EP0213991A1 - Process for rapid cementation in a continuous furnace - Google Patents

Process for rapid cementation in a continuous furnace Download PDF

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EP0213991A1
EP0213991A1 EP86401584A EP86401584A EP0213991A1 EP 0213991 A1 EP0213991 A1 EP 0213991A1 EP 86401584 A EP86401584 A EP 86401584A EP 86401584 A EP86401584 A EP 86401584A EP 0213991 A1 EP0213991 A1 EP 0213991A1
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Prior art keywords
concentration
atmosphere
carbon monoxide
continuous
furnace
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German (de)
French (fr)
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EP0213991B1 (en
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Philippe Queille
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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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
    • C23C8/08—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
    • C23C8/22—Carburising of ferrous surfaces

Definitions

  • the present invention relates to a rapid case-hardening process in a continuous closed furnace into which a carrier gas and optionally a hydrocarbon are injected capable of generating, at the usual case-hardening temperatures, an atmosphere of predetermined composition, having a nominal concentration of carbon monoxide, an oven door being opened with a determined periodicity to allow the passage of a charge to be cemented, the opening of this door generating in particular an increase in the concentration of oxidizing species in the atmosphere of said oven.
  • a continuous closed furnace is a furnace into which are introduced at regular time intervals the charges to be treated which advance at low speed therein, successively passing through a zone of temperature rise of the charges, a zone of case-hardening of the pieces of the charge and a diffusion zone of said coins.
  • a continuous closed oven may have entry and exit airlocks which partially decrease the increase in the concentration of oxidizing species in the atmosphere and may also have non-watertight separation doors between each zone.
  • This atmosphere consists of:
  • the method according to the invention makes it possible to avoid these drawbacks. It is characterized in that the carbon monoxide concentration of the atmosphere injected into the furnace is increased with the same periodicity, so as to compensate for the increase in the concentration of oxidizing species in the furnace and thus maintain substantially constant the carbon potential of the furnace carburizing atmosphere throughout the carburizing duration of said parts. If carbon monoxide is formed in the furnace after cracking of one of the source elements of the carrier gas, the increase in concentration of carbon monoxide is understood as the correlative increase in the generator element.
  • the carrier gas comprises nitrogen and an alcohol, preferably methanol (or ethanol).
  • the increase in concentration of carbon monoxide signifies in this case a corresponding increase in the concentration of methanol in the carrier gas.
  • the carbon monoxide concentration in the atmosphere is increased, so as to compensate for the increase in carbon dioxide in order to maintain a substantially constant carbon potential.
  • this increase in carbon monoxide concentration will preferably be accompanied by an increase in the flow rate of the carrier gas.
  • a carrier gas flow rate of 1.5 to 4 times the "nominal" carrier gas flow rate, corresponding to the charge treatment phase (case hardening and / or diffusion), will preferably be used.
  • the oven door will be closed before the injection of carrier gas with a high concentration of carbon monoxide begins.
  • a carrier gas economy is achieved since when the door is open, the increase in the concentration of oxidizing species cannot be avoided.
  • the opening of the oven door will be preceded for a few moments by an injection of carrier gas with a high concentration of carbon monoxide, this injection continuing at least until the door is closed. and possibly after closing thereof, under conditions of duration specified below.
  • the carbon monoxide boost can be timed when the cycle is programmed. Thus it is easy to provide a time delay after closing the door, before returning to the "nominal" carbon monoxide flow. Likewise, provision may be made for a pre-triggering of the carbon monoxide supercharging synchronized with the opening of the door.
  • the injection of carrier gas with a high concentration of carbon monoxide may or may not be accompanied by an increase in the flow rate of carrier gas, preferably within the limits mentioned above.
  • the duration of the injection of carrier gas having a concentration of carbon monoxide greater than the nominal value will be between 5% and 50% of the total duration of the treatment.
  • the carrier gas with a carbon monoxide concentration greater than the nominal value will preferably be obtained from a nitrogen-methanol mixture, with a volume ratio such as 1/20 ⁇ R1 ⁇ 3/7
  • the carrier gas with a carbon monoxide concentration equal to the nominal value will also be obtained from a nitrogen-methanol mixture in a volume ratio preferably having the value
  • a load consisting of steel parts to be cemented is introduced every few minutes (generally from 4 to 20 minutes).
  • This oven generally comprises successively an entry door, an entry airlock, a carburizing zone and a diffusion zone, possibly separated by doors, an exit airlock with quenching tank.
  • the atmosphere generated in the furnace is of the "endothermic" type, that is to say rich mainly in hydrogen, carbon monoxide and nitrogen species, obtained from a generator, or nitrogen and bodies intended for create in the oven the CO and H 2 species which may be methanol alone (preferred solution), ethanol-oxidant mixtures (H 2 0, Air, 00 2, etc.) or equivalent, to which up to 10% may be added of hydrocarbon (CH 4 , C 3 H 8 7) to control the carbon potential and sometimes up to 5% of ammonia for specific treatments such as carbonitriding (cementation activated with ammonia).
  • endothermic that is to say rich mainly in hydrogen, carbon monoxide and nitrogen species, obtained from a generator, or nitrogen and bodies intended for create in the oven the CO and H 2 species which may be methanol alone (preferred solution), ethanol-oxidant mixtures (H 2 0, Air, 00 2, etc.) or equivalent, to which up to 10% may be added of hydrocarbon (CH 4 , C 3 H 8 ...) to control the carbon potential and
  • the entry door is opened, which causes significant uncontrolled entries of oxidizing species (0 2 or CO 2 , H 2 0, resulting from the combustion of the atmosphere of the oven with the outside air).
  • the concentration of carbon monoxide can be considered constant during the whole process. Consequently, the carbon potential varies very strongly in the carburizing zone of the furnace, according to the curve C 1 illustrated in FIG. 5. It can decrease up to a PC M value of the order of 0.1 to 0.3 % for a case-hardening temperature of 920 ° C for example. (The setpoint for the carbon potential at this temperature is often in the range of 0.8 to 1.0%). Reconditioning the oven to the set value takes practically the entire time interval to to t 1 between two successive introductions.
  • FIG. 2 by way of indication represents the flow rate of carrier gas injected into the furnace according to the known solution of the American patent cited above, this flow rate normally having the value DL when the door is closed, and a value DH when the door of the furnace is open, substantially equal to 2 times DL or more.
  • the concentration of carbon monoxide in the atmosphere injected into the oven is increased during the charging of a new charge (or during the diversion, if the latter causes a disturbance similar) or little time previously so as to anticipate the increase in concentration of oxidizing species, without reaching a carbon activity of the atmosphere equal to 1, which would generate soot on the parts.
  • This increase in concentration is generally carried out during the entire duration of the opening of the oven door. It generally continues after the closing of this door in order to return more quickly to the set carbon potential.
  • This measure is doubly favorable because it allows, on the one hand, to maintain the carbon potential of the atmosphere at a sufficient value for there to be carbon transfer from the atmosphere in the room but it also allows other part to accelerate this transfer to the part, since the carbon transfer speed depends, in the carburizing phase, on the product pH 2 x pCo, which are the respective partial pressures of H 2 and CO in the furnace (here equal to concentrations).
  • This increase in carbon monoxide concentration is effected by injection into the furnace of carbon monoxide or, preferably, of a product liable to decompose, in the atmosphere of the furnace to generate this carbon monoxide.
  • the atmosphere injected into the oven is either that of an endo generator at constant flow rate, or preferably, a nitrogen / methanol mixture or equivalent as described above.
  • the injection is increased, during the time ⁇ t ', of carbon monoxide whose concentration increases from [CO] 1 (which is generally of the order of 20 % by volume) to [CO] 2 (which is around 27% by volume).
  • the simplest method for implementing the invention is to use a nitrogen-methanol mixture to generate the atmosphere of the furnace, and to vary the relative proportions of nitrogen and methanol.
  • the proportion of methanol in the mixture is increased, this increase possibly going as far as the introduction of pure methanol during or during this brief period.
  • the flow rate of the mixture and the proportions thereof can be varied simultaneously, so as to keep the nitrogen flow rate substantially constant.
  • This variant is that shown in FIG. 4 with a flow rate D ' H from to to to + ⁇ t', etc ... of a mixture peddling 20% nitrogen and 80% methanol and a flow rate D ' L , lower to D ' H of a mixture containing 40% nitrogen and 60% methanol.
  • This example represents the prior art typically used to date.
  • cementing of steel transmission parts of grade 16NC6 is carried out, for which the cementation depth sought at 550 HV1 is from 0.7 to 0.9 mm.
  • the oven temperature is 920 ° C, the charges, introduced every 7 minutes, being 150 kg.
  • the carbon potential that we are trying to maintain in the carburizing zone is 0.8%.
  • the duration of the opening of the loading door, at the entrance of the oven, is 27 seconds.
  • the atmosphere injected into the oven is obtained using a nitrogen-methanol mixture, in the ratio 40/60 (atrmsphere called "endothermic").
  • the flow rate of the injected atmosphere is 19 m3 / hour.
  • the consumption of atmosphere per cycle (of 7 minutes) is therefore 2.22m 3 .
  • Example 7 In the same oven, all other things being equal, the same parts are treated to obtain the same final conditions as in Example 1.
  • the atmosphere injected into the furnace in the preceding example is replaced by an atmosphere of variable composition, for variable durations, represented in FIG. 7.
  • the atmosphere Atm 2 is injected with a nitrogen / methanol ratio equal to 20/80 at a flow rate of 24 m 3 / h. Then the atmosphere Atm 1 is injected at a flow rate of 12 m 3 / h, for 3 minutes and 50 seconds.
  • the gas consumption during a cycle is 1.57 m 3 .
  • the variations in carbon potential are shown in Figure 8 to scale. (Note that on the time scale ( Figures 6, 7 and 8), F represents the instant of closing of the oven door).
  • the depth cemented at 550 HV1 of the parts in the batch is between 0.7 and 0.9 mm.

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  • Organic Chemistry (AREA)
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  • Mechanical Engineering (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

Procédé de cémentation rapide dans un four continu fermé dans lequel on injecte un gaz porteur et un hydrocarbure susceptible d'engendrer aux températures usuelles de cémentation, une atmosphère de composition prédéterminée ayant une concentration nominale en monoxyde de carbone, une porte du four étant ouverte avec une périodicité déterminée pour permettre le passage d'une charge à cémenter, l'ouverture de cette porte engendrant notamment une augmentation de la concentration des espèces oxydantes dans l'atmosphère dudit four. Selon l'invention, on augmente avec la même périodicité la concentration en monoxyde de carbone de l'atmosphère injectée dans le four, de manière à compenser l'augmentation de la concentration en espèces oxydantes du four et maintenir ainsi sensiblement constant le potentiel carbone de l'atmosphère de cémentation du four pendant toute la durée de cémentation desdites pièces.Fast cementation process in a closed continuous furnace into which a carrier gas and a hydrocarbon are injected capable of generating, at the usual cementation temperatures, an atmosphere of predetermined composition having a nominal concentration of carbon monoxide, an oven door being opened with a periodicity determined to allow the passage of a charge to be cemented, the opening of this door generating in particular an increase in the concentration of oxidizing species in the atmosphere of said furnace. According to the invention, the carbon monoxide concentration of the atmosphere injected into the furnace is increased with the same frequency, so as to compensate for the increase in the concentration of oxidizing species in the furnace and thus keep the carbon potential of the furnace carburizing atmosphere during the entire carburizing duration of said parts.

Description

La présente invention concerne un procédé de cémentation rapide dans un four continu fermé dans lequel on injecte un gaz porteur et éventuellement un hydrocarbure susceptibles d'engendrer aux températures usuelles de cémentation, une atmosphère de composition prédéterminée, ayant une concentration nominale en monoxyde de carbone, une porte du four étant ouverte avec une périodicité déterminée pour permettre le passage d'une charge à cémenter, l'ouverture de cette porte engendrant notamment une augmentation de la concentration des espèces oxydantes dans l'atmosphère dudit four.The present invention relates to a rapid case-hardening process in a continuous closed furnace into which a carrier gas and optionally a hydrocarbon are injected capable of generating, at the usual case-hardening temperatures, an atmosphere of predetermined composition, having a nominal concentration of carbon monoxide, an oven door being opened with a determined periodicity to allow the passage of a charge to be cemented, the opening of this door generating in particular an increase in the concentration of oxidizing species in the atmosphere of said oven.

Un four continu fermé est un four dans lequel on introduit à intervalles de temps réguliers des charges à traiter qui avancent à faible vitesse dans celui-ci, traversant successivement une zone de montée en température des charges, une zone de cémentation des pièces de la charge et une zone de diffusion desdites pièces. Un four continu fermé peut comporter des sas d'entrée et de sortie qui diminuent partiellement l'augmentation de la concentration des espèces oxydantes dans l'atmosphère et peut comporter également des portes de séparation non étanches entre chaque zone.A continuous closed furnace is a furnace into which are introduced at regular time intervals the charges to be treated which advance at low speed therein, successively passing through a zone of temperature rise of the charges, a zone of case-hardening of the pieces of the charge and a diffusion zone of said coins. A continuous closed oven may have entry and exit airlocks which partially decrease the increase in the concentration of oxidizing species in the atmosphere and may also have non-watertight separation doors between each zone.

L'injection de gaz porteur et d'hydrocarbure engendre une atmosphère de composition prédéterminée lorsque le four est en équilibre, c'est-à-dire notamment lorsque les portes du four sont fermées. Cette atmosphère est constituée de :

Figure imgb0001
The injection of carrier gas and of hydrocarbon generates an atmosphere of predetermined composition when the oven is in equilibrium, that is to say in particular when the doors of the oven are closed. This atmosphere consists of:
Figure imgb0001

Dans un four continu, l'introduction d'une charge provoque, lors de l'ouverture d'une porte, des entrées d'air inportantes engendrant des espèces oxydantes. L'augmentation de la concentration des espèces oxydantes dans l'atmosphère du four engendre une diminution rapide du potentiel carbone.In a continuous oven, the introduction of a charge causes, when a door is opened, significant air intakes generating oxidizing species. The increase in the concentration of oxidizing species in the furnace atmosphere generates a rapid decrease in the carbon potential.

Il a été proposé dans le brevet américain 4.145.232 de multiplier le débit de gaz porteur par deux lors de l'ouverture de la porte du four pour l'introduction de la charge et de revenir au débit initial habituel de gaz porteur lors de la fermeture de la porte.It has been proposed in American patent 4,145,232 to multiply the carrier gas flow rate by two when opening the oven door for the introduction of the charge and to return to the usual initial flow rate of carrier gas during the door closing.

Un tel procédé n'est pas satisfaisant.Such a process is not satisfactory.

En effet, dans un tel procédé, quelque soit le fort débit de gaz porteur injecté dans le four, on ne peut éviter une remontée des espèces oxydantes dans le four, donc une augmentation de leur concentration et une diminution corrélative du potentiel carbone.Indeed, in such a process, whatever the high flow rate of carrier gas injected into the furnace, it is not possible to avoid a rise in the oxidizing species in the furnace, therefore an increase in their concentration and a corresponding decrease in carbon potential.

Le potentiel carbone dans la zone de cémentation du four, où se produit la réaction d'équilibre :

Figure imgb0002
peut se définir par la relation :
Figure imgb0003

  • k(T) = cte fonction de la température
  • [CO] = concentration en monoxyde de carbone
  • [CO2] = concentration en dioxyde de carbone.
The carbon potential in the carburizing zone of the furnace, where the equilibrium reaction takes place:
Figure imgb0002
 can be defined by the relation:
Figure imgb0003
  • k (T) = this function of the temperature
  • [CO] = carbon monoxide concentration
  • [CO 2 ] = concentration of carbon dioxide.

Or, quelque soit le débit de gaz injecté dans le four, la concentration en monoxyde de carbone dans le four reste sensiblement constante. Par conséquent, une augmentation de la concentration en dioxyde de carbone entraîne nécessairement une diminution du potentiel carbone.However, whatever the flow rate of gas injected into the furnace, the concentration of carbon monoxide in the furnace remains substantially constant. Consequently, an increase in the carbon dioxide concentration necessarily results in a decrease in the carbon potential.

Le procédé selon l'invention permet d'éviter ces inconvénients. Il est caractérisé en ce que l'on augmente avec la même périodicité la concentration en monoxyde de carbone de l'atmosphère injectée dans le four, de manière à compenser l'augmentation de la concentration en espèces oxydantes du four et maintenir ainsi sensiblement constant le potentiel carbone de l'atmosphère de cémentation du four pendant toute la durée de cémentation desdites pièces. Si le monoxyde de carbone est formé dans le four après craquage d'un des éléments source du gaz porteur, l'augmentation de concentration de monoxyde de carbone s'entend comme l'augmentation corrélative de l'élément générateur. Ainsi, dans la pratique la plus courante, le gaz porteur comprend de l'azote et un alcool, de préférence le méthanol (ou l'éthanol). L'augmentation de concentration de monoxyde de carbone signifie dans ce cas une augmentation corrélative de la concentration de méthanol dans le gaz porteur.The method according to the invention makes it possible to avoid these drawbacks. It is characterized in that the carbon monoxide concentration of the atmosphere injected into the furnace is increased with the same periodicity, so as to compensate for the increase in the concentration of oxidizing species in the furnace and thus maintain substantially constant the carbon potential of the furnace carburizing atmosphere throughout the carburizing duration of said parts. If carbon monoxide is formed in the furnace after cracking of one of the source elements of the carrier gas, the increase in concentration of carbon monoxide is understood as the correlative increase in the generator element. Thus, in the most common practice, the carrier gas comprises nitrogen and an alcohol, preferably methanol (or ethanol). The increase in concentration of carbon monoxide signifies in this case a corresponding increase in the concentration of methanol in the carrier gas.

De préférence, dès l'ouverture de la porte du four on augmente la concentration en monoxyde de carbone de l'atmosphère, de manière à compenser l'augmentation de dioxyde de carbone en vue de maintenir un potentiel carbone sensiblement constant. Pour assurer un renouvellement rapide de l'atmosphère du four et donc une augmentation plus rapide de la concentration en monoxyde de carbone, on accompagnera de préférence cette augmentation de concentration de monoxyde de carbone par une augmentation de débit du gaz porteur.Preferably, as soon as the oven door is opened, the carbon monoxide concentration in the atmosphere is increased, so as to compensate for the increase in carbon dioxide in order to maintain a substantially constant carbon potential. To ensure rapid renewal of the furnace atmosphere and therefore a more rapid increase in the carbon monoxide concentration, this increase in carbon monoxide concentration will preferably be accompanied by an increase in the flow rate of the carrier gas.

Dans ce cas, on utilisera de préférence un débit de gaz porteur de 1,5 à 4 fois le débit "nominal" de gaz porteur, correspondant à la phase de traitement de la charge (cémentation et/ou diffusion).In this case, a carrier gas flow rate of 1.5 to 4 times the "nominal" carrier gas flow rate, corresponding to the charge treatment phase (case hardening and / or diffusion), will preferably be used.

Selon une première variante de réalisation de l'invention, on attendra la fermeture de la porte du four pour commencer l'injection de gaz porteur à forte concentration en monoxyde de carbone. De cette manière, on réalise une économie de gaz porteur puisque lorsque la porte est ouverte, l'augmentation de la concentration en espèces oxydantes ne peut être évitée.According to a first variant embodiment of the invention, the oven door will be closed before the injection of carrier gas with a high concentration of carbon monoxide begins. In this way, a carrier gas economy is achieved since when the door is open, the increase in the concentration of oxidizing species cannot be avoided.

Selon une variante préférentielle de l'invention, l'ouverture de la porte du four sera précédée de quelques instants par une injection de gaz porteur à forte concentration en monoxyde de carbone, cette injection se poursuivant au moins jusqu'à la fermeture de la porte et éventuellement après fermeture de celle-ci, dans des conditions de durée précisées ci-après. La suralimentation en monoxyde de carbone peut être temporisée lorsque le cycle se déroule de manière programmée. C'est ainsi qu'il est aisé de prévoir une temporisation après la fermeture de la porte, avant de revenir au débit "nominal" de monoxyde de carbone. De même, on peut prévoir un prédéclanchement de la suralimentation en monoxyde de carbone synchronisé sur l'ouverture de la porte.According to a preferred variant of the invention, the opening of the oven door will be preceded for a few moments by an injection of carrier gas with a high concentration of carbon monoxide, this injection continuing at least until the door is closed. and possibly after closing thereof, under conditions of duration specified below. The carbon monoxide boost can be timed when the cycle is programmed. Thus it is easy to provide a time delay after closing the door, before returning to the "nominal" carbon monoxide flow. Likewise, provision may be made for a pre-triggering of the carbon monoxide supercharging synchronized with the opening of the door.

Bien entendu, dans tous les cas décrits ci-dessus, l'injection de gaz porteur à forte concentration en monoxyde de carbone peut s'acompagner ou non d'une augmentation de débit de gaz porteur, de préférence dans les limites mentionnées plus haut.Of course, in all the cases described above, the injection of carrier gas with a high concentration of carbon monoxide may or may not be accompanied by an increase in the flow rate of carrier gas, preferably within the limits mentioned above.

Dans toutes les variantes envisagées ci-dessus, la durée de l'injection de gaz porteur ayant une concentration en monoxyde de carbone supérieure à la valeur nominale sera comprise entre 5 % et 50 % de la durée totale du traitement.In all the variants envisaged above, the duration of the injection of carrier gas having a concentration of carbon monoxide greater than the nominal value will be between 5% and 50% of the total duration of the treatment.

Le gaz porteur de concentration en monoxyde de carbone supérieure à la valeur nominale sera de préférence obtenu à partir d'un mélange azote-méthanol, avec un rapport en volume

Figure imgb0004
tel que 1/20 ≤ R1 ≤ 3/7The carrier gas with a carbon monoxide concentration greater than the nominal value will preferably be obtained from a nitrogen-methanol mixture, with a volume ratio
Figure imgb0004
 such as 1/20 ≤ R1 ≤ 3/7

Le gaz porteur de concentration en monoxyde de carbone égale à la valeur nominale sera également obtenu à partir d'un mélange azote-méthanol dans un rapport volumique ayant, de préférence, la valeur

Figure imgb0005
The carrier gas with a carbon monoxide concentration equal to the nominal value will also be obtained from a nitrogen-methanol mixture in a volume ratio preferably having the value
Figure imgb0005

L'invention sera mieux comprise à l'aide des exemples de réalisation suivants, donnés à titre non limitatif, conjointement avec les figures qui représentent :

  • - les figures 1 et 2, les variations d'atmosphère selon l'art antérieur ;
  • - les figures 3 et 4, les variations d'atmosphère selon l'invention ;
  • - la figure 5, les variations du potentiel carbone selon l'art antérieur et selon l'invention.
The invention will be better understood with the aid of the following embodiments, given without limitation, together with the figures which represent:
  • - Figures 1 and 2, the atmospheric variations according to the prior art;
  • - Figures 3 and 4, the atmospheric variations according to the invention;
  • - Figure 5, the variations of the carbon potential according to the prior art and according to the invention.

Dans un four continu (ou "push-furnace" en anglais), on introduit toutes les quelques minutes (généralement de 4 à 20 minutes) une charge constituée de pièces en acier à cémenter. Ce four comporte généralement successivement une porte d'entrée, un sas d'entrée, une zone de cémentation et une zone de diffusion , éventuellement séparée par des portes, un sas de sortie avec bac de trempe.In a continuous oven (or "push-furnace" in English), a load consisting of steel parts to be cemented is introduced every few minutes (generally from 4 to 20 minutes). This oven generally comprises successively an entry door, an entry airlock, a carburizing zone and a diffusion zone, possibly separated by doors, an exit airlock with quenching tank.

L'atmosphère engendrée dans le four est de type "endothermique", c'est-à-dire riche principalement en espèces hydrogène, monoxyde de carbone et azote, obtenue à partir d'un générateur, ou d'azote et de corps destinée à créer dans le four les espèces CO et H2 pouvant être du méthanol seul (solution préférée), des mélanges éthanol-oxydant (H20, Air, 002 ...) ou équivalents, auxquels on ajoute éventuellement jusqu'à 10 % d'hydrocarbure (CH4, C3H8 ...) pour contrôler le potentiel carbone et parfois jusqu'à 5 % d'ammoniac pour des traitements particuliers comme la carbonitruration (cémentation activée à l' ammoniac).The atmosphere generated in the furnace is of the "endothermic" type, that is to say rich mainly in hydrogen, carbon monoxide and nitrogen species, obtained from a generator, or nitrogen and bodies intended for create in the oven the CO and H 2 species which may be methanol alone (preferred solution), ethanol-oxidant mixtures (H 2 0, Air, 00 2, etc.) or equivalent, to which up to 10% may be added of hydrocarbon (CH 4 , C 3 H 8 ...) to control the carbon potential and sometimes up to 5% of ammonia for specific treatments such as carbonitriding (cementation activated with ammonia).

Pour l'introduction d'une charge dans le four, on ouvre la porte d'entrée, ce qui provoque des entrées importantes non contrôlées d'espèces oxydantes (02 ou CO2, H20, issus de la combustion de l'atmosphère du four avec l'air extérieur).For the introduction of a charge into the oven, the entry door is opened, which causes significant uncontrolled entries of oxidizing species (0 2 or CO 2 , H 2 0, resulting from the combustion of the atmosphere of the oven with the outside air).

Dans les procédés actuellement connus (figures 1 et 2), l'ouverture de la porte du four, périodiquement, aux instants to, t1, t2,..., provoque (figure 1) une très rapide augmentation de la concentration en dioxyde de carbone de l'atmosphère du four, celle-ci passant presque instantanément (quelques dizaines de secondes, ou plus) d'une concentration [CO2]1, par exemple de 0,15 % à une concentration [CO2]2 pouvant atteindre 1 %, soit environ 6 fois supérieure. (Valeurs très variables selon les fours et le traitement).In the currently known methods (FIGS. 1 and 2), the opening of the oven door, periodically, at times to, t 1 , t 2 , ..., causes (Figure 1) a very rapid increase in the concentration of carbon dioxide in the atmosphere of the oven, this going almost instantaneously (a few tens of seconds, or more) from a concentration [ CO 2 ] 1 , for example 0.15% at a concentration [CO 2 ] 2 of up to 1%, or approximately 6 times higher. (Values very variable depending on the ovens and the treatment).

Compte tenu de la faible concentration en dioxyde de carbone dans l'atmosphère du four, la concentration de monoxyde de carbone peut être considérée corme constante pendant tout le procédé. Par conséquent, le potentiel carbone varie très fortement dans la zone de cémentation du four, selon la courbe C1 illustrée sur la figure 5. Il peut diminuer jusqu'à une valeur P.CM de l'ordre de 0,1 à 0,3 % pour une température de cémentation de 920°C par exemple. (La valeur de consigne du potentiel carbone à cette température est souvent de l'ordre de 0,8 à 1,0 %). Le reoonditionnement du four jusqu'à la valeur de consigne prend pratiquement tout l'intervalle de temps to à t1 séparant deux introductions successives. Dans ces conditions, le transfert de carbone qui ne devient efficace qu'aux environs de la valeur P.C m (définie ci-après) valeur atteinte après un intervalle de temps T (T pouvant représenter jusqu'à la moitié de l'intervalle de temps t1 - to séparant l'introduction de 2 charges), la cémentation des pièces pendant chacune des périodes T sera pratiquement nulle et l'on risque même, dans certains cas, de provoquer une décarburation des pièces dans cette période.Taking into account the low concentration of carbon dioxide in the atmosphere of the furnace, the concentration of carbon monoxide can be considered constant during the whole process. Consequently, the carbon potential varies very strongly in the carburizing zone of the furnace, according to the curve C 1 illustrated in FIG. 5. It can decrease up to a PC M value of the order of 0.1 to 0.3 % for a case-hardening temperature of 920 ° C for example. (The setpoint for the carbon potential at this temperature is often in the range of 0.8 to 1.0%). Reconditioning the oven to the set value takes practically the entire time interval to to t 1 between two successive introductions. Under these conditions, the carbon transfer which becomes efficient only around the PC m value (defined below) value reached after a time interval T (T being able to represent up to half of the time interval t 1 - to separating the introduction of 2 charges), the case hardening of the parts during each of the periods T will be practically zero and there is even a risk, in certain cases, of causing decarburization of the parts in this period.

Par conséquent, la cémentation n'ayant lieu que pendant les intervalles de temps to + T à t1, t1 + T à t2, etc..., la profondeur de cémentation pour une dureté déterminée est faible. En fixant initialement une profondeur et une dureté déterminées, la durée du traitement de cémentation est donc considérablement allongée.Consequently, the cementation taking place only during the time intervals to + T to t 1 , t 1 + T to t 2 , etc., the depth of cementation for a determined hardness is small. By initially setting a given depth and hardness, the duration of the carburizing treatment is therefore considerably lengthened.

La figure 2, à titre indicatif représente le débit de gaz porteur injecté dans le four selon la solution connue du brevet américain cité plus haut, ce débit ayant normalement la valeur DL lorsque la porte est fermée, et une valeur DH lorsque la porte du four est ouverte, sensiblement égale à 2 fois DL ou plus.FIG. 2, by way of indication represents the flow rate of carrier gas injected into the furnace according to the known solution of the American patent cited above, this flow rate normally having the value DL when the door is closed, and a value DH when the door of the furnace is open, substantially equal to 2 times DL or more.

Selon l'invention (figures 3 et 4), on augmente la concentration en monoxyde de carbone de l'atmosphère injectée dans le four lors de l'enfournement d'une nouvelle charge (ou lors du détournement, si celui-ci provoque une perturbation similaire) ou peu de temps auparavant de manière à anticiper l'augmentation de concentration en espèces oxydantes, sans atteindre une activité carbone de l'atmosphère égale à 1, ce qui engendrerait de la suie sur les pièces. Cette augmentation de concentration se fait généralement pendant toute la durée de l'ouverture de la porte du four. Elle se poursuit généralement après la fermeture de cette porte afin de revenir plus rapidement au potentiel carbone de consigne. Cette mesure est doublement favorable car elle permet, d'une part, de maintenir le potentiel carbone de l'atmosphère à une valeur suffisante pour qu'il y ait transfert de carbone de l'atmosphère dans la pièce mais elle permet également d'autre part d'accélérer ce transfert vers la pièce, puisque la vitesse de transfert du carbone dépend, dans la phase de cémentation, du produit pH2 x pCo, qui sont les pressions partielles respectives de H2 et CO dans le four (égales ici aux concentrations).According to the invention (FIGS. 3 and 4), the concentration of carbon monoxide in the atmosphere injected into the oven is increased during the charging of a new charge (or during the diversion, if the latter causes a disturbance similar) or little time previously so as to anticipate the increase in concentration of oxidizing species, without reaching a carbon activity of the atmosphere equal to 1, which would generate soot on the parts. This increase in concentration is generally carried out during the entire duration of the opening of the oven door. It generally continues after the closing of this door in order to return more quickly to the set carbon potential. This measure is doubly favorable because it allows, on the one hand, to maintain the carbon potential of the atmosphere at a sufficient value for there to be carbon transfer from the atmosphere in the room but it also allows other part to accelerate this transfer to the part, since the carbon transfer speed depends, in the carburizing phase, on the product pH 2 x pCo, which are the respective partial pressures of H 2 and CO in the furnace (here equal to concentrations).

Cette augmentation de concentration en monoxyde de carbone se fait par injection dans le four de monoxyde de carbone ou, de préférence, d'un produit susceptible de se décomposer, dans l'atmosphère du four pour engendrer ce monoxyde de carbone.This increase in carbon monoxide concentration is effected by injection into the furnace of carbon monoxide or, preferably, of a product liable to decompose, in the atmosphere of the furnace to generate this carbon monoxide.

En régime "normal" (portes fermées), l'atmosphère injectée dans le four est soit, celle d'un générateur endo à débit constant, soit de préférence, un mélange azote/méthanol ou équivalent comme décrit précédemment. Ainsi, selon l'invention (figures 3, 4 et 5), on augmente l'injection, pendant le temps Δt', de monoxyde de carbone dont la concentration passe de [CO]1 (qui est généralement de l'ordre de 20 % en volume) à [CO]2 (qui est de l'ordre de 27 % en volume).In "normal" mode (doors closed), the atmosphere injected into the oven is either that of an endo generator at constant flow rate, or preferably, a nitrogen / methanol mixture or equivalent as described above. Thus, according to the invention (Figures 3, 4 and 5), the injection is increased, during the time Δt ', of carbon monoxide whose concentration increases from [CO] 1 (which is generally of the order of 20 % by volume) to [CO] 2 (which is around 27% by volume).

Ceci se traduit (figure 5) par un potentiel carbone dont les variations sont représentées par les courbes C2. On réglera le débit de cette suralimentation en monoxyde de carbone (ou du corps qui l'engendre) et sa durée pour ne pas descendre sensiblement sous la valeur P.Cm du potentiel carbone, valeur en-dessous de laquelle l'atmosphère ne serait pas cémentante. Par exemple, pour un acier de type 16NC6 et une température de cémentation de 920°C on règlera ces différents paramètres pour ne pas descendre sous une valeur d'environ 0,4 % de potentiel carbone. Ainsi, grâce également à l'augmentation de la vitesse de transfert du carbone, on améliore la rapidité des procédés de cémentation en continu, toutes choses égales par ailleurs.This is reflected (Figure 5) by a carbon potential whose variations are represented by the curves C2. We will regulate the flow rate of this supercharging of carbon monoxide (or of the body which generates it) and its duration so as not to fall significantly below the value PC m of the carbon potential, value below which the atmosphere would not be cementing . For example, for a 16NC6 type steel and a carburizing temperature of 920 ° C, these various parameters will be adjusted so as not to fall below a value of approximately 0.4% of carbon potential. Thus, also thanks to the increase in the carbon transfer speed, the speed of the continuous carburizing processes is improved, all other things being equal.

La méhtode la plus simple pour mettre en oeuvre l'invention est d'utiliser un mélange azote-méthanol pour engendrer l'atmosphère du four, et de faire varier les proportions relatives d'azote et de méthanol.The simplest method for implementing the invention is to use a nitrogen-methanol mixture to generate the atmosphere of the furnace, and to vary the relative proportions of nitrogen and methanol.

Pendant la période correspondant à l'ouverture, on augmente la proportion de méthanol dans le mélange, cette augmentation pouvant aller jusqu'à l'introduction de méthanol pur pendant ou au cours de cette brève période. Mais il est préférable de maintenir au moins 10 % et de préférence au moins 20 % d'azote dans le mélange injecté dans le four.During the period corresponding to the opening, the proportion of methanol in the mixture is increased, this increase possibly going as far as the introduction of pure methanol during or during this brief period. However, it is preferable to maintain at least 10% and preferably at least 20% nitrogen in the mixture injected into the oven.

Pour plus de simplicité, on peut simultanément faire varier le débit du mélange et les proportions de celui-ci, de manière à maintenir sensiblement constant le débit d'azote. Cette variante est celle représentée sur la figure 4 avec un débit D'H de to à to + Δt', etc... d'un mélange colportant 20 % d'azote et 80 % de méthanol et un débit D'L, inférieur à D'H d'un mélange contenant 40 % d'azote et 60 % de méthanol.For simplicity, the flow rate of the mixture and the proportions thereof can be varied simultaneously, so as to keep the nitrogen flow rate substantially constant. This variant is that shown in FIG. 4 with a flow rate D ' H from to to to + Δt', etc ... of a mixture peddling 20% nitrogen and 80% methanol and a flow rate D ' L , lower to D ' H of a mixture containing 40% nitrogen and 60% methanol.

L'invention sera mieux comprise à l'aide des exemples comparatifs ci-après :The invention will be better understood with the aid of the following comparative examples:

EXEMPLE 1 :EXAMPLE 1:

Cet exemple représente l'art antérieur typiquement utilisé jusqu'à ce jour.This example represents the prior art typically used to date.

Dans un four continu poussant, on réalise la cémentation de pièces de transmission en acier de nuance 16NC6, pour lesquelles la profondeur de cémentation recherchée à 550 HV1 est de 0,7 à 0,9 mm. La température du four est de 920°C, les charges, introduites toutes les 7 minutes, étant de 150 kg. Le potentiel carbone que l'on cherche à maintenir, en zone de cémentation, est de 0,8 %. La durée de l'ouverture de la porte de chargement, à l'entrée du four, est de 27 secondes.In a continuous push furnace, cementing of steel transmission parts of grade 16NC6 is carried out, for which the cementation depth sought at 550 HV1 is from 0.7 to 0.9 mm. The oven temperature is 920 ° C, the charges, introduced every 7 minutes, being 150 kg. The carbon potential that we are trying to maintain in the carburizing zone is 0.8%. The duration of the opening of the loading door, at the entrance of the oven, is 27 seconds.

L'atmosphère injectée dans le four est obtenue à l'aide d'un mélange azote-méthanol, dans le rapport 40/60 (atrmsphère dite "endothermique"). Le débit de l'atmosphère injectée est de 19 m3/heure. La consommation d'atmosphère par cycle (de 7 minutes) est donc de 2,22m3.The atmosphere injected into the oven is obtained using a nitrogen-methanol mixture, in the ratio 40/60 (atrmsphere called "endothermic"). The flow rate of the injected atmosphere is 19 m3 / hour. The consumption of atmosphere per cycle (of 7 minutes) is therefore 2.22m 3 .

Les variations du potentiel carbone relevées dans le four sont représentées sur la figure 6. Le potentiel carbone, qui était de 0,8 % avant l'ouverture de la porte, chute à 0,1 % après une minute puis remonte progressivement à 0,8 % (0,4 % après 3 minutes).The variations in carbon potential noted in the oven are shown in FIG. 6. The carbon potential, which was 0.8% before the door was opened, drops to 0.1% after one minute and then gradually rises to 0, 8% (0.4% after 3 minutes).

EXEMPLE 2 :EXAMPLE 2:

Dans le même four, toutes choses égales par ailleurs, on traite les mêmes pièces pour obtenir les mêmes conditions finales que dans l'exemple 1. L'atmosphère injectée dans le four dans l'exemple précédant est remplacée par une atmosphère de composition variable, pendant des durées variables, représentées sur la figure 7.In the same oven, all other things being equal, the same parts are treated to obtain the same final conditions as in Example 1. The atmosphere injected into the furnace in the preceding example is replaced by an atmosphere of variable composition, for variable durations, represented in FIG. 7.

Trente secondes avant l'ouverture de la porte et pendant deux minutes, on injecte l'atmosphère Atm ② avec un rapport azote/méthanol égal à 20/80 sous un débit de 24 m3/h.Puis on injecte l'atmosphère Atm ① sous un débit de 12 m3/h, pendant 3 minutes et 50 secondes. La consommation de gaz pendant un cycle est de 1,57 m3. Les variations du potentiel carbone sont représentées sur la figure 8 à l'échelle. (A noter que sur l'échelle des temps (figures 6, 7 et 8), F représente l'instant de fermeture de la porte du four). La profondeur cémentée à 550 HV1 des pièces du lot est comprise entre 0,7 et 0,9 mm.Thirty seconds before the door opens and for two minutes, the atmosphere Atm ② is injected with a nitrogen / methanol ratio equal to 20/80 at a flow rate of 24 m 3 / h. Then the atmosphere Atm ① is injected at a flow rate of 12 m 3 / h, for 3 minutes and 50 seconds. The gas consumption during a cycle is 1.57 m 3 . The variations in carbon potential are shown in Figure 8 to scale. (Note that on the time scale (Figures 6, 7 and 8), F represents the instant of closing of the oven door). The depth cemented at 550 HV1 of the parts in the batch is between 0.7 and 0.9 mm.

Ainsi, on a réduit la durée du cylce de 17 % (de 7 mn à 5 mn 50 s) et la consommation d'atmosphère de 29 %. Une telle réduction de temps de cycles, toutes choses égales par ailleurs, représente un gain considérable pour l'homme de métier.Thus, the duration of the cylce was reduced by 17% (from 7 min to 5 min 50 s) and the consumption of atmosphere by 29%. Such a reduction in cycle times, all other things being equal, represents a considerable gain for those skilled in the art.

Claims (12)

1. Procédé de cémentation rapide dans un four continu fermé dans lequel on injecte un gaz porteur et un hydrocarbure susceptibles d'engendrer aux températures usuelles de cémentation, une atmosphère de composition prédéterminée, ayant une concentration nominale en monoxyde de carbone, une porte du four étant ouverte avec une périodicité déterminée pour permettre le passage d'une charge à cémenter, l'ouverture de cette porte engendrant notamment une augmentation de la concentration des espèces oxydantes dans l'atmosphère dudit four, caractérisé en ce que l'on augmente avec la même périodicité la concentration en monoxyde de carbone de l'atmosphère injectée dans le four, de manière à compenser l'augmentation de la concentration en espèces oxydantes du four et maintenir ainsi sensiblement constant le potentiel carbone de l'atmosphère de cémentation du four pendant toute la durée de cémentation desdites pièces.1. Method of rapid carburization in a closed continuous furnace into which a carrier gas and a hydrocarbon are injected capable of generating, at the usual carburizing temperatures, an atmosphere of predetermined composition, having a nominal concentration of carbon monoxide, an oven door being open with a determined periodicity to allow the passage of a charge to be cemented, the opening of this door generating in particular an increase in the concentration of oxidizing species in the atmosphere of said furnace, characterized in that one increases with the same concentration of carbon monoxide in the atmosphere injected into the furnace, so as to compensate for the increase in the concentration of oxidizing species in the furnace and thus keep the carbon potential of the carburizing atmosphere of the furnace substantially constant throughout the duration of case hardening of said parts. 2. Procédé de cémentation rapide dans un four continu fermé selon la revendication 1, caractérisé en ce que l'augmentation de la concentration de monoxyde de carbone se fait dès l'ouverture de la porte.2. Method of rapid carburizing in a closed continuous furnace according to claim 1, characterized in that the increase in the concentration of carbon monoxide is done as soon as the door is opened. 3. Procédé de cémentation rapide dans un four continu ferme selon la revendication 2, caractérisé en ce que dès la fermeture de la porte du four, on ramène la concentration en monoxyde de carbne de l'atmosphère injectée à sa valeur nominale dans la composition prédéterminée.3. Method of rapid carburizing in a continuous continuous furnace according to claim 2, characterized in that as soon as the oven door is closed, the concentration of carbon monoxide in the injected atmosphere is brought back to its nominal value in the predetermined composition . 4. Procédé de cémentation rapide dans un four continu fermé selon la revendication 2, caractérisé en ce que dès la fermeture de la porte du four, mais avec une temporisation règlable, on ramène la concentration en monoxyde de carbone de l'atmosphère injectée à sa valeur nominale dans la composition prédéterminée.4. Method of rapid carburizing in a continuous closed furnace according to claim 2, characterized in that as soon as the oven door is closed, but with an adjustable time delay, the concentration of carbon monoxide in the injected atmosphere is reduced to its nominal value in the predetermined composition. 5. Procédé de cémentation rapide dans un four continu fermé selon les revendications 1 à 4, caractérisé en ce que l'injection de monoxyde de carbone précède de quelques instants l'ouverture de la porte.5. Method of rapid carburization in a continuous continuous furnace according to claims 1 to 4, characterized in that the injection of carbon monoxide precedes the opening of the door for a few moments. 6. Procédé de cémentation rapide dans un four continu ferme selon la revendication 1, caractérisé en ce que l'augmentation de la concentration en monoxyde de carbone se fait dès la fermeture de la porte ou précède celle-ci de quelques instants lorsque la durée de l'ouverture de la porte est prédéterminée, pendant un intervalle de temps prédéterminé, avant retour à la concentration nominale.6. Method for rapid carburization in a continuous continuous furnace according to claim 1, characterized in that the increase in the concentration of carbon monoxide takes place as soon as the door is closed or precedes it by a few moments when the duration of the opening of the door is predetermined, for a predetermined period of time, before returning to the nominal concentration. 7. Procédé de cémentation rapide dans un four continu ferme selon les revendications 1 à 6, caractérisé en ce que le retour à la valeur nominale de la concentration en monoxyde de carbone de l'atmosphère injectée s'effectue lorsque le potentiel carbone mesuré dans l'enceinte est revenu sensiblement à une valeur de consigne prédéterminée.7. Fast carburizing process in a continuous continuous furnace according to claims 1 to 6, characterized in that the return to nominal value of the carbon monoxide concentration of the injected atmosphere takes place when the carbon potential measured in l the enclosure has returned substantially to a predetermined set value. 8. Procédé de cémentation rapide dans un four continu fermé selon les revendications 1 à 7, caractérisé en ce que le débit de l'atmosphère injectée dans le four est augmenté au moins pendant une partie de la durée de l'injection d'atmosphère à concentration en monoxyde de carbone supérieure à la valeur nominale.8. Method of rapid carburization in a continuous continuous furnace according to claims 1 to 7, characterized in that the flow rate of the atmosphere injected into the furnace is increased at least for part of the duration of the injection of atmosphere at carbon monoxide concentration higher than the nominal value. 9. Procédé de cérentation rapide dans un four continu fermé selon la revendication 8, caractérisé en ce que l'augmentation de débit de gaz porteur correspond à 1,5 à 4 fois la valeur nominale du débit.9. A rapid cerentation process in a closed continuous oven according to claim 8, characterized in that the increase in carrier gas flow rate corresponds to 1.5 to 4 times the nominal value of the flow rate. 10. Procédé de cémentation rapide dans un four continu fermé selon la revendication 9, caractérisé en ce que la durée de l'injection du gaz porteur ayant une concentration en monoxyde de carbone supérieure à la valeur nominale est comprise entre 5 et 50 % de la durée totale du traitement.10. Method for rapid carburization in a closed continuous furnace according to claim 9, characterized in that the duration of the injection of the carrier gas having a carbon monoxide concentration greater than the nominal value is between 5 and 50% of the total duration of treatment. 11. Procédé de cémentation rapide dans un four continu fermé selon les revendications 1 à 10, caractérisé en ce que le gaz porteur à concentration en CO supérieure à la valeur nominale est obtenu au moins partiellement à partir d'un mélange azote-méthanol avec un rapport volumique
Figure imgb0006
tel que 1/20 ≤ R1 ≤ 3,7, N2 et MeoH représentant respectivement les concentrations en azote et en méthanol.11. Method for rapid carburization in a closed continuous furnace according to claims 1 to 10, characterized in that the carrier gas with a CO concentration greater than the nominal value is obtained at least partially from a nitrogen-methanol mixture with a volume ratio
Figure imgb0006
 such as 1/20 ≤ R1 ≤ 3.7, N2 and MeoH respectively representing the nitrogen and methanol concentrations. 12. Procédé de cémentation rapide dans un four continu fermé selon les revendications 1 à 11, dans lequel on utilise un mélange d'azote et de méthanol pour engendrer le gaz porteur, caractérisé en ce que le débit d'azote reste constant pendant toute la durée du procédé, le débit de méthanol variant selon les variations de concentration de l'atmosphère en monoxyde de carbone.12. Method for rapid carburization in a continuous closed furnace according to claims 1 to 11, in which a mixture of nitrogen and methanol is used to generate the carrier gas, characterized in that the nitrogen flow rate remains constant throughout the duration of the process, the methanol flow rate varying according to variations in the concentration of carbon monoxide in the atmosphere.
EP86401584A 1985-08-14 1986-07-16 Process for rapid cementation in a continuous furnace Expired EP0213991B1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2626292A1 (en) * 1988-01-26 1989-07-28 Paturle Aciers Process for thermochemical surface treatment of steel strips and in particular of thin strips and plant for its use
FR2639250A1 (en) * 1988-11-24 1990-05-25 Air Liquide
EP0465226A1 (en) * 1990-07-03 1992-01-08 Dowa Mining Co., Ltd. Gas-carburizing process and apparatus

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2586258B1 (en) * 1985-08-14 1987-10-30 Air Liquide PROCESS FOR THE QUICK AND HOMOGENEOUS CEMENTING OF A LOAD IN AN OVEN
FR2623209B1 (en) * 1987-11-17 1993-09-03 Air Liquide PROCESS OF HEAT TREATMENT UNDER NITROGEN AND HYDROCARBON GAS ATMOSPHERE
IT1229078B (en) * 1988-03-16 1991-07-18 Air Liquide METAL ARTICLES TREATMENT PROCESS AND DEVICE FOR TREATMENT.
DE4400391A1 (en) * 1994-01-08 1995-07-13 Messer Griesheim Gmbh Process to avoid edge oxidation when carburizing steels
US5934871A (en) * 1997-07-24 1999-08-10 Murphy; Donald G. Method and apparatus for supplying a anti-oxidizing gas to and simultaneously cooling a shaft and a fan in a heat treatment chamber
CN102828143A (en) * 2012-08-30 2012-12-19 天津创真金属科技有限公司 High-temperature carburizing technology for workpiece
CN113215519B (en) * 2021-04-19 2023-08-15 常州天山重工机械有限公司 Carbon saturation control process of muffle-free tank

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2439241A1 (en) * 1978-10-19 1980-05-16 Trw Inc METHOD OF ADJUSTING USING THE FLOW FOR THE INTRODUCTION OF AN INERATED GAS VEHICLE, OF HEAT TREATMENT SUCH AS CARBONITRURATION, CEMENTATION OR ANNEALING OF FERROUS OBJECTS
EP0049531A1 (en) * 1980-10-08 1982-04-14 Linde Aktiengesellschaft Method of case-hardening metallic pieces
EP0049532A1 (en) * 1980-10-08 1982-04-14 Linde Aktiengesellschaft Process for the carbonization and heat-treatment of steels in a non-carbon-affecting atmosphere
GB2092183A (en) * 1981-01-14 1982-08-11 Holcroft & Co Method of controlling furnace atmospheres
DE3310733A1 (en) * 1983-03-24 1984-10-04 Daimler-Benz Ag, 7000 Stuttgart Process of reducing the consumption of protective gas and the edge oxidation of structural members to be treated in sluice pusher plants with combustible protective gas

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US26935A (en) * 1860-01-24 Attaching bonnets to sails
FR439241A (en) * 1911-01-25 1912-06-08 Giovanni Romei Improvements in wheels for tanks and other vehicles in general
US2955062A (en) * 1952-02-27 1960-10-04 Midland Ross Corp Method for carburizing in a continuous furnace
US4049472A (en) * 1975-12-22 1977-09-20 Air Products And Chemicals, Inc. Atmosphere compositions and methods of using same for surface treating ferrous metals
US4145232A (en) * 1977-06-03 1979-03-20 Union Carbide Corporation Process for carburizing steel
CH632013A5 (en) * 1977-09-22 1982-09-15 Ipsen Ind Int Gmbh METHOD FOR GAS CARBONING WORKPIECE FROM STEEL.
US4306918A (en) * 1980-04-22 1981-12-22 Air Products And Chemicals, Inc. Process for carburizing ferrous metals
FR2527641A1 (en) * 1982-05-28 1983-12-02 Air Liquide PROCESS FOR THERMALLY TREATING METALLIC PARTS THROUGH CARBURATION
JPS6130659A (en) * 1984-07-20 1986-02-12 Tokyo Netsu Shiyori Kogyo Kk Gas carburizing method with nitrogen-base gas
FR2586258B1 (en) * 1985-08-14 1987-10-30 Air Liquide PROCESS FOR THE QUICK AND HOMOGENEOUS CEMENTING OF A LOAD IN AN OVEN

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2439241A1 (en) * 1978-10-19 1980-05-16 Trw Inc METHOD OF ADJUSTING USING THE FLOW FOR THE INTRODUCTION OF AN INERATED GAS VEHICLE, OF HEAT TREATMENT SUCH AS CARBONITRURATION, CEMENTATION OR ANNEALING OF FERROUS OBJECTS
EP0049531A1 (en) * 1980-10-08 1982-04-14 Linde Aktiengesellschaft Method of case-hardening metallic pieces
EP0049532A1 (en) * 1980-10-08 1982-04-14 Linde Aktiengesellschaft Process for the carbonization and heat-treatment of steels in a non-carbon-affecting atmosphere
GB2092183A (en) * 1981-01-14 1982-08-11 Holcroft & Co Method of controlling furnace atmospheres
DE3310733A1 (en) * 1983-03-24 1984-10-04 Daimler-Benz Ag, 7000 Stuttgart Process of reducing the consumption of protective gas and the edge oxidation of structural members to be treated in sluice pusher plants with combustible protective gas

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, vol. 87, no. 6, 1977, page 218, résumé no. 42820u, Columbus, Ohio, US; & JP-A-76 24 983 (NIPPON KINZOKU CO. LTD.) 28-07-1976 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2626292A1 (en) * 1988-01-26 1989-07-28 Paturle Aciers Process for thermochemical surface treatment of steel strips and in particular of thin strips and plant for its use
FR2639250A1 (en) * 1988-11-24 1990-05-25 Air Liquide
EP0375477A1 (en) * 1988-11-24 1990-06-27 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process for producing an atmosphere for thermal treatment by air separation by permeation
EP0465226A1 (en) * 1990-07-03 1992-01-08 Dowa Mining Co., Ltd. Gas-carburizing process and apparatus
EP0825274A2 (en) * 1990-07-03 1998-02-25 Dowa Mining Co., Ltd. Gas-carburizing process and apparatus
EP0825274A3 (en) * 1990-07-03 1998-05-13 Dowa Mining Co., Ltd. Gas-carburizing process and apparatus

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US4769090A (en) 1988-09-06
FR2586259B1 (en) 1987-10-30
ES556249A0 (en) 1987-07-01
AU6022586A (en) 1987-02-19
EP0213991B1 (en) 1989-01-25
JPS6356304B2 (en) 1988-11-08
ATE40416T1 (en) 1989-02-15
JPS6240359A (en) 1987-02-21
CA1259550A (en) 1989-09-19
AU587045B2 (en) 1989-08-03
ZA865392B (en) 1987-03-25
FR2586259A1 (en) 1987-02-20
DE3661943D1 (en) 1989-03-02
ES8706850A1 (en) 1987-07-01
BR8603865A (en) 1987-03-24

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