den Phase 1 und 2 ist in den Verfahren nach Fig. 1 und Fig. 2 identisch. In Phase 1 wird der Glühraum mit Stickstoff (N2) gespült, um den Luftsauerstoff zu entfernen. Die Heizung wird gestartet und es wird auf eine Temperatur von 600 bis 850 0C aufgeheizt und ggf. einige Stunden gehalten. In dieser Zeit wird mit Stickstoff gespült. Beim Spülen wird kontinuierlich oder in vorgegebenen Intervallen Schutzgas in den Glühraum eingeleitet, während die Schutzgasatmosphäre mit einem definierten Volumenstrom abströmt. Nach Verlassen der Phase 1 wird in Phase 2 der Glüh- räum mit einem Gemisch aus Stickstoff (N2) und Wasserstoff (H2) gespült. Der Wärmebehandlungsofen wird mit 10 bis 20 K/h langsam aufgeheizt. In dieser Zeit bildet sich in dem Elektroband die Ausrichtung der Kristalle in Form der GOSS-Textur aus.The course of the high-temperature annealing process in phases 1 and 2 is identical in the process according to FIGS. 1 and 2. In phase 1, the annealing space is purged with nitrogen (N 2 ) to remove atmospheric oxygen. The heating is started and it is heated to a temperature of 600 to 850 0 C and possibly held for a few hours. During this time, it is purged with nitrogen. When purging inert gas is introduced into the annealing space continuously or at predetermined intervals, while the inert gas atmosphere flows with a defined volume flow. After leaving phase 1, the annealing space is rinsed in phase 2 with a mixture of nitrogen (N 2 ) and hydrogen (H 2 ). The heat treatment furnace is heated slowly at 10 to 20 K / h. In this Time is the formation of the crystals in the form of the GOSS texture in the electrical steel.
Nach Beendigung der Kristall-Ausrichtung wird in Phase 3 die Spülung auf reinen Wasserstoff (H2) umgestellt. Die Heizung geht bei ca. 1200 0C für ca. 20 bis 30 h in den Haltebetrieb. Danach wird mit regelbarem Gradienten abgeheizt, d. h. die Temperatur bis auf 650 0C und darunter gesenkt (Abkühlperiode). In Fig. 1 ist dargestellt, dass am Ende der Phase 3 die wasserstoffhaltige Schutz- gasatmospäre mittels Stickstoff als Sicherheitsmedium ausgespült wird. Dies ist als verlängerter Balken am Anfang der Phase 4 dargestellt. In Fig. 2 ist dargestellt, dass am Ende von Phase 3 bei einer Temperatur oberhalb von 950 0C mit einer Spülung mit einem Edelgas E begonnen und während einer Phase 3 a fortgeführt wird. Zunächst erfolgt ein Ausspülen des Wasserstoffs mit Edelgas innerhalb von 1 bis 2 h. Dies ist als länglicher Balken zu Beginn der Phase 3a dargestellt. Die Spülrate richtet sich nach dem freien VoIu- men im Glühraum und beträgt typischerweise ca. 10 m3/h bis 20 m3/h. Danach wird mit einem geringeren Volumenstrom gespült, um einen sicheren Überdruck zum Heizraum zu gewährleisten. Der dafür notwendige Volumenstrom hängt hauptsächlich von der Leckrate der Sandtasse ab.After completion of the crystal orientation, the purge is switched to pure hydrogen (H 2 ) in phase 3. The heating is at about 1200 0 C for about 20 to 30 h in the holding operation. Then it is heated with adjustable gradient, ie the temperature down to 650 0 C and lowered below (cooling period). FIG. 1 shows that at the end of phase 3 the hydrogen-containing protective gas atmosphere is flushed out by means of nitrogen as the safety medium. This is shown as an extended bar at the beginning of Phase 4. In Fig. 2 it is shown that at the end of phase 3 at a temperature above 950 0 C started with a purge with a noble gas E and continued during a phase 3 a. First, the hydrogen is flushed out with inert gas within 1 to 2 h. This is shown as an elongated bar at the beginning of phase 3a. The flushing rate depends on the free volume in the annealing space and is typically approx. 10 m 3 / h to 20 m 3 / h. Then it is flushed with a lower volume flow to ensure a safe overpressure to the boiler room. The necessary volume flow depends mainly on the leak rate of the sand cup.
Alternativ kann der Volumenstrom auch konstant bleiben oder anderweitig sinn- voll variiert werden. Als Edelgas wird Argon verwendet. Dem Edelgas kann bis zu 5 % Wasserstoff beigemischt werden. Vorteilhaft ist, dass sich im Heizraum am Ende der Phase 3, wenn die Temperatur unter die Sicherheitsgrenze von 750 0C fällt, auch bei Anwesenheit von Sauerstoff keine explosionsfähige Atmosphäre bilden kann. Aufgrund der Verwendung eines edelgashaltigen Sicherheitsmediums zum Ausspülen der wasserstoffhaltige Schutzgas- atmospäre wird eine Beeinträchtigung der Charge während des Auspülens vermieden.Alternatively, the volumetric flow can also remain constant or otherwise be varied in a sensible way. The inert gas used is argon. The noble gas can be mixed with up to 5% hydrogen. It is advantageous that in the boiler room at the end of phase 3, when the temperature falls below the safety limit of 750 0 C, even in the presence of oxygen can not form an explosive atmosphere. Due to the use of a noble gas-containing safety medium for rinsing the hydrogen-containing inert gas atmospäre an impairment of the batch during rinsing is avoided.
Wenn Temperatur der Charge ca. 950 0C sicher unterschreitet, nimmt das Material keinen Stickstoff mehr auf. Dann kann die Spülung mit Edelgas beendet und zur weiteren Druckhaltung mit Stickstoff gespült werden. Dies ist in Fig. 2 in Phase 4 dargestellt.If the temperature of the batch falls below approximately 950 0 C, the material will no longer absorb nitrogen. Then the purge can be stopped with inert gas and purged with nitrogen for further pressure maintenance. This is shown in FIG. 2 in phase 4.
Im Rahmen der Erfindung sind ohne weiteres Abwandlungen möglich. Falls erforderlich, kann jederzeit während des Glühprozesses aus Sicherheitsgründen wasserstoffhaltige Schutzgasatmospäre mittels des edelgashaltigen Sicher- heitsmediums ausgespült werden. Ferner kann als Edelgas alternativ Helium verwendet oder ein Gemisch aus verschiedenen Edelgasen verwendet werden. Modifications are readily possible within the scope of the invention. If necessary, for safety reasons, hydrogen-containing inert gas atmosphere can be flushed out at any time during the annealing process by means of the noble gas-containing safety medium. Furthermore, helium can alternatively be used as noble gas or a mixture of different noble gases can be used.

Claims

Patentansprüche claims
1. Verfahren zum Hochtemperatur-Glühen von kornorientiertem Elektroband in einer Schutzgasatmospäre in einem Wärmebehandlungsofen, wobei die Schutzgasatmospäre Wasserstoff enthält und wobei ein Sicherheitsmedium zum Ausspülen der wasserstoffhaltiger Schutzgasatmosphäre verwendet wird, dadurch gekennzeichnet, dass das Sicherheitsmedium Edelgas enthält.A method for high temperature annealing of grain oriented electrical steel strip in a protective gas atmosphere in a heat treatment furnace, wherein the inert gas atmosphere contains hydrogen and wherein a safety medium is used for flushing the hydrogen-containing inert gas atmosphere, characterized in that the safety medium contains inert gas.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass das Sicherheitsmedium aus reinem Edelgas und/oder einem Gemisch aus hauptsächlich Edelgas und Wasserstoff besteht.2. The method according to claim 1, characterized in that the safety medium consists of pure noble gas and / or a mixture of mainly noble gas and hydrogen.
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, dass der Anteil von Wasserstoff in dem Gemisch maximal 5 Vol-% beträgt.3. The method according to claim 2, characterized in that the proportion of hydrogen in the mixture is at most 5% by volume.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das edelgashaltige Sicherheitsmedium zum Ausspülen der wasserstoffhaltiger Schutzgasatmosphäre verwendet wird, wenn die Temperatur der Charge mindestens 950 0C beträgt.4. The method according to any one of claims 1 to 3, characterized in that the noble gas-containing safety medium is used to flush the hydrogen-containing inert gas atmosphere when the temperature of the charge is at least 950 0 C.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass so lange mit dem edelgashaltigen Sicherheitsmedium gespült wird, bis die Temperatur der Charge unterhalb der Temperatur liegt, ab der das Elektroband keinen Stickstoff mehr aufnimmt.5. The method according to any one of claims 1 to 4, characterized in that so long rinsed with the noble gas-containing security medium until the temperature of the charge is below the temperature at which the electrical steel no longer absorbs nitrogen.
6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass als Edelgas Helium oder Argon verwendet wird. 6. The method according to any one of claims 1 to 5, characterized in that helium or argon is used as inert gas.
PCT/EP2009/004149 2008-06-13 2009-06-09 Process for the high-temperature annealing of grain-oriented magnetic steel strip in an inert gas atmosphere in a heat treatment furnace WO2009149903A1 (en)

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DE102008028083.6 2008-06-13

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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1233847A (en) * 1968-06-28 1971-06-03
US3971679A (en) * 1975-09-02 1976-07-27 Armco Steel Corporation Method of annealing oriented silicon steel
US4571273A (en) * 1983-07-05 1986-02-18 Ebner-Industrieofenbau Ing. Josef Ebner Kg Process of heating and cooling charges in batch-process industrial furnaces
FR2660744A1 (en) 1990-04-04 1991-10-11 Air Liquide Bell oven
US5129965A (en) * 1990-07-20 1992-07-14 Nippon Steel Corporation Method of producing grain oriented silicon steel sheets each having a low watt loss and a mirror surface
DE4428614A1 (en) * 1994-08-12 1996-02-22 Loi Thermprocess Gmbh Annealing steel sheet without causing annealing edges
DE19628136C1 (en) * 1996-07-12 1997-04-24 Thyssen Stahl Ag Production of grain-orientated electrical sheets
DE19840778A1 (en) 1998-09-07 2000-03-09 Messer Griesheim Gmbh Method and device for cleaning metal surfaces
WO2006058709A1 (en) * 2004-12-03 2006-06-08 Linde Aktiengesellschaft Method for gas quenching with helium-containing cooling gas

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1233847A (en) * 1968-06-28 1971-06-03
US3971679A (en) * 1975-09-02 1976-07-27 Armco Steel Corporation Method of annealing oriented silicon steel
US4571273A (en) * 1983-07-05 1986-02-18 Ebner-Industrieofenbau Ing. Josef Ebner Kg Process of heating and cooling charges in batch-process industrial furnaces
FR2660744A1 (en) 1990-04-04 1991-10-11 Air Liquide Bell oven
US5129965A (en) * 1990-07-20 1992-07-14 Nippon Steel Corporation Method of producing grain oriented silicon steel sheets each having a low watt loss and a mirror surface
DE4428614A1 (en) * 1994-08-12 1996-02-22 Loi Thermprocess Gmbh Annealing steel sheet without causing annealing edges
DE19628136C1 (en) * 1996-07-12 1997-04-24 Thyssen Stahl Ag Production of grain-orientated electrical sheets
DE19840778A1 (en) 1998-09-07 2000-03-09 Messer Griesheim Gmbh Method and device for cleaning metal surfaces
WO2006058709A1 (en) * 2004-12-03 2006-06-08 Linde Aktiengesellschaft Method for gas quenching with helium-containing cooling gas

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