EP1673483B1 - Method for heat-treating iron-containing materials - Google Patents

Method for heat-treating iron-containing materials Download PDF

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Publication number
EP1673483B1
EP1673483B1 EP04765727A EP04765727A EP1673483B1 EP 1673483 B1 EP1673483 B1 EP 1673483B1 EP 04765727 A EP04765727 A EP 04765727A EP 04765727 A EP04765727 A EP 04765727A EP 1673483 B1 EP1673483 B1 EP 1673483B1
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European Patent Office
Prior art keywords
endogas
nitrogen
hearth furnace
roller hearth
continuous roller
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EP04765727A
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German (de)
French (fr)
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EP1673483B8 (en
EP1673483A1 (en
Inventor
Philippe Grognet
Hans-Peter Schmidt
Günter WAGENDORFER
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Messer Austria GmbH
Air Liquide Deutschland GmbH
Messer Group GmbH
Messer France SAS
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Messer Austria GmbH
Air Liquide Deutschland GmbH
Messer Group GmbH
Messer France SAS
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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
    • 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
    • C21D1/763—Adjusting the composition of the atmosphere using a catalyst
    • 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
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/613—Gases; Liquefied or solidified normally gaseous material

Definitions

  • the invention relates to a method for the heat treatment of iron materials, in particular for the annealing of pipes, profiles, wires, rods and sheets of metal or steel, in a heat treatment plant with a cooling tunnel and a boiler room under a protective gas atmosphere of endogas mixtures.
  • exogas When annealing pipes, profiles, wires, rods and sheets, exogas is often used as protective gas.
  • This protective gas is produced in exogas generators.
  • the premixed natural gas / air gas stream is fed to a combustion chamber and reacted there. Since the CH4 / air ratio is greater than 2.41 (eg 6.5), there is no need for external heating of the gas mixture to the reaction temperature.
  • the very moist exogas produced in this way is cooled to room temperature and fed to a dryer.
  • the dew point of the dried gas is then about -30 ° C (0.10 vol .-% H2O).
  • a typical exogas has a composition of 7% H2, 7% CO, 7% CO2, 0.10% H2O, balance N2.
  • the gas mixture is then fed to a heat treatment plant and it turns in the boiler room - at a temperature of greater than 400 ° C - abruptly a moist furnace gas.
  • Boiler room reaction CO2 + H2 ⁇ CO + H2O (homogeneous water gas reaction)
  • the carbon activity decreases to less than 1, thereby decarburizing the iron-carbon alloys during the heat treatment.
  • Exogas as a protective gas in heat treatment furnaces, which is why endogas is also used as a protective gas in the heat treatment of iron materials.
  • endogas generators The production of endogas takes place in endogas generators.
  • the premixed natural gas / air mixture is fed to a heated retort with catalyst filling and reacted there.
  • the endogas is produced from a hydrocarbon and air, eg according to the following reaction equation: CH4 + 2.41 (0.79 N2 + 0.21 O2) ⁇ CO + 2 H2 + 0.79 N2 + traces H2O and CO2
  • the generated endogas is cooled to room temperature and is then ready for use.
  • the dew point of the endogas used in the heat treatment of iron materials as a protective gas is in the range of - 10 ° C and + 5 ° C with 0.30 to 0.86 Vol .-% H2O.
  • Endogenous gas commonly used in the conventional heat treatment of metals as inert gas has a composition of: 40% H2, 20% CO, 0.30% CO2, 0.86% H2O, balance N2.
  • This "pure” endogas is diluted with nitrogen and then added to the heat treatment equipment, e.g. a roller hearth furnace, fed.
  • the heat treatment equipment e.g. a roller hearth furnace
  • EP 0261461 A discloses a method for heat treating metallic materials in a continuous hearth furnace in a protective gas atmosphere, wherein endogas is generated by an internal gas generator, and in addition nitrogen is supplied on both sides of the treatment gas supply point.
  • the invention is therefore based on the object to provide a method for heat treatment of iron materials available, with which can be improved and made safer by a targeted inert gas metering of the heat treatment process.
  • the object is achieved by a method for heat treatment of iron materials with the features of claim 1.
  • pure gas or partially nitrogen-diluted endogas and additionally pure nitrogen are fed separately as protective gas into different regions of the heat treatment plant.
  • the endogas will enter the boiler room end, i. in the opposite end of the Schuraumeinlauf end of the boiler room, fed transversely to the transport direction of the heat treatment and additional nitrogen in different areas of the cooling tunnel of the heat treatment plant by means of conventional nozzle devices.
  • the inert gas entry into the heat treatment plant according to the invention causes the formation of a flow profile oriented to the heating chamber inlet, whereby a high protective gas concentration in the heating chamber and a much lower inert gas concentration in the cooling tunnel of the heat treatment plant is present.
  • the endogas produced in an external endogas generator and fed into the heat treatment plant has a slightly higher dew point (+5 to +10 ° C) than the endogas used in the conventional procedure (maximum dew point + 5 ° C).
  • the higher dew point temperature causes an increase in the service life of the catalyst and the retort of the heat treatment plant, since the risk of soot deposition in the catalyst bed is lower, thus preventing overheating of the catalyst during the necessary Rußabbrete to regenerate the catalyst.
  • the dosing quantity of endogas required for the respective heat treatment process is set automatically by means of a metering valve as a function of the respective process conditions, whereby the excess amount of endogas can be minimized and, in addition, as little endogas as possible has to be flared.
  • the dosing time of the endogas and nitrogen is detected in the usual way and is used to calculate the actual oxygen and carbon activities during the heat treatment process.
  • the endogas is mixed with a partial amount of nitrogen in an endomat arranged outside the heat treatment plant.
  • the endogas is introduced at an overpressure of 40 to 60 mbar through a, arranged in the nitrogen pipe, advantageously L-shaped tube formed in the means of a Feinbuchreglers to an excess pressure of 20 to 30 mbar regulated nitrogen.
  • the metered amount of natural gas and air is changed so that the required dosage of endogas reduced and / or the natural gas / air ratio is changed, whereby the composition of the endogases is adversely affected.
  • soot By changing the mixing ratio, soot can deposit in the catalyst, whereby the effectiveness of the catalyst is reduced. If the air supply is too high, the dew point rises unintentionally, so that overheating can occur at the beginning of the catalytic converter.
  • the nitrogen is introduced into different regions of the cooling tunnel of the heat treatment plant, but particularly advantageously injected into the cooling tunnel region arranged in front of the heating chamber inlet and into the cooling tunnel region arranged upstream of the cooling tunnel outlet.
  • the protective gas entry according to the invention an optimal concentration profile of the protective gas in the heating and cooling chamber of the heat treatment plant is adjusted and at the same time prevents the unwanted influx of atmospheric oxygen into the cooling tunnel of the heat treatment plant.
  • the heat treatment plant is equipped with a lambda probe arranged at the cooling tunnel outlet, by means of which the inflow of environmental pleasure, as well as the nitrogen feed, can be detected.
  • the cooling capacity of the cooling tunnel can be further increased.
  • the liquid nitrogen having a temperature of -196 ° C is advantageously introduced into the last third of the cooling tunnel, i. in the cooling tunnel area closest to the cooling tunnel outlet for lowering the outlet temperature of the heat treatment material transported out of the heating room or into the first third of the cooling tunnel, i. entered into the cooling tunnel entrance nearest cooling tunnel area to increase the cooling rate of the heat treatment material for hardening purposes.
  • the convection of the protective gas is significantly improved and also allows the heating enthalpy of the nitrogen, a faster cooling of the heat-treated workpieces.
  • thermocouple located at the heat treatment plant - process gas is taken to determine the optimum concentration profile of shielding gas over the entire plant length.
  • the gas sampling device can also be equipped with a gas analyzer, a lambda probe or other measuring systems, whereby no additional gas sampling points are required at the heat treatment plant.
  • the electronically determined measured values are used for the automatic protective gas control at a gas composition deviating from a predetermined nominal value.
  • the protective gas concentration in the heating chamber of the heat treatment plant is increased by about 50 to 60 percent, so that the entry amount of endogas can be reduced by about 30 to 40 percent.
  • the protective gas entry according to the invention forms a reaction front, which flows counter to the heat treatment material, ie, the partially reacted end gas escapes via the heating chamber inlet and thus only nitrogen-added endogas flows into the cooling tunnel, whereby the undesired oxidation of iron in the cooling tunnel of the heat treatment plant is substantially reduced because the H2O / H2 ratio in the cooling tunnel is much lower than in the boiler room of the heat treatment plant.
  • the protective gas in the cooling tunnel has a significantly lower dew point (for example -7 degrees Celsius) than in the heating chamber (for example +10 degrees Celsius) prevents water condensation in the cooling tunnel of the heat treatment plant.
  • the kinetics of carburizing or recarbonization during the heat treatment are greater, so that the residence time of the heat treatment material in the heating chamber is substantially reduced.
  • the kinetics of the reduction of iron oxide to hot-deformed iron alloys such as e.g. Wires, pipes, profiles, especially large, so that their oxide layers are completely reduced.
  • the oxide-free workpieces can then be machined with reduced effort, e.g. pickled, are and have a surface quality that meets the increasing demands.
  • the endogas used according to the invention for heat treatment also has a much higher "reduction power" than conventionally used exogas, ie it can form and absorb more water and carbon dioxide without the reduction being stopped becomes.
  • the higher concentration of hydrogen (H2) and carbon monoxide (CO) in the boiler room of the heat treatment plant results in a higher heat-up rate of the heat treatment than when using a conventional protective gas of exogas or monogas (N2 less than 5% H2).
  • the endogas and nitrogen feed according to the invention has the significant advantage that a concentration profile of the reactive components is advantageously established, whereby the risk of explosion is reduced and the reaction kinetics and Auffilge-speed are optimized.
  • Fig. 1 the controllability of the carbon activity of exogas and endogas (endolin) is shown in the heat treatment of typical iron-carbon alloys with a carbon content of 0.15 to 0.70%.
  • the carbon activities a c of a conventional shielding gas (exogas) and of several shielding gases (endogas in the form of endoline) with 1 to 5% CO are compared.
  • the nitrogen gas added endogenous gas must be added to the carbon activity a c to the value of 1 gas, preferably propane, because of its significantly better reactivity with water and carbon dioxide.
  • the carbon activity in the heating chamber gas can be increased by lowering the dew point in the generated endogenous gas at the endogenerator, since the carbon activity in the mixed gas increases with decreasing water concentration in the endogas.
  • Fig. 2 shows a furnace (boiler room) with cooling tunnel, which once endogas with a quantity of nitrogen premixed in the last third of the boiler room and the main amount of pure nitrogen in the middle / last third of the cooling tunnel are fed (variant 2).
  • variants 1 and 3 different amounts of endogas (10 and 30 m3 / h) are mixed with nitrogen externally of the furnace and fed completely into the feed point in the boiler room, ie the same concentrations of hydrogen and carbon monoxide prevail at each point in the boiler room and cooling tunnel have to. In all 3 variants is the Total amount of gas always kept constant at 140 m3 / h. With variant 2 results in external complete mixture of endogas and nitrogen, a hydrogen concentration of 5.8 vol .-% H2, ie, the explosion limit of 5 vol .-% H2, CO is significantly exceeded.
  • Variant 3 illustrates that it is only possible with a small amount of endogas (10m3 / h) to realize the safety condition of less than 5% by volume H2, CO. According to variant 2, the aspects of safety and the highest possible H2, CO concentration in the boiler room are thus realized.

Abstract

The invention relates to a method for heat-treating, in a protective atmosphere from endothermic gas mixtures, iron-containing materials, especially for annealing tubes, profiles, wires, rods and sheets that consist of metal or steel, in a heat-treating installation that comprises a cooling tunnel and a heating chamber. According to the invention, pure endothermic gas or endothermic gas partially rarefied with nitrogen and additionally pure nitrogen are supplied separately and in different areas of the installation, thereby reducing the time and costs required for the heat treatment process, increasing product quality and allowing for a safe process conduction. The flow profile generated throughout the entire furnace preferably in the heating chamber feed direction considerably reduces the deposition of solids in the cooling tunnel and the heating chamber end.

Description

Die Erfindung betrifft ein Verfahren zur Wärmebehandlung von Eisenwerkstoffen, insbesondere zum Glühen von Rohren, Profilen, Drähten, Stäben und Blechen aus Metall oder Stahl, in einer Wärmebehandlungsanlage mit einem Kühltunnel und einem Heizraum unter einer Schutzgasatmosphäre aus Endogas-Gemischen.The invention relates to a method for the heat treatment of iron materials, in particular for the annealing of pipes, profiles, wires, rods and sheets of metal or steel, in a heat treatment plant with a cooling tunnel and a boiler room under a protective gas atmosphere of endogas mixtures.

Beim Glühen von Rohren, Profilen, Drähten, Stäben und Blechen wird oftmals Exogas als Schutzgas eingesetzt. Dieses Exogas wird aus einem Kohlenwasserstoff und Luft hergestellt,
z. B.:

        CH4 + x (0,79 N2 + 0,21 O2) → CO + CO2 + H2 + H2O + N2

wobei Wert x von >2,41 und <9,64 (λ = >0,25 bis 1,00) liegt.When annealing pipes, profiles, wires, rods and sheets, exogas is often used as protective gas. This exogas is made from a hydrocarbon and air,
z. B .:

CH4 + x (0.79 N2 + 0.21 O2) → CO + CO2 + H2 + H2O + N2

where value x is> 2.41 and <9.64 (λ => 0.25 to 1.00).

Die Herstellung dieses Schutzgases erfolgt in Exogasgeneratoren.This protective gas is produced in exogas generators.

Dazu wird der vorgemischte Erdgas/Luft-Gasstrom einer Brennkammer zugeführt und dort zur Reaktion gebracht. Da das CH4/Luft-Verhältnis größer 2,41 (z. B. 6,5) ist, braucht kein externes Aufheizen des Gasgemisches auf Reaktionstemperatur erfolgen.For this purpose, the premixed natural gas / air gas stream is fed to a combustion chamber and reacted there. Since the CH4 / air ratio is greater than 2.41 (eg 6.5), there is no need for external heating of the gas mixture to the reaction temperature.

Es handelt sich hierbei um eine exotherme Reaktion, die Wärmeenergie im Überschuss erzeugt. Das so erzeugte, sehr feuchte Exogas wird auf Raumtemperatur abgekühlt und einem Trockner zugeführt. Der Taupunkt des getrockneten Gases beträgt dann ca. -30°C (0,10 Vol.-% H2O).It is an exothermic reaction that generates excess thermal energy. The very moist exogas produced in this way is cooled to room temperature and fed to a dryer. The dew point of the dried gas is then about -30 ° C (0.10 vol .-% H2O).

Ein typisches Exogas hat eine Zusammensetzung von 7% H2, 7% CO, 7% CO2, 0,10% H2O, Rest N2.A typical exogas has a composition of 7% H2, 7% CO, 7% CO2, 0.10% H2O, balance N2.

Das Gasgemisch wird dann einer Wärmebehandlungsanlage zugeführt und es stellt sich in deren Heizraum - bei einer Temperatur von größer 400°C - schlagartig ein feuchtes Ofengas ein.
Heizraumreaktion: CO2 + H2 → CO + H2O (homogene Wassergasreaktion)The gas mixture is then fed to a heat treatment plant and it turns in the boiler room - at a temperature of greater than 400 ° C - abruptly a moist furnace gas.
Boiler room reaction: CO2 + H2 → CO + H2O (homogeneous water gas reaction)

Im Heizraum verringert sich bei einer Temperatur von größer 650°C die Kohlenstoffaktivität auf kleiner 1, wodurch die Eisen-Kohlenstoff-Legierungen während der Wärmebehandlung entkohlt werden.In the boiler room, at a temperature greater than 650 ° C, the carbon activity decreases to less than 1, thereby decarburizing the iron-carbon alloys during the heat treatment.

Aufgrund der steigenden Qualitätsansprüche an die Fertigprodukte ist aber eine Entkohlung unerwünscht. Es besteht sogar im zunehmenden Maße der Wunsch nach einer Rückkohlung von entkohlten Eisen-Kohlenstoff-Legierungen während der Wärmebe-handlung (Glühen).Because of the increasing quality demands on the finished products, however, decarburization is undesirable. There is even an increasing desire to recarburize decarburized iron-carbon alloys during heat treatment (annealing).

Diese Qualitätsanforderungen sind mit dem Einsatz von Exogas als Schutzgas in Wärmebehandlungsöfen nicht zu realisieren, weshalb auch Endogas als Schutzgas bei der Wärmehandlung von Eisenwerkstoffen zum Einsatz kommt.These quality requirements can not be realized with the use of Exogas as a protective gas in heat treatment furnaces, which is why endogas is also used as a protective gas in the heat treatment of iron materials.

Die Herstellung von Endogas erfolgt in Endogasgeneratoren. Dazu wird das vorgemischte Erdgas/Luftgemisch einer beheizten Retorte mit Katalysatorfüllung zugeführt und dort zur Reaktion gebracht.The production of endogas takes place in endogas generators. For this purpose, the premixed natural gas / air mixture is fed to a heated retort with catalyst filling and reacted there.

Da das CH4/Luft-Verhältnis wenig größer 2,41 (λ = 0,26 - 0,28) ist, muss die Katalysatorretorte aufgeheizt und das durch die Retorte strömende Gasgemisch auf Reaktionstemperatur gebracht werden, um auf der Katalysatoroberfläche zu reagieren.Since the CH4 / air ratio is slightly greater than 2.41 (λ = 0.26-0.28), the catalyst retort must be heated and the gas mixture flowing through the retort be brought to the reaction temperature to react on the catalyst surface.

Es handelt sich hierbei um eine endotherme Reaktion, d.h., ein Teil der Aufheiz- und die gesamte Reaktionsenthalpie muss dem System zugeführt werden.This is an endothermic reaction, i.e., part of the heating and total reaction enthalpy must be supplied to the system.

Das Endogas wird aus einem Kohlenwasserstoff und Luft, z.B. nach folgender Reaktionsgleichung hergestellt:

        CH4 + 2,41 (0,79 N2 + 0,21 O2) → CO + 2 H2 + 0,79 N2 + Spuren H2O und CO2

The endogas is produced from a hydrocarbon and air, eg according to the following reaction equation:

CH4 + 2.41 (0.79 N2 + 0.21 O2) → CO + 2 H2 + 0.79 N2 + traces H2O and CO2

Das erzeugte Endogas wird auf Raumtemperatur abgekühlt und ist dann einsatzbereit.The generated endogas is cooled to room temperature and is then ready for use.

Der Taupunkt des bei der Wärmebehandlung von Eisenwerkstoffen als Schutzgas eingesetzten Endogases liegt im Bereich von - 10°C und +5°C mit 0,30 bis 0,86 Vol.-% H2O.The dew point of the endogas used in the heat treatment of iron materials as a protective gas is in the range of - 10 ° C and + 5 ° C with 0.30 to 0.86 Vol .-% H2O.

Ein bei der herkömmlichen Wärmebehandlung von Metallen als Schutzgas häufig eingesetztes Endogas hat eine Zusammensetzung von: 40% H2, 20% CO, 0,30% CO2, 0,86% H2O, Rest N2.Endogenous gas commonly used in the conventional heat treatment of metals as inert gas has a composition of: 40% H2, 20% CO, 0.30% CO2, 0.86% H2O, balance N2.

Dieses "reine" Endogas wird mit Stickstoff verdünnt (versetzt) und anschließend der Wärmebehandlungsanlage, z.B. einem Rollenherddurchlauf-Ofen, zugeführt.This "pure" endogas is diluted with nitrogen and then added to the heat treatment equipment, e.g. a roller hearth furnace, fed.

Bei diesen Schutzgasgemischen mit 1 bis 5% CO sinkt - aufgrund der starken Verdünnung mit Stickstoff - der Taupunkt auf Werte von -20 bis -30°C, so dass der Einsatz eines zusätzlichen Trockners, wie bei der Exogaserzeugung, nicht notwendig ist.With these shielding gas mixtures with 1 to 5% CO - due to the strong dilution with nitrogen - the dew point drops to values of -20 to -30 ° C, so that the use of an additional dryer, as in the Exogaserzeugung, is not necessary.

Dokument EP 0261461 A offenbart ein Verfahren zur Wärmebehandlung von metallischen Werkstoffen in einem Rollenherddurchlaufofen unter Schutzgasatmosphäre, wobei Endogas durch einen innenliegenden Gasgenerator erzeugt wird, und zusätzlich Stickstoff beidseitig der Zuführungsstelle für das Behandlungsgas zugeführt wird.document EP 0261461 A discloses a method for heat treating metallic materials in a continuous hearth furnace in a protective gas atmosphere, wherein endogas is generated by an internal gas generator, and in addition nitrogen is supplied on both sides of the treatment gas supply point.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren zur Wärmebehandlung von Eisenwerkstoffen zur Verfügung zu stellen, mit welchem durch eine gezielte Schutzgasdosierung der Wärmebehandlungsprozess verbessert und sicherer gestaltet werden kann.The invention is therefore based on the object to provide a method for heat treatment of iron materials available, with which can be improved and made safer by a targeted inert gas metering of the heat treatment process.

Die Aufgabe wird erfindungsgemäß durch ein Verfahren zur Wärmebehandlung von Eisenwerkstoffen mit den Merkmalen von Anspruch 1 gelöst.The object is achieved by a method for heat treatment of iron materials with the features of claim 1.

Die die Erfindung ausgestaltenden Merkmale sind den Unteransprüchen zu entnehmen.The features of the invention ausgestaltenden can be found in the dependent claims.

Erfindungsgemäß wird als Schutzgas reines Endogas oder teilweise mit Stickstoff verdünntes Endogas und zusätzlich reiner Stickstoff separat voneinander in unterschiedlichen Bereichen der Wärmebehandlungsanlage eingespeist.According to the invention, pure gas or partially nitrogen-diluted endogas and additionally pure nitrogen are fed separately as protective gas into different regions of the heat treatment plant.

Vorteilhaft wird das Endogas in das Heizraumende, d.h. in den dem Heizraumeinlauf gegenüberliegenden endseitigen Bereich des Heizraums, quer zur Transportrichtung des Wärmebehandlungsguts und zusätzlich Stickstoff in unterschiedlichen Bereichen des Kühltunnels der Wärmebehandlungsanlage mittels herkömmlicher Düsenvorrichtungen eingespeist.Advantageously, the endogas will enter the boiler room end, i. in the opposite end of the Heizraumeinlauf end of the boiler room, fed transversely to the transport direction of the heat treatment and additional nitrogen in different areas of the cooling tunnel of the heat treatment plant by means of conventional nozzle devices.

Der erfindungsgemäße Schutzgaseintrag in die Wärmebehandlungsanlage bewirkt die Ausbildung eines zum Heizraumeinlauf ausgerichteten Strömungsprofils, wodurch eine hohe Schutzgaskonzentration im Heizraum und eine wesentlich niedrigere Schutzgaskonzentration im Kühltunnel der Wärmebehandlungsanlage vorliegt.The inert gas entry into the heat treatment plant according to the invention causes the formation of a flow profile oriented to the heating chamber inlet, whereby a high protective gas concentration in the heating chamber and a much lower inert gas concentration in the cooling tunnel of the heat treatment plant is present.

Das in einem externen Endogasgenerator erzeugte und in die Wärmebehandlungsanlage eingespeiste Endogas weist einen etwas höheren Taupunkt (+5 bis +10°C) als das bei der herkömmlichen Verfahrensweise eingesetzte Endogas (Taupunkt maximal +5°C) auf.The endogas produced in an external endogas generator and fed into the heat treatment plant has a slightly higher dew point (+5 to +10 ° C) than the endogas used in the conventional procedure (maximum dew point + 5 ° C).

Die höhere Taupunkttemperatur bewirkt eine Erhöhung der Standzeit des Katalysators und der Retorte der Wärmebehandlungsanlage, da die Gefahr der Russabscheidung im Katalysatorbett geringer ist und somit Überhitzungen des Katalysators beim notwendigen Russabbrennen zum Regenerieren des Katalysators verhindert werden.The higher dew point temperature causes an increase in the service life of the catalyst and the retort of the heat treatment plant, since the risk of soot deposition in the catalyst bed is lower, thus preventing overheating of the catalyst during the necessary Rußabbrennen to regenerate the catalyst.

Die für den jeweiligen Wärmebehandlungsprozess erforderliche Dosiermenge an Endogas wird mittels eines Dosierventils in Abhängigkeit von den jeweiligen Prozessbedingungen automatisch eingestellt, wodurch die Überschussmenge an Endogas minimiert werden kann und zudem möglichst wenig Endogas abgefackelt werden muss.The dosing quantity of endogas required for the respective heat treatment process is set automatically by means of a metering valve as a function of the respective process conditions, whereby the excess amount of endogas can be minimized and, in addition, as little endogas as possible has to be flared.

Die Dosierzeit von dem Endogas und dem Stickstoff wird auf übliche Weise erfasst und findet zur Berechnung der aktuellen Sauerstoff- und Kohlenstoffaktivitäten während des Wärmebehandlungsprozesses Verwendung.The dosing time of the endogas and nitrogen is detected in the usual way and is used to calculate the actual oxygen and carbon activities during the heat treatment process.

Um die Konvektion des Endogases im Heizraum der Wärmebehandlungsanlage zu verbessern, wird das Endogas - in einem außerhalb der Wärmebehandlungsanlage angeordneten Endomat - mit einer Teilmenge an Stickstoff gemischt.In order to improve the convection of the endogases in the boiler room of the heat treatment plant, the endogas is mixed with a partial amount of nitrogen in an endomat arranged outside the heat treatment plant.

Zur möglichst schnellen homogenen Gasgemischbildung wird das Endogas mit einem Überdruck von 40 bis 60 mbar durch ein, in die Stickstoff-Rohrleitung angeordnetes, vorteilhaft L-förmig ausgebildetes Rohr, in den mittels eines Feindruckreglers auf einen Überdruck von 20 bis 30 mbar geregelten Stickstoff eingetragen.For the fastest possible homogeneous gas mixture formation, the endogas is introduced at an overpressure of 40 to 60 mbar through a, arranged in the nitrogen pipe, advantageously L-shaped tube formed in the means of a Feindruckreglers to an excess pressure of 20 to 30 mbar regulated nitrogen.

Bei einem erhöhten Staudruck in der Stickstoff-Endogas-Leitung wird die Dosiermenge an Erdgas und Luft so verändert, dass die erforderliche Dosiermenge an Endogas verringert und/oder das Erdgas/Luft Verhältnis verändert wird, wodurch die Zusammensetzung des Endogases negativ verändert wird.At an increased dynamic pressure in the nitrogen endogas line, the metered amount of natural gas and air is changed so that the required dosage of endogas reduced and / or the natural gas / air ratio is changed, whereby the composition of the endogases is adversely affected.

Durch die Änderung des Mischungsverhältnisses kann sich Russ im Katalysator abscheiden, wodurch die Wirksamkeit des Katalysators gemindert wird. Bei zuviel Luftzufuhr steigt der Taupunkt ungewollt an, so dass eine Überhitzung am Katalysatoranfang auftreten kann.By changing the mixing ratio, soot can deposit in the catalyst, whereby the effectiveness of the catalyst is reduced. If the air supply is too high, the dew point rises unintentionally, so that overheating can occur at the beginning of the catalytic converter.

Der Eintrag des zusätzlichen Stickstoffs in den Kühltunnel der Wärmebehandlungsanlage erfolgt mittels üblicher Düsen, vorteilhaft aber mittels eines herkömmlichen Düsenstocks.The entry of additional nitrogen in the cooling tunnel of the heat treatment plant by means of conventional nozzles, but advantageously by means of a conventional nozzle assembly.

Vorteilhaft wird der Stickstoff in unterschiedlichen Bereichen des Kühltunnels der Wärmebehandlungsanlage eingetragen, besonders vorteilhaft aber in den vor dem Heizraumeinlauf angeordneten Kühltunnelbereich und in den vor dem Kühltunnelauslauf angeordneten Kühltunnelbereich eingedüst.Advantageously, the nitrogen is introduced into different regions of the cooling tunnel of the heat treatment plant, but particularly advantageously injected into the cooling tunnel region arranged in front of the heating chamber inlet and into the cooling tunnel region arranged upstream of the cooling tunnel outlet.

Durch den erfindungsgemäßen Schutzgaseintrag wird ein optimales Konzentrationsprofil des Schutzgases im Heiz- und Kühlraum der Wärmebehandlungsanlage eingestellt und gleichzeitig das unerwünschte Einströmen von Luftsauerstoff in den Kühltunnel der Wärmebehandlungsanlage verhindert.The protective gas entry according to the invention an optimal concentration profile of the protective gas in the heating and cooling chamber of the heat treatment plant is adjusted and at the same time prevents the unwanted influx of atmospheric oxygen into the cooling tunnel of the heat treatment plant.

Zweckmäßigerweise ist die Wärmebehandlungsanlage mit einer am Kühltunnelauslauf angeordneten Lambda-Sonde ausgerüstet, mittels der das Einströmen von Umgebungslust, ebenso wie die Stickstoffeinspeisung, erfasst werden kann.Expediently, the heat treatment plant is equipped with a lambda probe arranged at the cooling tunnel outlet, by means of which the inflow of environmental pleasure, as well as the nitrogen feed, can be detected.

Um eine zum Heizraumeinlauf gerichtete Schutzgasströmung zu erhalten, werden die abdampfenden flüchtigen Bestandteile, der sich bei der Wärmebehandlung zersetzenden Hilfsschichten (Phosphate, Borate, Oxalate u.a.) und Ziehmittelrückstande des Wärmebehandlungsguts zum Heizraumeinlauf transportiert und dort abgefackelt.In order to obtain a directed to Heizraumeinlauf protective gas flow, the evaporating volatiles, which are transported in the heat treatment decomposing auxiliary layers (phosphates, borates, oxalates, etc.) and drawing agent residue of the heat treatment to Heizraumeinlauf and flared there.

Durch die nachfolgende Kondensation der abgedampften Bestandteile des Behandlungsguts an den kalten Wänden der wassergekühlten Kühlregister wird die Kühlleistung wesentlich verringert, so dass die Kühleinrichtungen in größeren Zeitabständen gereinigt werden müssen. Dies wird durch die neue Gastechnik verhindert bzw. stark verringert.The subsequent condensation of the evaporated components of the material to be treated on the cold walls of the water-cooled cooling coil, the cooling capacity is significantly reduced, so that the cooling devices must be cleaned at longer intervals. This is prevented or greatly reduced by the new gas technology.

Durch die Erfindung wird der zeitliche, personelle und finanzielle Aufwand bei der Wärmebehandlung von Eisenwerkstoffen wesentlich verringert und eine sichere Prozessführung möglich.Due to the invention, the time, personnel and financial expense in the heat treatment of ferrous materials is substantially reduced and a secure process management possible.

Durch den Eintrag von tiefkaltem flüssigem Stickstoff in den Kühltunnel der Wärmebehandlungsanlage kann die Kühlleistung des Kühltunnels weiter erhöht werden.By introducing cryogenic liquid nitrogen into the cooling tunnel of the heat treatment plant, the cooling capacity of the cooling tunnel can be further increased.

Der eine Temperatur von -196°C aufweisende flüssige Stickstoff wird vorteilhaft in das letzte Drittel des Kühltunnels, d.h. in den dem Kühltunnelauslauf nächstliegenden Kühltunnelbereich zur Senkung der Austrittstemperatur des aus dem Heizraum transportierten Wärmebehandlungsguts oder in das erste Drittel des Kühltunnels, d.h. in den Kühltunneleinlauf nächstliegenden Kühltunnelbereich zur Erhöhung der Abkühlgeschwindigkeit des Wärmebehandlungsguts zu Härtezwecke eingetragen.The liquid nitrogen having a temperature of -196 ° C is advantageously introduced into the last third of the cooling tunnel, i. in the cooling tunnel area closest to the cooling tunnel outlet for lowering the outlet temperature of the heat treatment material transported out of the heating room or into the first third of the cooling tunnel, i. entered into the cooling tunnel entrance nearest cooling tunnel area to increase the cooling rate of the heat treatment material for hardening purposes.

Durch die zusätzliche Dosierung von tiefkaltem flüssigen Stickstoff in die Wärmebehandlungsanlage wird die Konvektion des Schutzgases wesentlich verbessert und zudem durch die Aufheizenthalpie des Stickstoffs, eine schnellere Abkühlung der wärmebehandelten Werkstücke ermöglicht.Due to the additional dosage of cryogenic liquid nitrogen in the heat treatment plant, the convection of the protective gas is significantly improved and also allows the heating enthalpy of the nitrogen, a faster cooling of the heat-treated workpieces.

Durch eine entsprechend dem jeweiligen Einsatzzweck ausgebildete und an der Wärmebehandlungsanlage zweckentsprechend angeordnete Gasentnahmeeinrichtung kann - an jedem an der Wärmebehandlungsanlage angeordneten Thermoelement - Prozessgas zur Bestimmung des optimalen Konzentrationsprofils von Schutzgas über die gesamte Anlagenlänge entnommen werden.By a trained according to the particular application and appropriately arranged on the heat treatment system gas sampling device can - at each thermocouple located at the heat treatment plant - process gas is taken to determine the optimum concentration profile of shielding gas over the entire plant length.

Die Gasentnahmeeinrichtung kann zudem mit einem Gasanalysengerät, einer Lambda-Sonde oder anderen Meßsystemen ausgerüstet sein, wodurch keine zusätzliche Gasentnahmestellen an der Wärmebehandlungsanlage erforderlich sind.The gas sampling device can also be equipped with a gas analyzer, a lambda probe or other measuring systems, whereby no additional gas sampling points are required at the heat treatment plant.

Durch ein mit der Gasentnahmeeinrichtung gekoppeltes Meßsystem werden (taktweise) alle Messstellen angesteuert und die aktuelle Gaszusammensetzung gemessen.By means of a measuring system coupled to the gas sampling device, all measuring points are controlled (intermittently) and the current gas composition is measured.

Die elektronisch ermittelten Messwerte finden zur automatischen Schutzgasregelung bei einer von einem vorgegebenen Sollwert abweichenden Gaszusammensetzung Verwendung.The electronically determined measured values are used for the automatic protective gas control at a gas composition deviating from a predetermined nominal value.

Durch die erfindungsgemäße Schutzgasdosierung wird die Schutzgaskonzentration im Heizraum der Wärmebehandlungsanlage um etwa 50 bis 60 Prozent erhöht, so dass die Eintragsmenge an Endogas um etwa 30 bis 40 Prozent verringert werden kann.Due to the protective gas metering according to the invention, the protective gas concentration in the heating chamber of the heat treatment plant is increased by about 50 to 60 percent, so that the entry amount of endogas can be reduced by about 30 to 40 percent.

Zudem wird gewährleistet, dass die Summe der Konzentration an Kohlenmonoxid (CO) und Wasserstoff (H2) im Kühltunnelende kleiner als 5 Volumen-Prozent ist und damit unter der Explosionsgrenze des Schutzgases liegt. Dieses ist besonders wichtig, da die Schutzgastemperatur im Auslaufbereich der Wärmebehandlungsanlage annähernd Raumtemperatur aufweist und damit die Sicherheitstemperatur von 750°C weit unterschritten wird.In addition, it ensures that the sum of the concentration of carbon monoxide (CO) and hydrogen (H2) in the cooling tunnel end is less than 5% by volume, which is below the explosion limit of the protective gas. This is particularly important because the protective gas temperature in the outlet area of the heat treatment plant has approximately room temperature and thus far below the safety temperature of 750 ° C.

Durch den erfindungsgemäßen Schutzgaseintrag bildet sich eine - dem Wärmebehandlungsgut entgegenströmende Reaktionsfront aus, d.h., dass das teilweise reagierte Endogas über den Heizraumeinlauf entströmt und somit nur mit Stickstoff versetztes Endogas in den Kühltunnel einströmt, wodurch die unerwünschte Oxidation von Eisen im Kühltunnel der Wärmebehandlungsanlage wesentlich verringert wird, da das H2O/H2-Verhältnis im Kühltunnel viel niedriger als im Heizraum der Wärmebehandlungsanlage ist.The protective gas entry according to the invention forms a reaction front, which flows counter to the heat treatment material, ie, the partially reacted end gas escapes via the heating chamber inlet and thus only nitrogen-added endogas flows into the cooling tunnel, whereby the undesired oxidation of iron in the cooling tunnel of the heat treatment plant is substantially reduced because the H2O / H2 ratio in the cooling tunnel is much lower than in the boiler room of the heat treatment plant.

Dadurch, dass das Schutzgas im Kühltunnel einen deutlich niedrigeren Taupunkt (z.B. -7 Grad Celsius) als im Heizraum (z.B. +10 Grad Celsius) aufweist, wird eine Wasserkondensation im Kühltunnel der Wärmebehandlungsanlage verhindert.The fact that the protective gas in the cooling tunnel has a significantly lower dew point (for example -7 degrees Celsius) than in the heating chamber (for example +10 degrees Celsius) prevents water condensation in the cooling tunnel of the heat treatment plant.

Aufgrund der hohen Endogaskonzentration im Heizraum der Wärmebehandlungsanlage ist die Kinetik der Auf- oder Rückkohlung während der Wärmebehandlung größer, so dass die Verweilzeit des Wärmebehandlungsguts in Heizraum wesentlich verringert wird.Due to the high concentration of endogas in the heating chamber of the heat treatment plant, the kinetics of carburizing or recarbonization during the heat treatment are greater, so that the residence time of the heat treatment material in the heating chamber is substantially reduced.

Zudem ist durch die hohe Konzentration an Endogas im Heizraum der Wärmebehandlungsanlage die Kinetik der Reduktion von Eisenoxid auf warmverformten Eisenlegierungen, wie z.B. Drähten, Rohren, Profilen, besonders groß, so dass deren Oxidschichten vollständig reduziert werden. Die oxidfreien Werkstücke können anschließend mit verringertem Aufwand bearbeitet, wie z.B. gebeizt, werden und weisen eine den steigenden Anforderungen gerecht werdende Oberflächenqualität auf.In addition, due to the high concentration of endogas in the boiler room of the heat treatment plant, the kinetics of the reduction of iron oxide to hot-deformed iron alloys, such as e.g. Wires, pipes, profiles, especially large, so that their oxide layers are completely reduced. The oxide-free workpieces can then be machined with reduced effort, e.g. pickled, are and have a surface quality that meets the increasing demands.

Das erfindungsgemäß zur Wärmebehandlung eingesetzte Endogas besitzt auch eine wesentlich höhere "Reduktionskraft" als herkömmlich eingesetztes Exogas, d. h. es kann mehr Wasser und Kohlendioxid bilden und aufnehmen, ohne dass die Reduktion gestoppt wird.The endogas used according to the invention for heat treatment also has a much higher "reduction power" than conventionally used exogas, ie it can form and absorb more water and carbon dioxide without the reduction being stopped becomes.

Die höhere Konzentration an Wasserstoff (H2) und Kohlenmonoxid (CO) im Heizraum der Wärmebehandlungsanlage bewirkt eine höhere Aufheizgeschwindigkeit des Wärmebehandlungsguts als bei Einsatz eines herkömmlichen Schutzgases aus Exogas oder Monogas (N2 kleiner 5%H2).The higher concentration of hydrogen (H2) and carbon monoxide (CO) in the boiler room of the heat treatment plant results in a higher heat-up rate of the heat treatment than when using a conventional protective gas of exogas or monogas (N2 less than 5% H2).

Die erfindungsgemäße Endogas- und Stickstoffeinspeisung bewirkt den wesentlichen Vorteil, dass sich ein Konzentrationsprofil der reaktiven Komponenten vorteilhaft einstellt, wodurch die Explosionsgefahr verringert und die Reaktionskinetik und Aufheizge-schwindigkeit optimiert werden.The endogas and nitrogen feed according to the invention has the significant advantage that a concentration profile of the reactive components is advantageously established, whereby the risk of explosion is reduced and the reaction kinetics and Aufheizge-speed are optimized.

Nachfolgend wird die Erfindung anhand eines Ausführungsbeispiels näher erläutert.The invention will be explained in more detail with reference to an embodiment.

Es zeigen:

Fig.
1 Grafische Darstellung der Regelbarkeit der Kohlenstoffaktivität von Exogas und Endolin-Gas bei der Wärmebehandlung von Eisen-Kohlenstoff-Legierungen;
Fig. 2
Grafische Darstellung der Stickstoffkonzentration in Abhängigkeit von dem Endogas- Endolin-Schutzgaseinsatz in einer Wärmebehandlungsanlage mit Kühltunnel.
Show it:
FIG.
1 graphic representation of the controllability of the carbon activity of exogas and endolin gas in the heat treatment of iron-carbon alloys;
Fig. 2
Graphical representation of the nitrogen concentration as a function of the endogas protective gas insert in a heat treatment plant with a cooling tunnel.

In Fig. 1 ist die Regelbarkeit der Kohlenstoffaktivität von Exogas und Endogas (Endolin) bei der Wärmebehandlung von typischen Eisen-Kohlenstofflegierungen mit einem Kohlenstoffgehalt von 0,15 bis 0,70% dargestellt. Bei einer derartigen, in einem Temperaturbereich von 400 bis 900°C stattfindenden Wärmebehandlung sind die Kohlenstoffaktivitäten ac von einem herkömmlichen Schutzgas (Exogas) und von mehreren Schutzgasen (Endogas in Form von Endolin) mit 1 bis 5% CO gegenübergestellt. Aus Fig. 1 ist ersichtlich, dass bei Einsatz eines Endogases mit 1 % CO bei einer Temperatur von größer 650°C und bei Einsatz eines Endogases mit 5% CO die Kohlenstoffaktivität ac auf kleiner 1 verringert wird, bei der die Eisen-Kohlenstoff-Legierungen während der Wärmebehandlung entkohlt werden. Aus Fig. 1 ist weiterhin zu entnehmen, dass die im Temperaturbereich 650 bis 740°C bewirkte Kohlenstoffaktivität ac von gleich/kleiner 1 über das Mischungsverhältnis Endogas/Stickstoff, wie z.B. 1:19 bis 1:3, geregelt werden kann. Somit ist durch Einsatz von Schutzgasgemischen aus Endogas und Stickstoff eine Rückkohlung von entkohlten Eisen-Kohlenstoff-Legierungen während der Wärmebehandlung einfach zu realisieren. Bei Temperaturen von größer 740°C muss dem mit Stickstoff versetzten Endogas ein die Kohlenstoffaktivität ac auf den Wert von 1 steigerndes Gas, bevorzugt Propan, wegen seiner bedeutend besseren Reaktivität mit Wasser und Kohlendioxid zugesetzt werden. Weiterhin kann die Kohlenstoffaktivität im Heizraumgas durch Senkung des Taupunktes im erzeugten Endogas am Endogenerator erhöht werden, da mit fallender Wasserkonzentration im Endogas die Kohlenstoffaktivität im Mischgas ansteigt. Fig. 2 zeigt einen Ofen (Heizraum) mit Kühltunnel, worin einmal Endogas mit einer Menge an Stickstoff vorgemischt in das letzte Drittel des Heizraumes und die Hauptmenge an reinem Stickstoff in der Mitte/letztes Drittel des Kühltunnels eingespeist werden (Variante 2). In den Varianten 1 und 3 sind verschiedene Endogasmengen (10 und 30 m3/h) mit Stickstoff extern der Ofenanlage gemischt und in die Einspeisstelle im Heizraumende komplett eingespeist, d. h., dass an jeder Stelle im Heizraum und Kühltunnel die gleiche Konzentrationen an Wasserstoff und Kohlenmonoxid herrschen müssen. Bei allen 3 Varianten ist die Gesamtgasmenge immer auf 140 m3/h konstant gehalten. Mit Variante 2 ergibt sich bei externer vollständiger Mischung von Endogas und Stickstoff eine Wasserstoffkonzentration von 5,8 Vol.-%H2, d. h., die Explosionsgrenze von 5 Vol.-%H2,CO ist deutlich überschritten. Teilt man diese Gesamtmenge von Variante 2 auf, in Endogas/N2-Gemisch und N2 und speist die beide Teilströme an geeigneter Stelle ein, so ergeben sich Konzentrationen an Wasserstoff im Heizraum von 9 Vol.-%H2 und im Kühltunnel von 2,8 Vol.-%H2, also nahe der geforderten Explosionsgrenze. Die Wasserstoffkonzentration liegt somit im Heizraum um 40% höher und im Kühltunnel um 40% niedriger als die komplette Mischung von Endogas und Stickstoff. Es hat sich eine gerichtete Gasströmung von Stickstoff aus dem Kühltunnel in den Heizraum ausgebildet. Aufgrund der gemessenen Konzentrationen an Wasserstoff ist ersichtlich, dass die Stickstoffströme zu ungefähr zwei gleichen Teilen gerichtet sind, sodass die Verdünnung im Kühltunnel und Aufkonzentration im Heizraum und Gasabfuhr zum Heizraumeinlauf optimal sind. Variante 3 verdeutlicht, dass es nur mit einer kleinen Menge an Endogas (10m3/h) möglich ist, um die Sicherheitsbedingung von kleiner 5Vol.-%H2,CO zu realisieren.
Nach Variante 2 sind somit die Aspekte der Sicherheit und eine möglichst hohe H2,CO-Konzentration im Heizraum realisiert.In Fig. 1 the controllability of the carbon activity of exogas and endogas (endolin) is shown in the heat treatment of typical iron-carbon alloys with a carbon content of 0.15 to 0.70%. In such, taking place in a temperature range of 400 to 900 ° C heat treatment, the carbon activities a c of a conventional shielding gas (exogas) and of several shielding gases (endogas in the form of endoline) with 1 to 5% CO are compared. Out Fig. 1 It can be seen that when using an endo gas with 1% CO at a temperature of greater than 650 ° C and using a endo gas with 5% CO, the carbon activity a c is reduced to less than 1, during which the iron-carbon alloys during the heat treatment be decarburized. Out Fig. 1 Furthermore, it can be seen that the carbon activity a c of equal to / less than 1 caused in the temperature range 650 to 740 ° C. can be regulated via the mixing ratio endogas / nitrogen, such as 1:19 to 1: 3. Thus, by using protective gas mixtures of endogas and nitrogen recarbonization of decarburized iron-carbon alloys during the heat treatment is easy to implement. At temperatures greater than 740 ° C, the nitrogen gas added endogenous gas must be added to the carbon activity a c to the value of 1 gas, preferably propane, because of its significantly better reactivity with water and carbon dioxide. Furthermore, the carbon activity in the heating chamber gas can be increased by lowering the dew point in the generated endogenous gas at the endogenerator, since the carbon activity in the mixed gas increases with decreasing water concentration in the endogas. Fig. 2 shows a furnace (boiler room) with cooling tunnel, which once endogas with a quantity of nitrogen premixed in the last third of the boiler room and the main amount of pure nitrogen in the middle / last third of the cooling tunnel are fed (variant 2). In variants 1 and 3, different amounts of endogas (10 and 30 m3 / h) are mixed with nitrogen externally of the furnace and fed completely into the feed point in the boiler room, ie the same concentrations of hydrogen and carbon monoxide prevail at each point in the boiler room and cooling tunnel have to. In all 3 variants is the Total amount of gas always kept constant at 140 m3 / h. With variant 2 results in external complete mixture of endogas and nitrogen, a hydrogen concentration of 5.8 vol .-% H2, ie, the explosion limit of 5 vol .-% H2, CO is significantly exceeded. Dividing this total amount of variant 2, in endogas / N2 mixture and N2 and feeds the two streams at a suitable location, resulting in concentrations of hydrogen in the boiler room of 9 vol .-% H2 and in the cooling tunnel of 2.8 vol .-% H2, ie close to the required explosion limit. The hydrogen concentration is thus 40% higher in the boiler room and 40% lower in the cooling tunnel than the complete mixture of endogas and nitrogen. It has formed a directed gas flow of nitrogen from the cooling tunnel in the boiler room. Based on the measured concentrations of hydrogen, it can be seen that the nitrogen flows are directed to approximately two equal parts, so that the dilution in the cooling tunnel and concentration in the boiler room and gas removal to the boiler room inlet are optimal. Variant 3 illustrates that it is only possible with a small amount of endogas (10m3 / h) to realize the safety condition of less than 5% by volume H2, CO.
According to variant 2, the aspects of safety and the highest possible H2, CO concentration in the boiler room are thus realized.

Claims (19)

  1. Method for annealing tubes, profiled sections, wires, rods and sheets of metal made from ferrous materials in a continuous roller hearth furnace having a cooling tunnel and a heating space under a protective gas atmosphere of endogas mixtures, characterized in that endogas which has been partially diluted with nitrogen and additionally pure nitrogen are fed in separately from one another and into different regions of the installation, wherein the endogas, which is diluted with nitrogen in a mixing ratio in the range of between 1:19 to 1:3 outside the continuous roller hearth furnace, is introduced directly into the heating space and the nitrogen which is used in addition for the dilution of the endogas is injected into different regions of the cooling tunnel.
  2. Method according to Claim 1, characterized in that the endogas, which consists of carbon monoxide (CO), hydrogen (H2) and nitrogen (N2), is injected into the end of the heating space and transversely with respect to the conveying direction of the heat-treatment material.
  3. Method according to one of Claims 1 to 2, characterized in that the endogas has a dew point in the range from +5 to +15°C before the dilution with nitrogen.
  4. Method according to Claim 3, characterized in that the endogas is fed into the heating space of the continuous roller hearth furnace through at least one automatic metering valve.
  5. Method according to one of Claims 1 to 4, characterized in that the metered quantities of endogas and nitrogen fed into the continuous roller hearth furnace are recorded and are used to determine the current oxygen and carbon activities during the heat treatment.
  6. Method according to one of the preceding claims, characterized in that to improve the convention of the endogas in the heating space, nitrogen is metered to the endogas outside the continuous roller hearth furnace.
  7. Method according to one of the preceding claims, characterized in that the required carbon activity of the gas phase in the continuous roller hearth furnace heating space of the endogas is set by means of the dew point of the pure endogas generated in the generator.
  8. Method according to one of the preceding claims, characterized in that if the carbon activity is too high, air is metered into the endogas mixture fed to the heating space in the continuous roller hearth furnace and a homogenous gas phase is formed outside the location at which the gas is fed in.
  9. Method according to Claim 6, characterized in that the endogas is introduced into the nitrogen, which has a superatmospheric pressure of from 20 to 30 mbar, at a superatmospheric pressure of from 40 to 60 mbar.
  10. Method according to Claim 9, characterized in that the endogas is introduced through a curved mixing tube arranged in the nitrogen pipeline.
  11. Method according to Claim 9, characterized in that the endogas is introduced at a superatmospheric pressure of 60 mbar by an injector, which sucks in the endogas with the aid of the stream of nitrogen and thereby generates a homogenous dilute endogas.
  12. Method according to one of the preceding claims, characterized in that the metered quantities of natural gas and air and therefore the metered quantity of endogas are controlled as a function of the dynamic pressure prevailing in the endogas/nitrogen line arranged at the continuous roller hearth furnace.
  13. Method according to one of the preceding claims, characterized in that the nitrogen is injected into the cooling tunnel with a first part-stream in the direction of the heating space inlet and with a second part-stream in the direction of the cooling tunnel outlet of the continuous roller hearth furnace.
  14. Method according to Claim 8, characterized in that the metered quantity of nitrogen is controlled by means of a lambda sensor arranged in the outlet region of the continuous roller hearth furnace.
  15. Method according to one of the preceding claims, characterized in that the volatile constituents of the heat-treatment material which evaporate out of the heating space of the continuous roller hearth furnace are transported to the inlet of the continuous roller hearth furnace, where they are burnt off and discharged.
  16. Method according to one of the preceding claims, characterized in that liquid nitrogen is fed into the first third of the cooling tunnel region closest to the cooling tunnel outlet or into the last third of the cooling tunnel region closest to the heating space outlet, in the continuous roller hearth furnace.
  17. Method according to one of the preceding claims, characterized in that the protective gas, in order for its concentration profile to be determined during the heat treatment process over the entire length of the continuous roller hearth furnace, is removed from the continuous roller hearth furnace by means of at least one gas removal device arranged at the continuous roller hearth furnace, and after subsequent electronic processing is used for automatic control of the endogas and nitrogen feed into the continuous roller hearth furnace.
  18. Method according to one of the preceding claims, characterized in that the sum of the concentrations of carbon monoxide (CO) and hydrogen (H2) at the end of the cooling tunnel of the continuous roller hearth furnace is less than 5% by volume.
  19. Method according to one of the preceding claims, characterized in that the dew point of the protective gas that has been diluted with nitrogen in the cooling tunnel is lower than in the heating space of the continuous roller hearth furnace.
EP04765727A 2003-10-08 2004-10-01 Method for heat-treating iron-containing materials Active EP1673483B8 (en)

Priority Applications (1)

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PL04765727T PL1673483T3 (en) 2003-10-08 2004-10-01 Method for heat-treating iron-containing materials

Applications Claiming Priority (2)

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DE10347312A DE10347312B3 (en) 2003-10-08 2003-10-08 Process for the heat treatment of iron materials
PCT/EP2004/010951 WO2005035799A1 (en) 2003-10-08 2004-10-01 Method for heat-treating iron-containing materials

Publications (3)

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EP1673483A1 EP1673483A1 (en) 2006-06-28
EP1673483B1 true EP1673483B1 (en) 2010-02-24
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AT (1) ATE458837T1 (en)
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AT502238B1 (en) * 2005-05-12 2007-12-15 Ebner Ind Ofenbau PROCESS FOR BATCH HEAT TREATMENT OF REFRIGERATED PRODUCTS
EP2487268B1 (en) 2011-02-10 2014-10-22 Schwartz, Eva Oven
CN103805840B (en) * 2012-11-15 2016-12-21 宝山钢铁股份有限公司 A kind of high formability galvanizing ultrahigh-strength steel plates and manufacture method thereof
DE102013014815A1 (en) * 2013-09-10 2015-03-12 Ipsen International Gmbh Control system for an endogas generator, and method for controlling at least one endogas generator

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US3950192A (en) * 1974-10-30 1976-04-13 Monsanto Company Continuous carburizing method
US4288062A (en) * 1979-08-09 1981-09-08 Holcroft Apparatus for control and monitoring of the carbon potential of an atmosphere in a heat-processing furnace
DE3277843D1 (en) * 1981-09-19 1988-01-28 British Oxygen Co Ltd Heat treatment of metals
FR2527641A1 (en) * 1982-05-28 1983-12-02 Air Liquide PROCESS FOR THERMALLY TREATING METALLIC PARTS THROUGH CARBURATION
DE3630833A1 (en) * 1986-09-10 1988-03-17 Linde Ag METHOD AND DEVICE FOR HEAT TREATING METAL WORKPIECES
FR2623209B1 (en) * 1987-11-17 1993-09-03 Air Liquide PROCESS OF HEAT TREATMENT UNDER NITROGEN AND HYDROCARBON GAS ATMOSPHERE
DE3828134A1 (en) * 1988-08-18 1990-02-22 Linde Ag METHOD FOR THE HEAT TREATMENT OF WORKPIECES
FR2649123B1 (en) * 1989-06-30 1991-09-13 Air Liquide METHOD FOR HEAT TREATING METALS
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DE10023409A1 (en) * 2000-05-12 2001-11-15 Linde Gas Ag Gas generator used for producing carbon monoxide- and hydrogen-containing treatment gas for heat treating metallic material comprises catalyst retort and device for heating partial regions of retort

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DE502004010812D1 (en) 2010-04-08
EP1673483B8 (en) 2010-08-11
WO2005035799A1 (en) 2005-04-21
ATE458837T1 (en) 2010-03-15
DE10347312B3 (en) 2005-04-14
PL1673483T3 (en) 2010-12-31
ES2341861T3 (en) 2010-06-29
EP1673483A1 (en) 2006-06-28

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