EP0261461B1 - Method and apparatus for heat treating metal work pieces - Google Patents
Method and apparatus for heat treating metal work pieces Download PDFInfo
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- EP0261461B1 EP0261461B1 EP87112804A EP87112804A EP0261461B1 EP 0261461 B1 EP0261461 B1 EP 0261461B1 EP 87112804 A EP87112804 A EP 87112804A EP 87112804 A EP87112804 A EP 87112804A EP 0261461 B1 EP0261461 B1 EP 0261461B1
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- furnace
- gas
- continuous furnace
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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
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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
- C21D1/763—Adjusting the composition of the atmosphere using a catalyst
Definitions
- the invention relates to a method for the heat treatment of metallic workpieces with a gas-heated continuous furnace and under the action of a gas atmosphere which consists essentially of nitrogen and hydrogen and carbon monoxide generated by catalytic conversion of a hydrocarbon immediately before entering the continuous furnace, and a corresponding heat treatment furnace.
- the heat treatment of metallic workpieces is often carried out in continuous furnaces, to which a treatment gas which is based on the type of heat treatment is supplied from the outside.
- a treatment gas which is based on the type of heat treatment is supplied from the outside.
- roller hearth furnaces for annealing semi-finished products made of iron or non-ferrous metals are known, those with so-called exogas that are used in gas generators by exothermic combustion of hydrocarbons with air, or with so-called endogas that are also used in independent gas generators with catalysts - or also within heat treatment furnaces arranged catalytic reactors (see, for example, EP-A 0 180 953 or also DE-A 27 58 024) - is also produced from hydrocarbon-air mixtures with the addition of heat.
- the treatment gases generated in these processes essentially contain nitrogen, hydrogen and carbon monoxide and, under certain circumstances, also admixtures of carbon dioxide and water vapor.
- the exact mixing ratio of the components is chosen as it is with the respective type of Heat treatment in the main treatment zone, for example in the hot zone of the continuous furnace, is required.
- control and regulating methods are known with which the mixing ratio is influenced as a function of a variable measured in the furnace (VDI-Zeitung 98 (1956), No. 24, pages 1486 to 1490).
- the invention is therefore based on the object of making the known methods for the heat treatment of metallic workpieces in gas-fired continuous furnaces more economical.
- a nitrogen supply is additionally provided in a process as initially described with internal, catalytic generation of treatment gas, treatment gas consisting of nitrogen, hydrogen and carbon monoxide being supplied to the continuous furnace on the one hand, and nitrogen gas, on the other hand, separated therefrom is fed the treatment gas is fed to the continuous furnace in the region of its heating zone and the nitrogen is introduced at a distance from and on both sides thereof - between the inlet zone and the heating zone and between the heating zone and outlet zone of the continuous furnace - in such a way that the gas atmosphere enters the furnace inlet and the areas adjacent to the furnace outlet contain less than 20% CO and less than 30% H2.
- a gas atmosphere profile extending in the direction of the longitudinal extension of the continuous furnace is optimally built up, which starts from the furnace inlet with a zone of low reactivity, then reaches the highest reactivity in the region of the hot zone and finally in the region of the furnace outlet drops again to low reactivity.
- the process according to the invention thus leads to a higher reactivity in the hot zone of the furnace without the furnace atmosphere near the furnace inlet and outlet becoming more toxic or flammable than with exogas.
- a direct consequence of this procedure is a considerable saving in terms of the consumption of hydrocarbon-containing gases, which can cost up to over 30%.
- the process according to the invention in addition to the advantage of its increased economic efficiency compared to known processes, also brings about an improvement in the quality, in particular the uniformity, of the treated workpieces, which is based on the fact that the composition of the gas atmosphere at every point in the furnace can be set in an optimal manner.
- the gas atmosphere formed in the process according to the invention has a high buffering effect against air ingress and leaks in the radiant tube burners. In addition, soot formation and damage to the furnace lining are reliably avoided with the method according to the invention.
- the ratio between the treatment gas and the separately supplied nitrogen is advantageously chosen so that the furnace atmosphere in the regions adjacent to the furnace inlet and outlet contains even less than 10% carbon monoxide and also less than 10%, hydrogen.
- the continuous furnace is heated by means of a jet tube burner and the treatment gas is fed to the continuous furnace via a cross section which is arranged concentrically with the burner chamber and at least one of the jet tube burners which is arranged in the region of the hot zone and is filled with catalyst.
- Preferred areas of application of the method according to the invention are recrystallization and the carbon-neutral or decarburizing annealing of semi-finished products in roller hearth furnaces.
- a continuous furnace for carrying out the method according to the invention with jet tube burners arranged over its longitudinal extent is advantageously designed such that at least one of the jet tube burners arranged in the area of the hot zone of the continuous furnace has a cross section arranged concentrically with the burner chamber and filled with catalyst for the generation of the treatment gas and in With respect to the longitudinal extent of the continuous furnace, on both sides and at a distance from the one or more jet-tube burners having a cross-section filled with catalyst, gas feeds for nitrogen are arranged in the region between the furnace inlet and the hot zone and in the region between the hot zone and the furnace outlet.
- the roller hearth furnace 1 has a furnace inlet 2, from which metal workpieces are fed continuously or discontinuously through the furnace 1 to the furnace outlet 3 by means of transport rollers 4.
- the furnace 1 is heated by a number of radiant tube burners 5 with natural gas as the fuel gas so that the workpieces passing through the furnace 1, e.g. are to be annealed in a carbon-neutral manner, first heated slowly, then reaching the highest temperature approximately in the middle of the furnace and finally slowly cooling the furnace outlet 3 again.
- a 6 of the jet tube burner 5 is designed as an internally heated catalytic reactor in that the burner chamber is surrounded concentrically by an annular space filled with catalyst for generating the treatment gas. Also owns the furnace 1 has two gas feeds 7 which are arranged in the longitudinal direction of the furnace on both sides of the jet tube burner 6 which is designed as a catalytic reactor. In the case of larger or longer furnaces, several special jet tube burners 6 and / or further gas feeds 7 can also be provided.
- a natural gas / air mixture is supplied to the jet tube burners 5 for heating.
- the natural gas / air mixture also becomes the second one Cross-section containing catalyst supplied, where a treatment gas with approximately 40% nitrogen, 38% hydrogen and 18% carbon monoxide is generated by endothermic reaction and is blown into the interior of the furnace 1 by a gas distributor 8.
- pure nitrogen is introduced via the gas feeds 7 into the furnace 1, which dilutes the treatment gas in the region of the furnace inlet 2 and the furnace outlet 3 so that the gas atmosphere there only contains about 8% hydrogen and also about 8% carbon monoxide.
- a gas atmosphere profile is built up in this way in furnace 1 over its longitudinal extent, which has its highest reactivity in the hot zone and its lowest reactivity at furnace inlet 2 and at furnace outlet 3.
- the changing composition of the furnace atmosphere can be caused, on the one hand, by changes in the mixing ratio of the natural gas-air mixture which is fed to the furnace 1 via the jet tube burner 6 designed as a catalytic reactor, and, on the other hand, by changes in the amount of nitrogen introduced into the furnace 1 via the gas feeds 7 can be adapted in any way and extremely precisely to the respective requirements.
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- Crystallography & Structural Chemistry (AREA)
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- Chemical Kinetics & Catalysis (AREA)
- Furnace Details (AREA)
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- Heat Treatments In General, Especially Conveying And Cooling (AREA)
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Abstract
Description
Die Erfindung betrifft ein Verfahren zur Wärmebehandlung metallischer Werkstücke mit einem gasbeheizten Durchlaufofen und unter Einwirkung einer Gasatmosphäre, die im wesentlichen aus Stickstoff und aus durch katalytische Umsetzung eines Kohlenwasserstoffs unmittelbar vor dem Eintritt in den Durchlaufofen erzeugtem Wasserstoff und Kohlenmonoxid besteht, sowie einen entsprechenden Wärmebehandlungsofen.The invention relates to a method for the heat treatment of metallic workpieces with a gas-heated continuous furnace and under the action of a gas atmosphere which consists essentially of nitrogen and hydrogen and carbon monoxide generated by catalytic conversion of a hydrocarbon immediately before entering the continuous furnace, and a corresponding heat treatment furnace.
Die Wärmebehandlung metallischer Werkstücke wird häufig in Durchlauföfen durchgeführt, denen ein in seiner Zusammensetzung auf die Art der Wärmebehandlung abgestelltes Behandlungsgas von außen zugeleitet wird. So sind z.B. Rollenherdöfen zum Glühen von Halbzeugen aus Eisen oder auch Nichteisenmetallen bekannt, die mit sogenanntem Exogas, das in Gasgeneratoren durch exotherme Verbrennung von Kohlenwasserstoffen mit Luft, oder mit sogenanntem Endogas, das ebenfalls in eigenständigen Gasgeneratoren mit Katalysatoren - oder auch in innerhalb von Wärmebehandlungsöfen angeordneten katalytischen Reaktoren (s. z.B. EP-A 0 180 953 oder auch DE-A 27 58 024)-unter Wärmezufuhr auch aus Kohlenwasserstoff-Luft- Gemischen erzeugt wird, betrieben werden. Die bei diesen Verfahren entstehenden Behandlungsgase enthalten im wesentlichen Stickstoff, Wasserstoff und Kohlenmonoxid sowie unter Umständen noch Beimengungen von Kohlendioxid und Wasserdampf. Das genaue Mischungsverhältnis der Komponenten wird so gewählt, wie es bei der jeweils vorliegenden Art der Wärmebehandlung in der Hauptbehandlungszone, z.B. in der heißen Zone des Durchlaufofens, erforderlich ist. Zur Aufrechterhaltung des richtigen Mischungsverhältnisses oder zu einer gezielten Änderung desselben sind Steuer- und Regelverfahren bekannt, mit denen das Mischungsverhältnis in Abhängigkeit einer im Ofen gemessenen Größe beeinflußt wird (VDI-Zeitung 98 (1956), Nr. 24, Seiten 1486 bis 1490).The heat treatment of metallic workpieces is often carried out in continuous furnaces, to which a treatment gas which is based on the type of heat treatment is supplied from the outside. For example, roller hearth furnaces for annealing semi-finished products made of iron or non-ferrous metals are known, those with so-called exogas that are used in gas generators by exothermic combustion of hydrocarbons with air, or with so-called endogas that are also used in independent gas generators with catalysts - or also within heat treatment furnaces arranged catalytic reactors (see, for example, EP-A 0 180 953 or also DE-A 27 58 024) - is also produced from hydrocarbon-air mixtures with the addition of heat. The treatment gases generated in these processes essentially contain nitrogen, hydrogen and carbon monoxide and, under certain circumstances, also admixtures of carbon dioxide and water vapor. The exact mixing ratio of the components is chosen as it is with the respective type of Heat treatment in the main treatment zone, for example in the hot zone of the continuous furnace, is required. In order to maintain the correct mixing ratio or to change it in a targeted manner, control and regulating methods are known with which the mixing ratio is influenced as a function of a variable measured in the furnace (VDI-Zeitung 98 (1956), No. 24, pages 1486 to 1490).
Insbesondere ist aus der EP-A 0 180 953 zudem bekannt, bei der Herstellung einer aus CO, H₂ und N₂ bestehenden Schutzgasatmosphäre durch katalytische Umsetzung eines Gasgemisches z.B. aus Erdgas und Luft unmittelbar vor der Einleitung in einen Ofenraum erzeugten Wasserstoff und Kohlenmonoxid und zusätzlich Stickstoff direkt benachbart dazu in den Ofenraum einer Wärmebehandlungsanlage einzuleiten. Dies dient dort jedoch vor allem der Temperaturbeeinflußung des Katalysatorelements.In particular, it is known from EP-
Die bekannten Verfahren und ihre neueren Weiterentwicklungen arbeiten technisch weitgehend zufriedenstellend, jedoch ist ihre Anwendung auf große Öfen, insbesondere auf langgestreckte Durchlauföfen, nicht immer in dem Maße wirtschaftlich, wie es wünschenswert wäre. Der Gesamtgasverbrauch, d.h. der Verbrauch an Brenngas und Behandlungsgas, ist wegen der räumlichen Ausdehnung solcher Öfen größer als er zur eigentlichen Wärmebehandlung notwendig wäre. Dieser Nachteil ist, insbesondere wegen des Verbrauchs von wertvollen kohlenwasserstoffhaltigen Gasen, von nicht zu vernachlässigender Bedeutung.The known methods and their more recent developments work largely satisfactorily from a technical point of view, but their use on large furnaces, in particular on elongated continuous furnaces, is not always economical to the extent that it would be desirable. The total gas consumption, i.e. the consumption of fuel gas and treatment gas is greater than would be necessary for the actual heat treatment because of the spatial expansion of such furnaces. This disadvantage is of not insignificant importance, particularly because of the consumption of valuable hydrocarbon-containing gases.
Der Erfindung liegt deshalb die Aufgabe zugrunde, die bekannten Verfahren zur Wärmebehandlung metallischer Werkstücke in gasbeheizten Durchlauföfen wirtschaftlicher zu gestalten.The invention is therefore based on the object of making the known methods for the heat treatment of metallic workpieces in gas-fired continuous furnaces more economical.
Diese Aufgabe wird dadurch gelöst, daß bei einem wie eingangs gekennzeichneten Verfahren mit interner, katalytischer Erzeugung von Behandlungsgas zusätzlich eine Stickstoffzufuhr vorgesehen wird, wobei dem Durchlaufofen dann einerseits Behandlungsgas, bestehend aus Stickstoff, Wasserstoff und Kohlenmonoxid, zugeführt wird und andererseits - davon getrennt - Stickstoffgas zugeleitet wird,
wobei das Behandlungsgas dem Durchlaufofen im Bereich seiner Heizzone zugeführt wird und der Stickstoff mit Abstand dazu und beidseitig davon - zwischen Einlaufzone und Heizzone und zwischen Heizzone und Auslaufzone des Durchlaufofens - eingebracht wird, und zwar in der Weise, daß die Gasatmosphäre in den dem Ofeneinlauf und den dem Ofenauslauf benachbarten Bereichen weniger als 20% CO und weniger als 30% H₂, enthält.This object is achieved in that a nitrogen supply is additionally provided in a process as initially described with internal, catalytic generation of treatment gas, treatment gas consisting of nitrogen, hydrogen and carbon monoxide being supplied to the continuous furnace on the one hand, and nitrogen gas, on the other hand, separated therefrom is fed
the treatment gas is fed to the continuous furnace in the region of its heating zone and the nitrogen is introduced at a distance from and on both sides thereof - between the inlet zone and the heating zone and between the heating zone and outlet zone of the continuous furnace - in such a way that the gas atmosphere enters the furnace inlet and the areas adjacent to the furnace outlet contain less than 20% CO and less than 30% H₂.
Mit dem erfindungsgemäßen Verfahren wird in einem Durchlaufofen in optimaler Weise ein sich in Richtung der Längsausdehnung des Durchlaufofens erstreckendes Gasatmosphärenprofil aufgebaut, das vom Ofeneinlauf her mit einer Zone geringer Reaktivität beginnt, dann im Bereich der heißen Zone die höchste Reaktivität erreicht und schließlich im Bereich des Ofenauslaufs wieder zur geringer Reaktivität absinkt. Verglichen mit einer Exogasatmosphäre führt das erfindungsgemäße Verfahren somit zu einer höheren Reaktivität in der heißen Zone des Ofens, ohne daß die Ofenatmosphäre in der Nähe Von Ofenein- und auslauf giftiger oder brennbarer wird als bei Exogas. Eine unmittelbare Folge dieser Verfahrensweise ist eine erhebliche Einsparung bezüglich des Verbrauches kohlenwasserstoffhaltiger Gase, die kostenmäßig bis über 30 % betragen kann.With the method according to the invention, a gas atmosphere profile extending in the direction of the longitudinal extension of the continuous furnace is optimally built up, which starts from the furnace inlet with a zone of low reactivity, then reaches the highest reactivity in the region of the hot zone and finally in the region of the furnace outlet drops again to low reactivity. Compared to an exogas atmosphere, the process according to the invention thus leads to a higher reactivity in the hot zone of the furnace without the furnace atmosphere near the furnace inlet and outlet becoming more toxic or flammable than with exogas. A direct consequence of this procedure is a considerable saving in terms of the consumption of hydrocarbon-containing gases, which can cost up to over 30%.
Überraschenderweise wurde gefunden, daß das erfindungsgemäße Verfahren außer dem Vorteil seiner gegenüber bekannten Verfahren erhöhten Wirtschaftlichkeit auch eine Verbesserung der Qualität, insbesondere der Gleichmäßigkeit der Qualität, der behandelten Werkstücke mit sich bringt, die darauf beruht, daß die Zusammensetzung der Gasatmosphäre an jeder Stelle des Ofens in optimaler Weise eingestellt werden kann. Eine wesentliche Voraussetzung für diesen Vorteil ist neben der getrennten Stickstoffzufuhr die Erzeugung des Behandlungsgases unmittelbar vor seinem Eintritt in den Durchlaufofen durch katalytische Umsetzung. Darüber hinaus hat die beim erfindungsgemäßen Verfahren gebildete Gasatmosphäre eine hohe Pufferwirkung gegenüber Lufteinbrüchen und Undichtigkeiten in den Strahlrohrbrennern. Außerdem werden Rußbildung und Schäden an der Ofenausmauerung mit dem erfindungsgemäßen Verfahren sicher vermieden.Surprisingly, it was found that the process according to the invention, in addition to the advantage of its increased economic efficiency compared to known processes, also brings about an improvement in the quality, in particular the uniformity, of the treated workpieces, which is based on the fact that the composition of the gas atmosphere at every point in the furnace can be set in an optimal manner. An essential prerequisite for this advantage, in addition to the separate supply of nitrogen, is the generation of the treatment gas by catalytic conversion immediately before it enters the continuous furnace. In addition, the gas atmosphere formed in the process according to the invention has a high buffering effect against air ingress and leaks in the radiant tube burners. In addition, soot formation and damage to the furnace lining are reliably avoided with the method according to the invention.
Bei der Durchführung des erfindungsgemäßen Verfahrens wird vorteilhaft das Mengenverhältnis zwischen Behandlungsgas und dem getrennt zugeleiteten Stickstoff so gewählt, daß die Ofenatmosphäre in den dem Ofeneinlauf und dem Ofenauslauf benachbarten Bereichen sogar weniger als 10 % Kohlenmonoxid und auch weniger als 10 %, Wasserstoff enthält.When carrying out the process according to the invention, the ratio between the treatment gas and the separately supplied nitrogen is advantageously chosen so that the furnace atmosphere in the regions adjacent to the furnace inlet and outlet contains even less than 10% carbon monoxide and also less than 10%, hydrogen.
Besonders vorteilhaft ist auch eine Weiterentwicklung des erfindungsgemäßen Verfahrens, bei der der Durchlaufofen über Strahlrohrbrenner beheizt wird und das Behandlungsgas dem Durchlaufofen über einen konzentrisch zum Brennerraum mindestens eines der im Bereich der heißen Zone angeordneten Strahlrohrbrenner angeordneten und mit Katalysator gefüllten Querschnitt zugeleitet wird.Also particularly advantageous is a further development of the method according to the invention, in which the continuous furnace is heated by means of a jet tube burner and the treatment gas is fed to the continuous furnace via a cross section which is arranged concentrically with the burner chamber and at least one of the jet tube burners which is arranged in the region of the hot zone and is filled with catalyst.
Die Verwendung derartiger Katalysatorrohre ist zwar von anderen Wärmebehandlungsöfen her schon bekannt, doch hat es sich gezeigt, daß ihre Verwendung im Rahmen des erfindungsgemäßen Verfahrens besonders vorteilhaft ist.The use of such catalyst tubes is already known from other heat treatment furnaces, but it has been shown that their use is particularly advantageous in the process according to the invention.
Da in jüngster Zeit Durchlauföfen zur Wärmebehandlung überwiegend mit Erdgas beheizt werden, ist die Anwendung des erfindungsgemäßen Verfahrens bei solchen Öfen besonders wirtschaftlich, wenn das Behandlungsgas aus einem Erdgas-Luft-Gemisch erzeugt wird, da auf diese Weise lediglich Stickstoff als zusätzliches Medium am Durchlaufofen zur Verfügung stehen muß.Since continuous furnaces for heat treatment have recently been heated predominantly with natural gas, the use of the method according to the invention in such furnaces is particularly economical if the treatment gas is generated from a natural gas / air mixture, since in this way only nitrogen is used as an additional medium in the continuous furnace Must be available.
Bevorzugte Anwendungsgebiete des erfindungsgemäßen Verfahrens sind das Rekristallisieren und das kohlungsneutral- oder entkohlende Glühen von Halbzeugen in Rollenherdöfen.Preferred areas of application of the method according to the invention are recrystallization and the carbon-neutral or decarburizing annealing of semi-finished products in roller hearth furnaces.
Ein Durchlaufofen zur Durchführung des erfindungsgemäßen Verfahrens mit über seine Längsausdehnung angeordneten Strahlrohrbrennern ist mit Vorteil so ausgebildet, daß mindestens einer der im Bereich der heißen Zone des Durchlaufofens angeordneten Strahlrohrbrenner einen konzentrisch zum Brennerraum angeordneten und mit Katalysator gefüllten Querschnitt für die Erzeugung des Behandlungsgases aufweist und in Bezug auf die Längsausdehnung des Durchlaufofens, beidseitig und beabstandet zu dem oder den einen mit Katalysator gefüllten Querschnitt aufweisenden Strahlrohrbrennern, im Bereich zwischen Ofeneinlauf und heißer Zone sowie im Bereich zwischen heißer Zone und Ofenauslauf Gaszuführungen für Stickstoff angeordnet sind.A continuous furnace for carrying out the method according to the invention with jet tube burners arranged over its longitudinal extent is advantageously designed such that at least one of the jet tube burners arranged in the area of the hot zone of the continuous furnace has a cross section arranged concentrically with the burner chamber and filled with catalyst for the generation of the treatment gas and in With respect to the longitudinal extent of the continuous furnace, on both sides and at a distance from the one or more jet-tube burners having a cross-section filled with catalyst, gas feeds for nitrogen are arranged in the region between the furnace inlet and the hot zone and in the region between the hot zone and the furnace outlet.
Im folgenden wird ein Ausführungsbeispiel des erfindungsgemäßan Verfahrens anhand eines in der Figur schematisch dargestellten Rollenherdofens beschrieben.An exemplary embodiment of the method according to the invention is described below using a roller hearth furnace shown schematically in the figure.
Der Rollenherdofen 1 besitzt einen Ofeneinlaß 2, von dem mittels Transportrollen 4 metallische Werkstücke kontinuierlich oder diskontinuierlich durch den Ofen 1 hindurch dem Ofenauslauf 3 zugeführt werden. Der Ofen 1 wird über eine Anzahl von Strahlrohrbrennern 5 mit Erdgas als Brenngas so beheizt, daß die den Ofen 1 durchlaufenden Werkstücke, die z.B. kohlungsneutral geglüht werden sollen, zunächst langsam erhitzt werden, dann ungefähr in der Ofenmitte die höchste Temperatur erreichen und schließlich dem Ofenauslauf 3 zu wieder langsam abkühlen.The roller hearth furnace 1 has a
Im Bereich der heißen Zone des Ofens 1 ist einer 6 der Strahlrohrbrenner 5 dadurch als innenbeheizter katalytischer Reaktor ausgebildet, daß der Brennerraum konzentrisch von einem mit Katalysator gefüllten ringförmigen Raum zur Erzeugung des Behandlungsgases umgeben ist. Außerdem besitzt der Ofen 1 zwei Gaszuführungen 7, die in Längsrichtung des Ofens beidseitig zu dem als katalytischer Reaktor ausgebildeten Strahlrohrbrenner 6 angeordnet sind. Bei größern oder längeren Öfen können auch mehrere spezielle Strahlrohrbrenner 6 und/oder weitere Gaszuführungen 7 vorgesehen sein.In the area of the hot zone of the furnace 1, a 6 of the
Beim Betrieb des Ofens wird den Strahlrohrbrennern 5 ein Erdgas-Luft-Gemisch zur Beheizung zugeführt. Bei dem als katalytischen Reaktor ausgebildeten Strahlrohrbrenner 6 wird das Erdgas-Luft-Gemisch zusätzlich dem zweiten, den
Katalysator enthaltenden Querschnitt zugeführt, wo durch endotherme Umsetzung ein Behandlungsgas mit ungefähr 40 % Stickstoff, 38 % Wasserstoff und 18 % Kohlenmonoxid erzeugt und durch einen Gasverteiler 8 in den Innenraum des Ofens 1 eingeblasen wird. Zusätzlich wird über die Gaszuführungen 7 reiner Stickstoff in den Ofen 1 eingeleitet, der das Behandlungsgas im Bereich des Ofeneinlaufs 2 und des Ofenauslaufs 3 so verdünnt, daß dort die Gasatmosphäre nur noch etwa 8 % Wasserstoff und ebenfalls etwa 8% Kohlenmonoxid enthält. Ingesamt wird auf diese Weise in Ofen 1 über seine Längsausdehnung eine Gasatmosphärenprofil aufgebaut, das in der heißen Zone seine höchste und beim Ofeneinlauf 2 und beim Ofenauslauf 3 seine niedrigste Reaktivität aufweist. Die wechselnde Zusammensetzung der Ofenatmosphäre kann einerseits durch Änderungen des Mischungsverhältnisses des Erdgas-Luft-Gemisches, das über den als katalytischen Reaktor ausgebildeten Strahlrohrbrenner 6 dem Ofen 1 zugeführt wird, und andererseits durch Änderungen der Menge des über die Gaszuführungen 7 in den Ofen 1 eingebrachten Stickstoffs in beliebiger Weise und außerordentlich genau den jeweils vorliegenden Erfordernissen angepaßt werden.When the furnace is operating, a natural gas / air mixture is supplied to the
Cross-section containing catalyst supplied, where a treatment gas with approximately 40% nitrogen, 38% hydrogen and 18% carbon monoxide is generated by endothermic reaction and is blown into the interior of the furnace 1 by a
Durch das erfindungsgemäße Verfahren kann bei einem Durchlaufofen der beschriebenen Art eine erhebliche Einsparung an Behandlungsgas erzielt werden. So konnten beispielsweise in einem speziellen Fall einer Wärmebehandlung 220 m³/h Exogas durch nur 100 m³/h Stickstoff, 6 m³/h Erdgas und 15 m³/h Luft ersetzt werden.With the method according to the invention, a considerable saving in treatment gas can be achieved in a continuous furnace of the type described. For example, in a special case of heat treatment, 220 m³ / h of exogas could be replaced by only 100 m³ / h of nitrogen, 6 m³ / h of natural gas and 15 m³ / h of air.
Claims (5)
- A process for thermally treating metallic workpieces in a gas-heated continuous furnace under the influence of a gas atmosphere which consists substantially of nitrogen and of hydrogen and carbon monoxide produced by a catalytic reaction of a hydrocarbon directly prior to entry into the continuous furnace, wherein the continuous furnace is supplied on the one hand with a treatment gas consisting of nitrogen, hydrogen and carbon monoxide and on the other hand - separately therefrom - with nitrogen, the treatment gas is conveyed to the continuous furnace in the region of its hot zone and the nitrogen is introduced at a distance therefrom and on both sides thereof between the inlet zone and the hot zone and between the hot zone and the outlet zone of the continuous furnace in such manner that the gas atmosphere in the zones adjacent to the furnace inlet and the zones adjacent to the furnace outlet contains less than 20% CO and less than 30% H₂.
- A process as claimed in Claim 1, characterised in that the gas atmosphere in the zones adjacent to the inlet of the furnace and the zones adjacent to the outlet of the furnace contains less than 10% CO and less than 10% H₂.
- A process as claimed in Claim 1 or 2, characterised in that the continuous furnace is heated via radiant tube burners and the treatment gas is conveyed to the continuous furnace via a cross-section which is filled with catalyst and which is arranged concentrically with the burner chamber of at least one of the radiant tube burners disposed in the region of the hot zone.
- A process as claimed in one of Claims 1 to 3, characterised in that the continuous furnace is heated with natural gas and the treatment gas is produced from a natural gas - air mixture.
- A continuous furnace for the implementation of the process claimed in one of Claims 1 to 4 comprising radiant tube burners arranged in series along the longitudinal dimension of the continuous furnace and at least one catalyst tube (6) in the region of the hot zone of the continuous furnace, and comprising a cross-section, which is arranged concentrically with the burner chamber and is filled with catalyst, for the production of the treatment gas, characterised in that in the longitudinal dimension of the continuous furnace (1) gas supply lines (7) for nitrogen are arranged on both sides of and at a distance from the catalyst tube (6) in the region between the furnace inlet (2) and the hot zone and in the region between the hot zone and the furnace outlet (3).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT87112804T ATE89868T1 (en) | 1986-09-10 | 1987-09-02 | METHOD AND DEVICE FOR THE HEAT TREATMENT OF METALLIC WORKPIECES. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863630833 DE3630833A1 (en) | 1986-09-10 | 1986-09-10 | METHOD AND DEVICE FOR HEAT TREATING METAL WORKPIECES |
| DE3630833 | 1986-09-10 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0261461A2 EP0261461A2 (en) | 1988-03-30 |
| EP0261461A3 EP0261461A3 (en) | 1989-03-15 |
| EP0261461B1 true EP0261461B1 (en) | 1993-05-26 |
Family
ID=6309316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87112804A Expired - Lifetime EP0261461B1 (en) | 1986-09-10 | 1987-09-02 | Method and apparatus for heat treating metal work pieces |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0261461B1 (en) |
| AT (1) | ATE89868T1 (en) |
| BR (1) | BR8704618A (en) |
| DE (2) | DE3630833A1 (en) |
| ES (1) | ES2042524T3 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3842372C2 (en) * | 1988-12-16 | 1996-10-02 | Induktionserwaermung Fritz Due | Device for the heat treatment of metallic workpieces |
| DE3942810A1 (en) * | 1989-12-23 | 1991-06-27 | Linde Ag | METHOD FOR PROVIDING AND DISTRIBUTING TREATMENT GAS IN HEAT TREATMENTS |
| DE4016183A1 (en) * | 1990-05-19 | 1991-11-21 | Linde Ag | METHOD FOR IMPROVING THE PROVISION OF TREATMENT GAS IN HEAT TREATMENTS |
| FR2668584B1 (en) * | 1990-10-26 | 1994-03-18 | Lair Liquide | PROCESS FOR DEVELOPING A HEAT TREATMENT ATMOSPHERE AND HEAT TREATMENT PLANT. |
| DE4343927C1 (en) * | 1993-12-22 | 1995-01-05 | Linde Ag | Method for thermal treatment of workpieces under treatment gas |
| DE19545764C2 (en) * | 1995-12-07 | 2000-02-17 | Linde Ag | Process for producing protective gas for a heat treatment furnace and heat treatment plant |
| IT1291479B1 (en) * | 1997-01-29 | 1999-01-11 | Rivoira Spa | PROCESS OF HEAT TREATMENT OF METALLIC PIECES WITH A FERROUS BASE IN AN ACTIVE ATMOSPHERE WITH A HIGH CARBON POTENTIAL. |
| DE10347312B3 (en) * | 2003-10-08 | 2005-04-14 | Air Liquide Deutschland Gmbh | Process for the heat treatment of iron materials |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DD31283A (en) * | ||||
| DE1433735B1 (en) * | 1963-09-21 | 1969-09-04 | Werner Goehring | Process for achieving a furnace atmosphere with which an oxidation-free heat treatment of workpieces made of steel can be carried out while at the same time influencing the carbon content |
| DD131292A1 (en) * | 1977-03-28 | 1978-06-14 | Arnd Mueller | DEVICE FOR PROTECTING GAS GENERATION IN THE OVEN ROOM |
| DE3440876A1 (en) * | 1984-11-08 | 1986-05-15 | Linde Ag, 6200 Wiesbaden | METHOD AND DEVICE FOR PRODUCING A PROTECTIVE GAS ATMOSPHERE |
-
1986
- 1986-09-10 DE DE19863630833 patent/DE3630833A1/en not_active Withdrawn
-
1987
- 1987-09-02 ES ES87112804T patent/ES2042524T3/en not_active Expired - Lifetime
- 1987-09-02 EP EP87112804A patent/EP0261461B1/en not_active Expired - Lifetime
- 1987-09-02 AT AT87112804T patent/ATE89868T1/en not_active IP Right Cessation
- 1987-09-02 DE DE8787112804T patent/DE3785989D1/en not_active Expired - Fee Related
- 1987-09-04 BR BR8704618A patent/BR8704618A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0261461A2 (en) | 1988-03-30 |
| ES2042524T3 (en) | 1993-12-16 |
| BR8704618A (en) | 1988-04-26 |
| DE3785989D1 (en) | 1993-07-01 |
| EP0261461A3 (en) | 1989-03-15 |
| ATE89868T1 (en) | 1993-06-15 |
| DE3630833A1 (en) | 1988-03-17 |
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