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WO2019096616A1 - Method for the preoxidation of strip steel in a reaction chamber arranged in a furnace chamber - Google Patents

Method for the preoxidation of strip steel in a reaction chamber arranged in a furnace chamber Download PDF

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Publication number
WO2019096616A1
WO2019096616A1 PCT/EP2018/080242 EP2018080242W WO2019096616A1 WO 2019096616 A1 WO2019096616 A1 WO 2019096616A1 EP 2018080242 W EP2018080242 W EP 2018080242W WO 2019096616 A1 WO2019096616 A1 WO 2019096616A1
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Prior art keywords
reaction chamber
gas
oxidation
chamber
furnace
Prior art date
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Ceased
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PCT/EP2018/080242
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German (de)
French (fr)
Inventor
Frank Maschler
Lutz Kümmel
Jean-Pierre Crutzen
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SMS Group GmbH
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SMS Group GmbH
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Filing date
Publication date
Application filed by SMS Group GmbH filed Critical SMS Group GmbH
Priority to ES18807218T priority Critical patent/ES2942672T3/en
Priority to KR1020207017134A priority patent/KR102445685B1/en
Priority to CN201880074366.XA priority patent/CN111356775B/en
Priority to PL18807218.5T priority patent/PL3710605T3/en
Priority to FIEP18807218.5T priority patent/FI3710605T3/en
Priority to EP18807218.5A priority patent/EP3710605B1/en
Publication of WO2019096616A1 publication Critical patent/WO2019096616A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • 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
    • 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
    • C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0457—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
    • 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
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0222—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating in a reactive atmosphere, e.g. oxidising or reducing atmosphere
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/50—Controlling or regulating the coating processes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/10—Oxidising
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—After-treatment
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0257—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding

Definitions

  • the invention relates to an improved process for the preoxidation of oxidation-sensitive steel strip in a reaction chamber arranged in a furnace chamber, in order to thereby set suitable surface properties of the strip steel to be coated for a directly following hot-dip coating.
  • the surface, formed by the selective oxidation manganese, silicon, and / or aluminum oxides affect the wettability of the strip surface with a molten coating metal (for example, zinc), with the result of defects (so-called bare spots) or a poor the coating with the tape surface.
  • the alloy composition is decisive for the coating problems on high-strength steel, in particular the tendency to form non-reducible oxides at the surface. This applies, for example, to the following steel grades:
  • DE 102 004 059 566 describes a process in which the strip is pre-oxidized.
  • the method described in this document can be summarized as follows:
  • the reaction chamber with a strongly oxidizing atmosphere inside, is located in the furnace chamber of a continuous furnace with a hydrogen-containing, reducing atmosphere.
  • the belt inlet and belt outlet into the reaction chamber must be sealed to the greatest possible extent against gas exchange.
  • On Gas transfer from the furnace into the reaction chamber causes the penetrating hydrogen at least partially consumes the oxygen required for the oxidation and impairs the nature of the desired oxide layer on the strip surface. This problem is exacerbated by the lower the oxygen content in the reaction chamber.
  • a gas transfer from the reaction chamber into the furnace causes a higher water content (dew point) in the furnace and thus an increased oxidation potential. This is particularly disadvantageous for very high-strength steels with a higher content of oxygen-affine alloying elements.
  • the strip temperature is the decisive parameter for process control. This is preferably between 650 and 750 ° C. As long as the oxygen content is> 1% and the treatment time> 1 s, their influence on the thickness of the oxide layer formed is negligibly small. With oxygen contents in the range 2 to 5%, an insensitive process can be assumed.
  • this object is achieved by the features specified in claim 1, in particular by sealing the reaction chamber at a belt inlet and a belt outlet against gas exchange between the furnace chamber and the reaction chamber and a gas which oxidizes Atmosphere in the reaction chamber is formed, introduced and the gas within the reaction chamber in a closed circuit is permanently circulated, the composition of which is regulated and losses compensated by leakage and consumption.
  • the reaction chamber is in principle sealed towards the furnace chamber and in particular at the belt inlet and belt outlet against gas exchange.
  • the atmosphere is constantly being circulated.
  • the gas is sucked out of the reaction chamber, cooled, fed to a fan, enriched with fresh air and fed back into the chamber. This achieves good atmospheric homogeneity.
  • nozzle systems at least one nozzle system
  • evenly supplied gas with high kinetic energy density with the aid of nitrogen as the carrier gas of the strip surface This is necessary in order to avoid laminar boundary layer effects.
  • the oxygen content of the atmosphere in the reaction chamber is a minimum of 1.5 to a maximum of 5% by volume.
  • the reaction chamber has a trigger.
  • this trigger is controlled so that the internal pressure of the reaction chamber corresponds to the pressure of the surrounding furnace atmosphere and so the gas exchange over the unavoidable leaks is minimal.
  • the oxidation-sensitive steel may contain at least a selection of fol gender alloying components: Mn> 0.5%, Al> 0.2%, Si> 0.1%, Cr> 0.3%.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Coating With Molten Metal (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)

Abstract

Method for the preoxidation of high-strength strip steel. The invention relates to an improved method for the preoxidation of high-strength strip steel in a reaction chamber arranged in a furnace chamber. The reaction chamber is sealed at a strip entrance and a strip exit against gas exchange between the furnace chamber and the reaction chamber, and a gas that forms an oxidizing atmosphere in the reaction chamber is introduced, and the gas is continuously circulated within the reaction chamber.

Description

Verfahren zur Voroxidation von Bandstahl  Process for the pre-oxidation of steel strip

in einer in einem Ofenraum angeordneten Reaktionskammer  in a reaction chamber arranged in a furnace chamber

Beschreibung description

Die Erfindung betrifft ein verbessertes Verfahren zur Voroxidation von oxidationsempfindlichem Bandstahl in einer in einem Ofenraum angeordneten Reaktionskammer, um hierdurch für eine sich unmittelbar daran anschließende Schmelztauchbeschichtung geeignete Oberflächeneigenschaften des zu beschich- tenden Bandstahls einzustellen. The invention relates to an improved process for the preoxidation of oxidation-sensitive steel strip in a reaction chamber arranged in a furnace chamber, in order to thereby set suitable surface properties of the strip steel to be coated for a directly following hot-dip coating.

Übliche hochfeste Bandstähle enthalten als Legierungselemente Mangan, Silicium und /oder Aluminium. Während der möglichen rekristallisieren- den Glühung vor der Schmelztauchbeschichtung diffundieren diese Legierungs- elemente zur Bandoberfläche hin. Da diese Legierungselemente sehr sauerstof- faffin sind, werden sie, soweit sie sich an der Bandoberfläche bzw. in geringer Tie- fe im Band befinden, nahezu unvermeidlich oxidiert. Das Grundmaterial Eisen wird dabei allerdings nicht oxidiert. Dieses Phänomen ist auch als selektive Oxidation bekannt. Die an der Oberfläche durch die selektive Oxidation gebildeten Mangan-, Silicium-, und/oder Aluminiumoxide beeinträchtigen jedoch die Benetzbarkeit der Bandoberfläche mit einem schmelzflüssigen Überzugsmetall (beispielsweise Zink), mit der Folge von Fehlstellen (sog. bare spots) bzw. einer schlechten Flaftung des Überzugs mit der Bandoberfläche. Wobei für die Beschichtungsprobleme am hochfesten Stahl die Legierungszusammensetzung maßgeblich ist, vor allem die Neigung zur Bildung nicht reduzierbarer Oxide an der Oberfläche. Das betrifft beispielsweise folgende Stahlqualitäten : Conventional high-strength strip steels contain manganese, silicon and / or aluminum as alloying elements. During the possible recrystallizing annealing before the hot-dip coating, these alloying elements diffuse towards the surface of the strip. Since these alloying elements are very oxygen-affine, they are almost inevitably oxidized, as far as they are at the strip surface or at low depths in the strip. However, the basic material iron is not oxidized. This phenomenon is also known as selective oxidation. However, the surface, formed by the selective oxidation manganese, silicon, and / or aluminum oxides affect the wettability of the strip surface with a molten coating metal (for example, zinc), with the result of defects (so-called bare spots) or a poor the coating with the tape surface. The alloy composition is decisive for the coating problems on high-strength steel, in particular the tendency to form non-reducible oxides at the surface. This applies, for example, to the following steel grades:

Figure imgf000003_0001
Figure imgf000003_0001

Um die Haftung des Überzugs an der Bandoberfläche zu verbessern, ist in der DE 102 004 059 566 ein Verfahren beschrieben, bei dem das Band vor- oxidiert wird. Das in dieser Druckschrift beschriebene Verfahren kann wie folgt zu- sammengefasst werden: In order to improve the adhesion of the coating to the strip surface, DE 102 004 059 566 describes a process in which the strip is pre-oxidized. The method described in this document can be summarized as follows:

1. Erwärmen des Bandes unter reduzierender Atmosphäre, mit 2 bis 3 % Wasserstoffanteil, bis auf 650 bis 750°C; 1. heating the ribbon under reducing atmosphere, with 2 to 3% hydrogen content, up to 650 to 750 ° C;

2. Oxidieren der weitgehend aus Reineisen bestehenden Bandober- fläche in einer Reaktionskammer mit einer Atmosphäre mit 0,01 bis 1 % Sauerstoffanteil. Dabei wird eine Eisenoxidschicht gebil- det, welche die vorher gebildeten Legierungsoxide abdeckt. Die Behandlungsdauer soll 1 bis 10 sec und die Dicke der gebildeten Oxidschicht soll 300 nm betragen; 2. Oxidizing the strip surface, which largely consists of pure iron, in a reaction chamber having an atmosphere with 0.01 to 1% oxygen content. In this case, an iron oxide layer is formed, which covers the previously formed alloy oxides. The treatment time should be 1 to 10 sec and the thickness of the oxide layer formed should be 300 nm;

3. Glühen des Bandstahls unter reduzierender Atmosphäre mit 2 bis 8% Wasserstoffanteil bis auf maximal 900°C. Dabei wird die Ei- senoxidschicht wieder zu Reineisen reduziert, auf der dann das Überzugsmetall gut und sicher haftet. 3. annealing the strip steel under a reducing atmosphere with 2 to 8% hydrogen content up to a maximum of 900 ° C. In the process, the iron oxide layer is reduced again to pure iron, on which the coating metal then adheres well and securely.

Dabei befindet sich die Reaktionskammer, mit einer im Innern stark oxidierenden Atmosphäre, im Ofenraum eines Durchlaufofens mit einer wasser- stoffhaltigen, reduzierenden Atmosphäre. Bandeinlauf und Bandauslauf in die Re- aktionskammer müssen bestmöglich gegen Gasaustausch abgedichtet sein. Ein Gasübertritt vom Ofen in die Reaktionskammer bewirkt, dass der eindringende Wasserstoff den zur Oxidation benötigten Sauerstoff zumindest teilweise ver- braucht und die Beschaffenheit der angestrebten Oxidschicht auf der Bandoberflä- che beeinträchtigt. Dieses Problem verschärft sich, je geringer der Sauerstoffge- halt in der Reaktionskammer ist. Umgekehrt bewirkt ein Gasübertritt aus der Reak- tionskammer in den Ofen einen höheren Wassergehalt (Taupunkt) im Ofen und dadurch ein erhöhtes Oxidationspotential. Dieses ist insbesondere für höchstfeste Stähle mit einem höheren Anteil an sauerstoffaffinen Legierungselementen nach- teilig. In this case, the reaction chamber, with a strongly oxidizing atmosphere inside, is located in the furnace chamber of a continuous furnace with a hydrogen-containing, reducing atmosphere. The belt inlet and belt outlet into the reaction chamber must be sealed to the greatest possible extent against gas exchange. On Gas transfer from the furnace into the reaction chamber causes the penetrating hydrogen at least partially consumes the oxygen required for the oxidation and impairs the nature of the desired oxide layer on the strip surface. This problem is exacerbated by the lower the oxygen content in the reaction chamber. Conversely, a gas transfer from the reaction chamber into the furnace causes a higher water content (dew point) in the furnace and thus an increased oxidation potential. This is particularly disadvantageous for very high-strength steels with a higher content of oxygen-affine alloying elements.

Versuche haben ergeben, dass zur Einstellung einer gewünschten Oxidschicht die Bandtemperatur der zur Prozessführung entscheidende Parame- ter ist. Diese liegt vorzugsweise zwischen 650 und 750°C. Solange dabei der Sau- erstoffgehalt > 1 % und die Behandlungszeit > 1 s sind, ist deren Einfluss auf die Dicke der gebildeten Oxidschicht vernachlässigbar klein. Bei Sauerstoffgehalten im Bereich 2 bis 5% kann von einem unempfindlichen Prozess ausgegangen wer- den. Experiments have shown that for setting a desired oxide layer, the strip temperature is the decisive parameter for process control. This is preferably between 650 and 750 ° C. As long as the oxygen content is> 1% and the treatment time> 1 s, their influence on the thickness of the oxide layer formed is negligibly small. With oxygen contents in the range 2 to 5%, an insensitive process can be assumed.

Es ist daher Aufgabe der vorliegenden Erfindung, ein verbessertes Verfahren zur Voroxidation von hochfestem Bandstahl in einer Reaktionskammer innerhalb eines Ofenraums während der rekristallisierenden Glühung vor einer Schmelztauchbeschichtung zur Verfügung zu stellen. It is therefore an object of the present invention to provide an improved process for the pre-oxidation of high strength steel strip in a reaction chamber within a furnace chamber during the recrystallizing annealing prior to a hot dip coating.

Nach der Lehre der Erfindung wird diese Aufgabe durch die im An- spruch 1 angegebenen Merkmale gelöst, insbesondere dadurch, dass die Reakti- onskammer an einem Bandeintritt und einem Bandaustritt gegen Gasaustausch zwischen dem Ofenraum und der Reaktionskammer abgedichtet wird und ein Gas, das eine oxidierende Atmosphäre in der Reaktionskammer ausbildet, eingeleitet und das Gas innerhalb der Reaktionskammer in einem geschlossenen Kreislauf permanent umgewälzt wird, wobei dessen Zusammensetzung geregelt und Ver- luste durch Leckagen und Verbrauch ausgeglichen werden. According to the teachings of the invention, this object is achieved by the features specified in claim 1, in particular by sealing the reaction chamber at a belt inlet and a belt outlet against gas exchange between the furnace chamber and the reaction chamber and a gas which oxidizes Atmosphere in the reaction chamber is formed, introduced and the gas within the reaction chamber in a closed circuit is permanently circulated, the composition of which is regulated and losses compensated by leakage and consumption.

Auf diese Weise ist es möglich, eine besonders gleichmäßig ausge- bildete Oxidschicht auf der Bandoberfläche zu erzeugen, sodass Fehlstellen bei der sich anschließenden Schmelztauchbeschichtung vermieden werden und so die Qualität des Endprodukts verbessert und Ausschuss verringert wird. In this way, it is possible to produce a particularly uniformly formed oxide layer on the strip surface, so that defects in the subsequent hot-dip coating can be avoided, thus improving the quality of the final product and reducing rejects.

Die Reaktionskammer ist grundsätzlich zum Ofenraum hin und ins- besondere am Bandeintritt und Bandaustritt gegen Gasaustausch abgedichtet. The reaction chamber is in principle sealed towards the furnace chamber and in particular at the belt inlet and belt outlet against gas exchange.

Die Atmosphäre wird permanent umgewälzt. Das Gas wird dazu aus der Reaktionskammer abgesaugt, gekühlt, einem Ventilator zugeführt, mit frischer Luft angereichert und wieder in die Kammer eingespeist. Damit wird eine gute Ho- mogenität der Atmosphäre erreicht. The atmosphere is constantly being circulated. The gas is sucked out of the reaction chamber, cooled, fed to a fan, enriched with fresh air and fed back into the chamber. This achieves good atmospheric homogeneity.

Ein weiterer gewünschter Effekt ist, dass über Düsensysteme (min- destens ein Düsensystem) kontrolliert und gleichmäßig Gas mit hoher kinetischer Energiedichte unter Zuhilfenahme von Stickstoff als Trägergas der Bandoberflä- che zugeführt wird. Das ist notwendig, um laminare Grenzschichteffekte zu ver- meiden. Another desired effect is controlled by nozzle systems (at least one nozzle system) and evenly supplied gas with high kinetic energy density with the aid of nitrogen as the carrier gas of the strip surface. This is necessary in order to avoid laminar boundary layer effects.

Um einen ausreichenden Puffer gegen eindringenden Wasserstoff zu erreichen, beträgt der Sauerstoffgehalt der Atmosphäre in der Reaktionskammer minimal 1 ,5 bis maximal 5 vol%. In order to achieve a sufficient buffer against penetrating hydrogen, the oxygen content of the atmosphere in the reaction chamber is a minimum of 1.5 to a maximum of 5% by volume.

Zum Ausgleich von Volumenänderungen besitzt die Reaktionskam- mer einen Abzug. Vorzugsweise wird dieser Abzug so geregelt, dass der Innen- druck der Reaktionskammer dem Druck der umgebenden Ofenatmosphäre ent- spricht und so der Gasaustausch über die unvermeidlichen Undichtigkeiten mini- mal ist. To compensate for volume changes, the reaction chamber has a trigger. Preferably, this trigger is controlled so that the internal pressure of the reaction chamber corresponds to the pressure of the surrounding furnace atmosphere and so the gas exchange over the unavoidable leaks is minimal.

Durch diese Maßnahmen wird ein gutmütig beherrschbarer Oxidati- onsprozess erreicht und eine Beeinträchtigung der die Reaktionskammer umge- benden Ofenatmosphäre wird verhindert. As a result of these measures, a good-natured, controllable oxidation process is achieved and impairment of the furnace atmosphere surrounding the reaction chamber is prevented.

Der oxidationsempfindliche Stahl kann mindestens eine Auswahl fol gender Legierungsbestandteile enthalten: Mn > 0,5%, AI > 0,2%, Si > 0,1 %, Cr > 0,3%. The oxidation-sensitive steel may contain at least a selection of fol gender alloying components: Mn> 0.5%, Al> 0.2%, Si> 0.1%, Cr> 0.3%.

Claims

Patentansprüche claims 1. Verfahren zur Voroxidation von oxidationsempfindlichem Bandstahl in einer in einem Ofenraum angeordneten Reaktionskammer, gekennzeichnet dadurch, dass die Reaktionskammer an einem Bandeintritt und einem Band- austritt gegen Gasaustausch zwischen dem Ofenraum und der Reaktions- kammer abgedichtet wird und ein Gas, das eine oxidierende Atmosphäre in der Reaktionskammer ausbildet, eingeleitet und das Gas innerhalb der Re- aktionskammer in einem geschlossenen Kreislauf permanent umgewälzt wird, wobei dessen Zusammensetzung geregelt und Verluste durch Lecka- gen und Verbrauch ausgeglichen werden. 1. A method for pre-oxidation of oxidation-sensitive steel strip in a reaction chamber arranged in a furnace chamber, characterized in that the reaction chamber is sealed at a belt inlet and a belt outlet against gas exchange between the furnace chamber and the reaction chamber and a gas, the oxidizing atmosphere is formed in the reaction chamber, introduced and the gas within the reaction chamber in a closed circuit is permanently circulated, the composition of which is regulated and losses due to leakage and consumption are compensated. 2. Verfahren zur Voroxidation nach Anspruch 1 , dadurch gekennzeichnet, dass das oxidierende Gas aus der Reaktionskammer abgesaugt, gekühlt, einem Ventilator zugeführt, mit Luft angereichert und wieder in die Reakti- onskammer eingespeist wird, um eine gute Homogenität der Atmosphäre zu erreichen. 2. A method for pre-oxidation according to claim 1, characterized in that the oxidizing gas is sucked from the reaction chamber, cooled, fed to a fan, enriched with air and fed back into the reaction onskammer to achieve a good homogeneity of the atmosphere. 3. Verfahren zur Voroxidation nach Anspruch 2, dadurch gekennzeichnet, dass über mindestens ein der Reaktionskammer zugeordnetes Düsensys- tem kontrolliert und gleichmäßig das Gas mit hoher kinetischer Energiedich- te unter Zuhilfenahme von Stickstoff als Trägergas der Oberfläche des Bandstahls zugeführt wird, um laminare Grenzschichteffekte an der Band- oberfläche zu vermeiden. 3. A method for pre-oxidation according to claim 2, characterized in that controlled by at least one of the reaction chamber associated nozzle system and evenly the gas with high kinetic Energiedich- te with the aid of nitrogen as a carrier gas to the surface of the strip steel is supplied to laminar boundary layer effects avoid the tape surface. 4. Verfahren zur Voroxidation nach Anspruch 3, dadurch gekennzeichnet, dass der Sauerstoffgehalt der Atmosphäre in der Reaktionskammer bei minimal 1 ,5 bis maximal 5 vol% gehalten wird, um hierdurch einen ausrei- chend großen Puffer gegen aus dem Ofenraum in die Reaktionskammer eindringen Wasserstoff zu erreichen. 4. A method for pre-oxidation according to claim 3, characterized in that the oxygen content of the atmosphere in the reaction chamber is kept at a minimum of 1, 5 to a maximum of 5 vol%, to thereby hydrogen a sufficiently large buffer against penetrating from the furnace chamber in the reaction chamber to reach. 5. Verfahren zur Voroxidation nach einen oder mehreren der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass der Reaktionskammer zum Ausgleich von Volumenänderungen ein Abzug zugeordnet wird. 5. A method for pre-oxidation according to one or more of claims 1 to 4, characterized in that the reaction chamber to compensate for volume changes a deduction is assigned. 6. Verfahren zur Voroxidation nach Anspruch 5, dadurch gekennzeichnet, dass der Abzug vorzugsweise so geregelt wird, dass der Innendruck der Reaktionskammer dem Druck der umgebenden Ofenatmosphäre entspricht und so der Gasaustausch über unvermeidliche Undichtigkeiten minimal ge- halten wird. 6. A method for pre-oxidation according to claim 5, characterized in that the deduction is preferably controlled so that the internal pressure of the reaction chamber corresponds to the pressure of the surrounding furnace atmosphere and so the gas exchange is minimized via unavoidable leaks. 7. Verfahren nach einem oder mehreren der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass der oxidationsempfindliche Stahl mindestens eine Auswahl folgender Legierungsbestandteile enthält: Mn > 0,5%, AI > 0,2%, Si > 0,1 %, Cr > 0,3%. 7. The method according to one or more of claims 1 to 6, characterized in that the oxidation-sensitive steel contains at least one selection of the following alloying constituents: Mn> 0.5%, Al> 0.2%, Si> 0.1%, Cr> 0.3%.
PCT/EP2018/080242 2017-11-17 2018-11-06 Method for the preoxidation of strip steel in a reaction chamber arranged in a furnace chamber Ceased WO2019096616A1 (en)

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ES18807218T ES2942672T3 (en) 2017-11-17 2018-11-06 Procedure for the pre-oxidation of strip steel in a reaction chamber arranged in a furnace space
KR1020207017134A KR102445685B1 (en) 2017-11-17 2018-11-06 Method of pre-oxidation of strip steel in a reaction chamber arranged in a furnace chamber
CN201880074366.XA CN111356775B (en) 2017-11-17 2018-11-06 Method for pre-oxidizing strip steel in a reaction chamber arranged in a furnace chamber
PL18807218.5T PL3710605T3 (en) 2017-11-17 2018-11-06 Method for the preoxidation of strip steel in a reaction chamber arranged in a furnace chamber
FIEP18807218.5T FI3710605T3 (en) 2017-11-17 2018-11-06 Method for the preoxidation of strip steel in a reaction chamber arranged in a furnace chamber
EP18807218.5A EP3710605B1 (en) 2017-11-17 2018-11-06 Method for the preoxidation of strip steel in a reaction chamber arranged in a furnace chamber

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DE102004059566B3 (en) 2004-12-09 2006-08-03 Thyssenkrupp Steel Ag Process for hot dip coating a strip of high strength steel
EP2458022A1 (en) * 2010-11-30 2012-05-30 Tata Steel UK Limited Method of galvanising a steel strip in a continuous hot dip galvanising line
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