EP0703994B1 - Method and device for the heat treatment of workpieces - Google Patents

Method and device for the heat treatment of workpieces Download PDF

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Publication number
EP0703994B1
EP0703994B1 EP94917627A EP94917627A EP0703994B1 EP 0703994 B1 EP0703994 B1 EP 0703994B1 EP 94917627 A EP94917627 A EP 94917627A EP 94917627 A EP94917627 A EP 94917627A EP 0703994 B1 EP0703994 B1 EP 0703994B1
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Prior art keywords
workpieces
carbon dioxide
gas
flue gas
furnace chamber
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German (de)
French (fr)
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EP0703994A1 (en
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Friedhelm Kühn
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LOI Thermprocess GmbH
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LOI Thermprocess GmbH
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
    • C23C8/30—Carbo-nitriding
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising

Definitions

  • the invention relates to a method and an apparatus for the heat treatment of Workpieces, the workpieces being heated with radiant heat, Burning gaseous fuel, especially natural gas, is generated, and wherein at least some of the workpieces are subjected to a carburizing atmosphere becomes.
  • a jacket radiant tube is used as an exo generator formed and generates a carrier gas which is led into the treatment room, a secondary gas containing carbon or nitrogen can be added.
  • the invention has for its object the carburizing process from these points of view to optimize, d. H. reduce pollutant emissions and at the same time to improve the litigation at least so that no significant economic Losses have to be accepted.
  • the method according to the invention is characterized in that that arises from the combustion of the gaseous fuel Flue gas carbon dioxide is separated that the carbon dioxide containing hydrocarbon Gas is mixed and that the gas mixture to create the carburizing atmosphere is heated.
  • the environmental pollution is reduced considerably by separating the carbon dioxide from the flue gases of the radiant heating.
  • the proportion of carbon dioxide in the flue gas is approximately 11%. Most of this can be separated from this.
  • the residual flue gas contains only less than 1% carbon dioxide after the treatment.
  • the carbon dioxide is supplied to the carburizing process as an oxygen and carbon supplier, with the effect that that the carburizing time is reduced significantly, namely by 20 to 40%.
  • the carburizing time depends on the temperature, the diffusion coefficient and the mass transfer coefficient. At a given temperature, the latter two coefficients determine the speed, with equal to side by side at small to medium carburizing depths (0.2 to about 0.8 or 1.0 mm).
  • the invention has a particularly favorable effect in this area. It leads to an increase in the mass transfer coefficient of around a factor of 2.5.
  • a particular advantage of the invention is that the entire process is continuous can be driven, with the possibility, if necessary, of the separated Intermediate storage of carbon dioxide. Is preferably used as hydrocarbon Gas used natural gas.
  • the carburizing atmosphere is created by an endothermic reaction.
  • the for this required heat is preferably taken from the radiant heat used for heating of the workpieces. This can happen, for example, that the mixture of carbon dioxide and hydrocarbonaceous gas directly into the furnace chamber initiates. However, there is a risk that it will result in an inadmissible Soot comes. It may therefore be more advantageous to pass the gas mixture over a catalyst to ensure that the endothermic reaction without soot formation can expire.
  • the catalyst also ensures optimal mixing of the Components.
  • the endogas generator can be arranged outside the furnace chamber be. However, separate heating is usually required. Accordingly it may be more advantageous to arrange the generator in the furnace chamber, and preferably in the ceiling area, i.e. where there is a high temperature level prevails and where the fans are located.
  • the carbon dioxide by pressure change resulting from the combustion of the gaseous fuel Separate flue gas.
  • This process uses the pressure-dependent Accumulation properties of the carbon dioxide, for example Molecular sieves It can be easily in the continuous Integrate process and is economically favorable.
  • the carburization reaction produces carbon dioxide and Water. Since this reaction in the method according to the invention runs particularly quickly, a local surplus can accumulate Reaction products result, with the consequence that it too undesirable edge zone oxidation of the workpieces.
  • Inoculate carburizing atmosphere with heavy hydrocarbon Especially the slow reacting methane, which is preferred is made available in the form of natural gas Able to buffer the products of the carburization reaction and on prevent oxidation of the material. At the same time made sure that the carbon level in the Carburizing atmosphere is maintained. For prevention the edge zone oxidation must be ensured that the heavy hydrocarbon gets to the workpieces shield endangered surfaces.
  • one local hydrocarbon concentration of 4 to 6% to adjust.
  • the remaining flue gas after the removal of the carbon dioxide the radiant heater can be used as a purge gas are used, for example, to make locks inert.
  • this residual flue gas for nitro-carburizing part of the To use workpieces with the addition of ammonia.
  • nitro carburizing alongside the ammonia commercially available and commercially available use acquired carbon dioxide.
  • constituents are formed by the residual flue gas delivered. This leads to an additional increase in Profitability and thus to a considerable increase the desired optimization effect.
  • the nitro carburizing process can be easily in the continuous Integrate the entire process.
  • the removal of carbon dioxide from the Flue gas from the radiant heater is set so that both the needs of the carburizing process as well as those of the Nitro carburizing process can be taken into account. Overall, this results in an extremely economical process of extreme environmental friendliness.
  • the invention also provides an apparatus for Heat treatment of workpieces with at least one furnace chamber, which is equipped with gas powered radiant heating pipes, and with a generator for generating carburizing gas for the Furnace chamber, this device being characterized in that that the radiant heating pipes with their flue gas lines to a Pressure change device are connected and that the Pressure change device with its carbon dioxide outlet line the generator is connected.
  • the pressure change device separates carbon dioxide from the flue gas of the radiant heating pipes, whereupon the carbon dioxide as oxygen and Carbon supplier gets into the generator to be there with a hydrocarbon-containing gas, preferably natural gas, endothermic to react.
  • the generator is for heating it advantageously arranged in the furnace chamber, namely in their ceiling area.
  • the pressure change device with its residual flue gas outlet line to connect to a second oven chamber, which has an ammonia inlet line and serves a Part of the workpieces that should not be carburized Nitro carburizing.
  • a common control ensures that synchronize individual processes and to run continuously.
  • the invention is based on a preferred Embodiment of a device according to the invention in Connection with the accompanying drawing explained.
  • the drawing shows a schematic block diagram.
  • the device has a first furnace chamber 1, which is used for carburizing workpieces 2 and gas-powered radiant tubes 3 is heated. The latter are via its flue gas lines 4 to a pressure change device 5 connected.
  • the flue gas Radiant heating tubes 3 freed of carbon dioxide. This results a reduction in environmental pollution.
  • that serves Carbon dioxide to produce endogas by raising a significant increase in the mass transfer coefficient the carburizing rate is achieved. This increases the profitability of the carburizing process.
  • the device also has a second Furnace chamber 10 used for nitro-carburizing workpieces 11 serves.
  • the second furnace chamber is heated via Radiant heating tubes 12. These are with their flue gas lines 13 also connected to the pressure change device 5. Accordingly, they contribute to the generator 7 To supply carbon dioxide.
  • the pressure change device 5 has an outlet line 14 which serves to remove the residual flue gas from the radiant heating tubes 3 and 12 into the second furnace chamber.
  • the rest of the flue gas contains a share of carbon dioxide and also one Proportion of nitrogen.
  • ammonia which has a Line 15 is supplied, the residual flue gas forms the Atmosphere for nitro carburizing the workpieces 11.
  • a controller ensures that the Carbon dioxide content of the flue gases in the pressure change device according to the respective requirements for the furnace chambers 1 and 10 is split. Furthermore, the control causes one Synchronization of the individual processes, in such a way that the entire process can be operated continuously.
  • the second Oven chamber 10 can be dispensed with. Instead, that can be done the pressure change device 5 residual flue gas for Inerting locks or the like Find use.
  • the generator 7 can be arranged outside the furnace chamber 1 be, but then an additional heating is required. The generator 7 can also be used entirely to be dispensed with. That from the pressure change device 5 Coming carbon dioxide will come with the under these circumstances Mixed natural gas entered directly in the furnace chamber.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Incineration Of Waste (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

PCT No. PCT/EP94/01542 Sec. 371 Date Apr. 15, 1996 Sec. 102(e) Date Apr. 15, 1996 PCT Filed May 13, 1994 PCT Pub. No. WO94/29491 PCT Pub. Date Dec. 22, 1994The present invention involves a method and a device for the heat treatment of workpieces, which are heated with radiant heat generated through the combustion of gaseous fuel. Some of the workpieces are subjected to a carburisation atmosphere formed by a heated mixture of hydrocarbon containing gas and carbon dioxide, where the carbon dioxide has been separated from the exhaust gas of the gaseous fuel combustion. Other workpieces may be subjected to a nitrocarburisation atmosphere formed by a mixture of ammonia and the exhaust gas remaining after the carbon dioxide has been separated. By recycling some of the products of the combustion process, the present invention improves the efficiency of the carburisation process while reducing pollutant emissions.

Description

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zum Wärmebehandeln von Werkstücken, wobei die Werkstücke mit Strahlungwärme erwärmt werden, die durch Verbrennen von gasförmigen Brennstoff, insbesondere von Erdgas, erzeugt wird, und wobei mindestens ein Teil der Werkstücke mit einer Karburieratmosphäre beaufschlagt wird.The invention relates to a method and an apparatus for the heat treatment of Workpieces, the workpieces being heated with radiant heat, Burning gaseous fuel, especially natural gas, is generated, and wherein at least some of the workpieces are subjected to a carburizing atmosphere becomes.

Aus der DE 24 19 997 A1 ist ein Verfahren und eine Einrichtung zum Gasaufkohlen oder Nitrieren von Stahlteilen bekannt. Ein Mantelstrahlheizrohr ist als Exo-Generator ausgebildet und erzeugt ein Trägergas, das in den Behandlungsraum geleitet wird, wobei ein kohlen- oder stickstoffhaltiges Sekundärgas zugegeben werden kann.DE 24 19 997 A1 describes a method and a device for gas carburizing or nitriding of steel parts. A jacket radiant tube is used as an exo generator formed and generates a carrier gas which is led into the treatment room, a secondary gas containing carbon or nitrogen can be added.

Derartige Aufkohlungsverfahren und -vorrichtungen haben einen relativ hohen Energiebedarf. Dementsprechend ist ein ständiges Bestreben der Fachwelt, die Wirtschaftlichkeit der Aufkohlungsprozesse zu steigern. Gleichzeitig sind die Bedürfnisse des Umweltschutzes zu berücksichtigen. Der Verminderung der Schadstoffemissionen kommt ein entsprechend hoher Stellenwert zu. Allerdings sind diesbezügliche Maßnahmen kostenintensiv und dementsprechend gegenläufig zu den Wirtschaftlichkeitsbestrebungen.Such carburizing methods and devices have a relatively high energy requirement. Accordingly, the professional world is constantly striving for profitability to increase the carburizing processes. At the same time, the needs of the Environmental protection. The reduction of pollutant emissions has a correspondingly high priority. However, measures are in this regard cost-intensive and therefore contrary to the profitability efforts.

Der Erfindung liegt die Aufgabe zugrunde, den Aufkohlungsprozeß unter diesen Gesichtspunkten zu optimieren, d. h. die Schadstoffemissionen zu senken und gleichzeitig die Prozeßführung zumindest so zu verbessern, daß keine wesentlichen wirtschaftlichen Einbußen hingenommen werden müssen.The invention has for its object the carburizing process from these points of view to optimize, d. H. reduce pollutant emissions and at the same time to improve the litigation at least so that no significant economic Losses have to be accepted.

Zur Lösung dieser Aufgabe ist das Verfahren nach der Erfindung dadurch gekennzeichnet, daß aus dem bei der Verbrennung des gasförmigen Brennstoffs entstehenden Rauchgas Kohlendioxid abgetrennt wird, daß das Kohlendioxid mit kohlenwasserstoffhaltigem Gas gemischt wird und daß das Gasgemisch zur Erzeugung der Karburieratmosphäre erwärmt wird.To achieve this object, the method according to the invention is characterized in that that arises from the combustion of the gaseous fuel Flue gas carbon dioxide is separated that the carbon dioxide containing hydrocarbon Gas is mixed and that the gas mixture to create the carburizing atmosphere is heated.

Durch das Abtrennen des Kohlendioxids aus den Rauchgasen der Strahlungsheizung vermindert sich die Umweltbelastung ganz erheblich. Der Anteil an Kohlendioxid im Rauchgas beträgt ca. 11 %. Hiervon kann der überwiegende Teil abgetrennt werden. Bei entsprechender Prozeßsteuerung enthält das Rest-Rauchgas nach der Behandlung nur noch weniger als 1 % Kohlendioxid.
Das Kohlendioxid wird dem Aufkohlungsprozeß als Sauerstoff- und Kohlenstofflieferant zugeführt, und zwar mit dem Effekt,
daß die Aufkohlungszeit wesentlich reduziert wird, nämlich um 20 bis 40 %. Die Aufkohlungszeit hängt ab von der Temperatur, dem Diffusionskoeffizienten und dem Stoffübergangskoeffizienten. Bei vorgegebener Temperatur sind die beiden letztgenannten Koeffizienten geschwindigkeitsbestimmend, und zwar bei kleinen bis mittleren Aufkohlungstiefen (0,2 bis etwa 0,8 oder 1,0 mm) gleichrangig nebeneinander. In diesem Bereich wirkt sich die Erfindung besonders günstig aus. Sie führt zu einer Erhöhung des Stoffübergangskoeffizienten etwa um den Faktor 2,5.The environmental pollution is reduced considerably by separating the carbon dioxide from the flue gases of the radiant heating. The proportion of carbon dioxide in the flue gas is approximately 11%. Most of this can be separated from this. With appropriate process control, the residual flue gas contains only less than 1% carbon dioxide after the treatment.
The carbon dioxide is supplied to the carburizing process as an oxygen and carbon supplier, with the effect that
that the carburizing time is reduced significantly, namely by 20 to 40%. The carburizing time depends on the temperature, the diffusion coefficient and the mass transfer coefficient. At a given temperature, the latter two coefficients determine the speed, with equal to side by side at small to medium carburizing depths (0.2 to about 0.8 or 1.0 mm). The invention has a particularly favorable effect in this area. It leads to an increase in the mass transfer coefficient of around a factor of 2.5.

Ein besonderer Vorteil der Erfindung besteht darin, daß der gesamte Prozeß kontinuierlich gefahren werden kann, wobei ggf. die Möglichkeit besteht, das abgetrennte Kohlendioxid zwischenzuspeichern. Vorzugsweise wird als kohlenwasserstoffhaltiges Gas Erdgas verwendet.A particular advantage of the invention is that the entire process is continuous can be driven, with the possibility, if necessary, of the separated Intermediate storage of carbon dioxide. Is preferably used as hydrocarbon Gas used natural gas.

Die Karburieratmosphäre wird durch eine endotherme Reaktion erzeugt. Die hierzu erforderliche Wärme wird vorzugsweise der Strahlungswärme entnommen, die zur Beheizung der Werkstücke dient. Dies kann beispielsweise dadurch geschehen, daß man das Gemisch aus Kohlendioxid und kohlenwasserstoffhaltigem Gas direkt in den Ofenraum einleitet. Allerdings besteht dabei die Gefahr, daß es zu einer unzulässigen Rußbildung kommt. Daher kann es vorteilhafter sein, das Gasgemisch über einen Katalysator zu leiten, der sicherstellt, daß die endotherme Reaktion ohne Rußbildung ablaufen kann. Der Katalysator sorgt gleichzeitig für eine optimale Durchmischung der Komponenten. Der Endogas-Generator kann außerhalb des Ofenraums angeordnet sein. Dabei wird allerdings in der Regel eine gesonderte Beheizung erforderlich. Dementsprechend kann es vorteilhafter sein, den Generator im Ofenraum anzuordnen, und zwar vorzugsweise im Deckenbereich, also dort, wo ein hohes Temperaturniveau herrscht und wo sich darüberhinaus die Ventilatoren befinden.The carburizing atmosphere is created by an endothermic reaction. The for this required heat is preferably taken from the radiant heat used for heating of the workpieces. This can happen, for example, that the mixture of carbon dioxide and hydrocarbonaceous gas directly into the furnace chamber initiates. However, there is a risk that it will result in an inadmissible Soot comes. It may therefore be more advantageous to pass the gas mixture over a catalyst to ensure that the endothermic reaction without soot formation can expire. The catalyst also ensures optimal mixing of the Components. The endogas generator can be arranged outside the furnace chamber be. However, separate heating is usually required. Accordingly it may be more advantageous to arrange the generator in the furnace chamber, and preferably in the ceiling area, i.e. where there is a high temperature level prevails and where the fans are located.

In Weiterbildung der Erfindung wird vorgeschlagen, das Kohlendioxid durch Druckwechsel aus dem bei der Verbrennung des gasförmigen Brennstoffs entstehenden Rauchgas abzutrennen. Dieses Verfahren nutzt die druckabhängigen Anlagerungseigenschaften des Kohlendioxids beispielsweise an Molekularsieben Es läßt sich problemlos in den kontinuierlichen Prozeß einbinden und ist wirtschaftlich günstig.In a further development of the invention it is proposed that the carbon dioxide by pressure change resulting from the combustion of the gaseous fuel Separate flue gas. This process uses the pressure-dependent Accumulation properties of the carbon dioxide, for example Molecular sieves It can be easily in the continuous Integrate process and is economically favorable.

Bei der Aufkohlungsreaktion entsteht Kohlendioxid und Wasser. Da diese Reaktion bei dem Verfahren nach der Erfindung besonders schnell abläuft, kann sich ein örtlicher Überschuß an Reaktionsprodukten ergeben, und zwar mit der Folge, daß es zu einer unerwünschten Randzonenoxidation der Werkstücke kommt. Um diesem Effekt zu begegnen, wird vorgeschlagen, die Karburieratmosphäre mit schwerem Kohlenwasserstoff zu impfen. Insbesondere das langsam reagierende Methan, das vorzugsweise in Form von Erdgas zur Verfügung gestellt wird, ist in der Lage, die Produkte der Aufkohlungsreaktion abzupuffern und an einer Oxidation des Werkstoffs zu hindern. Gleichzeitig wird dafür gesorgt, daß der Kohlenstoffpegel in der Karburieratmosphäre aufrechterhalten bleibt. Zur Verhinderung der Randzonenoxidation muß sichergestellt werden, daß der schwere Kohlenwasserstoff zu den Werkstücken gelangt, um die gefährdeten Oberflächen abzuschirmen. Hier sollte sich eine örtliche Kohlenwasserstoffkonzentration von 4 bis 6 % einstellen.The carburization reaction produces carbon dioxide and Water. Since this reaction in the method according to the invention runs particularly quickly, a local surplus can accumulate Reaction products result, with the consequence that it too undesirable edge zone oxidation of the workpieces. Around To counter this effect, it is proposed that Inoculate carburizing atmosphere with heavy hydrocarbon. Especially the slow reacting methane, which is preferred is made available in the form of natural gas Able to buffer the products of the carburization reaction and on prevent oxidation of the material. At the same time made sure that the carbon level in the Carburizing atmosphere is maintained. For prevention the edge zone oxidation must be ensured that the heavy hydrocarbon gets to the workpieces shield endangered surfaces. Here should be one local hydrocarbon concentration of 4 to 6% to adjust.

Das nach dem Abtrennen des Kohlendioxids verbleibende Rest-Rauchgas der Strahlungsheizung kann als Spülgas eingesetzt werden, beispielsweise zum Inertisieren von Schleusen. In wesentlicher Weiterbildung der Erfindung wird vorgeschlagen, dieses Rest-Rauchgas zum Nitro-Karburieren eines Teils der Werkstücke zu verwenden, und zwar unter Zusatz von Ammoniak. Normalerweise ist es üblich, für das Nitro-Karburieren neben dem Ammoniak käuflich erworbenen Stickstoff und käuflich erworbenes Kohlendioxid einzusetzen. Die beiden letztgenannten Bestandteile werden erfindungsgemäß durch das Rest-Rauchgas geliefert. Dies führt zu einer zusätzlichen Erhöhung der Wirtschaftlichkeit und damit zu einer beträchtlichen Steigerung des angestrebten Optimierungseffektes. Der Nitro-Karburier-Prozeß läßt sich ohne weiteres in den kontinuierlichen Gesamtprozeß einbinden. Die Kohlendioxidentnahme aus dem Rauchgas der Strahlungsheizung wird so eingestellt, daß sowohl den Bedürfnissen des Aufkohlungsprozesses als auch denen des Nitro-Karburier-Prozesses Rechnung getragen werden kann. Insgesamt ergibt sich ein äußerst wirtschaftliches Verfahren von extremer Umweltfreundlichkeit.The remaining flue gas after the removal of the carbon dioxide the radiant heater can be used as a purge gas are used, for example, to make locks inert. In essential further development of the invention is proposed this residual flue gas for nitro-carburizing part of the To use workpieces with the addition of ammonia. Usually it is common for nitro carburizing alongside the ammonia commercially available and commercially available use acquired carbon dioxide. The latter two According to the invention, constituents are formed by the residual flue gas delivered. This leads to an additional increase in Profitability and thus to a considerable increase the desired optimization effect. The nitro carburizing process can be easily in the continuous Integrate the entire process. The removal of carbon dioxide from the Flue gas from the radiant heater is set so that both the needs of the carburizing process as well as those of the Nitro carburizing process can be taken into account. Overall, this results in an extremely economical process of extreme environmental friendliness.

Die Erfindung schafft ferner eine Vorrichtung zum Wärmebehandeln von Werkstücken mit mindestens einer Ofenkammer, die mit gasbetriebenen Strahlheizrohren versehen ist, und mit einem Generator zum Erzeugen von Karburiergas für die Ofenkammer, wobei diese Vorrichtung dadurch gekennzeichnet ist, daß die Strahlheizrohre mit ihren Rauchgasleitungen an eine Druckwechseleinrichtung angeschlossen sind und daß die Druckwechseleinrichtung mit ihrer Kohlendioxid-Auslaßleitung an den Generator angeschlossen ist. Die Druckwechseleinrichtung trennt Kohlendioxid aus dem Rauchgas der Strahlheizrohre ab, worauf das Kohlendioxid als Sauerstoff- und Kohlenstofflieferant in den Generator gelangt, um dort mit einem kohlenwasserhaltigem Gas, vorzugsweise Erdgas, endotherm zu reagieren. Der Generator ist zu seiner Beheizung vorteilhafterweise in der Ofenkammer angeordnet, und zwar in deren Deckenbereich.The invention also provides an apparatus for Heat treatment of workpieces with at least one furnace chamber, which is equipped with gas powered radiant heating pipes, and with a generator for generating carburizing gas for the Furnace chamber, this device being characterized in that that the radiant heating pipes with their flue gas lines to a Pressure change device are connected and that the Pressure change device with its carbon dioxide outlet line the generator is connected. The pressure change device separates carbon dioxide from the flue gas of the radiant heating pipes, whereupon the carbon dioxide as oxygen and Carbon supplier gets into the generator to be there with a hydrocarbon-containing gas, preferably natural gas, endothermic to react. The generator is for heating it advantageously arranged in the furnace chamber, namely in their ceiling area.

In wesentlicher Weiterbildung der Erfindung wird vorgeschlagen, die Druckwechseleinrichtung mit ihrer Rest-Rauchgas-Auslaßleitung an eine zweite Ofenkammer anzuschließen, die eine Ammoniak-Einlaßleitung aufweist und dazu dient, einen Teil der Werkstücke, die nicht aufgekohlt werden sollen, zu Nitro-Karburieren. Eine gemeinsame Steuerung sorgt dafür, die einzelnen Prozesse aufeinander zu synchronisieren und kontinuierlich ablaufen zu lassen.In an essential further development of the invention proposed the pressure change device with its residual flue gas outlet line to connect to a second oven chamber, which has an ammonia inlet line and serves a Part of the workpieces that should not be carburized Nitro carburizing. A common control ensures that synchronize individual processes and to run continuously.

Zur Beheizung der zweiten Ofenkammer wird man in der Regel ebenfalls gasbetriebene Strahlheizrohre einsetzen. Dabei ist es dann besonders vorteilhaft, deren Rauchgasleitungen auch an die Druckwechseleinrichtung anzuschließen, so daß das Rauchgas derselben Behandlung unterworfen wird wie das Rauchgas der in der Aufkohlungskammer arbeitenden Strahlheizrohre. One is usually used to heat the second furnace chamber also use gas powered radiant heating pipes. It is then particularly advantageous, the flue gas lines to the Connect pressure change device so that the flue gas is subjected to the same treatment as the flue gas in of the carburizing chamber.

Als erfindungswesentlich offenbart gelten auch solche Kombinationen der erfindungsgemäßen Merkmale, die von den vorstehend diskutierten Verknüpfungen abweichen.Such are also considered to be disclosed as essential to the invention Combinations of the features of the invention by the Links discussed above differ.

Die Erfindung wird im folgenden anhand eines bevorzugten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung im Zusammenhang mit der beiliegenden Zeichnung näher erläutert. Die Zeichnung zeigt ein schematisches Blockschaltbild.The invention is based on a preferred Embodiment of a device according to the invention in Connection with the accompanying drawing explained. The drawing shows a schematic block diagram.

Demnach weist die Vorrichtung eine erste Ofenkammer 1 auf, die zum Aufkohlen von Werkstücken 2 dient und von gasbetriebenen Strahlheizrohren 3 beheizt wird. Letztere sind über ihre Rauchgasleitungen 4 an eine Druckwechseleinrichtung 5 angeschlossen.Accordingly, the device has a first furnace chamber 1, which is used for carburizing workpieces 2 and gas-powered radiant tubes 3 is heated. The latter are via its flue gas lines 4 to a pressure change device 5 connected.

In der Druckwechseleinrichtung 5 wird Kohlendioxid aus dem Rauchgas der Strahlheizrohre 3 abgetrennt. Das Kohlendioxid gelangt über eine Auslaßleitung 6 zu einem Generator 7, der außerdem über eine Leitung 8 mit Erdgas beschickt wird. Da sich der Generator 7 innerhalb der Ofenkammer befindet, wird er von den Strahlheizrohren 3 beheizt. Im Generator 7 reagiert das Erdgas mit dem Kohlendioxid. Das dabei erzeugte Endogas gelangt in die Ofenkammer 1 und bewirkt dort an den Werkstücken 2 die Aufkohlungsreaktion.In the pressure change device 5, carbon dioxide from the Flue gas from the radiant heating tubes 3 separated. The carbon dioxide passes via an outlet line 6 to a generator 7 which is also supplied with natural gas via a line 8. That I the generator 7 is located inside the furnace chamber, it is from the radiant heating tubes 3 heated. This reacts in generator 7 Natural gas with the carbon dioxide. The endogas generated thereby arrives into the furnace chamber 1 and there causes the workpieces 2 Carburization reaction.

Auf diese Weise wird zum einen das Rauchgas der Strahlheizrohre 3 von Kohlendioxid befreit. Daraus resultiert eine Verminderung der Umweltbelastung. Andererseits dient das Kohlendioxid zur Erzeugung des Endogases, wobei durch Anhebung des Stoffübergangskoeffizienten eine beträchtliche Steigerung der Aufkohlungsgeschwindigkeit erzielt wird. Dadurch erhöht sich die Wirtschaftlichkeit des Aufkohlungsprozesses.In this way, on the one hand, the flue gas Radiant heating tubes 3 freed of carbon dioxide. This results a reduction in environmental pollution. On the other hand, that serves Carbon dioxide to produce endogas, by raising a significant increase in the mass transfer coefficient the carburizing rate is achieved. This increases the profitability of the carburizing process.

Durch die Beschleunigung der Aufkohlung kann sich an den Werkstoffoberflächen ein örtlicher Überschuß an Kohlendioxid und Wasserdampf bilden. Zur Abpufferung dieses Überschusses wird an geeigneter Stelle - schematisch angedeutet durch eine Leitung 9 - Methan in die Ofenkammer 1 eingeleitet.By accelerating the carburization, the Material surfaces a local excess of carbon dioxide and form water vapor. To buffer this excess is indicated at a suitable point - indicated schematically by a Line 9 - methane introduced into the furnace chamber 1.

Die Vorrichtung verfügung ferner über eine zweite Ofenkammer 10, die zum Nitro-Karburieren von Werkstücken 11 dient. Die Beheizung der zweiten Ofenkammer erfolgt über Strahlheizrohre 12. Diese sind mit ihren Rauchgasleitungen 13 ebenfalls an die Druckwechseleinrichtung 5 angeschlossen. Dementsprechend tragen sie dazu bei, den Generator 7 mit Kohlendioxid zu versorgen.The device also has a second Furnace chamber 10 used for nitro-carburizing workpieces 11 serves. The second furnace chamber is heated via Radiant heating tubes 12. These are with their flue gas lines 13 also connected to the pressure change device 5. Accordingly, they contribute to the generator 7 To supply carbon dioxide.

Die Druckwechseleinrichtung 5 weist eine Auslaßleitung 14 auf, die dazu dient, das Rest-Rauchgas der Strahlheizrohre 3 und 12 in die zweiten Ofenkammer einzuleiten. Das Rest-Rauchgas enthält noch einen Anteil an Kohlendioxid und ferner einen Anteil an Stickstoff. In Verbindung mit Ammoniak, der über eine Leitung 15 zugeführt wird, bildet das Rest-Rauchgas die Atmosphäre zum Nitro-Karburieren der Werkstücke 11.The pressure change device 5 has an outlet line 14 which serves to remove the residual flue gas from the radiant heating tubes 3 and 12 into the second furnace chamber. The rest of the flue gas contains a share of carbon dioxide and also one Proportion of nitrogen. In conjunction with ammonia, which has a Line 15 is supplied, the residual flue gas forms the Atmosphere for nitro carburizing the workpieces 11.

Eine nicht dargestellte Steuerung sorgt dafür, daß der Kohlendioxidgehalt der Rauchgase in der Druckwechseleinrichtung entsprechend den jeweiligen Anforderungen auf die Ofenkammern 1 und 10 aufgeteilt wird. Ferner bewirkt die Steuerung eine Synchronisierung der einzelnen Abläufe, und zwar derart, daß der Gesamtprozeß kontinuierlich betrieben werden kann.A controller, not shown, ensures that the Carbon dioxide content of the flue gases in the pressure change device according to the respective requirements for the furnace chambers 1 and 10 is split. Furthermore, the control causes one Synchronization of the individual processes, in such a way that the entire process can be operated continuously.

Im Rahmen der Erfindung sind durchaus Abwandlungsmöglichkeiten gegeben. So kann auf die zweite Ofenkammer 10 verzichtet werden. Anstelle dessen kann das aus der Druckwechseleinrichtung 5 stammende Rest-Rauchgas zum Inertisieren von Schleusen o.dgl. Verwendung finden. Ferner kann der Generator 7 außerhalb der Ofenkammer 1 angeordnet werden, wobei dann allerdings eine zusätzliche Beheizung erforderlich wird. Auf den Generator 7 kann auch ganz verzichtet werden. Das aus der Druckwechseleinrichtung 5 kommende Kohlendioxid wird unter diesen Umständen mit dem Erdgas gemischt direkt in der Ofenkammer eingegeben.Within the scope of the invention are quite Modifications given. So can the second Oven chamber 10 can be dispensed with. Instead, that can be done the pressure change device 5 residual flue gas for Inerting locks or the like Find use. Further the generator 7 can be arranged outside the furnace chamber 1 be, but then an additional heating is required. The generator 7 can also be used entirely to be dispensed with. That from the pressure change device 5 Coming carbon dioxide will come with the under these circumstances Mixed natural gas entered directly in the furnace chamber.

Claims (10)

  1. A method for the heat treatment of workpieces, wherein the workpieces are heated with radiant heat which is generated through the combustion of gaseous fuel, in particular natural gas, and wherein at least some of the workpieces are subjected to a carburisation atmosphere, characterised in that carbon dioxide is separated out of the flue gas formed during the combustion of the gaseous fuel, that the carbon dioxide is mixed with hydrocarbon-containing gas and that the gas mixture is heated to produce a carburisation atmosphere.
  2. A method according to claim 1, characterised in that natural gas is used as the hydrocarbon-containing gas.
  3. A method according to claim 1 or 2, characterised in that the gas mixture is heated with the radiant heat used to heat the workpieces.
  4. Method according to any one of claims 1 through 3, characterised in that the gas mixture is passed over a catalyst.
  5. A method according to any one of claims 1 through 4, characterised in that the carbon dioxide is removed by pressure-change from the flue gas formed during the combustion of the gaseous fuel.
  6. A method according to any one of claims 1 through 5, characterised in that the carburisation atmosphere is injected with heavy hydrocarbon.
  7. A method according to any one of claims 1 through 6, characterised in that the flue gas remaining after the removal of the carbon dioxide is used for nitrocarburisation of some of the workpieces, ammonia being added.
  8. A device for the heat treatment of workpieces with at least 1 furnace chamber, which is provided with gas-operated radiant heating tubes, and with a generator for producing carburisation gas for the furnace chamber, characterised in that the radiant heating tubes (3, 12) are connected by their flue gas pipes (4, 13) to a pressure-change device (5) and that the pressure-change device is connected by its carbon dioxide outlet pipe (6) to the generator (7).
  9. A device according to claim 8, characterised in that the pressure-change device (5) is connected by its remaining flue gas outlet pipe (14) to a second furnace chamber (10) which has an ammonia inlet pipe (15).
  10. A device according to claim 9, characterised in that the second furnace chamber (10) has gas-operated radiant heating tubes (12) which are connected by their flue gas pipes (13) to the pressure-change device (5).
EP94917627A 1993-06-03 1994-05-13 Method and device for the heat treatment of workpieces Expired - Lifetime EP0703994B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4318400A DE4318400C1 (en) 1993-06-03 1993-06-03 Method and device for heat treating workpieces
DE4318400 1993-06-03
PCT/EP1994/001542 WO1994029491A1 (en) 1993-06-03 1994-05-13 Method and device for the heat treatment of workpieces

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EP0703994A1 EP0703994A1 (en) 1996-04-03
EP0703994B1 true EP0703994B1 (en) 1998-04-22

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EP (1) EP0703994B1 (en)
JP (1) JPH08511063A (en)
AT (1) ATE165399T1 (en)
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WO (1) WO1994029491A1 (en)

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WO2003064637A1 (en) * 2001-11-06 2003-08-07 Medtronic, Inc. Method and system for myocardial infarction repair
DE10031921A1 (en) * 2000-06-30 2002-01-17 Bosch Gmbh Robert Carburizing steel workpieces made of steel comprises exposing a workpiece to a carrier or base gas in a gas jet field
US10196730B2 (en) 2009-09-10 2019-02-05 Ald Vacuum Technologies Gmbh Method and device for hardening workpieces, and workpieces hardened according to the method
DE102009041041B4 (en) 2009-09-10 2011-07-14 ALD Vacuum Technologies GmbH, 63450 Method and apparatus for hardening workpieces, as well as work hardened workpieces
DE102015117683B3 (en) * 2015-10-16 2016-09-29 Wienstroth Wärmebehandlungstechnik GmbH Method and device for producing and treating protective and / or reaction gases for the heat treatment of metals

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US1817345A (en) * 1927-07-19 1931-08-04 Carbide & Carbon Chem Corp Process for case carburizing and heat treating metals
GB1004573A (en) * 1962-08-17 1965-09-15 Incandescent Ltd Improvements in regenerative furnaces
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US3712597A (en) * 1970-11-18 1973-01-23 Air Preheater Glass manufacturing system
US3870474B1 (en) * 1972-11-13 1991-04-02 Regenerative incinerator systems for waste gases
DE2419997C2 (en) * 1974-04-25 1986-02-27 Ruhrgas Ag, 4300 Essen Method and device for producing hardenable or wear-resistant surface layers of steel parts in an annealing furnace
JPS5236610B2 (en) * 1974-05-09 1977-09-17
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DE4110361C2 (en) * 1991-03-28 1998-04-30 Linde Ag Process for gas carburizing iron workpieces and plants for their implementation

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ATE165399T1 (en) 1998-05-15
WO1994029491A1 (en) 1994-12-22
DE4318400C1 (en) 1994-06-23
US5830284A (en) 1998-11-03
EP0703994A1 (en) 1996-04-03
JPH08511063A (en) 1996-11-19
DE59405801D1 (en) 1998-05-28

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