EP0695807A1 - Procédé pour le traitement thermique, notamment carburation, de pièces métalliques - Google Patents

Procédé pour le traitement thermique, notamment carburation, de pièces métalliques Download PDF

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Publication number
EP0695807A1
EP0695807A1 EP95112146A EP95112146A EP0695807A1 EP 0695807 A1 EP0695807 A1 EP 0695807A1 EP 95112146 A EP95112146 A EP 95112146A EP 95112146 A EP95112146 A EP 95112146A EP 0695807 A1 EP0695807 A1 EP 0695807A1
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EP
European Patent Office
Prior art keywords
atmosphere
oxygen
treatment
carburizing
gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95112146A
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German (de)
English (en)
Inventor
Alexander Dipl.-Ing. Jurmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Linde GmbH
Original Assignee
Linde GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Linde GmbH filed Critical Linde GmbH
Publication of EP0695807A1 publication Critical patent/EP0695807A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • 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
    • 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 heat treatment, in particular carburizing, of metallic workpieces in a furnace in a treatment atmosphere at high temperatures, in which the atmosphere is converted by reacting at least one compound containing carbon and hydrogen and a further medium containing elemental oxygen (for example air). is produced.
  • the so-called generator endogas process for carburizing, carbon-neutral and, in certain cases, decarburizing heat treatment of goods
  • the required treatment gas is generated with large amounts of air, for example, under-stoichiometric combustion of natural gas, methane or propane with air at temperatures of around 1000 ° C Amounts of auxiliary energy generated.
  • an identical treatment gas is produced by a catalyst retort arranged in the heat treatment furnace and by supplying the same starting materials (see, for example, technical article "Basic requirements for reducing gas consumption in controlled gas carburizing" from HTM 35/1980 No. 5, page 230 to 237, in particular point 1.1 and, for example, DE 36 32 577).
  • nitrogen is often additionally provided as an atmospheric component, which leads to additional process engineering advantages, such as the possibility leads to the atomization of the often liquid, oxygen-bearing hydrocarbon compounds and also brings with it the general availability of an inert admixing and rinsing medium (see again technical article "Basic requirements for reducing gas consumption with regulated gas carburizing" from HTM 35/1980 No. 5, Pages 230 to 237, especially points 1.3 and 1.4).
  • the invention was therefore based on the object of specifying a cost-acceptable and easy to implement option with which a treatment gas with a CO-to-H2 ratio of approximately 1 to 1 can be produced.
  • gaseous alkenes ie hydrocarbon gases with a double bond
  • This atmosphere can optionally be diluted with an inert gas - usually nitrogen - this being particularly the case with carburizing in the beginning
  • Treatment part preferably does not happen or only to a small extent.
  • Pure oxygen is preferably used as the oxygen-containing medium, but oxygen-containing gases, in particular air or O2-enriched air, or also oxygen-containing, gaseous compounds are also suitable.
  • it is primarily thought of carbon gases (CO2, CO), nitrogen dioxide (NO2) or nitrous oxide (N2O).
  • Propylene or ethylene are the most important alkenes of the invention.
  • the figure shows a chamber furnace 1 in which a batch 2 of steel parts to be carburized is located.
  • a double jacket converter K consisting essentially of two concentric tubes, the external dimensions of which correspond to a conventional radiant tube.
  • the converter K is connected with its inner tube 3 to feed lines 4 and 5, which are used to supply the starting media for atmospheric formation, the atmosphere essentially formed in the inner tube finally flowing into the furnace interior via a nozzle 7.
  • the free space 6 between the outer and inner tube of the converter K is connected to a feed line 8, with which a heating medium for heating the inner tube 3 can optionally be supplied.
  • the furnace is equipped with - but not shown - jet pipes for its heating and with a fan 10 which serves to circulate the treatment gas.
  • a gas analyzer 11 here in particular a so-called C-flow probe, is connected to the furnace interior, which regulates the oxygen supply quantity via the associated signal processing unit 12 via an adjusting element 14 arranged in the oxygen supply line 4b.
  • a quantity control unit 13 is arranged in the feed line 4a, which serves to supply the propylene to the line 4.
  • their setting remains largely constant in the running process.
  • the workpiece batch 2 - as shown in the figure - is placed in the chamber furnace 1 and the batch is heated up via the feed line 5 and the converter K started supplying nitrogen to the furnace.
  • the final temperature for the carburizing treatment that is ultimately to be achieved is approximately 900 to 950 ° C - the nitrogen supply is terminated and a stoichiometrically coordinated propylene-oxygen mixture is fed to the double-jacket converter K via the feed line 4 started and thus the formation of a treatment gas atmosphere according to C3H6 + 3/2 O2 ---> 3 CO + 3 H2 initiated.
  • the starting temperature for this reaction is about 450 ° C., so that the reaction proceeds above 500 ° C. and in particular at normal carburizing temperatures without any problems.
  • the converter heating takes place from the interior of the furnace and is supported by the fact that hot combustion exhaust gases originating from the radiant heat pipes are introduced via line 8 into the free space 6 between the inner and outer pipes of the converter.
  • the conversion taking place in converter K and its inner tube 3 provides, according to the reaction equation shown, an approximately 50% CO and 50% H2 treatment gas, that is to say a treatment gas whose CO-to-H2 ratio is exactly "1".
  • This carbon transition number ⁇ of an atmosphere is of great importance for a carburizing process and especially its initialization phase, since in this initial phase the respective workpieces still have relatively low C components in the surface layers and therefore the C absorption of these workpieces in this phase is very important depends on the C delivery, for which in turn the said C transition number is a measure.
  • the importance of this C delivery increasingly takes a back seat, since the outer layers of the workpieces to be carburized have reached a saturated carbon content and then the carburization speed is essentially dominated by the diffusion of carbon from the surface into the interior of the workpiece.
  • the C transition number ⁇ of an atmosphere is no longer relevant for the carburization rate so pervasive meaning, and it can, as also partially provided according to the invention, then be converted to an atmosphere with a lower ⁇ number.
  • This is accomplished, for example, by a correspondingly arranged reduction in the propylene and oxygen supply according to the invention, with the simultaneous start of an adapted nitrogen supply.
  • nitrogen proportions of more than 20% up to 50% in the resulting atmosphere, it being important to ensure that no unacceptable decarburization of the workpieces occurs with this final phase atmosphere.
  • their C level - as well as the C level of the initial atmosphere - must be set appropriately.
  • an edge carbon content of approximately 0.9% is achieved in the present example case in particular in an approximately 90-minute treatment period (in the example case considered in more detail here with a relative low hardening depth of 0.5 mm and a relatively short treatment time, the maintenance of the pure propylene-oxygen atmosphere is basically justifiable over the entire treatment time without nitrogen dilution in the final phase).
  • the C level setting of the atmosphere according to the invention can be carried out in the usual way by an independent and controlled supply of an enrichment gas, e.g. of natural gas or acetylene, with the usual indicator of the C level being e.g. the dew point or the CO2 content of the atmosphere are applicable.
  • an enrichment gas e.g. of natural gas or acetylene
  • the usual indicator of the C level being e.g. the dew point or the CO2 content of the atmosphere are applicable.
  • Acetylene has the advantage that the CO to H2 ratio of the atmosphere is not “detuned". There is also the possibility of regulating the C level via the addition of propylene and / or oxygen via lines 4a and 4b with the setting members 12 and 14. If the addition ratio of propylene and oxygen differs from "one", the C level can be set via the O2 partial pressure of the atmosphere. The amount of the O2 excess determines the C level.
  • the excess propylene content does not contribute directly to the formation of CO-H2 carrier gas, but rather leads to an increase in the carbon level of the atmosphere which is formed.
  • the gas analyzer designated 11 in the figure, is used to regulate this process.
  • the O2 potential of the atmosphere that is to say all the O ions contained in the atmospheric constituents CO, CO2 and H2O, is determined and on this basis together with the processing unit 12 determines the appropriate amount of oxygen and adjusts this by means of the volume controller 14.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
EP95112146A 1994-08-03 1995-08-02 Procédé pour le traitement thermique, notamment carburation, de pièces métalliques Withdrawn EP0695807A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19944427507 DE4427507C1 (de) 1994-08-03 1994-08-03 Verfahren zur Wärmebehandlung, insbesondere Aufkohlung, metallischer Werkstücke
DE4427507 1994-08-03

Publications (1)

Publication Number Publication Date
EP0695807A1 true EP0695807A1 (fr) 1996-02-07

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EP95112146A Withdrawn EP0695807A1 (fr) 1994-08-03 1995-08-02 Procédé pour le traitement thermique, notamment carburation, de pièces métalliques

Country Status (3)

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EP (1) EP0695807A1 (fr)
CZ (1) CZ197695A3 (fr)
DE (1) DE4427507C1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3460075B2 (ja) * 1995-12-28 2003-10-27 同和鉱業株式会社 金属の浸炭方法
DE19814451A1 (de) * 1998-03-31 1999-10-07 Linde Ag Verfahren zur Wärmebehandlung von Werkstücken unter Behandlungsgas
US20070107818A1 (en) * 2005-11-16 2007-05-17 Bowe Donald J Deoxygenation of furnaces with hydrogen-containing atmoshperes
DE102008029001B3 (de) 2008-06-20 2009-09-17 Ipsen International Gmbh Verfahren und Einrichtung zur Wärmebehandlung von metallischen Werkstoffen
DE102009038598B4 (de) * 2009-08-26 2017-06-22 Ipsen International Gmbh Verfahren und Vorrichtung zur Aufbereitung von Prozessgasen für Wärmebehandlungen von metallischen Werkstoffen/Werkstücken in Industrieöfen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2934330A (en) * 1953-04-09 1960-04-26 Metallurg Processes Co Apparatus for producing controlled furnace atmospheres
FR1534943A (fr) * 1967-06-23 1968-08-02 Air Liquide Dispositif pour produire une atmosphère
DE1433735B1 (de) * 1963-09-21 1969-09-04 Werner Goehring Verfahren zur Erzielung einer Ofenatmosphaere,mit der eine oxydationsfreie Waermebehandlung von Werkstuecken aus Stahl unter gleichzeitiger Beeinflussung des Kohlenstoffgehalts durchfuehrbar ist
EP0261462A2 (fr) * 1986-09-25 1988-03-30 Linde Aktiengesellschaft Brûleur à tube radiant pourvu d'un lit de catalyseur pour four de traitement thermique
DE4110361A1 (de) * 1991-03-28 1992-10-01 Linde Ag Verfahren zum aufkohlen von eisenwerkstuecken
EP0603799A2 (fr) * 1992-12-22 1994-06-29 Air Products And Chemicals, Inc. Procédé pour la production d'atmosphères de traitement thermique

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2934330A (en) * 1953-04-09 1960-04-26 Metallurg Processes Co Apparatus for producing controlled furnace atmospheres
DE1433735B1 (de) * 1963-09-21 1969-09-04 Werner Goehring Verfahren zur Erzielung einer Ofenatmosphaere,mit der eine oxydationsfreie Waermebehandlung von Werkstuecken aus Stahl unter gleichzeitiger Beeinflussung des Kohlenstoffgehalts durchfuehrbar ist
FR1534943A (fr) * 1967-06-23 1968-08-02 Air Liquide Dispositif pour produire une atmosphère
EP0261462A2 (fr) * 1986-09-25 1988-03-30 Linde Aktiengesellschaft Brûleur à tube radiant pourvu d'un lit de catalyseur pour four de traitement thermique
DE4110361A1 (de) * 1991-03-28 1992-10-01 Linde Ag Verfahren zum aufkohlen von eisenwerkstuecken
EP0603799A2 (fr) * 1992-12-22 1994-06-29 Air Products And Chemicals, Inc. Procédé pour la production d'atmosphères de traitement thermique

Also Published As

Publication number Publication date
DE4427507C1 (de) 1995-06-01
CZ197695A3 (en) 1996-02-14

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