EP0106961A1 - Method of producing a gas atmosphere for annealing metallic work pieces - Google Patents

Method of producing a gas atmosphere for annealing metallic work pieces Download PDF

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Publication number
EP0106961A1
EP0106961A1 EP83108017A EP83108017A EP0106961A1 EP 0106961 A1 EP0106961 A1 EP 0106961A1 EP 83108017 A EP83108017 A EP 83108017A EP 83108017 A EP83108017 A EP 83108017A EP 0106961 A1 EP0106961 A1 EP 0106961A1
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EP
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Prior art keywords
furnace
gas
annealing
nitrogen
ammonia
Prior art date
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Granted
Application number
EP83108017A
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German (de)
French (fr)
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EP0106961B1 (en
Inventor
Reinhard Dipl.-Ing. Strigl
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Linde GmbH
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Linde GmbH
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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

Definitions

  • the invention relates to a method for producing a nitrogen and hydrogen-containing gas atmosphere for the annealing of metallic workpieces in an oven.
  • nitrogen and hydrogen are stored in storage containers, mixed in the required quantity in the gaseous state and the mixture is fed into the interior of the furnace.
  • nitrogen can be stored in gaseous or liquid state depending on consumption.
  • the quantitative ratio of the nitrogen-hydrogen mixture can be varied as desired (usually a hydrogen fraction between 2% by volume and 30% by volume is selected), but hydrogen is relatively expensive as the supply gas.
  • the invention is therefore based on the object of specifying a method with which a gas mixture containing nitrogen and hydrogen for the annealing of workpieces in a furnace can be produced in a simple and economical manner.
  • This object is achieved in that a gas mixture consisting of an inert gas and ammonia is introduced into the furnace interior and the furnace interior is heated to a temperature sufficient for catalytic decomposition of the ammonia before the introduction of the gas mixture.
  • the method according to the invention is based on the knowledge that ammonia is catalytically split into nitrogen and hydrogen in the interior of an annealing furnace and in this way together with additionally supplied nitrogen is used for the annealing treatment suitable work piece mixture can be formed within the furnace.
  • the furnaces used in the annealing process contain components that cause a catalytic breakdown of ammonia at a suitable temperature. Such components, usually made of chrome-nickel steels, are, for example, the furnace muffle or the conveyor belt. There is therefore a sufficiently large catalyst area in the furnace interior for the splitting of the ammonia. In the method according to the invention, the furnace itself therefore functions as a gas generator.
  • a nitrogen-hydrogen mixture can be provided in the heat treatment furnace, which is less expensive than a gas mixture produced in a cracked gas generator or by mixing the gases stored in component form.
  • the proportion of ammonia in the ammonia-nitrogen mixture can be easily adjusted based on the known ratio in the cracked gas and depends on the desired hydrogen content in the annealing furnace atmosphere.
  • the interior of the furnace is heated to a temperature above 500 ° C. for the process according to the invention.
  • nitrogen is expediently used as the inert gas, which is also easy to store.
  • a gas consisting of hydrocarbons for example natural gas or propane, is added to the nitrogen-ammonia mixture. passed into the oven.
  • the process according to the invention can be applied particularly advantageously to the annealing of chromium-nickel steels, since in this case the annealing material itself acts as a catalyst for the splitting of the ammonia. But it can also be used for the annealing of other steels and non-ferrous metals such as use when glowing nickel silver parts.
  • the process according to the invention can also be used for the annealing of other materials which have to be annealed at a temperature above 500 ° C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)
  • Chemical Vapour Deposition (AREA)

Abstract

1. A process for the production of a gas atmosphere containing nitrogen and hydrogen for the annealing of metallic workpieces in a furnace, characterised in that a gas mixture consisting of an inert gas and ammonia is introduced into the interior of the furnace and the interior of the furnace is heated to a temperature which is sufficient for the catalytic splitting of the ammonia prior to the introduction of the gas mixture.

Description

Die Erfindung betrifft ein Verfahren zum Herstellen einer Stickstoff und Wasserstoff enthaltenden Gasatmosphäre für das Glühen metallischer Werkstücke in einem Ofen.The invention relates to a method for producing a nitrogen and hydrogen-containing gas atmosphere for the annealing of metallic workpieces in an oven.

Zum Glühen von Werkstücken, beispielsweise zum Blankglühen, Rekristalisationsglühen, Spannungsfreiglühen u.ä. wird neben EXO-Gas als Schutzgas üblicherweise ein aus einem Inertgas wie Stickstoff und einem reduzierenden Gas wie Wasserstoff bestehendes Gasgemisch eingesetzt. Stickstoff-Wasserstoff-Gasmischungen werden herkömmlicherweise nach einem der beiden folgenden Verfahren hergestellt:

  • Die eine Möglichkeit ist die Herstellung eines Stickstoff-Wasserstoff-Gemisches durch Spalten von Ammoniak in einem Spaltgasgenerator. Das Ammoniak-Spaltgas wird erzeugt, indem Ammoniak in diesem Generator über einen auf ca. 900 °C erwärmten Nickelkatalysator geleitet wird. Dabei entsteht ein Gasgemisch, das aus 75 Vol.-% Wasserstoff und 25 Vol.-% Stickstoff besteht. In vielen Anwendungsfällen ist ein derartig hoher Anteil an Wasserstoff nicht notwendig. Aus diesem Grund wird das im Spaltgasgenerator erzeugte Gasgemisch häufig durch Zumischen von Stickstoff verdünnt. Die Anschaffung und Instandhaltung von Spaltgasgeneratoren ist aber sehr kostenaufwendig.
For annealing workpieces, e.g. for bright annealing, recrystallization annealing, stress relieving, etc. In addition to E X O gas, a gas mixture consisting of an inert gas such as nitrogen and a reducing gas such as hydrogen is usually used as the protective gas. Nitrogen-hydrogen gas mixtures are traditionally made by either of the following two methods:
  • One possibility is the production of a nitrogen-hydrogen mixture by splitting ammonia in a cracked gas generator. The ammonia cracked gas is generated by passing ammonia in this generator over a nickel catalyst heated to approx. 900 ° C. This creates a gas mixture consisting of 75 vol.% Hydrogen and 25 vol.% Nitrogen. Such a high proportion of hydrogen is not necessary in many applications. For this reason, the gas mixture generated in the cracked gas generator often diluted by adding nitrogen. The purchase and maintenance of fission gas generators is very expensive.

Der Einsatz eines Generators erübrigt sich bei dem zweiten Verfahren, das bisher zur Herstellung von Stickstoff-Wasserstoff-Gasgemischen verwendet wurde: Dabei werden Stickstoff und Wasserstoff in Vorratsbehältern gespeichert, in gasförmigem Zustand im erforderlichen Mengenverhältnis gemischt und das Gemisch in den Ofeninnenraum geleitet. Stickstoff kann in diesem Fall je nach Verbrauch in gasförmigem oder flüssigem Zustand gespeichert werden. Bei diesem Verfahren kann das Mengenverhältnis des Stickstoff-Wasserstoff-Gemisches zwar beliebig variiert werden (üblicherweise wird ein Wasserstoffanteil zwischen 2 Vol.-% und 30 Vol.-% gewählt), jedoch ist Wasserstoff als Liefergas relativ teuer.The use of a generator is not necessary in the second process, which was previously used to produce nitrogen-hydrogen gas mixtures: nitrogen and hydrogen are stored in storage containers, mixed in the required quantity in the gaseous state and the mixture is fed into the interior of the furnace. In this case, nitrogen can be stored in gaseous or liquid state depending on consumption. In this process, the quantitative ratio of the nitrogen-hydrogen mixture can be varied as desired (usually a hydrogen fraction between 2% by volume and 30% by volume is selected), but hydrogen is relatively expensive as the supply gas.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren anzugeben, mit dem ein Stickstoff und Wasserstoff enthaltendes Gasgemisch für das Glühen von Werkstücken in einem Ofen auf einfache und wirtschaftliche Weise hergestellt werden kann.The invention is therefore based on the object of specifying a method with which a gas mixture containing nitrogen and hydrogen for the annealing of workpieces in a furnace can be produced in a simple and economical manner.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß in den Ofeninnenraum ein aus einem Inertgas und Ammoniak bestehendes Gasgemisch eingeleitet wird und der Ofeninnenraum vor dem Einleiten des Gasgemisches auf eine zur katalytischen Spaltung des Ammoniaks ausreichende Temperatur erhitzt wird.This object is achieved in that a gas mixture consisting of an inert gas and ammonia is introduced into the furnace interior and the furnace interior is heated to a temperature sufficient for catalytic decomposition of the ammonia before the introduction of the gas mixture.

Erfindungsgemäß ist weder ein Spaltgasgenerator noch die Lieferung bzw. Speicherung von Wasserstoff erforderlich. Das erfindungsgemäße Verfahren beruht auf der Erkenntnis, daß Ammoniak im Innenraum eines Glühofens katalytisch in Stickstoff und Wasserstoff gespalten und auf diese Weise zusammen mit zusätzlich zugeführtem Stickstoff ein für die Glühbehandlung von Werkstücken geeignetes Gasgemisch innerhalb des Ofens gebildet werden kann. Die beim Glühen eingesetzten Öfen enthalten Bauteile, die bei einer geeigneten Temperatur eine katalytische Spaltung von Ammoniak bewirken. Derartige, üblicherweise aus Chrom-Nickel-Stählen gefertigte Bauteile sind beispielsweise die Ofenmuffeloder das Förderband. Somit ist im Ofeninnenraum eine für die Spaltung des Ammoniaks ausreichend große Katalysatorfläche vorhanden. Beim erfindungsgemäßen Verfahren fungiert demnach der Ofen selbst als Gasgenerator.According to the invention, neither a cracked gas generator nor the supply or storage of hydrogen is required. The method according to the invention is based on the knowledge that ammonia is catalytically split into nitrogen and hydrogen in the interior of an annealing furnace and in this way together with additionally supplied nitrogen is used for the annealing treatment suitable work piece mixture can be formed within the furnace. The furnaces used in the annealing process contain components that cause a catalytic breakdown of ammonia at a suitable temperature. Such components, usually made of chrome-nickel steels, are, for example, the furnace muffle or the conveyor belt. There is therefore a sufficiently large catalyst area in the furnace interior for the splitting of the ammonia. In the method according to the invention, the furnace itself therefore functions as a gas generator.

Durch das erfindungsgemäße Verfahren kann im Wärmebehandlungsofen ein Stickstoff-Wasserstoff-Gemisch bereitgestellt werden, das kostengünstiger ist, als ein in einem Spaltgasgenerator oder durch Mischen der in Komponentenform gespeicherten Gase hergestelltes Gasgemisch.By means of the method according to the invention, a nitrogen-hydrogen mixture can be provided in the heat treatment furnace, which is less expensive than a gas mixture produced in a cracked gas generator or by mixing the gases stored in component form.

Der Anteil des Ammoniaks im Ammoniak-Stickstoff-Gemisch kann anhand des bekannten Mengenverhältnisses im Spaltgas leicht eingestellt werden und richtet sich nach dem gewünschten Wasserstoffgehalt in der Glühofenatmosphäre.The proportion of ammonia in the ammonia-nitrogen mixture can be easily adjusted based on the known ratio in the cracked gas and depends on the desired hydrogen content in the annealing furnace atmosphere.

Bestehen die die katalytische Spaltung bewirkenden Teile des Ofens aus Chrom-Nickelstählen, so wird der Ofeninnenraum für das erfindungsgemäße Verfahren auf eine oberhalb von 500 °C liegende Temperatur erhitzt.If the parts of the furnace which bring about the catalytic cleavage consist of chromium-nickel steels, the interior of the furnace is heated to a temperature above 500 ° C. for the process according to the invention.

Wegen seiner Verfügbarkeit sowie des relativ niedrigen Preises wird als Inertgas zweckmäßigerweise Stickstoff verwendet, der zudem einfach zu speichern ist.Because of its availability and the relatively low price, nitrogen is expediently used as the inert gas, which is also easy to store.

In einer vorteilhaften Variante der Erfindung, die ein kohlungsneutrales Glühen von Werkstücken ermöglicht, wird zusätzlich zum Stickstoff-Ammoniak-Gemisch ein aus Kohlenwasserstoffen bestehendes Gas, beispielsweise Erdgas oder Propan, in den Ofen geleitet.In an advantageous variant of the invention, which enables workpieces to be annealed without carbon, a gas consisting of hydrocarbons, for example natural gas or propane, is added to the nitrogen-ammonia mixture. passed into the oven.

Besonders vorteilhaft läßt sich das erfindungsgemäße Verfahren auf das Glühen von Chrom-Nickelstählen anwenden, da das Glühgut in diesem Fall selbst als Katalysator für die Spaltung des Ammoniaks wirkt. Es läßt sich aber auch beim Glühen von anderen Stählen und bei NE-Metallen wie z.B. beim Glühen von Neusilberteilen einsetzen.The process according to the invention can be applied particularly advantageously to the annealing of chromium-nickel steels, since in this case the annealing material itself acts as a catalyst for the splitting of the ammonia. But it can also be used for the annealing of other steels and non-ferrous metals such as use when glowing nickel silver parts.

Eine weitere günstige Anwendung dieses erfindungsgemäßen Verfahrens ist in Anspruch 6 angegeben.Another favorable application of this method according to the invention is specified in claim 6.

Das erfindungsgemäße Verfahren kann aber auch zum Glühen anderer Materialien verwendet werden, die bei einer Temperatur über 500 °C reduzierend geglüht werden müssen.However, the process according to the invention can also be used for the annealing of other materials which have to be annealed at a temperature above 500 ° C.

Claims (6)

Verfahren zum Herstellen einer Stickstoff und Wasserstoff enthaltenden Gasatmosphäre für das Glühen metallischer Werkstücke in einem Ofen, dadurch gekennzeichnet, daß in den Ofeninnenraum ein aus einem Inertgas und Ammoniak bestehendes Gasgemisch eingeleitet wird und der Ofeninnenraum vor dem Einleiten des Gasgemisches auf eine zur katalytischen Spaltung des Ammoniaks ausreichende Temperatur erhitzt wird.A process for producing a nitrogen and hydrogen-containing gas atmosphere for the annealing of metallic workpieces in a furnace, characterized in that a gas mixture consisting of an inert gas and ammonia is introduced into the furnace interior and the furnace interior prior to the introduction of the gas mixture to a for the catalytic splitting of the ammonia sufficient temperature is heated. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Ofeninnenraum auf eine oberhalb ca. 500 °C liegende Temperatur erhitzt wird.2. The method according to claim 1, characterized in that the interior of the furnace is heated to a temperature above about 500 ° C. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das inerte Gas Stickstoff ist.3. The method according to claim 1 or 2, characterized in that the inert gas is nitrogen. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß dem Ofeninnenraum zusätzlich ein aus Kohlenwasserstoffen bestehendes Gas zugeführt wird.4. The method according to any one of claims 1 to 3, characterized in that a gas consisting of hydrocarbons is additionally supplied to the furnace interior. 5. Anwendung des Verfahrens nach einem der Ansprüche 1 bis,4 auf das Glühen von Stahlteilen und NE-Metallteilen.5. Application of the method according to one of claims 1 to 4 on the annealing of steel parts and non-ferrous metal parts. 6. Anwendung des Verfahrens nach einem der Ansprüche 1 bis 4 auf das isotherm Glühen von Gesenkschmiedeteilen oder von Teilen aus Grauguß (GG), Sphäroguß (GGG) , Stahlguß (GGS) oder Temperquß (GGT) .6. Application of the method according to one of claims 1 to 4 on the isothermal annealing of drop forgings or parts made of gray cast iron (GG), spheroidal cast iron (GGG), cast steel (GGS) or tempering (GGT).
EP83108017A 1982-08-18 1983-08-12 Method of producing a gas atmosphere for annealing metallic work pieces Expired EP0106961B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19823230723 DE3230723A1 (en) 1982-08-18 1982-08-18 METHOD FOR PRODUCING A GAS ATMOSPHERE FOR THE GLOWING OF METAL WORKPIECES
DE3230723 1982-08-18

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EP0106961A1 true EP0106961A1 (en) 1984-05-02
EP0106961B1 EP0106961B1 (en) 1986-02-19

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EP83108017A Expired EP0106961B1 (en) 1982-08-18 1983-08-12 Method of producing a gas atmosphere for annealing metallic work pieces

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EP (1) EP0106961B1 (en)
AT (1) AT376703B (en)
AU (1) AU1796983A (en)
BR (1) BR8301377A (en)
DE (2) DE3230723A1 (en)
NO (1) NO832957L (en)
ZA (1) ZA836052B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0180953A2 (en) * 1984-11-08 1986-05-14 Linde Aktiengesellschaft Method and device for producing a protective atmosphere

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE644980C (en) * 1930-12-20 1937-05-19 Benno Schilde Maschb Akt Ges Process for bright annealing of elongated work material made of metals and furnace to carry out the process
US3519257A (en) * 1967-03-23 1970-07-07 Degussa Process for the treatment of surfaces of workpieces in an annealing furnace
DE2017540B2 (en) * 1970-04-13 1972-06-08 Varta Ag, 6000 Frankfurt METHOD AND DEVICE FOR CLEARING AMMONIA INTO HYDROGEN AND NITROGEN
DE2657644A1 (en) * 1975-12-22 1977-06-30 Air Prod & Chem GAS MIXTURE FOR IMPORTING IN A FERROUS METAL TREATMENT FURNACE
DE2617962A1 (en) * 1976-04-24 1977-11-10 Eschweiler Bergwerksverein Protective atmospheres for heat treatment of metals - using mixt. of liq. nitrogen and hydrogen gas to eliminate need for gas generators

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1471880A (en) * 1973-10-26 1977-04-27 Air Prod & Chem Furnace atmosphere for the heat treatment of ferrous metal
GB1575342A (en) * 1977-04-27 1980-09-17 Air Prod & Chem Production of furnace atmospheres for the heat treatment of ferrous metals

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE644980C (en) * 1930-12-20 1937-05-19 Benno Schilde Maschb Akt Ges Process for bright annealing of elongated work material made of metals and furnace to carry out the process
US3519257A (en) * 1967-03-23 1970-07-07 Degussa Process for the treatment of surfaces of workpieces in an annealing furnace
DE2017540B2 (en) * 1970-04-13 1972-06-08 Varta Ag, 6000 Frankfurt METHOD AND DEVICE FOR CLEARING AMMONIA INTO HYDROGEN AND NITROGEN
DE2657644A1 (en) * 1975-12-22 1977-06-30 Air Prod & Chem GAS MIXTURE FOR IMPORTING IN A FERROUS METAL TREATMENT FURNACE
DE2617962A1 (en) * 1976-04-24 1977-11-10 Eschweiler Bergwerksverein Protective atmospheres for heat treatment of metals - using mixt. of liq. nitrogen and hydrogen gas to eliminate need for gas generators

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0180953A2 (en) * 1984-11-08 1986-05-14 Linde Aktiengesellschaft Method and device for producing a protective atmosphere
EP0180953A3 (en) * 1984-11-08 1988-07-27 Linde Aktiengesellschaft Method and device for producing a protective atmosphere

Also Published As

Publication number Publication date
ZA836052B (en) 1984-04-25
NO832957L (en) 1984-02-20
EP0106961B1 (en) 1986-02-19
ATA460482A (en) 1984-05-15
AT376703B (en) 1984-12-27
DE3362186D1 (en) 1986-03-27
DE3230723A1 (en) 1984-02-23
BR8301377A (en) 1984-04-17
AU1796983A (en) 1984-02-23

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